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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DIME V. Fajardo, Ed. 3 Internet-Draft Toshiba America Research 4 Intended status: Standards Track J. Arkko 5 Expires: May 19, 2008 Ericsson Research 6 J. Loughney 7 Nokia Research Center 8 November 16, 2007 10 Diameter Base Protocol 11 draft-ietf-dime-rfc3588bis-09.txt 13 Status of this Memo 15 By submitting this Internet-Draft, each author represents that any 16 applicable patent or other IPR claims of which he or she is aware 17 have been or will be disclosed, and any of which he or she becomes 18 aware will be disclosed, in accordance with Section 6 of BCP 79. 20 Internet-Drafts are working documents of the Internet Engineering 21 Task Force (IETF), its areas, and its working groups. Note that 22 other groups may also distribute working documents as Internet- 23 Drafts. 25 Internet-Drafts are draft documents valid for a maximum of six months 26 and may be updated, replaced, or obsoleted by other documents at any 27 time. It is inappropriate to use Internet-Drafts as reference 28 material or to cite them other than as "work in progress." 30 The list of current Internet-Drafts can be accessed at 31 http://www.ietf.org/ietf/1id-abstracts.txt. 33 The list of Internet-Draft Shadow Directories can be accessed at 34 http://www.ietf.org/shadow.html. 36 This Internet-Draft will expire on May 19, 2008. 38 Copyright Notice 40 Copyright (C) The IETF Trust (2007). 42 Abstract 44 The Diameter base protocol is intended to provide an Authentication, 45 Authorization and Accounting (AAA) framework for applications such as 46 network access or IP mobility. Diameter is also intended to work in 47 both local Authentication, Authorization & Accounting and roaming 48 situations. This document specifies the message format, transport, 49 error reporting, accounting and security services to be used by all 50 Diameter applications. The Diameter base application needs to be 51 supported by all Diameter implementations. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7 56 1.1. Diameter Protocol . . . . . . . . . . . . . . . . . . . . 10 57 1.1.1. Description of the Document Set . . . . . . . . . . 11 58 1.1.2. Conventions Used in This Document . . . . . . . . . 12 59 1.2. Approach to Extensibility . . . . . . . . . . . . . . . . 12 60 1.2.1. Defining New AVP Values . . . . . . . . . . . . . . 13 61 1.2.2. Creating New AVPs . . . . . . . . . . . . . . . . . 13 62 1.2.3. Creating New Commands . . . . . . . . . . . . . . . 13 63 1.2.4. Creating New Authentication Applications . . . . . . 13 64 1.2.5. Creating New Accounting Applications . . . . . . . . 14 65 1.2.6. Application Authentication Procedures . . . . . . . 15 66 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 16 67 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 22 68 2.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 23 69 2.1.1. SCTP Guidelines . . . . . . . . . . . . . . . . . . 24 70 2.2. Securing Diameter Messages . . . . . . . . . . . . . . . 24 71 2.3. Diameter Application Compliance . . . . . . . . . . . . . 24 72 2.4. Application Identifiers . . . . . . . . . . . . . . . . . 24 73 2.5. Connections vs. Sessions . . . . . . . . . . . . . . . . 25 74 2.6. Peer Table . . . . . . . . . . . . . . . . . . . . . . . 26 75 2.7. Routing Table . . . . . . . . . . . . . . . . . . . . . . 27 76 2.8. Role of Diameter Agents . . . . . . . . . . . . . . . . . 28 77 2.8.1. Relay Agents . . . . . . . . . . . . . . . . . . . . 30 78 2.8.2. Proxy Agents . . . . . . . . . . . . . . . . . . . . 31 79 2.8.3. Redirect Agents . . . . . . . . . . . . . . . . . . 31 80 2.8.4. Translation Agents . . . . . . . . . . . . . . . . . 32 81 2.9. Diameter Path Authorization . . . . . . . . . . . . . . . 33 82 3. Diameter Header . . . . . . . . . . . . . . . . . . . . . . . 35 83 3.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 38 84 3.2. Command Code ABNF specification . . . . . . . . . . . . . 38 85 3.3. Diameter Command Naming Conventions . . . . . . . . . . . 40 86 4. Diameter AVPs . . . . . . . . . . . . . . . . . . . . . . . . 42 87 4.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 42 88 4.1.1. Optional Header Elements . . . . . . . . . . . . . . 44 90 4.2. Basic AVP Data Formats . . . . . . . . . . . . . . . . . 44 91 4.3. Derived AVP Data Formats . . . . . . . . . . . . . . . . 46 92 4.4. Grouped AVP Values . . . . . . . . . . . . . . . . . . . 53 93 4.4.1. Example AVP with a Grouped Data type . . . . . . . . 54 94 4.5. Diameter Base Protocol AVPs . . . . . . . . . . . . . . . 57 95 5. Diameter Peers . . . . . . . . . . . . . . . . . . . . . . . 60 96 5.1. Peer Connections . . . . . . . . . . . . . . . . . . . . 60 97 5.2. Diameter Peer Discovery . . . . . . . . . . . . . . . . . 60 98 5.3. Capabilities Exchange . . . . . . . . . . . . . . . . . . 63 99 5.3.1. Capabilities-Exchange-Request . . . . . . . . . . . 64 100 5.3.2. Capabilities-Exchange-Answer . . . . . . . . . . . . 65 101 5.3.3. Vendor-Id AVP . . . . . . . . . . . . . . . . . . . 65 102 5.3.4. Firmware-Revision AVP . . . . . . . . . . . . . . . 65 103 5.3.5. Host-IP-Address AVP . . . . . . . . . . . . . . . . 66 104 5.3.6. Supported-Vendor-Id AVP . . . . . . . . . . . . . . 66 105 5.3.7. Product-Name AVP . . . . . . . . . . . . . . . . . . 66 106 5.4. Disconnecting Peer connections . . . . . . . . . . . . . 66 107 5.4.1. Disconnect-Peer-Request . . . . . . . . . . . . . . 67 108 5.4.2. Disconnect-Peer-Answer . . . . . . . . . . . . . . . 67 109 5.4.3. Disconnect-Cause AVP . . . . . . . . . . . . . . . . 67 110 5.5. Transport Failure Detection . . . . . . . . . . . . . . . 68 111 5.5.1. Device-Watchdog-Request . . . . . . . . . . . . . . 68 112 5.5.2. Device-Watchdog-Answer . . . . . . . . . . . . . . . 69 113 5.5.3. Transport Failure Algorithm . . . . . . . . . . . . 69 114 5.5.4. Failover and Failback Procedures . . . . . . . . . . 69 115 5.6. Peer State Machine . . . . . . . . . . . . . . . . . . . 70 116 5.6.1. Incoming connections . . . . . . . . . . . . . . . . 72 117 5.6.2. Events . . . . . . . . . . . . . . . . . . . . . . . 73 118 5.6.3. Actions . . . . . . . . . . . . . . . . . . . . . . 74 119 5.6.4. The Election Process . . . . . . . . . . . . . . . . 76 120 5.6.5. Capabilities Update . . . . . . . . . . . . . . . . 76 121 6. Diameter message processing . . . . . . . . . . . . . . . . . 77 122 6.1. Diameter Request Routing Overview . . . . . . . . . . . . 77 123 6.1.1. Originating a Request . . . . . . . . . . . . . . . 78 124 6.1.2. Sending a Request . . . . . . . . . . . . . . . . . 78 125 6.1.3. Receiving Requests . . . . . . . . . . . . . . . . . 79 126 6.1.4. Processing Local Requests . . . . . . . . . . . . . 79 127 6.1.5. Request Forwarding . . . . . . . . . . . . . . . . . 79 128 6.1.6. Request Routing . . . . . . . . . . . . . . . . . . 79 129 6.1.7. Predictive Loop Avoidance . . . . . . . . . . . . . 80 130 6.1.8. Redirecting requests . . . . . . . . . . . . . . . . 80 131 6.1.9. Relaying and Proxying Requests . . . . . . . . . . . 82 132 6.2. Diameter Answer Processing . . . . . . . . . . . . . . . 82 133 6.2.1. Processing received Answers . . . . . . . . . . . . 83 134 6.2.2. Relaying and Proxying Answers . . . . . . . . . . . 83 135 6.3. Origin-Host AVP . . . . . . . . . . . . . . . . . . . . . 84 136 6.4. Origin-Realm AVP . . . . . . . . . . . . . . . . . . . . 84 137 6.5. Destination-Host AVP . . . . . . . . . . . . . . . . . . 84 138 6.6. Destination-Realm AVP . . . . . . . . . . . . . . . . . . 85 139 6.7. Routing AVPs . . . . . . . . . . . . . . . . . . . . . . 85 140 6.7.1. Route-Record AVP . . . . . . . . . . . . . . . . . . 85 141 6.7.2. Proxy-Info AVP . . . . . . . . . . . . . . . . . . . 85 142 6.7.3. Proxy-Host AVP . . . . . . . . . . . . . . . . . . . 85 143 6.7.4. Proxy-State AVP . . . . . . . . . . . . . . . . . . 85 144 6.8. Auth-Application-Id AVP . . . . . . . . . . . . . . . . . 86 145 6.9. Acct-Application-Id AVP . . . . . . . . . . . . . . . . . 86 146 6.10. Inband-Security-Id AVP . . . . . . . . . . . . . . . . . 86 147 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 . . . . . . . . . . . . . . . 89 151 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 . . . . . . . . . . . . . . . . . . . 124 188 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 . . . . . . . . . . . . . . . . . . . 126 192 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 . . . . . . . . . . . . . . . . . . . 131 198 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 . . . . . . . . . . . . . . . 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) . . . . . . . . . 145 235 11.5. Diameter TCP/SCTP Port Numbers . . . . . . . . . . . . . 145 236 11.6. NAPTR Service Fields . . . . . . . . . . . . . . . . . . 145 237 12. Diameter protocol related configurable parameters . . . . . . 147 238 13. Security Considerations . . . . . . . . . . . . . . . . . . . 148 239 13.1. TLS Usage . . . . . . . . . . . . . . . . . . . . . . . . 148 240 13.2. Peer-to-Peer Considerations . . . . . . . . . . . . . . . 149 241 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 150 242 14.1. Normative References . . . . . . . . . . . . . . . . . . 150 243 14.2. Informational References . . . . . . . . . . . . . . . . 152 244 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 154 245 Appendix B. NAPTR Example . . . . . . . . . . . . . . . . . . . 155 246 Appendix C. Duplicate Detection . . . . . . . . . . . . . . . . 156 247 Appendix D. Internationalized Domain Names . . . . . . . . . . . 158 248 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 159 249 Intellectual Property and Copyright Statements . . . . . . . . . 160 251 1. Introduction 253 Authentication, Authorization and Accounting (AAA) protocols such as 254 TACACS [RFC1492] and RADIUS [RFC2865] were initially deployed to 255 provide dial-up PPP [RFC1661] and terminal server access. Over time, 256 with the growth of the Internet and the introduction of new access 257 technologies, including wireless, DSL, Mobile IP and Ethernet, 258 routers and network access servers (NAS) have increased in complexity 259 and density, putting new demands on 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 also 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 Auditability 325 RADIUS does not define data-object security mechanisms, and as a 326 result, untrusted proxies may modify attributes or even packet 327 headers without being detected. Combined with lack of support for 328 capabilities negotiation, this makes it very difficult to 329 determine what occurred in the event of a dispute. 331 Transition support 333 While Diameter does not share a common protocol data unit (PDU) 334 with RADIUS, considerable effort has been expended in enabling 335 backward compatibility with RADIUS, so that the two protocols may 336 be deployed in the same network. Initially, it is expected that 337 Diameter will be deployed within new network devices, as well as 338 within gateways enabling communication between legacy RADIUS 339 devices and Diameter agents. This capability, described in 341 [RFC4005], enables Diameter support to be added to legacy 342 networks, by addition of a gateway or server speaking both RADIUS 343 and Diameter. 345 In addition to addressing the above requirements, Diameter also 346 provides support for the following: 348 Capability negotiation 350 RADIUS does not support error messages, capability negotiation, or 351 a mandatory/non-mandatory flag for attributes. Since RADIUS 352 clients and servers are not aware of each other's capabilities, 353 they may not be able to successfully negotiate a mutually 354 acceptable service, or in some cases, even be aware of what 355 service has been implemented. Diameter includes support for error 356 handling (Section 7), capability negotiation (Section 5.3), and 357 mandatory/non-mandatory attribute-value pairs (AVPs) (Section 358 4.1). 360 Peer discovery and configuration 362 RADIUS implementations typically require that the name or address 363 of servers or clients be manually configured, along with the 364 corresponding shared secrets. This results in a large 365 administrative burden, and creates the temptation to reuse the 366 RADIUS shared secret, which can result in major security 367 vulnerabilities if the Request Authenticator is not globally and 368 temporally unique as required in [RFC2865]. Through DNS, Diameter 369 enables dynamic discovery of peers. Derivation of dynamic session 370 keys is enabled via transmission-level security. 372 Roaming support 374 The ROAMOPS WG provided a survey of roaming implementations 375 [RFC2194], detailed roaming requirements [RFC2477], defined the 376 Network Access Identifier (NAI)[RFC4282], and documented existing 377 implementations (and imitations) of RADIUS-based roaming 378 [RFC2607]. In order to improve scalability, [RFC2607] introduced 379 the concept of proxy chaining via an intermediate server, 380 facilitating roaming between providers. However, since RADIUS 381 does not provide explicit support for proxies, and lacks 382 auditability and transmission-level security features, RADIUS- 383 based roaming is vulnerable to attack from external parties as 384 well as susceptible to fraud perpetrated by the roaming partners 385 themselves. As a result, it is not suitable for wide-scale 386 deployment on the Internet [RFC2607]. By providing explicit 387 support for inter-domain roaming and message routing (Sections 2.7 388 and 6), and transmission-layer security (Section 13) features, 389 Diameter addresses these limitations and provides for secure and 390 scalable roaming. 392 In the decade since AAA protocols were first introduced, the 393 capabilities of Network Access Server (NAS) devices have increased 394 substantially. As a result, while Diameter is a considerably more 395 sophisticated protocol than RADIUS, it remains feasible to implement 396 within embedded devices, given improvements in processor speeds and 397 the widespread availability of embedded TLS implementations. 399 1.1. Diameter Protocol 401 The Diameter base protocol provides the following facilities: 403 o Delivery of AVPs (attribute value pairs) 405 o Capabilities negotiation 407 o Error notification 409 o Extensibility, through addition of new commands and AVPs (required 410 in [RFC2989]). 412 o Basic services necessary for applications, such as handling of 413 user sessions or accounting 415 All data delivered by the protocol is in the form of an AVP. Some of 416 these AVP values are used by the Diameter protocol itself, while 417 others deliver data associated with particular applications that 418 employ Diameter. AVPs may be added arbitrarily to Diameter messages, 419 so long as the requirements of a message's ABNF are met and the ABNF 420 allows for it. AVPs are used by the base Diameter protocol to 421 support the following required features: 423 o Transporting of user authentication information, for the purposes 424 of enabling the Diameter server to authenticate the user. 426 o Transporting of service specific authorization information, 427 between client and servers, allowing the peers to decide whether a 428 user's access request should be granted. 430 o Exchanging resource usage information, which MAY be used for 431 accounting purposes, capacity planning, etc. 433 o Relaying, proxying and redirecting of Diameter messages through a 434 server hierarchy. 436 The Diameter base protocol provides the minimum requirements needed 437 for a AAA protocol, as required by [RFC2989]. The base protocol may 438 be used by itself for accounting purposes only, or it may be used 439 with a Diameter application, such as Mobile IPv4 [RFC4004], or 440 network access [RFC4005]. It is also possible for the base protocol 441 to be extended for use in new applications, via the addition of new 442 commands or AVPs. At this time the focus of Diameter is network 443 access and accounting applications. A truly generic AAA protocol 444 used by many applications might provide functionality not provided by 445 Diameter. Therefore, it is imperative that the designers of new 446 applications understand their requirements before using Diameter. 447 See Section 2.4 for more information on Diameter applications. 449 Any node can initiate a request. In that sense, Diameter is a peer- 450 to-peer protocol. In this document, a Diameter Client is a device at 451 the edge of the network that performs access control, such as a 452 Network Access Server (NAS) or a Foreign Agent (FA). A Diameter 453 client generates Diameter messages to request authentication, 454 authorization, and accounting services for the user. A Diameter 455 agent is a node that does not authenticate and/or authorize messages 456 locally; agents include proxies, redirects and relay agents. A 457 Diameter server performs authentication and/or authorization of the 458 user. A Diameter node MAY act as an agent for certain requests while 459 acting as a server for others. 461 The Diameter protocol also supports server-initiated messages, such 462 as a request to abort service to a particular user. 464 1.1.1. Description of the Document Set 466 Currently, the Diameter specification consists of a base 467 specification (this document), Transport Profile [RFC3539] and 468 applications: Mobile IPv4 [RFC4004], NASREQ [RFC4005], Credit Control 469 [RFC4006], EAP [RFC4072] and SIP [RFC4740]. 471 The Transport Profile document [RFC3539] discusses transport layer 472 issues that arise with AAA protocols and recommendations on how to 473 overcome these issues. This document also defines the Diameter 474 failover algorithm and state machine. 476 The Mobile IPv4 [RFC4004] application defines a Diameter application 477 that allows a Diameter server to perform AAA functions for Mobile 478 IPv4 services to a mobile node. 480 The NASREQ [RFC4005] application defines a Diameter Application that 481 allows a Diameter server to be used in a PPP/SLIP Dial-Up and 482 Terminal Server Access environment. Consideration was given for 483 servers that need to perform protocol conversion between Diameter and 484 RADIUS. 486 The Credit Control [RFC4006] application defines a Diameter 487 Application that can be used to implement real-time credit-control 488 for a variety of end user services such as network access, SIP 489 services, messaging services, and download services. It provides a 490 general solution to real-time cost and credit-control. 492 The EAP [RFC4072] application defines a Diameter Application that can 493 be used to carry EAP packets between the Network Access Server (NAS) 494 working as an EAP authenticator and a back-end authentication server. 495 The Diameter EAP application is based on NASREQ and intended for a 496 similar environment. 498 The SIP [RFC4740] application defines a Diameter Application that 499 allows a Diameter client to request authentication and authorization 500 information to a Diameter server for SIP-based IP multimedia services 501 (see SIP [RFC3261]). 503 In summary, this document defines the base protocol specification for 504 AAA, which includes support for accounting. The applications 505 documents describe applications that use this base specification for 506 Authentication, Authorization and Accounting. 508 1.1.2. Conventions Used in This Document 510 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 511 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 512 document are to be interpreted as described in [RFC2119]. 514 1.2. Approach to Extensibility 516 The Diameter protocol is designed to be extensible, using several 517 mechanisms, including: 519 o Defining new AVP values 521 o Creating new AVPs 523 o Creating new commands 525 o Creating new authentication/authorization applications 527 o Creating new accounting applications 528 o Application authentication procedures 530 Reuse of existing AVP values, AVPs, commands and Diameter 531 applications are strongly recommended. Reuse simplifies 532 standardization and implementation and avoids potential 533 interoperability issues. 535 1.2.1. Defining New AVP Values 537 New applications should attempt to reuse AVPs defined in existing 538 applications when possible, as opposed to creating new AVPs. For 539 AVPs of type Enumerated, an application may require a new value to 540 communicate some service-specific information. 542 In order to allocate a new AVP value for a standards track AVP, a 543 request MUST be sent to IANA [RFC2434], along with an explanation of 544 the new AVP value. IANA considerations for AVP values are discussed 545 in Section 11.4. 547 1.2.2. Creating New AVPs 549 When no existing AVP can be reused, a new AVP should be created. The 550 new AVP being defined MUST use one of the data types listed in 551 Section 4.2 or 4.3. If an appropriate derived data type is already 552 defined, it MAY be used instead of the base data type. 554 In the event that a logical grouping of AVPs is necessary, and 555 multiple "groups" are possible in a given command, it is recommended 556 that a Grouped AVP be used (see Section 4.4). 558 In order to create a new standards track AVP, a request MUST be sent 559 to IANA with a reference to the specification that defines the AVP. 560 IANA considerations for AVPs are discussed in Section 11.1.1. 562 1.2.3. Creating New Commands 564 A new command should only be created when no suitable command can be 565 reused from an existing application. A new command MUST result in 566 the defintion of a new application. In order to create a new 567 command, a request MUST be sent to IANA. The IANA considerations for 568 commands are discussed in Section 11.2.1. 570 1.2.4. Creating New Authentication Applications 572 Every Diameter application specification MUST have an IANA assigned 573 Application Identifier (see Section 2.4 and Section 11.3). 575 Should a new Diameter usage scenario find itself unable to fit within 576 an existing application without requiring major changes to the 577 specification, it may be desirable to create a new Diameter 578 application. Major changes to an application include: 580 o Adding new AVPs to the command, which have the "M" bit set. 582 o Requiring a command that has a different number of round trips to 583 satisfy a request (e.g., application foo has a command that 584 requires one round trip, but new application bar has a command 585 that requires two round trips to complete). 587 o Adding support for an authentication method requiring definition 588 of new AVPs for use with the application. Since a new EAP 589 authentication method can be supported within Diameter without 590 requiring new AVPs, addition of EAP methods does not require the 591 creation of a new authentication application. 593 Creation of a new application should be viewed as a last resort. An 594 implementation MAY add arbitrary non-mandatory AVPs to any command 595 defined in an application, including vendor-specific AVPs without 596 needing to define a new application. Please refer to Section 11.1.1 597 for details. 599 In order to justify allocation of a new application identifier, 600 Diameter applications MUST define one Command Code, add new mandatory 601 AVPs to the ABNF or significantly change the state machine or 602 processing rules of an existing application. 604 The expected AVPs MUST be defined in an ABNF [RFC4234] grammar (see 605 Section 3.2). If the Diameter application has accounting 606 requirements, it MUST also specify the AVPs that are to be present in 607 the Diameter Accounting messages (see Section 9.3). However, just 608 because a new authentication application id is required, does not 609 imply that a new accounting application id is required. 611 When possible, a new Diameter application SHOULD reuse existing 612 Diameter AVPs, in order to avoid defining multiple AVPs that carry 613 similar information. 615 1.2.5. Creating New Accounting Applications 617 There are services that only require Diameter accounting. Such 618 services need to define the AVPs carried in the Accounting-Request 619 (ACR)/ Accounting-Answer (ACA) messages, but do not need to define 620 new command codes. An implementation MAY add arbitrary non-mandatory 621 AVPs (AVPs with the "M" bit not set) to any command defined in an 622 application, including vendor-specific AVPs, without needing to 623 define a new accounting application. Please refer to Section 11.1.1 624 for details. 626 Application Identifiers are still required for Diameter capability 627 exchange. Every Diameter accounting application specification MUST 628 have an IANA assigned Application Identifier (see Section 2.4) or a 629 vendor specific Application Identifier. 631 Every Diameter implementation MUST support accounting. Basic 632 accounting support is sufficient to handle any application that uses 633 the ACR/ACA commands defined in this document, as long as no new 634 mandatory AVPs are added. A mandatory AVP is defined as one which 635 has the "M" bit set when sent within an accounting command, 636 regardless of whether it is required or optional within the ABNF for 637 the accounting application. 639 The creation of a new accounting application should be viewed as a 640 last resort and MUST NOT be used unless a new command or additional 641 mechanisms (e.g., application defined state machine) is defined 642 within the application, or new mandatory AVPs are added to the ABNF. 644 Within an accounting command, setting the "M" bit implies that a 645 backend server (e.g., billing server) or the accounting server itself 646 MUST understand the AVP in order to compute a correct bill. If the 647 AVP is not relevant to the billing process, when the AVP is included 648 within an accounting command, it MUST NOT have the "M" bit set, even 649 if the "M" bit is set when the same AVP is used within other Diameter 650 commands (i.e., authentication/authorization commands). 652 A DIAMETER base accounting implementation MUST be configurable to 653 advertise supported accounting applications in order to prevent the 654 accounting server from accepting accounting requests for unbillable 655 services. The combination of the home domain and the accounting 656 application Id can be used in order to route the request to the 657 appropriate accounting server. 659 When possible, a new Diameter accounting application SHOULD attempt 660 to reuse existing AVPs, in order to avoid defining multiple AVPs that 661 carry similar information. 663 If the base accounting is used without any mandatory AVPs, new 664 commands or additional mechanisms (e.g., application defined state 665 machine), then the base protocol defined standard accounting 666 application Id (Section 2.4) MUST be used in ACR/ACA commands. 668 1.2.6. Application Authentication Procedures 670 When possible, applications SHOULD be designed such that new 671 authentication methods MAY be added without requiring changes to the 672 application. This MAY require that new AVP values be assigned to 673 represent the new authentication transform, or any other scheme that 674 produces similar results. When possible, authentication frameworks, 675 such as Extensible Authentication Protocol [RFC3748], SHOULD be used. 677 1.3. Terminology 679 AAA 681 Authentication, Authorization and Accounting. 683 Accounting 685 The act of collecting information on resource usage for the 686 purpose of capacity planning, auditing, billing or cost 687 allocation. 689 Accounting Record 691 An accounting record represents a summary of the resource 692 consumption of a user over the entire session. Accounting servers 693 creating the accounting record may do so by processing interim 694 accounting events or accounting events from several devices 695 serving the same user. 697 Authentication 699 The act of verifying the identity of an entity (subject). 701 Authorization 703 The act of determining whether a requesting entity (subject) will 704 be allowed access to a resource (object). 706 AVP 708 The Diameter protocol consists of a header followed by one or more 709 Attribute-Value-Pairs (AVPs). An AVP includes a header and is 710 used to encapsulate protocol-specific data (e.g., routing 711 information) as well as authentication, authorization or 712 accounting information. 714 Broker 716 A broker is a business term commonly used in AAA infrastructures. 717 A broker is either a relay, proxy or redirect agent, and MAY be 718 operated by roaming consortiums. Depending on the business model, 719 a broker may either choose to deploy relay agents or proxy agents. 721 Diameter Agent 723 A Diameter Agent is a Diameter node that provides either relay, 724 proxy, redirect or translation services. 726 Diameter Client 728 A Diameter Client is a device at the edge of the network that 729 performs access control. An example of a Diameter client is a 730 Network Access Server (NAS) or a Foreign Agent (FA). By its very 731 nature, a Diameter Client MUST support Diameter client 732 applications in addition to the base protocol. 734 Diameter Node 736 A Diameter node is a host process that implements the Diameter 737 protocol, and acts either as a Client, Agent or Server. 739 Diameter Peer 741 A Diameter Peer is a Diameter Node to which a given Diameter Node 742 has a direct transport connection. 744 Diameter Server 746 A Diameter Server is one that handles authentication, 747 authorization and accounting requests for a particular realm. By 748 its very nature, a Diameter Server MUST support Diameter server 749 applications in addition to the base protocol. 751 Downstream 753 Downstream is used to identify the direction of a particular 754 Diameter message from the home server towards the access device. 756 Home Realm 758 A Home Realm is the administrative domain with which the user 759 maintains an account relationship. 761 Home Server 763 A Diameter Server which serves the Home Realm. 765 Interim accounting 767 An interim accounting message provides a snapshot of usage during 768 a user's session. It is typically implemented in order to provide 769 for partial accounting of a user's session in the case of a device 770 reboot or other network problem prevents the reception of a 771 session summary message or session record. 773 Local Realm 775 A local realm is the administrative domain providing services to a 776 user. An administrative domain MAY act as a local realm for 777 certain users, while being a home realm for others. 779 Multi-session 781 A multi-session represents a logical linking of several sessions. 782 Multi-sessions are tracked by using the Acct-Multi-Session-Id. An 783 example of a multi-session would be a Multi-link PPP bundle. Each 784 leg of the bundle would be a session while the entire bundle would 785 be a multi-session. 787 Network Access Identifier 789 The Network Access Identifier, or NAI [RFC4282], is used in the 790 Diameter protocol to extract a user's identity and realm. The 791 identity is used to identify the user during authentication and/or 792 authorization, while the realm is used for message routing 793 purposes. 795 Proxy Agent or Proxy 797 In addition to forwarding requests and responses, proxies make 798 policy decisions relating to resource usage and provisioning. 799 This is typically accomplished by tracking the state of NAS 800 devices. While proxies typically do not respond to client 801 Requests prior to receiving a Response from the server, they may 802 originate Reject messages in cases where policies are violated. 803 As a result, proxies need to understand the semantics of the 804 messages passing through them, and may not support all Diameter 805 applications. 807 Realm 809 The string in the NAI that immediately follows the '@' character. 810 NAI realm names are required to be unique, and are piggybacked on 811 the administration of the DNS namespace. Diameter makes use of 812 the realm, also loosely referred to as domain, to determine 813 whether messages can be satisfied locally, or whether they must be 814 routed or redirected. In RADIUS, realm names are not necessarily 815 piggybacked on the DNS namespace but may be independent of it. 817 Real-time Accounting 819 Real-time accounting involves the processing of information on 820 resource usage within a defined time window. Time constraints are 821 typically imposed in order to limit financial risk. 823 Relay Agent or Relay 825 Relays forward requests and responses based on routing-related 826 AVPs and routing table entries. Since relays do not make policy 827 decisions, they do not examine or alter non-routing AVPs. As a 828 result, relays never originate messages, do not need to understand 829 the semantics of messages or non-routing AVPs, and are capable of 830 handling any Diameter application or message type. Since relays 831 make decisions based on information in routing AVPs and realm 832 forwarding tables they do not keep state on NAS resource usage or 833 sessions in progress. 835 Redirect Agent 837 Rather than forwarding requests and responses between clients and 838 servers, redirect agents refer clients to servers and allow them 839 to communicate directly. Since redirect agents do not sit in the 840 forwarding path, they do not alter any AVPs transiting between 841 client and server. Redirect agents do not originate messages and 842 are capable of handling any message type, although they may be 843 configured only to redirect messages of certain types, while 844 acting as relay or proxy agents for other types. As with proxy 845 agents, redirect agents do not keep state with respect to sessions 846 or NAS resources. 848 Roaming Relationships 850 Roaming relationships include relationships between companies and 851 ISPs, relationships among peer ISPs within a roaming consortium, 852 and relationships between an ISP and a roaming consortium. 854 Session 856 A session is a related progression of events devoted to a 857 particular activity. Each application SHOULD provide guidelines 858 as to when a session begins and ends. All Diameter packets with 859 the same Session-Identifier are considered to be part of the same 860 session. 862 Session state 864 A stateful agent is one that maintains session state information, 865 by keeping track of all authorized active sessions. Each 866 authorized session is bound to a particular service, and its state 867 is considered active either until it is notified otherwise, or by 868 expiration. 870 Sub-session 872 A sub-session represents a distinct service (e.g., QoS or data 873 characteristics) provided to a given session. These services may 874 happen concurrently (e.g., simultaneous voice and data transfer 875 during the same session) or serially. These changes in sessions 876 are tracked with the Accounting-Sub-Session-Id. 878 Transaction state 880 The Diameter protocol requires that agents maintain transaction 881 state, which is used for failover purposes. Transaction state 882 implies that upon forwarding a request, the Hop-by-Hop identifier 883 is saved; the field is replaced with a locally unique identifier, 884 which is restored to its original value when the corresponding 885 answer is received. The request's state is released upon receipt 886 of the answer. A stateless agent is one that only maintains 887 transaction state. 889 Translation Agent 891 A translation agent is a stateful Diameter node that performs 892 protocol translation between Diameter and another AAA protocol, 893 such as RADIUS. 895 Transport Connection 897 A transport connection is a TCP or SCTP connection existing 898 directly between two Diameter peers, otherwise known as a Peer- 899 to-Peer Connection. 