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** Obsolete normative reference: RFC 793 (Obsoleted by RFC 9293)
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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: May 28, 2009 J. Loughney
7 Nokia Research Center
8 G. Zorn
9 NetCube
10 November 24, 2008
12 Diameter Base Protocol
13 draft-ietf-dime-rfc3588bis-14.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 May 28, 2009.
40 Abstract
42 The Diameter base protocol is intended to provide an Authentication,
43 Authorization and Accounting (AAA) framework for applications such as
44 network access or IP mobility. Diameter is also intended to work in
45 both local Authentication, Authorization & Accounting and roaming
46 situations. This document specifies the message format, transport,
47 error reporting, accounting and security services to be used by all
48 Diameter applications. The Diameter base application needs to be
49 supported by all Diameter implementations.
51 Table of Contents
53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7
54 1.1. Diameter Protocol . . . . . . . . . . . . . . . . . . . . 9
55 1.1.1. Description of the Document Set . . . . . . . . . . 11
56 1.1.2. Conventions Used in This Document . . . . . . . . . 12
57 1.1.3. Changes from RFC3588 . . . . . . . . . . . . . . . . 12
58 1.2. Approach to Extensibility . . . . . . . . . . . . . . . . 13
59 1.2.1. Defining New AVP Values . . . . . . . . . . . . . . 13
60 1.2.2. Creating New AVPs . . . . . . . . . . . . . . . . . 13
61 1.2.3. Creating New Commands . . . . . . . . . . . . . . . 14
62 1.2.4. Creating New Diameter Applications . . . . . . . . . 14
63 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 15
64 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 22
65 2.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 23
66 2.1.1. SCTP Guidelines . . . . . . . . . . . . . . . . . . 24
67 2.2. Securing Diameter Messages . . . . . . . . . . . . . . . 24
68 2.3. Diameter Application Compliance . . . . . . . . . . . . . 24
69 2.4. Application Identifiers . . . . . . . . . . . . . . . . . 24
70 2.5. Connections vs. Sessions . . . . . . . . . . . . . . . . 25
71 2.6. Peer Table . . . . . . . . . . . . . . . . . . . . . . . 26
72 2.7. Routing Table . . . . . . . . . . . . . . . . . . . . . . 27
73 2.8. Role of Diameter Agents . . . . . . . . . . . . . . . . . 28
74 2.8.1. Relay Agents . . . . . . . . . . . . . . . . . . . . 30
75 2.8.2. Proxy Agents . . . . . . . . . . . . . . . . . . . . 31
76 2.8.3. Redirect Agents . . . . . . . . . . . . . . . . . . 31
77 2.8.4. Translation Agents . . . . . . . . . . . . . . . . . 32
78 2.9. Diameter Path Authorization . . . . . . . . . . . . . . . 33
79 3. Diameter Header . . . . . . . . . . . . . . . . . . . . . . . 35
80 3.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 38
81 3.2. Command Code ABNF specification . . . . . . . . . . . . . 38
82 3.3. Diameter Command Naming Conventions . . . . . . . . . . . 41
83 4. Diameter AVPs . . . . . . . . . . . . . . . . . . . . . . . . 42
84 4.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 42
85 4.1.1. Optional Header Elements . . . . . . . . . . . . . . 43
86 4.2. Basic AVP Data Formats . . . . . . . . . . . . . . . . . 44
87 4.3. Derived AVP Data Formats . . . . . . . . . . . . . . . . 45
88 4.4. Grouped AVP Values . . . . . . . . . . . . . . . . . . . 52
89 4.4.1. Example AVP with a Grouped Data type . . . . . . . . 53
90 4.5. Diameter Base Protocol AVPs . . . . . . . . . . . . . . . 56
91 5. Diameter Peers . . . . . . . . . . . . . . . . . . . . . . . 59
92 5.1. Peer Connections . . . . . . . . . . . . . . . . . . . . 59
93 5.2. Diameter Peer Discovery . . . . . . . . . . . . . . . . . 59
94 5.3. Capabilities Exchange . . . . . . . . . . . . . . . . . . 62
95 5.3.1. Capabilities-Exchange-Request . . . . . . . . . . . 63
96 5.3.2. Capabilities-Exchange-Answer . . . . . . . . . . . . 64
97 5.3.3. Vendor-Id AVP . . . . . . . . . . . . . . . . . . . 64
98 5.3.4. Firmware-Revision AVP . . . . . . . . . . . . . . . 64
99 5.3.5. Host-IP-Address AVP . . . . . . . . . . . . . . . . 65
100 5.3.6. Supported-Vendor-Id AVP . . . . . . . . . . . . . . 65
101 5.3.7. Product-Name AVP . . . . . . . . . . . . . . . . . . 65
102 5.4. Disconnecting Peer connections . . . . . . . . . . . . . 65
103 5.4.1. Disconnect-Peer-Request . . . . . . . . . . . . . . 66
104 5.4.2. Disconnect-Peer-Answer . . . . . . . . . . . . . . . 66
105 5.4.3. Disconnect-Cause AVP . . . . . . . . . . . . . . . . 67
106 5.5. Transport Failure Detection . . . . . . . . . . . . . . . 67
107 5.5.1. Device-Watchdog-Request . . . . . . . . . . . . . . 67
108 5.5.2. Device-Watchdog-Answer . . . . . . . . . . . . . . . 68
109 5.5.3. Transport Failure Algorithm . . . . . . . . . . . . 68
110 5.5.4. Failover and Failback Procedures . . . . . . . . . . 68
111 5.6. Peer State Machine . . . . . . . . . . . . . . . . . . . 69
112 5.6.1. Incoming connections . . . . . . . . . . . . . . . . 71
113 5.6.2. Events . . . . . . . . . . . . . . . . . . . . . . . 72
114 5.6.3. Actions . . . . . . . . . . . . . . . . . . . . . . 73
115 5.6.4. The Election Process . . . . . . . . . . . . . . . . 75
116 6. Diameter message processing . . . . . . . . . . . . . . . . . 76
117 6.1. Diameter Request Routing Overview . . . . . . . . . . . . 76
118 6.1.1. Originating a Request . . . . . . . . . . . . . . . 77
119 6.1.2. Sending a Request . . . . . . . . . . . . . . . . . 77
120 6.1.3. Receiving Requests . . . . . . . . . . . . . . . . . 78
121 6.1.4. Processing Local Requests . . . . . . . . . . . . . 78
122 6.1.5. Request Forwarding . . . . . . . . . . . . . . . . . 78
123 6.1.6. Request Routing . . . . . . . . . . . . . . . . . . 78
124 6.1.7. Predictive Loop Avoidance . . . . . . . . . . . . . 79
125 6.1.8. Redirecting Requests . . . . . . . . . . . . . . . . 79
126 6.1.9. Relaying and Proxying Requests . . . . . . . . . . . 80
127 6.2. Diameter Answer Processing . . . . . . . . . . . . . . . 82
128 6.2.1. Processing received Answers . . . . . . . . . . . . 82
129 6.2.2. Relaying and Proxying Answers . . . . . . . . . . . 82
130 6.3. Origin-Host AVP . . . . . . . . . . . . . . . . . . . . . 83
131 6.4. Origin-Realm AVP . . . . . . . . . . . . . . . . . . . . 83
132 6.5. Destination-Host AVP . . . . . . . . . . . . . . . . . . 83
133 6.6. Destination-Realm AVP . . . . . . . . . . . . . . . . . . 84
134 6.7. Routing AVPs . . . . . . . . . . . . . . . . . . . . . . 84
135 6.7.1. Route-Record AVP . . . . . . . . . . . . . . . . . . 84
136 6.7.2. Proxy-Info AVP . . . . . . . . . . . . . . . . . . . 84
137 6.7.3. Proxy-Host AVP . . . . . . . . . . . . . . . . . . . 85
138 6.7.4. Proxy-State AVP . . . . . . . . . . . . . . . . . . 85
139 6.8. Auth-Application-Id AVP . . . . . . . . . . . . . . . . . 85
140 6.9. Acct-Application-Id AVP . . . . . . . . . . . . . . . . . 85
141 6.10. Inband-Security-Id AVP . . . . . . . . . . . . . . . . . 85
142 6.11. Vendor-Specific-Application-Id AVP . . . . . . . . . . . 86
143 6.12. Redirect-Host AVP . . . . . . . . . . . . . . . . . . . . 87
144 6.13. Redirect-Host-Usage AVP . . . . . . . . . . . . . . . . . 87
145 6.14. Redirect-Max-Cache-Time AVP . . . . . . . . . . . . . . . 88
146 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 90
147 7.1. Result-Code AVP . . . . . . . . . . . . . . . . . . . . . 91
148 7.1.1. Informational . . . . . . . . . . . . . . . . . . . 92
149 7.1.2. Success . . . . . . . . . . . . . . . . . . . . . . 92
150 7.1.3. Protocol Errors . . . . . . . . . . . . . . . . . . 93
151 7.1.4. Transient Failures . . . . . . . . . . . . . . . . . 94
152 7.1.5. Permanent Failures . . . . . . . . . . . . . . . . . 95
153 7.2. Error Bit . . . . . . . . . . . . . . . . . . . . . . . . 98
154 7.3. Error-Message AVP . . . . . . . . . . . . . . . . . . . . 98
155 7.4. Error-Reporting-Host AVP . . . . . . . . . . . . . . . . 98
156 7.5. Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . . 99
157 7.6. Experimental-Result AVP . . . . . . . . . . . . . . . . . 100
158 7.7. Experimental-Result-Code AVP . . . . . . . . . . . . . . 100
159 8. Diameter User Sessions . . . . . . . . . . . . . . . . . . . 101
160 8.1. Authorization Session State Machine . . . . . . . . . . . 102
161 8.2. Accounting Session State Machine . . . . . . . . . . . . 107
162 8.3. Server-Initiated Re-Auth . . . . . . . . . . . . . . . . 112
163 8.3.1. Re-Auth-Request . . . . . . . . . . . . . . . . . . 112
164 8.3.2. Re-Auth-Answer . . . . . . . . . . . . . . . . . . . 113
165 8.4. Session Termination . . . . . . . . . . . . . . . . . . . 114
166 8.4.1. Session-Termination-Request . . . . . . . . . . . . 115
167 8.4.2. Session-Termination-Answer . . . . . . . . . . . . . 115
168 8.5. Aborting a Session . . . . . . . . . . . . . . . . . . . 116
169 8.5.1. Abort-Session-Request . . . . . . . . . . . . . . . 116
170 8.5.2. Abort-Session-Answer . . . . . . . . . . . . . . . . 117
171 8.6. Inferring Session Termination from Origin-State-Id . . . 118
172 8.7. Auth-Request-Type AVP . . . . . . . . . . . . . . . . . . 118
173 8.8. Session-Id AVP . . . . . . . . . . . . . . . . . . . . . 119
174 8.9. Authorization-Lifetime AVP . . . . . . . . . . . . . . . 120
175 8.10. Auth-Grace-Period AVP . . . . . . . . . . . . . . . . . . 121
176 8.11. Auth-Session-State AVP . . . . . . . . . . . . . . . . . 121
177 8.12. Re-Auth-Request-Type AVP . . . . . . . . . . . . . . . . 121
178 8.13. Session-Timeout AVP . . . . . . . . . . . . . . . . . . . 122
179 8.14. User-Name AVP . . . . . . . . . . . . . . . . . . . . . . 122
180 8.15. Termination-Cause AVP . . . . . . . . . . . . . . . . . . 122
181 8.16. Origin-State-Id AVP . . . . . . . . . . . . . . . . . . . 124
182 8.17. Session-Binding AVP . . . . . . . . . . . . . . . . . . . 124
183 8.18. Session-Server-Failover AVP . . . . . . . . . . . . . . . 125
184 8.19. Multi-Round-Time-Out AVP . . . . . . . . . . . . . . . . 126
185 8.20. Class AVP . . . . . . . . . . . . . . . . . . . . . . . . 126
186 8.21. Event-Timestamp AVP . . . . . . . . . . . . . . . . . . . 126
187 9. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . 127
188 9.1. Server Directed Model . . . . . . . . . . . . . . . . . . 127
189 9.2. Protocol Messages . . . . . . . . . . . . . . . . . . . . 128
190 9.3. Accounting Application Extension and Requirements . . . . 128
191 9.4. Fault Resilience . . . . . . . . . . . . . . . . . . . . 129
192 9.5. Accounting Records . . . . . . . . . . . . . . . . . . . 129
193 9.6. Correlation of Accounting Records . . . . . . . . . . . . 130
194 9.7. Accounting Command-Codes . . . . . . . . . . . . . . . . 131
195 9.7.1. Accounting-Request . . . . . . . . . . . . . . . . . 131
196 9.7.2. Accounting-Answer . . . . . . . . . . . . . . . . . 132
197 9.8. Accounting AVPs . . . . . . . . . . . . . . . . . . . . . 133
198 9.8.1. Accounting-Record-Type AVP . . . . . . . . . . . . . 133
199 9.8.2. Acct-Interim-Interval AVP . . . . . . . . . . . . . 134
200 9.8.3. Accounting-Record-Number AVP . . . . . . . . . . . . 135
201 9.8.4. Acct-Session-Id AVP . . . . . . . . . . . . . . . . 135
202 9.8.5. Acct-Multi-Session-Id AVP . . . . . . . . . . . . . 135
203 9.8.6. Accounting-Sub-Session-Id AVP . . . . . . . . . . . 135
204 9.8.7. Accounting-Realtime-Required AVP . . . . . . . . . . 136
205 10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . 137
206 10.1. Base Protocol Command AVP Table . . . . . . . . . . . . . 137
207 10.2. Accounting AVP Table . . . . . . . . . . . . . . . . . . 138
208 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 140
209 11.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 140
210 11.1.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . 140
211 11.1.2. AVP Flags . . . . . . . . . . . . . . . . . . . . . 141
212 11.2. Diameter Header . . . . . . . . . . . . . . . . . . . . . 141
213 11.2.1. Command Codes . . . . . . . . . . . . . . . . . . . 141
214 11.2.2. Command Flags . . . . . . . . . . . . . . . . . . . 142
215 11.3. Application Identifiers . . . . . . . . . . . . . . . . . 142
216 11.4. AVP Values . . . . . . . . . . . . . . . . . . . . . . . 142
217 11.4.1. Result-Code AVP Values . . . . . . . . . . . . . . . 143
218 11.4.2. Accounting-Record-Type AVP Values . . . . . . . . . 143
219 11.4.3. Termination-Cause AVP Values . . . . . . . . . . . . 143
220 11.4.4. Redirect-Host-Usage AVP Values . . . . . . . . . . . 143
221 11.4.5. Session-Server-Failover AVP Values . . . . . . . . . 143
222 11.4.6. Session-Binding AVP Values . . . . . . . . . . . . . 143
223 11.4.7. Disconnect-Cause AVP Values . . . . . . . . . . . . 143
224 11.4.8. Auth-Request-Type AVP Values . . . . . . . . . . . . 143
225 11.4.9. Auth-Session-State AVP Values . . . . . . . . . . . 144
226 11.4.10. Re-Auth-Request-Type AVP Values . . . . . . . . . . 144
227 11.4.11. Accounting-Realtime-Required AVP Values . . . . . . 144
228 11.4.12. Inband-Security-Id AVP (code 299) . . . . . . . . . 144
229 11.5. Diameter TCP/SCTP Port Numbers . . . . . . . . . . . . . 144
230 11.6. NAPTR Service Fields . . . . . . . . . . . . . . . . . . 144
232 12. Diameter protocol related configurable parameters . . . . . . 146
233 13. Security Considerations . . . . . . . . . . . . . . . . . . . 147
234 13.1. TLS Usage . . . . . . . . . . . . . . . . . . . . . . . . 147
235 13.2. Peer-to-Peer Considerations . . . . . . . . . . . . . . . 148
236 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 149
237 14.1. Normative References . . . . . . . . . . . . . . . . . . 149
238 14.2. Informational References . . . . . . . . . . . . . . . . 151
239 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 153
240 A.1. RFC3588bis . . . . . . . . . . . . . . . . . . . . . . . 153
241 A.2. RFC3588 . . . . . . . . . . . . . . . . . . . . . . . . . 154
242 Appendix B. NAPTR Example . . . . . . . . . . . . . . . . . . . 155
243 Appendix C. Duplicate Detection . . . . . . . . . . . . . . . . 156
244 Appendix D. Internationalized Domain Names . . . . . . . . . . . 158
245 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 159
246 Intellectual Property and Copyright Statements . . . . . . . . . 160
248 1. Introduction
250 Authentication, Authorization and Accounting (AAA) protocols such as
251 TACACS [RFC1492] and RADIUS [RFC2865] were initially deployed to
252 provide dial-up PPP [RFC1661] and terminal server access. Over time,
253 with the growth of the Internet and the introduction of new access
254 technologies (including wireless, DSL, Mobile IP and Ethernet), both
255 the amount and complexity of processing performed by routers and
256 network access servers (NAS) have increased, putting new demands on
257 AAA protocols.
259 Network access requirements for AAA protocols are summarized in
260 [RFC2989]. These include:
262 Failover
264 [RFC2865] does not define failover mechanisms, and as a result,
265 failover behavior differs between implementations. In order to
266 provide well defined failover behavior, Diameter supports
267 application-layer acknowledgements, and defines failover
268 algorithms and the associated state machine. This is described in
269 Section 5.5 and [RFC3539].
271 Transmission-level security
273 [RFC2865] defines an application-layer authentication and
274 integrity scheme that is required only for use with Response
275 packets. While [RFC2869] defines an additional authentication and
276 integrity mechanism, use is only required during Extensible
277 Authentication Protocol (EAP) sessions. While attribute-hiding is
278 supported, [RFC2865] does not provide support for per-packet
279 confidentiality. In accounting, [RFC2866] assumes that replay
280 protection is provided by the backend billing server, rather than
281 within the protocol itself.
283 While [RFC3162] defines the use of IPsec with RADIUS, support for
284 IPsec is not required. Since within [RFC4306] authentication
285 occurs only within Phase 1 prior to the establishment of IPsec SAs
286 in Phase 2, it is typically not possible to define separate trust
287 or authorization schemes for each application. This limits the
288 usefulness of IPsec in inter-domain AAA applications (such as
289 roaming) where it may be desirable to define a distinct
290 certificate hierarchy for use in a AAA deployment. In order to
291 provide universal support for transmission-level security, and
292 enable both intra- and inter-domain AAA deployments, Diameter
293 provides support for TLS. Security is discussed in Section 13.
295 Reliable transport
297 RADIUS runs over UDP, and does not define retransmission behavior;
298 as a result, reliability varies between implementations. As
299 described in [RFC2975], this is a major issue in accounting, where
300 packet loss may translate directly into revenue loss. In order to
301 provide well defined transport behavior, Diameter runs over
302 reliable transport mechanisms (TCP, SCTP) as defined in [RFC3539].
304 Agent support
306 [RFC2865] does not provide for explicit support for agents,
307 including Proxies, Redirects and Relays. Since the expected
308 behavior is not defined, it varies between implementations.
309 Diameter defines agent behavior explicitly; this is described in
310 Section 2.8.
312 Server-initiated messages
314 While RADIUS server-initiated messages are defined in [RFC3576],
315 support is optional. This makes it difficult to implement
316 features such as unsolicited disconnect or reauthentication/
317 reauthorization on demand across a heterogeneous deployment.
318 Support for server-initiated messages is mandatory in Diameter,
319 and is described in Section 8.
321 Transition support
323 While Diameter does not share a common protocol data unit (PDU)
324 with RADIUS, considerable effort has been expended in enabling
325 backward compatibility with RADIUS, so that the two protocols may
326 be deployed in the same network. Initially, it is expected that
327 Diameter will be deployed within new network devices, as well as
328 within gateways enabling communication between legacy RADIUS
329 devices and Diameter agents. This capability, described in
330 [RFC4005], enables Diameter support to be added to legacy
331 networks, by addition of a gateway or server speaking both RADIUS
332 and Diameter.
334 In addition to addressing the above requirements, Diameter also
335 provides support for the following:
337 Capability negotiation
339 RADIUS does not support error messages, capability negotiation, or
340 a mandatory/non-mandatory flag for attributes. Since RADIUS
341 clients and servers are not aware of each other's capabilities,
342 they may not be able to successfully negotiate a mutually
343 acceptable service, or in some cases, even be aware of what
344 service has been implemented. Diameter includes support for error
345 handling (Section 7), capability negotiation (Section 5.3), and
346 mandatory/non-mandatory attribute-value pairs (AVPs) (Section
347 4.1).
349 Peer discovery and configuration
351 RADIUS implementations typically require that the name or address
352 of servers or clients be manually configured, along with the
353 corresponding shared secrets. This results in a large
354 administrative burden, and creates the temptation to reuse the
355 RADIUS shared secret, which can result in major security
356 vulnerabilities if the Request Authenticator is not globally and
357 temporally unique as required in [RFC2865]. Through DNS, Diameter
358 enables dynamic discovery of peers. Derivation of dynamic session
359 keys is enabled via transmission-level security.
361 Over time, the capabilities of Network Access Server (NAS) devices
362 have increased substantially. As a result, while Diameter is a
363 considerably more sophisticated protocol than RADIUS, it remains
364 feasible to implement within embedded devices, given improvements in
365 processor speeds and the widespread availability of embedded TLS
366 implementations.
368 1.1. Diameter Protocol
370 The Diameter base protocol provides the following facilities:
372 o Delivery of AVPs (attribute value pairs)
374 o Capabilities negotiation
376 o Error notification
378 o Extensibility, through addition of new applications, commands and
379 AVPs (required in [RFC2989]).
381 o Basic services necessary for applications, such as handling of
382 user sessions or accounting
384 All data delivered by the protocol is in the form of an AVP. Some of
385 these AVP values are used by the Diameter protocol itself, while
386 others deliver data associated with particular applications that
387 employ Diameter. AVPs may be added arbitrarily to Diameter messages,
388 so long as the requirements of a message's ABNF are met. AVPs are
389 used by the base Diameter protocol to support the following required
390 features:
392 o Transporting of user authentication information, for the purposes
393 of enabling the Diameter server to authenticate the user.
395 o Transporting of service specific authorization information,
396 between client and servers, allowing the peers to decide whether a
397 user's access request should be granted.
399 o Exchanging resource usage information, which may be used for
400 accounting purposes, capacity planning, etc.
402 o Relaying, proxying and redirecting of Diameter messages through a
403 server hierarchy.
405 The Diameter base protocol provides the minimum requirements needed
406 for a AAA protocol, as required by [RFC2989]. The base protocol may
407 be used by itself for accounting purposes only, or it may be used
408 with a Diameter application, such as Mobile IPv4 [RFC4004], or
409 network access [RFC4005]. It is also possible for the base protocol
410 to be extended for use in new applications, via the addition of new
411 commands or AVPs. At this time the focus of Diameter is network
412 access and accounting applications. A truly generic AAA protocol
413 used by many applications might provide functionality not provided by
414 Diameter. Therefore, it is imperative that the designers of new
415 applications understand their requirements before using Diameter.
416 See Section 2.4 for more information on Diameter applications.
418 Any node can initiate a request. In that sense, Diameter is a peer-
419 to-peer protocol. In this document, a Diameter Client is a device at
420 the edge of the network that performs access control, such as a
421 Network Access Server (NAS) or a Foreign Agent (FA). A Diameter
422 client generates Diameter messages to request authentication,
423 authorization, and accounting services for the user. A Diameter
424 agent is a node that does not provide local user authentication or
425 authorization services; agents include proxies, redirects and relay
426 agents. A Diameter server performs authentication and/or
427 authorization of the user. A Diameter node may act as an agent for
428 certain requests while acting as a server for others.
430 The Diameter protocol also supports server-initiated messages, such
431 as a request to abort service to a particular user.
433 1.1.1. Description of the Document Set
435 Currently, the Diameter specification consists of an updated version
436 of the base protocol specification (this document), Transport Profile
437 [RFC3539] and applications: Mobile IPv4 [RFC4004], NASREQ [RFC4005],
438 Credit Control [RFC4006], EAP [RFC4072] and SIP [RFC4740]. Note that
439 this document obsoletes [RFC3588]. A summary of the base protocol
440 updates included in this document can be found in Section 1.1.3.
442 The Transport Profile document [RFC3539] discusses transport layer
443 issues that arise with AAA protocols and recommendations on how to
444 overcome these issues. This document also defines the Diameter
445 failover algorithm and state machine.
447 The Mobile IPv4 [RFC4004] application defines a Diameter application
448 that allows a Diameter server to perform AAA functions for Mobile
449 IPv4 services to a mobile node.
451 The NASREQ [RFC4005] application defines a Diameter Application that
452 allows a Diameter server to be used in a PPP/SLIP Dial-Up and
453 Terminal Server Access environment. Consideration was given for
454 servers that need to perform protocol conversion between Diameter and
455 RADIUS.
457 The Credit Control [RFC4006] application defines a Diameter
458 Application that can be used to implement real-time credit-control
459 for a variety of end user services such as network access, SIP
460 services, messaging services, and download services. It provides a
461 general solution to real-time cost and credit-control.
463 The EAP [RFC4072] application defines a Diameter Application that can
464 be used to carry EAP packets between the Network Access Server (NAS)
465 working as an EAP authenticator and a back-end authentication server.
466 The Diameter EAP application is based on NASREQ and intended for a
467 similar environment.
469 The SIP [RFC4740] application defines a Diameter Application that
470 allows a Diameter client to request authentication and authorization
471 information to a Diameter server for SIP-based IP multimedia services
472 (see SIP [RFC3261]).
474 In summary, this document defines the base protocol specification for
475 AAA, which includes support for accounting. The applications
476 documents describe applications that use this base specification for
477 Authentication, Authorization and Accounting.
479 1.1.2. Conventions Used in This Document
481 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
482 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
483 document are to be interpreted as described in [RFC2119].
485 1.1.3. Changes from RFC3588
487 This document deprecates [RFC3588] but is fully backward compatible
488 with that document. The changes introduced in this document focuses
489 on fixing issues that have surfaced during implementation of
490 [RFC3588]. An overview of some the major changes are shown below.
492 o Simplified Security Requirements. The use of a secured transport
493 for exchanging Diameter messages remains mandatory. However, TLS
494 has become the primary method of securing Diameter and IPsec is a
495 secondary alternative. See Section 13 for details. Along with
496 this, the support for the End-to-End security framework
497 (E2ESequence AVP and 'P'-bit in the AVP header) has also been
498 deprecated.
500 o Diameter Extensibility Changes. This includes fixes to the
501 Diameter extensibility description (Section 1.2 and others) to
502 better aid Diameter application designers. It also includes
503 allocation of vendor specific command code space. The new
504 specification relaxes the allocation of command codes for vendor
505 specific uses. See Section 11.2.1 for details.
507 o Application Id Usage. Clarify the proper use of Application Id
508 information which can be found in multiple places within a
509 Diameter message. This includes co-relating Application Ids found
510 in the message headers and AVPs. These changes also clearly
511 specifies the proper Application Id value to use for specific base
512 protocol messages (ASR/ASA, STR/STA) as well as clarifying the
513 content and use of Vendor-Specific-Application-Id.
515 o Routing Fixes. For general routing, specifies much more clearly
516 what information (AVPs and Application Id) can be used for making
517 routing decisions. Prioritization of redirect routing criterias
518 when multiple route entries are found via redirects has also been
519 added (See Section 6.13 for details).
521 o Simplification of Diameter Peer Discovery. The Diameter discovery
522 process now supports only well known discovery schemes. The rest
523 has been deprecated. (See Section 5.2 for details).
525 There are many other many miscellaneous fixes that has been
526 introduced in this document that may not be considered significant
527 but they are important nonetheless. Examples are removal of obsolete
528 types, fixes to command ABNFs, fixes to the state machine,
529 clarification on election process, message validation, fixes to
530 Failed-AVP and Result-Code AVP values etc. A comprehensive list of
531 changes is not shown here for practical reasons. Though, that can be
532 generated via a diff comparison between this document and [RFC3588].
534 1.2. Approach to Extensibility
536 The Diameter protocol is designed to be extensible, using several
537 mechanisms, including:
539 o Defining new AVP values
541 o Creating new AVPs
543 o Creating new commands
545 o Creating new applications
547 From the point of extensibility Diameter authentication,
548 authorization and accounting applications are treated in the same
549 way.
551 Note: Protocol designer should try to re-use existing functionality,
552 namely AVP values, AVPs, commands, and Diameter applications. Reuse
553 simplifies standardization and implementation. To avoid potential
554 interoperability issues it is important to ensure that the semantics
555 of the re-used features are well understood.
557 1.2.1. Defining New AVP Values
559 In order to allocate a new AVP value for AVPs defined in the Diameter
560 Base protocol, the IETF needs to approve a new RFC that describes the
561 AVP value. IANA considerations for these AVP values are discussed in
562 Section 11.4.
564 The allocation of AVP values for other AVPs is guided by the IANA
565 considerations of the documents that defines those AVPs. Typically,
566 allocation of new values for an AVP defined in an IETF RFC should
567 require IETF Review [RFC2434], where as values for vendor-specific
568 AVPs can be allocated by the vendor.
570 1.2.2. Creating New AVPs
572 A new AVP being defined MUST use one of the data types listed in
573 Section 4.2 or 4.3. If an appropriate derived data type is already
574 defined, it SHOULD be used instead of the base data type to encourage
575 reusability and good design practice.
577 In the event that a logical grouping of AVPs is necessary, and
578 multiple "groups" are possible in a given command, it is recommended
579 that a Grouped AVP be used (see Section 4.4).
581 The creation of new AVPs can happen in various ways. The recommended
582 approach is to define a new general-purpose AVP in a standards track
583 RFC approved by the IETF. However, as described in Section 11.1.1
584 there are also other mechanisms.
586 1.2.3. Creating New Commands
588 A new Command Code MUST be allocated when new required AVPs (those
589 indicated as {AVP}) are added, deleted or are redefined (for example
590 by changing a required AVP into an optional one).
592 Furthermore, when a command is modified with respect to the number of
593 round trips then a new Command Code has to be registered.
595 A change to the ABNF of a command, such as described above, MUST
596 result in the definition of a new Command Code. This subsequently
597 leads to the need to define a new Diameter Application for any
598 application that will use that new Command.
600 The IANA considerations for commands are discussed in Section 11.2.1.
602 1.2.4. Creating New Diameter Applications
604 Every Diameter application specification MUST have an IANA assigned
605 Application Id (see Section 2.4 and Section 11.3). The managed
606 Application ID space is flat and there is no relationship between
607 different Diameter applications with respect to their application
608 IDs. As such, there is no versioning supported provided by these
609 application IDs itself; every Diameter application is a standalone
610 application that may or may not have a semantical relationship with
611 one or more Diameter applications being defined elsewhere.
613 Before describing the rules for creating new Diameter applications it
614 is important to discuss the semantics of the AVPs occurrences as
615 stated in the ABNF and the M-bit flag for an AVP. There is no
616 relationship imposed between the two; they are set independently.
618 o The ABNF indicates what AVPs are placed into a Diameter Command by
619 the sender of that Command. Often, since there are multiple modes
620 of protocol interactions many of the AVPs are indicated as
621 optional.
623 o The M-bit allows the sender to indicate to the receiver whether
624 the semantics of an AVP and it's content has to be understood
625 mandatorily or not. If the M-bit is set by the sender and the
626 receiver does not understand the AVP or the values carried within
627 that AVP then a failure is generated (see Section 7).
629 It is the decision of the protocol designer when to develop a new
630 Diameter application rather than extending Diameter in other ways.
631 However, a new Diameter application MUST be created when one or more
632 of the following criteria are met:
634 M-bit Setting
636 Adding an AVP with the M-bit in the MUST column of the AVP flag
637 table to an existing Command/Application requires a new Diameter
638 Application Id to be assigned to that Application.
640 Adding an AVP with the M-bit in the MAY column of the AVP flag
641 table to an existing Command/Application requires a new Diameter
642 Application Id to be assigned to that Application.
644 Note: The M-bit setting for a given AVP is relevant to an
645 Application and each command within that application which
646 includes the AVP. That is, if an AVP appears in two commands for
647 application Foo and the M-bit settings are different in each
648 command, then there should be two AVP flag tables describing when
649 to set the M-bit.
651 Commands
653 A new command is used within the existing application either
654 because an additional command is added, an existing command has
655 been modified so that a new Command Code had to be registered, or
656 a command has been deleted.
