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-- Obsolete informational reference (is this intentional?): RFC 3576
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2 DIME V. Fajardo, Ed.
3 Internet-Draft Toshiba America Research
4 Obsoletes: 3588 (if approved) J. Arkko
5 Intended status: Standards Track Ericsson Research
6 Expires: March 12, 2009 J. Loughney
7 Nokia Research Center
8 G. Zorn
9 NetCube
10 September 8, 2008
12 Diameter Base Protocol
13 draft-ietf-dime-rfc3588bis-12.txt
15 Status of this Memo
17 By submitting this Internet-Draft, each author represents that any
18 applicable patent or other IPR claims of which he or she is aware
19 have been or will be disclosed, and any of which he or she becomes
20 aware will be disclosed, in accordance with Section 6 of BCP 79.
22 Internet-Drafts are working documents of the Internet Engineering
23 Task Force (IETF), its areas, and its working groups. Note that
24 other groups may also distribute working documents as Internet-
25 Drafts.
27 Internet-Drafts are draft documents valid for a maximum of six months
28 and may be updated, replaced, or obsoleted by other documents at any
29 time. It is inappropriate to use Internet-Drafts as reference
30 material or to cite them other than as "work in progress."
32 The list of current Internet-Drafts can be accessed at
33 http://www.ietf.org/ietf/1id-abstracts.txt.
35 The list of Internet-Draft Shadow Directories can be accessed at
36 http://www.ietf.org/shadow.html.
38 This Internet-Draft will expire on March 12, 2009.
40 Copyright Notice
42 Copyright (C) The IETF Trust (2008).
44 Abstract
46 The Diameter base protocol is intended to provide an Authentication,
47 Authorization and Accounting (AAA) framework for applications such as
48 network access or IP mobility. Diameter is also intended to work in
49 both local Authentication, Authorization & Accounting and roaming
50 situations. This document specifies the message format, transport,
51 error reporting, accounting and security services to be used by all
52 Diameter applications. The Diameter base application needs to be
53 supported by all Diameter implementations.
55 Table of Contents
57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7
58 1.1. Diameter Protocol . . . . . . . . . . . . . . . . . . . . 9
59 1.1.1. Description of the Document Set . . . . . . . . . . 11
60 1.1.2. Conventions Used in This Document . . . . . . . . . 12
61 1.1.3. Changes from RFC3588 . . . . . . . . . . . . . . . . 12
62 1.2. Approach to Extensibility . . . . . . . . . . . . . . . . 13
63 1.2.1. Defining New AVP Values . . . . . . . . . . . . . . 13
64 1.2.2. Creating New AVPs . . . . . . . . . . . . . . . . . 13
65 1.2.3. Creating New Commands . . . . . . . . . . . . . . . 14
66 1.2.4. Creating New Diameter Applications . . . . . . . . . 14
67 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 15
68 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 22
69 2.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 23
70 2.1.1. SCTP Guidelines . . . . . . . . . . . . . . . . . . 24
71 2.2. Securing Diameter Messages . . . . . . . . . . . . . . . 24
72 2.3. Diameter Application Compliance . . . . . . . . . . . . . 24
73 2.4. Application Identifiers . . . . . . . . . . . . . . . . . 24
74 2.5. Connections vs. Sessions . . . . . . . . . . . . . . . . 25
75 2.6. Peer Table . . . . . . . . . . . . . . . . . . . . . . . 26
76 2.7. Routing Table . . . . . . . . . . . . . . . . . . . . . . 27
77 2.8. Role of Diameter Agents . . . . . . . . . . . . . . . . . 28
78 2.8.1. Relay Agents . . . . . . . . . . . . . . . . . . . . 30
79 2.8.2. Proxy Agents . . . . . . . . . . . . . . . . . . . . 31
80 2.8.3. Redirect Agents . . . . . . . . . . . . . . . . . . 31
81 2.8.4. Translation Agents . . . . . . . . . . . . . . . . . 32
82 2.9. Diameter Path Authorization . . . . . . . . . . . . . . . 33
83 3. Diameter Header . . . . . . . . . . . . . . . . . . . . . . . 35
84 3.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 38
85 3.2. Command Code ABNF specification . . . . . . . . . . . . . 38
86 3.3. Diameter Command Naming Conventions . . . . . . . . . . . 40
87 4. Diameter AVPs . . . . . . . . . . . . . . . . . . . . . . . . 42
88 4.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 42
89 4.1.1. Optional Header Elements . . . . . . . . . . . . . . 43
90 4.2. Basic AVP Data Formats . . . . . . . . . . . . . . . . . 44
91 4.3. Derived AVP Data Formats . . . . . . . . . . . . . . . . 45
92 4.4. Grouped AVP Values . . . . . . . . . . . . . . . . . . . 52
93 4.4.1. Example AVP with a Grouped Data type . . . . . . . . 53
94 4.5. Diameter Base Protocol AVPs . . . . . . . . . . . . . . . 56
95 5. Diameter Peers . . . . . . . . . . . . . . . . . . . . . . . 59
96 5.1. Peer Connections . . . . . . . . . . . . . . . . . . . . 59
97 5.2. Diameter Peer Discovery . . . . . . . . . . . . . . . . . 59
98 5.3. Capabilities Exchange . . . . . . . . . . . . . . . . . . 62
99 5.3.1. Capabilities-Exchange-Request . . . . . . . . . . . 63
100 5.3.2. Capabilities-Exchange-Answer . . . . . . . . . . . . 64
101 5.3.3. Vendor-Id AVP . . . . . . . . . . . . . . . . . . . 64
102 5.3.4. Firmware-Revision AVP . . . . . . . . . . . . . . . 64
103 5.3.5. Host-IP-Address AVP . . . . . . . . . . . . . . . . 65
104 5.3.6. Supported-Vendor-Id AVP . . . . . . . . . . . . . . 65
105 5.3.7. Product-Name AVP . . . . . . . . . . . . . . . . . . 65
106 5.4. Disconnecting Peer connections . . . . . . . . . . . . . 65
107 5.4.1. Disconnect-Peer-Request . . . . . . . . . . . . . . 66
108 5.4.2. Disconnect-Peer-Answer . . . . . . . . . . . . . . . 66
109 5.4.3. Disconnect-Cause AVP . . . . . . . . . . . . . . . . 67
110 5.5. Transport Failure Detection . . . . . . . . . . . . . . . 67
111 5.5.1. Device-Watchdog-Request . . . . . . . . . . . . . . 67
112 5.5.2. Device-Watchdog-Answer . . . . . . . . . . . . . . . 68
113 5.5.3. Transport Failure Algorithm . . . . . . . . . . . . 68
114 5.5.4. Failover and Failback Procedures . . . . . . . . . . 68
115 5.6. Peer State Machine . . . . . . . . . . . . . . . . . . . 69
116 5.6.1. Incoming connections . . . . . . . . . . . . . . . . 71
117 5.6.2. Events . . . . . . . . . . . . . . . . . . . . . . . 72
118 5.6.3. Actions . . . . . . . . . . . . . . . . . . . . . . 73
119 5.6.4. The Election Process . . . . . . . . . . . . . . . . 75
120 6. Diameter message processing . . . . . . . . . . . . . . . . . 76
121 6.1. Diameter Request Routing Overview . . . . . . . . . . . . 76
122 6.1.1. Originating a Request . . . . . . . . . . . . . . . 77
123 6.1.2. Sending a Request . . . . . . . . . . . . . . . . . 77
124 6.1.3. Receiving Requests . . . . . . . . . . . . . . . . . 78
125 6.1.4. Processing Local Requests . . . . . . . . . . . . . 78
126 6.1.5. Request Forwarding . . . . . . . . . . . . . . . . . 78
127 6.1.6. Request Routing . . . . . . . . . . . . . . . . . . 78
128 6.1.7. Predictive Loop Avoidance . . . . . . . . . . . . . 79
129 6.1.8. Redirecting requests . . . . . . . . . . . . . . . . 79
130 6.1.9. Relaying and Proxying Requests . . . . . . . . . . . 81
131 6.2. Diameter Answer Processing . . . . . . . . . . . . . . . 82
132 6.2.1. Processing received Answers . . . . . . . . . . . . 82
133 6.2.2. Relaying and Proxying Answers . . . . . . . . . . . 82
134 6.3. Origin-Host AVP . . . . . . . . . . . . . . . . . . . . . 83
135 6.4. Origin-Realm AVP . . . . . . . . . . . . . . . . . . . . 83
136 6.5. Destination-Host AVP . . . . . . . . . . . . . . . . . . 83
137 6.6. Destination-Realm AVP . . . . . . . . . . . . . . . . . . 84
138 6.7. Routing AVPs . . . . . . . . . . . . . . . . . . . . . . 84
139 6.7.1. Route-Record AVP . . . . . . . . . . . . . . . . . . 84
140 6.7.2. Proxy-Info AVP . . . . . . . . . . . . . . . . . . . 84
141 6.7.3. Proxy-Host AVP . . . . . . . . . . . . . . . . . . . 85
142 6.7.4. Proxy-State AVP . . . . . . . . . . . . . . . . . . 85
143 6.8. Auth-Application-Id AVP . . . . . . . . . . . . . . . . . 85
144 6.9. Acct-Application-Id AVP . . . . . . . . . . . . . . . . . 85
145 6.10. Inband-Security-Id AVP . . . . . . . . . . . . . . . . . 85
146 6.11. Vendor-Specific-Application-Id AVP . . . . . . . . . . . 86
147 6.12. Redirect-Host AVP . . . . . . . . . . . . . . . . . . . . 87
148 6.13. Redirect-Host-Usage AVP . . . . . . . . . . . . . . . . . 87
149 6.14. Redirect-Max-Cache-Time AVP . . . . . . . . . . . . . . . 88
150 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 90
151 7.1. Result-Code AVP . . . . . . . . . . . . . . . . . . . . . 91
152 7.1.1. Informational . . . . . . . . . . . . . . . . . . . 92
153 7.1.2. Success . . . . . . . . . . . . . . . . . . . . . . 92
154 7.1.3. Protocol Errors . . . . . . . . . . . . . . . . . . 93
155 7.1.4. Transient Failures . . . . . . . . . . . . . . . . . 94
156 7.1.5. Permanent Failures . . . . . . . . . . . . . . . . . 95
157 7.2. Error Bit . . . . . . . . . . . . . . . . . . . . . . . . 98
158 7.3. Error-Message AVP . . . . . . . . . . . . . . . . . . . . 98
159 7.4. Error-Reporting-Host AVP . . . . . . . . . . . . . . . . 98
160 7.5. Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . . 99
161 7.6. Experimental-Result AVP . . . . . . . . . . . . . . . . . 100
162 7.7. Experimental-Result-Code AVP . . . . . . . . . . . . . . 100
163 8. Diameter User Sessions . . . . . . . . . . . . . . . . . . . 101
164 8.1. Authorization Session State Machine . . . . . . . . . . . 102
165 8.2. Accounting Session State Machine . . . . . . . . . . . . 107
166 8.3. Server-Initiated Re-Auth . . . . . . . . . . . . . . . . 112
167 8.3.1. Re-Auth-Request . . . . . . . . . . . . . . . . . . 112
168 8.3.2. Re-Auth-Answer . . . . . . . . . . . . . . . . . . . 113
169 8.4. Session Termination . . . . . . . . . . . . . . . . . . . 114
170 8.4.1. Session-Termination-Request . . . . . . . . . . . . 115
171 8.4.2. Session-Termination-Answer . . . . . . . . . . . . . 115
172 8.5. Aborting a Session . . . . . . . . . . . . . . . . . . . 116
173 8.5.1. Abort-Session-Request . . . . . . . . . . . . . . . 117
174 8.5.2. Abort-Session-Answer . . . . . . . . . . . . . . . . 117
175 8.6. Inferring Session Termination from Origin-State-Id . . . 118
176 8.7. Auth-Request-Type AVP . . . . . . . . . . . . . . . . . . 119
177 8.8. Session-Id AVP . . . . . . . . . . . . . . . . . . . . . 119
178 8.9. Authorization-Lifetime AVP . . . . . . . . . . . . . . . 120
179 8.10. Auth-Grace-Period AVP . . . . . . . . . . . . . . . . . . 121
180 8.11. Auth-Session-State AVP . . . . . . . . . . . . . . . . . 121
181 8.12. Re-Auth-Request-Type AVP . . . . . . . . . . . . . . . . 122
182 8.13. Session-Timeout AVP . . . . . . . . . . . . . . . . . . . 122
183 8.14. User-Name AVP . . . . . . . . . . . . . . . . . . . . . . 123
184 8.15. Termination-Cause AVP . . . . . . . . . . . . . . . . . . 123
185 8.16. Origin-State-Id AVP . . . . . . . . . . . . . . . . . . . 124
186 8.17. Session-Binding AVP . . . . . . . . . . . . . . . . . . . 125
187 8.18. Session-Server-Failover AVP . . . . . . . . . . . . . . . 125
188 8.19. Multi-Round-Time-Out AVP . . . . . . . . . . . . . . . . 126
189 8.20. Class AVP . . . . . . . . . . . . . . . . . . . . . . . . 126
190 8.21. Event-Timestamp AVP . . . . . . . . . . . . . . . . . . . 127
191 9. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . 128
192 9.1. Server Directed Model . . . . . . . . . . . . . . . . . . 128
193 9.2. Protocol Messages . . . . . . . . . . . . . . . . . . . . 129
194 9.3. Accounting Application Extension and Requirements . . . . 129
195 9.4. Fault Resilience . . . . . . . . . . . . . . . . . . . . 130
196 9.5. Accounting Records . . . . . . . . . . . . . . . . . . . 130
197 9.6. Correlation of Accounting Records . . . . . . . . . . . . 131
198 9.7. Accounting Command-Codes . . . . . . . . . . . . . . . . 132
199 9.7.1. Accounting-Request . . . . . . . . . . . . . . . . . 132
200 9.7.2. Accounting-Answer . . . . . . . . . . . . . . . . . 133
201 9.8. Accounting AVPs . . . . . . . . . . . . . . . . . . . . . 134
202 9.8.1. Accounting-Record-Type AVP . . . . . . . . . . . . . 134
203 9.8.2. Acct-Interim-Interval AVP . . . . . . . . . . . . . 135
204 9.8.3. Accounting-Record-Number AVP . . . . . . . . . . . . 136
205 9.8.4. Acct-Session-Id AVP . . . . . . . . . . . . . . . . 136
206 9.8.5. Acct-Multi-Session-Id AVP . . . . . . . . . . . . . 136
207 9.8.6. Accounting-Sub-Session-Id AVP . . . . . . . . . . . 136
208 9.8.7. Accounting-Realtime-Required AVP . . . . . . . . . . 137
209 10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . 138
210 10.1. Base Protocol Command AVP Table . . . . . . . . . . . . . 138
211 10.2. Accounting AVP Table . . . . . . . . . . . . . . . . . . 139
212 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 141
213 11.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 141
214 11.1.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . 141
215 11.1.2. AVP Flags . . . . . . . . . . . . . . . . . . . . . 142
216 11.2. Diameter Header . . . . . . . . . . . . . . . . . . . . . 142
217 11.2.1. Command Codes . . . . . . . . . . . . . . . . . . . 142
218 11.2.2. Command Flags . . . . . . . . . . . . . . . . . . . 143
219 11.3. Application Identifiers . . . . . . . . . . . . . . . . . 143
220 11.4. AVP Values . . . . . . . . . . . . . . . . . . . . . . . 144
221 11.4.1. Result-Code AVP Values . . . . . . . . . . . . . . . 144
222 11.4.2. Accounting-Record-Type AVP Values . . . . . . . . . 144
223 11.4.3. Termination-Cause AVP Values . . . . . . . . . . . . 144
224 11.4.4. Redirect-Host-Usage AVP Values . . . . . . . . . . . 144
225 11.4.5. Session-Server-Failover AVP Values . . . . . . . . . 144
226 11.4.6. Session-Binding AVP Values . . . . . . . . . . . . . 144
227 11.4.7. Disconnect-Cause AVP Values . . . . . . . . . . . . 145
228 11.4.8. Auth-Request-Type AVP Values . . . . . . . . . . . . 145
229 11.4.9. Auth-Session-State AVP Values . . . . . . . . . . . 145
230 11.4.10. Re-Auth-Request-Type AVP Values . . . . . . . . . . 145
231 11.4.11. Accounting-Realtime-Required AVP Values . . . . . . 145
232 11.4.12. Inband-Security-Id AVP (code 299) . . . . . . . . . 145
233 11.5. Diameter TCP/SCTP Port Numbers . . . . . . . . . . . . . 145
234 11.6. NAPTR Service Fields . . . . . . . . . . . . . . . . . . 145
236 12. Diameter protocol related configurable parameters . . . . . . 147
237 13. Security Considerations . . . . . . . . . . . . . . . . . . . 148
238 13.1. TLS Usage . . . . . . . . . . . . . . . . . . . . . . . . 148
239 13.2. Peer-to-Peer Considerations . . . . . . . . . . . . . . . 149
240 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 150
241 14.1. Normative References . . . . . . . . . . . . . . . . . . 150
242 14.2. Informational References . . . . . . . . . . . . . . . . 152
243 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 154
244 Appendix B. NAPTR Example . . . . . . . . . . . . . . . . . . . 155
245 Appendix C. Duplicate Detection . . . . . . . . . . . . . . . . 156
246 Appendix D. Internationalized Domain Names . . . . . . . . . . . 158
247 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 159
248 Intellectual Property and Copyright Statements . . . . . . . . . 160
250 1. Introduction
252 Authentication, Authorization and Accounting (AAA) protocols such as
253 TACACS [RFC1492] and RADIUS [RFC2865] were initially deployed to
254 provide dial-up PPP [RFC1661] and terminal server access. Over time,
255 with the growth of the Internet and the introduction of new access
256 technologies (including wireless, DSL, Mobile IP and Ethernet), both
257 the amount and complexity of processing performed by routers and
258 network access servers (NAS) have increased, putting new demands on
259 AAA protocols.
261 Network access requirements for AAA protocols are summarized in
262 [RFC2989]. These include:
264 Failover
266 [RFC2865] does not define failover mechanisms, and as a result,
267 failover behavior differs between implementations. In order to
268 provide well defined failover behavior, Diameter supports
269 application-layer acknowledgements, and defines failover
270 algorithms and the associated state machine. This is described in
271 Section 5.5 and [RFC3539].
273 Transmission-level security
275 [RFC2865] defines an application-layer authentication and
276 integrity scheme that is required only for use with Response
277 packets. While [RFC2869] defines an additional authentication and
278 integrity mechanism, use is only required during Extensible
279 Authentication Protocol (EAP) sessions. While attribute-hiding is
280 supported, [RFC2865] does not provide support for per-packet
281 confidentiality. In accounting, [RFC2866] assumes that replay
282 protection is provided by the backend billing server, rather than
283 within the protocol itself.
285 While [RFC3162] defines the use of IPsec with RADIUS, support for
286 IPsec is not required. Since within [RFC4306] authentication
287 occurs only within Phase 1 prior to the establishment of IPsec SAs
288 in Phase 2, it is typically not possible to define separate trust
289 or authorization schemes for each application. This limits the
290 usefulness of IPsec in inter-domain AAA applications (such as
291 roaming) where it may be desirable to define a distinct
292 certificate hierarchy for use in a AAA deployment. In order to
293 provide universal support for transmission-level security, and
294 enable both intra- and inter-domain AAA deployments, Diameter
295 provides support for TLS. Security is discussed in Section 13.
297 Reliable transport
299 RADIUS runs over UDP, and does not define retransmission behavior;
300 as a result, reliability varies between implementations. As
301 described in [RFC2975], this is a major issue in accounting, where
302 packet loss may translate directly into revenue loss. In order to
303 provide well defined transport behavior, Diameter runs over
304 reliable transport mechanisms (TCP, SCTP) as defined in [RFC3539].
306 Agent support
308 [RFC2865] does not provide for explicit support for agents,
309 including Proxies, Redirects and Relays. Since the expected
310 behavior is not defined, it varies between implementations.
311 Diameter defines agent behavior explicitly; this is described in
312 Section 2.8.
314 Server-initiated messages
316 While RADIUS server-initiated messages are defined in [RFC3576],
317 support is optional. This makes it difficult to implement
318 features such as unsolicited disconnect or reauthentication/
319 reauthorization on demand across a heterogeneous deployment.
320 Support for server-initiated messages is mandatory in Diameter,
321 and is described in Section 8.
323 Transition support
325 While Diameter does not share a common protocol data unit (PDU)
326 with RADIUS, considerable effort has been expended in enabling
327 backward compatibility with RADIUS, so that the two protocols may
328 be deployed in the same network. Initially, it is expected that
329 Diameter will be deployed within new network devices, as well as
330 within gateways enabling communication between legacy RADIUS
331 devices and Diameter agents. This capability, described in
332 [RFC4005], enables Diameter support to be added to legacy
333 networks, by addition of a gateway or server speaking both RADIUS
334 and Diameter.
336 In addition to addressing the above requirements, Diameter also
337 provides support for the following:
339 Capability negotiation
341 RADIUS does not support error messages, capability negotiation, or
342 a mandatory/non-mandatory flag for attributes. Since RADIUS
343 clients and servers are not aware of each other's capabilities,
344 they may not be able to successfully negotiate a mutually
345 acceptable service, or in some cases, even be aware of what
346 service has been implemented. Diameter includes support for error
347 handling (Section 7), capability negotiation (Section 5.3), and
348 mandatory/non-mandatory attribute-value pairs (AVPs) (Section
349 4.1).
351 Peer discovery and configuration
353 RADIUS implementations typically require that the name or address
354 of servers or clients be manually configured, along with the
355 corresponding shared secrets. This results in a large
356 administrative burden, and creates the temptation to reuse the
357 RADIUS shared secret, which can result in major security
358 vulnerabilities if the Request Authenticator is not globally and
359 temporally unique as required in [RFC2865]. Through DNS, Diameter
360 enables dynamic discovery of peers. Derivation of dynamic session
361 keys is enabled via transmission-level security.
363 Over time, the capabilities of Network Access Server (NAS) devices
364 have increased substantially. As a result, while Diameter is a
365 considerably more sophisticated protocol than RADIUS, it remains
366 feasible to implement within embedded devices, given improvements in
367 processor speeds and the widespread availability of embedded TLS
368 implementations.
370 1.1. Diameter Protocol
372 The Diameter base protocol provides the following facilities:
374 o Delivery of AVPs (attribute value pairs)
376 o Capabilities negotiation
378 o Error notification
380 o Extensibility, through addition of new applications, commands and
381 AVPs (required in [RFC2989]).
383 o Basic services necessary for applications, such as handling of
384 user sessions or accounting
386 All data delivered by the protocol is in the form of an AVP. Some of
387 these AVP values are used by the Diameter protocol itself, while
388 others deliver data associated with particular applications that
389 employ Diameter. AVPs may be added arbitrarily to Diameter messages,
390 so long as the requirements of a message's ABNF are met. AVPs are
391 used by the base Diameter protocol to support the following required
392 features:
394 o Transporting of user authentication information, for the purposes
395 of enabling the Diameter server to authenticate the user.
397 o Transporting of service specific authorization information,
398 between client and servers, allowing the peers to decide whether a
399 user's access request should be granted.
401 o Exchanging resource usage information, which MAY be used for
402 accounting purposes, capacity planning, etc.
404 o Relaying, proxying and redirecting of Diameter messages through a
405 server hierarchy.
407 The Diameter base protocol provides the minimum requirements needed
408 for a AAA protocol, as required by [RFC2989]. The base protocol may
409 be used by itself for accounting purposes only, or it may be used
410 with a Diameter application, such as Mobile IPv4 [RFC4004], or
411 network access [RFC4005]. It is also possible for the base protocol
412 to be extended for use in new applications, via the addition of new
413 commands or AVPs. At this time the focus of Diameter is network
414 access and accounting applications. A truly generic AAA protocol
415 used by many applications might provide functionality not provided by
416 Diameter. Therefore, it is imperative that the designers of new
417 applications understand their requirements before using Diameter.
418 See Section 2.4 for more information on Diameter applications.
420 Any node can initiate a request. In that sense, Diameter is a peer-
421 to-peer protocol. In this document, a Diameter Client is a device at
422 the edge of the network that performs access control, such as a
423 Network Access Server (NAS) or a Foreign Agent (FA). A Diameter
424 client generates Diameter messages to request authentication,
425 authorization, and accounting services for the user. A Diameter
426 agent is a node that does not provide local user authentication or
427 authorization services; agents include proxies, redirects and relay
428 agents. A Diameter server performs authentication and/or
429 authorization of the user. A Diameter node MAY act as an agent for
430 certain requests while acting as a server for others.
432 The Diameter protocol also supports server-initiated messages, such
433 as a request to abort service to a particular user.
435 1.1.1. Description of the Document Set
437 Currently, the Diameter specification consists of an updated version
438 of the base protocol specification (this document), Transport Profile
439 [RFC3539] and applications: Mobile IPv4 [RFC4004], NASREQ [RFC4005],
440 Credit Control [RFC4006], EAP [RFC4072] and SIP [RFC4740]. Note that
441 this document obsoletes [RFC3588]. A summary of the base protocol
442 updates included in this document can be found in Section 1.1.3.
444 The Transport Profile document [RFC3539] discusses transport layer
445 issues that arise with AAA protocols and recommendations on how to
446 overcome these issues. This document also defines the Diameter
447 failover algorithm and state machine.
449 The Mobile IPv4 [RFC4004] application defines a Diameter application
450 that allows a Diameter server to perform AAA functions for Mobile
451 IPv4 services to a mobile node.
453 The NASREQ [RFC4005] application defines a Diameter Application that
454 allows a Diameter server to be used in a PPP/SLIP Dial-Up and
455 Terminal Server Access environment. Consideration was given for
456 servers that need to perform protocol conversion between Diameter and
457 RADIUS.
459 The Credit Control [RFC4006] application defines a Diameter
460 Application that can be used to implement real-time credit-control
461 for a variety of end user services such as network access, SIP
462 services, messaging services, and download services. It provides a
463 general solution to real-time cost and credit-control.
465 The EAP [RFC4072] application defines a Diameter Application that can
466 be used to carry EAP packets between the Network Access Server (NAS)
467 working as an EAP authenticator and a back-end authentication server.
468 The Diameter EAP application is based on NASREQ and intended for a
469 similar environment.
471 The SIP [RFC4740] application defines a Diameter Application that
472 allows a Diameter client to request authentication and authorization
473 information to a Diameter server for SIP-based IP multimedia services
474 (see SIP [RFC3261]).
476 In summary, this document defines the base protocol specification for
477 AAA, which includes support for accounting. The applications
478 documents describe applications that use this base specification for
479 Authentication, Authorization and Accounting.
481 1.1.2. Conventions Used in This Document
483 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
484 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
485 document are to be interpreted as described in [RFC2119].
487 1.1.3. Changes from RFC3588
489 This document deprecates [RFC3588] but is fully backward compatible
490 with that document. The changes introduced in this document focuses
491 on fixing issues that has surfaced during implementation of
492 [RFC3588]. An overview of some the major changes are shown below.
494 o Simplified Security Requirements. The use of a secured transport
495 for exchanging Diameter messages remains mandatory. However, TLS
496 has become the primary method of securing Diameter and IPSec is a
497 secondary alternative. See Section 13 for details. Along with
498 this, support for the End-to-End security framework (E2ESequence
499 AVP and 'P'-bit in the AVP header) has also been deprecated.
501 o Diameter Extensibility Changes. This includes fixes to the
502 Diameter extensibility specification (Section 1.2 and others) to
503 better aid Diameter application designers. It also includes
504 allocation of vendor specific command code space. The new
505 specification relaxes the allocation of command codes for vendor
506 specific uses. See Section 11.2.1 for details.
508 o Application Id Usage. Clarify the proper use of Application Id
509 information which can be found in multiple places within a
510 Diameter message. This includes co-relating Application Ids found
511 in the message headers and AVPs. These changes also clearly
512 specifies the proper Application Id value to use for specific base
513 protocol messages (ASR/ASA, STR/STA) as well as clarifying the
514 content and use of Vendor-Specific-Application-Id.
516 o Routing Fixes. For general routing, specifies much more clearly
517 what information (AVPs and Application Id) can be used for making
518 routing decisions. Prioritization of redirect routing criterias
519 when multiple route entries are found via redirects has also been
520 added (See Section 6.13 for details).
522 o Simplification of Diameter Peer Discovery. The Diameter discovery
523 process now supports only well known discovery schemes. The rest
524 has been deprecated. (See Section 5.2 for details).
526 There are many other many miscellaneous fixes that has been
527 introduced in this document that may not be considered significant
528 but they are important nonetheless. Examples are removal of obsolete
529 types, fixes to command ABNFs, fixes to the state machine,
530 clarification on election process, message validation, fixes to
531 Failed-AVP and Result-Code AVP values etc. A comprehensive list of
532 changes is not shown here for practical reasons. Though, that can be
533 generated via a diff comparison between this document and [RFC3588].
535 1.2. Approach to Extensibility
537 The Diameter protocol is designed to be extensible, using several
538 mechanisms, including:
540 o Defining new AVP values
542 o Creating new AVPs
544 o Creating new commands
546 o Creating new applications
548 From the point of extensibility Diameter authentication,
549 authorization and accounting applications are treated in the same
550 way.
552 Note: Protocol designer should try to re-use existing functionality,
553 namely AVP values, AVPs, commands, and Diameter applications. Reuse
554 simplifies standardization and implementation. To avoid potential
555 interoperability issues it is important to ensure that the semantics
556 of the re-used features are well understood.
558 1.2.1. Defining New AVP Values
560 In order to allocate a new AVP value for AVPs defined in the Diameter
561 Base protocol, the IETF needs to approve a new RFC that describes the
562 AVP value. IANA considerations for these AVP values are discussed in
563 Section 11.4.
565 The allocation of AVP values for other AVPs is guided by the IANA
566 considerations of the documents that defines those AVPs. Typically,
567 allocation of new values for an AVP defined in an IETF RFC should
568 require IETF Review [RFC2434], where as values for vendor-specific
569 AVPs can be allocated by the vendor.
571 1.2.2. Creating New AVPs
573 A new AVP being defined MUST use one of the data types listed in
574 Section 4.2 or 4.3. If an appropriate derived data type is already
575 defined, it SHOULD be used instead of the base data type to encourage
576 reusability and good design practice.
578 In the event that a logical grouping of AVPs is necessary, and
579 multiple "groups" are possible in a given command, it is recommended
580 that a Grouped AVP be used (see Section 4.4).
582 The creation of new AVPs can happen in various ways. The recommended
583 approach is to define a new general-purpose AVP in a standards track
584 RFC approved by the IETF. However, as described in Section 11.1.1
585 there are also other mechanisms.
587 1.2.3. Creating New Commands
589 A new Command Code MUST be allocated when new required AVPs (those
590 indicated as {AVP}) are added, deleted or are redefined (for example
591 by changing a required AVP into an optional one).
593 Furthermore, when a command is modified with respect to the number of
594 round trips then a new Command Code has to be registered.
596 A change to the ABNF of a command, such as described above, MUST
597 result in the definition of a new Command Code. This subsequently
598 leads to the need to define a new Diameter Application for any
599 application that will use that new Command.
601 The IANA considerations for commands are discussed in Section 11.2.1.
603 1.2.4. Creating New Diameter Applications
605 Every Diameter application specification MUST have an IANA assigned
606 Application Id (see Section 2.4 and Section 11.3). The managed
607 Application ID space is flat and there is no relationship between
608 different Diameter applications with respect to their application
609 IDs. As such, there is no versioning supported provided by these
610 application IDs itself; every Diameter application is a standalone
611 application that may or may not have a semantical relationship with
612 one or more Diameter applications being defined elsewhere.
614 Before describing the rules for creating new Diameter applications it
615 is important to discuss the semantics of the AVPs occurrences as
616 stated in the ABNF and the M-bit flag for an AVP. There is no
617 relationship imposed between the two; they are set independently.
619 o The ABNF indicates what AVPs are placed into a Diameter Command by
620 the sender of that Command. Often, since there are multiple modes
621 of protocol interactions many of the AVPs are indicated as
622 optional.
624 o The M-bit allows the sender to indicate to the receiver whether
625 the semantics of an AVP and it's content has to be understood
626 mandatorily or not. If the M-bit is set by the sender and the
627 receiver does not understand the AVP or the values carried within
628 that AVP then a failure is generated (see Section 7).
630 It is the decision of the protocol designer when to develop a new
631 Diameter application rather than extending Diameter in other ways.
632 However, a new Diameter application MUST be created when one or more
633 of the following criteria are met:
635 M-bit Setting
637 Adding an AVP with the M-bit in the MUST column of the AVP flag
638 table to an existing Command/Application requires a new Diameter
639 Application Id to be assigned to that Application.
641 Adding an AVP with the M-bit in the MAY column of the AVP flag
642 table to an existing Command/Application requires a new Diameter
643 Application Id to be assigned to that Application.
645 Note: The M-bit setting for a given AVP is relevant to an
646 Application and each command within that application which
647 includes the AVP. That is, if an AVP appears in two commands for
648 application Foo and the M-bit settings are different in each
649 command, then there should be two AVP flag tables describing when
650 to set the M-bit.
