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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 4539 has weird spacing: '...ly with wit...' == Line 4747 has weird spacing: '...ealtime user...' == Line 4775 has weird spacing: '... record inter...' == Line 4785 has weird spacing: '...ealtime user...' == Line 4793 has weird spacing: '...ealtime user...' == (1 more instance...) == 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 receiver of the Capabilities-Exchange-Request (CER) MUST determine common applications by computing the intersection of its own set of supported application identifiers against all of the application indentifier AVPs (Auth-Application-Id, Acct-Application-Id and Vendor-Specific-Application-Id) present in the CER. The value of the Vendor-Id AVP in the Vendor-Specific-Application-Id MUST not be used during computation. The sender of the Capabilities-Exchange-Answer (CEA) SHOULD include all of its supported applications as a hint to the receiver regarding all of its application capabilities. == 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 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 (August 20, 2007) is 6093 days in the past. Is this intentional? 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: 'PXY' is mentioned on line 4254, but not defined -- Possible downref: Non-RFC (?) normative reference: ref. 'FLOATPOINT' -- Possible downref: Non-RFC (?) normative reference: ref. 'IANAADFAM' -- 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 4234 (Obsoleted by RFC 5234) ** Obsolete normative reference: RFC 3588 (Obsoleted by RFC 6733) ** Obsolete normative reference: RFC 2434 (Obsoleted by RFC 5226) ** Obsolete normative reference: RFC 4306 (Obsoleted by RFC 5996) ** Obsolete normative reference: RFC 4282 (Obsoleted by RFC 7542) ** Obsolete normative reference: RFC 2960 (Obsoleted by RFC 4960) ** Obsolete normative reference: RFC 4346 (Obsoleted by RFC 5246) -- Obsolete informational reference (is this intentional?): RFC 3576 (Obsoleted by RFC 5176) -- Obsolete informational reference (is this intentional?): RFC 4330 (Obsoleted by RFC 5905) Summary: 11 errors (**), 0 flaws (~~), 12 warnings (==), 12 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. Arkko 5 Expires: February 21, 2008 Ericsson Research 6 J. Loughney 7 Nokia Research Center 8 August 20, 2007 10 Diameter Base Protocol 11 draft-ietf-dime-rfc3588bis-06.txt 13 Status of this Memo 15 By submitting this Internet-Draft, each author represents that any 16 applicable patent or other IPR claims of which he or she is aware 17 have been or will be disclosed, and any of which he or she becomes 18 aware will be disclosed, in accordance with Section 6 of BCP 79. 20 Internet-Drafts are working documents of the Internet Engineering 21 Task Force (IETF), its areas, and its working groups. Note that 22 other groups may also distribute working documents as Internet- 23 Drafts. 25 Internet-Drafts are draft documents valid for a maximum of six months 26 and may be updated, replaced, or obsoleted by other documents at any 27 time. It is inappropriate to use Internet-Drafts as reference 28 material or to cite them other than as "work in progress." 30 The list of current Internet-Drafts can be accessed at 31 http://www.ietf.org/ietf/1id-abstracts.txt. 33 The list of Internet-Draft Shadow Directories can be accessed at 34 http://www.ietf.org/shadow.html. 36 This Internet-Draft will expire on February 21, 2008. 38 Copyright Notice 40 Copyright (C) The IETF Trust (2007). 42 Abstract 44 The Diameter base protocol is intended to provide an Authentication, 45 Authorization and Accounting (AAA) framework for applications such as 46 network access or IP mobility. Diameter is also intended to work in 47 both local Authentication, Authorization & Accounting and roaming 48 situations. This document specifies the message format, transport, 49 error reporting, accounting and security services to be used by all 50 Diameter applications. The Diameter base application needs to be 51 supported by all Diameter implementations. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7 56 1.1. Diameter Protocol . . . . . . . . . . . . . . . . . . . . 10 57 1.1.1. Description of the Document Set . . . . . . . . . . 11 58 1.1.2. Conventions Used in This Document . . . . . . . . . 12 59 1.2. Approach to Extensibility . . . . . . . . . . . . . . . . 12 60 1.2.1. Defining New AVP Values . . . . . . . . . . . . . . 13 61 1.2.2. Creating New AVPs . . . . . . . . . . . . . . . . . 13 62 1.2.3. Creating New Commands . . . . . . . . . . . . . . . 13 63 1.2.4. Creating New Authentication Applications . . . . . . 13 64 1.2.5. Creating New Accounting Applications . . . . . . . . 14 65 1.2.6. Application Authentication Procedures . . . . . . . 15 66 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 16 67 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 22 68 2.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 23 69 2.1.1. SCTP Guidelines . . . . . . . . . . . . . . . . . . 24 70 2.2. Securing Diameter Messages . . . . . . . . . . . . . . . 24 71 2.3. Diameter Application Compliance . . . . . . . . . . . . . 24 72 2.4. Application Identifiers . . . . . . . . . . . . . . . . . 24 73 2.5. Connections vs. Sessions . . . . . . . . . . . . . . . . 25 74 2.6. Peer Table . . . . . . . . . . . . . . . . . . . . . . . 26 75 2.7. Routing Table . . . . . . . . . . . . . . . . . . . . . . 27 76 2.8. Role of Diameter Agents . . . . . . . . . . . . . . . . . 28 77 2.8.1. Relay Agents . . . . . . . . . . . . . . . . . . . . 30 78 2.8.2. Proxy Agents . . . . . . . . . . . . . . . . . . . . 31 79 2.8.3. Redirect Agents . . . . . . . . . . . . . . . . . . 31 80 2.8.4. Translation Agents . . . . . . . . . . . . . . . . . 32 81 2.9. Diameter Path Authorization . . . . . . . . . . . . . . . 33 82 3. Diameter Header . . . . . . . . . . . . . . . . . . . . . . . 35 83 3.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 38 84 3.2. Command Code ABNF specification . . . . . . . . . . . . . 38 85 3.3. Diameter Command Naming Conventions . . . . . . . . . . . 40 86 4. Diameter AVPs . . . . . . . . . . . . . . . . . . . . . . . . 42 87 4.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 42 88 4.1.1. Optional Header Elements . . . . . . . . . . . . . . 44 90 4.2. Basic AVP Data Formats . . . . . . . . . . . . . . . . . 44 91 4.3. Derived AVP Data Formats . . . . . . . . . . . . . . . . 46 92 4.4. Grouped AVP Values . . . . . . . . . . . . . . . . . . . 52 93 4.4.1. Example AVP with a Grouped Data type . . . . . . . . 53 94 4.5. Diameter Base Protocol AVPs . . . . . . . . . . . . . . . 56 95 5. Diameter Peers . . . . . . . . . . . . . . . . . . . . . . . 59 96 5.1. Peer Connections . . . . . . . . . . . . . . . . . . . . 59 97 5.2. Diameter Peer Discovery . . . . . . . . . . . . . . . . . 59 98 5.3. Capabilities Exchange . . . . . . . . . . . . . . . . . . 62 99 5.3.1. Capabilities-Exchange-Request . . . . . . . . . . . 63 100 5.3.2. Capabilities-Exchange-Answer . . . . . . . . . . . . 64 101 5.3.3. Vendor-Id AVP . . . . . . . . . . . . . . . . . . . 64 102 5.3.4. Firmware-Revision AVP . . . . . . . . . . . . . . . 65 103 5.3.5. Host-IP-Address AVP . . . . . . . . . . . . . . . . 65 104 5.3.6. Supported-Vendor-Id AVP . . . . . . . . . . . . . . 65 105 5.3.7. Product-Name AVP . . . . . . . . . . . . . . . . . . 65 106 5.4. Disconnecting Peer connections . . . . . . . . . . . . . 65 107 5.4.1. Disconnect-Peer-Request . . . . . . . . . . . . . . 66 108 5.4.2. Disconnect-Peer-Answer . . . . . . . . . . . . . . . 66 109 5.4.3. Disconnect-Cause AVP . . . . . . . . . . . . . . . . 67 110 5.5. Transport Failure Detection . . . . . . . . . . . . . . . 67 111 5.5.1. Device-Watchdog-Request . . . . . . . . . . . . . . 67 112 5.5.2. Device-Watchdog-Answer . . . . . . . . . . . . . . . 68 113 5.5.3. Transport Failure Algorithm . . . . . . . . . . . . 68 114 5.5.4. Failover and Failback Procedures . . . . . . . . . . 68 115 5.6. Peer State Machine . . . . . . . . . . . . . . . . . . . 69 116 5.6.1. Incoming connections . . . . . . . . . . . . . . . . 71 117 5.6.2. Events . . . . . . . . . . . . . . . . . . . . . . . 72 118 5.6.3. Actions . . . . . . . . . . . . . . . . . . . . . . 73 119 5.6.4. The Election Process . . . . . . . . . . . . . . . . 75 120 5.6.5. Capabilities Update . . . . . . . . . . . . . . . . 75 121 6. Diameter message processing . . . . . . . . . . . . . . . . . 76 122 6.1. Diameter Request Routing Overview . . . . . . . . . . . . 76 123 6.1.1. Originating a Request . . . . . . . . . . . . . . . 77 124 6.1.2. Sending a Request . . . . . . . . . . . . . . . . . 78 125 6.1.3. Receiving Requests . . . . . . . . . . . . . . . . . 78 126 6.1.4. Processing Local Requests . . . . . . . . . . . . . 78 127 6.1.5. Request Forwarding . . . . . . . . . . . . . . . . . 78 128 6.1.6. Request Routing . . . . . . . . . . . . . . . . . . 79 129 6.1.7. Predictive Loop Avoidance . . . . . . . . . . . . . 79 130 6.1.8. Redirecting requests . . . . . . . . . . . . . . . . 79 131 6.1.9. Relaying and Proxying Requests . . . . . . . . . . . 81 132 6.2. Diameter Answer Processing . . . . . . . . . . . . . . . 81 133 6.2.1. Processing received Answers . . . . . . . . . . . . 82 134 6.2.2. Relaying and Proxying Answers . . . . . . . . . . . 82 135 6.3. Origin-Host AVP . . . . . . . . . . . . . . . . . . . . . 83 136 6.4. Origin-Realm AVP . . . . . . . . . . . . . . . . . . . . 83 137 6.5. Destination-Host AVP . . . . . . . . . . . . . . . . . . 83 138 6.6. Destination-Realm AVP . . . . . . . . . . . . . . . . . . 84 139 6.7. Routing AVPs . . . . . . . . . . . . . . . . . . . . . . 84 140 6.7.1. Route-Record AVP . . . . . . . . . . . . . . . . . . 84 141 6.7.2. Proxy-Info AVP . . . . . . . . . . . . . . . . . . . 84 142 6.7.3. Proxy-Host AVP . . . . . . . . . . . . . . . . . . . 84 143 6.7.4. Proxy-State AVP . . . . . . . . . . . . . . . . . . 84 144 6.8. Auth-Application-Id AVP . . . . . . . . . . . . . . . . . 85 145 6.9. Acct-Application-Id AVP . . . . . . . . . . . . . . . . . 85 146 6.10. Inband-Security-Id AVP . . . . . . . . . . . . . . . . . 85 147 6.11. Vendor-Specific-Application-Id AVP . . . . . . . . . . . 85 148 6.12. Redirect-Host AVP . . . . . . . . . . . . . . . . . . . . 86 149 6.13. Redirect-Host-Usage AVP . . . . . . . . . . . . . . . . . 86 150 6.14. Redirect-Max-Cache-Time AVP . . . . . . . . . . . . . . . 88 151 6.15. E2E-Sequence AVP . . . . . . . . . . . . . . . . . . . . 88 152 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 89 153 7.1. Result-Code AVP . . . . . . . . . . . . . . . . . . . . . 90 154 7.1.1. Informational . . . . . . . . . . . . . . . . . . . 91 155 7.1.2. Success . . . . . . . . . . . . . . . . . . . . . . 91 156 7.1.3. Protocol Errors . . . . . . . . . . . . . . . . . . 92 157 7.1.4. Transient Failures . . . . . . . . . . . . . . . . . 93 158 7.1.5. Permanent Failures . . . . . . . . . . . . . . . . . 94 159 7.2. Error Bit . . . . . . . . . . . . . . . . . . . . . . . . 97 160 7.3. Error-Message AVP . . . . . . . . . . . . . . . . . . . . 97 161 7.4. Error-Reporting-Host AVP . . . . . . . . . . . . . . . . 97 162 7.5. Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . . 98 163 7.6. Experimental-Result AVP . . . . . . . . . . . . . . . . . 99 164 7.7. Experimental-Result-Code AVP . . . . . . . . . . . . . . 99 165 8. Diameter User Sessions . . . . . . . . . . . . . . . . . . . 100 166 8.1. Authorization Session State Machine . . . . . . . . . . . 101 167 8.2. Accounting Session State Machine . . . . . . . . . . . . 106 168 8.3. Server-Initiated Re-Auth . . . . . . . . . . . . . . . . 111 169 8.3.1. Re-Auth-Request . . . . . . . . . . . . . . . . . . 111 170 8.3.2. Re-Auth-Answer . . . . . . . . . . . . . . . . . . . 112 171 8.4. Session Termination . . . . . . . . . . . . . . . . . . . 113 172 8.4.1. Session-Termination-Request . . . . . . . . . . . . 114 173 8.4.2. Session-Termination-Answer . . . . . . . . . . . . . 114 174 8.5. Aborting a Session . . . . . . . . . . . . . . . . . . . 115 175 8.5.1. Abort-Session-Request . . . . . . . . . . . . . . . 116 176 8.5.2. Abort-Session-Answer . . . . . . . . . . . . . . . . 116 177 8.6. Inferring Session Termination from Origin-State-Id . . . 117 178 8.7. Auth-Request-Type AVP . . . . . . . . . . . . . . . . . . 118 179 8.8. Session-Id AVP . . . . . . . . . . . . . . . . . . . . . 118 180 8.9. Authorization-Lifetime AVP . . . . . . . . . . . . . . . 119 181 8.10. Auth-Grace-Period AVP . . . . . . . . . . . . . . . . . . 120 182 8.11. Auth-Session-State AVP . . . . . . . . . . . . . . . . . 120 183 8.12. Re-Auth-Request-Type AVP . . . . . . . . . . . . . . . . 121 184 8.13. Session-Timeout AVP . . . . . . . . . . . . . . . . . . . 121 185 8.14. User-Name AVP . . . . . . . . . . . . . . . . . . . . . . 122 186 8.15. Termination-Cause AVP . . . . . . . . . . . . . . . . . . 122 187 8.16. Origin-State-Id AVP . . . . . . . . . . . . . . . . . . . 123 188 8.17. Session-Binding AVP . . . . . . . . . . . . . . . . . . . 123 189 8.18. Session-Server-Failover AVP . . . . . . . . . . . . . . . 124 190 8.19. Multi-Round-Time-Out AVP . . . . . . . . . . . . . . . . 125 191 8.20. Class AVP . . . . . . . . . . . . . . . . . . . . . . . . 125 192 8.21. Event-Timestamp AVP . . . . . . . . . . . . . . . . . . . 125 193 9. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . 127 194 9.1. Server Directed Model . . . . . . . . . . . . . . . . . . 127 195 9.2. Protocol Messages . . . . . . . . . . . . . . . . . . . . 128 196 9.3. Accounting Application Extension and Requirements . . . . 128 197 9.4. Fault Resilience . . . . . . . . . . . . . . . . . . . . 129 198 9.5. Accounting Records . . . . . . . . . . . . . . . . . . . 130 199 9.6. Correlation of Accounting Records . . . . . . . . . . . . 130 200 9.7. Accounting Command-Codes . . . . . . . . . . . . . . . . 131 201 9.7.1. Accounting-Request . . . . . . . . . . . . . . . . . 131 202 9.7.2. Accounting-Answer . . . . . . . . . . . . . . . . . 132 203 9.8. Accounting AVPs . . . . . . . . . . . . . . . . . . . . . 133 204 9.8.1. Accounting-Record-Type AVP . . . . . . . . . . . . . 133 205 9.8.2. Acct-Interim-Interval . . . . . . . . . . . . . . . 134 206 9.8.3. Accounting-Record-Number AVP . . . . . . . . . . . . 135 207 9.8.4. Acct-Session-Id AVP . . . . . . . . . . . . . . . . 135 208 9.8.5. Acct-Multi-Session-Id AVP . . . . . . . . . . . . . 135 209 9.8.6. Accounting-Sub-Session-Id AVP . . . . . . . . . . . 135 210 9.8.7. Accounting-Realtime-Required AVP . . . . . . . . . . 136 211 10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . 137 212 10.1. Base Protocol Command AVP Table . . . . . . . . . . . . . 137 213 10.2. Accounting AVP Table . . . . . . . . . . . . . . . . . . 138 214 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 140 215 11.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 140 216 11.1.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . 140 217 11.1.2. AVP Flags . . . . . . . . . . . . . . . . . . . . . 141 218 11.2. Diameter Header . . . . . . . . . . . . . . . . . . . . . 141 219 11.2.1. Command Codes . . . . . . . . . . . . . . . . . . . 141 220 11.2.2. Command Flags . . . . . . . . . . . . . . . . . . . 142 221 11.3. Application Identifiers . . . . . . . . . . . . . . . . . 142 222 11.4. AVP Values . . . . . . . . . . . . . . . . . . . . . . . 143 223 11.4.1. Result-Code AVP Values . . . . . . . . . . . . . . . 143 224 11.4.2. Accounting-Record-Type AVP Values . . . . . . . . . 143 225 11.4.3. Termination-Cause AVP Values . . . . . . . . . . . . 143 226 11.4.4. Redirect-Host-Usage AVP Values . . . . . . . . . . . 143 227 11.4.5. Session-Server-Failover AVP Values . . . . . . . . . 143 228 11.4.6. Session-Binding AVP Values . . . . . . . . . . . . . 143 229 11.4.7. Disconnect-Cause AVP Values . . . . . . . . . . . . 144 230 11.4.8. Auth-Request-Type AVP Values . . . . . . . . . . . . 144 231 11.4.9. Auth-Session-State AVP Values . . . . . . . . . . . 144 232 11.4.10. Re-Auth-Request-Type AVP Values . . . . . . . . . . 144 233 11.4.11. Accounting-Realtime-Required AVP Values . . . . . . 144 234 11.4.12. Inband-Security-Id AVP (code 299) . . . . . . . . . 144 235 11.5. Diameter TCP/SCTP Port Numbers . . . . . . . . . . . . . 144 236 11.6. NAPTR Service Fields . . . . . . . . . . . . . . . . . . 144 237 12. Diameter protocol related configurable parameters . . . . . . 146 238 13. Security Considerations . . . . . . . . . . . . . . . . . . . 147 239 13.1. TLS Usage . . . . . . . . . . . . . . . . . . . . . . . . 147 240 13.2. Peer-to-Peer Considerations . . . . . . . . . . . . . . . 148 241 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 149 242 14.1. Normative References . . . . . . . . . . . . . . . . . . 149 243 14.2. Informational References . . . . . . . . . . . . . . . . 151 244 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 153 245 Appendix B. NAPTR Example . . . . . . . . . . . . . . . . . . . 154 246 Appendix C. Duplicate Detection . . . . . . . . . . . . . . . . 155 247 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 157 248 Intellectual Property and Copyright Statements . . . . . . . . . 158 250 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 [RFC4306] 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, Diameter also 294 provides support for TLS. Security is discussed in Section 13. 296 Reliable transport 298 RADIUS runs over UDP, and does not define retransmission behavior; 299 as a result, reliability varies between implementations. As 300 described in [RFC2975], this is a major issue in accounting, where 301 packet loss may translate directly into revenue loss. In order to 302 provide well defined transport behavior, Diameter runs over 303 reliable transport mechanisms (TCP, SCTP) as defined in [RFC3539]. 305 Agent support 307 [RFC2865] does not provide for explicit support for agents, 308 including Proxies, Redirects and Relays. Since the expected 309 behavior is not defined, it varies between implementations. 310 Diameter defines agent behavior explicitly; this is described in 311 Section 2.8. 313 Server-initiated messages 315 While RADIUS server-initiated messages are defined in [RFC3576], 316 support is optional. This makes it difficult to implement 317 features such as unsolicited disconnect or reauthentication/ 318 reauthorization on demand across a heterogeneous deployment. 319 Support for server-initiated messages is mandatory in Diameter, 320 and is described in Section 8. 322 Auditability 324 RADIUS does not define data-object security mechanisms, and as a 325 result, untrusted proxies may modify attributes or even packet 326 headers without being detected. Combined with lack of support for 327 capabilities negotiation, this makes it very difficult to 328 determine what occurred in the event of a dispute. 330 Transition support 332 While Diameter does not share a common protocol data unit (PDU) 333 with RADIUS, considerable effort has been expended in enabling 334 backward compatibility with RADIUS, so that the two protocols may 335 be deployed in the same network. Initially, it is expected that 336 Diameter will be deployed within new network devices, as well as 337 within gateways enabling communication between legacy RADIUS 338 devices and Diameter agents. This capability, described in 340 [RFC4005], enables Diameter support to be added to legacy 341 networks, by addition of a gateway or server speaking both RADIUS 342 and Diameter. 344 In addition to addressing the above requirements, Diameter also 345 provides support for the following: 347 Capability negotiation 349 RADIUS does not support error messages, capability negotiation, or 350 a mandatory/non-mandatory flag for attributes. Since RADIUS 351 clients and servers are not aware of each other's capabilities, 352 they may not be able to successfully negotiate a mutually 353 acceptable service, or in some cases, even be aware of what 354 service has been implemented. Diameter includes support for error 355 handling (Section 7), capability negotiation (Section 5.3), and 356 mandatory/non-mandatory attribute-value pairs (AVPs) (Section 357 4.1). 359 Peer discovery and configuration 361 RADIUS implementations typically require that the name or address 362 of servers or clients be manually configured, along with the 363 corresponding shared secrets. This results in a large 364 administrative burden, and creates the temptation to reuse the 365 RADIUS shared secret, which can result in major security 366 vulnerabilities if the Request Authenticator is not globally and 367 temporally unique as required in [RFC2865]. Through DNS, Diameter 368 enables dynamic discovery of peers. Derivation of dynamic session 369 keys is enabled via transmission-level security. 371 Roaming support 373 The ROAMOPS WG provided a survey of roaming implementations 374 [RFC2194], detailed roaming requirements [RFC2477], defined the 375 Network Access Identifier (NAI)[RFC4282], and documented existing 376 implementations (and imitations) of RADIUS-based roaming 377 [RFC2607]. In order to improve scalability, [RFC2607] introduced 378 the concept of proxy chaining via an intermediate server, 379 facilitating roaming between providers. However, since RADIUS 380 does not provide explicit support for proxies, and lacks 381 auditability and transmission-level security features, RADIUS- 382 based roaming is vulnerable to attack from external parties as 383 well as susceptible to fraud perpetrated by the roaming partners 384 themselves. As a result, it is not suitable for wide-scale 385 deployment on the Internet [RFC2607]. By providing explicit 386 support for inter-domain roaming and message routing (Sections 2.7 387 and 6), and transmission-layer security (Section 13) features, 388 Diameter addresses these limitations and provides for secure and 389 scalable roaming. 391 In the decade since AAA protocols were first introduced, the 392 capabilities of Network Access Server (NAS) devices have increased 393 substantially. As a result, while Diameter is a considerably more 394 sophisticated protocol than RADIUS, it remains feasible to implement 395 within embedded devices, given improvements in processor speeds and 396 the widespread availability of embedded TLS implementations. 398 1.1. Diameter Protocol 400 The Diameter base protocol provides the following facilities: 402 o Delivery of AVPs (attribute value pairs) 404 o Capabilities negotiation 406 o Error notification 408 o Extensibility, through addition of new commands and AVPs (required 409 in [RFC2989]). 411 o Basic services necessary for applications, such as handling of 412 user sessions or accounting 414 All data delivered by the protocol is in the form of an AVP. Some of 415 these AVP values are used by the Diameter protocol itself, while 416 others deliver data associated with particular applications that 417 employ Diameter. AVPs may be added arbitrarily to Diameter messages, 418 so long as the requirements of a message's ABNF are met and the ABNF 419 allows for it. AVPs are used by the base Diameter protocol to 420 support the following required features: 422 o Transporting of user authentication information, for the purposes 423 of enabling the Diameter server to authenticate the user. 425 o Transporting of service specific authorization information, 426 between client and servers, allowing the peers to decide whether a 427 user's access request should be granted. 429 o Exchanging resource usage information, which MAY be used for 430 accounting purposes, capacity planning, etc. 432 o Relaying, proxying and redirecting of Diameter messages through a 433 server hierarchy. 435 The Diameter base protocol provides the minimum requirements needed 436 for a AAA protocol, as required by [RFC2989]. The base protocol may 437 be used by itself for accounting purposes only, or it may be used 438 with a Diameter application, such as Mobile IPv4 [RFC4004], or 439 network access [RFC4005]. It is also possible for the base protocol 440 to be extended for use in new applications, via the addition of new 441 commands or AVPs. At this time the focus of Diameter is network 442 access and accounting applications. A truly generic AAA protocol 443 used by many applications might provide functionality not provided by 444 Diameter. Therefore, it is imperative that the designers of new 445 applications understand their requirements before using Diameter. 446 See Section 2.4 for more information on Diameter applications. 448 Any node can initiate a request. In that sense, Diameter is a peer- 449 to-peer protocol. In this document, a Diameter Client is a device at 450 the edge of the network that performs access control, such as a 451 Network Access Server (NAS) or a Foreign Agent (FA). A Diameter 452 client generates Diameter messages to request authentication, 453 authorization, and accounting services for the user. A Diameter 454 agent is a node that does not authenticate and/or authorize messages 455 locally; agents include proxies, redirects and relay agents. A 456 Diameter server performs authentication and/or authorization of the 457 user. A Diameter node MAY act as an agent for certain requests while 458 acting as a server for others. 460 The Diameter protocol also supports server-initiated messages, such 461 as a request to abort service to a particular user. 463 1.1.1. Description of the Document Set 465 Currently, the Diameter specification consists of a base 466 specification (this document), Transport Profile [RFC3539] and 467 applications: Mobile IPv4 [RFC4004], NASREQ [RFC4005], Credit Control 468 [RFC4006], EAP [RFC4072] and SIP [RFC4740]. 470 The Transport Profile document [RFC3539] discusses transport layer 471 issues that arise with AAA protocols and recommendations on how to 472 overcome these issues. This document also defines the Diameter 473 failover algorithm and state machine. 475 The Mobile IPv4 [RFC4004] application defines a Diameter application 476 that allows a Diameter server to perform AAA functions for Mobile 477 IPv4 services to a mobile node. 479 The NASREQ [RFC4005] application defines a Diameter Application that 480 allows a Diameter server to be used in a PPP/SLIP Dial-Up and 481 Terminal Server Access environment. Consideration was given for 482 servers that need to perform protocol conversion between Diameter and 483 RADIUS. 485 The Credit Control [RFC4006] application defines a Diameter 486 Application that can be used to implement real-time credit-control 487 for a variety of end user services such as network access, SIP 488 services, messaging services, and download services. It provides a 489 general solution to real-time cost and credit-control. 491 The EAP [RFC4072] application defines a Diameter Application that can 492 be used to carry EAP packets between the Network Access Server (NAS) 493 working as an EAP authenticator and a back-end authentication server. 494 The Diameter EAP application is based on NASREQ and intended for a 495 similar environment. 497 The SIP [RFC4740] application defines a Diameter Application that 498 allows a Diameter client to request authentication and authorization 499 information to a Diameter server for SIP-based IP multimedia services 500 (see SIP [RFC3261]). 502 In summary, this document defines the base protocol specification for 503 AAA, which includes support for accounting. The applications 504 documents describe applications that use this base specification for 505 Authentication, Authorization and Accounting. 507 1.1.2. Conventions Used in This Document 509 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 510 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 511 document are to be interpreted as described in [RFC2119]. 513 1.2. Approach to Extensibility 515 The Diameter protocol is designed to be extensible, using several 516 mechanisms, including: 518 o Defining new AVP values 520 o Creating new AVPs 522 o Creating new commands 524 o Creating new authentication/authorization applications 526 o Creating new accounting applications 527 o Application authentication procedures 529 Reuse of existing AVP values, AVPs, commands and Diameter 530 applications are strongly recommended. Reuse simplifies 531 standardization and implementation and avoids potential 532 interoperability issues. 534 1.2.1. Defining New AVP Values 536 New applications should attempt to reuse AVPs defined in existing 537 applications when possible, as opposed to creating new AVPs. For 538 AVPs of type Enumerated, an application may require a new value to 539 communicate some service-specific information. 541 In order to allocate a new AVP value for a standards track AVP, a 542 request MUST be sent to IANA [RFC2434], along with an explanation of 543 the new AVP value. IANA considerations for AVP values are discussed 544 in Section 11.4. 546 1.2.2. Creating New AVPs 548 When no existing AVP can be reused, a new AVP should be created. The 549 new AVP being defined MUST use one of the data types listed in 550 Section 4.2 or 4.3. If an appropriate derived data type is already 551 defined, it MAY be used instead of the base data type. 553 In the event that a logical grouping of AVPs is necessary, and 554 multiple "groups" are possible in a given command, it is recommended 555 that a Grouped AVP be used (see Section 4.4). 557 In order to create a new standards track AVP, a request MUST be sent 558 to IANA with a reference to the specification that defines the AVP. 559 IANA considerations for AVPs are discussed in Section 11.1.1. 561 1.2.3. Creating New Commands 563 A new command should only be created when no suitable command can be 564 reused from an existing application. A new command MUST result in 565 the defintion of a new application. In order to create a new 566 command, a request MUST be sent to IANA. The IANA considerations for 567 commands are discussed in Section 11.2.1. 569 1.2.4. Creating New Authentication Applications 571 Every Diameter application specification MUST have an IANA assigned 572 Application Identifier (see Section 2.4 and Section 11.3). 574 Should a new Diameter usage scenario find itself unable to fit within 575 an existing application without requiring major changes to the 576 specification, it may be desirable to create a new Diameter 577 application. Major changes to an application include: 579 o Adding new AVPs to the command, which have the "M" bit set. 581 o Requiring a command that has a different number of round trips to 582 satisfy a request (e.g., application foo has a command that 583 requires one round trip, but new application bar has a command 584 that requires two round trips to complete). 586 o Adding support for an authentication method requiring definition 587 of new AVPs for use with the application. Since a new EAP 588 authentication method can be supported within Diameter without 589 requiring new AVPs, addition of EAP methods does not require the 590 creation of a new authentication application. 592 Creation of a new application should be viewed as a last resort. An 593 implementation MAY add arbitrary non-mandatory AVPs to any command 594 defined in an application, including vendor-specific AVPs without 595 needing to define a new application. Please refer to Section 11.1.1 596 for details. 598 In order to justify allocation of a new application identifier, 599 Diameter applications MUST define one Command Code, add new mandatory 600 AVPs to the ABNF or significantly change the state machine or 601 processing rules of an existing application. 603 The expected AVPs MUST be defined in an ABNF [RFC4234] grammar (see 604 Section 3.2). If the Diameter application has accounting 605 requirements, it MUST also specify the AVPs that are to be present in 606 the Diameter Accounting messages (see Section 9.3). However, just 607 because a new authentication application id is required, does not 608 imply that a new accounting application id is required. 610 When possible, a new Diameter application SHOULD reuse existing 611 Diameter AVPs, in order to avoid defining multiple AVPs that carry 612 similar information. 614 1.2.5. Creating New Accounting Applications 616 There are services that only require Diameter accounting. Such 617 services need to define the AVPs carried in the Accounting-Request 618 (ACR)/ Accounting-Answer (ACA) messages, but do not need to define 619 new command codes. An implementation MAY add arbitrary non-mandatory 620 AVPs (AVPs with the "M" bit not set) to any command defined in an 621 application, including vendor-specific AVPs, without needing to 622 define a new accounting application. Please refer to Section 11.1.1 623 for details. 625 Application Identifiers are still required for Diameter capability 626 exchange. Every Diameter accounting application specification MUST 627 have an IANA assigned Application Identifier (see Section 2.4) or a 628 vendor specific Application Identifier. 630 Every Diameter implementation MUST support accounting. Basic 631 accounting support is sufficient to handle any application that uses 632 the ACR/ACA commands defined in this document, as long as no new 633 mandatory AVPs are added. A mandatory AVP is defined as one which 634 has the "M" bit set when sent within an accounting command, 635 regardless of whether it is required or optional within the ABNF for 636 the accounting application. 638 The creation of a new accounting application should be viewed as a 639 last resort and MUST NOT be used unless a new command or additional 640 mechanisms (e.g., application defined state machine) is defined 641 within the application, or new mandatory AVPs are added to the ABNF. 643 Within an accounting command, setting the "M" bit implies that a 644 backend server (e.g., billing server) or the accounting server itself 645 MUST understand the AVP in order to compute a correct bill. If the 646 AVP is not relevant to the billing process, when the AVP is included 647 within an accounting command, it MUST NOT have the "M" bit set, even 648 if the "M" bit is set when the same AVP is used within other Diameter 649 commands (i.e., authentication/authorization commands). 651 A DIAMETER base accounting implementation MUST be configurable to 652 advertise supported accounting applications in order to prevent the 653 accounting server from accepting accounting requests for unbillable 654 services. The combination of the home domain and the accounting 655 application Id can be used in order to route the request to the 656 appropriate accounting server. 658 When possible, a new Diameter accounting application SHOULD attempt 659 to reuse existing AVPs, in order to avoid defining multiple AVPs that 660 carry similar information. 662 If the base accounting is used without any mandatory AVPs, new 663 commands or additional mechanisms (e.g., application defined state 664 machine), then the base protocol defined standard accounting 665 application Id (Section 2.4) MUST be used in ACR/ACA commands. 667 1.2.6. Application Authentication Procedures 669 When possible, applications SHOULD be designed such that new 670 authentication methods MAY be added without requiring changes to the 671 application. This MAY require that new AVP values be assigned to 672 represent the new authentication transform, or any other scheme that 673 produces similar results. When possible, authentication frameworks, 674 such as Extensible Authentication Protocol [RFC3748], SHOULD be used. 676 1.3. Terminology 678 AAA 680 Authentication, Authorization and Accounting. 682 Accounting 684 The act of collecting information on resource usage for the 685 purpose of capacity planning, auditing, billing or cost 686 allocation. 688 Accounting Record 690 An accounting record represents a summary of the resource 691 consumption of a user over the entire session. Accounting servers 692 creating the accounting record may do so by processing interim 693 accounting events or accounting events from several devices 694 serving the same user. 696 Authentication 698 The act of verifying the identity of an entity (subject). 700 Authorization 702 The act of determining whether a requesting entity (subject) will 703 be allowed access to a resource (object). 705 AVP 707 The Diameter protocol consists of a header followed by one or more 708 Attribute-Value-Pairs (AVPs). An AVP includes a header and is 709 used to encapsulate protocol-specific data (e.g., routing 710 information) as well as authentication, authorization or 711 accounting information. 