658 An implementation MAY add arbitrary optional AVPs with the M-bit
659 cleared to a command defined in an application, including vendor-
660 specific AVPs without needing to define a new application. This can
661 be done if the commands ABNF allows for it. Please refer to Section
662 11.1.1 for details.
664 1.3. Terminology
665 AAA
667 Authentication, Authorization and Accounting.
669 Accounting
671 The act of collecting information on resource usage for the
672 purpose of capacity planning, auditing, billing or cost
673 allocation.
675 Accounting Record
677 An accounting record represents a summary of the resource
678 consumption of a user over the entire session. Accounting servers
679 creating the accounting record may do so by processing interim
680 accounting events or accounting events from several devices
681 serving the same user.
683 Authentication
685 The act of verifying the identity of an entity (subject).
687 Authorization
689 The act of determining whether a requesting entity (subject) will
690 be allowed access to a resource (object).
692 AVP
694 The Diameter protocol consists of a header followed by one or more
695 Attribute-Value-Pairs (AVPs). An AVP includes a header and is
696 used to encapsulate protocol-specific data (e.g., routing
697 information) as well as authentication, authorization or
698 accounting information.
700 Broker
702 A broker is a business term commonly used in AAA infrastructures.
703 A broker is either a relay, proxy or redirect agent, and may be
704 operated by roaming consortiums. Depending on the business model,
705 a broker may either choose to deploy relay agents or proxy agents.
707 Diameter Agent
709 A Diameter Agent is a Diameter node that provides either relay,
710 proxy, redirect or translation services.
712 Diameter Client
714 A Diameter Client is a device at the edge of the network that
715 performs access control. An example of a Diameter client is a
716 Network Access Server (NAS) or a Foreign Agent (FA). By its very
717 nature, a Diameter Client must support Diameter client
718 applications in addition to the base protocol.
720 Diameter Node
722 A Diameter node is a host process that implements the Diameter
723 protocol, and acts either as a Client, Agent or Server.
725 Diameter Peer
727 A Diameter Peer is a Diameter Node to which a given Diameter Node
728 has a direct transport connection.
730 Diameter Server
732 A Diameter Server is one that handles authentication,
733 authorization and accounting requests for a particular realm. By
734 its very nature, a Diameter Server must support Diameter server
735 applications in addition to the base protocol.
737 Downstream
739 Downstream is used to identify the direction of a particular
740 Diameter message from the home server towards the access device.
742 Home Realm
744 A Home Realm is the administrative domain with which the user
745 maintains an account relationship.
747 Home Server
749 A Diameter Server which serves the Home Realm.
751 Interim accounting
753 An interim accounting message provides a snapshot of usage during
754 a user's session. It is typically implemented in order to provide
755 for partial accounting of a user's session in the case of a device
756 reboot or other network problem prevents the reception of a
757 session summary message or session record.
759 Local Realm
761 A local realm is the administrative domain providing services to a
762 user. An administrative domain may act as a local realm for
763 certain users, while being a home realm for others.
765 Multi-session
767 A multi-session represents a logical linking of several sessions.
768 Multi-sessions are tracked by using the Acct-Multi-Session-Id. An
769 example of a multi-session would be a Multi-link PPP bundle. Each
770 leg of the bundle would be a session while the entire bundle would
771 be a multi-session.
773 Network Access Identifier
775 The Network Access Identifier, or NAI [RFC4282], is used in the
776 Diameter protocol to extract a user's identity and realm. The
777 identity is used to identify the user during authentication and/or
778 authorization, while the realm is used for message routing
779 purposes.
781 Proxy Agent or Proxy
783 In addition to forwarding requests and responses, proxies make
784 policy decisions relating to resource usage and provisioning.
785 This is typically accomplished by tracking the state of NAS
786 devices. While proxies typically do not respond to client
787 Requests prior to receiving a Response from the server, they may
788 originate Reject messages in cases where policies are violated.
789 As a result, proxies need to understand the semantics of the
790 messages passing through them, and may not support all Diameter
791 applications.
793 Realm
795 The string in the NAI that immediately follows the '@' character.
796 NAI realm names are required to be unique, and are piggybacked on
797 the administration of the DNS namespace. Diameter makes use of
798 the realm, also loosely referred to as domain, to determine
799 whether messages can be satisfied locally, or whether they must be
800 routed or redirected. In RADIUS, realm names are not necessarily
801 piggybacked on the DNS namespace but may be independent of it.
803 Real-time Accounting
805 Real-time accounting involves the processing of information on
806 resource usage within a defined time window. Time constraints are
807 typically imposed in order to limit financial risk. The Diameter
808 Credit Control Application [RFC4006] is the application that
809 defines real-time accounting functionality.
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. Diameter application documents provide
846 guidelines as to when a session begins and ends. All Diameter
847 packets with the same Session-Id are considered to be part of the
848 same session.
850 Session state
852 A stateful agent is one that maintains session state information,
853 by keeping track of all authorized active sessions. Each
854 authorized session is bound to a particular service, and its state
855 is considered active either until it is notified otherwise, or by
856 expiration.
858 Sub-session
860 A sub-session represents a distinct service (e.g., QoS or data
861 characteristics) provided to a given session. These services may
862 happen concurrently (e.g., simultaneous voice and data transfer
863 during the same session) or serially. These changes in sessions
864 are tracked with the Accounting-Sub-Session-Id.
866 Transaction state
868 The Diameter protocol requires that agents maintain transaction
869 state, which is used for failover purposes. Transaction state
870 implies that upon forwarding a request, the Hop-by-Hop identifier
871 is saved; the field is replaced with a locally unique identifier,
872 which is restored to its original value when the corresponding
873 answer is received. The request's state is released upon receipt
874 of the answer. A stateless agent is one that only maintains
875 transaction state.
877 Translation Agent
879 A translation agent is a stateful Diameter node that performs
880 protocol translation between Diameter and another AAA protocol,
881 such as RADIUS.
883 Transport Connection
885 A transport connection is a TCP or SCTP connection existing
886 directly between two Diameter peers, otherwise known as a Peer-to-
887 Peer Connection.
889 Upstream
891 Upstream is used to identify the direction of a particular
892 Diameter message from the access device towards the home server.
894 User
896 The entity or client device requesting or using some resource, in
897 support of which a Diameter client has generated a request.
899 2. Protocol Overview
901 The base Diameter protocol concerns itself with capabilities
902 negotiation, how messages are sent and how peers may eventually be
903 abandoned. The base protocol also defines certain rules that apply
904 to all exchanges of messages between Diameter nodes.
906 Communication between Diameter peers begins with one peer sending a
907 message to another Diameter peer. The set of AVPs included in the
908 message is determined by a particular Diameter application. One AVP
909 that is included to reference a user's session is the Session-Id.
911 The initial request for authentication and/or authorization of a user
912 would include the Session-Id. The Session-Id is then used in all
913 subsequent messages to identify the user's session (see Section 8 for
914 more information). The communicating party may accept the request,
915 or reject it by returning an answer message with the Result-Code AVP
916 set to indicate an error occurred. The specific behavior of the
917 Diameter server or client receiving a request depends on the Diameter
918 application employed.
920 Session state (associated with a Session-Id) MUST be freed upon
921 receipt of the Session-Termination-Request, Session-Termination-
922 Answer, expiration of authorized service time in the Session-Timeout
923 AVP, and according to rules established in a particular Diameter
924 application.
926 The base Diameter protocol may be used by itself for accounting
927 applications. For authentication and authorization, it is always
928 extended for a particular application.
930 Diameter Clients MUST support the base protocol, which includes
931 accounting. In addition, they MUST fully support each Diameter
932 application that is needed to implement the client's service, e.g.,
933 NASREQ and/or Mobile IPv4. A Diameter Client that does not support
934 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
935 Client" where X is the application which it supports, and not a
936 "Diameter Client".
938 Diameter Servers MUST support the base protocol, which includes
939 accounting. In addition, they MUST fully support each Diameter
940 application that is needed to implement the intended service, e.g.,
941 NASREQ and/or Mobile IPv4. A Diameter Server that does not support
942 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
943 Server" where X is the application which it supports, and not a
944 "Diameter Server".
946 Diameter Relays and redirect agents are, by definition, protocol
947 transparent, and MUST transparently support the Diameter base
948 protocol, which includes accounting, and all Diameter applications.
950 Diameter proxies MUST support the base protocol, which includes
951 accounting. In addition, they MUST fully support each Diameter
952 application that is needed to implement proxied services, e.g.,
953 NASREQ and/or Mobile IPv4. A Diameter proxy which does not support
954 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
955 Proxy" where X is the application which it supports, and not a
956 "Diameter Proxy".
958 2.1. Transport
960 The Diameter Transport profile is defined in [RFC3539].
962 The base Diameter protocol is run on port 3868 of both TCP [RFC793]
963 and SCTP [RFC2960].
965 Diameter clients MUST support either TCP or SCTP, while agents and
966 servers SHOULD support both.
968 A Diameter node MAY initiate connections from a source port other
969 than the one that it declares it accepts incoming connections on, and
970 MUST be prepared to receive connections on port 3868. A given
971 Diameter instance of the peer state machine MUST NOT use more than
972 one transport connection to communicate with a given peer, unless
973 multiple instances exist on the peer in which case a separate
974 connection per process is allowed.
976 When no transport connection exists with a peer, an attempt to
977 connect SHOULD be periodically made. This behavior is handled via
978 the Tc timer, whose recommended value is 30 seconds. There are
979 certain exceptions to this rule, such as when a peer has terminated
980 the transport connection stating that it does not wish to
981 communicate.
983 When connecting to a peer and either zero or more transports are
984 specified, TCP SHOULD be tried first, followed by SCTP. See Section
985 5.2 for more information on peer discovery.
987 Diameter implementations SHOULD be able to interpret ICMP protocol
988 port unreachable messages as explicit indications that the server is
989 not reachable, subject to security policy on trusting such messages.
990 Diameter implementations SHOULD also be able to interpret a reset
991 from the transport and timed-out connection attempts. If Diameter
992 receives data up from TCP that cannot be parsed or identified as a
993 Diameter error made by the peer, the stream is compromised and cannot
994 be recovered. The transport connection MUST be closed using a RESET
995 call (send a TCP RST bit) or an SCTP ABORT message (graceful closure
996 is compromised).
998 2.1.1. SCTP Guidelines
1000 The following are guidelines for Diameter implementations that
1001 support SCTP:
1003 1. For interoperability: All Diameter nodes MUST be prepared to
1004 receive Diameter messages on any SCTP stream in the association.
1006 2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP
1007 streams available to the association to prevent head-of-the-line
1008 blocking.
1010 2.2. Securing Diameter Messages
1012 Connections between Diameter peers SHOULD be protected by TLS. All
1013 Diameter base protocol implementations MUST support the use of TLS.
1014 If desired, additional security measures that are transparent to and
1015 independent of Diameter, such as IPsec [RFC4301], can be deployed to
1016 secure connections between peers. The Diameter protocol MUST NOT be
1017 used without any security mechanism.
1019 2.3. Diameter Application Compliance
1021 Application Ids are advertised during the capabilities exchange phase
1022 (see Section 5.3). For a given application, advertising support of
1023 an application implies that the sender supports the functionality
1024 specified in the respective Diameter application specification.
1026 An implementation MAY add arbitrary optional AVPs with the M-bit
1027 cleared to a command defined in an application, including vendor-
1028 specific AVPs only if the commands ABNF allows for it. Please refer
1029 to Section 11.1.1 for details.
1031 2.4. Application Identifiers
1033 Each Diameter application MUST have an IANA assigned Application Id
1034 (see Section 11.3). The base protocol does not require an
1035 Application Id since its support is mandatory. During the
1036 capabilities exchange, Diameter nodes inform their peers of locally
1037 supported applications. Furthermore, all Diameter messages contain
1038 an Application Id, which is used in the message forwarding process.
1040 The following Application Id values are defined:
1042 Diameter Common Messages 0
1043 Diameter Base Accounting 3
1044 Relay 0xffffffff
1046 Relay and redirect agents MUST advertise the Relay Application
1047 Identifier, while all other Diameter nodes MUST advertise locally
1048 supported applications. The receiver of a Capabilities Exchange
1049 message advertising Relay service MUST assume that the sender
1050 supports all current and future applications.
1052 Diameter relay and proxy agents are responsible for finding an
1053 upstream server that supports the application of a particular
1054 message. If none can be found, an error message is returned with the
1055 Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER.
1057 2.5. Connections vs. Sessions
1059 This section attempts to provide the reader with an understanding of
1060 the difference between connection and session, which are terms used
1061 extensively throughout this document.
1063 A connection refers to a transport level connection between two peers
1064 that is used to send and receive Diameter messages. A session is a
1065 logical concept at the application layer, it spawns from the Diameter
1066 client to the Diameter server and is identified via the Session-Id
1067 AVP.
1069 +--------+ +-------+ +--------+
1070 | Client | | Relay | | Server |
1071 +--------+ +-------+ +--------+
1072 <----------> <---------->
1073 peer connection A peer connection B
1075 <----------------------------->
1076 User session x
1078 Figure 1: Diameter connections and sessions
1080 In the example provided in Figure 1, peer connection A is established
1081 between the Client and the Relay. Peer connection B is established
1082 between the Relay and the Server. User session X spans from the
1083 Client via the Relay to the Server. Each "user" of a service causes
1084 an auth request to be sent, with a unique session identifier. Once
1085 accepted by the server, both the client and the server are aware of
1086 the session.
1088 It is important to note that there is no relationship between a
1089 connection and a session, and that Diameter messages for multiple
1090 sessions are all multiplexed through a single connection. Also note
1091 that Diameter messages pertaining to the session, both application
1092 specific and those that are defined in this document such as ASR/ASA,
1093 RAR/RAA and STR/STA MUST carry the Application Id of the application.
1094 Diameter messages pertaining to peer connection establishment and
1095 maintenance such as CER/CEA, DWR/DWA and DPR/DPA MUST carry an
1096 Application Id of zero (0).
1098 2.6. Peer Table
1100 The Diameter Peer Table is used in message forwarding, and referenced
1101 by the Routing Table. A Peer Table entry contains the following
1102 fields:
1104 Host identity
1106 Following the conventions described for the DiameterIdentity
1107 derived AVP data format in Section 4.4. This field contains the
1108 contents of the Origin-Host (Section 6.3) AVP found in the CER or
1109 CEA message.
1111 StatusT
1113 This is the state of the peer entry, and MUST match one of the
1114 values listed in Section 5.6.
1116 Static or Dynamic
1118 Specifies whether a peer entry was statically configured, or
1119 dynamically discovered.
1121 Expiration time
1123 Specifies the time at which dynamically discovered peer table
1124 entries are to be either refreshed, or expired.
1126 TLS Enabled
1128 Specifies whether TLS is to be used when communicating with the
1129 peer.
1131 Additional security information, when needed (e.g., keys,
1132 certificates)
1134 2.7. Routing Table
1136 All Realm-Based routing lookups are performed against what is
1137 commonly known as the Routing Table (see Section 12). A Routing
1138 Table Entry contains the following fields:
1140 Realm Name
1142 This is the field that is MUST be used as a primary key in the
1143 routing table lookups. Note that some implementations perform
1144 their lookups based on longest-match-from-the-right on the realm
1145 rather than requiring an exact match.
1147 Application Identifier
1149 An application is identified by an Application Id. A route entry
1150 can have a different destination based on the Application Id in
1151 the message header. This field MUST be used as a secondary key
1152 field in routing table lookups.
1154 Local Action
1156 The Local Action field is used to identify how a message should be
1157 treated. The following actions are supported:
1159 1. LOCAL - Diameter messages that can be satisfied locally, and
1160 do not need to be routed to another Diameter entity.
1162 2. RELAY - All Diameter messages that fall within this category
1163 MUST be routed to a next hop Diameter entity that is indicated
1164 by the identifier described below. Routing is done without
1165 modifying any non-routing AVPs. See Section 6.1.9 for
1166 relaying guidelines
1168 3. PROXY - All Diameter messages that fall within this category
1169 MUST be routed to a next Diameter entity that is indicated by
1170 the identifier described below. The local server MAY apply
1171 its local policies to the message by including new AVPs to the
1172 message prior to routing. See Section 6.1.9 for proxying
1173 guidelines.
1175 4. REDIRECT - Diameter messages that fall within this category
1176 MUST have the identity of the home Diameter server(s)
1177 appended, and returned to the sender of the message. See
1178 Section 6.1.9 for redirect guidelines.
1180 Server Identifier
1182 One or more servers the message is to be routed to. These servers
1183 MUST also be present in the Peer table. When the Local Action is
1184 set to RELAY or PROXY, this field contains the identity of the
1185 server(s) the message MUST be routed to. When the Local Action
1186 field is set to REDIRECT, this field contains the identity of one
1187 or more servers the message MUST be redirected to.
1189 Static or Dynamic
1191 Specifies whether a route entry was statically configured, or
1192 dynamically discovered.
1194 Expiration time
1196 Specifies the time which a dynamically discovered route table
1197 entry expires.
1199 It is important to note that Diameter agents MUST support at least
1200 one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation.
1201 Agents do not need to support all modes of operation in order to
1202 conform with the protocol specification, but MUST follow the protocol
1203 compliance guidelines in Section 2. Relay agents and proxies MUST
1204 NOT reorder AVPs.
1206 The routing table MAY include a default entry that MUST be used for
1207 any requests not matching any of the other entries. The routing
1208 table MAY consist of only such an entry.
1210 When a request is routed, the target server MUST have advertised the
1211 Application Id (see Section 2.4) for the given message, or have
1212 advertised itself as a relay or proxy agent. Otherwise, an error is
1213 returned with the Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER.
1215 2.8. Role of Diameter Agents
1217 In addition to client and servers, the Diameter protocol introduces
1218 relay, proxy, redirect, and translation agents, each of which is
1219 defined in Section 1.3. These Diameter agents are useful for several
1220 reasons:
1222 o They can distribute administration of systems to a configurable
1223 grouping, including the maintenance of security associations.
1225 o They can be used for concentration of requests from an number of
1226 co-located or distributed NAS equipment sets to a set of like user
1227 groups.
1229 o They can do value-added processing to the requests or responses.
1231 o They can be used for load balancing.
1233 o A complex network will have multiple authentication sources, they
1234 can sort requests and forward towards the correct target.
1236 The Diameter protocol requires that agents maintain transaction
1237 state, which is used for failover purposes. Transaction state
1238 implies that upon forwarding a request, its Hop-by-Hop identifier is
1239 saved; the field is replaced with a locally unique identifier, which
1240 is restored to its original value when the corresponding answer is
1241 received. The request's state is released upon receipt of the
1242 answer. A stateless agent is one that only maintains transaction
1243 state.
1245 The Proxy-Info AVP allows stateless agents to add local state to a
1246 Diameter request, with the guarantee that the same state will be
1247 present in the answer. However, the protocol's failover procedures
1248 require that agents maintain a copy of pending requests.
1250 A stateful agent is one that maintains session state information; by
1251 keeping track of all authorized active sessions. Each authorized
1252 session is bound to a particular service, and its state is considered
1253 active either until it is notified otherwise, or by expiration. Each
1254 authorized session has an expiration, which is communicated by
1255 Diameter servers via the Session-Timeout AVP.
1257 Maintaining session state may be useful in certain applications, such
1258 as:
1260 o Protocol translation (e.g., RADIUS <-> Diameter)
1262 o Limiting resources authorized to a particular user
1264 o Per user or transaction auditing
1266 A Diameter agent MAY act in a stateful manner for some requests and
1267 be stateless for others. A Diameter implementation MAY act as one
1268 type of agent for some requests, and as another type of agent for
1269 others.
1271 2.8.1. Relay Agents
1273 Relay Agents are Diameter agents that accept requests and route
1274 messages to other Diameter nodes based on information found in the
1275 messages (e.g., Destination-Realm). This routing decision is
1276 performed using a list of supported realms, and known peers. This is
1277 known as the Routing Table, as is defined further in Section 2.7.
1279 Relays may, for example, be used to aggregate requests from multiple
1280 Network Access Servers (NASes) within a common geographical area
1281 (POP). The use of Relays is advantageous since it eliminates the
1282 need for NASes to be configured with the necessary security
1283 information they would otherwise require to communicate with Diameter
1284 servers in other realms. Likewise, this reduces the configuration
1285 load on Diameter servers that would otherwise be necessary when NASes
1286 are added, changed or deleted.
1288 Relays modify Diameter messages by inserting and removing routing
1289 information, but do not modify any other portion of a message.
1290 Relays SHOULD NOT maintain session state but MUST maintain
1291 transaction state.
1293 +------+ ---------> +------+ ---------> +------+
1294 | | 1. Request | | 2. Request | |
1295 | NAS | | DRL | | HMS |
1296 | | 4. Answer | | 3. Answer | |
1297 +------+ <--------- +------+ <--------- +------+
1298 example.net example.net example.com
1300 Figure 2: Relaying of Diameter messages
1302 The example provided in Figure 2 depicts a request issued from NAS,
1303 which is an access device, for the user bob@example.com. Prior to
1304 issuing the request, NAS performs a Diameter route lookup, using
1305 "example.com" as the key, and determines that the message is to be
1306 relayed to DRL, which is a Diameter Relay. DRL performs the same
1307 route lookup as NAS, and relays the message to HMS, which is
1308 example.com's Home Diameter Server. HMS identifies that the request
1309 can be locally supported (via the realm), processes the
1310 authentication and/or authorization request, and replies with an
1311 answer, which is routed back to NAS using saved transaction state.
1313 Since Relays do not perform any application level processing, they
1314 provide relaying services for all Diameter applications, and
1315 therefore MUST advertise the Relay Application Id.
1317 2.8.2. Proxy Agents
1319 Similarly to relays, proxy agents route Diameter messages using the
1320 Diameter Routing Table. However, they differ since they modify
1321 messages to implement policy enforcement. This requires that proxies
1322 maintain the state of their downstream peers (e.g., access devices)
1323 to enforce resource usage, provide admission control, and
1324 provisioning.
1326 Proxies may, for example, be used in call control centers or access
1327 ISPs that provide outsourced connections, they can monitor the number
1328 and types of ports in use, and make allocation and admission
1329 decisions according to their configuration.
1331 Since enforcing policies requires an understanding of the service
1332 being provided, Proxies MUST only advertise the Diameter applications
1333 they support.
1335 2.8.3. Redirect Agents
1337 Redirect agents are useful in scenarios where the Diameter routing
1338 configuration needs to be centralized. An example is a redirect
1339 agent that provides services to all members of a consortium, but does
1340 not wish to be burdened with relaying all messages between realms.
1341 This scenario is advantageous since it does not require that the
1342 consortium provide routing updates to its members when changes are
1343 made to a member's infrastructure.
1345 Since redirect agents do not relay messages, and only return an
1346 answer with the information necessary for Diameter agents to
1347 communicate directly, they do not modify messages. Since redirect
1348 agents do not receive answer messages, they cannot maintain session
1349 state.
1351 The example provided in Figure 3 depicts a request issued from the
1352 access device, NAS, for the user bob@example.com. The message is
1353 forwarded by the NAS to its relay, DRL, which does not have a routing
1354 entry in its Diameter Routing Table for example.com. DRL has a
1355 default route configured to DRD, which is a redirect agent that
1356 returns a redirect notification to DRL, as well as HMS' contact
1357 information. Upon receipt of the redirect notification, DRL
1358 establishes a transport connection with HMS, if one doesn't already
1359 exist, and forwards the request to it.
1361 +------+
1362 | |
1363 | DRD |
1364 | |
1365 +------+
1366 ^ |
1367 2. Request | | 3. Redirection
1368 | | Notification
1369 | v
1370 +------+ ---------> +------+ ---------> +------+
1371 | | 1. Request | | 4. Request | |
1372 | NAS | | DRL | | HMS |
1373 | | 6. Answer | | 5. Answer | |
1374 +------+ <--------- +------+ <--------- +------+
1375 example.net example.net example.com
1377 Figure 3: Redirecting a Diameter Message
1379 Since redirect agents do not perform any application level
1380 processing, they provide relaying services for all Diameter
1381 applications, and therefore MUST advertise the Relay Application
1382 Identifier.
1384 2.8.4. Translation Agents
1386 A translation agent is a device that provides translation between two
1387 protocols (e.g., RADIUS<->Diameter, TACACS+<->Diameter). Translation
1388 agents are likely to be used as aggregation servers to communicate
1389 with a Diameter infrastructure, while allowing for the embedded
1390 systems to be migrated at a slower pace.
1392 Given that the Diameter protocol introduces the concept of long-lived
1393 authorized sessions, translation agents MUST be session stateful and
1394 MUST maintain transaction state.
1396 Translation of messages can only occur if the agent recognizes the
1397 application of a particular request, and therefore translation agents
1398 MUST only advertise their locally supported applications.
1400 +------+ ---------> +------+ ---------> +------+
1401 | | RADIUS Request | | Diameter Request | |
1402 | NAS | | TLA | | HMS |
1403 | | RADIUS Answer | | Diameter Answer | |
1404 +------+ <--------- +------+ <--------- +------+
1405 example.net example.net example.com
1407 Figure 4: Translation of RADIUS to Diameter
1409 2.9. Diameter Path Authorization
1411 As noted in Section 2.2, Diameter provides transmission level
1412 security for each connection using TLS. Therefore, each connection
1413 can be authenticated, replay and integrity protected.
1415 In addition to authenticating each connection, each connection as
1416 well as the entire session MUST also be authorized. Before
1417 initiating a connection, a Diameter Peer MUST check that its peers
1418 are authorized to act in their roles. For example, a Diameter peer
1419 may be authentic, but that does not mean that it is authorized to act
1420 as a Diameter Server advertising a set of Diameter applications.
1422 Prior to bringing up a connection, authorization checks are performed
1423 at each connection along the path. Diameter capabilities negotiation
1424 (CER/CEA) also MUST be carried out, in order to determine what
1425 Diameter applications are supported by each peer. Diameter sessions
1426 MUST be routed only through authorized nodes that have advertised
1427 support for the Diameter application required by the session.
1429 As noted in Section 6.1.9, a relay or proxy agent MUST append a
1430 Route-Record AVP to all requests forwarded. The AVP contains the
1431 identity of the peer the request was received from.
1433 The home Diameter server, prior to authorizing a session, MUST check
1434 the Route-Record AVPs to make sure that the route traversed by the
1435 request is acceptable. For example, administrators within the home
1436 realm may not wish to honor requests that have been routed through an
1437 untrusted realm. By authorizing a request, the home Diameter server
1438 is implicitly indicating its willingness to engage in the business
1439 transaction as specified by the contractual relationship between the
1440 server and the previous hop. A DIAMETER_AUTHORIZATION_REJECTED error
1441 message (see Section 7.1.5) is sent if the route traversed by the
1442 request is unacceptable.
1444 A home realm may also wish to check that each accounting request
1445 message corresponds to a Diameter response authorizing the session.
1446 Accounting requests without corresponding authorization responses
1447 SHOULD be subjected to further scrutiny, as should accounting
1448 requests indicating a difference between the requested and provided
1449 service.
1451 Forwarding of an authorization response is considered evidence of a
1452 willingness to take on financial risk relative to the session. A
1453 local realm may wish to limit this exposure, for example, by
1454 establishing credit limits for intermediate realms and refusing to
1455 accept responses which would violate those limits. By issuing an
1456 accounting request corresponding to the authorization response, the
1457 local realm implicitly indicates its agreement to provide the service
1458 indicated in the authorization response. If the service cannot be
1459 provided by the local realm, then a DIAMETER_UNABLE_TO_COMPLY error
1460 message MUST be sent within the accounting request; a Diameter client
1461 receiving an authorization response for a service that it cannot
1462 perform MUST NOT substitute an alternate service, and then send
1463 accounting requests for the alternate service instead.
1465 3. Diameter Header
1467 A summary of the Diameter header format is shown below. The fields
1468 are transmitted in network byte order.
1470 0 1 2 3
1471 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
1472 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1473 | Version | Message Length |
1474 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1475 | command flags | Command-Code |
1476 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1477 | Application-ID |
1478 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1479 | Hop-by-Hop Identifier |
1480 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1481 | End-to-End Identifier |
1482 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1483 | AVPs ...
1484 +-+-+-+-+-+-+-+-+-+-+-+-+-
1486 Version
1488 This Version field MUST be set to 1 to indicate Diameter Version
1489 1.
1491 Message Length
1493 The Message Length field is three octets and indicates the length
1494 of the Diameter message including the header fields.
1496 Command Flags
1498 The Command Flags field is eight bits. The following bits are
1499 assigned:
1501 0 1 2 3 4 5 6 7
1502 +-+-+-+-+-+-+-+-+
1503 |R P E T r r r r|
1504 +-+-+-+-+-+-+-+-+
1506 R(equest)
1508 If set, the message is a request. If cleared, the message is
1509 an answer.
1511 P(roxiable)
1513 If set, the message MAY be proxied, relayed or redirected. If
1514 cleared, the message MUST be locally processed.
1516 E(rror)
1518 If set, the message contains a protocol error, and the message
1519 will not conform to the ABNF described for this command.
1520 Messages with the 'E' bit set are commonly referred to as error
1521 messages. This bit MUST NOT be set in request messages. See
1522 Section 7.2.
1524 T(Potentially re-transmitted message)
1526 This flag is set after a link failover procedure, to aid the
1527 removal of duplicate requests. It is set when resending
1528 requests not yet acknowledged, as an indication of a possible
1529 duplicate due to a link failure. This bit MUST be cleared when
1530 sending a request for the first time, otherwise the sender MUST
1531 set this flag. Diameter agents only need to be concerned about
1532 the number of requests they send based on a single received
1533 request; retransmissions by other entities need not be tracked.
1534 Diameter agents that receive a request with the T flag set,
1535 MUST keep the T flag set in the forwarded request. This flag
1536 MUST NOT be set if an error answer message (e.g., a protocol
1537 error) has been received for the earlier message. It can be
1538 set only in cases where no answer has been received from the
1539 server for a request and the request is sent again. This flag
1540 MUST NOT be set in answer messages.
1542 r(eserved)
1544 These flag bits are reserved for future use, and MUST be set to
1545 zero, and ignored by the receiver.
1547 Command-Code
1549 The Command-Code field is three octets, and is used in order to
1550 communicate the command associated with the message. The 24-bit
1551 address space is managed by IANA (see Section 11.2.1).
1553 Command-Code values 16,777,214 and 16,777,215 (hexadecimal values
1554 FFFFFE -FFFFFF) are reserved for experimental use (See Section
1555 11.3).
1557 Application-ID
1559 Application-ID is four octets and is used to identify to which
1560 application the message is applicable for. The application can be
1561 an authentication application, an accounting application or a
1562 vendor specific application. See Section 11.3 for the possible
1563 values that the application-id may use.
1565 The value of the application-id field in the header MUST be the
1566 same as any relevant application-id AVPs contained in the message.
1568 Hop-by-Hop Identifier
1570 The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in
1571 network byte order) and aids in matching requests and replies.
1572 The sender MUST ensure that the Hop-by-Hop identifier in a request
1573 is unique on a given connection at any given time, and MAY attempt
1574 to ensure that the number is unique across reboots. The sender of
1575 an Answer message MUST ensure that the Hop-by-Hop Identifier field
1576 contains the same value that was found in the corresponding
1577 request. The Hop-by-Hop identifier is normally a monotonically
1578 increasing number, whose start value was randomly generated. An
1579 answer message that is received with an unknown Hop-by-Hop
1580 Identifier MUST be discarded.
1582 End-to-End Identifier
1584 The End-to-End Identifier is an unsigned 32-bit integer field (in
1585 network byte order) and is used to detect duplicate messages.
1586 Upon reboot implementations MAY set the high order 12 bits to
1587 contain the low order 12 bits of current time, and the low order
1588 20 bits to a random value. Senders of request messages MUST
1589 insert a unique identifier on each message. The identifier MUST
1590 remain locally unique for a period of at least 4 minutes, even
1591 across reboots. The originator of an Answer message MUST ensure
1592 that the End-to-End Identifier field contains the same value that
1593 was found in the corresponding request. The End-to-End Identifier
1594 MUST NOT be modified by Diameter agents of any kind. The
1595 combination of the Origin-Host (see Section 6.3) and this field is
1596 used to detect duplicates. Duplicate requests SHOULD cause the
1597 same answer to be transmitted (modulo the hop-by-hop Identifier
1598 field and any routing AVPs that may be present), and MUST NOT
1599 affect any state that was set when the original request was
1600 processed. Duplicate answer messages that are to be locally
1601 consumed (see Section 6.2) SHOULD be silently discarded.
