idnits 2.17.1
draft-ietf-dime-rfc3588bis-05.txt:
Checking boilerplate required by RFC 5378 and the IETF Trust (see
https://trustee.ietf.org/license-info):
----------------------------------------------------------------------------
** It looks like you're using RFC 3978 boilerplate. You should update this
to the boilerplate described in the IETF Trust License Policy document
(see https://trustee.ietf.org/license-info), which is required now.
-- Found old boilerplate from RFC 3978, Section 5.1 on line 18.
-- Found old boilerplate from RFC 3978, Section 5.5, updated by RFC 4748 on
line 6778.
-- Found old boilerplate from RFC 3979, Section 5, paragraph 1 on line 6789.
-- Found old boilerplate from RFC 3979, Section 5, paragraph 2 on line 6796.
-- Found old boilerplate from RFC 3979, Section 5, paragraph 3 on line 6802.
Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt:
----------------------------------------------------------------------------
No issues found here.
Checking nits according to https://www.ietf.org/id-info/checklist :
----------------------------------------------------------------------------
== 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:
----------------------------------------------------------------------------
== The copyright year in the IETF Trust Copyright Line does not match the
current year
== Line 4517 has weird spacing: '...ly with wit...'
== Line 4725 has weird spacing: '...ealtime user...'
== Line 4753 has weird spacing: '... record inter...'
== Line 4763 has weird spacing: '...ealtime user...'
== Line 4771 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 (July 6, 2007) is 6110 days in the past. Is this
intentional?
Checking references for intended status: Proposed Standard
----------------------------------------------------------------------------
(See RFCs 3967 and 4897 for information about using normative references
to lower-maturity documents in RFCs)
== Missing Reference: 'PXY' is mentioned on line 4234, 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: January 7, 2008 Ericsson Research
6 J. Loughney
7 Nokia Research Center
8 July 6, 2007
10 Diameter Base Protocol
11 draft-ietf-dime-rfc3588bis-05.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 January 7, 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 Authentication Applications . . . . . . 13
63 1.2.4. Creating New Accounting Applications . . . . . . . . 14
64 1.2.5. Application Authentication Procedures . . . . . . . 15
65 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 15
66 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 22
67 2.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 23
68 2.1.1. SCTP Guidelines . . . . . . . . . . . . . . . . . . 24
69 2.2. Securing Diameter Messages . . . . . . . . . . . . . . . 24
70 2.3. Diameter Application Compliance . . . . . . . . . . . . . 24
71 2.4. Application Identifiers . . . . . . . . . . . . . . . . . 24
72 2.5. Connections vs. Sessions . . . . . . . . . . . . . . . . 25
73 2.6. Peer Table . . . . . . . . . . . . . . . . . . . . . . . 26
74 2.7. Routing Table . . . . . . . . . . . . . . . . . . . . . . 27
75 2.8. Role of Diameter Agents . . . . . . . . . . . . . . . . . 28
76 2.8.1. Relay Agents . . . . . . . . . . . . . . . . . . . . 30
77 2.8.2. Proxy Agents . . . . . . . . . . . . . . . . . . . . 31
78 2.8.3. Redirect Agents . . . . . . . . . . . . . . . . . . 31
79 2.8.4. Translation Agents . . . . . . . . . . . . . . . . . 32
80 2.9. Diameter Path Authorization . . . . . . . . . . . . . . . 33
81 3. Diameter Header . . . . . . . . . . . . . . . . . . . . . . . 35
82 3.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 38
83 3.2. Command Code ABNF specification . . . . . . . . . . . . . 38
84 3.3. Diameter Command Naming Conventions . . . . . . . . . . . 40
85 4. Diameter AVPs . . . . . . . . . . . . . . . . . . . . . . . . 42
86 4.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 42
87 4.1.1. Optional Header Elements . . . . . . . . . . . . . . 44
88 4.2. Basic AVP Data Formats . . . . . . . . . . . . . . . . . 44
89 4.3. Derived AVP Data Formats . . . . . . . . . . . . . . . . 46
90 4.4. Grouped AVP Values . . . . . . . . . . . . . . . . . . . 52
91 4.4.1. Example AVP with a Grouped Data type . . . . . . . . 53
92 4.5. Diameter Base Protocol AVPs . . . . . . . . . . . . . . . 56
93 5. Diameter Peers . . . . . . . . . . . . . . . . . . . . . . . 59
94 5.1. Peer Connections . . . . . . . . . . . . . . . . . . . . 59
95 5.2. Diameter Peer Discovery . . . . . . . . . . . . . . . . . 59
96 5.3. Capabilities Exchange . . . . . . . . . . . . . . . . . . 62
97 5.3.1. Capabilities-Exchange-Request . . . . . . . . . . . 63
98 5.3.2. Capabilities-Exchange-Answer . . . . . . . . . . . . 64
99 5.3.3. Vendor-Id AVP . . . . . . . . . . . . . . . . . . . 64
100 5.3.4. Firmware-Revision AVP . . . . . . . . . . . . . . . 65
101 5.3.5. Host-IP-Address AVP . . . . . . . . . . . . . . . . 65
102 5.3.6. Supported-Vendor-Id AVP . . . . . . . . . . . . . . 65
103 5.3.7. Product-Name AVP . . . . . . . . . . . . . . . . . . 65
104 5.4. Disconnecting Peer connections . . . . . . . . . . . . . 65
105 5.4.1. Disconnect-Peer-Request . . . . . . . . . . . . . . 66
106 5.4.2. Disconnect-Peer-Answer . . . . . . . . . . . . . . . 66
107 5.4.3. Disconnect-Cause AVP . . . . . . . . . . . . . . . . 67
108 5.5. Transport Failure Detection . . . . . . . . . . . . . . . 67
109 5.5.1. Device-Watchdog-Request . . . . . . . . . . . . . . 67
110 5.5.2. Device-Watchdog-Answer . . . . . . . . . . . . . . . 68
111 5.5.3. Transport Failure Algorithm . . . . . . . . . . . . 68
112 5.5.4. Failover and Failback Procedures . . . . . . . . . . 68
113 5.6. Peer State Machine . . . . . . . . . . . . . . . . . . . 69
114 5.6.1. Incoming connections . . . . . . . . . . . . . . . . 71
115 5.6.2. Events . . . . . . . . . . . . . . . . . . . . . . . 72
116 5.6.3. Actions . . . . . . . . . . . . . . . . . . . . . . 73
117 5.6.4. The Election Process . . . . . . . . . . . . . . . . 75
118 5.6.5. Capabilities Update . . . . . . . . . . . . . . . . 75
119 6. Diameter message processing . . . . . . . . . . . . . . . . . 76
120 6.1. Diameter Request Routing Overview . . . . . . . . . . . . 76
121 6.1.1. Originating a Request . . . . . . . . . . . . . . . 77
122 6.1.2. Sending a Request . . . . . . . . . . . . . . . . . 78
123 6.1.3. Receiving Requests . . . . . . . . . . . . . . . . . 78
124 6.1.4. Processing Local Requests . . . . . . . . . . . . . 78
125 6.1.5. Request Forwarding . . . . . . . . . . . . . . . . . 78
126 6.1.6. Request Routing . . . . . . . . . . . . . . . . . . 79
127 6.1.7. Predictive Loop Avoidance . . . . . . . . . . . . . 79
128 6.1.8. Redirecting requests . . . . . . . . . . . . . . . . 79
129 6.1.9. Relaying and Proxying Requests . . . . . . . . . . . 81
130 6.2. Diameter Answer Processing . . . . . . . . . . . . . . . 81
131 6.2.1. Processing received Answers . . . . . . . . . . . . 82
132 6.2.2. Relaying and Proxying Answers . . . . . . . . . . . 82
133 6.3. Origin-Host AVP . . . . . . . . . . . . . . . . . . . . . 83
134 6.4. Origin-Realm AVP . . . . . . . . . . . . . . . . . . . . 83
135 6.5. Destination-Host AVP . . . . . . . . . . . . . . . . . . 83
136 6.6. Destination-Realm AVP . . . . . . . . . . . . . . . . . . 84
137 6.7. Routing AVPs . . . . . . . . . . . . . . . . . . . . . . 84
138 6.7.1. Route-Record AVP . . . . . . . . . . . . . . . . . . 84
139 6.7.2. Proxy-Info AVP . . . . . . . . . . . . . . . . . . . 84
140 6.7.3. Proxy-Host AVP . . . . . . . . . . . . . . . . . . . 84
141 6.7.4. Proxy-State AVP . . . . . . . . . . . . . . . . . . 84
142 6.8. Auth-Application-Id AVP . . . . . . . . . . . . . . . . . 85
143 6.9. Acct-Application-Id AVP . . . . . . . . . . . . . . . . . 85
144 6.10. Inband-Security-Id AVP . . . . . . . . . . . . . . . . . 85
145 6.11. Vendor-Specific-Application-Id AVP . . . . . . . . . . . 85
146 6.12. Redirect-Host AVP . . . . . . . . . . . . . . . . . . . . 86
147 6.13. Redirect-Host-Usage AVP . . . . . . . . . . . . . . . . . 86
148 6.14. Redirect-Max-Cache-Time AVP . . . . . . . . . . . . . . . 88
149 6.15. E2E-Sequence AVP . . . . . . . . . . . . . . . . . . . . 88
150 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 89
151 7.1. Result-Code AVP . . . . . . . . . . . . . . . . . . . . . 90
152 7.1.1. Informational . . . . . . . . . . . . . . . . . . . 91
153 7.1.2. Success . . . . . . . . . . . . . . . . . . . . . . 91
154 7.1.3. Protocol Errors . . . . . . . . . . . . . . . . . . 92
155 7.1.4. Transient Failures . . . . . . . . . . . . . . . . . 93
156 7.1.5. Permanent Failures . . . . . . . . . . . . . . . . . 94
157 7.2. Error Bit . . . . . . . . . . . . . . . . . . . . . . . . 97
158 7.3. Error-Message AVP . . . . . . . . . . . . . . . . . . . . 97
159 7.4. Error-Reporting-Host AVP . . . . . . . . . . . . . . . . 97
160 7.5. Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . . 97
161 7.6. Experimental-Result AVP . . . . . . . . . . . . . . . . . 98
162 7.7. Experimental-Result-Code AVP . . . . . . . . . . . . . . 99
163 8. Diameter User Sessions . . . . . . . . . . . . . . . . . . . 100
164 8.1. Authorization Session State Machine . . . . . . . . . . . 101
165 8.2. Accounting Session State Machine . . . . . . . . . . . . 106
166 8.3. Server-Initiated Re-Auth . . . . . . . . . . . . . . . . 111
167 8.3.1. Re-Auth-Request . . . . . . . . . . . . . . . . . . 111
168 8.3.2. Re-Auth-Answer . . . . . . . . . . . . . . . . . . . 112
169 8.4. Session Termination . . . . . . . . . . . . . . . . . . . 113
170 8.4.1. Session-Termination-Request . . . . . . . . . . . . 114
171 8.4.2. Session-Termination-Answer . . . . . . . . . . . . . 114
172 8.5. Aborting a Session . . . . . . . . . . . . . . . . . . . 115
173 8.5.1. Abort-Session-Request . . . . . . . . . . . . . . . 116
174 8.5.2. Abort-Session-Answer . . . . . . . . . . . . . . . . 116
175 8.6. Inferring Session Termination from Origin-State-Id . . . 117
176 8.7. Auth-Request-Type AVP . . . . . . . . . . . . . . . . . . 118
177 8.8. Session-Id AVP . . . . . . . . . . . . . . . . . . . . . 118
178 8.9. Authorization-Lifetime AVP . . . . . . . . . . . . . . . 119
179 8.10. Auth-Grace-Period AVP . . . . . . . . . . . . . . . . . . 120
180 8.11. Auth-Session-State AVP . . . . . . . . . . . . . . . . . 120
181 8.12. Re-Auth-Request-Type AVP . . . . . . . . . . . . . . . . 121
182 8.13. Session-Timeout AVP . . . . . . . . . . . . . . . . . . . 121
183 8.14. User-Name AVP . . . . . . . . . . . . . . . . . . . . . . 122
184 8.15. Termination-Cause AVP . . . . . . . . . . . . . . . . . . 122
185 8.16. Origin-State-Id AVP . . . . . . . . . . . . . . . . . . . 123
186 8.17. Session-Binding AVP . . . . . . . . . . . . . . . . . . . 123
187 8.18. Session-Server-Failover AVP . . . . . . . . . . . . . . . 124
188 8.19. Multi-Round-Time-Out AVP . . . . . . . . . . . . . . . . 125
189 8.20. Class AVP . . . . . . . . . . . . . . . . . . . . . . . . 125
190 8.21. Event-Timestamp AVP . . . . . . . . . . . . . . . . . . . 125
191 9. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . 127
192 9.1. Server Directed Model . . . . . . . . . . . . . . . . . . 127
193 9.2. Protocol Messages . . . . . . . . . . . . . . . . . . . . 128
194 9.3. Accounting Application Extension and Requirements . . . . 128
195 9.4. Fault Resilience . . . . . . . . . . . . . . . . . . . . 129
196 9.5. Accounting Records . . . . . . . . . . . . . . . . . . . 130
197 9.6. Correlation of Accounting Records . . . . . . . . . . . . 130
198 9.7. Accounting Command-Codes . . . . . . . . . . . . . . . . 131
199 9.7.1. Accounting-Request . . . . . . . . . . . . . . . . . 131
200 9.7.2. Accounting-Answer . . . . . . . . . . . . . . . . . 132
201 9.8. Accounting AVPs . . . . . . . . . . . . . . . . . . . . . 133
202 9.8.1. Accounting-Record-Type AVP . . . . . . . . . . . . . 133
203 9.8.2. Acct-Interim-Interval . . . . . . . . . . . . . . . 134
204 9.8.3. Accounting-Record-Number AVP . . . . . . . . . . . . 135
205 9.8.4. Acct-Session-Id AVP . . . . . . . . . . . . . . . . 135
206 9.8.5. Acct-Multi-Session-Id AVP . . . . . . . . . . . . . 135
207 9.8.6. Accounting-Sub-Session-Id AVP . . . . . . . . . . . 135
208 9.8.7. Accounting-Realtime-Required AVP . . . . . . . . . . 136
209 10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . 137
210 10.1. Base Protocol Command AVP Table . . . . . . . . . . . . . 137
211 10.2. Accounting AVP Table . . . . . . . . . . . . . . . . . . 138
212 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 140
213 11.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 140
214 11.1.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . 140
215 11.1.2. AVP Flags . . . . . . . . . . . . . . . . . . . . . 141
216 11.2. Diameter Header . . . . . . . . . . . . . . . . . . . . . 141
217 11.2.1. Command Codes . . . . . . . . . . . . . . . . . . . 141
218 11.2.2. Command Flags . . . . . . . . . . . . . . . . . . . 142
219 11.3. Application Identifiers . . . . . . . . . . . . . . . . . 142
220 11.4. AVP Values . . . . . . . . . . . . . . . . . . . . . . . 142
221 11.4.1. Result-Code AVP Values . . . . . . . . . . . . . . . 143
222 11.4.2. Accounting-Record-Type AVP Values . . . . . . . . . 143
223 11.4.3. Termination-Cause AVP Values . . . . . . . . . . . . 143
224 11.4.4. Redirect-Host-Usage AVP Values . . . . . . . . . . . 143
225 11.4.5. Session-Server-Failover AVP Values . . . . . . . . . 143
226 11.4.6. Session-Binding AVP Values . . . . . . . . . . . . . 143
227 11.4.7. Disconnect-Cause AVP Values . . . . . . . . . . . . 143
228 11.4.8. Auth-Request-Type AVP Values . . . . . . . . . . . . 143
229 11.4.9. Auth-Session-State AVP Values . . . . . . . . . . . 144
230 11.4.10. Re-Auth-Request-Type AVP Values . . . . . . . . . . 144
231 11.4.11. Accounting-Realtime-Required AVP Values . . . . . . 144
232 11.4.12. Inband-Security-Id AVP (code 299) . . . . . . . . . 144
234 11.5. Diameter TCP/SCTP Port Numbers . . . . . . . . . . . . . 144
235 11.6. NAPTR Service Fields . . . . . . . . . . . . . . . . . . 144
236 12. Diameter protocol related configurable parameters . . . . . . 146
237 13. Security Considerations . . . . . . . . . . . . . . . . . . . 147
238 13.1. TLS Usage . . . . . . . . . . . . . . . . . . . . . . . . 147
239 13.2. Peer-to-Peer Considerations . . . . . . . . . . . . . . . 148
240 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 149
241 14.1. Normative References . . . . . . . . . . . . . . . . . . 149
242 14.2. Informational References . . . . . . . . . . . . . . . . 151
243 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 153
244 Appendix B. NAPTR Example . . . . . . . . . . . . . . . . . . . 154
245 Appendix C. Duplicate Detection . . . . . . . . . . . . . . . . 155
246 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 157
247 Intellectual Property and Copyright Statements . . . . . . . . . 158
249 1. Introduction
251 Authentication, Authorization and Accounting (AAA) protocols such as
252 TACACS [RFC1492] and RADIUS [RFC2865] were initially deployed to
253 provide dial-up PPP [RFC1661] and terminal server access. Over time,
254 with the growth of the Internet and the introduction of new access
255 technologies, including wireless, DSL, Mobile IP and Ethernet,
256 routers and network access servers (NAS) have increased in complexity
257 and density, putting new demands on AAA protocols.
259 Network access requirements for AAA protocols are summarized in
260 [RFC2989]. These include:
262 Failover
264 [RFC2865] does not define failover mechanisms, and as a result,
265 failover behavior differs between implementations. In order to
266 provide well defined failover behavior, Diameter supports
267 application-layer acknowledgements, and defines failover
268 algorithms and the associated state machine. This is described in
269 Section 5.5 and [RFC3539].
271 Transmission-level security
273 [RFC2865] defines an application-layer authentication and
274 integrity scheme that is required only for use with Response
275 packets. While [RFC2869] defines an additional authentication and
276 integrity mechanism, use is only required during Extensible
277 Authentication Protocol (EAP) sessions. While attribute-hiding is
278 supported, [RFC2865] does not provide support for per-packet
279 confidentiality. In accounting, [RFC2866] assumes that replay
280 protection is provided by the backend billing server, rather than
281 within the protocol itself.
283 While [RFC3162] defines the use of IPsec with RADIUS, support for
284 IPsec is not required. Since within [RFC4306] authentication
285 occurs only within Phase 1 prior to the establishment of IPsec SAs
286 in Phase 2, it is typically not possible to define separate trust
287 or authorization schemes for each application. This limits the
288 usefulness of IPsec in inter-domain AAA applications (such as
289 roaming) where it may be desirable to define a distinct
290 certificate hierarchy for use in a AAA deployment. In order to
291 provide universal support for transmission-level security, and
292 enable both intra- and inter-domain AAA deployments, Diameter also
293 provides support for TLS. Security is discussed in Section 13.
295 Reliable transport
297 RADIUS runs over UDP, and does not define retransmission behavior;
298 as a result, reliability varies between implementations. As
299 described in [RFC2975], this is a major issue in accounting, where
300 packet loss may translate directly into revenue loss. In order to
301 provide well defined transport behavior, Diameter runs over
302 reliable transport mechanisms (TCP, SCTP) as defined in [RFC3539].
304 Agent support
306 [RFC2865] does not provide for explicit support for agents,
307 including Proxies, Redirects and Relays. Since the expected
308 behavior is not defined, it varies between implementations.
309 Diameter defines agent behavior explicitly; this is described in
310 Section 2.8.
312 Server-initiated messages
314 While RADIUS server-initiated messages are defined in [RFC3576],
315 support is optional. This makes it difficult to implement
316 features such as unsolicited disconnect or reauthentication/
317 reauthorization on demand across a heterogeneous deployment.
318 Support for server-initiated messages is mandatory in Diameter,
319 and is described in Section 8.
321 Auditability
323 RADIUS does not define data-object security mechanisms, and as a
324 result, untrusted proxies may modify attributes or even packet
325 headers without being detected. Combined with lack of support for
326 capabilities negotiation, this makes it very difficult to
327 determine what occurred in the event of a dispute.
329 Transition support
331 While Diameter does not share a common protocol data unit (PDU)
332 with RADIUS, considerable effort has been expended in enabling
333 backward compatibility with RADIUS, so that the two protocols may
334 be deployed in the same network. Initially, it is expected that
335 Diameter will be deployed within new network devices, as well as
336 within gateways enabling communication between legacy RADIUS
337 devices and Diameter agents. This capability, described in
339 [RFC4005], enables Diameter support to be added to legacy
340 networks, by addition of a gateway or server speaking both RADIUS
341 and Diameter.
343 In addition to addressing the above requirements, Diameter also
344 provides support for the following:
346 Capability negotiation
348 RADIUS does not support error messages, capability negotiation, or
349 a mandatory/non-mandatory flag for attributes. Since RADIUS
350 clients and servers are not aware of each other's capabilities,
351 they may not be able to successfully negotiate a mutually
352 acceptable service, or in some cases, even be aware of what
353 service has been implemented. Diameter includes support for error
354 handling (Section 7), capability negotiation (Section 5.3), and
355 mandatory/non-mandatory attribute-value pairs (AVPs) (Section
356 4.1).
358 Peer discovery and configuration
360 RADIUS implementations typically require that the name or address
361 of servers or clients be manually configured, along with the
362 corresponding shared secrets. This results in a large
363 administrative burden, and creates the temptation to reuse the
364 RADIUS shared secret, which can result in major security
365 vulnerabilities if the Request Authenticator is not globally and
366 temporally unique as required in [RFC2865]. Through DNS, Diameter
367 enables dynamic discovery of peers. Derivation of dynamic session
368 keys is enabled via transmission-level security.
370 Roaming support
372 The ROAMOPS WG provided a survey of roaming implementations
373 [RFC2194], detailed roaming requirements [RFC2477], defined the
374 Network Access Identifier (NAI)[RFC4282], and documented existing
375 implementations (and imitations) of RADIUS-based roaming
376 [RFC2607]. In order to improve scalability, [RFC2607] introduced
377 the concept of proxy chaining via an intermediate server,
378 facilitating roaming between providers. However, since RADIUS
379 does not provide explicit support for proxies, and lacks
380 auditability and transmission-level security features, RADIUS-
381 based roaming is vulnerable to attack from external parties as
382 well as susceptible to fraud perpetrated by the roaming partners
383 themselves. As a result, it is not suitable for wide-scale
384 deployment on the Internet [RFC2607]. By providing explicit
385 support for inter-domain roaming and message routing (Sections 2.7
386 and 6), and transmission-layer security (Section 13) features,
387 Diameter addresses these limitations and provides for secure and
388 scalable roaming.
390 In the decade since AAA protocols were first introduced, the
391 capabilities of Network Access Server (NAS) devices have increased
392 substantially. As a result, while Diameter is a considerably more
393 sophisticated protocol than RADIUS, it remains feasible to implement
394 within embedded devices, given improvements in processor speeds and
395 the widespread availability of embedded TLS implementations.
397 1.1. Diameter Protocol
399 The Diameter base protocol provides the following facilities:
401 o Delivery of AVPs (attribute value pairs)
403 o Capabilities negotiation
405 o Error notification
407 o Extensibility, through addition of new commands and AVPs (required
408 in [RFC2989]).
410 o Basic services necessary for applications, such as handling of
411 user sessions or accounting
413 All data delivered by the protocol is in the form of an AVP. Some of
414 these AVP values are used by the Diameter protocol itself, while
415 others deliver data associated with particular applications that
416 employ Diameter. AVPs may be added arbitrarily to Diameter messages,
417 so long as the required AVPs are included and AVPs that are
418 explicitly excluded are not included. AVPs are used by the base
419 Diameter protocol to support the following required features:
421 o Transporting of user authentication information, for the purposes
422 of enabling the Diameter server to authenticate the user.
424 o Transporting of service specific authorization information,
425 between client and servers, allowing the peers to decide whether a
426 user's access request should be granted.
428 o Exchanging resource usage information, which MAY be used for
429 accounting purposes, capacity planning, etc.
431 o Relaying, proxying and redirecting of Diameter messages through a
432 server hierarchy.
434 The Diameter base protocol provides the minimum requirements needed
435 for a AAA protocol, as required by [RFC2989]. The base protocol may
436 be used by itself for accounting purposes only, or it may be used
437 with a Diameter application, such as Mobile IPv4 [RFC4004], or
438 network access [RFC4005]. It is also possible for the base protocol
439 to be extended for use in new applications, via the addition of new
440 commands or AVPs. At this time the focus of Diameter is network
441 access and accounting applications. A truly generic AAA protocol
442 used by many applications might provide functionality not provided by
443 Diameter. Therefore, it is imperative that the designers of new
444 applications understand their requirements before using Diameter.
445 See Section 2.4 for more information on Diameter applications.
447 Any node can initiate a request. In that sense, Diameter is a peer-
448 to-peer protocol. In this document, a Diameter Client is a device at
449 the edge of the network that performs access control, such as a
450 Network Access Server (NAS) or a Foreign Agent (FA). A Diameter
451 client generates Diameter messages to request authentication,
452 authorization, and accounting services for the user. A Diameter
453 agent is a node that does not authenticate and/or authorize messages
454 locally; agents include proxies, redirects and relay agents. A
455 Diameter server performs authentication and/or authorization of the
456 user. A Diameter node MAY act as an agent for certain requests while
457 acting as a server for others.
459 The Diameter protocol also supports server-initiated messages, such
460 as a request to abort service to a particular user.
462 1.1.1. Description of the Document Set
464 Currently, the Diameter specification consists of a base
465 specification (this document), Transport Profile [RFC3539] and
466 applications: Mobile IPv4 [RFC4004], NASREQ [RFC4005], Credit Control
467 [RFC4006], EAP [RFC4072] and SIP [RFC4740].
469 The Transport Profile document [RFC3539] discusses transport layer
470 issues that arise with AAA protocols and recommendations on how to
471 overcome these issues. This document also defines the Diameter
472 failover algorithm and state machine.
474 The Mobile IPv4 [RFC4004] application defines a Diameter application
475 that allows a Diameter server to perform AAA functions for Mobile
476 IPv4 services to a mobile node.
478 The NASREQ [RFC4005] application defines a Diameter Application that
479 allows a Diameter server to be used in a PPP/SLIP Dial-Up and
480 Terminal Server Access environment. Consideration was given for
481 servers that need to perform protocol conversion between Diameter and
482 RADIUS.
484 The Credit Control [RFC4006] application defines a Diameter
485 Application that can be used to implement real-time credit-control
486 for a variety of end user services such as network access, SIP
487 services, messaging services, and download services. It provides a
488 general solution to real-time cost and credit-control.
490 The EAP [RFC4072] application defines a Diameter Application that can
491 be used to carry EAP packets between the Network Access Server (NAS)
492 working as an EAP authenticator and a back-end authentication server.
493 The Diameter EAP application is based on NASREQ and intended for a
494 similar environment.
496 The SIP [RFC4740] application defines a Diameter Application that
497 allows a Diameter client to request authentication and authorization
498 information to a Diameter server for SIP-based IP multimedia services
499 (see SIP [RFC3261]).
501 In summary, this document defines the base protocol specification for
502 AAA, which includes support for accounting. The applications
503 documents describe applications that use this base specification for
504 Authentication, Authorization and Accounting.
506 1.1.2. Conventions Used in This Document
508 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
509 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
510 document are to be interpreted as described in [RFC2119].
512 1.2. Approach to Extensibility
514 The Diameter protocol is designed to be extensible, using several
515 mechanisms, including:
517 o Defining new AVP values
519 o Creating new AVPs
521 o Creating new authentication/authorization applications
523 o Creating new accounting applications
525 o Application authentication procedures
526 Reuse of existing AVP values, AVPs and Diameter applications are
527 strongly recommended. Reuse simplifies standardization and
528 implementation and avoids potential interoperability issues. It is
529 expected that command codes are reused; new command codes can only be
530 created by Expert Review (see Section 11.2.1).
532 1.2.1. Defining New AVP Values
534 New applications should attempt to reuse AVPs defined in existing
535 applications when possible, as opposed to creating new AVPs. For
536 AVPs of type Enumerated, an application may require a new value to
537 communicate some service-specific information.
539 In order to allocate a new AVP value, a request MUST be sent to IANA
540 [RFC2434], along with an explanation of the new AVP value. IANA
541 considerations for Diameter are discussed in Section 11.
543 1.2.2. Creating New AVPs
545 When no existing AVP can be used, a new AVP should be created. The
546 new AVP being defined MUST use one of the data types listed in
547 Section 4.2.
549 In the event that a logical grouping of AVPs is necessary, and
550 multiple "groups" are possible in a given command, it is recommended
551 that a Grouped AVP be used (see Section 4.4).
553 In order to create a new AVP, a request MUST be sent to IANA, with a
554 specification for the AVP. The request MUST include the commands
555 that would make use of the AVP.
557 1.2.3. Creating New Authentication Applications
559 Every Diameter application specification MUST have an IANA assigned
560 Application Identifier (see Section 2.4 and Section 11.3).
562 Should a new Diameter usage scenario find itself unable to fit within
563 an existing application without requiring major changes to the
564 specification, it may be desirable to create a new Diameter
565 application. Major changes to an application include:
567 o Adding new AVPs to the command, which have the "M" bit set.
569 o Requiring a command that has a different number of round trips to
570 satisfy a request (e.g., application foo has a command that
571 requires one round trip, but new application bar has a command
572 that requires two round trips to complete).
574 o Adding support for an authentication method requiring definition
575 of new AVPs for use with the application. Since a new EAP
576 authentication method can be supported within Diameter without
577 requiring new AVPs, addition of EAP methods does not require the
578 creation of a new authentication application.
580 Creation of a new application should be viewed as a last resort. An
581 implementation MAY add arbitrary non-mandatory AVPs to any command
582 defined in an application, including vendor-specific AVPs without
583 needing to define a new application. Please refer to Section 11.1.1
584 for details.
586 In order to justify allocation of a new application identifier,
587 Diameter applications MUST define one Command Code, add new mandatory
588 AVPs to the ABNF or significantly change the state machine or
589 processing rules of an existing application.
591 The expected AVPs MUST be defined in an ABNF [RFC4234] grammar (see
592 Section 3.2). If the Diameter application has accounting
593 requirements, it MUST also specify the AVPs that are to be present in
594 the Diameter Accounting messages (see Section 9.3). However, just
595 because a new authentication application id is required, does not
596 imply that a new accounting application id is required.
598 When possible, a new Diameter application SHOULD reuse existing
599 Diameter AVPs, in order to avoid defining multiple AVPs that carry
600 similar information.
602 1.2.4. Creating New Accounting Applications
604 There are services that only require Diameter accounting. Such
605 services need to define the AVPs carried in the Accounting-Request
606 (ACR)/ Accounting-Answer (ACA) messages, but do not need to define
607 new command codes. An implementation MAY add arbitrary non-mandatory
608 AVPs (AVPs with the "M" bit not set) to any command defined in an
609 application, including vendor-specific AVPs, without needing to
610 define a new accounting application. Please refer to Section 11.1.1
611 for details.
613 Application Identifiers are still required for Diameter capability
614 exchange. Every Diameter accounting application specification MUST
615 have an IANA assigned Application Identifier (see Section 2.4) or a
616 vendor specific Application Identifier.
618 Every Diameter implementation MUST support accounting. Basic
619 accounting support is sufficient to handle any application that uses
620 the ACR/ACA commands defined in this document, as long as no new
621 mandatory AVPs are added. A mandatory AVP is defined as one which
622 has the "M" bit set when sent within an accounting command,
623 regardless of whether it is required or optional within the ABNF for
624 the accounting application.
626 The creation of a new accounting application should be viewed as a
627 last resort and MUST NOT be used unless a new command or additional
628 mechanisms (e.g., application defined state machine) is defined
629 within the application, or new mandatory AVPs are added to the ABNF.
631 Within an accounting command, setting the "M" bit implies that a
632 backend server (e.g., billing server) or the accounting server itself
633 MUST understand the AVP in order to compute a correct bill. If the
634 AVP is not relevant to the billing process, when the AVP is included
635 within an accounting command, it MUST NOT have the "M" bit set, even
636 if the "M" bit is set when the same AVP is used within other Diameter
637 commands (i.e., authentication/authorization commands).
639 A DIAMETER base accounting implementation MUST be configurable to
640 advertise supported accounting applications in order to prevent the
641 accounting server from accepting accounting requests for unbillable
642 services. The combination of the home domain and the accounting
643 application Id can be used in order to route the request to the
644 appropriate accounting server.
646 When possible, a new Diameter accounting application SHOULD attempt
647 to reuse existing AVPs, in order to avoid defining multiple AVPs that
648 carry similar information.
650 If the base accounting is used without any mandatory AVPs, new
651 commands or additional mechanisms (e.g., application defined state
652 machine), then the base protocol defined standard accounting
653 application Id (Section 2.4) MUST be used in ACR/ACA commands.