713 Broker 715 A broker is a business term commonly used in AAA infrastructures. 716 A broker is either a relay, proxy or redirect agent, and MAY be 717 operated by roaming consortiums. Depending on the business model, 718 a broker may either choose to deploy relay agents or proxy agents. 720 Diameter Agent 722 A Diameter Agent is a Diameter node that provides either relay, 723 proxy, redirect or translation services. 725 Diameter Client 727 A Diameter Client is a device at the edge of the network that 728 performs access control. An example of a Diameter client is a 729 Network Access Server (NAS) or a Foreign Agent (FA). 731 Diameter Node 733 A Diameter node is a host process that implements the Diameter 734 protocol, and acts either as a Client, Agent or Server. 736 Diameter Peer 738 A Diameter Peer is a Diameter Node to which a given Diameter Node 739 has a direct transport connection. 741 Diameter Server 743 A Diameter Server is one that handles authentication, 744 authorization and accounting requests for a particular realm. By 745 its very nature, a Diameter Server MUST support Diameter 746 applications in addition to the base protocol. 748 Downstream 750 Downstream is used to identify the direction of a particular 751 Diameter message from the home server towards the access device. 753 Home Realm 755 A Home Realm is the administrative domain with which the user 756 maintains an account relationship. 758 Home Server 760 A Diameter Server which serves the Home Realm. 762 Interim accounting 764 An interim accounting message provides a snapshot of usage during 765 a user's session. It is typically implemented in order to provide 766 for partial accounting of a user's session in the case of a device 767 reboot or other network problem prevents the reception of a 768 session summary message or session record. 770 Local Realm 772 A local realm is the administrative domain providing services to a 773 user. An administrative domain MAY act as a local realm for 774 certain users, while being a home realm for others. 776 Multi-session 778 A multi-session represents a logical linking of several sessions. 779 Multi-sessions are tracked by using the Acct-Multi-Session-Id. An 780 example of a multi-session would be a Multi-link PPP bundle. Each 781 leg of the bundle would be a session while the entire bundle would 782 be a multi-session. 784 Network Access Identifier 786 The Network Access Identifier, or NAI [RFC4282], is used in the 787 Diameter protocol to extract a user's identity and realm. The 788 identity is used to identify the user during authentication and/or 789 authorization, while the realm is used for message routing 790 purposes. 792 Proxy Agent or Proxy 794 In addition to forwarding requests and responses, proxies make 795 policy decisions relating to resource usage and provisioning. 796 This is typically accomplished by tracking the state of NAS 797 devices. While proxies typically do not respond to client 798 Requests prior to receiving a Response from the server, they may 799 originate Reject messages in cases where policies are violated. 800 As a result, proxies need to understand the semantics of the 801 messages passing through them, and may not support all Diameter 802 applications. 804 Realm 806 The string in the NAI that immediately follows the '@' character. 807 NAI realm names are required to be unique, and are piggybacked on 808 the administration of the DNS namespace. Diameter makes use of 809 the realm, also loosely referred to as domain, to determine 810 whether messages can be satisfied locally, or whether they must be 811 routed or redirected. In RADIUS, realm names are not necessarily 812 piggybacked on the DNS namespace but may be independent of it. 814 Real-time Accounting 816 Real-time accounting involves the processing of information on 817 resource usage within a defined time window. Time constraints are 818 typically imposed in order to limit financial risk. 820 Relay Agent or Relay 822 Relays forward requests and responses based on routing-related 823 AVPs and routing table entries. Since relays do not make policy 824 decisions, they do not examine or alter non-routing AVPs. As a 825 result, relays never originate messages, do not need to understand 826 the semantics of messages or non-routing AVPs, and are capable of 827 handling any Diameter application or message type. Since relays 828 make decisions based on information in routing AVPs and realm 829 forwarding tables they do not keep state on NAS resource usage or 830 sessions in progress. 832 Redirect Agent 834 Rather than forwarding requests and responses between clients and 835 servers, redirect agents refer clients to servers and allow them 836 to communicate directly. Since redirect agents do not sit in the 837 forwarding path, they do not alter any AVPs transiting between 838 client and server. Redirect agents do not originate messages and 839 are capable of handling any message type, although they may be 840 configured only to redirect messages of certain types, while 841 acting as relay or proxy agents for other types. As with proxy 842 agents, redirect agents do not keep state with respect to sessions 843 or NAS resources. 845 Roaming Relationships 847 Roaming relationships include relationships between companies and 848 ISPs, relationships among peer ISPs within a roaming consortium, 849 and relationships between an ISP and a roaming consortium. 851 Session 853 A session is a related progression of events devoted to a 854 particular activity. Each application SHOULD provide guidelines 855 as to when a session begins and ends. All Diameter packets with 856 the same Session-Identifier are considered to be part of the same 857 session. 859 Session state 861 A stateful agent is one that maintains session state information, 862 by keeping track of all authorized active sessions. Each 863 authorized session is bound to a particular service, and its state 864 is considered active either until it is notified otherwise, or by 865 expiration. 867 Sub-session 869 A sub-session represents a distinct service (e.g., QoS or data 870 characteristics) provided to a given session. These services may 871 happen concurrently (e.g., simultaneous voice and data transfer 872 during the same session) or serially. These changes in sessions 873 are tracked with the Accounting-Sub-Session-Id. 875 Transaction state 877 The Diameter protocol requires that agents maintain transaction 878 state, which is used for failover purposes. Transaction state 879 implies that upon forwarding a request, the Hop-by-Hop identifier 880 is saved; the field is replaced with a locally unique identifier, 881 which is restored to its original value when the corresponding 882 answer is received. The request's state is released upon receipt 883 of the answer. A stateless agent is one that only maintains 884 transaction state. 886 Translation Agent 888 A translation agent is a stateful Diameter node that performs 889 protocol translation between Diameter and another AAA protocol, 890 such as RADIUS. 892 Transport Connection 894 A transport connection is a TCP or SCTP connection existing 895 directly between two Diameter peers, otherwise known as a Peer- 896 to-Peer Connection. 898 Upstream 900 Upstream is used to identify the direction of a particular 901 Diameter message from the access device towards the home server. 903 User 905 The entity requesting or using some resource, in support of which 906 a Diameter client has generated a request. 908 2. Protocol Overview 910 The base Diameter protocol may be used by itself for accounting 911 applications, but for use in authentication and authorization it is 912 always extended for a particular application. Two Diameter 913 applications are defined by companion documents: NASREQ [RFC4005], 914 Mobile IPv4 [RFC4004]. These applications are introduced in this 915 document but specified elsewhere. Additional Diameter applications 916 MAY be defined in the future (see Section 11.3). 918 Diameter Clients MUST support the base protocol, which includes 919 accounting. In addition, they MUST fully support each Diameter 920 application that is needed to implement the client's service, e.g., 921 NASREQ and/or Mobile IPv4. A Diameter Client that does not support 922 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 923 Client" where X is the application which it supports, and not a 924 "Diameter Client". 926 Diameter Servers MUST support the base protocol, which includes 927 accounting. In addition, they MUST fully support each Diameter 928 application that is needed to implement the intended service, e.g., 929 NASREQ and/or Mobile IPv4. A Diameter Server that does not support 930 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 931 Server" where X is the application which it supports, and not a 932 "Diameter Server". 934 Diameter Relays and redirect agents are, by definition, protocol 935 transparent, and MUST transparently support the Diameter base 936 protocol, which includes accounting, and all Diameter applications. 938 Diameter proxies MUST support the base protocol, which includes 939 accounting. In addition, they MUST fully support each Diameter 940 application that is needed to implement proxied services, e.g., 941 NASREQ and/or Mobile IPv4. A Diameter proxy which does not support 942 also both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 943 Proxy" where X is the application which it supports, and not a 944 "Diameter Proxy". 946 The base Diameter protocol concerns itself with capabilities 947 negotiation, how messages are sent and how peers may eventually be 948 abandoned. The base protocol also defines certain rules that apply 949 to all exchanges of messages between Diameter nodes. 951 Communication between Diameter peers begins with one peer sending a 952 message to another Diameter peer. The set of AVPs included in the 953 message is determined by a particular Diameter application. One AVP 954 that is included to reference a user's session is the Session-Id. 956 The initial request for authentication and/or authorization of a user 957 would include the Session-Id. The Session-Id is then used in all 958 subsequent messages to identify the user's session (see Section 8 for 959 more information). The communicating party may accept the request, 960 or reject it by returning an answer message with the Result-Code AVP 961 set to indicate an error occurred. The specific behavior of the 962 Diameter server or client receiving a request depends on the Diameter 963 application employed. 965 Session state (associated with a Session-Id) MUST be freed upon 966 receipt of the Session-Termination-Request, Session-Termination- 967 Answer, expiration of authorized service time in the Session-Timeout 968 AVP, and according to rules established in a particular Diameter 969 application. 971 2.1. Transport 973 Transport profile is defined in [RFC3539]. 975 The base Diameter protocol is run on port 3868 of both TCP [TCP] and 976 SCTP [RFC2960] transport protocols. 978 Diameter clients MUST support either TCP or SCTP, while agents and 979 servers MUST support both. Future versions of this specification MAY 980 mandate that clients support SCTP. 982 A Diameter node MAY initiate connections from a source port other 983 than the one that it declares it accepts incoming connections on, and 984 MUST be prepared to receive connections on port 3868. A given 985 Diameter instance of the peer state machine MUST NOT use more than 986 one transport connection to communicate with a given peer, unless 987 multiple instances exist on the peer in which case a separate 988 connection per process is allowed. 990 When no transport connection exists with a peer, an attempt to 991 connect SHOULD be periodically made. This behavior is handled via 992 the Tc timer, whose recommended value is 30 seconds. There are 993 certain exceptions to this rule, such as when a peer has terminated 994 the transport connection stating that it does not wish to 995 communicate. 997 When connecting to a peer and either zero or more transports are 998 specified, SCTP SHOULD be tried first, followed by TCP. See Section 999 5.2 for more information on peer discovery. 1001 Diameter implementations SHOULD be able to interpret ICMP protocol 1002 port unreachable messages as explicit indications that the server is 1003 not reachable, subject to security policy on trusting such messages. 1005 Diameter implementations SHOULD also be able to interpret a reset 1006 from the transport and timed-out connection attempts. If Diameter 1007 receives data up from TCP that cannot be parsed or identified as a 1008 Diameter error made by the peer, the stream is compromised and cannot 1009 be recovered. The transport connection MUST be closed using a RESET 1010 call (send a TCP RST bit) or an SCTP ABORT message (graceful closure 1011 is compromised). 1013 2.1.1. SCTP Guidelines 1015 The following are guidelines for Diameter implementations that 1016 support SCTP: 1018 1. For interoperability: All Diameter nodes MUST be prepared to 1019 receive Diameter messages on any SCTP stream in the association. 1021 2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP 1022 streams available to the association to prevent head-of-the-line 1023 blocking. 1025 2.2. Securing Diameter Messages 1027 Diameter clients, such as Network Access Servers (NASes) and Mobility 1028 Agents MAY support TLS [RFC4346]. Diameter servers MUST support TLS. 1029 IPSec [RFC4301] can be deployed between Diameter peers as an 1030 additional security measure independent of the Diameter protocol. 1031 The Diameter protocol SHOULD NOT be used without any security 1032 mechanism. 1034 2.3. Diameter Application Compliance 1036 Application Identifiers are advertised during the capabilities 1037 exchange phase (see Section 5.3). For a given application, 1038 advertising support of an application implies that the sender 1039 supports all command codes, and the AVPs specified in the associated 1040 ABNFs, described in the specification. 1042 An implementation MAY add arbitrary non-mandatory AVPs to any command 1043 defined in an application, including vendor-specific AVPs. Please 1044 refer to Section 11.1.1 for details. 1046 2.4. Application Identifiers 1048 Each Diameter application MUST have an IANA assigned Application 1049 Identifier (see Section 11.3). The base protocol does not require an 1050 Application Identifier since its support is mandatory. During the 1051 capabilities exchange, Diameter nodes inform their peers of locally 1052 supported applications. Furthermore, all Diameter messages contain 1053 an Application Identifier, which is used in the message forwarding 1054 process. 1056 The following Application Identifier values are defined: 1058 Diameter Common Messages 0 1059 NASREQ 1 [RFC4005] 1060 Mobile-IP 2 [RFC4004] 1061 Diameter Base Accounting 3 1062 Relay 0xffffffff 1064 Relay and redirect agents MUST advertise the Relay Application 1065 Identifier, while all other Diameter nodes MUST advertise locally 1066 supported applications. The receiver of a Capabilities Exchange 1067 message advertising Relay service MUST assume that the sender 1068 supports all current and future applications. 1070 Diameter relay and proxy agents are responsible for finding an 1071 upstream server that supports the application of a particular 1072 message. If none can be found, an error message is returned with the 1073 Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. 1075 2.5. Connections vs. Sessions 1077 This section attempts to provide the reader with an understanding of 1078 the difference between connection and session, which are terms used 1079 extensively throughout this document. 1081 A connection is a transport level connection between two peers, used 1082 to send and receive Diameter messages. A session is a logical 1083 concept at the application layer, and is shared between an access 1084 device and a server, and is identified via the Session-Id AVP. 1086 +--------+ +-------+ +--------+ 1087 | Client | | Relay | | Server | 1088 +--------+ +-------+ +--------+ 1089 <----------> <----------> 1090 peer connection A peer connection B 1092 <-----------------------------> 1093 User session x 1095 Figure 1: Diameter connections and sessions 1097 In the example provided in Figure 1, peer connection A is established 1098 between the Client and its local Relay. Peer connection B is 1099 established between the Relay and the Server. User session X spans 1100 from the Client via the Relay to the Server. Each "user" of a 1101 service causes an auth request to be sent, with a unique session 1102 identifier. Once accepted by the server, both the client and the 1103 server are aware of the session. 1105 It is important to note that there is no relationship between a 1106 connection and a session, and that Diameter messages for multiple 1107 sessions are all multiplexed through a single connection. Also note 1108 that Diameter messages pertaining to the session, both application 1109 specific and those that are defined in this document such as ASR/ASA, 1110 RAR/RAA and STR/STA MUST carry the application identifier of the 1111 application. Diameter messages pertaining to peer connection 1112 establishment and maintenance such as CER/CEA, DWR/DWA and DPR/DPA 1113 MUST carry an application id of zero (0). 1115 2.6. Peer Table 1117 The Diameter Peer Table is used in message forwarding, and referenced 1118 by the Routing Table. A Peer Table entry contains the following 1119 fields: 1121 Host identity 1123 Following the conventions described for the DiameterIdentity 1124 derived AVP data format in Section 4.4. This field contains the 1125 contents of the Origin-Host (Section 6.3) AVP found in the CER or 1126 CEA message. 1128 StatusT 1130 This is the state of the peer entry, and MUST match one of the 1131 values listed in Section 5.6. 1133 Static or Dynamic 1135 Specifies whether a peer entry was statically configured, or 1136 dynamically discovered. 1138 Expiration time 1140 Specifies the time at which dynamically discovered peer table 1141 entries are to be either refreshed, or expired. 1143 TLS Enabled 1145 Specifies whether TLS is to be used when communicating with the 1146 peer. 1148 Additional security information, when needed (e.g., keys, 1149 certificates) 1151 2.7. Routing Table 1153 All Realm-Based routing lookups are performed against what is 1154 commonly known as the Routing Table (see Section 12). A Routing 1155 Table Entry contains the following fields: 1157 Realm Name 1159 This is the field that is typically used as a primary key in the 1160 routing table lookups. Note that some implementations perform 1161 their lookups based on longest-match-from-the-right on the realm 1162 rather than requiring an exact match. 1164 Application Identifier 1166 An application is identified by an application id. A route entry 1167 can have a different destination based on the application 1168 identification in the message header. This field MUST be used as 1169 a secondary key field in routing table lookups. 1171 Local Action 1173 The Local Action field is used to identify how a message should be 1174 treated. The following actions are supported: 1176 1. LOCAL - Diameter messages that resolve to a route entry with 1177 the Local Action set to Local can be satisfied locally, and do 1178 not need to be routed to another server. 1180 2. RELAY - All Diameter messages that fall within this category 1181 MUST be routed to a next hop server, without modifying any 1182 non-routing AVPs. See Section 6.1.9 for relaying guidelines 1184 3. PROXY - All Diameter messages that fall within this category 1185 MUST be routed to a next hop server. The local server MAY 1186 apply its local policies to the message by including new AVPs 1187 to the message prior to routing. See Section 6.1.9 for 1188 proxying guidelines. 1190 4. REDIRECT - Diameter messages that fall within this category 1191 MUST have the identity of the home Diameter server(s) 1192 appended, and returned to the sender of the message. See 1193 Section 6.1.9 for redirect guidelines. 1195 Server Identifier 1197 One or more servers the message is to be routed to. These servers 1198 MUST also be present in the Peer table. When the Local Action is 1199 set to RELAY or PROXY, this field contains the identity of the 1200 server(s) the message must be routed to. When the Local Action 1201 field is set to REDIRECT, this field contains the identity of one 1202 or more servers the message should be redirected to. 1204 Static or Dynamic 1206 Specifies whether a route entry was statically configured, or 1207 dynamically discovered. 1209 Expiration time 1211 Specifies the time which a dynamically discovered route table 1212 entry expires. 1214 It is important to note that Diameter agents MUST support at least 1215 one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation. 1216 Agents do not need to support all modes of operation in order to 1217 conform with the protocol specification, but MUST follow the protocol 1218 compliance guidelines in Section 2. Relay agents MUST NOT reorder 1219 AVPs, and proxies MUST NOT reorder AVPs. 1221 The routing table MAY include a default entry that MUST be used for 1222 any requests not matching any of the other entries. The routing 1223 table MAY consist of only such an entry. 1225 When a request is routed, the target server MUST have advertised the 1226 Application Identifier (see Section 2.4) for the given message, or 1227 have advertised itself as a relay or proxy agent. Otherwise, an 1228 error is returned with the Result-Code AVP set to 1229 DIAMETER_UNABLE_TO_DELIVER. 1231 2.8. Role of Diameter Agents 1233 In addition to client and servers, the Diameter protocol introduces 1234 relay, proxy, redirect, and translation agents, each of which is 1235 defined in Section 1.3. These Diameter agents are useful for several 1236 reasons: 1238 o They can distribute administration of systems to a configurable 1239 grouping, including the maintenance of security associations. 1241 o They can be used for concentration of requests from an number of 1242 co-located or distributed NAS equipment sets to a set of like user 1243 groups. 1245 o They can do value-added processing to the requests or responses. 1247 o They can be used for load balancing. 1249 o A complex network will have multiple authentication sources, they 1250 can sort requests and forward towards the correct target. 1252 The Diameter protocol requires that agents maintain transaction 1253 state, which is used for failover purposes. Transaction state 1254 implies that upon forwarding a request, its Hop-by-Hop identifier is 1255 saved; the field is replaced with a locally unique identifier, which 1256 is restored to its original value when the corresponding answer is 1257 received. The request's state is released upon receipt of the 1258 answer. A stateless agent is one that only maintains transaction 1259 state. 1261 The Proxy-Info AVP allows stateless agents to add local state to a 1262 Diameter request, with the guarantee that the same state will be 1263 present in the answer. However, the protocol's failover procedures 1264 require that agents maintain a copy of pending requests. 1266 A stateful agent is one that maintains session state information; by 1267 keeping track of all authorized active sessions. Each authorized 1268 session is bound to a particular service, and its state is considered 1269 active either until it is notified otherwise, or by expiration. Each 1270 authorized session has an expiration, which is communicated by 1271 Diameter servers via the Session-Timeout AVP. 1273 Maintaining session state MAY be useful in certain applications, such 1274 as: 1276 o Protocol translation (e.g., RADIUS <-> Diameter) 1278 o Limiting resources authorized to a particular user 1280 o Per user or transaction auditing 1282 A Diameter agent MAY act in a stateful manner for some requests and 1283 be stateless for others. A Diameter implementation MAY act as one 1284 type of agent for some requests, and as another type of agent for 1285 others. 1287 2.8.1. Relay Agents 1289 Relay Agents are Diameter agents that accept requests and route 1290 messages to other Diameter nodes based on information found in the 1291 messages (e.g., Destination-Realm). This routing decision is 1292 performed using a list of supported realms, and known peers. This is 1293 known as the Routing Table, as is defined further in Section 2.7. 1295 Relays MAY be used to aggregate requests from multiple Network Access 1296 Servers (NASes) within a common geographical area (POP). The use of 1297 Relays is advantageous since it eliminates the need for NASes to be 1298 configured with the necessary security information they would 1299 otherwise require to communicate with Diameter servers in other 1300 realms. Likewise, this reduces the configuration load on Diameter 1301 servers that would otherwise be necessary when NASes are added, 1302 changed or deleted. 1304 Relays modify Diameter messages by inserting and removing routing 1305 information, but do not modify any other portion of a message. 1306 Relays SHOULD NOT maintain session state but MUST maintain 1307 transaction state. 1309 +------+ ---------> +------+ ---------> +------+ 1310 | | 1. Request | | 2. Request | | 1311 | NAS | | DRL | | HMS | 1312 | | 4. Answer | | 3. Answer | | 1313 +------+ <--------- +------+ <--------- +------+ 1314 example.net example.net example.com 1316 Figure 2: Relaying of Diameter messages 1318 The example provided in Figure 2 depicts a request issued from NAS, 1319 which is an access device, for the user bob@example.com. Prior to 1320 issuing the request, NAS performs a Diameter route lookup, using 1321 "example.com" as the key, and determines that the message is to be 1322 relayed to DRL, which is a Diameter Relay. DRL performs the same 1323 route lookup as NAS, and relays the message to HMS, which is 1324 example.com's Home Diameter Server. HMS identifies that the request 1325 can be locally supported (via the realm), processes the 1326 authentication and/or authorization request, and replies with an 1327 answer, which is routed back to NAS using saved transaction state. 1329 Since Relays do not perform any application level processing, they 1330 provide relaying services for all Diameter applications, and 1331 therefore MUST advertise the Relay Application Identifier. 1333 2.8.2. Proxy Agents 1335 Similarly to relays, proxy agents route Diameter messages using the 1336 Diameter Routing Table. However, they differ since they modify 1337 messages to implement policy enforcement. This requires that proxies 1338 maintain the state of their downstream peers (e.g., access devices) 1339 to enforce resource usage, provide admission control, and 1340 provisioning. 1342 Proxies MAY be used in call control centers or access ISPs that 1343 provide outsourced connections, they can monitor the number and types 1344 of ports in use, and make allocation and admission decisions 1345 according to their configuration. 1347 Proxies that wish to limit resources MUST maintain session state. 1348 All proxies MUST maintain transaction state. 1350 Since enforcing policies requires an understanding of the service 1351 being provided, Proxies MUST only advertise the Diameter applications 1352 they support. 1354 2.8.3. Redirect Agents 1356 Redirect agents are useful in scenarios where the Diameter routing 1357 configuration needs to be centralized. An example is a redirect 1358 agent that provides services to all members of a consortium, but does 1359 not wish to be burdened with relaying all messages between realms. 1360 This scenario is advantageous since it does not require that the 1361 consortium provide routing updates to its members when changes are 1362 made to a member's infrastructure. 1364 Since redirect agents do not relay messages, and only return an 1365 answer with the information necessary for Diameter agents to 1366 communicate directly, they do not modify messages. Since redirect 1367 agents do not receive answer messages, they cannot maintain session 1368 state. Further, since redirect agents never relay requests, they are 1369 not required to maintain transaction state. 1371 The example provided in Figure 3 depicts a request issued from the 1372 access device, NAS, for the user bob@example.com. The message is 1373 forwarded by the NAS to its relay, DRL, which does not have a routing 1374 entry in its Diameter Routing Table for example.com. DRL has a 1375 default route configured to DRD, which is a redirect agent that 1376 returns a redirect notification to DRL, as well as HMS' contact 1377 information. Upon receipt of the redirect notification, DRL 1378 establishes a transport connection with HMS, if one doesn't already 1379 exist, and forwards the request to it. 1381 +------+ 1382 | | 1383 | DRD | 1384 | | 1385 +------+ 1386 ^ | 1387 2. Request | | 3. Redirection 1388 | | Notification 1389 | v 1390 +------+ ---------> +------+ ---------> +------+ 1391 | | 1. Request | | 4. Request | | 1392 | NAS | | DRL | | HMS | 1393 | | 6. Answer | | 5. Answer | | 1394 +------+ <--------- +------+ <--------- +------+ 1395 example.net example.net example.com 1397 Figure 3: Redirecting a Diameter Message 1399 Since redirect agents do not perform any application level 1400 processing, they provide relaying services for all Diameter 1401 applications, and therefore MUST advertise the Relay Application 1402 Identifier. 1404 2.8.4. Translation Agents 1406 A translation agent is a device that provides translation between two 1407 protocols (e.g., RADIUS<->Diameter, TACACS+<->Diameter). Translation 1408 agents are likely to be used as aggregation servers to communicate 1409 with a Diameter infrastructure, while allowing for the embedded 1410 systems to be migrated at a slower pace. 1412 Given that the Diameter protocol introduces the concept of long-lived 1413 authorized sessions, translation agents MUST be session stateful and 1414 MUST maintain transaction state. 1416 Translation of messages can only occur if the agent recognizes the 1417 application of a particular request, and therefore translation agents 1418 MUST only advertise their locally supported applications. 1420 +------+ ---------> +------+ ---------> +------+ 1421 | | RADIUS Request | | Diameter Request | | 1422 | NAS | | TLA | | HMS | 1423 | | RADIUS Answer | | Diameter Answer | | 1424 +------+ <--------- +------+ <--------- +------+ 1425 example.net example.net example.com 1426 Figure 4: Translation of RADIUS to Diameter 1428 2.9. Diameter Path Authorization 1430 As noted in Section 2.2, Diameter provides transmission level 1431 security for each connection using TLS. Therefore, each connection 1432 can be authenticated, replay and integrity protected. 1434 In addition to authenticating each connection, each connection as 1435 well as the entire session MUST also be authorized. Before 1436 initiating a connection, a Diameter Peer MUST check that its peers 1437 are authorized to act in their roles. For example, a Diameter peer 1438 may be authentic, but that does not mean that it is authorized to act 1439 as a Diameter Server advertising a set of Diameter applications. 1441 Prior to bringing up a connection, authorization checks are performed 1442 at each connection along the path. Diameter capabilities negotiation 1443 (CER/CEA) also MUST be carried out, in order to determine what 1444 Diameter applications are supported by each peer. Diameter sessions 1445 MUST be routed only through authorized nodes that have advertised 1446 support for the Diameter application required by the session. 1448 As noted in Section 6.1.9, a relay or proxy agent MUST append a 1449 Route-Record AVP to all requests forwarded. The AVP contains the 1450 identity of the peer the request was received from. 1452 The home Diameter server, prior to authorizing a session, MUST check 1453 the Route-Record AVPs to make sure that the route traversed by the 1454 request is acceptable. For example, administrators within the home 1455 realm may not wish to honor requests that have been routed through an 1456 untrusted realm. By authorizing a request, the home Diameter server 1457 is implicitly indicating its willingness to engage in the business 1458 transaction as specified by the contractual relationship between the 1459 server and the previous hop. A DIAMETER_AUTHORIZATION_REJECTED error 1460 message (see Section 7.1.5) is sent if the route traversed by the 1461 request is unacceptable. 1463 A home realm may also wish to check that each accounting request 1464 message corresponds to a Diameter response authorizing the session. 1465 Accounting requests without corresponding authorization responses 1466 SHOULD be subjected to further scrutiny, as should accounting 1467 requests indicating a difference between the requested and provided 1468 service. 1470 Similarly, the local Diameter agent, on receiving a Diameter response 1471 authorizing a session, MUST check the Route-Record AVPs to make sure 1472 that the route traversed by the response is acceptable. At each 1473 step, forwarding of an authorization response is considered evidence 1474 of a willingness to take on financial risk relative to the session. 1475 A local realm may wish to limit this exposure, for example, by 1476 establishing credit limits for intermediate realms and refusing to 1477 accept responses which would violate those limits. By issuing an 1478 accounting request corresponding to the authorization response, the 1479 local realm implicitly indicates its agreement to provide the service 1480 indicated in the authorization response. If the service cannot be 1481 provided by the local realm, then a DIAMETER_UNABLE_TO_COMPLY error 1482 message MUST be sent within the accounting request; a Diameter client 1483 receiving an authorization response for a service that it cannot 1484 perform MUST NOT substitute an alternate service, and then send 1485 accounting requests for the alternate service instead. 1487 3. Diameter Header 1489 A summary of the Diameter header format is shown below. The fields 1490 are transmitted in network byte order. 1492 0 1 2 3 1493 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 1494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1495 | Version | Message Length | 1496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1497 | command flags | Command-Code | 1498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1499 | Application-ID | 1500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1501 | Hop-by-Hop Identifier | 1502 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1503 | End-to-End Identifier | 1504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1505 | AVPs ... 1506 +-+-+-+-+-+-+-+-+-+-+-+-+- 1508 Version 1510 This Version field MUST be set to 1 to indicate Diameter Version 1511 1. 1513 Message Length 1515 The Message Length field is three octets and indicates the length 1516 of the Diameter message including the header fields. 1518 Command Flags 1520 The Command Flags field is eight bits. The following bits are 1521 assigned: 1523 0 1 2 3 4 5 6 7 1524 +-+-+-+-+-+-+-+-+ 1525 |R P E T r r r r| 1526 +-+-+-+-+-+-+-+-+ 1528 R(equest) 1530 If set, the message is a request. If cleared, the message is 1531 an answer. 1533 P(roxiable) 1535 If set, the message MAY be proxied, relayed or redirected. If 1536 cleared, the message MUST be locally processed. 1538 E(rror) 1540 If set, the message contains a protocol error, and the message 1541 will not conform to the ABNF described for this command. 1542 Messages with the 'E' bit set are commonly referred to as error 1543 messages. This bit MUST NOT be set in request messages. See 1544 Section 7.2. 1546 T(Potentially re-transmitted message) 1548 This flag is set after a link failover procedure, to aid the 1549 removal of duplicate requests. It is set when resending 1550 requests not yet acknowledged, as an indication of a possible 1551 duplicate due to a link failure. This bit MUST be cleared when 1552 sending a request for the first time, otherwise the sender MUST 1553 set this flag. Diameter agents only need to be concerned about 1554 the number of requests they send based on a single received 1555 request; retransmissions by other entities need not be tracked. 