1603 AVPs
1605 AVPs are a method of encapsulating information relevant to the
1606 Diameter message. See Section 4 for more information on AVPs.
1608 3.1. Command Codes
1610 Each command Request/Answer pair is assigned a command code, and the
1611 sub-type (i.e., request or answer) is identified via the 'R' bit in
1612 the Command Flags field of the Diameter header.
1614 Every Diameter message MUST contain a command code in its header's
1615 Command-Code field, which is used to determine the action that is to
1616 be taken for a particular message. The following Command Codes are
1617 defined in the Diameter base protocol:
1619 Command-Name Abbrev. Code Reference
1620 --------------------------------------------------------
1621 Abort-Session-Request ASR 274 8.5.1
1622 Abort-Session-Answer ASA 274 8.5.2
1623 Accounting-Request ACR 271 9.7.1
1624 Accounting-Answer ACA 271 9.7.2
1625 Capabilities-Exchange- CER 257 5.3.1
1626 Request
1627 Capabilities-Exchange- CEA 257 5.3.2
1628 Answer
1629 Device-Watchdog-Request DWR 280 5.5.1
1630 Device-Watchdog-Answer DWA 280 5.5.2
1631 Disconnect-Peer-Request DPR 282 5.4.1
1632 Disconnect-Peer-Answer DPA 282 5.4.2
1633 Re-Auth-Request RAR 258 8.3.1
1634 Re-Auth-Answer RAA 258 8.3.2
1635 Session-Termination- STR 275 8.4.1
1636 Request
1637 Session-Termination- STA 275 8.4.2
1638 Answer
1640 3.2. Command Code ABNF specification
1642 Every Command Code defined MUST include a corresponding ABNF
1643 specification, which is used to define the AVPs that MUST or MAY be
1644 present when sending the message. The following format is used in
1645 the definition:
1647 command-def = command-name "::=" diameter-message
1649 command-name = diameter-name
1650 diameter-name = ALPHA *(ALPHA / DIGIT / "-")
1652 diameter-message = header [ *fixed] [ *required] [ *optional]
1654 header = "<" "Diameter Header:" command-id
1655 [r-bit] [p-bit] [e-bit] [application-id] ">"
1657 application-id = 1*DIGIT
1659 command-id = 1*DIGIT
1660 ; The Command Code assigned to the command
1662 r-bit = ", REQ"
1663 ; If present, the 'R' bit in the Command
1664 ; Flags is set, indicating that the message
1665 ; is a request, as opposed to an answer.
1667 p-bit = ", PXY"
1668 ; If present, the 'P' bit in the Command
1669 ; Flags is set, indicating that the message
1670 ; is proxiable.
1672 e-bit = ", ERR"
1673 ; If present, the 'E' bit in the Command
1674 ; Flags is set, indicating that the answer
1675 ; message contains a Result-Code AVP in
1676 ; the "protocol error" class.
1678 fixed = [qual] "<" avp-spec ">"
1679 ; Defines the fixed position of an AVP
1681 required = [qual] "{" avp-spec "}"
1682 ; The AVP MUST be present and can appear
1683 ; anywhere in the message.
1685 optional = [qual] "[" avp-name "]"
1686 ; The avp-name in the 'optional' rule cannot
1687 ; evaluate to any AVP Name which is included
1688 ; in a fixed or required rule. The AVP can
1689 ; appear anywhere in the message.
1691 qual = [min] "*" [max]
1692 ; See ABNF conventions, RFC 4234 Section 6.6.
1693 ; The absence of any qualifiers depends on
1694 ; whether it precedes a fixed, required, or
1695 ; optional rule. If a fixed or required rule has
1696 ; no qualifier, then exactly one such AVP MUST
1697 ; be present. If an optional rule has no
1698 ; qualifier, then 0 or 1 such AVP may be
1699 ; present. If an optional rule has a qualifier,
1700 ; then the value of min MUST be 0 if present.
1701 ;
1702 ; NOTE: "[" and "]" have a different meaning
1703 ; than in ABNF (see the optional rule, above).
1704 ; These braces cannot be used to express
1705 ; optional fixed rules (such as an optional
1706 ; ICV at the end). To do this, the convention
1707 ; is '0*1fixed'.
1709 min = 1*DIGIT
1710 ; The minimum number of times the element may
1711 ; be present. The default value is zero for
1712 ; fixed and optional rules. The default value
1713 ; is one for required rules. The value of zero
1714 ; is not allowed for required rules.
1716 max = 1*DIGIT
1717 ; The maximum number of times the element may
1718 ; be present. The default value is infinity. A
1719 ; value of zero implies the AVP MUST NOT be
1720 ; present.
1722 avp-spec = diameter-name
1723 ; The avp-spec has to be an AVP Name, defined
1724 ; in the base or extended Diameter
1725 ; specifications.
1727 avp-name = avp-spec / "AVP"
1728 ; The string "AVP" stands for *any* arbitrary AVP
1729 ; Name, not otherwise listed in that command code
1730 ; definition. Addition this AVP is recommended for
1731 ; all command ABNFs to allow for extensibility.
1733 The following is a definition of a fictitious command code:
1735 Example-Request ::= < Diameter Header: 9999999, REQ, PXY >
1736 { User-Name }
1737 * { Origin-Host }
1738 * [ AVP ]
1740 3.3. Diameter Command Naming Conventions
1742 Diameter command names typically includes one or more English words
1743 followed by the verb Request or Answer. Each English word is
1744 delimited by a hyphen. A three-letter acronym for both the request
1745 and answer is also normally provided.
1747 An example is a message set used to terminate a session. The command
1748 name is Session-Terminate-Request and Session-Terminate-Answer, while
1749 the acronyms are STR and STA, respectively.
1751 Both the request and the answer for a given command share the same
1752 command code. The request is identified by the R(equest) bit in the
1753 Diameter header set to one (1), to ask that a particular action be
1754 performed, such as authorizing a user or terminating a session. Once
1755 the receiver has completed the request it issues the corresponding
1756 answer, which includes a result code that communicates one of the
1757 following:
1759 o The request was successful
1761 o The request failed
1763 o An additional request has to be sent to provide information the
1764 peer requires prior to returning a successful or failed answer.
1766 o The receiver could not process the request, but provides
1767 information about a Diameter peer that is able to satisfy the
1768 request, known as redirect.
1770 Additional information, encoded within AVPs, may also be included in
1771 answer messages.
1773 4. Diameter AVPs
1775 Diameter AVPs carry specific authentication, accounting,
1776 authorization and routing information as well as configuration
1777 details for the request and reply.
1779 Each AVP of type OctetString MUST be padded to align on a 32-bit
1780 boundary, while other AVP types align naturally. A number of zero-
1781 valued bytes are added to the end of the AVP Data field till a word
1782 boundary is reached. The length of the padding is not reflected in
1783 the AVP Length field.
1785 4.1. AVP Header
1787 The fields in the AVP header MUST be sent in network byte order. The
1788 format of the header is:
1790 0 1 2 3
1791 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
1792 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1793 | AVP Code |
1794 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1795 |V M P r r r r r| AVP Length |
1796 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1797 | Vendor-ID (opt) |
1798 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1799 | Data ...
1800 +-+-+-+-+-+-+-+-+
1802 AVP Code
1804 The AVP Code, combined with the Vendor-Id field, identifies the
1805 attribute uniquely. AVP numbers 1 through 255 are reserved for
1806 backward compatibility with RADIUS, without setting the Vendor-Id
1807 field. AVP numbers 256 and above are used for Diameter, which are
1808 allocated by IANA (see Section 11.1).
1810 AVP Flags
1812 The AVP Flags field informs the receiver how each attribute must
1813 be handled. The 'r' (reserved) bits are unused and SHOULD be set
1814 to 0. Note that subsequent Diameter applications MAY define
1815 additional bits within the AVP Header, and an unrecognized bit
1816 SHOULD be considered an error. The 'P' bit has been reserved for
1817 future usage of end-to-end security. At the time of writing there
1818 are no end-to-end security mechanisms specified therefore the 'P'
1819 bit SHOULD be set to 0.
1821 The 'M' Bit, known as the Mandatory bit, indicates whether the
1822 receiver of the AVP MUST parse and understand the semantic of the
1823 AVP including its content. The receiving entity MUST return an
1824 appropriate error message if it receives an AVP that has the M-bit
1825 set but does not understand it. An exception applies when the AVP
1826 is embedded within a Grouped AVP. See Section 4.4 for details.
1827 Diameter Relay and redirect agents MUST NOT reject messages with
1828 unrecognized AVPs.
1830 The 'M' bit MUST be set according to the rules defined in the
1831 application specification which introduces or re-uses this AVP.
1832 Within a given application, the M-bit setting for an AVP is either
1833 defined for all command types or for each command type.
1835 AVPs with the 'M' bit cleared are informational only and a
1836 receiver that receives a message with such an AVP that is not
1837 supported, or whose value is not supported, MAY simply ignore the
1838 AVP.
1840 The 'V' bit, known as the Vendor-Specific bit, indicates whether
1841 the optional Vendor-ID field is present in the AVP header. When
1842 set the AVP Code belongs to the specific vendor code address
1843 space.
1845 AVP Length
1847 The AVP Length field is three octets, and indicates the number of
1848 octets in this AVP including the AVP Code, AVP Length, AVP Flags,
1849 Vendor-ID field (if present) and the AVP data. If a message is
1850 received with an invalid attribute length, the message MUST be
1851 rejected.
1853 4.1.1. Optional Header Elements
1855 The AVP Header contains one optional field. This field is only
1856 present if the respective bit-flag is enabled.
1858 Vendor-ID
1860 The Vendor-ID field is present if the 'V' bit is set in the AVP
1861 Flags field. The optional four-octet Vendor-ID field contains the
1862 IANA assigned "SMI Network Management Private Enterprise Codes"
1863 [RFC3232] value, encoded in network byte order. Any vendor or
1864 standardization organization that are also treated like vendors in
1865 the IANA managed"SMI Network Management Private Enterprise Codes"
1866 space wishing to implement a vendor-specific Diameter AVP MUST use
1867 their own Vendor-ID along with their privately managed AVP address
1868 space, guaranteeing that they will not collide with any other
1869 vendor's vendor-specific AVP(s), nor with future IETF AVPs.
1871 A vendor ID value of zero (0) corresponds to the IETF adopted AVP
1872 values, as managed by the IANA. Since the absence of the vendor
1873 ID field implies that the AVP in question is not vendor specific,
1874 implementations MUST NOT use the zero (0) vendor ID.
1876 4.2. Basic AVP Data Formats
1878 The Data field is zero or more octets and contains information
1879 specific to the Attribute. The format and length of the Data field
1880 is determined by the AVP Code and AVP Length fields. The format of
1881 the Data field MUST be one of the following base data types or a data
1882 type derived from the base data types. In the event that a new Basic
1883 AVP Data Format is needed, a new version of this RFC MUST be created.
1885 OctetString
1887 The data contains arbitrary data of variable length. Unless
1888 otherwise noted, the AVP Length field MUST be set to at least 8
1889 (12 if the 'V' bit is enabled). AVP Values of this type that are
1890 not a multiple of four-octets in length is followed by the
1891 necessary padding so that the next AVP (if any) will start on a
1892 32-bit boundary.
1894 Integer32
1896 32 bit signed value, in network byte order. The AVP Length field
1897 MUST be set to 12 (16 if the 'V' bit is enabled).
1899 Integer64
1901 64 bit signed value, in network byte order. The AVP Length field
1902 MUST be set to 16 (20 if the 'V' bit is enabled).
1904 Unsigned32
1906 32 bit unsigned value, in network byte order. The AVP Length
1907 field MUST be set to 12 (16 if the 'V' bit is enabled).
1909 Unsigned64
1911 64 bit unsigned value, in network byte order. The AVP Length
1912 field MUST be set to 16 (20 if the 'V' bit is enabled).
1914 Float32
1916 This represents floating point values of single precision as
1917 described by [FLOATPOINT]. The 32-bit value is transmitted in
1918 network byte order. The AVP Length field MUST be set to 12 (16 if
1919 the 'V' bit is enabled).
1921 Float64
1923 This represents floating point values of double precision as
1924 described by [FLOATPOINT]. The 64-bit value is transmitted in
1925 network byte order. The AVP Length field MUST be set to 16 (20 if
1926 the 'V' bit is enabled).
1928 Grouped
1930 The Data field is specified as a sequence of AVPs. Each of these
1931 AVPs follows - in the order in which they are specified -
1932 including their headers and padding. The AVP Length field is set
1933 to 8 (12 if the 'V' bit is enabled) plus the total length of all
1934 included AVPs, including their headers and padding. Thus the AVP
1935 length field of an AVP of type Grouped is always a multiple of 4.
1937 4.3. Derived AVP Data Formats
1939 In addition to using the Basic AVP Data Formats, applications may
1940 define data formats derived from the Basic AVP Data Formats. An
1941 application that defines new AVP Derived Data Formats MUST include
1942 them in a section entitled "AVP Derived Data Formats", using the same
1943 format as the definitions below. Each new definition MUST be either
1944 defined or listed with a reference to the RFC that defines the
1945 format.
1947 The below AVP Derived Data Formats are commonly used by applications.
1949 Address
1951 The Address format is derived from the OctetString AVP Base
1952 Format. It is a discriminated union, representing, for example a
1953 32-bit (IPv4) [RFC791] or 128-bit (IPv6) [RFC4291] address, most
1954 significant octet first. The first two octets of the Address AVP
1955 represents the AddressType, which contains an Address Family
1956 defined in [IANAADFAM]. The AddressType is used to discriminate
1957 the content and format of the remaining octets.
1959 Time
1961 The Time format is derived from the OctetString AVP Base Format.
1962 The string MUST contain four octets, in the same format as the
1963 first four bytes are in the NTP timestamp format. The NTP
1964 Timestamp format is defined in Chapter 3 of [RFC4330].
1966 This represents the number of seconds since 0h on 1 January 1900
1967 with respect to the Coordinated Universal Time (UTC).
1969 On 6h 28m 16s UTC, 7 February 2036 the time value will overflow.
1970 SNTP [RFC4330] describes a procedure to extend the time to 2104.
1971 This procedure MUST be supported by all Diameter nodes.
1973 UTF8String
1975 The UTF8String format is derived from the OctetString AVP Base
1976 Format. This is a human readable string represented using the
1977 ISO/IEC IS 10646-1 character set, encoded as an OctetString using
1978 the UTF-8 [RFC3629] transformation format described in RFC 3629.
1980 Since additional code points are added by amendments to the 10646
1981 standard from time to time, implementations MUST be prepared to
1982 encounter any code point from 0x00000001 to 0x7fffffff. Byte
1983 sequences that do not correspond to the valid encoding of a code
1984 point into UTF-8 charset or are outside this range are prohibited.
1986 The use of control codes SHOULD be avoided. When it is necessary
1987 to represent a new line, the control code sequence CR LF SHOULD be
1988 used.
1990 The use of leading or trailing white space SHOULD be avoided.
1992 For code points not directly supported by user interface hardware
1993 or software, an alternative means of entry and display, such as
1994 hexadecimal, MAY be provided.
1996 For information encoded in 7-bit US-ASCII, the UTF-8 charset is
1997 identical to the US-ASCII charset.
1999 UTF-8 may require multiple bytes to represent a single character /
2000 code point; thus the length of an UTF8String in octets may be
2001 different from the number of characters encoded.
2003 Note that the AVP Length field of an UTF8String is measured in
2004 octets, not characters.
2006 DiameterIdentity
2008 The DiameterIdentity format is derived from the OctetString AVP
2009 Base Format.
2011 DiameterIdentity = FQDN
2013 DiameterIdentity value is used to uniquely identify a Diameter
2014 node for purposes of duplicate connection and routing loop
2015 detection.
2017 The contents of the string MUST be the FQDN of the Diameter node.
2018 If multiple Diameter nodes run on the same host, each Diameter
2019 node MUST be assigned a unique DiameterIdentity. If a Diameter
2020 node can be identified by several FQDNs, a single FQDN should be
2021 picked at startup, and used as the only DiameterIdentity for that
2022 node, whatever the connection it is sent on. Note that in this
2023 document, DiameterIdentity is in ASCII form in order to be
2024 compatible with existing DNS infrastructure. See Appendix D for
2025 interactions between the Diameter protocol and Internationalized
2026 Domain Name (IDNs).
2028 DiameterURI
2030 The DiameterURI MUST follow the Uniform Resource Identifiers (URI)
2031 syntax [RFC3986] rules specified below:
2033 "aaa://" FQDN [ port ] [ transport ] [ protocol ]
2035 ; No transport security
2037 "aaas://" FQDN [ port ] [ transport ] [ protocol ]
2039 ; Transport security used
2041 FQDN = Fully Qualified Host Name
2043 port = ":" 1*DIGIT
2045 ; One of the ports used to listen for
2046 ; incoming connections.
2047 ; If absent,
2048 ; the default Diameter port (3868) is
2049 ; assumed.
2051 transport = ";transport=" transport-protocol
2053 ; One of the transports used to listen
2054 ; for incoming connections. If absent,
2055 ; the default protocol is assumed to be TCP.
2056 ; UDP MUST NOT be used when the aaa-protocol
2057 ; field is set to diameter.
2059 transport-protocol = ( "tcp" / "sctp" / "udp" )
2061 protocol = ";protocol=" aaa-protocol
2063 ; If absent, the default AAA protocol
2064 ; is Diameter.
2066 aaa-protocol = ( "diameter" / "radius" / "tacacs+" )
2068 The following are examples of valid Diameter host identities:
2070 aaa://host.example.com;transport=tcp
2071 aaa://host.example.com:6666;transport=tcp
2072 aaa://host.example.com;protocol=diameter
2073 aaa://host.example.com:6666;protocol=diameter
2074 aaa://host.example.com:6666;transport=tcp;protocol=diameter
2075 aaa://host.example.com:1813;transport=udp;protocol=radius
2077 Enumerated
2079 Enumerated is derived from the Integer32 AVP Base Format. The
2080 definition contains a list of valid values and their
2081 interpretation and is described in the Diameter application
2082 introducing the AVP.
2084 IPFilterRule
2086 The IPFilterRule format is derived from the OctetString AVP Base
2087 Format and uses the ASCII charset. The rule syntax is a modified
2088 subset of ipfw(8) from FreeBSD. Packets may be filtered based on
2089 the following information that is associated with it:
2091 Direction (in or out)
2092 Source and destination IP address (possibly masked)
2093 Protocol
2094 Source and destination port (lists or ranges)
2095 TCP flags
2096 IP fragment flag
2097 IP options
2098 ICMP types
2100 Rules for the appropriate direction are evaluated in order, with
2101 the first matched rule terminating the evaluation. Each packet is
2102 evaluated once. If no rule matches, the packet is dropped if the
2103 last rule evaluated was a permit, and passed if the last rule was
2104 a deny.
2106 IPFilterRule filters MUST follow the format:
2108 action dir proto from src to dst [options]
2110 action permit - Allow packets that match the rule.
2111 deny - Drop packets that match the rule.
2113 dir "in" is from the terminal, "out" is to the
2114 terminal.
2116 proto An IP protocol specified by number. The "ip"
2117 keyword means any protocol will match.
2119 src and dst
[ports]
2121 The may be specified as:
2122 ipno An IPv4 or IPv6 number in dotted-
2123 quad or canonical IPv6 form. Only
2124 this exact IP number will match the
2125 rule.
2126 ipno/bits An IP number as above with a mask
2127 width of the form 1.2.3.4/24. In
2128 this case, all IP numbers from
2129 1.2.3.0 to 1.2.3.255 will match.
2130 The bit width MUST be valid for the
2131 IP version and the IP number MUST
2132 NOT have bits set beyond the mask.
2133 For a match to occur, the same IP
2134 version must be present in the
2135 packet that was used in describing
2136 the IP address. To test for a
2137 particular IP version, the bits part
2138 can be set to zero. The keyword
2139 "any" is 0.0.0.0/0 or the IPv6
2140 equivalent. The keyword "assigned"
2141 is the address or set of addresses
2142 assigned to the terminal. For IPv4,
2143 a typical first rule is often "deny
2144 in ip! assigned"
2146 The sense of the match can be inverted by
2147 preceding an address with the not modifier (!),
2148 causing all other addresses to be matched
2149 instead. This does not affect the selection of
2150 port numbers.
2152 With the TCP, UDP and SCTP protocols, optional
2153 ports may be specified as:
2155 {port/port-port}[,ports[,...]]
2157 The '-' notation specifies a range of ports
2158 (including boundaries).
2160 Fragmented packets that have a non-zero offset
2161 (i.e., not the first fragment) will never match
2162 a rule that has one or more port
2163 specifications. See the frag option for
2164 details on matching fragmented packets.
2166 options:
2167 frag Match if the packet is a fragment and this is not
2168 the first fragment of the datagram. frag may not
2169 be used in conjunction with either tcpflags or
2170 TCP/UDP port specifications.
2172 ipoptions spec
2173 Match if the IP header contains the comma
2174 separated list of options specified in spec. The
2175 supported IP options are:
2177 ssrr (strict source route), lsrr (loose source
2178 route), rr (record packet route) and ts
2179 (timestamp). The absence of a particular option
2180 may be denoted with a '!'.
2182 tcpoptions spec
2183 Match if the TCP header contains the comma
2184 separated list of options specified in spec. The
2185 supported TCP options are:
2187 mss (maximum segment size), window (tcp window
2188 advertisement), sack (selective ack), ts (rfc1323
2189 timestamp) and cc (rfc1644 t/tcp connection
2190 count). The absence of a particular option may
2191 be denoted with a '!'.
2193 established
2194 TCP packets only. Match packets that have the RST
2195 or ACK bits set.
2197 setup TCP packets only. Match packets that have the SYN
2198 bit set but no ACK bit.
2200 tcpflags spec
2201 TCP packets only. Match if the TCP header
2202 contains the comma separated list of flags
2203 specified in spec. The supported TCP flags are:
2205 fin, syn, rst, psh, ack and urg. The absence of a
2206 particular flag may be denoted with a '!'. A rule
2207 that contains a tcpflags specification can never
2208 match a fragmented packet that has a non-zero
2209 offset. See the frag option for details on
2210 matching fragmented packets.
2212 icmptypes types
2213 ICMP packets only. Match if the ICMP type is in
2214 the list types. The list may be specified as any
2215 combination of ranges or individual types
2216 separated by commas. Both the numeric values and
2217 the symbolic values listed below can be used. The
2218 supported ICMP types are:
2220 echo reply (0), destination unreachable (3),
2221 source quench (4), redirect (5), echo request
2222 (8), router advertisement (9), router
2223 solicitation (10), time-to-live exceeded (11), IP
2224 header bad (12), timestamp request (13),
2225 timestamp reply (14), information request (15),
2226 information reply (16), address mask request (17)
2227 and address mask reply (18).
2229 There is one kind of packet that the access device MUST always
2230 discard, that is an IP fragment with a fragment offset of one.
2231 This is a valid packet, but it only has one use, to try to
2232 circumvent firewalls.
2234 An access device that is unable to interpret or apply a deny rule
2235 MUST terminate the session. An access device that is unable to
2236 interpret or apply a permit rule MAY apply a more restrictive
2237 rule. An access device MAY apply deny rules of its own before the
2238 supplied rules, for example to protect the access device owner's
2239 infrastructure.
2241 4.4. Grouped AVP Values
2243 The Diameter protocol allows AVP values of type 'Grouped'. This
2244 implies that the Data field is actually a sequence of AVPs. It is
2245 possible to include an AVP with a Grouped type within a Grouped type,
2246 that is, to nest them. AVPs within an AVP of type Grouped have the
2247 same padding requirements as non-Grouped AVPs, as defined in Section
2248 4.
2250 The AVP Code numbering space of all AVPs included in a Grouped AVP is
2251 the same as for non-grouped AVPs. Receivers of a Grouped AVP that
2252 does not have the 'M' (mandatory) bit set and one or more of the
2253 encapsulated AVPs within the group has the 'M' (mandatory) bit set
2254 MAY simply be ignored if the Grouped AVP itself is unrecognized. The
2255 rule applies even if the encapsulated AVP with its 'M' (mandatory)
2256 bit set is further encapsulated within other sub-groups; i.e. other
2257 Grouped AVPs embedded within the Grouped AVP.
2259 Every Grouped AVP defined MUST include a corresponding grammar, using
2260 ABNF [RFC4234] (with modifications), as defined below.
2262 grouped-avp-def = name "::=" avp
2264 name-fmt = ALPHA *(ALPHA / DIGIT / "-")
2266 name = name-fmt
2267 ; The name has to be the name of an AVP,
2268 ; defined in the base or extended Diameter
2269 ; specifications.
2271 avp = header [ *fixed] [ *required] [ *optional]
2273 header = "<" "AVP-Header:" avpcode [vendor] ">"
2275 avpcode = 1*DIGIT
2276 ; The AVP Code assigned to the Grouped AVP
2278 vendor = 1*DIGIT
2279 ; The Vendor-ID assigned to the Grouped AVP.
2280 ; If absent, the default value of zero is
2281 ; used.
2283 4.4.1. Example AVP with a Grouped Data type
2285 The Example-AVP (AVP Code 999999) is of type Grouped and is used to
2286 clarify how Grouped AVP values work. The Grouped Data field has the
2287 following ABNF grammar:
2289 Example-AVP ::= < AVP Header: 999999 >
2290 { Origin-Host }
2291 1*{ Session-Id }
2292 *[ AVP ]
2294 An Example-AVP with Grouped Data follows.
2296 The Origin-Host AVP is required (Section 6.3). In this case:
2298 Origin-Host = "example.com".
2300 One or more Session-Ids must follow. Here there are two:
2302 Session-Id =
2303 "grump.example.com:33041;23432;893;0AF3B81"
2305 Session-Id =
2306 "grump.example.com:33054;23561;2358;0AF3B82"
2308 optional AVPs included are
2310 Recovery-Policy =
2311 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35
2312 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5
2313 c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd
2314 f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a
2315 cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119
2316 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c
2317 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92
2319 Futuristic-Acct-Record =
2320 fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0
2321 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8
2322 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c
2323 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067
2324 d3427475e49968f841
2326 The data for the optional AVPs is represented in hex since the format
2327 of these AVPs is neither known at the time of definition of the
2328 Example-AVP group, nor (likely) at the time when the example instance
2329 of this AVP is interpreted - except by Diameter implementations which
2330 support the same set of AVPs. The encoding example illustrates how
2331 padding is used and how length fields are calculated. Also note that
2332 AVPs may be present in the Grouped AVP value which the receiver
2333 cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record
2334 AVPs). The length of the Example-AVP is the sum of all the length of
2335 the member AVPs including their padding plus the Example-AVP header
2336 size.
2338 This AVP would be encoded as follows:
2340 0 1 2 3 4 5 6 7
2341 +-------+-------+-------+-------+-------+-------+-------+-------+
2342 0 | Example AVP Header (AVP Code = 999999), Length = 496 |
2343 +-------+-------+-------+-------+-------+-------+-------+-------+
2344 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 |
2345 +-------+-------+-------+-------+-------+-------+-------+-------+
2346 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' |
2347 +-------+-------+-------+-------+-------+-------+-------+-------+
2348 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header |
2349 +-------+-------+-------+-------+-------+-------+-------+-------+
2350 32 | (AVP Code = 263), Length = 49 | 'g' | 'r' | 'u' | 'm' |
2351 +-------+-------+-------+-------+-------+-------+-------+-------+
2352 . . .
2353 +-------+-------+-------+-------+-------+-------+-------+-------+
2354 72 | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding|Padding|
2355 +-------+-------+-------+-------+-------+-------+-------+-------+
2356 80 | Session-Id AVP Header (AVP Code = 263), Length = 50 |
2357 +-------+-------+-------+-------+-------+-------+-------+-------+
2358 88 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' |
2359 +-------+-------+-------+-------+-------+-------+-------+-------+
2360 . . .
2361 +-------+-------+-------+-------+-------+-------+-------+-------+
2362 120| '5' | '8' | ';' | '0' | 'A' | 'F' | '3' | 'B' |
2363 +-------+-------+-------+-------+-------+-------+-------+-------+
2364 128| '8' | '2' |Padding|Padding| Recovery-Policy Header (AVP |
2365 +-------+-------+-------+-------+-------+-------+-------+-------+
2366 136| Code = 8341), Length = 223 | 0x21 | 0x63 | 0xbc | 0x1d |
2367 +-------+-------+-------+-------+-------+-------+-------+-------+
2368 144| 0x0a | 0xd8 | 0x23 | 0x71 | 0xf6 | 0xbc | 0x09 | 0x48 |
2369 +-------+-------+-------+-------+-------+-------+-------+-------+
2370 . . .
2371 +-------+-------+-------+-------+-------+-------+-------+-------+
2372 352| 0x8c | 0x7f | 0x92 |Padding| Futuristic-Acct-Record Header |
2373 +-------+-------+-------+-------+-------+-------+-------+-------+
2374 328|(AVP Code = 15930),Length = 137| 0xfe | 0x19 | 0xda | 0x58 |
2375 +-------+-------+-------+-------+-------+-------+-------+-------+
2376 336| 0x02 | 0xac | 0xd9 | 0x8b | 0x07 | 0xa5 | 0xb8 | 0xc6 |
2377 +-------+-------+-------+-------+-------+-------+-------+-------+
2378 . . .
2379 +-------+-------+-------+-------+-------+-------+-------+-------+
2380 488| 0xe4 | 0x99 | 0x68 | 0xf8 | 0x41 |Padding|Padding|Padding|
2381 +-------+-------+-------+-------+-------+-------+-------+-------+
2383 4.5. Diameter Base Protocol AVPs
2385 The following table describes the Diameter AVPs defined in the base
2386 protocol, their AVP Code values, types, possible flag values.
2388 Due to space constraints, the short form DiamIdent is used to
2389 represent DiameterIdentity.
2391 +----------+
2392 | AVP Flag |
2393 | rules |
2394 |----+-----|
2395 AVP Section | |MUST |
2396 Attribute Name Code Defined Data Type |MUST| NOT |
2397 -----------------------------------------|----+-----|
2398 Acct- 85 9.8.2 Unsigned32 | M | V |
2399 Interim-Interval | | |
2400 Accounting- 483 9.8.7 Enumerated | M | V |
2401 Realtime-Required | | |
2402 Acct- 50 9.8.5 UTF8String | M | V |
2403 Multi-Session-Id | | |
2404 Accounting- 485 9.8.3 Unsigned32 | M | V |
2405 Record-Number | | |
2406 Accounting- 480 9.8.1 Enumerated | M | V |
2407 Record-Type | | |
2408 Accounting- 44 9.8.4 OctetString| M | V |
2409 Session-Id | | |
2410 Accounting- 287 9.8.6 Unsigned64 | M | V |
2411 Sub-Session-Id | | |
2412 Acct- 259 6.9 Unsigned32 | M | V |
2413 Application-Id | | |
2414 Auth- 258 6.8 Unsigned32 | M | V |
2415 Application-Id | | |
2416 Auth-Request- 274 8.7 Enumerated | M | V |
2417 Type | | |
2418 Authorization- 291 8.9 Unsigned32 | M | V |
2419 Lifetime | | |
2420 Auth-Grace- 276 8.10 Unsigned32 | M | V |
2421 Period | | |
2422 Auth-Session- 277 8.11 Enumerated | M | V |
2423 State | | |
2424 Re-Auth-Request- 285 8.12 Enumerated | M | V |
2425 Type | | |
2426 Class 25 8.20 OctetString| M | V |
2427 Destination-Host 293 6.5 DiamIdent | M | V |
2428 Destination- 283 6.6 DiamIdent | M | V |
2429 Realm | | |
2430 Disconnect-Cause 273 5.4.3 Enumerated | M | V |
2431 Error-Message 281 7.3 UTF8String | | V,M |
2432 Error-Reporting- 294 7.4 DiamIdent | | V,M |
2433 Host | | |
2434 Event-Timestamp 55 8.21 Time | M | V |
2435 Experimental- 297 7.6 Grouped | M | V |
2436 Result | | |
2437 -----------------------------------------|----+-----|
2438 +----------+
2439 | AVP Flag |
2440 | rules |
2441 |----+-----|
2442 AVP Section | |MUST |
2443 Attribute Name Code Defined Data Type |MUST| NOT |
2444 -----------------------------------------|----+-----|
2445 Experimental- 298 7.7 Unsigned32 | M | V |
2446 Result-Code | | |
2447 Failed-AVP 279 7.5 Grouped | M | V |
2448 Firmware- 267 5.3.4 Unsigned32 | | V,M |
2449 Revision | | |
2450 Host-IP-Address 257 5.3.5 Address | M | V |
2451 Inband-Security | M | V |
2452 -Id 299 6.10 Unsigned32 | | |
2453 Multi-Round- 272 8.19 Unsigned32 | M | V |
2454 Time-Out | | |
2455 Origin-Host 264 6.3 DiamIdent | M | V |
2456 Origin-Realm 296 6.4 DiamIdent | M | V |
2457 Origin-State-Id 278 8.16 Unsigned32 | M | V |
2458 Product-Name 269 5.3.7 UTF8String | | V,M |
2459 Proxy-Host 280 6.7.3 DiamIdent | M | V |
2460 Proxy-Info 284 6.7.2 Grouped | M | V |
2461 Proxy-State 33 6.7.4 OctetString| M | V |
2462 Redirect-Host 292 6.12 DiamURI | M | V |
2463 Redirect-Host- 261 6.13 Enumerated | M | V |
2464 Usage | | |
2465 Redirect-Max- 262 6.14 Unsigned32 | M | V |
2466 Cache-Time | | |
2467 Result-Code 268 7.1 Unsigned32 | M | V |
2468 Route-Record 282 6.7.1 DiamIdent | M | V |
2469 Session-Id 263 8.8 UTF8String | M | V |
2470 Session-Timeout 27 8.13 Unsigned32 | M | V |
2471 Session-Binding 270 8.17 Unsigned32 | M | V |
2472 Session-Server- 271 8.18 Enumerated | M | V |
2473 Failover | | |
2474 Supported- 265 5.3.6 Unsigned32 | M | V |
2475 Vendor-Id | | |
2476 Termination- 295 8.15 Enumerated | M | V |
2477 Cause | | |
2478 User-Name 1 8.14 UTF8String | M | V |
2479 Vendor-Id 266 5.3.3 Unsigned32 | M | V |
2480 Vendor-Specific- 260 6.11 Grouped | M | V |
2481 Application-Id | | |
2482 -----------------------------------------|----+-----|
2484 5. Diameter Peers
2486 This section describes how Diameter nodes establish connections and
2487 communicate with peers.
