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'RADTYPE' ** Obsolete normative reference: RFC 793 (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 normative reference: RFC 3280 (Obsoleted by RFC 5280) ** Obsolete normative reference: RFC 3490 (Obsoleted by RFC 5890, RFC 5891) ** Obsolete normative reference: RFC 3491 (Obsoleted by RFC 5891) -- 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: 14 errors (**), 0 flaws (~~), 10 warnings (==), 13 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 Obsoletes: 3588 (if approved) J. Arkko 5 Intended status: Standards Track Ericsson Research 6 Expires: January 10, 2009 J. Loughney 7 Nokia Research Center 8 G. Zorn 9 NetCube 10 July 9, 2008 12 Diameter Base Protocol 13 draft-ietf-dime-rfc3588bis-11.txt 15 Status of this Memo 17 By submitting this Internet-Draft, each author represents that any 18 applicable patent or other IPR claims of which he or she is aware 19 have been or will be disclosed, and any of which he or she becomes 20 aware will be disclosed, in accordance with Section 6 of BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF), its areas, and its working groups. Note that 24 other groups may also distribute working documents as Internet- 25 Drafts. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 The list of current Internet-Drafts can be accessed at 33 http://www.ietf.org/ietf/1id-abstracts.txt. 35 The list of Internet-Draft Shadow Directories can be accessed at 36 http://www.ietf.org/shadow.html. 38 This Internet-Draft will expire on January 10, 2009. 40 Copyright Notice 42 Copyright (C) The IETF Trust (2008). 44 Abstract 46 The Diameter base protocol is intended to provide an Authentication, 47 Authorization and Accounting (AAA) framework for applications such as 48 network access or IP mobility. Diameter is also intended to work in 49 both local Authentication, Authorization & Accounting and roaming 50 situations. This document specifies the message format, transport, 51 error reporting, accounting and security services to be used by all 52 Diameter applications. The Diameter base application needs to be 53 supported by all Diameter implementations. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7 58 1.1. Diameter Protocol . . . . . . . . . . . . . . . . . . . . 9 59 1.1.1. Description of the Document Set . . . . . . . . . . 11 60 1.1.2. Conventions Used in This Document . . . . . . . . . 12 61 1.1.3. Changes from RFC3588 . . . . . . . . . . . . . . . . 12 62 1.2. Approach to Extensibility . . . . . . . . . . . . . . . . 13 63 1.2.1. Defining New AVP Values . . . . . . . . . . . . . . 13 64 1.2.2. Creating New AVPs . . . . . . . . . . . . . . . . . 13 65 1.2.3. Creating New Commands . . . . . . . . . . . . . . . 14 66 1.2.4. Creating New Diameter Applications . . . . . . . . . 14 67 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 15 68 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 22 69 2.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 23 70 2.1.1. SCTP Guidelines . . . . . . . . . . . . . . . . . . 24 71 2.2. Securing Diameter Messages . . . . . . . . . . . . . . . 24 72 2.3. Diameter Application Compliance . . . . . . . . . . . . . 24 73 2.4. Application Identifiers . . . . . . . . . . . . . . . . . 24 74 2.5. Connections vs. Sessions . . . . . . . . . . . . . . . . 25 75 2.6. Peer Table . . . . . . . . . . . . . . . . . . . . . . . 26 76 2.7. Routing Table . . . . . . . . . . . . . . . . . . . . . . 27 77 2.8. Role of Diameter Agents . . . . . . . . . . . . . . . . . 28 78 2.8.1. Relay Agents . . . . . . . . . . . . . . . . . . . . 30 79 2.8.2. Proxy Agents . . . . . . . . . . . . . . . . . . . . 31 80 2.8.3. Redirect Agents . . . . . . . . . . . . . . . . . . 31 81 2.8.4. Translation Agents . . . . . . . . . . . . . . . . . 32 82 2.9. Diameter Path Authorization . . . . . . . . . . . . . . . 33 83 3. Diameter Header . . . . . . . . . . . . . . . . . . . . . . . 35 84 3.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 38 85 3.2. Command Code ABNF specification . . . . . . . . . . . . . 38 86 3.3. Diameter Command Naming Conventions . . . . . . . . . . . 40 87 4. Diameter AVPs . . . . . . . . . . . . . . . . . . . . . . . . 42 88 4.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 42 89 4.1.1. Optional Header Elements . . . . . . . . . . . . . . 43 90 4.2. Basic AVP Data Formats . . . . . . . . . . . . . . . . . 44 91 4.3. Derived AVP Data Formats . . . . . . . . . . . . . . . . 45 92 4.4. Grouped AVP Values . . . . . . . . . . . . . . . . . . . 52 93 4.4.1. Example AVP with a Grouped Data type . . . . . . . . 53 94 4.5. Diameter Base Protocol AVPs . . . . . . . . . . . . . . . 56 95 5. Diameter Peers . . . . . . . . . . . . . . . . . . . . . . . 59 96 5.1. Peer Connections . . . . . . . . . . . . . . . . . . . . 59 97 5.2. Diameter Peer Discovery . . . . . . . . . . . . . . . . . 59 98 5.3. Capabilities Exchange . . . . . . . . . . . . . . . . . . 62 99 5.3.1. Capabilities-Exchange-Request . . . . . . . . . . . 63 100 5.3.2. Capabilities-Exchange-Answer . . . . . . . . . . . . 64 101 5.3.3. Vendor-Id AVP . . . . . . . . . . . . . . . . . . . 64 102 5.3.4. Firmware-Revision AVP . . . . . . . . . . . . . . . 64 103 5.3.5. Host-IP-Address AVP . . . . . . . . . . . . . . . . 65 104 5.3.6. Supported-Vendor-Id AVP . . . . . . . . . . . . . . 65 105 5.3.7. Product-Name AVP . . . . . . . . . . . . . . . . . . 65 106 5.4. Disconnecting Peer connections . . . . . . . . . . . . . 65 107 5.4.1. Disconnect-Peer-Request . . . . . . . . . . . . . . 66 108 5.4.2. Disconnect-Peer-Answer . . . . . . . . . . . . . . . 66 109 5.4.3. Disconnect-Cause AVP . . . . . . . . . . . . . . . . 67 110 5.5. Transport Failure Detection . . . . . . . . . . . . . . . 67 111 5.5.1. Device-Watchdog-Request . . . . . . . . . . . . . . 67 112 5.5.2. Device-Watchdog-Answer . . . . . . . . . . . . . . . 68 113 5.5.3. Transport Failure Algorithm . . . . . . . . . . . . 68 114 5.5.4. Failover and Failback Procedures . . . . . . . . . . 68 115 5.6. Peer State Machine . . . . . . . . . . . . . . . . . . . 69 116 5.6.1. Incoming connections . . . . . . . . . . . . . . . . 71 117 5.6.2. Events . . . . . . . . . . . . . . . . . . . . . . . 72 118 5.6.3. Actions . . . . . . . . . . . . . . . . . . . . . . 73 119 5.6.4. The Election Process . . . . . . . . . . . . . . . . 75 120 5.6.5. Capabilities Update . . . . . . . . . . . . . . . . 75 121 6. Diameter message processing . . . . . . . . . . . . . . . . . 76 122 6.1. Diameter Request Routing Overview . . . . . . . . . . . . 76 123 6.1.1. Originating a Request . . . . . . . . . . . . . . . 77 124 6.1.2. Sending a Request . . . . . . . . . . . . . . . . . 77 125 6.1.3. Receiving Requests . . . . . . . . . . . . . . . . . 78 126 6.1.4. Processing Local Requests . . . . . . . . . . . . . 78 127 6.1.5. Request Forwarding . . . . . . . . . . . . . . . . . 78 128 6.1.6. Request Routing . . . . . . . . . . . . . . . . . . 78 129 6.1.7. Predictive Loop Avoidance . . . . . . . . . . . . . 79 130 6.1.8. Redirecting requests . . . . . . . . . . . . . . . . 79 131 6.1.9. Relaying and Proxying Requests . . . . . . . . . . . 81 132 6.2. Diameter Answer Processing . . . . . . . . . . . . . . . 82 133 6.2.1. Processing received Answers . . . . . . . . . . . . 82 134 6.2.2. Relaying and Proxying Answers . . . . . . . . . . . 82 135 6.3. Origin-Host AVP . . . . . . . . . . . . . . . . . . . . . 83 136 6.4. Origin-Realm AVP . . . . . . . . . . . . . . . . . . . . 83 137 6.5. Destination-Host AVP . . . . . . . . . . . . . . . . . . 83 138 6.6. Destination-Realm AVP . . . . . . . . . . . . . . . . . . 84 139 6.7. Routing AVPs . . . . . . . . . . . . . . . . . . . . . . 84 140 6.7.1. Route-Record AVP . . . . . . . . . . . . . . . . . . 84 141 6.7.2. Proxy-Info AVP . . . . . . . . . . . . . . . . . . . 84 142 6.7.3. Proxy-Host AVP . . . . . . . . . . . . . . . . . . . 85 143 6.7.4. Proxy-State AVP . . . . . . . . . . . . . . . . . . 85 144 6.8. Auth-Application-Id AVP . . . . . . . . . . . . . . . . . 85 145 6.9. Acct-Application-Id AVP . . . . . . . . . . . . . . . . . 85 146 6.10. Inband-Security-Id AVP . . . . . . . . . . . . . . . . . 85 147 6.11. Vendor-Specific-Application-Id AVP . . . . . . . . . . . 86 148 6.12. Redirect-Host AVP . . . . . . . . . . . . . . . . . . . . 87 149 6.13. Redirect-Host-Usage AVP . . . . . . . . . . . . . . . . . 87 150 6.14. Redirect-Max-Cache-Time AVP . . . . . . . . . . . . . . . 88 151 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 90 152 7.1. Result-Code AVP . . . . . . . . . . . . . . . . . . . . . 91 153 7.1.1. Informational . . . . . . . . . . . . . . . . . . . 92 154 7.1.2. Success . . . . . . . . . . . . . . . . . . . . . . 92 155 7.1.3. Protocol Errors . . . . . . . . . . . . . . . . . . 93 156 7.1.4. Transient Failures . . . . . . . . . . . . . . . . . 94 157 7.1.5. Permanent Failures . . . . . . . . . . . . . . . . . 95 158 7.2. Error Bit . . . . . . . . . . . . . . . . . . . . . . . . 98 159 7.3. Error-Message AVP . . . . . . . . . . . . . . . . . . . . 98 160 7.4. Error-Reporting-Host AVP . . . . . . . . . . . . . . . . 98 161 7.5. Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . . 99 162 7.6. Experimental-Result AVP . . . . . . . . . . . . . . . . . 100 163 7.7. Experimental-Result-Code AVP . . . . . . . . . . . . . . 100 164 8. Diameter User Sessions . . . . . . . . . . . . . . . . . . . 101 165 8.1. Authorization Session State Machine . . . . . . . . . . . 102 166 8.2. Accounting Session State Machine . . . . . . . . . . . . 107 167 8.3. Server-Initiated Re-Auth . . . . . . . . . . . . . . . . 112 168 8.3.1. Re-Auth-Request . . . . . . . . . . . . . . . . . . 112 169 8.3.2. Re-Auth-Answer . . . . . . . . . . . . . . . . . . . 113 170 8.4. Session Termination . . . . . . . . . . . . . . . . . . . 114 171 8.4.1. Session-Termination-Request . . . . . . . . . . . . 115 172 8.4.2. Session-Termination-Answer . . . . . . . . . . . . . 115 173 8.5. Aborting a Session . . . . . . . . . . . . . . . . . . . 116 174 8.5.1. Abort-Session-Request . . . . . . . . . . . . . . . 117 175 8.5.2. Abort-Session-Answer . . . . . . . . . . . . . . . . 117 176 8.6. Inferring Session Termination from Origin-State-Id . . . 118 177 8.7. Auth-Request-Type AVP . . . . . . . . . . . . . . . . . . 119 178 8.8. Session-Id AVP . . . . . . . . . . . . . . . . . . . . . 119 179 8.9. Authorization-Lifetime AVP . . . . . . . . . . . . . . . 120 180 8.10. Auth-Grace-Period AVP . . . . . . . . . . . . . . . . . . 121 181 8.11. Auth-Session-State AVP . . . . . . . . . . . . . . . . . 121 182 8.12. Re-Auth-Request-Type AVP . . . . . . . . . . . . . . . . 122 183 8.13. Session-Timeout AVP . . . . . . . . . . . . . . . . . . . 122 184 8.14. User-Name AVP . . . . . . . . . . . . . . . . . . . . . . 123 185 8.15. Termination-Cause AVP . . . . . . . . . . . . . . . . . . 123 186 8.16. Origin-State-Id AVP . . . . . . . . . . . . . . . . . . . 124 187 8.17. Session-Binding AVP . . . . . . . . . . . . . . . . . . . 125 188 8.18. Session-Server-Failover AVP . . . . . . . . . . . . . . . 125 189 8.19. Multi-Round-Time-Out AVP . . . . . . . . . . . . . . . . 126 190 8.20. Class AVP . . . . . . . . . . . . . . . . . . . . . . . . 126 191 8.21. Event-Timestamp AVP . . . . . . . . . . . . . . . . . . . 127 192 9. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . 128 193 9.1. Server Directed Model . . . . . . . . . . . . . . . . . . 128 194 9.2. Protocol Messages . . . . . . . . . . . . . . . . . . . . 129 195 9.3. Accounting Application Extension and Requirements . . . . 129 196 9.4. Fault Resilience . . . . . . . . . . . . . . . . . . . . 130 197 9.5. Accounting Records . . . . . . . . . . . . . . . . . . . 130 198 9.6. Correlation of Accounting Records . . . . . . . . . . . . 131 199 9.7. Accounting Command-Codes . . . . . . . . . . . . . . . . 132 200 9.7.1. Accounting-Request . . . . . . . . . . . . . . . . . 132 201 9.7.2. Accounting-Answer . . . . . . . . . . . . . . . . . 133 202 9.8. Accounting AVPs . . . . . . . . . . . . . . . . . . . . . 134 203 9.8.1. Accounting-Record-Type AVP . . . . . . . . . . . . . 134 204 9.8.2. Acct-Interim-Interval AVP . . . . . . . . . . . . . 135 205 9.8.3. Accounting-Record-Number AVP . . . . . . . . . . . . 136 206 9.8.4. Acct-Session-Id AVP . . . . . . . . . . . . . . . . 136 207 9.8.5. Acct-Multi-Session-Id AVP . . . . . . . . . . . . . 136 208 9.8.6. Accounting-Sub-Session-Id AVP . . . . . . . . . . . 136 209 9.8.7. Accounting-Realtime-Required AVP . . . . . . . . . . 137 210 10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . 138 211 10.1. Base Protocol Command AVP Table . . . . . . . . . . . . . 138 212 10.2. Accounting AVP Table . . . . . . . . . . . . . . . . . . 139 213 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 141 214 11.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 141 215 11.1.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . 141 216 11.1.2. AVP Flags . . . . . . . . . . . . . . . . . . . . . 142 217 11.2. Diameter Header . . . . . . . . . . . . . . . . . . . . . 142 218 11.2.1. Command Codes . . . . . . . . . . . . . . . . . . . 142 219 11.2.2. Command Flags . . . . . . . . . . . . . . . . . . . 143 220 11.3. Application Identifiers . . . . . . . . . . . . . . . . . 143 221 11.4. AVP Values . . . . . . . . . . . . . . . . . . . . . . . 144 222 11.4.1. Result-Code AVP Values . . . . . . . . . . . . . . . 144 223 11.4.2. Accounting-Record-Type AVP Values . . . . . . . . . 144 224 11.4.3. Termination-Cause AVP Values . . . . . . . . . . . . 144 225 11.4.4. Redirect-Host-Usage AVP Values . . . . . . . . . . . 144 226 11.4.5. Session-Server-Failover AVP Values . . . . . . . . . 144 227 11.4.6. Session-Binding AVP Values . . . . . . . . . . . . . 144 228 11.4.7. Disconnect-Cause AVP Values . . . . . . . . . . . . 145 229 11.4.8. Auth-Request-Type AVP Values . . . . . . . . . . . . 145 230 11.4.9. Auth-Session-State AVP Values . . . . . . . . . . . 145 231 11.4.10. Re-Auth-Request-Type AVP Values . . . . . . . . . . 145 232 11.4.11. Accounting-Realtime-Required AVP Values . . . . . . 145 233 11.4.12. Inband-Security-Id AVP (code 299) . . . . . . . . . 145 234 11.5. Diameter TCP/SCTP Port Numbers . . . . . . . . . . . . . 145 235 11.6. NAPTR Service Fields . . . . . . . . . . . . . . . . . . 145 236 12. Diameter protocol related configurable parameters . . . . . . 147 237 13. Security Considerations . . . . . . . . . . . . . . . . . . . 148 238 13.1. TLS Usage . . . . . . . . . . . . . . . . . . . . . . . . 148 239 13.2. Peer-to-Peer Considerations . . . . . . . . . . . . . . . 149 240 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 150 241 14.1. Normative References . . . . . . . . . . . . . . . . . . 150 242 14.2. Informational References . . . . . . . . . . . . . . . . 152 243 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 154 244 Appendix B. NAPTR Example . . . . . . . . . . . . . . . . . . . 155 245 Appendix C. Duplicate Detection . . . . . . . . . . . . . . . . 156 246 Appendix D. Internationalized Domain Names . . . . . . . . . . . 158 247 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 159 248 Intellectual Property and Copyright Statements . . . . . . . . . 160 250 1. Introduction 252 Authentication, Authorization and Accounting (AAA) protocols such as 253 TACACS [RFC1492] and RADIUS [RFC2865] were initially deployed to 254 provide dial-up PPP [RFC1661] and terminal server access. Over time, 255 with the growth of the Internet and the introduction of new access 256 technologies (including wireless, DSL, Mobile IP and Ethernet), both 257 the amount and complexity of processing performed by routers and 258 network access servers (NAS) have increased, putting new demands on 259 AAA protocols. 261 Network access requirements for AAA protocols are summarized in 262 [RFC2989]. These include: 264 Failover 266 [RFC2865] does not define failover mechanisms, and as a result, 267 failover behavior differs between implementations. In order to 268 provide well defined failover behavior, Diameter supports 269 application-layer acknowledgements, and defines failover 270 algorithms and the associated state machine. This is described in 271 Section 5.5 and [RFC3539]. 273 Transmission-level security 275 [RFC2865] defines an application-layer authentication and 276 integrity scheme that is required only for use with Response 277 packets. While [RFC2869] defines an additional authentication and 278 integrity mechanism, use is only required during Extensible 279 Authentication Protocol (EAP) sessions. While attribute-hiding is 280 supported, [RFC2865] does not provide support for per-packet 281 confidentiality. In accounting, [RFC2866] assumes that replay 282 protection is provided by the backend billing server, rather than 283 within the protocol itself. 285 While [RFC3162] defines the use of IPsec with RADIUS, support for 286 IPsec is not required. Since within [RFC4306] authentication 287 occurs only within Phase 1 prior to the establishment of IPsec SAs 288 in Phase 2, it is typically not possible to define separate trust 289 or authorization schemes for each application. This limits the 290 usefulness of IPsec in inter-domain AAA applications (such as 291 roaming) where it may be desirable to define a distinct 292 certificate hierarchy for use in a AAA deployment. In order to 293 provide universal support for transmission-level security, and 294 enable both intra- and inter-domain AAA deployments, Diameter 295 provides support for TLS. Security is discussed in Section 13. 297 Reliable transport 299 RADIUS runs over UDP, and does not define retransmission behavior; 300 as a result, reliability varies between implementations. As 301 described in [RFC2975], this is a major issue in accounting, where 302 packet loss may translate directly into revenue loss. In order to 303 provide well defined transport behavior, Diameter runs over 304 reliable transport mechanisms (TCP, SCTP) as defined in [RFC3539]. 306 Agent support 308 [RFC2865] does not provide for explicit support for agents, 309 including Proxies, Redirects and Relays. Since the expected 310 behavior is not defined, it varies between implementations. 311 Diameter defines agent behavior explicitly; this is described in 312 Section 2.8. 314 Server-initiated messages 316 While RADIUS server-initiated messages are defined in [RFC3576], 317 support is optional. This makes it difficult to implement 318 features such as unsolicited disconnect or reauthentication/ 319 reauthorization on demand across a heterogeneous deployment. 320 Support for server-initiated messages is mandatory in Diameter, 321 and is described in Section 8. 323 Transition support 325 While Diameter does not share a common protocol data unit (PDU) 326 with RADIUS, considerable effort has been expended in enabling 327 backward compatibility with RADIUS, so that the two protocols may 328 be deployed in the same network. Initially, it is expected that 329 Diameter will be deployed within new network devices, as well as 330 within gateways enabling communication between legacy RADIUS 331 devices and Diameter agents. This capability, described in 332 [RFC4005], enables Diameter support to be added to legacy 333 networks, by addition of a gateway or server speaking both RADIUS 334 and Diameter. 336 In addition to addressing the above requirements, Diameter also 337 provides support for the following: 339 Capability negotiation 341 RADIUS does not support error messages, capability negotiation, or 342 a mandatory/non-mandatory flag for attributes. Since RADIUS 343 clients and servers are not aware of each other's capabilities, 344 they may not be able to successfully negotiate a mutually 345 acceptable service, or in some cases, even be aware of what 346 service has been implemented. Diameter includes support for error 347 handling (Section 7), capability negotiation (Section 5.3), and 348 mandatory/non-mandatory attribute-value pairs (AVPs) (Section 349 4.1). 351 Peer discovery and configuration 353 RADIUS implementations typically require that the name or address 354 of servers or clients be manually configured, along with the 355 corresponding shared secrets. This results in a large 356 administrative burden, and creates the temptation to reuse the 357 RADIUS shared secret, which can result in major security 358 vulnerabilities if the Request Authenticator is not globally and 359 temporally unique as required in [RFC2865]. Through DNS, Diameter 360 enables dynamic discovery of peers. Derivation of dynamic session 361 keys is enabled via transmission-level security. 363 Over time, the capabilities of Network Access Server (NAS) devices 364 have increased substantially. As a result, while Diameter is a 365 considerably more sophisticated protocol than RADIUS, it remains 366 feasible to implement within embedded devices, given improvements in 367 processor speeds and the widespread availability of embedded TLS 368 implementations. 370 1.1. Diameter Protocol 372 The Diameter base protocol provides the following facilities: 374 o Delivery of AVPs (attribute value pairs) 376 o Capabilities negotiation 378 o Error notification 380 o Extensibility, through addition of new applications, commands and 381 AVPs (required in [RFC2989]). 383 o Basic services necessary for applications, such as handling of 384 user sessions or accounting 386 All data delivered by the protocol is in the form of an AVP. Some of 387 these AVP values are used by the Diameter protocol itself, while 388 others deliver data associated with particular applications that 389 employ Diameter. AVPs may be added arbitrarily to Diameter messages, 390 so long as the requirements of a message's ABNF are met and the ABNF 391 allows for it. AVPs are used by the base Diameter protocol to 392 support the following required features: 394 o Transporting of user authentication information, for the purposes 395 of enabling the Diameter server to authenticate the user. 397 o Transporting of service specific authorization information, 398 between client and servers, allowing the peers to decide whether a 399 user's access request should be granted. 401 o Exchanging resource usage information, which MAY be used for 402 accounting purposes, capacity planning, etc. 404 o Relaying, proxying and redirecting of Diameter messages through a 405 server hierarchy. 407 The Diameter base protocol provides the minimum requirements needed 408 for a AAA protocol, as required by [RFC2989]. The base protocol may 409 be used by itself for accounting purposes only, or it may be used 410 with a Diameter application, such as Mobile IPv4 [RFC4004], or 411 network access [RFC4005]. It is also possible for the base protocol 412 to be extended for use in new applications, via the addition of new 413 commands or AVPs. At this time the focus of Diameter is network 414 access and accounting applications. A truly generic AAA protocol 415 used by many applications might provide functionality not provided by 416 Diameter. Therefore, it is imperative that the designers of new 417 applications understand their requirements before using Diameter. 418 See Section 2.4 for more information on Diameter applications. 420 Any node can initiate a request. In that sense, Diameter is a peer- 421 to-peer protocol. In this document, a Diameter Client is a device at 422 the edge of the network that performs access control, such as a 423 Network Access Server (NAS) or a Foreign Agent (FA). A Diameter 424 client generates Diameter messages to request authentication, 425 authorization, and accounting services for the user. A Diameter 426 agent is a node that does not provide local user authentication or 427 authorization services; agents include proxies, redirects and relay 428 agents. A Diameter server performs authentication and/or 429 authorization of the user. A Diameter node MAY act as an agent for 430 certain requests while acting as a server for others. 432 The Diameter protocol also supports server-initiated messages, such 433 as a request to abort service to a particular user. 435 1.1.1. Description of the Document Set 437 Currently, the Diameter specification consists of an updated version 438 of the base protocol specification (this document), Transport Profile 439 [RFC3539] and applications: Mobile IPv4 [RFC4004], NASREQ [RFC4005], 440 Credit Control [RFC4006], EAP [RFC4072] and SIP [RFC4740]. Note that 441 this document obsoletes [RFC3588]. A summary of the base protocol 442 updates included in this document can be found in Section 1.1.3. 444 The Transport Profile document [RFC3539] discusses transport layer 445 issues that arise with AAA protocols and recommendations on how to 446 overcome these issues. This document also defines the Diameter 447 failover algorithm and state machine. 449 The Mobile IPv4 [RFC4004] application defines a Diameter application 450 that allows a Diameter server to perform AAA functions for Mobile 451 IPv4 services to a mobile node. 453 The NASREQ [RFC4005] application defines a Diameter Application that 454 allows a Diameter server to be used in a PPP/SLIP Dial-Up and 455 Terminal Server Access environment. Consideration was given for 456 servers that need to perform protocol conversion between Diameter and 457 RADIUS. 459 The Credit Control [RFC4006] application defines a Diameter 460 Application that can be used to implement real-time credit-control 461 for a variety of end user services such as network access, SIP 462 services, messaging services, and download services. It provides a 463 general solution to real-time cost and credit-control. 465 The EAP [RFC4072] application defines a Diameter Application that can 466 be used to carry EAP packets between the Network Access Server (NAS) 467 working as an EAP authenticator and a back-end authentication server. 468 The Diameter EAP application is based on NASREQ and intended for a 469 similar environment. 471 The SIP [RFC4740] application defines a Diameter Application that 472 allows a Diameter client to request authentication and authorization 473 information to a Diameter server for SIP-based IP multimedia services 474 (see SIP [RFC3261]). 476 In summary, this document defines the base protocol specification for 477 AAA, which includes support for accounting. The applications 478 documents describe applications that use this base specification for 479 Authentication, Authorization and Accounting. 481 1.1.2. Conventions Used in This Document 483 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 484 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 485 document are to be interpreted as described in [RFC2119]. 487 1.1.3. Changes from RFC3588 489 This document deprecates [RFC3588] but is fully backward compatible 490 with that document. The changes introduced in this document focuses 491 on fixing issues that has surfaced during implementation of 492 [RFC3588]. An overview of some the major changes are shown below. 494 o Simplified Security Requirements. The use of a secured transport 495 for exchanging diameter messages remains mandatory. However, TLS 496 has become the primary method of securing diameter and IPSec is a 497 secondary alternative. See Section 13 for details. Along with 498 this, support for the End-to-End security framework (E2ESequence 499 AVP and 'P'-bit in the AVP header) has also been deprecated. 501 o Diameter Extensibility Changes. This includes fixes to the 502 diameter extensibility specification (Section 1.2 and others) to 503 better aid diameter application designers. It also includes 504 allocation of vendor specific command code space. The new 505 specification relaxes the allocation of command codes for vendor 506 specific uses. See Section 11.2.1 for details. 508 o Application Id Usage. Clarify the proper use of Application Id 509 information which can be found in multiple places within a 510 diameter message. This includes co-relating Application Ids found 511 in the message headers and AVPs. These changes also clearly 512 specifies the proper Application Id value to use for specific base 513 protocol messages (ASR/ASA, STR/STA) as well as clarifying the 514 content and use of Vendor-Specific-Application-Id. 516 o Routing Fixes. For general routing, specifies much more clearly 517 what information (AVPs and Application Id) can be used for making 518 routing decisions. Prioritization of redirect routing criterias 519 when multiple route entries are found via redirects has also been 520 added (See Section 6.13 for details). 522 o Simplification of Diameter Peer Discovery. The diameter discovery 523 process now supports only well known discovery schemes. The rest 524 has been deprecated. (See Section 5.2 for details). 526 There are many other many miscellaneous fixes that has been 527 introduced in this document that may not be considered significant 528 but they are important nonetheless. Examples are removal of obselete 529 types, fixes to command ABNFs, fixes state machine, clarification on 530 election process, message validation, fixes to Failed-AVP and Result- 531 Code AVP values etc. A comprehensive list of changes is now shown 532 here for practical reasons. Though, that can be generated via a diff 533 comparison between this document and [RFC3588]. 535 1.2. Approach to Extensibility 537 The Diameter protocol is designed to be extensible, using several 538 mechanisms, including: 540 o Defining new AVP values 542 o Creating new AVPs 544 o Creating new commands 546 o Creating new applications 548 From the point of extensibility Diameter authentication, 549 authorization and accounting applications are treated in the same 550 way. 552 Note: Protocol designer should try to re-use existing functionality, 553 namely AVP values, AVPs, commands, and Diameter applications. Reuse 554 simplifies standardization and implementation. To avoid potential 555 interoperability issues it is important to ensure that the semantic 556 of the re-used features are well understood. 558 1.2.1. Defining New AVP Values 560 In order to allocate a new AVP value for AVPs defined in the Diameter 561 Base protocol, the IETF needs to approve a new RFC that describes the 562 AVP value. IANA considerations for these AVP values are discussed in 563 Section 11.4. 565 The allocation of AVP values for other AVPs is guided by the IANA 566 considerations of the documents that defines those AVPs. Typically, 567 allocation of new values for an AVP defined in an IETF RFC should 568 require IETF Review [RFC2434], where as values for vendor-specific 569 AVPs can be allocated by the vendor. 571 1.2.2. Creating New AVPs 573 A new AVP being defined MUST use one of the data types listed in 574 Section 4.2 or 4.3. If an appropriate derived data type is already 575 defined, it SHOULD be used instead of the base data type to encourage 576 reusability and good design practice. 578 In the event that a logical grouping of AVPs is necessary, and 579 multiple "groups" are possible in a given command, it is recommended 580 that a Grouped AVP be used (see Section 4.4). 582 The creation of new AVPs can happen in various ways. The recommended 583 approach is to define a new general-purpose AVP in a standards track 584 RFC approved by the IETF. However, as described in Section 11.1.1 585 there are also other mechanisms. 587 1.2.3. Creating New Commands 589 A new Command Code has to be allocated when new required AVPs (those 590 indicated as {AVP}) are added, deleted or are redefined (for example 591 by changing a required AVP into an optional one). 593 Furthermore, when a command is modified with respect to the number of 594 round trips then a new Command Code has to be registered. 596 A change to the ABNF of a command, such as described above, MUST 597 result in the definition of a new Command Code. This subsequently 598 leads to the need to define a new Diameter Application for any 599 application that will use that new Command. 601 The IANA considerations for commands are discussed in Section 11.2.1. 603 1.2.4. Creating New Diameter Applications 605 Every Diameter application specification MUST have an IANA assigned 606 Application Id (see Section 2.4 and Section 11.3). The managed 607 Application ID space is flat and there is no relationship between 608 different Diameter applications with respect to their application 609 IDs. As such, there is no versioning supported provided by these 610 application IDs itself; every Diameter application is a standalone 611 application that may or may not have a semantical relationship with 612 one or more Diameter applications being defined elsewhere. 614 Before describing the rules for creating new Diameter applications it 615 is important to discuss the semantic of the AVPs occurrences as 616 stated in the ABNF and the M-bit flag for an AVP. There is no 617 relationship imposed between the two; they are set independently. 619 o The ABNF indicates what AVPs are placed into a Diameter Command by 620 the sender of that Command. Often, since there are multiple modes 621 of protocol interactions many of the AVPs are indicated as 622 optional. 624 o The M-bit allows the sender to indicate to the receiver whether 625 the semantic of an AVP and it's content has to be understood 626 mandatorily or not. If the M-bit is set by the sender and the 627 receiver does not understand the AVP or the values carried within 628 that AVP then a failure is generated (see Section 7). 630 It is the decision of the protocol designer when to develop a new 631 Diameter application rather than extending Diameter in other ways. 632 However, a new Diameter application MUST be created when one or more 633 of the following criteria are met: 635 M-bit Setting 637 Adding an AVP with the M-bit in the MUST column of the AVP flag 638 table to an existing Command/Application requires a new Diameter 639 Application Id to be assigned to that Application. 641 Adding an AVP with the M-bit in the MAY column of the AVP flag 642 table to an existing Command/Application requires a new Diameter 643 Application Id to be assigned to that Application. 645 Note: The M-bit setting for a given AVP is relevant to an 646 Application and each command supported by that application where 647 the AVP is inlcuded. That is, if an AVP appears in two commands 648 for application Foo, then there should be two AVP flag tables 649 describing when to set the M-bit. 651 Commands 653 A new command is used within the existing application either 654 because an additional command is added, an existing command has 655 been modified so that a new Command Code had to be registered, or 656 a command has been deleted. 658 An implementation MAY add arbitrary optional AVPs to a command 659 defined in an application, including vendor-specific AVPs without 660 needing to define a new application. This can be done if the 661 commands ABNF allows for it. Please refer to Section 11.1.1 for 662 details. 664 1.3. Terminology 666 AAA 668 Authentication, Authorization and Accounting. 670 Accounting 672 The act of collecting information on resource usage for the 673 purpose of capacity planning, auditing, billing or cost 674 allocation. 