652 Commands
654 A new command is used within the existing application either
655 because an additional command is added, an existing command has
656 been modified so that a new Command Code had to be registered, or
657 a command has been deleted.
659 An implementation MAY add arbitrary optional AVPs with the M-bit
660 cleared to a command defined in an application, including vendor-
661 specific AVPs without needing to define a new application. This can
662 be done if the commands ABNF allows for it. Please refer to Section
663 11.1.1 for details.
665 1.3. Terminology
667 AAA
669 Authentication, Authorization and Accounting.
671 Accounting
673 The act of collecting information on resource usage for the
674 purpose of capacity planning, auditing, billing or cost
675 allocation.
677 Accounting Record
679 An accounting record represents a summary of the resource
680 consumption of a user over the entire session. Accounting servers
681 creating the accounting record may do so by processing interim
682 accounting events or accounting events from several devices
683 serving the same user.
685 Authentication
687 The act of verifying the identity of an entity (subject).
689 Authorization
691 The act of determining whether a requesting entity (subject) will
692 be allowed access to a resource (object).
694 AVP
696 The Diameter protocol consists of a header followed by one or more
697 Attribute-Value-Pairs (AVPs). An AVP includes a header and is
698 used to encapsulate protocol-specific data (e.g., routing
699 information) as well as authentication, authorization or
700 accounting information.
702 Broker
704 A broker is a business term commonly used in AAA infrastructures.
705 A broker is either a relay, proxy or redirect agent, and MAY be
706 operated by roaming consortiums. Depending on the business model,
707 a broker may either choose to deploy relay agents or proxy agents.
709 Diameter Agent
711 A Diameter Agent is a Diameter node that provides either relay,
712 proxy, redirect or translation services.
714 Diameter Client
716 A Diameter Client is a device at the edge of the network that
717 performs access control. An example of a Diameter client is a
718 Network Access Server (NAS) or a Foreign Agent (FA). By its very
719 nature, a Diameter Client MUST support Diameter client
720 applications in addition to the base protocol.
722 Diameter Node
724 A Diameter node is a host process that implements the Diameter
725 protocol, and acts either as a Client, Agent or Server.
727 Diameter Peer
729 A Diameter Peer is a Diameter Node to which a given Diameter Node
730 has a direct transport connection.
732 Diameter Server
734 A Diameter Server is one that handles authentication,
735 authorization and accounting requests for a particular realm. By
736 its very nature, a Diameter Server MUST support Diameter server
737 applications in addition to the base protocol.
739 Downstream
741 Downstream is used to identify the direction of a particular
742 Diameter message from the home server towards the access device.
744 Home Realm
746 A Home Realm is the administrative domain with which the user
747 maintains an account relationship.
749 Home Server
751 A Diameter Server which serves the Home Realm.
753 Interim accounting
755 An interim accounting message provides a snapshot of usage during
756 a user's session. It is typically implemented in order to provide
757 for partial accounting of a user's session in the case of a device
758 reboot or other network problem prevents the reception of a
759 session summary message or session record.
761 Local Realm
763 A local realm is the administrative domain providing services to a
764 user. An administrative domain MAY act as a local realm for
765 certain users, while being a home realm for others.
767 Multi-session
769 A multi-session represents a logical linking of several sessions.
770 Multi-sessions are tracked by using the Acct-Multi-Session-Id. An
771 example of a multi-session would be a Multi-link PPP bundle. Each
772 leg of the bundle would be a session while the entire bundle would
773 be a multi-session.
775 Network Access Identifier
777 The Network Access Identifier, or NAI [RFC4282], is used in the
778 Diameter protocol to extract a user's identity and realm. The
779 identity is used to identify the user during authentication and/or
780 authorization, while the realm is used for message routing
781 purposes.
783 Proxy Agent or Proxy
785 In addition to forwarding requests and responses, proxies make
786 policy decisions relating to resource usage and provisioning.
787 This is typically accomplished by tracking the state of NAS
788 devices. While proxies typically do not respond to client
789 Requests prior to receiving a Response from the server, they may
790 originate Reject messages in cases where policies are violated.
791 As a result, proxies need to understand the semantics of the
792 messages passing through them, and may not support all Diameter
793 applications.
795 Realm
797 The string in the NAI that immediately follows the '@' character.
798 NAI realm names are required to be unique, and are piggybacked on
799 the administration of the DNS namespace. Diameter makes use of
800 the realm, also loosely referred to as domain, to determine
801 whether messages can be satisfied locally, or whether they must be
802 routed or redirected. In RADIUS, realm names are not necessarily
803 piggybacked on the DNS namespace but may be independent of it.
805 Real-time Accounting
807 Real-time accounting involves the processing of information on
808 resource usage within a defined time window. Time constraints are
809 typically imposed in order to limit financial risk.
811 Relay Agent or Relay
813 Relays forward requests and responses based on routing-related
814 AVPs and routing table entries. Since relays do not make policy
815 decisions, they do not examine or alter non-routing AVPs. As a
816 result, relays never originate messages, do not need to understand
817 the semantics of messages or non-routing AVPs, and are capable of
818 handling any Diameter application or message type. Since relays
819 make decisions based on information in routing AVPs and realm
820 forwarding tables they do not keep state on NAS resource usage or
821 sessions in progress.
823 Redirect Agent
825 Rather than forwarding requests and responses between clients and
826 servers, redirect agents refer clients to servers and allow them
827 to communicate directly. Since redirect agents do not sit in the
828 forwarding path, they do not alter any AVPs transiting between
829 client and server. Redirect agents do not originate messages and
830 are capable of handling any message type, although they may be
831 configured only to redirect messages of certain types, while
832 acting as relay or proxy agents for other types. As with proxy
833 agents, redirect agents do not keep state with respect to sessions
834 or NAS resources.
836 Roaming Relationships
838 Roaming relationships include relationships between companies and
839 ISPs, relationships among peer ISPs within a roaming consortium,
840 and relationships between an ISP and a roaming consortium.
842 Session
844 A session is a related progression of events devoted to a
845 particular activity. Each application SHOULD provide guidelines
846 as to when a session begins and ends. All Diameter packets with
847 the same Session-Id are considered to be part of the same session.
849 Session state
851 A stateful agent is one that maintains session state information,
852 by keeping track of all authorized active sessions. Each
853 authorized session is bound to a particular service, and its state
854 is considered active either until it is notified otherwise, or by
855 expiration.
857 Sub-session
859 A sub-session represents a distinct service (e.g., QoS or data
860 characteristics) provided to a given session. These services may
861 happen concurrently (e.g., simultaneous voice and data transfer
862 during the same session) or serially. These changes in sessions
863 are tracked with the Accounting-Sub-Session-Id.
865 Transaction state
867 The Diameter protocol requires that agents maintain transaction
868 state, which is used for failover purposes. Transaction state
869 implies that upon forwarding a request, the Hop-by-Hop identifier
870 is saved; the field is replaced with a locally unique identifier,
871 which is restored to its original value when the corresponding
872 answer is received. The request's state is released upon receipt
873 of the answer. A stateless agent is one that only maintains
874 transaction state.
876 Translation Agent
878 A translation agent is a stateful Diameter node that performs
879 protocol translation between Diameter and another AAA protocol,
880 such as RADIUS.
882 Transport Connection
884 A transport connection is a TCP or SCTP connection existing
885 directly between two Diameter peers, otherwise known as a Peer-
886 to-Peer Connection.
888 Upstream
890 Upstream is used to identify the direction of a particular
891 Diameter message from the access device towards the home server.
893 User
895 The entity requesting or using some resource, in support of which
896 a Diameter client has generated a request.
898 2. Protocol Overview
900 The base Diameter protocol may be used by itself for accounting
901 applications, but for use in authentication and authorization it is
902 always extended for a particular application. Two Diameter
903 applications are defined by companion documents: NASREQ [RFC4005],
904 Mobile IPv4 [RFC4004]. These applications are introduced in this
905 document but specified elsewhere. Additional Diameter applications
906 MAY be defined in the future (see Section 11.3).
908 Diameter Clients MUST support the base protocol, which includes
909 accounting. In addition, they MUST fully support each Diameter
910 application that is needed to implement the client's service, e.g.,
911 NASREQ and/or Mobile IPv4. A Diameter Client that does not support
912 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
913 Client" where X is the application which it supports, and not a
914 "Diameter Client".
916 Diameter Servers MUST support the base protocol, which includes
917 accounting. In addition, they MUST fully support each Diameter
918 application that is needed to implement the intended service, e.g.,
919 NASREQ and/or Mobile IPv4. A Diameter Server that does not support
920 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
921 Server" where X is the application which it supports, and not a
922 "Diameter Server".
924 Diameter Relays and redirect agents are, by definition, protocol
925 transparent, and MUST transparently support the Diameter base
926 protocol, which includes accounting, and all Diameter applications.
928 Diameter proxies MUST support the base protocol, which includes
929 accounting. In addition, they MUST fully support each Diameter
930 application that is needed to implement proxied services, e.g.,
931 NASREQ and/or Mobile IPv4. A Diameter proxy which does not support
932 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
933 Proxy" where X is the application which it supports, and not a
934 "Diameter Proxy".
936 The base Diameter protocol concerns itself with capabilities
937 negotiation, how messages are sent and how peers may eventually be
938 abandoned. The base protocol also defines certain rules that apply
939 to all exchanges of messages between Diameter nodes.
941 Communication between Diameter peers begins with one peer sending a
942 message to another Diameter peer. The set of AVPs included in the
943 message is determined by a particular Diameter application. One AVP
944 that is included to reference a user's session is the Session-Id.
946 The initial request for authentication and/or authorization of a user
947 would include the Session-Id. The Session-Id is then used in all
948 subsequent messages to identify the user's session (see Section 8 for
949 more information). The communicating party may accept the request,
950 or reject it by returning an answer message with the Result-Code AVP
951 set to indicate an error occurred. The specific behavior of the
952 Diameter server or client receiving a request depends on the Diameter
953 application employed.
955 Session state (associated with a Session-Id) MUST be freed upon
956 receipt of the Session-Termination-Request, Session-Termination-
957 Answer, expiration of authorized service time in the Session-Timeout
958 AVP, and according to rules established in a particular Diameter
959 application.
961 2.1. Transport
963 Transport profile is defined in [RFC3539].
965 The base Diameter protocol is run on port 3868 of both TCP [RFC793]
966 and SCTP [RFC2960] transport protocols.
968 Diameter clients MUST support either TCP or SCTP, while agents and
969 servers MUST support both. Future versions of this specification MAY
970 mandate that clients support SCTP.
972 A Diameter node MAY initiate connections from a source port other
973 than the one that it declares it accepts incoming connections on, and
974 MUST be prepared to receive connections on port 3868. A given
975 Diameter instance of the peer state machine MUST NOT use more than
976 one transport connection to communicate with a given peer, unless
977 multiple instances exist on the peer in which case a separate
978 connection per process is allowed.
980 When no transport connection exists with a peer, an attempt to
981 connect SHOULD be periodically made. This behavior is handled via
982 the Tc timer, whose recommended value is 30 seconds. There are
983 certain exceptions to this rule, such as when a peer has terminated
984 the transport connection stating that it does not wish to
985 communicate.
987 When connecting to a peer and either zero or more transports are
988 specified, SCTP SHOULD be tried first, followed by TCP. See Section
989 5.2 for more information on peer discovery.
991 Diameter implementations SHOULD be able to interpret ICMP protocol
992 port unreachable messages as explicit indications that the server is
993 not reachable, subject to security policy on trusting such messages.
995 Diameter implementations SHOULD also be able to interpret a reset
996 from the transport and timed-out connection attempts. If Diameter
997 receives data up from TCP that cannot be parsed or identified as a
998 Diameter error made by the peer, the stream is compromised and cannot
999 be recovered. The transport connection MUST be closed using a RESET
1000 call (send a TCP RST bit) or an SCTP ABORT message (graceful closure
1001 is compromised).
1003 2.1.1. SCTP Guidelines
1005 The following are guidelines for Diameter implementations that
1006 support SCTP:
1008 1. For interoperability: All Diameter nodes MUST be prepared to
1009 receive Diameter messages on any SCTP stream in the association.
1011 2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP
1012 streams available to the association to prevent head-of-the-line
1013 blocking.
1015 2.2. Securing Diameter Messages
1017 Connections between Diameter peers SHOULD be protected by TLS. All
1018 Diameter base protocol implementations MUST support the use of TLS.
1019 If desired, additional security measures that are transparent to and
1020 independent of Diameter, such as IPSec [RFC4301], can be deployed to
1021 secure connections between peers. The Diameter protocol MUST NOT be
1022 used without any security mechanism.
1024 2.3. Diameter Application Compliance
1026 Application Ids are advertised during the capabilities exchange phase
1027 (see Section 5.3). For a given application, advertising support of
1028 an application implies that the sender supports all command codes,
1029 and the AVPs specified in the associated ABNFs, described in the
1030 specification.
1032 An implementation MAY add arbitrary optional AVPs with the M-bit
1033 cleared to a command defined in an application, including vendor-
1034 specific AVPs only if the commands ABNF allows for it. Please refer
1035 to Section 11.1.1 for details.
1037 2.4. Application Identifiers
1039 Each Diameter application MUST have an IANA assigned Application Id
1040 (see Section 11.3). The base protocol does not require an
1041 Application Id since its support is mandatory. During the
1042 capabilities exchange, Diameter nodes inform their peers of locally
1043 supported applications. Furthermore, all Diameter messages contain
1044 an Application Id, which is used in the message forwarding process.
1046 The following Application Id values are defined:
1048 Diameter Common Messages 0
1049 NASREQ 1 [RFC4005]
1050 Mobile-IP 2 [RFC4004]
1051 Diameter Base Accounting 3
1052 Relay 0xffffffff
1054 Relay and redirect agents MUST advertise the Relay Application
1055 Identifier, while all other Diameter nodes MUST advertise locally
1056 supported applications. The receiver of a Capabilities Exchange
1057 message advertising Relay service MUST assume that the sender
1058 supports all current and future applications.
1060 Diameter relay and proxy agents are responsible for finding an
1061 upstream server that supports the application of a particular
1062 message. If none can be found, an error message is returned with the
1063 Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER.
1065 2.5. Connections vs. Sessions
1067 This section attempts to provide the reader with an understanding of
1068 the difference between connection and session, which are terms used
1069 extensively throughout this document.
1071 A connection is a transport level connection between two peers, used
1072 to send and receive Diameter messages. A session is a logical
1073 concept at the application layer, and is shared between an access
1074 device and a server, and is identified via the Session-Id AVP.
1076 +--------+ +-------+ +--------+
1077 | Client | | Relay | | Server |
1078 +--------+ +-------+ +--------+
1079 <----------> <---------->
1080 peer connection A peer connection B
1082 <----------------------------->
1083 User session x
1085 Figure 1: Diameter connections and sessions
1087 In the example provided in Figure 1, peer connection A is established
1088 between the Client and its local Relay. Peer connection B is
1089 established between the Relay and the Server. User session X spans
1090 from the Client via the Relay to the Server. Each "user" of a
1091 service causes an auth request to be sent, with a unique session
1092 identifier. Once accepted by the server, both the client and the
1093 server are aware of the session.
1095 It is important to note that there is no relationship between a
1096 connection and a session, and that Diameter messages for multiple
1097 sessions are all multiplexed through a single connection. Also note
1098 that Diameter messages pertaining to the session, both application
1099 specific and those that are defined in this document such as ASR/ASA,
1100 RAR/RAA and STR/STA MUST carry the Application Id of the application.
1101 Diameter messages pertaining to peer connection establishment and
1102 maintenance such as CER/CEA, DWR/DWA and DPR/DPA MUST carry an
1103 Application Id of zero (0).
1105 2.6. Peer Table
1107 The Diameter Peer Table is used in message forwarding, and referenced
1108 by the Routing Table. A Peer Table entry contains the following
1109 fields:
1111 Host identity
1113 Following the conventions described for the DiameterIdentity
1114 derived AVP data format in Section 4.4. This field contains the
1115 contents of the Origin-Host (Section 6.3) AVP found in the CER or
1116 CEA message.
1118 StatusT
1120 This is the state of the peer entry, and MUST match one of the
1121 values listed in Section 5.6.
1123 Static or Dynamic
1125 Specifies whether a peer entry was statically configured, or
1126 dynamically discovered.
1128 Expiration time
1130 Specifies the time at which dynamically discovered peer table
1131 entries are to be either refreshed, or expired.
1133 TLS Enabled
1135 Specifies whether TLS is to be used when communicating with the
1136 peer.
1138 Additional security information, when needed (e.g., keys,
1139 certificates)
1141 2.7. Routing Table
1143 All Realm-Based routing lookups are performed against what is
1144 commonly known as the Routing Table (see Section 12). A Routing
1145 Table Entry contains the following fields:
1147 Realm Name
1149 This is the field that is MUST be used as a primary key in the
1150 routing table lookups. Note that some implementations perform
1151 their lookups based on longest-match-from-the-right on the realm
1152 rather than requiring an exact match.
1154 Application Identifier
1156 An application is identified by an Application Id. A route entry
1157 can have a different destination based on the Application Id in
1158 the message header. This field MUST be used as a secondary key
1159 field in routing table lookups.
1161 Local Action
1163 The Local Action field is used to identify how a message should be
1164 treated. The following actions are supported:
1166 1. LOCAL - Diameter messages that resolve to a route entry with
1167 the Local Action set to Local can be satisfied locally, and do
1168 not need to be routed to another server.
1170 2. RELAY - All Diameter messages that fall within this category
1171 MUST be routed to a next hop server, without modifying any
1172 non-routing AVPs. See Section 6.1.9 for relaying guidelines
1174 3. PROXY - All Diameter messages that fall within this category
1175 MUST be routed to a next hop server. The local server MAY
1176 apply its local policies to the message by including new AVPs
1177 to the message prior to routing. See Section 6.1.9 for
1178 proxying guidelines.
1180 4. REDIRECT - Diameter messages that fall within this category
1181 MUST have the identity of the home Diameter server(s)
1182 appended, and returned to the sender of the message. See
1183 Section 6.1.9 for redirect guidelines.
1185 Server Identifier
1187 One or more servers the message is to be routed to. These servers
1188 MUST also be present in the Peer table. When the Local Action is
1189 set to RELAY or PROXY, this field contains the identity of the
1190 server(s) the message must be routed to. When the Local Action
1191 field is set to REDIRECT, this field contains the identity of one
1192 or more servers the message should be redirected to.
1194 Static or Dynamic
1196 Specifies whether a route entry was statically configured, or
1197 dynamically discovered.
1199 Expiration time
1201 Specifies the time which a dynamically discovered route table
1202 entry expires.
1204 It is important to note that Diameter agents MUST support at least
1205 one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation.
1206 Agents do not need to support all modes of operation in order to
1207 conform with the protocol specification, but MUST follow the protocol
1208 compliance guidelines in Section 2. Relay agents MUST NOT reorder
1209 AVPs, and proxies MUST NOT reorder AVPs.
1211 The routing table MAY include a default entry that MUST be used for
1212 any requests not matching any of the other entries. The routing
1213 table MAY consist of only such an entry.
1215 When a request is routed, the target server MUST have advertised the
1216 Application Id (see Section 2.4) for the given message, or have
1217 advertised itself as a relay or proxy agent. Otherwise, an error is
1218 returned with the Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER.
1220 2.8. Role of Diameter Agents
1222 In addition to client and servers, the Diameter protocol introduces
1223 relay, proxy, redirect, and translation agents, each of which is
1224 defined in Section 1.3. These Diameter agents are useful for several
1225 reasons:
1227 o They can distribute administration of systems to a configurable
1228 grouping, including the maintenance of security associations.
1230 o They can be used for concentration of requests from an number of
1231 co-located or distributed NAS equipment sets to a set of like user
1232 groups.
1234 o They can do value-added processing to the requests or responses.
1236 o They can be used for load balancing.
1238 o A complex network will have multiple authentication sources, they
1239 can sort requests and forward towards the correct target.
1241 The Diameter protocol requires that agents maintain transaction
1242 state, which is used for failover purposes. Transaction state
1243 implies that upon forwarding a request, its Hop-by-Hop identifier is
1244 saved; the field is replaced with a locally unique identifier, which
1245 is restored to its original value when the corresponding answer is
1246 received. The request's state is released upon receipt of the
1247 answer. A stateless agent is one that only maintains transaction
1248 state.
1250 The Proxy-Info AVP allows stateless agents to add local state to a
1251 Diameter request, with the guarantee that the same state will be
1252 present in the answer. However, the protocol's failover procedures
1253 require that agents maintain a copy of pending requests.
1255 A stateful agent is one that maintains session state information; by
1256 keeping track of all authorized active sessions. Each authorized
1257 session is bound to a particular service, and its state is considered
1258 active either until it is notified otherwise, or by expiration. Each
1259 authorized session has an expiration, which is communicated by
1260 Diameter servers via the Session-Timeout AVP.
1262 Maintaining session state MAY be useful in certain applications, such
1263 as:
1265 o Protocol translation (e.g., RADIUS <-> Diameter)
1267 o Limiting resources authorized to a particular user
1269 o Per user or transaction auditing
1271 A Diameter agent MAY act in a stateful manner for some requests and
1272 be stateless for others. A Diameter implementation MAY act as one
1273 type of agent for some requests, and as another type of agent for
1274 others.
1276 2.8.1. Relay Agents
1278 Relay Agents are Diameter agents that accept requests and route
1279 messages to other Diameter nodes based on information found in the
1280 messages (e.g., Destination-Realm). This routing decision is
1281 performed using a list of supported realms, and known peers. This is
1282 known as the Routing Table, as is defined further in Section 2.7.
1284 Relays MAY be used to aggregate requests from multiple Network Access
1285 Servers (NASes) within a common geographical area (POP). The use of
1286 Relays is advantageous since it eliminates the need for NASes to be
1287 configured with the necessary security information they would
1288 otherwise require to communicate with Diameter servers in other
1289 realms. Likewise, this reduces the configuration load on Diameter
1290 servers that would otherwise be necessary when NASes are added,
1291 changed or deleted.
1293 Relays modify Diameter messages by inserting and removing routing
1294 information, but do not modify any other portion of a message.
1295 Relays SHOULD NOT maintain session state but MUST maintain
1296 transaction state.
1298 +------+ ---------> +------+ ---------> +------+
1299 | | 1. Request | | 2. Request | |
1300 | NAS | | DRL | | HMS |
1301 | | 4. Answer | | 3. Answer | |
1302 +------+ <--------- +------+ <--------- +------+
1303 example.net example.net example.com
1305 Figure 2: Relaying of Diameter messages
1307 The example provided in Figure 2 depicts a request issued from NAS,
1308 which is an access device, for the user bob@example.com. Prior to
1309 issuing the request, NAS performs a Diameter route lookup, using
1310 "example.com" as the key, and determines that the message is to be
1311 relayed to DRL, which is a Diameter Relay. DRL performs the same
1312 route lookup as NAS, and relays the message to HMS, which is
1313 example.com's Home Diameter Server. HMS identifies that the request
1314 can be locally supported (via the realm), processes the
1315 authentication and/or authorization request, and replies with an
1316 answer, which is routed back to NAS using saved transaction state.
1318 Since Relays do not perform any application level processing, they
1319 provide relaying services for all Diameter applications, and
1320 therefore MUST advertise the Relay Application Id.
1322 2.8.2. Proxy Agents
1324 Similarly to relays, proxy agents route Diameter messages using the
1325 Diameter Routing Table. However, they differ since they modify
1326 messages to implement policy enforcement. This requires that proxies
1327 maintain the state of their downstream peers (e.g., access devices)
1328 to enforce resource usage, provide admission control, and
1329 provisioning.
1331 Proxies MAY be used in call control centers or access ISPs that
1332 provide outsourced connections, they can monitor the number and types
1333 of ports in use, and make allocation and admission decisions
1334 according to their configuration.
1336 Proxies that wish to limit resources MUST maintain session state.
1337 All proxies MUST maintain transaction state.
1339 Since enforcing policies requires an understanding of the service
1340 being provided, Proxies MUST only advertise the Diameter applications
1341 they support.
1343 2.8.3. Redirect Agents
1345 Redirect agents are useful in scenarios where the Diameter routing
1346 configuration needs to be centralized. An example is a redirect
1347 agent that provides services to all members of a consortium, but does
1348 not wish to be burdened with relaying all messages between realms.
1349 This scenario is advantageous since it does not require that the
1350 consortium provide routing updates to its members when changes are
1351 made to a member's infrastructure.
1353 Since redirect agents do not relay messages, and only return an
1354 answer with the information necessary for Diameter agents to
1355 communicate directly, they do not modify messages. Since redirect
1356 agents do not receive answer messages, they cannot maintain session
1357 state. Further, since redirect agents never relay requests, they are
1358 not required to maintain transaction state.
1360 The example provided in Figure 3 depicts a request issued from the
1361 access device, NAS, for the user bob@example.com. The message is
1362 forwarded by the NAS to its relay, DRL, which does not have a routing
1363 entry in its Diameter Routing Table for example.com. DRL has a
1364 default route configured to DRD, which is a redirect agent that
1365 returns a redirect notification to DRL, as well as HMS' contact
1366 information. Upon receipt of the redirect notification, DRL
1367 establishes a transport connection with HMS, if one doesn't already
1368 exist, and forwards the request to it.
1370 +------+
1371 | |
1372 | DRD |
1373 | |
1374 +------+
1375 ^ |
1376 2. Request | | 3. Redirection
1377 | | Notification
1378 | v
1379 +------+ ---------> +------+ ---------> +------+
1380 | | 1. Request | | 4. Request | |
1381 | NAS | | DRL | | HMS |
1382 | | 6. Answer | | 5. Answer | |
1383 +------+ <--------- +------+ <--------- +------+
1384 example.net example.net example.com
1386 Figure 3: Redirecting a Diameter Message
1388 Since redirect agents do not perform any application level
1389 processing, they provide relaying services for all Diameter
1390 applications, and therefore MUST advertise the Relay Application
1391 Identifier.
1393 2.8.4. Translation Agents
1395 A translation agent is a device that provides translation between two
1396 protocols (e.g., RADIUS<->Diameter, TACACS+<->Diameter). Translation
1397 agents are likely to be used as aggregation servers to communicate
1398 with a Diameter infrastructure, while allowing for the embedded
1399 systems to be migrated at a slower pace.
1401 Given that the Diameter protocol introduces the concept of long-lived
1402 authorized sessions, translation agents MUST be session stateful and
1403 MUST maintain transaction state.
1405 Translation of messages can only occur if the agent recognizes the
1406 application of a particular request, and therefore translation agents
1407 MUST only advertise their locally supported applications.
1409 +------+ ---------> +------+ ---------> +------+
1410 | | RADIUS Request | | Diameter Request | |
1411 | NAS | | TLA | | HMS |
1412 | | RADIUS Answer | | Diameter Answer | |
1413 +------+ <--------- +------+ <--------- +------+
1414 example.net example.net example.com
1416 Figure 4: Translation of RADIUS to Diameter
1418 2.9. Diameter Path Authorization
1420 As noted in Section 2.2, Diameter provides transmission level
1421 security for each connection using TLS. Therefore, each connection
1422 can be authenticated, replay and integrity protected.
1424 In addition to authenticating each connection, each connection as
1425 well as the entire session MUST also be authorized. Before
1426 initiating a connection, a Diameter Peer MUST check that its peers
1427 are authorized to act in their roles. For example, a Diameter peer
1428 may be authentic, but that does not mean that it is authorized to act
1429 as a Diameter Server advertising a set of Diameter applications.
1431 Prior to bringing up a connection, authorization checks are performed
1432 at each connection along the path. Diameter capabilities negotiation
1433 (CER/CEA) also MUST be carried out, in order to determine what
1434 Diameter applications are supported by each peer. Diameter sessions
1435 MUST be routed only through authorized nodes that have advertised
1436 support for the Diameter application required by the session.
1438 As noted in Section 6.1.9, a relay or proxy agent MUST append a
1439 Route-Record AVP to all requests forwarded. The AVP contains the
1440 identity of the peer the request was received from.
1442 The home Diameter server, prior to authorizing a session, MUST check
1443 the Route-Record AVPs to make sure that the route traversed by the
1444 request is acceptable. For example, administrators within the home
1445 realm may not wish to honor requests that have been routed through an
1446 untrusted realm. By authorizing a request, the home Diameter server
1447 is implicitly indicating its willingness to engage in the business
1448 transaction as specified by the contractual relationship between the
1449 server and the previous hop. A DIAMETER_AUTHORIZATION_REJECTED error
1450 message (see Section 7.1.5) is sent if the route traversed by the
1451 request is unacceptable.
1453 A home realm may also wish to check that each accounting request
1454 message corresponds to a Diameter response authorizing the session.
1455 Accounting requests without corresponding authorization responses
1456 SHOULD be subjected to further scrutiny, as should accounting
1457 requests indicating a difference between the requested and provided
1458 service.
1460 Forwarding of an authorization response is considered evidence of a
1461 willingness to take on financial risk relative to the session. A
1462 local realm may wish to limit this exposure, for example, by
1463 establishing credit limits for intermediate realms and refusing to
1464 accept responses which would violate those limits. By issuing an
1465 accounting request corresponding to the authorization response, the
1466 local realm implicitly indicates its agreement to provide the service
1467 indicated in the authorization response. If the service cannot be
1468 provided by the local realm, then a DIAMETER_UNABLE_TO_COMPLY error
1469 message MUST be sent within the accounting request; a Diameter client
1470 receiving an authorization response for a service that it cannot
1471 perform MUST NOT substitute an alternate service, and then send
1472 accounting requests for the alternate service instead.
1474 3. Diameter Header
1476 A summary of the Diameter header format is shown below. The fields
1477 are transmitted in network byte order.
1479 0 1 2 3
1480 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
1481 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1482 | Version | Message Length |
1483 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1484 | command flags | Command-Code |
1485 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1486 | Application-ID |
1487 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1488 | Hop-by-Hop Identifier |
1489 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1490 | End-to-End Identifier |
1491 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1492 | AVPs ...
1493 +-+-+-+-+-+-+-+-+-+-+-+-+-
1495 Version
1497 This Version field MUST be set to 1 to indicate Diameter Version
1498 1.
1500 Message Length
1502 The Message Length field is three octets and indicates the length
1503 of the Diameter message including the header fields.
1505 Command Flags
1507 The Command Flags field is eight bits. The following bits are
1508 assigned:
1510 0 1 2 3 4 5 6 7
1511 +-+-+-+-+-+-+-+-+
1512 |R P E T r r r r|
1513 +-+-+-+-+-+-+-+-+
1515 R(equest)
1517 If set, the message is a request. If cleared, the message is
1518 an answer.
1520 P(roxiable)
1522 If set, the message MAY be proxied, relayed or redirected. If
1523 cleared, the message MUST be locally processed.
1525 E(rror)
1527 If set, the message contains a protocol error, and the message
1528 will not conform to the ABNF described for this command.
1529 Messages with the 'E' bit set are commonly referred to as error
1530 messages. This bit MUST NOT be set in request messages. See
1531 Section 7.2.
1533 T(Potentially re-transmitted message)
1535 This flag is set after a link failover procedure, to aid the
1536 removal of duplicate requests. It is set when resending
1537 requests not yet acknowledged, as an indication of a possible
1538 duplicate due to a link failure. This bit MUST be cleared when
1539 sending a request for the first time, otherwise the sender MUST
1540 set this flag. Diameter agents only need to be concerned about
1541 the number of requests they send based on a single received
1542 request; retransmissions by other entities need not be tracked.
1543 Diameter agents that receive a request with the T flag set,
1544 MUST keep the T flag set in the forwarded request. This flag
1545 MUST NOT be set if an error answer message (e.g., a protocol
1546 error) has been received for the earlier message. It can be
1547 set only in cases where no answer has been received from the
1548 server for a request and the request is sent again. This flag
1549 MUST NOT be set in answer messages.
1551 r(eserved)
1553 These flag bits are reserved for future use, and MUST be set to
1554 zero, and ignored by the receiver.
1556 Command-Code
1558 The Command-Code field is three octets, and is used in order to
1559 communicate the command associated with the message. The 24-bit
1560 address space is managed by IANA (see Section 11.2.1).
1562 Command-Code values 16,777,214 and 16,777,215 (hexadecimal values
1563 FFFFFE -FFFFFF) are reserved for experimental use (See Section
1564 11.3).
1566 Application-ID
1568 Application-ID is four octets and is used to identify to which
1569 application the message is applicable for. The application can be
1570 an authentication application, an accounting application or a
1571 vendor specific application. See Section 11.3 for the possible
1572 values that the application-id may use.
