idnits 2.17.1 draft-ietf-dime-rfc3588bis-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** It looks like you're using RFC 3978 boilerplate. You should update this to the boilerplate described in the IETF Trust License Policy document (see https://trustee.ietf.org/license-info), which is required now. -- Found old boilerplate from RFC 3978, Section 5.1 on line 16. -- Found old boilerplate from RFC 3978, Section 5.5, updated by RFC 4748 on line 7001. -- Found old boilerplate from RFC 3979, Section 5, paragraph 1 on line 7012. -- Found old boilerplate from RFC 3979, Section 5, paragraph 2 on line 7019. -- Found old boilerplate from RFC 3979, Section 5, paragraph 3 on line 7025. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- == There are 2 instances of lines with non-RFC2606-compliant FQDNs in the document. == There are 2 instances of lines with non-RFC6890-compliant IPv4 addresses in the document. If these are example addresses, they should be changed. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust Copyright Line does not match the current year == Line 4544 has weird spacing: '...ly with wit...' == Line 4740 has weird spacing: '...ealtime user...' == Line 4768 has weird spacing: '... record inter...' == Line 4778 has weird spacing: '...ealtime user...' == Line 4786 has weird spacing: '...ealtime user...' == (1 more instance...) -- The exact meaning of the all-uppercase expression 'MAY NOT' is not defined in RFC 2119. If it is intended as a requirements expression, it should be rewritten using one of the combinations defined in RFC 2119; otherwise it should not be all-uppercase. == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: The Destination-Realm AVP MUST be present if the message is proxiable. Request messages that may be forwarded by Diameter agents (proxies, redirects or relays) MUST also contain an Acct-Application-Id AVP, an Auth-Application-Id AVP or a Vendor-Specific-Application-Id AVP. A message that MUST NOT be forwarded by Diameter agents (proxies, redirects or relays) MUST not include the Destination-Realm in its ABNF. The value of the Destination-Realm AVP MAY be extracted from the User-Name AVP, or other application-specific methods. == The expression 'MAY NOT', while looking like RFC 2119 requirements text, is not defined in RFC 2119, and should not be used. Consider using 'MUST NOT' instead (if that is what you mean). Found 'MAY NOT' in this paragraph: The following tables presents the AVPs defined in this document, and specifies in which Diameter messages they MAY, or MAY NOT be present. Note that AVPs that can only be present within a Grouped AVP are not represented in this table. -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (January 29, 2007) is 6296 days in the past. Is this intentional? -- Found something which looks like a code comment -- if you have code sections in the document, please surround them with '' and '' lines. Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'DIFFSERV' is mentioned on line 2368, but not defined == Missing Reference: 'PXY' is mentioned on line 4304, but not defined == Unused Reference: 'IANAWEB' is defined on line 6538, but no explicit reference was found in the text == Unused Reference: 'RFC2474' is defined on line 6581, but no explicit reference was found in the text == Unused Reference: 'RFC2597' is defined on line 6586, but no explicit reference was found in the text == Unused Reference: 'RFC3246' is defined on line 6589, but no explicit reference was found in the text == Unused Reference: 'RFC2782' is defined on line 6594, but no explicit reference was found in the text == Unused Reference: 'RFC3436' is defined on line 6649, but no explicit reference was found in the text == Unused Reference: 'RFC3141' is defined on line 6670, but no explicit reference was found in the text == Unused Reference: 'RFC3344' is defined on line 6685, but no explicit reference was found in the text == Unused Reference: 'RFC2977' is defined on line 6688, but no explicit reference was found in the text == Unused Reference: 'RFC2881' is defined on line 6692, but no explicit reference was found in the text == Unused Reference: 'RFC3169' is defined on line 6696, but no explicit reference was found in the text -- Possible downref: Non-RFC (?) normative reference: ref. 'FLOATPOINT' -- Possible downref: Non-RFC (?) normative reference: ref. 'IANAADFAM' -- Possible downref: Non-RFC (?) normative reference: ref. 'IANAWEB' -- Possible downref: Non-RFC (?) normative reference: ref. 'RADTYPE' ** Obsolete normative reference: RFC 793 (ref. 'TCP') (Obsoleted by RFC 9293) ** Obsolete normative reference: RFC 4005 (Obsoleted by RFC 7155) ** Obsolete normative reference: RFC 4006 (Obsoleted by RFC 8506) ** Obsolete normative reference: RFC 2234 (Obsoleted by RFC 4234) ** Downref: Normative reference to an Informational RFC: RFC 3232 ** Obsolete normative reference: RFC 3588 (Obsoleted by RFC 6733) ** Obsolete normative reference: RFC 2284 (Obsoleted by RFC 3748) ** Obsolete normative reference: RFC 2434 (Obsoleted by RFC 5226) ** Obsolete normative reference: RFC 2409 (Obsoleted by RFC 4306) ** Obsolete normative reference: RFC 2407 (Obsoleted by RFC 4306) ** Obsolete normative reference: RFC 2373 (Obsoleted by RFC 3513) ** Obsolete normative reference: RFC 4282 (Obsoleted by RFC 7542) ** Obsolete normative reference: RFC 2915 (Obsoleted by RFC 3401, RFC 3402, RFC 3403, RFC 3404) ** Obsolete normative reference: RFC 2960 (Obsoleted by RFC 4960) ** Obsolete normative reference: RFC 2030 (Obsoleted by RFC 4330) ** Obsolete normative reference: RFC 2246 (Obsoleted by RFC 4346) ** Obsolete normative reference: RFC 2396 (Obsoleted by RFC 3986) ** Obsolete normative reference: RFC 2279 (Obsoleted by RFC 3629) -- Obsolete informational reference (is this intentional?): RFC 3576 (Obsoleted by RFC 5176) -- Obsolete informational reference (is this intentional?): RFC 3344 (Obsoleted by RFC 5944) -- Obsolete informational reference (is this intentional?): RFC 2401 (Obsoleted by RFC 4301) Summary: 19 errors (**), 0 flaws (~~), 24 warnings (==), 16 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DIME V. Fajardo, Ed. 3 Internet-Draft Toshiba America Research 4 Intended status: Standards Track J. Loughney 5 Expires: August 2, 2007 Nokia Research Center 6 January 29, 2007 8 Diameter Base Protocol 9 draft-ietf-dime-rfc3588bis-01.txt 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on August 2, 2007. 36 Copyright Notice 38 Copyright (C) The IETF Trust (2007). 40 Abstract 42 The Diameter base protocol is intended to provide an Authentication, 43 Authorization and Accounting (AAA) framework for applications such as 44 network access or IP mobility. Diameter is also intended to work in 45 both local Authentication, Authorization & Accounting and roaming 46 situations. This document specifies the message format, transport, 47 error reporting, accounting and security services to be used by all 48 Diameter applications. The Diameter base application needs to be 49 supported by all Diameter implementations. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7 54 1.1. Diameter Protocol . . . . . . . . . . . . . . . . . . . . 10 55 1.1.1. Description of the Document Set . . . . . . . . . . 11 56 1.1.2. Conventions Used in This Document . . . . . . . . . 12 57 1.2. Approach to Extensibility . . . . . . . . . . . . . . . . 12 58 1.2.1. Defining New AVP Values . . . . . . . . . . . . . . 13 59 1.2.2. Creating New AVPs . . . . . . . . . . . . . . . . . 13 60 1.2.3. Creating New Authentication Applications . . . . . . 13 61 1.2.4. Creating New Accounting Applications . . . . . . . . 14 62 1.2.5. Application Authentication Procedures . . . . . . . 15 63 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 16 64 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 23 65 2.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 24 66 2.1.1. SCTP Guidelines . . . . . . . . . . . . . . . . . . 25 67 2.2. Securing Diameter Messages . . . . . . . . . . . . . . . 25 68 2.3. Diameter Application Compliance . . . . . . . . . . . . . 25 69 2.4. Application Identifiers . . . . . . . . . . . . . . . . . 26 70 2.5. Connections vs. Sessions . . . . . . . . . . . . . . . . 26 71 2.6. Peer Table . . . . . . . . . . . . . . . . . . . . . . . 27 72 2.7. Realm-Based Routing Table . . . . . . . . . . . . . . . . 28 73 2.8. Role of Diameter Agents . . . . . . . . . . . . . . . . . 30 74 2.8.1. Relay Agents . . . . . . . . . . . . . . . . . . . . 31 75 2.8.2. Proxy Agents . . . . . . . . . . . . . . . . . . . . 32 76 2.8.3. Redirect Agents . . . . . . . . . . . . . . . . . . 32 77 2.8.4. Translation Agents . . . . . . . . . . . . . . . . . 33 78 2.9. End-to-End Security Framework . . . . . . . . . . . . . . 34 79 2.10. Diameter Path Authorization . . . . . . . . . . . . . . . 35 80 3. Diameter Header . . . . . . . . . . . . . . . . . . . . . . . 37 81 3.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 40 82 3.2. Command Code ABNF specification . . . . . . . . . . . . . 41 83 3.3. Diameter Command Naming Conventions . . . . . . . . . . . 43 84 4. Diameter AVPs . . . . . . . . . . . . . . . . . . . . . . . . 44 85 4.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 44 86 4.1.1. Optional Header Elements . . . . . . . . . . . . . . 46 88 4.2. Basic AVP Data Formats . . . . . . . . . . . . . . . . . 46 89 4.3. Derived AVP Data Formats . . . . . . . . . . . . . . . . 48 90 4.4. Grouped AVP Values . . . . . . . . . . . . . . . . . . . 56 91 4.4.1. Example AVP with a Grouped Data type . . . . . . . . 57 92 4.5. Diameter Base Protocol AVPs . . . . . . . . . . . . . . . 60 93 5. Diameter Peers . . . . . . . . . . . . . . . . . . . . . . . 63 94 5.1. Peer Connections . . . . . . . . . . . . . . . . . . . . 63 95 5.2. Diameter Peer Discovery . . . . . . . . . . . . . . . . . 63 96 5.3. Capabilities Exchange . . . . . . . . . . . . . . . . . . 66 97 5.3.1. Capabilities-Exchange-Request . . . . . . . . . . . 67 98 5.3.2. Capabilities-Exchange-Answer . . . . . . . . . . . . 68 99 5.3.3. Vendor-Id AVP . . . . . . . . . . . . . . . . . . . 68 100 5.3.4. Firmware-Revision AVP . . . . . . . . . . . . . . . 69 101 5.3.5. Host-IP-Address AVP . . . . . . . . . . . . . . . . 69 102 5.3.6. Supported-Vendor-Id AVP . . . . . . . . . . . . . . 69 103 5.3.7. Product-Name AVP . . . . . . . . . . . . . . . . . . 69 104 5.4. Disconnecting Peer connections . . . . . . . . . . . . . 69 105 5.4.1. Disconnect-Peer-Request . . . . . . . . . . . . . . 70 106 5.4.2. Disconnect-Peer-Answer . . . . . . . . . . . . . . . 70 107 5.4.3. Disconnect-Cause AVP . . . . . . . . . . . . . . . . 71 108 5.5. Transport Failure Detection . . . . . . . . . . . . . . . 71 109 5.5.1. Device-Watchdog-Request . . . . . . . . . . . . . . 71 110 5.5.2. Device-Watchdog-Answer . . . . . . . . . . . . . . . 72 111 5.5.3. Transport Failure Algorithm . . . . . . . . . . . . 72 112 5.5.4. Failover and Failback Procedures . . . . . . . . . . 72 113 5.6. Peer State Machine . . . . . . . . . . . . . . . . . . . 73 114 5.6.1. Incoming connections . . . . . . . . . . . . . . . . 75 115 5.6.2. Events . . . . . . . . . . . . . . . . . . . . . . . 76 116 5.6.3. Actions . . . . . . . . . . . . . . . . . . . . . . 77 117 5.6.4. The Election Process . . . . . . . . . . . . . . . . 79 118 5.6.5. Capabilities Update . . . . . . . . . . . . . . . . 79 119 6. Diameter message processing . . . . . . . . . . . . . . . . . 80 120 6.1. Diameter Request Routing Overview . . . . . . . . . . . . 80 121 6.1.1. Originating a Request . . . . . . . . . . . . . . . 81 122 6.1.2. Sending a Request . . . . . . . . . . . . . . . . . 82 123 6.1.3. Receiving Requests . . . . . . . . . . . . . . . . . 82 124 6.1.4. Processing Local Requests . . . . . . . . . . . . . 82 125 6.1.5. Request Forwarding . . . . . . . . . . . . . . . . . 82 126 6.1.6. Request Routing . . . . . . . . . . . . . . . . . . 83 127 6.1.7. Predictive Loop Avoidance . . . . . . . . . . . . . 83 128 6.1.8. Redirecting requests . . . . . . . . . . . . . . . . 83 129 6.1.9. Relaying and Proxying Requests . . . . . . . . . . . 84 130 6.2. Diameter Answer Processing . . . . . . . . . . . . . . . 85 131 6.2.1. Processing received Answers . . . . . . . . . . . . 86 132 6.2.2. Relaying and Proxying Answers . . . . . . . . . . . 86 133 6.3. Origin-Host AVP . . . . . . . . . . . . . . . . . . . . . 86 134 6.4. Origin-Realm AVP . . . . . . . . . . . . . . . . . . . . 87 135 6.5. Destination-Host AVP . . . . . . . . . . . . . . . . . . 87 136 6.6. Destination-Realm AVP . . . . . . . . . . . . . . . . . . 87 137 6.7. Routing AVPs . . . . . . . . . . . . . . . . . . . . . . 88 138 6.7.1. Route-Record AVP . . . . . . . . . . . . . . . . . . 88 139 6.7.2. Proxy-Info AVP . . . . . . . . . . . . . . . . . . . 88 140 6.7.3. Proxy-Host AVP . . . . . . . . . . . . . . . . . . . 88 141 6.7.4. Proxy-State AVP . . . . . . . . . . . . . . . . . . 88 142 6.8. Auth-Application-Id AVP . . . . . . . . . . . . . . . . . 88 143 6.9. Acct-Application-Id AVP . . . . . . . . . . . . . . . . . 89 144 6.10. Inband-Security-Id AVP . . . . . . . . . . . . . . . . . 89 145 6.11. Vendor-Specific-Application-Id AVP . . . . . . . . . . . 89 146 6.12. Redirect-Host AVP . . . . . . . . . . . . . . . . . . . . 90 147 6.13. Redirect-Host-Usage AVP . . . . . . . . . . . . . . . . . 90 148 6.14. Redirect-Max-Cache-Time AVP . . . . . . . . . . . . . . . 91 149 6.15. E2E-Sequence AVP . . . . . . . . . . . . . . . . . . . . 91 150 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 93 151 7.1. Result-Code AVP . . . . . . . . . . . . . . . . . . . . . 95 152 7.1.1. Informational . . . . . . . . . . . . . . . . . . . 95 153 7.1.2. Success . . . . . . . . . . . . . . . . . . . . . . 96 154 7.1.3. Protocol Errors . . . . . . . . . . . . . . . . . . 96 155 7.1.4. Transient Failures . . . . . . . . . . . . . . . . . 97 156 7.1.5. Permanent Failures . . . . . . . . . . . . . . . . . 98 157 7.2. Error Bit . . . . . . . . . . . . . . . . . . . . . . . . 101 158 7.3. Error-Message AVP . . . . . . . . . . . . . . . . . . . . 101 159 7.4. Error-Reporting-Host AVP . . . . . . . . . . . . . . . . 102 160 7.5. Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . . 102 161 7.6. Experimental-Result AVP . . . . . . . . . . . . . . . . . 103 162 7.7. Experimental-Result-Code AVP . . . . . . . . . . . . . . 103 163 8. Diameter User Sessions . . . . . . . . . . . . . . . . . . . 104 164 8.1. Authorization Session State Machine . . . . . . . . . . . 105 165 8.2. Accounting Session State Machine . . . . . . . . . . . . 109 166 8.3. Server-Initiated Re-Auth . . . . . . . . . . . . . . . . 115 167 8.3.1. Re-Auth-Request . . . . . . . . . . . . . . . . . . 115 168 8.3.2. Re-Auth-Answer . . . . . . . . . . . . . . . . . . . 116 169 8.4. Session Termination . . . . . . . . . . . . . . . . . . . 117 170 8.4.1. Session-Termination-Request . . . . . . . . . . . . 118 171 8.4.2. Session-Termination-Answer . . . . . . . . . . . . . 118 172 8.5. Aborting a Session . . . . . . . . . . . . . . . . . . . 119 173 8.5.1. Abort-Session-Request . . . . . . . . . . . . . . . 120 174 8.5.2. Abort-Session-Answer . . . . . . . . . . . . . . . . 120 175 8.6. Inferring Session Termination from Origin-State-Id . . . 121 176 8.7. Auth-Request-Type AVP . . . . . . . . . . . . . . . . . . 122 177 8.8. Session-Id AVP . . . . . . . . . . . . . . . . . . . . . 122 178 8.9. Authorization-Lifetime AVP . . . . . . . . . . . . . . . 123 179 8.10. Auth-Grace-Period AVP . . . . . . . . . . . . . . . . . . 124 180 8.11. Auth-Session-State AVP . . . . . . . . . . . . . . . . . 124 181 8.12. Re-Auth-Request-Type AVP . . . . . . . . . . . . . . . . 125 182 8.13. Session-Timeout AVP . . . . . . . . . . . . . . . . . . . 125 183 8.14. User-Name AVP . . . . . . . . . . . . . . . . . . . . . . 126 184 8.15. Termination-Cause AVP . . . . . . . . . . . . . . . . . . 126 185 8.16. Origin-State-Id AVP . . . . . . . . . . . . . . . . . . . 127 186 8.17. Session-Binding AVP . . . . . . . . . . . . . . . . . . . 128 187 8.18. Session-Server-Failover AVP . . . . . . . . . . . . . . . 128 188 8.19. Multi-Round-Time-Out AVP . . . . . . . . . . . . . . . . 129 189 8.20. Class AVP . . . . . . . . . . . . . . . . . . . . . . . . 129 190 8.21. Event-Timestamp AVP . . . . . . . . . . . . . . . . . . . 130 191 9. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . 131 192 9.1. Server Directed Model . . . . . . . . . . . . . . . . . . 131 193 9.2. Protocol Messages . . . . . . . . . . . . . . . . . . . . 132 194 9.3. Application document requirements . . . . . . . . . . . . 132 195 9.4. Fault Resilience . . . . . . . . . . . . . . . . . . . . 132 196 9.5. Accounting Records . . . . . . . . . . . . . . . . . . . 133 197 9.6. Correlation of Accounting Records . . . . . . . . . . . . 134 198 9.7. Accounting Command-Codes . . . . . . . . . . . . . . . . 135 199 9.7.1. Accounting-Request . . . . . . . . . . . . . . . . . 135 200 9.7.2. Accounting-Answer . . . . . . . . . . . . . . . . . 136 201 9.8. Accounting AVPs . . . . . . . . . . . . . . . . . . . . . 137 202 9.8.1. Accounting-Record-Type AVP . . . . . . . . . . . . . 137 203 9.8.2. Acct-Interim-Interval . . . . . . . . . . . . . . . 138 204 9.8.3. Accounting-Record-Number AVP . . . . . . . . . . . . 138 205 9.8.4. Acct-Session-Id AVP . . . . . . . . . . . . . . . . 139 206 9.8.5. Acct-Multi-Session-Id AVP . . . . . . . . . . . . . 139 207 9.8.6. Accounting-Sub-Session-Id AVP . . . . . . . . . . . 139 208 9.8.7. Accounting-Realtime-Required AVP . . . . . . . . . . 139 209 10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . 141 210 10.1. Base Protocol Command AVP Table . . . . . . . . . . . . . 141 211 10.2. Accounting AVP Table . . . . . . . . . . . . . . . . . . 142 212 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 144 213 11.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 144 214 11.1.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . 144 215 11.1.2. AVP Flags . . . . . . . . . . . . . . . . . . . . . 145 216 11.2. Diameter Header . . . . . . . . . . . . . . . . . . . . . 145 217 11.2.1. Command Codes . . . . . . . . . . . . . . . . . . . 145 218 11.2.2. Command Flags . . . . . . . . . . . . . . . . . . . 146 219 11.3. Application Identifiers . . . . . . . . . . . . . . . . . 146 220 11.4. AVP Values . . . . . . . . . . . . . . . . . . . . . . . 146 221 11.4.1. Result-Code AVP Values . . . . . . . . . . . . . . . 147 222 11.4.2. Accounting-Record-Type AVP Values . . . . . . . . . 147 223 11.4.3. Termination-Cause AVP Values . . . . . . . . . . . . 147 224 11.4.4. Redirect-Host-Usage AVP Values . . . . . . . . . . . 147 225 11.4.5. Session-Server-Failover AVP Values . . . . . . . . . 147 226 11.4.6. Session-Binding AVP Values . . . . . . . . . . . . . 147 227 11.4.7. Disconnect-Cause AVP Values . . . . . . . . . . . . 147 228 11.4.8. Auth-Request-Type AVP Values . . . . . . . . . . . . 147 229 11.4.9. Auth-Session-State AVP Values . . . . . . . . . . . 148 230 11.4.10. Re-Auth-Request-Type AVP Values . . . . . . . . . . 148 231 11.4.11. Accounting-Realtime-Required AVP Values . . . . . . 148 232 11.4.12. Inband-Security-Id AVP (code 299) . . . . . . . . . 148 233 11.5. Diameter TCP/SCTP Port Numbers . . . . . . . . . . . . . 148 234 11.6. NAPTR Service Fields . . . . . . . . . . . . . . . . . . 148 235 12. Diameter protocol related configurable parameters . . . . . . 150 236 13. Security Considerations . . . . . . . . . . . . . . . . . . . 151 237 13.1. IPsec Usage . . . . . . . . . . . . . . . . . . . . . . . 151 238 13.2. TLS Usage . . . . . . . . . . . . . . . . . . . . . . . . 152 239 13.3. Peer-to-Peer Considerations . . . . . . . . . . . . . . . 153 240 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 155 241 14.1. Normative References . . . . . . . . . . . . . . . . . . 155 242 14.2. Informational References . . . . . . . . . . . . . . . . 157 243 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 160 244 Appendix B. Diameter Service Template . . . . . . . . . . . . . 161 245 Appendix C. NAPTR Example . . . . . . . . . . . . . . . . . . . 163 246 Appendix D. Duplicate Detection . . . . . . . . . . . . . . . . 164 247 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 166 248 Intellectual Property and Copyright Statements . . . . . . . . . 167 250 1. Introduction 252 Authentication, Authorization and Accounting (AAA) protocols such as 253 TACACS [RFC1492] and RADIUS [RFC2865] were initially deployed to 254 provide dial-up PPP [RFC1661] and terminal server access. Over time, 255 with the growth of the Internet and the introduction of new access 256 technologies, including wireless, DSL, Mobile IP and Ethernet, 257 routers and network access servers (NAS) have increased in complexity 258 and density, putting new demands on AAA protocols. 260 Network access requirements for AAA protocols are summarized in 261 [RFC2989]. These include: 263 Failover 265 [RFC2865] does not define failover mechanisms, and as a result, 266 failover behavior differs between implementations. In order to 267 provide well defined failover behavior, Diameter supports 268 application-layer acknowledgements, and defines failover 269 algorithms and the associated state machine. This is described in 270 Section 5.5 and [RFC3539]. 272 Transmission-level security 274 [RFC2865] defines an application-layer authentication and 275 integrity scheme that is required only for use with Response 276 packets. While [RFC2869] defines an additional authentication and 277 integrity mechanism, use is only required during Extensible 278 Authentication Protocol (EAP) sessions. While attribute-hiding is 279 supported, [RFC2865] does not provide support for per-packet 280 confidentiality. In accounting, [RFC2866] assumes that replay 281 protection is provided by the backend billing server, rather than 282 within the protocol itself. 284 While [RFC3162] defines the use of IPsec with RADIUS, support for 285 IPsec is not required. Since within [RFC2409] authentication 286 occurs only within Phase 1 prior to the establishment of IPsec SAs 287 in Phase 2, it is typically not possible to define separate trust 288 or authorization schemes for each application. This limits the 289 usefulness of IPsec in inter-domain AAA applications (such as 290 roaming) where it may be desirable to define a distinct 291 certificate hierarchy for use in a AAA deployment. In order to 292 provide universal support for transmission-level security, and 293 enable both intra- and inter-domain AAA deployments, IPsec support 294 is mandatory in Diameter, and TLS support is optional. Security 295 is discussed in Section 13. 297 Reliable transport 299 RADIUS runs over UDP, and does not define retransmission behavior; 300 as a result, reliability varies between implementations. As 301 described in [RFC2975], this is a major issue in accounting, where 302 packet loss may translate directly into revenue loss. In order to 303 provide well defined transport behavior, Diameter runs over 304 reliable transport mechanisms (TCP, SCTP) as defined in [RFC3539]. 306 Agent support 308 [RFC2865] does not provide for explicit support for agents, 309 including Proxies, Redirects and Relays. Since the expected 310 behavior is not defined, it varies between implementations. 311 Diameter defines agent behavior explicitly; this is described in 312 Section 2.8. 314 Server-initiated messages 316 While RADIUS server-initiated messages are defined in [RFC3576], 317 support is optional. This makes it difficult to implement 318 features such as unsolicited disconnect or reauthentication/ 319 reauthorization on demand across a heterogeneous deployment. 320 Support for server-initiated messages is mandatory in Diameter, 321 and is described in Section 8. 323 Auditability 325 RADIUS does not define data-object security mechanisms, and as a 326 result, untrusted proxies may modify attributes or even packet 327 headers without being detected. Combined with lack of support for 328 capabilities negotiation, this makes it very difficult to 329 determine what occurred in the event of a dispute. While 330 implementation of data object security is not mandatory within 331 Diameter, these capabilities are supported, and are described in 332 [AAACMS]. 334 Transition support 336 While Diameter does not share a common protocol data unit (PDU) 337 with RADIUS, considerable effort has been expended in enabling 338 backward compatibility with RADIUS, so that the two protocols may 339 be deployed in the same network. Initially, it is expected that 340 Diameter will be deployed within new network devices, as well as 341 within gateways enabling communication between legacy RADIUS 342 devices and Diameter agents. This capability, described in 343 [RFC4005], enables Diameter support to be added to legacy 344 networks, by addition of a gateway or server speaking both RADIUS 345 and Diameter. 347 In addition to addressing the above requirements, Diameter also 348 provides support for the following: 350 Capability negotiation 352 RADIUS does not support error messages, capability negotiation, or 353 a mandatory/non-mandatory flag for attributes. Since RADIUS 354 clients and servers are not aware of each other's capabilities, 355 they may not be able to successfully negotiate a mutually 356 acceptable service, or in some cases, even be aware of what 357 service has been implemented. Diameter includes support for error 358 handling (Section 7), capability negotiation (Section 5.3), and 359 mandatory/non-mandatory attribute-value pairs (AVPs) (Section 360 4.1). 362 Peer discovery and configuration 364 RADIUS implementations typically require that the name or address 365 of servers or clients be manually configured, along with the 366 corresponding shared secrets. This results in a large 367 administrative burden, and creates the temptation to reuse the 368 RADIUS shared secret, which can result in major security 369 vulnerabilities if the Request Authenticator is not globally and 370 temporally unique as required in [RFC2865]. Through DNS, Diameter 371 enables dynamic discovery of peers. Derivation of dynamic session 372 keys is enabled via transmission-level security. 374 Roaming support 376 The ROAMOPS WG provided a survey of roaming implementations 377 [RFC2194], detailed roaming requirements [RFC2477], defined the 378 Network Access Identifier (NAI)[RFC4282], and documented existing 379 implementations (and imitations) of RADIUS-based roaming 380 [RFC2607]. In order to improve scalability, [RFC2607] introduced 381 the concept of proxy chaining via an intermediate server, 382 facilitating roaming between providers. However, since RADIUS 383 does not provide explicit support for proxies, and lacks 384 auditability and transmission-level security features, RADIUS- 385 based roaming is vulnerable to attack from external parties as 386 well as susceptible to fraud perpetrated by the roaming partners 387 themselves. As a result, it is not suitable for wide-scale 388 deployment on the Internet [RFC2607]. By providing explicit 389 support for inter-domain roaming and message routing (Sections 2.7 390 and 6), auditability [AAACMS], and transmission-layer security 391 (Section 13) features, Diameter addresses these limitations and 392 provides for secure and scalable roaming. 394 In the decade since AAA protocols were first introduced, the 395 capabilities of Network Access Server (NAS) devices have increased 396 substantially. As a result, while Diameter is a considerably more 397 sophisticated protocol than RADIUS, it remains feasible to implement 398 within embedded devices, given improvements in processor speeds and 399 the widespread availability of embedded IPsec and TLS 400 implementations. 402 1.1. Diameter Protocol 404 The Diameter base protocol provides the following facilities: 406 o Delivery of AVPs (attribute value pairs) 408 o Capabilities negotiation 410 o Error notification 412 o Extensibility, through addition of new commands and AVPs (required 413 in [RFC2989]). 415 o Basic services necessary for applications, such as handling of 416 user sessions or accounting 418 All data delivered by the protocol is in the form of an AVP. Some of 419 these AVP values are used by the Diameter protocol itself, while 420 others deliver data associated with particular applications that 421 employ Diameter. AVPs may be added arbitrarily to Diameter messages, 422 so long as the required AVPs are included and AVPs that are 423 explicitly excluded are not included. AVPs are used by the base 424 Diameter protocol to support the following required features: 426 o Transporting of user authentication information, for the purposes 427 of enabling the Diameter server to authenticate the user. 429 o Transporting of service specific authorization information, 430 between client and servers, allowing the peers to decide whether a 431 user's access request should be granted. 433 o Exchanging resource usage information, which MAY be used for 434 accounting purposes, capacity planning, etc. 436 o Relaying, proxying and redirecting of Diameter messages through a 437 server hierarchy. 439 The Diameter base protocol provides the minimum requirements needed 440 for a AAA protocol, as required by [RFC2989]. The base protocol may 441 be used by itself for accounting purposes only, or it may be used 442 with a Diameter application, such as Mobile IPv4 [RFC4004], or 443 network access [RFC4005]. It is also possible for the base protocol 444 to be extended for use in new applications, via the addition of new 445 commands or AVPs. At this time the focus of Diameter is network 446 access and accounting applications. A truly generic AAA protocol 447 used by many applications might provide functionality not provided by 448 Diameter. Therefore, it is imperative that the designers of new 449 applications understand their requirements before using Diameter. 450 See Section 2.4 for more information on Diameter applications. 452 Any node can initiate a request. In that sense, Diameter is a peer- 453 to-peer protocol. In this document, a Diameter Client is a device at 454 the edge of the network that performs access control, such as a 455 Network Access Server (NAS) or a Foreign Agent (FA). A Diameter 456 client generates Diameter messages to request authentication, 457 authorization, and accounting services for the user. A Diameter 458 agent is a node that does not authenticate and/or authorize messages 459 locally; agents include proxies, redirects and relay agents. A 460 Diameter server performs authentication and/or authorization of the 461 user. A Diameter node MAY act as an agent for certain requests while 462 acting as a server for others. 464 The Diameter protocol also supports server-initiated messages, such 465 as a request to abort service to a particular user. 467 1.1.1. Description of the Document Set 469 Currently, the Diameter specification consists of a base 470 specification (this document), Transport Profile [RFC3539] and 471 applications: Mobile IPv4 [RFC4004], NASREQ [RFC4005], Credit Control 472 [RFC4006], EAP [RFC4072] and SIP [RFC4740]. 474 The Transport Profile document [RFC3539] discusses transport layer 475 issues that arise with AAA protocols and recommendations on how to 476 overcome these issues. This document also defines the Diameter 477 failover algorithm and state machine. 479 The Mobile IPv4 [RFC4004] application defines a Diameter application 480 that allows a Diameter server to perform AAA functions for Mobile 481 IPv4 services to a mobile node. 483 The NASREQ [RFC4005] application defines a Diameter Application that 484 allows a Diameter server to be used in a PPP/SLIP Dial-Up and 485 Terminal Server Access environment. Consideration was given for 486 servers that need to perform protocol conversion between Diameter and 487 RADIUS. 489 The Credit Control [RFC4006] application defines a Diameter 490 Application that can be used to implement real-time credit-control 491 for a variety of end user services such as network access, SIP 492 services, messaging services, and download services. It provides a 493 general solution to real-time cost and credit-control. 495 The EAP [RFC4072] application defines a Diameter Application that can 496 be used to carry EAP packets between the Network Access Server (NAS) 497 working as an EAP authenticator and a back-end authentication server. 498 The Diameter EAP application is based on NASREQ and intended for a 499 similar environment. 501 The SIP [RFC4740] application defines a Diameter Application that 502 allows a Diameter client to request authentication and authorization 503 information to a Diameter server for SIP-based IP multimedia services 504 (see SIP [RFC3261]). 506 In summary, this document defines the base protocol specification for 507 AAA, which includes support for accounting. The applications 508 documents describe applications that use this base specification for 509 Authentication, Authorization and Accounting. 511 1.1.2. Conventions Used in This Document 513 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 514 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 515 document are to be interpreted as described in [RFC2119]. 517 1.2. Approach to Extensibility 519 The Diameter protocol is designed to be extensible, using several 520 mechanisms, including: 522 o Defining new AVP values 524 o Creating new AVPs 526 o Creating new authentication/authorization applications 527 o Creating new accounting applications 529 o Application authentication procedures 531 Reuse of existing AVP values, AVPs and Diameter applications are 532 strongly recommended. Reuse simplifies standardization and 533 implementation and avoids potential interoperability issues. It is 534 expected that command codes are reused; new command codes can only be 535 created by IETF Consensus (see Section 11.2.1). 537 1.2.1. Defining New AVP Values 539 New applications should attempt to reuse AVPs defined in existing 540 applications when possible, as opposed to creating new AVPs. For 541 AVPs of type Enumerated, an application may require a new value to 542 communicate some service-specific information. 544 In order to allocate a new AVP value, a request MUST be sent to IANA 545 [RFC2434], along with an explanation of the new AVP value. IANA 546 considerations for Diameter are discussed in Section 11. 548 1.2.2. Creating New AVPs 550 When no existing AVP can be used, a new AVP should be created. The 551 new AVP being defined MUST use one of the data types listed in 552 Section 4.2. 554 In the event that a logical grouping of AVPs is necessary, and 555 multiple "groups" are possible in a given command, it is recommended 556 that a Grouped AVP be used (see Section 4.4). 558 In order to create a new AVP, a request MUST be sent to IANA, with a 559 specification for the AVP. The request MUST include the commands 560 that would make use of the AVP. 562 1.2.3. Creating New Authentication Applications 564 Every Diameter application specification MUST have an IANA assigned 565 Application Identifier (see Section 2.4 and Section 11.3). 567 Should a new Diameter usage scenario find itself unable to fit within 568 an existing application without requiring major changes to the 569 specification, it may be desirable to create a new Diameter 570 application. Major changes to an application include: 572 o Adding new AVPs to the command, which have the "M" bit set. 574 o Requiring a command that has a different number of round trips to 575 satisfy a request (e.g., application foo has a command that 576 requires one round trip, but new application bar has a command 577 that requires two round trips to complete). 579 o Adding support for an authentication method requiring definition 580 of new AVPs for use with the application. Since a new EAP 581 authentication method can be supported within Diameter without 582 requiring new AVPs, addition of EAP methods does not require the 583 creation of a new authentication application. 585 Creation of a new application should be viewed as a last resort. An 586 implementation MAY add arbitrary non-mandatory AVPs to any command 587 defined in an application, including vendor-specific AVPs without 588 needing to define a new application. Please refer to Section 11.1.1 589 for details. 591 In order to justify allocation of a new application identifier, 592 Diameter applications MUST define one Command Code, or add new 593 mandatory AVPs to the ABNF. 595 The expected AVPs MUST be defined in an ABNF [RFC2234] grammar (see 596 Section 3.2). If the Diameter application has accounting 597 requirements, it MUST also specify the AVPs that are to be present in 598 the Diameter Accounting messages (see Section 9.3). However, just 599 because a new authentication application id is required, does not 600 imply that a new accounting application id is required. 602 When possible, a new Diameter application SHOULD reuse existing 603 Diameter AVPs, in order to avoid defining multiple AVPs that carry 604 similar information. 606 1.2.4. Creating New Accounting Applications 608 There are services that only require Diameter accounting. Such 609 services need to define the AVPs carried in the Accounting-Request 610 (ACR)/ Accounting-Answer (ACA) messages, but do not need to define 611 new command codes. An implementation MAY add arbitrary non-mandatory 612 AVPs (AVPs with the "M" bit not set) to any command defined in an 613 application, including vendor-specific AVPs, without needing to 614 define a new accounting application. Please refer to Section 11.1.1 615 for details. 617 Application Identifiers are still required for Diameter capability 618 exchange. Every Diameter accounting application specification MUST 619 have an IANA assigned Application Identifier (see Section 2.4) or a 620 vendor specific Application Identifier. 622 Every Diameter implementation MUST support accounting. Basic 623 accounting support is sufficient to handle any application that uses 624 the ACR/ACA commands defined in this document, as long as no new 625 mandatory AVPs are added. A mandatory AVP is defined as one which 626 has the "M" bit set when sent within an accounting command, 627 regardless of whether it is required or optional within the ABNF for 628 the accounting application. 