1556 Diameter agents that receive a request with the T flag set, 1557 MUST keep the T flag set in the forwarded request. This flag 1558 MUST NOT be set if an error answer message (e.g., a protocol 1559 error) has been received for the earlier message. It can be 1560 set only in cases where no answer has been received from the 1561 server for a request and the request is sent again. This flag 1562 MUST NOT be set in answer messages. 1564 r(eserved) 1566 These flag bits are reserved for future use, and MUST be set to 1567 zero, and ignored by the receiver. 1569 Command-Code 1571 The Command-Code field is three octets, and is used in order to 1572 communicate the command associated with the message. The 24-bit 1573 address space is managed by IANA (see Section 11.2.1). 1575 Command-Code values 16,777,214 and 16,777,215 (hexadecimal values 1576 FFFFFE -FFFFFF) are reserved for experimental use (See Section 1577 11.3). 1579 Application-ID 1581 Application-ID is four octets and is used to identify to which 1582 application the message is applicable for. The application can be 1583 an authentication application, an accounting application or a 1584 vendor specific application. See Section 11.3 for the possible 1585 values that the application-id may use. 1587 The application-id in the header MUST be the same as what is 1588 contained in any relevant application-id AVPs contained in the 1589 message. 1591 Hop-by-Hop Identifier 1593 The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in 1594 network byte order) and aids in matching requests and replies. 1595 The sender MUST ensure that the Hop-by-Hop identifier in a request 1596 is unique on a given connection at any given time, and MAY attempt 1597 to ensure that the number is unique across reboots. The sender of 1598 an Answer message MUST ensure that the Hop-by-Hop Identifier field 1599 contains the same value that was found in the corresponding 1600 request. The Hop-by-Hop identifier is normally a monotonically 1601 increasing number, whose start value was randomly generated. An 1602 answer message that is received with an unknown Hop-by-Hop 1603 Identifier MUST be discarded. 1605 End-to-End Identifier 1607 The End-to-End Identifier is an unsigned 32-bit integer field (in 1608 network byte order) and is used to detect duplicate messages. 1609 Upon reboot implementations MAY set the high order 12 bits to 1610 contain the low order 12 bits of current time, and the low order 1611 20 bits to a random value. Senders of request messages MUST 1612 insert a unique identifier on each message. The identifier MUST 1613 remain locally unique for a period of at least 4 minutes, even 1614 across reboots. The originator of an Answer message MUST ensure 1615 that the End-to-End Identifier field contains the same value that 1616 was found in the corresponding request. The End-to-End Identifier 1617 MUST NOT be modified by Diameter agents of any kind. The 1618 combination of the Origin-Host (see Section 6.3) and this field is 1619 used to detect duplicates. Duplicate requests SHOULD cause the 1620 same answer to be transmitted (modulo the hop-by-hop Identifier 1621 field and any routing AVPs that may be present), and MUST NOT 1622 affect any state that was set when the original request was 1623 processed. Duplicate answer messages that are to be locally 1624 consumed (see Section 6.2) SHOULD be silently discarded. 1626 AVPs 1628 AVPs are a method of encapsulating information relevant to the 1629 Diameter message. See Section 4 for more information on AVPs. 1631 3.1. Command Codes 1633 Each command Request/Answer pair is assigned a command code, and the 1634 sub-type (i.e., request or answer) is identified via the 'R' bit in 1635 the Command Flags field of the Diameter header. 1637 Every Diameter message MUST contain a command code in its header's 1638 Command-Code field, which is used to determine the action that is to 1639 be taken for a particular message. The following Command Codes are 1640 defined in the Diameter base protocol: 1642 Command-Name Abbrev. Code Reference 1643 -------------------------------------------------------- 1644 Abort-Session-Request ASR 274 8.5.1 1645 Abort-Session-Answer ASA 274 8.5.2 1646 Accounting-Request ACR 271 9.7.1 1647 Accounting-Answer ACA 271 9.7.2 1648 Capabilities-Exchange- CER 257 5.3.1 1649 Request 1650 Capabilities-Exchange- CEA 257 5.3.2 1651 Answer 1652 Device-Watchdog-Request DWR 280 5.5.1 1653 Device-Watchdog-Answer DWA 280 5.5.2 1654 Disconnect-Peer-Request DPR 282 5.4.1 1655 Disconnect-Peer-Answer DPA 282 5.4.2 1656 Re-Auth-Request RAR 258 8.3.1 1657 Re-Auth-Answer RAA 258 8.3.2 1658 Session-Termination- STR 275 8.4.1 1659 Request 1660 Session-Termination- STA 275 8.4.2 1661 Answer 1663 3.2. Command Code ABNF specification 1665 Every Command Code defined MUST include a corresponding ABNF 1666 specification, which is used to define the AVPs that MUST or MAY be 1667 present. The following format is used in the definition: 1669 command-def = command-name "::=" diameter-message 1671 command-name = diameter-name 1672 diameter-name = ALPHA *(ALPHA / DIGIT / "-") 1674 diameter-message = header [ *fixed] [ *required] [ *optional] 1676 header = "<" "Diameter Header:" command-id 1677 [r-bit] [p-bit] [e-bit] [application-id] ">" 1679 application-id = 1*DIGIT 1681 command-id = 1*DIGIT 1682 ; The Command Code assigned to the command 1684 r-bit = ", REQ" 1685 ; If present, the 'R' bit in the Command 1686 ; Flags is set, indicating that the message 1687 ; is a request, as opposed to an answer. 1689 p-bit = ", PXY" 1690 ; If present, the 'P' bit in the Command 1691 ; Flags is set, indicating that the message 1692 ; is proxiable. 1694 e-bit = ", ERR" 1695 ; If present, the 'E' bit in the Command 1696 ; Flags is set, indicating that the answer 1697 ; message contains a Result-Code AVP in 1698 ; the "protocol error" class. 1700 fixed = [qual] "<" avp-spec ">" 1701 ; Defines the fixed position of an AVP 1703 required = [qual] "{" avp-spec "}" 1704 ; The AVP MUST be present and can appear 1705 ; anywhere in the message. 1707 optional = [qual] "[" avp-name "]" 1708 ; The avp-name in the 'optional' rule cannot 1709 ; evaluate to any AVP Name which is included 1710 ; in a fixed or required rule. The AVP can 1711 ; appear anywhere in the message. 1713 qual = [min] "*" [max] 1714 ; See ABNF conventions, RFC 4234 Section 6.6. 1715 ; The absence of any qualifiers depends on 1716 ; whether it precedes a fixed, required, or 1717 ; optional rule. If a fixed or required rule has 1718 ; no qualifier, then exactly one such AVP MUST 1719 ; be present. If an optional rule has no 1720 ; qualifier, then 0 or 1 such AVP may be 1721 ; present. 1722 ; 1723 ; NOTE: "[" and "]" have a different meaning 1724 ; than in ABNF (see the optional rule, above). 1725 ; These braces cannot be used to express 1726 ; optional fixed rules (such as an optional 1727 ; ICV at the end). To do this, the convention 1728 ; is '0*1fixed'. 1730 min = 1*DIGIT 1731 ; The minimum number of times the element may 1732 ; be present. The default value is zero. 1734 max = 1*DIGIT 1735 ; The maximum number of times the element may 1736 ; be present. The default value is infinity. A 1737 ; value of zero implies the AVP MUST NOT be 1738 ; present. 1740 avp-spec = diameter-name 1741 ; The avp-spec has to be an AVP Name, defined 1742 ; in the base or extended Diameter 1743 ; specifications. 1745 avp-name = avp-spec / "AVP" 1746 ; The string "AVP" stands for *any* arbitrary AVP 1747 ; Name, not otherwise listed in that command code 1748 ; definition. 1750 The following is a definition of a fictitious command code: 1752 Example-Request ::= < Diameter Header: 9999999, REQ, PXY > 1753 { User-Name } 1754 * { Origin-Host } 1755 * [ AVP 1757 3.3. Diameter Command Naming Conventions 1759 Diameter command names typically includes one or more English words 1760 followed by the verb Request or Answer. Each English word is 1761 delimited by a hyphen. A three-letter acronym for both the request 1762 and answer is also normally provided. 1764 An example is a message set used to terminate a session. The command 1765 name is Session-Terminate-Request and Session-Terminate-Answer, while 1766 the acronyms are STR and STA, respectively. 1768 Both the request and the answer for a given command share the same 1769 command code. The request is identified by the R(equest) bit in the 1770 Diameter header set to one (1), to ask that a particular action be 1771 performed, such as authorizing a user or terminating a session. Once 1772 the receiver has completed the request it issues the corresponding 1773 answer, which includes a result code that communicates one of the 1774 following: 1776 o The request was successful 1778 o The request failed 1780 o An additional request must be sent to provide information the peer 1781 requires prior to returning a successful or failed answer. 1783 o The receiver could not process the request, but provides 1784 information about a Diameter peer that is able to satisfy the 1785 request, known as redirect. 1787 Additional information, encoded within AVPs, MAY also be included in 1788 answer messages. 1790 4. Diameter AVPs 1792 Diameter AVPs carry specific authentication, accounting, 1793 authorization and routing information as well as configuration 1794 details for the request and reply. 1796 Some AVPs MAY be listed more than once. The effect of such an AVP is 1797 specific, and is specified in each case by the AVP description. 1799 Each AVP of type OctetString MUST be padded to align on a 32-bit 1800 boundary, while other AVP types align naturally. A number of zero- 1801 valued bytes are added to the end of the AVP Data field till a word 1802 boundary is reached. The length of the padding is not reflected in 1803 the AVP Length field. 1805 4.1. AVP Header 1807 The fields in the AVP header MUST be sent in network byte order. The 1808 format of the header is: 1810 0 1 2 3 1811 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 1812 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1813 | AVP Code | 1814 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1815 |V M r r r r r r| AVP Length | 1816 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1817 | Vendor-ID (opt) | 1818 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1819 | Data ... 1820 +-+-+-+-+-+-+-+-+ 1822 AVP Code 1824 The AVP Code, combined with the Vendor-Id field, identifies the 1825 attribute uniquely. AVP numbers 1 through 255 are reserved for 1826 backward compatibility with RADIUS, without setting the Vendor-Id 1827 field. AVP numbers 256 and above are used for Diameter, which are 1828 allocated by IANA (see Section 11.1). 1830 AVP Flags 1832 The AVP Flags field informs the receiver how each attribute must 1833 be handled. The 'r' (reserved) bits are unused and SHOULD be set 1834 to 0. Note that subsequent Diameter applications MAY define 1835 additional bits within the AVP Header, and an unrecognized bit 1836 SHOULD be considered an error. 1838 The 'M' Bit, known as the Mandatory bit, indicates whether support 1839 of the AVP is required. If an AVP with the 'M' bit set is 1840 received by a Diameter client, server, proxy, or translation agent 1841 and either the AVP or its value is unrecognized, the message MUST 1842 be rejected. Diameter Relay and redirect agents MUST NOT reject 1843 messages with unrecognized AVPs. 1845 The 'M' bit MUST be set according to the rules defined for the AVP 1846 containing it. In order to preserve interoperability, a Diameter 1847 implementation MUST be able to exclude from a Diameter message any 1848 Mandatory AVP which is neither defined in the base Diameter 1849 protocol nor in any of the Diameter Application specifications 1850 governing the message in which it appears. It MAY do this in one 1851 of the following ways: 1853 1. If a message is rejected because it contains a Mandatory AVP 1854 which is neither defined in the base Diameter standard nor in 1855 any of the Diameter Application specifications governing the 1856 message in which it appears, the implementation may resend the 1857 message without the AVP, possibly inserting additional 1858 standard AVPs instead. 1860 2. A configuration option may be provided on a system wide, per 1861 peer, or per realm basis that would allow/prevent particular 1862 Mandatory AVPs to be sent. Thus an administrator could change 1863 the configuration to avoid interoperability problems. 1865 Diameter implementations are required to support all Mandatory 1866 AVPs which are allowed by the message's formal syntax and defined 1867 either in the base Diameter standard or in one of the Diameter 1868 Application specifications governing the message. 1870 AVPs with the 'M' bit cleared are informational only and a 1871 receiver that receives a message with such an AVP that is not 1872 supported, or whose value is not supported, MAY simply ignore the 1873 AVP. 1875 The 'V' bit, known as the Vendor-Specific bit, indicates whether 1876 the optional Vendor-ID field is present in the AVP header. When 1877 set the AVP Code belongs to the specific vendor code address 1878 space. 1880 Unless otherwise noted, AVPs will have the following default AVP 1881 Flags field settings: 1883 The 'M' bit MUST be set. The 'V' bit MUST NOT be set. 1885 AVP Length 1887 The AVP Length field is three octets, and indicates the number of 1888 octets in this AVP including the AVP Code, AVP Length, AVP Flags, 1889 Vendor-ID field (if present) and the AVP data. If a message is 1890 received with an invalid attribute length, the message SHOULD be 1891 rejected. 1893 4.1.1. Optional Header Elements 1895 The AVP Header contains one optional field. This field is only 1896 present if the respective bit-flag is enabled. 1898 Vendor-ID 1900 The Vendor-ID field is present if the 'V' bit is set in the AVP 1901 Flags field. The optional four-octet Vendor-ID field contains the 1902 IANA assigned "SMI Network Management Private Enterprise Codes" 1903 [RFC3232] value, encoded in network byte order. Any vendor 1904 wishing to implement a vendor-specific Diameter AVP MUST use their 1905 own Vendor-ID along with their privately managed AVP address 1906 space, guaranteeing that they will not collide with any other 1907 vendor's vendor-specific AVP(s), nor with future IETF 1908 applications. 1910 A vendor ID value of zero (0) corresponds to the IETF adopted AVP 1911 values, as managed by the IANA. Since the absence of the vendor 1912 ID field implies that the AVP in question is not vendor specific, 1913 implementations MUST NOT use the zero (0) vendor ID. 1915 4.2. Basic AVP Data Formats 1917 The Data field is zero or more octets and contains information 1918 specific to the Attribute. The format and length of the Data field 1919 is determined by the AVP Code and AVP Length fields. The format of 1920 the Data field MUST be one of the following base data types or a data 1921 type derived from the base data types. In the event that a new Basic 1922 AVP Data Format is needed, a new version of this RFC must be created. 1924 OctetString 1926 The data contains arbitrary data of variable length. Unless 1927 otherwise noted, the AVP Length field MUST be set to at least 8 1928 (12 if the 'V' bit is enabled). AVP Values of this type that are 1929 not a multiple of four-octets in length is followed by the 1930 necessary padding so that the next AVP (if any) will start on a 1931 32-bit boundary. 1933 Integer32 1935 32 bit signed value, in network byte order. The AVP Length field 1936 MUST be set to 12 (16 if the 'V' bit is enabled). 1938 Integer64 1940 64 bit signed value, in network byte order. The AVP Length field 1941 MUST be set to 16 (20 if the 'V' bit is enabled). 1943 Unsigned32 1945 32 bit unsigned value, in network byte order. The AVP Length 1946 field MUST be set to 12 (16 if the 'V' bit is enabled). 1948 Unsigned64 1950 64 bit unsigned value, in network byte order. The AVP Length 1951 field MUST be set to 16 (20 if the 'V' bit is enabled). 1953 Float32 1955 This represents floating point values of single precision as 1956 described by [FLOATPOINT]. The 32-bit value is transmitted in 1957 network byte order. The AVP Length field MUST be set to 12 (16 if 1958 the 'V' bit is enabled). 1960 Float64 1962 This represents floating point values of double precision as 1963 described by [FLOATPOINT]. The 64-bit value is transmitted in 1964 network byte order. The AVP Length field MUST be set to 16 (20 if 1965 the 'V' bit is enabled). 1967 Grouped 1969 The Data field is specified as a sequence of AVPs. Each of these 1970 AVPs follows - in the order in which they are specified - 1971 including their headers and padding. The AVP Length field is set 1972 to 8 (12 if the 'V' bit is enabled) plus the total length of all 1973 included AVPs, including their headers and padding. Thus the AVP 1974 length field of an AVP of type Grouped is always a multiple of 4. 1976 4.3. Derived AVP Data Formats 1978 In addition to using the Basic AVP Data Formats, applications may 1979 define data formats derived from the Basic AVP Data Formats. An 1980 application that defines new AVP Derived Data Formats MUST include 1981 them in a section entitled "AVP Derived Data Formats", using the same 1982 format as the definitions below. Each new definition must be either 1983 defined or listed with a reference to the RFC that defines the 1984 format. 1986 The below AVP Derived Data Formats are commonly used by applications. 1988 Address 1990 The Address format is derived from the OctetString AVP Base 1991 Format. It is a discriminated union, representing, for example a 1992 32-bit (IPv4) [IPV4] or 128-bit (IPv6) [RFC4291] address, most 1993 significant octet first. The first two octets of the Address AVP 1994 represents the AddressType, which contains an Address Family 1995 defined in [IANAADFAM]. The AddressType is used to discriminate 1996 the content and format of the remaining octets. 1998 Time 2000 The Time format is derived from the OctetString AVP Base Format. 2001 The string MUST contain four octets, in the same format as the 2002 first four bytes are in the NTP timestamp format. The NTP 2003 Timestamp format is defined in chapter 3 of [RFC4330]. 2005 This represents the number of seconds since 0h on 1 January 1900 2006 with respect to the Coordinated Universal Time (UTC). 2008 On 6h 28m 16s UTC, 7 February 2036 the time value will overflow. 2009 SNTP [RFC4330] describes a procedure to extend the time to 2104. 2010 This procedure MUST be supported by all DIAMETER nodes. 2012 UTF8String 2014 The UTF8String format is derived from the OctetString AVP Base 2015 Format. This is a human readable string represented using the 2016 ISO/IEC IS 10646-1 character set, encoded as an OctetString using 2017 the UTF-8 [RFC3629] transformation format described in RFC 3629. 2019 Since additional code points are added by amendments to the 10646 2020 standard from time to time, implementations MUST be prepared to 2021 encounter any code point from 0x00000001 to 0x7fffffff. Byte 2022 sequences that do not correspond to the valid encoding of a code 2023 point into UTF-8 charset or are outside this range are prohibited. 2025 The use of control codes SHOULD be avoided. When it is necessary 2026 to represent a new line, the control code sequence CR LF SHOULD be 2027 used. 2029 The use of leading or trailing white space SHOULD be avoided. 2031 For code points not directly supported by user interface hardware 2032 or software, an alternative means of entry and display, such as 2033 hexadecimal, MAY be provided. 2035 For information encoded in 7-bit US-ASCII, the UTF-8 charset is 2036 identical to the US-ASCII charset. 2038 UTF-8 may require multiple bytes to represent a single character / 2039 code point; thus the length of an UTF8String in octets may be 2040 different from the number of characters encoded. 2042 Note that the AVP Length field of an UTF8String is measured in 2043 octets, not characters. 2045 DiameterIdentity 2047 The DiameterIdentity format is derived from the OctetString AVP 2048 Base Format. 2050 DiameterIdentity = FQDN 2052 DiameterIdentity value is used to uniquely identify a Diameter 2053 node for purposes of duplicate connection and routing loop 2054 detection. 2056 The contents of the string MUST be the FQDN of the Diameter node. 2057 If multiple Diameter nodes run on the same host, each Diameter 2058 node MUST be assigned a unique DiameterIdentity. If a Diameter 2059 node can be identified by several FQDNs, a single FQDN should be 2060 picked at startup, and used as the only DiameterIdentity for that 2061 node, whatever the connection it is sent on. 2063 DiameterURI 2065 The DiameterURI MUST follow the Uniform Resource Identifiers (URI) 2066 syntax [RFC3986] rules specified below: 2068 "aaa://" FQDN [ port ] [ transport ] [ protocol ] 2070 ; No transport security 2072 "aaas://" FQDN [ port ] [ transport ] [ protocol ] 2074 ; Transport security used 2076 FQDN = Fully Qualified Host Name 2078 port = ":" 1*DIGIT 2080 ; One of the ports used to listen for 2081 ; incoming connections. 2082 ; If absent, 2083 ; the default Diameter port (3868) is 2084 ; assumed. 2086 transport = ";transport=" transport-protocol 2088 ; One of the transports used to listen 2089 ; for incoming connections. If absent, 2090 ; the default SCTP [RFC2960] protocol is 2091 ; assumed. UDP MUST NOT be used when 2092 ; the aaa-protocol field is set to 2093 ; diameter. 2095 transport-protocol = ( "tcp" / "sctp" / "udp" ) 2097 protocol = ";protocol=" aaa-protocol 2099 ; If absent, the default AAA protocol 2100 ; is diameter. 2102 aaa-protocol = ( "diameter" / "radius" / "tacacs+" ) 2104 The following are examples of valid Diameter host identities: 2106 aaa://host.example.com;transport=tcp 2107 aaa://host.example.com:6666;transport=tcp 2108 aaa://host.example.com;protocol=diameter 2109 aaa://host.example.com:6666;protocol=diameter 2110 aaa://host.example.com:6666;transport=tcp;protocol=diameter 2111 aaa://host.example.com:1813;transport=udp;protocol=radius 2113 Enumerated 2115 Enumerated is derived from the Integer32 AVP Base Format. The 2116 definition contains a list of valid values and their 2117 interpretation and is described in the Diameter application 2118 introducing the AVP. 2120 IPFilterRule 2122 The IPFilterRule format is derived from the OctetString AVP Base 2123 Format. It uses the ASCII charset. Packets may be filtered based 2124 on the following information that is associated with it: 2126 Direction (in or out) 2127 Source and destination IP address (possibly masked) 2128 Protocol 2129 Source and destination port (lists or ranges) 2130 TCP flags 2131 IP fragment flag 2132 IP options 2133 ICMP types 2135 Rules for the appropriate direction are evaluated in order, with 2136 the first matched rule terminating the evaluation. Each packet is 2137 evaluated once. If no rule matches, the packet is dropped if the 2138 last rule evaluated was a permit, and passed if the last rule was 2139 a deny. 2141 IPFilterRule filters MUST follow the format: 2143 action dir proto from src to dst [options] 2145 action permit - Allow packets that match the rule. 2146 deny - Drop packets that match the rule. 2148 dir "in" is from the terminal, "out" is to the 2149 terminal. 2151 proto An IP protocol specified by number. The "ip" 2152 keyword means any protocol will match. 2154 src and dst
[ports] 2156 The
may be specified as: 2157 ipno An IPv4 or IPv6 number in dotted- 2158 quad or canonical IPv6 form. Only 2159 this exact IP number will match the 2160 rule. 2161 ipno/bits An IP number as above with a mask 2162 width of the form 1.2.3.4/24. In 2163 this case, all IP numbers from 2164 1.2.3.0 to 1.2.3.255 will match. 2165 The bit width MUST be valid for the 2166 IP version and the IP number MUST 2167 NOT have bits set beyond the mask. 2168 For a match to occur, the same IP 2169 version must be present in the 2170 packet that was used in describing 2171 the IP address. To test for a 2172 particular IP version, the bits part 2173 can be set to zero. The keyword 2174 "any" is 0.0.0.0/0 or the IPv6 2175 equivalent. The keyword "assigned" 2176 is the address or set of addresses 2177 assigned to the terminal. For IPv4, 2178 a typical first rule is often "deny 2179 in ip! assigned" 2181 The sense of the match can be inverted by 2182 preceding an address with the not modifier (!), 2183 causing all other addresses to be matched 2184 instead. This does not affect the selection of 2185 port numbers. 2187 With the TCP, UDP and SCTP protocols, optional 2188 ports may be specified as: 2190 {port/port-port}[,ports[,...]] 2192 The '-' notation specifies a range of ports 2193 (including boundaries). 2195 Fragmented packets that have a non-zero offset 2196 (i.e., not the first fragment) will never match 2197 a rule that has one or more port 2198 specifications. See the frag option for 2199 details on matching fragmented packets. 2201 options: 2202 frag Match if the packet is a fragment and this is not 2203 the first fragment of the datagram. frag may not 2204 be used in conjunction with either tcpflags or 2205 TCP/UDP port specifications. 2207 ipoptions spec 2208 Match if the IP header contains the comma 2209 separated list of options specified in spec. The 2210 supported IP options are: 2212 ssrr (strict source route), lsrr (loose source 2213 route), rr (record packet route) and ts 2214 (timestamp). The absence of a particular option 2215 may be denoted with a '!'. 2217 tcpoptions spec 2218 Match if the TCP header contains the comma 2219 separated list of options specified in spec. The 2220 supported TCP options are: 2222 mss (maximum segment size), window (tcp window 2223 advertisement), sack (selective ack), ts (rfc1323 2224 timestamp) and cc (rfc1644 t/tcp connection 2225 count). The absence of a particular option may 2226 be denoted with a '!'. 2228 established 2229 TCP packets only. Match packets that have the RST 2230 or ACK bits set. 2232 setup TCP packets only. Match packets that have the SYN 2233 bit set but no ACK bit. 2235 tcpflags spec 2236 TCP packets only. Match if the TCP header 2237 contains the comma separated list of flags 2238 specified in spec. The supported TCP flags are: 2240 fin, syn, rst, psh, ack and urg. The absence of a 2241 particular flag may be denoted with a '!'. A rule 2242 that contains a tcpflags specification can never 2243 match a fragmented packet that has a non-zero 2244 offset. See the frag option for details on 2245 matching fragmented packets. 2247 icmptypes types 2248 ICMP packets only. Match if the ICMP type is in 2249 the list types. The list may be specified as any 2250 combination of ranges or individual types 2251 separated by commas. Both the numeric values and 2252 the symbolic values listed below can be used. The 2253 supported ICMP types are: 2255 echo reply (0), destination unreachable (3), 2256 source quench (4), redirect (5), echo request 2257 (8), router advertisement (9), router 2258 solicitation (10), time-to-live exceeded (11), IP 2259 header bad (12), timestamp request (13), 2260 timestamp reply (14), information request (15), 2261 information reply (16), address mask request (17) 2262 and address mask reply (18). 2264 There is one kind of packet that the access device MUST always 2265 discard, that is an IP fragment with a fragment offset of one. 2266 This is a valid packet, but it only has one use, to try to 2267 circumvent firewalls. 2269 An access device that is unable to interpret or apply a deny rule 2270 MUST terminate the session. An access device that is unable to 2271 interpret or apply a permit rule MAY apply a more restrictive 2272 rule. An access device MAY apply deny rules of its own before the 2273 supplied rules, for example to protect the access device owner's 2274 infrastructure. 2276 The rule syntax is a modified subset of ipfw(8) from FreeBSD, and 2277 the ipfw.c code may provide a useful base for implementations. 2279 4.4. Grouped AVP Values 2281 The Diameter protocol allows AVP values of type 'Grouped.' This 2282 implies that the Data field is actually a sequence of AVPs. It is 2283 possible to include an AVP with a Grouped type within a Grouped type, 2284 that is, to nest them. AVPs within an AVP of type Grouped have the 2285 same padding requirements as non-Grouped AVPs, as defined in Section 2286 4. 2288 The AVP Code numbering space of all AVPs included in a Grouped AVP is 2289 the same as for non-grouped AVPs. Further, if any of the AVPs 2290 encapsulated within a Grouped AVP has the 'M' (mandatory) bit set, 2291 the Grouped AVP itself MUST also include the 'M' bit set. 2293 Every Grouped AVP defined MUST include a corresponding grammar, using 2294 ABNF [RFC4234] (with modifications), as defined below. 2296 grouped-avp-def = name "::=" avp 2298 name-fmt = ALPHA *(ALPHA / DIGIT / "-") 2300 name = name-fmt 2301 ; The name has to be the name of an AVP, 2302 ; defined in the base or extended Diameter 2303 ; specifications. 2305 avp = header [ *fixed] [ *required] [ *optional] 2306 [ *fixed] 2308 header = "<" "AVP-Header:" avpcode [vendor] ">" 2310 avpcode = 1*DIGIT 2311 ; The AVP Code assigned to the Grouped AVP 2313 vendor = 1*DIGIT 2314 ; The Vendor-ID assigned to the Grouped AVP. 2315 ; If absent, the default value of zero is 2316 ; used. 2318 4.4.1. Example AVP with a Grouped Data type 2320 The Example-AVP (AVP Code 999999) is of type Grouped and is used to 2321 clarify how Grouped AVP values work. The Grouped Data field has the 2322 following ABNF grammar: 2324 Example-AVP ::= < AVP Header: 999999 > 2325 { Origin-Host } 2326 1*{ Session-Id } 2327 *[ AVP ] 2329 An Example-AVP with Grouped Data follows. 2331 The Origin-Host AVP is required (Section 6.3). In this case: 2333 Origin-Host = "example.com". 2335 One or more Session-Ids must follow. Here there are two: 2337 Session-Id = 2338 "grump.example.com:33041;23432;893;0AF3B81" 2340 Session-Id = 2341 "grump.example.com:33054;23561;2358;0AF3B82" 2343 optional AVPs included are 2345 Recovery-Policy = 2346 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35 2347 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5 2348 c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd 2349 f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a 2350 cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119 2351 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c 2352 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92 2354 Futuristic-Acct-Record = 2355 fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0 2356 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8 2357 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c 2358 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067 2359 d3427475e49968f841 2361 The data for the optional AVPs is represented in hex since the format 2362 of these AVPs is neither known at the time of definition of the 2363 Example-AVP group, nor (likely) at the time when the example instance 2364 of this AVP is interpreted - except by Diameter implementations which 2365 support the same set of AVPs. The encoding example illustrates how 2366 padding is used and how length fields are calculated. Also note that 2367 AVPs may be present in the Grouped AVP value which the receiver 2368 cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record 2369 AVPs). The length of the Example-AVP is the sum of all the length of 2370 the member AVPs including their padding plus the Example-AVP header 2371 size. 2373 This AVP would be encoded as follows: 2375 0 1 2 3 4 5 6 7 2376 +-------+-------+-------+-------+-------+-------+-------+-------+ 2377 0 | Example AVP Header (AVP Code = 999999), Length = 496 | 2378 +-------+-------+-------+-------+-------+-------+-------+-------+ 2379 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 | 2380 +-------+-------+-------+-------+-------+-------+-------+-------+ 2381 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' | 2382 +-------+-------+-------+-------+-------+-------+-------+-------+ 2383 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header | 2384 +-------+-------+-------+-------+-------+-------+-------+-------+ 2385 32 | (AVP Code = 263), Length = 49 | 'g' | 'r' | 'u' | 'm' | 2386 +-------+-------+-------+-------+-------+-------+-------+-------+ 2387 . . . 2388 +-------+-------+-------+-------+-------+-------+-------+-------+ 2389 72 | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding|Padding| 2390 +-------+-------+-------+-------+-------+-------+-------+-------+ 2391 80 | Session-Id AVP Header (AVP Code = 263), Length = 50 | 2392 +-------+-------+-------+-------+-------+-------+-------+-------+ 2393 88 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' | 2394 +-------+-------+-------+-------+-------+-------+-------+-------+ 2395 . . . 2396 +-------+-------+-------+-------+-------+-------+-------+-------+ 2397 120| '5' | '8' | ';' | '0' | 'A' | 'F' | '3' | 'B' | 2398 +-------+-------+-------+-------+-------+-------+-------+-------+ 2399 128| '8' | '2' |Padding|Padding| Recovery-Policy Header (AVP | 2400 +-------+-------+-------+-------+-------+-------+-------+-------+ 2401 136| Code = 8341), Length = 223 | 0x21 | 0x63 | 0xbc | 0x1d | 2402 +-------+-------+-------+-------+-------+-------+-------+-------+ 2403 144| 0x0a | 0xd8 | 0x23 | 0x71 | 0xf6 | 0xbc | 0x09 | 0x48 | 2404 +-------+-------+-------+-------+-------+-------+-------+-------+ 2405 . . . 2406 +-------+-------+-------+-------+-------+-------+-------+-------+ 2407 352| 0x8c | 0x7f | 0x92 |Padding| Futuristic-Acct-Record Header | 2408 +-------+-------+-------+-------+-------+-------+-------+-------+ 2409 328|(AVP Code = 15930),Length = 137| 0xfe | 0x19 | 0xda | 0x58 | 2410 +-------+-------+-------+-------+-------+-------+-------+-------+ 2411 336| 0x02 | 0xac | 0xd9 | 0x8b | 0x07 | 0xa5 | 0xb8 | 0xc6 | 2412 +-------+-------+-------+-------+-------+-------+-------+-------+ 2413 . . . 2414 +-------+-------+-------+-------+-------+-------+-------+-------+ 2415 488| 0xe4 | 0x99 | 0x68 | 0xf8 | 0x41 |Padding|Padding|Padding| 2416 +-------+-------+-------+-------+-------+-------+-------+-------+ 2418 4.5. Diameter Base Protocol AVPs 2420 The following table describes the Diameter AVPs defined in the base 2421 protocol, their AVP Code values, types, possible flag values. 2423 Due to space constraints, the short form DiamIdent is used to 2424 represent DiameterIdentity. 2426 +---------------------+ 2427 | AVP Flag rules | 2428 |----+-----+----+-----| 2429 AVP Section | | |SHLD| MUST| 2430 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT| 2431 -----------------------------------------|----+-----+----+-----| 2432 Acct- 85 9.8.2 Unsigned32 | M | | | V | 2433 Interim-Interval | | | | | 2434 Accounting- 483 9.8.7 Enumerated | M | | | V | 2435 Realtime-Required | | | | | 2436 Acct- 50 9.8.5 UTF8String | M | | | V | 2437 Multi-Session-Id | | | | | 2438 Accounting- 485 9.8.3 Unsigned32 | M | | | V | 2439 Record-Number | | | | | 2440 Accounting- 480 9.8.1 Enumerated | M | | | V | 2441 Record-Type | | | | | 2442 Accounting- 44 9.8.4 OctetString| M | | | V | 2443 Session-Id | | | | | 2444 Accounting- 287 9.8.6 Unsigned64 | M | | | V | 2445 Sub-Session-Id | | | | | 2446 Acct- 259 6.9 Unsigned32 | M | | | V | 2447 Application-Id | | | | | 2448 Auth- 258 6.8 Unsigned32 | M | | | V | 2449 Application-Id | | | | | 2450 Auth-Request- 274 8.7 Enumerated | M | | | V | 2451 Type | | | | | 2452 Authorization- 291 8.9 Unsigned32 | M | | | V | 2453 Lifetime | | | | | 2454 Auth-Grace- 276 8.10 Unsigned32 | M | | | V | 2455 Period | | | | | 2456 Auth-Session- 277 8.11 Enumerated | M | | | V | 2457 State | | | | | 2458 Re-Auth-Request- 285 8.12 Enumerated | M | | | V | 2459 Type | | | | | 2460 Class 25 8.20 OctetString| M | | | V | 2461 Destination-Host 293 6.5 DiamIdent | M | | | V | 2462 Destination- 283 6.6 DiamIdent | M | | | V | 2463 Realm | | | | | 2464 Disconnect-Cause 273 5.4.3 Enumerated | M | | | V | 2465 E2E-Sequence AVP 300 6.15 Grouped | M | | | V | 2466 Error-Message 281 7.3 UTF8String | | | | V,M | 2467 Error-Reporting- 294 7.4 DiamIdent | | | | V,M | 2468 Host | | | | | 2469 Event-Timestamp 55 8.21 Time | M | | | V | 2470 Experimental- 297 7.6 Grouped | M | | | V | 2471 Result | | | | | 2472 -----------------------------------------|----+-----+----+-----| 2473 +---------------------+ 2474 | AVP Flag rules | 2475 |----+-----+----+-----| 2476 AVP Section | | |SHLD| MUST| 2477 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT| 2478 -----------------------------------------|----+-----+----+-----| 2479 Experimental- 298 7.7 Unsigned32 | M | | | V | 2480 Result-Code | | | | | 2481 Failed-AVP 279 7.5 Grouped | M | | | V | 2482 Firmware- 267 5.3.4 Unsigned32 | | | | V,M | 2483 Revision | | | | | 2484 Host-IP-Address 257 5.3.5 Address | M | | | V | 2485 Inband-Security | M | | | V | 2486 -Id 299 6.10 Unsigned32 | | | | | 2487 Multi-Round- 272 8.19 Unsigned32 | M | | | V | 2488 Time-Out | | | | | 2489 Origin-Host 264 6.3 DiamIdent | M | | | V | 2490 Origin-Realm 296 6.4 DiamIdent | M | | | V | 2491 Origin-State-Id 278 8.16 Unsigned32 | M | | | V | 2492 Product-Name 269 5.3.7 UTF8String | | | | V,M | 2493 Proxy-Host 280 6.7.3 DiamIdent | M | | | V | 2494 Proxy-Info 284 6.7.2 Grouped | M | | | V | 2495 Proxy-State 33 6.7.4 OctetString| M | | | V | 2496 Redirect-Host 292 6.12 DiamURI | M | | | V | 2497 Redirect-Host- 261 6.13 Enumerated | M | | | V | 2498 Usage | | | | | 2499 Redirect-Max- 262 6.14 Unsigned32 | M | | | V | 2500 Cache-Time | | | | | 2501 Result-Code 268 7.1 Unsigned32 | M | | | V | 2502 Route-Record 282 6.7.1 DiamIdent | M | | | V | 2503 Session-Id 263 8.8 UTF8String | M | | | V | 2504 Session-Timeout 27 8.13 Unsigned32 | M | | | V | 2505 Session-Binding 270 8.17 Unsigned32 | M | | | V | 2506 Session-Server- 271 8.18 Enumerated | M | | | V | 2507 Failover | | | | | 2508 Supported- 265 5.3.6 Unsigned32 | M | | | V | 2509 Vendor-Id | | | | | 2510 Termination- 295 8.15 Enumerated | M | | | V | 2511 Cause | | | | | 2512 User-Name 1 8.14 UTF8String | M | | | V | 2513 Vendor-Id 266 5.3.3 Unsigned32 | M | | | V | 2514 Vendor-Specific- 260 6.11 Grouped | M | | | V | 2515 Application-Id | | | | | 2516 -----------------------------------------|----+-----+----+-----| 2518 5. Diameter Peers 2520 This section describes how Diameter nodes establish connections and 2521 communicate with peers. 