idnits 2.17.1
draft-ietf-dime-rfc3588bis-06.txt:
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line 6805.
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== There are 2 instances of lines with non-RFC2606-compliant FQDNs in the
document.
== There are 2 instances of lines with non-RFC6890-compliant IPv4 addresses
in the document. If these are example addresses, they should be changed.
Miscellaneous warnings:
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== The copyright year in the IETF Trust Copyright Line does not match the
current year
== Line 4539 has weird spacing: '...ly with wit...'
== Line 4747 has weird spacing: '...ealtime user...'
== Line 4775 has weird spacing: '... record inter...'
== Line 4785 has weird spacing: '...ealtime user...'
== Line 4793 has weird spacing: '...ealtime user...'
== (1 more instance...)
== Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD',
or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please
use uppercase 'NOT' together with RFC 2119 keywords (if that is what you
mean).
Found 'MUST not' in this paragraph:
The receiver of the Capabilities-Exchange-Request (CER) MUST
determine common applications by computing the intersection of its own
set of supported application identifiers against all of the application
indentifier AVPs (Auth-Application-Id, Acct-Application-Id and
Vendor-Specific-Application-Id) present in the CER. The value of the
Vendor-Id AVP in the Vendor-Specific-Application-Id MUST not be used
during computation. The sender of the Capabilities-Exchange-Answer (CEA)
SHOULD include all of its supported applications as a hint to the
receiver regarding all of its application capabilities.
== Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD',
or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please
use uppercase 'NOT' together with RFC 2119 keywords (if that is what you
mean).
Found 'MUST not' in this paragraph:
The Destination-Realm AVP MUST be present if the message is
proxiable. Request messages that may be forwarded by Diameter agents
(proxies, redirects or relays) MUST also contain an Acct-Application-Id
AVP, an Auth-Application-Id AVP or a Vendor-Specific-Application-Id AVP.
A message that MUST NOT be forwarded by Diameter agents (proxies,
redirects or relays) MUST not include the Destination-Realm in its ABNF.
The value of the Destination-Realm AVP MAY be extracted from the
User-Name AVP, or other application-specific methods.
-- The document seems to lack a disclaimer for pre-RFC5378 work, but may
have content which was first submitted before 10 November 2008. If you
have contacted all the original authors and they are all willing to grant
the BCP78 rights to the IETF Trust, then this is fine, and you can ignore
this comment. If not, you may need to add the pre-RFC5378 disclaimer.
(See the Legal Provisions document at
https://trustee.ietf.org/license-info for more information.)
-- The document date (August 20, 2007) is 6093 days in the past. Is this
intentional?
Checking references for intended status: Proposed Standard
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(See RFCs 3967 and 4897 for information about using normative references
to lower-maturity documents in RFCs)
== Missing Reference: 'PXY' is mentioned on line 4254, but not defined
-- Possible downref: Non-RFC (?) normative reference: ref. 'FLOATPOINT'
-- Possible downref: Non-RFC (?) normative reference: ref. 'IANAADFAM'
-- Possible downref: Non-RFC (?) normative reference: ref. 'RADTYPE'
** Obsolete normative reference: RFC 793 (ref. 'TCP') (Obsoleted by RFC
9293)
** Obsolete normative reference: RFC 4005 (Obsoleted by RFC 7155)
** Obsolete normative reference: RFC 4006 (Obsoleted by RFC 8506)
** Obsolete normative reference: RFC 4234 (Obsoleted by RFC 5234)
** Obsolete normative reference: RFC 3588 (Obsoleted by RFC 6733)
** Obsolete normative reference: RFC 2434 (Obsoleted by RFC 5226)
** Obsolete normative reference: RFC 4306 (Obsoleted by RFC 5996)
** Obsolete normative reference: RFC 4282 (Obsoleted by RFC 7542)
** Obsolete normative reference: RFC 2960 (Obsoleted by RFC 4960)
** Obsolete normative reference: RFC 4346 (Obsoleted by RFC 5246)
-- Obsolete informational reference (is this intentional?): RFC 3576
(Obsoleted by RFC 5176)
-- Obsolete informational reference (is this intentional?): RFC 4330
(Obsoleted by RFC 5905)
Summary: 11 errors (**), 0 flaws (~~), 12 warnings (==), 12 comments
(--).
Run idnits with the --verbose option for more detailed information about
the items above.
--------------------------------------------------------------------------------
2 DIME V. Fajardo, Ed.
3 Internet-Draft Toshiba America Research
4 Intended status: Standards Track J. Arkko
5 Expires: February 21, 2008 Ericsson Research
6 J. Loughney
7 Nokia Research Center
8 August 20, 2007
10 Diameter Base Protocol
11 draft-ietf-dime-rfc3588bis-06.txt
13 Status of this Memo
15 By submitting this Internet-Draft, each author represents that any
16 applicable patent or other IPR claims of which he or she is aware
17 have been or will be disclosed, and any of which he or she becomes
18 aware will be disclosed, in accordance with Section 6 of BCP 79.
20 Internet-Drafts are working documents of the Internet Engineering
21 Task Force (IETF), its areas, and its working groups. Note that
22 other groups may also distribute working documents as Internet-
23 Drafts.
25 Internet-Drafts are draft documents valid for a maximum of six months
26 and may be updated, replaced, or obsoleted by other documents at any
27 time. It is inappropriate to use Internet-Drafts as reference
28 material or to cite them other than as "work in progress."
30 The list of current Internet-Drafts can be accessed at
31 http://www.ietf.org/ietf/1id-abstracts.txt.
33 The list of Internet-Draft Shadow Directories can be accessed at
34 http://www.ietf.org/shadow.html.
36 This Internet-Draft will expire on February 21, 2008.
38 Copyright Notice
40 Copyright (C) The IETF Trust (2007).
42 Abstract
44 The Diameter base protocol is intended to provide an Authentication,
45 Authorization and Accounting (AAA) framework for applications such as
46 network access or IP mobility. Diameter is also intended to work in
47 both local Authentication, Authorization & Accounting and roaming
48 situations. This document specifies the message format, transport,
49 error reporting, accounting and security services to be used by all
50 Diameter applications. The Diameter base application needs to be
51 supported by all Diameter implementations.
53 Table of Contents
55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7
56 1.1. Diameter Protocol . . . . . . . . . . . . . . . . . . . . 10
57 1.1.1. Description of the Document Set . . . . . . . . . . 11
58 1.1.2. Conventions Used in This Document . . . . . . . . . 12
59 1.2. Approach to Extensibility . . . . . . . . . . . . . . . . 12
60 1.2.1. Defining New AVP Values . . . . . . . . . . . . . . 13
61 1.2.2. Creating New AVPs . . . . . . . . . . . . . . . . . 13
62 1.2.3. Creating New Commands . . . . . . . . . . . . . . . 13
63 1.2.4. Creating New Authentication Applications . . . . . . 13
64 1.2.5. Creating New Accounting Applications . . . . . . . . 14
65 1.2.6. Application Authentication Procedures . . . . . . . 15
66 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 16
67 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 22
68 2.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 23
69 2.1.1. SCTP Guidelines . . . . . . . . . . . . . . . . . . 24
70 2.2. Securing Diameter Messages . . . . . . . . . . . . . . . 24
71 2.3. Diameter Application Compliance . . . . . . . . . . . . . 24
72 2.4. Application Identifiers . . . . . . . . . . . . . . . . . 24
73 2.5. Connections vs. Sessions . . . . . . . . . . . . . . . . 25
74 2.6. Peer Table . . . . . . . . . . . . . . . . . . . . . . . 26
75 2.7. Routing Table . . . . . . . . . . . . . . . . . . . . . . 27
76 2.8. Role of Diameter Agents . . . . . . . . . . . . . . . . . 28
77 2.8.1. Relay Agents . . . . . . . . . . . . . . . . . . . . 30
78 2.8.2. Proxy Agents . . . . . . . . . . . . . . . . . . . . 31
79 2.8.3. Redirect Agents . . . . . . . . . . . . . . . . . . 31
80 2.8.4. Translation Agents . . . . . . . . . . . . . . . . . 32
81 2.9. Diameter Path Authorization . . . . . . . . . . . . . . . 33
82 3. Diameter Header . . . . . . . . . . . . . . . . . . . . . . . 35
83 3.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 38
84 3.2. Command Code ABNF specification . . . . . . . . . . . . . 38
85 3.3. Diameter Command Naming Conventions . . . . . . . . . . . 40
86 4. Diameter AVPs . . . . . . . . . . . . . . . . . . . . . . . . 42
87 4.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 42
88 4.1.1. Optional Header Elements . . . . . . . . . . . . . . 44
90 4.2. Basic AVP Data Formats . . . . . . . . . . . . . . . . . 44
91 4.3. Derived AVP Data Formats . . . . . . . . . . . . . . . . 46
92 4.4. Grouped AVP Values . . . . . . . . . . . . . . . . . . . 52
93 4.4.1. Example AVP with a Grouped Data type . . . . . . . . 53
94 4.5. Diameter Base Protocol AVPs . . . . . . . . . . . . . . . 56
95 5. Diameter Peers . . . . . . . . . . . . . . . . . . . . . . . 59
96 5.1. Peer Connections . . . . . . . . . . . . . . . . . . . . 59
97 5.2. Diameter Peer Discovery . . . . . . . . . . . . . . . . . 59
98 5.3. Capabilities Exchange . . . . . . . . . . . . . . . . . . 62
99 5.3.1. Capabilities-Exchange-Request . . . . . . . . . . . 63
100 5.3.2. Capabilities-Exchange-Answer . . . . . . . . . . . . 64
101 5.3.3. Vendor-Id AVP . . . . . . . . . . . . . . . . . . . 64
102 5.3.4. Firmware-Revision AVP . . . . . . . . . . . . . . . 65
103 5.3.5. Host-IP-Address AVP . . . . . . . . . . . . . . . . 65
104 5.3.6. Supported-Vendor-Id AVP . . . . . . . . . . . . . . 65
105 5.3.7. Product-Name AVP . . . . . . . . . . . . . . . . . . 65
106 5.4. Disconnecting Peer connections . . . . . . . . . . . . . 65
107 5.4.1. Disconnect-Peer-Request . . . . . . . . . . . . . . 66
108 5.4.2. Disconnect-Peer-Answer . . . . . . . . . . . . . . . 66
109 5.4.3. Disconnect-Cause AVP . . . . . . . . . . . . . . . . 67
110 5.5. Transport Failure Detection . . . . . . . . . . . . . . . 67
111 5.5.1. Device-Watchdog-Request . . . . . . . . . . . . . . 67
112 5.5.2. Device-Watchdog-Answer . . . . . . . . . . . . . . . 68
113 5.5.3. Transport Failure Algorithm . . . . . . . . . . . . 68
114 5.5.4. Failover and Failback Procedures . . . . . . . . . . 68
115 5.6. Peer State Machine . . . . . . . . . . . . . . . . . . . 69
116 5.6.1. Incoming connections . . . . . . . . . . . . . . . . 71
117 5.6.2. Events . . . . . . . . . . . . . . . . . . . . . . . 72
118 5.6.3. Actions . . . . . . . . . . . . . . . . . . . . . . 73
119 5.6.4. The Election Process . . . . . . . . . . . . . . . . 75
120 5.6.5. Capabilities Update . . . . . . . . . . . . . . . . 75
121 6. Diameter message processing . . . . . . . . . . . . . . . . . 76
122 6.1. Diameter Request Routing Overview . . . . . . . . . . . . 76
123 6.1.1. Originating a Request . . . . . . . . . . . . . . . 77
124 6.1.2. Sending a Request . . . . . . . . . . . . . . . . . 78
125 6.1.3. Receiving Requests . . . . . . . . . . . . . . . . . 78
126 6.1.4. Processing Local Requests . . . . . . . . . . . . . 78
127 6.1.5. Request Forwarding . . . . . . . . . . . . . . . . . 78
128 6.1.6. Request Routing . . . . . . . . . . . . . . . . . . 79
129 6.1.7. Predictive Loop Avoidance . . . . . . . . . . . . . 79
130 6.1.8. Redirecting requests . . . . . . . . . . . . . . . . 79
131 6.1.9. Relaying and Proxying Requests . . . . . . . . . . . 81
132 6.2. Diameter Answer Processing . . . . . . . . . . . . . . . 81
133 6.2.1. Processing received Answers . . . . . . . . . . . . 82
134 6.2.2. Relaying and Proxying Answers . . . . . . . . . . . 82
135 6.3. Origin-Host AVP . . . . . . . . . . . . . . . . . . . . . 83
136 6.4. Origin-Realm AVP . . . . . . . . . . . . . . . . . . . . 83
137 6.5. Destination-Host AVP . . . . . . . . . . . . . . . . . . 83
138 6.6. Destination-Realm AVP . . . . . . . . . . . . . . . . . . 84
139 6.7. Routing AVPs . . . . . . . . . . . . . . . . . . . . . . 84
140 6.7.1. Route-Record AVP . . . . . . . . . . . . . . . . . . 84
141 6.7.2. Proxy-Info AVP . . . . . . . . . . . . . . . . . . . 84
142 6.7.3. Proxy-Host AVP . . . . . . . . . . . . . . . . . . . 84
143 6.7.4. Proxy-State AVP . . . . . . . . . . . . . . . . . . 84
144 6.8. Auth-Application-Id AVP . . . . . . . . . . . . . . . . . 85
145 6.9. Acct-Application-Id AVP . . . . . . . . . . . . . . . . . 85
146 6.10. Inband-Security-Id AVP . . . . . . . . . . . . . . . . . 85
147 6.11. Vendor-Specific-Application-Id AVP . . . . . . . . . . . 85
148 6.12. Redirect-Host AVP . . . . . . . . . . . . . . . . . . . . 86
149 6.13. Redirect-Host-Usage AVP . . . . . . . . . . . . . . . . . 86
150 6.14. Redirect-Max-Cache-Time AVP . . . . . . . . . . . . . . . 88
151 6.15. E2E-Sequence AVP . . . . . . . . . . . . . . . . . . . . 88
152 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 89
153 7.1. Result-Code AVP . . . . . . . . . . . . . . . . . . . . . 90
154 7.1.1. Informational . . . . . . . . . . . . . . . . . . . 91
155 7.1.2. Success . . . . . . . . . . . . . . . . . . . . . . 91
156 7.1.3. Protocol Errors . . . . . . . . . . . . . . . . . . 92
157 7.1.4. Transient Failures . . . . . . . . . . . . . . . . . 93
158 7.1.5. Permanent Failures . . . . . . . . . . . . . . . . . 94
159 7.2. Error Bit . . . . . . . . . . . . . . . . . . . . . . . . 97
160 7.3. Error-Message AVP . . . . . . . . . . . . . . . . . . . . 97
161 7.4. Error-Reporting-Host AVP . . . . . . . . . . . . . . . . 97
162 7.5. Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . . 98
163 7.6. Experimental-Result AVP . . . . . . . . . . . . . . . . . 99
164 7.7. Experimental-Result-Code AVP . . . . . . . . . . . . . . 99
165 8. Diameter User Sessions . . . . . . . . . . . . . . . . . . . 100
166 8.1. Authorization Session State Machine . . . . . . . . . . . 101
167 8.2. Accounting Session State Machine . . . . . . . . . . . . 106
168 8.3. Server-Initiated Re-Auth . . . . . . . . . . . . . . . . 111
169 8.3.1. Re-Auth-Request . . . . . . . . . . . . . . . . . . 111
170 8.3.2. Re-Auth-Answer . . . . . . . . . . . . . . . . . . . 112
171 8.4. Session Termination . . . . . . . . . . . . . . . . . . . 113
172 8.4.1. Session-Termination-Request . . . . . . . . . . . . 114
173 8.4.2. Session-Termination-Answer . . . . . . . . . . . . . 114
174 8.5. Aborting a Session . . . . . . . . . . . . . . . . . . . 115
175 8.5.1. Abort-Session-Request . . . . . . . . . . . . . . . 116
176 8.5.2. Abort-Session-Answer . . . . . . . . . . . . . . . . 116
177 8.6. Inferring Session Termination from Origin-State-Id . . . 117
178 8.7. Auth-Request-Type AVP . . . . . . . . . . . . . . . . . . 118
179 8.8. Session-Id AVP . . . . . . . . . . . . . . . . . . . . . 118
180 8.9. Authorization-Lifetime AVP . . . . . . . . . . . . . . . 119
181 8.10. Auth-Grace-Period AVP . . . . . . . . . . . . . . . . . . 120
182 8.11. Auth-Session-State AVP . . . . . . . . . . . . . . . . . 120
183 8.12. Re-Auth-Request-Type AVP . . . . . . . . . . . . . . . . 121
184 8.13. Session-Timeout AVP . . . . . . . . . . . . . . . . . . . 121
185 8.14. User-Name AVP . . . . . . . . . . . . . . . . . . . . . . 122
186 8.15. Termination-Cause AVP . . . . . . . . . . . . . . . . . . 122
187 8.16. Origin-State-Id AVP . . . . . . . . . . . . . . . . . . . 123
188 8.17. Session-Binding AVP . . . . . . . . . . . . . . . . . . . 123
189 8.18. Session-Server-Failover AVP . . . . . . . . . . . . . . . 124
190 8.19. Multi-Round-Time-Out AVP . . . . . . . . . . . . . . . . 125
191 8.20. Class AVP . . . . . . . . . . . . . . . . . . . . . . . . 125
192 8.21. Event-Timestamp AVP . . . . . . . . . . . . . . . . . . . 125
193 9. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . 127
194 9.1. Server Directed Model . . . . . . . . . . . . . . . . . . 127
195 9.2. Protocol Messages . . . . . . . . . . . . . . . . . . . . 128
196 9.3. Accounting Application Extension and Requirements . . . . 128
197 9.4. Fault Resilience . . . . . . . . . . . . . . . . . . . . 129
198 9.5. Accounting Records . . . . . . . . . . . . . . . . . . . 130
199 9.6. Correlation of Accounting Records . . . . . . . . . . . . 130
200 9.7. Accounting Command-Codes . . . . . . . . . . . . . . . . 131
201 9.7.1. Accounting-Request . . . . . . . . . . . . . . . . . 131
202 9.7.2. Accounting-Answer . . . . . . . . . . . . . . . . . 132
203 9.8. Accounting AVPs . . . . . . . . . . . . . . . . . . . . . 133
204 9.8.1. Accounting-Record-Type AVP . . . . . . . . . . . . . 133
205 9.8.2. Acct-Interim-Interval . . . . . . . . . . . . . . . 134
206 9.8.3. Accounting-Record-Number AVP . . . . . . . . . . . . 135
207 9.8.4. Acct-Session-Id AVP . . . . . . . . . . . . . . . . 135
208 9.8.5. Acct-Multi-Session-Id AVP . . . . . . . . . . . . . 135
209 9.8.6. Accounting-Sub-Session-Id AVP . . . . . . . . . . . 135
210 9.8.7. Accounting-Realtime-Required AVP . . . . . . . . . . 136
211 10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . 137
212 10.1. Base Protocol Command AVP Table . . . . . . . . . . . . . 137
213 10.2. Accounting AVP Table . . . . . . . . . . . . . . . . . . 138
214 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 140
215 11.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 140
216 11.1.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . 140
217 11.1.2. AVP Flags . . . . . . . . . . . . . . . . . . . . . 141
218 11.2. Diameter Header . . . . . . . . . . . . . . . . . . . . . 141
219 11.2.1. Command Codes . . . . . . . . . . . . . . . . . . . 141
220 11.2.2. Command Flags . . . . . . . . . . . . . . . . . . . 142
221 11.3. Application Identifiers . . . . . . . . . . . . . . . . . 142
222 11.4. AVP Values . . . . . . . . . . . . . . . . . . . . . . . 143
223 11.4.1. Result-Code AVP Values . . . . . . . . . . . . . . . 143
224 11.4.2. Accounting-Record-Type AVP Values . . . . . . . . . 143
225 11.4.3. Termination-Cause AVP Values . . . . . . . . . . . . 143
226 11.4.4. Redirect-Host-Usage AVP Values . . . . . . . . . . . 143
227 11.4.5. Session-Server-Failover AVP Values . . . . . . . . . 143
228 11.4.6. Session-Binding AVP Values . . . . . . . . . . . . . 143
229 11.4.7. Disconnect-Cause AVP Values . . . . . . . . . . . . 144
230 11.4.8. Auth-Request-Type AVP Values . . . . . . . . . . . . 144
231 11.4.9. Auth-Session-State AVP Values . . . . . . . . . . . 144
232 11.4.10. Re-Auth-Request-Type AVP Values . . . . . . . . . . 144
233 11.4.11. Accounting-Realtime-Required AVP Values . . . . . . 144
234 11.4.12. Inband-Security-Id AVP (code 299) . . . . . . . . . 144
235 11.5. Diameter TCP/SCTP Port Numbers . . . . . . . . . . . . . 144
236 11.6. NAPTR Service Fields . . . . . . . . . . . . . . . . . . 144
237 12. Diameter protocol related configurable parameters . . . . . . 146
238 13. Security Considerations . . . . . . . . . . . . . . . . . . . 147
239 13.1. TLS Usage . . . . . . . . . . . . . . . . . . . . . . . . 147
240 13.2. Peer-to-Peer Considerations . . . . . . . . . . . . . . . 148
241 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 149
242 14.1. Normative References . . . . . . . . . . . . . . . . . . 149
243 14.2. Informational References . . . . . . . . . . . . . . . . 151
244 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 153
245 Appendix B. NAPTR Example . . . . . . . . . . . . . . . . . . . 154
246 Appendix C. Duplicate Detection . . . . . . . . . . . . . . . . 155
247 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 157
248 Intellectual Property and Copyright Statements . . . . . . . . . 158
250 1. Introduction
252 Authentication, Authorization and Accounting (AAA) protocols such as
253 TACACS [RFC1492] and RADIUS [RFC2865] were initially deployed to
254 provide dial-up PPP [RFC1661] and terminal server access. Over time,
255 with the growth of the Internet and the introduction of new access
256 technologies, including wireless, DSL, Mobile IP and Ethernet,
257 routers and network access servers (NAS) have increased in complexity
258 and density, putting new demands on AAA protocols.
260 Network access requirements for AAA protocols are summarized in
261 [RFC2989]. These include:
263 Failover
265 [RFC2865] does not define failover mechanisms, and as a result,
266 failover behavior differs between implementations. In order to
267 provide well defined failover behavior, Diameter supports
268 application-layer acknowledgements, and defines failover
269 algorithms and the associated state machine. This is described in
270 Section 5.5 and [RFC3539].
272 Transmission-level security
274 [RFC2865] defines an application-layer authentication and
275 integrity scheme that is required only for use with Response
276 packets. While [RFC2869] defines an additional authentication and
277 integrity mechanism, use is only required during Extensible
278 Authentication Protocol (EAP) sessions. While attribute-hiding is
279 supported, [RFC2865] does not provide support for per-packet
280 confidentiality. In accounting, [RFC2866] assumes that replay
281 protection is provided by the backend billing server, rather than
282 within the protocol itself.
284 While [RFC3162] defines the use of IPsec with RADIUS, support for
285 IPsec is not required. Since within [RFC4306] authentication
286 occurs only within Phase 1 prior to the establishment of IPsec SAs
287 in Phase 2, it is typically not possible to define separate trust
288 or authorization schemes for each application. This limits the
289 usefulness of IPsec in inter-domain AAA applications (such as
290 roaming) where it may be desirable to define a distinct
291 certificate hierarchy for use in a AAA deployment. In order to
292 provide universal support for transmission-level security, and
293 enable both intra- and inter-domain AAA deployments, Diameter also
294 provides support for TLS. Security is discussed in Section 13.
296 Reliable transport
298 RADIUS runs over UDP, and does not define retransmission behavior;
299 as a result, reliability varies between implementations. As
300 described in [RFC2975], this is a major issue in accounting, where
301 packet loss may translate directly into revenue loss. In order to
302 provide well defined transport behavior, Diameter runs over
303 reliable transport mechanisms (TCP, SCTP) as defined in [RFC3539].
305 Agent support
307 [RFC2865] does not provide for explicit support for agents,
308 including Proxies, Redirects and Relays. Since the expected
309 behavior is not defined, it varies between implementations.
310 Diameter defines agent behavior explicitly; this is described in
311 Section 2.8.
313 Server-initiated messages
315 While RADIUS server-initiated messages are defined in [RFC3576],
316 support is optional. This makes it difficult to implement
317 features such as unsolicited disconnect or reauthentication/
318 reauthorization on demand across a heterogeneous deployment.
319 Support for server-initiated messages is mandatory in Diameter,
320 and is described in Section 8.
322 Auditability
324 RADIUS does not define data-object security mechanisms, and as a
325 result, untrusted proxies may modify attributes or even packet
326 headers without being detected. Combined with lack of support for
327 capabilities negotiation, this makes it very difficult to
328 determine what occurred in the event of a dispute.
330 Transition support
332 While Diameter does not share a common protocol data unit (PDU)
333 with RADIUS, considerable effort has been expended in enabling
334 backward compatibility with RADIUS, so that the two protocols may
335 be deployed in the same network. Initially, it is expected that
336 Diameter will be deployed within new network devices, as well as
337 within gateways enabling communication between legacy RADIUS
338 devices and Diameter agents. This capability, described in
340 [RFC4005], enables Diameter support to be added to legacy
341 networks, by addition of a gateway or server speaking both RADIUS
342 and Diameter.
344 In addition to addressing the above requirements, Diameter also
345 provides support for the following:
347 Capability negotiation
349 RADIUS does not support error messages, capability negotiation, or
350 a mandatory/non-mandatory flag for attributes. Since RADIUS
351 clients and servers are not aware of each other's capabilities,
352 they may not be able to successfully negotiate a mutually
353 acceptable service, or in some cases, even be aware of what
354 service has been implemented. Diameter includes support for error
355 handling (Section 7), capability negotiation (Section 5.3), and
356 mandatory/non-mandatory attribute-value pairs (AVPs) (Section
357 4.1).
359 Peer discovery and configuration
361 RADIUS implementations typically require that the name or address
362 of servers or clients be manually configured, along with the
363 corresponding shared secrets. This results in a large
364 administrative burden, and creates the temptation to reuse the
365 RADIUS shared secret, which can result in major security
366 vulnerabilities if the Request Authenticator is not globally and
367 temporally unique as required in [RFC2865]. Through DNS, Diameter
368 enables dynamic discovery of peers. Derivation of dynamic session
369 keys is enabled via transmission-level security.
371 Roaming support
373 The ROAMOPS WG provided a survey of roaming implementations
374 [RFC2194], detailed roaming requirements [RFC2477], defined the
375 Network Access Identifier (NAI)[RFC4282], and documented existing
376 implementations (and imitations) of RADIUS-based roaming
377 [RFC2607]. In order to improve scalability, [RFC2607] introduced
378 the concept of proxy chaining via an intermediate server,
379 facilitating roaming between providers. However, since RADIUS
380 does not provide explicit support for proxies, and lacks
381 auditability and transmission-level security features, RADIUS-
382 based roaming is vulnerable to attack from external parties as
383 well as susceptible to fraud perpetrated by the roaming partners
384 themselves. As a result, it is not suitable for wide-scale
385 deployment on the Internet [RFC2607]. By providing explicit
386 support for inter-domain roaming and message routing (Sections 2.7
387 and 6), and transmission-layer security (Section 13) features,
388 Diameter addresses these limitations and provides for secure and
389 scalable roaming.
391 In the decade since AAA protocols were first introduced, the
392 capabilities of Network Access Server (NAS) devices have increased
393 substantially. As a result, while Diameter is a considerably more
394 sophisticated protocol than RADIUS, it remains feasible to implement
395 within embedded devices, given improvements in processor speeds and
396 the widespread availability of embedded TLS implementations.
398 1.1. Diameter Protocol
400 The Diameter base protocol provides the following facilities:
402 o Delivery of AVPs (attribute value pairs)
404 o Capabilities negotiation
406 o Error notification
408 o Extensibility, through addition of new commands and AVPs (required
409 in [RFC2989]).
411 o Basic services necessary for applications, such as handling of
412 user sessions or accounting
414 All data delivered by the protocol is in the form of an AVP. Some of
415 these AVP values are used by the Diameter protocol itself, while
416 others deliver data associated with particular applications that
417 employ Diameter. AVPs may be added arbitrarily to Diameter messages,
418 so long as the requirements of a message's ABNF are met and the ABNF
419 allows for it. AVPs are used by the base Diameter protocol to
420 support the following required features:
422 o Transporting of user authentication information, for the purposes
423 of enabling the Diameter server to authenticate the user.
425 o Transporting of service specific authorization information,
426 between client and servers, allowing the peers to decide whether a
427 user's access request should be granted.
429 o Exchanging resource usage information, which MAY be used for
430 accounting purposes, capacity planning, etc.
432 o Relaying, proxying and redirecting of Diameter messages through a
433 server hierarchy.
435 The Diameter base protocol provides the minimum requirements needed
436 for a AAA protocol, as required by [RFC2989]. The base protocol may
437 be used by itself for accounting purposes only, or it may be used
438 with a Diameter application, such as Mobile IPv4 [RFC4004], or
439 network access [RFC4005]. It is also possible for the base protocol
440 to be extended for use in new applications, via the addition of new
441 commands or AVPs. At this time the focus of Diameter is network
442 access and accounting applications. A truly generic AAA protocol
443 used by many applications might provide functionality not provided by
444 Diameter. Therefore, it is imperative that the designers of new
445 applications understand their requirements before using Diameter.
446 See Section 2.4 for more information on Diameter applications.
448 Any node can initiate a request. In that sense, Diameter is a peer-
449 to-peer protocol. In this document, a Diameter Client is a device at
450 the edge of the network that performs access control, such as a
451 Network Access Server (NAS) or a Foreign Agent (FA). A Diameter
452 client generates Diameter messages to request authentication,
453 authorization, and accounting services for the user. A Diameter
454 agent is a node that does not authenticate and/or authorize messages
455 locally; agents include proxies, redirects and relay agents. A
456 Diameter server performs authentication and/or authorization of the
457 user. A Diameter node MAY act as an agent for certain requests while
458 acting as a server for others.
460 The Diameter protocol also supports server-initiated messages, such
461 as a request to abort service to a particular user.
463 1.1.1. Description of the Document Set
465 Currently, the Diameter specification consists of a base
466 specification (this document), Transport Profile [RFC3539] and
467 applications: Mobile IPv4 [RFC4004], NASREQ [RFC4005], Credit Control
468 [RFC4006], EAP [RFC4072] and SIP [RFC4740].
470 The Transport Profile document [RFC3539] discusses transport layer
471 issues that arise with AAA protocols and recommendations on how to
472 overcome these issues. This document also defines the Diameter
473 failover algorithm and state machine.
475 The Mobile IPv4 [RFC4004] application defines a Diameter application
476 that allows a Diameter server to perform AAA functions for Mobile
477 IPv4 services to a mobile node.
479 The NASREQ [RFC4005] application defines a Diameter Application that
480 allows a Diameter server to be used in a PPP/SLIP Dial-Up and
481 Terminal Server Access environment. Consideration was given for
482 servers that need to perform protocol conversion between Diameter and
483 RADIUS.
485 The Credit Control [RFC4006] application defines a Diameter
486 Application that can be used to implement real-time credit-control
487 for a variety of end user services such as network access, SIP
488 services, messaging services, and download services. It provides a
489 general solution to real-time cost and credit-control.
491 The EAP [RFC4072] application defines a Diameter Application that can
492 be used to carry EAP packets between the Network Access Server (NAS)
493 working as an EAP authenticator and a back-end authentication server.
494 The Diameter EAP application is based on NASREQ and intended for a
495 similar environment.
497 The SIP [RFC4740] application defines a Diameter Application that
498 allows a Diameter client to request authentication and authorization
499 information to a Diameter server for SIP-based IP multimedia services
500 (see SIP [RFC3261]).
502 In summary, this document defines the base protocol specification for
503 AAA, which includes support for accounting. The applications
504 documents describe applications that use this base specification for
505 Authentication, Authorization and Accounting.
507 1.1.2. Conventions Used in This Document
509 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
510 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
511 document are to be interpreted as described in [RFC2119].
513 1.2. Approach to Extensibility
515 The Diameter protocol is designed to be extensible, using several
516 mechanisms, including:
518 o Defining new AVP values
520 o Creating new AVPs
522 o Creating new commands
524 o Creating new authentication/authorization applications
526 o Creating new accounting applications
527 o Application authentication procedures
529 Reuse of existing AVP values, AVPs, commands and Diameter
530 applications are strongly recommended. Reuse simplifies
531 standardization and implementation and avoids potential
532 interoperability issues.
534 1.2.1. Defining New AVP Values
536 New applications should attempt to reuse AVPs defined in existing
537 applications when possible, as opposed to creating new AVPs. For
538 AVPs of type Enumerated, an application may require a new value to
539 communicate some service-specific information.
541 In order to allocate a new AVP value for a standards track AVP, a
542 request MUST be sent to IANA [RFC2434], along with an explanation of
543 the new AVP value. IANA considerations for AVP values are discussed
544 in Section 11.4.
546 1.2.2. Creating New AVPs
548 When no existing AVP can be reused, a new AVP should be created. The
549 new AVP being defined MUST use one of the data types listed in
550 Section 4.2 or 4.3. If an appropriate derived data type is already
551 defined, it MAY be used instead of the base data type.
553 In the event that a logical grouping of AVPs is necessary, and
554 multiple "groups" are possible in a given command, it is recommended
555 that a Grouped AVP be used (see Section 4.4).