901 Upstream 903 Upstream is used to identify the direction of a particular 904 Diameter message from the access device towards the home server. 906 User 908 The entity requesting or using some resource, in support of which 909 a Diameter client has generated a request. 911 2. Protocol Overview 913 The base Diameter protocol may be used by itself for accounting 914 applications, but for use in authentication and authorization it is 915 always extended for a particular application. Two Diameter 916 applications are defined by companion documents: NASREQ [RFC4005], 917 Mobile IPv4 [RFC4004]. These applications are introduced in this 918 document but specified elsewhere. Additional Diameter applications 919 MAY be defined in the future (see Section 11.3). 921 Diameter Clients MUST support the base protocol, which includes 922 accounting. In addition, they MUST fully support each Diameter 923 application that is needed to implement the client's service, e.g., 924 NASREQ and/or Mobile IPv4. A Diameter Client that does not support 925 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 926 Client" where X is the application which it supports, and not a 927 "Diameter Client". 929 Diameter Servers MUST support the base protocol, which includes 930 accounting. In addition, they MUST fully support each Diameter 931 application that is needed to implement the intended service, e.g., 932 NASREQ and/or Mobile IPv4. A Diameter Server that does not support 933 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 934 Server" where X is the application which it supports, and not a 935 "Diameter Server". 937 Diameter Relays and redirect agents are, by definition, protocol 938 transparent, and MUST transparently support the Diameter base 939 protocol, which includes accounting, and all Diameter applications. 941 Diameter proxies MUST support the base protocol, which includes 942 accounting. In addition, they MUST fully support each Diameter 943 application that is needed to implement proxied services, e.g., 944 NASREQ and/or Mobile IPv4. A Diameter proxy which does not support 945 also both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X 946 Proxy" where X is the application which it supports, and not a 947 "Diameter Proxy". 949 The base Diameter protocol concerns itself with capabilities 950 negotiation, how messages are sent and how peers may eventually be 951 abandoned. The base protocol also defines certain rules that apply 952 to all exchanges of messages between Diameter nodes. 954 Communication between Diameter peers begins with one peer sending a 955 message to another Diameter peer. The set of AVPs included in the 956 message is determined by a particular Diameter application. One AVP 957 that is included to reference a user's session is the Session-Id. 959 The initial request for authentication and/or authorization of a user 960 would include the Session-Id. The Session-Id is then used in all 961 subsequent messages to identify the user's session (see Section 8 for 962 more information). The communicating party may accept the request, 963 or reject it by returning an answer message with the Result-Code AVP 964 set to indicate an error occurred. The specific behavior of the 965 Diameter server or client receiving a request depends on the Diameter 966 application employed. 968 Session state (associated with a Session-Id) MUST be freed upon 969 receipt of the Session-Termination-Request, Session-Termination- 970 Answer, expiration of authorized service time in the Session-Timeout 971 AVP, and according to rules established in a particular Diameter 972 application. 974 2.1. Transport 976 Transport profile is defined in [RFC3539]. 978 The base Diameter protocol is run on port 3868 of both TCP [TCP] and 979 SCTP [RFC2960] transport protocols. 981 Diameter clients MUST support either TCP or SCTP, while agents and 982 servers MUST support both. Future versions of this specification MAY 983 mandate that clients support SCTP. 985 A Diameter node MAY initiate connections from a source port other 986 than the one that it declares it accepts incoming connections on, and 987 MUST be prepared to receive connections on port 3868. A given 988 Diameter instance of the peer state machine MUST NOT use more than 989 one transport connection to communicate with a given peer, unless 990 multiple instances exist on the peer in which case a separate 991 connection per process is allowed. 993 When no transport connection exists with a peer, an attempt to 994 connect SHOULD be periodically made. This behavior is handled via 995 the Tc timer, whose recommended value is 30 seconds. There are 996 certain exceptions to this rule, such as when a peer has terminated 997 the transport connection stating that it does not wish to 998 communicate. 1000 When connecting to a peer and either zero or more transports are 1001 specified, SCTP SHOULD be tried first, followed by TCP. See Section 1002 5.2 for more information on peer discovery. 1004 Diameter implementations SHOULD be able to interpret ICMP protocol 1005 port unreachable messages as explicit indications that the server is 1006 not reachable, subject to security policy on trusting such messages. 1008 Diameter implementations SHOULD also be able to interpret a reset 1009 from the transport and timed-out connection attempts. If Diameter 1010 receives data up from TCP that cannot be parsed or identified as a 1011 Diameter error made by the peer, the stream is compromised and cannot 1012 be recovered. The transport connection MUST be closed using a RESET 1013 call (send a TCP RST bit) or an SCTP ABORT message (graceful closure 1014 is compromised). 1016 2.1.1. SCTP Guidelines 1018 The following are guidelines for Diameter implementations that 1019 support SCTP: 1021 1. For interoperability: All Diameter nodes MUST be prepared to 1022 receive Diameter messages on any SCTP stream in the association. 1024 2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP 1025 streams available to the association to prevent head-of-the-line 1026 blocking. 1028 2.2. Securing Diameter Messages 1030 Connections between Diameter peers SHOULD be protected by TLS. All 1031 Diameter base protocol implementations MUST support the use of TLS. 1032 If desired, additional security measures that are transparent to and 1033 independent of Diameter, such as IPSec [RFC4301], can be deployed to 1034 secure connections between peers. The Diameter protocol SHOULD NOT 1035 be used without any security mechanism. 1037 2.3. Diameter Application Compliance 1039 Application Identifiers are advertised during the capabilities 1040 exchange phase (see Section 5.3). For a given application, 1041 advertising support of an application implies that the sender 1042 supports all command codes, and the AVPs specified in the associated 1043 ABNFs, described in the specification. 1045 An implementation MAY add arbitrary non-mandatory AVPs to any command 1046 defined in an application, including vendor-specific AVPs. Please 1047 refer to Section 11.1.1 for details. 1049 2.4. Application Identifiers 1051 Each Diameter application MUST have an IANA assigned Application 1052 Identifier (see Section 11.3). The base protocol does not require an 1053 Application Identifier since its support is mandatory. During the 1054 capabilities exchange, Diameter nodes inform their peers of locally 1055 supported applications. Furthermore, all Diameter messages contain 1056 an Application Identifier, which is used in the message forwarding 1057 process. 1059 The following Application Identifier values are defined: 1061 Diameter Common Messages 0 1062 NASREQ 1 [RFC4005] 1063 Mobile-IP 2 [RFC4004] 1064 Diameter Base Accounting 3 1065 Relay 0xffffffff 1067 Relay and redirect agents MUST advertise the Relay Application 1068 Identifier, while all other Diameter nodes MUST advertise locally 1069 supported applications. The receiver of a Capabilities Exchange 1070 message advertising Relay service MUST assume that the sender 1071 supports all current and future applications. 1073 Diameter relay and proxy agents are responsible for finding an 1074 upstream server that supports the application of a particular 1075 message. If none can be found, an error message is returned with the 1076 Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER. 1078 2.5. Connections vs. Sessions 1080 This section attempts to provide the reader with an understanding of 1081 the difference between connection and session, which are terms used 1082 extensively throughout this document. 1084 A connection is a transport level connection between two peers, used 1085 to send and receive Diameter messages. A session is a logical 1086 concept at the application layer, and is shared between an access 1087 device and a server, and is identified via the Session-Id AVP. 1089 +--------+ +-------+ +--------+ 1090 | Client | | Relay | | Server | 1091 +--------+ +-------+ +--------+ 1092 <----------> <----------> 1093 peer connection A peer connection B 1095 <-----------------------------> 1096 User session x 1098 Figure 1: Diameter connections and sessions 1100 In the example provided in Figure 1, peer connection A is established 1101 between the Client and its local Relay. Peer connection B is 1102 established between the Relay and the Server. User session X spans 1103 from the Client via the Relay to the Server. Each "user" of a 1104 service causes an auth request to be sent, with a unique session 1105 identifier. Once accepted by the server, both the client and the 1106 server are aware of the session. 1108 It is important to note that there is no relationship between a 1109 connection and a session, and that Diameter messages for multiple 1110 sessions are all multiplexed through a single connection. Also note 1111 that Diameter messages pertaining to the session, both application 1112 specific and those that are defined in this document such as ASR/ASA, 1113 RAR/RAA and STR/STA MUST carry the application identifier of the 1114 application. Diameter messages pertaining to peer connection 1115 establishment and maintenance such as CER/CEA, DWR/DWA and DPR/DPA 1116 MUST carry an application id of zero (0). 1118 2.6. Peer Table 1120 The Diameter Peer Table is used in message forwarding, and referenced 1121 by the Routing Table. A Peer Table entry contains the following 1122 fields: 1124 Host identity 1126 Following the conventions described for the DiameterIdentity 1127 derived AVP data format in Section 4.4. This field contains the 1128 contents of the Origin-Host (Section 6.3) AVP found in the CER or 1129 CEA message. 1131 StatusT 1133 This is the state of the peer entry, and MUST match one of the 1134 values listed in Section 5.6. 1136 Static or Dynamic 1138 Specifies whether a peer entry was statically configured, or 1139 dynamically discovered. 1141 Expiration time 1143 Specifies the time at which dynamically discovered peer table 1144 entries are to be either refreshed, or expired. 1146 TLS Enabled 1148 Specifies whether TLS is to be used when communicating with the 1149 peer. 1151 Additional security information, when needed (e.g., keys, 1152 certificates) 1154 2.7. Routing Table 1156 All Realm-Based routing lookups are performed against what is 1157 commonly known as the Routing Table (see Section 12). A Routing 1158 Table Entry contains the following fields: 1160 Realm Name 1162 This is the field that is typically used as a primary key in the 1163 routing table lookups. Note that some implementations perform 1164 their lookups based on longest-match-from-the-right on the realm 1165 rather than requiring an exact match. 1167 Application Identifier 1169 An application is identified by an application id. A route entry 1170 can have a different destination based on the application 1171 identification in the message header. This field MUST be used as 1172 a secondary key field in routing table lookups. 1174 Local Action 1176 The Local Action field is used to identify how a message should be 1177 treated. The following actions are supported: 1179 1. LOCAL - Diameter messages that resolve to a route entry with 1180 the Local Action set to Local can be satisfied locally, and do 1181 not need to be routed to another server. 1183 2. RELAY - All Diameter messages that fall within this category 1184 MUST be routed to a next hop server, without modifying any 1185 non-routing AVPs. See Section 6.1.9 for relaying guidelines 1187 3. PROXY - All Diameter messages that fall within this category 1188 MUST be routed to a next hop server. The local server MAY 1189 apply its local policies to the message by including new AVPs 1190 to the message prior to routing. See Section 6.1.9 for 1191 proxying guidelines. 1193 4. REDIRECT - Diameter messages that fall within this category 1194 MUST have the identity of the home Diameter server(s) 1195 appended, and returned to the sender of the message. See 1196 Section 6.1.9 for redirect guidelines. 1198 Server Identifier 1200 One or more servers the message is to be routed to. These servers 1201 MUST also be present in the Peer table. When the Local Action is 1202 set to RELAY or PROXY, this field contains the identity of the 1203 server(s) the message must be routed to. When the Local Action 1204 field is set to REDIRECT, this field contains the identity of one 1205 or more servers the message should be redirected to. 1207 Static or Dynamic 1209 Specifies whether a route entry was statically configured, or 1210 dynamically discovered. 1212 Expiration time 1214 Specifies the time which a dynamically discovered route table 1215 entry expires. 1217 It is important to note that Diameter agents MUST support at least 1218 one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation. 1219 Agents do not need to support all modes of operation in order to 1220 conform with the protocol specification, but MUST follow the protocol 1221 compliance guidelines in Section 2. Relay agents MUST NOT reorder 1222 AVPs, and proxies MUST NOT reorder AVPs. 1224 The routing table MAY include a default entry that MUST be used for 1225 any requests not matching any of the other entries. The routing 1226 table MAY consist of only such an entry. 1228 When a request is routed, the target server MUST have advertised the 1229 Application Identifier (see Section 2.4) for the given message, or 1230 have advertised itself as a relay or proxy agent. Otherwise, an 1231 error is returned with the Result-Code AVP set to 1232 DIAMETER_UNABLE_TO_DELIVER. 1234 2.8. Role of Diameter Agents 1236 In addition to client and servers, the Diameter protocol introduces 1237 relay, proxy, redirect, and translation agents, each of which is 1238 defined in Section 1.3. These Diameter agents are useful for several 1239 reasons: 1241 o They can distribute administration of systems to a configurable 1242 grouping, including the maintenance of security associations. 1244 o They can be used for concentration of requests from an number of 1245 co-located or distributed NAS equipment sets to a set of like user 1246 groups. 1248 o They can do value-added processing to the requests or responses. 1250 o They can be used for load balancing. 1252 o A complex network will have multiple authentication sources, they 1253 can sort requests and forward towards the correct target. 1255 The Diameter protocol requires that agents maintain transaction 1256 state, which is used for failover purposes. Transaction state 1257 implies that upon forwarding a request, its Hop-by-Hop identifier is 1258 saved; the field is replaced with a locally unique identifier, which 1259 is restored to its original value when the corresponding answer is 1260 received. The request's state is released upon receipt of the 1261 answer. A stateless agent is one that only maintains transaction 1262 state. 1264 The Proxy-Info AVP allows stateless agents to add local state to a 1265 Diameter request, with the guarantee that the same state will be 1266 present in the answer. However, the protocol's failover procedures 1267 require that agents maintain a copy of pending requests. 1269 A stateful agent is one that maintains session state information; by 1270 keeping track of all authorized active sessions. Each authorized 1271 session is bound to a particular service, and its state is considered 1272 active either until it is notified otherwise, or by expiration. Each 1273 authorized session has an expiration, which is communicated by 1274 Diameter servers via the Session-Timeout AVP. 1276 Maintaining session state MAY be useful in certain applications, such 1277 as: 1279 o Protocol translation (e.g., RADIUS <-> Diameter) 1281 o Limiting resources authorized to a particular user 1283 o Per user or transaction auditing 1285 A Diameter agent MAY act in a stateful manner for some requests and 1286 be stateless for others. A Diameter implementation MAY act as one 1287 type of agent for some requests, and as another type of agent for 1288 others. 1290 2.8.1. Relay Agents 1292 Relay Agents are Diameter agents that accept requests and route 1293 messages to other Diameter nodes based on information found in the 1294 messages (e.g., Destination-Realm). This routing decision is 1295 performed using a list of supported realms, and known peers. This is 1296 known as the Routing Table, as is defined further in Section 2.7. 1298 Relays MAY be used to aggregate requests from multiple Network Access 1299 Servers (NASes) within a common geographical area (POP). The use of 1300 Relays is advantageous since it eliminates the need for NASes to be 1301 configured with the necessary security information they would 1302 otherwise require to communicate with Diameter servers in other 1303 realms. Likewise, this reduces the configuration load on Diameter 1304 servers that would otherwise be necessary when NASes are added, 1305 changed or deleted. 1307 Relays modify Diameter messages by inserting and removing routing 1308 information, but do not modify any other portion of a message. 1309 Relays SHOULD NOT maintain session state but MUST maintain 1310 transaction state. 1312 +------+ ---------> +------+ ---------> +------+ 1313 | | 1. Request | | 2. Request | | 1314 | NAS | | DRL | | HMS | 1315 | | 4. Answer | | 3. Answer | | 1316 +------+ <--------- +------+ <--------- +------+ 1317 example.net example.net example.com 1319 Figure 2: Relaying of Diameter messages 1321 The example provided in Figure 2 depicts a request issued from NAS, 1322 which is an access device, for the user bob@example.com. Prior to 1323 issuing the request, NAS performs a Diameter route lookup, using 1324 "example.com" as the key, and determines that the message is to be 1325 relayed to DRL, which is a Diameter Relay. DRL performs the same 1326 route lookup as NAS, and relays the message to HMS, which is 1327 example.com's Home Diameter Server. HMS identifies that the request 1328 can be locally supported (via the realm), processes the 1329 authentication and/or authorization request, and replies with an 1330 answer, which is routed back to NAS using saved transaction state. 1332 Since Relays do not perform any application level processing, they 1333 provide relaying services for all Diameter applications, and 1334 therefore MUST advertise the Relay Application Identifier. 1336 2.8.2. Proxy Agents 1338 Similarly to relays, proxy agents route Diameter messages using the 1339 Diameter Routing Table. However, they differ since they modify 1340 messages to implement policy enforcement. This requires that proxies 1341 maintain the state of their downstream peers (e.g., access devices) 1342 to enforce resource usage, provide admission control, and 1343 provisioning. 1345 Proxies MAY be used in call control centers or access ISPs that 1346 provide outsourced connections, they can monitor the number and types 1347 of ports in use, and make allocation and admission decisions 1348 according to their configuration. 1350 Proxies that wish to limit resources MUST maintain session state. 1351 All proxies MUST maintain transaction state. 1353 Since enforcing policies requires an understanding of the service 1354 being provided, Proxies MUST only advertise the Diameter applications 1355 they support. 1357 2.8.3. Redirect Agents 1359 Redirect agents are useful in scenarios where the Diameter routing 1360 configuration needs to be centralized. An example is a redirect 1361 agent that provides services to all members of a consortium, but does 1362 not wish to be burdened with relaying all messages between realms. 1363 This scenario is advantageous since it does not require that the 1364 consortium provide routing updates to its members when changes are 1365 made to a member's infrastructure. 1367 Since redirect agents do not relay messages, and only return an 1368 answer with the information necessary for Diameter agents to 1369 communicate directly, they do not modify messages. Since redirect 1370 agents do not receive answer messages, they cannot maintain session 1371 state. Further, since redirect agents never relay requests, they are 1372 not required to maintain transaction state. 1374 The example provided in Figure 3 depicts a request issued from the 1375 access device, NAS, for the user bob@example.com. The message is 1376 forwarded by the NAS to its relay, DRL, which does not have a routing 1377 entry in its Diameter Routing Table for example.com. DRL has a 1378 default route configured to DRD, which is a redirect agent that 1379 returns a redirect notification to DRL, as well as HMS' contact 1380 information. Upon receipt of the redirect notification, DRL 1381 establishes a transport connection with HMS, if one doesn't already 1382 exist, and forwards the request to it. 1384 +------+ 1385 | | 1386 | DRD | 1387 | | 1388 +------+ 1389 ^ | 1390 2. Request | | 3. Redirection 1391 | | Notification 1392 | v 1393 +------+ ---------> +------+ ---------> +------+ 1394 | | 1. Request | | 4. Request | | 1395 | NAS | | DRL | | HMS | 1396 | | 6. Answer | | 5. Answer | | 1397 +------+ <--------- +------+ <--------- +------+ 1398 example.net example.net example.com 1400 Figure 3: Redirecting a Diameter Message 1402 Since redirect agents do not perform any application level 1403 processing, they provide relaying services for all Diameter 1404 applications, and therefore MUST advertise the Relay Application 1405 Identifier. 1407 2.8.4. Translation Agents 1409 A translation agent is a device that provides translation between two 1410 protocols (e.g., RADIUS<->Diameter, TACACS+<->Diameter). Translation 1411 agents are likely to be used as aggregation servers to communicate 1412 with a Diameter infrastructure, while allowing for the embedded 1413 systems to be migrated at a slower pace. 1415 Given that the Diameter protocol introduces the concept of long-lived 1416 authorized sessions, translation agents MUST be session stateful and 1417 MUST maintain transaction state. 1419 Translation of messages can only occur if the agent recognizes the 1420 application of a particular request, and therefore translation agents 1421 MUST only advertise their locally supported applications. 1423 +------+ ---------> +------+ ---------> +------+ 1424 | | RADIUS Request | | Diameter Request | | 1425 | NAS | | TLA | | HMS | 1426 | | RADIUS Answer | | Diameter Answer | | 1427 +------+ <--------- +------+ <--------- +------+ 1428 example.net example.net example.com 1429 Figure 4: Translation of RADIUS to Diameter 1431 2.9. Diameter Path Authorization 1433 As noted in Section 2.2, Diameter provides transmission level 1434 security for each connection using TLS. Therefore, each connection 1435 can be authenticated, replay and integrity protected. 1437 In addition to authenticating each connection, each connection as 1438 well as the entire session MUST also be authorized. Before 1439 initiating a connection, a Diameter Peer MUST check that its peers 1440 are authorized to act in their roles. For example, a Diameter peer 1441 may be authentic, but that does not mean that it is authorized to act 1442 as a Diameter Server advertising a set of Diameter applications. 1444 Prior to bringing up a connection, authorization checks are performed 1445 at each connection along the path. Diameter capabilities negotiation 1446 (CER/CEA) also MUST be carried out, in order to determine what 1447 Diameter applications are supported by each peer. Diameter sessions 1448 MUST be routed only through authorized nodes that have advertised 1449 support for the Diameter application required by the session. 1451 As noted in Section 6.1.9, a relay or proxy agent MUST append a 1452 Route-Record AVP to all requests forwarded. The AVP contains the 1453 identity of the peer the request was received from. 1455 The home Diameter server, prior to authorizing a session, MUST check 1456 the Route-Record AVPs to make sure that the route traversed by the 1457 request is acceptable. For example, administrators within the home 1458 realm may not wish to honor requests that have been routed through an 1459 untrusted realm. By authorizing a request, the home Diameter server 1460 is implicitly indicating its willingness to engage in the business 1461 transaction as specified by the contractual relationship between the 1462 server and the previous hop. A DIAMETER_AUTHORIZATION_REJECTED error 1463 message (see Section 7.1.5) is sent if the route traversed by the 1464 request is unacceptable. 1466 A home realm may also wish to check that each accounting request 1467 message corresponds to a Diameter response authorizing the session. 1468 Accounting requests without corresponding authorization responses 1469 SHOULD be subjected to further scrutiny, as should accounting 1470 requests indicating a difference between the requested and provided 1471 service. 1473 Forwarding of an authorization response is considered evidence of a 1474 willingness to take on financial risk relative to the session. A 1475 local realm may wish to limit this exposure, for example, by 1476 establishing credit limits for intermediate realms and refusing to 1477 accept responses which would violate those limits. By issuing an 1478 accounting request corresponding to the authorization response, the 1479 local realm implicitly indicates its agreement to provide the service 1480 indicated in the authorization response. If the service cannot be 1481 provided by the local realm, then a DIAMETER_UNABLE_TO_COMPLY error 1482 message MUST be sent within the accounting request; a Diameter client 1483 receiving an authorization response for a service that it cannot 1484 perform MUST NOT substitute an alternate service, and then send 1485 accounting requests for the alternate service instead. 1487 3. Diameter Header 1489 A summary of the Diameter header format is shown below. The fields 1490 are transmitted in network byte order. 1492 0 1 2 3 1493 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1495 | Version | Message Length | 1496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1497 | command flags | Command-Code | 1498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1499 | Application-ID | 1500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1501 | Hop-by-Hop Identifier | 1502 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1503 | End-to-End Identifier | 1504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1505 | AVPs ... 1506 +-+-+-+-+-+-+-+-+-+-+-+-+- 1508 Version 1510 This Version field MUST be set to 1 to indicate Diameter Version 1511 1. 1513 Message Length 1515 The Message Length field is three octets and indicates the length 1516 of the Diameter message including the header fields. 1518 Command Flags 1520 The Command Flags field is eight bits. The following bits are 1521 assigned: 1523 0 1 2 3 4 5 6 7 1524 +-+-+-+-+-+-+-+-+ 1525 |R P E T r r r r| 1526 +-+-+-+-+-+-+-+-+ 1528 R(equest) 1530 If set, the message is a request. If cleared, the message is 1531 an answer. 1533 P(roxiable) 1535 If set, the message MAY be proxied, relayed or redirected. If 1536 cleared, the message MUST be locally processed. 1538 E(rror) 1540 If set, the message contains a protocol error, and the message 1541 will not conform to the ABNF described for this command. 1542 Messages with the 'E' bit set are commonly referred to as error 1543 messages. This bit MUST NOT be set in request messages. See 1544 Section 7.2. 1546 T(Potentially re-transmitted message) 1548 This flag is set after a link failover procedure, to aid the 1549 removal of duplicate requests. It is set when resending 1550 requests not yet acknowledged, as an indication of a possible 1551 duplicate due to a link failure. This bit MUST be cleared when 1552 sending a request for the first time, otherwise the sender MUST 1553 set this flag. Diameter agents only need to be concerned about 1554 the number of requests they send based on a single received 1555 request; retransmissions by other entities need not be tracked. 1556 Diameter agents that receive a request with the T flag set, 1557 MUST keep the T flag set in the forwarded request. This flag 1558 MUST NOT be set if an error answer message (e.g., a protocol 1559 error) has been received for the earlier message. It can be 1560 set only in cases where no answer has been received from the 1561 server for a request and the request is sent again. This flag 1562 MUST NOT be set in answer messages. 1564 r(eserved) 1566 These flag bits are reserved for future use, and MUST be set to 1567 zero, and ignored by the receiver. 1569 Command-Code 1571 The Command-Code field is three octets, and is used in order to 1572 communicate the command associated with the message. The 24-bit 1573 address space is managed by IANA (see Section 11.2.1). 1575 Command-Code values 16,777,214 and 16,777,215 (hexadecimal values 1576 FFFFFE -FFFFFF) are reserved for experimental use (See Section 1577 11.3). 1579 Application-ID 1581 Application-ID is four octets and is used to identify to which 1582 application the message is applicable for. The application can be 1583 an authentication application, an accounting application or a 1584 vendor specific application. See Section 11.3 for the possible 1585 values that the application-id may use. 1587 The application-id in the header MUST be the same as what is 1588 contained in any relevant application-id AVPs contained in the 1589 message. 1591 Hop-by-Hop Identifier 1593 The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in 1594 network byte order) and aids in matching requests and replies. 1595 The sender MUST ensure that the Hop-by-Hop identifier in a request 1596 is unique on a given connection at any given time, and MAY attempt 1597 to ensure that the number is unique across reboots. The sender of 1598 an Answer message MUST ensure that the Hop-by-Hop Identifier field 1599 contains the same value that was found in the corresponding 1600 request. The Hop-by-Hop identifier is normally a monotonically 1601 increasing number, whose start value was randomly generated. An 1602 answer message that is received with an unknown Hop-by-Hop 1603 Identifier MUST be discarded. 1605 End-to-End Identifier 1607 The End-to-End Identifier is an unsigned 32-bit integer field (in 1608 network byte order) and is used to detect duplicate messages. 1609 Upon reboot implementations MAY set the high order 12 bits to 1610 contain the low order 12 bits of current time, and the low order 1611 20 bits to a random value. Senders of request messages MUST 1612 insert a unique identifier on each message. The identifier MUST 1613 remain locally unique for a period of at least 4 minutes, even 1614 across reboots. The originator of an Answer message MUST ensure 1615 that the End-to-End Identifier field contains the same value that 1616 was found in the corresponding request. The End-to-End Identifier 1617 MUST NOT be modified by Diameter agents of any kind. The 1618 combination of the Origin-Host (see Section 6.3) and this field is 1619 used to detect duplicates. Duplicate requests SHOULD cause the 1620 same answer to be transmitted (modulo the hop-by-hop Identifier 1621 field and any routing AVPs that may be present), and MUST NOT 1622 affect any state that was set when the original request was 1623 processed. Duplicate answer messages that are to be locally 1624 consumed (see Section 6.2) SHOULD be silently discarded. 1626 AVPs 1628 AVPs are a method of encapsulating information relevant to the 1629 Diameter message. See Section 4 for more information on AVPs. 1631 3.1. Command Codes 1633 Each command Request/Answer pair is assigned a command code, and the 1634 sub-type (i.e., request or answer) is identified via the 'R' bit in 1635 the Command Flags field of the Diameter header. 1637 Every Diameter message MUST contain a command code in its header's 1638 Command-Code field, which is used to determine the action that is to 1639 be taken for a particular message. The following Command Codes are 1640 defined in the Diameter base protocol: 1642 Command-Name Abbrev. Code Reference 1643 -------------------------------------------------------- 1644 Abort-Session-Request ASR 274 8.5.1 1645 Abort-Session-Answer ASA 274 8.5.2 1646 Accounting-Request ACR 271 9.7.1 1647 Accounting-Answer ACA 271 9.7.2 1648 Capabilities-Exchange- CER 257 5.3.1 1649 Request 1650 Capabilities-Exchange- CEA 257 5.3.2 1651 Answer 1652 Device-Watchdog-Request DWR 280 5.5.1 1653 Device-Watchdog-Answer DWA 280 5.5.2 1654 Disconnect-Peer-Request DPR 282 5.4.1 1655 Disconnect-Peer-Answer DPA 282 5.4.2 1656 Re-Auth-Request RAR 258 8.3.1 1657 Re-Auth-Answer RAA 258 8.3.2 1658 Session-Termination- STR 275 8.4.1 1659 Request 1660 Session-Termination- STA 275 8.4.2 1661 Answer 1663 3.2. Command Code ABNF specification 1665 Every Command Code defined MUST include a corresponding ABNF 1666 specification, which is used to define the AVPs that MUST or MAY be 1667 present. The following format is used in the definition: 1669 command-def = command-name "::=" diameter-message 1671 command-name = diameter-name 1672 diameter-name = ALPHA *(ALPHA / DIGIT / "-") 1674 diameter-message = header [ *fixed] [ *required] [ *optional] 1676 header = "<" "Diameter Header:" command-id 1677 [r-bit] [p-bit] [e-bit] [application-id] ">" 1679 application-id = 1*DIGIT 1681 command-id = 1*DIGIT 1682 ; The Command Code assigned to the command 1684 r-bit = ", REQ" 1685 ; If present, the 'R' bit in the Command 1686 ; Flags is set, indicating that the message 1687 ; is a request, as opposed to an answer. 1689 p-bit = ", PXY" 1690 ; If present, the 'P' bit in the Command 1691 ; Flags is set, indicating that the message 1692 ; is proxiable. 1694 e-bit = ", ERR" 1695 ; If present, the 'E' bit in the Command 1696 ; Flags is set, indicating that the answer 1697 ; message contains a Result-Code AVP in 1698 ; the "protocol error" class. 1700 fixed = [qual] "<" avp-spec ">" 1701 ; Defines the fixed position of an AVP 1703 required = [qual] "{" avp-spec "}" 1704 ; The AVP MUST be present and can appear 1705 ; anywhere in the message. 1707 optional = [qual] "[" avp-name "]" 1708 ; The avp-name in the 'optional' rule cannot 1709 ; evaluate to any AVP Name which is included 1710 ; in a fixed or required rule. The AVP can 1711 ; appear anywhere in the message. 1713 qual = [min] "*" [max] 1714 ; See ABNF conventions, RFC 4234 Section 6.6. 1715 ; The absence of any qualifiers depends on 1716 ; whether it precedes a fixed, required, or 1717 ; optional rule. If a fixed or required rule has 1718 ; no qualifier, then exactly one such AVP MUST 1719 ; be present. If an optional rule has no 1720 ; qualifier, then 0 or 1 such AVP may be 1721 ; present. If an optional rule has a qualifier, 1722 ; then the value of min MUST be 0 if present. 