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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust Copyright Line does not match the current year == Line 4517 has weird spacing: '...ly with wit...' == Line 4725 has weird spacing: '...ealtime user...' == Line 4753 has weird spacing: '... record inter...' == Line 4763 has weird spacing: '...ealtime user...' == Line 4771 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 (July 6, 2007) is 6110 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 4234, 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: January 7, 2008 Ericsson Research 6 J. Loughney 7 Nokia Research Center 8 July 6, 2007 10 Diameter Base Protocol 11 draft-ietf-dime-rfc3588bis-05.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 January 7, 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 Authentication Applications . . . . . . 13 63 1.2.4. Creating New Accounting Applications . . . . . . . . 14 64 1.2.5. Application Authentication Procedures . . . . . . . 15 65 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 15 66 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 22 67 2.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 23 68 2.1.1. SCTP Guidelines . . . . . . . . . . . . . . . . . . 24 69 2.2. Securing Diameter Messages . . . . . . . . . . . . . . . 24 70 2.3. Diameter Application Compliance . . . . . . . . . . . . . 24 71 2.4. Application Identifiers . . . . . . . . . . . . . . . . . 24 72 2.5. Connections vs. Sessions . . . . . . . . . . . . . . . . 25 73 2.6. Peer Table . . . . . . . . . . . . . . . . . . . . . . . 26 74 2.7. Routing Table . . . . . . . . . . . . . . . . . . . . . . 27 75 2.8. Role of Diameter Agents . . . . . . . . . . . . . . . . . 28 76 2.8.1. Relay Agents . . . . . . . . . . . . . . . . . . . . 30 77 2.8.2. Proxy Agents . . . . . . . . . . . . . . . . . . . . 31 78 2.8.3. Redirect Agents . . . . . . . . . . . . . . . . . . 31 79 2.8.4. Translation Agents . . . . . . . . . . . . . . . . . 32 80 2.9. Diameter Path Authorization . . . . . . . . . . . . . . . 33 81 3. Diameter Header . . . . . . . . . . . . . . . . . . . . . . . 35 82 3.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 38 83 3.2. Command Code ABNF specification . . . . . . . . . . . . . 38 84 3.3. Diameter Command Naming Conventions . . . . . . . . . . . 40 85 4. Diameter AVPs . . . . . . . . . . . . . . . . . . . . . . . . 42 86 4.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 42 87 4.1.1. Optional Header Elements . . . . . . . . . . . . . . 44 88 4.2. Basic AVP Data Formats . . . . . . . . . . . . . . . . . 44 89 4.3. Derived AVP Data Formats . . . . . . . . . . . . . . . . 46 90 4.4. Grouped AVP Values . . . . . . . . . . . . . . . . . . . 52 91 4.4.1. Example AVP with a Grouped Data type . . . . . . . . 53 92 4.5. Diameter Base Protocol AVPs . . . . . . . . . . . . . . . 56 93 5. Diameter Peers . . . . . . . . . . . . . . . . . . . . . . . 59 94 5.1. Peer Connections . . . . . . . . . . . . . . . . . . . . 59 95 5.2. Diameter Peer Discovery . . . . . . . . . . . . . . . . . 59 96 5.3. Capabilities Exchange . . . . . . . . . . . . . . . . . . 62 97 5.3.1. Capabilities-Exchange-Request . . . . . . . . . . . 63 98 5.3.2. Capabilities-Exchange-Answer . . . . . . . . . . . . 64 99 5.3.3. Vendor-Id AVP . . . . . . . . . . . . . . . . . . . 64 100 5.3.4. Firmware-Revision AVP . . . . . . . . . . . . . . . 65 101 5.3.5. Host-IP-Address AVP . . . . . . . . . . . . . . . . 65 102 5.3.6. Supported-Vendor-Id AVP . . . . . . . . . . . . . . 65 103 5.3.7. Product-Name AVP . . . . . . . . . . . . . . . . . . 65 104 5.4. Disconnecting Peer connections . . . . . . . . . . . . . 65 105 5.4.1. Disconnect-Peer-Request . . . . . . . . . . . . . . 66 106 5.4.2. Disconnect-Peer-Answer . . . . . . . . . . . . . . . 66 107 5.4.3. Disconnect-Cause AVP . . . . . . . . . . . . . . . . 67 108 5.5. Transport Failure Detection . . . . . . . . . . . . . . . 67 109 5.5.1. Device-Watchdog-Request . . . . . . . . . . . . . . 67 110 5.5.2. Device-Watchdog-Answer . . . . . . . . . . . . . . . 68 111 5.5.3. Transport Failure Algorithm . . . . . . . . . . . . 68 112 5.5.4. Failover and Failback Procedures . . . . . . . . . . 68 113 5.6. Peer State Machine . . . . . . . . . . . . . . . . . . . 69 114 5.6.1. Incoming connections . . . . . . . . . . . . . . . . 71 115 5.6.2. Events . . . . . . . . . . . . . . . . . . . . . . . 72 116 5.6.3. Actions . . . . . . . . . . . . . . . . . . . . . . 73 117 5.6.4. The Election Process . . . . . . . . . . . . . . . . 75 118 5.6.5. Capabilities Update . . . . . . . . . . . . . . . . 75 119 6. Diameter message processing . . . . . . . . . . . . . . . . . 76 120 6.1. Diameter Request Routing Overview . . . . . . . . . . . . 76 121 6.1.1. Originating a Request . . . . . . . . . . . . . . . 77 122 6.1.2. Sending a Request . . . . . . . . . . . . . . . . . 78 123 6.1.3. Receiving Requests . . . . . . . . . . . . . . . . . 78 124 6.1.4. Processing Local Requests . . . . . . . . . . . . . 78 125 6.1.5. Request Forwarding . . . . . . . . . . . . . . . . . 78 126 6.1.6. Request Routing . . . . . . . . . . . . . . . . . . 79 127 6.1.7. Predictive Loop Avoidance . . . . . . . . . . . . . 79 128 6.1.8. Redirecting requests . . . . . . . . . . . . . . . . 79 129 6.1.9. Relaying and Proxying Requests . . . . . . . . . . . 81 130 6.2. Diameter Answer Processing . . . . . . . . . . . . . . . 81 131 6.2.1. Processing received Answers . . . . . . . . . . . . 82 132 6.2.2. Relaying and Proxying Answers . . . . . . . . . . . 82 133 6.3. Origin-Host AVP . . . . . . . . . . . . . . . . . . . . . 83 134 6.4. Origin-Realm AVP . . . . . . . . . . . . . . . . . . . . 83 135 6.5. Destination-Host AVP . . . . . . . . . . . . . . . . . . 83 136 6.6. Destination-Realm AVP . . . . . . . . . . . . . . . . . . 84 137 6.7. Routing AVPs . . . . . . . . . . . . . . . . . . . . . . 84 138 6.7.1. Route-Record AVP . . . . . . . . . . . . . . . . . . 84 139 6.7.2. Proxy-Info AVP . . . . . . . . . . . . . . . . . . . 84 140 6.7.3. Proxy-Host AVP . . . . . . . . . . . . . . . . . . . 84 141 6.7.4. Proxy-State AVP . . . . . . . . . . . . . . . . . . 84 142 6.8. Auth-Application-Id AVP . . . . . . . . . . . . . . . . . 85 143 6.9. Acct-Application-Id AVP . . . . . . . . . . . . . . . . . 85 144 6.10. Inband-Security-Id AVP . . . . . . . . . . . . . . . . . 85 145 6.11. Vendor-Specific-Application-Id AVP . . . . . . . . . . . 85 146 6.12. Redirect-Host AVP . . . . . . . . . . . . . . . . . . . . 86 147 6.13. Redirect-Host-Usage AVP . . . . . . . . . . . . . . . . . 86 148 6.14. Redirect-Max-Cache-Time AVP . . . . . . . . . . . . . . . 88 149 6.15. E2E-Sequence AVP . . . . . . . . . . . . . . . . . . . . 88 150 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 89 151 7.1. Result-Code AVP . . . . . . . . . . . . . . . . . . . . . 90 152 7.1.1. Informational . . . . . . . . . . . . . . . . . . . 91 153 7.1.2. Success . . . . . . . . . . . . . . . . . . . . . . 91 154 7.1.3. Protocol Errors . . . . . . . . . . . . . . . . . . 92 155 7.1.4. Transient Failures . . . . . . . . . . . . . . . . . 93 156 7.1.5. Permanent Failures . . . . . . . . . . . . . . . . . 94 157 7.2. Error Bit . . . . . . . . . . . . . . . . . . . . . . . . 97 158 7.3. Error-Message AVP . . . . . . . . . . . . . . . . . . . . 97 159 7.4. Error-Reporting-Host AVP . . . . . . . . . . . . . . . . 97 160 7.5. Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . . 97 161 7.6. Experimental-Result AVP . . . . . . . . . . . . . . . . . 98 162 7.7. Experimental-Result-Code AVP . . . . . . . . . . . . . . 99 163 8. Diameter User Sessions . . . . . . . . . . . . . . . . . . . 100 164 8.1. Authorization Session State Machine . . . . . . . . . . . 101 165 8.2. Accounting Session State Machine . . . . . . . . . . . . 106 166 8.3. Server-Initiated Re-Auth . . . . . . . . . . . . . . . . 111 167 8.3.1. Re-Auth-Request . . . . . . . . . . . . . . . . . . 111 168 8.3.2. Re-Auth-Answer . . . . . . . . . . . . . . . . . . . 112 169 8.4. Session Termination . . . . . . . . . . . . . . . . . . . 113 170 8.4.1. Session-Termination-Request . . . . . . . . . . . . 114 171 8.4.2. Session-Termination-Answer . . . . . . . . . . . . . 114 172 8.5. Aborting a Session . . . . . . . . . . . . . . . . . . . 115 173 8.5.1. Abort-Session-Request . . . . . . . . . . . . . . . 116 174 8.5.2. Abort-Session-Answer . . . . . . . . . . . . . . . . 116 175 8.6. Inferring Session Termination from Origin-State-Id . . . 117 176 8.7. Auth-Request-Type AVP . . . . . . . . . . . . . . . . . . 118 177 8.8. Session-Id AVP . . . . . . . . . . . . . . . . . . . . . 118 178 8.9. Authorization-Lifetime AVP . . . . . . . . . . . . . . . 119 179 8.10. Auth-Grace-Period AVP . . . . . . . . . . . . . . . . . . 120 180 8.11. Auth-Session-State AVP . . . . . . . . . . . . . . . . . 120 181 8.12. Re-Auth-Request-Type AVP . . . . . . . . . . . . . . . . 121 182 8.13. Session-Timeout AVP . . . . . . . . . . . . . . . . . . . 121 183 8.14. User-Name AVP . . . . . . . . . . . . . . . . . . . . . . 122 184 8.15. Termination-Cause AVP . . . . . . . . . . . . . . . . . . 122 185 8.16. Origin-State-Id AVP . . . . . . . . . . . . . . . . . . . 123 186 8.17. Session-Binding AVP . . . . . . . . . . . . . . . . . . . 123 187 8.18. Session-Server-Failover AVP . . . . . . . . . . . . . . . 124 188 8.19. Multi-Round-Time-Out AVP . . . . . . . . . . . . . . . . 125 189 8.20. Class AVP . . . . . . . . . . . . . . . . . . . . . . . . 125 190 8.21. Event-Timestamp AVP . . . . . . . . . . . . . . . . . . . 125 191 9. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . 127 192 9.1. Server Directed Model . . . . . . . . . . . . . . . . . . 127 193 9.2. Protocol Messages . . . . . . . . . . . . . . . . . . . . 128 194 9.3. Accounting Application Extension and Requirements . . . . 128 195 9.4. Fault Resilience . . . . . . . . . . . . . . . . . . . . 129 196 9.5. Accounting Records . . . . . . . . . . . . . . . . . . . 130 197 9.6. Correlation of Accounting Records . . . . . . . . . . . . 130 198 9.7. Accounting Command-Codes . . . . . . . . . . . . . . . . 131 199 9.7.1. Accounting-Request . . . . . . . . . . . . . . . . . 131 200 9.7.2. Accounting-Answer . . . . . . . . . . . . . . . . . 132 201 9.8. Accounting AVPs . . . . . . . . . . . . . . . . . . . . . 133 202 9.8.1. Accounting-Record-Type AVP . . . . . . . . . . . . . 133 203 9.8.2. Acct-Interim-Interval . . . . . . . . . . . . . . . 134 204 9.8.3. Accounting-Record-Number AVP . . . . . . . . . . . . 135 205 9.8.4. Acct-Session-Id AVP . . . . . . . . . . . . . . . . 135 206 9.8.5. Acct-Multi-Session-Id AVP . . . . . . . . . . . . . 135 207 9.8.6. Accounting-Sub-Session-Id AVP . . . . . . . . . . . 135 208 9.8.7. Accounting-Realtime-Required AVP . . . . . . . . . . 136 209 10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . 137 210 10.1. Base Protocol Command AVP Table . . . . . . . . . . . . . 137 211 10.2. Accounting AVP Table . . . . . . . . . . . . . . . . . . 138 212 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 140 213 11.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 140 214 11.1.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . 140 215 11.1.2. AVP Flags . . . . . . . . . . . . . . . . . . . . . 141 216 11.2. Diameter Header . . . . . . . . . . . . . . . . . . . . . 141 217 11.2.1. Command Codes . . . . . . . . . . . . . . . . . . . 141 218 11.2.2. Command Flags . . . . . . . . . . . . . . . . . . . 142 219 11.3. Application Identifiers . . . . . . . . . . . . . . . . . 142 220 11.4. AVP Values . . . . . . . . . . . . . . . . . . . . . . . 142 221 11.4.1. Result-Code AVP Values . . . . . . . . . . . . . . . 143 222 11.4.2. Accounting-Record-Type AVP Values . . . . . . . . . 143 223 11.4.3. Termination-Cause AVP Values . . . . . . . . . . . . 143 224 11.4.4. Redirect-Host-Usage AVP Values . . . . . . . . . . . 143 225 11.4.5. Session-Server-Failover AVP Values . . . . . . . . . 143 226 11.4.6. Session-Binding AVP Values . . . . . . . . . . . . . 143 227 11.4.7. Disconnect-Cause AVP Values . . . . . . . . . . . . 143 228 11.4.8. Auth-Request-Type AVP Values . . . . . . . . . . . . 143 229 11.4.9. Auth-Session-State AVP Values . . . . . . . . . . . 144 230 11.4.10. Re-Auth-Request-Type AVP Values . . . . . . . . . . 144 231 11.4.11. Accounting-Realtime-Required AVP Values . . . . . . 144 232 11.4.12. Inband-Security-Id AVP (code 299) . . . . . . . . . 144 234 11.5. Diameter TCP/SCTP Port Numbers . . . . . . . . . . . . . 144 235 11.6. NAPTR Service Fields . . . . . . . . . . . . . . . . . . 144 236 12. Diameter protocol related configurable parameters . . . . . . 146 237 13. Security Considerations . . . . . . . . . . . . . . . . . . . 147 238 13.1. TLS Usage . . . . . . . . . . . . . . . . . . . . . . . . 147 239 13.2. Peer-to-Peer Considerations . . . . . . . . . . . . . . . 148 240 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 149 241 14.1. Normative References . . . . . . . . . . . . . . . . . . 149 242 14.2. Informational References . . . . . . . . . . . . . . . . 151 243 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 153 244 Appendix B. NAPTR Example . . . . . . . . . . . . . . . . . . . 154 245 Appendix C. Duplicate Detection . . . . . . . . . . . . . . . . 155 246 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 157 247 Intellectual Property and Copyright Statements . . . . . . . . . 158 249 1. Introduction 251 Authentication, Authorization and Accounting (AAA) protocols such as 252 TACACS [RFC1492] and RADIUS [RFC2865] were initially deployed to 253 provide dial-up PPP [RFC1661] and terminal server access. Over time, 254 with the growth of the Internet and the introduction of new access 255 technologies, including wireless, DSL, Mobile IP and Ethernet, 256 routers and network access servers (NAS) have increased in complexity 257 and density, putting new demands on AAA protocols. 259 Network access requirements for AAA protocols are summarized in 260 [RFC2989]. These include: 262 Failover 264 [RFC2865] does not define failover mechanisms, and as a result, 265 failover behavior differs between implementations. In order to 266 provide well defined failover behavior, Diameter supports 267 application-layer acknowledgements, and defines failover 268 algorithms and the associated state machine. This is described in 269 Section 5.5 and [RFC3539]. 271 Transmission-level security 273 [RFC2865] defines an application-layer authentication and 274 integrity scheme that is required only for use with Response 275 packets. While [RFC2869] defines an additional authentication and 276 integrity mechanism, use is only required during Extensible 277 Authentication Protocol (EAP) sessions. While attribute-hiding is 278 supported, [RFC2865] does not provide support for per-packet 279 confidentiality. In accounting, [RFC2866] assumes that replay 280 protection is provided by the backend billing server, rather than 281 within the protocol itself. 283 While [RFC3162] defines the use of IPsec with RADIUS, support for 284 IPsec is not required. Since within [RFC4306] authentication 285 occurs only within Phase 1 prior to the establishment of IPsec SAs 286 in Phase 2, it is typically not possible to define separate trust 287 or authorization schemes for each application. This limits the 288 usefulness of IPsec in inter-domain AAA applications (such as 289 roaming) where it may be desirable to define a distinct 290 certificate hierarchy for use in a AAA deployment. In order to 291 provide universal support for transmission-level security, and 292 enable both intra- and inter-domain AAA deployments, Diameter also 293 provides support for TLS. Security is discussed in Section 13. 295 Reliable transport 297 RADIUS runs over UDP, and does not define retransmission behavior; 298 as a result, reliability varies between implementations. As 299 described in [RFC2975], this is a major issue in accounting, where 300 packet loss may translate directly into revenue loss. In order to 301 provide well defined transport behavior, Diameter runs over 302 reliable transport mechanisms (TCP, SCTP) as defined in [RFC3539]. 304 Agent support 306 [RFC2865] does not provide for explicit support for agents, 307 including Proxies, Redirects and Relays. Since the expected 308 behavior is not defined, it varies between implementations. 309 Diameter defines agent behavior explicitly; this is described in 310 Section 2.8. 312 Server-initiated messages 314 While RADIUS server-initiated messages are defined in [RFC3576], 315 support is optional. This makes it difficult to implement 316 features such as unsolicited disconnect or reauthentication/ 317 reauthorization on demand across a heterogeneous deployment. 318 Support for server-initiated messages is mandatory in Diameter, 319 and is described in Section 8. 321 Auditability 323 RADIUS does not define data-object security mechanisms, and as a 324 result, untrusted proxies may modify attributes or even packet 325 headers without being detected. Combined with lack of support for 326 capabilities negotiation, this makes it very difficult to 327 determine what occurred in the event of a dispute. 329 Transition support 331 While Diameter does not share a common protocol data unit (PDU) 332 with RADIUS, considerable effort has been expended in enabling 333 backward compatibility with RADIUS, so that the two protocols may 334 be deployed in the same network. Initially, it is expected that 335 Diameter will be deployed within new network devices, as well as 336 within gateways enabling communication between legacy RADIUS 337 devices and Diameter agents. This capability, described in 339 [RFC4005], enables Diameter support to be added to legacy 340 networks, by addition of a gateway or server speaking both RADIUS 341 and Diameter. 343 In addition to addressing the above requirements, Diameter also 344 provides support for the following: 346 Capability negotiation 348 RADIUS does not support error messages, capability negotiation, or 349 a mandatory/non-mandatory flag for attributes. Since RADIUS 350 clients and servers are not aware of each other's capabilities, 351 they may not be able to successfully negotiate a mutually 352 acceptable service, or in some cases, even be aware of what 353 service has been implemented. Diameter includes support for error 354 handling (Section 7), capability negotiation (Section 5.3), and 355 mandatory/non-mandatory attribute-value pairs (AVPs) (Section 356 4.1). 358 Peer discovery and configuration 360 RADIUS implementations typically require that the name or address 361 of servers or clients be manually configured, along with the 362 corresponding shared secrets. This results in a large 363 administrative burden, and creates the temptation to reuse the 364 RADIUS shared secret, which can result in major security 365 vulnerabilities if the Request Authenticator is not globally and 366 temporally unique as required in [RFC2865]. Through DNS, Diameter 367 enables dynamic discovery of peers. Derivation of dynamic session 368 keys is enabled via transmission-level security. 370 Roaming support 372 The ROAMOPS WG provided a survey of roaming implementations 373 [RFC2194], detailed roaming requirements [RFC2477], defined the 374 Network Access Identifier (NAI)[RFC4282], and documented existing 375 implementations (and imitations) of RADIUS-based roaming 376 [RFC2607]. In order to improve scalability, [RFC2607] introduced 377 the concept of proxy chaining via an intermediate server, 378 facilitating roaming between providers. However, since RADIUS 379 does not provide explicit support for proxies, and lacks 380 auditability and transmission-level security features, RADIUS- 381 based roaming is vulnerable to attack from external parties as 382 well as susceptible to fraud perpetrated by the roaming partners 383 themselves. As a result, it is not suitable for wide-scale 384 deployment on the Internet [RFC2607]. By providing explicit 385 support for inter-domain roaming and message routing (Sections 2.7 386 and 6), and transmission-layer security (Section 13) features, 387 Diameter addresses these limitations and provides for secure and 388 scalable roaming. 390 In the decade since AAA protocols were first introduced, the 391 capabilities of Network Access Server (NAS) devices have increased 392 substantially. As a result, while Diameter is a considerably more 393 sophisticated protocol than RADIUS, it remains feasible to implement 394 within embedded devices, given improvements in processor speeds and 395 the widespread availability of embedded TLS implementations. 397 1.1. Diameter Protocol 399 The Diameter base protocol provides the following facilities: 401 o Delivery of AVPs (attribute value pairs) 403 o Capabilities negotiation 405 o Error notification 407 o Extensibility, through addition of new commands and AVPs (required 408 in [RFC2989]). 410 o Basic services necessary for applications, such as handling of 411 user sessions or accounting 413 All data delivered by the protocol is in the form of an AVP. Some of 414 these AVP values are used by the Diameter protocol itself, while 415 others deliver data associated with particular applications that 416 employ Diameter. AVPs may be added arbitrarily to Diameter messages, 417 so long as the required AVPs are included and AVPs that are 418 explicitly excluded are not included. AVPs are used by the base 419 Diameter protocol to support the following required features: 421 o Transporting of user authentication information, for the purposes 422 of enabling the Diameter server to authenticate the user. 424 o Transporting of service specific authorization information, 425 between client and servers, allowing the peers to decide whether a 426 user's access request should be granted. 428 o Exchanging resource usage information, which MAY be used for 429 accounting purposes, capacity planning, etc. 431 o Relaying, proxying and redirecting of Diameter messages through a 432 server hierarchy. 434 The Diameter base protocol provides the minimum requirements needed 435 for a AAA protocol, as required by [RFC2989]. The base protocol may 436 be used by itself for accounting purposes only, or it may be used 437 with a Diameter application, such as Mobile IPv4 [RFC4004], or 438 network access [RFC4005]. It is also possible for the base protocol 439 to be extended for use in new applications, via the addition of new 440 commands or AVPs. At this time the focus of Diameter is network 441 access and accounting applications. A truly generic AAA protocol 442 used by many applications might provide functionality not provided by 443 Diameter. Therefore, it is imperative that the designers of new 444 applications understand their requirements before using Diameter. 445 See Section 2.4 for more information on Diameter applications. 447 Any node can initiate a request. In that sense, Diameter is a peer- 448 to-peer protocol. In this document, a Diameter Client is a device at 449 the edge of the network that performs access control, such as a 450 Network Access Server (NAS) or a Foreign Agent (FA). A Diameter 451 client generates Diameter messages to request authentication, 452 authorization, and accounting services for the user. A Diameter 453 agent is a node that does not authenticate and/or authorize messages 454 locally; agents include proxies, redirects and relay agents. A 455 Diameter server performs authentication and/or authorization of the 456 user. A Diameter node MAY act as an agent for certain requests while 457 acting as a server for others. 459 The Diameter protocol also supports server-initiated messages, such 460 as a request to abort service to a particular user. 462 1.1.1. Description of the Document Set 464 Currently, the Diameter specification consists of a base 465 specification (this document), Transport Profile [RFC3539] and 466 applications: Mobile IPv4 [RFC4004], NASREQ [RFC4005], Credit Control 467 [RFC4006], EAP [RFC4072] and SIP [RFC4740]. 469 The Transport Profile document [RFC3539] discusses transport layer 470 issues that arise with AAA protocols and recommendations on how to 471 overcome these issues. This document also defines the Diameter 472 failover algorithm and state machine. 474 The Mobile IPv4 [RFC4004] application defines a Diameter application 475 that allows a Diameter server to perform AAA functions for Mobile 476 IPv4 services to a mobile node. 478 The NASREQ [RFC4005] application defines a Diameter Application that 479 allows a Diameter server to be used in a PPP/SLIP Dial-Up and 480 Terminal Server Access environment. Consideration was given for 481 servers that need to perform protocol conversion between Diameter and 482 RADIUS. 484 The Credit Control [RFC4006] application defines a Diameter 485 Application that can be used to implement real-time credit-control 486 for a variety of end user services such as network access, SIP 487 services, messaging services, and download services. It provides a 488 general solution to real-time cost and credit-control. 490 The EAP [RFC4072] application defines a Diameter Application that can 491 be used to carry EAP packets between the Network Access Server (NAS) 492 working as an EAP authenticator and a back-end authentication server. 493 The Diameter EAP application is based on NASREQ and intended for a 494 similar environment. 496 The SIP [RFC4740] application defines a Diameter Application that 497 allows a Diameter client to request authentication and authorization 498 information to a Diameter server for SIP-based IP multimedia services 499 (see SIP [RFC3261]). 501 In summary, this document defines the base protocol specification for 502 AAA, which includes support for accounting. The applications 503 documents describe applications that use this base specification for 504 Authentication, Authorization and Accounting. 506 1.1.2. Conventions Used in This Document 508 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 509 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 510 document are to be interpreted as described in [RFC2119]. 512 1.2. Approach to Extensibility 514 The Diameter protocol is designed to be extensible, using several 515 mechanisms, including: 517 o Defining new AVP values 519 o Creating new AVPs 521 o Creating new authentication/authorization applications 523 o Creating new accounting applications 525 o Application authentication procedures 526 Reuse of existing AVP values, AVPs and Diameter applications are 527 strongly recommended. Reuse simplifies standardization and 528 implementation and avoids potential interoperability issues. It is 529 expected that command codes are reused; new command codes can only be 530 created by Expert Review (see Section 11.2.1). 532 1.2.1. Defining New AVP Values 534 New applications should attempt to reuse AVPs defined in existing 535 applications when possible, as opposed to creating new AVPs. For 536 AVPs of type Enumerated, an application may require a new value to 537 communicate some service-specific information. 539 In order to allocate a new AVP value, a request MUST be sent to IANA 540 [RFC2434], along with an explanation of the new AVP value. IANA 541 considerations for Diameter are discussed in Section 11. 543 1.2.2. Creating New AVPs 545 When no existing AVP can be used, a new AVP should be created. The 546 new AVP being defined MUST use one of the data types listed in 547 Section 4.2. 549 In the event that a logical grouping of AVPs is necessary, and 550 multiple "groups" are possible in a given command, it is recommended 551 that a Grouped AVP be used (see Section 4.4). 553 In order to create a new AVP, a request MUST be sent to IANA, with a 554 specification for the AVP. The request MUST include the commands 555 that would make use of the AVP. 557 1.2.3. Creating New Authentication Applications 559 Every Diameter application specification MUST have an IANA assigned 560 Application Identifier (see Section 2.4 and Section 11.3). 562 Should a new Diameter usage scenario find itself unable to fit within 563 an existing application without requiring major changes to the 564 specification, it may be desirable to create a new Diameter 565 application. Major changes to an application include: 567 o Adding new AVPs to the command, which have the "M" bit set. 569 o Requiring a command that has a different number of round trips to 570 satisfy a request (e.g., application foo has a command that 571 requires one round trip, but new application bar has a command 572 that requires two round trips to complete). 574 o Adding support for an authentication method requiring definition 575 of new AVPs for use with the application. Since a new EAP 576 authentication method can be supported within Diameter without 577 requiring new AVPs, addition of EAP methods does not require the 578 creation of a new authentication application. 580 Creation of a new application should be viewed as a last resort. An 581 implementation MAY add arbitrary non-mandatory AVPs to any command 582 defined in an application, including vendor-specific AVPs without 583 needing to define a new application. Please refer to Section 11.1.1 584 for details. 586 In order to justify allocation of a new application identifier, 587 Diameter applications MUST define one Command Code, add new mandatory 588 AVPs to the ABNF or significantly change the state machine or 589 processing rules of an existing application. 591 The expected AVPs MUST be defined in an ABNF [RFC4234] grammar (see 592 Section 3.2). If the Diameter application has accounting 593 requirements, it MUST also specify the AVPs that are to be present in 594 the Diameter Accounting messages (see Section 9.3). However, just 595 because a new authentication application id is required, does not 596 imply that a new accounting application id is required. 598 When possible, a new Diameter application SHOULD reuse existing 599 Diameter AVPs, in order to avoid defining multiple AVPs that carry 600 similar information. 602 1.2.4. Creating New Accounting Applications 604 There are services that only require Diameter accounting. Such 605 services need to define the AVPs carried in the Accounting-Request 606 (ACR)/ Accounting-Answer (ACA) messages, but do not need to define 607 new command codes. An implementation MAY add arbitrary non-mandatory 608 AVPs (AVPs with the "M" bit not set) to any command defined in an 609 application, including vendor-specific AVPs, without needing to 610 define a new accounting application. Please refer to Section 11.1.1 611 for details. 613 Application Identifiers are still required for Diameter capability 614 exchange. Every Diameter accounting application specification MUST 615 have an IANA assigned Application Identifier (see Section 2.4) or a 616 vendor specific Application Identifier. 618 Every Diameter implementation MUST support accounting. Basic 619 accounting support is sufficient to handle any application that uses 620 the ACR/ACA commands defined in this document, as long as no new 621 mandatory AVPs are added. A mandatory AVP is defined as one which 622 has the "M" bit set when sent within an accounting command, 623 regardless of whether it is required or optional within the ABNF for 624 the accounting application. 626 The creation of a new accounting application should be viewed as a 627 last resort and MUST NOT be used unless a new command or additional 628 mechanisms (e.g., application defined state machine) is defined 629 within the application, or new mandatory AVPs are added to the ABNF. 631 Within an accounting command, setting the "M" bit implies that a 632 backend server (e.g., billing server) or the accounting server itself 633 MUST understand the AVP in order to compute a correct bill. If the 634 AVP is not relevant to the billing process, when the AVP is included 635 within an accounting command, it MUST NOT have the "M" bit set, even 636 if the "M" bit is set when the same AVP is used within other Diameter 637 commands (i.e., authentication/authorization commands). 639 A DIAMETER base accounting implementation MUST be configurable to 640 advertise supported accounting applications in order to prevent the 641 accounting server from accepting accounting requests for unbillable 642 services. The combination of the home domain and the accounting 643 application Id can be used in order to route the request to the 644 appropriate accounting server. 646 When possible, a new Diameter accounting application SHOULD attempt 647 to reuse existing AVPs, in order to avoid defining multiple AVPs that 648 carry similar information. 650 If the base accounting is used without any mandatory AVPs, new 651 commands or additional mechanisms (e.g., application defined state 652 machine), then the base protocol defined standard accounting 653 application Id (Section 2.4) MUST be used in ACR/ACA commands. 655 1.2.5. Application Authentication Procedures 657 When possible, applications SHOULD be designed such that new 658 authentication methods MAY be added without requiring changes to the 659 application. This MAY require that new AVP values be assigned to 660 represent the new authentication transform, or any other scheme that 661 produces similar results. When possible, authentication frameworks, 662 such as Extensible Authentication Protocol [RFC3748], SHOULD be used. 664 1.3. Terminology 665 AAA 667 Authentication, Authorization and Accounting. 669 Accounting 671 The act of collecting information on resource usage for the 672 purpose of capacity planning, auditing, billing or cost 673 allocation. 675 Accounting Record 677 An accounting record represents a summary of the resource 678 consumption of a user over the entire session. Accounting servers 679 creating the accounting record may do so by processing interim 680 accounting events or accounting events from several devices 681 serving the same user. 683 Authentication 685 The act of verifying the identity of an entity (subject). 687 Authorization 689 The act of determining whether a requesting entity (subject) will 690 be allowed access to a resource (object). 692 AVP 694 The Diameter protocol consists of a header followed by one or more 695 Attribute-Value-Pairs (AVPs). An AVP includes a header and is 696 used to encapsulate protocol-specific data (e.g., routing 697 information) as well as authentication, authorization or 698 accounting information. 700 Broker 702 A broker is a business term commonly used in AAA infrastructures. 703 A broker is either a relay, proxy or redirect agent, and MAY be 704 operated by roaming consortiums. Depending on the business model, 705 a broker may either choose to deploy relay agents or proxy agents. 707 Diameter Agent 709 A Diameter Agent is a Diameter node that provides either relay, 710 proxy, redirect or translation services. 712 Diameter Client 714 A Diameter Client is a device at the edge of the network that 715 performs access control. An example of a Diameter client is a 716 Network Access Server (NAS) or a Foreign Agent (FA). 718 Diameter Node 720 A Diameter node is a host process that implements the Diameter 721 protocol, and acts either as a Client, Agent or Server. 723 Diameter Peer 725 A Diameter Peer is a Diameter Node to which a given Diameter Node 726 has a direct transport connection. 728 Diameter Server 730 A Diameter Server is one that handles authentication, 731 authorization and accounting requests for a particular realm. By 732 its very nature, a Diameter Server MUST support Diameter 733 applications in addition to the base protocol. 735 Downstream 737 Downstream is used to identify the direction of a particular 738 Diameter message from the home server towards the access device. 740 Home Realm 742 A Home Realm is the administrative domain with which the user 743 maintains an account relationship. 745 Home Server 747 See Diameter Server. 749 Interim accounting 751 An interim accounting message provides a snapshot of usage during 752 a user's session. It is typically implemented in order to provide 753 for partial accounting of a user's session in the case of a device 754 reboot or other network problem prevents the reception of a 755 session summary message or session record. 