630 The creation of a new accounting application should be viewed as a 631 last resort and MUST NOT be used unless a new command or additional 632 mechanisms (e.g., application defined state machine) is defined 633 within the application, or new mandatory AVPs are added to the ABNF. 635 Within an accounting command, setting the "M" bit implies that a 636 backend server (e.g., billing server) or the accounting server itself 637 MUST understand the AVP in order to compute a correct bill. If the 638 AVP is not relevant to the billing process, when the AVP is included 639 within an accounting command, it MUST NOT have the "M" bit set, even 640 if the "M" bit is set when the same AVP is used within other Diameter 641 commands (i.e., authentication/authorization commands). 643 A DIAMETER base accounting implementation MUST be configurable to 644 advertise supported accounting applications in order to prevent the 645 accounting server from accepting accounting requests for unbillable 646 services. The combination of the home domain and the accounting 647 application Id can be used in order to route the request to the 648 appropriate accounting server. 650 When possible, a new Diameter accounting application SHOULD attempt 651 to reuse existing AVPs, in order to avoid defining multiple AVPs that 652 carry similar information. 654 If the base accounting is used without any mandatory AVPs, new 655 commands or additional mechanisms (e.g., application defined state 656 machine), then the base protocol defined standard accounting 657 application Id (Section 2.4) MUST be used in ACR/ACA commands. 659 1.2.5. Application Authentication Procedures 661 When possible, applications SHOULD be designed such that new 662 authentication methods MAY be added without requiring changes to the 663 application. This MAY require that new AVP values be assigned to 664 represent the new authentication transform, or any other scheme that 665 produces similar results. When possible, authentication frameworks, 666 such as Extensible Authentication Protocol [RFC2284], SHOULD be used. 668 1.3. Terminology 670 AAA 672 Authentication, Authorization and Accounting. 674 Accounting 676 The act of collecting information on resource usage for the 677 purpose of capacity planning, auditing, billing or cost 678 allocation. 680 Accounting Record 682 An accounting record represents a summary of the resource 683 consumption of a user over the entire session. Accounting servers 684 creating the accounting record may do so by processing interim 685 accounting events or accounting events from several devices 686 serving the same user. 688 Authentication 690 The act of verifying the identity of an entity (subject). 692 Authorization 694 The act of determining whether a requesting entity (subject) will 695 be allowed access to a resource (object). 697 AVP 699 The Diameter protocol consists of a header followed by one or more 700 Attribute-Value-Pairs (AVPs). An AVP includes a header and is 701 used to encapsulate protocol-specific data (e.g., routing 702 information) as well as authentication, authorization or 703 accounting information. 705 Broker 707 A broker is a business term commonly used in AAA infrastructures. 708 A broker is either a relay, proxy or redirect agent, and MAY be 709 operated by roaming consortiums. Depending on the business model, 710 a broker may either choose to deploy relay agents or proxy agents. 712 Diameter Agent 714 A Diameter Agent is a Diameter node that provides either relay, 715 proxy, redirect or translation services. 717 Diameter Client 719 A Diameter Client is a device at the edge of the network that 720 performs access control. An example of a Diameter client is a 721 Network Access Server (NAS) or a Foreign Agent (FA). 723 Diameter Node 725 A Diameter node is a host process that implements the Diameter 726 protocol, and acts either as a Client, Agent or Server. 728 Diameter Peer 730 A Diameter Peer is a Diameter Node to which a given Diameter Node 731 has a direct transport connection. 733 Diameter Security Exchange 735 A Diameter Security Exchange is a process through which two 736 Diameter nodes establish end-to-end security. 738 Diameter Server 740 A Diameter Server is one that handles authentication, 741 authorization and accounting requests for a particular realm. By 742 its very nature, a Diameter Server MUST support Diameter 743 applications in addition to the base protocol. 745 Downstream 747 Downstream is used to identify the direction of a particular 748 Diameter message from the home server towards the access device. 750 End-to-End Security 752 TLS and IPsec provide hop-by-hop security, or security across a 753 transport connection. When relays or proxy are involved, this 754 hop-by-hop security does not protect the entire Diameter user 755 session. End-to-end security is security between two Diameter 756 nodes, possibly communicating through Diameter Agents. This 757 security protects the entire Diameter communications path from the 758 originating Diameter node to the terminating Diameter node. 760 Home Realm 762 A Home Realm is the administrative domain with which the user 763 maintains an account relationship. 765 Home Server 767 See Diameter Server. 769 Interim accounting 771 An interim accounting message provides a snapshot of usage during 772 a user's session. It is typically implemented in order to provide 773 for partial accounting of a user's session in the case of a device 774 reboot or other network problem prevents the reception of a 775 session summary message or session record. 777 Local Realm 779 A local realm is the administrative domain providing services to a 780 user. An administrative domain MAY act as a local realm for 781 certain users, while being a home realm for others. 783 Multi-session 785 A multi-session represents a logical linking of several sessions. 786 Multi-sessions are tracked by using the Acct-Multi-Session-Id. An 787 example of a multi-session would be a Multi-link PPP bundle. Each 788 leg of the bundle would be a session while the entire bundle would 789 be a multi-session. 791 Network Access Identifier 793 The Network Access Identifier, or NAI [RFC4282], is used in the 794 Diameter protocol to extract a user's identity and realm. The 795 identity is used to identify the user during authentication and/or 796 authorization, while the realm is used for message routing 797 purposes. 799 Proxy Agent or Proxy 801 In addition to forwarding requests and responses, proxies make 802 policy decisions relating to resource usage and provisioning. 803 This is typically accomplished by tracking the state of NAS 804 devices. While proxies typically do not respond to client 805 Requests prior to receiving a Response from the server, they may 806 originate Reject messages in cases where policies are violated. 807 As a result, proxies need to understand the semantics of the 808 messages passing through them, and may not support all Diameter 809 applications. 811 Realm 813 The string in the NAI that immediately follows the '@' character. 814 NAI realm names are required to be unique, and are piggybacked on 815 the administration of the DNS namespace. Diameter makes use of 816 the realm, also loosely referred to as domain, to determine 817 whether messages can be satisfied locally, or whether they must be 818 routed or redirected. In RADIUS, realm names are not necessarily 819 piggybacked on the DNS namespace but may be independent of it. 821 Real-time Accounting 823 Real-time accounting involves the processing of information on 824 resource usage within a defined time window. Time constraints are 825 typically imposed in order to limit financial risk. 827 Relay Agent or Relay 829 Relays forward requests and responses based on routing-related 830 AVPs and realm routing table entries. Since relays do not make 831 policy decisions, they do not examine or alter non-routing AVPs. 832 As a result, relays never originate messages, do not need to 833 understand the semantics of messages or non-routing AVPs, and are 834 capable of handling any Diameter application or message type. 836 Since relays make decisions based on information in routing AVPs 837 and realm forwarding tables they do not keep state on NAS resource 838 usage or sessions in progress. 840 Redirect Agent 842 Rather than forwarding requests and responses between clients and 843 servers, redirect agents refer clients to servers and allow them 844 to communicate directly. Since redirect agents do not sit in the 845 forwarding path, they do not alter any AVPs transiting between 846 client and server. Redirect agents do not originate messages and 847 are capable of handling any message type, although they may be 848 configured only to redirect messages of certain types, while 849 acting as relay or proxy agents for other types. As with proxy 850 agents, redirect agents do not keep state with respect to sessions 851 or NAS resources. 853 Roaming Relationships 855 Roaming relationships include relationships between companies and 856 ISPs, relationships among peer ISPs within a roaming consortium, 857 and relationships between an ISP and a roaming consortium. 859 Security Association 861 A security association is an association between two endpoints in 862 a Diameter session which allows the endpoints to communicate with 863 integrity and confidentially, even in the presence of relays 864 and/or proxies. 866 Session 868 A session is a related progression of events devoted to a 869 particular activity. Each application SHOULD provide guidelines 870 as to when a session begins and ends. All Diameter packets with 871 the same Session-Identifier are considered to be part of the same 872 session. 874 Session state 876 A stateful agent is one that maintains session state information, 877 by keeping track of all authorized active sessions. Each 878 authorized session is bound to a particular service, and its state 879 is considered active either until it is notified otherwise, or by 880 expiration. 882 Sub-session 884 A sub-session represents a distinct service (e.g., QoS or data 885 characteristics) provided to a given session. These services may 886 happen concurrently (e.g., simultaneous voice and data transfer 887 during the same session) or serially. These changes in sessions 888 are tracked with the Accounting-Sub-Session-Id. 890 Transaction state 892 The Diameter protocol requires that agents maintain transaction 893 state, which is used for failover purposes. Transaction state 894 implies that upon forwarding a request, the Hop-by-Hop identifier 895 is saved; the field is replaced with a locally unique identifier, 896 which is restored to its original value when the corresponding 897 answer is received. The request's state is released upon receipt 898 of the answer. A stateless agent is one that only maintains 899 transaction state. 901 Translation Agent 903 A translation agent is a stateful Diameter node that performs 904 protocol translation between Diameter and another AAA protocol, 905 such as RADIUS. 907 Transport Connection 909 A transport connection is a TCP or SCTP connection existing 910 directly between two Diameter peers, otherwise known as a Peer- 911 to-Peer Connection. 913 Upstream 915 Upstream is used to identify the direction of a particular 916 Diameter message from the access device towards the home server. 918 User 920 The entity requesting or using some resource, in support of which 921 a Diameter client has generated a request. 923 2. Protocol Overview 925 The base Diameter protocol may be used by itself for accounting 926 applications, but for use in authentication and authorization it is 927 always extended for a particular application. Two Diameter 928 applications are defined by companion documents: NASREQ [RFC4005], 929 Mobile IPv4 [RFC4004]. These applications are introduced in this 930 document but specified elsewhere. Additional Diameter applications 931 MAY be defined in the future (see Section 11.3). 933 Diameter Clients MUST support the base protocol, which includes 934 accounting. In addition, they MUST fully support each Diameter 935 application that is needed to implement the client's service, e.g., 936 NASREQ and/or Mobile IPv4. A Diameter Client that does not support 937 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 938 Client" where X is the application which it supports, and not a 939 "Diameter Client". 941 Diameter Servers MUST support the base protocol, which includes 942 accounting. In addition, they MUST fully support each Diameter 943 application that is needed to implement the intended service, e.g., 944 NASREQ and/or Mobile IPv4. A Diameter Server that does not support 945 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 946 Server" where X is the application which it supports, and not a 947 "Diameter Server". 949 Diameter Relays and redirect agents are, by definition, protocol 950 transparent, and MUST transparently support the Diameter base 951 protocol, which includes accounting, and all Diameter applications. 953 Diameter proxies MUST support the base protocol, which includes 954 accounting. In addition, they MUST fully support each Diameter 955 application that is needed to implement proxied services, e.g., 956 NASREQ and/or Mobile IPv4. A Diameter proxy which does not support 957 also both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 958 Proxy" where X is the application which it supports, and not a 959 "Diameter Proxy". 961 The base Diameter protocol concerns itself with capabilities 962 negotiation, how messages are sent and how peers may eventually be 963 abandoned. The base protocol also defines certain rules that apply 964 to all exchanges of messages between Diameter nodes. 966 Communication between Diameter peers begins with one peer sending a 967 message to another Diameter peer. The set of AVPs included in the 968 message is determined by a particular Diameter application. One AVP 969 that is included to reference a user's session is the Session-Id. 971 The initial request for authentication and/or authorization of a user 972 would include the Session-Id. The Session-Id is then used in all 973 subsequent messages to identify the user's session (see Section 8 for 974 more information). The communicating party may accept the request, 975 or reject it by returning an answer message with the Result-Code AVP 976 set to indicate an error occurred. The specific behavior of the 977 Diameter server or client receiving a request depends on the Diameter 978 application employed. 980 Session state (associated with a Session-Id) MUST be freed upon 981 receipt of the Session-Termination-Request, Session-Termination- 982 Answer, expiration of authorized service time in the Session-Timeout 983 AVP, and according to rules established in a particular Diameter 984 application. 986 2.1. Transport 988 Transport profile is defined in [RFC3539]. 990 The base Diameter protocol is run on port 3868 of both TCP [TCP] and 991 SCTP [RFC2960] transport protocols. 993 Diameter clients MUST support either TCP or SCTP, while agents and 994 servers MUST support both. Future versions of this specification MAY 995 mandate that clients support SCTP. 997 A Diameter node MAY initiate connections from a source port other 998 than the one that it declares it accepts incoming connections on, and 999 MUST be prepared to receive connections on port 3868. A given 1000 Diameter instance of the peer state machine MUST NOT use more than 1001 one transport connection to communicate with a given peer, unless 1002 multiple instances exist on the peer in which case a separate 1003 connection per process is allowed. 1005 When no transport connection exists with a peer, an attempt to 1006 connect SHOULD be periodically made. This behavior is handled via 1007 the Tc timer, whose recommended value is 30 seconds. There are 1008 certain exceptions to this rule, such as when a peer has terminated 1009 the transport connection stating that it does not wish to 1010 communicate. 1012 When connecting to a peer and either zero or more transports are 1013 specified, SCTP SHOULD be tried first, followed by TCP. See Section 1014 5.2 for more information on peer discovery. 1016 Diameter implementations SHOULD be able to interpret ICMP protocol 1017 port unreachable messages as explicit indications that the server is 1018 not reachable, subject to security policy on trusting such messages. 1020 Diameter implementations SHOULD also be able to interpret a reset 1021 from the transport and timed-out connection attempts. If Diameter 1022 receives data up from TCP that cannot be parsed or identified as a 1023 Diameter error made by the peer, the stream is compromised and cannot 1024 be recovered. The transport connection MUST be closed using a RESET 1025 call (send a TCP RST bit) or an SCTP ABORT message (graceful closure 1026 is compromised). 1028 2.1.1. SCTP Guidelines 1030 The following are guidelines for Diameter implementations that 1031 support SCTP: 1033 1. For interoperability: All Diameter nodes MUST be prepared to 1034 receive Diameter messages on any SCTP stream in the association. 1036 2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP 1037 streams available to the association to prevent head-of-the-line 1038 blocking. 1040 2.2. Securing Diameter Messages 1042 Diameter clients, such as Network Access Servers (NASes) and Mobility 1043 Agents MUST support IP Security [RFC2401], and MAY support TLS 1044 [RFC2246]. Diameter servers MUST support TLS and IPsec. The 1045 Diameter protocol MUST NOT be used without any security mechanism 1046 (TLS or IPsec). 1048 It is suggested that IPsec can be used primarily at the edges and in 1049 intra-domain traffic, such as using pre-shared keys between a NAS a 1050 local AAA proxy. This also eases the requirements on the NAS to 1051 support certificates. It is also suggested that inter-domain traffic 1052 would primarily use TLS. See Sections 13.1 and 13.2 for more details 1053 on IPsec and TLS usage. 1055 2.3. Diameter Application Compliance 1057 Application Identifiers are advertised during the capabilities 1058 exchange phase (see Section 5.3). For a given application, 1059 advertising support of an application implies that the sender 1060 supports all command codes, and the AVPs specified in the associated 1061 ABNFs, described in the specification. 1063 An implementation MAY add arbitrary non-mandatory AVPs to any command 1064 defined in an application, including vendor-specific AVPs. Please 1065 refer to Section 11.1.1 for details. 1067 2.4. Application Identifiers 1069 Each Diameter application MUST have an IANA assigned Application 1070 Identifier (see Section 11.3). The base protocol does not require an 1071 Application Identifier since its support is mandatory. During the 1072 capabilities exchange, Diameter nodes inform their peers of locally 1073 supported applications. Furthermore, all Diameter messages contain 1074 an Application Identifier, which is used in the message forwarding 1075 process. 1077 The following Application Identifier values are defined: 1079 Diameter Common Messages 0 1080 NASREQ 1 [RFC4005] 1081 Mobile-IP 2 [RFC4004] 1082 Diameter Base Accounting 3 1083 Relay 0xffffffff 1085 Relay and redirect agents MUST advertise the Relay Application 1086 Identifier, while all other Diameter nodes MUST advertise locally 1087 supported applications. The receiver of a Capabilities Exchange 1088 message advertising Relay service MUST assume that the sender 1089 supports all current and future applications. 1091 Diameter relay and proxy agents are responsible for finding an 1092 upstream server that supports the application of a particular 1093 message. If none can be found, an error message is returned with the 1094 Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. 1096 2.5. Connections vs. Sessions 1098 This section attempts to provide the reader with an understanding of 1099 the difference between connection and session, which are terms used 1100 extensively throughout this document. 1102 A connection is a transport level connection between two peers, used 1103 to send and receive Diameter messages. A session is a logical 1104 concept at the application layer, and is shared between an access 1105 device and a server, and is identified via the Session-Id AVP. 1107 +--------+ +-------+ +--------+ 1108 | Client | | Relay | | Server | 1109 +--------+ +-------+ +--------+ 1110 <----------> <----------> 1111 peer connection A peer connection B 1113 <-----------------------------> 1114 User session x 1116 Figure 1: Diameter connections and sessions 1118 In the example provided in Figure 1, peer connection A is established 1119 between the Client and its local Relay. Peer connection B is 1120 established between the Relay and the Server. User session X spans 1121 from the Client via the Relay to the Server. Each "user" of a 1122 service causes an auth request to be sent, with a unique session 1123 identifier. Once accepted by the server, both the client and the 1124 server are aware of the session. 1126 It is important to note that there is no relationship between a 1127 connection and a session, and that Diameter messages for multiple 1128 sessions are all multiplexed through a single connection. Also note 1129 that Diameter messages pertaining to the session, both application 1130 specific and those that are defined in this document such as ASR/ASA, 1131 RAR/RAA and STR/STA MUST carry the application identifier of the 1132 application. Diameter messages pertaining to peer connection 1133 establishment and maintenance such as CER/CEA, DWR/DWA and DPR/DPA 1134 MUST carry an application id of zero (0). 1136 2.6. Peer Table 1138 The Diameter Peer Table is used in message forwarding, and referenced 1139 by the Realm Routing Table. A Peer Table entry contains the 1140 following fields: 1142 Host identity 1144 Following the conventions described for the DiameterIdentity 1145 derived AVP data format in Section 4.4. This field contains the 1146 contents of the Origin-Host (Section 6.3) AVP found in the CER or 1147 CEA message. 1149 StatusT 1151 This is the state of the peer entry, and MUST match one of the 1152 values listed in Section 5.6. 1154 Static or Dynamic 1156 Specifies whether a peer entry was statically configured, or 1157 dynamically discovered. 1159 Expiration time 1161 Specifies the time at which dynamically discovered peer table 1162 entries are to be either refreshed, or expired. 1164 TLS Enabled 1166 Specifies whether TLS is to be used when communicating with the 1167 peer. 1169 Additional security information, when needed (e.g., keys, 1170 certificates) 1172 2.7. Realm-Based Routing Table 1174 All Realm-Based routing lookups are performed against what is 1175 commonly known as the Realm Routing Table (see Section 12). A Realm 1176 Routing Table Entry contains the following fields: 1178 Realm Name 1180 This is the field that is typically used as a primary key in the 1181 routing table lookups. Note that some implementations perform 1182 their lookups based on longest-match-from-the-right on the realm 1183 rather than requiring an exact match. 1185 Application Identifier 1187 An application is identified by an application id. A route entry 1188 can have a different destination based on the application 1189 identification in the message header. This field MUST be used as 1190 a secondary key field in routing table lookups. 1192 Local Action 1194 The Local Action field is used to identify how a message should be 1195 treated. The following actions are supported: 1197 1. LOCAL - Diameter messages that resolve to a route entry with 1198 the Local Action set to Local can be satisfied locally, and do 1199 not need to be routed to another server. 1201 2. RELAY - All Diameter messages that fall within this category 1202 MUST be routed to a next hop server, without modifying any 1203 non-routing AVPs. See Section 6.1.9 for relaying guidelines 1205 3. PROXY - All Diameter messages that fall within this category 1206 MUST be routed to a next hop server. The local server MAY 1207 apply its local policies to the message by including new AVPs 1208 to the message prior to routing. See Section 6.1.9 for 1209 proxying guidelines. 1211 4. REDIRECT - Diameter messages that fall within this category 1212 MUST have the identity of the home Diameter server(s) 1213 appended, and returned to the sender of the message. See 1214 Section 6.1.9 for redirect guidelines. 1216 Server Identifier 1218 One or more servers the message is to be routed to. These servers 1219 MUST also be present in the Peer table. When the Local Action is 1220 set to RELAY or PROXY, this field contains the identity of the 1221 server(s) the message must be routed to. When the Local Action 1222 field is set to REDIRECT, this field contains the identity of one 1223 or more servers the message should be redirected to. 1225 Static or Dynamic 1227 Specifies whether a route entry was statically configured, or 1228 dynamically discovered. 1230 Expiration time 1232 Specifies the time which a dynamically discovered route table 1233 entry expires. 1235 It is important to note that Diameter agents MUST support at least 1236 one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation. 1237 Agents do not need to support all modes of operation in order to 1238 conform with the protocol specification, but MUST follow the protocol 1239 compliance guidelines in Section 2. Relay agents MUST NOT reorder 1240 AVPs, and proxies MUST NOT reorder AVPs. 1242 The routing table MAY include a default entry that MUST be used for 1243 any requests not matching any of the other entries. The routing 1244 table MAY consist of only such an entry. 1246 When a request is routed, the target server MUST have advertised the 1247 Application Identifier (see Section 2.4) for the given message, or 1248 have advertised itself as a relay or proxy agent. Otherwise, an 1249 error is returned with the Result-Code AVP set to 1250 DIAMETER_UNABLE_TO_DELIVER. 1252 2.8. Role of Diameter Agents 1254 In addition to client and servers, the Diameter protocol introduces 1255 relay, proxy, redirect, and translation agents, each of which is 1256 defined in Section 1.3. These Diameter agents are useful for several 1257 reasons: 1259 o They can distribute administration of systems to a configurable 1260 grouping, including the maintenance of security associations. 1262 o They can be used for concentration of requests from an number of 1263 co-located or distributed NAS equipment sets to a set of like user 1264 groups. 1266 o They can do value-added processing to the requests or responses. 1268 o They can be used for load balancing. 1270 o A complex network will have multiple authentication sources, they 1271 can sort requests and forward towards the correct target. 1273 The Diameter protocol requires that agents maintain transaction 1274 state, which is used for failover purposes. Transaction state 1275 implies that upon forwarding a request, its Hop-by-Hop identifier is 1276 saved; the field is replaced with a locally unique identifier, which 1277 is restored to its original value when the corresponding answer is 1278 received. The request's state is released upon receipt of the 1279 answer. A stateless agent is one that only maintains transaction 1280 state. 1282 The Proxy-Info AVP allows stateless agents to add local state to a 1283 Diameter request, with the guarantee that the same state will be 1284 present in the answer. However, the protocol's failover procedures 1285 require that agents maintain a copy of pending requests. 1287 A stateful agent is one that maintains session state information; by 1288 keeping track of all authorized active sessions. Each authorized 1289 session is bound to a particular service, and its state is considered 1290 active either until it is notified otherwise, or by expiration. Each 1291 authorized session has an expiration, which is communicated by 1292 Diameter servers via the Session-Timeout AVP. 1294 Maintaining session state MAY be useful in certain applications, such 1295 as: 1297 o Protocol translation (e.g., RADIUS <-> Diameter) 1299 o Limiting resources authorized to a particular user 1301 o Per user or transaction auditing 1303 A Diameter agent MAY act in a stateful manner for some requests and 1304 be stateless for others. A Diameter implementation MAY act as one 1305 type of agent for some requests, and as another type of agent for 1306 others. 1308 2.8.1. Relay Agents 1310 Relay Agents are Diameter agents that accept requests and route 1311 messages to other Diameter nodes based on information found in the 1312 messages (e.g., Destination-Realm). This routing decision is 1313 performed using a list of supported realms, and known peers. This is 1314 known as the Realm Routing Table, as is defined further in Section 1315 2.7. 1317 Relays MAY be used to aggregate requests from multiple Network Access 1318 Servers (NASes) within a common geographical area (POP). The use of 1319 Relays is advantageous since it eliminates the need for NASes to be 1320 configured with the necessary security information they would 1321 otherwise require to communicate with Diameter servers in other 1322 realms. Likewise, this reduces the configuration load on Diameter 1323 servers that would otherwise be necessary when NASes are added, 1324 changed or deleted. 1326 Relays modify Diameter messages by inserting and removing routing 1327 information, but do not modify any other portion of a message. 1328 Relays SHOULD NOT maintain session state but MUST maintain 1329 transaction state. 1331 +------+ ---------> +------+ ---------> +------+ 1332 | | 1. Request | | 2. Request | | 1333 | NAS | | DRL | | HMS | 1334 | | 4. Answer | | 3. Answer | | 1335 +------+ <--------- +------+ <--------- +------+ 1336 example.net example.net example.com 1338 Figure 2: Relaying of Diameter messages 1340 The example provided in Figure 2 depicts a request issued from NAS, 1341 which is an access device, for the user bob@example.com. Prior to 1342 issuing the request, NAS performs a Diameter route lookup, using 1343 "example.com" as the key, and determines that the message is to be 1344 relayed to DRL, which is a Diameter Relay. DRL performs the same 1345 route lookup as NAS, and relays the message to HMS, which is 1346 example.com's Home Diameter Server. HMS identifies that the request 1347 can be locally supported (via the realm), processes the 1348 authentication and/or authorization request, and replies with an 1349 answer, which is routed back to NAS using saved transaction state. 1351 Since Relays do not perform any application level processing, they 1352 provide relaying services for all Diameter applications, and 1353 therefore MUST advertise the Relay Application Identifier. 1355 2.8.2. Proxy Agents 1357 Similarly to relays, proxy agents route Diameter messages using the 1358 Diameter Routing Table. However, they differ since they modify 1359 messages to implement policy enforcement. This requires that proxies 1360 maintain the state of their downstream peers (e.g., access devices) 1361 to enforce resource usage, provide admission control, and 1362 provisioning. 1364 It is important to note that although proxies MAY provide a value-add 1365 function for NASes, they do not allow access devices to use end-to- 1366 end security, since modifying messages breaks authentication. 1368 Proxies MAY be used in call control centers or access ISPs that 1369 provide outsourced connections, they can monitor the number and types 1370 of ports in use, and make allocation and admission decisions 1371 according to their configuration. 1373 Proxies that wish to limit resources MUST maintain session state. 1374 All proxies MUST maintain transaction state. 1376 Since enforcing policies requires an understanding of the service 1377 being provided, Proxies MUST only advertise the Diameter applications 1378 they support. 1380 2.8.3. Redirect Agents 1382 Redirect agents are useful in scenarios where the Diameter routing 1383 configuration needs to be centralized. An example is a redirect 1384 agent that provides services to all members of a consortium, but does 1385 not wish to be burdened with relaying all messages between realms. 1386 This scenario is advantageous since it does not require that the 1387 consortium provide routing updates to its members when changes are 1388 made to a member's infrastructure. 1390 Since redirect agents do not relay messages, and only return an 1391 answer with the information necessary for Diameter agents to 1392 communicate directly, they do not modify messages. Since redirect 1393 agents do not receive answer messages, they cannot maintain session 1394 state. Further, since redirect agents never relay requests, they are 1395 not required to maintain transaction state. 1397 The example provided in Figure 3 depicts a request issued from the 1398 access device, NAS, for the user bob@example.com. The message is 1399 forwarded by the NAS to its relay, DRL, which does not have a routing 1400 entry in its Diameter Routing Table for example.com. DRL has a 1401 default route configured to DRD, which is a redirect agent that 1402 returns a redirect notification to DRL, as well as HMS' contact 1403 information. Upon receipt of the redirect notification, DRL 1404 establishes a transport connection with HMS, if one doesn't already 1405 exist, and forwards the request to it. 1407 +------+ 1408 | | 1409 | DRD | 1410 | | 1411 +------+ 1412 ^ | 1413 2. Request | | 3. Redirection 1414 | | Notification 1415 | v 1416 +------+ ---------> +------+ ---------> +------+ 1417 | | 1. Request | | 4. Request | | 1418 | NAS | | DRL | | HMS | 1419 | | 6. Answer | | 5. Answer | | 1420 +------+ <--------- +------+ <--------- +------+ 1421 example.net example.net example.com 1423 Figure 3: Redirecting a Diameter Message 1425 Since redirect agents do not perform any application level 1426 processing, they provide relaying services for all Diameter 1427 applications, and therefore MUST advertise the Relay Application 1428 Identifier. 1430 2.8.4. Translation Agents 1432 A translation agent is a device that provides translation between two 1433 protocols (e.g., RADIUS<->Diameter, TACACS+<->Diameter). Translation 1434 agents are likely to be used as aggregation servers to communicate 1435 with a Diameter infrastructure, while allowing for the embedded 1436 systems to be migrated at a slower pace. 1438 Given that the Diameter protocol introduces the concept of long-lived 1439 authorized sessions, translation agents MUST be session stateful and 1440 MUST maintain transaction state. 1442 Translation of messages can only occur if the agent recognizes the 1443 application of a particular request, and therefore translation agents 1444 MUST only advertise their locally supported applications. 1446 +------+ ---------> +------+ ---------> +------+ 1447 | | RADIUS Request | | Diameter Request | | 1448 | NAS | | TLA | | HMS | 1449 | | RADIUS Answer | | Diameter Answer | | 1450 +------+ <--------- +------+ <--------- +------+ 1451 example.net example.net example.com 1453 Figure 4: Translation of RADIUS to Diameter 1455 2.9. End-to-End Security Framework 1457 End-to-end security services include confidentiality and message 1458 origin authentication. These services are provided by supporting AVP 1459 integrity and confidentiality between two peers, communicating 1460 through agents. 1462 End-to-end security is provided via the End-to-End security 1463 extension, described in [AAACMS]. The circumstances requiring the 1464 use of end-to-end security are determined by policy on each of the 1465 peers. Security policies, which are not the subject of 1466 standardization, may be applied by next hop Diameter peer or by 1467 destination realm. For example, where TLS or IPsec transmission- 1468 level security is sufficient, there may be no need for end-to-end 1469 security. 1471 End-to-end security policies include: 1473 o Never use end-to-end security. 1475 o Use end-to-end security on messages containing sensitive AVPs. 1476 Which AVPs are sensitive is determined by service provider policy. 1477 AVPs containing keys and passwords should be considered sensitive. 1478 Accounting AVPs may be considered sensitive. Any AVP for which 1479 the P bit may be set or which may be encrypted may be considered 1480 sensitive. 1482 o Always use end-to-end security. 1484 It is strongly RECOMMENDED that all Diameter implementations support 1485 end-to-end security. 1487 2.10. Diameter Path Authorization 1489 As noted in Section 2.2, Diameter requires transmission level 1490 security to be used on each connection (TLS or IPsec). Therefore, 1491 each connection is authenticated, replay and integrity protected and 1492 confidential on a per-packet basis. 1494 In addition to authenticating each connection, each connection as 1495 well as the entire session MUST also be authorized. Before 1496 initiating a connection, a Diameter Peer MUST check that its peers 1497 are authorized to act in their roles. For example, a Diameter peer 1498 may be authentic, but that does not mean that it is authorized to act 1499 as a Diameter Server advertising a set of Diameter applications. 1501 Prior to bringing up a connection, authorization checks are performed 1502 at each connection along the path. Diameter capabilities negotiation 1503 (CER/CEA) also MUST be carried out, in order to determine what 1504 Diameter applications are supported by each peer. Diameter sessions 1505 MUST be routed only through authorized nodes that have advertised 1506 support for the Diameter application required by the session. 1508 As noted in Section 6.1.9, a relay or proxy agent MUST append a 1509 Route-Record AVP to all requests forwarded. The AVP contains the 1510 identity of the peer the request was received from. 1512 The home Diameter server, prior to authorizing a session, MUST check 1513 the Route-Record AVPs to make sure that the route traversed by the 1514 request is acceptable. For example, administrators within the home 1515 realm may not wish to honor requests that have been routed through an 1516 untrusted realm. By authorizing a request, the home Diameter server 1517 is implicitly indicating its willingness to engage in the business 1518 transaction as specified by the contractual relationship between the 1519 server and the previous hop. A DIAMETER_AUTHORIZATION_REJECTED error 1520 message (see Section 7.1.5) is sent if the route traversed by the 1521 request is unacceptable. 