655 1.2.5. Application Authentication Procedures
657 When possible, applications SHOULD be designed such that new
658 authentication methods MAY be added without requiring changes to the
659 application. This MAY require that new AVP values be assigned to
660 represent the new authentication transform, or any other scheme that
661 produces similar results. When possible, authentication frameworks,
662 such as Extensible Authentication Protocol [RFC3748], SHOULD be used.
664 1.3. Terminology
665 AAA
667 Authentication, Authorization and Accounting.
669 Accounting
671 The act of collecting information on resource usage for the
672 purpose of capacity planning, auditing, billing or cost
673 allocation.
675 Accounting Record
677 An accounting record represents a summary of the resource
678 consumption of a user over the entire session. Accounting servers
679 creating the accounting record may do so by processing interim
680 accounting events or accounting events from several devices
681 serving the same user.
683 Authentication
685 The act of verifying the identity of an entity (subject).
687 Authorization
689 The act of determining whether a requesting entity (subject) will
690 be allowed access to a resource (object).
692 AVP
694 The Diameter protocol consists of a header followed by one or more
695 Attribute-Value-Pairs (AVPs). An AVP includes a header and is
696 used to encapsulate protocol-specific data (e.g., routing
697 information) as well as authentication, authorization or
698 accounting information.
700 Broker
702 A broker is a business term commonly used in AAA infrastructures.
703 A broker is either a relay, proxy or redirect agent, and MAY be
704 operated by roaming consortiums. Depending on the business model,
705 a broker may either choose to deploy relay agents or proxy agents.
707 Diameter Agent
709 A Diameter Agent is a Diameter node that provides either relay,
710 proxy, redirect or translation services.
712 Diameter Client
714 A Diameter Client is a device at the edge of the network that
715 performs access control. An example of a Diameter client is a
716 Network Access Server (NAS) or a Foreign Agent (FA).
718 Diameter Node
720 A Diameter node is a host process that implements the Diameter
721 protocol, and acts either as a Client, Agent or Server.
723 Diameter Peer
725 A Diameter Peer is a Diameter Node to which a given Diameter Node
726 has a direct transport connection.
728 Diameter Server
730 A Diameter Server is one that handles authentication,
731 authorization and accounting requests for a particular realm. By
732 its very nature, a Diameter Server MUST support Diameter
733 applications in addition to the base protocol.
735 Downstream
737 Downstream is used to identify the direction of a particular
738 Diameter message from the home server towards the access device.
740 Home Realm
742 A Home Realm is the administrative domain with which the user
743 maintains an account relationship.
745 Home Server
747 See Diameter Server.
749 Interim accounting
751 An interim accounting message provides a snapshot of usage during
752 a user's session. It is typically implemented in order to provide
753 for partial accounting of a user's session in the case of a device
754 reboot or other network problem prevents the reception of a
755 session summary message or session record.
757 Local Realm
759 A local realm is the administrative domain providing services to a
760 user. An administrative domain MAY act as a local realm for
761 certain users, while being a home realm for others.
763 Multi-session
765 A multi-session represents a logical linking of several sessions.
766 Multi-sessions are tracked by using the Acct-Multi-Session-Id. An
767 example of a multi-session would be a Multi-link PPP bundle. Each
768 leg of the bundle would be a session while the entire bundle would
769 be a multi-session.
771 Network Access Identifier
773 The Network Access Identifier, or NAI [RFC4282], is used in the
774 Diameter protocol to extract a user's identity and realm. The
775 identity is used to identify the user during authentication and/or
776 authorization, while the realm is used for message routing
777 purposes.
779 Proxy Agent or Proxy
781 In addition to forwarding requests and responses, proxies make
782 policy decisions relating to resource usage and provisioning.
783 This is typically accomplished by tracking the state of NAS
784 devices. While proxies typically do not respond to client
785 Requests prior to receiving a Response from the server, they may
786 originate Reject messages in cases where policies are violated.
787 As a result, proxies need to understand the semantics of the
788 messages passing through them, and may not support all Diameter
789 applications.
791 Realm
793 The string in the NAI that immediately follows the '@' character.
794 NAI realm names are required to be unique, and are piggybacked on
795 the administration of the DNS namespace. Diameter makes use of
796 the realm, also loosely referred to as domain, to determine
797 whether messages can be satisfied locally, or whether they must be
798 routed or redirected. In RADIUS, realm names are not necessarily
799 piggybacked on the DNS namespace but may be independent of it.
801 Real-time Accounting
803 Real-time accounting involves the processing of information on
804 resource usage within a defined time window. Time constraints are
805 typically imposed in order to limit financial risk.
807 Relay Agent or Relay
809 Relays forward requests and responses based on routing-related
810 AVPs and routing table entries. Since relays do not make policy
811 decisions, they do not examine or alter non-routing AVPs. As a
812 result, relays never originate messages, do not need to understand
813 the semantics of messages or non-routing AVPs, and are capable of
814 handling any Diameter application or message type. Since relays
815 make decisions based on information in routing AVPs and realm
816 forwarding tables they do not keep state on NAS resource usage or
817 sessions in progress.
819 Redirect Agent
821 Rather than forwarding requests and responses between clients and
822 servers, redirect agents refer clients to servers and allow them
823 to communicate directly. Since redirect agents do not sit in the
824 forwarding path, they do not alter any AVPs transiting between
825 client and server. Redirect agents do not originate messages and
826 are capable of handling any message type, although they may be
827 configured only to redirect messages of certain types, while
828 acting as relay or proxy agents for other types. As with proxy
829 agents, redirect agents do not keep state with respect to sessions
830 or NAS resources.
832 Roaming Relationships
834 Roaming relationships include relationships between companies and
835 ISPs, relationships among peer ISPs within a roaming consortium,
836 and relationships between an ISP and a roaming consortium.
838 Session
840 A session is a related progression of events devoted to a
841 particular activity. Each application SHOULD provide guidelines
842 as to when a session begins and ends. All Diameter packets with
843 the same Session-Identifier are considered to be part of the same
844 session.
846 Session state
848 A stateful agent is one that maintains session state information,
849 by keeping track of all authorized active sessions. Each
850 authorized session is bound to a particular service, and its state
851 is considered active either until it is notified otherwise, or by
852 expiration.
854 Sub-session
856 A sub-session represents a distinct service (e.g., QoS or data
857 characteristics) provided to a given session. These services may
858 happen concurrently (e.g., simultaneous voice and data transfer
859 during the same session) or serially. These changes in sessions
860 are tracked with the Accounting-Sub-Session-Id.
862 Transaction state
864 The Diameter protocol requires that agents maintain transaction
865 state, which is used for failover purposes. Transaction state
866 implies that upon forwarding a request, the Hop-by-Hop identifier
867 is saved; the field is replaced with a locally unique identifier,
868 which is restored to its original value when the corresponding
869 answer is received. The request's state is released upon receipt
870 of the answer. A stateless agent is one that only maintains
871 transaction state.
873 Translation Agent
875 A translation agent is a stateful Diameter node that performs
876 protocol translation between Diameter and another AAA protocol,
877 such as RADIUS.
879 Transport Connection
881 A transport connection is a TCP or SCTP connection existing
882 directly between two Diameter peers, otherwise known as a Peer-
883 to-Peer Connection.
885 Upstream
887 Upstream is used to identify the direction of a particular
888 Diameter message from the access device towards the home server.
890 User
892 The entity requesting or using some resource, in support of which
893 a Diameter client has generated a request.
895 2. Protocol Overview
897 The base Diameter protocol may be used by itself for accounting
898 applications, but for use in authentication and authorization it is
899 always extended for a particular application. Two Diameter
900 applications are defined by companion documents: NASREQ [RFC4005],
901 Mobile IPv4 [RFC4004]. These applications are introduced in this
902 document but specified elsewhere. Additional Diameter applications
903 MAY be defined in the future (see Section 11.3).
905 Diameter Clients MUST support the base protocol, which includes
906 accounting. In addition, they MUST fully support each Diameter
907 application that is needed to implement the client's service, e.g.,
908 NASREQ and/or Mobile IPv4. A Diameter Client that does not support
909 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
910 Client" where X is the application which it supports, and not a
911 "Diameter Client".
913 Diameter Servers MUST support the base protocol, which includes
914 accounting. In addition, they MUST fully support each Diameter
915 application that is needed to implement the intended service, e.g.,
916 NASREQ and/or Mobile IPv4. A Diameter Server that does not support
917 both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
918 Server" where X is the application which it supports, and not a
919 "Diameter Server".
921 Diameter Relays and redirect agents are, by definition, protocol
922 transparent, and MUST transparently support the Diameter base
923 protocol, which includes accounting, and all Diameter applications.
925 Diameter proxies MUST support the base protocol, which includes
926 accounting. In addition, they MUST fully support each Diameter
927 application that is needed to implement proxied services, e.g.,
928 NASREQ and/or Mobile IPv4. A Diameter proxy which does not support
929 also both NASREQ and Mobile IPv4, MUST be referred to as "Diameter X
930 Proxy" where X is the application which it supports, and not a
931 "Diameter Proxy".
933 The base Diameter protocol concerns itself with capabilities
934 negotiation, how messages are sent and how peers may eventually be
935 abandoned. The base protocol also defines certain rules that apply
936 to all exchanges of messages between Diameter nodes.
938 Communication between Diameter peers begins with one peer sending a
939 message to another Diameter peer. The set of AVPs included in the
940 message is determined by a particular Diameter application. One AVP
941 that is included to reference a user's session is the Session-Id.
943 The initial request for authentication and/or authorization of a user
944 would include the Session-Id. The Session-Id is then used in all
945 subsequent messages to identify the user's session (see Section 8 for
946 more information). The communicating party may accept the request,
947 or reject it by returning an answer message with the Result-Code AVP
948 set to indicate an error occurred. The specific behavior of the
949 Diameter server or client receiving a request depends on the Diameter
950 application employed.
952 Session state (associated with a Session-Id) MUST be freed upon
953 receipt of the Session-Termination-Request, Session-Termination-
954 Answer, expiration of authorized service time in the Session-Timeout
955 AVP, and according to rules established in a particular Diameter
956 application.
958 2.1. Transport
960 Transport profile is defined in [RFC3539].
962 The base Diameter protocol is run on port 3868 of both TCP [TCP] and
963 SCTP [RFC2960] transport protocols.
965 Diameter clients MUST support either TCP or SCTP, while agents and
966 servers MUST support both. Future versions of this specification MAY
967 mandate that clients support SCTP.
969 A Diameter node MAY initiate connections from a source port other
970 than the one that it declares it accepts incoming connections on, and
971 MUST be prepared to receive connections on port 3868. A given
972 Diameter instance of the peer state machine MUST NOT use more than
973 one transport connection to communicate with a given peer, unless
974 multiple instances exist on the peer in which case a separate
975 connection per process is allowed.
977 When no transport connection exists with a peer, an attempt to
978 connect SHOULD be periodically made. This behavior is handled via
979 the Tc timer, whose recommended value is 30 seconds. There are
980 certain exceptions to this rule, such as when a peer has terminated
981 the transport connection stating that it does not wish to
982 communicate.
984 When connecting to a peer and either zero or more transports are
985 specified, SCTP SHOULD be tried first, followed by TCP. See Section
986 5.2 for more information on peer discovery.
988 Diameter implementations SHOULD be able to interpret ICMP protocol
989 port unreachable messages as explicit indications that the server is
990 not reachable, subject to security policy on trusting such messages.
992 Diameter implementations SHOULD also be able to interpret a reset
993 from the transport and timed-out connection attempts. If Diameter
994 receives data up from TCP that cannot be parsed or identified as a
995 Diameter error made by the peer, the stream is compromised and cannot
996 be recovered. The transport connection MUST be closed using a RESET
997 call (send a TCP RST bit) or an SCTP ABORT message (graceful closure
998 is compromised).
1000 2.1.1. SCTP Guidelines
1002 The following are guidelines for Diameter implementations that
1003 support SCTP:
1005 1. For interoperability: All Diameter nodes MUST be prepared to
1006 receive Diameter messages on any SCTP stream in the association.
1008 2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP
1009 streams available to the association to prevent head-of-the-line
1010 blocking.
1012 2.2. Securing Diameter Messages
1014 Diameter clients, such as Network Access Servers (NASes) and Mobility
1015 Agents MAY support TLS [RFC4346]. Diameter servers MUST support TLS.
1016 IPSec [RFC4301] can be deployed between Diameter peers as an
1017 additional security measure independent of the Diameter protocol.
1018 The Diameter protocol SHOULD NOT be used without any security
1019 mechanism.
1021 2.3. Diameter Application Compliance
1023 Application Identifiers are advertised during the capabilities
1024 exchange phase (see Section 5.3). For a given application,
1025 advertising support of an application implies that the sender
1026 supports all command codes, and the AVPs specified in the associated
1027 ABNFs, described in the specification.
1029 An implementation MAY add arbitrary non-mandatory AVPs to any command
1030 defined in an application, including vendor-specific AVPs. Please
1031 refer to Section 11.1.1 for details.
1033 2.4. Application Identifiers
1035 Each Diameter application MUST have an IANA assigned Application
1036 Identifier (see Section 11.3). The base protocol does not require an
1037 Application Identifier since its support is mandatory. During the
1038 capabilities exchange, Diameter nodes inform their peers of locally
1039 supported applications. Furthermore, all Diameter messages contain
1040 an Application Identifier, which is used in the message forwarding
1041 process.
1043 The following Application Identifier values are defined:
1045 Diameter Common Messages 0
1046 NASREQ 1 [RFC4005]
1047 Mobile-IP 2 [RFC4004]
1048 Diameter Base Accounting 3
1049 Relay 0xffffffff
1051 Relay and redirect agents MUST advertise the Relay Application
1052 Identifier, while all other Diameter nodes MUST advertise locally
1053 supported applications. The receiver of a Capabilities Exchange
1054 message advertising Relay service MUST assume that the sender
1055 supports all current and future applications.
1057 Diameter relay and proxy agents are responsible for finding an
1058 upstream server that supports the application of a particular
1059 message. If none can be found, an error message is returned with the
1060 Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER.
1062 2.5. Connections vs. Sessions
1064 This section attempts to provide the reader with an understanding of
1065 the difference between connection and session, which are terms used
1066 extensively throughout this document.
1068 A connection is a transport level connection between two peers, used
1069 to send and receive Diameter messages. A session is a logical
1070 concept at the application layer, and is shared between an access
1071 device and a server, and is identified via the Session-Id AVP.
1073 +--------+ +-------+ +--------+
1074 | Client | | Relay | | Server |
1075 +--------+ +-------+ +--------+
1076 <----------> <---------->
1077 peer connection A peer connection B
1079 <----------------------------->
1080 User session x
1082 Figure 1: Diameter connections and sessions
1084 In the example provided in Figure 1, peer connection A is established
1085 between the Client and its local Relay. Peer connection B is
1086 established between the Relay and the Server. User session X spans
1087 from the Client via the Relay to the Server. Each "user" of a
1088 service causes an auth request to be sent, with a unique session
1089 identifier. Once accepted by the server, both the client and the
1090 server are aware of the session.
1092 It is important to note that there is no relationship between a
1093 connection and a session, and that Diameter messages for multiple
1094 sessions are all multiplexed through a single connection. Also note
1095 that Diameter messages pertaining to the session, both application
1096 specific and those that are defined in this document such as ASR/ASA,
1097 RAR/RAA and STR/STA MUST carry the application identifier of the
1098 application. Diameter messages pertaining to peer connection
1099 establishment and maintenance such as CER/CEA, DWR/DWA and DPR/DPA
1100 MUST carry an application id of zero (0).
1102 2.6. Peer Table
1104 The Diameter Peer Table is used in message forwarding, and referenced
1105 by the Routing Table. A Peer Table entry contains the following
1106 fields:
1108 Host identity
1110 Following the conventions described for the DiameterIdentity
1111 derived AVP data format in Section 4.4. This field contains the
1112 contents of the Origin-Host (Section 6.3) AVP found in the CER or
1113 CEA message.
1115 StatusT
1117 This is the state of the peer entry, and MUST match one of the
1118 values listed in Section 5.6.
1120 Static or Dynamic
1122 Specifies whether a peer entry was statically configured, or
1123 dynamically discovered.
1125 Expiration time
1127 Specifies the time at which dynamically discovered peer table
1128 entries are to be either refreshed, or expired.
1130 TLS Enabled
1132 Specifies whether TLS is to be used when communicating with the
1133 peer.
1135 Additional security information, when needed (e.g., keys,
1136 certificates)
1138 2.7. Routing Table
1140 All Realm-Based routing lookups are performed against what is
1141 commonly known as the Routing Table (see Section 12). A Routing
1142 Table Entry contains the following fields:
1144 Realm Name
1146 This is the field that is typically used as a primary key in the
1147 routing table lookups. Note that some implementations perform
1148 their lookups based on longest-match-from-the-right on the realm
1149 rather than requiring an exact match.
1151 Application Identifier
1153 An application is identified by an application id. A route entry
1154 can have a different destination based on the application
1155 identification in the message header. This field MUST be used as
1156 a secondary key field in routing table lookups.
1158 Local Action
1160 The Local Action field is used to identify how a message should be
1161 treated. The following actions are supported:
1163 1. LOCAL - Diameter messages that resolve to a route entry with
1164 the Local Action set to Local can be satisfied locally, and do
1165 not need to be routed to another server.
1167 2. RELAY - All Diameter messages that fall within this category
1168 MUST be routed to a next hop server, without modifying any
1169 non-routing AVPs. See Section 6.1.9 for relaying guidelines
1171 3. PROXY - All Diameter messages that fall within this category
1172 MUST be routed to a next hop server. The local server MAY
1173 apply its local policies to the message by including new AVPs
1174 to the message prior to routing. See Section 6.1.9 for
1175 proxying guidelines.
1177 4. REDIRECT - Diameter messages that fall within this category
1178 MUST have the identity of the home Diameter server(s)
1179 appended, and returned to the sender of the message. See
1180 Section 6.1.9 for redirect guidelines.
1182 Server Identifier
1184 One or more servers the message is to be routed to. These servers
1185 MUST also be present in the Peer table. When the Local Action is
1186 set to RELAY or PROXY, this field contains the identity of the
1187 server(s) the message must be routed to. When the Local Action
1188 field is set to REDIRECT, this field contains the identity of one
1189 or more servers the message should be redirected to.
1191 Static or Dynamic
1193 Specifies whether a route entry was statically configured, or
1194 dynamically discovered.
1196 Expiration time
1198 Specifies the time which a dynamically discovered route table
1199 entry expires.
1201 It is important to note that Diameter agents MUST support at least
1202 one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation.
1203 Agents do not need to support all modes of operation in order to
1204 conform with the protocol specification, but MUST follow the protocol
1205 compliance guidelines in Section 2. Relay agents MUST NOT reorder
1206 AVPs, and proxies MUST NOT reorder AVPs.
1208 The routing table MAY include a default entry that MUST be used for
1209 any requests not matching any of the other entries. The routing
1210 table MAY consist of only such an entry.
1212 When a request is routed, the target server MUST have advertised the
1213 Application Identifier (see Section 2.4) for the given message, or
1214 have advertised itself as a relay or proxy agent. Otherwise, an
1215 error is returned with the Result-Code AVP set to
1216 DIAMETER_UNABLE_TO_DELIVER.
1218 2.8. Role of Diameter Agents
1220 In addition to client and servers, the Diameter protocol introduces
1221 relay, proxy, redirect, and translation agents, each of which is
1222 defined in Section 1.3. These Diameter agents are useful for several
1223 reasons:
1225 o They can distribute administration of systems to a configurable
1226 grouping, including the maintenance of security associations.
1228 o They can be used for concentration of requests from an number of
1229 co-located or distributed NAS equipment sets to a set of like user
1230 groups.
1232 o They can do value-added processing to the requests or responses.
1234 o They can be used for load balancing.
1236 o A complex network will have multiple authentication sources, they
1237 can sort requests and forward towards the correct target.
1239 The Diameter protocol requires that agents maintain transaction
1240 state, which is used for failover purposes. Transaction state
1241 implies that upon forwarding a request, its Hop-by-Hop identifier is
1242 saved; the field is replaced with a locally unique identifier, which
1243 is restored to its original value when the corresponding answer is
1244 received. The request's state is released upon receipt of the
1245 answer. A stateless agent is one that only maintains transaction
1246 state.
1248 The Proxy-Info AVP allows stateless agents to add local state to a
1249 Diameter request, with the guarantee that the same state will be
1250 present in the answer. However, the protocol's failover procedures
1251 require that agents maintain a copy of pending requests.
1253 A stateful agent is one that maintains session state information; by
1254 keeping track of all authorized active sessions. Each authorized
1255 session is bound to a particular service, and its state is considered
1256 active either until it is notified otherwise, or by expiration. Each
1257 authorized session has an expiration, which is communicated by
1258 Diameter servers via the Session-Timeout AVP.
1260 Maintaining session state MAY be useful in certain applications, such
1261 as:
1263 o Protocol translation (e.g., RADIUS <-> Diameter)
1265 o Limiting resources authorized to a particular user
1267 o Per user or transaction auditing
1269 A Diameter agent MAY act in a stateful manner for some requests and
1270 be stateless for others. A Diameter implementation MAY act as one
1271 type of agent for some requests, and as another type of agent for
1272 others.
1274 2.8.1. Relay Agents
1276 Relay Agents are Diameter agents that accept requests and route
1277 messages to other Diameter nodes based on information found in the
1278 messages (e.g., Destination-Realm). This routing decision is
1279 performed using a list of supported realms, and known peers. This is
1280 known as the Routing Table, as is defined further in Section 2.7.
1282 Relays MAY be used to aggregate requests from multiple Network Access
1283 Servers (NASes) within a common geographical area (POP). The use of
1284 Relays is advantageous since it eliminates the need for NASes to be
1285 configured with the necessary security information they would
1286 otherwise require to communicate with Diameter servers in other
1287 realms. Likewise, this reduces the configuration load on Diameter
1288 servers that would otherwise be necessary when NASes are added,
1289 changed or deleted.
1291 Relays modify Diameter messages by inserting and removing routing
1292 information, but do not modify any other portion of a message.
1293 Relays SHOULD NOT maintain session state but MUST maintain
1294 transaction state.
1296 +------+ ---------> +------+ ---------> +------+
1297 | | 1. Request | | 2. Request | |
1298 | NAS | | DRL | | HMS |
1299 | | 4. Answer | | 3. Answer | |
1300 +------+ <--------- +------+ <--------- +------+
1301 example.net example.net example.com
1303 Figure 2: Relaying of Diameter messages
1305 The example provided in Figure 2 depicts a request issued from NAS,
1306 which is an access device, for the user bob@example.com. Prior to
1307 issuing the request, NAS performs a Diameter route lookup, using
1308 "example.com" as the key, and determines that the message is to be
1309 relayed to DRL, which is a Diameter Relay. DRL performs the same
1310 route lookup as NAS, and relays the message to HMS, which is
1311 example.com's Home Diameter Server. HMS identifies that the request
1312 can be locally supported (via the realm), processes the
1313 authentication and/or authorization request, and replies with an
1314 answer, which is routed back to NAS using saved transaction state.
1316 Since Relays do not perform any application level processing, they
1317 provide relaying services for all Diameter applications, and
1318 therefore MUST advertise the Relay Application Identifier.
1320 2.8.2. Proxy Agents
1322 Similarly to relays, proxy agents route Diameter messages using the
1323 Diameter Routing Table. However, they differ since they modify
1324 messages to implement policy enforcement. This requires that proxies
1325 maintain the state of their downstream peers (e.g., access devices)
1326 to enforce resource usage, provide admission control, and
1327 provisioning.
1329 Proxies MAY be used in call control centers or access ISPs that
1330 provide outsourced connections, they can monitor the number and types
1331 of ports in use, and make allocation and admission decisions
1332 according to their configuration.
1334 Proxies that wish to limit resources MUST maintain session state.
1335 All proxies MUST maintain transaction state.
1337 Since enforcing policies requires an understanding of the service
1338 being provided, Proxies MUST only advertise the Diameter applications
1339 they support.
1341 2.8.3. Redirect Agents
1343 Redirect agents are useful in scenarios where the Diameter routing
1344 configuration needs to be centralized. An example is a redirect
1345 agent that provides services to all members of a consortium, but does
1346 not wish to be burdened with relaying all messages between realms.
1347 This scenario is advantageous since it does not require that the
1348 consortium provide routing updates to its members when changes are
1349 made to a member's infrastructure.
1351 Since redirect agents do not relay messages, and only return an
1352 answer with the information necessary for Diameter agents to
1353 communicate directly, they do not modify messages. Since redirect
1354 agents do not receive answer messages, they cannot maintain session
1355 state. Further, since redirect agents never relay requests, they are
1356 not required to maintain transaction state.
1358 The example provided in Figure 3 depicts a request issued from the
1359 access device, NAS, for the user bob@example.com. The message is
1360 forwarded by the NAS to its relay, DRL, which does not have a routing
1361 entry in its Diameter Routing Table for example.com. DRL has a
1362 default route configured to DRD, which is a redirect agent that
1363 returns a redirect notification to DRL, as well as HMS' contact
1364 information. Upon receipt of the redirect notification, DRL
1365 establishes a transport connection with HMS, if one doesn't already
1366 exist, and forwards the request to it.
1368 +------+
1369 | |
1370 | DRD |
1371 | |
1372 +------+
1373 ^ |
1374 2. Request | | 3. Redirection
1375 | | Notification
1376 | v
1377 +------+ ---------> +------+ ---------> +------+
1378 | | 1. Request | | 4. Request | |
1379 | NAS | | DRL | | HMS |
1380 | | 6. Answer | | 5. Answer | |
1381 +------+ <--------- +------+ <--------- +------+
1382 example.net example.net example.com
1384 Figure 3: Redirecting a Diameter Message
1386 Since redirect agents do not perform any application level
1387 processing, they provide relaying services for all Diameter
1388 applications, and therefore MUST advertise the Relay Application
1389 Identifier.
1391 2.8.4. Translation Agents
1393 A translation agent is a device that provides translation between two
1394 protocols (e.g., RADIUS<->Diameter, TACACS+<->Diameter). Translation
1395 agents are likely to be used as aggregation servers to communicate
1396 with a Diameter infrastructure, while allowing for the embedded
1397 systems to be migrated at a slower pace.
1399 Given that the Diameter protocol introduces the concept of long-lived
1400 authorized sessions, translation agents MUST be session stateful and
1401 MUST maintain transaction state.
1403 Translation of messages can only occur if the agent recognizes the
1404 application of a particular request, and therefore translation agents
1405 MUST only advertise their locally supported applications.
1407 +------+ ---------> +------+ ---------> +------+
1408 | | RADIUS Request | | Diameter Request | |
1409 | NAS | | TLA | | HMS |
1410 | | RADIUS Answer | | Diameter Answer | |
1411 +------+ <--------- +------+ <--------- +------+
1412 example.net example.net example.com
1413 Figure 4: Translation of RADIUS to Diameter
1415 2.9. Diameter Path Authorization
1417 As noted in Section 2.2, Diameter provides transmission level
1418 security for each connection using TLS. Therefore, each connection
1419 can be authenticated, replay and integrity protected.
1421 In addition to authenticating each connection, each connection as
1422 well as the entire session MUST also be authorized. Before
1423 initiating a connection, a Diameter Peer MUST check that its peers
1424 are authorized to act in their roles. For example, a Diameter peer
1425 may be authentic, but that does not mean that it is authorized to act
1426 as a Diameter Server advertising a set of Diameter applications.
1428 Prior to bringing up a connection, authorization checks are performed
1429 at each connection along the path. Diameter capabilities negotiation
1430 (CER/CEA) also MUST be carried out, in order to determine what
1431 Diameter applications are supported by each peer. Diameter sessions
1432 MUST be routed only through authorized nodes that have advertised
1433 support for the Diameter application required by the session.
1435 As noted in Section 6.1.9, a relay or proxy agent MUST append a
1436 Route-Record AVP to all requests forwarded. The AVP contains the
1437 identity of the peer the request was received from.
1439 The home Diameter server, prior to authorizing a session, MUST check
1440 the Route-Record AVPs to make sure that the route traversed by the
1441 request is acceptable. For example, administrators within the home
1442 realm may not wish to honor requests that have been routed through an
1443 untrusted realm. By authorizing a request, the home Diameter server
1444 is implicitly indicating its willingness to engage in the business
1445 transaction as specified by the contractual relationship between the
1446 server and the previous hop. A DIAMETER_AUTHORIZATION_REJECTED error
1447 message (see Section 7.1.5) is sent if the route traversed by the
1448 request is unacceptable.
1450 A home realm may also wish to check that each accounting request
1451 message corresponds to a Diameter response authorizing the session.
1452 Accounting requests without corresponding authorization responses
1453 SHOULD be subjected to further scrutiny, as should accounting
1454 requests indicating a difference between the requested and provided
1455 service.
1457 Similarly, the local Diameter agent, on receiving a Diameter response
1458 authorizing a session, MUST check the Route-Record AVPs to make sure
1459 that the route traversed by the response is acceptable. At each
1460 step, forwarding of an authorization response is considered evidence
1461 of a willingness to take on financial risk relative to the session.
1462 A local realm may wish to limit this exposure, for example, by
1463 establishing credit limits for intermediate realms and refusing to
1464 accept responses which would violate those limits. By issuing an
1465 accounting request corresponding to the authorization response, the
1466 local realm implicitly indicates its agreement to provide the service
1467 indicated in the authorization response. If the service cannot be
1468 provided by the local realm, then a DIAMETER_UNABLE_TO_COMPLY error
1469 message MUST be sent within the accounting request; a Diameter client
1470 receiving an authorization response for a service that it cannot
1471 perform MUST NOT substitute an alternate service, and then send
1472 accounting requests for the alternate service instead.
1474 3. Diameter Header
1476 A summary of the Diameter header format is shown below. The fields
1477 are transmitted in network byte order.
1479 0 1 2 3
1480 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
1481 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1482 | Version | Message Length |
1483 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1484 | command flags | Command-Code |
1485 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1486 | Application-ID |
1487 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1488 | Hop-by-Hop Identifier |
1489 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1490 | End-to-End Identifier |
1491 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1492 | AVPs ...
1493 +-+-+-+-+-+-+-+-+-+-+-+-+-
1495 Version
1497 This Version field MUST be set to 1 to indicate Diameter Version
1498 1.
1500 Message Length
1502 The Message Length field is three octets and indicates the length
1503 of the Diameter message including the header fields.
1505 Command Flags
1507 The Command Flags field is eight bits. The following bits are
1508 assigned:
1510 0 1 2 3 4 5 6 7
1511 +-+-+-+-+-+-+-+-+
1512 |R P E T r r r r|
1513 +-+-+-+-+-+-+-+-+
1515 R(equest)
1517 If set, the message is a request. If cleared, the message is
1518 an answer.
1520 P(roxiable)
1522 If set, the message MAY be proxied, relayed or redirected. If
1523 cleared, the message MUST be locally processed.
1525 E(rror)
1527 If set, the message contains a protocol error, and the message
1528 will not conform to the ABNF described for this command.
1529 Messages with the 'E' bit set are commonly referred to as error
1530 messages. This bit MUST NOT be set in request messages. See
1531 Section 7.2.
1533 T(Potentially re-transmitted message)
1535 This flag is set after a link failover procedure, to aid the
1536 removal of duplicate requests. It is set when resending
1537 requests not yet acknowledged, as an indication of a possible
1538 duplicate due to a link failure. This bit MUST be cleared when
1539 sending a request for the first time, otherwise the sender MUST
1540 set this flag. Diameter agents only need to be concerned about
1541 the number of requests they send based on a single received
1542 request; retransmissions by other entities need not be tracked.
1543 Diameter agents that receive a request with the T flag set,
1544 MUST keep the T flag set in the forwarded request. This flag
1545 MUST NOT be set if an error answer message (e.g., a protocol
1546 error) has been received for the earlier message. It can be
1547 set only in cases where no answer has been received from the
1548 server for a request and the request is sent again. This flag
1549 MUST NOT be set in answer messages.
1551 r(eserved)
1553 These flag bits are reserved for future use, and MUST be set to
1554 zero, and ignored by the receiver.
1556 Command-Code
1558 The Command-Code field is three octets, and is used in order to
1559 communicate the command associated with the message. The 24-bit
1560 address space is managed by IANA (see Section 11.2.1).
1562 Command-Code values 16,777,214 and 16,777,215 (hexadecimal values
1563 FFFFFE -FFFFFF) are reserved for experimental use (See Section
1564 11.3).
1566 Application-ID
1568 Application-ID is four octets and is used to identify to which
1569 application the message is applicable for. The application can be
1570 an authentication application, an accounting application or a
1571 vendor specific application. See Section 11.3 for the possible
1572 values that the application-id may use.