1723 ; 1724 ; NOTE: "[" and "]" have a different meaning 1725 ; than in ABNF (see the optional rule, above). 1726 ; These braces cannot be used to express 1727 ; optional fixed rules (such as an optional 1728 ; ICV at the end). To do this, the convention 1729 ; is '0*1fixed'. 1731 min = 1*DIGIT 1732 ; The minimum number of times the element may 1733 ; be present. The default value is zero. 1735 max = 1*DIGIT 1736 ; The maximum number of times the element may 1737 ; be present. The default value is infinity. A 1738 ; value of zero implies the AVP MUST NOT be 1739 ; present. 1741 avp-spec = diameter-name 1742 ; The avp-spec has to be an AVP Name, defined 1743 ; in the base or extended Diameter 1744 ; specifications. 1746 avp-name = avp-spec / "AVP" 1747 ; The string "AVP" stands for *any* arbitrary AVP 1748 ; Name, not otherwise listed in that command code 1749 ; definition. 1751 The following is a definition of a fictitious command code: 1753 Example-Request ::= < Diameter Header: 9999999, REQ, PXY > 1754 { User-Name } 1755 * { Origin-Host } 1756 * [ AVP 1758 3.3. Diameter Command Naming Conventions 1760 Diameter command names typically includes one or more English words 1761 followed by the verb Request or Answer. Each English word is 1762 delimited by a hyphen. A three-letter acronym for both the request 1763 and answer is also normally provided. 1765 An example is a message set used to terminate a session. The command 1766 name is Session-Terminate-Request and Session-Terminate-Answer, while 1767 the acronyms are STR and STA, respectively. 1769 Both the request and the answer for a given command share the same 1770 command code. The request is identified by the R(equest) bit in the 1771 Diameter header set to one (1), to ask that a particular action be 1772 performed, such as authorizing a user or terminating a session. Once 1773 the receiver has completed the request it issues the corresponding 1774 answer, which includes a result code that communicates one of the 1775 following: 1777 o The request was successful 1779 o The request failed 1781 o An additional request must be sent to provide information the peer 1782 requires prior to returning a successful or failed answer. 1784 o The receiver could not process the request, but provides 1785 information about a Diameter peer that is able to satisfy the 1786 request, known as redirect. 1788 Additional information, encoded within AVPs, MAY also be included in 1789 answer messages. 1791 4. Diameter AVPs 1793 Diameter AVPs carry specific authentication, accounting, 1794 authorization and routing information as well as configuration 1795 details for the request and reply. 1797 Some AVPs MAY be listed more than once. The effect of such an AVP is 1798 specific, and is specified in each case by the AVP description. 1800 Each AVP of type OctetString MUST be padded to align on a 32-bit 1801 boundary, while other AVP types align naturally. A number of zero- 1802 valued bytes are added to the end of the AVP Data field till a word 1803 boundary is reached. The length of the padding is not reflected in 1804 the AVP Length field. 1806 4.1. AVP Header 1808 The fields in the AVP header MUST be sent in network byte order. The 1809 format of the header is: 1811 0 1 2 3 1812 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 1813 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1814 | AVP Code | 1815 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1816 |V M r r r r r r| AVP Length | 1817 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1818 | Vendor-ID (opt) | 1819 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1820 | Data ... 1821 +-+-+-+-+-+-+-+-+ 1823 AVP Code 1825 The AVP Code, combined with the Vendor-Id field, identifies the 1826 attribute uniquely. AVP numbers 1 through 255 are reserved for 1827 backward compatibility with RADIUS, without setting the Vendor-Id 1828 field. AVP numbers 256 and above are used for Diameter, which are 1829 allocated by IANA (see Section 11.1). 1831 AVP Flags 1833 The AVP Flags field informs the receiver how each attribute must 1834 be handled. The 'r' (reserved) bits are unused and SHOULD be set 1835 to 0. Note that subsequent Diameter applications MAY define 1836 additional bits within the AVP Header, and an unrecognized bit 1837 SHOULD be considered an error. 1839 The 'M' Bit, known as the Mandatory bit, indicates whether support 1840 of the AVP is required. If an AVP with the 'M' bit set is 1841 received by a Diameter client, server, proxy, or translation agent 1842 and either the AVP or its value is unrecognized, the message MUST 1843 be rejected. An exception to this rule applies when the AVP is 1844 embedded within a Grouped AVP. See Section 4.4 for details. 1845 Diameter Relay and redirect agents MUST NOT reject messages with 1846 unrecognized AVPs. 1848 The 'M' bit MUST be set according to the rules defined for the AVP 1849 containing it. In order to preserve interoperability, a Diameter 1850 implementation MUST be able to exclude from a Diameter message any 1851 Mandatory AVP which is neither defined in the base Diameter 1852 protocol nor in any of the Diameter Application specifications 1853 governing the message in which it appears. It MAY do this in one 1854 of the following ways: 1856 1. If a message is rejected because it contains a Mandatory AVP 1857 which is neither defined in the base Diameter standard nor in 1858 any of the Diameter Application specifications governing the 1859 message in which it appears, the implementation may resend the 1860 message without the AVP, possibly inserting additional 1861 standard AVPs instead. 1863 2. A configuration option may be provided on a system wide, per 1864 peer, or per realm basis that would allow/prevent particular 1865 Mandatory AVPs to be sent. Thus an administrator could change 1866 the configuration to avoid interoperability problems. 1868 Diameter implementations are required to support all Mandatory 1869 AVPs which are allowed by the message's formal syntax and defined 1870 either in the base Diameter standard or in one of the Diameter 1871 Application specifications governing the message. 1873 AVPs with the 'M' bit cleared are informational only and a 1874 receiver that receives a message with such an AVP that is not 1875 supported, or whose value is not supported, MAY simply ignore the 1876 AVP. 1878 The 'V' bit, known as the Vendor-Specific bit, indicates whether 1879 the optional Vendor-ID field is present in the AVP header. When 1880 set the AVP Code belongs to the specific vendor code address 1881 space. 1883 Unless otherwise noted, AVPs will have the following default AVP 1884 Flags field settings: 1886 The 'M' bit MUST be set. The 'V' bit MUST NOT be set. 1888 AVP Length 1890 The AVP Length field is three octets, and indicates the number of 1891 octets in this AVP including the AVP Code, AVP Length, AVP Flags, 1892 Vendor-ID field (if present) and the AVP data. If a message is 1893 received with an invalid attribute length, the message SHOULD be 1894 rejected. 1896 4.1.1. Optional Header Elements 1898 The AVP Header contains one optional field. This field is only 1899 present if the respective bit-flag is enabled. 1901 Vendor-ID 1903 The Vendor-ID field is present if the 'V' bit is set in the AVP 1904 Flags field. The optional four-octet Vendor-ID field contains the 1905 IANA assigned "SMI Network Management Private Enterprise Codes" 1906 [RFC3232] value, encoded in network byte order. Any vendor 1907 wishing to implement a vendor-specific Diameter AVP MUST use their 1908 own Vendor-ID along with their privately managed AVP address 1909 space, guaranteeing that they will not collide with any other 1910 vendor's vendor-specific AVP(s), nor with future IETF 1911 applications. 1913 A vendor ID value of zero (0) corresponds to the IETF adopted AVP 1914 values, as managed by the IANA. Since the absence of the vendor 1915 ID field implies that the AVP in question is not vendor specific, 1916 implementations MUST NOT use the zero (0) vendor ID. 1918 4.2. Basic AVP Data Formats 1920 The Data field is zero or more octets and contains information 1921 specific to the Attribute. The format and length of the Data field 1922 is determined by the AVP Code and AVP Length fields. The format of 1923 the Data field MUST be one of the following base data types or a data 1924 type derived from the base data types. In the event that a new Basic 1925 AVP Data Format is needed, a new version of this RFC must be created. 1927 OctetString 1929 The data contains arbitrary data of variable length. Unless 1930 otherwise noted, the AVP Length field MUST be set to at least 8 1931 (12 if the 'V' bit is enabled). AVP Values of this type that are 1932 not a multiple of four-octets in length is followed by the 1933 necessary padding so that the next AVP (if any) will start on a 1934 32-bit boundary. 1936 Integer32 1938 32 bit signed value, in network byte order. The AVP Length field 1939 MUST be set to 12 (16 if the 'V' bit is enabled). 1941 Integer64 1943 64 bit signed value, in network byte order. The AVP Length field 1944 MUST be set to 16 (20 if the 'V' bit is enabled). 1946 Unsigned32 1948 32 bit unsigned value, in network byte order. The AVP Length 1949 field MUST be set to 12 (16 if the 'V' bit is enabled). 1951 Unsigned64 1953 64 bit unsigned value, in network byte order. The AVP Length 1954 field MUST be set to 16 (20 if the 'V' bit is enabled). 1956 Float32 1958 This represents floating point values of single precision as 1959 described by [FLOATPOINT]. The 32-bit value is transmitted in 1960 network byte order. The AVP Length field MUST be set to 12 (16 if 1961 the 'V' bit is enabled). 1963 Float64 1965 This represents floating point values of double precision as 1966 described by [FLOATPOINT]. The 64-bit value is transmitted in 1967 network byte order. The AVP Length field MUST be set to 16 (20 if 1968 the 'V' bit is enabled). 1970 Grouped 1972 The Data field is specified as a sequence of AVPs. Each of these 1973 AVPs follows - in the order in which they are specified - 1974 including their headers and padding. The AVP Length field is set 1975 to 8 (12 if the 'V' bit is enabled) plus the total length of all 1976 included AVPs, including their headers and padding. Thus the AVP 1977 length field of an AVP of type Grouped is always a multiple of 4. 1979 4.3. Derived AVP Data Formats 1981 In addition to using the Basic AVP Data Formats, applications may 1982 define data formats derived from the Basic AVP Data Formats. An 1983 application that defines new AVP Derived Data Formats MUST include 1984 them in a section entitled "AVP Derived Data Formats", using the same 1985 format as the definitions below. Each new definition must be either 1986 defined or listed with a reference to the RFC that defines the 1987 format. 1989 The below AVP Derived Data Formats are commonly used by applications. 1991 Address 1993 The Address format is derived from the OctetString AVP Base 1994 Format. It is a discriminated union, representing, for example a 1995 32-bit (IPv4) [IPV4] or 128-bit (IPv6) [RFC4291] address, most 1996 significant octet first. The first two octets of the Address AVP 1997 represents the AddressType, which contains an Address Family 1998 defined in [IANAADFAM]. The AddressType is used to discriminate 1999 the content and format of the remaining octets. 2001 Time 2003 The Time format is derived from the OctetString AVP Base Format. 2004 The string MUST contain four octets, in the same format as the 2005 first four bytes are in the NTP timestamp format. The NTP 2006 Timestamp format is defined in chapter 3 of [RFC4330]. 2008 This represents the number of seconds since 0h on 1 January 1900 2009 with respect to the Coordinated Universal Time (UTC). 2011 On 6h 28m 16s UTC, 7 February 2036 the time value will overflow. 2012 SNTP [RFC4330] describes a procedure to extend the time to 2104. 2013 This procedure MUST be supported by all DIAMETER nodes. 2015 UTF8String 2017 The UTF8String format is derived from the OctetString AVP Base 2018 Format. This is a human readable string represented using the 2019 ISO/IEC IS 10646-1 character set, encoded as an OctetString using 2020 the UTF-8 [RFC3629] transformation format described in RFC 3629. 2022 Since additional code points are added by amendments to the 10646 2023 standard from time to time, implementations MUST be prepared to 2024 encounter any code point from 0x00000001 to 0x7fffffff. Byte 2025 sequences that do not correspond to the valid encoding of a code 2026 point into UTF-8 charset or are outside this range are prohibited. 2028 The use of control codes SHOULD be avoided. When it is necessary 2029 to represent a new line, the control code sequence CR LF SHOULD be 2030 used. 2032 The use of leading or trailing white space SHOULD be avoided. 2034 For code points not directly supported by user interface hardware 2035 or software, an alternative means of entry and display, such as 2036 hexadecimal, MAY be provided. 2038 For information encoded in 7-bit US-ASCII, the UTF-8 charset is 2039 identical to the US-ASCII charset. 2041 UTF-8 may require multiple bytes to represent a single character / 2042 code point; thus the length of an UTF8String in octets may be 2043 different from the number of characters encoded. 2045 Note that the AVP Length field of an UTF8String is measured in 2046 octets, not characters. 2048 DiameterIdentity 2050 The DiameterIdentity format is derived from the OctetString AVP 2051 Base Format. 2053 DiameterIdentity = FQDN 2055 DiameterIdentity value is used to uniquely identify a Diameter 2056 node for purposes of duplicate connection and routing loop 2057 detection. 2059 The contents of the string MUST be the FQDN of the Diameter node. 2060 If multiple Diameter nodes run on the same host, each Diameter 2061 node MUST be assigned a unique DiameterIdentity. If a Diameter 2062 node can be identified by several FQDNs, a single FQDN should be 2063 picked at startup, and used as the only DiameterIdentity for that 2064 node, whatever the connection it is sent on. Note that in this 2065 document, DiameterIdentity is in ASCII form in order to be 2066 compatible with existing DNS infrastructure. See Appendix D for 2067 interactions between the Diameter protocol and Internationalized 2068 Domain Name (IDNs). 2070 DiameterURI 2072 The DiameterURI MUST follow the Uniform Resource Identifiers (URI) 2073 syntax [RFC3986] rules specified below: 2075 "aaa://" FQDN [ port ] [ transport ] [ protocol ] 2077 ; No transport security 2079 "aaas://" FQDN [ port ] [ transport ] [ protocol ] 2081 ; Transport security used 2083 FQDN = Fully Qualified Host Name 2085 port = ":" 1*DIGIT 2087 ; One of the ports used to listen for 2088 ; incoming connections. 2089 ; If absent, 2090 ; the default Diameter port (3868) is 2091 ; assumed. 2093 transport = ";transport=" transport-protocol 2095 ; One of the transports used to listen 2096 ; for incoming connections. If absent, 2097 ; the default SCTP [RFC2960] protocol is 2098 ; assumed. UDP MUST NOT be used when 2099 ; the aaa-protocol field is set to 2100 ; diameter. 2102 transport-protocol = ( "tcp" / "sctp" / "udp" ) 2104 protocol = ";protocol=" aaa-protocol 2106 ; If absent, the default AAA protocol 2107 ; is diameter. 2109 aaa-protocol = ( "diameter" / "radius" / "tacacs+" ) 2111 The following are examples of valid Diameter host identities: 2113 aaa://host.example.com;transport=tcp 2114 aaa://host.example.com:6666;transport=tcp 2115 aaa://host.example.com;protocol=diameter 2116 aaa://host.example.com:6666;protocol=diameter 2117 aaa://host.example.com:6666;transport=tcp;protocol=diameter 2118 aaa://host.example.com:1813;transport=udp;protocol=radius 2120 Enumerated 2122 Enumerated is derived from the Integer32 AVP Base Format. The 2123 definition contains a list of valid values and their 2124 interpretation and is described in the Diameter application 2125 introducing the AVP. 2127 IPFilterRule 2129 The IPFilterRule format is derived from the OctetString AVP Base 2130 Format. It uses the ASCII charset. Packets may be filtered based 2131 on the following information that is associated with it: 2133 Direction (in or out) 2134 Source and destination IP address (possibly masked) 2135 Protocol 2136 Source and destination port (lists or ranges) 2137 TCP flags 2138 IP fragment flag 2139 IP options 2140 ICMP types 2142 Rules for the appropriate direction are evaluated in order, with 2143 the first matched rule terminating the evaluation. Each packet is 2144 evaluated once. If no rule matches, the packet is dropped if the 2145 last rule evaluated was a permit, and passed if the last rule was 2146 a deny. 2148 IPFilterRule filters MUST follow the format: 2150 action dir proto from src to dst [options] 2152 action permit - Allow packets that match the rule. 2153 deny - Drop packets that match the rule. 2155 dir "in" is from the terminal, "out" is to the 2156 terminal. 2158 proto An IP protocol specified by number. The "ip" 2159 keyword means any protocol will match. 2161 src and dst
[ports] 2163 The
may be specified as: 2164 ipno An IPv4 or IPv6 number in dotted- 2165 quad or canonical IPv6 form. Only 2166 this exact IP number will match the 2167 rule. 2168 ipno/bits An IP number as above with a mask 2169 width of the form 1.2.3.4/24. In 2170 this case, all IP numbers from 2171 1.2.3.0 to 1.2.3.255 will match. 2172 The bit width MUST be valid for the 2173 IP version and the IP number MUST 2174 NOT have bits set beyond the mask. 2175 For a match to occur, the same IP 2176 version must be present in the 2177 packet that was used in describing 2178 the IP address. To test for a 2179 particular IP version, the bits part 2180 can be set to zero. The keyword 2181 "any" is 0.0.0.0/0 or the IPv6 2182 equivalent. The keyword "assigned" 2183 is the address or set of addresses 2184 assigned to the terminal. For IPv4, 2185 a typical first rule is often "deny 2186 in ip! assigned" 2188 The sense of the match can be inverted by 2189 preceding an address with the not modifier (!), 2190 causing all other addresses to be matched 2191 instead. This does not affect the selection of 2192 port numbers. 2194 With the TCP, UDP and SCTP protocols, optional 2195 ports may be specified as: 2197 {port/port-port}[,ports[,...]] 2199 The '-' notation specifies a range of ports 2200 (including boundaries). 2202 Fragmented packets that have a non-zero offset 2203 (i.e., not the first fragment) will never match 2204 a rule that has one or more port 2205 specifications. See the frag option for 2206 details on matching fragmented packets. 2208 options: 2209 frag Match if the packet is a fragment and this is not 2210 the first fragment of the datagram. frag may not 2211 be used in conjunction with either tcpflags or 2212 TCP/UDP port specifications. 2214 ipoptions spec 2215 Match if the IP header contains the comma 2216 separated list of options specified in spec. The 2217 supported IP options are: 2219 ssrr (strict source route), lsrr (loose source 2220 route), rr (record packet route) and ts 2221 (timestamp). The absence of a particular option 2222 may be denoted with a '!'. 2224 tcpoptions spec 2225 Match if the TCP header contains the comma 2226 separated list of options specified in spec. The 2227 supported TCP options are: 2229 mss (maximum segment size), window (tcp window 2230 advertisement), sack (selective ack), ts (rfc1323 2231 timestamp) and cc (rfc1644 t/tcp connection 2232 count). The absence of a particular option may 2233 be denoted with a '!'. 2235 established 2236 TCP packets only. Match packets that have the RST 2237 or ACK bits set. 2239 setup TCP packets only. Match packets that have the SYN 2240 bit set but no ACK bit. 2242 tcpflags spec 2243 TCP packets only. Match if the TCP header 2244 contains the comma separated list of flags 2245 specified in spec. The supported TCP flags are: 2247 fin, syn, rst, psh, ack and urg. The absence of a 2248 particular flag may be denoted with a '!'. A rule 2249 that contains a tcpflags specification can never 2250 match a fragmented packet that has a non-zero 2251 offset. See the frag option for details on 2252 matching fragmented packets. 2254 icmptypes types 2255 ICMP packets only. Match if the ICMP type is in 2256 the list types. The list may be specified as any 2257 combination of ranges or individual types 2258 separated by commas. Both the numeric values and 2259 the symbolic values listed below can be used. The 2260 supported ICMP types are: 2262 echo reply (0), destination unreachable (3), 2263 source quench (4), redirect (5), echo request 2264 (8), router advertisement (9), router 2265 solicitation (10), time-to-live exceeded (11), IP 2266 header bad (12), timestamp request (13), 2267 timestamp reply (14), information request (15), 2268 information reply (16), address mask request (17) 2269 and address mask reply (18). 2271 There is one kind of packet that the access device MUST always 2272 discard, that is an IP fragment with a fragment offset of one. 2273 This is a valid packet, but it only has one use, to try to 2274 circumvent firewalls. 2276 An access device that is unable to interpret or apply a deny rule 2277 MUST terminate the session. An access device that is unable to 2278 interpret or apply a permit rule MAY apply a more restrictive 2279 rule. An access device MAY apply deny rules of its own before the 2280 supplied rules, for example to protect the access device owner's 2281 infrastructure. 2283 The rule syntax is a modified subset of ipfw(8) from FreeBSD, and 2284 the ipfw.c code may provide a useful base for implementations. 2286 4.4. Grouped AVP Values 2288 The Diameter protocol allows AVP values of type 'Grouped.' This 2289 implies that the Data field is actually a sequence of AVPs. It is 2290 possible to include an AVP with a Grouped type within a Grouped type, 2291 that is, to nest them. AVPs within an AVP of type Grouped have the 2292 same padding requirements as non-Grouped AVPs, as defined in Section 2293 4. 2295 The AVP Code numbering space of all AVPs included in a Grouped AVP is 2296 the same as for non-grouped AVPs. Receivers of a Grouped AVP that 2297 does not have the 'M' (mandatory) bit set and one or more of the 2298 encapsulated AVPs within the group has the 'M' (mandatory) bit set 2299 MAY simply be ignored if the Grouped AVP itself is unrecognized. The 2300 rule applies even if the encapsulated AVP with its 'M' (mandatory) 2301 bit set is further encapsulated within other sub-groups; i.e. other 2302 Grouped AVPs embedded within the Grouped AVP. 2304 Every Grouped AVP defined MUST include a corresponding grammar, using 2305 ABNF [RFC4234] (with modifications), as defined below. 2307 grouped-avp-def = name "::=" avp 2309 name-fmt = ALPHA *(ALPHA / DIGIT / "-") 2311 name = name-fmt 2312 ; The name has to be the name of an AVP, 2313 ; defined in the base or extended Diameter 2314 ; specifications. 2316 avp = header [ *fixed] [ *required] [ *optional] 2317 [ *fixed] 2319 header = "<" "AVP-Header:" avpcode [vendor] ">" 2321 avpcode = 1*DIGIT 2322 ; The AVP Code assigned to the Grouped AVP 2324 vendor = 1*DIGIT 2325 ; The Vendor-ID assigned to the Grouped AVP. 2326 ; If absent, the default value of zero is 2327 ; used. 2329 4.4.1. Example AVP with a Grouped Data type 2331 The Example-AVP (AVP Code 999999) is of type Grouped and is used to 2332 clarify how Grouped AVP values work. The Grouped Data field has the 2333 following ABNF grammar: 2335 Example-AVP ::= < AVP Header: 999999 > 2336 { Origin-Host } 2337 1*{ Session-Id } 2338 *[ AVP ] 2340 An Example-AVP with Grouped Data follows. 2342 The Origin-Host AVP is required (Section 6.3). In this case: 2344 Origin-Host = "example.com". 2346 One or more Session-Ids must follow. Here there are two: 2348 Session-Id = 2349 "grump.example.com:33041;23432;893;0AF3B81" 2351 Session-Id = 2352 "grump.example.com:33054;23561;2358;0AF3B82" 2354 optional AVPs included are 2356 Recovery-Policy = 2357 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35 2358 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5 2359 c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd 2360 f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a 2361 cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119 2362 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c 2363 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92 2365 Futuristic-Acct-Record = 2366 fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0 2367 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8 2368 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c 2369 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067 2370 d3427475e49968f841 2372 The data for the optional AVPs is represented in hex since the format 2373 of these AVPs is neither known at the time of definition of the 2374 Example-AVP group, nor (likely) at the time when the example instance 2375 of this AVP is interpreted - except by Diameter implementations which 2376 support the same set of AVPs. The encoding example illustrates how 2377 padding is used and how length fields are calculated. Also note that 2378 AVPs may be present in the Grouped AVP value which the receiver 2379 cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record 2380 AVPs). The length of the Example-AVP is the sum of all the length of 2381 the member AVPs including their padding plus the Example-AVP header 2382 size. 2384 This AVP would be encoded as follows: 2386 0 1 2 3 4 5 6 7 2387 +-------+-------+-------+-------+-------+-------+-------+-------+ 2388 0 | Example AVP Header (AVP Code = 999999), Length = 496 | 2389 +-------+-------+-------+-------+-------+-------+-------+-------+ 2390 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 | 2391 +-------+-------+-------+-------+-------+-------+-------+-------+ 2392 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' | 2393 +-------+-------+-------+-------+-------+-------+-------+-------+ 2394 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header | 2395 +-------+-------+-------+-------+-------+-------+-------+-------+ 2396 32 | (AVP Code = 263), Length = 49 | 'g' | 'r' | 'u' | 'm' | 2397 +-------+-------+-------+-------+-------+-------+-------+-------+ 2398 . . . 2399 +-------+-------+-------+-------+-------+-------+-------+-------+ 2400 72 | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding|Padding| 2401 +-------+-------+-------+-------+-------+-------+-------+-------+ 2402 80 | Session-Id AVP Header (AVP Code = 263), Length = 50 | 2403 +-------+-------+-------+-------+-------+-------+-------+-------+ 2404 88 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' | 2405 +-------+-------+-------+-------+-------+-------+-------+-------+ 2406 . . . 2407 +-------+-------+-------+-------+-------+-------+-------+-------+ 2408 120| '5' | '8' | ';' | '0' | 'A' | 'F' | '3' | 'B' | 2409 +-------+-------+-------+-------+-------+-------+-------+-------+ 2410 128| '8' | '2' |Padding|Padding| Recovery-Policy Header (AVP | 2411 +-------+-------+-------+-------+-------+-------+-------+-------+ 2412 136| Code = 8341), Length = 223 | 0x21 | 0x63 | 0xbc | 0x1d | 2413 +-------+-------+-------+-------+-------+-------+-------+-------+ 2414 144| 0x0a | 0xd8 | 0x23 | 0x71 | 0xf6 | 0xbc | 0x09 | 0x48 | 2415 +-------+-------+-------+-------+-------+-------+-------+-------+ 2416 . . . 2417 +-------+-------+-------+-------+-------+-------+-------+-------+ 2418 352| 0x8c | 0x7f | 0x92 |Padding| Futuristic-Acct-Record Header | 2419 +-------+-------+-------+-------+-------+-------+-------+-------+ 2420 328|(AVP Code = 15930),Length = 137| 0xfe | 0x19 | 0xda | 0x58 | 2421 +-------+-------+-------+-------+-------+-------+-------+-------+ 2422 336| 0x02 | 0xac | 0xd9 | 0x8b | 0x07 | 0xa5 | 0xb8 | 0xc6 | 2423 +-------+-------+-------+-------+-------+-------+-------+-------+ 2424 . . . 2425 +-------+-------+-------+-------+-------+-------+-------+-------+ 2426 488| 0xe4 | 0x99 | 0x68 | 0xf8 | 0x41 |Padding|Padding|Padding| 2427 +-------+-------+-------+-------+-------+-------+-------+-------+ 2429 4.5. Diameter Base Protocol AVPs 2431 The following table describes the Diameter AVPs defined in the base 2432 protocol, their AVP Code values, types, possible flag values. 2434 Due to space constraints, the short form DiamIdent is used to 2435 represent DiameterIdentity. 2437 +---------------------+ 2438 | AVP Flag rules | 2439 |----+-----+----+-----| 2440 AVP Section | | |SHLD| MUST| 2441 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT| 2442 -----------------------------------------|----+-----+----+-----| 2443 Acct- 85 9.8.2 Unsigned32 | M | | | V | 2444 Interim-Interval | | | | | 2445 Accounting- 483 9.8.7 Enumerated | M | | | V | 2446 Realtime-Required | | | | | 2447 Acct- 50 9.8.5 UTF8String | M | | | V | 2448 Multi-Session-Id | | | | | 2449 Accounting- 485 9.8.3 Unsigned32 | M | | | V | 2450 Record-Number | | | | | 2451 Accounting- 480 9.8.1 Enumerated | M | | | V | 2452 Record-Type | | | | | 2453 Accounting- 44 9.8.4 OctetString| M | | | V | 2454 Session-Id | | | | | 2455 Accounting- 287 9.8.6 Unsigned64 | M | | | V | 2456 Sub-Session-Id | | | | | 2457 Acct- 259 6.9 Unsigned32 | M | | | V | 2458 Application-Id | | | | | 2459 Auth- 258 6.8 Unsigned32 | M | | | V | 2460 Application-Id | | | | | 2461 Auth-Request- 274 8.7 Enumerated | M | | | V | 2462 Type | | | | | 2463 Authorization- 291 8.9 Unsigned32 | M | | | V | 2464 Lifetime | | | | | 2465 Auth-Grace- 276 8.10 Unsigned32 | M | | | V | 2466 Period | | | | | 2467 Auth-Session- 277 8.11 Enumerated | M | | | V | 2468 State | | | | | 2469 Re-Auth-Request- 285 8.12 Enumerated | M | | | V | 2470 Type | | | | | 2471 Class 25 8.20 OctetString| M | | | V | 2472 Destination-Host 293 6.5 DiamIdent | M | | | V | 2473 Destination- 283 6.6 DiamIdent | M | | | V | 2474 Realm | | | | | 2475 Disconnect-Cause 273 5.4.3 Enumerated | M | | | V | 2476 Error-Message 281 7.3 UTF8String | | | | V,M | 2477 Error-Reporting- 294 7.4 DiamIdent | | | | V,M | 2478 Host | | | | | 2479 Event-Timestamp 55 8.21 Time | M | | | V | 2480 Experimental- 297 7.6 Grouped | M | | | V | 2481 Result | | | | | 2482 -----------------------------------------|----+-----+----+-----| 2483 +---------------------+ 2484 | AVP Flag rules | 2485 |----+-----+----+-----| 2486 AVP Section | | |SHLD| MUST| 2487 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT| 2488 -----------------------------------------|----+-----+----+-----| 2489 Experimental- 298 7.7 Unsigned32 | M | | | V | 2490 Result-Code | | | | | 2491 Failed-AVP 279 7.5 Grouped | M | | | V | 2492 Firmware- 267 5.3.4 Unsigned32 | | | | V,M | 2493 Revision | | | | | 2494 Host-IP-Address 257 5.3.5 Address | M | | | V | 2495 Inband-Security | M | | | V | 2496 -Id 299 6.10 Unsigned32 | | | | | 2497 Multi-Round- 272 8.19 Unsigned32 | M | | | V | 2498 Time-Out | | | | | 2499 Origin-Host 264 6.3 DiamIdent | M | | | V | 2500 Origin-Realm 296 6.4 DiamIdent | M | | | V | 2501 Origin-State-Id 278 8.16 Unsigned32 | M | | | V | 2502 Product-Name 269 5.3.7 UTF8String | | | | V,M | 2503 Proxy-Host 280 6.7.3 DiamIdent | M | | | V | 2504 Proxy-Info 284 6.7.2 Grouped | M | | | V | 2505 Proxy-State 33 6.7.4 OctetString| M | | | V | 2506 Redirect-Host 292 6.12 DiamURI | M | | | V | 2507 Redirect-Host- 261 6.13 Enumerated | M | | | V | 2508 Usage | | | | | 2509 Redirect-Max- 262 6.14 Unsigned32 | M | | | V | 2510 Cache-Time | | | | | 2511 Result-Code 268 7.1 Unsigned32 | M | | | V | 2512 Route-Record 282 6.7.1 DiamIdent | M | | | V | 2513 Session-Id 263 8.8 UTF8String | M | | | V | 2514 Session-Timeout 27 8.13 Unsigned32 | M | | | V | 2515 Session-Binding 270 8.17 Unsigned32 | M | | | V | 2516 Session-Server- 271 8.18 Enumerated | M | | | V | 2517 Failover | | | | | 2518 Supported- 265 5.3.6 Unsigned32 | M | | | V | 2519 Vendor-Id | | | | | 2520 Termination- 295 8.15 Enumerated | M | | | V | 2521 Cause | | | | | 2522 User-Name 1 8.14 UTF8String | M | | | V | 2523 Vendor-Id 266 5.3.3 Unsigned32 | M | | | V | 2524 Vendor-Specific- 260 6.11 Grouped | M | | | V | 2525 Application-Id | | | | | 2526 -----------------------------------------|----+-----+----+-----| 2528 5. Diameter Peers 2530 This section describes how Diameter nodes establish connections and 2531 communicate with peers. 2533 5.1. Peer Connections 2535 Although a Diameter node may have many possible peers that it is able 2536 to communicate with, it may not be economical to have an established 2537 connection to all of them. At a minimum, a Diameter node SHOULD have 2538 an established connection with two peers per realm, known as the 2539 primary and secondary peers. Of course, a node MAY have additional 2540 connections, if it is deemed necessary. Typically, all messages for 2541 a realm are sent to the primary peer, but in the event that failover 2542 procedures are invoked, any pending requests are sent to the 2543 secondary peer. However, implementations are free to load balance 2544 requests between a set of peers. 2546 Note that a given peer MAY act as a primary for a given realm, while 2547 acting as a secondary for another realm. 2549 When a peer is deemed suspect, which could occur for various reasons, 2550 including not receiving a DWA within an allotted timeframe, no new 2551 requests should be forwarded to the peer, but failover procedures are 2552 invoked. When an active peer is moved to this mode, additional 2553 connections SHOULD be established to ensure that the necessary number 2554 of active connections exists. 2556 There are two ways that a peer is removed from the suspect peer list: 2558 1. The peer is no longer reachable, causing the transport connection 2559 to be shutdown. The peer is moved to the closed state. 2561 2. Three watchdog messages are exchanged with accepted round trip 2562 times, and the connection to the peer is considered stabilized. 2564 In the event the peer being removed is either the primary or 2565 secondary, an alternate peer SHOULD replace the deleted peer, and 2566 assume the role of either primary or secondary. 2568 5.2. Diameter Peer Discovery 2570 Allowing for dynamic Diameter agent discovery will make it possible 2571 for simpler and more robust deployment of Diameter services. In 2572 order to promote interoperable implementations of Diameter peer 2573 discovery, the following mechanisms are described. These are based 2574 on existing IETF standards. The first option (manual configuration) 2575 MUST be supported by all DIAMETER nodes, while the latter option 2576 (DNS) MAY be supported. 2578 There are two cases where Diameter peer discovery may be performed. 2579 The first is when a Diameter client needs to discover a first-hop 2580 Diameter agent. The second case is when a Diameter agent needs to 2581 discover another agent - for further handling of a Diameter 2582 operation. In both cases, the following 'search order' is 2583 recommended: 2585 1. The Diameter implementation consults its list of static 2586 (manually) configured Diameter agent locations. These will be 2587 used if they exist and respond. 2589 2. The Diameter implementation performs a NAPTR query for a server 2590 in a particular realm. The Diameter implementation has to know 2591 in advance which realm to look for a Diameter agent in. This 2592 could be deduced, for example, from the 'realm' in a NAI that a 2593 Diameter implementation needed to perform a Diameter operation 2594 on. 2596 * The services relevant for the task of transport protocol 2597 selection are those with NAPTR service fields with values 2598 "AAA+D2x", where x is a letter that corresponds to a transport 2599 protocol supported by the domain. This specification defines 2600 D2T for TCP and D2S for SCTP. We also establish an IANA 2601 registry for NAPTR service name to transport protocol 2602 mappings. 