557 In order to create a new standards track AVP, a request MUST be sent
558 to IANA with a reference to the specification that defines the AVP.
559 IANA considerations for AVPs are discussed in Section 11.1.1.
561 1.2.3. Creating New Commands
563 A new command should only be created when no suitable command can be
564 reused from an existing application. A new command MUST result in
565 the defintion of a new application. In order to create a new
566 command, a request MUST be sent to IANA. The IANA considerations for
567 commands are discussed in Section 11.2.1.
569 1.2.4. Creating New Authentication Applications
571 Every Diameter application specification MUST have an IANA assigned
572 Application Identifier (see Section 2.4 and Section 11.3).
574 Should a new Diameter usage scenario find itself unable to fit within
575 an existing application without requiring major changes to the
576 specification, it may be desirable to create a new Diameter
577 application. Major changes to an application include:
579 o Adding new AVPs to the command, which have the "M" bit set.
581 o Requiring a command that has a different number of round trips to
582 satisfy a request (e.g., application foo has a command that
583 requires one round trip, but new application bar has a command
584 that requires two round trips to complete).
586 o Adding support for an authentication method requiring definition
587 of new AVPs for use with the application. Since a new EAP
588 authentication method can be supported within Diameter without
589 requiring new AVPs, addition of EAP methods does not require the
590 creation of a new authentication application.
592 Creation of a new application should be viewed as a last resort. An
593 implementation MAY add arbitrary non-mandatory AVPs to any command
594 defined in an application, including vendor-specific AVPs without
595 needing to define a new application. Please refer to Section 11.1.1
596 for details.
598 In order to justify allocation of a new application identifier,
599 Diameter applications MUST define one Command Code, add new mandatory
600 AVPs to the ABNF or significantly change the state machine or
601 processing rules of an existing application.
603 The expected AVPs MUST be defined in an ABNF [RFC4234] grammar (see
604 Section 3.2). If the Diameter application has accounting
605 requirements, it MUST also specify the AVPs that are to be present in
606 the Diameter Accounting messages (see Section 9.3). However, just
607 because a new authentication application id is required, does not
608 imply that a new accounting application id is required.
610 When possible, a new Diameter application SHOULD reuse existing
611 Diameter AVPs, in order to avoid defining multiple AVPs that carry
612 similar information.
614 1.2.5. Creating New Accounting Applications
616 There are services that only require Diameter accounting. Such
617 services need to define the AVPs carried in the Accounting-Request
618 (ACR)/ Accounting-Answer (ACA) messages, but do not need to define
619 new command codes. An implementation MAY add arbitrary non-mandatory
620 AVPs (AVPs with the "M" bit not set) to any command defined in an
621 application, including vendor-specific AVPs, without needing to
622 define a new accounting application. Please refer to Section 11.1.1
623 for details.
625 Application Identifiers are still required for Diameter capability
626 exchange. Every Diameter accounting application specification MUST
627 have an IANA assigned Application Identifier (see Section 2.4) or a
628 vendor specific Application Identifier.
630 Every Diameter implementation MUST support accounting. Basic
631 accounting support is sufficient to handle any application that uses
632 the ACR/ACA commands defined in this document, as long as no new
633 mandatory AVPs are added. A mandatory AVP is defined as one which
634 has the "M" bit set when sent within an accounting command,
635 regardless of whether it is required or optional within the ABNF for
636 the accounting application.
638 The creation of a new accounting application should be viewed as a
639 last resort and MUST NOT be used unless a new command or additional
640 mechanisms (e.g., application defined state machine) is defined
641 within the application, or new mandatory AVPs are added to the ABNF.
643 Within an accounting command, setting the "M" bit implies that a
644 backend server (e.g., billing server) or the accounting server itself
645 MUST understand the AVP in order to compute a correct bill. If the
646 AVP is not relevant to the billing process, when the AVP is included
647 within an accounting command, it MUST NOT have the "M" bit set, even
648 if the "M" bit is set when the same AVP is used within other Diameter
649 commands (i.e., authentication/authorization commands).
651 A DIAMETER base accounting implementation MUST be configurable to
652 advertise supported accounting applications in order to prevent the
653 accounting server from accepting accounting requests for unbillable
654 services. The combination of the home domain and the accounting
655 application Id can be used in order to route the request to the
656 appropriate accounting server.
658 When possible, a new Diameter accounting application SHOULD attempt
659 to reuse existing AVPs, in order to avoid defining multiple AVPs that
660 carry similar information.
662 If the base accounting is used without any mandatory AVPs, new
663 commands or additional mechanisms (e.g., application defined state
664 machine), then the base protocol defined standard accounting
665 application Id (Section 2.4) MUST be used in ACR/ACA commands.
667 1.2.6. Application Authentication Procedures
669 When possible, applications SHOULD be designed such that new
670 authentication methods MAY be added without requiring changes to the
671 application. This MAY require that new AVP values be assigned to
672 represent the new authentication transform, or any other scheme that
673 produces similar results. When possible, authentication frameworks,
674 such as Extensible Authentication Protocol [RFC3748], SHOULD be used.
676 1.3. Terminology
678 AAA
680 Authentication, Authorization and Accounting.
682 Accounting
684 The act of collecting information on resource usage for the
685 purpose of capacity planning, auditing, billing or cost
686 allocation.
688 Accounting Record
690 An accounting record represents a summary of the resource
691 consumption of a user over the entire session. Accounting servers
692 creating the accounting record may do so by processing interim
693 accounting events or accounting events from several devices
694 serving the same user.
696 Authentication
698 The act of verifying the identity of an entity (subject).
700 Authorization
702 The act of determining whether a requesting entity (subject) will
703 be allowed access to a resource (object).
705 AVP
707 The Diameter protocol consists of a header followed by one or more
708 Attribute-Value-Pairs (AVPs). An AVP includes a header and is
709 used to encapsulate protocol-specific data (e.g., routing
710 information) as well as authentication, authorization or
711 accounting information.
713 Broker
715 A broker is a business term commonly used in AAA infrastructures.
716 A broker is either a relay, proxy or redirect agent, and MAY be
717 operated by roaming consortiums. Depending on the business model,
718 a broker may either choose to deploy relay agents or proxy agents.
720 Diameter Agent
722 A Diameter Agent is a Diameter node that provides either relay,
723 proxy, redirect or translation services.
725 Diameter Client
727 A Diameter Client is a device at the edge of the network that
728 performs access control. An example of a Diameter client is a
729 Network Access Server (NAS) or a Foreign Agent (FA).
731 Diameter Node
733 A Diameter node is a host process that implements the Diameter
734 protocol, and acts either as a Client, Agent or Server.
736 Diameter Peer
738 A Diameter Peer is a Diameter Node to which a given Diameter Node
739 has a direct transport connection.
741 Diameter Server
743 A Diameter Server is one that handles authentication,
744 authorization and accounting requests for a particular realm. By
745 its very nature, a Diameter Server MUST support Diameter
746 applications in addition to the base protocol.
748 Downstream
750 Downstream is used to identify the direction of a particular
751 Diameter message from the home server towards the access device.
753 Home Realm
755 A Home Realm is the administrative domain with which the user
756 maintains an account relationship.
758 Home Server
760 A Diameter Server which serves the Home Realm.
762 Interim accounting
764 An interim accounting message provides a snapshot of usage during
765 a user's session. It is typically implemented in order to provide
766 for partial accounting of a user's session in the case of a device
767 reboot or other network problem prevents the reception of a
768 session summary message or session record.
770 Local Realm
772 A local realm is the administrative domain providing services to a
773 user. An administrative domain MAY act as a local realm for
774 certain users, while being a home realm for others.
776 Multi-session
778 A multi-session represents a logical linking of several sessions.
779 Multi-sessions are tracked by using the Acct-Multi-Session-Id. An
780 example of a multi-session would be a Multi-link PPP bundle. Each
781 leg of the bundle would be a session while the entire bundle would
782 be a multi-session.
784 Network Access Identifier
786 The Network Access Identifier, or NAI [RFC4282], is used in the
787 Diameter protocol to extract a user's identity and realm. The
788 identity is used to identify the user during authentication and/or
789 authorization, while the realm is used for message routing
790 purposes.
792 Proxy Agent or Proxy
794 In addition to forwarding requests and responses, proxies make
795 policy decisions relating to resource usage and provisioning.
796 This is typically accomplished by tracking the state of NAS
797 devices. While proxies typically do not respond to client
798 Requests prior to receiving a Response from the server, they may
799 originate Reject messages in cases where policies are violated.
800 As a result, proxies need to understand the semantics of the
801 messages passing through them, and may not support all Diameter
802 applications.
804 Realm
806 The string in the NAI that immediately follows the '@' character.
807 NAI realm names are required to be unique, and are piggybacked on
808 the administration of the DNS namespace. Diameter makes use of
809 the realm, also loosely referred to as domain, to determine
810 whether messages can be satisfied locally, or whether they must be
811 routed or redirected. In RADIUS, realm names are not necessarily
812 piggybacked on the DNS namespace but may be independent of it.
814 Real-time Accounting
816 Real-time accounting involves the processing of information on
817 resource usage within a defined time window. Time constraints are
818 typically imposed in order to limit financial risk.
820 Relay Agent or Relay
822 Relays forward requests and responses based on routing-related
823 AVPs and routing table entries. Since relays do not make policy
824 decisions, they do not examine or alter non-routing AVPs. As a
825 result, relays never originate messages, do not need to understand
826 the semantics of messages or non-routing AVPs, and are capable of
827 handling any Diameter application or message type. Since relays
828 make decisions based on information in routing AVPs and realm
829 forwarding tables they do not keep state on NAS resource usage or
830 sessions in progress.
832 Redirect Agent
834 Rather than forwarding requests and responses between clients and
835 servers, redirect agents refer clients to servers and allow them
836 to communicate directly. Since redirect agents do not sit in the
837 forwarding path, they do not alter any AVPs transiting between
838 client and server. Redirect agents do not originate messages and
839 are capable of handling any message type, although they may be
840 configured only to redirect messages of certain types, while
841 acting as relay or proxy agents for other types. As with proxy
842 agents, redirect agents do not keep state with respect to sessions
843 or NAS resources.
845 Roaming Relationships
847 Roaming relationships include relationships between companies and
848 ISPs, relationships among peer ISPs within a roaming consortium,
849 and relationships between an ISP and a roaming consortium.
851 Session
853 A session is a related progression of events devoted to a
854 particular activity. Each application SHOULD provide guidelines
855 as to when a session begins and ends. All Diameter packets with
856 the same Session-Identifier are considered to be part of the same
857 session.
859 Session state
861 A stateful agent is one that maintains session state information,
862 by keeping track of all authorized active sessions. Each
863 authorized session is bound to a particular service, and its state
864 is considered active either until it is notified otherwise, or by
865 expiration.
867 Sub-session
869 A sub-session represents a distinct service (e.g., QoS or data
870 characteristics) provided to a given session. These services may
871 happen concurrently (e.g., simultaneous voice and data transfer
872 during the same session) or serially. These changes in sessions
873 are tracked with the Accounting-Sub-Session-Id.
875 Transaction state
877 The Diameter protocol requires that agents maintain transaction
878 state, which is used for failover purposes. Transaction state
879 implies that upon forwarding a request, the Hop-by-Hop identifier
880 is saved; the field is replaced with a locally unique identifier,
881 which is restored to its original value when the corresponding
882 answer is received. The request's state is released upon receipt
883 of the answer. A stateless agent is one that only maintains
884 transaction state.
886 Translation Agent
888 A translation agent is a stateful Diameter node that performs
889 protocol translation between Diameter and another AAA protocol,
890 such as RADIUS.
892 Transport Connection
894 A transport connection is a TCP or SCTP connection existing
895 directly between two Diameter peers, otherwise known as a Peer-
896 to-Peer Connection.
898 Upstream
900 Upstream is used to identify the direction of a particular
901 Diameter message from the access device towards the home server.
903 User
905 The entity requesting or using some resource, in support of which
906 a Diameter client has generated a request.
908 2. Protocol Overview
910 The base Diameter protocol may be used by itself for accounting
911 applications, but for use in authentication and authorization it is
912 always extended for a particular application. Two Diameter
913 applications are defined by companion documents: NASREQ [RFC4005],
914 Mobile IPv4 [RFC4004]. These applications are introduced in this
915 document but specified elsewhere. Additional Diameter applications
916 MAY be defined in the future (see Section 11.3).
918 Diameter Clients MUST support the base protocol, which includes
919 accounting. In addition, they MUST fully support each Diameter
920 application that is needed to implement the client's service, e.g.,
921 NASREQ and/or Mobile IPv4. A Diameter Client that does not support
922 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
923 Client" where X is the application which it supports, and not a
924 "Diameter Client".
926 Diameter Servers MUST support the base protocol, which includes
927 accounting. In addition, they MUST fully support each Diameter
928 application that is needed to implement the intended service, e.g.,
929 NASREQ and/or Mobile IPv4. A Diameter Server that does not support
930 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
931 Server" where X is the application which it supports, and not a
932 "Diameter Server".
934 Diameter Relays and redirect agents are, by definition, protocol
935 transparent, and MUST transparently support the Diameter base
936 protocol, which includes accounting, and all Diameter applications.
938 Diameter proxies MUST support the base protocol, which includes
939 accounting. In addition, they MUST fully support each Diameter
940 application that is needed to implement proxied services, e.g.,
941 NASREQ and/or Mobile IPv4. A Diameter proxy which does not support
942 also both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
943 Proxy" where X is the application which it supports, and not a
944 "Diameter Proxy".
946 The base Diameter protocol concerns itself with capabilities
947 negotiation, how messages are sent and how peers may eventually be
948 abandoned. The base protocol also defines certain rules that apply
949 to all exchanges of messages between Diameter nodes.
951 Communication between Diameter peers begins with one peer sending a
952 message to another Diameter peer. The set of AVPs included in the
953 message is determined by a particular Diameter application. One AVP
954 that is included to reference a user's session is the Session-Id.
956 The initial request for authentication and/or authorization of a user
957 would include the Session-Id. The Session-Id is then used in all
958 subsequent messages to identify the user's session (see Section 8 for
959 more information). The communicating party may accept the request,
960 or reject it by returning an answer message with the Result-Code AVP
961 set to indicate an error occurred. The specific behavior of the
962 Diameter server or client receiving a request depends on the Diameter
963 application employed.
965 Session state (associated with a Session-Id) MUST be freed upon
966 receipt of the Session-Termination-Request, Session-Termination-
967 Answer, expiration of authorized service time in the Session-Timeout
968 AVP, and according to rules established in a particular Diameter
969 application.
971 2.1. Transport
973 Transport profile is defined in [RFC3539].
975 The base Diameter protocol is run on port 3868 of both TCP [TCP] and
976 SCTP [RFC2960] transport protocols.
978 Diameter clients MUST support either TCP or SCTP, while agents and
979 servers MUST support both. Future versions of this specification MAY
980 mandate that clients support SCTP.
982 A Diameter node MAY initiate connections from a source port other
983 than the one that it declares it accepts incoming connections on, and
984 MUST be prepared to receive connections on port 3868. A given
985 Diameter instance of the peer state machine MUST NOT use more than
986 one transport connection to communicate with a given peer, unless
987 multiple instances exist on the peer in which case a separate
988 connection per process is allowed.
990 When no transport connection exists with a peer, an attempt to
991 connect SHOULD be periodically made. This behavior is handled via
992 the Tc timer, whose recommended value is 30 seconds. There are
993 certain exceptions to this rule, such as when a peer has terminated
994 the transport connection stating that it does not wish to
995 communicate.
997 When connecting to a peer and either zero or more transports are
998 specified, SCTP SHOULD be tried first, followed by TCP. See Section
999 5.2 for more information on peer discovery.
1001 Diameter implementations SHOULD be able to interpret ICMP protocol
1002 port unreachable messages as explicit indications that the server is
1003 not reachable, subject to security policy on trusting such messages.
1005 Diameter implementations SHOULD also be able to interpret a reset
1006 from the transport and timed-out connection attempts. If Diameter
1007 receives data up from TCP that cannot be parsed or identified as a
1008 Diameter error made by the peer, the stream is compromised and cannot
1009 be recovered. The transport connection MUST be closed using a RESET
1010 call (send a TCP RST bit) or an SCTP ABORT message (graceful closure
1011 is compromised).
1013 2.1.1. SCTP Guidelines
1015 The following are guidelines for Diameter implementations that
1016 support SCTP:
1018 1. For interoperability: All Diameter nodes MUST be prepared to
1019 receive Diameter messages on any SCTP stream in the association.
1021 2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP
1022 streams available to the association to prevent head-of-the-line
1023 blocking.
1025 2.2. Securing Diameter Messages
1027 Diameter clients, such as Network Access Servers (NASes) and Mobility
1028 Agents MAY support TLS [RFC4346]. Diameter servers MUST support TLS.
1029 IPSec [RFC4301] can be deployed between Diameter peers as an
1030 additional security measure independent of the Diameter protocol.
1031 The Diameter protocol SHOULD NOT be used without any security
1032 mechanism.
1034 2.3. Diameter Application Compliance
1036 Application Identifiers are advertised during the capabilities
1037 exchange phase (see Section 5.3). For a given application,
1038 advertising support of an application implies that the sender
1039 supports all command codes, and the AVPs specified in the associated
1040 ABNFs, described in the specification.
1042 An implementation MAY add arbitrary non-mandatory AVPs to any command
1043 defined in an application, including vendor-specific AVPs. Please
1044 refer to Section 11.1.1 for details.
1046 2.4. Application Identifiers
1048 Each Diameter application MUST have an IANA assigned Application
1049 Identifier (see Section 11.3). The base protocol does not require an
1050 Application Identifier since its support is mandatory. During the
1051 capabilities exchange, Diameter nodes inform their peers of locally
1052 supported applications. Furthermore, all Diameter messages contain
1053 an Application Identifier, which is used in the message forwarding
1054 process.
1056 The following Application Identifier values are defined:
1058 Diameter Common Messages 0
1059 NASREQ 1 [RFC4005]
1060 Mobile-IP 2 [RFC4004]
1061 Diameter Base Accounting 3
1062 Relay 0xffffffff
1064 Relay and redirect agents MUST advertise the Relay Application
1065 Identifier, while all other Diameter nodes MUST advertise locally
1066 supported applications. The receiver of a Capabilities Exchange
1067 message advertising Relay service MUST assume that the sender
1068 supports all current and future applications.
1070 Diameter relay and proxy agents are responsible for finding an
1071 upstream server that supports the application of a particular
1072 message. If none can be found, an error message is returned with the
1073 Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER.
1075 2.5. Connections vs. Sessions
1077 This section attempts to provide the reader with an understanding of
1078 the difference between connection and session, which are terms used
1079 extensively throughout this document.
1081 A connection is a transport level connection between two peers, used
1082 to send and receive Diameter messages. A session is a logical
1083 concept at the application layer, and is shared between an access
1084 device and a server, and is identified via the Session-Id AVP.
1086 +--------+ +-------+ +--------+
1087 | Client | | Relay | | Server |
1088 +--------+ +-------+ +--------+
1089 <----------> <---------->
1090 peer connection A peer connection B
1092 <----------------------------->
1093 User session x
1095 Figure 1: Diameter connections and sessions
1097 In the example provided in Figure 1, peer connection A is established
1098 between the Client and its local Relay. Peer connection B is
1099 established between the Relay and the Server. User session X spans
1100 from the Client via the Relay to the Server. Each "user" of a
1101 service causes an auth request to be sent, with a unique session
1102 identifier. Once accepted by the server, both the client and the
1103 server are aware of the session.
1105 It is important to note that there is no relationship between a
1106 connection and a session, and that Diameter messages for multiple
1107 sessions are all multiplexed through a single connection. Also note
1108 that Diameter messages pertaining to the session, both application
1109 specific and those that are defined in this document such as ASR/ASA,
1110 RAR/RAA and STR/STA MUST carry the application identifier of the
1111 application. Diameter messages pertaining to peer connection
1112 establishment and maintenance such as CER/CEA, DWR/DWA and DPR/DPA
1113 MUST carry an application id of zero (0).
1115 2.6. Peer Table
1117 The Diameter Peer Table is used in message forwarding, and referenced
1118 by the Routing Table. A Peer Table entry contains the following
1119 fields:
1121 Host identity
1123 Following the conventions described for the DiameterIdentity
1124 derived AVP data format in Section 4.4. This field contains the
1125 contents of the Origin-Host (Section 6.3) AVP found in the CER or
1126 CEA message.
1128 StatusT
1130 This is the state of the peer entry, and MUST match one of the
1131 values listed in Section 5.6.
1133 Static or Dynamic
1135 Specifies whether a peer entry was statically configured, or
1136 dynamically discovered.
1138 Expiration time
1140 Specifies the time at which dynamically discovered peer table
1141 entries are to be either refreshed, or expired.
1143 TLS Enabled
1145 Specifies whether TLS is to be used when communicating with the
1146 peer.
1148 Additional security information, when needed (e.g., keys,
1149 certificates)
1151 2.7. Routing Table
1153 All Realm-Based routing lookups are performed against what is
1154 commonly known as the Routing Table (see Section 12). A Routing
1155 Table Entry contains the following fields:
1157 Realm Name
1159 This is the field that is typically used as a primary key in the
1160 routing table lookups. Note that some implementations perform
1161 their lookups based on longest-match-from-the-right on the realm
1162 rather than requiring an exact match.
1164 Application Identifier
1166 An application is identified by an application id. A route entry
1167 can have a different destination based on the application
1168 identification in the message header. This field MUST be used as
1169 a secondary key field in routing table lookups.
1171 Local Action
1173 The Local Action field is used to identify how a message should be
1174 treated. The following actions are supported:
1176 1. LOCAL - Diameter messages that resolve to a route entry with
1177 the Local Action set to Local can be satisfied locally, and do
1178 not need to be routed to another server.
1180 2. RELAY - All Diameter messages that fall within this category
1181 MUST be routed to a next hop server, without modifying any
1182 non-routing AVPs. See Section 6.1.9 for relaying guidelines
1184 3. PROXY - All Diameter messages that fall within this category
1185 MUST be routed to a next hop server. The local server MAY
1186 apply its local policies to the message by including new AVPs
1187 to the message prior to routing. See Section 6.1.9 for
1188 proxying guidelines.
1190 4. REDIRECT - Diameter messages that fall within this category
1191 MUST have the identity of the home Diameter server(s)
1192 appended, and returned to the sender of the message. See
1193 Section 6.1.9 for redirect guidelines.
1195 Server Identifier
1197 One or more servers the message is to be routed to. These servers
1198 MUST also be present in the Peer table. When the Local Action is
1199 set to RELAY or PROXY, this field contains the identity of the
1200 server(s) the message must be routed to. When the Local Action
1201 field is set to REDIRECT, this field contains the identity of one
1202 or more servers the message should be redirected to.
1204 Static or Dynamic
1206 Specifies whether a route entry was statically configured, or
1207 dynamically discovered.
1209 Expiration time
1211 Specifies the time which a dynamically discovered route table
1212 entry expires.
1214 It is important to note that Diameter agents MUST support at least
1215 one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation.
1216 Agents do not need to support all modes of operation in order to
1217 conform with the protocol specification, but MUST follow the protocol
1218 compliance guidelines in Section 2. Relay agents MUST NOT reorder
1219 AVPs, and proxies MUST NOT reorder AVPs.
1221 The routing table MAY include a default entry that MUST be used for
1222 any requests not matching any of the other entries. The routing
1223 table MAY consist of only such an entry.
1225 When a request is routed, the target server MUST have advertised the
1226 Application Identifier (see Section 2.4) for the given message, or
1227 have advertised itself as a relay or proxy agent. Otherwise, an
1228 error is returned with the Result-Code AVP set to
1229 DIAMETER_UNABLE_TO_DELIVER.
1231 2.8. Role of Diameter Agents
1233 In addition to client and servers, the Diameter protocol introduces
1234 relay, proxy, redirect, and translation agents, each of which is
1235 defined in Section 1.3. These Diameter agents are useful for several
1236 reasons:
1238 o They can distribute administration of systems to a configurable
1239 grouping, including the maintenance of security associations.
1241 o They can be used for concentration of requests from an number of
1242 co-located or distributed NAS equipment sets to a set of like user
1243 groups.
1245 o They can do value-added processing to the requests or responses.
1247 o They can be used for load balancing.
1249 o A complex network will have multiple authentication sources, they
1250 can sort requests and forward towards the correct target.
1252 The Diameter protocol requires that agents maintain transaction
1253 state, which is used for failover purposes. Transaction state
1254 implies that upon forwarding a request, its Hop-by-Hop identifier is
1255 saved; the field is replaced with a locally unique identifier, which
1256 is restored to its original value when the corresponding answer is
1257 received. The request's state is released upon receipt of the
1258 answer. A stateless agent is one that only maintains transaction
1259 state.
1261 The Proxy-Info AVP allows stateless agents to add local state to a
1262 Diameter request, with the guarantee that the same state will be
1263 present in the answer. However, the protocol's failover procedures
1264 require that agents maintain a copy of pending requests.
1266 A stateful agent is one that maintains session state information; by
1267 keeping track of all authorized active sessions. Each authorized
1268 session is bound to a particular service, and its state is considered
1269 active either until it is notified otherwise, or by expiration. Each
1270 authorized session has an expiration, which is communicated by
1271 Diameter servers via the Session-Timeout AVP.
1273 Maintaining session state MAY be useful in certain applications, such
1274 as:
1276 o Protocol translation (e.g., RADIUS <-> Diameter)
1278 o Limiting resources authorized to a particular user
1280 o Per user or transaction auditing
1282 A Diameter agent MAY act in a stateful manner for some requests and
1283 be stateless for others. A Diameter implementation MAY act as one
1284 type of agent for some requests, and as another type of agent for
1285 others.
1287 2.8.1. Relay Agents
1289 Relay Agents are Diameter agents that accept requests and route
1290 messages to other Diameter nodes based on information found in the
1291 messages (e.g., Destination-Realm). This routing decision is
1292 performed using a list of supported realms, and known peers. This is
1293 known as the Routing Table, as is defined further in Section 2.7.
1295 Relays MAY be used to aggregate requests from multiple Network Access
1296 Servers (NASes) within a common geographical area (POP). The use of
1297 Relays is advantageous since it eliminates the need for NASes to be
1298 configured with the necessary security information they would
1299 otherwise require to communicate with Diameter servers in other
1300 realms. Likewise, this reduces the configuration load on Diameter
1301 servers that would otherwise be necessary when NASes are added,
1302 changed or deleted.
1304 Relays modify Diameter messages by inserting and removing routing
1305 information, but do not modify any other portion of a message.
1306 Relays SHOULD NOT maintain session state but MUST maintain
1307 transaction state.
1309 +------+ ---------> +------+ ---------> +------+
1310 | | 1. Request | | 2. Request | |
1311 | NAS | | DRL | | HMS |
1312 | | 4. Answer | | 3. Answer | |
1313 +------+ <--------- +------+ <--------- +------+
1314 example.net example.net example.com
1316 Figure 2: Relaying of Diameter messages
1318 The example provided in Figure 2 depicts a request issued from NAS,
1319 which is an access device, for the user bob@example.com. Prior to
1320 issuing the request, NAS performs a Diameter route lookup, using
1321 "example.com" as the key, and determines that the message is to be
1322 relayed to DRL, which is a Diameter Relay. DRL performs the same
1323 route lookup as NAS, and relays the message to HMS, which is
1324 example.com's Home Diameter Server. HMS identifies that the request
1325 can be locally supported (via the realm), processes the
1326 authentication and/or authorization request, and replies with an
1327 answer, which is routed back to NAS using saved transaction state.
1329 Since Relays do not perform any application level processing, they
1330 provide relaying services for all Diameter applications, and
1331 therefore MUST advertise the Relay Application Identifier.
1333 2.8.2. Proxy Agents
1335 Similarly to relays, proxy agents route Diameter messages using the
1336 Diameter Routing Table. However, they differ since they modify
1337 messages to implement policy enforcement. This requires that proxies
1338 maintain the state of their downstream peers (e.g., access devices)
1339 to enforce resource usage, provide admission control, and
1340 provisioning.
1342 Proxies MAY be used in call control centers or access ISPs that
1343 provide outsourced connections, they can monitor the number and types
1344 of ports in use, and make allocation and admission decisions
1345 according to their configuration.
1347 Proxies that wish to limit resources MUST maintain session state.
1348 All proxies MUST maintain transaction state.
1350 Since enforcing policies requires an understanding of the service
1351 being provided, Proxies MUST only advertise the Diameter applications
1352 they support.
1354 2.8.3. Redirect Agents
1356 Redirect agents are useful in scenarios where the Diameter routing
1357 configuration needs to be centralized. An example is a redirect
1358 agent that provides services to all members of a consortium, but does
1359 not wish to be burdened with relaying all messages between realms.
1360 This scenario is advantageous since it does not require that the
1361 consortium provide routing updates to its members when changes are
1362 made to a member's infrastructure.
1364 Since redirect agents do not relay messages, and only return an
1365 answer with the information necessary for Diameter agents to
1366 communicate directly, they do not modify messages. Since redirect
1367 agents do not receive answer messages, they cannot maintain session
1368 state. Further, since redirect agents never relay requests, they are
1369 not required to maintain transaction state.
1371 The example provided in Figure 3 depicts a request issued from the
1372 access device, NAS, for the user bob@example.com. The message is
1373 forwarded by the NAS to its relay, DRL, which does not have a routing
1374 entry in its Diameter Routing Table for example.com. DRL has a
1375 default route configured to DRD, which is a redirect agent that
1376 returns a redirect notification to DRL, as well as HMS' contact
1377 information. Upon receipt of the redirect notification, DRL
1378 establishes a transport connection with HMS, if one doesn't already
1379 exist, and forwards the request to it.
1381 +------+
1382 | |
1383 | DRD |
1384 | |
1385 +------+
1386 ^ |
1387 2. Request | | 3. Redirection
1388 | | Notification
1389 | v
1390 +------+ ---------> +------+ ---------> +------+
1391 | | 1. Request | | 4. Request | |
1392 | NAS | | DRL | | HMS |
1393 | | 6. Answer | | 5. Answer | |
1394 +------+ <--------- +------+ <--------- +------+
1395 example.net example.net example.com
1397 Figure 3: Redirecting a Diameter Message
1399 Since redirect agents do not perform any application level
1400 processing, they provide relaying services for all Diameter
1401 applications, and therefore MUST advertise the Relay Application
1402 Identifier.
1404 2.8.4. Translation Agents
1406 A translation agent is a device that provides translation between two
1407 protocols (e.g., RADIUS<->Diameter, TACACS+<->Diameter). Translation
1408 agents are likely to be used as aggregation servers to communicate
1409 with a Diameter infrastructure, while allowing for the embedded
1410 systems to be migrated at a slower pace.
1412 Given that the Diameter protocol introduces the concept of long-lived
1413 authorized sessions, translation agents MUST be session stateful and
1414 MUST maintain transaction state.
1416 Translation of messages can only occur if the agent recognizes the
1417 application of a particular request, and therefore translation agents
1418 MUST only advertise their locally supported applications.
1420 +------+ ---------> +------+ ---------> +------+
1421 | | RADIUS Request | | Diameter Request | |
1422 | NAS | | TLA | | HMS |
1423 | | RADIUS Answer | | Diameter Answer | |
1424 +------+ <--------- +------+ <--------- +------+
1425 example.net example.net example.com
1426 Figure 4: Translation of RADIUS to Diameter
1428 2.9. Diameter Path Authorization
1430 As noted in Section 2.2, Diameter provides transmission level
1431 security for each connection using TLS. Therefore, each connection
1432 can be authenticated, replay and integrity protected.
1434 In addition to authenticating each connection, each connection as
1435 well as the entire session MUST also be authorized. Before
1436 initiating a connection, a Diameter Peer MUST check that its peers
1437 are authorized to act in their roles. For example, a Diameter peer
1438 may be authentic, but that does not mean that it is authorized to act
1439 as a Diameter Server advertising a set of Diameter applications.
1441 Prior to bringing up a connection, authorization checks are performed
1442 at each connection along the path. Diameter capabilities negotiation
1443 (CER/CEA) also MUST be carried out, in order to determine what
1444 Diameter applications are supported by each peer. Diameter sessions
1445 MUST be routed only through authorized nodes that have advertised
1446 support for the Diameter application required by the session.
1448 As noted in Section 6.1.9, a relay or proxy agent MUST append a
1449 Route-Record AVP to all requests forwarded. The AVP contains the
1450 identity of the peer the request was received from.
1452 The home Diameter server, prior to authorizing a session, MUST check
1453 the Route-Record AVPs to make sure that the route traversed by the
1454 request is acceptable. For example, administrators within the home
1455 realm may not wish to honor requests that have been routed through an
1456 untrusted realm. By authorizing a request, the home Diameter server
1457 is implicitly indicating its willingness to engage in the business
1458 transaction as specified by the contractual relationship between the
1459 server and the previous hop. A DIAMETER_AUTHORIZATION_REJECTED error
1460 message (see Section 7.1.5) is sent if the route traversed by the
1461 request is unacceptable.
1463 A home realm may also wish to check that each accounting request
1464 message corresponds to a Diameter response authorizing the session.
1465 Accounting requests without corresponding authorization responses
1466 SHOULD be subjected to further scrutiny, as should accounting
1467 requests indicating a difference between the requested and provided
1468 service.
1470 Similarly, the local Diameter agent, on receiving a Diameter response
1471 authorizing a session, MUST check the Route-Record AVPs to make sure
1472 that the route traversed by the response is acceptable. At each
1473 step, forwarding of an authorization response is considered evidence
1474 of a willingness to take on financial risk relative to the session.
