idnits 2.17.1
draft-ietf-dime-rfc3588bis-04.txt:
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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 6798.
-- Found old boilerplate from RFC 3979, Section 5, paragraph 1 on line 6809.
-- Found old boilerplate from RFC 3979, Section 5, paragraph 2 on line 6816.
-- Found old boilerplate from RFC 3979, Section 5, paragraph 3 on line 6822.
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== There are 2 instances of lines with non-RFC2606-compliant FQDNs in the
document.
== There are 2 instances of lines with non-RFC6890-compliant IPv4 addresses
in the document. If these are example addresses, they should be changed.
Miscellaneous warnings:
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== The copyright year in the IETF Trust Copyright Line does not match the
current year
== Line 4542 has weird spacing: '...ly with wit...'
== Line 4750 has weird spacing: '...ealtime user...'
== Line 4778 has weird spacing: '... record inter...'
== Line 4788 has weird spacing: '...ealtime user...'
== Line 4796 has weird spacing: '...ealtime user...'
== (1 more instance...)
-- The exact meaning of the all-uppercase expression 'MAY NOT' is not
defined in RFC 2119. If it is intended as a requirements expression, it
should be rewritten using one of the combinations defined in RFC 2119;
otherwise it should not be all-uppercase.
== 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 expression 'MAY NOT', while looking like RFC 2119 requirements text,
is not defined in RFC 2119, and should not be used. Consider using 'MUST
NOT' instead (if that is what you mean).
Found 'MAY NOT' in this paragraph:
The following tables presents the AVPs defined in this document,
and specifies in which Diameter messages they MAY, or MAY NOT be present.
Note that AVPs that can only be present within a Grouped AVP are not
represented in this table.
-- 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 (June 5, 2007) is 6163 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 4267, 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 2234 (Obsoleted by RFC 4234)
** Downref: Normative reference to an Informational RFC: RFC 3232
** Obsolete normative reference: RFC 3588 (Obsoleted by RFC 6733)
** Obsolete normative reference: RFC 2284 (Obsoleted by RFC 3748)
** Obsolete normative reference: RFC 2434 (Obsoleted by RFC 5226)
** Obsolete normative reference: RFC 2409 (Obsoleted by RFC 4306)
** Obsolete normative reference: RFC 2373 (Obsoleted by RFC 3513)
** Obsolete normative reference: RFC 4282 (Obsoleted by RFC 7542)
** Obsolete normative reference: RFC 2915 (Obsoleted by RFC 3401, RFC 3402,
RFC 3403, RFC 3404)
** Obsolete normative reference: RFC 2960 (Obsoleted by RFC 4960)
** Obsolete normative reference: RFC 2030 (Obsoleted by RFC 4330)
** Obsolete normative reference: RFC 2246 (Obsoleted by RFC 4346)
** Obsolete normative reference: RFC 2396 (Obsoleted by RFC 3986)
** Obsolete normative reference: RFC 2279 (Obsoleted by RFC 3629)
-- Obsolete informational reference (is this intentional?): RFC 3576
(Obsoleted by RFC 5176)
-- Obsolete informational reference (is this intentional?): RFC 2401
(Obsoleted by RFC 4301)
Summary: 18 errors (**), 0 flaws (~~), 13 warnings (==), 13 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: December 7, 2007 Ericsson Research
6 J. Loughney
7 Nokia Research Center
8 June 5, 2007
10 Diameter Base Protocol
11 draft-ietf-dime-rfc3588bis-04.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 December 7, 2007.
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 . . . . . . . . . . . . . . . . . . . 53
91 4.4.1. Example AVP with a Grouped Data type . . . . . . . . 54
92 4.5. Diameter Base Protocol AVPs . . . . . . . . . . . . . . . 56
93 5. Diameter Peers . . . . . . . . . . . . . . . . . . . . . . . 60
94 5.1. Peer Connections . . . . . . . . . . . . . . . . . . . . 60
95 5.2. Diameter Peer Discovery . . . . . . . . . . . . . . . . . 60
96 5.3. Capabilities Exchange . . . . . . . . . . . . . . . . . . 63
97 5.3.1. Capabilities-Exchange-Request . . . . . . . . . . . 64
98 5.3.2. Capabilities-Exchange-Answer . . . . . . . . . . . . 65
99 5.3.3. Vendor-Id AVP . . . . . . . . . . . . . . . . . . . 65
100 5.3.4. Firmware-Revision AVP . . . . . . . . . . . . . . . 66
101 5.3.5. Host-IP-Address AVP . . . . . . . . . . . . . . . . 66
102 5.3.6. Supported-Vendor-Id AVP . . . . . . . . . . . . . . 66
103 5.3.7. Product-Name AVP . . . . . . . . . . . . . . . . . . 66
104 5.4. Disconnecting Peer connections . . . . . . . . . . . . . 66
105 5.4.1. Disconnect-Peer-Request . . . . . . . . . . . . . . 67
106 5.4.2. Disconnect-Peer-Answer . . . . . . . . . . . . . . . 67
107 5.4.3. Disconnect-Cause AVP . . . . . . . . . . . . . . . . 68
108 5.5. Transport Failure Detection . . . . . . . . . . . . . . . 68
109 5.5.1. Device-Watchdog-Request . . . . . . . . . . . . . . 68
110 5.5.2. Device-Watchdog-Answer . . . . . . . . . . . . . . . 69
111 5.5.3. Transport Failure Algorithm . . . . . . . . . . . . 69
112 5.5.4. Failover and Failback Procedures . . . . . . . . . . 69
113 5.6. Peer State Machine . . . . . . . . . . . . . . . . . . . 70
114 5.6.1. Incoming connections . . . . . . . . . . . . . . . . 72
115 5.6.2. Events . . . . . . . . . . . . . . . . . . . . . . . 73
116 5.6.3. Actions . . . . . . . . . . . . . . . . . . . . . . 74
117 5.6.4. The Election Process . . . . . . . . . . . . . . . . 76
118 5.6.5. Capabilities Update . . . . . . . . . . . . . . . . 76
119 6. Diameter message processing . . . . . . . . . . . . . . . . . 77
120 6.1. Diameter Request Routing Overview . . . . . . . . . . . . 77
121 6.1.1. Originating a Request . . . . . . . . . . . . . . . 78
122 6.1.2. Sending a Request . . . . . . . . . . . . . . . . . 79
123 6.1.3. Receiving Requests . . . . . . . . . . . . . . . . . 79
124 6.1.4. Processing Local Requests . . . . . . . . . . . . . 79
125 6.1.5. Request Forwarding . . . . . . . . . . . . . . . . . 79
126 6.1.6. Request Routing . . . . . . . . . . . . . . . . . . 80
127 6.1.7. Predictive Loop Avoidance . . . . . . . . . . . . . 80
128 6.1.8. Redirecting requests . . . . . . . . . . . . . . . . 80
129 6.1.9. Relaying and Proxying Requests . . . . . . . . . . . 82
130 6.2. Diameter Answer Processing . . . . . . . . . . . . . . . 82
131 6.2.1. Processing received Answers . . . . . . . . . . . . 83
132 6.2.2. Relaying and Proxying Answers . . . . . . . . . . . 83
133 6.3. Origin-Host AVP . . . . . . . . . . . . . . . . . . . . . 84
134 6.4. Origin-Realm AVP . . . . . . . . . . . . . . . . . . . . 84
135 6.5. Destination-Host AVP . . . . . . . . . . . . . . . . . . 84
136 6.6. Destination-Realm AVP . . . . . . . . . . . . . . . . . . 85
137 6.7. Routing AVPs . . . . . . . . . . . . . . . . . . . . . . 85
138 6.7.1. Route-Record AVP . . . . . . . . . . . . . . . . . . 85
139 6.7.2. Proxy-Info AVP . . . . . . . . . . . . . . . . . . . 85
140 6.7.3. Proxy-Host AVP . . . . . . . . . . . . . . . . . . . 85
141 6.7.4. Proxy-State AVP . . . . . . . . . . . . . . . . . . 85
142 6.8. Auth-Application-Id AVP . . . . . . . . . . . . . . . . . 86
143 6.9. Acct-Application-Id AVP . . . . . . . . . . . . . . . . . 86
144 6.10. Inband-Security-Id AVP . . . . . . . . . . . . . . . . . 86
145 6.11. Vendor-Specific-Application-Id AVP . . . . . . . . . . . 86
146 6.12. Redirect-Host AVP . . . . . . . . . . . . . . . . . . . . 87
147 6.13. Redirect-Host-Usage AVP . . . . . . . . . . . . . . . . . 87
148 6.14. Redirect-Max-Cache-Time AVP . . . . . . . . . . . . . . . 89
149 6.15. E2E-Sequence AVP . . . . . . . . . . . . . . . . . . . . 89
150 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 90
151 7.1. Result-Code AVP . . . . . . . . . . . . . . . . . . . . . 91
152 7.1.1. Informational . . . . . . . . . . . . . . . . . . . 92
153 7.1.2. Success . . . . . . . . . . . . . . . . . . . . . . 92
154 7.1.3. Protocol Errors . . . . . . . . . . . . . . . . . . 93
155 7.1.4. Transient Failures . . . . . . . . . . . . . . . . . 94
156 7.1.5. Permanent Failures . . . . . . . . . . . . . . . . . 95
157 7.2. Error Bit . . . . . . . . . . . . . . . . . . . . . . . . 98
158 7.3. Error-Message AVP . . . . . . . . . . . . . . . . . . . . 98
159 7.4. Error-Reporting-Host AVP . . . . . . . . . . . . . . . . 98
160 7.5. Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . . 98
161 7.6. Experimental-Result AVP . . . . . . . . . . . . . . . . . 99
162 7.7. Experimental-Result-Code AVP . . . . . . . . . . . . . . 100
163 8. Diameter User Sessions . . . . . . . . . . . . . . . . . . . 101
164 8.1. Authorization Session State Machine . . . . . . . . . . . 102
165 8.2. Accounting Session State Machine . . . . . . . . . . . . 107
166 8.3. Server-Initiated Re-Auth . . . . . . . . . . . . . . . . 112
167 8.3.1. Re-Auth-Request . . . . . . . . . . . . . . . . . . 112
168 8.3.2. Re-Auth-Answer . . . . . . . . . . . . . . . . . . . 113
169 8.4. Session Termination . . . . . . . . . . . . . . . . . . . 114
170 8.4.1. Session-Termination-Request . . . . . . . . . . . . 115
171 8.4.2. Session-Termination-Answer . . . . . . . . . . . . . 115
172 8.5. Aborting a Session . . . . . . . . . . . . . . . . . . . 116
173 8.5.1. Abort-Session-Request . . . . . . . . . . . . . . . 117
174 8.5.2. Abort-Session-Answer . . . . . . . . . . . . . . . . 117
175 8.6. Inferring Session Termination from Origin-State-Id . . . 118
176 8.7. Auth-Request-Type AVP . . . . . . . . . . . . . . . . . . 119
177 8.8. Session-Id AVP . . . . . . . . . . . . . . . . . . . . . 119
178 8.9. Authorization-Lifetime AVP . . . . . . . . . . . . . . . 120
179 8.10. Auth-Grace-Period AVP . . . . . . . . . . . . . . . . . . 121
180 8.11. Auth-Session-State AVP . . . . . . . . . . . . . . . . . 121
181 8.12. Re-Auth-Request-Type AVP . . . . . . . . . . . . . . . . 122
182 8.13. Session-Timeout AVP . . . . . . . . . . . . . . . . . . . 122
183 8.14. User-Name AVP . . . . . . . . . . . . . . . . . . . . . . 123
184 8.15. Termination-Cause AVP . . . . . . . . . . . . . . . . . . 123
185 8.16. Origin-State-Id AVP . . . . . . . . . . . . . . . . . . . 124
186 8.17. Session-Binding AVP . . . . . . . . . . . . . . . . . . . 124
187 8.18. Session-Server-Failover AVP . . . . . . . . . . . . . . . 125
188 8.19. Multi-Round-Time-Out AVP . . . . . . . . . . . . . . . . 126