1574 The value of the application-id field in the header MUST be the
1575 same as any relevant application-id AVPs contained in the message.
1577 Hop-by-Hop Identifier
1579 The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in
1580 network byte order) and aids in matching requests and replies.
1581 The sender MUST ensure that the Hop-by-Hop identifier in a request
1582 is unique on a given connection at any given time, and MAY attempt
1583 to ensure that the number is unique across reboots. The sender of
1584 an Answer message MUST ensure that the Hop-by-Hop Identifier field
1585 contains the same value that was found in the corresponding
1586 request. The Hop-by-Hop identifier is normally a monotonically
1587 increasing number, whose start value was randomly generated. An
1588 answer message that is received with an unknown Hop-by-Hop
1589 Identifier MUST be discarded.
1591 End-to-End Identifier
1593 The End-to-End Identifier is an unsigned 32-bit integer field (in
1594 network byte order) and is used to detect duplicate messages.
1595 Upon reboot implementations MAY set the high order 12 bits to
1596 contain the low order 12 bits of current time, and the low order
1597 20 bits to a random value. Senders of request messages MUST
1598 insert a unique identifier on each message. The identifier MUST
1599 remain locally unique for a period of at least 4 minutes, even
1600 across reboots. The originator of an Answer message MUST ensure
1601 that the End-to-End Identifier field contains the same value that
1602 was found in the corresponding request. The End-to-End Identifier
1603 MUST NOT be modified by Diameter agents of any kind. The
1604 combination of the Origin-Host (see Section 6.3) and this field is
1605 used to detect duplicates. Duplicate requests SHOULD cause the
1606 same answer to be transmitted (modulo the hop-by-hop Identifier
1607 field and any routing AVPs that may be present), and MUST NOT
1608 affect any state that was set when the original request was
1609 processed. Duplicate answer messages that are to be locally
1610 consumed (see Section 6.2) SHOULD be silently discarded.
1612 AVPs
1614 AVPs are a method of encapsulating information relevant to the
1615 Diameter message. See Section 4 for more information on AVPs.
1617 3.1. Command Codes
1619 Each command Request/Answer pair is assigned a command code, and the
1620 sub-type (i.e., request or answer) is identified via the 'R' bit in
1621 the Command Flags field of the Diameter header.
1623 Every Diameter message MUST contain a command code in its header's
1624 Command-Code field, which is used to determine the action that is to
1625 be taken for a particular message. The following Command Codes are
1626 defined in the Diameter base protocol:
1628 Command-Name Abbrev. Code Reference
1629 --------------------------------------------------------
1630 Abort-Session-Request ASR 274 8.5.1
1631 Abort-Session-Answer ASA 274 8.5.2
1632 Accounting-Request ACR 271 9.7.1
1633 Accounting-Answer ACA 271 9.7.2
1634 Capabilities-Exchange- CER 257 5.3.1
1635 Request
1636 Capabilities-Exchange- CEA 257 5.3.2
1637 Answer
1638 Device-Watchdog-Request DWR 280 5.5.1
1639 Device-Watchdog-Answer DWA 280 5.5.2
1640 Disconnect-Peer-Request DPR 282 5.4.1
1641 Disconnect-Peer-Answer DPA 282 5.4.2
1642 Re-Auth-Request RAR 258 8.3.1
1643 Re-Auth-Answer RAA 258 8.3.2
1644 Session-Termination- STR 275 8.4.1
1645 Request
1646 Session-Termination- STA 275 8.4.2
1647 Answer
1649 3.2. Command Code ABNF specification
1651 Every Command Code defined MUST include a corresponding ABNF
1652 specification, which is used to define the AVPs that MUST or MAY be
1653 present. The following format is used in the definition:
1655 command-def = command-name "::=" diameter-message
1657 command-name = diameter-name
1658 diameter-name = ALPHA *(ALPHA / DIGIT / "-")
1660 diameter-message = header [ *fixed] [ *required] [ *optional]
1662 header = "<" "Diameter Header:" command-id
1663 [r-bit] [p-bit] [e-bit] [application-id] ">"
1665 application-id = 1*DIGIT
1667 command-id = 1*DIGIT
1668 ; The Command Code assigned to the command
1670 r-bit = ", REQ"
1671 ; If present, the 'R' bit in the Command
1672 ; Flags is set, indicating that the message
1673 ; is a request, as opposed to an answer.
1675 p-bit = ", PXY"
1676 ; If present, the 'P' bit in the Command
1677 ; Flags is set, indicating that the message
1678 ; is proxiable.
1680 e-bit = ", ERR"
1681 ; If present, the 'E' bit in the Command
1682 ; Flags is set, indicating that the answer
1683 ; message contains a Result-Code AVP in
1684 ; the "protocol error" class.
1686 fixed = [qual] "<" avp-spec ">"
1687 ; Defines the fixed position of an AVP
1689 required = [qual] "{" avp-spec "}"
1690 ; The AVP MUST be present and can appear
1691 ; anywhere in the message.
1693 optional = [qual] "[" avp-name "]"
1694 ; The avp-name in the 'optional' rule cannot
1695 ; evaluate to any AVP Name which is included
1696 ; in a fixed or required rule. The AVP can
1697 ; appear anywhere in the message.
1699 qual = [min] "*" [max]
1700 ; See ABNF conventions, RFC 4234 Section 6.6.
1701 ; The absence of any qualifiers depends on
1702 ; whether it precedes a fixed, required, or
1703 ; optional rule. If a fixed or required rule has
1704 ; no qualifier, then exactly one such AVP MUST
1705 ; be present. If an optional rule has no
1706 ; qualifier, then 0 or 1 such AVP may be
1707 ; present. If an optional rule has a qualifier,
1708 ; then the value of min MUST be 0 if present.
1709 ;
1710 ; NOTE: "[" and "]" have a different meaning
1711 ; than in ABNF (see the optional rule, above).
1712 ; These braces cannot be used to express
1713 ; optional fixed rules (such as an optional
1714 ; ICV at the end). To do this, the convention
1715 ; is '0*1fixed'.
1717 min = 1*DIGIT
1718 ; The minimum number of times the element may
1719 ; be present. The default value is zero.
1721 max = 1*DIGIT
1722 ; The maximum number of times the element may
1723 ; be present. The default value is infinity. A
1724 ; value of zero implies the AVP MUST NOT be
1725 ; present.
1727 avp-spec = diameter-name
1728 ; The avp-spec has to be an AVP Name, defined
1729 ; in the base or extended Diameter
1730 ; specifications.
1732 avp-name = avp-spec / "AVP"
1733 ; The string "AVP" stands for *any* arbitrary AVP
1734 ; Name, not otherwise listed in that command code
1735 ; definition. Addition this AVP is recommended for
1736 ; all command ABNFs to allow for extensibility.
1738 The following is a definition of a fictitious command code:
1740 Example-Request ::= < Diameter Header: 9999999, REQ, PXY >
1741 { User-Name }
1742 * { Origin-Host }
1743 * [ AVP ]
1745 3.3. Diameter Command Naming Conventions
1747 Diameter command names typically includes one or more English words
1748 followed by the verb Request or Answer. Each English word is
1749 delimited by a hyphen. A three-letter acronym for both the request
1750 and answer is also normally provided.
1752 An example is a message set used to terminate a session. The command
1753 name is Session-Terminate-Request and Session-Terminate-Answer, while
1754 the acronyms are STR and STA, respectively.
1756 Both the request and the answer for a given command share the same
1757 command code. The request is identified by the R(equest) bit in the
1758 Diameter header set to one (1), to ask that a particular action be
1759 performed, such as authorizing a user or terminating a session. Once
1760 the receiver has completed the request it issues the corresponding
1761 answer, which includes a result code that communicates one of the
1762 following:
1764 o The request was successful
1766 o The request failed
1768 o An additional request MUST be sent to provide information the peer
1769 requires prior to returning a successful or failed answer.
1771 o The receiver could not process the request, but provides
1772 information about a Diameter peer that is able to satisfy the
1773 request, known as redirect.
1775 Additional information, encoded within AVPs, MAY also be included in
1776 answer messages.
1778 4. Diameter AVPs
1780 Diameter AVPs carry specific authentication, accounting,
1781 authorization and routing information as well as configuration
1782 details for the request and reply.
1784 Some AVPs MAY be listed more than once. The effect of such an AVP is
1785 specific, and is specified in each case by the AVP description.
1787 Each AVP of type OctetString MUST be padded to align on a 32-bit
1788 boundary, while other AVP types align naturally. A number of zero-
1789 valued bytes are added to the end of the AVP Data field till a word
1790 boundary is reached. The length of the padding is not reflected in
1791 the AVP Length field.
1793 4.1. AVP Header
1795 The fields in the AVP header MUST be sent in network byte order. The
1796 format of the header is:
1798 0 1 2 3
1799 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
1800 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1801 | AVP Code |
1802 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1803 |V M P r r r r r| AVP Length |
1804 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1805 | Vendor-ID (opt) |
1806 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1807 | Data ...
1808 +-+-+-+-+-+-+-+-+
1810 AVP Code
1812 The AVP Code, combined with the Vendor-Id field, identifies the
1813 attribute uniquely. AVP numbers 1 through 255 are reserved for
1814 backward compatibility with RADIUS, without setting the Vendor-Id
1815 field. AVP numbers 256 and above are used for Diameter, which are
1816 allocated by IANA (see Section 11.1).
1818 AVP Flags
1820 The AVP Flags field informs the receiver how each attribute must
1821 be handled. The 'r' (reserved) bits are unused and SHOULD be set
1822 to 0. Note that subsequent Diameter applications MAY define
1823 additional bits within the AVP Header, and an unrecognized bit
1824 SHOULD be considered an error. The 'P' bit indicates the need for
1825 encryption for end-to-end security. Note that the 'P' bit has
1826 been deprecated and MUST be to zero(0) when sending an AVP and
1827 ignored on receipt of an AVP.
1829 The 'M' Bit, known as the Mandatory bit, indicates whether support
1830 of the AVP is required. If an AVP with the 'M' bit set is
1831 received by a Diameter client, server or translation agent and
1832 either the AVP or its value is unrecognized, the message MUST be
1833 rejected. An exception to this rule applies when the AVP is
1834 embedded within a Grouped AVP. See Section 4.4 for details.
1835 Diameter Relay and redirect agents MUST NOT reject messages with
1836 unrecognized AVPs.
1838 The 'M' bit MUST be set according to the rules defined in the
1839 application specification which introduces or re-uses this AVP.
1840 Within a given application, the M-bit setting for an AVP is either
1841 defined for all command types or for each command type.
1843 AVPs with the 'M' bit cleared are informational only and a
1844 receiver that receives a message with such an AVP that is not
1845 supported, or whose value is not supported, MAY simply ignore the
1846 AVP.
1848 The 'V' bit, known as the Vendor-Specific bit, indicates whether
1849 the optional Vendor-ID field is present in the AVP header. When
1850 set the AVP Code belongs to the specific vendor code address
1851 space.
1853 AVP Length
1855 The AVP Length field is three octets, and indicates the number of
1856 octets in this AVP including the AVP Code, AVP Length, AVP Flags,
1857 Vendor-ID field (if present) and the AVP data. If a message is
1858 received with an invalid attribute length, the message SHOULD be
1859 rejected.
1861 4.1.1. Optional Header Elements
1863 The AVP Header contains one optional field. This field is only
1864 present if the respective bit-flag is enabled.
1866 Vendor-ID
1868 The Vendor-ID field is present if the 'V' bit is set in the AVP
1869 Flags field. The optional four-octet Vendor-ID field contains the
1870 IANA assigned "SMI Network Management Private Enterprise Codes"
1871 [RFC3232] value, encoded in network byte order. Any vendor
1872 wishing to implement a vendor-specific Diameter AVP MUST use their
1873 own Vendor-ID along with their privately managed AVP address
1874 space, guaranteeing that they will not collide with any other
1875 vendor's vendor-specific AVP(s), nor with future IETF
1876 applications.
1878 A vendor ID value of zero (0) corresponds to the IETF adopted AVP
1879 values, as managed by the IANA. Since the absence of the vendor
1880 ID field implies that the AVP in question is not vendor specific,
1881 implementations MUST NOT use the zero (0) vendor ID.
1883 4.2. Basic AVP Data Formats
1885 The Data field is zero or more octets and contains information
1886 specific to the Attribute. The format and length of the Data field
1887 is determined by the AVP Code and AVP Length fields. The format of
1888 the Data field MUST be one of the following base data types or a data
1889 type derived from the base data types. In the event that a new Basic
1890 AVP Data Format is needed, a new version of this RFC MUST be created.
1892 OctetString
1894 The data contains arbitrary data of variable length. Unless
1895 otherwise noted, the AVP Length field MUST be set to at least 8
1896 (12 if the 'V' bit is enabled). AVP Values of this type that are
1897 not a multiple of four-octets in length is followed by the
1898 necessary padding so that the next AVP (if any) will start on a
1899 32-bit boundary.
1901 Integer32
1903 32 bit signed value, in network byte order. The AVP Length field
1904 MUST be set to 12 (16 if the 'V' bit is enabled).
1906 Integer64
1908 64 bit signed value, in network byte order. The AVP Length field
1909 MUST be set to 16 (20 if the 'V' bit is enabled).
1911 Unsigned32
1913 32 bit unsigned value, in network byte order. The AVP Length
1914 field MUST be set to 12 (16 if the 'V' bit is enabled).
1916 Unsigned64
1918 64 bit unsigned value, in network byte order. The AVP Length
1919 field MUST be set to 16 (20 if the 'V' bit is enabled).
1921 Float32
1923 This represents floating point values of single precision as
1924 described by [FLOATPOINT]. The 32-bit value is transmitted in
1925 network byte order. The AVP Length field MUST be set to 12 (16 if
1926 the 'V' bit is enabled).
1928 Float64
1930 This represents floating point values of double precision as
1931 described by [FLOATPOINT]. The 64-bit value is transmitted in
1932 network byte order. The AVP Length field MUST be set to 16 (20 if
1933 the 'V' bit is enabled).
1935 Grouped
1937 The Data field is specified as a sequence of AVPs. Each of these
1938 AVPs follows - in the order in which they are specified -
1939 including their headers and padding. The AVP Length field is set
1940 to 8 (12 if the 'V' bit is enabled) plus the total length of all
1941 included AVPs, including their headers and padding. Thus the AVP
1942 length field of an AVP of type Grouped is always a multiple of 4.
1944 4.3. Derived AVP Data Formats
1946 In addition to using the Basic AVP Data Formats, applications may
1947 define data formats derived from the Basic AVP Data Formats. An
1948 application that defines new AVP Derived Data Formats MUST include
1949 them in a section entitled "AVP Derived Data Formats", using the same
1950 format as the definitions below. Each new definition MUST be either
1951 defined or listed with a reference to the RFC that defines the
1952 format.
1954 The below AVP Derived Data Formats are commonly used by applications.
1956 Address
1958 The Address format is derived from the OctetString AVP Base
1959 Format. It is a discriminated union, representing, for example a
1960 32-bit (IPv4) [RFC791] or 128-bit (IPv6) [RFC4291] address, most
1961 significant octet first. The first two octets of the Address AVP
1962 represents the AddressType, which contains an Address Family
1963 defined in [IANAADFAM]. The AddressType is used to discriminate
1964 the content and format of the remaining octets.
1966 Time
1968 The Time format is derived from the OctetString AVP Base Format.
1969 The string MUST contain four octets, in the same format as the
1970 first four bytes are in the NTP timestamp format. The NTP
1971 Timestamp format is defined in chapter 3 of [RFC4330].
1973 This represents the number of seconds since 0h on 1 January 1900
1974 with respect to the Coordinated Universal Time (UTC).
1976 On 6h 28m 16s UTC, 7 February 2036 the time value will overflow.
1977 SNTP [RFC4330] describes a procedure to extend the time to 2104.
1978 This procedure MUST be supported by all DIAMETER nodes.
1980 UTF8String
1982 The UTF8String format is derived from the OctetString AVP Base
1983 Format. This is a human readable string represented using the
1984 ISO/IEC IS 10646-1 character set, encoded as an OctetString using
1985 the UTF-8 [RFC3629] transformation format described in RFC 3629.
1987 Since additional code points are added by amendments to the 10646
1988 standard from time to time, implementations MUST be prepared to
1989 encounter any code point from 0x00000001 to 0x7fffffff. Byte
1990 sequences that do not correspond to the valid encoding of a code
1991 point into UTF-8 charset or are outside this range are prohibited.
1993 The use of control codes SHOULD be avoided. When it is necessary
1994 to represent a new line, the control code sequence CR LF SHOULD be
1995 used.
1997 The use of leading or trailing white space SHOULD be avoided.
1999 For code points not directly supported by user interface hardware
2000 or software, an alternative means of entry and display, such as
2001 hexadecimal, MAY be provided.
2003 For information encoded in 7-bit US-ASCII, the UTF-8 charset is
2004 identical to the US-ASCII charset.
2006 UTF-8 may require multiple bytes to represent a single character /
2007 code point; thus the length of an UTF8String in octets may be
2008 different from the number of characters encoded.
2010 Note that the AVP Length field of an UTF8String is measured in
2011 octets, not characters.
2013 DiameterIdentity
2015 The DiameterIdentity format is derived from the OctetString AVP
2016 Base Format.
2018 DiameterIdentity = FQDN
2020 DiameterIdentity value is used to uniquely identify a Diameter
2021 node for purposes of duplicate connection and routing loop
2022 detection.
2024 The contents of the string MUST be the FQDN of the Diameter node.
2025 If multiple Diameter nodes run on the same host, each Diameter
2026 node MUST be assigned a unique DiameterIdentity. If a Diameter
2027 node can be identified by several FQDNs, a single FQDN should be
2028 picked at startup, and used as the only DiameterIdentity for that
2029 node, whatever the connection it is sent on. Note that in this
2030 document, DiameterIdentity is in ASCII form in order to be
2031 compatible with existing DNS infrastructure. See Appendix D for
2032 interactions between the Diameter protocol and Internationalized
2033 Domain Name (IDNs).
2035 DiameterURI
2037 The DiameterURI MUST follow the Uniform Resource Identifiers (URI)
2038 syntax [RFC3986] rules specified below:
2040 "aaa://" FQDN [ port ] [ transport ] [ protocol ]
2042 ; No transport security
2044 "aaas://" FQDN [ port ] [ transport ] [ protocol ]
2046 ; Transport security used
2048 FQDN = Fully Qualified Host Name
2050 port = ":" 1*DIGIT
2052 ; One of the ports used to listen for
2053 ; incoming connections.
2054 ; If absent,
2055 ; the default Diameter port (3868) is
2056 ; assumed.
2058 transport = ";transport=" transport-protocol
2060 ; One of the transports used to listen
2061 ; for incoming connections. If absent,
2062 ; the default SCTP [RFC2960] protocol is
2063 ; assumed. UDP MUST NOT be used when
2064 ; the aaa-protocol field is set to
2065 ; diameter.
2067 transport-protocol = ( "tcp" / "sctp" / "udp" )
2069 protocol = ";protocol=" aaa-protocol
2071 ; If absent, the default AAA protocol
2072 ; is Diameter.
2074 aaa-protocol = ( "diameter" / "radius" / "tacacs+" )
2076 The following are examples of valid Diameter host identities:
2078 aaa://host.example.com;transport=tcp
2079 aaa://host.example.com:6666;transport=tcp
2080 aaa://host.example.com;protocol=diameter
2081 aaa://host.example.com:6666;protocol=diameter
2082 aaa://host.example.com:6666;transport=tcp;protocol=diameter
2083 aaa://host.example.com:1813;transport=udp;protocol=radius
2085 Enumerated
2087 Enumerated is derived from the Integer32 AVP Base Format. The
2088 definition contains a list of valid values and their
2089 interpretation and is described in the Diameter application
2090 introducing the AVP.
2092 IPFilterRule
2094 The IPFilterRule format is derived from the OctetString AVP Base
2095 Format and uses the ASCII charset. The rule syntax is a modified
2096 subset of ipfw(8) from FreeBSD. Packets may be filtered based on
2097 the following information that is associated with it:
2099 Direction (in or out)
2100 Source and destination IP address (possibly masked)
2101 Protocol
2102 Source and destination port (lists or ranges)
2103 TCP flags
2104 IP fragment flag
2105 IP options
2106 ICMP types
2108 Rules for the appropriate direction are evaluated in order, with
2109 the first matched rule terminating the evaluation. Each packet is
2110 evaluated once. If no rule matches, the packet is dropped if the
2111 last rule evaluated was a permit, and passed if the last rule was
2112 a deny.
2114 IPFilterRule filters MUST follow the format:
2116 action dir proto from src to dst [options]
2118 action permit - Allow packets that match the rule.
2119 deny - Drop packets that match the rule.
2121 dir "in" is from the terminal, "out" is to the
2122 terminal.
2124 proto An IP protocol specified by number. The "ip"
2125 keyword means any protocol will match.
2127 src and dst
[ports]
2129 The may be specified as:
2130 ipno An IPv4 or IPv6 number in dotted-
2131 quad or canonical IPv6 form. Only
2132 this exact IP number will match the
2133 rule.
2134 ipno/bits An IP number as above with a mask
2135 width of the form 1.2.3.4/24. In
2136 this case, all IP numbers from
2137 1.2.3.0 to 1.2.3.255 will match.
2138 The bit width MUST be valid for the
2139 IP version and the IP number MUST
2140 NOT have bits set beyond the mask.
2141 For a match to occur, the same IP
2142 version must be present in the
2143 packet that was used in describing
2144 the IP address. To test for a
2145 particular IP version, the bits part
2146 can be set to zero. The keyword
2147 "any" is 0.0.0.0/0 or the IPv6
2148 equivalent. The keyword "assigned"
2149 is the address or set of addresses
2150 assigned to the terminal. For IPv4,
2151 a typical first rule is often "deny
2152 in ip! assigned"
2154 The sense of the match can be inverted by
2155 preceding an address with the not modifier (!),
2156 causing all other addresses to be matched
2157 instead. This does not affect the selection of
2158 port numbers.
2160 With the TCP, UDP and SCTP protocols, optional
2161 ports may be specified as:
2163 {port/port-port}[,ports[,...]]
2165 The '-' notation specifies a range of ports
2166 (including boundaries).
2168 Fragmented packets that have a non-zero offset
2169 (i.e., not the first fragment) will never match
2170 a rule that has one or more port
2171 specifications. See the frag option for
2172 details on matching fragmented packets.
2174 options:
2175 frag Match if the packet is a fragment and this is not
2176 the first fragment of the datagram. frag may not
2177 be used in conjunction with either tcpflags or
2178 TCP/UDP port specifications.
2180 ipoptions spec
2181 Match if the IP header contains the comma
2182 separated list of options specified in spec. The
2183 supported IP options are:
2185 ssrr (strict source route), lsrr (loose source
2186 route), rr (record packet route) and ts
2187 (timestamp). The absence of a particular option
2188 may be denoted with a '!'.
2190 tcpoptions spec
2191 Match if the TCP header contains the comma
2192 separated list of options specified in spec. The
2193 supported TCP options are:
2195 mss (maximum segment size), window (tcp window
2196 advertisement), sack (selective ack), ts (rfc1323
2197 timestamp) and cc (rfc1644 t/tcp connection
2198 count). The absence of a particular option may
2199 be denoted with a '!'.
2201 established
2202 TCP packets only. Match packets that have the RST
2203 or ACK bits set.
2205 setup TCP packets only. Match packets that have the SYN
2206 bit set but no ACK bit.
2208 tcpflags spec
2209 TCP packets only. Match if the TCP header
2210 contains the comma separated list of flags
2211 specified in spec. The supported TCP flags are:
2213 fin, syn, rst, psh, ack and urg. The absence of a
2214 particular flag may be denoted with a '!'. A rule
2215 that contains a tcpflags specification can never
2216 match a fragmented packet that has a non-zero
2217 offset. See the frag option for details on
2218 matching fragmented packets.
2220 icmptypes types
2221 ICMP packets only. Match if the ICMP type is in
2222 the list types. The list may be specified as any
2223 combination of ranges or individual types
2224 separated by commas. Both the numeric values and
2225 the symbolic values listed below can be used. The
2226 supported ICMP types are:
2228 echo reply (0), destination unreachable (3),
2229 source quench (4), redirect (5), echo request
2230 (8), router advertisement (9), router
2231 solicitation (10), time-to-live exceeded (11), IP
2232 header bad (12), timestamp request (13),
2233 timestamp reply (14), information request (15),
2234 information reply (16), address mask request (17)
2235 and address mask reply (18).
2237 There is one kind of packet that the access device MUST always
2238 discard, that is an IP fragment with a fragment offset of one.
2239 This is a valid packet, but it only has one use, to try to
2240 circumvent firewalls.
2242 An access device that is unable to interpret or apply a deny rule
2243 MUST terminate the session. An access device that is unable to
2244 interpret or apply a permit rule MAY apply a more restrictive
2245 rule. An access device MAY apply deny rules of its own before the
2246 supplied rules, for example to protect the access device owner's
2247 infrastructure.
2249 4.4. Grouped AVP Values
2251 The Diameter protocol allows AVP values of type 'Grouped'. This
2252 implies that the Data field is actually a sequence of AVPs. It is
2253 possible to include an AVP with a Grouped type within a Grouped type,
2254 that is, to nest them. AVPs within an AVP of type Grouped have the
2255 same padding requirements as non-Grouped AVPs, as defined in Section
2256 4.
2258 The AVP Code numbering space of all AVPs included in a Grouped AVP is
2259 the same as for non-grouped AVPs. Receivers of a Grouped AVP that
2260 does not have the 'M' (mandatory) bit set and one or more of the
2261 encapsulated AVPs within the group has the 'M' (mandatory) bit set
2262 MAY simply be ignored if the Grouped AVP itself is unrecognized. The
2263 rule applies even if the encapsulated AVP with its 'M' (mandatory)
2264 bit set is further encapsulated within other sub-groups; i.e. other
2265 Grouped AVPs embedded within the Grouped AVP.
2267 Every Grouped AVP defined MUST include a corresponding grammar, using
2268 ABNF [RFC4234] (with modifications), as defined below.
2270 grouped-avp-def = name "::=" avp
2272 name-fmt = ALPHA *(ALPHA / DIGIT / "-")
2274 name = name-fmt
2275 ; The name has to be the name of an AVP,
2276 ; defined in the base or extended Diameter
2277 ; specifications.
2279 avp = header [ *fixed] [ *required] [ *optional]
2281 header = "<" "AVP-Header:" avpcode [vendor] ">"
2283 avpcode = 1*DIGIT
2284 ; The AVP Code assigned to the Grouped AVP
2286 vendor = 1*DIGIT
2287 ; The Vendor-ID assigned to the Grouped AVP.
2288 ; If absent, the default value of zero is
2289 ; used.
2291 4.4.1. Example AVP with a Grouped Data type
2293 The Example-AVP (AVP Code 999999) is of type Grouped and is used to
2294 clarify how Grouped AVP values work. The Grouped Data field has the
2295 following ABNF grammar:
2297 Example-AVP ::= < AVP Header: 999999 >
2298 { Origin-Host }
2299 1*{ Session-Id }
2300 *[ AVP ]
2302 An Example-AVP with Grouped Data follows.
2304 The Origin-Host AVP is required (Section 6.3). In this case:
2306 Origin-Host = "example.com".
2308 One or more Session-Ids must follow. Here there are two:
2310 Session-Id =
2311 "grump.example.com:33041;23432;893;0AF3B81"
2313 Session-Id =
2314 "grump.example.com:33054;23561;2358;0AF3B82"
2316 optional AVPs included are
2318 Recovery-Policy =
2319 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35
2320 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5
2321 c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd
2322 f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a
2323 cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119
2324 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c
2325 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92
2327 Futuristic-Acct-Record =
2328 fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0
2329 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8
2330 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c
2331 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067
2332 d3427475e49968f841
2334 The data for the optional AVPs is represented in hex since the format
2335 of these AVPs is neither known at the time of definition of the
2336 Example-AVP group, nor (likely) at the time when the example instance
2337 of this AVP is interpreted - except by Diameter implementations which
2338 support the same set of AVPs. The encoding example illustrates how
2339 padding is used and how length fields are calculated. Also note that
2340 AVPs may be present in the Grouped AVP value which the receiver
2341 cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record
2342 AVPs). The length of the Example-AVP is the sum of all the length of
2343 the member AVPs including their padding plus the Example-AVP header
2344 size.
2346 This AVP would be encoded as follows:
2348 0 1 2 3 4 5 6 7
2349 +-------+-------+-------+-------+-------+-------+-------+-------+
2350 0 | Example AVP Header (AVP Code = 999999), Length = 496 |
2351 +-------+-------+-------+-------+-------+-------+-------+-------+
2352 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 |
2353 +-------+-------+-------+-------+-------+-------+-------+-------+
2354 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' |
2355 +-------+-------+-------+-------+-------+-------+-------+-------+
2356 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header |
2357 +-------+-------+-------+-------+-------+-------+-------+-------+
2358 32 | (AVP Code = 263), Length = 49 | 'g' | 'r' | 'u' | 'm' |
2359 +-------+-------+-------+-------+-------+-------+-------+-------+
2360 . . .
2361 +-------+-------+-------+-------+-------+-------+-------+-------+
2362 72 | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding|Padding|
2363 +-------+-------+-------+-------+-------+-------+-------+-------+
2364 80 | Session-Id AVP Header (AVP Code = 263), Length = 50 |
2365 +-------+-------+-------+-------+-------+-------+-------+-------+
2366 88 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' |
2367 +-------+-------+-------+-------+-------+-------+-------+-------+
2368 . . .
2369 +-------+-------+-------+-------+-------+-------+-------+-------+
2370 120| '5' | '8' | ';' | '0' | 'A' | 'F' | '3' | 'B' |
2371 +-------+-------+-------+-------+-------+-------+-------+-------+
2372 128| '8' | '2' |Padding|Padding| Recovery-Policy Header (AVP |
2373 +-------+-------+-------+-------+-------+-------+-------+-------+
2374 136| Code = 8341), Length = 223 | 0x21 | 0x63 | 0xbc | 0x1d |
2375 +-------+-------+-------+-------+-------+-------+-------+-------+
2376 144| 0x0a | 0xd8 | 0x23 | 0x71 | 0xf6 | 0xbc | 0x09 | 0x48 |
2377 +-------+-------+-------+-------+-------+-------+-------+-------+
2378 . . .
2379 +-------+-------+-------+-------+-------+-------+-------+-------+
2380 352| 0x8c | 0x7f | 0x92 |Padding| Futuristic-Acct-Record Header |
2381 +-------+-------+-------+-------+-------+-------+-------+-------+
2382 328|(AVP Code = 15930),Length = 137| 0xfe | 0x19 | 0xda | 0x58 |
2383 +-------+-------+-------+-------+-------+-------+-------+-------+
2384 336| 0x02 | 0xac | 0xd9 | 0x8b | 0x07 | 0xa5 | 0xb8 | 0xc6 |
2385 +-------+-------+-------+-------+-------+-------+-------+-------+
2386 . . .
2387 +-------+-------+-------+-------+-------+-------+-------+-------+
2388 488| 0xe4 | 0x99 | 0x68 | 0xf8 | 0x41 |Padding|Padding|Padding|
2389 +-------+-------+-------+-------+-------+-------+-------+-------+
2391 4.5. Diameter Base Protocol AVPs
2393 The following table describes the Diameter AVPs defined in the base
2394 protocol, their AVP Code values, types, possible flag values.
2396 Due to space constraints, the short form DiamIdent is used to
2397 represent DiameterIdentity.