2489 5.1. Peer Connections
2491 Although a Diameter node may have many possible peers that it is able
2492 to communicate with, it may not be economical to have an established
2493 connection to all of them. At a minimum, a Diameter node SHOULD have
2494 an established connection with two peers per realm, known as the
2495 primary and secondary peers. Of course, a node MAY have additional
2496 connections, if it is deemed necessary. Typically, all messages for
2497 a realm are sent to the primary peer, but in the event that failover
2498 procedures are invoked, any pending requests are sent to the
2499 secondary peer. However, implementations are free to load balance
2500 requests between a set of peers.
2502 Note that a given peer MAY act as a primary for a given realm, while
2503 acting as a secondary for another realm.
2505 When a peer is deemed suspect, which could occur for various reasons,
2506 including not receiving a DWA within an allotted timeframe, no new
2507 requests should be forwarded to the peer, but failover procedures are
2508 invoked. When an active peer is moved to this mode, additional
2509 connections SHOULD be established to ensure that the necessary number
2510 of active connections exists.
2512 There are two ways that a peer is removed from the suspect peer list:
2514 1. The peer is no longer reachable, causing the transport connection
2515 to be shutdown. The peer is moved to the closed state.
2517 2. Three watchdog messages are exchanged with accepted round trip
2518 times, and the connection to the peer is considered stabilized.
2520 In the event the peer being removed is either the primary or
2521 secondary, an alternate peer SHOULD replace the deleted peer, and
2522 assume the role of either primary or secondary.
2524 5.2. Diameter Peer Discovery
2526 Allowing for dynamic Diameter agent discovery will make it possible
2527 for simpler and more robust deployment of Diameter services. In
2528 order to promote interoperable implementations of Diameter peer
2529 discovery, the following mechanisms are described. These are based
2530 on existing IETF standards. The first option (manual configuration)
2531 MUST be supported by all Diameter nodes, while the latter option
2532 (DNS) MAY be supported.
2534 There are two cases where Diameter peer discovery may be performed.
2535 The first is when a Diameter client needs to discover a first-hop
2536 Diameter agent. The second case is when a Diameter agent needs to
2537 discover another agent - for further handling of a Diameter
2538 operation. In both cases, the following 'search order' is
2539 recommended:
2541 1. The Diameter implementation consults its list of static
2542 (manually) configured Diameter agent locations. These will be
2543 used if they exist and respond.
2545 2. The Diameter implementation performs a NAPTR query for a server
2546 in a particular realm. The Diameter implementation has to know
2547 in advance which realm to look for a Diameter agent in. This
2548 could be deduced, for example, from the 'realm' in a NAI that a
2549 Diameter implementation needed to perform a Diameter operation
2550 on.
2552 * The services relevant for the task of transport protocol
2553 selection are those with NAPTR service fields with values
2554 "AAA+D2x", where x is a letter that corresponds to a transport
2555 protocol supported by the domain. This specification defines
2556 D2T for TCP and D2S for SCTP. An IANA registry for NAPTR
2557 service name to transport protocol mappings is defined in
2558 Section 11.6.
2560 These NAPTR records provide a mapping from a domain, to the
2561 SRV record for contacting a server with the specific transport
2562 protocol in the NAPTR services field. The resource record
2563 will contain an empty regular expression and the replacement
2564 value will contain the SRV record for that particular
2565 transport protocol. If the server supports multiple transport
2566 protocols, there will be multiple NAPTR records, each with a
2567 different service value. As per [RFC3403], the client
2568 discards any records whose services fields are not applicable.
2569 For the purposes of this specification, several rules are
2570 defined.
2572 * A client MUST discard any service fields that identify a
2573 resolution service whose value is not "D2X", for values of X
2574 that indicate transport protocols supported by the client.
2575 The NAPTR processing as described in [RFC3403] will result in
2576 discovery of the most preferred transport protocol of the
2577 server that is supported by the client, as well as an SRV
2578 record for the server.
2580 The domain suffixes in the NAPTR replacement field SHOULD
2581 match the domain of the original query.
2583 3. If no NAPTR records are found, the requester directly queries for
2584 SRV records '_diameter._sctp'.realm or '_diameter._tcp'.realm
2585 depending on the requesters network protocol capabilities. If
2586 SRV records are found then the requester can perform address
2587 record query (A RR's and/or AAAA RR's) for the target hostname
2588 specified in the SRV records. If no SRV records are found, the
2589 requester gives up.
2591 If the server is using a site certificate, the domain name in the
2592 NAPTR query and the domain name in the replacement field MUST both be
2593 valid based on the site certificate handed out by the server in the
2594 TLS or IKE exchange. Similarly, the domain name in the SRV query and
2595 the domain name in the target in the SRV record MUST both be valid
2596 based on the same site certificate. Otherwise, an attacker could
2597 modify the DNS records to contain replacement values in a different
2598 domain, and the client could not validate that this was the desired
2599 behavior, or the result of an attack.
2601 Also, the Diameter Peer MUST check to make sure that the discovered
2602 peers are authorized to act in its role. Authentication via IKE or
2603 TLS, or validation of DNS RRs via DNSSEC is not sufficient to
2604 conclude this. For example, a web server may have obtained a valid
2605 TLS certificate, and secured RRs may be included in the DNS, but this
2606 does not imply that it is authorized to act as a Diameter Server.
2608 Authorization can be achieved for example, by configuration of a
2609 Diameter Server CA. Alternatively this can be achieved by definition
2610 of OIDs within TLS or IKE certificates so as to signify Diameter
2611 Server authorization.
2613 A dynamically discovered peer causes an entry in the Peer Table (see
2614 Section 2.6) to be created. Note that entries created via DNS MUST
2615 expire (or be refreshed) within the DNS TTL. If a peer is discovered
2616 outside of the local realm, a routing table entry (see Section 2.7)
2617 for the peer's realm is created. The routing table entry's
2618 expiration MUST match the peer's expiration value.
2620 5.3. Capabilities Exchange
2622 When two Diameter peers establish a transport connection, they MUST
2623 exchange the Capabilities Exchange messages, as specified in the peer
2624 state machine (see Section 5.6). This message allows the discovery
2625 of a peer's identity and its capabilities (protocol version number,
2626 supported Diameter applications, security mechanisms, etc.)
2628 The receiver only issues commands to its peers that have advertised
2629 support for the Diameter application that defines the command. A
2630 Diameter node MUST cache the supported applications in order to
2631 ensure that unrecognized commands and/or AVPs are not unnecessarily
2632 sent to a peer.
2634 A receiver of a Capabilities-Exchange-Req (CER) message that does not
2635 have any applications in common with the sender MUST return a
2636 Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to
2637 DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport
2638 layer connection. Note that receiving a CER or CEA from a peer
2639 advertising itself as a Relay (see Section 2.4) MUST be interpreted
2640 as having common applications with the peer.
2642 The receiver of the Capabilities-Exchange-Request (CER) MUST
2643 determine common applications by computing the intersection of its
2644 own set of supported Application Id against all of the application
2645 identifier AVPs (Auth-Application-Id, Acct-Application-Id and Vendor-
2646 Specific-Application-Id) present in the CER. The value of the
2647 Vendor-Id AVP in the Vendor-Specific-Application-Id MUST NOT be used
2648 during computation. The sender of the Capabilities-Exchange-Answer
2649 (CEA) SHOULD include all of its supported applications as a hint to
2650 the receiver regarding all of its application capabilities.
2652 Similarly, a receiver of a Capabilities-Exchange-Req (CER) message
2653 that does not have any security mechanisms in common with the sender
2654 MUST return a Capabilities-Exchange-Answer (CEA) with the Result-Code
2655 AVP set to DIAMETER_NO_COMMON_SECURITY, and SHOULD disconnect the
2656 transport layer connection.
2658 CERs received from unknown peers MAY be silently discarded, or a CEA
2659 MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER.
2660 In both cases, the transport connection is closed. If the local
2661 policy permits receiving CERs from unknown hosts, a successful CEA
2662 MAY be returned. If a CER from an unknown peer is answered with a
2663 successful CEA, the lifetime of the peer entry is equal to the
2664 lifetime of the transport connection. In case of a transport
2665 failure, all the pending transactions destined to the unknown peer
2666 can be discarded.
2668 The CER and CEA messages MUST NOT be proxied, redirected or relayed.
2670 Since the CER/CEA messages cannot be proxied, it is still possible
2671 that an upstream agent receives a message for which it has no
2672 available peers to handle the application that corresponds to the
2673 Command-Code. In such instances, the 'E' bit is set in the answer
2674 message (see Section 7.) with the Result-Code AVP set to
2675 DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action
2676 (e.g., re-routing request to an alternate peer).
2678 With the exception of the Capabilities-Exchange-Request message, a
2679 message of type Request that includes the Auth-Application-Id or
2680 Acct-Application-Id AVPs, or a message with an application-specific
2681 command code, MAY only be forwarded to a host that has explicitly
2682 advertised support for the application (or has advertised the Relay
2683 Application Id).
2685 5.3.1. Capabilities-Exchange-Request
2687 The Capabilities-Exchange-Request (CER), indicated by the Command-
2688 Code set to 257 and the Command Flags' 'R' bit set, is sent to
2689 exchange local capabilities. Upon detection of a transport failure,
2690 this message MUST NOT be sent to an alternate peer.
2692 When Diameter is run over SCTP [RFC2960], which allows for
2693 connections to span multiple interfaces and multiple IP addresses,
2694 the Capabilities-Exchange-Request message MUST contain one Host-IP-
2695 Address AVP for each potential IP address that MAY be locally used
2696 when transmitting Diameter messages.
2698 Message Format
2700 ::= < Diameter Header: 257, REQ >
2701 { Origin-Host }
2702 { Origin-Realm }
2703 1* { Host-IP-Address }
2704 { Vendor-Id }
2705 { Product-Name }
2706 [ Origin-State-Id ]
2707 * [ Supported-Vendor-Id ]
2708 * [ Auth-Application-Id ]
2709 * [ Inband-Security-Id ]
2710 * [ Acct-Application-Id ]
2711 * [ Vendor-Specific-Application-Id ]
2712 [ Firmware-Revision ]
2713 * [ AVP ]
2715 5.3.2. Capabilities-Exchange-Answer
2717 The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code
2718 set to 257 and the Command Flags' 'R' bit cleared, is sent in
2719 response to a CER message.
2721 When Diameter is run over SCTP [RFC2960], which allows connections to
2722 span multiple interfaces, hence, multiple IP addresses, the
2723 Capabilities-Exchange-Answer message MUST contain one Host-IP-Address
2724 AVP for each potential IP address that MAY be locally used when
2725 transmitting Diameter messages.
2727 Message Format
2729 ::= < Diameter Header: 257 >
2730 { Result-Code }
2731 { Origin-Host }
2732 { Origin-Realm }
2733 1* { Host-IP-Address }
2734 { Vendor-Id }
2735 { Product-Name }
2736 [ Origin-State-Id ]
2737 [ Error-Message ]
2738 [ Failed-AVP ]
2739 * [ Supported-Vendor-Id ]
2740 * [ Auth-Application-Id ]
2741 * [ Inband-Security-Id ]
2742 * [ Acct-Application-Id ]
2743 * [ Vendor-Specific-Application-Id ]
2744 [ Firmware-Revision ]
2745 * [ AVP ]
2747 5.3.3. Vendor-Id AVP
2749 The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains
2750 the IANA "SMI Network Management Private Enterprise Codes" [RFC3232]
2751 value assigned to the vendor of the Diameter device. It is
2752 envisioned that the combination of the Vendor-Id, Product-Name
2753 (Section 5.3.7) and the Firmware-Revision (Section 5.3.4) AVPs may
2754 provide useful debugging information.
2756 A Vendor-Id value of zero in the CER or CEA messages is reserved and
2757 indicates that this field is ignored.
2759 5.3.4. Firmware-Revision AVP
2761 The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is
2762 used to inform a Diameter peer of the firmware revision of the
2763 issuing device.
2765 For devices that do not have a firmware revision (general purpose
2766 computers running Diameter software modules, for instance), the
2767 revision of the Diameter software module may be reported instead.
2769 5.3.5. Host-IP-Address AVP
2771 The Host-IP-Address AVP (AVP Code 257) is of type Address and is used
2772 to inform a Diameter peer of the sender's IP address. All source
2773 addresses that a Diameter node expects to use with SCTP [RFC2960]
2774 MUST be advertised in the CER and CEA messages by including a Host-
2775 IP-Address AVP for each address.
2777 5.3.6. Supported-Vendor-Id AVP
2779 The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and
2780 contains the IANA "SMI Network Management Private Enterprise Codes"
2781 [RFC3232] value assigned to a vendor other than the device vendor but
2782 including the application vendor. This is used in the CER and CEA
2783 messages in order to inform the peer that the sender supports (a
2784 subset of) the vendor-specific AVPs defined by the vendor identified
2785 in this AVP. The value of this AVP MUST NOT be set to zero.
2786 Multiple instances of this AVP containing the same value SHOULD NOT
2787 be sent.
2789 5.3.7. Product-Name AVP
2791 The Product-Name AVP (AVP Code 269) is of type UTF8String, and
2792 contains the vendor assigned name for the product. The Product-Name
2793 AVP SHOULD remain constant across firmware revisions for the same
2794 product.
2796 5.4. Disconnecting Peer connections
2798 When a Diameter node disconnects one of its transport connections,
2799 its peer cannot know the reason for the disconnect, and will most
2800 likely assume that a connectivity problem occurred, or that the peer
2801 has rebooted. In these cases, the peer may periodically attempt to
2802 reconnect, as stated in Section 2.1. In the event that the
2803 disconnect was a result of either a shortage of internal resources,
2804 or simply that the node in question has no intentions of forwarding
2805 any Diameter messages to the peer in the foreseeable future, a
2806 periodic connection request would not be welcomed. The
2807 Disconnection-Reason AVP contains the reason the Diameter node issued
2808 the Disconnect-Peer-Request message.
2810 The Disconnect-Peer-Request message is used by a Diameter node to
2811 inform its peer of its intent to disconnect the transport layer, and
2812 that the peer shouldn't reconnect unless it has a valid reason to do
2813 so (e.g., message to be forwarded). Upon receipt of the message, the
2814 Disconnect-Peer-Answer is returned, which SHOULD contain an error if
2815 messages have recently been forwarded, and are likely in flight,
2816 which would otherwise cause a race condition.
2818 The receiver of the Disconnect-Peer-Answer initiates the transport
2819 disconnect. The sender of the Disconnect-Peer-Answer should be able
2820 to detect the transport closure and cleanup the connection.
2822 5.4.1. Disconnect-Peer-Request
2824 The Disconnect-Peer-Request (DPR), indicated by the Command-Code set
2825 to 282 and the Command Flags' 'R' bit set, is sent to a peer to
2826 inform its intentions to shutdown the transport connection. Upon
2827 detection of a transport failure, this message MUST NOT be sent to an
2828 alternate peer.
2830 Message Format
2832 ::= < Diameter Header: 282, REQ >
2833 { Origin-Host }
2834 { Origin-Realm }
2835 { Disconnect-Cause }
2836 * [ AVP ]
2838 5.4.2. Disconnect-Peer-Answer
2840 The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set
2841 to 282 and the Command Flags' 'R' bit cleared, is sent as a response
2842 to the Disconnect-Peer-Request message. Upon receipt of this
2843 message, the transport connection is shutdown.
2845 Message Format
2847 ::= < Diameter Header: 282 >
2848 { Result-Code }
2849 { Origin-Host }
2850 { Origin-Realm }
2851 [ Error-Message ]
2852 [ Failed-AVP ]
2853 * [ AVP ]
2855 5.4.3. Disconnect-Cause AVP
2857 The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A
2858 Diameter node MUST include this AVP in the Disconnect-Peer-Request
2859 message to inform the peer of the reason for its intention to
2860 shutdown the transport connection. The following values are
2861 supported:
2863 REBOOTING 0
2864 A scheduled reboot is imminent. Receiver of DPR with above result
2865 code MAY attempt reconnection.
2867 BUSY 1
2868 The peer's internal resources are constrained, and it has
2869 determined that the transport connection needs to be closed.
2870 Receiver of DPR with above result code SHOULD NOT attempt
2871 reconnection.
2873 DO_NOT_WANT_TO_TALK_TO_YOU 2
2874 The peer has determined that it does not see a need for the
2875 transport connection to exist, since it does not expect any
2876 messages to be exchanged in the near future. Receiver of DPR
2877 with above result code SHOULD NOT attempt reconnection.
2879 5.5. Transport Failure Detection
2881 Given the nature of the Diameter protocol, it is recommended that
2882 transport failures be detected as soon as possible. Detecting such
2883 failures will minimize the occurrence of messages sent to unavailable
2884 agents, resulting in unnecessary delays, and will provide better
2885 failover performance. The Device-Watchdog-Request and Device-
2886 Watchdog-Answer messages, defined in this section, are used to pro-
2887 actively detect transport failures.
2889 5.5.1. Device-Watchdog-Request
2891 The Device-Watchdog-Request (DWR), indicated by the Command-Code set
2892 to 280 and the Command Flags' 'R' bit set, is sent to a peer when no
2893 traffic has been exchanged between two peers (see Section 5.5.3).
2894 Upon detection of a transport failure, this message MUST NOT be sent
2895 to an alternate peer.
2897 Message Format
2899 ::= < Diameter Header: 280, REQ >
2900 { Origin-Host }
2901 { Origin-Realm }
2902 [ Origin-State-Id ]
2904 * [ AVP ]
2906 5.5.2. Device-Watchdog-Answer
2908 The Device-Watchdog-Answer (DWA), indicated by the Command-Code set
2909 to 280 and the Command Flags' 'R' bit cleared, is sent as a response
2910 to the Device-Watchdog-Request message.
2912 Message Format
2914 ::= < Diameter Header: 280 >
2915 { Result-Code }
2916 { Origin-Host }
2917 { Origin-Realm }
2918 [ Error-Message ]
2919 [ Failed-AVP ]
2920 [ Origin-State-Id ]
2921 * [ AVP ]
2923 5.5.3. Transport Failure Algorithm
2925 The transport failure algorithm is defined in [RFC3539]. All
2926 Diameter implementations MUST support the algorithm defined in the
2927 specification in order to be compliant to the Diameter base protocol.
2929 5.5.4. Failover and Failback Procedures
2931 In the event that a transport failure is detected with a peer, it is
2932 necessary for all pending request messages to be forwarded to an
2933 alternate agent, if possible. This is commonly referred to as
2934 failover.
2936 In order for a Diameter node to perform failover procedures, it is
2937 necessary for the node to maintain a pending message queue for a
2938 given peer. When an answer message is received, the corresponding
2939 request is removed from the queue. The Hop-by-Hop Identifier field
2940 is used to match the answer with the queued request.
2942 When a transport failure is detected, if possible all messages in the
2943 queue are sent to an alternate agent with the T flag set. On booting
2944 a Diameter client or agent, the T flag is also set on any records
2945 still remaining to be transmitted in non-volatile storage. An
2946 example of a case where it is not possible to forward the message to
2947 an alternate server is when the message has a fixed destination, and
2948 the unavailable peer is the message's final destination (see
2949 Destination-Host AVP). Such an error requires that the agent return
2950 an answer message with the 'E' bit set and the Result-Code AVP set to
2951 DIAMETER_UNABLE_TO_DELIVER.
2953 It is important to note that multiple identical requests or answers
2954 MAY be received as a result of a failover. The End-to-End Identifier
2955 field in the Diameter header along with the Origin-Host AVP MUST be
2956 used to identify duplicate messages.
2958 As described in Section 2.1, a connection request should be
2959 periodically attempted with the failed peer in order to re-establish
2960 the transport connection. Once a connection has been successfully
2961 established, messages can once again be forwarded to the peer. This
2962 is commonly referred to as failback.
2964 5.6. Peer State Machine
2966 This section contains a finite state machine that MUST be observed by
2967 all Diameter implementations. Each Diameter node MUST follow the
2968 state machine described below when communicating with each peer.
2969 Multiple actions are separated by commas, and may continue on
2970 succeeding lines, as space requires. Similarly, state and next state
2971 may also span multiple lines, as space requires.
2973 This state machine is closely coupled with the state machine
2974 described in [RFC3539], which is used to open, close, failover,
2975 probe, and reopen transport connections. Note in particular that
2976 [RFC3539] requires the use of watchdog messages to probe connections.
2977 For Diameter, DWR and DWA messages are to be used.
2979 I- is used to represent the initiator (connecting) connection, while
2980 the R- is used to represent the responder (listening) connection.
2981 The lack of a prefix indicates that the event or action is the same
2982 regardless of the connection on which the event occurred.
2984 The stable states that a state machine may be in are Closed, I-Open
2985 and R-Open; all other states are intermediate. Note that I-Open and
2986 R-Open are equivalent except for whether the initiator or responder
2987 transport connection is used for communication.
2989 A CER message is always sent on the initiating connection immediately
2990 after the connection request is successfully completed. In the case
2991 of an election, one of the two connections will shut down. The
2992 responder connection will survive if the Origin-Host of the local
2993 Diameter entity is higher than that of the peer; the initiator
2994 connection will survive if the peer's Origin-Host is higher. All
2995 subsequent messages are sent on the surviving connection. Note that
2996 the results of an election on one peer are guaranteed to be the
2997 inverse of the results on the other.
2999 For TLS usage, a TLS handshake will begin when both ends are in the
3000 open state. If the TLS handshake is successful, all further messages
3001 will be sent via TLS. If the handshake fails, both ends move to the
3002 closed state.
3004 The state machine constrains only the behavior of a Diameter
3005 implementation as seen by Diameter peers through events on the wire.
3007 Any implementation that produces equivalent results is considered
3008 compliant.
3010 state event action next state
3011 -----------------------------------------------------------------
3012 Closed Start I-Snd-Conn-Req Wait-Conn-Ack
3013 R-Conn-CER R-Accept, R-Open
3014 Process-CER,
3015 R-Snd-CEA
3017 Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA
3018 I-Rcv-Conn-Nack Cleanup Closed
3019 R-Conn-CER R-Accept, Wait-Conn-Ack/
3020 Process-CER Elect
3021 Timeout Error Closed
3023 Wait-I-CEA I-Rcv-CEA Process-CEA I-Open
3024 R-Conn-CER R-Accept, Wait-Returns
3025 Process-CER,
3026 Elect
3027 I-Peer-Disc I-Disc Closed
3028 I-Rcv-Non-CEA Error Closed
3029 Timeout Error Closed
3031 Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns
3032 Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open
3033 R-Peer-Disc R-Disc Wait-Conn-Ack
3034 R-Conn-CER R-Reject Wait-Conn-Ack/
3035 Elect
3036 Timeout Error Closed
3038 Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open
3039 I-Peer-Disc I-Disc, R-Open
3040 R-Snd-CEA
3041 I-Rcv-CEA R-Disc I-Open
3042 R-Peer-Disc R-Disc Wait-I-CEA
3043 R-Conn-CER R-Reject Wait-Returns
3044 Timeout Error Closed
3046 R-Open Send-Message R-Snd-Message R-Open
3047 R-Rcv-Message Process R-Open
3048 R-Rcv-DWR Process-DWR, R-Open
3049 R-Snd-DWA
3050 R-Rcv-DWA Process-DWA R-Open
3051 R-Conn-CER R-Reject R-Open
3052 Stop R-Snd-DPR Closing
3053 R-Rcv-DPR R-Snd-DPA, Closed
3054 R-Disc
3055 R-Peer-Disc R-Disc Closed
3057 I-Open Send-Message I-Snd-Message I-Open
3058 I-Rcv-Message Process I-Open
3059 I-Rcv-DWR Process-DWR, I-Open
3060 I-Snd-DWA
3061 I-Rcv-DWA Process-DWA I-Open
3062 R-Conn-CER R-Reject I-Open
3063 Stop I-Snd-DPR Closing
3064 I-Rcv-DPR I-Snd-DPA, Closed
3065 I-Disc
3066 I-Peer-Disc I-Disc Closed
3068 Closing I-Rcv-DPA I-Disc Closed
3069 R-Rcv-DPA R-Disc Closed
3070 Timeout Error Closed
3071 I-Peer-Disc I-Disc Closed
3072 R-Peer-Disc R-Disc Closed
3074 5.6.1. Incoming connections
3076 When a connection request is received from a Diameter peer, it is
3077 not, in the general case, possible to know the identity of that peer
3078 until a CER is received from it. This is because host and port
3079 determine the identity of a Diameter peer; and the source port of an
3080 incoming connection is arbitrary. Upon receipt of CER, the identity
3081 of the connecting peer can be uniquely determined from Origin-Host.
3083 For this reason, a Diameter peer must employ logic separate from the
3084 state machine to receive connection requests, accept them, and await
3085 CER. Once CER arrives on a new connection, the Origin-Host that
3086 identifies the peer is used to locate the state machine associated
3087 with that peer, and the new connection and CER are passed to the
3088 state machine as an R-Conn-CER event.
3090 The logic that handles incoming connections SHOULD close and discard
3091 the connection if any message other than CER arrives, or if an
3092 implementation-defined timeout occurs prior to receipt of CER.
3094 Because handling of incoming connections up to and including receipt
3095 of CER requires logic, separate from that of any individual state
3096 machine associated with a particular peer, it is described separately
3097 in this section rather than in the state machine above.
3099 5.6.2. Events
3101 Transitions and actions in the automaton are caused by events. In
3102 this section, we will ignore the -I and -R prefix, since the actual
3103 event would be identical, but would occur on one of two possible
3104 connections.
3106 Start The Diameter application has signaled that a
3107 connection should be initiated with the peer.
3109 R-Conn-CER An acknowledgement is received stating that the
3110 transport connection has been established, and the
3111 associated CER has arrived.
3113 Rcv-Conn-Ack A positive acknowledgement is received confirming that
3114 the transport connection is established.
3116 Rcv-Conn-Nack A negative acknowledgement was received stating that
3117 the transport connection was not established.
3119 Timeout An application-defined timer has expired while waiting
3120 for some event.
3122 Rcv-CER A CER message from the peer was received.
3124 Rcv-CEA A CEA message from the peer was received.
3126 Rcv-Non-CEA A message other than CEA from the peer was received.
3128 Peer-Disc A disconnection indication from the peer was received.
3130 Rcv-DPR A DPR message from the peer was received.
3132 Rcv-DPA A DPA message from the peer was received.
3134 Win-Election An election was held, and the local node was the
3135 winner.
3137 Send-Message A message is to be sent.
3139 Rcv-Message A message other than CER, CEA, DPR, DPA, DWR or DWA
3140 was received.
3142 Stop The Diameter application has signaled that a
3143 connection should be terminated (e.g., on system
3144 shutdown).
3146 5.6.3. Actions
3148 Actions in the automaton are caused by events and typically indicate
3149 the transmission of packets and/or an action to be taken on the
3150 connection. In this section we will ignore the I- and R-prefix,
3151 since the actual action would be identical, but would occur on one of
3152 two possible connections.
3154 Snd-Conn-Req A transport connection is initiated with the peer.
3156 Accept The incoming connection associated with the R-Conn-CER
3157 is accepted as the responder connection.
3159 Reject The incoming connection associated with the R-Conn-CER
3160 is disconnected.
3162 Process-CER The CER associated with the R-Conn-CER is processed.
3163 Snd-CER A CER message is sent to the peer.
3165 Snd-CEA A CEA message is sent to the peer.
3167 Cleanup If necessary, the connection is shutdown, and any
3168 local resources are freed.
3170 Error The transport layer connection is disconnected,
3171 either politely or abortively, in response to
3172 an error condition. Local resources are freed.
3174 Process-CEA A received CEA is processed.
3176 Snd-DPR A DPR message is sent to the peer.
3178 Snd-DPA A DPA message is sent to the peer.
3180 Disc The transport layer connection is disconnected,
3181 and local resources are freed.
3183 Elect An election occurs (see Section 5.6.4 for more
3184 information).
3186 Snd-Message A message is sent.
3188 Snd-DWR A DWR message is sent.
3190 Snd-DWA A DWA message is sent.
3192 Process-DWR The DWR message is serviced.
3194 Process-DWA The DWA message is serviced.
3196 Process A message is serviced.
3198 5.6.4. The Election Process
3200 The election is performed on the responder. The responder compares
3201 the Origin-Host received in the CER with its own Origin-Host as two
3202 streams of octets. If the local Origin-Host lexicographically
3203 succeeds the received Origin-Host a Win-Election event is issued
3204 locally. Diameter identities are in ASCII form therefore the lexical
3205 comparison is consistent with DNS case insensitivity where octets
3206 that fall in the ASCII range 'a' through 'z' MUST compare equally to
3207 their upper-case counterparts between 'A' and 'Z'. See Appendix D
3208 for interactions between the Diameter protocol and Internationalized
3209 Domain Name (IDNs).
3211 The winner of the election MUST close the connection it initiated.
3212 Historically, maintaining the responder side of a connection was more
3213 efficient than maintaining the initiator side. However, current
3214 practices makes this distinction irrelevant.
3216 6. Diameter message processing
3218 This section describes how Diameter requests and answers are created
3219 and processed.
3221 6.1. Diameter Request Routing Overview
3223 A request is sent towards its final destination using a combination
3224 of the Destination-Realm and Destination-Host AVPs, in one of these
3225 three combinations:
3227 o a request that is not able to be proxied (such as CER) MUST NOT
3228 contain either Destination-Realm or Destination-Host AVPs.
3230 o a request that needs to be sent to a home server serving a
3231 specific realm, but not to a specific server (such as the first
3232 request of a series of round-trips), MUST contain a Destination-
3233 Realm AVP, but MUST NOT contain a Destination-Host AVP. For
3234 Diameter clients, the value of the Destination-Realm AVP MAY be
3235 extracted from the User-Name AVP, or other methods.
3237 o otherwise, a request that needs to be sent to a specific home
3238 server among those serving a given realm, MUST contain both the
3239 Destination-Realm and Destination-Host AVPs.
3241 The Destination-Host AVP is used as described above when the
3242 destination of the request is fixed, which includes:
3244 o Authentication requests that span multiple round trips
3246 o A Diameter message that uses a security mechanism that makes use
3247 of a pre-established session key shared between the source and the
3248 final destination of the message.
3250 o Server initiated messages that MUST be received by a specific
3251 Diameter client (e.g., access device), such as the Abort-Session-
3252 Request message, which is used to request that a particular user's
3253 session be terminated.