2523 5.1. Peer Connections 2525 Although a Diameter node may have many possible peers that it is able 2526 to communicate with, it may not be economical to have an established 2527 connection to all of them. At a minimum, a Diameter node SHOULD have 2528 an established connection with two peers per realm, known as the 2529 primary and secondary peers. Of course, a node MAY have additional 2530 connections, if it is deemed necessary. Typically, all messages for 2531 a realm are sent to the primary peer, but in the event that failover 2532 procedures are invoked, any pending requests are sent to the 2533 secondary peer. However, implementations are free to load balance 2534 requests between a set of peers. 2536 Note that a given peer MAY act as a primary for a given realm, while 2537 acting as a secondary for another realm. 2539 When a peer is deemed suspect, which could occur for various reasons, 2540 including not receiving a DWA within an allotted timeframe, no new 2541 requests should be forwarded to the peer, but failover procedures are 2542 invoked. When an active peer is moved to this mode, additional 2543 connections SHOULD be established to ensure that the necessary number 2544 of active connections exists. 2546 There are two ways that a peer is removed from the suspect peer list: 2548 1. The peer is no longer reachable, causing the transport connection 2549 to be shutdown. The peer is moved to the closed state. 2551 2. Three watchdog messages are exchanged with accepted round trip 2552 times, and the connection to the peer is considered stabilized. 2554 In the event the peer being removed is either the primary or 2555 secondary, an alternate peer SHOULD replace the deleted peer, and 2556 assume the role of either primary or secondary. 2558 5.2. Diameter Peer Discovery 2560 Allowing for dynamic Diameter agent discovery will make it possible 2561 for simpler and more robust deployment of Diameter services. In 2562 order to promote interoperable implementations of Diameter peer 2563 discovery, the following mechanisms are described. These are based 2564 on existing IETF standards. The first option (manual configuration) 2565 MUST be supported by all DIAMETER nodes, while the latter option 2566 (DNS) MAY be supported. 2568 There are two cases where Diameter peer discovery may be performed. 2569 The first is when a Diameter client needs to discover a first-hop 2570 Diameter agent. The second case is when a Diameter agent needs to 2571 discover another agent - for further handling of a Diameter 2572 operation. In both cases, the following 'search order' is 2573 recommended: 2575 1. The Diameter implementation consults its list of static 2576 (manually) configured Diameter agent locations. These will be 2577 used if they exist and respond. 2579 2. The Diameter implementation performs a NAPTR query for a server 2580 in a particular realm. The Diameter implementation has to know 2581 in advance which realm to look for a Diameter agent in. This 2582 could be deduced, for example, from the 'realm' in a NAI that a 2583 Diameter implementation needed to perform a Diameter operation 2584 on. 2586 * The services relevant for the task of transport protocol 2587 selection are those with NAPTR service fields with values 2588 "AAA+D2x", where x is a letter that corresponds to a transport 2589 protocol supported by the domain. This specification defines 2590 D2T for TCP and D2S for SCTP. We also establish an IANA 2591 registry for NAPTR service name to transport protocol 2592 mappings. 2594 These NAPTR records provide a mapping from a domain, to the 2595 SRV record for contacting a server with the specific transport 2596 protocol in the NAPTR services field. The resource record 2597 will contain an empty regular expression and a replacement 2598 value, which is the SRV record for that particular transport 2599 protocol. If the server supports multiple transport 2600 protocols, there will be multiple NAPTR records, each with a 2601 different service value. As per [RFC3403], the client 2602 discards any records whose services fields are not applicable. 2603 For the purposes of this specification, several rules are 2604 defined. 2606 * A client MUST discard any service fields that identify a 2607 resolution service whose value is not "D2X", for values of X 2608 that indicate transport protocols supported by the client. 2609 The NAPTR processing as described in [RFC3403] will result in 2610 discovery of the most preferred transport protocol of the 2611 server that is supported by the client, as well as an SRV 2612 record for the server. 2614 The domain suffixes in the NAPTR replacement field SHOULD 2615 match the domain of the original query. 2617 3. If no NAPTR records are found, the requester queries for those 2618 address records for the destination address, 2619 '_diameter._sctp'.realm or '_diameter._tcp'.realm. Address 2620 records include A RR's, AAAA RR's or other similar records, 2621 chosen according to the requestor's network protocol 2622 capabilities. If the DNS server returns no address records, the 2623 requestor gives up. 2625 If the server is using a site certificate, the domain name in the 2626 query and the domain name in the replacement field MUST both be 2627 valid based on the site certificate handed out by the server in 2628 the TLS or IKE exchange. Similarly, the domain name in the SRV 2629 query and the domain name in the target in the SRV record MUST 2630 both be valid based on the same site certificate. Otherwise, an 2631 attacker could modify the DNS records to contain replacement 2632 values in a different domain, and the client could not validate 2633 that this was the desired behavior, or the result of an attack 2635 Also, the Diameter Peer MUST check to make sure that the 2636 discovered peers are authorized to act in its role. 2637 Authentication via IKE or TLS, or validation of DNS RRs via 2638 DNSSEC is not sufficient to conclude this. For example, a web 2639 server may have obtained a valid TLS certificate, and secured RRs 2640 may be included in the DNS, but this does not imply that it is 2641 authorized to act as a Diameter Server. 2643 Authorization can be achieved for example, by configuration of a 2644 Diameter Server CA. Alternatively this can be achieved by 2645 definition of OIDs within TLS or IKE certificates so as to 2646 signify Diameter Server authorization. 2648 A dynamically discovered peer causes an entry in the Peer Table (see 2649 Section 2.6) to be created. Note that entries created via DNS MUST 2650 expire (or be refreshed) within the DNS TTL. If a peer is discovered 2651 outside of the local realm, a routing table entry (see Section 2.7) 2652 for the peer's realm is created. The routing table entry's 2653 expiration MUST match the peer's expiration value. 2655 5.3. Capabilities Exchange 2657 When two Diameter peers establish a transport connection, they MUST 2658 exchange the Capabilities Exchange messages, as specified in the peer 2659 state machine (see Section 5.6). This message allows the discovery 2660 of a peer's identity and its capabilities (protocol version number, 2661 supported Diameter applications, security mechanisms, etc.) 2663 The receiver only issues commands to its peers that have advertised 2664 support for the Diameter application that defines the command. A 2665 Diameter node MUST cache the supported applications in order to 2666 ensure that unrecognized commands and/or AVPs are not unnecessarily 2667 sent to a peer. 2669 A receiver of a Capabilities-Exchange-Req (CER) message that does not 2670 have any applications in common with the sender MUST return a 2671 Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to 2672 DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport 2673 layer connection. Note that receiving a CER or CEA from a peer 2674 advertising itself as a Relay (see Section 2.4) MUST be interpreted 2675 as having common applications with the peer. 2677 The receiver of the Capabilities-Exchange-Request (CER) MUST 2678 determine common applications by computing the intersection of its 2679 own set of supported application identifiers against all of the 2680 application indentifier AVPs (Auth-Application-Id, 2681 Acct-Application-Id and Vendor-Specific-Application-Id) present in 2682 the CER. The value of the Vendor-Id AVP in the Vendor-Specific- 2683 Application-Id MUST not be used during computation. The sender of 2684 the Capabilities-Exchange-Answer (CEA) SHOULD include all of its 2685 supported applications as a hint to the receiver regarding all of its 2686 application capabilities. 2688 Similarly, a receiver of a Capabilities-Exchange-Req (CER) message 2689 that does not have any security mechanisms in common with the sender 2690 MUST return a Capabilities-Exchange-Answer (CEA) with the Result-Code 2691 AVP set to DIAMETER_NO_COMMON_SECURITY, and SHOULD disconnect the 2692 transport layer connection. 2694 CERs received from unknown peers MAY be silently discarded, or a CEA 2695 MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER. 2696 In both cases, the transport connection is closed. If the local 2697 policy permits receiving CERs from unknown hosts, a successful CEA 2698 MAY be returned. If a CER from an unknown peer is answered with a 2699 successful CEA, the lifetime of the peer entry is equal to the 2700 lifetime of the transport connection. In case of a transport 2701 failure, all the pending transactions destined to the unknown peer 2702 can be discarded. 2704 The CER and CEA messages MUST NOT be proxied, redirected or relayed. 2706 Since the CER/CEA messages cannot be proxied, it is still possible 2707 that an upstream agent receives a message for which it has no 2708 available peers to handle the application that corresponds to the 2709 Command-Code. In such instances, the 'E' bit is set in the answer 2710 message (see Section 7.) with the Result-Code AVP set to 2711 DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action 2712 (e.g., re-routing request to an alternate peer). 2714 With the exception of the Capabilities-Exchange-Request message, a 2715 message of type Request that includes the Auth-Application-Id or 2716 Acct-Application-Id AVPs, or a message with an application-specific 2717 command code, MAY only be forwarded to a host that has explicitly 2718 advertised support for the application (or has advertised the Relay 2719 Application Identifier). 2721 5.3.1. Capabilities-Exchange-Request 2723 The Capabilities-Exchange-Request (CER), indicated by the Command- 2724 Code set to 257 and the Command Flags' 'R' bit set, is sent to 2725 exchange local capabilities. Upon detection of a transport failure, 2726 this message MUST NOT be sent to an alternate peer. 2728 When Diameter is run over SCTP [RFC2960], which allows for 2729 connections to span multiple interfaces and multiple IP addresses, 2730 the Capabilities-Exchange-Request message MUST contain one Host-IP- 2731 Address AVP for each potential IP address that MAY be locally used 2732 when transmitting Diameter messages. 2734 Message Format 2736 ::= < Diameter Header: 257, REQ > 2737 { Origin-Host } 2738 { Origin-Realm } 2739 1* { Host-IP-Address } 2740 { Vendor-Id } 2741 { Product-Name } 2742 [ Origin-State-Id ] 2743 * [ Supported-Vendor-Id ] 2744 * [ Auth-Application-Id ] 2745 * [ Inband-Security-Id ] 2746 * [ Acct-Application-Id ] 2747 * [ Vendor-Specific-Application-Id ] 2748 [ Firmware-Revision ] 2749 * [ AVP ] 2751 5.3.2. Capabilities-Exchange-Answer 2753 The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code 2754 set to 257 and the Command Flags' 'R' bit cleared, is sent in 2755 response to a CER message. 2757 When Diameter is run over SCTP [RFC2960], which allows connections to 2758 span multiple interfaces, hence, multiple IP addresses, the 2759 Capabilities-Exchange-Answer message MUST contain one Host-IP-Address 2760 AVP for each potential IP address that MAY be locally used when 2761 transmitting Diameter messages. 2763 Message Format 2765 ::= < Diameter Header: 257 > 2766 { Result-Code } 2767 { Origin-Host } 2768 { Origin-Realm } 2769 1* { Host-IP-Address } 2770 { Vendor-Id } 2771 { Product-Name } 2772 [ Origin-State-Id ] 2773 [ Error-Message ] 2774 [ Failed-AVP ] 2775 * [ Supported-Vendor-Id ] 2776 * [ Auth-Application-Id ] 2777 * [ Inband-Security-Id ] 2778 * [ Acct-Application-Id ] 2779 * [ Vendor-Specific-Application-Id ] 2780 [ Firmware-Revision ] 2781 * [ AVP ] 2783 5.3.3. Vendor-Id AVP 2785 The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains 2786 the IANA "SMI Network Management Private Enterprise Codes" [RFC3232] 2787 value assigned to the vendor of the Diameter application. In 2788 combination with the Supported-Vendor-Id AVP (Section 5.3.6), this 2789 MAY be used in order to know which vendor specific attributes may be 2790 sent to the peer. It is also envisioned that the combination of the 2791 Vendor-Id, Product-Name (Section 5.3.7) and the Firmware-Revision 2792 (Section 5.3.4) AVPs MAY provide very useful debugging information. 2794 A Vendor-Id value of zero in the CER or CEA messages is reserved and 2795 indicates that this field is ignored. 2797 5.3.4. Firmware-Revision AVP 2799 The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is 2800 used to inform a Diameter peer of the firmware revision of the 2801 issuing device. 2803 For devices that do not have a firmware revision (general purpose 2804 computers running Diameter software modules, for instance), the 2805 revision of the Diameter software module may be reported instead. 2807 5.3.5. Host-IP-Address AVP 2809 The Host-IP-Address AVP (AVP Code 257) is of type Address and is used 2810 to inform a Diameter peer of the sender's IP address. All source 2811 addresses that a Diameter node expects to use with SCTP [RFC2960] 2812 MUST be advertised in the CER and CEA messages by including a 2813 Host-IP- Address AVP for each address. This AVP MUST ONLY be used in 2814 the CER and CEA messages. 2816 5.3.6. Supported-Vendor-Id AVP 2818 The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and 2819 contains the IANA "SMI Network Management Private Enterprise Codes" 2820 [RFC3232] value assigned to a vendor other than the device vendor. 2821 This is used in the CER and CEA messages in order to inform the peer 2822 that the sender supports (a subset of) the vendor-specific AVPs 2823 defined by the vendor identified in this AVP. The value of this AVP 2824 SHOULD NOT be set to zero. Multiple instances of this AVP containing 2825 the same value SHOULD NOT be sent. 2827 5.3.7. Product-Name AVP 2829 The Product-Name AVP (AVP Code 269) is of type UTF8String, and 2830 contains the vendor assigned name for the product. The Product-Name 2831 AVP SHOULD remain constant across firmware revisions for the same 2832 product. 2834 5.4. Disconnecting Peer connections 2836 When a Diameter node disconnects one of its transport connections, 2837 its peer cannot know the reason for the disconnect, and will most 2838 likely assume that a connectivity problem occurred, or that the peer 2839 has rebooted. In these cases, the peer may periodically attempt to 2840 reconnect, as stated in Section 2.1. In the event that the 2841 disconnect was a result of either a shortage of internal resources, 2842 or simply that the node in question has no intentions of forwarding 2843 any Diameter messages to the peer in the foreseeable future, a 2844 periodic connection request would not be welcomed. The 2845 Disconnection-Reason AVP contains the reason the Diameter node issued 2846 the Disconnect-Peer-Request message. 2848 The Disconnect-Peer-Request message is used by a Diameter node to 2849 inform its peer of its intent to disconnect the transport layer, and 2850 that the peer shouldn't reconnect unless it has a valid reason to do 2851 so (e.g., message to be forwarded). Upon receipt of the message, the 2852 Disconnect-Peer-Answer is returned, which SHOULD contain an error if 2853 messages have recently been forwarded, and are likely in flight, 2854 which would otherwise cause a race condition. 2856 The receiver of the Disconnect-Peer-Answer initiates the transport 2857 disconnect. The sender of the Disconnect-Peer-Answer should be able 2858 to detect the transport closure and cleanup the connection. 2860 5.4.1. Disconnect-Peer-Request 2862 The Disconnect-Peer-Request (DPR), indicated by the Command-Code set 2863 to 282 and the Command Flags' 'R' bit set, is sent to a peer to 2864 inform its intentions to shutdown the transport connection. Upon 2865 detection of a transport failure, this message MUST NOT be sent to an 2866 alternate peer. 2868 Message Format 2870 ::= < Diameter Header: 282, REQ > 2871 { Origin-Host } 2872 { Origin-Realm } 2873 { Disconnect-Cause } 2875 5.4.2. Disconnect-Peer-Answer 2877 The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set 2878 to 282 and the Command Flags' 'R' bit cleared, is sent as a response 2879 to the Disconnect-Peer-Request message. Upon receipt of this 2880 message, the transport connection is shutdown. 2882 Message Format 2884 ::= < Diameter Header: 282 > 2885 { Result-Code } 2886 { Origin-Host } 2887 { Origin-Realm } 2888 [ Error-Message ] 2889 [ Failed-AVP ] 2891 5.4.3. Disconnect-Cause AVP 2893 The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A 2894 Diameter node MUST include this AVP in the Disconnect-Peer-Request 2895 message to inform the peer of the reason for its intention to 2896 shutdown the transport connection. The following values are 2897 supported: 2899 REBOOTING 0 2900 A scheduled reboot is imminent. Receiver of DPR with above result 2901 code MAY attempt reconnection. 2903 BUSY 1 2904 The peer's internal resources are constrained, and it has 2905 determined that the transport connection needs to be closed. 2906 Receiver of DPR with above result code SHOULD NOT attempt 2907 reconnection. 2909 DO_NOT_WANT_TO_TALK_TO_YOU 2 2910 The peer has determined that it does not see a need for the 2911 transport connection to exist, since it does not expect any 2912 messages to be exchanged in the near future. Receiver of DPR 2913 with above result code SHOULD NOT attempt reconnection. 2915 5.5. Transport Failure Detection 2917 Given the nature of the Diameter protocol, it is recommended that 2918 transport failures be detected as soon as possible. Detecting such 2919 failures will minimize the occurrence of messages sent to unavailable 2920 agents, resulting in unnecessary delays, and will provide better 2921 failover performance. The Device-Watchdog-Request and Device- 2922 Watchdog-Answer messages, defined in this section, are used to pro- 2923 actively detect transport failures. 2925 5.5.1. Device-Watchdog-Request 2927 The Device-Watchdog-Request (DWR), indicated by the Command-Code set 2928 to 280 and the Command Flags' 'R' bit set, is sent to a peer when no 2929 traffic has been exchanged between two peers (see Section 5.5.3). 2930 Upon detection of a transport failure, this message MUST NOT be sent 2931 to an alternate peer. 2933 Message Format 2935 ::= < Diameter Header: 280, REQ > 2936 { Origin-Host } 2937 { Origin-Realm } 2938 [ Origin-State-Id ] 2940 5.5.2. Device-Watchdog-Answer 2942 The Device-Watchdog-Answer (DWA), indicated by the Command-Code set 2943 to 280 and the Command Flags' 'R' bit cleared, is sent as a response 2944 to the Device-Watchdog-Request message. 2946 Message Format 2948 ::= < Diameter Header: 280 > 2949 { Result-Code } 2950 { Origin-Host } 2951 { Origin-Realm } 2952 [ Error-Message ] 2953 [ Failed-AVP ] 2954 [ Origin-State-Id ] 2956 5.5.3. Transport Failure Algorithm 2958 The transport failure algorithm is defined in [RFC3539]. All 2959 Diameter implementations MUST support the algorithm defined in the 2960 specification in order to be compliant to the Diameter base protocol. 2962 5.5.4. Failover and Failback Procedures 2964 In the event that a transport failure is detected with a peer, it is 2965 necessary for all pending request messages to be forwarded to an 2966 alternate agent, if possible. This is commonly referred to as 2967 failover. 2969 In order for a Diameter node to perform failover procedures, it is 2970 necessary for the node to maintain a pending message queue for a 2971 given peer. When an answer message is received, the corresponding 2972 request is removed from the queue. The Hop-by-Hop Identifier field 2973 is used to match the answer with the queued request. 2975 When a transport failure is detected, if possible all messages in the 2976 queue are sent to an alternate agent with the T flag set. On booting 2977 a Diameter client or agent, the T flag is also set on any records 2978 still remaining to be transmitted in non-volatile storage. An 2979 example of a case where it is not possible to forward the message to 2980 an alternate server is when the message has a fixed destination, and 2981 the unavailable peer is the message's final destination (see 2982 Destination-Host AVP). Such an error requires that the agent return 2983 an answer message with the 'E' bit set and the Result-Code AVP set to 2984 DIAMETER_UNABLE_TO_DELIVER. 2986 It is important to note that multiple identical requests or answers 2987 MAY be received as a result of a failover. The End-to-End Identifier 2988 field in the Diameter header along with the Origin-Host AVP MUST be 2989 used to identify duplicate messages. 2991 As described in Section 2.1, a connection request should be 2992 periodically attempted with the failed peer in order to re-establish 2993 the transport connection. Once a connection has been successfully 2994 established, messages can once again be forwarded to the peer. This 2995 is commonly referred to as failback. 2997 5.6. Peer State Machine 2999 This section contains a finite state machine that MUST be observed by 3000 all Diameter implementations. Each Diameter node MUST follow the 3001 state machine described below when communicating with each peer. 3002 Multiple actions are separated by commas, and may continue on 3003 succeeding lines, as space requires. Similarly, state and next state 3004 may also span multiple lines, as space requires. 3006 This state machine is closely coupled with the state machine 3007 described in [RFC3539], which is used to open, close, failover, 3008 probe, and reopen transport connections. Note in particular that 3009 [RFC3539] requires the use of watchdog messages to probe connections. 3010 For Diameter, DWR and DWA messages are to be used. 3012 I- is used to represent the initiator (connecting) connection, while 3013 the R- is used to represent the responder (listening) connection. 3014 The lack of a prefix indicates that the event or action is the same 3015 regardless of the connection on which the event occurred. 3017 The stable states that a state machine may be in are Closed, I-Open 3018 and R-Open; all other states are intermediate. Note that I-Open and 3019 R-Open are equivalent except for whether the initiator or responder 3020 transport connection is used for communication. 3022 A CER message is always sent on the initiating connection immediately 3023 after the connection request is successfully completed. In the case 3024 of an election, one of the two connections will shut down. The 3025 responder connection will survive if the Origin-Host of the local 3026 Diameter entity is higher than that of the peer; the initiator 3027 connection will survive if the peer's Origin-Host is higher. All 3028 subsequent messages are sent on the surviving connection. Note that 3029 the results of an election on one peer are guaranteed to be the 3030 inverse of the results on the other. 3032 For TLS usage, a TLS handshake will begin when both ends are in the 3033 open state. If the TLS handshake is successful, all further messages 3034 will be sent via TLS. If the handshake fails, both ends move to the 3035 closed state. 3037 The state machine constrains only the behavior of a Diameter 3038 implementation as seen by Diameter peers through events on the wire. 3040 Any implementation that produces equivalent results is considered 3041 compliant. 3043 state event action next state 3044 ----------------------------------------------------------------- 3045 Closed Start I-Snd-Conn-Req Wait-Conn-Ack 3046 R-Conn-CER R-Accept, R-Open 3047 Process-CER, 3048 R-Snd-CEA 3050 Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA 3051 I-Rcv-Conn-Nack Cleanup Closed 3052 R-Conn-CER R-Accept, Wait-Conn-Ack/ 3053 Process-CER Elect 3054 Timeout Error Closed 3056 Wait-I-CEA I-Rcv-CEA Process-CEA I-Open 3057 R-Conn-CER R-Accept, Wait-Returns 3058 Process-CER, 3059 Elect 3060 I-Peer-Disc I-Disc Closed 3061 I-Rcv-Non-CEA Error Closed 3062 Timeout Error Closed 3064 Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns 3065 Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open 3066 R-Peer-Disc R-Disc Wait-Conn-Ack 3067 R-Conn-CER R-Reject Wait-Conn-Ack/ 3068 Elect 3069 Timeout Error Closed 3071 Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open 3072 I-Peer-Disc I-Disc, R-Open 3073 R-Snd-CEA 3074 I-Rcv-CEA R-Disc I-Open 3075 R-Peer-Disc R-Disc Wait-I-CEA 3076 R-Conn-CER R-Reject Wait-Returns 3077 Timeout Error Closed 3079 R-Open Send-Message R-Snd-Message R-Open 3080 R-Rcv-Message Process R-Open 3081 R-Rcv-DWR Process-DWR, R-Open 3082 R-Snd-DWA 3083 R-Rcv-DWA Process-DWA R-Open 3084 R-Conn-CER R-Reject R-Open 3085 Stop R-Snd-DPR Closing 3086 R-Rcv-DPR R-Snd-DPA, Closed 3087 R-Disc 3089 R-Peer-Disc R-Disc Closed 3090 R-Rcv-CER R-Snd-CEA R-Open 3091 R-Rcv-CEA Process-CEA R-Open 3093 I-Open Send-Message I-Snd-Message I-Open 3094 I-Rcv-Message Process I-Open 3095 I-Rcv-DWR Process-DWR, I-Open 3096 I-Snd-DWA 3097 I-Rcv-DWA Process-DWA I-Open 3098 R-Conn-CER R-Reject I-Open 3099 Stop I-Snd-DPR Closing 3100 I-Rcv-DPR I-Snd-DPA, Closed 3101 I-Disc 3102 I-Peer-Disc I-Disc Closed 3103 I-Rcv-CER I-Snd-CEA I-Open 3104 I-Rcv-CEA Process-CEA I-Open 3106 Closing I-Rcv-DPA I-Disc Closed 3107 R-Rcv-DPA R-Disc Closed 3108 Timeout Error Closed 3109 I-Peer-Disc I-Disc Closed 3110 R-Peer-Disc R-Disc Closed 3112 5.6.1. Incoming connections 3114 When a connection request is received from a Diameter peer, it is 3115 not, in the general case, possible to know the identity of that peer 3116 until a CER is received from it. This is because host and port 3117 determine the identity of a Diameter peer; and the source port of an 3118 incoming connection is arbitrary. Upon receipt of CER, the identity 3119 of the connecting peer can be uniquely determined from Origin-Host. 3121 For this reason, a Diameter peer must employ logic separate from the 3122 state machine to receive connection requests, accept them, and await 3123 CER. Once CER arrives on a new connection, the Origin-Host that 3124 identifies the peer is used to locate the state machine associated 3125 with that peer, and the new connection and CER are passed to the 3126 state machine as an R-Conn-CER event. 3128 The logic that handles incoming connections SHOULD close and discard 3129 the connection if any message other than CER arrives, or if an 3130 implementation-defined timeout occurs prior to receipt of CER. 3132 Because handling of incoming connections up to and including receipt 3133 of CER requires logic, separate from that of any individual state 3134 machine associated with a particular peer, it is described separately 3135 in this section rather than in the state machine above. 3137 5.6.2. Events 3139 Transitions and actions in the automaton are caused by events. In 3140 this section, we will ignore the -I and -R prefix, since the actual 3141 event would be identical, but would occur on one of two possible 3142 connections. 3144 Start The Diameter application has signaled that a 3145 connection should be initiated with the peer. 3147 R-Conn-CER An acknowledgement is received stating that the 3148 transport connection has been established, and the 3149 associated CER has arrived. 3151 Rcv-Conn-Ack A positive acknowledgement is received confirming that 3152 the transport connection is established. 3154 Rcv-Conn-Nack A negative acknowledgement was received stating that 3155 the transport connection was not established. 3157 Timeout An application-defined timer has expired while waiting 3158 for some event. 3160 Rcv-CER A CER message from the peer was received. 3162 Rcv-CEA A CEA message from the peer was received. 3164 Rcv-Non-CEA A message other than CEA from the peer was received. 3166 Peer-Disc A disconnection indication from the peer was received. 3168 Rcv-DPR A DPR message from the peer was received. 3170 Rcv-DPA A DPA message from the peer was received. 3172 Win-Election An election was held, and the local node was the 3173 winner. 3175 Send-Message A message is to be sent. 3177 Rcv-Message A message other than CER, CEA, DPR, DPA, DWR or DWA 3178 was received. 3180 Stop The Diameter application has signaled that a 3181 connection should be terminated (e.g., on system 3182 shutdown). 3184 5.6.3. Actions 3186 Actions in the automaton are caused by events and typically indicate 3187 the transmission of packets and/or an action to be taken on the 3188 connection. In this section we will ignore the I- and R-prefix, 3189 since the actual action would be identical, but would occur on one of 3190 two possible connections. 3192 Snd-Conn-Req A transport connection is initiated with the peer. 3194 Accept The incoming connection associated with the R-Conn-CER 3195 is accepted as the responder connection. 3197 Reject The incoming connection associated with the R-Conn-CER 3198 is disconnected. 3200 Process-CER The CER associated with the R-Conn-CER is processed. 3201 Snd-CER A CER message is sent to the peer. 3203 Snd-CEA A CEA message is sent to the peer. 3205 Cleanup If necessary, the connection is shutdown, and any 3206 local resources are freed. 3208 Error The transport layer connection is disconnected, either 3209 politely or abortively, in response to an error 3210 condition. Local resources are freed. 3212 Process-CEA A received CEA is processed. 3214 Snd-DPR A DPR message is sent to the peer. 3216 Snd-DPA A DPA message is sent to the peer. 3218 Disc The transport layer connection is disconnected, and 3219 local resources are freed. 3221 Elect An election occurs (see Section 5.6.4 for more 3222 information). 3224 Snd-Message A message is sent. 3226 Snd-DWR A DWR message is sent. 3228 Snd-DWA A DWA message is sent. 3230 Process-DWR The DWR message is serviced. 3232 Process-DWA The DWA message is serviced. 3234 Process A message is serviced. 3236 5.6.4. The Election Process 3238 The election is performed on the responder. The responder compares 3239 the Origin-Host received in the CER with its own Origin-Host as two 3240 streams of octets. If the local Origin-Host lexicographically 3241 succeeds the received Origin-Host a Win-Election event is issued 3242 locally. 3244 To be consistent with DNS case insensitivity, octets that fall in the 3245 ASCII range 'a' through 'z' MUST compare equally to their upper-case 3246 counterparts between 'A' and 'Z', i.e. value 0x41 compares equal to 3247 0x61, 0x42 to 0x62 and so forth up to and including 0x5a and 0x7a. 3249 The winner of the election MUST close the connection it initiated. 3250 Historically, maintaining the responder side of a connection was more 3251 efficient than maintaining the initiator side. However, current 3252 practices makes this distinction irrelevant. 3254 5.6.5. Capabilities Update 3256 A Diameter node MUST initiate peer capabilities update by sending a 3257 Capabilities-Exchange-Req (CER) to all its peers which supports peer 3258 capabilities update and is in OPEN state. The receiver of CER in 3259 open state MUST process and reply to the CER as a described in 3260 Section 5.3. The CEA which the receiver sends MUST contain its 3261 latest capabilities. Note that peers which successfully process the 3262 peer capabilities update SHOULD also update their routing tables to 3263 reflect the change. The receiver of the CEA, with a Result-Code AVP 3264 other than DIAMETER_SUCCESS, initiates the transport disconnect. The 3265 peer may periodically attempt to reconnect, as stated in Section 2.1. 3267 Peer capabilities update in the open state SHOULD be limited to the 3268 advertisement of the new list of supported applications and MUST 3269 preclude re-negotiation of security mechanism or other capabilities. 3270 If any capabilities change happens in the node (e.g. change in 3271 security mechanisms), other than a change in the supported 3272 applications, the node SHOULD gracefully terminate (setting the 3273 Disconnect-Cause AVP value to REBOOTING) and re-establish the 3274 diameter connections to all the peers. 3276 6. Diameter message processing 3278 This section describes how Diameter requests and answers are created 3279 and processed. 3281 6.1. Diameter Request Routing Overview 3283 A request is sent towards its final destination using a combination 3284 of the Destination-Realm and Destination-Host AVPs, in one of these 3285 three combinations: 3287 o a request that is not able to be proxied (such as CER) MUST NOT 3288 contain either Destination-Realm or Destination-Host AVPs. 3290 o a request that needs to be sent to a home server serving a 3291 specific realm, but not to a specific server (such as the first 3292 request of a series of round-trips), MUST contain a Destination- 3293 Realm AVP, but MUST NOT contain a Destination-Host AVP. 3295 o otherwise, a request that needs to be sent to a specific home 3296 server among those serving a given realm, MUST contain both the 3297 Destination-Realm and Destination-Host AVPs. 3299 The Destination-Host AVP is used as described above when the 3300 destination of the request is fixed, which includes: 3302 o Authentication requests that span multiple round trips 3304 o A Diameter message that uses a security mechanism that makes use 3305 of a pre-established session key shared between the source and the 3306 final destination of the message. 3308 o Server initiated messages that MUST be received by a specific 3309 Diameter client (e.g., access device), such as the Abort-Session- 3310 Request message, which is used to request that a particular user's 3311 session be terminated. 3313 Note that an agent can forward a request to a host described in the 3314 Destination-Host AVP only if the host in question is included in its 3315 peer table (see Section 2.7). Otherwise, the request is routed based 3316 on the Destination-Realm only (see Sections 6.1.6). 3318 The Destination-Realm AVP MUST be present if the message is 3319 proxiable. Request messages that may be forwarded by Diameter agents 3320 (proxies, redirects or relays) MUST also contain an Acct- 3321 Application-Id AVP, an Auth-Application-Id AVP or a Vendor-Specific- 3322 Application-Id AVP. A message that MUST NOT be forwarded by Diameter 3323 agents (proxies, redirects or relays) MUST not include the 3324 Destination-Realm in its ABNF. The value of the Destination-Realm 3325 AVP MAY be extracted from the User-Name AVP, or other application- 3326 specific methods. 