2399 +----------+
2400 | AVP Flag |
2401 | rules |
2402 |----+-----|
2403 AVP Section | |MUST |
2404 Attribute Name Code Defined Data Type |MUST| NOT |
2405 -----------------------------------------|----+-----|
2406 Acct- 85 9.8.2 Unsigned32 | M | V |
2407 Interim-Interval | | |
2408 Accounting- 483 9.8.7 Enumerated | M | V |
2409 Realtime-Required | | |
2410 Acct- 50 9.8.5 UTF8String | M | V |
2411 Multi-Session-Id | | |
2412 Accounting- 485 9.8.3 Unsigned32 | M | V |
2413 Record-Number | | |
2414 Accounting- 480 9.8.1 Enumerated | M | V |
2415 Record-Type | | |
2416 Accounting- 44 9.8.4 OctetString| M | V |
2417 Session-Id | | |
2418 Accounting- 287 9.8.6 Unsigned64 | M | V |
2419 Sub-Session-Id | | |
2420 Acct- 259 6.9 Unsigned32 | M | V |
2421 Application-Id | | |
2422 Auth- 258 6.8 Unsigned32 | M | V |
2423 Application-Id | | |
2424 Auth-Request- 274 8.7 Enumerated | M | V |
2425 Type | | |
2426 Authorization- 291 8.9 Unsigned32 | M | V |
2427 Lifetime | | |
2428 Auth-Grace- 276 8.10 Unsigned32 | M | V |
2429 Period | | |
2430 Auth-Session- 277 8.11 Enumerated | M | V |
2431 State | | |
2432 Re-Auth-Request- 285 8.12 Enumerated | M | V |
2433 Type | | |
2434 Class 25 8.20 OctetString| M | V |
2435 Destination-Host 293 6.5 DiamIdent | M | V |
2436 Destination- 283 6.6 DiamIdent | M | V |
2437 Realm | | |
2438 Disconnect-Cause 273 5.4.3 Enumerated | M | V |
2439 Error-Message 281 7.3 UTF8String | | V,M |
2440 Error-Reporting- 294 7.4 DiamIdent | | V,M |
2441 Host | | |
2442 Event-Timestamp 55 8.21 Time | M | V |
2443 Experimental- 297 7.6 Grouped | M | V |
2444 Result | | |
2445 -----------------------------------------|----+-----|
2446 +----------+
2447 | AVP Flag |
2448 | rules |
2449 |----+-----|
2450 AVP Section | |MUST |
2451 Attribute Name Code Defined Data Type |MUST| NOT |
2452 -----------------------------------------|----+-----|
2453 Experimental- 298 7.7 Unsigned32 | M | V |
2454 Result-Code | | |
2455 Failed-AVP 279 7.5 Grouped | M | V |
2456 Firmware- 267 5.3.4 Unsigned32 | | V,M |
2457 Revision | | |
2458 Host-IP-Address 257 5.3.5 Address | M | V |
2459 Inband-Security | M | V |
2460 -Id 299 6.10 Unsigned32 | | |
2461 Multi-Round- 272 8.19 Unsigned32 | M | V |
2462 Time-Out | | |
2463 Origin-Host 264 6.3 DiamIdent | M | V |
2464 Origin-Realm 296 6.4 DiamIdent | M | V |
2465 Origin-State-Id 278 8.16 Unsigned32 | M | V |
2466 Product-Name 269 5.3.7 UTF8String | | V,M |
2467 Proxy-Host 280 6.7.3 DiamIdent | M | V |
2468 Proxy-Info 284 6.7.2 Grouped | M | V |
2469 Proxy-State 33 6.7.4 OctetString| M | V |
2470 Redirect-Host 292 6.12 DiamURI | M | V |
2471 Redirect-Host- 261 6.13 Enumerated | M | V |
2472 Usage | | |
2473 Redirect-Max- 262 6.14 Unsigned32 | M | V |
2474 Cache-Time | | |
2475 Result-Code 268 7.1 Unsigned32 | M | V |
2476 Route-Record 282 6.7.1 DiamIdent | M | V |
2477 Session-Id 263 8.8 UTF8String | M | V |
2478 Session-Timeout 27 8.13 Unsigned32 | M | V |
2479 Session-Binding 270 8.17 Unsigned32 | M | V |
2480 Session-Server- 271 8.18 Enumerated | M | V |
2481 Failover | | |
2482 Supported- 265 5.3.6 Unsigned32 | M | V |
2483 Vendor-Id | | |
2484 Termination- 295 8.15 Enumerated | M | V |
2485 Cause | | |
2486 User-Name 1 8.14 UTF8String | M | V |
2487 Vendor-Id 266 5.3.3 Unsigned32 | M | V |
2488 Vendor-Specific- 260 6.11 Grouped | M | V |
2489 Application-Id | | |
2490 -----------------------------------------|----+-----|
2492 5. Diameter Peers
2494 This section describes how Diameter nodes establish connections and
2495 communicate with peers.
2497 5.1. Peer Connections
2499 Although a Diameter node may have many possible peers that it is able
2500 to communicate with, it may not be economical to have an established
2501 connection to all of them. At a minimum, a Diameter node SHOULD have
2502 an established connection with two peers per realm, known as the
2503 primary and secondary peers. Of course, a node MAY have additional
2504 connections, if it is deemed necessary. Typically, all messages for
2505 a realm are sent to the primary peer, but in the event that failover
2506 procedures are invoked, any pending requests are sent to the
2507 secondary peer. However, implementations are free to load balance
2508 requests between a set of peers.
2510 Note that a given peer MAY act as a primary for a given realm, while
2511 acting as a secondary for another realm.
2513 When a peer is deemed suspect, which could occur for various reasons,
2514 including not receiving a DWA within an allotted timeframe, no new
2515 requests should be forwarded to the peer, but failover procedures are
2516 invoked. When an active peer is moved to this mode, additional
2517 connections SHOULD be established to ensure that the necessary number
2518 of active connections exists.
2520 There are two ways that a peer is removed from the suspect peer list:
2522 1. The peer is no longer reachable, causing the transport connection
2523 to be shutdown. The peer is moved to the closed state.
2525 2. Three watchdog messages are exchanged with accepted round trip
2526 times, and the connection to the peer is considered stabilized.
2528 In the event the peer being removed is either the primary or
2529 secondary, an alternate peer SHOULD replace the deleted peer, and
2530 assume the role of either primary or secondary.
2532 5.2. Diameter Peer Discovery
2534 Allowing for dynamic Diameter agent discovery will make it possible
2535 for simpler and more robust deployment of Diameter services. In
2536 order to promote interoperable implementations of Diameter peer
2537 discovery, the following mechanisms are described. These are based
2538 on existing IETF standards. The first option (manual configuration)
2539 MUST be supported by all DIAMETER nodes, while the latter option
2540 (DNS) MAY be supported.
2542 There are two cases where Diameter peer discovery may be performed.
2543 The first is when a Diameter client needs to discover a first-hop
2544 Diameter agent. The second case is when a Diameter agent needs to
2545 discover another agent - for further handling of a Diameter
2546 operation. In both cases, the following 'search order' is
2547 recommended:
2549 1. The Diameter implementation consults its list of static
2550 (manually) configured Diameter agent locations. These will be
2551 used if they exist and respond.
2553 2. The Diameter implementation performs a NAPTR query for a server
2554 in a particular realm. The Diameter implementation has to know
2555 in advance which realm to look for a Diameter agent in. This
2556 could be deduced, for example, from the 'realm' in a NAI that a
2557 Diameter implementation needed to perform a Diameter operation
2558 on.
2560 * The services relevant for the task of transport protocol
2561 selection are those with NAPTR service fields with values
2562 "AAA+D2x", where x is a letter that corresponds to a transport
2563 protocol supported by the domain. This specification defines
2564 D2T for TCP and D2S for SCTP. We also establish an IANA
2565 registry for NAPTR service name to transport protocol
2566 mappings.
2568 These NAPTR records provide a mapping from a domain, to the
2569 SRV record for contacting a server with the specific transport
2570 protocol in the NAPTR services field. The resource record
2571 will contain an empty regular expression and a replacement
2572 value, which is the SRV record for that particular transport
2573 protocol. If the server supports multiple transport
2574 protocols, there will be multiple NAPTR records, each with a
2575 different service value. As per [RFC3403], the client
2576 discards any records whose services fields are not applicable.
2577 For the purposes of this specification, several rules are
2578 defined.
2580 * A client MUST discard any service fields that identify a
2581 resolution service whose value is not "D2X", for values of X
2582 that indicate transport protocols supported by the client.
2583 The NAPTR processing as described in [RFC3403] will result in
2584 discovery of the most preferred transport protocol of the
2585 server that is supported by the client, as well as an SRV
2586 record for the server.
2588 The domain suffixes in the NAPTR replacement field SHOULD
2589 match the domain of the original query.
2591 3. If no NAPTR records are found, the requester queries for those
2592 address records for the destination address,
2593 '_diameter._sctp'.realm or '_diameter._tcp'.realm. Address
2594 records include A RR's, AAAA RR's or other similar records,
2595 chosen according to the requester's network protocol
2596 capabilities. If the DNS server returns no address records, the
2597 requester gives up.
2599 If the server is using a site certificate, the domain name in the
2600 query and the domain name in the replacement field MUST both be
2601 valid based on the site certificate handed out by the server in
2602 the TLS or IKE exchange. Similarly, the domain name in the SRV
2603 query and the domain name in the target in the SRV record MUST
2604 both be valid based on the same site certificate. Otherwise, an
2605 attacker could modify the DNS records to contain replacement
2606 values in a different domain, and the client could not validate
2607 that this was the desired behavior, or the result of an attack
2609 Also, the Diameter Peer MUST check to make sure that the
2610 discovered peers are authorized to act in its role.
2611 Authentication via IKE or TLS, or validation of DNS RRs via
2612 DNSSEC is not sufficient to conclude this. For example, a web
2613 server may have obtained a valid TLS certificate, and secured RRs
2614 may be included in the DNS, but this does not imply that it is
2615 authorized to act as a Diameter Server.
2617 Authorization can be achieved for example, by configuration of a
2618 Diameter Server CA. Alternatively this can be achieved by
2619 definition of OIDs within TLS or IKE certificates so as to
2620 signify Diameter Server authorization.
2622 A dynamically discovered peer causes an entry in the Peer Table (see
2623 Section 2.6) to be created. Note that entries created via DNS MUST
2624 expire (or be refreshed) within the DNS TTL. If a peer is discovered
2625 outside of the local realm, a routing table entry (see Section 2.7)
2626 for the peer's realm is created. The routing table entry's
2627 expiration MUST match the peer's expiration value.
2629 5.3. Capabilities Exchange
2631 When two Diameter peers establish a transport connection, they MUST
2632 exchange the Capabilities Exchange messages, as specified in the peer
2633 state machine (see Section 5.6). This message allows the discovery
2634 of a peer's identity and its capabilities (protocol version number,
2635 supported Diameter applications, security mechanisms, etc.)
2637 The receiver only issues commands to its peers that have advertised
2638 support for the Diameter application that defines the command. A
2639 Diameter node MUST cache the supported applications in order to
2640 ensure that unrecognized commands and/or AVPs are not unnecessarily
2641 sent to a peer.
2643 A receiver of a Capabilities-Exchange-Req (CER) message that does not
2644 have any applications in common with the sender MUST return a
2645 Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to
2646 DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport
2647 layer connection. Note that receiving a CER or CEA from a peer
2648 advertising itself as a Relay (see Section 2.4) MUST be interpreted
2649 as having common applications with the peer.
2651 The receiver of the Capabilities-Exchange-Request (CER) MUST
2652 determine common applications by computing the intersection of its
2653 own set of supported Application Id against all of the application
2654 identifier AVPs (Auth-Application-Id, Acct-Application-Id and Vendor-
2655 Specific-Application-Id) present in the CER. The value of the
2656 Vendor-Id AVP in the Vendor-Specific-Application-Id MUST NOT be used
2657 during computation. The sender of the Capabilities-Exchange-Answer
2658 (CEA) SHOULD include all of its supported applications as a hint to
2659 the receiver regarding all of its application capabilities.
2661 Similarly, a receiver of a Capabilities-Exchange-Req (CER) message
2662 that does not have any security mechanisms in common with the sender
2663 MUST return a Capabilities-Exchange-Answer (CEA) with the Result-Code
2664 AVP set to DIAMETER_NO_COMMON_SECURITY, and SHOULD disconnect the
2665 transport layer connection.
2667 CERs received from unknown peers MAY be silently discarded, or a CEA
2668 MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER.
2669 In both cases, the transport connection is closed. If the local
2670 policy permits receiving CERs from unknown hosts, a successful CEA
2671 MAY be returned. If a CER from an unknown peer is answered with a
2672 successful CEA, the lifetime of the peer entry is equal to the
2673 lifetime of the transport connection. In case of a transport
2674 failure, all the pending transactions destined to the unknown peer
2675 can be discarded.
2677 The CER and CEA messages MUST NOT be proxied, redirected or relayed.
2679 Since the CER/CEA messages cannot be proxied, it is still possible
2680 that an upstream agent receives a message for which it has no
2681 available peers to handle the application that corresponds to the
2682 Command-Code. In such instances, the 'E' bit is set in the answer
2683 message (see Section 7.) with the Result-Code AVP set to
2684 DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action
2685 (e.g., re-routing request to an alternate peer).
2687 With the exception of the Capabilities-Exchange-Request message, a
2688 message of type Request that includes the Auth-Application-Id or
2689 Acct-Application-Id AVPs, or a message with an application-specific
2690 command code, MAY only be forwarded to a host that has explicitly
2691 advertised support for the application (or has advertised the Relay
2692 Application Id).
2694 5.3.1. Capabilities-Exchange-Request
2696 The Capabilities-Exchange-Request (CER), indicated by the Command-
2697 Code set to 257 and the Command Flags' 'R' bit set, is sent to
2698 exchange local capabilities. Upon detection of a transport failure,
2699 this message MUST NOT be sent to an alternate peer.
2701 When Diameter is run over SCTP [RFC2960], which allows for
2702 connections to span multiple interfaces and multiple IP addresses,
2703 the Capabilities-Exchange-Request message MUST contain one Host-IP-
2704 Address AVP for each potential IP address that MAY be locally used
2705 when transmitting Diameter messages.
2707 Message Format
2709 ::= < Diameter Header: 257, REQ >
2710 { Origin-Host }
2711 { Origin-Realm }
2712 1* { Host-IP-Address }
2713 { Vendor-Id }
2714 { Product-Name }
2715 [ Origin-State-Id ]
2716 * [ Supported-Vendor-Id ]
2717 * [ Auth-Application-Id ]
2718 * [ Inband-Security-Id ]
2719 * [ Acct-Application-Id ]
2720 * [ Vendor-Specific-Application-Id ]
2721 [ Firmware-Revision ]
2722 * [ AVP ]
2724 5.3.2. Capabilities-Exchange-Answer
2726 The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code
2727 set to 257 and the Command Flags' 'R' bit cleared, is sent in
2728 response to a CER message.
2730 When Diameter is run over SCTP [RFC2960], which allows connections to
2731 span multiple interfaces, hence, multiple IP addresses, the
2732 Capabilities-Exchange-Answer message MUST contain one Host-IP-Address
2733 AVP for each potential IP address that MAY be locally used when
2734 transmitting Diameter messages.
2736 Message Format
2738 ::= < Diameter Header: 257 >
2739 { Result-Code }
2740 { Origin-Host }
2741 { Origin-Realm }
2742 1* { Host-IP-Address }
2743 { Vendor-Id }
2744 { Product-Name }
2745 [ Origin-State-Id ]
2746 [ Error-Message ]
2747 [ Failed-AVP ]
2748 * [ Supported-Vendor-Id ]
2749 * [ Auth-Application-Id ]
2750 * [ Inband-Security-Id ]
2751 * [ Acct-Application-Id ]
2752 * [ Vendor-Specific-Application-Id ]
2753 [ Firmware-Revision ]
2754 * [ AVP ]
2756 5.3.3. Vendor-Id AVP
2758 The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains
2759 the IANA "SMI Network Management Private Enterprise Codes" [RFC3232]
2760 value assigned to the vendor of the Diameter device. It is
2761 envisioned that the combination of the Vendor-Id, Product-Name
2762 (Section 5.3.7) and the Firmware-Revision (Section 5.3.4) AVPs may
2763 provide useful debugging information.
2765 A Vendor-Id value of zero in the CER or CEA messages is reserved and
2766 indicates that this field is ignored.
2768 5.3.4. Firmware-Revision AVP
2770 The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is
2771 used to inform a Diameter peer of the firmware revision of the
2772 issuing device.
2774 For devices that do not have a firmware revision (general purpose
2775 computers running Diameter software modules, for instance), the
2776 revision of the Diameter software module may be reported instead.
2778 5.3.5. Host-IP-Address AVP
2780 The Host-IP-Address AVP (AVP Code 257) is of type Address and is used
2781 to inform a Diameter peer of the sender's IP address. All source
2782 addresses that a Diameter node expects to use with SCTP [RFC2960]
2783 MUST be advertised in the CER and CEA messages by including a
2784 Host-IP- Address AVP for each address. This AVP MUST ONLY be used in
2785 the CER and CEA messages.
2787 5.3.6. Supported-Vendor-Id AVP
2789 The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and
2790 contains the IANA "SMI Network Management Private Enterprise Codes"
2791 [RFC3232] value assigned to a vendor other than the device vendor but
2792 including the application vendor. This is used in the CER and CEA
2793 messages in order to inform the peer that the sender supports (a
2794 subset of) the vendor-specific AVPs defined by the vendor identified
2795 in this AVP. The value of this AVP SHOULD NOT be set to zero.
2796 Multiple instances of this AVP containing the same value SHOULD NOT
2797 be sent.
2799 5.3.7. Product-Name AVP
2801 The Product-Name AVP (AVP Code 269) is of type UTF8String, and
2802 contains the vendor assigned name for the product. The Product-Name
2803 AVP SHOULD remain constant across firmware revisions for the same
2804 product.
2806 5.4. Disconnecting Peer connections
2808 When a Diameter node disconnects one of its transport connections,
2809 its peer cannot know the reason for the disconnect, and will most
2810 likely assume that a connectivity problem occurred, or that the peer
2811 has rebooted. In these cases, the peer may periodically attempt to
2812 reconnect, as stated in Section 2.1. In the event that the
2813 disconnect was a result of either a shortage of internal resources,
2814 or simply that the node in question has no intentions of forwarding
2815 any Diameter messages to the peer in the foreseeable future, a
2816 periodic connection request would not be welcomed. The
2817 Disconnection-Reason AVP contains the reason the Diameter node issued
2818 the Disconnect-Peer-Request message.
2820 The Disconnect-Peer-Request message is used by a Diameter node to
2821 inform its peer of its intent to disconnect the transport layer, and
2822 that the peer shouldn't reconnect unless it has a valid reason to do
2823 so (e.g., message to be forwarded). Upon receipt of the message, the
2824 Disconnect-Peer-Answer is returned, which SHOULD contain an error if
2825 messages have recently been forwarded, and are likely in flight,
2826 which would otherwise cause a race condition.
2828 The receiver of the Disconnect-Peer-Answer initiates the transport
2829 disconnect. The sender of the Disconnect-Peer-Answer should be able
2830 to detect the transport closure and cleanup the connection.
2832 5.4.1. Disconnect-Peer-Request
2834 The Disconnect-Peer-Request (DPR), indicated by the Command-Code set
2835 to 282 and the Command Flags' 'R' bit set, is sent to a peer to
2836 inform its intentions to shutdown the transport connection. Upon
2837 detection of a transport failure, this message MUST NOT be sent to an
2838 alternate peer.
2840 Message Format
2842 ::= < Diameter Header: 282, REQ >
2843 { Origin-Host }
2844 { Origin-Realm }
2845 { Disconnect-Cause }
2846 * [ AVP ]
2848 5.4.2. Disconnect-Peer-Answer
2850 The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set
2851 to 282 and the Command Flags' 'R' bit cleared, is sent as a response
2852 to the Disconnect-Peer-Request message. Upon receipt of this
2853 message, the transport connection is shutdown.
2855 Message Format
2857 ::= < Diameter Header: 282 >
2858 { Result-Code }
2859 { Origin-Host }
2860 { Origin-Realm }
2861 [ Error-Message ]
2862 [ Failed-AVP ]
2863 * [ AVP ]
2865 5.4.3. Disconnect-Cause AVP
2867 The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A
2868 Diameter node MUST include this AVP in the Disconnect-Peer-Request
2869 message to inform the peer of the reason for its intention to
2870 shutdown the transport connection. The following values are
2871 supported:
2873 REBOOTING 0
2874 A scheduled reboot is imminent. Receiver of DPR with above result
2875 code MAY attempt reconnection.
2877 BUSY 1
2878 The peer's internal resources are constrained, and it has
2879 determined that the transport connection needs to be closed.
2880 Receiver of DPR with above result code SHOULD NOT attempt
2881 reconnection.
2883 DO_NOT_WANT_TO_TALK_TO_YOU 2
2884 The peer has determined that it does not see a need for the
2885 transport connection to exist, since it does not expect any
2886 messages to be exchanged in the near future. Receiver of DPR
2887 with above result code SHOULD NOT attempt reconnection.
2889 5.5. Transport Failure Detection
2891 Given the nature of the Diameter protocol, it is recommended that
2892 transport failures be detected as soon as possible. Detecting such
2893 failures will minimize the occurrence of messages sent to unavailable
2894 agents, resulting in unnecessary delays, and will provide better
2895 failover performance. The Device-Watchdog-Request and Device-
2896 Watchdog-Answer messages, defined in this section, are used to pro-
2897 actively detect transport failures.
2899 5.5.1. Device-Watchdog-Request
2901 The Device-Watchdog-Request (DWR), indicated by the Command-Code set
2902 to 280 and the Command Flags' 'R' bit set, is sent to a peer when no
2903 traffic has been exchanged between two peers (see Section 5.5.3).
2904 Upon detection of a transport failure, this message MUST NOT be sent
2905 to an alternate peer.
2907 Message Format
2909 ::= < Diameter Header: 280, REQ >
2910 { Origin-Host }
2911 { Origin-Realm }
2912 [ Origin-State-Id ]
2914 * [ AVP ]
2916 5.5.2. Device-Watchdog-Answer
2918 The Device-Watchdog-Answer (DWA), indicated by the Command-Code set
2919 to 280 and the Command Flags' 'R' bit cleared, is sent as a response
2920 to the Device-Watchdog-Request message.
2922 Message Format
2924 ::= < Diameter Header: 280 >
2925 { Result-Code }
2926 { Origin-Host }
2927 { Origin-Realm }
2928 [ Error-Message ]
2929 [ Failed-AVP ]
2930 [ Origin-State-Id ]
2931 * [ AVP ]
2933 5.5.3. Transport Failure Algorithm
2935 The transport failure algorithm is defined in [RFC3539]. All
2936 Diameter implementations MUST support the algorithm defined in the
2937 specification in order to be compliant to the Diameter base protocol.
2939 5.5.4. Failover and Failback Procedures
2941 In the event that a transport failure is detected with a peer, it is
2942 necessary for all pending request messages to be forwarded to an
2943 alternate agent, if possible. This is commonly referred to as
2944 failover.
2946 In order for a Diameter node to perform failover procedures, it is
2947 necessary for the node to maintain a pending message queue for a
2948 given peer. When an answer message is received, the corresponding
2949 request is removed from the queue. The Hop-by-Hop Identifier field
2950 is used to match the answer with the queued request.
2952 When a transport failure is detected, if possible all messages in the
2953 queue are sent to an alternate agent with the T flag set. On booting
2954 a Diameter client or agent, the T flag is also set on any records
2955 still remaining to be transmitted in non-volatile storage. An
2956 example of a case where it is not possible to forward the message to
2957 an alternate server is when the message has a fixed destination, and
2958 the unavailable peer is the message's final destination (see
2959 Destination-Host AVP). Such an error requires that the agent return
2960 an answer message with the 'E' bit set and the Result-Code AVP set to
2961 DIAMETER_UNABLE_TO_DELIVER.
2963 It is important to note that multiple identical requests or answers
2964 MAY be received as a result of a failover. The End-to-End Identifier
2965 field in the Diameter header along with the Origin-Host AVP MUST be
2966 used to identify duplicate messages.
2968 As described in Section 2.1, a connection request should be
2969 periodically attempted with the failed peer in order to re-establish
2970 the transport connection. Once a connection has been successfully
2971 established, messages can once again be forwarded to the peer. This
2972 is commonly referred to as failback.
2974 5.6. Peer State Machine
2976 This section contains a finite state machine that MUST be observed by
2977 all Diameter implementations. Each Diameter node MUST follow the
2978 state machine described below when communicating with each peer.
2979 Multiple actions are separated by commas, and may continue on
2980 succeeding lines, as space requires. Similarly, state and next state
2981 may also span multiple lines, as space requires.
2983 This state machine is closely coupled with the state machine
2984 described in [RFC3539], which is used to open, close, failover,
2985 probe, and reopen transport connections. Note in particular that
2986 [RFC3539] requires the use of watchdog messages to probe connections.
2987 For Diameter, DWR and DWA messages are to be used.
2989 I- is used to represent the initiator (connecting) connection, while
2990 the R- is used to represent the responder (listening) connection.
2991 The lack of a prefix indicates that the event or action is the same
2992 regardless of the connection on which the event occurred.
2994 The stable states that a state machine may be in are Closed, I-Open
2995 and R-Open; all other states are intermediate. Note that I-Open and
2996 R-Open are equivalent except for whether the initiator or responder
2997 transport connection is used for communication.
2999 A CER message is always sent on the initiating connection immediately
3000 after the connection request is successfully completed. In the case
3001 of an election, one of the two connections will shut down. The
3002 responder connection will survive if the Origin-Host of the local
3003 Diameter entity is higher than that of the peer; the initiator
3004 connection will survive if the peer's Origin-Host is higher. All
3005 subsequent messages are sent on the surviving connection. Note that
3006 the results of an election on one peer are guaranteed to be the
3007 inverse of the results on the other.
3009 For TLS usage, a TLS handshake will begin when both ends are in the
3010 open state. If the TLS handshake is successful, all further messages
3011 will be sent via TLS. If the handshake fails, both ends move to the
3012 closed state.
3014 The state machine constrains only the behavior of a Diameter
3015 implementation as seen by Diameter peers through events on the wire.
3017 Any implementation that produces equivalent results is considered
3018 compliant.
3020 state event action next state
3021 -----------------------------------------------------------------
3022 Closed Start I-Snd-Conn-Req Wait-Conn-Ack
3023 R-Conn-CER R-Accept, R-Open
3024 Process-CER,
3025 R-Snd-CEA
3027 Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA
3028 I-Rcv-Conn-Nack Cleanup Closed
3029 R-Conn-CER R-Accept, Wait-Conn-Ack/
3030 Process-CER Elect
3031 Timeout Error Closed
3033 Wait-I-CEA I-Rcv-CEA Process-CEA I-Open
3034 R-Conn-CER R-Accept, Wait-Returns
3035 Process-CER,
3036 Elect
3037 I-Peer-Disc I-Disc Closed
3038 I-Rcv-Non-CEA Error Closed
3039 Timeout Error Closed
3041 Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns
3042 Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open
3043 R-Peer-Disc R-Disc Wait-Conn-Ack
3044 R-Conn-CER R-Reject Wait-Conn-Ack/
3045 Elect
3046 Timeout Error Closed
3048 Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open
3049 I-Peer-Disc I-Disc, R-Open
3050 R-Snd-CEA
3051 I-Rcv-CEA R-Disc I-Open
3052 R-Peer-Disc R-Disc Wait-I-CEA
3053 R-Conn-CER R-Reject Wait-Returns
3054 Timeout Error Closed
3056 R-Open Send-Message R-Snd-Message R-Open
3057 R-Rcv-Message Process R-Open
3058 R-Rcv-DWR Process-DWR, R-Open
3059 R-Snd-DWA
3060 R-Rcv-DWA Process-DWA R-Open
3061 R-Conn-CER R-Reject R-Open
3062 Stop R-Snd-DPR Closing
3063 R-Rcv-DPR R-Snd-DPA, Closed
3064 R-Disc
3065 R-Peer-Disc R-Disc Closed
3067 I-Open Send-Message I-Snd-Message I-Open
3068 I-Rcv-Message Process I-Open
3069 I-Rcv-DWR Process-DWR, I-Open
3070 I-Snd-DWA
3071 I-Rcv-DWA Process-DWA I-Open
3072 R-Conn-CER R-Reject I-Open
3073 Stop I-Snd-DPR Closing
3074 I-Rcv-DPR I-Snd-DPA, Closed
3075 I-Disc
3076 I-Peer-Disc I-Disc Closed
3078 Closing I-Rcv-DPA I-Disc Closed
3079 R-Rcv-DPA R-Disc Closed
3080 Timeout Error Closed
3081 I-Peer-Disc I-Disc Closed
3082 R-Peer-Disc R-Disc Closed
3084 5.6.1. Incoming connections
3086 When a connection request is received from a Diameter peer, it is
3087 not, in the general case, possible to know the identity of that peer
3088 until a CER is received from it. This is because host and port
3089 determine the identity of a Diameter peer; and the source port of an
3090 incoming connection is arbitrary. Upon receipt of CER, the identity
3091 of the connecting peer can be uniquely determined from Origin-Host.
3093 For this reason, a Diameter peer must employ logic separate from the
3094 state machine to receive connection requests, accept them, and await
3095 CER. Once CER arrives on a new connection, the Origin-Host that
3096 identifies the peer is used to locate the state machine associated
3097 with that peer, and the new connection and CER are passed to the
3098 state machine as an R-Conn-CER event.
3100 The logic that handles incoming connections SHOULD close and discard
3101 the connection if any message other than CER arrives, or if an
3102 implementation-defined timeout occurs prior to receipt of CER.
3104 Because handling of incoming connections up to and including receipt
3105 of CER requires logic, separate from that of any individual state
3106 machine associated with a particular peer, it is described separately
3107 in this section rather than in the state machine above.
3109 5.6.2. Events
3111 Transitions and actions in the automaton are caused by events. In
3112 this section, we will ignore the -I and -R prefix, since the actual
3113 event would be identical, but would occur on one of two possible
3114 connections.
3116 Start The Diameter application has signaled that a
3117 connection should be initiated with the peer.
3119 R-Conn-CER An acknowledgement is received stating that the
3120 transport connection has been established, and the
3121 associated CER has arrived.
3123 Rcv-Conn-Ack A positive acknowledgement is received confirming that
3124 the transport connection is established.
3126 Rcv-Conn-Nack A negative acknowledgement was received stating that
3127 the transport connection was not established.
3129 Timeout An application-defined timer has expired while waiting
3130 for some event.
3132 Rcv-CER A CER message from the peer was received.
3134 Rcv-CEA A CEA message from the peer was received.
3136 Rcv-Non-CEA A message other than CEA from the peer was received.
3138 Peer-Disc A disconnection indication from the peer was received.
3140 Rcv-DPR A DPR message from the peer was received.
3142 Rcv-DPA A DPA message from the peer was received.
3144 Win-Election An election was held, and the local node was the
3145 winner.
3147 Send-Message A message is to be sent.
3149 Rcv-Message A message other than CER, CEA, DPR, DPA, DWR or DWA
3150 was received.
3152 Stop The Diameter application has signaled that a
3153 connection should be terminated (e.g., on system
3154 shutdown).
3156 5.6.3. Actions
3158 Actions in the automaton are caused by events and typically indicate
3159 the transmission of packets and/or an action to be taken on the
3160 connection. In this section we will ignore the I- and R-prefix,
3161 since the actual action would be identical, but would occur on one of
3162 two possible connections.
3164 Snd-Conn-Req A transport connection is initiated with the peer.
3166 Accept The incoming connection associated with the R-Conn-CER
3167 is accepted as the responder connection.
3169 Reject The incoming connection associated with the R-Conn-CER
3170 is disconnected.
3172 Process-CER The CER associated with the R-Conn-CER is processed.
3173 Snd-CER A CER message is sent to the peer.
3175 Snd-CEA A CEA message is sent to the peer.
3177 Cleanup If necessary, the connection is shutdown, and any
3178 local resources are freed.
3180 Error The transport layer connection is disconnected, either
3181 politely or abortively, in response to an error
3182 condition. Local resources are freed.
3184 Process-CEA A received CEA is processed.
3186 Snd-DPR A DPR message is sent to the peer.
3188 Snd-DPA A DPA message is sent to the peer.
3190 Disc The transport layer connection is disconnected, and
3191 local resources are freed.
3193 Elect An election occurs (see Section 5.6.4 for more
3194 information).
3196 Snd-Message A message is sent.
3198 Snd-DWR A DWR message is sent.
3200 Snd-DWA A DWA message is sent.
3202 Process-DWR The DWR message is serviced.
3204 Process-DWA The DWA message is serviced.
3206 Process A message is serviced.
3208 5.6.4. The Election Process
3210 The election is performed on the responder. The responder compares
3211 the Origin-Host received in the CER with its own Origin-Host as two
3212 streams of octets. If the local Origin-Host lexicographically
3213 succeeds the received Origin-Host a Win-Election event is issued
3214 locally. Diameter identities are in ASCII form therefore the lexical
3215 comparison is consistent with DNS case insensitivity where octets
3216 that fall in the ASCII range 'a' through 'z' MUST compare equally to
3217 their upper-case counterparts between 'A' and 'Z'. See Appendix D
3218 for interactions between the Diameter protocol and Internationalized
3219 Domain Name (IDNs).
3221 The winner of the election MUST close the connection it initiated.
3222 Historically, maintaining the responder side of a connection was more
3223 efficient than maintaining the initiator side. However, current
3224 practices makes this distinction irrelevant.
3226 6. Diameter message processing
3228 This section describes how Diameter requests and answers are created
3229 and processed.
3231 6.1. Diameter Request Routing Overview
3233 A request is sent towards its final destination using a combination
3234 of the Destination-Realm and Destination-Host AVPs, in one of these
3235 three combinations:
3237 o a request that is not able to be proxied (such as CER) MUST NOT
3238 contain either Destination-Realm or Destination-Host AVPs.