1475 A local realm may wish to limit this exposure, for example, by
1476 establishing credit limits for intermediate realms and refusing to
1477 accept responses which would violate those limits. By issuing an
1478 accounting request corresponding to the authorization response, the
1479 local realm implicitly indicates its agreement to provide the service
1480 indicated in the authorization response. If the service cannot be
1481 provided by the local realm, then a DIAMETER_UNABLE_TO_COMPLY error
1482 message MUST be sent within the accounting request; a Diameter client
1483 receiving an authorization response for a service that it cannot
1484 perform MUST NOT substitute an alternate service, and then send
1485 accounting requests for the alternate service instead.
1487 3. Diameter Header
1489 A summary of the Diameter header format is shown below. The fields
1490 are transmitted in network byte order.
1492 0 1 2 3
1493 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
1494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1495 | Version | Message Length |
1496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1497 | command flags | Command-Code |
1498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1499 | Application-ID |
1500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1501 | Hop-by-Hop Identifier |
1502 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1503 | End-to-End Identifier |
1504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1505 | AVPs ...
1506 +-+-+-+-+-+-+-+-+-+-+-+-+-
1508 Version
1510 This Version field MUST be set to 1 to indicate Diameter Version
1511 1.
1513 Message Length
1515 The Message Length field is three octets and indicates the length
1516 of the Diameter message including the header fields.
1518 Command Flags
1520 The Command Flags field is eight bits. The following bits are
1521 assigned:
1523 0 1 2 3 4 5 6 7
1524 +-+-+-+-+-+-+-+-+
1525 |R P E T r r r r|
1526 +-+-+-+-+-+-+-+-+
1528 R(equest)
1530 If set, the message is a request. If cleared, the message is
1531 an answer.
1533 P(roxiable)
1535 If set, the message MAY be proxied, relayed or redirected. If
1536 cleared, the message MUST be locally processed.
1538 E(rror)
1540 If set, the message contains a protocol error, and the message
1541 will not conform to the ABNF described for this command.
1542 Messages with the 'E' bit set are commonly referred to as error
1543 messages. This bit MUST NOT be set in request messages. See
1544 Section 7.2.
1546 T(Potentially re-transmitted message)
1548 This flag is set after a link failover procedure, to aid the
1549 removal of duplicate requests. It is set when resending
1550 requests not yet acknowledged, as an indication of a possible
1551 duplicate due to a link failure. This bit MUST be cleared when
1552 sending a request for the first time, otherwise the sender MUST
1553 set this flag. Diameter agents only need to be concerned about
1554 the number of requests they send based on a single received
1555 request; retransmissions by other entities need not be tracked.
1556 Diameter agents that receive a request with the T flag set,
1557 MUST keep the T flag set in the forwarded request. This flag
1558 MUST NOT be set if an error answer message (e.g., a protocol
1559 error) has been received for the earlier message. It can be
1560 set only in cases where no answer has been received from the
1561 server for a request and the request is sent again. This flag
1562 MUST NOT be set in answer messages.
1564 r(eserved)
1566 These flag bits are reserved for future use, and MUST be set to
1567 zero, and ignored by the receiver.
1569 Command-Code
1571 The Command-Code field is three octets, and is used in order to
1572 communicate the command associated with the message. The 24-bit
1573 address space is managed by IANA (see Section 11.2.1).
1575 Command-Code values 16,777,214 and 16,777,215 (hexadecimal values
1576 FFFFFE -FFFFFF) are reserved for experimental use (See Section
1577 11.3).
1579 Application-ID
1581 Application-ID is four octets and is used to identify to which
1582 application the message is applicable for. The application can be
1583 an authentication application, an accounting application or a
1584 vendor specific application. See Section 11.3 for the possible
1585 values that the application-id may use.
1587 The application-id in the header MUST be the same as what is
1588 contained in any relevant application-id AVPs contained in the
1589 message.
1591 Hop-by-Hop Identifier
1593 The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in
1594 network byte order) and aids in matching requests and replies.
1595 The sender MUST ensure that the Hop-by-Hop identifier in a request
1596 is unique on a given connection at any given time, and MAY attempt
1597 to ensure that the number is unique across reboots. The sender of
1598 an Answer message MUST ensure that the Hop-by-Hop Identifier field
1599 contains the same value that was found in the corresponding
1600 request. The Hop-by-Hop identifier is normally a monotonically
1601 increasing number, whose start value was randomly generated. An
1602 answer message that is received with an unknown Hop-by-Hop
1603 Identifier MUST be discarded.
1605 End-to-End Identifier
1607 The End-to-End Identifier is an unsigned 32-bit integer field (in
1608 network byte order) and is used to detect duplicate messages.
1609 Upon reboot implementations MAY set the high order 12 bits to
1610 contain the low order 12 bits of current time, and the low order
1611 20 bits to a random value. Senders of request messages MUST
1612 insert a unique identifier on each message. The identifier MUST
1613 remain locally unique for a period of at least 4 minutes, even
1614 across reboots. The originator of an Answer message MUST ensure
1615 that the End-to-End Identifier field contains the same value that
1616 was found in the corresponding request. The End-to-End Identifier
1617 MUST NOT be modified by Diameter agents of any kind. The
1618 combination of the Origin-Host (see Section 6.3) and this field is
1619 used to detect duplicates. Duplicate requests SHOULD cause the
1620 same answer to be transmitted (modulo the hop-by-hop Identifier
1621 field and any routing AVPs that may be present), and MUST NOT
1622 affect any state that was set when the original request was
1623 processed. Duplicate answer messages that are to be locally
1624 consumed (see Section 6.2) SHOULD be silently discarded.
1626 AVPs
1628 AVPs are a method of encapsulating information relevant to the
1629 Diameter message. See Section 4 for more information on AVPs.
1631 3.1. Command Codes
1633 Each command Request/Answer pair is assigned a command code, and the
1634 sub-type (i.e., request or answer) is identified via the 'R' bit in
1635 the Command Flags field of the Diameter header.
1637 Every Diameter message MUST contain a command code in its header's
1638 Command-Code field, which is used to determine the action that is to
1639 be taken for a particular message. The following Command Codes are
1640 defined in the Diameter base protocol:
1642 Command-Name Abbrev. Code Reference
1643 --------------------------------------------------------
1644 Abort-Session-Request ASR 274 8.5.1
1645 Abort-Session-Answer ASA 274 8.5.2
1646 Accounting-Request ACR 271 9.7.1
1647 Accounting-Answer ACA 271 9.7.2
1648 Capabilities-Exchange- CER 257 5.3.1
1649 Request
1650 Capabilities-Exchange- CEA 257 5.3.2
1651 Answer
1652 Device-Watchdog-Request DWR 280 5.5.1
1653 Device-Watchdog-Answer DWA 280 5.5.2
1654 Disconnect-Peer-Request DPR 282 5.4.1
1655 Disconnect-Peer-Answer DPA 282 5.4.2
1656 Re-Auth-Request RAR 258 8.3.1
1657 Re-Auth-Answer RAA 258 8.3.2
1658 Session-Termination- STR 275 8.4.1
1659 Request
1660 Session-Termination- STA 275 8.4.2
1661 Answer
1663 3.2. Command Code ABNF specification
1665 Every Command Code defined MUST include a corresponding ABNF
1666 specification, which is used to define the AVPs that MUST or MAY be
1667 present. The following format is used in the definition:
1669 command-def = command-name "::=" diameter-message
1671 command-name = diameter-name
1672 diameter-name = ALPHA *(ALPHA / DIGIT / "-")
1674 diameter-message = header [ *fixed] [ *required] [ *optional]
1676 header = "<" "Diameter Header:" command-id
1677 [r-bit] [p-bit] [e-bit] [application-id] ">"
1679 application-id = 1*DIGIT
1681 command-id = 1*DIGIT
1682 ; The Command Code assigned to the command
1684 r-bit = ", REQ"
1685 ; If present, the 'R' bit in the Command
1686 ; Flags is set, indicating that the message
1687 ; is a request, as opposed to an answer.
1689 p-bit = ", PXY"
1690 ; If present, the 'P' bit in the Command
1691 ; Flags is set, indicating that the message
1692 ; is proxiable.
1694 e-bit = ", ERR"
1695 ; If present, the 'E' bit in the Command
1696 ; Flags is set, indicating that the answer
1697 ; message contains a Result-Code AVP in
1698 ; the "protocol error" class.
1700 fixed = [qual] "<" avp-spec ">"
1701 ; Defines the fixed position of an AVP
1703 required = [qual] "{" avp-spec "}"
1704 ; The AVP MUST be present and can appear
1705 ; anywhere in the message.
1707 optional = [qual] "[" avp-name "]"
1708 ; The avp-name in the 'optional' rule cannot
1709 ; evaluate to any AVP Name which is included
1710 ; in a fixed or required rule. The AVP can
1711 ; appear anywhere in the message.
1713 qual = [min] "*" [max]
1714 ; See ABNF conventions, RFC 4234 Section 6.6.
1715 ; The absence of any qualifiers depends on
1716 ; whether it precedes a fixed, required, or
1717 ; optional rule. If a fixed or required rule has
1718 ; no qualifier, then exactly one such AVP MUST
1719 ; be present. If an optional rule has no
1720 ; qualifier, then 0 or 1 such AVP may be
1721 ; present.
1722 ;
1723 ; NOTE: "[" and "]" have a different meaning
1724 ; than in ABNF (see the optional rule, above).
1725 ; These braces cannot be used to express
1726 ; optional fixed rules (such as an optional
1727 ; ICV at the end). To do this, the convention
1728 ; is '0*1fixed'.
1730 min = 1*DIGIT
1731 ; The minimum number of times the element may
1732 ; be present. The default value is zero.
1734 max = 1*DIGIT
1735 ; The maximum number of times the element may
1736 ; be present. The default value is infinity. A
1737 ; value of zero implies the AVP MUST NOT be
1738 ; present.
1740 avp-spec = diameter-name
1741 ; The avp-spec has to be an AVP Name, defined
1742 ; in the base or extended Diameter
1743 ; specifications.
1745 avp-name = avp-spec / "AVP"
1746 ; The string "AVP" stands for *any* arbitrary AVP
1747 ; Name, not otherwise listed in that command code
1748 ; definition.
1750 The following is a definition of a fictitious command code:
1752 Example-Request ::= < Diameter Header: 9999999, REQ, PXY >
1753 { User-Name }
1754 * { Origin-Host }
1755 * [ AVP
1757 3.3. Diameter Command Naming Conventions
1759 Diameter command names typically includes one or more English words
1760 followed by the verb Request or Answer. Each English word is
1761 delimited by a hyphen. A three-letter acronym for both the request
1762 and answer is also normally provided.
1764 An example is a message set used to terminate a session. The command
1765 name is Session-Terminate-Request and Session-Terminate-Answer, while
1766 the acronyms are STR and STA, respectively.
1768 Both the request and the answer for a given command share the same
1769 command code. The request is identified by the R(equest) bit in the
1770 Diameter header set to one (1), to ask that a particular action be
1771 performed, such as authorizing a user or terminating a session. Once
1772 the receiver has completed the request it issues the corresponding
1773 answer, which includes a result code that communicates one of the
1774 following:
1776 o The request was successful
1778 o The request failed
1780 o An additional request must be sent to provide information the peer
1781 requires prior to returning a successful or failed answer.
1783 o The receiver could not process the request, but provides
1784 information about a Diameter peer that is able to satisfy the
1785 request, known as redirect.
1787 Additional information, encoded within AVPs, MAY also be included in
1788 answer messages.
1790 4. Diameter AVPs
1792 Diameter AVPs carry specific authentication, accounting,
1793 authorization and routing information as well as configuration
1794 details for the request and reply.
1796 Some AVPs MAY be listed more than once. The effect of such an AVP is
1797 specific, and is specified in each case by the AVP description.
1799 Each AVP of type OctetString MUST be padded to align on a 32-bit
1800 boundary, while other AVP types align naturally. A number of zero-
1801 valued bytes are added to the end of the AVP Data field till a word
1802 boundary is reached. The length of the padding is not reflected in
1803 the AVP Length field.
1805 4.1. AVP Header
1807 The fields in the AVP header MUST be sent in network byte order. The
1808 format of the header is:
1810 0 1 2 3
1811 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
1812 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1813 | AVP Code |
1814 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1815 |V M r r r r r r| AVP Length |
1816 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1817 | Vendor-ID (opt) |
1818 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1819 | Data ...
1820 +-+-+-+-+-+-+-+-+
1822 AVP Code
1824 The AVP Code, combined with the Vendor-Id field, identifies the
1825 attribute uniquely. AVP numbers 1 through 255 are reserved for
1826 backward compatibility with RADIUS, without setting the Vendor-Id
1827 field. AVP numbers 256 and above are used for Diameter, which are
1828 allocated by IANA (see Section 11.1).
1830 AVP Flags
1832 The AVP Flags field informs the receiver how each attribute must
1833 be handled. The 'r' (reserved) bits are unused and SHOULD be set
1834 to 0. Note that subsequent Diameter applications MAY define
1835 additional bits within the AVP Header, and an unrecognized bit
1836 SHOULD be considered an error.
1838 The 'M' Bit, known as the Mandatory bit, indicates whether support
1839 of the AVP is required. If an AVP with the 'M' bit set is
1840 received by a Diameter client, server, proxy, or translation agent
1841 and either the AVP or its value is unrecognized, the message MUST
1842 be rejected. Diameter Relay and redirect agents MUST NOT reject
1843 messages with unrecognized AVPs.
1845 The 'M' bit MUST be set according to the rules defined for the AVP
1846 containing it. In order to preserve interoperability, a Diameter
1847 implementation MUST be able to exclude from a Diameter message any
1848 Mandatory AVP which is neither defined in the base Diameter
1849 protocol nor in any of the Diameter Application specifications
1850 governing the message in which it appears. It MAY do this in one
1851 of the following ways:
1853 1. If a message is rejected because it contains a Mandatory AVP
1854 which is neither defined in the base Diameter standard nor in
1855 any of the Diameter Application specifications governing the
1856 message in which it appears, the implementation may resend the
1857 message without the AVP, possibly inserting additional
1858 standard AVPs instead.
1860 2. A configuration option may be provided on a system wide, per
1861 peer, or per realm basis that would allow/prevent particular
1862 Mandatory AVPs to be sent. Thus an administrator could change
1863 the configuration to avoid interoperability problems.
1865 Diameter implementations are required to support all Mandatory
1866 AVPs which are allowed by the message's formal syntax and defined
1867 either in the base Diameter standard or in one of the Diameter
1868 Application specifications governing the message.
1870 AVPs with the 'M' bit cleared are informational only and a
1871 receiver that receives a message with such an AVP that is not
1872 supported, or whose value is not supported, MAY simply ignore the
1873 AVP.
1875 The 'V' bit, known as the Vendor-Specific bit, indicates whether
1876 the optional Vendor-ID field is present in the AVP header. When
1877 set the AVP Code belongs to the specific vendor code address
1878 space.
1880 Unless otherwise noted, AVPs will have the following default AVP
1881 Flags field settings:
1883 The 'M' bit MUST be set. The 'V' bit MUST NOT be set.
1885 AVP Length
1887 The AVP Length field is three octets, and indicates the number of
1888 octets in this AVP including the AVP Code, AVP Length, AVP Flags,
1889 Vendor-ID field (if present) and the AVP data. If a message is
1890 received with an invalid attribute length, the message SHOULD be
1891 rejected.
1893 4.1.1. Optional Header Elements
1895 The AVP Header contains one optional field. This field is only
1896 present if the respective bit-flag is enabled.
1898 Vendor-ID
1900 The Vendor-ID field is present if the 'V' bit is set in the AVP
1901 Flags field. The optional four-octet Vendor-ID field contains the
1902 IANA assigned "SMI Network Management Private Enterprise Codes"
1903 [RFC3232] value, encoded in network byte order. Any vendor
1904 wishing to implement a vendor-specific Diameter AVP MUST use their
1905 own Vendor-ID along with their privately managed AVP address
1906 space, guaranteeing that they will not collide with any other
1907 vendor's vendor-specific AVP(s), nor with future IETF
1908 applications.
1910 A vendor ID value of zero (0) corresponds to the IETF adopted AVP
1911 values, as managed by the IANA. Since the absence of the vendor
1912 ID field implies that the AVP in question is not vendor specific,
1913 implementations MUST NOT use the zero (0) vendor ID.
1915 4.2. Basic AVP Data Formats
1917 The Data field is zero or more octets and contains information
1918 specific to the Attribute. The format and length of the Data field
1919 is determined by the AVP Code and AVP Length fields. The format of
1920 the Data field MUST be one of the following base data types or a data
1921 type derived from the base data types. In the event that a new Basic
1922 AVP Data Format is needed, a new version of this RFC must be created.
1924 OctetString
1926 The data contains arbitrary data of variable length. Unless
1927 otherwise noted, the AVP Length field MUST be set to at least 8
1928 (12 if the 'V' bit is enabled). AVP Values of this type that are
1929 not a multiple of four-octets in length is followed by the
1930 necessary padding so that the next AVP (if any) will start on a
1931 32-bit boundary.
1933 Integer32
1935 32 bit signed value, in network byte order. The AVP Length field
1936 MUST be set to 12 (16 if the 'V' bit is enabled).
1938 Integer64
1940 64 bit signed value, in network byte order. The AVP Length field
1941 MUST be set to 16 (20 if the 'V' bit is enabled).
1943 Unsigned32
1945 32 bit unsigned value, in network byte order. The AVP Length
1946 field MUST be set to 12 (16 if the 'V' bit is enabled).
1948 Unsigned64
1950 64 bit unsigned value, in network byte order. The AVP Length
1951 field MUST be set to 16 (20 if the 'V' bit is enabled).
1953 Float32
1955 This represents floating point values of single precision as
1956 described by [FLOATPOINT]. The 32-bit value is transmitted in
1957 network byte order. The AVP Length field MUST be set to 12 (16 if
1958 the 'V' bit is enabled).
1960 Float64
1962 This represents floating point values of double precision as
1963 described by [FLOATPOINT]. The 64-bit value is transmitted in
1964 network byte order. The AVP Length field MUST be set to 16 (20 if
1965 the 'V' bit is enabled).
1967 Grouped
1969 The Data field is specified as a sequence of AVPs. Each of these
1970 AVPs follows - in the order in which they are specified -
1971 including their headers and padding. The AVP Length field is set
1972 to 8 (12 if the 'V' bit is enabled) plus the total length of all
1973 included AVPs, including their headers and padding. Thus the AVP
1974 length field of an AVP of type Grouped is always a multiple of 4.
1976 4.3. Derived AVP Data Formats
1978 In addition to using the Basic AVP Data Formats, applications may
1979 define data formats derived from the Basic AVP Data Formats. An
1980 application that defines new AVP Derived Data Formats MUST include
1981 them in a section entitled "AVP Derived Data Formats", using the same
1982 format as the definitions below. Each new definition must be either
1983 defined or listed with a reference to the RFC that defines the
1984 format.
1986 The below AVP Derived Data Formats are commonly used by applications.
1988 Address
1990 The Address format is derived from the OctetString AVP Base
1991 Format. It is a discriminated union, representing, for example a
1992 32-bit (IPv4) [IPV4] or 128-bit (IPv6) [RFC4291] address, most
1993 significant octet first. The first two octets of the Address AVP
1994 represents the AddressType, which contains an Address Family
1995 defined in [IANAADFAM]. The AddressType is used to discriminate
1996 the content and format of the remaining octets.
1998 Time
2000 The Time format is derived from the OctetString AVP Base Format.
2001 The string MUST contain four octets, in the same format as the
2002 first four bytes are in the NTP timestamp format. The NTP
2003 Timestamp format is defined in chapter 3 of [RFC4330].
2005 This represents the number of seconds since 0h on 1 January 1900
2006 with respect to the Coordinated Universal Time (UTC).
2008 On 6h 28m 16s UTC, 7 February 2036 the time value will overflow.
2009 SNTP [RFC4330] describes a procedure to extend the time to 2104.
2010 This procedure MUST be supported by all DIAMETER nodes.
2012 UTF8String
2014 The UTF8String format is derived from the OctetString AVP Base
2015 Format. This is a human readable string represented using the
2016 ISO/IEC IS 10646-1 character set, encoded as an OctetString using
2017 the UTF-8 [RFC3629] transformation format described in RFC 3629.
2019 Since additional code points are added by amendments to the 10646
2020 standard from time to time, implementations MUST be prepared to
2021 encounter any code point from 0x00000001 to 0x7fffffff. Byte
2022 sequences that do not correspond to the valid encoding of a code
2023 point into UTF-8 charset or are outside this range are prohibited.
2025 The use of control codes SHOULD be avoided. When it is necessary
2026 to represent a new line, the control code sequence CR LF SHOULD be
2027 used.
2029 The use of leading or trailing white space SHOULD be avoided.
2031 For code points not directly supported by user interface hardware
2032 or software, an alternative means of entry and display, such as
2033 hexadecimal, MAY be provided.
2035 For information encoded in 7-bit US-ASCII, the UTF-8 charset is
2036 identical to the US-ASCII charset.
2038 UTF-8 may require multiple bytes to represent a single character /
2039 code point; thus the length of an UTF8String in octets may be
2040 different from the number of characters encoded.
2042 Note that the AVP Length field of an UTF8String is measured in
2043 octets, not characters.
2045 DiameterIdentity
2047 The DiameterIdentity format is derived from the OctetString AVP
2048 Base Format.
2050 DiameterIdentity = FQDN
2052 DiameterIdentity value is used to uniquely identify a Diameter
2053 node for purposes of duplicate connection and routing loop
2054 detection.
2056 The contents of the string MUST be the FQDN of the Diameter node.
2057 If multiple Diameter nodes run on the same host, each Diameter
2058 node MUST be assigned a unique DiameterIdentity. If a Diameter
2059 node can be identified by several FQDNs, a single FQDN should be
2060 picked at startup, and used as the only DiameterIdentity for that
2061 node, whatever the connection it is sent on.
2063 DiameterURI
2065 The DiameterURI MUST follow the Uniform Resource Identifiers (URI)
2066 syntax [RFC3986] rules specified below:
2068 "aaa://" FQDN [ port ] [ transport ] [ protocol ]
2070 ; No transport security
2072 "aaas://" FQDN [ port ] [ transport ] [ protocol ]
2074 ; Transport security used
2076 FQDN = Fully Qualified Host Name
2078 port = ":" 1*DIGIT
2080 ; One of the ports used to listen for
2081 ; incoming connections.
2082 ; If absent,
2083 ; the default Diameter port (3868) is
2084 ; assumed.
2086 transport = ";transport=" transport-protocol
2088 ; One of the transports used to listen
2089 ; for incoming connections. If absent,
2090 ; the default SCTP [RFC2960] protocol is
2091 ; assumed. UDP MUST NOT be used when
2092 ; the aaa-protocol field is set to
2093 ; diameter.
2095 transport-protocol = ( "tcp" / "sctp" / "udp" )
2097 protocol = ";protocol=" aaa-protocol
2099 ; If absent, the default AAA protocol
2100 ; is diameter.
2102 aaa-protocol = ( "diameter" / "radius" / "tacacs+" )
2104 The following are examples of valid Diameter host identities:
2106 aaa://host.example.com;transport=tcp
2107 aaa://host.example.com:6666;transport=tcp
2108 aaa://host.example.com;protocol=diameter
2109 aaa://host.example.com:6666;protocol=diameter
2110 aaa://host.example.com:6666;transport=tcp;protocol=diameter
2111 aaa://host.example.com:1813;transport=udp;protocol=radius
2113 Enumerated
2115 Enumerated is derived from the Integer32 AVP Base Format. The
2116 definition contains a list of valid values and their
2117 interpretation and is described in the Diameter application
2118 introducing the AVP.
2120 IPFilterRule
2122 The IPFilterRule format is derived from the OctetString AVP Base
2123 Format. It uses the ASCII charset. Packets may be filtered based
2124 on the following information that is associated with it:
2126 Direction (in or out)
2127 Source and destination IP address (possibly masked)
2128 Protocol
2129 Source and destination port (lists or ranges)
2130 TCP flags
2131 IP fragment flag
2132 IP options
2133 ICMP types
2135 Rules for the appropriate direction are evaluated in order, with
2136 the first matched rule terminating the evaluation. Each packet is
2137 evaluated once. If no rule matches, the packet is dropped if the
2138 last rule evaluated was a permit, and passed if the last rule was
2139 a deny.
2141 IPFilterRule filters MUST follow the format:
2143 action dir proto from src to dst [options]
2145 action permit - Allow packets that match the rule.
2146 deny - Drop packets that match the rule.
2148 dir "in" is from the terminal, "out" is to the
2149 terminal.
2151 proto An IP protocol specified by number. The "ip"
2152 keyword means any protocol will match.
2154 src and dst
[ports]
2156 The may be specified as:
2157 ipno An IPv4 or IPv6 number in dotted-
2158 quad or canonical IPv6 form. Only
2159 this exact IP number will match the
2160 rule.
2161 ipno/bits An IP number as above with a mask
2162 width of the form 1.2.3.4/24. In
2163 this case, all IP numbers from
2164 1.2.3.0 to 1.2.3.255 will match.
2165 The bit width MUST be valid for the
2166 IP version and the IP number MUST
2167 NOT have bits set beyond the mask.
2168 For a match to occur, the same IP
2169 version must be present in the
2170 packet that was used in describing
2171 the IP address. To test for a
2172 particular IP version, the bits part
2173 can be set to zero. The keyword
2174 "any" is 0.0.0.0/0 or the IPv6
2175 equivalent. The keyword "assigned"
2176 is the address or set of addresses
2177 assigned to the terminal. For IPv4,
2178 a typical first rule is often "deny
2179 in ip! assigned"
2181 The sense of the match can be inverted by
2182 preceding an address with the not modifier (!),
2183 causing all other addresses to be matched
2184 instead. This does not affect the selection of
2185 port numbers.
2187 With the TCP, UDP and SCTP protocols, optional
2188 ports may be specified as:
2190 {port/port-port}[,ports[,...]]
2192 The '-' notation specifies a range of ports
2193 (including boundaries).
2195 Fragmented packets that have a non-zero offset
2196 (i.e., not the first fragment) will never match
2197 a rule that has one or more port
2198 specifications. See the frag option for
2199 details on matching fragmented packets.
2201 options:
2202 frag Match if the packet is a fragment and this is not
2203 the first fragment of the datagram. frag may not
2204 be used in conjunction with either tcpflags or
2205 TCP/UDP port specifications.
2207 ipoptions spec
2208 Match if the IP header contains the comma
2209 separated list of options specified in spec. The
2210 supported IP options are:
2212 ssrr (strict source route), lsrr (loose source
2213 route), rr (record packet route) and ts
2214 (timestamp). The absence of a particular option
2215 may be denoted with a '!'.
2217 tcpoptions spec
2218 Match if the TCP header contains the comma
2219 separated list of options specified in spec. The
2220 supported TCP options are:
2222 mss (maximum segment size), window (tcp window
2223 advertisement), sack (selective ack), ts (rfc1323
2224 timestamp) and cc (rfc1644 t/tcp connection
2225 count). The absence of a particular option may
2226 be denoted with a '!'.
2228 established
2229 TCP packets only. Match packets that have the RST
2230 or ACK bits set.
2232 setup TCP packets only. Match packets that have the SYN
2233 bit set but no ACK bit.
2235 tcpflags spec
2236 TCP packets only. Match if the TCP header
2237 contains the comma separated list of flags
2238 specified in spec. The supported TCP flags are:
2240 fin, syn, rst, psh, ack and urg. The absence of a
2241 particular flag may be denoted with a '!'. A rule
2242 that contains a tcpflags specification can never
2243 match a fragmented packet that has a non-zero
2244 offset. See the frag option for details on
2245 matching fragmented packets.
2247 icmptypes types
2248 ICMP packets only. Match if the ICMP type is in
2249 the list types. The list may be specified as any
2250 combination of ranges or individual types
2251 separated by commas. Both the numeric values and
2252 the symbolic values listed below can be used. The
2253 supported ICMP types are:
2255 echo reply (0), destination unreachable (3),
2256 source quench (4), redirect (5), echo request
2257 (8), router advertisement (9), router
2258 solicitation (10), time-to-live exceeded (11), IP
2259 header bad (12), timestamp request (13),
2260 timestamp reply (14), information request (15),
2261 information reply (16), address mask request (17)
2262 and address mask reply (18).
2264 There is one kind of packet that the access device MUST always
2265 discard, that is an IP fragment with a fragment offset of one.
2266 This is a valid packet, but it only has one use, to try to
2267 circumvent firewalls.
2269 An access device that is unable to interpret or apply a deny rule
2270 MUST terminate the session. An access device that is unable to
2271 interpret or apply a permit rule MAY apply a more restrictive
2272 rule. An access device MAY apply deny rules of its own before the
2273 supplied rules, for example to protect the access device owner's
2274 infrastructure.
2276 The rule syntax is a modified subset of ipfw(8) from FreeBSD, and
2277 the ipfw.c code may provide a useful base for implementations.
2279 4.4. Grouped AVP Values
2281 The Diameter protocol allows AVP values of type 'Grouped.' This
2282 implies that the Data field is actually a sequence of AVPs. It is
2283 possible to include an AVP with a Grouped type within a Grouped type,
2284 that is, to nest them. AVPs within an AVP of type Grouped have the
2285 same padding requirements as non-Grouped AVPs, as defined in Section
2286 4.
2288 The AVP Code numbering space of all AVPs included in a Grouped AVP is
2289 the same as for non-grouped AVPs. Further, if any of the AVPs
2290 encapsulated within a Grouped AVP has the 'M' (mandatory) bit set,
2291 the Grouped AVP itself MUST also include the 'M' bit set.
2293 Every Grouped AVP defined MUST include a corresponding grammar, using
2294 ABNF [RFC4234] (with modifications), as defined below.
2296 grouped-avp-def = name "::=" avp
2298 name-fmt = ALPHA *(ALPHA / DIGIT / "-")
2300 name = name-fmt
2301 ; The name has to be the name of an AVP,
2302 ; defined in the base or extended Diameter
2303 ; specifications.
2305 avp = header [ *fixed] [ *required] [ *optional]
2306 [ *fixed]
2308 header = "<" "AVP-Header:" avpcode [vendor] ">"
2310 avpcode = 1*DIGIT
2311 ; The AVP Code assigned to the Grouped AVP
2313 vendor = 1*DIGIT
2314 ; The Vendor-ID assigned to the Grouped AVP.
2315 ; If absent, the default value of zero is
2316 ; used.
2318 4.4.1. Example AVP with a Grouped Data type
2320 The Example-AVP (AVP Code 999999) is of type Grouped and is used to
2321 clarify how Grouped AVP values work. The Grouped Data field has the
2322 following ABNF grammar:
2324 Example-AVP ::= < AVP Header: 999999 >
2325 { Origin-Host }
2326 1*{ Session-Id }
2327 *[ AVP ]
2329 An Example-AVP with Grouped Data follows.
2331 The Origin-Host AVP is required (Section 6.3). In this case:
2333 Origin-Host = "example.com".
2335 One or more Session-Ids must follow. Here there are two:
2337 Session-Id =
2338 "grump.example.com:33041;23432;893;0AF3B81"
2340 Session-Id =
2341 "grump.example.com:33054;23561;2358;0AF3B82"
2343 optional AVPs included are
2345 Recovery-Policy =
2346 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35
2347 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5
2348 c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd
2349 f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a
2350 cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119
2351 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c
2352 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92
2354 Futuristic-Acct-Record =
2355 fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0
2356 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8
2357 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c
2358 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067
2359 d3427475e49968f841
2361 The data for the optional AVPs is represented in hex since the format
2362 of these AVPs is neither known at the time of definition of the
2363 Example-AVP group, nor (likely) at the time when the example instance
2364 of this AVP is interpreted - except by Diameter implementations which
2365 support the same set of AVPs. The encoding example illustrates how
2366 padding is used and how length fields are calculated. Also note that
2367 AVPs may be present in the Grouped AVP value which the receiver
2368 cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record
2369 AVPs). The length of the Example-AVP is the sum of all the length of
2370 the member AVPs including their padding plus the Example-AVP header
2371 size.
2373 This AVP would be encoded as follows:
2375 0 1 2 3 4 5 6 7
2376 +-------+-------+-------+-------+-------+-------+-------+-------+
2377 0 | Example AVP Header (AVP Code = 999999), Length = 496 |
2378 +-------+-------+-------+-------+-------+-------+-------+-------+
2379 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 |
2380 +-------+-------+-------+-------+-------+-------+-------+-------+
2381 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' |
2382 +-------+-------+-------+-------+-------+-------+-------+-------+
2383 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header |
2384 +-------+-------+-------+-------+-------+-------+-------+-------+
2385 32 | (AVP Code = 263), Length = 49 | 'g' | 'r' | 'u' | 'm' |
2386 +-------+-------+-------+-------+-------+-------+-------+-------+
2387 . . .
2388 +-------+-------+-------+-------+-------+-------+-------+-------+
2389 72 | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding|Padding|
2390 +-------+-------+-------+-------+-------+-------+-------+-------+
2391 80 | Session-Id AVP Header (AVP Code = 263), Length = 50 |
2392 +-------+-------+-------+-------+-------+-------+-------+-------+
2393 88 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' |
2394 +-------+-------+-------+-------+-------+-------+-------+-------+
2395 . . .