676 Accounting Record 678 An accounting record represents a summary of the resource 679 consumption of a user over the entire session. Accounting servers 680 creating the accounting record may do so by processing interim 681 accounting events or accounting events from several devices 682 serving the same user. 684 Authentication 686 The act of verifying the identity of an entity (subject). 688 Authorization 690 The act of determining whether a requesting entity (subject) will 691 be allowed access to a resource (object). 693 AVP 695 The Diameter protocol consists of a header followed by one or more 696 Attribute-Value-Pairs (AVPs). An AVP includes a header and is 697 used to encapsulate protocol-specific data (e.g., routing 698 information) as well as authentication, authorization or 699 accounting information. 701 Broker 703 A broker is a business term commonly used in AAA infrastructures. 704 A broker is either a relay, proxy or redirect agent, and MAY be 705 operated by roaming consortiums. Depending on the business model, 706 a broker may either choose to deploy relay agents or proxy agents. 708 Diameter Agent 710 A Diameter Agent is a Diameter node that provides either relay, 711 proxy, redirect or translation services. 713 Diameter Client 715 A Diameter Client is a device at the edge of the network that 716 performs access control. An example of a Diameter client is a 717 Network Access Server (NAS) or a Foreign Agent (FA). By its very 718 nature, a Diameter Client MUST support Diameter client 719 applications in addition to the base protocol. 721 Diameter Node 723 A Diameter node is a host process that implements the Diameter 724 protocol, and acts either as a Client, Agent or Server. 726 Diameter Peer 728 A Diameter Peer is a Diameter Node to which a given Diameter Node 729 has a direct transport connection. 731 Diameter Server 733 A Diameter Server is one that handles authentication, 734 authorization and accounting requests for a particular realm. By 735 its very nature, a Diameter Server MUST support Diameter server 736 applications in addition to the base protocol. 738 Downstream 740 Downstream is used to identify the direction of a particular 741 Diameter message from the home server towards the access device. 743 Home Realm 745 A Home Realm is the administrative domain with which the user 746 maintains an account relationship. 748 Home Server 750 A Diameter Server which serves the Home Realm. 752 Interim accounting 754 An interim accounting message provides a snapshot of usage during 755 a user's session. It is typically implemented in order to provide 756 for partial accounting of a user's session in the case of a device 757 reboot or other network problem prevents the reception of a 758 session summary message or session record. 760 Local Realm 762 A local realm is the administrative domain providing services to a 763 user. An administrative domain MAY act as a local realm for 764 certain users, while being a home realm for others. 766 Multi-session 768 A multi-session represents a logical linking of several sessions. 769 Multi-sessions are tracked by using the Acct-Multi-Session-Id. An 770 example of a multi-session would be a Multi-link PPP bundle. Each 771 leg of the bundle would be a session while the entire bundle would 772 be a multi-session. 774 Network Access Identifier 776 The Network Access Identifier, or NAI [RFC4282], is used in the 777 Diameter protocol to extract a user's identity and realm. The 778 identity is used to identify the user during authentication and/or 779 authorization, while the realm is used for message routing 780 purposes. 782 Proxy Agent or Proxy 784 In addition to forwarding requests and responses, proxies make 785 policy decisions relating to resource usage and provisioning. 786 This is typically accomplished by tracking the state of NAS 787 devices. While proxies typically do not respond to client 788 Requests prior to receiving a Response from the server, they may 789 originate Reject messages in cases where policies are violated. 790 As a result, proxies need to understand the semantics of the 791 messages passing through them, and may not support all Diameter 792 applications. 794 Realm 796 The string in the NAI that immediately follows the '@' character. 797 NAI realm names are required to be unique, and are piggybacked on 798 the administration of the DNS namespace. Diameter makes use of 799 the realm, also loosely referred to as domain, to determine 800 whether messages can be satisfied locally, or whether they must be 801 routed or redirected. In RADIUS, realm names are not necessarily 802 piggybacked on the DNS namespace but may be independent of it. 804 Real-time Accounting 806 Real-time accounting involves the processing of information on 807 resource usage within a defined time window. Time constraints are 808 typically imposed in order to limit financial risk. 810 Relay Agent or Relay 812 Relays forward requests and responses based on routing-related 813 AVPs and routing table entries. Since relays do not make policy 814 decisions, they do not examine or alter non-routing AVPs. As a 815 result, relays never originate messages, do not need to understand 816 the semantics of messages or non-routing AVPs, and are capable of 817 handling any Diameter application or message type. Since relays 818 make decisions based on information in routing AVPs and realm 819 forwarding tables they do not keep state on NAS resource usage or 820 sessions in progress. 822 Redirect Agent 824 Rather than forwarding requests and responses between clients and 825 servers, redirect agents refer clients to servers and allow them 826 to communicate directly. Since redirect agents do not sit in the 827 forwarding path, they do not alter any AVPs transiting between 828 client and server. Redirect agents do not originate messages and 829 are capable of handling any message type, although they may be 830 configured only to redirect messages of certain types, while 831 acting as relay or proxy agents for other types. As with proxy 832 agents, redirect agents do not keep state with respect to sessions 833 or NAS resources. 835 Roaming Relationships 837 Roaming relationships include relationships between companies and 838 ISPs, relationships among peer ISPs within a roaming consortium, 839 and relationships between an ISP and a roaming consortium. 841 Session 843 A session is a related progression of events devoted to a 844 particular activity. Each application SHOULD provide guidelines 845 as to when a session begins and ends. All Diameter packets with 846 the same Session-Identifier are considered to be part of the same 847 session. 849 Session state 851 A stateful agent is one that maintains session state information, 852 by keeping track of all authorized active sessions. Each 853 authorized session is bound to a particular service, and its state 854 is considered active either until it is notified otherwise, or by 855 expiration. 857 Sub-session 859 A sub-session represents a distinct service (e.g., QoS or data 860 characteristics) provided to a given session. These services may 861 happen concurrently (e.g., simultaneous voice and data transfer 862 during the same session) or serially. These changes in sessions 863 are tracked with the Accounting-Sub-Session-Id. 865 Transaction state 867 The Diameter protocol requires that agents maintain transaction 868 state, which is used for failover purposes. Transaction state 869 implies that upon forwarding a request, the Hop-by-Hop identifier 870 is saved; the field is replaced with a locally unique identifier, 871 which is restored to its original value when the corresponding 872 answer is received. The request's state is released upon receipt 873 of the answer. A stateless agent is one that only maintains 874 transaction state. 876 Translation Agent 878 A translation agent is a stateful Diameter node that performs 879 protocol translation between Diameter and another AAA protocol, 880 such as RADIUS. 882 Transport Connection 884 A transport connection is a TCP or SCTP connection existing 885 directly between two Diameter peers, otherwise known as a Peer- 886 to-Peer Connection. 888 Upstream 890 Upstream is used to identify the direction of a particular 891 Diameter message from the access device towards the home server. 893 User 895 The entity requesting or using some resource, in support of which 896 a Diameter client has generated a request. 898 2. Protocol Overview 900 The base Diameter protocol may be used by itself for accounting 901 applications, but for use in authentication and authorization it is 902 always extended for a particular application. Two Diameter 903 applications are defined by companion documents: NASREQ [RFC4005], 904 Mobile IPv4 [RFC4004]. These applications are introduced in this 905 document but specified elsewhere. Additional Diameter applications 906 MAY be defined in the future (see Section 11.3). 908 Diameter Clients MUST support the base protocol, which includes 909 accounting. In addition, they MUST fully support each Diameter 910 application that is needed to implement the client's service, e.g., 911 NASREQ and/or Mobile IPv4. A Diameter Client that does not support 912 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 913 Client" where X is the application which it supports, and not a 914 "Diameter Client". 916 Diameter Servers MUST support the base protocol, which includes 917 accounting. In addition, they MUST fully support each Diameter 918 application that is needed to implement the intended service, e.g., 919 NASREQ and/or Mobile IPv4. A Diameter Server that does not support 920 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 921 Server" where X is the application which it supports, and not a 922 "Diameter Server". 924 Diameter Relays and redirect agents are, by definition, protocol 925 transparent, and MUST transparently support the Diameter base 926 protocol, which includes accounting, and all Diameter applications. 928 Diameter proxies MUST support the base protocol, which includes 929 accounting. In addition, they MUST fully support each Diameter 930 application that is needed to implement proxied services, e.g., 931 NASREQ and/or Mobile IPv4. A Diameter proxy which does not support 932 also both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 933 Proxy" where X is the application which it supports, and not a 934 "Diameter Proxy". 936 The base Diameter protocol concerns itself with capabilities 937 negotiation, how messages are sent and how peers may eventually be 938 abandoned. The base protocol also defines certain rules that apply 939 to all exchanges of messages between Diameter nodes. 941 Communication between Diameter peers begins with one peer sending a 942 message to another Diameter peer. The set of AVPs included in the 943 message is determined by a particular Diameter application. One AVP 944 that is included to reference a user's session is the Session-Id. 946 The initial request for authentication and/or authorization of a user 947 would include the Session-Id. The Session-Id is then used in all 948 subsequent messages to identify the user's session (see Section 8 for 949 more information). The communicating party may accept the request, 950 or reject it by returning an answer message with the Result-Code AVP 951 set to indicate an error occurred. The specific behavior of the 952 Diameter server or client receiving a request depends on the Diameter 953 application employed. 955 Session state (associated with a Session-Id) MUST be freed upon 956 receipt of the Session-Termination-Request, Session-Termination- 957 Answer, expiration of authorized service time in the Session-Timeout 958 AVP, and according to rules established in a particular Diameter 959 application. 961 2.1. Transport 963 Transport profile is defined in [RFC3539]. 965 The base Diameter protocol is run on port 3868 of both TCP [RFC793] 966 and SCTP [RFC2960] transport protocols. 968 Diameter clients MUST support either TCP or SCTP, while agents and 969 servers MUST support both. Future versions of this specification MAY 970 mandate that clients support SCTP. 972 A Diameter node MAY initiate connections from a source port other 973 than the one that it declares it accepts incoming connections on, and 974 MUST be prepared to receive connections on port 3868. A given 975 Diameter instance of the peer state machine MUST NOT use more than 976 one transport connection to communicate with a given peer, unless 977 multiple instances exist on the peer in which case a separate 978 connection per process is allowed. 980 When no transport connection exists with a peer, an attempt to 981 connect SHOULD be periodically made. This behavior is handled via 982 the Tc timer, whose recommended value is 30 seconds. There are 983 certain exceptions to this rule, such as when a peer has terminated 984 the transport connection stating that it does not wish to 985 communicate. 987 When connecting to a peer and either zero or more transports are 988 specified, SCTP SHOULD be tried first, followed by TCP. See Section 989 5.2 for more information on peer discovery. 991 Diameter implementations SHOULD be able to interpret ICMP protocol 992 port unreachable messages as explicit indications that the server is 993 not reachable, subject to security policy on trusting such messages. 995 Diameter implementations SHOULD also be able to interpret a reset 996 from the transport and timed-out connection attempts. If Diameter 997 receives data up from TCP that cannot be parsed or identified as a 998 Diameter error made by the peer, the stream is compromised and cannot 999 be recovered. The transport connection MUST be closed using a RESET 1000 call (send a TCP RST bit) or an SCTP ABORT message (graceful closure 1001 is compromised). 1003 2.1.1. SCTP Guidelines 1005 The following are guidelines for Diameter implementations that 1006 support SCTP: 1008 1. For interoperability: All Diameter nodes MUST be prepared to 1009 receive Diameter messages on any SCTP stream in the association. 1011 2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP 1012 streams available to the association to prevent head-of-the-line 1013 blocking. 1015 2.2. Securing Diameter Messages 1017 Connections between Diameter peers SHOULD be protected by TLS. All 1018 Diameter base protocol implementations MUST support the use of TLS. 1019 If desired, additional security measures that are transparent to and 1020 independent of Diameter, such as IPSec [RFC4301], can be deployed to 1021 secure connections between peers. The Diameter protocol MUST NOT be 1022 used without any security mechanism. 1024 2.3. Diameter Application Compliance 1026 Application Ids are advertised during the capabilities exchange phase 1027 (see Section 5.3). For a given application, advertising support of 1028 an application implies that the sender supports all command codes, 1029 and the AVPs specified in the associated ABNFs, described in the 1030 specification. 1032 An implementation MAY add arbitrary non-mandatory AVPs to a command 1033 defined in an application, including vendor-specific AVPs only if the 1034 commands ABNF allows for it. Please refer to Section 11.1.1 for 1035 details. 1037 2.4. Application Identifiers 1039 Each Diameter application MUST have an IANA assigned Application Id 1040 (see Section 11.3). The base protocol does not require an 1041 Application Id since its support is mandatory. During the 1042 capabilities exchange, Diameter nodes inform their peers of locally 1043 supported applications. Furthermore, all Diameter messages contain 1044 an Application Id, which is used in the message forwarding process. 1046 The following Application Id values are defined: 1048 Diameter Common Messages 0 1049 NASREQ 1 [RFC4005] 1050 Mobile-IP 2 [RFC4004] 1051 Diameter Base Accounting 3 1052 Relay 0xffffffff 1054 Relay and redirect agents MUST advertise the Relay Application 1055 Identifier, while all other Diameter nodes MUST advertise locally 1056 supported applications. The receiver of a Capabilities Exchange 1057 message advertising Relay service MUST assume that the sender 1058 supports all current and future applications. 1060 Diameter relay and proxy agents are responsible for finding an 1061 upstream server that supports the application of a particular 1062 message. If none can be found, an error message is returned with the 1063 Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. 1065 2.5. Connections vs. Sessions 1067 This section attempts to provide the reader with an understanding of 1068 the difference between connection and session, which are terms used 1069 extensively throughout this document. 1071 A connection is a transport level connection between two peers, used 1072 to send and receive Diameter messages. A session is a logical 1073 concept at the application layer, and is shared between an access 1074 device and a server, and is identified via the Session-Id AVP. 1076 +--------+ +-------+ +--------+ 1077 | Client | | Relay | | Server | 1078 +--------+ +-------+ +--------+ 1079 <----------> <----------> 1080 peer connection A peer connection B 1082 <-----------------------------> 1083 User session x 1085 Figure 1: Diameter connections and sessions 1087 In the example provided in Figure 1, peer connection A is established 1088 between the Client and its local Relay. Peer connection B is 1089 established between the Relay and the Server. User session X spans 1090 from the Client via the Relay to the Server. Each "user" of a 1091 service causes an auth request to be sent, with a unique session 1092 identifier. Once accepted by the server, both the client and the 1093 server are aware of the session. 1095 It is important to note that there is no relationship between a 1096 connection and a session, and that Diameter messages for multiple 1097 sessions are all multiplexed through a single connection. Also note 1098 that Diameter messages pertaining to the session, both application 1099 specific and those that are defined in this document such as ASR/ASA, 1100 RAR/RAA and STR/STA MUST carry the Application Id of the application. 1101 Diameter messages pertaining to peer connection establishment and 1102 maintenance such as CER/CEA, DWR/DWA and DPR/DPA MUST carry an 1103 Application Id of zero (0). 1105 2.6. Peer Table 1107 The Diameter Peer Table is used in message forwarding, and referenced 1108 by the Routing Table. A Peer Table entry contains the following 1109 fields: 1111 Host identity 1113 Following the conventions described for the DiameterIdentity 1114 derived AVP data format in Section 4.4. This field contains the 1115 contents of the Origin-Host (Section 6.3) AVP found in the CER or 1116 CEA message. 1118 StatusT 1120 This is the state of the peer entry, and MUST match one of the 1121 values listed in Section 5.6. 1123 Static or Dynamic 1125 Specifies whether a peer entry was statically configured, or 1126 dynamically discovered. 1128 Expiration time 1130 Specifies the time at which dynamically discovered peer table 1131 entries are to be either refreshed, or expired. 1133 TLS Enabled 1135 Specifies whether TLS is to be used when communicating with the 1136 peer. 1138 Additional security information, when needed (e.g., keys, 1139 certificates) 1141 2.7. Routing Table 1143 All Realm-Based routing lookups are performed against what is 1144 commonly known as the Routing Table (see Section 12). A Routing 1145 Table Entry contains the following fields: 1147 Realm Name 1149 This is the field that is typically used as a primary key in the 1150 routing table lookups. Note that some implementations perform 1151 their lookups based on longest-match-from-the-right on the realm 1152 rather than requiring an exact match. 1154 Application Identifier 1156 An application is identified by an Application Id. A route entry 1157 can have a different destination based on the Application Id in 1158 the message header. This field MUST be used as a secondary key 1159 field in routing table lookups. 1161 Local Action 1163 The Local Action field is used to identify how a message should be 1164 treated. The following actions are supported: 1166 1. LOCAL - Diameter messages that resolve to a route entry with 1167 the Local Action set to Local can be satisfied locally, and do 1168 not need to be routed to another server. 1170 2. RELAY - All Diameter messages that fall within this category 1171 MUST be routed to a next hop server, without modifying any 1172 non-routing AVPs. See Section 6.1.9 for relaying guidelines 1174 3. PROXY - All Diameter messages that fall within this category 1175 MUST be routed to a next hop server. The local server MAY 1176 apply its local policies to the message by including new AVPs 1177 to the message prior to routing. See Section 6.1.9 for 1178 proxying guidelines. 1180 4. REDIRECT - Diameter messages that fall within this category 1181 MUST have the identity of the home Diameter server(s) 1182 appended, and returned to the sender of the message. See 1183 Section 6.1.9 for redirect guidelines. 1185 Server Identifier 1187 One or more servers the message is to be routed to. These servers 1188 MUST also be present in the Peer table. When the Local Action is 1189 set to RELAY or PROXY, this field contains the identity of the 1190 server(s) the message must be routed to. When the Local Action 1191 field is set to REDIRECT, this field contains the identity of one 1192 or more servers the message should be redirected to. 1194 Static or Dynamic 1196 Specifies whether a route entry was statically configured, or 1197 dynamically discovered. 1199 Expiration time 1201 Specifies the time which a dynamically discovered route table 1202 entry expires. 1204 It is important to note that Diameter agents MUST support at least 1205 one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation. 1206 Agents do not need to support all modes of operation in order to 1207 conform with the protocol specification, but MUST follow the protocol 1208 compliance guidelines in Section 2. Relay agents MUST NOT reorder 1209 AVPs, and proxies MUST NOT reorder AVPs. 1211 The routing table MAY include a default entry that MUST be used for 1212 any requests not matching any of the other entries. The routing 1213 table MAY consist of only such an entry. 1215 When a request is routed, the target server MUST have advertised the 1216 Application Id (see Section 2.4) for the given message, or have 1217 advertised itself as a relay or proxy agent. Otherwise, an error is 1218 returned with the Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. 1220 2.8. Role of Diameter Agents 1222 In addition to client and servers, the Diameter protocol introduces 1223 relay, proxy, redirect, and translation agents, each of which is 1224 defined in Section 1.3. These Diameter agents are useful for several 1225 reasons: 1227 o They can distribute administration of systems to a configurable 1228 grouping, including the maintenance of security associations. 1230 o They can be used for concentration of requests from an number of 1231 co-located or distributed NAS equipment sets to a set of like user 1232 groups. 1234 o They can do value-added processing to the requests or responses. 1236 o They can be used for load balancing. 1238 o A complex network will have multiple authentication sources, they 1239 can sort requests and forward towards the correct target. 1241 The Diameter protocol requires that agents maintain transaction 1242 state, which is used for failover purposes. Transaction state 1243 implies that upon forwarding a request, its Hop-by-Hop identifier is 1244 saved; the field is replaced with a locally unique identifier, which 1245 is restored to its original value when the corresponding answer is 1246 received. The request's state is released upon receipt of the 1247 answer. A stateless agent is one that only maintains transaction 1248 state. 1250 The Proxy-Info AVP allows stateless agents to add local state to a 1251 Diameter request, with the guarantee that the same state will be 1252 present in the answer. However, the protocol's failover procedures 1253 require that agents maintain a copy of pending requests. 1255 A stateful agent is one that maintains session state information; by 1256 keeping track of all authorized active sessions. Each authorized 1257 session is bound to a particular service, and its state is considered 1258 active either until it is notified otherwise, or by expiration. Each 1259 authorized session has an expiration, which is communicated by 1260 Diameter servers via the Session-Timeout AVP. 1262 Maintaining session state MAY be useful in certain applications, such 1263 as: 1265 o Protocol translation (e.g., RADIUS <-> Diameter) 1267 o Limiting resources authorized to a particular user 1269 o Per user or transaction auditing 1271 A Diameter agent MAY act in a stateful manner for some requests and 1272 be stateless for others. A Diameter implementation MAY act as one 1273 type of agent for some requests, and as another type of agent for 1274 others. 1276 2.8.1. Relay Agents 1278 Relay Agents are Diameter agents that accept requests and route 1279 messages to other Diameter nodes based on information found in the 1280 messages (e.g., Destination-Realm). This routing decision is 1281 performed using a list of supported realms, and known peers. This is 1282 known as the Routing Table, as is defined further in Section 2.7. 1284 Relays MAY be used to aggregate requests from multiple Network Access 1285 Servers (NASes) within a common geographical area (POP). The use of 1286 Relays is advantageous since it eliminates the need for NASes to be 1287 configured with the necessary security information they would 1288 otherwise require to communicate with Diameter servers in other 1289 realms. Likewise, this reduces the configuration load on Diameter 1290 servers that would otherwise be necessary when NASes are added, 1291 changed or deleted. 1293 Relays modify Diameter messages by inserting and removing routing 1294 information, but do not modify any other portion of a message. 1295 Relays SHOULD NOT maintain session state but MUST maintain 1296 transaction state. 1298 +------+ ---------> +------+ ---------> +------+ 1299 | | 1. Request | | 2. Request | | 1300 | NAS | | DRL | | HMS | 1301 | | 4. Answer | | 3. Answer | | 1302 +------+ <--------- +------+ <--------- +------+ 1303 example.net example.net example.com 1305 Figure 2: Relaying of Diameter messages 1307 The example provided in Figure 2 depicts a request issued from NAS, 1308 which is an access device, for the user bob@example.com. Prior to 1309 issuing the request, NAS performs a Diameter route lookup, using 1310 "example.com" as the key, and determines that the message is to be 1311 relayed to DRL, which is a Diameter Relay. DRL performs the same 1312 route lookup as NAS, and relays the message to HMS, which is 1313 example.com's Home Diameter Server. HMS identifies that the request 1314 can be locally supported (via the realm), processes the 1315 authentication and/or authorization request, and replies with an 1316 answer, which is routed back to NAS using saved transaction state. 1318 Since Relays do not perform any application level processing, they 1319 provide relaying services for all Diameter applications, and 1320 therefore MUST advertise the Relay Application Id. 1322 2.8.2. Proxy Agents 1324 Similarly to relays, proxy agents route Diameter messages using the 1325 Diameter Routing Table. However, they differ since they modify 1326 messages to implement policy enforcement. This requires that proxies 1327 maintain the state of their downstream peers (e.g., access devices) 1328 to enforce resource usage, provide admission control, and 1329 provisioning. 1331 Proxies MAY be used in call control centers or access ISPs that 1332 provide outsourced connections, they can monitor the number and types 1333 of ports in use, and make allocation and admission decisions 1334 according to their configuration. 1336 Proxies that wish to limit resources MUST maintain session state. 1337 All proxies MUST maintain transaction state. 1339 Since enforcing policies requires an understanding of the service 1340 being provided, Proxies MUST only advertise the Diameter applications 1341 they support. 1343 2.8.3. Redirect Agents 1345 Redirect agents are useful in scenarios where the Diameter routing 1346 configuration needs to be centralized. An example is a redirect 1347 agent that provides services to all members of a consortium, but does 1348 not wish to be burdened with relaying all messages between realms. 1349 This scenario is advantageous since it does not require that the 1350 consortium provide routing updates to its members when changes are 1351 made to a member's infrastructure. 1353 Since redirect agents do not relay messages, and only return an 1354 answer with the information necessary for Diameter agents to 1355 communicate directly, they do not modify messages. Since redirect 1356 agents do not receive answer messages, they cannot maintain session 1357 state. Further, since redirect agents never relay requests, they are 1358 not required to maintain transaction state. 1360 The example provided in Figure 3 depicts a request issued from the 1361 access device, NAS, for the user bob@example.com. The message is 1362 forwarded by the NAS to its relay, DRL, which does not have a routing 1363 entry in its Diameter Routing Table for example.com. DRL has a 1364 default route configured to DRD, which is a redirect agent that 1365 returns a redirect notification to DRL, as well as HMS' contact 1366 information. Upon receipt of the redirect notification, DRL 1367 establishes a transport connection with HMS, if one doesn't already 1368 exist, and forwards the request to it. 1370 +------+ 1371 | | 1372 | DRD | 1373 | | 1374 +------+ 1375 ^ | 1376 2. Request | | 3. Redirection 1377 | | Notification 1378 | v 1379 +------+ ---------> +------+ ---------> +------+ 1380 | | 1. Request | | 4. Request | | 1381 | NAS | | DRL | | HMS | 1382 | | 6. Answer | | 5. Answer | | 1383 +------+ <--------- +------+ <--------- +------+ 1384 example.net example.net example.com 1386 Figure 3: Redirecting a Diameter Message 1388 Since redirect agents do not perform any application level 1389 processing, they provide relaying services for all Diameter 1390 applications, and therefore MUST advertise the Relay Application 1391 Identifier. 1393 2.8.4. Translation Agents 1395 A translation agent is a device that provides translation between two 1396 protocols (e.g., RADIUS<->Diameter, TACACS+<->Diameter). Translation 1397 agents are likely to be used as aggregation servers to communicate 1398 with a Diameter infrastructure, while allowing for the embedded 1399 systems to be migrated at a slower pace. 1401 Given that the Diameter protocol introduces the concept of long-lived 1402 authorized sessions, translation agents MUST be session stateful and 1403 MUST maintain transaction state. 1405 Translation of messages can only occur if the agent recognizes the 1406 application of a particular request, and therefore translation agents 1407 MUST only advertise their locally supported applications. 1409 +------+ ---------> +------+ ---------> +------+ 1410 | | RADIUS Request | | Diameter Request | | 1411 | NAS | | TLA | | HMS | 1412 | | RADIUS Answer | | Diameter Answer | | 1413 +------+ <--------- +------+ <--------- +------+ 1414 example.net example.net example.com 1416 Figure 4: Translation of RADIUS to Diameter 1418 2.9. Diameter Path Authorization 1420 As noted in Section 2.2, Diameter provides transmission level 1421 security for each connection using TLS. Therefore, each connection 1422 can be authenticated, replay and integrity protected. 1424 In addition to authenticating each connection, each connection as 1425 well as the entire session MUST also be authorized. Before 1426 initiating a connection, a Diameter Peer MUST check that its peers 1427 are authorized to act in their roles. For example, a Diameter peer 1428 may be authentic, but that does not mean that it is authorized to act 1429 as a Diameter Server advertising a set of Diameter applications. 1431 Prior to bringing up a connection, authorization checks are performed 1432 at each connection along the path. Diameter capabilities negotiation 1433 (CER/CEA) also MUST be carried out, in order to determine what 1434 Diameter applications are supported by each peer. Diameter sessions 1435 MUST be routed only through authorized nodes that have advertised 1436 support for the Diameter application required by the session. 1438 As noted in Section 6.1.9, a relay or proxy agent MUST append a 1439 Route-Record AVP to all requests forwarded. The AVP contains the 1440 identity of the peer the request was received from. 1442 The home Diameter server, prior to authorizing a session, MUST check 1443 the Route-Record AVPs to make sure that the route traversed by the 1444 request is acceptable. For example, administrators within the home 1445 realm may not wish to honor requests that have been routed through an 1446 untrusted realm. By authorizing a request, the home Diameter server 1447 is implicitly indicating its willingness to engage in the business 1448 transaction as specified by the contractual relationship between the 1449 server and the previous hop. A DIAMETER_AUTHORIZATION_REJECTED error 1450 message (see Section 7.1.5) is sent if the route traversed by the 1451 request is unacceptable. 1453 A home realm may also wish to check that each accounting request 1454 message corresponds to a Diameter response authorizing the session. 1455 Accounting requests without corresponding authorization responses 1456 SHOULD be subjected to further scrutiny, as should accounting 1457 requests indicating a difference between the requested and provided 1458 service. 1460 Forwarding of an authorization response is considered evidence of a 1461 willingness to take on financial risk relative to the session. A 1462 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. If an optional rule has a qualifier, 1709 ; then the value of min MUST be 0 if present. 1710 ; 1711 ; NOTE: "[" and "]" have a different meaning 1712 ; than in ABNF (see the optional rule, above). 1713 ; These braces cannot be used to express 1714 ; optional fixed rules (such as an optional 1715 ; ICV at the end). To do this, the convention 1716 ; is '0*1fixed'. 1718 min = 1*DIGIT 1719 ; The minimum number of times the element may 1720 ; be present. The default value is zero. 1722 max = 1*DIGIT 1723 ; The maximum number of times the element may 1724 ; be present. The default value is infinity. A 1725 ; value of zero implies the AVP MUST NOT be 1726 ; present. 1728 avp-spec = diameter-name 1729 ; The avp-spec has to be an AVP Name, defined 1730 ; in the base or extended Diameter 1731 ; specifications. 1733 avp-name = avp-spec / "AVP" 1734 ; The string "AVP" stands for *any* arbitrary AVP 1735 ; Name, not otherwise listed in that command code 1736 ; definition. Addition this AVP is recommended for 1737 ; all command ABNFs to allow for extensibility. 1739 The following is a definition of a fictitious command code: 1741 Example-Request ::= < Diameter Header: 9999999, REQ, PXY > 1742 { User-Name } 1743 * { Origin-Host } 1744 * [ AVP ] 1746 3.3. Diameter Command Naming Conventions 1748 Diameter command names typically includes one or more English words 1749 followed by the verb Request or Answer. Each English word is 1750 delimited by a hyphen. A three-letter acronym for both the request 1751 and answer is also normally provided. 