1523 A home realm may also wish to check that each accounting request 1524 message corresponds to a Diameter response authorizing the session. 1525 Accounting requests without corresponding authorization responses 1526 SHOULD be subjected to further scrutiny, as should accounting 1527 requests indicating a difference between the requested and provided 1528 service. 1530 Similarly, the local Diameter agent, on receiving a Diameter response 1531 authorizing a session, MUST check the Route-Record AVPs to make sure 1532 that the route traversed by the response is acceptable. At each 1533 step, forwarding of an authorization response is considered evidence 1534 of a willingness to take on financial risk relative to the session. 1535 A local realm may wish to limit this exposure, for example, by 1536 establishing credit limits for intermediate realms and refusing to 1537 accept responses which would violate those limits. By issuing an 1538 accounting request corresponding to the authorization response, the 1539 local realm implicitly indicates its agreement to provide the service 1540 indicated in the authorization response. If the service cannot be 1541 provided by the local realm, then a DIAMETER_UNABLE_TO_COMPLY error 1542 message MUST be sent within the accounting request; a Diameter client 1543 receiving an authorization response for a service that it cannot 1544 perform MUST NOT substitute an alternate service, and then send 1545 accounting requests for the alternate service instead. 1547 3. Diameter Header 1549 A summary of the Diameter header format is shown below. The fields 1550 are transmitted in network byte order. 1552 0 1 2 3 1553 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1554 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1555 | Version | Message Length | 1556 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1557 | command flags | Command-Code | 1558 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1559 | Application-ID | 1560 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1561 | Hop-by-Hop Identifier | 1562 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1563 | End-to-End Identifier | 1564 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1565 | AVPs ... 1566 +-+-+-+-+-+-+-+-+-+-+-+-+- 1568 Version 1570 This Version field MUST be set to 1 to indicate Diameter Version 1571 1. 1573 Message Length 1575 The Message Length field is three octets and indicates the length 1576 of the Diameter message including the header fields. 1578 Command Flags 1580 The Command Flags field is eight bits. The following bits are 1581 assigned: 1583 0 1 2 3 4 5 6 7 1584 +-+-+-+-+-+-+-+-+ 1585 |R P E T r r r r| 1586 +-+-+-+-+-+-+-+-+ 1588 R(equest) 1590 If set, the message is a request. If cleared, the message is 1591 an answer. 1593 P(roxiable) 1595 If set, the message MAY be proxied, relayed or redirected. If 1596 cleared, the message MUST be locally processed. 1598 E(rror) 1600 If set, the message contains a protocol error, and the message 1601 will not conform to the ABNF described for this command. 1602 Messages with the 'E' bit set are commonly referred to as error 1603 messages. This bit MUST NOT be set in request messages. See 1604 Section 7.2. 1606 T(Potentially re-transmitted message) 1608 This flag is set after a link failover procedure, to aid the 1609 removal of duplicate requests. It is set when resending 1610 requests not yet acknowledged, as an indication of a possible 1611 duplicate due to a link failure. This bit MUST be cleared when 1612 sending a request for the first time, otherwise the sender MUST 1613 set this flag. Diameter agents only need to be concerned about 1614 the number of requests they send based on a single received 1615 request; retransmissions by other entities need not be tracked. 1616 Diameter agents that receive a request with the T flag set, 1617 MUST keep the T flag set in the forwarded request. This flag 1618 MUST NOT be set if an error answer message (e.g., a protocol 1619 error) has been received for the earlier message. It can be 1620 set only in cases where no answer has been received from the 1621 server for a request and the request is sent again. This flag 1622 MUST NOT be set in answer messages. 1624 r(eserved) 1626 These flag bits are reserved for future use, and MUST be set to 1627 zero, and ignored by the receiver. 1629 Command-Code 1631 The Command-Code field is three octets, and is used in order to 1632 communicate the command associated with the message. The 24-bit 1633 address space is managed by IANA (see Section 11.2.1). 1635 Command-Code values 16,777,214 and 16,777,215 (hexadecimal values 1636 FFFFFE -FFFFFF) are reserved for experimental use (See Section 1637 11.3). 1639 Application-ID 1641 Application-ID is four octets and is used to identify to which 1642 application the message is applicable for. The application can be 1643 an authentication application, an accounting application or a 1644 vendor specific application. See Section 11.3 for the possible 1645 values that the application-id may use. 1647 The application-id in the header MUST be the same as what is 1648 contained in any relevant application-id AVPs contained in the 1649 message. 1651 Hop-by-Hop Identifier 1653 The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in 1654 network byte order) and aids in matching requests and replies. 1655 The sender MUST ensure that the Hop-by-Hop identifier in a request 1656 is unique on a given connection at any given time, and MAY attempt 1657 to ensure that the number is unique across reboots. The sender of 1658 an Answer message MUST ensure that the Hop-by-Hop Identifier field 1659 contains the same value that was found in the corresponding 1660 request. The Hop-by-Hop identifier is normally a monotonically 1661 increasing number, whose start value was randomly generated. An 1662 answer message that is received with an unknown Hop-by-Hop 1663 Identifier MUST be discarded. 1665 End-to-End Identifier 1667 The End-to-End Identifier is an unsigned 32-bit integer field (in 1668 network byte order) and is used to detect duplicate messages. 1669 Upon reboot implementations MAY set the high order 12 bits to 1670 contain the low order 12 bits of current time, and the low order 1671 20 bits to a random value. Senders of request messages MUST 1672 insert a unique identifier on each message. The identifier MUST 1673 remain locally unique for a period of at least 4 minutes, even 1674 across reboots. The originator of an Answer message MUST ensure 1675 that the End-to-End Identifier field contains the same value that 1676 was found in the corresponding request. The End-to-End Identifier 1677 MUST NOT be modified by Diameter agents of any kind. The 1678 combination of the Origin-Host (see Section 6.3) and this field is 1679 used to detect duplicates. Duplicate requests SHOULD cause the 1680 same answer to be transmitted (modulo the hop-by-hop Identifier 1681 field and any routing AVPs that may be present), and MUST NOT 1682 affect any state that was set when the original request was 1683 processed. Duplicate answer messages that are to be locally 1684 consumed (see Section 6.2) SHOULD be silently discarded. 1686 AVPs 1688 AVPs are a method of encapsulating information relevant to the 1689 Diameter message. See Section 4 for more information on AVPs. 1691 3.1. Command Codes 1693 Each command Request/Answer pair is assigned a command code, and the 1694 sub-type (i.e., request or answer) is identified via the 'R' bit in 1695 the Command Flags field of the Diameter header. 1697 Every Diameter message MUST contain a command code in its header's 1698 Command-Code field, which is used to determine the action that is to 1699 be taken for a particular message. The following Command Codes are 1700 defined in the Diameter base protocol: 1702 Command-Name Abbrev. Code Reference 1703 -------------------------------------------------------- 1704 Abort-Session-Request ASR 274 8.5.1 1705 Abort-Session-Answer ASA 274 8.5.2 1706 Accounting-Request ACR 271 9.7.1 1707 Accounting-Answer ACA 271 9.7.2 1708 Capabilities-Exchange- CER 257 5.3.1 1709 Request 1710 Capabilities-Exchange- CEA 257 5.3.2 1711 Answer 1712 Device-Watchdog-Request DWR 280 5.5.1 1713 Device-Watchdog-Answer DWA 280 5.5.2 1714 Disconnect-Peer-Request DPR 282 5.4.1 1715 Disconnect-Peer-Answer DPA 282 5.4.2 1716 Re-Auth-Request RAR 258 8.3.1 1717 Re-Auth-Answer RAA 258 8.3.2 1718 Session-Termination- STR 275 8.4.1 1719 Request 1720 Session-Termination- STA 275 8.4.2 1721 Answer 1723 3.2. Command Code ABNF specification 1725 Every Command Code defined MUST include a corresponding ABNF 1726 specification, which is used to define the AVPs that MUST or MAY be 1727 present. The following format is used in the definition: 1729 command-def = command-name "::=" diameter-message 1731 command-name = diameter-name 1733 diameter-name = ALPHA *(ALPHA / DIGIT / "-") 1735 diameter-message = header [ *fixed] [ *required] [ *optional] 1737 header = "<" "Diameter Header:" command-id 1738 [r-bit] [p-bit] [e-bit] [application-id] ">" 1740 application-id = 1*DIGIT 1742 command-id = 1*DIGIT 1743 ; The Command Code assigned to the command 1745 r-bit = ", REQ" 1746 ; If present, the 'R' bit in the Command 1747 ; Flags is set, indicating that the message 1748 ; is a request, as opposed to an answer. 1750 p-bit = ", PXY" 1751 ; If present, the 'P' bit in the Command 1752 ; Flags is set, indicating that the message 1753 ; is proxiable. 1755 e-bit = ", ERR" 1756 ; If present, the 'E' bit in the Command 1757 ; Flags is set, indicating that the answer 1758 ; message contains a Result-Code AVP in 1759 ; the "protocol error" class. 1761 fixed = [qual] "<" avp-spec ">" 1762 ; Defines the fixed position of an AVP 1764 required = [qual] "{" avp-spec "}" 1765 ; The AVP MUST be present and can appear 1766 ; anywhere in the message. 1768 optional = [qual] "[" avp-name "]" 1769 ; The avp-name in the 'optional' rule cannot 1770 ; evaluate to any AVP Name which is included 1771 ; in a fixed or required rule. The AVP can 1772 ; appear anywhere in the message. 1774 qual = [min] "*" [max] 1775 ; See ABNF conventions, RFC 2234 Section 6.6. 1776 ; The absence of any qualifiers depends on 1777 ; whether it precedes a fixed, required, or 1778 ; optional rule. If a fixed or required rule has 1779 ; no qualifier, then exactly one such AVP MUST 1780 ; be present. If an optional rule has no 1781 ; qualifier, then 0 or 1 such AVP may be 1782 ; present. 1783 ; 1784 ; NOTE: "[" and "]" have a different meaning 1785 ; than in ABNF (see the optional rule, above). 1786 ; These braces cannot be used to express 1787 ; optional fixed rules (such as an optional 1788 ; ICV at the end). To do this, the convention 1789 ; is '0*1fixed'. 1791 min = 1*DIGIT 1792 ; The minimum number of times the element may 1793 ; be present. The default value is zero. 1795 max = 1*DIGIT 1796 ; The maximum number of times the element may 1797 ; be present. The default value is infinity. A 1798 ; value of zero implies the AVP MUST NOT be 1799 ; present. 1801 avp-spec = diameter-name 1802 ; The avp-spec has to be an AVP Name, defined 1803 ; in the base or extended Diameter 1804 ; specifications. 1806 avp-name = avp-spec / "AVP" 1807 ; The string "AVP" stands for *any* arbitrary 1808 ; AVP Name, which does not conflict with the 1809 ; required or fixed position AVPs defined in 1810 ; the command code definition. 1812 The following is a definition of a fictitious command code: 1814 Example-Request ::= < Diameter Header: 9999999, REQ, PXY > 1815 { User-Name } 1816 * { Origin-Host } 1817 * [ AVP 1819 3.3. Diameter Command Naming Conventions 1821 Diameter command names typically includes one or more English words 1822 followed by the verb Request or Answer. Each English word is 1823 delimited by a hyphen. A three-letter acronym for both the request 1824 and answer is also normally provided. 1826 An example is a message set used to terminate a session. The command 1827 name is Session-Terminate-Request and Session-Terminate-Answer, while 1828 the acronyms are STR and STA, respectively. 1830 Both the request and the answer for a given command share the same 1831 command code. The request is identified by the R(equest) bit in the 1832 Diameter header set to one (1), to ask that a particular action be 1833 performed, such as authorizing a user or terminating a session. Once 1834 the receiver has completed the request it issues the corresponding 1835 answer, which includes a result code that communicates one of the 1836 following: 1838 o The request was successful 1840 o The request failed 1842 o An additional request must be sent to provide information the peer 1843 requires prior to returning a successful or failed answer. 1845 o The receiver could not process the request, but provides 1846 information about a Diameter peer that is able to satisfy the 1847 request, known as redirect. 1849 Additional information, encoded within AVPs, MAY also be included in 1850 answer messages. 1852 4. Diameter AVPs 1854 Diameter AVPs carry specific authentication, accounting, 1855 authorization, routing and security information as well as 1856 configuration details for the request and reply. 1858 Some AVPs MAY be listed more than once. The effect of such an AVP is 1859 specific, and is specified in each case by the AVP description. 1861 Each AVP of type OctetString MUST be padded to align on a 32-bit 1862 boundary, while other AVP types align naturally. A number of zero- 1863 valued bytes are added to the end of the AVP Data field till a word 1864 boundary is reached. The length of the padding is not reflected in 1865 the AVP Length field. 1867 4.1. AVP Header 1869 The fields in the AVP header MUST be sent in network byte order. The 1870 format of the header is: 1872 0 1 2 3 1873 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1874 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1875 | AVP Code | 1876 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1877 |V M P r r r r r| AVP Length | 1878 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1879 | Vendor-ID (opt) | 1880 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1881 | Data ... 1882 +-+-+-+-+-+-+-+-+ 1884 AVP Code 1886 The AVP Code, combined with the Vendor-Id field, identifies the 1887 attribute uniquely. AVP numbers 1 through 255 are reserved for 1888 backward compatibility with RADIUS, without setting the Vendor-Id 1889 field. AVP numbers 256 and above are used for Diameter, which are 1890 allocated by IANA (see Section 11.1). 1892 AVP Flags 1894 The AVP Flags field informs the receiver how each attribute must 1895 be handled. The 'r' (reserved) bits are unused and SHOULD be set 1896 to 0. Note that subsequent Diameter applications MAY define 1897 additional bits within the AVP Header, and an unrecognized bit 1898 SHOULD be considered an error. The 'P' bit indicates the need for 1899 encryption for end-to-end security. 1901 The 'M' Bit, known as the Mandatory bit, indicates whether support 1902 of the AVP is required. If an AVP with the 'M' bit set is 1903 received by a Diameter client, server, proxy, or translation agent 1904 and either the AVP or its value is unrecognized, the message MUST 1905 be rejected. Diameter Relay and redirect agents MUST NOT reject 1906 messages with unrecognized AVPs. 1908 The 'M' bit MUST be set according to the rules defined for the AVP 1909 containing it. In order to preserve interoperability, a Diameter 1910 implementation MUST be able to exclude from a Diameter message any 1911 Mandatory AVP which is neither defined in the base Diameter 1912 protocol nor in any of the Diameter Application specifications 1913 governing the message in which it appears. It MAY do this in one 1914 of the following ways: 1916 1. If a message is rejected because it contains a Mandatory AVP 1917 which is neither defined in the base Diameter standard nor in 1918 any of the Diameter Application specifications governing the 1919 message in which it appears, the implementation may resend the 1920 message without the AVP, possibly inserting additional 1921 standard AVPs instead. 1923 2. A configuration option may be provided on a system wide, per 1924 peer, or per realm basis that would allow/prevent particular 1925 Mandatory AVPs to be sent. Thus an administrator could change 1926 the configuration to avoid interoperability problems. 1928 Diameter implementations are required to support all Mandatory 1929 AVPs which are allowed by the message's formal syntax and defined 1930 either in the base Diameter standard or in one of the Diameter 1931 Application specifications governing the message. 1933 AVPs with the 'M' bit cleared are informational only and a 1934 receiver that receives a message with such an AVP that is not 1935 supported, or whose value is not supported, MAY simply ignore the 1936 AVP. 1938 The 'V' bit, known as the Vendor-Specific bit, indicates whether 1939 the optional Vendor-ID field is present in the AVP header. When 1940 set the AVP Code belongs to the specific vendor code address 1941 space. 1943 Unless otherwise noted, AVPs will have the following default AVP 1944 Flags field settings: 1946 The 'M' bit MUST be set. The 'V' bit MUST NOT be set. 1948 AVP Length 1950 The AVP Length field is three octets, and indicates the number of 1951 octets in this AVP including the AVP Code, AVP Length, AVP Flags, 1952 Vendor-ID field (if present) and the AVP data. If a message is 1953 received with an invalid attribute length, the message SHOULD be 1954 rejected. 1956 4.1.1. Optional Header Elements 1958 The AVP Header contains one optional field. This field is only 1959 present if the respective bit-flag is enabled. 1961 Vendor-ID 1963 The Vendor-ID field is present if the 'V' bit is set in the AVP 1964 Flags field. The optional four-octet Vendor-ID field contains the 1965 IANA assigned "SMI Network Management Private Enterprise Codes" 1966 [RFC3232] value, encoded in network byte order. Any vendor 1967 wishing to implement a vendor-specific Diameter AVP MUST use their 1968 own Vendor-ID along with their privately managed AVP address 1969 space, guaranteeing that they will not collide with any other 1970 vendor's vendor-specific AVP(s), nor with future IETF 1971 applications. 1973 A vendor ID value of zero (0) corresponds to the IETF adopted AVP 1974 values, as managed by the IANA. Since the absence of the vendor 1975 ID field implies that the AVP in question is not vendor specific, 1976 implementations MUST NOT use the zero (0) vendor ID. 1978 4.2. Basic AVP Data Formats 1980 The Data field is zero or more octets and contains information 1981 specific to the Attribute. The format and length of the Data field 1982 is determined by the AVP Code and AVP Length fields. The format of 1983 the Data field MUST be one of the following base data types or a data 1984 type derived from the base data types. In the event that a new Basic 1985 AVP Data Format is needed, a new version of this RFC must be created. 1987 OctetString 1989 The data contains arbitrary data of variable length. Unless 1990 otherwise noted, the AVP Length field MUST be set to at least 8 1991 (12 if the 'V' bit is enabled). AVP Values of this type that are 1992 not a multiple of four-octets in length is followed by the 1993 necessary padding so that the next AVP (if any) will start on a 1994 32-bit boundary. 1996 Integer32 1998 32 bit signed value, in network byte order. The AVP Length field 1999 MUST be set to 12 (16 if the 'V' bit is enabled). 2001 Integer64 2003 64 bit signed value, in network byte order. The AVP Length field 2004 MUST be set to 16 (20 if the 'V' bit is enabled). 2006 Unsigned32 2008 32 bit unsigned value, in network byte order. The AVP Length 2009 field MUST be set to 12 (16 if the 'V' bit is enabled). 2011 Unsigned64 2013 64 bit unsigned value, in network byte order. The AVP Length 2014 field MUST be set to 16 (20 if the 'V' bit is enabled). 2016 Float32 2018 This represents floating point values of single precision as 2019 described by [FLOATPOINT]. The 32-bit value is transmitted in 2020 network byte order. The AVP Length field MUST be set to 12 (16 if 2021 the 'V' bit is enabled). 2023 Float64 2025 This represents floating point values of double precision as 2026 described by [FLOATPOINT]. The 64-bit value is transmitted in 2027 network byte order. The AVP Length field MUST be set to 16 (20 if 2028 the 'V' bit is enabled). 2030 Grouped 2032 The Data field is specified as a sequence of AVPs. Each of these 2033 AVPs follows - in the order in which they are specified - 2034 including their headers and padding. The AVP Length field is set 2035 to 8 (12 if the 'V' bit is enabled) plus the total length of all 2036 included AVPs, including their headers and padding. Thus the AVP 2037 length field of an AVP of type Grouped is always a multiple of 4. 2039 4.3. Derived AVP Data Formats 2041 In addition to using the Basic AVP Data Formats, applications may 2042 define data formats derived from the Basic AVP Data Formats. An 2043 application that defines new AVP Derived Data Formats MUST include 2044 them in a section entitled "AVP Derived Data Formats", using the same 2045 format as the definitions below. Each new definition must be either 2046 defined or listed with a reference to the RFC that defines the 2047 format. 2049 The below AVP Derived Data Formats are commonly used by applications. 2051 Address 2053 The Address format is derived from the OctetString AVP Base 2054 Format. It is a discriminated union, representing, for example a 2055 32-bit (IPv4) [IPV4] or 128-bit (IPv6) [RFC2373] address, most 2056 significant octet first. The first two octets of the Address AVP 2057 represents the AddressType, which contains an Address Family 2058 defined in [IANAADFAM]. The AddressType is used to discriminate 2059 the content and format of the remaining octets. 2061 Time 2063 The Time format is derived from the OctetString AVP Base Format. 2064 The string MUST contain four octets, in the same format as the 2065 first four bytes are in the NTP timestamp format. The NTP 2066 Timestamp format is defined in chapter 3 of [RFC2030]. 2068 This represents the number of seconds since 0h on 1 January 1900 2069 with respect to the Coordinated Universal Time (UTC). 2071 On 6h 28m 16s UTC, 7 February 2036 the time value will overflow. 2072 SNTP [RFC2030] describes a procedure to extend the time to 2104. 2073 This procedure MUST be supported by all DIAMETER nodes. 2075 UTF8String 2077 The UTF8String format is derived from the OctetString AVP Base 2078 Format. This is a human readable string represented using the 2079 ISO/IEC IS 10646-1 character set, encoded as an OctetString using 2080 the UTF-8 [RFC2279] transformation format described in RFC 2279. 2082 Since additional code points are added by amendments to the 10646 2083 standard from time to time, implementations MUST be prepared to 2084 encounter any code point from 0x00000001 to 0x7fffffff. Byte 2085 sequences that do not correspond to the valid encoding of a code 2086 point into UTF-8 charset or are outside this range are prohibited. 2088 The use of control codes SHOULD be avoided. When it is necessary 2089 to represent a new line, the control code sequence CR LF SHOULD be 2090 used. 2092 The use of leading or trailing white space SHOULD be avoided. 2094 For code points not directly supported by user interface hardware 2095 or software, an alternative means of entry and display, such as 2096 hexadecimal, MAY be provided. 2098 For information encoded in 7-bit US-ASCII, the UTF-8 charset is 2099 identical to the US-ASCII charset. 2101 UTF-8 may require multiple bytes to represent a single character / 2102 code point; thus the length of an UTF8String in octets may be 2103 different from the number of characters encoded. 2105 Note that the AVP Length field of an UTF8String is measured in 2106 octets, not characters. 2108 DiameterIdentity 2110 The DiameterIdentity format is derived from the OctetString AVP 2111 Base Format. 2113 DiameterIdentity = FQDN 2115 DiameterIdentity value is used to uniquely identify a Diameter 2116 node for purposes of duplicate connection and routing loop 2117 detection. 2119 The contents of the string MUST be the FQDN of the Diameter node. 2121 If multiple Diameter nodes run on the same host, each Diameter 2122 node MUST be assigned a unique DiameterIdentity. If a Diameter 2123 node can be identified by several FQDNs, a single FQDN should be 2124 picked at startup, and used as the only DiameterIdentity for that 2125 node, whatever the connection it is sent on. 2127 DiameterURI 2129 The DiameterURI MUST follow the Uniform Resource Identifiers (URI) 2130 syntax [RFC2396] rules specified below: 2132 "aaa://" FQDN [ port ] [ transport ] [ protocol ] 2134 ; No transport security 2136 "aaas://" FQDN [ port ] [ transport ] [ protocol ] 2138 ; Transport security used 2140 FQDN = Fully Qualified Host Name 2142 port = ":" 1*DIGIT 2144 ; One of the ports used to listen for 2145 ; incoming connections. 2146 ; If absent, 2147 ; the default Diameter port (3868) is 2148 ; assumed. 2150 transport = ";transport=" transport-protocol 2152 ; One of the transports used to listen 2153 ; for incoming connections. If absent, 2154 ; the default SCTP [RFC2960] protocol is 2155 ; assumed. UDP MUST NOT be used when 2156 ; the aaa-protocol field is set to 2157 ; diameter. 2159 transport-protocol = ( "tcp" / "sctp" / "udp" ) 2161 protocol = ";protocol=" aaa-protocol 2163 ; If absent, the default AAA protocol 2164 ; is diameter. 2166 aaa-protocol = ( "diameter" / "radius" / "tacacs+" ) 2168 The following are examples of valid Diameter host identities: 2170 aaa://host.example.com;transport=tcp 2171 aaa://host.example.com:6666;transport=tcp 2172 aaa://host.example.com;protocol=diameter 2173 aaa://host.example.com:6666;protocol=diameter 2174 aaa://host.example.com:6666;transport=tcp;protocol=diameter 2175 aaa://host.example.com:1813;transport=udp;protocol=radius 2177 Enumerated 2179 Enumerated is derived from the Integer32 AVP Base Format. The 2180 definition contains a list of valid values and their 2181 interpretation and is described in the Diameter application 2182 introducing the AVP. 2184 IPFilterRule 2186 The IPFilterRule format is derived from the OctetString AVP Base 2187 Format. It uses the ASCII charset. Packets may be filtered based 2188 on the following information that is associated with it: 2190 Direction (in or out) 2191 Source and destination IP address (possibly masked) 2192 Protocol 2193 Source and destination port (lists or ranges) 2194 TCP flags 2195 IP fragment flag 2196 IP options 2197 ICMP types 2199 Rules for the appropriate direction are evaluated in order, with 2200 the first matched rule terminating the evaluation. Each packet is 2201 evaluated once. If no rule matches, the packet is dropped if the 2202 last rule evaluated was a permit, and passed if the last rule was 2203 a deny. 2205 IPFilterRule filters MUST follow the format: 2207 action dir proto from src to dst [options] 2209 action permit - Allow packets that match the rule. 2210 deny - Drop packets that match the rule. 2212 dir "in" is from the terminal, "out" is to the 2213 terminal. 2215 proto An IP protocol specified by number. The "ip" 2216 keyword means any protocol will match. 2218 src and dst
[ports] 2220 The
may be specified as: 2222 ipno An IPv4 or IPv6 number in dotted- 2223 quad or canonical IPv6 form. Only 2224 this exact IP number will match the 2225 rule. 2226 ipno/bits An IP number as above with a mask 2227 width of the form 1.2.3.4/24. In 2228 this case, all IP numbers from 2229 1.2.3.0 to 1.2.3.255 will match. 2230 The bit width MUST be valid for the 2231 IP version and the IP number MUST 2232 NOT have bits set beyond the mask. 2233 For a match to occur, the same IP 2234 version must be present in the 2235 packet that was used in describing 2236 the IP address. To test for a 2237 particular IP version, the bits part 2238 can be set to zero. The keyword 2239 "any" is 0.0.0.0/0 or the IPv6 2240 equivalent. The keyword "assigned" 2241 is the address or set of addresses 2242 assigned to the terminal. For IPv4, 2243 a typical first rule is often "deny 2244 in ip! assigned" 2246 The sense of the match can be inverted by 2247 preceding an address with the not modifier (!), 2248 causing all other addresses to be matched 2249 instead. This does not affect the selection of 2250 port numbers. 2252 With the TCP, UDP and SCTP protocols, optional 2253 ports may be specified as: 2255 {port/port-port}[,ports[,...]] 2257 The '-' notation specifies a range of ports 2258 (including boundaries). 2260 Fragmented packets that have a non-zero offset 2261 (i.e., not the first fragment) will never match 2262 a rule that has one or more port 2263 specifications. See the frag option for 2264 details on matching fragmented packets. 2266 options: 2267 frag Match if the packet is a fragment and this is not 2268 the first fragment of the datagram. frag may not 2269 be used in conjunction with either tcpflags or 2270 TCP/UDP port specifications. 2272 ipoptions spec 2273 Match if the IP header contains the comma 2274 separated list of options specified in spec. The 2275 supported IP options are: 2277 ssrr (strict source route), lsrr (loose source 2278 route), rr (record packet route) and ts 2279 (timestamp). The absence of a particular option 2280 may be denoted with a '!'. 2282 tcpoptions spec 2283 Match if the TCP header contains the comma 2284 separated list of options specified in spec. The 2285 supported TCP options are: 2287 mss (maximum segment size), window (tcp window 2288 advertisement), sack (selective ack), ts (rfc1323 2289 timestamp) and cc (rfc1644 t/tcp connection 2290 count). The absence of a particular option may 2291 be denoted with a '!'. 2293 established 2294 TCP packets only. Match packets that have the RST 2295 or ACK bits set. 2297 setup TCP packets only. Match packets that have the SYN 2298 bit set but no ACK bit. 2300 tcpflags spec 2301 TCP packets only. Match if the TCP header 2302 contains the comma separated list of flags 2303 specified in spec. The supported TCP flags are: 2305 fin, syn, rst, psh, ack and urg. The absence of a 2306 particular flag may be denoted with a '!'. A rule 2307 that contains a tcpflags specification can never 2308 match a fragmented packet that has a non-zero 2309 offset. See the frag option for details on 2310 matching fragmented packets. 2312 icmptypes types 2313 ICMP packets only. Match if the ICMP type is in 2314 the list types. The list may be specified as any 2315 combination of ranges or individual types 2316 separated by commas. Both the numeric values and 2317 the symbolic values listed below can be used. The 2318 supported ICMP types are: 2320 echo reply (0), destination unreachable (3), 2321 source quench (4), redirect (5), echo request 2322 (8), router advertisement (9), router 2323 solicitation (10), time-to-live exceeded (11), IP 2324 header bad (12), timestamp request (13), 2325 timestamp reply (14), information request (15), 2326 information reply (16), address mask request (17) 2327 and address mask reply (18). 2329 There is one kind of packet that the access device MUST always 2330 discard, that is an IP fragment with a fragment offset of one. 2331 This is a valid packet, but it only has one use, to try to 2332 circumvent firewalls. 2334 An access device that is unable to interpret or apply a deny rule 2335 MUST terminate the session. An access device that is unable to 2336 interpret or apply a permit rule MAY apply a more restrictive 2337 rule. An access device MAY apply deny rules of its own before the 2338 supplied rules, for example to protect the access device owner's 2339 infrastructure. 2341 The rule syntax is a modified subset of ipfw(8) from FreeBSD, and 2342 the ipfw.c code may provide a useful base for implementations. 2344 QoSFilterRule 2346 The QosFilterRule format is derived from the OctetString AVP Base 2347 Format. It uses the ASCII charset. Packets may be marked or 2348 metered based on the following information that is associated with 2349 it: 2351 Direction (in or out) 2352 Source and destination IP address (possibly masked) 2353 Protocol 2354 Source and destination port (lists or ranges) 2355 DSCP values (no mask or range) 2357 Rules for the appropriate direction are evaluated in order, with 2358 the first matched rule terminating the evaluation. Each packet is 2359 evaluated once. If no rule matches, the packet is treated as best 2360 effort. An access device that is unable to interpret or apply a 2361 QoS rule SHOULD NOT terminate the session. 2363 QoSFilterRule filters MUST follow the format: 2365 action dir proto from src to dst [options] 2367 tag - Mark packet with a specific DSCP 2368 [DIFFSERV]. The DSCP option MUST be 2369 included. 2370 meter - Meter traffic. The metering options 2371 MUST be included. 2373 dir The format is as described under IPFilterRule. 2375 proto The format is as described under 2376 IPFilterRule. 2378 src and dst The format is as described under 2379 IPFilterRule. 2381 4.4. Grouped AVP Values 2383 The Diameter protocol allows AVP values of type 'Grouped.' This 2384 implies that the Data field is actually a sequence of AVPs. It is 2385 possible to include an AVP with a Grouped type within a Grouped type, 2386 that is, to nest them. AVPs within an AVP of type Grouped have the 2387 same padding requirements as non-Grouped AVPs, as defined in Section 2388 4. 2390 The AVP Code numbering space of all AVPs included in a Grouped AVP is 2391 the same as for non-grouped AVPs. Further, if any of the AVPs 2392 encapsulated within a Grouped AVP has the 'M' (mandatory) bit set, 2393 the Grouped AVP itself MUST also include the 'M' bit set. 2395 Every Grouped AVP defined MUST include a corresponding grammar, using 2396 ABNF [RFC2234] (with modifications), as defined below. 2398 grouped-avp-def = name "::=" avp 2400 name-fmt = ALPHA *(ALPHA / DIGIT / "-") 2402 name = name-fmt 2403 ; The name has to be the name of an AVP, 2404 ; defined in the base or extended Diameter 2405 ; specifications. 2407 avp = header [ *fixed] [ *required] [ *optional] 2408 [ *fixed] 2410 header = "<" "AVP-Header:" avpcode [vendor] ">" 2412 avpcode = 1*DIGIT 2413 ; The AVP Code assigned to the Grouped AVP 2415 vendor = 1*DIGIT 2416 ; The Vendor-ID assigned to the Grouped AVP. 2417 ; If absent, the default value of zero is 2418 ; used. 2420 4.4.1. Example AVP with a Grouped Data type 2422 The Example-AVP (AVP Code 999999) is of type Grouped and is used to 2423 clarify how Grouped AVP values work. The Grouped Data field has the 2424 following ABNF grammar: 2426 Example-AVP ::= < AVP Header: 999999 > 2427 { Origin-Host } 2428 1*{ Session-Id } 2429 *[ AVP ] 2431 An Example-AVP with Grouped Data follows. 2433 The Origin-Host AVP is required (Section 6.3). In this case: 2435 Origin-Host = "example.com". 2437 One or more Session-Ids must follow. Here there are two: 2439 Session-Id = 2440 "grump.example.com:33041;23432;893;0AF3B81" 2442 Session-Id = 2443 "grump.example.com:33054;23561;2358;0AF3B82" 2445 optional AVPs included are 2447 Recovery-Policy = 2448 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35 2449 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5 2450 c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd 2451 f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a 2452 cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119 2453 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c 2454 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92 2456 Futuristic-Acct-Record = 2457 fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0 2458 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8 2459 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c 2460 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067 2461 d3427475e49968f841 2463 The data for the optional AVPs is represented in hex since the format 2464 of these AVPs is neither known at the time of definition of the 2465 Example-AVP group, nor (likely) at the time when the example instance 2466 of this AVP is interpreted - except by Diameter implementations which 2467 support the same set of AVPs. The encoding example illustrates how 2468 padding is used and how length fields are calculated. Also note that 2469 AVPs may be present in the Grouped AVP value which the receiver 2470 cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record 2471 AVPs). 2473 This AVP would be encoded as follows: 2475 0 1 2 3 4 5 6 7 2476 +-------+-------+-------+-------+-------+-------+-------+-------+ 2477 0 | Example AVP Header (AVP Code = 999999), Length = 468 | 2478 +-------+-------+-------+-------+-------+-------+-------+-------+ 2479 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 | 2480 +-------+-------+-------+-------+-------+-------+-------+-------+ 2481 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' | 2482 +-------+-------+-------+-------+-------+-------+-------+-------+ 2483 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header | 2484 +-------+-------+-------+-------+-------+-------+-------+-------+ 2485 32 | (AVP Code = 263), Length = 50 | 'g' | 'r' | 'u' | 'm' | 2486 +-------+-------+-------+-------+-------+-------+-------+-------+ 2487 . . . 2488 +-------+-------+-------+-------+-------+-------+-------+-------+ 2489 64 | 'A' | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding| 2490 +-------+-------+-------+-------+-------+-------+-------+-------+ 2491 72 | Session-Id AVP Header (AVP Code = 263), Length = 51 | 2492 +-------+-------+-------+-------+-------+-------+-------+-------+ 2493 80 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' | 2494 +-------+-------+-------+-------+-------+-------+-------+-------+ 2495 . . . 2496 +-------+-------+-------+-------+-------+-------+-------+-------+ 2497 104| '0' | 'A' | 'F' | '3' | 'B' | '8' | '2' |Padding| 2498 +-------+-------+-------+-------+-------+-------+-------+-------+ 2499 112| Recovery-Policy Header (AVP Code = 8341), Length = 223 | 2500 +-------+-------+-------+-------+-------+-------+-------+-------+ 2501 120| 0x21 | 0x63 | 0xbc | 0x1d | 0x0a | 0xd8 | 0x23 | 0x71 | 2502 +-------+-------+-------+-------+-------+-------+-------+-------+ 2503 . . . 