2396 +-------+-------+-------+-------+-------+-------+-------+-------+
2397 120| '5' | '8' | ';' | '0' | 'A' | 'F' | '3' | 'B' |
2398 +-------+-------+-------+-------+-------+-------+-------+-------+
2399 128| '8' | '2' |Padding|Padding| Recovery-Policy Header (AVP |
2400 +-------+-------+-------+-------+-------+-------+-------+-------+
2401 136| Code = 8341), Length = 223 | 0x21 | 0x63 | 0xbc | 0x1d |
2402 +-------+-------+-------+-------+-------+-------+-------+-------+
2403 144| 0x0a | 0xd8 | 0x23 | 0x71 | 0xf6 | 0xbc | 0x09 | 0x48 |
2404 +-------+-------+-------+-------+-------+-------+-------+-------+
2405 . . .
2406 +-------+-------+-------+-------+-------+-------+-------+-------+
2407 352| 0x8c | 0x7f | 0x92 |Padding| Futuristic-Acct-Record Header |
2408 +-------+-------+-------+-------+-------+-------+-------+-------+
2409 328|(AVP Code = 15930),Length = 137| 0xfe | 0x19 | 0xda | 0x58 |
2410 +-------+-------+-------+-------+-------+-------+-------+-------+
2411 336| 0x02 | 0xac | 0xd9 | 0x8b | 0x07 | 0xa5 | 0xb8 | 0xc6 |
2412 +-------+-------+-------+-------+-------+-------+-------+-------+
2413 . . .
2414 +-------+-------+-------+-------+-------+-------+-------+-------+
2415 488| 0xe4 | 0x99 | 0x68 | 0xf8 | 0x41 |Padding|Padding|Padding|
2416 +-------+-------+-------+-------+-------+-------+-------+-------+
2418 4.5. Diameter Base Protocol AVPs
2420 The following table describes the Diameter AVPs defined in the base
2421 protocol, their AVP Code values, types, possible flag values.
2423 Due to space constraints, the short form DiamIdent is used to
2424 represent DiameterIdentity.
2426 +---------------------+
2427 | AVP Flag rules |
2428 |----+-----+----+-----|
2429 AVP Section | | |SHLD| MUST|
2430 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|
2431 -----------------------------------------|----+-----+----+-----|
2432 Acct- 85 9.8.2 Unsigned32 | M | | | V |
2433 Interim-Interval | | | | |
2434 Accounting- 483 9.8.7 Enumerated | M | | | V |
2435 Realtime-Required | | | | |
2436 Acct- 50 9.8.5 UTF8String | M | | | V |
2437 Multi-Session-Id | | | | |
2438 Accounting- 485 9.8.3 Unsigned32 | M | | | V |
2439 Record-Number | | | | |
2440 Accounting- 480 9.8.1 Enumerated | M | | | V |
2441 Record-Type | | | | |
2442 Accounting- 44 9.8.4 OctetString| M | | | V |
2443 Session-Id | | | | |
2444 Accounting- 287 9.8.6 Unsigned64 | M | | | V |
2445 Sub-Session-Id | | | | |
2446 Acct- 259 6.9 Unsigned32 | M | | | V |
2447 Application-Id | | | | |
2448 Auth- 258 6.8 Unsigned32 | M | | | V |
2449 Application-Id | | | | |
2450 Auth-Request- 274 8.7 Enumerated | M | | | V |
2451 Type | | | | |
2452 Authorization- 291 8.9 Unsigned32 | M | | | V |
2453 Lifetime | | | | |
2454 Auth-Grace- 276 8.10 Unsigned32 | M | | | V |
2455 Period | | | | |
2456 Auth-Session- 277 8.11 Enumerated | M | | | V |
2457 State | | | | |
2458 Re-Auth-Request- 285 8.12 Enumerated | M | | | V |
2459 Type | | | | |
2460 Class 25 8.20 OctetString| M | | | V |
2461 Destination-Host 293 6.5 DiamIdent | M | | | V |
2462 Destination- 283 6.6 DiamIdent | M | | | V |
2463 Realm | | | | |
2464 Disconnect-Cause 273 5.4.3 Enumerated | M | | | V |
2465 E2E-Sequence AVP 300 6.15 Grouped | M | | | V |
2466 Error-Message 281 7.3 UTF8String | | | | V,M |
2467 Error-Reporting- 294 7.4 DiamIdent | | | | V,M |
2468 Host | | | | |
2469 Event-Timestamp 55 8.21 Time | M | | | V |
2470 Experimental- 297 7.6 Grouped | M | | | V |
2471 Result | | | | |
2472 -----------------------------------------|----+-----+----+-----|
2473 +---------------------+
2474 | AVP Flag rules |
2475 |----+-----+----+-----|
2476 AVP Section | | |SHLD| MUST|
2477 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|
2478 -----------------------------------------|----+-----+----+-----|
2479 Experimental- 298 7.7 Unsigned32 | M | | | V |
2480 Result-Code | | | | |
2481 Failed-AVP 279 7.5 Grouped | M | | | V |
2482 Firmware- 267 5.3.4 Unsigned32 | | | | V,M |
2483 Revision | | | | |
2484 Host-IP-Address 257 5.3.5 Address | M | | | V |
2485 Inband-Security | M | | | V |
2486 -Id 299 6.10 Unsigned32 | | | | |
2487 Multi-Round- 272 8.19 Unsigned32 | M | | | V |
2488 Time-Out | | | | |
2489 Origin-Host 264 6.3 DiamIdent | M | | | V |
2490 Origin-Realm 296 6.4 DiamIdent | M | | | V |
2491 Origin-State-Id 278 8.16 Unsigned32 | M | | | V |
2492 Product-Name 269 5.3.7 UTF8String | | | | V,M |
2493 Proxy-Host 280 6.7.3 DiamIdent | M | | | V |
2494 Proxy-Info 284 6.7.2 Grouped | M | | | V |
2495 Proxy-State 33 6.7.4 OctetString| M | | | V |
2496 Redirect-Host 292 6.12 DiamURI | M | | | V |
2497 Redirect-Host- 261 6.13 Enumerated | M | | | V |
2498 Usage | | | | |
2499 Redirect-Max- 262 6.14 Unsigned32 | M | | | V |
2500 Cache-Time | | | | |
2501 Result-Code 268 7.1 Unsigned32 | M | | | V |
2502 Route-Record 282 6.7.1 DiamIdent | M | | | V |
2503 Session-Id 263 8.8 UTF8String | M | | | V |
2504 Session-Timeout 27 8.13 Unsigned32 | M | | | V |
2505 Session-Binding 270 8.17 Unsigned32 | M | | | V |
2506 Session-Server- 271 8.18 Enumerated | M | | | V |
2507 Failover | | | | |
2508 Supported- 265 5.3.6 Unsigned32 | M | | | V |
2509 Vendor-Id | | | | |
2510 Termination- 295 8.15 Enumerated | M | | | V |
2511 Cause | | | | |
2512 User-Name 1 8.14 UTF8String | M | | | V |
2513 Vendor-Id 266 5.3.3 Unsigned32 | M | | | V |
2514 Vendor-Specific- 260 6.11 Grouped | M | | | V |
2515 Application-Id | | | | |
2516 -----------------------------------------|----+-----+----+-----|
2518 5. Diameter Peers
2520 This section describes how Diameter nodes establish connections and
2521 communicate with peers.
2523 5.1. Peer Connections
2525 Although a Diameter node may have many possible peers that it is able
2526 to communicate with, it may not be economical to have an established
2527 connection to all of them. At a minimum, a Diameter node SHOULD have
2528 an established connection with two peers per realm, known as the
2529 primary and secondary peers. Of course, a node MAY have additional
2530 connections, if it is deemed necessary. Typically, all messages for
2531 a realm are sent to the primary peer, but in the event that failover
2532 procedures are invoked, any pending requests are sent to the
2533 secondary peer. However, implementations are free to load balance
2534 requests between a set of peers.
2536 Note that a given peer MAY act as a primary for a given realm, while
2537 acting as a secondary for another realm.
2539 When a peer is deemed suspect, which could occur for various reasons,
2540 including not receiving a DWA within an allotted timeframe, no new
2541 requests should be forwarded to the peer, but failover procedures are
2542 invoked. When an active peer is moved to this mode, additional
2543 connections SHOULD be established to ensure that the necessary number
2544 of active connections exists.
2546 There are two ways that a peer is removed from the suspect peer list:
2548 1. The peer is no longer reachable, causing the transport connection
2549 to be shutdown. The peer is moved to the closed state.
2551 2. Three watchdog messages are exchanged with accepted round trip
2552 times, and the connection to the peer is considered stabilized.
2554 In the event the peer being removed is either the primary or
2555 secondary, an alternate peer SHOULD replace the deleted peer, and
2556 assume the role of either primary or secondary.
2558 5.2. Diameter Peer Discovery
2560 Allowing for dynamic Diameter agent discovery will make it possible
2561 for simpler and more robust deployment of Diameter services. In
2562 order to promote interoperable implementations of Diameter peer
2563 discovery, the following mechanisms are described. These are based
2564 on existing IETF standards. The first option (manual configuration)
2565 MUST be supported by all DIAMETER nodes, while the latter option
2566 (DNS) MAY be supported.
2568 There are two cases where Diameter peer discovery may be performed.
2569 The first is when a Diameter client needs to discover a first-hop
2570 Diameter agent. The second case is when a Diameter agent needs to
2571 discover another agent - for further handling of a Diameter
2572 operation. In both cases, the following 'search order' is
2573 recommended:
2575 1. The Diameter implementation consults its list of static
2576 (manually) configured Diameter agent locations. These will be
2577 used if they exist and respond.
2579 2. The Diameter implementation performs a NAPTR query for a server
2580 in a particular realm. The Diameter implementation has to know
2581 in advance which realm to look for a Diameter agent in. This
2582 could be deduced, for example, from the 'realm' in a NAI that a
2583 Diameter implementation needed to perform a Diameter operation
2584 on.
2586 * The services relevant for the task of transport protocol
2587 selection are those with NAPTR service fields with values
2588 "AAA+D2x", where x is a letter that corresponds to a transport
2589 protocol supported by the domain. This specification defines
2590 D2T for TCP and D2S for SCTP. We also establish an IANA
2591 registry for NAPTR service name to transport protocol
2592 mappings.
2594 These NAPTR records provide a mapping from a domain, to the
2595 SRV record for contacting a server with the specific transport
2596 protocol in the NAPTR services field. The resource record
2597 will contain an empty regular expression and a replacement
2598 value, which is the SRV record for that particular transport
2599 protocol. If the server supports multiple transport
2600 protocols, there will be multiple NAPTR records, each with a
2601 different service value. As per [RFC3403], the client
2602 discards any records whose services fields are not applicable.
2603 For the purposes of this specification, several rules are
2604 defined.
2606 * A client MUST discard any service fields that identify a
2607 resolution service whose value is not "D2X", for values of X
2608 that indicate transport protocols supported by the client.
2609 The NAPTR processing as described in [RFC3403] will result in
2610 discovery of the most preferred transport protocol of the
2611 server that is supported by the client, as well as an SRV
2612 record for the server.
2614 The domain suffixes in the NAPTR replacement field SHOULD
2615 match the domain of the original query.
2617 3. If no NAPTR records are found, the requester queries for those
2618 address records for the destination address,
2619 '_diameter._sctp'.realm or '_diameter._tcp'.realm. Address
2620 records include A RR's, AAAA RR's or other similar records,
2621 chosen according to the requestor's network protocol
2622 capabilities. If the DNS server returns no address records, the
2623 requestor gives up.
2625 If the server is using a site certificate, the domain name in the
2626 query and the domain name in the replacement field MUST both be
2627 valid based on the site certificate handed out by the server in
2628 the TLS or IKE exchange. Similarly, the domain name in the SRV
2629 query and the domain name in the target in the SRV record MUST
2630 both be valid based on the same site certificate. Otherwise, an
2631 attacker could modify the DNS records to contain replacement
2632 values in a different domain, and the client could not validate
2633 that this was the desired behavior, or the result of an attack
2635 Also, the Diameter Peer MUST check to make sure that the
2636 discovered peers are authorized to act in its role.
2637 Authentication via IKE or TLS, or validation of DNS RRs via
2638 DNSSEC is not sufficient to conclude this. For example, a web
2639 server may have obtained a valid TLS certificate, and secured RRs
2640 may be included in the DNS, but this does not imply that it is
2641 authorized to act as a Diameter Server.
2643 Authorization can be achieved for example, by configuration of a
2644 Diameter Server CA. Alternatively this can be achieved by
2645 definition of OIDs within TLS or IKE certificates so as to
2646 signify Diameter Server authorization.
2648 A dynamically discovered peer causes an entry in the Peer Table (see
2649 Section 2.6) to be created. Note that entries created via DNS MUST
2650 expire (or be refreshed) within the DNS TTL. If a peer is discovered
2651 outside of the local realm, a routing table entry (see Section 2.7)
2652 for the peer's realm is created. The routing table entry's
2653 expiration MUST match the peer's expiration value.
2655 5.3. Capabilities Exchange
2657 When two Diameter peers establish a transport connection, they MUST
2658 exchange the Capabilities Exchange messages, as specified in the peer
2659 state machine (see Section 5.6). This message allows the discovery
2660 of a peer's identity and its capabilities (protocol version number,
2661 supported Diameter applications, security mechanisms, etc.)
2663 The receiver only issues commands to its peers that have advertised
2664 support for the Diameter application that defines the command. A
2665 Diameter node MUST cache the supported applications in order to
2666 ensure that unrecognized commands and/or AVPs are not unnecessarily
2667 sent to a peer.
2669 A receiver of a Capabilities-Exchange-Req (CER) message that does not
2670 have any applications in common with the sender MUST return a
2671 Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to
2672 DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport
2673 layer connection. Note that receiving a CER or CEA from a peer
2674 advertising itself as a Relay (see Section 2.4) MUST be interpreted
2675 as having common applications with the peer.
2677 The receiver of the Capabilities-Exchange-Request (CER) MUST
2678 determine common applications by computing the intersection of its
2679 own set of supported application identifiers against all of the
2680 application indentifier AVPs (Auth-Application-Id,
2681 Acct-Application-Id and Vendor-Specific-Application-Id) present in
2682 the CER. The value of the Vendor-Id AVP in the Vendor-Specific-
2683 Application-Id MUST not be used during computation. The sender of
2684 the Capabilities-Exchange-Answer (CEA) SHOULD include all of its
2685 supported applications as a hint to the receiver regarding all of its
2686 application capabilities.
2688 Similarly, a receiver of a Capabilities-Exchange-Req (CER) message
2689 that does not have any security mechanisms in common with the sender
2690 MUST return a Capabilities-Exchange-Answer (CEA) with the Result-Code
2691 AVP set to DIAMETER_NO_COMMON_SECURITY, and SHOULD disconnect the
2692 transport layer connection.
2694 CERs received from unknown peers MAY be silently discarded, or a CEA
2695 MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER.
2696 In both cases, the transport connection is closed. If the local
2697 policy permits receiving CERs from unknown hosts, a successful CEA
2698 MAY be returned. If a CER from an unknown peer is answered with a
2699 successful CEA, the lifetime of the peer entry is equal to the
2700 lifetime of the transport connection. In case of a transport
2701 failure, all the pending transactions destined to the unknown peer
2702 can be discarded.
2704 The CER and CEA messages MUST NOT be proxied, redirected or relayed.
2706 Since the CER/CEA messages cannot be proxied, it is still possible
2707 that an upstream agent receives a message for which it has no
2708 available peers to handle the application that corresponds to the
2709 Command-Code. In such instances, the 'E' bit is set in the answer
2710 message (see Section 7.) with the Result-Code AVP set to
2711 DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action
2712 (e.g., re-routing request to an alternate peer).
2714 With the exception of the Capabilities-Exchange-Request message, a
2715 message of type Request that includes the Auth-Application-Id or
2716 Acct-Application-Id AVPs, or a message with an application-specific
2717 command code, MAY only be forwarded to a host that has explicitly
2718 advertised support for the application (or has advertised the Relay
2719 Application Identifier).
2721 5.3.1. Capabilities-Exchange-Request
2723 The Capabilities-Exchange-Request (CER), indicated by the Command-
2724 Code set to 257 and the Command Flags' 'R' bit set, is sent to
2725 exchange local capabilities. Upon detection of a transport failure,
2726 this message MUST NOT be sent to an alternate peer.
2728 When Diameter is run over SCTP [RFC2960], which allows for
2729 connections to span multiple interfaces and multiple IP addresses,
2730 the Capabilities-Exchange-Request message MUST contain one Host-IP-
2731 Address AVP for each potential IP address that MAY be locally used
2732 when transmitting Diameter messages.
2734 Message Format
2736 ::= < Diameter Header: 257, REQ >
2737 { Origin-Host }
2738 { Origin-Realm }
2739 1* { Host-IP-Address }
2740 { Vendor-Id }
2741 { Product-Name }
2742 [ Origin-State-Id ]
2743 * [ Supported-Vendor-Id ]
2744 * [ Auth-Application-Id ]
2745 * [ Inband-Security-Id ]
2746 * [ Acct-Application-Id ]
2747 * [ Vendor-Specific-Application-Id ]
2748 [ Firmware-Revision ]
2749 * [ AVP ]
2751 5.3.2. Capabilities-Exchange-Answer
2753 The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code
2754 set to 257 and the Command Flags' 'R' bit cleared, is sent in
2755 response to a CER message.
2757 When Diameter is run over SCTP [RFC2960], which allows connections to
2758 span multiple interfaces, hence, multiple IP addresses, the
2759 Capabilities-Exchange-Answer message MUST contain one Host-IP-Address
2760 AVP for each potential IP address that MAY be locally used when
2761 transmitting Diameter messages.
2763 Message Format
2765 ::= < Diameter Header: 257 >
2766 { Result-Code }
2767 { Origin-Host }
2768 { Origin-Realm }
2769 1* { Host-IP-Address }
2770 { Vendor-Id }
2771 { Product-Name }
2772 [ Origin-State-Id ]
2773 [ Error-Message ]
2774 [ Failed-AVP ]
2775 * [ Supported-Vendor-Id ]
2776 * [ Auth-Application-Id ]
2777 * [ Inband-Security-Id ]
2778 * [ Acct-Application-Id ]
2779 * [ Vendor-Specific-Application-Id ]
2780 [ Firmware-Revision ]
2781 * [ AVP ]
2783 5.3.3. Vendor-Id AVP
2785 The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains
2786 the IANA "SMI Network Management Private Enterprise Codes" [RFC3232]
2787 value assigned to the vendor of the Diameter application. In
2788 combination with the Supported-Vendor-Id AVP (Section 5.3.6), this
2789 MAY be used in order to know which vendor specific attributes may be
2790 sent to the peer. It is also envisioned that the combination of the
2791 Vendor-Id, Product-Name (Section 5.3.7) and the Firmware-Revision
2792 (Section 5.3.4) AVPs MAY provide very useful debugging information.
2794 A Vendor-Id value of zero in the CER or CEA messages is reserved and
2795 indicates that this field is ignored.
2797 5.3.4. Firmware-Revision AVP
2799 The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is
2800 used to inform a Diameter peer of the firmware revision of the
2801 issuing device.
2803 For devices that do not have a firmware revision (general purpose
2804 computers running Diameter software modules, for instance), the
2805 revision of the Diameter software module may be reported instead.
2807 5.3.5. Host-IP-Address AVP
2809 The Host-IP-Address AVP (AVP Code 257) is of type Address and is used
2810 to inform a Diameter peer of the sender's IP address. All source
2811 addresses that a Diameter node expects to use with SCTP [RFC2960]
2812 MUST be advertised in the CER and CEA messages by including a
2813 Host-IP- Address AVP for each address. This AVP MUST ONLY be used in
2814 the CER and CEA messages.
2816 5.3.6. Supported-Vendor-Id AVP
2818 The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and
2819 contains the IANA "SMI Network Management Private Enterprise Codes"
2820 [RFC3232] value assigned to a vendor other than the device vendor.
2821 This is used in the CER and CEA messages in order to inform the peer
2822 that the sender supports (a subset of) the vendor-specific AVPs
2823 defined by the vendor identified in this AVP. The value of this AVP
2824 SHOULD NOT be set to zero. Multiple instances of this AVP containing
2825 the same value SHOULD NOT be sent.
2827 5.3.7. Product-Name AVP
2829 The Product-Name AVP (AVP Code 269) is of type UTF8String, and
2830 contains the vendor assigned name for the product. The Product-Name
2831 AVP SHOULD remain constant across firmware revisions for the same
2832 product.
2834 5.4. Disconnecting Peer connections
2836 When a Diameter node disconnects one of its transport connections,
2837 its peer cannot know the reason for the disconnect, and will most
2838 likely assume that a connectivity problem occurred, or that the peer
2839 has rebooted. In these cases, the peer may periodically attempt to
2840 reconnect, as stated in Section 2.1. In the event that the
2841 disconnect was a result of either a shortage of internal resources,
2842 or simply that the node in question has no intentions of forwarding
2843 any Diameter messages to the peer in the foreseeable future, a
2844 periodic connection request would not be welcomed. The
2845 Disconnection-Reason AVP contains the reason the Diameter node issued
2846 the Disconnect-Peer-Request message.
2848 The Disconnect-Peer-Request message is used by a Diameter node to
2849 inform its peer of its intent to disconnect the transport layer, and
2850 that the peer shouldn't reconnect unless it has a valid reason to do
2851 so (e.g., message to be forwarded). Upon receipt of the message, the
2852 Disconnect-Peer-Answer is returned, which SHOULD contain an error if
2853 messages have recently been forwarded, and are likely in flight,
2854 which would otherwise cause a race condition.
2856 The receiver of the Disconnect-Peer-Answer initiates the transport
2857 disconnect. The sender of the Disconnect-Peer-Answer should be able
2858 to detect the transport closure and cleanup the connection.
2860 5.4.1. Disconnect-Peer-Request
2862 The Disconnect-Peer-Request (DPR), indicated by the Command-Code set
2863 to 282 and the Command Flags' 'R' bit set, is sent to a peer to
2864 inform its intentions to shutdown the transport connection. Upon
2865 detection of a transport failure, this message MUST NOT be sent to an
2866 alternate peer.
2868 Message Format
2870 ::= < Diameter Header: 282, REQ >
2871 { Origin-Host }
2872 { Origin-Realm }
2873 { Disconnect-Cause }
2875 5.4.2. Disconnect-Peer-Answer
2877 The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set
2878 to 282 and the Command Flags' 'R' bit cleared, is sent as a response
2879 to the Disconnect-Peer-Request message. Upon receipt of this
2880 message, the transport connection is shutdown.
2882 Message Format
2884 ::= < Diameter Header: 282 >
2885 { Result-Code }
2886 { Origin-Host }
2887 { Origin-Realm }
2888 [ Error-Message ]
2889 [ Failed-AVP ]
2891 5.4.3. Disconnect-Cause AVP
2893 The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A
2894 Diameter node MUST include this AVP in the Disconnect-Peer-Request
2895 message to inform the peer of the reason for its intention to
2896 shutdown the transport connection. The following values are
2897 supported:
2899 REBOOTING 0
2900 A scheduled reboot is imminent. Receiver of DPR with above result
2901 code MAY attempt reconnection.
2903 BUSY 1
2904 The peer's internal resources are constrained, and it has
2905 determined that the transport connection needs to be closed.
2906 Receiver of DPR with above result code SHOULD NOT attempt
2907 reconnection.
2909 DO_NOT_WANT_TO_TALK_TO_YOU 2
2910 The peer has determined that it does not see a need for the
2911 transport connection to exist, since it does not expect any
2912 messages to be exchanged in the near future. Receiver of DPR
2913 with above result code SHOULD NOT attempt reconnection.
2915 5.5. Transport Failure Detection
2917 Given the nature of the Diameter protocol, it is recommended that
2918 transport failures be detected as soon as possible. Detecting such
2919 failures will minimize the occurrence of messages sent to unavailable
2920 agents, resulting in unnecessary delays, and will provide better
2921 failover performance. The Device-Watchdog-Request and Device-
2922 Watchdog-Answer messages, defined in this section, are used to pro-
2923 actively detect transport failures.
2925 5.5.1. Device-Watchdog-Request
2927 The Device-Watchdog-Request (DWR), indicated by the Command-Code set
2928 to 280 and the Command Flags' 'R' bit set, is sent to a peer when no
2929 traffic has been exchanged between two peers (see Section 5.5.3).
2930 Upon detection of a transport failure, this message MUST NOT be sent
2931 to an alternate peer.
2933 Message Format
2935 ::= < Diameter Header: 280, REQ >
2936 { Origin-Host }
2937 { Origin-Realm }
2938 [ Origin-State-Id ]
2940 5.5.2. Device-Watchdog-Answer
2942 The Device-Watchdog-Answer (DWA), indicated by the Command-Code set
2943 to 280 and the Command Flags' 'R' bit cleared, is sent as a response
2944 to the Device-Watchdog-Request message.
2946 Message Format
2948 ::= < Diameter Header: 280 >
2949 { Result-Code }
2950 { Origin-Host }
2951 { Origin-Realm }
2952 [ Error-Message ]
2953 [ Failed-AVP ]
2954 [ Origin-State-Id ]
2956 5.5.3. Transport Failure Algorithm
2958 The transport failure algorithm is defined in [RFC3539]. All
2959 Diameter implementations MUST support the algorithm defined in the
2960 specification in order to be compliant to the Diameter base protocol.
2962 5.5.4. Failover and Failback Procedures
2964 In the event that a transport failure is detected with a peer, it is
2965 necessary for all pending request messages to be forwarded to an
2966 alternate agent, if possible. This is commonly referred to as
2967 failover.
2969 In order for a Diameter node to perform failover procedures, it is
2970 necessary for the node to maintain a pending message queue for a
2971 given peer. When an answer message is received, the corresponding
2972 request is removed from the queue. The Hop-by-Hop Identifier field
2973 is used to match the answer with the queued request.
2975 When a transport failure is detected, if possible all messages in the
2976 queue are sent to an alternate agent with the T flag set. On booting
2977 a Diameter client or agent, the T flag is also set on any records
2978 still remaining to be transmitted in non-volatile storage. An
2979 example of a case where it is not possible to forward the message to
2980 an alternate server is when the message has a fixed destination, and
2981 the unavailable peer is the message's final destination (see
2982 Destination-Host AVP). Such an error requires that the agent return
2983 an answer message with the 'E' bit set and the Result-Code AVP set to
2984 DIAMETER_UNABLE_TO_DELIVER.
2986 It is important to note that multiple identical requests or answers
2987 MAY be received as a result of a failover. The End-to-End Identifier
2988 field in the Diameter header along with the Origin-Host AVP MUST be
2989 used to identify duplicate messages.
2991 As described in Section 2.1, a connection request should be
2992 periodically attempted with the failed peer in order to re-establish
2993 the transport connection. Once a connection has been successfully
2994 established, messages can once again be forwarded to the peer. This
2995 is commonly referred to as failback.
2997 5.6. Peer State Machine
2999 This section contains a finite state machine that MUST be observed by
3000 all Diameter implementations. Each Diameter node MUST follow the
3001 state machine described below when communicating with each peer.
3002 Multiple actions are separated by commas, and may continue on
3003 succeeding lines, as space requires. Similarly, state and next state
3004 may also span multiple lines, as space requires.
3006 This state machine is closely coupled with the state machine
3007 described in [RFC3539], which is used to open, close, failover,
3008 probe, and reopen transport connections. Note in particular that
3009 [RFC3539] requires the use of watchdog messages to probe connections.
3010 For Diameter, DWR and DWA messages are to be used.
3012 I- is used to represent the initiator (connecting) connection, while
3013 the R- is used to represent the responder (listening) connection.
3014 The lack of a prefix indicates that the event or action is the same
3015 regardless of the connection on which the event occurred.
3017 The stable states that a state machine may be in are Closed, I-Open
3018 and R-Open; all other states are intermediate. Note that I-Open and
3019 R-Open are equivalent except for whether the initiator or responder
3020 transport connection is used for communication.
3022 A CER message is always sent on the initiating connection immediately
3023 after the connection request is successfully completed. In the case
3024 of an election, one of the two connections will shut down. The
3025 responder connection will survive if the Origin-Host of the local
3026 Diameter entity is higher than that of the peer; the initiator
3027 connection will survive if the peer's Origin-Host is higher. All
3028 subsequent messages are sent on the surviving connection. Note that
3029 the results of an election on one peer are guaranteed to be the
3030 inverse of the results on the other.
3032 For TLS usage, a TLS handshake will begin when both ends are in the
3033 open state. If the TLS handshake is successful, all further messages
3034 will be sent via TLS. If the handshake fails, both ends move to the
3035 closed state.
3037 The state machine constrains only the behavior of a Diameter
3038 implementation as seen by Diameter peers through events on the wire.
3040 Any implementation that produces equivalent results is considered
3041 compliant.
3043 state event action next state
3044 -----------------------------------------------------------------
3045 Closed Start I-Snd-Conn-Req Wait-Conn-Ack
3046 R-Conn-CER R-Accept, R-Open
3047 Process-CER,
3048 R-Snd-CEA
3050 Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA
3051 I-Rcv-Conn-Nack Cleanup Closed
3052 R-Conn-CER R-Accept, Wait-Conn-Ack/
3053 Process-CER Elect
3054 Timeout Error Closed
3056 Wait-I-CEA I-Rcv-CEA Process-CEA I-Open
3057 R-Conn-CER R-Accept, Wait-Returns
3058 Process-CER,
3059 Elect
3060 I-Peer-Disc I-Disc Closed
3061 I-Rcv-Non-CEA Error Closed
3062 Timeout Error Closed
3064 Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns
3065 Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open
3066 R-Peer-Disc R-Disc Wait-Conn-Ack
3067 R-Conn-CER R-Reject Wait-Conn-Ack/
3068 Elect
3069 Timeout Error Closed
3071 Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open
3072 I-Peer-Disc I-Disc, R-Open
3073 R-Snd-CEA
3074 I-Rcv-CEA R-Disc I-Open
3075 R-Peer-Disc R-Disc Wait-I-CEA
3076 R-Conn-CER R-Reject Wait-Returns
3077 Timeout Error Closed
3079 R-Open Send-Message R-Snd-Message R-Open
3080 R-Rcv-Message Process R-Open
3081 R-Rcv-DWR Process-DWR, R-Open
3082 R-Snd-DWA
3083 R-Rcv-DWA Process-DWA R-Open
3084 R-Conn-CER R-Reject R-Open
3085 Stop R-Snd-DPR Closing
3086 R-Rcv-DPR R-Snd-DPA, Closed
3087 R-Disc
3089 R-Peer-Disc R-Disc Closed
3090 R-Rcv-CER R-Snd-CEA R-Open
3091 R-Rcv-CEA Process-CEA R-Open
3093 I-Open Send-Message I-Snd-Message I-Open
3094 I-Rcv-Message Process I-Open
3095 I-Rcv-DWR Process-DWR, I-Open
3096 I-Snd-DWA
3097 I-Rcv-DWA Process-DWA I-Open
3098 R-Conn-CER R-Reject I-Open
3099 Stop I-Snd-DPR Closing
3100 I-Rcv-DPR I-Snd-DPA, Closed
3101 I-Disc
3102 I-Peer-Disc I-Disc Closed
3103 I-Rcv-CER I-Snd-CEA I-Open
3104 I-Rcv-CEA Process-CEA I-Open
3106 Closing I-Rcv-DPA I-Disc Closed
3107 R-Rcv-DPA R-Disc Closed
3108 Timeout Error Closed
3109 I-Peer-Disc I-Disc Closed
3110 R-Peer-Disc R-Disc Closed
3112 5.6.1. Incoming connections
3114 When a connection request is received from a Diameter peer, it is
3115 not, in the general case, possible to know the identity of that peer
3116 until a CER is received from it. This is because host and port
3117 determine the identity of a Diameter peer; and the source port of an
3118 incoming connection is arbitrary. Upon receipt of CER, the identity
3119 of the connecting peer can be uniquely determined from Origin-Host.
3121 For this reason, a Diameter peer must employ logic separate from the
3122 state machine to receive connection requests, accept them, and await
3123 CER. Once CER arrives on a new connection, the Origin-Host that
3124 identifies the peer is used to locate the state machine associated
3125 with that peer, and the new connection and CER are passed to the
3126 state machine as an R-Conn-CER event.
3128 The logic that handles incoming connections SHOULD close and discard
3129 the connection if any message other than CER arrives, or if an
3130 implementation-defined timeout occurs prior to receipt of CER.
3132 Because handling of incoming connections up to and including receipt
3133 of CER requires logic, separate from that of any individual state
3134 machine associated with a particular peer, it is described separately
3135 in this section rather than in the state machine above.
3137 5.6.2. Events
3139 Transitions and actions in the automaton are caused by events. In
3140 this section, we will ignore the -I and -R prefix, since the actual
3141 event would be identical, but would occur on one of two possible
3142 connections.
3144 Start The Diameter application has signaled that a
3145 connection should be initiated with the peer.
3147 R-Conn-CER An acknowledgement is received stating that the
3148 transport connection has been established, and the
3149 associated CER has arrived.
3151 Rcv-Conn-Ack A positive acknowledgement is received confirming that
3152 the transport connection is established.
3154 Rcv-Conn-Nack A negative acknowledgement was received stating that
3155 the transport connection was not established.
3157 Timeout An application-defined timer has expired while waiting
3158 for some event.
3160 Rcv-CER A CER message from the peer was received.
3162 Rcv-CEA A CEA message from the peer was received.
3164 Rcv-Non-CEA A message other than CEA from the peer was received.
3166 Peer-Disc A disconnection indication from the peer was received.
3168 Rcv-DPR A DPR message from the peer was received.
3170 Rcv-DPA A DPA message from the peer was received.
3172 Win-Election An election was held, and the local node was the
3173 winner.