3328 When a message is received, the message is processed in the following 3329 order: 3331 o If the message is destined for the local host, the procedures 3332 listed in Section 6.1.4 are followed. 3334 o If the message is intended for a Diameter peer with whom the local 3335 host is able to directly communicate, the procedures listed in 3336 Section 6.1.5 are followed. This is known as Request Forwarding. 3338 o The procedures listed in Section 6.1.6 are followed, which is 3339 known as Request Routing. 3341 o If none of the above is successful, an answer is returned with the 3342 Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the E-bit set. 3344 For routing of Diameter messages to work within an administrative 3345 domain, all Diameter nodes within the realm MUST be peers. 3347 Note the processing rules contained in this section are intended to 3348 be used as general guidelines to Diameter developers. Certain 3349 implementations MAY use different methods than the ones described 3350 here, and still comply with the protocol specification. See Section 3351 7 for more detail on error handling. 3353 6.1.1. Originating a Request 3355 When creating a request, in addition to any other procedures 3356 described in the application definition for that specific request, 3357 the following procedures MUST be followed: 3359 o the Command-Code is set to the appropriate value 3361 o the 'R' bit is set 3363 o the End-to-End Identifier is set to a locally unique value 3365 o the Origin-Host and Origin-Realm AVPs MUST be set to the 3366 appropriate values, used to identify the source of the message 3368 o the Destination-Host and Destination-Realm AVPs MUST be set to the 3369 appropriate values as described in Section 6.1. 3371 o an Acct-Application-Id AVP, an Auth-Application-Id or a Vendor- 3372 Specific-Application-Id AVP must be included if the request is 3373 proxiable. The application id present in one of these relevant 3374 AVPs must match the application id present in the diameter message 3375 header. 3377 6.1.2. Sending a Request 3379 When sending a request, originated either locally, or as the result 3380 of a forwarding or routing operation, the following procedures MUST 3381 be followed: 3383 o the Hop-by-Hop Identifier should be set to a locally unique value. 3385 o The message should be saved in the list of pending requests. 3387 Other actions to perform on the message based on the particular role 3388 the agent is playing are described in the following sections. 3390 6.1.3. Receiving Requests 3392 A relay or proxy agent MUST check for forwarding loops when receiving 3393 requests. A loop is detected if the server finds its own identity in 3394 a Route-Record AVP. When such an event occurs, the agent MUST answer 3395 with the Result-Code AVP set to DIAMETER_LOOP_DETECTED. 3397 6.1.4. Processing Local Requests 3399 A request is known to be for local consumption when one of the 3400 following conditions occur: 3402 o The Destination-Host AVP contains the local host's identity, 3404 o The Destination-Host AVP is not present, the Destination-Realm AVP 3405 contains a realm the server is configured to process locally, and 3406 the Diameter application is locally supported, or 3408 o Both the Destination-Host and the Destination-Realm are not 3409 present. 3411 When a request is locally processed, the rules in Section 6.2 should 3412 be used to generate the corresponding answer. 3414 6.1.5. Request Forwarding 3416 Request forwarding is done using the Diameter Peer Table. The 3417 Diameter peer table contains all of the peers that the local node is 3418 able to directly communicate with. 3420 When a request is received, and the host encoded in the Destination- 3421 Host AVP is one that is present in the peer table, the message SHOULD 3422 be forwarded to the peer. 3424 6.1.6. Request Routing 3426 Diameter request message routing is done via realms and applications. 3427 A Diameter message that may be forwarded by Diameter agents (proxies, 3428 redirects or relays) MUST include the target realm in the 3429 Destination-Realm AVP. Request routing SHOULD rely on the 3430 Destination-Realm AVP and the application id present in the request 3431 message header to aid in the routing decision. It MAY also rely on 3432 the application identification AVPs Auth-Application-Id, Acct- 3433 Application-Id or Vendor-Specific-Application-Id instead of the 3434 application id in the message header as a secondary measure. The 3435 realm MAY be retrieved from the User-Name AVP, which is in the form 3436 of a Network Access Identifier (NAI). The realm portion of the NAI 3437 is inserted in the Destination-Realm AVP. 3439 Diameter agents MAY have a list of locally supported realms and 3440 applications, and MAY have a list of externally supported realms and 3441 applications. When a request is received that includes a realm 3442 and/or application that is not locally supported, the message is 3443 routed to the peer configured in the Routing Table (see Section 2.7). 3445 Realm names and application identifiers are the minimum supported 3446 routing criteria, additional routing information maybe needed to 3447 support redirect semantics. 3449 6.1.7. Predictive Loop Avoidance 3451 Before forwarding or routing a request, Diameter agents, in addition 3452 to processing done in Section 6.1.3, SHOULD check for the presence of 3453 candidate route's peer identity in any of the Route-Record AVPs. In 3454 an event of the agent detecting the presence of a candidate route's 3455 peer identity in a Route-Record AVP, the agent MUST ignore such route 3456 for the Diameter request message and attempt alternate routes if any. 3457 In case all the candidate routes are eliminated by the above 3458 criteria, the agent SHOULD return DIAMETER_UNABLE_TO_DELIVER message. 3460 6.1.8. Redirecting requests 3462 When a redirect agent receives a request whose routing entry is set 3463 to REDIRECT, it MUST reply with an answer message with the 'E' bit 3464 set, while maintaining the Hop-by-Hop Identifier in the header, and 3465 include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of 3466 the servers associated with the routing entry are added in separate 3467 Redirect-Host AVP. 3469 +------------------+ 3470 | Diameter | 3471 | Redirect Agent | 3472 +------------------+ 3473 ^ | 2. command + 'E' bit 3474 1. Request | | Result-Code = 3475 joe@example.com | | DIAMETER_REDIRECT_INDICATION + 3476 | | Redirect-Host AVP(s) 3477 | v 3478 +-------------+ 3. Request +-------------+ 3479 | example.com |------------->| example.net | 3480 | Relay | | Diameter | 3481 | Agent |<-------------| Server | 3482 +-------------+ 4. Answer +-------------+ 3484 Figure 5: Diameter Redirect Agent 3486 The receiver of the answer message with the 'E' bit set, and the 3487 Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by- 3488 hop field in the Diameter header to identify the request in the 3489 pending message queue (see Section 5.3) that is to be redirected. If 3490 no transport connection exists with the new agent, one is created, 3491 and the request is sent directly to it. 3493 Multiple Redirect-Host AVPs are allowed. The receiver of the answer 3494 message with the 'E' bit set selects exactly one of these hosts as 3495 the destination of the redirected message. 3497 When the Redirect-Host-Usage AVP included in the answer message has a 3498 non-zero value, a route entry for the redirect indications is created 3499 and cached by the receiver. The redirect usage for such route entry 3500 is set by the value of Redirect-Host-Usage AVP and the lifetime of 3501 the cached route entry is set by Redirect-Max-Cache-Time AVP value. 3503 It is possible that multiple redirect indications can create multiple 3504 cached route entries differing only in their redirect usage and the 3505 peer to forward messages to. As an example, two(2) route entries 3506 that are created by two(2) redirect indications results in two(2) 3507 cached routes for the same realm and application Id. However, one 3508 has a redirect usage of ALL_SESSION where matching request will be 3509 forwarded to one peer and the other has a redirect usage of ALL_REALM 3510 where request are forwarded to another peer. Therefore, an incoming 3511 request that matches the realm and application Id of both routes will 3512 need additional resolution. In such a case, a routing precedence 3513 rule MUST be used againts the redirect usage value to resolve the 3514 contention. The precedence rule can be found in Section 6.13. 3516 6.1.9. Relaying and Proxying Requests 3518 A relay or proxy agent MUST append a Route-Record AVP to all requests 3519 forwarded. The AVP contains the identity of the peer the request was 3520 received from. 3522 The Hop-by-Hop identifier in the request is saved, and replaced with 3523 a locally unique value. The source of the request is also saved, 3524 which includes the IP address, port and protocol. 3526 A relay or proxy agent MAY include the Proxy-Info AVP in requests if 3527 it requires access to any local state information when the 3528 corresponding response is received. Proxy-Info AVP has certain 3529 security implications and SHOULD contain an embedded HMAC with a 3530 node-local key. Alternatively, it MAY simply use local storage to 3531 store state information. 3533 The message is then forwarded to the next hop, as identified in the 3534 Routing Table. 3536 Figure 6 provides an example of message routing using the procedures 3537 listed in these sections. 3539 (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net) 3540 (Origin-Realm=mno.net) (Origin-Realm=mno.net) 3541 (Destination-Realm=example.com) (Destination- 3542 Realm=example.com) 3543 (Route-Record=nas.example.net) 3544 +------+ ------> +------+ ------> +------+ 3545 | | (Request) | | (Request) | | 3546 | NAS +-------------------+ DRL +-------------------+ HMS | 3547 | | | | | | 3548 +------+ <------ +------+ <------ +------+ 3549 example.net (Answer) example.net (Answer) example.com 3550 (Origin-Host=hms.example.com) (Origin-Host=hms.example.com) 3551 (Origin-Realm=example.com) (Origin-Realm=example.com) 3553 Figure 6: Routing of Diameter messages 3555 Relay agents do not require full validation of incoming messages. At 3556 a minimum, validation of the message header and relevant routing AVPs 3557 has to be done when relaying messages. 3559 6.2. Diameter Answer Processing 3561 When a request is locally processed, the following procedures MUST be 3562 applied to create the associated answer, in addition to any 3563 additional procedures that MAY be discussed in the Diameter 3564 application defining the command: 3566 o The same Hop-by-Hop identifier in the request is used in the 3567 answer. 3569 o The local host's identity is encoded in the Origin-Host AVP. 3571 o The Destination-Host and Destination-Realm AVPs MUST NOT be 3572 present in the answer message. 3574 o The Result-Code AVP is added with its value indicating success or 3575 failure. 3577 o If the Session-Id is present in the request, it MUST be included 3578 in the answer. 3580 o Any Proxy-Info AVPs in the request MUST be added to the answer 3581 message, in the same order they were present in the request. 3583 o The 'P' bit is set to the same value as the one in the request. 3585 o The same End-to-End identifier in the request is used in the 3586 answer. 3588 Note that the error messages (see Section 7.3) are also subjected to 3589 the above processing rules. 3591 6.2.1. Processing received Answers 3593 A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an 3594 answer received against the list of pending requests. The 3595 corresponding message should be removed from the list of pending 3596 requests. It SHOULD ignore answers received that do not match a 3597 known Hop-by-Hop Identifier. 3599 6.2.2. Relaying and Proxying Answers 3601 If the answer is for a request which was proxied or relayed, the 3602 agent MUST restore the original value of the Diameter header's Hop- 3603 by-Hop Identifier field. 3605 If the last Proxy-Info AVP in the message is targeted to the local 3606 Diameter server, the AVP MUST be removed before the answer is 3607 forwarded. 3609 If a relay or proxy agent receives an answer with a Result-Code AVP 3610 indicating a failure, it MUST NOT modify the contents of the AVP. 3611 Any additional local errors detected SHOULD be logged, but not 3612 reflected in the Result-Code AVP. If the agent receives an answer 3613 message with a Result-Code AVP indicating success, and it wishes to 3614 modify the AVP to indicate an error, it MUST modify the Result-Code 3615 AVP to contain the appropriate error in the message destined towards 3616 the access device as well as include the Error-Reporting-Host AVP and 3617 it MUST issue an STR on behalf of the access device. 3619 The agent MUST then send the answer to the host that it received the 3620 original request from. 3622 6.3. Origin-Host AVP 3624 The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and 3625 MUST be present in all Diameter messages. This AVP identifies the 3626 endpoint that originated the Diameter message. Relay agents MUST NOT 3627 modify this AVP. 3629 The value of the Origin-Host AVP is guaranteed to be unique within a 3630 single host. 3632 Note that the Origin-Host AVP may resolve to more than one address as 3633 the Diameter peer may support more than one address. 3635 This AVP SHOULD be placed as close to the Diameter header as 3636 possible. 6.10 3638 6.4. Origin-Realm AVP 3640 The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity. 3641 This AVP contains the Realm of the originator of any Diameter message 3642 and MUST be present in all messages. 3644 This AVP SHOULD be placed as close to the Diameter header as 3645 possible. 3647 6.5. Destination-Host AVP 3649 The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity. 3650 This AVP MUST be present in all unsolicited agent initiated messages, 3651 MAY be present in request messages, and MUST NOT be present in Answer 3652 messages. 3654 The absence of the Destination-Host AVP will cause a message to be 3655 sent to any Diameter server supporting the application within the 3656 realm specified in Destination-Realm AVP. 3658 This AVP SHOULD be placed as close to the Diameter header as 3659 possible. 3661 6.6. Destination-Realm AVP 3663 The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity, 3664 and contains the realm the message is to be routed to. The 3665 Destination-Realm AVP MUST NOT be present in Answer messages. 3666 Diameter Clients insert the realm portion of the User-Name AVP. 3667 Diameter servers initiating a request message use the value of the 3668 Origin-Realm AVP from a previous message received from the intended 3669 target host (unless it is known a priori). When present, the 3670 Destination-Realm AVP is used to perform message routing decisions. 3672 Request messages whose ABNF does not list the Destination-Realm AVP 3673 as a mandatory AVP are inherently non-routable messages. 3675 This AVP SHOULD be placed as close to the Diameter header as 3676 possible. 3678 6.7. Routing AVPs 3680 The AVPs defined in this section are Diameter AVPs used for routing 3681 purposes. These AVPs change as Diameter messages are processed by 3682 agents. 3684 6.7.1. Route-Record AVP 3686 The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The 3687 identity added in this AVP MUST be the same as the one received in 3688 the Origin-Host of the Capabilities Exchange message. 3690 6.7.2. Proxy-Info AVP 3692 The Proxy-Info AVP (AVP Code 284) is of type Grouped. The Grouped 3693 Data field has the following ABNF grammar: 3695 Proxy-Info ::= < AVP Header: 284 > 3696 { Proxy-Host } 3697 { Proxy-State } 3698 * [ AVP ] 3700 6.7.3. Proxy-Host AVP 3702 The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This 3703 AVP contains the identity of the host that added the Proxy-Info AVP. 3705 6.7.4. Proxy-State AVP 3707 The Proxy-State AVP (AVP Code 33) is of type OctetString, and 3708 contains state local information, and MUST be treated as opaque data. 3710 6.8. Auth-Application-Id AVP 3712 The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and 3713 is used in order to advertise support of the Authentication and 3714 Authorization portion of an application (see Section 2.4). The Auth- 3715 Application-Id MUST also be present in all Authentication and/or 3716 Authorization messages that are defined in a separate Diameter 3717 specification and have an Application ID assigned. If present in a 3718 message, the value of the Auth-Application-Id AVP MUST match the 3719 application id present in the diameter message header except when 3720 used in a CER or CEA messages. 3722 6.9. Acct-Application-Id AVP 3724 The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and 3725 is used in order to advertise support of the Accounting portion of an 3726 application (see Section 2.4). The Acct-Application-Id MUST also be 3727 present in all Accounting messages. Exactly one of the Auth- 3728 Application-Id and Acct-Application-Id AVPs MAY be present. If 3729 present in a message, the value of the Acct-Application-Id AVP MUST 3730 match the application id present in the diameter message header 3731 except when used in a CER or CEA messages. 3733 6.10. Inband-Security-Id AVP 3735 The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and 3736 is used in order to advertise support of the Security portion of the 3737 application. 3739 Currently, the following values are supported, but there is ample 3740 room to add new security Ids. 3742 NO_INBAND_SECURITY 0 3744 This peer does not support TLS. This is the default value, if the 3745 AVP is omitted. 3747 TLS 1 3749 This node supports TLS security, as defined by [RFC4346]. 3751 6.11. Vendor-Specific-Application-Id AVP 3753 The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type 3754 Grouped and is used to advertise support of a vendor-specific 3755 Diameter Application. Exactly one instance of either Auth- 3756 Application-Id or Acct-Application-Id AVP MAY be present. The 3757 application identifier carried by either Auth-Application-Id or Acct- 3758 Application-Id AVP MUST comply with vendor specific application 3759 identifier assignment described in Sec 11.3. It MUST also match the 3760 application id present in the diameter header except when used in a 3761 CER or CEA messages. 3763 The Vendor-Id AVP is an informational AVP pertaining to the vendor 3764 who may have authorship of the vendor-specific diameter application. 3765 It should not be used as a means of defining a completely separate 3766 vendor-specific application identifier space. 3768 This AVP MUST also be present as the first AVP in all experimental 3769 commands defined in the vendor-specific application. 3771 This AVP SHOULD be placed as close to the Diameter header as 3772 possible. 3774 AVP Format 3776 ::= < AVP Header: 260 > 3777 { Vendor-Id } 3778 ({ Auth-Application-Id } / 3779 { Acct-Application-Id }) 3781 6.12. Redirect-Host AVP 3783 One or more of instances of this AVP MUST be present if the answer 3784 message's 'E' bit is set and the Result-Code AVP is set to 3785 DIAMETER_REDIRECT_INDICATION. 3787 Upon receiving the above, the receiving Diameter node SHOULD forward 3788 the request directly to one of the hosts identified in these AVPs. 3789 The server contained in the selected Redirect-Host AVP SHOULD be used 3790 for all messages pertaining to this session. 3792 6.13. Redirect-Host-Usage AVP 3794 The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated. 3795 This AVP MAY be present in answer messages whose 'E' bit is set and 3796 the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION. 3798 When present, this AVP dictates how the routing entry resulting from 3799 the Redirect-Host is to be used. The following values are supported: 3801 DONT_CACHE 0 3803 The host specified in the Redirect-Host AVP should not be cached. 3804 This is the default value. 3806 ALL_SESSION 1 3808 All messages within the same session, as defined by the same value 3809 of the Session-ID AVP MAY be sent to the host specified in the 3810 Redirect-Host AVP. 3812 ALL_REALM 2 3814 All messages destined for the realm requested MAY be sent to the 3815 host specified in the Redirect-Host AVP. 3817 REALM_AND_APPLICATION 3 3819 All messages for the application requested to the realm specified 3820 MAY be sent to the host specified in the Redirect-Host AVP. 3822 ALL_APPLICATION 4 3824 All messages for the application requested MAY be sent to the host 3825 specified in the Redirect-Host AVP. 3827 ALL_HOST 5 3829 All messages that would be sent to the host that generated the 3830 Redirect-Host MAY be sent to the host specified in the Redirect- 3831 Host AVP. 3833 ALL_USER 6 3835 All messages for the user requested MAY be sent to the host 3836 specified in the Redirect-Host AVP. 3838 When multiple cached routes are created by redirect indications and 3839 they differs only in redirect usage and peers to forward requests to 3840 (see Section 6.1.8), a precedence rule MUST be applied to the 3841 redirect usage values of the cached routes during normal routing to 3842 resolve contentions that may occur. The precedence rule is the order 3843 that dictate which redirect usage should be considered before any 3844 other as they appear. The order is as follows: 3846 1. ALL_SESSION 3848 2. ALL_USER 3850 3. REALM_AND_APPLICATION 3852 4. ALL_REALM 3854 5. ALL_APPLICATION 3856 6. ALL_HOST 3858 6.14. Redirect-Max-Cache-Time AVP 3860 The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32. 3861 This AVP MUST be present in answer messages whose 'E' bit is set, the 3862 Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the 3863 Redirect-Host-Usage AVP set to a non-zero value. 3865 This AVP contains the maximum number of seconds the peer and route 3866 table entries, created as a result of the Redirect-Host, will be 3867 cached. Note that once a host created due to a redirect indication 3868 is no longer reachable, any associated peer and routing table entries 3869 MUST be deleted. 3871 6.15. E2E-Sequence AVP 3873 The E2E-Sequence AVP (AVP Code 300) provides anti-replay protection 3874 for end to end messages and is of type grouped. It contains a random 3875 value (an OctetString with a nonce) and counter (an Integer). For 3876 each end-to-end peer with which a node communicates (or remembers 3877 communicating) a different nonce value MUST be used and the counter 3878 is initiated at zero and increases by one each time this AVP is 3879 emitted to that peer. 3881 7. Error Handling 3883 There are two different types of errors in Diameter; protocol and 3884 application errors. A protocol error is one that occurs at the base 3885 protocol level, and MAY require per hop attention (e.g., message 3886 routing error). Application errors, on the other hand, generally 3887 occur due to a problem with a function specified in a Diameter 3888 application (e.g., user authentication, Missing AVP). 3890 Result-Code AVP values that are used to report protocol errors MUST 3891 only be present in answer messages whose 'E' bit is set. When a 3892 request message is received that causes a protocol error, an answer 3893 message is returned with the 'E' bit set, and the Result-Code AVP is 3894 set to the appropriate protocol error value. As the answer is sent 3895 back towards the originator of the request, each proxy or relay agent 3896 MAY take action on the message. 3898 1. Request +---------+ Link Broken 3899 +-------------------------->|Diameter |----///----+ 3900 | +---------------------| | v 3901 +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+ 3902 |Diameter |<-+ (Unable to Forward) +---------+ |Diameter| 3903 | | | Home | 3904 | Relay 1 |--+ +---------+ | Server | 3905 +---------+ | 3. Request |Diameter | +--------+ 3906 +-------------------->| | ^ 3907 | Relay 3 |-----------+ 3908 +---------+ 3910 Figure 7: Example of Protocol Error causing answer message 3912 Figure 7 provides an example of a message forwarded upstream by a 3913 Diameter relay. When the message is received by Relay 2, and it 3914 detects that it cannot forward the request to the home server, an 3915 answer message is returned with the 'E' bit set and the Result-Code 3916 AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls 3917 within the protocol error category, Relay 1 would take special 3918 action, and given the error, attempt to route the message through its 3919 alternate Relay 3. 3921 +---------+ 1. Request +---------+ 2. Request +---------+ 3922 | Access |------------>|Diameter |------------>|Diameter | 3923 | | | | | Home | 3924 | Device |<------------| Relay |<------------| Server | 3925 +---------+ 4. Answer +---------+ 3. Answer +---------+ 3926 (Missing AVP) (Missing AVP) 3928 Figure 8: Example of Application Error Answer message 3930 Figure 8 provides an example of a Diameter message that caused an 3931 application error. When application errors occur, the Diameter 3932 entity reporting the error clears the 'R' bit in the Command Flags, 3933 and adds the Result-Code AVP with the proper value. Application 3934 errors do not require any proxy or relay agent involvement, and 3935 therefore the message would be forwarded back to the originator of 3936 the request. 3938 There are certain Result-Code AVP application errors that require 3939 additional AVPs to be present in the answer. In these cases, the 3940 Diameter node that sets the Result-Code AVP to indicate the error 3941 MUST add the AVPs. Examples are: 3943 o An unrecognized AVP is received with the 'M' bit (Mandatory bit) 3944 set, causes an answer to be sent with the Result-Code AVP set to 3945 DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the 3946 offending AVP. 3948 o An AVP that is received with an unrecognized value causes an 3949 answer to be returned with the Result-Code AVP set to 3950 DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the 3951 AVP causing the error. 3953 o A command is received with an AVP that is omitted, yet is 3954 mandatory according to the command's ABNF. The receiver issues an 3955 answer with the Result-Code set to DIAMETER_MISSING_AVP, and 3956 creates an AVP with the AVP Code and other fields set as expected 3957 in the missing AVP. The created AVP is then added to the Failed- 3958 AVP AVP. 3960 The Result-Code AVP describes the error that the Diameter node 3961 encountered in its processing. In case there are multiple errors, 3962 the Diameter node MUST report only the first error it encountered 3963 (detected possibly in some implementation dependent order). The 3964 specific errors that can be described by this AVP are described in 3965 the following section. 3967 7.1. Result-Code AVP 3969 The Result-Code AVP (AVP Code 268) is of type Unsigned32 and 3970 indicates whether a particular request was completed successfully or 3971 whether an error occurred. All Diameter answer messages defined in 3972 IETF applications MUST include one Result-Code AVP. A non-successful 3973 Result-Code AVP (one containing a non 2xxx value other than 3974 DIAMETER_REDIRECT_INDICATION) MUST include the Error-Reporting-Host 3975 AVP if the host setting the Result-Code AVP is different from the 3976 identity encoded in the Origin-Host AVP. 3978 The Result-Code data field contains an IANA-managed 32-bit address 3979 space representing errors (see Section 11.4). Diameter provides the 3980 following classes of errors, all identified by the thousands digit in 3981 the decimal notation: 3983 o 1xxx (Informational) 3985 o 2xxx (Success) 3987 o 3xxx (Protocol Errors) 3989 o 4xxx (Transient Failures) 3991 o 5xxx (Permanent Failure) 3993 A non-recognized class (one whose first digit is not defined in this 3994 section) MUST be handled as a permanent failure. 3996 7.1.1. Informational 3998 Errors that fall within this category are used to inform the 3999 requester that a request could not be satisfied, and additional 4000 action is required on its part before access is granted. 4002 DIAMETER_MULTI_ROUND_AUTH 1001 4004 This informational error is returned by a Diameter server to 4005 inform the access device that the authentication mechanism being 4006 used requires multiple round trips, and a subsequent request needs 4007 to be issued in order for access to be granted. 4009 7.1.2. Success 4011 Errors that fall within the Success category are used to inform a 4012 peer that a request has been successfully completed. 4014 DIAMETER_SUCCESS 2001 4016 The Request was successfully completed. 4018 DIAMETER_LIMITED_SUCCESS 2002 4020 When returned, the request was successfully completed, but 4021 additional processing is required by the application in order to 4022 provide service to the user. 4024 7.1.3. Protocol Errors 4026 Errors that fall within the Protocol Error category SHOULD be treated 4027 on a per-hop basis, and Diameter proxies MAY attempt to correct the 4028 error, if it is possible. Note that these and only these errors MUST 4029 only be used in answer messages whose 'E' bit is set. To provide 4030 backward compatibility with existing implementations that follow 4031 [RFC3588], some of the error values that have previously been used in 4032 this category by [RFC3588] will not be re-used. Therefore the error 4033 values enumerated here maybe non-sequential. 4035 DIAMETER_UNABLE_TO_DELIVER 3002 4037 This error is given when Diameter can not deliver the message to 4038 the destination, either because no host within the realm 4039 supporting the required application was available to process the 4040 request, or because Destination-Host AVP was given without the 4041 associated Destination-Realm AVP. 4043 DIAMETER_REALM_NOT_SERVED 3003 4045 The intended realm of the request is not recognized. 4047 DIAMETER_TOO_BUSY 3004 4049 When returned, a Diameter node SHOULD attempt to send the message 4050 to an alternate peer. This error MUST only be used when a 4051 specific server is requested, and it cannot provide the requested 4052 service. 4054 DIAMETER_LOOP_DETECTED 3005 4056 An agent detected a loop while trying to get the message to the 4057 intended recipient. The message MAY be sent to an alternate peer, 4058 if one is available, but the peer reporting the error has 4059 identified a configuration problem. 4061 DIAMETER_REDIRECT_INDICATION 3006 4063 A redirect agent has determined that the request could not be 4064 satisfied locally and the initiator of the request should direct 4065 the request directly to the server, whose contact information has 4066 been added to the response. When set, the Redirect-Host AVP MUST 4067 be present. 4069 DIAMETER_APPLICATION_UNSUPPORTED 3007 4071 A request was sent for an application that is not supported. 4073 DIAMETER_INVALID_BIT_IN_HEADER 3011 4075 This error is returned when an unrecognized bit in the Diameter 4076 header is set to one (1). 4078 DIAMETER_INVALID_MESSAGE_LENGTH 3012 4080 This error is returned when a request is received with an invalid 4081 message length. 4083 7.1.4. Transient Failures 4085 Errors that fall within the transient failures category are used to 4086 inform a peer that the request could not be satisfied at the time it 4087 was received, but MAY be able to satisfy the request in the future. 4088 Note that these errors MUST be used in answer messages whose 'E' bit 4089 is not set. 4091 DIAMETER_AUTHENTICATION_REJECTED 4001 4093 The authentication process for the user failed, most likely due to 4094 an invalid password used by the user. Further attempts MUST only 4095 be tried after prompting the user for a new password. 4097 DIAMETER_OUT_OF_SPACE 4002 4099 A Diameter node received the accounting request but was unable to 4100 commit it to stable storage due to a temporary lack of space. 4102 ELECTION_LOST 4003 4104 The peer has determined that it has lost the election process and 4105 has therefore disconnected the transport connection. 4107 7.1.5. Permanent Failures 4109 Errors that fall within the permanent failures category are used to 4110 inform the peer that the request failed, and should not be attempted 4111 again. Note that these errors SHOULD be used in answer messages 4112 whose 'E' bit is not set. In error conditions where it is not 4113 possible or efficient to compose application specific answer grammar 4114 then answer messages with E-bit set and complying to the grammar 4115 described in 7.2 MAY also be used for permanent errors. 4117 To provide backward compatibility with existing implementations that 4118 follow [RFC3588], some of the error values that have previously been 4119 used in this category by [RFC3588] will not be re-used. Therefore 4120 the error values enumerated here maybe non-sequential. 4122 DIAMETER_AVP_UNSUPPORTED 5001 4124 The peer received a message that contained an AVP that is not 4125 recognized or supported and was marked with the Mandatory bit. A 4126 Diameter message with this error MUST contain one or more Failed- 4127 AVP AVP containing the AVPs that caused the failure. 4129 DIAMETER_UNKNOWN_SESSION_ID 5002 4131 The request contained an unknown Session-Id. 4133 DIAMETER_AUTHORIZATION_REJECTED 5003 4135 A request was received for which the user could not be authorized. 4136 This error could occur if the service requested is not permitted 4137 to the user. 4139 DIAMETER_INVALID_AVP_VALUE 5004 4141 The request contained an AVP with an invalid value in its data 4142 portion. A Diameter message indicating this error MUST include 4143 the offending AVPs within a Failed-AVP AVP. 4145 DIAMETER_MISSING_AVP 5005 4147 The request did not contain an AVP that is required by the Command 4148 Code definition. If this value is sent in the Result-Code AVP, a 4149 Failed-AVP AVP SHOULD be included in the message. The Failed-AVP 4150 AVP MUST contain an example of the missing AVP complete with the 4151 Vendor-Id if applicable. The value field of the missing AVP 4152 should be of correct minimum length and contain zeroes. 4154 DIAMETER_RESOURCES_EXCEEDED 5006 4156 A request was received that cannot be authorized because the user 4157 has already expended allowed resources. An example of this error 4158 condition is a user that is restricted to one dial-up PPP port, 4159 attempts to establish a second PPP connection. 4161 DIAMETER_CONTRADICTING_AVPS 5007 4163 The Home Diameter server has detected AVPs in the request that 4164 contradicted each other, and is not willing to provide service to 4165 the user. The Failed-AVP AVPs MUST be present which contains the 4166 AVPs that contradicted each other. 4168 DIAMETER_AVP_NOT_ALLOWED 5008 4170 A message was received with an AVP that MUST NOT be present. The 4171 Failed-AVP AVP MUST be included and contain a copy of the 4172 offending AVP. 4174 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009 4176 A message was received that included an AVP that appeared more 4177 often than permitted in the message definition. The Failed-AVP 4178 AVP MUST be included and contain a copy of the first instance of 4179 the offending AVP that exceeded the maximum number of occurrences 4181 DIAMETER_NO_COMMON_APPLICATION 5010 4183 This error is returned by a Diameter node that is not acting as a 4184 relay when it receives a CER which advertises a set of 4185 applications that it does not support. 4187 DIAMETER_UNSUPPORTED_VERSION 5011 4189 This error is returned when a request was received, whose version 4190 number is unsupported. 4192 DIAMETER_UNABLE_TO_COMPLY 5012 4194 This error is returned when a request is rejected for unspecified 4195 reasons. 4197 DIAMETER_INVALID_AVP_LENGTH 5014 4199 The request contained an AVP with an invalid length. A Diameter 4200 message indicating this error MUST include the offending AVPs 4201 within a Failed-AVP AVP. In cases where the erroneous avp length 4202 value exceeds the message length or is less than the minimum AVP 4203 header length, it is sufficient to include the offending AVP 4204 header and a zero filled payload of the minimum required length 4205 for the payloads data type. If the AVP is a grouped AVP, the 4206 grouped AVP header with an empty payload would be sufficient to 4207 indicate the offending AVP. In the case where the offending AVP 4208 header cannot be fully decoded when avp length is less than the 4209 minimum AVP header length, it is sufficient to include an 4210 offending AVP header that is formulated by padding the incomplete 4211 AVP header with zero up to the minimum AVP header length. 