3240 o a request that needs to be sent to a home server serving a
3241 specific realm, but not to a specific server (such as the first
3242 request of a series of round-trips), MUST contain a Destination-
3243 Realm AVP, but MUST NOT contain a Destination-Host AVP.
3245 o otherwise, a request that needs to be sent to a specific home
3246 server among those serving a given realm, MUST contain both the
3247 Destination-Realm and Destination-Host AVPs.
3249 The Destination-Host AVP is used as described above when the
3250 destination of the request is fixed, which includes:
3252 o Authentication requests that span multiple round trips
3254 o A Diameter message that uses a security mechanism that makes use
3255 of a pre-established session key shared between the source and the
3256 final destination of the message.
3258 o Server initiated messages that MUST be received by a specific
3259 Diameter client (e.g., access device), such as the Abort-Session-
3260 Request message, which is used to request that a particular user's
3261 session be terminated.
3263 Note that an agent can forward a request to a host described in the
3264 Destination-Host AVP only if the host in question is included in its
3265 peer table (see Section 2.7). Otherwise, the request is routed based
3266 on the Destination-Realm only (see Sections 6.1.6).
3268 The Destination-Realm AVP MUST be present if the message is
3269 proxiable. A message that MUST NOT be forwarded by Diameter agents
3270 (proxies, redirects or relays) MUST NOT include the Destination-Realm
3271 in its ABNF. For Diameter clients, the value of the Destination-
3272 Realm AVP MAY be extracted from the User-Name AVP, or other
3273 application-specific methods.
3275 When a message is received, the message is processed in the following
3276 order:
3278 o If the message is destined for the local host, the procedures
3279 listed in Section 6.1.4 are followed.
3281 o If the message is intended for a Diameter peer with whom the local
3282 host is able to directly communicate, the procedures listed in
3283 Section 6.1.5 are followed. This is known as Request Forwarding.
3285 o The procedures listed in Section 6.1.6 are followed, which is
3286 known as Request Routing.
3288 o If none of the above is successful, an answer is returned with the
3289 Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the E-bit set.
3291 For routing of Diameter messages to work within an administrative
3292 domain, all Diameter nodes within the realm MUST be peers.
3294 Note the processing rules contained in this section are intended to
3295 be used as general guidelines to Diameter developers. Certain
3296 implementations MAY use different methods than the ones described
3297 here, and still comply with the protocol specification. See Section
3298 7 for more detail on error handling.
3300 6.1.1. Originating a Request
3302 When creating a request, in addition to any other procedures
3303 described in the application definition for that specific request,
3304 the following procedures MUST be followed:
3306 o the Command-Code is set to the appropriate value
3308 o the 'R' bit is set
3310 o the End-to-End Identifier is set to a locally unique value
3312 o the Origin-Host and Origin-Realm AVPs MUST be set to the
3313 appropriate values, used to identify the source of the message
3315 o the Destination-Host and Destination-Realm AVPs MUST be set to the
3316 appropriate values as described in Section 6.1.
3318 6.1.2. Sending a Request
3320 When sending a request, originated either locally, or as the result
3321 of a forwarding or routing operation, the following procedures MUST
3322 be followed:
3324 o the Hop-by-Hop Identifier should be set to a locally unique value.
3326 o The message should be saved in the list of pending requests.
3328 Other actions to perform on the message based on the particular role
3329 the agent is playing are described in the following sections.
3331 6.1.3. Receiving Requests
3333 A relay or proxy agent MUST check for forwarding loops when receiving
3334 requests. A loop is detected if the server finds its own identity in
3335 a Route-Record AVP. When such an event occurs, the agent MUST answer
3336 with the Result-Code AVP set to DIAMETER_LOOP_DETECTED.
3338 6.1.4. Processing Local Requests
3340 A request is known to be for local consumption when one of the
3341 following conditions occur:
3343 o The Destination-Host AVP contains the local host's identity,
3345 o The Destination-Host AVP is not present, the Destination-Realm AVP
3346 contains a realm the server is configured to process locally, and
3347 the Diameter application is locally supported, or
3349 o Both the Destination-Host and the Destination-Realm are not
3350 present.
3352 When a request is locally processed, the rules in Section 6.2 should
3353 be used to generate the corresponding answer.
3355 6.1.5. Request Forwarding
3357 Request forwarding is done using the Diameter Peer Table. The
3358 Diameter peer table contains all of the peers that the local node is
3359 able to directly communicate with.
3361 When a request is received, and the host encoded in the Destination-
3362 Host AVP is one that is present in the peer table, the message SHOULD
3363 be forwarded to the peer.
3365 6.1.6. Request Routing
3367 Diameter request message routing is done via realms and applications.
3368 A Diameter message that may be forwarded by Diameter agents (proxies,
3369 redirects or relays) MUST include the target realm in the
3370 Destination-Realm AVP. Request routing SHOULD rely on the
3371 Destination-Realm AVP and the Application Id present in the request
3372 message header to aid in the routing decision. The realm MAY be
3373 retrieved from the User-Name AVP, which is in the form of a Network
3374 Access Identifier (NAI). The realm portion of the NAI is inserted in
3375 the Destination-Realm AVP.
3377 Diameter agents MAY have a list of locally supported realms and
3378 applications, and MAY have a list of externally supported realms and
3379 applications. When a request is received that includes a realm
3380 and/or application that is not locally supported, the message is
3381 routed to the peer configured in the Routing Table (see Section 2.7).
3383 Realm names and Application Ids are the minimum supported routing
3384 criteria, additional routing information maybe needed to support
3385 redirect semantics.
3387 6.1.7. Predictive Loop Avoidance
3389 Before forwarding or routing a request, Diameter agents, in addition
3390 to processing done in Section 6.1.3, SHOULD check for the presence of
3391 candidate route's peer identity in any of the Route-Record AVPs. In
3392 an event of the agent detecting the presence of a candidate route's
3393 peer identity in a Route-Record AVP, the agent MUST ignore such route
3394 for the Diameter request message and attempt alternate routes if any.
3395 In case all the candidate routes are eliminated by the above
3396 criteria, the agent SHOULD return DIAMETER_UNABLE_TO_DELIVER message.
3398 6.1.8. Redirecting requests
3400 When a redirect agent receives a request whose routing entry is set
3401 to REDIRECT, it MUST reply with an answer message with the 'E' bit
3402 set, while maintaining the Hop-by-Hop Identifier in the header, and
3403 include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of
3404 the servers associated with the routing entry are added in separate
3405 Redirect-Host AVP.
3407 +------------------+
3408 | Diameter |
3409 | Redirect Agent |
3410 +------------------+
3411 ^ | 2. command + 'E' bit
3412 1. Request | | Result-Code =
3413 joe@example.com | | DIAMETER_REDIRECT_INDICATION +
3414 | | Redirect-Host AVP(s)
3415 | v
3416 +-------------+ 3. Request +-------------+
3417 | example.com |------------->| example.net |
3418 | Relay | | Diameter |
3419 | Agent |<-------------| Server |
3420 +-------------+ 4. Answer +-------------+
3422 Figure 5: Diameter Redirect Agent
3424 The receiver of the answer message with the 'E' bit set, and the
3425 Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by-
3426 hop field in the Diameter header to identify the request in the
3427 pending message queue (see Section 5.3) that is to be redirected. If
3428 no transport connection exists with the new agent, one is created,
3429 and the request is sent directly to it.
3431 Multiple Redirect-Host AVPs are allowed. The receiver of the answer
3432 message with the 'E' bit set selects exactly one of these hosts as
3433 the destination of the redirected message.
3435 When the Redirect-Host-Usage AVP included in the answer message has a
3436 non-zero value, a route entry for the redirect indications is created
3437 and cached by the receiver. The redirect usage for such route entry
3438 is set by the value of Redirect-Host-Usage AVP and the lifetime of
3439 the cached route entry is set by Redirect-Max-Cache-Time AVP value.
3441 It is possible that multiple redirect indications can create multiple
3442 cached route entries differing only in their redirect usage and the
3443 peer to forward messages to. As an example, two(2) route entries
3444 that are created by two(2) redirect indications results in two(2)
3445 cached routes for the same realm and Application Id. However, one
3446 has a redirect usage of ALL_SESSION where matching request will be
3447 forwarded to one peer and the other has a redirect usage of ALL_REALM
3448 where request are forwarded to another peer. Therefore, an incoming
3449 request that matches the realm and Application Id of both routes will
3450 need additional resolution. In such a case, a routing precedence
3451 rule MUST be used againts the redirect usage value to resolve the
3452 contention. The precedence rule can be found in Section 6.13.
3454 6.1.9. Relaying and Proxying Requests
3456 A relay or proxy agent MUST append a Route-Record AVP to all requests
3457 forwarded. The AVP contains the identity of the peer the request was
3458 received from.
3460 The Hop-by-Hop identifier in the request is saved, and replaced with
3461 a locally unique value. The source of the request is also saved,
3462 which includes the IP address, port and protocol.
3464 A relay or proxy agent MAY include the Proxy-Info AVP in requests if
3465 it requires access to any local state information when the
3466 corresponding response is received. Proxy-Info AVP has certain
3467 security implications and SHOULD contain an embedded HMAC with a
3468 node-local key. Alternatively, it MAY simply use local storage to
3469 store state information.
3471 The message is then forwarded to the next hop, as identified in the
3472 Routing Table.
3474 Figure 6 provides an example of message routing using the procedures
3475 listed in these sections.
3477 (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net)
3478 (Origin-Realm=mno.net) (Origin-Realm=mno.net)
3479 (Destination-Realm=example.com) (Destination-
3480 Realm=example.com)
3481 (Route-Record=nas.example.net)
3482 +------+ ------> +------+ ------> +------+
3483 | | (Request) | | (Request) | |
3484 | NAS +-------------------+ DRL +-------------------+ HMS |
3485 | | | | | |
3486 +------+ <------ +------+ <------ +------+
3487 example.net (Answer) example.net (Answer) example.com
3488 (Origin-Host=hms.example.com) (Origin-Host=hms.example.com)
3489 (Origin-Realm=example.com) (Origin-Realm=example.com)
3491 Figure 6: Routing of Diameter messages
3493 Relay and proxy agents are not required to perform full validation of
3494 incoming messages. At a minimum, validation of the message header
3495 and relevant routing AVPs has to be done when relaying messages.
3496 Proxy agents may optionally perform more in-depth message validation
3497 for applications it is interested in.
3499 6.2. Diameter Answer Processing
3501 When a request is locally processed, the following procedures MUST be
3502 applied to create the associated answer, in addition to any
3503 additional procedures that MAY be discussed in the Diameter
3504 application defining the command:
3506 o The same Hop-by-Hop identifier in the request is used in the
3507 answer.
3509 o The local host's identity is encoded in the Origin-Host AVP.
3511 o The Destination-Host and Destination-Realm AVPs MUST NOT be
3512 present in the answer message.
3514 o The Result-Code AVP is added with its value indicating success or
3515 failure.
3517 o If the Session-Id is present in the request, it MUST be included
3518 in the answer.
3520 o Any Proxy-Info AVPs in the request MUST be added to the answer
3521 message, in the same order they were present in the request.
3523 o The 'P' bit is set to the same value as the one in the request.
3525 o The same End-to-End identifier in the request is used in the
3526 answer.
3528 Note that the error messages (see Section 7.3) are also subjected to
3529 the above processing rules.
3531 6.2.1. Processing received Answers
3533 A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an
3534 answer received against the list of pending requests. The
3535 corresponding message should be removed from the list of pending
3536 requests. It SHOULD ignore answers received that do not match a
3537 known Hop-by-Hop Identifier.
3539 6.2.2. Relaying and Proxying Answers
3541 If the answer is for a request which was proxied or relayed, the
3542 agent MUST restore the original value of the Diameter header's Hop-
3543 by-Hop Identifier field.
3545 If the last Proxy-Info AVP in the message is targeted to the local
3546 Diameter server, the AVP MUST be removed before the answer is
3547 forwarded.
3549 If a relay or proxy agent receives an answer with a Result-Code AVP
3550 indicating a failure, it MUST NOT modify the contents of the AVP.
3551 Any additional local errors detected SHOULD be logged, but not
3552 reflected in the Result-Code AVP. If the agent receives an answer
3553 message with a Result-Code AVP indicating success, and it wishes to
3554 modify the AVP to indicate an error, it MUST modify the Result-Code
3555 AVP to contain the appropriate error in the message destined towards
3556 the access device as well as include the Error-Reporting-Host AVP and
3557 it MUST issue an STR on behalf of the access device.
3559 The agent MUST then send the answer to the host that it received the
3560 original request from.
3562 6.3. Origin-Host AVP
3564 The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and
3565 MUST be present in all Diameter messages. This AVP identifies the
3566 endpoint that originated the Diameter message. Relay agents MUST NOT
3567 modify this AVP.
3569 The value of the Origin-Host AVP is guaranteed to be unique within a
3570 single host.
3572 Note that the Origin-Host AVP may resolve to more than one address as
3573 the Diameter peer may support more than one address.
3575 This AVP SHOULD be placed as close to the Diameter header as
3576 possible.
3578 6.4. Origin-Realm AVP
3580 The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity.
3581 This AVP contains the Realm of the originator of any Diameter message
3582 and MUST be present in all messages.
3584 This AVP SHOULD be placed as close to the Diameter header as
3585 possible.
3587 6.5. Destination-Host AVP
3589 The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity.
3590 This AVP MUST be present in all unsolicited agent initiated messages,
3591 MAY be present in request messages, and MUST NOT be present in Answer
3592 messages.
3594 The absence of the Destination-Host AVP will cause a message to be
3595 sent to any Diameter server supporting the application within the
3596 realm specified in Destination-Realm AVP.
3598 This AVP SHOULD be placed as close to the Diameter header as
3599 possible.
3601 6.6. Destination-Realm AVP
3603 The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity,
3604 and contains the realm the message is to be routed to. The
3605 Destination-Realm AVP MUST NOT be present in Answer messages.
3606 Diameter Clients insert the realm portion of the User-Name AVP.
3607 Diameter servers initiating a request message use the value of the
3608 Origin-Realm AVP from a previous message received from the intended
3609 target host (unless it is known a priori). When present, the
3610 Destination-Realm AVP is used to perform message routing decisions.
3612 An ABNF for a request message that includes the Destination-Realm AVP
3613 SHOULD list the Destination-Realm AVP as a required AVP (an AVP
3614 indicated as {AVP}) otherwise the message is inherently a non-
3615 routable messages.
3617 This AVP SHOULD be placed as close to the Diameter header as
3618 possible.
3620 6.7. Routing AVPs
3622 The AVPs defined in this section are Diameter AVPs used for routing
3623 purposes. These AVPs change as Diameter messages are processed by
3624 agents.
3626 6.7.1. Route-Record AVP
3628 The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The
3629 identity added in this AVP MUST be the same as the one received in
3630 the Origin-Host of the Capabilities Exchange message.
3632 6.7.2. Proxy-Info AVP
3634 The Proxy-Info AVP (AVP Code 284) is of type Grouped. The Grouped
3635 Data field has the following ABNF grammar:
3637 Proxy-Info ::= < AVP Header: 284 >
3638 { Proxy-Host }
3639 { Proxy-State }
3640 * [ AVP ]
3642 6.7.3. Proxy-Host AVP
3644 The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This
3645 AVP contains the identity of the host that added the Proxy-Info AVP.
3647 6.7.4. Proxy-State AVP
3649 The Proxy-State AVP (AVP Code 33) is of type OctetString. It
3650 generally contains information related to the local state of a
3651 Diameter node. It MUST be treated as opaque data.
3653 6.8. Auth-Application-Id AVP
3655 The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and
3656 is used in order to advertise support of the Authentication and
3657 Authorization portion of an application (see Section 2.4). If
3658 present in a message other than CER and CEA, the value of the Auth-
3659 Application-Id AVP MUST match the Application Id present in the
3660 Diameter message header.
3662 6.9. Acct-Application-Id AVP
3664 The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and
3665 is used in order to advertise support of the Accounting portion of an
3666 application (see Section 2.4). If present in a message other than
3667 CER and CEA, the value of the Acct-Application-Id AVP MUST match the
3668 Application Id present in the Diameter message header.
3670 6.10. Inband-Security-Id AVP
3672 The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and
3673 is used in order to advertise support of the Security portion of the
3674 application.
3676 Currently, the following values are supported, but there is ample
3677 room to add new security Ids.
3679 NO_INBAND_SECURITY 0
3681 This peer does not support TLS. This is the default value, if the
3682 AVP is omitted.
3684 TLS 1
3686 This node supports TLS security, as defined by [RFC4346].
3688 6.11. Vendor-Specific-Application-Id AVP
3690 The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type
3691 Grouped and is used to advertise support of a vendor-specific
3692 Diameter Application. Exactly one instance of either Auth-
3693 Application-Id or Acct-Application-Id AVP MUST be present. The
3694 Application Id carried by either Auth-Application-Id or Acct-
3695 Application-Id AVP MUST comply with vendor specific Application Id
3696 assignment described in Sec 11.3. It MUST also match the Application
3697 Id present in the Diameter header except when used in a CER or CEA
3698 messages.
3700 The Vendor-Id AVP is an informational AVP pertaining to the vendor
3701 who may have authorship of the vendor-specific Diameter application.
3702 It MUST NOT be used as a means of defining a completely separate
3703 vendor-specific Application Id space.
3705 This AVP MUST also be present as the first AVP in all experimental
3706 commands defined in the vendor-specific application.
3708 This AVP SHOULD be placed as close to the Diameter header as
3709 possible.
3711 AVP Format
3713 ::= < AVP Header: 260 >
3714 { Vendor-Id }
3715 [ Auth-Application-Id ]
3716 [ Acct-Application-Id ]
3718 A Vendor-Specific-Application-Id AVP MUST contain exactly one of
3719 either Auth-Application-Id or Acct-Application-Id. If a Vendor-
3720 Specific-Application-Id is received without any of these two AVPs,
3721 then the recipient SHOULD issue an answer with a Result-Code set to
3722 DIAMETER_MISSING_AVP. The answer SHOULD also include a Failed-AVP
3723 which MUST contain an example of an Auth-Application-Id AVP and an
3724 Acct-Application-Id AVP.
3726 If a Vendor-Specific-Application-Id is received that contains both
3727 Auth-Application-Id and Acct-Application-Id, then the recipient
3728 SHOULD issue an answer with Result-Code set to
3729 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES. The answer SHOULD also include a
3730 Failed-AVP which MUST contain the received Auth-Application-Id AVP
3731 and Acct-Application-Id AVP.
3733 6.12. Redirect-Host AVP
3735 One or more of instances of this AVP MUST be present if the answer
3736 message's 'E' bit is set and the Result-Code AVP is set to
3737 DIAMETER_REDIRECT_INDICATION.
3739 Upon receiving the above, the receiving Diameter node SHOULD forward
3740 the request directly to one of the hosts identified in these AVPs.
3741 The server contained in the selected Redirect-Host AVP SHOULD be used
3742 for all messages pertaining to this session.
3744 6.13. Redirect-Host-Usage AVP
3746 The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated.
3747 This AVP MAY be present in answer messages whose 'E' bit is set and
3748 the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION.
3750 When present, this AVP dictates how the routing entry resulting from
3751 the Redirect-Host is to be used. The following values are supported:
3753 DONT_CACHE 0
3755 The host specified in the Redirect-Host AVP should not be cached.
3756 This is the default value.
3758 ALL_SESSION 1
3760 All messages within the same session, as defined by the same value
3761 of the Session-ID AVP MAY be sent to the host specified in the
3762 Redirect-Host AVP.
3764 ALL_REALM 2
3766 All messages destined for the realm requested MAY be sent to the
3767 host specified in the Redirect-Host AVP.
3769 REALM_AND_APPLICATION 3
3771 All messages for the application requested to the realm specified
3772 MAY be sent to the host specified in the Redirect-Host AVP.
3774 ALL_APPLICATION 4
3776 All messages for the application requested MAY be sent to the host
3777 specified in the Redirect-Host AVP.
3779 ALL_HOST 5
3781 All messages that would be sent to the host that generated the
3782 Redirect-Host MAY be sent to the host specified in the Redirect-
3783 Host AVP.
3785 ALL_USER 6
3787 All messages for the user requested MAY be sent to the host
3788 specified in the Redirect-Host AVP.
3790 When multiple cached routes are created by redirect indications and
3791 they differ only in redirect usage and peers to forward requests to
3792 (see Section 6.1.8), a precedence rule MUST be applied to the
3793 redirect usage values of the cached routes during normal routing to
3794 resolve contentions that may occur. The precedence rule is the order
3795 that dictate which redirect usage should be considered before any
3796 other as they appear. The order is as follows:
3798 1. ALL_SESSION
3800 2. ALL_USER
3802 3. REALM_AND_APPLICATION
3804 4. ALL_REALM
3806 5. ALL_APPLICATION
3808 6. ALL_HOST
3810 6.14. Redirect-Max-Cache-Time AVP
3812 The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32.
3813 This AVP MUST be present in answer messages whose 'E' bit is set, the
3814 Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the
3815 Redirect-Host-Usage AVP set to a non-zero value.
3817 This AVP contains the maximum number of seconds the peer and route
3818 table entries, created as a result of the Redirect-Host, will be
3819 cached. Note that once a host created due to a redirect indication
3820 is no longer reachable, any associated peer and routing table entries
3821 MUST be deleted.
3823 7. Error Handling
3825 There are two different types of errors in Diameter; protocol and
3826 application errors. A protocol error is one that occurs at the base
3827 protocol level, and MAY require per hop attention (e.g., message
3828 routing error). Application errors, on the other hand, generally
3829 occur due to a problem with a function specified in a Diameter
3830 application (e.g., user authentication, Missing AVP).
3832 Result-Code AVP values that are used to report protocol errors MUST
3833 only be present in answer messages whose 'E' bit is set. When a
3834 request message is received that causes a protocol error, an answer
3835 message is returned with the 'E' bit set, and the Result-Code AVP is
3836 set to the appropriate protocol error value. As the answer is sent
3837 back towards the originator of the request, each proxy or relay agent
3838 MAY take action on the message.
3840 1. Request +---------+ Link Broken
3841 +-------------------------->|Diameter |----///----+
3842 | +---------------------| | v
3843 +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+
3844 |Diameter |<-+ (Unable to Forward) +---------+ |Diameter|
3845 | | | Home |
3846 | Relay 1 |--+ +---------+ | Server |
3847 +---------+ | 3. Request |Diameter | +--------+
3848 +-------------------->| | ^
3849 | Relay 3 |-----------+
3850 +---------+
3852 Figure 7: Example of Protocol Error causing answer message
3854 Figure 7 provides an example of a message forwarded upstream by a
3855 Diameter relay. When the message is received by Relay 2, and it
3856 detects that it cannot forward the request to the home server, an
3857 answer message is returned with the 'E' bit set and the Result-Code
3858 AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls
3859 within the protocol error category, Relay 1 would take special
3860 action, and given the error, attempt to route the message through its
3861 alternate Relay 3.
3863 +---------+ 1. Request +---------+ 2. Request +---------+
3864 | Access |------------>|Diameter |------------>|Diameter |
3865 | | | | | Home |
3866 | Device |<------------| Relay |<------------| Server |
3867 +---------+ 4. Answer +---------+ 3. Answer +---------+
3868 (Missing AVP) (Missing AVP)
3870 Figure 8: Example of Application Error Answer message
3872 Figure 8 provides an example of a Diameter message that caused an
3873 application error. When application errors occur, the Diameter
3874 entity reporting the error clears the 'R' bit in the Command Flags,
3875 and adds the Result-Code AVP with the proper value. Application
3876 errors do not require any proxy or relay agent involvement, and
3877 therefore the message would be forwarded back to the originator of
3878 the request.
3880 There are certain Result-Code AVP application errors that require
3881 additional AVPs to be present in the answer. In these cases, the
3882 Diameter node that sets the Result-Code AVP to indicate the error
3883 MUST add the AVPs. Examples are:
3885 o An unrecognized AVP is received with the 'M' bit (Mandatory bit)
3886 set, causes an answer to be sent with the Result-Code AVP set to
3887 DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the
3888 offending AVP.
3890 o An AVP that is received with an unrecognized value causes an
3891 answer to be returned with the Result-Code AVP set to
3892 DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the
3893 AVP causing the error.
3895 o A command is received that is missing AVP(s) that are defined as
3896 required in the commands ABNF; examples are AVPs indicated as
3897 {AVP}. The receiver issues an answer with the Result-Code set to
3898 DIAMETER_MISSING_AVP, and creates an AVP with the AVP Code and
3899 other fields set as expected in the missing AVP. The created AVP
3900 is then added to the Failed- AVP AVP.
3902 The Result-Code AVP describes the error that the Diameter node
3903 encountered in its processing. In case there are multiple errors,
3904 the Diameter node MUST report only the first error it encountered
3905 (detected possibly in some implementation dependent order). The
3906 specific errors that can be described by this AVP are described in
3907 the following section.
3909 7.1. Result-Code AVP
3911 The Result-Code AVP (AVP Code 268) is of type Unsigned32 and
3912 indicates whether a particular request was completed successfully or
3913 whether an error occurred. All Diameter answer messages defined in
3914 IETF applications MUST include one Result-Code AVP. A non-successful
3915 Result-Code AVP (one containing a non 2xxx value other than
3916 DIAMETER_REDIRECT_INDICATION) MUST include the Error-Reporting-Host
3917 AVP if the host setting the Result-Code AVP is different from the
3918 identity encoded in the Origin-Host AVP.
3920 The Result-Code data field contains an IANA-managed 32-bit address
3921 space representing errors (see Section 11.4). Diameter provides the
3922 following classes of errors, all identified by the thousands digit in
3923 the decimal notation:
3925 o 1xxx (Informational)
3927 o 2xxx (Success)
3929 o 3xxx (Protocol Errors)
3931 o 4xxx (Transient Failures)
3933 o 5xxx (Permanent Failure)
3935 A non-recognized class (one whose first digit is not defined in this
3936 section) MUST be handled as a permanent failure.
3938 7.1.1. Informational
3940 Errors that fall within this category are used to inform the
3941 requester that a request could not be satisfied, and additional
3942 action is required on its part before access is granted.
3944 DIAMETER_MULTI_ROUND_AUTH 1001
3946 This informational error is returned by a Diameter server to
3947 inform the access device that the authentication mechanism being
3948 used requires multiple round trips, and a subsequent request needs
3949 to be issued in order for access to be granted.
3951 7.1.2. Success
3953 Errors that fall within the Success category are used to inform a
3954 peer that a request has been successfully completed.
3956 DIAMETER_SUCCESS 2001
3958 The Request was successfully completed.
3960 DIAMETER_LIMITED_SUCCESS 2002
3962 When returned, the request was successfully completed, but
3963 additional processing is required by the application in order to
3964 provide service to the user.
3966 7.1.3. Protocol Errors
3968 Errors that fall within the Protocol Error category SHOULD be treated
3969 on a per-hop basis, and Diameter proxies MAY attempt to correct the
3970 error, if it is possible. Note that these errors MUST only be used
3971 in answer messages whose 'E' bit is set. To provide backward
3972 compatibility with existing implementations that follow [RFC3588],
3973 some of the error values that have previously been used in this
3974 category by [RFC3588] will not be re-used. Therefore the error
3975 values enumerated here may be non-sequential.
3977 DIAMETER_UNABLE_TO_DELIVER 3002
3979 This error is given when Diameter can not deliver the message to
3980 the destination, either because no host within the realm
3981 supporting the required application was available to process the
3982 request, or because Destination-Host AVP was given without the
3983 associated Destination-Realm AVP.
3985 DIAMETER_REALM_NOT_SERVED 3003
3987 The intended realm of the request is not recognized.
3989 DIAMETER_TOO_BUSY 3004
3991 When returned, a Diameter node SHOULD attempt to send the message
3992 to an alternate peer. This error MUST only be used when a
3993 specific server is requested, and it cannot provide the requested
3994 service.
3996 DIAMETER_LOOP_DETECTED 3005
3998 An agent detected a loop while trying to get the message to the
3999 intended recipient. The message MAY be sent to an alternate peer,
4000 if one is available, but the peer reporting the error has
4001 identified a configuration problem.
4003 DIAMETER_REDIRECT_INDICATION 3006
4005 A redirect agent has determined that the request could not be
4006 satisfied locally and the initiator of the request should direct
4007 the request directly to the server, whose contact information has
4008 been added to the response. When set, the Redirect-Host AVP MUST
4009 be present.
4011 DIAMETER_APPLICATION_UNSUPPORTED 3007
4013 A request was sent for an application that is not supported.
4015 DIAMETER_INVALID_BIT_IN_HEADER 3011
4017 This error is returned when a reserved bit in the Diameter header
4018 is set to one (1) or the bits in the Diameter header defined in
4019 Section 3 are set incorrectly.
4021 DIAMETER_INVALID_MESSAGE_LENGTH 3012
4023 This error is returned when a request is received with an invalid
4024 message length.
4026 7.1.4. Transient Failures
4028 Errors that fall within the transient failures category are used to
4029 inform a peer that the request could not be satisfied at the time it
4030 was received, but MAY be able to satisfy the request in the future.
4031 Note that these errors MUST be used in answer messages whose 'E' bit
4032 is not set.
4034 DIAMETER_AUTHENTICATION_REJECTED 4001
4036 The authentication process for the user failed, most likely due to
4037 an invalid password used by the user. Further attempts MUST only
4038 be tried after prompting the user for a new password.
4040 DIAMETER_OUT_OF_SPACE 4002
4042 A Diameter node received the accounting request but was unable to
4043 commit it to stable storage due to a temporary lack of space.
4045 ELECTION_LOST 4003
4047 The peer has determined that it has lost the election process and
4048 has therefore disconnected the transport connection.
4050 7.1.5. Permanent Failures
4052 Errors that fall within the permanent failures category are used to
4053 inform the peer that the request failed, and should not be attempted
4054 again. Note that these errors SHOULD be used in answer messages
4055 whose 'E' bit is not set. In error conditions where it is not
4056 possible or efficient to compose application specific answer grammar
4057 then answer messages with E-bit set and complying to the grammar
4058 described in 7.2 MAY also be used for permanent errors.
4060 To provide backward compatibility with existing implementations that
4061 follow [RFC3588], some of the error values that have previously been
4062 used in this category by [RFC3588] will not be re-used. Therefore
4063 the error values enumerated here maybe non-sequential.
4065 DIAMETER_AVP_UNSUPPORTED 5001
4067 The peer received a message that contained an AVP that is not
4068 recognized or supported and was marked with the Mandatory bit. A
4069 Diameter message with this error MUST contain one or more Failed-
4070 AVP AVP containing the AVPs that caused the failure.
4072 DIAMETER_UNKNOWN_SESSION_ID 5002
4074 The request contained an unknown Session-Id.
4076 DIAMETER_AUTHORIZATION_REJECTED 5003
4078 A request was received for which the user could not be authorized.
4079 This error could occur if the service requested is not permitted
4080 to the user.
4082 DIAMETER_INVALID_AVP_VALUE 5004
4084 The request contained an AVP with an invalid value in its data
4085 portion. A Diameter message indicating this error MUST include
4086 the offending AVPs within a Failed-AVP AVP.
4088 DIAMETER_MISSING_AVP 5005
4090 The request did not contain an AVP that is required by the Command
4091 Code definition. If this value is sent in the Result-Code AVP, a
4092 Failed-AVP AVP SHOULD be included in the message. The Failed-AVP
4093 AVP MUST contain an example of the missing AVP complete with the
4094 Vendor-Id if applicable. The value field of the missing AVP
4095 should be of correct minimum length and contain zeroes.
4097 DIAMETER_RESOURCES_EXCEEDED 5006
4099 A request was received that cannot be authorized because the user
4100 has already expended allowed resources. An example of this error
4101 condition is a user that is restricted to one dial-up PPP port,
4102 attempts to establish a second PPP connection.
4104 DIAMETER_CONTRADICTING_AVPS 5007
4106 The Home Diameter server has detected AVPs in the request that
4107 contradicted each other, and is not willing to provide service to
4108 the user. The Failed-AVP AVPs MUST be present which contains the
4109 AVPs that contradicted each other.
4111 DIAMETER_AVP_NOT_ALLOWED 5008
4113 A message was received with an AVP that MUST NOT be present. The
4114 Failed-AVP AVP MUST be included and contain a copy of the
4115 offending AVP.
4117 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009
4119 A message was received that included an AVP that appeared more
4120 often than permitted in the message definition. The Failed-AVP
4121 AVP MUST be included and contain a copy of the first instance of
4122 the offending AVP that exceeded the maximum number of occurrences
4124 DIAMETER_NO_COMMON_APPLICATION 5010
4126 This error is returned by a Diameter node that is not acting as a
4127 relay when it receives a CER which advertises a set of
4128 applications that it does not support.