2504 +-------+-------+-------+-------+-------+-------+-------+-------+ 2505 320| 0x2f | 0xd7 | 0x96 | 0x6b | 0x8c | 0x7f | 0x92 |Padding| 2506 +-------+-------+-------+-------+-------+-------+-------+-------+ 2507 328| Futuristic-Acct-Record Header (AVP Code = 15930), Length = 137| 2508 +-------+-------+-------+-------+-------+-------+-------+-------+ 2509 336| 0xfe | 0x19 | 0xda | 0x58 | 0x02 | 0xac | 0xd9 | 0x8b | 2510 +-------+-------+-------+-------+-------+-------+-------+-------+ 2511 . . . 2512 +-------+-------+-------+-------+-------+-------+-------+-------+ 2513 464| 0x41 |Padding|Padding|Padding| 2514 +-------+-------+-------+-------+ 2516 4.5. Diameter Base Protocol AVPs 2518 The following table describes the Diameter AVPs defined in the base 2519 protocol, their AVP Code values, types, possible flag values and 2520 whether the AVP MAY be encrypted. For the originator of a Diameter 2521 message, "Encr" (Encryption) means that if a message containing that 2522 AVP is to be sent via a Diameter agent (proxy, redirect or relay) 2523 then the message MUST NOT be sent unless there is end-to-end security 2524 between the originator and the recipient and integrity / 2525 confidentiality protection is offered for this AVP OR the originator 2526 has locally trusted configuration that indicates that end-to-end 2527 security is not needed. Similarly, for the originator of a Diameter 2528 message, a "P" in the "MAY" column means that if a message containing 2529 that AVP is to be sent via a Diameter agent (proxy, redirect or 2530 relay) then the message MUST NOT be sent unless there is end-to-end 2531 security between the originator and the recipient or the originator 2532 has locally trusted configuration that indicates that end-to-end 2533 security is not needed. 2535 Due to space constraints, the short form DiamIdent is used to 2536 represent DiameterIdentity. 2538 +---------------------+ 2539 | AVP Flag rules | 2540 |----+-----+----+-----|----+ 2541 AVP Section | | |SHLD| MUST| | 2542 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr| 2543 -----------------------------------------|----+-----+----+-----|----| 2544 Acct- 85 9.8.2 Unsigned32 | M | P | | V | Y | 2545 Interim-Interval | | | | | | 2546 Accounting- 483 9.8.7 Enumerated | M | P | | V | Y | 2547 Realtime-Required | | | | | | 2548 Acct- 50 9.8.5 UTF8String | M | P | | V | Y | 2549 Multi-Session-Id | | | | | | 2550 Accounting- 485 9.8.3 Unsigned32 | M | P | | V | Y | 2551 Record-Number | | | | | | 2552 Accounting- 480 9.8.1 Enumerated | M | P | | V | Y | 2553 Record-Type | | | | | | 2554 Accounting- 44 9.8.4 OctetString| M | P | | V | Y | 2555 Session-Id | | | | | | 2556 Accounting- 287 9.8.6 Unsigned64 | M | P | | V | Y | 2557 Sub-Session-Id | | | | | | 2558 Acct- 259 6.9 Unsigned32 | M | P | | V | N | 2559 Application-Id | | | | | | 2560 Auth- 258 6.8 Unsigned32 | M | P | | V | N | 2561 Application-Id | | | | | | 2562 Auth-Request- 274 8.7 Enumerated | M | P | | V | N | 2563 Type | | | | | | 2564 Authorization- 291 8.9 Unsigned32 | M | P | | V | N | 2565 Lifetime | | | | | | 2566 Auth-Grace- 276 8.10 Unsigned32 | M | P | | V | N | 2567 Period | | | | | | 2568 Auth-Session- 277 8.11 Enumerated | M | P | | V | N | 2569 State | | | | | | 2570 Re-Auth-Request- 285 8.12 Enumerated | M | P | | V | N | 2571 Type | | | | | | 2572 Class 25 8.20 OctetString| M | P | | V | Y | 2573 Destination-Host 293 6.5 DiamIdent | M | P | | V | N | 2574 Destination- 283 6.6 DiamIdent | M | P | | V | N | 2575 Realm | | | | | | 2576 Disconnect-Cause 273 5.4.3 Enumerated | M | P | | V | N | 2577 E2E-Sequence AVP 300 6.15 Grouped | M | P | | V | Y | 2578 Error-Message 281 7.3 UTF8String | | P | | V,M | N | 2579 Error-Reporting- 294 7.4 DiamIdent | | P | | V,M | N | 2580 Host | | | | | | 2581 Event-Timestamp 55 8.21 Time | M | P | | V | N | 2582 Experimental- 297 7.6 Grouped | M | P | | V | N | 2583 Result | | | | | | 2584 -----------------------------------------|----+-----+----+-----|----| 2585 +---------------------+ 2586 | AVP Flag rules | 2587 |----+-----+----+-----|----+ 2588 AVP Section | | |SHLD| MUST|MAY | 2589 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr| 2590 -----------------------------------------|----+-----+----+-----|----| 2591 Experimental- 298 7.7 Unsigned32 | M | P | | V | N | 2592 Result-Code | | | | | | 2593 Failed-AVP 279 7.5 Grouped | M | P | | V | N | 2594 Firmware- 267 5.3.4 Unsigned32 | | | |P,V,M| N | 2595 Revision | | | | | | 2596 Host-IP-Address 257 5.3.5 Address | M | P | | V | N | 2597 Inband-Security | M | P | | V | N | 2598 -Id 299 6.10 Unsigned32 | | | | | | 2599 Multi-Round- 272 8.19 Unsigned32 | M | P | | V | Y | 2600 Time-Out | | | | | | 2601 Origin-Host 264 6.3 DiamIdent | M | P | | V | N | 2602 Origin-Realm 296 6.4 DiamIdent | M | P | | V | N | 2603 Origin-State-Id 278 8.16 Unsigned32 | M | P | | V | N | 2604 Product-Name 269 5.3.7 UTF8String | | | |P,V,M| N | 2605 Proxy-Host 280 6.7.3 DiamIdent | M | | | P,V | N | 2606 Proxy-Info 284 6.7.2 Grouped | M | | | P,V | N | 2607 Proxy-State 33 6.7.4 OctetString| M | | | P,V | N | 2608 Redirect-Host 292 6.12 DiamURI | M | P | | V | N | 2609 Redirect-Host- 261 6.13 Enumerated | M | P | | V | N | 2610 Usage | | | | | | 2611 Redirect-Max- 262 6.14 Unsigned32 | M | P | | V | N | 2612 Cache-Time | | | | | | 2613 Result-Code 268 7.1 Unsigned32 | M | P | | V | N | 2614 Route-Record 282 6.7.1 DiamIdent | M | | | P,V | N | 2615 Session-Id 263 8.8 UTF8String | M | P | | V | Y | 2616 Session-Timeout 27 8.13 Unsigned32 | M | P | | V | N | 2617 Session-Binding 270 8.17 Unsigned32 | M | P | | V | Y | 2618 Session-Server- 271 8.18 Enumerated | M | P | | V | Y | 2619 Failover | | | | | | 2620 Supported- 265 5.3.6 Unsigned32 | M | P | | V | N | 2621 Vendor-Id | | | | | | 2622 Termination- 295 8.15 Enumerated | M | P | | V | N | 2623 Cause | | | | | | 2624 User-Name 1 8.14 UTF8String | M | P | | V | Y | 2625 Vendor-Id 266 5.3.3 Unsigned32 | M | P | | V | N | 2626 Vendor-Specific- 260 6.11 Grouped | M | P | | V | N | 2627 Application-Id | | | | | | 2628 -----------------------------------------|----+-----+----+-----|----| 2630 5. Diameter Peers 2632 This section describes how Diameter nodes establish connections and 2633 communicate with peers. 2635 5.1. Peer Connections 2637 Although a Diameter node may have many possible peers that it is able 2638 to communicate with, it may not be economical to have an established 2639 connection to all of them. At a minimum, a Diameter node SHOULD have 2640 an established connection with two peers per realm, known as the 2641 primary and secondary peers. Of course, a node MAY have additional 2642 connections, if it is deemed necessary. Typically, all messages for 2643 a realm are sent to the primary peer, but in the event that failover 2644 procedures are invoked, any pending requests are sent to the 2645 secondary peer. However, implementations are free to load balance 2646 requests between a set of peers. 2648 Note that a given peer MAY act as a primary for a given realm, while 2649 acting as a secondary for another realm. 2651 When a peer is deemed suspect, which could occur for various reasons, 2652 including not receiving a DWA within an allotted timeframe, no new 2653 requests should be forwarded to the peer, but failover procedures are 2654 invoked. When an active peer is moved to this mode, additional 2655 connections SHOULD be established to ensure that the necessary number 2656 of active connections exists. 2658 There are two ways that a peer is removed from the suspect peer list: 2660 1. The peer is no longer reachable, causing the transport connection 2661 to be shutdown. The peer is moved to the closed state. 2663 2. Three watchdog messages are exchanged with accepted round trip 2664 times, and the connection to the peer is considered stabilized. 2666 In the event the peer being removed is either the primary or 2667 secondary, an alternate peer SHOULD replace the deleted peer, and 2668 assume the role of either primary or secondary. 2670 5.2. Diameter Peer Discovery 2672 Allowing for dynamic Diameter agent discovery will make it possible 2673 for simpler and more robust deployment of Diameter services. In 2674 order to promote interoperable implementations of Diameter peer 2675 discovery, the following mechanisms are described. These are based 2676 on existing IETF standards. The first option (manual configuration) 2677 MUST be supported by all DIAMETER nodes, while the latter two options 2678 (SRVLOC and DNS) MAY be supported. 2680 There are two cases where Diameter peer discovery may be performed. 2681 The first is when a Diameter client needs to discover a first-hop 2682 Diameter agent. The second case is when a Diameter agent needs to 2683 discover another agent - for further handling of a Diameter 2684 operation. In both cases, the following 'search order' is 2685 recommended: 2687 1. The Diameter implementation consults its list of static 2688 (manually) configured Diameter agent locations. These will be 2689 used if they exist and respond. 2691 2. The Diameter implementation uses SLPv2 [RFC2165] to discover 2692 Diameter services. The Diameter service template [RFC2609] is 2693 included in Appendix B. 2695 It is recommended that SLPv2 security be deployed (this requires 2696 distributing keys to SLPv2 agents). This is discussed further in 2697 Appendix B. SLPv2 security SHOULD be used (requiring 2698 distribution of keys to SLPv2 agents) in order to ensure that 2699 discovered peers are authorized for their roles. SLPv2 is 2700 discussed further in Appendix B. 2702 3. The Diameter implementation performs a NAPTR query for a server 2703 in a particular realm. The Diameter implementation has to know 2704 in advance which realm to look for a Diameter agent in. This 2705 could be deduced, for example, from the 'realm' in a NAI that a 2706 Diameter implementation needed to perform a Diameter operation 2707 on. 2709 * The services relevant for the task of transport protocol 2710 selection are those with NAPTR service fields with values 2711 "AAA+D2x", where x is a letter that corresponds to a transport 2712 protocol supported by the domain. This specification defines 2713 D2T for TCP and D2S for SCTP. We also establish an IANA 2714 registry for NAPTR service name to transport protocol 2715 mappings. 2717 These NAPTR records provide a mapping from a domain, to the 2718 SRV record for contacting a server with the specific transport 2719 protocol in the NAPTR services field. The resource record 2720 will contain an empty regular expression and a replacement 2721 value, which is the SRV record for that particular transport 2722 protocol. If the server supports multiple transport 2723 protocols, there will be multiple NAPTR records, each with a 2724 different service value. As per RFC 2915 [RFC2915], the 2725 client discards any records whose services fields are not 2726 applicable. For the purposes of this specification, several 2727 rules are defined. 2729 * A client MUST discard any service fields that identify a 2730 resolution service whose value is not "D2X", for values of X 2731 that indicate transport protocols supported by the client. 2732 The NAPTR processing as described in RFC 2915 will result in 2733 discovery of the most preferred transport protocol of the 2734 server that is supported by the client, as well as an SRV 2735 record for the server. 2737 The domain suffixes in the NAPTR replacement field SHOULD 2738 match the domain of the original query. 2740 4. If no NAPTR records are found, the requester queries for those 2741 address records for the destination address, 2742 '_diameter._sctp'.realm or '_diameter._tcp'.realm. Address 2743 records include A RR's, AAAA RR's or other similar records, 2744 chosen according to the requestor's network protocol 2745 capabilities. If the DNS server returns no address records, the 2746 requestor gives up. 2748 If the server is using a site certificate, the domain name in the 2749 query and the domain name in the replacement field MUST both be 2750 valid based on the site certificate handed out by the server in 2751 the TLS or IKE exchange. Similarly, the domain name in the SRV 2752 query and the domain name in the target in the SRV record MUST 2753 both be valid based on the same site certificate. Otherwise, an 2754 attacker could modify the DNS records to contain replacement 2755 values in a different domain, and the client could not validate 2756 that this was the desired behavior, or the result of an attack 2758 Also, the Diameter Peer MUST check to make sure that the 2759 discovered peers are authorized to act in its role. 2760 Authentication via IKE or TLS, or validation of DNS RRs via 2761 DNSSEC is not sufficient to conclude this. For example, a web 2762 server may have obtained a valid TLS certificate, and secured RRs 2763 may be included in the DNS, but this does not imply that it is 2764 authorized to act as a Diameter Server. 2766 Authorization can be achieved for example, by configuration of a 2767 Diameter Server CA. Alternatively this can be achieved by 2768 definition of OIDs within TLS or IKE certificates so as to 2769 signify Diameter Server authorization. 2771 A dynamically discovered peer causes an entry in the Peer Table (see 2772 Section 2.6) to be created. Note that entries created via DNS MUST 2773 expire (or be refreshed) within the DNS TTL. If a peer is discovered 2774 outside of the local realm, a routing table entry (see Section 2.7) 2775 for the peer's realm is created. The routing table entry's 2776 expiration MUST match the peer's expiration value. 2778 5.3. Capabilities Exchange 2780 When two Diameter peers establish a transport connection, they MUST 2781 exchange the Capabilities Exchange messages, as specified in the peer 2782 state machine (see Section 5.6). This message allows the discovery 2783 of a peer's identity and its capabilities (protocol version number, 2784 supported Diameter applications, security mechanisms, etc.) 2786 The receiver only issues commands to its peers that have advertised 2787 support for the Diameter application that defines the command. A 2788 Diameter node MUST cache the supported applications in order to 2789 ensure that unrecognized commands and/or AVPs are not unnecessarily 2790 sent to a peer. 2792 A receiver of a Capabilities-Exchange-Req (CER) message that does not 2793 have any applications in common with the sender MUST return a 2794 Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to 2795 DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport 2796 layer connection. Note that receiving a CER or CEA from a peer 2797 advertising itself as a Relay (see Section 2.4) MUST be interpreted 2798 as having common applications with the peer. 2800 Similarly, a receiver of a Capabilities-Exchange-Req (CER) message 2801 that does not have any security mechanisms in common with the sender 2802 MUST return a Capabilities-Exchange-Answer (CEA) with the Result-Code 2803 AVP set to DIAMETER_NO_COMMON_SECURITY, and SHOULD disconnect the 2804 transport layer connection. 2806 CERs received from unknown peers MAY be silently discarded, or a CEA 2807 MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER. 2808 In both cases, the transport connection is closed. If the local 2809 policy permits receiving CERs from unknown hosts, a successful CEA 2810 MAY be returned. If a CER from an unknown peer is answered with a 2811 successful CEA, the lifetime of the peer entry is equal to the 2812 lifetime of the transport connection. In case of a transport 2813 failure, all the pending transactions destined to the unknown peer 2814 can be discarded. 2816 The CER and CEA messages MUST NOT be proxied, redirected or relayed. 2818 Since the CER/CEA messages cannot be proxied, it is still possible 2819 that an upstream agent receives a message for which it has no 2820 available peers to handle the application that corresponds to the 2821 Command-Code. In such instances, the 'E' bit is set in the answer 2822 message (see Section 7.) with the Result-Code AVP set to 2823 DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action 2824 (e.g., re-routing request to an alternate peer). 2826 With the exception of the Capabilities-Exchange-Request message, a 2827 message of type Request that includes the Auth-Application-Id or 2828 Acct-Application-Id AVPs, or a message with an application-specific 2829 command code, MAY only be forwarded to a host that has explicitly 2830 advertised support for the application (or has advertised the Relay 2831 Application Identifier). 2833 5.3.1. Capabilities-Exchange-Request 2835 The Capabilities-Exchange-Request (CER), indicated by the Command- 2836 Code set to 257 and the Command Flags' 'R' bit set, is sent to 2837 exchange local capabilities. Upon detection of a transport failure, 2838 this message MUST NOT be sent to an alternate peer. 2840 When Diameter is run over SCTP [RFC2960], which allows for 2841 connections to span multiple interfaces and multiple IP addresses, 2842 the Capabilities-Exchange-Request message MUST contain one Host-IP- 2843 Address AVP for each potential IP address that MAY be locally used 2844 when transmitting Diameter messages. 2846 Message Format 2848 ::= < Diameter Header: 257, REQ > 2849 { Origin-Host } 2850 { Origin-Realm } 2851 1* { Host-IP-Address } 2852 { Vendor-Id } 2853 { Product-Name } 2854 [ Origin-State-Id ] 2855 * [ Supported-Vendor-Id ] 2856 * [ Auth-Application-Id ] 2857 * [ Inband-Security-Id ] 2858 * [ Acct-Application-Id ] 2859 * [ Vendor-Specific-Application-Id ] 2860 [ Firmware-Revision ] 2861 * [ AVP ] 2863 5.3.2. Capabilities-Exchange-Answer 2865 The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code 2866 set to 257 and the Command Flags' 'R' bit cleared, is sent in 2867 response to a CER message. 2869 When Diameter is run over SCTP [RFC2960], which allows connections to 2870 span multiple interfaces, hence, multiple IP addresses, the 2871 Capabilities-Exchange-Answer message MUST contain one Host-IP-Address 2872 AVP for each potential IP address that MAY be locally used when 2873 transmitting Diameter messages. 2875 Message Format 2877 ::= < Diameter Header: 257 > 2878 { Result-Code } 2879 { Origin-Host } 2880 { Origin-Realm } 2881 1* { Host-IP-Address } 2882 { Vendor-Id } 2883 { Product-Name } 2884 [ Origin-State-Id ] 2885 [ Error-Message ] 2886 * [ Failed-AVP ] 2887 * [ Supported-Vendor-Id ] 2888 * [ Auth-Application-Id ] 2889 * [ Inband-Security-Id ] 2890 * [ Acct-Application-Id ] 2891 * [ Vendor-Specific-Application-Id ] 2892 [ Firmware-Revision ] 2893 * [ AVP ] 2895 5.3.3. Vendor-Id AVP 2897 The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains 2898 the IANA "SMI Network Management Private Enterprise Codes" [RFC3232] 2899 value assigned to the vendor of the Diameter application. In 2900 combination with the Supported-Vendor-Id AVP (Section 5.3.6), this 2901 MAY be used in order to know which vendor specific attributes may be 2902 sent to the peer. It is also envisioned that the combination of the 2903 Vendor-Id, Product-Name (Section 5.3.7) and the Firmware-Revision 2904 (Section 5.3.4) AVPs MAY provide very useful debugging information. 2906 A Vendor-Id value of zero in the CER or CEA messages is reserved and 2907 indicates that this field is ignored. 2909 5.3.4. Firmware-Revision AVP 2911 The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is 2912 used to inform a Diameter peer of the firmware revision of the 2913 issuing device. 2915 For devices that do not have a firmware revision (general purpose 2916 computers running Diameter software modules, for instance), the 2917 revision of the Diameter software module may be reported instead. 2919 5.3.5. Host-IP-Address AVP 2921 The Host-IP-Address AVP (AVP Code 257) is of type Address and is used 2922 to inform a Diameter peer of the sender's IP address. All source 2923 addresses that a Diameter node expects to use with SCTP [RFC2960] 2924 MUST be advertised in the CER and CEA messages by including a 2925 Host-IP- Address AVP for each address. This AVP MUST ONLY be used in 2926 the CER and CEA messages. 2928 5.3.6. Supported-Vendor-Id AVP 2930 The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and 2931 contains the IANA "SMI Network Management Private Enterprise Codes" 2932 [RFC3232] value assigned to a vendor other than the device vendor. 2933 This is used in the CER and CEA messages in order to inform the peer 2934 that the sender supports (a subset of) the vendor-specific AVPs 2935 defined by the vendor identified in this AVP. 2937 5.3.7. Product-Name AVP 2939 The Product-Name AVP (AVP Code 269) is of type UTF8String, and 2940 contains the vendor assigned name for the product. The Product-Name 2941 AVP SHOULD remain constant across firmware revisions for the same 2942 product. 2944 5.4. Disconnecting Peer connections 2946 When a Diameter node disconnects one of its transport connections, 2947 its peer cannot know the reason for the disconnect, and will most 2948 likely assume that a connectivity problem occurred, or that the peer 2949 has rebooted. In these cases, the peer may periodically attempt to 2950 reconnect, as stated in Section 2.1. In the event that the 2951 disconnect was a result of either a shortage of internal resources, 2952 or simply that the node in question has no intentions of forwarding 2953 any Diameter messages to the peer in the foreseeable future, a 2954 periodic connection request would not be welcomed. The 2955 Disconnection-Reason AVP contains the reason the Diameter node issued 2956 the Disconnect-Peer-Request message. 2958 The Disconnect-Peer-Request message is used by a Diameter node to 2959 inform its peer of its intent to disconnect the transport layer, and 2960 that the peer shouldn't reconnect unless it has a valid reason to do 2961 so (e.g., message to be forwarded). Upon receipt of the message, the 2962 Disconnect-Peer-Answer is returned, which SHOULD contain an error if 2963 messages have recently been forwarded, and are likely in flight, 2964 which would otherwise cause a race condition. 2966 The receiver of the Disconnect-Peer-Answer initiates the transport 2967 disconnect. 2969 5.4.1. Disconnect-Peer-Request 2971 The Disconnect-Peer-Request (DPR), indicated by the Command-Code set 2972 to 282 and the Command Flags' 'R' bit set, is sent to a peer to 2973 inform its intentions to shutdown the transport connection. Upon 2974 detection of a transport failure, this message MUST NOT be sent to an 2975 alternate peer. 2977 Message Format 2979 ::= < Diameter Header: 282, REQ > 2980 { Origin-Host } 2981 { Origin-Realm } 2982 { Disconnect-Cause } 2984 5.4.2. Disconnect-Peer-Answer 2986 The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set 2987 to 282 and the Command Flags' 'R' bit cleared, is sent as a response 2988 to the Disconnect-Peer-Request message. Upon receipt of this 2989 message, the transport connection is shutdown. 2991 Message Format 2993 ::= < Diameter Header: 282 > 2994 { Result-Code } 2995 { Origin-Host } 2996 { Origin-Realm } 2997 [ Error-Message ] 2998 * [ Failed-AVP ] 3000 5.4.3. Disconnect-Cause AVP 3002 The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A 3003 Diameter node MUST include this AVP in the Disconnect-Peer-Request 3004 message to inform the peer of the reason for its intention to 3005 shutdown the transport connection. The following values are 3006 supported: 3008 REBOOTING 0 3009 A scheduled reboot is imminent. Receiver of DPR with above result 3010 code MAY attempt reconnection. 3012 BUSY 1 3013 The peer's internal resources are constrained, and it has 3014 determined that the transport connection needs to be closed. 3015 Receiver of DPR with above result code SHOULD NOT attempt 3016 reconnection. 3018 DO_NOT_WANT_TO_TALK_TO_YOU 2 3019 The peer has determined that it does not see a need for the 3020 transport connection to exist, since it does not expect any 3021 messages to be exchanged in the near future. Receiver of DPR 3022 with above result code SHOULD NOT attempt reconnection. 3024 5.5. Transport Failure Detection 3026 Given the nature of the Diameter protocol, it is recommended that 3027 transport failures be detected as soon as possible. Detecting such 3028 failures will minimize the occurrence of messages sent to unavailable 3029 agents, resulting in unnecessary delays, and will provide better 3030 failover performance. The Device-Watchdog-Request and Device- 3031 Watchdog-Answer messages, defined in this section, are used to pro- 3032 actively detect transport failures. 3034 5.5.1. Device-Watchdog-Request 3036 The Device-Watchdog-Request (DWR), indicated by the Command-Code set 3037 to 280 and the Command Flags' 'R' bit set, is sent to a peer when no 3038 traffic has been exchanged between two peers (see Section 5.5.3). 3039 Upon detection of a transport failure, this message MUST NOT be sent 3040 to an alternate peer. 3042 Message Format 3044 ::= < Diameter Header: 280, REQ > 3045 { Origin-Host } 3046 { Origin-Realm } 3047 [ Origin-State-Id ] 3049 5.5.2. Device-Watchdog-Answer 3051 The Device-Watchdog-Answer (DWA), indicated by the Command-Code set 3052 to 280 and the Command Flags' 'R' bit cleared, is sent as a response 3053 to the Device-Watchdog-Request message. 3055 Message Format 3057 ::= < Diameter Header: 280 > 3058 { Result-Code } 3059 { Origin-Host } 3060 { Origin-Realm } 3061 [ Error-Message ] 3062 * [ Failed-AVP ] 3063 [ Origin-State-Id ] 3065 5.5.3. Transport Failure Algorithm 3067 The transport failure algorithm is defined in [RFC3539]. All 3068 Diameter implementations MUST support the algorithm defined in the 3069 specification in order to be compliant to the Diameter base protocol. 3071 5.5.4. Failover and Failback Procedures 3073 In the event that a transport failure is detected with a peer, it is 3074 necessary for all pending request messages to be forwarded to an 3075 alternate agent, if possible. This is commonly referred to as 3076 failover. 3078 In order for a Diameter node to perform failover procedures, it is 3079 necessary for the node to maintain a pending message queue for a 3080 given peer. When an answer message is received, the corresponding 3081 request is removed from the queue. The Hop-by-Hop Identifier field 3082 is used to match the answer with the queued request. 3084 When a transport failure is detected, if possible all messages in the 3085 queue are sent to an alternate agent with the T flag set. On booting 3086 a Diameter client or agent, the T flag is also set on any records 3087 still remaining to be transmitted in non-volatile storage. An 3088 example of a case where it is not possible to forward the message to 3089 an alternate server is when the message has a fixed destination, and 3090 the unavailable peer is the message's final destination (see 3091 Destination-Host AVP). Such an error requires that the agent return 3092 an answer message with the 'E' bit set and the Result-Code AVP set to 3093 DIAMETER_UNABLE_TO_DELIVER. 3095 It is important to note that multiple identical requests or answers 3096 MAY be received as a result of a failover. The End-to-End Identifier 3097 field in the Diameter header along with the Origin-Host AVP MUST be 3098 used to identify duplicate messages. 3100 As described in Section 2.1, a connection request should be 3101 periodically attempted with the failed peer in order to re-establish 3102 the transport connection. Once a connection has been successfully 3103 established, messages can once again be forwarded to the peer. This 3104 is commonly referred to as failback. 3106 5.6. Peer State Machine 3108 This section contains a finite state machine that MUST be observed by 3109 all Diameter implementations. Each Diameter node MUST follow the 3110 state machine described below when communicating with each peer. 3111 Multiple actions are separated by commas, and may continue on 3112 succeeding lines, as space requires. Similarly, state and next state 3113 may also span multiple lines, as space requires. 3115 This state machine is closely coupled with the state machine 3116 described in [RFC3539], which is used to open, close, failover, 3117 probe, and reopen transport connections. Note in particular that 3118 [RFC3539] requires the use of watchdog messages to probe connections. 3119 For Diameter, DWR and DWA messages are to be used. 3121 I- is used to represent the initiator (connecting) connection, while 3122 the R- is used to represent the responder (listening) connection. 3123 The lack of a prefix indicates that the event or action is the same 3124 regardless of the connection on which the event occurred. 3126 The stable states that a state machine may be in are Closed, I-Open 3127 and R-Open; all other states are intermediate. Note that I-Open and 3128 R-Open are equivalent except for whether the initiator or responder 3129 transport connection is used for communication. 3131 A CER message is always sent on the initiating connection immediately 3132 after the connection request is successfully completed. In the case 3133 of an election, one of the two connections will shut down. The 3134 responder connection will survive if the Origin-Host of the local 3135 Diameter entity is higher than that of the peer; the initiator 3136 connection will survive if the peer's Origin-Host is higher. All 3137 subsequent messages are sent on the surviving connection. Note that 3138 the results of an election on one peer are guaranteed to be the 3139 inverse of the results on the other. 3141 For TLS usage, a TLS handshake will begin when both ends are in the 3142 open state. If the TLS handshake is successful, all further messages 3143 will be sent via TLS. If the handshake fails, both ends move to the 3144 closed state. 3146 The state machine constrains only the behavior of a Diameter 3147 implementation as seen by Diameter peers through events on the wire. 3149 Any implementation that produces equivalent results is considered 3150 compliant. 3152 state event action next state 3153 ----------------------------------------------------------------- 3154 Closed Start I-Snd-Conn-Req Wait-Conn-Ack 3155 R-Conn-CER R-Accept, R-Open 3156 Process-CER, 3157 R-Snd-CEA 3159 Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA 3160 I-Rcv-Conn-Nack Cleanup Closed 3161 R-Conn-CER R-Accept, Wait-Conn-Ack/ 3162 Process-CER Elect 3163 Timeout Error Closed 3165 Wait-I-CEA I-Rcv-CEA Process-CEA I-Open 3166 R-Conn-CER R-Accept, Wait-Returns 3167 Process-CER, 3168 Elect 3169 I-Peer-Disc I-Disc Closed 3170 I-Rcv-Non-CEA Error Closed 3171 Timeout Error Closed 3173 Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns 3174 Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open 3175 R-Peer-Disc R-Disc Wait-Conn-Ack 3176 R-Conn-CER R-Reject Wait-Conn-Ack/ 3177 Elect 3178 Timeout Error Closed 3180 Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open 3181 I-Peer-Disc I-Disc, R-Open 3182 R-Snd-CEA 3183 I-Rcv-CEA R-Disc I-Open 3184 R-Peer-Disc R-Disc Wait-I-CEA 3185 R-Conn-CER R-Reject Wait-Returns 3186 Timeout Error Closed 3188 R-Open Send-Message R-Snd-Message R-Open 3189 R-Rcv-Message Process R-Open 3190 R-Rcv-DWR Process-DWR, R-Open 3191 R-Snd-DWA 3192 R-Rcv-DWA Process-DWA R-Open 3193 R-Conn-CER R-Reject R-Open 3194 Stop R-Snd-DPR Closing 3195 R-Rcv-DPR R-Snd-DPA, Closed 3196 R-Disc 3198 R-Peer-Disc R-Disc Closed 3199 R-Rcv-CER R-Snd-CEA R-Open 3200 R-Rcv-CEA Process-CEA R-Open 3202 I-Open Send-Message I-Snd-Message I-Open 3203 I-Rcv-Message Process I-Open 3204 I-Rcv-DWR Process-DWR, I-Open 3205 I-Snd-DWA 3206 I-Rcv-DWA Process-DWA I-Open 3207 R-Conn-CER R-Reject I-Open 3208 Stop I-Snd-DPR Closing 3209 I-Rcv-DPR I-Snd-DPA, Closed 3210 I-Disc 3211 I-Peer-Disc I-Disc Closed 3212 I-Rcv-CER I-Snd-CEA I-Open 3213 I-Rcv-CEA Process-CEA I-Open 3215 Closing I-Rcv-DPA I-Disc Closed 3216 R-Rcv-DPA R-Disc Closed 3217 Timeout Error Closed 3218 I-Peer-Disc I-Disc Closed 3219 R-Peer-Disc R-Disc Closed 3221 5.6.1. Incoming connections 3223 When a connection request is received from a Diameter peer, it is 3224 not, in the general case, possible to know the identity of that peer 3225 until a CER is received from it. This is because host and port 3226 determine the identity of a Diameter peer; and the source port of an 3227 incoming connection is arbitrary. Upon receipt of CER, the identity 3228 of the connecting peer can be uniquely determined from Origin-Host. 3230 For this reason, a Diameter peer must employ logic separate from the 3231 state machine to receive connection requests, accept them, and await 3232 CER. Once CER arrives on a new connection, the Origin-Host that 3233 identifies the peer is used to locate the state machine associated 3234 with that peer, and the new connection and CER are passed to the 3235 state machine as an R-Conn-CER event. 3237 The logic that handles incoming connections SHOULD close and discard 3238 the connection if any message other than CER arrives, or if an 3239 implementation-defined timeout occurs prior to receipt of CER. 3241 Because handling of incoming connections up to and including receipt 3242 of CER requires logic, separate from that of any individual state 3243 machine associated with a particular peer, it is described separately 3244 in this section rather than in the state machine above. 3246 5.6.2. Events 3248 Transitions and actions in the automaton are caused by events. In 3249 this section, we will ignore the -I and -R prefix, since the actual 3250 event would be identical, but would occur on one of two possible 3251 connections. 3253 Start The Diameter application has signaled that a 3254 connection should be initiated with the peer. 3256 R-Conn-CER An acknowledgement is received stating that the 3257 transport connection has been established, and the 3258 associated CER has arrived. 3260 Rcv-Conn-Ack A positive acknowledgement is received confirming that 3261 the transport connection is established. 3263 Rcv-Conn-Nack A negative acknowledgement was received stating that 3264 the transport connection was not established. 3266 Timeout An application-defined timer has expired while waiting 3267 for some event. 3269 Rcv-CER A CER message from the peer was received. 3271 Rcv-CEA A CEA message from the peer was received. 3273 Rcv-Non-CEA A message other than CEA from the peer was received. 3275 Peer-Disc A disconnection indication from the peer was received. 3277 Rcv-DPR A DPR message from the peer was received. 3279 Rcv-DPA A DPA message from the peer was received. 3281 Win-Election An election was held, and the local node was the 3282 winner. 3284 Send-Message A message is to be sent. 3286 Rcv-Message A message other than CER, CEA, DPR, DPA, DWR or DWA 3287 was received. 3289 Stop The Diameter application has signaled that a 3290 connection should be terminated (e.g., on system 3291 shutdown). 3293 5.6.3. Actions 3295 Actions in the automaton are caused by events and typically indicate 3296 the transmission of packets and/or an action to be taken on the 3297 connection. In this section we will ignore the I- and R-prefix, 3298 since the actual action would be identical, but would occur on one of 3299 two possible connections. 3301 Snd-Conn-Req A transport connection is initiated with the peer. 3303 Accept The incoming connection associated with the R-Conn-CER 3304 is accepted as the responder connection. 3306 Reject The incoming connection associated with the R-Conn-CER 3307 is disconnected. 3309 Process-CER The CER associated with the R-Conn-CER is processed. 3310 Snd-CER A CER message is sent to the peer. 3312 Snd-CEA A CEA message is sent to the peer. 3314 Cleanup If necessary, the connection is shutdown, and any 3315 local resources are freed. 3317 Error The transport layer connection is disconnected, either 3318 politely or abortively, in response to an error 3319 condition. Local resources are freed. 3321 Process-CEA A received CEA is processed. 3323 Snd-DPR A DPR message is sent to the peer. 3325 Snd-DPA A DPA message is sent to the peer. 3327 Disc The transport layer connection is disconnected, and 3328 local resources are freed. 3330 Elect An election occurs (see Section 5.6.4 for more 3331 information). 3333 Snd-Message A message is sent. 3335 Snd-DWR A DWR message is sent. 3337 Snd-DWA A DWA message is sent. 3339 Process-DWR The DWR message is serviced. 3341 Process-DWA The DWA message is serviced. 3343 Process A message is serviced. 3345 5.6.4. The Election Process 3347 The election is performed on the responder. The responder compares 3348 the Origin-Host received in the CER sent by its peer with its own 3349 Origin-Host. If the local Diameter entity's Origin-Host is higher 3350 than the peer's, a Win-Election event is issued locally. 3352 The comparison proceeds by considering the shorter OctetString to be 3353 padded with zeros so that it length is the same as the length of the 3354 longer, then performing an octet-by-octet unsigned comparison with 3355 the first octet being most significant. Any remaining octets are 3356 assumed to have value 0x80. 3358 5.6.5. Capabilities Update 3360 A Diameter node MUST initiate peer capabilities update by sending a 3361 Capabilities-Exchange-Req (CER) to all its peers which supports peer 3362 capabilities update and is in OPEN state. The receiver of CER in 3363 open state MUST process and reply to the CER as a described in 3364 Section 5.3. The CEA which the receiver sends MUST contain its 3365 latest capabilities. Note that peers which successfully process the 3366 peer capabilities update SHOULD also update their routing tables to 3367 reflect the change. The receiver of the CEA, with a Result-Code AVP 3368 other than DIAMETER_SUCCESS, initiates the transport disconnect. The 3369 peer may periodically attempt to reconnect, as stated in Section 2.1. 3371 Peer capabilities update in the open state SHOULD be limited to the 3372 advertisement of the new list of supported applications and MUST 3373 preclude re-negotiation of security mechanism or other capabilities. 3374 If any capabilities change happens in the node (e.g. change in 3375 security mechanisms), other than a change in the supported 3376 applications, the node SHOULD gracefully terminate (setting the 3377 Disconnect-Cause AVP value to REBOOTING) and re-establish the 3378 diameter connections to all the peers. 