2604 These NAPTR records provide a mapping from a domain, to the 2605 SRV record for contacting a server with the specific transport 2606 protocol in the NAPTR services field. The resource record 2607 will contain an empty regular expression and a replacement 2608 value, which is the SRV record for that particular transport 2609 protocol. If the server supports multiple transport 2610 protocols, there will be multiple NAPTR records, each with a 2611 different service value. As per [RFC3403], the client 2612 discards any records whose services fields are not applicable. 2613 For the purposes of this specification, several rules are 2614 defined. 2616 * A client MUST discard any service fields that identify a 2617 resolution service whose value is not "D2X", for values of X 2618 that indicate transport protocols supported by the client. 2619 The NAPTR processing as described in [RFC3403] will result in 2620 discovery of the most preferred transport protocol of the 2621 server that is supported by the client, as well as an SRV 2622 record for the server. 2624 The domain suffixes in the NAPTR replacement field SHOULD 2625 match the domain of the original query. 2627 3. If no NAPTR records are found, the requester queries for those 2628 address records for the destination address, 2629 '_diameter._sctp'.realm or '_diameter._tcp'.realm. Address 2630 records include A RR's, AAAA RR's or other similar records, 2631 chosen according to the requestor's network protocol 2632 capabilities. If the DNS server returns no address records, the 2633 requestor gives up. 2635 If the server is using a site certificate, the domain name in the 2636 query and the domain name in the replacement field MUST both be 2637 valid based on the site certificate handed out by the server in 2638 the TLS or IKE exchange. Similarly, the domain name in the SRV 2639 query and the domain name in the target in the SRV record MUST 2640 both be valid based on the same site certificate. Otherwise, an 2641 attacker could modify the DNS records to contain replacement 2642 values in a different domain, and the client could not validate 2643 that this was the desired behavior, or the result of an attack 2645 Also, the Diameter Peer MUST check to make sure that the 2646 discovered peers are authorized to act in its role. 2647 Authentication via IKE or TLS, or validation of DNS RRs via 2648 DNSSEC is not sufficient to conclude this. For example, a web 2649 server may have obtained a valid TLS certificate, and secured RRs 2650 may be included in the DNS, but this does not imply that it is 2651 authorized to act as a Diameter Server. 2653 Authorization can be achieved for example, by configuration of a 2654 Diameter Server CA. Alternatively this can be achieved by 2655 definition of OIDs within TLS or IKE certificates so as to 2656 signify Diameter Server authorization. 2658 A dynamically discovered peer causes an entry in the Peer Table (see 2659 Section 2.6) to be created. Note that entries created via DNS MUST 2660 expire (or be refreshed) within the DNS TTL. If a peer is discovered 2661 outside of the local realm, a routing table entry (see Section 2.7) 2662 for the peer's realm is created. The routing table entry's 2663 expiration MUST match the peer's expiration value. 2665 5.3. Capabilities Exchange 2667 When two Diameter peers establish a transport connection, they MUST 2668 exchange the Capabilities Exchange messages, as specified in the peer 2669 state machine (see Section 5.6). This message allows the discovery 2670 of a peer's identity and its capabilities (protocol version number, 2671 supported Diameter applications, security mechanisms, etc.) 2673 The receiver only issues commands to its peers that have advertised 2674 support for the Diameter application that defines the command. A 2675 Diameter node MUST cache the supported applications in order to 2676 ensure that unrecognized commands and/or AVPs are not unnecessarily 2677 sent to a peer. 2679 A receiver of a Capabilities-Exchange-Req (CER) message that does not 2680 have any applications in common with the sender MUST return a 2681 Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to 2682 DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport 2683 layer connection. Note that receiving a CER or CEA from a peer 2684 advertising itself as a Relay (see Section 2.4) MUST be interpreted 2685 as having common applications with the peer. 2687 The receiver of the Capabilities-Exchange-Request (CER) MUST 2688 determine common applications by computing the intersection of its 2689 own set of supported application identifiers against all of the 2690 application indentifier AVPs (Auth-Application-Id, 2691 Acct-Application-Id and Vendor-Specific-Application-Id) present in 2692 the CER. The value of the Vendor-Id AVP in the Vendor-Specific- 2693 Application-Id MUST NOT be used during computation. The sender of 2694 the Capabilities-Exchange-Answer (CEA) SHOULD include all of its 2695 supported applications as a hint to the receiver regarding all of its 2696 application capabilities. 2698 Similarly, a receiver of a Capabilities-Exchange-Req (CER) message 2699 that does not have any security mechanisms in common with the sender 2700 MUST return a Capabilities-Exchange-Answer (CEA) with the Result-Code 2701 AVP set to DIAMETER_NO_COMMON_SECURITY, and SHOULD disconnect the 2702 transport layer connection. 2704 CERs received from unknown peers MAY be silently discarded, or a CEA 2705 MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER. 2706 In both cases, the transport connection is closed. If the local 2707 policy permits receiving CERs from unknown hosts, a successful CEA 2708 MAY be returned. If a CER from an unknown peer is answered with a 2709 successful CEA, the lifetime of the peer entry is equal to the 2710 lifetime of the transport connection. In case of a transport 2711 failure, all the pending transactions destined to the unknown peer 2712 can be discarded. 2714 The CER and CEA messages MUST NOT be proxied, redirected or relayed. 2716 Since the CER/CEA messages cannot be proxied, it is still possible 2717 that an upstream agent receives a message for which it has no 2718 available peers to handle the application that corresponds to the 2719 Command-Code. In such instances, the 'E' bit is set in the answer 2720 message (see Section 7.) with the Result-Code AVP set to 2721 DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action 2722 (e.g., re-routing request to an alternate peer). 2724 With the exception of the Capabilities-Exchange-Request message, a 2725 message of type Request that includes the Auth-Application-Id or 2726 Acct-Application-Id AVPs, or a message with an application-specific 2727 command code, MAY only be forwarded to a host that has explicitly 2728 advertised support for the application (or has advertised the Relay 2729 Application Identifier). 2731 5.3.1. Capabilities-Exchange-Request 2733 The Capabilities-Exchange-Request (CER), indicated by the Command- 2734 Code set to 257 and the Command Flags' 'R' bit set, is sent to 2735 exchange local capabilities. Upon detection of a transport failure, 2736 this message MUST NOT be sent to an alternate peer. 2738 When Diameter is run over SCTP [RFC2960], which allows for 2739 connections to span multiple interfaces and multiple IP addresses, 2740 the Capabilities-Exchange-Request message MUST contain one Host-IP- 2741 Address AVP for each potential IP address that MAY be locally used 2742 when transmitting Diameter messages. 2744 Message Format 2746 ::= < Diameter Header: 257, REQ > 2747 { Origin-Host } 2748 { Origin-Realm } 2749 1* { Host-IP-Address } 2750 { Vendor-Id } 2751 { Product-Name } 2752 [ Origin-State-Id ] 2753 * [ Supported-Vendor-Id ] 2754 * [ Auth-Application-Id ] 2755 * [ Inband-Security-Id ] 2756 * [ Acct-Application-Id ] 2757 * [ Vendor-Specific-Application-Id ] 2758 [ Firmware-Revision ] 2759 * [ AVP ] 2761 5.3.2. Capabilities-Exchange-Answer 2763 The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code 2764 set to 257 and the Command Flags' 'R' bit cleared, is sent in 2765 response to a CER message. 2767 When Diameter is run over SCTP [RFC2960], which allows connections to 2768 span multiple interfaces, hence, multiple IP addresses, the 2769 Capabilities-Exchange-Answer message MUST contain one Host-IP-Address 2770 AVP for each potential IP address that MAY be locally used when 2771 transmitting Diameter messages. 2773 Message Format 2775 ::= < Diameter Header: 257 > 2776 { Result-Code } 2777 { Origin-Host } 2778 { Origin-Realm } 2779 1* { Host-IP-Address } 2780 { Vendor-Id } 2781 { Product-Name } 2782 [ Origin-State-Id ] 2783 [ Error-Message ] 2784 [ Failed-AVP ] 2785 * [ Supported-Vendor-Id ] 2786 * [ Auth-Application-Id ] 2787 * [ Inband-Security-Id ] 2788 * [ Acct-Application-Id ] 2789 * [ Vendor-Specific-Application-Id ] 2790 [ Firmware-Revision ] 2791 * [ AVP ] 2793 5.3.3. Vendor-Id AVP 2795 The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains 2796 the IANA "SMI Network Management Private Enterprise Codes" [RFC3232] 2797 value assigned to the vendor of the Diameter device. It is 2798 envisioned that the combination of the Vendor-Id, Product-Name 2799 (Section 5.3.7) and the Firmware-Revision (Section 5.3.4) AVPs may 2800 provide useful debugging information. 2802 A Vendor-Id value of zero in the CER or CEA messages is reserved and 2803 indicates that this field is ignored. 2805 5.3.4. Firmware-Revision AVP 2807 The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is 2808 used to inform a Diameter peer of the firmware revision of the 2809 issuing device. 2811 For devices that do not have a firmware revision (general purpose 2812 computers running Diameter software modules, for instance), the 2813 revision of the Diameter software module may be reported instead. 2815 5.3.5. Host-IP-Address AVP 2817 The Host-IP-Address AVP (AVP Code 257) is of type Address and is used 2818 to inform a Diameter peer of the sender's IP address. All source 2819 addresses that a Diameter node expects to use with SCTP [RFC2960] 2820 MUST be advertised in the CER and CEA messages by including a 2821 Host-IP- Address AVP for each address. This AVP MUST ONLY be used in 2822 the CER and CEA messages. 2824 5.3.6. Supported-Vendor-Id AVP 2826 The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and 2827 contains the IANA "SMI Network Management Private Enterprise Codes" 2828 [RFC3232] value assigned to a vendor other than the device vendor but 2829 including the application vendor. This is used in the CER and CEA 2830 messages in order to inform the peer that the sender supports (a 2831 subset of) the vendor-specific AVPs defined by the vendor identified 2832 in this AVP. The value of this AVP SHOULD NOT be set to zero. 2833 Multiple instances of this AVP containing the same value SHOULD NOT 2834 be sent. 2836 5.3.7. Product-Name AVP 2838 The Product-Name AVP (AVP Code 269) is of type UTF8String, and 2839 contains the vendor assigned name for the product. The Product-Name 2840 AVP SHOULD remain constant across firmware revisions for the same 2841 product. 2843 5.4. Disconnecting Peer connections 2845 When a Diameter node disconnects one of its transport connections, 2846 its peer cannot know the reason for the disconnect, and will most 2847 likely assume that a connectivity problem occurred, or that the peer 2848 has rebooted. In these cases, the peer may periodically attempt to 2849 reconnect, as stated in Section 2.1. In the event that the 2850 disconnect was a result of either a shortage of internal resources, 2851 or simply that the node in question has no intentions of forwarding 2852 any Diameter messages to the peer in the foreseeable future, a 2853 periodic connection request would not be welcomed. The 2854 Disconnection-Reason AVP contains the reason the Diameter node issued 2855 the Disconnect-Peer-Request message. 2857 The Disconnect-Peer-Request message is used by a Diameter node to 2858 inform its peer of its intent to disconnect the transport layer, and 2859 that the peer shouldn't reconnect unless it has a valid reason to do 2860 so (e.g., message to be forwarded). Upon receipt of the message, the 2861 Disconnect-Peer-Answer is returned, which SHOULD contain an error if 2862 messages have recently been forwarded, and are likely in flight, 2863 which would otherwise cause a race condition. 2865 The receiver of the Disconnect-Peer-Answer initiates the transport 2866 disconnect. The sender of the Disconnect-Peer-Answer should be able 2867 to detect the transport closure and cleanup the connection. 2869 5.4.1. Disconnect-Peer-Request 2871 The Disconnect-Peer-Request (DPR), indicated by the Command-Code set 2872 to 282 and the Command Flags' 'R' bit set, is sent to a peer to 2873 inform its intentions to shutdown the transport connection. Upon 2874 detection of a transport failure, this message MUST NOT be sent to an 2875 alternate peer. 2877 Message Format 2879 ::= < Diameter Header: 282, REQ > 2880 { Origin-Host } 2881 { Origin-Realm } 2882 { Disconnect-Cause } 2884 5.4.2. Disconnect-Peer-Answer 2886 The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set 2887 to 282 and the Command Flags' 'R' bit cleared, is sent as a response 2888 to the Disconnect-Peer-Request message. Upon receipt of this 2889 message, the transport connection is shutdown. 2891 Message Format 2893 ::= < Diameter Header: 282 > 2894 { Result-Code } 2895 { Origin-Host } 2896 { Origin-Realm } 2897 [ Error-Message ] 2898 [ Failed-AVP ] 2900 5.4.3. Disconnect-Cause AVP 2902 The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A 2903 Diameter node MUST include this AVP in the Disconnect-Peer-Request 2904 message to inform the peer of the reason for its intention to 2905 shutdown the transport connection. The following values are 2906 supported: 2908 REBOOTING 0 2909 A scheduled reboot is imminent. Receiver of DPR with above result 2910 code MAY attempt reconnection. 2912 BUSY 1 2913 The peer's internal resources are constrained, and it has 2914 determined that the transport connection needs to be closed. 2915 Receiver of DPR with above result code SHOULD NOT attempt 2916 reconnection. 2918 DO_NOT_WANT_TO_TALK_TO_YOU 2 2919 The peer has determined that it does not see a need for the 2920 transport connection to exist, since it does not expect any 2921 messages to be exchanged in the near future. Receiver of DPR 2922 with above result code SHOULD NOT attempt reconnection. 2924 5.5. Transport Failure Detection 2926 Given the nature of the Diameter protocol, it is recommended that 2927 transport failures be detected as soon as possible. Detecting such 2928 failures will minimize the occurrence of messages sent to unavailable 2929 agents, resulting in unnecessary delays, and will provide better 2930 failover performance. The Device-Watchdog-Request and Device- 2931 Watchdog-Answer messages, defined in this section, are used to pro- 2932 actively detect transport failures. 2934 5.5.1. Device-Watchdog-Request 2936 The Device-Watchdog-Request (DWR), indicated by the Command-Code set 2937 to 280 and the Command Flags' 'R' bit set, is sent to a peer when no 2938 traffic has been exchanged between two peers (see Section 5.5.3). 2939 Upon detection of a transport failure, this message MUST NOT be sent 2940 to an alternate peer. 2942 Message Format 2944 ::= < Diameter Header: 280, REQ > 2945 { Origin-Host } 2946 { Origin-Realm } 2947 [ Origin-State-Id ] 2949 5.5.2. Device-Watchdog-Answer 2951 The Device-Watchdog-Answer (DWA), indicated by the Command-Code set 2952 to 280 and the Command Flags' 'R' bit cleared, is sent as a response 2953 to the Device-Watchdog-Request message. 2955 Message Format 2957 ::= < Diameter Header: 280 > 2958 { Result-Code } 2959 { Origin-Host } 2960 { Origin-Realm } 2961 [ Error-Message ] 2962 [ Failed-AVP ] 2963 [ Origin-State-Id ] 2965 5.5.3. Transport Failure Algorithm 2967 The transport failure algorithm is defined in [RFC3539]. All 2968 Diameter implementations MUST support the algorithm defined in the 2969 specification in order to be compliant to the Diameter base protocol. 2971 5.5.4. Failover and Failback Procedures 2973 In the event that a transport failure is detected with a peer, it is 2974 necessary for all pending request messages to be forwarded to an 2975 alternate agent, if possible. This is commonly referred to as 2976 failover. 2978 In order for a Diameter node to perform failover procedures, it is 2979 necessary for the node to maintain a pending message queue for a 2980 given peer. When an answer message is received, the corresponding 2981 request is removed from the queue. The Hop-by-Hop Identifier field 2982 is used to match the answer with the queued request. 2984 When a transport failure is detected, if possible all messages in the 2985 queue are sent to an alternate agent with the T flag set. On booting 2986 a Diameter client or agent, the T flag is also set on any records 2987 still remaining to be transmitted in non-volatile storage. An 2988 example of a case where it is not possible to forward the message to 2989 an alternate server is when the message has a fixed destination, and 2990 the unavailable peer is the message's final destination (see 2991 Destination-Host AVP). Such an error requires that the agent return 2992 an answer message with the 'E' bit set and the Result-Code AVP set to 2993 DIAMETER_UNABLE_TO_DELIVER. 2995 It is important to note that multiple identical requests or answers 2996 MAY be received as a result of a failover. The End-to-End Identifier 2997 field in the Diameter header along with the Origin-Host AVP MUST be 2998 used to identify duplicate messages. 3000 As described in Section 2.1, a connection request should be 3001 periodically attempted with the failed peer in order to re-establish 3002 the transport connection. Once a connection has been successfully 3003 established, messages can once again be forwarded to the peer. This 3004 is commonly referred to as failback. 3006 5.6. Peer State Machine 3008 This section contains a finite state machine that MUST be observed by 3009 all Diameter implementations. Each Diameter node MUST follow the 3010 state machine described below when communicating with each peer. 3011 Multiple actions are separated by commas, and may continue on 3012 succeeding lines, as space requires. Similarly, state and next state 3013 may also span multiple lines, as space requires. 3015 This state machine is closely coupled with the state machine 3016 described in [RFC3539], which is used to open, close, failover, 3017 probe, and reopen transport connections. Note in particular that 3018 [RFC3539] requires the use of watchdog messages to probe connections. 3019 For Diameter, DWR and DWA messages are to be used. 3021 I- is used to represent the initiator (connecting) connection, while 3022 the R- is used to represent the responder (listening) connection. 3023 The lack of a prefix indicates that the event or action is the same 3024 regardless of the connection on which the event occurred. 3026 The stable states that a state machine may be in are Closed, I-Open 3027 and R-Open; all other states are intermediate. Note that I-Open and 3028 R-Open are equivalent except for whether the initiator or responder 3029 transport connection is used for communication. 3031 A CER message is always sent on the initiating connection immediately 3032 after the connection request is successfully completed. In the case 3033 of an election, one of the two connections will shut down. The 3034 responder connection will survive if the Origin-Host of the local 3035 Diameter entity is higher than that of the peer; the initiator 3036 connection will survive if the peer's Origin-Host is higher. All 3037 subsequent messages are sent on the surviving connection. Note that 3038 the results of an election on one peer are guaranteed to be the 3039 inverse of the results on the other. 3041 For TLS usage, a TLS handshake will begin when both ends are in the 3042 open state. If the TLS handshake is successful, all further messages 3043 will be sent via TLS. If the handshake fails, both ends move to the 3044 closed state. 3046 The state machine constrains only the behavior of a Diameter 3047 implementation as seen by Diameter peers through events on the wire. 3049 Any implementation that produces equivalent results is considered 3050 compliant. 3052 state event action next state 3053 ----------------------------------------------------------------- 3054 Closed Start I-Snd-Conn-Req Wait-Conn-Ack 3055 R-Conn-CER R-Accept, R-Open 3056 Process-CER, 3057 R-Snd-CEA 3059 Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA 3060 I-Rcv-Conn-Nack Cleanup Closed 3061 R-Conn-CER R-Accept, Wait-Conn-Ack/ 3062 Process-CER Elect 3063 Timeout Error Closed 3065 Wait-I-CEA I-Rcv-CEA Process-CEA I-Open 3066 R-Conn-CER R-Accept, Wait-Returns 3067 Process-CER, 3068 Elect 3069 I-Peer-Disc I-Disc Closed 3070 I-Rcv-Non-CEA Error Closed 3071 Timeout Error Closed 3073 Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns 3074 Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open 3075 R-Peer-Disc R-Disc Wait-Conn-Ack 3076 R-Conn-CER R-Reject Wait-Conn-Ack/ 3077 Elect 3078 Timeout Error Closed 3080 Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open 3081 I-Peer-Disc I-Disc, R-Open 3082 R-Snd-CEA 3083 I-Rcv-CEA R-Disc I-Open 3084 R-Peer-Disc R-Disc Wait-I-CEA 3085 R-Conn-CER R-Reject Wait-Returns 3086 Timeout Error Closed 3088 R-Open Send-Message R-Snd-Message R-Open 3089 R-Rcv-Message Process R-Open 3090 R-Rcv-DWR Process-DWR, R-Open 3091 R-Snd-DWA 3092 R-Rcv-DWA Process-DWA R-Open 3093 R-Conn-CER R-Reject R-Open 3094 Stop R-Snd-DPR Closing 3095 R-Rcv-DPR R-Snd-DPA, Closed 3096 R-Disc 3098 R-Peer-Disc R-Disc Closed 3099 R-Rcv-CER R-Snd-CEA R-Open 3100 R-Rcv-CEA Process-CEA R-Open 3102 I-Open Send-Message I-Snd-Message I-Open 3103 I-Rcv-Message Process I-Open 3104 I-Rcv-DWR Process-DWR, I-Open 3105 I-Snd-DWA 3106 I-Rcv-DWA Process-DWA I-Open 3107 R-Conn-CER R-Reject I-Open 3108 Stop I-Snd-DPR Closing 3109 I-Rcv-DPR I-Snd-DPA, Closed 3110 I-Disc 3111 I-Peer-Disc I-Disc Closed 3112 I-Rcv-CER I-Snd-CEA I-Open 3113 I-Rcv-CEA Process-CEA I-Open 3115 Closing I-Rcv-DPA I-Disc Closed 3116 R-Rcv-DPA R-Disc Closed 3117 Timeout Error Closed 3118 I-Peer-Disc I-Disc Closed 3119 R-Peer-Disc R-Disc Closed 3121 5.6.1. Incoming connections 3123 When a connection request is received from a Diameter peer, it is 3124 not, in the general case, possible to know the identity of that peer 3125 until a CER is received from it. This is because host and port 3126 determine the identity of a Diameter peer; and the source port of an 3127 incoming connection is arbitrary. Upon receipt of CER, the identity 3128 of the connecting peer can be uniquely determined from Origin-Host. 3130 For this reason, a Diameter peer must employ logic separate from the 3131 state machine to receive connection requests, accept them, and await 3132 CER. Once CER arrives on a new connection, the Origin-Host that 3133 identifies the peer is used to locate the state machine associated 3134 with that peer, and the new connection and CER are passed to the 3135 state machine as an R-Conn-CER event. 3137 The logic that handles incoming connections SHOULD close and discard 3138 the connection if any message other than CER arrives, or if an 3139 implementation-defined timeout occurs prior to receipt of CER. 3141 Because handling of incoming connections up to and including receipt 3142 of CER requires logic, separate from that of any individual state 3143 machine associated with a particular peer, it is described separately 3144 in this section rather than in the state machine above. 3146 5.6.2. Events 3148 Transitions and actions in the automaton are caused by events. In 3149 this section, we will ignore the -I and -R prefix, since the actual 3150 event would be identical, but would occur on one of two possible 3151 connections. 3153 Start The Diameter application has signaled that a 3154 connection should be initiated with the peer. 3156 R-Conn-CER An acknowledgement is received stating that the 3157 transport connection has been established, and the 3158 associated CER has arrived. 3160 Rcv-Conn-Ack A positive acknowledgement is received confirming that 3161 the transport connection is established. 3163 Rcv-Conn-Nack A negative acknowledgement was received stating that 3164 the transport connection was not established. 3166 Timeout An application-defined timer has expired while waiting 3167 for some event. 3169 Rcv-CER A CER message from the peer was received. 3171 Rcv-CEA A CEA message from the peer was received. 3173 Rcv-Non-CEA A message other than CEA from the peer was received. 3175 Peer-Disc A disconnection indication from the peer was received. 3177 Rcv-DPR A DPR message from the peer was received. 3179 Rcv-DPA A DPA message from the peer was received. 3181 Win-Election An election was held, and the local node was the 3182 winner. 3184 Send-Message A message is to be sent. 3186 Rcv-Message A message other than CER, CEA, DPR, DPA, DWR or DWA 3187 was received. 3189 Stop The Diameter application has signaled that a 3190 connection should be terminated (e.g., on system 3191 shutdown). 3193 5.6.3. Actions 3195 Actions in the automaton are caused by events and typically indicate 3196 the transmission of packets and/or an action to be taken on the 3197 connection. In this section we will ignore the I- and R-prefix, 3198 since the actual action would be identical, but would occur on one of 3199 two possible connections. 3201 Snd-Conn-Req A transport connection is initiated with the peer. 3203 Accept The incoming connection associated with the R-Conn-CER 3204 is accepted as the responder connection. 3206 Reject The incoming connection associated with the R-Conn-CER 3207 is disconnected. 3209 Process-CER The CER associated with the R-Conn-CER is processed. 3210 Snd-CER A CER message is sent to the peer. 3212 Snd-CEA A CEA message is sent to the peer. 3214 Cleanup If necessary, the connection is shutdown, and any 3215 local resources are freed. 3217 Error The transport layer connection is disconnected, either 3218 politely or abortively, in response to an error 3219 condition. Local resources are freed. 3221 Process-CEA A received CEA is processed. 3223 Snd-DPR A DPR message is sent to the peer. 3225 Snd-DPA A DPA message is sent to the peer. 3227 Disc The transport layer connection is disconnected, and 3228 local resources are freed. 3230 Elect An election occurs (see Section 5.6.4 for more 3231 information). 3233 Snd-Message A message is sent. 3235 Snd-DWR A DWR message is sent. 3237 Snd-DWA A DWA message is sent. 3239 Process-DWR The DWR message is serviced. 3241 Process-DWA The DWA message is serviced. 3243 Process A message is serviced. 3245 5.6.4. The Election Process 3247 The election is performed on the responder. The responder compares 3248 the Origin-Host received in the CER with its own Origin-Host as two 3249 streams of octets. If the local Origin-Host lexicographically 3250 succeeds the received Origin-Host a Win-Election event is issued 3251 locally. Diameter identities are in ASCII form therefore the lexical 3252 comparison is consistent with DNS case insensitivity where octets 3253 that fall in the ASCII range 'a' through 'z' MUST compare equally to 3254 their upper-case counterparts between 'A' and 'Z'. See Appendix D 3255 for interactions between the Diameter protocol and Internationalized 3256 Domain Name (IDNs). 3258 The winner of the election MUST close the connection it initiated. 3259 Historically, maintaining the responder side of a connection was more 3260 efficient than maintaining the initiator side. However, current 3261 practices makes this distinction irrelevant. 3263 5.6.5. Capabilities Update 3265 A Diameter node MUST initiate peer capabilities update by sending a 3266 Capabilities-Exchange-Req (CER) to all its peers which supports peer 3267 capabilities update and is in OPEN state. The receiver of CER in 3268 open state MUST process and reply to the CER as a described in 3269 Section 5.3. The CEA which the receiver sends MUST contain its 3270 latest capabilities. Note that peers which successfully process the 3271 peer capabilities update SHOULD also update their routing tables to 3272 reflect the change. The receiver of the CEA, with a Result-Code AVP 3273 other than DIAMETER_SUCCESS, initiates the transport disconnect. The 3274 peer may periodically attempt to reconnect, as stated in Section 2.1. 3276 Peer capabilities update in the open state SHOULD be limited to the 3277 advertisement of the new list of supported applications and MUST 3278 preclude re-negotiation of security mechanism or other capabilities. 3279 If any capabilities change happens in the node (e.g. change in 3280 security mechanisms), other than a change in the supported 3281 applications, the node SHOULD gracefully terminate (setting the 3282 Disconnect-Cause AVP value to REBOOTING) and re-establish the 3283 diameter connections to all the peers. 3285 6. Diameter message processing 3287 This section describes how Diameter requests and answers are created 3288 and processed. 3290 6.1. Diameter Request Routing Overview 3292 A request is sent towards its final destination using a combination 3293 of the Destination-Realm and Destination-Host AVPs, in one of these 3294 three combinations: 3296 o a request that is not able to be proxied (such as CER) MUST NOT 3297 contain either Destination-Realm or Destination-Host AVPs. 3299 o a request that needs to be sent to a home server serving a 3300 specific realm, but not to a specific server (such as the first 3301 request of a series of round-trips), MUST contain a Destination- 3302 Realm AVP, but MUST NOT contain a Destination-Host AVP. 3304 o otherwise, a request that needs to be sent to a specific home 3305 server among those serving a given realm, MUST contain both the 3306 Destination-Realm and Destination-Host AVPs. 3308 The Destination-Host AVP is used as described above when the 3309 destination of the request is fixed, which includes: 3311 o Authentication requests that span multiple round trips 3313 o A Diameter message that uses a security mechanism that makes use 3314 of a pre-established session key shared between the source and the 3315 final destination of the message. 3317 o Server initiated messages that MUST be received by a specific 3318 Diameter client (e.g., access device), such as the Abort-Session- 3319 Request message, which is used to request that a particular user's 3320 session be terminated. 3322 Note that an agent can forward a request to a host described in the 3323 Destination-Host AVP only if the host in question is included in its 3324 peer table (see Section 2.7). Otherwise, the request is routed based 3325 on the Destination-Realm only (see Sections 6.1.6). 3327 The Destination-Realm AVP MUST be present if the message is 3328 proxiable. A message that MUST NOT be forwarded by Diameter agents 3329 (proxies, redirects or relays) MUST NOT include the Destination-Realm 3330 in its ABNF. The value of the Destination-Realm AVP MAY be extracted 3331 from the User-Name AVP, or other application- specific methods. 3333 When a message is received, the message is processed in the following 3334 order: 3336 o If the message is destined for the local host, the procedures 3337 listed in Section 6.1.4 are followed. 3339 o If the message is intended for a Diameter peer with whom the local 3340 host is able to directly communicate, the procedures listed in 3341 Section 6.1.5 are followed. This is known as Request Forwarding. 3343 o The procedures listed in Section 6.1.6 are followed, which is 3344 known as Request Routing. 3346 o If none of the above is successful, an answer is returned with the 3347 Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the E-bit set. 3349 For routing of Diameter messages to work within an administrative 3350 domain, all Diameter nodes within the realm MUST be peers. 3352 Note the processing rules contained in this section are intended to 3353 be used as general guidelines to Diameter developers. Certain 3354 implementations MAY use different methods than the ones described 3355 here, and still comply with the protocol specification. See Section 3356 7 for more detail on error handling. 3358 6.1.1. Originating a Request 3360 When creating a request, in addition to any other procedures 3361 described in the application definition for that specific request, 3362 the following procedures MUST be followed: 3364 o the Command-Code is set to the appropriate value 3366 o the 'R' bit is set 3368 o the End-to-End Identifier is set to a locally unique value 3370 o the Origin-Host and Origin-Realm AVPs MUST be set to the 3371 appropriate values, used to identify the source of the message 3373 o the Destination-Host and Destination-Realm AVPs MUST be set to the 3374 appropriate values as described in Section 6.1. 3376 6.1.2. Sending a Request 3378 When sending a request, originated either locally, or as the result 3379 of a forwarding or routing operation, the following procedures MUST 3380 be followed: 3382 o the Hop-by-Hop Identifier should be set to a locally unique value. 3384 o The message should be saved in the list of pending requests. 3386 Other actions to perform on the message based on the particular role 3387 the agent is playing are described in the following sections. 3389 6.1.3. Receiving Requests 3391 A relay or proxy agent MUST check for forwarding loops when receiving 3392 requests. A loop is detected if the server finds its own identity in 3393 a Route-Record AVP. When such an event occurs, the agent MUST answer 3394 with the Result-Code AVP set to DIAMETER_LOOP_DETECTED. 3396 6.1.4. Processing Local Requests 3398 A request is known to be for local consumption when one of the 3399 following conditions occur: 3401 o The Destination-Host AVP contains the local host's identity, 3403 o The Destination-Host AVP is not present, the Destination-Realm AVP 3404 contains a realm the server is configured to process locally, and 3405 the Diameter application is locally supported, or 3407 o Both the Destination-Host and the Destination-Realm are not 3408 present. 3410 When a request is locally processed, the rules in Section 6.2 should 3411 be used to generate the corresponding answer. 3413 6.1.5. Request Forwarding 3415 Request forwarding is done using the Diameter Peer Table. The 3416 Diameter peer table contains all of the peers that the local node is 3417 able to directly communicate with. 3419 When a request is received, and the host encoded in the Destination- 3420 Host AVP is one that is present in the peer table, the message SHOULD 3421 be forwarded to the peer. 3423 6.1.6. Request Routing 3425 Diameter request message routing is done via realms and applications. 3426 A Diameter message that may be forwarded by Diameter agents (proxies, 3427 redirects or relays) MUST include the target realm in the 3428 Destination-Realm AVP. Request routing SHOULD rely on the 3429 Destination-Realm AVP and the application id present in the request 3430 message header to aid in the routing decision. The realm MAY be 3431 retrieved from the User-Name AVP, which is in the form of a Network 3432 Access Identifier (NAI). The realm portion of the NAI is inserted in 3433 the Destination-Realm AVP. 3435 Diameter agents MAY have a list of locally supported realms and 3436 applications, and MAY have a list of externally supported realms and 3437 applications. When a request is received that includes a realm 3438 and/or application that is not locally supported, the message is 3439 routed to the peer configured in the Routing Table (see Section 2.7). 