1753 An example is a message set used to terminate a session. The command 1754 name is Session-Terminate-Request and Session-Terminate-Answer, while 1755 the acronyms are STR and STA, respectively. 1757 Both the request and the answer for a given command share the same 1758 command code. The request is identified by the R(equest) bit in the 1759 Diameter header set to one (1), to ask that a particular action be 1760 performed, such as authorizing a user or terminating a session. Once 1761 the receiver has completed the request it issues the corresponding 1762 answer, which includes a result code that communicates one of the 1763 following: 1765 o The request was successful 1767 o The request failed 1769 o An additional request MUST be sent to provide information the peer 1770 requires prior to returning a successful or failed answer. 1772 o The receiver could not process the request, but provides 1773 information about a Diameter peer that is able to satisfy the 1774 request, known as redirect. 1776 Additional information, encoded within AVPs, MAY also be included in 1777 answer messages. 1779 4. Diameter AVPs 1781 Diameter AVPs carry specific authentication, accounting, 1782 authorization and routing information as well as configuration 1783 details for the request and reply. 1785 Some AVPs MAY be listed more than once. The effect of such an AVP is 1786 specific, and is specified in each case by the AVP description. 1788 Each AVP of type OctetString MUST be padded to align on a 32-bit 1789 boundary, while other AVP types align naturally. A number of zero- 1790 valued bytes are added to the end of the AVP Data field till a word 1791 boundary is reached. The length of the padding is not reflected in 1792 the AVP Length field. 1794 4.1. AVP Header 1796 The fields in the AVP header MUST be sent in network byte order. The 1797 format of the header is: 1799 0 1 2 3 1800 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 1801 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1802 | AVP Code | 1803 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1804 |V M P r r r r r| AVP Length | 1805 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1806 | Vendor-ID (opt) | 1807 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1808 | Data ... 1809 +-+-+-+-+-+-+-+-+ 1811 AVP Code 1813 The AVP Code, combined with the Vendor-Id field, identifies the 1814 attribute uniquely. AVP numbers 1 through 255 are reserved for 1815 backward compatibility with RADIUS, without setting the Vendor-Id 1816 field. AVP numbers 256 and above are used for Diameter, which are 1817 allocated by IANA (see Section 11.1). 1819 AVP Flags 1821 The AVP Flags field informs the receiver how each attribute must 1822 be handled. The 'r' (reserved) bits are unused and SHOULD be set 1823 to 0. Note that subsequent Diameter applications MAY define 1824 additional bits within the AVP Header, and an unrecognized bit 1825 SHOULD be considered an error. The 'P' bit indicates the need for 1826 encryption for end-to-end security. Note that the 'P' bit has 1827 been deprecated and MUST be to zero(0) when sending an AVP and 1828 ingnored on receipt of an AVP. 1830 The 'M' Bit, known as the Mandatory bit, indicates whether support 1831 of the AVP is required. If an AVP with the 'M' bit set is 1832 received by a Diameter client, server or translation agent and 1833 either the AVP or its value is unrecognized, the message MUST be 1834 rejected. An exception to this rule applies when the AVP is 1835 embedded within a Grouped AVP. See Section 4.4 for details. 1836 Diameter Relay and redirect agents MUST NOT reject messages with 1837 unrecognized AVPs. 1839 The 'M' bit MUST be set according to the rules defined within the 1840 Application/Command carrying this AVP. 1842 AVPs with the 'M' bit cleared are informational only and a 1843 receiver that receives a message with such an AVP that is not 1844 supported, or whose value is not supported, MAY simply ignore the 1845 AVP. 1847 The 'V' bit, known as the Vendor-Specific bit, indicates whether 1848 the optional Vendor-ID field is present in the AVP header. When 1849 set the AVP Code belongs to the specific vendor code address 1850 space. 1852 AVP Length 1854 The AVP Length field is three octets, and indicates the number of 1855 octets in this AVP including the AVP Code, AVP Length, AVP Flags, 1856 Vendor-ID field (if present) and the AVP data. If a message is 1857 received with an invalid attribute length, the message SHOULD be 1858 rejected. 1860 4.1.1. Optional Header Elements 1862 The AVP Header contains one optional field. This field is only 1863 present if the respective bit-flag is enabled. 1865 Vendor-ID 1867 The Vendor-ID field is present if the 'V' bit is set in the AVP 1868 Flags field. The optional four-octet Vendor-ID field contains the 1869 IANA assigned "SMI Network Management Private Enterprise Codes" 1870 [RFC3232] value, encoded in network byte order. Any vendor 1871 wishing to implement a vendor-specific Diameter AVP MUST use their 1872 own Vendor-ID along with their privately managed AVP address 1873 space, guaranteeing that they will not collide with any other 1874 vendor's vendor-specific AVP(s), nor with future IETF 1875 applications. 1877 A vendor ID value of zero (0) corresponds to the IETF adopted AVP 1878 values, as managed by the IANA. Since the absence of the vendor 1879 ID field implies that the AVP in question is not vendor specific, 1880 implementations MUST NOT use the zero (0) vendor ID. 1882 4.2. Basic AVP Data Formats 1884 The Data field is zero or more octets and contains information 1885 specific to the Attribute. The format and length of the Data field 1886 is determined by the AVP Code and AVP Length fields. The format of 1887 the Data field MUST be one of the following base data types or a data 1888 type derived from the base data types. In the event that a new Basic 1889 AVP Data Format is needed, a new version of this RFC MUST be created. 1891 OctetString 1893 The data contains arbitrary data of variable length. Unless 1894 otherwise noted, the AVP Length field MUST be set to at least 8 1895 (12 if the 'V' bit is enabled). AVP Values of this type that are 1896 not a multiple of four-octets in length is followed by the 1897 necessary padding so that the next AVP (if any) will start on a 1898 32-bit boundary. 1900 Integer32 1902 32 bit signed value, in network byte order. The AVP Length field 1903 MUST be set to 12 (16 if the 'V' bit is enabled). 1905 Integer64 1907 64 bit signed value, in network byte order. The AVP Length field 1908 MUST be set to 16 (20 if the 'V' bit is enabled). 1910 Unsigned32 1912 32 bit unsigned value, in network byte order. The AVP Length 1913 field MUST be set to 12 (16 if the 'V' bit is enabled). 1915 Unsigned64 1917 64 bit unsigned value, in network byte order. The AVP Length 1918 field MUST be set to 16 (20 if the 'V' bit is enabled). 1920 Float32 1922 This represents floating point values of single precision as 1923 described by [FLOATPOINT]. The 32-bit value is transmitted in 1924 network byte order. The AVP Length field MUST be set to 12 (16 if 1925 the 'V' bit is enabled). 1927 Float64 1929 This represents floating point values of double precision as 1930 described by [FLOATPOINT]. The 64-bit value is transmitted in 1931 network byte order. The AVP Length field MUST be set to 16 (20 if 1932 the 'V' bit is enabled). 1934 Grouped 1936 The Data field is specified as a sequence of AVPs. Each of these 1937 AVPs follows - in the order in which they are specified - 1938 including their headers and padding. The AVP Length field is set 1939 to 8 (12 if the 'V' bit is enabled) plus the total length of all 1940 included AVPs, including their headers and padding. Thus the AVP 1941 length field of an AVP of type Grouped is always a multiple of 4. 1943 4.3. Derived AVP Data Formats 1945 In addition to using the Basic AVP Data Formats, applications may 1946 define data formats derived from the Basic AVP Data Formats. An 1947 application that defines new AVP Derived Data Formats MUST include 1948 them in a section entitled "AVP Derived Data Formats", using the same 1949 format as the definitions below. Each new definition MUST be either 1950 defined or listed with a reference to the RFC that defines the 1951 format. 1953 The below AVP Derived Data Formats are commonly used by applications. 1955 Address 1957 The Address format is derived from the OctetString AVP Base 1958 Format. It is a discriminated union, representing, for example a 1959 32-bit (IPv4) [RFC791] or 128-bit (IPv6) [RFC4291] address, most 1960 significant octet first. The first two octets of the Address AVP 1961 represents the AddressType, which contains an Address Family 1962 defined in [IANAADFAM]. The AddressType is used to discriminate 1963 the content and format of the remaining octets. 1965 Time 1967 The Time format is derived from the OctetString AVP Base Format. 1968 The string MUST contain four octets, in the same format as the 1969 first four bytes are in the NTP timestamp format. The NTP 1970 Timestamp format is defined in chapter 3 of [RFC4330]. 1972 This represents the number of seconds since 0h on 1 January 1900 1973 with respect to the Coordinated Universal Time (UTC). 1975 On 6h 28m 16s UTC, 7 February 2036 the time value will overflow. 1976 SNTP [RFC4330] describes a procedure to extend the time to 2104. 1977 This procedure MUST be supported by all DIAMETER nodes. 1979 UTF8String 1981 The UTF8String format is derived from the OctetString AVP Base 1982 Format. This is a human readable string represented using the 1983 ISO/IEC IS 10646-1 character set, encoded as an OctetString using 1984 the UTF-8 [RFC3629] transformation format described in RFC 3629. 1986 Since additional code points are added by amendments to the 10646 1987 standard from time to time, implementations MUST be prepared to 1988 encounter any code point from 0x00000001 to 0x7fffffff. Byte 1989 sequences that do not correspond to the valid encoding of a code 1990 point into UTF-8 charset or are outside this range are prohibited. 1992 The use of control codes SHOULD be avoided. When it is necessary 1993 to represent a new line, the control code sequence CR LF SHOULD be 1994 used. 1996 The use of leading or trailing white space SHOULD be avoided. 1998 For code points not directly supported by user interface hardware 1999 or software, an alternative means of entry and display, such as 2000 hexadecimal, MAY be provided. 2002 For information encoded in 7-bit US-ASCII, the UTF-8 charset is 2003 identical to the US-ASCII charset. 2005 UTF-8 may require multiple bytes to represent a single character / 2006 code point; thus the length of an UTF8String in octets may be 2007 different from the number of characters encoded. 2009 Note that the AVP Length field of an UTF8String is measured in 2010 octets, not characters. 2012 DiameterIdentity 2014 The DiameterIdentity format is derived from the OctetString AVP 2015 Base Format. 2017 DiameterIdentity = FQDN 2019 DiameterIdentity value is used to uniquely identify a Diameter 2020 node for purposes of duplicate connection and routing loop 2021 detection. 2023 The contents of the string MUST be the FQDN of the Diameter node. 2024 If multiple Diameter nodes run on the same host, each Diameter 2025 node MUST be assigned a unique DiameterIdentity. If a Diameter 2026 node can be identified by several FQDNs, a single FQDN should be 2027 picked at startup, and used as the only DiameterIdentity for that 2028 node, whatever the connection it is sent on. Note that in this 2029 document, DiameterIdentity is in ASCII form in order to be 2030 compatible with existing DNS infrastructure. See Appendix D for 2031 interactions between the Diameter protocol and Internationalized 2032 Domain Name (IDNs). 2034 DiameterURI 2036 The DiameterURI MUST follow the Uniform Resource Identifiers (URI) 2037 syntax [RFC3986] rules specified below: 2039 "aaa://" FQDN [ port ] [ transport ] [ protocol ] 2041 ; No transport security 2043 "aaas://" FQDN [ port ] [ transport ] [ protocol ] 2045 ; Transport security used 2047 FQDN = Fully Qualified Host Name 2049 port = ":" 1*DIGIT 2051 ; One of the ports used to listen for 2052 ; incoming connections. 2053 ; If absent, 2054 ; the default Diameter port (3868) is 2055 ; assumed. 2057 transport = ";transport=" transport-protocol 2059 ; One of the transports used to listen 2060 ; for incoming connections. If absent, 2061 ; the default SCTP [RFC2960] protocol is 2062 ; assumed. UDP MUST NOT be used when 2063 ; the aaa-protocol field is set to 2064 ; diameter. 2066 transport-protocol = ( "tcp" / "sctp" / "udp" ) 2068 protocol = ";protocol=" aaa-protocol 2070 ; If absent, the default AAA protocol 2071 ; is diameter. 2073 aaa-protocol = ( "diameter" / "radius" / "tacacs+" ) 2075 The following are examples of valid Diameter host identities: 2077 aaa://host.example.com;transport=tcp 2078 aaa://host.example.com:6666;transport=tcp 2079 aaa://host.example.com;protocol=diameter 2080 aaa://host.example.com:6666;protocol=diameter 2081 aaa://host.example.com:6666;transport=tcp;protocol=diameter 2082 aaa://host.example.com:1813;transport=udp;protocol=radius 2084 Enumerated 2086 Enumerated is derived from the Integer32 AVP Base Format. The 2087 definition contains a list of valid values and their 2088 interpretation and is described in the Diameter application 2089 introducing the AVP. 2091 IPFilterRule 2093 The IPFilterRule format is derived from the OctetString AVP Base 2094 Format and uses the ASCII charset. The rule syntax is a modified 2095 subset of ipfw(8) from FreeBSD. Packets may be filtered based on 2096 the following information that is associated with it: 2098 Direction (in or out) 2099 Source and destination IP address (possibly masked) 2100 Protocol 2101 Source and destination port (lists or ranges) 2102 TCP flags 2103 IP fragment flag 2104 IP options 2105 ICMP types 2107 Rules for the appropriate direction are evaluated in order, with 2108 the first matched rule terminating the evaluation. Each packet is 2109 evaluated once. If no rule matches, the packet is dropped if the 2110 last rule evaluated was a permit, and passed if the last rule was 2111 a deny. 2113 IPFilterRule filters MUST follow the format: 2115 action dir proto from src to dst [options] 2117 action permit - Allow packets that match the rule. 2118 deny - Drop packets that match the rule. 2120 dir "in" is from the terminal, "out" is to the 2121 terminal. 2123 proto An IP protocol specified by number. The "ip" 2124 keyword means any protocol will match. 2126 src and dst
[ports] 2128 The
may be specified as: 2129 ipno An IPv4 or IPv6 number in dotted- 2130 quad or canonical IPv6 form. Only 2131 this exact IP number will match the 2132 rule. 2133 ipno/bits An IP number as above with a mask 2134 width of the form 1.2.3.4/24. In 2135 this case, all IP numbers from 2136 1.2.3.0 to 1.2.3.255 will match. 2137 The bit width MUST be valid for the 2138 IP version and the IP number MUST 2139 NOT have bits set beyond the mask. 2140 For a match to occur, the same IP 2141 version must be present in the 2142 packet that was used in describing 2143 the IP address. To test for a 2144 particular IP version, the bits part 2145 can be set to zero. The keyword 2146 "any" is 0.0.0.0/0 or the IPv6 2147 equivalent. The keyword "assigned" 2148 is the address or set of addresses 2149 assigned to the terminal. For IPv4, 2150 a typical first rule is often "deny 2151 in ip! assigned" 2153 The sense of the match can be inverted by 2154 preceding an address with the not modifier (!), 2155 causing all other addresses to be matched 2156 instead. This does not affect the selection of 2157 port numbers. 2159 With the TCP, UDP and SCTP protocols, optional 2160 ports may be specified as: 2162 {port/port-port}[,ports[,...]] 2164 The '-' notation specifies a range of ports 2165 (including boundaries). 2167 Fragmented packets that have a non-zero offset 2168 (i.e., not the first fragment) will never match 2169 a rule that has one or more port 2170 specifications. See the frag option for 2171 details on matching fragmented packets. 2173 options: 2174 frag Match if the packet is a fragment and this is not 2175 the first fragment of the datagram. frag may not 2176 be used in conjunction with either tcpflags or 2177 TCP/UDP port specifications. 2179 ipoptions spec 2180 Match if the IP header contains the comma 2181 separated list of options specified in spec. The 2182 supported IP options are: 2184 ssrr (strict source route), lsrr (loose source 2185 route), rr (record packet route) and ts 2186 (timestamp). The absence of a particular option 2187 may be denoted with a '!'. 2189 tcpoptions spec 2190 Match if the TCP header contains the comma 2191 separated list of options specified in spec. The 2192 supported TCP options are: 2194 mss (maximum segment size), window (tcp window 2195 advertisement), sack (selective ack), ts (rfc1323 2196 timestamp) and cc (rfc1644 t/tcp connection 2197 count). The absence of a particular option may 2198 be denoted with a '!'. 2200 established 2201 TCP packets only. Match packets that have the RST 2202 or ACK bits set. 2204 setup TCP packets only. Match packets that have the SYN 2205 bit set but no ACK bit. 2207 tcpflags spec 2208 TCP packets only. Match if the TCP header 2209 contains the comma separated list of flags 2210 specified in spec. The supported TCP flags are: 2212 fin, syn, rst, psh, ack and urg. The absence of a 2213 particular flag may be denoted with a '!'. A rule 2214 that contains a tcpflags specification can never 2215 match a fragmented packet that has a non-zero 2216 offset. See the frag option for details on 2217 matching fragmented packets. 2219 icmptypes types 2220 ICMP packets only. Match if the ICMP type is in 2221 the list types. The list may be specified as any 2222 combination of ranges or individual types 2223 separated by commas. Both the numeric values and 2224 the symbolic values listed below can be used. The 2225 supported ICMP types are: 2227 echo reply (0), destination unreachable (3), 2228 source quench (4), redirect (5), echo request 2229 (8), router advertisement (9), router 2230 solicitation (10), time-to-live exceeded (11), IP 2231 header bad (12), timestamp request (13), 2232 timestamp reply (14), information request (15), 2233 information reply (16), address mask request (17) 2234 and address mask reply (18). 2236 There is one kind of packet that the access device MUST always 2237 discard, that is an IP fragment with a fragment offset of one. 2238 This is a valid packet, but it only has one use, to try to 2239 circumvent firewalls. 2241 An access device that is unable to interpret or apply a deny rule 2242 MUST terminate the session. An access device that is unable to 2243 interpret or apply a permit rule MAY apply a more restrictive 2244 rule. An access device MAY apply deny rules of its own before the 2245 supplied rules, for example to protect the access device owner's 2246 infrastructure. 2248 4.4. Grouped AVP Values 2250 The Diameter protocol allows AVP values of type 'Grouped'. This 2251 implies that the Data field is actually a sequence of AVPs. It is 2252 possible to include an AVP with a Grouped type within a Grouped type, 2253 that is, to nest them. AVPs within an AVP of type Grouped have the 2254 same padding requirements as non-Grouped AVPs, as defined in Section 2255 4. 2257 The AVP Code numbering space of all AVPs included in a Grouped AVP is 2258 the same as for non-grouped AVPs. Receivers of a Grouped AVP that 2259 does not have the 'M' (mandatory) bit set and one or more of the 2260 encapsulated AVPs within the group has the 'M' (mandatory) bit set 2261 MAY simply be ignored if the Grouped AVP itself is unrecognized. 2262 However, the encapsulated AVPs with 'M' (mandatory) bit set MUST 2263 belong to the Diameter application the Grouped APV is used in. The 2264 rule applies even if the encapsulated AVP with its 'M' (mandatory) 2265 bit set is further encapsulated within other sub-groups; i.e. other 2266 Grouped AVPs embedded within the Grouped AVP. 2268 Every Grouped AVP defined MUST include a corresponding grammar, using 2269 ABNF [RFC4234] (with modifications), as defined below. 2271 grouped-avp-def = name "::=" avp 2273 name-fmt = ALPHA *(ALPHA / DIGIT / "-") 2275 name = name-fmt 2276 ; The name has to be the name of an AVP, 2277 ; defined in the base or extended Diameter 2278 ; specifications. 2280 avp = header [ *fixed] [ *required] [ *optional] 2282 header = "<" "AVP-Header:" avpcode [vendor] ">" 2284 avpcode = 1*DIGIT 2285 ; The AVP Code assigned to the Grouped AVP 2287 vendor = 1*DIGIT 2288 ; The Vendor-ID assigned to the Grouped AVP. 2289 ; If absent, the default value of zero is 2290 ; used. 2292 4.4.1. Example AVP with a Grouped Data type 2294 The Example-AVP (AVP Code 999999) is of type Grouped and is used to 2295 clarify how Grouped AVP values work. The Grouped Data field has the 2296 following ABNF grammar: 2298 Example-AVP ::= < AVP Header: 999999 > 2299 { Origin-Host } 2300 1*{ Session-Id } 2301 *[ AVP ] 2303 An Example-AVP with Grouped Data follows. 2305 The Origin-Host AVP is required (Section 6.3). In this case: 2307 Origin-Host = "example.com". 2309 One or more Session-Ids must follow. Here there are two: 2311 Session-Id = 2312 "grump.example.com:33041;23432;893;0AF3B81" 2314 Session-Id = 2315 "grump.example.com:33054;23561;2358;0AF3B82" 2317 optional AVPs included are 2319 Recovery-Policy = 2320 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35 2321 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5 2322 c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd 2323 f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a 2324 cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119 2325 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c 2326 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92 2328 Futuristic-Acct-Record = 2329 fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0 2330 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8 2331 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c 2332 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067 2333 d3427475e49968f841 2335 The data for the optional AVPs is represented in hex since the format 2336 of these AVPs is neither known at the time of definition of the 2337 Example-AVP group, nor (likely) at the time when the example instance 2338 of this AVP is interpreted - except by Diameter implementations which 2339 support the same set of AVPs. The encoding example illustrates how 2340 padding is used and how length fields are calculated. Also note that 2341 AVPs may be present in the Grouped AVP value which the receiver 2342 cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record 2343 AVPs). The length of the Example-AVP is the sum of all the length of 2344 the member AVPs including their padding plus the Example-AVP header 2345 size. 2347 This AVP would be encoded as follows: 2349 0 1 2 3 4 5 6 7 2350 +-------+-------+-------+-------+-------+-------+-------+-------+ 2351 0 | Example AVP Header (AVP Code = 999999), Length = 496 | 2352 +-------+-------+-------+-------+-------+-------+-------+-------+ 2353 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 | 2354 +-------+-------+-------+-------+-------+-------+-------+-------+ 2355 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' | 2356 +-------+-------+-------+-------+-------+-------+-------+-------+ 2357 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header | 2358 +-------+-------+-------+-------+-------+-------+-------+-------+ 2359 32 | (AVP Code = 263), Length = 49 | 'g' | 'r' | 'u' | 'm' | 2360 +-------+-------+-------+-------+-------+-------+-------+-------+ 2361 . . . 2362 +-------+-------+-------+-------+-------+-------+-------+-------+ 2363 72 | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding|Padding| 2364 +-------+-------+-------+-------+-------+-------+-------+-------+ 2365 80 | Session-Id AVP Header (AVP Code = 263), Length = 50 | 2366 +-------+-------+-------+-------+-------+-------+-------+-------+ 2367 88 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' | 2368 +-------+-------+-------+-------+-------+-------+-------+-------+ 2369 . . . 2370 +-------+-------+-------+-------+-------+-------+-------+-------+ 2371 120| '5' | '8' | ';' | '0' | 'A' | 'F' | '3' | 'B' | 2372 +-------+-------+-------+-------+-------+-------+-------+-------+ 2373 128| '8' | '2' |Padding|Padding| Recovery-Policy Header (AVP | 2374 +-------+-------+-------+-------+-------+-------+-------+-------+ 2375 136| Code = 8341), Length = 223 | 0x21 | 0x63 | 0xbc | 0x1d | 2376 +-------+-------+-------+-------+-------+-------+-------+-------+ 2377 144| 0x0a | 0xd8 | 0x23 | 0x71 | 0xf6 | 0xbc | 0x09 | 0x48 | 2378 +-------+-------+-------+-------+-------+-------+-------+-------+ 2379 . . . 2380 +-------+-------+-------+-------+-------+-------+-------+-------+ 2381 352| 0x8c | 0x7f | 0x92 |Padding| Futuristic-Acct-Record Header | 2382 +-------+-------+-------+-------+-------+-------+-------+-------+ 2383 328|(AVP Code = 15930),Length = 137| 0xfe | 0x19 | 0xda | 0x58 | 2384 +-------+-------+-------+-------+-------+-------+-------+-------+ 2385 336| 0x02 | 0xac | 0xd9 | 0x8b | 0x07 | 0xa5 | 0xb8 | 0xc6 | 2386 +-------+-------+-------+-------+-------+-------+-------+-------+ 2387 . . . 2388 +-------+-------+-------+-------+-------+-------+-------+-------+ 2389 488| 0xe4 | 0x99 | 0x68 | 0xf8 | 0x41 |Padding|Padding|Padding| 2390 +-------+-------+-------+-------+-------+-------+-------+-------+ 2392 4.5. Diameter Base Protocol AVPs 2394 The following table describes the Diameter AVPs defined in the base 2395 protocol, their AVP Code values, types, possible flag values. 2397 Due to space constraints, the short form DiamIdent is used to 2398 represent DiameterIdentity. 2400 +----------------+ 2401 | AVP Flag rules | 2402 |----+-----+-----| 2403 AVP Section | | |MUST | 2404 Attribute Name Code Defined Data Type |MUST| MAY | NOT | 2405 -----------------------------------------|----+-----+-----| 2406 Acct- 85 9.8.2 Unsigned32 | M | | V | 2407 Interim-Interval | | | | 2408 Accounting- 483 9.8.7 Enumerated | M | | V | 2409 Realtime-Required | | | | 2410 Acct- 50 9.8.5 UTF8String | M | | V | 2411 Multi-Session-Id | | | | 2412 Accounting- 485 9.8.3 Unsigned32 | M | | V | 2413 Record-Number | | | | 2414 Accounting- 480 9.8.1 Enumerated | M | | V | 2415 Record-Type | | | | 2416 Accounting- 44 9.8.4 OctetString| M | | V | 2417 Session-Id | | | | 2418 Accounting- 287 9.8.6 Unsigned64 | M | | V | 2419 Sub-Session-Id | | | | 2420 Acct- 259 6.9 Unsigned32 | M | | V | 2421 Application-Id | | | | 2422 Auth- 258 6.8 Unsigned32 | M | | V | 2423 Application-Id | | | | 2424 Auth-Request- 274 8.7 Enumerated | M | | V | 2425 Type | | | | 2426 Authorization- 291 8.9 Unsigned32 | M | | V | 2427 Lifetime | | | | 2428 Auth-Grace- 276 8.10 Unsigned32 | M | | V | 2429 Period | | | | 2430 Auth-Session- 277 8.11 Enumerated | M | | V | 2431 State | | | | 2432 Re-Auth-Request- 285 8.12 Enumerated | M | | V | 2433 Type | | | | 2434 Class 25 8.20 OctetString| M | | V | 2435 Destination-Host 293 6.5 DiamIdent | M | | V | 2436 Destination- 283 6.6 DiamIdent | M | | V | 2437 Realm | | | | 2438 Disconnect-Cause 273 5.4.3 Enumerated | M | | V | 2439 Error-Message 281 7.3 UTF8String | | | V,M | 2440 Error-Reporting- 294 7.4 DiamIdent | | | V,M | 2441 Host | | | | 2442 Event-Timestamp 55 8.21 Time | M | | V | 2443 Experimental- 297 7.6 Grouped | M | | V | 2444 Result | | | | 2445 -----------------------------------------|----+-----+-----| 2446 +----------------+ 2447 | AVP Flag rules | 2448 |----+-----+-----| 2449 AVP Section | | | MUST| 2450 Attribute Name Code Defined Data Type |MUST| MAY | NOT| 2451 -----------------------------------------|----+-----+-----| 2452 Experimental- 298 7.7 Unsigned32 | M | | V | 2453 Result-Code | | | | 2454 Failed-AVP 279 7.5 Grouped | M | | V | 2455 Firmware- 267 5.3.4 Unsigned32 | | | V,M | 2456 Revision | | | | 2457 Host-IP-Address 257 5.3.5 Address | M | | V | 2458 Inband-Security | M | | V | 2459 -Id 299 6.10 Unsigned32 | | | | 2460 Multi-Round- 272 8.19 Unsigned32 | M | | V | 2461 Time-Out | | | | 2462 Origin-Host 264 6.3 DiamIdent | M | | V | 2463 Origin-Realm 296 6.4 DiamIdent | M | | V | 2464 Origin-State-Id 278 8.16 Unsigned32 | M | | V | 2465 Product-Name 269 5.3.7 UTF8String | | | V,M | 2466 Proxy-Host 280 6.7.3 DiamIdent | M | | V | 2467 Proxy-Info 284 6.7.2 Grouped | M | | V | 2468 Proxy-State 33 6.7.4 OctetString| M | | V | 2469 Redirect-Host 292 6.12 DiamURI | M | | V | 2470 Redirect-Host- 261 6.13 Enumerated | M | | V | 2471 Usage | | | | 2472 Redirect-Max- 262 6.14 Unsigned32 | M | | V | 2473 Cache-Time | | | | 2474 Result-Code 268 7.1 Unsigned32 | M | | V | 2475 Route-Record 282 6.7.1 DiamIdent | M | | V | 2476 Session-Id 263 8.8 UTF8String | M | | V | 2477 Session-Timeout 27 8.13 Unsigned32 | M | | V | 2478 Session-Binding 270 8.17 Unsigned32 | M | | V | 2479 Session-Server- 271 8.18 Enumerated | M | | V | 2480 Failover | | | | 2481 Supported- 265 5.3.6 Unsigned32 | M | | V | 2482 Vendor-Id | | | | 2483 Termination- 295 8.15 Enumerated | M | | V | 2484 Cause | | | | 2485 User-Name 1 8.14 UTF8String | M | | V | 2486 Vendor-Id 266 5.3.3 Unsigned32 | M | | V | 2487 Vendor-Specific- 260 6.11 Grouped | M | | V | 2488 Application-Id | | | | 2489 -----------------------------------------|----+-----+-----| 2491 5. Diameter Peers 2493 This section describes how Diameter nodes establish connections and 2494 communicate with peers. 2496 5.1. Peer Connections 2498 Although a Diameter node may have many possible peers that it is able 2499 to communicate with, it may not be economical to have an established 2500 connection to all of them. At a minimum, a Diameter node SHOULD have 2501 an established connection with two peers per realm, known as the 2502 primary and secondary peers. Of course, a node MAY have additional 2503 connections, if it is deemed necessary. Typically, all messages for 2504 a realm are sent to the primary peer, but in the event that failover 2505 procedures are invoked, any pending requests are sent to the 2506 secondary peer. However, implementations are free to load balance 2507 requests between a set of peers. 2509 Note that a given peer MAY act as a primary for a given realm, while 2510 acting as a secondary for another realm. 2512 When a peer is deemed suspect, which could occur for various reasons, 2513 including not receiving a DWA within an allotted timeframe, no new 2514 requests should be forwarded to the peer, but failover procedures are 2515 invoked. When an active peer is moved to this mode, additional 2516 connections SHOULD be established to ensure that the necessary number 2517 of active connections exists. 2519 There are two ways that a peer is removed from the suspect peer list: 2521 1. The peer is no longer reachable, causing the transport connection 2522 to be shutdown. The peer is moved to the closed state. 2524 2. Three watchdog messages are exchanged with accepted round trip 2525 times, and the connection to the peer is considered stabilized. 2527 In the event the peer being removed is either the primary or 2528 secondary, an alternate peer SHOULD replace the deleted peer, and 2529 assume the role of either primary or secondary. 2531 5.2. Diameter Peer Discovery 2533 Allowing for dynamic Diameter agent discovery will make it possible 2534 for simpler and more robust deployment of Diameter services. In 2535 order to promote interoperable implementations of Diameter peer 2536 discovery, the following mechanisms are described. These are based 2537 on existing IETF standards. The first option (manual configuration) 2538 MUST be supported by all DIAMETER nodes, while the latter option 2539 (DNS) MAY be supported. 2541 There are two cases where Diameter peer discovery may be performed. 2542 The first is when a Diameter client needs to discover a first-hop 2543 Diameter agent. The second case is when a Diameter agent needs to 2544 discover another agent - for further handling of a Diameter 2545 operation. In both cases, the following 'search order' is 2546 recommended: 2548 1. The Diameter implementation consults its list of static 2549 (manually) configured Diameter agent locations. These will be 2550 used if they exist and respond. 2552 2. The Diameter implementation performs a NAPTR query for a server 2553 in a particular realm. The Diameter implementation has to know 2554 in advance which realm to look for a Diameter agent in. This 2555 could be deduced, for example, from the 'realm' in a NAI that a 2556 Diameter implementation needed to perform a Diameter operation 2557 on. 2559 * The services relevant for the task of transport protocol 2560 selection are those with NAPTR service fields with values 2561 "AAA+D2x", where x is a letter that corresponds to a transport 2562 protocol supported by the domain. This specification defines 2563 D2T for TCP and D2S for SCTP. We also establish an IANA 2564 registry for NAPTR service name to transport protocol 2565 mappings. 2567 These NAPTR records provide a mapping from a domain, to the 2568 SRV record for contacting a server with the specific transport 2569 protocol in the NAPTR services field. The resource record 2570 will contain an empty regular expression and a replacement 2571 value, which is the SRV record for that particular transport 2572 protocol. If the server supports multiple transport 2573 protocols, there will be multiple NAPTR records, each with a 2574 different service value. As per [RFC3403], the client 2575 discards any records whose services fields are not applicable. 2576 For the purposes of this specification, several rules are 2577 defined. 2579 * A client MUST discard any service fields that identify a 2580 resolution service whose value is not "D2X", for values of X 2581 that indicate transport protocols supported by the client. 2582 The NAPTR processing as described in [RFC3403] will result in 2583 discovery of the most preferred transport protocol of the 2584 server that is supported by the client, as well as an SRV 2585 record for the server. 2587 The domain suffixes in the NAPTR replacement field SHOULD 2588 match the domain of the original query. 2590 3. If no NAPTR records are found, the requester queries for those 2591 address records for the destination address, 2592 '_diameter._sctp'.realm or '_diameter._tcp'.realm. Address 2593 records include A RR's, AAAA RR's or other similar records, 2594 chosen according to the requestor's network protocol 2595 capabilities. If the DNS server returns no address records, the 2596 requestor gives up. 2598 If the server is using a site certificate, the domain name in the 2599 query and the domain name in the replacement field MUST both be 2600 valid based on the site certificate handed out by the server in 2601 the TLS or IKE exchange. Similarly, the domain name in the SRV 2602 query and the domain name in the target in the SRV record MUST 2603 both be valid based on the same site certificate. Otherwise, an 2604 attacker could modify the DNS records to contain replacement 2605 values in a different domain, and the client could not validate 2606 that this was the desired behavior, or the result of an attack 2608 Also, the Diameter Peer MUST check to make sure that the 2609 discovered peers are authorized to act in its role. 2610 Authentication via IKE or TLS, or validation of DNS RRs via 2611 DNSSEC is not sufficient to conclude this. For example, a web 2612 server may have obtained a valid TLS certificate, and secured RRs 2613 may be included in the DNS, but this does not imply that it is 2614 authorized to act as a Diameter Server. 