757 Local Realm 759 A local realm is the administrative domain providing services to a 760 user. An administrative domain MAY act as a local realm for 761 certain users, while being a home realm for others. 763 Multi-session 765 A multi-session represents a logical linking of several sessions. 766 Multi-sessions are tracked by using the Acct-Multi-Session-Id. An 767 example of a multi-session would be a Multi-link PPP bundle. Each 768 leg of the bundle would be a session while the entire bundle would 769 be a multi-session. 771 Network Access Identifier 773 The Network Access Identifier, or NAI [RFC4282], is used in the 774 Diameter protocol to extract a user's identity and realm. The 775 identity is used to identify the user during authentication and/or 776 authorization, while the realm is used for message routing 777 purposes. 779 Proxy Agent or Proxy 781 In addition to forwarding requests and responses, proxies make 782 policy decisions relating to resource usage and provisioning. 783 This is typically accomplished by tracking the state of NAS 784 devices. While proxies typically do not respond to client 785 Requests prior to receiving a Response from the server, they may 786 originate Reject messages in cases where policies are violated. 787 As a result, proxies need to understand the semantics of the 788 messages passing through them, and may not support all Diameter 789 applications. 791 Realm 793 The string in the NAI that immediately follows the '@' character. 794 NAI realm names are required to be unique, and are piggybacked on 795 the administration of the DNS namespace. Diameter makes use of 796 the realm, also loosely referred to as domain, to determine 797 whether messages can be satisfied locally, or whether they must be 798 routed or redirected. In RADIUS, realm names are not necessarily 799 piggybacked on the DNS namespace but may be independent of it. 801 Real-time Accounting 803 Real-time accounting involves the processing of information on 804 resource usage within a defined time window. Time constraints are 805 typically imposed in order to limit financial risk. 807 Relay Agent or Relay 809 Relays forward requests and responses based on routing-related 810 AVPs and routing table entries. Since relays do not make policy 811 decisions, they do not examine or alter non-routing AVPs. As a 812 result, relays never originate messages, do not need to understand 813 the semantics of messages or non-routing AVPs, and are capable of 814 handling any Diameter application or message type. Since relays 815 make decisions based on information in routing AVPs and realm 816 forwarding tables they do not keep state on NAS resource usage or 817 sessions in progress. 819 Redirect Agent 821 Rather than forwarding requests and responses between clients and 822 servers, redirect agents refer clients to servers and allow them 823 to communicate directly. Since redirect agents do not sit in the 824 forwarding path, they do not alter any AVPs transiting between 825 client and server. Redirect agents do not originate messages and 826 are capable of handling any message type, although they may be 827 configured only to redirect messages of certain types, while 828 acting as relay or proxy agents for other types. As with proxy 829 agents, redirect agents do not keep state with respect to sessions 830 or NAS resources. 832 Roaming Relationships 834 Roaming relationships include relationships between companies and 835 ISPs, relationships among peer ISPs within a roaming consortium, 836 and relationships between an ISP and a roaming consortium. 838 Session 840 A session is a related progression of events devoted to a 841 particular activity. Each application SHOULD provide guidelines 842 as to when a session begins and ends. All Diameter packets with 843 the same Session-Identifier are considered to be part of the same 844 session. 846 Session state 848 A stateful agent is one that maintains session state information, 849 by keeping track of all authorized active sessions. Each 850 authorized session is bound to a particular service, and its state 851 is considered active either until it is notified otherwise, or by 852 expiration. 854 Sub-session 856 A sub-session represents a distinct service (e.g., QoS or data 857 characteristics) provided to a given session. These services may 858 happen concurrently (e.g., simultaneous voice and data transfer 859 during the same session) or serially. These changes in sessions 860 are tracked with the Accounting-Sub-Session-Id. 862 Transaction state 864 The Diameter protocol requires that agents maintain transaction 865 state, which is used for failover purposes. Transaction state 866 implies that upon forwarding a request, the Hop-by-Hop identifier 867 is saved; the field is replaced with a locally unique identifier, 868 which is restored to its original value when the corresponding 869 answer is received. The request's state is released upon receipt 870 of the answer. A stateless agent is one that only maintains 871 transaction state. 873 Translation Agent 875 A translation agent is a stateful Diameter node that performs 876 protocol translation between Diameter and another AAA protocol, 877 such as RADIUS. 879 Transport Connection 881 A transport connection is a TCP or SCTP connection existing 882 directly between two Diameter peers, otherwise known as a Peer- 883 to-Peer Connection. 885 Upstream 887 Upstream is used to identify the direction of a particular 888 Diameter message from the access device towards the home server. 890 User 892 The entity requesting or using some resource, in support of which 893 a Diameter client has generated a request. 895 2. Protocol Overview 897 The base Diameter protocol may be used by itself for accounting 898 applications, but for use in authentication and authorization it is 899 always extended for a particular application. Two Diameter 900 applications are defined by companion documents: NASREQ [RFC4005], 901 Mobile IPv4 [RFC4004]. These applications are introduced in this 902 document but specified elsewhere. Additional Diameter applications 903 MAY be defined in the future (see Section 11.3). 905 Diameter Clients MUST support the base protocol, which includes 906 accounting. In addition, they MUST fully support each Diameter 907 application that is needed to implement the client's service, e.g., 908 NASREQ and/or Mobile IPv4. A Diameter Client that does not support 909 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 910 Client" where X is the application which it supports, and not a 911 "Diameter Client". 913 Diameter Servers MUST support the base protocol, which includes 914 accounting. In addition, they MUST fully support each Diameter 915 application that is needed to implement the intended service, e.g., 916 NASREQ and/or Mobile IPv4. A Diameter Server that does not support 917 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 918 Server" where X is the application which it supports, and not a 919 "Diameter Server". 921 Diameter Relays and redirect agents are, by definition, protocol 922 transparent, and MUST transparently support the Diameter base 923 protocol, which includes accounting, and all Diameter applications. 925 Diameter proxies MUST support the base protocol, which includes 926 accounting. In addition, they MUST fully support each Diameter 927 application that is needed to implement proxied services, e.g., 928 NASREQ and/or Mobile IPv4. A Diameter proxy which does not support 929 also both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 930 Proxy" where X is the application which it supports, and not a 931 "Diameter Proxy". 933 The base Diameter protocol concerns itself with capabilities 934 negotiation, how messages are sent and how peers may eventually be 935 abandoned. The base protocol also defines certain rules that apply 936 to all exchanges of messages between Diameter nodes. 938 Communication between Diameter peers begins with one peer sending a 939 message to another Diameter peer. The set of AVPs included in the 940 message is determined by a particular Diameter application. One AVP 941 that is included to reference a user's session is the Session-Id. 943 The initial request for authentication and/or authorization of a user 944 would include the Session-Id. The Session-Id is then used in all 945 subsequent messages to identify the user's session (see Section 8 for 946 more information). The communicating party may accept the request, 947 or reject it by returning an answer message with the Result-Code AVP 948 set to indicate an error occurred. The specific behavior of the 949 Diameter server or client receiving a request depends on the Diameter 950 application employed. 952 Session state (associated with a Session-Id) MUST be freed upon 953 receipt of the Session-Termination-Request, Session-Termination- 954 Answer, expiration of authorized service time in the Session-Timeout 955 AVP, and according to rules established in a particular Diameter 956 application. 958 2.1. Transport 960 Transport profile is defined in [RFC3539]. 962 The base Diameter protocol is run on port 3868 of both TCP [TCP] and 963 SCTP [RFC2960] transport protocols. 965 Diameter clients MUST support either TCP or SCTP, while agents and 966 servers MUST support both. Future versions of this specification MAY 967 mandate that clients support SCTP. 969 A Diameter node MAY initiate connections from a source port other 970 than the one that it declares it accepts incoming connections on, and 971 MUST be prepared to receive connections on port 3868. A given 972 Diameter instance of the peer state machine MUST NOT use more than 973 one transport connection to communicate with a given peer, unless 974 multiple instances exist on the peer in which case a separate 975 connection per process is allowed. 977 When no transport connection exists with a peer, an attempt to 978 connect SHOULD be periodically made. This behavior is handled via 979 the Tc timer, whose recommended value is 30 seconds. There are 980 certain exceptions to this rule, such as when a peer has terminated 981 the transport connection stating that it does not wish to 982 communicate. 984 When connecting to a peer and either zero or more transports are 985 specified, SCTP SHOULD be tried first, followed by TCP. See Section 986 5.2 for more information on peer discovery. 988 Diameter implementations SHOULD be able to interpret ICMP protocol 989 port unreachable messages as explicit indications that the server is 990 not reachable, subject to security policy on trusting such messages. 992 Diameter implementations SHOULD also be able to interpret a reset 993 from the transport and timed-out connection attempts. If Diameter 994 receives data up from TCP that cannot be parsed or identified as a 995 Diameter error made by the peer, the stream is compromised and cannot 996 be recovered. The transport connection MUST be closed using a RESET 997 call (send a TCP RST bit) or an SCTP ABORT message (graceful closure 998 is compromised). 1000 2.1.1. SCTP Guidelines 1002 The following are guidelines for Diameter implementations that 1003 support SCTP: 1005 1. For interoperability: All Diameter nodes MUST be prepared to 1006 receive Diameter messages on any SCTP stream in the association. 1008 2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP 1009 streams available to the association to prevent head-of-the-line 1010 blocking. 1012 2.2. Securing Diameter Messages 1014 Diameter clients, such as Network Access Servers (NASes) and Mobility 1015 Agents MAY support TLS [RFC4346]. Diameter servers MUST support TLS. 1016 IPSec [RFC4301] can be deployed between Diameter peers as an 1017 additional security measure independent of the Diameter protocol. 1018 The Diameter protocol SHOULD NOT be used without any security 1019 mechanism. 1021 2.3. Diameter Application Compliance 1023 Application Identifiers are advertised during the capabilities 1024 exchange phase (see Section 5.3). For a given application, 1025 advertising support of an application implies that the sender 1026 supports all command codes, and the AVPs specified in the associated 1027 ABNFs, described in the specification. 1029 An implementation MAY add arbitrary non-mandatory AVPs to any command 1030 defined in an application, including vendor-specific AVPs. Please 1031 refer to Section 11.1.1 for details. 1033 2.4. Application Identifiers 1035 Each Diameter application MUST have an IANA assigned Application 1036 Identifier (see Section 11.3). The base protocol does not require an 1037 Application Identifier since its support is mandatory. During the 1038 capabilities exchange, Diameter nodes inform their peers of locally 1039 supported applications. Furthermore, all Diameter messages contain 1040 an Application Identifier, which is used in the message forwarding 1041 process. 1043 The following Application Identifier values are defined: 1045 Diameter Common Messages 0 1046 NASREQ 1 [RFC4005] 1047 Mobile-IP 2 [RFC4004] 1048 Diameter Base Accounting 3 1049 Relay 0xffffffff 1051 Relay and redirect agents MUST advertise the Relay Application 1052 Identifier, while all other Diameter nodes MUST advertise locally 1053 supported applications. The receiver of a Capabilities Exchange 1054 message advertising Relay service MUST assume that the sender 1055 supports all current and future applications. 1057 Diameter relay and proxy agents are responsible for finding an 1058 upstream server that supports the application of a particular 1059 message. If none can be found, an error message is returned with the 1060 Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. 1062 2.5. Connections vs. Sessions 1064 This section attempts to provide the reader with an understanding of 1065 the difference between connection and session, which are terms used 1066 extensively throughout this document. 1068 A connection is a transport level connection between two peers, used 1069 to send and receive Diameter messages. A session is a logical 1070 concept at the application layer, and is shared between an access 1071 device and a server, and is identified via the Session-Id AVP. 1073 +--------+ +-------+ +--------+ 1074 | Client | | Relay | | Server | 1075 +--------+ +-------+ +--------+ 1076 <----------> <----------> 1077 peer connection A peer connection B 1079 <-----------------------------> 1080 User session x 1082 Figure 1: Diameter connections and sessions 1084 In the example provided in Figure 1, peer connection A is established 1085 between the Client and its local Relay. Peer connection B is 1086 established between the Relay and the Server. User session X spans 1087 from the Client via the Relay to the Server. Each "user" of a 1088 service causes an auth request to be sent, with a unique session 1089 identifier. Once accepted by the server, both the client and the 1090 server are aware of the session. 1092 It is important to note that there is no relationship between a 1093 connection and a session, and that Diameter messages for multiple 1094 sessions are all multiplexed through a single connection. Also note 1095 that Diameter messages pertaining to the session, both application 1096 specific and those that are defined in this document such as ASR/ASA, 1097 RAR/RAA and STR/STA MUST carry the application identifier of the 1098 application. Diameter messages pertaining to peer connection 1099 establishment and maintenance such as CER/CEA, DWR/DWA and DPR/DPA 1100 MUST carry an application id of zero (0). 1102 2.6. Peer Table 1104 The Diameter Peer Table is used in message forwarding, and referenced 1105 by the Routing Table. A Peer Table entry contains the following 1106 fields: 1108 Host identity 1110 Following the conventions described for the DiameterIdentity 1111 derived AVP data format in Section 4.4. This field contains the 1112 contents of the Origin-Host (Section 6.3) AVP found in the CER or 1113 CEA message. 1115 StatusT 1117 This is the state of the peer entry, and MUST match one of the 1118 values listed in Section 5.6. 1120 Static or Dynamic 1122 Specifies whether a peer entry was statically configured, or 1123 dynamically discovered. 1125 Expiration time 1127 Specifies the time at which dynamically discovered peer table 1128 entries are to be either refreshed, or expired. 1130 TLS Enabled 1132 Specifies whether TLS is to be used when communicating with the 1133 peer. 1135 Additional security information, when needed (e.g., keys, 1136 certificates) 1138 2.7. Routing Table 1140 All Realm-Based routing lookups are performed against what is 1141 commonly known as the Routing Table (see Section 12). A Routing 1142 Table Entry contains the following fields: 1144 Realm Name 1146 This is the field that is typically used as a primary key in the 1147 routing table lookups. Note that some implementations perform 1148 their lookups based on longest-match-from-the-right on the realm 1149 rather than requiring an exact match. 1151 Application Identifier 1153 An application is identified by an application id. A route entry 1154 can have a different destination based on the application 1155 identification in the message header. This field MUST be used as 1156 a secondary key field in routing table lookups. 1158 Local Action 1160 The Local Action field is used to identify how a message should be 1161 treated. The following actions are supported: 1163 1. LOCAL - Diameter messages that resolve to a route entry with 1164 the Local Action set to Local can be satisfied locally, and do 1165 not need to be routed to another server. 1167 2. RELAY - All Diameter messages that fall within this category 1168 MUST be routed to a next hop server, without modifying any 1169 non-routing AVPs. See Section 6.1.9 for relaying guidelines 1171 3. PROXY - All Diameter messages that fall within this category 1172 MUST be routed to a next hop server. The local server MAY 1173 apply its local policies to the message by including new AVPs 1174 to the message prior to routing. See Section 6.1.9 for 1175 proxying guidelines. 1177 4. REDIRECT - Diameter messages that fall within this category 1178 MUST have the identity of the home Diameter server(s) 1179 appended, and returned to the sender of the message. See 1180 Section 6.1.9 for redirect guidelines. 1182 Server Identifier 1184 One or more servers the message is to be routed to. These servers 1185 MUST also be present in the Peer table. When the Local Action is 1186 set to RELAY or PROXY, this field contains the identity of the 1187 server(s) the message must be routed to. When the Local Action 1188 field is set to REDIRECT, this field contains the identity of one 1189 or more servers the message should be redirected to. 1191 Static or Dynamic 1193 Specifies whether a route entry was statically configured, or 1194 dynamically discovered. 1196 Expiration time 1198 Specifies the time which a dynamically discovered route table 1199 entry expires. 1201 It is important to note that Diameter agents MUST support at least 1202 one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation. 1203 Agents do not need to support all modes of operation in order to 1204 conform with the protocol specification, but MUST follow the protocol 1205 compliance guidelines in Section 2. Relay agents MUST NOT reorder 1206 AVPs, and proxies MUST NOT reorder AVPs. 1208 The routing table MAY include a default entry that MUST be used for 1209 any requests not matching any of the other entries. The routing 1210 table MAY consist of only such an entry. 1212 When a request is routed, the target server MUST have advertised the 1213 Application Identifier (see Section 2.4) for the given message, or 1214 have advertised itself as a relay or proxy agent. Otherwise, an 1215 error is returned with the Result-Code AVP set to 1216 DIAMETER_UNABLE_TO_DELIVER. 1218 2.8. Role of Diameter Agents 1220 In addition to client and servers, the Diameter protocol introduces 1221 relay, proxy, redirect, and translation agents, each of which is 1222 defined in Section 1.3. These Diameter agents are useful for several 1223 reasons: 1225 o They can distribute administration of systems to a configurable 1226 grouping, including the maintenance of security associations. 1228 o They can be used for concentration of requests from an number of 1229 co-located or distributed NAS equipment sets to a set of like user 1230 groups. 1232 o They can do value-added processing to the requests or responses. 1234 o They can be used for load balancing. 1236 o A complex network will have multiple authentication sources, they 1237 can sort requests and forward towards the correct target. 1239 The Diameter protocol requires that agents maintain transaction 1240 state, which is used for failover purposes. Transaction state 1241 implies that upon forwarding a request, its Hop-by-Hop identifier is 1242 saved; the field is replaced with a locally unique identifier, which 1243 is restored to its original value when the corresponding answer is 1244 received. The request's state is released upon receipt of the 1245 answer. A stateless agent is one that only maintains transaction 1246 state. 1248 The Proxy-Info AVP allows stateless agents to add local state to a 1249 Diameter request, with the guarantee that the same state will be 1250 present in the answer. However, the protocol's failover procedures 1251 require that agents maintain a copy of pending requests. 1253 A stateful agent is one that maintains session state information; by 1254 keeping track of all authorized active sessions. Each authorized 1255 session is bound to a particular service, and its state is considered 1256 active either until it is notified otherwise, or by expiration. Each 1257 authorized session has an expiration, which is communicated by 1258 Diameter servers via the Session-Timeout AVP. 1260 Maintaining session state MAY be useful in certain applications, such 1261 as: 1263 o Protocol translation (e.g., RADIUS <-> Diameter) 1265 o Limiting resources authorized to a particular user 1267 o Per user or transaction auditing 1269 A Diameter agent MAY act in a stateful manner for some requests and 1270 be stateless for others. A Diameter implementation MAY act as one 1271 type of agent for some requests, and as another type of agent for 1272 others. 1274 2.8.1. Relay Agents 1276 Relay Agents are Diameter agents that accept requests and route 1277 messages to other Diameter nodes based on information found in the 1278 messages (e.g., Destination-Realm). This routing decision is 1279 performed using a list of supported realms, and known peers. This is 1280 known as the Routing Table, as is defined further in Section 2.7. 1282 Relays MAY be used to aggregate requests from multiple Network Access 1283 Servers (NASes) within a common geographical area (POP). The use of 1284 Relays is advantageous since it eliminates the need for NASes to be 1285 configured with the necessary security information they would 1286 otherwise require to communicate with Diameter servers in other 1287 realms. Likewise, this reduces the configuration load on Diameter 1288 servers that would otherwise be necessary when NASes are added, 1289 changed or deleted. 1291 Relays modify Diameter messages by inserting and removing routing 1292 information, but do not modify any other portion of a message. 1293 Relays SHOULD NOT maintain session state but MUST maintain 1294 transaction state. 1296 +------+ ---------> +------+ ---------> +------+ 1297 | | 1. Request | | 2. Request | | 1298 | NAS | | DRL | | HMS | 1299 | | 4. Answer | | 3. Answer | | 1300 +------+ <--------- +------+ <--------- +------+ 1301 example.net example.net example.com 1303 Figure 2: Relaying of Diameter messages 1305 The example provided in Figure 2 depicts a request issued from NAS, 1306 which is an access device, for the user bob@example.com. Prior to 1307 issuing the request, NAS performs a Diameter route lookup, using 1308 "example.com" as the key, and determines that the message is to be 1309 relayed to DRL, which is a Diameter Relay. DRL performs the same 1310 route lookup as NAS, and relays the message to HMS, which is 1311 example.com's Home Diameter Server. HMS identifies that the request 1312 can be locally supported (via the realm), processes the 1313 authentication and/or authorization request, and replies with an 1314 answer, which is routed back to NAS using saved transaction state. 1316 Since Relays do not perform any application level processing, they 1317 provide relaying services for all Diameter applications, and 1318 therefore MUST advertise the Relay Application Identifier. 1320 2.8.2. Proxy Agents 1322 Similarly to relays, proxy agents route Diameter messages using the 1323 Diameter Routing Table. However, they differ since they modify 1324 messages to implement policy enforcement. This requires that proxies 1325 maintain the state of their downstream peers (e.g., access devices) 1326 to enforce resource usage, provide admission control, and 1327 provisioning. 1329 Proxies MAY be used in call control centers or access ISPs that 1330 provide outsourced connections, they can monitor the number and types 1331 of ports in use, and make allocation and admission decisions 1332 according to their configuration. 1334 Proxies that wish to limit resources MUST maintain session state. 1335 All proxies MUST maintain transaction state. 1337 Since enforcing policies requires an understanding of the service 1338 being provided, Proxies MUST only advertise the Diameter applications 1339 they support. 1341 2.8.3. Redirect Agents 1343 Redirect agents are useful in scenarios where the Diameter routing 1344 configuration needs to be centralized. An example is a redirect 1345 agent that provides services to all members of a consortium, but does 1346 not wish to be burdened with relaying all messages between realms. 1347 This scenario is advantageous since it does not require that the 1348 consortium provide routing updates to its members when changes are 1349 made to a member's infrastructure. 1351 Since redirect agents do not relay messages, and only return an 1352 answer with the information necessary for Diameter agents to 1353 communicate directly, they do not modify messages. Since redirect 1354 agents do not receive answer messages, they cannot maintain session 1355 state. Further, since redirect agents never relay requests, they are 1356 not required to maintain transaction state. 1358 The example provided in Figure 3 depicts a request issued from the 1359 access device, NAS, for the user bob@example.com. The message is 1360 forwarded by the NAS to its relay, DRL, which does not have a routing 1361 entry in its Diameter Routing Table for example.com. DRL has a 1362 default route configured to DRD, which is a redirect agent that 1363 returns a redirect notification to DRL, as well as HMS' contact 1364 information. Upon receipt of the redirect notification, DRL 1365 establishes a transport connection with HMS, if one doesn't already 1366 exist, and forwards the request to it. 1368 +------+ 1369 | | 1370 | DRD | 1371 | | 1372 +------+ 1373 ^ | 1374 2. Request | | 3. Redirection 1375 | | Notification 1376 | v 1377 +------+ ---------> +------+ ---------> +------+ 1378 | | 1. Request | | 4. Request | | 1379 | NAS | | DRL | | HMS | 1380 | | 6. Answer | | 5. Answer | | 1381 +------+ <--------- +------+ <--------- +------+ 1382 example.net example.net example.com 1384 Figure 3: Redirecting a Diameter Message 1386 Since redirect agents do not perform any application level 1387 processing, they provide relaying services for all Diameter 1388 applications, and therefore MUST advertise the Relay Application 1389 Identifier. 1391 2.8.4. Translation Agents 1393 A translation agent is a device that provides translation between two 1394 protocols (e.g., RADIUS<->Diameter, TACACS+<->Diameter). Translation 1395 agents are likely to be used as aggregation servers to communicate 1396 with a Diameter infrastructure, while allowing for the embedded 1397 systems to be migrated at a slower pace. 1399 Given that the Diameter protocol introduces the concept of long-lived 1400 authorized sessions, translation agents MUST be session stateful and 1401 MUST maintain transaction state. 1403 Translation of messages can only occur if the agent recognizes the 1404 application of a particular request, and therefore translation agents 1405 MUST only advertise their locally supported applications. 1407 +------+ ---------> +------+ ---------> +------+ 1408 | | RADIUS Request | | Diameter Request | | 1409 | NAS | | TLA | | HMS | 1410 | | RADIUS Answer | | Diameter Answer | | 1411 +------+ <--------- +------+ <--------- +------+ 1412 example.net example.net example.com 1413 Figure 4: Translation of RADIUS to Diameter 1415 2.9. Diameter Path Authorization 1417 As noted in Section 2.2, Diameter provides transmission level 1418 security for each connection using TLS. Therefore, each connection 1419 can be authenticated, replay and integrity protected. 1421 In addition to authenticating each connection, each connection as 1422 well as the entire session MUST also be authorized. Before 1423 initiating a connection, a Diameter Peer MUST check that its peers 1424 are authorized to act in their roles. For example, a Diameter peer 1425 may be authentic, but that does not mean that it is authorized to act 1426 as a Diameter Server advertising a set of Diameter applications. 1428 Prior to bringing up a connection, authorization checks are performed 1429 at each connection along the path. Diameter capabilities negotiation 1430 (CER/CEA) also MUST be carried out, in order to determine what 1431 Diameter applications are supported by each peer. Diameter sessions 1432 MUST be routed only through authorized nodes that have advertised 1433 support for the Diameter application required by the session. 1435 As noted in Section 6.1.9, a relay or proxy agent MUST append a 1436 Route-Record AVP to all requests forwarded. The AVP contains the 1437 identity of the peer the request was received from. 1439 The home Diameter server, prior to authorizing a session, MUST check 1440 the Route-Record AVPs to make sure that the route traversed by the 1441 request is acceptable. For example, administrators within the home 1442 realm may not wish to honor requests that have been routed through an 1443 untrusted realm. By authorizing a request, the home Diameter server 1444 is implicitly indicating its willingness to engage in the business 1445 transaction as specified by the contractual relationship between the 1446 server and the previous hop. A DIAMETER_AUTHORIZATION_REJECTED error 1447 message (see Section 7.1.5) is sent if the route traversed by the 1448 request is unacceptable. 1450 A home realm may also wish to check that each accounting request 1451 message corresponds to a Diameter response authorizing the session. 1452 Accounting requests without corresponding authorization responses 1453 SHOULD be subjected to further scrutiny, as should accounting 1454 requests indicating a difference between the requested and provided 1455 service. 1457 Similarly, the local Diameter agent, on receiving a Diameter response 1458 authorizing a session, MUST check the Route-Record AVPs to make sure 1459 that the route traversed by the response is acceptable. At each 1460 step, forwarding of an authorization response is considered evidence 1461 of a willingness to take on financial risk relative to the session. 1462 A local realm may wish to limit this exposure, for example, by 1463 establishing credit limits for intermediate realms and refusing to 1464 accept responses which would violate those limits. By issuing an 1465 accounting request corresponding to the authorization response, the 1466 local realm implicitly indicates its agreement to provide the service 1467 indicated in the authorization response. If the service cannot be 1468 provided by the local realm, then a DIAMETER_UNABLE_TO_COMPLY error 1469 message MUST be sent within the accounting request; a Diameter client 1470 receiving an authorization response for a service that it cannot 1471 perform MUST NOT substitute an alternate service, and then send 1472 accounting requests for the alternate service instead. 1474 3. Diameter Header 1476 A summary of the Diameter header format is shown below. The fields 1477 are transmitted in network byte order. 1479 0 1 2 3 1480 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 1481 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1482 | Version | Message Length | 1483 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1484 | command flags | Command-Code | 1485 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1486 | Application-ID | 1487 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1488 | Hop-by-Hop Identifier | 1489 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1490 | End-to-End Identifier | 1491 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1492 | AVPs ... 1493 +-+-+-+-+-+-+-+-+-+-+-+-+- 1495 Version 1497 This Version field MUST be set to 1 to indicate Diameter Version 1498 1. 1500 Message Length 1502 The Message Length field is three octets and indicates the length 1503 of the Diameter message including the header fields. 1505 Command Flags 1507 The Command Flags field is eight bits. The following bits are 1508 assigned: 1510 0 1 2 3 4 5 6 7 1511 +-+-+-+-+-+-+-+-+ 1512 |R P E T r r r r| 1513 +-+-+-+-+-+-+-+-+ 1515 R(equest) 1517 If set, the message is a request. If cleared, the message is 1518 an answer. 1520 P(roxiable) 1522 If set, the message MAY be proxied, relayed or redirected. If 1523 cleared, the message MUST be locally processed. 1525 E(rror) 1527 If set, the message contains a protocol error, and the message 1528 will not conform to the ABNF described for this command. 1529 Messages with the 'E' bit set are commonly referred to as error 1530 messages. This bit MUST NOT be set in request messages. See 1531 Section 7.2. 1533 T(Potentially re-transmitted message) 1535 This flag is set after a link failover procedure, to aid the 1536 removal of duplicate requests. It is set when resending 1537 requests not yet acknowledged, as an indication of a possible 1538 duplicate due to a link failure. This bit MUST be cleared when 1539 sending a request for the first time, otherwise the sender MUST 1540 set this flag. Diameter agents only need to be concerned about 1541 the number of requests they send based on a single received 1542 request; retransmissions by other entities need not be tracked. 1543 Diameter agents that receive a request with the T flag set, 1544 MUST keep the T flag set in the forwarded request. This flag 1545 MUST NOT be set if an error answer message (e.g., a protocol 1546 error) has been received for the earlier message. It can be 1547 set only in cases where no answer has been received from the 1548 server for a request and the request is sent again. This flag 1549 MUST NOT be set in answer messages. 1551 r(eserved) 1553 These flag bits are reserved for future use, and MUST be set to 1554 zero, and ignored by the receiver. 1556 Command-Code 1558 The Command-Code field is three octets, and is used in order to 1559 communicate the command associated with the message. The 24-bit 1560 address space is managed by IANA (see Section 11.2.1). 1562 Command-Code values 16,777,214 and 16,777,215 (hexadecimal values 1563 FFFFFE -FFFFFF) are reserved for experimental use (See Section 1564 11.3). 1566 Application-ID 1568 Application-ID is four octets and is used to identify to which 1569 application the message is applicable for. The application can be 1570 an authentication application, an accounting application or a 1571 vendor specific application. See Section 11.3 for the possible 1572 values that the application-id may use. 1574 The application-id in the header MUST be the same as what is 1575 contained in any relevant application-id AVPs contained in the 1576 message. 1578 Hop-by-Hop Identifier 1580 The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in 1581 network byte order) and aids in matching requests and replies. 