3441 Realm names and application identifiers are the minimum supported 3442 routing criteria, additional routing information maybe needed to 3443 support redirect semantics. 3445 6.1.7. Predictive Loop Avoidance 3447 Before forwarding or routing a request, Diameter agents, in addition 3448 to processing done in Section 6.1.3, SHOULD check for the presence of 3449 candidate route's peer identity in any of the Route-Record AVPs. In 3450 an event of the agent detecting the presence of a candidate route's 3451 peer identity in a Route-Record AVP, the agent MUST ignore such route 3452 for the Diameter request message and attempt alternate routes if any. 3453 In case all the candidate routes are eliminated by the above 3454 criteria, the agent SHOULD return DIAMETER_UNABLE_TO_DELIVER message. 3456 6.1.8. Redirecting requests 3458 When a redirect agent receives a request whose routing entry is set 3459 to REDIRECT, it MUST reply with an answer message with the 'E' bit 3460 set, while maintaining the Hop-by-Hop Identifier in the header, and 3461 include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of 3462 the servers associated with the routing entry are added in separate 3463 Redirect-Host AVP. 3465 +------------------+ 3466 | Diameter | 3467 | Redirect Agent | 3468 +------------------+ 3469 ^ | 2. command + 'E' bit 3470 1. Request | | Result-Code = 3471 joe@example.com | | DIAMETER_REDIRECT_INDICATION + 3472 | | Redirect-Host AVP(s) 3473 | v 3474 +-------------+ 3. Request +-------------+ 3475 | example.com |------------->| example.net | 3476 | Relay | | Diameter | 3477 | Agent |<-------------| Server | 3478 +-------------+ 4. Answer +-------------+ 3480 Figure 5: Diameter Redirect Agent 3482 The receiver of the answer message with the 'E' bit set, and the 3483 Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by- 3484 hop field in the Diameter header to identify the request in the 3485 pending message queue (see Section 5.3) that is to be redirected. If 3486 no transport connection exists with the new agent, one is created, 3487 and the request is sent directly to it. 3489 Multiple Redirect-Host AVPs are allowed. The receiver of the answer 3490 message with the 'E' bit set selects exactly one of these hosts as 3491 the destination of the redirected message. 3493 When the Redirect-Host-Usage AVP included in the answer message has a 3494 non-zero value, a route entry for the redirect indications is created 3495 and cached by the receiver. The redirect usage for such route entry 3496 is set by the value of Redirect-Host-Usage AVP and the lifetime of 3497 the cached route entry is set by Redirect-Max-Cache-Time AVP value. 3499 It is possible that multiple redirect indications can create multiple 3500 cached route entries differing only in their redirect usage and the 3501 peer to forward messages to. As an example, two(2) route entries 3502 that are created by two(2) redirect indications results in two(2) 3503 cached routes for the same realm and application Id. However, one 3504 has a redirect usage of ALL_SESSION where matching request will be 3505 forwarded to one peer and the other has a redirect usage of ALL_REALM 3506 where request are forwarded to another peer. Therefore, an incoming 3507 request that matches the realm and application Id of both routes will 3508 need additional resolution. In such a case, a routing precedence 3509 rule MUST be used againts the redirect usage value to resolve the 3510 contention. The precedence rule can be found in Section 6.13. 3512 6.1.9. Relaying and Proxying Requests 3514 A relay or proxy agent MUST append a Route-Record AVP to all requests 3515 forwarded. The AVP contains the identity of the peer the request was 3516 received from. 3518 The Hop-by-Hop identifier in the request is saved, and replaced with 3519 a locally unique value. The source of the request is also saved, 3520 which includes the IP address, port and protocol. 3522 A relay or proxy agent MAY include the Proxy-Info AVP in requests if 3523 it requires access to any local state information when the 3524 corresponding response is received. Proxy-Info AVP has certain 3525 security implications and SHOULD contain an embedded HMAC with a 3526 node-local key. Alternatively, it MAY simply use local storage to 3527 store state information. 3529 The message is then forwarded to the next hop, as identified in the 3530 Routing Table. 3532 Figure 6 provides an example of message routing using the procedures 3533 listed in these sections. 3535 (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net) 3536 (Origin-Realm=mno.net) (Origin-Realm=mno.net) 3537 (Destination-Realm=example.com) (Destination- 3538 Realm=example.com) 3539 (Route-Record=nas.example.net) 3540 +------+ ------> +------+ ------> +------+ 3541 | | (Request) | | (Request) | | 3542 | NAS +-------------------+ DRL +-------------------+ HMS | 3543 | | | | | | 3544 +------+ <------ +------+ <------ +------+ 3545 example.net (Answer) example.net (Answer) example.com 3546 (Origin-Host=hms.example.com) (Origin-Host=hms.example.com) 3547 (Origin-Realm=example.com) (Origin-Realm=example.com) 3549 Figure 6: Routing of Diameter messages 3551 Relay agents do not require full validation of incoming messages. At 3552 a minimum, validation of the message header and relevant routing AVPs 3553 has to be done when relaying messages. 3555 6.2. Diameter Answer Processing 3557 When a request is locally processed, the following procedures MUST be 3558 applied to create the associated answer, in addition to any 3559 additional procedures that MAY be discussed in the Diameter 3560 application defining the command: 3562 o The same Hop-by-Hop identifier in the request is used in the 3563 answer. 3565 o The local host's identity is encoded in the Origin-Host AVP. 3567 o The Destination-Host and Destination-Realm AVPs MUST NOT be 3568 present in the answer message. 3570 o The Result-Code AVP is added with its value indicating success or 3571 failure. 3573 o If the Session-Id is present in the request, it MUST be included 3574 in the answer. 3576 o Any Proxy-Info AVPs in the request MUST be added to the answer 3577 message, in the same order they were present in the request. 3579 o The 'P' bit is set to the same value as the one in the request. 3581 o The same End-to-End identifier in the request is used in the 3582 answer. 3584 Note that the error messages (see Section 7.3) are also subjected to 3585 the above processing rules. 3587 6.2.1. Processing received Answers 3589 A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an 3590 answer received against the list of pending requests. The 3591 corresponding message should be removed from the list of pending 3592 requests. It SHOULD ignore answers received that do not match a 3593 known Hop-by-Hop Identifier. 3595 6.2.2. Relaying and Proxying Answers 3597 If the answer is for a request which was proxied or relayed, the 3598 agent MUST restore the original value of the Diameter header's Hop- 3599 by-Hop Identifier field. 3601 If the last Proxy-Info AVP in the message is targeted to the local 3602 Diameter server, the AVP MUST be removed before the answer is 3603 forwarded. 3605 If a relay or proxy agent receives an answer with a Result-Code AVP 3606 indicating a failure, it MUST NOT modify the contents of the AVP. 3607 Any additional local errors detected SHOULD be logged, but not 3608 reflected in the Result-Code AVP. If the agent receives an answer 3609 message with a Result-Code AVP indicating success, and it wishes to 3610 modify the AVP to indicate an error, it MUST modify the Result-Code 3611 AVP to contain the appropriate error in the message destined towards 3612 the access device as well as include the Error-Reporting-Host AVP and 3613 it MUST issue an STR on behalf of the access device. 3615 The agent MUST then send the answer to the host that it received the 3616 original request from. 3618 6.3. Origin-Host AVP 3620 The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and 3621 MUST be present in all Diameter messages. This AVP identifies the 3622 endpoint that originated the Diameter message. Relay agents MUST NOT 3623 modify this AVP. 3625 The value of the Origin-Host AVP is guaranteed to be unique within a 3626 single host. 3628 Note that the Origin-Host AVP may resolve to more than one address as 3629 the Diameter peer may support more than one address. 3631 This AVP SHOULD be placed as close to the Diameter header as 3632 possible. 6.10 3634 6.4. Origin-Realm AVP 3636 The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity. 3637 This AVP contains the Realm of the originator of any Diameter message 3638 and MUST be present in all messages. 3640 This AVP SHOULD be placed as close to the Diameter header as 3641 possible. 3643 6.5. Destination-Host AVP 3645 The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity. 3646 This AVP MUST be present in all unsolicited agent initiated messages, 3647 MAY be present in request messages, and MUST NOT be present in Answer 3648 messages. 3650 The absence of the Destination-Host AVP will cause a message to be 3651 sent to any Diameter server supporting the application within the 3652 realm specified in Destination-Realm AVP. 3654 This AVP SHOULD be placed as close to the Diameter header as 3655 possible. 3657 6.6. Destination-Realm AVP 3659 The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity, 3660 and contains the realm the message is to be routed to. The 3661 Destination-Realm AVP MUST NOT be present in Answer messages. 3662 Diameter Clients insert the realm portion of the User-Name AVP. 3663 Diameter servers initiating a request message use the value of the 3664 Origin-Realm AVP from a previous message received from the intended 3665 target host (unless it is known a priori). When present, the 3666 Destination-Realm AVP is used to perform message routing decisions. 3668 Request messages whose ABNF does not list the Destination-Realm AVP 3669 as a mandatory AVP are inherently non-routable messages. 3671 This AVP SHOULD be placed as close to the Diameter header as 3672 possible. 3674 6.7. Routing AVPs 3676 The AVPs defined in this section are Diameter AVPs used for routing 3677 purposes. These AVPs change as Diameter messages are processed by 3678 agents. 3680 6.7.1. Route-Record AVP 3682 The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The 3683 identity added in this AVP MUST be the same as the one received in 3684 the Origin-Host of the Capabilities Exchange message. 3686 6.7.2. Proxy-Info AVP 3688 The Proxy-Info AVP (AVP Code 284) is of type Grouped. The Grouped 3689 Data field has the following ABNF grammar: 3691 Proxy-Info ::= < AVP Header: 284 > 3692 { Proxy-Host } 3693 { Proxy-State } 3694 * [ AVP ] 3696 6.7.3. Proxy-Host AVP 3698 The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This 3699 AVP contains the identity of the host that added the Proxy-Info AVP. 3701 6.7.4. Proxy-State AVP 3703 The Proxy-State AVP (AVP Code 33) is of type OctetString, and 3704 contains state local information, and MUST be treated as opaque data. 3706 6.8. Auth-Application-Id AVP 3708 The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and 3709 is used in order to advertise support of the Authentication and 3710 Authorization portion of an application (see Section 2.4). If 3711 present in a message other than CER and CEA, the value of the Auth- 3712 Application-Id AVP MUST match the application id present in the 3713 diameter message header except when used in a CER or CEA messages. 3715 6.9. Acct-Application-Id AVP 3717 The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and 3718 is used in order to advertise support of the Accounting portion of an 3719 application (see Section 2.4). If present in a message other than 3720 CER and CEA, the value of the Acct-Application-Id AVP MUST match the 3721 application id present in the diameter message header except when 3722 used in a CER or CEA messages. 3724 6.10. Inband-Security-Id AVP 3726 The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and 3727 is used in order to advertise support of the Security portion of the 3728 application. 3730 Currently, the following values are supported, but there is ample 3731 room to add new security Ids. 3733 NO_INBAND_SECURITY 0 3735 This peer does not support TLS. This is the default value, if the 3736 AVP is omitted. 3738 TLS 1 3740 This node supports TLS security, as defined by [RFC4346]. 3742 6.11. Vendor-Specific-Application-Id AVP 3744 The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type 3745 Grouped and is used to advertise support of a vendor-specific 3746 Diameter Application. Exactly one instance of either Auth- 3747 Application-Id or Acct-Application-Id AVP MAY be present. The 3748 application identifier carried by either Auth-Application-Id or Acct- 3749 Application-Id AVP MUST comply with vendor specific application 3750 identifier assignment described in Sec 11.3. It MUST also match the 3751 application id present in the diameter header except when used in a 3752 CER or CEA messages. 3754 The Vendor-Id AVP is an informational AVP pertaining to the vendor 3755 who may have authorship of the vendor-specific Diameter application. 3756 It MUST NOT be used as a means of defining a completely separate 3757 vendor-specific application identifier space. 3759 This AVP MUST also be present as the first AVP in all experimental 3760 commands defined in the vendor-specific application. 3762 This AVP SHOULD be placed as close to the Diameter header as 3763 possible. 3765 AVP Format 3767 ::= < AVP Header: 260 > 3768 { Vendor-Id } 3769 ({ Auth-Application-Id } / 3770 { Acct-Application-Id }) 3772 6.12. Redirect-Host AVP 3774 One or more of instances of this AVP MUST be present if the answer 3775 message's 'E' bit is set and the Result-Code AVP is set to 3776 DIAMETER_REDIRECT_INDICATION. 3778 Upon receiving the above, the receiving Diameter node SHOULD forward 3779 the request directly to one of the hosts identified in these AVPs. 3780 The server contained in the selected Redirect-Host AVP SHOULD be used 3781 for all messages pertaining to this session. 3783 6.13. Redirect-Host-Usage AVP 3785 The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated. 3786 This AVP MAY be present in answer messages whose 'E' bit is set and 3787 the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION. 3789 When present, this AVP dictates how the routing entry resulting from 3790 the Redirect-Host is to be used. The following values are supported: 3792 DONT_CACHE 0 3794 The host specified in the Redirect-Host AVP should not be cached. 3795 This is the default value. 3797 ALL_SESSION 1 3799 All messages within the same session, as defined by the same value 3800 of the Session-ID AVP MAY be sent to the host specified in the 3801 Redirect-Host AVP. 3803 ALL_REALM 2 3805 All messages destined for the realm requested MAY be sent to the 3806 host specified in the Redirect-Host AVP. 3808 REALM_AND_APPLICATION 3 3810 All messages for the application requested to the realm specified 3811 MAY be sent to the host specified in the Redirect-Host AVP. 3813 ALL_APPLICATION 4 3815 All messages for the application requested MAY be sent to the host 3816 specified in the Redirect-Host AVP. 3818 ALL_HOST 5 3820 All messages that would be sent to the host that generated the 3821 Redirect-Host MAY be sent to the host specified in the Redirect- 3822 Host AVP. 3824 ALL_USER 6 3826 All messages for the user requested MAY be sent to the host 3827 specified in the Redirect-Host AVP. 3829 When multiple cached routes are created by redirect indications and 3830 they differs only in redirect usage and peers to forward requests to 3831 (see Section 6.1.8), a precedence rule MUST be applied to the 3832 redirect usage values of the cached routes during normal routing to 3833 resolve contentions that may occur. The precedence rule is the order 3834 that dictate which redirect usage should be considered before any 3835 other as they appear. The order is as follows: 3837 1. ALL_SESSION 3839 2. ALL_USER 3841 3. REALM_AND_APPLICATION 3843 4. ALL_REALM 3845 5. ALL_APPLICATION 3847 6. ALL_HOST 3849 6.14. Redirect-Max-Cache-Time AVP 3851 The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32. 3852 This AVP MUST be present in answer messages whose 'E' bit is set, the 3853 Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the 3854 Redirect-Host-Usage AVP set to a non-zero value. 3856 This AVP contains the maximum number of seconds the peer and route 3857 table entries, created as a result of the Redirect-Host, will be 3858 cached. Note that once a host created due to a redirect indication 3859 is no longer reachable, any associated peer and routing table entries 3860 MUST be deleted. 3862 7. Error Handling 3864 There are two different types of errors in Diameter; protocol and 3865 application errors. A protocol error is one that occurs at the base 3866 protocol level, and MAY require per hop attention (e.g., message 3867 routing error). Application errors, on the other hand, generally 3868 occur due to a problem with a function specified in a Diameter 3869 application (e.g., user authentication, Missing AVP). 3871 Result-Code AVP values that are used to report protocol errors MUST 3872 only be present in answer messages whose 'E' bit is set. When a 3873 request message is received that causes a protocol error, an answer 3874 message is returned with the 'E' bit set, and the Result-Code AVP is 3875 set to the appropriate protocol error value. As the answer is sent 3876 back towards the originator of the request, each proxy or relay agent 3877 MAY take action on the message. 3879 1. Request +---------+ Link Broken 3880 +-------------------------->|Diameter |----///----+ 3881 | +---------------------| | v 3882 +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+ 3883 |Diameter |<-+ (Unable to Forward) +---------+ |Diameter| 3884 | | | Home | 3885 | Relay 1 |--+ +---------+ | Server | 3886 +---------+ | 3. Request |Diameter | +--------+ 3887 +-------------------->| | ^ 3888 | Relay 3 |-----------+ 3889 +---------+ 3891 Figure 7: Example of Protocol Error causing answer message 3893 Figure 7 provides an example of a message forwarded upstream by a 3894 Diameter relay. When the message is received by Relay 2, and it 3895 detects that it cannot forward the request to the home server, an 3896 answer message is returned with the 'E' bit set and the Result-Code 3897 AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls 3898 within the protocol error category, Relay 1 would take special 3899 action, and given the error, attempt to route the message through its 3900 alternate Relay 3. 3902 +---------+ 1. Request +---------+ 2. Request +---------+ 3903 | Access |------------>|Diameter |------------>|Diameter | 3904 | | | | | Home | 3905 | Device |<------------| Relay |<------------| Server | 3906 +---------+ 4. Answer +---------+ 3. Answer +---------+ 3907 (Missing AVP) (Missing AVP) 3909 Figure 8: Example of Application Error Answer message 3911 Figure 8 provides an example of a Diameter message that caused an 3912 application error. When application errors occur, the Diameter 3913 entity reporting the error clears the 'R' bit in the Command Flags, 3914 and adds the Result-Code AVP with the proper value. Application 3915 errors do not require any proxy or relay agent involvement, and 3916 therefore the message would be forwarded back to the originator of 3917 the request. 3919 There are certain Result-Code AVP application errors that require 3920 additional AVPs to be present in the answer. In these cases, the 3921 Diameter node that sets the Result-Code AVP to indicate the error 3922 MUST add the AVPs. Examples are: 3924 o An unrecognized AVP is received with the 'M' bit (Mandatory bit) 3925 set, causes an answer to be sent with the Result-Code AVP set to 3926 DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the 3927 offending AVP. 3929 o An AVP that is received with an unrecognized value causes an 3930 answer to be returned with the Result-Code AVP set to 3931 DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the 3932 AVP causing the error. 3934 o A command is received with an AVP that is omitted, yet is 3935 mandatory according to the command's ABNF. The receiver issues an 3936 answer with the Result-Code set to DIAMETER_MISSING_AVP, and 3937 creates an AVP with the AVP Code and other fields set as expected 3938 in the missing AVP. The created AVP is then added to the Failed- 3939 AVP AVP. 3941 The Result-Code AVP describes the error that the Diameter node 3942 encountered in its processing. In case there are multiple errors, 3943 the Diameter node MUST report only the first error it encountered 3944 (detected possibly in some implementation dependent order). The 3945 specific errors that can be described by this AVP are described in 3946 the following section. 3948 7.1. Result-Code AVP 3950 The Result-Code AVP (AVP Code 268) is of type Unsigned32 and 3951 indicates whether a particular request was completed successfully or 3952 whether an error occurred. All Diameter answer messages defined in 3953 IETF applications MUST include one Result-Code AVP. A non-successful 3954 Result-Code AVP (one containing a non 2xxx value other than 3955 DIAMETER_REDIRECT_INDICATION) MUST include the Error-Reporting-Host 3956 AVP if the host setting the Result-Code AVP is different from the 3957 identity encoded in the Origin-Host AVP. 3959 The Result-Code data field contains an IANA-managed 32-bit address 3960 space representing errors (see Section 11.4). Diameter provides the 3961 following classes of errors, all identified by the thousands digit in 3962 the decimal notation: 3964 o 1xxx (Informational) 3966 o 2xxx (Success) 3968 o 3xxx (Protocol Errors) 3970 o 4xxx (Transient Failures) 3972 o 5xxx (Permanent Failure) 3974 A non-recognized class (one whose first digit is not defined in this 3975 section) MUST be handled as a permanent failure. 3977 7.1.1. Informational 3979 Errors that fall within this category are used to inform the 3980 requester that a request could not be satisfied, and additional 3981 action is required on its part before access is granted. 3983 DIAMETER_MULTI_ROUND_AUTH 1001 3985 This informational error is returned by a Diameter server to 3986 inform the access device that the authentication mechanism being 3987 used requires multiple round trips, and a subsequent request needs 3988 to be issued in order for access to be granted. 3990 7.1.2. Success 3992 Errors that fall within the Success category are used to inform a 3993 peer that a request has been successfully completed. 3995 DIAMETER_SUCCESS 2001 3997 The Request was successfully completed. 3999 DIAMETER_LIMITED_SUCCESS 2002 4001 When returned, the request was successfully completed, but 4002 additional processing is required by the application in order to 4003 provide service to the user. 4005 7.1.3. Protocol Errors 4007 Errors that fall within the Protocol Error category SHOULD be treated 4008 on a per-hop basis, and Diameter proxies MAY attempt to correct the 4009 error, if it is possible. Note that these and only these errors MUST 4010 only be used in answer messages whose 'E' bit is set. To provide 4011 backward compatibility with existing implementations that follow 4012 [RFC3588], some of the error values that have previously been used in 4013 this category by [RFC3588] will not be re-used. Therefore the error 4014 values enumerated here maybe non-sequential. 4016 DIAMETER_UNABLE_TO_DELIVER 3002 4018 This error is given when Diameter can not deliver the message to 4019 the destination, either because no host within the realm 4020 supporting the required application was available to process the 4021 request, or because Destination-Host AVP was given without the 4022 associated Destination-Realm AVP. 4024 DIAMETER_REALM_NOT_SERVED 3003 4026 The intended realm of the request is not recognized. 4028 DIAMETER_TOO_BUSY 3004 4030 When returned, a Diameter node SHOULD attempt to send the message 4031 to an alternate peer. This error MUST only be used when a 4032 specific server is requested, and it cannot provide the requested 4033 service. 4035 DIAMETER_LOOP_DETECTED 3005 4037 An agent detected a loop while trying to get the message to the 4038 intended recipient. The message MAY be sent to an alternate peer, 4039 if one is available, but the peer reporting the error has 4040 identified a configuration problem. 4042 DIAMETER_REDIRECT_INDICATION 3006 4044 A redirect agent has determined that the request could not be 4045 satisfied locally and the initiator of the request should direct 4046 the request directly to the server, whose contact information has 4047 been added to the response. When set, the Redirect-Host AVP MUST 4048 be present. 4050 DIAMETER_APPLICATION_UNSUPPORTED 3007 4052 A request was sent for an application that is not supported. 4054 DIAMETER_INVALID_BIT_IN_HEADER 3011 4056 This error is returned when a reserved bit in the Diameter header 4057 is set to one (1) or the bits in the Diameter header defined in 4058 Sec 3 are set incorrectly. 4060 DIAMETER_INVALID_MESSAGE_LENGTH 3012 4062 This error is returned when a request is received with an invalid 4063 message length. 4065 7.1.4. Transient Failures 4067 Errors that fall within the transient failures category are used to 4068 inform a peer that the request could not be satisfied at the time it 4069 was received, but MAY be able to satisfy the request in the future. 4070 Note that these errors MUST be used in answer messages whose 'E' bit 4071 is not set. 4073 DIAMETER_AUTHENTICATION_REJECTED 4001 4075 The authentication process for the user failed, most likely due to 4076 an invalid password used by the user. Further attempts MUST only 4077 be tried after prompting the user for a new password. 4079 DIAMETER_OUT_OF_SPACE 4002 4081 A Diameter node received the accounting request but was unable to 4082 commit it to stable storage due to a temporary lack of space. 4084 ELECTION_LOST 4003 4086 The peer has determined that it has lost the election process and 4087 has therefore disconnected the transport connection. 4089 7.1.5. Permanent Failures 4091 Errors that fall within the permanent failures category are used to 4092 inform the peer that the request failed, and should not be attempted 4093 again. Note that these errors SHOULD be used in answer messages 4094 whose 'E' bit is not set. In error conditions where it is not 4095 possible or efficient to compose application specific answer grammar 4096 then answer messages with E-bit set and complying to the grammar 4097 described in 7.2 MAY also be used for permanent errors. 4099 To provide backward compatibility with existing implementations that 4100 follow [RFC3588], some of the error values that have previously been 4101 used in this category by [RFC3588] will not be re-used. Therefore 4102 the error values enumerated here maybe non-sequential. 4104 DIAMETER_AVP_UNSUPPORTED 5001 4106 The peer received a message that contained an AVP that is not 4107 recognized or supported and was marked with the Mandatory bit. A 4108 Diameter message with this error MUST contain one or more Failed- 4109 AVP AVP containing the AVPs that caused the failure. 4111 DIAMETER_UNKNOWN_SESSION_ID 5002 4113 The request contained an unknown Session-Id. 4115 DIAMETER_AUTHORIZATION_REJECTED 5003 4117 A request was received for which the user could not be authorized. 4118 This error could occur if the service requested is not permitted 4119 to the user. 4121 DIAMETER_INVALID_AVP_VALUE 5004 4123 The request contained an AVP with an invalid value in its data 4124 portion. A Diameter message indicating this error MUST include 4125 the offending AVPs within a Failed-AVP AVP. 4127 DIAMETER_MISSING_AVP 5005 4129 The request did not contain an AVP that is required by the Command 4130 Code definition. If this value is sent in the Result-Code AVP, a 4131 Failed-AVP AVP SHOULD be included in the message. The Failed-AVP 4132 AVP MUST contain an example of the missing AVP complete with the 4133 Vendor-Id if applicable. The value field of the missing AVP 4134 should be of correct minimum length and contain zeroes. 4136 DIAMETER_RESOURCES_EXCEEDED 5006 4138 A request was received that cannot be authorized because the user 4139 has already expended allowed resources. An example of this error 4140 condition is a user that is restricted to one dial-up PPP port, 4141 attempts to establish a second PPP connection. 4143 DIAMETER_CONTRADICTING_AVPS 5007 4145 The Home Diameter server has detected AVPs in the request that 4146 contradicted each other, and is not willing to provide service to 4147 the user. The Failed-AVP AVPs MUST be present which contains the 4148 AVPs that contradicted each other. 4150 DIAMETER_AVP_NOT_ALLOWED 5008 4152 A message was received with an AVP that MUST NOT be present. The 4153 Failed-AVP AVP MUST be included and contain a copy of the 4154 offending AVP. 4156 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009 4158 A message was received that included an AVP that appeared more 4159 often than permitted in the message definition. The Failed-AVP 4160 AVP MUST be included and contain a copy of the first instance of 4161 the offending AVP that exceeded the maximum number of occurrences 4163 DIAMETER_NO_COMMON_APPLICATION 5010 4165 This error is returned by a Diameter node that is not acting as a 4166 relay when it receives a CER which advertises a set of 4167 applications that it does not support. 4169 DIAMETER_UNSUPPORTED_VERSION 5011 4171 This error is returned when a request was received, whose version 4172 number is unsupported. 4174 DIAMETER_UNABLE_TO_COMPLY 5012 4176 This error is returned when a request is rejected for unspecified 4177 reasons. 4179 DIAMETER_INVALID_AVP_LENGTH 5014 4181 The request contained an AVP with an invalid length. A Diameter 4182 message indicating this error MUST include the offending AVPs 4183 within a Failed-AVP AVP. In cases where the erroneous avp length 4184 value exceeds the message length or is less than the minimum AVP 4185 header length, it is sufficient to include the offending AVP 4186 header and a zero filled payload of the minimum required length 4187 for the payloads data type. If the AVP is a grouped AVP, the 4188 grouped AVP header with an empty payload would be sufficient to 4189 indicate the offending AVP. In the case where the offending AVP 4190 header cannot be fully decoded when avp length is less than the 4191 minimum AVP header length, it is sufficient to include an 4192 offending AVP header that is formulated by padding the incomplete 4193 AVP header with zero up to the minimum AVP header length. 4195 DIAMETER_NO_COMMON_SECURITY 5017 4197 This error is returned when a CER message is received, and there 4198 are no common security mechanisms supported between the peers. A 4199 Capabilities-Exchange-Answer (CEA) MUST be returned with the 4200 Result-Code AVP set to DIAMETER_NO_COMMON_SECURITY. 4202 DIAMETER_UNKNOWN_PEER 5018 4204 A CER was received from an unknown peer. 4206 DIAMETER_COMMAND_UNSUPPORTED 5019 4208 The Request contained a Command-Code that the receiver did not 4209 recognize or support. This MUST be used when a Diameter node 4210 receives an experimental command that it does not understand. 4212 DIAMETER_INVALID_HDR_BITS 5020 4214 A request was received whose bits in the Diameter header were 4215 either set to an invalid combination, or to a value that is 4216 inconsistent with the command code's definition. 4218 DIAMETER_INVALID_AVP_BITS 5021 4220 A request was received that included an AVP whose flag bits are 4221 set to an unrecognized value, or that is inconsistent with the 4222 AVP's definition. 4224 7.2. Error Bit 4226 The 'E' (Error Bit) in the Diameter header is set when the request 4227 caused a protocol-related error (see Section 7.1.3). A message with 4228 the 'E' bit MUST NOT be sent as a response to an answer message. 4229 Note that a message with the 'E' bit set is still subjected to the 4230 processing rules defined in Section 6.2. When set, the answer 4231 message will not conform to the ABNF specification for the command, 4232 and will instead conform to the following ABNF: 4234 Message Format 4236 ::= < Diameter Header: code, ERR [PXY] > 4237 0*1< Session-Id > 4238 { Origin-Host } 4239 { Origin-Realm } 4240 { Result-Code } 4241 [ Origin-State-Id ] 4242 [ Error-Message ] 4243 [ Error-Reporting-Host ] 4244 [ Failed-AVP ] 4245 * [ Proxy-Info ] 4246 * [ AVP ] 4248 Note that the code used in the header is the same than the one found 4249 in the request message, but with the 'R' bit cleared and the 'E' bit 4250 set. The 'P' bit in the header is set to the same value as the one 4251 found in the request message. 4253 7.3. Error-Message AVP 4255 The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY 4256 accompany a Result-Code AVP as a human readable error message. The 4257 Error-Message AVP is not intended to be useful in real-time, and 4258 SHOULD NOT be expected to be parsed by network entities. 4260 7.4. Error-Reporting-Host AVP 4262 The Error-Reporting-Host AVP (AVP Code 294) is of type 4263 DiameterIdentity. This AVP contains the identity of the Diameter 4264 host that sent the Result-Code AVP to a value other than 2001 4265 (Success), only if the host setting the Result-Code is different from 4266 the one encoded in the Origin-Host AVP. This AVP is intended to be 4267 used for troubleshooting purposes, and MUST be set when the Result- 4268 Code AVP indicates a failure. 4270 7.5. Failed-AVP AVP 4272 The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides 4273 debugging information in cases where a request is rejected or not 4274 fully processed due to erroneous information in a specific AVP. The 4275 value of the Result-Code AVP will provide information on the reason 4276 for the Failed-AVP AVP. A Diameter message SHOULD contain only one 4277 Failed-AVP that corresponds to the error indicated by the Result-Code 4278 AVP. For practical purposes, this Failed-AVP would typically refer 4279 to the first AVP processing error that a Diameter node encounters. 4281 The possible reasons for this AVP are the presence of an improperly 4282 constructed AVP, an unsupported or unrecognized AVP, an invalid AVP 4283 value, the omission of a required AVP, the presence of an explicitly 4284 excluded AVP (see tables in Section 10), or the presence of two or 4285 more occurrences of an AVP which is restricted to 0, 1, or 0-1 4286 occurrences. 4288 A Diameter message SHOULD contain one Failed-AVP AVP, containing the 4289 entire AVP that could not be processed successfully. If the failure 4290 reason is omission of a required AVP, an AVP with the missing AVP 4291 code, the missing vendor id, and a zero filled payload of the minimum 4292 required length for the omitted AVP will be added. If the failure 4293 reason is an invalid AVP length where the reported length is less 4294 than the minimum AVP header length or greater than the reported 4295 message length, a copy of the offending AVP header and a zero filled 4296 payload of the minimum required length SHOULD be added. 4298 In the case where the offending AVP is embedded within a grouped AVP, 4299 the Failed-AVP MAY contain the grouped AVP which in turn contains the 4300 single offending AVP. The same method MAY be employed if the grouped 4301 AVP itself is embedded in yet another grouped AVP and so on. In this 4302 case, the Failed-AVP MAY contain the grouped AVP heirarchy up to the 4303 single offending AVP. This enables the recipient to detect the 4304 location of the offending AVP when embedded in a group. 