4130 DIAMETER_UNSUPPORTED_VERSION 5011
4132 This error is returned when a request was received, whose version
4133 number is unsupported.
4135 DIAMETER_UNABLE_TO_COMPLY 5012
4137 This error is returned when a request is rejected for unspecified
4138 reasons.
4140 DIAMETER_INVALID_AVP_LENGTH 5014
4142 The request contained an AVP with an invalid length. A Diameter
4143 message indicating this error MUST include the offending AVPs
4144 within a Failed-AVP AVP. In cases where the erroneous avp length
4145 value exceeds the message length or is less than the minimum AVP
4146 header length, it is sufficient to include the offending AVP
4147 header and a zero filled payload of the minimum required length
4148 for the payloads data type. If the AVP is a grouped AVP, the
4149 grouped AVP header with an empty payload would be sufficient to
4150 indicate the offending AVP. In the case where the offending AVP
4151 header cannot be fully decoded when avp length is less than the
4152 minimum AVP header length, it is sufficient to include an
4153 offending AVP header that is formulated by padding the incomplete
4154 AVP header with zero up to the minimum AVP header length.
4156 DIAMETER_NO_COMMON_SECURITY 5017
4158 This error is returned when a CER message is received, and there
4159 are no common security mechanisms supported between the peers. A
4160 Capabilities-Exchange-Answer (CEA) MUST be returned with the
4161 Result-Code AVP set to DIAMETER_NO_COMMON_SECURITY.
4163 DIAMETER_UNKNOWN_PEER 5018
4165 A CER was received from an unknown peer.
4167 DIAMETER_COMMAND_UNSUPPORTED 5019
4169 The Request contained a Command-Code that the receiver did not
4170 recognize or doest not support.
4172 DIAMETER_INVALID_HDR_BITS 5020
4174 A request was received whose bits in the Diameter header were
4175 either set to an invalid combination, or to a value that is
4176 inconsistent with the command code's definition.
4178 DIAMETER_INVALID_AVP_BITS 5021
4180 A request was received that included an AVP whose flag bits are
4181 set to an unrecognized value, or that is inconsistent with the
4182 AVP's definition.
4184 7.2. Error Bit
4186 The 'E' (Error Bit) in the Diameter header is set when the request
4187 caused a protocol-related error (see Section 7.1.3). A message with
4188 the 'E' bit MUST NOT be sent as a response to an answer message.
4189 Note that a message with the 'E' bit set is still subjected to the
4190 processing rules defined in Section 6.2. When set, the answer
4191 message will not conform to the ABNF specification for the command,
4192 and will instead conform to the following ABNF:
4194 Message Format
4196 ::= < Diameter Header: code, ERR [PXY] >
4197 0*1< Session-Id >
4198 { Origin-Host }
4199 { Origin-Realm }
4200 { Result-Code }
4201 [ Origin-State-Id ]
4202 [ Error-Message ]
4203 [ Error-Reporting-Host ]
4204 [ Failed-AVP ]
4205 * [ Proxy-Info ]
4206 * [ AVP ]
4208 Note that the code used in the header is the same than the one found
4209 in the request message, but with the 'R' bit cleared and the 'E' bit
4210 set. The 'P' bit in the header is set to the same value as the one
4211 found in the request message.
4213 7.3. Error-Message AVP
4215 The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY
4216 accompany a Result-Code AVP as a human readable error message. The
4217 Error-Message AVP is not intended to be useful in real-time, and
4218 SHOULD NOT be expected to be parsed by network entities.
4220 7.4. Error-Reporting-Host AVP
4222 The Error-Reporting-Host AVP (AVP Code 294) is of type
4223 DiameterIdentity. This AVP contains the identity of the Diameter
4224 host that sent the Result-Code AVP to a value other than 2001
4225 (Success), only if the host setting the Result-Code is different from
4226 the one encoded in the Origin-Host AVP. This AVP is intended to be
4227 used for troubleshooting purposes, and MUST be set when the Result-
4228 Code AVP indicates a failure.
4230 7.5. Failed-AVP AVP
4232 The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides
4233 debugging information in cases where a request is rejected or not
4234 fully processed due to erroneous information in a specific AVP. The
4235 value of the Result-Code AVP will provide information on the reason
4236 for the Failed-AVP AVP. A Diameter message SHOULD contain only one
4237 Failed-AVP that corresponds to the error indicated by the Result-Code
4238 AVP. For practical purposes, this Failed-AVP would typically refer
4239 to the first AVP processing error that a Diameter node encounters.
4241 The possible reasons for this AVP are the presence of an improperly
4242 constructed AVP, an unsupported or unrecognized AVP, an invalid AVP
4243 value, the omission of a required AVP, the presence of an explicitly
4244 excluded AVP (see tables in Section 10), or the presence of two or
4245 more occurrences of an AVP which is restricted to 0, 1, or 0-1
4246 occurrences.
4248 A Diameter message SHOULD contain one Failed-AVP AVP, containing the
4249 entire AVP that could not be processed successfully. If the failure
4250 reason is omission of a required AVP, an AVP with the missing AVP
4251 code, the missing vendor id, and a zero filled payload of the minimum
4252 required length for the omitted AVP will be added. If the failure
4253 reason is an invalid AVP length where the reported length is less
4254 than the minimum AVP header length or greater than the reported
4255 message length, a copy of the offending AVP header and a zero filled
4256 payload of the minimum required length SHOULD be added.
4258 In the case where the offending AVP is embedded within a grouped AVP,
4259 the Failed-AVP MAY contain the grouped AVP which in turn contains the
4260 single offending AVP. The same method MAY be employed if the grouped
4261 AVP itself is embedded in yet another grouped AVP and so on. In this
4262 case, the Failed-AVP MAY contain the grouped AVP heirarchy up to the
4263 single offending AVP. This enables the recipient to detect the
4264 location of the offending AVP when embedded in a group.
4266 AVP Format
4268 ::= < AVP Header: 279 >
4269 1* {AVP}
4271 7.6. Experimental-Result AVP
4273 The Experimental-Result AVP (AVP Code 297) is of type Grouped, and
4274 indicates whether a particular vendor-specific request was completed
4275 successfully or whether an error occurred. Its Data field has the
4276 following ABNF grammar:
4278 AVP Format
4280 Experimental-Result ::= < AVP Header: 297 >
4281 { Vendor-Id }
4282 { Experimental-Result-Code }
4284 The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies
4285 the vendor responsible for the assignment of the result code which
4286 follows. All Diameter answer messages defined in vendor-specific
4287 applications MUST include either one Result-Code AVP or one
4288 Experimental-Result AVP.
4290 7.7. Experimental-Result-Code AVP
4292 The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32
4293 and contains a vendor-assigned value representing the result of
4294 processing the request.
4296 It is recommended that vendor-specific result codes follow the same
4297 conventions given for the Result-Code AVP regarding the different
4298 types of result codes and the handling of errors (for non 2xxx
4299 values).
4301 8. Diameter User Sessions
4303 In general, Diameter can provide two different types of services to
4304 applications. The first involves authentication and authorization,
4305 and can optionally make use of accounting. The second only makes use
4306 of accounting.
4308 When a service makes use of the authentication and/or authorization
4309 portion of an application, and a user requests access to the network,
4310 the Diameter client issues an auth request to its local server. The
4311 auth request is defined in a service specific Diameter application
4312 (e.g., NASREQ). The request contains a Session-Id AVP, which is used
4313 in subsequent messages (e.g., subsequent authorization, accounting,
4314 etc) relating to the user's session. The Session-Id AVP is a means
4315 for the client and servers to correlate a Diameter message with a
4316 user session.
4318 When a Diameter server authorizes a user to use network resources for
4319 a finite amount of time, and it is willing to extend the
4320 authorization via a future request, it MUST add the Authorization-
4321 Lifetime AVP to the answer message. The Authorization-Lifetime AVP
4322 defines the maximum number of seconds a user MAY make use of the
4323 resources before another authorization request is expected by the
4324 server. The Auth-Grace-Period AVP contains the number of seconds
4325 following the expiration of the Authorization-Lifetime, after which
4326 the server will release all state information related to the user's
4327 session. Note that if payment for services is expected by the
4328 serving realm from the user's home realm, the Authorization-Lifetime
4329 AVP, combined with the Auth-Grace-Period AVP, implies the maximum
4330 length of the session the home realm is willing to be fiscally
4331 responsible for. Services provided past the expiration of the
4332 Authorization-Lifetime and Auth-Grace-Period AVPs are the
4333 responsibility of the access device. Of course, the actual cost of
4334 services rendered is clearly outside the scope of the protocol.
4336 An access device that does not expect to send a re-authorization or a
4337 session termination request to the server MAY include the Auth-
4338 Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint
4339 to the server. If the server accepts the hint, it agrees that since
4340 no session termination message will be received once service to the
4341 user is terminated, it cannot maintain state for the session. If the
4342 answer message from the server contains a different value in the
4343 Auth-Session-State AVP (or the default value if the AVP is absent),
4344 the access device MUST follow the server's directives. Note that the
4345 value NO_STATE_MAINTAINED MUST NOT be set in subsequent re-
4346 authorization requests and answers.
4348 The base protocol does not include any authorization request
4349 messages, since these are largely application-specific and are
4350 defined in a Diameter application document. However, the base
4351 protocol does define a set of messages that is used to terminate user
4352 sessions. These are used to allow servers that maintain state
4353 information to free resources.
4355 When a service only makes use of the Accounting portion of the
4356 Diameter protocol, even in combination with an application, the
4357 Session-Id is still used to identify user sessions. However, the
4358 session termination messages are not used, since a session is
4359 signaled as being terminated by issuing an accounting stop message.
4361 Diameter may also be used for services that cannot be easily
4362 categorized as authentication, authorization or accounting (e.g.,
4363 certain 3GPP IMS interfaces). In such cases, the finite state
4364 machine defined in subsequent sections may not be applicable.
4365 Therefore, the applications itself MAY need to define its own finite
4366 state machine. However, such application specific state machines
4367 MUST comply with general Diameter user session requirements such co-
4368 relating all message exchanges via Session-Id AVP.
4370 8.1. Authorization Session State Machine
4372 This section contains a set of finite state machines, representing
4373 the life cycle of Diameter sessions, and which MUST be observed by
4374 all Diameter implementations that make use of the authentication
4375 and/or authorization portion of a Diameter application. The term
4376 Service-Specific below refers to a message defined in a Diameter
4377 application (e.g., Mobile IPv4, NASREQ).
4379 There are four different authorization session state machines
4380 supported in the Diameter base protocol. The first two describe a
4381 session in which the server is maintaining session state, indicated
4382 by the value of the Auth-Session-State AVP (or its absence). One
4383 describes the session from a client perspective, the other from a
4384 server perspective. The second two state machines are used when the
4385 server does not maintain session state. Here again, one describes
4386 the session from a client perspective, the other from a server
4387 perspective.
4389 When a session is moved to the Idle state, any resources that were
4390 allocated for the particular session must be released. Any event not
4391 listed in the state machines MUST be considered as an error
4392 condition, and an answer, if applicable, MUST be returned to the
4393 originator of the message.
4395 In the case that an application does not support re-auth, the state
4396 transitions related to server-initiated re-auth when both client and
4397 server sessions maintains state (e.g., Send RAR, Pending, Receive
4398 RAA) MAY be ignored.
4400 In the state table, the event 'Failure to send X' means that the
4401 Diameter agent is unable to send command X to the desired
4402 destination. This could be due to the peer being down, or due to the
4403 peer sending back a transient failure or temporary protocol error
4404 notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the
4405 Result-Code AVP of the corresponding Answer command. The event 'X
4406 successfully sent' is the complement of 'Failure to send X'.
4408 The following state machine is observed by a client when state is
4409 maintained on the server:
4411 CLIENT, STATEFUL
4412 State Event Action New State
4413 -------------------------------------------------------------
4414 Idle Client or Device Requests Send Pending
4415 access service
4416 specific
4417 auth req
4419 Idle ASR Received Send ASA Idle
4420 for unknown session with
4421 Result-Code
4422 = UNKNOWN_
4423 SESSION_ID
4425 Idle RAR Received Send RAA Idle
4426 for unknown session with
4427 Result-Code
4428 = UNKNOWN_
4429 SESSION_ID
4431 Pending Successful Service-specific Grant Open
4432 authorization answer Access
4433 received with default
4434 Auth-Session-State value
4436 Pending Successful Service-specific Sent STR Discon
4437 authorization answer received
4438 but service not provided
4440 Pending Error processing successful Sent STR Discon
4441 Service-specific authorization
4442 answer
4444 Pending Failed Service-specific Cleanup Idle
4445 authorization answer received
4447 Open User or client device Send Open
4448 requests access to service service
4449 specific
4450 auth req
4452 Open Successful Service-specific Provide Open
4453 authorization answer received Service
4455 Open Failed Service-specific Discon. Idle
4456 authorization answer user/device
4457 received.
4459 Open RAR received and client will Send RAA Open
4460 perform subsequent re-auth with
4461 Result-Code
4462 = SUCCESS
4464 Open RAR received and client will Send RAA Idle
4465 not perform subsequent with
4466 re-auth Result-Code
4467 != SUCCESS,
4468 Discon.
4469 user/device
4471 Open Session-Timeout Expires on Send STR Discon
4472 Access Device
4474 Open ASR Received, Send ASA Discon
4475 client will comply with with
4476 request to end the session Result-Code
4477 = SUCCESS,
4478 Send STR.
4480 Open ASR Received, Send ASA Open
4481 client will not comply with with
4482 request to end the session Result-Code
4483 != SUCCESS
4485 Open Authorization-Lifetime + Send STR Discon
4486 Auth-Grace-Period expires on
4487 access device
4489 Discon ASR Received Send ASA Discon
4491 Discon STA Received Discon. Idle
4492 user/device
4494 The following state machine is observed by a server when it is
4495 maintaining state for the session:
4497 SERVER, STATEFUL
4498 State Event Action New State
4499 -------------------------------------------------------------
4500 Idle Service-specific authorization Send Open
4501 request received, and successful
4502 user is authorized serv.
4503 specific
4504 answer
4506 Idle Service-specific authorization Send Idle
4507 request received, and failed serv.
4508 user is not authorized specific
4509 answer
4511 Open Service-specific authorization Send Open
4512 request received, and user successful
4513 is authorized serv. specific
4514 answer
4516 Open Service-specific authorization Send Idle
4517 request received, and user failed serv.
4518 is not authorized specific
4519 answer,
4520 Cleanup
4522 Open Home server wants to confirm Send RAR Pending
4523 authentication and/or
4524 authorization of the user
4526 Pending Received RAA with a failed Cleanup Idle
4527 Result-Code
4529 Pending Received RAA with Result-Code Update Open
4530 = SUCCESS session
4532 Open Home server wants to Send ASR Discon
4533 terminate the service
4535 Open Authorization-Lifetime (and Cleanup Idle
4536 Auth-Grace-Period) expires
4537 on home server.
4539 Open Session-Timeout expires on Cleanup Idle
4540 home server
4542 Discon Failure to send ASR Wait, Discon
4543 resend ASR
4545 Discon ASR successfully sent and Cleanup Idle
4546 ASA Received with Result-Code
4548 Not ASA Received None No Change.
4549 Discon
4551 Any STR Received Send STA, Idle
4552 Cleanup.
4554 The following state machine is observed by a client when state is not
4555 maintained on the server:
4557 CLIENT, STATELESS
4558 State Event Action New State
4559 -------------------------------------------------------------
4560 Idle Client or Device Requests Send Pending
4561 access service
4562 specific
4563 auth req
4565 Pending Successful Service-specific Grant Open
4566 authorization answer Access
4567 received with Auth-Session-
4568 State set to
4569 NO_STATE_MAINTAINED
4571 Pending Failed Service-specific Cleanup Idle
4572 authorization answer
4573 received
4575 Open Session-Timeout Expires on Discon. Idle
4576 Access Device user/device
4578 Open Service to user is terminated Discon. Idle
4579 user/device
4581 The following state machine is observed by a server when it is not
4582 maintaining state for the session:
4584 SERVER, STATELESS
4585 State Event Action New State
4586 -------------------------------------------------------------
4587 Idle Service-specific authorization Send serv. Idle
4588 request received, and specific
4589 successfully processed answer
4591 8.2. Accounting Session State Machine
4593 The following state machines MUST be supported for applications that
4594 have an accounting portion or that require only accounting services.
4595 The first state machine is to be observed by clients.
4597 See Section 9.7 for Accounting Command Codes and Section 9.8 for
4598 Accounting AVPs.
4600 The server side in the accounting state machine depends in some cases
4601 on the particular application. The Diameter base protocol defines a
4602 default state machine that MUST be followed by all applications that
4603 have not specified other state machines. This is the second state
4604 machine in this section described below.
4606 The default server side state machine requires the reception of
4607 accounting records in any order and at any time, and does not place
4608 any standards requirement on the processing of these records.
4609 Implementations of Diameter MAY perform checking, ordering,
4610 correlation, fraud detection, and other tasks based on these records.
4611 Both base Diameter AVPs as well as application specific AVPs MAY be
4612 inspected as a part of these tasks. The tasks can happen either
4613 immediately after record reception or in a post-processing phase.
4614 However, as these tasks are typically application or even policy
4615 dependent, they are not standardized by the Diameter specifications.
4616 Applications MAY define requirements on when to accept accounting
4617 records based on the used value of Accounting-Realtime-Required AVP,
4618 credit limits checks, and so on.
4620 However, the Diameter base protocol defines one optional server side
4621 state machine that MAY be followed by applications that require
4622 keeping track of the session state at the accounting server. Note
4623 that such tracking is incompatible with the ability to sustain long
4624 duration connectivity problems. Therefore, the use of this state
4625 machine is recommended only in applications where the value of the
4626 Accounting-Realtime-Required AVP is DELIVER_AND_GRANT, and hence
4627 accounting connectivity problems are required to cause the serviced
4628 user to be disconnected. Otherwise, records produced by the client
4629 may be lost by the server which no longer accepts them after the
4630 connectivity is re-established. This state machine is the third
4631 state machine in this section. The state machine is supervised by a
4632 supervision session timer Ts, which the value should be reasonably
4633 higher than the Acct_Interim_Interval value. Ts MAY be set to two
4634 times the value of the Acct_Interim_Interval so as to avoid the
4635 accounting session in the Diameter server to change to Idle state in
4636 case of short transient network failure.
4638 Any event not listed in the state machines MUST be considered as an
4639 error condition, and a corresponding answer, if applicable, MUST be
4640 returned to the originator of the message.
4642 In the state table, the event 'Failure to send' means that the
4643 Diameter client is unable to communicate with the desired
4644 destination. This could be due to the peer being down, or due to the
4645 peer sending back a transient failure or temporary protocol error
4646 notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or
4647 DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting
4648 Answer command.
4650 The event 'Failed answer' means that the Diameter client received a
4651 non-transient failure notification in the Accounting Answer command.
4653 Note that the action 'Disconnect user/dev' MUST have an effect also
4654 to the authorization session state table, e.g., cause the STR message
4655 to be sent, if the given application has both authentication/
4656 authorization and accounting portions.
4658 The states PendingS, PendingI, PendingL, PendingE and PendingB stand
4659 for pending states to wait for an answer to an accounting request
4660 related to a Start, Interim, Stop, Event or buffered record,
4661 respectively.
4663 CLIENT, ACCOUNTING
4664 State Event Action New State
4665 -------------------------------------------------------------
4666 Idle Client or device requests Send PendingS
4667 access accounting
4668 start req.
4670 Idle Client or device requests Send PendingE
4671 a one-time service accounting
4672 event req
4674 Idle Records in storage Send PendingB
4675 record
4677 PendingS Successful accounting Open
4678 start answer received
4680 PendingS Failure to send and buffer Store Open
4681 space available and realtime Start
4682 not equal to DELIVER_AND_GRANT Record
4684 PendingS Failure to send and no buffer Open
4685 space available and realtime
4686 equal to GRANT_AND_LOSE
4688 PendingS Failure to send and no buffer Disconnect Idle
4689 space available and realtime user/dev
4690 not equal to
4691 GRANT_AND_LOSE
4693 PendingS Failed accounting start answer Open
4694 received and realtime equal
4695 to GRANT_AND_LOSE
4697 PendingS Failed accounting start answer Disconnect Idle
4698 received and realtime not user/dev
4699 equal to GRANT_AND_LOSE
4701 PendingS User service terminated Store PendingS
4702 stop
4703 record
4705 Open Interim interval elapses Send PendingI
4706 accounting
4707 interim
4708 record
4709 Open User service terminated Send PendingL
4710 accounting
4711 stop req.
4713 PendingI Successful accounting interim Open
4714 answer received
4716 PendingI Failure to send and (buffer Store Open
4717 space available or old record interim
4718 can be overwritten) and record
4719 realtime not equal to
4720 DELIVER_AND_GRANT
4722 PendingI Failure to send and no buffer Open
4723 space available and realtime
4724 equal to GRANT_AND_LOSE
4726 PendingI Failure to send and no buffer Disconnect Idle
4727 space available and realtime user/dev
4728 not equal to GRANT_AND_LOSE
4730 PendingI Failed accounting interim Open
4731 answer received and realtime
4732 equal to GRANT_AND_LOSE
4734 PendingI Failed accounting interim Disconnect Idle
4735 answer received and realtime user/dev
4736 not equal to GRANT_AND_LOSE
4738 PendingI User service terminated Store PendingI
4739 stop
4740 record
4741 PendingE Successful accounting Idle
4742 event answer received
4744 PendingE Failure to send and buffer Store Idle
4745 space available event
4746 record
4748 PendingE Failure to send and no buffer Idle
4749 space available
4751 PendingE Failed accounting event answer Idle
4752 received
4754 PendingB Successful accounting answer Delete Idle
4755 received record
4757 PendingB Failure to send Idle
4759 PendingB Failed accounting answer Delete Idle
4760 received record
4762 PendingL Successful accounting Idle
4763 stop answer received
4765 PendingL Failure to send and buffer Store Idle
4766 space available stop
4767 record
4769 PendingL Failure to send and no buffer Idle
4770 space available
4772 PendingL Failed accounting stop answer Idle
4773 received
4775 SERVER, STATELESS ACCOUNTING
4776 State Event Action New State
4777 -------------------------------------------------------------
4779 Idle Accounting start request Send Idle
4780 received, and successfully accounting
4781 processed. start
4782 answer
4784 Idle Accounting event request Send Idle
4785 received, and successfully accounting
4786 processed. event
4787 answer
4789 Idle Interim record received, Send Idle
4790 and successfully processed. accounting
4791 interim
4792 answer
4794 Idle Accounting stop request Send Idle
4795 received, and successfully accounting
4796 processed stop answer
4798 Idle Accounting request received, Send Idle
4799 no space left to store accounting
4800 records answer,
4801 Result-Code
4802 = OUT_OF_
4803 SPACE
4805 SERVER, STATEFUL ACCOUNTING
4806 State Event Action New State
4807 -------------------------------------------------------------
4809 Idle Accounting start request Send Open
4810 received, and successfully accounting
4811 processed. start
4812 answer,
4813 Start Ts
4815 Idle Accounting event request Send Idle
4816 received, and successfully accounting
4817 processed. event
4818 answer
4820 Idle Accounting request received, Send Idle
4821 no space left to store accounting
4822 records answer,
4823 Result-Code
4824 = OUT_OF_
4825 SPACE
4827 Open Interim record received, Send Open
4828 and successfully processed. accounting
4829 interim
4830 answer,
4831 Restart Ts
4833 Open Accounting stop request Send Idle
4834 received, and successfully accounting
4835 processed stop answer,
4836 Stop Ts
4838 Open Accounting request received, Send Idle
4839 no space left to store accounting
4840 records answer,
4841 Result-Code
4842 = OUT_OF_
4843 SPACE,
4844 Stop Ts
4846 Open Session supervision timer Ts Stop Ts Idle
4847 expired
4849 8.3. Server-Initiated Re-Auth
4851 A Diameter server may initiate a re-authentication and/or re-
4852 authorization service for a particular session by issuing a Re-Auth-
4853 Request (RAR).
4855 For example, for pre-paid services, the Diameter server that
4856 originally authorized a session may need some confirmation that the
4857 user is still using the services.
4859 An access device that receives a RAR message with Session-Id equal to
4860 a currently active session MUST initiate a re-auth towards the user,
4861 if the service supports this particular feature. Each Diameter
4862 application MUST state whether service-initiated re-auth is
4863 supported, since some applications do not allow access devices to
4864 prompt the user for re-auth.
4866 8.3.1. Re-Auth-Request
4868 The Re-Auth-Request (RAR), indicated by the Command-Code set to 258
4869 and the message flags' 'R' bit set, may be sent by any server to the
4870 access device that is providing session service, to request that the
4871 user be re-authenticated and/or re-authorized.
4873 Message Format
4875 ::= < Diameter Header: 258, REQ, PXY >
4876 < Session-Id >
4877 { Origin-Host }
4878 { Origin-Realm }
4879 { Destination-Realm }
4880 { Destination-Host }
4881 { Auth-Application-Id }
4882 { Re-Auth-Request-Type }
4883 [ User-Name ]
4884 [ Origin-State-Id ]
4885 * [ Proxy-Info ]
4886 * [ Route-Record ]
4887 * [ AVP ]
4889 8.3.2. Re-Auth-Answer
4891 The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258
4892 and the message flags' 'R' bit clear, is sent in response to the RAR.
4893 The Result-Code AVP MUST be present, and indicates the disposition of
4894 the request.
4896 A successful RAA message MUST be followed by an application-specific
4897 authentication and/or authorization message.
4899 Message Format
4901 ::= < Diameter Header: 258, PXY >
4902 < Session-Id >
4903 { Result-Code }
4904 { Origin-Host }
4905 { Origin-Realm }
4906 [ User-Name ]
4907 [ Origin-State-Id ]
4908 [ Error-Message ]
4909 [ Error-Reporting-Host ]
4910 [ Failed-AVP ]
4911 * [ Redirect-Host ]
4912 [ Redirect-Host-Usage ]
4913 [ Redirect-Max-Cache-Time ]
4914 * [ Proxy-Info ]
4915 * [ AVP ]
4917 8.4. Session Termination
4919 It is necessary for a Diameter server that authorized a session, for
4920 which it is maintaining state, to be notified when that session is no
4921 longer active, both for tracking purposes as well as to allow
4922 stateful agents to release any resources that they may have provided
4923 for the user's session. For sessions whose state is not being
4924 maintained, this section is not used.
4926 When a user session that required Diameter authorization terminates,
4927 the access device that provided the service MUST issue a Session-
4928 Termination-Request (STR) message to the Diameter server that
4929 authorized the service, to notify it that the session is no longer
4930 active. An STR MUST be issued when a user session terminates for any
4931 reason, including user logoff, expiration of Session-Timeout,
4932 administrative action, termination upon receipt of an Abort-Session-
4933 Request (see below), orderly shutdown of the access device, etc.
4935 The access device also MUST issue an STR for a session that was
4936 authorized but never actually started. This could occur, for
4937 example, due to a sudden resource shortage in the access device, or
4938 because the access device is unwilling to provide the type of service
4939 requested in the authorization, or because the access device does not
4940 support a mandatory AVP returned in the authorization, etc.
4942 It is also possible that a session that was authorized is never
4943 actually started due to action of a proxy. For example, a proxy may
4944 modify an authorization answer, converting the result from success to
4945 failure, prior to forwarding the message to the access device. If
4946 the answer did not contain an Auth-Session-State AVP with the value
4947 NO_STATE_MAINTAINED, a proxy that causes an authorized session not to
4948 be started MUST issue an STR to the Diameter server that authorized
4949 the session, since the access device has no way of knowing that the
4950 session had been authorized.
4952 A Diameter server that receives an STR message MUST clean up
4953 resources (e.g., session state) associated with the Session-Id
4954 specified in the STR, and return a Session-Termination-Answer.
4956 A Diameter server also MUST clean up resources when the Session-
4957 Timeout expires, or when the Authorization-Lifetime and the Auth-
4958 Grace-Period AVPs expires without receipt of a re-authorization
4959 request, regardless of whether an STR for that session is received.
4960 The access device is not expected to provide service beyond the
4961 expiration of these timers; thus, expiration of either of these
4962 timers implies that the access device may have unexpectedly shut
4963 down.
4965 8.4.1. Session-Termination-Request
4967 The Session-Termination-Request (STR), indicated by the Command-Code
4968 set to 275 and the Command Flags' 'R' bit set, is sent by the access
4969 device to inform the Diameter Server that an authenticated and/or
4970 authorized session is being terminated.
4972 Message Format
4974 ::= < Diameter Header: 275, REQ, PXY >
4975 < Session-Id >
4976 { Origin-Host }
4977 { Origin-Realm }
4978 { Destination-Realm }
4979 { Auth-Application-Id }
4980 { Termination-Cause }
4981 [ User-Name ]
4982 [ Destination-Host ]
4983 * [ Class ]
4984 [ Origin-State-Id ]
4985 * [ Proxy-Info ]
4986 * [ Route-Record ]
4987 * [ AVP ]
4989 8.4.2. Session-Termination-Answer
4991 The Session-Termination-Answer (STA), indicated by the Command-Code
4992 set to 275 and the message flags' 'R' bit clear, is sent by the
4993 Diameter Server to acknowledge the notification that the session has
4994 been terminated. The Result-Code AVP MUST be present, and MAY
4995 contain an indication that an error occurred while servicing the STR.
4997 Upon sending or receipt of the STA, the Diameter Server MUST release
4998 all resources for the session indicated by the Session-Id AVP. Any
4999 intermediate server in the Proxy-Chain MAY also release any
5000 resources, if necessary.
5002 Message Format
5004 ::= < Diameter Header: 275, PXY >
5005 < Session-Id >
5006 { Result-Code }
5007 { Origin-Host }
5008 { Origin-Realm }
5009 [ User-Name ]
5010 * [ Class ]
5011 [ Error-Message ]
5012 [ Error-Reporting-Host ]
5013 [ Failed-AVP ]
5014 [ Origin-State-Id ]
5015 * [ Redirect-Host ]
5016 [ Redirect-Host-Usage ]
5017 [ Redirect-Max-Cache-Time ]
5018 * [ Proxy-Info ]
5019 * [ AVP ]
5021 8.5. Aborting a Session
5023 A Diameter server may request that the access device stop providing
5024 service for a particular session by issuing an Abort-Session-Request
5025 (ASR).
5027 For example, the Diameter server that originally authorized the
5028 session may be required to cause that session to be stopped for
5029 credit or other reasons that were not anticipated when the session
5030 was first authorized. On the other hand, an operator may maintain a
5031 management server for the purpose of issuing ASRs to administratively
5032 remove users from the network.
5034 An access device that receives an ASR with Session-ID equal to a
5035 currently active session MAY stop the session. Whether the access
5036 device stops the session or not is implementation- and/or
5037 configuration-dependent. For example, an access device may honor
5038 ASRs from certain agents only. In any case, the access device MUST
5039 respond with an Abort-Session-Answer, including a Result-Code AVP to
5040 indicate what action it took.
5042 Note that if the access device does stop the session upon receipt of
5043 an ASR, it issues an STR to the authorizing server (which may or may
5044 not be the agent issuing the ASR) just as it would if the session
5045 were terminated for any other reason.
5047 8.5.1. Abort-Session-Request
5049 The Abort-Session-Request (ASR), indicated by the Command-Code set to
5050 274 and the message flags' 'R' bit set, may be sent by any server to
5051 the access device that is providing session service, to request that
5052 the session identified by the Session-Id be stopped.
5054 Message Format
5056 ::= < Diameter Header: 274, REQ, PXY >
5057 < Session-Id >
5058 { Origin-Host }
5059 { Origin-Realm }
5060 { Destination-Realm }
5061 { Destination-Host }
5062 { Auth-Application-Id }
5063 [ User-Name ]
5064 [ Origin-State-Id ]
5065 * [ Proxy-Info ]
5066 * [ Route-Record ]
5067 * [ AVP ]
5069 8.5.2. Abort-Session-Answer
5071 The Abort-Session-Answer (ASA), indicated by the Command-Code set to
5072 274 and the message flags' 'R' bit clear, is sent in response to the
5073 ASR. The Result-Code AVP MUST be present, and indicates the
5074 disposition of the request.
5076 If the session identified by Session-Id in the ASR was successfully
5077 terminated, Result-Code is set to DIAMETER_SUCCESS. If the session
5078 is not currently active, Result-Code is set to
5079 DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the
5080 session for any other reason, Result-Code is set to
5081 DIAMETER_UNABLE_TO_COMPLY.
5083 Message Format
5085 ::= < Diameter Header: 274, PXY >
5086 < Session-Id >
5087 { Result-Code }
5088 { Origin-Host }
5089 { Origin-Realm }
5090 [ User-Name ]
5091 [ Origin-State-Id ]
5092 [ Error-Message ]
5093 [ Error-Reporting-Host ]
5094 [ Failed-AVP ]
5095 * [ Redirect-Host ]
5096 [ Redirect-Host-Usage ]
5097 [ Redirect-Max-Cache-Time ]
5098 * [ Proxy-Info ]
5099 * [ AVP ]
5101 8.6. Inferring Session Termination from Origin-State-Id
5103 Origin-State-Id is used to allow rapid detection of terminated
5104 sessions for which no STR would have been issued, due to
5105 unanticipated shutdown of an access device.