1582 The sender MUST ensure that the Hop-by-Hop identifier in a request 1583 is unique on a given connection at any given time, and MAY attempt 1584 to ensure that the number is unique across reboots. The sender of 1585 an Answer message MUST ensure that the Hop-by-Hop Identifier field 1586 contains the same value that was found in the corresponding 1587 request. The Hop-by-Hop identifier is normally a monotonically 1588 increasing number, whose start value was randomly generated. An 1589 answer message that is received with an unknown Hop-by-Hop 1590 Identifier MUST be discarded. 1592 End-to-End Identifier 1594 The End-to-End Identifier is an unsigned 32-bit integer field (in 1595 network byte order) and is used to detect duplicate messages. 1596 Upon reboot implementations MAY set the high order 12 bits to 1597 contain the low order 12 bits of current time, and the low order 1598 20 bits to a random value. Senders of request messages MUST 1599 insert a unique identifier on each message. The identifier MUST 1600 remain locally unique for a period of at least 4 minutes, even 1601 across reboots. The originator of an Answer message MUST ensure 1602 that the End-to-End Identifier field contains the same value that 1603 was found in the corresponding request. The End-to-End Identifier 1604 MUST NOT be modified by Diameter agents of any kind. The 1605 combination of the Origin-Host (see Section 6.3) and this field is 1606 used to detect duplicates. Duplicate requests SHOULD cause the 1607 same answer to be transmitted (modulo the hop-by-hop Identifier 1608 field and any routing AVPs that may be present), and MUST NOT 1609 affect any state that was set when the original request was 1610 processed. Duplicate answer messages that are to be locally 1611 consumed (see Section 6.2) SHOULD be silently discarded. 1613 AVPs 1615 AVPs are a method of encapsulating information relevant to the 1616 Diameter message. See Section 4 for more information on AVPs. 1618 3.1. Command Codes 1620 Each command Request/Answer pair is assigned a command code, and the 1621 sub-type (i.e., request or answer) is identified via the 'R' bit in 1622 the Command Flags field of the Diameter header. 1624 Every Diameter message MUST contain a command code in its header's 1625 Command-Code field, which is used to determine the action that is to 1626 be taken for a particular message. The following Command Codes are 1627 defined in the Diameter base protocol: 1629 Command-Name Abbrev. Code Reference 1630 -------------------------------------------------------- 1631 Abort-Session-Request ASR 274 8.5.1 1632 Abort-Session-Answer ASA 274 8.5.2 1633 Accounting-Request ACR 271 9.7.1 1634 Accounting-Answer ACA 271 9.7.2 1635 Capabilities-Exchange- CER 257 5.3.1 1636 Request 1637 Capabilities-Exchange- CEA 257 5.3.2 1638 Answer 1639 Device-Watchdog-Request DWR 280 5.5.1 1640 Device-Watchdog-Answer DWA 280 5.5.2 1641 Disconnect-Peer-Request DPR 282 5.4.1 1642 Disconnect-Peer-Answer DPA 282 5.4.2 1643 Re-Auth-Request RAR 258 8.3.1 1644 Re-Auth-Answer RAA 258 8.3.2 1645 Session-Termination- STR 275 8.4.1 1646 Request 1647 Session-Termination- STA 275 8.4.2 1648 Answer 1650 3.2. Command Code ABNF specification 1652 Every Command Code defined MUST include a corresponding ABNF 1653 specification, which is used to define the AVPs that MUST or MAY be 1654 present. The following format is used in the definition: 1656 command-def = command-name "::=" diameter-message 1658 command-name = diameter-name 1659 diameter-name = ALPHA *(ALPHA / DIGIT / "-") 1661 diameter-message = header [ *fixed] [ *required] [ *optional] 1663 header = "<" "Diameter Header:" command-id 1664 [r-bit] [p-bit] [e-bit] [application-id] ">" 1666 application-id = 1*DIGIT 1668 command-id = 1*DIGIT 1669 ; The Command Code assigned to the command 1671 r-bit = ", REQ" 1672 ; If present, the 'R' bit in the Command 1673 ; Flags is set, indicating that the message 1674 ; is a request, as opposed to an answer. 1676 p-bit = ", PXY" 1677 ; If present, the 'P' bit in the Command 1678 ; Flags is set, indicating that the message 1679 ; is proxiable. 1681 e-bit = ", ERR" 1682 ; If present, the 'E' bit in the Command 1683 ; Flags is set, indicating that the answer 1684 ; message contains a Result-Code AVP in 1685 ; the "protocol error" class. 1687 fixed = [qual] "<" avp-spec ">" 1688 ; Defines the fixed position of an AVP 1690 required = [qual] "{" avp-spec "}" 1691 ; The AVP MUST be present and can appear 1692 ; anywhere in the message. 1694 optional = [qual] "[" avp-name "]" 1695 ; The avp-name in the 'optional' rule cannot 1696 ; evaluate to any AVP Name which is included 1697 ; in a fixed or required rule. The AVP can 1698 ; appear anywhere in the message. 1700 qual = [min] "*" [max] 1701 ; See ABNF conventions, RFC 4234 Section 6.6. 1702 ; The absence of any qualifiers depends on 1703 ; whether it precedes a fixed, required, or 1704 ; optional rule. If a fixed or required rule has 1705 ; no qualifier, then exactly one such AVP MUST 1706 ; be present. If an optional rule has no 1707 ; qualifier, then 0 or 1 such AVP may be 1708 ; present. 1709 ; 1710 ; NOTE: "[" and "]" have a different meaning 1711 ; than in ABNF (see the optional rule, above). 1712 ; These braces cannot be used to express 1713 ; optional fixed rules (such as an optional 1714 ; ICV at the end). To do this, the convention 1715 ; is '0*1fixed'. 1717 min = 1*DIGIT 1718 ; The minimum number of times the element may 1719 ; be present. The default value is zero. 1721 max = 1*DIGIT 1722 ; The maximum number of times the element may 1723 ; be present. The default value is infinity. A 1724 ; value of zero implies the AVP MUST NOT be 1725 ; present. 1727 avp-spec = diameter-name 1728 ; The avp-spec has to be an AVP Name, defined 1729 ; in the base or extended Diameter 1730 ; specifications. 1732 avp-name = avp-spec / "AVP" 1733 ; The string "AVP" stands for *any* arbitrary 1734 ; AVP Name, which does not conflict with the 1735 ; required or fixed position AVPs defined in 1736 ; the command code definition. 1738 The following is a definition of a fictitious command code: 1740 Example-Request ::= < Diameter Header: 9999999, REQ, PXY > 1741 { User-Name } 1742 * { Origin-Host } 1743 * [ AVP 1745 3.3. Diameter Command Naming Conventions 1747 Diameter command names typically includes one or more English words 1748 followed by the verb Request or Answer. Each English word is 1749 delimited by a hyphen. A three-letter acronym for both the request 1750 and answer is also normally provided. 1752 An example is a message set used to terminate a session. The command 1753 name is Session-Terminate-Request and Session-Terminate-Answer, while 1754 the acronyms are STR and STA, respectively. 1756 Both the request and the answer for a given command share the same 1757 command code. The request is identified by the R(equest) bit in the 1758 Diameter header set to one (1), to ask that a particular action be 1759 performed, such as authorizing a user or terminating a session. Once 1760 the receiver has completed the request it issues the corresponding 1761 answer, which includes a result code that communicates one of the 1762 following: 1764 o The request was successful 1766 o The request failed 1768 o An additional request must be sent to provide information the peer 1769 requires prior to returning a successful or failed answer. 1771 o The receiver could not process the request, but provides 1772 information about a Diameter peer that is able to satisfy the 1773 request, known as redirect. 1775 Additional information, encoded within AVPs, MAY also be included in 1776 answer messages. 1778 4. Diameter AVPs 1780 Diameter AVPs carry specific authentication, accounting, 1781 authorization and routing information as well as configuration 1782 details for the request and reply. 1784 Some AVPs MAY be listed more than once. The effect of such an AVP is 1785 specific, and is specified in each case by the AVP description. 1787 Each AVP of type OctetString MUST be padded to align on a 32-bit 1788 boundary, while other AVP types align naturally. A number of zero- 1789 valued bytes are added to the end of the AVP Data field till a word 1790 boundary is reached. The length of the padding is not reflected in 1791 the AVP Length field. 1793 4.1. AVP Header 1795 The fields in the AVP header MUST be sent in network byte order. The 1796 format of the header is: 1798 0 1 2 3 1799 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 1800 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1801 | AVP Code | 1802 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1803 |V M r r r r r r| AVP Length | 1804 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1805 | Vendor-ID (opt) | 1806 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1807 | Data ... 1808 +-+-+-+-+-+-+-+-+ 1810 AVP Code 1812 The AVP Code, combined with the Vendor-Id field, identifies the 1813 attribute uniquely. AVP numbers 1 through 255 are reserved for 1814 backward compatibility with RADIUS, without setting the Vendor-Id 1815 field. AVP numbers 256 and above are used for Diameter, which are 1816 allocated by IANA (see Section 11.1). 1818 AVP Flags 1820 The AVP Flags field informs the receiver how each attribute must 1821 be handled. The 'r' (reserved) bits are unused and SHOULD be set 1822 to 0. Note that subsequent Diameter applications MAY define 1823 additional bits within the AVP Header, and an unrecognized bit 1824 SHOULD be considered an error. 1826 The 'M' Bit, known as the Mandatory bit, indicates whether support 1827 of the AVP is required. If an AVP with the 'M' bit set is 1828 received by a Diameter client, server, proxy, or translation agent 1829 and either the AVP or its value is unrecognized, the message MUST 1830 be rejected. Diameter Relay and redirect agents MUST NOT reject 1831 messages with unrecognized AVPs. 1833 The 'M' bit MUST be set according to the rules defined for the AVP 1834 containing it. In order to preserve interoperability, a Diameter 1835 implementation MUST be able to exclude from a Diameter message any 1836 Mandatory AVP which is neither defined in the base Diameter 1837 protocol nor in any of the Diameter Application specifications 1838 governing the message in which it appears. It MAY do this in one 1839 of the following ways: 1841 1. If a message is rejected because it contains a Mandatory AVP 1842 which is neither defined in the base Diameter standard nor in 1843 any of the Diameter Application specifications governing the 1844 message in which it appears, the implementation may resend the 1845 message without the AVP, possibly inserting additional 1846 standard AVPs instead. 1848 2. A configuration option may be provided on a system wide, per 1849 peer, or per realm basis that would allow/prevent particular 1850 Mandatory AVPs to be sent. Thus an administrator could change 1851 the configuration to avoid interoperability problems. 1853 Diameter implementations are required to support all Mandatory 1854 AVPs which are allowed by the message's formal syntax and defined 1855 either in the base Diameter standard or in one of the Diameter 1856 Application specifications governing the message. 1858 AVPs with the 'M' bit cleared are informational only and a 1859 receiver that receives a message with such an AVP that is not 1860 supported, or whose value is not supported, MAY simply ignore the 1861 AVP. 1863 The 'V' bit, known as the Vendor-Specific bit, indicates whether 1864 the optional Vendor-ID field is present in the AVP header. When 1865 set the AVP Code belongs to the specific vendor code address 1866 space. 1868 Unless otherwise noted, AVPs will have the following default AVP 1869 Flags field settings: 1871 The 'M' bit MUST be set. The 'V' bit MUST NOT be set. 1873 AVP Length 1875 The AVP Length field is three octets, and indicates the number of 1876 octets in this AVP including the AVP Code, AVP Length, AVP Flags, 1877 Vendor-ID field (if present) and the AVP data. If a message is 1878 received with an invalid attribute length, the message SHOULD be 1879 rejected. 1881 4.1.1. Optional Header Elements 1883 The AVP Header contains one optional field. This field is only 1884 present if the respective bit-flag is enabled. 1886 Vendor-ID 1888 The Vendor-ID field is present if the 'V' bit is set in the AVP 1889 Flags field. The optional four-octet Vendor-ID field contains the 1890 IANA assigned "SMI Network Management Private Enterprise Codes" 1891 [RFC3232] value, encoded in network byte order. Any vendor 1892 wishing to implement a vendor-specific Diameter AVP MUST use their 1893 own Vendor-ID along with their privately managed AVP address 1894 space, guaranteeing that they will not collide with any other 1895 vendor's vendor-specific AVP(s), nor with future IETF 1896 applications. 1898 A vendor ID value of zero (0) corresponds to the IETF adopted AVP 1899 values, as managed by the IANA. Since the absence of the vendor 1900 ID field implies that the AVP in question is not vendor specific, 1901 implementations MUST NOT use the zero (0) vendor ID. 1903 4.2. Basic AVP Data Formats 1905 The Data field is zero or more octets and contains information 1906 specific to the Attribute. The format and length of the Data field 1907 is determined by the AVP Code and AVP Length fields. The format of 1908 the Data field MUST be one of the following base data types or a data 1909 type derived from the base data types. In the event that a new Basic 1910 AVP Data Format is needed, a new version of this RFC must be created. 1912 OctetString 1914 The data contains arbitrary data of variable length. Unless 1915 otherwise noted, the AVP Length field MUST be set to at least 8 1916 (12 if the 'V' bit is enabled). AVP Values of this type that are 1917 not a multiple of four-octets in length is followed by the 1918 necessary padding so that the next AVP (if any) will start on a 1919 32-bit boundary. 1921 Integer32 1923 32 bit signed value, in network byte order. The AVP Length field 1924 MUST be set to 12 (16 if the 'V' bit is enabled). 1926 Integer64 1928 64 bit signed value, in network byte order. The AVP Length field 1929 MUST be set to 16 (20 if the 'V' bit is enabled). 1931 Unsigned32 1933 32 bit unsigned value, in network byte order. The AVP Length 1934 field MUST be set to 12 (16 if the 'V' bit is enabled). 1936 Unsigned64 1938 64 bit unsigned value, in network byte order. The AVP Length 1939 field MUST be set to 16 (20 if the 'V' bit is enabled). 1941 Float32 1943 This represents floating point values of single precision as 1944 described by [FLOATPOINT]. The 32-bit value is transmitted in 1945 network byte order. The AVP Length field MUST be set to 12 (16 if 1946 the 'V' bit is enabled). 1948 Float64 1950 This represents floating point values of double precision as 1951 described by [FLOATPOINT]. The 64-bit value is transmitted in 1952 network byte order. The AVP Length field MUST be set to 16 (20 if 1953 the 'V' bit is enabled). 1955 Grouped 1957 The Data field is specified as a sequence of AVPs. Each of these 1958 AVPs follows - in the order in which they are specified - 1959 including their headers and padding. The AVP Length field is set 1960 to 8 (12 if the 'V' bit is enabled) plus the total length of all 1961 included AVPs, including their headers and padding. Thus the AVP 1962 length field of an AVP of type Grouped is always a multiple of 4. 1964 4.3. Derived AVP Data Formats 1966 In addition to using the Basic AVP Data Formats, applications may 1967 define data formats derived from the Basic AVP Data Formats. An 1968 application that defines new AVP Derived Data Formats MUST include 1969 them in a section entitled "AVP Derived Data Formats", using the same 1970 format as the definitions below. Each new definition must be either 1971 defined or listed with a reference to the RFC that defines the 1972 format. 1974 The below AVP Derived Data Formats are commonly used by applications. 1976 Address 1978 The Address format is derived from the OctetString AVP Base 1979 Format. It is a discriminated union, representing, for example a 1980 32-bit (IPv4) [IPV4] or 128-bit (IPv6) [RFC4291] address, most 1981 significant octet first. The first two octets of the Address AVP 1982 represents the AddressType, which contains an Address Family 1983 defined in [IANAADFAM]. The AddressType is used to discriminate 1984 the content and format of the remaining octets. 1986 Time 1988 The Time format is derived from the OctetString AVP Base Format. 1989 The string MUST contain four octets, in the same format as the 1990 first four bytes are in the NTP timestamp format. The NTP 1991 Timestamp format is defined in chapter 3 of [RFC4330]. 1993 This represents the number of seconds since 0h on 1 January 1900 1994 with respect to the Coordinated Universal Time (UTC). 1996 On 6h 28m 16s UTC, 7 February 2036 the time value will overflow. 1997 SNTP [RFC4330] describes a procedure to extend the time to 2104. 1998 This procedure MUST be supported by all DIAMETER nodes. 2000 UTF8String 2002 The UTF8String format is derived from the OctetString AVP Base 2003 Format. This is a human readable string represented using the 2004 ISO/IEC IS 10646-1 character set, encoded as an OctetString using 2005 the UTF-8 [RFC3629] transformation format described in RFC 3629. 2007 Since additional code points are added by amendments to the 10646 2008 standard from time to time, implementations MUST be prepared to 2009 encounter any code point from 0x00000001 to 0x7fffffff. Byte 2010 sequences that do not correspond to the valid encoding of a code 2011 point into UTF-8 charset or are outside this range are prohibited. 2013 The use of control codes SHOULD be avoided. When it is necessary 2014 to represent a new line, the control code sequence CR LF SHOULD be 2015 used. 2017 The use of leading or trailing white space SHOULD be avoided. 2019 For code points not directly supported by user interface hardware 2020 or software, an alternative means of entry and display, such as 2021 hexadecimal, MAY be provided. 2023 For information encoded in 7-bit US-ASCII, the UTF-8 charset is 2024 identical to the US-ASCII charset. 2026 UTF-8 may require multiple bytes to represent a single character / 2027 code point; thus the length of an UTF8String in octets may be 2028 different from the number of characters encoded. 2030 Note that the AVP Length field of an UTF8String is measured in 2031 octets, not characters. 2033 DiameterIdentity 2035 The DiameterIdentity format is derived from the OctetString AVP 2036 Base Format. 2038 DiameterIdentity = FQDN 2040 DiameterIdentity value is used to uniquely identify a Diameter 2041 node for purposes of duplicate connection and routing loop 2042 detection. 2044 The contents of the string MUST be the FQDN of the Diameter node. 2045 If multiple Diameter nodes run on the same host, each Diameter 2046 node MUST be assigned a unique DiameterIdentity. If a Diameter 2047 node can be identified by several FQDNs, a single FQDN should be 2048 picked at startup, and used as the only DiameterIdentity for that 2049 node, whatever the connection it is sent on. 2051 DiameterURI 2053 The DiameterURI MUST follow the Uniform Resource Identifiers (URI) 2054 syntax [RFC3986] rules specified below: 2056 "aaa://" FQDN [ port ] [ transport ] [ protocol ] 2058 ; No transport security 2060 "aaas://" FQDN [ port ] [ transport ] [ protocol ] 2062 ; Transport security used 2064 FQDN = Fully Qualified Host Name 2066 port = ":" 1*DIGIT 2068 ; One of the ports used to listen for 2069 ; incoming connections. 2070 ; If absent, 2071 ; the default Diameter port (3868) is 2072 ; assumed. 2074 transport = ";transport=" transport-protocol 2076 ; One of the transports used to listen 2077 ; for incoming connections. If absent, 2078 ; the default SCTP [RFC2960] protocol is 2079 ; assumed. UDP MUST NOT be used when 2080 ; the aaa-protocol field is set to 2081 ; diameter. 2083 transport-protocol = ( "tcp" / "sctp" / "udp" ) 2085 protocol = ";protocol=" aaa-protocol 2087 ; If absent, the default AAA protocol 2088 ; is diameter. 2090 aaa-protocol = ( "diameter" / "radius" / "tacacs+" ) 2092 The following are examples of valid Diameter host identities: 2094 aaa://host.example.com;transport=tcp 2095 aaa://host.example.com:6666;transport=tcp 2096 aaa://host.example.com;protocol=diameter 2097 aaa://host.example.com:6666;protocol=diameter 2098 aaa://host.example.com:6666;transport=tcp;protocol=diameter 2099 aaa://host.example.com:1813;transport=udp;protocol=radius 2101 Enumerated 2103 Enumerated is derived from the Integer32 AVP Base Format. The 2104 definition contains a list of valid values and their 2105 interpretation and is described in the Diameter application 2106 introducing the AVP. 2108 IPFilterRule 2110 The IPFilterRule format is derived from the OctetString AVP Base 2111 Format. It uses the ASCII charset. Packets may be filtered based 2112 on the following information that is associated with it: 2114 Direction (in or out) 2115 Source and destination IP address (possibly masked) 2116 Protocol 2117 Source and destination port (lists or ranges) 2118 TCP flags 2119 IP fragment flag 2120 IP options 2121 ICMP types 2123 Rules for the appropriate direction are evaluated in order, with 2124 the first matched rule terminating the evaluation. Each packet is 2125 evaluated once. If no rule matches, the packet is dropped if the 2126 last rule evaluated was a permit, and passed if the last rule was 2127 a deny. 2129 IPFilterRule filters MUST follow the format: 2131 action dir proto from src to dst [options] 2133 action permit - Allow packets that match the rule. 2134 deny - Drop packets that match the rule. 2136 dir "in" is from the terminal, "out" is to the 2137 terminal. 2139 proto An IP protocol specified by number. The "ip" 2140 keyword means any protocol will match. 2142 src and dst
[ports] 2144 The
may be specified as: 2145 ipno An IPv4 or IPv6 number in dotted- 2146 quad or canonical IPv6 form. Only 2147 this exact IP number will match the 2148 rule. 2149 ipno/bits An IP number as above with a mask 2150 width of the form 1.2.3.4/24. In 2151 this case, all IP numbers from 2152 1.2.3.0 to 1.2.3.255 will match. 2153 The bit width MUST be valid for the 2154 IP version and the IP number MUST 2155 NOT have bits set beyond the mask. 2156 For a match to occur, the same IP 2157 version must be present in the 2158 packet that was used in describing 2159 the IP address. To test for a 2160 particular IP version, the bits part 2161 can be set to zero. The keyword 2162 "any" is 0.0.0.0/0 or the IPv6 2163 equivalent. The keyword "assigned" 2164 is the address or set of addresses 2165 assigned to the terminal. For IPv4, 2166 a typical first rule is often "deny 2167 in ip! assigned" 2169 The sense of the match can be inverted by 2170 preceding an address with the not modifier (!), 2171 causing all other addresses to be matched 2172 instead. This does not affect the selection of 2173 port numbers. 2175 With the TCP, UDP and SCTP protocols, optional 2176 ports may be specified as: 2178 {port/port-port}[,ports[,...]] 2180 The '-' notation specifies a range of ports 2181 (including boundaries). 2183 Fragmented packets that have a non-zero offset 2184 (i.e., not the first fragment) will never match 2185 a rule that has one or more port 2186 specifications. See the frag option for 2187 details on matching fragmented packets. 2189 options: 2190 frag Match if the packet is a fragment and this is not 2191 the first fragment of the datagram. frag may not 2192 be used in conjunction with either tcpflags or 2193 TCP/UDP port specifications. 2195 ipoptions spec 2196 Match if the IP header contains the comma 2197 separated list of options specified in spec. The 2198 supported IP options are: 2200 ssrr (strict source route), lsrr (loose source 2201 route), rr (record packet route) and ts 2202 (timestamp). The absence of a particular option 2203 may be denoted with a '!'. 2205 tcpoptions spec 2206 Match if the TCP header contains the comma 2207 separated list of options specified in spec. The 2208 supported TCP options are: 2210 mss (maximum segment size), window (tcp window 2211 advertisement), sack (selective ack), ts (rfc1323 2212 timestamp) and cc (rfc1644 t/tcp connection 2213 count). The absence of a particular option may 2214 be denoted with a '!'. 2216 established 2217 TCP packets only. Match packets that have the RST 2218 or ACK bits set. 2220 setup TCP packets only. Match packets that have the SYN 2221 bit set but no ACK bit. 2223 tcpflags spec 2224 TCP packets only. Match if the TCP header 2225 contains the comma separated list of flags 2226 specified in spec. The supported TCP flags are: 2228 fin, syn, rst, psh, ack and urg. The absence of a 2229 particular flag may be denoted with a '!'. A rule 2230 that contains a tcpflags specification can never 2231 match a fragmented packet that has a non-zero 2232 offset. See the frag option for details on 2233 matching fragmented packets. 2235 icmptypes types 2236 ICMP packets only. Match if the ICMP type is in 2237 the list types. The list may be specified as any 2238 combination of ranges or individual types 2239 separated by commas. Both the numeric values and 2240 the symbolic values listed below can be used. The 2241 supported ICMP types are: 2243 echo reply (0), destination unreachable (3), 2244 source quench (4), redirect (5), echo request 2245 (8), router advertisement (9), router 2246 solicitation (10), time-to-live exceeded (11), IP 2247 header bad (12), timestamp request (13), 2248 timestamp reply (14), information request (15), 2249 information reply (16), address mask request (17) 2250 and address mask reply (18). 2252 There is one kind of packet that the access device MUST always 2253 discard, that is an IP fragment with a fragment offset of one. 2254 This is a valid packet, but it only has one use, to try to 2255 circumvent firewalls. 2257 An access device that is unable to interpret or apply a deny rule 2258 MUST terminate the session. An access device that is unable to 2259 interpret or apply a permit rule MAY apply a more restrictive 2260 rule. An access device MAY apply deny rules of its own before the 2261 supplied rules, for example to protect the access device owner's 2262 infrastructure. 2264 The rule syntax is a modified subset of ipfw(8) from FreeBSD, and 2265 the ipfw.c code may provide a useful base for implementations. 2267 4.4. Grouped AVP Values 2269 The Diameter protocol allows AVP values of type 'Grouped.' This 2270 implies that the Data field is actually a sequence of AVPs. It is 2271 possible to include an AVP with a Grouped type within a Grouped type, 2272 that is, to nest them. AVPs within an AVP of type Grouped have the 2273 same padding requirements as non-Grouped AVPs, as defined in Section 2274 4. 2276 The AVP Code numbering space of all AVPs included in a Grouped AVP is 2277 the same as for non-grouped AVPs. Further, if any of the AVPs 2278 encapsulated within a Grouped AVP has the 'M' (mandatory) bit set, 2279 the Grouped AVP itself MUST also include the 'M' bit set. 2281 Every Grouped AVP defined MUST include a corresponding grammar, using 2282 ABNF [RFC4234] (with modifications), as defined below. 2284 grouped-avp-def = name "::=" avp 2286 name-fmt = ALPHA *(ALPHA / DIGIT / "-") 2288 name = name-fmt 2289 ; The name has to be the name of an AVP, 2290 ; defined in the base or extended Diameter 2291 ; specifications. 2293 avp = header [ *fixed] [ *required] [ *optional] 2294 [ *fixed] 2296 header = "<" "AVP-Header:" avpcode [vendor] ">" 2298 avpcode = 1*DIGIT 2299 ; The AVP Code assigned to the Grouped AVP 2301 vendor = 1*DIGIT 2302 ; The Vendor-ID assigned to the Grouped AVP. 2303 ; If absent, the default value of zero is 2304 ; used. 2306 4.4.1. Example AVP with a Grouped Data type 2308 The Example-AVP (AVP Code 999999) is of type Grouped and is used to 2309 clarify how Grouped AVP values work. The Grouped Data field has the 2310 following ABNF grammar: 2312 Example-AVP ::= < AVP Header: 999999 > 2313 { Origin-Host } 2314 1*{ Session-Id } 2315 *[ AVP ] 2317 An Example-AVP with Grouped Data follows. 2319 The Origin-Host AVP is required (Section 6.3). In this case: 2321 Origin-Host = "example.com". 2323 One or more Session-Ids must follow. Here there are two: 2325 Session-Id = 2326 "grump.example.com:33041;23432;893;0AF3B81" 2328 Session-Id = 2329 "grump.example.com:33054;23561;2358;0AF3B82" 2331 optional AVPs included are 2333 Recovery-Policy = 2334 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35 2335 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5 2336 c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd 2337 f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a 2338 cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119 2339 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c 2340 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92 2342 Futuristic-Acct-Record = 2343 fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0 2344 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8 2345 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c 2346 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067 2347 d3427475e49968f841 2349 The data for the optional AVPs is represented in hex since the format 2350 of these AVPs is neither known at the time of definition of the 2351 Example-AVP group, nor (likely) at the time when the example instance 2352 of this AVP is interpreted - except by Diameter implementations which 2353 support the same set of AVPs. The encoding example illustrates how 2354 padding is used and how length fields are calculated. Also note that 2355 AVPs may be present in the Grouped AVP value which the receiver 2356 cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record 2357 AVPs). The length of the Example-AVP is the sum of all the length of 2358 the member AVPs including their padding plus the Example-AVP header 2359 size. 2361 This AVP would be encoded as follows: 2363 0 1 2 3 4 5 6 7 2364 +-------+-------+-------+-------+-------+-------+-------+-------+ 2365 0 | Example AVP Header (AVP Code = 999999), Length = 496 | 2366 +-------+-------+-------+-------+-------+-------+-------+-------+ 2367 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 | 2368 +-------+-------+-------+-------+-------+-------+-------+-------+ 2369 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' | 2370 +-------+-------+-------+-------+-------+-------+-------+-------+ 2371 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header | 2372 +-------+-------+-------+-------+-------+-------+-------+-------+ 2373 32 | (AVP Code = 263), Length = 49 | 'g' | 'r' | 'u' | 'm' | 2374 +-------+-------+-------+-------+-------+-------+-------+-------+ 2375 . . . 2376 +-------+-------+-------+-------+-------+-------+-------+-------+ 2377 72 | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding|Padding| 2378 +-------+-------+-------+-------+-------+-------+-------+-------+ 2379 80 | Session-Id AVP Header (AVP Code = 263), Length = 50 | 2380 +-------+-------+-------+-------+-------+-------+-------+-------+ 2381 88 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' | 2382 +-------+-------+-------+-------+-------+-------+-------+-------+ 2383 . . . 2384 +-------+-------+-------+-------+-------+-------+-------+-------+ 2385 120| '5' | '8' | ';' | '0' | 'A' | 'F' | '3' | 'B' | 2386 +-------+-------+-------+-------+-------+-------+-------+-------+ 2387 128| '8' | '2' |Padding|Padding| Recovery-Policy Header (AVP | 2388 +-------+-------+-------+-------+-------+-------+-------+-------+ 2389 136| Code = 8341), Length = 223 | 0x21 | 0x63 | 0xbc | 0x1d | 2390 +-------+-------+-------+-------+-------+-------+-------+-------+ 2391 144| 0x0a | 0xd8 | 0x23 | 0x71 | 0xf6 | 0xbc | 0x09 | 0x48 | 2392 +-------+-------+-------+-------+-------+-------+-------+-------+ 2393 . . . 2394 +-------+-------+-------+-------+-------+-------+-------+-------+ 2395 352| 0x8c | 0x7f | 0x92 |Padding| Futuristic-Acct-Record Header | 2396 +-------+-------+-------+-------+-------+-------+-------+-------+ 2397 328|(AVP Code = 15930),Length = 137| 0xfe | 0x19 | 0xda | 0x58 | 2398 +-------+-------+-------+-------+-------+-------+-------+-------+ 2399 336| 0x02 | 0xac | 0xd9 | 0x8b | 0x07 | 0xa5 | 0xb8 | 0xc6 | 2400 +-------+-------+-------+-------+-------+-------+-------+-------+ 2401 . . . 2402 +-------+-------+-------+-------+-------+-------+-------+-------+ 2403 488| 0xe4 | 0x99 | 0x68 | 0xf8 | 0x41 |Padding|Padding|Padding| 2404 +-------+-------+-------+-------+-------+-------+-------+-------+ 2406 4.5. Diameter Base Protocol AVPs 2408 The following table describes the Diameter AVPs defined in the base 2409 protocol, their AVP Code values, types, possible flag values. 2411 Due to space constraints, the short form DiamIdent is used to 2412 represent DiameterIdentity. 2414 +---------------------+ 2415 | AVP Flag rules | 2416 |----+-----+----+-----| 2417 AVP Section | | |SHLD| MUST| 2418 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT| 2419 -----------------------------------------|----+-----+----+-----| 2420 Acct- 85 9.8.2 Unsigned32 | M | P | | V | 2421 Interim-Interval | | | | | 2422 Accounting- 483 9.8.7 Enumerated | M | P | | V | 2423 Realtime-Required | | | | | 2424 Acct- 50 9.8.5 UTF8String | M | P | | V | 2425 Multi-Session-Id | | | | | 2426 Accounting- 485 9.8.3 Unsigned32 | M | P | | V | 2427 Record-Number | | | | | 2428 Accounting- 480 9.8.1 Enumerated | M | P | | V | 2429 Record-Type | | | | | 2430 Accounting- 44 9.8.4 OctetString| M | P | | V | 2431 Session-Id | | | | | 2432 Accounting- 287 9.8.6 Unsigned64 | M | P | | V | 2433 Sub-Session-Id | | | | | 2434 Acct- 259 6.9 Unsigned32 | M | P | | V | 2435 Application-Id | | | | | 2436 Auth- 258 6.8 Unsigned32 | M | P | | V | 2437 Application-Id | | | | | 2438 Auth-Request- 274 8.7 Enumerated | M | P | | V | 2439 Type | | | | | 2440 Authorization- 291 8.9 Unsigned32 | M | P | | V | 2441 Lifetime | | | | | 2442 Auth-Grace- 276 8.10 Unsigned32 | M | P | | V | 2443 Period | | | | | 2444 Auth-Session- 277 8.11 Enumerated | M | P | | V | 2445 State | | | | | 2446 Re-Auth-Request- 285 8.12 Enumerated | M | P | | V | 2447 Type | | | | | 2448 Class 25 8.20 OctetString| M | P | | V | 2449 Destination-Host 293 6.5 DiamIdent | M | P | | V | 2450 Destination- 283 6.6 DiamIdent | M | P | | V | 2451 Realm | | | | | 2452 Disconnect-Cause 273 5.4.3 Enumerated | M | P | | V | 2453 E2E-Sequence AVP 300 6.15 Grouped | M | P | | V | 2454 Error-Message 281 7.3 UTF8String | | P | | V,M | 2455 Error-Reporting- 294 7.4 DiamIdent | | P | | V,M | 2456 Host | | | | | 2457 Event-Timestamp 55 8.21 Time | M | P | | V | 2458 Experimental- 297 7.6 Grouped | M | P | | V | 2459 Result | | | | | 2460 -----------------------------------------|----+-----+----+-----| 2461 +---------------------+ 2462 | AVP Flag rules | 2463 |----+-----+----+-----| 2464 AVP Section | | |SHLD| MUST| 2465 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT| 2466 -----------------------------------------|----+-----+----+-----| 2467 Experimental- 298 7.7 Unsigned32 | M | P | | V | 2468 Result-Code | | | | | 2469 Failed-AVP 279 7.5 Grouped | M | P | | V | 2470 Firmware- 267 5.3.4 Unsigned32 | | | |P,V,M| 2471 Revision | | | | | 2472 Host-IP-Address 257 5.3.5 Address | M | P | | V | 2473 Inband-Security | M | P | | V | 2474 -Id 299 6.10 Unsigned32 | | | | | 2475 Multi-Round- 272 8.19 Unsigned32 | M | P | | V | 2476 Time-Out | | | | | 2477 Origin-Host 264 6.3 DiamIdent | M | P | | V | 2478 Origin-Realm 296 6.4 DiamIdent | M | P | | V | 2479 Origin-State-Id 278 8.16 Unsigned32 | M | P | | V | 2480 Product-Name 269 5.3.7 UTF8String | | | |P,V,M| 2481 Proxy-Host 280 6.7.3 DiamIdent | M | | | P,V | 2482 Proxy-Info 284 6.7.2 Grouped | M | | | P,V | 2483 Proxy-State 33 6.7.4 OctetString| M | | | P,V | 2484 Redirect-Host 292 6.12 DiamURI | M | P | | V | 2485 Redirect-Host- 261 6.13 Enumerated | M | P | | V | 2486 Usage | | | | | 2487 Redirect-Max- 262 6.14 Unsigned32 | M | P | | V | 2488 Cache-Time | | | | | 2489 Result-Code 268 7.1 Unsigned32 | M | P | | V | 2490 Route-Record 282 6.7.1 DiamIdent | M | | | P,V | 2491 Session-Id 263 8.8 UTF8String | M | P | | V | 2492 Session-Timeout 27 8.13 Unsigned32 | M | P | | V | 2493 Session-Binding 270 8.17 Unsigned32 | M | P | | V | 2494 Session-Server- 271 8.18 Enumerated | M | P | | V | 2495 Failover | | | | | 2496 Supported- 265 5.3.6 Unsigned32 | M | P | | V | 2497 Vendor-Id | | | | | 2498 Termination- 295 8.15 Enumerated | M | P | | V | 2499 Cause | | | | | 2500 User-Name 1 8.14 UTF8String | M | P | | V | 2501 Vendor-Id 266 5.3.3 Unsigned32 | M | P | | V | 2502 Vendor-Specific- 260 6.11 Grouped | M | P | | V | 2503 Application-Id | | | | | 2504 -----------------------------------------|----+-----+----+-----| 2506 5. Diameter Peers 2508 This section describes how Diameter nodes establish connections and 2509 communicate with peers. 