2616 Authorization can be achieved for example, by configuration of a 2617 Diameter Server CA. Alternatively this can be achieved by 2618 definition of OIDs within TLS or IKE certificates so as to 2619 signify Diameter Server authorization. 2621 A dynamically discovered peer causes an entry in the Peer Table (see 2622 Section 2.6) to be created. Note that entries created via DNS MUST 2623 expire (or be refreshed) within the DNS TTL. If a peer is discovered 2624 outside of the local realm, a routing table entry (see Section 2.7) 2625 for the peer's realm is created. The routing table entry's 2626 expiration MUST match the peer's expiration value. 2628 5.3. Capabilities Exchange 2630 When two Diameter peers establish a transport connection, they MUST 2631 exchange the Capabilities Exchange messages, as specified in the peer 2632 state machine (see Section 5.6). This message allows the discovery 2633 of a peer's identity and its capabilities (protocol version number, 2634 supported Diameter applications, security mechanisms, etc.) 2636 The receiver only issues commands to its peers that have advertised 2637 support for the Diameter application that defines the command. A 2638 Diameter node MUST cache the supported applications in order to 2639 ensure that unrecognized commands and/or AVPs are not unnecessarily 2640 sent to a peer. 2642 A receiver of a Capabilities-Exchange-Req (CER) message that does not 2643 have any applications in common with the sender MUST return a 2644 Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to 2645 DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport 2646 layer connection. Note that receiving a CER or CEA from a peer 2647 advertising itself as a Relay (see Section 2.4) MUST be interpreted 2648 as having common applications with the peer. 2650 The receiver of the Capabilities-Exchange-Request (CER) MUST 2651 determine common applications by computing the intersection of its 2652 own set of supported Application Id against all of the application 2653 indentifier AVPs (Auth-Application-Id, Acct-Application-Id and 2654 Vendor-Specific-Application-Id) present in the CER. The value of the 2655 Vendor-Id AVP in the Vendor-Specific-Application-Id MUST NOT be used 2656 during computation. The sender of the Capabilities-Exchange-Answer 2657 (CEA) SHOULD include all of its supported applications as a hint to 2658 the receiver regarding all of its application capabilities. 2660 Similarly, a receiver of a Capabilities-Exchange-Req (CER) message 2661 that does not have any security mechanisms in common with the sender 2662 MUST return a Capabilities-Exchange-Answer (CEA) with the Result-Code 2663 AVP set to DIAMETER_NO_COMMON_SECURITY, and SHOULD disconnect the 2664 transport layer connection. 2666 CERs received from unknown peers MAY be silently discarded, or a CEA 2667 MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER. 2668 In both cases, the transport connection is closed. If the local 2669 policy permits receiving CERs from unknown hosts, a successful CEA 2670 MAY be returned. If a CER from an unknown peer is answered with a 2671 successful CEA, the lifetime of the peer entry is equal to the 2672 lifetime of the transport connection. In case of a transport 2673 failure, all the pending transactions destined to the unknown peer 2674 can be discarded. 2676 The CER and CEA messages MUST NOT be proxied, redirected or relayed. 2678 Since the CER/CEA messages cannot be proxied, it is still possible 2679 that an upstream agent receives a message for which it has no 2680 available peers to handle the application that corresponds to the 2681 Command-Code. In such instances, the 'E' bit is set in the answer 2682 message (see Section 7.) with the Result-Code AVP set to 2683 DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action 2684 (e.g., re-routing request to an alternate peer). 2686 With the exception of the Capabilities-Exchange-Request message, a 2687 message of type Request that includes the Auth-Application-Id or 2688 Acct-Application-Id AVPs, or a message with an application-specific 2689 command code, MAY only be forwarded to a host that has explicitly 2690 advertised support for the application (or has advertised the Relay 2691 Application Id). 2693 5.3.1. Capabilities-Exchange-Request 2695 The Capabilities-Exchange-Request (CER), indicated by the Command- 2696 Code set to 257 and the Command Flags' 'R' bit set, is sent to 2697 exchange local capabilities. Upon detection of a transport failure, 2698 this message MUST NOT be sent to an alternate peer. 2700 When Diameter is run over SCTP [RFC2960], which allows for 2701 connections to span multiple interfaces and multiple IP addresses, 2702 the Capabilities-Exchange-Request message MUST contain one Host-IP- 2703 Address AVP for each potential IP address that MAY be locally used 2704 when transmitting Diameter messages. 2706 Message Format 2708 ::= < Diameter Header: 257, REQ > 2709 { Origin-Host } 2710 { Origin-Realm } 2711 1* { Host-IP-Address } 2712 { Vendor-Id } 2713 { Product-Name } 2714 [ Origin-State-Id ] 2715 * [ Supported-Vendor-Id ] 2716 * [ Auth-Application-Id ] 2717 * [ Inband-Security-Id ] 2718 * [ Acct-Application-Id ] 2719 * [ Vendor-Specific-Application-Id ] 2720 [ Firmware-Revision ] 2721 * [ AVP ] 2723 5.3.2. Capabilities-Exchange-Answer 2725 The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code 2726 set to 257 and the Command Flags' 'R' bit cleared, is sent in 2727 response to a CER message. 2729 When Diameter is run over SCTP [RFC2960], which allows connections to 2730 span multiple interfaces, hence, multiple IP addresses, the 2731 Capabilities-Exchange-Answer message MUST contain one Host-IP-Address 2732 AVP for each potential IP address that MAY be locally used when 2733 transmitting Diameter messages. 2735 Message Format 2737 ::= < Diameter Header: 257 > 2738 { Result-Code } 2739 { Origin-Host } 2740 { Origin-Realm } 2741 1* { Host-IP-Address } 2742 { Vendor-Id } 2743 { Product-Name } 2744 [ Origin-State-Id ] 2745 [ Error-Message ] 2746 [ Failed-AVP ] 2747 * [ Supported-Vendor-Id ] 2748 * [ Auth-Application-Id ] 2749 * [ Inband-Security-Id ] 2750 * [ Acct-Application-Id ] 2751 * [ Vendor-Specific-Application-Id ] 2752 [ Firmware-Revision ] 2753 * [ AVP ] 2755 5.3.3. Vendor-Id AVP 2757 The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains 2758 the IANA "SMI Network Management Private Enterprise Codes" [RFC3232] 2759 value assigned to the vendor of the Diameter device. It is 2760 envisioned that the combination of the Vendor-Id, Product-Name 2761 (Section 5.3.7) and the Firmware-Revision (Section 5.3.4) AVPs may 2762 provide useful debugging information. 2764 A Vendor-Id value of zero in the CER or CEA messages is reserved and 2765 indicates that this field is ignored. 2767 5.3.4. Firmware-Revision AVP 2769 The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is 2770 used to inform a Diameter peer of the firmware revision of the 2771 issuing device. 2773 For devices that do not have a firmware revision (general purpose 2774 computers running Diameter software modules, for instance), the 2775 revision of the Diameter software module may be reported instead. 2777 5.3.5. Host-IP-Address AVP 2779 The Host-IP-Address AVP (AVP Code 257) is of type Address and is used 2780 to inform a Diameter peer of the sender's IP address. All source 2781 addresses that a Diameter node expects to use with SCTP [RFC2960] 2782 MUST be advertised in the CER and CEA messages by including a 2783 Host-IP- Address AVP for each address. This AVP MUST ONLY be used in 2784 the CER and CEA messages. 2786 5.3.6. Supported-Vendor-Id AVP 2788 The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and 2789 contains the IANA "SMI Network Management Private Enterprise Codes" 2790 [RFC3232] value assigned to a vendor other than the device vendor but 2791 including the application vendor. This is used in the CER and CEA 2792 messages in order to inform the peer that the sender supports (a 2793 subset of) the vendor-specific AVPs defined by the vendor identified 2794 in this AVP. The value of this AVP SHOULD NOT be set to zero. 2795 Multiple instances of this AVP containing the same value SHOULD NOT 2796 be sent. 2798 5.3.7. Product-Name AVP 2800 The Product-Name AVP (AVP Code 269) is of type UTF8String, and 2801 contains the vendor assigned name for the product. The Product-Name 2802 AVP SHOULD remain constant across firmware revisions for the same 2803 product. 2805 5.4. Disconnecting Peer connections 2807 When a Diameter node disconnects one of its transport connections, 2808 its peer cannot know the reason for the disconnect, and will most 2809 likely assume that a connectivity problem occurred, or that the peer 2810 has rebooted. In these cases, the peer may periodically attempt to 2811 reconnect, as stated in Section 2.1. In the event that the 2812 disconnect was a result of either a shortage of internal resources, 2813 or simply that the node in question has no intentions of forwarding 2814 any Diameter messages to the peer in the foreseeable future, a 2815 periodic connection request would not be welcomed. The 2816 Disconnection-Reason AVP contains the reason the Diameter node issued 2817 the Disconnect-Peer-Request message. 2819 The Disconnect-Peer-Request message is used by a Diameter node to 2820 inform its peer of its intent to disconnect the transport layer, and 2821 that the peer shouldn't reconnect unless it has a valid reason to do 2822 so (e.g., message to be forwarded). Upon receipt of the message, the 2823 Disconnect-Peer-Answer is returned, which SHOULD contain an error if 2824 messages have recently been forwarded, and are likely in flight, 2825 which would otherwise cause a race condition. 2827 The receiver of the Disconnect-Peer-Answer initiates the transport 2828 disconnect. The sender of the Disconnect-Peer-Answer should be able 2829 to detect the transport closure and cleanup the connection. 2831 5.4.1. Disconnect-Peer-Request 2833 The Disconnect-Peer-Request (DPR), indicated by the Command-Code set 2834 to 282 and the Command Flags' 'R' bit set, is sent to a peer to 2835 inform its intentions to shutdown the transport connection. Upon 2836 detection of a transport failure, this message MUST NOT be sent to an 2837 alternate peer. 2839 Message Format 2841 ::= < Diameter Header: 282, REQ > 2842 { Origin-Host } 2843 { Origin-Realm } 2844 { Disconnect-Cause } 2845 * [ AVP ] 2847 5.4.2. Disconnect-Peer-Answer 2849 The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set 2850 to 282 and the Command Flags' 'R' bit cleared, is sent as a response 2851 to the Disconnect-Peer-Request message. Upon receipt of this 2852 message, the transport connection is shutdown. 2854 Message Format 2856 ::= < Diameter Header: 282 > 2857 { Result-Code } 2858 { Origin-Host } 2859 { Origin-Realm } 2860 [ Error-Message ] 2861 [ Failed-AVP ] 2862 * [ AVP ] 2864 5.4.3. Disconnect-Cause AVP 2866 The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A 2867 Diameter node MUST include this AVP in the Disconnect-Peer-Request 2868 message to inform the peer of the reason for its intention to 2869 shutdown the transport connection. The following values are 2870 supported: 2872 REBOOTING 0 2873 A scheduled reboot is imminent. Receiver of DPR with above result 2874 code MAY attempt reconnection. 2876 BUSY 1 2877 The peer's internal resources are constrained, and it has 2878 determined that the transport connection needs to be closed. 2879 Receiver of DPR with above result code SHOULD NOT attempt 2880 reconnection. 2882 DO_NOT_WANT_TO_TALK_TO_YOU 2 2883 The peer has determined that it does not see a need for the 2884 transport connection to exist, since it does not expect any 2885 messages to be exchanged in the near future. Receiver of DPR 2886 with above result code SHOULD NOT attempt reconnection. 2888 5.5. Transport Failure Detection 2890 Given the nature of the Diameter protocol, it is recommended that 2891 transport failures be detected as soon as possible. Detecting such 2892 failures will minimize the occurrence of messages sent to unavailable 2893 agents, resulting in unnecessary delays, and will provide better 2894 failover performance. The Device-Watchdog-Request and Device- 2895 Watchdog-Answer messages, defined in this section, are used to pro- 2896 actively detect transport failures. 2898 5.5.1. Device-Watchdog-Request 2900 The Device-Watchdog-Request (DWR), indicated by the Command-Code set 2901 to 280 and the Command Flags' 'R' bit set, is sent to a peer when no 2902 traffic has been exchanged between two peers (see Section 5.5.3). 2903 Upon detection of a transport failure, this message MUST NOT be sent 2904 to an alternate peer. 2906 Message Format 2908 ::= < Diameter Header: 280, REQ > 2909 { Origin-Host } 2910 { Origin-Realm } 2911 [ Origin-State-Id ] 2913 * [ AVP ] 2915 5.5.2. Device-Watchdog-Answer 2917 The Device-Watchdog-Answer (DWA), indicated by the Command-Code set 2918 to 280 and the Command Flags' 'R' bit cleared, is sent as a response 2919 to the Device-Watchdog-Request message. 2921 Message Format 2923 ::= < Diameter Header: 280 > 2924 { Result-Code } 2925 { Origin-Host } 2926 { Origin-Realm } 2927 [ Error-Message ] 2928 [ Failed-AVP ] 2929 [ Origin-State-Id ] 2930 * [ AVP ] 2932 5.5.3. Transport Failure Algorithm 2934 The transport failure algorithm is defined in [RFC3539]. All 2935 Diameter implementations MUST support the algorithm defined in the 2936 specification in order to be compliant to the Diameter base protocol. 2938 5.5.4. Failover and Failback Procedures 2940 In the event that a transport failure is detected with a peer, it is 2941 necessary for all pending request messages to be forwarded to an 2942 alternate agent, if possible. This is commonly referred to as 2943 failover. 2945 In order for a Diameter node to perform failover procedures, it is 2946 necessary for the node to maintain a pending message queue for a 2947 given peer. When an answer message is received, the corresponding 2948 request is removed from the queue. The Hop-by-Hop Identifier field 2949 is used to match the answer with the queued request. 2951 When a transport failure is detected, if possible all messages in the 2952 queue are sent to an alternate agent with the T flag set. On booting 2953 a Diameter client or agent, the T flag is also set on any records 2954 still remaining to be transmitted in non-volatile storage. An 2955 example of a case where it is not possible to forward the message to 2956 an alternate server is when the message has a fixed destination, and 2957 the unavailable peer is the message's final destination (see 2958 Destination-Host AVP). Such an error requires that the agent return 2959 an answer message with the 'E' bit set and the Result-Code AVP set to 2960 DIAMETER_UNABLE_TO_DELIVER. 2962 It is important to note that multiple identical requests or answers 2963 MAY be received as a result of a failover. The End-to-End Identifier 2964 field in the Diameter header along with the Origin-Host AVP MUST be 2965 used to identify duplicate messages. 2967 As described in Section 2.1, a connection request should be 2968 periodically attempted with the failed peer in order to re-establish 2969 the transport connection. Once a connection has been successfully 2970 established, messages can once again be forwarded to the peer. This 2971 is commonly referred to as failback. 2973 5.6. Peer State Machine 2975 This section contains a finite state machine that MUST be observed by 2976 all Diameter implementations. Each Diameter node MUST follow the 2977 state machine described below when communicating with each peer. 2978 Multiple actions are separated by commas, and may continue on 2979 succeeding lines, as space requires. Similarly, state and next state 2980 may also span multiple lines, as space requires. 2982 This state machine is closely coupled with the state machine 2983 described in [RFC3539], which is used to open, close, failover, 2984 probe, and reopen transport connections. Note in particular that 2985 [RFC3539] requires the use of watchdog messages to probe connections. 2986 For Diameter, DWR and DWA messages are to be used. 2988 I- is used to represent the initiator (connecting) connection, while 2989 the R- is used to represent the responder (listening) connection. 2990 The lack of a prefix indicates that the event or action is the same 2991 regardless of the connection on which the event occurred. 2993 The stable states that a state machine may be in are Closed, I-Open 2994 and R-Open; all other states are intermediate. Note that I-Open and 2995 R-Open are equivalent except for whether the initiator or responder 2996 transport connection is used for communication. 2998 A CER message is always sent on the initiating connection immediately 2999 after the connection request is successfully completed. In the case 3000 of an election, one of the two connections will shut down. The 3001 responder connection will survive if the Origin-Host of the local 3002 Diameter entity is higher than that of the peer; the initiator 3003 connection will survive if the peer's Origin-Host is higher. All 3004 subsequent messages are sent on the surviving connection. Note that 3005 the results of an election on one peer are guaranteed to be the 3006 inverse of the results on the other. 3008 For TLS usage, a TLS handshake will begin when both ends are in the 3009 open state. If the TLS handshake is successful, all further messages 3010 will be sent via TLS. If the handshake fails, both ends move to the 3011 closed state. 3013 The state machine constrains only the behavior of a Diameter 3014 implementation as seen by Diameter peers through events on the wire. 3016 Any implementation that produces equivalent results is considered 3017 compliant. 3019 state event action next state 3020 ----------------------------------------------------------------- 3021 Closed Start I-Snd-Conn-Req Wait-Conn-Ack 3022 R-Conn-CER R-Accept, R-Open 3023 Process-CER, 3024 R-Snd-CEA 3026 Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA 3027 I-Rcv-Conn-Nack Cleanup Closed 3028 R-Conn-CER R-Accept, Wait-Conn-Ack/ 3029 Process-CER Elect 3030 Timeout Error Closed 3032 Wait-I-CEA I-Rcv-CEA Process-CEA I-Open 3033 R-Conn-CER R-Accept, Wait-Returns 3034 Process-CER, 3035 Elect 3036 I-Peer-Disc I-Disc Closed 3037 I-Rcv-Non-CEA Error Closed 3038 Timeout Error Closed 3040 Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns 3041 Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open 3042 R-Peer-Disc R-Disc Wait-Conn-Ack 3043 R-Conn-CER R-Reject Wait-Conn-Ack/ 3044 Elect 3045 Timeout Error Closed 3047 Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open 3048 I-Peer-Disc I-Disc, R-Open 3049 R-Snd-CEA 3050 I-Rcv-CEA R-Disc I-Open 3051 R-Peer-Disc R-Disc Wait-I-CEA 3052 R-Conn-CER R-Reject Wait-Returns 3053 Timeout Error Closed 3055 R-Open Send-Message R-Snd-Message R-Open 3056 R-Rcv-Message Process R-Open 3057 R-Rcv-DWR Process-DWR, R-Open 3058 R-Snd-DWA 3059 R-Rcv-DWA Process-DWA R-Open 3060 R-Conn-CER R-Reject R-Open 3061 Stop R-Snd-DPR Closing 3062 R-Rcv-DPR R-Snd-DPA, Closed 3063 R-Disc 3065 R-Peer-Disc R-Disc Closed 3066 R-Rcv-CER R-Snd-CEA R-Open 3067 R-Rcv-CEA Process-CEA R-Open 3069 I-Open Send-Message I-Snd-Message I-Open 3070 I-Rcv-Message Process I-Open 3071 I-Rcv-DWR Process-DWR, I-Open 3072 I-Snd-DWA 3073 I-Rcv-DWA Process-DWA I-Open 3074 R-Conn-CER R-Reject I-Open 3075 Stop I-Snd-DPR Closing 3076 I-Rcv-DPR I-Snd-DPA, Closed 3077 I-Disc 3078 I-Peer-Disc I-Disc Closed 3079 I-Rcv-CER I-Snd-CEA I-Open 3080 I-Rcv-CEA Process-CEA I-Open 3082 Closing I-Rcv-DPA I-Disc Closed 3083 R-Rcv-DPA R-Disc Closed 3084 Timeout Error Closed 3085 I-Peer-Disc I-Disc Closed 3086 R-Peer-Disc R-Disc Closed 3088 5.6.1. Incoming connections 3090 When a connection request is received from a Diameter peer, it is 3091 not, in the general case, possible to know the identity of that peer 3092 until a CER is received from it. This is because host and port 3093 determine the identity of a Diameter peer; and the source port of an 3094 incoming connection is arbitrary. Upon receipt of CER, the identity 3095 of the connecting peer can be uniquely determined from Origin-Host. 3097 For this reason, a Diameter peer must employ logic separate from the 3098 state machine to receive connection requests, accept them, and await 3099 CER. Once CER arrives on a new connection, the Origin-Host that 3100 identifies the peer is used to locate the state machine associated 3101 with that peer, and the new connection and CER are passed to the 3102 state machine as an R-Conn-CER event. 3104 The logic that handles incoming connections SHOULD close and discard 3105 the connection if any message other than CER arrives, or if an 3106 implementation-defined timeout occurs prior to receipt of CER. 3108 Because handling of incoming connections up to and including receipt 3109 of CER requires logic, separate from that of any individual state 3110 machine associated with a particular peer, it is described separately 3111 in this section rather than in the state machine above. 3113 5.6.2. Events 3115 Transitions and actions in the automaton are caused by events. In 3116 this section, we will ignore the -I and -R prefix, since the actual 3117 event would be identical, but would occur on one of two possible 3118 connections. 3120 Start The Diameter application has signaled that a 3121 connection should be initiated with the peer. 3123 R-Conn-CER An acknowledgement is received stating that the 3124 transport connection has been established, and the 3125 associated CER has arrived. 3127 Rcv-Conn-Ack A positive acknowledgement is received confirming that 3128 the transport connection is established. 3130 Rcv-Conn-Nack A negative acknowledgement was received stating that 3131 the transport connection was not established. 3133 Timeout An application-defined timer has expired while waiting 3134 for some event. 3136 Rcv-CER A CER message from the peer was received. 3138 Rcv-CEA A CEA message from the peer was received. 3140 Rcv-Non-CEA A message other than CEA from the peer was received. 3142 Peer-Disc A disconnection indication from the peer was received. 3144 Rcv-DPR A DPR message from the peer was received. 3146 Rcv-DPA A DPA message from the peer was received. 3148 Win-Election An election was held, and the local node was the 3149 winner. 3151 Send-Message A message is to be sent. 3153 Rcv-Message A message other than CER, CEA, DPR, DPA, DWR or DWA 3154 was received. 3156 Stop The Diameter application has signaled that a 3157 connection should be terminated (e.g., on system 3158 shutdown). 3160 5.6.3. Actions 3162 Actions in the automaton are caused by events and typically indicate 3163 the transmission of packets and/or an action to be taken on the 3164 connection. In this section we will ignore the I- and R-prefix, 3165 since the actual action would be identical, but would occur on one of 3166 two possible connections. 3168 Snd-Conn-Req A transport connection is initiated with the peer. 3170 Accept The incoming connection associated with the R-Conn-CER 3171 is accepted as the responder connection. 3173 Reject The incoming connection associated with the R-Conn-CER 3174 is disconnected. 3176 Process-CER The CER associated with the R-Conn-CER is processed. 3177 Snd-CER A CER message is sent to the peer. 3179 Snd-CEA A CEA message is sent to the peer. 3181 Cleanup If necessary, the connection is shutdown, and any 3182 local resources are freed. 3184 Error The transport layer connection is disconnected, either 3185 politely or abortively, in response to an error 3186 condition. Local resources are freed. 3188 Process-CEA A received CEA is processed. 3190 Snd-DPR A DPR message is sent to the peer. 3192 Snd-DPA A DPA message is sent to the peer. 3194 Disc The transport layer connection is disconnected, and 3195 local resources are freed. 3197 Elect An election occurs (see Section 5.6.4 for more 3198 information). 3200 Snd-Message A message is sent. 3202 Snd-DWR A DWR message is sent. 3204 Snd-DWA A DWA message is sent. 3206 Process-DWR The DWR message is serviced. 3208 Process-DWA The DWA message is serviced. 3210 Process A message is serviced. 3212 5.6.4. The Election Process 3214 The election is performed on the responder. The responder compares 3215 the Origin-Host received in the CER with its own Origin-Host as two 3216 streams of octets. If the local Origin-Host lexicographically 3217 succeeds the received Origin-Host a Win-Election event is issued 3218 locally. Diameter identities are in ASCII form therefore the lexical 3219 comparison is consistent with DNS case insensitivity where octets 3220 that fall in the ASCII range 'a' through 'z' MUST compare equally to 3221 their upper-case counterparts between 'A' and 'Z'. See Appendix D 3222 for interactions between the Diameter protocol and Internationalized 3223 Domain Name (IDNs). 3225 The winner of the election MUST close the connection it initiated. 3226 Historically, maintaining the responder side of a connection was more 3227 efficient than maintaining the initiator side. However, current 3228 practices makes this distinction irrelevant. 3230 5.6.5. Capabilities Update 3232 A Diameter node MUST initiate peer capabilities update by sending a 3233 Capabilities-Exchange-Req (CER) to all its peers which supports peer 3234 capabilities update and is in OPEN state. The receiver of CER in 3235 open state MUST process and reply to the CER as a described in 3236 Section 5.3. The CEA which the receiver sends MUST contain its 3237 latest capabilities. Note that peers which successfully process the 3238 peer capabilities update SHOULD also update their routing tables to 3239 reflect the change. The receiver of the CEA, with a Result-Code AVP 3240 other than DIAMETER_SUCCESS, initiates the transport disconnect. The 3241 peer may periodically attempt to reconnect, as stated in Section 2.1. 3243 Peer capabilities update in the open state SHOULD be limited to the 3244 advertisement of the new list of supported applications and MUST 3245 preclude re-negotiation of security mechanism or other capabilities. 3246 If any capabilities change happens in the node (e.g. change in 3247 security mechanisms), other than a change in the supported 3248 applications, the node SHOULD gracefully terminate (setting the 3249 Disconnect-Cause AVP value to REBOOTING) and re-establish the 3250 diameter connections to all the peers. 3252 6. Diameter message processing 3254 This section describes how Diameter requests and answers are created 3255 and processed. 3257 6.1. Diameter Request Routing Overview 3259 A request is sent towards its final destination using a combination 3260 of the Destination-Realm and Destination-Host AVPs, in one of these 3261 three combinations: 3263 o a request that is not able to be proxied (such as CER) MUST NOT 3264 contain either Destination-Realm or Destination-Host AVPs. 3266 o a request that needs to be sent to a home server serving a 3267 specific realm, but not to a specific server (such as the first 3268 request of a series of round-trips), MUST contain a Destination- 3269 Realm AVP, but MUST NOT contain a Destination-Host AVP. 3271 o otherwise, a request that needs to be sent to a specific home 3272 server among those serving a given realm, MUST contain both the 3273 Destination-Realm and Destination-Host AVPs. 3275 The Destination-Host AVP is used as described above when the 3276 destination of the request is fixed, which includes: 3278 o Authentication requests that span multiple round trips 3280 o A Diameter message that uses a security mechanism that makes use 3281 of a pre-established session key shared between the source and the 3282 final destination of the message. 3284 o Server initiated messages that MUST be received by a specific 3285 Diameter client (e.g., access device), such as the Abort-Session- 3286 Request message, which is used to request that a particular user's 3287 session be terminated. 3289 Note that an agent can forward a request to a host described in the 3290 Destination-Host AVP only if the host in question is included in its 3291 peer table (see Section 2.7). Otherwise, the request is routed based 3292 on the Destination-Realm only (see Sections 6.1.6). 3294 The Destination-Realm AVP MUST be present if the message is 3295 proxiable. A message that MUST NOT be forwarded by Diameter agents 3296 (proxies, redirects or relays) MUST NOT include the Destination-Realm 3297 in its ABNF. For Diameter clients, the value of the Destination- 3298 Realm AVP MAY be extracted from the User-Name AVP, or other 3299 application-specific methods. 3301 When a message is received, the message is processed in the following 3302 order: 3304 o If the message is destined for the local host, the procedures 3305 listed in Section 6.1.4 are followed. 3307 o If the message is intended for a Diameter peer with whom the local 3308 host is able to directly communicate, the procedures listed in 3309 Section 6.1.5 are followed. This is known as Request Forwarding. 3311 o The procedures listed in Section 6.1.6 are followed, which is 3312 known as Request Routing. 3314 o If none of the above is successful, an answer is returned with the 3315 Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the E-bit set. 3317 For routing of Diameter messages to work within an administrative 3318 domain, all Diameter nodes within the realm MUST be peers. 3320 Note the processing rules contained in this section are intended to 3321 be used as general guidelines to Diameter developers. Certain 3322 implementations MAY use different methods than the ones described 3323 here, and still comply with the protocol specification. See Section 3324 7 for more detail on error handling. 3326 6.1.1. Originating a Request 3328 When creating a request, in addition to any other procedures 3329 described in the application definition for that specific request, 3330 the following procedures MUST be followed: 3332 o the Command-Code is set to the appropriate value 3334 o the 'R' bit is set 3336 o the End-to-End Identifier is set to a locally unique value 3338 o the Origin-Host and Origin-Realm AVPs MUST be set to the 3339 appropriate values, used to identify the source of the message 3341 o the Destination-Host and Destination-Realm AVPs MUST be set to the 3342 appropriate values as described in Section 6.1. 3344 6.1.2. Sending a Request 3346 When sending a request, originated either locally, or as the result 3347 of a forwarding or routing operation, the following procedures MUST 3348 be followed: 3350 o the Hop-by-Hop Identifier should be set to a locally unique value. 3352 o The message should be saved in the list of pending requests. 3354 Other actions to perform on the message based on the particular role 3355 the agent is playing are described in the following sections. 3357 6.1.3. Receiving Requests 3359 A relay or proxy agent MUST check for forwarding loops when receiving 3360 requests. A loop is detected if the server finds its own identity in 3361 a Route-Record AVP. When such an event occurs, the agent MUST answer 3362 with the Result-Code AVP set to DIAMETER_LOOP_DETECTED. 3364 6.1.4. Processing Local Requests 3366 A request is known to be for local consumption when one of the 3367 following conditions occur: 3369 o The Destination-Host AVP contains the local host's identity, 3371 o The Destination-Host AVP is not present, the Destination-Realm AVP 3372 contains a realm the server is configured to process locally, and 3373 the Diameter application is locally supported, or 3375 o Both the Destination-Host and the Destination-Realm are not 3376 present. 3378 When a request is locally processed, the rules in Section 6.2 should 3379 be used to generate the corresponding answer. 3381 6.1.5. Request Forwarding 3383 Request forwarding is done using the Diameter Peer Table. The 3384 Diameter peer table contains all of the peers that the local node is 3385 able to directly communicate with. 3387 When a request is received, and the host encoded in the Destination- 3388 Host AVP is one that is present in the peer table, the message SHOULD 3389 be forwarded to the peer. 3391 6.1.6. Request Routing 3393 Diameter request message routing is done via realms and applications. 3394 A Diameter message that may be forwarded by Diameter agents (proxies, 3395 redirects or relays) MUST include the target realm in the 3396 Destination-Realm AVP. Request routing SHOULD rely on the 3397 Destination-Realm AVP and the Application Id present in the request 3398 message header to aid in the routing decision. The realm MAY be 3399 retrieved from the User-Name AVP, which is in the form of a Network 3400 Access Identifier (NAI). The realm portion of the NAI is inserted in 3401 the Destination-Realm AVP. 3403 Diameter agents MAY have a list of locally supported realms and 3404 applications, and MAY have a list of externally supported realms and 3405 applications. When a request is received that includes a realm 3406 and/or application that is not locally supported, the message is 3407 routed to the peer configured in the Routing Table (see Section 2.7). 3409 Realm names and Application Ids are the minimum supported routing 3410 criteria, additional routing information maybe needed to support 3411 redirect semantics. 3413 6.1.7. Predictive Loop Avoidance 3415 Before forwarding or routing a request, Diameter agents, in addition 3416 to processing done in Section 6.1.3, SHOULD check for the presence of 3417 candidate route's peer identity in any of the Route-Record AVPs. In 3418 an event of the agent detecting the presence of a candidate route's 3419 peer identity in a Route-Record AVP, the agent MUST ignore such route 3420 for the Diameter request message and attempt alternate routes if any. 3421 In case all the candidate routes are eliminated by the above 3422 criteria, the agent SHOULD return DIAMETER_UNABLE_TO_DELIVER message. 