3175 Send-Message A message is to be sent.
3177 Rcv-Message A message other than CER, CEA, DPR, DPA, DWR or DWA
3178 was received.
3180 Stop The Diameter application has signaled that a
3181 connection should be terminated (e.g., on system
3182 shutdown).
3184 5.6.3. Actions
3186 Actions in the automaton are caused by events and typically indicate
3187 the transmission of packets and/or an action to be taken on the
3188 connection. In this section we will ignore the I- and R-prefix,
3189 since the actual action would be identical, but would occur on one of
3190 two possible connections.
3192 Snd-Conn-Req A transport connection is initiated with the peer.
3194 Accept The incoming connection associated with the R-Conn-CER
3195 is accepted as the responder connection.
3197 Reject The incoming connection associated with the R-Conn-CER
3198 is disconnected.
3200 Process-CER The CER associated with the R-Conn-CER is processed.
3201 Snd-CER A CER message is sent to the peer.
3203 Snd-CEA A CEA message is sent to the peer.
3205 Cleanup If necessary, the connection is shutdown, and any
3206 local resources are freed.
3208 Error The transport layer connection is disconnected, either
3209 politely or abortively, in response to an error
3210 condition. Local resources are freed.
3212 Process-CEA A received CEA is processed.
3214 Snd-DPR A DPR message is sent to the peer.
3216 Snd-DPA A DPA message is sent to the peer.
3218 Disc The transport layer connection is disconnected, and
3219 local resources are freed.
3221 Elect An election occurs (see Section 5.6.4 for more
3222 information).
3224 Snd-Message A message is sent.
3226 Snd-DWR A DWR message is sent.
3228 Snd-DWA A DWA message is sent.
3230 Process-DWR The DWR message is serviced.
3232 Process-DWA The DWA message is serviced.
3234 Process A message is serviced.
3236 5.6.4. The Election Process
3238 The election is performed on the responder. The responder compares
3239 the Origin-Host received in the CER with its own Origin-Host as two
3240 streams of octets. If the local Origin-Host lexicographically
3241 succeeds the received Origin-Host a Win-Election event is issued
3242 locally.
3244 To be consistent with DNS case insensitivity, octets that fall in the
3245 ASCII range 'a' through 'z' MUST compare equally to their upper-case
3246 counterparts between 'A' and 'Z', i.e. value 0x41 compares equal to
3247 0x61, 0x42 to 0x62 and so forth up to and including 0x5a and 0x7a.
3249 The winner of the election MUST close the connection it initiated.
3250 Historically, maintaining the responder side of a connection was more
3251 efficient than maintaining the initiator side. However, current
3252 practices makes this distinction irrelevant.
3254 5.6.5. Capabilities Update
3256 A Diameter node MUST initiate peer capabilities update by sending a
3257 Capabilities-Exchange-Req (CER) to all its peers which supports peer
3258 capabilities update and is in OPEN state. The receiver of CER in
3259 open state MUST process and reply to the CER as a described in
3260 Section 5.3. The CEA which the receiver sends MUST contain its
3261 latest capabilities. Note that peers which successfully process the
3262 peer capabilities update SHOULD also update their routing tables to
3263 reflect the change. The receiver of the CEA, with a Result-Code AVP
3264 other than DIAMETER_SUCCESS, initiates the transport disconnect. The
3265 peer may periodically attempt to reconnect, as stated in Section 2.1.
3267 Peer capabilities update in the open state SHOULD be limited to the
3268 advertisement of the new list of supported applications and MUST
3269 preclude re-negotiation of security mechanism or other capabilities.
3270 If any capabilities change happens in the node (e.g. change in
3271 security mechanisms), other than a change in the supported
3272 applications, the node SHOULD gracefully terminate (setting the
3273 Disconnect-Cause AVP value to REBOOTING) and re-establish the
3274 diameter connections to all the peers.
3276 6. Diameter message processing
3278 This section describes how Diameter requests and answers are created
3279 and processed.
3281 6.1. Diameter Request Routing Overview
3283 A request is sent towards its final destination using a combination
3284 of the Destination-Realm and Destination-Host AVPs, in one of these
3285 three combinations:
3287 o a request that is not able to be proxied (such as CER) MUST NOT
3288 contain either Destination-Realm or Destination-Host AVPs.
3290 o a request that needs to be sent to a home server serving a
3291 specific realm, but not to a specific server (such as the first
3292 request of a series of round-trips), MUST contain a Destination-
3293 Realm AVP, but MUST NOT contain a Destination-Host AVP.
3295 o otherwise, a request that needs to be sent to a specific home
3296 server among those serving a given realm, MUST contain both the
3297 Destination-Realm and Destination-Host AVPs.
3299 The Destination-Host AVP is used as described above when the
3300 destination of the request is fixed, which includes:
3302 o Authentication requests that span multiple round trips
3304 o A Diameter message that uses a security mechanism that makes use
3305 of a pre-established session key shared between the source and the
3306 final destination of the message.
3308 o Server initiated messages that MUST be received by a specific
3309 Diameter client (e.g., access device), such as the Abort-Session-
3310 Request message, which is used to request that a particular user's
3311 session be terminated.
3313 Note that an agent can forward a request to a host described in the
3314 Destination-Host AVP only if the host in question is included in its
3315 peer table (see Section 2.7). Otherwise, the request is routed based
3316 on the Destination-Realm only (see Sections 6.1.6).
3318 The Destination-Realm AVP MUST be present if the message is
3319 proxiable. Request messages that may be forwarded by Diameter agents
3320 (proxies, redirects or relays) MUST also contain an Acct-
3321 Application-Id AVP, an Auth-Application-Id AVP or a Vendor-Specific-
3322 Application-Id AVP. A message that MUST NOT be forwarded by Diameter
3323 agents (proxies, redirects or relays) MUST not include the
3324 Destination-Realm in its ABNF. The value of the Destination-Realm
3325 AVP MAY be extracted from the User-Name AVP, or other application-
3326 specific methods.
3328 When a message is received, the message is processed in the following
3329 order:
3331 o If the message is destined for the local host, the procedures
3332 listed in Section 6.1.4 are followed.
3334 o If the message is intended for a Diameter peer with whom the local
3335 host is able to directly communicate, the procedures listed in
3336 Section 6.1.5 are followed. This is known as Request Forwarding.
3338 o The procedures listed in Section 6.1.6 are followed, which is
3339 known as Request Routing.
3341 o If none of the above is successful, an answer is returned with the
3342 Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the E-bit set.
3344 For routing of Diameter messages to work within an administrative
3345 domain, all Diameter nodes within the realm MUST be peers.
3347 Note the processing rules contained in this section are intended to
3348 be used as general guidelines to Diameter developers. Certain
3349 implementations MAY use different methods than the ones described
3350 here, and still comply with the protocol specification. See Section
3351 7 for more detail on error handling.
3353 6.1.1. Originating a Request
3355 When creating a request, in addition to any other procedures
3356 described in the application definition for that specific request,
3357 the following procedures MUST be followed:
3359 o the Command-Code is set to the appropriate value
3361 o the 'R' bit is set
3363 o the End-to-End Identifier is set to a locally unique value
3365 o the Origin-Host and Origin-Realm AVPs MUST be set to the
3366 appropriate values, used to identify the source of the message
3368 o the Destination-Host and Destination-Realm AVPs MUST be set to the
3369 appropriate values as described in Section 6.1.
3371 o an Acct-Application-Id AVP, an Auth-Application-Id or a Vendor-
3372 Specific-Application-Id AVP must be included if the request is
3373 proxiable. The application id present in one of these relevant
3374 AVPs must match the application id present in the diameter message
3375 header.
3377 6.1.2. Sending a Request
3379 When sending a request, originated either locally, or as the result
3380 of a forwarding or routing operation, the following procedures MUST
3381 be followed:
3383 o the Hop-by-Hop Identifier should be set to a locally unique value.
3385 o The message should be saved in the list of pending requests.
3387 Other actions to perform on the message based on the particular role
3388 the agent is playing are described in the following sections.
3390 6.1.3. Receiving Requests
3392 A relay or proxy agent MUST check for forwarding loops when receiving
3393 requests. A loop is detected if the server finds its own identity in
3394 a Route-Record AVP. When such an event occurs, the agent MUST answer
3395 with the Result-Code AVP set to DIAMETER_LOOP_DETECTED.
3397 6.1.4. Processing Local Requests
3399 A request is known to be for local consumption when one of the
3400 following conditions occur:
3402 o The Destination-Host AVP contains the local host's identity,
3404 o The Destination-Host AVP is not present, the Destination-Realm AVP
3405 contains a realm the server is configured to process locally, and
3406 the Diameter application is locally supported, or
3408 o Both the Destination-Host and the Destination-Realm are not
3409 present.
3411 When a request is locally processed, the rules in Section 6.2 should
3412 be used to generate the corresponding answer.
3414 6.1.5. Request Forwarding
3416 Request forwarding is done using the Diameter Peer Table. The
3417 Diameter peer table contains all of the peers that the local node is
3418 able to directly communicate with.
3420 When a request is received, and the host encoded in the Destination-
3421 Host AVP is one that is present in the peer table, the message SHOULD
3422 be forwarded to the peer.
3424 6.1.6. Request Routing
3426 Diameter request message routing is done via realms and applications.
3427 A Diameter message that may be forwarded by Diameter agents (proxies,
3428 redirects or relays) MUST include the target realm in the
3429 Destination-Realm AVP. Request routing SHOULD rely on the
3430 Destination-Realm AVP and the application id present in the request
3431 message header to aid in the routing decision. It MAY also rely on
3432 the application identification AVPs Auth-Application-Id, Acct-
3433 Application-Id or Vendor-Specific-Application-Id instead of the
3434 application id in the message header as a secondary measure. The
3435 realm MAY be retrieved from the User-Name AVP, which is in the form
3436 of a Network Access Identifier (NAI). The realm portion of the NAI
3437 is inserted in the Destination-Realm AVP.
3439 Diameter agents MAY have a list of locally supported realms and
3440 applications, and MAY have a list of externally supported realms and
3441 applications. When a request is received that includes a realm
3442 and/or application that is not locally supported, the message is
3443 routed to the peer configured in the Routing Table (see Section 2.7).
3445 Realm names and application identifiers are the minimum supported
3446 routing criteria, additional routing information maybe needed to
3447 support redirect semantics.
3449 6.1.7. Predictive Loop Avoidance
3451 Before forwarding or routing a request, Diameter agents, in addition
3452 to processing done in Section 6.1.3, SHOULD check for the presence of
3453 candidate route's peer identity in any of the Route-Record AVPs. In
3454 an event of the agent detecting the presence of a candidate route's
3455 peer identity in a Route-Record AVP, the agent MUST ignore such route
3456 for the Diameter request message and attempt alternate routes if any.
3457 In case all the candidate routes are eliminated by the above
3458 criteria, the agent SHOULD return DIAMETER_UNABLE_TO_DELIVER message.
3460 6.1.8. Redirecting requests
3462 When a redirect agent receives a request whose routing entry is set
3463 to REDIRECT, it MUST reply with an answer message with the 'E' bit
3464 set, while maintaining the Hop-by-Hop Identifier in the header, and
3465 include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of
3466 the servers associated with the routing entry are added in separate
3467 Redirect-Host AVP.
3469 +------------------+
3470 | Diameter |
3471 | Redirect Agent |
3472 +------------------+
3473 ^ | 2. command + 'E' bit
3474 1. Request | | Result-Code =
3475 joe@example.com | | DIAMETER_REDIRECT_INDICATION +
3476 | | Redirect-Host AVP(s)
3477 | v
3478 +-------------+ 3. Request +-------------+
3479 | example.com |------------->| example.net |
3480 | Relay | | Diameter |
3481 | Agent |<-------------| Server |
3482 +-------------+ 4. Answer +-------------+
3484 Figure 5: Diameter Redirect Agent
3486 The receiver of the answer message with the 'E' bit set, and the
3487 Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by-
3488 hop field in the Diameter header to identify the request in the
3489 pending message queue (see Section 5.3) that is to be redirected. If
3490 no transport connection exists with the new agent, one is created,
3491 and the request is sent directly to it.
3493 Multiple Redirect-Host AVPs are allowed. The receiver of the answer
3494 message with the 'E' bit set selects exactly one of these hosts as
3495 the destination of the redirected message.
3497 When the Redirect-Host-Usage AVP included in the answer message has a
3498 non-zero value, a route entry for the redirect indications is created
3499 and cached by the receiver. The redirect usage for such route entry
3500 is set by the value of Redirect-Host-Usage AVP and the lifetime of
3501 the cached route entry is set by Redirect-Max-Cache-Time AVP value.
3503 It is possible that multiple redirect indications can create multiple
3504 cached route entries differing only in their redirect usage and the
3505 peer to forward messages to. As an example, two(2) route entries
3506 that are created by two(2) redirect indications results in two(2)
3507 cached routes for the same realm and application Id. However, one
3508 has a redirect usage of ALL_SESSION where matching request will be
3509 forwarded to one peer and the other has a redirect usage of ALL_REALM
3510 where request are forwarded to another peer. Therefore, an incoming
3511 request that matches the realm and application Id of both routes will
3512 need additional resolution. In such a case, a routing precedence
3513 rule MUST be used againts the redirect usage value to resolve the
3514 contention. The precedence rule can be found in Section 6.13.
3516 6.1.9. Relaying and Proxying Requests
3518 A relay or proxy agent MUST append a Route-Record AVP to all requests
3519 forwarded. The AVP contains the identity of the peer the request was
3520 received from.
3522 The Hop-by-Hop identifier in the request is saved, and replaced with
3523 a locally unique value. The source of the request is also saved,
3524 which includes the IP address, port and protocol.
3526 A relay or proxy agent MAY include the Proxy-Info AVP in requests if
3527 it requires access to any local state information when the
3528 corresponding response is received. Proxy-Info AVP has certain
3529 security implications and SHOULD contain an embedded HMAC with a
3530 node-local key. Alternatively, it MAY simply use local storage to
3531 store state information.
3533 The message is then forwarded to the next hop, as identified in the
3534 Routing Table.
3536 Figure 6 provides an example of message routing using the procedures
3537 listed in these sections.
3539 (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net)
3540 (Origin-Realm=mno.net) (Origin-Realm=mno.net)
3541 (Destination-Realm=example.com) (Destination-
3542 Realm=example.com)
3543 (Route-Record=nas.example.net)
3544 +------+ ------> +------+ ------> +------+
3545 | | (Request) | | (Request) | |
3546 | NAS +-------------------+ DRL +-------------------+ HMS |
3547 | | | | | |
3548 +------+ <------ +------+ <------ +------+
3549 example.net (Answer) example.net (Answer) example.com
3550 (Origin-Host=hms.example.com) (Origin-Host=hms.example.com)
3551 (Origin-Realm=example.com) (Origin-Realm=example.com)
3553 Figure 6: Routing of Diameter messages
3555 Relay agents do not require full validation of incoming messages. At
3556 a minimum, validation of the message header and relevant routing AVPs
3557 has to be done when relaying messages.
3559 6.2. Diameter Answer Processing
3561 When a request is locally processed, the following procedures MUST be
3562 applied to create the associated answer, in addition to any
3563 additional procedures that MAY be discussed in the Diameter
3564 application defining the command:
3566 o The same Hop-by-Hop identifier in the request is used in the
3567 answer.
3569 o The local host's identity is encoded in the Origin-Host AVP.
3571 o The Destination-Host and Destination-Realm AVPs MUST NOT be
3572 present in the answer message.
3574 o The Result-Code AVP is added with its value indicating success or
3575 failure.
3577 o If the Session-Id is present in the request, it MUST be included
3578 in the answer.
3580 o Any Proxy-Info AVPs in the request MUST be added to the answer
3581 message, in the same order they were present in the request.
3583 o The 'P' bit is set to the same value as the one in the request.
3585 o The same End-to-End identifier in the request is used in the
3586 answer.
3588 Note that the error messages (see Section 7.3) are also subjected to
3589 the above processing rules.
3591 6.2.1. Processing received Answers
3593 A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an
3594 answer received against the list of pending requests. The
3595 corresponding message should be removed from the list of pending
3596 requests. It SHOULD ignore answers received that do not match a
3597 known Hop-by-Hop Identifier.
3599 6.2.2. Relaying and Proxying Answers
3601 If the answer is for a request which was proxied or relayed, the
3602 agent MUST restore the original value of the Diameter header's Hop-
3603 by-Hop Identifier field.
3605 If the last Proxy-Info AVP in the message is targeted to the local
3606 Diameter server, the AVP MUST be removed before the answer is
3607 forwarded.
3609 If a relay or proxy agent receives an answer with a Result-Code AVP
3610 indicating a failure, it MUST NOT modify the contents of the AVP.
3611 Any additional local errors detected SHOULD be logged, but not
3612 reflected in the Result-Code AVP. If the agent receives an answer
3613 message with a Result-Code AVP indicating success, and it wishes to
3614 modify the AVP to indicate an error, it MUST modify the Result-Code
3615 AVP to contain the appropriate error in the message destined towards
3616 the access device as well as include the Error-Reporting-Host AVP and
3617 it MUST issue an STR on behalf of the access device.
3619 The agent MUST then send the answer to the host that it received the
3620 original request from.
3622 6.3. Origin-Host AVP
3624 The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and
3625 MUST be present in all Diameter messages. This AVP identifies the
3626 endpoint that originated the Diameter message. Relay agents MUST NOT
3627 modify this AVP.
3629 The value of the Origin-Host AVP is guaranteed to be unique within a
3630 single host.
3632 Note that the Origin-Host AVP may resolve to more than one address as
3633 the Diameter peer may support more than one address.
3635 This AVP SHOULD be placed as close to the Diameter header as
3636 possible. 6.10
3638 6.4. Origin-Realm AVP
3640 The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity.
3641 This AVP contains the Realm of the originator of any Diameter message
3642 and MUST be present in all messages.
3644 This AVP SHOULD be placed as close to the Diameter header as
3645 possible.
3647 6.5. Destination-Host AVP
3649 The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity.
3650 This AVP MUST be present in all unsolicited agent initiated messages,
3651 MAY be present in request messages, and MUST NOT be present in Answer
3652 messages.
3654 The absence of the Destination-Host AVP will cause a message to be
3655 sent to any Diameter server supporting the application within the
3656 realm specified in Destination-Realm AVP.
3658 This AVP SHOULD be placed as close to the Diameter header as
3659 possible.
3661 6.6. Destination-Realm AVP
3663 The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity,
3664 and contains the realm the message is to be routed to. The
3665 Destination-Realm AVP MUST NOT be present in Answer messages.
3666 Diameter Clients insert the realm portion of the User-Name AVP.
3667 Diameter servers initiating a request message use the value of the
3668 Origin-Realm AVP from a previous message received from the intended
3669 target host (unless it is known a priori). When present, the
3670 Destination-Realm AVP is used to perform message routing decisions.
3672 Request messages whose ABNF does not list the Destination-Realm AVP
3673 as a mandatory AVP are inherently non-routable messages.
3675 This AVP SHOULD be placed as close to the Diameter header as
3676 possible.
3678 6.7. Routing AVPs
3680 The AVPs defined in this section are Diameter AVPs used for routing
3681 purposes. These AVPs change as Diameter messages are processed by
3682 agents.
3684 6.7.1. Route-Record AVP
3686 The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The
3687 identity added in this AVP MUST be the same as the one received in
3688 the Origin-Host of the Capabilities Exchange message.
3690 6.7.2. Proxy-Info AVP
3692 The Proxy-Info AVP (AVP Code 284) is of type Grouped. The Grouped
3693 Data field has the following ABNF grammar:
3695 Proxy-Info ::= < AVP Header: 284 >
3696 { Proxy-Host }
3697 { Proxy-State }
3698 * [ AVP ]
3700 6.7.3. Proxy-Host AVP
3702 The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This
3703 AVP contains the identity of the host that added the Proxy-Info AVP.
3705 6.7.4. Proxy-State AVP
3707 The Proxy-State AVP (AVP Code 33) is of type OctetString, and
3708 contains state local information, and MUST be treated as opaque data.
3710 6.8. Auth-Application-Id AVP
3712 The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and
3713 is used in order to advertise support of the Authentication and
3714 Authorization portion of an application (see Section 2.4). The Auth-
3715 Application-Id MUST also be present in all Authentication and/or
3716 Authorization messages that are defined in a separate Diameter
3717 specification and have an Application ID assigned. If present in a
3718 message, the value of the Auth-Application-Id AVP MUST match the
3719 application id present in the diameter message header except when
3720 used in a CER or CEA messages.
3722 6.9. Acct-Application-Id AVP
3724 The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and
3725 is used in order to advertise support of the Accounting portion of an
3726 application (see Section 2.4). The Acct-Application-Id MUST also be
3727 present in all Accounting messages. Exactly one of the Auth-
3728 Application-Id and Acct-Application-Id AVPs MAY be present. If
3729 present in a message, the value of the Acct-Application-Id AVP MUST
3730 match the application id present in the diameter message header
3731 except when used in a CER or CEA messages.
3733 6.10. Inband-Security-Id AVP
3735 The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and
3736 is used in order to advertise support of the Security portion of the
3737 application.
3739 Currently, the following values are supported, but there is ample
3740 room to add new security Ids.
3742 NO_INBAND_SECURITY 0
3744 This peer does not support TLS. This is the default value, if the
3745 AVP is omitted.
3747 TLS 1
3749 This node supports TLS security, as defined by [RFC4346].
3751 6.11. Vendor-Specific-Application-Id AVP
3753 The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type
3754 Grouped and is used to advertise support of a vendor-specific
3755 Diameter Application. Exactly one instance of either Auth-
3756 Application-Id or Acct-Application-Id AVP MAY be present. The
3757 application identifier carried by either Auth-Application-Id or Acct-
3758 Application-Id AVP MUST comply with vendor specific application
3759 identifier assignment described in Sec 11.3. It MUST also match the
3760 application id present in the diameter header except when used in a
3761 CER or CEA messages.
3763 The Vendor-Id AVP is an informational AVP pertaining to the vendor
3764 who may have authorship of the vendor-specific diameter application.
3765 It should not be used as a means of defining a completely separate
3766 vendor-specific application identifier space.
3768 This AVP MUST also be present as the first AVP in all experimental
3769 commands defined in the vendor-specific application.
3771 This AVP SHOULD be placed as close to the Diameter header as
3772 possible.
3774 AVP Format
3776 ::= < AVP Header: 260 >
3777 { Vendor-Id }
3778 ({ Auth-Application-Id } /
3779 { Acct-Application-Id })
3781 6.12. Redirect-Host AVP
3783 One or more of instances of this AVP MUST be present if the answer
3784 message's 'E' bit is set and the Result-Code AVP is set to
3785 DIAMETER_REDIRECT_INDICATION.
3787 Upon receiving the above, the receiving Diameter node SHOULD forward
3788 the request directly to one of the hosts identified in these AVPs.
3789 The server contained in the selected Redirect-Host AVP SHOULD be used
3790 for all messages pertaining to this session.
3792 6.13. Redirect-Host-Usage AVP
3794 The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated.
3795 This AVP MAY be present in answer messages whose 'E' bit is set and
3796 the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION.
3798 When present, this AVP dictates how the routing entry resulting from
3799 the Redirect-Host is to be used. The following values are supported:
3801 DONT_CACHE 0
3803 The host specified in the Redirect-Host AVP should not be cached.
3804 This is the default value.
3806 ALL_SESSION 1
3808 All messages within the same session, as defined by the same value
3809 of the Session-ID AVP MAY be sent to the host specified in the
3810 Redirect-Host AVP.
3812 ALL_REALM 2
3814 All messages destined for the realm requested MAY be sent to the
3815 host specified in the Redirect-Host AVP.
3817 REALM_AND_APPLICATION 3
3819 All messages for the application requested to the realm specified
3820 MAY be sent to the host specified in the Redirect-Host AVP.
3822 ALL_APPLICATION 4
3824 All messages for the application requested MAY be sent to the host
3825 specified in the Redirect-Host AVP.
3827 ALL_HOST 5
3829 All messages that would be sent to the host that generated the
3830 Redirect-Host MAY be sent to the host specified in the Redirect-
3831 Host AVP.
3833 ALL_USER 6
3835 All messages for the user requested MAY be sent to the host
3836 specified in the Redirect-Host AVP.
3838 When multiple cached routes are created by redirect indications and
3839 they differs only in redirect usage and peers to forward requests to
3840 (see Section 6.1.8), a precedence rule MUST be applied to the
3841 redirect usage values of the cached routes during normal routing to
3842 resolve contentions that may occur. The precedence rule is the order
3843 that dictate which redirect usage should be considered before any
3844 other as they appear. The order is as follows:
3846 1. ALL_SESSION
3848 2. ALL_USER
3850 3. REALM_AND_APPLICATION
3852 4. ALL_REALM
3854 5. ALL_APPLICATION
3856 6. ALL_HOST
3858 6.14. Redirect-Max-Cache-Time AVP
3860 The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32.
3861 This AVP MUST be present in answer messages whose 'E' bit is set, the
3862 Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the
3863 Redirect-Host-Usage AVP set to a non-zero value.
3865 This AVP contains the maximum number of seconds the peer and route
3866 table entries, created as a result of the Redirect-Host, will be
3867 cached. Note that once a host created due to a redirect indication
3868 is no longer reachable, any associated peer and routing table entries
3869 MUST be deleted.
3871 6.15. E2E-Sequence AVP
3873 The E2E-Sequence AVP (AVP Code 300) provides anti-replay protection
3874 for end to end messages and is of type grouped. It contains a random
3875 value (an OctetString with a nonce) and counter (an Integer). For
3876 each end-to-end peer with which a node communicates (or remembers
3877 communicating) a different nonce value MUST be used and the counter
3878 is initiated at zero and increases by one each time this AVP is
3879 emitted to that peer.
3881 7. Error Handling
3883 There are two different types of errors in Diameter; protocol and
3884 application errors. A protocol error is one that occurs at the base
3885 protocol level, and MAY require per hop attention (e.g., message
3886 routing error). Application errors, on the other hand, generally
3887 occur due to a problem with a function specified in a Diameter
3888 application (e.g., user authentication, Missing AVP).
3890 Result-Code AVP values that are used to report protocol errors MUST
3891 only be present in answer messages whose 'E' bit is set. When a
3892 request message is received that causes a protocol error, an answer
3893 message is returned with the 'E' bit set, and the Result-Code AVP is
3894 set to the appropriate protocol error value. As the answer is sent
3895 back towards the originator of the request, each proxy or relay agent
3896 MAY take action on the message.
3898 1. Request +---------+ Link Broken
3899 +-------------------------->|Diameter |----///----+
3900 | +---------------------| | v
3901 +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+
3902 |Diameter |<-+ (Unable to Forward) +---------+ |Diameter|
3903 | | | Home |
3904 | Relay 1 |--+ +---------+ | Server |
3905 +---------+ | 3. Request |Diameter | +--------+
3906 +-------------------->| | ^
3907 | Relay 3 |-----------+
3908 +---------+
3910 Figure 7: Example of Protocol Error causing answer message
3912 Figure 7 provides an example of a message forwarded upstream by a
3913 Diameter relay. When the message is received by Relay 2, and it
3914 detects that it cannot forward the request to the home server, an
3915 answer message is returned with the 'E' bit set and the Result-Code
3916 AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls
3917 within the protocol error category, Relay 1 would take special
3918 action, and given the error, attempt to route the message through its
3919 alternate Relay 3.
3921 +---------+ 1. Request +---------+ 2. Request +---------+
3922 | Access |------------>|Diameter |------------>|Diameter |
3923 | | | | | Home |
3924 | Device |<------------| Relay |<------------| Server |
3925 +---------+ 4. Answer +---------+ 3. Answer +---------+
3926 (Missing AVP) (Missing AVP)
3928 Figure 8: Example of Application Error Answer message
3930 Figure 8 provides an example of a Diameter message that caused an
3931 application error. When application errors occur, the Diameter
3932 entity reporting the error clears the 'R' bit in the Command Flags,
3933 and adds the Result-Code AVP with the proper value. Application
3934 errors do not require any proxy or relay agent involvement, and
3935 therefore the message would be forwarded back to the originator of
3936 the request.
3938 There are certain Result-Code AVP application errors that require
3939 additional AVPs to be present in the answer. In these cases, the
3940 Diameter node that sets the Result-Code AVP to indicate the error
3941 MUST add the AVPs. Examples are:
3943 o An unrecognized AVP is received with the 'M' bit (Mandatory bit)
3944 set, causes an answer to be sent with the Result-Code AVP set to
3945 DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the
3946 offending AVP.
3948 o An AVP that is received with an unrecognized value causes an
3949 answer to be returned with the Result-Code AVP set to
3950 DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the
3951 AVP causing the error.
3953 o A command is received with an AVP that is omitted, yet is
3954 mandatory according to the command's ABNF. The receiver issues an
3955 answer with the Result-Code set to DIAMETER_MISSING_AVP, and
3956 creates an AVP with the AVP Code and other fields set as expected
3957 in the missing AVP. The created AVP is then added to the Failed-
3958 AVP AVP.
3960 The Result-Code AVP describes the error that the Diameter node
3961 encountered in its processing. In case there are multiple errors,
3962 the Diameter node MUST report only the first error it encountered
3963 (detected possibly in some implementation dependent order). The
3964 specific errors that can be described by this AVP are described in
3965 the following section.
3967 7.1. Result-Code AVP
3969 The Result-Code AVP (AVP Code 268) is of type Unsigned32 and
3970 indicates whether a particular request was completed successfully or
3971 whether an error occurred. All Diameter answer messages defined in
3972 IETF applications MUST include one Result-Code AVP. A non-successful
3973 Result-Code AVP (one containing a non 2xxx value other than
3974 DIAMETER_REDIRECT_INDICATION) MUST include the Error-Reporting-Host
3975 AVP if the host setting the Result-Code AVP is different from the
3976 identity encoded in the Origin-Host AVP.
3978 The Result-Code data field contains an IANA-managed 32-bit address
3979 space representing errors (see Section 11.4). Diameter provides the
3980 following classes of errors, all identified by the thousands digit in
3981 the decimal notation:
3983 o 1xxx (Informational)
3985 o 2xxx (Success)
3987 o 3xxx (Protocol Errors)
3989 o 4xxx (Transient Failures)
3991 o 5xxx (Permanent Failure)
3993 A non-recognized class (one whose first digit is not defined in this
3994 section) MUST be handled as a permanent failure.
3996 7.1.1. Informational
3998 Errors that fall within this category are used to inform the
3999 requester that a request could not be satisfied, and additional
4000 action is required on its part before access is granted.
4002 DIAMETER_MULTI_ROUND_AUTH 1001
4004 This informational error is returned by a Diameter server to
4005 inform the access device that the authentication mechanism being
4006 used requires multiple round trips, and a subsequent request needs
4007 to be issued in order for access to be granted.
4009 7.1.2. Success
4011 Errors that fall within the Success category are used to inform a
4012 peer that a request has been successfully completed.
4014 DIAMETER_SUCCESS 2001
4016 The Request was successfully completed.
4018 DIAMETER_LIMITED_SUCCESS 2002
4020 When returned, the request was successfully completed, but
4021 additional processing is required by the application in order to
4022 provide service to the user.
4024 7.1.3. Protocol Errors
4026 Errors that fall within the Protocol Error category SHOULD be treated
4027 on a per-hop basis, and Diameter proxies MAY attempt to correct the
4028 error, if it is possible. Note that these and only these errors MUST
4029 only be used in answer messages whose 'E' bit is set. To provide
4030 backward compatibility with existing implementations that follow
4031 [RFC3588], some of the error values that have previously been used in
4032 this category by [RFC3588] will not be re-used. Therefore the error
4033 values enumerated here maybe non-sequential.
4035 DIAMETER_UNABLE_TO_DELIVER 3002
4037 This error is given when Diameter can not deliver the message to
4038 the destination, either because no host within the realm
4039 supporting the required application was available to process the
4040 request, or because Destination-Host AVP was given without the
4041 associated Destination-Realm AVP.
4043 DIAMETER_REALM_NOT_SERVED 3003
4045 The intended realm of the request is not recognized.
4047 DIAMETER_TOO_BUSY 3004
4049 When returned, a Diameter node SHOULD attempt to send the message
4050 to an alternate peer. This error MUST only be used when a
4051 specific server is requested, and it cannot provide the requested
4052 service.
4054 DIAMETER_LOOP_DETECTED 3005
4056 An agent detected a loop while trying to get the message to the
4057 intended recipient. The message MAY be sent to an alternate peer,
4058 if one is available, but the peer reporting the error has
4059 identified a configuration problem.
4061 DIAMETER_REDIRECT_INDICATION 3006
4063 A redirect agent has determined that the request could not be
4064 satisfied locally and the initiator of the request should direct
4065 the request directly to the server, whose contact information has
4066 been added to the response. When set, the Redirect-Host AVP MUST
4067 be present.
4069 DIAMETER_APPLICATION_UNSUPPORTED 3007
4071 A request was sent for an application that is not supported.
4073 DIAMETER_INVALID_BIT_IN_HEADER 3011
4075 This error is returned when an unrecognized bit in the Diameter
4076 header is set to one (1).
4078 DIAMETER_INVALID_MESSAGE_LENGTH 3012
4080 This error is returned when a request is received with an invalid
4081 message length.