3255 Note that an agent can forward a request to a host described in the
3256 Destination-Host AVP only if the host in question is included in its
3257 peer table (see Section 2.7). Otherwise, the request is routed based
3258 on the Destination-Realm only (see Sections 6.1.6).
3260 When a message is received, the message is processed in the following
3261 order:
3263 o If the message is destined for the local host, the procedures
3264 listed in Section 6.1.4 are followed.
3266 o If the message is intended for a Diameter peer with whom the local
3267 host is able to directly communicate, the procedures listed in
3268 Section 6.1.5 are followed. This is known as Request Forwarding.
3270 o The procedures listed in Section 6.1.6 are followed, which is
3271 known as Request Routing.
3273 o If none of the above is successful, an answer is returned with the
3274 Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the E-bit set.
3276 For routing of Diameter messages to work within an administrative
3277 domain, all Diameter nodes within the realm MUST be peers.
3279 Note the processing rules contained in this section are intended to
3280 be used as general guidelines to Diameter developers. Certain
3281 implementations MAY use different methods than the ones described
3282 here, and still comply with the protocol specification. See Section
3283 7 for more detail on error handling.
3285 6.1.1. Originating a Request
3287 When creating a request, in addition to any other procedures
3288 described in the application definition for that specific request,
3289 the following procedures MUST be followed:
3291 o the Command-Code is set to the appropriate value
3293 o the 'R' bit is set
3295 o the End-to-End Identifier is set to a locally unique value
3297 o the Origin-Host and Origin-Realm AVPs MUST be set to the
3298 appropriate values, used to identify the source of the message
3300 o the Destination-Host and Destination-Realm AVPs MUST be set to the
3301 appropriate values as described in Section 6.1.
3303 6.1.2. Sending a Request
3305 When sending a request, originated either locally, or as the result
3306 of a forwarding or routing operation, the following procedures SHOULD
3307 be followed:
3309 o The Hop-by-Hop Identifier SHOULD be set to a locally unique value.
3311 o The message SHOULD be saved in the list of pending requests.
3313 Other actions to perform on the message based on the particular role
3314 the agent is playing are described in the following sections.
3316 6.1.3. Receiving Requests
3318 A relay or proxy agent MUST check for forwarding loops when receiving
3319 requests. A loop is detected if the server finds its own identity in
3320 a Route-Record AVP. When such an event occurs, the agent MUST answer
3321 with the Result-Code AVP set to DIAMETER_LOOP_DETECTED.
3323 6.1.4. Processing Local Requests
3325 A request is known to be for local consumption when one of the
3326 following conditions occur:
3328 o The Destination-Host AVP contains the local host's identity,
3330 o The Destination-Host AVP is not present, the Destination-Realm AVP
3331 contains a realm the server is configured to process locally, and
3332 the Diameter application is locally supported, or
3334 o Both the Destination-Host and the Destination-Realm are not
3335 present.
3337 When a request is locally processed, the rules in Section 6.2 should
3338 be used to generate the corresponding answer.
3340 6.1.5. Request Forwarding
3342 Request forwarding is done using the Diameter Peer Table. The
3343 Diameter peer table contains all of the peers that the local node is
3344 able to directly communicate with.
3346 When a request is received, and the host encoded in the Destination-
3347 Host AVP is one that is present in the peer table, the message SHOULD
3348 be forwarded to the peer.
3350 6.1.6. Request Routing
3352 Diameter request message routing is done via realms and application
3353 identifiers. A Diameter message that may be forwarded by Diameter
3354 agents (proxies, redirect or relay agents) MUST include the target
3355 realm in the Destination-Realm AVP. Request routing SHOULD rely on
3356 the Destination-Realm AVP and the Application Id present in the
3357 request message header to aid in the routing decision. The realm MAY
3358 be retrieved from the User-Name AVP, which is in the form of a
3359 Network Access Identifier (NAI). The realm portion of the NAI is
3360 inserted in the Destination-Realm AVP.
3362 Diameter agents MAY have a list of locally supported realms and
3363 applications, and MAY have a list of externally supported realms and
3364 applications. When a request is received that includes a realm
3365 and/or application that is not locally supported, the message is
3366 routed to the peer configured in the Routing Table (see Section 2.7).
3368 Realm names and Application Ids are the minimum supported routing
3369 criteria, additional information maybe needed to support redirect
3370 semantics.
3372 6.1.7. Predictive Loop Avoidance
3374 Before forwarding or routing a request, Diameter agents, in addition
3375 to processing done in Section 6.1.3, SHOULD check for the presence of
3376 candidate route's peer identity in any of the Route-Record AVPs. In
3377 an event of the agent detecting the presence of a candidate route's
3378 peer identity in a Route-Record AVP, the agent MUST ignore such route
3379 for the Diameter request message and attempt alternate routes if any.
3380 In case all the candidate routes are eliminated by the above
3381 criteria, the agent SHOULD return DIAMETER_UNABLE_TO_DELIVER message.
3383 6.1.8. Redirecting Requests
3385 When a redirect agent receives a request whose routing entry is set
3386 to REDIRECT, it MUST reply with an answer message with the 'E' bit
3387 set, while maintaining the Hop-by-Hop Identifier in the header, and
3388 include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of
3389 the servers associated with the routing entry are added in separate
3390 Redirect-Host AVP.
3392 +------------------+
3393 | Diameter |
3394 | Redirect Agent |
3395 +------------------+
3396 ^ | 2. command + 'E' bit
3397 1. Request | | Result-Code =
3398 joe@example.com | | DIAMETER_REDIRECT_INDICATION +
3399 | | Redirect-Host AVP(s)
3400 | v
3401 +-------------+ 3. Request +-------------+
3402 | example.com |------------->| example.net |
3403 | Relay | | Diameter |
3404 | Agent |<-------------| Server |
3405 +-------------+ 4. Answer +-------------+
3406 Figure 5: Diameter Redirect Agent
3408 The receiver of the answer message with the 'E' bit set, and the
3409 Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by-
3410 hop field in the Diameter header to identify the request in the
3411 pending message queue (see Section 5.3) that is to be redirected. If
3412 no transport connection exists with the new agent, one is created,
3413 and the request is sent directly to it.
3415 Multiple Redirect-Host AVPs are allowed. The receiver of the answer
3416 message with the 'E' bit set selects exactly one of these hosts as
3417 the destination of the redirected message.
3419 When the Redirect-Host-Usage AVP included in the answer message has a
3420 non-zero value, a route entry for the redirect indications is created
3421 and cached by the receiver. The redirect usage for such route entry
3422 is set by the value of Redirect-Host-Usage AVP and the lifetime of
3423 the cached route entry is set by Redirect-Max-Cache-Time AVP value.
3425 It is possible that multiple redirect indications can create multiple
3426 cached route entries differing only in their redirect usage and the
3427 peer to forward messages to. As an example, two(2) route entries
3428 that are created by two(2) redirect indications results in two(2)
3429 cached routes for the same realm and Application Id. However, one
3430 has a redirect usage of ALL_SESSION where matching request will be
3431 forwarded to one peer and the other has a redirect usage of ALL_REALM
3432 where request are forwarded to another peer. Therefore, an incoming
3433 request that matches the realm and Application Id of both routes will
3434 need additional resolution. In such a case, a routing precedence
3435 rule MUST be used againts the redirect usage value to resolve the
3436 contention. The precedence rule can be found in Section 6.13.
3438 6.1.9. Relaying and Proxying Requests
3440 A relay or proxy agent MUST append a Route-Record AVP to all requests
3441 forwarded. The AVP contains the identity of the peer the request was
3442 received from.
3444 The Hop-by-Hop identifier in the request is saved, and replaced with
3445 a locally unique value. The source of the request is also saved,
3446 which includes the IP address, port and protocol.
3448 A relay or proxy agent MAY include the Proxy-Info AVP in requests if
3449 it requires access to any local state information when the
3450 corresponding response is received. The Proxy-Info AVP has security
3451 implications as state information is distribute to other entities.
3452 As such, it is RECOMMMENDED to protect the content of the Proxy-Info
3453 AVP with cryptographic mechanisms, for example by using a keyed
3454 message digest. Such a mechanism, however, requires the management
3455 of keys, although only locally at the Diameter server. Still, a full
3456 description of the management of the keys used to protect the Proxy-
3457 Info AVP is beyond the scope of this document. Below is a list of
3458 commonly recommended:
3460 o The keys should be generated securely following the randomness
3461 recommendations in [RFC4086].
3463 o The keys and cryptographic protection algorithms should be at
3464 least 128 bits in strength.
3466 o The keys should not be used for any other purpose than generating
3467 and verifying tickets.
3469 o The keys should be changed regularly.
3471 o The keys should be changed if the ticket format or cryptographic
3472 protection algorithms change.
3474 The message is then forwarded to the next hop, as identified in the
3475 Routing Table.
3477 Figure 6 provides an example of message routing using the procedures
3478 listed in these sections.
3480 (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net)
3481 (Origin-Realm=mno.net) (Origin-Realm=mno.net)
3482 (Destination-Realm=example.com) (Destination-
3483 Realm=example.com)
3484 (Route-Record=nas.example.net)
3485 +------+ ------> +------+ ------> +------+
3486 | | (Request) | | (Request) | |
3487 | NAS +-------------------+ DRL +-------------------+ HMS |
3488 | | | | | |
3489 +------+ <------ +------+ <------ +------+
3490 example.net (Answer) example.net (Answer) example.com
3491 (Origin-Host=hms.example.com) (Origin-Host=hms.example.com)
3492 (Origin-Realm=example.com) (Origin-Realm=example.com)
3494 Figure 6: Routing of Diameter messages
3496 Relay and proxy agents are not required to perform full inspection of
3497 incoming messages. At a minimum, validation of the message header
3498 and relevant routing AVPs has to be done when relaying messages.
3499 Proxy agents may optionally perform more in-depth message validation
3500 for applications it is interested in.
3502 6.2. Diameter Answer Processing
3504 When a request is locally processed, the following procedures MUST be
3505 applied to create the associated answer, in addition to any
3506 additional procedures that MAY be discussed in the Diameter
3507 application defining the command:
3509 o The same Hop-by-Hop identifier in the request is used in the
3510 answer.
3512 o The local host's identity is encoded in the Origin-Host AVP.
3514 o The Destination-Host and Destination-Realm AVPs MUST NOT be
3515 present in the answer message.
3517 o The Result-Code AVP is added with its value indicating success or
3518 failure.
3520 o If the Session-Id is present in the request, it MUST be included
3521 in the answer.
3523 o Any Proxy-Info AVPs in the request MUST be added to the answer
3524 message, in the same order they were present in the request.
3526 o The 'P' bit is set to the same value as the one in the request.
3528 o The same End-to-End identifier in the request is used in the
3529 answer.
3531 Note that the error messages (see Section 7.3) are also subjected to
3532 the above processing rules.
3534 6.2.1. Processing received Answers
3536 A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an
3537 answer received against the list of pending requests. The
3538 corresponding message should be removed from the list of pending
3539 requests. It SHOULD ignore answers received that do not match a
3540 known Hop-by-Hop Identifier.
3542 6.2.2. Relaying and Proxying Answers
3544 If the answer is for a request which was proxied or relayed, the
3545 agent MUST restore the original value of the Diameter header's Hop-
3546 by-Hop Identifier field.
3548 If the last Proxy-Info AVP in the message is targeted to the local
3549 Diameter server, the AVP MUST be removed before the answer is
3550 forwarded.
3552 If a relay or proxy agent receives an answer with a Result-Code AVP
3553 indicating a failure, it MUST NOT modify the contents of the AVP.
3554 Any additional local errors detected SHOULD be logged, but not
3555 reflected in the Result-Code AVP. If the agent receives an answer
3556 message with a Result-Code AVP indicating success, and it wishes to
3557 modify the AVP to indicate an error, it MUST modify the Result-Code
3558 AVP to contain the appropriate error in the message destined towards
3559 the access device as well as include the Error-Reporting-Host AVP and
3560 it MUST issue an STR on behalf of the access device towards the
3561 Diameter server.
3563 The agent MUST then send the answer to the host that it received the
3564 original request from.
3566 6.3. Origin-Host AVP
3568 The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and
3569 MUST be present in all Diameter messages. This AVP identifies the
3570 endpoint that originated the Diameter message. Relay agents MUST NOT
3571 modify this AVP.
3573 The value of the Origin-Host AVP is guaranteed to be unique within a
3574 single host.
3576 Note that the Origin-Host AVP may resolve to more than one address as
3577 the Diameter peer may support more than one address.
3579 This AVP SHOULD be placed as close to the Diameter header as
3580 possible.
3582 6.4. Origin-Realm AVP
3584 The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity.
3585 This AVP contains the Realm of the originator of any Diameter message
3586 and MUST be present in all messages.
3588 This AVP SHOULD be placed as close to the Diameter header as
3589 possible.
3591 6.5. Destination-Host AVP
3593 The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity.
3594 This AVP MUST be present in all unsolicited agent initiated messages,
3595 MAY be present in request messages, and MUST NOT be present in Answer
3596 messages.
3598 The absence of the Destination-Host AVP will cause a message to be
3599 sent to any Diameter server supporting the application within the
3600 realm specified in Destination-Realm AVP.
3602 This AVP SHOULD be placed as close to the Diameter header as
3603 possible.
3605 6.6. Destination-Realm AVP
3607 The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity,
3608 and contains the realm the message is to be routed to. The
3609 Destination-Realm AVP MUST NOT be present in Answer messages.
3610 Diameter Clients insert the realm portion of the User-Name AVP.
3611 Diameter servers initiating a request message use the value of the
3612 Origin-Realm AVP from a previous message received from the intended
3613 target host (unless it is known a priori). When present, the
3614 Destination-Realm AVP is used to perform message routing decisions.
3616 An ABNF for a request message that includes the Destination-Realm AVP
3617 SHOULD list the Destination-Realm AVP as a required AVP (an AVP
3618 indicated as {AVP}) otherwise the message is inherently a non-
3619 routable messages.
3621 This AVP SHOULD be placed as close to the Diameter header as
3622 possible.
3624 6.7. Routing AVPs
3626 The AVPs defined in this section are Diameter AVPs used for routing
3627 purposes. These AVPs change as Diameter messages are processed by
3628 agents.
3630 6.7.1. Route-Record AVP
3632 The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The
3633 identity added in this AVP MUST be the same as the one received in
3634 the Origin-Host of the Capabilities Exchange message.
3636 6.7.2. Proxy-Info AVP
3638 The Proxy-Info AVP (AVP Code 284) is of type Grouped. This AVP
3639 contains the identity and local state information of Diameter node
3640 that creates and adds it to a message. The Grouped Data field has
3641 the following ABNF grammar:
3643 Proxy-Info ::= < AVP Header: 284 >
3644 { Proxy-Host }
3645 { Proxy-State }
3647 * [ AVP ]
3649 6.7.3. Proxy-Host AVP
3651 The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This
3652 AVP contains the identity of the host that added the Proxy-Info AVP.
3654 6.7.4. Proxy-State AVP
3656 The Proxy-State AVP (AVP Code 33) is of type OctetString. It
3657 contains state information that would otherwise be stored at the
3658 Diameter entity that created it. As such, this AVP MUST be treated
3659 as opaque data by entities other Diameter entities.
3661 6.8. Auth-Application-Id AVP
3663 The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and
3664 is used in order to advertise support of the Authentication and
3665 Authorization portion of an application (see Section 2.4). If
3666 present in a message other than CER and CEA, the value of the Auth-
3667 Application-Id AVP MUST match the Application Id present in the
3668 Diameter message header.
3670 6.9. Acct-Application-Id AVP
3672 The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and
3673 is used in order to advertise support of the Accounting portion of an
3674 application (see Section 2.4). If present in a message other than
3675 CER and CEA, the value of the Acct-Application-Id AVP MUST match the
3676 Application Id present in the Diameter message header.
3678 6.10. Inband-Security-Id AVP
3680 The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and
3681 is used in order to advertise support of the security portion of the
3682 application.
3684 Currently, the following values are supported, but there is ample
3685 room to add new security Ids.
3687 NO_INBAND_SECURITY 0
3689 This peer does not support TLS. This is the default value, if the
3690 AVP is omitted.
3692 TLS 1
3694 This node supports TLS security, as defined by [RFC4346].
3696 6.11. Vendor-Specific-Application-Id AVP
3698 The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type
3699 Grouped and is used to advertise support of a vendor-specific
3700 Diameter Application. Exactly one instance of either Auth-
3701 Application-Id or Acct-Application-Id AVP MUST be present. The
3702 Application Id carried by either Auth-Application-Id or Acct-
3703 Application-Id AVP MUST comply with vendor specific Application Id
3704 assignment described in Sec 11.3. It MUST also match the Application
3705 Id present in the Diameter header except when used in a CER or CEA
3706 messages.
3708 The Vendor-Id AVP is an informational AVP pertaining to the vendor
3709 who may have authorship of the vendor-specific Diameter application.
3710 It MUST NOT be used as a means of defining a completely separate
3711 vendor-specific Application Id space.
3713 The Vendor-Specific-Application-Id AVP SHOULD be placed as close to
3714 the Diameter header as possible.
3716 AVP Format
3718 ::= < AVP Header: 260 >
3719 { Vendor-Id }
3720 [ Auth-Application-Id ]
3721 [ Acct-Application-Id ]
3723 A Vendor-Specific-Application-Id AVP MUST contain exactly one of
3724 either Auth-Application-Id or Acct-Application-Id. If a Vendor-
3725 Specific-Application-Id is received without any of these two AVPs,
3726 then the recipient SHOULD issue an answer with a Result-Code set to
3727 DIAMETER_MISSING_AVP. The answer SHOULD also include a Failed-AVP
3728 which MUST contain an example of an Auth-Application-Id AVP and an
3729 Acct-Application-Id AVP.
3731 If a Vendor-Specific-Application-Id is received that contains both
3732 Auth-Application-Id and Acct-Application-Id, then the recipient MUST
3733 issue an answer with Result-Code set to
3734 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES. The answer MUST also include a
3735 Failed-AVP which MUST contain the received Auth-Application-Id AVP
3736 and Acct-Application-Id AVP.
3738 6.12. Redirect-Host AVP
3740 One or more of instances of this AVP MUST be present if the answer
3741 message's 'E' bit is set and the Result-Code AVP is set to
3742 DIAMETER_REDIRECT_INDICATION.
3744 Upon receiving the above, the receiving Diameter node SHOULD forward
3745 the request directly to one of the hosts identified in these AVPs.
3746 The server contained in the selected Redirect-Host AVP SHOULD be used
3747 for all messages matching the criteria set by the Redirect-Host-Usage
3748 AVP.
3750 6.13. Redirect-Host-Usage AVP
3752 The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated.
3753 This AVP MAY be present in answer messages whose 'E' bit is set and
3754 the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION.
3756 When present, this AVP provides a hints about how the routing entry
3757 resulting from the Redirect-Host is to be used. The following values
3758 are supported:
3760 DONT_CACHE 0
3762 The host specified in the Redirect-Host AVP SHOULD NOT be cached.
3763 This is the default value.
3765 ALL_SESSION 1
3767 All messages within the same session, as defined by the same value
3768 of the Session-ID AVP SHOULD be sent to the host specified in the
3769 Redirect-Host AVP.
3771 ALL_REALM 2
3773 All messages destined for the realm requested SHOULD be sent to
3774 the host specified in the Redirect-Host AVP.
3776 REALM_AND_APPLICATION 3
3778 All messages for the application requested to the realm specified
3779 SHOULD be sent to the host specified in the Redirect-Host AVP.
3781 ALL_APPLICATION 4
3783 All messages for the application requested SHOULD be sent to the
3784 host specified in the Redirect-Host AVP.
3786 ALL_HOST 5
3788 All messages that would be sent to the host that generated the
3789 Redirect-Host SHOULD be sent to the host specified in the
3790 Redirect- Host AVP.
3792 ALL_USER 6
3794 All messages for the user requested SHOULD be sent to the host
3795 specified in the Redirect-Host AVP.
3797 When multiple cached routes are created by redirect indications and
3798 they differ only in redirect usage and peers to forward requests to
3799 (see Section 6.1.8), a precedence rule MUST be applied to the
3800 redirect usage values of the cached routes during normal routing to
3801 resolve contentions that may occur. The precedence rule is the order
3802 that dictate which redirect usage should be considered before any
3803 other as they appear. The order is as follows:
3805 1. ALL_SESSION
3807 2. ALL_USER
3809 3. REALM_AND_APPLICATION
3811 4. ALL_REALM
3813 5. ALL_APPLICATION
3815 6. ALL_HOST
3817 6.14. Redirect-Max-Cache-Time AVP
3819 The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32.
3820 This AVP MUST be present in answer messages whose 'E' bit is set, the
3821 Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the
3822 Redirect-Host-Usage AVP set to a non-zero value.
3824 This AVP contains the maximum number of seconds the peer and route
3825 table entries, created as a result of the Redirect-Host, SHOULD be
3826 cached. Note that once a host is no longer reachable, any associated
3827 cache, peer and routing table entries MUST be deleted.
3829 7. Error Handling
3831 There are two different types of errors in Diameter; protocol and
3832 application errors. A protocol error is one that occurs at the base
3833 protocol level, and MAY require per hop attention (e.g., message
3834 routing error). Application errors, on the other hand, generally
3835 occur due to a problem with a function specified in a Diameter
3836 application (e.g., user authentication, missing AVP).
3838 Result-Code AVP values that are used to report protocol errors MUST
3839 only be present in answer messages whose 'E' bit is set. When a
3840 request message is received that causes a protocol error, an answer
3841 message is returned with the 'E' bit set, and the Result-Code AVP is
3842 set to the appropriate protocol error value. As the answer is sent
3843 back towards the originator of the request, each proxy or relay agent
3844 MAY take action on the message.
3846 1. Request +---------+ Link Broken
3847 +-------------------------->|Diameter |----///----+
3848 | +---------------------| | v
3849 +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+
3850 |Diameter |<-+ (Unable to Forward) +---------+ |Diameter|
3851 | | | Home |
3852 | Relay 1 |--+ +---------+ | Server |
3853 +---------+ | 3. Request |Diameter | +--------+
3854 +-------------------->| | ^
3855 | Relay 3 |-----------+
3856 +---------+
3858 Figure 7: Example of Protocol Error causing answer message
3860 Figure 7 provides an example of a message forwarded upstream by a
3861 Diameter relay. When the message is received by Relay 2, and it
3862 detects that it cannot forward the request to the home server, an
3863 answer message is returned with the 'E' bit set and the Result-Code
3864 AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls
3865 within the protocol error category, Relay 1 would take special
3866 action, and given the error, attempt to route the message through its
3867 alternate Relay 3.
3869 +---------+ 1. Request +---------+ 2. Request +---------+
3870 | Access |------------>|Diameter |------------>|Diameter |
3871 | | | | | Home |
3872 | Device |<------------| Relay |<------------| Server |
3873 +---------+ 4. Answer +---------+ 3. Answer +---------+
3874 (Missing AVP) (Missing AVP)
3876 Figure 8: Example of Application Error Answer message
3878 Figure 8 provides an example of a Diameter message that caused an
3879 application error. When application errors occur, the Diameter
3880 entity reporting the error clears the 'R' bit in the Command Flags,
3881 and adds the Result-Code AVP with the proper value. Application
3882 errors do not require any proxy or relay agent involvement, and
3883 therefore the message would be forwarded back to the originator of
3884 the request.
3886 There are certain Result-Code AVP application errors that require
3887 additional AVPs to be present in the answer. In these cases, the
3888 Diameter node that sets the Result-Code AVP to indicate the error
3889 MUST add the AVPs. Examples are:
3891 o An unrecognized AVP is received with the 'M' bit (Mandatory bit)
3892 set, causes an answer to be sent with the Result-Code AVP set to
3893 DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the
3894 offending AVP.
3896 o An AVP that is received with an unrecognized value causes an
3897 answer to be returned with the Result-Code AVP set to
3898 DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the
3899 AVP causing the error.
3901 o A command is received that is missing AVP(s) that are defined as
3902 required in the commands ABNF; examples are AVPs indicated as
3903 {AVP}. The receiver issues an answer with the Result-Code set to
3904 DIAMETER_MISSING_AVP, and creates an AVP with the AVP Code and
3905 other fields set as expected in the missing AVP. The created AVP
3906 is then added to the Failed- AVP AVP.
3908 The Result-Code AVP describes the error that the Diameter node
3909 encountered in its processing. In case there are multiple errors,
3910 the Diameter node MUST report only the first error it encountered
3911 (detected possibly in some implementation dependent order). The
3912 specific errors that can be described by this AVP are described in
3913 the following section.
3915 7.1. Result-Code AVP
3917 The Result-Code AVP (AVP Code 268) is of type Unsigned32 and
3918 indicates whether a particular request was completed successfully or
3919 whether an error occurred. All Diameter answer messages in IETF
3920 defined Diameter application specification MUST include one Result-
3921 Code AVP. A non-successful Result-Code AVP (one containing a non
3922 2xxx value other than DIAMETER_REDIRECT_INDICATION) MUST include the
3923 Error-Reporting-Host AVP if the host setting the Result-Code AVP is
3924 different from the identity encoded in the Origin-Host AVP.
3926 The Result-Code data field contains an IANA-managed 32-bit address
3927 space representing errors (see Section 11.4). Diameter provides the
3928 following classes of errors, all identified by the thousands digit in
3929 the decimal notation:
3931 o 1xxx (Informational)
3933 o 2xxx (Success)
3935 o 3xxx (Protocol Errors)
3937 o 4xxx (Transient Failures)
3939 o 5xxx (Permanent Failure)
3941 A non-recognized class (one whose first digit is not defined in this
3942 section) MUST be handled as a permanent failure.
3944 7.1.1. Informational
3946 Errors that fall within this category are used to inform the
3947 requester that a request could not be satisfied, and additional
3948 action is required on its part before access is granted.
3950 DIAMETER_MULTI_ROUND_AUTH 1001
3952 This informational error is returned by a Diameter server to
3953 inform the access device that the authentication mechanism being
3954 used requires multiple round trips, and a subsequent request needs
3955 to be issued in order for access to be granted.
3957 7.1.2. Success
3959 Errors that fall within the Success category are used to inform a
3960 peer that a request has been successfully completed.
3962 DIAMETER_SUCCESS 2001
3964 The request was successfully completed.
3966 DIAMETER_LIMITED_SUCCESS 2002
3968 When returned, the request was successfully completed, but
3969 additional processing is required by the application in order to
3970 provide service to the user.
3972 7.1.3. Protocol Errors
3974 Errors that fall within the Protocol Error category SHOULD be treated
3975 on a per-hop basis, and Diameter proxies MAY attempt to correct the
3976 error, if it is possible. Note that these errors MUST only be used
3977 in answer messages whose 'E' bit is set. This document omits some
3978 error codes defined in [RFC3588]. To provide backward compatibility
3979 with [RFC3588] implementations these error code values are not re-
3980 used and hence the error codes values enumerated below are non-
3981 sequential.
3983 DIAMETER_UNABLE_TO_DELIVER 3002
3985 This error is given when Diameter can not deliver the message to
3986 the destination, either because no host within the realm
3987 supporting the required application was available to process the
3988 request, or because Destination-Host AVP was given without the
3989 associated Destination-Realm AVP.
3991 DIAMETER_REALM_NOT_SERVED 3003
3993 The intended realm of the request is not recognized.
3995 DIAMETER_TOO_BUSY 3004
3997 When returned, a Diameter node SHOULD attempt to send the message
3998 to an alternate peer. This error MUST only be used when a
3999 specific server is requested, and it cannot provide the requested
4000 service.
4002 DIAMETER_LOOP_DETECTED 3005
4004 An agent detected a loop while trying to get the message to the
4005 intended recipient. The message MAY be sent to an alternate peer,
4006 if one is available, but the peer reporting the error has
4007 identified a configuration problem.
4009 DIAMETER_REDIRECT_INDICATION 3006
4011 A redirect agent has determined that the request could not be
4012 satisfied locally and the initiator of the request SHOULD direct
4013 the request directly to the server, whose contact information has
4014 been added to the response. When set, the Redirect-Host AVP MUST
4015 be present.
4017 DIAMETER_APPLICATION_UNSUPPORTED 3007
4019 A request was sent for an application that is not supported.
4021 DIAMETER_INVALID_BIT_IN_HEADER 3011
4023 This error is returned when a reserved bit in the Diameter header
4024 is set to one (1) or the bits in the Diameter header defined in
4025 Section 3 are set incorrectly.
4027 DIAMETER_INVALID_MESSAGE_LENGTH 3012
4029 This error is returned when a request is received with an invalid
4030 message length.
4032 7.1.4. Transient Failures
4034 Errors that fall within the transient failures category are used to
4035 inform a peer that the request could not be satisfied at the time it
4036 was received, but MAY be able to satisfy the request in the future.
4037 Note that these errors MUST be used in answer messages whose 'E' bit
4038 is not set.
4040 DIAMETER_AUTHENTICATION_REJECTED 4001
4042 The authentication process for the user failed, most likely due to
4043 an invalid password used by the user. Further attempts MUST only
4044 be tried after prompting the user for a new password.
4046 DIAMETER_OUT_OF_SPACE 4002
4048 A Diameter node received the accounting request but was unable to
4049 commit it to stable storage due to a temporary lack of space.
4051 ELECTION_LOST 4003
4053 The peer has determined that it has lost the election process and
4054 has therefore disconnected the transport connection.
4056 7.1.5. Permanent Failures
4058 Errors that fall within the permanent failures category are used to
4059 inform the peer that the request failed, and should not be attempted
4060 again. Note that these errors SHOULD be used in answer messages
4061 whose 'E' bit is not set. In error conditions where it is not
4062 possible or efficient to compose application specific answer grammar
4063 then answer messages with E-bit set and complying to the grammar
4064 described in 7.2 MAY also be used for permanent errors.
4066 To provide backward compatibility with existing implementations that
4067 follow [RFC3588], some of the error values that have previously been
4068 used in this category by [RFC3588] will not be re-used. Therefore
4069 the error values enumerated here maybe non-sequential.
4071 DIAMETER_AVP_UNSUPPORTED 5001
4073 The peer received a message that contained an AVP that is not
4074 recognized or supported and was marked with the Mandatory bit. A
4075 Diameter message with this error MUST contain one or more Failed-
4076 AVP AVP containing the AVPs that caused the failure.
4078 DIAMETER_UNKNOWN_SESSION_ID 5002
4080 The request contained an unknown Session-Id.
4082 DIAMETER_AUTHORIZATION_REJECTED 5003
4084 A request was received for which the user could not be authorized.
4085 This error could occur if the service requested is not permitted
4086 to the user.
4088 DIAMETER_INVALID_AVP_VALUE 5004
4090 The request contained an AVP with an invalid value in its data
4091 portion. A Diameter message indicating this error MUST include
4092 the offending AVPs within a Failed-AVP AVP.
4094 DIAMETER_MISSING_AVP 5005
4096 The request did not contain an AVP that is required by the Command
4097 Code definition. If this value is sent in the Result-Code AVP, a
4098 Failed-AVP AVP SHOULD be included in the message. The Failed-AVP
4099 AVP MUST contain an example of the missing AVP complete with the
4100 Vendor-Id if applicable. The value field of the missing AVP
4101 should be of correct minimum length and contain zeroes.
4103 DIAMETER_RESOURCES_EXCEEDED 5006
4105 A request was received that cannot be authorized because the user
4106 has already expended allowed resources. An example of this error
4107 condition is a user that is restricted to one dial-up PPP port,
4108 attempts to establish a second PPP connection.
4110 DIAMETER_CONTRADICTING_AVPS 5007
4112 The Home Diameter server has detected AVPs in the request that
4113 contradicted each other, and is not willing to provide service to
4114 the user. The Failed-AVP AVPs MUST be present which contains the
4115 AVPs that contradicted each other.
4117 DIAMETER_AVP_NOT_ALLOWED 5008
4119 A message was received with an AVP that MUST NOT be present. The
4120 Failed-AVP AVP MUST be included and contain a copy of the
4121 offending AVP.
4123 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009
4125 A message was received that included an AVP that appeared more
4126 often than permitted in the message definition. The Failed-AVP
4127 AVP MUST be included and contain a copy of the first instance of
4128 the offending AVP that exceeded the maximum number of occurrences
4130 DIAMETER_NO_COMMON_APPLICATION 5010
4132 This error is returned by a Diameter node that receives a CER
4133 whereby no applications are common between the CER sending peer
4134 and the CER receiving peer.