1574 The application-id in the header MUST be the same as what is
1575 contained in any relevant application-id AVPs contained in the
1576 message.
1578 Hop-by-Hop Identifier
1580 The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in
1581 network byte order) and aids in matching requests and replies.
1582 The sender MUST ensure that the Hop-by-Hop identifier in a request
1583 is unique on a given connection at any given time, and MAY attempt
1584 to ensure that the number is unique across reboots. The sender of
1585 an Answer message MUST ensure that the Hop-by-Hop Identifier field
1586 contains the same value that was found in the corresponding
1587 request. The Hop-by-Hop identifier is normally a monotonically
1588 increasing number, whose start value was randomly generated. An
1589 answer message that is received with an unknown Hop-by-Hop
1590 Identifier MUST be discarded.
1592 End-to-End Identifier
1594 The End-to-End Identifier is an unsigned 32-bit integer field (in
1595 network byte order) and is used to detect duplicate messages.
1596 Upon reboot implementations MAY set the high order 12 bits to
1597 contain the low order 12 bits of current time, and the low order
1598 20 bits to a random value. Senders of request messages MUST
1599 insert a unique identifier on each message. The identifier MUST
1600 remain locally unique for a period of at least 4 minutes, even
1601 across reboots. The originator of an Answer message MUST ensure
1602 that the End-to-End Identifier field contains the same value that
1603 was found in the corresponding request. The End-to-End Identifier
1604 MUST NOT be modified by Diameter agents of any kind. The
1605 combination of the Origin-Host (see Section 6.3) and this field is
1606 used to detect duplicates. Duplicate requests SHOULD cause the
1607 same answer to be transmitted (modulo the hop-by-hop Identifier
1608 field and any routing AVPs that may be present), and MUST NOT
1609 affect any state that was set when the original request was
1610 processed. Duplicate answer messages that are to be locally
1611 consumed (see Section 6.2) SHOULD be silently discarded.
1613 AVPs
1615 AVPs are a method of encapsulating information relevant to the
1616 Diameter message. See Section 4 for more information on AVPs.
1618 3.1. Command Codes
1620 Each command Request/Answer pair is assigned a command code, and the
1621 sub-type (i.e., request or answer) is identified via the 'R' bit in
1622 the Command Flags field of the Diameter header.
1624 Every Diameter message MUST contain a command code in its header's
1625 Command-Code field, which is used to determine the action that is to
1626 be taken for a particular message. The following Command Codes are
1627 defined in the Diameter base protocol:
1629 Command-Name Abbrev. Code Reference
1630 --------------------------------------------------------
1631 Abort-Session-Request ASR 274 8.5.1
1632 Abort-Session-Answer ASA 274 8.5.2
1633 Accounting-Request ACR 271 9.7.1
1634 Accounting-Answer ACA 271 9.7.2
1635 Capabilities-Exchange- CER 257 5.3.1
1636 Request
1637 Capabilities-Exchange- CEA 257 5.3.2
1638 Answer
1639 Device-Watchdog-Request DWR 280 5.5.1
1640 Device-Watchdog-Answer DWA 280 5.5.2
1641 Disconnect-Peer-Request DPR 282 5.4.1
1642 Disconnect-Peer-Answer DPA 282 5.4.2
1643 Re-Auth-Request RAR 258 8.3.1
1644 Re-Auth-Answer RAA 258 8.3.2
1645 Session-Termination- STR 275 8.4.1
1646 Request
1647 Session-Termination- STA 275 8.4.2
1648 Answer
1650 3.2. Command Code ABNF specification
1652 Every Command Code defined MUST include a corresponding ABNF
1653 specification, which is used to define the AVPs that MUST or MAY be
1654 present. The following format is used in the definition:
1656 command-def = command-name "::=" diameter-message
1658 command-name = diameter-name
1659 diameter-name = ALPHA *(ALPHA / DIGIT / "-")
1661 diameter-message = header [ *fixed] [ *required] [ *optional]
1663 header = "<" "Diameter Header:" command-id
1664 [r-bit] [p-bit] [e-bit] [application-id] ">"
1666 application-id = 1*DIGIT
1668 command-id = 1*DIGIT
1669 ; The Command Code assigned to the command
1671 r-bit = ", REQ"
1672 ; If present, the 'R' bit in the Command
1673 ; Flags is set, indicating that the message
1674 ; is a request, as opposed to an answer.
1676 p-bit = ", PXY"
1677 ; If present, the 'P' bit in the Command
1678 ; Flags is set, indicating that the message
1679 ; is proxiable.
1681 e-bit = ", ERR"
1682 ; If present, the 'E' bit in the Command
1683 ; Flags is set, indicating that the answer
1684 ; message contains a Result-Code AVP in
1685 ; the "protocol error" class.
1687 fixed = [qual] "<" avp-spec ">"
1688 ; Defines the fixed position of an AVP
1690 required = [qual] "{" avp-spec "}"
1691 ; The AVP MUST be present and can appear
1692 ; anywhere in the message.
1694 optional = [qual] "[" avp-name "]"
1695 ; The avp-name in the 'optional' rule cannot
1696 ; evaluate to any AVP Name which is included
1697 ; in a fixed or required rule. The AVP can
1698 ; appear anywhere in the message.
1700 qual = [min] "*" [max]
1701 ; See ABNF conventions, RFC 4234 Section 6.6.
1702 ; The absence of any qualifiers depends on
1703 ; whether it precedes a fixed, required, or
1704 ; optional rule. If a fixed or required rule has
1705 ; no qualifier, then exactly one such AVP MUST
1706 ; be present. If an optional rule has no
1707 ; qualifier, then 0 or 1 such AVP may be
1708 ; present.
1709 ;
1710 ; NOTE: "[" and "]" have a different meaning
1711 ; than in ABNF (see the optional rule, above).
1712 ; These braces cannot be used to express
1713 ; optional fixed rules (such as an optional
1714 ; ICV at the end). To do this, the convention
1715 ; is '0*1fixed'.
1717 min = 1*DIGIT
1718 ; The minimum number of times the element may
1719 ; be present. The default value is zero.
1721 max = 1*DIGIT
1722 ; The maximum number of times the element may
1723 ; be present. The default value is infinity. A
1724 ; value of zero implies the AVP MUST NOT be
1725 ; present.
1727 avp-spec = diameter-name
1728 ; The avp-spec has to be an AVP Name, defined
1729 ; in the base or extended Diameter
1730 ; specifications.
1732 avp-name = avp-spec / "AVP"
1733 ; The string "AVP" stands for *any* arbitrary
1734 ; AVP Name, which does not conflict with the
1735 ; required or fixed position AVPs defined in
1736 ; the command code definition.
1738 The following is a definition of a fictitious command code:
1740 Example-Request ::= < Diameter Header: 9999999, REQ, PXY >
1741 { User-Name }
1742 * { Origin-Host }
1743 * [ AVP
1745 3.3. Diameter Command Naming Conventions
1747 Diameter command names typically includes one or more English words
1748 followed by the verb Request or Answer. Each English word is
1749 delimited by a hyphen. A three-letter acronym for both the request
1750 and answer is also normally provided.
1752 An example is a message set used to terminate a session. The command
1753 name is Session-Terminate-Request and Session-Terminate-Answer, while
1754 the acronyms are STR and STA, respectively.
1756 Both the request and the answer for a given command share the same
1757 command code. The request is identified by the R(equest) bit in the
1758 Diameter header set to one (1), to ask that a particular action be
1759 performed, such as authorizing a user or terminating a session. Once
1760 the receiver has completed the request it issues the corresponding
1761 answer, which includes a result code that communicates one of the
1762 following:
1764 o The request was successful
1766 o The request failed
1768 o An additional request must be sent to provide information the peer
1769 requires prior to returning a successful or failed answer.
1771 o The receiver could not process the request, but provides
1772 information about a Diameter peer that is able to satisfy the
1773 request, known as redirect.
1775 Additional information, encoded within AVPs, MAY also be included in
1776 answer messages.
1778 4. Diameter AVPs
1780 Diameter AVPs carry specific authentication, accounting,
1781 authorization and routing information as well as configuration
1782 details for the request and reply.
1784 Some AVPs MAY be listed more than once. The effect of such an AVP is
1785 specific, and is specified in each case by the AVP description.
1787 Each AVP of type OctetString MUST be padded to align on a 32-bit
1788 boundary, while other AVP types align naturally. A number of zero-
1789 valued bytes are added to the end of the AVP Data field till a word
1790 boundary is reached. The length of the padding is not reflected in
1791 the AVP Length field.
1793 4.1. AVP Header
1795 The fields in the AVP header MUST be sent in network byte order. The
1796 format of the header is:
1798 0 1 2 3
1799 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
1800 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1801 | AVP Code |
1802 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1803 |V M r r r r r r| AVP Length |
1804 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1805 | Vendor-ID (opt) |
1806 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1807 | Data ...
1808 +-+-+-+-+-+-+-+-+
1810 AVP Code
1812 The AVP Code, combined with the Vendor-Id field, identifies the
1813 attribute uniquely. AVP numbers 1 through 255 are reserved for
1814 backward compatibility with RADIUS, without setting the Vendor-Id
1815 field. AVP numbers 256 and above are used for Diameter, which are
1816 allocated by IANA (see Section 11.1).
1818 AVP Flags
1820 The AVP Flags field informs the receiver how each attribute must
1821 be handled. The 'r' (reserved) bits are unused and SHOULD be set
1822 to 0. Note that subsequent Diameter applications MAY define
1823 additional bits within the AVP Header, and an unrecognized bit
1824 SHOULD be considered an error.
1826 The 'M' Bit, known as the Mandatory bit, indicates whether support
1827 of the AVP is required. If an AVP with the 'M' bit set is
1828 received by a Diameter client, server, proxy, or translation agent
1829 and either the AVP or its value is unrecognized, the message MUST
1830 be rejected. Diameter Relay and redirect agents MUST NOT reject
1831 messages with unrecognized AVPs.
1833 The 'M' bit MUST be set according to the rules defined for the AVP
1834 containing it. In order to preserve interoperability, a Diameter
1835 implementation MUST be able to exclude from a Diameter message any
1836 Mandatory AVP which is neither defined in the base Diameter
1837 protocol nor in any of the Diameter Application specifications
1838 governing the message in which it appears. It MAY do this in one
1839 of the following ways:
1841 1. If a message is rejected because it contains a Mandatory AVP
1842 which is neither defined in the base Diameter standard nor in
1843 any of the Diameter Application specifications governing the
1844 message in which it appears, the implementation may resend the
1845 message without the AVP, possibly inserting additional
1846 standard AVPs instead.
1848 2. A configuration option may be provided on a system wide, per
1849 peer, or per realm basis that would allow/prevent particular
1850 Mandatory AVPs to be sent. Thus an administrator could change
1851 the configuration to avoid interoperability problems.
1853 Diameter implementations are required to support all Mandatory
1854 AVPs which are allowed by the message's formal syntax and defined
1855 either in the base Diameter standard or in one of the Diameter
1856 Application specifications governing the message.
1858 AVPs with the 'M' bit cleared are informational only and a
1859 receiver that receives a message with such an AVP that is not
1860 supported, or whose value is not supported, MAY simply ignore the
1861 AVP.
1863 The 'V' bit, known as the Vendor-Specific bit, indicates whether
1864 the optional Vendor-ID field is present in the AVP header. When
1865 set the AVP Code belongs to the specific vendor code address
1866 space.
1868 Unless otherwise noted, AVPs will have the following default AVP
1869 Flags field settings:
1871 The 'M' bit MUST be set. The 'V' bit MUST NOT be set.
1873 AVP Length
1875 The AVP Length field is three octets, and indicates the number of
1876 octets in this AVP including the AVP Code, AVP Length, AVP Flags,
1877 Vendor-ID field (if present) and the AVP data. If a message is
1878 received with an invalid attribute length, the message SHOULD be
1879 rejected.
1881 4.1.1. Optional Header Elements
1883 The AVP Header contains one optional field. This field is only
1884 present if the respective bit-flag is enabled.
1886 Vendor-ID
1888 The Vendor-ID field is present if the 'V' bit is set in the AVP
1889 Flags field. The optional four-octet Vendor-ID field contains the
1890 IANA assigned "SMI Network Management Private Enterprise Codes"
1891 [RFC3232] value, encoded in network byte order. Any vendor
1892 wishing to implement a vendor-specific Diameter AVP MUST use their
1893 own Vendor-ID along with their privately managed AVP address
1894 space, guaranteeing that they will not collide with any other
1895 vendor's vendor-specific AVP(s), nor with future IETF
1896 applications.
1898 A vendor ID value of zero (0) corresponds to the IETF adopted AVP
1899 values, as managed by the IANA. Since the absence of the vendor
1900 ID field implies that the AVP in question is not vendor specific,
1901 implementations MUST NOT use the zero (0) vendor ID.
1903 4.2. Basic AVP Data Formats
1905 The Data field is zero or more octets and contains information
1906 specific to the Attribute. The format and length of the Data field
1907 is determined by the AVP Code and AVP Length fields. The format of
1908 the Data field MUST be one of the following base data types or a data
1909 type derived from the base data types. In the event that a new Basic
1910 AVP Data Format is needed, a new version of this RFC must be created.
1912 OctetString
1914 The data contains arbitrary data of variable length. Unless
1915 otherwise noted, the AVP Length field MUST be set to at least 8
1916 (12 if the 'V' bit is enabled). AVP Values of this type that are
1917 not a multiple of four-octets in length is followed by the
1918 necessary padding so that the next AVP (if any) will start on a
1919 32-bit boundary.
1921 Integer32
1923 32 bit signed value, in network byte order. The AVP Length field
1924 MUST be set to 12 (16 if the 'V' bit is enabled).
1926 Integer64
1928 64 bit signed value, in network byte order. The AVP Length field
1929 MUST be set to 16 (20 if the 'V' bit is enabled).
1931 Unsigned32
1933 32 bit unsigned value, in network byte order. The AVP Length
1934 field MUST be set to 12 (16 if the 'V' bit is enabled).
1936 Unsigned64
1938 64 bit unsigned value, in network byte order. The AVP Length
1939 field MUST be set to 16 (20 if the 'V' bit is enabled).
1941 Float32
1943 This represents floating point values of single precision as
1944 described by [FLOATPOINT]. The 32-bit value is transmitted in
1945 network byte order. The AVP Length field MUST be set to 12 (16 if
1946 the 'V' bit is enabled).
1948 Float64
1950 This represents floating point values of double precision as
1951 described by [FLOATPOINT]. The 64-bit value is transmitted in
1952 network byte order. The AVP Length field MUST be set to 16 (20 if
1953 the 'V' bit is enabled).
1955 Grouped
1957 The Data field is specified as a sequence of AVPs. Each of these
1958 AVPs follows - in the order in which they are specified -
1959 including their headers and padding. The AVP Length field is set
1960 to 8 (12 if the 'V' bit is enabled) plus the total length of all
1961 included AVPs, including their headers and padding. Thus the AVP
1962 length field of an AVP of type Grouped is always a multiple of 4.
1964 4.3. Derived AVP Data Formats
1966 In addition to using the Basic AVP Data Formats, applications may
1967 define data formats derived from the Basic AVP Data Formats. An
1968 application that defines new AVP Derived Data Formats MUST include
1969 them in a section entitled "AVP Derived Data Formats", using the same
1970 format as the definitions below. Each new definition must be either
1971 defined or listed with a reference to the RFC that defines the
1972 format.
1974 The below AVP Derived Data Formats are commonly used by applications.
1976 Address
1978 The Address format is derived from the OctetString AVP Base
1979 Format. It is a discriminated union, representing, for example a
1980 32-bit (IPv4) [IPV4] or 128-bit (IPv6) [RFC4291] address, most
1981 significant octet first. The first two octets of the Address AVP
1982 represents the AddressType, which contains an Address Family
1983 defined in [IANAADFAM]. The AddressType is used to discriminate
1984 the content and format of the remaining octets.
1986 Time
1988 The Time format is derived from the OctetString AVP Base Format.
1989 The string MUST contain four octets, in the same format as the
1990 first four bytes are in the NTP timestamp format. The NTP
1991 Timestamp format is defined in chapter 3 of [RFC4330].
1993 This represents the number of seconds since 0h on 1 January 1900
1994 with respect to the Coordinated Universal Time (UTC).
1996 On 6h 28m 16s UTC, 7 February 2036 the time value will overflow.
1997 SNTP [RFC4330] describes a procedure to extend the time to 2104.
1998 This procedure MUST be supported by all DIAMETER nodes.
2000 UTF8String
2002 The UTF8String format is derived from the OctetString AVP Base
2003 Format. This is a human readable string represented using the
2004 ISO/IEC IS 10646-1 character set, encoded as an OctetString using
2005 the UTF-8 [RFC3629] transformation format described in RFC 3629.
2007 Since additional code points are added by amendments to the 10646
2008 standard from time to time, implementations MUST be prepared to
2009 encounter any code point from 0x00000001 to 0x7fffffff. Byte
2010 sequences that do not correspond to the valid encoding of a code
2011 point into UTF-8 charset or are outside this range are prohibited.
2013 The use of control codes SHOULD be avoided. When it is necessary
2014 to represent a new line, the control code sequence CR LF SHOULD be
2015 used.
2017 The use of leading or trailing white space SHOULD be avoided.
2019 For code points not directly supported by user interface hardware
2020 or software, an alternative means of entry and display, such as
2021 hexadecimal, MAY be provided.
2023 For information encoded in 7-bit US-ASCII, the UTF-8 charset is
2024 identical to the US-ASCII charset.
2026 UTF-8 may require multiple bytes to represent a single character /
2027 code point; thus the length of an UTF8String in octets may be
2028 different from the number of characters encoded.
2030 Note that the AVP Length field of an UTF8String is measured in
2031 octets, not characters.
2033 DiameterIdentity
2035 The DiameterIdentity format is derived from the OctetString AVP
2036 Base Format.
2038 DiameterIdentity = FQDN
2040 DiameterIdentity value is used to uniquely identify a Diameter
2041 node for purposes of duplicate connection and routing loop
2042 detection.
2044 The contents of the string MUST be the FQDN of the Diameter node.
2045 If multiple Diameter nodes run on the same host, each Diameter
2046 node MUST be assigned a unique DiameterIdentity. If a Diameter
2047 node can be identified by several FQDNs, a single FQDN should be
2048 picked at startup, and used as the only DiameterIdentity for that
2049 node, whatever the connection it is sent on.
2051 DiameterURI
2053 The DiameterURI MUST follow the Uniform Resource Identifiers (URI)
2054 syntax [RFC3986] rules specified below:
2056 "aaa://" FQDN [ port ] [ transport ] [ protocol ]
2058 ; No transport security
2060 "aaas://" FQDN [ port ] [ transport ] [ protocol ]
2062 ; Transport security used
2064 FQDN = Fully Qualified Host Name
2066 port = ":" 1*DIGIT
2068 ; One of the ports used to listen for
2069 ; incoming connections.
2070 ; If absent,
2071 ; the default Diameter port (3868) is
2072 ; assumed.
2074 transport = ";transport=" transport-protocol
2076 ; One of the transports used to listen
2077 ; for incoming connections. If absent,
2078 ; the default SCTP [RFC2960] protocol is
2079 ; assumed. UDP MUST NOT be used when
2080 ; the aaa-protocol field is set to
2081 ; diameter.
2083 transport-protocol = ( "tcp" / "sctp" / "udp" )
2085 protocol = ";protocol=" aaa-protocol
2087 ; If absent, the default AAA protocol
2088 ; is diameter.
2090 aaa-protocol = ( "diameter" / "radius" / "tacacs+" )
2092 The following are examples of valid Diameter host identities:
2094 aaa://host.example.com;transport=tcp
2095 aaa://host.example.com:6666;transport=tcp
2096 aaa://host.example.com;protocol=diameter
2097 aaa://host.example.com:6666;protocol=diameter
2098 aaa://host.example.com:6666;transport=tcp;protocol=diameter
2099 aaa://host.example.com:1813;transport=udp;protocol=radius
2101 Enumerated
2103 Enumerated is derived from the Integer32 AVP Base Format. The
2104 definition contains a list of valid values and their
2105 interpretation and is described in the Diameter application
2106 introducing the AVP.
2108 IPFilterRule
2110 The IPFilterRule format is derived from the OctetString AVP Base
2111 Format. It uses the ASCII charset. Packets may be filtered based
2112 on the following information that is associated with it:
2114 Direction (in or out)
2115 Source and destination IP address (possibly masked)
2116 Protocol
2117 Source and destination port (lists or ranges)
2118 TCP flags
2119 IP fragment flag
2120 IP options
2121 ICMP types
2123 Rules for the appropriate direction are evaluated in order, with
2124 the first matched rule terminating the evaluation. Each packet is
2125 evaluated once. If no rule matches, the packet is dropped if the
2126 last rule evaluated was a permit, and passed if the last rule was
2127 a deny.
2129 IPFilterRule filters MUST follow the format:
2131 action dir proto from src to dst [options]
2133 action permit - Allow packets that match the rule.
2134 deny - Drop packets that match the rule.
2136 dir "in" is from the terminal, "out" is to the
2137 terminal.
2139 proto An IP protocol specified by number. The "ip"
2140 keyword means any protocol will match.
2142 src and dst
[ports]
2144 The may be specified as:
2145 ipno An IPv4 or IPv6 number in dotted-
2146 quad or canonical IPv6 form. Only
2147 this exact IP number will match the
2148 rule.
2149 ipno/bits An IP number as above with a mask
2150 width of the form 1.2.3.4/24. In
2151 this case, all IP numbers from
2152 1.2.3.0 to 1.2.3.255 will match.
2153 The bit width MUST be valid for the
2154 IP version and the IP number MUST
2155 NOT have bits set beyond the mask.
2156 For a match to occur, the same IP
2157 version must be present in the
2158 packet that was used in describing
2159 the IP address. To test for a
2160 particular IP version, the bits part
2161 can be set to zero. The keyword
2162 "any" is 0.0.0.0/0 or the IPv6
2163 equivalent. The keyword "assigned"
2164 is the address or set of addresses
2165 assigned to the terminal. For IPv4,
2166 a typical first rule is often "deny
2167 in ip! assigned"
2169 The sense of the match can be inverted by
2170 preceding an address with the not modifier (!),
2171 causing all other addresses to be matched
2172 instead. This does not affect the selection of
2173 port numbers.
2175 With the TCP, UDP and SCTP protocols, optional
2176 ports may be specified as:
2178 {port/port-port}[,ports[,...]]
2180 The '-' notation specifies a range of ports
2181 (including boundaries).
2183 Fragmented packets that have a non-zero offset
2184 (i.e., not the first fragment) will never match
2185 a rule that has one or more port
2186 specifications. See the frag option for
2187 details on matching fragmented packets.
2189 options:
2190 frag Match if the packet is a fragment and this is not
2191 the first fragment of the datagram. frag may not
2192 be used in conjunction with either tcpflags or
2193 TCP/UDP port specifications.
2195 ipoptions spec
2196 Match if the IP header contains the comma
2197 separated list of options specified in spec. The
2198 supported IP options are:
2200 ssrr (strict source route), lsrr (loose source
2201 route), rr (record packet route) and ts
2202 (timestamp). The absence of a particular option
2203 may be denoted with a '!'.
2205 tcpoptions spec
2206 Match if the TCP header contains the comma
2207 separated list of options specified in spec. The
2208 supported TCP options are:
2210 mss (maximum segment size), window (tcp window
2211 advertisement), sack (selective ack), ts (rfc1323
2212 timestamp) and cc (rfc1644 t/tcp connection
2213 count). The absence of a particular option may
2214 be denoted with a '!'.
2216 established
2217 TCP packets only. Match packets that have the RST
2218 or ACK bits set.
2220 setup TCP packets only. Match packets that have the SYN
2221 bit set but no ACK bit.
2223 tcpflags spec
2224 TCP packets only. Match if the TCP header
2225 contains the comma separated list of flags
2226 specified in spec. The supported TCP flags are:
2228 fin, syn, rst, psh, ack and urg. The absence of a
2229 particular flag may be denoted with a '!'. A rule
2230 that contains a tcpflags specification can never
2231 match a fragmented packet that has a non-zero
2232 offset. See the frag option for details on
2233 matching fragmented packets.
2235 icmptypes types
2236 ICMP packets only. Match if the ICMP type is in
2237 the list types. The list may be specified as any
2238 combination of ranges or individual types
2239 separated by commas. Both the numeric values and
2240 the symbolic values listed below can be used. The
2241 supported ICMP types are:
2243 echo reply (0), destination unreachable (3),
2244 source quench (4), redirect (5), echo request
2245 (8), router advertisement (9), router
2246 solicitation (10), time-to-live exceeded (11), IP
2247 header bad (12), timestamp request (13),
2248 timestamp reply (14), information request (15),
2249 information reply (16), address mask request (17)
2250 and address mask reply (18).
2252 There is one kind of packet that the access device MUST always
2253 discard, that is an IP fragment with a fragment offset of one.
2254 This is a valid packet, but it only has one use, to try to
2255 circumvent firewalls.
2257 An access device that is unable to interpret or apply a deny rule
2258 MUST terminate the session. An access device that is unable to
2259 interpret or apply a permit rule MAY apply a more restrictive
2260 rule. An access device MAY apply deny rules of its own before the
2261 supplied rules, for example to protect the access device owner's
2262 infrastructure.
2264 The rule syntax is a modified subset of ipfw(8) from FreeBSD, and
2265 the ipfw.c code may provide a useful base for implementations.
2267 4.4. Grouped AVP Values
2269 The Diameter protocol allows AVP values of type 'Grouped.' This
2270 implies that the Data field is actually a sequence of AVPs. It is
2271 possible to include an AVP with a Grouped type within a Grouped type,
2272 that is, to nest them. AVPs within an AVP of type Grouped have the
2273 same padding requirements as non-Grouped AVPs, as defined in Section
2274 4.
2276 The AVP Code numbering space of all AVPs included in a Grouped AVP is
2277 the same as for non-grouped AVPs. Further, if any of the AVPs
2278 encapsulated within a Grouped AVP has the 'M' (mandatory) bit set,
2279 the Grouped AVP itself MUST also include the 'M' bit set.
2281 Every Grouped AVP defined MUST include a corresponding grammar, using
2282 ABNF [RFC4234] (with modifications), as defined below.
2284 grouped-avp-def = name "::=" avp
2286 name-fmt = ALPHA *(ALPHA / DIGIT / "-")
2288 name = name-fmt
2289 ; The name has to be the name of an AVP,
2290 ; defined in the base or extended Diameter
2291 ; specifications.
2293 avp = header [ *fixed] [ *required] [ *optional]
2294 [ *fixed]
2296 header = "<" "AVP-Header:" avpcode [vendor] ">"
2298 avpcode = 1*DIGIT
2299 ; The AVP Code assigned to the Grouped AVP
2301 vendor = 1*DIGIT
2302 ; The Vendor-ID assigned to the Grouped AVP.
2303 ; If absent, the default value of zero is
2304 ; used.
2306 4.4.1. Example AVP with a Grouped Data type
2308 The Example-AVP (AVP Code 999999) is of type Grouped and is used to
2309 clarify how Grouped AVP values work. The Grouped Data field has the
2310 following ABNF grammar:
2312 Example-AVP ::= < AVP Header: 999999 >
2313 { Origin-Host }
2314 1*{ Session-Id }
2315 *[ AVP ]
2317 An Example-AVP with Grouped Data follows.
2319 The Origin-Host AVP is required (Section 6.3). In this case:
2321 Origin-Host = "example.com".
2323 One or more Session-Ids must follow. Here there are two:
2325 Session-Id =
2326 "grump.example.com:33041;23432;893;0AF3B81"
2328 Session-Id =
2329 "grump.example.com:33054;23561;2358;0AF3B82"
2331 optional AVPs included are
2333 Recovery-Policy =
2334 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35
2335 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5
2336 c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd
2337 f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a
2338 cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119
2339 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c
2340 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92
2342 Futuristic-Acct-Record =
2343 fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0
2344 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8
2345 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c
2346 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067
2347 d3427475e49968f841
2349 The data for the optional AVPs is represented in hex since the format
2350 of these AVPs is neither known at the time of definition of the
2351 Example-AVP group, nor (likely) at the time when the example instance
2352 of this AVP is interpreted - except by Diameter implementations which
2353 support the same set of AVPs. The encoding example illustrates how
2354 padding is used and how length fields are calculated. Also note that
2355 AVPs may be present in the Grouped AVP value which the receiver
2356 cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record
2357 AVPs). The length of the Example-AVP is the sum of all the length of
2358 the member AVPs including their padding plus the Example-AVP header
2359 size.
2361 This AVP would be encoded as follows:
2363 0 1 2 3 4 5 6 7
2364 +-------+-------+-------+-------+-------+-------+-------+-------+
2365 0 | Example AVP Header (AVP Code = 999999), Length = 496 |
2366 +-------+-------+-------+-------+-------+-------+-------+-------+
2367 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 |
2368 +-------+-------+-------+-------+-------+-------+-------+-------+
2369 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' |
2370 +-------+-------+-------+-------+-------+-------+-------+-------+
2371 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header |
2372 +-------+-------+-------+-------+-------+-------+-------+-------+
2373 32 | (AVP Code = 263), Length = 49 | 'g' | 'r' | 'u' | 'm' |
2374 +-------+-------+-------+-------+-------+-------+-------+-------+
2375 . . .
2376 +-------+-------+-------+-------+-------+-------+-------+-------+
2377 72 | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding|Padding|
2378 +-------+-------+-------+-------+-------+-------+-------+-------+
2379 80 | Session-Id AVP Header (AVP Code = 263), Length = 50 |
2380 +-------+-------+-------+-------+-------+-------+-------+-------+
2381 88 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' |
2382 +-------+-------+-------+-------+-------+-------+-------+-------+
2383 . . .
2384 +-------+-------+-------+-------+-------+-------+-------+-------+
2385 120| '5' | '8' | ';' | '0' | 'A' | 'F' | '3' | 'B' |
2386 +-------+-------+-------+-------+-------+-------+-------+-------+
2387 128| '8' | '2' |Padding|Padding| Recovery-Policy Header (AVP |
2388 +-------+-------+-------+-------+-------+-------+-------+-------+
2389 136| Code = 8341), Length = 223 | 0x21 | 0x63 | 0xbc | 0x1d |
2390 +-------+-------+-------+-------+-------+-------+-------+-------+
2391 144| 0x0a | 0xd8 | 0x23 | 0x71 | 0xf6 | 0xbc | 0x09 | 0x48 |
2392 +-------+-------+-------+-------+-------+-------+-------+-------+
2393 . . .
2394 +-------+-------+-------+-------+-------+-------+-------+-------+
2395 352| 0x8c | 0x7f | 0x92 |Padding| Futuristic-Acct-Record Header |
2396 +-------+-------+-------+-------+-------+-------+-------+-------+
2397 328|(AVP Code = 15930),Length = 137| 0xfe | 0x19 | 0xda | 0x58 |
2398 +-------+-------+-------+-------+-------+-------+-------+-------+
2399 336| 0x02 | 0xac | 0xd9 | 0x8b | 0x07 | 0xa5 | 0xb8 | 0xc6 |
2400 +-------+-------+-------+-------+-------+-------+-------+-------+
2401 . . .
2402 +-------+-------+-------+-------+-------+-------+-------+-------+
2403 488| 0xe4 | 0x99 | 0x68 | 0xf8 | 0x41 |Padding|Padding|Padding|
2404 +-------+-------+-------+-------+-------+-------+-------+-------+
2406 4.5. Diameter Base Protocol AVPs
2408 The following table describes the Diameter AVPs defined in the base
2409 protocol, their AVP Code values, types, possible flag values.
2411 Due to space constraints, the short form DiamIdent is used to
2412 represent DiameterIdentity.