189 8.20. Class AVP . . . . . . . . . . . . . . . . . . . . . . . . 126
190 8.21. Event-Timestamp AVP . . . . . . . . . . . . . . . . . . . 126
191 9. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . 128
192 9.1. Server Directed Model . . . . . . . . . . . . . . . . . . 128
193 9.2. Protocol Messages . . . . . . . . . . . . . . . . . . . . 129
194 9.3. Accounting Application Extension and Requirements . . . . 129
195 9.4. Fault Resilience . . . . . . . . . . . . . . . . . . . . 130
196 9.5. Accounting Records . . . . . . . . . . . . . . . . . . . 131
197 9.6. Correlation of Accounting Records . . . . . . . . . . . . 131
198 9.7. Accounting Command-Codes . . . . . . . . . . . . . . . . 132
199 9.7.1. Accounting-Request . . . . . . . . . . . . . . . . . 132
200 9.7.2. Accounting-Answer . . . . . . . . . . . . . . . . . 133
201 9.8. Accounting AVPs . . . . . . . . . . . . . . . . . . . . . 134
202 9.8.1. Accounting-Record-Type AVP . . . . . . . . . . . . . 134
203 9.8.2. Acct-Interim-Interval . . . . . . . . . . . . . . . 135
204 9.8.3. Accounting-Record-Number AVP . . . . . . . . . . . . 136
205 9.8.4. Acct-Session-Id AVP . . . . . . . . . . . . . . . . 136
206 9.8.5. Acct-Multi-Session-Id AVP . . . . . . . . . . . . . 136
207 9.8.6. Accounting-Sub-Session-Id AVP . . . . . . . . . . . 136
208 9.8.7. Accounting-Realtime-Required AVP . . . . . . . . . . 137
209 10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . 138
210 10.1. Base Protocol Command AVP Table . . . . . . . . . . . . . 138
211 10.2. Accounting AVP Table . . . . . . . . . . . . . . . . . . 139
212 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 141
213 11.1. AVP Header . . . . . . . . . . . . . . . . . . . . . . . 141
214 11.1.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . 141
215 11.1.2. AVP Flags . . . . . . . . . . . . . . . . . . . . . 142
216 11.2. Diameter Header . . . . . . . . . . . . . . . . . . . . . 142
217 11.2.1. Command Codes . . . . . . . . . . . . . . . . . . . 142
218 11.2.2. Command Flags . . . . . . . . . . . . . . . . . . . 143
219 11.3. Application Identifiers . . . . . . . . . . . . . . . . . 143
220 11.4. AVP Values . . . . . . . . . . . . . . . . . . . . . . . 143
221 11.4.1. Result-Code AVP Values . . . . . . . . . . . . . . . 143
222 11.4.2. Accounting-Record-Type AVP Values . . . . . . . . . 144
223 11.4.3. Termination-Cause AVP Values . . . . . . . . . . . . 144
224 11.4.4. Redirect-Host-Usage AVP Values . . . . . . . . . . . 144
225 11.4.5. Session-Server-Failover AVP Values . . . . . . . . . 144
226 11.4.6. Session-Binding AVP Values . . . . . . . . . . . . . 144
227 11.4.7. Disconnect-Cause AVP Values . . . . . . . . . . . . 144
228 11.4.8. Auth-Request-Type AVP Values . . . . . . . . . . . . 144
229 11.4.9. Auth-Session-State AVP Values . . . . . . . . . . . 145
230 11.4.10. Re-Auth-Request-Type AVP Values . . . . . . . . . . 145
231 11.4.11. Accounting-Realtime-Required AVP Values . . . . . . 145
232 11.4.12. Inband-Security-Id AVP (code 299) . . . . . . . . . 145
234 11.5. Diameter TCP/SCTP Port Numbers . . . . . . . . . . . . . 145
235 11.6. NAPTR Service Fields . . . . . . . . . . . . . . . . . . 145
236 12. Diameter protocol related configurable parameters . . . . . . 147
237 13. Security Considerations . . . . . . . . . . . . . . . . . . . 148
238 13.1. TLS Usage . . . . . . . . . . . . . . . . . . . . . . . . 148
239 13.2. Peer-to-Peer Considerations . . . . . . . . . . . . . . . 149
240 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 150
241 14.1. Normative References . . . . . . . . . . . . . . . . . . 150
242 14.2. Informational References . . . . . . . . . . . . . . . . 152
243 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 154
244 Appendix B. NAPTR Example . . . . . . . . . . . . . . . . . . . 155
245 Appendix C. Duplicate Detection . . . . . . . . . . . . . . . . 156
246 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 158
247 Intellectual Property and Copyright Statements . . . . . . . . . 159
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 [RFC2409] 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 IETF Consensus (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 [RFC2234] 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 [RFC2284], 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 [RFC2246]. Diameter servers MUST support TLS.
1016 IPSec [RFC2401] 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 2234 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) [RFC2373] 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 [RFC2030].
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 [RFC2030] 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 [RFC2279] transformation format described in RFC 2279.
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 [RFC2396] 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 QoSFilterRule
2269 The QosFilterRule format is derived from the OctetString AVP Base
2270 Format. It uses the ASCII charset. Packets may be marked or
2271 metered based on the following information that is associated with
2272 it:
2274 Direction (in or out)
2275 Source and destination IP address (possibly masked)
2276 Protocol
2277 Source and destination port (lists or ranges)
2278 DSCP values (no mask or range)
2280 Rules for the appropriate direction are evaluated in order, with
2281 the first matched rule terminating the evaluation. Each packet is
2282 evaluated once. If no rule matches, the packet is treated as best
2283 effort. An access device that is unable to interpret or apply a
2284 QoS rule SHOULD NOT terminate the session.
2286 QoSFilterRule filters MUST follow the format:
2288 action dir proto from src to dst [options]
2290 tag - Mark packet with a specific DSCP
2291 [RFC2474]. The DSCP option MUST be
2292 included.
2293 meter - Meter traffic. The metering options
2294 MUST be included.
2296 dir The format is as described under IPFilterRule.
2298 proto The format is as described under
2299 IPFilterRule.
2301 src and dst The format is as described under
2302 IPFilterRule.
2304 4.4. Grouped AVP Values
2306 The Diameter protocol allows AVP values of type 'Grouped.' This
2307 implies that the Data field is actually a sequence of AVPs. It is
2308 possible to include an AVP with a Grouped type within a Grouped type,
2309 that is, to nest them. AVPs within an AVP of type Grouped have the
2310 same padding requirements as non-Grouped AVPs, as defined in Section
2311 4.
2313 The AVP Code numbering space of all AVPs included in a Grouped AVP is
2314 the same as for non-grouped AVPs. Further, if any of the AVPs
2315 encapsulated within a Grouped AVP has the 'M' (mandatory) bit set,
2316 the Grouped AVP itself MUST also include the 'M' bit set.
2318 Every Grouped AVP defined MUST include a corresponding grammar, using
2319 ABNF [RFC2234] (with modifications), as defined below.
2321 grouped-avp-def = name "::=" avp
2323 name-fmt = ALPHA *(ALPHA / DIGIT / "-")
2325 name = name-fmt
2326 ; The name has to be the name of an AVP,
2327 ; defined in the base or extended Diameter
2328 ; specifications.
2330 avp = header [ *fixed] [ *required] [ *optional]
2331 [ *fixed]
2333 header = "<" "AVP-Header:" avpcode [vendor] ">"
2335 avpcode = 1*DIGIT
2336 ; The AVP Code assigned to the Grouped AVP
2338 vendor = 1*DIGIT
2339 ; The Vendor-ID assigned to the Grouped AVP.
2340 ; If absent, the default value of zero is
2341 ; used.
2343 4.4.1. Example AVP with a Grouped Data type
2345 The Example-AVP (AVP Code 999999) is of type Grouped and is used to
2346 clarify how Grouped AVP values work. The Grouped Data field has the
2347 following ABNF grammar:
2349 Example-AVP ::= < AVP Header: 999999 >
2350 { Origin-Host }
2351 1*{ Session-Id }
2352 *[ AVP ]
2354 An Example-AVP with Grouped Data follows.
2356 The Origin-Host AVP is required (Section 6.3). In this case:
2358 Origin-Host = "example.com".
2360 One or more Session-Ids must follow. Here there are two:
2362 Session-Id =
2363 "grump.example.com:33041;23432;893;0AF3B81"
2365 Session-Id =
2366 "grump.example.com:33054;23561;2358;0AF3B82"
2368 optional AVPs included are
2370 Recovery-Policy =
2371 2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35
2372 2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5
2373 c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd
2374 f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a
2375 cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119
2376 26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c
2377 1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92
2379 Futuristic-Acct-Record =
2380 fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0
2381 57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8
2382 17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c
2383 41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067
2384 d3427475e49968f841
2386 The data for the optional AVPs is represented in hex since the format
2387 of these AVPs is neither known at the time of definition of the
2388 Example-AVP group, nor (likely) at the time when the example instance
2389 of this AVP is interpreted - except by Diameter implementations which
2390 support the same set of AVPs. The encoding example illustrates how
2391 padding is used and how length fields are calculated. Also note that
2392 AVPs may be present in the Grouped AVP value which the receiver
2393 cannot interpret (here, the Recover-Policy and Futuristic-Acct-Record
2394 AVPs).
2396 This AVP would be encoded as follows:
2398 0 1 2 3 4 5 6 7
2399 +-------+-------+-------+-------+-------+-------+-------+-------+
2400 0 | Example AVP Header (AVP Code = 999999), Length = 468 |
2401 +-------+-------+-------+-------+-------+-------+-------+-------+
2402 8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 |
2403 +-------+-------+-------+-------+-------+-------+-------+-------+
2404 16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' |
2405 +-------+-------+-------+-------+-------+-------+-------+-------+
2406 24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header |
2407 +-------+-------+-------+-------+-------+-------+-------+-------+
2408 32 | (AVP Code = 263), Length = 50 | 'g' | 'r' | 'u' | 'm' |
2409 +-------+-------+-------+-------+-------+-------+-------+-------+
2410 . . .