4083 7.1.4. Transient Failures
4085 Errors that fall within the transient failures category are used to
4086 inform a peer that the request could not be satisfied at the time it
4087 was received, but MAY be able to satisfy the request in the future.
4088 Note that these errors MUST be used in answer messages whose 'E' bit
4089 is not set.
4091 DIAMETER_AUTHENTICATION_REJECTED 4001
4093 The authentication process for the user failed, most likely due to
4094 an invalid password used by the user. Further attempts MUST only
4095 be tried after prompting the user for a new password.
4097 DIAMETER_OUT_OF_SPACE 4002
4099 A Diameter node received the accounting request but was unable to
4100 commit it to stable storage due to a temporary lack of space.
4102 ELECTION_LOST 4003
4104 The peer has determined that it has lost the election process and
4105 has therefore disconnected the transport connection.
4107 7.1.5. Permanent Failures
4109 Errors that fall within the permanent failures category are used to
4110 inform the peer that the request failed, and should not be attempted
4111 again. Note that these errors SHOULD be used in answer messages
4112 whose 'E' bit is not set. In error conditions where it is not
4113 possible or efficient to compose application specific answer grammar
4114 then answer messages with E-bit set and complying to the grammar
4115 described in 7.2 MAY also be used for permanent errors.
4117 To provide backward compatibility with existing implementations that
4118 follow [RFC3588], some of the error values that have previously been
4119 used in this category by [RFC3588] will not be re-used. Therefore
4120 the error values enumerated here maybe non-sequential.
4122 DIAMETER_AVP_UNSUPPORTED 5001
4124 The peer received a message that contained an AVP that is not
4125 recognized or supported and was marked with the Mandatory bit. A
4126 Diameter message with this error MUST contain one or more Failed-
4127 AVP AVP containing the AVPs that caused the failure.
4129 DIAMETER_UNKNOWN_SESSION_ID 5002
4131 The request contained an unknown Session-Id.
4133 DIAMETER_AUTHORIZATION_REJECTED 5003
4135 A request was received for which the user could not be authorized.
4136 This error could occur if the service requested is not permitted
4137 to the user.
4139 DIAMETER_INVALID_AVP_VALUE 5004
4141 The request contained an AVP with an invalid value in its data
4142 portion. A Diameter message indicating this error MUST include
4143 the offending AVPs within a Failed-AVP AVP.
4145 DIAMETER_MISSING_AVP 5005
4147 The request did not contain an AVP that is required by the Command
4148 Code definition. If this value is sent in the Result-Code AVP, a
4149 Failed-AVP AVP SHOULD be included in the message. The Failed-AVP
4150 AVP MUST contain an example of the missing AVP complete with the
4151 Vendor-Id if applicable. The value field of the missing AVP
4152 should be of correct minimum length and contain zeroes.
4154 DIAMETER_RESOURCES_EXCEEDED 5006
4156 A request was received that cannot be authorized because the user
4157 has already expended allowed resources. An example of this error
4158 condition is a user that is restricted to one dial-up PPP port,
4159 attempts to establish a second PPP connection.
4161 DIAMETER_CONTRADICTING_AVPS 5007
4163 The Home Diameter server has detected AVPs in the request that
4164 contradicted each other, and is not willing to provide service to
4165 the user. The Failed-AVP AVPs MUST be present which contains the
4166 AVPs that contradicted each other.
4168 DIAMETER_AVP_NOT_ALLOWED 5008
4170 A message was received with an AVP that MUST NOT be present. The
4171 Failed-AVP AVP MUST be included and contain a copy of the
4172 offending AVP.
4174 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009
4176 A message was received that included an AVP that appeared more
4177 often than permitted in the message definition. The Failed-AVP
4178 AVP MUST be included and contain a copy of the first instance of
4179 the offending AVP that exceeded the maximum number of occurrences
4181 DIAMETER_NO_COMMON_APPLICATION 5010
4183 This error is returned by a Diameter node that is not acting as a
4184 relay when it receives a CER which advertises a set of
4185 applications that it does not support.
4187 DIAMETER_UNSUPPORTED_VERSION 5011
4189 This error is returned when a request was received, whose version
4190 number is unsupported.
4192 DIAMETER_UNABLE_TO_COMPLY 5012
4194 This error is returned when a request is rejected for unspecified
4195 reasons.
4197 DIAMETER_INVALID_AVP_LENGTH 5014
4199 The request contained an AVP with an invalid length. A Diameter
4200 message indicating this error MUST include the offending AVPs
4201 within a Failed-AVP AVP. In cases where the erroneous avp length
4202 value exceeds the message length or is less than the minimum AVP
4203 header length, it is sufficient to include the offending AVP
4204 header and a zero filled payload of the minimum required length
4205 for the payloads data type. If the AVP is a grouped AVP, the
4206 grouped AVP header with an empty payload would be sufficient to
4207 indicate the offending AVP. In the case where the offending AVP
4208 header cannot be fully decoded when avp length is less than the
4209 minimum AVP header length, it is sufficient to include an
4210 offending AVP header that is formulated by padding the incomplete
4211 AVP header with zero up to the minimum AVP header length.
4213 DIAMETER_NO_COMMON_SECURITY 5017
4215 This error is returned when a CER message is received, and there
4216 are no common security mechanisms supported between the peers. A
4217 Capabilities-Exchange-Answer (CEA) MUST be returned with the
4218 Result-Code AVP set to DIAMETER_NO_COMMON_SECURITY.
4220 DIAMETER_UNKNOWN_PEER 5018
4222 A CER was received from an unknown peer.
4224 DIAMETER_COMMAND_UNSUPPORTED 5019
4226 The Request contained a Command-Code that the receiver did not
4227 recognize or support. This MUST be used when a Diameter node
4228 receives an experimental command that it does not understand.
4230 DIAMETER_INVALID_HDR_BITS 5020
4232 A request was received whose bits in the Diameter header were
4233 either set to an invalid combination, or to a value that is
4234 inconsistent with the command code's definition.
4236 DIAMETER_INVALID_AVP_BITS 5021
4238 A request was received that included an AVP whose flag bits are
4239 set to an unrecognized value, or that is inconsistent with the
4240 AVP's definition.
4242 7.2. Error Bit
4244 The 'E' (Error Bit) in the Diameter header is set when the request
4245 caused a protocol-related error (see Section 7.1.3). A message with
4246 the 'E' bit MUST NOT be sent as a response to an answer message.
4247 Note that a message with the 'E' bit set is still subjected to the
4248 processing rules defined in Section 6.2. When set, the answer
4249 message will not conform to the ABNF specification for the command,
4250 and will instead conform to the following ABNF:
4252 Message Format
4254 ::= < Diameter Header: code, ERR [PXY] >
4255 0*1< Session-Id >
4256 { Origin-Host }
4257 { Origin-Realm }
4258 { Result-Code }
4259 [ Origin-State-Id ]
4260 [ Error-Message ]
4261 [ Error-Reporting-Host ]
4262 [ Failed-AVP ]
4263 * [ Proxy-Info ]
4264 * [ AVP ]
4266 Note that the code used in the header is the same than the one found
4267 in the request message, but with the 'R' bit cleared and the 'E' bit
4268 set. The 'P' bit in the header is set to the same value as the one
4269 found in the request message.
4271 7.3. Error-Message AVP
4273 The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY
4274 accompany a Result-Code AVP as a human readable error message. The
4275 Error-Message AVP is not intended to be useful in real-time, and
4276 SHOULD NOT be expected to be parsed by network entities.
4278 7.4. Error-Reporting-Host AVP
4280 The Error-Reporting-Host AVP (AVP Code 294) is of type
4281 DiameterIdentity. This AVP contains the identity of the Diameter
4282 host that sent the Result-Code AVP to a value other than 2001
4283 (Success), only if the host setting the Result-Code is different from
4284 the one encoded in the Origin-Host AVP. This AVP is intended to be
4285 used for troubleshooting purposes, and MUST be set when the Result-
4286 Code AVP indicates a failure.
4288 7.5. Failed-AVP AVP
4290 The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides
4291 debugging information in cases where a request is rejected or not
4292 fully processed due to erroneous information in a specific AVP. The
4293 value of the Result-Code AVP will provide information on the reason
4294 for the Failed-AVP AVP. A Diameter message SHOULD contain only one
4295 Failed-AVP that corresponds to the error indicated by the Result-Code
4296 AVP. For practical purposes, this Failed-AVP would typically refer
4297 to the first AVP processing error that a Diameter node encounters.
4299 The possible reasons for this AVP are the presence of an improperly
4300 constructed AVP, an unsupported or unrecognized AVP, an invalid AVP
4301 value, the omission of a required AVP, the presence of an explicitly
4302 excluded AVP (see tables in Section 10), or the presence of two or
4303 more occurrences of an AVP which is restricted to 0, 1, or 0-1
4304 occurrences.
4306 A Diameter message SHOULD contain one Failed-AVP AVP, containing the
4307 entire AVP that could not be processed successfully. If the failure
4308 reason is omission of a required AVP, an AVP with the missing AVP
4309 code, the missing vendor id, and a zero filled payload of the minimum
4310 required length for the omitted AVP will be added. If the failure
4311 reason is an invalid AVP length where the reported length is less
4312 than the minimum AVP header length or greater than the reported
4313 message length, a copy of the offending AVP header and a zero filled
4314 payload of the minimum required length SHOULD be added.
4316 In the case where the offending AVP is embedded within a grouped AVP,
4317 the Failed-AVP MAY contain the grouped AVP which in turn contains the
4318 single offending AVP. The same method MAY be employed if the grouped
4319 AVP itself is embedded in yet another grouped AVP and so on. In this
4320 case, the Failed-AVP MAY contain the grouped AVP heirarchy up to the
4321 single offending AVP. This enables the recipient to detect the
4322 location of the offending AVP when embedded in a group.
4324 AVP Format
4326 ::= < AVP Header: 279 >
4327 1* {AVP}
4329 7.6. Experimental-Result AVP
4331 The Experimental-Result AVP (AVP Code 297) is of type Grouped, and
4332 indicates whether a particular vendor-specific request was completed
4333 successfully or whether an error occurred. Its Data field has the
4334 following ABNF grammar:
4336 AVP Format
4338 Experimental-Result ::= < AVP Header: 297 >
4339 { Vendor-Id }
4340 { Experimental-Result-Code }
4342 The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies
4343 the vendor responsible for the assignment of the result code which
4344 follows. All Diameter answer messages defined in vendor-specific
4345 applications MUST include either one Result-Code AVP or one
4346 Experimental-Result AVP.
4348 7.7. Experimental-Result-Code AVP
4350 The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32
4351 and contains a vendor-assigned value representing the result of
4352 processing the request.
4354 It is recommended that vendor-specific result codes follow the same
4355 conventions given for the Result-Code AVP regarding the different
4356 types of result codes and the handling of errors (for non 2xxx
4357 values).
4359 8. Diameter User Sessions
4361 In general, Diameter can provide two different types of services to
4362 applications. The first involves authentication and authorization,
4363 and can optionally make use of accounting. The second only makes use
4364 of accounting.
4366 When a service makes use of the authentication and/or authorization
4367 portion of an application, and a user requests access to the network,
4368 the Diameter client issues an auth request to its local server. The
4369 auth request is defined in a service specific Diameter application
4370 (e.g., NASREQ). The request contains a Session-Id AVP, which is used
4371 in subsequent messages (e.g., subsequent authorization, accounting,
4372 etc) relating to the user's session. The Session-Id AVP is a means
4373 for the client and servers to correlate a Diameter message with a
4374 user session.
4376 When a Diameter server authorizes a user to use network resources for
4377 a finite amount of time, and it is willing to extend the
4378 authorization via a future request, it MUST add the Authorization-
4379 Lifetime AVP to the answer message. The Authorization-Lifetime AVP
4380 defines the maximum number of seconds a user MAY make use of the
4381 resources before another authorization request is expected by the
4382 server. The Auth-Grace-Period AVP contains the number of seconds
4383 following the expiration of the Authorization-Lifetime, after which
4384 the server will release all state information related to the user's
4385 session. Note that if payment for services is expected by the
4386 serving realm from the user's home realm, the Authorization-Lifetime
4387 AVP, combined with the Auth-Grace-Period AVP, implies the maximum
4388 length of the session the home realm is willing to be fiscally
4389 responsible for. Services provided past the expiration of the
4390 Authorization-Lifetime and Auth-Grace-Period AVPs are the
4391 responsibility of the access device. Of course, the actual cost of
4392 services rendered is clearly outside the scope of the protocol.
4394 An access device that does not expect to send a re-authorization or a
4395 session termination request to the server MAY include the Auth-
4396 Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint
4397 to the server. If the server accepts the hint, it agrees that since
4398 no session termination message will be received once service to the
4399 user is terminated, it cannot maintain state for the session. If the
4400 answer message from the server contains a different value in the
4401 Auth-Session-State AVP (or the default value if the AVP is absent),
4402 the access device MUST follow the server's directives. Note that the
4403 value NO_STATE_MAINTAINED MUST NOT be set in subsequent re-
4404 authorization requests and answers.
4406 The base protocol does not include any authorization request
4407 messages, since these are largely application-specific and are
4408 defined in a Diameter application document. However, the base
4409 protocol does define a set of messages that is used to terminate user
4410 sessions. These are used to allow servers that maintain state
4411 information to free resources.
4413 When a service only makes use of the Accounting portion of the
4414 Diameter protocol, even in combination with an application, the
4415 Session-Id is still used to identify user sessions. However, the
4416 session termination messages are not used, since a session is
4417 signaled as being terminated by issuing an accounting stop message.
4419 Diameter may also be used for services that cannot be easily
4420 categorized as authentication, authorization or accounting (e.g.,
4421 certain 3GPP IMS interfaces). In such cases, the finite state
4422 machine defined in subsequent sections may not be applicable.
4423 Therefore, the applications itself MAY need to define its own finite
4424 state machine. However, such application specific statemachines MUST
4425 comply with general Diameter user session requirements such co-
4426 relating all message exchanges via Session-Id AVP.
4428 8.1. Authorization Session State Machine
4430 This section contains a set of finite state machines, representing
4431 the life cycle of Diameter sessions, and which MUST be observed by
4432 all Diameter implementations that make use of the authentication
4433 and/or authorization portion of a Diameter application. The term
4434 Service-Specific below refers to a message defined in a Diameter
4435 application (e.g., Mobile IPv4, NASREQ).
4437 There are four different authorization session state machines
4438 supported in the Diameter base protocol. The first two describe a
4439 session in which the server is maintaining session state, indicated
4440 by the value of the Auth-Session-State AVP (or its absence). One
4441 describes the session from a client perspective, the other from a
4442 server perspective. The second two state machines are used when the
4443 server does not maintain session state. Here again, one describes
4444 the session from a client perspective, the other from a server
4445 perspective.
4447 When a session is moved to the Idle state, any resources that were
4448 allocated for the particular session must be released. Any event not
4449 listed in the state machines MUST be considered as an error
4450 condition, and an answer, if applicable, MUST be returned to the
4451 originator of the message.
4453 In the case that an application does not support re-auth, the state
4454 transitions related to server-initiated re-auth when both client and
4455 server sessions maintains state (e.g., Send RAR, Pending, Receive
4456 RAA) MAY be ignored.
4458 In the state table, the event 'Failure to send X' means that the
4459 Diameter agent is unable to send command X to the desired
4460 destination. This could be due to the peer being down, or due to the
4461 peer sending back a transient failure or temporary protocol error
4462 notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the
4463 Result-Code AVP of the corresponding Answer command. The event 'X
4464 successfully sent' is the complement of 'Failure to send X'.
4466 The following state machine is observed by a client when state is
4467 maintained on the server:
4469 CLIENT, STATEFUL
4470 State Event Action New State
4471 -------------------------------------------------------------
4472 Idle Client or Device Requests Send Pending
4473 access service
4474 specific
4475 auth req
4477 Idle ASR Received Send ASA Idle
4478 for unknown session with
4479 Result-Code
4480 = UNKNOWN_
4481 SESSION_ID
4483 Idle RAR Received Send RAA Idle
4484 for unknown session with
4485 Result-Code
4486 = UNKNOWN_
4487 SESSION_ID
4489 Pending Successful Service-specific Grant Open
4490 authorization answer Access
4491 received with default
4492 Auth-Session-State value
4494 Pending Successful Service-specific Sent STR Discon
4495 authorization answer received
4496 but service not provided
4498 Pending Error processing successful Sent STR Discon
4499 Service-specific authorization
4500 answer
4502 Pending Failed Service-specific Cleanup Idle
4503 authorization answer received
4505 Open User or client device Send Open
4506 requests access to service service
4507 specific
4508 auth req
4510 Open Successful Service-specific Provide Open
4511 authorization answer received Service
4513 Open Failed Service-specific Discon. Idle
4514 authorization answer user/device
4515 received.
4517 Open RAR received and client will Send RAA Open
4518 perform subsequent re-auth with
4519 Result-Code
4520 = SUCCESS
4522 Open RAR received and client will Send RAA Idle
4523 not perform subsequent with
4524 re-auth Result-Code
4525 != SUCCESS,
4526 Discon.
4527 user/device
4529 Open Session-Timeout Expires on Send STR Discon
4530 Access Device
4532 Open ASR Received, Send ASA Discon
4533 client will comply with with
4534 request to end the session Result-Code
4535 = SUCCESS,
4536 Send STR.
4538 Open ASR Received, Send ASA Open
4539 client will not comply with with
4540 request to end the session Result-Code
4541 != SUCCESS
4543 Open Authorization-Lifetime + Send STR Discon
4544 Auth-Grace-Period expires on
4545 access device
4547 Discon ASR Received Send ASA Discon
4549 Discon STA Received Discon. Idle
4550 user/device
4552 The following state machine is observed by a server when it is
4553 maintaining state for the session:
4555 SERVER, STATEFUL
4556 State Event Action New State
4557 -------------------------------------------------------------
4558 Idle Service-specific authorization Send Open
4559 request received, and successful
4560 user is authorized serv.
4561 specific
4562 answer
4564 Idle Service-specific authorization Send Idle
4565 request received, and failed serv.
4566 user is not authorized specific
4567 answer
4569 Open Service-specific authorization Send Open
4570 request received, and user successful
4571 is authorized serv. specific
4572 answer
4574 Open Service-specific authorization Send Idle
4575 request received, and user failed serv.
4576 is not authorized specific
4577 answer,
4578 Cleanup
4580 Open Home server wants to confirm Send RAR Pending
4581 authentication and/or
4582 authorization of the user
4584 Pending Received RAA with a failed Cleanup Idle
4585 Result-Code
4587 Pending Received RAA with Result-Code Update Open
4588 = SUCCESS session
4590 Open Home server wants to Send ASR Discon
4591 terminate the service
4593 Open Authorization-Lifetime (and Cleanup Idle
4594 Auth-Grace-Period) expires
4595 on home server.
4597 Open Session-Timeout expires on Cleanup Idle
4598 home server
4600 Discon Failure to send ASR Wait, Discon
4601 resend ASR
4603 Discon ASR successfully sent and Cleanup Idle
4604 ASA Received with Result-Code
4606 Not ASA Received None No Change.
4607 Discon
4609 Any STR Received Send STA, Idle
4610 Cleanup.
4612 The following state machine is observed by a client when state is not
4613 maintained on the server:
4615 CLIENT, STATELESS
4616 State Event Action New State
4617 -------------------------------------------------------------
4618 Idle Client or Device Requests Send Pending
4619 access service
4620 specific
4621 auth req
4623 Pending Successful Service-specific Grant Open
4624 authorization answer Access
4625 received with Auth-Session-
4626 State set to
4627 NO_STATE_MAINTAINED
4629 Pending Failed Service-specific Cleanup Idle
4630 authorization answer
4631 received
4633 Open Session-Timeout Expires on Discon. Idle
4634 Access Device user/device
4636 Open Service to user is terminated Discon. Idle
4637 user/device
4639 The following state machine is observed by a server when it is not
4640 maintaining state for the session:
4642 SERVER, STATELESS
4643 State Event Action New State
4644 -------------------------------------------------------------
4645 Idle Service-specific authorization Send serv. Idle
4646 request received, and specific
4647 successfully processed answer
4649 8.2. Accounting Session State Machine
4651 The following state machines MUST be supported for applications that
4652 have an accounting portion or that require only accounting services.
4653 The first state machine is to be observed by clients.
4655 See Section 9.7 for Accounting Command Codes and Section 9.8 for
4656 Accounting AVPs.
4658 The server side in the accounting state machine depends in some cases
4659 on the particular application. The Diameter base protocol defines a
4660 default state machine that MUST be followed by all applications that
4661 have not specified other state machines. This is the second state
4662 machine in this section described below.
4664 The default server side state machine requires the reception of
4665 accounting records in any order and at any time, and does not place
4666 any standards requirement on the processing of these records.
4667 Implementations of Diameter MAY perform checking, ordering,
4668 correlation, fraud detection, and other tasks based on these records.
4669 Both base Diameter AVPs as well as application specific AVPs MAY be
4670 inspected as a part of these tasks. The tasks can happen either
4671 immediately after record reception or in a post-processing phase.
4672 However, as these tasks are typically application or even policy
4673 dependent, they are not standardized by the Diameter specifications.
4674 Applications MAY define requirements on when to accept accounting
4675 records based on the used value of Accounting-Realtime-Required AVP,
4676 credit limits checks, and so on.
4678 However, the Diameter base protocol defines one optional server side
4679 state machine that MAY be followed by applications that require
4680 keeping track of the session state at the accounting server. Note
4681 that such tracking is incompatible with the ability to sustain long
4682 duration connectivity problems. Therefore, the use of this state
4683 machine is recommended only in applications where the value of the
4684 Accounting-Realtime-Required AVP is DELIVER_AND_GRANT, and hence
4685 accounting connectivity problems are required to cause the serviced
4686 user to be disconnected. Otherwise, records produced by the client
4687 may be lost by the server which no longer accepts them after the
4688 connectivity is re-established. This state machine is the third
4689 state machine in this section. The state machine is supervised by a
4690 supervision session timer Ts, which the value should be reasonably
4691 higher than the Acct_Interim_Interval value. Ts MAY be set to two
4692 times the value of the Acct_Interim_Interval so as to avoid the
4693 accounting session in the Diameter server to change to Idle state in
4694 case of short transient network failure.
4696 Any event not listed in the state machines MUST be considered as an
4697 error condition, and a corresponding answer, if applicable, MUST be
4698 returned to the originator of the message.
4700 In the state table, the event 'Failure to send' means that the
4701 Diameter client is unable to communicate with the desired
4702 destination. This could be due to the peer being down, or due to the
4703 peer sending back a transient failure or temporary protocol error
4704 notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or
4705 DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting
4706 Answer command.
4708 The event 'Failed answer' means that the Diameter client received a
4709 non-transient failure notification in the Accounting Answer command.
4711 Note that the action 'Disconnect user/dev' MUST have an effect also
4712 to the authorization session state table, e.g., cause the STR message
4713 to be sent, if the given application has both authentication/
4714 authorization and accounting portions.
4716 The states PendingS, PendingI, PendingL, PendingE and PendingB stand
4717 for pending states to wait for an answer to an accounting request
4718 related to a Start, Interim, Stop, Event or buffered record,
4719 respectively.
4721 CLIENT, ACCOUNTING
4722 State Event Action New State
4723 -------------------------------------------------------------
4724 Idle Client or device requests Send PendingS
4725 access accounting
4726 start req.
4728 Idle Client or device requests Send PendingE
4729 a one-time service accounting
4730 event req
4732 Idle Records in storage Send PendingB
4733 record
4735 PendingS Successful accounting Open
4736 start answer received
4738 PendingS Failure to send and buffer Store Open
4739 space available and realtime Start
4740 not equal to DELIVER_AND_GRANT Record
4742 PendingS Failure to send and no buffer Open
4743 space available and realtime
4744 equal to GRANT_AND_LOSE
4746 PendingS Failure to send and no buffer Disconnect Idle
4747 space available and realtime user/dev
4748 not equal to
4749 GRANT_AND_LOSE
4751 PendingS Failed accounting start answer Open
4752 received and realtime equal
4753 to GRANT_AND_LOSE
4755 PendingS Failed accounting start answer Disconnect Idle
4756 received and realtime not user/dev
4757 equal to GRANT_AND_LOSE
4759 PendingS User service terminated Store PendingS
4760 stop
4761 record
4763 Open Interim interval elapses Send PendingI
4764 accounting
4765 interim
4766 record
4767 Open User service terminated Send PendingL
4768 accounting
4769 stop req.
4771 PendingI Successful accounting interim Open
4772 answer received
4774 PendingI Failure to send and (buffer Store Open
4775 space available or old record interim
4776 can be overwritten) and record
4777 realtime not equal to
4778 DELIVER_AND_GRANT
4780 PendingI Failure to send and no buffer Open
4781 space available and realtime
4782 equal to GRANT_AND_LOSE
4784 PendingI Failure to send and no buffer Disconnect Idle
4785 space available and realtime user/dev
4786 not equal to GRANT_AND_LOSE
4788 PendingI Failed accounting interim Open
4789 answer received and realtime
4790 equal to GRANT_AND_LOSE
4792 PendingI Failed accounting interim Disconnect Idle
4793 answer received and realtime user/dev
4794 not equal to GRANT_AND_LOSE
4796 PendingI User service terminated Store PendingI
4797 stop
4798 record
4799 PendingE Successful accounting Idle
4800 event answer received
4802 PendingE Failure to send and buffer Store Idle
4803 space available event
4804 record
4806 PendingE Failure to send and no buffer Idle
4807 space available
4809 PendingE Failed accounting event answer Idle
4810 received
4812 PendingB Successful accounting answer Delete Idle
4813 received record
4815 PendingB Failure to send Idle
4817 PendingB Failed accounting answer Delete Idle
4818 received record
4820 PendingL Successful accounting Idle
4821 stop answer received
4823 PendingL Failure to send and buffer Store Idle
4824 space available stop
4825 record
4827 PendingL Failure to send and no buffer Idle
4828 space available
4830 PendingL Failed accounting stop answer Idle
4831 received
4833 SERVER, STATELESS ACCOUNTING
4834 State Event Action New State
4835 -------------------------------------------------------------
4837 Idle Accounting start request Send Idle
4838 received, and successfully accounting
4839 processed. start
4840 answer
4842 Idle Accounting event request Send Idle
4843 received, and successfully accounting
4844 processed. event
4845 answer
4847 Idle Interim record received, Send Idle
4848 and successfully processed. accounting
4849 interim
4850 answer
4852 Idle Accounting stop request Send Idle
4853 received, and successfully accounting
4854 processed stop answer
4856 Idle Accounting request received, Send Idle
4857 no space left to store accounting
4858 records answer,
4859 Result-Code
4860 = OUT_OF_
4861 SPACE
4863 SERVER, STATEFUL ACCOUNTING
4864 State Event Action New State
4865 -------------------------------------------------------------
4867 Idle Accounting start request Send Open
4868 received, and successfully accounting
4869 processed. start
4870 answer,
4871 Start Ts
4873 Idle Accounting event request Send Idle
4874 received, and successfully accounting
4875 processed. event
4876 answer
4878 Idle Accounting request received, Send Idle
4879 no space left to store accounting
4880 records answer,
4881 Result-Code
4882 = OUT_OF_
4883 SPACE
4885 Open Interim record received, Send Open
4886 and successfully processed. accounting
4887 interim
4888 answer,
4889 Restart Ts
4891 Open Accounting stop request Send Idle
4892 received, and successfully accounting
4893 processed stop answer,
4894 Stop Ts
4896 Open Accounting request received, Send Idle
4897 no space left to store accounting
4898 records answer,
4899 Result-Code
4900 = OUT_OF_
4901 SPACE,
4902 Stop Ts
4904 Open Session supervision timer Ts Stop Ts Idle
4905 expired
4907 8.3. Server-Initiated Re-Auth
4909 A Diameter server may initiate a re-authentication and/or re-
4910 authorization service for a particular session by issuing a Re-Auth-
4911 Request (RAR).
4913 For example, for pre-paid services, the Diameter server that
4914 originally authorized a session may need some confirmation that the
4915 user is still using the services.
4917 An access device that receives a RAR message with Session-Id equal to
4918 a currently active session MUST initiate a re-auth towards the user,
4919 if the service supports this particular feature. Each Diameter
4920 application MUST state whether service-initiated re-auth is
4921 supported, since some applications do not allow access devices to
4922 prompt the user for re-auth.
4924 8.3.1. Re-Auth-Request
4926 The Re-Auth-Request (RAR), indicated by the Command-Code set to 258
4927 and the message flags' 'R' bit set, may be sent by any server to the
4928 access device that is providing session service, to request that the
4929 user be re-authenticated and/or re-authorized.
4931 Message Format
4933 ::= < Diameter Header: 258, REQ, PXY >
4934 < Session-Id >
4935 { Origin-Host }
4936 { Origin-Realm }
4937 { Destination-Realm }
4938 { Destination-Host }
4939 { Auth-Application-Id }
4940 { Re-Auth-Request-Type }
4941 [ User-Name ]
4942 [ Origin-State-Id ]
4943 * [ Proxy-Info ]
4944 * [ Route-Record ]
4945 * [ AVP ]
4947 8.3.2. Re-Auth-Answer
4949 The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258
4950 and the message flags' 'R' bit clear, is sent in response to the RAR.
4951 The Result-Code AVP MUST be present, and indicates the disposition of
4952 the request.
4954 A successful RAA message MUST be followed by an application-specific
4955 authentication and/or authorization message.
4957 Message Format
4959 ::= < Diameter Header: 258, PXY >
4960 < Session-Id >
4961 { Result-Code }
4962 { Origin-Host }
4963 { Origin-Realm }
4964 [ User-Name ]
4965 [ Origin-State-Id ]
4966 [ Error-Message ]
4967 [ Error-Reporting-Host ]
4968 [ Failed-AVP ]
4969 * [ Redirect-Host ]
4970 [ Redirect-Host-Usage ]
4971 [ Redirect-Max-Cache-Time ]
4972 * [ Proxy-Info ]
4973 * [ AVP ]
4975 8.4. Session Termination
4977 It is necessary for a Diameter server that authorized a session, for
4978 which it is maintaining state, to be notified when that session is no
4979 longer active, both for tracking purposes as well as to allow
4980 stateful agents to release any resources that they may have provided
4981 for the user's session. For sessions whose state is not being
4982 maintained, this section is not used.
4984 When a user session that required Diameter authorization terminates,
4985 the access device that provided the service MUST issue a Session-
4986 Termination-Request (STR) message to the Diameter server that
4987 authorized the service, to notify it that the session is no longer
4988 active. An STR MUST be issued when a user session terminates for any
4989 reason, including user logoff, expiration of Session-Timeout,
4990 administrative action, termination upon receipt of an Abort-Session-
4991 Request (see below), orderly shutdown of the access device, etc.
4993 The access device also MUST issue an STR for a session that was
4994 authorized but never actually started. This could occur, for
4995 example, due to a sudden resource shortage in the access device, or
4996 because the access device is unwilling to provide the type of service
4997 requested in the authorization, or because the access device does not
4998 support a mandatory AVP returned in the authorization, etc.
5000 It is also possible that a session that was authorized is never
5001 actually started due to action of a proxy. For example, a proxy may
5002 modify an authorization answer, converting the result from success to
5003 failure, prior to forwarding the message to the access device. If
5004 the answer did not contain an Auth-Session-State AVP with the value
5005 NO_STATE_MAINTAINED, a proxy that causes an authorized session not to
5006 be started MUST issue an STR to the Diameter server that authorized
5007 the session, since the access device has no way of knowing that the
5008 session had been authorized.
5010 A Diameter server that receives an STR message MUST clean up
5011 resources (e.g., session state) associated with the Session-Id
5012 specified in the STR, and return a Session-Termination-Answer.
5014 A Diameter server also MUST clean up resources when the Session-
5015 Timeout expires, or when the Authorization-Lifetime and the Auth-
5016 Grace-Period AVPs expires without receipt of a re-authorization
5017 request, regardless of whether an STR for that session is received.
5018 The access device is not expected to provide service beyond the
5019 expiration of these timers; thus, expiration of either of these
5020 timers implies that the access device may have unexpectedly shut
5021 down.
5023 8.4.1. Session-Termination-Request
5025 The Session-Termination-Request (STR), indicated by the Command-Code
5026 set to 275 and the Command Flags' 'R' bit set, is sent by the access
5027 device to inform the Diameter Server that an authenticated and/or
5028 authorized session is being terminated.
5030 Message Format
5032 ::= < Diameter Header: 275, REQ, PXY >
5033 < Session-Id >
5034 { Origin-Host }
5035 { Origin-Realm }
5036 { Destination-Realm }
5037 { Auth-Application-Id }
5038 { Termination-Cause }
5039 [ User-Name ]
5040 [ Destination-Host ]
5041 * [ Class ]
5042 [ Origin-State-Id ]
5043 * [ Proxy-Info ]
5044 * [ Route-Record ]
5045 * [ AVP ]
5047 8.4.2. Session-Termination-Answer
5049 The Session-Termination-Answer (STA), indicated by the Command-Code
5050 set to 275 and the message flags' 'R' bit clear, is sent by the
5051 Diameter Server to acknowledge the notification that the session has
5052 been terminated. The Result-Code AVP MUST be present, and MAY
5053 contain an indication that an error occurred while servicing the STR.
5055 Upon sending or receipt of the STA, the Diameter Server MUST release
5056 all resources for the session indicated by the Session-Id AVP. Any
5057 intermediate server in the Proxy-Chain MAY also release any
5058 resources, if necessary.