2414 +---------------------+
2415 | AVP Flag rules |
2416 |----+-----+----+-----|
2417 AVP Section | | |SHLD| MUST|
2418 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|
2419 -----------------------------------------|----+-----+----+-----|
2420 Acct- 85 9.8.2 Unsigned32 | M | P | | V |
2421 Interim-Interval | | | | |
2422 Accounting- 483 9.8.7 Enumerated | M | P | | V |
2423 Realtime-Required | | | | |
2424 Acct- 50 9.8.5 UTF8String | M | P | | V |
2425 Multi-Session-Id | | | | |
2426 Accounting- 485 9.8.3 Unsigned32 | M | P | | V |
2427 Record-Number | | | | |
2428 Accounting- 480 9.8.1 Enumerated | M | P | | V |
2429 Record-Type | | | | |
2430 Accounting- 44 9.8.4 OctetString| M | P | | V |
2431 Session-Id | | | | |
2432 Accounting- 287 9.8.6 Unsigned64 | M | P | | V |
2433 Sub-Session-Id | | | | |
2434 Acct- 259 6.9 Unsigned32 | M | P | | V |
2435 Application-Id | | | | |
2436 Auth- 258 6.8 Unsigned32 | M | P | | V |
2437 Application-Id | | | | |
2438 Auth-Request- 274 8.7 Enumerated | M | P | | V |
2439 Type | | | | |
2440 Authorization- 291 8.9 Unsigned32 | M | P | | V |
2441 Lifetime | | | | |
2442 Auth-Grace- 276 8.10 Unsigned32 | M | P | | V |
2443 Period | | | | |
2444 Auth-Session- 277 8.11 Enumerated | M | P | | V |
2445 State | | | | |
2446 Re-Auth-Request- 285 8.12 Enumerated | M | P | | V |
2447 Type | | | | |
2448 Class 25 8.20 OctetString| M | P | | V |
2449 Destination-Host 293 6.5 DiamIdent | M | P | | V |
2450 Destination- 283 6.6 DiamIdent | M | P | | V |
2451 Realm | | | | |
2452 Disconnect-Cause 273 5.4.3 Enumerated | M | P | | V |
2453 E2E-Sequence AVP 300 6.15 Grouped | M | P | | V |
2454 Error-Message 281 7.3 UTF8String | | P | | V,M |
2455 Error-Reporting- 294 7.4 DiamIdent | | P | | V,M |
2456 Host | | | | |
2457 Event-Timestamp 55 8.21 Time | M | P | | V |
2458 Experimental- 297 7.6 Grouped | M | P | | V |
2459 Result | | | | |
2460 -----------------------------------------|----+-----+----+-----|
2461 +---------------------+
2462 | AVP Flag rules |
2463 |----+-----+----+-----|
2464 AVP Section | | |SHLD| MUST|
2465 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|
2466 -----------------------------------------|----+-----+----+-----|
2467 Experimental- 298 7.7 Unsigned32 | M | P | | V |
2468 Result-Code | | | | |
2469 Failed-AVP 279 7.5 Grouped | M | P | | V |
2470 Firmware- 267 5.3.4 Unsigned32 | | | |P,V,M|
2471 Revision | | | | |
2472 Host-IP-Address 257 5.3.5 Address | M | P | | V |
2473 Inband-Security | M | P | | V |
2474 -Id 299 6.10 Unsigned32 | | | | |
2475 Multi-Round- 272 8.19 Unsigned32 | M | P | | V |
2476 Time-Out | | | | |
2477 Origin-Host 264 6.3 DiamIdent | M | P | | V |
2478 Origin-Realm 296 6.4 DiamIdent | M | P | | V |
2479 Origin-State-Id 278 8.16 Unsigned32 | M | P | | V |
2480 Product-Name 269 5.3.7 UTF8String | | | |P,V,M|
2481 Proxy-Host 280 6.7.3 DiamIdent | M | | | P,V |
2482 Proxy-Info 284 6.7.2 Grouped | M | | | P,V |
2483 Proxy-State 33 6.7.4 OctetString| M | | | P,V |
2484 Redirect-Host 292 6.12 DiamURI | M | P | | V |
2485 Redirect-Host- 261 6.13 Enumerated | M | P | | V |
2486 Usage | | | | |
2487 Redirect-Max- 262 6.14 Unsigned32 | M | P | | V |
2488 Cache-Time | | | | |
2489 Result-Code 268 7.1 Unsigned32 | M | P | | V |
2490 Route-Record 282 6.7.1 DiamIdent | M | | | P,V |
2491 Session-Id 263 8.8 UTF8String | M | P | | V |
2492 Session-Timeout 27 8.13 Unsigned32 | M | P | | V |
2493 Session-Binding 270 8.17 Unsigned32 | M | P | | V |
2494 Session-Server- 271 8.18 Enumerated | M | P | | V |
2495 Failover | | | | |
2496 Supported- 265 5.3.6 Unsigned32 | M | P | | V |
2497 Vendor-Id | | | | |
2498 Termination- 295 8.15 Enumerated | M | P | | V |
2499 Cause | | | | |
2500 User-Name 1 8.14 UTF8String | M | P | | V |
2501 Vendor-Id 266 5.3.3 Unsigned32 | M | P | | V |
2502 Vendor-Specific- 260 6.11 Grouped | M | P | | V |
2503 Application-Id | | | | |
2504 -----------------------------------------|----+-----+----+-----|
2506 5. Diameter Peers
2508 This section describes how Diameter nodes establish connections and
2509 communicate with peers.
2511 5.1. Peer Connections
2513 Although a Diameter node may have many possible peers that it is able
2514 to communicate with, it may not be economical to have an established
2515 connection to all of them. At a minimum, a Diameter node SHOULD have
2516 an established connection with two peers per realm, known as the
2517 primary and secondary peers. Of course, a node MAY have additional
2518 connections, if it is deemed necessary. Typically, all messages for
2519 a realm are sent to the primary peer, but in the event that failover
2520 procedures are invoked, any pending requests are sent to the
2521 secondary peer. However, implementations are free to load balance
2522 requests between a set of peers.
2524 Note that a given peer MAY act as a primary for a given realm, while
2525 acting as a secondary for another realm.
2527 When a peer is deemed suspect, which could occur for various reasons,
2528 including not receiving a DWA within an allotted timeframe, no new
2529 requests should be forwarded to the peer, but failover procedures are
2530 invoked. When an active peer is moved to this mode, additional
2531 connections SHOULD be established to ensure that the necessary number
2532 of active connections exists.
2534 There are two ways that a peer is removed from the suspect peer list:
2536 1. The peer is no longer reachable, causing the transport connection
2537 to be shutdown. The peer is moved to the closed state.
2539 2. Three watchdog messages are exchanged with accepted round trip
2540 times, and the connection to the peer is considered stabilized.
2542 In the event the peer being removed is either the primary or
2543 secondary, an alternate peer SHOULD replace the deleted peer, and
2544 assume the role of either primary or secondary.
2546 5.2. Diameter Peer Discovery
2548 Allowing for dynamic Diameter agent discovery will make it possible
2549 for simpler and more robust deployment of Diameter services. In
2550 order to promote interoperable implementations of Diameter peer
2551 discovery, the following mechanisms are described. These are based
2552 on existing IETF standards. The first option (manual configuration)
2553 MUST be supported by all DIAMETER nodes, while the latter option
2554 (DNS) MAY be supported.
2556 There are two cases where Diameter peer discovery may be performed.
2557 The first is when a Diameter client needs to discover a first-hop
2558 Diameter agent. The second case is when a Diameter agent needs to
2559 discover another agent - for further handling of a Diameter
2560 operation. In both cases, the following 'search order' is
2561 recommended:
2563 1. The Diameter implementation consults its list of static
2564 (manually) configured Diameter agent locations. These will be
2565 used if they exist and respond.
2567 2. The Diameter implementation performs a NAPTR query for a server
2568 in a particular realm. The Diameter implementation has to know
2569 in advance which realm to look for a Diameter agent in. This
2570 could be deduced, for example, from the 'realm' in a NAI that a
2571 Diameter implementation needed to perform a Diameter operation
2572 on.
2574 * The services relevant for the task of transport protocol
2575 selection are those with NAPTR service fields with values
2576 "AAA+D2x", where x is a letter that corresponds to a transport
2577 protocol supported by the domain. This specification defines
2578 D2T for TCP and D2S for SCTP. We also establish an IANA
2579 registry for NAPTR service name to transport protocol
2580 mappings.
2582 These NAPTR records provide a mapping from a domain, to the
2583 SRV record for contacting a server with the specific transport
2584 protocol in the NAPTR services field. The resource record
2585 will contain an empty regular expression and a replacement
2586 value, which is the SRV record for that particular transport
2587 protocol. If the server supports multiple transport
2588 protocols, there will be multiple NAPTR records, each with a
2589 different service value. As per [RFC3403], the client
2590 discards any records whose services fields are not applicable.
2591 For the purposes of this specification, several rules are
2592 defined.
2594 * A client MUST discard any service fields that identify a
2595 resolution service whose value is not "D2X", for values of X
2596 that indicate transport protocols supported by the client.
2597 The NAPTR processing as described in [RFC3403] will result in
2598 discovery of the most preferred transport protocol of the
2599 server that is supported by the client, as well as an SRV
2600 record for the server.
2602 The domain suffixes in the NAPTR replacement field SHOULD
2603 match the domain of the original query.
2605 3. If no NAPTR records are found, the requester queries for those
2606 address records for the destination address,
2607 '_diameter._sctp'.realm or '_diameter._tcp'.realm. Address
2608 records include A RR's, AAAA RR's or other similar records,
2609 chosen according to the requestor's network protocol
2610 capabilities. If the DNS server returns no address records, the
2611 requestor gives up.
2613 If the server is using a site certificate, the domain name in the
2614 query and the domain name in the replacement field MUST both be
2615 valid based on the site certificate handed out by the server in
2616 the TLS or IKE exchange. Similarly, the domain name in the SRV
2617 query and the domain name in the target in the SRV record MUST
2618 both be valid based on the same site certificate. Otherwise, an
2619 attacker could modify the DNS records to contain replacement
2620 values in a different domain, and the client could not validate
2621 that this was the desired behavior, or the result of an attack
2623 Also, the Diameter Peer MUST check to make sure that the
2624 discovered peers are authorized to act in its role.
2625 Authentication via IKE or TLS, or validation of DNS RRs via
2626 DNSSEC is not sufficient to conclude this. For example, a web
2627 server may have obtained a valid TLS certificate, and secured RRs
2628 may be included in the DNS, but this does not imply that it is
2629 authorized to act as a Diameter Server.
2631 Authorization can be achieved for example, by configuration of a
2632 Diameter Server CA. Alternatively this can be achieved by
2633 definition of OIDs within TLS or IKE certificates so as to
2634 signify Diameter Server authorization.
2636 A dynamically discovered peer causes an entry in the Peer Table (see
2637 Section 2.6) to be created. Note that entries created via DNS MUST
2638 expire (or be refreshed) within the DNS TTL. If a peer is discovered
2639 outside of the local realm, a routing table entry (see Section 2.7)
2640 for the peer's realm is created. The routing table entry's
2641 expiration MUST match the peer's expiration value.
2643 5.3. Capabilities Exchange
2645 When two Diameter peers establish a transport connection, they MUST
2646 exchange the Capabilities Exchange messages, as specified in the peer
2647 state machine (see Section 5.6). This message allows the discovery
2648 of a peer's identity and its capabilities (protocol version number,
2649 supported Diameter applications, security mechanisms, etc.)
2651 The receiver only issues commands to its peers that have advertised
2652 support for the Diameter application that defines the command. A
2653 Diameter node MUST cache the supported applications in order to
2654 ensure that unrecognized commands and/or AVPs are not unnecessarily
2655 sent to a peer.
2657 A receiver of a Capabilities-Exchange-Req (CER) message that does not
2658 have any applications in common with the sender MUST return a
2659 Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to
2660 DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport
2661 layer connection. Note that receiving a CER or CEA from a peer
2662 advertising itself as a Relay (see Section 2.4) MUST be interpreted
2663 as having common applications with the peer.
2665 The receiver of the Capabilities-Exchange-Request (CER) MUST
2666 determine common applications by computing the intersection of its
2667 own set of supported application identifiers against all of the
2668 application indentifier AVPs (Auth-Application-Id,
2669 Acct-Application-Id and Vendor-Specific-Application-Id) present in
2670 the CER. The value of the Vendor-Id AVP in the Vendor-Specific-
2671 Application-Id MUST not be used during computation. The sender of
2672 the Capabilities-Exchange-Answer (CEA) SHOULD include all of its
2673 supported applications as a hint to the receiver regarding all of its
2674 application capabilities.
2676 Similarly, a receiver of a Capabilities-Exchange-Req (CER) message
2677 that does not have any security mechanisms in common with the sender
2678 MUST return a Capabilities-Exchange-Answer (CEA) with the Result-Code
2679 AVP set to DIAMETER_NO_COMMON_SECURITY, and SHOULD disconnect the
2680 transport layer connection.
2682 CERs received from unknown peers MAY be silently discarded, or a CEA
2683 MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER.
2684 In both cases, the transport connection is closed. If the local
2685 policy permits receiving CERs from unknown hosts, a successful CEA
2686 MAY be returned. If a CER from an unknown peer is answered with a
2687 successful CEA, the lifetime of the peer entry is equal to the
2688 lifetime of the transport connection. In case of a transport
2689 failure, all the pending transactions destined to the unknown peer
2690 can be discarded.
2692 The CER and CEA messages MUST NOT be proxied, redirected or relayed.
2694 Since the CER/CEA messages cannot be proxied, it is still possible
2695 that an upstream agent receives a message for which it has no
2696 available peers to handle the application that corresponds to the
2697 Command-Code. In such instances, the 'E' bit is set in the answer
2698 message (see Section 7.) with the Result-Code AVP set to
2699 DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action
2700 (e.g., re-routing request to an alternate peer).
2702 With the exception of the Capabilities-Exchange-Request message, a
2703 message of type Request that includes the Auth-Application-Id or
2704 Acct-Application-Id AVPs, or a message with an application-specific
2705 command code, MAY only be forwarded to a host that has explicitly
2706 advertised support for the application (or has advertised the Relay
2707 Application Identifier).
2709 5.3.1. Capabilities-Exchange-Request
2711 The Capabilities-Exchange-Request (CER), indicated by the Command-
2712 Code set to 257 and the Command Flags' 'R' bit set, is sent to
2713 exchange local capabilities. Upon detection of a transport failure,
2714 this message MUST NOT be sent to an alternate peer.
2716 When Diameter is run over SCTP [RFC2960], which allows for
2717 connections to span multiple interfaces and multiple IP addresses,
2718 the Capabilities-Exchange-Request message MUST contain one Host-IP-
2719 Address AVP for each potential IP address that MAY be locally used
2720 when transmitting Diameter messages.
2722 Message Format
2724 ::= < Diameter Header: 257, REQ >
2725 { Origin-Host }
2726 { Origin-Realm }
2727 1* { Host-IP-Address }
2728 { Vendor-Id }
2729 { Product-Name }
2730 [ Origin-State-Id ]
2731 * [ Supported-Vendor-Id ]
2732 * [ Auth-Application-Id ]
2733 * [ Inband-Security-Id ]
2734 * [ Acct-Application-Id ]
2735 * [ Vendor-Specific-Application-Id ]
2736 [ Firmware-Revision ]
2737 * [ AVP ]
2739 5.3.2. Capabilities-Exchange-Answer
2741 The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code
2742 set to 257 and the Command Flags' 'R' bit cleared, is sent in
2743 response to a CER message.
2745 When Diameter is run over SCTP [RFC2960], which allows connections to
2746 span multiple interfaces, hence, multiple IP addresses, the
2747 Capabilities-Exchange-Answer message MUST contain one Host-IP-Address
2748 AVP for each potential IP address that MAY be locally used when
2749 transmitting Diameter messages.
2751 Message Format
2753 ::= < Diameter Header: 257 >
2754 { Result-Code }
2755 { Origin-Host }
2756 { Origin-Realm }
2757 1* { Host-IP-Address }
2758 { Vendor-Id }
2759 { Product-Name }
2760 [ Origin-State-Id ]
2761 [ Error-Message ]
2762 [ Failed-AVP ]
2763 * [ Supported-Vendor-Id ]
2764 * [ Auth-Application-Id ]
2765 * [ Inband-Security-Id ]
2766 * [ Acct-Application-Id ]
2767 * [ Vendor-Specific-Application-Id ]
2768 [ Firmware-Revision ]
2769 * [ AVP ]
2771 5.3.3. Vendor-Id AVP
2773 The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains
2774 the IANA "SMI Network Management Private Enterprise Codes" [RFC3232]
2775 value assigned to the vendor of the Diameter application. In
2776 combination with the Supported-Vendor-Id AVP (Section 5.3.6), this
2777 MAY be used in order to know which vendor specific attributes may be
2778 sent to the peer. It is also envisioned that the combination of the
2779 Vendor-Id, Product-Name (Section 5.3.7) and the Firmware-Revision
2780 (Section 5.3.4) AVPs MAY provide very useful debugging information.
2782 A Vendor-Id value of zero in the CER or CEA messages is reserved and
2783 indicates that this field is ignored.
2785 5.3.4. Firmware-Revision AVP
2787 The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is
2788 used to inform a Diameter peer of the firmware revision of the
2789 issuing device.
2791 For devices that do not have a firmware revision (general purpose
2792 computers running Diameter software modules, for instance), the
2793 revision of the Diameter software module may be reported instead.
2795 5.3.5. Host-IP-Address AVP
2797 The Host-IP-Address AVP (AVP Code 257) is of type Address and is used
2798 to inform a Diameter peer of the sender's IP address. All source
2799 addresses that a Diameter node expects to use with SCTP [RFC2960]
2800 MUST be advertised in the CER and CEA messages by including a
2801 Host-IP- Address AVP for each address. This AVP MUST ONLY be used in
2802 the CER and CEA messages.
2804 5.3.6. Supported-Vendor-Id AVP
2806 The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and
2807 contains the IANA "SMI Network Management Private Enterprise Codes"
2808 [RFC3232] value assigned to a vendor other than the device vendor.
2809 This is used in the CER and CEA messages in order to inform the peer
2810 that the sender supports (a subset of) the vendor-specific AVPs
2811 defined by the vendor identified in this AVP. The value of this AVP
2812 SHOULD NOT be set to zero. Multiple instances of this AVP containing
2813 the same value SHOULD NOT be sent.
2815 5.3.7. Product-Name AVP
2817 The Product-Name AVP (AVP Code 269) is of type UTF8String, and
2818 contains the vendor assigned name for the product. The Product-Name
2819 AVP SHOULD remain constant across firmware revisions for the same
2820 product.
2822 5.4. Disconnecting Peer connections
2824 When a Diameter node disconnects one of its transport connections,
2825 its peer cannot know the reason for the disconnect, and will most
2826 likely assume that a connectivity problem occurred, or that the peer
2827 has rebooted. In these cases, the peer may periodically attempt to
2828 reconnect, as stated in Section 2.1. In the event that the
2829 disconnect was a result of either a shortage of internal resources,
2830 or simply that the node in question has no intentions of forwarding
2831 any Diameter messages to the peer in the foreseeable future, a
2832 periodic connection request would not be welcomed. The
2833 Disconnection-Reason AVP contains the reason the Diameter node issued
2834 the Disconnect-Peer-Request message.
2836 The Disconnect-Peer-Request message is used by a Diameter node to
2837 inform its peer of its intent to disconnect the transport layer, and
2838 that the peer shouldn't reconnect unless it has a valid reason to do
2839 so (e.g., message to be forwarded). Upon receipt of the message, the
2840 Disconnect-Peer-Answer is returned, which SHOULD contain an error if
2841 messages have recently been forwarded, and are likely in flight,
2842 which would otherwise cause a race condition.
2844 The receiver of the Disconnect-Peer-Answer initiates the transport
2845 disconnect. The sender of the Disconnect-Peer-Answer should be able
2846 to detect the transport closure and cleanup the connection.
2848 5.4.1. Disconnect-Peer-Request
2850 The Disconnect-Peer-Request (DPR), indicated by the Command-Code set
2851 to 282 and the Command Flags' 'R' bit set, is sent to a peer to
2852 inform its intentions to shutdown the transport connection. Upon
2853 detection of a transport failure, this message MUST NOT be sent to an
2854 alternate peer.
2856 Message Format
2858 ::= < Diameter Header: 282, REQ >
2859 { Origin-Host }
2860 { Origin-Realm }
2861 { Disconnect-Cause }
2863 5.4.2. Disconnect-Peer-Answer
2865 The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set
2866 to 282 and the Command Flags' 'R' bit cleared, is sent as a response
2867 to the Disconnect-Peer-Request message. Upon receipt of this
2868 message, the transport connection is shutdown.
2870 Message Format
2872 ::= < Diameter Header: 282 >
2873 { Result-Code }
2874 { Origin-Host }
2875 { Origin-Realm }
2876 [ Error-Message ]
2877 [ Failed-AVP ]
2879 5.4.3. Disconnect-Cause AVP
2881 The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A
2882 Diameter node MUST include this AVP in the Disconnect-Peer-Request
2883 message to inform the peer of the reason for its intention to
2884 shutdown the transport connection. The following values are
2885 supported:
2887 REBOOTING 0
2888 A scheduled reboot is imminent. Receiver of DPR with above result
2889 code MAY attempt reconnection.
2891 BUSY 1
2892 The peer's internal resources are constrained, and it has
2893 determined that the transport connection needs to be closed.
2894 Receiver of DPR with above result code SHOULD NOT attempt
2895 reconnection.
2897 DO_NOT_WANT_TO_TALK_TO_YOU 2
2898 The peer has determined that it does not see a need for the
2899 transport connection to exist, since it does not expect any
2900 messages to be exchanged in the near future. Receiver of DPR
2901 with above result code SHOULD NOT attempt reconnection.
2903 5.5. Transport Failure Detection
2905 Given the nature of the Diameter protocol, it is recommended that
2906 transport failures be detected as soon as possible. Detecting such
2907 failures will minimize the occurrence of messages sent to unavailable
2908 agents, resulting in unnecessary delays, and will provide better
2909 failover performance. The Device-Watchdog-Request and Device-
2910 Watchdog-Answer messages, defined in this section, are used to pro-
2911 actively detect transport failures.
2913 5.5.1. Device-Watchdog-Request
2915 The Device-Watchdog-Request (DWR), indicated by the Command-Code set
2916 to 280 and the Command Flags' 'R' bit set, is sent to a peer when no
2917 traffic has been exchanged between two peers (see Section 5.5.3).
2918 Upon detection of a transport failure, this message MUST NOT be sent
2919 to an alternate peer.
2921 Message Format
2923 ::= < Diameter Header: 280, REQ >
2924 { Origin-Host }
2925 { Origin-Realm }
2926 [ Origin-State-Id ]
2928 5.5.2. Device-Watchdog-Answer
2930 The Device-Watchdog-Answer (DWA), indicated by the Command-Code set
2931 to 280 and the Command Flags' 'R' bit cleared, is sent as a response
2932 to the Device-Watchdog-Request message.
2934 Message Format
2936 ::= < Diameter Header: 280 >
2937 { Result-Code }
2938 { Origin-Host }
2939 { Origin-Realm }
2940 [ Error-Message ]
2941 [ Failed-AVP ]
2942 [ Origin-State-Id ]
2944 5.5.3. Transport Failure Algorithm
2946 The transport failure algorithm is defined in [RFC3539]. All
2947 Diameter implementations MUST support the algorithm defined in the
2948 specification in order to be compliant to the Diameter base protocol.
2950 5.5.4. Failover and Failback Procedures
2952 In the event that a transport failure is detected with a peer, it is
2953 necessary for all pending request messages to be forwarded to an
2954 alternate agent, if possible. This is commonly referred to as
2955 failover.
2957 In order for a Diameter node to perform failover procedures, it is
2958 necessary for the node to maintain a pending message queue for a
2959 given peer. When an answer message is received, the corresponding
2960 request is removed from the queue. The Hop-by-Hop Identifier field
2961 is used to match the answer with the queued request.
2963 When a transport failure is detected, if possible all messages in the
2964 queue are sent to an alternate agent with the T flag set. On booting
2965 a Diameter client or agent, the T flag is also set on any records
2966 still remaining to be transmitted in non-volatile storage. An
2967 example of a case where it is not possible to forward the message to
2968 an alternate server is when the message has a fixed destination, and
2969 the unavailable peer is the message's final destination (see
2970 Destination-Host AVP). Such an error requires that the agent return
2971 an answer message with the 'E' bit set and the Result-Code AVP set to
2972 DIAMETER_UNABLE_TO_DELIVER.
2974 It is important to note that multiple identical requests or answers
2975 MAY be received as a result of a failover. The End-to-End Identifier
2976 field in the Diameter header along with the Origin-Host AVP MUST be
2977 used to identify duplicate messages.
2979 As described in Section 2.1, a connection request should be
2980 periodically attempted with the failed peer in order to re-establish
2981 the transport connection. Once a connection has been successfully
2982 established, messages can once again be forwarded to the peer. This
2983 is commonly referred to as failback.
2985 5.6. Peer State Machine
2987 This section contains a finite state machine that MUST be observed by
2988 all Diameter implementations. Each Diameter node MUST follow the
2989 state machine described below when communicating with each peer.
2990 Multiple actions are separated by commas, and may continue on
2991 succeeding lines, as space requires. Similarly, state and next state
2992 may also span multiple lines, as space requires.
2994 This state machine is closely coupled with the state machine
2995 described in [RFC3539], which is used to open, close, failover,
2996 probe, and reopen transport connections. Note in particular that
2997 [RFC3539] requires the use of watchdog messages to probe connections.
2998 For Diameter, DWR and DWA messages are to be used.
3000 I- is used to represent the initiator (connecting) connection, while
3001 the R- is used to represent the responder (listening) connection.
3002 The lack of a prefix indicates that the event or action is the same
3003 regardless of the connection on which the event occurred.
3005 The stable states that a state machine may be in are Closed, I-Open
3006 and R-Open; all other states are intermediate. Note that I-Open and
3007 R-Open are equivalent except for whether the initiator or responder
3008 transport connection is used for communication.
3010 A CER message is always sent on the initiating connection immediately
3011 after the connection request is successfully completed. In the case
3012 of an election, one of the two connections will shut down. The
3013 responder connection will survive if the Origin-Host of the local
3014 Diameter entity is higher than that of the peer; the initiator
3015 connection will survive if the peer's Origin-Host is higher. All
3016 subsequent messages are sent on the surviving connection. Note that
3017 the results of an election on one peer are guaranteed to be the
3018 inverse of the results on the other.
3020 For TLS usage, a TLS handshake will begin when both ends are in the
3021 open state. If the TLS handshake is successful, all further messages
3022 will be sent via TLS. If the handshake fails, both ends move to the
3023 closed state.
3025 The state machine constrains only the behavior of a Diameter
3026 implementation as seen by Diameter peers through events on the wire.
3028 Any implementation that produces equivalent results is considered
3029 compliant.
3031 state event action next state
3032 -----------------------------------------------------------------
3033 Closed Start I-Snd-Conn-Req Wait-Conn-Ack
3034 R-Conn-CER R-Accept, R-Open
3035 Process-CER,
3036 R-Snd-CEA
3038 Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA
3039 I-Rcv-Conn-Nack Cleanup Closed
3040 R-Conn-CER R-Accept, Wait-Conn-Ack/
3041 Process-CER Elect
3042 Timeout Error Closed
3044 Wait-I-CEA I-Rcv-CEA Process-CEA I-Open
3045 R-Conn-CER R-Accept, Wait-Returns
3046 Process-CER,
3047 Elect
3048 I-Peer-Disc I-Disc Closed
3049 I-Rcv-Non-CEA Error Closed
3050 Timeout Error Closed
3052 Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns
3053 Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open
3054 R-Peer-Disc R-Disc Wait-Conn-Ack
3055 R-Conn-CER R-Reject Wait-Conn-Ack/
3056 Elect
3057 Timeout Error Closed
3059 Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open
3060 I-Peer-Disc I-Disc, R-Open
3061 R-Snd-CEA
3062 I-Rcv-CEA R-Disc I-Open
3063 R-Peer-Disc R-Disc Wait-I-CEA
3064 R-Conn-CER R-Reject Wait-Returns
3065 Timeout Error Closed
3067 R-Open Send-Message R-Snd-Message R-Open
3068 R-Rcv-Message Process R-Open
3069 R-Rcv-DWR Process-DWR, R-Open
3070 R-Snd-DWA
3071 R-Rcv-DWA Process-DWA R-Open
3072 R-Conn-CER R-Reject R-Open
3073 Stop R-Snd-DPR Closing
3074 R-Rcv-DPR R-Snd-DPA, Closed
3075 R-Disc
3077 R-Peer-Disc R-Disc Closed
3078 R-Rcv-CER R-Snd-CEA R-Open
3079 R-Rcv-CEA Process-CEA R-Open
3081 I-Open Send-Message I-Snd-Message I-Open
3082 I-Rcv-Message Process I-Open
3083 I-Rcv-DWR Process-DWR, I-Open
3084 I-Snd-DWA
3085 I-Rcv-DWA Process-DWA I-Open
3086 R-Conn-CER R-Reject I-Open
3087 Stop I-Snd-DPR Closing
3088 I-Rcv-DPR I-Snd-DPA, Closed
3089 I-Disc
3090 I-Peer-Disc I-Disc Closed
3091 I-Rcv-CER I-Snd-CEA I-Open
3092 I-Rcv-CEA Process-CEA I-Open
3094 Closing I-Rcv-DPA I-Disc Closed
3095 R-Rcv-DPA R-Disc Closed
3096 Timeout Error Closed
3097 I-Peer-Disc I-Disc Closed
3098 R-Peer-Disc R-Disc Closed
3100 5.6.1. Incoming connections
3102 When a connection request is received from a Diameter peer, it is
3103 not, in the general case, possible to know the identity of that peer
3104 until a CER is received from it. This is because host and port
3105 determine the identity of a Diameter peer; and the source port of an
3106 incoming connection is arbitrary. Upon receipt of CER, the identity
3107 of the connecting peer can be uniquely determined from Origin-Host.
3109 For this reason, a Diameter peer must employ logic separate from the
3110 state machine to receive connection requests, accept them, and await
3111 CER. Once CER arrives on a new connection, the Origin-Host that
3112 identifies the peer is used to locate the state machine associated
3113 with that peer, and the new connection and CER are passed to the
3114 state machine as an R-Conn-CER event.
3116 The logic that handles incoming connections SHOULD close and discard
3117 the connection if any message other than CER arrives, or if an
3118 implementation-defined timeout occurs prior to receipt of CER.
3120 Because handling of incoming connections up to and including receipt
3121 of CER requires logic, separate from that of any individual state
3122 machine associated with a particular peer, it is described separately
3123 in this section rather than in the state machine above.
3125 5.6.2. Events
3127 Transitions and actions in the automaton are caused by events. In
3128 this section, we will ignore the -I and -R prefix, since the actual
3129 event would be identical, but would occur on one of two possible
3130 connections.
3132 Start The Diameter application has signaled that a
3133 connection should be initiated with the peer.
3135 R-Conn-CER An acknowledgement is received stating that the
3136 transport connection has been established, and the
3137 associated CER has arrived.
3139 Rcv-Conn-Ack A positive acknowledgement is received confirming that
3140 the transport connection is established.
3142 Rcv-Conn-Nack A negative acknowledgement was received stating that
3143 the transport connection was not established.
3145 Timeout An application-defined timer has expired while waiting
3146 for some event.
3148 Rcv-CER A CER message from the peer was received.
3150 Rcv-CEA A CEA message from the peer was received.
3152 Rcv-Non-CEA A message other than CEA from the peer was received.
3154 Peer-Disc A disconnection indication from the peer was received.
3156 Rcv-DPR A DPR message from the peer was received.
3158 Rcv-DPA A DPA message from the peer was received.
3160 Win-Election An election was held, and the local node was the
3161 winner.
3163 Send-Message A message is to be sent.
3165 Rcv-Message A message other than CER, CEA, DPR, DPA, DWR or DWA
3166 was received.
3168 Stop The Diameter application has signaled that a
3169 connection should be terminated (e.g., on system
3170 shutdown).
3172 5.6.3. Actions
3174 Actions in the automaton are caused by events and typically indicate
3175 the transmission of packets and/or an action to be taken on the
3176 connection. In this section we will ignore the I- and R-prefix,
3177 since the actual action would be identical, but would occur on one of
3178 two possible connections.
3180 Snd-Conn-Req A transport connection is initiated with the peer.
3182 Accept The incoming connection associated with the R-Conn-CER
3183 is accepted as the responder connection.
3185 Reject The incoming connection associated with the R-Conn-CER
3186 is disconnected.
3188 Process-CER The CER associated with the R-Conn-CER is processed.
3189 Snd-CER A CER message is sent to the peer.
3191 Snd-CEA A CEA message is sent to the peer.
3193 Cleanup If necessary, the connection is shutdown, and any
3194 local resources are freed.
3196 Error The transport layer connection is disconnected, either
3197 politely or abortively, in response to an error
3198 condition. Local resources are freed.
3200 Process-CEA A received CEA is processed.
3202 Snd-DPR A DPR message is sent to the peer.
3204 Snd-DPA A DPA message is sent to the peer.
3206 Disc The transport layer connection is disconnected, and
3207 local resources are freed.
3209 Elect An election occurs (see Section 5.6.4 for more
3210 information).
3212 Snd-Message A message is sent.
3214 Snd-DWR A DWR message is sent.
3216 Snd-DWA A DWA message is sent.
3218 Process-DWR The DWR message is serviced.
3220 Process-DWA The DWA message is serviced.
3222 Process A message is serviced.
3224 5.6.4. The Election Process
3226 The election is performed on the responder. The responder compares
3227 the Origin-Host received in the CER with its own Origin-Host as two
3228 streams of octets. If the local Origin-Host lexicographically
3229 succeeds the received Origin-Host a Win-Election event is issued
3230 locally.