4136 DIAMETER_UNSUPPORTED_VERSION 5011
4138 This error is returned when a request was received, whose version
4139 number is unsupported.
4141 DIAMETER_UNABLE_TO_COMPLY 5012
4143 This error is returned when a request is rejected for unspecified
4144 reasons.
4146 DIAMETER_INVALID_AVP_LENGTH 5014
4148 The request contained an AVP with an invalid length. A Diameter
4149 message indicating this error MUST include the offending AVPs
4150 within a Failed-AVP AVP. In cases where the erroneous avp length
4151 value exceeds the message length or is less than the minimum AVP
4152 header length, it is sufficient to include the offending AVP
4153 header and a zero filled payload of the minimum required length
4154 for the payloads data type. If the AVP is a grouped AVP, the
4155 grouped AVP header with an empty payload would be sufficient to
4156 indicate the offending AVP. In the case where the offending AVP
4157 header cannot be fully decoded when the AVP length is less than
4158 the minimum AVP header length, it is sufficient to include an
4159 offending AVP header that is formulated by padding the incomplete
4160 AVP header with zero up to the minimum AVP header length.
4162 DIAMETER_NO_COMMON_SECURITY 5017
4164 This error is returned when a CER message is received, and there
4165 are no common security mechanisms supported between the peers. A
4166 Capabilities-Exchange-Answer (CEA) MUST be returned with the
4167 Result-Code AVP set to DIAMETER_NO_COMMON_SECURITY.
4169 DIAMETER_UNKNOWN_PEER 5018
4171 A CER was received from an unknown peer.
4173 DIAMETER_COMMAND_UNSUPPORTED 5019
4175 This error code is used when a Diameter entity receives a message
4176 with a Command Code that it does not support.
4178 DIAMETER_INVALID_HDR_BITS 5020
4180 A request was received whose bits in the Diameter header were
4181 either set to an invalid combination, or to a value that is
4182 inconsistent with the command code's definition.
4184 DIAMETER_INVALID_AVP_BITS 5021
4186 A request was received that included an AVP whose flag bits are
4187 set to an unrecognized value, or that is inconsistent with the
4188 AVP's definition.
4190 7.2. Error Bit
4192 The 'E' (Error Bit) in the Diameter header is set when the request
4193 caused a protocol-related error (see Section 7.1.3). A message with
4194 the 'E' bit MUST NOT be sent as a response to an answer message.
4195 Note that a message with the 'E' bit set is still subjected to the
4196 processing rules defined in Section 6.2. When set, the answer
4197 message will not conform to the ABNF specification for the command,
4198 and will instead conform to the following ABNF:
4200 Message Format
4202 ::= < Diameter Header: code, ERR [PXY] >
4203 0*1< Session-Id >
4204 { Origin-Host }
4205 { Origin-Realm }
4206 { Result-Code }
4207 [ Origin-State-Id ]
4208 [ Error-Message ]
4209 [ Error-Reporting-Host ]
4210 [ Failed-AVP ]
4211 * [ Proxy-Info ]
4212 * [ AVP ]
4214 Note that the code used in the header is the same than the one found
4215 in the request message, but with the 'R' bit cleared and the 'E' bit
4216 set. The 'P' bit in the header is set to the same value as the one
4217 found in the request message.
4219 7.3. Error-Message AVP
4221 The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY
4222 accompany a Result-Code AVP as a human readable error message. The
4223 Error-Message AVP is not intended to be useful in an environment
4224 where error messages are processed automatically. It SHOULD NOT be
4225 expected that the content of this AVP is parsed by network entities.
4227 7.4. Error-Reporting-Host AVP
4229 The Error-Reporting-Host AVP (AVP Code 294) is of type
4230 DiameterIdentity. This AVP contains the identity of the Diameter
4231 host that sent the Result-Code AVP to a value other than 2001
4232 (Success), only if the host setting the Result-Code is different from
4233 the one encoded in the Origin-Host AVP. This AVP is intended to be
4234 used for troubleshooting purposes, and MUST be set when the Result-
4235 Code AVP indicates a failure.
4237 7.5. Failed-AVP AVP
4239 The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides
4240 debugging information in cases where a request is rejected or not
4241 fully processed due to erroneous information in a specific AVP. The
4242 value of the Result-Code AVP will provide information on the reason
4243 for the Failed-AVP AVP. A Diameter message SHOULD contain only one
4244 Failed-AVP that corresponds to the error indicated by the Result-Code
4245 AVP. For practical purposes, this Failed-AVP would typically refer
4246 to the first AVP processing error that a Diameter node encounters.
4248 The possible reasons for this AVP are the presence of an improperly
4249 constructed AVP, an unsupported or unrecognized AVP, an invalid AVP
4250 value, the omission of a required AVP, the presence of an explicitly
4251 excluded AVP (see tables in Section 10), or the presence of two or
4252 more occurrences of an AVP which is restricted to 0, 1, or 0-1
4253 occurrences.
4255 A Diameter message SHOULD contain one Failed-AVP AVP, containing the
4256 entire AVP that could not be processed successfully. If the failure
4257 reason is omission of a required AVP, an AVP with the missing AVP
4258 code, the missing vendor id, and a zero filled payload of the minimum
4259 required length for the omitted AVP will be added. If the failure
4260 reason is an invalid AVP length where the reported length is less
4261 than the minimum AVP header length or greater than the reported
4262 message length, a copy of the offending AVP header and a zero filled
4263 payload of the minimum required length SHOULD be added.
4265 In the case where the offending AVP is embedded within a grouped AVP,
4266 the Failed-AVP MAY contain the grouped AVP which in turn contains the
4267 single offending AVP. The same method MAY be employed if the grouped
4268 AVP itself is embedded in yet another grouped AVP and so on. In this
4269 case, the Failed-AVP MAY contain the grouped AVP heirarchy up to the
4270 single offending AVP. This enables the recipient to detect the
4271 location of the offending AVP when embedded in a group.
4273 AVP Format
4275 ::= < AVP Header: 279 >
4276 1* {AVP}
4278 7.6. Experimental-Result AVP
4280 The Experimental-Result AVP (AVP Code 297) is of type Grouped, and
4281 indicates whether a particular vendor-specific request was completed
4282 successfully or whether an error occurred. This AVP has the
4283 following structure:
4285 AVP Format
4287 Experimental-Result ::= < AVP Header: 297 >
4288 { Vendor-Id }
4289 { Experimental-Result-Code }
4291 The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies
4292 the vendor responsible for the assignment of the result code which
4293 follows. All Diameter answer messages defined in vendor-specific
4294 applications MUST include either one Result-Code AVP or one
4295 Experimental-Result AVP.
4297 7.7. Experimental-Result-Code AVP
4299 The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32
4300 and contains a vendor-assigned value representing the result of
4301 processing the request.
4303 It is recommended that vendor-specific result codes follow the same
4304 conventions given for the Result-Code AVP regarding the different
4305 types of result codes and the handling of errors (for non 2xxx
4306 values).
4308 8. Diameter User Sessions
4310 In general, Diameter can provide two different types of services to
4311 applications. The first involves authentication and authorization,
4312 and can optionally make use of accounting. The second only makes use
4313 of accounting.
4315 When a service makes use of the authentication and/or authorization
4316 portion of an application, and a user requests access to the network,
4317 the Diameter client issues an auth request to its local server. The
4318 auth request is defined in a service specific Diameter application
4319 (e.g., NASREQ). The request contains a Session-Id AVP, which is used
4320 in subsequent messages (e.g., subsequent authorization, accounting,
4321 etc) relating to the user's session. The Session-Id AVP is a means
4322 for the client and servers to correlate a Diameter message with a
4323 user session.
4325 When a Diameter server authorizes a user to use network resources for
4326 a finite amount of time, and it is willing to extend the
4327 authorization via a future request, it MUST add the Authorization-
4328 Lifetime AVP to the answer message. The Authorization-Lifetime AVP
4329 defines the maximum number of seconds a user MAY make use of the
4330 resources before another authorization request is expected by the
4331 server. The Auth-Grace-Period AVP contains the number of seconds
4332 following the expiration of the Authorization-Lifetime, after which
4333 the server will release all state information related to the user's
4334 session. Note that if payment for services is expected by the
4335 serving realm from the user's home realm, the Authorization-Lifetime
4336 AVP, combined with the Auth-Grace-Period AVP, implies the maximum
4337 length of the session the home realm is willing to be fiscally
4338 responsible for. Services provided past the expiration of the
4339 Authorization-Lifetime and Auth-Grace-Period AVPs are the
4340 responsibility of the access device. Of course, the actual cost of
4341 services rendered is clearly outside the scope of the protocol.
4343 An access device that does not expect to send a re-authorization or a
4344 session termination request to the server MAY include the Auth-
4345 Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint
4346 to the server. If the server accepts the hint, it agrees that since
4347 no session termination message will be received once service to the
4348 user is terminated, it cannot maintain state for the session. If the
4349 answer message from the server contains a different value in the
4350 Auth-Session-State AVP (or the default value if the AVP is absent),
4351 the access device MUST follow the server's directives. Note that the
4352 value NO_STATE_MAINTAINED MUST NOT be set in subsequent re-
4353 authorization requests and answers.
4355 The base protocol does not include any authorization request
4356 messages, since these are largely application-specific and are
4357 defined in a Diameter application document. However, the base
4358 protocol does define a set of messages that are used to terminate
4359 user sessions. These are used to allow servers that maintain state
4360 information to free resources.
4362 When a service only makes use of the Accounting portion of the
4363 Diameter protocol, even in combination with an application, the
4364 Session-Id is still used to identify user sessions. However, the
4365 session termination messages are not used, since a session is
4366 signaled as being terminated by issuing an accounting stop message.
4368 Diameter may also be used for services that cannot be easily
4369 categorized as authentication, authorization or accounting (e.g.,
4370 certain 3GPP IMS interfaces). In such cases, the finite state
4371 machine defined in subsequent sections may not be applicable.
4372 Therefore, the applications itself MAY need to define its own finite
4373 state machine. However, such application specific state machines
4374 SHOULD follow the general state machine framework outlined in this
4375 document such as the use of Session-Id AVPs and the use of STR/STA,
4376 ASR/ASA messages for stateful sessions.
4378 8.1. Authorization Session State Machine
4380 This section contains a set of finite state machines, representing
4381 the life cycle of Diameter sessions, and which MUST be observed by
4382 all Diameter implementations that make use of the authentication
4383 and/or authorization portion of a Diameter application. The term
4384 Service-Specific below refers to a message defined in a Diameter
4385 application (e.g., Mobile IPv4, NASREQ).
4387 There are four different authorization session state machines
4388 supported in the Diameter base protocol. The first two describe a
4389 session in which the server is maintaining session state, indicated
4390 by the value of the Auth-Session-State AVP (or its absence). One
4391 describes the session from a client perspective, the other from a
4392 server perspective. The second two state machines are used when the
4393 server does not maintain session state. Here again, one describes
4394 the session from a client perspective, the other from a server
4395 perspective.
4397 When a session is moved to the Idle state, any resources that were
4398 allocated for the particular session must be released. Any event not
4399 listed in the state machines MUST be considered as an error
4400 condition, and an answer, if applicable, MUST be returned to the
4401 originator of the message.
4403 In the case that an application does not support re-auth, the state
4404 transitions related to server-initiated re-auth when both client and
4405 server sessions maintains state (e.g., Send RAR, Pending, Receive
4406 RAA) MAY be ignored.
4408 In the state table, the event 'Failure to send X' means that the
4409 Diameter agent is unable to send command X to the desired
4410 destination. This could be due to the peer being down, or due to the
4411 peer sending back a transient failure or temporary protocol error
4412 notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the
4413 Result-Code AVP of the corresponding Answer command. The event 'X
4414 successfully sent' is the complement of 'Failure to send X'.
4416 The following state machine is observed by a client when state is
4417 maintained on the server:
4419 CLIENT, STATEFUL
4420 State Event Action New State
4421 -------------------------------------------------------------
4422 Idle Client or Device Requests Send Pending
4423 access service
4424 specific
4425 auth req
4427 Idle ASR Received Send ASA Idle
4428 for unknown session with
4429 Result-Code
4430 = UNKNOWN_
4431 SESSION_ID
4433 Idle RAR Received Send RAA Idle
4434 for unknown session with
4435 Result-Code
4436 = UNKNOWN_
4437 SESSION_ID
4439 Pending Successful Service-specific Grant Open
4440 authorization answer Access
4441 received with default
4442 Auth-Session-State value
4444 Pending Successful Service-specific Sent STR Discon
4445 authorization answer received
4446 but service not provided
4448 Pending Error processing successful Sent STR Discon
4449 Service-specific authorization
4450 answer
4452 Pending Failed Service-specific Cleanup Idle
4453 authorization answer received
4455 Open User or client device Send Open
4456 requests access to service service
4457 specific
4458 auth req
4460 Open Successful Service-specific Provide Open
4461 authorization answer received Service
4463 Open Failed Service-specific Discon. Idle
4464 authorization answer user/device
4465 received.
4467 Open RAR received and client will Send RAA Open
4468 perform subsequent re-auth with
4469 Result-Code
4470 = SUCCESS
4472 Open RAR received and client will Send RAA Idle
4473 not perform subsequent with
4474 re-auth Result-Code
4475 != SUCCESS,
4476 Discon.
4477 user/device
4479 Open Session-Timeout Expires on Send STR Discon
4480 Access Device
4482 Open ASR Received, Send ASA Discon
4483 client will comply with with
4484 request to end the session Result-Code
4485 = SUCCESS,
4486 Send STR.
4488 Open ASR Received, Send ASA Open
4489 client will not comply with with
4490 request to end the session Result-Code
4491 != SUCCESS
4493 Open Authorization-Lifetime + Send STR Discon
4494 Auth-Grace-Period expires on
4495 access device
4497 Discon ASR Received Send ASA Discon
4499 Discon STA Received Discon. Idle
4500 user/device
4502 The following state machine is observed by a server when it is
4503 maintaining state for the session:
4505 SERVER, STATEFUL
4506 State Event Action New State
4507 -------------------------------------------------------------
4508 Idle Service-specific authorization Send Open
4509 request received, and successful
4510 user is authorized serv.
4511 specific
4512 answer
4514 Idle Service-specific authorization Send Idle
4515 request received, and failed serv.
4516 user is not authorized specific
4517 answer
4519 Open Service-specific authorization Send Open
4520 request received, and user successful
4521 is authorized serv. specific
4522 answer
4524 Open Service-specific authorization Send Idle
4525 request received, and user failed serv.
4526 is not authorized specific
4527 answer,
4528 Cleanup
4530 Open Home server wants to confirm Send RAR Pending
4531 authentication and/or
4532 authorization of the user
4534 Pending Received RAA with a failed Cleanup Idle
4535 Result-Code
4537 Pending Received RAA with Result-Code Update Open
4538 = SUCCESS session
4540 Open Home server wants to Send ASR Discon
4541 terminate the service
4543 Open Authorization-Lifetime (and Cleanup Idle
4544 Auth-Grace-Period) expires
4545 on home server.
4547 Open Session-Timeout expires on Cleanup Idle
4548 home server
4550 Discon Failure to send ASR Wait, Discon
4551 resend ASR
4553 Discon ASR successfully sent and Cleanup Idle
4554 ASA Received with Result-Code
4556 Not ASA Received None No Change.
4557 Discon
4559 Any STR Received Send STA, Idle
4560 Cleanup.
4562 The following state machine is observed by a client when state is not
4563 maintained on the server:
4565 CLIENT, STATELESS
4566 State Event Action New State
4567 -------------------------------------------------------------
4568 Idle Client or Device Requests Send Pending
4569 access service
4570 specific
4571 auth req
4573 Pending Successful Service-specific Grant Open
4574 authorization answer Access
4575 received with Auth-Session-
4576 State set to
4577 NO_STATE_MAINTAINED
4579 Pending Failed Service-specific Cleanup Idle
4580 authorization answer
4581 received
4583 Open Session-Timeout Expires on Discon. Idle
4584 Access Device user/device
4586 Open Service to user is terminated Discon. Idle
4587 user/device
4589 The following state machine is observed by a server when it is not
4590 maintaining state for the session:
4592 SERVER, STATELESS
4593 State Event Action New State
4594 -------------------------------------------------------------
4595 Idle Service-specific authorization Send serv. Idle
4596 request received, and specific
4597 successfully processed answer
4599 8.2. Accounting Session State Machine
4601 The following state machines MUST be supported for applications that
4602 have an accounting portion or that require only accounting services.
4603 The first state machine is to be observed by clients.
4605 See Section 9.7 for Accounting Command Codes and Section 9.8 for
4606 Accounting AVPs.
4608 The server side in the accounting state machine depends in some cases
4609 on the particular application. The Diameter base protocol defines a
4610 default state machine that MUST be followed by all applications that
4611 have not specified other state machines. This is the second state
4612 machine in this section described below.
4614 The default server side state machine requires the reception of
4615 accounting records in any order and at any time, and does not place
4616 any standards requirement on the processing of these records.
4617 Implementations of Diameter may perform checking, ordering,
4618 correlation, fraud detection, and other tasks based on these records.
4619 AVPs may need to be inspected as a part of these tasks. The tasks
4620 can happen either immediately after record reception or in a post-
4621 processing phase. However, as these tasks are typically application
4622 or even policy dependent, they are not standardized by the Diameter
4623 specifications. Applications MAY define requirements on when to
4624 accept accounting records based on the used value of Accounting-
4625 Realtime-Required AVP, credit limits checks, and so on.
4627 However, the Diameter base protocol defines one optional server side
4628 state machine that MAY be followed by applications that require
4629 keeping track of the session state at the accounting server. Note
4630 that such tracking is incompatible with the ability to sustain long
4631 duration connectivity problems. Therefore, the use of this state
4632 machine is recommended only in applications where the value of the
4633 Accounting-Realtime-Required AVP is DELIVER_AND_GRANT, and hence
4634 accounting connectivity problems are required to cause the serviced
4635 user to be disconnected. Otherwise, records produced by the client
4636 may be lost by the server which no longer accepts them after the
4637 connectivity is re-established. This state machine is the third
4638 state machine in this section. The state machine is supervised by a
4639 supervision session timer Ts, which the value should be reasonably
4640 higher than the Acct_Interim_Interval value. Ts MAY be set to two
4641 times the value of the Acct_Interim_Interval so as to avoid the
4642 accounting session in the Diameter server to change to Idle state in
4643 case of short transient network failure.
4645 Any event not listed in the state machines MUST be considered as an
4646 error condition, and a corresponding answer, if applicable, MUST be
4647 returned to the originator of the message.
4649 In the state table, the event 'Failure to send' means that the
4650 Diameter client is unable to communicate with the desired
4651 destination. This could be due to the peer being down, or due to the
4652 peer sending back a transient failure or temporary protocol error
4653 notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or
4654 DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting
4655 Answer command.
4657 The event 'Failed answer' means that the Diameter client received a
4658 non-transient failure notification in the Accounting Answer command.
4660 Note that the action 'Disconnect user/dev' MUST have an effect also
4661 to the authorization session state table, e.g., cause the STR message
4662 to be sent, if the given application has both authentication/
4663 authorization and accounting portions.
4665 The states PendingS, PendingI, PendingL, PendingE and PendingB stand
4666 for pending states to wait for an answer to an accounting request
4667 related to a Start, Interim, Stop, Event or buffered record,
4668 respectively.
4670 CLIENT, ACCOUNTING
4671 State Event Action New State
4672 -------------------------------------------------------------
4673 Idle Client or device requests Send PendingS
4674 access accounting
4675 start req.
4677 Idle Client or device requests Send PendingE
4678 a one-time service accounting
4679 event req
4681 Idle Records in storage Send PendingB
4682 record
4684 PendingS Successful accounting Open
4685 start answer received
4687 PendingS Failure to send and buffer Store Open
4688 space available and realtime Start
4689 not equal to DELIVER_AND_GRANT Record
4691 PendingS Failure to send and no buffer Open
4692 space available and realtime
4693 equal to GRANT_AND_LOSE
4695 PendingS Failure to send and no buffer Disconnect Idle
4696 space available and realtime user/dev
4697 not equal to
4698 GRANT_AND_LOSE
4700 PendingS Failed accounting start answer Open
4701 received and realtime equal
4702 to GRANT_AND_LOSE
4704 PendingS Failed accounting start answer Disconnect Idle
4705 received and realtime not user/dev
4706 equal to GRANT_AND_LOSE
4708 PendingS User service terminated Store PendingS
4709 stop
4710 record
4712 Open Interim interval elapses Send PendingI
4713 accounting
4714 interim
4715 record
4716 Open User service terminated Send PendingL
4717 accounting
4718 stop req.
4720 PendingI Successful accounting interim Open
4721 answer received
4723 PendingI Failure to send and (buffer Store Open
4724 space available or old record interim
4725 can be overwritten) and record
4726 realtime not equal to
4727 DELIVER_AND_GRANT
4729 PendingI Failure to send and no buffer Open
4730 space available and realtime
4731 equal to GRANT_AND_LOSE
4733 PendingI Failure to send and no buffer Disconnect Idle
4734 space available and realtime user/dev
4735 not equal to GRANT_AND_LOSE
4737 PendingI Failed accounting interim Open
4738 answer received and realtime
4739 equal to GRANT_AND_LOSE
4741 PendingI Failed accounting interim Disconnect Idle
4742 answer received and realtime user/dev
4743 not equal to GRANT_AND_LOSE
4745 PendingI User service terminated Store PendingI
4746 stop
4747 record
4748 PendingE Successful accounting Idle
4749 event answer received
4751 PendingE Failure to send and buffer Store Idle
4752 space available event
4753 record
4755 PendingE Failure to send and no buffer Idle
4756 space available
4758 PendingE Failed accounting event answer Idle
4759 received
4761 PendingB Successful accounting answer Delete Idle
4762 received record
4764 PendingB Failure to send Idle
4766 PendingB Failed accounting answer Delete Idle
4767 received record
4769 PendingL Successful accounting Idle
4770 stop answer received
4772 PendingL Failure to send and buffer Store Idle
4773 space available stop
4774 record
4776 PendingL Failure to send and no buffer Idle
4777 space available
4779 PendingL Failed accounting stop answer Idle
4780 received
4781 SERVER, STATELESS ACCOUNTING
4782 State Event Action New State
4783 -------------------------------------------------------------
4785 Idle Accounting start request Send Idle
4786 received, and successfully accounting
4787 processed. start
4788 answer
4790 Idle Accounting event request Send Idle
4791 received, and successfully accounting
4792 processed. event
4793 answer
4795 Idle Interim record received, Send Idle
4796 and successfully processed. accounting
4797 interim
4798 answer
4800 Idle Accounting stop request Send Idle
4801 received, and successfully accounting
4802 processed stop answer
4804 Idle Accounting request received, Send Idle
4805 no space left to store accounting
4806 records answer,
4807 Result-Code
4808 = OUT_OF_
4809 SPACE
4811 SERVER, STATEFUL ACCOUNTING
4812 State Event Action New State
4813 -------------------------------------------------------------
4815 Idle Accounting start request Send Open
4816 received, and successfully accounting
4817 processed. start
4818 answer,
4819 Start Ts
4821 Idle Accounting event request Send Idle
4822 received, and successfully accounting
4823 processed. event
4824 answer
4826 Idle Accounting request received, Send Idle
4827 no space left to store accounting
4828 records answer,
4829 Result-Code
4830 = OUT_OF_
4831 SPACE
4833 Open Interim record received, Send Open
4834 and successfully processed. accounting
4835 interim
4836 answer,
4837 Restart Ts
4839 Open Accounting stop request Send Idle
4840 received, and successfully accounting
4841 processed stop answer,
4842 Stop Ts
4844 Open Accounting request received, Send Idle
4845 no space left to store accounting
4846 records answer,
4847 Result-Code
4848 = OUT_OF_
4849 SPACE,
4850 Stop Ts
4852 Open Session supervision timer Ts Stop Ts Idle
4853 expired
4855 8.3. Server-Initiated Re-Auth
4857 A Diameter server may initiate a re-authentication and/or re-
4858 authorization service for a particular session by issuing a Re-Auth-
4859 Request (RAR).
4861 For example, for pre-paid services, the Diameter server that
4862 originally authorized a session may need some confirmation that the
4863 user is still using the services.
4865 An access device that receives a RAR message with Session-Id equal to
4866 a currently active session MUST initiate a re-auth towards the user,
4867 if the service supports this particular feature. Each Diameter
4868 application MUST state whether service-initiated re-auth is
4869 supported, since some applications do not allow access devices to
4870 prompt the user for re-auth.
4872 8.3.1. Re-Auth-Request
4874 The Re-Auth-Request (RAR), indicated by the Command-Code set to 258
4875 and the message flags' 'R' bit set, may be sent by any server to the
4876 access device that is providing session service, to request that the
4877 user be re-authenticated and/or re-authorized.
4879 Message Format
4881 ::= < Diameter Header: 258, REQ, PXY >
4882 < Session-Id >
4883 { Origin-Host }
4884 { Origin-Realm }
4885 { Destination-Realm }
4886 { Destination-Host }
4887 { Auth-Application-Id }
4888 { Re-Auth-Request-Type }
4889 [ User-Name ]
4890 [ Origin-State-Id ]
4891 * [ Proxy-Info ]
4892 * [ Route-Record ]
4893 * [ AVP ]
4895 8.3.2. Re-Auth-Answer
4897 The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258
4898 and the message flags' 'R' bit clear, is sent in response to the RAR.
4899 The Result-Code AVP MUST be present, and indicates the disposition of
4900 the request.
4902 A successful RAA message MUST be followed by an application-specific
4903 authentication and/or authorization message.
4905 Message Format
4907 ::= < Diameter Header: 258, PXY >
4908 < Session-Id >
4909 { Result-Code }
4910 { Origin-Host }
4911 { Origin-Realm }
4912 [ User-Name ]
4913 [ Origin-State-Id ]
4914 [ Error-Message ]
4915 [ Error-Reporting-Host ]
4916 [ Failed-AVP ]
4917 * [ Redirect-Host ]
4918 [ Redirect-Host-Usage ]
4919 [ Redirect-Max-Cache-Time ]
4920 * [ Proxy-Info ]
4921 * [ AVP ]
4923 8.4. Session Termination
4925 It is necessary for a Diameter server that authorized a session, for
4926 which it is maintaining state, to be notified when that session is no
4927 longer active, both for tracking purposes as well as to allow
4928 stateful agents to release any resources that they may have provided
4929 for the user's session. For sessions whose state is not being
4930 maintained, this section is not used.
4932 When a user session that required Diameter authorization terminates,
4933 the access device that provided the service MUST issue a Session-
4934 Termination-Request (STR) message to the Diameter server that
4935 authorized the service, to notify it that the session is no longer
4936 active. An STR MUST be issued when a user session terminates for any
4937 reason, including user logoff, expiration of Session-Timeout,
4938 administrative action, termination upon receipt of an Abort-Session-
4939 Request (see below), orderly shutdown of the access device, etc.
4941 The access device also MUST issue an STR for a session that was
4942 authorized but never actually started. This could occur, for
4943 example, due to a sudden resource shortage in the access device, or
4944 because the access device is unwilling to provide the type of service
4945 requested in the authorization, or because the access device does not
4946 support a mandatory AVP returned in the authorization, etc.
4948 It is also possible that a session that was authorized is never
4949 actually started due to action of a proxy. For example, a proxy may
4950 modify an authorization answer, converting the result from success to
4951 failure, prior to forwarding the message to the access device. If
4952 the answer did not contain an Auth-Session-State AVP with the value
4953 NO_STATE_MAINTAINED, a proxy that causes an authorized session not to
4954 be started MUST issue an STR to the Diameter server that authorized
4955 the session, since the access device has no way of knowing that the
4956 session had been authorized.
4958 A Diameter server that receives an STR message MUST clean up
4959 resources (e.g., session state) associated with the Session-Id
4960 specified in the STR, and return a Session-Termination-Answer.
4962 A Diameter server also MUST clean up resources when the Session-
4963 Timeout expires, or when the Authorization-Lifetime and the Auth-
4964 Grace-Period AVPs expires without receipt of a re-authorization
4965 request, regardless of whether an STR for that session is received.
4966 The access device is not expected to provide service beyond the
4967 expiration of these timers; thus, expiration of either of these
4968 timers implies that the access device may have unexpectedly shut
4969 down.
4971 8.4.1. Session-Termination-Request
4973 The Session-Termination-Request (STR), indicated by the Command-Code
4974 set to 275 and the Command Flags' 'R' bit set, is sent by a Diameter
4975 client or by a Diameter proxy to inform the Diameter Server that an
4976 authenticated and/or authorized session is being terminated.
4978 Message Format
4980 ::= < Diameter Header: 275, REQ, PXY >
4981 < Session-Id >
4982 { Origin-Host }
4983 { Origin-Realm }
4984 { Destination-Realm }
4985 { Auth-Application-Id }
4986 { Termination-Cause }
4987 [ User-Name ]
4988 [ Destination-Host ]
4989 * [ Class ]
4990 [ Origin-State-Id ]
4991 * [ Proxy-Info ]
4992 * [ Route-Record ]
4993 * [ AVP ]
4995 8.4.2. Session-Termination-Answer
4997 The Session-Termination-Answer (STA), indicated by the Command-Code
4998 set to 275 and the message flags' 'R' bit clear, is sent by the
4999 Diameter Server to acknowledge the notification that the session has
5000 been terminated. The Result-Code AVP MUST be present, and MAY
5001 contain an indication that an error occurred while servicing the STR.
5003 Upon sending or receipt of the STA, the Diameter Server MUST release
5004 all resources for the session indicated by the Session-Id AVP. Any
5005 intermediate server in the Proxy-Chain MAY also release any
5006 resources, if necessary.
5008 Message Format
5010 ::= < Diameter Header: 275, PXY >
5011 < Session-Id >
5012 { Result-Code }
5013 { Origin-Host }
5014 { Origin-Realm }
5015 [ User-Name ]
5016 * [ Class ]
5017 [ Error-Message ]
5018 [ Error-Reporting-Host ]
5019 [ Failed-AVP ]
5020 [ Origin-State-Id ]
5021 * [ Redirect-Host ]
5022 [ Redirect-Host-Usage ]
5023 [ Redirect-Max-Cache-Time ]
5024 * [ Proxy-Info ]
5025 * [ AVP ]
5027 8.5. Aborting a Session
5029 A Diameter server may request that the access device stop providing
5030 service for a particular session by issuing an Abort-Session-Request
5031 (ASR).
5033 For example, the Diameter server that originally authorized the
5034 session may be required to cause that session to be stopped for lack
5035 of credit or other reasons that were not anticipated when the session
5036 was first authorized.
5038 An access device that receives an ASR with Session-ID equal to a
5039 currently active session MAY stop the session. Whether the access
5040 device stops the session or not is implementation- and/or
5041 configuration-dependent. For example, an access device may honor
5042 ASRs from certain agents only. In any case, the access device MUST
5043 respond with an Abort-Session-Answer, including a Result-Code AVP to
5044 indicate what action it took.
5046 8.5.1. Abort-Session-Request
5048 The Abort-Session-Request (ASR), indicated by the Command-Code set to
5049 274 and the message flags' 'R' bit set, may be sent by any Diameter
5050 server or any Diameter proxy to the access device that is providing
5051 session service, to request that the session identified by the
5052 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 The Origin-State-Id is used to allow detection of terminated sessions
5104 for which no STR would have been issued, due to unanticipated
5105 shutdown of an access device.
5107 A Diameter client or access device increments the value of the
5108 Origin-State-Id every time it is started or powered-up. The new
5109 Origin-State-Id is then sent in the CER/CEA message immediately upon
5110 connection to the server. The Diameter server receiving the new
5111 Origin-State-Id can determine whether the sending Diameter client had
5112 abrubtly shutdown by comparing the old value of the Origin-State-Id
5113 it has kept for that specific client is less than the new value and
5114 whether it has un-terminated sessions originating from that client.
5116 An access device can also include the Origin-State-Id in request
5117 messages other than CER if there are relays or proxies in between the
5118 access device and the server. In this case, however, the server
5119 cannot discover that the access device has been restarted unless and
5120 until it receives a new request from it. Therefore this mechanism is
5121 more opportunistic across proxies and relays.
5123 The Diameter server may assume that all sessions that were active
5124 prior to detection of a client restart have been terminated. The
5125 Diameter server MAY clean up all session state associated with such
5126 lost sessions, and MAY also issues STRs for all such lost sessions
5127 that were authorized on upstream servers, to allow session state to
5128 be cleaned up globally.