4213 DIAMETER_NO_COMMON_SECURITY 5017 4215 This error is returned when a CER message is received, and there 4216 are no common security mechanisms supported between the peers. A 4217 Capabilities-Exchange-Answer (CEA) MUST be returned with the 4218 Result-Code AVP set to DIAMETER_NO_COMMON_SECURITY. 4220 DIAMETER_UNKNOWN_PEER 5018 4222 A CER was received from an unknown peer. 4224 DIAMETER_COMMAND_UNSUPPORTED 5019 4226 The Request contained a Command-Code that the receiver did not 4227 recognize or support. This MUST be used when a Diameter node 4228 receives an experimental command that it does not understand. 4230 DIAMETER_INVALID_HDR_BITS 5020 4232 A request was received whose bits in the Diameter header were 4233 either set to an invalid combination, or to a value that is 4234 inconsistent with the command code's definition. 4236 DIAMETER_INVALID_AVP_BITS 5021 4238 A request was received that included an AVP whose flag bits are 4239 set to an unrecognized value, or that is inconsistent with the 4240 AVP's definition. 4242 7.2. Error Bit 4244 The 'E' (Error Bit) in the Diameter header is set when the request 4245 caused a protocol-related error (see Section 7.1.3). A message with 4246 the 'E' bit MUST NOT be sent as a response to an answer message. 4247 Note that a message with the 'E' bit set is still subjected to the 4248 processing rules defined in Section 6.2. When set, the answer 4249 message will not conform to the ABNF specification for the command, 4250 and will instead conform to the following ABNF: 4252 Message Format 4254 ::= < Diameter Header: code, ERR [PXY] > 4255 0*1< Session-Id > 4256 { Origin-Host } 4257 { Origin-Realm } 4258 { Result-Code } 4259 [ Origin-State-Id ] 4260 [ Error-Message ] 4261 [ Error-Reporting-Host ] 4262 [ Failed-AVP ] 4263 * [ Proxy-Info ] 4264 * [ AVP ] 4266 Note that the code used in the header is the same than the one found 4267 in the request message, but with the 'R' bit cleared and the 'E' bit 4268 set. The 'P' bit in the header is set to the same value as the one 4269 found in the request message. 4271 7.3. Error-Message AVP 4273 The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY 4274 accompany a Result-Code AVP as a human readable error message. The 4275 Error-Message AVP is not intended to be useful in real-time, and 4276 SHOULD NOT be expected to be parsed by network entities. 4278 7.4. Error-Reporting-Host AVP 4280 The Error-Reporting-Host AVP (AVP Code 294) is of type 4281 DiameterIdentity. This AVP contains the identity of the Diameter 4282 host that sent the Result-Code AVP to a value other than 2001 4283 (Success), only if the host setting the Result-Code is different from 4284 the one encoded in the Origin-Host AVP. This AVP is intended to be 4285 used for troubleshooting purposes, and MUST be set when the Result- 4286 Code AVP indicates a failure. 4288 7.5. Failed-AVP AVP 4290 The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides 4291 debugging information in cases where a request is rejected or not 4292 fully processed due to erroneous information in a specific AVP. The 4293 value of the Result-Code AVP will provide information on the reason 4294 for the Failed-AVP AVP. A Diameter message SHOULD contain only one 4295 Failed-AVP that corresponds to the error indicated by the Result-Code 4296 AVP. For practical purposes, this Failed-AVP would typically refer 4297 to the first AVP processing error that a Diameter node encounters. 4299 The possible reasons for this AVP are the presence of an improperly 4300 constructed AVP, an unsupported or unrecognized AVP, an invalid AVP 4301 value, the omission of a required AVP, the presence of an explicitly 4302 excluded AVP (see tables in Section 10), or the presence of two or 4303 more occurrences of an AVP which is restricted to 0, 1, or 0-1 4304 occurrences. 4306 A Diameter message SHOULD contain one Failed-AVP AVP, containing the 4307 entire AVP that could not be processed successfully. If the failure 4308 reason is omission of a required AVP, an AVP with the missing AVP 4309 code, the missing vendor id, and a zero filled payload of the minimum 4310 required length for the omitted AVP will be added. If the failure 4311 reason is an invalid AVP length where the reported length is less 4312 than the minimum AVP header length or greater than the reported 4313 message length, a copy of the offending AVP header and a zero filled 4314 payload of the minimum required length SHOULD be added. 4316 In the case where the offending AVP is embedded within a grouped AVP, 4317 the Failed-AVP MAY contain the grouped AVP which in turn contains the 4318 single offending AVP. The same method MAY be employed if the grouped 4319 AVP itself is embedded in yet another grouped AVP and so on. In this 4320 case, the Failed-AVP MAY contain the grouped AVP heirarchy up to the 4321 single offending AVP. This enables the recipient to detect the 4322 location of the offending AVP when embedded in a group. 4324 AVP Format 4326 ::= < AVP Header: 279 > 4327 1* {AVP} 4329 7.6. Experimental-Result AVP 4331 The Experimental-Result AVP (AVP Code 297) is of type Grouped, and 4332 indicates whether a particular vendor-specific request was completed 4333 successfully or whether an error occurred. Its Data field has the 4334 following ABNF grammar: 4336 AVP Format 4338 Experimental-Result ::= < AVP Header: 297 > 4339 { Vendor-Id } 4340 { Experimental-Result-Code } 4342 The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies 4343 the vendor responsible for the assignment of the result code which 4344 follows. All Diameter answer messages defined in vendor-specific 4345 applications MUST include either one Result-Code AVP or one 4346 Experimental-Result AVP. 4348 7.7. Experimental-Result-Code AVP 4350 The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32 4351 and contains a vendor-assigned value representing the result of 4352 processing the request. 4354 It is recommended that vendor-specific result codes follow the same 4355 conventions given for the Result-Code AVP regarding the different 4356 types of result codes and the handling of errors (for non 2xxx 4357 values). 4359 8. Diameter User Sessions 4361 In general, Diameter can provide two different types of services to 4362 applications. The first involves authentication and authorization, 4363 and can optionally make use of accounting. The second only makes use 4364 of accounting. 4366 When a service makes use of the authentication and/or authorization 4367 portion of an application, and a user requests access to the network, 4368 the Diameter client issues an auth request to its local server. The 4369 auth request is defined in a service specific Diameter application 4370 (e.g., NASREQ). The request contains a Session-Id AVP, which is used 4371 in subsequent messages (e.g., subsequent authorization, accounting, 4372 etc) relating to the user's session. The Session-Id AVP is a means 4373 for the client and servers to correlate a Diameter message with a 4374 user session. 4376 When a Diameter server authorizes a user to use network resources for 4377 a finite amount of time, and it is willing to extend the 4378 authorization via a future request, it MUST add the Authorization- 4379 Lifetime AVP to the answer message. The Authorization-Lifetime AVP 4380 defines the maximum number of seconds a user MAY make use of the 4381 resources before another authorization request is expected by the 4382 server. The Auth-Grace-Period AVP contains the number of seconds 4383 following the expiration of the Authorization-Lifetime, after which 4384 the server will release all state information related to the user's 4385 session. Note that if payment for services is expected by the 4386 serving realm from the user's home realm, the Authorization-Lifetime 4387 AVP, combined with the Auth-Grace-Period AVP, implies the maximum 4388 length of the session the home realm is willing to be fiscally 4389 responsible for. Services provided past the expiration of the 4390 Authorization-Lifetime and Auth-Grace-Period AVPs are the 4391 responsibility of the access device. Of course, the actual cost of 4392 services rendered is clearly outside the scope of the protocol. 4394 An access device that does not expect to send a re-authorization or a 4395 session termination request to the server MAY include the Auth- 4396 Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint 4397 to the server. If the server accepts the hint, it agrees that since 4398 no session termination message will be received once service to the 4399 user is terminated, it cannot maintain state for the session. If the 4400 answer message from the server contains a different value in the 4401 Auth-Session-State AVP (or the default value if the AVP is absent), 4402 the access device MUST follow the server's directives. Note that the 4403 value NO_STATE_MAINTAINED MUST NOT be set in subsequent re- 4404 authorization requests and answers. 4406 The base protocol does not include any authorization request 4407 messages, since these are largely application-specific and are 4408 defined in a Diameter application document. However, the base 4409 protocol does define a set of messages that is used to terminate user 4410 sessions. These are used to allow servers that maintain state 4411 information to free resources. 4413 When a service only makes use of the Accounting portion of the 4414 Diameter protocol, even in combination with an application, the 4415 Session-Id is still used to identify user sessions. However, the 4416 session termination messages are not used, since a session is 4417 signaled as being terminated by issuing an accounting stop message. 4419 Diameter may also be used for services that cannot be easily 4420 categorized as authentication, authorization or accounting (e.g., 4421 certain 3GPP IMS interfaces). In such cases, the finite state 4422 machine defined in subsequent sections may not be applicable. 4423 Therefore, the applications itself MAY need to define its own finite 4424 state machine. However, such application specific statemachines MUST 4425 comply with general Diameter user session requirements such co- 4426 relating all message exchanges via Session-Id AVP. 4428 8.1. Authorization Session State Machine 4430 This section contains a set of finite state machines, representing 4431 the life cycle of Diameter sessions, and which MUST be observed by 4432 all Diameter implementations that make use of the authentication 4433 and/or authorization portion of a Diameter application. The term 4434 Service-Specific below refers to a message defined in a Diameter 4435 application (e.g., Mobile IPv4, NASREQ). 4437 There are four different authorization session state machines 4438 supported in the Diameter base protocol. The first two describe a 4439 session in which the server is maintaining session state, indicated 4440 by the value of the Auth-Session-State AVP (or its absence). One 4441 describes the session from a client perspective, the other from a 4442 server perspective. The second two state machines are used when the 4443 server does not maintain session state. Here again, one describes 4444 the session from a client perspective, the other from a server 4445 perspective. 4447 When a session is moved to the Idle state, any resources that were 4448 allocated for the particular session must be released. Any event not 4449 listed in the state machines MUST be considered as an error 4450 condition, and an answer, if applicable, MUST be returned to the 4451 originator of the message. 4453 In the case that an application does not support re-auth, the state 4454 transitions related to server-initiated re-auth when both client and 4455 server sessions maintains state (e.g., Send RAR, Pending, Receive 4456 RAA) MAY be ignored. 4458 In the state table, the event 'Failure to send X' means that the 4459 Diameter agent is unable to send command X to the desired 4460 destination. This could be due to the peer being down, or due to the 4461 peer sending back a transient failure or temporary protocol error 4462 notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the 4463 Result-Code AVP of the corresponding Answer command. The event 'X 4464 successfully sent' is the complement of 'Failure to send X'. 4466 The following state machine is observed by a client when state is 4467 maintained on the server: 4469 CLIENT, STATEFUL 4470 State Event Action New State 4471 ------------------------------------------------------------- 4472 Idle Client or Device Requests Send Pending 4473 access service 4474 specific 4475 auth req 4477 Idle ASR Received Send ASA Idle 4478 for unknown session with 4479 Result-Code 4480 = UNKNOWN_ 4481 SESSION_ID 4483 Idle RAR Received Send RAA Idle 4484 for unknown session with 4485 Result-Code 4486 = UNKNOWN_ 4487 SESSION_ID 4489 Pending Successful Service-specific Grant Open 4490 authorization answer Access 4491 received with default 4492 Auth-Session-State value 4494 Pending Successful Service-specific Sent STR Discon 4495 authorization answer received 4496 but service not provided 4498 Pending Error processing successful Sent STR Discon 4499 Service-specific authorization 4500 answer 4502 Pending Failed Service-specific Cleanup Idle 4503 authorization answer received 4505 Open User or client device Send Open 4506 requests access to service service 4507 specific 4508 auth req 4510 Open Successful Service-specific Provide Open 4511 authorization answer received Service 4513 Open Failed Service-specific Discon. Idle 4514 authorization answer user/device 4515 received. 4517 Open RAR received and client will Send RAA Open 4518 perform subsequent re-auth with 4519 Result-Code 4520 = SUCCESS 4522 Open RAR received and client will Send RAA Idle 4523 not perform subsequent with 4524 re-auth Result-Code 4525 != SUCCESS, 4526 Discon. 4527 user/device 4529 Open Session-Timeout Expires on Send STR Discon 4530 Access Device 4532 Open ASR Received, Send ASA Discon 4533 client will comply with with 4534 request to end the session Result-Code 4535 = SUCCESS, 4536 Send STR. 4538 Open ASR Received, Send ASA Open 4539 client will not comply with with 4540 request to end the session Result-Code 4541 != SUCCESS 4543 Open Authorization-Lifetime + Send STR Discon 4544 Auth-Grace-Period expires on 4545 access device 4547 Discon ASR Received Send ASA Discon 4549 Discon STA Received Discon. Idle 4550 user/device 4552 The following state machine is observed by a server when it is 4553 maintaining state for the session: 4555 SERVER, STATEFUL 4556 State Event Action New State 4557 ------------------------------------------------------------- 4558 Idle Service-specific authorization Send Open 4559 request received, and successful 4560 user is authorized serv. 4561 specific 4562 answer 4564 Idle Service-specific authorization Send Idle 4565 request received, and failed serv. 4566 user is not authorized specific 4567 answer 4569 Open Service-specific authorization Send Open 4570 request received, and user successful 4571 is authorized serv. specific 4572 answer 4574 Open Service-specific authorization Send Idle 4575 request received, and user failed serv. 4576 is not authorized specific 4577 answer, 4578 Cleanup 4580 Open Home server wants to confirm Send RAR Pending 4581 authentication and/or 4582 authorization of the user 4584 Pending Received RAA with a failed Cleanup Idle 4585 Result-Code 4587 Pending Received RAA with Result-Code Update Open 4588 = SUCCESS session 4590 Open Home server wants to Send ASR Discon 4591 terminate the service 4593 Open Authorization-Lifetime (and Cleanup Idle 4594 Auth-Grace-Period) expires 4595 on home server. 4597 Open Session-Timeout expires on Cleanup Idle 4598 home server 4600 Discon Failure to send ASR Wait, Discon 4601 resend ASR 4603 Discon ASR successfully sent and Cleanup Idle 4604 ASA Received with Result-Code 4606 Not ASA Received None No Change. 4607 Discon 4609 Any STR Received Send STA, Idle 4610 Cleanup. 4612 The following state machine is observed by a client when state is not 4613 maintained on the server: 4615 CLIENT, STATELESS 4616 State Event Action New State 4617 ------------------------------------------------------------- 4618 Idle Client or Device Requests Send Pending 4619 access service 4620 specific 4621 auth req 4623 Pending Successful Service-specific Grant Open 4624 authorization answer Access 4625 received with Auth-Session- 4626 State set to 4627 NO_STATE_MAINTAINED 4629 Pending Failed Service-specific Cleanup Idle 4630 authorization answer 4631 received 4633 Open Session-Timeout Expires on Discon. Idle 4634 Access Device user/device 4636 Open Service to user is terminated Discon. Idle 4637 user/device 4639 The following state machine is observed by a server when it is not 4640 maintaining state for the session: 4642 SERVER, STATELESS 4643 State Event Action New State 4644 ------------------------------------------------------------- 4645 Idle Service-specific authorization Send serv. Idle 4646 request received, and specific 4647 successfully processed answer 4649 8.2. Accounting Session State Machine 4651 The following state machines MUST be supported for applications that 4652 have an accounting portion or that require only accounting services. 4653 The first state machine is to be observed by clients. 4655 See Section 9.7 for Accounting Command Codes and Section 9.8 for 4656 Accounting AVPs. 4658 The server side in the accounting state machine depends in some cases 4659 on the particular application. The Diameter base protocol defines a 4660 default state machine that MUST be followed by all applications that 4661 have not specified other state machines. This is the second state 4662 machine in this section described below. 4664 The default server side state machine requires the reception of 4665 accounting records in any order and at any time, and does not place 4666 any standards requirement on the processing of these records. 4667 Implementations of Diameter MAY perform checking, ordering, 4668 correlation, fraud detection, and other tasks based on these records. 4669 Both base Diameter AVPs as well as application specific AVPs MAY be 4670 inspected as a part of these tasks. The tasks can happen either 4671 immediately after record reception or in a post-processing phase. 4672 However, as these tasks are typically application or even policy 4673 dependent, they are not standardized by the Diameter specifications. 4674 Applications MAY define requirements on when to accept accounting 4675 records based on the used value of Accounting-Realtime-Required AVP, 4676 credit limits checks, and so on. 4678 However, the Diameter base protocol defines one optional server side 4679 state machine that MAY be followed by applications that require 4680 keeping track of the session state at the accounting server. Note 4681 that such tracking is incompatible with the ability to sustain long 4682 duration connectivity problems. Therefore, the use of this state 4683 machine is recommended only in applications where the value of the 4684 Accounting-Realtime-Required AVP is DELIVER_AND_GRANT, and hence 4685 accounting connectivity problems are required to cause the serviced 4686 user to be disconnected. Otherwise, records produced by the client 4687 may be lost by the server which no longer accepts them after the 4688 connectivity is re-established. This state machine is the third 4689 state machine in this section. The state machine is supervised by a 4690 supervision session timer Ts, which the value should be reasonably 4691 higher than the Acct_Interim_Interval value. Ts MAY be set to two 4692 times the value of the Acct_Interim_Interval so as to avoid the 4693 accounting session in the Diameter server to change to Idle state in 4694 case of short transient network failure. 4696 Any event not listed in the state machines MUST be considered as an 4697 error condition, and a corresponding answer, if applicable, MUST be 4698 returned to the originator of the message. 4700 In the state table, the event 'Failure to send' means that the 4701 Diameter client is unable to communicate with the desired 4702 destination. This could be due to the peer being down, or due to the 4703 peer sending back a transient failure or temporary protocol error 4704 notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or 4705 DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting 4706 Answer command. 4708 The event 'Failed answer' means that the Diameter client received a 4709 non-transient failure notification in the Accounting Answer command. 4711 Note that the action 'Disconnect user/dev' MUST have an effect also 4712 to the authorization session state table, e.g., cause the STR message 4713 to be sent, if the given application has both authentication/ 4714 authorization and accounting portions. 4716 The states PendingS, PendingI, PendingL, PendingE and PendingB stand 4717 for pending states to wait for an answer to an accounting request 4718 related to a Start, Interim, Stop, Event or buffered record, 4719 respectively. 4721 CLIENT, ACCOUNTING 4722 State Event Action New State 4723 ------------------------------------------------------------- 4724 Idle Client or device requests Send PendingS 4725 access accounting 4726 start req. 4728 Idle Client or device requests Send PendingE 4729 a one-time service accounting 4730 event req 4732 Idle Records in storage Send PendingB 4733 record 4735 PendingS Successful accounting Open 4736 start answer received 4738 PendingS Failure to send and buffer Store Open 4739 space available and realtime Start 4740 not equal to DELIVER_AND_GRANT Record 4742 PendingS Failure to send and no buffer Open 4743 space available and realtime 4744 equal to GRANT_AND_LOSE 4746 PendingS Failure to send and no buffer Disconnect Idle 4747 space available and realtime user/dev 4748 not equal to 4749 GRANT_AND_LOSE 4751 PendingS Failed accounting start answer Open 4752 received and realtime equal 4753 to GRANT_AND_LOSE 4755 PendingS Failed accounting start answer Disconnect Idle 4756 received and realtime not user/dev 4757 equal to GRANT_AND_LOSE 4759 PendingS User service terminated Store PendingS 4760 stop 4761 record 4763 Open Interim interval elapses Send PendingI 4764 accounting 4765 interim 4766 record 4767 Open User service terminated Send PendingL 4768 accounting 4769 stop req. 4771 PendingI Successful accounting interim Open 4772 answer received 4774 PendingI Failure to send and (buffer Store Open 4775 space available or old record interim 4776 can be overwritten) and record 4777 realtime not equal to 4778 DELIVER_AND_GRANT 4780 PendingI Failure to send and no buffer Open 4781 space available and realtime 4782 equal to GRANT_AND_LOSE 4784 PendingI Failure to send and no buffer Disconnect Idle 4785 space available and realtime user/dev 4786 not equal to GRANT_AND_LOSE 4788 PendingI Failed accounting interim Open 4789 answer received and realtime 4790 equal to GRANT_AND_LOSE 4792 PendingI Failed accounting interim Disconnect Idle 4793 answer received and realtime user/dev 4794 not equal to GRANT_AND_LOSE 4796 PendingI User service terminated Store PendingI 4797 stop 4798 record 4799 PendingE Successful accounting Idle 4800 event answer received 4802 PendingE Failure to send and buffer Store Idle 4803 space available event 4804 record 4806 PendingE Failure to send and no buffer Idle 4807 space available 4809 PendingE Failed accounting event answer Idle 4810 received 4812 PendingB Successful accounting answer Delete Idle 4813 received record 4815 PendingB Failure to send Idle 4817 PendingB Failed accounting answer Delete Idle 4818 received record 4820 PendingL Successful accounting Idle 4821 stop answer received 4823 PendingL Failure to send and buffer Store Idle 4824 space available stop 4825 record 4827 PendingL Failure to send and no buffer Idle 4828 space available 4830 PendingL Failed accounting stop answer Idle 4831 received 4833 SERVER, STATELESS ACCOUNTING 4834 State Event Action New State 4835 ------------------------------------------------------------- 4837 Idle Accounting start request Send Idle 4838 received, and successfully accounting 4839 processed. start 4840 answer 4842 Idle Accounting event request Send Idle 4843 received, and successfully accounting 4844 processed. event 4845 answer 4847 Idle Interim record received, Send Idle 4848 and successfully processed. accounting 4849 interim 4850 answer 4852 Idle Accounting stop request Send Idle 4853 received, and successfully accounting 4854 processed stop answer 4856 Idle Accounting request received, Send Idle 4857 no space left to store accounting 4858 records answer, 4859 Result-Code 4860 = OUT_OF_ 4861 SPACE 4863 SERVER, STATEFUL ACCOUNTING 4864 State Event Action New State 4865 ------------------------------------------------------------- 4867 Idle Accounting start request Send Open 4868 received, and successfully accounting 4869 processed. start 4870 answer, 4871 Start Ts 4873 Idle Accounting event request Send Idle 4874 received, and successfully accounting 4875 processed. event 4876 answer 4878 Idle Accounting request received, Send Idle 4879 no space left to store accounting 4880 records answer, 4881 Result-Code 4882 = OUT_OF_ 4883 SPACE 4885 Open Interim record received, Send Open 4886 and successfully processed. accounting 4887 interim 4888 answer, 4889 Restart Ts 4891 Open Accounting stop request Send Idle 4892 received, and successfully accounting 4893 processed stop answer, 4894 Stop Ts 4896 Open Accounting request received, Send Idle 4897 no space left to store accounting 4898 records answer, 4899 Result-Code 4900 = OUT_OF_ 4901 SPACE, 4902 Stop Ts 4904 Open Session supervision timer Ts Stop Ts Idle 4905 expired 4907 8.3. Server-Initiated Re-Auth 4909 A Diameter server may initiate a re-authentication and/or re- 4910 authorization service for a particular session by issuing a Re-Auth- 4911 Request (RAR). 4913 For example, for pre-paid services, the Diameter server that 4914 originally authorized a session may need some confirmation that the 4915 user is still using the services. 4917 An access device that receives a RAR message with Session-Id equal to 4918 a currently active session MUST initiate a re-auth towards the user, 4919 if the service supports this particular feature. Each Diameter 4920 application MUST state whether service-initiated re-auth is 4921 supported, since some applications do not allow access devices to 4922 prompt the user for re-auth. 4924 8.3.1. Re-Auth-Request 4926 The Re-Auth-Request (RAR), indicated by the Command-Code set to 258 4927 and the message flags' 'R' bit set, may be sent by any server to the 4928 access device that is providing session service, to request that the 4929 user be re-authenticated and/or re-authorized. 4931 Message Format 4933 ::= < Diameter Header: 258, REQ, PXY > 4934 < Session-Id > 4935 { Origin-Host } 4936 { Origin-Realm } 4937 { Destination-Realm } 4938 { Destination-Host } 4939 { Auth-Application-Id } 4940 { Re-Auth-Request-Type } 4941 [ User-Name ] 4942 [ Origin-State-Id ] 4943 * [ Proxy-Info ] 4944 * [ Route-Record ] 4945 * [ AVP ] 4947 8.3.2. Re-Auth-Answer 4949 The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258 4950 and the message flags' 'R' bit clear, is sent in response to the RAR. 4951 The Result-Code AVP MUST be present, and indicates the disposition of 4952 the request. 4954 A successful RAA message MUST be followed by an application-specific 4955 authentication and/or authorization message. 4957 Message Format 4959 ::= < Diameter Header: 258, PXY > 4960 < Session-Id > 4961 { Result-Code } 4962 { Origin-Host } 4963 { Origin-Realm } 4964 [ User-Name ] 4965 [ Origin-State-Id ] 4966 [ Error-Message ] 4967 [ Error-Reporting-Host ] 4968 [ Failed-AVP ] 4969 * [ Redirect-Host ] 4970 [ Redirect-Host-Usage ] 4971 [ Redirect-Max-Cache-Time ] 4972 * [ Proxy-Info ] 4973 * [ AVP ] 4975 8.4. Session Termination 4977 It is necessary for a Diameter server that authorized a session, for 4978 which it is maintaining state, to be notified when that session is no 4979 longer active, both for tracking purposes as well as to allow 4980 stateful agents to release any resources that they may have provided 4981 for the user's session. For sessions whose state is not being 4982 maintained, this section is not used. 4984 When a user session that required Diameter authorization terminates, 4985 the access device that provided the service MUST issue a Session- 4986 Termination-Request (STR) message to the Diameter server that 4987 authorized the service, to notify it that the session is no longer 4988 active. An STR MUST be issued when a user session terminates for any 4989 reason, including user logoff, expiration of Session-Timeout, 4990 administrative action, termination upon receipt of an Abort-Session- 4991 Request (see below), orderly shutdown of the access device, etc. 4993 The access device also MUST issue an STR for a session that was 4994 authorized but never actually started. This could occur, for 4995 example, due to a sudden resource shortage in the access device, or 4996 because the access device is unwilling to provide the type of service 4997 requested in the authorization, or because the access device does not 4998 support a mandatory AVP returned in the authorization, etc. 5000 It is also possible that a session that was authorized is never 5001 actually started due to action of a proxy. For example, a proxy may 5002 modify an authorization answer, converting the result from success to 5003 failure, prior to forwarding the message to the access device. If 5004 the answer did not contain an Auth-Session-State AVP with the value 5005 NO_STATE_MAINTAINED, a proxy that causes an authorized session not to 5006 be started MUST issue an STR to the Diameter server that authorized 5007 the session, since the access device has no way of knowing that the 5008 session had been authorized. 5010 A Diameter server that receives an STR message MUST clean up 5011 resources (e.g., session state) associated with the Session-Id 5012 specified in the STR, and return a Session-Termination-Answer. 5014 A Diameter server also MUST clean up resources when the Session- 5015 Timeout expires, or when the Authorization-Lifetime and the Auth- 5016 Grace-Period AVPs expires without receipt of a re-authorization 5017 request, regardless of whether an STR for that session is received. 5018 The access device is not expected to provide service beyond the 5019 expiration of these timers; thus, expiration of either of these 5020 timers implies that the access device may have unexpectedly shut 5021 down. 5023 8.4.1. Session-Termination-Request 5025 The Session-Termination-Request (STR), indicated by the Command-Code 5026 set to 275 and the Command Flags' 'R' bit set, is sent by the access 5027 device to inform the Diameter Server that an authenticated and/or 5028 authorized session is being terminated. 5030 Message Format 5032 ::= < Diameter Header: 275, REQ, PXY > 5033 < Session-Id > 5034 { Origin-Host } 5035 { Origin-Realm } 5036 { Destination-Realm } 5037 { Auth-Application-Id } 5038 { Termination-Cause } 5039 [ User-Name ] 5040 [ Destination-Host ] 5041 * [ Class ] 5042 [ Origin-State-Id ] 5043 * [ Proxy-Info ] 5044 * [ Route-Record ] 5045 * [ AVP ] 5047 8.4.2. Session-Termination-Answer 5049 The Session-Termination-Answer (STA), indicated by the Command-Code 5050 set to 275 and the message flags' 'R' bit clear, is sent by the 5051 Diameter Server to acknowledge the notification that the session has 5052 been terminated. The Result-Code AVP MUST be present, and MAY 5053 contain an indication that an error occurred while servicing the STR. 5055 Upon sending or receipt of the STA, the Diameter Server MUST release 5056 all resources for the session indicated by the Session-Id AVP. Any 5057 intermediate server in the Proxy-Chain MAY also release any 5058 resources, if necessary. 5060 Message Format 5062 ::= < Diameter Header: 275, PXY > 5063 < Session-Id > 5064 { Result-Code } 5065 { Origin-Host } 5066 { Origin-Realm } 5067 [ User-Name ] 5068 * [ Class ] 5069 [ Error-Message ] 5070 [ Error-Reporting-Host ] 5071 [ Failed-AVP ] 5072 [ Origin-State-Id ] 5073 * [ Redirect-Host ] 5074 [ Redirect-Host-Usage ] 5075 ^ 5076 [ Redirect-Max-Cache-Time ] 5077 * [ Proxy-Info ] 5078 * [ AVP ] 5080 8.5. Aborting a Session 5082 A Diameter server may request that the access device stop providing 5083 service for a particular session by issuing an Abort-Session-Request 5084 (ASR). 5086 For example, the Diameter server that originally authorized the 5087 session may be required to cause that session to be stopped for 5088 credit or other reasons that were not anticipated when the session 5089 was first authorized. On the other hand, an operator may maintain a 5090 management server for the purpose of issuing ASRs to administratively 5091 remove users from the network. 5093 An access device that receives an ASR with Session-ID equal to a 5094 currently active session MAY stop the session. Whether the access 5095 device stops the session or not is implementation- and/or 5096 configuration-dependent. For example, an access device may honor 5097 ASRs from certain agents only. In any case, the access device MUST 5098 respond with an Abort-Session-Answer, including a Result-Code AVP to 5099 indicate what action it took. 5101 Note that if the access device does stop the session upon receipt of 5102 an ASR, it issues an STR to the authorizing server (which may or may 5103 not be the agent issuing the ASR) just as it would if the session 5104 were terminated for any other reason. 5106 8.5.1. Abort-Session-Request 5108 The Abort-Session-Request (ASR), indicated by the Command-Code set to 5109 274 and the message flags' 'R' bit set, may be sent by any server to 5110 the access device that is providing session service, to request that 5111 the session identified by the Session-Id be stopped. 5113 Message Format 5115 ::= < Diameter Header: 274, REQ, PXY > 5116 < Session-Id > 5117 { Origin-Host } 5118 { Origin-Realm } 5119 { Destination-Realm } 5120 { Destination-Host } 5121 { Auth-Application-Id } 5122 [ User-Name ] 5123 [ Origin-State-Id ] 5124 * [ Proxy-Info ] 5125 * [ Route-Record ] 5126 * [ AVP ] 5128 8.5.2. Abort-Session-Answer 5130 The Abort-Session-Answer (ASA), indicated by the Command-Code set to 5131 274 and the message flags' 'R' bit clear, is sent in response to the 5132 ASR. The Result-Code AVP MUST be present, and indicates the 5133 disposition of the request. 5135 If the session identified by Session-Id in the ASR was successfully 5136 terminated, Result-Code is set to DIAMETER_SUCCESS. If the session 5137 is not currently active, Result-Code is set to 5138 DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the 5139 session for any other reason, Result-Code is set to 5140 DIAMETER_UNABLE_TO_COMPLY. 5142 Message Format 5144 ::= < Diameter Header: 274, PXY > 5145 < Session-Id > 5146 { Result-Code } 5147 { Origin-Host } 5148 { Origin-Realm } 5149 [ User-Name ] 5150 [ Origin-State-Id ] 5151 [ Error-Message ] 5152 [ Error-Reporting-Host ] 5153 [ Failed-AVP ] 5154 * [ Redirect-Host ] 5155 [ Redirect-Host-Usage ] 5156 [ Redirect-Max-Cache-Time ] 5157 * [ Proxy-Info ] 5158 * [ AVP ] 5160 8.6. Inferring Session Termination from Origin-State-Id 5162 Origin-State-Id is used to allow rapid detection of terminated 5163 sessions for which no STR would have been issued, due to 5164 unanticipated shutdown of an access device. 5166 By including Origin-State-Id in CER/CEA messages, an access device 5167 allows a next-hop server to determine immediately upon connection 5168 whether the device has lost its sessions since the last connection. 5170 By including Origin-State-Id in request messages, an access device 5171 also allows a server with which it communicates via proxy to make 5172 such a determination. However, a server that is not directly 5173 connected with the access device will not discover that the access 5174 device has been restarted unless and until it receives a new request 5175 from the access device. Thus, use of this mechanism across proxies 5176 is opportunistic rather than reliable, but useful nonetheless. 