4306 AVP Format 4308 ::= < AVP Header: 279 > 4309 1* {AVP} 4311 7.6. Experimental-Result AVP 4313 The Experimental-Result AVP (AVP Code 297) is of type Grouped, and 4314 indicates whether a particular vendor-specific request was completed 4315 successfully or whether an error occurred. Its Data field has the 4316 following ABNF grammar: 4318 AVP Format 4320 Experimental-Result ::= < AVP Header: 297 > 4321 { Vendor-Id } 4322 { Experimental-Result-Code } 4324 The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies 4325 the vendor responsible for the assignment of the result code which 4326 follows. All Diameter answer messages defined in vendor-specific 4327 applications MUST include either one Result-Code AVP or one 4328 Experimental-Result AVP. 4330 7.7. Experimental-Result-Code AVP 4332 The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32 4333 and contains a vendor-assigned value representing the result of 4334 processing the request. 4336 It is recommended that vendor-specific result codes follow the same 4337 conventions given for the Result-Code AVP regarding the different 4338 types of result codes and the handling of errors (for non 2xxx 4339 values). 4341 8. Diameter User Sessions 4343 In general, Diameter can provide two different types of services to 4344 applications. The first involves authentication and authorization, 4345 and can optionally make use of accounting. The second only makes use 4346 of accounting. 4348 When a service makes use of the authentication and/or authorization 4349 portion of an application, and a user requests access to the network, 4350 the Diameter client issues an auth request to its local server. The 4351 auth request is defined in a service specific Diameter application 4352 (e.g., NASREQ). The request contains a Session-Id AVP, which is used 4353 in subsequent messages (e.g., subsequent authorization, accounting, 4354 etc) relating to the user's session. The Session-Id AVP is a means 4355 for the client and servers to correlate a Diameter message with a 4356 user session. 4358 When a Diameter server authorizes a user to use network resources for 4359 a finite amount of time, and it is willing to extend the 4360 authorization via a future request, it MUST add the Authorization- 4361 Lifetime AVP to the answer message. The Authorization-Lifetime AVP 4362 defines the maximum number of seconds a user MAY make use of the 4363 resources before another authorization request is expected by the 4364 server. The Auth-Grace-Period AVP contains the number of seconds 4365 following the expiration of the Authorization-Lifetime, after which 4366 the server will release all state information related to the user's 4367 session. Note that if payment for services is expected by the 4368 serving realm from the user's home realm, the Authorization-Lifetime 4369 AVP, combined with the Auth-Grace-Period AVP, implies the maximum 4370 length of the session the home realm is willing to be fiscally 4371 responsible for. Services provided past the expiration of the 4372 Authorization-Lifetime and Auth-Grace-Period AVPs are the 4373 responsibility of the access device. Of course, the actual cost of 4374 services rendered is clearly outside the scope of the protocol. 4376 An access device that does not expect to send a re-authorization or a 4377 session termination request to the server MAY include the Auth- 4378 Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint 4379 to the server. If the server accepts the hint, it agrees that since 4380 no session termination message will be received once service to the 4381 user is terminated, it cannot maintain state for the session. If the 4382 answer message from the server contains a different value in the 4383 Auth-Session-State AVP (or the default value if the AVP is absent), 4384 the access device MUST follow the server's directives. Note that the 4385 value NO_STATE_MAINTAINED MUST NOT be set in subsequent re- 4386 authorization requests and answers. 4388 The base protocol does not include any authorization request 4389 messages, since these are largely application-specific and are 4390 defined in a Diameter application document. However, the base 4391 protocol does define a set of messages that is used to terminate user 4392 sessions. These are used to allow servers that maintain state 4393 information to free resources. 4395 When a service only makes use of the Accounting portion of the 4396 Diameter protocol, even in combination with an application, the 4397 Session-Id is still used to identify user sessions. However, the 4398 session termination messages are not used, since a session is 4399 signaled as being terminated by issuing an accounting stop message. 4401 Diameter may also be used for services that cannot be easily 4402 categorized as authentication, authorization or accounting (e.g., 4403 certain 3GPP IMS interfaces). In such cases, the finite state 4404 machine defined in subsequent sections may not be applicable. 4405 Therefore, the applications itself MAY need to define its own finite 4406 state machine. However, such application specific statemachines MUST 4407 comply with general Diameter user session requirements such co- 4408 relating all message exchanges via Session-Id AVP. 4410 8.1. Authorization Session State Machine 4412 This section contains a set of finite state machines, representing 4413 the life cycle of Diameter sessions, and which MUST be observed by 4414 all Diameter implementations that make use of the authentication 4415 and/or authorization portion of a Diameter application. The term 4416 Service-Specific below refers to a message defined in a Diameter 4417 application (e.g., Mobile IPv4, NASREQ). 4419 There are four different authorization session state machines 4420 supported in the Diameter base protocol. The first two describe a 4421 session in which the server is maintaining session state, indicated 4422 by the value of the Auth-Session-State AVP (or its absence). One 4423 describes the session from a client perspective, the other from a 4424 server perspective. The second two state machines are used when the 4425 server does not maintain session state. Here again, one describes 4426 the session from a client perspective, the other from a server 4427 perspective. 4429 When a session is moved to the Idle state, any resources that were 4430 allocated for the particular session must be released. Any event not 4431 listed in the state machines MUST be considered as an error 4432 condition, and an answer, if applicable, MUST be returned to the 4433 originator of the message. 4435 In the case that an application does not support re-auth, the state 4436 transitions related to server-initiated re-auth when both client and 4437 server sessions maintains state (e.g., Send RAR, Pending, Receive 4438 RAA) MAY be ignored. 4440 In the state table, the event 'Failure to send X' means that the 4441 Diameter agent is unable to send command X to the desired 4442 destination. This could be due to the peer being down, or due to the 4443 peer sending back a transient failure or temporary protocol error 4444 notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the 4445 Result-Code AVP of the corresponding Answer command. The event 'X 4446 successfully sent' is the complement of 'Failure to send X'. 4448 The following state machine is observed by a client when state is 4449 maintained on the server: 4451 CLIENT, STATEFUL 4452 State Event Action New State 4453 ------------------------------------------------------------- 4454 Idle Client or Device Requests Send Pending 4455 access service 4456 specific 4457 auth req 4459 Idle ASR Received Send ASA Idle 4460 for unknown session with 4461 Result-Code 4462 = UNKNOWN_ 4463 SESSION_ID 4465 Idle RAR Received Send RAA Idle 4466 for unknown session with 4467 Result-Code 4468 = UNKNOWN_ 4469 SESSION_ID 4471 Pending Successful Service-specific Grant Open 4472 authorization answer Access 4473 received with default 4474 Auth-Session-State value 4476 Pending Successful Service-specific Sent STR Discon 4477 authorization answer received 4478 but service not provided 4480 Pending Error processing successful Sent STR Discon 4481 Service-specific authorization 4482 answer 4484 Pending Failed Service-specific Cleanup Idle 4485 authorization answer received 4487 Open User or client device Send Open 4488 requests access to service service 4489 specific 4490 auth req 4492 Open Successful Service-specific Provide Open 4493 authorization answer received Service 4495 Open Failed Service-specific Discon. Idle 4496 authorization answer user/device 4497 received. 4499 Open RAR received and client will Send RAA Open 4500 perform subsequent re-auth with 4501 Result-Code 4502 = SUCCESS 4504 Open RAR received and client will Send RAA Idle 4505 not perform subsequent with 4506 re-auth Result-Code 4507 != SUCCESS, 4508 Discon. 4509 user/device 4511 Open Session-Timeout Expires on Send STR Discon 4512 Access Device 4514 Open ASR Received, Send ASA Discon 4515 client will comply with with 4516 request to end the session Result-Code 4517 = SUCCESS, 4518 Send STR. 4520 Open ASR Received, Send ASA Open 4521 client will not comply with with 4522 request to end the session Result-Code 4523 != SUCCESS 4525 Open Authorization-Lifetime + Send STR Discon 4526 Auth-Grace-Period expires on 4527 access device 4529 Discon ASR Received Send ASA Discon 4531 Discon STA Received Discon. Idle 4532 user/device 4534 The following state machine is observed by a server when it is 4535 maintaining state for the session: 4537 SERVER, STATEFUL 4538 State Event Action New State 4539 ------------------------------------------------------------- 4540 Idle Service-specific authorization Send Open 4541 request received, and successful 4542 user is authorized serv. 4543 specific 4544 answer 4546 Idle Service-specific authorization Send Idle 4547 request received, and failed serv. 4548 user is not authorized specific 4549 answer 4551 Open Service-specific authorization Send Open 4552 request received, and user successful 4553 is authorized serv. specific 4554 answer 4556 Open Service-specific authorization Send Idle 4557 request received, and user failed serv. 4558 is not authorized specific 4559 answer, 4560 Cleanup 4562 Open Home server wants to confirm Send RAR Pending 4563 authentication and/or 4564 authorization of the user 4566 Pending Received RAA with a failed Cleanup Idle 4567 Result-Code 4569 Pending Received RAA with Result-Code Update Open 4570 = SUCCESS session 4572 Open Home server wants to Send ASR Discon 4573 terminate the service 4575 Open Authorization-Lifetime (and Cleanup Idle 4576 Auth-Grace-Period) expires 4577 on home server. 4579 Open Session-Timeout expires on Cleanup Idle 4580 home server 4582 Discon Failure to send ASR Wait, Discon 4583 resend ASR 4585 Discon ASR successfully sent and Cleanup Idle 4586 ASA Received with Result-Code 4588 Not ASA Received None No Change. 4589 Discon 4591 Any STR Received Send STA, Idle 4592 Cleanup. 4594 The following state machine is observed by a client when state is not 4595 maintained on the server: 4597 CLIENT, STATELESS 4598 State Event Action New State 4599 ------------------------------------------------------------- 4600 Idle Client or Device Requests Send Pending 4601 access service 4602 specific 4603 auth req 4605 Pending Successful Service-specific Grant Open 4606 authorization answer Access 4607 received with Auth-Session- 4608 State set to 4609 NO_STATE_MAINTAINED 4611 Pending Failed Service-specific Cleanup Idle 4612 authorization answer 4613 received 4615 Open Session-Timeout Expires on Discon. Idle 4616 Access Device user/device 4618 Open Service to user is terminated Discon. Idle 4619 user/device 4621 The following state machine is observed by a server when it is not 4622 maintaining state for the session: 4624 SERVER, STATELESS 4625 State Event Action New State 4626 ------------------------------------------------------------- 4627 Idle Service-specific authorization Send serv. Idle 4628 request received, and specific 4629 successfully processed answer 4631 8.2. Accounting Session State Machine 4633 The following state machines MUST be supported for applications that 4634 have an accounting portion or that require only accounting services. 4635 The first state machine is to be observed by clients. 4637 See Section 9.7 for Accounting Command Codes and Section 9.8 for 4638 Accounting AVPs. 4640 The server side in the accounting state machine depends in some cases 4641 on the particular application. The Diameter base protocol defines a 4642 default state machine that MUST be followed by all applications that 4643 have not specified other state machines. This is the second state 4644 machine in this section described below. 4646 The default server side state machine requires the reception of 4647 accounting records in any order and at any time, and does not place 4648 any standards requirement on the processing of these records. 4649 Implementations of Diameter MAY perform checking, ordering, 4650 correlation, fraud detection, and other tasks based on these records. 4651 Both base Diameter AVPs as well as application specific AVPs MAY be 4652 inspected as a part of these tasks. The tasks can happen either 4653 immediately after record reception or in a post-processing phase. 4654 However, as these tasks are typically application or even policy 4655 dependent, they are not standardized by the Diameter specifications. 4656 Applications MAY define requirements on when to accept accounting 4657 records based on the used value of Accounting-Realtime-Required AVP, 4658 credit limits checks, and so on. 4660 However, the Diameter base protocol defines one optional server side 4661 state machine that MAY be followed by applications that require 4662 keeping track of the session state at the accounting server. Note 4663 that such tracking is incompatible with the ability to sustain long 4664 duration connectivity problems. Therefore, the use of this state 4665 machine is recommended only in applications where the value of the 4666 Accounting-Realtime-Required AVP is DELIVER_AND_GRANT, and hence 4667 accounting connectivity problems are required to cause the serviced 4668 user to be disconnected. Otherwise, records produced by the client 4669 may be lost by the server which no longer accepts them after the 4670 connectivity is re-established. This state machine is the third 4671 state machine in this section. The state machine is supervised by a 4672 supervision session timer Ts, which the value should be reasonably 4673 higher than the Acct_Interim_Interval value. Ts MAY be set to two 4674 times the value of the Acct_Interim_Interval so as to avoid the 4675 accounting session in the Diameter server to change to Idle state in 4676 case of short transient network failure. 4678 Any event not listed in the state machines MUST be considered as an 4679 error condition, and a corresponding answer, if applicable, MUST be 4680 returned to the originator of the message. 4682 In the state table, the event 'Failure to send' means that the 4683 Diameter client is unable to communicate with the desired 4684 destination. This could be due to the peer being down, or due to the 4685 peer sending back a transient failure or temporary protocol error 4686 notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or 4687 DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting 4688 Answer command. 4690 The event 'Failed answer' means that the Diameter client received a 4691 non-transient failure notification in the Accounting Answer command. 4693 Note that the action 'Disconnect user/dev' MUST have an effect also 4694 to the authorization session state table, e.g., cause the STR message 4695 to be sent, if the given application has both authentication/ 4696 authorization and accounting portions. 4698 The states PendingS, PendingI, PendingL, PendingE and PendingB stand 4699 for pending states to wait for an answer to an accounting request 4700 related to a Start, Interim, Stop, Event or buffered record, 4701 respectively. 4703 CLIENT, ACCOUNTING 4704 State Event Action New State 4705 ------------------------------------------------------------- 4706 Idle Client or device requests Send PendingS 4707 access accounting 4708 start req. 4710 Idle Client or device requests Send PendingE 4711 a one-time service accounting 4712 event req 4714 Idle Records in storage Send PendingB 4715 record 4717 PendingS Successful accounting Open 4718 start answer received 4720 PendingS Failure to send and buffer Store Open 4721 space available and realtime Start 4722 not equal to DELIVER_AND_GRANT Record 4724 PendingS Failure to send and no buffer Open 4725 space available and realtime 4726 equal to GRANT_AND_LOSE 4728 PendingS Failure to send and no buffer Disconnect Idle 4729 space available and realtime user/dev 4730 not equal to 4731 GRANT_AND_LOSE 4733 PendingS Failed accounting start answer Open 4734 received and realtime equal 4735 to GRANT_AND_LOSE 4737 PendingS Failed accounting start answer Disconnect Idle 4738 received and realtime not user/dev 4739 equal to GRANT_AND_LOSE 4741 PendingS User service terminated Store PendingS 4742 stop 4743 record 4745 Open Interim interval elapses Send PendingI 4746 accounting 4747 interim 4748 record 4749 Open User service terminated Send PendingL 4750 accounting 4751 stop req. 4753 PendingI Successful accounting interim Open 4754 answer received 4756 PendingI Failure to send and (buffer Store Open 4757 space available or old record interim 4758 can be overwritten) and record 4759 realtime not equal to 4760 DELIVER_AND_GRANT 4762 PendingI Failure to send and no buffer Open 4763 space available and realtime 4764 equal to GRANT_AND_LOSE 4766 PendingI Failure to send and no buffer Disconnect Idle 4767 space available and realtime user/dev 4768 not equal to GRANT_AND_LOSE 4770 PendingI Failed accounting interim Open 4771 answer received and realtime 4772 equal to GRANT_AND_LOSE 4774 PendingI Failed accounting interim Disconnect Idle 4775 answer received and realtime user/dev 4776 not equal to GRANT_AND_LOSE 4778 PendingI User service terminated Store PendingI 4779 stop 4780 record 4781 PendingE Successful accounting Idle 4782 event answer received 4784 PendingE Failure to send and buffer Store Idle 4785 space available event 4786 record 4788 PendingE Failure to send and no buffer Idle 4789 space available 4791 PendingE Failed accounting event answer Idle 4792 received 4794 PendingB Successful accounting answer Delete Idle 4795 received record 4797 PendingB Failure to send Idle 4799 PendingB Failed accounting answer Delete Idle 4800 received record 4802 PendingL Successful accounting Idle 4803 stop answer received 4805 PendingL Failure to send and buffer Store Idle 4806 space available stop 4807 record 4809 PendingL Failure to send and no buffer Idle 4810 space available 4812 PendingL Failed accounting stop answer Idle 4813 received 4815 SERVER, STATELESS ACCOUNTING 4816 State Event Action New State 4817 ------------------------------------------------------------- 4819 Idle Accounting start request Send Idle 4820 received, and successfully accounting 4821 processed. start 4822 answer 4824 Idle Accounting event request Send Idle 4825 received, and successfully accounting 4826 processed. event 4827 answer 4829 Idle Interim record received, Send Idle 4830 and successfully processed. accounting 4831 interim 4832 answer 4834 Idle Accounting stop request Send Idle 4835 received, and successfully accounting 4836 processed stop answer 4838 Idle Accounting request received, Send Idle 4839 no space left to store accounting 4840 records answer, 4841 Result-Code 4842 = OUT_OF_ 4843 SPACE 4845 SERVER, STATEFUL ACCOUNTING 4846 State Event Action New State 4847 ------------------------------------------------------------- 4849 Idle Accounting start request Send Open 4850 received, and successfully accounting 4851 processed. start 4852 answer, 4853 Start Ts 4855 Idle Accounting event request Send Idle 4856 received, and successfully accounting 4857 processed. event 4858 answer 4860 Idle Accounting request received, Send Idle 4861 no space left to store accounting 4862 records answer, 4863 Result-Code 4864 = OUT_OF_ 4865 SPACE 4867 Open Interim record received, Send Open 4868 and successfully processed. accounting 4869 interim 4870 answer, 4871 Restart Ts 4873 Open Accounting stop request Send Idle 4874 received, and successfully accounting 4875 processed stop answer, 4876 Stop Ts 4878 Open Accounting request received, Send Idle 4879 no space left to store accounting 4880 records answer, 4881 Result-Code 4882 = OUT_OF_ 4883 SPACE, 4884 Stop Ts 4886 Open Session supervision timer Ts Stop Ts Idle 4887 expired 4889 8.3. Server-Initiated Re-Auth 4891 A Diameter server may initiate a re-authentication and/or re- 4892 authorization service for a particular session by issuing a Re-Auth- 4893 Request (RAR). 4895 For example, for pre-paid services, the Diameter server that 4896 originally authorized a session may need some confirmation that the 4897 user is still using the services. 4899 An access device that receives a RAR message with Session-Id equal to 4900 a currently active session MUST initiate a re-auth towards the user, 4901 if the service supports this particular feature. Each Diameter 4902 application MUST state whether service-initiated re-auth is 4903 supported, since some applications do not allow access devices to 4904 prompt the user for re-auth. 4906 8.3.1. Re-Auth-Request 4908 The Re-Auth-Request (RAR), indicated by the Command-Code set to 258 4909 and the message flags' 'R' bit set, may be sent by any server to the 4910 access device that is providing session service, to request that the 4911 user be re-authenticated and/or re-authorized. 4913 Message Format 4915 ::= < Diameter Header: 258, REQ, PXY > 4916 < Session-Id > 4917 { Origin-Host } 4918 { Origin-Realm } 4919 { Destination-Realm } 4920 { Destination-Host } 4921 { Auth-Application-Id } 4922 { Re-Auth-Request-Type } 4923 [ User-Name ] 4924 [ Origin-State-Id ] 4925 * [ Proxy-Info ] 4926 * [ Route-Record ] 4927 * [ AVP ] 4929 8.3.2. Re-Auth-Answer 4931 The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258 4932 and the message flags' 'R' bit clear, is sent in response to the RAR. 4933 The Result-Code AVP MUST be present, and indicates the disposition of 4934 the request. 4936 A successful RAA message MUST be followed by an application-specific 4937 authentication and/or authorization message. 4939 Message Format 4941 ::= < Diameter Header: 258, PXY > 4942 < Session-Id > 4943 { Result-Code } 4944 { Origin-Host } 4945 { Origin-Realm } 4946 [ User-Name ] 4947 [ Origin-State-Id ] 4948 [ Error-Message ] 4949 [ Error-Reporting-Host ] 4950 [ Failed-AVP ] 4951 * [ Redirect-Host ] 4952 [ Redirect-Host-Usage ] 4953 [ Redirect-Max-Cache-Time ] 4954 * [ Proxy-Info ] 4955 * [ AVP ] 4957 8.4. Session Termination 4959 It is necessary for a Diameter server that authorized a session, for 4960 which it is maintaining state, to be notified when that session is no 4961 longer active, both for tracking purposes as well as to allow 4962 stateful agents to release any resources that they may have provided 4963 for the user's session. For sessions whose state is not being 4964 maintained, this section is not used. 4966 When a user session that required Diameter authorization terminates, 4967 the access device that provided the service MUST issue a Session- 4968 Termination-Request (STR) message to the Diameter server that 4969 authorized the service, to notify it that the session is no longer 4970 active. An STR MUST be issued when a user session terminates for any 4971 reason, including user logoff, expiration of Session-Timeout, 4972 administrative action, termination upon receipt of an Abort-Session- 4973 Request (see below), orderly shutdown of the access device, etc. 4975 The access device also MUST issue an STR for a session that was 4976 authorized but never actually started. This could occur, for 4977 example, due to a sudden resource shortage in the access device, or 4978 because the access device is unwilling to provide the type of service 4979 requested in the authorization, or because the access device does not 4980 support a mandatory AVP returned in the authorization, etc. 4982 It is also possible that a session that was authorized is never 4983 actually started due to action of a proxy. For example, a proxy may 4984 modify an authorization answer, converting the result from success to 4985 failure, prior to forwarding the message to the access device. If 4986 the answer did not contain an Auth-Session-State AVP with the value 4987 NO_STATE_MAINTAINED, a proxy that causes an authorized session not to 4988 be started MUST issue an STR to the Diameter server that authorized 4989 the session, since the access device has no way of knowing that the 4990 session had been authorized. 4992 A Diameter server that receives an STR message MUST clean up 4993 resources (e.g., session state) associated with the Session-Id 4994 specified in the STR, and return a Session-Termination-Answer. 4996 A Diameter server also MUST clean up resources when the Session- 4997 Timeout expires, or when the Authorization-Lifetime and the Auth- 4998 Grace-Period AVPs expires without receipt of a re-authorization 4999 request, regardless of whether an STR for that session is received. 5000 The access device is not expected to provide service beyond the 5001 expiration of these timers; thus, expiration of either of these 5002 timers implies that the access device may have unexpectedly shut 5003 down. 5005 8.4.1. Session-Termination-Request 5007 The Session-Termination-Request (STR), indicated by the Command-Code 5008 set to 275 and the Command Flags' 'R' bit set, is sent by the access 5009 device to inform the Diameter Server that an authenticated and/or 5010 authorized session is being terminated. 5012 Message Format 5014 ::= < Diameter Header: 275, REQ, PXY > 5015 < Session-Id > 5016 { Origin-Host } 5017 { Origin-Realm } 5018 { Destination-Realm } 5019 { Auth-Application-Id } 5020 { Termination-Cause } 5021 [ User-Name ] 5022 [ Destination-Host ] 5023 * [ Class ] 5024 [ Origin-State-Id ] 5025 * [ Proxy-Info ] 5026 * [ Route-Record ] 5027 * [ AVP ] 5029 8.4.2. Session-Termination-Answer 5031 The Session-Termination-Answer (STA), indicated by the Command-Code 5032 set to 275 and the message flags' 'R' bit clear, is sent by the 5033 Diameter Server to acknowledge the notification that the session has 5034 been terminated. The Result-Code AVP MUST be present, and MAY 5035 contain an indication that an error occurred while servicing the STR. 5037 Upon sending or receipt of the STA, the Diameter Server MUST release 5038 all resources for the session indicated by the Session-Id AVP. Any 5039 intermediate server in the Proxy-Chain MAY also release any 5040 resources, if necessary. 5042 Message Format 5044 ::= < Diameter Header: 275, PXY > 5045 < Session-Id > 5046 { Result-Code } 5047 { Origin-Host } 5048 { Origin-Realm } 5049 [ User-Name ] 5050 * [ Class ] 5051 [ Error-Message ] 5052 [ Error-Reporting-Host ] 5053 [ Failed-AVP ] 5054 [ Origin-State-Id ] 5055 * [ Redirect-Host ] 5056 [ Redirect-Host-Usage ] 5057 ^ 5058 [ Redirect-Max-Cache-Time ] 5059 * [ Proxy-Info ] 5060 * [ AVP ] 5062 8.5. Aborting a Session 5064 A Diameter server may request that the access device stop providing 5065 service for a particular session by issuing an Abort-Session-Request 5066 (ASR). 5068 For example, the Diameter server that originally authorized the 5069 session may be required to cause that session to be stopped for 5070 credit or other reasons that were not anticipated when the session 5071 was first authorized. On the other hand, an operator may maintain a 5072 management server for the purpose of issuing ASRs to administratively 5073 remove users from the network. 5075 An access device that receives an ASR with Session-ID equal to a 5076 currently active session MAY stop the session. Whether the access 5077 device stops the session or not is implementation- and/or 5078 configuration-dependent. For example, an access device may honor 5079 ASRs from certain agents only. In any case, the access device MUST 5080 respond with an Abort-Session-Answer, including a Result-Code AVP to 5081 indicate what action it took. 5083 Note that if the access device does stop the session upon receipt of 5084 an ASR, it issues an STR to the authorizing server (which may or may 5085 not be the agent issuing the ASR) just as it would if the session 5086 were terminated for any other reason. 5088 8.5.1. Abort-Session-Request 5090 The Abort-Session-Request (ASR), indicated by the Command-Code set to 5091 274 and the message flags' 'R' bit set, may be sent by any server to 5092 the access device that is providing session service, to request that 5093 the session identified by the Session-Id be stopped. 5095 Message Format 5097 ::= < Diameter Header: 274, REQ, PXY > 5098 < Session-Id > 5099 { Origin-Host } 5100 { Origin-Realm } 5101 { Destination-Realm } 5102 { Destination-Host } 5103 { Auth-Application-Id } 5104 [ User-Name ] 5105 [ Origin-State-Id ] 5106 * [ Proxy-Info ] 5107 * [ Route-Record ] 5108 * [ AVP ] 5110 8.5.2. Abort-Session-Answer 5112 The Abort-Session-Answer (ASA), indicated by the Command-Code set to 5113 274 and the message flags' 'R' bit clear, is sent in response to the 5114 ASR. The Result-Code AVP MUST be present, and indicates the 5115 disposition of the request. 5117 If the session identified by Session-Id in the ASR was successfully 5118 terminated, Result-Code is set to DIAMETER_SUCCESS. If the session 5119 is not currently active, Result-Code is set to 5120 DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the 5121 session for any other reason, Result-Code is set to 5122 DIAMETER_UNABLE_TO_COMPLY. 5124 Message Format 5126 ::= < Diameter Header: 274, PXY > 5127 < Session-Id > 5128 { Result-Code } 5129 { Origin-Host } 5130 { Origin-Realm } 5131 [ User-Name ] 5132 [ Origin-State-Id ] 5133 [ Error-Message ] 5134 [ Error-Reporting-Host ] 5135 [ Failed-AVP ] 5136 * [ Redirect-Host ] 5137 [ Redirect-Host-Usage ] 5138 [ Redirect-Max-Cache-Time ] 5139 * [ Proxy-Info ] 5140 * [ AVP ] 5142 8.6. Inferring Session Termination from Origin-State-Id 5144 Origin-State-Id is used to allow rapid detection of terminated 5145 sessions for which no STR would have been issued, due to 5146 unanticipated shutdown of an access device. 5148 By including Origin-State-Id in CER/CEA messages, an access device 5149 allows a next-hop server to determine immediately upon connection 5150 whether the device has lost its sessions since the last connection. 5152 By including Origin-State-Id in request messages, an access device 5153 also allows a server with which it communicates via proxy to make 5154 such a determination. However, a server that is not directly 5155 connected with the access device will not discover that the access 5156 device has been restarted unless and until it receives a new request 5157 from the access device. Thus, use of this mechanism across proxies 5158 is opportunistic rather than reliable, but useful nonetheless. 5160 When a Diameter server receives an Origin-State-Id that is greater 5161 than the Origin-State-Id previously received from the same issuer, it 5162 may assume that the issuer has lost state since the previous message 5163 and that all sessions that were active under the lower Origin-State- 5164 Id have been terminated. The Diameter server MAY clean up all 5165 session state associated with such lost sessions, and MAY also issues 5166 STRs for all such lost sessions that were authorized on upstream 5167 servers, to allow session state to be cleaned up globally. 5169 8.7. Auth-Request-Type AVP 5171 The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is 5172 included in application-specific auth requests to inform the peers 5173 whether a user is to be authenticated only, authorized only or both. 5174 Note any value other than both MAY cause RADIUS interoperability 5175 issues. The following values are defined: 5177 AUTHENTICATE_ONLY 1 5179 The request being sent is for authentication only, and MUST 5180 contain the relevant application specific authentication AVPs that 5181 are needed by the Diameter server to authenticate the user. 5183 AUTHORIZE_ONLY 2 5185 The request being sent is for authorization only, and MUST contain 5186 the application specific authorization AVPs that are necessary to 5187 identify the service being requested/offered. 5189 AUTHORIZE_AUTHENTICATE 3 5191 The request contains a request for both authentication and 5192 authorization. The request MUST include both the relevant 5193 application specific authentication information, and authorization 5194 information necessary to identify the service being requested/ 5195 offered. 5197 8.8. Session-Id AVP 5199 The Session-Id AVP (AVP Code 263) is of type UTF8String and is used 5200 to identify a specific session (see Section 8). All messages 5201 pertaining to a specific session MUST include only one Session-Id AVP 5202 and the same value MUST be used throughout the life of a session. 5203 When present, the Session-Id SHOULD appear immediately following the 5204 Diameter Header (see Section 3). 5206 The Session-Id MUST be globally and eternally unique, as it is meant 5207 to uniquely identify a user session without reference to any other 5208 information, and may be needed to correlate historical authentication 5209 information with accounting information. The Session-Id includes a 5210 mandatory portion and an implementation-defined portion; a 5211 recommended format for the implementation-defined portion is outlined 5212 below. 5214 The Session-Id MUST begin with the sender's identity encoded in the 5215 DiameterIdentity type (see Section 4.4). The remainder of the 5216 Session-Id is delimited by a ";" character, and MAY be any sequence 5217 that the client can guarantee to be eternally unique; however, the 5218 following format is recommended, (square brackets [] indicate an 5219 optional element): 5221 ;;[;] 5223 and are decimal representations of the 5224 high and low 32 bits of a monotonically increasing 64-bit value. The 5225 64-bit value is rendered in two part to simplify formatting by 32-bit 5226 processors. At startup, the high 32 bits of the 64-bit value MAY be 5227 initialized to the time, and the low 32 bits MAY be initialized to 5228 zero. This will for practical purposes eliminate the possibility of 5229 overlapping Session-Ids after a reboot, assuming the reboot process 5230 takes longer than a second. Alternatively, an implementation MAY 5231 keep track of the increasing value in non-volatile memory. 5233 is implementation specific but may include a modem's 5234 device Id, a layer 2 address, timestamp, etc. 5236 Example, in which there is no optional value: 5238 accesspoint7.acme.com;1876543210;523 5240 Example, in which there is an optional value: 5242 accesspoint7.acme.com;1876543210;523;mobile@200.1.1.88 5244 The Session-Id is created by the Diameter application initiating the 5245 session, which in most cases is done by the client. Note that a 5246 Session-Id MAY be used for both the authorization and accounting 5247 commands of a given application. 