3380 6. Diameter message processing 3382 This section describes how Diameter requests and answers are created 3383 and processed. 3385 6.1. Diameter Request Routing Overview 3387 A request is sent towards its final destination using a combination 3388 of the Destination-Realm and Destination-Host AVPs, in one of these 3389 three combinations: 3391 o a request that is not able to be proxied (such as CER) MUST NOT 3392 contain either Destination-Realm or Destination-Host AVPs. 3394 o a request that needs to be sent to a home server serving a 3395 specific realm, but not to a specific server (such as the first 3396 request of a series of round-trips), MUST contain a Destination- 3397 Realm AVP, but MUST NOT contain a Destination-Host AVP. 3399 o otherwise, a request that needs to be sent to a specific home 3400 server among those serving a given realm, MUST contain both the 3401 Destination-Realm and Destination-Host AVPs. 3403 The Destination-Host AVP is used as described above when the 3404 destination of the request is fixed, which includes: 3406 o Authentication requests that span multiple round trips 3408 o A Diameter message that uses a security mechanism that makes use 3409 of a pre-established session key shared between the source and the 3410 final destination of the message. 3412 o Server initiated messages that MUST be received by a specific 3413 Diameter client (e.g., access device), such as the Abort-Session- 3414 Request message, which is used to request that a particular user's 3415 session be terminated. 3417 Note that an agent can forward a request to a host described in the 3418 Destination-Host AVP only if the host in question is included in its 3419 peer table (see Section 2.7). Otherwise, the request is routed based 3420 on the Destination-Realm only (see Sections 6.1.6). 3422 The Destination-Realm AVP MUST be present if the message is 3423 proxiable. Request messages that may be forwarded by Diameter agents 3424 (proxies, redirects or relays) MUST also contain an Acct- 3425 Application-Id AVP, an Auth-Application-Id AVP or a Vendor-Specific- 3426 Application-Id AVP. A message that MUST NOT be forwarded by Diameter 3427 agents (proxies, redirects or relays) MUST not include the 3428 Destination-Realm in its ABNF. The value of the Destination-Realm 3429 AVP MAY be extracted from the User-Name AVP, or other application- 3430 specific methods. 3432 When a message is received, the message is processed in the following 3433 order: 3435 o If the message is destined for the local host, the procedures 3436 listed in Section 6.1.4 are followed. 3438 o If the message is intended for a Diameter peer with whom the local 3439 host is able to directly communicate, the procedures listed in 3440 Section 6.1.5 are followed. This is known as Request Forwarding. 3442 o The procedures listed in Section 6.1.6 are followed, which is 3443 known as Request Routing. 3445 o If none of the above is successful, an answer is returned with the 3446 Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the E-bit set. 3448 For routing of Diameter messages to work within an administrative 3449 domain, all Diameter nodes within the realm MUST be peers. 3451 Note the processing rules contained in this section are intended to 3452 be used as general guidelines to Diameter developers. Certain 3453 implementations MAY use different methods than the ones described 3454 here, and still comply with the protocol specification. See Section 3455 7 for more detail on error handling. 3457 6.1.1. Originating a Request 3459 When creating a request, in addition to any other procedures 3460 described in the application definition for that specific request, 3461 the following procedures MUST be followed: 3463 o the Command-Code is set to the appropriate value 3465 o the 'R' bit is set 3467 o the End-to-End Identifier is set to a locally unique value 3469 o the Origin-Host and Origin-Realm AVPs MUST be set to the 3470 appropriate values, used to identify the source of the message 3472 o the Destination-Host and Destination-Realm AVPs MUST be set to the 3473 appropriate values as described in Section 6.1. 3475 o an Acct-Application-Id AVP, an Auth-Application-Id or a Vendor- 3476 Specific-Application-Id AVP must be included if the request is 3477 proxiable. The application id present in one of these relevant 3478 AVPs must match the application id present in the diameter message 3479 header. 3481 6.1.2. Sending a Request 3483 When sending a request, originated either locally, or as the result 3484 of a forwarding or routing operation, the following procedures MUST 3485 be followed: 3487 o the Hop-by-Hop Identifier should be set to a locally unique value. 3489 o The message should be saved in the list of pending requests. 3491 Other actions to perform on the message based on the particular role 3492 the agent is playing are described in the following sections. 3494 6.1.3. Receiving Requests 3496 A relay or proxy agent MUST check for forwarding loops when receiving 3497 requests. A loop is detected if the server finds its own identity in 3498 a Route-Record AVP. When such an event occurs, the agent MUST answer 3499 with the Result-Code AVP set to DIAMETER_LOOP_DETECTED. 3501 6.1.4. Processing Local Requests 3503 A request is known to be for local consumption when one of the 3504 following conditions occur: 3506 o The Destination-Host AVP contains the local host's identity, 3508 o The Destination-Host AVP is not present, the Destination-Realm AVP 3509 contains a realm the server is configured to process locally, and 3510 the Diameter application is locally supported, or 3512 o Both the Destination-Host and the Destination-Realm are not 3513 present. 3515 When a request is locally processed, the rules in Section 6.2 should 3516 be used to generate the corresponding answer. 3518 6.1.5. Request Forwarding 3520 Request forwarding is done using the Diameter Peer Table. The 3521 Diameter peer table contains all of the peers that the local node is 3522 able to directly communicate with. 3524 When a request is received, and the host encoded in the Destination- 3525 Host AVP is one that is present in the peer table, the message SHOULD 3526 be forwarded to the peer. 3528 6.1.6. Request Routing 3530 Diameter request message routing is done via realms and applications. 3531 A Diameter message that may be forwarded by Diameter agents (proxies, 3532 redirects or relays) MUST include the target realm in the 3533 Destination-Realm AVP. Request routing SHOULD rely on the 3534 Destination-Realm AVP and the application id present in the request 3535 message header to aid in the routing decision. It MAY also rely on 3536 the application identification AVPs Auth-Application-Id, Acct- 3537 Application-Id or Vendor-Specific-Application-Id instead of the 3538 application id in the message header as a secondary measure. The 3539 realm MAY be retrieved from the User-Name AVP, which is in the form 3540 of a Network Access Identifier (NAI). The realm portion of the NAI 3541 is inserted in the Destination-Realm AVP. 3543 Diameter agents MAY have a list of locally supported realms and 3544 applications, and MAY have a list of externally supported realms and 3545 applications. When a request is received that includes a realm 3546 and/or application that is not locally supported, the message is 3547 routed to the peer configured in the Realm Routing Table (see Section 3548 2.7). 3550 6.1.7. Predictive Loop Avoidance 3552 Before forwarding or routing a request, Diameter agents, in addition 3553 to processing done in Section 6.1.3, SHOULD check for the presence of 3554 candidate route's peer identity in any of the Route-Record AVPs. In 3555 an event of the agent detecting the presence of a candidate route's 3556 peer identity in a Route-Record AVP, the agent MUST ignore such route 3557 for the Diameter request message and attempt alternate routes if any. 3558 In case all the candidate routes are eliminated by the above 3559 criteria, the agent SHOULD return DIAMETER_UNABLE_TO_DELIVER message. 3561 6.1.8. Redirecting requests 3563 When a redirect agent receives a request whose routing entry is set 3564 to REDIRECT, it MUST reply with an answer message with the 'E' bit 3565 set, while maintaining the Hop-by-Hop Identifier in the header, and 3566 include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of 3567 the servers associated with the routing entry are added in separate 3568 Redirect-Host AVP. 3570 +------------------+ 3571 | Diameter | 3572 | Redirect Agent | 3573 +------------------+ 3574 ^ | 2. command + 'E' bit 3575 1. Request | | Result-Code = 3576 joe@example.com | | DIAMETER_REDIRECT_INDICATION + 3577 | | Redirect-Host AVP(s) 3578 | v 3579 +-------------+ 3. Request +-------------+ 3580 | example.com |------------->| example.net | 3581 | Relay | | Diameter | 3582 | Agent |<-------------| Server | 3583 +-------------+ 4. Answer +-------------+ 3585 Figure 5: Diameter Redirect Agent 3587 The receiver of the answer message with the 'E' bit set, and the 3588 Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by- 3589 hop field in the Diameter header to identify the request in the 3590 pending message queue (see Section 5.3) that is to be redirected. If 3591 no transport connection exists with the new agent, one is created, 3592 and the request is sent directly to it. 3594 Multiple Redirect-Host AVPs are allowed. The receiver of the answer 3595 message with the 'E' bit set selects exactly one of these hosts as 3596 the destination of the redirected message. 3598 6.1.9. Relaying and Proxying Requests 3600 A relay or proxy agent MUST append a Route-Record AVP to all requests 3601 forwarded. The AVP contains the identity of the peer the request was 3602 received from. 3604 The Hop-by-Hop identifier in the request is saved, and replaced with 3605 a locally unique value. The source of the request is also saved, 3606 which includes the IP address, port and protocol. 3608 A relay or proxy agent MAY include the Proxy-Info AVP in requests if 3609 it requires access to any local state information when the 3610 corresponding response is received. Proxy-Info AVP has certain 3611 security implications and SHOULD contain an embedded HMAC with a 3612 node-local key. Alternatively, it MAY simply use local storage to 3613 store state information. 3615 The message is then forwarded to the next hop, as identified in the 3616 Realm Routing Table. 3618 Figure 6 provides an example of message routing using the procedures 3619 listed in these sections. 3621 (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net) 3622 (Origin-Realm=mno.net) (Origin-Realm=mno.net) 3623 (Destination-Realm=example.com) (Destination- 3624 Realm=example.com) 3625 (Route-Record=nas.example.net) 3626 +------+ ------> +------+ ------> +------+ 3627 | | (Request) | | (Request) | | 3628 | NAS +-------------------+ DRL +-------------------+ HMS | 3629 | | | | | | 3630 +------+ <------ +------+ <------ +------+ 3631 example.net (Answer) example.net (Answer) example.com 3632 (Origin-Host=hms.example.com) (Origin-Host=hms.example.com) 3633 (Origin-Realm=example.com) (Origin-Realm=example.com) 3635 Figure 6: Routing of Diameter messages 3637 6.2. Diameter Answer Processing 3639 When a request is locally processed, the following procedures MUST be 3640 applied to create the associated answer, in addition to any 3641 additional procedures that MAY be discussed in the Diameter 3642 application defining the command: 3644 o The same Hop-by-Hop identifier in the request is used in the 3645 answer. 3647 o The local host's identity is encoded in the Origin-Host AVP. 3649 o The Destination-Host and Destination-Realm AVPs MUST NOT be 3650 present in the answer message. 3652 o The Result-Code AVP is added with its value indicating success or 3653 failure. 3655 o If the Session-Id is present in the request, it MUST be included 3656 in the answer. 3658 o Any Proxy-Info AVPs in the request MUST be added to the answer 3659 message, in the same order they were present in the request. 3661 o The 'P' bit is set to the same value as the one in the request. 3663 o The same End-to-End identifier in the request is used in the 3664 answer. 3666 Note that the error messages (see Section 7.3) are also subjected to 3667 the above processing rules. 3669 6.2.1. Processing received Answers 3671 A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an 3672 answer received against the list of pending requests. The 3673 corresponding message should be removed from the list of pending 3674 requests. It SHOULD ignore answers received that do not match a 3675 known Hop-by-Hop Identifier. 3677 6.2.2. Relaying and Proxying Answers 3679 If the answer is for a request which was proxied or relayed, the 3680 agent MUST restore the original value of the Diameter header's Hop- 3681 by-Hop Identifier field. 3683 If the last Proxy-Info AVP in the message is targeted to the local 3684 Diameter server, the AVP MUST be removed before the answer is 3685 forwarded. 3687 If a relay or proxy agent receives an answer with a Result-Code AVP 3688 indicating a failure, it MUST NOT modify the contents of the AVP. 3689 Any additional local errors detected SHOULD be logged, but not 3690 reflected in the Result-Code AVP. If the agent receives an answer 3691 message with a Result-Code AVP indicating success, and it wishes to 3692 modify the AVP to indicate an error, it MUST modify the Result-Code 3693 AVP to contain the appropriate error in the message destined towards 3694 the access device as well as include the Error-Reporting-Host AVP and 3695 it MUST issue an STR on behalf of the access device. 3697 The agent MUST then send the answer to the host that it received the 3698 original request from. 3700 6.3. Origin-Host AVP 3702 The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and 3703 MUST be present in all Diameter messages. This AVP identifies the 3704 endpoint that originated the Diameter message. Relay agents MUST NOT 3705 modify this AVP. 3707 The value of the Origin-Host AVP is guaranteed to be unique within a 3708 single host. 3710 Note that the Origin-Host AVP may resolve to more than one address as 3711 the Diameter peer may support more than one address. 3713 This AVP SHOULD be placed as close to the Diameter header as 3714 possible. 6.10 3716 6.4. Origin-Realm AVP 3718 The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity. 3719 This AVP contains the Realm of the originator of any Diameter message 3720 and MUST be present in all messages. 3722 This AVP SHOULD be placed as close to the Diameter header as 3723 possible. 3725 6.5. Destination-Host AVP 3727 The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity. 3728 This AVP MUST be present in all unsolicited agent initiated messages, 3729 MAY be present in request messages, and MUST NOT be present in Answer 3730 messages. 3732 The absence of the Destination-Host AVP will cause a message to be 3733 sent to any Diameter server supporting the application within the 3734 realm specified in Destination-Realm AVP. 3736 This AVP SHOULD be placed as close to the Diameter header as 3737 possible. 3739 6.6. Destination-Realm AVP 3741 The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity, 3742 and contains the realm the message is to be routed to. The 3743 Destination-Realm AVP MUST NOT be present in Answer messages. 3744 Diameter Clients insert the realm portion of the User-Name AVP. 3745 Diameter servers initiating a request message use the value of the 3746 Origin-Realm AVP from a previous message received from the intended 3747 target host (unless it is known a priori). When present, the 3748 Destination-Realm AVP is used to perform message routing decisions. 3750 Request messages whose ABNF does not list the Destination-Realm AVP 3751 as a mandatory AVP are inherently non-routable messages. 3753 This AVP SHOULD be placed as close to the Diameter header as 3754 possible. 3756 6.7. Routing AVPs 3758 The AVPs defined in this section are Diameter AVPs used for routing 3759 purposes. These AVPs change as Diameter messages are processed by 3760 agents, and therefore MUST NOT be protected by end-to-end security. 3762 6.7.1. Route-Record AVP 3764 The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The 3765 identity added in this AVP MUST be the same as the one received in 3766 the Origin-Host of the Capabilities Exchange message. 3768 6.7.2. Proxy-Info AVP 3770 The Proxy-Info AVP (AVP Code 284) is of type Grouped. The Grouped 3771 Data field has the following ABNF grammar: 3773 Proxy-Info ::= < AVP Header: 284 > 3774 { Proxy-Host } 3775 { Proxy-State } 3776 * [ AVP ] 3778 6.7.3. Proxy-Host AVP 3780 The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This 3781 AVP contains the identity of the host that added the Proxy-Info AVP. 3783 6.7.4. Proxy-State AVP 3785 The Proxy-State AVP (AVP Code 33) is of type OctetString, and 3786 contains state local information, and MUST be treated as opaque data. 3788 6.8. Auth-Application-Id AVP 3790 The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and 3791 is used in order to advertise support of the Authentication and 3792 Authorization portion of an application (see Section 2.4). The Auth- 3793 Application-Id MUST also be present in all Authentication and/or 3794 Authorization messages that are defined in a separate Diameter 3795 specification and have an Application ID assigned. If present in a 3796 message, the value of the Auth-Application-Id AVP MUST match the 3797 application id present in the diameter message header except when 3798 used in a CER or CEA messages. 3800 6.9. Acct-Application-Id AVP 3802 The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and 3803 is used in order to advertise support of the Accounting portion of an 3804 application (see Section 2.4). The Acct-Application-Id MUST also be 3805 present in all Accounting messages. Exactly one of the Auth- 3806 Application-Id and Acct-Application-Id AVPs MAY be present. If 3807 present in a message, the value of the Acct-Application-Id AVP MUST 3808 match the application id present in the diameter message header 3809 except when used in a CER or CEA messages. 3811 6.10. Inband-Security-Id AVP 3813 The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and 3814 is used in order to advertise support of the Security portion of the 3815 application. 3817 Currently, the following values are supported, but there is ample 3818 room to add new security Ids. 3820 NO_INBAND_SECURITY 0 3822 This peer does not support TLS. This is the default value, if the 3823 AVP is omitted. 3825 TLS 1 3827 This node supports TLS security, as defined by [RFC2246]. 3829 6.11. Vendor-Specific-Application-Id AVP 3831 The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type 3832 Grouped and is used to advertise support of a vendor-specific 3833 Diameter Application. Exactly one instance of Auth-Application-Id or 3834 Acct-Application-Id AVP MAY be present. The application identifier 3835 carried by either Auth-Application-Id or Acct-Application-Id AVP MUST 3836 comply with vendor specific application identifier assignment 3837 described in Sec 11.3. It MUST also match the application id present 3838 in the diameter header except when used in a CER or CEA messages. 3840 The Vendor-Id AVP is an informational AVP pertaining to the vendor 3841 who may have authorship of the vendor-specific diameter application. 3842 It should not be used as a means of defining a vendor-specific 3843 application identifiers space. 3845 This AVP MUST also be present as the first AVP in all experimental 3846 commands defined in the vendor-specific application. 3848 This AVP SHOULD be placed as close to the Diameter header as 3849 possible. 3851 AVP Format 3853 ::= < AVP Header: 260 > 3854 { Vendor-Id } 3855 { Auth-Application-Id } / 3856 { Acct-Application-Id } 3858 6.12. Redirect-Host AVP 3860 One or more of instances of this AVP MUST be present if the answer 3861 message's 'E' bit is set and the Result-Code AVP is set to 3862 DIAMETER_REDIRECT_INDICATION. 3864 Upon receiving the above, the receiving Diameter node SHOULD forward 3865 the request directly to one of the hosts identified in these AVPs. 3866 The server contained in the selected Redirect-Host AVP SHOULD be used 3867 for all messages pertaining to this session. 3869 6.13. Redirect-Host-Usage AVP 3871 The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated. 3872 This AVP MAY be present in answer messages whose 'E' bit is set and 3873 the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION. 3875 When present, this AVP dictates how the routing entry resulting from 3876 the Redirect-Host is to be used. The following values are supported: 3878 DONT_CACHE 0 3880 The host specified in the Redirect-Host AVP should not be cached. 3881 This is the default value. 3883 ALL_SESSION 1 3885 All messages within the same session, as defined by the same value 3886 of the Session-ID AVP MAY be sent to the host specified in the 3887 Redirect-Host AVP. 3889 ALL_REALM 2 3891 All messages destined for the realm requested MAY be sent to the 3892 host specified in the Redirect-Host AVP. 3894 REALM_AND_APPLICATION 3 3896 All messages for the application requested to the realm specified 3897 MAY be sent to the host specified in the Redirect-Host AVP. 3899 ALL_APPLICATION 4 3901 All messages for the application requested MAY be sent to the host 3902 specified in the Redirect-Host AVP. 3904 ALL_HOST 5 3906 All messages that would be sent to the host that generated the 3907 Redirect-Host MAY be sent to the host specified in the Redirect- 3908 Host AVP. 3910 ALL_USER 6 3912 All messages for the user requested MAY be sent to the host 3913 specified in the Redirect-Host AVP. 3915 6.14. Redirect-Max-Cache-Time AVP 3917 The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32. 3918 This AVP MUST be present in answer messages whose 'E' bit is set, the 3919 Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the 3920 Redirect-Host-Usage AVP set to a non-zero value. 3922 This AVP contains the maximum number of seconds the peer and route 3923 table entries, created as a result of the Redirect-Host, will be 3924 cached. Note that once a host created due to a redirect indication 3925 is no longer reachable, any associated peer and routing table entries 3926 MUST be deleted. 3928 6.15. E2E-Sequence AVP 3930 The E2E-Sequence AVP (AVP Code 300) provides anti-replay protection 3931 for end to end messages and is of type grouped. It contains a random 3932 value (an OctetString with a nonce) and counter (an Integer). For 3933 each end-to-end peer with which a node communicates (or remembers 3934 communicating) a different nonce value MUST be used and the counter 3935 is initiated at zero and increases by one each time this AVP is 3936 emitted to that peer. This AVP MUST be included in all messages 3937 which use end-to-end protection (e.g., CMS signing or encryption). 3939 7. Error Handling 3941 There are two different types of errors in Diameter; protocol and 3942 application errors. A protocol error is one that occurs at the base 3943 protocol level, and MAY require per hop attention (e.g., message 3944 routing error). Application errors, on the other hand, generally 3945 occur due to a problem with a function specified in a Diameter 3946 application (e.g., user authentication, Missing AVP). 3948 Result-Code AVP values that are used to report protocol errors MUST 3949 only be present in answer messages whose 'E' bit is set. When a 3950 request message is received that causes a protocol error, an answer 3951 message is returned with the 'E' bit set, and the Result-Code AVP is 3952 set to the appropriate protocol error value. As the answer is sent 3953 back towards the originator of the request, each proxy or relay agent 3954 MAY take action on the message. 3956 1. Request +---------+ Link Broken 3957 +-------------------------->|Diameter |----///----+ 3958 | +---------------------| | v 3959 +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+ 3960 |Diameter |<-+ (Unable to Forward) +---------+ |Diameter| 3961 | | | Home | 3962 | Relay 1 |--+ +---------+ | Server | 3963 +---------+ | 3. Request |Diameter | +--------+ 3964 +-------------------->| | ^ 3965 | Relay 3 |-----------+ 3966 +---------+ 3968 Figure 7: Example of Protocol Error causing answer message 3970 Figure 7 provides an example of a message forwarded upstream by a 3971 Diameter relay. When the message is received by Relay 2, and it 3972 detects that it cannot forward the request to the home server, an 3973 answer message is returned with the 'E' bit set and the Result-Code 3974 AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls 3975 within the protocol error category, Relay 1 would take special 3976 action, and given the error, attempt to route the message through its 3977 alternate Relay 3. 3979 +---------+ 1. Request +---------+ 2. Request +---------+ 3980 | Access |------------>|Diameter |------------>|Diameter | 3981 | | | | | Home | 3982 | Device |<------------| Relay |<------------| Server | 3983 +---------+ 4. Answer +---------+ 3. Answer +---------+ 3984 (Missing AVP) (Missing AVP) 3986 Figure 8: Example of Application Error Answer message 3988 Figure 8 provides an example of a Diameter message that caused an 3989 application error. When application errors occur, the Diameter 3990 entity reporting the error clears the 'R' bit in the Command Flags, 3991 and adds the Result-Code AVP with the proper value. Application 3992 errors do not require any proxy or relay agent involvement, and 3993 therefore the message would be forwarded back to the originator of 3994 the request. 3996 There are certain Result-Code AVP application errors that require 3997 additional AVPs to be present in the answer. In these cases, the 3998 Diameter node that sets the Result-Code AVP to indicate the error 3999 MUST add the AVPs. Examples are: 4001 o An unrecognized AVP is received with the 'M' bit (Mandatory bit) 4002 set, causes an answer to be sent with the Result-Code AVP set to 4003 DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the 4004 offending AVP. 4006 o An AVP that is received with an unrecognized value causes an 4007 answer to be returned with the Result-Code AVP set to 4008 DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the 4009 AVP causing the error. 4011 o A command is received with an AVP that is omitted, yet is 4012 mandatory according to the command's ABNF. The receiver issues an 4013 answer with the Result-Code set to DIAMETER_MISSING_AVP, and 4014 creates an AVP with the AVP Code and other fields set as expected 4015 in the missing AVP. The created AVP is then added to the Failed- 4016 AVP AVP. 4018 The Result-Code AVP describes the error that the Diameter node 4019 encountered in its processing. In case there are multiple errors, 4020 the Diameter node MUST report only the first error it encountered 4021 (detected possibly in some implementation dependent order). The 4022 specific errors that can be described by this AVP are described in 4023 the following section. 4025 7.1. Result-Code AVP 4027 The Result-Code AVP (AVP Code 268) is of type Unsigned32 and 4028 indicates whether a particular request was completed successfully or 4029 whether an error occurred. All Diameter answer messages defined in 4030 IETF applications MUST include one Result-Code AVP. A non-successful 4031 Result-Code AVP (one containing a non 2xxx value other than 4032 DIAMETER_REDIRECT_INDICATION) MUST include the Error-Reporting-Host 4033 AVP if the host setting the Result-Code AVP is different from the 4034 identity encoded in the Origin-Host AVP. 4036 The Result-Code data field contains an IANA-managed 32-bit address 4037 space representing errors (see Section 11.4). Diameter provides the 4038 following classes of errors, all identified by the thousands digit in 4039 the decimal notation: 4041 o 1xxx (Informational) 4043 o 2xxx (Success) 4045 o 3xxx (Protocol Errors) 4047 o 4xxx (Transient Failures) 4049 o 5xxx (Permanent Failure) 4051 A non-recognized class (one whose first digit is not defined in this 4052 section) MUST be handled as a permanent failure. 4054 7.1.1. Informational 4056 Errors that fall within this category are used to inform the 4057 requester that a request could not be satisfied, and additional 4058 action is required on its part before access is granted. 4060 DIAMETER_MULTI_ROUND_AUTH 1001 4062 This informational error is returned by a Diameter server to 4063 inform the access device that the authentication mechanism being 4064 used requires multiple round trips, and a subsequent request needs 4065 to be issued in order for access to be granted. 4067 7.1.2. Success 4069 Errors that fall within the Success category are used to inform a 4070 peer that a request has been successfully completed. 4072 DIAMETER_SUCCESS 2001 4074 The Request was successfully completed. 4076 DIAMETER_LIMITED_SUCCESS 2002 4078 When returned, the request was successfully completed, but 4079 additional processing is required by the application in order to 4080 provide service to the user. 4082 7.1.3. Protocol Errors 4084 Errors that fall within the Protocol Error category SHOULD be treated 4085 on a per-hop basis, and Diameter proxies MAY attempt to correct the 4086 error, if it is possible. Note that these and only these errors MUST 4087 only be used in answer messages whose 'E' bit is set. To provide 4088 backward compatibility with existing implementations that follows 4089 [RFC3588], some of the error values that have previously been used in 4090 this category by [RFC3588] will not be re-used. Therefore the error 4091 values enumerated here maybe non-sequential. 4093 DIAMETER_UNABLE_TO_DELIVER 3002 4095 This error is given when Diameter can not deliver the message to 4096 the destination, either because no host within the realm 4097 supporting the required application was available to process the 4098 request, or because Destination-Host AVP was given without the 4099 associated Destination-Realm AVP. 4101 DIAMETER_REALM_NOT_SERVED 3003 4103 The intended realm of the request is not recognized. 4105 DIAMETER_TOO_BUSY 3004 4107 When returned, a Diameter node SHOULD attempt to send the message 4108 to an alternate peer. This error MUST only be used when a 4109 specific server is requested, and it cannot provide the requested 4110 service. 4112 DIAMETER_LOOP_DETECTED 3005 4114 An agent detected a loop while trying to get the message to the 4115 intended recipient. The message MAY be sent to an alternate peer, 4116 if one is available, but the peer reporting the error has 4117 identified a configuration problem. 4119 DIAMETER_REDIRECT_INDICATION 3006 4121 A redirect agent has determined that the request could not be 4122 satisfied locally and the initiator of the request should direct 4123 the request directly to the server, whose contact information has 4124 been added to the response. When set, the Redirect-Host AVP MUST 4125 be present. 4127 DIAMETER_APPLICATION_UNSUPPORTED 3007 4129 A request was sent for an application that is not supported. 4131 DIAMETER_INVALID_BIT_IN_HEADER 3011 4133 This error is returned when an unrecognized bit in the Diameter 4134 header is set to one (1). 4136 DIAMETER_INVALID_MESSAGE_LENGTH 3012 4138 This error is returned when a request is received with an invalid 4139 message length. 4141 7.1.4. Transient Failures 4143 Errors that fall within the transient failures category are used to 4144 inform a peer that the request could not be satisfied at the time it 4145 was received, but MAY be able to satisfy the request in the future. 4146 Note that these errors MUST be used in answer messages whose 'E' bit 4147 not is set. 4149 DIAMETER_AUTHENTICATION_REJECTED 4001 4151 The authentication process for the user failed, most likely due to 4152 an invalid password used by the user. Further attempts MUST only 4153 be tried after prompting the user for a new password. 4155 DIAMETER_OUT_OF_SPACE 4002 4157 A Diameter node received the accounting request but was unable to 4158 commit it to stable storage due to a temporary lack of space. 4160 ELECTION_LOST 4003 4162 The peer has determined that it has lost the election process and 4163 has therefore disconnected the transport connection. 4165 7.1.5. Permanent Failures 4167 Errors that fall within the permanent failures category are used to 4168 inform the peer that the request failed, and should not be attempted 4169 again. Note that these errors SHOULD be used in answer messages 4170 whose 'E' bit is not set. In error conditions where it is not 4171 possible or efficient to compose application specific answer grammar 4172 then answer messages with E-bit set and complying to the grammar 4173 described in 7.2 MAY also be used for permanent errors. 4175 To provide backward compatibility with existing implementations that 4176 follows [RFC3588], some of the error values that have previously been 4177 used in this category by [RFC3588] will not be re-used. Therefore 4178 the error values enumerated here maybe non-sequential. 4180 DIAMETER_AVP_UNSUPPORTED 5001 4182 The peer received a message that contained an AVP that is not 4183 recognized or supported and was marked with the Mandatory bit. A 4184 Diameter message with this error MUST contain one or more Failed- 4185 AVP AVP containing the AVPs that caused the failure. 4187 DIAMETER_UNKNOWN_SESSION_ID 5002 4189 The request contained an unknown Session-Id. 4191 DIAMETER_AUTHORIZATION_REJECTED 5003 4193 A request was received for which the user could not be authorized. 4194 This error could occur if the service requested is not permitted 4195 to the user. 4197 DIAMETER_INVALID_AVP_VALUE 5004 4199 The request contained an AVP with an invalid value in its data 4200 portion. A Diameter message indicating this error MUST include 4201 the offending AVPs within a Failed-AVP AVP. 4203 DIAMETER_MISSING_AVP 5005 4205 The request did not contain an AVP that is required by the Command 4206 Code definition. If this value is sent in the Result-Code AVP, a 4207 Failed-AVP AVP SHOULD be included in the message. The Failed-AVP 4208 AVP MUST contain an example of the missing AVP complete with the 4209 Vendor-Id if applicable. The value field of the missing AVP 4210 should be of correct minimum length and contain zeroes. 4212 DIAMETER_RESOURCES_EXCEEDED 5006 4214 A request was received that cannot be authorized because the user 4215 has already expended allowed resources. An example of this error 4216 condition is a user that is restricted to one dial-up PPP port, 4217 attempts to establish a second PPP connection. 4219 DIAMETER_CONTRADICTING_AVPS 5007 4221 The Home Diameter server has detected AVPs in the request that 4222 contradicted each other, and is not willing to provide service to 4223 the user. One or more Failed-AVP AVPs MUST be present, containing 4224 the AVPs that contradicted each other. 4226 DIAMETER_AVP_NOT_ALLOWED 5008 4228 A message was received with an AVP that MUST NOT be present. The 4229 Failed-AVP AVP MUST be included and contain a copy of the 4230 offending AVP. 4232 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009 4234 A message was received that included an AVP that appeared more 4235 often than permitted in the message definition. The Failed-AVP 4236 AVP MUST be included and contain a copy of the first instance of 4237 the offending AVP that exceeded the maximum number of occurrences 4239 DIAMETER_NO_COMMON_APPLICATION 5010 4241 This error is returned when a CER message is received, and there 4242 are no common applications supported between the peers. 4244 DIAMETER_UNSUPPORTED_VERSION 5011 4246 This error is returned when a request was received, whose version 4247 number is unsupported. 4249 DIAMETER_UNABLE_TO_COMPLY 5012 4251 This error is returned when a request is rejected for unspecified 4252 reasons. 4254 DIAMETER_INVALID_AVP_LENGTH 5014 4256 The request contained an AVP with an invalid length. A Diameter 4257 message indicating this error MUST include the offending AVPs 4258 within a Failed-AVP AVP. In cases where the erroneous avp length 4259 value exceeds the message length or is less than the minimum AVP 4260 header length, it is sufficient to include the offending AVP 4261 header and a zero filled payload of the minimum required length. 4263 DIAMETER_NO_COMMON_SECURITY 5017 4265 This error is returned when a CER message is received, and there 4266 are no common security mechanisms supported between the peers. A 4267 Capabilities-Exchange-Answer (CEA) MUST be returned with the 4268 Result-Code AVP set to DIAMETER_NO_COMMON_SECURITY. 4270 DIAMETER_UNKNOWN_PEER 5018 4272 A CER was received from an unknown peer. 4274 DIAMETER_COMMAND_UNSUPPORTED 5019 4276 The Request contained a Command-Code that the receiver did not 4277 recognize or support. This MUST be used when a Diameter node 4278 receives an experimental command that it does not understand. 4280 DIAMETER_INVALID_HDR_BITS 5020 4282 A request was received whose bits in the Diameter header were 4283 either set to an invalid combination, or to a value that is 4284 inconsistent with the command code's definition. 4286 DIAMETER_INVALID_AVP_BITS 5021 4288 A request was received that included an AVP whose flag bits are 4289 set to an unrecognized value, or that is inconsistent with the 4290 AVP's definition. 4292 7.2. Error Bit 4294 The 'E' (Error Bit) in the Diameter header is set when the request 4295 caused a protocol-related error (see Section 7.1.3). A message with 4296 the 'E' bit MUST NOT be sent as a response to an answer message. 4297 Note that a message with the 'E' bit set is still subjected to the 4298 processing rules defined in Section 6.2. When set, the answer 4299 message will not conform to the ABNF specification for the command, 4300 and will instead conform to the following ABNF: 4302 Message Format 4304 ::= < Diameter Header: code, ERR [PXY] > 4305 0*1< Session-Id > 4306 { Origin-Host } 4307 { Origin-Realm } 4308 { Result-Code } 4309 [ Origin-State-Id ] 4310 [ Error-Reporting-Host ] 4311 [ Proxy-Info ] 4312 * [ AVP ] 4314 Note that the code used in the header is the same than the one found 4315 in the request message, but with the 'R' bit cleared and the 'E' bit 4316 set. The 'P' bit in the header is set to the same value as the one 4317 found in the request message. 