5060 Message Format
5062 ::= < Diameter Header: 275, PXY >
5063 < Session-Id >
5064 { Result-Code }
5065 { Origin-Host }
5066 { Origin-Realm }
5067 [ User-Name ]
5068 * [ Class ]
5069 [ Error-Message ]
5070 [ Error-Reporting-Host ]
5071 [ Failed-AVP ]
5072 [ Origin-State-Id ]
5073 * [ Redirect-Host ]
5074 [ Redirect-Host-Usage ]
5075 ^
5076 [ Redirect-Max-Cache-Time ]
5077 * [ Proxy-Info ]
5078 * [ AVP ]
5080 8.5. Aborting a Session
5082 A Diameter server may request that the access device stop providing
5083 service for a particular session by issuing an Abort-Session-Request
5084 (ASR).
5086 For example, the Diameter server that originally authorized the
5087 session may be required to cause that session to be stopped for
5088 credit or other reasons that were not anticipated when the session
5089 was first authorized. On the other hand, an operator may maintain a
5090 management server for the purpose of issuing ASRs to administratively
5091 remove users from the network.
5093 An access device that receives an ASR with Session-ID equal to a
5094 currently active session MAY stop the session. Whether the access
5095 device stops the session or not is implementation- and/or
5096 configuration-dependent. For example, an access device may honor
5097 ASRs from certain agents only. In any case, the access device MUST
5098 respond with an Abort-Session-Answer, including a Result-Code AVP to
5099 indicate what action it took.
5101 Note that if the access device does stop the session upon receipt of
5102 an ASR, it issues an STR to the authorizing server (which may or may
5103 not be the agent issuing the ASR) just as it would if the session
5104 were terminated for any other reason.
5106 8.5.1. Abort-Session-Request
5108 The Abort-Session-Request (ASR), indicated by the Command-Code set to
5109 274 and the message flags' 'R' bit set, may be sent by any server to
5110 the access device that is providing session service, to request that
5111 the session identified by the Session-Id be stopped.
5113 Message Format
5115 ::= < Diameter Header: 274, REQ, PXY >
5116 < Session-Id >
5117 { Origin-Host }
5118 { Origin-Realm }
5119 { Destination-Realm }
5120 { Destination-Host }
5121 { Auth-Application-Id }
5122 [ User-Name ]
5123 [ Origin-State-Id ]
5124 * [ Proxy-Info ]
5125 * [ Route-Record ]
5126 * [ AVP ]
5128 8.5.2. Abort-Session-Answer
5130 The Abort-Session-Answer (ASA), indicated by the Command-Code set to
5131 274 and the message flags' 'R' bit clear, is sent in response to the
5132 ASR. The Result-Code AVP MUST be present, and indicates the
5133 disposition of the request.
5135 If the session identified by Session-Id in the ASR was successfully
5136 terminated, Result-Code is set to DIAMETER_SUCCESS. If the session
5137 is not currently active, Result-Code is set to
5138 DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the
5139 session for any other reason, Result-Code is set to
5140 DIAMETER_UNABLE_TO_COMPLY.
5142 Message Format
5144 ::= < Diameter Header: 274, PXY >
5145 < Session-Id >
5146 { Result-Code }
5147 { Origin-Host }
5148 { Origin-Realm }
5149 [ User-Name ]
5150 [ Origin-State-Id ]
5151 [ Error-Message ]
5152 [ Error-Reporting-Host ]
5153 [ Failed-AVP ]
5154 * [ Redirect-Host ]
5155 [ Redirect-Host-Usage ]
5156 [ Redirect-Max-Cache-Time ]
5157 * [ Proxy-Info ]
5158 * [ AVP ]
5160 8.6. Inferring Session Termination from Origin-State-Id
5162 Origin-State-Id is used to allow rapid detection of terminated
5163 sessions for which no STR would have been issued, due to
5164 unanticipated shutdown of an access device.
5166 By including Origin-State-Id in CER/CEA messages, an access device
5167 allows a next-hop server to determine immediately upon connection
5168 whether the device has lost its sessions since the last connection.
5170 By including Origin-State-Id in request messages, an access device
5171 also allows a server with which it communicates via proxy to make
5172 such a determination. However, a server that is not directly
5173 connected with the access device will not discover that the access
5174 device has been restarted unless and until it receives a new request
5175 from the access device. Thus, use of this mechanism across proxies
5176 is opportunistic rather than reliable, but useful nonetheless.
5178 When a Diameter server receives an Origin-State-Id that is greater
5179 than the Origin-State-Id previously received from the same issuer, it
5180 may assume that the issuer has lost state since the previous message
5181 and that all sessions that were active under the lower Origin-State-
5182 Id have been terminated. The Diameter server MAY clean up all
5183 session state associated with such lost sessions, and MAY also issues
5184 STRs for all such lost sessions that were authorized on upstream
5185 servers, to allow session state to be cleaned up globally.
5187 8.7. Auth-Request-Type AVP
5189 The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is
5190 included in application-specific auth requests to inform the peers
5191 whether a user is to be authenticated only, authorized only or both.
5192 Note any value other than both MAY cause RADIUS interoperability
5193 issues. The following values are defined:
5195 AUTHENTICATE_ONLY 1
5197 The request being sent is for authentication only, and MUST
5198 contain the relevant application specific authentication AVPs that
5199 are needed by the Diameter server to authenticate the user.
5201 AUTHORIZE_ONLY 2
5203 The request being sent is for authorization only, and MUST contain
5204 the application specific authorization AVPs that are necessary to
5205 identify the service being requested/offered.
5207 AUTHORIZE_AUTHENTICATE 3
5209 The request contains a request for both authentication and
5210 authorization. The request MUST include both the relevant
5211 application specific authentication information, and authorization
5212 information necessary to identify the service being requested/
5213 offered.
5215 8.8. Session-Id AVP
5217 The Session-Id AVP (AVP Code 263) is of type UTF8String and is used
5218 to identify a specific session (see Section 8). All messages
5219 pertaining to a specific session MUST include only one Session-Id AVP
5220 and the same value MUST be used throughout the life of a session.
5221 When present, the Session-Id SHOULD appear immediately following the
5222 Diameter Header (see Section 3).
5224 The Session-Id MUST be globally and eternally unique, as it is meant
5225 to uniquely identify a user session without reference to any other
5226 information, and may be needed to correlate historical authentication
5227 information with accounting information. The Session-Id includes a
5228 mandatory portion and an implementation-defined portion; a
5229 recommended format for the implementation-defined portion is outlined
5230 below.
5232 The Session-Id MUST begin with the sender's identity encoded in the
5233 DiameterIdentity type (see Section 4.4). The remainder of the
5234 Session-Id is delimited by a ";" character, and MAY be any sequence
5235 that the client can guarantee to be eternally unique; however, the
5236 following format is recommended, (square brackets [] indicate an
5237 optional element):
5239 ;;[;]
5241 and are decimal representations of the
5242 high and low 32 bits of a monotonically increasing 64-bit value. The
5243 64-bit value is rendered in two part to simplify formatting by 32-bit
5244 processors. At startup, the high 32 bits of the 64-bit value MAY be
5245 initialized to the time, and the low 32 bits MAY be initialized to
5246 zero. This will for practical purposes eliminate the possibility of
5247 overlapping Session-Ids after a reboot, assuming the reboot process
5248 takes longer than a second. Alternatively, an implementation MAY
5249 keep track of the increasing value in non-volatile memory.
5251 is implementation specific but may include a modem's
5252 device Id, a layer 2 address, timestamp, etc.
5254 Example, in which there is no optional value:
5256 accesspoint7.acme.com;1876543210;523
5258 Example, in which there is an optional value:
5260 accesspoint7.acme.com;1876543210;523;mobile@200.1.1.88
5262 The Session-Id is created by the Diameter application initiating the
5263 session, which in most cases is done by the client. Note that a
5264 Session-Id MAY be used for both the authorization and accounting
5265 commands of a given application.
5267 8.9. Authorization-Lifetime AVP
5269 The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32
5270 and contains the maximum number of seconds of service to be provided
5271 to the user before the user is to be re-authenticated and/or re-
5272 authorized. Great care should be taken when the Authorization-
5273 Lifetime value is determined, since a low, non-zero, value could
5274 create significant Diameter traffic, which could congest both the
5275 network and the agents.
5277 A value of zero (0) means that immediate re-auth is necessary by the
5278 access device. This is typically used in cases where multiple
5279 authentication methods are used, and a successful auth response with
5280 this AVP set to zero is used to signal that the next authentication
5281 method is to be immediately initiated. The absence of this AVP, or a
5282 value of all ones (meaning all bits in the 32 bit field are set to
5283 one) means no re-auth is expected.
5285 If both this AVP and the Session-Timeout AVP are present in a
5286 message, the value of the latter MUST NOT be smaller than the
5287 Authorization-Lifetime AVP.
5289 An Authorization-Lifetime AVP MAY be present in re-authorization
5290 messages, and contains the number of seconds the user is authorized
5291 to receive service from the time the re-auth answer message is
5292 received by the access device.
5294 This AVP MAY be provided by the client as a hint of the maximum
5295 lifetime that it is willing to accept. However, the server MAY
5296 return a value that is equal to, or smaller, than the one provided by
5297 the client.
5299 8.10. Auth-Grace-Period AVP
5301 The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and
5302 contains the number of seconds the Diameter server will wait
5303 following the expiration of the Authorization-Lifetime AVP before
5304 cleaning up resources for the session.
5306 8.11. Auth-Session-State AVP
5308 The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and
5309 specifies whether state is maintained for a particular session. The
5310 client MAY include this AVP in requests as a hint to the server, but
5311 the value in the server's answer message is binding. The following
5312 values are supported:
5314 STATE_MAINTAINED 0
5316 This value is used to specify that session state is being
5317 maintained, and the access device MUST issue a session termination
5318 message when service to the user is terminated. This is the
5319 default value.
5321 NO_STATE_MAINTAINED 1
5323 This value is used to specify that no session termination messages
5324 will be sent by the access device upon expiration of the
5325 Authorization-Lifetime.
5327 8.12. Re-Auth-Request-Type AVP
5329 The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and
5330 is included in application-specific auth answers to inform the client
5331 of the action expected upon expiration of the Authorization-Lifetime.
5332 If the answer message contains an Authorization-Lifetime AVP with a
5333 positive value, the Re-Auth-Request-Type AVP MUST be present in an
5334 answer message. The following values are defined:
5336 AUTHORIZE_ONLY 0
5338 An authorization only re-auth is expected upon expiration of the
5339 Authorization-Lifetime. This is the default value if the AVP is
5340 not present in answer messages that include the Authorization-
5341 Lifetime.
5343 AUTHORIZE_AUTHENTICATE 1
5345 An authentication and authorization re-auth is expected upon
5346 expiration of the Authorization-Lifetime.
5348 8.13. Session-Timeout AVP
5350 The Session-Timeout AVP (AVP Code 27) [RFC2865] is of type Unsigned32
5351 and contains the maximum number of seconds of service to be provided
5352 to the user before termination of the session. When both the
5353 Session-Timeout and the Authorization-Lifetime AVPs are present in an
5354 answer message, the former MUST be equal to or greater than the value
5355 of the latter.
5357 A session that terminates on an access device due to the expiration
5358 of the Session-Timeout MUST cause an STR to be issued, unless both
5359 the access device and the home server had previously agreed that no
5360 session termination messages would be sent (see Section 8.9).
5362 A Session-Timeout AVP MAY be present in a re-authorization answer
5363 message, and contains the remaining number of seconds from the
5364 beginning of the re-auth.
5366 A value of zero, or the absence of this AVP, means that this session
5367 has an unlimited number of seconds before termination.
5369 This AVP MAY be provided by the client as a hint of the maximum
5370 timeout that it is willing to accept. However, the server MAY return
5371 a value that is equal to, or smaller, than the one provided by the
5372 client.
5374 8.14. User-Name AVP
5376 The User-Name AVP (AVP Code 1) [RFC2865] is of type UTF8String, which
5377 contains the User-Name, in a format consistent with the NAI
5378 specification [RFC4282].
5380 8.15. Termination-Cause AVP
5382 The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and
5383 is used to indicate the reason why a session was terminated on the
5384 access device. The following values are defined:
5386 DIAMETER_LOGOUT 1
5388 The user initiated a disconnect
5390 DIAMETER_SERVICE_NOT_PROVIDED 2
5392 This value is used when the user disconnected prior to the receipt
5393 of the authorization answer message.
5395 DIAMETER_BAD_ANSWER 3
5397 This value indicates that the authorization answer received by the
5398 access device was not processed successfully.
5400 DIAMETER_ADMINISTRATIVE 4
5402 The user was not granted access, or was disconnected, due to
5403 administrative reasons, such as the receipt of a Abort-Session-
5404 Request message.
5406 DIAMETER_LINK_BROKEN 5
5408 The communication to the user was abruptly disconnected.
5410 DIAMETER_AUTH_EXPIRED 6
5412 The user's access was terminated since its authorized session time
5413 has expired.
5415 DIAMETER_USER_MOVED 7
5417 The user is receiving services from another access device.
5419 DIAMETER_SESSION_TIMEOUT 8
5421 The user's session has timed out, and service has been terminated.
5423 8.16. Origin-State-Id AVP
5425 The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a
5426 monotonically increasing value that is advanced whenever a Diameter
5427 entity restarts with loss of previous state, for example upon reboot.
5428 Origin-State-Id MAY be included in any Diameter message, including
5429 CER.
5431 A Diameter entity issuing this AVP MUST create a higher value for
5432 this AVP each time its state is reset. A Diameter entity MAY set
5433 Origin-State-Id to the time of startup, or it MAY use an incrementing
5434 counter retained in non-volatile memory across restarts.
5436 The Origin-State-Id, if present, MUST reflect the state of the entity
5437 indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST
5438 either remove Origin-State-Id or modify it appropriately as well.
5439 Typically, Origin-State-Id is used by an access device that always
5440 starts up with no active sessions; that is, any session active prior
5441 to restart will have been lost. By including Origin-State-Id in a
5442 message, it allows other Diameter entities to infer that sessions
5443 associated with a lower Origin-State-Id are no longer active. If an
5444 access device does not intend for such inferences to be made, it MUST
5445 either not include Origin-State-Id in any message, or set its value
5446 to 0.
5448 8.17. Session-Binding AVP
5450 The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY
5451 be present in application-specific authorization answer messages. If
5452 present, this AVP MAY inform the Diameter client that all future
5453 application-specific re-auth messages for this session MUST be sent
5454 to the same authorization server. This AVP MAY also specify that a
5455 Session-Termination-Request message for this session MUST be sent to
5456 the same authorizing server.
5458 This field is a bit mask, and the following bits have been defined:
5460 RE_AUTH 1
5462 When set, future re-auth messages for this session MUST NOT
5463 include the Destination-Host AVP. When cleared, the default
5464 value, the Destination-Host AVP MUST be present in all re-auth
5465 messages for this session.
5467 STR 2
5469 When set, the STR message for this session MUST NOT include the
5470 Destination-Host AVP. When cleared, the default value, the
5471 Destination-Host AVP MUST be present in the STR message for this
5472 session.
5474 ACCOUNTING 4
5476 When set, all accounting messages for this session MUST NOT
5477 include the Destination-Host AVP. When cleared, the default
5478 value, the Destination-Host AVP, if known, MUST be present in all
5479 accounting messages for this session.
5481 8.18. Session-Server-Failover AVP
5483 The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated,
5484 and MAY be present in application-specific authorization answer
5485 messages that either do not include the Session-Binding AVP or
5486 include the Session-Binding AVP with any of the bits set to a zero
5487 value. If present, this AVP MAY inform the Diameter client that if a
5488 re-auth or STR message fails due to a delivery problem, the Diameter
5489 client SHOULD issue a subsequent message without the Destination-Host
5490 AVP. When absent, the default value is REFUSE_SERVICE.
5492 The following values are supported:
5494 REFUSE_SERVICE 0
5496 If either the re-auth or the STR message delivery fails, terminate
5497 service with the user, and do not attempt any subsequent attempts.
5499 TRY_AGAIN 1
5501 If either the re-auth or the STR message delivery fails, resend
5502 the failed message without the Destination-Host AVP present.
5504 ALLOW_SERVICE 2
5506 If re-auth message delivery fails, assume that re-authorization
5507 succeeded. If STR message delivery fails, terminate the session.
5509 TRY_AGAIN_ALLOW_SERVICE 3
5511 If either the re-auth or the STR message delivery fails, resend
5512 the failed message without the Destination-Host AVP present. If
5513 the second delivery fails for re-auth, assume re-authorization
5514 succeeded. If the second delivery fails for STR, terminate the
5515 session.
5517 8.19. Multi-Round-Time-Out AVP
5519 The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32,
5520 and SHOULD be present in application-specific authorization answer
5521 messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH.
5522 This AVP contains the maximum number of seconds that the access
5523 device MUST provide the user in responding to an authentication
5524 request.
5526 8.20. Class AVP
5528 The Class AVP (AVP Code 25) is of type OctetString and is used to by
5529 Diameter servers to return state information to the access device.
5530 When one or more Class AVPs are present in application-specific
5531 authorization answer messages, they MUST be present in subsequent re-
5532 authorization, session termination and accounting messages. Class
5533 AVPs found in a re-authorization answer message override the ones
5534 found in any previous authorization answer message. Diameter server
5535 implementations SHOULD NOT return Class AVPs that require more than
5536 4096 bytes of storage on the Diameter client. A Diameter client that
5537 receives Class AVPs whose size exceeds local available storage MUST
5538 terminate the session.
5540 8.21. Event-Timestamp AVP
5542 The Event-Timestamp (AVP Code 55) is of type Time, and MAY be
5543 included in an Accounting-Request and Accounting-Answer messages to
5544 record the time that the reported event occurred, in seconds since
5545 January 1, 1900 00:00 UTC.
5547 9. Accounting
5549 This accounting protocol is based on a server directed model with
5550 capabilities for real-time delivery of accounting information.
5551 Several fault resilience methods [RFC2975] have been built in to the
5552 protocol in order minimize loss of accounting data in various fault
5553 situations and under different assumptions about the capabilities of
5554 the used devices.
5556 9.1. Server Directed Model
5558 The server directed model means that the device generating the
5559 accounting data gets information from either the authorization server
5560 (if contacted) or the accounting server regarding the way accounting
5561 data shall be forwarded. This information includes accounting record
5562 timeliness requirements.
5564 As discussed in [RFC2975], real-time transfer of accounting records
5565 is a requirement, such as the need to perform credit limit checks and
5566 fraud detection. Note that batch accounting is not a requirement,
5567 and is therefore not supported by Diameter. Should batched
5568 accounting be required in the future, a new Diameter application will
5569 need to be created, or it could be handled using another protocol.
5570 Note, however, that even if at the Diameter layer accounting requests
5571 are processed one by one, transport protocols used under Diameter
5572 typically batch several requests in the same packet under heavy
5573 traffic conditions. This may be sufficient for many applications.
5575 The authorization server (chain) directs the selection of proper
5576 transfer strategy, based on its knowledge of the user and
5577 relationships of roaming partnerships. The server (or agents) uses
5578 the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to
5579 control the operation of the Diameter peer operating as a client.
5580 The Acct-Interim-Interval AVP, when present, instructs the Diameter
5581 node acting as a client to produce accounting records continuously
5582 even during a session. Accounting-Realtime-Required AVP is used to
5583 control the behavior of the client when the transfer of accounting
5584 records from the Diameter client is delayed or unsuccessful.
5586 The Diameter accounting server MAY override the interim interval or
5587 the realtime requirements by including the Acct-Interim-Interval or
5588 Accounting-Realtime-Required AVP in the Accounting-Answer message.
5589 When one of these AVPs is present, the latest value received SHOULD
5590 be used in further accounting activities for the same session.
5592 9.2. Protocol Messages
5594 A Diameter node that receives a successful authentication and/or
5595 authorization messages from the Home AAA server MUST collect
5596 accounting information for the session. The Accounting-Request
5597 message is used to transmit the accounting information to the Home
5598 AAA server, which MUST reply with the Accounting-Answer message to
5599 confirm reception. The Accounting-Answer message includes the
5600 Result-Code AVP, which MAY indicate that an error was present in the
5601 accounting message. A rejected Accounting-Request message MAY cause
5602 the user's session to be terminated, depending on the value of the
5603 Accounting-Realtime-Required AVP received earlier for the session in
5604 question.
5606 Each Diameter Accounting protocol message MAY be compressed, in order
5607 to reduce network bandwidth usage. If TLS is used to secure the
5608 Diameter session, then TLS compression [RFC4346] MAY be used.
5610 9.3. Accounting Application Extension and Requirements
5612 Each Diameter application (e.g., NASREQ, MobileIP), MUST define their
5613 Service-Specific AVPs that MUST be present in the Accounting-Request
5614 message in a section entitled "Accounting AVPs". The application
5615 MUST assume that the AVPs described in this document will be present
5616 in all Accounting messages, so only their respective service-specific
5617 AVPs need to be defined in this section.
5619 Applications have the option of using one or both of the following
5620 accounting application extension models:
5622 Split Accounting Service
5624 The accounting message will carry the application identifier of
5625 the Diameter base accounting application (see Section 2.4).
5626 Accounting messages maybe routed to Diameter nodes other than the
5627 corresponding Diameter application. These nodes might be
5628 centralized accounting servers that provide accounting service for
5629 multiple different Diameter applications. These nodes MUST
5630 advertise the Diameter base accounting application identifier
5631 during capabilities exchange.
5633 Accounting messages which uses the Diameter base accounting
5634 application identifier in its header MUST include the application
5635 identifier of the Diameter application it is providing service for
5636 in the Acct-Application-Id AVP. This allows the accounting server
5637 to determine which Diameter application the accounting records are
5638 for.
5640 Coupled Accounting Service
5642 The accounting messages will carry the application identifier of
5643 the application that is using it. The application itself will
5644 process the received accounting records or forward them to an
5645 accounting server. There is no accounting application
5646 advertisement required during capabilities exchange and the
5647 accounting messages will be routed the same as any of the other
5648 application messages.
5650 In cases where an application does not define its own accounting
5651 service, it is preferred that the split accounting model be used.
5653 9.4. Fault Resilience
5655 Diameter Base protocol mechanisms are used to overcome small message
5656 loss and network faults of temporary nature.
5658 Diameter peers acting as clients MUST implement the use of failover
5659 to guard against server failures and certain network failures.
5660 Diameter peers acting as agents or related off-line processing
5661 systems MUST detect duplicate accounting records caused by the
5662 sending of same record to several servers and duplication of messages
5663 in transit. This detection MUST be based on the inspection of the
5664 Session-Id and Accounting-Record-Number AVP pairs. Appendix C
5665 discusses duplicate detection needs and implementation issues.
5667 Diameter clients MAY have non-volatile memory for the safe storage of
5668 accounting records over reboots or extended network failures, network
5669 partitions, and server failures. If such memory is available, the
5670 client SHOULD store new accounting records there as soon as the
5671 records are created and until a positive acknowledgement of their
5672 reception from the Diameter Server has been received. Upon a reboot,
5673 the client MUST starting sending the records in the non-volatile
5674 memory to the accounting server with appropriate modifications in
5675 termination cause, session length, and other relevant information in
5676 the records.
5678 A further application of this protocol may include AVPs to control
5679 how many accounting records may at most be stored in the Diameter
5680 client without committing them to the non-volatile memory or
5681 transferring them to the Diameter server.
5683 The client SHOULD NOT remove the accounting data from any of its
5684 memory areas before the correct Accounting-Answer has been received.
5685 The client MAY remove oldest, undelivered or yet unacknowledged
5686 accounting data if it runs out of resources such as memory. It is an
5687 implementation dependent matter for the client to accept new sessions
5688 under this condition.
5690 9.5. Accounting Records
5692 In all accounting records, the Session-Id AVP MUST be present; the
5693 User-Name AVP MUST be present if it is available to the Diameter
5694 client.
5696 Different types of accounting records are sent depending on the
5697 actual type of accounted service and the authorization server's
5698 directions for interim accounting. If the accounted service is a
5699 one-time event, meaning that the start and stop of the event are
5700 simultaneous, then the Accounting-Record-Type AVP MUST be present and
5701 set to the value EVENT_RECORD.
5703 If the accounted service is of a measurable length, then the AVP MUST
5704 use the values START_RECORD, STOP_RECORD, and possibly,
5705 INTERIM_RECORD. If the authorization server has not directed interim
5706 accounting to be enabled for the session, two accounting records MUST
5707 be generated for each service of type session. When the initial
5708 Accounting-Request for a given session is sent, the Accounting-
5709 Record-Type AVP MUST be set to the value START_RECORD. When the last
5710 Accounting-Request is sent, the value MUST be STOP_RECORD.
5712 If the authorization server has directed interim accounting to be
5713 enabled, the Diameter client MUST produce additional records between
5714 the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The
5715 production of these records is directed by Acct-Interim-Interval as
5716 well as any re-authentication or re-authorization of the session.
5717 The Diameter client MUST overwrite any previous interim accounting
5718 records that are locally stored for delivery, if a new record is
5719 being generated for the same session. This ensures that only one
5720 pending interim record can exist on an access device for any given
5721 session.
5723 A particular value of Accounting-Sub-Session-Id MUST appear only in
5724 one sequence of accounting records from a DIAMETER client, except for
5725 the purposes of retransmission. The one sequence that is sent MUST
5726 be either one record with Accounting-Record-Type AVP set to the value
5727 EVENT_RECORD, or several records starting with one having the value
5728 START_RECORD, followed by zero or more INTERIM_RECORD and a single
5729 STOP_RECORD. A particular Diameter application specification MUST
5730 define the type of sequences that MUST be used.
5732 9.6. Correlation of Accounting Records
5734 The Diameter protocol's Session-Id AVP, which is globally unique (see
5735 Section 8.8), is used during the authorization phase to identify a
5736 particular session. Services that do not require any authorization
5737 still use the Session-Id AVP to identify sessions. Accounting
5738 messages MAY use a different Session-Id from that sent in
5739 authorization messages. Specific applications MAY require different
5740 a Session-ID for accounting messages.
5742 However, there are certain applications that require multiple
5743 accounting sub-sessions. Such applications would send messages with
5744 a constant Session-Id AVP, but a different Accounting-Sub-Session-Id
5745 AVP. In these cases, correlation is performed using the Session-Id.
5746 It is important to note that receiving a STOP_RECORD with no
5747 Accounting-Sub-Session-Id AVP when sub-sessions were originally used
5748 in the START_RECORD messages implies that all sub-sessions are
5749 terminated.
5751 Furthermore, there are certain applications where a user receives
5752 service from different access devices (e.g., Mobile IPv4), each with
5753 their own unique Session-Id. In such cases, the Acct-Multi-Session-
5754 Id AVP is used for correlation. During authorization, a server that
5755 determines that a request is for an existing session SHOULD include
5756 the Acct-Multi-Session-Id AVP, which the access device MUST include
5757 in all subsequent accounting messages.
5759 The Acct-Multi-Session-Id AVP MAY include the value of the original
5760 Session-Id. It's contents are implementation specific, but MUST be
5761 globally unique across other Acct-Multi-Session-Id, and MUST NOT
5762 change during the life of a session.
5764 A Diameter application document MUST define the exact concept of a
5765 session that is being accounted, and MAY define the concept of a
5766 multi-session. For instance, the NASREQ DIAMETER application treats
5767 a single PPP connection to a Network Access Server as one session,
5768 and a set of Multilink PPP sessions as one multi-session.
5770 9.7. Accounting Command-Codes
5772 This section defines Command-Code values that MUST be supported by
5773 all Diameter implementations that provide Accounting services.
5775 9.7.1. Accounting-Request
5777 The Accounting-Request (ACR) command, indicated by the Command-Code
5778 field set to 271 and the Command Flags' 'R' bit set, is sent by a
5779 Diameter node, acting as a client, in order to exchange accounting
5780 information with a peer.
5782 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs
5783 MUST be present. If the Vendor-Specific-Application-Id grouped AVP
5784 is present, it must have an Acct-Application-Id inside.
5786 The AVP listed below SHOULD include service specific accounting AVPs,
5787 as described in Section 9.3.
5789 Message Format
5791 ::= < Diameter Header: 271, REQ, PXY >
5792 < Session-Id >
5793 { Origin-Host }
5794 { Origin-Realm }
5795 { Destination-Realm }
5796 { Accounting-Record-Type }
5797 { Accounting-Record-Number }
5798 [ Acct-Application-Id ]
5799 [ Vendor-Specific-Application-Id ]
5800 [ User-Name ]
5801 [ Destination-Host ]
5802 [ Accounting-Sub-Session-Id ]
5803 [ Acct-Session-Id ]
5804 [ Acct-Multi-Session-Id ]
5805 [ Acct-Interim-Interval ]
5806 [ Accounting-Realtime-Required ]
5807 [ Origin-State-Id ]
5808 [ Event-Timestamp ]
5809 * [ Proxy-Info ]
5810 * [ Route-Record ]
5811 * [ AVP ]
5813 9.7.2. Accounting-Answer
5815 The Accounting-Answer (ACA) command, indicated by the Command-Code
5816 field set to 271 and the Command Flags' 'R' bit cleared, is used to
5817 acknowledge an Accounting-Request command. The Accounting-Answer
5818 command contains the same Session-Id as the corresponding request.
5820 Only the target Diameter Server, known as the home Diameter Server,
5821 SHOULD respond with the Accounting-Answer command.
5823 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs
5824 MUST be present. If the Vendor-Specific-Application-Id grouped AVP
5825 is present, it must have an Acct-Application-Id inside.
5827 The AVP listed below SHOULD include service specific accounting AVPs,
5828 as described in Section 9.3.
5830 Message Format
5832 ::= < Diameter Header: 271, PXY >
5833 < Session-Id >
5834 { Result-Code }
5835 { Origin-Host }
5836 { Origin-Realm }
5837 { Accounting-Record-Type }
5838 { Accounting-Record-Number }
5839 [ Acct-Application-Id ]
5840 [ Vendor-Specific-Application-Id ]
5841 [ User-Name ]
5842 [ Accounting-Sub-Session-Id ]
5843 [ Acct-Session-Id ]
5844 [ Acct-Multi-Session-Id ]
5845 [ Error-Reporting-Host ]
5846 [ Acct-Interim-Interval ]
5847 [ Accounting-Realtime-Required ]
5848 [ Origin-State-Id ]
5849 [ Event-Timestamp ]
5850 * [ Proxy-Info ]
5851 * [ AVP ]
5853 9.8. Accounting AVPs
5855 This section contains AVPs that describe accounting usage information
5856 related to a specific session.
5858 9.8.1. Accounting-Record-Type AVP
5860 The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated
5861 and contains the type of accounting record being sent. The following
5862 values are currently defined for the Accounting-Record-Type AVP:
5864 EVENT_RECORD 1
5866 An Accounting Event Record is used to indicate that a one-time
5867 event has occurred (meaning that the start and end of the event
5868 are simultaneous). This record contains all information relevant
5869 to the service, and is the only record of the service.
5871 START_RECORD 2
5873 An Accounting Start, Interim, and Stop Records are used to
5874 indicate that a service of a measurable length has been given. An
5875 Accounting Start Record is used to initiate an accounting session,
5876 and contains accounting information that is relevant to the
5877 initiation of the session.
5879 INTERIM_RECORD 3
5881 An Interim Accounting Record contains cumulative accounting
5882 information for an existing accounting session. Interim
5883 Accounting Records SHOULD be sent every time a re-authentication
5884 or re-authorization occurs. Further, additional interim record
5885 triggers MAY be defined by application-specific Diameter
5886 applications. The selection of whether to use INTERIM_RECORD
5887 records is done by the Acct-Interim-Interval AVP.
5889 STOP_RECORD 4
5891 An Accounting Stop Record is sent to terminate an accounting
5892 session and contains cumulative accounting information relevant to
5893 the existing session.
5895 9.8.2. Acct-Interim-Interval
5897 The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and
5898 is sent from the Diameter home authorization server to the Diameter
5899 client. The client uses information in this AVP to decide how and
5900 when to produce accounting records. With different values in this
5901 AVP, service sessions can result in one, two, or two+N accounting
5902 records, based on the needs of the home-organization. The following
5903 accounting record production behavior is directed by the inclusion of
5904 this AVP:
5906 1. The omission of the Acct-Interim-Interval AVP or its inclusion
5907 with Value field set to 0 means that EVENT_RECORD, START_RECORD,
5908 and STOP_RECORD are produced, as appropriate for the service.
5910 2. The inclusion of the AVP with Value field set to a non-zero value
5911 means that INTERIM_RECORD records MUST be produced between the
5912 START_RECORD and STOP_RECORD records. The Value field of this
5913 AVP is the nominal interval between these records in seconds.
5914 The Diameter node that originates the accounting information,
5915 known as the client, MUST produce the first INTERIM_RECORD record
5916 roughly at the time when this nominal interval has elapsed from
5917 the START_RECORD, the next one again as the interval has elapsed
5918 once more, and so on until the session ends and a STOP_RECORD
5919 record is produced.
5921 The client MUST ensure that the interim record production times
5922 are randomized so that large accounting message storms are not
5923 created either among records or around a common service start
5924 time.
5926 9.8.3. Accounting-Record-Number AVP
5928 The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32
5929 and identifies this record within one session. As Session-Id AVPs
5930 are globally unique, the combination of Session-Id and Accounting-
5931 Record-Number AVPs is also globally unique, and can be used in
5932 matching accounting records with confirmations. An easy way to
5933 produce unique numbers is to set the value to 0 for records of type
5934 EVENT_RECORD and START_RECORD, and set the value to 1 for the first
5935 INTERIM_RECORD, 2 for the second, and so on until the value for
5936 STOP_RECORD is one more than for the last INTERIM_RECORD.
5938 9.8.4. Acct-Session-Id AVP
5940 The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only
5941 used when RADIUS/Diameter translation occurs. This AVP contains the
5942 contents of the RADIUS Acct-Session-Id attribute.