5178 When a Diameter server receives an Origin-State-Id that is greater 5179 than the Origin-State-Id previously received from the same issuer, it 5180 may assume that the issuer has lost state since the previous message 5181 and that all sessions that were active under the lower Origin-State- 5182 Id have been terminated. The Diameter server MAY clean up all 5183 session state associated with such lost sessions, and MAY also issues 5184 STRs for all such lost sessions that were authorized on upstream 5185 servers, to allow session state to be cleaned up globally. 5187 8.7. Auth-Request-Type AVP 5189 The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is 5190 included in application-specific auth requests to inform the peers 5191 whether a user is to be authenticated only, authorized only or both. 5192 Note any value other than both MAY cause RADIUS interoperability 5193 issues. The following values are defined: 5195 AUTHENTICATE_ONLY 1 5197 The request being sent is for authentication only, and MUST 5198 contain the relevant application specific authentication AVPs that 5199 are needed by the Diameter server to authenticate the user. 5201 AUTHORIZE_ONLY 2 5203 The request being sent is for authorization only, and MUST contain 5204 the application specific authorization AVPs that are necessary to 5205 identify the service being requested/offered. 5207 AUTHORIZE_AUTHENTICATE 3 5209 The request contains a request for both authentication and 5210 authorization. The request MUST include both the relevant 5211 application specific authentication information, and authorization 5212 information necessary to identify the service being requested/ 5213 offered. 5215 8.8. Session-Id AVP 5217 The Session-Id AVP (AVP Code 263) is of type UTF8String and is used 5218 to identify a specific session (see Section 8). All messages 5219 pertaining to a specific session MUST include only one Session-Id AVP 5220 and the same value MUST be used throughout the life of a session. 5221 When present, the Session-Id SHOULD appear immediately following the 5222 Diameter Header (see Section 3). 5224 The Session-Id MUST be globally and eternally unique, as it is meant 5225 to uniquely identify a user session without reference to any other 5226 information, and may be needed to correlate historical authentication 5227 information with accounting information. The Session-Id includes a 5228 mandatory portion and an implementation-defined portion; a 5229 recommended format for the implementation-defined portion is outlined 5230 below. 5232 The Session-Id MUST begin with the sender's identity encoded in the 5233 DiameterIdentity type (see Section 4.4). The remainder of the 5234 Session-Id is delimited by a ";" character, and MAY be any sequence 5235 that the client can guarantee to be eternally unique; however, the 5236 following format is recommended, (square brackets [] indicate an 5237 optional element): 5239 ;;[;] 5241 and are decimal representations of the 5242 high and low 32 bits of a monotonically increasing 64-bit value. The 5243 64-bit value is rendered in two part to simplify formatting by 32-bit 5244 processors. At startup, the high 32 bits of the 64-bit value MAY be 5245 initialized to the time, and the low 32 bits MAY be initialized to 5246 zero. This will for practical purposes eliminate the possibility of 5247 overlapping Session-Ids after a reboot, assuming the reboot process 5248 takes longer than a second. Alternatively, an implementation MAY 5249 keep track of the increasing value in non-volatile memory. 5251 is implementation specific but may include a modem's 5252 device Id, a layer 2 address, timestamp, etc. 5254 Example, in which there is no optional value: 5256 accesspoint7.acme.com;1876543210;523 5258 Example, in which there is an optional value: 5260 accesspoint7.acme.com;1876543210;523;mobile@200.1.1.88 5262 The Session-Id is created by the Diameter application initiating the 5263 session, which in most cases is done by the client. Note that a 5264 Session-Id MAY be used for both the authorization and accounting 5265 commands of a given application. 5267 8.9. Authorization-Lifetime AVP 5269 The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32 5270 and contains the maximum number of seconds of service to be provided 5271 to the user before the user is to be re-authenticated and/or re- 5272 authorized. Great care should be taken when the Authorization- 5273 Lifetime value is determined, since a low, non-zero, value could 5274 create significant Diameter traffic, which could congest both the 5275 network and the agents. 5277 A value of zero (0) means that immediate re-auth is necessary by the 5278 access device. This is typically used in cases where multiple 5279 authentication methods are used, and a successful auth response with 5280 this AVP set to zero is used to signal that the next authentication 5281 method is to be immediately initiated. The absence of this AVP, or a 5282 value of all ones (meaning all bits in the 32 bit field are set to 5283 one) means no re-auth is expected. 5285 If both this AVP and the Session-Timeout AVP are present in a 5286 message, the value of the latter MUST NOT be smaller than the 5287 Authorization-Lifetime AVP. 5289 An Authorization-Lifetime AVP MAY be present in re-authorization 5290 messages, and contains the number of seconds the user is authorized 5291 to receive service from the time the re-auth answer message is 5292 received by the access device. 5294 This AVP MAY be provided by the client as a hint of the maximum 5295 lifetime that it is willing to accept. However, the server MAY 5296 return a value that is equal to, or smaller, than the one provided by 5297 the client. 5299 8.10. Auth-Grace-Period AVP 5301 The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and 5302 contains the number of seconds the Diameter server will wait 5303 following the expiration of the Authorization-Lifetime AVP before 5304 cleaning up resources for the session. 5306 8.11. Auth-Session-State AVP 5308 The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and 5309 specifies whether state is maintained for a particular session. The 5310 client MAY include this AVP in requests as a hint to the server, but 5311 the value in the server's answer message is binding. The following 5312 values are supported: 5314 STATE_MAINTAINED 0 5316 This value is used to specify that session state is being 5317 maintained, and the access device MUST issue a session termination 5318 message when service to the user is terminated. This is the 5319 default value. 5321 NO_STATE_MAINTAINED 1 5323 This value is used to specify that no session termination messages 5324 will be sent by the access device upon expiration of the 5325 Authorization-Lifetime. 5327 8.12. Re-Auth-Request-Type AVP 5329 The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and 5330 is included in application-specific auth answers to inform the client 5331 of the action expected upon expiration of the Authorization-Lifetime. 5332 If the answer message contains an Authorization-Lifetime AVP with a 5333 positive value, the Re-Auth-Request-Type AVP MUST be present in an 5334 answer message. The following values are defined: 5336 AUTHORIZE_ONLY 0 5338 An authorization only re-auth is expected upon expiration of the 5339 Authorization-Lifetime. This is the default value if the AVP is 5340 not present in answer messages that include the Authorization- 5341 Lifetime. 5343 AUTHORIZE_AUTHENTICATE 1 5345 An authentication and authorization re-auth is expected upon 5346 expiration of the Authorization-Lifetime. 5348 8.13. Session-Timeout AVP 5350 The Session-Timeout AVP (AVP Code 27) [RFC2865] is of type Unsigned32 5351 and contains the maximum number of seconds of service to be provided 5352 to the user before termination of the session. When both the 5353 Session-Timeout and the Authorization-Lifetime AVPs are present in an 5354 answer message, the former MUST be equal to or greater than the value 5355 of the latter. 5357 A session that terminates on an access device due to the expiration 5358 of the Session-Timeout MUST cause an STR to be issued, unless both 5359 the access device and the home server had previously agreed that no 5360 session termination messages would be sent (see Section 8.9). 5362 A Session-Timeout AVP MAY be present in a re-authorization answer 5363 message, and contains the remaining number of seconds from the 5364 beginning of the re-auth. 5366 A value of zero, or the absence of this AVP, means that this session 5367 has an unlimited number of seconds before termination. 5369 This AVP MAY be provided by the client as a hint of the maximum 5370 timeout that it is willing to accept. However, the server MAY return 5371 a value that is equal to, or smaller, than the one provided by the 5372 client. 5374 8.14. User-Name AVP 5376 The User-Name AVP (AVP Code 1) [RFC2865] is of type UTF8String, which 5377 contains the User-Name, in a format consistent with the NAI 5378 specification [RFC4282]. 5380 8.15. Termination-Cause AVP 5382 The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and 5383 is used to indicate the reason why a session was terminated on the 5384 access device. The following values are defined: 5386 DIAMETER_LOGOUT 1 5388 The user initiated a disconnect 5390 DIAMETER_SERVICE_NOT_PROVIDED 2 5392 This value is used when the user disconnected prior to the receipt 5393 of the authorization answer message. 5395 DIAMETER_BAD_ANSWER 3 5397 This value indicates that the authorization answer received by the 5398 access device was not processed successfully. 5400 DIAMETER_ADMINISTRATIVE 4 5402 The user was not granted access, or was disconnected, due to 5403 administrative reasons, such as the receipt of a Abort-Session- 5404 Request message. 5406 DIAMETER_LINK_BROKEN 5 5408 The communication to the user was abruptly disconnected. 5410 DIAMETER_AUTH_EXPIRED 6 5412 The user's access was terminated since its authorized session time 5413 has expired. 5415 DIAMETER_USER_MOVED 7 5417 The user is receiving services from another access device. 5419 DIAMETER_SESSION_TIMEOUT 8 5421 The user's session has timed out, and service has been terminated. 5423 8.16. Origin-State-Id AVP 5425 The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a 5426 monotonically increasing value that is advanced whenever a Diameter 5427 entity restarts with loss of previous state, for example upon reboot. 5428 Origin-State-Id MAY be included in any Diameter message, including 5429 CER. 5431 A Diameter entity issuing this AVP MUST create a higher value for 5432 this AVP each time its state is reset. A Diameter entity MAY set 5433 Origin-State-Id to the time of startup, or it MAY use an incrementing 5434 counter retained in non-volatile memory across restarts. 5436 The Origin-State-Id, if present, MUST reflect the state of the entity 5437 indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST 5438 either remove Origin-State-Id or modify it appropriately as well. 5439 Typically, Origin-State-Id is used by an access device that always 5440 starts up with no active sessions; that is, any session active prior 5441 to restart will have been lost. By including Origin-State-Id in a 5442 message, it allows other Diameter entities to infer that sessions 5443 associated with a lower Origin-State-Id are no longer active. If an 5444 access device does not intend for such inferences to be made, it MUST 5445 either not include Origin-State-Id in any message, or set its value 5446 to 0. 5448 8.17. Session-Binding AVP 5450 The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY 5451 be present in application-specific authorization answer messages. If 5452 present, this AVP MAY inform the Diameter client that all future 5453 application-specific re-auth messages for this session MUST be sent 5454 to the same authorization server. This AVP MAY also specify that a 5455 Session-Termination-Request message for this session MUST be sent to 5456 the same authorizing server. 5458 This field is a bit mask, and the following bits have been defined: 5460 RE_AUTH 1 5462 When set, future re-auth messages for this session MUST NOT 5463 include the Destination-Host AVP. When cleared, the default 5464 value, the Destination-Host AVP MUST be present in all re-auth 5465 messages for this session. 5467 STR 2 5469 When set, the STR message for this session MUST NOT include the 5470 Destination-Host AVP. When cleared, the default value, the 5471 Destination-Host AVP MUST be present in the STR message for this 5472 session. 5474 ACCOUNTING 4 5476 When set, all accounting messages for this session MUST NOT 5477 include the Destination-Host AVP. When cleared, the default 5478 value, the Destination-Host AVP, if known, MUST be present in all 5479 accounting messages for this session. 5481 8.18. Session-Server-Failover AVP 5483 The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated, 5484 and MAY be present in application-specific authorization answer 5485 messages that either do not include the Session-Binding AVP or 5486 include the Session-Binding AVP with any of the bits set to a zero 5487 value. If present, this AVP MAY inform the Diameter client that if a 5488 re-auth or STR message fails due to a delivery problem, the Diameter 5489 client SHOULD issue a subsequent message without the Destination-Host 5490 AVP. When absent, the default value is REFUSE_SERVICE. 5492 The following values are supported: 5494 REFUSE_SERVICE 0 5496 If either the re-auth or the STR message delivery fails, terminate 5497 service with the user, and do not attempt any subsequent attempts. 5499 TRY_AGAIN 1 5501 If either the re-auth or the STR message delivery fails, resend 5502 the failed message without the Destination-Host AVP present. 5504 ALLOW_SERVICE 2 5506 If re-auth message delivery fails, assume that re-authorization 5507 succeeded. If STR message delivery fails, terminate the session. 5509 TRY_AGAIN_ALLOW_SERVICE 3 5511 If either the re-auth or the STR message delivery fails, resend 5512 the failed message without the Destination-Host AVP present. If 5513 the second delivery fails for re-auth, assume re-authorization 5514 succeeded. If the second delivery fails for STR, terminate the 5515 session. 5517 8.19. Multi-Round-Time-Out AVP 5519 The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32, 5520 and SHOULD be present in application-specific authorization answer 5521 messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH. 5522 This AVP contains the maximum number of seconds that the access 5523 device MUST provide the user in responding to an authentication 5524 request. 5526 8.20. Class AVP 5528 The Class AVP (AVP Code 25) is of type OctetString and is used to by 5529 Diameter servers to return state information to the access device. 5530 When one or more Class AVPs are present in application-specific 5531 authorization answer messages, they MUST be present in subsequent re- 5532 authorization, session termination and accounting messages. Class 5533 AVPs found in a re-authorization answer message override the ones 5534 found in any previous authorization answer message. Diameter server 5535 implementations SHOULD NOT return Class AVPs that require more than 5536 4096 bytes of storage on the Diameter client. A Diameter client that 5537 receives Class AVPs whose size exceeds local available storage MUST 5538 terminate the session. 5540 8.21. Event-Timestamp AVP 5542 The Event-Timestamp (AVP Code 55) is of type Time, and MAY be 5543 included in an Accounting-Request and Accounting-Answer messages to 5544 record the time that the reported event occurred, in seconds since 5545 January 1, 1900 00:00 UTC. 5547 9. Accounting 5549 This accounting protocol is based on a server directed model with 5550 capabilities for real-time delivery of accounting information. 5551 Several fault resilience methods [RFC2975] have been built in to the 5552 protocol in order minimize loss of accounting data in various fault 5553 situations and under different assumptions about the capabilities of 5554 the used devices. 5556 9.1. Server Directed Model 5558 The server directed model means that the device generating the 5559 accounting data gets information from either the authorization server 5560 (if contacted) or the accounting server regarding the way accounting 5561 data shall be forwarded. This information includes accounting record 5562 timeliness requirements. 5564 As discussed in [RFC2975], real-time transfer of accounting records 5565 is a requirement, such as the need to perform credit limit checks and 5566 fraud detection. Note that batch accounting is not a requirement, 5567 and is therefore not supported by Diameter. Should batched 5568 accounting be required in the future, a new Diameter application will 5569 need to be created, or it could be handled using another protocol. 5570 Note, however, that even if at the Diameter layer accounting requests 5571 are processed one by one, transport protocols used under Diameter 5572 typically batch several requests in the same packet under heavy 5573 traffic conditions. This may be sufficient for many applications. 5575 The authorization server (chain) directs the selection of proper 5576 transfer strategy, based on its knowledge of the user and 5577 relationships of roaming partnerships. The server (or agents) uses 5578 the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to 5579 control the operation of the Diameter peer operating as a client. 5580 The Acct-Interim-Interval AVP, when present, instructs the Diameter 5581 node acting as a client to produce accounting records continuously 5582 even during a session. Accounting-Realtime-Required AVP is used to 5583 control the behavior of the client when the transfer of accounting 5584 records from the Diameter client is delayed or unsuccessful. 5586 The Diameter accounting server MAY override the interim interval or 5587 the realtime requirements by including the Acct-Interim-Interval or 5588 Accounting-Realtime-Required AVP in the Accounting-Answer message. 5589 When one of these AVPs is present, the latest value received SHOULD 5590 be used in further accounting activities for the same session. 5592 9.2. Protocol Messages 5594 A Diameter node that receives a successful authentication and/or 5595 authorization messages from the Home AAA server MUST collect 5596 accounting information for the session. The Accounting-Request 5597 message is used to transmit the accounting information to the Home 5598 AAA server, which MUST reply with the Accounting-Answer message to 5599 confirm reception. The Accounting-Answer message includes the 5600 Result-Code AVP, which MAY indicate that an error was present in the 5601 accounting message. A rejected Accounting-Request message MAY cause 5602 the user's session to be terminated, depending on the value of the 5603 Accounting-Realtime-Required AVP received earlier for the session in 5604 question. 5606 Each Diameter Accounting protocol message MAY be compressed, in order 5607 to reduce network bandwidth usage. If TLS is used to secure the 5608 Diameter session, then TLS compression [RFC4346] MAY be used. 5610 9.3. Accounting Application Extension and Requirements 5612 Each Diameter application (e.g., NASREQ, MobileIP), MUST define their 5613 Service-Specific AVPs that MUST be present in the Accounting-Request 5614 message in a section entitled "Accounting AVPs". The application 5615 MUST assume that the AVPs described in this document will be present 5616 in all Accounting messages, so only their respective service-specific 5617 AVPs need to be defined in this section. 5619 Applications have the option of using one or both of the following 5620 accounting application extension models: 5622 Split Accounting Service 5624 The accounting message will carry the application identifier of 5625 the Diameter base accounting application (see Section 2.4). 5626 Accounting messages maybe routed to Diameter nodes other than the 5627 corresponding Diameter application. These nodes might be 5628 centralized accounting servers that provide accounting service for 5629 multiple different Diameter applications. These nodes MUST 5630 advertise the Diameter base accounting application identifier 5631 during capabilities exchange. 5633 Accounting messages which uses the Diameter base accounting 5634 application identifier in its header MUST include the application 5635 identifier of the Diameter application it is providing service for 5636 in the Acct-Application-Id AVP. This allows the accounting server 5637 to determine which Diameter application the accounting records are 5638 for. 5640 Coupled Accounting Service 5642 The accounting messages will carry the application identifier of 5643 the application that is using it. The application itself will 5644 process the received accounting records or forward them to an 5645 accounting server. There is no accounting application 5646 advertisement required during capabilities exchange and the 5647 accounting messages will be routed the same as any of the other 5648 application messages. 5650 In cases where an application does not define its own accounting 5651 service, it is preferred that the split accounting model be used. 5653 9.4. Fault Resilience 5655 Diameter Base protocol mechanisms are used to overcome small message 5656 loss and network faults of temporary nature. 5658 Diameter peers acting as clients MUST implement the use of failover 5659 to guard against server failures and certain network failures. 5660 Diameter peers acting as agents or related off-line processing 5661 systems MUST detect duplicate accounting records caused by the 5662 sending of same record to several servers and duplication of messages 5663 in transit. This detection MUST be based on the inspection of the 5664 Session-Id and Accounting-Record-Number AVP pairs. Appendix C 5665 discusses duplicate detection needs and implementation issues. 5667 Diameter clients MAY have non-volatile memory for the safe storage of 5668 accounting records over reboots or extended network failures, network 5669 partitions, and server failures. If such memory is available, the 5670 client SHOULD store new accounting records there as soon as the 5671 records are created and until a positive acknowledgement of their 5672 reception from the Diameter Server has been received. Upon a reboot, 5673 the client MUST starting sending the records in the non-volatile 5674 memory to the accounting server with appropriate modifications in 5675 termination cause, session length, and other relevant information in 5676 the records. 5678 A further application of this protocol may include AVPs to control 5679 how many accounting records may at most be stored in the Diameter 5680 client without committing them to the non-volatile memory or 5681 transferring them to the Diameter server. 5683 The client SHOULD NOT remove the accounting data from any of its 5684 memory areas before the correct Accounting-Answer has been received. 5685 The client MAY remove oldest, undelivered or yet unacknowledged 5686 accounting data if it runs out of resources such as memory. It is an 5687 implementation dependent matter for the client to accept new sessions 5688 under this condition. 5690 9.5. Accounting Records 5692 In all accounting records, the Session-Id AVP MUST be present; the 5693 User-Name AVP MUST be present if it is available to the Diameter 5694 client. 5696 Different types of accounting records are sent depending on the 5697 actual type of accounted service and the authorization server's 5698 directions for interim accounting. If the accounted service is a 5699 one-time event, meaning that the start and stop of the event are 5700 simultaneous, then the Accounting-Record-Type AVP MUST be present and 5701 set to the value EVENT_RECORD. 5703 If the accounted service is of a measurable length, then the AVP MUST 5704 use the values START_RECORD, STOP_RECORD, and possibly, 5705 INTERIM_RECORD. If the authorization server has not directed interim 5706 accounting to be enabled for the session, two accounting records MUST 5707 be generated for each service of type session. When the initial 5708 Accounting-Request for a given session is sent, the Accounting- 5709 Record-Type AVP MUST be set to the value START_RECORD. When the last 5710 Accounting-Request is sent, the value MUST be STOP_RECORD. 5712 If the authorization server has directed interim accounting to be 5713 enabled, the Diameter client MUST produce additional records between 5714 the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The 5715 production of these records is directed by Acct-Interim-Interval as 5716 well as any re-authentication or re-authorization of the session. 5717 The Diameter client MUST overwrite any previous interim accounting 5718 records that are locally stored for delivery, if a new record is 5719 being generated for the same session. This ensures that only one 5720 pending interim record can exist on an access device for any given 5721 session. 5723 A particular value of Accounting-Sub-Session-Id MUST appear only in 5724 one sequence of accounting records from a DIAMETER client, except for 5725 the purposes of retransmission. The one sequence that is sent MUST 5726 be either one record with Accounting-Record-Type AVP set to the value 5727 EVENT_RECORD, or several records starting with one having the value 5728 START_RECORD, followed by zero or more INTERIM_RECORD and a single 5729 STOP_RECORD. A particular Diameter application specification MUST 5730 define the type of sequences that MUST be used. 5732 9.6. Correlation of Accounting Records 5734 The Diameter protocol's Session-Id AVP, which is globally unique (see 5735 Section 8.8), is used during the authorization phase to identify a 5736 particular session. Services that do not require any authorization 5737 still use the Session-Id AVP to identify sessions. Accounting 5738 messages MAY use a different Session-Id from that sent in 5739 authorization messages. Specific applications MAY require different 5740 a Session-ID for accounting messages. 5742 However, there are certain applications that require multiple 5743 accounting sub-sessions. Such applications would send messages with 5744 a constant Session-Id AVP, but a different Accounting-Sub-Session-Id 5745 AVP. In these cases, correlation is performed using the Session-Id. 5746 It is important to note that receiving a STOP_RECORD with no 5747 Accounting-Sub-Session-Id AVP when sub-sessions were originally used 5748 in the START_RECORD messages implies that all sub-sessions are 5749 terminated. 5751 Furthermore, there are certain applications where a user receives 5752 service from different access devices (e.g., Mobile IPv4), each with 5753 their own unique Session-Id. In such cases, the Acct-Multi-Session- 5754 Id AVP is used for correlation. During authorization, a server that 5755 determines that a request is for an existing session SHOULD include 5756 the Acct-Multi-Session-Id AVP, which the access device MUST include 5757 in all subsequent accounting messages. 5759 The Acct-Multi-Session-Id AVP MAY include the value of the original 5760 Session-Id. It's contents are implementation specific, but MUST be 5761 globally unique across other Acct-Multi-Session-Id, and MUST NOT 5762 change during the life of a session. 5764 A Diameter application document MUST define the exact concept of a 5765 session that is being accounted, and MAY define the concept of a 5766 multi-session. For instance, the NASREQ DIAMETER application treats 5767 a single PPP connection to a Network Access Server as one session, 5768 and a set of Multilink PPP sessions as one multi-session. 5770 9.7. Accounting Command-Codes 5772 This section defines Command-Code values that MUST be supported by 5773 all Diameter implementations that provide Accounting services. 5775 9.7.1. Accounting-Request 5777 The Accounting-Request (ACR) command, indicated by the Command-Code 5778 field set to 271 and the Command Flags' 'R' bit set, is sent by a 5779 Diameter node, acting as a client, in order to exchange accounting 5780 information with a peer. 5782 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs 5783 MUST be present. If the Vendor-Specific-Application-Id grouped AVP 5784 is present, it must have an Acct-Application-Id inside. 5786 The AVP listed below SHOULD include service specific accounting AVPs, 5787 as described in Section 9.3. 5789 Message Format 5791 ::= < Diameter Header: 271, REQ, PXY > 5792 < Session-Id > 5793 { Origin-Host } 5794 { Origin-Realm } 5795 { Destination-Realm } 5796 { Accounting-Record-Type } 5797 { Accounting-Record-Number } 5798 [ Acct-Application-Id ] 5799 [ Vendor-Specific-Application-Id ] 5800 [ User-Name ] 5801 [ Destination-Host ] 5802 [ Accounting-Sub-Session-Id ] 5803 [ Acct-Session-Id ] 5804 [ Acct-Multi-Session-Id ] 5805 [ Acct-Interim-Interval ] 5806 [ Accounting-Realtime-Required ] 5807 [ Origin-State-Id ] 5808 [ Event-Timestamp ] 5809 * [ Proxy-Info ] 5810 * [ Route-Record ] 5811 * [ AVP ] 5813 9.7.2. Accounting-Answer 5815 The Accounting-Answer (ACA) command, indicated by the Command-Code 5816 field set to 271 and the Command Flags' 'R' bit cleared, is used to 5817 acknowledge an Accounting-Request command. The Accounting-Answer 5818 command contains the same Session-Id as the corresponding request. 5820 Only the target Diameter Server, known as the home Diameter Server, 5821 SHOULD respond with the Accounting-Answer command. 5823 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs 5824 MUST be present. If the Vendor-Specific-Application-Id grouped AVP 5825 is present, it must have an Acct-Application-Id inside. 5827 The AVP listed below SHOULD include service specific accounting AVPs, 5828 as described in Section 9.3. 5830 Message Format 5832 ::= < Diameter Header: 271, PXY > 5833 < Session-Id > 5834 { Result-Code } 5835 { Origin-Host } 5836 { Origin-Realm } 5837 { Accounting-Record-Type } 5838 { Accounting-Record-Number } 5839 [ Acct-Application-Id ] 5840 [ Vendor-Specific-Application-Id ] 5841 [ User-Name ] 5842 [ Accounting-Sub-Session-Id ] 5843 [ Acct-Session-Id ] 5844 [ Acct-Multi-Session-Id ] 5845 [ Error-Reporting-Host ] 5846 [ Acct-Interim-Interval ] 5847 [ Accounting-Realtime-Required ] 5848 [ Origin-State-Id ] 5849 [ Event-Timestamp ] 5850 * [ Proxy-Info ] 5851 * [ AVP ] 5853 9.8. Accounting AVPs 5855 This section contains AVPs that describe accounting usage information 5856 related to a specific session. 5858 9.8.1. Accounting-Record-Type AVP 5860 The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated 5861 and contains the type of accounting record being sent. The following 5862 values are currently defined for the Accounting-Record-Type AVP: 5864 EVENT_RECORD 1 5866 An Accounting Event Record is used to indicate that a one-time 5867 event has occurred (meaning that the start and end of the event 5868 are simultaneous). This record contains all information relevant 5869 to the service, and is the only record of the service. 5871 START_RECORD 2 5873 An Accounting Start, Interim, and Stop Records are used to 5874 indicate that a service of a measurable length has been given. An 5875 Accounting Start Record is used to initiate an accounting session, 5876 and contains accounting information that is relevant to the 5877 initiation of the session. 5879 INTERIM_RECORD 3 5881 An Interim Accounting Record contains cumulative accounting 5882 information for an existing accounting session. Interim 5883 Accounting Records SHOULD be sent every time a re-authentication 5884 or re-authorization occurs. Further, additional interim record 5885 triggers MAY be defined by application-specific Diameter 5886 applications. The selection of whether to use INTERIM_RECORD 5887 records is done by the Acct-Interim-Interval AVP. 5889 STOP_RECORD 4 5891 An Accounting Stop Record is sent to terminate an accounting 5892 session and contains cumulative accounting information relevant to 5893 the existing session. 5895 9.8.2. Acct-Interim-Interval 5897 The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and 5898 is sent from the Diameter home authorization server to the Diameter 5899 client. The client uses information in this AVP to decide how and 5900 when to produce accounting records. With different values in this 5901 AVP, service sessions can result in one, two, or two+N accounting 5902 records, based on the needs of the home-organization. The following 5903 accounting record production behavior is directed by the inclusion of 5904 this AVP: 5906 1. The omission of the Acct-Interim-Interval AVP or its inclusion 5907 with Value field set to 0 means that EVENT_RECORD, START_RECORD, 5908 and STOP_RECORD are produced, as appropriate for the service. 5910 2. The inclusion of the AVP with Value field set to a non-zero value 5911 means that INTERIM_RECORD records MUST be produced between the 5912 START_RECORD and STOP_RECORD records. The Value field of this 5913 AVP is the nominal interval between these records in seconds. 5914 The Diameter node that originates the accounting information, 5915 known as the client, MUST produce the first INTERIM_RECORD record 5916 roughly at the time when this nominal interval has elapsed from 5917 the START_RECORD, the next one again as the interval has elapsed 5918 once more, and so on until the session ends and a STOP_RECORD 5919 record is produced. 5921 The client MUST ensure that the interim record production times 5922 are randomized so that large accounting message storms are not 5923 created either among records or around a common service start 5924 time. 5926 9.8.3. Accounting-Record-Number AVP 5928 The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32 5929 and identifies this record within one session. As Session-Id AVPs 5930 are globally unique, the combination of Session-Id and Accounting- 5931 Record-Number AVPs is also globally unique, and can be used in 5932 matching accounting records with confirmations. An easy way to 5933 produce unique numbers is to set the value to 0 for records of type 5934 EVENT_RECORD and START_RECORD, and set the value to 1 for the first 5935 INTERIM_RECORD, 2 for the second, and so on until the value for 5936 STOP_RECORD is one more than for the last INTERIM_RECORD. 5938 9.8.4. Acct-Session-Id AVP 5940 The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only 5941 used when RADIUS/Diameter translation occurs. This AVP contains the 5942 contents of the RADIUS Acct-Session-Id attribute. 5944 9.8.5. Acct-Multi-Session-Id AVP 5946 The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String, 5947 following the format specified in Section 8.8. The Acct-Multi- 5948 Session-Id AVP is used to link together multiple related accounting 5949 sessions, where each session would have a unique Session-Id, but the 5950 same Acct-Multi-Session-Id AVP. This AVP MAY be returned by the 5951 Diameter server in an authorization answer, and MUST be used in all 5952 accounting messages for the given session. 5954 9.8.6. Accounting-Sub-Session-Id AVP 5956 The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type 5957 Unsigned64 and contains the accounting sub-session identifier. The 5958 combination of the Session-Id and this AVP MUST be unique per sub- 5959 session, and the value of this AVP MUST be monotonically increased by 5960 one for all new sub-sessions. The absence of this AVP implies no 5961 sub-sessions are in use, with the exception of an Accounting-Request 5962 whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD 5963 message with no Accounting-Sub-Session-Id AVP present will signal the 5964 termination of all sub-sessions for a given Session-Id. 5966 9.8.7. Accounting-Realtime-Required AVP 5968 The Accounting-Realtime-Required AVP (AVP Code 483) is of type 5969 Enumerated and is sent from the Diameter home authorization server to 5970 the Diameter client or in the Accounting-Answer from the accounting 5971 server. The client uses information in this AVP to decide what to do 5972 if the sending of accounting records to the accounting server has 5973 been temporarily prevented due to, for instance, a network problem. 5975 DELIVER_AND_GRANT 1 5977 The AVP with Value field set to DELIVER_AND_GRANT means that the 5978 service MUST only be granted as long as there is a connection to 5979 an accounting server. Note that the set of alternative accounting 5980 servers are treated as one server in this sense. Having to move 5981 the accounting record stream to a backup server is not a reason to 5982 discontinue the service to the user. 5984 GRANT_AND_STORE 2 5986 The AVP with Value field set to GRANT_AND_STORE means that service 5987 SHOULD be granted if there is a connection, or as long as records 5988 can still be stored as described in Section 9.4. 