5107 By including Origin-State-Id in CER/CEA messages, an access device
5108 allows a next-hop server to determine immediately upon connection
5109 whether the device has lost its sessions since the last connection.
5111 By including Origin-State-Id in request messages, an access device
5112 also allows a server with which it communicates via proxy to make
5113 such a determination. However, a server that is not directly
5114 connected with the access device will not discover that the access
5115 device has been restarted unless and until it receives a new request
5116 from the access device. Thus, use of this mechanism across proxies
5117 is opportunistic rather than reliable, but useful nonetheless.
5119 When a Diameter server receives an Origin-State-Id that is greater
5120 than the Origin-State-Id previously received from the same issuer, it
5121 may assume that the issuer has lost state since the previous message
5122 and that all sessions that were active under the lower Origin-State-
5123 Id have been terminated. The Diameter server MAY clean up all
5124 session state associated with such lost sessions, and MAY also issues
5125 STRs for all such lost sessions that were authorized on upstream
5126 servers, to allow session state to be cleaned up globally.
5128 8.7. Auth-Request-Type AVP
5130 The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is
5131 included in application-specific auth requests to inform the peers
5132 whether a user is to be authenticated only, authorized only or both.
5133 Note any value other than both MAY cause RADIUS interoperability
5134 issues. The following values are defined:
5136 AUTHENTICATE_ONLY 1
5138 The request being sent is for authentication only, and MUST
5139 contain the relevant application specific authentication AVPs that
5140 are needed by the Diameter server to authenticate the user.
5142 AUTHORIZE_ONLY 2
5144 The request being sent is for authorization only, and MUST contain
5145 the application specific authorization AVPs that are necessary to
5146 identify the service being requested/offered.
5148 AUTHORIZE_AUTHENTICATE 3
5150 The request contains a request for both authentication and
5151 authorization. The request MUST include both the relevant
5152 application specific authentication information, and authorization
5153 information necessary to identify the service being requested/
5154 offered.
5156 8.8. Session-Id AVP
5158 The Session-Id AVP (AVP Code 263) is of type UTF8String and is used
5159 to identify a specific session (see Section 8). All messages
5160 pertaining to a specific session MUST include only one Session-Id AVP
5161 and the same value MUST be used throughout the life of a session.
5162 When present, the Session-Id SHOULD appear immediately following the
5163 Diameter Header (see Section 3).
5165 The Session-Id MUST be globally and eternally unique, as it is meant
5166 to uniquely identify a user session without reference to any other
5167 information, and may be needed to correlate historical authentication
5168 information with accounting information. The Session-Id includes a
5169 mandatory portion and an implementation-defined portion; a
5170 recommended format for the implementation-defined portion is outlined
5171 below.
5173 The Session-Id MUST begin with the sender's identity encoded in the
5174 DiameterIdentity type (see Section 4.4). The remainder of the
5175 Session-Id is delimited by a ";" character, and MAY be any sequence
5176 that the client can guarantee to be eternally unique; however, the
5177 following format is recommended, (square brackets [] indicate an
5178 optional element):
5180 ;;[;]
5182 and are decimal representations of the
5183 high and low 32 bits of a monotonically increasing 64-bit value. The
5184 64-bit value is rendered in two part to simplify formatting by 32-bit
5185 processors. At startup, the high 32 bits of the 64-bit value MAY be
5186 initialized to the time in NTP format [RFC4330], and the low 32 bits
5187 MAY be initialized to zero. This will for practical purposes
5188 eliminate the possibility of overlapping Session-Ids after a reboot,
5189 assuming the reboot process takes longer than a second.
5190 Alternatively, an implementation MAY keep track of the increasing
5191 value in non-volatile memory.
5193 is implementation specific but may include a modem's
5194 device Id, a layer 2 address, timestamp, etc.
5196 Example, in which there is no optional value:
5198 accesspoint7.acme.com;1876543210;523
5200 Example, in which there is an optional value:
5202 accesspoint7.acme.com;1876543210;523;mobile@200.1.1.88
5204 The Session-Id is created by the Diameter application initiating the
5205 session, which in most cases is done by the client. Note that a
5206 Session-Id MAY be used for both the authorization and accounting
5207 commands of a given application.
5209 8.9. Authorization-Lifetime AVP
5211 The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32
5212 and contains the maximum number of seconds of service to be provided
5213 to the user before the user is to be re-authenticated and/or re-
5214 authorized. Great care should be taken when the Authorization-
5215 Lifetime value is determined, since a low, non-zero, value could
5216 create significant Diameter traffic, which could congest both the
5217 network and the agents.
5219 A value of zero (0) means that immediate re-auth is necessary by the
5220 access device. This is typically used in cases where multiple
5221 authentication methods are used, and a successful auth response with
5222 this AVP set to zero is used to signal that the next authentication
5223 method is to be immediately initiated. The absence of this AVP, or a
5224 value of all ones (meaning all bits in the 32 bit field are set to
5225 one) means no re-auth is expected.
5227 If both this AVP and the Session-Timeout AVP are present in a
5228 message, the value of the latter MUST NOT be smaller than the
5229 Authorization-Lifetime AVP.
5231 An Authorization-Lifetime AVP MAY be present in re-authorization
5232 messages, and contains the number of seconds the user is authorized
5233 to receive service from the time the re-auth answer message is
5234 received by the access device.
5236 This AVP MAY be provided by the client as a hint of the maximum
5237 lifetime that it is willing to accept. However, the server MAY
5238 return a value that is equal to, or smaller, than the one provided by
5239 the client.
5241 8.10. Auth-Grace-Period AVP
5243 The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and
5244 contains the number of seconds the Diameter server will wait
5245 following the expiration of the Authorization-Lifetime AVP before
5246 cleaning up resources for the session.
5248 8.11. Auth-Session-State AVP
5250 The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and
5251 specifies whether state is maintained for a particular session. The
5252 client MAY include this AVP in requests as a hint to the server, but
5253 the value in the server's answer message is binding. The following
5254 values are supported:
5256 STATE_MAINTAINED 0
5258 This value is used to specify that session state is being
5259 maintained, and the access device MUST issue a session termination
5260 message when service to the user is terminated. This is the
5261 default value.
5263 NO_STATE_MAINTAINED 1
5265 This value is used to specify that no session termination messages
5266 will be sent by the access device upon expiration of the
5267 Authorization-Lifetime.
5269 8.12. Re-Auth-Request-Type AVP
5271 The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and
5272 is included in application-specific auth answers to inform the client
5273 of the action expected upon expiration of the Authorization-Lifetime.
5274 If the answer message contains an Authorization-Lifetime AVP with a
5275 positive value, the Re-Auth-Request-Type AVP MUST be present in an
5276 answer message. The following values are defined:
5278 AUTHORIZE_ONLY 0
5280 An authorization only re-auth is expected upon expiration of the
5281 Authorization-Lifetime. This is the default value if the AVP is
5282 not present in answer messages that include the Authorization-
5283 Lifetime.
5285 AUTHORIZE_AUTHENTICATE 1
5287 An authentication and authorization re-auth is expected upon
5288 expiration of the Authorization-Lifetime.
5290 8.13. Session-Timeout AVP
5292 The Session-Timeout AVP (AVP Code 27) [RFC2865] is of type Unsigned32
5293 and contains the maximum number of seconds of service to be provided
5294 to the user before termination of the session. When both the
5295 Session-Timeout and the Authorization-Lifetime AVPs are present in an
5296 answer message, the former MUST be equal to or greater than the value
5297 of the latter.
5299 A session that terminates on an access device due to the expiration
5300 of the Session-Timeout MUST cause an STR to be issued, unless both
5301 the access device and the home server had previously agreed that no
5302 session termination messages would be sent (see Section 8.11).
5304 A Session-Timeout AVP MAY be present in a re-authorization answer
5305 message, and contains the remaining number of seconds from the
5306 beginning of the re-auth.
5308 A value of zero, or the absence of this AVP, means that this session
5309 has an unlimited number of seconds before termination.
5311 This AVP MAY be provided by the client as a hint of the maximum
5312 timeout that it is willing to accept. However, the server MAY return
5313 a value that is equal to, or smaller, than the one provided by the
5314 client.
5316 8.14. User-Name AVP
5318 The User-Name AVP (AVP Code 1) [RFC2865] is of type UTF8String, which
5319 contains the User-Name, in a format consistent with the NAI
5320 specification [RFC4282].
5322 8.15. Termination-Cause AVP
5324 The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and
5325 is used to indicate the reason why a session was terminated on the
5326 access device. The following values are defined:
5328 DIAMETER_LOGOUT 1
5330 The user initiated a disconnect
5332 DIAMETER_SERVICE_NOT_PROVIDED 2
5334 This value is used when the user disconnected prior to the receipt
5335 of the authorization answer message.
5337 DIAMETER_BAD_ANSWER 3
5339 This value indicates that the authorization answer received by the
5340 access device was not processed successfully.
5342 DIAMETER_ADMINISTRATIVE 4
5344 The user was not granted access, or was disconnected, due to
5345 administrative reasons, such as the receipt of a Abort-Session-
5346 Request message.
5348 DIAMETER_LINK_BROKEN 5
5350 The communication to the user was abruptly disconnected.
5352 DIAMETER_AUTH_EXPIRED 6
5354 The user's access was terminated since its authorized session time
5355 has expired.
5357 DIAMETER_USER_MOVED 7
5359 The user is receiving services from another access device.
5361 DIAMETER_SESSION_TIMEOUT 8
5363 The user's session has timed out, and service has been terminated.
5365 8.16. Origin-State-Id AVP
5367 The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a
5368 monotonically increasing value that is advanced whenever a Diameter
5369 entity restarts with loss of previous state, for example upon reboot.
5370 Origin-State-Id MAY be included in any Diameter message, including
5371 CER.
5373 A Diameter entity issuing this AVP MUST create a higher value for
5374 this AVP each time its state is reset. A Diameter entity MAY set
5375 Origin-State-Id to the time of startup, or it MAY use an incrementing
5376 counter retained in non-volatile memory across restarts.
5378 The Origin-State-Id, if present, MUST reflect the state of the entity
5379 indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST
5380 either remove Origin-State-Id or modify it appropriately as well.
5381 Typically, Origin-State-Id is used by an access device that always
5382 starts up with no active sessions; that is, any session active prior
5383 to restart will have been lost. By including Origin-State-Id in a
5384 message, it allows other Diameter entities to infer that sessions
5385 associated with a lower Origin-State-Id are no longer active. If an
5386 access device does not intend for such inferences to be made, it MUST
5387 either not include Origin-State-Id in any message, or set its value
5388 to 0.
5390 8.17. Session-Binding AVP
5392 The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY
5393 be present in application-specific authorization answer messages. If
5394 present, this AVP MAY inform the Diameter client that all future
5395 application-specific re-auth messages for this session MUST be sent
5396 to the same authorization server. This AVP MAY also specify that a
5397 Session-Termination-Request message for this session MUST be sent to
5398 the same authorizing server.
5400 This field is a bit mask, and the following bits have been defined:
5402 RE_AUTH 1
5404 When set, future re-auth messages for this session MUST NOT
5405 include the Destination-Host AVP. When cleared, the default
5406 value, the Destination-Host AVP MUST be present in all re-auth
5407 messages for this session.
5409 STR 2
5411 When set, the STR message for this session MUST NOT include the
5412 Destination-Host AVP. When cleared, the default value, the
5413 Destination-Host AVP MUST be present in the STR message for this
5414 session.
5416 ACCOUNTING 4
5418 When set, all accounting messages for this session MUST NOT
5419 include the Destination-Host AVP. When cleared, the default
5420 value, the Destination-Host AVP, if known, MUST be present in all
5421 accounting messages for this session.
5423 8.18. Session-Server-Failover AVP
5425 The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated,
5426 and MAY be present in application-specific authorization answer
5427 messages that either do not include the Session-Binding AVP or
5428 include the Session-Binding AVP with any of the bits set to a zero
5429 value. If present, this AVP MAY inform the Diameter client that if a
5430 re-auth or STR message fails due to a delivery problem, the Diameter
5431 client SHOULD issue a subsequent message without the Destination-Host
5432 AVP. When absent, the default value is REFUSE_SERVICE.
5434 The following values are supported:
5436 REFUSE_SERVICE 0
5438 If either the re-auth or the STR message delivery fails, terminate
5439 service with the user, and do not attempt any subsequent attempts.
5441 TRY_AGAIN 1
5443 If either the re-auth or the STR message delivery fails, resend
5444 the failed message without the Destination-Host AVP present.
5446 ALLOW_SERVICE 2
5448 If re-auth message delivery fails, assume that re-authorization
5449 succeeded. If STR message delivery fails, terminate the session.
5451 TRY_AGAIN_ALLOW_SERVICE 3
5453 If either the re-auth or the STR message delivery fails, resend
5454 the failed message without the Destination-Host AVP present. If
5455 the second delivery fails for re-auth, assume re-authorization
5456 succeeded. If the second delivery fails for STR, terminate the
5457 session.
5459 8.19. Multi-Round-Time-Out AVP
5461 The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32,
5462 and SHOULD be present in application-specific authorization answer
5463 messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH.
5464 This AVP contains the maximum number of seconds that the access
5465 device MUST provide the user in responding to an authentication
5466 request.
5468 8.20. Class AVP
5470 The Class AVP (AVP Code 25) is of type OctetString and is used by
5471 Diameter servers to return state information to the access device.
5472 When one or more Class AVPs are present in application-specific
5473 authorization answer messages, they MUST be present in subsequent re-
5474 authorization, session termination and accounting messages. Class
5475 AVPs found in a re-authorization answer message override the ones
5476 found in any previous authorization answer message. Diameter server
5477 implementations SHOULD NOT return Class AVPs that require more than
5478 4096 bytes of storage on the Diameter client. A Diameter client that
5479 receives Class AVPs whose size exceeds local available storage MUST
5480 terminate the session.
5482 8.21. Event-Timestamp AVP
5484 The Event-Timestamp (AVP Code 55) is of type Time, and MAY be
5485 included in an Accounting-Request and Accounting-Answer messages to
5486 record the time that the reported event occurred, in seconds since
5487 January 1, 1900 00:00 UTC.
5489 9. Accounting
5491 This accounting protocol is based on a server directed model with
5492 capabilities for real-time delivery of accounting information.
5493 Several fault resilience methods [RFC2975] have been built in to the
5494 protocol in order minimize loss of accounting data in various fault
5495 situations and under different assumptions about the capabilities of
5496 the used devices.
5498 9.1. Server Directed Model
5500 The server directed model means that the device generating the
5501 accounting data gets information from either the authorization server
5502 (if contacted) or the accounting server regarding the way accounting
5503 data shall be forwarded. This information includes accounting record
5504 timeliness requirements.
5506 As discussed in [RFC2975], real-time transfer of accounting records
5507 is a requirement, such as the need to perform credit limit checks and
5508 fraud detection. Note that batch accounting is not a requirement,
5509 and is therefore not supported by Diameter. Should batched
5510 accounting be required in the future, a new Diameter application will
5511 need to be created, or it could be handled using another protocol.
5512 Note, however, that even if at the Diameter layer accounting requests
5513 are processed one by one, transport protocols used under Diameter
5514 typically batch several requests in the same packet under heavy
5515 traffic conditions. This may be sufficient for many applications.
5517 The authorization server (chain) directs the selection of proper
5518 transfer strategy, based on its knowledge of the user and
5519 relationships of roaming partnerships. The server (or agents) uses
5520 the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to
5521 control the operation of the Diameter peer operating as a client.
5522 The Acct-Interim-Interval AVP, when present, instructs the Diameter
5523 node acting as a client to produce accounting records continuously
5524 even during a session. Accounting-Realtime-Required AVP is used to
5525 control the behavior of the client when the transfer of accounting
5526 records from the Diameter client is delayed or unsuccessful.
5528 The Diameter accounting server MAY override the interim interval or
5529 the realtime requirements by including the Acct-Interim-Interval or
5530 Accounting-Realtime-Required AVP in the Accounting-Answer message.
5531 When one of these AVPs is present, the latest value received SHOULD
5532 be used in further accounting activities for the same session.
5534 9.2. Protocol Messages
5536 A Diameter node that receives a successful authentication and/or
5537 authorization messages from the Home AAA server MUST collect
5538 accounting information for the session. The Accounting-Request
5539 message is used to transmit the accounting information to the Home
5540 AAA server, which MUST reply with the Accounting-Answer message to
5541 confirm reception. The Accounting-Answer message includes the
5542 Result-Code AVP, which MAY indicate that an error was present in the
5543 accounting message. A rejected Accounting-Request message MAY cause
5544 the user's session to be terminated, depending on the value of the
5545 Accounting-Realtime-Required AVP received earlier for the session in
5546 question.
5548 Each Diameter Accounting protocol message MAY be compressed, in order
5549 to reduce network bandwidth usage. If TLS is used to secure the
5550 Diameter session, then TLS compression [RFC4346] MAY be used.
5552 9.3. Accounting Application Extension and Requirements
5554 Each Diameter application (e.g., NASREQ, MobileIP), MUST define their
5555 Service-Specific AVPs that MUST be present in the Accounting-Request
5556 message in a section entitled "Accounting AVPs". The application
5557 MUST assume that the AVPs described in this document will be present
5558 in all Accounting messages, so only their respective service-specific
5559 AVPs need to be defined in this section.
5561 Applications have the option of using one or both of the following
5562 accounting application extension models:
5564 Split Accounting Service
5566 The accounting message will carry the Application Id of the
5567 Diameter base accounting application (see Section 2.4).
5568 Accounting messages maybe routed to Diameter nodes other than the
5569 corresponding Diameter application. These nodes might be
5570 centralized accounting servers that provide accounting service for
5571 multiple different Diameter applications. These nodes MUST
5572 advertise the Diameter base accounting Application Id during
5573 capabilities exchange.
5575 Coupled Accounting Service
5577 The accounting messages will carry the Application Id of the
5578 application that is using it. The application itself will process
5579 the received accounting records or forward them to an accounting
5580 server. There is no accounting application advertisement required
5581 during capabilities exchange and the accounting messages will be
5582 routed the same as any of the other application messages.
5584 In cases where an application does not define its own accounting
5585 service, it is preferred that the split accounting model be used.
5587 9.4. Fault Resilience
5589 Diameter Base protocol mechanisms are used to overcome small message
5590 loss and network faults of temporary nature.
5592 Diameter peers acting as clients MUST implement the use of failover
5593 to guard against server failures and certain network failures.
5594 Diameter peers acting as agents or related off-line processing
5595 systems MUST detect duplicate accounting records caused by the
5596 sending of same record to several servers and duplication of messages
5597 in transit. This detection MUST be based on the inspection of the
5598 Session-Id and Accounting-Record-Number AVP pairs. Appendix C
5599 discusses duplicate detection needs and implementation issues.
5601 Diameter clients MAY have non-volatile memory for the safe storage of
5602 accounting records over reboots or extended network failures, network
5603 partitions, and server failures. If such memory is available, the
5604 client SHOULD store new accounting records there as soon as the
5605 records are created and until a positive acknowledgement of their
5606 reception from the Diameter Server has been received. Upon a reboot,
5607 the client MUST starting sending the records in the non-volatile
5608 memory to the accounting server with appropriate modifications in
5609 termination cause, session length, and other relevant information in
5610 the records.
5612 A further application of this protocol may include AVPs to control
5613 how many accounting records may at most be stored in the Diameter
5614 client without committing them to the non-volatile memory or
5615 transferring them to the Diameter server.
5617 The client SHOULD NOT remove the accounting data from any of its
5618 memory areas before the correct Accounting-Answer has been received.
5619 The client MAY remove oldest, undelivered or yet unacknowledged
5620 accounting data if it runs out of resources such as memory. It is an
5621 implementation dependent matter for the client to accept new sessions
5622 under this condition.
5624 9.5. Accounting Records
5626 In all accounting records, the Session-Id AVP MUST be present; the
5627 User-Name AVP MUST be present if it is available to the Diameter
5628 client.
5630 Different types of accounting records are sent depending on the
5631 actual type of accounted service and the authorization server's
5632 directions for interim accounting. If the accounted service is a
5633 one-time event, meaning that the start and stop of the event are
5634 simultaneous, then the Accounting-Record-Type AVP MUST be present and
5635 set to the value EVENT_RECORD.
5637 If the accounted service is of a measurable length, then the AVP MUST
5638 use the values START_RECORD, STOP_RECORD, and possibly,
5639 INTERIM_RECORD. If the authorization server has not directed interim
5640 accounting to be enabled for the session, two accounting records MUST
5641 be generated for each service of type session. When the initial
5642 Accounting-Request for a given session is sent, the Accounting-
5643 Record-Type AVP MUST be set to the value START_RECORD. When the last
5644 Accounting-Request is sent, the value MUST be STOP_RECORD.
5646 If the authorization server has directed interim accounting to be
5647 enabled, the Diameter client MUST produce additional records between
5648 the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The
5649 production of these records is directed by Acct-Interim-Interval as
5650 well as any re-authentication or re-authorization of the session.
5651 The Diameter client MUST overwrite any previous interim accounting
5652 records that are locally stored for delivery, if a new record is
5653 being generated for the same session. This ensures that only one
5654 pending interim record can exist on an access device for any given
5655 session.
5657 A particular value of Accounting-Sub-Session-Id MUST appear only in
5658 one sequence of accounting records from a DIAMETER client, except for
5659 the purposes of retransmission. The one sequence that is sent MUST
5660 be either one record with Accounting-Record-Type AVP set to the value
5661 EVENT_RECORD, or several records starting with one having the value
5662 START_RECORD, followed by zero or more INTERIM_RECORD and a single
5663 STOP_RECORD. A particular Diameter application specification MUST
5664 define the type of sequences that MUST be used.
5666 9.6. Correlation of Accounting Records
5668 The Diameter protocol's Session-Id AVP, which is globally unique (see
5669 Section 8.8), is used during the authorization phase to identify a
5670 particular session. Services that do not require any authorization
5671 still use the Session-Id AVP to identify sessions. Accounting
5672 messages MAY use a different Session-Id from that sent in
5673 authorization messages. Specific applications MAY require different
5674 a Session-ID for accounting messages.
5676 However, there are certain applications that require multiple
5677 accounting sub-sessions. Such applications would send messages with
5678 a constant Session-Id AVP, but a different Accounting-Sub-Session-Id
5679 AVP. In these cases, correlation is performed using the Session-Id.
5680 It is important to note that receiving a STOP_RECORD with no
5681 Accounting-Sub-Session-Id AVP when sub-sessions were originally used
5682 in the START_RECORD messages implies that all sub-sessions are
5683 terminated.
5685 Furthermore, there are certain applications where a user receives
5686 service from different access devices (e.g., Mobile IPv4), each with
5687 their own unique Session-Id. In such cases, the Acct-Multi-Session-
5688 Id AVP is used for correlation. During authorization, a server that
5689 determines that a request is for an existing session SHOULD include
5690 the Acct-Multi-Session-Id AVP, which the access device MUST include
5691 in all subsequent accounting messages.
5693 The Acct-Multi-Session-Id AVP MAY include the value of the original
5694 Session-Id. It's contents are implementation specific, but MUST be
5695 globally unique across other Acct-Multi-Session-Id, and MUST NOT
5696 change during the life of a session.
5698 A Diameter application document MUST define the exact concept of a
5699 session that is being accounted, and MAY define the concept of a
5700 multi-session. For instance, the NASREQ DIAMETER application treats
5701 a single PPP connection to a Network Access Server as one session,
5702 and a set of Multilink PPP sessions as one multi-session.
5704 9.7. Accounting Command-Codes
5706 This section defines Command-Code values that MUST be supported by
5707 all Diameter implementations that provide Accounting services.
5709 9.7.1. Accounting-Request
5711 The Accounting-Request (ACR) command, indicated by the Command-Code
5712 field set to 271 and the Command Flags' 'R' bit set, is sent by a
5713 Diameter node, acting as a client, in order to exchange accounting
5714 information with a peer.
5716 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs
5717 MUST be present. If the Vendor-Specific-Application-Id grouped AVP
5718 is present, it MUST include an Acct-Application-Id AVP.
5720 The AVP listed below SHOULD include service specific accounting AVPs,
5721 as described in Section 9.3.
5723 Message Format
5725 ::= < Diameter Header: 271, REQ, PXY >
5726 < Session-Id >
5727 { Origin-Host }
5728 { Origin-Realm }
5729 { Destination-Realm }
5730 { Accounting-Record-Type }
5731 { Accounting-Record-Number }
5732 [ Acct-Application-Id ]
5733 [ Vendor-Specific-Application-Id ]
5734 [ User-Name ]
5735 [ Destination-Host ]
5736 [ Accounting-Sub-Session-Id ]
5737 [ Acct-Session-Id ]
5738 [ Acct-Multi-Session-Id ]
5739 [ Acct-Interim-Interval ]
5740 [ Accounting-Realtime-Required ]
5741 [ Origin-State-Id ]
5742 [ Event-Timestamp ]
5743 * [ Proxy-Info ]
5744 * [ Route-Record ]
5745 * [ AVP ]
5747 9.7.2. Accounting-Answer
5749 The Accounting-Answer (ACA) command, indicated by the Command-Code
5750 field set to 271 and the Command Flags' 'R' bit cleared, is used to
5751 acknowledge an Accounting-Request command. The Accounting-Answer
5752 command contains the same Session-Id as the corresponding request.
5754 Only the target Diameter Server, known as the home Diameter Server,
5755 SHOULD respond with the Accounting-Answer command.
5757 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs
5758 MUST be present. If the Vendor-Specific-Application-Id grouped AVP
5759 is present, it MUST contain an Acct-Application-Id AVP.
5761 The AVP listed below SHOULD include service specific accounting AVPs,
5762 as described in Section 9.3.
5764 Message Format
5766 ::= < Diameter Header: 271, PXY >
5767 < Session-Id >
5768 { Result-Code }
5769 { Origin-Host }
5770 { Origin-Realm }
5771 { Accounting-Record-Type }
5772 { Accounting-Record-Number }
5773 [ Acct-Application-Id ]
5774 [ Vendor-Specific-Application-Id ]
5775 [ User-Name ]
5776 [ Accounting-Sub-Session-Id ]
5777 [ Acct-Session-Id ]
5778 [ Acct-Multi-Session-Id ]
5779 [ Error-Message ]
5780 [ Error-Reporting-Host ]
5781 [ Failed-AVP ]
5782 [ Acct-Interim-Interval ]
5783 [ Accounting-Realtime-Required ]
5784 [ Origin-State-Id ]
5785 [ Event-Timestamp ]
5786 * [ Proxy-Info ]
5787 * [ AVP ]
5789 9.8. Accounting AVPs
5791 This section contains AVPs that describe accounting usage information
5792 related to a specific session.
5794 9.8.1. Accounting-Record-Type AVP
5796 The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated
5797 and contains the type of accounting record being sent. The following
5798 values are currently defined for the Accounting-Record-Type AVP:
5800 EVENT_RECORD 1
5802 An Accounting Event Record is used to indicate that a one-time
5803 event has occurred (meaning that the start and end of the event
5804 are simultaneous). This record contains all information relevant
5805 to the service, and is the only record of the service.
5807 START_RECORD 2
5809 An Accounting Start, Interim, and Stop Records are used to
5810 indicate that a service of a measurable length has been given. An
5811 Accounting Start Record is used to initiate an accounting session,
5812 and contains accounting information that is relevant to the
5813 initiation of the session.
5815 INTERIM_RECORD 3
5817 An Interim Accounting Record contains cumulative accounting
5818 information for an existing accounting session. Interim
5819 Accounting Records SHOULD be sent every time a re-authentication
5820 or re-authorization occurs. Further, additional interim record
5821 triggers MAY be defined by application-specific Diameter
5822 applications. The selection of whether to use INTERIM_RECORD
5823 records is done by the Acct-Interim-Interval AVP.
5825 STOP_RECORD 4
5827 An Accounting Stop Record is sent to terminate an accounting
5828 session and contains cumulative accounting information relevant to
5829 the existing session.
5831 9.8.2. Acct-Interim-Interval AVP
5833 The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and
5834 is sent from the Diameter home authorization server to the Diameter
5835 client. The client uses information in this AVP to decide how and
5836 when to produce accounting records. With different values in this
5837 AVP, service sessions can result in one, two, or two+N accounting
5838 records, based on the needs of the home-organization. The following
5839 accounting record production behavior is directed by the inclusion of
5840 this AVP:
5842 1. The omission of the Acct-Interim-Interval AVP or its inclusion
5843 with Value field set to 0 means that EVENT_RECORD, START_RECORD,
5844 and STOP_RECORD are produced, as appropriate for the service.
5846 2. The inclusion of the AVP with Value field set to a non-zero value
5847 means that INTERIM_RECORD records MUST be produced between the
5848 START_RECORD and STOP_RECORD records. The Value field of this
5849 AVP is the nominal interval between these records in seconds.
5851 The Diameter node that originates the accounting information,
5852 known as the client, MUST produce the first INTERIM_RECORD record
5853 roughly at the time when this nominal interval has elapsed from
5854 the START_RECORD, the next one again as the interval has elapsed
5855 once more, and so on until the session ends and a STOP_RECORD
5856 record is produced.
5858 The client MUST ensure that the interim record production times
5859 are randomized so that large accounting message storms are not
5860 created either among records or around a common service start
5861 time.
5863 9.8.3. Accounting-Record-Number AVP
5865 The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32
5866 and identifies this record within one session. As Session-Id AVPs
5867 are globally unique, the combination of Session-Id and Accounting-
5868 Record-Number AVPs is also globally unique, and can be used in
5869 matching accounting records with confirmations. An easy way to
5870 produce unique numbers is to set the value to 0 for records of type
5871 EVENT_RECORD and START_RECORD, and set the value to 1 for the first
5872 INTERIM_RECORD, 2 for the second, and so on until the value for
5873 STOP_RECORD is one more than for the last INTERIM_RECORD.
5875 9.8.4. Acct-Session-Id AVP
5877 The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only
5878 used when RADIUS/Diameter translation occurs. This AVP contains the
5879 contents of the RADIUS Acct-Session-Id attribute.
5881 9.8.5. Acct-Multi-Session-Id AVP
5883 The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String,
5884 following the format specified in Section 8.8. The Acct-Multi-
5885 Session-Id AVP is used to link together multiple related accounting
5886 sessions, where each session would have a unique Session-Id, but the
5887 same Acct-Multi-Session-Id AVP. This AVP MAY be returned by the
5888 Diameter server in an authorization answer, and MUST be used in all
5889 accounting messages for the given session.
5891 9.8.6. Accounting-Sub-Session-Id AVP
5893 The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type
5894 Unsigned64 and contains the accounting sub-session identifier. The
5895 combination of the Session-Id and this AVP MUST be unique per sub-
5896 session, and the value of this AVP MUST be monotonically increased by
5897 one for all new sub-sessions. The absence of this AVP implies no
5898 sub-sessions are in use, with the exception of an Accounting-Request
5899 whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD
5900 message with no Accounting-Sub-Session-Id AVP present will signal the
5901 termination of all sub-sessions for a given Session-Id.
5903 9.8.7. Accounting-Realtime-Required AVP
5905 The Accounting-Realtime-Required AVP (AVP Code 483) is of type
5906 Enumerated and is sent from the Diameter home authorization server to
5907 the Diameter client or in the Accounting-Answer from the accounting
5908 server. The client uses information in this AVP to decide what to do
5909 if the sending of accounting records to the accounting server has
5910 been temporarily prevented due to, for instance, a network problem.
5912 DELIVER_AND_GRANT 1
5914 The AVP with Value field set to DELIVER_AND_GRANT means that the
5915 service MUST only be granted as long as there is a connection to
5916 an accounting server. Note that the set of alternative accounting
5917 servers are treated as one server in this sense. Having to move
5918 the accounting record stream to a backup server is not a reason to
5919 discontinue the service to the user.
5921 GRANT_AND_STORE 2
5923 The AVP with Value field set to GRANT_AND_STORE means that service
5924 SHOULD be granted if there is a connection, or as long as records
5925 can still be stored as described in Section 9.4.
5927 This is the default behavior if the AVP isn't included in the
5928 reply from the authorization server.
5930 GRANT_AND_LOSE 3
5932 The AVP with Value field set to GRANT_AND_LOSE means that service
5933 SHOULD be granted even if the records can not be delivered or
5934 stored.