3232 To be consistent with DNS case insensitivity, octets that fall in the
3233 ASCII range 'a' through 'z' MUST compare equally to their upper-case
3234 counterparts between 'A' and 'Z', i.e. value 0x41 compares equal to
3235 0x61, 0x42 to 0x62 and so forth up to and including 0x5a and 0x7a.
3237 The winner of the election MUST close the connection it initiated.
3238 Historically, maintaining the responder side of a connection was more
3239 efficient than maintaining the initiator side. However, current
3240 practices makes this distinction irrelevant.
3242 5.6.5. Capabilities Update
3244 A Diameter node MUST initiate peer capabilities update by sending a
3245 Capabilities-Exchange-Req (CER) to all its peers which supports peer
3246 capabilities update and is in OPEN state. The receiver of CER in
3247 open state MUST process and reply to the CER as a described in
3248 Section 5.3. The CEA which the receiver sends MUST contain its
3249 latest capabilities. Note that peers which successfully process the
3250 peer capabilities update SHOULD also update their routing tables to
3251 reflect the change. The receiver of the CEA, with a Result-Code AVP
3252 other than DIAMETER_SUCCESS, initiates the transport disconnect. The
3253 peer may periodically attempt to reconnect, as stated in Section 2.1.
3255 Peer capabilities update in the open state SHOULD be limited to the
3256 advertisement of the new list of supported applications and MUST
3257 preclude re-negotiation of security mechanism or other capabilities.
3258 If any capabilities change happens in the node (e.g. change in
3259 security mechanisms), other than a change in the supported
3260 applications, the node SHOULD gracefully terminate (setting the
3261 Disconnect-Cause AVP value to REBOOTING) and re-establish the
3262 diameter connections to all the peers.
3264 6. Diameter message processing
3266 This section describes how Diameter requests and answers are created
3267 and processed.
3269 6.1. Diameter Request Routing Overview
3271 A request is sent towards its final destination using a combination
3272 of the Destination-Realm and Destination-Host AVPs, in one of these
3273 three combinations:
3275 o a request that is not able to be proxied (such as CER) MUST NOT
3276 contain either Destination-Realm or Destination-Host AVPs.
3278 o a request that needs to be sent to a home server serving a
3279 specific realm, but not to a specific server (such as the first
3280 request of a series of round-trips), MUST contain a Destination-
3281 Realm AVP, but MUST NOT contain a Destination-Host AVP.
3283 o otherwise, a request that needs to be sent to a specific home
3284 server among those serving a given realm, MUST contain both the
3285 Destination-Realm and Destination-Host AVPs.
3287 The Destination-Host AVP is used as described above when the
3288 destination of the request is fixed, which includes:
3290 o Authentication requests that span multiple round trips
3292 o A Diameter message that uses a security mechanism that makes use
3293 of a pre-established session key shared between the source and the
3294 final destination of the message.
3296 o Server initiated messages that MUST be received by a specific
3297 Diameter client (e.g., access device), such as the Abort-Session-
3298 Request message, which is used to request that a particular user's
3299 session be terminated.
3301 Note that an agent can forward a request to a host described in the
3302 Destination-Host AVP only if the host in question is included in its
3303 peer table (see Section 2.7). Otherwise, the request is routed based
3304 on the Destination-Realm only (see Sections 6.1.6).
3306 The Destination-Realm AVP MUST be present if the message is
3307 proxiable. Request messages that may be forwarded by Diameter agents
3308 (proxies, redirects or relays) MUST also contain an Acct-
3309 Application-Id AVP, an Auth-Application-Id AVP or a Vendor-Specific-
3310 Application-Id AVP. A message that MUST NOT be forwarded by Diameter
3311 agents (proxies, redirects or relays) MUST not include the
3312 Destination-Realm in its ABNF. The value of the Destination-Realm
3313 AVP MAY be extracted from the User-Name AVP, or other application-
3314 specific methods.
3316 When a message is received, the message is processed in the following
3317 order:
3319 o If the message is destined for the local host, the procedures
3320 listed in Section 6.1.4 are followed.
3322 o If the message is intended for a Diameter peer with whom the local
3323 host is able to directly communicate, the procedures listed in
3324 Section 6.1.5 are followed. This is known as Request Forwarding.
3326 o The procedures listed in Section 6.1.6 are followed, which is
3327 known as Request Routing.
3329 o If none of the above is successful, an answer is returned with the
3330 Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the E-bit set.
3332 For routing of Diameter messages to work within an administrative
3333 domain, all Diameter nodes within the realm MUST be peers.
3335 Note the processing rules contained in this section are intended to
3336 be used as general guidelines to Diameter developers. Certain
3337 implementations MAY use different methods than the ones described
3338 here, and still comply with the protocol specification. See Section
3339 7 for more detail on error handling.
3341 6.1.1. Originating a Request
3343 When creating a request, in addition to any other procedures
3344 described in the application definition for that specific request,
3345 the following procedures MUST be followed:
3347 o the Command-Code is set to the appropriate value
3349 o the 'R' bit is set
3351 o the End-to-End Identifier is set to a locally unique value
3353 o the Origin-Host and Origin-Realm AVPs MUST be set to the
3354 appropriate values, used to identify the source of the message
3356 o the Destination-Host and Destination-Realm AVPs MUST be set to the
3357 appropriate values as described in Section 6.1.
3359 o an Acct-Application-Id AVP, an Auth-Application-Id or a Vendor-
3360 Specific-Application-Id AVP must be included if the request is
3361 proxiable. The application id present in one of these relevant
3362 AVPs must match the application id present in the diameter message
3363 header.
3365 6.1.2. Sending a Request
3367 When sending a request, originated either locally, or as the result
3368 of a forwarding or routing operation, the following procedures MUST
3369 be followed:
3371 o the Hop-by-Hop Identifier should be set to a locally unique value.
3373 o The message should be saved in the list of pending requests.
3375 Other actions to perform on the message based on the particular role
3376 the agent is playing are described in the following sections.
3378 6.1.3. Receiving Requests
3380 A relay or proxy agent MUST check for forwarding loops when receiving
3381 requests. A loop is detected if the server finds its own identity in
3382 a Route-Record AVP. When such an event occurs, the agent MUST answer
3383 with the Result-Code AVP set to DIAMETER_LOOP_DETECTED.
3385 6.1.4. Processing Local Requests
3387 A request is known to be for local consumption when one of the
3388 following conditions occur:
3390 o The Destination-Host AVP contains the local host's identity,
3392 o The Destination-Host AVP is not present, the Destination-Realm AVP
3393 contains a realm the server is configured to process locally, and
3394 the Diameter application is locally supported, or
3396 o Both the Destination-Host and the Destination-Realm are not
3397 present.
3399 When a request is locally processed, the rules in Section 6.2 should
3400 be used to generate the corresponding answer.
3402 6.1.5. Request Forwarding
3404 Request forwarding is done using the Diameter Peer Table. The
3405 Diameter peer table contains all of the peers that the local node is
3406 able to directly communicate with.
3408 When a request is received, and the host encoded in the Destination-
3409 Host AVP is one that is present in the peer table, the message SHOULD
3410 be forwarded to the peer.
3412 6.1.6. Request Routing
3414 Diameter request message routing is done via realms and applications.
3415 A Diameter message that may be forwarded by Diameter agents (proxies,
3416 redirects or relays) MUST include the target realm in the
3417 Destination-Realm AVP. Request routing SHOULD rely on the
3418 Destination-Realm AVP and the application id present in the request
3419 message header to aid in the routing decision. It MAY also rely on
3420 the application identification AVPs Auth-Application-Id, Acct-
3421 Application-Id or Vendor-Specific-Application-Id instead of the
3422 application id in the message header as a secondary measure. The
3423 realm MAY be retrieved from the User-Name AVP, which is in the form
3424 of a Network Access Identifier (NAI). The realm portion of the NAI
3425 is inserted in the Destination-Realm AVP.
3427 Diameter agents MAY have a list of locally supported realms and
3428 applications, and MAY have a list of externally supported realms and
3429 applications. When a request is received that includes a realm
3430 and/or application that is not locally supported, the message is
3431 routed to the peer configured in the Routing Table (see Section 2.7).
3433 Realm names and application identifiers are the minimum supported
3434 routing criteria, additional routing information maybe needed to
3435 support redirect semantics.
3437 6.1.7. Predictive Loop Avoidance
3439 Before forwarding or routing a request, Diameter agents, in addition
3440 to processing done in Section 6.1.3, SHOULD check for the presence of
3441 candidate route's peer identity in any of the Route-Record AVPs. In
3442 an event of the agent detecting the presence of a candidate route's
3443 peer identity in a Route-Record AVP, the agent MUST ignore such route
3444 for the Diameter request message and attempt alternate routes if any.
3445 In case all the candidate routes are eliminated by the above
3446 criteria, the agent SHOULD return DIAMETER_UNABLE_TO_DELIVER message.
3448 6.1.8. Redirecting requests
3450 When a redirect agent receives a request whose routing entry is set
3451 to REDIRECT, it MUST reply with an answer message with the 'E' bit
3452 set, while maintaining the Hop-by-Hop Identifier in the header, and
3453 include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of
3454 the servers associated with the routing entry are added in separate
3455 Redirect-Host AVP.
3457 +------------------+
3458 | Diameter |
3459 | Redirect Agent |
3460 +------------------+
3461 ^ | 2. command + 'E' bit
3462 1. Request | | Result-Code =
3463 joe@example.com | | DIAMETER_REDIRECT_INDICATION +
3464 | | Redirect-Host AVP(s)
3465 | v
3466 +-------------+ 3. Request +-------------+
3467 | example.com |------------->| example.net |
3468 | Relay | | Diameter |
3469 | Agent |<-------------| Server |
3470 +-------------+ 4. Answer +-------------+
3472 Figure 5: Diameter Redirect Agent
3474 The receiver of the answer message with the 'E' bit set, and the
3475 Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by-
3476 hop field in the Diameter header to identify the request in the
3477 pending message queue (see Section 5.3) that is to be redirected. If
3478 no transport connection exists with the new agent, one is created,
3479 and the request is sent directly to it.
3481 Multiple Redirect-Host AVPs are allowed. The receiver of the answer
3482 message with the 'E' bit set selects exactly one of these hosts as
3483 the destination of the redirected message.
3485 When the Redirect-Host-Usage AVP included in the answer message has a
3486 non-zero value, a route entry for the redirect indications is created
3487 and cached by the receiver. The redirect usage for such route entry
3488 is set by the value of Redirect-Host-Usage AVP and the lifetime of
3489 the cached route entry is set by Redirect-Max-Cache-Time AVP value.
3491 It is possible that multiple redirect indications can create multiple
3492 cached route entries differing only in their redirect usage and the
3493 peer to forward messages to. As an example, two(2) route entries
3494 that are created by two(2) redirect indications results in two(2)
3495 cached routes for the same realm and application Id. However, one
3496 has a redirect usage of ALL_SESSION where matching request will be
3497 forwarded to one peer and the other has a redirect usage of ALL_REALM
3498 where request are forwarded to another peer. Therefore, an incoming
3499 request that matches the realm and application Id of both routes will
3500 need additional resolution. In such a case, a routing precedence
3501 rule MUST be used againts the redirect usage value to resolve the
3502 contention. The precedence rule can be found in Section 6.13.
3504 6.1.9. Relaying and Proxying Requests
3506 A relay or proxy agent MUST append a Route-Record AVP to all requests
3507 forwarded. The AVP contains the identity of the peer the request was
3508 received from.
3510 The Hop-by-Hop identifier in the request is saved, and replaced with
3511 a locally unique value. The source of the request is also saved,
3512 which includes the IP address, port and protocol.
3514 A relay or proxy agent MAY include the Proxy-Info AVP in requests if
3515 it requires access to any local state information when the
3516 corresponding response is received. Proxy-Info AVP has certain
3517 security implications and SHOULD contain an embedded HMAC with a
3518 node-local key. Alternatively, it MAY simply use local storage to
3519 store state information.
3521 The message is then forwarded to the next hop, as identified in the
3522 Routing Table.
3524 Figure 6 provides an example of message routing using the procedures
3525 listed in these sections.
3527 (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net)
3528 (Origin-Realm=mno.net) (Origin-Realm=mno.net)
3529 (Destination-Realm=example.com) (Destination-
3530 Realm=example.com)
3531 (Route-Record=nas.example.net)
3532 +------+ ------> +------+ ------> +------+
3533 | | (Request) | | (Request) | |
3534 | NAS +-------------------+ DRL +-------------------+ HMS |
3535 | | | | | |
3536 +------+ <------ +------+ <------ +------+
3537 example.net (Answer) example.net (Answer) example.com
3538 (Origin-Host=hms.example.com) (Origin-Host=hms.example.com)
3539 (Origin-Realm=example.com) (Origin-Realm=example.com)
3541 Figure 6: Routing of Diameter messages
3543 Relay agents do not require full validation of incoming messages. At
3544 a minimum, validation of the message header and relevant routing AVPs
3545 has to be done when relaying messages.
3547 6.2. Diameter Answer Processing
3549 When a request is locally processed, the following procedures MUST be
3550 applied to create the associated answer, in addition to any
3551 additional procedures that MAY be discussed in the Diameter
3552 application defining the command:
3554 o The same Hop-by-Hop identifier in the request is used in the
3555 answer.
3557 o The local host's identity is encoded in the Origin-Host AVP.
3559 o The Destination-Host and Destination-Realm AVPs MUST NOT be
3560 present in the answer message.
3562 o The Result-Code AVP is added with its value indicating success or
3563 failure.
3565 o If the Session-Id is present in the request, it MUST be included
3566 in the answer.
3568 o Any Proxy-Info AVPs in the request MUST be added to the answer
3569 message, in the same order they were present in the request.
3571 o The 'P' bit is set to the same value as the one in the request.
3573 o The same End-to-End identifier in the request is used in the
3574 answer.
3576 Note that the error messages (see Section 7.3) are also subjected to
3577 the above processing rules.
3579 6.2.1. Processing received Answers
3581 A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an
3582 answer received against the list of pending requests. The
3583 corresponding message should be removed from the list of pending
3584 requests. It SHOULD ignore answers received that do not match a
3585 known Hop-by-Hop Identifier.
3587 6.2.2. Relaying and Proxying Answers
3589 If the answer is for a request which was proxied or relayed, the
3590 agent MUST restore the original value of the Diameter header's Hop-
3591 by-Hop Identifier field.
3593 If the last Proxy-Info AVP in the message is targeted to the local
3594 Diameter server, the AVP MUST be removed before the answer is
3595 forwarded.
3597 If a relay or proxy agent receives an answer with a Result-Code AVP
3598 indicating a failure, it MUST NOT modify the contents of the AVP.
3599 Any additional local errors detected SHOULD be logged, but not
3600 reflected in the Result-Code AVP. If the agent receives an answer
3601 message with a Result-Code AVP indicating success, and it wishes to
3602 modify the AVP to indicate an error, it MUST modify the Result-Code
3603 AVP to contain the appropriate error in the message destined towards
3604 the access device as well as include the Error-Reporting-Host AVP and
3605 it MUST issue an STR on behalf of the access device.
3607 The agent MUST then send the answer to the host that it received the
3608 original request from.
3610 6.3. Origin-Host AVP
3612 The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and
3613 MUST be present in all Diameter messages. This AVP identifies the
3614 endpoint that originated the Diameter message. Relay agents MUST NOT
3615 modify this AVP.
3617 The value of the Origin-Host AVP is guaranteed to be unique within a
3618 single host.
3620 Note that the Origin-Host AVP may resolve to more than one address as
3621 the Diameter peer may support more than one address.
3623 This AVP SHOULD be placed as close to the Diameter header as
3624 possible. 6.10
3626 6.4. Origin-Realm AVP
3628 The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity.
3629 This AVP contains the Realm of the originator of any Diameter message
3630 and MUST be present in all messages.
3632 This AVP SHOULD be placed as close to the Diameter header as
3633 possible.
3635 6.5. Destination-Host AVP
3637 The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity.
3638 This AVP MUST be present in all unsolicited agent initiated messages,
3639 MAY be present in request messages, and MUST NOT be present in Answer
3640 messages.
3642 The absence of the Destination-Host AVP will cause a message to be
3643 sent to any Diameter server supporting the application within the
3644 realm specified in Destination-Realm AVP.
3646 This AVP SHOULD be placed as close to the Diameter header as
3647 possible.
3649 6.6. Destination-Realm AVP
3651 The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity,
3652 and contains the realm the message is to be routed to. The
3653 Destination-Realm AVP MUST NOT be present in Answer messages.
3654 Diameter Clients insert the realm portion of the User-Name AVP.
3655 Diameter servers initiating a request message use the value of the
3656 Origin-Realm AVP from a previous message received from the intended
3657 target host (unless it is known a priori). When present, the
3658 Destination-Realm AVP is used to perform message routing decisions.
3660 Request messages whose ABNF does not list the Destination-Realm AVP
3661 as a mandatory AVP are inherently non-routable messages.
3663 This AVP SHOULD be placed as close to the Diameter header as
3664 possible.
3666 6.7. Routing AVPs
3668 The AVPs defined in this section are Diameter AVPs used for routing
3669 purposes. These AVPs change as Diameter messages are processed by
3670 agents.
3672 6.7.1. Route-Record AVP
3674 The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The
3675 identity added in this AVP MUST be the same as the one received in
3676 the Origin-Host of the Capabilities Exchange message.
3678 6.7.2. Proxy-Info AVP
3680 The Proxy-Info AVP (AVP Code 284) is of type Grouped. The Grouped
3681 Data field has the following ABNF grammar:
3683 Proxy-Info ::= < AVP Header: 284 >
3684 { Proxy-Host }
3685 { Proxy-State }
3686 * [ AVP ]
3688 6.7.3. Proxy-Host AVP
3690 The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This
3691 AVP contains the identity of the host that added the Proxy-Info AVP.
3693 6.7.4. Proxy-State AVP
3695 The Proxy-State AVP (AVP Code 33) is of type OctetString, and
3696 contains state local information, and MUST be treated as opaque data.
3698 6.8. Auth-Application-Id AVP
3700 The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and
3701 is used in order to advertise support of the Authentication and
3702 Authorization portion of an application (see Section 2.4). The Auth-
3703 Application-Id MUST also be present in all Authentication and/or
3704 Authorization messages that are defined in a separate Diameter
3705 specification and have an Application ID assigned. If present in a
3706 message, the value of the Auth-Application-Id AVP MUST match the
3707 application id present in the diameter message header except when
3708 used in a CER or CEA messages.
3710 6.9. Acct-Application-Id AVP
3712 The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and
3713 is used in order to advertise support of the Accounting portion of an
3714 application (see Section 2.4). The Acct-Application-Id MUST also be
3715 present in all Accounting messages. Exactly one of the Auth-
3716 Application-Id and Acct-Application-Id AVPs MAY be present. If
3717 present in a message, the value of the Acct-Application-Id AVP MUST
3718 match the application id present in the diameter message header
3719 except when used in a CER or CEA messages.
3721 6.10. Inband-Security-Id AVP
3723 The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and
3724 is used in order to advertise support of the Security portion of the
3725 application.
3727 Currently, the following values are supported, but there is ample
3728 room to add new security Ids.
3730 NO_INBAND_SECURITY 0
3732 This peer does not support TLS. This is the default value, if the
3733 AVP is omitted.
3735 TLS 1
3737 This node supports TLS security, as defined by [RFC4346].
3739 6.11. Vendor-Specific-Application-Id AVP
3741 The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type
3742 Grouped and is used to advertise support of a vendor-specific
3743 Diameter Application. Exactly one instance of Auth-Application-Id or
3744 Acct-Application-Id AVP MAY be present. The application identifier
3745 carried by either Auth-Application-Id or Acct-Application-Id AVP MUST
3746 comply with vendor specific application identifier assignment
3747 described in Sec 11.3. It MUST also match the application id present
3748 in the diameter header except when used in a CER or CEA messages.
3750 The Vendor-Id AVP is an informational AVP pertaining to the vendor
3751 who may have authorship of the vendor-specific diameter application.
3752 It should not be used as a means of defining a completely separate
3753 vendor-specific application identifier space.
3755 This AVP MUST also be present as the first AVP in all experimental
3756 commands defined in the vendor-specific application.
3758 This AVP SHOULD be placed as close to the Diameter header as
3759 possible.
3761 AVP Format
3763 ::= < AVP Header: 260 >
3764 { Vendor-Id }
3765 { Auth-Application-Id } /
3766 { Acct-Application-Id }
3768 6.12. Redirect-Host AVP
3770 One or more of instances of this AVP MUST be present if the answer
3771 message's 'E' bit is set and the Result-Code AVP is set to
3772 DIAMETER_REDIRECT_INDICATION.
3774 Upon receiving the above, the receiving Diameter node SHOULD forward
3775 the request directly to one of the hosts identified in these AVPs.
3776 The server contained in the selected Redirect-Host AVP SHOULD be used
3777 for all messages pertaining to this session.
3779 6.13. Redirect-Host-Usage AVP
3781 The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated.
3782 This AVP MAY be present in answer messages whose 'E' bit is set and
3783 the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION.
3785 When present, this AVP dictates how the routing entry resulting from
3786 the Redirect-Host is to be used. The following values are supported:
3788 DONT_CACHE 0
3790 The host specified in the Redirect-Host AVP should not be cached.
3791 This is the default value.
3793 ALL_SESSION 1
3795 All messages within the same session, as defined by the same value
3796 of the Session-ID AVP MAY be sent to the host specified in the
3797 Redirect-Host AVP.
3799 ALL_REALM 2
3801 All messages destined for the realm requested MAY be sent to the
3802 host specified in the Redirect-Host AVP.
3804 REALM_AND_APPLICATION 3
3806 All messages for the application requested to the realm specified
3807 MAY be sent to the host specified in the Redirect-Host AVP.
3809 ALL_APPLICATION 4
3811 All messages for the application requested MAY be sent to the host
3812 specified in the Redirect-Host AVP.
3814 ALL_HOST 5
3816 All messages that would be sent to the host that generated the
3817 Redirect-Host MAY be sent to the host specified in the Redirect-
3818 Host AVP.
3820 ALL_USER 6
3822 All messages for the user requested MAY be sent to the host
3823 specified in the Redirect-Host AVP.
3825 When multiple cached routes are created by redirect indications and
3826 they differs only in redirect usage and peers to forward requests to
3827 (see Section 6.1.8), a precedence rule MUST be applied to the
3828 redirect usage values of the cached routes during normal routing to
3829 resolve contentions that may occur. The precedence rule is the order
3830 that dictate which redirect usage should be considered before any
3831 other as they appear. The order is as follows:
3833 1. ALL_SESSION
3835 2. ALL_USER
3837 3. REALM_AND_APPLICATION
3839 4. ALL_REALM
3841 5. ALL_APPLICATION
3843 6. ALL_HOST
3845 6.14. Redirect-Max-Cache-Time AVP
3847 The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32.
3848 This AVP MUST be present in answer messages whose 'E' bit is set, the
3849 Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the
3850 Redirect-Host-Usage AVP set to a non-zero value.
3852 This AVP contains the maximum number of seconds the peer and route
3853 table entries, created as a result of the Redirect-Host, will be
3854 cached. Note that once a host created due to a redirect indication
3855 is no longer reachable, any associated peer and routing table entries
3856 MUST be deleted.
3858 6.15. E2E-Sequence AVP
3860 The E2E-Sequence AVP (AVP Code 300) provides anti-replay protection
3861 for end to end messages and is of type grouped. It contains a random
3862 value (an OctetString with a nonce) and counter (an Integer). For
3863 each end-to-end peer with which a node communicates (or remembers
3864 communicating) a different nonce value MUST be used and the counter
3865 is initiated at zero and increases by one each time this AVP is
3866 emitted to that peer.
3868 7. Error Handling
3870 There are two different types of errors in Diameter; protocol and
3871 application errors. A protocol error is one that occurs at the base
3872 protocol level, and MAY require per hop attention (e.g., message
3873 routing error). Application errors, on the other hand, generally
3874 occur due to a problem with a function specified in a Diameter
3875 application (e.g., user authentication, Missing AVP).
3877 Result-Code AVP values that are used to report protocol errors MUST
3878 only be present in answer messages whose 'E' bit is set. When a
3879 request message is received that causes a protocol error, an answer
3880 message is returned with the 'E' bit set, and the Result-Code AVP is
3881 set to the appropriate protocol error value. As the answer is sent
3882 back towards the originator of the request, each proxy or relay agent
3883 MAY take action on the message.
3885 1. Request +---------+ Link Broken
3886 +-------------------------->|Diameter |----///----+
3887 | +---------------------| | v
3888 +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+
3889 |Diameter |<-+ (Unable to Forward) +---------+ |Diameter|
3890 | | | Home |
3891 | Relay 1 |--+ +---------+ | Server |
3892 +---------+ | 3. Request |Diameter | +--------+
3893 +-------------------->| | ^
3894 | Relay 3 |-----------+
3895 +---------+
3897 Figure 7: Example of Protocol Error causing answer message
3899 Figure 7 provides an example of a message forwarded upstream by a
3900 Diameter relay. When the message is received by Relay 2, and it
3901 detects that it cannot forward the request to the home server, an
3902 answer message is returned with the 'E' bit set and the Result-Code
3903 AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls
3904 within the protocol error category, Relay 1 would take special
3905 action, and given the error, attempt to route the message through its
3906 alternate Relay 3.
3908 +---------+ 1. Request +---------+ 2. Request +---------+
3909 | Access |------------>|Diameter |------------>|Diameter |
3910 | | | | | Home |
3911 | Device |<------------| Relay |<------------| Server |
3912 +---------+ 4. Answer +---------+ 3. Answer +---------+
3913 (Missing AVP) (Missing AVP)
3915 Figure 8: Example of Application Error Answer message
3917 Figure 8 provides an example of a Diameter message that caused an
3918 application error. When application errors occur, the Diameter
3919 entity reporting the error clears the 'R' bit in the Command Flags,
3920 and adds the Result-Code AVP with the proper value. Application
3921 errors do not require any proxy or relay agent involvement, and
3922 therefore the message would be forwarded back to the originator of
3923 the request.
3925 There are certain Result-Code AVP application errors that require
3926 additional AVPs to be present in the answer. In these cases, the
3927 Diameter node that sets the Result-Code AVP to indicate the error
3928 MUST add the AVPs. Examples are:
3930 o An unrecognized AVP is received with the 'M' bit (Mandatory bit)
3931 set, causes an answer to be sent with the Result-Code AVP set to
3932 DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the
3933 offending AVP.
3935 o An AVP that is received with an unrecognized value causes an
3936 answer to be returned with the Result-Code AVP set to
3937 DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the
3938 AVP causing the error.
3940 o A command is received with an AVP that is omitted, yet is
3941 mandatory according to the command's ABNF. The receiver issues an
3942 answer with the Result-Code set to DIAMETER_MISSING_AVP, and
3943 creates an AVP with the AVP Code and other fields set as expected
3944 in the missing AVP. The created AVP is then added to the Failed-
3945 AVP AVP.
3947 The Result-Code AVP describes the error that the Diameter node
3948 encountered in its processing. In case there are multiple errors,
3949 the Diameter node MUST report only the first error it encountered
3950 (detected possibly in some implementation dependent order). The
3951 specific errors that can be described by this AVP are described in
3952 the following section.
3954 7.1. Result-Code AVP
3956 The Result-Code AVP (AVP Code 268) is of type Unsigned32 and
3957 indicates whether a particular request was completed successfully or
3958 whether an error occurred. All Diameter answer messages defined in
3959 IETF applications MUST include one Result-Code AVP. A non-successful
3960 Result-Code AVP (one containing a non 2xxx value other than
3961 DIAMETER_REDIRECT_INDICATION) MUST include the Error-Reporting-Host
3962 AVP if the host setting the Result-Code AVP is different from the
3963 identity encoded in the Origin-Host AVP.
3965 The Result-Code data field contains an IANA-managed 32-bit address
3966 space representing errors (see Section 11.4). Diameter provides the
3967 following classes of errors, all identified by the thousands digit in
3968 the decimal notation:
3970 o 1xxx (Informational)
3972 o 2xxx (Success)
3974 o 3xxx (Protocol Errors)
3976 o 4xxx (Transient Failures)
3978 o 5xxx (Permanent Failure)
3980 A non-recognized class (one whose first digit is not defined in this
3981 section) MUST be handled as a permanent failure.
3983 7.1.1. Informational
3985 Errors that fall within this category are used to inform the
3986 requester that a request could not be satisfied, and additional
3987 action is required on its part before access is granted.
3989 DIAMETER_MULTI_ROUND_AUTH 1001
3991 This informational error is returned by a Diameter server to
3992 inform the access device that the authentication mechanism being
3993 used requires multiple round trips, and a subsequent request needs
3994 to be issued in order for access to be granted.
3996 7.1.2. Success
3998 Errors that fall within the Success category are used to inform a
3999 peer that a request has been successfully completed.
4001 DIAMETER_SUCCESS 2001
4003 The Request was successfully completed.
4005 DIAMETER_LIMITED_SUCCESS 2002
4007 When returned, the request was successfully completed, but
4008 additional processing is required by the application in order to
4009 provide service to the user.
4011 7.1.3. Protocol Errors
4013 Errors that fall within the Protocol Error category SHOULD be treated
4014 on a per-hop basis, and Diameter proxies MAY attempt to correct the
4015 error, if it is possible. Note that these and only these errors MUST
4016 only be used in answer messages whose 'E' bit is set. To provide
4017 backward compatibility with existing implementations that follow
4018 [RFC3588], some of the error values that have previously been used in
4019 this category by [RFC3588] will not be re-used. Therefore the error
4020 values enumerated here maybe non-sequential.
4022 DIAMETER_UNABLE_TO_DELIVER 3002
4024 This error is given when Diameter can not deliver the message to
4025 the destination, either because no host within the realm
4026 supporting the required application was available to process the
4027 request, or because Destination-Host AVP was given without the
4028 associated Destination-Realm AVP.
4030 DIAMETER_REALM_NOT_SERVED 3003
4032 The intended realm of the request is not recognized.
4034 DIAMETER_TOO_BUSY 3004
4036 When returned, a Diameter node SHOULD attempt to send the message
4037 to an alternate peer. This error MUST only be used when a
4038 specific server is requested, and it cannot provide the requested
4039 service.
4041 DIAMETER_LOOP_DETECTED 3005
4043 An agent detected a loop while trying to get the message to the
4044 intended recipient. The message MAY be sent to an alternate peer,
4045 if one is available, but the peer reporting the error has
4046 identified a configuration problem.
4048 DIAMETER_REDIRECT_INDICATION 3006
4050 A redirect agent has determined that the request could not be
4051 satisfied locally and the initiator of the request should direct
4052 the request directly to the server, whose contact information has
4053 been added to the response. When set, the Redirect-Host AVP MUST
4054 be present.
4056 DIAMETER_APPLICATION_UNSUPPORTED 3007
4058 A request was sent for an application that is not supported.
4060 DIAMETER_INVALID_BIT_IN_HEADER 3011
4062 This error is returned when an unrecognized bit in the Diameter
4063 header is set to one (1).
4065 DIAMETER_INVALID_MESSAGE_LENGTH 3012
4067 This error is returned when a request is received with an invalid
4068 message length.
4070 7.1.4. Transient Failures
4072 Errors that fall within the transient failures category are used to
4073 inform a peer that the request could not be satisfied at the time it
4074 was received, but MAY be able to satisfy the request in the future.
4075 Note that these errors MUST be used in answer messages whose 'E' bit
4076 is not set.
4078 DIAMETER_AUTHENTICATION_REJECTED 4001
4080 The authentication process for the user failed, most likely due to
4081 an invalid password used by the user. Further attempts MUST only
4082 be tried after prompting the user for a new password.
4084 DIAMETER_OUT_OF_SPACE 4002
4086 A Diameter node received the accounting request but was unable to
4087 commit it to stable storage due to a temporary lack of space.
4089 ELECTION_LOST 4003
4091 The peer has determined that it has lost the election process and
4092 has therefore disconnected the transport connection.
4094 7.1.5. Permanent Failures
4096 Errors that fall within the permanent failures category are used to
4097 inform the peer that the request failed, and should not be attempted
4098 again. Note that these errors SHOULD be used in answer messages
4099 whose 'E' bit is not set. In error conditions where it is not
4100 possible or efficient to compose application specific answer grammar
4101 then answer messages with E-bit set and complying to the grammar
4102 described in 7.2 MAY also be used for permanent errors.
4104 To provide backward compatibility with existing implementations that
4105 follow [RFC3588], some of the error values that have previously been
4106 used in this category by [RFC3588] will not be re-used. Therefore
4107 the error values enumerated here maybe non-sequential.