5249 8.9. Authorization-Lifetime AVP 5251 The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32 5252 and contains the maximum number of seconds of service to be provided 5253 to the user before the user is to be re-authenticated and/or re- 5254 authorized. Great care should be taken when the Authorization- 5255 Lifetime value is determined, since a low, non-zero, value could 5256 create significant Diameter traffic, which could congest both the 5257 network and the agents. 5259 A value of zero (0) means that immediate re-auth is necessary by the 5260 access device. This is typically used in cases where multiple 5261 authentication methods are used, and a successful auth response with 5262 this AVP set to zero is used to signal that the next authentication 5263 method is to be immediately initiated. The absence of this AVP, or a 5264 value of all ones (meaning all bits in the 32 bit field are set to 5265 one) means no re-auth is expected. 5267 If both this AVP and the Session-Timeout AVP are present in a 5268 message, the value of the latter MUST NOT be smaller than the 5269 Authorization-Lifetime AVP. 5271 An Authorization-Lifetime AVP MAY be present in re-authorization 5272 messages, and contains the number of seconds the user is authorized 5273 to receive service from the time the re-auth answer message is 5274 received by the access device. 5276 This AVP MAY be provided by the client as a hint of the maximum 5277 lifetime that it is willing to accept. However, the server MAY 5278 return a value that is equal to, or smaller, than the one provided by 5279 the client. 5281 8.10. Auth-Grace-Period AVP 5283 The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and 5284 contains the number of seconds the Diameter server will wait 5285 following the expiration of the Authorization-Lifetime AVP before 5286 cleaning up resources for the session. 5288 8.11. Auth-Session-State AVP 5290 The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and 5291 specifies whether state is maintained for a particular session. The 5292 client MAY include this AVP in requests as a hint to the server, but 5293 the value in the server's answer message is binding. The following 5294 values are supported: 5296 STATE_MAINTAINED 0 5298 This value is used to specify that session state is being 5299 maintained, and the access device MUST issue a session termination 5300 message when service to the user is terminated. This is the 5301 default value. 5303 NO_STATE_MAINTAINED 1 5305 This value is used to specify that no session termination messages 5306 will be sent by the access device upon expiration of the 5307 Authorization-Lifetime. 5309 8.12. Re-Auth-Request-Type AVP 5311 The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and 5312 is included in application-specific auth answers to inform the client 5313 of the action expected upon expiration of the Authorization-Lifetime. 5314 If the answer message contains an Authorization-Lifetime AVP with a 5315 positive value, the Re-Auth-Request-Type AVP MUST be present in an 5316 answer message. The following values are defined: 5318 AUTHORIZE_ONLY 0 5320 An authorization only re-auth is expected upon expiration of the 5321 Authorization-Lifetime. This is the default value if the AVP is 5322 not present in answer messages that include the Authorization- 5323 Lifetime. 5325 AUTHORIZE_AUTHENTICATE 1 5327 An authentication and authorization re-auth is expected upon 5328 expiration of the Authorization-Lifetime. 5330 8.13. Session-Timeout AVP 5332 The Session-Timeout AVP (AVP Code 27) [RFC2865] is of type Unsigned32 5333 and contains the maximum number of seconds of service to be provided 5334 to the user before termination of the session. When both the 5335 Session-Timeout and the Authorization-Lifetime AVPs are present in an 5336 answer message, the former MUST be equal to or greater than the value 5337 of the latter. 5339 A session that terminates on an access device due to the expiration 5340 of the Session-Timeout MUST cause an STR to be issued, unless both 5341 the access device and the home server had previously agreed that no 5342 session termination messages would be sent (see Section 8.9). 5344 A Session-Timeout AVP MAY be present in a re-authorization answer 5345 message, and contains the remaining number of seconds from the 5346 beginning of the re-auth. 5348 A value of zero, or the absence of this AVP, means that this session 5349 has an unlimited number of seconds before termination. 5351 This AVP MAY be provided by the client as a hint of the maximum 5352 timeout that it is willing to accept. However, the server MAY return 5353 a value that is equal to, or smaller, than the one provided by the 5354 client. 5356 8.14. User-Name AVP 5358 The User-Name AVP (AVP Code 1) [RFC2865] is of type UTF8String, which 5359 contains the User-Name, in a format consistent with the NAI 5360 specification [RFC4282]. 5362 8.15. Termination-Cause AVP 5364 The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and 5365 is used to indicate the reason why a session was terminated on the 5366 access device. The following values are defined: 5368 DIAMETER_LOGOUT 1 5370 The user initiated a disconnect 5372 DIAMETER_SERVICE_NOT_PROVIDED 2 5374 This value is used when the user disconnected prior to the receipt 5375 of the authorization answer message. 5377 DIAMETER_BAD_ANSWER 3 5379 This value indicates that the authorization answer received by the 5380 access device was not processed successfully. 5382 DIAMETER_ADMINISTRATIVE 4 5384 The user was not granted access, or was disconnected, due to 5385 administrative reasons, such as the receipt of a Abort-Session- 5386 Request message. 5388 DIAMETER_LINK_BROKEN 5 5390 The communication to the user was abruptly disconnected. 5392 DIAMETER_AUTH_EXPIRED 6 5394 The user's access was terminated since its authorized session time 5395 has expired. 5397 DIAMETER_USER_MOVED 7 5399 The user is receiving services from another access device. 5401 DIAMETER_SESSION_TIMEOUT 8 5403 The user's session has timed out, and service has been terminated. 5405 8.16. Origin-State-Id AVP 5407 The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a 5408 monotonically increasing value that is advanced whenever a Diameter 5409 entity restarts with loss of previous state, for example upon reboot. 5410 Origin-State-Id MAY be included in any Diameter message, including 5411 CER. 5413 A Diameter entity issuing this AVP MUST create a higher value for 5414 this AVP each time its state is reset. A Diameter entity MAY set 5415 Origin-State-Id to the time of startup, or it MAY use an incrementing 5416 counter retained in non-volatile memory across restarts. 5418 The Origin-State-Id, if present, MUST reflect the state of the entity 5419 indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST 5420 either remove Origin-State-Id or modify it appropriately as well. 5421 Typically, Origin-State-Id is used by an access device that always 5422 starts up with no active sessions; that is, any session active prior 5423 to restart will have been lost. By including Origin-State-Id in a 5424 message, it allows other Diameter entities to infer that sessions 5425 associated with a lower Origin-State-Id are no longer active. If an 5426 access device does not intend for such inferences to be made, it MUST 5427 either not include Origin-State-Id in any message, or set its value 5428 to 0. 5430 8.17. Session-Binding AVP 5432 The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY 5433 be present in application-specific authorization answer messages. If 5434 present, this AVP MAY inform the Diameter client that all future 5435 application-specific re-auth messages for this session MUST be sent 5436 to the same authorization server. This AVP MAY also specify that a 5437 Session-Termination-Request message for this session MUST be sent to 5438 the same authorizing server. 5440 This field is a bit mask, and the following bits have been defined: 5442 RE_AUTH 1 5444 When set, future re-auth messages for this session MUST NOT 5445 include the Destination-Host AVP. When cleared, the default 5446 value, the Destination-Host AVP MUST be present in all re-auth 5447 messages for this session. 5449 STR 2 5451 When set, the STR message for this session MUST NOT include the 5452 Destination-Host AVP. When cleared, the default value, the 5453 Destination-Host AVP MUST be present in the STR message for this 5454 session. 5456 ACCOUNTING 4 5458 When set, all accounting messages for this session MUST NOT 5459 include the Destination-Host AVP. When cleared, the default 5460 value, the Destination-Host AVP, if known, MUST be present in all 5461 accounting messages for this session. 5463 8.18. Session-Server-Failover AVP 5465 The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated, 5466 and MAY be present in application-specific authorization answer 5467 messages that either do not include the Session-Binding AVP or 5468 include the Session-Binding AVP with any of the bits set to a zero 5469 value. If present, this AVP MAY inform the Diameter client that if a 5470 re-auth or STR message fails due to a delivery problem, the Diameter 5471 client SHOULD issue a subsequent message without the Destination-Host 5472 AVP. When absent, the default value is REFUSE_SERVICE. 5474 The following values are supported: 5476 REFUSE_SERVICE 0 5478 If either the re-auth or the STR message delivery fails, terminate 5479 service with the user, and do not attempt any subsequent attempts. 5481 TRY_AGAIN 1 5483 If either the re-auth or the STR message delivery fails, resend 5484 the failed message without the Destination-Host AVP present. 5486 ALLOW_SERVICE 2 5488 If re-auth message delivery fails, assume that re-authorization 5489 succeeded. If STR message delivery fails, terminate the session. 5491 TRY_AGAIN_ALLOW_SERVICE 3 5493 If either the re-auth or the STR message delivery fails, resend 5494 the failed message without the Destination-Host AVP present. If 5495 the second delivery fails for re-auth, assume re-authorization 5496 succeeded. If the second delivery fails for STR, terminate the 5497 session. 5499 8.19. Multi-Round-Time-Out AVP 5501 The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32, 5502 and SHOULD be present in application-specific authorization answer 5503 messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH. 5504 This AVP contains the maximum number of seconds that the access 5505 device MUST provide the user in responding to an authentication 5506 request. 5508 8.20. Class AVP 5510 The Class AVP (AVP Code 25) is of type OctetString and is used to by 5511 Diameter servers to return state information to the access device. 5512 When one or more Class AVPs are present in application-specific 5513 authorization answer messages, they MUST be present in subsequent re- 5514 authorization, session termination and accounting messages. Class 5515 AVPs found in a re-authorization answer message override the ones 5516 found in any previous authorization answer message. Diameter server 5517 implementations SHOULD NOT return Class AVPs that require more than 5518 4096 bytes of storage on the Diameter client. A Diameter client that 5519 receives Class AVPs whose size exceeds local available storage MUST 5520 terminate the session. 5522 8.21. Event-Timestamp AVP 5524 The Event-Timestamp (AVP Code 55) is of type Time, and MAY be 5525 included in an Accounting-Request and Accounting-Answer messages to 5526 record the time that the reported event occurred, in seconds since 5527 January 1, 1900 00:00 UTC. 5529 9. Accounting 5531 This accounting protocol is based on a server directed model with 5532 capabilities for real-time delivery of accounting information. 5533 Several fault resilience methods [RFC2975] have been built in to the 5534 protocol in order minimize loss of accounting data in various fault 5535 situations and under different assumptions about the capabilities of 5536 the used devices. 5538 9.1. Server Directed Model 5540 The server directed model means that the device generating the 5541 accounting data gets information from either the authorization server 5542 (if contacted) or the accounting server regarding the way accounting 5543 data shall be forwarded. This information includes accounting record 5544 timeliness requirements. 5546 As discussed in [RFC2975], real-time transfer of accounting records 5547 is a requirement, such as the need to perform credit limit checks and 5548 fraud detection. Note that batch accounting is not a requirement, 5549 and is therefore not supported by Diameter. Should batched 5550 accounting be required in the future, a new Diameter application will 5551 need to be created, or it could be handled using another protocol. 5552 Note, however, that even if at the Diameter layer accounting requests 5553 are processed one by one, transport protocols used under Diameter 5554 typically batch several requests in the same packet under heavy 5555 traffic conditions. This may be sufficient for many applications. 5557 The authorization server (chain) directs the selection of proper 5558 transfer strategy, based on its knowledge of the user and 5559 relationships of roaming partnerships. The server (or agents) uses 5560 the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to 5561 control the operation of the Diameter peer operating as a client. 5562 The Acct-Interim-Interval AVP, when present, instructs the Diameter 5563 node acting as a client to produce accounting records continuously 5564 even during a session. Accounting-Realtime-Required AVP is used to 5565 control the behavior of the client when the transfer of accounting 5566 records from the Diameter client is delayed or unsuccessful. 5568 The Diameter accounting server MAY override the interim interval or 5569 the realtime requirements by including the Acct-Interim-Interval or 5570 Accounting-Realtime-Required AVP in the Accounting-Answer message. 5571 When one of these AVPs is present, the latest value received SHOULD 5572 be used in further accounting activities for the same session. 5574 9.2. Protocol Messages 5576 A Diameter node that receives a successful authentication and/or 5577 authorization messages from the Home AAA server MUST collect 5578 accounting information for the session. The Accounting-Request 5579 message is used to transmit the accounting information to the Home 5580 AAA server, which MUST reply with the Accounting-Answer message to 5581 confirm reception. The Accounting-Answer message includes the 5582 Result-Code AVP, which MAY indicate that an error was present in the 5583 accounting message. A rejected Accounting-Request message MAY cause 5584 the user's session to be terminated, depending on the value of the 5585 Accounting-Realtime-Required AVP received earlier for the session in 5586 question. 5588 Each Diameter Accounting protocol message MAY be compressed, in order 5589 to reduce network bandwidth usage. If TLS is used to secure the 5590 Diameter session, then TLS compression [RFC4346] MAY be used. 5592 9.3. Accounting Application Extension and Requirements 5594 Each Diameter application (e.g., NASREQ, MobileIP), MUST define their 5595 Service-Specific AVPs that MUST be present in the Accounting-Request 5596 message in a section entitled "Accounting AVPs". The application 5597 MUST assume that the AVPs described in this document will be present 5598 in all Accounting messages, so only their respective service-specific 5599 AVPs need to be defined in this section. 5601 Applications have the option of using one or both of the following 5602 accounting application extension models: 5604 Split Accounting Service 5606 The accounting message will carry the application identifier of 5607 the Diameter base accounting application (see Section 2.4). 5608 Accounting messages maybe routed to Diameter nodes other than the 5609 corresponding Diameter application. These nodes might be 5610 centralized accounting servers that provide accounting service for 5611 multiple different Diameter applications. These nodes MUST 5612 advertise the Diameter base accounting application identifier 5613 during capabilities exchange. 5615 Accounting messages which uses the Diameter base accounting 5616 application identifier in its header as well as in the Acct- 5617 Application-Id AVP. 5619 Coupled Accounting Service 5621 The accounting messages will carry the application identifier of 5622 the application that is using it. The application itself will 5623 process the received accounting records or forward them to an 5624 accounting server. There is no accounting application 5625 advertisement required during capabilities exchange and the 5626 accounting messages will be routed the same as any of the other 5627 application messages. 5629 In cases where an application does not define its own accounting 5630 service, it is preferred that the split accounting model be used. 5632 9.4. Fault Resilience 5634 Diameter Base protocol mechanisms are used to overcome small message 5635 loss and network faults of temporary nature. 5637 Diameter peers acting as clients MUST implement the use of failover 5638 to guard against server failures and certain network failures. 5639 Diameter peers acting as agents or related off-line processing 5640 systems MUST detect duplicate accounting records caused by the 5641 sending of same record to several servers and duplication of messages 5642 in transit. This detection MUST be based on the inspection of the 5643 Session-Id and Accounting-Record-Number AVP pairs. Appendix C 5644 discusses duplicate detection needs and implementation issues. 5646 Diameter clients MAY have non-volatile memory for the safe storage of 5647 accounting records over reboots or extended network failures, network 5648 partitions, and server failures. If such memory is available, the 5649 client SHOULD store new accounting records there as soon as the 5650 records are created and until a positive acknowledgement of their 5651 reception from the Diameter Server has been received. Upon a reboot, 5652 the client MUST starting sending the records in the non-volatile 5653 memory to the accounting server with appropriate modifications in 5654 termination cause, session length, and other relevant information in 5655 the records. 5657 A further application of this protocol may include AVPs to control 5658 how many accounting records may at most be stored in the Diameter 5659 client without committing them to the non-volatile memory or 5660 transferring them to the Diameter server. 5662 The client SHOULD NOT remove the accounting data from any of its 5663 memory areas before the correct Accounting-Answer has been received. 5664 The client MAY remove oldest, undelivered or yet unacknowledged 5665 accounting data if it runs out of resources such as memory. It is an 5666 implementation dependent matter for the client to accept new sessions 5667 under this condition. 5669 9.5. Accounting Records 5671 In all accounting records, the Session-Id AVP MUST be present; the 5672 User-Name AVP MUST be present if it is available to the Diameter 5673 client. 5675 Different types of accounting records are sent depending on the 5676 actual type of accounted service and the authorization server's 5677 directions for interim accounting. If the accounted service is a 5678 one-time event, meaning that the start and stop of the event are 5679 simultaneous, then the Accounting-Record-Type AVP MUST be present and 5680 set to the value EVENT_RECORD. 5682 If the accounted service is of a measurable length, then the AVP MUST 5683 use the values START_RECORD, STOP_RECORD, and possibly, 5684 INTERIM_RECORD. If the authorization server has not directed interim 5685 accounting to be enabled for the session, two accounting records MUST 5686 be generated for each service of type session. When the initial 5687 Accounting-Request for a given session is sent, the Accounting- 5688 Record-Type AVP MUST be set to the value START_RECORD. When the last 5689 Accounting-Request is sent, the value MUST be STOP_RECORD. 5691 If the authorization server has directed interim accounting to be 5692 enabled, the Diameter client MUST produce additional records between 5693 the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The 5694 production of these records is directed by Acct-Interim-Interval as 5695 well as any re-authentication or re-authorization of the session. 5696 The Diameter client MUST overwrite any previous interim accounting 5697 records that are locally stored for delivery, if a new record is 5698 being generated for the same session. This ensures that only one 5699 pending interim record can exist on an access device for any given 5700 session. 5702 A particular value of Accounting-Sub-Session-Id MUST appear only in 5703 one sequence of accounting records from a DIAMETER client, except for 5704 the purposes of retransmission. The one sequence that is sent MUST 5705 be either one record with Accounting-Record-Type AVP set to the value 5706 EVENT_RECORD, or several records starting with one having the value 5707 START_RECORD, followed by zero or more INTERIM_RECORD and a single 5708 STOP_RECORD. A particular Diameter application specification MUST 5709 define the type of sequences that MUST be used. 5711 9.6. Correlation of Accounting Records 5713 The Diameter protocol's Session-Id AVP, which is globally unique (see 5714 Section 8.8), is used during the authorization phase to identify a 5715 particular session. Services that do not require any authorization 5716 still use the Session-Id AVP to identify sessions. Accounting 5717 messages MAY use a different Session-Id from that sent in 5718 authorization messages. Specific applications MAY require different 5719 a Session-ID for accounting messages. 5721 However, there are certain applications that require multiple 5722 accounting sub-sessions. Such applications would send messages with 5723 a constant Session-Id AVP, but a different Accounting-Sub-Session-Id 5724 AVP. In these cases, correlation is performed using the Session-Id. 5725 It is important to note that receiving a STOP_RECORD with no 5726 Accounting-Sub-Session-Id AVP when sub-sessions were originally used 5727 in the START_RECORD messages implies that all sub-sessions are 5728 terminated. 5730 Furthermore, there are certain applications where a user receives 5731 service from different access devices (e.g., Mobile IPv4), each with 5732 their own unique Session-Id. In such cases, the Acct-Multi-Session- 5733 Id AVP is used for correlation. During authorization, a server that 5734 determines that a request is for an existing session SHOULD include 5735 the Acct-Multi-Session-Id AVP, which the access device MUST include 5736 in all subsequent accounting messages. 5738 The Acct-Multi-Session-Id AVP MAY include the value of the original 5739 Session-Id. It's contents are implementation specific, but MUST be 5740 globally unique across other Acct-Multi-Session-Id, and MUST NOT 5741 change during the life of a session. 5743 A Diameter application document MUST define the exact concept of a 5744 session that is being accounted, and MAY define the concept of a 5745 multi-session. For instance, the NASREQ DIAMETER application treats 5746 a single PPP connection to a Network Access Server as one session, 5747 and a set of Multilink PPP sessions as one multi-session. 5749 9.7. Accounting Command-Codes 5751 This section defines Command-Code values that MUST be supported by 5752 all Diameter implementations that provide Accounting services. 5754 9.7.1. Accounting-Request 5756 The Accounting-Request (ACR) command, indicated by the Command-Code 5757 field set to 271 and the Command Flags' 'R' bit set, is sent by a 5758 Diameter node, acting as a client, in order to exchange accounting 5759 information with a peer. 5761 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs 5762 MUST be present. If the Vendor-Specific-Application-Id grouped AVP 5763 is present, it must have an Acct-Application-Id inside. 5765 The AVP listed below SHOULD include service specific accounting AVPs, 5766 as described in Section 9.3. 5768 Message Format 5770 ::= < Diameter Header: 271, REQ, PXY > 5771 < Session-Id > 5772 { Origin-Host } 5773 { Origin-Realm } 5774 { Destination-Realm } 5775 { Accounting-Record-Type } 5776 { Accounting-Record-Number } 5777 [ Acct-Application-Id ] 5778 [ Vendor-Specific-Application-Id ] 5779 [ User-Name ] 5780 [ Destination-Host ] 5781 [ Accounting-Sub-Session-Id ] 5782 [ Acct-Session-Id ] 5783 [ Acct-Multi-Session-Id ] 5784 [ Acct-Interim-Interval ] 5785 [ Accounting-Realtime-Required ] 5786 [ Origin-State-Id ] 5787 [ Event-Timestamp ] 5788 * [ Proxy-Info ] 5789 * [ Route-Record ] 5790 * [ AVP ] 5792 9.7.2. Accounting-Answer 5794 The Accounting-Answer (ACA) command, indicated by the Command-Code 5795 field set to 271 and the Command Flags' 'R' bit cleared, is used to 5796 acknowledge an Accounting-Request command. The Accounting-Answer 5797 command contains the same Session-Id as the corresponding request. 5799 Only the target Diameter Server, known as the home Diameter Server, 5800 SHOULD respond with the Accounting-Answer command. 5802 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs 5803 MUST be present. If the Vendor-Specific-Application-Id grouped AVP 5804 is present, it must have an Acct-Application-Id inside. 5806 The AVP listed below SHOULD include service specific accounting AVPs, 5807 as described in Section 9.3. 5809 Message Format 5811 ::= < Diameter Header: 271, PXY > 5812 < Session-Id > 5813 { Result-Code } 5814 { Origin-Host } 5815 { Origin-Realm } 5816 { Accounting-Record-Type } 5817 { Accounting-Record-Number } 5818 [ Acct-Application-Id ] 5819 [ Vendor-Specific-Application-Id ] 5820 [ User-Name ] 5821 [ Accounting-Sub-Session-Id ] 5822 [ Acct-Session-Id ] 5823 [ Acct-Multi-Session-Id ] 5824 [ Error-Message ] 5825 [ Error-Reporting-Host ] 5826 [ Failed-AVP ] 5827 [ Acct-Interim-Interval ] 5828 [ Accounting-Realtime-Required ] 5829 [ Origin-State-Id ] 5830 [ Event-Timestamp ] 5831 * [ Proxy-Info ] 5832 * [ AVP ] 5834 9.8. Accounting AVPs 5836 This section contains AVPs that describe accounting usage information 5837 related to a specific session. 5839 9.8.1. Accounting-Record-Type AVP 5841 The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated 5842 and contains the type of accounting record being sent. The following 5843 values are currently defined for the Accounting-Record-Type AVP: 5845 EVENT_RECORD 1 5847 An Accounting Event Record is used to indicate that a one-time 5848 event has occurred (meaning that the start and end of the event 5849 are simultaneous). This record contains all information relevant 5850 to the service, and is the only record of the service. 5852 START_RECORD 2 5854 An Accounting Start, Interim, and Stop Records are used to 5855 indicate that a service of a measurable length has been given. An 5856 Accounting Start Record is used to initiate an accounting session, 5857 and contains accounting information that is relevant to the 5858 initiation of the session. 5860 INTERIM_RECORD 3 5862 An Interim Accounting Record contains cumulative accounting 5863 information for an existing accounting session. Interim 5864 Accounting Records SHOULD be sent every time a re-authentication 5865 or re-authorization occurs. Further, additional interim record 5866 triggers MAY be defined by application-specific Diameter 5867 applications. The selection of whether to use INTERIM_RECORD 5868 records is done by the Acct-Interim-Interval AVP. 5870 STOP_RECORD 4 5872 An Accounting Stop Record is sent to terminate an accounting 5873 session and contains cumulative accounting information relevant to 5874 the existing session. 5876 9.8.2. Acct-Interim-Interval 5878 The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and 5879 is sent from the Diameter home authorization server to the Diameter 5880 client. The client uses information in this AVP to decide how and 5881 when to produce accounting records. With different values in this 5882 AVP, service sessions can result in one, two, or two+N accounting 5883 records, based on the needs of the home-organization. The following 5884 accounting record production behavior is directed by the inclusion of 5885 this AVP: 5887 1. The omission of the Acct-Interim-Interval AVP or its inclusion 5888 with Value field set to 0 means that EVENT_RECORD, START_RECORD, 5889 and STOP_RECORD are produced, as appropriate for the service. 5891 2. The inclusion of the AVP with Value field set to a non-zero value 5892 means that INTERIM_RECORD records MUST be produced between the 5893 START_RECORD and STOP_RECORD records. The Value field of this 5894 AVP is the nominal interval between these records in seconds. 5896 The Diameter node that originates the accounting information, 5897 known as the client, MUST produce the first INTERIM_RECORD record 5898 roughly at the time when this nominal interval has elapsed from 5899 the START_RECORD, the next one again as the interval has elapsed 5900 once more, and so on until the session ends and a STOP_RECORD 5901 record is produced. 5903 The client MUST ensure that the interim record production times 5904 are randomized so that large accounting message storms are not 5905 created either among records or around a common service start 5906 time. 5908 9.8.3. Accounting-Record-Number AVP 5910 The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32 5911 and identifies this record within one session. As Session-Id AVPs 5912 are globally unique, the combination of Session-Id and Accounting- 5913 Record-Number AVPs is also globally unique, and can be used in 5914 matching accounting records with confirmations. An easy way to 5915 produce unique numbers is to set the value to 0 for records of type 5916 EVENT_RECORD and START_RECORD, and set the value to 1 for the first 5917 INTERIM_RECORD, 2 for the second, and so on until the value for 5918 STOP_RECORD is one more than for the last INTERIM_RECORD. 5920 9.8.4. Acct-Session-Id AVP 5922 The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only 5923 used when RADIUS/Diameter translation occurs. This AVP contains the 5924 contents of the RADIUS Acct-Session-Id attribute. 5926 9.8.5. Acct-Multi-Session-Id AVP 5928 The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String, 5929 following the format specified in Section 8.8. The Acct-Multi- 5930 Session-Id AVP is used to link together multiple related accounting 5931 sessions, where each session would have a unique Session-Id, but the 5932 same Acct-Multi-Session-Id AVP. This AVP MAY be returned by the 5933 Diameter server in an authorization answer, and MUST be used in all 5934 accounting messages for the given session. 5936 9.8.6. Accounting-Sub-Session-Id AVP 5938 The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type 5939 Unsigned64 and contains the accounting sub-session identifier. The 5940 combination of the Session-Id and this AVP MUST be unique per sub- 5941 session, and the value of this AVP MUST be monotonically increased by 5942 one for all new sub-sessions. The absence of this AVP implies no 5943 sub-sessions are in use, with the exception of an Accounting-Request 5944 whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD 5945 message with no Accounting-Sub-Session-Id AVP present will signal the 5946 termination of all sub-sessions for a given Session-Id. 5948 9.8.7. Accounting-Realtime-Required AVP 5950 The Accounting-Realtime-Required AVP (AVP Code 483) is of type 5951 Enumerated and is sent from the Diameter home authorization server to 5952 the Diameter client or in the Accounting-Answer from the accounting 5953 server. The client uses information in this AVP to decide what to do 5954 if the sending of accounting records to the accounting server has 5955 been temporarily prevented due to, for instance, a network problem. 5957 DELIVER_AND_GRANT 1 5959 The AVP with Value field set to DELIVER_AND_GRANT means that the 5960 service MUST only be granted as long as there is a connection to 5961 an accounting server. Note that the set of alternative accounting 5962 servers are treated as one server in this sense. Having to move 5963 the accounting record stream to a backup server is not a reason to 5964 discontinue the service to the user. 5966 GRANT_AND_STORE 2 5968 The AVP with Value field set to GRANT_AND_STORE means that service 5969 SHOULD be granted if there is a connection, or as long as records 5970 can still be stored as described in Section 9.4. 5972 This is the default behavior if the AVP isn't included in the 5973 reply from the authorization server. 5975 GRANT_AND_LOSE 3 5977 The AVP with Value field set to GRANT_AND_LOSE means that service 5978 SHOULD be granted even if the records can not be delivered or 5979 stored. 5981 10. AVP Occurrence Table 5983 The following tables presents the AVPs defined in this document, and 5984 specifies in which Diameter messages they MAY be present or not. 5985 AVPs that occur only inside a Grouped AVP are not shown in this 5986 table. 5988 The table uses the following symbols: 5990 0 The AVP MUST NOT be present in the message. 5992 0+ Zero or more instances of the AVP MAY be present in the 5993 message. 5995 0-1 Zero or one instance of the AVP MAY be present in the message. 5996 It is considered an error if there are more than one instance of 5997 the AVP. 5999 1 One instance of the AVP MUST be present in the message. 6001 1+ At least one instance of the AVP MUST be present in the 6002 message. 6004 10.1. Base Protocol Command AVP Table 6006 The table in this section is limited to the non-accounting Command 6007 Codes defined in this specification. 6009 +-----------------------------------------------+ 6010 | Command-Code | 6011 +---+---+---+---+---+---+---+---+---+---+---+---+ 6012 Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA| 6013 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ 6014 Acct-Interim- |0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | 6015 Interval | | | | | | | | | | | | | 6016 Accounting-Realtime-|0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 | 6017 Required | | | | | | | | | | | | | 6018 Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6019 Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | 6020 Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6021 Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6022 Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6023 Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6024 Lifetime | | | | | | | | | | | | | 6025 Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ | 6026 Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 | 6027 Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 | 6028 Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6029 Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1| 6030 Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6031 Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ | 6032 Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6033 Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6034 Inband-Security-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6035 Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6036 Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | 6037 Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 | 6038 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| 6039 Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6040 Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ | 6041 Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ | 6042 Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6043 Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1| 6044 Time | | | | | | | | | | | | | 6045 Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 | 6046 Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 | 6047 Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 | 6048 Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6049 Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 | 6050 Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6051 Failover | | | | | | | | | | | | | 6052 Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6053 Supported-Vendor-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6054 Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 | 6055 User-Name |0 |0 |0 |0 |0 |0 |0-1|0-1|0-1|0-1|0-1|0-1| 6056 Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6057 Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 | 6058 Application-Id | | | | | | | | | | | | | 6059 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+ 6061 10.2. Accounting AVP Table 6063 The table in this section is used to represent which AVPs defined in 6064 this document are to be present in the Accounting messages. These 6065 AVP occurrence requirements are guidelines, which may be expanded, 6066 and/or overridden by application-specific requirements in the 6067 Diameter applications documents. 