2411 +-------+-------+-------+-------+-------+-------+-------+-------+
2412 64 | 'A' | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding|
2413 +-------+-------+-------+-------+-------+-------+-------+-------+
2414 72 | Session-Id AVP Header (AVP Code = 263), Length = 51 |
2415 +-------+-------+-------+-------+-------+-------+-------+-------+
2416 80 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' |
2417 +-------+-------+-------+-------+-------+-------+-------+-------+
2418 . . .
2419 +-------+-------+-------+-------+-------+-------+-------+-------+
2420 104| '0' | 'A' | 'F' | '3' | 'B' | '8' | '2' |Padding|
2421 +-------+-------+-------+-------+-------+-------+-------+-------+
2422 112| Recovery-Policy Header (AVP Code = 8341), Length = 223 |
2423 +-------+-------+-------+-------+-------+-------+-------+-------+
2424 120| 0x21 | 0x63 | 0xbc | 0x1d | 0x0a | 0xd8 | 0x23 | 0x71 |
2425 +-------+-------+-------+-------+-------+-------+-------+-------+
2426 . . .
2427 +-------+-------+-------+-------+-------+-------+-------+-------+
2428 320| 0x2f | 0xd7 | 0x96 | 0x6b | 0x8c | 0x7f | 0x92 |Padding|
2429 +-------+-------+-------+-------+-------+-------+-------+-------+
2430 328| Futuristic-Acct-Record Header (AVP Code = 15930), Length = 137|
2431 +-------+-------+-------+-------+-------+-------+-------+-------+
2432 336| 0xfe | 0x19 | 0xda | 0x58 | 0x02 | 0xac | 0xd9 | 0x8b |
2433 +-------+-------+-------+-------+-------+-------+-------+-------+
2434 . . .
2435 +-------+-------+-------+-------+-------+-------+-------+-------+
2436 464| 0x41 |Padding|Padding|Padding|
2437 +-------+-------+-------+-------+
2439 4.5. Diameter Base Protocol AVPs
2441 The following table describes the Diameter AVPs defined in the base
2442 protocol, their AVP Code values, types, possible flag values.
2444 Due to space constraints, the short form DiamIdent is used to
2445 represent DiameterIdentity.
2447 +---------------------+
2448 | AVP Flag rules |
2449 |----+-----+----+-----|
2450 AVP Section | | |SHLD| MUST|
2451 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|
2452 -----------------------------------------|----+-----+----+-----|
2453 Acct- 85 9.8.2 Unsigned32 | M | P | | V |
2454 Interim-Interval | | | | |
2455 Accounting- 483 9.8.7 Enumerated | M | P | | V |
2456 Realtime-Required | | | | |
2457 Acct- 50 9.8.5 UTF8String | M | P | | V |
2458 Multi-Session-Id | | | | |
2459 Accounting- 485 9.8.3 Unsigned32 | M | P | | V |
2460 Record-Number | | | | |
2461 Accounting- 480 9.8.1 Enumerated | M | P | | V |
2462 Record-Type | | | | |
2463 Accounting- 44 9.8.4 OctetString| M | P | | V |
2464 Session-Id | | | | |
2465 Accounting- 287 9.8.6 Unsigned64 | M | P | | V |
2466 Sub-Session-Id | | | | |
2467 Acct- 259 6.9 Unsigned32 | M | P | | V |
2468 Application-Id | | | | |
2469 Auth- 258 6.8 Unsigned32 | M | P | | V |
2470 Application-Id | | | | |
2471 Auth-Request- 274 8.7 Enumerated | M | P | | V |
2472 Type | | | | |
2473 Authorization- 291 8.9 Unsigned32 | M | P | | V |
2474 Lifetime | | | | |
2475 Auth-Grace- 276 8.10 Unsigned32 | M | P | | V |
2476 Period | | | | |
2477 Auth-Session- 277 8.11 Enumerated | M | P | | V |
2478 State | | | | |
2479 Re-Auth-Request- 285 8.12 Enumerated | M | P | | V |
2480 Type | | | | |
2481 Class 25 8.20 OctetString| M | P | | V |
2482 Destination-Host 293 6.5 DiamIdent | M | P | | V |
2483 Destination- 283 6.6 DiamIdent | M | P | | V |
2484 Realm | | | | |
2485 Disconnect-Cause 273 5.4.3 Enumerated | M | P | | V |
2486 E2E-Sequence AVP 300 6.15 Grouped | M | P | | V |
2487 Error-Message 281 7.3 UTF8String | | P | | V,M |
2488 Error-Reporting- 294 7.4 DiamIdent | | P | | V,M |
2489 Host | | | | |
2490 Event-Timestamp 55 8.21 Time | M | P | | V |
2491 Experimental- 297 7.6 Grouped | M | P | | V |
2492 Result | | | | |
2493 -----------------------------------------|----+-----+----+-----|
2494 +---------------------+
2495 | AVP Flag rules |
2496 |----+-----+----+-----|
2497 AVP Section | | |SHLD| MUST|
2498 Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|
2499 -----------------------------------------|----+-----+----+-----|
2500 Experimental- 298 7.7 Unsigned32 | M | P | | V |
2501 Result-Code | | | | |
2502 Failed-AVP 279 7.5 Grouped | M | P | | V |
2503 Firmware- 267 5.3.4 Unsigned32 | | | |P,V,M|
2504 Revision | | | | |
2505 Host-IP-Address 257 5.3.5 Address | M | P | | V |
2506 Inband-Security | M | P | | V |
2507 -Id 299 6.10 Unsigned32 | | | | |
2508 Multi-Round- 272 8.19 Unsigned32 | M | P | | V |
2509 Time-Out | | | | |
2510 Origin-Host 264 6.3 DiamIdent | M | P | | V |
2511 Origin-Realm 296 6.4 DiamIdent | M | P | | V |
2512 Origin-State-Id 278 8.16 Unsigned32 | M | P | | V |
2513 Product-Name 269 5.3.7 UTF8String | | | |P,V,M|
2514 Proxy-Host 280 6.7.3 DiamIdent | M | | | P,V |
2515 Proxy-Info 284 6.7.2 Grouped | M | | | P,V |
2516 Proxy-State 33 6.7.4 OctetString| M | | | P,V |
2517 Redirect-Host 292 6.12 DiamURI | M | P | | V |
2518 Redirect-Host- 261 6.13 Enumerated | M | P | | V |
2519 Usage | | | | |
2520 Redirect-Max- 262 6.14 Unsigned32 | M | P | | V |
2521 Cache-Time | | | | |
2522 Result-Code 268 7.1 Unsigned32 | M | P | | V |
2523 Route-Record 282 6.7.1 DiamIdent | M | | | P,V |
2524 Session-Id 263 8.8 UTF8String | M | P | | V |
2525 Session-Timeout 27 8.13 Unsigned32 | M | P | | V |
2526 Session-Binding 270 8.17 Unsigned32 | M | P | | V |
2527 Session-Server- 271 8.18 Enumerated | M | P | | V |
2528 Failover | | | | |
2529 Supported- 265 5.3.6 Unsigned32 | M | P | | V |
2530 Vendor-Id | | | | |
2531 Termination- 295 8.15 Enumerated | M | P | | V |
2532 Cause | | | | |
2533 User-Name 1 8.14 UTF8String | M | P | | V |
2534 Vendor-Id 266 5.3.3 Unsigned32 | M | P | | V |
2535 Vendor-Specific- 260 6.11 Grouped | M | P | | V |
2536 Application-Id | | | | |
2537 -----------------------------------------|----+-----+----+-----|
2539 5. Diameter Peers
2541 This section describes how Diameter nodes establish connections and
2542 communicate with peers.
2544 5.1. Peer Connections
2546 Although a Diameter node may have many possible peers that it is able
2547 to communicate with, it may not be economical to have an established
2548 connection to all of them. At a minimum, a Diameter node SHOULD have
2549 an established connection with two peers per realm, known as the
2550 primary and secondary peers. Of course, a node MAY have additional
2551 connections, if it is deemed necessary. Typically, all messages for
2552 a realm are sent to the primary peer, but in the event that failover
2553 procedures are invoked, any pending requests are sent to the
2554 secondary peer. However, implementations are free to load balance
2555 requests between a set of peers.
2557 Note that a given peer MAY act as a primary for a given realm, while
2558 acting as a secondary for another realm.
2560 When a peer is deemed suspect, which could occur for various reasons,
2561 including not receiving a DWA within an allotted timeframe, no new
2562 requests should be forwarded to the peer, but failover procedures are
2563 invoked. When an active peer is moved to this mode, additional
2564 connections SHOULD be established to ensure that the necessary number
2565 of active connections exists.
2567 There are two ways that a peer is removed from the suspect peer list:
2569 1. The peer is no longer reachable, causing the transport connection
2570 to be shutdown. The peer is moved to the closed state.
2572 2. Three watchdog messages are exchanged with accepted round trip
2573 times, and the connection to the peer is considered stabilized.
2575 In the event the peer being removed is either the primary or
2576 secondary, an alternate peer SHOULD replace the deleted peer, and
2577 assume the role of either primary or secondary.
2579 5.2. Diameter Peer Discovery
2581 Allowing for dynamic Diameter agent discovery will make it possible
2582 for simpler and more robust deployment of Diameter services. In
2583 order to promote interoperable implementations of Diameter peer
2584 discovery, the following mechanisms are described. These are based
2585 on existing IETF standards. The first option (manual configuration)
2586 MUST be supported by all DIAMETER nodes, while the latter option
2587 (DNS) MAY be supported.