5990 This is the default behavior if the AVP isn't included in the 5991 reply from the authorization server. 5993 GRANT_AND_LOSE 3 5995 The AVP with Value field set to GRANT_AND_LOSE means that service 5996 SHOULD be granted even if the records can not be delivered or 5997 stored. 5999 10. AVP Occurrence Table 6001 The following tables presents the AVPs defined in this document, and 6002 specifies in which Diameter messages they MAY be present or not. 6003 AVPs that occur only inside a Grouped AVP are not shown in this 6004 table. 6006 The table uses the following symbols: 6008 0 The AVP MUST NOT be present in the message. 6010 0+ Zero or more instances of the AVP MAY be present in the 6011 message. 6013 0-1 Zero or one instance of the AVP MAY be present in the message. 6014 It is considered an error if there are more than one instance of 6015 the AVP. 6017 1 One instance of the AVP MUST be present in the message. 6019 1+ At least one instance of the AVP MUST be present in the 6020 message. 6022 10.1. Base Protocol Command AVP Table 6024 The table in this section is limited to the non-accounting Command 6025 Codes defined in this specification. 6027 +-----------------------------------------------+ 6028 | Command-Code | 6029 +---+---+---+---+---+---+---+---+---+---+---+---+ 6030 Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA| 6031 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ 6032 Acct-Interim- |0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | 6033 Interval | | | | | | | | | | | | | 6034 Accounting-Realtime-|0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | 6035 Required | | | | | | | | | | | | | 6036 Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6037 Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | 6038 Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6039 Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6040 Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6041 Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6042 Lifetime | | | | | | | | | | | | | 6043 Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ | 6044 Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 | 6045 Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | 6046 Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6047 Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1| 6048 Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6049 Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ | 6050 Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6051 Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6052 Inband-Security-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6053 Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6054 Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | 6055 Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | 6056 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| 6057 Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6058 Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ | 6059 Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ | 6060 Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6061 Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6062 Time | | | | | | | | | | | | | 6063 Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 | 6064 Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 | 6065 Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 | 6066 Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6067 Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 | 6068 Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6069 Failover | | | | | | | | | | | | | 6070 Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6071 Supported-Vendor-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6072 Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 | 6073 User-Name |0 |0 |0 |0 |0 |0 |0-1|0-1|0-1|0-1|0-1|0-1| 6074 Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6075 Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6076 Application-Id | | | | | | | | | | | | | 6077 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ 6079 10.2. Accounting AVP Table 6081 The table in this section is used to represent which AVPs defined in 6082 this document are to be present in the Accounting messages. These 6083 AVP occurrence requirements are guidelines, which may be expanded, 6084 and/or overridden by application-specific requirements in the 6085 Diameter applications documents. 6087 +-----------+ 6088 | Command | 6089 | Code | 6090 +-----+-----+ 6091 Attribute Name | ACR | ACA | 6092 ------------------------------+-----+-----+ 6093 Acct-Interim-Interval | 0-1 | 0-1 | 6094 Acct-Multi-Session-Id | 0-1 | 0-1 | 6095 Accounting-Record-Number | 1 | 1 | 6096 Accounting-Record-Type | 1 | 1 | 6097 Acct-Session-Id | 0-1 | 0-1 | 6098 Accounting-Sub-Session-Id | 0-1 | 0-1 | 6099 Accounting-Realtime-Required | 0-1 | 0-1 | 6100 Acct-Application-Id | 0-1 | 0-1 | 6101 Auth-Application-Id | 0 | 0 | 6102 Class | 0+ | 0+ | 6103 Destination-Host | 0-1 | 0 | 6104 Destination-Realm | 1 | 0 | 6105 Error-Reporting-Host | 0 | 0+ | 6106 Event-Timestamp | 0-1 | 0-1 | 6107 Origin-Host | 1 | 1 | 6108 Origin-Realm | 1 | 1 | 6109 Proxy-Info | 0+ | 0+ | 6110 Route-Record | 0+ | 0+ | 6111 Result-Code | 0 | 1 | 6112 Session-Id | 1 | 1 | 6113 Termination-Cause | 0 | 0 | 6114 User-Name | 0-1 | 0-1 | 6115 Vendor-Specific-Application-Id| 0-1 | 0-1 | 6116 ------------------------------+-----+-----+ 6118 11. IANA Considerations 6120 This section provides guidance to the Internet Assigned Numbers 6121 Authority (IANA) regarding registration of values related to the 6122 Diameter protocol, in accordance with BCP 26 [RFC2434]. The 6123 following policies are used here with the meanings defined in BCP 26: 6124 "Private Use", "First Come First Served", "Expert Review", 6125 "Specification Required", "IETF Consensus", "Standards Action". 6127 This section explains the criteria to be used by the IANA for 6128 assignment of numbers within namespaces defined within this document. 6130 Diameter is not intended as a general purpose protocol, and 6131 allocations SHOULD NOT be made for purposes unrelated to 6132 authentication, authorization or accounting. 6134 For registration requests where a Designated Expert should be 6135 consulted, the responsible IESG area director should appoint the 6136 Designated Expert. For Designated Expert with Specification 6137 Required, the request is posted to the DIME WG mailing list (or, if 6138 it has been disbanded, a successor designated by the Area Director) 6139 for comment and review, and MUST include a pointer to a public 6140 specification. Before a period of 30 days has passed, the Designated 6141 Expert will either approve or deny the registration request and 6142 publish a notice of the decision to the DIME WG mailing list or its 6143 successor. A denial notice must be justified by an explanation and, 6144 in the cases where it is possible, concrete suggestions on how the 6145 request can be modified so as to become acceptable. 6147 11.1. AVP Header 6149 As defined in Section 4, the AVP header contains three fields that 6150 requires IANA namespace management; the AVP Code, Vendor-ID and Flags 6151 field. 6153 11.1.1. AVP Codes 6155 The AVP Code namespace is used to identify attributes. There are 6156 multiple namespaces. Vendors can have their own AVP Codes namespace 6157 which will be identified by their Vendor-ID (also known as 6158 Enterprise-Number) and they control the assignments of their vendor- 6159 specific AVP codes within their own namespace. The absence of a 6160 Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA 6161 controlled AVP Codes namespace. The AVP Codes and sometimes also 6162 possible values in an AVP are controlled and maintained by IANA. 6164 AVP Code 0 is not used. AVP Codes 1-255 are managed separately as 6165 RADIUS Attribute Types [RADTYPE]. This document defines the AVP 6166 Codes 257-274, 276-285, 287, 291-300, 480, 483 and 485-486. See 6167 Section 4.5 for the assignment of the namespace in this 6168 specification. 6170 AVPs may be allocated following Designated Expert with Specification 6171 Required [RFC2434]. Release of blocks of AVPs (more than 3 at a time 6172 for a given purpose) should require IETF Consensus. 6174 Note that Diameter defines a mechanism for Vendor-Specific AVPs, 6175 where the Vendor-Id field in the AVP header is set to a non-zero 6176 value. Vendor-Specific AVPs codes are for Private Use and should be 6177 encouraged instead of allocation of global attribute types, for 6178 functions specific only to one vendor's implementation of Diameter, 6179 where no interoperability is deemed useful. Where a Vendor-Specific 6180 AVP is implemented by more than one vendor, allocation of global AVPs 6181 should be encouraged instead. 6183 11.1.2. AVP Flags 6185 There are 8 bits in the AVP Flags field of the AVP header, defined in 6186 Section 4. This document assigns bit 0 ('V'endor Specific), bit 1 6187 ('M'andatory) and bit 2 ('P'rotected). The remaining bits should 6188 only be assigned via a Standards Action [RFC2434]. 6190 11.2. Diameter Header 6192 As defined in Section 3, the Diameter header contains two fields that 6193 require IANA namespace management; Command Code and Command Flags. 6195 11.2.1. Command Codes 6197 The Command Code namespace is used to identify Diameter commands. 6198 The values 0-255 (0x00-0xff) are reserved for RADIUS backward 6199 compatibility, and are defined as "RADIUS Packet Type Codes" in 6200 [RADTYPE]. Values 256 - 8,388,607 (0x100 to 0x7fffff) are for 6201 permanent, standard commands, allocated by IETF Consensus [RFC2434]. 6202 This document defines the Command Codes 257, 258, 271, 274-275, 280 6203 and 282. See Section 3.1 for the assignment of the namespace in this 6204 specification. 6206 The values 8,388,608 - 16,777,213 (0x800000 - 0xfffffd) are reserved 6207 for vendor-specific command codes, to be allocated on a First Come, 6208 First Served basis by IANA [RFC2434]. The request to IANA for a 6209 Vendor-Specific Command Code SHOULD include a reference to a publicly 6210 available specification which documents the command in sufficient 6211 detail to aid in interoperability between independent 6212 implementations. If the specification cannot be made publicly 6213 available, the request for a vendor-specific command code MUST 6214 include the contact information of persons and/or entities 6215 responsible for authoring and maintaining the command. 6217 The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe - 6218 0xffffff) are reserved for experimental commands. As these codes are 6219 only for experimental and testing purposes, no guarantee is made for 6220 interoperability between Diameter peers using experimental commands, 6221 as outlined in [IANA-EXP]. 6223 11.2.2. Command Flags 6225 There are eight bits in the Command Flags field of the Diameter 6226 header. This document assigns bit 0 ('R'equest), bit 1 ('P'roxy), 6227 bit 2 ('E'rror) and bit 3 ('T'). Bits 4 through 7 MUST only be 6228 assigned via a Standards Action [RFC2434]. 6230 11.3. Application Identifiers 6232 As defined in Section 2.4, the Application Identifier is used to 6233 identify a specific Diameter Application. There are standards-track 6234 application ids and vendor specific application ids. 6236 IANA [RFC2434] has assigned the range 0x00000001 to 0x00ffffff for 6237 standards-track applications; and 0x01000000 - 0xfffffffe for vendor 6238 specific applications, on a first-come, first-served basis. The 6239 following values are allocated. 6241 Diameter Common Messages 0 6242 NASREQ 1 [RFC4005] 6243 Mobile-IP 2 [RFC4004] 6244 Diameter Base Accounting 3 6245 Relay 0xffffffff 6247 Assignment of standards-track application IDs are by Designated 6248 Expert with Specification Required [RFC2434]. 6250 Both Auth-Application-Id and Acct-Application-Id AVPs use the same 6251 Application Identifier space. A diameter node advertising itself as 6252 a relay agent MUST set either Application-Id or Acct-Application-Id 6253 to 0xffffffff. 6255 Vendor-Specific Application Identifiers, are for Private Use. Vendor- 6256 Specific Application Identifiers are assigned on a First Come, First 6257 Served basis by IANA. 6259 11.4. AVP Values 6261 Certain AVPs in Diameter define a list of values with various 6262 meanings. For attributes other than those specified in this section, 6263 adding additional values to the list can be done on a First Come, 6264 First Served basis by IANA. 6266 11.4.1. Result-Code AVP Values 6268 As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines 6269 the values 1001, 2001-2002, 3001-3012, 4001-4003 and 5001-5021. 6271 All remaining values are available for assignment via IETF Consensus 6272 [RFC2434]. 6274 11.4.2. Accounting-Record-Type AVP Values 6276 As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code 6277 480) defines the values 1-4. All remaining values are available for 6278 assignment via IETF Consensus [RFC2434]. 6280 11.4.3. Termination-Cause AVP Values 6282 As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295) 6283 defines the values 1-8. All remaining values are available for 6284 assignment via IETF Consensus [RFC2434]. 6286 11.4.4. Redirect-Host-Usage AVP Values 6288 As defined in Section 6.13, the Redirect-Host-Usage AVP (AVP Code 6289 261) defines the values 0-5. All remaining values are available for 6290 assignment via IETF Consensus [RFC2434]. 6292 11.4.5. Session-Server-Failover AVP Values 6294 As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code 6295 271) defines the values 0-3. All remaining values are available for 6296 assignment via IETF Consensus [RFC2434]. 6298 11.4.6. Session-Binding AVP Values 6300 As defined in Section 8.17, the Session-Binding AVP (AVP Code 270) 6301 defines the bits 1-4. All remaining bits are available for 6302 assignment via IETF Consensus [RFC2434]. 6304 11.4.7. Disconnect-Cause AVP Values 6306 As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273) 6307 defines the values 0-2. All remaining values are available for 6308 assignment via IETF Consensus [RFC2434]. 6310 11.4.8. Auth-Request-Type AVP Values 6312 As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274) 6313 defines the values 1-3. All remaining values are available for 6314 assignment via IETF Consensus [RFC2434]. 6316 11.4.9. Auth-Session-State AVP Values 6318 As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277) 6319 defines the values 0-1. All remaining values are available for 6320 assignment via IETF Consensus [RFC2434]. 6322 11.4.10. Re-Auth-Request-Type AVP Values 6324 As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code 6325 285) defines the values 0-1. All remaining values are available for 6326 assignment via IETF Consensus [RFC2434]. 6328 11.4.11. Accounting-Realtime-Required AVP Values 6330 As defined in Section 9.8.7, the Accounting-Realtime-Required AVP 6331 (AVP Code 483) defines the values 1-3. All remaining values are 6332 available for assignment via IETF Consensus [RFC2434]. 6334 11.4.12. Inband-Security-Id AVP (code 299) 6336 As defined in Section 6.10, the Inband-Security-Id AVP (AVP Code 299) 6337 defines the values 0-1. All remaining values are available for 6338 assignment via IETF Consensus [RFC2434]. 6340 11.5. Diameter TCP/SCTP Port Numbers 6342 The IANA has assigned TCP and SCTP port number 3868 to Diameter. 6344 11.6. NAPTR Service Fields 6346 The registration in the RFC MUST include the following information: 6348 Service Field: The service field being registered. An example for a 6349 new fictitious transport protocol called NCTP might be "AAA+D2N". 6351 Protocol: The specific transport protocol associated with that 6352 service field. This MUST include the name and acronym for the 6353 protocol, along with reference to a document that describes the 6354 transport protocol. For example - "New Connectionless Transport 6355 Protocol (NCTP), RFC 5766". 6357 Name and Contact Information: The name, address, email address and 6358 telephone number for the person performing the registration. 6360 The following values have been placed into the registry: 6362 Services Field Protocol 6364 AAA+D2T TCP 6365 AAA+D2S SCTP 6367 12. Diameter protocol related configurable parameters 6369 This section contains the configurable parameters that are found 6370 throughout this document: 6372 Diameter Peer 6374 A Diameter entity MAY communicate with peers that are statically 6375 configured. A statically configured Diameter peer would require 6376 that either the IP address or the fully qualified domain name 6377 (FQDN) be supplied, which would then be used to resolve through 6378 DNS. 6380 Routing Table 6382 A Diameter proxy server routes messages based on the realm portion 6383 of a Network Access Identifier (NAI). The server MUST have a 6384 table of Realm Names, and the address of the peer to which the 6385 message must be forwarded to. The routing table MAY also include 6386 a "default route", which is typically used for all messages that 6387 cannot be locally processed. 6389 Tc timer 6391 The Tc timer controls the frequency that transport connection 6392 attempts are done to a peer with whom no active transport 6393 connection exists. The recommended value is 30 seconds. 6395 13. Security Considerations 6397 The Diameter base protocol assumes that messages maybe secured by 6398 using TLS. As an alternative, IPSec can be also be used to secure 6399 Diameter peer connections but its usage is transparent from the 6400 Diameter node and Diameter protocol perspective. These security 6401 mechanism is acceptable in environments where there is no untrusted 6402 third party agent. 6404 Diameter clients, such as Network Access Servers (NASes) and Mobility 6405 Agents MAY support TLS [RFC4346]. Diameter servers MUST support TLS. 6406 Diameter implementations SHOULD use transmission-level security of 6407 some kind (IPsec or TLS) on each connection. 6409 If a Diameter connection is to be protected via TLS, then the CER/CEA 6410 exchange MUST include an Inband-Security-ID AVP with a value of TLS. 6411 For TLS usage, a TLS handshake will begin when both ends are in the 6412 open state, after completion of the CER/CEA exchange. If the TLS 6413 handshake is successful, all further messages will be sent via TLS. 6414 If the handshake fails, both ends move to the closed state. See 6415 Sections 13.1 for more details. 6417 13.1. TLS Usage 6419 A Diameter node that initiates a connection to another Diameter node 6420 acts as a TLS client according to [RFC4346], and a Diameter node that 6421 accepts a connection acts as a TLS server. Diameter nodes 6422 implementing TLS for security MUST mutually authenticate as part of 6423 TLS session establishment. In order to ensure mutual authentication, 6424 the Diameter node acting as TLS server must request a certificate 6425 from the Diameter node acting as TLS client, and the Diameter node 6426 acting as TLS client MUST be prepared to supply a certificate on 6427 request. 6429 Diameter nodes MUST be able to negotiate the following TLS cipher 6430 suites: 6432 TLS_RSA_WITH_RC4_128_MD5 6433 TLS_RSA_WITH_RC4_128_SHA 6434 TLS_RSA_WITH_3DES_EDE_CBC_SHA 6436 Diameter nodes SHOULD be able to negotiate the following TLS cipher 6437 suite: 6439 TLS_RSA_WITH_AES_128_CBC_SHA 6441 Diameter nodes MAY negotiate other TLS cipher suites. 6443 13.2. Peer-to-Peer Considerations 6445 As with any peer-to-peer protocol, proper configuration of the trust 6446 model within a Diameter peer is essential to security. When 6447 certificates are used, it is necessary to configure the root 6448 certificate authorities trusted by the Diameter peer. These root CAs 6449 are likely to be unique to Diameter usage and distinct from the root 6450 CAs that might be trusted for other purposes such as Web browsing. 6451 In general, it is expected that those root CAs will be configured so 6452 as to reflect the business relationships between the organization 6453 hosting the Diameter peer and other organizations. As a result, a 6454 Diameter peer will typically not be configured to allow connectivity 6455 with any arbitrary peer. With certificate authentication, Diameter 6456 peers may not be known beforehand and therefore peer discovery may be 6457 required. 6459 14. References 6461 14.1. Normative References 6463 [FLOATPOINT] 6464 Institute of Electrical and Electronics Engineers, "IEEE 6465 Standard for Binary Floating-Point Arithmetic, ANSI/IEEE 6466 Standard 754-1985", August 1985. 6468 [IANAADFAM] 6469 IANA,, "Address Family Numbers", 6470 http://www.iana.org/assignments/address-family-numbers. 6472 [RADTYPE] IANA,, "RADIUS Types", 6473 http://www.iana.org/assignments/radius-types. 6475 [IPV4] Postel, J., "Internet Protocol", RFC 791, September 1981. 6477 [TCP] Postel, J., "Transmission Control Protocol", RFC 793, 6478 January 1981. 6480 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and 6481 Accounting (AAA) Transport Profile", RFC 3539, June 2003. 6483 [RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and 6484 P. McCann, "Diameter Mobile IPv4 Application", RFC 4004, 6485 August 2005. 6487 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton, 6488 "Diameter Network Access Server Application", RFC 4005, 6489 August 2005. 6491 [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J. 6492 Loughney, "Diameter Credit-Control Application", RFC 4006, 6493 August 2005. 6495 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible 6496 Authentication Protocol (EAP) Application", RFC 4072, 6497 August 2005. 6499 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M., 6500 Canales-Valenzuela, C., and K. Tammi, "Diameter Session 6501 Initiation Protocol (SIP) Application", RFC 4740, 6502 November 2006. 6504 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 6505 Specifications: ABNF", RFC 4234, October 2005. 6507 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. 6508 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 6510 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 6511 Levkowetz, "Extensible Authentication Protocol (EAP)", 6512 RFC 3748, June 2004. 6514 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 6515 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 6516 October 1998. 6518 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 6519 RFC 4306, December 2005. 6521 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 6522 Architecture", RFC 4291, February 2006. 6524 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 6525 Requirement Levels", BCP 14, RFC 2119, March 1997. 6527 [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The 6528 Network Access Identifier", RFC 4282, December 2005. 6530 [RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS) 6531 Part Three: The Domain Name System (DNS) Database", 6532 RFC 3403, October 2002. 6534 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 6535 A., Peterson, J., Sparks, R., Handley, M., and E. 6536 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 6537 June 2002. 6539 [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C., 6540 Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M., 6541 Zhang, L., and V. Paxson, "Stream Control Transmission 6542 Protocol", RFC 2960, October 2000. 6544 [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security 6545 (TLS) Protocol Version 1.1", RFC 4346, April 2006. 6547 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 6548 Resource Identifier (URI): Generic Syntax", STD 66, 6549 RFC 3986, January 2005. 6551 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 6552 10646", STD 63, RFC 3629, November 2003. 6554 14.2. Informational References 6556 [RFC2989] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, P., 6557 Shiino, H., Zorn, G., Dommety, G., C.Perkins, B.Patil, 6558 D.Mitton, S.Manning, M.Beadles, P.Walsh, X.Chen, 6559 S.Sivalingham, A.Hameed, M.Munson, S.Jacobs, B.Lim, 6560 B.Hirschman, R.Hsu, Y.Xu, E.Campell, S.Baba, and E.Jaques, 6561 "Criteria for Evaluating AAA Protocols for Network 6562 Access", RFC 2989, November 2000. 6564 [RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction to 6565 Accounting Management", RFC 2975, October 2000. 6567 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by 6568 an On-line Database", RFC 3232, January 2002. 6570 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B. 6571 Aboba, "Dynamic Authorization Extensions to Remote 6572 Authentication Dial In User Service (RADIUS)", RFC 3576, 6573 July 2003. 6575 [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, 6576 RFC 1661, July 1994. 6578 [RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy 6579 Implementation in Roaming", RFC 2607, June 1999. 6581 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. 6583 [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS 6584 Extensions", RFC 2869, June 2000. 6586 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 6587 "Remote Authentication Dial In User Service (RADIUS)", 6588 RFC 2865, June 2000. 6590 [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6", 6591 RFC 3162, August 2001. 6593 [RFC2194] Aboba, B., Lu, J., Alsop, J., Ding, J., and W. Wang, 6594 "Review of Roaming Implementations", RFC 2194, 6595 September 1997. 6597 [RFC2477] Aboba, B. and G. Zorn, "Criteria for Evaluating Roaming 6598 Protocols", RFC 2477, January 1999. 6600 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 6601 Internet Protocol", RFC 4301, December 2005. 6603 [RFC4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 6604 for IPv4, IPv6 and OSI", RFC 4330, January 2006. 6606 [RFC1492] Finseth, C., "An Access Control Protocol, Sometimes Called 6607 TACACS", RFC 1492, July 1993. 6609 [IANA-EXP] 6610 Narten, T., "Assigning Experimental and Testing Numbers 6611 Considered Useful, Work in Progress.". 6613 Appendix A. Acknowledgements 6615 The authors would like to thank the following people that have 6616 provided proposals and contributions to this document: 6618 To Vishnu Ram and Satendra Gera for their contributions on 6619 Capabilities Updates, Predictive Loop Avoidance as well as many other 6620 technical proposals. To Tolga Asveren for his insights and 6621 contributions on almost all of the proposed solutions incorporated 6622 into this document. To Timothy Smith for helping on the Capabilities 6623 Updates and other topics. To Tony Zhang for providing fixes to loop 6624 holes on composing Failed-AVPs as well as many other issues and 6625 topics. To Jan Nordqvist for clearly stating the usage of 6626 application ids. To Anders Kristensen for providing needed technical 6627 opinions. To David Frascone for providing invaluable review of the 6628 document. 6630 Special thanks also to people who have provided invaluable comments 6631 and inputs especially in resolving controversial issues: 6633 Glen Zorn, Yoshihiro Ohba, Marco Stura, and Pasi Eronen. 6635 Finally, we would like to thank the original authors of this 6636 document: 6638 Pat Calhoun, John Loughney, Jari Arkko, Erik Guttman and Glen Zorn. 6640 Their invaluable knowledge and experience has given us a robust and 6641 flexible AAA protocol that many people have seen great value in 6642 adopting. We greatly appreciate their support and stewardship for 6643 the continued improvements of Diameter as a protocol. We would also 6644 like to extend our gratitude to folks aside from the authors who have 6645 assisted and contributed to the original version of this document. 6646 Their efforts significantly contributed to the success of Diameter. 6648 Appendix B. NAPTR Example 6650 As an example, consider a client that wishes to resolve aaa:ex.com. 6651 The client performs a NAPTR query for that domain, and the following 6652 NAPTR records are returned: 6654 ;; order pref flags service regexp replacement 6655 IN NAPTR 50 50 "s" "AAA+D2S" "" 6656 _diameter._sctp.example.com IN NAPTR 100 50 "s" "AAA+D2T" 6657 "" _aaa._tcp.example.com 6659 This indicates that the server supports SCTP, and TCP, in that order. 6660 If the client supports over SCTP, SCTP will be used, targeted to a 6661 host determined by an SRV lookup of _diameter._sctp.ex.com. That 6662 lookup would return: 6664 ;; Priority Weight Port Target 6665 IN SRV 0 1 5060 server1.example.com IN SRV 0 6666 2 5060 server2.example.com 6668 Appendix C. Duplicate Detection 6670 As described in Section 9.4, accounting record duplicate detection is 6671 based on session identifiers. Duplicates can appear for various 6672 reasons: 6674 o Failover to an alternate server. Where close to real-time 6675 performance is required, failover thresholds need to be kept low 6676 and this may lead to an increased likelihood of duplicates. 6677 Failover can occur at the client or within Diameter agents. 6679 o Failure of a client or agent after sending of a record from non- 6680 volatile memory, but prior to receipt of an application layer ACK 6681 and deletion of the record. record to be sent. This will result 6682 in retransmission of the record soon after the client or agent has 6683 rebooted. 6685 o Duplicates received from RADIUS gateways. Since the 6686 retransmission behavior of RADIUS is not defined within [RFC2865], 6687 the likelihood of duplication will vary according to the 6688 implementation. 6690 o Implementation problems and misconfiguration. 6692 The T flag is used as an indication of an application layer 6693 retransmission event, e.g., due to failover to an alternate server. 6694 It is defined only for request messages sent by Diameter clients or 6695 agents. For instance, after a reboot, a client may not know whether 6696 it has already tried to send the accounting records in its non- 6697 volatile memory before the reboot occurred. Diameter servers MAY use 6698 the T flag as an aid when processing requests and detecting duplicate 6699 messages. However, servers that do this MUST ensure that duplicates 6700 are found even when the first transmitted request arrives at the 6701 server after the retransmitted request. It can be used only in cases 6702 where no answer has been received from the Server for a request and 6703 the request is sent again, (e.g., due to a failover to an alternate 6704 peer, due to a recovered primary peer or due to a client re-sending a 6705 stored record from non-volatile memory such as after reboot of a 6706 client or agent). 6708 In some cases the Diameter accounting server can delay the duplicate 6709 detection and accounting record processing until a post-processing 6710 phase takes place. At that time records are likely to be sorted 6711 according to the included User-Name and duplicate elimination is easy 6712 in this case. In other situations it may be necessary to perform 6713 real-time duplicate detection, such as when credit limits are imposed 6714 or real-time fraud detection is desired. 6716 In general, only generation of duplicates due to failover or re- 6717 sending of records in non-volatile storage can be reliably detected 6718 by Diameter clients or agents. In such cases the Diameter client or 6719 agents can mark the message as possible duplicate by setting the T 6720 flag. Since the Diameter server is responsible for duplicate 6721 detection, it can choose to make use of the T flag or not, in order 6722 to optimize duplicate detection. Since the T flag does not affect 6723 interoperability, and may not be needed by some servers, generation 6724 of the T flag is REQUIRED for Diameter clients and agents, but MAY be 6725 implemented by Diameter servers. 6727 As an example, it can be usually be assumed that duplicates appear 6728 within a time window of longest recorded network partition or device 6729 fault, perhaps a day. So only records within this time window need 6730 to be looked at in the backward direction. Secondly, hashing 6731 techniques or other schemes, such as the use of the T flag in the 6732 received messages, may be used to eliminate the need to do a full 6733 search even in this set except for rare cases. 6735 The following is an example of how the T flag may be used by the 6736 server to detect duplicate requests. 6738 A Diameter server MAY check the T flag of the received message to 6739 determine if the record is a possible duplicate. If the T flag is 6740 set in the request message, the server searches for a duplicate 6741 within a configurable duplication time window backward and 6742 forward. This limits database searching to those records where 6743 the T flag is set. In a well run network, network partitions and 6744 device faults will presumably be rare events, so this approach 6745 represents a substantial optimization of the duplicate detection 6746 process. During failover, it is possible for the original record 6747 to be received after the T flag marked record, due to differences 6748 in network delays experienced along the path by the original and 6749 duplicate transmissions. The likelihood of this occurring 6750 increases as the failover interval is decreased. In order to be 6751 able to detect out of order duplicates, the Diameter server should 6752 use backward and forward time windows when performing duplicate 6753 checking for the T flag marked request. For example, in order to 6754 allow time for the original record to exit the network and be 6755 recorded by the accounting server, the Diameter server can delay 6756 processing records with the T flag set until a time period 6757 TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after the closing 6758 of the original transport connection. After this time period has 6759 expired, then it may check the T flag marked records against the 6760 database with relative assurance that the original records, if 6761 sent, have been received and recorded. 6763 Authors' Addresses 6765 Victor Fajardo (editor) 6766 Toshiba America Research 6767 One Telcordia Drive, 1S-222 6768 Piscataway, NJ 08854 6769 USA 6771 Phone: 1 908-421-1845 6772 Email: vfajardo@tari.toshiba.com 6774 Jari Arkko 6775 Ericsson Research 6776 02420 Jorvas 6777 Finland 6779 Phone: +358 40 5079256 6780 Email: jari.arkko@ericsson.com 6782 John Loughney 6783 Nokia Research Center 6784 955 Page Mill Road 6785 Palo Alto, CA 94304 6786 US 6788 Phone: 1-650-283-8068 6789 Email: john.loughney@nokia.com 6791 Full Copyright Statement 6793 Copyright (C) The IETF Trust (2007). 6795 This document is subject to the rights, licenses and restrictions 6796 contained in BCP 78, and except as set forth therein, the authors 6797 retain all their rights. 6799 This document and the information contained herein are provided on an 6800 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 6801 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 6802 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 6803 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 6804 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 6805 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 6807 Intellectual Property 6809 The IETF takes no position regarding the validity or scope of any 6810 Intellectual Property Rights or other rights that might be claimed to 6811 pertain to the implementation or use of the technology described in 6812 this document or the extent to which any license under such rights 6813 might or might not be available; nor does it represent that it has 6814 made any independent effort to identify any such rights. Information 6815 on the procedures with respect to rights in RFC documents can be 6816 found in BCP 78 and BCP 79. 6818 Copies of IPR disclosures made to the IETF Secretariat and any 6819 assurances of licenses to be made available, or the result of an 6820 attempt made to obtain a general license or permission for the use of 6821 such proprietary rights by implementers or users of this 6822 specification can be obtained from the IETF on-line IPR repository at 6823 http://www.ietf.org/ipr. 6825 The IETF invites any interested party to bring to its attention any 6826 copyrights, patents or patent applications, or other proprietary 6827 rights that may cover technology that may be required to implement 6828 this standard. Please address the information to the IETF at 6829 ietf-ipr@ietf.org. 6831 Acknowledgment 6833 Funding for the RFC Editor function is provided by the IETF 6834 Administrative Support Activity (IASA).