2511 5.1. Peer Connections 2513 Although a Diameter node may have many possible peers that it is able 2514 to communicate with, it may not be economical to have an established 2515 connection to all of them. At a minimum, a Diameter node SHOULD have 2516 an established connection with two peers per realm, known as the 2517 primary and secondary peers. Of course, a node MAY have additional 2518 connections, if it is deemed necessary. Typically, all messages for 2519 a realm are sent to the primary peer, but in the event that failover 2520 procedures are invoked, any pending requests are sent to the 2521 secondary peer. However, implementations are free to load balance 2522 requests between a set of peers. 2524 Note that a given peer MAY act as a primary for a given realm, while 2525 acting as a secondary for another realm. 2527 When a peer is deemed suspect, which could occur for various reasons, 2528 including not receiving a DWA within an allotted timeframe, no new 2529 requests should be forwarded to the peer, but failover procedures are 2530 invoked. When an active peer is moved to this mode, additional 2531 connections SHOULD be established to ensure that the necessary number 2532 of active connections exists. 2534 There are two ways that a peer is removed from the suspect peer list: 2536 1. The peer is no longer reachable, causing the transport connection 2537 to be shutdown. The peer is moved to the closed state. 2539 2. Three watchdog messages are exchanged with accepted round trip 2540 times, and the connection to the peer is considered stabilized. 2542 In the event the peer being removed is either the primary or 2543 secondary, an alternate peer SHOULD replace the deleted peer, and 2544 assume the role of either primary or secondary. 2546 5.2. Diameter Peer Discovery 2548 Allowing for dynamic Diameter agent discovery will make it possible 2549 for simpler and more robust deployment of Diameter services. In 2550 order to promote interoperable implementations of Diameter peer 2551 discovery, the following mechanisms are described. These are based 2552 on existing IETF standards. The first option (manual configuration) 2553 MUST be supported by all DIAMETER nodes, while the latter option 2554 (DNS) MAY be supported. 2556 There are two cases where Diameter peer discovery may be performed. 2557 The first is when a Diameter client needs to discover a first-hop 2558 Diameter agent. The second case is when a Diameter agent needs to 2559 discover another agent - for further handling of a Diameter 2560 operation. In both cases, the following 'search order' is 2561 recommended: 2563 1. The Diameter implementation consults its list of static 2564 (manually) configured Diameter agent locations. These will be 2565 used if they exist and respond. 2567 2. The Diameter implementation performs a NAPTR query for a server 2568 in a particular realm. The Diameter implementation has to know 2569 in advance which realm to look for a Diameter agent in. This 2570 could be deduced, for example, from the 'realm' in a NAI that a 2571 Diameter implementation needed to perform a Diameter operation 2572 on. 2574 * The services relevant for the task of transport protocol 2575 selection are those with NAPTR service fields with values 2576 "AAA+D2x", where x is a letter that corresponds to a transport 2577 protocol supported by the domain. This specification defines 2578 D2T for TCP and D2S for SCTP. We also establish an IANA 2579 registry for NAPTR service name to transport protocol 2580 mappings. 2582 These NAPTR records provide a mapping from a domain, to the 2583 SRV record for contacting a server with the specific transport 2584 protocol in the NAPTR services field. The resource record 2585 will contain an empty regular expression and a replacement 2586 value, which is the SRV record for that particular transport 2587 protocol. If the server supports multiple transport 2588 protocols, there will be multiple NAPTR records, each with a 2589 different service value. As per [RFC3403], the client 2590 discards any records whose services fields are not applicable. 2591 For the purposes of this specification, several rules are 2592 defined. 2594 * A client MUST discard any service fields that identify a 2595 resolution service whose value is not "D2X", for values of X 2596 that indicate transport protocols supported by the client. 2597 The NAPTR processing as described in [RFC3403] will result in 2598 discovery of the most preferred transport protocol of the 2599 server that is supported by the client, as well as an SRV 2600 record for the server. 2602 The domain suffixes in the NAPTR replacement field SHOULD 2603 match the domain of the original query. 2605 3. If no NAPTR records are found, the requester queries for those 2606 address records for the destination address, 2607 '_diameter._sctp'.realm or '_diameter._tcp'.realm. Address 2608 records include A RR's, AAAA RR's or other similar records, 2609 chosen according to the requestor's network protocol 2610 capabilities. If the DNS server returns no address records, the 2611 requestor gives up. 2613 If the server is using a site certificate, the domain name in the 2614 query and the domain name in the replacement field MUST both be 2615 valid based on the site certificate handed out by the server in 2616 the TLS or IKE exchange. Similarly, the domain name in the SRV 2617 query and the domain name in the target in the SRV record MUST 2618 both be valid based on the same site certificate. Otherwise, an 2619 attacker could modify the DNS records to contain replacement 2620 values in a different domain, and the client could not validate 2621 that this was the desired behavior, or the result of an attack 2623 Also, the Diameter Peer MUST check to make sure that the 2624 discovered peers are authorized to act in its role. 2625 Authentication via IKE or TLS, or validation of DNS RRs via 2626 DNSSEC is not sufficient to conclude this. For example, a web 2627 server may have obtained a valid TLS certificate, and secured RRs 2628 may be included in the DNS, but this does not imply that it is 2629 authorized to act as a Diameter Server. 2631 Authorization can be achieved for example, by configuration of a 2632 Diameter Server CA. Alternatively this can be achieved by 2633 definition of OIDs within TLS or IKE certificates so as to 2634 signify Diameter Server authorization. 2636 A dynamically discovered peer causes an entry in the Peer Table (see 2637 Section 2.6) to be created. Note that entries created via DNS MUST 2638 expire (or be refreshed) within the DNS TTL. If a peer is discovered 2639 outside of the local realm, a routing table entry (see Section 2.7) 2640 for the peer's realm is created. The routing table entry's 2641 expiration MUST match the peer's expiration value. 2643 5.3. Capabilities Exchange 2645 When two Diameter peers establish a transport connection, they MUST 2646 exchange the Capabilities Exchange messages, as specified in the peer 2647 state machine (see Section 5.6). This message allows the discovery 2648 of a peer's identity and its capabilities (protocol version number, 2649 supported Diameter applications, security mechanisms, etc.) 2651 The receiver only issues commands to its peers that have advertised 2652 support for the Diameter application that defines the command. A 2653 Diameter node MUST cache the supported applications in order to 2654 ensure that unrecognized commands and/or AVPs are not unnecessarily 2655 sent to a peer. 2657 A receiver of a Capabilities-Exchange-Req (CER) message that does not 2658 have any applications in common with the sender MUST return a 2659 Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to 2660 DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport 2661 layer connection. Note that receiving a CER or CEA from a peer 2662 advertising itself as a Relay (see Section 2.4) MUST be interpreted 2663 as having common applications with the peer. 2665 The receiver of the Capabilities-Exchange-Request (CER) MUST 2666 determine common applications by computing the intersection of its 2667 own set of supported application identifiers against all of the 2668 application indentifier AVPs (Auth-Application-Id, 2669 Acct-Application-Id and Vendor-Specific-Application-Id) present in 2670 the CER. The value of the Vendor-Id AVP in the Vendor-Specific- 2671 Application-Id MUST not be used during computation. The sender of 2672 the Capabilities-Exchange-Answer (CEA) SHOULD include all of its 2673 supported applications as a hint to the receiver regarding all of its 2674 application capabilities. 2676 Similarly, a receiver of a Capabilities-Exchange-Req (CER) message 2677 that does not have any security mechanisms in common with the sender 2678 MUST return a Capabilities-Exchange-Answer (CEA) with the Result-Code 2679 AVP set to DIAMETER_NO_COMMON_SECURITY, and SHOULD disconnect the 2680 transport layer connection. 2682 CERs received from unknown peers MAY be silently discarded, or a CEA 2683 MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER. 2684 In both cases, the transport connection is closed. If the local 2685 policy permits receiving CERs from unknown hosts, a successful CEA 2686 MAY be returned. If a CER from an unknown peer is answered with a 2687 successful CEA, the lifetime of the peer entry is equal to the 2688 lifetime of the transport connection. In case of a transport 2689 failure, all the pending transactions destined to the unknown peer 2690 can be discarded. 2692 The CER and CEA messages MUST NOT be proxied, redirected or relayed. 2694 Since the CER/CEA messages cannot be proxied, it is still possible 2695 that an upstream agent receives a message for which it has no 2696 available peers to handle the application that corresponds to the 2697 Command-Code. In such instances, the 'E' bit is set in the answer 2698 message (see Section 7.) with the Result-Code AVP set to 2699 DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action 2700 (e.g., re-routing request to an alternate peer). 2702 With the exception of the Capabilities-Exchange-Request message, a 2703 message of type Request that includes the Auth-Application-Id or 2704 Acct-Application-Id AVPs, or a message with an application-specific 2705 command code, MAY only be forwarded to a host that has explicitly 2706 advertised support for the application (or has advertised the Relay 2707 Application Identifier). 2709 5.3.1. Capabilities-Exchange-Request 2711 The Capabilities-Exchange-Request (CER), indicated by the Command- 2712 Code set to 257 and the Command Flags' 'R' bit set, is sent to 2713 exchange local capabilities. Upon detection of a transport failure, 2714 this message MUST NOT be sent to an alternate peer. 2716 When Diameter is run over SCTP [RFC2960], which allows for 2717 connections to span multiple interfaces and multiple IP addresses, 2718 the Capabilities-Exchange-Request message MUST contain one Host-IP- 2719 Address AVP for each potential IP address that MAY be locally used 2720 when transmitting Diameter messages. 2722 Message Format 2724 ::= < Diameter Header: 257, REQ > 2725 { Origin-Host } 2726 { Origin-Realm } 2727 1* { Host-IP-Address } 2728 { Vendor-Id } 2729 { Product-Name } 2730 [ Origin-State-Id ] 2731 * [ Supported-Vendor-Id ] 2732 * [ Auth-Application-Id ] 2733 * [ Inband-Security-Id ] 2734 * [ Acct-Application-Id ] 2735 * [ Vendor-Specific-Application-Id ] 2736 [ Firmware-Revision ] 2737 * [ AVP ] 2739 5.3.2. Capabilities-Exchange-Answer 2741 The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code 2742 set to 257 and the Command Flags' 'R' bit cleared, is sent in 2743 response to a CER message. 2745 When Diameter is run over SCTP [RFC2960], which allows connections to 2746 span multiple interfaces, hence, multiple IP addresses, the 2747 Capabilities-Exchange-Answer message MUST contain one Host-IP-Address 2748 AVP for each potential IP address that MAY be locally used when 2749 transmitting Diameter messages. 2751 Message Format 2753 ::= < Diameter Header: 257 > 2754 { Result-Code } 2755 { Origin-Host } 2756 { Origin-Realm } 2757 1* { Host-IP-Address } 2758 { Vendor-Id } 2759 { Product-Name } 2760 [ Origin-State-Id ] 2761 [ Error-Message ] 2762 [ Failed-AVP ] 2763 * [ Supported-Vendor-Id ] 2764 * [ Auth-Application-Id ] 2765 * [ Inband-Security-Id ] 2766 * [ Acct-Application-Id ] 2767 * [ Vendor-Specific-Application-Id ] 2768 [ Firmware-Revision ] 2769 * [ AVP ] 2771 5.3.3. Vendor-Id AVP 2773 The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains 2774 the IANA "SMI Network Management Private Enterprise Codes" [RFC3232] 2775 value assigned to the vendor of the Diameter application. In 2776 combination with the Supported-Vendor-Id AVP (Section 5.3.6), this 2777 MAY be used in order to know which vendor specific attributes may be 2778 sent to the peer. It is also envisioned that the combination of the 2779 Vendor-Id, Product-Name (Section 5.3.7) and the Firmware-Revision 2780 (Section 5.3.4) AVPs MAY provide very useful debugging information. 2782 A Vendor-Id value of zero in the CER or CEA messages is reserved and 2783 indicates that this field is ignored. 2785 5.3.4. Firmware-Revision AVP 2787 The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is 2788 used to inform a Diameter peer of the firmware revision of the 2789 issuing device. 2791 For devices that do not have a firmware revision (general purpose 2792 computers running Diameter software modules, for instance), the 2793 revision of the Diameter software module may be reported instead. 2795 5.3.5. Host-IP-Address AVP 2797 The Host-IP-Address AVP (AVP Code 257) is of type Address and is used 2798 to inform a Diameter peer of the sender's IP address. All source 2799 addresses that a Diameter node expects to use with SCTP [RFC2960] 2800 MUST be advertised in the CER and CEA messages by including a 2801 Host-IP- Address AVP for each address. This AVP MUST ONLY be used in 2802 the CER and CEA messages. 2804 5.3.6. Supported-Vendor-Id AVP 2806 The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and 2807 contains the IANA "SMI Network Management Private Enterprise Codes" 2808 [RFC3232] value assigned to a vendor other than the device vendor. 2809 This is used in the CER and CEA messages in order to inform the peer 2810 that the sender supports (a subset of) the vendor-specific AVPs 2811 defined by the vendor identified in this AVP. The value of this AVP 2812 SHOULD NOT be set to zero. Multiple instances of this AVP containing 2813 the same value SHOULD NOT be sent. 2815 5.3.7. Product-Name AVP 2817 The Product-Name AVP (AVP Code 269) is of type UTF8String, and 2818 contains the vendor assigned name for the product. The Product-Name 2819 AVP SHOULD remain constant across firmware revisions for the same 2820 product. 2822 5.4. Disconnecting Peer connections 2824 When a Diameter node disconnects one of its transport connections, 2825 its peer cannot know the reason for the disconnect, and will most 2826 likely assume that a connectivity problem occurred, or that the peer 2827 has rebooted. In these cases, the peer may periodically attempt to 2828 reconnect, as stated in Section 2.1. In the event that the 2829 disconnect was a result of either a shortage of internal resources, 2830 or simply that the node in question has no intentions of forwarding 2831 any Diameter messages to the peer in the foreseeable future, a 2832 periodic connection request would not be welcomed. The 2833 Disconnection-Reason AVP contains the reason the Diameter node issued 2834 the Disconnect-Peer-Request message. 2836 The Disconnect-Peer-Request message is used by a Diameter node to 2837 inform its peer of its intent to disconnect the transport layer, and 2838 that the peer shouldn't reconnect unless it has a valid reason to do 2839 so (e.g., message to be forwarded). Upon receipt of the message, the 2840 Disconnect-Peer-Answer is returned, which SHOULD contain an error if 2841 messages have recently been forwarded, and are likely in flight, 2842 which would otherwise cause a race condition. 2844 The receiver of the Disconnect-Peer-Answer initiates the transport 2845 disconnect. The sender of the Disconnect-Peer-Answer should be able 2846 to detect the transport closure and cleanup the connection. 2848 5.4.1. Disconnect-Peer-Request 2850 The Disconnect-Peer-Request (DPR), indicated by the Command-Code set 2851 to 282 and the Command Flags' 'R' bit set, is sent to a peer to 2852 inform its intentions to shutdown the transport connection. Upon 2853 detection of a transport failure, this message MUST NOT be sent to an 2854 alternate peer. 2856 Message Format 2858 ::= < Diameter Header: 282, REQ > 2859 { Origin-Host } 2860 { Origin-Realm } 2861 { Disconnect-Cause } 2863 5.4.2. Disconnect-Peer-Answer 2865 The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set 2866 to 282 and the Command Flags' 'R' bit cleared, is sent as a response 2867 to the Disconnect-Peer-Request message. Upon receipt of this 2868 message, the transport connection is shutdown. 2870 Message Format 2872 ::= < Diameter Header: 282 > 2873 { Result-Code } 2874 { Origin-Host } 2875 { Origin-Realm } 2876 [ Error-Message ] 2877 [ Failed-AVP ] 2879 5.4.3. Disconnect-Cause AVP 2881 The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A 2882 Diameter node MUST include this AVP in the Disconnect-Peer-Request 2883 message to inform the peer of the reason for its intention to 2884 shutdown the transport connection. The following values are 2885 supported: 2887 REBOOTING 0 2888 A scheduled reboot is imminent. Receiver of DPR with above result 2889 code MAY attempt reconnection. 2891 BUSY 1 2892 The peer's internal resources are constrained, and it has 2893 determined that the transport connection needs to be closed. 2894 Receiver of DPR with above result code SHOULD NOT attempt 2895 reconnection. 2897 DO_NOT_WANT_TO_TALK_TO_YOU 2 2898 The peer has determined that it does not see a need for the 2899 transport connection to exist, since it does not expect any 2900 messages to be exchanged in the near future. Receiver of DPR 2901 with above result code SHOULD NOT attempt reconnection. 2903 5.5. Transport Failure Detection 2905 Given the nature of the Diameter protocol, it is recommended that 2906 transport failures be detected as soon as possible. Detecting such 2907 failures will minimize the occurrence of messages sent to unavailable 2908 agents, resulting in unnecessary delays, and will provide better 2909 failover performance. The Device-Watchdog-Request and Device- 2910 Watchdog-Answer messages, defined in this section, are used to pro- 2911 actively detect transport failures. 2913 5.5.1. Device-Watchdog-Request 2915 The Device-Watchdog-Request (DWR), indicated by the Command-Code set 2916 to 280 and the Command Flags' 'R' bit set, is sent to a peer when no 2917 traffic has been exchanged between two peers (see Section 5.5.3). 2918 Upon detection of a transport failure, this message MUST NOT be sent 2919 to an alternate peer. 2921 Message Format 2923 ::= < Diameter Header: 280, REQ > 2924 { Origin-Host } 2925 { Origin-Realm } 2926 [ Origin-State-Id ] 2928 5.5.2. Device-Watchdog-Answer 2930 The Device-Watchdog-Answer (DWA), indicated by the Command-Code set 2931 to 280 and the Command Flags' 'R' bit cleared, is sent as a response 2932 to the Device-Watchdog-Request message. 2934 Message Format 2936 ::= < Diameter Header: 280 > 2937 { Result-Code } 2938 { Origin-Host } 2939 { Origin-Realm } 2940 [ Error-Message ] 2941 [ Failed-AVP ] 2942 [ Origin-State-Id ] 2944 5.5.3. Transport Failure Algorithm 2946 The transport failure algorithm is defined in [RFC3539]. All 2947 Diameter implementations MUST support the algorithm defined in the 2948 specification in order to be compliant to the Diameter base protocol. 2950 5.5.4. Failover and Failback Procedures 2952 In the event that a transport failure is detected with a peer, it is 2953 necessary for all pending request messages to be forwarded to an 2954 alternate agent, if possible. This is commonly referred to as 2955 failover. 2957 In order for a Diameter node to perform failover procedures, it is 2958 necessary for the node to maintain a pending message queue for a 2959 given peer. When an answer message is received, the corresponding 2960 request is removed from the queue. The Hop-by-Hop Identifier field 2961 is used to match the answer with the queued request. 2963 When a transport failure is detected, if possible all messages in the 2964 queue are sent to an alternate agent with the T flag set. On booting 2965 a Diameter client or agent, the T flag is also set on any records 2966 still remaining to be transmitted in non-volatile storage. An 2967 example of a case where it is not possible to forward the message to 2968 an alternate server is when the message has a fixed destination, and 2969 the unavailable peer is the message's final destination (see 2970 Destination-Host AVP). Such an error requires that the agent return 2971 an answer message with the 'E' bit set and the Result-Code AVP set to 2972 DIAMETER_UNABLE_TO_DELIVER. 2974 It is important to note that multiple identical requests or answers 2975 MAY be received as a result of a failover. The End-to-End Identifier 2976 field in the Diameter header along with the Origin-Host AVP MUST be 2977 used to identify duplicate messages. 2979 As described in Section 2.1, a connection request should be 2980 periodically attempted with the failed peer in order to re-establish 2981 the transport connection. Once a connection has been successfully 2982 established, messages can once again be forwarded to the peer. This 2983 is commonly referred to as failback. 2985 5.6. Peer State Machine 2987 This section contains a finite state machine that MUST be observed by 2988 all Diameter implementations. Each Diameter node MUST follow the 2989 state machine described below when communicating with each peer. 2990 Multiple actions are separated by commas, and may continue on 2991 succeeding lines, as space requires. Similarly, state and next state 2992 may also span multiple lines, as space requires. 2994 This state machine is closely coupled with the state machine 2995 described in [RFC3539], which is used to open, close, failover, 2996 probe, and reopen transport connections. Note in particular that 2997 [RFC3539] requires the use of watchdog messages to probe connections. 2998 For Diameter, DWR and DWA messages are to be used. 3000 I- is used to represent the initiator (connecting) connection, while 3001 the R- is used to represent the responder (listening) connection. 3002 The lack of a prefix indicates that the event or action is the same 3003 regardless of the connection on which the event occurred. 3005 The stable states that a state machine may be in are Closed, I-Open 3006 and R-Open; all other states are intermediate. Note that I-Open and 3007 R-Open are equivalent except for whether the initiator or responder 3008 transport connection is used for communication. 3010 A CER message is always sent on the initiating connection immediately 3011 after the connection request is successfully completed. In the case 3012 of an election, one of the two connections will shut down. The 3013 responder connection will survive if the Origin-Host of the local 3014 Diameter entity is higher than that of the peer; the initiator 3015 connection will survive if the peer's Origin-Host is higher. All 3016 subsequent messages are sent on the surviving connection. Note that 3017 the results of an election on one peer are guaranteed to be the 3018 inverse of the results on the other. 3020 For TLS usage, a TLS handshake will begin when both ends are in the 3021 open state. If the TLS handshake is successful, all further messages 3022 will be sent via TLS. If the handshake fails, both ends move to the 3023 closed state. 3025 The state machine constrains only the behavior of a Diameter 3026 implementation as seen by Diameter peers through events on the wire. 3028 Any implementation that produces equivalent results is considered 3029 compliant. 3031 state event action next state 3032 ----------------------------------------------------------------- 3033 Closed Start I-Snd-Conn-Req Wait-Conn-Ack 3034 R-Conn-CER R-Accept, R-Open 3035 Process-CER, 3036 R-Snd-CEA 3038 Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA 3039 I-Rcv-Conn-Nack Cleanup Closed 3040 R-Conn-CER R-Accept, Wait-Conn-Ack/ 3041 Process-CER Elect 3042 Timeout Error Closed 3044 Wait-I-CEA I-Rcv-CEA Process-CEA I-Open 3045 R-Conn-CER R-Accept, Wait-Returns 3046 Process-CER, 3047 Elect 3048 I-Peer-Disc I-Disc Closed 3049 I-Rcv-Non-CEA Error Closed 3050 Timeout Error Closed 3052 Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns 3053 Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open 3054 R-Peer-Disc R-Disc Wait-Conn-Ack 3055 R-Conn-CER R-Reject Wait-Conn-Ack/ 3056 Elect 3057 Timeout Error Closed 3059 Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open 3060 I-Peer-Disc I-Disc, R-Open 3061 R-Snd-CEA 3062 I-Rcv-CEA R-Disc I-Open 3063 R-Peer-Disc R-Disc Wait-I-CEA 3064 R-Conn-CER R-Reject Wait-Returns 3065 Timeout Error Closed 3067 R-Open Send-Message R-Snd-Message R-Open 3068 R-Rcv-Message Process R-Open 3069 R-Rcv-DWR Process-DWR, R-Open 3070 R-Snd-DWA 3071 R-Rcv-DWA Process-DWA R-Open 3072 R-Conn-CER R-Reject R-Open 3073 Stop R-Snd-DPR Closing 3074 R-Rcv-DPR R-Snd-DPA, Closed 3075 R-Disc 3077 R-Peer-Disc R-Disc Closed 3078 R-Rcv-CER R-Snd-CEA R-Open 3079 R-Rcv-CEA Process-CEA R-Open 3081 I-Open Send-Message I-Snd-Message I-Open 3082 I-Rcv-Message Process I-Open 3083 I-Rcv-DWR Process-DWR, I-Open 3084 I-Snd-DWA 3085 I-Rcv-DWA Process-DWA I-Open 3086 R-Conn-CER R-Reject I-Open 3087 Stop I-Snd-DPR Closing 3088 I-Rcv-DPR I-Snd-DPA, Closed 3089 I-Disc 3090 I-Peer-Disc I-Disc Closed 3091 I-Rcv-CER I-Snd-CEA I-Open 3092 I-Rcv-CEA Process-CEA I-Open 3094 Closing I-Rcv-DPA I-Disc Closed 3095 R-Rcv-DPA R-Disc Closed 3096 Timeout Error Closed 3097 I-Peer-Disc I-Disc Closed 3098 R-Peer-Disc R-Disc Closed 3100 5.6.1. Incoming connections 3102 When a connection request is received from a Diameter peer, it is 3103 not, in the general case, possible to know the identity of that peer 3104 until a CER is received from it. This is because host and port 3105 determine the identity of a Diameter peer; and the source port of an 3106 incoming connection is arbitrary. Upon receipt of CER, the identity 3107 of the connecting peer can be uniquely determined from Origin-Host. 3109 For this reason, a Diameter peer must employ logic separate from the 3110 state machine to receive connection requests, accept them, and await 3111 CER. Once CER arrives on a new connection, the Origin-Host that 3112 identifies the peer is used to locate the state machine associated 3113 with that peer, and the new connection and CER are passed to the 3114 state machine as an R-Conn-CER event. 3116 The logic that handles incoming connections SHOULD close and discard 3117 the connection if any message other than CER arrives, or if an 3118 implementation-defined timeout occurs prior to receipt of CER. 3120 Because handling of incoming connections up to and including receipt 3121 of CER requires logic, separate from that of any individual state 3122 machine associated with a particular peer, it is described separately 3123 in this section rather than in the state machine above. 3125 5.6.2. Events 3127 Transitions and actions in the automaton are caused by events. In 3128 this section, we will ignore the -I and -R prefix, since the actual 3129 event would be identical, but would occur on one of two possible 3130 connections. 3132 Start The Diameter application has signaled that a 3133 connection should be initiated with the peer. 3135 R-Conn-CER An acknowledgement is received stating that the 3136 transport connection has been established, and the 3137 associated CER has arrived. 3139 Rcv-Conn-Ack A positive acknowledgement is received confirming that 3140 the transport connection is established. 3142 Rcv-Conn-Nack A negative acknowledgement was received stating that 3143 the transport connection was not established. 3145 Timeout An application-defined timer has expired while waiting 3146 for some event. 3148 Rcv-CER A CER message from the peer was received. 3150 Rcv-CEA A CEA message from the peer was received. 3152 Rcv-Non-CEA A message other than CEA from the peer was received. 3154 Peer-Disc A disconnection indication from the peer was received. 3156 Rcv-DPR A DPR message from the peer was received. 3158 Rcv-DPA A DPA message from the peer was received. 3160 Win-Election An election was held, and the local node was the 3161 winner. 3163 Send-Message A message is to be sent. 3165 Rcv-Message A message other than CER, CEA, DPR, DPA, DWR or DWA 3166 was received. 3168 Stop The Diameter application has signaled that a 3169 connection should be terminated (e.g., on system 3170 shutdown). 3172 5.6.3. Actions 3174 Actions in the automaton are caused by events and typically indicate 3175 the transmission of packets and/or an action to be taken on the 3176 connection. In this section we will ignore the I- and R-prefix, 3177 since the actual action would be identical, but would occur on one of 3178 two possible connections. 3180 Snd-Conn-Req A transport connection is initiated with the peer. 3182 Accept The incoming connection associated with the R-Conn-CER 3183 is accepted as the responder connection. 3185 Reject The incoming connection associated with the R-Conn-CER 3186 is disconnected. 3188 Process-CER The CER associated with the R-Conn-CER is processed. 3189 Snd-CER A CER message is sent to the peer. 3191 Snd-CEA A CEA message is sent to the peer. 3193 Cleanup If necessary, the connection is shutdown, and any 3194 local resources are freed. 3196 Error The transport layer connection is disconnected, either 3197 politely or abortively, in response to an error 3198 condition. Local resources are freed. 3200 Process-CEA A received CEA is processed. 3202 Snd-DPR A DPR message is sent to the peer. 3204 Snd-DPA A DPA message is sent to the peer. 3206 Disc The transport layer connection is disconnected, and 3207 local resources are freed. 3209 Elect An election occurs (see Section 5.6.4 for more 3210 information). 3212 Snd-Message A message is sent. 3214 Snd-DWR A DWR message is sent. 3216 Snd-DWA A DWA message is sent. 3218 Process-DWR The DWR message is serviced. 3220 Process-DWA The DWA message is serviced. 3222 Process A message is serviced. 3224 5.6.4. The Election Process 3226 The election is performed on the responder. The responder compares 3227 the Origin-Host received in the CER with its own Origin-Host as two 3228 streams of octets. If the local Origin-Host lexicographically 3229 succeeds the received Origin-Host a Win-Election event is issued 3230 locally. 3232 To be consistent with DNS case insensitivity, octets that fall in the 3233 ASCII range 'a' through 'z' MUST compare equally to their upper-case 3234 counterparts between 'A' and 'Z', i.e. value 0x41 compares equal to 3235 0x61, 0x42 to 0x62 and so forth up to and including 0x5a and 0x7a. 3237 The winner of the election MUST close the connection it initiated. 3238 Historically, maintaining the responder side of a connection was more 3239 efficient than maintaining the initiator side. However, current 3240 practices makes this distinction irrelevant. 3242 5.6.5. Capabilities Update 3244 A Diameter node MUST initiate peer capabilities update by sending a 3245 Capabilities-Exchange-Req (CER) to all its peers which supports peer 3246 capabilities update and is in OPEN state. The receiver of CER in 3247 open state MUST process and reply to the CER as a described in 3248 Section 5.3. The CEA which the receiver sends MUST contain its 3249 latest capabilities. Note that peers which successfully process the 3250 peer capabilities update SHOULD also update their routing tables to 3251 reflect the change. The receiver of the CEA, with a Result-Code AVP 3252 other than DIAMETER_SUCCESS, initiates the transport disconnect. The 3253 peer may periodically attempt to reconnect, as stated in Section 2.1. 3255 Peer capabilities update in the open state SHOULD be limited to the 3256 advertisement of the new list of supported applications and MUST 3257 preclude re-negotiation of security mechanism or other capabilities. 3258 If any capabilities change happens in the node (e.g. change in 3259 security mechanisms), other than a change in the supported 3260 applications, the node SHOULD gracefully terminate (setting the 3261 Disconnect-Cause AVP value to REBOOTING) and re-establish the 3262 diameter connections to all the peers. 3264 6. Diameter message processing 3266 This section describes how Diameter requests and answers are created 3267 and processed. 3269 6.1. Diameter Request Routing Overview 3271 A request is sent towards its final destination using a combination 3272 of the Destination-Realm and Destination-Host AVPs, in one of these 3273 three combinations: 3275 o a request that is not able to be proxied (such as CER) MUST NOT 3276 contain either Destination-Realm or Destination-Host AVPs. 3278 o a request that needs to be sent to a home server serving a 3279 specific realm, but not to a specific server (such as the first 3280 request of a series of round-trips), MUST contain a Destination- 3281 Realm AVP, but MUST NOT contain a Destination-Host AVP. 3283 o otherwise, a request that needs to be sent to a specific home 3284 server among those serving a given realm, MUST contain both the 3285 Destination-Realm and Destination-Host AVPs. 3287 The Destination-Host AVP is used as described above when the 3288 destination of the request is fixed, which includes: 3290 o Authentication requests that span multiple round trips 3292 o A Diameter message that uses a security mechanism that makes use 3293 of a pre-established session key shared between the source and the 3294 final destination of the message. 3296 o Server initiated messages that MUST be received by a specific 3297 Diameter client (e.g., access device), such as the Abort-Session- 3298 Request message, which is used to request that a particular user's 3299 session be terminated. 3301 Note that an agent can forward a request to a host described in the 3302 Destination-Host AVP only if the host in question is included in its 3303 peer table (see Section 2.7). Otherwise, the request is routed based 3304 on the Destination-Realm only (see Sections 6.1.6). 3306 The Destination-Realm AVP MUST be present if the message is 3307 proxiable. Request messages that may be forwarded by Diameter agents 3308 (proxies, redirects or relays) MUST also contain an Acct- 3309 Application-Id AVP, an Auth-Application-Id AVP or a Vendor-Specific- 3310 Application-Id AVP. A message that MUST NOT be forwarded by Diameter 3311 agents (proxies, redirects or relays) MUST not include the 3312 Destination-Realm in its ABNF. The value of the Destination-Realm 3313 AVP MAY be extracted from the User-Name AVP, or other application- 3314 specific methods. 3316 When a message is received, the message is processed in the following 3317 order: 3319 o If the message is destined for the local host, the procedures 3320 listed in Section 6.1.4 are followed. 