5130 8.7. Auth-Request-Type AVP
5132 The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is
5133 included in application-specific auth requests to inform the peers
5134 whether a user is to be authenticated only, authorized only or both.
5135 Note any value other than both MAY cause RADIUS interoperability
5136 issues. The following values are defined:
5138 AUTHENTICATE_ONLY 1
5140 The request being sent is for authentication only, and MUST
5141 contain the relevant application specific authentication AVPs that
5142 are needed by the Diameter server to authenticate the user.
5144 AUTHORIZE_ONLY 2
5146 The request being sent is for authorization only, and MUST contain
5147 the application specific authorization AVPs that are necessary to
5148 identify the service being requested/offered.
5150 AUTHORIZE_AUTHENTICATE 3
5152 The request contains a request for both authentication and
5153 authorization. The request MUST include both the relevant
5154 application specific authentication information, and authorization
5155 information necessary to identify the service being requested/
5156 offered.
5158 8.8. Session-Id AVP
5160 The Session-Id AVP (AVP Code 263) is of type UTF8String and is used
5161 to identify a specific session (see Section 8). All messages
5162 pertaining to a specific session MUST include only one Session-Id AVP
5163 and the same value MUST be used throughout the life of a session.
5164 When present, the Session-Id SHOULD appear immediately following the
5165 Diameter Header (see Section 3).
5167 The Session-Id MUST be globally and eternally unique, as it is meant
5168 to uniquely identify a user session without reference to any other
5169 information, and may be needed to correlate historical authentication
5170 information with accounting information. The Session-Id includes a
5171 mandatory portion and an implementation-defined portion; a
5172 recommended format for the implementation-defined portion is outlined
5173 below.
5175 The Session-Id MUST begin with the sender's identity encoded in the
5176 DiameterIdentity type (see Section 4.4). The remainder of the
5177 Session-Id is delimited by a ";" character, and MAY be any sequence
5178 that the client can guarantee to be eternally unique; however, the
5179 following format is recommended, (square brackets [] indicate an
5180 optional element):
5182 ;;[;]
5184 and are decimal representations of the
5185 high and low 32 bits of a monotonically increasing 64-bit value. The
5186 64-bit value is rendered in two part to simplify formatting by 32-bit
5187 processors. At startup, the high 32 bits of the 64-bit value MAY be
5188 initialized to the time in NTP format [RFC4330], and the low 32 bits
5189 MAY be initialized to zero. This will for practical purposes
5190 eliminate the possibility of overlapping Session-Ids after a reboot,
5191 assuming the reboot process takes longer than a second.
5192 Alternatively, an implementation MAY keep track of the increasing
5193 value in non-volatile memory.
5195 is implementation specific but may include a modem's
5196 device Id, a layer 2 address, timestamp, etc.
5198 Example, in which there is no optional value:
5200 accesspoint7.example.com;1876543210;523
5202 Example, in which there is an optional value:
5204 accesspoint7.example.com;1876543210;523;mobile@200.1.1.88
5206 The Session-Id is created by the Diameter application initiating the
5207 session, which in most cases is done by the client. Note that a
5208 Session-Id MAY be used for both the authentication, authorization and
5209 accounting commands of a given application.
5211 8.9. Authorization-Lifetime AVP
5213 The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32
5214 and contains the maximum number of seconds of service to be provided
5215 to the user before the user is to be re-authenticated and/or re-
5216 authorized. Care should be taken when the Authorization- Lifetime
5217 value is determined, since a low, non-zero, value could create
5218 significant Diameter traffic, which could congest both the network
5219 and the agents.
5221 A value of zero (0) means that immediate re-auth is necessary by the
5222 access device. The absence of this AVP, or a value of all ones
5223 (meaning all bits in the 32 bit field are set to one) means no re-
5224 auth is expected.
5226 If both this AVP and the Session-Timeout AVP are present in a
5227 message, the value of the latter MUST NOT be smaller than the
5228 Authorization-Lifetime AVP.
5230 An Authorization-Lifetime AVP MAY be present in re-authorization
5231 messages, and contains the number of seconds the user is authorized
5232 to receive service from the time the re-auth answer message is
5233 received by the access device.
5235 This AVP MAY be provided by the client as a hint of the maximum
5236 lifetime that it is willing to accept. The server MUST return a
5237 value that is equal to, or smaller, than the one provided by the
5238 client.
5240 8.10. Auth-Grace-Period AVP
5242 The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and
5243 contains the number of seconds the Diameter server will wait
5244 following the expiration of the Authorization-Lifetime AVP before
5245 cleaning up resources for the session.
5247 8.11. Auth-Session-State AVP
5249 The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and
5250 specifies whether state is maintained for a particular session. The
5251 client MAY include this AVP in requests as a hint to the server, but
5252 the value in the server's answer message is binding. The following
5253 values are supported:
5255 STATE_MAINTAINED 0
5257 This value is used to specify that session state is being
5258 maintained, and the access device MUST issue a session termination
5259 message when service to the user is terminated.
5261 NO_STATE_MAINTAINED 1
5263 This value is used to specify that no session termination messages
5264 will be sent by the access device upon expiration of the
5265 Authorization-Lifetime. This is the default value.
5267 8.12. Re-Auth-Request-Type AVP
5269 The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and
5270 is included in application-specific auth answers to inform the client
5271 of the action expected upon expiration of the Authorization-Lifetime.
5272 If the answer message contains an Authorization-Lifetime AVP with a
5273 positive value, the Re-Auth-Request-Type AVP MUST be present in an
5274 answer message. The following values are defined:
5276 AUTHORIZE_ONLY 0
5278 An authorization only re-auth is expected upon expiration of the
5279 Authorization-Lifetime. This is the default value if the AVP is
5280 not present in answer messages that include the Authorization-
5281 Lifetime.
5283 AUTHORIZE_AUTHENTICATE 1
5285 An authentication and authorization re-auth is expected upon
5286 expiration of the Authorization-Lifetime.
5288 8.13. Session-Timeout AVP
5290 The Session-Timeout AVP (AVP Code 27) [RFC2865] is of type Unsigned32
5291 and contains the maximum number of seconds of service to be provided
5292 to the user before termination of the session. When both the
5293 Session-Timeout and the Authorization-Lifetime AVPs are present in an
5294 answer message, the former MUST be equal to or greater than the value
5295 of the latter.
5297 A session that terminates on an access device due to the expiration
5298 of the Session-Timeout MUST cause an STR to be issued, unless both
5299 the access device and the home server had previously agreed that no
5300 session termination messages would be sent (see Section 8.11).
5302 A Session-Timeout AVP MAY be present in a re-authorization answer
5303 message, and contains the remaining number of seconds from the
5304 beginning of the re-auth.
5306 A value of zero, or the absence of this AVP, means that this session
5307 has an unlimited number of seconds before termination.
5309 This AVP MAY be provided by the client as a hint of the maximum
5310 timeout that it is willing to accept. However, the server MAY return
5311 a value that is equal to, or smaller, than the one provided by the
5312 client.
5314 8.14. User-Name AVP
5316 The User-Name AVP (AVP Code 1) [RFC2865] is of type UTF8String, which
5317 contains the User-Name, in a format consistent with the NAI
5318 specification [RFC4282].
5320 8.15. Termination-Cause AVP
5322 The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and
5323 is used to indicate the reason why a session was terminated on the
5324 access device. The following values are defined:
5326 DIAMETER_LOGOUT 1
5328 The user initiated a disconnect
5330 DIAMETER_SERVICE_NOT_PROVIDED 2
5332 This value is used when the user disconnected prior to the receipt
5333 of the authorization answer message.
5335 DIAMETER_BAD_ANSWER 3
5337 This value indicates that the authorization answer received by the
5338 access device was not processed successfully.
5340 DIAMETER_ADMINISTRATIVE 4
5342 The user was not granted access, or was disconnected, due to
5343 administrative reasons, such as the receipt of a Abort-Session-
5344 Request message.
5346 DIAMETER_LINK_BROKEN 5
5348 The communication to the user was abruptly disconnected.
5350 DIAMETER_AUTH_EXPIRED 6
5352 The user's access was terminated since its authorized session time
5353 has expired.
5355 DIAMETER_USER_MOVED 7
5357 The user is receiving services from another access device.
5359 DIAMETER_SESSION_TIMEOUT 8
5361 The user's session has timed out, and service has been terminated.
5363 8.16. Origin-State-Id AVP
5365 The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a
5366 monotonically increasing value that is advanced whenever a Diameter
5367 entity restarts with loss of previous state, for example upon reboot.
5368 Origin-State-Id MAY be included in any Diameter message, including
5369 CER.
5371 A Diameter entity issuing this AVP MUST create a higher value for
5372 this AVP each time its state is reset. A Diameter entity MAY set
5373 Origin-State-Id to the time of startup, or it MAY use an incrementing
5374 counter retained in non-volatile memory across restarts.
5376 The Origin-State-Id, if present, MUST reflect the state of the entity
5377 indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST
5378 either remove Origin-State-Id or modify it appropriately as well.
5379 Typically, Origin-State-Id is used by an access device that always
5380 starts up with no active sessions; that is, any session active prior
5381 to restart will have been lost. By including Origin-State-Id in a
5382 message, it allows other Diameter entities to infer that sessions
5383 associated with a lower Origin-State-Id are no longer active. If an
5384 access device does not intend for such inferences to be made, it MUST
5385 either not include Origin-State-Id in any message, or set its value
5386 to 0.
5388 8.17. Session-Binding AVP
5390 The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY
5391 be present in application-specific authorization answer messages. If
5392 present, this AVP MAY inform the Diameter client that all future
5393 application-specific re-auth and Session-Termination-Request messages
5394 for this session MUST be sent to the same authorization server.
5396 This field is a bit mask, and the following bits have been defined:
5398 RE_AUTH 1
5400 When set, future re-auth messages for this session MUST NOT
5401 include the Destination-Host AVP. When cleared, the default
5402 value, the Destination-Host AVP MUST be present in all re-auth
5403 messages for this session.
5405 STR 2
5407 When set, the STR message for this session MUST NOT include the
5408 Destination-Host AVP. When cleared, the default value, the
5409 Destination-Host AVP MUST be present in the STR message for this
5410 session.
5412 ACCOUNTING 4
5414 When set, all accounting messages for this session MUST NOT
5415 include the Destination-Host AVP. When cleared, the default
5416 value, the Destination-Host AVP, if known, MUST be present in all
5417 accounting messages for this session.
5419 8.18. Session-Server-Failover AVP
5421 The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated,
5422 and MAY be present in application-specific authorization answer
5423 messages that either do not include the Session-Binding AVP or
5424 include the Session-Binding AVP with any of the bits set to a zero
5425 value. If present, this AVP MAY inform the Diameter client that if a
5426 re-auth or STR message fails due to a delivery problem, the Diameter
5427 client SHOULD issue a subsequent message without the Destination-Host
5428 AVP. When absent, the default value is REFUSE_SERVICE.
5430 The following values are supported:
5432 REFUSE_SERVICE 0
5434 If either the re-auth or the STR message delivery fails, terminate
5435 service with the user, and do not attempt any subsequent attempts.
5437 TRY_AGAIN 1
5439 If either the re-auth or the STR message delivery fails, resend
5440 the failed message without the Destination-Host AVP present.
5442 ALLOW_SERVICE 2
5444 If re-auth message delivery fails, assume that re-authorization
5445 succeeded. If STR message delivery fails, terminate the session.
5447 TRY_AGAIN_ALLOW_SERVICE 3
5449 If either the re-auth or the STR message delivery fails, resend
5450 the failed message without the Destination-Host AVP present. If
5451 the second delivery fails for re-auth, assume re-authorization
5452 succeeded. If the second delivery fails for STR, terminate the
5453 session.
5455 8.19. Multi-Round-Time-Out AVP
5457 The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32,
5458 and SHOULD be present in application-specific authorization answer
5459 messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH.
5460 This AVP contains the maximum number of seconds that the access
5461 device MUST provide the user in responding to an authentication
5462 request.
5464 8.20. Class AVP
5466 The Class AVP (AVP Code 25) is of type OctetString and is used by
5467 Diameter servers to return state information to the access device.
5468 When one or more Class AVPs are present in application-specific
5469 authorization answer messages, they MUST be present in subsequent re-
5470 authorization, session termination and accounting messages. Class
5471 AVPs found in a re-authorization answer message override the ones
5472 found in any previous authorization answer message. Diameter server
5473 implementations SHOULD NOT return Class AVPs that require more than
5474 4096 bytes of storage on the Diameter client. A Diameter client that
5475 receives Class AVPs whose size exceeds local available storage MUST
5476 terminate the session.
5478 8.21. Event-Timestamp AVP
5480 The Event-Timestamp (AVP Code 55) is of type Time, and MAY be
5481 included in an Accounting-Request and Accounting-Answer messages to
5482 record the time that the reported event occurred, in seconds since
5483 January 1, 1900 00:00 UTC.
5485 9. Accounting
5487 This accounting protocol is based on a server directed model with
5488 capabilities for real-time delivery of accounting information.
5489 Several fault resilience methods [RFC2975] have been built in to the
5490 protocol in order minimize loss of accounting data in various fault
5491 situations and under different assumptions about the capabilities of
5492 the used devices.
5494 9.1. Server Directed Model
5496 The server directed model means that the device generating the
5497 accounting data gets information from either the authorization server
5498 (if contacted) or the accounting server regarding the way accounting
5499 data shall be forwarded. This information includes accounting record
5500 timeliness requirements.
5502 As discussed in [RFC2975], real-time transfer of accounting records
5503 is a requirement, such as the need to perform credit limit checks and
5504 fraud detection. Note that batch accounting is not a requirement,
5505 and is therefore not supported by Diameter. Should batched
5506 accounting be required in the future, a new Diameter application will
5507 need to be created, or it could be handled using another protocol.
5508 Note, however, that even if at the Diameter layer accounting requests
5509 are processed one by one, transport protocols used under Diameter
5510 typically batch several requests in the same packet under heavy
5511 traffic conditions. This may be sufficient for many applications.
5513 The authorization server (chain) directs the selection of proper
5514 transfer strategy, based on its knowledge of the user and
5515 relationships of roaming partnerships. The server (or agents) uses
5516 the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to
5517 control the operation of the Diameter peer operating as a client.
5518 The Acct-Interim-Interval AVP, when present, instructs the Diameter
5519 node acting as a client to produce accounting records continuously
5520 even during a session. Accounting-Realtime-Required AVP is used to
5521 control the behavior of the client when the transfer of accounting
5522 records from the Diameter client is delayed or unsuccessful.
5524 The Diameter accounting server MAY override the interim interval or
5525 the realtime requirements by including the Acct-Interim-Interval or
5526 Accounting-Realtime-Required AVP in the Accounting-Answer message.
5527 When one of these AVPs is present, the latest value received SHOULD
5528 be used in further accounting activities for the same session.
5530 9.2. Protocol Messages
5532 A Diameter node that receives a successful authentication and/or
5533 authorization messages from the Diameter server SHOULD collect
5534 accounting information for the session. The Accounting-Request
5535 message is used to transmit the accounting information to the
5536 Diameter server, which MUST reply with the Accounting-Answer message
5537 to confirm reception. The Accounting-Answer message includes the
5538 Result-Code AVP, which MAY indicate that an error was present in the
5539 accounting message. The value of the Accounting-Realtime-Required
5540 AVP received earlier for the session in question may indicate that
5541 the user's session has to be terminated when a rejected Accounting-
5542 Request message was received.
5544 9.3. Accounting Application Extension and Requirements
5546 Each Diameter application (e.g., NASREQ, MobileIP), SHOULD define
5547 their Service-Specific AVPs that MUST be present in the Accounting-
5548 Request message in a section entitled "Accounting AVPs". The
5549 application MUST assume that the AVPs described in this document will
5550 be present in all Accounting messages, so only their respective
5551 service-specific AVPs need to be defined in that section.
5553 Applications have the option of using one or both of the following
5554 accounting application extension models:
5556 Split Accounting Service
5558 The accounting message will carry the Application Id of the
5559 Diameter base accounting application (see Section 2.4).
5560 Accounting messages maybe routed to Diameter nodes other than the
5561 corresponding Diameter application. These nodes might be
5562 centralized accounting servers that provide accounting service for
5563 multiple different Diameter applications. These nodes MUST
5564 advertise the Diameter base accounting Application Id during
5565 capabilities exchange.
5567 Coupled Accounting Service
5569 The accounting messages will carry the Application Id of the
5570 application that is using it. The application itself will process
5571 the received accounting records or forward them to an accounting
5572 server. There is no accounting application advertisement required
5573 during capabilities exchange and the accounting messages will be
5574 routed the same as any of the other application messages.
5576 In cases where an application does not define its own accounting
5577 service, it is preferred that the split accounting model be used.
5579 9.4. Fault Resilience
5581 Diameter Base protocol mechanisms are used to overcome small message
5582 loss and network faults of temporary nature.
5584 Diameter peers acting as clients MUST implement the use of failover
5585 to guard against server failures and certain network failures.
5586 Diameter peers acting as agents or related off-line processing
5587 systems MUST detect duplicate accounting records caused by the
5588 sending of same record to several servers and duplication of messages
5589 in transit. This detection MUST be based on the inspection of the
5590 Session-Id and Accounting-Record-Number AVP pairs. Appendix C
5591 discusses duplicate detection needs and implementation issues.
5593 Diameter clients MAY have non-volatile memory for the safe storage of
5594 accounting records over reboots or extended network failures, network
5595 partitions, and server failures. If such memory is available, the
5596 client SHOULD store new accounting records there as soon as the
5597 records are created and until a positive acknowledgement of their
5598 reception from the Diameter Server has been received. Upon a reboot,
5599 the client MUST starting sending the records in the non-volatile
5600 memory to the accounting server with appropriate modifications in
5601 termination cause, session length, and other relevant information in
5602 the records.
5604 A further application of this protocol may include AVPs to control
5605 how many accounting records may at most be stored in the Diameter
5606 client without committing them to the non-volatile memory or
5607 transferring them to the Diameter server.
5609 The client SHOULD NOT remove the accounting data from any of its
5610 memory areas before the correct Accounting-Answer has been received.
5611 The client MAY remove oldest, undelivered or yet unacknowledged
5612 accounting data if it runs out of resources such as memory. It is an
5613 implementation dependent matter for the client to accept new sessions
5614 under this condition.
5616 9.5. Accounting Records
5618 In all accounting records, the Session-Id AVP MUST be present; the
5619 User-Name AVP MUST be present if it is available to the Diameter
5620 client.
5622 Different types of accounting records are sent depending on the
5623 actual type of accounted service and the authorization server's
5624 directions for interim accounting. If the accounted service is a
5625 one-time event, meaning that the start and stop of the event are
5626 simultaneous, then the Accounting-Record-Type AVP MUST be present and
5627 set to the value EVENT_RECORD.
5629 If the accounted service is of a measurable length, then the AVP MUST
5630 use the values START_RECORD, STOP_RECORD, and possibly,
5631 INTERIM_RECORD. If the authorization server has not directed interim
5632 accounting to be enabled for the session, two accounting records MUST
5633 be generated for each service of type session. When the initial
5634 Accounting-Request for a given session is sent, the Accounting-
5635 Record-Type AVP MUST be set to the value START_RECORD. When the last
5636 Accounting-Request is sent, the value MUST be STOP_RECORD.
5638 If the authorization server has directed interim accounting to be
5639 enabled, the Diameter client MUST produce additional records between
5640 the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The
5641 production of these records is directed by Acct-Interim-Interval as
5642 well as any re-authentication or re-authorization of the session.
5643 The Diameter client MUST overwrite any previous interim accounting
5644 records that are locally stored for delivery, if a new record is
5645 being generated for the same session. This ensures that only one
5646 pending interim record can exist on an access device for any given
5647 session.
5649 A particular value of Accounting-Sub-Session-Id MUST appear only in
5650 one sequence of accounting records from a DIAMETER client, except for
5651 the purposes of retransmission. The one sequence that is sent MUST
5652 be either one record with Accounting-Record-Type AVP set to the value
5653 EVENT_RECORD, or several records starting with one having the value
5654 START_RECORD, followed by zero or more INTERIM_RECORD and a single
5655 STOP_RECORD. A particular Diameter application specification MUST
5656 define the type of sequences that MUST be used.
5658 9.6. Correlation of Accounting Records
5660 If an application uses accounting messages, it can correlate
5661 accounting records with a specific application session by using the
5662 Session-Id of the particular application session in the accounting
5663 messages. Accounting messages MAY also use a different Session-Id
5664 from that of the application sessions in which case other session
5665 related information is needed to perform correlation.
5667 In cases where an application requires multiple accounting sub-
5668 session, an Accounting-Sub-Session-Id AVP is used to differentiate
5669 each sub-session. The Session-Id would remain constant for all sub-
5670 sessions and is be used to correlate all the sub-sessions to a
5671 particular application session. Note that receiving a STOP_RECORD
5672 with no Accounting-Sub-Session-Id AVP when sub-sessions were
5673 originally used in the START_RECORD messages implies that all sub-
5674 sessions are terminated.
5676 There are also cases where an application needs to correlate multiple
5677 application sessions into a single accounting record; the accounting
5678 record may span multiple different Diameter applications and sessions
5679 used by the same user at a given time. In such cases, the Acct-
5680 Multi-Session- Id AVP is used. The Acct-Multi-Session-Id AVP SHOULD
5681 be signalled by the server to the access device (typically during
5682 authorization) when it determines that a request belongs to an
5683 existing session. The access device MUST then include the Acct-
5684 Multi-Session-Id AVP in all subsequent accounting messages.
5686 The Acct-Multi-Session-Id AVP MAY include the value of the original
5687 Session-Id. It's contents are implementation specific, but MUST be
5688 globally unique across other Acct-Multi-Session-Id, and MUST NOT
5689 change during the life of a session.
5691 A Diameter application document MUST define the exact concept of a
5692 session that is being accounted, and MAY define the concept of a
5693 multi-session. For instance, the NASREQ DIAMETER application treats
5694 a single PPP connection to a Network Access Server as one session,
5695 and a set of Multilink PPP sessions as one multi-session.
5697 9.7. Accounting Command-Codes
5699 This section defines Command-Code values that MUST be supported by
5700 all Diameter implementations that provide Accounting services.
5702 9.7.1. Accounting-Request
5704 The Accounting-Request (ACR) command, indicated by the Command-Code
5705 field set to 271 and the Command Flags' 'R' bit set, is sent by a
5706 Diameter node, acting as a client, in order to exchange accounting
5707 information with a peer.
5709 The AVP listed below SHOULD include service specific accounting AVPs,
5710 as described in Section 9.3.
5712 Message Format
5714 ::= < Diameter Header: 271, REQ, PXY >
5715 < Session-Id >
5716 { Origin-Host }
5717 { Origin-Realm }
5718 { Destination-Realm }
5719 { Accounting-Record-Type }
5720 { Accounting-Record-Number }
5721 [ Acct-Application-Id ]
5722 [ Vendor-Specific-Application-Id ]
5723 [ User-Name ]
5724 [ Destination-Host ]
5725 [ Accounting-Sub-Session-Id ]
5726 [ Acct-Session-Id ]
5727 [ Acct-Multi-Session-Id ]
5728 [ Acct-Interim-Interval ]
5729 [ Accounting-Realtime-Required ]
5730 [ Origin-State-Id ]
5731 [ Event-Timestamp ]
5732 * [ Proxy-Info ]
5733 * [ Route-Record ]
5734 * [ AVP ]
5736 9.7.2. Accounting-Answer
5738 The Accounting-Answer (ACA) command, indicated by the Command-Code
5739 field set to 271 and the Command Flags' 'R' bit cleared, is used to
5740 acknowledge an Accounting-Request command. The Accounting-Answer
5741 command contains the same Session-Id as the corresponding request.
5743 Only the target Diameter Server, known as the home Diameter Server,
5744 SHOULD respond with the Accounting-Answer command.
5746 The AVP listed below SHOULD include service specific accounting AVPs,
5747 as described in Section 9.3.
5749 Message Format
5751 ::= < Diameter Header: 271, PXY >
5752 < Session-Id >
5753 { Result-Code }
5754 { Origin-Host }
5755 { Origin-Realm }
5756 { Accounting-Record-Type }
5757 { Accounting-Record-Number }
5758 [ Acct-Application-Id ]
5759 [ Vendor-Specific-Application-Id ]
5760 [ User-Name ]
5761 [ Accounting-Sub-Session-Id ]
5762 [ Acct-Session-Id ]
5763 [ Acct-Multi-Session-Id ]
5764 [ Error-Message ]
5765 [ Error-Reporting-Host ]
5766 [ Failed-AVP ]
5767 [ Acct-Interim-Interval ]
5768 [ Accounting-Realtime-Required ]
5769 [ Origin-State-Id ]
5770 [ Event-Timestamp ]
5771 * [ Proxy-Info ]
5772 * [ AVP ]
5774 9.8. Accounting AVPs
5776 This section contains AVPs that describe accounting usage information
5777 related to a specific session.
5779 9.8.1. Accounting-Record-Type AVP
5781 The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated
5782 and contains the type of accounting record being sent. The following
5783 values are currently defined for the Accounting-Record-Type AVP:
5785 EVENT_RECORD 1
5787 An Accounting Event Record is used to indicate that a one-time
5788 event has occurred (meaning that the start and end of the event
5789 are simultaneous). This record contains all information relevant
5790 to the service, and is the only record of the service.
5792 START_RECORD 2
5794 An Accounting Start, Interim, and Stop Records are used to
5795 indicate that a service of a measurable length has been given. An
5796 Accounting Start Record is used to initiate an accounting session,
5797 and contains accounting information that is relevant to the
5798 initiation of the session.
5800 INTERIM_RECORD 3
5802 An Interim Accounting Record contains cumulative accounting
5803 information for an existing accounting session. Interim
5804 Accounting Records SHOULD be sent every time a re-authentication
5805 or re-authorization occurs. Further, additional interim record
5806 triggers MAY be defined by application-specific Diameter
5807 applications. The selection of whether to use INTERIM_RECORD
5808 records is done by the Acct-Interim-Interval AVP.
5810 STOP_RECORD 4
5812 An Accounting Stop Record is sent to terminate an accounting
5813 session and contains cumulative accounting information relevant to
5814 the existing session.
5816 9.8.2. Acct-Interim-Interval AVP
5818 The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and
5819 is sent from the Diameter home authorization server to the Diameter
5820 client. The client uses information in this AVP to decide how and
5821 when to produce accounting records. With different values in this
5822 AVP, service sessions can result in one, two, or two+N accounting
5823 records, based on the needs of the home-organization. The following
5824 accounting record production behavior is directed by the inclusion of
5825 this AVP:
5827 1. The omission of the Acct-Interim-Interval AVP or its inclusion
5828 with Value field set to 0 means that EVENT_RECORD, START_RECORD,
5829 and STOP_RECORD are produced, as appropriate for the service.
5831 2. The inclusion of the AVP with Value field set to a non-zero value
5832 means that INTERIM_RECORD records MUST be produced between the
5833 START_RECORD and STOP_RECORD records. The Value field of this
5834 AVP is the nominal interval between these records in seconds.
5836 The Diameter node that originates the accounting information,
5837 known as the client, MUST produce the first INTERIM_RECORD record
5838 roughly at the time when this nominal interval has elapsed from
5839 the START_RECORD, the next one again as the interval has elapsed
5840 once more, and so on until the session ends and a STOP_RECORD
5841 record is produced.
5843 The client MUST ensure that the interim record production times
5844 are randomized so that large accounting message storms are not
5845 created either among records or around a common service start
5846 time.
5848 9.8.3. Accounting-Record-Number AVP
5850 The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32
5851 and identifies this record within one session. As Session-Id AVPs
5852 are globally unique, the combination of Session-Id and Accounting-
5853 Record-Number AVPs is also globally unique, and can be used in
5854 matching accounting records with confirmations. An easy way to
5855 produce unique numbers is to set the value to 0 for records of type
5856 EVENT_RECORD and START_RECORD, and set the value to 1 for the first
5857 INTERIM_RECORD, 2 for the second, and so on until the value for
5858 STOP_RECORD is one more than for the last INTERIM_RECORD.
5860 9.8.4. Acct-Session-Id AVP
5862 The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only
5863 used when RADIUS/Diameter translation occurs. This AVP contains the
5864 contents of the RADIUS Acct-Session-Id attribute.
5866 9.8.5. Acct-Multi-Session-Id AVP
5868 The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String,
5869 following the format specified in Section 8.8. The Acct-Multi-
5870 Session-Id AVP is used to link together multiple related accounting
5871 sessions, where each session would have a unique Session-Id, but the
5872 same Acct-Multi-Session-Id AVP. This AVP MAY be returned by the
5873 Diameter server in an authorization answer, and MUST be used in all
5874 accounting messages for the given session.
5876 9.8.6. Accounting-Sub-Session-Id AVP
5878 The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type
5879 Unsigned64 and contains the accounting sub-session identifier. The
5880 combination of the Session-Id and this AVP MUST be unique per sub-
5881 session, and the value of this AVP MUST be monotonically increased by
5882 one for all new sub-sessions. The absence of this AVP implies no
5883 sub-sessions are in use, with the exception of an Accounting-Request
5884 whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD
5885 message with no Accounting-Sub-Session-Id AVP present will signal the
5886 termination of all sub-sessions for a given Session-Id.
5888 9.8.7. Accounting-Realtime-Required AVP
5890 The Accounting-Realtime-Required AVP (AVP Code 483) is of type
5891 Enumerated and is sent from the Diameter home authorization server to
5892 the Diameter client or in the Accounting-Answer from the accounting
5893 server. The client uses information in this AVP to decide what to do
5894 if the sending of accounting records to the accounting server has
5895 been temporarily prevented due to, for instance, a network problem.
5897 DELIVER_AND_GRANT 1
5899 The AVP with Value field set to DELIVER_AND_GRANT means that the
5900 service MUST only be granted as long as there is a connection to
5901 an accounting server. Note that the set of alternative accounting
5902 servers are treated as one server in this sense. Having to move
5903 the accounting record stream to a backup server is not a reason to
5904 discontinue the service to the user.
5906 GRANT_AND_STORE 2
5908 The AVP with Value field set to GRANT_AND_STORE means that service
5909 SHOULD be granted if there is a connection, or as long as records
5910 can still be stored as described in Section 9.4.
5912 This is the default behavior if the AVP isn't included in the
5913 reply from the authorization server.
5915 GRANT_AND_LOSE 3
5917 The AVP with Value field set to GRANT_AND_LOSE means that service
5918 SHOULD be granted even if the records can not be delivered or
5919 stored.
5921 10. AVP Occurrence Table
5923 The following tables presents the AVPs defined in this document, and
5924 specifies in which Diameter messages they MAY be present or not.
5925 AVPs that occur only inside a Grouped AVP are not shown in this
5926 table.
5928 The table uses the following symbols:
5930 0 The AVP MUST NOT be present in the message.
5932 0+ Zero or more instances of the AVP MAY be present in the
5933 message.
5935 0-1 Zero or one instance of the AVP MAY be present in the message.
5936 It is considered an error if there are more than one instance of
5937 the AVP.
5939 1 One instance of the AVP MUST be present in the message.
5941 1+ At least one instance of the AVP MUST be present in the
5942 message.