2589 There are two cases where Diameter peer discovery may be performed.
2590 The first is when a Diameter client needs to discover a first-hop
2591 Diameter agent. The second case is when a Diameter agent needs to
2592 discover another agent - for further handling of a Diameter
2593 operation. In both cases, the following 'search order' is
2594 recommended:
2596 1. The Diameter implementation consults its list of static
2597 (manually) configured Diameter agent locations. These will be
2598 used if they exist and respond.
2600 2. The Diameter implementation performs a NAPTR query for a server
2601 in a particular realm. The Diameter implementation has to know
2602 in advance which realm to look for a Diameter agent in. This
2603 could be deduced, for example, from the 'realm' in a NAI that a
2604 Diameter implementation needed to perform a Diameter operation
2605 on.
2607 * The services relevant for the task of transport protocol
2608 selection are those with NAPTR service fields with values
2609 "AAA+D2x", where x is a letter that corresponds to a transport
2610 protocol supported by the domain. This specification defines
2611 D2T for TCP and D2S for SCTP. We also establish an IANA
2612 registry for NAPTR service name to transport protocol
2613 mappings.
2615 These NAPTR records provide a mapping from a domain, to the
2616 SRV record for contacting a server with the specific transport
2617 protocol in the NAPTR services field. The resource record
2618 will contain an empty regular expression and a replacement
2619 value, which is the SRV record for that particular transport
2620 protocol. If the server supports multiple transport
2621 protocols, there will be multiple NAPTR records, each with a
2622 different service value. As per RFC 2915 [RFC2915], the
2623 client discards any records whose services fields are not
2624 applicable. For the purposes of this specification, several
2625 rules are defined.
2627 * A client MUST discard any service fields that identify a
2628 resolution service whose value is not "D2X", for values of X
2629 that indicate transport protocols supported by the client.
2630 The NAPTR processing as described in RFC 2915 will result in
2631 discovery of the most preferred transport protocol of the
2632 server that is supported by the client, as well as an SRV
2633 record for the server.
2635 The domain suffixes in the NAPTR replacement field SHOULD
2636 match the domain of the original query.
2638 3. If no NAPTR records are found, the requester queries for those
2639 address records for the destination address,
2640 '_diameter._sctp'.realm or '_diameter._tcp'.realm. Address
2641 records include A RR's, AAAA RR's or other similar records,
2642 chosen according to the requestor's network protocol
2643 capabilities. If the DNS server returns no address records, the
2644 requestor gives up.
2646 If the server is using a site certificate, the domain name in the
2647 query and the domain name in the replacement field MUST both be
2648 valid based on the site certificate handed out by the server in
2649 the TLS or IKE exchange. Similarly, the domain name in the SRV
2650 query and the domain name in the target in the SRV record MUST
2651 both be valid based on the same site certificate. Otherwise, an
2652 attacker could modify the DNS records to contain replacement
2653 values in a different domain, and the client could not validate
2654 that this was the desired behavior, or the result of an attack
2656 Also, the Diameter Peer MUST check to make sure that the
2657 discovered peers are authorized to act in its role.
2658 Authentication via IKE or TLS, or validation of DNS RRs via
2659 DNSSEC is not sufficient to conclude this. For example, a web
2660 server may have obtained a valid TLS certificate, and secured RRs
2661 may be included in the DNS, but this does not imply that it is
2662 authorized to act as a Diameter Server.
2664 Authorization can be achieved for example, by configuration of a
2665 Diameter Server CA. Alternatively this can be achieved by
2666 definition of OIDs within TLS or IKE certificates so as to
2667 signify Diameter Server authorization.
2669 A dynamically discovered peer causes an entry in the Peer Table (see
2670 Section 2.6) to be created. Note that entries created via DNS MUST
2671 expire (or be refreshed) within the DNS TTL. If a peer is discovered
2672 outside of the local realm, a routing table entry (see Section 2.7)
2673 for the peer's realm is created. The routing table entry's
2674 expiration MUST match the peer's expiration value.
2676 5.3. Capabilities Exchange
2678 When two Diameter peers establish a transport connection, they MUST
2679 exchange the Capabilities Exchange messages, as specified in the peer
2680 state machine (see Section 5.6). This message allows the discovery
2681 of a peer's identity and its capabilities (protocol version number,
2682 supported Diameter applications, security mechanisms, etc.)
2684 The receiver only issues commands to its peers that have advertised
2685 support for the Diameter application that defines the command. A
2686 Diameter node MUST cache the supported applications in order to
2687 ensure that unrecognized commands and/or AVPs are not unnecessarily
2688 sent to a peer.
2690 A receiver of a Capabilities-Exchange-Req (CER) message that does not
2691 have any applications in common with the sender MUST return a
2692 Capabilities-Exchange-Answer (CEA) with the Result-Code AVP set to
2693 DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport
2694 layer connection. Note that receiving a CER or CEA from a peer
2695 advertising itself as a Relay (see Section 2.4) MUST be interpreted
2696 as having common applications with the peer.
2698 The receiver of the Capabilities-Exchange-Request (CER) MUST
2699 determine common applications by computing the intersection of its
2700 own set of supported application identifiers against all of the
2701 application indentifier AVPs (Auth-Application-Id,
2702 Acct-Application-Id and Vendor-Specific-Application-Id) present in
2703 the CER. The value of the Vendor-Id AVP in the Vendor-Specific-
2704 Application-Id MUST not be used during computation. The sender of
2705 the Capabilities-Exchange-Answer (CEA) SHOULD include all of its
2706 supported applications as a hint to the receiver regarding all of its
2707 application capabilities.
2709 Similarly, a receiver of a Capabilities-Exchange-Req (CER) message
2710 that does not have any security mechanisms in common with the sender
2711 MUST return a Capabilities-Exchange-Answer (CEA) with the Result-Code
2712 AVP set to DIAMETER_NO_COMMON_SECURITY, and SHOULD disconnect the
2713 transport layer connection.
2715 CERs received from unknown peers MAY be silently discarded, or a CEA
2716 MAY be issued with the Result-Code AVP set to DIAMETER_UNKNOWN_PEER.
2717 In both cases, the transport connection is closed. If the local
2718 policy permits receiving CERs from unknown hosts, a successful CEA
2719 MAY be returned. If a CER from an unknown peer is answered with a
2720 successful CEA, the lifetime of the peer entry is equal to the
2721 lifetime of the transport connection. In case of a transport
2722 failure, all the pending transactions destined to the unknown peer
2723 can be discarded.
2725 The CER and CEA messages MUST NOT be proxied, redirected or relayed.
2727 Since the CER/CEA messages cannot be proxied, it is still possible
2728 that an upstream agent receives a message for which it has no
2729 available peers to handle the application that corresponds to the
2730 Command-Code. In such instances, the 'E' bit is set in the answer
2731 message (see Section 7.) with the Result-Code AVP set to
2732 DIAMETER_UNABLE_TO_DELIVER to inform the downstream to take action
2733 (e.g., re-routing request to an alternate peer).
2735 With the exception of the Capabilities-Exchange-Request message, a
2736 message of type Request that includes the Auth-Application-Id or
2737 Acct-Application-Id AVPs, or a message with an application-specific
2738 command code, MAY only be forwarded to a host that has explicitly
2739 advertised support for the application (or has advertised the Relay
2740 Application Identifier).
2742 5.3.1. Capabilities-Exchange-Request
2744 The Capabilities-Exchange-Request (CER), indicated by the Command-
2745 Code set to 257 and the Command Flags' 'R' bit set, is sent to
2746 exchange local capabilities. Upon detection of a transport failure,
2747 this message MUST NOT be sent to an alternate peer.
2749 When Diameter is run over SCTP [RFC2960], which allows for
2750 connections to span multiple interfaces and multiple IP addresses,
2751 the Capabilities-Exchange-Request message MUST contain one Host-IP-
2752 Address AVP for each potential IP address that MAY be locally used
2753 when transmitting Diameter messages.
2755 Message Format
2757 ::= < Diameter Header: 257, REQ >
2758 { Origin-Host }
2759 { Origin-Realm }
2760 1* { Host-IP-Address }
2761 { Vendor-Id }
2762 { Product-Name }
2763 [ Origin-State-Id ]
2764 * [ Supported-Vendor-Id ]
2765 * [ Auth-Application-Id ]
2766 * [ Inband-Security-Id ]
2767 * [ Acct-Application-Id ]
2768 * [ Vendor-Specific-Application-Id ]
2769 [ Firmware-Revision ]
2770 * [ AVP ]
2772 5.3.2. Capabilities-Exchange-Answer
2774 The Capabilities-Exchange-Answer (CEA), indicated by the Command-Code
2775 set to 257 and the Command Flags' 'R' bit cleared, is sent in
2776 response to a CER message.
2778 When Diameter is run over SCTP [RFC2960], which allows connections to
2779 span multiple interfaces, hence, multiple IP addresses, the
2780 Capabilities-Exchange-Answer message MUST contain one Host-IP-Address
2781 AVP for each potential IP address that MAY be locally used when
2782 transmitting Diameter messages.
2784 Message Format
2786 ::= < Diameter Header: 257 >
2787 { Result-Code }
2788 { Origin-Host }
2789 { Origin-Realm }
2790 1* { Host-IP-Address }
2791 { Vendor-Id }
2792 { Product-Name }
2793 [ Origin-State-Id ]
2794 [ Error-Message ]
2795 * [ Failed-AVP ]
2796 * [ Supported-Vendor-Id ]
2797 * [ Auth-Application-Id ]
2798 * [ Inband-Security-Id ]
2799 * [ Acct-Application-Id ]
2800 * [ Vendor-Specific-Application-Id ]
2801 [ Firmware-Revision ]
2802 * [ AVP ]
2804 5.3.3. Vendor-Id AVP
2806 The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains
2807 the IANA "SMI Network Management Private Enterprise Codes" [RFC3232]
2808 value assigned to the vendor of the Diameter application. In
2809 combination with the Supported-Vendor-Id AVP (Section 5.3.6), this
2810 MAY be used in order to know which vendor specific attributes may be
2811 sent to the peer. It is also envisioned that the combination of the
2812 Vendor-Id, Product-Name (Section 5.3.7) and the Firmware-Revision
2813 (Section 5.3.4) AVPs MAY provide very useful debugging information.
2815 A Vendor-Id value of zero in the CER or CEA messages is reserved and
2816 indicates that this field is ignored.
2818 5.3.4. Firmware-Revision AVP
2820 The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is
2821 used to inform a Diameter peer of the firmware revision of the
2822 issuing device.