3322 o If the message is intended for a Diameter peer with whom the local 3323 host is able to directly communicate, the procedures listed in 3324 Section 6.1.5 are followed. This is known as Request Forwarding. 3326 o The procedures listed in Section 6.1.6 are followed, which is 3327 known as Request Routing. 3329 o If none of the above is successful, an answer is returned with the 3330 Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the E-bit set. 3332 For routing of Diameter messages to work within an administrative 3333 domain, all Diameter nodes within the realm MUST be peers. 3335 Note the processing rules contained in this section are intended to 3336 be used as general guidelines to Diameter developers. Certain 3337 implementations MAY use different methods than the ones described 3338 here, and still comply with the protocol specification. See Section 3339 7 for more detail on error handling. 3341 6.1.1. Originating a Request 3343 When creating a request, in addition to any other procedures 3344 described in the application definition for that specific request, 3345 the following procedures MUST be followed: 3347 o the Command-Code is set to the appropriate value 3349 o the 'R' bit is set 3351 o the End-to-End Identifier is set to a locally unique value 3353 o the Origin-Host and Origin-Realm AVPs MUST be set to the 3354 appropriate values, used to identify the source of the message 3356 o the Destination-Host and Destination-Realm AVPs MUST be set to the 3357 appropriate values as described in Section 6.1. 3359 o an Acct-Application-Id AVP, an Auth-Application-Id or a Vendor- 3360 Specific-Application-Id AVP must be included if the request is 3361 proxiable. The application id present in one of these relevant 3362 AVPs must match the application id present in the diameter message 3363 header. 3365 6.1.2. Sending a Request 3367 When sending a request, originated either locally, or as the result 3368 of a forwarding or routing operation, the following procedures MUST 3369 be followed: 3371 o the Hop-by-Hop Identifier should be set to a locally unique value. 3373 o The message should be saved in the list of pending requests. 3375 Other actions to perform on the message based on the particular role 3376 the agent is playing are described in the following sections. 3378 6.1.3. Receiving Requests 3380 A relay or proxy agent MUST check for forwarding loops when receiving 3381 requests. A loop is detected if the server finds its own identity in 3382 a Route-Record AVP. When such an event occurs, the agent MUST answer 3383 with the Result-Code AVP set to DIAMETER_LOOP_DETECTED. 3385 6.1.4. Processing Local Requests 3387 A request is known to be for local consumption when one of the 3388 following conditions occur: 3390 o The Destination-Host AVP contains the local host's identity, 3392 o The Destination-Host AVP is not present, the Destination-Realm AVP 3393 contains a realm the server is configured to process locally, and 3394 the Diameter application is locally supported, or 3396 o Both the Destination-Host and the Destination-Realm are not 3397 present. 3399 When a request is locally processed, the rules in Section 6.2 should 3400 be used to generate the corresponding answer. 3402 6.1.5. Request Forwarding 3404 Request forwarding is done using the Diameter Peer Table. The 3405 Diameter peer table contains all of the peers that the local node is 3406 able to directly communicate with. 3408 When a request is received, and the host encoded in the Destination- 3409 Host AVP is one that is present in the peer table, the message SHOULD 3410 be forwarded to the peer. 3412 6.1.6. Request Routing 3414 Diameter request message routing is done via realms and applications. 3415 A Diameter message that may be forwarded by Diameter agents (proxies, 3416 redirects or relays) MUST include the target realm in the 3417 Destination-Realm AVP. Request routing SHOULD rely on the 3418 Destination-Realm AVP and the application id present in the request 3419 message header to aid in the routing decision. It MAY also rely on 3420 the application identification AVPs Auth-Application-Id, Acct- 3421 Application-Id or Vendor-Specific-Application-Id instead of the 3422 application id in the message header as a secondary measure. The 3423 realm MAY be retrieved from the User-Name AVP, which is in the form 3424 of a Network Access Identifier (NAI). The realm portion of the NAI 3425 is inserted in the Destination-Realm AVP. 3427 Diameter agents MAY have a list of locally supported realms and 3428 applications, and MAY have a list of externally supported realms and 3429 applications. When a request is received that includes a realm 3430 and/or application that is not locally supported, the message is 3431 routed to the peer configured in the Routing Table (see Section 2.7). 3433 Realm names and application identifiers are the minimum supported 3434 routing criteria, additional routing information maybe needed to 3435 support redirect semantics. 3437 6.1.7. Predictive Loop Avoidance 3439 Before forwarding or routing a request, Diameter agents, in addition 3440 to processing done in Section 6.1.3, SHOULD check for the presence of 3441 candidate route's peer identity in any of the Route-Record AVPs. In 3442 an event of the agent detecting the presence of a candidate route's 3443 peer identity in a Route-Record AVP, the agent MUST ignore such route 3444 for the Diameter request message and attempt alternate routes if any. 3445 In case all the candidate routes are eliminated by the above 3446 criteria, the agent SHOULD return DIAMETER_UNABLE_TO_DELIVER message. 3448 6.1.8. Redirecting requests 3450 When a redirect agent receives a request whose routing entry is set 3451 to REDIRECT, it MUST reply with an answer message with the 'E' bit 3452 set, while maintaining the Hop-by-Hop Identifier in the header, and 3453 include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of 3454 the servers associated with the routing entry are added in separate 3455 Redirect-Host AVP. 3457 +------------------+ 3458 | Diameter | 3459 | Redirect Agent | 3460 +------------------+ 3461 ^ | 2. command + 'E' bit 3462 1. Request | | Result-Code = 3463 joe@example.com | | DIAMETER_REDIRECT_INDICATION + 3464 | | Redirect-Host AVP(s) 3465 | v 3466 +-------------+ 3. Request +-------------+ 3467 | example.com |------------->| example.net | 3468 | Relay | | Diameter | 3469 | Agent |<-------------| Server | 3470 +-------------+ 4. Answer +-------------+ 3472 Figure 5: Diameter Redirect Agent 3474 The receiver of the answer message with the 'E' bit set, and the 3475 Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by- 3476 hop field in the Diameter header to identify the request in the 3477 pending message queue (see Section 5.3) that is to be redirected. If 3478 no transport connection exists with the new agent, one is created, 3479 and the request is sent directly to it. 3481 Multiple Redirect-Host AVPs are allowed. The receiver of the answer 3482 message with the 'E' bit set selects exactly one of these hosts as 3483 the destination of the redirected message. 3485 When the Redirect-Host-Usage AVP included in the answer message has a 3486 non-zero value, a route entry for the redirect indications is created 3487 and cached by the receiver. The redirect usage for such route entry 3488 is set by the value of Redirect-Host-Usage AVP and the lifetime of 3489 the cached route entry is set by Redirect-Max-Cache-Time AVP value. 3491 It is possible that multiple redirect indications can create multiple 3492 cached route entries differing only in their redirect usage and the 3493 peer to forward messages to. As an example, two(2) route entries 3494 that are created by two(2) redirect indications results in two(2) 3495 cached routes for the same realm and application Id. However, one 3496 has a redirect usage of ALL_SESSION where matching request will be 3497 forwarded to one peer and the other has a redirect usage of ALL_REALM 3498 where request are forwarded to another peer. Therefore, an incoming 3499 request that matches the realm and application Id of both routes will 3500 need additional resolution. In such a case, a routing precedence 3501 rule MUST be used againts the redirect usage value to resolve the 3502 contention. The precedence rule can be found in Section 6.13. 3504 6.1.9. Relaying and Proxying Requests 3506 A relay or proxy agent MUST append a Route-Record AVP to all requests 3507 forwarded. The AVP contains the identity of the peer the request was 3508 received from. 3510 The Hop-by-Hop identifier in the request is saved, and replaced with 3511 a locally unique value. The source of the request is also saved, 3512 which includes the IP address, port and protocol. 3514 A relay or proxy agent MAY include the Proxy-Info AVP in requests if 3515 it requires access to any local state information when the 3516 corresponding response is received. Proxy-Info AVP has certain 3517 security implications and SHOULD contain an embedded HMAC with a 3518 node-local key. Alternatively, it MAY simply use local storage to 3519 store state information. 3521 The message is then forwarded to the next hop, as identified in the 3522 Routing Table. 3524 Figure 6 provides an example of message routing using the procedures 3525 listed in these sections. 3527 (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net) 3528 (Origin-Realm=mno.net) (Origin-Realm=mno.net) 3529 (Destination-Realm=example.com) (Destination- 3530 Realm=example.com) 3531 (Route-Record=nas.example.net) 3532 +------+ ------> +------+ ------> +------+ 3533 | | (Request) | | (Request) | | 3534 | NAS +-------------------+ DRL +-------------------+ HMS | 3535 | | | | | | 3536 +------+ <------ +------+ <------ +------+ 3537 example.net (Answer) example.net (Answer) example.com 3538 (Origin-Host=hms.example.com) (Origin-Host=hms.example.com) 3539 (Origin-Realm=example.com) (Origin-Realm=example.com) 3541 Figure 6: Routing of Diameter messages 3543 Relay agents do not require full validation of incoming messages. At 3544 a minimum, validation of the message header and relevant routing AVPs 3545 has to be done when relaying messages. 3547 6.2. Diameter Answer Processing 3549 When a request is locally processed, the following procedures MUST be 3550 applied to create the associated answer, in addition to any 3551 additional procedures that MAY be discussed in the Diameter 3552 application defining the command: 3554 o The same Hop-by-Hop identifier in the request is used in the 3555 answer. 3557 o The local host's identity is encoded in the Origin-Host AVP. 3559 o The Destination-Host and Destination-Realm AVPs MUST NOT be 3560 present in the answer message. 3562 o The Result-Code AVP is added with its value indicating success or 3563 failure. 3565 o If the Session-Id is present in the request, it MUST be included 3566 in the answer. 3568 o Any Proxy-Info AVPs in the request MUST be added to the answer 3569 message, in the same order they were present in the request. 3571 o The 'P' bit is set to the same value as the one in the request. 3573 o The same End-to-End identifier in the request is used in the 3574 answer. 3576 Note that the error messages (see Section 7.3) are also subjected to 3577 the above processing rules. 3579 6.2.1. Processing received Answers 3581 A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an 3582 answer received against the list of pending requests. The 3583 corresponding message should be removed from the list of pending 3584 requests. It SHOULD ignore answers received that do not match a 3585 known Hop-by-Hop Identifier. 3587 6.2.2. Relaying and Proxying Answers 3589 If the answer is for a request which was proxied or relayed, the 3590 agent MUST restore the original value of the Diameter header's Hop- 3591 by-Hop Identifier field. 3593 If the last Proxy-Info AVP in the message is targeted to the local 3594 Diameter server, the AVP MUST be removed before the answer is 3595 forwarded. 3597 If a relay or proxy agent receives an answer with a Result-Code AVP 3598 indicating a failure, it MUST NOT modify the contents of the AVP. 3599 Any additional local errors detected SHOULD be logged, but not 3600 reflected in the Result-Code AVP. If the agent receives an answer 3601 message with a Result-Code AVP indicating success, and it wishes to 3602 modify the AVP to indicate an error, it MUST modify the Result-Code 3603 AVP to contain the appropriate error in the message destined towards 3604 the access device as well as include the Error-Reporting-Host AVP and 3605 it MUST issue an STR on behalf of the access device. 3607 The agent MUST then send the answer to the host that it received the 3608 original request from. 3610 6.3. Origin-Host AVP 3612 The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and 3613 MUST be present in all Diameter messages. This AVP identifies the 3614 endpoint that originated the Diameter message. Relay agents MUST NOT 3615 modify this AVP. 3617 The value of the Origin-Host AVP is guaranteed to be unique within a 3618 single host. 3620 Note that the Origin-Host AVP may resolve to more than one address as 3621 the Diameter peer may support more than one address. 3623 This AVP SHOULD be placed as close to the Diameter header as 3624 possible. 6.10 3626 6.4. Origin-Realm AVP 3628 The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity. 3629 This AVP contains the Realm of the originator of any Diameter message 3630 and MUST be present in all messages. 3632 This AVP SHOULD be placed as close to the Diameter header as 3633 possible. 3635 6.5. Destination-Host AVP 3637 The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity. 3638 This AVP MUST be present in all unsolicited agent initiated messages, 3639 MAY be present in request messages, and MUST NOT be present in Answer 3640 messages. 3642 The absence of the Destination-Host AVP will cause a message to be 3643 sent to any Diameter server supporting the application within the 3644 realm specified in Destination-Realm AVP. 3646 This AVP SHOULD be placed as close to the Diameter header as 3647 possible. 3649 6.6. Destination-Realm AVP 3651 The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity, 3652 and contains the realm the message is to be routed to. The 3653 Destination-Realm AVP MUST NOT be present in Answer messages. 3654 Diameter Clients insert the realm portion of the User-Name AVP. 3655 Diameter servers initiating a request message use the value of the 3656 Origin-Realm AVP from a previous message received from the intended 3657 target host (unless it is known a priori). When present, the 3658 Destination-Realm AVP is used to perform message routing decisions. 3660 Request messages whose ABNF does not list the Destination-Realm AVP 3661 as a mandatory AVP are inherently non-routable messages. 3663 This AVP SHOULD be placed as close to the Diameter header as 3664 possible. 3666 6.7. Routing AVPs 3668 The AVPs defined in this section are Diameter AVPs used for routing 3669 purposes. These AVPs change as Diameter messages are processed by 3670 agents. 3672 6.7.1. Route-Record AVP 3674 The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The 3675 identity added in this AVP MUST be the same as the one received in 3676 the Origin-Host of the Capabilities Exchange message. 3678 6.7.2. Proxy-Info AVP 3680 The Proxy-Info AVP (AVP Code 284) is of type Grouped. The Grouped 3681 Data field has the following ABNF grammar: 3683 Proxy-Info ::= < AVP Header: 284 > 3684 { Proxy-Host } 3685 { Proxy-State } 3686 * [ AVP ] 3688 6.7.3. Proxy-Host AVP 3690 The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This 3691 AVP contains the identity of the host that added the Proxy-Info AVP. 3693 6.7.4. Proxy-State AVP 3695 The Proxy-State AVP (AVP Code 33) is of type OctetString, and 3696 contains state local information, and MUST be treated as opaque data. 3698 6.8. Auth-Application-Id AVP 3700 The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and 3701 is used in order to advertise support of the Authentication and 3702 Authorization portion of an application (see Section 2.4). The Auth- 3703 Application-Id MUST also be present in all Authentication and/or 3704 Authorization messages that are defined in a separate Diameter 3705 specification and have an Application ID assigned. If present in a 3706 message, the value of the Auth-Application-Id AVP MUST match the 3707 application id present in the diameter message header except when 3708 used in a CER or CEA messages. 3710 6.9. Acct-Application-Id AVP 3712 The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and 3713 is used in order to advertise support of the Accounting portion of an 3714 application (see Section 2.4). The Acct-Application-Id MUST also be 3715 present in all Accounting messages. Exactly one of the Auth- 3716 Application-Id and Acct-Application-Id AVPs MAY be present. If 3717 present in a message, the value of the Acct-Application-Id AVP MUST 3718 match the application id present in the diameter message header 3719 except when used in a CER or CEA messages. 3721 6.10. Inband-Security-Id AVP 3723 The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and 3724 is used in order to advertise support of the Security portion of the 3725 application. 3727 Currently, the following values are supported, but there is ample 3728 room to add new security Ids. 3730 NO_INBAND_SECURITY 0 3732 This peer does not support TLS. This is the default value, if the 3733 AVP is omitted. 3735 TLS 1 3737 This node supports TLS security, as defined by [RFC4346]. 3739 6.11. Vendor-Specific-Application-Id AVP 3741 The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type 3742 Grouped and is used to advertise support of a vendor-specific 3743 Diameter Application. Exactly one instance of Auth-Application-Id or 3744 Acct-Application-Id AVP MAY be present. The application identifier 3745 carried by either Auth-Application-Id or Acct-Application-Id AVP MUST 3746 comply with vendor specific application identifier assignment 3747 described in Sec 11.3. It MUST also match the application id present 3748 in the diameter header except when used in a CER or CEA messages. 3750 The Vendor-Id AVP is an informational AVP pertaining to the vendor 3751 who may have authorship of the vendor-specific diameter application. 3752 It should not be used as a means of defining a completely separate 3753 vendor-specific application identifier space. 3755 This AVP MUST also be present as the first AVP in all experimental 3756 commands defined in the vendor-specific application. 3758 This AVP SHOULD be placed as close to the Diameter header as 3759 possible. 3761 AVP Format 3763 ::= < AVP Header: 260 > 3764 { Vendor-Id } 3765 { Auth-Application-Id } / 3766 { Acct-Application-Id } 3768 6.12. Redirect-Host AVP 3770 One or more of instances of this AVP MUST be present if the answer 3771 message's 'E' bit is set and the Result-Code AVP is set to 3772 DIAMETER_REDIRECT_INDICATION. 3774 Upon receiving the above, the receiving Diameter node SHOULD forward 3775 the request directly to one of the hosts identified in these AVPs. 3776 The server contained in the selected Redirect-Host AVP SHOULD be used 3777 for all messages pertaining to this session. 3779 6.13. Redirect-Host-Usage AVP 3781 The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated. 3782 This AVP MAY be present in answer messages whose 'E' bit is set and 3783 the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION. 3785 When present, this AVP dictates how the routing entry resulting from 3786 the Redirect-Host is to be used. The following values are supported: 3788 DONT_CACHE 0 3790 The host specified in the Redirect-Host AVP should not be cached. 3791 This is the default value. 3793 ALL_SESSION 1 3795 All messages within the same session, as defined by the same value 3796 of the Session-ID AVP MAY be sent to the host specified in the 3797 Redirect-Host AVP. 3799 ALL_REALM 2 3801 All messages destined for the realm requested MAY be sent to the 3802 host specified in the Redirect-Host AVP. 3804 REALM_AND_APPLICATION 3 3806 All messages for the application requested to the realm specified 3807 MAY be sent to the host specified in the Redirect-Host AVP. 3809 ALL_APPLICATION 4 3811 All messages for the application requested MAY be sent to the host 3812 specified in the Redirect-Host AVP. 3814 ALL_HOST 5 3816 All messages that would be sent to the host that generated the 3817 Redirect-Host MAY be sent to the host specified in the Redirect- 3818 Host AVP. 3820 ALL_USER 6 3822 All messages for the user requested MAY be sent to the host 3823 specified in the Redirect-Host AVP. 3825 When multiple cached routes are created by redirect indications and 3826 they differs only in redirect usage and peers to forward requests to 3827 (see Section 6.1.8), a precedence rule MUST be applied to the 3828 redirect usage values of the cached routes during normal routing to 3829 resolve contentions that may occur. The precedence rule is the order 3830 that dictate which redirect usage should be considered before any 3831 other as they appear. The order is as follows: 3833 1. ALL_SESSION 3835 2. ALL_USER 3837 3. REALM_AND_APPLICATION 3839 4. ALL_REALM 3841 5. ALL_APPLICATION 3843 6. ALL_HOST 3845 6.14. Redirect-Max-Cache-Time AVP 3847 The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32. 3848 This AVP MUST be present in answer messages whose 'E' bit is set, the 3849 Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the 3850 Redirect-Host-Usage AVP set to a non-zero value. 3852 This AVP contains the maximum number of seconds the peer and route 3853 table entries, created as a result of the Redirect-Host, will be 3854 cached. Note that once a host created due to a redirect indication 3855 is no longer reachable, any associated peer and routing table entries 3856 MUST be deleted. 3858 6.15. E2E-Sequence AVP 3860 The E2E-Sequence AVP (AVP Code 300) provides anti-replay protection 3861 for end to end messages and is of type grouped. It contains a random 3862 value (an OctetString with a nonce) and counter (an Integer). For 3863 each end-to-end peer with which a node communicates (or remembers 3864 communicating) a different nonce value MUST be used and the counter 3865 is initiated at zero and increases by one each time this AVP is 3866 emitted to that peer. 3868 7. Error Handling 3870 There are two different types of errors in Diameter; protocol and 3871 application errors. A protocol error is one that occurs at the base 3872 protocol level, and MAY require per hop attention (e.g., message 3873 routing error). Application errors, on the other hand, generally 3874 occur due to a problem with a function specified in a Diameter 3875 application (e.g., user authentication, Missing AVP). 3877 Result-Code AVP values that are used to report protocol errors MUST 3878 only be present in answer messages whose 'E' bit is set. When a 3879 request message is received that causes a protocol error, an answer 3880 message is returned with the 'E' bit set, and the Result-Code AVP is 3881 set to the appropriate protocol error value. As the answer is sent 3882 back towards the originator of the request, each proxy or relay agent 3883 MAY take action on the message. 3885 1. Request +---------+ Link Broken 3886 +-------------------------->|Diameter |----///----+ 3887 | +---------------------| | v 3888 +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+ 3889 |Diameter |<-+ (Unable to Forward) +---------+ |Diameter| 3890 | | | Home | 3891 | Relay 1 |--+ +---------+ | Server | 3892 +---------+ | 3. Request |Diameter | +--------+ 3893 +-------------------->| | ^ 3894 | Relay 3 |-----------+ 3895 +---------+ 3897 Figure 7: Example of Protocol Error causing answer message 3899 Figure 7 provides an example of a message forwarded upstream by a 3900 Diameter relay. When the message is received by Relay 2, and it 3901 detects that it cannot forward the request to the home server, an 3902 answer message is returned with the 'E' bit set and the Result-Code 3903 AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls 3904 within the protocol error category, Relay 1 would take special 3905 action, and given the error, attempt to route the message through its 3906 alternate Relay 3. 3908 +---------+ 1. Request +---------+ 2. Request +---------+ 3909 | Access |------------>|Diameter |------------>|Diameter | 3910 | | | | | Home | 3911 | Device |<------------| Relay |<------------| Server | 3912 +---------+ 4. Answer +---------+ 3. Answer +---------+ 3913 (Missing AVP) (Missing AVP) 3915 Figure 8: Example of Application Error Answer message 3917 Figure 8 provides an example of a Diameter message that caused an 3918 application error. When application errors occur, the Diameter 3919 entity reporting the error clears the 'R' bit in the Command Flags, 3920 and adds the Result-Code AVP with the proper value. Application 3921 errors do not require any proxy or relay agent involvement, and 3922 therefore the message would be forwarded back to the originator of 3923 the request. 3925 There are certain Result-Code AVP application errors that require 3926 additional AVPs to be present in the answer. In these cases, the 3927 Diameter node that sets the Result-Code AVP to indicate the error 3928 MUST add the AVPs. Examples are: 3930 o An unrecognized AVP is received with the 'M' bit (Mandatory bit) 3931 set, causes an answer to be sent with the Result-Code AVP set to 3932 DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the 3933 offending AVP. 3935 o An AVP that is received with an unrecognized value causes an 3936 answer to be returned with the Result-Code AVP set to 3937 DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the 3938 AVP causing the error. 3940 o A command is received with an AVP that is omitted, yet is 3941 mandatory according to the command's ABNF. The receiver issues an 3942 answer with the Result-Code set to DIAMETER_MISSING_AVP, and 3943 creates an AVP with the AVP Code and other fields set as expected 3944 in the missing AVP. The created AVP is then added to the Failed- 3945 AVP AVP. 3947 The Result-Code AVP describes the error that the Diameter node 3948 encountered in its processing. In case there are multiple errors, 3949 the Diameter node MUST report only the first error it encountered 3950 (detected possibly in some implementation dependent order). The 3951 specific errors that can be described by this AVP are described in 3952 the following section. 3954 7.1. Result-Code AVP 3956 The Result-Code AVP (AVP Code 268) is of type Unsigned32 and 3957 indicates whether a particular request was completed successfully or 3958 whether an error occurred. All Diameter answer messages defined in 3959 IETF applications MUST include one Result-Code AVP. A non-successful 3960 Result-Code AVP (one containing a non 2xxx value other than 3961 DIAMETER_REDIRECT_INDICATION) MUST include the Error-Reporting-Host 3962 AVP if the host setting the Result-Code AVP is different from the 3963 identity encoded in the Origin-Host AVP. 3965 The Result-Code data field contains an IANA-managed 32-bit address 3966 space representing errors (see Section 11.4). Diameter provides the 3967 following classes of errors, all identified by the thousands digit in 3968 the decimal notation: 3970 o 1xxx (Informational) 3972 o 2xxx (Success) 3974 o 3xxx (Protocol Errors) 3976 o 4xxx (Transient Failures) 3978 o 5xxx (Permanent Failure) 3980 A non-recognized class (one whose first digit is not defined in this 3981 section) MUST be handled as a permanent failure. 3983 7.1.1. Informational 3985 Errors that fall within this category are used to inform the 3986 requester that a request could not be satisfied, and additional 3987 action is required on its part before access is granted. 3989 DIAMETER_MULTI_ROUND_AUTH 1001 3991 This informational error is returned by a Diameter server to 3992 inform the access device that the authentication mechanism being 3993 used requires multiple round trips, and a subsequent request needs 3994 to be issued in order for access to be granted. 3996 7.1.2. Success 3998 Errors that fall within the Success category are used to inform a 3999 peer that a request has been successfully completed. 4001 DIAMETER_SUCCESS 2001 4003 The Request was successfully completed. 4005 DIAMETER_LIMITED_SUCCESS 2002 4007 When returned, the request was successfully completed, but 4008 additional processing is required by the application in order to 4009 provide service to the user. 4011 7.1.3. Protocol Errors 4013 Errors that fall within the Protocol Error category SHOULD be treated 4014 on a per-hop basis, and Diameter proxies MAY attempt to correct the 4015 error, if it is possible. Note that these and only these errors MUST 4016 only be used in answer messages whose 'E' bit is set. To provide 4017 backward compatibility with existing implementations that follow 4018 [RFC3588], some of the error values that have previously been used in 4019 this category by [RFC3588] will not be re-used. Therefore the error 4020 values enumerated here maybe non-sequential. 4022 DIAMETER_UNABLE_TO_DELIVER 3002 4024 This error is given when Diameter can not deliver the message to 4025 the destination, either because no host within the realm 4026 supporting the required application was available to process the 4027 request, or because Destination-Host AVP was given without the 4028 associated Destination-Realm AVP. 4030 DIAMETER_REALM_NOT_SERVED 3003 4032 The intended realm of the request is not recognized. 4034 DIAMETER_TOO_BUSY 3004 4036 When returned, a Diameter node SHOULD attempt to send the message 4037 to an alternate peer. This error MUST only be used when a 4038 specific server is requested, and it cannot provide the requested 4039 service. 4041 DIAMETER_LOOP_DETECTED 3005 4043 An agent detected a loop while trying to get the message to the 4044 intended recipient. The message MAY be sent to an alternate peer, 4045 if one is available, but the peer reporting the error has 4046 identified a configuration problem. 4048 DIAMETER_REDIRECT_INDICATION 3006 4050 A redirect agent has determined that the request could not be 4051 satisfied locally and the initiator of the request should direct 4052 the request directly to the server, whose contact information has 4053 been added to the response. When set, the Redirect-Host AVP MUST 4054 be present. 4056 DIAMETER_APPLICATION_UNSUPPORTED 3007 4058 A request was sent for an application that is not supported. 4060 DIAMETER_INVALID_BIT_IN_HEADER 3011 4062 This error is returned when an unrecognized bit in the Diameter 4063 header is set to one (1). 4065 DIAMETER_INVALID_MESSAGE_LENGTH 3012 4067 This error is returned when a request is received with an invalid 4068 message length. 4070 7.1.4. Transient Failures 4072 Errors that fall within the transient failures category are used to 4073 inform a peer that the request could not be satisfied at the time it 4074 was received, but MAY be able to satisfy the request in the future. 4075 Note that these errors MUST be used in answer messages whose 'E' bit 4076 is not set. 4078 DIAMETER_AUTHENTICATION_REJECTED 4001 4080 The authentication process for the user failed, most likely due to 4081 an invalid password used by the user. Further attempts MUST only 4082 be tried after prompting the user for a new password. 4084 DIAMETER_OUT_OF_SPACE 4002 4086 A Diameter node received the accounting request but was unable to 4087 commit it to stable storage due to a temporary lack of space. 4089 ELECTION_LOST 4003 4091 The peer has determined that it has lost the election process and 4092 has therefore disconnected the transport connection. 4094 7.1.5. Permanent Failures 4096 Errors that fall within the permanent failures category are used to 4097 inform the peer that the request failed, and should not be attempted 4098 again. Note that these errors SHOULD be used in answer messages 4099 whose 'E' bit is not set. In error conditions where it is not 4100 possible or efficient to compose application specific answer grammar 4101 then answer messages with E-bit set and complying to the grammar 4102 described in 7.2 MAY also be used for permanent errors. 4104 To provide backward compatibility with existing implementations that 4105 follow [RFC3588], some of the error values that have previously been 4106 used in this category by [RFC3588] will not be re-used. Therefore 4107 the error values enumerated here maybe non-sequential. 4109 DIAMETER_AVP_UNSUPPORTED 5001 4111 The peer received a message that contained an AVP that is not 4112 recognized or supported and was marked with the Mandatory bit. A 4113 Diameter message with this error MUST contain one or more Failed- 4114 AVP AVP containing the AVPs that caused the failure. 4116 DIAMETER_UNKNOWN_SESSION_ID 5002 4118 The request contained an unknown Session-Id. 4120 DIAMETER_AUTHORIZATION_REJECTED 5003 4122 A request was received for which the user could not be authorized. 4123 This error could occur if the service requested is not permitted 4124 to the user. 4126 DIAMETER_INVALID_AVP_VALUE 5004 4128 The request contained an AVP with an invalid value in its data 4129 portion. A Diameter message indicating this error MUST include 4130 the offending AVPs within a Failed-AVP AVP. 4132 DIAMETER_MISSING_AVP 5005 4134 The request did not contain an AVP that is required by the Command 4135 Code definition. If this value is sent in the Result-Code AVP, a 4136 Failed-AVP AVP SHOULD be included in the message. The Failed-AVP 4137 AVP MUST contain an example of the missing AVP complete with the 4138 Vendor-Id if applicable. The value field of the missing AVP 4139 should be of correct minimum length and contain zeroes. 4141 DIAMETER_RESOURCES_EXCEEDED 5006 4143 A request was received that cannot be authorized because the user 4144 has already expended allowed resources. An example of this error 4145 condition is a user that is restricted to one dial-up PPP port, 4146 attempts to establish a second PPP connection. 4148 DIAMETER_CONTRADICTING_AVPS 5007 4150 The Home Diameter server has detected AVPs in the request that 4151 contradicted each other, and is not willing to provide service to 4152 the user. The Failed-AVP AVPs MUST be present which contains the 4153 AVPs that contradicted each other. 4155 DIAMETER_AVP_NOT_ALLOWED 5008 4157 A message was received with an AVP that MUST NOT be present. The 4158 Failed-AVP AVP MUST be included and contain a copy of the 4159 offending AVP. 4161 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009 4163 A message was received that included an AVP that appeared more 4164 often than permitted in the message definition. The Failed-AVP 4165 AVP MUST be included and contain a copy of the first instance of 4166 the offending AVP that exceeded the maximum number of occurrences 4168 DIAMETER_NO_COMMON_APPLICATION 5010 4170 This error is returned by a Diameter node that is not acting as a 4171 relay when it receives a CER which advertises a set of 4172 applications that it does not support. 4174 DIAMETER_UNSUPPORTED_VERSION 5011 4176 This error is returned when a request was received, whose version 4177 number is unsupported. 4179 DIAMETER_UNABLE_TO_COMPLY 5012 4181 This error is returned when a request is rejected for unspecified 4182 reasons. 4184 DIAMETER_INVALID_AVP_LENGTH 5014 4186 The request contained an AVP with an invalid length. A Diameter 4187 message indicating this error MUST include the offending AVPs 4188 within a Failed-AVP AVP. In cases where the erroneous avp length 4189 value exceeds the message length or is less than the minimum AVP 4190 header length, it is sufficient to include the offending AVP 4191 header and a zero filled payload of the minimum required length. 4193 DIAMETER_NO_COMMON_SECURITY 5017 4195 This error is returned when a CER message is received, and there 4196 are no common security mechanisms supported between the peers. A 4197 Capabilities-Exchange-Answer (CEA) MUST be returned with the 4198 Result-Code AVP set to DIAMETER_NO_COMMON_SECURITY. 