4319 7.3. Error-Message AVP 4321 The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY 4322 accompany a Result-Code AVP as a human readable error message. The 4323 Error-Message AVP is not intended to be useful in real-time, and 4324 SHOULD NOT be expected to be parsed by network entities. 4326 7.4. Error-Reporting-Host AVP 4328 The Error-Reporting-Host AVP (AVP Code 294) is of type 4329 DiameterIdentity. This AVP contains the identity of the Diameter 4330 host that sent the Result-Code AVP to a value other than 2001 4331 (Success), only if the host setting the Result-Code is different from 4332 the one encoded in the Origin-Host AVP. This AVP is intended to be 4333 used for troubleshooting purposes, and MUST be set when the Result- 4334 Code AVP indicates a failure. 4336 7.5. Failed-AVP AVP 4338 The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides 4339 debugging information in cases where a request is rejected or not 4340 fully processed due to erroneous information in a specific AVP. The 4341 value of the Result-Code AVP will provide information on the reason 4342 for the Failed-AVP AVP. 4344 The possible reasons for this AVP are the presence of an improperly 4345 constructed AVP, an unsupported or unrecognized AVP, an invalid AVP 4346 value, the omission of a required AVP, the presence of an explicitly 4347 excluded AVP (see tables in Section 10), or the presence of two or 4348 more occurrences of an AVP which is restricted to 0, 1, or 0-1 4349 occurrences. 4351 A Diameter message MAY contain one Failed-AVP AVP, containing the 4352 entire AVP that could not be processed successfully. If the failure 4353 reason is omission of a required AVP, an AVP with the missing AVP 4354 code, the missing vendor id, and a zero filled payload of the minimum 4355 required length for the omitted AVP will be added. If the failure 4356 reason is an invalid AVP length where the reported length is less 4357 than the minimum AVP header length or greater than the reported 4358 message length, a copy of the offending AVP header and a zero filled 4359 payload of the minimum required length SHOULD be added. 4361 AVP Format 4363 ::= < AVP Header: 279 > 4364 1* {AVP} 4366 7.6. Experimental-Result AVP 4368 The Experimental-Result AVP (AVP Code 297) is of type Grouped, and 4369 indicates whether a particular vendor-specific request was completed 4370 successfully or whether an error occurred. Its Data field has the 4371 following ABNF grammar: 4373 AVP Format 4375 Experimental-Result ::= < AVP Header: 297 > 4376 { Vendor-Id } 4377 { Experimental-Result-Code } 4379 The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies 4380 the vendor responsible for the assignment of the result code which 4381 follows. All Diameter answer messages defined in vendor-specific 4382 applications MUST include either one Result-Code AVP or one 4383 Experimental-Result AVP. 4385 7.7. Experimental-Result-Code AVP 4387 The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32 4388 and contains a vendor-assigned value representing the result of 4389 processing the request. 4391 It is recommended that vendor-specific result codes follow the same 4392 conventions given for the Result-Code AVP regarding the different 4393 types of result codes and the handling of errors (for non 2xxx 4394 values). 4396 8. Diameter User Sessions 4398 Diameter can provide two different types of services to applications. 4399 The first involves authentication and authorization, and can 4400 optionally make use of accounting. The second only makes use of 4401 accounting. 4403 When a service makes use of the authentication and/or authorization 4404 portion of an application, and a user requests access to the network, 4405 the Diameter client issues an auth request to its local server. The 4406 auth request is defined in a service specific Diameter application 4407 (e.g., NASREQ). The request contains a Session-Id AVP, which is used 4408 in subsequent messages (e.g., subsequent authorization, accounting, 4409 etc) relating to the user's session. The Session-Id AVP is a means 4410 for the client and servers to correlate a Diameter message with a 4411 user session. 4413 When a Diameter server authorizes a user to use network resources for 4414 a finite amount of time, and it is willing to extend the 4415 authorization via a future request, it MUST add the Authorization- 4416 Lifetime AVP to the answer message. The Authorization-Lifetime AVP 4417 defines the maximum number of seconds a user MAY make use of the 4418 resources before another authorization request is expected by the 4419 server. The Auth-Grace-Period AVP contains the number of seconds 4420 following the expiration of the Authorization-Lifetime, after which 4421 the server will release all state information related to the user's 4422 session. Note that if payment for services is expected by the 4423 serving realm from the user's home realm, the Authorization-Lifetime 4424 AVP, combined with the Auth-Grace-Period AVP, implies the maximum 4425 length of the session the home realm is willing to be fiscally 4426 responsible for. Services provided past the expiration of the 4427 Authorization-Lifetime and Auth-Grace-Period AVPs are the 4428 responsibility of the access device. Of course, the actual cost of 4429 services rendered is clearly outside the scope of the protocol. 4431 An access device that does not expect to send a re-authorization or a 4432 session termination request to the server MAY include the Auth- 4433 Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint 4434 to the server. If the server accepts the hint, it agrees that since 4435 no session termination message will be received once service to the 4436 user is terminated, it cannot maintain state for the session. If the 4437 answer message from the server contains a different value in the 4438 Auth-Session-State AVP (or the default value if the AVP is absent), 4439 the access device MUST follow the server's directives. Note that the 4440 value NO_STATE_MAINTAINED MUST NOT be set in subsequent re- 4441 authorization requests and answers. 4443 The base protocol does not include any authorization request 4444 messages, since these are largely application-specific and are 4445 defined in a Diameter application document. However, the base 4446 protocol does define a set of messages that is used to terminate user 4447 sessions. These are used to allow servers that maintain state 4448 information to free resources. 4450 When a service only makes use of the Accounting portion of the 4451 Diameter protocol, even in combination with an application, the 4452 Session-Id is still used to identify user sessions. However, the 4453 session termination messages are not used, since a session is 4454 signaled as being terminated by issuing an accounting stop message. 4456 8.1. Authorization Session State Machine 4458 This section contains a set of finite state machines, representing 4459 the life cycle of Diameter sessions, and which MUST be observed by 4460 all Diameter implementations that make use of the authentication 4461 and/or authorization portion of a Diameter application. The term 4462 Service-Specific below refers to a message defined in a Diameter 4463 application (e.g., Mobile IPv4, NASREQ). 4465 There are four different authorization session state machines 4466 supported in the Diameter base protocol. The first two describe a 4467 session in which the server is maintaining session state, indicated 4468 by the value of the Auth-Session-State AVP (or its absence). One 4469 describes the session from a client perspective, the other from a 4470 server perspective. The second two state machines are used when the 4471 server does not maintain session state. Here again, one describes 4472 the session from a client perspective, the other from a server 4473 perspective. 4475 When a session is moved to the Idle state, any resources that were 4476 allocated for the particular session must be released. Any event not 4477 listed in the state machines MUST be considered as an error 4478 condition, and an answer, if applicable, MUST be returned to the 4479 originator of the message. 4481 In the state table, the event 'Failure to send X' means that the 4482 Diameter agent is unable to send command X to the desired 4483 destination. This could be due to the peer being down, or due to the 4484 peer sending back a transient failure or temporary protocol error 4485 notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the 4486 Result-Code AVP of the corresponding Answer command. The event 'X 4487 successfully sent' is the complement of 'Failure to send X'. 4489 The following state machine is observed by a client when state is 4490 maintained on the server: 4492 CLIENT, STATEFUL 4493 State Event Action New State 4494 ------------------------------------------------------------- 4495 Idle Client or Device Requests Send Pending 4496 access service 4497 specific 4498 auth req 4500 Idle ASR Received Send ASA Idle 4501 for unknown session with 4502 Result-Code 4503 = UNKNOWN_ 4504 SESSION_ID 4506 Pending Successful Service-specific Grant Open 4507 authorization answer Access 4508 received with default 4509 Auth-Session-State value 4511 Pending Successful Service-specific Sent STR Discon 4512 authorization answer received 4513 but service not provided 4515 Pending Error processing successful Sent STR Discon 4516 Service-specific authorization 4517 answer 4519 Pending Failed Service-specific Cleanup Idle 4520 authorization answer received 4522 Open User or client device Send Open 4523 requests access to service service 4524 specific 4525 auth req 4527 Open Successful Service-specific Provide Open 4528 authorization answer received Service 4530 Open Failed Service-specific Discon. Idle 4531 authorization answer user/device 4532 received. 4534 Open Session-Timeout Expires on Send STR Discon 4535 Access Device 4537 Open ASR Received, Send ASA Discon 4538 client will comply with with 4539 request to end the session Result-Code 4540 = SUCCESS, 4541 Send STR. 4543 Open ASR Received, Send ASA Open 4544 client will not comply with with 4545 request to end the session Result-Code 4546 != SUCCESS 4548 Open Authorization-Lifetime + Send STR Discon 4549 Auth-Grace-Period expires on 4550 access device 4552 Discon ASR Received Send ASA Discon 4554 Discon STA Received Discon. Idle 4555 user/device 4557 The following state machine is observed by a server when it is 4558 maintaining state for the session: 4560 SERVER, STATEFUL 4561 State Event Action New State 4562 ------------------------------------------------------------- 4563 Idle Service-specific authorization Send Open 4564 request received, and successful 4565 user is authorized serv. 4566 specific answer 4568 Idle Service-specific authorization Send Idle 4569 request received, and failed serv. 4570 user is not authorized specific answer 4572 Open Service-specific authorization Send Open 4573 request received, and user successful 4574 is authorized serv. specific 4575 answer 4577 Open Service-specific authorization Send Idle 4578 request received, and user failed serv. 4579 is not authorized specific 4580 answer, 4581 Cleanup 4583 Open Home server wants to Send ASR Discon 4584 terminate the service 4586 Open Authorization-Lifetime (and Cleanup Idle 4587 Auth-Grace-Period) expires 4588 on home server. 4590 Open Session-Timeout expires on Cleanup Idle 4591 home server 4593 Discon Failure to send ASR Wait, Discon 4594 resend ASR 4596 Discon ASR successfully sent and Cleanup Idle 4597 ASA Received with Result-Code 4599 Not ASA Received None No Change. 4600 Discon 4602 Any STR Received Send STA, Idle 4603 Cleanup. 4605 The following state machine is observed by a client when state is not 4606 maintained on the server: 4608 CLIENT, STATELESS 4609 State Event Action New State 4610 ------------------------------------------------------------- 4611 Idle Client or Device Requests Send Pending 4612 access service 4613 specific 4614 auth req 4616 Pending Successful Service-specific Grant Open 4617 authorization answer Access 4618 received with Auth-Session- 4619 State set to 4620 NO_STATE_MAINTAINED 4622 Pending Failed Service-specific Cleanup Idle 4623 authorization answer 4624 received 4626 Open Session-Timeout Expires on Discon. Idle 4627 Access Device user/device 4629 Open Service to user is terminated Discon. Idle 4630 user/device 4632 The following state machine is observed by a server when it is not 4633 maintaining state for the session: 4635 SERVER, STATELESS 4636 State Event Action New State 4637 ------------------------------------------------------------- 4638 Idle Service-specific authorization Send serv. Idle 4639 request received, and specific 4640 successfully processed answer 4642 8.2. Accounting Session State Machine 4644 The following state machines MUST be supported for applications that 4645 have an accounting portion or that require only accounting services. 4646 The first state machine is to be observed by clients. 4648 See Section 9.7 for Accounting Command Codes and Section 9.8 for 4649 Accounting AVPs. 4651 The server side in the accounting state machine depends in some cases 4652 on the particular application. The Diameter base protocol defines a 4653 default state machine that MUST be followed by all applications that 4654 have not specified other state machines. This is the second state 4655 machine in this section described below. 4657 The default server side state machine requires the reception of 4658 accounting records in any order and at any time, and does not place 4659 any standards requirement on the processing of these records. 4660 Implementations of Diameter MAY perform checking, ordering, 4661 correlation, fraud detection, and other tasks based on these records. 4662 Both base Diameter AVPs as well as application specific AVPs MAY be 4663 inspected as a part of these tasks. The tasks can happen either 4664 immediately after record reception or in a post-processing phase. 4665 However, as these tasks are typically application or even policy 4666 dependent, they are not standardized by the Diameter specifications. 4667 Applications MAY define requirements on when to accept accounting 4668 records based on the used value of Accounting-Realtime-Required AVP, 4669 credit limits checks, and so on. 4671 However, the Diameter base protocol defines one optional server side 4672 state machine that MAY be followed by applications that require 4673 keeping track of the session state at the accounting server. Note 4674 that such tracking is incompatible with the ability to sustain long 4675 duration connectivity problems. Therefore, the use of this state 4676 machine is recommended only in applications where the value of the 4677 Accounting-Realtime-Required AVP is DELIVER_AND_GRANT, and hence 4678 accounting connectivity problems are required to cause the serviced 4679 user to be disconnected. Otherwise, records produced by the client 4680 may be lost by the server which no longer accepts them after the 4681 connectivity is re-established. This state machine is the third 4682 state machine in this section. The state machine is supervised by a 4683 supervision session timer Ts, which the value should be reasonably 4684 higher than the Acct_Interim_Interval value. Ts MAY be set to two 4685 times the value of the Acct_Interim_Interval so as to avoid the 4686 accounting session in the Diameter server to change to Idle state in 4687 case of short transient network failure. 4689 Any event not listed in the state machines MUST be considered as an 4690 error condition, and a corresponding answer, if applicable, MUST be 4691 returned to the originator of the message. 4693 In the state table, the event 'Failure to send' means that the 4694 Diameter client is unable to communicate with the desired 4695 destination. This could be due to the peer being down, or due to the 4696 peer sending back a transient failure or temporary protocol error 4697 notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or 4698 DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting 4699 Answer command. 4701 The event 'Failed answer' means that the Diameter client received a 4702 non-transient failure notification in the Accounting Answer command. 4704 Note that the action 'Disconnect user/dev' MUST have an effect also 4705 to the authorization session state table, e.g., cause the STR message 4706 to be sent, if the given application has both authentication/ 4707 authorization and accounting portions. 4709 The states PendingS, PendingI, PendingL, PendingE and PendingB stand 4710 for pending states to wait for an answer to an accounting request 4711 related to a Start, Interim, Stop, Event or buffered record, 4712 respectively. 4714 CLIENT, ACCOUNTING 4715 State Event Action New State 4716 ------------------------------------------------------------- 4717 Idle Client or device requests Send PendingS 4718 access accounting 4719 start req. 4721 Idle Client or device requests Send PendingE 4722 a one-time service accounting 4723 event req 4725 Idle Records in storage Send PendingB 4726 record 4728 PendingS Successful accounting Open 4729 start answer received 4731 PendingS Failure to send and buffer Store Open 4732 space available and realtime Start 4733 not equal to DELIVER_AND_GRANT Record 4735 PendingS Failure to send and no buffer Open 4736 space available and realtime 4737 equal to GRANT_AND_LOSE 4739 PendingS Failure to send and no buffer Disconnect Idle 4740 space available and realtime user/dev 4741 not equal to 4742 GRANT_AND_LOSE 4744 PendingS Failed accounting start answer Open 4745 received and realtime equal 4746 to GRANT_AND_LOSE 4748 PendingS Failed accounting start answer Disconnect Idle 4749 received and realtime not user/dev 4750 equal to GRANT_AND_LOSE 4752 PendingS User service terminated Store PendingS 4753 stop 4754 record 4756 Open Interim interval elapses Send PendingI 4757 accounting 4758 interim 4759 record 4760 Open User service terminated Send PendingL 4761 accounting 4762 stop req. 4764 PendingI Successful accounting interim Open 4765 answer received 4767 PendingI Failure to send and (buffer Store Open 4768 space available or old record interim 4769 can be overwritten) and record 4770 realtime not equal to 4771 DELIVER_AND_GRANT 4773 PendingI Failure to send and no buffer Open 4774 space available and realtime 4775 equal to GRANT_AND_LOSE 4777 PendingI Failure to send and no buffer Disconnect Idle 4778 space available and realtime user/dev 4779 not equal to GRANT_AND_LOSE 4781 PendingI Failed accounting interim Open 4782 answer received and realtime 4783 equal to GRANT_AND_LOSE 4785 PendingI Failed accounting interim Disconnect Idle 4786 answer received and realtime user/dev 4787 not equal to GRANT_AND_LOSE 4789 PendingI User service terminated Store PendingI 4790 stop 4791 record 4793 PendingE Successful accounting Idle 4794 event answer received 4796 PendingE Failure to send and buffer Store Idle 4797 space available event 4798 record 4800 PendingE Failure to send and no buffer Idle 4801 space available 4803 PendingE Failed accounting event answer Idle 4804 received 4806 PendingB Successful accounting answer Delete Idle 4807 received record 4809 PendingB Failure to send Idle 4811 PendingB Failed accounting answer Delete Idle 4812 received record 4814 PendingL Successful accounting Idle 4815 stop answer received 4817 PendingL Failure to send and buffer Store Idle 4818 space available stop 4819 record 4821 PendingL Failure to send and no buffer Idle 4822 space available 4824 PendingL Failed accounting stop answer Idle 4825 received 4827 SERVER, STATELESS ACCOUNTING 4828 State Event Action New State 4829 ------------------------------------------------------------- 4831 Idle Accounting start request Send Idle 4832 received, and successfully accounting 4833 processed. start 4834 answer 4836 Idle Accounting event request Send Idle 4837 received, and successfully accounting 4838 processed. event 4839 answer 4841 Idle Interim record received, Send Idle 4842 and successfully processed. accounting 4843 interim 4844 answer 4846 Idle Accounting stop request Send Idle 4847 received, and successfully accounting 4848 processed stop answer 4850 Idle Accounting request received, Send Idle 4851 no space left to store accounting 4852 records answer, 4853 Result-Code 4854 = OUT_OF_ 4855 SPACE 4857 SERVER, STATEFUL ACCOUNTING 4858 State Event Action New State 4859 ------------------------------------------------------------- 4861 Idle Accounting start request Send Open 4862 received, and successfully accounting 4863 processed. start 4864 answer, 4865 Start Ts 4867 Idle Accounting event request Send Idle 4868 received, and successfully accounting 4869 processed. event 4870 answer 4872 Idle Accounting request received, Send Idle 4873 no space left to store accounting 4874 records answer, 4875 Result-Code 4876 = OUT_OF_ 4877 SPACE 4879 Open Interim record received, Send Open 4880 and successfully processed. accounting 4881 interim 4882 answer, 4883 Restart Ts 4885 Open Accounting stop request Send Idle 4886 received, and successfully accounting 4887 processed stop answer, 4888 Stop Ts 4890 Open Accounting request received, Send Idle 4891 no space left to store accounting 4892 records answer, 4893 Result-Code 4894 = OUT_OF_ 4895 SPACE, 4896 Stop Ts 4898 Open Session supervision timer Ts Stop Ts Idle 4899 expired 4901 8.3. Server-Initiated Re-Auth 4903 A Diameter server may initiate a re-authentication and/or re- 4904 authorization service for a particular session by issuing a Re-Auth- 4905 Request (RAR). 4907 For example, for pre-paid services, the Diameter server that 4908 originally authorized a session may need some confirmation that the 4909 user is still using the services. 4911 An access device that receives a RAR message with Session-Id equal to 4912 a currently active session MUST initiate a re-auth towards the user, 4913 if the service supports this particular feature. Each Diameter 4914 application MUST state whether service-initiated re-auth is 4915 supported, since some applications do not allow access devices to 4916 prompt the user for re-auth. 4918 8.3.1. Re-Auth-Request 4920 The Re-Auth-Request (RAR), indicated by the Command-Code set to 258 4921 and the message flags' 'R' bit set, may be sent by any server to the 4922 access device that is providing session service, to request that the 4923 user be re-authenticated and/or re-authorized. 4925 Message Format 4927 ::= < Diameter Header: 258, REQ, PXY > 4928 < Session-Id > 4929 { Origin-Host } 4930 { Origin-Realm } 4931 { Destination-Realm } 4932 { Destination-Host } 4933 { Auth-Application-Id } 4934 { Re-Auth-Request-Type } 4935 [ User-Name ] 4936 [ Origin-State-Id ] 4937 * [ Proxy-Info ] 4938 * [ Route-Record ] 4939 * [ AVP ] 4941 8.3.2. Re-Auth-Answer 4943 The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258 4944 and the message flags' 'R' bit clear, is sent in response to the RAR. 4945 The Result-Code AVP MUST be present, and indicates the disposition of 4946 the request. 4948 A successful RAA message MUST be followed by an application-specific 4949 authentication and/or authorization message. 4951 Message Format 4953 ::= < Diameter Header: 258, PXY > 4954 < Session-Id > 4955 { Result-Code } 4956 { Origin-Host } 4957 { Origin-Realm } 4958 [ User-Name ] 4959 [ Origin-State-Id ] 4960 [ Error-Message ] 4961 [ Error-Reporting-Host ] 4962 * [ Failed-AVP ] 4963 * [ Redirect-Host ] 4964 [ Redirect-Host-Usage ] 4965 [ Redirect-Host-Cache-Time ] 4966 * [ Proxy-Info ] 4967 * [ AVP ] 4969 8.4. Session Termination 4971 It is necessary for a Diameter server that authorized a session, for 4972 which it is maintaining state, to be notified when that session is no 4973 longer active, both for tracking purposes as well as to allow 4974 stateful agents to release any resources that they may have provided 4975 for the user's session. For sessions whose state is not being 4976 maintained, this section is not used. 4978 When a user session that required Diameter authorization terminates, 4979 the access device that provided the service MUST issue a Session- 4980 Termination-Request (STR) message to the Diameter server that 4981 authorized the service, to notify it that the session is no longer 4982 active. An STR MUST be issued when a user session terminates for any 4983 reason, including user logoff, expiration of Session-Timeout, 4984 administrative action, termination upon receipt of an Abort-Session- 4985 Request (see below), orderly shutdown of the access device, etc. 4987 The access device also MUST issue an STR for a session that was 4988 authorized but never actually started. This could occur, for 4989 example, due to a sudden resource shortage in the access device, or 4990 because the access device is unwilling to provide the type of service 4991 requested in the authorization, or because the access device does not 4992 support a mandatory AVP returned in the authorization, etc. 4994 It is also possible that a session that was authorized is never 4995 actually started due to action of a proxy. For example, a proxy may 4996 modify an authorization answer, converting the result from success to 4997 failure, prior to forwarding the message to the access device. If 4998 the answer did not contain an Auth-Session-State AVP with the value 4999 NO_STATE_MAINTAINED, a proxy that causes an authorized session not to 5000 be started MUST issue an STR to the Diameter server that authorized 5001 the session, since the access device has no way of knowing that the 5002 session had been authorized. 5004 A Diameter server that receives an STR message MUST clean up 5005 resources (e.g., session state) associated with the Session-Id 5006 specified in the STR, and return a Session-Termination-Answer. 5008 A Diameter server also MUST clean up resources when the Session- 5009 Timeout expires, or when the Authorization-Lifetime and the Auth- 5010 Grace-Period AVPs expires without receipt of a re-authorization 5011 request, regardless of whether an STR for that session is received. 5012 The access device is not expected to provide service beyond the 5013 expiration of these timers; thus, expiration of either of these 5014 timers implies that the access device may have unexpectedly shut 5015 down. 5017 8.4.1. Session-Termination-Request 5019 The Session-Termination-Request (STR), indicated by the Command-Code 5020 set to 275 and the Command Flags' 'R' bit set, is sent by the access 5021 device to inform the Diameter Server that an authenticated and/or 5022 authorized session is being terminated. 5024 Message Format 5026 ::= < Diameter Header: 275, REQ, PXY > 5027 < Session-Id > 5028 { Origin-Host } 5029 { Origin-Realm } 5030 { Destination-Realm } 5031 { Auth-Application-Id } 5032 { Termination-Cause } 5033 [ User-Name ] 5034 [ Destination-Host ] 5035 * [ Class ] 5036 [ Origin-State-Id ] 5037 * [ Proxy-Info ] 5038 * [ Route-Record ] 5039 * [ AVP ] 5041 8.4.2. Session-Termination-Answer 5043 The Session-Termination-Answer (STA), indicated by the Command-Code 5044 set to 275 and the message flags' 'R' bit clear, is sent by the 5045 Diameter Server to acknowledge the notification that the session has 5046 been terminated. The Result-Code AVP MUST be present, and MAY 5047 contain an indication that an error occurred while servicing the STR. 5049 Upon sending or receipt of the STA, the Diameter Server MUST release 5050 all resources for the session indicated by the Session-Id AVP. Any 5051 intermediate server in the Proxy-Chain MAY also release any 5052 resources, if necessary. 5054 Message Format 5056 ::= < Diameter Header: 275, PXY > 5057 < Session-Id > 5058 { Result-Code } 5059 { Origin-Host } 5060 { Origin-Realm } 5061 [ User-Name ] 5062 * [ Class ] 5063 [ Error-Message ] 5064 [ Error-Reporting-Host ] 5065 * [ Failed-AVP ] 5066 [ Origin-State-Id ] 5067 * [ Redirect-Host ] 5068 [ Redirect-Host-Usage ] 5069 ^ 5070 [ Redirect-Max-Cache-Time ] 5071 * [ Proxy-Info ] 5072 * [ AVP ] 5074 8.5. Aborting a Session 5076 A Diameter server may request that the access device stop providing 5077 service for a particular session by issuing an Abort-Session-Request 5078 (ASR). 5080 For example, the Diameter server that originally authorized the 5081 session may be required to cause that session to be stopped for 5082 credit or other reasons that were not anticipated when the session 5083 was first authorized. On the other hand, an operator may maintain a 5084 management server for the purpose of issuing ASRs to administratively 5085 remove users from the network. 5087 An access device that receives an ASR with Session-ID equal to a 5088 currently active session MAY stop the session. Whether the access 5089 device stops the session or not is implementation- and/or 5090 configuration-dependent. For example, an access device may honor 5091 ASRs from certain agents only. In any case, the access device MUST 5092 respond with an Abort-Session-Answer, including a Result-Code AVP to 5093 indicate what action it took. 5095 Note that if the access device does stop the session upon receipt of 5096 an ASR, it issues an STR to the authorizing server (which may or may 5097 not be the agent issuing the ASR) just as it would if the session 5098 were terminated for any other reason. 5100 8.5.1. Abort-Session-Request 5102 The Abort-Session-Request (ASR), indicated by the Command-Code set to 5103 274 and the message flags' 'R' bit set, may be sent by any server to 5104 the access device that is providing session service, to request that 5105 the session identified by the Session-Id be stopped. 5107 Message Format 5109 ::= < Diameter Header: 274, REQ, PXY > 5110 < Session-Id > 5111 { Origin-Host } 5112 { Origin-Realm } 5113 { Destination-Realm } 5114 { Destination-Host } 5115 { Auth-Application-Id } 5116 [ User-Name ] 5117 [ Origin-State-Id ] 5118 * [ Proxy-Info ] 5119 * [ Route-Record ] 5120 * [ AVP ] 5122 8.5.2. Abort-Session-Answer 5124 The Abort-Session-Answer (ASA), indicated by the Command-Code set to 5125 274 and the message flags' 'R' bit clear, is sent in response to the 5126 ASR. The Result-Code AVP MUST be present, and indicates the 5127 disposition of the request. 5129 If the session identified by Session-Id in the ASR was successfully 5130 terminated, Result-Code is set to DIAMETER_SUCCESS. If the session 5131 is not currently active, Result-Code is set to 5132 DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the 5133 session for any other reason, Result-Code is set to 5134 DIAMETER_UNABLE_TO_COMPLY. 5136 Message Format 5138 ::= < Diameter Header: 274, PXY > 5139 < Session-Id > 5140 { Result-Code } 5141 { Origin-Host } 5142 { Origin-Realm } 5143 [ User-Name ] 5144 [ Origin-State-Id ] 5145 [ Error-Message ] 5146 [ Error-Reporting-Host ] 5147 * [ Failed-AVP ] 5148 * [ Redirect-Host ] 5149 [ Redirect-Host-Usage ] 5150 [ Redirect-Max-Cache-Time ] 5151 * [ Proxy-Info ] 5152 * [ AVP ] 5154 8.6. Inferring Session Termination from Origin-State-Id 5156 Origin-State-Id is used to allow rapid detection of terminated 5157 sessions for which no STR would have been issued, due to 5158 unanticipated shutdown of an access device. 5160 By including Origin-State-Id in CER/CEA messages, an access device 5161 allows a next-hop server to determine immediately upon connection 5162 whether the device has lost its sessions since the last connection. 5164 By including Origin-State-Id in request messages, an access device 5165 also allows a server with which it communicates via proxy to make 5166 such a determination. However, a server that is not directly 5167 connected with the access device will not discover that the access 5168 device has been restarted unless and until it receives a new request 5169 from the access device. Thus, use of this mechanism across proxies 5170 is opportunistic rather than reliable, but useful nonetheless. 5172 When a Diameter server receives an Origin-State-Id that is greater 5173 than the Origin-State-Id previously received from the same issuer, it 5174 may assume that the issuer has lost state since the previous message 5175 and that all sessions that were active under the lower Origin-State- 5176 Id have been terminated. The Diameter server MAY clean up all 5177 session state associated with such lost sessions, and MAY also issues 5178 STRs for all such lost sessions that were authorized on upstream 5179 servers, to allow session state to be cleaned up globally. 5181 8.7. Auth-Request-Type AVP 5183 The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is 5184 included in application-specific auth requests to inform the peers 5185 whether a user is to be authenticated only, authorized only or both. 5186 Note any value other than both MAY cause RADIUS interoperability 5187 issues. The following values are defined: 5189 AUTHENTICATE_ONLY 1 5191 The request being sent is for authentication only, and MUST 5192 contain the relevant application specific authentication AVPs that 5193 are needed by the Diameter server to authenticate the user. 5195 AUTHORIZE_ONLY 2 5197 The request being sent is for authorization only, and MUST contain 5198 the application specific authorization AVPs that are necessary to 5199 identify the service being requested/offered. 5201 AUTHORIZE_AUTHENTICATE 3 5203 The request contains a request for both authentication and 5204 authorization. The request MUST include both the relevant 5205 application specific authentication information, and authorization 5206 information necessary to identify the service being requested/ 5207 offered. 5209 8.8. Session-Id AVP 5211 The Session-Id AVP (AVP Code 263) is of type UTF8String and is used 5212 to identify a specific session (see Section 8). All messages 5213 pertaining to a specific session MUST include only one Session-Id AVP 5214 and the same value MUST be used throughout the life of a session. 5215 When present, the Session-Id SHOULD appear immediately following the 5216 Diameter Header (see Section 3). 5218 The Session-Id MUST be globally and eternally unique, as it is meant 5219 to uniquely identify a user session without reference to any other 5220 information, and may be needed to correlate historical authentication 5221 information with accounting information. The Session-Id includes a 5222 mandatory portion and an implementation-defined portion; a 5223 recommended format for the implementation-defined portion is outlined 5224 below. 5226 The Session-Id MUST begin with the sender's identity encoded in the 5227 DiameterIdentity type (see Section 4.4). The remainder of the 5228 Session-Id is delimited by a ";" character, and MAY be any sequence 5229 that the client can guarantee to be eternally unique; however, the 5230 following format is recommended, (square brackets [] indicate an 5231 optional element): 5233 ;;[;] 5235 and are decimal representations of the 5236 high and low 32 bits of a monotonically increasing 64-bit value. The 5237 64-bit value is rendered in two part to simplify formatting by 32-bit 5238 processors. At startup, the high 32 bits of the 64-bit value MAY be 5239 initialized to the time, and the low 32 bits MAY be initialized to 5240 zero. This will for practical purposes eliminate the possibility of 5241 overlapping Session-Ids after a reboot, assuming the reboot process 5242 takes longer than a second. Alternatively, an implementation MAY 5243 keep track of the increasing value in non-volatile memory. 5245 is implementation specific but may include a modem's 5246 device Id, a layer 2 address, timestamp, etc. 5248 Example, in which there is no optional value: 5249 accesspoint7.acme.com;1876543210;523 5251 Example, in which there is an optional value: 5252 accesspoint7.acme.com;1876543210;523;mobile@200.1.1.88 5254 The Session-Id is created by the Diameter application initiating the 5255 session, which in most cases is done by the client. Note that a 5256 Session-Id MAY be used for both the authorization and accounting 5257 commands of a given application. 5259 8.9. Authorization-Lifetime AVP 5261 The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32 5262 and contains the maximum number of seconds of service to be provided 5263 to the user before the user is to be re-authenticated and/or re- 5264 authorized. Great care should be taken when the Authorization- 5265 Lifetime value is determined, since a low, non-zero, value could 5266 create significant Diameter traffic, which could congest both the 5267 network and the agents. 5269 A value of zero (0) means that immediate re-auth is necessary by the 5270 access device. This is typically used in cases where multiple 5271 authentication methods are used, and a successful auth response with 5272 this AVP set to zero is used to signal that the next authentication 5273 method is to be immediately initiated. The absence of this AVP, or a 5274 value of all ones (meaning all bits in the 32 bit field are set to 5275 one) means no re-auth is expected. 5277 If both this AVP and the Session-Timeout AVP are present in a 5278 message, the value of the latter MUST NOT be smaller than the 5279 Authorization-Lifetime AVP. 5281 An Authorization-Lifetime AVP MAY be present in re-authorization 5282 messages, and contains the number of seconds the user is authorized 5283 to receive service from the time the re-auth answer message is 5284 received by the access device. 5286 This AVP MAY be provided by the client as a hint of the maximum 5287 lifetime that it is willing to accept. However, the server MAY 5288 return a value that is equal to, or smaller, than the one provided by 5289 the client. 5291 8.10. Auth-Grace-Period AVP 5293 The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and 5294 contains the number of seconds the Diameter server will wait 5295 following the expiration of the Authorization-Lifetime AVP before 5296 cleaning up resources for the session. 5298 8.11. Auth-Session-State AVP 5300 The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and 5301 specifies whether state is maintained for a particular session. The 5302 client MAY include this AVP in requests as a hint to the server, but 5303 the value in the server's answer message is binding. The following 5304 values are supported: 5306 STATE_MAINTAINED 0 5308 This value is used to specify that session state is being 5309 maintained, and the access device MUST issue a session termination 5310 message when service to the user is terminated. This is the 5311 default value. 