2824 For devices that do not have a firmware revision (general purpose
2825 computers running Diameter software modules, for instance), the
2826 revision of the Diameter software module may be reported instead.
2828 5.3.5. Host-IP-Address AVP
2830 The Host-IP-Address AVP (AVP Code 257) is of type Address and is used
2831 to inform a Diameter peer of the sender's IP address. All source
2832 addresses that a Diameter node expects to use with SCTP [RFC2960]
2833 MUST be advertised in the CER and CEA messages by including a
2834 Host-IP- Address AVP for each address. This AVP MUST ONLY be used in
2835 the CER and CEA messages.
2837 5.3.6. Supported-Vendor-Id AVP
2839 The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and
2840 contains the IANA "SMI Network Management Private Enterprise Codes"
2841 [RFC3232] value assigned to a vendor other than the device vendor.
2842 This is used in the CER and CEA messages in order to inform the peer
2843 that the sender supports (a subset of) the vendor-specific AVPs
2844 defined by the vendor identified in this AVP. The value of this AVP
2845 SHOULD NOT be set to zero. Multiple instances of this AVP containing
2846 the same value SHOULD NOT be sent.
2848 5.3.7. Product-Name AVP
2850 The Product-Name AVP (AVP Code 269) is of type UTF8String, and
2851 contains the vendor assigned name for the product. The Product-Name
2852 AVP SHOULD remain constant across firmware revisions for the same
2853 product.
2855 5.4. Disconnecting Peer connections
2857 When a Diameter node disconnects one of its transport connections,
2858 its peer cannot know the reason for the disconnect, and will most
2859 likely assume that a connectivity problem occurred, or that the peer
2860 has rebooted. In these cases, the peer may periodically attempt to
2861 reconnect, as stated in Section 2.1. In the event that the
2862 disconnect was a result of either a shortage of internal resources,
2863 or simply that the node in question has no intentions of forwarding
2864 any Diameter messages to the peer in the foreseeable future, a
2865 periodic connection request would not be welcomed. The
2866 Disconnection-Reason AVP contains the reason the Diameter node issued
2867 the Disconnect-Peer-Request message.
2869 The Disconnect-Peer-Request message is used by a Diameter node to
2870 inform its peer of its intent to disconnect the transport layer, and
2871 that the peer shouldn't reconnect unless it has a valid reason to do
2872 so (e.g., message to be forwarded). Upon receipt of the message, the
2873 Disconnect-Peer-Answer is returned, which SHOULD contain an error if
2874 messages have recently been forwarded, and are likely in flight,
2875 which would otherwise cause a race condition.
2877 The receiver of the Disconnect-Peer-Answer initiates the transport
2878 disconnect. The sender of the Disconnect-Peer-Answer should be able
2879 to detect the transport closure and cleanup the connection.
2881 5.4.1. Disconnect-Peer-Request
2883 The Disconnect-Peer-Request (DPR), indicated by the Command-Code set
2884 to 282 and the Command Flags' 'R' bit set, is sent to a peer to
2885 inform its intentions to shutdown the transport connection. Upon
2886 detection of a transport failure, this message MUST NOT be sent to an
2887 alternate peer.
2889 Message Format
2891 ::= < Diameter Header: 282, REQ >
2892 { Origin-Host }
2893 { Origin-Realm }
2894 { Disconnect-Cause }
2896 5.4.2. Disconnect-Peer-Answer
2898 The Disconnect-Peer-Answer (DPA), indicated by the Command-Code set
2899 to 282 and the Command Flags' 'R' bit cleared, is sent as a response
2900 to the Disconnect-Peer-Request message. Upon receipt of this
2901 message, the transport connection is shutdown.
2903 Message Format
2905 ::= < Diameter Header: 282 >
2906 { Result-Code }
2907 { Origin-Host }
2908 { Origin-Realm }
2909 [ Error-Message ]
2910 * [ Failed-AVP ]
2912 5.4.3. Disconnect-Cause AVP
2914 The Disconnect-Cause AVP (AVP Code 273) is of type Enumerated. A
2915 Diameter node MUST include this AVP in the Disconnect-Peer-Request
2916 message to inform the peer of the reason for its intention to
2917 shutdown the transport connection. The following values are
2918 supported:
2920 REBOOTING 0
2921 A scheduled reboot is imminent. Receiver of DPR with above result
2922 code MAY attempt reconnection.
2924 BUSY 1
2925 The peer's internal resources are constrained, and it has
2926 determined that the transport connection needs to be closed.
2927 Receiver of DPR with above result code SHOULD NOT attempt
2928 reconnection.
2930 DO_NOT_WANT_TO_TALK_TO_YOU 2
2931 The peer has determined that it does not see a need for the
2932 transport connection to exist, since it does not expect any
2933 messages to be exchanged in the near future. Receiver of DPR
2934 with above result code SHOULD NOT attempt reconnection.
2936 5.5. Transport Failure Detection
2938 Given the nature of the Diameter protocol, it is recommended that
2939 transport failures be detected as soon as possible. Detecting such
2940 failures will minimize the occurrence of messages sent to unavailable
2941 agents, resulting in unnecessary delays, and will provide better
2942 failover performance. The Device-Watchdog-Request and Device-
2943 Watchdog-Answer messages, defined in this section, are used to pro-
2944 actively detect transport failures.
2946 5.5.1. Device-Watchdog-Request
2948 The Device-Watchdog-Request (DWR), indicated by the Command-Code set
2949 to 280 and the Command Flags' 'R' bit set, is sent to a peer when no
2950 traffic has been exchanged between two peers (see Section 5.5.3).
2951 Upon detection of a transport failure, this message MUST NOT be sent
2952 to an alternate peer.
2954 Message Format
2956 ::= < Diameter Header: 280, REQ >
2957 { Origin-Host }
2958 { Origin-Realm }
2959 [ Origin-State-Id ]
2961 5.5.2. Device-Watchdog-Answer
2963 The Device-Watchdog-Answer (DWA), indicated by the Command-Code set
2964 to 280 and the Command Flags' 'R' bit cleared, is sent as a response
2965 to the Device-Watchdog-Request message.
2967 Message Format
2969 ::= < Diameter Header: 280 >
2970 { Result-Code }
2971 { Origin-Host }
2972 { Origin-Realm }
2973 [ Error-Message ]
2974 * [ Failed-AVP ]
2975 [ Origin-State-Id ]
2977 5.5.3. Transport Failure Algorithm
2979 The transport failure algorithm is defined in [RFC3539]. All
2980 Diameter implementations MUST support the algorithm defined in the
2981 specification in order to be compliant to the Diameter base protocol.
2983 5.5.4. Failover and Failback Procedures
2985 In the event that a transport failure is detected with a peer, it is
2986 necessary for all pending request messages to be forwarded to an
2987 alternate agent, if possible. This is commonly referred to as
2988 failover.
2990 In order for a Diameter node to perform failover procedures, it is
2991 necessary for the node to maintain a pending message queue for a
2992 given peer. When an answer message is received, the corresponding
2993 request is removed from the queue. The Hop-by-Hop Identifier field
2994 is used to match the answer with the queued request.
2996 When a transport failure is detected, if possible all messages in the
2997 queue are sent to an alternate agent with the T flag set. On booting
2998 a Diameter client or agent, the T flag is also set on any records
2999 still remaining to be transmitted in non-volatile storage. An
3000 example of a case where it is not possible to forward the message to
3001 an alternate server is when the message has a fixed destination, and
3002 the unavailable peer is the message's final destination (see
3003 Destination-Host AVP). Such an error requires that the agent return
3004 an answer message with the 'E' bit set and the Result-Code AVP set to
3005 DIAMETER_UNABLE_TO_DELIVER.
3007 It is important to note that multiple identical requests or answers
3008 MAY be received as a result of a failover. The End-to-End Identifier
3009 field in the Diameter header along with the Origin-Host AVP MUST be
3010 used to identify duplicate messages.
3012 As described in Section 2.1, a connection request should be
3013 periodically attempted with the failed peer in order to re-establish
3014 the transport connection. Once a connection has been successfully
3015 established, messages can once again be forwarded to the peer. This
3016 is commonly referred to as failback.
3018 5.6. Peer State Machine
3020 This section contains a finite state machine that MUST be observed by
3021 all Diameter implementations. Each Diameter node MUST follow the
3022 state machine described below when communicating with each peer.
3023 Multiple actions are separated by commas, and may continue on
3024 succeeding lines, as space requires. Similarly, state and next state
3025 may also span multiple lines, as space requires.
3027 This state machine is closely coupled with the state machine
3028 described in [RFC3539], which is used to open, close, failover,
3029 probe, and reopen transport connections. Note in particular that
3030 [RFC3539] requires the use of watchdog messages to probe connections.
3031 For Diameter, DWR and DWA messages are to be used.
3033 I- is used to represent the initiator (connecting) connection, while
3034 the R- is used to represent the responder (listening) connection.
3035 The lack of a prefix indicates that the event or action is the same
3036 regardless of the connection on which the event occurred.
3038 The stable states that a state machine may be in are Closed, I-Open
3039 and R-Open; all other states are intermediate. Note that I-Open and
3040 R-Open are equivalent except for whether the initiator or responder
3041 transport connection is used for communication.
3043 A CER message is always sent on the initiating connection immediately
3044 after the connection request is successfully completed. In the case
3045 of an election, one of the two connections will shut down. The
3046 responder connection will survive if the Origin-Host of the local
3047 Diameter entity is higher than that of the peer; the initiator
3048 connection will survive if the peer's Origin-Host is higher. All
3049 subsequent messages are sent on the surviving connection. Note that
3050 the results of an election on one peer are guaranteed to be the
3051 inverse of the results on the other.
3053 For TLS usage, a TLS handshake will begin when both ends are in the
3054 open state. If the TLS handshake is successful, all further messages
3055 will be sent via TLS. If the handshake fails, both ends move to the
3056 closed state.
3058 The state machine constrains only the behavior of a Diameter
3059 implementation as seen by Diameter peers through events on the wire.
3061 Any implementation that produces equivalent results is considered
3062 compliant.