4200 DIAMETER_UNKNOWN_PEER 5018 4202 A CER was received from an unknown peer. 4204 DIAMETER_COMMAND_UNSUPPORTED 5019 4206 The Request contained a Command-Code that the receiver did not 4207 recognize or support. This MUST be used when a Diameter node 4208 receives an experimental command that it does not understand. 4210 DIAMETER_INVALID_HDR_BITS 5020 4212 A request was received whose bits in the Diameter header were 4213 either set to an invalid combination, or to a value that is 4214 inconsistent with the command code's definition. 4216 DIAMETER_INVALID_AVP_BITS 5021 4218 A request was received that included an AVP whose flag bits are 4219 set to an unrecognized value, or that is inconsistent with the 4220 AVP's definition. 4222 7.2. Error Bit 4224 The 'E' (Error Bit) in the Diameter header is set when the request 4225 caused a protocol-related error (see Section 7.1.3). A message with 4226 the 'E' bit MUST NOT be sent as a response to an answer message. 4227 Note that a message with the 'E' bit set is still subjected to the 4228 processing rules defined in Section 6.2. When set, the answer 4229 message will not conform to the ABNF specification for the command, 4230 and will instead conform to the following ABNF: 4232 Message Format 4234 ::= < Diameter Header: code, ERR [PXY] > 4235 0*1< Session-Id > 4236 { Origin-Host } 4237 { Origin-Realm } 4238 { Result-Code } 4239 [ Origin-State-Id ] 4240 [ Error-Reporting-Host ] 4241 [ Proxy-Info ] 4242 * [ AVP ] 4244 Note that the code used in the header is the same than the one found 4245 in the request message, but with the 'R' bit cleared and the 'E' bit 4246 set. The 'P' bit in the header is set to the same value as the one 4247 found in the request message. 4249 7.3. Error-Message AVP 4251 The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY 4252 accompany a Result-Code AVP as a human readable error message. The 4253 Error-Message AVP is not intended to be useful in real-time, and 4254 SHOULD NOT be expected to be parsed by network entities. 4256 7.4. Error-Reporting-Host AVP 4258 The Error-Reporting-Host AVP (AVP Code 294) is of type 4259 DiameterIdentity. This AVP contains the identity of the Diameter 4260 host that sent the Result-Code AVP to a value other than 2001 4261 (Success), only if the host setting the Result-Code is different from 4262 the one encoded in the Origin-Host AVP. This AVP is intended to be 4263 used for troubleshooting purposes, and MUST be set when the Result- 4264 Code AVP indicates a failure. 4266 7.5. Failed-AVP AVP 4268 The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides 4269 debugging information in cases where a request is rejected or not 4270 fully processed due to erroneous information in a specific AVP. The 4271 value of the Result-Code AVP will provide information on the reason 4272 for the Failed-AVP AVP. A Diameter message SHOULD contain only one 4273 Failed-AVP that corresponds to the error indicated by the Result-Code 4274 AVP. For practical purposes, this Failed-AVP would typically refer 4275 to the first AVP processing error that a Diameter node encounters. 4277 The possible reasons for this AVP are the presence of an improperly 4278 constructed AVP, an unsupported or unrecognized AVP, an invalid AVP 4279 value, the omission of a required AVP, the presence of an explicitly 4280 excluded AVP (see tables in Section 10), or the presence of two or 4281 more occurrences of an AVP which is restricted to 0, 1, or 0-1 4282 occurrences. 4284 A Diameter message SHOULD contain one Failed-AVP AVP, containing the 4285 entire AVP that could not be processed successfully. If the failure 4286 reason is omission of a required AVP, an AVP with the missing AVP 4287 code, the missing vendor id, and a zero filled payload of the minimum 4288 required length for the omitted AVP will be added. If the failure 4289 reason is an invalid AVP length where the reported length is less 4290 than the minimum AVP header length or greater than the reported 4291 message length, a copy of the offending AVP header and a zero filled 4292 payload of the minimum required length SHOULD be added. 4294 In the case where the offending AVP is embedded within a grouped AVP, 4295 the Failed-AVP MAY contain the grouped AVP which in turn contains the 4296 single offending AVP. The same method MAY be employed if the grouped 4297 AVP itself is embedded in yet another grouped AVP and so on. In this 4298 case, the Failed-AVP MAY contain the grouped AVP heirarchy up to the 4299 single offending AVP. This enables the recipient to detect the 4300 location of the offending AVP when embedded in a group. 4302 AVP Format 4304 ::= < AVP Header: 279 > 4305 1* {AVP} 4307 7.6. Experimental-Result AVP 4309 The Experimental-Result AVP (AVP Code 297) is of type Grouped, and 4310 indicates whether a particular vendor-specific request was completed 4311 successfully or whether an error occurred. Its Data field has the 4312 following ABNF grammar: 4314 AVP Format 4316 Experimental-Result ::= < AVP Header: 297 > 4317 { Vendor-Id } 4318 { Experimental-Result-Code } 4320 The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies 4321 the vendor responsible for the assignment of the result code which 4322 follows. All Diameter answer messages defined in vendor-specific 4323 applications MUST include either one Result-Code AVP or one 4324 Experimental-Result AVP. 4326 7.7. Experimental-Result-Code AVP 4328 The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32 4329 and contains a vendor-assigned value representing the result of 4330 processing the request. 4332 It is recommended that vendor-specific result codes follow the same 4333 conventions given for the Result-Code AVP regarding the different 4334 types of result codes and the handling of errors (for non 2xxx 4335 values). 4337 8. Diameter User Sessions 4339 In general, Diameter can provide two different types of services to 4340 applications. The first involves authentication and authorization, 4341 and can optionally make use of accounting. The second only makes use 4342 of accounting. 4344 When a service makes use of the authentication and/or authorization 4345 portion of an application, and a user requests access to the network, 4346 the Diameter client issues an auth request to its local server. The 4347 auth request is defined in a service specific Diameter application 4348 (e.g., NASREQ). The request contains a Session-Id AVP, which is used 4349 in subsequent messages (e.g., subsequent authorization, accounting, 4350 etc) relating to the user's session. The Session-Id AVP is a means 4351 for the client and servers to correlate a Diameter message with a 4352 user session. 4354 When a Diameter server authorizes a user to use network resources for 4355 a finite amount of time, and it is willing to extend the 4356 authorization via a future request, it MUST add the Authorization- 4357 Lifetime AVP to the answer message. The Authorization-Lifetime AVP 4358 defines the maximum number of seconds a user MAY make use of the 4359 resources before another authorization request is expected by the 4360 server. The Auth-Grace-Period AVP contains the number of seconds 4361 following the expiration of the Authorization-Lifetime, after which 4362 the server will release all state information related to the user's 4363 session. Note that if payment for services is expected by the 4364 serving realm from the user's home realm, the Authorization-Lifetime 4365 AVP, combined with the Auth-Grace-Period AVP, implies the maximum 4366 length of the session the home realm is willing to be fiscally 4367 responsible for. Services provided past the expiration of the 4368 Authorization-Lifetime and Auth-Grace-Period AVPs are the 4369 responsibility of the access device. Of course, the actual cost of 4370 services rendered is clearly outside the scope of the protocol. 4372 An access device that does not expect to send a re-authorization or a 4373 session termination request to the server MAY include the Auth- 4374 Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint 4375 to the server. If the server accepts the hint, it agrees that since 4376 no session termination message will be received once service to the 4377 user is terminated, it cannot maintain state for the session. If the 4378 answer message from the server contains a different value in the 4379 Auth-Session-State AVP (or the default value if the AVP is absent), 4380 the access device MUST follow the server's directives. Note that the 4381 value NO_STATE_MAINTAINED MUST NOT be set in subsequent re- 4382 authorization requests and answers. 4384 The base protocol does not include any authorization request 4385 messages, since these are largely application-specific and are 4386 defined in a Diameter application document. However, the base 4387 protocol does define a set of messages that is used to terminate user 4388 sessions. These are used to allow servers that maintain state 4389 information to free resources. 4391 When a service only makes use of the Accounting portion of the 4392 Diameter protocol, even in combination with an application, the 4393 Session-Id is still used to identify user sessions. However, the 4394 session termination messages are not used, since a session is 4395 signaled as being terminated by issuing an accounting stop message. 4397 Diameter may also be used for services that cannot be easily 4398 categorized as authentication, authorization or accounting (e.g., 4399 certain 3GPP IMS interfaces). In such cases, the finite state 4400 machine defined in subsequent sections may not be applicable. 4401 Therefore, the applications itself MAY need to define its own finite 4402 state machine. However, such application specific statemachines MUST 4403 comply with general Diameter user session requirements such co- 4404 relating all message exchanges via Session-Id AVP. 4406 8.1. Authorization Session State Machine 4408 This section contains a set of finite state machines, representing 4409 the life cycle of Diameter sessions, and which MUST be observed by 4410 all Diameter implementations that make use of the authentication 4411 and/or authorization portion of a Diameter application. The term 4412 Service-Specific below refers to a message defined in a Diameter 4413 application (e.g., Mobile IPv4, NASREQ). 4415 There are four different authorization session state machines 4416 supported in the Diameter base protocol. The first two describe a 4417 session in which the server is maintaining session state, indicated 4418 by the value of the Auth-Session-State AVP (or its absence). One 4419 describes the session from a client perspective, the other from a 4420 server perspective. The second two state machines are used when the 4421 server does not maintain session state. Here again, one describes 4422 the session from a client perspective, the other from a server 4423 perspective. 4425 When a session is moved to the Idle state, any resources that were 4426 allocated for the particular session must be released. Any event not 4427 listed in the state machines MUST be considered as an error 4428 condition, and an answer, if applicable, MUST be returned to the 4429 originator of the message. 4431 In the case that an application does not support re-auth, the state 4432 transitions related to server-initiated re-auth when both client and 4433 server sessions maintains state (e.g., Send RAR, Pending, Receive 4434 RAA) MAY be ignored. 4436 In the state table, the event 'Failure to send X' means that the 4437 Diameter agent is unable to send command X to the desired 4438 destination. This could be due to the peer being down, or due to the 4439 peer sending back a transient failure or temporary protocol error 4440 notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the 4441 Result-Code AVP of the corresponding Answer command. The event 'X 4442 successfully sent' is the complement of 'Failure to send X'. 4444 The following state machine is observed by a client when state is 4445 maintained on the server: 4447 CLIENT, STATEFUL 4448 State Event Action New State 4449 ------------------------------------------------------------- 4450 Idle Client or Device Requests Send Pending 4451 access service 4452 specific 4453 auth req 4455 Idle ASR Received Send ASA Idle 4456 for unknown session with 4457 Result-Code 4458 = UNKNOWN_ 4459 SESSION_ID 4461 Idle RAR Received Send RAA Idle 4462 for unknown session with 4463 Result-Code 4464 = UNKNOWN_ 4465 SESSION_ID 4467 Pending Successful Service-specific Grant Open 4468 authorization answer Access 4469 received with default 4470 Auth-Session-State value 4472 Pending Successful Service-specific Sent STR Discon 4473 authorization answer received 4474 but service not provided 4476 Pending Error processing successful Sent STR Discon 4477 Service-specific authorization 4478 answer 4480 Pending Failed Service-specific Cleanup Idle 4481 authorization answer received 4483 Open User or client device Send Open 4484 requests access to service service 4485 specific 4486 auth req 4488 Open Successful Service-specific Provide Open 4489 authorization answer received Service 4491 Open Failed Service-specific Discon. Idle 4492 authorization answer user/device 4493 received. 4495 Open RAR received and client will Send RAA Open 4496 perform subsequent re-auth with 4497 Result-Code 4498 = SUCCESS 4500 Open RAR received and client will Send RAA Idle 4501 not perform subsequent with 4502 re-auth Result-Code 4503 != SUCCESS, 4504 Discon. 4505 user/device 4507 Open Session-Timeout Expires on Send STR Discon 4508 Access Device 4510 Open ASR Received, Send ASA Discon 4511 client will comply with with 4512 request to end the session Result-Code 4513 = SUCCESS, 4514 Send STR. 4516 Open ASR Received, Send ASA Open 4517 client will not comply with with 4518 request to end the session Result-Code 4519 != SUCCESS 4521 Open Authorization-Lifetime + Send STR Discon 4522 Auth-Grace-Period expires on 4523 access device 4525 Discon ASR Received Send ASA Discon 4527 Discon STA Received Discon. Idle 4528 user/device 4530 The following state machine is observed by a server when it is 4531 maintaining state for the session: 4533 SERVER, STATEFUL 4534 State Event Action New State 4535 ------------------------------------------------------------- 4536 Idle Service-specific authorization Send Open 4537 request received, and successful 4538 user is authorized serv. 4539 specific 4540 answer 4542 Idle Service-specific authorization Send Idle 4543 request received, and failed serv. 4544 user is not authorized specific 4545 answer 4547 Open Service-specific authorization Send Open 4548 request received, and user successful 4549 is authorized serv. specific 4550 answer 4552 Open Service-specific authorization Send Idle 4553 request received, and user failed serv. 4554 is not authorized specific 4555 answer, 4556 Cleanup 4558 Open Home server wants to confirm Send RAR Pending 4559 authentication and/or 4560 authorization of the user 4562 Pending Received RAA with a failed Cleanup Idle 4563 Result-Code 4565 Pending Received RAA with Result-Code Update Open 4566 = SUCCESS session 4568 Open Home server wants to Send ASR Discon 4569 terminate the service 4571 Open Authorization-Lifetime (and Cleanup Idle 4572 Auth-Grace-Period) expires 4573 on home server. 4575 Open Session-Timeout expires on Cleanup Idle 4576 home server 4578 Discon Failure to send ASR Wait, Discon 4579 resend ASR 4581 Discon ASR successfully sent and Cleanup Idle 4582 ASA Received with Result-Code 4584 Not ASA Received None No Change. 4585 Discon 4587 Any STR Received Send STA, Idle 4588 Cleanup. 4590 The following state machine is observed by a client when state is not 4591 maintained on the server: 4593 CLIENT, STATELESS 4594 State Event Action New State 4595 ------------------------------------------------------------- 4596 Idle Client or Device Requests Send Pending 4597 access service 4598 specific 4599 auth req 4601 Pending Successful Service-specific Grant Open 4602 authorization answer Access 4603 received with Auth-Session- 4604 State set to 4605 NO_STATE_MAINTAINED 4607 Pending Failed Service-specific Cleanup Idle 4608 authorization answer 4609 received 4611 Open Session-Timeout Expires on Discon. Idle 4612 Access Device user/device 4614 Open Service to user is terminated Discon. Idle 4615 user/device 4617 The following state machine is observed by a server when it is not 4618 maintaining state for the session: 4620 SERVER, STATELESS 4621 State Event Action New State 4622 ------------------------------------------------------------- 4623 Idle Service-specific authorization Send serv. Idle 4624 request received, and specific 4625 successfully processed answer 4627 8.2. Accounting Session State Machine 4629 The following state machines MUST be supported for applications that 4630 have an accounting portion or that require only accounting services. 4631 The first state machine is to be observed by clients. 4633 See Section 9.7 for Accounting Command Codes and Section 9.8 for 4634 Accounting AVPs. 4636 The server side in the accounting state machine depends in some cases 4637 on the particular application. The Diameter base protocol defines a 4638 default state machine that MUST be followed by all applications that 4639 have not specified other state machines. This is the second state 4640 machine in this section described below. 4642 The default server side state machine requires the reception of 4643 accounting records in any order and at any time, and does not place 4644 any standards requirement on the processing of these records. 4645 Implementations of Diameter MAY perform checking, ordering, 4646 correlation, fraud detection, and other tasks based on these records. 4647 Both base Diameter AVPs as well as application specific AVPs MAY be 4648 inspected as a part of these tasks. The tasks can happen either 4649 immediately after record reception or in a post-processing phase. 4650 However, as these tasks are typically application or even policy 4651 dependent, they are not standardized by the Diameter specifications. 4652 Applications MAY define requirements on when to accept accounting 4653 records based on the used value of Accounting-Realtime-Required AVP, 4654 credit limits checks, and so on. 4656 However, the Diameter base protocol defines one optional server side 4657 state machine that MAY be followed by applications that require 4658 keeping track of the session state at the accounting server. Note 4659 that such tracking is incompatible with the ability to sustain long 4660 duration connectivity problems. Therefore, the use of this state 4661 machine is recommended only in applications where the value of the 4662 Accounting-Realtime-Required AVP is DELIVER_AND_GRANT, and hence 4663 accounting connectivity problems are required to cause the serviced 4664 user to be disconnected. Otherwise, records produced by the client 4665 may be lost by the server which no longer accepts them after the 4666 connectivity is re-established. This state machine is the third 4667 state machine in this section. The state machine is supervised by a 4668 supervision session timer Ts, which the value should be reasonably 4669 higher than the Acct_Interim_Interval value. Ts MAY be set to two 4670 times the value of the Acct_Interim_Interval so as to avoid the 4671 accounting session in the Diameter server to change to Idle state in 4672 case of short transient network failure. 4674 Any event not listed in the state machines MUST be considered as an 4675 error condition, and a corresponding answer, if applicable, MUST be 4676 returned to the originator of the message. 4678 In the state table, the event 'Failure to send' means that the 4679 Diameter client is unable to communicate with the desired 4680 destination. This could be due to the peer being down, or due to the 4681 peer sending back a transient failure or temporary protocol error 4682 notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or 4683 DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting 4684 Answer command. 4686 The event 'Failed answer' means that the Diameter client received a 4687 non-transient failure notification in the Accounting Answer command. 4689 Note that the action 'Disconnect user/dev' MUST have an effect also 4690 to the authorization session state table, e.g., cause the STR message 4691 to be sent, if the given application has both authentication/ 4692 authorization and accounting portions. 4694 The states PendingS, PendingI, PendingL, PendingE and PendingB stand 4695 for pending states to wait for an answer to an accounting request 4696 related to a Start, Interim, Stop, Event or buffered record, 4697 respectively. 4699 CLIENT, ACCOUNTING 4700 State Event Action New State 4701 ------------------------------------------------------------- 4702 Idle Client or device requests Send PendingS 4703 access accounting 4704 start req. 4706 Idle Client or device requests Send PendingE 4707 a one-time service accounting 4708 event req 4710 Idle Records in storage Send PendingB 4711 record 4713 PendingS Successful accounting Open 4714 start answer received 4716 PendingS Failure to send and buffer Store Open 4717 space available and realtime Start 4718 not equal to DELIVER_AND_GRANT Record 4720 PendingS Failure to send and no buffer Open 4721 space available and realtime 4722 equal to GRANT_AND_LOSE 4724 PendingS Failure to send and no buffer Disconnect Idle 4725 space available and realtime user/dev 4726 not equal to 4727 GRANT_AND_LOSE 4729 PendingS Failed accounting start answer Open 4730 received and realtime equal 4731 to GRANT_AND_LOSE 4733 PendingS Failed accounting start answer Disconnect Idle 4734 received and realtime not user/dev 4735 equal to GRANT_AND_LOSE 4737 PendingS User service terminated Store PendingS 4738 stop 4739 record 4741 Open Interim interval elapses Send PendingI 4742 accounting 4743 interim 4744 record 4745 Open User service terminated Send PendingL 4746 accounting 4747 stop req. 4749 PendingI Successful accounting interim Open 4750 answer received 4752 PendingI Failure to send and (buffer Store Open 4753 space available or old record interim 4754 can be overwritten) and record 4755 realtime not equal to 4756 DELIVER_AND_GRANT 4758 PendingI Failure to send and no buffer Open 4759 space available and realtime 4760 equal to GRANT_AND_LOSE 4762 PendingI Failure to send and no buffer Disconnect Idle 4763 space available and realtime user/dev 4764 not equal to GRANT_AND_LOSE 4766 PendingI Failed accounting interim Open 4767 answer received and realtime 4768 equal to GRANT_AND_LOSE 4770 PendingI Failed accounting interim Disconnect Idle 4771 answer received and realtime user/dev 4772 not equal to GRANT_AND_LOSE 4774 PendingI User service terminated Store PendingI 4775 stop 4776 record 4777 PendingE Successful accounting Idle 4778 event answer received 4780 PendingE Failure to send and buffer Store Idle 4781 space available event 4782 record 4784 PendingE Failure to send and no buffer Idle 4785 space available 4787 PendingE Failed accounting event answer Idle 4788 received 4790 PendingB Successful accounting answer Delete Idle 4791 received record 4793 PendingB Failure to send Idle 4795 PendingB Failed accounting answer Delete Idle 4796 received record 4798 PendingL Successful accounting Idle 4799 stop answer received 4801 PendingL Failure to send and buffer Store Idle 4802 space available stop 4803 record 4805 PendingL Failure to send and no buffer Idle 4806 space available 4808 PendingL Failed accounting stop answer Idle 4809 received 4811 SERVER, STATELESS ACCOUNTING 4812 State Event Action New State 4813 ------------------------------------------------------------- 4815 Idle Accounting start request Send Idle 4816 received, and successfully accounting 4817 processed. start 4818 answer 4820 Idle Accounting event request Send Idle 4821 received, and successfully accounting 4822 processed. event 4823 answer 4825 Idle Interim record received, Send Idle 4826 and successfully processed. accounting 4827 interim 4828 answer 4830 Idle Accounting stop request Send Idle 4831 received, and successfully accounting 4832 processed stop answer 4834 Idle Accounting request received, Send Idle 4835 no space left to store accounting 4836 records answer, 4837 Result-Code 4838 = OUT_OF_ 4839 SPACE 4841 SERVER, STATEFUL ACCOUNTING 4842 State Event Action New State 4843 ------------------------------------------------------------- 4845 Idle Accounting start request Send Open 4846 received, and successfully accounting 4847 processed. start 4848 answer, 4849 Start Ts 4851 Idle Accounting event request Send Idle 4852 received, and successfully accounting 4853 processed. event 4854 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 Open Interim record received, Send Open 4864 and successfully processed. accounting 4865 interim 4866 answer, 4867 Restart Ts 4869 Open Accounting stop request Send Idle 4870 received, and successfully accounting 4871 processed stop answer, 4872 Stop Ts 4874 Open Accounting request received, Send Idle 4875 no space left to store accounting 4876 records answer, 4877 Result-Code 4878 = OUT_OF_ 4879 SPACE, 4880 Stop Ts 4882 Open Session supervision timer Ts Stop Ts Idle 4883 expired 4885 8.3. Server-Initiated Re-Auth 4887 A Diameter server may initiate a re-authentication and/or re- 4888 authorization service for a particular session by issuing a Re-Auth- 4889 Request (RAR). 4891 For example, for pre-paid services, the Diameter server that 4892 originally authorized a session may need some confirmation that the 4893 user is still using the services. 4895 An access device that receives a RAR message with Session-Id equal to 4896 a currently active session MUST initiate a re-auth towards the user, 4897 if the service supports this particular feature. Each Diameter 4898 application MUST state whether service-initiated re-auth is 4899 supported, since some applications do not allow access devices to 4900 prompt the user for re-auth. 4902 8.3.1. Re-Auth-Request 4904 The Re-Auth-Request (RAR), indicated by the Command-Code set to 258 4905 and the message flags' 'R' bit set, may be sent by any server to the 4906 access device that is providing session service, to request that the 4907 user be re-authenticated and/or re-authorized. 4909 Message Format 4911 ::= < Diameter Header: 258, REQ, PXY > 4912 < Session-Id > 4913 { Origin-Host } 4914 { Origin-Realm } 4915 { Destination-Realm } 4916 { Destination-Host } 4917 { Auth-Application-Id } 4918 { Re-Auth-Request-Type } 4919 [ User-Name ] 4920 [ Origin-State-Id ] 4921 * [ Proxy-Info ] 4922 * [ Route-Record ] 4923 * [ AVP ] 4925 8.3.2. Re-Auth-Answer 4927 The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258 4928 and the message flags' 'R' bit clear, is sent in response to the RAR. 4929 The Result-Code AVP MUST be present, and indicates the disposition of 4930 the request. 4932 A successful RAA message MUST be followed by an application-specific 4933 authentication and/or authorization message. 4935 Message Format 4937 ::= < Diameter Header: 258, PXY > 4938 < Session-Id > 4939 { Result-Code } 4940 { Origin-Host } 4941 { Origin-Realm } 4942 [ User-Name ] 4943 [ Origin-State-Id ] 4944 [ Error-Message ] 4945 [ Error-Reporting-Host ] 4946 [ Failed-AVP ] 4947 * [ Redirect-Host ] 4948 [ Redirect-Host-Usage ] 4949 [ Redirect-Max-Cache-Time ] 4950 * [ Proxy-Info ] 4951 * [ AVP ] 4953 8.4. Session Termination 4955 It is necessary for a Diameter server that authorized a session, for 4956 which it is maintaining state, to be notified when that session is no 4957 longer active, both for tracking purposes as well as to allow 4958 stateful agents to release any resources that they may have provided 4959 for the user's session. For sessions whose state is not being 4960 maintained, this section is not used. 4962 When a user session that required Diameter authorization terminates, 4963 the access device that provided the service MUST issue a Session- 4964 Termination-Request (STR) message to the Diameter server that 4965 authorized the service, to notify it that the session is no longer 4966 active. An STR MUST be issued when a user session terminates for any 4967 reason, including user logoff, expiration of Session-Timeout, 4968 administrative action, termination upon receipt of an Abort-Session- 4969 Request (see below), orderly shutdown of the access device, etc. 4971 The access device also MUST issue an STR for a session that was 4972 authorized but never actually started. This could occur, for 4973 example, due to a sudden resource shortage in the access device, or 4974 because the access device is unwilling to provide the type of service 4975 requested in the authorization, or because the access device does not 4976 support a mandatory AVP returned in the authorization, etc. 4978 It is also possible that a session that was authorized is never 4979 actually started due to action of a proxy. For example, a proxy may 4980 modify an authorization answer, converting the result from success to 4981 failure, prior to forwarding the message to the access device. If 4982 the answer did not contain an Auth-Session-State AVP with the value 4983 NO_STATE_MAINTAINED, a proxy that causes an authorized session not to 4984 be started MUST issue an STR to the Diameter server that authorized 4985 the session, since the access device has no way of knowing that the 4986 session had been authorized. 4988 A Diameter server that receives an STR message MUST clean up 4989 resources (e.g., session state) associated with the Session-Id 4990 specified in the STR, and return a Session-Termination-Answer. 4992 A Diameter server also MUST clean up resources when the Session- 4993 Timeout expires, or when the Authorization-Lifetime and the Auth- 4994 Grace-Period AVPs expires without receipt of a re-authorization 4995 request, regardless of whether an STR for that session is received. 4996 The access device is not expected to provide service beyond the 4997 expiration of these timers; thus, expiration of either of these 4998 timers implies that the access device may have unexpectedly shut 4999 down. 5001 8.4.1. Session-Termination-Request 5003 The Session-Termination-Request (STR), indicated by the Command-Code 5004 set to 275 and the Command Flags' 'R' bit set, is sent by the access 5005 device to inform the Diameter Server that an authenticated and/or 5006 authorized session is being terminated. 5008 Message Format 5010 ::= < Diameter Header: 275, REQ, PXY > 5011 < Session-Id > 5012 { Origin-Host } 5013 { Origin-Realm } 5014 { Destination-Realm } 5015 { Auth-Application-Id } 5016 { Termination-Cause } 5017 [ User-Name ] 5018 [ Destination-Host ] 5019 * [ Class ] 5020 [ Origin-State-Id ] 5021 * [ Proxy-Info ] 5022 * [ Route-Record ] 5023 * [ AVP ] 5025 8.4.2. Session-Termination-Answer 5027 The Session-Termination-Answer (STA), indicated by the Command-Code 5028 set to 275 and the message flags' 'R' bit clear, is sent by the 5029 Diameter Server to acknowledge the notification that the session has 5030 been terminated. The Result-Code AVP MUST be present, and MAY 5031 contain an indication that an error occurred while servicing the STR. 5033 Upon sending or receipt of the STA, the Diameter Server MUST release 5034 all resources for the session indicated by the Session-Id AVP. Any 5035 intermediate server in the Proxy-Chain MAY also release any 5036 resources, if necessary. 5038 Message Format 5040 ::= < Diameter Header: 275, PXY > 5041 < Session-Id > 5042 { Result-Code } 5043 { Origin-Host } 5044 { Origin-Realm } 5045 [ User-Name ] 5046 * [ Class ] 5047 [ Error-Message ] 5048 [ Error-Reporting-Host ] 5049 [ Failed-AVP ] 5050 [ Origin-State-Id ] 5051 * [ Redirect-Host ] 5052 [ Redirect-Host-Usage ] 5053 ^ 5054 [ Redirect-Max-Cache-Time ] 5055 * [ Proxy-Info ] 5056 * [ AVP ] 5058 8.5. Aborting a Session 5060 A Diameter server may request that the access device stop providing 5061 service for a particular session by issuing an Abort-Session-Request 5062 (ASR). 5064 For example, the Diameter server that originally authorized the 5065 session may be required to cause that session to be stopped for 5066 credit or other reasons that were not anticipated when the session 5067 was first authorized. On the other hand, an operator may maintain a 5068 management server for the purpose of issuing ASRs to administratively 5069 remove users from the network. 5071 An access device that receives an ASR with Session-ID equal to a 5072 currently active session MAY stop the session. Whether the access 5073 device stops the session or not is implementation- and/or 5074 configuration-dependent. For example, an access device may honor 5075 ASRs from certain agents only. In any case, the access device MUST 5076 respond with an Abort-Session-Answer, including a Result-Code AVP to 5077 indicate what action it took. 5079 Note that if the access device does stop the session upon receipt of 5080 an ASR, it issues an STR to the authorizing server (which may or may 5081 not be the agent issuing the ASR) just as it would if the session 5082 were terminated for any other reason. 5084 8.5.1. Abort-Session-Request 5086 The Abort-Session-Request (ASR), indicated by the Command-Code set to 5087 274 and the message flags' 'R' bit set, may be sent by any server to 5088 the access device that is providing session service, to request that 5089 the session identified by the Session-Id be stopped. 5091 Message Format 5093 ::= < Diameter Header: 274, REQ, PXY > 5094 < Session-Id > 5095 { Origin-Host } 5096 { Origin-Realm } 5097 { Destination-Realm } 5098 { Destination-Host } 5099 { Auth-Application-Id } 5100 [ User-Name ] 5101 [ Origin-State-Id ] 5102 * [ Proxy-Info ] 5103 * [ Route-Record ] 5104 * [ AVP ] 5106 8.5.2. Abort-Session-Answer 5108 The Abort-Session-Answer (ASA), indicated by the Command-Code set to 5109 274 and the message flags' 'R' bit clear, is sent in response to the 5110 ASR. The Result-Code AVP MUST be present, and indicates the 5111 disposition of the request. 5113 If the session identified by Session-Id in the ASR was successfully 5114 terminated, Result-Code is set to DIAMETER_SUCCESS. If the session 5115 is not currently active, Result-Code is set to 5116 DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the 5117 session for any other reason, Result-Code is set to 5118 DIAMETER_UNABLE_TO_COMPLY. 5120 Message Format 5122 ::= < Diameter Header: 274, PXY > 5123 < Session-Id > 5124 { Result-Code } 5125 { Origin-Host } 5126 { Origin-Realm } 5127 [ User-Name ] 5128 [ Origin-State-Id ] 5129 [ Error-Message ] 5130 [ Error-Reporting-Host ] 5131 [ Failed-AVP ] 5132 * [ Redirect-Host ] 5133 [ Redirect-Host-Usage ] 5134 [ Redirect-Max-Cache-Time ] 5135 * [ Proxy-Info ] 5136 * [ AVP ] 5138 8.6. Inferring Session Termination from Origin-State-Id 5140 Origin-State-Id is used to allow rapid detection of terminated 5141 sessions for which no STR would have been issued, due to 5142 unanticipated shutdown of an access device. 5144 By including Origin-State-Id in CER/CEA messages, an access device 5145 allows a next-hop server to determine immediately upon connection 5146 whether the device has lost its sessions since the last connection. 5148 By including Origin-State-Id in request messages, an access device 5149 also allows a server with which it communicates via proxy to make 5150 such a determination. However, a server that is not directly 5151 connected with the access device will not discover that the access 5152 device has been restarted unless and until it receives a new request 5153 from the access device. Thus, use of this mechanism across proxies 5154 is opportunistic rather than reliable, but useful nonetheless. 5156 When a Diameter server receives an Origin-State-Id that is greater 5157 than the Origin-State-Id previously received from the same issuer, it 5158 may assume that the issuer has lost state since the previous message 5159 and that all sessions that were active under the lower Origin-State- 5160 Id have been terminated. The Diameter server MAY clean up all 5161 session state associated with such lost sessions, and MAY also issues 5162 STRs for all such lost sessions that were authorized on upstream 5163 servers, to allow session state to be cleaned up globally. 