4109 DIAMETER_AVP_UNSUPPORTED 5001
4111 The peer received a message that contained an AVP that is not
4112 recognized or supported and was marked with the Mandatory bit. A
4113 Diameter message with this error MUST contain one or more Failed-
4114 AVP AVP containing the AVPs that caused the failure.
4116 DIAMETER_UNKNOWN_SESSION_ID 5002
4118 The request contained an unknown Session-Id.
4120 DIAMETER_AUTHORIZATION_REJECTED 5003
4122 A request was received for which the user could not be authorized.
4123 This error could occur if the service requested is not permitted
4124 to the user.
4126 DIAMETER_INVALID_AVP_VALUE 5004
4128 The request contained an AVP with an invalid value in its data
4129 portion. A Diameter message indicating this error MUST include
4130 the offending AVPs within a Failed-AVP AVP.
4132 DIAMETER_MISSING_AVP 5005
4134 The request did not contain an AVP that is required by the Command
4135 Code definition. If this value is sent in the Result-Code AVP, a
4136 Failed-AVP AVP SHOULD be included in the message. The Failed-AVP
4137 AVP MUST contain an example of the missing AVP complete with the
4138 Vendor-Id if applicable. The value field of the missing AVP
4139 should be of correct minimum length and contain zeroes.
4141 DIAMETER_RESOURCES_EXCEEDED 5006
4143 A request was received that cannot be authorized because the user
4144 has already expended allowed resources. An example of this error
4145 condition is a user that is restricted to one dial-up PPP port,
4146 attempts to establish a second PPP connection.
4148 DIAMETER_CONTRADICTING_AVPS 5007
4150 The Home Diameter server has detected AVPs in the request that
4151 contradicted each other, and is not willing to provide service to
4152 the user. The Failed-AVP AVPs MUST be present which contains the
4153 AVPs that contradicted each other.
4155 DIAMETER_AVP_NOT_ALLOWED 5008
4157 A message was received with an AVP that MUST NOT be present. The
4158 Failed-AVP AVP MUST be included and contain a copy of the
4159 offending AVP.
4161 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009
4163 A message was received that included an AVP that appeared more
4164 often than permitted in the message definition. The Failed-AVP
4165 AVP MUST be included and contain a copy of the first instance of
4166 the offending AVP that exceeded the maximum number of occurrences
4168 DIAMETER_NO_COMMON_APPLICATION 5010
4170 This error is returned by a Diameter node that is not acting as a
4171 relay when it receives a CER which advertises a set of
4172 applications that it does not support.
4174 DIAMETER_UNSUPPORTED_VERSION 5011
4176 This error is returned when a request was received, whose version
4177 number is unsupported.
4179 DIAMETER_UNABLE_TO_COMPLY 5012
4181 This error is returned when a request is rejected for unspecified
4182 reasons.
4184 DIAMETER_INVALID_AVP_LENGTH 5014
4186 The request contained an AVP with an invalid length. A Diameter
4187 message indicating this error MUST include the offending AVPs
4188 within a Failed-AVP AVP. In cases where the erroneous avp length
4189 value exceeds the message length or is less than the minimum AVP
4190 header length, it is sufficient to include the offending AVP
4191 header and a zero filled payload of the minimum required length.
4193 DIAMETER_NO_COMMON_SECURITY 5017
4195 This error is returned when a CER message is received, and there
4196 are no common security mechanisms supported between the peers. A
4197 Capabilities-Exchange-Answer (CEA) MUST be returned with the
4198 Result-Code AVP set to DIAMETER_NO_COMMON_SECURITY.
4200 DIAMETER_UNKNOWN_PEER 5018
4202 A CER was received from an unknown peer.
4204 DIAMETER_COMMAND_UNSUPPORTED 5019
4206 The Request contained a Command-Code that the receiver did not
4207 recognize or support. This MUST be used when a Diameter node
4208 receives an experimental command that it does not understand.
4210 DIAMETER_INVALID_HDR_BITS 5020
4212 A request was received whose bits in the Diameter header were
4213 either set to an invalid combination, or to a value that is
4214 inconsistent with the command code's definition.
4216 DIAMETER_INVALID_AVP_BITS 5021
4218 A request was received that included an AVP whose flag bits are
4219 set to an unrecognized value, or that is inconsistent with the
4220 AVP's definition.
4222 7.2. Error Bit
4224 The 'E' (Error Bit) in the Diameter header is set when the request
4225 caused a protocol-related error (see Section 7.1.3). A message with
4226 the 'E' bit MUST NOT be sent as a response to an answer message.
4227 Note that a message with the 'E' bit set is still subjected to the
4228 processing rules defined in Section 6.2. When set, the answer
4229 message will not conform to the ABNF specification for the command,
4230 and will instead conform to the following ABNF:
4232 Message Format
4234 ::= < Diameter Header: code, ERR [PXY] >
4235 0*1< Session-Id >
4236 { Origin-Host }
4237 { Origin-Realm }
4238 { Result-Code }
4239 [ Origin-State-Id ]
4240 [ Error-Reporting-Host ]
4241 [ Proxy-Info ]
4242 * [ AVP ]
4244 Note that the code used in the header is the same than the one found
4245 in the request message, but with the 'R' bit cleared and the 'E' bit
4246 set. The 'P' bit in the header is set to the same value as the one
4247 found in the request message.
4249 7.3. Error-Message AVP
4251 The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY
4252 accompany a Result-Code AVP as a human readable error message. The
4253 Error-Message AVP is not intended to be useful in real-time, and
4254 SHOULD NOT be expected to be parsed by network entities.
4256 7.4. Error-Reporting-Host AVP
4258 The Error-Reporting-Host AVP (AVP Code 294) is of type
4259 DiameterIdentity. This AVP contains the identity of the Diameter
4260 host that sent the Result-Code AVP to a value other than 2001
4261 (Success), only if the host setting the Result-Code is different from
4262 the one encoded in the Origin-Host AVP. This AVP is intended to be
4263 used for troubleshooting purposes, and MUST be set when the Result-
4264 Code AVP indicates a failure.
4266 7.5. Failed-AVP AVP
4268 The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides
4269 debugging information in cases where a request is rejected or not
4270 fully processed due to erroneous information in a specific AVP. The
4271 value of the Result-Code AVP will provide information on the reason
4272 for the Failed-AVP AVP. A Diameter message SHOULD contain only one
4273 Failed-AVP that corresponds to the error indicated by the Result-Code
4274 AVP. For practical purposes, this Failed-AVP would typically refer
4275 to the first AVP processing error that a Diameter node encounters.
4277 The possible reasons for this AVP are the presence of an improperly
4278 constructed AVP, an unsupported or unrecognized AVP, an invalid AVP
4279 value, the omission of a required AVP, the presence of an explicitly
4280 excluded AVP (see tables in Section 10), or the presence of two or
4281 more occurrences of an AVP which is restricted to 0, 1, or 0-1
4282 occurrences.
4284 A Diameter message SHOULD contain one Failed-AVP AVP, containing the
4285 entire AVP that could not be processed successfully. If the failure
4286 reason is omission of a required AVP, an AVP with the missing AVP
4287 code, the missing vendor id, and a zero filled payload of the minimum
4288 required length for the omitted AVP will be added. If the failure
4289 reason is an invalid AVP length where the reported length is less
4290 than the minimum AVP header length or greater than the reported
4291 message length, a copy of the offending AVP header and a zero filled
4292 payload of the minimum required length SHOULD be added.
4294 In the case where the offending AVP is embedded within a grouped AVP,
4295 the Failed-AVP MAY contain the grouped AVP which in turn contains the
4296 single offending AVP. The same method MAY be employed if the grouped
4297 AVP itself is embedded in yet another grouped AVP and so on. In this
4298 case, the Failed-AVP MAY contain the grouped AVP heirarchy up to the
4299 single offending AVP. This enables the recipient to detect the
4300 location of the offending AVP when embedded in a group.
4302 AVP Format
4304 ::= < AVP Header: 279 >
4305 1* {AVP}
4307 7.6. Experimental-Result AVP
4309 The Experimental-Result AVP (AVP Code 297) is of type Grouped, and
4310 indicates whether a particular vendor-specific request was completed
4311 successfully or whether an error occurred. Its Data field has the
4312 following ABNF grammar:
4314 AVP Format
4316 Experimental-Result ::= < AVP Header: 297 >
4317 { Vendor-Id }
4318 { Experimental-Result-Code }
4320 The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies
4321 the vendor responsible for the assignment of the result code which
4322 follows. All Diameter answer messages defined in vendor-specific
4323 applications MUST include either one Result-Code AVP or one
4324 Experimental-Result AVP.
4326 7.7. Experimental-Result-Code AVP
4328 The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32
4329 and contains a vendor-assigned value representing the result of
4330 processing the request.
4332 It is recommended that vendor-specific result codes follow the same
4333 conventions given for the Result-Code AVP regarding the different
4334 types of result codes and the handling of errors (for non 2xxx
4335 values).
4337 8. Diameter User Sessions
4339 In general, Diameter can provide two different types of services to
4340 applications. The first involves authentication and authorization,
4341 and can optionally make use of accounting. The second only makes use
4342 of accounting.
4344 When a service makes use of the authentication and/or authorization
4345 portion of an application, and a user requests access to the network,
4346 the Diameter client issues an auth request to its local server. The
4347 auth request is defined in a service specific Diameter application
4348 (e.g., NASREQ). The request contains a Session-Id AVP, which is used
4349 in subsequent messages (e.g., subsequent authorization, accounting,
4350 etc) relating to the user's session. The Session-Id AVP is a means
4351 for the client and servers to correlate a Diameter message with a
4352 user session.
4354 When a Diameter server authorizes a user to use network resources for
4355 a finite amount of time, and it is willing to extend the
4356 authorization via a future request, it MUST add the Authorization-
4357 Lifetime AVP to the answer message. The Authorization-Lifetime AVP
4358 defines the maximum number of seconds a user MAY make use of the
4359 resources before another authorization request is expected by the
4360 server. The Auth-Grace-Period AVP contains the number of seconds
4361 following the expiration of the Authorization-Lifetime, after which
4362 the server will release all state information related to the user's
4363 session. Note that if payment for services is expected by the
4364 serving realm from the user's home realm, the Authorization-Lifetime
4365 AVP, combined with the Auth-Grace-Period AVP, implies the maximum
4366 length of the session the home realm is willing to be fiscally
4367 responsible for. Services provided past the expiration of the
4368 Authorization-Lifetime and Auth-Grace-Period AVPs are the
4369 responsibility of the access device. Of course, the actual cost of
4370 services rendered is clearly outside the scope of the protocol.
4372 An access device that does not expect to send a re-authorization or a
4373 session termination request to the server MAY include the Auth-
4374 Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint
4375 to the server. If the server accepts the hint, it agrees that since
4376 no session termination message will be received once service to the
4377 user is terminated, it cannot maintain state for the session. If the
4378 answer message from the server contains a different value in the
4379 Auth-Session-State AVP (or the default value if the AVP is absent),
4380 the access device MUST follow the server's directives. Note that the
4381 value NO_STATE_MAINTAINED MUST NOT be set in subsequent re-
4382 authorization requests and answers.
4384 The base protocol does not include any authorization request
4385 messages, since these are largely application-specific and are
4386 defined in a Diameter application document. However, the base
4387 protocol does define a set of messages that is used to terminate user
4388 sessions. These are used to allow servers that maintain state
4389 information to free resources.
4391 When a service only makes use of the Accounting portion of the
4392 Diameter protocol, even in combination with an application, the
4393 Session-Id is still used to identify user sessions. However, the
4394 session termination messages are not used, since a session is
4395 signaled as being terminated by issuing an accounting stop message.
4397 Diameter may also be used for services that cannot be easily
4398 categorized as authentication, authorization or accounting (e.g.,
4399 certain 3GPP IMS interfaces). In such cases, the finite state
4400 machine defined in subsequent sections may not be applicable.
4401 Therefore, the applications itself MAY need to define its own finite
4402 state machine. However, such application specific statemachines MUST
4403 comply with general Diameter user session requirements such co-
4404 relating all message exchanges via Session-Id AVP.
4406 8.1. Authorization Session State Machine
4408 This section contains a set of finite state machines, representing
4409 the life cycle of Diameter sessions, and which MUST be observed by
4410 all Diameter implementations that make use of the authentication
4411 and/or authorization portion of a Diameter application. The term
4412 Service-Specific below refers to a message defined in a Diameter
4413 application (e.g., Mobile IPv4, NASREQ).
4415 There are four different authorization session state machines
4416 supported in the Diameter base protocol. The first two describe a
4417 session in which the server is maintaining session state, indicated
4418 by the value of the Auth-Session-State AVP (or its absence). One
4419 describes the session from a client perspective, the other from a
4420 server perspective. The second two state machines are used when the
4421 server does not maintain session state. Here again, one describes
4422 the session from a client perspective, the other from a server
4423 perspective.
4425 When a session is moved to the Idle state, any resources that were
4426 allocated for the particular session must be released. Any event not
4427 listed in the state machines MUST be considered as an error
4428 condition, and an answer, if applicable, MUST be returned to the
4429 originator of the message.
4431 In the case that an application does not support re-auth, the state
4432 transitions related to server-initiated re-auth when both client and
4433 server sessions maintains state (e.g., Send RAR, Pending, Receive
4434 RAA) MAY be ignored.
4436 In the state table, the event 'Failure to send X' means that the
4437 Diameter agent is unable to send command X to the desired
4438 destination. This could be due to the peer being down, or due to the
4439 peer sending back a transient failure or temporary protocol error
4440 notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the
4441 Result-Code AVP of the corresponding Answer command. The event 'X
4442 successfully sent' is the complement of 'Failure to send X'.
4444 The following state machine is observed by a client when state is
4445 maintained on the server:
4447 CLIENT, STATEFUL
4448 State Event Action New State
4449 -------------------------------------------------------------
4450 Idle Client or Device Requests Send Pending
4451 access service
4452 specific
4453 auth req
4455 Idle ASR Received Send ASA Idle
4456 for unknown session with
4457 Result-Code
4458 = UNKNOWN_
4459 SESSION_ID
4461 Idle RAR Received Send RAA Idle
4462 for unknown session with
4463 Result-Code
4464 = UNKNOWN_
4465 SESSION_ID
4467 Pending Successful Service-specific Grant Open
4468 authorization answer Access
4469 received with default
4470 Auth-Session-State value
4472 Pending Successful Service-specific Sent STR Discon
4473 authorization answer received
4474 but service not provided
4476 Pending Error processing successful Sent STR Discon
4477 Service-specific authorization
4478 answer
4480 Pending Failed Service-specific Cleanup Idle
4481 authorization answer received
4483 Open User or client device Send Open
4484 requests access to service service
4485 specific
4486 auth req
4488 Open Successful Service-specific Provide Open
4489 authorization answer received Service
4491 Open Failed Service-specific Discon. Idle
4492 authorization answer user/device
4493 received.
4495 Open RAR received and client will Send RAA Open
4496 perform subsequent re-auth with
4497 Result-Code
4498 = SUCCESS
4500 Open RAR received and client will Send RAA Idle
4501 not perform subsequent with
4502 re-auth Result-Code
4503 != SUCCESS,
4504 Discon.
4505 user/device
4507 Open Session-Timeout Expires on Send STR Discon
4508 Access Device
4510 Open ASR Received, Send ASA Discon
4511 client will comply with with
4512 request to end the session Result-Code
4513 = SUCCESS,
4514 Send STR.
4516 Open ASR Received, Send ASA Open
4517 client will not comply with with
4518 request to end the session Result-Code
4519 != SUCCESS
4521 Open Authorization-Lifetime + Send STR Discon
4522 Auth-Grace-Period expires on
4523 access device
4525 Discon ASR Received Send ASA Discon
4527 Discon STA Received Discon. Idle
4528 user/device
4530 The following state machine is observed by a server when it is
4531 maintaining state for the session:
4533 SERVER, STATEFUL
4534 State Event Action New State
4535 -------------------------------------------------------------
4536 Idle Service-specific authorization Send Open
4537 request received, and successful
4538 user is authorized serv.
4539 specific
4540 answer
4542 Idle Service-specific authorization Send Idle
4543 request received, and failed serv.
4544 user is not authorized specific
4545 answer
4547 Open Service-specific authorization Send Open
4548 request received, and user successful
4549 is authorized serv. specific
4550 answer
4552 Open Service-specific authorization Send Idle
4553 request received, and user failed serv.
4554 is not authorized specific
4555 answer,
4556 Cleanup
4558 Open Home server wants to confirm Send RAR Pending
4559 authentication and/or
4560 authorization of the user
4562 Pending Received RAA with a failed Cleanup Idle
4563 Result-Code
4565 Pending Received RAA with Result-Code Update Open
4566 = SUCCESS session
4568 Open Home server wants to Send ASR Discon
4569 terminate the service
4571 Open Authorization-Lifetime (and Cleanup Idle
4572 Auth-Grace-Period) expires
4573 on home server.
4575 Open Session-Timeout expires on Cleanup Idle
4576 home server
4578 Discon Failure to send ASR Wait, Discon
4579 resend ASR
4581 Discon ASR successfully sent and Cleanup Idle
4582 ASA Received with Result-Code
4584 Not ASA Received None No Change.
4585 Discon
4587 Any STR Received Send STA, Idle
4588 Cleanup.
4590 The following state machine is observed by a client when state is not
4591 maintained on the server:
4593 CLIENT, STATELESS
4594 State Event Action New State
4595 -------------------------------------------------------------
4596 Idle Client or Device Requests Send Pending
4597 access service
4598 specific
4599 auth req
4601 Pending Successful Service-specific Grant Open
4602 authorization answer Access
4603 received with Auth-Session-
4604 State set to
4605 NO_STATE_MAINTAINED
4607 Pending Failed Service-specific Cleanup Idle
4608 authorization answer
4609 received
4611 Open Session-Timeout Expires on Discon. Idle
4612 Access Device user/device
4614 Open Service to user is terminated Discon. Idle
4615 user/device
4617 The following state machine is observed by a server when it is not
4618 maintaining state for the session:
4620 SERVER, STATELESS
4621 State Event Action New State
4622 -------------------------------------------------------------
4623 Idle Service-specific authorization Send serv. Idle
4624 request received, and specific
4625 successfully processed answer
4627 8.2. Accounting Session State Machine
4629 The following state machines MUST be supported for applications that
4630 have an accounting portion or that require only accounting services.
4631 The first state machine is to be observed by clients.
4633 See Section 9.7 for Accounting Command Codes and Section 9.8 for
4634 Accounting AVPs.
4636 The server side in the accounting state machine depends in some cases
4637 on the particular application. The Diameter base protocol defines a
4638 default state machine that MUST be followed by all applications that
4639 have not specified other state machines. This is the second state
4640 machine in this section described below.
4642 The default server side state machine requires the reception of
4643 accounting records in any order and at any time, and does not place
4644 any standards requirement on the processing of these records.
4645 Implementations of Diameter MAY perform checking, ordering,
4646 correlation, fraud detection, and other tasks based on these records.
4647 Both base Diameter AVPs as well as application specific AVPs MAY be
4648 inspected as a part of these tasks. The tasks can happen either
4649 immediately after record reception or in a post-processing phase.
4650 However, as these tasks are typically application or even policy
4651 dependent, they are not standardized by the Diameter specifications.
4652 Applications MAY define requirements on when to accept accounting
4653 records based on the used value of Accounting-Realtime-Required AVP,
4654 credit limits checks, and so on.
4656 However, the Diameter base protocol defines one optional server side
4657 state machine that MAY be followed by applications that require
4658 keeping track of the session state at the accounting server. Note
4659 that such tracking is incompatible with the ability to sustain long
4660 duration connectivity problems. Therefore, the use of this state
4661 machine is recommended only in applications where the value of the
4662 Accounting-Realtime-Required AVP is DELIVER_AND_GRANT, and hence
4663 accounting connectivity problems are required to cause the serviced
4664 user to be disconnected. Otherwise, records produced by the client
4665 may be lost by the server which no longer accepts them after the
4666 connectivity is re-established. This state machine is the third
4667 state machine in this section. The state machine is supervised by a
4668 supervision session timer Ts, which the value should be reasonably
4669 higher than the Acct_Interim_Interval value. Ts MAY be set to two
4670 times the value of the Acct_Interim_Interval so as to avoid the
4671 accounting session in the Diameter server to change to Idle state in
4672 case of short transient network failure.
4674 Any event not listed in the state machines MUST be considered as an
4675 error condition, and a corresponding answer, if applicable, MUST be
4676 returned to the originator of the message.
4678 In the state table, the event 'Failure to send' means that the
4679 Diameter client is unable to communicate with the desired
4680 destination. This could be due to the peer being down, or due to the
4681 peer sending back a transient failure or temporary protocol error
4682 notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or
4683 DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting
4684 Answer command.
4686 The event 'Failed answer' means that the Diameter client received a
4687 non-transient failure notification in the Accounting Answer command.
4689 Note that the action 'Disconnect user/dev' MUST have an effect also
4690 to the authorization session state table, e.g., cause the STR message
4691 to be sent, if the given application has both authentication/
4692 authorization and accounting portions.
4694 The states PendingS, PendingI, PendingL, PendingE and PendingB stand
4695 for pending states to wait for an answer to an accounting request
4696 related to a Start, Interim, Stop, Event or buffered record,
4697 respectively.
4699 CLIENT, ACCOUNTING
4700 State Event Action New State
4701 -------------------------------------------------------------
4702 Idle Client or device requests Send PendingS
4703 access accounting
4704 start req.
4706 Idle Client or device requests Send PendingE
4707 a one-time service accounting
4708 event req
4710 Idle Records in storage Send PendingB
4711 record
4713 PendingS Successful accounting Open
4714 start answer received
4716 PendingS Failure to send and buffer Store Open
4717 space available and realtime Start
4718 not equal to DELIVER_AND_GRANT Record
4720 PendingS Failure to send and no buffer Open
4721 space available and realtime
4722 equal to GRANT_AND_LOSE
4724 PendingS Failure to send and no buffer Disconnect Idle
4725 space available and realtime user/dev
4726 not equal to
4727 GRANT_AND_LOSE
4729 PendingS Failed accounting start answer Open
4730 received and realtime equal
4731 to GRANT_AND_LOSE
4733 PendingS Failed accounting start answer Disconnect Idle
4734 received and realtime not user/dev
4735 equal to GRANT_AND_LOSE
4737 PendingS User service terminated Store PendingS
4738 stop
4739 record
4741 Open Interim interval elapses Send PendingI
4742 accounting
4743 interim
4744 record
4745 Open User service terminated Send PendingL
4746 accounting
4747 stop req.
4749 PendingI Successful accounting interim Open
4750 answer received
4752 PendingI Failure to send and (buffer Store Open
4753 space available or old record interim
4754 can be overwritten) and record
4755 realtime not equal to
4756 DELIVER_AND_GRANT
4758 PendingI Failure to send and no buffer Open
4759 space available and realtime
4760 equal to GRANT_AND_LOSE
4762 PendingI Failure to send and no buffer Disconnect Idle
4763 space available and realtime user/dev
4764 not equal to GRANT_AND_LOSE
4766 PendingI Failed accounting interim Open
4767 answer received and realtime
4768 equal to GRANT_AND_LOSE
4770 PendingI Failed accounting interim Disconnect Idle
4771 answer received and realtime user/dev
4772 not equal to GRANT_AND_LOSE
4774 PendingI User service terminated Store PendingI
4775 stop
4776 record
4777 PendingE Successful accounting Idle
4778 event answer received
4780 PendingE Failure to send and buffer Store Idle
4781 space available event
4782 record
4784 PendingE Failure to send and no buffer Idle
4785 space available
4787 PendingE Failed accounting event answer Idle
4788 received
4790 PendingB Successful accounting answer Delete Idle
4791 received record
4793 PendingB Failure to send Idle
4795 PendingB Failed accounting answer Delete Idle
4796 received record
4798 PendingL Successful accounting Idle
4799 stop answer received
4801 PendingL Failure to send and buffer Store Idle
4802 space available stop
4803 record
4805 PendingL Failure to send and no buffer Idle
4806 space available
4808 PendingL Failed accounting stop answer Idle
4809 received
4811 SERVER, STATELESS ACCOUNTING
4812 State Event Action New State
4813 -------------------------------------------------------------
4815 Idle Accounting start request Send Idle
4816 received, and successfully accounting
4817 processed. start
4818 answer
4820 Idle Accounting event request Send Idle
4821 received, and successfully accounting
4822 processed. event
4823 answer
4825 Idle Interim record received, Send Idle
4826 and successfully processed. accounting
4827 interim
4828 answer
4830 Idle Accounting stop request Send Idle
4831 received, and successfully accounting
4832 processed stop answer
4834 Idle Accounting request received, Send Idle
4835 no space left to store accounting
4836 records answer,
4837 Result-Code
4838 = OUT_OF_
4839 SPACE
4841 SERVER, STATEFUL ACCOUNTING
4842 State Event Action New State
4843 -------------------------------------------------------------
4845 Idle Accounting start request Send Open
4846 received, and successfully accounting
4847 processed. start
4848 answer,
4849 Start Ts
4851 Idle Accounting event request Send Idle
4852 received, and successfully accounting
4853 processed. event
4854 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 Open Interim record received, Send Open
4864 and successfully processed. accounting
4865 interim
4866 answer,
4867 Restart Ts
4869 Open Accounting stop request Send Idle
4870 received, and successfully accounting
4871 processed stop answer,
4872 Stop Ts
4874 Open Accounting request received, Send Idle
4875 no space left to store accounting
4876 records answer,
4877 Result-Code
4878 = OUT_OF_
4879 SPACE,
4880 Stop Ts
4882 Open Session supervision timer Ts Stop Ts Idle
4883 expired
4885 8.3. Server-Initiated Re-Auth
4887 A Diameter server may initiate a re-authentication and/or re-
4888 authorization service for a particular session by issuing a Re-Auth-
4889 Request (RAR).
4891 For example, for pre-paid services, the Diameter server that
4892 originally authorized a session may need some confirmation that the
4893 user is still using the services.
4895 An access device that receives a RAR message with Session-Id equal to
4896 a currently active session MUST initiate a re-auth towards the user,
4897 if the service supports this particular feature. Each Diameter
4898 application MUST state whether service-initiated re-auth is
4899 supported, since some applications do not allow access devices to
4900 prompt the user for re-auth.
4902 8.3.1. Re-Auth-Request
4904 The Re-Auth-Request (RAR), indicated by the Command-Code set to 258
4905 and the message flags' 'R' bit set, may be sent by any server to the
4906 access device that is providing session service, to request that the
4907 user be re-authenticated and/or re-authorized.
4909 Message Format
4911 ::= < Diameter Header: 258, REQ, PXY >
4912 < Session-Id >
4913 { Origin-Host }
4914 { Origin-Realm }
4915 { Destination-Realm }
4916 { Destination-Host }
4917 { Auth-Application-Id }
4918 { Re-Auth-Request-Type }
4919 [ User-Name ]
4920 [ Origin-State-Id ]
4921 * [ Proxy-Info ]
4922 * [ Route-Record ]
4923 * [ AVP ]
4925 8.3.2. Re-Auth-Answer
4927 The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258
4928 and the message flags' 'R' bit clear, is sent in response to the RAR.
4929 The Result-Code AVP MUST be present, and indicates the disposition of
4930 the request.
4932 A successful RAA message MUST be followed by an application-specific
4933 authentication and/or authorization message.
4935 Message Format
4937 ::= < Diameter Header: 258, PXY >
4938 < Session-Id >
4939 { Result-Code }
4940 { Origin-Host }
4941 { Origin-Realm }
4942 [ User-Name ]
4943 [ Origin-State-Id ]
4944 [ Error-Message ]
4945 [ Error-Reporting-Host ]
4946 [ Failed-AVP ]
4947 * [ Redirect-Host ]
4948 [ Redirect-Host-Usage ]
4949 [ Redirect-Max-Cache-Time ]
4950 * [ Proxy-Info ]
4951 * [ AVP ]
4953 8.4. Session Termination
4955 It is necessary for a Diameter server that authorized a session, for
4956 which it is maintaining state, to be notified when that session is no
4957 longer active, both for tracking purposes as well as to allow
4958 stateful agents to release any resources that they may have provided
4959 for the user's session. For sessions whose state is not being
4960 maintained, this section is not used.
4962 When a user session that required Diameter authorization terminates,
4963 the access device that provided the service MUST issue a Session-
4964 Termination-Request (STR) message to the Diameter server that
4965 authorized the service, to notify it that the session is no longer
4966 active. An STR MUST be issued when a user session terminates for any
4967 reason, including user logoff, expiration of Session-Timeout,
4968 administrative action, termination upon receipt of an Abort-Session-
4969 Request (see below), orderly shutdown of the access device, etc.
4971 The access device also MUST issue an STR for a session that was
4972 authorized but never actually started. This could occur, for
4973 example, due to a sudden resource shortage in the access device, or
4974 because the access device is unwilling to provide the type of service
4975 requested in the authorization, or because the access device does not
4976 support a mandatory AVP returned in the authorization, etc.
4978 It is also possible that a session that was authorized is never
4979 actually started due to action of a proxy. For example, a proxy may
4980 modify an authorization answer, converting the result from success to
4981 failure, prior to forwarding the message to the access device. If
4982 the answer did not contain an Auth-Session-State AVP with the value
4983 NO_STATE_MAINTAINED, a proxy that causes an authorized session not to
4984 be started MUST issue an STR to the Diameter server that authorized
4985 the session, since the access device has no way of knowing that the
4986 session had been authorized.
4988 A Diameter server that receives an STR message MUST clean up
4989 resources (e.g., session state) associated with the Session-Id
4990 specified in the STR, and return a Session-Termination-Answer.
4992 A Diameter server also MUST clean up resources when the Session-
4993 Timeout expires, or when the Authorization-Lifetime and the Auth-
4994 Grace-Period AVPs expires without receipt of a re-authorization
4995 request, regardless of whether an STR for that session is received.
4996 The access device is not expected to provide service beyond the
4997 expiration of these timers; thus, expiration of either of these
4998 timers implies that the access device may have unexpectedly shut
4999 down.
5001 8.4.1. Session-Termination-Request
5003 The Session-Termination-Request (STR), indicated by the Command-Code
5004 set to 275 and the Command Flags' 'R' bit set, is sent by the access
5005 device to inform the Diameter Server that an authenticated and/or
5006 authorized session is being terminated.
5008 Message Format
5010 ::= < Diameter Header: 275, REQ, PXY >
5011 < Session-Id >
5012 { Origin-Host }
5013 { Origin-Realm }
5014 { Destination-Realm }
5015 { Auth-Application-Id }
5016 { Termination-Cause }
5017 [ User-Name ]
5018 [ Destination-Host ]
5019 * [ Class ]
5020 [ Origin-State-Id ]
5021 * [ Proxy-Info ]
5022 * [ Route-Record ]
5023 * [ AVP ]
5025 8.4.2. Session-Termination-Answer
5027 The Session-Termination-Answer (STA), indicated by the Command-Code
5028 set to 275 and the message flags' 'R' bit clear, is sent by the
5029 Diameter Server to acknowledge the notification that the session has
5030 been terminated. The Result-Code AVP MUST be present, and MAY
5031 contain an indication that an error occurred while servicing the STR.
5033 Upon sending or receipt of the STA, the Diameter Server MUST release
5034 all resources for the session indicated by the Session-Id AVP. Any
5035 intermediate server in the Proxy-Chain MAY also release any
5036 resources, if necessary.
5038 Message Format
5040 ::= < Diameter Header: 275, PXY >
5041 < Session-Id >
5042 { Result-Code }
5043 { Origin-Host }
5044 { Origin-Realm }
5045 [ User-Name ]
5046 * [ Class ]
5047 [ Error-Message ]
5048 [ Error-Reporting-Host ]
5049 [ Failed-AVP ]
5050 [ Origin-State-Id ]
5051 * [ Redirect-Host ]
5052 [ Redirect-Host-Usage ]
5053 ^
5054 [ Redirect-Max-Cache-Time ]
5055 * [ Proxy-Info ]
5056 * [ AVP ]
5058 8.5. Aborting a Session
5060 A Diameter server may request that the access device stop providing
5061 service for a particular session by issuing an Abort-Session-Request
5062 (ASR).
5064 For example, the Diameter server that originally authorized the
5065 session may be required to cause that session to be stopped for
5066 credit or other reasons that were not anticipated when the session
5067 was first authorized. On the other hand, an operator may maintain a
5068 management server for the purpose of issuing ASRs to administratively
5069 remove users from the network.
5071 An access device that receives an ASR with Session-ID equal to a
5072 currently active session MAY stop the session. Whether the access
5073 device stops the session or not is implementation- and/or
5074 configuration-dependent. For example, an access device may honor
5075 ASRs from certain agents only. In any case, the access device MUST
5076 respond with an Abort-Session-Answer, including a Result-Code AVP to
5077 indicate what action it took.