3064 state event action next state
3065 -----------------------------------------------------------------
3066 Closed Start I-Snd-Conn-Req Wait-Conn-Ack
3067 R-Conn-CER R-Accept, R-Open
3068 Process-CER,
3069 R-Snd-CEA
3071 Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA
3072 I-Rcv-Conn-Nack Cleanup Closed
3073 R-Conn-CER R-Accept, Wait-Conn-Ack/
3074 Process-CER Elect
3075 Timeout Error Closed
3077 Wait-I-CEA I-Rcv-CEA Process-CEA I-Open
3078 R-Conn-CER R-Accept, Wait-Returns
3079 Process-CER,
3080 Elect
3081 I-Peer-Disc I-Disc Closed
3082 I-Rcv-Non-CEA Error Closed
3083 Timeout Error Closed
3085 Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns
3086 Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open
3087 R-Peer-Disc R-Disc Wait-Conn-Ack
3088 R-Conn-CER R-Reject Wait-Conn-Ack/
3089 Elect
3090 Timeout Error Closed
3092 Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open
3093 I-Peer-Disc I-Disc, R-Open
3094 R-Snd-CEA
3095 I-Rcv-CEA R-Disc I-Open
3096 R-Peer-Disc R-Disc Wait-I-CEA
3097 R-Conn-CER R-Reject Wait-Returns
3098 Timeout Error Closed
3100 R-Open Send-Message R-Snd-Message R-Open
3101 R-Rcv-Message Process R-Open
3102 R-Rcv-DWR Process-DWR, R-Open
3103 R-Snd-DWA
3104 R-Rcv-DWA Process-DWA R-Open
3105 R-Conn-CER R-Reject R-Open
3106 Stop R-Snd-DPR Closing
3107 R-Rcv-DPR R-Snd-DPA, Closed
3108 R-Disc
3110 R-Peer-Disc R-Disc Closed
3111 R-Rcv-CER R-Snd-CEA R-Open
3112 R-Rcv-CEA Process-CEA R-Open
3114 I-Open Send-Message I-Snd-Message I-Open
3115 I-Rcv-Message Process I-Open
3116 I-Rcv-DWR Process-DWR, I-Open
3117 I-Snd-DWA
3118 I-Rcv-DWA Process-DWA I-Open
3119 R-Conn-CER R-Reject I-Open
3120 Stop I-Snd-DPR Closing
3121 I-Rcv-DPR I-Snd-DPA, Closed
3122 I-Disc
3123 I-Peer-Disc I-Disc Closed
3124 I-Rcv-CER I-Snd-CEA I-Open
3125 I-Rcv-CEA Process-CEA I-Open
3127 Closing I-Rcv-DPA I-Disc Closed
3128 R-Rcv-DPA R-Disc Closed
3129 Timeout Error Closed
3130 I-Peer-Disc I-Disc Closed
3131 R-Peer-Disc R-Disc Closed
3133 5.6.1. Incoming connections
3135 When a connection request is received from a Diameter peer, it is
3136 not, in the general case, possible to know the identity of that peer
3137 until a CER is received from it. This is because host and port
3138 determine the identity of a Diameter peer; and the source port of an
3139 incoming connection is arbitrary. Upon receipt of CER, the identity
3140 of the connecting peer can be uniquely determined from Origin-Host.
3142 For this reason, a Diameter peer must employ logic separate from the
3143 state machine to receive connection requests, accept them, and await
3144 CER. Once CER arrives on a new connection, the Origin-Host that
3145 identifies the peer is used to locate the state machine associated
3146 with that peer, and the new connection and CER are passed to the
3147 state machine as an R-Conn-CER event.
3149 The logic that handles incoming connections SHOULD close and discard
3150 the connection if any message other than CER arrives, or if an
3151 implementation-defined timeout occurs prior to receipt of CER.
3153 Because handling of incoming connections up to and including receipt
3154 of CER requires logic, separate from that of any individual state
3155 machine associated with a particular peer, it is described separately
3156 in this section rather than in the state machine above.
3158 5.6.2. Events
3160 Transitions and actions in the automaton are caused by events. In
3161 this section, we will ignore the -I and -R prefix, since the actual
3162 event would be identical, but would occur on one of two possible
3163 connections.
3165 Start The Diameter application has signaled that a
3166 connection should be initiated with the peer.
3168 R-Conn-CER An acknowledgement is received stating that the
3169 transport connection has been established, and the
3170 associated CER has arrived.
3172 Rcv-Conn-Ack A positive acknowledgement is received confirming that
3173 the transport connection is established.
3175 Rcv-Conn-Nack A negative acknowledgement was received stating that
3176 the transport connection was not established.
3178 Timeout An application-defined timer has expired while waiting
3179 for some event.
3181 Rcv-CER A CER message from the peer was received.
3183 Rcv-CEA A CEA message from the peer was received.
3185 Rcv-Non-CEA A message other than CEA from the peer was received.
3187 Peer-Disc A disconnection indication from the peer was received.
3189 Rcv-DPR A DPR message from the peer was received.
3191 Rcv-DPA A DPA message from the peer was received.
3193 Win-Election An election was held, and the local node was the
3194 winner.
3196 Send-Message A message is to be sent.
3198 Rcv-Message A message other than CER, CEA, DPR, DPA, DWR or DWA
3199 was received.
3201 Stop The Diameter application has signaled that a
3202 connection should be terminated (e.g., on system
3203 shutdown).
3205 5.6.3. Actions
3207 Actions in the automaton are caused by events and typically indicate
3208 the transmission of packets and/or an action to be taken on the
3209 connection. In this section we will ignore the I- and R-prefix,
3210 since the actual action would be identical, but would occur on one of
3211 two possible connections.
3213 Snd-Conn-Req A transport connection is initiated with the peer.
3215 Accept The incoming connection associated with the R-Conn-CER
3216 is accepted as the responder connection.
3218 Reject The incoming connection associated with the R-Conn-CER
3219 is disconnected.
3221 Process-CER The CER associated with the R-Conn-CER is processed.
3222 Snd-CER A CER message is sent to the peer.
3224 Snd-CEA A CEA message is sent to the peer.
3226 Cleanup If necessary, the connection is shutdown, and any
3227 local resources are freed.
3229 Error The transport layer connection is disconnected, either
3230 politely or abortively, in response to an error
3231 condition. Local resources are freed.
3233 Process-CEA A received CEA is processed.
3235 Snd-DPR A DPR message is sent to the peer.
3237 Snd-DPA A DPA message is sent to the peer.
3239 Disc The transport layer connection is disconnected, and
3240 local resources are freed.
3242 Elect An election occurs (see Section 5.6.4 for more
3243 information).
3245 Snd-Message A message is sent.
3247 Snd-DWR A DWR message is sent.
3249 Snd-DWA A DWA message is sent.
3251 Process-DWR The DWR message is serviced.
3253 Process-DWA The DWA message is serviced.
3255 Process A message is serviced.
3257 5.6.4. The Election Process
3259 The election is performed on the responder. The responder compares
3260 the Origin-Host received in the CER with its own Origin-Host as two
3261 streams of octets. If the local Origin-Host lexicographically
3262 succeeds the received Origin-Host a Win-Election event is issued
3263 locally.
3265 To be consistent with DNS case insensitivity, octets that fall in the
3266 ASCII range 'a' through 'z' MUST compare equally to their upper-case
3267 counterparts between 'A' and 'Z', i.e. value 0x41 compares equal to
3268 0x61, 0x42 to 0x62 and so forth up to and including 0x5a and 0x7a.
3270 The winner of the election MUST close the connection it initiated.
3271 Historically, maintaining the responder side of a connection was more
3272 efficient than maintaining the initiator side. However, current
3273 practices makes this distinction irrelevant.
3275 5.6.5. Capabilities Update
3277 A Diameter node MUST initiate peer capabilities update by sending a
3278 Capabilities-Exchange-Req (CER) to all its peers which supports peer
3279 capabilities update and is in OPEN state. The receiver of CER in
3280 open state MUST process and reply to the CER as a described in
3281 Section 5.3. The CEA which the receiver sends MUST contain its
3282 latest capabilities. Note that peers which successfully process the
3283 peer capabilities update SHOULD also update their routing tables to
3284 reflect the change. The receiver of the CEA, with a Result-Code AVP
3285 other than DIAMETER_SUCCESS, initiates the transport disconnect. The
3286 peer may periodically attempt to reconnect, as stated in Section 2.1.
3288 Peer capabilities update in the open state SHOULD be limited to the
3289 advertisement of the new list of supported applications and MUST
3290 preclude re-negotiation of security mechanism or other capabilities.
3291 If any capabilities change happens in the node (e.g. change in
3292 security mechanisms), other than a change in the supported
3293 applications, the node SHOULD gracefully terminate (setting the
3294 Disconnect-Cause AVP value to REBOOTING) and re-establish the
3295 diameter connections to all the peers.
3297 6. Diameter message processing
3299 This section describes how Diameter requests and answers are created
3300 and processed.
3302 6.1. Diameter Request Routing Overview
3304 A request is sent towards its final destination using a combination
3305 of the Destination-Realm and Destination-Host AVPs, in one of these
3306 three combinations:
3308 o a request that is not able to be proxied (such as CER) MUST NOT
3309 contain either Destination-Realm or Destination-Host AVPs.
3311 o a request that needs to be sent to a home server serving a
3312 specific realm, but not to a specific server (such as the first
3313 request of a series of round-trips), MUST contain a Destination-
3314 Realm AVP, but MUST NOT contain a Destination-Host AVP.
3316 o otherwise, a request that needs to be sent to a specific home
3317 server among those serving a given realm, MUST contain both the
3318 Destination-Realm and Destination-Host AVPs.
3320 The Destination-Host AVP is used as described above when the
3321 destination of the request is fixed, which includes:
3323 o Authentication requests that span multiple round trips
3325 o A Diameter message that uses a security mechanism that makes use
3326 of a pre-established session key shared between the source and the
3327 final destination of the message.
3329 o Server initiated messages that MUST be received by a specific
3330 Diameter client (e.g., access device), such as the Abort-Session-
3331 Request message, which is used to request that a particular user's
3332 session be terminated.
3334 Note that an agent can forward a request to a host described in the
3335 Destination-Host AVP only if the host in question is included in its
3336 peer table (see Section 2.7). Otherwise, the request is routed based
3337 on the Destination-Realm only (see Sections 6.1.6).
3339 The Destination-Realm AVP MUST be present if the message is
3340 proxiable. Request messages that may be forwarded by Diameter agents
3341 (proxies, redirects or relays) MUST also contain an Acct-
3342 Application-Id AVP, an Auth-Application-Id AVP or a Vendor-Specific-
3343 Application-Id AVP. A message that MUST NOT be forwarded by Diameter
3344 agents (proxies, redirects or relays) MUST not include the
3345 Destination-Realm in its ABNF. The value of the Destination-Realm
3346 AVP MAY be extracted from the User-Name AVP, or other application-
3347 specific methods.
3349 When a message is received, the message is processed in the following
3350 order:
3352 o If the message is destined for the local host, the procedures
3353 listed in Section 6.1.4 are followed.