5165 8.7. Auth-Request-Type AVP 5167 The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is 5168 included in application-specific auth requests to inform the peers 5169 whether a user is to be authenticated only, authorized only or both. 5170 Note any value other than both MAY cause RADIUS interoperability 5171 issues. The following values are defined: 5173 AUTHENTICATE_ONLY 1 5175 The request being sent is for authentication only, and MUST 5176 contain the relevant application specific authentication AVPs that 5177 are needed by the Diameter server to authenticate the user. 5179 AUTHORIZE_ONLY 2 5181 The request being sent is for authorization only, and MUST contain 5182 the application specific authorization AVPs that are necessary to 5183 identify the service being requested/offered. 5185 AUTHORIZE_AUTHENTICATE 3 5187 The request contains a request for both authentication and 5188 authorization. The request MUST include both the relevant 5189 application specific authentication information, and authorization 5190 information necessary to identify the service being requested/ 5191 offered. 5193 8.8. Session-Id AVP 5195 The Session-Id AVP (AVP Code 263) is of type UTF8String and is used 5196 to identify a specific session (see Section 8). All messages 5197 pertaining to a specific session MUST include only one Session-Id AVP 5198 and the same value MUST be used throughout the life of a session. 5199 When present, the Session-Id SHOULD appear immediately following the 5200 Diameter Header (see Section 3). 5202 The Session-Id MUST be globally and eternally unique, as it is meant 5203 to uniquely identify a user session without reference to any other 5204 information, and may be needed to correlate historical authentication 5205 information with accounting information. The Session-Id includes a 5206 mandatory portion and an implementation-defined portion; a 5207 recommended format for the implementation-defined portion is outlined 5208 below. 5210 The Session-Id MUST begin with the sender's identity encoded in the 5211 DiameterIdentity type (see Section 4.4). The remainder of the 5212 Session-Id is delimited by a ";" character, and MAY be any sequence 5213 that the client can guarantee to be eternally unique; however, the 5214 following format is recommended, (square brackets [] indicate an 5215 optional element): 5217 ;;[;] 5219 and are decimal representations of the 5220 high and low 32 bits of a monotonically increasing 64-bit value. The 5221 64-bit value is rendered in two part to simplify formatting by 32-bit 5222 processors. At startup, the high 32 bits of the 64-bit value MAY be 5223 initialized to the time, and the low 32 bits MAY be initialized to 5224 zero. This will for practical purposes eliminate the possibility of 5225 overlapping Session-Ids after a reboot, assuming the reboot process 5226 takes longer than a second. Alternatively, an implementation MAY 5227 keep track of the increasing value in non-volatile memory. 5229 is implementation specific but may include a modem's 5230 device Id, a layer 2 address, timestamp, etc. 5232 Example, in which there is no optional value: 5234 accesspoint7.acme.com;1876543210;523 5236 Example, in which there is an optional value: 5238 accesspoint7.acme.com;1876543210;523;mobile@200.1.1.88 5240 The Session-Id is created by the Diameter application initiating the 5241 session, which in most cases is done by the client. Note that a 5242 Session-Id MAY be used for both the authorization and accounting 5243 commands of a given application. 5245 8.9. Authorization-Lifetime AVP 5247 The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32 5248 and contains the maximum number of seconds of service to be provided 5249 to the user before the user is to be re-authenticated and/or re- 5250 authorized. Great care should be taken when the Authorization- 5251 Lifetime value is determined, since a low, non-zero, value could 5252 create significant Diameter traffic, which could congest both the 5253 network and the agents. 5255 A value of zero (0) means that immediate re-auth is necessary by the 5256 access device. This is typically used in cases where multiple 5257 authentication methods are used, and a successful auth response with 5258 this AVP set to zero is used to signal that the next authentication 5259 method is to be immediately initiated. The absence of this AVP, or a 5260 value of all ones (meaning all bits in the 32 bit field are set to 5261 one) means no re-auth is expected. 5263 If both this AVP and the Session-Timeout AVP are present in a 5264 message, the value of the latter MUST NOT be smaller than the 5265 Authorization-Lifetime AVP. 5267 An Authorization-Lifetime AVP MAY be present in re-authorization 5268 messages, and contains the number of seconds the user is authorized 5269 to receive service from the time the re-auth answer message is 5270 received by the access device. 5272 This AVP MAY be provided by the client as a hint of the maximum 5273 lifetime that it is willing to accept. However, the server MAY 5274 return a value that is equal to, or smaller, than the one provided by 5275 the client. 5277 8.10. Auth-Grace-Period AVP 5279 The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and 5280 contains the number of seconds the Diameter server will wait 5281 following the expiration of the Authorization-Lifetime AVP before 5282 cleaning up resources for the session. 5284 8.11. Auth-Session-State AVP 5286 The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and 5287 specifies whether state is maintained for a particular session. The 5288 client MAY include this AVP in requests as a hint to the server, but 5289 the value in the server's answer message is binding. The following 5290 values are supported: 5292 STATE_MAINTAINED 0 5294 This value is used to specify that session state is being 5295 maintained, and the access device MUST issue a session termination 5296 message when service to the user is terminated. This is the 5297 default value. 5299 NO_STATE_MAINTAINED 1 5301 This value is used to specify that no session termination messages 5302 will be sent by the access device upon expiration of the 5303 Authorization-Lifetime. 5305 8.12. Re-Auth-Request-Type AVP 5307 The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and 5308 is included in application-specific auth answers to inform the client 5309 of the action expected upon expiration of the Authorization-Lifetime. 5310 If the answer message contains an Authorization-Lifetime AVP with a 5311 positive value, the Re-Auth-Request-Type AVP MUST be present in an 5312 answer message. The following values are defined: 5314 AUTHORIZE_ONLY 0 5316 An authorization only re-auth is expected upon expiration of the 5317 Authorization-Lifetime. This is the default value if the AVP is 5318 not present in answer messages that include the Authorization- 5319 Lifetime. 5321 AUTHORIZE_AUTHENTICATE 1 5323 An authentication and authorization re-auth is expected upon 5324 expiration of the Authorization-Lifetime. 5326 8.13. Session-Timeout AVP 5328 The Session-Timeout AVP (AVP Code 27) [RFC2865] is of type Unsigned32 5329 and contains the maximum number of seconds of service to be provided 5330 to the user before termination of the session. When both the 5331 Session-Timeout and the Authorization-Lifetime AVPs are present in an 5332 answer message, the former MUST be equal to or greater than the value 5333 of the latter. 5335 A session that terminates on an access device due to the expiration 5336 of the Session-Timeout MUST cause an STR to be issued, unless both 5337 the access device and the home server had previously agreed that no 5338 session termination messages would be sent (see Section 8.9). 5340 A Session-Timeout AVP MAY be present in a re-authorization answer 5341 message, and contains the remaining number of seconds from the 5342 beginning of the re-auth. 5344 A value of zero, or the absence of this AVP, means that this session 5345 has an unlimited number of seconds before termination. 5347 This AVP MAY be provided by the client as a hint of the maximum 5348 timeout that it is willing to accept. However, the server MAY return 5349 a value that is equal to, or smaller, than the one provided by the 5350 client. 5352 8.14. User-Name AVP 5354 The User-Name AVP (AVP Code 1) [RFC2865] is of type UTF8String, which 5355 contains the User-Name, in a format consistent with the NAI 5356 specification [RFC4282]. 5358 8.15. Termination-Cause AVP 5360 The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and 5361 is used to indicate the reason why a session was terminated on the 5362 access device. The following values are defined: 5364 DIAMETER_LOGOUT 1 5366 The user initiated a disconnect 5368 DIAMETER_SERVICE_NOT_PROVIDED 2 5370 This value is used when the user disconnected prior to the receipt 5371 of the authorization answer message. 5373 DIAMETER_BAD_ANSWER 3 5375 This value indicates that the authorization answer received by the 5376 access device was not processed successfully. 5378 DIAMETER_ADMINISTRATIVE 4 5380 The user was not granted access, or was disconnected, due to 5381 administrative reasons, such as the receipt of a Abort-Session- 5382 Request message. 5384 DIAMETER_LINK_BROKEN 5 5386 The communication to the user was abruptly disconnected. 5388 DIAMETER_AUTH_EXPIRED 6 5390 The user's access was terminated since its authorized session time 5391 has expired. 5393 DIAMETER_USER_MOVED 7 5395 The user is receiving services from another access device. 5397 DIAMETER_SESSION_TIMEOUT 8 5399 The user's session has timed out, and service has been terminated. 5401 8.16. Origin-State-Id AVP 5403 The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a 5404 monotonically increasing value that is advanced whenever a Diameter 5405 entity restarts with loss of previous state, for example upon reboot. 5406 Origin-State-Id MAY be included in any Diameter message, including 5407 CER. 5409 A Diameter entity issuing this AVP MUST create a higher value for 5410 this AVP each time its state is reset. A Diameter entity MAY set 5411 Origin-State-Id to the time of startup, or it MAY use an incrementing 5412 counter retained in non-volatile memory across restarts. 5414 The Origin-State-Id, if present, MUST reflect the state of the entity 5415 indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST 5416 either remove Origin-State-Id or modify it appropriately as well. 5417 Typically, Origin-State-Id is used by an access device that always 5418 starts up with no active sessions; that is, any session active prior 5419 to restart will have been lost. By including Origin-State-Id in a 5420 message, it allows other Diameter entities to infer that sessions 5421 associated with a lower Origin-State-Id are no longer active. If an 5422 access device does not intend for such inferences to be made, it MUST 5423 either not include Origin-State-Id in any message, or set its value 5424 to 0. 5426 8.17. Session-Binding AVP 5428 The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY 5429 be present in application-specific authorization answer messages. If 5430 present, this AVP MAY inform the Diameter client that all future 5431 application-specific re-auth messages for this session MUST be sent 5432 to the same authorization server. This AVP MAY also specify that a 5433 Session-Termination-Request message for this session MUST be sent to 5434 the same authorizing server. 5436 This field is a bit mask, and the following bits have been defined: 5438 RE_AUTH 1 5440 When set, future re-auth messages for this session MUST NOT 5441 include the Destination-Host AVP. When cleared, the default 5442 value, the Destination-Host AVP MUST be present in all re-auth 5443 messages for this session. 5445 STR 2 5447 When set, the STR message for this session MUST NOT include the 5448 Destination-Host AVP. When cleared, the default value, the 5449 Destination-Host AVP MUST be present in the STR message for this 5450 session. 5452 ACCOUNTING 4 5454 When set, all accounting messages for this session MUST NOT 5455 include the Destination-Host AVP. When cleared, the default 5456 value, the Destination-Host AVP, if known, MUST be present in all 5457 accounting messages for this session. 5459 8.18. Session-Server-Failover AVP 5461 The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated, 5462 and MAY be present in application-specific authorization answer 5463 messages that either do not include the Session-Binding AVP or 5464 include the Session-Binding AVP with any of the bits set to a zero 5465 value. If present, this AVP MAY inform the Diameter client that if a 5466 re-auth or STR message fails due to a delivery problem, the Diameter 5467 client SHOULD issue a subsequent message without the Destination-Host 5468 AVP. When absent, the default value is REFUSE_SERVICE. 5470 The following values are supported: 5472 REFUSE_SERVICE 0 5474 If either the re-auth or the STR message delivery fails, terminate 5475 service with the user, and do not attempt any subsequent attempts. 5477 TRY_AGAIN 1 5479 If either the re-auth or the STR message delivery fails, resend 5480 the failed message without the Destination-Host AVP present. 5482 ALLOW_SERVICE 2 5484 If re-auth message delivery fails, assume that re-authorization 5485 succeeded. If STR message delivery fails, terminate the session. 5487 TRY_AGAIN_ALLOW_SERVICE 3 5489 If either the re-auth or the STR message delivery fails, resend 5490 the failed message without the Destination-Host AVP present. If 5491 the second delivery fails for re-auth, assume re-authorization 5492 succeeded. If the second delivery fails for STR, terminate the 5493 session. 5495 8.19. Multi-Round-Time-Out AVP 5497 The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32, 5498 and SHOULD be present in application-specific authorization answer 5499 messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH. 5500 This AVP contains the maximum number of seconds that the access 5501 device MUST provide the user in responding to an authentication 5502 request. 5504 8.20. Class AVP 5506 The Class AVP (AVP Code 25) is of type OctetString and is used to by 5507 Diameter servers to return state information to the access device. 5508 When one or more Class AVPs are present in application-specific 5509 authorization answer messages, they MUST be present in subsequent re- 5510 authorization, session termination and accounting messages. Class 5511 AVPs found in a re-authorization answer message override the ones 5512 found in any previous authorization answer message. Diameter server 5513 implementations SHOULD NOT return Class AVPs that require more than 5514 4096 bytes of storage on the Diameter client. A Diameter client that 5515 receives Class AVPs whose size exceeds local available storage MUST 5516 terminate the session. 5518 8.21. Event-Timestamp AVP 5520 The Event-Timestamp (AVP Code 55) is of type Time, and MAY be 5521 included in an Accounting-Request and Accounting-Answer messages to 5522 record the time that the reported event occurred, in seconds since 5523 January 1, 1900 00:00 UTC. 5525 9. Accounting 5527 This accounting protocol is based on a server directed model with 5528 capabilities for real-time delivery of accounting information. 5529 Several fault resilience methods [RFC2975] have been built in to the 5530 protocol in order minimize loss of accounting data in various fault 5531 situations and under different assumptions about the capabilities of 5532 the used devices. 5534 9.1. Server Directed Model 5536 The server directed model means that the device generating the 5537 accounting data gets information from either the authorization server 5538 (if contacted) or the accounting server regarding the way accounting 5539 data shall be forwarded. This information includes accounting record 5540 timeliness requirements. 5542 As discussed in [RFC2975], real-time transfer of accounting records 5543 is a requirement, such as the need to perform credit limit checks and 5544 fraud detection. Note that batch accounting is not a requirement, 5545 and is therefore not supported by Diameter. Should batched 5546 accounting be required in the future, a new Diameter application will 5547 need to be created, or it could be handled using another protocol. 5548 Note, however, that even if at the Diameter layer accounting requests 5549 are processed one by one, transport protocols used under Diameter 5550 typically batch several requests in the same packet under heavy 5551 traffic conditions. This may be sufficient for many applications. 5553 The authorization server (chain) directs the selection of proper 5554 transfer strategy, based on its knowledge of the user and 5555 relationships of roaming partnerships. The server (or agents) uses 5556 the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to 5557 control the operation of the Diameter peer operating as a client. 5558 The Acct-Interim-Interval AVP, when present, instructs the Diameter 5559 node acting as a client to produce accounting records continuously 5560 even during a session. Accounting-Realtime-Required AVP is used to 5561 control the behavior of the client when the transfer of accounting 5562 records from the Diameter client is delayed or unsuccessful. 5564 The Diameter accounting server MAY override the interim interval or 5565 the realtime requirements by including the Acct-Interim-Interval or 5566 Accounting-Realtime-Required AVP in the Accounting-Answer message. 5567 When one of these AVPs is present, the latest value received SHOULD 5568 be used in further accounting activities for the same session. 5570 9.2. Protocol Messages 5572 A Diameter node that receives a successful authentication and/or 5573 authorization messages from the Home AAA server MUST collect 5574 accounting information for the session. The Accounting-Request 5575 message is used to transmit the accounting information to the Home 5576 AAA server, which MUST reply with the Accounting-Answer message to 5577 confirm reception. The Accounting-Answer message includes the 5578 Result-Code AVP, which MAY indicate that an error was present in the 5579 accounting message. A rejected Accounting-Request message MAY cause 5580 the user's session to be terminated, depending on the value of the 5581 Accounting-Realtime-Required AVP received earlier for the session in 5582 question. 5584 Each Diameter Accounting protocol message MAY be compressed, in order 5585 to reduce network bandwidth usage. If TLS is used to secure the 5586 Diameter session, then TLS compression [RFC4346] MAY be used. 5588 9.3. Accounting Application Extension and Requirements 5590 Each Diameter application (e.g., NASREQ, MobileIP), MUST define their 5591 Service-Specific AVPs that MUST be present in the Accounting-Request 5592 message in a section entitled "Accounting AVPs". The application 5593 MUST assume that the AVPs described in this document will be present 5594 in all Accounting messages, so only their respective service-specific 5595 AVPs need to be defined in this section. 5597 Applications have the option of using one or both of the following 5598 accounting application extension models: 5600 Split Accounting Service 5602 The accounting message will carry the application identifier of 5603 the Diameter base accounting application (see Section 2.4). 5604 Accounting messages maybe routed to Diameter nodes other than the 5605 corresponding Diameter application. These nodes might be 5606 centralized accounting servers that provide accounting service for 5607 multiple different Diameter applications. These nodes MUST 5608 advertise the Diameter base accounting application identifier 5609 during capabilities exchange. 5611 Accounting messages which uses the Diameter base accounting 5612 application identifier in its header MUST include the application 5613 identifier of the Diameter application it is providing service for 5614 in the Acct-Application-Id AVP. This allows the accounting server 5615 to determine which Diameter application the accounting records are 5616 for. 5618 Coupled Accounting Service 5620 The accounting messages will carry the application identifier of 5621 the application that is using it. The application itself will 5622 process the received accounting records or forward them to an 5623 accounting server. There is no accounting application 5624 advertisement required during capabilities exchange and the 5625 accounting messages will be routed the same as any of the other 5626 application messages. 5628 In cases where an application does not define its own accounting 5629 service, it is preferred that the split accounting model be used. 5631 9.4. Fault Resilience 5633 Diameter Base protocol mechanisms are used to overcome small message 5634 loss and network faults of temporary nature. 5636 Diameter peers acting as clients MUST implement the use of failover 5637 to guard against server failures and certain network failures. 5638 Diameter peers acting as agents or related off-line processing 5639 systems MUST detect duplicate accounting records caused by the 5640 sending of same record to several servers and duplication of messages 5641 in transit. This detection MUST be based on the inspection of the 5642 Session-Id and Accounting-Record-Number AVP pairs. Appendix C 5643 discusses duplicate detection needs and implementation issues. 5645 Diameter clients MAY have non-volatile memory for the safe storage of 5646 accounting records over reboots or extended network failures, network 5647 partitions, and server failures. If such memory is available, the 5648 client SHOULD store new accounting records there as soon as the 5649 records are created and until a positive acknowledgement of their 5650 reception from the Diameter Server has been received. Upon a reboot, 5651 the client MUST starting sending the records in the non-volatile 5652 memory to the accounting server with appropriate modifications in 5653 termination cause, session length, and other relevant information in 5654 the records. 5656 A further application of this protocol may include AVPs to control 5657 how many accounting records may at most be stored in the Diameter 5658 client without committing them to the non-volatile memory or 5659 transferring them to the Diameter server. 5661 The client SHOULD NOT remove the accounting data from any of its 5662 memory areas before the correct Accounting-Answer has been received. 5663 The client MAY remove oldest, undelivered or yet unacknowledged 5664 accounting data if it runs out of resources such as memory. It is an 5665 implementation dependent matter for the client to accept new sessions 5666 under this condition. 5668 9.5. Accounting Records 5670 In all accounting records, the Session-Id AVP MUST be present; the 5671 User-Name AVP MUST be present if it is available to the Diameter 5672 client. 5674 Different types of accounting records are sent depending on the 5675 actual type of accounted service and the authorization server's 5676 directions for interim accounting. If the accounted service is a 5677 one-time event, meaning that the start and stop of the event are 5678 simultaneous, then the Accounting-Record-Type AVP MUST be present and 5679 set to the value EVENT_RECORD. 5681 If the accounted service is of a measurable length, then the AVP MUST 5682 use the values START_RECORD, STOP_RECORD, and possibly, 5683 INTERIM_RECORD. If the authorization server has not directed interim 5684 accounting to be enabled for the session, two accounting records MUST 5685 be generated for each service of type session. When the initial 5686 Accounting-Request for a given session is sent, the Accounting- 5687 Record-Type AVP MUST be set to the value START_RECORD. When the last 5688 Accounting-Request is sent, the value MUST be STOP_RECORD. 5690 If the authorization server has directed interim accounting to be 5691 enabled, the Diameter client MUST produce additional records between 5692 the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The 5693 production of these records is directed by Acct-Interim-Interval as 5694 well as any re-authentication or re-authorization of the session. 5695 The Diameter client MUST overwrite any previous interim accounting 5696 records that are locally stored for delivery, if a new record is 5697 being generated for the same session. This ensures that only one 5698 pending interim record can exist on an access device for any given 5699 session. 5701 A particular value of Accounting-Sub-Session-Id MUST appear only in 5702 one sequence of accounting records from a DIAMETER client, except for 5703 the purposes of retransmission. The one sequence that is sent MUST 5704 be either one record with Accounting-Record-Type AVP set to the value 5705 EVENT_RECORD, or several records starting with one having the value 5706 START_RECORD, followed by zero or more INTERIM_RECORD and a single 5707 STOP_RECORD. A particular Diameter application specification MUST 5708 define the type of sequences that MUST be used. 5710 9.6. Correlation of Accounting Records 5712 The Diameter protocol's Session-Id AVP, which is globally unique (see 5713 Section 8.8), is used during the authorization phase to identify a 5714 particular session. Services that do not require any authorization 5715 still use the Session-Id AVP to identify sessions. Accounting 5716 messages MAY use a different Session-Id from that sent in 5717 authorization messages. Specific applications MAY require different 5718 a Session-ID for accounting messages. 5720 However, there are certain applications that require multiple 5721 accounting sub-sessions. Such applications would send messages with 5722 a constant Session-Id AVP, but a different Accounting-Sub-Session-Id 5723 AVP. In these cases, correlation is performed using the Session-Id. 5724 It is important to note that receiving a STOP_RECORD with no 5725 Accounting-Sub-Session-Id AVP when sub-sessions were originally used 5726 in the START_RECORD messages implies that all sub-sessions are 5727 terminated. 5729 Furthermore, there are certain applications where a user receives 5730 service from different access devices (e.g., Mobile IPv4), each with 5731 their own unique Session-Id. In such cases, the Acct-Multi-Session- 5732 Id AVP is used for correlation. During authorization, a server that 5733 determines that a request is for an existing session SHOULD include 5734 the Acct-Multi-Session-Id AVP, which the access device MUST include 5735 in all subsequent accounting messages. 5737 The Acct-Multi-Session-Id AVP MAY include the value of the original 5738 Session-Id. It's contents are implementation specific, but MUST be 5739 globally unique across other Acct-Multi-Session-Id, and MUST NOT 5740 change during the life of a session. 5742 A Diameter application document MUST define the exact concept of a 5743 session that is being accounted, and MAY define the concept of a 5744 multi-session. For instance, the NASREQ DIAMETER application treats 5745 a single PPP connection to a Network Access Server as one session, 5746 and a set of Multilink PPP sessions as one multi-session. 5748 9.7. Accounting Command-Codes 5750 This section defines Command-Code values that MUST be supported by 5751 all Diameter implementations that provide Accounting services. 5753 9.7.1. Accounting-Request 5755 The Accounting-Request (ACR) command, indicated by the Command-Code 5756 field set to 271 and the Command Flags' 'R' bit set, is sent by a 5757 Diameter node, acting as a client, in order to exchange accounting 5758 information with a peer. 5760 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs 5761 MUST be present. If the Vendor-Specific-Application-Id grouped AVP 5762 is present, it must have an Acct-Application-Id inside. 5764 The AVP listed below SHOULD include service specific accounting AVPs, 5765 as described in Section 9.3. 5767 Message Format 5769 ::= < Diameter Header: 271, REQ, PXY > 5770 < Session-Id > 5771 { Origin-Host } 5772 { Origin-Realm } 5773 { Destination-Realm } 5774 { Accounting-Record-Type } 5775 { Accounting-Record-Number } 5776 [ Acct-Application-Id ] 5777 [ Vendor-Specific-Application-Id ] 5778 [ User-Name ] 5779 [ Destination-Host ] 5780 [ Accounting-Sub-Session-Id ] 5781 [ Acct-Session-Id ] 5782 [ Acct-Multi-Session-Id ] 5783 [ Acct-Interim-Interval ] 5784 [ Accounting-Realtime-Required ] 5785 [ Origin-State-Id ] 5786 [ Event-Timestamp ] 5787 * [ Proxy-Info ] 5788 * [ Route-Record ] 5789 * [ AVP ] 5791 9.7.2. Accounting-Answer 5793 The Accounting-Answer (ACA) command, indicated by the Command-Code 5794 field set to 271 and the Command Flags' 'R' bit cleared, is used to 5795 acknowledge an Accounting-Request command. The Accounting-Answer 5796 command contains the same Session-Id as the corresponding request. 5798 Only the target Diameter Server, known as the home Diameter Server, 5799 SHOULD respond with the Accounting-Answer command. 5801 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs 5802 MUST be present. If the Vendor-Specific-Application-Id grouped AVP 5803 is present, it must have an Acct-Application-Id inside. 5805 The AVP listed below SHOULD include service specific accounting AVPs, 5806 as described in Section 9.3. 5808 Message Format 5810 ::= < Diameter Header: 271, PXY > 5811 < Session-Id > 5812 { Result-Code } 5813 { Origin-Host } 5814 { Origin-Realm } 5815 { Accounting-Record-Type } 5816 { Accounting-Record-Number } 5817 [ Acct-Application-Id ] 5818 [ Vendor-Specific-Application-Id ] 5819 [ User-Name ] 5820 [ Accounting-Sub-Session-Id ] 5821 [ Acct-Session-Id ] 5822 [ Acct-Multi-Session-Id ] 5823 [ Error-Reporting-Host ] 5824 [ Acct-Interim-Interval ] 5825 [ Accounting-Realtime-Required ] 5826 [ Origin-State-Id ] 5827 [ Event-Timestamp ] 5828 * [ Proxy-Info ] 5829 * [ AVP ] 5831 9.8. Accounting AVPs 5833 This section contains AVPs that describe accounting usage information 5834 related to a specific session. 5836 9.8.1. Accounting-Record-Type AVP 5838 The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated 5839 and contains the type of accounting record being sent. The following 5840 values are currently defined for the Accounting-Record-Type AVP: 5842 EVENT_RECORD 1 5844 An Accounting Event Record is used to indicate that a one-time 5845 event has occurred (meaning that the start and end of the event 5846 are simultaneous). This record contains all information relevant 5847 to the service, and is the only record of the service. 5849 START_RECORD 2 5851 An Accounting Start, Interim, and Stop Records are used to 5852 indicate that a service of a measurable length has been given. An 5853 Accounting Start Record is used to initiate an accounting session, 5854 and contains accounting information that is relevant to the 5855 initiation of the session. 5857 INTERIM_RECORD 3 5859 An Interim Accounting Record contains cumulative accounting 5860 information for an existing accounting session. Interim 5861 Accounting Records SHOULD be sent every time a re-authentication 5862 or re-authorization occurs. Further, additional interim record 5863 triggers MAY be defined by application-specific Diameter 5864 applications. The selection of whether to use INTERIM_RECORD 5865 records is done by the Acct-Interim-Interval AVP. 5867 STOP_RECORD 4 5869 An Accounting Stop Record is sent to terminate an accounting 5870 session and contains cumulative accounting information relevant to 5871 the existing session. 5873 9.8.2. Acct-Interim-Interval 5875 The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and 5876 is sent from the Diameter home authorization server to the Diameter 5877 client. The client uses information in this AVP to decide how and 5878 when to produce accounting records. With different values in this 5879 AVP, service sessions can result in one, two, or two+N accounting 5880 records, based on the needs of the home-organization. The following 5881 accounting record production behavior is directed by the inclusion of 5882 this AVP: 5884 1. The omission of the Acct-Interim-Interval AVP or its inclusion 5885 with Value field set to 0 means that EVENT_RECORD, START_RECORD, 5886 and STOP_RECORD are produced, as appropriate for the service. 5888 2. The inclusion of the AVP with Value field set to a non-zero value 5889 means that INTERIM_RECORD records MUST be produced between the 5890 START_RECORD and STOP_RECORD records. The Value field of this 5891 AVP is the nominal interval between these records in seconds. 5892 The Diameter node that originates the accounting information, 5893 known as the client, MUST produce the first INTERIM_RECORD record 5894 roughly at the time when this nominal interval has elapsed from 5895 the START_RECORD, the next one again as the interval has elapsed 5896 once more, and so on until the session ends and a STOP_RECORD 5897 record is produced. 5899 The client MUST ensure that the interim record production times 5900 are randomized so that large accounting message storms are not 5901 created either among records or around a common service start 5902 time. 5904 9.8.3. Accounting-Record-Number AVP 5906 The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32 5907 and identifies this record within one session. As Session-Id AVPs 5908 are globally unique, the combination of Session-Id and Accounting- 5909 Record-Number AVPs is also globally unique, and can be used in 5910 matching accounting records with confirmations. An easy way to 5911 produce unique numbers is to set the value to 0 for records of type 5912 EVENT_RECORD and START_RECORD, and set the value to 1 for the first 5913 INTERIM_RECORD, 2 for the second, and so on until the value for 5914 STOP_RECORD is one more than for the last INTERIM_RECORD. 5916 9.8.4. Acct-Session-Id AVP 5918 The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only 5919 used when RADIUS/Diameter translation occurs. This AVP contains the 5920 contents of the RADIUS Acct-Session-Id attribute. 5922 9.8.5. Acct-Multi-Session-Id AVP 5924 The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String, 5925 following the format specified in Section 8.8. The Acct-Multi- 5926 Session-Id AVP is used to link together multiple related accounting 5927 sessions, where each session would have a unique Session-Id, but the 5928 same Acct-Multi-Session-Id AVP. This AVP MAY be returned by the 5929 Diameter server in an authorization answer, and MUST be used in all 5930 accounting messages for the given session. 5932 9.8.6. Accounting-Sub-Session-Id AVP 5934 The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type 5935 Unsigned64 and contains the accounting sub-session identifier. The 5936 combination of the Session-Id and this AVP MUST be unique per sub- 5937 session, and the value of this AVP MUST be monotonically increased by 5938 one for all new sub-sessions. The absence of this AVP implies no 5939 sub-sessions are in use, with the exception of an Accounting-Request 5940 whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD 5941 message with no Accounting-Sub-Session-Id AVP present will signal the 5942 termination of all sub-sessions for a given Session-Id. 5944 9.8.7. Accounting-Realtime-Required AVP 5946 The Accounting-Realtime-Required AVP (AVP Code 483) is of type 5947 Enumerated and is sent from the Diameter home authorization server to 5948 the Diameter client or in the Accounting-Answer from the accounting 5949 server. The client uses information in this AVP to decide what to do 5950 if the sending of accounting records to the accounting server has 5951 been temporarily prevented due to, for instance, a network problem. 5953 DELIVER_AND_GRANT 1 5955 The AVP with Value field set to DELIVER_AND_GRANT means that the 5956 service MUST only be granted as long as there is a connection to 5957 an accounting server. Note that the set of alternative accounting 5958 servers are treated as one server in this sense. Having to move 5959 the accounting record stream to a backup server is not a reason to 5960 discontinue the service to the user. 5962 GRANT_AND_STORE 2 5964 The AVP with Value field set to GRANT_AND_STORE means that service 5965 SHOULD be granted if there is a connection, or as long as records 5966 can still be stored as described in Section 9.4. 