6069 +-----------+ 6070 | Command | 6071 | Code | 6072 +-----+-----+ 6073 Attribute Name | ACR | ACA | 6074 ------------------------------+-----+-----+ 6075 Acct-Interim-Interval | 0-1 | 0-1 | 6076 Acct-Multi-Session-Id | 0-1 | 0-1 | 6077 Accounting-Record-Number | 1 | 1 | 6078 Accounting-Record-Type | 1 | 1 | 6079 Acct-Session-Id | 0-1 | 0-1 | 6080 Accounting-Sub-Session-Id | 0-1 | 0-1 | 6081 Accounting-Realtime-Required | 0-1 | 0-1 | 6082 Acct-Application-Id | 0-1 | 0-1 | 6083 Auth-Application-Id | 0 | 0 | 6084 Class | 0+ | 0+ | 6085 Destination-Host | 0-1 | 0 | 6086 Destination-Realm | 1 | 0 | 6087 Error-Reporting-Host | 0 | 0+ | 6088 Event-Timestamp | 0-1 | 0-1 | 6089 Origin-Host | 1 | 1 | 6090 Origin-Realm | 1 | 1 | 6091 Proxy-Info | 0+ | 0+ | 6092 Route-Record | 0+ | 0 | 6093 Result-Code | 0 | 1 | 6094 Session-Id | 1 | 1 | 6095 Termination-Cause | 0 | 0 | 6096 User-Name | 0-1 | 0-1 | 6097 Vendor-Specific-Application-Id| 0-1 | 0-1 | 6098 ------------------------------+-----+-----+ 6100 11. IANA Considerations 6102 This section provides guidance to the Internet Assigned Numbers 6103 Authority (IANA) regarding registration of values related to the 6104 Diameter protocol, in accordance with BCP 26 [RFC2434]. The 6105 following policies are used here with the meanings defined in BCP 26: 6106 "Private Use", "First Come First Served", "Expert Review", 6107 "Specification Required", "IETF Consensus", "Standards Action". 6109 This section explains the criteria to be used by the IANA for 6110 assignment of numbers within namespaces defined within this document. 6112 Diameter is not intended as a general purpose protocol, and 6113 allocations SHOULD NOT be made for purposes unrelated to 6114 authentication, authorization or accounting. 6116 For registration requests where a Designated Expert should be 6117 consulted, the responsible IESG area director should appoint the 6118 Designated Expert. For Designated Expert with Specification 6119 Required, the request is posted to the DIME WG mailing list (or, if 6120 it has been disbanded, a successor designated by the Area Director) 6121 for comment and review, and MUST include a pointer to a public 6122 specification. Before a period of 30 days has passed, the Designated 6123 Expert will either approve or deny the registration request and 6124 publish a notice of the decision to the DIME WG mailing list or its 6125 successor. A denial notice must be justified by an explanation and, 6126 in the cases where it is possible, concrete suggestions on how the 6127 request can be modified so as to become acceptable. 6129 11.1. AVP Header 6131 As defined in Section 4, the AVP header contains three fields that 6132 requires IANA namespace management; the AVP Code, Vendor-ID and Flags 6133 field. 6135 11.1.1. AVP Codes 6137 The AVP Code namespace is used to identify attributes. There are 6138 multiple namespaces. Vendors can have their own AVP Codes namespace 6139 which will be identified by their Vendor-ID (also known as 6140 Enterprise-Number) and they control the assignments of their vendor- 6141 specific AVP codes within their own namespace. The absence of a 6142 Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA 6143 controlled AVP Codes namespace. The AVP Codes and sometimes also 6144 possible values in an AVP are controlled and maintained by IANA. 6146 AVP Code 0 is not used. AVP Codes 1-255 are managed separately as 6147 RADIUS Attribute Types [RADTYPE]. This document defines the AVP 6148 Codes 257-274, 276-285, 287, 291-300, 480, 483 and 485-486. See 6149 Section 4.5 for the assignment of the namespace in this 6150 specification. 6152 AVPs may be allocated following Designated Expert with Specification 6153 Required [RFC2434]. Release of blocks of AVPs (more than 3 at a time 6154 for a given purpose) should require IETF Consensus. 6156 Note that Diameter defines a mechanism for Vendor-Specific AVPs, 6157 where the Vendor-Id field in the AVP header is set to a non-zero 6158 value. Vendor-Specific AVPs codes are for Private Use and should be 6159 encouraged instead of allocation of global attribute types, for 6160 functions specific only to one vendor's implementation of Diameter, 6161 where no interoperability is deemed useful. Where a Vendor-Specific 6162 AVP is implemented by more than one vendor, allocation of global AVPs 6163 should be encouraged instead. 6165 11.1.2. AVP Flags 6167 There are 8 bits in the AVP Flags field of the AVP header, defined in 6168 Section 4. This document assigns bit 0 ('V'endor Specific), bit 1 6169 ('M'andatory) and bit 2 ('P'rotected). The remaining bits should 6170 only be assigned via a Standards Action [RFC2434]. 6172 11.2. Diameter Header 6174 As defined in Section 3, the Diameter header contains two fields that 6175 require IANA namespace management; Command Code and Command Flags. 6177 11.2.1. Command Codes 6179 The Command Code namespace is used to identify Diameter commands. 6180 The values 0-255 (0x00-0xff) are reserved for RADIUS backward 6181 compatibility, and are defined as "RADIUS Packet Type Codes" in 6182 [RADTYPE]. Values 256 - 8,388,607 (0x100 to 0x7fffff) are for 6183 permanent, standard commands, allocated by IETF Consensus [RFC2434]. 6184 This document defines the Command Codes 257, 258, 271, 274-275, 280 6185 and 282. See Section 3.1 for the assignment of the namespace in this 6186 specification. 6188 The values 8,388,608 - 16,777,213 (0x800000 - 0xfffffd) are reserved 6189 for vendor-specific command codes, to be allocated on a First Come, 6190 First Served basis by IANA [RFC2434]. The request to IANA for a 6191 Vendor-Specific Command Code SHOULD include a reference to a publicly 6192 available specification which documents the command in sufficient 6193 detail to aid in interoperability between independent 6194 implementations. If the specification cannot be made publicly 6195 available, the request for a vendor-specific command code MUST 6196 include the contact information of persons and/or entities 6197 responsible for authoring and maintaining the command. 6199 The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe - 6200 0xffffff) are reserved for experimental commands. As these codes are 6201 only for experimental and testing purposes, no guarantee is made for 6202 interoperability between Diameter peers using experimental commands, 6203 as outlined in [IANA-EXP]. 6205 11.2.2. Command Flags 6207 There are eight bits in the Command Flags field of the Diameter 6208 header. This document assigns bit 0 ('R'equest), bit 1 ('P'roxy), 6209 bit 2 ('E'rror) and bit 3 ('T'). Bits 4 through 7 MUST only be 6210 assigned via a Standards Action [RFC2434]. 6212 11.3. Application Identifiers 6214 As defined in Section 2.4, the Application Identifier is used to 6215 identify a specific Diameter Application. There are standards-track 6216 application ids and vendor specific application ids. 6218 IANA [RFC2434] has assigned the range 0x00000001 to 0x00ffffff for 6219 standards-track applications; and 0x01000000 - 0xfffffffe for vendor 6220 specific applications, on a first-come, first-served basis. The 6221 following values are allocated. 6223 Diameter Common Messages 0 6224 NASREQ 1 [RFC4005] 6225 Mobile-IP 2 [RFC4004] 6226 Diameter Base Accounting 3 6227 Relay 0xffffffff 6229 Assignment of standards-track application IDs are by Designated 6230 Expert with Specification Required [RFC2434]. 6232 Both Auth-Application-Id and Acct-Application-Id AVPs use the same 6233 Application Identifier space. A diameter node advertising itself as 6234 a relay agent MUST set either Application-Id or Acct-Application-Id 6235 to 0xffffffff. 6237 Vendor-Specific Application Identifiers, are for Private Use. Vendor- 6238 Specific Application Identifiers are assigned on a First Come, First 6239 Served basis by IANA. 6241 11.4. AVP Values 6243 Certain AVPs in Diameter define a list of values with various 6244 meanings. For attributes other than those specified in this section, 6245 adding additional values to the list can be done on a First Come, 6246 First Served basis by IANA. 6248 11.4.1. Result-Code AVP Values 6250 As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines 6251 the values 1001, 2001-2002, 3001-3012, 4001-4003 and 5001-5021. 6253 All remaining values are available for assignment via IETF Consensus 6254 [RFC2434]. 6256 11.4.2. Accounting-Record-Type AVP Values 6258 As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code 6259 480) defines the values 1-4. All remaining values are available for 6260 assignment via IETF Consensus [RFC2434]. 6262 11.4.3. Termination-Cause AVP Values 6264 As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295) 6265 defines the values 1-8. All remaining values are available for 6266 assignment via IETF Consensus [RFC2434]. 6268 11.4.4. Redirect-Host-Usage AVP Values 6270 As defined in Section 6.13, the Redirect-Host-Usage AVP (AVP Code 6271 261) defines the values 0-5. All remaining values are available for 6272 assignment via IETF Consensus [RFC2434]. 6274 11.4.5. Session-Server-Failover AVP Values 6276 As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code 6277 271) defines the values 0-3. All remaining values are available for 6278 assignment via IETF Consensus [RFC2434]. 6280 11.4.6. Session-Binding AVP Values 6282 As defined in Section 8.17, the Session-Binding AVP (AVP Code 270) 6283 defines the bits 1-4. All remaining bits are available for 6284 assignment via IETF Consensus [RFC2434]. 6286 11.4.7. Disconnect-Cause AVP Values 6288 As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273) 6289 defines the values 0-2. All remaining values are available for 6290 assignment via IETF Consensus [RFC2434]. 6292 11.4.8. Auth-Request-Type AVP Values 6294 As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274) 6295 defines the values 1-3. All remaining values are available for 6296 assignment via IETF Consensus [RFC2434]. 6298 11.4.9. Auth-Session-State AVP Values 6300 As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277) 6301 defines the values 0-1. All remaining values are available for 6302 assignment via IETF Consensus [RFC2434]. 6304 11.4.10. Re-Auth-Request-Type AVP Values 6306 As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code 6307 285) defines the values 0-1. All remaining values are available for 6308 assignment via IETF Consensus [RFC2434]. 6310 11.4.11. Accounting-Realtime-Required AVP Values 6312 As defined in Section 9.8.7, the Accounting-Realtime-Required AVP 6313 (AVP Code 483) defines the values 1-3. All remaining values are 6314 available for assignment via IETF Consensus [RFC2434]. 6316 11.4.12. Inband-Security-Id AVP (code 299) 6318 As defined in Section 6.10, the Inband-Security-Id AVP (AVP Code 299) 6319 defines the values 0-1. All remaining values are available for 6320 assignment via IETF Consensus [RFC2434]. 6322 11.5. Diameter TCP/SCTP Port Numbers 6324 The IANA has assigned TCP and SCTP port number 3868 to Diameter. 6326 11.6. NAPTR Service Fields 6328 The registration in the RFC MUST include the following information: 6330 Service Field: The service field being registered. An example for a 6331 new fictitious transport protocol called NCTP might be "AAA+D2N". 6333 Protocol: The specific transport protocol associated with that 6334 service field. This MUST include the name and acronym for the 6335 protocol, along with reference to a document that describes the 6336 transport protocol. For example - "New Connectionless Transport 6337 Protocol (NCTP), RFC 5766". 6339 Name and Contact Information: The name, address, email address and 6340 telephone number for the person performing the registration. 6342 The following values have been placed into the registry: 6344 Services Field Protocol 6346 AAA+D2T TCP 6347 AAA+D2S SCTP 6349 12. Diameter protocol related configurable parameters 6351 This section contains the configurable parameters that are found 6352 throughout this document: 6354 Diameter Peer 6356 A Diameter entity MAY communicate with peers that are statically 6357 configured. A statically configured Diameter peer would require 6358 that either the IP address or the fully qualified domain name 6359 (FQDN) be supplied, which would then be used to resolve through 6360 DNS. 6362 Routing Table 6364 A Diameter proxy server routes messages based on the realm portion 6365 of a Network Access Identifier (NAI). The server MUST have a 6366 table of Realm Names, and the address of the peer to which the 6367 message must be forwarded to. The routing table MAY also include 6368 a "default route", which is typically used for all messages that 6369 cannot be locally processed. 6371 Tc timer 6373 The Tc timer controls the frequency that transport connection 6374 attempts are done to a peer with whom no active transport 6375 connection exists. The recommended value is 30 seconds. 6377 13. Security Considerations 6379 The Diameter base protocol messages SHOULD be secured by using TLS 6380 [RFC4346]. Additional security measures that are transparent to and 6381 independent of Diameter, such as IPSec [RFC4301], can also be 6382 deployed to secure connections between peers. 6384 During deployment, connections between Diameter nodes SHOULD be 6385 protected by TLS. All Diameter base protocol implementations MUST 6386 support the use of TLS. The Diameter protocol SHOULD NOT be used 6387 without any security mechanism. 6389 If a Diameter connection is to be protected via TLS, then the CER/CEA 6390 exchange MUST include an Inband-Security-ID AVP with a value of TLS. 6391 For TLS usage, a TLS handshake will begin when both ends are in the 6392 open state, after completion of the CER/CEA exchange. If the TLS 6393 handshake is successful, all further messages will be sent via TLS. 6394 If the handshake fails, both ends move to the closed state. See 6395 Sections 13.1 for more details. 6397 13.1. TLS Usage 6399 A Diameter node that initiates a connection to another Diameter node 6400 acts as a TLS client according to [RFC4346], and a Diameter node that 6401 accepts a connection acts as a TLS server. Diameter nodes 6402 implementing TLS for security MUST mutually authenticate as part of 6403 TLS session establishment. In order to ensure mutual authentication, 6404 the Diameter node acting as TLS server must request a certificate 6405 from the Diameter node acting as TLS client, and the Diameter node 6406 acting as TLS client MUST be prepared to supply a certificate on 6407 request. 6409 Diameter nodes MUST be able to negotiate the following TLS cipher 6410 suites: 6412 TLS_RSA_WITH_RC4_128_MD5 6413 TLS_RSA_WITH_RC4_128_SHA 6414 TLS_RSA_WITH_3DES_EDE_CBC_SHA 6416 Diameter nodes SHOULD be able to negotiate the following TLS cipher 6417 suite: 6419 TLS_RSA_WITH_AES_128_CBC_SHA 6421 Diameter nodes MAY negotiate other TLS cipher suites. 6423 Upon receiving the peers certificate, Diameter nodes SHOULD further 6424 validate the identity of the peer by matching the received Origin- 6425 Host and/or Origin-Realm in the CER and CEA exchange against the 6426 content of the peers certificate. Diameter peer hostname and/or 6427 realm validation can be performed in the following order: 6429 o If one ore more 'Subject Alternate Name (subjectAltName)' 6430 extension of type dNSName is present in the certificate (See 6431 [RFC3280]), then the Origin-Host value can be used to find a 6432 matching extension. 6434 o If there are no matches found, then the Origin-Realm value can be 6435 used to find a matching subjectAltName extension. 6437 o Otherwise, the Origin-Host value should be found within the 6438 'Common Name (CN)' field in the Subject field of the certificate 6439 (See [RFC3280]). 6441 Identity validation MAY be omitted by a Diameter node if the 6442 information contained in the certificate cannot be co-related or 6443 mapped to the Origin-Host and Origin-Realm presented by a peer. 6444 However, the Diameter node SHOULD have external information or other 6445 means to validate the identity of a peer. 6447 13.2. Peer-to-Peer Considerations 6449 As with any peer-to-peer protocol, proper configuration of the trust 6450 model within a Diameter peer is essential to security. When 6451 certificates are used, it is necessary to configure the root 6452 certificate authorities trusted by the Diameter peer. These root CAs 6453 are likely to be unique to Diameter usage and distinct from the root 6454 CAs that might be trusted for other purposes such as Web browsing. 6455 In general, it is expected that those root CAs will be configured so 6456 as to reflect the business relationships between the organization 6457 hosting the Diameter peer and other organizations. As a result, a 6458 Diameter peer will typically not be configured to allow connectivity 6459 with any arbitrary peer. With certificate authentication, Diameter 6460 peers may not be known beforehand and therefore peer discovery may be 6461 required. 6463 14. References 6465 14.1. Normative References 6467 [FLOATPOINT] 6468 Institute of Electrical and Electronics Engineers, "IEEE 6469 Standard for Binary Floating-Point Arithmetic, ANSI/IEEE 6470 Standard 754-1985", August 1985. 6472 [IANAADFAM] 6473 IANA,, "Address Family Numbers", 6474 http://www.iana.org/assignments/address-family-numbers. 6476 [RADTYPE] IANA,, "RADIUS Types", 6477 http://www.iana.org/assignments/radius-types. 6479 [IPV4] Postel, J., "Internet Protocol", RFC 791, September 1981. 6481 [TCP] Postel, J., "Transmission Control Protocol", RFC 793, 6482 January 1981. 6484 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and 6485 Accounting (AAA) Transport Profile", RFC 3539, June 2003. 6487 [RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and 6488 P. McCann, "Diameter Mobile IPv4 Application", RFC 4004, 6489 August 2005. 6491 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton, 6492 "Diameter Network Access Server Application", RFC 4005, 6493 August 2005. 6495 [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J. 6496 Loughney, "Diameter Credit-Control Application", RFC 4006, 6497 August 2005. 6499 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible 6500 Authentication Protocol (EAP) Application", RFC 4072, 6501 August 2005. 6503 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M., 6504 Canales-Valenzuela, C., and K. Tammi, "Diameter Session 6505 Initiation Protocol (SIP) Application", RFC 4740, 6506 November 2006. 6508 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 6509 Specifications: ABNF", RFC 4234, October 2005. 6511 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. 6512 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 6514 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 6515 Levkowetz, "Extensible Authentication Protocol (EAP)", 6516 RFC 3748, June 2004. 6518 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 6519 IANA Considerations Section in RFCs", BCP 26, RFC 2434, 6520 October 1998. 6522 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 6523 RFC 4306, December 2005. 6525 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 6526 Architecture", RFC 4291, February 2006. 6528 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 6529 Requirement Levels", BCP 14, RFC 2119, March 1997. 6531 [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The 6532 Network Access Identifier", RFC 4282, December 2005. 6534 [RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS) 6535 Part Three: The Domain Name System (DNS) Database", 6536 RFC 3403, October 2002. 6538 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 6539 A., Peterson, J., Sparks, R., Handley, M., and E. 6540 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 6541 June 2002. 6543 [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C., 6544 Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M., 6545 Zhang, L., and V. Paxson, "Stream Control Transmission 6546 Protocol", RFC 2960, October 2000. 6548 [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security 6549 (TLS) Protocol Version 1.1", RFC 4346, April 2006. 6551 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 6552 Resource Identifier (URI): Generic Syntax", STD 66, 6553 RFC 3986, January 2005. 6555 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 6556 10646", STD 63, RFC 3629, November 2003. 6558 [RFC3280] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet 6559 X.509 Public Key Infrastructure Certificate and 6560 Certificate Revocation List (CRL) Profile", RFC 3280, 6561 April 2002. 6563 [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, 6564 "Internationalizing Domain Names in Applications (IDNA)", 6565 RFC 3490, March 2003. 6567 [RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep 6568 Profile for Internationalized Domain Names (IDN)", 6569 RFC 3491, March 2003. 6571 [RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode 6572 for Internationalized Domain Names in Applications 6573 (IDNA)", RFC 3492, March 2003. 6575 14.2. Informational References 6577 [RFC2989] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, P., 6578 Shiino, H., Zorn, G., Dommety, G., C.Perkins, B.Patil, 6579 D.Mitton, S.Manning, M.Beadles, P.Walsh, X.Chen, 6580 S.Sivalingham, A.Hameed, M.Munson, S.Jacobs, B.Lim, 6581 B.Hirschman, R.Hsu, Y.Xu, E.Campell, S.Baba, and E.Jaques, 6582 "Criteria for Evaluating AAA Protocols for Network 6583 Access", RFC 2989, November 2000. 6585 [RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction to 6586 Accounting Management", RFC 2975, October 2000. 6588 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by 6589 an On-line Database", RFC 3232, January 2002. 6591 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B. 6592 Aboba, "Dynamic Authorization Extensions to Remote 6593 Authentication Dial In User Service (RADIUS)", RFC 3576, 6594 July 2003. 6596 [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, 6597 RFC 1661, July 1994. 6599 [RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy 6600 Implementation in Roaming", RFC 2607, June 1999. 6602 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. 6604 [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS 6605 Extensions", RFC 2869, June 2000. 6607 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 6608 "Remote Authentication Dial In User Service (RADIUS)", 6609 RFC 2865, June 2000. 6611 [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6", 6612 RFC 3162, August 2001. 6614 [RFC2194] Aboba, B., Lu, J., Alsop, J., Ding, J., and W. Wang, 6615 "Review of Roaming Implementations", RFC 2194, 6616 September 1997. 6618 [RFC2477] Aboba, B. and G. Zorn, "Criteria for Evaluating Roaming 6619 Protocols", RFC 2477, January 1999. 6621 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 6622 Internet Protocol", RFC 4301, December 2005. 6624 [RFC4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 6625 for IPv4, IPv6 and OSI", RFC 4330, January 2006. 6627 [RFC1492] Finseth, C., "An Access Control Protocol, Sometimes Called 6628 TACACS", RFC 1492, July 1993. 6630 [RFC4690] Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and 6631 Recommendations for Internationalized Domain Names 6632 (IDNs)", RFC 4690, September 2006. 6634 [IANA-EXP] 6635 Narten, T., "Assigning Experimental and Testing Numbers 6636 Considered Useful, Work in Progress.". 6638 Appendix A. Acknowledgements 6640 The authors would like to thank the following people that have 6641 provided proposals and contributions to this document: 6643 To Vishnu Ram and Satendra Gera for their contributions on 6644 Capabilities Updates, Predictive Loop Avoidance as well as many other 6645 technical proposals. To Tolga Asveren for his insights and 6646 contributions on almost all of the proposed solutions incorporated 6647 into this document. To Timothy Smith for helping on the Capabilities 6648 Updates and other topics. To Tony Zhang for providing fixes to loop 6649 holes on composing Failed-AVPs as well as many other issues and 6650 topics. To Jan Nordqvist for clearly stating the usage of 6651 application ids. To Anders Kristensen for providing needed technical 6652 opinions. To David Frascone for providing invaluable review of the 6653 document. To Mark Jones for providing clarifying text on vendor 6654 command codes and other vendor specific indicators. 6656 Special thanks also to people who have provided invaluable comments 6657 and inputs especially in resolving controversial issues: 6659 Glen Zorn, Yoshihiro Ohba, Marco Stura, and Pasi Eronen. 6661 Finally, we would like to thank the original authors of this 6662 document: 6664 Pat Calhoun, John Loughney, Jari Arkko, Erik Guttman and Glen Zorn. 6666 Their invaluable knowledge and experience has given us a robust and 6667 flexible AAA protocol that many people have seen great value in 6668 adopting. We greatly appreciate their support and stewardship for 6669 the continued improvements of Diameter as a protocol. We would also 6670 like to extend our gratitude to folks aside from the authors who have 6671 assisted and contributed to the original version of this document. 6672 Their efforts significantly contributed to the success of Diameter. 6674 Appendix B. NAPTR Example 6676 As an example, consider a client that wishes to resolve aaa:ex.com. 6677 The client performs a NAPTR query for that domain, and the following 6678 NAPTR records are returned: 6680 ;; order pref flags service regexp replacement 6681 IN NAPTR 50 50 "s" "AAA+D2S" "" 6682 _diameter._sctp.example.com IN NAPTR 100 50 "s" "AAA+D2T" 6683 "" _aaa._tcp.example.com 6685 This indicates that the server supports SCTP, and TCP, in that order. 6686 If the client supports over SCTP, SCTP will be used, targeted to a 6687 host determined by an SRV lookup of _diameter._sctp.ex.com. That 6688 lookup would return: 6690 ;; Priority Weight Port Target 6691 IN SRV 0 1 5060 server1.example.com IN SRV 0 6692 2 5060 server2.example.com 6694 Appendix C. Duplicate Detection 6696 As described in Section 9.4, accounting record duplicate detection is 6697 based on session identifiers. Duplicates can appear for various 6698 reasons: 6700 o Failover to an alternate server. Where close to real-time 6701 performance is required, failover thresholds need to be kept low 6702 and this may lead to an increased likelihood of duplicates. 6703 Failover can occur at the client or within Diameter agents. 6705 o Failure of a client or agent after sending of a record from non- 6706 volatile memory, but prior to receipt of an application layer ACK 6707 and deletion of the record. record to be sent. This will result 6708 in retransmission of the record soon after the client or agent has 6709 rebooted. 6711 o Duplicates received from RADIUS gateways. Since the 6712 retransmission behavior of RADIUS is not defined within [RFC2865], 6713 the likelihood of duplication will vary according to the 6714 implementation. 6716 o Implementation problems and misconfiguration. 6718 The T flag is used as an indication of an application layer 6719 retransmission event, e.g., due to failover to an alternate server. 6720 It is defined only for request messages sent by Diameter clients or 6721 agents. For instance, after a reboot, a client may not know whether 6722 it has already tried to send the accounting records in its non- 6723 volatile memory before the reboot occurred. Diameter servers MAY use 6724 the T flag as an aid when processing requests and detecting duplicate 6725 messages. However, servers that do this MUST ensure that duplicates 6726 are found even when the first transmitted request arrives at the 6727 server after the retransmitted request. It can be used only in cases 6728 where no answer has been received from the Server for a request and 6729 the request is sent again, (e.g., due to a failover to an alternate 6730 peer, due to a recovered primary peer or due to a client re-sending a 6731 stored record from non-volatile memory such as after reboot of a 6732 client or agent). 6734 In some cases the Diameter accounting server can delay the duplicate 6735 detection and accounting record processing until a post-processing 6736 phase takes place. At that time records are likely to be sorted 6737 according to the included User-Name and duplicate elimination is easy 6738 in this case. In other situations it may be necessary to perform 6739 real-time duplicate detection, such as when credit limits are imposed 6740 or real-time fraud detection is desired. 6742 In general, only generation of duplicates due to failover or re- 6743 sending of records in non-volatile storage can be reliably detected 6744 by Diameter clients or agents. In such cases the Diameter client or 6745 agents can mark the message as possible duplicate by setting the T 6746 flag. Since the Diameter server is responsible for duplicate 6747 detection, it can choose to make use of the T flag or not, in order 6748 to optimize duplicate detection. Since the T flag does not affect 6749 interoperability, and may not be needed by some servers, generation 6750 of the T flag is REQUIRED for Diameter clients and agents, but MAY be 6751 implemented by Diameter servers. 6753 As an example, it can be usually be assumed that duplicates appear 6754 within a time window of longest recorded network partition or device 6755 fault, perhaps a day. So only records within this time window need 6756 to be looked at in the backward direction. Secondly, hashing 6757 techniques or other schemes, such as the use of the T flag in the 6758 received messages, may be used to eliminate the need to do a full 6759 search even in this set except for rare cases. 6761 The following is an example of how the T flag may be used by the 6762 server to detect duplicate requests. 6764 A Diameter server MAY check the T flag of the received message to 6765 determine if the record is a possible duplicate. If the T flag is 6766 set in the request message, the server searches for a duplicate 6767 within a configurable duplication time window backward and 6768 forward. This limits database searching to those records where 6769 the T flag is set. In a well run network, network partitions and 6770 device faults will presumably be rare events, so this approach 6771 represents a substantial optimization of the duplicate detection 6772 process. During failover, it is possible for the original record 6773 to be received after the T flag marked record, due to differences 6774 in network delays experienced along the path by the original and 6775 duplicate transmissions. The likelihood of this occurring 6776 increases as the failover interval is decreased. In order to be 6777 able to detect out of order duplicates, the Diameter server should 6778 use backward and forward time windows when performing duplicate 6779 checking for the T flag marked request. For example, in order to 6780 allow time for the original record to exit the network and be 6781 recorded by the accounting server, the Diameter server can delay 6782 processing records with the T flag set until a time period 6783 TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after the closing 6784 of the original transport connection. After this time period has 6785 expired, then it may check the T flag marked records against the 6786 database with relative assurance that the original records, if 6787 sent, have been received and recorded. 6789 Appendix D. Internationalized Domain Names 6791 To be compatible with the existing DNS infrastructure and simplify 6792 host and domain name comparison, Diameter identities (FQDNs) are 6793 represented in ASCII form. This allows the Diameter protocol to fall 6794 in-line with the DNS strategy of being transparent from the effects 6795 of Internationalized Domain Names (IDNs) by following the 6796 recommnedations in [RFC4690] and [RFC3490]. Applications that 6797 provide support for IDNs outside of the Diameter protocol but 6798 interacting with it SHOULD use the representation and conversion 6799 framework described in [RFC3490], [RFC3491] and [RFC3492]. 6801 Authors' Addresses 6803 Victor Fajardo (editor) 6804 Toshiba America Research 6805 One Telcordia Drive, 1S-222 6806 Piscataway, NJ 08854 6807 USA 6809 Phone: 1 908-421-1845 6810 Email: vfajardo@tari.toshiba.com 6812 Jari Arkko 6813 Ericsson Research 6814 02420 Jorvas 6815 Finland 6817 Phone: +358 40 5079256 6818 Email: jari.arkko@ericsson.com 6820 John Loughney 6821 Nokia Research Center 6822 955 Page Mill Road 6823 Palo Alto, CA 94304 6824 US 6826 Phone: 1-650-283-8068 6827 Email: john.loughney@nokia.com 6829 Full Copyright Statement 6831 Copyright (C) The IETF Trust (2007). 6833 This document is subject to the rights, licenses and restrictions 6834 contained in BCP 78, and except as set forth therein, the authors 6835 retain all their rights. 6837 This document and the information contained herein are provided on an 6838 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 6839 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 6840 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 6841 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 6842 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 6843 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 6845 Intellectual Property 6847 The IETF takes no position regarding the validity or scope of any 6848 Intellectual Property Rights or other rights that might be claimed to 6849 pertain to the implementation or use of the technology described in 6850 this document or the extent to which any license under such rights 6851 might or might not be available; nor does it represent that it has 6852 made any independent effort to identify any such rights. Information 6853 on the procedures with respect to rights in RFC documents can be 6854 found in BCP 78 and BCP 79. 6856 Copies of IPR disclosures made to the IETF Secretariat and any 6857 assurances of licenses to be made available, or the result of an 6858 attempt made to obtain a general license or permission for the use of 6859 such proprietary rights by implementers or users of this 6860 specification can be obtained from the IETF on-line IPR repository at 6861 http://www.ietf.org/ipr. 6863 The IETF invites any interested party to bring to its attention any 6864 copyrights, patents or patent applications, or other proprietary 6865 rights that may cover technology that may be required to implement 6866 this standard. Please address the information to the IETF at 6867 ietf-ipr@ietf.org. 6869 Acknowledgment 6871 Funding for the RFC Editor function is provided by the IETF 6872 Administrative Support Activity (IASA).