5944 9.8.5. Acct-Multi-Session-Id AVP
5946 The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String,
5947 following the format specified in Section 8.8. The Acct-Multi-
5948 Session-Id AVP is used to link together multiple related accounting
5949 sessions, where each session would have a unique Session-Id, but the
5950 same Acct-Multi-Session-Id AVP. This AVP MAY be returned by the
5951 Diameter server in an authorization answer, and MUST be used in all
5952 accounting messages for the given session.
5954 9.8.6. Accounting-Sub-Session-Id AVP
5956 The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type
5957 Unsigned64 and contains the accounting sub-session identifier. The
5958 combination of the Session-Id and this AVP MUST be unique per sub-
5959 session, and the value of this AVP MUST be monotonically increased by
5960 one for all new sub-sessions. The absence of this AVP implies no
5961 sub-sessions are in use, with the exception of an Accounting-Request
5962 whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD
5963 message with no Accounting-Sub-Session-Id AVP present will signal the
5964 termination of all sub-sessions for a given Session-Id.
5966 9.8.7. Accounting-Realtime-Required AVP
5968 The Accounting-Realtime-Required AVP (AVP Code 483) is of type
5969 Enumerated and is sent from the Diameter home authorization server to
5970 the Diameter client or in the Accounting-Answer from the accounting
5971 server. The client uses information in this AVP to decide what to do
5972 if the sending of accounting records to the accounting server has
5973 been temporarily prevented due to, for instance, a network problem.
5975 DELIVER_AND_GRANT 1
5977 The AVP with Value field set to DELIVER_AND_GRANT means that the
5978 service MUST only be granted as long as there is a connection to
5979 an accounting server. Note that the set of alternative accounting
5980 servers are treated as one server in this sense. Having to move
5981 the accounting record stream to a backup server is not a reason to
5982 discontinue the service to the user.
5984 GRANT_AND_STORE 2
5986 The AVP with Value field set to GRANT_AND_STORE means that service
5987 SHOULD be granted if there is a connection, or as long as records
5988 can still be stored as described in Section 9.4.
5990 This is the default behavior if the AVP isn't included in the
5991 reply from the authorization server.
5993 GRANT_AND_LOSE 3
5995 The AVP with Value field set to GRANT_AND_LOSE means that service
5996 SHOULD be granted even if the records can not be delivered or
5997 stored.
5999 10. AVP Occurrence Table
6001 The following tables presents the AVPs defined in this document, and
6002 specifies in which Diameter messages they MAY be present or not.
6003 AVPs that occur only inside a Grouped AVP are not shown in this
6004 table.
6006 The table uses the following symbols:
6008 0 The AVP MUST NOT be present in the message.
6010 0+ Zero or more instances of the AVP MAY be present in the
6011 message.
6013 0-1 Zero or one instance of the AVP MAY be present in the message.
6014 It is considered an error if there are more than one instance of
6015 the AVP.
6017 1 One instance of the AVP MUST be present in the message.
6019 1+ At least one instance of the AVP MUST be present in the
6020 message.
6022 10.1. Base Protocol Command AVP Table
6024 The table in this section is limited to the non-accounting Command
6025 Codes defined in this specification.
6027 +-----------------------------------------------+
6028 | Command-Code |
6029 +---+---+---+---+---+---+---+---+---+---+---+---+
6030 Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA|
6031 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+
6032 Acct-Interim- |0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 |
6033 Interval | | | | | | | | | | | | |
6034 Accounting-Realtime-|0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 |
6035 Required | | | | | | | | | | | | |
6036 Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6037 Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 |
6038 Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6039 Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6040 Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6041 Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6042 Lifetime | | | | | | | | | | | | |
6043 Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ |
6044 Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 |
6045 Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 |
6046 Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6047 Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|
6048 Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
6049 Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |
6050 Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6051 Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6052 Inband-Security-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6053 Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6054 Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |
6055 Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |
6056 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|
6057 Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6058 Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ |
6059 Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |
6060 Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
6061 Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
6062 Time | | | | | | | | | | | | |
6063 Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 |0 |1 |
6064 Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 |
6065 Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 |
6066 Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6067 Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 |
6068 Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6069 Failover | | | | | | | | | | | | |
6070 Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6071 Supported-Vendor-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6072 Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 |
6073 User-Name |0 |0 |0 |0 |0 |0 |0-1|0-1|0-1|0-1|0-1|0-1|
6074 Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6075 Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6076 Application-Id | | | | | | | | | | | | |
6077 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+
6079 10.2. Accounting AVP Table
6081 The table in this section is used to represent which AVPs defined in
6082 this document are to be present in the Accounting messages. These
6083 AVP occurrence requirements are guidelines, which may be expanded,
6084 and/or overridden by application-specific requirements in the
6085 Diameter applications documents.
6087 +-----------+
6088 | Command |
6089 | Code |
6090 +-----+-----+
6091 Attribute Name | ACR | ACA |
6092 ------------------------------+-----+-----+
6093 Acct-Interim-Interval | 0-1 | 0-1 |
6094 Acct-Multi-Session-Id | 0-1 | 0-1 |
6095 Accounting-Record-Number | 1 | 1 |
6096 Accounting-Record-Type | 1 | 1 |
6097 Acct-Session-Id | 0-1 | 0-1 |
6098 Accounting-Sub-Session-Id | 0-1 | 0-1 |
6099 Accounting-Realtime-Required | 0-1 | 0-1 |
6100 Acct-Application-Id | 0-1 | 0-1 |
6101 Auth-Application-Id | 0 | 0 |
6102 Class | 0+ | 0+ |
6103 Destination-Host | 0-1 | 0 |
6104 Destination-Realm | 1 | 0 |
6105 Error-Reporting-Host | 0 | 0+ |
6106 Event-Timestamp | 0-1 | 0-1 |
6107 Origin-Host | 1 | 1 |
6108 Origin-Realm | 1 | 1 |
6109 Proxy-Info | 0+ | 0+ |
6110 Route-Record | 0+ | 0+ |
6111 Result-Code | 0 | 1 |
6112 Session-Id | 1 | 1 |
6113 Termination-Cause | 0 | 0 |
6114 User-Name | 0-1 | 0-1 |
6115 Vendor-Specific-Application-Id| 0-1 | 0-1 |
6116 ------------------------------+-----+-----+
6118 11. IANA Considerations
6120 This section provides guidance to the Internet Assigned Numbers
6121 Authority (IANA) regarding registration of values related to the
6122 Diameter protocol, in accordance with BCP 26 [RFC2434]. The
6123 following policies are used here with the meanings defined in BCP 26:
6124 "Private Use", "First Come First Served", "Expert Review",
6125 "Specification Required", "IETF Consensus", "Standards Action".
6127 This section explains the criteria to be used by the IANA for
6128 assignment of numbers within namespaces defined within this document.
6130 Diameter is not intended as a general purpose protocol, and
6131 allocations SHOULD NOT be made for purposes unrelated to
6132 authentication, authorization or accounting.
6134 For registration requests where a Designated Expert should be
6135 consulted, the responsible IESG area director should appoint the
6136 Designated Expert. For Designated Expert with Specification
6137 Required, the request is posted to the DIME WG mailing list (or, if
6138 it has been disbanded, a successor designated by the Area Director)
6139 for comment and review, and MUST include a pointer to a public
6140 specification. Before a period of 30 days has passed, the Designated
6141 Expert will either approve or deny the registration request and
6142 publish a notice of the decision to the DIME WG mailing list or its
6143 successor. A denial notice must be justified by an explanation and,
6144 in the cases where it is possible, concrete suggestions on how the
6145 request can be modified so as to become acceptable.
6147 11.1. AVP Header
6149 As defined in Section 4, the AVP header contains three fields that
6150 requires IANA namespace management; the AVP Code, Vendor-ID and Flags
6151 field.
6153 11.1.1. AVP Codes
6155 The AVP Code namespace is used to identify attributes. There are
6156 multiple namespaces. Vendors can have their own AVP Codes namespace
6157 which will be identified by their Vendor-ID (also known as
6158 Enterprise-Number) and they control the assignments of their vendor-
6159 specific AVP codes within their own namespace. The absence of a
6160 Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA
6161 controlled AVP Codes namespace. The AVP Codes and sometimes also
6162 possible values in an AVP are controlled and maintained by IANA.
6164 AVP Code 0 is not used. AVP Codes 1-255 are managed separately as
6165 RADIUS Attribute Types [RADTYPE]. This document defines the AVP
6166 Codes 257-274, 276-285, 287, 291-300, 480, 483 and 485-486. See
6167 Section 4.5 for the assignment of the namespace in this
6168 specification.
6170 AVPs may be allocated following Designated Expert with Specification
6171 Required [RFC2434]. Release of blocks of AVPs (more than 3 at a time
6172 for a given purpose) should require IETF Consensus.
6174 Note that Diameter defines a mechanism for Vendor-Specific AVPs,
6175 where the Vendor-Id field in the AVP header is set to a non-zero
6176 value. Vendor-Specific AVPs codes are for Private Use and should be
6177 encouraged instead of allocation of global attribute types, for
6178 functions specific only to one vendor's implementation of Diameter,
6179 where no interoperability is deemed useful. Where a Vendor-Specific
6180 AVP is implemented by more than one vendor, allocation of global AVPs
6181 should be encouraged instead.
6183 11.1.2. AVP Flags
6185 There are 8 bits in the AVP Flags field of the AVP header, defined in
6186 Section 4. This document assigns bit 0 ('V'endor Specific), bit 1
6187 ('M'andatory) and bit 2 ('P'rotected). The remaining bits should
6188 only be assigned via a Standards Action [RFC2434].
6190 11.2. Diameter Header
6192 As defined in Section 3, the Diameter header contains two fields that
6193 require IANA namespace management; Command Code and Command Flags.
6195 11.2.1. Command Codes
6197 The Command Code namespace is used to identify Diameter commands.
6198 The values 0-255 (0x00-0xff) are reserved for RADIUS backward
6199 compatibility, and are defined as "RADIUS Packet Type Codes" in
6200 [RADTYPE]. Values 256 - 8,388,607 (0x100 to 0x7fffff) are for
6201 permanent, standard commands, allocated by IETF Consensus [RFC2434].
6202 This document defines the Command Codes 257, 258, 271, 274-275, 280
6203 and 282. See Section 3.1 for the assignment of the namespace in this
6204 specification.
6206 The values 8,388,608 - 16,777,213 (0x800000 - 0xfffffd) are reserved
6207 for vendor-specific command codes, to be allocated on a First Come,
6208 First Served basis by IANA [RFC2434]. The request to IANA for a
6209 Vendor-Specific Command Code SHOULD include a reference to a publicly
6210 available specification which documents the command in sufficient
6211 detail to aid in interoperability between independent
6212 implementations. If the specification cannot be made publicly
6213 available, the request for a vendor-specific command code MUST
6214 include the contact information of persons and/or entities
6215 responsible for authoring and maintaining the command.
6217 The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe -
6218 0xffffff) are reserved for experimental commands. As these codes are
6219 only for experimental and testing purposes, no guarantee is made for
6220 interoperability between Diameter peers using experimental commands,
6221 as outlined in [IANA-EXP].
6223 11.2.2. Command Flags
6225 There are eight bits in the Command Flags field of the Diameter
6226 header. This document assigns bit 0 ('R'equest), bit 1 ('P'roxy),
6227 bit 2 ('E'rror) and bit 3 ('T'). Bits 4 through 7 MUST only be
6228 assigned via a Standards Action [RFC2434].
6230 11.3. Application Identifiers
6232 As defined in Section 2.4, the Application Identifier is used to
6233 identify a specific Diameter Application. There are standards-track
6234 application ids and vendor specific application ids.
6236 IANA [RFC2434] has assigned the range 0x00000001 to 0x00ffffff for
6237 standards-track applications; and 0x01000000 - 0xfffffffe for vendor
6238 specific applications, on a first-come, first-served basis. The
6239 following values are allocated.
6241 Diameter Common Messages 0
6242 NASREQ 1 [RFC4005]
6243 Mobile-IP 2 [RFC4004]
6244 Diameter Base Accounting 3
6245 Relay 0xffffffff
6247 Assignment of standards-track application IDs are by Designated
6248 Expert with Specification Required [RFC2434].
6250 Both Auth-Application-Id and Acct-Application-Id AVPs use the same
6251 Application Identifier space. A diameter node advertising itself as
6252 a relay agent MUST set either Application-Id or Acct-Application-Id
6253 to 0xffffffff.
6255 Vendor-Specific Application Identifiers, are for Private Use. Vendor-
6256 Specific Application Identifiers are assigned on a First Come, First
6257 Served basis by IANA.
6259 11.4. AVP Values
6261 Certain AVPs in Diameter define a list of values with various
6262 meanings. For attributes other than those specified in this section,
6263 adding additional values to the list can be done on a First Come,
6264 First Served basis by IANA.
6266 11.4.1. Result-Code AVP Values
6268 As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines
6269 the values 1001, 2001-2002, 3001-3012, 4001-4003 and 5001-5021.
6271 All remaining values are available for assignment via IETF Consensus
6272 [RFC2434].
6274 11.4.2. Accounting-Record-Type AVP Values
6276 As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code
6277 480) defines the values 1-4. All remaining values are available for
6278 assignment via IETF Consensus [RFC2434].
6280 11.4.3. Termination-Cause AVP Values
6282 As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295)
6283 defines the values 1-8. All remaining values are available for
6284 assignment via IETF Consensus [RFC2434].
6286 11.4.4. Redirect-Host-Usage AVP Values
6288 As defined in Section 6.13, the Redirect-Host-Usage AVP (AVP Code
6289 261) defines the values 0-5. All remaining values are available for
6290 assignment via IETF Consensus [RFC2434].
6292 11.4.5. Session-Server-Failover AVP Values
6294 As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code
6295 271) defines the values 0-3. All remaining values are available for
6296 assignment via IETF Consensus [RFC2434].
6298 11.4.6. Session-Binding AVP Values
6300 As defined in Section 8.17, the Session-Binding AVP (AVP Code 270)
6301 defines the bits 1-4. All remaining bits are available for
6302 assignment via IETF Consensus [RFC2434].
6304 11.4.7. Disconnect-Cause AVP Values
6306 As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273)
6307 defines the values 0-2. All remaining values are available for
6308 assignment via IETF Consensus [RFC2434].
6310 11.4.8. Auth-Request-Type AVP Values
6312 As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274)
6313 defines the values 1-3. All remaining values are available for
6314 assignment via IETF Consensus [RFC2434].
6316 11.4.9. Auth-Session-State AVP Values
6318 As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277)
6319 defines the values 0-1. All remaining values are available for
6320 assignment via IETF Consensus [RFC2434].
6322 11.4.10. Re-Auth-Request-Type AVP Values
6324 As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code
6325 285) defines the values 0-1. All remaining values are available for
6326 assignment via IETF Consensus [RFC2434].
6328 11.4.11. Accounting-Realtime-Required AVP Values
6330 As defined in Section 9.8.7, the Accounting-Realtime-Required AVP
6331 (AVP Code 483) defines the values 1-3. All remaining values are
6332 available for assignment via IETF Consensus [RFC2434].
6334 11.4.12. Inband-Security-Id AVP (code 299)
6336 As defined in Section 6.10, the Inband-Security-Id AVP (AVP Code 299)
6337 defines the values 0-1. All remaining values are available for
6338 assignment via IETF Consensus [RFC2434].
6340 11.5. Diameter TCP/SCTP Port Numbers
6342 The IANA has assigned TCP and SCTP port number 3868 to Diameter.
6344 11.6. NAPTR Service Fields
6346 The registration in the RFC MUST include the following information:
6348 Service Field: The service field being registered. An example for a
6349 new fictitious transport protocol called NCTP might be "AAA+D2N".
6351 Protocol: The specific transport protocol associated with that
6352 service field. This MUST include the name and acronym for the
6353 protocol, along with reference to a document that describes the
6354 transport protocol. For example - "New Connectionless Transport
6355 Protocol (NCTP), RFC 5766".
6357 Name and Contact Information: The name, address, email address and
6358 telephone number for the person performing the registration.
6360 The following values have been placed into the registry:
6362 Services Field Protocol
6364 AAA+D2T TCP
6365 AAA+D2S SCTP
6367 12. Diameter protocol related configurable parameters
6369 This section contains the configurable parameters that are found
6370 throughout this document:
6372 Diameter Peer
6374 A Diameter entity MAY communicate with peers that are statically
6375 configured. A statically configured Diameter peer would require
6376 that either the IP address or the fully qualified domain name
6377 (FQDN) be supplied, which would then be used to resolve through
6378 DNS.
6380 Routing Table
6382 A Diameter proxy server routes messages based on the realm portion
6383 of a Network Access Identifier (NAI). The server MUST have a
6384 table of Realm Names, and the address of the peer to which the
6385 message must be forwarded to. The routing table MAY also include
6386 a "default route", which is typically used for all messages that
6387 cannot be locally processed.
6389 Tc timer
6391 The Tc timer controls the frequency that transport connection
6392 attempts are done to a peer with whom no active transport
6393 connection exists. The recommended value is 30 seconds.
6395 13. Security Considerations
6397 The Diameter base protocol assumes that messages maybe secured by
6398 using TLS. As an alternative, IPSec can be also be used to secure
6399 Diameter peer connections but its usage is transparent from the
6400 Diameter node and Diameter protocol perspective. These security
6401 mechanism is acceptable in environments where there is no untrusted
6402 third party agent.
6404 Diameter clients, such as Network Access Servers (NASes) and Mobility
6405 Agents MAY support TLS [RFC4346]. Diameter servers MUST support TLS.
6406 Diameter implementations SHOULD use transmission-level security of
6407 some kind (IPsec or TLS) on each connection.
6409 If a Diameter connection is to be protected via TLS, then the CER/CEA
6410 exchange MUST include an Inband-Security-ID AVP with a value of TLS.
6411 For TLS usage, a TLS handshake will begin when both ends are in the
6412 open state, after completion of the CER/CEA exchange. If the TLS
6413 handshake is successful, all further messages will be sent via TLS.
6414 If the handshake fails, both ends move to the closed state. See
6415 Sections 13.1 for more details.
6417 13.1. TLS Usage
6419 A Diameter node that initiates a connection to another Diameter node
6420 acts as a TLS client according to [RFC4346], and a Diameter node that
6421 accepts a connection acts as a TLS server. Diameter nodes
6422 implementing TLS for security MUST mutually authenticate as part of
6423 TLS session establishment. In order to ensure mutual authentication,
6424 the Diameter node acting as TLS server must request a certificate
6425 from the Diameter node acting as TLS client, and the Diameter node
6426 acting as TLS client MUST be prepared to supply a certificate on
6427 request.
6429 Diameter nodes MUST be able to negotiate the following TLS cipher
6430 suites:
6432 TLS_RSA_WITH_RC4_128_MD5
6433 TLS_RSA_WITH_RC4_128_SHA
6434 TLS_RSA_WITH_3DES_EDE_CBC_SHA
6436 Diameter nodes SHOULD be able to negotiate the following TLS cipher
6437 suite:
6439 TLS_RSA_WITH_AES_128_CBC_SHA
6441 Diameter nodes MAY negotiate other TLS cipher suites.
6443 13.2. Peer-to-Peer Considerations
6445 As with any peer-to-peer protocol, proper configuration of the trust
6446 model within a Diameter peer is essential to security. When
6447 certificates are used, it is necessary to configure the root
6448 certificate authorities trusted by the Diameter peer. These root CAs
6449 are likely to be unique to Diameter usage and distinct from the root
6450 CAs that might be trusted for other purposes such as Web browsing.
6451 In general, it is expected that those root CAs will be configured so
6452 as to reflect the business relationships between the organization
6453 hosting the Diameter peer and other organizations. As a result, a
6454 Diameter peer will typically not be configured to allow connectivity
6455 with any arbitrary peer. With certificate authentication, Diameter
6456 peers may not be known beforehand and therefore peer discovery may be
6457 required.
6459 14. References
6461 14.1. Normative References
6463 [FLOATPOINT]
6464 Institute of Electrical and Electronics Engineers, "IEEE
6465 Standard for Binary Floating-Point Arithmetic, ANSI/IEEE
6466 Standard 754-1985", August 1985.
6468 [IANAADFAM]
6469 IANA,, "Address Family Numbers",
6470 http://www.iana.org/assignments/address-family-numbers.
6472 [RADTYPE] IANA,, "RADIUS Types",
6473 http://www.iana.org/assignments/radius-types.
6475 [IPV4] Postel, J., "Internet Protocol", RFC 791, September 1981.
6477 [TCP] Postel, J., "Transmission Control Protocol", RFC 793,
6478 January 1981.
6480 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and
6481 Accounting (AAA) Transport Profile", RFC 3539, June 2003.
6483 [RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and
6484 P. McCann, "Diameter Mobile IPv4 Application", RFC 4004,
6485 August 2005.
6487 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
6488 "Diameter Network Access Server Application", RFC 4005,
6489 August 2005.
6491 [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
6492 Loughney, "Diameter Credit-Control Application", RFC 4006,
6493 August 2005.
6495 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
6496 Authentication Protocol (EAP) Application", RFC 4072,
6497 August 2005.
6499 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M.,
6500 Canales-Valenzuela, C., and K. Tammi, "Diameter Session
6501 Initiation Protocol (SIP) Application", RFC 4740,
6502 November 2006.
6504 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
6505 Specifications: ABNF", RFC 4234, October 2005.
6507 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
6508 Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
6510 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
6511 Levkowetz, "Extensible Authentication Protocol (EAP)",
6512 RFC 3748, June 2004.
6514 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
6515 IANA Considerations Section in RFCs", BCP 26, RFC 2434,
6516 October 1998.
6518 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
6519 RFC 4306, December 2005.
6521 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
6522 Architecture", RFC 4291, February 2006.
6524 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
6525 Requirement Levels", BCP 14, RFC 2119, March 1997.
6527 [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
6528 Network Access Identifier", RFC 4282, December 2005.
6530 [RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS)
6531 Part Three: The Domain Name System (DNS) Database",
6532 RFC 3403, October 2002.
6534 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
6535 A., Peterson, J., Sparks, R., Handley, M., and E.
6536 Schooler, "SIP: Session Initiation Protocol", RFC 3261,
6537 June 2002.
6539 [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
6540 Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
6541 Zhang, L., and V. Paxson, "Stream Control Transmission
6542 Protocol", RFC 2960, October 2000.
6544 [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
6545 (TLS) Protocol Version 1.1", RFC 4346, April 2006.
6547 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
6548 Resource Identifier (URI): Generic Syntax", STD 66,
6549 RFC 3986, January 2005.
6551 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
6552 10646", STD 63, RFC 3629, November 2003.
6554 14.2. Informational References
6556 [RFC2989] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, P.,
6557 Shiino, H., Zorn, G., Dommety, G., C.Perkins, B.Patil,
6558 D.Mitton, S.Manning, M.Beadles, P.Walsh, X.Chen,
6559 S.Sivalingham, A.Hameed, M.Munson, S.Jacobs, B.Lim,
6560 B.Hirschman, R.Hsu, Y.Xu, E.Campell, S.Baba, and E.Jaques,
6561 "Criteria for Evaluating AAA Protocols for Network
6562 Access", RFC 2989, November 2000.
6564 [RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction to
6565 Accounting Management", RFC 2975, October 2000.
6567 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by
6568 an On-line Database", RFC 3232, January 2002.
6570 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
6571 Aboba, "Dynamic Authorization Extensions to Remote
6572 Authentication Dial In User Service (RADIUS)", RFC 3576,
6573 July 2003.
6575 [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,
6576 RFC 1661, July 1994.
6578 [RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy
6579 Implementation in Roaming", RFC 2607, June 1999.
6581 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.
6583 [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS
6584 Extensions", RFC 2869, June 2000.
6586 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
6587 "Remote Authentication Dial In User Service (RADIUS)",
6588 RFC 2865, June 2000.
6590 [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6",
6591 RFC 3162, August 2001.
6593 [RFC2194] Aboba, B., Lu, J., Alsop, J., Ding, J., and W. Wang,
6594 "Review of Roaming Implementations", RFC 2194,
6595 September 1997.
6597 [RFC2477] Aboba, B. and G. Zorn, "Criteria for Evaluating Roaming
6598 Protocols", RFC 2477, January 1999.
6600 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
6601 Internet Protocol", RFC 4301, December 2005.
6603 [RFC4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
6604 for IPv4, IPv6 and OSI", RFC 4330, January 2006.
6606 [RFC1492] Finseth, C., "An Access Control Protocol, Sometimes Called
6607 TACACS", RFC 1492, July 1993.
6609 [IANA-EXP]
6610 Narten, T., "Assigning Experimental and Testing Numbers
6611 Considered Useful, Work in Progress.".
6613 Appendix A. Acknowledgements
6615 The authors would like to thank the following people that have
6616 provided proposals and contributions to this document:
6618 To Vishnu Ram and Satendra Gera for their contributions on
6619 Capabilities Updates, Predictive Loop Avoidance as well as many other
6620 technical proposals. To Tolga Asveren for his insights and
6621 contributions on almost all of the proposed solutions incorporated
6622 into this document. To Timothy Smith for helping on the Capabilities
6623 Updates and other topics. To Tony Zhang for providing fixes to loop
6624 holes on composing Failed-AVPs as well as many other issues and
6625 topics. To Jan Nordqvist for clearly stating the usage of
6626 application ids. To Anders Kristensen for providing needed technical
6627 opinions. To David Frascone for providing invaluable review of the
6628 document.
6630 Special thanks also to people who have provided invaluable comments
6631 and inputs especially in resolving controversial issues:
6633 Glen Zorn, Yoshihiro Ohba, Marco Stura, and Pasi Eronen.
6635 Finally, we would like to thank the original authors of this
6636 document:
6638 Pat Calhoun, John Loughney, Jari Arkko, Erik Guttman and Glen Zorn.
6640 Their invaluable knowledge and experience has given us a robust and
6641 flexible AAA protocol that many people have seen great value in
6642 adopting. We greatly appreciate their support and stewardship for
6643 the continued improvements of Diameter as a protocol. We would also
6644 like to extend our gratitude to folks aside from the authors who have
6645 assisted and contributed to the original version of this document.
6646 Their efforts significantly contributed to the success of Diameter.
6648 Appendix B. NAPTR Example
6650 As an example, consider a client that wishes to resolve aaa:ex.com.
6651 The client performs a NAPTR query for that domain, and the following
6652 NAPTR records are returned:
6654 ;; order pref flags service regexp replacement
6655 IN NAPTR 50 50 "s" "AAA+D2S" ""
6656 _diameter._sctp.example.com IN NAPTR 100 50 "s" "AAA+D2T"
6657 "" _aaa._tcp.example.com
6659 This indicates that the server supports SCTP, and TCP, in that order.
6660 If the client supports over SCTP, SCTP will be used, targeted to a
6661 host determined by an SRV lookup of _diameter._sctp.ex.com. That
6662 lookup would return:
6664 ;; Priority Weight Port Target
6665 IN SRV 0 1 5060 server1.example.com IN SRV 0
6666 2 5060 server2.example.com
6668 Appendix C. Duplicate Detection
6670 As described in Section 9.4, accounting record duplicate detection is
6671 based on session identifiers. Duplicates can appear for various
6672 reasons:
6674 o Failover to an alternate server. Where close to real-time
6675 performance is required, failover thresholds need to be kept low
6676 and this may lead to an increased likelihood of duplicates.
6677 Failover can occur at the client or within Diameter agents.
6679 o Failure of a client or agent after sending of a record from non-
6680 volatile memory, but prior to receipt of an application layer ACK
6681 and deletion of the record. record to be sent. This will result
6682 in retransmission of the record soon after the client or agent has
6683 rebooted.
6685 o Duplicates received from RADIUS gateways. Since the
6686 retransmission behavior of RADIUS is not defined within [RFC2865],
6687 the likelihood of duplication will vary according to the
6688 implementation.
6690 o Implementation problems and misconfiguration.
6692 The T flag is used as an indication of an application layer
6693 retransmission event, e.g., due to failover to an alternate server.
6694 It is defined only for request messages sent by Diameter clients or
6695 agents. For instance, after a reboot, a client may not know whether
6696 it has already tried to send the accounting records in its non-
6697 volatile memory before the reboot occurred. Diameter servers MAY use
6698 the T flag as an aid when processing requests and detecting duplicate
6699 messages. However, servers that do this MUST ensure that duplicates
6700 are found even when the first transmitted request arrives at the
6701 server after the retransmitted request. It can be used only in cases
6702 where no answer has been received from the Server for a request and
6703 the request is sent again, (e.g., due to a failover to an alternate
6704 peer, due to a recovered primary peer or due to a client re-sending a
6705 stored record from non-volatile memory such as after reboot of a
6706 client or agent).
6708 In some cases the Diameter accounting server can delay the duplicate
6709 detection and accounting record processing until a post-processing
6710 phase takes place. At that time records are likely to be sorted
6711 according to the included User-Name and duplicate elimination is easy
6712 in this case. In other situations it may be necessary to perform
6713 real-time duplicate detection, such as when credit limits are imposed
6714 or real-time fraud detection is desired.
6716 In general, only generation of duplicates due to failover or re-
6717 sending of records in non-volatile storage can be reliably detected
6718 by Diameter clients or agents. In such cases the Diameter client or
6719 agents can mark the message as possible duplicate by setting the T
6720 flag. Since the Diameter server is responsible for duplicate
6721 detection, it can choose to make use of the T flag or not, in order
6722 to optimize duplicate detection. Since the T flag does not affect
6723 interoperability, and may not be needed by some servers, generation
6724 of the T flag is REQUIRED for Diameter clients and agents, but MAY be
6725 implemented by Diameter servers.
6727 As an example, it can be usually be assumed that duplicates appear
6728 within a time window of longest recorded network partition or device
6729 fault, perhaps a day. So only records within this time window need
6730 to be looked at in the backward direction. Secondly, hashing
6731 techniques or other schemes, such as the use of the T flag in the
6732 received messages, may be used to eliminate the need to do a full
6733 search even in this set except for rare cases.
6735 The following is an example of how the T flag may be used by the
6736 server to detect duplicate requests.
6738 A Diameter server MAY check the T flag of the received message to
6739 determine if the record is a possible duplicate. If the T flag is
6740 set in the request message, the server searches for a duplicate
6741 within a configurable duplication time window backward and
6742 forward. This limits database searching to those records where
6743 the T flag is set. In a well run network, network partitions and
6744 device faults will presumably be rare events, so this approach
6745 represents a substantial optimization of the duplicate detection
6746 process. During failover, it is possible for the original record
6747 to be received after the T flag marked record, due to differences
6748 in network delays experienced along the path by the original and
6749 duplicate transmissions. The likelihood of this occurring
6750 increases as the failover interval is decreased. In order to be
6751 able to detect out of order duplicates, the Diameter server should
6752 use backward and forward time windows when performing duplicate
6753 checking for the T flag marked request. For example, in order to
6754 allow time for the original record to exit the network and be
6755 recorded by the accounting server, the Diameter server can delay
6756 processing records with the T flag set until a time period
6757 TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after the closing
6758 of the original transport connection. After this time period has
6759 expired, then it may check the T flag marked records against the
6760 database with relative assurance that the original records, if
6761 sent, have been received and recorded.
6763 Authors' Addresses
6765 Victor Fajardo (editor)
6766 Toshiba America Research
6767 One Telcordia Drive, 1S-222
6768 Piscataway, NJ 08854
6769 USA
6771 Phone: 1 908-421-1845
6772 Email: vfajardo@tari.toshiba.com
6774 Jari Arkko
6775 Ericsson Research
6776 02420 Jorvas
6777 Finland
6779 Phone: +358 40 5079256
6780 Email: jari.arkko@ericsson.com
6782 John Loughney
6783 Nokia Research Center
6784 955 Page Mill Road
6785 Palo Alto, CA 94304
6786 US
6788 Phone: 1-650-283-8068
6789 Email: john.loughney@nokia.com
6791 Full Copyright Statement
6793 Copyright (C) The IETF Trust (2007).
6795 This document is subject to the rights, licenses and restrictions
6796 contained in BCP 78, and except as set forth therein, the authors
6797 retain all their rights.
6799 This document and the information contained herein are provided on an
6800 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
6801 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
6802 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
6803 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
6804 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
6805 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
6807 Intellectual Property
6809 The IETF takes no position regarding the validity or scope of any
6810 Intellectual Property Rights or other rights that might be claimed to
6811 pertain to the implementation or use of the technology described in
6812 this document or the extent to which any license under such rights
6813 might or might not be available; nor does it represent that it has
6814 made any independent effort to identify any such rights. Information
6815 on the procedures with respect to rights in RFC documents can be
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6818 Copies of IPR disclosures made to the IETF Secretariat and any
6819 assurances of licenses to be made available, or the result of an
6820 attempt made to obtain a general license or permission for the use of
6821 such proprietary rights by implementers or users of this
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6823 http://www.ietf.org/ipr.
6825 The IETF invites any interested party to bring to its attention any
6826 copyrights, patents or patent applications, or other proprietary
6827 rights that may cover technology that may be required to implement
6828 this standard. Please address the information to the IETF at
6829 ietf-ipr@ietf.org.
6831 Acknowledgment
6833 Funding for the RFC Editor function is provided by the IETF
6834 Administrative Support Activity (IASA).