5313 NO_STATE_MAINTAINED 1 5315 This value is used to specify that no session termination messages 5316 will be sent by the access device upon expiration of the 5317 Authorization-Lifetime. 5319 8.12. Re-Auth-Request-Type AVP 5321 The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and 5322 is included in application-specific auth answers to inform the client 5323 of the action expected upon expiration of the Authorization-Lifetime. 5324 If the answer message contains an Authorization-Lifetime AVP with a 5325 positive value, the Re-Auth-Request-Type AVP MUST be present in an 5326 answer message. The following values are defined: 5328 AUTHORIZE_ONLY 0 5330 An authorization only re-auth is expected upon expiration of the 5331 Authorization-Lifetime. This is the default value if the AVP is 5332 not present in answer messages that include the Authorization- 5333 Lifetime. 5335 AUTHORIZE_AUTHENTICATE 1 5337 An authentication and authorization re-auth is expected upon 5338 expiration of the Authorization-Lifetime. 5340 8.13. Session-Timeout AVP 5342 The Session-Timeout AVP (AVP Code 27) [RFC2865] is of type Unsigned32 5343 and contains the maximum number of seconds of service to be provided 5344 to the user before termination of the session. When both the 5345 Session-Timeout and the Authorization-Lifetime AVPs are present in an 5346 answer message, the former MUST be equal to or greater than the value 5347 of the latter. 5349 A session that terminates on an access device due to the expiration 5350 of the Session-Timeout MUST cause an STR to be issued, unless both 5351 the access device and the home server had previously agreed that no 5352 session termination messages would be sent (see Section 8.9). 5354 A Session-Timeout AVP MAY be present in a re-authorization answer 5355 message, and contains the remaining number of seconds from the 5356 beginning of the re-auth. 5358 A value of zero, or the absence of this AVP, means that this session 5359 has an unlimited number of seconds before termination. 5361 This AVP MAY be provided by the client as a hint of the maximum 5362 timeout that it is willing to accept. However, the server MAY return 5363 a value that is equal to, or smaller, than the one provided by the 5364 client. 5366 8.14. User-Name AVP 5368 The User-Name AVP (AVP Code 1) [RFC2865] is of type UTF8String, which 5369 contains the User-Name, in a format consistent with the NAI 5370 specification [RFC4282]. 5372 8.15. Termination-Cause AVP 5374 The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and 5375 is used to indicate the reason why a session was terminated on the 5376 access device. The following values are defined: 5378 DIAMETER_LOGOUT 1 5380 The user initiated a disconnect 5382 DIAMETER_SERVICE_NOT_PROVIDED 2 5384 This value is used when the user disconnected prior to the receipt 5385 of the authorization answer message. 5387 DIAMETER_BAD_ANSWER 3 5389 This value indicates that the authorization answer received by the 5390 access device was not processed successfully. 5392 DIAMETER_ADMINISTRATIVE 4 5394 The user was not granted access, or was disconnected, due to 5395 administrative reasons, such as the receipt of a Abort-Session- 5396 Request message. 5398 DIAMETER_LINK_BROKEN 5 5400 The communication to the user was abruptly disconnected. 5402 DIAMETER_AUTH_EXPIRED 6 5404 The user's access was terminated since its authorized session time 5405 has expired. 5407 DIAMETER_USER_MOVED 7 5409 The user is receiving services from another access device. 5411 DIAMETER_SESSION_TIMEOUT 8 5413 The user's session has timed out, and service has been terminated. 5415 8.16. Origin-State-Id AVP 5417 The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a 5418 monotonically increasing value that is advanced whenever a Diameter 5419 entity restarts with loss of previous state, for example upon reboot. 5420 Origin-State-Id MAY be included in any Diameter message, including 5421 CER. 5423 A Diameter entity issuing this AVP MUST create a higher value for 5424 this AVP each time its state is reset. A Diameter entity MAY set 5425 Origin-State-Id to the time of startup, or it MAY use an incrementing 5426 counter retained in non-volatile memory across restarts. 5428 The Origin-State-Id, if present, MUST reflect the state of the entity 5429 indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST 5430 either remove Origin-State-Id or modify it appropriately as well. 5431 Typically, Origin-State-Id is used by an access device that always 5432 starts up with no active sessions; that is, any session active prior 5433 to restart will have been lost. By including Origin-State-Id in a 5434 message, it allows other Diameter entities to infer that sessions 5435 associated with a lower Origin-State-Id are no longer active. If an 5436 access device does not intend for such inferences to be made, it MUST 5437 either not include Origin-State-Id in any message, or set its value 5438 to 0. 5440 8.17. Session-Binding AVP 5442 The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY 5443 be present in application-specific authorization answer messages. If 5444 present, this AVP MAY inform the Diameter client that all future 5445 application-specific re-auth messages for this session MUST be sent 5446 to the same authorization server. This AVP MAY also specify that a 5447 Session-Termination-Request message for this session MUST be sent to 5448 the same authorizing server. 5450 This field is a bit mask, and the following bits have been defined: 5452 RE_AUTH 1 5454 When set, future re-auth messages for this session MUST NOT 5455 include the Destination-Host AVP. When cleared, the default 5456 value, the Destination-Host AVP MUST be present in all re-auth 5457 messages for this session. 5459 STR 2 5461 When set, the STR message for this session MUST NOT include the 5462 Destination-Host AVP. When cleared, the default value, the 5463 Destination-Host AVP MUST be present in the STR message for this 5464 session. 5466 ACCOUNTING 4 5468 When set, all accounting messages for this session MUST NOT 5469 include the Destination-Host AVP. When cleared, the default 5470 value, the Destination-Host AVP, if known, MUST be present in all 5471 accounting messages for this session. 5473 8.18. Session-Server-Failover AVP 5475 The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated, 5476 and MAY be present in application-specific authorization answer 5477 messages that either do not include the Session-Binding AVP or 5478 include the Session-Binding AVP with any of the bits set to a zero 5479 value. If present, this AVP MAY inform the Diameter client that if a 5480 re-auth or STR message fails due to a delivery problem, the Diameter 5481 client SHOULD issue a subsequent message without the Destination-Host 5482 AVP. When absent, the default value is REFUSE_SERVICE. 5484 The following values are supported: 5486 REFUSE_SERVICE 0 5488 If either the re-auth or the STR message delivery fails, terminate 5489 service with the user, and do not attempt any subsequent attempts. 5491 TRY_AGAIN 1 5493 If either the re-auth or the STR message delivery fails, resend 5494 the failed message without the Destination-Host AVP present. 5496 ALLOW_SERVICE 2 5498 If re-auth message delivery fails, assume that re-authorization 5499 succeeded. If STR message delivery fails, terminate the session. 5501 TRY_AGAIN_ALLOW_SERVICE 3 5503 If either the re-auth or the STR message delivery fails, resend 5504 the failed message without the Destination-Host AVP present. If 5505 the second delivery fails for re-auth, assume re-authorization 5506 succeeded. If the second delivery fails for STR, terminate the 5507 session. 5509 8.19. Multi-Round-Time-Out AVP 5511 The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32, 5512 and SHOULD be present in application-specific authorization answer 5513 messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH. 5514 This AVP contains the maximum number of seconds that the access 5515 device MUST provide the user in responding to an authentication 5516 request. 5518 8.20. Class AVP 5520 The Class AVP (AVP Code 25) is of type OctetString and is used to by 5521 Diameter servers to return state information to the access device. 5522 When one or more Class AVPs are present in application-specific 5523 authorization answer messages, they MUST be present in subsequent re- 5524 authorization, session termination and accounting messages. Class 5525 AVPs found in a re-authorization answer message override the ones 5526 found in any previous authorization answer message. Diameter server 5527 implementations SHOULD NOT return Class AVPs that require more than 5528 4096 bytes of storage on the Diameter client. A Diameter client that 5529 receives Class AVPs whose size exceeds local available storage MUST 5530 terminate the session. 5532 8.21. Event-Timestamp AVP 5534 The Event-Timestamp (AVP Code 55) is of type Time, and MAY be 5535 included in an Accounting-Request and Accounting-Answer messages to 5536 record the time that the reported event occurred, in seconds since 5537 January 1, 1900 00:00 UTC. 5539 9. Accounting 5541 This accounting protocol is based on a server directed model with 5542 capabilities for real-time delivery of accounting information. 5543 Several fault resilience methods [RFC2975] have been built in to the 5544 protocol in order minimize loss of accounting data in various fault 5545 situations and under different assumptions about the capabilities of 5546 the used devices. 5548 9.1. Server Directed Model 5550 The server directed model means that the device generating the 5551 accounting data gets information from either the authorization server 5552 (if contacted) or the accounting server regarding the way accounting 5553 data shall be forwarded. This information includes accounting record 5554 timeliness requirements. 5556 As discussed in [RFC2975], real-time transfer of accounting records 5557 is a requirement, such as the need to perform credit limit checks and 5558 fraud detection. Note that batch accounting is not a requirement, 5559 and is therefore not supported by Diameter. Should batched 5560 accounting be required in the future, a new Diameter application will 5561 need to be created, or it could be handled using another protocol. 5562 Note, however, that even if at the Diameter layer accounting requests 5563 are processed one by one, transport protocols used under Diameter 5564 typically batch several requests in the same packet under heavy 5565 traffic conditions. This may be sufficient for many applications. 5567 The authorization server (chain) directs the selection of proper 5568 transfer strategy, based on its knowledge of the user and 5569 relationships of roaming partnerships. The server (or agents) uses 5570 the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to 5571 control the operation of the Diameter peer operating as a client. 5572 The Acct-Interim-Interval AVP, when present, instructs the Diameter 5573 node acting as a client to produce accounting records continuously 5574 even during a session. Accounting-Realtime-Required AVP is used to 5575 control the behavior of the client when the transfer of accounting 5576 records from the Diameter client is delayed or unsuccessful. 5578 The Diameter accounting server MAY override the interim interval or 5579 the realtime requirements by including the Acct-Interim-Interval or 5580 Accounting-Realtime-Required AVP in the Accounting-Answer message. 5581 When one of these AVPs is present, the latest value received SHOULD 5582 be used in further accounting activities for the same session. 5584 9.2. Protocol Messages 5586 A Diameter node that receives a successful authentication and/or 5587 authorization messages from the Home AAA server MUST collect 5588 accounting information for the session. The Accounting-Request 5589 message is used to transmit the accounting information to the Home 5590 AAA server, which MUST reply with the Accounting-Answer message to 5591 confirm reception. The Accounting-Answer message includes the 5592 Result-Code AVP, which MAY indicate that an error was present in the 5593 accounting message. A rejected Accounting-Request message MAY cause 5594 the user's session to be terminated, depending on the value of the 5595 Accounting-Realtime-Required AVP received earlier for the session in 5596 question. 5598 Each Diameter Accounting protocol message MAY be compressed, in order 5599 to reduce network bandwidth usage. If IPsec and IKE are used to 5600 secure the Diameter session, then IP compression [RFC3173] MAY be 5601 used and IKE [RFC2409] MAY be used to negotiate the compression 5602 parameters. If TLS is used to secure the Diameter session, then TLS 5603 compression [RFC2246] MAY be used. 5605 9.3. Application document requirements 5607 Each Diameter application (e.g., NASREQ, MobileIP), MUST define their 5608 Service-Specific AVPs that MUST be present in the Accounting-Request 5609 message in a section entitled "Accounting AVPs". The application 5610 MUST assume that the AVPs described in this document will be present 5611 in all Accounting messages, so only their respective service-specific 5612 AVPs need to be defined in this section. 5614 9.4. Fault Resilience 5616 Diameter Base protocol mechanisms are used to overcome small message 5617 loss and network faults of temporary nature. 5619 Diameter peers acting as clients MUST implement the use of failover 5620 to guard against server failures and certain network failures. 5621 Diameter peers acting as agents or related off-line processing 5622 systems MUST detect duplicate accounting records caused by the 5623 sending of same record to several servers and duplication of messages 5624 in transit. This detection MUST be based on the inspection of the 5625 Session-Id and Accounting-Record-Number AVP pairs. Appendix D 5626 discusses duplicate detection needs and implementation issues. 5628 Diameter clients MAY have non-volatile memory for the safe storage of 5629 accounting records over reboots or extended network failures, network 5630 partitions, and server failures. If such memory is available, the 5631 client SHOULD store new accounting records there as soon as the 5632 records are created and until a positive acknowledgement of their 5633 reception from the Diameter Server has been received. Upon a reboot, 5634 the client MUST starting sending the records in the non-volatile 5635 memory to the accounting server with appropriate modifications in 5636 termination cause, session length, and other relevant information in 5637 the records. 5639 A further application of this protocol may include AVPs to control 5640 how many accounting records may at most be stored in the Diameter 5641 client without committing them to the non-volatile memory or 5642 transferring them to the Diameter server. 5644 The client SHOULD NOT remove the accounting data from any of its 5645 memory areas before the correct Accounting-Answer has been received. 5646 The client MAY remove oldest, undelivered or yet unacknowledged 5647 accounting data if it runs out of resources such as memory. It is an 5648 implementation dependent matter for the client to accept new sessions 5649 under this condition. 5651 9.5. Accounting Records 5653 In all accounting records, the Session-Id AVP MUST be present; the 5654 User-Name AVP MUST be present if it is available to the Diameter 5655 client. If strong authentication across agents is required, end-to- 5656 end security may be used for authentication purposes. 5658 Different types of accounting records are sent depending on the 5659 actual type of accounted service and the authorization server's 5660 directions for interim accounting. If the accounted service is a 5661 one-time event, meaning that the start and stop of the event are 5662 simultaneous, then the Accounting-Record-Type AVP MUST be present and 5663 set to the value EVENT_RECORD. 5665 If the accounted service is of a measurable length, then the AVP MUST 5666 use the values START_RECORD, STOP_RECORD, and possibly, 5667 INTERIM_RECORD. If the authorization server has not directed interim 5668 accounting to be enabled for the session, two accounting records MUST 5669 be generated for each service of type session. When the initial 5670 Accounting-Request for a given session is sent, the Accounting- 5671 Record-Type AVP MUST be set to the value START_RECORD. When the last 5672 Accounting-Request is sent, the value MUST be STOP_RECORD. 5674 If the authorization server has directed interim accounting to be 5675 enabled, the Diameter client MUST produce additional records between 5676 the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The 5677 production of these records is directed by Acct-Interim-Interval as 5678 well as any re-authentication or re-authorization of the session. 5679 The Diameter client MUST overwrite any previous interim accounting 5680 records that are locally stored for delivery, if a new record is 5681 being generated for the same session. This ensures that only one 5682 pending interim record can exist on an access device for any given 5683 session. 5685 A particular value of Accounting-Sub-Session-Id MUST appear only in 5686 one sequence of accounting records from a DIAMETER client, except for 5687 the purposes of retransmission. The one sequence that is sent MUST 5688 be either one record with Accounting-Record-Type AVP set to the value 5689 EVENT_RECORD, or several records starting with one having the value 5690 START_RECORD, followed by zero or more INTERIM_RECORD and a single 5691 STOP_RECORD. A particular Diameter application specification MUST 5692 define the type of sequences that MUST be used. 5694 9.6. Correlation of Accounting Records 5696 The Diameter protocol's Session-Id AVP, which is globally unique (see 5697 Section 8.8), is used during the authorization phase to identify a 5698 particular session. Services that do not require any authorization 5699 still use the Session-Id AVP to identify sessions. Accounting 5700 messages MAY use a different Session-Id from that sent in 5701 authorization messages. Specific applications MAY require different 5702 a Session-ID for accounting messages. 5704 However, there are certain applications that require multiple 5705 accounting sub-sessions. Such applications would send messages with 5706 a constant Session-Id AVP, but a different Accounting-Sub-Session-Id 5707 AVP. In these cases, correlation is performed using the Session-Id. 5708 It is important to note that receiving a STOP_RECORD with no 5709 Accounting-Sub-Session-Id AVP when sub-sessions were originally used 5710 in the START_RECORD messages implies that all sub-sessions are 5711 terminated. 5713 Furthermore, there are certain applications where a user receives 5714 service from different access devices (e.g., Mobile IPv4), each with 5715 their own unique Session-Id. In such cases, the Acct-Multi-Session- 5716 Id AVP is used for correlation. During authorization, a server that 5717 determines that a request is for an existing session SHOULD include 5718 the Acct-Multi-Session-Id AVP, which the access device MUST include 5719 in all subsequent accounting messages. 5721 The Acct-Multi-Session-Id AVP MAY include the value of the original 5722 Session-Id. It's contents are implementation specific, but MUST be 5723 globally unique across other Acct-Multi-Session-Id, and MUST NOT 5724 change during the life of a session. 5726 A Diameter application document MUST define the exact concept of a 5727 session that is being accounted, and MAY define the concept of a 5728 multi-session. For instance, the NASREQ DIAMETER application treats 5729 a single PPP connection to a Network Access Server as one session, 5730 and a set of Multilink PPP sessions as one multi-session. 5732 9.7. Accounting Command-Codes 5734 This section defines Command-Code values that MUST be supported by 5735 all Diameter implementations that provide Accounting services. 5737 9.7.1. Accounting-Request 5739 The Accounting-Request (ACR) command, indicated by the Command-Code 5740 field set to 271 and the Command Flags' 'R' bit set, is sent by a 5741 Diameter node, acting as a client, in order to exchange accounting 5742 information with a peer. 5744 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs 5745 MUST be present. If the Vendor-Specific-Application-Id grouped AVP 5746 is present, it must have an Acct-Application-Id inside. 5748 The AVP listed below SHOULD include service specific accounting AVPs, 5749 as described in Section 9.3. 5751 Message Format 5753 ::= < Diameter Header: 271, REQ, PXY > 5754 < Session-Id > 5755 { Origin-Host } 5756 { Origin-Realm } 5757 { Destination-Realm } 5758 { Accounting-Record-Type } 5759 { Accounting-Record-Number } 5760 [ Acct-Application-Id ] 5761 [ Vendor-Specific-Application-Id ] 5762 [ User-Name ] 5763 [ Accounting-Sub-Session-Id ] 5764 [ Acct-Session-Id ] 5765 [ Acct-Multi-Session-Id ] 5766 [ Acct-Interim-Interval ] 5767 [ Accounting-Realtime-Required ] 5768 [ Origin-State-Id ] 5769 [ Event-Timestamp ] 5770 * [ Proxy-Info ] 5771 * [ Route-Record ] 5772 * [ AVP ] 5774 9.7.2. Accounting-Answer 5776 The Accounting-Answer (ACA) command, indicated by the Command-Code 5777 field set to 271 and the Command Flags' 'R' bit cleared, is used to 5778 acknowledge an Accounting-Request command. The Accounting-Answer 5779 command contains the same Session-Id and includes the usage AVPs only 5780 if CMS is in use when sending this command. Note that the inclusion 5781 of the usage AVPs when CMS is not being used leads to unnecessarily 5782 large answer messages, and can not be used as a server's proof of the 5783 receipt of these AVPs in an end-to-end fashion. If the Accounting- 5784 Request was protected by end-to-end security, then the corresponding 5785 ACA message MUST be protected by end-to-end security. 5787 Only the target Diameter Server, known as the home Diameter Server, 5788 SHOULD respond with the Accounting-Answer command. 5790 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs 5791 MUST be present. If the Vendor-Specific-Application-Id grouped AVP 5792 is present, it must have an Acct-Application-Id inside. 5794 The AVP listed below SHOULD include service specific accounting AVPs, 5795 as described in Section 9.3. 5797 Message Format 5799 ::= < Diameter Header: 271, PXY > 5800 < Session-Id > 5801 { Result-Code } 5802 { Origin-Host } 5803 { Origin-Realm } 5804 { Accounting-Record-Type } 5805 { Accounting-Record-Number } 5806 [ Acct-Application-Id ] 5807 [ Vendor-Specific-Application-Id ] 5808 [ User-Name ] 5809 [ Accounting-Sub-Session-Id ] 5810 [ Acct-Session-Id ] 5811 [ Acct-Multi-Session-Id ] 5812 [ Error-Reporting-Host ] 5813 [ Acct-Interim-Interval ] 5814 [ Accounting-Realtime-Required ] 5815 [ Origin-State-Id ] 5816 [ Event-Timestamp ] 5817 * [ Proxy-Info ] 5818 * [ AVP ] 5820 9.8. Accounting AVPs 5822 This section contains AVPs that describe accounting usage information 5823 related to a specific session. 5825 9.8.1. Accounting-Record-Type AVP 5827 The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated 5828 and contains the type of accounting record being sent. The following 5829 values are currently defined for the Accounting-Record-Type AVP: 5831 EVENT_RECORD 1 5833 An Accounting Event Record is used to indicate that a one-time 5834 event has occurred (meaning that the start and end of the event 5835 are simultaneous). This record contains all information relevant 5836 to the service, and is the only record of the service. 5838 START_RECORD 2 5840 An Accounting Start, Interim, and Stop Records are used to 5841 indicate that a service of a measurable length has been given. An 5842 Accounting Start Record is used to initiate an accounting session, 5843 and contains accounting information that is relevant to the 5844 initiation of the session. 5846 INTERIM_RECORD 3 5848 An Interim Accounting Record contains cumulative accounting 5849 information for an existing accounting session. Interim 5850 Accounting Records SHOULD be sent every time a re-authentication 5851 or re-authorization occurs. Further, additional interim record 5852 triggers MAY be defined by application-specific Diameter 5853 applications. The selection of whether to use INTERIM_RECORD 5854 records is done by the Acct-Interim-Interval AVP. 5856 STOP_RECORD 4 5858 An Accounting Stop Record is sent to terminate an accounting 5859 session and contains cumulative accounting information relevant to 5860 the existing session. 5862 9.8.2. Acct-Interim-Interval 5864 The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and 5865 is sent from the Diameter home authorization server to the Diameter 5866 client. The client uses information in this AVP to decide how and 5867 when to produce accounting records. With different values in this 5868 AVP, service sessions can result in one, two, or two+N accounting 5869 records, based on the needs of the home-organization. The following 5870 accounting record production behavior is directed by the inclusion of 5871 this AVP: 5873 1. The omission of the Acct-Interim-Interval AVP or its inclusion 5874 with Value field set to 0 means that EVENT_RECORD, START_RECORD, 5875 and STOP_RECORD are produced, as appropriate for the service. 5877 2. The inclusion of the AVP with Value field set to a non-zero value 5878 means that INTERIM_RECORD records MUST be produced between the 5879 START_RECORD and STOP_RECORD records. The Value field of this 5880 AVP is the nominal interval between these records in seconds. 5881 The Diameter node that originates the accounting information, 5882 known as the client, MUST produce the first INTERIM_RECORD record 5883 roughly at the time when this nominal interval has elapsed from 5884 the START_RECORD, the next one again as the interval has elapsed 5885 once more, and so on until the session ends and a STOP_RECORD 5886 record is produced. 5888 The client MUST ensure that the interim record production times 5889 are randomized so that large accounting message storms are not 5890 created either among records or around a common service start 5891 time. 5893 9.8.3. Accounting-Record-Number AVP 5895 The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32 5896 and identifies this record within one session. As Session-Id AVPs 5897 are globally unique, the combination of Session-Id and Accounting- 5898 Record-Number AVPs is also globally unique, and can be used in 5899 matching accounting records with confirmations. An easy way to 5900 produce unique numbers is to set the value to 0 for records of type 5901 EVENT_RECORD and START_RECORD, and set the value to 1 for the first 5902 INTERIM_RECORD, 2 for the second, and so on until the value for 5903 STOP_RECORD is one more than for the last INTERIM_RECORD. 5905 9.8.4. Acct-Session-Id AVP 5907 The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only 5908 used when RADIUS/Diameter translation occurs. This AVP contains the 5909 contents of the RADIUS Acct-Session-Id attribute. 5911 9.8.5. Acct-Multi-Session-Id AVP 5913 The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String, 5914 following the format specified in Section 8.8. The Acct-Multi- 5915 Session-Id AVP is used to link together multiple related accounting 5916 sessions, where each session would have a unique Session-Id, but the 5917 same Acct-Multi-Session-Id AVP. This AVP MAY be returned by the 5918 Diameter server in an authorization answer, and MUST be used in all 5919 accounting messages for the given session. 5921 9.8.6. Accounting-Sub-Session-Id AVP 5923 The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type 5924 Unsigned64 and contains the accounting sub-session identifier. The 5925 combination of the Session-Id and this AVP MUST be unique per sub- 5926 session, and the value of this AVP MUST be monotonically increased by 5927 one for all new sub-sessions. The absence of this AVP implies no 5928 sub-sessions are in use, with the exception of an Accounting-Request 5929 whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD 5930 message with no Accounting-Sub-Session-Id AVP present will signal the 5931 termination of all sub-sessions for a given Session-Id. 5933 9.8.7. Accounting-Realtime-Required AVP 5935 The Accounting-Realtime-Required AVP (AVP Code 483) is of type 5936 Enumerated and is sent from the Diameter home authorization server to 5937 the Diameter client or in the Accounting-Answer from the accounting 5938 server. The client uses information in this AVP to decide what to do 5939 if the sending of accounting records to the accounting server has 5940 been temporarily prevented due to, for instance, a network problem. 5942 DELIVER_AND_GRANT 1 5944 The AVP with Value field set to DELIVER_AND_GRANT means that the 5945 service MUST only be granted as long as there is a connection to 5946 an accounting server. Note that the set of alternative accounting 5947 servers are treated as one server in this sense. Having to move 5948 the accounting record stream to a backup server is not a reason to 5949 discontinue the service to the user. 5951 GRANT_AND_STORE 2 5953 The AVP with Value field set to GRANT_AND_STORE means that service 5954 SHOULD be granted if there is a connection, or as long as records 5955 can still be stored as described in Section 9.4. 5957 This is the default behavior if the AVP isn't included in the 5958 reply from the authorization server. 5960 GRANT_AND_LOSE 3 5962 The AVP with Value field set to GRANT_AND_LOSE means that service 5963 SHOULD be granted even if the records can not be delivered or 5964 stored. 5966 10. AVP Occurrence Table 5968 The following tables presents the AVPs defined in this document, and 5969 specifies in which Diameter messages they MAY, or MAY NOT be present. 5970 Note that AVPs that can only be present within a Grouped AVP are not 5971 represented in this table. 5973 The table uses the following symbols: 5975 0 The AVP MUST NOT be present in the message. 5977 0+ Zero or more instances of the AVP MAY be present in the 5978 message. 5980 0-1 Zero or one instance of the AVP MAY be present in the message. 5981 It is considered an error if there are more than one instance of 5982 the AVP. 5984 1 One instance of the AVP MUST be present in the message. 5986 1+ At least one instance of the AVP MUST be present in the 5987 message. 5989 10.1. Base Protocol Command AVP Table 5991 The table in this section is limited to the non-accounting Command 5992 Codes defined in this specification. 5994 +-----------------------------------------------+ 5995 | Command-Code | 5996 +---+---+---+---+---+---+---+---+---+---+---+---+ 5997 Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA| 5998 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ 5999 Acct-Interim- |0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | 6000 Interval | | | | | | | | | | | | | 6001 Accounting-Realtime-|0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | 6002 Required | | | | | | | | | | | | | 6003 Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6004 Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | 6005 Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6006 Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6007 Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6008 Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6009 Lifetime | | | | | | | | | | | | | 6010 Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ | 6011 Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 | 6012 Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | 6013 Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6014 Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1| 6015 Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6016 Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ | 6017 Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6018 Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6019 Inband-Security-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6020 Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6021 Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | 6022 Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | 6023 Origin-State-Id |0-1|0-1|0 |0 |0-1|0-1|0-1|0-1|0-1|0-1|0-1|0-1| 6024 Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6025 Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ | 6026 Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ | 6027 Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6028 Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6029 Time | | | | | | | | | | | | | 6030 Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |0 |0 |1 | 6031 Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 | 6032 Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 | 6033 Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6034 Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 | 6035 Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6036 Failover | | | | | | | | | | | | | 6037 Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6038 Supported-Vendor-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6039 Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 | 6040 User-Name |0 |0 |0 |0 |0 |0 |0-1|0-1|0-1|0-1|0-1|0-1| 6041 Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6042 Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6043 Application-Id | | | | | | | | | | | | | 6044 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ 6046 10.2. Accounting AVP Table 6048 The table in this section is used to represent which AVPs defined in 6049 this document are to be present in the Accounting messages. These 6050 AVP occurrence requirements are guidelines, which may be expanded, 6051 and/or overridden by application-specific requirements in the 6052 Diameter applications documents. 6054 +-----------+ 6055 | Command | 6056 | Code | 6057 +-----+-----+ 6058 Attribute Name | ACR | ACA | 6059 ------------------------------+-----+-----+ 6060 Acct-Interim-Interval | 0-1 | 0-1 | 6061 Acct-Multi-Session-Id | 0-1 | 0-1 | 6062 Accounting-Record-Number | 1 | 1 | 6063 Accounting-Record-Type | 1 | 1 | 6064 Acct-Session-Id | 0-1 | 0-1 | 6065 Accounting-Sub-Session-Id | 0-1 | 0-1 | 6066 Accounting-Realtime-Required | 0-1 | 0-1 | 6067 Acct-Application-Id | 0-1 | 0-1 | 6068 Auth-Application-Id | 0 | 0 | 6069 Class | 0+ | 0+ | 6070 Destination-Host | 0-1 | 0 | 6071 Destination-Realm | 1 | 0 | 6072 Error-Reporting-Host | 0 | 0+ | 6073 Event-Timestamp | 0-1 | 0-1 | 6074 Origin-Host | 1 | 1 | 6075 Origin-Realm | 1 | 1 | 6076 Proxy-Info | 0+ | 0+ | 6077 Route-Record | 0+ | 0+ | 6078 Result-Code | 0 | 1 | 6079 Session-Id | 1 | 1 | 6080 Termination-Cause | 0-1 | 0-1 | 6081 User-Name | 0-1 | 0-1 | 6082 Vendor-Specific-Application-Id| 0-1 | 0-1 | 6083 ------------------------------+-----+-----+ 6085 11. IANA Considerations 6087 This section provides guidance to the Internet Assigned Numbers 6088 Authority (IANA) regarding registration of values related to the 6089 Diameter protocol, in accordance with BCP 26 [RFC2434]. The 6090 following policies are used here with the meanings defined in BCP 26: 6091 "Private Use", "First Come First Served", "Expert Review", 6092 "Specification Required", "IETF Consensus", "Standards Action". 6094 This section explains the criteria to be used by the IANA for 6095 assignment of numbers within namespaces defined within this document. 6097 Diameter is not intended as a general purpose protocol, and 6098 allocations SHOULD NOT be made for purposes unrelated to 6099 authentication, authorization or accounting. 6101 For registration requests where a Designated Expert should be 6102 consulted, the responsible IESG area director should appoint the 6103 Designated Expert. For Designated Expert with Specification 6104 Required, the request is posted to the AAA WG mailing list (or, if it 6105 has been disbanded, a successor designated by the Area Director) for 6106 comment and review, and MUST include a pointer to a public 6107 specification. Before a period of 30 days has passed, the Designated 6108 Expert will either approve or deny the registration request and 6109 publish a notice of the decision to the AAA WG mailing list or its 6110 successor. A denial notice must be justified by an explanation and, 6111 in the cases where it is possible, concrete suggestions on how the 6112 request can be modified so as to become acceptable. 6114 11.1. AVP Header 6116 As defined in Section 4, the AVP header contains three fields that 6117 requires IANA namespace management; the AVP Code, Vendor-ID and Flags 6118 field. 6120 11.1.1. AVP Codes 6122 The AVP Code namespace is used to identify attributes. There are 6123 multiple namespaces. Vendors can have their own AVP Codes namespace 6124 which will be identified by their Vendor-ID (also known as 6125 Enterprise-Number) and they control the assignments of their vendor- 6126 specific AVP codes within their own namespace. The absence of a 6127 Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA 6128 controlled AVP Codes namespace. The AVP Codes and sometimes also 6129 possible values in an AVP are controlled and maintained by IANA. 6131 AVP Code 0 is not used. AVP Codes 1-255 are managed separately as 6132 RADIUS Attribute Types [RADTYPE]. This document defines the AVP 6133 Codes 257-274, 276-285, 287, 291-300, 480, 483 and 485-486. See 6134 Section 4.5 for the assignment of the namespace in this 6135 specification. 6137 AVPs may be allocated following Designated Expert with Specification 6138 Required [RFC2434]. Release of blocks of AVPs (more than 3 at a time 6139 for a given purpose) should require IETF Consensus. 6141 Note that Diameter defines a mechanism for Vendor-Specific AVPs, 6142 where the Vendor-Id field in the AVP header is set to a non-zero 6143 value. Vendor-Specific AVPs codes are for Private Use and should be 6144 encouraged instead of allocation of global attribute types, for 6145 functions specific only to one vendor's implementation of Diameter, 6146 where no interoperability is deemed useful. Where a Vendor-Specific 6147 AVP is implemented by more than one vendor, allocation of global AVPs 6148 should be encouraged instead. 