5079 Note that if the access device does stop the session upon receipt of
5080 an ASR, it issues an STR to the authorizing server (which may or may
5081 not be the agent issuing the ASR) just as it would if the session
5082 were terminated for any other reason.
5084 8.5.1. Abort-Session-Request
5086 The Abort-Session-Request (ASR), indicated by the Command-Code set to
5087 274 and the message flags' 'R' bit set, may be sent by any server to
5088 the access device that is providing session service, to request that
5089 the session identified by the Session-Id be stopped.
5091 Message Format
5093 ::= < Diameter Header: 274, REQ, PXY >
5094 < Session-Id >
5095 { Origin-Host }
5096 { Origin-Realm }
5097 { Destination-Realm }
5098 { Destination-Host }
5099 { Auth-Application-Id }
5100 [ User-Name ]
5101 [ Origin-State-Id ]
5102 * [ Proxy-Info ]
5103 * [ Route-Record ]
5104 * [ AVP ]
5106 8.5.2. Abort-Session-Answer
5108 The Abort-Session-Answer (ASA), indicated by the Command-Code set to
5109 274 and the message flags' 'R' bit clear, is sent in response to the
5110 ASR. The Result-Code AVP MUST be present, and indicates the
5111 disposition of the request.
5113 If the session identified by Session-Id in the ASR was successfully
5114 terminated, Result-Code is set to DIAMETER_SUCCESS. If the session
5115 is not currently active, Result-Code is set to
5116 DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the
5117 session for any other reason, Result-Code is set to
5118 DIAMETER_UNABLE_TO_COMPLY.
5120 Message Format
5122 ::= < Diameter Header: 274, PXY >
5123 < Session-Id >
5124 { Result-Code }
5125 { Origin-Host }
5126 { Origin-Realm }
5127 [ User-Name ]
5128 [ Origin-State-Id ]
5129 [ Error-Message ]
5130 [ Error-Reporting-Host ]
5131 [ Failed-AVP ]
5132 * [ Redirect-Host ]
5133 [ Redirect-Host-Usage ]
5134 [ Redirect-Max-Cache-Time ]
5135 * [ Proxy-Info ]
5136 * [ AVP ]
5138 8.6. Inferring Session Termination from Origin-State-Id
5140 Origin-State-Id is used to allow rapid detection of terminated
5141 sessions for which no STR would have been issued, due to
5142 unanticipated shutdown of an access device.
5144 By including Origin-State-Id in CER/CEA messages, an access device
5145 allows a next-hop server to determine immediately upon connection
5146 whether the device has lost its sessions since the last connection.
5148 By including Origin-State-Id in request messages, an access device
5149 also allows a server with which it communicates via proxy to make
5150 such a determination. However, a server that is not directly
5151 connected with the access device will not discover that the access
5152 device has been restarted unless and until it receives a new request
5153 from the access device. Thus, use of this mechanism across proxies
5154 is opportunistic rather than reliable, but useful nonetheless.
5156 When a Diameter server receives an Origin-State-Id that is greater
5157 than the Origin-State-Id previously received from the same issuer, it
5158 may assume that the issuer has lost state since the previous message
5159 and that all sessions that were active under the lower Origin-State-
5160 Id have been terminated. The Diameter server MAY clean up all
5161 session state associated with such lost sessions, and MAY also issues
5162 STRs for all such lost sessions that were authorized on upstream
5163 servers, to allow session state to be cleaned up globally.
5165 8.7. Auth-Request-Type AVP
5167 The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is
5168 included in application-specific auth requests to inform the peers
5169 whether a user is to be authenticated only, authorized only or both.
5170 Note any value other than both MAY cause RADIUS interoperability
5171 issues. The following values are defined:
5173 AUTHENTICATE_ONLY 1
5175 The request being sent is for authentication only, and MUST
5176 contain the relevant application specific authentication AVPs that
5177 are needed by the Diameter server to authenticate the user.
5179 AUTHORIZE_ONLY 2
5181 The request being sent is for authorization only, and MUST contain
5182 the application specific authorization AVPs that are necessary to
5183 identify the service being requested/offered.
5185 AUTHORIZE_AUTHENTICATE 3
5187 The request contains a request for both authentication and
5188 authorization. The request MUST include both the relevant
5189 application specific authentication information, and authorization
5190 information necessary to identify the service being requested/
5191 offered.
5193 8.8. Session-Id AVP
5195 The Session-Id AVP (AVP Code 263) is of type UTF8String and is used
5196 to identify a specific session (see Section 8). All messages
5197 pertaining to a specific session MUST include only one Session-Id AVP
5198 and the same value MUST be used throughout the life of a session.
5199 When present, the Session-Id SHOULD appear immediately following the
5200 Diameter Header (see Section 3).
5202 The Session-Id MUST be globally and eternally unique, as it is meant
5203 to uniquely identify a user session without reference to any other
5204 information, and may be needed to correlate historical authentication
5205 information with accounting information. The Session-Id includes a
5206 mandatory portion and an implementation-defined portion; a
5207 recommended format for the implementation-defined portion is outlined
5208 below.
5210 The Session-Id MUST begin with the sender's identity encoded in the
5211 DiameterIdentity type (see Section 4.4). The remainder of the
5212 Session-Id is delimited by a ";" character, and MAY be any sequence
5213 that the client can guarantee to be eternally unique; however, the
5214 following format is recommended, (square brackets [] indicate an
5215 optional element):
5217 ;;[;]
5219 and are decimal representations of the
5220 high and low 32 bits of a monotonically increasing 64-bit value. The
5221 64-bit value is rendered in two part to simplify formatting by 32-bit
5222 processors. At startup, the high 32 bits of the 64-bit value MAY be
5223 initialized to the time, and the low 32 bits MAY be initialized to
5224 zero. This will for practical purposes eliminate the possibility of
5225 overlapping Session-Ids after a reboot, assuming the reboot process
5226 takes longer than a second. Alternatively, an implementation MAY
5227 keep track of the increasing value in non-volatile memory.
5229 is implementation specific but may include a modem's
5230 device Id, a layer 2 address, timestamp, etc.
5232 Example, in which there is no optional value:
5234 accesspoint7.acme.com;1876543210;523
5236 Example, in which there is an optional value:
5238 accesspoint7.acme.com;1876543210;523;mobile@200.1.1.88
5240 The Session-Id is created by the Diameter application initiating the
5241 session, which in most cases is done by the client. Note that a
5242 Session-Id MAY be used for both the authorization and accounting
5243 commands of a given application.
5245 8.9. Authorization-Lifetime AVP
5247 The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32
5248 and contains the maximum number of seconds of service to be provided
5249 to the user before the user is to be re-authenticated and/or re-
5250 authorized. Great care should be taken when the Authorization-
5251 Lifetime value is determined, since a low, non-zero, value could
5252 create significant Diameter traffic, which could congest both the
5253 network and the agents.
5255 A value of zero (0) means that immediate re-auth is necessary by the
5256 access device. This is typically used in cases where multiple
5257 authentication methods are used, and a successful auth response with
5258 this AVP set to zero is used to signal that the next authentication
5259 method is to be immediately initiated. The absence of this AVP, or a
5260 value of all ones (meaning all bits in the 32 bit field are set to
5261 one) means no re-auth is expected.
5263 If both this AVP and the Session-Timeout AVP are present in a
5264 message, the value of the latter MUST NOT be smaller than the
5265 Authorization-Lifetime AVP.
5267 An Authorization-Lifetime AVP MAY be present in re-authorization
5268 messages, and contains the number of seconds the user is authorized
5269 to receive service from the time the re-auth answer message is
5270 received by the access device.
5272 This AVP MAY be provided by the client as a hint of the maximum
5273 lifetime that it is willing to accept. However, the server MAY
5274 return a value that is equal to, or smaller, than the one provided by
5275 the client.
5277 8.10. Auth-Grace-Period AVP
5279 The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and
5280 contains the number of seconds the Diameter server will wait
5281 following the expiration of the Authorization-Lifetime AVP before
5282 cleaning up resources for the session.
5284 8.11. Auth-Session-State AVP
5286 The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and
5287 specifies whether state is maintained for a particular session. The
5288 client MAY include this AVP in requests as a hint to the server, but
5289 the value in the server's answer message is binding. The following
5290 values are supported:
5292 STATE_MAINTAINED 0
5294 This value is used to specify that session state is being
5295 maintained, and the access device MUST issue a session termination
5296 message when service to the user is terminated. This is the
5297 default value.
5299 NO_STATE_MAINTAINED 1
5301 This value is used to specify that no session termination messages
5302 will be sent by the access device upon expiration of the
5303 Authorization-Lifetime.
5305 8.12. Re-Auth-Request-Type AVP
5307 The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and
5308 is included in application-specific auth answers to inform the client
5309 of the action expected upon expiration of the Authorization-Lifetime.
5310 If the answer message contains an Authorization-Lifetime AVP with a
5311 positive value, the Re-Auth-Request-Type AVP MUST be present in an
5312 answer message. The following values are defined:
5314 AUTHORIZE_ONLY 0
5316 An authorization only re-auth is expected upon expiration of the
5317 Authorization-Lifetime. This is the default value if the AVP is
5318 not present in answer messages that include the Authorization-
5319 Lifetime.
5321 AUTHORIZE_AUTHENTICATE 1
5323 An authentication and authorization re-auth is expected upon
5324 expiration of the Authorization-Lifetime.
5326 8.13. Session-Timeout AVP
5328 The Session-Timeout AVP (AVP Code 27) [RFC2865] is of type Unsigned32
5329 and contains the maximum number of seconds of service to be provided
5330 to the user before termination of the session. When both the
5331 Session-Timeout and the Authorization-Lifetime AVPs are present in an
5332 answer message, the former MUST be equal to or greater than the value
5333 of the latter.
5335 A session that terminates on an access device due to the expiration
5336 of the Session-Timeout MUST cause an STR to be issued, unless both
5337 the access device and the home server had previously agreed that no
5338 session termination messages would be sent (see Section 8.9).
5340 A Session-Timeout AVP MAY be present in a re-authorization answer
5341 message, and contains the remaining number of seconds from the
5342 beginning of the re-auth.
5344 A value of zero, or the absence of this AVP, means that this session
5345 has an unlimited number of seconds before termination.
5347 This AVP MAY be provided by the client as a hint of the maximum
5348 timeout that it is willing to accept. However, the server MAY return
5349 a value that is equal to, or smaller, than the one provided by the
5350 client.
5352 8.14. User-Name AVP
5354 The User-Name AVP (AVP Code 1) [RFC2865] is of type UTF8String, which
5355 contains the User-Name, in a format consistent with the NAI
5356 specification [RFC4282].
5358 8.15. Termination-Cause AVP
5360 The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and
5361 is used to indicate the reason why a session was terminated on the
5362 access device. The following values are defined:
5364 DIAMETER_LOGOUT 1
5366 The user initiated a disconnect
5368 DIAMETER_SERVICE_NOT_PROVIDED 2
5370 This value is used when the user disconnected prior to the receipt
5371 of the authorization answer message.
5373 DIAMETER_BAD_ANSWER 3
5375 This value indicates that the authorization answer received by the
5376 access device was not processed successfully.
5378 DIAMETER_ADMINISTRATIVE 4
5380 The user was not granted access, or was disconnected, due to
5381 administrative reasons, such as the receipt of a Abort-Session-
5382 Request message.
5384 DIAMETER_LINK_BROKEN 5
5386 The communication to the user was abruptly disconnected.
5388 DIAMETER_AUTH_EXPIRED 6
5390 The user's access was terminated since its authorized session time
5391 has expired.
5393 DIAMETER_USER_MOVED 7
5395 The user is receiving services from another access device.
5397 DIAMETER_SESSION_TIMEOUT 8
5399 The user's session has timed out, and service has been terminated.
5401 8.16. Origin-State-Id AVP
5403 The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a
5404 monotonically increasing value that is advanced whenever a Diameter
5405 entity restarts with loss of previous state, for example upon reboot.
5406 Origin-State-Id MAY be included in any Diameter message, including
5407 CER.
5409 A Diameter entity issuing this AVP MUST create a higher value for
5410 this AVP each time its state is reset. A Diameter entity MAY set
5411 Origin-State-Id to the time of startup, or it MAY use an incrementing
5412 counter retained in non-volatile memory across restarts.
5414 The Origin-State-Id, if present, MUST reflect the state of the entity
5415 indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST
5416 either remove Origin-State-Id or modify it appropriately as well.
5417 Typically, Origin-State-Id is used by an access device that always
5418 starts up with no active sessions; that is, any session active prior
5419 to restart will have been lost. By including Origin-State-Id in a
5420 message, it allows other Diameter entities to infer that sessions
5421 associated with a lower Origin-State-Id are no longer active. If an
5422 access device does not intend for such inferences to be made, it MUST
5423 either not include Origin-State-Id in any message, or set its value
5424 to 0.
5426 8.17. Session-Binding AVP
5428 The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY
5429 be present in application-specific authorization answer messages. If
5430 present, this AVP MAY inform the Diameter client that all future
5431 application-specific re-auth messages for this session MUST be sent
5432 to the same authorization server. This AVP MAY also specify that a
5433 Session-Termination-Request message for this session MUST be sent to
5434 the same authorizing server.
5436 This field is a bit mask, and the following bits have been defined:
5438 RE_AUTH 1
5440 When set, future re-auth messages for this session MUST NOT
5441 include the Destination-Host AVP. When cleared, the default
5442 value, the Destination-Host AVP MUST be present in all re-auth
5443 messages for this session.
5445 STR 2
5447 When set, the STR message for this session MUST NOT include the
5448 Destination-Host AVP. When cleared, the default value, the
5449 Destination-Host AVP MUST be present in the STR message for this
5450 session.
5452 ACCOUNTING 4
5454 When set, all accounting messages for this session MUST NOT
5455 include the Destination-Host AVP. When cleared, the default
5456 value, the Destination-Host AVP, if known, MUST be present in all
5457 accounting messages for this session.
5459 8.18. Session-Server-Failover AVP
5461 The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated,
5462 and MAY be present in application-specific authorization answer
5463 messages that either do not include the Session-Binding AVP or
5464 include the Session-Binding AVP with any of the bits set to a zero
5465 value. If present, this AVP MAY inform the Diameter client that if a
5466 re-auth or STR message fails due to a delivery problem, the Diameter
5467 client SHOULD issue a subsequent message without the Destination-Host
5468 AVP. When absent, the default value is REFUSE_SERVICE.
5470 The following values are supported:
5472 REFUSE_SERVICE 0
5474 If either the re-auth or the STR message delivery fails, terminate
5475 service with the user, and do not attempt any subsequent attempts.
5477 TRY_AGAIN 1
5479 If either the re-auth or the STR message delivery fails, resend
5480 the failed message without the Destination-Host AVP present.
5482 ALLOW_SERVICE 2
5484 If re-auth message delivery fails, assume that re-authorization
5485 succeeded. If STR message delivery fails, terminate the session.
5487 TRY_AGAIN_ALLOW_SERVICE 3
5489 If either the re-auth or the STR message delivery fails, resend
5490 the failed message without the Destination-Host AVP present. If
5491 the second delivery fails for re-auth, assume re-authorization
5492 succeeded. If the second delivery fails for STR, terminate the
5493 session.
5495 8.19. Multi-Round-Time-Out AVP
5497 The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32,
5498 and SHOULD be present in application-specific authorization answer
5499 messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH.
5500 This AVP contains the maximum number of seconds that the access
5501 device MUST provide the user in responding to an authentication
5502 request.
5504 8.20. Class AVP
5506 The Class AVP (AVP Code 25) is of type OctetString and is used to by
5507 Diameter servers to return state information to the access device.
5508 When one or more Class AVPs are present in application-specific
5509 authorization answer messages, they MUST be present in subsequent re-
5510 authorization, session termination and accounting messages. Class
5511 AVPs found in a re-authorization answer message override the ones
5512 found in any previous authorization answer message. Diameter server
5513 implementations SHOULD NOT return Class AVPs that require more than
5514 4096 bytes of storage on the Diameter client. A Diameter client that
5515 receives Class AVPs whose size exceeds local available storage MUST
5516 terminate the session.
5518 8.21. Event-Timestamp AVP
5520 The Event-Timestamp (AVP Code 55) is of type Time, and MAY be
5521 included in an Accounting-Request and Accounting-Answer messages to
5522 record the time that the reported event occurred, in seconds since
5523 January 1, 1900 00:00 UTC.
5525 9. Accounting
5527 This accounting protocol is based on a server directed model with
5528 capabilities for real-time delivery of accounting information.
5529 Several fault resilience methods [RFC2975] have been built in to the
5530 protocol in order minimize loss of accounting data in various fault
5531 situations and under different assumptions about the capabilities of
5532 the used devices.
5534 9.1. Server Directed Model
5536 The server directed model means that the device generating the
5537 accounting data gets information from either the authorization server
5538 (if contacted) or the accounting server regarding the way accounting
5539 data shall be forwarded. This information includes accounting record
5540 timeliness requirements.
5542 As discussed in [RFC2975], real-time transfer of accounting records
5543 is a requirement, such as the need to perform credit limit checks and
5544 fraud detection. Note that batch accounting is not a requirement,
5545 and is therefore not supported by Diameter. Should batched
5546 accounting be required in the future, a new Diameter application will
5547 need to be created, or it could be handled using another protocol.
5548 Note, however, that even if at the Diameter layer accounting requests
5549 are processed one by one, transport protocols used under Diameter
5550 typically batch several requests in the same packet under heavy
5551 traffic conditions. This may be sufficient for many applications.
5553 The authorization server (chain) directs the selection of proper
5554 transfer strategy, based on its knowledge of the user and
5555 relationships of roaming partnerships. The server (or agents) uses
5556 the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to
5557 control the operation of the Diameter peer operating as a client.
5558 The Acct-Interim-Interval AVP, when present, instructs the Diameter
5559 node acting as a client to produce accounting records continuously
5560 even during a session. Accounting-Realtime-Required AVP is used to
5561 control the behavior of the client when the transfer of accounting
5562 records from the Diameter client is delayed or unsuccessful.
5564 The Diameter accounting server MAY override the interim interval or
5565 the realtime requirements by including the Acct-Interim-Interval or
5566 Accounting-Realtime-Required AVP in the Accounting-Answer message.
5567 When one of these AVPs is present, the latest value received SHOULD
5568 be used in further accounting activities for the same session.
5570 9.2. Protocol Messages
5572 A Diameter node that receives a successful authentication and/or
5573 authorization messages from the Home AAA server MUST collect
5574 accounting information for the session. The Accounting-Request
5575 message is used to transmit the accounting information to the Home
5576 AAA server, which MUST reply with the Accounting-Answer message to
5577 confirm reception. The Accounting-Answer message includes the
5578 Result-Code AVP, which MAY indicate that an error was present in the
5579 accounting message. A rejected Accounting-Request message MAY cause
5580 the user's session to be terminated, depending on the value of the
5581 Accounting-Realtime-Required AVP received earlier for the session in
5582 question.
5584 Each Diameter Accounting protocol message MAY be compressed, in order
5585 to reduce network bandwidth usage. If TLS is used to secure the
5586 Diameter session, then TLS compression [RFC4346] MAY be used.
5588 9.3. Accounting Application Extension and Requirements
5590 Each Diameter application (e.g., NASREQ, MobileIP), MUST define their
5591 Service-Specific AVPs that MUST be present in the Accounting-Request
5592 message in a section entitled "Accounting AVPs". The application
5593 MUST assume that the AVPs described in this document will be present
5594 in all Accounting messages, so only their respective service-specific
5595 AVPs need to be defined in this section.
5597 Applications have the option of using one or both of the following
5598 accounting application extension models:
5600 Split Accounting Service
5602 The accounting message will carry the application identifier of
5603 the Diameter base accounting application (see Section 2.4).
5604 Accounting messages maybe routed to Diameter nodes other than the
5605 corresponding Diameter application. These nodes might be
5606 centralized accounting servers that provide accounting service for
5607 multiple different Diameter applications. These nodes MUST
5608 advertise the Diameter base accounting application identifier
5609 during capabilities exchange.
5611 Accounting messages which uses the Diameter base accounting
5612 application identifier in its header MUST include the application
5613 identifier of the Diameter application it is providing service for
5614 in the Acct-Application-Id AVP. This allows the accounting server
5615 to determine which Diameter application the accounting records are
5616 for.
5618 Coupled Accounting Service
5620 The accounting messages will carry the application identifier of
5621 the application that is using it. The application itself will
5622 process the received accounting records or forward them to an
5623 accounting server. There is no accounting application
5624 advertisement required during capabilities exchange and the
5625 accounting messages will be routed the same as any of the other
5626 application messages.
5628 In cases where an application does not define its own accounting
5629 service, it is preferred that the split accounting model be used.
5631 9.4. Fault Resilience
5633 Diameter Base protocol mechanisms are used to overcome small message
5634 loss and network faults of temporary nature.
5636 Diameter peers acting as clients MUST implement the use of failover
5637 to guard against server failures and certain network failures.
5638 Diameter peers acting as agents or related off-line processing
5639 systems MUST detect duplicate accounting records caused by the
5640 sending of same record to several servers and duplication of messages
5641 in transit. This detection MUST be based on the inspection of the
5642 Session-Id and Accounting-Record-Number AVP pairs. Appendix C
5643 discusses duplicate detection needs and implementation issues.
5645 Diameter clients MAY have non-volatile memory for the safe storage of
5646 accounting records over reboots or extended network failures, network
5647 partitions, and server failures. If such memory is available, the
5648 client SHOULD store new accounting records there as soon as the
5649 records are created and until a positive acknowledgement of their
5650 reception from the Diameter Server has been received. Upon a reboot,
5651 the client MUST starting sending the records in the non-volatile
5652 memory to the accounting server with appropriate modifications in
5653 termination cause, session length, and other relevant information in
5654 the records.
5656 A further application of this protocol may include AVPs to control
5657 how many accounting records may at most be stored in the Diameter
5658 client without committing them to the non-volatile memory or
5659 transferring them to the Diameter server.
5661 The client SHOULD NOT remove the accounting data from any of its
5662 memory areas before the correct Accounting-Answer has been received.
5663 The client MAY remove oldest, undelivered or yet unacknowledged
5664 accounting data if it runs out of resources such as memory. It is an
5665 implementation dependent matter for the client to accept new sessions
5666 under this condition.
5668 9.5. Accounting Records
5670 In all accounting records, the Session-Id AVP MUST be present; the
5671 User-Name AVP MUST be present if it is available to the Diameter
5672 client.
5674 Different types of accounting records are sent depending on the
5675 actual type of accounted service and the authorization server's
5676 directions for interim accounting. If the accounted service is a
5677 one-time event, meaning that the start and stop of the event are
5678 simultaneous, then the Accounting-Record-Type AVP MUST be present and
5679 set to the value EVENT_RECORD.
5681 If the accounted service is of a measurable length, then the AVP MUST
5682 use the values START_RECORD, STOP_RECORD, and possibly,
5683 INTERIM_RECORD. If the authorization server has not directed interim
5684 accounting to be enabled for the session, two accounting records MUST
5685 be generated for each service of type session. When the initial
5686 Accounting-Request for a given session is sent, the Accounting-
5687 Record-Type AVP MUST be set to the value START_RECORD. When the last
5688 Accounting-Request is sent, the value MUST be STOP_RECORD.
5690 If the authorization server has directed interim accounting to be
5691 enabled, the Diameter client MUST produce additional records between
5692 the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The
5693 production of these records is directed by Acct-Interim-Interval as
5694 well as any re-authentication or re-authorization of the session.
5695 The Diameter client MUST overwrite any previous interim accounting
5696 records that are locally stored for delivery, if a new record is
5697 being generated for the same session. This ensures that only one
5698 pending interim record can exist on an access device for any given
5699 session.
5701 A particular value of Accounting-Sub-Session-Id MUST appear only in
5702 one sequence of accounting records from a DIAMETER client, except for
5703 the purposes of retransmission. The one sequence that is sent MUST
5704 be either one record with Accounting-Record-Type AVP set to the value
5705 EVENT_RECORD, or several records starting with one having the value
5706 START_RECORD, followed by zero or more INTERIM_RECORD and a single
5707 STOP_RECORD. A particular Diameter application specification MUST
5708 define the type of sequences that MUST be used.
5710 9.6. Correlation of Accounting Records
5712 The Diameter protocol's Session-Id AVP, which is globally unique (see
5713 Section 8.8), is used during the authorization phase to identify a
5714 particular session. Services that do not require any authorization
5715 still use the Session-Id AVP to identify sessions. Accounting
5716 messages MAY use a different Session-Id from that sent in
5717 authorization messages. Specific applications MAY require different
5718 a Session-ID for accounting messages.
5720 However, there are certain applications that require multiple
5721 accounting sub-sessions. Such applications would send messages with
5722 a constant Session-Id AVP, but a different Accounting-Sub-Session-Id
5723 AVP. In these cases, correlation is performed using the Session-Id.
5724 It is important to note that receiving a STOP_RECORD with no
5725 Accounting-Sub-Session-Id AVP when sub-sessions were originally used
5726 in the START_RECORD messages implies that all sub-sessions are
5727 terminated.
5729 Furthermore, there are certain applications where a user receives
5730 service from different access devices (e.g., Mobile IPv4), each with
5731 their own unique Session-Id. In such cases, the Acct-Multi-Session-
5732 Id AVP is used for correlation. During authorization, a server that
5733 determines that a request is for an existing session SHOULD include
5734 the Acct-Multi-Session-Id AVP, which the access device MUST include
5735 in all subsequent accounting messages.
5737 The Acct-Multi-Session-Id AVP MAY include the value of the original
5738 Session-Id. It's contents are implementation specific, but MUST be
5739 globally unique across other Acct-Multi-Session-Id, and MUST NOT
5740 change during the life of a session.
5742 A Diameter application document MUST define the exact concept of a
5743 session that is being accounted, and MAY define the concept of a
5744 multi-session. For instance, the NASREQ DIAMETER application treats
5745 a single PPP connection to a Network Access Server as one session,
5746 and a set of Multilink PPP sessions as one multi-session.
5748 9.7. Accounting Command-Codes
5750 This section defines Command-Code values that MUST be supported by
5751 all Diameter implementations that provide Accounting services.
5753 9.7.1. Accounting-Request
5755 The Accounting-Request (ACR) command, indicated by the Command-Code
5756 field set to 271 and the Command Flags' 'R' bit set, is sent by a
5757 Diameter node, acting as a client, in order to exchange accounting
5758 information with a peer.
5760 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs
5761 MUST be present. If the Vendor-Specific-Application-Id grouped AVP
5762 is present, it must have an Acct-Application-Id inside.
5764 The AVP listed below SHOULD include service specific accounting AVPs,
5765 as described in Section 9.3.
5767 Message Format
5769 ::= < Diameter Header: 271, REQ, PXY >
5770 < Session-Id >
5771 { Origin-Host }
5772 { Origin-Realm }
5773 { Destination-Realm }
5774 { Accounting-Record-Type }
5775 { Accounting-Record-Number }
5776 [ Acct-Application-Id ]
5777 [ Vendor-Specific-Application-Id ]
5778 [ User-Name ]
5779 [ Destination-Host ]
5780 [ Accounting-Sub-Session-Id ]
5781 [ Acct-Session-Id ]
5782 [ Acct-Multi-Session-Id ]
5783 [ Acct-Interim-Interval ]
5784 [ Accounting-Realtime-Required ]
5785 [ Origin-State-Id ]
5786 [ Event-Timestamp ]
5787 * [ Proxy-Info ]
5788 * [ Route-Record ]
5789 * [ AVP ]
5791 9.7.2. Accounting-Answer
5793 The Accounting-Answer (ACA) command, indicated by the Command-Code
5794 field set to 271 and the Command Flags' 'R' bit cleared, is used to
5795 acknowledge an Accounting-Request command. The Accounting-Answer
5796 command contains the same Session-Id as the corresponding request.
5798 Only the target Diameter Server, known as the home Diameter Server,
5799 SHOULD respond with the Accounting-Answer command.
5801 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs
5802 MUST be present. If the Vendor-Specific-Application-Id grouped AVP
5803 is present, it must have an Acct-Application-Id inside.
5805 The AVP listed below SHOULD include service specific accounting AVPs,
5806 as described in Section 9.3.
5808 Message Format
5810 ::= < Diameter Header: 271, PXY >
5811 < Session-Id >
5812 { Result-Code }
5813 { Origin-Host }
5814 { Origin-Realm }
5815 { Accounting-Record-Type }
5816 { Accounting-Record-Number }
5817 [ Acct-Application-Id ]
5818 [ Vendor-Specific-Application-Id ]
5819 [ User-Name ]
5820 [ Accounting-Sub-Session-Id ]
5821 [ Acct-Session-Id ]
5822 [ Acct-Multi-Session-Id ]
5823 [ Error-Reporting-Host ]
5824 [ Acct-Interim-Interval ]
5825 [ Accounting-Realtime-Required ]
5826 [ Origin-State-Id ]
5827 [ Event-Timestamp ]
5828 * [ Proxy-Info ]
5829 * [ AVP ]
5831 9.8. Accounting AVPs
5833 This section contains AVPs that describe accounting usage information
5834 related to a specific session.
5836 9.8.1. Accounting-Record-Type AVP
5838 The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated
5839 and contains the type of accounting record being sent. The following
5840 values are currently defined for the Accounting-Record-Type AVP:
5842 EVENT_RECORD 1
5844 An Accounting Event Record is used to indicate that a one-time
5845 event has occurred (meaning that the start and end of the event
5846 are simultaneous). This record contains all information relevant
5847 to the service, and is the only record of the service.
5849 START_RECORD 2
5851 An Accounting Start, Interim, and Stop Records are used to
5852 indicate that a service of a measurable length has been given. An
5853 Accounting Start Record is used to initiate an accounting session,
5854 and contains accounting information that is relevant to the
5855 initiation of the session.
5857 INTERIM_RECORD 3
5859 An Interim Accounting Record contains cumulative accounting
5860 information for an existing accounting session. Interim
5861 Accounting Records SHOULD be sent every time a re-authentication
5862 or re-authorization occurs. Further, additional interim record
5863 triggers MAY be defined by application-specific Diameter
5864 applications. The selection of whether to use INTERIM_RECORD
5865 records is done by the Acct-Interim-Interval AVP.
5867 STOP_RECORD 4
5869 An Accounting Stop Record is sent to terminate an accounting
5870 session and contains cumulative accounting information relevant to
5871 the existing session.
5873 9.8.2. Acct-Interim-Interval
5875 The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and
5876 is sent from the Diameter home authorization server to the Diameter
5877 client. The client uses information in this AVP to decide how and
5878 when to produce accounting records. With different values in this
5879 AVP, service sessions can result in one, two, or two+N accounting
5880 records, based on the needs of the home-organization. The following
5881 accounting record production behavior is directed by the inclusion of
5882 this AVP:
5884 1. The omission of the Acct-Interim-Interval AVP or its inclusion
5885 with Value field set to 0 means that EVENT_RECORD, START_RECORD,
5886 and STOP_RECORD are produced, as appropriate for the service.
5888 2. The inclusion of the AVP with Value field set to a non-zero value
5889 means that INTERIM_RECORD records MUST be produced between the
5890 START_RECORD and STOP_RECORD records. The Value field of this
5891 AVP is the nominal interval between these records in seconds.
5892 The Diameter node that originates the accounting information,
5893 known as the client, MUST produce the first INTERIM_RECORD record
5894 roughly at the time when this nominal interval has elapsed from
5895 the START_RECORD, the next one again as the interval has elapsed
5896 once more, and so on until the session ends and a STOP_RECORD
5897 record is produced.
5899 The client MUST ensure that the interim record production times
5900 are randomized so that large accounting message storms are not
5901 created either among records or around a common service start
5902 time.
5904 9.8.3. Accounting-Record-Number AVP
5906 The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32
5907 and identifies this record within one session. As Session-Id AVPs
5908 are globally unique, the combination of Session-Id and Accounting-
5909 Record-Number AVPs is also globally unique, and can be used in
5910 matching accounting records with confirmations. An easy way to
5911 produce unique numbers is to set the value to 0 for records of type
5912 EVENT_RECORD and START_RECORD, and set the value to 1 for the first
5913 INTERIM_RECORD, 2 for the second, and so on until the value for
5914 STOP_RECORD is one more than for the last INTERIM_RECORD.
5916 9.8.4. Acct-Session-Id AVP
5918 The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only
5919 used when RADIUS/Diameter translation occurs. This AVP contains the
5920 contents of the RADIUS Acct-Session-Id attribute.