5944 10.1. Base Protocol Command AVP Table
5946 The table in this section is limited to the non-accounting Command
5947 Codes defined in this specification.
5949 +-----------------------------------------------+
5950 | Command-Code |
5951 +---+---+---+---+---+---+---+---+---+---+---+---+
5952 Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA|
5953 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+
5954 Acct-Interim- |0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 |
5955 Interval | | | | | | | | | | | | |
5956 Accounting-Realtime-|0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 |
5957 Required | | | | | | | | | | | | |
5958 Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5959 Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 |
5960 Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5961 Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5962 Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5963 Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5964 Lifetime | | | | | | | | | | | | |
5965 Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ |
5966 Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 |
5967 Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 |
5968 Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5969 Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|
5970 Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
5971 Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |
5972 Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5973 Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5974 Inband-Security-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5975 Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5976 Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |
5977 Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |
5978 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|
5979 Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5980 Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ |
5981 Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |
5982 Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
5983 Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
5984 Time | | | | | | | | | | | | |
5985 Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 |
5986 Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 |
5987 Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 |
5988 Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5989 Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 |
5990 Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5991 Failover | | | | | | | | | | | | |
5992 Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5993 Supported-Vendor-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5994 Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 |
5995 User-Name |0 |0 |0 |0 |0 |0 |0-1|0-1|0-1|0-1|0-1|0-1|
5996 Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5997 Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
5998 Application-Id | | | | | | | | | | | | |
5999 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+
6001 10.2. Accounting AVP Table
6003 The table in this section is used to represent which AVPs defined in
6004 this document are to be present in the Accounting messages. These
6005 AVP occurrence requirements are guidelines, which may be expanded,
6006 and/or overridden by application-specific requirements in the
6007 Diameter applications documents.
6009 +-----------+
6010 | Command |
6011 | Code |
6012 +-----+-----+
6013 Attribute Name | ACR | ACA |
6014 ------------------------------+-----+-----+
6015 Acct-Interim-Interval | 0-1 | 0-1 |
6016 Acct-Multi-Session-Id | 0-1 | 0-1 |
6017 Accounting-Record-Number | 1 | 1 |
6018 Accounting-Record-Type | 1 | 1 |
6019 Acct-Session-Id | 0-1 | 0-1 |
6020 Accounting-Sub-Session-Id | 0-1 | 0-1 |
6021 Accounting-Realtime-Required | 0-1 | 0-1 |
6022 Acct-Application-Id | 0-1 | 0-1 |
6023 Auth-Application-Id | 0 | 0 |
6024 Class | 0+ | 0+ |
6025 Destination-Host | 0-1 | 0 |
6026 Destination-Realm | 1 | 0 |
6027 Error-Reporting-Host | 0 | 0+ |
6028 Event-Timestamp | 0-1 | 0-1 |
6029 Origin-Host | 1 | 1 |
6030 Origin-Realm | 1 | 1 |
6031 Proxy-Info | 0+ | 0+ |
6032 Route-Record | 0+ | 0 |
6033 Result-Code | 0 | 1 |
6034 Session-Id | 1 | 1 |
6035 Termination-Cause | 0 | 0 |
6036 User-Name | 0-1 | 0-1 |
6037 Vendor-Specific-Application-Id| 0-1 | 0-1 |
6038 ------------------------------+-----+-----+
6040 11. IANA Considerations
6042 This section provides guidance to the Internet Assigned Numbers
6043 Authority (IANA) regarding registration of values related to the
6044 Diameter protocol, in accordance with BCP 26 [RFC2434]. The
6045 following policies are used here with the meanings defined in BCP 26:
6046 "Private Use", "First Come First Served", "Expert Review",
6047 "Specification Required", "IETF Review", "Standards Action".
6049 This section explains the criteria to be used by the IANA for
6050 assignment of numbers within namespaces defined within this document.
6052 For registration requests where a Designated Expert should be
6053 consulted, the responsible IESG area director should appoint the
6054 Designated Expert. For Designated Expert with Specification
6055 Required, the request is posted to the DIME WG mailing list (or, if
6056 it has been disbanded, a successor designated by the Area Director)
6057 for comment and review, and MUST include a pointer to a public
6058 specification. Before a period of 30 days has passed, the Designated
6059 Expert will either approve or deny the registration request and
6060 publish a notice of the decision to the DIME WG mailing list or its
6061 successor. A denial notice MUST be justified by an explanation and,
6062 in the cases where it is possible, concrete suggestions on how the
6063 request can be modified so as to become acceptable.
6065 11.1. AVP Header
6067 As defined in Section 4, the AVP header contains three fields that
6068 requires IANA namespace management; the AVP Code, Vendor-ID and Flags
6069 field.
6071 11.1.1. AVP Codes
6073 The AVP Code namespace is used to identify attributes. There are
6074 multiple namespaces. Vendors can have their own AVP Codes namespace
6075 which will be identified by their Vendor-ID (also known as
6076 Enterprise-Number) and they control the assignments of their vendor-
6077 specific AVP codes within their own namespace. The absence of a
6078 Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA
6079 controlled AVP Codes namespace. The AVP Codes and sometimes also
6080 possible values in an AVP are controlled and maintained by IANA.
6082 AVP Code 0 is not used. AVP Codes 1-255 are managed separately as
6083 RADIUS Attribute Types [RADTYPE]. This document defines the AVP
6084 Codes 257-274, 276-285, 287, 291-300, 480, 483 and 485-486. See
6085 Section 4.5 for the assignment of the namespace in this
6086 specification.
6088 AVPs may be allocated following Designated Expert with Specification
6089 Required [RFC2434]. Release of blocks of AVPs (more than 3 at a time
6090 for a given purpose) should require IETF Review.
6092 Note that Diameter defines a mechanism for Vendor-Specific AVPs,
6093 where the Vendor-Id field in the AVP header is set to a non-zero
6094 value. Vendor-Specific AVPs codes are for Private Use and should be
6095 encouraged instead of allocation of global attribute types, for
6096 functions specific only to one vendor's implementation of Diameter,
6097 where no interoperability is deemed useful. Where a Vendor-Specific
6098 AVP is implemented by more than one vendor, allocation of global AVPs
6099 should be encouraged instead.
6101 11.1.2. AVP Flags
6103 There are 8 bits in the AVP Flags field of the AVP header, defined in
6104 Section 4. This document assigns bit 0 ('V'endor Specific), bit 1
6105 ('M'andatory) and bit 2 ('P'rotected). The remaining bits should
6106 only be assigned via a Standards Action [RFC2434].
6108 11.2. Diameter Header
6110 As defined in Section 3, the Diameter header contains two fields that
6111 require IANA namespace management; Command Code and Command Flags.
6113 11.2.1. Command Codes
6115 The Command Code namespace is used to identify Diameter commands.
6116 The values 0-255 (0x00-0xff) are reserved for RADIUS backward
6117 compatibility, and are defined as "RADIUS Packet Type Codes" in
6118 [RADTYPE]. Values 256 - 8,388,607 (0x100 to 0x7fffff) are for
6119 permanent, standard commands, allocated by IETF Review [RFC2434].
6120 This document defines the Command Codes 257, 258, 271, 274-275, 280
6121 and 282. See Section 3.1 for the assignment of the namespace in this
6122 specification.
6124 The values 8,388,608 - 16,777,213 (0x800000 - 0xfffffd) are reserved
6125 for vendor-specific command codes, to be allocated on a First Come,
6126 First Served basis by IANA [RFC2434]. The request to IANA for a
6127 Vendor-Specific Command Code SHOULD include a reference to a publicly
6128 available specification which documents the command in sufficient
6129 detail to aid in interoperability between independent
6130 implementations. If the specification cannot be made publicly
6131 available, the request for a vendor-specific command code MUST
6132 include the contact information of persons and/or entities
6133 responsible for authoring and maintaining the command.
6135 The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe -
6136 0xffffff) are reserved for experimental commands. As these codes are
6137 only for experimental and testing purposes, no guarantee is made for
6138 interoperability between Diameter peers using experimental commands,
6139 as outlined in [IANA-EXP].
6141 11.2.2. Command Flags
6143 There are eight bits in the Command Flags field of the Diameter
6144 header. This document assigns bit 0 ('R'equest), bit 1 ('P'roxy),
6145 bit 2 ('E'rror) and bit 3 ('T'). Bits 4 through 7 MUST only be
6146 assigned via a Standards Action [RFC2434].
6148 11.3. Application Identifiers
6150 As defined in Section 2.4, the Application Id is used to identify a
6151 specific Diameter Application. There are standards-track Application
6152 Ids and vendor specific Application Ids.
6154 IANA [RFC2434] has assigned the range 0x00000001 to 0x00ffffff for
6155 standards-track applications; and 0x01000000 - 0xfffffffe for vendor
6156 specific applications, on a first-come, first-served basis. The
6157 following values are allocated.
6159 Diameter Common Messages 0
6160 Diameter Base Accounting 3
6161 Relay 0xffffffff
6163 Assignment of standards-track Application Ids are by Designated
6164 Expert with Specification Required [RFC2434].
6166 Both Auth-Application-Id and Acct-Application-Id AVPs use the same
6167 Application Id space. A Diameter node advertising itself as a relay
6168 agent MUST set either Application-Id or Acct-Application-Id to
6169 0xffffffff.
6171 Vendor-Specific Application Ids, are for Private Use. Vendor-Specific
6172 Application Ids are assigned on a First Come, First Served basis by
6173 IANA.
6175 11.4. AVP Values
6177 Certain AVPs in Diameter define a list of values with various
6178 meanings. For attributes other than those specified in this section,
6179 adding additional values to the list can be done on a First Come,
6180 First Served basis by IANA.
6182 11.4.1. Result-Code AVP Values
6184 As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines
6185 the values 1001, 2001-2002, 3001-3012, 4001-4003 and 5001-5021.
6187 All remaining values are available for assignment via IETF Review
6188 [RFC2434].
6190 11.4.2. Accounting-Record-Type AVP Values
6192 As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code
6193 480) defines the values 1-4. All remaining values are available for
6194 assignment via IETF Review [RFC2434].
6196 11.4.3. Termination-Cause AVP Values
6198 As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295)
6199 defines the values 1-8. All remaining values are available for
6200 assignment via IETF Review [RFC2434].
6202 11.4.4. Redirect-Host-Usage AVP Values
6204 As defined in Section 6.13, the Redirect-Host-Usage AVP (AVP Code
6205 261) defines the values 0-5. All remaining values are available for
6206 assignment via IETF Review [RFC2434].
6208 11.4.5. Session-Server-Failover AVP Values
6210 As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code
6211 271) defines the values 0-3. All remaining values are available for
6212 assignment via IETF Review [RFC2434].
6214 11.4.6. Session-Binding AVP Values
6216 As defined in Section 8.17, the Session-Binding AVP (AVP Code 270)
6217 defines the bits 1-4. All remaining bits are available for
6218 assignment via IETF Review [RFC2434].
6220 11.4.7. Disconnect-Cause AVP Values
6222 As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273)
6223 defines the values 0-2. All remaining values are available for
6224 assignment via IETF Review [RFC2434].
6226 11.4.8. Auth-Request-Type AVP Values
6228 As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274)
6229 defines the values 1-3. All remaining values are available for
6230 assignment via IETF Review [RFC2434].
6232 11.4.9. Auth-Session-State AVP Values
6234 As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277)
6235 defines the values 0-1. All remaining values are available for
6236 assignment via IETF Review [RFC2434].
6238 11.4.10. Re-Auth-Request-Type AVP Values
6240 As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code
6241 285) defines the values 0-1. All remaining values are available for
6242 assignment via IETF Review [RFC2434].
6244 11.4.11. Accounting-Realtime-Required AVP Values
6246 As defined in Section 9.8.7, the Accounting-Realtime-Required AVP
6247 (AVP Code 483) defines the values 1-3. All remaining values are
6248 available for assignment via IETF Review [RFC2434].
6250 11.4.12. Inband-Security-Id AVP (code 299)
6252 As defined in Section 6.10, the Inband-Security-Id AVP (AVP Code 299)
6253 defines the values 0-1. All remaining values are available for
6254 assignment via IETF Review [RFC2434].
6256 11.5. Diameter TCP/SCTP Port Numbers
6258 The IANA has assigned TCP and SCTP port number 3868 to Diameter.
6260 11.6. NAPTR Service Fields
6262 The registration in the RFC MUST include the following information:
6264 Service Field: The service field being registered. An example for a
6265 new fictitious transport protocol called NCTP might be "AAA+D2N".
6267 Protocol: The specific transport protocol associated with that
6268 service field. This MUST include the name and acronym for the
6269 protocol, along with reference to a document that describes the
6270 transport protocol. For example - "New Connectionless Transport
6271 Protocol (NCTP), RFC XYZ".
6273 Name and Contact Information: The name, address, email address and
6274 telephone number for the person performing the registration.
6276 The following values have been placed into the registry:
6278 Services Field Protocol
6280 AAA+D2T TCP
6281 AAA+D2S SCTP
6283 12. Diameter protocol related configurable parameters
6285 This section contains the configurable parameters that are found
6286 throughout this document:
6288 Diameter Peer
6290 A Diameter entity MAY communicate with peers that are statically
6291 configured. A statically configured Diameter peer would require
6292 that either the IP address or the fully qualified domain name
6293 (FQDN) be supplied, which would then be used to resolve through
6294 DNS.
6296 Routing Table
6298 A Diameter proxy server routes messages based on the realm portion
6299 of a Network Access Identifier (NAI). The server MUST have a
6300 table of Realm Names, and the address of the peer to which the
6301 message must be forwarded to. The routing table MAY also include
6302 a "default route", which is typically used for all messages that
6303 cannot be locally processed.
6305 Tc timer
6307 The Tc timer controls the frequency that transport connection
6308 attempts are done to a peer with whom no active transport
6309 connection exists. The recommended value is 30 seconds.
6311 13. Security Considerations
6313 The Diameter base protocol messages SHOULD be secured by using TLS
6314 [RFC4346]. Additional security measures that are transparent to and
6315 independent of Diameter, such as IPsec [RFC4301], can also be
6316 deployed to secure connections between peers.
6318 During deployment, connections between Diameter nodes SHOULD be
6319 protected by TLS. All Diameter base protocol implementations MUST
6320 support the use of TLS. The Diameter protocol MUST NOT be used
6321 without any security mechanism.
6323 If a Diameter connection is to be protected via TLS, then the CER/CEA
6324 exchange MUST include an Inband-Security-ID AVP with a value of TLS.
6325 For TLS usage, a TLS handshake will begin when both ends are in the
6326 open state, after completion of the CER/CEA exchange. If the TLS
6327 handshake is successful, all further messages will be sent via TLS.
6328 If the handshake fails, both ends move to the closed state. See
6329 Sections 13.1 for more details.
6331 13.1. TLS Usage
6333 A Diameter node that initiates a connection to another Diameter node
6334 acts as a TLS client according to [RFC4346], and a Diameter node that
6335 accepts a connection acts as a TLS server. Diameter nodes
6336 implementing TLS for security MUST mutually authenticate as part of
6337 TLS session establishment. In order to ensure mutual authentication,
6338 the Diameter node acting as TLS server MUST request a certificate
6339 from the Diameter node acting as TLS client, and the Diameter node
6340 acting as TLS client MUST be prepared to supply a certificate on
6341 request.
6343 Diameter nodes MUST be able to negotiate the following TLS cipher
6344 suites:
6346 TLS_RSA_WITH_RC4_128_MD5
6347 TLS_RSA_WITH_RC4_128_SHA
6348 TLS_RSA_WITH_3DES_EDE_CBC_SHA
6350 Diameter nodes SHOULD be able to negotiate the following TLS cipher
6351 suite:
6353 TLS_RSA_WITH_AES_128_CBC_SHA
6355 Diameter nodes MAY negotiate other TLS cipher suites.
6357 Upon receiving the peers certificate, Diameter nodes SHOULD further
6358 validate the identity of the peer by matching the received Origin-
6359 Host and/or Origin-Realm in the CER and CEA exchange against the
6360 content of the peers certificate. Diameter peer hostname and/or
6361 realm validation can be performed in the following order:
6363 o If one or more 'Subject Alternate Name (subjectAltName)' extension
6364 of type dNSName is present in the certificate (See [RFC3280]),
6365 then the Origin-Host value can be used to find a matching
6366 extension.
6368 o If there are no matches found, then the Origin-Realm value can be
6369 used to find a matching subjectAltName extension.
6371 o Otherwise, the Origin-Host value should be found within the
6372 'Common Name (CN)' field in the Subject field of the certificate
6373 (See [RFC3280]).
6375 Identity validation MAY be omitted by a Diameter node if the
6376 information contained in the certificate cannot be correlated or
6377 mapped to the Origin-Host and Origin-Realm presented by a peer.
6378 However, the Diameter node SHOULD have external information or other
6379 means to validate the identity of a peer.
6381 13.2. Peer-to-Peer Considerations
6383 As with any peer-to-peer protocol, proper configuration of the trust
6384 model within a Diameter peer is essential to security. When
6385 certificates are used, it is necessary to configure the root
6386 certificate authorities trusted by the Diameter peer. These root CAs
6387 are likely to be unique to Diameter usage and distinct from the root
6388 CAs that might be trusted for other purposes such as Web browsing.
6389 In general, it is expected that those root CAs will be configured so
6390 as to reflect the business relationships between the organization
6391 hosting the Diameter peer and other organizations. As a result, a
6392 Diameter peer will typically not be configured to allow connectivity
6393 with any arbitrary peer. With certificate authentication, Diameter
6394 peers may not be known beforehand and therefore peer discovery may be
6395 required.
6397 14. References
6399 14.1. Normative References
6401 [FLOATPOINT]
6402 Institute of Electrical and Electronics Engineers, "IEEE
6403 Standard for Binary Floating-Point Arithmetic, ANSI/IEEE
6404 Standard 754-1985", August 1985.
6406 [IANAADFAM]
6407 IANA,, "Address Family Numbers",
6408 http://www.iana.org/assignments/address-family-numbers.
6410 [RADTYPE] IANA,, "RADIUS Types",
6411 http://www.iana.org/assignments/radius-types.
6413 [RFC791] Postel, J., "Internet Protocol", RFC 791, September 1981.
6415 [RFC793] Postel, J., "Transmission Control Protocol", RFC 793,
6416 January 1981.
6418 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and
6419 Accounting (AAA) Transport Profile", RFC 3539, June 2003.
6421 [RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and
6422 P. McCann, "Diameter Mobile IPv4 Application", RFC 4004,
6423 August 2005.
6425 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
6426 "Diameter Network Access Server Application", RFC 4005,
6427 August 2005.
6429 [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
6430 Loughney, "Diameter Credit-Control Application", RFC 4006,
6431 August 2005.
6433 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
6434 Authentication Protocol (EAP) Application", RFC 4072,
6435 August 2005.
6437 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M.,
6438 Canales-Valenzuela, C., and K. Tammi, "Diameter Session
6439 Initiation Protocol (SIP) Application", RFC 4740,
6440 November 2006.
6442 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
6443 Specifications: ABNF", RFC 4234, October 2005.
6445 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
6446 Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
6448 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
6449 IANA Considerations Section in RFCs", BCP 26, RFC 2434,
6450 October 1998.
6452 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
6453 RFC 4306, December 2005.
6455 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
6456 Architecture", RFC 4291, February 2006.
6458 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
6459 Requirement Levels", BCP 14, RFC 2119, March 1997.
6461 [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
6462 Network Access Identifier", RFC 4282, December 2005.
6464 [RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS)
6465 Part Three: The Domain Name System (DNS) Database",
6466 RFC 3403, October 2002.
6468 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
6469 Requirements for Security", BCP 106, RFC 4086, June 2005.
6471 [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
6472 Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
6473 Zhang, L., and V. Paxson, "Stream Control Transmission
6474 Protocol", RFC 2960, October 2000.
6476 [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
6477 (TLS) Protocol Version 1.1", RFC 4346, April 2006.
6479 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
6480 Resource Identifier (URI): Generic Syntax", STD 66,
6481 RFC 3986, January 2005.
6483 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
6484 10646", STD 63, RFC 3629, November 2003.
6486 [RFC3280] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
6487 X.509 Public Key Infrastructure Certificate and
6488 Certificate Revocation List (CRL) Profile", RFC 3280,
6489 April 2002.
6491 [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
6492 "Internationalizing Domain Names in Applications (IDNA)",
6493 RFC 3490, March 2003.
6495 [RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
6496 Profile for Internationalized Domain Names (IDN)",
6497 RFC 3491, March 2003.
6499 [RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode
6500 for Internationalized Domain Names in Applications
6501 (IDNA)", RFC 3492, March 2003.
6503 14.2. Informational References
6505 [RFC2989] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, P.,
6506 Shiino, H., Zorn, G., Dommety, G., C.Perkins, B.Patil,
6507 D.Mitton, S.Manning, M.Beadles, P.Walsh, X.Chen,
6508 S.Sivalingham, A.Hameed, M.Munson, S.Jacobs, B.Lim,
6509 B.Hirschman, R.Hsu, Y.Xu, E.Campell, S.Baba, and E.Jaques,
6510 "Criteria for Evaluating AAA Protocols for Network
6511 Access", RFC 2989, November 2000.
6513 [RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction to
6514 Accounting Management", RFC 2975, October 2000.
6516 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by
6517 an On-line Database", RFC 3232, January 2002.
6519 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
6520 Aboba, "Dynamic Authorization Extensions to Remote
6521 Authentication Dial In User Service (RADIUS)", RFC 3576,
6522 July 2003.
6524 [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,
6525 RFC 1661, July 1994.
6527 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.
6529 [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS
6530 Extensions", RFC 2869, June 2000.
6532 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
6533 "Remote Authentication Dial In User Service (RADIUS)",
6534 RFC 2865, June 2000.
6536 [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6",
6537 RFC 3162, August 2001.
6539 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
6540 Internet Protocol", RFC 4301, December 2005.
6542 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
6543 A., Peterson, J., Sparks, R., Handley, M., and E.
6544 Schooler, "SIP: Session Initiation Protocol", RFC 3261,
6545 June 2002.
6547 [RFC4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
6548 for IPv4, IPv6 and OSI", RFC 4330, January 2006.
6550 [RFC1492] Finseth, C., "An Access Control Protocol, Sometimes Called
6551 TACACS", RFC 1492, July 1993.
6553 [RFC4690] Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and
6554 Recommendations for Internationalized Domain Names
6555 (IDNs)", RFC 4690, September 2006.
6557 [IANA-EXP]
6558 Narten, T., "Assigning Experimental and Testing Numbers
6559 Considered Useful, Work in Progress.".
6561 Appendix A. Acknowledgements
6563 A.1. RFC3588bis
6565 The authors would like to thank the following people that have
6566 provided proposals and contributions to this document:
6568 To Vishnu Ram and Satendra Gera for their contributions on
6569 Capabilities Updates, Predictive Loop Avoidance as well as many other
6570 technical proposals. To Tolga Asveren for his insights and
6571 contributions on almost all of the proposed solutions incorporated
6572 into this document. To Timothy Smith for helping on the Capabilities
6573 Updates and other topics. To Tony Zhang for providing fixes to loop
6574 holes on composing Failed-AVPs as well as many other issues and
6575 topics. To Jan Nordqvist for clearly stating the usage of
6576 Application Ids. To Anders Kristensen for providing needed technical
6577 opinions. To David Frascone for providing invaluable review of the
6578 document. To Mark Jones for providing clarifying text on vendor
6579 command codes and other vendor specific indicators.
6581 Special thanks to the Diameter extensibility design team which helped
6582 resolve the tricky question of mandatory AVPs and ABNF semantics.
6583 The members of this team are as follows:
6585 Avi Lior, Jari Arkko, Glen Zorn, Lionel Morand, Mark Jones, Tolga
6586 Asveren Jouni Korhonen, Glenn McGregor.
6588 Special thanks also to people who have provided invaluable comments
6589 and inputs especially in resolving controversial issues:
6591 Glen Zorn, Yoshihiro Ohba, Marco Stura, and Pasi Eronen.
6593 Finally, we would like to thank the original authors of this
6594 document:
6596 Pat Calhoun, John Loughney, Jari Arkko, Erik Guttman and Glen Zorn.
6598 Their invaluable knowledge and experience has given us a robust and
6599 flexible AAA protocol that many people have seen great value in
6600 adopting. We greatly appreciate their support and stewardship for
6601 the continued improvements of Diameter as a protocol. We would also
6602 like to extend our gratitude to folks aside from the authors who have
6603 assisted and contributed to the original version of this document.
6604 Their efforts significantly contributed to the success of Diameter.
6606 A.2. RFC3588
6608 The authors would like to thank Nenad Trifunovic, Tony Johansson and
6609 Pankaj Patel for their participation in the pre-IETF Document Reading
6610 Party. Allison Mankin, Jonathan Wood and Bernard Aboba provided
6611 invaluable assistance in working out transport issues, and similarly
6612 with Steven Bellovin in the security area.
6614 Paul Funk and David Mitton were instrumental in getting the Peer
6615 State Machine correct, and our deep thanks go to them for their time.
6617 Text in this document was also provided by Paul Funk, Mark Eklund,
6618 Mark Jones and Dave Spence. Jacques Caron provided many great
6619 comments as a result of a thorough review of the spec.
6621 The authors would also like to acknowledge the following people for
6622 their contribution in the development of the Diameter protocol:
6624 Allan C. Rubens, Haseeb Akhtar, William Bulley, Stephen Farrell,
6625 David Frascone, Daniel C. Fox, Lol Grant, Ignacio Goyret, Nancy
6626 Greene, Peter Heitman, Fredrik Johansson, Mark Jones, Martin Julien,
6627 Bob Kopacz, Paul Krumviede, Fergal Ladley, Ryan Moats, Victor Muslin,
6628 Kenneth Peirce, John Schnizlein, Sumit Vakil, John R. Vollbrecht and
6629 Jeff Weisberg.
6631 Finally, Pat Calhoun would like to thank Sun Microsystems since most
6632 of the effort put into this document was done while he was in their
6633 employ.
6635 Appendix B. NAPTR Example
6637 As an example, consider a client that wishes to resolve aaa:ex.com.
6638 The client performs a NAPTR query for that domain, and the following
6639 NAPTR records are returned:
6641 ;; order pref flags service regexp replacement
6642 IN NAPTR 50 50 "s" "AAA+D2S" "" _diameter._sctp.example.com
6643 IN NAPTR 100 50 "s" "AAA+D2T" "" _aaa._tcp.example.com
6645 This indicates that the server supports SCTP, and TCP, in that order.
6646 If the client supports over SCTP, SCTP will be used, targeted to a
6647 host determined by an SRV lookup of _diameter._sctp.ex.com. That
6648 lookup would return:
6650 ;; Priority Weight Port Target
6651 IN SRV 0 1 5060 server1.example.com
6652 IN SRV 0 2 5060 server2.example.com
6654 Appendix C. Duplicate Detection
6656 As described in Section 9.4, accounting record duplicate detection is
6657 based on session identifiers. Duplicates can appear for various
6658 reasons:
6660 o Failover to an alternate server. Where close to real-time
6661 performance is required, failover thresholds need to be kept low
6662 and this may lead to an increased likelihood of duplicates.
6663 Failover can occur at the client or within Diameter agents.
6665 o Failure of a client or agent after sending of a record from non-
6666 volatile memory, but prior to receipt of an application layer ACK
6667 and deletion of the record. record to be sent. This will result
6668 in retransmission of the record soon after the client or agent has
6669 rebooted.
6671 o Duplicates received from RADIUS gateways. Since the
6672 retransmission behavior of RADIUS is not defined within [RFC2865],
6673 the likelihood of duplication will vary according to the
6674 implementation.
6676 o Implementation problems and misconfiguration.
6678 The T flag is used as an indication of an application layer
6679 retransmission event, e.g., due to failover to an alternate server.
6680 It is defined only for request messages sent by Diameter clients or
6681 agents. For instance, after a reboot, a client may not know whether
6682 it has already tried to send the accounting records in its non-
6683 volatile memory before the reboot occurred. Diameter servers MAY use
6684 the T flag as an aid when processing requests and detecting duplicate
6685 messages. However, servers that do this MUST ensure that duplicates
6686 are found even when the first transmitted request arrives at the
6687 server after the retransmitted request. It can be used only in cases
6688 where no answer has been received from the Server for a request and
6689 the request is sent again, (e.g., due to a failover to an alternate
6690 peer, due to a recovered primary peer or due to a client re-sending a
6691 stored record from non-volatile memory such as after reboot of a
6692 client or agent).
6694 In some cases the Diameter accounting server can delay the duplicate
6695 detection and accounting record processing until a post-processing
6696 phase takes place. At that time records are likely to be sorted
6697 according to the included User-Name and duplicate elimination is easy
6698 in this case. In other situations it may be necessary to perform
6699 real-time duplicate detection, such as when credit limits are imposed
6700 or real-time fraud detection is desired.
6702 In general, only generation of duplicates due to failover or re-
6703 sending of records in non-volatile storage can be reliably detected
6704 by Diameter clients or agents. In such cases the Diameter client or
6705 agents can mark the message as possible duplicate by setting the T
6706 flag. Since the Diameter server is responsible for duplicate
6707 detection, it can choose to make use of the T flag or not, in order
6708 to optimize duplicate detection. Since the T flag does not affect
6709 interoperability, and may not be needed by some servers, generation
6710 of the T flag is REQUIRED for Diameter clients and agents, but MAY be
6711 implemented by Diameter servers.
6713 As an example, it can be usually be assumed that duplicates appear
6714 within a time window of longest recorded network partition or device
6715 fault, perhaps a day. So only records within this time window need
6716 to be looked at in the backward direction. Secondly, hashing
6717 techniques or other schemes, such as the use of the T flag in the
6718 received messages, may be used to eliminate the need to do a full
6719 search even in this set except for rare cases.
6721 The following is an example of how the T flag may be used by the
6722 server to detect duplicate requests.
6724 A Diameter server MAY check the T flag of the received message to
6725 determine if the record is a possible duplicate. If the T flag is
6726 set in the request message, the server searches for a duplicate
6727 within a configurable duplication time window backward and
6728 forward. This limits database searching to those records where
6729 the T flag is set. In a well run network, network partitions and
6730 device faults will presumably be rare events, so this approach
6731 represents a substantial optimization of the duplicate detection
6732 process. During failover, it is possible for the original record
6733 to be received after the T flag marked record, due to differences
6734 in network delays experienced along the path by the original and
6735 duplicate transmissions. The likelihood of this occurring
6736 increases as the failover interval is decreased. In order to be
6737 able to detect out of order duplicates, the Diameter server should
6738 use backward and forward time windows when performing duplicate
6739 checking for the T flag marked request. For example, in order to
6740 allow time for the original record to exit the network and be
6741 recorded by the accounting server, the Diameter server can delay
6742 processing records with the T flag set until a time period
6743 TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after the closing
6744 of the original transport connection. After this time period has
6745 expired, then it may check the T flag marked records against the
6746 database with relative assurance that the original records, if
6747 sent, have been received and recorded.
6749 Appendix D. Internationalized Domain Names
6751 To be compatible with the existing DNS infrastructure and simplify
6752 host and domain name comparison, Diameter identities (FQDNs) are
6753 represented in ASCII form. This allows the Diameter protocol to fall
6754 in-line with the DNS strategy of being transparent from the effects
6755 of Internationalized Domain Names (IDNs) by following the
6756 recommnedations in [RFC4690] and [RFC3490]. Applications that
6757 provide support for IDNs outside of the Diameter protocol but
6758 interacting with it SHOULD use the representation and conversion
6759 framework described in [RFC3490], [RFC3491] and [RFC3492].
6761 Authors' Addresses
6763 Victor Fajardo (editor)
6764 Toshiba America Research
6765 One Telcordia Drive, 1S-222
6766 Piscataway, NJ 08854
6767 USA
6769 Phone: 1 908-421-1845
6770 Email: vfajardo@tari.toshiba.com
6772 Jari Arkko
6773 Ericsson Research
6774 02420 Jorvas
6775 Finland
6777 Phone: +358 40 5079256
6778 Email: jari.arkko@ericsson.com
6780 John Loughney
6781 Nokia Research Center
6782 955 Page Mill Road
6783 Palo Alto, CA 94304
6784 US
6786 Phone: 1-650-283-8068
6787 Email: john.loughney@nokia.com
6789 Glenn Zorn
6790 NetCube
6791 1310 East Thomas Street, #306
6792 Seattle, WA 98102
6793 US
6795 Phone:
6796 Email: glenzorn@comcast.net
6798 Full Copyright Statement
6800 Copyright (C) The IETF Trust (2008).
6802 This document is subject to the rights, licenses and restrictions
6803 contained in BCP 78, and except as set forth therein, the authors
6804 retain all their rights.
6806 This document and the information contained herein are provided on an
6807 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
6808 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
6809 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
6810 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
6811 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
6812 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
6814 Intellectual Property
6816 The IETF takes no position regarding the validity or scope of any
6817 Intellectual Property Rights or other rights that might be claimed to
6818 pertain to the implementation or use of the technology described in
6819 this document or the extent to which any license under such rights
6820 might or might not be available; nor does it represent that it has
6821 made any independent effort to identify any such rights. Information
6822 on the procedures with respect to rights in RFC documents can be
6823 found in BCP 78 and BCP 79.
6825 Copies of IPR disclosures made to the IETF Secretariat and any
6826 assurances of licenses to be made available, or the result of an
6827 attempt made to obtain a general license or permission for the use of
6828 such proprietary rights by implementers or users of this
6829 specification can be obtained from the IETF on-line IPR repository at
6830 http://www.ietf.org/ipr.
6832 The IETF invites any interested party to bring to its attention any
6833 copyrights, patents or patent applications, or other proprietary
6834 rights that may cover technology that may be required to implement
6835 this standard. Please address the information to the IETF at
6836 ietf-ipr@ietf.org.