3424 6.1.8. Redirecting requests 3426 When a redirect agent receives a request whose routing entry is set 3427 to REDIRECT, it MUST reply with an answer message with the 'E' bit 3428 set, while maintaining the Hop-by-Hop Identifier in the header, and 3429 include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of 3430 the servers associated with the routing entry are added in separate 3431 Redirect-Host AVP. 3433 +------------------+ 3434 | Diameter | 3435 | Redirect Agent | 3436 +------------------+ 3437 ^ | 2. command + 'E' bit 3438 1. Request | | Result-Code = 3439 joe@example.com | | DIAMETER_REDIRECT_INDICATION + 3440 | | Redirect-Host AVP(s) 3441 | v 3442 +-------------+ 3. Request +-------------+ 3443 | example.com |------------->| example.net | 3444 | Relay | | Diameter | 3445 | Agent |<-------------| Server | 3446 +-------------+ 4. Answer +-------------+ 3448 Figure 5: Diameter Redirect Agent 3450 The receiver of the answer message with the 'E' bit set, and the 3451 Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by- 3452 hop field in the Diameter header to identify the request in the 3453 pending message queue (see Section 5.3) that is to be redirected. If 3454 no transport connection exists with the new agent, one is created, 3455 and the request is sent directly to it. 3457 Multiple Redirect-Host AVPs are allowed. The receiver of the answer 3458 message with the 'E' bit set selects exactly one of these hosts as 3459 the destination of the redirected message. 3461 When the Redirect-Host-Usage AVP included in the answer message has a 3462 non-zero value, a route entry for the redirect indications is created 3463 and cached by the receiver. The redirect usage for such route entry 3464 is set by the value of Redirect-Host-Usage AVP and the lifetime of 3465 the cached route entry is set by Redirect-Max-Cache-Time AVP value. 3467 It is possible that multiple redirect indications can create multiple 3468 cached route entries differing only in their redirect usage and the 3469 peer to forward messages to. As an example, two(2) route entries 3470 that are created by two(2) redirect indications results in two(2) 3471 cached routes for the same realm and Application Id. However, one 3472 has a redirect usage of ALL_SESSION where matching request will be 3473 forwarded to one peer and the other has a redirect usage of ALL_REALM 3474 where request are forwarded to another peer. Therefore, an incoming 3475 request that matches the realm and Application Id of both routes will 3476 need additional resolution. In such a case, a routing precedence 3477 rule MUST be used againt the redirect usage value to resolve the 3478 contention. The precedence rule can be found in Section 6.13. 3480 6.1.9. Relaying and Proxying Requests 3482 A relay or proxy agent MUST append a Route-Record AVP to all requests 3483 forwarded. The AVP contains the identity of the peer the request was 3484 received from. 3486 The Hop-by-Hop identifier in the request is saved, and replaced with 3487 a locally unique value. The source of the request is also saved, 3488 which includes the IP address, port and protocol. 3490 A relay or proxy agent MAY include the Proxy-Info AVP in requests if 3491 it requires access to any local state information when the 3492 corresponding response is received. Proxy-Info AVP has certain 3493 security implications and SHOULD contain an embedded HMAC with a 3494 node-local key. Alternatively, it MAY simply use local storage to 3495 store state information. 3497 The message is then forwarded to the next hop, as identified in the 3498 Routing Table. 3500 Figure 6 provides an example of message routing using the procedures 3501 listed in these sections. 3503 (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net) 3504 (Origin-Realm=mno.net) (Origin-Realm=mno.net) 3505 (Destination-Realm=example.com) (Destination- 3506 Realm=example.com) 3507 (Route-Record=nas.example.net) 3508 +------+ ------> +------+ ------> +------+ 3509 | | (Request) | | (Request) | | 3510 | NAS +-------------------+ DRL +-------------------+ HMS | 3511 | | | | | | 3512 +------+ <------ +------+ <------ +------+ 3513 example.net (Answer) example.net (Answer) example.com 3514 (Origin-Host=hms.example.com) (Origin-Host=hms.example.com) 3515 (Origin-Realm=example.com) (Origin-Realm=example.com) 3517 Figure 6: Routing of Diameter messages 3519 Relay and proxy agents are not required to perform full validation of 3520 incoming messages. At a minimum, validation of the message header 3521 and relevant routing AVPs has to be done when relaying messages. 3522 Proxy agents may optionally perform more in-depth message validation 3523 for applications it is interested in. 3525 6.2. Diameter Answer Processing 3527 When a request is locally processed, the following procedures MUST be 3528 applied to create the associated answer, in addition to any 3529 additional procedures that MAY be discussed in the Diameter 3530 application defining the command: 3532 o The same Hop-by-Hop identifier in the request is used in the 3533 answer. 3535 o The local host's identity is encoded in the Origin-Host AVP. 3537 o The Destination-Host and Destination-Realm AVPs MUST NOT be 3538 present in the answer message. 3540 o The Result-Code AVP is added with its value indicating success or 3541 failure. 3543 o If the Session-Id is present in the request, it MUST be included 3544 in the answer. 3546 o Any Proxy-Info AVPs in the request MUST be added to the answer 3547 message, in the same order they were present in the request. 3549 o The 'P' bit is set to the same value as the one in the request. 3551 o The same End-to-End identifier in the request is used in the 3552 answer. 3554 Note that the error messages (see Section 7.3) are also subjected to 3555 the above processing rules. 3557 6.2.1. Processing received Answers 3559 A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an 3560 answer received against the list of pending requests. The 3561 corresponding message should be removed from the list of pending 3562 requests. It SHOULD ignore answers received that do not match a 3563 known Hop-by-Hop Identifier. 3565 6.2.2. Relaying and Proxying Answers 3567 If the answer is for a request which was proxied or relayed, the 3568 agent MUST restore the original value of the Diameter header's Hop- 3569 by-Hop Identifier field. 3571 If the last Proxy-Info AVP in the message is targeted to the local 3572 Diameter server, the AVP MUST be removed before the answer is 3573 forwarded. 3575 If a relay or proxy agent receives an answer with a Result-Code AVP 3576 indicating a failure, it MUST NOT modify the contents of the AVP. 3577 Any additional local errors detected SHOULD be logged, but not 3578 reflected in the Result-Code AVP. If the agent receives an answer 3579 message with a Result-Code AVP indicating success, and it wishes to 3580 modify the AVP to indicate an error, it MUST modify the Result-Code 3581 AVP to contain the appropriate error in the message destined towards 3582 the access device as well as include the Error-Reporting-Host AVP and 3583 it MUST issue an STR on behalf of the access device. 3585 The agent MUST then send the answer to the host that it received the 3586 original request from. 3588 6.3. Origin-Host AVP 3590 The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and 3591 MUST be present in all Diameter messages. This AVP identifies the 3592 endpoint that originated the Diameter message. Relay agents MUST NOT 3593 modify this AVP. 3595 The value of the Origin-Host AVP is guaranteed to be unique within a 3596 single host. 3598 Note that the Origin-Host AVP may resolve to more than one address as 3599 the Diameter peer may support more than one address. 3601 This AVP SHOULD be placed as close to the Diameter header as 3602 possible. 3604 6.4. Origin-Realm AVP 3606 The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity. 3607 This AVP contains the Realm of the originator of any Diameter message 3608 and MUST be present in all messages. 3610 This AVP SHOULD be placed as close to the Diameter header as 3611 possible. 3613 6.5. Destination-Host AVP 3615 The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity. 3616 This AVP MUST be present in all unsolicited agent initiated messages, 3617 MAY be present in request messages, and MUST NOT be present in Answer 3618 messages. 3620 The absence of the Destination-Host AVP will cause a message to be 3621 sent to any Diameter server supporting the application within the 3622 realm specified in Destination-Realm AVP. 3624 This AVP SHOULD be placed as close to the Diameter header as 3625 possible. 3627 6.6. Destination-Realm AVP 3629 The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity, 3630 and contains the realm the message is to be routed to. The 3631 Destination-Realm AVP MUST NOT be present in Answer messages. 3632 Diameter Clients insert the realm portion of the User-Name AVP. 3633 Diameter servers initiating a request message use the value of the 3634 Origin-Realm AVP from a previous message received from the intended 3635 target host (unless it is known a priori). When present, the 3636 Destination-Realm AVP is used to perform message routing decisions. 3638 Request messages whose ABNF does not list the Destination-Realm AVP 3639 as a mandatory AVP are inherently non-routable messages. 3641 This AVP SHOULD be placed as close to the Diameter header as 3642 possible. 3644 6.7. Routing AVPs 3646 The AVPs defined in this section are Diameter AVPs used for routing 3647 purposes. These AVPs change as Diameter messages are processed by 3648 agents. 3650 6.7.1. Route-Record AVP 3652 The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The 3653 identity added in this AVP MUST be the same as the one received in 3654 the Origin-Host of the Capabilities Exchange message. 3656 6.7.2. Proxy-Info AVP 3658 The Proxy-Info AVP (AVP Code 284) is of type Grouped. The Grouped 3659 Data field has the following ABNF grammar: 3661 Proxy-Info ::= < AVP Header: 284 > 3662 { Proxy-Host } 3663 { Proxy-State } 3664 * [ AVP ] 3666 6.7.3. Proxy-Host AVP 3668 The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This 3669 AVP contains the identity of the host that added the Proxy-Info AVP. 3671 6.7.4. Proxy-State AVP 3673 The Proxy-State AVP (AVP Code 33) is of type OctetString, and 3674 contains state local information, and MUST be treated as opaque data. 3676 6.8. Auth-Application-Id AVP 3678 The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and 3679 is used in order to advertise support of the Authentication and 3680 Authorization portion of an application (see Section 2.4). If 3681 present in a message other than CER and CEA, the value of the Auth- 3682 Application-Id AVP MUST match the Application Id present in the 3683 Diameter message header. 3685 6.9. Acct-Application-Id AVP 3687 The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and 3688 is used in order to advertise support of the Accounting portion of an 3689 application (see Section 2.4). If present in a message other than 3690 CER and CEA, the value of the Acct-Application-Id AVP MUST match the 3691 Application Id present in the Diameter message header. 3693 6.10. Inband-Security-Id AVP 3695 The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and 3696 is used in order to advertise support of the Security portion of the 3697 application. 3699 Currently, the following values are supported, but there is ample 3700 room to add new security Ids. 3702 NO_INBAND_SECURITY 0 3704 This peer does not support TLS. This is the default value, if the 3705 AVP is omitted. 3707 TLS 1 3709 This node supports TLS security, as defined by [RFC4346]. 3711 6.11. Vendor-Specific-Application-Id AVP 3713 The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type 3714 Grouped and is used to advertise support of a vendor-specific 3715 Diameter Application. Exactly one instance of either Auth- 3716 Application-Id or Acct-Application-Id AVP MUST be present. The 3717 Application Id carried by either Auth-Application-Id or Acct- 3718 Application-Id AVP MUST comply with vendor specific Application Id 3719 assignment described in Sec 11.3. It MUST also match the Application 3720 Id present in the diameter header except when used in a CER or CEA 3721 messages. 3723 The Vendor-Id AVP is an informational AVP pertaining to the vendor 3724 who may have authorship of the vendor-specific Diameter application. 3725 It MUST NOT be used as a means of defining a completely separate 3726 vendor-specific Application Id space. 3728 This AVP MUST also be present as the first AVP in all experimental 3729 commands defined in the vendor-specific application. 3731 This AVP SHOULD be placed as close to the Diameter header as 3732 possible. 3734 AVP Format 3736 ::= < AVP Header: 260 > 3737 { Vendor-Id } 3738 [ Auth-Application-Id ] 3739 [ Acct-Application-Id ] 3741 A Vendor-Specific-Application-Id AVP MUST contain exactly one of 3742 either Auth-Application-Id or Acct-Application-Id. If a Vendor- 3743 Specific-Application-Id is received without any of these two AVPs, 3744 then the recipient SHOULD issue an answer with a Result-Code set to 3745 DIAMETER_MISSING_AVP. The answer SHOULD also include a Failed-AVP 3746 which MUST contain an example of an Auth-Application-Id AVP and an 3747 Acct-Application-Id AVP. 3749 If a Vendor-Specific-Application-Id is received that contains both 3750 Auth-Application-Id and Acct-Application-Id, then the recipient 3751 SHOULD issue an answer with Result-Code set to 3752 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES. The answer SHOULD also include a 3753 Failed-AVP which MUST contain the received Auth-Application-Id AVP 3754 and Acct-Application-Id AVP. 3756 6.12. Redirect-Host AVP 3758 One or more of instances of this AVP MUST be present if the answer 3759 message's 'E' bit is set and the Result-Code AVP is set to 3760 DIAMETER_REDIRECT_INDICATION. 3762 Upon receiving the above, the receiving Diameter node SHOULD forward 3763 the request directly to one of the hosts identified in these AVPs. 3764 The server contained in the selected Redirect-Host AVP SHOULD be used 3765 for all messages pertaining to this session. 3767 6.13. Redirect-Host-Usage AVP 3769 The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated. 3770 This AVP MAY be present in answer messages whose 'E' bit is set and 3771 the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION. 3773 When present, this AVP dictates how the routing entry resulting from 3774 the Redirect-Host is to be used. The following values are supported: 3776 DONT_CACHE 0 3778 The host specified in the Redirect-Host AVP should not be cached. 3779 This is the default value. 3781 ALL_SESSION 1 3783 All messages within the same session, as defined by the same value 3784 of the Session-ID AVP MAY be sent to the host specified in the 3785 Redirect-Host AVP. 3787 ALL_REALM 2 3789 All messages destined for the realm requested MAY be sent to the 3790 host specified in the Redirect-Host AVP. 3792 REALM_AND_APPLICATION 3 3794 All messages for the application requested to the realm specified 3795 MAY be sent to the host specified in the Redirect-Host AVP. 3797 ALL_APPLICATION 4 3799 All messages for the application requested MAY be sent to the host 3800 specified in the Redirect-Host AVP. 3802 ALL_HOST 5 3804 All messages that would be sent to the host that generated the 3805 Redirect-Host MAY be sent to the host specified in the Redirect- 3806 Host AVP. 3808 ALL_USER 6 3810 All messages for the user requested MAY be sent to the host 3811 specified in the Redirect-Host AVP. 3813 When multiple cached routes are created by redirect indications and 3814 they differ only in redirect usage and peers to forward requests to 3815 (see Section 6.1.8), a precedence rule MUST be applied to the 3816 redirect usage values of the cached routes during normal routing to 3817 resolve contentions that may occur. The precedence rule is the order 3818 that dictate which redirect usage should be considered before any 3819 other as they appear. The order is as follows: 3821 1. ALL_SESSION 3823 2. ALL_USER 3825 3. REALM_AND_APPLICATION 3827 4. ALL_REALM 3829 5. ALL_APPLICATION 3831 6. ALL_HOST 3833 6.14. Redirect-Max-Cache-Time AVP 3835 The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32. 3836 This AVP MUST be present in answer messages whose 'E' bit is set, the 3837 Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the 3838 Redirect-Host-Usage AVP set to a non-zero value. 3840 This AVP contains the maximum number of seconds the peer and route 3841 table entries, created as a result of the Redirect-Host, will be 3842 cached. Note that once a host created due to a redirect indication 3843 is no longer reachable, any associated peer and routing table entries 3844 MUST be deleted. 3846 7. Error Handling 3848 There are two different types of errors in Diameter; protocol and 3849 application errors. A protocol error is one that occurs at the base 3850 protocol level, and MAY require per hop attention (e.g., message 3851 routing error). Application errors, on the other hand, generally 3852 occur due to a problem with a function specified in a Diameter 3853 application (e.g., user authentication, Missing AVP). 3855 Result-Code AVP values that are used to report protocol errors MUST 3856 only be present in answer messages whose 'E' bit is set. When a 3857 request message is received that causes a protocol error, an answer 3858 message is returned with the 'E' bit set, and the Result-Code AVP is 3859 set to the appropriate protocol error value. As the answer is sent 3860 back towards the originator of the request, each proxy or relay agent 3861 MAY take action on the message. 3863 1. Request +---------+ Link Broken 3864 +-------------------------->|Diameter |----///----+ 3865 | +---------------------| | v 3866 +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+ 3867 |Diameter |<-+ (Unable to Forward) +---------+ |Diameter| 3868 | | | Home | 3869 | Relay 1 |--+ +---------+ | Server | 3870 +---------+ | 3. Request |Diameter | +--------+ 3871 +-------------------->| | ^ 3872 | Relay 3 |-----------+ 3873 +---------+ 3875 Figure 7: Example of Protocol Error causing answer message 3877 Figure 7 provides an example of a message forwarded upstream by a 3878 Diameter relay. When the message is received by Relay 2, and it 3879 detects that it cannot forward the request to the home server, an 3880 answer message is returned with the 'E' bit set and the Result-Code 3881 AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls 3882 within the protocol error category, Relay 1 would take special 3883 action, and given the error, attempt to route the message through its 3884 alternate Relay 3. 3886 +---------+ 1. Request +---------+ 2. Request +---------+ 3887 | Access |------------>|Diameter |------------>|Diameter | 3888 | | | | | Home | 3889 | Device |<------------| Relay |<------------| Server | 3890 +---------+ 4. Answer +---------+ 3. Answer +---------+ 3891 (Missing AVP) (Missing AVP) 3893 Figure 8: Example of Application Error Answer message 3895 Figure 8 provides an example of a Diameter message that caused an 3896 application error. When application errors occur, the Diameter 3897 entity reporting the error clears the 'R' bit in the Command Flags, 3898 and adds the Result-Code AVP with the proper value. Application 3899 errors do not require any proxy or relay agent involvement, and 3900 therefore the message would be forwarded back to the originator of 3901 the request. 3903 There are certain Result-Code AVP application errors that require 3904 additional AVPs to be present in the answer. In these cases, the 3905 Diameter node that sets the Result-Code AVP to indicate the error 3906 MUST add the AVPs. Examples are: 3908 o An unrecognized AVP is received with the 'M' bit (Mandatory bit) 3909 set, causes an answer to be sent with the Result-Code AVP set to 3910 DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the 3911 offending AVP. 3913 o An AVP that is received with an unrecognized value causes an 3914 answer to be returned with the Result-Code AVP set to 3915 DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the 3916 AVP causing the error. 3918 o A command is received with an AVP that is omitted, yet is 3919 mandatory according to the command's ABNF. The receiver issues an 3920 answer with the Result-Code set to DIAMETER_MISSING_AVP, and 3921 creates an AVP with the AVP Code and other fields set as expected 3922 in the missing AVP. The created AVP is then added to the Failed- 3923 AVP AVP. 3925 The Result-Code AVP describes the error that the Diameter node 3926 encountered in its processing. In case there are multiple errors, 3927 the Diameter node MUST report only the first error it encountered 3928 (detected possibly in some implementation dependent order). The 3929 specific errors that can be described by this AVP are described in 3930 the following section. 3932 7.1. Result-Code AVP 3934 The Result-Code AVP (AVP Code 268) is of type Unsigned32 and 3935 indicates whether a particular request was completed successfully or 3936 whether an error occurred. All Diameter answer messages defined in 3937 IETF applications MUST include one Result-Code AVP. A non-successful 3938 Result-Code AVP (one containing a non 2xxx value other than 3939 DIAMETER_REDIRECT_INDICATION) MUST include the Error-Reporting-Host 3940 AVP if the host setting the Result-Code AVP is different from the 3941 identity encoded in the Origin-Host AVP. 3943 The Result-Code data field contains an IANA-managed 32-bit address 3944 space representing errors (see Section 11.4). Diameter provides the 3945 following classes of errors, all identified by the thousands digit in 3946 the decimal notation: 3948 o 1xxx (Informational) 3950 o 2xxx (Success) 3952 o 3xxx (Protocol Errors) 3954 o 4xxx (Transient Failures) 3956 o 5xxx (Permanent Failure) 3958 A non-recognized class (one whose first digit is not defined in this 3959 section) MUST be handled as a permanent failure. 3961 7.1.1. Informational 3963 Errors that fall within this category are used to inform the 3964 requester that a request could not be satisfied, and additional 3965 action is required on its part before access is granted. 3967 DIAMETER_MULTI_ROUND_AUTH 1001 3969 This informational error is returned by a Diameter server to 3970 inform the access device that the authentication mechanism being 3971 used requires multiple round trips, and a subsequent request needs 3972 to be issued in order for access to be granted. 3974 7.1.2. Success 3976 Errors that fall within the Success category are used to inform a 3977 peer that a request has been successfully completed. 3979 DIAMETER_SUCCESS 2001 3981 The Request was successfully completed. 3983 DIAMETER_LIMITED_SUCCESS 2002 3985 When returned, the request was successfully completed, but 3986 additional processing is required by the application in order to 3987 provide service to the user. 3989 7.1.3. Protocol Errors 3991 Errors that fall within the Protocol Error category SHOULD be treated 3992 on a per-hop basis, and Diameter proxies MAY attempt to correct the 3993 error, if it is possible. Note that these errors MUST only be used 3994 in answer messages whose 'E' bit is set. To provide backward 3995 compatibility with existing implementations that follow [RFC3588], 3996 some of the error values that have previously been used in this 3997 category by [RFC3588] will not be re-used. Therefore the error 3998 values enumerated here may be non-sequential. 4000 DIAMETER_UNABLE_TO_DELIVER 3002 4002 This error is given when Diameter can not deliver the message to 4003 the destination, either because no host within the realm 4004 supporting the required application was available to process the 4005 request, or because Destination-Host AVP was given without the 4006 associated Destination-Realm AVP. 4008 DIAMETER_REALM_NOT_SERVED 3003 4010 The intended realm of the request is not recognized. 4012 DIAMETER_TOO_BUSY 3004 4014 When returned, a Diameter node SHOULD attempt to send the message 4015 to an alternate peer. This error MUST only be used when a 4016 specific server is requested, and it cannot provide the requested 4017 service. 4019 DIAMETER_LOOP_DETECTED 3005 4021 An agent detected a loop while trying to get the message to the 4022 intended recipient. The message MAY be sent to an alternate peer, 4023 if one is available, but the peer reporting the error has 4024 identified a configuration problem. 4026 DIAMETER_REDIRECT_INDICATION 3006 4028 A redirect agent has determined that the request could not be 4029 satisfied locally and the initiator of the request should direct 4030 the request directly to the server, whose contact information has 4031 been added to the response. When set, the Redirect-Host AVP MUST 4032 be present. 4034 DIAMETER_APPLICATION_UNSUPPORTED 3007 4036 A request was sent for an application that is not supported. 4038 DIAMETER_INVALID_BIT_IN_HEADER 3011 4040 This error is returned when a reserved bit in the Diameter header 4041 is set to one (1) or the bits in the Diameter header defined in 4042 Sec 3 are set incorrectly. 4044 DIAMETER_INVALID_MESSAGE_LENGTH 3012 4046 This error is returned when a request is received with an invalid 4047 message length. 4049 7.1.4. Transient Failures 4051 Errors that fall within the transient failures category are used to 4052 inform a peer that the request could not be satisfied at the time it 4053 was received, but MAY be able to satisfy the request in the future. 4054 Note that these errors MUST be used in answer messages whose 'E' bit 4055 is not set. 4057 DIAMETER_AUTHENTICATION_REJECTED 4001 4059 The authentication process for the user failed, most likely due to 4060 an invalid password used by the user. Further attempts MUST only 4061 be tried after prompting the user for a new password. 4063 DIAMETER_OUT_OF_SPACE 4002 4065 A Diameter node received the accounting request but was unable to 4066 commit it to stable storage due to a temporary lack of space. 4068 ELECTION_LOST 4003 4070 The peer has determined that it has lost the election process and 4071 has therefore disconnected the transport connection. 4073 7.1.5. Permanent Failures 4075 Errors that fall within the permanent failures category are used to 4076 inform the peer that the request failed, and should not be attempted 4077 again. Note that these errors SHOULD be used in answer messages 4078 whose 'E' bit is not set. In error conditions where it is not 4079 possible or efficient to compose application specific answer grammar 4080 then answer messages with E-bit set and complying to the grammar 4081 described in 7.2 MAY also be used for permanent errors. 4083 To provide backward compatibility with existing implementations that 4084 follow [RFC3588], some of the error values that have previously been 4085 used in this category by [RFC3588] will not be re-used. Therefore 4086 the error values enumerated here maybe non-sequential. 4088 DIAMETER_AVP_UNSUPPORTED 5001 4090 The peer received a message that contained an AVP that is not 4091 recognized or supported and was marked with the Mandatory bit. A 4092 Diameter message with this error MUST contain one or more Failed- 4093 AVP AVP containing the AVPs that caused the failure. 4095 DIAMETER_UNKNOWN_SESSION_ID 5002 4097 The request contained an unknown Session-Id. 4099 DIAMETER_AUTHORIZATION_REJECTED 5003 4101 A request was received for which the user could not be authorized. 4102 This error could occur if the service requested is not permitted 4103 to the user. 4105 DIAMETER_INVALID_AVP_VALUE 5004 4107 The request contained an AVP with an invalid value in its data 4108 portion. A Diameter message indicating this error MUST include 4109 the offending AVPs within a Failed-AVP AVP. 4111 DIAMETER_MISSING_AVP 5005 4113 The request did not contain an AVP that is required by the Command 4114 Code definition. If this value is sent in the Result-Code AVP, a 4115 Failed-AVP AVP SHOULD be included in the message. The Failed-AVP 4116 AVP MUST contain an example of the missing AVP complete with the 4117 Vendor-Id if applicable. The value field of the missing AVP 4118 should be of correct minimum length and contain zeroes. 4120 DIAMETER_RESOURCES_EXCEEDED 5006 4122 A request was received that cannot be authorized because the user 4123 has already expended allowed resources. An example of this error 4124 condition is a user that is restricted to one dial-up PPP port, 4125 attempts to establish a second PPP connection. 4127 DIAMETER_CONTRADICTING_AVPS 5007 4129 The Home Diameter server has detected AVPs in the request that 4130 contradicted each other, and is not willing to provide service to 4131 the user. The Failed-AVP AVPs MUST be present which contains the 4132 AVPs that contradicted each other. 4134 DIAMETER_AVP_NOT_ALLOWED 5008 4136 A message was received with an AVP that MUST NOT be present. The 4137 Failed-AVP AVP MUST be included and contain a copy of the 4138 offending AVP. 4140 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009 4142 A message was received that included an AVP that appeared more 4143 often than permitted in the message definition. The Failed-AVP 4144 AVP MUST be included and contain a copy of the first instance of 4145 the offending AVP that exceeded the maximum number of occurrences 4147 DIAMETER_NO_COMMON_APPLICATION 5010 4149 This error is returned by a Diameter node that is not acting as a 4150 relay when it receives a CER which advertises a set of 4151 applications that it does not support. 4153 DIAMETER_UNSUPPORTED_VERSION 5011 4155 This error is returned when a request was received, whose version 4156 number is unsupported. 4158 DIAMETER_UNABLE_TO_COMPLY 5012 4160 This error is returned when a request is rejected for unspecified 4161 reasons. 4163 DIAMETER_INVALID_AVP_LENGTH 5014 4165 The request contained an AVP with an invalid length. A Diameter 4166 message indicating this error MUST include the offending AVPs 4167 within a Failed-AVP AVP. In cases where the erroneous avp length 4168 value exceeds the message length or is less than the minimum AVP 4169 header length, it is sufficient to include the offending AVP 4170 header and a zero filled payload of the minimum required length 4171 for the payloads data type. If the AVP is a grouped AVP, the 4172 grouped AVP header with an empty payload would be sufficient to 4173 indicate the offending AVP. In the case where the offending AVP 4174 header cannot be fully decoded when avp length is less than the 4175 minimum AVP header length, it is sufficient to include an 4176 offending AVP header that is formulated by padding the incomplete 4177 AVP header with zero up to the minimum AVP header length. 4179 DIAMETER_NO_COMMON_SECURITY 5017 4181 This error is returned when a CER message is received, and there 4182 are no common security mechanisms supported between the peers. A 4183 Capabilities-Exchange-Answer (CEA) MUST be returned with the 4184 Result-Code AVP set to DIAMETER_NO_COMMON_SECURITY. 4186 DIAMETER_UNKNOWN_PEER 5018 4188 A CER was received from an unknown peer. 4190 DIAMETER_COMMAND_UNSUPPORTED 5019 4192 The Request contained a Command-Code that the receiver did not 4193 recognize or support. This MUST be used when a Diameter node 4194 receives an experimental command that it does not understand. 4196 DIAMETER_INVALID_HDR_BITS 5020 4198 A request was received whose bits in the Diameter header were 4199 either set to an invalid combination, or to a value that is 4200 inconsistent with the command code's definition. 4202 DIAMETER_INVALID_AVP_BITS 5021 4204 A request was received that included an AVP whose flag bits are 4205 set to an unrecognized value, or that is inconsistent with the 4206 AVP's definition. 4208 7.2. Error Bit 4210 The 'E' (Error Bit) in the Diameter header is set when the request 4211 caused a protocol-related error (see Section 7.1.3). A message with 4212 the 'E' bit MUST NOT be sent as a response to an answer message. 4213 Note that a message with the 'E' bit set is still subjected to the 4214 processing rules defined in Section 6.2. When set, the answer 4215 message will not conform to the ABNF specification for the command, 4216 and will instead conform to the following ABNF: 4218 Message Format 4220 ::= < Diameter Header: code, ERR [PXY] > 4221 0*1< Session-Id > 4222 { Origin-Host } 4223 { Origin-Realm } 4224 { Result-Code } 4225 [ Origin-State-Id ] 4226 [ Error-Message ] 4227 [ Error-Reporting-Host ] 4228 [ Failed-AVP ] 4229 * [ Proxy-Info ] 4230 * [ AVP ] 4232 Note that the code used in the header is the same than the one found 4233 in the request message, but with the 'R' bit cleared and the 'E' bit 4234 set. The 'P' bit in the header is set to the same value as the one 4235 found in the request message. 4237 7.3. Error-Message AVP 4239 The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY 4240 accompany a Result-Code AVP as a human readable error message. The 4241 Error-Message AVP is not intended to be useful in real-time, and 4242 SHOULD NOT be expected to be parsed by network entities. 4244 7.4. Error-Reporting-Host AVP 4246 The Error-Reporting-Host AVP (AVP Code 294) is of type 4247 DiameterIdentity. This AVP contains the identity of the Diameter 4248 host that sent the Result-Code AVP to a value other than 2001 4249 (Success), only if the host setting the Result-Code is different from 4250 the one encoded in the Origin-Host AVP. This AVP is intended to be 4251 used for troubleshooting purposes, and MUST be set when the Result- 4252 Code AVP indicates a failure. 4254 7.5. Failed-AVP AVP 4256 The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides 4257 debugging information in cases where a request is rejected or not 4258 fully processed due to erroneous information in a specific AVP. The 4259 value of the Result-Code AVP will provide information on the reason 4260 for the Failed-AVP AVP. A Diameter message SHOULD contain only one 4261 Failed-AVP that corresponds to the error indicated by the Result-Code 4262 AVP. For practical purposes, this Failed-AVP would typically refer 4263 to the first AVP processing error that a Diameter node encounters. 4265 The possible reasons for this AVP are the presence of an improperly 4266 constructed AVP, an unsupported or unrecognized AVP, an invalid AVP 4267 value, the omission of a required AVP, the presence of an explicitly 4268 excluded AVP (see tables in Section 10), or the presence of two or 4269 more occurrences of an AVP which is restricted to 0, 1, or 0-1 4270 occurrences. 4272 A Diameter message SHOULD contain one Failed-AVP AVP, containing the 4273 entire AVP that could not be processed successfully. If the failure 4274 reason is omission of a required AVP, an AVP with the missing AVP 4275 code, the missing vendor id, and a zero filled payload of the minimum 4276 required length for the omitted AVP will be added. If the failure 4277 reason is an invalid AVP length where the reported length is less 4278 than the minimum AVP header length or greater than the reported 4279 message length, a copy of the offending AVP header and a zero filled 4280 payload of the minimum required length SHOULD be added. 4282 In the case where the offending AVP is embedded within a grouped AVP, 4283 the Failed-AVP MAY contain the grouped AVP which in turn contains the 4284 single offending AVP. The same method MAY be employed if the grouped 4285 AVP itself is embedded in yet another grouped AVP and so on. In this 4286 case, the Failed-AVP MAY contain the grouped AVP heirarchy up to the 4287 single offending AVP. This enables the recipient to detect the 4288 location of the offending AVP when embedded in a group. 