5968 This is the default behavior if the AVP isn't included in the 5969 reply from the authorization server. 5971 GRANT_AND_LOSE 3 5973 The AVP with Value field set to GRANT_AND_LOSE means that service 5974 SHOULD be granted even if the records can not be delivered or 5975 stored. 5977 10. AVP Occurrence Table 5979 The following tables presents the AVPs defined in this document, and 5980 specifies in which Diameter messages they MAY be present or not. 5981 Note that AVPs that can only be present within a Grouped AVP are not 5982 represented in this table. 5984 The table uses the following symbols: 5986 0 The AVP MUST NOT be present in the message. 5988 0+ Zero or more instances of the AVP MAY be present in the 5989 message. 5991 0-1 Zero or one instance of the AVP MAY be present in the message. 5992 It is considered an error if there are more than one instance of 5993 the AVP. 5995 1 One instance of the AVP MUST be present in the message. 5997 1+ At least one instance of the AVP MUST be present in the 5998 message. 6000 10.1. Base Protocol Command AVP Table 6002 The table in this section is limited to the non-accounting Command 6003 Codes defined in this specification. 6005 +-----------------------------------------------+ 6006 | Command-Code | 6007 +---+---+---+---+---+---+---+---+---+---+---+---+ 6008 Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA| 6009 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ 6010 Acct-Interim- |0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | 6011 Interval | | | | | | | | | | | | | 6012 Accounting-Realtime-|0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | 6013 Required | | | | | | | | | | | | | 6014 Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6015 Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | 6016 Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6017 Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6018 Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6019 Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6020 Lifetime | | | | | | | | | | | | | 6021 Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ | 6022 Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 | 6023 Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | 6024 Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6025 Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1| 6026 Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6027 Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ | 6028 Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6029 Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6030 Inband-Security-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6031 Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6032 Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | 6033 Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | 6034 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| 6035 Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6036 Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ | 6037 Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ | 6038 Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6039 Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6040 Time | | | | | | | | | | | | | 6041 Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |0 |0 |1 | 6042 Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 | 6043 Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 | 6044 Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6045 Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 | 6046 Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6047 Failover | | | | | | | | | | | | | 6048 Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6049 Supported-Vendor-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6050 Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 | 6051 User-Name |0 |0 |0 |0 |0 |0 |0-1|0-1|0-1|0-1|0-1|0-1| 6052 Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6053 Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6054 Application-Id | | | | | | | | | | | | | 6055 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ 6057 10.2. Accounting AVP Table 6059 The table in this section is used to represent which AVPs defined in 6060 this document are to be present in the Accounting messages. These 6061 AVP occurrence requirements are guidelines, which may be expanded, 6062 and/or overridden by application-specific requirements in the 6063 Diameter applications documents. 6065 +-----------+ 6066 | Command | 6067 | Code | 6068 +-----+-----+ 6069 Attribute Name | ACR | ACA | 6070 ------------------------------+-----+-----+ 6071 Acct-Interim-Interval | 0-1 | 0-1 | 6072 Acct-Multi-Session-Id | 0-1 | 0-1 | 6073 Accounting-Record-Number | 1 | 1 | 6074 Accounting-Record-Type | 1 | 1 | 6075 Acct-Session-Id | 0-1 | 0-1 | 6076 Accounting-Sub-Session-Id | 0-1 | 0-1 | 6077 Accounting-Realtime-Required | 0-1 | 0-1 | 6078 Acct-Application-Id | 0-1 | 0-1 | 6079 Auth-Application-Id | 0 | 0 | 6080 Class | 0+ | 0+ | 6081 Destination-Host | 0-1 | 0 | 6082 Destination-Realm | 1 | 0 | 6083 Error-Reporting-Host | 0 | 0+ | 6084 Event-Timestamp | 0-1 | 0-1 | 6085 Origin-Host | 1 | 1 | 6086 Origin-Realm | 1 | 1 | 6087 Proxy-Info | 0+ | 0+ | 6088 Route-Record | 0+ | 0+ | 6089 Result-Code | 0 | 1 | 6090 Session-Id | 1 | 1 | 6091 Termination-Cause | 0 | 0 | 6092 User-Name | 0-1 | 0-1 | 6093 Vendor-Specific-Application-Id| 0-1 | 0-1 | 6094 ------------------------------+-----+-----+ 6096 11. IANA Considerations 6098 This section provides guidance to the Internet Assigned Numbers 6099 Authority (IANA) regarding registration of values related to the 6100 Diameter protocol, in accordance with BCP 26 [RFC2434]. The 6101 following policies are used here with the meanings defined in BCP 26: 6102 "Private Use", "First Come First Served", "Expert Review", 6103 "Specification Required", "IETF Consensus", "Standards Action". 6105 This section explains the criteria to be used by the IANA for 6106 assignment of numbers within namespaces defined within this document. 6108 Diameter is not intended as a general purpose protocol, and 6109 allocations SHOULD NOT be made for purposes unrelated to 6110 authentication, authorization or accounting. 6112 For registration requests where a Designated Expert should be 6113 consulted, the responsible IESG area director should appoint the 6114 Designated Expert. For Designated Expert with Specification 6115 Required, the request is posted to the DIME WG mailing list (or, if 6116 it has been disbanded, a successor designated by the Area Director) 6117 for comment and review, and MUST include a pointer to a public 6118 specification. Before a period of 30 days has passed, the Designated 6119 Expert will either approve or deny the registration request and 6120 publish a notice of the decision to the DIME WG mailing list or its 6121 successor. A denial notice must be justified by an explanation and, 6122 in the cases where it is possible, concrete suggestions on how the 6123 request can be modified so as to become acceptable. 6125 11.1. AVP Header 6127 As defined in Section 4, the AVP header contains three fields that 6128 requires IANA namespace management; the AVP Code, Vendor-ID and Flags 6129 field. 6131 11.1.1. AVP Codes 6133 The AVP Code namespace is used to identify attributes. There are 6134 multiple namespaces. Vendors can have their own AVP Codes namespace 6135 which will be identified by their Vendor-ID (also known as 6136 Enterprise-Number) and they control the assignments of their vendor- 6137 specific AVP codes within their own namespace. The absence of a 6138 Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA 6139 controlled AVP Codes namespace. The AVP Codes and sometimes also 6140 possible values in an AVP are controlled and maintained by IANA. 6142 AVP Code 0 is not used. AVP Codes 1-255 are managed separately as 6143 RADIUS Attribute Types [RADTYPE]. This document defines the AVP 6144 Codes 257-274, 276-285, 287, 291-300, 480, 483 and 485-486. See 6145 Section 4.5 for the assignment of the namespace in this 6146 specification. 6148 AVPs may be allocated following Designated Expert with Specification 6149 Required [RFC2434]. Release of blocks of AVPs (more than 3 at a time 6150 for a given purpose) should require IETF Consensus. 6152 Note that Diameter defines a mechanism for Vendor-Specific AVPs, 6153 where the Vendor-Id field in the AVP header is set to a non-zero 6154 value. Vendor-Specific AVPs codes are for Private Use and should be 6155 encouraged instead of allocation of global attribute types, for 6156 functions specific only to one vendor's implementation of Diameter, 6157 where no interoperability is deemed useful. Where a Vendor-Specific 6158 AVP is implemented by more than one vendor, allocation of global AVPs 6159 should be encouraged instead. 6161 11.1.2. AVP Flags 6163 There are 8 bits in the AVP Flags field of the AVP header, defined in 6164 Section 4. This document assigns bit 0 ('V'endor Specific), bit 1 6165 ('M'andatory) and bit 2 ('P'rotected). The remaining bits should 6166 only be assigned via a Standards Action [RFC2434]. 6168 11.2. Diameter Header 6170 As defined in Section 3, the Diameter header contains two fields that 6171 require IANA namespace management; Command Code and Command Flags. 6173 11.2.1. Command Codes 6175 The Command Code namespace is used to identify Diameter commands. 6176 The values 0-255 are reserved for RADIUS backward compatibility, and 6177 are defined as "RADIUS Packet Type Codes" in [RADTYPE]. Values 256- 6178 16,777,213 are for permanent, standard commands, allocated by Expert 6179 Review [RFC2434]. This document defines the Command Codes 257, 258, 6180 271, 274-275, 280 and 282. See Section 3.1 for the assignment of the 6181 namespace in this specification. 6183 The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe - 6184 0xffffff) are reserved for experimental commands. As these codes are 6185 only for experimental and testing purposes, no guarantee is made for 6186 interoperability between Diameter peers using experimental commands, 6187 as outlined in [IANA-EXP]. 6189 [Editor's note: The expert review process for command code allocation 6190 is being introduced to hasten the allocation process itself. 6191 Hopefully this will lessen the tendency to circumvent this process. 6193 Details will be added in subsequent revisions and more complete 6194 description will be added in the design guidelines document.] 6196 11.2.2. Command Flags 6198 There are eight bits in the Command Flags field of the Diameter 6199 header. This document assigns bit 0 ('R'equest), bit 1 ('P'roxy), 6200 bit 2 ('E'rror) and bit 3 ('T'). Bits 4 through 7 MUST only be 6201 assigned via a Standards Action [RFC2434]. 6203 11.3. Application Identifiers 6205 As defined in Section 2.4, the Application Identifier is used to 6206 identify a specific Diameter Application. There are standards-track 6207 application ids and vendor specific application ids. 6209 IANA [RFC2434] has assigned the range 0x00000001 to 0x00ffffff for 6210 standards-track applications; and 0x01000000 - 0xfffffffe for vendor 6211 specific applications, on a first-come, first-served basis. The 6212 following values are allocated. 6214 Diameter Common Messages 0 6215 NASREQ 1 [RFC4005] 6216 Mobile-IP 2 [RFC4004] 6217 Diameter Base Accounting 3 6218 Relay 0xffffffff 6220 Assignment of standards-track application IDs are by Designated 6221 Expert with Specification Required [RFC2434]. 6223 Both Auth-Application-Id and Acct-Application-Id AVPs use the same 6224 Application Identifier space. A diameter node advertising itself as 6225 a relay agent MUST set either Application-Id or Acct-Application-Id 6226 to 0xffffffff. 6228 Vendor-Specific Application Identifiers, are for Private Use. Vendor- 6229 Specific Application Identifiers are assigned on a First Come, First 6230 Served basis by IANA. 6232 11.4. AVP Values 6234 Certain AVPs in Diameter define a list of values with various 6235 meanings. For attributes other than those specified in this section, 6236 adding additional values to the list can be done on a First Come, 6237 First Served basis by IANA. 6239 11.4.1. Result-Code AVP Values 6241 As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines 6242 the values 1001, 2001-2002, 3001-3012, 4001-4003 and 5001-5021. 6244 All remaining values are available for assignment via IETF Consensus 6245 [RFC2434]. 6247 11.4.2. Accounting-Record-Type AVP Values 6249 As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code 6250 480) defines the values 1-4. All remaining values are available for 6251 assignment via IETF Consensus [RFC2434]. 6253 11.4.3. Termination-Cause AVP Values 6255 As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295) 6256 defines the values 1-8. All remaining values are available for 6257 assignment via IETF Consensus [RFC2434]. 6259 11.4.4. Redirect-Host-Usage AVP Values 6261 As defined in Section 6.13, the Redirect-Host-Usage AVP (AVP Code 6262 261) defines the values 0-5. All remaining values are available for 6263 assignment via IETF Consensus [RFC2434]. 6265 11.4.5. Session-Server-Failover AVP Values 6267 As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code 6268 271) defines the values 0-3. All remaining values are available for 6269 assignment via IETF Consensus [RFC2434]. 6271 11.4.6. Session-Binding AVP Values 6273 As defined in Section 8.17, the Session-Binding AVP (AVP Code 270) 6274 defines the bits 1-4. All remaining bits are available for 6275 assignment via IETF Consensus [RFC2434]. 6277 11.4.7. Disconnect-Cause AVP Values 6279 As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273) 6280 defines the values 0-2. All remaining values are available for 6281 assignment via IETF Consensus [RFC2434]. 6283 11.4.8. Auth-Request-Type AVP Values 6285 As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274) 6286 defines the values 1-3. All remaining values are available for 6287 assignment via IETF Consensus [RFC2434]. 6289 11.4.9. Auth-Session-State AVP Values 6291 As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277) 6292 defines the values 0-1. All remaining values are available for 6293 assignment via IETF Consensus [RFC2434]. 6295 11.4.10. Re-Auth-Request-Type AVP Values 6297 As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code 6298 285) defines the values 0-1. All remaining values are available for 6299 assignment via IETF Consensus [RFC2434]. 6301 11.4.11. Accounting-Realtime-Required AVP Values 6303 As defined in Section 9.8.7, the Accounting-Realtime-Required AVP 6304 (AVP Code 483) defines the values 1-3. All remaining values are 6305 available for assignment via IETF Consensus [RFC2434]. 6307 11.4.12. Inband-Security-Id AVP (code 299) 6309 As defined in Section 6.10, the Inband-Security-Id AVP (AVP Code 299) 6310 defines the values 0-1. All remaining values are available for 6311 assignment via IETF Consensus [RFC2434]. 6313 11.5. Diameter TCP/SCTP Port Numbers 6315 The IANA has assigned TCP and SCTP port number 3868 to Diameter. 6317 11.6. NAPTR Service Fields 6319 The registration in the RFC MUST include the following information: 6321 Service Field: The service field being registered. An example for a 6322 new fictitious transport protocol called NCTP might be "AAA+D2N". 6324 Protocol: The specific transport protocol associated with that 6325 service field. This MUST include the name and acronym for the 6326 protocol, along with reference to a document that describes the 6327 transport protocol. For example - "New Connectionless Transport 6328 Protocol (NCTP), RFC 5766". 6330 Name and Contact Information: The name, address, email address and 6331 telephone number for the person performing the registration. 6333 The following values have been placed into the registry: 6335 Services Field Protocol 6337 AAA+D2T TCP 6338 AAA+D2S SCTP 6340 12. Diameter protocol related configurable parameters 6342 This section contains the configurable parameters that are found 6343 throughout this document: 6345 Diameter Peer 6347 A Diameter entity MAY communicate with peers that are statically 6348 configured. A statically configured Diameter peer would require 6349 that either the IP address or the fully qualified domain name 6350 (FQDN) be supplied, which would then be used to resolve through 6351 DNS. 6353 Routing Table 6355 A Diameter proxy server routes messages based on the realm portion 6356 of a Network Access Identifier (NAI). The server MUST have a 6357 table of Realm Names, and the address of the peer to which the 6358 message must be forwarded to. The routing table MAY also include 6359 a "default route", which is typically used for all messages that 6360 cannot be locally processed. 6362 Tc timer 6364 The Tc timer controls the frequency that transport connection 6365 attempts are done to a peer with whom no active transport 6366 connection exists. The recommended value is 30 seconds. 6368 13. Security Considerations 6370 The Diameter base protocol assumes that messages maybe secured by 6371 using TLS. As an alternative, IPSec can be also be used to secure 6372 Diameter peer connections but its usage is transparent from the 6373 Diameter node and Diameter protocol perspective. These security 6374 mechanism is acceptable in environments where there is no untrusted 6375 third party agent. 6377 Diameter clients, such as Network Access Servers (NASes) and Mobility 6378 Agents MAY support TLS [RFC4346]. Diameter servers MUST support TLS. 6379 Diameter implementations SHOULD use transmission-level security of 6380 some kind (IPsec or TLS) on each connection. 6382 If a Diameter connection is to be protected via TLS, then the CER/CEA 6383 exchange MUST include an Inband-Security-ID AVP with a value of TLS. 6384 For TLS usage, a TLS handshake will begin when both ends are in the 6385 open state, after completion of the CER/CEA exchange. If the TLS 6386 handshake is successful, all further messages will be sent via TLS. 6387 If the handshake fails, both ends move to the closed state. See 6388 Sections 13.1 for more details. 6390 13.1. TLS Usage 6392 A Diameter node that initiates a connection to another Diameter node 6393 acts as a TLS client according to [RFC4346], and a Diameter node that 6394 accepts a connection acts as a TLS server. Diameter nodes 6395 implementing TLS for security MUST mutually authenticate as part of 6396 TLS session establishment. In order to ensure mutual authentication, 6397 the Diameter node acting as TLS server must request a certificate 6398 from the Diameter node acting as TLS client, and the Diameter node 6399 acting as TLS client MUST be prepared to supply a certificate on 6400 request. 6402 Diameter nodes MUST be able to negotiate the following TLS cipher 6403 suites: 6405 TLS_RSA_WITH_RC4_128_MD5 6406 TLS_RSA_WITH_RC4_128_SHA 6407 TLS_RSA_WITH_3DES_EDE_CBC_SHA 6409 Diameter nodes SHOULD be able to negotiate the following TLS cipher 6410 suite: 6412 TLS_RSA_WITH_AES_128_CBC_SHA 6414 Diameter nodes MAY negotiate other TLS cipher suites. 6416 13.2. Peer-to-Peer Considerations 6418 As with any peer-to-peer protocol, proper configuration of the trust 6419 model within a Diameter peer is essential to security. When 6420 certificates are used, it is necessary to configure the root 6421 certificate authorities trusted by the Diameter peer. These root CAs 6422 are likely to be unique to Diameter usage and distinct from the root 6423 CAs that might be trusted for other purposes such as Web browsing. 6424 In general, it is expected that those root CAs will be configured so 6425 as to reflect the business relationships between the organization 6426 hosting the Diameter peer and other organizations. As a result, a 6427 Diameter peer will typically not be configured to allow connectivity 6428 with any arbitrary peer. With certificate authentication, Diameter 6429 peers may not be known beforehand and therefore peer discovery may be 6430 required. 6432 14. References 6434 14.1. Normative References 6436 [FLOATPOINT] 6437 Institute of Electrical and Electronics Engineers, "IEEE 6438 Standard for Binary Floating-Point Arithmetic, ANSI/IEEE 6439 Standard 754-1985", August 1985. 6441 [IANAADFAM] 6442 IANA,, "Address Family Numbers", 6443 http://www.iana.org/assignments/address-family-numbers. 6445 [RADTYPE] IANA,, "RADIUS Types", 6446 http://www.iana.org/assignments/radius-types. 6448 [IPV4] Postel, J., "Internet Protocol", RFC 791, September 1981. 6450 [TCP] Postel, J., "Transmission Control Protocol", RFC 793, 6451 January 1981. 6453 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and 6454 Accounting (AAA) Transport Profile", RFC 3539, June 2003. 6456 [RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and 6457 P. McCann, "Diameter Mobile IPv4 Application", RFC 4004, 6458 August 2005. 6460 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton, 6461 "Diameter Network Access Server Application", RFC 4005, 6462 August 2005. 6464 [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J. 6465 Loughney, "Diameter Credit-Control Application", RFC 4006, 6466 August 2005. 6468 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible 6469 Authentication Protocol (EAP) Application", RFC 4072, 6470 August 2005. 6472 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M., 6473 Canales-Valenzuela, C., and K. Tammi, "Diameter Session 6474 Initiation Protocol (SIP) Application", RFC 4740, 6475 November 2006. 6477 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 6478 Specifications: ABNF", RFC 4234, October 2005. 6480 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. 6481 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 6483 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 6484 Levkowetz, "Extensible Authentication Protocol (EAP)", 6485 RFC 3748, June 2004. 6487 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 6488 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 6489 October 1998. 6491 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 6492 RFC 4306, December 2005. 6494 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 6495 Architecture", RFC 4291, February 2006. 6497 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 6498 Requirement Levels", BCP 14, RFC 2119, March 1997. 6500 [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The 6501 Network Access Identifier", RFC 4282, December 2005. 6503 [RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS) 6504 Part Three: The Domain Name System (DNS) Database", 6505 RFC 3403, October 2002. 6507 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 6508 A., Peterson, J., Sparks, R., Handley, M., and E. 6509 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 6510 June 2002. 6512 [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C., 6513 Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M., 6514 Zhang, L., and V. Paxson, "Stream Control Transmission 6515 Protocol", RFC 2960, October 2000. 6517 [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security 6518 (TLS) Protocol Version 1.1", RFC 4346, April 2006. 6520 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 6521 Resource Identifier (URI): Generic Syntax", STD 66, 6522 RFC 3986, January 2005. 6524 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 6525 10646", STD 63, RFC 3629, November 2003. 6527 14.2. Informational References 6529 [RFC2989] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, P., 6530 Shiino, H., Zorn, G., Dommety, G., C.Perkins, B.Patil, 6531 D.Mitton, S.Manning, M.Beadles, P.Walsh, X.Chen, 6532 S.Sivalingham, A.Hameed, M.Munson, S.Jacobs, B.Lim, 6533 B.Hirschman, R.Hsu, Y.Xu, E.Campell, S.Baba, and E.Jaques, 6534 "Criteria for Evaluating AAA Protocols for Network 6535 Access", RFC 2989, November 2000. 6537 [RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction to 6538 Accounting Management", RFC 2975, October 2000. 6540 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by 6541 an On-line Database", RFC 3232, January 2002. 6543 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B. 6544 Aboba, "Dynamic Authorization Extensions to Remote 6545 Authentication Dial In User Service (RADIUS)", RFC 3576, 6546 July 2003. 6548 [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, 6549 RFC 1661, July 1994. 6551 [RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy 6552 Implementation in Roaming", RFC 2607, June 1999. 6554 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. 6556 [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS 6557 Extensions", RFC 2869, June 2000. 6559 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 6560 "Remote Authentication Dial In User Service (RADIUS)", 6561 RFC 2865, June 2000. 6563 [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6", 6564 RFC 3162, August 2001. 6566 [RFC2194] Aboba, B., Lu, J., Alsop, J., Ding, J., and W. Wang, 6567 "Review of Roaming Implementations", RFC 2194, 6568 September 1997. 6570 [RFC2477] Aboba, B. and G. Zorn, "Criteria for Evaluating Roaming 6571 Protocols", RFC 2477, January 1999. 6573 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 6574 Internet Protocol", RFC 4301, December 2005. 6576 [RFC4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 6577 for IPv4, IPv6 and OSI", RFC 4330, January 2006. 6579 [RFC1492] Finseth, C., "An Access Control Protocol, Sometimes Called 6580 TACACS", RFC 1492, July 1993. 6582 [IANA-EXP] 6583 Narten, T., "Assigning Experimental and Testing Numbers 6584 Considered Useful, Work in Progress.". 6586 Appendix A. Acknowledgements 6588 The authors would like to thank the following people that have 6589 provided proposals and contributions to this document: 6591 To Vishnu Ram and Satendra Gera for their contributions on 6592 Capabilities Updates, Predictive Loop Avoidance as well as many other 6593 technical proposals. To Tolga Asveren for his insights and 6594 contributions on almost all of the proposed solutions incorporated 6595 into this document. To Timothy Smith for helping on the Capabilities 6596 Updates and other topics. To Tony Zhang for providing fixes to loop 6597 holes on composing Failed-AVPs as well as many other issues and 6598 topics. To Jan Nordqvist for clearly stating the usage of 6599 application ids. To Anders Kristensen for providing needed technical 6600 opinions. To David Frascone for providing invaluable review of the 6601 document. 6603 Special thanks also to people who have provided invaluable comments 6604 and inputs especially in resolving controversial issues: 6606 Glen Zorn, Yoshihiro Ohba, Marco Stura, and Pasi Eronen. 6608 Finally, we would like to thank the original authors of this 6609 document: 6611 Pat Calhoun, John Loughney, Jari Arkko, Erik Guttman and Glen Zorn. 6613 Their invaluable knowledge and experience has given us a robust and 6614 flexible AAA protocol that many people have seen great value in 6615 adopting. We greatly appreciate their support and stewardship for 6616 the continued improvements of Diameter as a protocol. We would also 6617 like to extend our gratitude to folks aside from the authors who have 6618 assisted and contributed to the original version of this document. 6619 Their efforts significantly contributed to the success of Diameter. 6621 Appendix B. NAPTR Example 6623 As an example, consider a client that wishes to resolve aaa:ex.com. 6624 The client performs a NAPTR query for that domain, and the following 6625 NAPTR records are returned: 6627 ;; order pref flags service regexp replacement 6628 IN NAPTR 50 50 "s" "AAA+D2S" "" 6629 _diameter._sctp.example.com IN NAPTR 100 50 "s" "AAA+D2T" 6630 "" _aaa._tcp.example.com 6632 This indicates that the server supports SCTP, and TCP, in that order. 6633 If the client supports over SCTP, SCTP will be used, targeted to a 6634 host determined by an SRV lookup of _diameter._sctp.ex.com. That 6635 lookup would return: 6637 ;; Priority Weight Port Target 6638 IN SRV 0 1 5060 server1.example.com IN SRV 0 6639 2 5060 server2.example.com 6641 Appendix C. Duplicate Detection 6643 As described in Section 9.4, accounting record duplicate detection is 6644 based on session identifiers. Duplicates can appear for various 6645 reasons: 6647 o Failover to an alternate server. Where close to real-time 6648 performance is required, failover thresholds need to be kept low 6649 and this may lead to an increased likelihood of duplicates. 6650 Failover can occur at the client or within Diameter agents. 6652 o Failure of a client or agent after sending of a record from non- 6653 volatile memory, but prior to receipt of an application layer ACK 6654 and deletion of the record. record to be sent. This will result 6655 in retransmission of the record soon after the client or agent has 6656 rebooted. 6658 o Duplicates received from RADIUS gateways. Since the 6659 retransmission behavior of RADIUS is not defined within [RFC2865], 6660 the likelihood of duplication will vary according to the 6661 implementation. 6663 o Implementation problems and misconfiguration. 6665 The T flag is used as an indication of an application layer 6666 retransmission event, e.g., due to failover to an alternate server. 6667 It is defined only for request messages sent by Diameter clients or 6668 agents. For instance, after a reboot, a client may not know whether 6669 it has already tried to send the accounting records in its non- 6670 volatile memory before the reboot occurred. Diameter servers MAY use 6671 the T flag as an aid when processing requests and detecting duplicate 6672 messages. However, servers that do this MUST ensure that duplicates 6673 are found even when the first transmitted request arrives at the 6674 server after the retransmitted request. It can be used only in cases 6675 where no answer has been received from the Server for a request and 6676 the request is sent again, (e.g., due to a failover to an alternate 6677 peer, due to a recovered primary peer or due to a client re-sending a 6678 stored record from non-volatile memory such as after reboot of a 6679 client or agent). 6681 In some cases the Diameter accounting server can delay the duplicate 6682 detection and accounting record processing until a post-processing 6683 phase takes place. At that time records are likely to be sorted 6684 according to the included User-Name and duplicate elimination is easy 6685 in this case. In other situations it may be necessary to perform 6686 real-time duplicate detection, such as when credit limits are imposed 6687 or real-time fraud detection is desired. 6689 In general, only generation of duplicates due to failover or re- 6690 sending of records in non-volatile storage can be reliably detected 6691 by Diameter clients or agents. In such cases the Diameter client or 6692 agents can mark the message as possible duplicate by setting the T 6693 flag. Since the Diameter server is responsible for duplicate 6694 detection, it can choose to make use of the T flag or not, in order 6695 to optimize duplicate detection. Since the T flag does not affect 6696 interoperability, and may not be needed by some servers, generation 6697 of the T flag is REQUIRED for Diameter clients and agents, but MAY be 6698 implemented by Diameter servers. 6700 As an example, it can be usually be assumed that duplicates appear 6701 within a time window of longest recorded network partition or device 6702 fault, perhaps a day. So only records within this time window need 6703 to be looked at in the backward direction. Secondly, hashing 6704 techniques or other schemes, such as the use of the T flag in the 6705 received messages, may be used to eliminate the need to do a full 6706 search even in this set except for rare cases. 6708 The following is an example of how the T flag may be used by the 6709 server to detect duplicate requests. 6711 A Diameter server MAY check the T flag of the received message to 6712 determine if the record is a possible duplicate. If the T flag is 6713 set in the request message, the server searches for a duplicate 6714 within a configurable duplication time window backward and 6715 forward. This limits database searching to those records where 6716 the T flag is set. In a well run network, network partitions and 6717 device faults will presumably be rare events, so this approach 6718 represents a substantial optimization of the duplicate detection 6719 process. During failover, it is possible for the original record 6720 to be received after the T flag marked record, due to differences 6721 in network delays experienced along the path by the original and 6722 duplicate transmissions. The likelihood of this occurring 6723 increases as the failover interval is decreased. In order to be 6724 able to detect out of order duplicates, the Diameter server should 6725 use backward and forward time windows when performing duplicate 6726 checking for the T flag marked request. For example, in order to 6727 allow time for the original record to exit the network and be 6728 recorded by the accounting server, the Diameter server can delay 6729 processing records with the T flag set until a time period 6730 TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after the closing 6731 of the original transport connection. After this time period has 6732 expired, then it may check the T flag marked records against the 6733 database with relative assurance that the original records, if 6734 sent, have been received and recorded. 6736 Authors' Addresses 6738 Victor Fajardo (editor) 6739 Toshiba America Research 6740 One Telcordia Drive, 1S-222 6741 Piscataway, NJ 08854 6742 USA 6744 Phone: 1 908-421-1845 6745 Email: vfajardo@tari.toshiba.com 6747 Jari Arkko 6748 Ericsson Research 6749 02420 Jorvas 6750 Finland 6752 Phone: +358 40 5079256 6753 Email: jari.arkko@ericsson.com 6755 John Loughney 6756 Nokia Research Center 6757 955 Page Mill Road 6758 Palo Alto, CA 94304 6759 US 6761 Phone: 1-650-283-8068 6762 Email: john.loughney@nokia.com 6764 Full Copyright Statement 6766 Copyright (C) The IETF Trust (2007). 6768 This document is subject to the rights, licenses and restrictions 6769 contained in BCP 78, and except as set forth therein, the authors 6770 retain all their rights. 6772 This document and the information contained herein are provided on an 6773 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 6774 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 6775 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 6776 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 6777 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 6778 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 6780 Intellectual Property 6782 The IETF takes no position regarding the validity or scope of any 6783 Intellectual Property Rights or other rights that might be claimed to 6784 pertain to the implementation or use of the technology described in 6785 this document or the extent to which any license under such rights 6786 might or might not be available; nor does it represent that it has 6787 made any independent effort to identify any such rights. Information 6788 on the procedures with respect to rights in RFC documents can be 6789 found in BCP 78 and BCP 79. 6791 Copies of IPR disclosures made to the IETF Secretariat and any 6792 assurances of licenses to be made available, or the result of an 6793 attempt made to obtain a general license or permission for the use of 6794 such proprietary rights by implementers or users of this 6795 specification can be obtained from the IETF on-line IPR repository at 6796 http://www.ietf.org/ipr. 6798 The IETF invites any interested party to bring to its attention any 6799 copyrights, patents or patent applications, or other proprietary 6800 rights that may cover technology that may be required to implement 6801 this standard. Please address the information to the IETF at 6802 ietf-ipr@ietf.org. 6804 Acknowledgment 6806 Funding for the RFC Editor function is provided by the IETF 6807 Administrative Support Activity (IASA).