5922 9.8.5. Acct-Multi-Session-Id AVP
5924 The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String,
5925 following the format specified in Section 8.8. The Acct-Multi-
5926 Session-Id AVP is used to link together multiple related accounting
5927 sessions, where each session would have a unique Session-Id, but the
5928 same Acct-Multi-Session-Id AVP. This AVP MAY be returned by the
5929 Diameter server in an authorization answer, and MUST be used in all
5930 accounting messages for the given session.
5932 9.8.6. Accounting-Sub-Session-Id AVP
5934 The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type
5935 Unsigned64 and contains the accounting sub-session identifier. The
5936 combination of the Session-Id and this AVP MUST be unique per sub-
5937 session, and the value of this AVP MUST be monotonically increased by
5938 one for all new sub-sessions. The absence of this AVP implies no
5939 sub-sessions are in use, with the exception of an Accounting-Request
5940 whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD
5941 message with no Accounting-Sub-Session-Id AVP present will signal the
5942 termination of all sub-sessions for a given Session-Id.
5944 9.8.7. Accounting-Realtime-Required AVP
5946 The Accounting-Realtime-Required AVP (AVP Code 483) is of type
5947 Enumerated and is sent from the Diameter home authorization server to
5948 the Diameter client or in the Accounting-Answer from the accounting
5949 server. The client uses information in this AVP to decide what to do
5950 if the sending of accounting records to the accounting server has
5951 been temporarily prevented due to, for instance, a network problem.
5953 DELIVER_AND_GRANT 1
5955 The AVP with Value field set to DELIVER_AND_GRANT means that the
5956 service MUST only be granted as long as there is a connection to
5957 an accounting server. Note that the set of alternative accounting
5958 servers are treated as one server in this sense. Having to move
5959 the accounting record stream to a backup server is not a reason to
5960 discontinue the service to the user.
5962 GRANT_AND_STORE 2
5964 The AVP with Value field set to GRANT_AND_STORE means that service
5965 SHOULD be granted if there is a connection, or as long as records
5966 can still be stored as described in Section 9.4.
5968 This is the default behavior if the AVP isn't included in the
5969 reply from the authorization server.
5971 GRANT_AND_LOSE 3
5973 The AVP with Value field set to GRANT_AND_LOSE means that service
5974 SHOULD be granted even if the records can not be delivered or
5975 stored.
5977 10. AVP Occurrence Table
5979 The following tables presents the AVPs defined in this document, and
5980 specifies in which Diameter messages they MAY be present or not.
5981 Note that AVPs that can only be present within a Grouped AVP are not
5982 represented in this table.
5984 The table uses the following symbols:
5986 0 The AVP MUST NOT be present in the message.
5988 0+ Zero or more instances of the AVP MAY be present in the
5989 message.
5991 0-1 Zero or one instance of the AVP MAY be present in the message.
5992 It is considered an error if there are more than one instance of
5993 the AVP.
5995 1 One instance of the AVP MUST be present in the message.
5997 1+ At least one instance of the AVP MUST be present in the
5998 message.
6000 10.1. Base Protocol Command AVP Table
6002 The table in this section is limited to the non-accounting Command
6003 Codes defined in this specification.
6005 +-----------------------------------------------+
6006 | Command-Code |
6007 +---+---+---+---+---+---+---+---+---+---+---+---+
6008 Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA|
6009 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+
6010 Acct-Interim- |0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 |
6011 Interval | | | | | | | | | | | | |
6012 Accounting-Realtime-|0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 |
6013 Required | | | | | | | | | | | | |
6014 Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6015 Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 |
6016 Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6017 Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6018 Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6019 Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6020 Lifetime | | | | | | | | | | | | |
6021 Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ |
6022 Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 |
6023 Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 |
6024 Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6025 Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|
6026 Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
6027 Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |
6028 Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6029 Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6030 Inband-Security-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6031 Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6032 Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |
6033 Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |
6034 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|
6035 Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6036 Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ |
6037 Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |
6038 Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
6039 Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
6040 Time | | | | | | | | | | | | |
6041 Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |0 |0 |1 |
6042 Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 |
6043 Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 |
6044 Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6045 Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 |
6046 Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6047 Failover | | | | | | | | | | | | |
6048 Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6049 Supported-Vendor-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6050 Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 |
6051 User-Name |0 |0 |0 |0 |0 |0 |0-1|0-1|0-1|0-1|0-1|0-1|
6052 Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6053 Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6054 Application-Id | | | | | | | | | | | | |
6055 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+
6057 10.2. Accounting AVP Table
6059 The table in this section is used to represent which AVPs defined in
6060 this document are to be present in the Accounting messages. These
6061 AVP occurrence requirements are guidelines, which may be expanded,
6062 and/or overridden by application-specific requirements in the
6063 Diameter applications documents.
6065 +-----------+
6066 | Command |
6067 | Code |
6068 +-----+-----+
6069 Attribute Name | ACR | ACA |
6070 ------------------------------+-----+-----+
6071 Acct-Interim-Interval | 0-1 | 0-1 |
6072 Acct-Multi-Session-Id | 0-1 | 0-1 |
6073 Accounting-Record-Number | 1 | 1 |
6074 Accounting-Record-Type | 1 | 1 |
6075 Acct-Session-Id | 0-1 | 0-1 |
6076 Accounting-Sub-Session-Id | 0-1 | 0-1 |
6077 Accounting-Realtime-Required | 0-1 | 0-1 |
6078 Acct-Application-Id | 0-1 | 0-1 |
6079 Auth-Application-Id | 0 | 0 |
6080 Class | 0+ | 0+ |
6081 Destination-Host | 0-1 | 0 |
6082 Destination-Realm | 1 | 0 |
6083 Error-Reporting-Host | 0 | 0+ |
6084 Event-Timestamp | 0-1 | 0-1 |
6085 Origin-Host | 1 | 1 |
6086 Origin-Realm | 1 | 1 |
6087 Proxy-Info | 0+ | 0+ |
6088 Route-Record | 0+ | 0+ |
6089 Result-Code | 0 | 1 |
6090 Session-Id | 1 | 1 |
6091 Termination-Cause | 0 | 0 |
6092 User-Name | 0-1 | 0-1 |
6093 Vendor-Specific-Application-Id| 0-1 | 0-1 |
6094 ------------------------------+-----+-----+
6096 11. IANA Considerations
6098 This section provides guidance to the Internet Assigned Numbers
6099 Authority (IANA) regarding registration of values related to the
6100 Diameter protocol, in accordance with BCP 26 [RFC2434]. The
6101 following policies are used here with the meanings defined in BCP 26:
6102 "Private Use", "First Come First Served", "Expert Review",
6103 "Specification Required", "IETF Consensus", "Standards Action".
6105 This section explains the criteria to be used by the IANA for
6106 assignment of numbers within namespaces defined within this document.
6108 Diameter is not intended as a general purpose protocol, and
6109 allocations SHOULD NOT be made for purposes unrelated to
6110 authentication, authorization or accounting.
6112 For registration requests where a Designated Expert should be
6113 consulted, the responsible IESG area director should appoint the
6114 Designated Expert. For Designated Expert with Specification
6115 Required, the request is posted to the DIME WG mailing list (or, if
6116 it has been disbanded, a successor designated by the Area Director)
6117 for comment and review, and MUST include a pointer to a public
6118 specification. Before a period of 30 days has passed, the Designated
6119 Expert will either approve or deny the registration request and
6120 publish a notice of the decision to the DIME WG mailing list or its
6121 successor. A denial notice must be justified by an explanation and,
6122 in the cases where it is possible, concrete suggestions on how the
6123 request can be modified so as to become acceptable.
6125 11.1. AVP Header
6127 As defined in Section 4, the AVP header contains three fields that
6128 requires IANA namespace management; the AVP Code, Vendor-ID and Flags
6129 field.
6131 11.1.1. AVP Codes
6133 The AVP Code namespace is used to identify attributes. There are
6134 multiple namespaces. Vendors can have their own AVP Codes namespace
6135 which will be identified by their Vendor-ID (also known as
6136 Enterprise-Number) and they control the assignments of their vendor-
6137 specific AVP codes within their own namespace. The absence of a
6138 Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA
6139 controlled AVP Codes namespace. The AVP Codes and sometimes also
6140 possible values in an AVP are controlled and maintained by IANA.
6142 AVP Code 0 is not used. AVP Codes 1-255 are managed separately as
6143 RADIUS Attribute Types [RADTYPE]. This document defines the AVP
6144 Codes 257-274, 276-285, 287, 291-300, 480, 483 and 485-486. See
6145 Section 4.5 for the assignment of the namespace in this
6146 specification.
6148 AVPs may be allocated following Designated Expert with Specification
6149 Required [RFC2434]. Release of blocks of AVPs (more than 3 at a time
6150 for a given purpose) should require IETF Consensus.
6152 Note that Diameter defines a mechanism for Vendor-Specific AVPs,
6153 where the Vendor-Id field in the AVP header is set to a non-zero
6154 value. Vendor-Specific AVPs codes are for Private Use and should be
6155 encouraged instead of allocation of global attribute types, for
6156 functions specific only to one vendor's implementation of Diameter,
6157 where no interoperability is deemed useful. Where a Vendor-Specific
6158 AVP is implemented by more than one vendor, allocation of global AVPs
6159 should be encouraged instead.
6161 11.1.2. AVP Flags
6163 There are 8 bits in the AVP Flags field of the AVP header, defined in
6164 Section 4. This document assigns bit 0 ('V'endor Specific), bit 1
6165 ('M'andatory) and bit 2 ('P'rotected). The remaining bits should
6166 only be assigned via a Standards Action [RFC2434].
6168 11.2. Diameter Header
6170 As defined in Section 3, the Diameter header contains two fields that
6171 require IANA namespace management; Command Code and Command Flags.
6173 11.2.1. Command Codes
6175 The Command Code namespace is used to identify Diameter commands.
6176 The values 0-255 are reserved for RADIUS backward compatibility, and
6177 are defined as "RADIUS Packet Type Codes" in [RADTYPE]. Values 256-
6178 16,777,213 are for permanent, standard commands, allocated by Expert
6179 Review [RFC2434]. This document defines the Command Codes 257, 258,
6180 271, 274-275, 280 and 282. See Section 3.1 for the assignment of the
6181 namespace in this specification.
6183 The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe -
6184 0xffffff) are reserved for experimental commands. As these codes are
6185 only for experimental and testing purposes, no guarantee is made for
6186 interoperability between Diameter peers using experimental commands,
6187 as outlined in [IANA-EXP].
6189 [Editor's note: The expert review process for command code allocation
6190 is being introduced to hasten the allocation process itself.
6191 Hopefully this will lessen the tendency to circumvent this process.
6193 Details will be added in subsequent revisions and more complete
6194 description will be added in the design guidelines document.]
6196 11.2.2. Command Flags
6198 There are eight bits in the Command Flags field of the Diameter
6199 header. This document assigns bit 0 ('R'equest), bit 1 ('P'roxy),
6200 bit 2 ('E'rror) and bit 3 ('T'). Bits 4 through 7 MUST only be
6201 assigned via a Standards Action [RFC2434].
6203 11.3. Application Identifiers
6205 As defined in Section 2.4, the Application Identifier is used to
6206 identify a specific Diameter Application. There are standards-track
6207 application ids and vendor specific application ids.
6209 IANA [RFC2434] has assigned the range 0x00000001 to 0x00ffffff for
6210 standards-track applications; and 0x01000000 - 0xfffffffe for vendor
6211 specific applications, on a first-come, first-served basis. The
6212 following values are allocated.
6214 Diameter Common Messages 0
6215 NASREQ 1 [RFC4005]
6216 Mobile-IP 2 [RFC4004]
6217 Diameter Base Accounting 3
6218 Relay 0xffffffff
6220 Assignment of standards-track application IDs are by Designated
6221 Expert with Specification Required [RFC2434].
6223 Both Auth-Application-Id and Acct-Application-Id AVPs use the same
6224 Application Identifier space. A diameter node advertising itself as
6225 a relay agent MUST set either Application-Id or Acct-Application-Id
6226 to 0xffffffff.
6228 Vendor-Specific Application Identifiers, are for Private Use. Vendor-
6229 Specific Application Identifiers are assigned on a First Come, First
6230 Served basis by IANA.
6232 11.4. AVP Values
6234 Certain AVPs in Diameter define a list of values with various
6235 meanings. For attributes other than those specified in this section,
6236 adding additional values to the list can be done on a First Come,
6237 First Served basis by IANA.
6239 11.4.1. Result-Code AVP Values
6241 As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines
6242 the values 1001, 2001-2002, 3001-3012, 4001-4003 and 5001-5021.
6244 All remaining values are available for assignment via IETF Consensus
6245 [RFC2434].
6247 11.4.2. Accounting-Record-Type AVP Values
6249 As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code
6250 480) defines the values 1-4. All remaining values are available for
6251 assignment via IETF Consensus [RFC2434].
6253 11.4.3. Termination-Cause AVP Values
6255 As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295)
6256 defines the values 1-8. All remaining values are available for
6257 assignment via IETF Consensus [RFC2434].
6259 11.4.4. Redirect-Host-Usage AVP Values
6261 As defined in Section 6.13, the Redirect-Host-Usage AVP (AVP Code
6262 261) defines the values 0-5. All remaining values are available for
6263 assignment via IETF Consensus [RFC2434].
6265 11.4.5. Session-Server-Failover AVP Values
6267 As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code
6268 271) defines the values 0-3. All remaining values are available for
6269 assignment via IETF Consensus [RFC2434].
6271 11.4.6. Session-Binding AVP Values
6273 As defined in Section 8.17, the Session-Binding AVP (AVP Code 270)
6274 defines the bits 1-4. All remaining bits are available for
6275 assignment via IETF Consensus [RFC2434].
6277 11.4.7. Disconnect-Cause AVP Values
6279 As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273)
6280 defines the values 0-2. All remaining values are available for
6281 assignment via IETF Consensus [RFC2434].
6283 11.4.8. Auth-Request-Type AVP Values
6285 As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274)
6286 defines the values 1-3. All remaining values are available for
6287 assignment via IETF Consensus [RFC2434].
6289 11.4.9. Auth-Session-State AVP Values
6291 As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277)
6292 defines the values 0-1. All remaining values are available for
6293 assignment via IETF Consensus [RFC2434].
6295 11.4.10. Re-Auth-Request-Type AVP Values
6297 As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code
6298 285) defines the values 0-1. All remaining values are available for
6299 assignment via IETF Consensus [RFC2434].
6301 11.4.11. Accounting-Realtime-Required AVP Values
6303 As defined in Section 9.8.7, the Accounting-Realtime-Required AVP
6304 (AVP Code 483) defines the values 1-3. All remaining values are
6305 available for assignment via IETF Consensus [RFC2434].
6307 11.4.12. Inband-Security-Id AVP (code 299)
6309 As defined in Section 6.10, the Inband-Security-Id AVP (AVP Code 299)
6310 defines the values 0-1. All remaining values are available for
6311 assignment via IETF Consensus [RFC2434].
6313 11.5. Diameter TCP/SCTP Port Numbers
6315 The IANA has assigned TCP and SCTP port number 3868 to Diameter.
6317 11.6. NAPTR Service Fields
6319 The registration in the RFC MUST include the following information:
6321 Service Field: The service field being registered. An example for a
6322 new fictitious transport protocol called NCTP might be "AAA+D2N".
6324 Protocol: The specific transport protocol associated with that
6325 service field. This MUST include the name and acronym for the
6326 protocol, along with reference to a document that describes the
6327 transport protocol. For example - "New Connectionless Transport
6328 Protocol (NCTP), RFC 5766".
6330 Name and Contact Information: The name, address, email address and
6331 telephone number for the person performing the registration.
6333 The following values have been placed into the registry:
6335 Services Field Protocol
6337 AAA+D2T TCP
6338 AAA+D2S SCTP
6340 12. Diameter protocol related configurable parameters
6342 This section contains the configurable parameters that are found
6343 throughout this document:
6345 Diameter Peer
6347 A Diameter entity MAY communicate with peers that are statically
6348 configured. A statically configured Diameter peer would require
6349 that either the IP address or the fully qualified domain name
6350 (FQDN) be supplied, which would then be used to resolve through
6351 DNS.
6353 Routing Table
6355 A Diameter proxy server routes messages based on the realm portion
6356 of a Network Access Identifier (NAI). The server MUST have a
6357 table of Realm Names, and the address of the peer to which the
6358 message must be forwarded to. The routing table MAY also include
6359 a "default route", which is typically used for all messages that
6360 cannot be locally processed.
6362 Tc timer
6364 The Tc timer controls the frequency that transport connection
6365 attempts are done to a peer with whom no active transport
6366 connection exists. The recommended value is 30 seconds.
6368 13. Security Considerations
6370 The Diameter base protocol assumes that messages maybe secured by
6371 using TLS. As an alternative, IPSec can be also be used to secure
6372 Diameter peer connections but its usage is transparent from the
6373 Diameter node and Diameter protocol perspective. These security
6374 mechanism is acceptable in environments where there is no untrusted
6375 third party agent.
6377 Diameter clients, such as Network Access Servers (NASes) and Mobility
6378 Agents MAY support TLS [RFC4346]. Diameter servers MUST support TLS.
6379 Diameter implementations SHOULD use transmission-level security of
6380 some kind (IPsec or TLS) on each connection.
6382 If a Diameter connection is to be protected via TLS, then the CER/CEA
6383 exchange MUST include an Inband-Security-ID AVP with a value of TLS.
6384 For TLS usage, a TLS handshake will begin when both ends are in the
6385 open state, after completion of the CER/CEA exchange. If the TLS
6386 handshake is successful, all further messages will be sent via TLS.
6387 If the handshake fails, both ends move to the closed state. See
6388 Sections 13.1 for more details.
6390 13.1. TLS Usage
6392 A Diameter node that initiates a connection to another Diameter node
6393 acts as a TLS client according to [RFC4346], and a Diameter node that
6394 accepts a connection acts as a TLS server. Diameter nodes
6395 implementing TLS for security MUST mutually authenticate as part of
6396 TLS session establishment. In order to ensure mutual authentication,
6397 the Diameter node acting as TLS server must request a certificate
6398 from the Diameter node acting as TLS client, and the Diameter node
6399 acting as TLS client MUST be prepared to supply a certificate on
6400 request.
6402 Diameter nodes MUST be able to negotiate the following TLS cipher
6403 suites:
6405 TLS_RSA_WITH_RC4_128_MD5
6406 TLS_RSA_WITH_RC4_128_SHA
6407 TLS_RSA_WITH_3DES_EDE_CBC_SHA
6409 Diameter nodes SHOULD be able to negotiate the following TLS cipher
6410 suite:
6412 TLS_RSA_WITH_AES_128_CBC_SHA
6414 Diameter nodes MAY negotiate other TLS cipher suites.
6416 13.2. Peer-to-Peer Considerations
6418 As with any peer-to-peer protocol, proper configuration of the trust
6419 model within a Diameter peer is essential to security. When
6420 certificates are used, it is necessary to configure the root
6421 certificate authorities trusted by the Diameter peer. These root CAs
6422 are likely to be unique to Diameter usage and distinct from the root
6423 CAs that might be trusted for other purposes such as Web browsing.
6424 In general, it is expected that those root CAs will be configured so
6425 as to reflect the business relationships between the organization
6426 hosting the Diameter peer and other organizations. As a result, a
6427 Diameter peer will typically not be configured to allow connectivity
6428 with any arbitrary peer. With certificate authentication, Diameter
6429 peers may not be known beforehand and therefore peer discovery may be
6430 required.
6432 14. References
6434 14.1. Normative References
6436 [FLOATPOINT]
6437 Institute of Electrical and Electronics Engineers, "IEEE
6438 Standard for Binary Floating-Point Arithmetic, ANSI/IEEE
6439 Standard 754-1985", August 1985.
6441 [IANAADFAM]
6442 IANA,, "Address Family Numbers",
6443 http://www.iana.org/assignments/address-family-numbers.
6445 [RADTYPE] IANA,, "RADIUS Types",
6446 http://www.iana.org/assignments/radius-types.
6448 [IPV4] Postel, J., "Internet Protocol", RFC 791, September 1981.
6450 [TCP] Postel, J., "Transmission Control Protocol", RFC 793,
6451 January 1981.
6453 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and
6454 Accounting (AAA) Transport Profile", RFC 3539, June 2003.
6456 [RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and
6457 P. McCann, "Diameter Mobile IPv4 Application", RFC 4004,
6458 August 2005.
6460 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
6461 "Diameter Network Access Server Application", RFC 4005,
6462 August 2005.
6464 [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
6465 Loughney, "Diameter Credit-Control Application", RFC 4006,
6466 August 2005.
6468 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
6469 Authentication Protocol (EAP) Application", RFC 4072,
6470 August 2005.
6472 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M.,
6473 Canales-Valenzuela, C., and K. Tammi, "Diameter Session
6474 Initiation Protocol (SIP) Application", RFC 4740,
6475 November 2006.
6477 [RFC4234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
6478 Specifications: ABNF", RFC 4234, October 2005.
6480 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
6481 Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
6483 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
6484 Levkowetz, "Extensible Authentication Protocol (EAP)",
6485 RFC 3748, June 2004.
6487 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
6488 IANA Considerations Section in RFCs", BCP 26, RFC 2434,
6489 October 1998.
6491 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
6492 RFC 4306, December 2005.
6494 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
6495 Architecture", RFC 4291, February 2006.
6497 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
6498 Requirement Levels", BCP 14, RFC 2119, March 1997.
6500 [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
6501 Network Access Identifier", RFC 4282, December 2005.
6503 [RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS)
6504 Part Three: The Domain Name System (DNS) Database",
6505 RFC 3403, October 2002.
6507 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
6508 A., Peterson, J., Sparks, R., Handley, M., and E.
6509 Schooler, "SIP: Session Initiation Protocol", RFC 3261,
6510 June 2002.
6512 [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
6513 Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
6514 Zhang, L., and V. Paxson, "Stream Control Transmission
6515 Protocol", RFC 2960, October 2000.
6517 [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
6518 (TLS) Protocol Version 1.1", RFC 4346, April 2006.
6520 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
6521 Resource Identifier (URI): Generic Syntax", STD 66,
6522 RFC 3986, January 2005.
6524 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
6525 10646", STD 63, RFC 3629, November 2003.
6527 14.2. Informational References
6529 [RFC2989] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, P.,
6530 Shiino, H., Zorn, G., Dommety, G., C.Perkins, B.Patil,
6531 D.Mitton, S.Manning, M.Beadles, P.Walsh, X.Chen,
6532 S.Sivalingham, A.Hameed, M.Munson, S.Jacobs, B.Lim,
6533 B.Hirschman, R.Hsu, Y.Xu, E.Campell, S.Baba, and E.Jaques,
6534 "Criteria for Evaluating AAA Protocols for Network
6535 Access", RFC 2989, November 2000.
6537 [RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction to
6538 Accounting Management", RFC 2975, October 2000.
6540 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by
6541 an On-line Database", RFC 3232, January 2002.
6543 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
6544 Aboba, "Dynamic Authorization Extensions to Remote
6545 Authentication Dial In User Service (RADIUS)", RFC 3576,
6546 July 2003.
6548 [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,
6549 RFC 1661, July 1994.
6551 [RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy
6552 Implementation in Roaming", RFC 2607, June 1999.
6554 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.
6556 [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS
6557 Extensions", RFC 2869, June 2000.
6559 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
6560 "Remote Authentication Dial In User Service (RADIUS)",
6561 RFC 2865, June 2000.
6563 [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6",
6564 RFC 3162, August 2001.
6566 [RFC2194] Aboba, B., Lu, J., Alsop, J., Ding, J., and W. Wang,
6567 "Review of Roaming Implementations", RFC 2194,
6568 September 1997.
6570 [RFC2477] Aboba, B. and G. Zorn, "Criteria for Evaluating Roaming
6571 Protocols", RFC 2477, January 1999.
6573 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
6574 Internet Protocol", RFC 4301, December 2005.
6576 [RFC4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
6577 for IPv4, IPv6 and OSI", RFC 4330, January 2006.
6579 [RFC1492] Finseth, C., "An Access Control Protocol, Sometimes Called
6580 TACACS", RFC 1492, July 1993.
6582 [IANA-EXP]
6583 Narten, T., "Assigning Experimental and Testing Numbers
6584 Considered Useful, Work in Progress.".
6586 Appendix A. Acknowledgements
6588 The authors would like to thank the following people that have
6589 provided proposals and contributions to this document:
6591 To Vishnu Ram and Satendra Gera for their contributions on
6592 Capabilities Updates, Predictive Loop Avoidance as well as many other
6593 technical proposals. To Tolga Asveren for his insights and
6594 contributions on almost all of the proposed solutions incorporated
6595 into this document. To Timothy Smith for helping on the Capabilities
6596 Updates and other topics. To Tony Zhang for providing fixes to loop
6597 holes on composing Failed-AVPs as well as many other issues and
6598 topics. To Jan Nordqvist for clearly stating the usage of
6599 application ids. To Anders Kristensen for providing needed technical
6600 opinions. To David Frascone for providing invaluable review of the
6601 document.
6603 Special thanks also to people who have provided invaluable comments
6604 and inputs especially in resolving controversial issues:
6606 Glen Zorn, Yoshihiro Ohba, Marco Stura, and Pasi Eronen.
6608 Finally, we would like to thank the original authors of this
6609 document:
6611 Pat Calhoun, John Loughney, Jari Arkko, Erik Guttman and Glen Zorn.
6613 Their invaluable knowledge and experience has given us a robust and
6614 flexible AAA protocol that many people have seen great value in
6615 adopting. We greatly appreciate their support and stewardship for
6616 the continued improvements of Diameter as a protocol. We would also
6617 like to extend our gratitude to folks aside from the authors who have
6618 assisted and contributed to the original version of this document.
6619 Their efforts significantly contributed to the success of Diameter.
6621 Appendix B. NAPTR Example
6623 As an example, consider a client that wishes to resolve aaa:ex.com.
6624 The client performs a NAPTR query for that domain, and the following
6625 NAPTR records are returned:
6627 ;; order pref flags service regexp replacement
6628 IN NAPTR 50 50 "s" "AAA+D2S" ""
6629 _diameter._sctp.example.com IN NAPTR 100 50 "s" "AAA+D2T"
6630 "" _aaa._tcp.example.com
6632 This indicates that the server supports SCTP, and TCP, in that order.
6633 If the client supports over SCTP, SCTP will be used, targeted to a
6634 host determined by an SRV lookup of _diameter._sctp.ex.com. That
6635 lookup would return:
6637 ;; Priority Weight Port Target
6638 IN SRV 0 1 5060 server1.example.com IN SRV 0
6639 2 5060 server2.example.com
6641 Appendix C. Duplicate Detection
6643 As described in Section 9.4, accounting record duplicate detection is
6644 based on session identifiers. Duplicates can appear for various
6645 reasons:
6647 o Failover to an alternate server. Where close to real-time
6648 performance is required, failover thresholds need to be kept low
6649 and this may lead to an increased likelihood of duplicates.
6650 Failover can occur at the client or within Diameter agents.
6652 o Failure of a client or agent after sending of a record from non-
6653 volatile memory, but prior to receipt of an application layer ACK
6654 and deletion of the record. record to be sent. This will result
6655 in retransmission of the record soon after the client or agent has
6656 rebooted.
6658 o Duplicates received from RADIUS gateways. Since the
6659 retransmission behavior of RADIUS is not defined within [RFC2865],
6660 the likelihood of duplication will vary according to the
6661 implementation.
6663 o Implementation problems and misconfiguration.
6665 The T flag is used as an indication of an application layer
6666 retransmission event, e.g., due to failover to an alternate server.
6667 It is defined only for request messages sent by Diameter clients or
6668 agents. For instance, after a reboot, a client may not know whether
6669 it has already tried to send the accounting records in its non-
6670 volatile memory before the reboot occurred. Diameter servers MAY use
6671 the T flag as an aid when processing requests and detecting duplicate
6672 messages. However, servers that do this MUST ensure that duplicates
6673 are found even when the first transmitted request arrives at the
6674 server after the retransmitted request. It can be used only in cases
6675 where no answer has been received from the Server for a request and
6676 the request is sent again, (e.g., due to a failover to an alternate
6677 peer, due to a recovered primary peer or due to a client re-sending a
6678 stored record from non-volatile memory such as after reboot of a
6679 client or agent).
6681 In some cases the Diameter accounting server can delay the duplicate
6682 detection and accounting record processing until a post-processing
6683 phase takes place. At that time records are likely to be sorted
6684 according to the included User-Name and duplicate elimination is easy
6685 in this case. In other situations it may be necessary to perform
6686 real-time duplicate detection, such as when credit limits are imposed
6687 or real-time fraud detection is desired.
6689 In general, only generation of duplicates due to failover or re-
6690 sending of records in non-volatile storage can be reliably detected
6691 by Diameter clients or agents. In such cases the Diameter client or
6692 agents can mark the message as possible duplicate by setting the T
6693 flag. Since the Diameter server is responsible for duplicate
6694 detection, it can choose to make use of the T flag or not, in order
6695 to optimize duplicate detection. Since the T flag does not affect
6696 interoperability, and may not be needed by some servers, generation
6697 of the T flag is REQUIRED for Diameter clients and agents, but MAY be
6698 implemented by Diameter servers.
6700 As an example, it can be usually be assumed that duplicates appear
6701 within a time window of longest recorded network partition or device
6702 fault, perhaps a day. So only records within this time window need
6703 to be looked at in the backward direction. Secondly, hashing
6704 techniques or other schemes, such as the use of the T flag in the
6705 received messages, may be used to eliminate the need to do a full
6706 search even in this set except for rare cases.
6708 The following is an example of how the T flag may be used by the
6709 server to detect duplicate requests.
6711 A Diameter server MAY check the T flag of the received message to
6712 determine if the record is a possible duplicate. If the T flag is
6713 set in the request message, the server searches for a duplicate
6714 within a configurable duplication time window backward and
6715 forward. This limits database searching to those records where
6716 the T flag is set. In a well run network, network partitions and
6717 device faults will presumably be rare events, so this approach
6718 represents a substantial optimization of the duplicate detection
6719 process. During failover, it is possible for the original record
6720 to be received after the T flag marked record, due to differences
6721 in network delays experienced along the path by the original and
6722 duplicate transmissions. The likelihood of this occurring
6723 increases as the failover interval is decreased. In order to be
6724 able to detect out of order duplicates, the Diameter server should
6725 use backward and forward time windows when performing duplicate
6726 checking for the T flag marked request. For example, in order to
6727 allow time for the original record to exit the network and be
6728 recorded by the accounting server, the Diameter server can delay
6729 processing records with the T flag set until a time period
6730 TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after the closing
6731 of the original transport connection. After this time period has
6732 expired, then it may check the T flag marked records against the
6733 database with relative assurance that the original records, if
6734 sent, have been received and recorded.
6736 Authors' Addresses
6738 Victor Fajardo (editor)
6739 Toshiba America Research
6740 One Telcordia Drive, 1S-222
6741 Piscataway, NJ 08854
6742 USA
6744 Phone: 1 908-421-1845
6745 Email: vfajardo@tari.toshiba.com
6747 Jari Arkko
6748 Ericsson Research
6749 02420 Jorvas
6750 Finland
6752 Phone: +358 40 5079256
6753 Email: jari.arkko@ericsson.com
6755 John Loughney
6756 Nokia Research Center
6757 955 Page Mill Road
6758 Palo Alto, CA 94304
6759 US
6761 Phone: 1-650-283-8068
6762 Email: john.loughney@nokia.com
6764 Full Copyright Statement
6766 Copyright (C) The IETF Trust (2007).
6768 This document is subject to the rights, licenses and restrictions
6769 contained in BCP 78, and except as set forth therein, the authors
6770 retain all their rights.
6772 This document and the information contained herein are provided on an
6773 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
6774 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
6775 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
6776 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
6777 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
6778 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
6780 Intellectual Property
6782 The IETF takes no position regarding the validity or scope of any
6783 Intellectual Property Rights or other rights that might be claimed to
6784 pertain to the implementation or use of the technology described in
6785 this document or the extent to which any license under such rights
6786 might or might not be available; nor does it represent that it has
6787 made any independent effort to identify any such rights. Information
6788 on the procedures with respect to rights in RFC documents can be
6789 found in BCP 78 and BCP 79.
6791 Copies of IPR disclosures made to the IETF Secretariat and any
6792 assurances of licenses to be made available, or the result of an
6793 attempt made to obtain a general license or permission for the use of
6794 such proprietary rights by implementers or users of this
6795 specification can be obtained from the IETF on-line IPR repository at
6796 http://www.ietf.org/ipr.
6798 The IETF invites any interested party to bring to its attention any
6799 copyrights, patents or patent applications, or other proprietary
6800 rights that may cover technology that may be required to implement
6801 this standard. Please address the information to the IETF at
6802 ietf-ipr@ietf.org.
6804 Acknowledgment
6806 Funding for the RFC Editor function is provided by the IETF
6807 Administrative Support Activity (IASA).