4290 AVP Format 4292 ::= < AVP Header: 279 > 4293 1* {AVP} 4295 7.6. Experimental-Result AVP 4297 The Experimental-Result AVP (AVP Code 297) is of type Grouped, and 4298 indicates whether a particular vendor-specific request was completed 4299 successfully or whether an error occurred. Its Data field has the 4300 following ABNF grammar: 4302 AVP Format 4304 Experimental-Result ::= < AVP Header: 297 > 4305 { Vendor-Id } 4306 { Experimental-Result-Code } 4308 The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies 4309 the vendor responsible for the assignment of the result code which 4310 follows. All Diameter answer messages defined in vendor-specific 4311 applications MUST include either one Result-Code AVP or one 4312 Experimental-Result AVP. 4314 7.7. Experimental-Result-Code AVP 4316 The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32 4317 and contains a vendor-assigned value representing the result of 4318 processing the request. 4320 It is recommended that vendor-specific result codes follow the same 4321 conventions given for the Result-Code AVP regarding the different 4322 types of result codes and the handling of errors (for non 2xxx 4323 values). 4325 8. Diameter User Sessions 4327 In general, Diameter can provide two different types of services to 4328 applications. The first involves authentication and authorization, 4329 and can optionally make use of accounting. The second only makes use 4330 of accounting. 4332 When a service makes use of the authentication and/or authorization 4333 portion of an application, and a user requests access to the network, 4334 the Diameter client issues an auth request to its local server. The 4335 auth request is defined in a service specific Diameter application 4336 (e.g., NASREQ). The request contains a Session-Id AVP, which is used 4337 in subsequent messages (e.g., subsequent authorization, accounting, 4338 etc) relating to the user's session. The Session-Id AVP is a means 4339 for the client and servers to correlate a Diameter message with a 4340 user session. 4342 When a Diameter server authorizes a user to use network resources for 4343 a finite amount of time, and it is willing to extend the 4344 authorization via a future request, it MUST add the Authorization- 4345 Lifetime AVP to the answer message. The Authorization-Lifetime AVP 4346 defines the maximum number of seconds a user MAY make use of the 4347 resources before another authorization request is expected by the 4348 server. The Auth-Grace-Period AVP contains the number of seconds 4349 following the expiration of the Authorization-Lifetime, after which 4350 the server will release all state information related to the user's 4351 session. Note that if payment for services is expected by the 4352 serving realm from the user's home realm, the Authorization-Lifetime 4353 AVP, combined with the Auth-Grace-Period AVP, implies the maximum 4354 length of the session the home realm is willing to be fiscally 4355 responsible for. Services provided past the expiration of the 4356 Authorization-Lifetime and Auth-Grace-Period AVPs are the 4357 responsibility of the access device. Of course, the actual cost of 4358 services rendered is clearly outside the scope of the protocol. 4360 An access device that does not expect to send a re-authorization or a 4361 session termination request to the server MAY include the Auth- 4362 Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint 4363 to the server. If the server accepts the hint, it agrees that since 4364 no session termination message will be received once service to the 4365 user is terminated, it cannot maintain state for the session. If the 4366 answer message from the server contains a different value in the 4367 Auth-Session-State AVP (or the default value if the AVP is absent), 4368 the access device MUST follow the server's directives. Note that the 4369 value NO_STATE_MAINTAINED MUST NOT be set in subsequent re- 4370 authorization requests and answers. 4372 The base protocol does not include any authorization request 4373 messages, since these are largely application-specific and are 4374 defined in a Diameter application document. However, the base 4375 protocol does define a set of messages that is used to terminate user 4376 sessions. These are used to allow servers that maintain state 4377 information to free resources. 4379 When a service only makes use of the Accounting portion of the 4380 Diameter protocol, even in combination with an application, the 4381 Session-Id is still used to identify user sessions. However, the 4382 session termination messages are not used, since a session is 4383 signaled as being terminated by issuing an accounting stop message. 4385 Diameter may also be used for services that cannot be easily 4386 categorized as authentication, authorization or accounting (e.g., 4387 certain 3GPP IMS interfaces). In such cases, the finite state 4388 machine defined in subsequent sections may not be applicable. 4389 Therefore, the applications itself MAY need to define its own finite 4390 state machine. However, such application specific state machines 4391 MUST comply with general Diameter user session requirements such co- 4392 relating all message exchanges via Session-Id AVP. 4394 8.1. Authorization Session State Machine 4396 This section contains a set of finite state machines, representing 4397 the life cycle of Diameter sessions, and which MUST be observed by 4398 all Diameter implementations that make use of the authentication 4399 and/or authorization portion of a Diameter application. The term 4400 Service-Specific below refers to a message defined in a Diameter 4401 application (e.g., Mobile IPv4, NASREQ). 4403 There are four different authorization session state machines 4404 supported in the Diameter base protocol. The first two describe a 4405 session in which the server is maintaining session state, indicated 4406 by the value of the Auth-Session-State AVP (or its absence). One 4407 describes the session from a client perspective, the other from a 4408 server perspective. The second two state machines are used when the 4409 server does not maintain session state. Here again, one describes 4410 the session from a client perspective, the other from a server 4411 perspective. 4413 When a session is moved to the Idle state, any resources that were 4414 allocated for the particular session must be released. Any event not 4415 listed in the state machines MUST be considered as an error 4416 condition, and an answer, if applicable, MUST be returned to the 4417 originator of the message. 4419 In the case that an application does not support re-auth, the state 4420 transitions related to server-initiated re-auth when both client and 4421 server sessions maintains state (e.g., Send RAR, Pending, Receive 4422 RAA) MAY be ignored. 4424 In the state table, the event 'Failure to send X' means that the 4425 Diameter agent is unable to send command X to the desired 4426 destination. This could be due to the peer being down, or due to the 4427 peer sending back a transient failure or temporary protocol error 4428 notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the 4429 Result-Code AVP of the corresponding Answer command. The event 'X 4430 successfully sent' is the complement of 'Failure to send X'. 4432 The following state machine is observed by a client when state is 4433 maintained on the server: 4435 CLIENT, STATEFUL 4436 State Event Action New State 4437 ------------------------------------------------------------- 4438 Idle Client or Device Requests Send Pending 4439 access service 4440 specific 4441 auth req 4443 Idle ASR Received Send ASA Idle 4444 for unknown session with 4445 Result-Code 4446 = UNKNOWN_ 4447 SESSION_ID 4449 Idle RAR Received Send RAA Idle 4450 for unknown session with 4451 Result-Code 4452 = UNKNOWN_ 4453 SESSION_ID 4455 Pending Successful Service-specific Grant Open 4456 authorization answer Access 4457 received with default 4458 Auth-Session-State value 4460 Pending Successful Service-specific Sent STR Discon 4461 authorization answer received 4462 but service not provided 4464 Pending Error processing successful Sent STR Discon 4465 Service-specific authorization 4466 answer 4468 Pending Failed Service-specific Cleanup Idle 4469 authorization answer received 4471 Open User or client device Send Open 4472 requests access to service service 4473 specific 4474 auth req 4476 Open Successful Service-specific Provide Open 4477 authorization answer received Service 4479 Open Failed Service-specific Discon. Idle 4480 authorization answer user/device 4481 received. 4483 Open RAR received and client will Send RAA Open 4484 perform subsequent re-auth with 4485 Result-Code 4486 = SUCCESS 4488 Open RAR received and client will Send RAA Idle 4489 not perform subsequent with 4490 re-auth Result-Code 4491 != SUCCESS, 4492 Discon. 4493 user/device 4495 Open Session-Timeout Expires on Send STR Discon 4496 Access Device 4498 Open ASR Received, Send ASA Discon 4499 client will comply with with 4500 request to end the session Result-Code 4501 = SUCCESS, 4502 Send STR. 4504 Open ASR Received, Send ASA Open 4505 client will not comply with with 4506 request to end the session Result-Code 4507 != SUCCESS 4509 Open Authorization-Lifetime + Send STR Discon 4510 Auth-Grace-Period expires on 4511 access device 4513 Discon ASR Received Send ASA Discon 4515 Discon STA Received Discon. Idle 4516 user/device 4518 The following state machine is observed by a server when it is 4519 maintaining state for the session: 4521 SERVER, STATEFUL 4522 State Event Action New State 4523 ------------------------------------------------------------- 4524 Idle Service-specific authorization Send Open 4525 request received, and successful 4526 user is authorized serv. 4527 specific 4528 answer 4530 Idle Service-specific authorization Send Idle 4531 request received, and failed serv. 4532 user is not authorized specific 4533 answer 4535 Open Service-specific authorization Send Open 4536 request received, and user successful 4537 is authorized serv. specific 4538 answer 4540 Open Service-specific authorization Send Idle 4541 request received, and user failed serv. 4542 is not authorized specific 4543 answer, 4544 Cleanup 4546 Open Home server wants to confirm Send RAR Pending 4547 authentication and/or 4548 authorization of the user 4550 Pending Received RAA with a failed Cleanup Idle 4551 Result-Code 4553 Pending Received RAA with Result-Code Update Open 4554 = SUCCESS session 4556 Open Home server wants to Send ASR Discon 4557 terminate the service 4559 Open Authorization-Lifetime (and Cleanup Idle 4560 Auth-Grace-Period) expires 4561 on home server. 4563 Open Session-Timeout expires on Cleanup Idle 4564 home server 4566 Discon Failure to send ASR Wait, Discon 4567 resend ASR 4569 Discon ASR successfully sent and Cleanup Idle 4570 ASA Received with Result-Code 4572 Not ASA Received None No Change. 4573 Discon 4575 Any STR Received Send STA, Idle 4576 Cleanup. 4578 The following state machine is observed by a client when state is not 4579 maintained on the server: 4581 CLIENT, STATELESS 4582 State Event Action New State 4583 ------------------------------------------------------------- 4584 Idle Client or Device Requests Send Pending 4585 access service 4586 specific 4587 auth req 4589 Pending Successful Service-specific Grant Open 4590 authorization answer Access 4591 received with Auth-Session- 4592 State set to 4593 NO_STATE_MAINTAINED 4595 Pending Failed Service-specific Cleanup Idle 4596 authorization answer 4597 received 4599 Open Session-Timeout Expires on Discon. Idle 4600 Access Device user/device 4602 Open Service to user is terminated Discon. Idle 4603 user/device 4605 The following state machine is observed by a server when it is not 4606 maintaining state for the session: 4608 SERVER, STATELESS 4609 State Event Action New State 4610 ------------------------------------------------------------- 4611 Idle Service-specific authorization Send serv. Idle 4612 request received, and specific 4613 successfully processed answer 4615 8.2. Accounting Session State Machine 4617 The following state machines MUST be supported for applications that 4618 have an accounting portion or that require only accounting services. 4619 The first state machine is to be observed by clients. 4621 See Section 9.7 for Accounting Command Codes and Section 9.8 for 4622 Accounting AVPs. 4624 The server side in the accounting state machine depends in some cases 4625 on the particular application. The Diameter base protocol defines a 4626 default state machine that MUST be followed by all applications that 4627 have not specified other state machines. This is the second state 4628 machine in this section described below. 4630 The default server side state machine requires the reception of 4631 accounting records in any order and at any time, and does not place 4632 any standards requirement on the processing of these records. 4633 Implementations of Diameter MAY perform checking, ordering, 4634 correlation, fraud detection, and other tasks based on these records. 4635 Both base Diameter AVPs as well as application specific AVPs MAY be 4636 inspected as a part of these tasks. The tasks can happen either 4637 immediately after record reception or in a post-processing phase. 4638 However, as these tasks are typically application or even policy 4639 dependent, they are not standardized by the Diameter specifications. 4640 Applications MAY define requirements on when to accept accounting 4641 records based on the used value of Accounting-Realtime-Required AVP, 4642 credit limits checks, and so on. 4644 However, the Diameter base protocol defines one optional server side 4645 state machine that MAY be followed by applications that require 4646 keeping track of the session state at the accounting server. Note 4647 that such tracking is incompatible with the ability to sustain long 4648 duration connectivity problems. Therefore, the use of this state 4649 machine is recommended only in applications where the value of the 4650 Accounting-Realtime-Required AVP is DELIVER_AND_GRANT, and hence 4651 accounting connectivity problems are required to cause the serviced 4652 user to be disconnected. Otherwise, records produced by the client 4653 may be lost by the server which no longer accepts them after the 4654 connectivity is re-established. This state machine is the third 4655 state machine in this section. The state machine is supervised by a 4656 supervision session timer Ts, which the value should be reasonably 4657 higher than the Acct_Interim_Interval value. Ts MAY be set to two 4658 times the value of the Acct_Interim_Interval so as to avoid the 4659 accounting session in the Diameter server to change to Idle state in 4660 case of short transient network failure. 4662 Any event not listed in the state machines MUST be considered as an 4663 error condition, and a corresponding answer, if applicable, MUST be 4664 returned to the originator of the message. 4666 In the state table, the event 'Failure to send' means that the 4667 Diameter client is unable to communicate with the desired 4668 destination. This could be due to the peer being down, or due to the 4669 peer sending back a transient failure or temporary protocol error 4670 notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or 4671 DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting 4672 Answer command. 4674 The event 'Failed answer' means that the Diameter client received a 4675 non-transient failure notification in the Accounting Answer command. 4677 Note that the action 'Disconnect user/dev' MUST have an effect also 4678 to the authorization session state table, e.g., cause the STR message 4679 to be sent, if the given application has both authentication/ 4680 authorization and accounting portions. 4682 The states PendingS, PendingI, PendingL, PendingE and PendingB stand 4683 for pending states to wait for an answer to an accounting request 4684 related to a Start, Interim, Stop, Event or buffered record, 4685 respectively. 4687 CLIENT, ACCOUNTING 4688 State Event Action New State 4689 ------------------------------------------------------------- 4690 Idle Client or device requests Send PendingS 4691 access accounting 4692 start req. 4694 Idle Client or device requests Send PendingE 4695 a one-time service accounting 4696 event req 4698 Idle Records in storage Send PendingB 4699 record 4701 PendingS Successful accounting Open 4702 start answer received 4704 PendingS Failure to send and buffer Store Open 4705 space available and realtime Start 4706 not equal to DELIVER_AND_GRANT Record 4708 PendingS Failure to send and no buffer Open 4709 space available and realtime 4710 equal to GRANT_AND_LOSE 4712 PendingS Failure to send and no buffer Disconnect Idle 4713 space available and realtime user/dev 4714 not equal to 4715 GRANT_AND_LOSE 4717 PendingS Failed accounting start answer Open 4718 received and realtime equal 4719 to GRANT_AND_LOSE 4721 PendingS Failed accounting start answer Disconnect Idle 4722 received and realtime not user/dev 4723 equal to GRANT_AND_LOSE 4725 PendingS User service terminated Store PendingS 4726 stop 4727 record 4729 Open Interim interval elapses Send PendingI 4730 accounting 4731 interim 4732 record 4733 Open User service terminated Send PendingL 4734 accounting 4735 stop req. 4737 PendingI Successful accounting interim Open 4738 answer received 4740 PendingI Failure to send and (buffer Store Open 4741 space available or old record interim 4742 can be overwritten) and record 4743 realtime not equal to 4744 DELIVER_AND_GRANT 4746 PendingI Failure to send and no buffer Open 4747 space available and realtime 4748 equal to GRANT_AND_LOSE 4750 PendingI Failure to send and no buffer Disconnect Idle 4751 space available and realtime user/dev 4752 not equal to GRANT_AND_LOSE 4754 PendingI Failed accounting interim Open 4755 answer received and realtime 4756 equal to GRANT_AND_LOSE 4758 PendingI Failed accounting interim Disconnect Idle 4759 answer received and realtime user/dev 4760 not equal to GRANT_AND_LOSE 4762 PendingI User service terminated Store PendingI 4763 stop 4764 record 4765 PendingE Successful accounting Idle 4766 event answer received 4768 PendingE Failure to send and buffer Store Idle 4769 space available event 4770 record 4772 PendingE Failure to send and no buffer Idle 4773 space available 4775 PendingE Failed accounting event answer Idle 4776 received 4778 PendingB Successful accounting answer Delete Idle 4779 received record 4781 PendingB Failure to send Idle 4783 PendingB Failed accounting answer Delete Idle 4784 received record 4786 PendingL Successful accounting Idle 4787 stop answer received 4789 PendingL Failure to send and buffer Store Idle 4790 space available stop 4791 record 4793 PendingL Failure to send and no buffer Idle 4794 space available 4796 PendingL Failed accounting stop answer Idle 4797 received 4799 SERVER, STATELESS ACCOUNTING 4800 State Event Action New State 4801 ------------------------------------------------------------- 4803 Idle Accounting start request Send Idle 4804 received, and successfully accounting 4805 processed. start 4806 answer 4808 Idle Accounting event request Send Idle 4809 received, and successfully accounting 4810 processed. event 4811 answer 4813 Idle Interim record received, Send Idle 4814 and successfully processed. accounting 4815 interim 4816 answer 4818 Idle Accounting stop request Send Idle 4819 received, and successfully accounting 4820 processed stop answer 4822 Idle Accounting request received, Send Idle 4823 no space left to store accounting 4824 records answer, 4825 Result-Code 4826 = OUT_OF_ 4827 SPACE 4829 SERVER, STATEFUL ACCOUNTING 4830 State Event Action New State 4831 ------------------------------------------------------------- 4833 Idle Accounting start request Send Open 4834 received, and successfully accounting 4835 processed. start 4836 answer, 4837 Start Ts 4839 Idle Accounting event request Send Idle 4840 received, and successfully accounting 4841 processed. event 4842 answer 4844 Idle Accounting request received, Send Idle 4845 no space left to store accounting 4846 records answer, 4847 Result-Code 4848 = OUT_OF_ 4849 SPACE 4851 Open Interim record received, Send Open 4852 and successfully processed. accounting 4853 interim 4854 answer, 4855 Restart Ts 4857 Open Accounting stop request Send Idle 4858 received, and successfully accounting 4859 processed stop answer, 4860 Stop Ts 4862 Open Accounting request received, Send Idle 4863 no space left to store accounting 4864 records answer, 4865 Result-Code 4866 = OUT_OF_ 4867 SPACE, 4868 Stop Ts 4870 Open Session supervision timer Ts Stop Ts Idle 4871 expired 4873 8.3. Server-Initiated Re-Auth 4875 A Diameter server may initiate a re-authentication and/or re- 4876 authorization service for a particular session by issuing a Re-Auth- 4877 Request (RAR). 4879 For example, for pre-paid services, the Diameter server that 4880 originally authorized a session may need some confirmation that the 4881 user is still using the services. 4883 An access device that receives a RAR message with Session-Id equal to 4884 a currently active session MUST initiate a re-auth towards the user, 4885 if the service supports this particular feature. Each Diameter 4886 application MUST state whether service-initiated re-auth is 4887 supported, since some applications do not allow access devices to 4888 prompt the user for re-auth. 4890 8.3.1. Re-Auth-Request 4892 The Re-Auth-Request (RAR), indicated by the Command-Code set to 258 4893 and the message flags' 'R' bit set, may be sent by any server to the 4894 access device that is providing session service, to request that the 4895 user be re-authenticated and/or re-authorized. 4897 Message Format 4899 ::= < Diameter Header: 258, REQ, PXY > 4900 < Session-Id > 4901 { Origin-Host } 4902 { Origin-Realm } 4903 { Destination-Realm } 4904 { Destination-Host } 4905 { Auth-Application-Id } 4906 { Re-Auth-Request-Type } 4907 [ User-Name ] 4908 [ Origin-State-Id ] 4909 * [ Proxy-Info ] 4910 * [ Route-Record ] 4911 * [ AVP ] 4913 8.3.2. Re-Auth-Answer 4915 The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258 4916 and the message flags' 'R' bit clear, is sent in response to the RAR. 4917 The Result-Code AVP MUST be present, and indicates the disposition of 4918 the request. 4920 A successful RAA message MUST be followed by an application-specific 4921 authentication and/or authorization message. 4923 Message Format 4925 ::= < Diameter Header: 258, PXY > 4926 < Session-Id > 4927 { Result-Code } 4928 { Origin-Host } 4929 { Origin-Realm } 4930 [ User-Name ] 4931 [ Origin-State-Id ] 4932 [ Error-Message ] 4933 [ Error-Reporting-Host ] 4934 [ Failed-AVP ] 4935 * [ Redirect-Host ] 4936 [ Redirect-Host-Usage ] 4937 [ Redirect-Max-Cache-Time ] 4938 * [ Proxy-Info ] 4939 * [ AVP ] 4941 8.4. Session Termination 4943 It is necessary for a Diameter server that authorized a session, for 4944 which it is maintaining state, to be notified when that session is no 4945 longer active, both for tracking purposes as well as to allow 4946 stateful agents to release any resources that they may have provided 4947 for the user's session. For sessions whose state is not being 4948 maintained, this section is not used. 4950 When a user session that required Diameter authorization terminates, 4951 the access device that provided the service MUST issue a Session- 4952 Termination-Request (STR) message to the Diameter server that 4953 authorized the service, to notify it that the session is no longer 4954 active. An STR MUST be issued when a user session terminates for any 4955 reason, including user logoff, expiration of Session-Timeout, 4956 administrative action, termination upon receipt of an Abort-Session- 4957 Request (see below), orderly shutdown of the access device, etc. 4959 The access device also MUST issue an STR for a session that was 4960 authorized but never actually started. This could occur, for 4961 example, due to a sudden resource shortage in the access device, or 4962 because the access device is unwilling to provide the type of service 4963 requested in the authorization, or because the access device does not 4964 support a mandatory AVP returned in the authorization, etc. 4966 It is also possible that a session that was authorized is never 4967 actually started due to action of a proxy. For example, a proxy may 4968 modify an authorization answer, converting the result from success to 4969 failure, prior to forwarding the message to the access device. If 4970 the answer did not contain an Auth-Session-State AVP with the value 4971 NO_STATE_MAINTAINED, a proxy that causes an authorized session not to 4972 be started MUST issue an STR to the Diameter server that authorized 4973 the session, since the access device has no way of knowing that the 4974 session had been authorized. 4976 A Diameter server that receives an STR message MUST clean up 4977 resources (e.g., session state) associated with the Session-Id 4978 specified in the STR, and return a Session-Termination-Answer. 4980 A Diameter server also MUST clean up resources when the Session- 4981 Timeout expires, or when the Authorization-Lifetime and the Auth- 4982 Grace-Period AVPs expires without receipt of a re-authorization 4983 request, regardless of whether an STR for that session is received. 4984 The access device is not expected to provide service beyond the 4985 expiration of these timers; thus, expiration of either of these 4986 timers implies that the access device may have unexpectedly shut 4987 down. 4989 8.4.1. Session-Termination-Request 4991 The Session-Termination-Request (STR), indicated by the Command-Code 4992 set to 275 and the Command Flags' 'R' bit set, is sent by the access 4993 device to inform the Diameter Server that an authenticated and/or 4994 authorized session is being terminated. 4996 Message Format 4998 ::= < Diameter Header: 275, REQ, PXY > 4999 < Session-Id > 5000 { Origin-Host } 5001 { Origin-Realm } 5002 { Destination-Realm } 5003 { Auth-Application-Id } 5004 { Termination-Cause } 5005 [ User-Name ] 5006 [ Destination-Host ] 5007 * [ Class ] 5008 [ Origin-State-Id ] 5009 * [ Proxy-Info ] 5010 * [ Route-Record ] 5011 * [ AVP ] 5013 8.4.2. Session-Termination-Answer 5015 The Session-Termination-Answer (STA), indicated by the Command-Code 5016 set to 275 and the message flags' 'R' bit clear, is sent by the 5017 Diameter Server to acknowledge the notification that the session has 5018 been terminated. The Result-Code AVP MUST be present, and MAY 5019 contain an indication that an error occurred while servicing the STR. 5021 Upon sending or receipt of the STA, the Diameter Server MUST release 5022 all resources for the session indicated by the Session-Id AVP. Any 5023 intermediate server in the Proxy-Chain MAY also release any 5024 resources, if necessary. 5026 Message Format 5028 ::= < Diameter Header: 275, PXY > 5029 < Session-Id > 5030 { Result-Code } 5031 { Origin-Host } 5032 { Origin-Realm } 5033 [ User-Name ] 5034 * [ Class ] 5035 [ Error-Message ] 5036 [ Error-Reporting-Host ] 5037 [ Failed-AVP ] 5038 [ Origin-State-Id ] 5039 * [ Redirect-Host ] 5040 [ Redirect-Host-Usage ] 5041 [ Redirect-Max-Cache-Time ] 5042 * [ Proxy-Info ] 5043 * [ AVP ] 5045 8.5. Aborting a Session 5047 A Diameter server may request that the access device stop providing 5048 service for a particular session by issuing an Abort-Session-Request 5049 (ASR). 5051 For example, the Diameter server that originally authorized the 5052 session may be required to cause that session to be stopped for 5053 credit or other reasons that were not anticipated when the session 5054 was first authorized. On the other hand, an operator may maintain a 5055 management server for the purpose of issuing ASRs to administratively 5056 remove users from the network. 5058 An access device that receives an ASR with Session-ID equal to a 5059 currently active session MAY stop the session. Whether the access 5060 device stops the session or not is implementation- and/or 5061 configuration-dependent. For example, an access device may honor 5062 ASRs from certain agents only. In any case, the access device MUST 5063 respond with an Abort-Session-Answer, including a Result-Code AVP to 5064 indicate what action it took. 5066 Note that if the access device does stop the session upon receipt of 5067 an ASR, it issues an STR to the authorizing server (which may or may 5068 not be the agent issuing the ASR) just as it would if the session 5069 were terminated for any other reason. 5071 8.5.1. Abort-Session-Request 5073 The Abort-Session-Request (ASR), indicated by the Command-Code set to 5074 274 and the message flags' 'R' bit set, may be sent by any server to 5075 the access device that is providing session service, to request that 5076 the session identified by the Session-Id be stopped. 5078 Message Format 5080 ::= < Diameter Header: 274, REQ, PXY > 5081 < Session-Id > 5082 { Origin-Host } 5083 { Origin-Realm } 5084 { Destination-Realm } 5085 { Destination-Host } 5086 { Auth-Application-Id } 5087 [ User-Name ] 5088 [ Origin-State-Id ] 5089 * [ Proxy-Info ] 5090 * [ Route-Record ] 5091 * [ AVP ] 5093 8.5.2. Abort-Session-Answer 5095 The Abort-Session-Answer (ASA), indicated by the Command-Code set to 5096 274 and the message flags' 'R' bit clear, is sent in response to the 5097 ASR. The Result-Code AVP MUST be present, and indicates the 5098 disposition of the request. 5100 If the session identified by Session-Id in the ASR was successfully 5101 terminated, Result-Code is set to DIAMETER_SUCCESS. If the session 5102 is not currently active, Result-Code is set to 5103 DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the 5104 session for any other reason, Result-Code is set to 5105 DIAMETER_UNABLE_TO_COMPLY. 5107 Message Format 5109 ::= < Diameter Header: 274, PXY > 5110 < Session-Id > 5111 { Result-Code } 5112 { Origin-Host } 5113 { Origin-Realm } 5114 [ User-Name ] 5115 [ Origin-State-Id ] 5116 [ Error-Message ] 5117 [ Error-Reporting-Host ] 5118 [ Failed-AVP ] 5119 * [ Redirect-Host ] 5120 [ Redirect-Host-Usage ] 5121 [ Redirect-Max-Cache-Time ] 5122 * [ Proxy-Info ] 5123 * [ AVP ] 5125 8.6. Inferring Session Termination from Origin-State-Id 5127 Origin-State-Id is used to allow rapid detection of terminated 5128 sessions for which no STR would have been issued, due to 5129 unanticipated shutdown of an access device. 5131 By including Origin-State-Id in CER/CEA messages, an access device 5132 allows a next-hop server to determine immediately upon connection 5133 whether the device has lost its sessions since the last connection. 5135 By including Origin-State-Id in request messages, an access device 5136 also allows a server with which it communicates via proxy to make 5137 such a determination. However, a server that is not directly 5138 connected with the access device will not discover that the access 5139 device has been restarted unless and until it receives a new request 5140 from the access device. Thus, use of this mechanism across proxies 5141 is opportunistic rather than reliable, but useful nonetheless. 5143 When a Diameter server receives an Origin-State-Id that is greater 5144 than the Origin-State-Id previously received from the same issuer, it 5145 may assume that the issuer has lost state since the previous message 5146 and that all sessions that were active under the lower Origin-State- 5147 Id have been terminated. The Diameter server MAY clean up all 5148 session state associated with such lost sessions, and MAY also issues 5149 STRs for all such lost sessions that were authorized on upstream 5150 servers, to allow session state to be cleaned up globally. 5152 8.7. Auth-Request-Type AVP 5154 The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is 5155 included in application-specific auth requests to inform the peers 5156 whether a user is to be authenticated only, authorized only or both. 5157 Note any value other than both MAY cause RADIUS interoperability 5158 issues. The following values are defined: 5160 AUTHENTICATE_ONLY 1 5162 The request being sent is for authentication only, and MUST 5163 contain the relevant application specific authentication AVPs that 5164 are needed by the Diameter server to authenticate the user. 5166 AUTHORIZE_ONLY 2 5168 The request being sent is for authorization only, and MUST contain 5169 the application specific authorization AVPs that are necessary to 5170 identify the service being requested/offered. 5172 AUTHORIZE_AUTHENTICATE 3 5174 The request contains a request for both authentication and 5175 authorization. The request MUST include both the relevant 5176 application specific authentication information, and authorization 5177 information necessary to identify the service being requested/ 5178 offered. 5180 8.8. Session-Id AVP 5182 The Session-Id AVP (AVP Code 263) is of type UTF8String and is used 5183 to identify a specific session (see Section 8). All messages 5184 pertaining to a specific session MUST include only one Session-Id AVP 5185 and the same value MUST be used throughout the life of a session. 5186 When present, the Session-Id SHOULD appear immediately following the 5187 Diameter Header (see Section 3). 5189 The Session-Id MUST be globally and eternally unique, as it is meant 5190 to uniquely identify a user session without reference to any other 5191 information, and may be needed to correlate historical authentication 5192 information with accounting information. The Session-Id includes a 5193 mandatory portion and an implementation-defined portion; a 5194 recommended format for the implementation-defined portion is outlined 5195 below. 5197 The Session-Id MUST begin with the sender's identity encoded in the 5198 DiameterIdentity type (see Section 4.4). The remainder of the 5199 Session-Id is delimited by a ";" character, and MAY be any sequence 5200 that the client can guarantee to be eternally unique; however, the 5201 following format is recommended, (square brackets [] indicate an 5202 optional element): 5204 ;;[;] 5206 and are decimal representations of the 5207 high and low 32 bits of a monotonically increasing 64-bit value. The 5208 64-bit value is rendered in two part to simplify formatting by 32-bit 5209 processors. At startup, the high 32 bits of the 64-bit value MAY be 5210 initialized to the time in NTP format [RFC4330], and the low 32 bits 5211 MAY be initialized to zero. This will for practical purposes 5212 eliminate the possibility of overlapping Session-Ids after a reboot, 5213 assuming the reboot process takes longer than a second. 5214 Alternatively, an implementation MAY keep track of the increasing 5215 value in non-volatile memory. 5217 is implementation specific but may include a modem's 5218 device Id, a layer 2 address, timestamp, etc. 5220 Example, in which there is no optional value: 5222 accesspoint7.acme.com;1876543210;523 5224 Example, in which there is an optional value: 5226 accesspoint7.acme.com;1876543210;523;mobile@200.1.1.88 5228 The Session-Id is created by the Diameter application initiating the 5229 session, which in most cases is done by the client. Note that a 5230 Session-Id MAY be used for both the authorization and accounting 5231 commands of a given application. 