3355 o If the message is intended for a Diameter peer with whom the local
3356 host is able to directly communicate, the procedures listed in
3357 Section 6.1.5 are followed. This is known as Request Forwarding.
3359 o The procedures listed in Section 6.1.6 are followed, which is
3360 known as Request Routing.
3362 o If none of the above is successful, an answer is returned with the
3363 Result-Code set to DIAMETER_UNABLE_TO_DELIVER, with the E-bit set.
3365 For routing of Diameter messages to work within an administrative
3366 domain, all Diameter nodes within the realm MUST be peers.
3368 Note the processing rules contained in this section are intended to
3369 be used as general guidelines to Diameter developers. Certain
3370 implementations MAY use different methods than the ones described
3371 here, and still comply with the protocol specification. See Section
3372 7 for more detail on error handling.
3374 6.1.1. Originating a Request
3376 When creating a request, in addition to any other procedures
3377 described in the application definition for that specific request,
3378 the following procedures MUST be followed:
3380 o the Command-Code is set to the appropriate value
3382 o the 'R' bit is set
3384 o the End-to-End Identifier is set to a locally unique value
3386 o the Origin-Host and Origin-Realm AVPs MUST be set to the
3387 appropriate values, used to identify the source of the message
3389 o the Destination-Host and Destination-Realm AVPs MUST be set to the
3390 appropriate values as described in Section 6.1.
3392 o an Acct-Application-Id AVP, an Auth-Application-Id or a Vendor-
3393 Specific-Application-Id AVP must be included if the request is
3394 proxiable. The application id present in one of these relevant
3395 AVPs must match the application id present in the diameter message
3396 header.
3398 6.1.2. Sending a Request
3400 When sending a request, originated either locally, or as the result
3401 of a forwarding or routing operation, the following procedures MUST
3402 be followed:
3404 o the Hop-by-Hop Identifier should be set to a locally unique value.
3406 o The message should be saved in the list of pending requests.
3408 Other actions to perform on the message based on the particular role
3409 the agent is playing are described in the following sections.
3411 6.1.3. Receiving Requests
3413 A relay or proxy agent MUST check for forwarding loops when receiving
3414 requests. A loop is detected if the server finds its own identity in
3415 a Route-Record AVP. When such an event occurs, the agent MUST answer
3416 with the Result-Code AVP set to DIAMETER_LOOP_DETECTED.
3418 6.1.4. Processing Local Requests
3420 A request is known to be for local consumption when one of the
3421 following conditions occur:
3423 o The Destination-Host AVP contains the local host's identity,
3425 o The Destination-Host AVP is not present, the Destination-Realm AVP
3426 contains a realm the server is configured to process locally, and
3427 the Diameter application is locally supported, or
3429 o Both the Destination-Host and the Destination-Realm are not
3430 present.
3432 When a request is locally processed, the rules in Section 6.2 should
3433 be used to generate the corresponding answer.
3435 6.1.5. Request Forwarding
3437 Request forwarding is done using the Diameter Peer Table. The
3438 Diameter peer table contains all of the peers that the local node is
3439 able to directly communicate with.
3441 When a request is received, and the host encoded in the Destination-
3442 Host AVP is one that is present in the peer table, the message SHOULD
3443 be forwarded to the peer.
3445 6.1.6. Request Routing
3447 Diameter request message routing is done via realms and applications.
3448 A Diameter message that may be forwarded by Diameter agents (proxies,
3449 redirects or relays) MUST include the target realm in the
3450 Destination-Realm AVP. Request routing SHOULD rely on the
3451 Destination-Realm AVP and the application id present in the request
3452 message header to aid in the routing decision. It MAY also rely on
3453 the application identification AVPs Auth-Application-Id, Acct-
3454 Application-Id or Vendor-Specific-Application-Id instead of the
3455 application id in the message header as a secondary measure. The
3456 realm MAY be retrieved from the User-Name AVP, which is in the form
3457 of a Network Access Identifier (NAI). The realm portion of the NAI
3458 is inserted in the Destination-Realm AVP.
3460 Diameter agents MAY have a list of locally supported realms and
3461 applications, and MAY have a list of externally supported realms and
3462 applications. When a request is received that includes a realm
3463 and/or application that is not locally supported, the message is
3464 routed to the peer configured in the Routing Table (see Section 2.7).
3466 Realm names and application identifiers are the minimum supported
3467 routing criteria, additional routing information maybe needed to
3468 support redirect semantics.
3470 6.1.7. Predictive Loop Avoidance
3472 Before forwarding or routing a request, Diameter agents, in addition
3473 to processing done in Section 6.1.3, SHOULD check for the presence of
3474 candidate route's peer identity in any of the Route-Record AVPs. In
3475 an event of the agent detecting the presence of a candidate route's
3476 peer identity in a Route-Record AVP, the agent MUST ignore such route
3477 for the Diameter request message and attempt alternate routes if any.
3478 In case all the candidate routes are eliminated by the above
3479 criteria, the agent SHOULD return DIAMETER_UNABLE_TO_DELIVER message.
3481 6.1.8. Redirecting requests
3483 When a redirect agent receives a request whose routing entry is set
3484 to REDIRECT, it MUST reply with an answer message with the 'E' bit
3485 set, while maintaining the Hop-by-Hop Identifier in the header, and
3486 include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of
3487 the servers associated with the routing entry are added in separate
3488 Redirect-Host AVP.
3490 +------------------+
3491 | Diameter |
3492 | Redirect Agent |
3493 +------------------+
3494 ^ | 2. command + 'E' bit
3495 1. Request | | Result-Code =
3496 joe@example.com | | DIAMETER_REDIRECT_INDICATION +
3497 | | Redirect-Host AVP(s)
3498 | v
3499 +-------------+ 3. Request +-------------+
3500 | example.com |------------->| example.net |
3501 | Relay | | Diameter |
3502 | Agent |<-------------| Server |
3503 +-------------+ 4. Answer +-------------+
3505 Figure 5: Diameter Redirect Agent
3507 The receiver of the answer message with the 'E' bit set, and the
3508 Result-Code AVP set to DIAMETER_REDIRECT_INDICATION uses the hop-by-
3509 hop field in the Diameter header to identify the request in the
3510 pending message queue (see Section 5.3) that is to be redirected. If
3511 no transport connection exists with the new agent, one is created,
3512 and the request is sent directly to it.
3514 Multiple Redirect-Host AVPs are allowed. The receiver of the answer
3515 message with the 'E' bit set selects exactly one of these hosts as
3516 the destination of the redirected message.
3518 When the Redirect-Host-Usage AVP included in the answer message has a
3519 non-zero value, a route entry for the redirect indications is created
3520 and cached by the receiver. The redirect usage for such route entry
3521 is set by the value of Redirect-Host-Usage AVP and the lifetime of
3522 the cached route entry is set by Redirect-Max-Cache-Time AVP value.
3524 It is possible that multiple redirect indications can create multiple
3525 cached route entries differing only in their redirect usage and the
3526 peer to forward messages to. As an example, two(2) route entries
3527 that are created by two(2) redirect indications results in two(2)
3528 cached routes for the same realm and application Id. However, one
3529 has a redirect usage of ALL_SESSION where matching request will be
3530 forwarded to one peer and the other has a redirect usage of ALL_REALM
3531 where request are forwarded to another peer. Therefore, an incoming
3532 request that matches the realm and application Id of both routes will
3533 need additional resolution. In such a case, a routing precedence
3534 rule MUST be used againts the redirect usage value to resolve the
3535 contention. The precedence rule can be found in Section 6.13.
3537 6.1.9. Relaying and Proxying Requests
3539 A relay or proxy agent MUST append a Route-Record AVP to all requests
3540 forwarded. The AVP contains the identity of the peer the request was
3541 received from.
3543 The Hop-by-Hop identifier in the request is saved, and replaced with
3544 a locally unique value. The source of the request is also saved,
3545 which includes the IP address, port and protocol.
3547 A relay or proxy agent MAY include the Proxy-Info AVP in requests if
3548 it requires access to any local state information when the
3549 corresponding response is received. Proxy-Info AVP has certain
3550 security implications and SHOULD contain an embedded HMAC with a
3551 node-local key. Alternatively, it MAY simply use local storage to
3552 store state information.
3554 The message is then forwarded to the next hop, as identified in the
3555 Routing Table.
3557 Figure 6 provides an example of message routing using the procedures
3558 listed in these sections.
3560 (Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net)
3561 (Origin-Realm=mno.net) (Origin-Realm=mno.net)
3562 (Destination-Realm=example.com) (Destination-
3563 Realm=example.com)
3564 (Route-Record=nas.example.net)
3565 +------+ ------> +------+ ------> +------+
3566 | | (Request) | | (Request) | |
3567 | NAS +-------------------+ DRL +-------------------+ HMS |
3568 | | | | | |
3569 +------+ <------ +------+ <------ +------+
3570 example.net (Answer) example.net (Answer) example.com
3571 (Origin-Host=hms.example.com) (Origin-Host=hms.example.com)
3572 (Origin-Realm=example.com) (Origin-Realm=example.com)
3574 Figure 6: Routing of Diameter messages
3576 Relay agents do not require full validation of incoming messages. At
3577 a minimum, validation of the message header and relevant routing AVPs
3578 has to be done when relaying messages.
3580 6.2. Diameter Answer Processing
3582 When a request is locally processed, the following procedures MUST be
3583 applied to create the associated answer, in addition to any
3584 additional procedures that MAY be discussed in the Diameter
3585 application defining the command:
3587 o The same Hop-by-Hop identifier in the request is used in the
3588 answer.
3590 o The local host's identity is encoded in the Origin-Host AVP.
3592 o The Destination-Host and Destination-Realm AVPs MUST NOT be
3593 present in the answer message.
3595 o The Result-Code AVP is added with its value indicating success or
3596 failure.
3598 o If the Session-Id is present in the request, it MUST be included
3599 in the answer.
3601 o Any Proxy-Info AVPs in the request MUST be added to the answer
3602 message, in the same order they were present in the request.
3604 o The 'P' bit is set to the same value as the one in the request.
3606 o The same End-to-End identifier in the request is used in the
3607 answer.
3609 Note that the error messages (see Section 7.3) are also subjected to
3610 the above processing rules.
3612 6.2.1. Processing received Answers
3614 A Diameter client or proxy MUST match the Hop-by-Hop Identifier in an
3615 answer received against the list of pending requests. The
3616 corresponding message should be removed from the list of pending
3617 requests. It SHOULD ignore answers received that do not match a
3618 known Hop-by-Hop Identifier.