5936 10. AVP Occurrence Table
5938 The following tables presents the AVPs defined in this document, and
5939 specifies in which Diameter messages they MAY be present or not.
5940 AVPs that occur only inside a Grouped AVP are not shown in this
5941 table.
5943 The table uses the following symbols:
5945 0 The AVP MUST NOT be present in the message.
5947 0+ Zero or more instances of the AVP MAY be present in the
5948 message.
5950 0-1 Zero or one instance of the AVP MAY be present in the message.
5951 It is considered an error if there are more than one instance of
5952 the AVP.
5954 1 One instance of the AVP MUST be present in the message.
5956 1+ At least one instance of the AVP MUST be present in the
5957 message.
5959 10.1. Base Protocol Command AVP Table
5961 The table in this section is limited to the non-accounting Command
5962 Codes defined in this specification.
5964 +-----------------------------------------------+
5965 | Command-Code |
5966 +---+---+---+---+---+---+---+---+---+---+---+---+
5967 Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA|
5968 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+
5969 Acct-Interim- |0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 |
5970 Interval | | | | | | | | | | | | |
5971 Accounting-Realtime-|0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 |
5972 Required | | | | | | | | | | | | |
5973 Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5974 Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 |
5975 Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5976 Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5977 Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5978 Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5979 Lifetime | | | | | | | | | | | | |
5980 Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ |
5981 Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 |
5982 Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 |
5983 Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5984 Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|
5985 Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
5986 Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |
5987 Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5988 Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5989 Inband-Security-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5990 Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5991 Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |
5992 Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |
5993 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|
5994 Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5995 Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ |
5996 Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |
5997 Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
5998 Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
5999 Time | | | | | | | | | | | | |
6000 Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 |
6001 Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 |
6002 Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 |
6003 Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6004 Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 |
6005 Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6006 Failover | | | | | | | | | | | | |
6007 Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6008 Supported-Vendor-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6009 Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 |
6010 User-Name |0 |0 |0 |0 |0 |0 |0-1|0-1|0-1|0-1|0-1|0-1|
6011 Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6012 Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6013 Application-Id | | | | | | | | | | | | |
6014 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+
6016 10.2. Accounting AVP Table
6018 The table in this section is used to represent which AVPs defined in
6019 this document are to be present in the Accounting messages. These
6020 AVP occurrence requirements are guidelines, which may be expanded,
6021 and/or overridden by application-specific requirements in the
6022 Diameter applications documents.
6024 +-----------+
6025 | Command |
6026 | Code |
6027 +-----+-----+
6028 Attribute Name | ACR | ACA |
6029 ------------------------------+-----+-----+
6030 Acct-Interim-Interval | 0-1 | 0-1 |
6031 Acct-Multi-Session-Id | 0-1 | 0-1 |
6032 Accounting-Record-Number | 1 | 1 |
6033 Accounting-Record-Type | 1 | 1 |
6034 Acct-Session-Id | 0-1 | 0-1 |
6035 Accounting-Sub-Session-Id | 0-1 | 0-1 |
6036 Accounting-Realtime-Required | 0-1 | 0-1 |
6037 Acct-Application-Id | 0-1 | 0-1 |
6038 Auth-Application-Id | 0 | 0 |
6039 Class | 0+ | 0+ |
6040 Destination-Host | 0-1 | 0 |
6041 Destination-Realm | 1 | 0 |
6042 Error-Reporting-Host | 0 | 0+ |
6043 Event-Timestamp | 0-1 | 0-1 |
6044 Origin-Host | 1 | 1 |
6045 Origin-Realm | 1 | 1 |
6046 Proxy-Info | 0+ | 0+ |
6047 Route-Record | 0+ | 0 |
6048 Result-Code | 0 | 1 |
6049 Session-Id | 1 | 1 |
6050 Termination-Cause | 0 | 0 |
6051 User-Name | 0-1 | 0-1 |
6052 Vendor-Specific-Application-Id| 0-1 | 0-1 |
6053 ------------------------------+-----+-----+
6055 11. IANA Considerations
6057 This section provides guidance to the Internet Assigned Numbers
6058 Authority (IANA) regarding registration of values related to the
6059 Diameter protocol, in accordance with BCP 26 [RFC2434]. The
6060 following policies are used here with the meanings defined in BCP 26:
6061 "Private Use", "First Come First Served", "Expert Review",
6062 "Specification Required", "IETF Review", "Standards Action".
6064 This section explains the criteria to be used by the IANA for
6065 assignment of numbers within namespaces defined within this document.
6067 Diameter is not intended as a general purpose protocol, and
6068 allocations SHOULD NOT be made for purposes unrelated to
6069 authentication, authorization or accounting.
6071 For registration requests where a Designated Expert should be
6072 consulted, the responsible IESG area director should appoint the
6073 Designated Expert. For Designated Expert with Specification
6074 Required, the request is posted to the DIME WG mailing list (or, if
6075 it has been disbanded, a successor designated by the Area Director)
6076 for comment and review, and MUST include a pointer to a public
6077 specification. Before a period of 30 days has passed, the Designated
6078 Expert will either approve or deny the registration request and
6079 publish a notice of the decision to the DIME WG mailing list or its
6080 successor. A denial notice MUST be justified by an explanation and,
6081 in the cases where it is possible, concrete suggestions on how the
6082 request can be modified so as to become acceptable.
6084 11.1. AVP Header
6086 As defined in Section 4, the AVP header contains three fields that
6087 requires IANA namespace management; the AVP Code, Vendor-ID and Flags
6088 field.
6090 11.1.1. AVP Codes
6092 The AVP Code namespace is used to identify attributes. There are
6093 multiple namespaces. Vendors can have their own AVP Codes namespace
6094 which will be identified by their Vendor-ID (also known as
6095 Enterprise-Number) and they control the assignments of their vendor-
6096 specific AVP codes within their own namespace. The absence of a
6097 Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA
6098 controlled AVP Codes namespace. The AVP Codes and sometimes also
6099 possible values in an AVP are controlled and maintained by IANA.
6101 AVP Code 0 is not used. AVP Codes 1-255 are managed separately as
6102 RADIUS Attribute Types [RADTYPE]. This document defines the AVP
6103 Codes 257-274, 276-285, 287, 291-300, 480, 483 and 485-486. See
6104 Section 4.5 for the assignment of the namespace in this
6105 specification.
6107 AVPs may be allocated following Designated Expert with Specification
6108 Required [RFC2434]. Release of blocks of AVPs (more than 3 at a time
6109 for a given purpose) should require IETF Review.
6111 Note that Diameter defines a mechanism for Vendor-Specific AVPs,
6112 where the Vendor-Id field in the AVP header is set to a non-zero
6113 value. Vendor-Specific AVPs codes are for Private Use and should be
6114 encouraged instead of allocation of global attribute types, for
6115 functions specific only to one vendor's implementation of Diameter,
6116 where no interoperability is deemed useful. Where a Vendor-Specific
6117 AVP is implemented by more than one vendor, allocation of global AVPs
6118 should be encouraged instead.
6120 11.1.2. AVP Flags
6122 There are 8 bits in the AVP Flags field of the AVP header, defined in
6123 Section 4. This document assigns bit 0 ('V'endor Specific), bit 1
6124 ('M'andatory) and bit 2 ('P'rotected). The remaining bits should
6125 only be assigned via a Standards Action [RFC2434].
6127 11.2. Diameter Header
6129 As defined in Section 3, the Diameter header contains two fields that
6130 require IANA namespace management; Command Code and Command Flags.
6132 11.2.1. Command Codes
6134 The Command Code namespace is used to identify Diameter commands.
6135 The values 0-255 (0x00-0xff) are reserved for RADIUS backward
6136 compatibility, and are defined as "RADIUS Packet Type Codes" in
6137 [RADTYPE]. Values 256 - 8,388,607 (0x100 to 0x7fffff) are for
6138 permanent, standard commands, allocated by IETF Review [RFC2434].
6139 This document defines the Command Codes 257, 258, 271, 274-275, 280
6140 and 282. See Section 3.1 for the assignment of the namespace in this
6141 specification.
6143 The values 8,388,608 - 16,777,213 (0x800000 - 0xfffffd) are reserved
6144 for vendor-specific command codes, to be allocated on a First Come,
6145 First Served basis by IANA [RFC2434]. The request to IANA for a
6146 Vendor-Specific Command Code SHOULD include a reference to a publicly
6147 available specification which documents the command in sufficient
6148 detail to aid in interoperability between independent
6149 implementations. If the specification cannot be made publicly
6150 available, the request for a vendor-specific command code MUST
6151 include the contact information of persons and/or entities
6152 responsible for authoring and maintaining the command.
6154 The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe -
6155 0xffffff) are reserved for experimental commands. As these codes are
6156 only for experimental and testing purposes, no guarantee is made for
6157 interoperability between Diameter peers using experimental commands,
6158 as outlined in [IANA-EXP].
6160 11.2.2. Command Flags
6162 There are eight bits in the Command Flags field of the Diameter
6163 header. This document assigns bit 0 ('R'equest), bit 1 ('P'roxy),
6164 bit 2 ('E'rror) and bit 3 ('T'). Bits 4 through 7 MUST only be
6165 assigned via a Standards Action [RFC2434].
6167 11.3. Application Identifiers
6169 As defined in Section 2.4, the Application Id is used to identify a
6170 specific Diameter Application. There are standards-track Application
6171 Ids and vendor specific Application Ids.
6173 IANA [RFC2434] has assigned the range 0x00000001 to 0x00ffffff for
6174 standards-track applications; and 0x01000000 - 0xfffffffe for vendor
6175 specific applications, on a first-come, first-served basis. The
6176 following values are allocated.
6178 Diameter Common Messages 0
6179 NASREQ 1 [RFC4005]
6180 Mobile-IP 2 [RFC4004]
6181 Diameter Base Accounting 3
6182 Relay 0xffffffff
6184 Assignment of standards-track Application Ids are by Designated
6185 Expert with Specification Required [RFC2434].
6187 Both Auth-Application-Id and Acct-Application-Id AVPs use the same
6188 Application Id space. A Diameter node advertising itself as a relay
6189 agent MUST set either Application-Id or Acct-Application-Id to
6190 0xffffffff.
6192 Vendor-Specific Application Ids, are for Private Use. Vendor-Specific
6193 Application Ids are assigned on a First Come, First Served basis by
6194 IANA.
6196 11.4. AVP Values
6198 Certain AVPs in Diameter define a list of values with various
6199 meanings. For attributes other than those specified in this section,
6200 adding additional values to the list can be done on a First Come,
6201 First Served basis by IANA.
6203 11.4.1. Result-Code AVP Values
6205 As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines
6206 the values 1001, 2001-2002, 3001-3012, 4001-4003 and 5001-5021.
6208 All remaining values are available for assignment via IETF Review
6209 [RFC2434].
6211 11.4.2. Accounting-Record-Type AVP Values
6213 As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code
6214 480) defines the values 1-4. All remaining values are available for
6215 assignment via IETF Review [RFC2434].
6217 11.4.3. Termination-Cause AVP Values
6219 As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295)
6220 defines the values 1-8. All remaining values are available for
6221 assignment via IETF Review [RFC2434].
6223 11.4.4. Redirect-Host-Usage AVP Values
6225 As defined in Section 6.13, the Redirect-Host-Usage AVP (AVP Code
6226 261) defines the values 0-5. All remaining values are available for
6227 assignment via IETF Review [RFC2434].
6229 11.4.5. Session-Server-Failover AVP Values
6231 As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code
6232 271) defines the values 0-3. All remaining values are available for
6233 assignment via IETF Review [RFC2434].
6235 11.4.6. Session-Binding AVP Values
6237 As defined in Section 8.17, the Session-Binding AVP (AVP Code 270)
6238 defines the bits 1-4. All remaining bits are available for
6239 assignment via IETF Review [RFC2434].
6241 11.4.7. Disconnect-Cause AVP Values
6243 As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273)
6244 defines the values 0-2. All remaining values are available for
6245 assignment via IETF Review [RFC2434].
6247 11.4.8. Auth-Request-Type AVP Values
6249 As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274)
6250 defines the values 1-3. All remaining values are available for
6251 assignment via IETF Review [RFC2434].
6253 11.4.9. Auth-Session-State AVP Values
6255 As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277)
6256 defines the values 0-1. All remaining values are available for
6257 assignment via IETF Review [RFC2434].
6259 11.4.10. Re-Auth-Request-Type AVP Values
6261 As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code
6262 285) defines the values 0-1. All remaining values are available for
6263 assignment via IETF Review [RFC2434].
6265 11.4.11. Accounting-Realtime-Required AVP Values
6267 As defined in Section 9.8.7, the Accounting-Realtime-Required AVP
6268 (AVP Code 483) defines the values 1-3. All remaining values are
6269 available for assignment via IETF Review [RFC2434].
6271 11.4.12. Inband-Security-Id AVP (code 299)
6273 As defined in Section 6.10, the Inband-Security-Id AVP (AVP Code 299)
6274 defines the values 0-1. All remaining values are available for
6275 assignment via IETF Review [RFC2434].
6277 11.5. Diameter TCP/SCTP Port Numbers
6279 The IANA has assigned TCP and SCTP port number 3868 to Diameter.
6281 11.6. NAPTR Service Fields
6283 The registration in the RFC MUST include the following information:
6285 Service Field: The service field being registered. An example for a
6286 new fictitious transport protocol called NCTP might be "AAA+D2N".
6288 Protocol: The specific transport protocol associated with that
6289 service field. This MUST include the name and acronym for the
6290 protocol, along with reference to a document that describes the
6291 transport protocol. For example - "New Connectionless Transport
6292 Protocol (NCTP), RFC XYZ".
6294 Name and Contact Information: The name, address, email address and
6295 telephone number for the person performing the registration.
6297 The following values have been placed into the registry:
6299 Services Field Protocol
6301 AAA+D2T TCP
6302 AAA+D2S SCTP
6304 12. Diameter protocol related configurable parameters
6306 This section contains the configurable parameters that are found
6307 throughout this document:
6309 Diameter Peer
6311 A Diameter entity MAY communicate with peers that are statically
6312 configured. A statically configured Diameter peer would require
6313 that either the IP address or the fully qualified domain name
6314 (FQDN) be supplied, which would then be used to resolve through
6315 DNS.
6317 Routing Table
6319 A Diameter proxy server routes messages based on the realm portion
6320 of a Network Access Identifier (NAI). The server MUST have a
6321 table of Realm Names, and the address of the peer to which the
6322 message must be forwarded to. The routing table MAY also include
6323 a "default route", which is typically used for all messages that
6324 cannot be locally processed.
6326 Tc timer
6328 The Tc timer controls the frequency that transport connection
6329 attempts are done to a peer with whom no active transport
6330 connection exists. The recommended value is 30 seconds.
6332 13. Security Considerations
6334 The Diameter base protocol messages SHOULD be secured by using TLS
6335 [RFC4346]. Additional security measures that are transparent to and
6336 independent of Diameter, such as IPSec [RFC4301], can also be
6337 deployed to secure connections between peers.
6339 During deployment, connections between Diameter nodes SHOULD be
6340 protected by TLS. All Diameter base protocol implementations MUST
6341 support the use of TLS. The Diameter protocol MUST NOT be used
6342 without any security mechanism.
6344 If a Diameter connection is to be protected via TLS, then the CER/CEA
6345 exchange MUST include an Inband-Security-ID AVP with a value of TLS.
6346 For TLS usage, a TLS handshake will begin when both ends are in the
6347 open state, after completion of the CER/CEA exchange. If the TLS
6348 handshake is successful, all further messages will be sent via TLS.
6349 If the handshake fails, both ends move to the closed state. See
6350 Sections 13.1 for more details.
6352 13.1. TLS Usage
6354 A Diameter node that initiates a connection to another Diameter node
6355 acts as a TLS client according to [RFC4346], and a Diameter node that
6356 accepts a connection acts as a TLS server. Diameter nodes
6357 implementing TLS for security MUST mutually authenticate as part of
6358 TLS session establishment. In order to ensure mutual authentication,
6359 the Diameter node acting as TLS server MUST request a certificate
6360 from the Diameter node acting as TLS client, and the Diameter node
6361 acting as TLS client MUST be prepared to supply a certificate on
6362 request.
6364 Diameter nodes MUST be able to negotiate the following TLS cipher
6365 suites:
6367 TLS_RSA_WITH_RC4_128_MD5
6368 TLS_RSA_WITH_RC4_128_SHA
6369 TLS_RSA_WITH_3DES_EDE_CBC_SHA
6371 Diameter nodes SHOULD be able to negotiate the following TLS cipher
6372 suite:
6374 TLS_RSA_WITH_AES_128_CBC_SHA
6376 Diameter nodes MAY negotiate other TLS cipher suites.
6378 Upon receiving the peers certificate, Diameter nodes SHOULD further
6379 validate the identity of the peer by matching the received Origin-
6380 Host and/or Origin-Realm in the CER and CEA exchange against the
6381 content of the peers certificate. Diameter peer hostname and/or
6382 realm validation can be performed in the following order:
6384 o If one or more 'Subject Alternate Name (subjectAltName)' extension
6385 of type dNSName is present in the certificate (See [RFC3280]),
6386 then the Origin-Host value can be used to find a matching
6387 extension.
6389 o If there are no matches found, then the Origin-Realm value can be
6390 used to find a matching subjectAltName extension.
6392 o Otherwise, the Origin-Host value should be found within the
6393 'Common Name (CN)' field in the Subject field of the certificate
6394 (See [RFC3280]).
6396 Identity validation MAY be omitted by a Diameter node if the
6397 information contained in the certificate cannot be correlated or
6398 mapped to the Origin-Host and Origin-Realm presented by a peer.
6399 However, the Diameter node SHOULD have external information or other
6400 means to validate the identity of a peer.
6402 13.2. Peer-to-Peer Considerations
6404 As with any peer-to-peer protocol, proper configuration of the trust
6405 model within a Diameter peer is essential to security. When
6406 certificates are used, it is necessary to configure the root
6407 certificate authorities trusted by the Diameter peer. These root CAs
6408 are likely to be unique to Diameter usage and distinct from the root
6409 CAs that might be trusted for other purposes such as Web browsing.
6410 In general, it is expected that those root CAs will be configured so
6411 as to reflect the business relationships between the organization
6412 hosting the Diameter peer and other organizations. As a result, a
6413 Diameter peer will typically not be configured to allow connectivity
6414 with any arbitrary peer. With certificate authentication, Diameter
6415 peers may not be known beforehand and therefore peer discovery may be
6416 required.
6418 14. References
6420 14.1. Normative References
6422 [FLOATPOINT]
6423 Institute of Electrical and Electronics Engineers, "IEEE
6424 Standard for Binary Floating-Point Arithmetic, ANSI/IEEE
6425 Standard 754-1985", August 1985.
6427 [IANAADFAM]
6428 IANA,, "Address Family Numbers",
6429 http://www.iana.org/assignments/address-family-numbers.
6431 [RADTYPE] IANA,, "RADIUS Types",
6432 http://www.iana.org/assignments/radius-types.
6434 [RFC791] Postel, J., "Internet Protocol", RFC 791, September 1981.
6436 [RFC793] Postel, J., "Transmission Control Protocol", RFC 793,
6437 January 1981.
6439 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and
6440 Accounting (AAA) Transport Profile", RFC 3539, June 2003.
6442 [RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and
6443 P. McCann, "Diameter Mobile IPv4 Application", RFC 4004,
6444 August 2005.
6446 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
6447 "Diameter Network Access Server Application", RFC 4005,
6448 August 2005.
6450 [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
6451 Loughney, "Diameter Credit-Control Application", RFC 4006,
6452 August 2005.
6454 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
6455 Authentication Protocol (EAP) Application", RFC 4072,
6456 August 2005.
6458 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M.,
6459 Canales-Valenzuela, C., and K. Tammi, "Diameter Session
6460 Initiation Protocol (SIP) Application", RFC 4740,
6461 November 2006.
6463 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
6464 Specifications: ABNF", RFC 4234, October 2005.
6466 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
6467 Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
6469 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
6470 IANA Considerations Section in RFCs", BCP 26, RFC 2434,
6471 October 1998.
6473 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
6474 RFC 4306, December 2005.
6476 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
6477 Architecture", RFC 4291, February 2006.
6479 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
6480 Requirement Levels", BCP 14, RFC 2119, March 1997.
6482 [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
6483 Network Access Identifier", RFC 4282, December 2005.
6485 [RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS)
6486 Part Three: The Domain Name System (DNS) Database",
6487 RFC 3403, October 2002.
6489 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
6490 A., Peterson, J., Sparks, R., Handley, M., and E.
6491 Schooler, "SIP: Session Initiation Protocol", RFC 3261,
6492 June 2002.
6494 [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
6495 Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
6496 Zhang, L., and V. Paxson, "Stream Control Transmission
6497 Protocol", RFC 2960, October 2000.
6499 [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
6500 (TLS) Protocol Version 1.1", RFC 4346, April 2006.
6502 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
6503 Resource Identifier (URI): Generic Syntax", STD 66,
6504 RFC 3986, January 2005.
6506 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
6507 10646", STD 63, RFC 3629, November 2003.
6509 [RFC3280] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
6510 X.509 Public Key Infrastructure Certificate and
6511 Certificate Revocation List (CRL) Profile", RFC 3280,
6512 April 2002.
6514 [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
6515 "Internationalizing Domain Names in Applications (IDNA)",
6516 RFC 3490, March 2003.
6518 [RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
6519 Profile for Internationalized Domain Names (IDN)",
6520 RFC 3491, March 2003.
6522 [RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode
6523 for Internationalized Domain Names in Applications
6524 (IDNA)", RFC 3492, March 2003.
6526 14.2. Informational References
6528 [RFC2989] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, P.,
6529 Shiino, H., Zorn, G., Dommety, G., C.Perkins, B.Patil,
6530 D.Mitton, S.Manning, M.Beadles, P.Walsh, X.Chen,
6531 S.Sivalingham, A.Hameed, M.Munson, S.Jacobs, B.Lim,
6532 B.Hirschman, R.Hsu, Y.Xu, E.Campell, S.Baba, and E.Jaques,
6533 "Criteria for Evaluating AAA Protocols for Network
6534 Access", RFC 2989, November 2000.
6536 [RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction to
6537 Accounting Management", RFC 2975, October 2000.
6539 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by
6540 an On-line Database", RFC 3232, January 2002.
6542 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
6543 Aboba, "Dynamic Authorization Extensions to Remote
6544 Authentication Dial In User Service (RADIUS)", RFC 3576,
6545 July 2003.
6547 [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,
6548 RFC 1661, July 1994.
6550 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.
6552 [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS
6553 Extensions", RFC 2869, June 2000.
6555 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
6556 "Remote Authentication Dial In User Service (RADIUS)",
6557 RFC 2865, June 2000.
6559 [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6",
6560 RFC 3162, August 2001.
6562 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
6563 Internet Protocol", RFC 4301, December 2005.
6565 [RFC4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
6566 for IPv4, IPv6 and OSI", RFC 4330, January 2006.
6568 [RFC1492] Finseth, C., "An Access Control Protocol, Sometimes Called
6569 TACACS", RFC 1492, July 1993.
6571 [RFC4690] Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and
6572 Recommendations for Internationalized Domain Names
6573 (IDNs)", RFC 4690, September 2006.
6575 [IANA-EXP]
6576 Narten, T., "Assigning Experimental and Testing Numbers
6577 Considered Useful, Work in Progress.".
6579 Appendix A. Acknowledgements
6581 The authors would like to thank the following people that have
6582 provided proposals and contributions to this document:
6584 To Vishnu Ram and Satendra Gera for their contributions on
6585 Capabilities Updates, Predictive Loop Avoidance as well as many other
6586 technical proposals. To Tolga Asveren for his insights and
6587 contributions on almost all of the proposed solutions incorporated
6588 into this document. To Timothy Smith for helping on the Capabilities
6589 Updates and other topics. To Tony Zhang for providing fixes to loop
6590 holes on composing Failed-AVPs as well as many other issues and
6591 topics. To Jan Nordqvist for clearly stating the usage of
6592 Application Ids. To Anders Kristensen for providing needed technical
6593 opinions. To David Frascone for providing invaluable review of the
6594 document. To Mark Jones for providing clarifying text on vendor
6595 command codes and other vendor specific indicators.
6597 Special thanks also to people who have provided invaluable comments
6598 and inputs especially in resolving controversial issues:
6600 Glen Zorn, Yoshihiro Ohba, Marco Stura, and Pasi Eronen.
6602 Finally, we would like to thank the original authors of this
6603 document:
6605 Pat Calhoun, John Loughney, Jari Arkko, Erik Guttman and Glen Zorn.
6607 Their invaluable knowledge and experience has given us a robust and
6608 flexible AAA protocol that many people have seen great value in
6609 adopting. We greatly appreciate their support and stewardship for
6610 the continued improvements of Diameter as a protocol. We would also
6611 like to extend our gratitude to folks aside from the authors who have
6612 assisted and contributed to the original version of this document.
6613 Their efforts significantly contributed to the success of Diameter.
6615 Appendix B. NAPTR Example
6617 As an example, consider a client that wishes to resolve aaa:ex.com.
6618 The client performs a NAPTR query for that domain, and the following
6619 NAPTR records are returned:
6621 ;; order pref flags service regexp replacement
6622 IN NAPTR 50 50 "s" "AAA+D2S" "" _diameter._sctp.example.com
6623 IN NAPTR 100 50 "s" "AAA+D2T" "" _aaa._tcp.example.com
6625 This indicates that the server supports SCTP, and TCP, in that order.
6626 If the client supports over SCTP, SCTP will be used, targeted to a
6627 host determined by an SRV lookup of _diameter._sctp.ex.com. That
6628 lookup would return:
6630 ;; Priority Weight Port Target
6631 IN SRV 0 1 5060 server1.example.com
6632 IN SRV 0 2 5060 server2.example.com
6634 Appendix C. Duplicate Detection
6636 As described in Section 9.4, accounting record duplicate detection is
6637 based on session identifiers. Duplicates can appear for various
6638 reasons:
6640 o Failover to an alternate server. Where close to real-time
6641 performance is required, failover thresholds need to be kept low
6642 and this may lead to an increased likelihood of duplicates.
6643 Failover can occur at the client or within Diameter agents.
6645 o Failure of a client or agent after sending of a record from non-
6646 volatile memory, but prior to receipt of an application layer ACK
6647 and deletion of the record. record to be sent. This will result
6648 in retransmission of the record soon after the client or agent has
6649 rebooted.
6651 o Duplicates received from RADIUS gateways. Since the
6652 retransmission behavior of RADIUS is not defined within [RFC2865],
6653 the likelihood of duplication will vary according to the
6654 implementation.
6656 o Implementation problems and misconfiguration.
6658 The T flag is used as an indication of an application layer
6659 retransmission event, e.g., due to failover to an alternate server.
6660 It is defined only for request messages sent by Diameter clients or
6661 agents. For instance, after a reboot, a client may not know whether
6662 it has already tried to send the accounting records in its non-
6663 volatile memory before the reboot occurred. Diameter servers MAY use
6664 the T flag as an aid when processing requests and detecting duplicate
6665 messages. However, servers that do this MUST ensure that duplicates
6666 are found even when the first transmitted request arrives at the
6667 server after the retransmitted request. It can be used only in cases
6668 where no answer has been received from the Server for a request and
6669 the request is sent again, (e.g., due to a failover to an alternate
6670 peer, due to a recovered primary peer or due to a client re-sending a
6671 stored record from non-volatile memory such as after reboot of a
6672 client or agent).
6674 In some cases the Diameter accounting server can delay the duplicate
6675 detection and accounting record processing until a post-processing
6676 phase takes place. At that time records are likely to be sorted
6677 according to the included User-Name and duplicate elimination is easy
6678 in this case. In other situations it may be necessary to perform
6679 real-time duplicate detection, such as when credit limits are imposed
6680 or real-time fraud detection is desired.
6682 In general, only generation of duplicates due to failover or re-
6683 sending of records in non-volatile storage can be reliably detected
6684 by Diameter clients or agents. In such cases the Diameter client or
6685 agents can mark the message as possible duplicate by setting the T
6686 flag. Since the Diameter server is responsible for duplicate
6687 detection, it can choose to make use of the T flag or not, in order
6688 to optimize duplicate detection. Since the T flag does not affect
6689 interoperability, and may not be needed by some servers, generation
6690 of the T flag is REQUIRED for Diameter clients and agents, but MAY be
6691 implemented by Diameter servers.
6693 As an example, it can be usually be assumed that duplicates appear
6694 within a time window of longest recorded network partition or device
6695 fault, perhaps a day. So only records within this time window need
6696 to be looked at in the backward direction. Secondly, hashing
6697 techniques or other schemes, such as the use of the T flag in the
6698 received messages, may be used to eliminate the need to do a full
6699 search even in this set except for rare cases.
6701 The following is an example of how the T flag may be used by the
6702 server to detect duplicate requests.
6704 A Diameter server MAY check the T flag of the received message to
6705 determine if the record is a possible duplicate. If the T flag is
6706 set in the request message, the server searches for a duplicate
6707 within a configurable duplication time window backward and
6708 forward. This limits database searching to those records where
6709 the T flag is set. In a well run network, network partitions and
6710 device faults will presumably be rare events, so this approach
6711 represents a substantial optimization of the duplicate detection
6712 process. During failover, it is possible for the original record
6713 to be received after the T flag marked record, due to differences
6714 in network delays experienced along the path by the original and
6715 duplicate transmissions. The likelihood of this occurring
6716 increases as the failover interval is decreased. In order to be
6717 able to detect out of order duplicates, the Diameter server should
6718 use backward and forward time windows when performing duplicate
6719 checking for the T flag marked request. For example, in order to
6720 allow time for the original record to exit the network and be
6721 recorded by the accounting server, the Diameter server can delay
6722 processing records with the T flag set until a time period
6723 TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after the closing
6724 of the original transport connection. After this time period has
6725 expired, then it may check the T flag marked records against the
6726 database with relative assurance that the original records, if
6727 sent, have been received and recorded.
6729 Appendix D. Internationalized Domain Names
6731 To be compatible with the existing DNS infrastructure and simplify
6732 host and domain name comparison, Diameter identities (FQDNs) are
6733 represented in ASCII form. This allows the Diameter protocol to fall
6734 in-line with the DNS strategy of being transparent from the effects
6735 of Internationalized Domain Names (IDNs) by following the
6736 recommnedations in [RFC4690] and [RFC3490]. Applications that
6737 provide support for IDNs outside of the Diameter protocol but
6738 interacting with it SHOULD use the representation and conversion
6739 framework described in [RFC3490], [RFC3491] and [RFC3492].
6741 Authors' Addresses
6743 Victor Fajardo (editor)
6744 Toshiba America Research
6745 One Telcordia Drive, 1S-222
6746 Piscataway, NJ 08854
6747 USA
6749 Phone: 1 908-421-1845
6750 Email: vfajardo@tari.toshiba.com
6752 Jari Arkko
6753 Ericsson Research
6754 02420 Jorvas
6755 Finland
6757 Phone: +358 40 5079256
6758 Email: jari.arkko@ericsson.com
6760 John Loughney
6761 Nokia Research Center
6762 955 Page Mill Road
6763 Palo Alto, CA 94304
6764 US
6766 Phone: 1-650-283-8068
6767 Email: john.loughney@nokia.com
6769 Glenn Zorn
6770 NetCube
6771 1310 East Thomas Street, #306
6772 Seattle, WA 98102
6773 US
6775 Phone:
6776 Email: glenzorn@comcast.net
6778 Full Copyright Statement
6780 Copyright (C) The IETF Trust (2008).
6782 This document is subject to the rights, licenses and restrictions
6783 contained in BCP 78, and except as set forth therein, the authors
6784 retain all their rights.
6786 This document and the information contained herein are provided on an
6787 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
6788 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
6789 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
6790 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
6791 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
6792 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
6794 Intellectual Property
6796 The IETF takes no position regarding the validity or scope of any
6797 Intellectual Property Rights or other rights that might be claimed to
6798 pertain to the implementation or use of the technology described in
6799 this document or the extent to which any license under such rights
6800 might or might not be available; nor does it represent that it has
6801 made any independent effort to identify any such rights. Information
6802 on the procedures with respect to rights in RFC documents can be
6803 found in BCP 78 and BCP 79.
6805 Copies of IPR disclosures made to the IETF Secretariat and any
6806 assurances of licenses to be made available, or the result of an
6807 attempt made to obtain a general license or permission for the use of
6808 such proprietary rights by implementers or users of this
6809 specification can be obtained from the IETF on-line IPR repository at
6810 http://www.ietf.org/ipr.
6812 The IETF invites any interested party to bring to its attention any
6813 copyrights, patents or patent applications, or other proprietary
6814 rights that may cover technology that may be required to implement
6815 this standard. Please address the information to the IETF at
6816 ietf-ipr@ietf.org.
6818 Acknowledgment
6820 Funding for the RFC Editor function is provided by the IETF
6821 Administrative Support Activity (IASA).