5233 8.9. Authorization-Lifetime AVP 5235 The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32 5236 and contains the maximum number of seconds of service to be provided 5237 to the user before the user is to be re-authenticated and/or re- 5238 authorized. Great care should be taken when the Authorization- 5239 Lifetime value is determined, since a low, non-zero, value could 5240 create significant Diameter traffic, which could congest both the 5241 network and the agents. 5243 A value of zero (0) means that immediate re-auth is necessary by the 5244 access device. This is typically used in cases where multiple 5245 authentication methods are used, and a successful auth response with 5246 this AVP set to zero is used to signal that the next authentication 5247 method is to be immediately initiated. The absence of this AVP, or a 5248 value of all ones (meaning all bits in the 32 bit field are set to 5249 one) means no re-auth is expected. 5251 If both this AVP and the Session-Timeout AVP are present in a 5252 message, the value of the latter MUST NOT be smaller than the 5253 Authorization-Lifetime AVP. 5255 An Authorization-Lifetime AVP MAY be present in re-authorization 5256 messages, and contains the number of seconds the user is authorized 5257 to receive service from the time the re-auth answer message is 5258 received by the access device. 5260 This AVP MAY be provided by the client as a hint of the maximum 5261 lifetime that it is willing to accept. However, the server MAY 5262 return a value that is equal to, or smaller, than the one provided by 5263 the client. 5265 8.10. Auth-Grace-Period AVP 5267 The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and 5268 contains the number of seconds the Diameter server will wait 5269 following the expiration of the Authorization-Lifetime AVP before 5270 cleaning up resources for the session. 5272 8.11. Auth-Session-State AVP 5274 The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and 5275 specifies whether state is maintained for a particular session. The 5276 client MAY include this AVP in requests as a hint to the server, but 5277 the value in the server's answer message is binding. The following 5278 values are supported: 5280 STATE_MAINTAINED 0 5282 This value is used to specify that session state is being 5283 maintained, and the access device MUST issue a session termination 5284 message when service to the user is terminated. This is the 5285 default value. 5287 NO_STATE_MAINTAINED 1 5289 This value is used to specify that no session termination messages 5290 will be sent by the access device upon expiration of the 5291 Authorization-Lifetime. 5293 8.12. Re-Auth-Request-Type AVP 5295 The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and 5296 is included in application-specific auth answers to inform the client 5297 of the action expected upon expiration of the Authorization-Lifetime. 5298 If the answer message contains an Authorization-Lifetime AVP with a 5299 positive value, the Re-Auth-Request-Type AVP MUST be present in an 5300 answer message. The following values are defined: 5302 AUTHORIZE_ONLY 0 5304 An authorization only re-auth is expected upon expiration of the 5305 Authorization-Lifetime. This is the default value if the AVP is 5306 not present in answer messages that include the Authorization- 5307 Lifetime. 5309 AUTHORIZE_AUTHENTICATE 1 5311 An authentication and authorization re-auth is expected upon 5312 expiration of the Authorization-Lifetime. 5314 8.13. Session-Timeout AVP 5316 The Session-Timeout AVP (AVP Code 27) [RFC2865] is of type Unsigned32 5317 and contains the maximum number of seconds of service to be provided 5318 to the user before termination of the session. When both the 5319 Session-Timeout and the Authorization-Lifetime AVPs are present in an 5320 answer message, the former MUST be equal to or greater than the value 5321 of the latter. 5323 A session that terminates on an access device due to the expiration 5324 of the Session-Timeout MUST cause an STR to be issued, unless both 5325 the access device and the home server had previously agreed that no 5326 session termination messages would be sent (see Section 8.11). 5328 A Session-Timeout AVP MAY be present in a re-authorization answer 5329 message, and contains the remaining number of seconds from the 5330 beginning of the re-auth. 5332 A value of zero, or the absence of this AVP, means that this session 5333 has an unlimited number of seconds before termination. 5335 This AVP MAY be provided by the client as a hint of the maximum 5336 timeout that it is willing to accept. However, the server MAY return 5337 a value that is equal to, or smaller, than the one provided by the 5338 client. 5340 8.14. User-Name AVP 5342 The User-Name AVP (AVP Code 1) [RFC2865] is of type UTF8String, which 5343 contains the User-Name, in a format consistent with the NAI 5344 specification [RFC4282]. 5346 8.15. Termination-Cause AVP 5348 The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and 5349 is used to indicate the reason why a session was terminated on the 5350 access device. The following values are defined: 5352 DIAMETER_LOGOUT 1 5354 The user initiated a disconnect 5356 DIAMETER_SERVICE_NOT_PROVIDED 2 5358 This value is used when the user disconnected prior to the receipt 5359 of the authorization answer message. 5361 DIAMETER_BAD_ANSWER 3 5363 This value indicates that the authorization answer received by the 5364 access device was not processed successfully. 5366 DIAMETER_ADMINISTRATIVE 4 5368 The user was not granted access, or was disconnected, due to 5369 administrative reasons, such as the receipt of a Abort-Session- 5370 Request message. 5372 DIAMETER_LINK_BROKEN 5 5374 The communication to the user was abruptly disconnected. 5376 DIAMETER_AUTH_EXPIRED 6 5378 The user's access was terminated since its authorized session time 5379 has expired. 5381 DIAMETER_USER_MOVED 7 5383 The user is receiving services from another access device. 5385 DIAMETER_SESSION_TIMEOUT 8 5387 The user's session has timed out, and service has been terminated. 5389 8.16. Origin-State-Id AVP 5391 The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a 5392 monotonically increasing value that is advanced whenever a Diameter 5393 entity restarts with loss of previous state, for example upon reboot. 5394 Origin-State-Id MAY be included in any Diameter message, including 5395 CER. 5397 A Diameter entity issuing this AVP MUST create a higher value for 5398 this AVP each time its state is reset. A Diameter entity MAY set 5399 Origin-State-Id to the time of startup, or it MAY use an incrementing 5400 counter retained in non-volatile memory across restarts. 5402 The Origin-State-Id, if present, MUST reflect the state of the entity 5403 indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST 5404 either remove Origin-State-Id or modify it appropriately as well. 5405 Typically, Origin-State-Id is used by an access device that always 5406 starts up with no active sessions; that is, any session active prior 5407 to restart will have been lost. By including Origin-State-Id in a 5408 message, it allows other Diameter entities to infer that sessions 5409 associated with a lower Origin-State-Id are no longer active. If an 5410 access device does not intend for such inferences to be made, it MUST 5411 either not include Origin-State-Id in any message, or set its value 5412 to 0. 5414 8.17. Session-Binding AVP 5416 The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY 5417 be present in application-specific authorization answer messages. If 5418 present, this AVP MAY inform the Diameter client that all future 5419 application-specific re-auth messages for this session MUST be sent 5420 to the same authorization server. This AVP MAY also specify that a 5421 Session-Termination-Request message for this session MUST be sent to 5422 the same authorizing server. 5424 This field is a bit mask, and the following bits have been defined: 5426 RE_AUTH 1 5428 When set, future re-auth messages for this session MUST NOT 5429 include the Destination-Host AVP. When cleared, the default 5430 value, the Destination-Host AVP MUST be present in all re-auth 5431 messages for this session. 5433 STR 2 5435 When set, the STR message for this session MUST NOT include the 5436 Destination-Host AVP. When cleared, the default value, the 5437 Destination-Host AVP MUST be present in the STR message for this 5438 session. 5440 ACCOUNTING 4 5442 When set, all accounting messages for this session MUST NOT 5443 include the Destination-Host AVP. When cleared, the default 5444 value, the Destination-Host AVP, if known, MUST be present in all 5445 accounting messages for this session. 5447 8.18. Session-Server-Failover AVP 5449 The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated, 5450 and MAY be present in application-specific authorization answer 5451 messages that either do not include the Session-Binding AVP or 5452 include the Session-Binding AVP with any of the bits set to a zero 5453 value. If present, this AVP MAY inform the Diameter client that if a 5454 re-auth or STR message fails due to a delivery problem, the Diameter 5455 client SHOULD issue a subsequent message without the Destination-Host 5456 AVP. When absent, the default value is REFUSE_SERVICE. 5458 The following values are supported: 5460 REFUSE_SERVICE 0 5462 If either the re-auth or the STR message delivery fails, terminate 5463 service with the user, and do not attempt any subsequent attempts. 5465 TRY_AGAIN 1 5467 If either the re-auth or the STR message delivery fails, resend 5468 the failed message without the Destination-Host AVP present. 5470 ALLOW_SERVICE 2 5472 If re-auth message delivery fails, assume that re-authorization 5473 succeeded. If STR message delivery fails, terminate the session. 5475 TRY_AGAIN_ALLOW_SERVICE 3 5477 If either the re-auth or the STR message delivery fails, resend 5478 the failed message without the Destination-Host AVP present. If 5479 the second delivery fails for re-auth, assume re-authorization 5480 succeeded. If the second delivery fails for STR, terminate the 5481 session. 5483 8.19. Multi-Round-Time-Out AVP 5485 The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32, 5486 and SHOULD be present in application-specific authorization answer 5487 messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH. 5488 This AVP contains the maximum number of seconds that the access 5489 device MUST provide the user in responding to an authentication 5490 request. 5492 8.20. Class AVP 5494 The Class AVP (AVP Code 25) is of type OctetString and is used to by 5495 Diameter servers to return state information to the access device. 5496 When one or more Class AVPs are present in application-specific 5497 authorization answer messages, they MUST be present in subsequent re- 5498 authorization, session termination and accounting messages. Class 5499 AVPs found in a re-authorization answer message override the ones 5500 found in any previous authorization answer message. Diameter server 5501 implementations SHOULD NOT return Class AVPs that require more than 5502 4096 bytes of storage on the Diameter client. A Diameter client that 5503 receives Class AVPs whose size exceeds local available storage MUST 5504 terminate the session. 5506 8.21. Event-Timestamp AVP 5508 The Event-Timestamp (AVP Code 55) is of type Time, and MAY be 5509 included in an Accounting-Request and Accounting-Answer messages to 5510 record the time that the reported event occurred, in seconds since 5511 January 1, 1900 00:00 UTC. 5513 9. Accounting 5515 This accounting protocol is based on a server directed model with 5516 capabilities for real-time delivery of accounting information. 5517 Several fault resilience methods [RFC2975] have been built in to the 5518 protocol in order minimize loss of accounting data in various fault 5519 situations and under different assumptions about the capabilities of 5520 the used devices. 5522 9.1. Server Directed Model 5524 The server directed model means that the device generating the 5525 accounting data gets information from either the authorization server 5526 (if contacted) or the accounting server regarding the way accounting 5527 data shall be forwarded. This information includes accounting record 5528 timeliness requirements. 5530 As discussed in [RFC2975], real-time transfer of accounting records 5531 is a requirement, such as the need to perform credit limit checks and 5532 fraud detection. Note that batch accounting is not a requirement, 5533 and is therefore not supported by Diameter. Should batched 5534 accounting be required in the future, a new Diameter application will 5535 need to be created, or it could be handled using another protocol. 5536 Note, however, that even if at the Diameter layer accounting requests 5537 are processed one by one, transport protocols used under Diameter 5538 typically batch several requests in the same packet under heavy 5539 traffic conditions. This may be sufficient for many applications. 5541 The authorization server (chain) directs the selection of proper 5542 transfer strategy, based on its knowledge of the user and 5543 relationships of roaming partnerships. The server (or agents) uses 5544 the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to 5545 control the operation of the Diameter peer operating as a client. 5546 The Acct-Interim-Interval AVP, when present, instructs the Diameter 5547 node acting as a client to produce accounting records continuously 5548 even during a session. Accounting-Realtime-Required AVP is used to 5549 control the behavior of the client when the transfer of accounting 5550 records from the Diameter client is delayed or unsuccessful. 5552 The Diameter accounting server MAY override the interim interval or 5553 the realtime requirements by including the Acct-Interim-Interval or 5554 Accounting-Realtime-Required AVP in the Accounting-Answer message. 5555 When one of these AVPs is present, the latest value received SHOULD 5556 be used in further accounting activities for the same session. 5558 9.2. Protocol Messages 5560 A Diameter node that receives a successful authentication and/or 5561 authorization messages from the Home AAA server MUST collect 5562 accounting information for the session. The Accounting-Request 5563 message is used to transmit the accounting information to the Home 5564 AAA server, which MUST reply with the Accounting-Answer message to 5565 confirm reception. The Accounting-Answer message includes the 5566 Result-Code AVP, which MAY indicate that an error was present in the 5567 accounting message. A rejected Accounting-Request message MAY cause 5568 the user's session to be terminated, depending on the value of the 5569 Accounting-Realtime-Required AVP received earlier for the session in 5570 question. 5572 Each Diameter Accounting protocol message MAY be compressed, in order 5573 to reduce network bandwidth usage. If TLS is used to secure the 5574 Diameter session, then TLS compression [RFC4346] MAY be used. 5576 9.3. Accounting Application Extension and Requirements 5578 Each Diameter application (e.g., NASREQ, MobileIP), MUST define their 5579 Service-Specific AVPs that MUST be present in the Accounting-Request 5580 message in a section entitled "Accounting AVPs". The application 5581 MUST assume that the AVPs described in this document will be present 5582 in all Accounting messages, so only their respective service-specific 5583 AVPs need to be defined in this section. 5585 Applications have the option of using one or both of the following 5586 accounting application extension models: 5588 Split Accounting Service 5590 The accounting message will carry the Application Id of the 5591 Diameter base accounting application (see Section 2.4). 5592 Accounting messages maybe routed to Diameter nodes other than the 5593 corresponding Diameter application. These nodes might be 5594 centralized accounting servers that provide accounting service for 5595 multiple different Diameter applications. These nodes MUST 5596 advertise the Diameter base accounting Application Id during 5597 capabilities exchange. 5599 Coupled Accounting Service 5601 The accounting messages will carry the Application Id of the 5602 application that is using it. The application itself will process 5603 the received accounting records or forward them to an accounting 5604 server. There is no accounting application advertisement required 5605 during capabilities exchange and the accounting messages will be 5606 routed the same as any of the other application messages. 5608 In cases where an application does not define its own accounting 5609 service, it is preferred that the split accounting model be used. 5611 9.4. Fault Resilience 5613 Diameter Base protocol mechanisms are used to overcome small message 5614 loss and network faults of temporary nature. 5616 Diameter peers acting as clients MUST implement the use of failover 5617 to guard against server failures and certain network failures. 5618 Diameter peers acting as agents or related off-line processing 5619 systems MUST detect duplicate accounting records caused by the 5620 sending of same record to several servers and duplication of messages 5621 in transit. This detection MUST be based on the inspection of the 5622 Session-Id and Accounting-Record-Number AVP pairs. Appendix C 5623 discusses duplicate detection needs and implementation issues. 5625 Diameter clients MAY have non-volatile memory for the safe storage of 5626 accounting records over reboots or extended network failures, network 5627 partitions, and server failures. If such memory is available, the 5628 client SHOULD store new accounting records there as soon as the 5629 records are created and until a positive acknowledgement of their 5630 reception from the Diameter Server has been received. Upon a reboot, 5631 the client MUST starting sending the records in the non-volatile 5632 memory to the accounting server with appropriate modifications in 5633 termination cause, session length, and other relevant information in 5634 the records. 5636 A further application of this protocol may include AVPs to control 5637 how many accounting records may at most be stored in the Diameter 5638 client without committing them to the non-volatile memory or 5639 transferring them to the Diameter server. 5641 The client SHOULD NOT remove the accounting data from any of its 5642 memory areas before the correct Accounting-Answer has been received. 5643 The client MAY remove oldest, undelivered or yet unacknowledged 5644 accounting data if it runs out of resources such as memory. It is an 5645 implementation dependent matter for the client to accept new sessions 5646 under this condition. 5648 9.5. Accounting Records 5650 In all accounting records, the Session-Id AVP MUST be present; the 5651 User-Name AVP MUST be present if it is available to the Diameter 5652 client. 5654 Different types of accounting records are sent depending on the 5655 actual type of accounted service and the authorization server's 5656 directions for interim accounting. If the accounted service is a 5657 one-time event, meaning that the start and stop of the event are 5658 simultaneous, then the Accounting-Record-Type AVP MUST be present and 5659 set to the value EVENT_RECORD. 5661 If the accounted service is of a measurable length, then the AVP MUST 5662 use the values START_RECORD, STOP_RECORD, and possibly, 5663 INTERIM_RECORD. If the authorization server has not directed interim 5664 accounting to be enabled for the session, two accounting records MUST 5665 be generated for each service of type session. When the initial 5666 Accounting-Request for a given session is sent, the Accounting- 5667 Record-Type AVP MUST be set to the value START_RECORD. When the last 5668 Accounting-Request is sent, the value MUST be STOP_RECORD. 5670 If the authorization server has directed interim accounting to be 5671 enabled, the Diameter client MUST produce additional records between 5672 the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The 5673 production of these records is directed by Acct-Interim-Interval as 5674 well as any re-authentication or re-authorization of the session. 5675 The Diameter client MUST overwrite any previous interim accounting 5676 records that are locally stored for delivery, if a new record is 5677 being generated for the same session. This ensures that only one 5678 pending interim record can exist on an access device for any given 5679 session. 5681 A particular value of Accounting-Sub-Session-Id MUST appear only in 5682 one sequence of accounting records from a DIAMETER client, except for 5683 the purposes of retransmission. The one sequence that is sent MUST 5684 be either one record with Accounting-Record-Type AVP set to the value 5685 EVENT_RECORD, or several records starting with one having the value 5686 START_RECORD, followed by zero or more INTERIM_RECORD and a single 5687 STOP_RECORD. A particular Diameter application specification MUST 5688 define the type of sequences that MUST be used. 5690 9.6. Correlation of Accounting Records 5692 The Diameter protocol's Session-Id AVP, which is globally unique (see 5693 Section 8.8), is used during the authorization phase to identify a 5694 particular session. Services that do not require any authorization 5695 still use the Session-Id AVP to identify sessions. Accounting 5696 messages MAY use a different Session-Id from that sent in 5697 authorization messages. Specific applications MAY require different 5698 a Session-ID for accounting messages. 5700 However, there are certain applications that require multiple 5701 accounting sub-sessions. Such applications would send messages with 5702 a constant Session-Id AVP, but a different Accounting-Sub-Session-Id 5703 AVP. In these cases, correlation is performed using the Session-Id. 5704 It is important to note that receiving a STOP_RECORD with no 5705 Accounting-Sub-Session-Id AVP when sub-sessions were originally used 5706 in the START_RECORD messages implies that all sub-sessions are 5707 terminated. 5709 Furthermore, there are certain applications where a user receives 5710 service from different access devices (e.g., Mobile IPv4), each with 5711 their own unique Session-Id. In such cases, the Acct-Multi-Session- 5712 Id AVP is used for correlation. During authorization, a server that 5713 determines that a request is for an existing session SHOULD include 5714 the Acct-Multi-Session-Id AVP, which the access device MUST include 5715 in all subsequent accounting messages. 5717 The Acct-Multi-Session-Id AVP MAY include the value of the original 5718 Session-Id. It's contents are implementation specific, but MUST be 5719 globally unique across other Acct-Multi-Session-Id, and MUST NOT 5720 change during the life of a session. 5722 A Diameter application document MUST define the exact concept of a 5723 session that is being accounted, and MAY define the concept of a 5724 multi-session. For instance, the NASREQ DIAMETER application treats 5725 a single PPP connection to a Network Access Server as one session, 5726 and a set of Multilink PPP sessions as one multi-session. 5728 9.7. Accounting Command-Codes 5730 This section defines Command-Code values that MUST be supported by 5731 all Diameter implementations that provide Accounting services. 5733 9.7.1. Accounting-Request 5735 The Accounting-Request (ACR) command, indicated by the Command-Code 5736 field set to 271 and the Command Flags' 'R' bit set, is sent by a 5737 Diameter node, acting as a client, in order to exchange accounting 5738 information with a peer. 5740 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs 5741 MUST be present. If the Vendor-Specific-Application-Id grouped AVP 5742 is present, it MUST include an Acct-Application-Id AVP. 5744 The AVP listed below SHOULD include service specific accounting AVPs, 5745 as described in Section 9.3. 5747 Message Format 5749 ::= < Diameter Header: 271, REQ, PXY > 5750 < Session-Id > 5751 { Origin-Host } 5752 { Origin-Realm } 5753 { Destination-Realm } 5754 { Accounting-Record-Type } 5755 { Accounting-Record-Number } 5756 [ Acct-Application-Id ] 5757 [ Vendor-Specific-Application-Id ] 5758 [ User-Name ] 5759 [ Destination-Host ] 5760 [ Accounting-Sub-Session-Id ] 5761 [ Acct-Session-Id ] 5762 [ Acct-Multi-Session-Id ] 5763 [ Acct-Interim-Interval ] 5764 [ Accounting-Realtime-Required ] 5765 [ Origin-State-Id ] 5766 [ Event-Timestamp ] 5767 * [ Proxy-Info ] 5768 * [ Route-Record ] 5769 * [ AVP ] 5771 9.7.2. Accounting-Answer 5773 The Accounting-Answer (ACA) command, indicated by the Command-Code 5774 field set to 271 and the Command Flags' 'R' bit cleared, is used to 5775 acknowledge an Accounting-Request command. The Accounting-Answer 5776 command contains the same Session-Id as the corresponding request. 5778 Only the target Diameter Server, known as the home Diameter Server, 5779 SHOULD respond with the Accounting-Answer command. 5781 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs 5782 MUST be present. If the Vendor-Specific-Application-Id grouped AVP 5783 is present, it MUST contain an Acct-Application-Id AVP. 5785 The AVP listed below SHOULD include service specific accounting AVPs, 5786 as described in Section 9.3. 5788 Message Format 5790 ::= < Diameter Header: 271, PXY > 5791 < Session-Id > 5792 { Result-Code } 5793 { Origin-Host } 5794 { Origin-Realm } 5795 { Accounting-Record-Type } 5796 { Accounting-Record-Number } 5797 [ Acct-Application-Id ] 5798 [ Vendor-Specific-Application-Id ] 5799 [ User-Name ] 5800 [ Accounting-Sub-Session-Id ] 5801 [ Acct-Session-Id ] 5802 [ Acct-Multi-Session-Id ] 5803 [ Error-Message ] 5804 [ Error-Reporting-Host ] 5805 [ Failed-AVP ] 5806 [ Acct-Interim-Interval ] 5807 [ Accounting-Realtime-Required ] 5808 [ Origin-State-Id ] 5809 [ Event-Timestamp ] 5810 * [ Proxy-Info ] 5811 * [ AVP ] 5813 9.8. Accounting AVPs 5815 This section contains AVPs that describe accounting usage information 5816 related to a specific session. 5818 9.8.1. Accounting-Record-Type AVP 5820 The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated 5821 and contains the type of accounting record being sent. The following 5822 values are currently defined for the Accounting-Record-Type AVP: 5824 EVENT_RECORD 1 5826 An Accounting Event Record is used to indicate that a one-time 5827 event has occurred (meaning that the start and end of the event 5828 are simultaneous). This record contains all information relevant 5829 to the service, and is the only record of the service. 5831 START_RECORD 2 5833 An Accounting Start, Interim, and Stop Records are used to 5834 indicate that a service of a measurable length has been given. An 5835 Accounting Start Record is used to initiate an accounting session, 5836 and contains accounting information that is relevant to the 5837 initiation of the session. 5839 INTERIM_RECORD 3 5841 An Interim Accounting Record contains cumulative accounting 5842 information for an existing accounting session. Interim 5843 Accounting Records SHOULD be sent every time a re-authentication 5844 or re-authorization occurs. Further, additional interim record 5845 triggers MAY be defined by application-specific Diameter 5846 applications. The selection of whether to use INTERIM_RECORD 5847 records is done by the Acct-Interim-Interval AVP. 5849 STOP_RECORD 4 5851 An Accounting Stop Record is sent to terminate an accounting 5852 session and contains cumulative accounting information relevant to 5853 the existing session. 5855 9.8.2. Acct-Interim-Interval AVP 5857 The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and 5858 is sent from the Diameter home authorization server to the Diameter 5859 client. The client uses information in this AVP to decide how and 5860 when to produce accounting records. With different values in this 5861 AVP, service sessions can result in one, two, or two+N accounting 5862 records, based on the needs of the home-organization. The following 5863 accounting record production behavior is directed by the inclusion of 5864 this AVP: 5866 1. The omission of the Acct-Interim-Interval AVP or its inclusion 5867 with Value field set to 0 means that EVENT_RECORD, START_RECORD, 5868 and STOP_RECORD are produced, as appropriate for the service. 5870 2. The inclusion of the AVP with Value field set to a non-zero value 5871 means that INTERIM_RECORD records MUST be produced between the 5872 START_RECORD and STOP_RECORD records. The Value field of this 5873 AVP is the nominal interval between these records in seconds. 5875 The Diameter node that originates the accounting information, 5876 known as the client, MUST produce the first INTERIM_RECORD record 5877 roughly at the time when this nominal interval has elapsed from 5878 the START_RECORD, the next one again as the interval has elapsed 5879 once more, and so on until the session ends and a STOP_RECORD 5880 record is produced. 5882 The client MUST ensure that the interim record production times 5883 are randomized so that large accounting message storms are not 5884 created either among records or around a common service start 5885 time. 5887 9.8.3. Accounting-Record-Number AVP 5889 The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32 5890 and identifies this record within one session. As Session-Id AVPs 5891 are globally unique, the combination of Session-Id and Accounting- 5892 Record-Number AVPs is also globally unique, and can be used in 5893 matching accounting records with confirmations. An easy way to 5894 produce unique numbers is to set the value to 0 for records of type 5895 EVENT_RECORD and START_RECORD, and set the value to 1 for the first 5896 INTERIM_RECORD, 2 for the second, and so on until the value for 5897 STOP_RECORD is one more than for the last INTERIM_RECORD. 5899 9.8.4. Acct-Session-Id AVP 5901 The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only 5902 used when RADIUS/Diameter translation occurs. This AVP contains the 5903 contents of the RADIUS Acct-Session-Id attribute. 5905 9.8.5. Acct-Multi-Session-Id AVP 5907 The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String, 5908 following the format specified in Section 8.8. The Acct-Multi- 5909 Session-Id AVP is used to link together multiple related accounting 5910 sessions, where each session would have a unique Session-Id, but the 5911 same Acct-Multi-Session-Id AVP. This AVP MAY be returned by the 5912 Diameter server in an authorization answer, and MUST be used in all 5913 accounting messages for the given session. 5915 9.8.6. Accounting-Sub-Session-Id AVP 5917 The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type 5918 Unsigned64 and contains the accounting sub-session identifier. The 5919 combination of the Session-Id and this AVP MUST be unique per sub- 5920 session, and the value of this AVP MUST be monotonically increased by 5921 one for all new sub-sessions. The absence of this AVP implies no 5922 sub-sessions are in use, with the exception of an Accounting-Request 5923 whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD 5924 message with no Accounting-Sub-Session-Id AVP present will signal the 5925 termination of all sub-sessions for a given Session-Id. 5927 9.8.7. Accounting-Realtime-Required AVP 5929 The Accounting-Realtime-Required AVP (AVP Code 483) is of type 5930 Enumerated and is sent from the Diameter home authorization server to 5931 the Diameter client or in the Accounting-Answer from the accounting 5932 server. The client uses information in this AVP to decide what to do 5933 if the sending of accounting records to the accounting server has 5934 been temporarily prevented due to, for instance, a network problem. 5936 DELIVER_AND_GRANT 1 5938 The AVP with Value field set to DELIVER_AND_GRANT means that the 5939 service MUST only be granted as long as there is a connection to 5940 an accounting server. Note that the set of alternative accounting 5941 servers are treated as one server in this sense. Having to move 5942 the accounting record stream to a backup server is not a reason to 5943 discontinue the service to the user. 5945 GRANT_AND_STORE 2 5947 The AVP with Value field set to GRANT_AND_STORE means that service 5948 SHOULD be granted if there is a connection, or as long as records 5949 can still be stored as described in Section 9.4. 5951 This is the default behavior if the AVP isn't included in the 5952 reply from the authorization server. 5954 GRANT_AND_LOSE 3 5956 The AVP with Value field set to GRANT_AND_LOSE means that service 5957 SHOULD be granted even if the records can not be delivered or 5958 stored. 5960 10. AVP Occurrence Table 5962 The following tables presents the AVPs defined in this document, and 5963 specifies in which Diameter messages they MAY be present or not. 5964 AVPs that occur only inside a Grouped AVP are not shown in this 5965 table. 5967 The table uses the following symbols: 5969 0 The AVP MUST NOT be present in the message. 5971 0+ Zero or more instances of the AVP MAY be present in the 5972 message. 5974 0-1 Zero or one instance of the AVP MAY be present in the message. 5975 It is considered an error if there are more than one instance of 5976 the AVP. 5978 1 One instance of the AVP MUST be present in the message. 5980 1+ At least one instance of the AVP MUST be present in the 5981 message. 5983 10.1. Base Protocol Command AVP Table 5985 The table in this section is limited to the non-accounting Command 5986 Codes defined in this specification. 5988 +-----------------------------------------------+ 5989 | Command-Code | 5990 +---+---+---+---+---+---+---+---+---+---+---+---+ 5991 Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA| 5992 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ 5993 Acct-Interim- |0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | 5994 Interval | | | | | | | | | | | | | 5995 Accounting-Realtime-|0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | 5996 Required | | | | | | | | | | | | | 5997 Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 5998 Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | 5999 Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6000 Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6001 Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6002 Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6003 Lifetime | | | | | | | | | | | | | 6004 Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ | 6005 Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 | 6006 Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | 6007 Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6008 Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1| 6009 Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6010 Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ | 6011 Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6012 Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6013 Inband-Security-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6014 Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6015 Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | 6016 Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | 6017 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| 6018 Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6019 Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ | 6020 Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ | 6021 Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6022 Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6023 Time | | | | | | | | | | | | | 6024 Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 | 6025 Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 | 6026 Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 | 6027 Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6028 Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 | 6029 Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6030 Failover | | | | | | | | | | | | | 6031 Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6032 Supported-Vendor-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6033 Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 | 6034 User-Name |0 |0 |0 |0 |0 |0 |0-1|0-1|0-1|0-1|0-1|0-1| 6035 Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6036 Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6037 Application-Id | | | | | | | | | | | | | 6038 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ 6040 10.2. Accounting AVP Table 6042 The table in this section is used to represent which AVPs defined in 6043 this document are to be present in the Accounting messages. These 6044 AVP occurrence requirements are guidelines, which may be expanded, 6045 and/or overridden by application-specific requirements in the 6046 Diameter applications documents. 