6150 11.1.2. AVP Flags 6152 There are 8 bits in the AVP Flags field of the AVP header, defined in 6153 Section 4. This document assigns bit 0 ('V'endor Specific), bit 1 6154 ('M'andatory) and bit 2 ('P'rotected). The remaining bits should 6155 only be assigned via a Standards Action [RFC2434]. 6157 11.2. Diameter Header 6159 As defined in Section 3, the Diameter header contains two fields that 6160 require IANA namespace management; Command Code and Command Flags. 6162 11.2.1. Command Codes 6164 The Command Code namespace is used to identify Diameter commands. 6165 The values 0-255 are reserved for RADIUS backward compatibility, and 6166 are defined as "RADIUS Packet Type Codes" in [RADTYPE]. Values 256- 6167 16,777,213 are for permanent, standard commands, allocated by IETF 6168 Consensus [RFC2434]. This document defines the Command Codes 257, 6169 258, 271, 274-275, 280 and 282. See Section 3.1 for the assignment 6170 of the namespace in this specification. 6172 The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe - 6173 0xffffff) are reserved for experimental commands. As these codes are 6174 only for experimental and testing purposes, no guarantee is made for 6175 interoperability between Diameter peers using experimental commands, 6176 as outlined in [IANA-EXP]. 6178 11.2.2. Command Flags 6180 There are eight bits in the Command Flags field of the Diameter 6181 header. This document assigns bit 0 ('R'equest), bit 1 ('P'roxy), 6182 bit 2 ('E'rror) and bit 3 ('T'). Bits 4 through 7 MUST only be 6183 assigned via a Standards Action [RFC2434]. 6185 11.3. Application Identifiers 6187 As defined in Section 2.4, the Application Identifier is used to 6188 identify a specific Diameter Application. There are standards-track 6189 application ids and vendor specific application ids. 6191 IANA [RFC2434] has assigned the range 0x00000001 to 0x00ffffff for 6192 standards-track applications; and 0x01000000 - 0xfffffffe for vendor 6193 specific applications, on a first-come, first-served basis. The 6194 following values are allocated. 6196 Diameter Common Messages 0 6197 NASREQ 1 [RFC4005] 6198 Mobile-IP 2 [RFC4004] 6199 Diameter Base Accounting 3 6200 Relay 0xffffffff 6202 Assignment of standards-track application IDs are by Designated 6203 Expert with Specification Required [RFC2434]. 6205 Both Auth-Application-Id and Acct-Application-Id AVPs use the same 6206 Application Identifier space. A diameter node advertising itself as 6207 a relay agent MUST set either Application-Id or Acct-Application-Id 6208 to 0xffffffff. 6210 Vendor-Specific Application Identifiers, are for Private Use. Vendor- 6211 Specific Application Identifiers are assigned on a First Come, First 6212 Served basis by IANA. 6214 11.4. AVP Values 6216 Certain AVPs in Diameter define a list of values with various 6217 meanings. For attributes other than those specified in this section, 6218 adding additional values to the list can be done on a First Come, 6219 First Served basis by IANA. 6221 11.4.1. Result-Code AVP Values 6223 As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines 6224 the values 1001, 2001-2002, 3001-3012, 4001-4003 and 5001-5021. 6226 All remaining values are available for assignment via IETF Consensus 6227 [RFC2434]. 6229 11.4.2. Accounting-Record-Type AVP Values 6231 As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code 6232 480) defines the values 1-4. All remaining values are available for 6233 assignment via IETF Consensus [RFC2434]. 6235 11.4.3. Termination-Cause AVP Values 6237 As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295) 6238 defines the values 1-8. All remaining values are available for 6239 assignment via IETF Consensus [RFC2434]. 6241 11.4.4. Redirect-Host-Usage AVP Values 6243 As defined in Section 6.13, the Redirect-Host-Usage AVP (AVP Code 6244 261) defines the values 0-5. All remaining values are available for 6245 assignment via IETF Consensus [RFC2434]. 6247 11.4.5. Session-Server-Failover AVP Values 6249 As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code 6250 271) defines the values 0-3. All remaining values are available for 6251 assignment via IETF Consensus [RFC2434]. 6253 11.4.6. Session-Binding AVP Values 6255 As defined in Section 8.17, the Session-Binding AVP (AVP Code 270) 6256 defines the bits 1-4. All remaining bits are available for 6257 assignment via IETF Consensus [RFC2434]. 6259 11.4.7. Disconnect-Cause AVP Values 6261 As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273) 6262 defines the values 0-2. All remaining values are available for 6263 assignment via IETF Consensus [RFC2434]. 6265 11.4.8. Auth-Request-Type AVP Values 6267 As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274) 6268 defines the values 1-3. All remaining values are available for 6269 assignment via IETF Consensus [RFC2434]. 6271 11.4.9. Auth-Session-State AVP Values 6273 As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277) 6274 defines the values 0-1. All remaining values are available for 6275 assignment via IETF Consensus [RFC2434]. 6277 11.4.10. Re-Auth-Request-Type AVP Values 6279 As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code 6280 285) defines the values 0-1. All remaining values are available for 6281 assignment via IETF Consensus [RFC2434]. 6283 11.4.11. Accounting-Realtime-Required AVP Values 6285 As defined in Section 9.8.7, the Accounting-Realtime-Required AVP 6286 (AVP Code 483) defines the values 1-3. All remaining values are 6287 available for assignment via IETF Consensus [RFC2434]. 6289 11.4.12. Inband-Security-Id AVP (code 299) 6291 As defined in Section 6.10, the Inband-Security-Id AVP (AVP Code 299) 6292 defines the values 0-1. All remaining values are available for 6293 assignment via IETF Consensus [RFC2434]. 6295 11.5. Diameter TCP/SCTP Port Numbers 6297 The IANA has assigned TCP and SCTP port number 3868 to Diameter. 6299 11.6. NAPTR Service Fields 6301 The registration in the RFC MUST include the following information: 6303 Service Field: The service field being registered. An example for a 6304 new fictitious transport protocol called NCTP might be "AAA+D2N". 6306 Protocol: The specific transport protocol associated with that 6307 service field. This MUST include the name and acronym for the 6308 protocol, along with reference to a document that describes the 6309 transport protocol. For example - "New Connectionless Transport 6310 Protocol (NCTP), RFC 5766". 6312 Name and Contact Information: The name, address, email address and 6313 telephone number for the person performing the registration. 6315 The following values have been placed into the registry: 6317 Services Field Protocol 6319 AAA+D2T TCP 6320 AAA+D2S SCTP 6322 12. Diameter protocol related configurable parameters 6324 This section contains the configurable parameters that are found 6325 throughout this document: 6327 Diameter Peer 6329 A Diameter entity MAY communicate with peers that are statically 6330 configured. A statically configured Diameter peer would require 6331 that either the IP address or the fully qualified domain name 6332 (FQDN) be supplied, which would then be used to resolve through 6333 DNS. 6335 Realm Routing Table 6337 A Diameter proxy server routes messages based on the realm portion 6338 of a Network Access Identifier (NAI). The server MUST have a 6339 table of Realm Names, and the address of the peer to which the 6340 message must be forwarded to. The routing table MAY also include 6341 a "default route", which is typically used for all messages that 6342 cannot be locally processed. 6344 Tc timer 6346 The Tc timer controls the frequency that transport connection 6347 attempts are done to a peer with whom no active transport 6348 connection exists. The recommended value is 30 seconds. 6350 13. Security Considerations 6352 The Diameter base protocol assumes that messages are secured by using 6353 either IPSec or TLS. This security mechanism is acceptable in 6354 environments where there is no untrusted third party agent. In other 6355 situations, end-to-end security is needed. 6357 Diameter clients, such as Network Access Servers (NASes) and Mobility 6358 Agents MUST support IP Security [RFC2401] and MAY support TLS 6359 [RFC2246]. Diameter servers MUST support TLS and IPsec. Diameter 6360 implementations MUST use transmission-level security of some kind 6361 (IPsec or TLS) on each connection. 6363 If a Diameter connection is not protected by IPsec, then the CER/CEA 6364 exchange MUST include an Inband-Security-ID AVP with a value of TLS. 6365 For TLS usage, a TLS handshake will begin when both ends are in the 6366 open state, after completion of the CER/CEA exchange. If the TLS 6367 handshake is successful, all further messages will be sent via TLS. 6368 If the handshake fails, both ends move to the closed state. 6370 It is suggested that IPsec be used primarily at the edges for intra- 6371 domain exchanges. For NAS devices without certificate support, pre- 6372 shared keys can be used between the NAS and a local AAA proxy. 6374 For protection of inter-domain exchanges, TLS is recommended. See 6375 Sections 13.1 and 13.2 for more details on IPsec and TLS usage. 6377 13.1. IPsec Usage 6379 All Diameter implementations MUST support IPsec ESP [RFC2401] in 6380 transport mode with non-null encryption and authentication algorithms 6381 to provide per-packet authentication, integrity protection and 6382 confidentiality, and MUST support the replay protection mechanisms of 6383 IPsec. 6385 Diameter implementations MUST support IKE for peer authentication, 6386 negotiation of security associations, and key management, using the 6387 IPsec DOI [RFC2407]. Diameter implementations MUST support peer 6388 authentication using a pre-shared key, and MAY support certificate- 6389 based peer authentication using digital signatures. Peer 6390 authentication using the public key encryption methods outlined in 6391 IKE's Sections 5.2 and 5.3 [RFC2409] SHOULD NOT be used. 6393 Conformant implementations MUST support both IKE Main Mode and 6394 Aggressive Mode. When pre-shared keys are used for authentication, 6395 IKE Aggressive Mode SHOULD be used, and IKE Main Mode SHOULD NOT be 6396 used. When digital signatures are used for authentication, either 6397 IKE Main Mode or IKE Aggressive Mode MAY be used. 6399 When digital signatures are used to achieve authentication, an IKE 6400 negotiator SHOULD use IKE Certificate Request Payload(s) to specify 6401 the certificate authority (or authorities) that are trusted in 6402 accordance with its local policy. IKE negotiators SHOULD use 6403 pertinent certificate revocation checks before accepting a PKI 6404 certificate for use in IKE's authentication procedures. 6406 The Phase 2 Quick Mode exchanges used to negotiate protection for 6407 Diameter connections MUST explicitly carry the Identity Payload 6408 fields (IDci and IDcr). The DOI provides for several types of 6409 identification data. However, when used in conformant 6410 implementations, each ID Payload MUST carry a single IP address and a 6411 single non-zero port number, and MUST NOT use the IP Subnet or IP 6412 Address Range formats. This allows the Phase 2 security association 6413 to correspond to specific TCP and SCTP connections. 6415 Since IPsec acceleration hardware may only be able to handle a 6416 limited number of active IKE Phase 2 SAs, Phase 2 delete messages may 6417 be sent for idle SAs, as a means of keeping the number of active 6418 Phase 2 SAs to a minimum. The receipt of an IKE Phase 2 delete 6419 message SHOULD NOT be interpreted as a reason for tearing down a 6420 Diameter connection. Rather, it is preferable to leave the 6421 connection up, and if additional traffic is sent on it, to bring up 6422 another IKE Phase 2 SA to protect it. This avoids the potential for 6423 continually bringing connections up and down. 6425 13.2. TLS Usage 6427 A Diameter node that initiates a connection to another Diameter node 6428 acts as a TLS client according to [RFC2246], and a Diameter node that 6429 accepts a connection acts as a TLS server. Diameter nodes 6430 implementing TLS for security MUST mutually authenticate as part of 6431 TLS session establishment. In order to ensure mutual authentication, 6432 the Diameter node acting as TLS server must request a certificate 6433 from the Diameter node acting as TLS client, and the Diameter node 6434 acting as TLS client MUST be prepared to supply a certificate on 6435 request. 6437 Diameter nodes MUST be able to negotiate the following TLS cipher 6438 suites: 6440 TLS_RSA_WITH_RC4_128_MD5 6441 TLS_RSA_WITH_RC4_128_SHA 6442 TLS_RSA_WITH_3DES_EDE_CBC_SHA 6444 Diameter nodes SHOULD be able to negotiate the following TLS cipher 6445 suite: 6447 TLS_RSA_WITH_AES_128_CBC_SHA 6449 Diameter nodes MAY negotiate other TLS cipher suites. 6451 13.3. Peer-to-Peer Considerations 6453 As with any peer-to-peer protocol, proper configuration of the trust 6454 model within a Diameter peer is essential to security. When 6455 certificates are used, it is necessary to configure the root 6456 certificate authorities trusted by the Diameter peer. These root CAs 6457 are likely to be unique to Diameter usage and distinct from the root 6458 CAs that might be trusted for other purposes such as Web browsing. 6459 In general, it is expected that those root CAs will be configured so 6460 as to reflect the business relationships between the organization 6461 hosting the Diameter peer and other organizations. As a result, a 6462 Diameter peer will typically not be configured to allow connectivity 6463 with any arbitrary peer. When certificate authentication Diameter 6464 peers may not be known beforehand, and therefore peer discovery may 6465 be required. 6467 Note that IPsec is considerably less flexible than TLS when it comes 6468 to configuring root CAs. Since use of Port identifiers is prohibited 6469 within IKE Phase 1, within IPsec it is not possible to uniquely 6470 configure trusted root CAs for each application individually; the 6471 same policy must be used for all applications. This implies, for 6472 example, that a root CA trusted for use with Diameter must also be 6473 trusted to protect SNMP. These restrictions can be awkward at best. 6474 Since TLS supports application-level granularity in certificate 6475 policy, TLS SHOULD be used to protect Diameter connections between 6476 administrative domains. IPsec is most appropriate for intra-domain 6477 usage when pre-shared keys are used as a security mechanism. 6479 When pre-shared key authentication is used with IPsec to protect 6480 Diameter, unique pre-shared keys are configured with Diameter peers, 6481 who are identified by their IP address (Main Mode), or possibly their 6482 FQDN (Aggressive Mode). As a result, it is necessary for the set of 6483 Diameter peers to be known beforehand. Therefore, peer discovery is 6484 typically not necessary. 6486 The following is intended to provide some guidance on the issue. 6488 It is recommended that a Diameter peer implement the same security 6489 mechanism (IPsec or TLS) across all its peer-to-peer connections. 6490 Inconsistent use of security mechanisms can result in redundant 6491 security mechanisms being used (e.g., TLS over IPsec) or worse, 6492 potential security vulnerabilities. When IPsec is used with 6493 Diameter, a typical security policy for outbound traffic is "Initiate 6494 IPsec, from me to any, destination port Diameter"; for inbound 6495 traffic, the policy would be "Require IPsec, from any to me, 6496 destination port Diameter". 6498 This policy causes IPsec to be used whenever a Diameter peer 6499 initiates a connection to another Diameter peer, and to be required 6500 whenever an inbound Diameter connection occurs. This policy is 6501 attractive, since it does not require policy to be set for each peer 6502 or dynamically modified each time a new Diameter connection is 6503 created; an IPsec SA is automatically created based on a simple 6504 static policy. Since IPsec extensions are typically not available to 6505 the sockets API on most platforms, and IPsec policy functionality is 6506 implementation dependent, use of a simple static policy is the often 6507 the simplest route to IPsec-enabling a Diameter implementation. 6509 One implication of the recommended policy is that if a node is using 6510 both TLS and IPsec, there is not a convenient way in which to use 6511 either TLS or IPsec, but not both, without reserving an additional 6512 port for TLS usage. Since Diameter uses the same port for TLS and 6513 non-TLS usage, where the recommended IPsec policy is put in place, a 6514 TLS-protected connection will match the IPsec policy, and both IPsec 6515 and TLS will be used to protect the Diameter connection. To avoid 6516 this, it would be necessary to plumb peer-specific policies either 6517 statically or dynamically. 6519 If IPsec is used to secure Diameter peer-to-peer connections, IPsec 6520 policy SHOULD be set so as to require IPsec protection for inbound 6521 connections, and to initiate IPsec protection for outbound 6522 connections. This can be accomplished via use of inbound and 6523 outbound filter policy. 6525 14. References 6527 14.1. Normative References 6529 [FLOATPOINT] 6530 Institute of Electrical and Electronics Engineers, "IEEE 6531 Standard for Binary Floating-Point Arithmetic, ANSI/IEEE 6532 Standard 754-1985", August 1985. 6534 [IANAADFAM] 6535 IANA,, "Address Family Numbers", 6536 http://www.iana.org/assignments/address-family-numbers. 6538 [IANAWEB] IANA,, "Number assignment", http://www.iana.org. 6540 [RADTYPE] IANA,, "RADIUS Types", 6541 http://www.iana.org/assignments/radius-types. 6543 [IPV4] Postel, J., "Internet Protocol", RFC 791, September 1981. 6545 [TCP] Postel, J., "Transmission Control Protocol", RFC 793, 6546 January 1981. 6548 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and 6549 Accounting (AAA) Transport Profile", RFC 3539, June 2003. 6551 [RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and 6552 P. McCann, "Diameter Mobile IPv4 Application", RFC 4004, 6553 August 2005. 6555 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton, 6556 "Diameter Network Access Server Application", RFC 4005, 6557 August 2005. 6559 [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J. 6560 Loughney, "Diameter Credit-Control Application", RFC 4006, 6561 August 2005. 6563 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible 6564 Authentication Protocol (EAP) Application", RFC 4072, 6565 August 2005. 6567 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M., 6568 Canales-Valenzuela, C., and K. Tammi, "Diameter Session 6569 Initiation Protocol (SIP) Application", RFC 4740, 6570 November 2006. 6572 [RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 6573 Specifications: ABNF", RFC 2234, November 1997. 6575 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by 6576 an On-line Database", RFC 3232, January 2002. 6578 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. 6579 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 6581 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 6582 "Definition of the Differentiated Services Field (DS 6583 Field) in the IPv4 and IPv6 Headers", RFC 2474, 6584 December 1998. 6586 [RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski, 6587 "Assured Forwarding PHB Group", RFC 2597, June 1999. 6589 [RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec, 6590 J., Courtney, W., Davari, S., Firoiu, V., and D. 6591 Stiliadis, "An Expedited Forwarding PHB (Per-Hop 6592 Behavior)", RFC 3246, March 2002. 6594 [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for 6595 specifying the location of services (DNS SRV)", RFC 2782, 6596 February 2000. 6598 [RFC2284] Blunk, L. and J. Vollbrecht, "PPP Extensible 6599 Authentication Protocol (EAP)", RFC 2284, March 1998. 6601 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 6602 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 6603 October 1998. 6605 [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange 6606 (IKE)", RFC 2409, November 1998. 6608 [RFC3173] Shacham, A., Monsour, B., Pereira, R., and M. Thomas, "IP 6609 Payload Compression Protocol (IPComp)", RFC 3173, 6610 September 2001. 6612 [RFC2407] Piper, D., "The Internet IP Security Domain of 6613 Interpretation for ISAKMP", RFC 2407, November 1998. 6615 [RFC2373] Hinden, R. and S. Deering, "IP Version 6 Addressing 6616 Architecture", RFC 2373, July 1998. 6618 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 6619 Requirement Levels", BCP 14, RFC 2119, March 1997. 6621 [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The 6622 Network Access Identifier", RFC 4282, December 2005. 6624 [RFC2915] Mealling, M. and R. Daniel, "The Naming Authority Pointer 6625 (NAPTR) DNS Resource Record", RFC 2915, September 2000. 6627 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 6628 A., Peterson, J., Sparks, R., Handley, M., and E. 6629 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 6630 June 2002. 6632 [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C., 6633 Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M., 6634 Zhang, L., and V. Paxson, "Stream Control Transmission 6635 Protocol", RFC 2960, October 2000. 6637 [RFC2165] Veizades, J., Guttman, E., Perkins, C., and S. Kaplan, 6638 "Service Location Protocol", RFC 2165, June 1997. 6640 [RFC2030] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 6641 for IPv4, IPv6 and OSI", RFC 2030, October 1996. 6643 [RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", 6644 RFC 2246, January 1999. 6646 [RFC2609] Guttman, E., Perkins, C., and J. Kempf, "Service Templates 6647 and Service: Schemes", RFC 2609, June 1999. 6649 [RFC3436] Jungmaier, A., Rescorla, E., and M. Tuexen, "Transport 6650 Layer Security over Stream Control Transmission Protocol", 6651 RFC 3436, December 2002. 6653 [RFC2396] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 6654 Resource Identifiers (URI): Generic Syntax", RFC 2396, 6655 August 1998. 6657 [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO 6658 10646", RFC 2279, January 1998. 6660 14.2. Informational References 6662 [RFC2989] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, P., 6663 Shiino, H., Zorn, G., Dommety, G., C.Perkins, B.Patil, 6664 D.Mitton, S.Manning, M.Beadles, P.Walsh, X.Chen, 6665 S.Sivalingham, A.Hameed, M.Munson, S.Jacobs, B.Lim, 6666 B.Hirschman, R.Hsu, Y.Xu, E.Campell, S.Baba, and E.Jaques, 6667 "Criteria for Evaluating AAA Protocols for Network 6668 Access", RFC 2989, November 2000. 6670 [RFC3141] Hiller, T., Walsh, P., Chen, X., Munson, M., Dommety, G., 6671 Sivalingham, S., Lim, B., McCann, P., Shiino, H., 6672 Hirschman, B., Manning, S., Hsu, R., Koo, H., Lipford, M., 6673 Calhoun, P., Lo, C., Jaques, E., Campbell, E., Y.Xu, 6674 S.Baba, T.Ayaki, T.Seki, and A.Hameed, "CDMA2000 Wireless 6675 Data Requirements for AAA", RFC 3141, June 2001. 6677 [RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction to 6678 Accounting Management", RFC 2975, October 2000. 6680 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B. 6681 Aboba, "Dynamic Authorization Extensions to Remote 6682 Authentication Dial In User Service (RADIUS)", RFC 3576, 6683 July 2003. 6685 [RFC3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, 6686 August 2002. 6688 [RFC2977] Glass, S., Hiller, T., Jacobs, S., and C. Perkins, "Mobile 6689 IP Authentication, Authorization, and Accounting 6690 Requirements", RFC 2977, October 2000. 6692 [RFC2881] Mitton, D. and M. Beadles, "Network Access Server 6693 Requirements Next Generation (NASREQNG) NAS Model", 6694 RFC 2881, July 2000. 6696 [RFC3169] Beadles, M. and D. Mitton, "Criteria for Evaluating 6697 Network Access Server Protocols", RFC 3169, 6698 September 2001. 6700 [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, 6701 RFC 1661, July 1994. 6703 [RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy 6704 Implementation in Roaming", RFC 2607, June 1999. 6706 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. 6708 [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS 6709 Extensions", RFC 2869, June 2000. 6711 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 6712 "Remote Authentication Dial In User Service (RADIUS)", 6713 RFC 2865, June 2000. 6715 [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6", 6716 RFC 3162, August 2001. 6718 [RFC2194] Aboba, B., Lu, J., Alsop, J., Ding, J., and W. Wang, 6719 "Review of Roaming Implementations", RFC 2194, 6720 September 1997. 6722 [RFC2477] Aboba, B. and G. Zorn, "Criteria for Evaluating Roaming 6723 Protocols", RFC 2477, January 1999. 6725 [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the 6726 Internet Protocol", RFC 2401, November 1998. 6728 [RFC1492] Finseth, C., "An Access Control Protocol, Sometimes Called 6729 TACACS", RFC 1492, July 1993. 6731 [AAACMS] Calhoun, P., Bulley, W., and S. Farrell, "Diameter CMS 6732 Security Application", Work in Progress. 6734 [IANA-EXP] 6735 Narten, T., "Assigning Experimental and Testing Numbers 6736 Considered Useful, Work in Progress.". 6738 Appendix A. Acknowledgements 6740 The authors would like to thank the following people that have 6741 provided proposals and contributions to this document: 6743 To Vishnu Ram and Satendra Gera for their contributions on 6744 Capabilities Updates, Predictive Loop Avoidance as well as many other 6745 technical proposals. To Tolga Asveren for his insights and 6746 contributions on almost all of the proposed solutions incorporated 6747 into this document. To Timothy Smith for helping on the Capabilities 6748 Updates and other topics. To Tony Zhang for providing fixes to loop 6749 holes on composing Failed-AVPs as well as many other issues and 6750 topics. To Jan Nordqvist for clearly stating the usage of 6751 application ids. To Anders Kristensen for providing needed technical 6752 opinions. 6754 Special thanks also to people who have provided invaluable comments 6755 and inputs especially in resolving controversial issues: 6757 Glen Zorn, Yoshihiro Ohba, Marco Stura, and Pasi Eronen. 6759 Finally, we would like to thank the original authors of this 6760 document: 6762 Pat Calhoun, John Loughney, Jari Arkko, Erik Guttman and Glen Zorn. 6764 Their invaluable knowledge and experience has given us a robust and 6765 flexible AAA protocol that many people have seen great value in 6766 adopting. We greatly appreciate their support and stewardship for 6767 the continued improvements of Diameter as a protocol. We would also 6768 like to extend our gratitude to folks aside from the authors who have 6769 assisted and contributed to the original version of this document. 6770 Their efforts significantly contributed to the success of Diameter. 6772 Appendix B. Diameter Service Template 6774 The following service template describes the attributes used by 6775 Diameter servers to advertise themselves. This simplifies the 6776 process of selecting an appropriate server to communicate with. A 6777 Diameter client can request specific Diameter servers based on 6778 characteristics of the Diameter service desired (for example, an AAA 6779 server to use for accounting.) 6781 Name of submitter: "Erik Guttman" Language of 6782 service template: en 6784 Security Considerations: 6786 Diameter clients and servers use various cryptographic mechanisms 6787 to protect communication integrity, confidentiality as well as 6788 perform end-point authentication. It would thus be difficult if 6789 not impossible for an attacker to advertise itself using SLPv2 and 6790 pose as a legitimate Diameter peer without proper preconfigured 6791 secrets or cryptographic keys. Still, as Diameter services are 6792 vital for network operation it is important to use SLPv2 6793 authentication to prevent an attacker from modifying or 6794 eliminating service advertisements for legitimate Diameter 6795 servers. 6797 Template text: 6798 -------------------------template begins here----------------------- 6799 template-type=service:diameter 6801 template-version=0.0 6803 template-description= 6804 The Diameter protocol is defined by RFC 3588. 6806 template-url-syntax= 6807 url-path= ; The Diameter URL format is described in Section 2.9. 6808 ; Example: 'aaa://aaa.example.com:1812;transport=tcp 6809 supported-auth-applications= string L M 6811 # This attribute lists the Diameter applications supported by the 6812 # AAA implementation. The applications currently defined are: 6813 # 6814 # Application Name Defined by 6815 # ---------------- ----------------------------------- 6816 # NASREQ Diameter Network Access Server Application 6817 # MobileIP Diameter Mobile IP Application 6818 # 6819 # Notes: 6820 # . Diameter implementations support one or more applications. 6821 # . Additional applications may be defined in the future. 6822 # An updated service template will be created at that time. 6823 # 6825 NASREQ,MobileIP 6826 supported-acct-applications= string L M 6828 # This attribute lists the Diameter applications supported by the 6829 # AAA implementation. The applications currently defined are: 6830 # Application Name Defined by 6831 # ---------------- ----------------------------------- 6832 # NASREQ Diameter Network Access Server Application 6833 # MobileIP Diameter Mobile IP Application 6834 # 6835 # Notes: 6836 # . Diameter implementations support one or more applications. 6837 # . Additional applications may be defined in the future. 6838 # An updated service template will be created at that time. 6839 # 6840 NASREQ,MobileIP 6841 supported-transports= string L M 6843 SCTP 6844 # This attribute lists the supported transports that the Diameter 6845 # implementation accepts. Note that a compliant Diameter 6846 # implementation MUST support SCTP, though it MAY support other 6847 # transports, too. 6848 SCTP,TCP 6850 -------------------------template ends here----------------------- 6852 Appendix C. NAPTR Example 6854 As an example, consider a client that wishes to resolve aaa:ex.com. 6855 The client performs a NAPTR query for that domain, and the following 6856 NAPTR records are returned: 6858 ;; order pref flags service regexp replacement 6859 IN NAPTR 50 50 "s" "AAA+D2S" "" 6860 _diameter._sctp.example.com IN NAPTR 100 50 "s" "AAA+D2T" 6861 "" _aaa._tcp.example.com 6863 This indicates that the server supports SCTP, and TCP, in that order. 6864 If the client supports over SCTP, SCTP will be used, targeted to a 6865 host determined by an SRV lookup of _diameter._sctp.ex.com. That 6866 lookup would return: 6868 ;; Priority Weight Port Target 6869 IN SRV 0 1 5060 server1.example.com IN SRV 0 6870 2 5060 server2.example.com 6872 Appendix D. Duplicate Detection 6874 As described in Section 9.4, accounting record duplicate detection is 6875 based on session identifiers. Duplicates can appear for various 6876 reasons: 6878 o Failover to an alternate server. Where close to real-time 6879 performance is required, failover thresholds need to be kept low 6880 and this may lead to an increased likelihood of duplicates. 6881 Failover can occur at the client or within Diameter agents. 6883 o Failure of a client or agent after sending of a record from non- 6884 volatile memory, but prior to receipt of an application layer ACK 6885 and deletion of the record. record to be sent. This will result 6886 in retransmission of the record soon after the client or agent has 6887 rebooted. 6889 o Duplicates received from RADIUS gateways. Since the 6890 retransmission behavior of RADIUS is not defined within [RFC2865], 6891 the likelihood of duplication will vary according to the 6892 implementation. 6894 o Implementation problems and misconfiguration. 6896 The T flag is used as an indication of an application layer 6897 retransmission event, e.g., due to failover to an alternate server. 6898 It is defined only for request messages sent by Diameter clients or 6899 agents. For instance, after a reboot, a client may not know whether 6900 it has already tried to send the accounting records in its non- 6901 volatile memory before the reboot occurred. Diameter servers MAY use 6902 the T flag as an aid when processing requests and detecting duplicate 6903 messages. However, servers that do this MUST ensure that duplicates 6904 are found even when the first transmitted request arrives at the 6905 server after the retransmitted request. It can be used only in cases 6906 where no answer has been received from the Server for a request and 6907 the request is sent again, (e.g., due to a failover to an alternate 6908 peer, due to a recovered primary peer or due to a client re-sending a 6909 stored record from non-volatile memory such as after reboot of a 6910 client or agent). 6912 In some cases the Diameter accounting server can delay the duplicate 6913 detection and accounting record processing until a post-processing 6914 phase takes place. At that time records are likely to be sorted 6915 according to the included User-Name and duplicate elimination is easy 6916 in this case. In other situations it may be necessary to perform 6917 real-time duplicate detection, such as when credit limits are imposed 6918 or real-time fraud detection is desired. 6920 In general, only generation of duplicates due to failover or re- 6921 sending of records in non-volatile storage can be reliably detected 6922 by Diameter clients or agents. In such cases the Diameter client or 6923 agents can mark the message as possible duplicate by setting the T 6924 flag. Since the Diameter server is responsible for duplicate 6925 detection, it can choose to make use of the T flag or not, in order 6926 to optimize duplicate detection. Since the T flag does not affect 6927 interoperability, and may not be needed by some servers, generation 6928 of the T flag is REQUIRED for Diameter clients and agents, but MAY be 6929 implemented by Diameter servers. 6931 As an example, it can be usually be assumed that duplicates appear 6932 within a time window of longest recorded network partition or device 6933 fault, perhaps a day. So only records within this time window need 6934 to be looked at in the backward direction. Secondly, hashing 6935 techniques or other schemes, such as the use of the T flag in the 6936 received messages, may be used to eliminate the need to do a full 6937 search even in this set except for rare cases. 6939 The following is an example of how the T flag may be used by the 6940 server to detect duplicate requests. 6942 A Diameter server MAY check the T flag of the received message to 6943 determine if the record is a possible duplicate. If the T flag is 6944 set in the request message, the server searches for a duplicate 6945 within a configurable duplication time window backward and 6946 forward. This limits database searching to those records where 6947 the T flag is set. In a well run network, network partitions and 6948 device faults will presumably be rare events, so this approach 6949 represents a substantial optimization of the duplicate detection 6950 process. During failover, it is possible for the original record 6951 to be received after the T flag marked record, due to differences 6952 in network delays experienced along the path by the original and 6953 duplicate transmissions. The likelihood of this occurring 6954 increases as the failover interval is decreased. In order to be 6955 able to detect out of order duplicates, the Diameter server should 6956 use backward and forward time windows when performing duplicate 6957 checking for the T flag marked request. For example, in order to 6958 allow time for the original record to exit the network and be 6959 recorded by the accounting server, the Diameter server can delay 6960 processing records with the T flag set until a time period 6961 TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after the closing 6962 of the original transport connection. After this time period has 6963 expired, then it may check the T flag marked records against the 6964 database with relative assurance that the original records, if 6965 sent, have been received and recorded. 6967 Authors' Addresses 6969 Victor Fajardo (editor) 6970 Toshiba America Research 6971 One Telcordia Drive, 1S-222 6972 Piscataway, NJ 08854 6973 USA 6975 Phone: 1 908-421-1845 6976 Email: vfajardo@tari.toshiba.com 6978 John Loughney 6979 Nokia Research Center 6980 Itamerenkatu 11-13 6981 Helsinki, 00180 6982 Finland 6984 Phone: +358 50 483 6242 6985 Email: john.loughney@nokia.com 6987 Full Copyright Statement 6989 Copyright (C) The IETF Trust (2007). 6991 This document is subject to the rights, licenses and restrictions 6992 contained in BCP 78, and except as set forth therein, the authors 6993 retain all their rights. 6995 This document and the information contained herein are provided on an 6996 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 6997 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 6998 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 6999 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 7000 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 7001 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 7003 Intellectual Property 7005 The IETF takes no position regarding the validity or scope of any 7006 Intellectual Property Rights or other rights that might be claimed to 7007 pertain to the implementation or use of the technology described in 7008 this document or the extent to which any license under such rights 7009 might or might not be available; nor does it represent that it has 7010 made any independent effort to identify any such rights. Information 7011 on the procedures with respect to rights in RFC documents can be 7012 found in BCP 78 and BCP 79. 7014 Copies of IPR disclosures made to the IETF Secretariat and any 7015 assurances of licenses to be made available, or the result of an 7016 attempt made to obtain a general license or permission for the use of 7017 such proprietary rights by implementers or users of this 7018 specification can be obtained from the IETF on-line IPR repository at 7019 http://www.ietf.org/ipr. 7021 The IETF invites any interested party to bring to its attention any 7022 copyrights, patents or patent applications, or other proprietary 7023 rights that may cover technology that may be required to implement 7024 this standard. Please address the information to the IETF at 7025 ietf-ipr@ietf.org. 7027 Acknowledgment 7029 Funding for the RFC Editor function is provided by the IETF 7030 Administrative Support Activity (IASA).