6048 +-----------+ 6049 | Command | 6050 | Code | 6051 +-----+-----+ 6052 Attribute Name | ACR | ACA | 6053 ------------------------------+-----+-----+ 6054 Acct-Interim-Interval | 0-1 | 0-1 | 6055 Acct-Multi-Session-Id | 0-1 | 0-1 | 6056 Accounting-Record-Number | 1 | 1 | 6057 Accounting-Record-Type | 1 | 1 | 6058 Acct-Session-Id | 0-1 | 0-1 | 6059 Accounting-Sub-Session-Id | 0-1 | 0-1 | 6060 Accounting-Realtime-Required | 0-1 | 0-1 | 6061 Acct-Application-Id | 0-1 | 0-1 | 6062 Auth-Application-Id | 0 | 0 | 6063 Class | 0+ | 0+ | 6064 Destination-Host | 0-1 | 0 | 6065 Destination-Realm | 1 | 0 | 6066 Error-Reporting-Host | 0 | 0+ | 6067 Event-Timestamp | 0-1 | 0-1 | 6068 Origin-Host | 1 | 1 | 6069 Origin-Realm | 1 | 1 | 6070 Proxy-Info | 0+ | 0+ | 6071 Route-Record | 0+ | 0 | 6072 Result-Code | 0 | 1 | 6073 Session-Id | 1 | 1 | 6074 Termination-Cause | 0 | 0 | 6075 User-Name | 0-1 | 0-1 | 6076 Vendor-Specific-Application-Id| 0-1 | 0-1 | 6077 ------------------------------+-----+-----+ 6079 11. IANA Considerations 6081 This section provides guidance to the Internet Assigned Numbers 6082 Authority (IANA) regarding registration of values related to the 6083 Diameter protocol, in accordance with BCP 26 [RFC2434]. The 6084 following policies are used here with the meanings defined in BCP 26: 6085 "Private Use", "First Come First Served", "Expert Review", 6086 "Specification Required", "IETF Review", "Standards Action". 6088 This section explains the criteria to be used by the IANA for 6089 assignment of numbers within namespaces defined within this document. 6091 Diameter is not intended as a general purpose protocol, and 6092 allocations SHOULD NOT be made for purposes unrelated to 6093 authentication, authorization or accounting. 6095 For registration requests where a Designated Expert should be 6096 consulted, the responsible IESG area director should appoint the 6097 Designated Expert. For Designated Expert with Specification 6098 Required, the request is posted to the DIME WG mailing list (or, if 6099 it has been disbanded, a successor designated by the Area Director) 6100 for comment and review, and MUST include a pointer to a public 6101 specification. Before a period of 30 days has passed, the Designated 6102 Expert will either approve or deny the registration request and 6103 publish a notice of the decision to the DIME WG mailing list or its 6104 successor. A denial notice MUST be justified by an explanation and, 6105 in the cases where it is possible, concrete suggestions on how the 6106 request can be modified so as to become acceptable. 6108 11.1. AVP Header 6110 As defined in Section 4, the AVP header contains three fields that 6111 requires IANA namespace management; the AVP Code, Vendor-ID and Flags 6112 field. 6114 11.1.1. AVP Codes 6116 The AVP Code namespace is used to identify attributes. There are 6117 multiple namespaces. Vendors can have their own AVP Codes namespace 6118 which will be identified by their Vendor-ID (also known as 6119 Enterprise-Number) and they control the assignments of their vendor- 6120 specific AVP codes within their own namespace. The absence of a 6121 Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA 6122 controlled AVP Codes namespace. The AVP Codes and sometimes also 6123 possible values in an AVP are controlled and maintained by IANA. 6125 AVP Code 0 is not used. AVP Codes 1-255 are managed separately as 6126 RADIUS Attribute Types [RADTYPE]. This document defines the AVP 6127 Codes 257-274, 276-285, 287, 291-300, 480, 483 and 485-486. See 6128 Section 4.5 for the assignment of the namespace in this 6129 specification. 6131 AVPs may be allocated following Designated Expert with Specification 6132 Required [RFC2434]. Release of blocks of AVPs (more than 3 at a time 6133 for a given purpose) should require IETF Review. 6135 Note that Diameter defines a mechanism for Vendor-Specific AVPs, 6136 where the Vendor-Id field in the AVP header is set to a non-zero 6137 value. Vendor-Specific AVPs codes are for Private Use and should be 6138 encouraged instead of allocation of global attribute types, for 6139 functions specific only to one vendor's implementation of Diameter, 6140 where no interoperability is deemed useful. Where a Vendor-Specific 6141 AVP is implemented by more than one vendor, allocation of global AVPs 6142 should be encouraged instead. 6144 11.1.2. AVP Flags 6146 There are 8 bits in the AVP Flags field of the AVP header, defined in 6147 Section 4. This document assigns bit 0 ('V'endor Specific), bit 1 6148 ('M'andatory) and bit 2 ('P'rotected). The remaining bits should 6149 only be assigned via a Standards Action [RFC2434]. 6151 11.2. Diameter Header 6153 As defined in Section 3, the Diameter header contains two fields that 6154 require IANA namespace management; Command Code and Command Flags. 6156 11.2.1. Command Codes 6158 The Command Code namespace is used to identify Diameter commands. 6159 The values 0-255 (0x00-0xff) are reserved for RADIUS backward 6160 compatibility, and are defined as "RADIUS Packet Type Codes" in 6161 [RADTYPE]. Values 256 - 8,388,607 (0x100 to 0x7fffff) are for 6162 permanent, standard commands, allocated by IETF Review [RFC2434]. 6163 This document defines the Command Codes 257, 258, 271, 274-275, 280 6164 and 282. See Section 3.1 for the assignment of the namespace in this 6165 specification. 6167 The values 8,388,608 - 16,777,213 (0x800000 - 0xfffffd) are reserved 6168 for vendor-specific command codes, to be allocated on a First Come, 6169 First Served basis by IANA [RFC2434]. The request to IANA for a 6170 Vendor-Specific Command Code SHOULD include a reference to a publicly 6171 available specification which documents the command in sufficient 6172 detail to aid in interoperability between independent 6173 implementations. If the specification cannot be made publicly 6174 available, the request for a vendor-specific command code MUST 6175 include the contact information of persons and/or entities 6176 responsible for authoring and maintaining the command. 6178 The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe - 6179 0xffffff) are reserved for experimental commands. As these codes are 6180 only for experimental and testing purposes, no guarantee is made for 6181 interoperability between Diameter peers using experimental commands, 6182 as outlined in [IANA-EXP]. 6184 11.2.2. Command Flags 6186 There are eight bits in the Command Flags field of the Diameter 6187 header. This document assigns bit 0 ('R'equest), bit 1 ('P'roxy), 6188 bit 2 ('E'rror) and bit 3 ('T'). Bits 4 through 7 MUST only be 6189 assigned via a Standards Action [RFC2434]. 6191 11.3. Application Identifiers 6193 As defined in Section 2.4, the Application Id is used to identify a 6194 specific Diameter Application. There are standards-track Application 6195 Ids and vendor specific Application Ids. 6197 IANA [RFC2434] has assigned the range 0x00000001 to 0x00ffffff for 6198 standards-track applications; and 0x01000000 - 0xfffffffe for vendor 6199 specific applications, on a first-come, first-served basis. The 6200 following values are allocated. 6202 Diameter Common Messages 0 6203 NASREQ 1 [RFC4005] 6204 Mobile-IP 2 [RFC4004] 6205 Diameter Base Accounting 3 6206 Relay 0xffffffff 6208 Assignment of standards-track Application Ids are by Designated 6209 Expert with Specification Required [RFC2434]. 6211 Both Auth-Application-Id and Acct-Application-Id AVPs use the same 6212 Application Id space. A diameter node advertising itself as a relay 6213 agent MUST set either Application-Id or Acct-Application-Id to 6214 0xffffffff. 6216 Vendor-Specific Application Ids, are for Private Use. Vendor-Specific 6217 Application Ids are assigned on a First Come, First Served basis by 6218 IANA. 6220 11.4. AVP Values 6222 Certain AVPs in Diameter define a list of values with various 6223 meanings. For attributes other than those specified in this section, 6224 adding additional values to the list can be done on a First Come, 6225 First Served basis by IANA. 6227 11.4.1. Result-Code AVP Values 6229 As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines 6230 the values 1001, 2001-2002, 3001-3012, 4001-4003 and 5001-5021. 6232 All remaining values are available for assignment via IETF Review 6233 [RFC2434]. 6235 11.4.2. Accounting-Record-Type AVP Values 6237 As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code 6238 480) defines the values 1-4. All remaining values are available for 6239 assignment via IETF Review [RFC2434]. 6241 11.4.3. Termination-Cause AVP Values 6243 As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295) 6244 defines the values 1-8. All remaining values are available for 6245 assignment via IETF Review [RFC2434]. 6247 11.4.4. Redirect-Host-Usage AVP Values 6249 As defined in Section 6.13, the Redirect-Host-Usage AVP (AVP Code 6250 261) defines the values 0-5. All remaining values are available for 6251 assignment via IETF Review [RFC2434]. 6253 11.4.5. Session-Server-Failover AVP Values 6255 As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code 6256 271) defines the values 0-3. All remaining values are available for 6257 assignment via IETF Review [RFC2434]. 6259 11.4.6. Session-Binding AVP Values 6261 As defined in Section 8.17, the Session-Binding AVP (AVP Code 270) 6262 defines the bits 1-4. All remaining bits are available for 6263 assignment via IETF Review [RFC2434]. 6265 11.4.7. Disconnect-Cause AVP Values 6267 As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273) 6268 defines the values 0-2. All remaining values are available for 6269 assignment via IETF Review [RFC2434]. 6271 11.4.8. Auth-Request-Type AVP Values 6273 As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274) 6274 defines the values 1-3. All remaining values are available for 6275 assignment via IETF Review [RFC2434]. 6277 11.4.9. Auth-Session-State AVP Values 6279 As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277) 6280 defines the values 0-1. All remaining values are available for 6281 assignment via IETF Review [RFC2434]. 6283 11.4.10. Re-Auth-Request-Type AVP Values 6285 As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code 6286 285) defines the values 0-1. All remaining values are available for 6287 assignment via IETF Review [RFC2434]. 6289 11.4.11. Accounting-Realtime-Required AVP Values 6291 As defined in Section 9.8.7, the Accounting-Realtime-Required AVP 6292 (AVP Code 483) defines the values 1-3. All remaining values are 6293 available for assignment via IETF Review [RFC2434]. 6295 11.4.12. Inband-Security-Id AVP (code 299) 6297 As defined in Section 6.10, the Inband-Security-Id AVP (AVP Code 299) 6298 defines the values 0-1. All remaining values are available for 6299 assignment via IETF Review [RFC2434]. 6301 11.5. Diameter TCP/SCTP Port Numbers 6303 The IANA has assigned TCP and SCTP port number 3868 to Diameter. 6305 11.6. NAPTR Service Fields 6307 The registration in the RFC MUST include the following information: 6309 Service Field: The service field being registered. An example for a 6310 new fictitious transport protocol called NCTP might be "AAA+D2N". 6312 Protocol: The specific transport protocol associated with that 6313 service field. This MUST include the name and acronym for the 6314 protocol, along with reference to a document that describes the 6315 transport protocol. For example - "New Connectionless Transport 6316 Protocol (NCTP), RFC XYZ". 6318 Name and Contact Information: The name, address, email address and 6319 telephone number for the person performing the registration. 6321 The following values have been placed into the registry: 6323 Services Field Protocol 6325 AAA+D2T TCP 6326 AAA+D2S SCTP 6328 12. Diameter protocol related configurable parameters 6330 This section contains the configurable parameters that are found 6331 throughout this document: 6333 Diameter Peer 6335 A Diameter entity MAY communicate with peers that are statically 6336 configured. A statically configured Diameter peer would require 6337 that either the IP address or the fully qualified domain name 6338 (FQDN) be supplied, which would then be used to resolve through 6339 DNS. 6341 Routing Table 6343 A Diameter proxy server routes messages based on the realm portion 6344 of a Network Access Identifier (NAI). The server MUST have a 6345 table of Realm Names, and the address of the peer to which the 6346 message must be forwarded to. The routing table MAY also include 6347 a "default route", which is typically used for all messages that 6348 cannot be locally processed. 6350 Tc timer 6352 The Tc timer controls the frequency that transport connection 6353 attempts are done to a peer with whom no active transport 6354 connection exists. The recommended value is 30 seconds. 6356 13. Security Considerations 6358 The Diameter base protocol messages SHOULD be secured by using TLS 6359 [RFC4346]. Additional security measures that are transparent to and 6360 independent of Diameter, such as IPSec [RFC4301], can also be 6361 deployed to secure connections between peers. 6363 During deployment, connections between Diameter nodes SHOULD be 6364 protected by TLS. All Diameter base protocol implementations MUST 6365 support the use of TLS. The Diameter protocol MUST NOT be used 6366 without any security mechanism. 6368 If a Diameter connection is to be protected via TLS, then the CER/CEA 6369 exchange MUST include an Inband-Security-ID AVP with a value of TLS. 6370 For TLS usage, a TLS handshake will begin when both ends are in the 6371 open state, after completion of the CER/CEA exchange. If the TLS 6372 handshake is successful, all further messages will be sent via TLS. 6373 If the handshake fails, both ends move to the closed state. See 6374 Sections 13.1 for more details. 6376 13.1. TLS Usage 6378 A Diameter node that initiates a connection to another Diameter node 6379 acts as a TLS client according to [RFC4346], and a Diameter node that 6380 accepts a connection acts as a TLS server. Diameter nodes 6381 implementing TLS for security MUST mutually authenticate as part of 6382 TLS session establishment. In order to ensure mutual authentication, 6383 the Diameter node acting as TLS server MUST request a certificate 6384 from the Diameter node acting as TLS client, and the Diameter node 6385 acting as TLS client MUST be prepared to supply a certificate on 6386 request. 6388 Diameter nodes MUST be able to negotiate the following TLS cipher 6389 suites: 6391 TLS_RSA_WITH_RC4_128_MD5 6392 TLS_RSA_WITH_RC4_128_SHA 6393 TLS_RSA_WITH_3DES_EDE_CBC_SHA 6395 Diameter nodes SHOULD be able to negotiate the following TLS cipher 6396 suite: 6398 TLS_RSA_WITH_AES_128_CBC_SHA 6400 Diameter nodes MAY negotiate other TLS cipher suites. 6402 Upon receiving the peers certificate, Diameter nodes SHOULD further 6403 validate the identity of the peer by matching the received Origin- 6404 Host and/or Origin-Realm in the CER and CEA exchange against the 6405 content of the peers certificate. Diameter peer hostname and/or 6406 realm validation can be performed in the following order: 6408 o If one ore more 'Subject Alternate Name (subjectAltName)' 6409 extension of type dNSName is present in the certificate (See 6410 [RFC3280]), then the Origin-Host value can be used to find a 6411 matching extension. 6413 o If there are no matches found, then the Origin-Realm value can be 6414 used to find a matching subjectAltName extension. 6416 o Otherwise, the Origin-Host value should be found within the 6417 'Common Name (CN)' field in the Subject field of the certificate 6418 (See [RFC3280]). 6420 Identity validation MAY be omitted by a Diameter node if the 6421 information contained in the certificate cannot be co-related or 6422 mapped to the Origin-Host and Origin-Realm presented by a peer. 6423 However, the Diameter node SHOULD have external information or other 6424 means to validate the identity of a peer. 6426 13.2. Peer-to-Peer Considerations 6428 As with any peer-to-peer protocol, proper configuration of the trust 6429 model within a Diameter peer is essential to security. When 6430 certificates are used, it is necessary to configure the root 6431 certificate authorities trusted by the Diameter peer. These root CAs 6432 are likely to be unique to Diameter usage and distinct from the root 6433 CAs that might be trusted for other purposes such as Web browsing. 6434 In general, it is expected that those root CAs will be configured so 6435 as to reflect the business relationships between the organization 6436 hosting the Diameter peer and other organizations. As a result, a 6437 Diameter peer will typically not be configured to allow connectivity 6438 with any arbitrary peer. With certificate authentication, Diameter 6439 peers may not be known beforehand and therefore peer discovery may be 6440 required. 6442 14. References 6444 14.1. Normative References 6446 [FLOATPOINT] 6447 Institute of Electrical and Electronics Engineers, "IEEE 6448 Standard for Binary Floating-Point Arithmetic, ANSI/IEEE 6449 Standard 754-1985", August 1985. 6451 [IANAADFAM] 6452 IANA,, "Address Family Numbers", 6453 http://www.iana.org/assignments/address-family-numbers. 6455 [RADTYPE] IANA,, "RADIUS Types", 6456 http://www.iana.org/assignments/radius-types. 6458 [RFC791] Postel, J., "Internet Protocol", RFC 791, September 1981. 6460 [RFC793] Postel, J., "Transmission Control Protocol", RFC 793, 6461 January 1981. 6463 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and 6464 Accounting (AAA) Transport Profile", RFC 3539, June 2003. 6466 [RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and 6467 P. McCann, "Diameter Mobile IPv4 Application", RFC 4004, 6468 August 2005. 6470 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton, 6471 "Diameter Network Access Server Application", RFC 4005, 6472 August 2005. 6474 [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J. 6475 Loughney, "Diameter Credit-Control Application", RFC 4006, 6476 August 2005. 6478 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible 6479 Authentication Protocol (EAP) Application", RFC 4072, 6480 August 2005. 6482 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M., 6483 Canales-Valenzuela, C., and K. Tammi, "Diameter Session 6484 Initiation Protocol (SIP) Application", RFC 4740, 6485 November 2006. 6487 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 6488 Specifications: ABNF", RFC 4234, October 2005. 6490 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. 6491 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 6493 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 6494 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 6495 October 1998. 6497 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 6498 RFC 4306, December 2005. 6500 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 6501 Architecture", RFC 4291, February 2006. 6503 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 6504 Requirement Levels", BCP 14, RFC 2119, March 1997. 6506 [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The 6507 Network Access Identifier", RFC 4282, December 2005. 6509 [RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS) 6510 Part Three: The Domain Name System (DNS) Database", 6511 RFC 3403, October 2002. 6513 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 6514 A., Peterson, J., Sparks, R., Handley, M., and E. 6515 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 6516 June 2002. 6518 [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C., 6519 Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M., 6520 Zhang, L., and V. Paxson, "Stream Control Transmission 6521 Protocol", RFC 2960, October 2000. 6523 [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security 6524 (TLS) Protocol Version 1.1", RFC 4346, April 2006. 6526 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 6527 Resource Identifier (URI): Generic Syntax", STD 66, 6528 RFC 3986, January 2005. 6530 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 6531 10646", STD 63, RFC 3629, November 2003. 6533 [RFC3280] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet 6534 X.509 Public Key Infrastructure Certificate and 6535 Certificate Revocation List (CRL) Profile", RFC 3280, 6536 April 2002. 6538 [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, 6539 "Internationalizing Domain Names in Applications (IDNA)", 6540 RFC 3490, March 2003. 6542 [RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep 6543 Profile for Internationalized Domain Names (IDN)", 6544 RFC 3491, March 2003. 6546 [RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode 6547 for Internationalized Domain Names in Applications 6548 (IDNA)", RFC 3492, March 2003. 6550 14.2. Informational References 6552 [RFC2989] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, P., 6553 Shiino, H., Zorn, G., Dommety, G., C.Perkins, B.Patil, 6554 D.Mitton, S.Manning, M.Beadles, P.Walsh, X.Chen, 6555 S.Sivalingham, A.Hameed, M.Munson, S.Jacobs, B.Lim, 6556 B.Hirschman, R.Hsu, Y.Xu, E.Campell, S.Baba, and E.Jaques, 6557 "Criteria for Evaluating AAA Protocols for Network 6558 Access", RFC 2989, November 2000. 6560 [RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction to 6561 Accounting Management", RFC 2975, October 2000. 6563 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by 6564 an On-line Database", RFC 3232, January 2002. 6566 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B. 6567 Aboba, "Dynamic Authorization Extensions to Remote 6568 Authentication Dial In User Service (RADIUS)", RFC 3576, 6569 July 2003. 6571 [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, 6572 RFC 1661, July 1994. 6574 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. 6576 [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS 6577 Extensions", RFC 2869, June 2000. 6579 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 6580 "Remote Authentication Dial In User Service (RADIUS)", 6581 RFC 2865, June 2000. 6583 [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6", 6584 RFC 3162, August 2001. 6586 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 6587 Internet Protocol", RFC 4301, December 2005. 6589 [RFC4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 6590 for IPv4, IPv6 and OSI", RFC 4330, January 2006. 6592 [RFC1492] Finseth, C., "An Access Control Protocol, Sometimes Called 6593 TACACS", RFC 1492, July 1993. 6595 [RFC4690] Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and 6596 Recommendations for Internationalized Domain Names 6597 (IDNs)", RFC 4690, September 2006. 6599 [IANA-EXP] 6600 Narten, T., "Assigning Experimental and Testing Numbers 6601 Considered Useful, Work in Progress.". 6603 Appendix A. Acknowledgements 6605 The authors would like to thank the following people that have 6606 provided proposals and contributions to this document: 6608 To Vishnu Ram and Satendra Gera for their contributions on 6609 Capabilities Updates, Predictive Loop Avoidance as well as many other 6610 technical proposals. To Tolga Asveren for his insights and 6611 contributions on almost all of the proposed solutions incorporated 6612 into this document. To Timothy Smith for helping on the Capabilities 6613 Updates and other topics. To Tony Zhang for providing fixes to loop 6614 holes on composing Failed-AVPs as well as many other issues and 6615 topics. To Jan Nordqvist for clearly stating the usage of 6616 Application Ids. To Anders Kristensen for providing needed technical 6617 opinions. To David Frascone for providing invaluable review of the 6618 document. To Mark Jones for providing clarifying text on vendor 6619 command codes and other vendor specific indicators. 6621 Special thanks also to people who have provided invaluable comments 6622 and inputs especially in resolving controversial issues: 6624 Glen Zorn, Yoshihiro Ohba, Marco Stura, and Pasi Eronen. 6626 Finally, we would like to thank the original authors of this 6627 document: 6629 Pat Calhoun, John Loughney, Jari Arkko, Erik Guttman and Glen Zorn. 6631 Their invaluable knowledge and experience has given us a robust and 6632 flexible AAA protocol that many people have seen great value in 6633 adopting. We greatly appreciate their support and stewardship for 6634 the continued improvements of Diameter as a protocol. We would also 6635 like to extend our gratitude to folks aside from the authors who have 6636 assisted and contributed to the original version of this document. 6637 Their efforts significantly contributed to the success of Diameter. 6639 Appendix B. NAPTR Example 6641 As an example, consider a client that wishes to resolve aaa:ex.com. 6642 The client performs a NAPTR query for that domain, and the following 6643 NAPTR records are returned: 6645 ;; order pref flags service regexp replacement 6646 IN NAPTR 50 50 "s" "AAA+D2S" "" _diameter._sctp.example.com 6647 IN NAPTR 100 50 "s" "AAA+D2T" "" _aaa._tcp.example.com 6649 This indicates that the server supports SCTP, and TCP, in that order. 6650 If the client supports over SCTP, SCTP will be used, targeted to a 6651 host determined by an SRV lookup of _diameter._sctp.ex.com. That 6652 lookup would return: 6654 ;; Priority Weight Port Target 6655 IN SRV 0 1 5060 server1.example.com 6656 IN SRV 0 2 5060 server2.example.com 6658 Appendix C. Duplicate Detection 6660 As described in Section 9.4, accounting record duplicate detection is 6661 based on session identifiers. Duplicates can appear for various 6662 reasons: 6664 o Failover to an alternate server. Where close to real-time 6665 performance is required, failover thresholds need to be kept low 6666 and this may lead to an increased likelihood of duplicates. 6667 Failover can occur at the client or within Diameter agents. 6669 o Failure of a client or agent after sending of a record from non- 6670 volatile memory, but prior to receipt of an application layer ACK 6671 and deletion of the record. record to be sent. This will result 6672 in retransmission of the record soon after the client or agent has 6673 rebooted. 6675 o Duplicates received from RADIUS gateways. Since the 6676 retransmission behavior of RADIUS is not defined within [RFC2865], 6677 the likelihood of duplication will vary according to the 6678 implementation. 6680 o Implementation problems and misconfiguration. 6682 The T flag is used as an indication of an application layer 6683 retransmission event, e.g., due to failover to an alternate server. 6684 It is defined only for request messages sent by Diameter clients or 6685 agents. For instance, after a reboot, a client may not know whether 6686 it has already tried to send the accounting records in its non- 6687 volatile memory before the reboot occurred. Diameter servers MAY use 6688 the T flag as an aid when processing requests and detecting duplicate 6689 messages. However, servers that do this MUST ensure that duplicates 6690 are found even when the first transmitted request arrives at the 6691 server after the retransmitted request. It can be used only in cases 6692 where no answer has been received from the Server for a request and 6693 the request is sent again, (e.g., due to a failover to an alternate 6694 peer, due to a recovered primary peer or due to a client re-sending a 6695 stored record from non-volatile memory such as after reboot of a 6696 client or agent). 6698 In some cases the Diameter accounting server can delay the duplicate 6699 detection and accounting record processing until a post-processing 6700 phase takes place. At that time records are likely to be sorted 6701 according to the included User-Name and duplicate elimination is easy 6702 in this case. In other situations it may be necessary to perform 6703 real-time duplicate detection, such as when credit limits are imposed 6704 or real-time fraud detection is desired. 6706 In general, only generation of duplicates due to failover or re- 6707 sending of records in non-volatile storage can be reliably detected 6708 by Diameter clients or agents. In such cases the Diameter client or 6709 agents can mark the message as possible duplicate by setting the T 6710 flag. Since the Diameter server is responsible for duplicate 6711 detection, it can choose to make use of the T flag or not, in order 6712 to optimize duplicate detection. Since the T flag does not affect 6713 interoperability, and may not be needed by some servers, generation 6714 of the T flag is REQUIRED for Diameter clients and agents, but MAY be 6715 implemented by Diameter servers. 6717 As an example, it can be usually be assumed that duplicates appear 6718 within a time window of longest recorded network partition or device 6719 fault, perhaps a day. So only records within this time window need 6720 to be looked at in the backward direction. Secondly, hashing 6721 techniques or other schemes, such as the use of the T flag in the 6722 received messages, may be used to eliminate the need to do a full 6723 search even in this set except for rare cases. 6725 The following is an example of how the T flag may be used by the 6726 server to detect duplicate requests. 6728 A Diameter server MAY check the T flag of the received message to 6729 determine if the record is a possible duplicate. If the T flag is 6730 set in the request message, the server searches for a duplicate 6731 within a configurable duplication time window backward and 6732 forward. This limits database searching to those records where 6733 the T flag is set. In a well run network, network partitions and 6734 device faults will presumably be rare events, so this approach 6735 represents a substantial optimization of the duplicate detection 6736 process. During failover, it is possible for the original record 6737 to be received after the T flag marked record, due to differences 6738 in network delays experienced along the path by the original and 6739 duplicate transmissions. The likelihood of this occurring 6740 increases as the failover interval is decreased. In order to be 6741 able to detect out of order duplicates, the Diameter server should 6742 use backward and forward time windows when performing duplicate 6743 checking for the T flag marked request. For example, in order to 6744 allow time for the original record to exit the network and be 6745 recorded by the accounting server, the Diameter server can delay 6746 processing records with the T flag set until a time period 6747 TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after the closing 6748 of the original transport connection. After this time period has 6749 expired, then it may check the T flag marked records against the 6750 database with relative assurance that the original records, if 6751 sent, have been received and recorded. 6753 Appendix D. Internationalized Domain Names 6755 To be compatible with the existing DNS infrastructure and simplify 6756 host and domain name comparison, Diameter identities (FQDNs) are 6757 represented in ASCII form. This allows the Diameter protocol to fall 6758 in-line with the DNS strategy of being transparent from the effects 6759 of Internationalized Domain Names (IDNs) by following the 6760 recommnedations in [RFC4690] and [RFC3490]. Applications that 6761 provide support for IDNs outside of the Diameter protocol but 6762 interacting with it SHOULD use the representation and conversion 6763 framework described in [RFC3490], [RFC3491] and [RFC3492]. 6765 Authors' Addresses 6767 Victor Fajardo (editor) 6768 Toshiba America Research 6769 One Telcordia Drive, 1S-222 6770 Piscataway, NJ 08854 6771 USA 6773 Phone: 1 908-421-1845 6774 Email: vfajardo@tari.toshiba.com 6776 Jari Arkko 6777 Ericsson Research 6778 02420 Jorvas 6779 Finland 6781 Phone: +358 40 5079256 6782 Email: jari.arkko@ericsson.com 6784 John Loughney 6785 Nokia Research Center 6786 955 Page Mill Road 6787 Palo Alto, CA 94304 6788 US 6790 Phone: 1-650-283-8068 6791 Email: john.loughney@nokia.com 6793 Glenn Zorn 6794 NetCube 6795 1310 East Thomas Street, #306 6796 Seattle, WA 98102 6797 US 6799 Phone: 6800 Email: glenzorn@comcast.net 6802 Full Copyright Statement 6804 Copyright (C) The IETF Trust (2008). 6806 This document is subject to the rights, licenses and restrictions 6807 contained in BCP 78, and except as set forth therein, the authors 6808 retain all their rights. 6810 This document and the information contained herein are provided on an 6811 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 6812 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 6813 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 6814 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 6815 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 6816 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 6818 Intellectual Property 6820 The IETF takes no position regarding the validity or scope of any 6821 Intellectual Property Rights or other rights that might be claimed to 6822 pertain to the implementation or use of the technology described in 6823 this document or the extent to which any license under such rights 6824 might or might not be available; nor does it represent that it has 6825 made any independent effort to identify any such rights. Information 6826 on the procedures with respect to rights in RFC documents can be 6827 found in BCP 78 and BCP 79. 6829 Copies of IPR disclosures made to the IETF Secretariat and any 6830 assurances of licenses to be made available, or the result of an 6831 attempt made to obtain a general license or permission for the use of 6832 such proprietary rights by implementers or users of this 6833 specification can be obtained from the IETF on-line IPR repository at 6834 http://www.ietf.org/ipr. 6836 The IETF invites any interested party to bring to its attention any 6837 copyrights, patents or patent applications, or other proprietary 6838 rights that may cover technology that may be required to implement 6839 this standard. Please address the information to the IETF at 6840 ietf-ipr@ietf.org. 6842 Acknowledgment 6844 Funding for the RFC Editor function is provided by the IETF 6845 Administrative Support Activity (IASA).