3620 6.2.2. Relaying and Proxying Answers
3622 If the answer is for a request which was proxied or relayed, the
3623 agent MUST restore the original value of the Diameter header's Hop-
3624 by-Hop Identifier field.
3626 If the last Proxy-Info AVP in the message is targeted to the local
3627 Diameter server, the AVP MUST be removed before the answer is
3628 forwarded.
3630 If a relay or proxy agent receives an answer with a Result-Code AVP
3631 indicating a failure, it MUST NOT modify the contents of the AVP.
3632 Any additional local errors detected SHOULD be logged, but not
3633 reflected in the Result-Code AVP. If the agent receives an answer
3634 message with a Result-Code AVP indicating success, and it wishes to
3635 modify the AVP to indicate an error, it MUST modify the Result-Code
3636 AVP to contain the appropriate error in the message destined towards
3637 the access device as well as include the Error-Reporting-Host AVP and
3638 it MUST issue an STR on behalf of the access device.
3640 The agent MUST then send the answer to the host that it received the
3641 original request from.
3643 6.3. Origin-Host AVP
3645 The Origin-Host AVP (AVP Code 264) is of type DiameterIdentity, and
3646 MUST be present in all Diameter messages. This AVP identifies the
3647 endpoint that originated the Diameter message. Relay agents MUST NOT
3648 modify this AVP.
3650 The value of the Origin-Host AVP is guaranteed to be unique within a
3651 single host.
3653 Note that the Origin-Host AVP may resolve to more than one address as
3654 the Diameter peer may support more than one address.
3656 This AVP SHOULD be placed as close to the Diameter header as
3657 possible. 6.10
3659 6.4. Origin-Realm AVP
3661 The Origin-Realm AVP (AVP Code 296) is of type DiameterIdentity.
3662 This AVP contains the Realm of the originator of any Diameter message
3663 and MUST be present in all messages.
3665 This AVP SHOULD be placed as close to the Diameter header as
3666 possible.
3668 6.5. Destination-Host AVP
3670 The Destination-Host AVP (AVP Code 293) is of type DiameterIdentity.
3671 This AVP MUST be present in all unsolicited agent initiated messages,
3672 MAY be present in request messages, and MUST NOT be present in Answer
3673 messages.
3675 The absence of the Destination-Host AVP will cause a message to be
3676 sent to any Diameter server supporting the application within the
3677 realm specified in Destination-Realm AVP.
3679 This AVP SHOULD be placed as close to the Diameter header as
3680 possible.
3682 6.6. Destination-Realm AVP
3684 The Destination-Realm AVP (AVP Code 283) is of type DiameterIdentity,
3685 and contains the realm the message is to be routed to. The
3686 Destination-Realm AVP MUST NOT be present in Answer messages.
3687 Diameter Clients insert the realm portion of the User-Name AVP.
3688 Diameter servers initiating a request message use the value of the
3689 Origin-Realm AVP from a previous message received from the intended
3690 target host (unless it is known a priori). When present, the
3691 Destination-Realm AVP is used to perform message routing decisions.
3693 Request messages whose ABNF does not list the Destination-Realm AVP
3694 as a mandatory AVP are inherently non-routable messages.
3696 This AVP SHOULD be placed as close to the Diameter header as
3697 possible.
3699 6.7. Routing AVPs
3701 The AVPs defined in this section are Diameter AVPs used for routing
3702 purposes. These AVPs change as Diameter messages are processed by
3703 agents.
3705 6.7.1. Route-Record AVP
3707 The Route-Record AVP (AVP Code 282) is of type DiameterIdentity. The
3708 identity added in this AVP MUST be the same as the one received in
3709 the Origin-Host of the Capabilities Exchange message.
3711 6.7.2. Proxy-Info AVP
3713 The Proxy-Info AVP (AVP Code 284) is of type Grouped. The Grouped
3714 Data field has the following ABNF grammar:
3716 Proxy-Info ::= < AVP Header: 284 >
3717 { Proxy-Host }
3718 { Proxy-State }
3719 * [ AVP ]
3721 6.7.3. Proxy-Host AVP
3723 The Proxy-Host AVP (AVP Code 280) is of type DiameterIdentity. This
3724 AVP contains the identity of the host that added the Proxy-Info AVP.
3726 6.7.4. Proxy-State AVP
3728 The Proxy-State AVP (AVP Code 33) is of type OctetString, and
3729 contains state local information, and MUST be treated as opaque data.
3731 6.8. Auth-Application-Id AVP
3733 The Auth-Application-Id AVP (AVP Code 258) is of type Unsigned32 and
3734 is used in order to advertise support of the Authentication and
3735 Authorization portion of an application (see Section 2.4). The Auth-
3736 Application-Id MUST also be present in all Authentication and/or
3737 Authorization messages that are defined in a separate Diameter
3738 specification and have an Application ID assigned. If present in a
3739 message, the value of the Auth-Application-Id AVP MUST match the
3740 application id present in the diameter message header except when
3741 used in a CER or CEA messages.
3743 6.9. Acct-Application-Id AVP
3745 The Acct-Application-Id AVP (AVP Code 259) is of type Unsigned32 and
3746 is used in order to advertise support of the Accounting portion of an
3747 application (see Section 2.4). The Acct-Application-Id MUST also be
3748 present in all Accounting messages. Exactly one of the Auth-
3749 Application-Id and Acct-Application-Id AVPs MAY be present. If
3750 present in a message, the value of the Acct-Application-Id AVP MUST
3751 match the application id present in the diameter message header
3752 except when used in a CER or CEA messages.
3754 6.10. Inband-Security-Id AVP
3756 The Inband-Security-Id AVP (AVP Code 299) is of type Unsigned32 and
3757 is used in order to advertise support of the Security portion of the
3758 application.
3760 Currently, the following values are supported, but there is ample
3761 room to add new security Ids.
3763 NO_INBAND_SECURITY 0
3765 This peer does not support TLS. This is the default value, if the
3766 AVP is omitted.
3768 TLS 1
3770 This node supports TLS security, as defined by [RFC2246].
3772 6.11. Vendor-Specific-Application-Id AVP
3774 The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type
3775 Grouped and is used to advertise support of a vendor-specific
3776 Diameter Application. Exactly one instance of Auth-Application-Id or
3777 Acct-Application-Id AVP MAY be present. The application identifier
3778 carried by either Auth-Application-Id or Acct-Application-Id AVP MUST
3779 comply with vendor specific application identifier assignment
3780 described in Sec 11.3. It MUST also match the application id present
3781 in the diameter header except when used in a CER or CEA messages.
3783 The Vendor-Id AVP is an informational AVP pertaining to the vendor
3784 who may have authorship of the vendor-specific diameter application.
3785 It should not be used as a means of defining a completely separate
3786 vendor-specific application identifier space.
3788 This AVP MUST also be present as the first AVP in all experimental
3789 commands defined in the vendor-specific application.
3791 This AVP SHOULD be placed as close to the Diameter header as
3792 possible.
3794 AVP Format
3796 ::= < AVP Header: 260 >
3797 { Vendor-Id }
3798 { Auth-Application-Id } /
3799 { Acct-Application-Id }
3801 6.12. Redirect-Host AVP
3803 One or more of instances of this AVP MUST be present if the answer
3804 message's 'E' bit is set and the Result-Code AVP is set to
3805 DIAMETER_REDIRECT_INDICATION.
3807 Upon receiving the above, the receiving Diameter node SHOULD forward
3808 the request directly to one of the hosts identified in these AVPs.
3809 The server contained in the selected Redirect-Host AVP SHOULD be used
3810 for all messages pertaining to this session.
3812 6.13. Redirect-Host-Usage AVP
3814 The Redirect-Host-Usage AVP (AVP Code 261) is of type Enumerated.
3815 This AVP MAY be present in answer messages whose 'E' bit is set and
3816 the Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION.
3818 When present, this AVP dictates how the routing entry resulting from
3819 the Redirect-Host is to be used. The following values are supported:
3821 DONT_CACHE 0
3823 The host specified in the Redirect-Host AVP should not be cached.
3824 This is the default value.
3826 ALL_SESSION 1
3828 All messages within the same session, as defined by the same value
3829 of the Session-ID AVP MAY be sent to the host specified in the
3830 Redirect-Host AVP.
3832 ALL_REALM 2
3834 All messages destined for the realm requested MAY be sent to the
3835 host specified in the Redirect-Host AVP.
3837 REALM_AND_APPLICATION 3
3839 All messages for the application requested to the realm specified
3840 MAY be sent to the host specified in the Redirect-Host AVP.
3842 ALL_APPLICATION 4
3844 All messages for the application requested MAY be sent to the host
3845 specified in the Redirect-Host AVP.
3847 ALL_HOST 5
3849 All messages that would be sent to the host that generated the
3850 Redirect-Host MAY be sent to the host specified in the Redirect-
3851 Host AVP.
3853 ALL_USER 6
3855 All messages for the user requested MAY be sent to the host
3856 specified in the Redirect-Host AVP.
3858 When multiple cached routes are created by redirect indications and
3859 they differs only in redirect usage and peers to forward requests to
3860 (see Section 6.1.8), a precedence rule MUST be applied to the
3861 redirect usage values of the cached routes during normal routing to
3862 resolve contentions that may occur. The precedence rule is the order
3863 that dictate which redirect usage should be considered before any
3864 other as they appear. The order is as follows:
3866 1. ALL_SESSION
3868 2. ALL_USER
3870 3. REALM_AND_APPLICATION
3872 4. ALL_REALM
3874 5. ALL_APPLICATION
3876 6. ALL_HOST
3878 6.14. Redirect-Max-Cache-Time AVP
3880 The Redirect-Max-Cache-Time AVP (AVP Code 262) is of type Unsigned32.
3881 This AVP MUST be present in answer messages whose 'E' bit is set, the
3882 Result-Code AVP is set to DIAMETER_REDIRECT_INDICATION and the
3883 Redirect-Host-Usage AVP set to a non-zero value.
3885 This AVP contains the maximum number of seconds the peer and route
3886 table entries, created as a result of the Redirect-Host, will be
3887 cached. Note that once a host created due to a redirect indication
3888 is no longer reachable, any associated peer and routing table entries
3889 MUST be deleted.
3891 6.15. E2E-Sequence AVP
3893 The E2E-Sequence AVP (AVP Code 300) provides anti-replay protection
3894 for end to end messages and is of type grouped. It contains a random
3895 value (an OctetString with a nonce) and counter (an Integer). For
3896 each end-to-end peer with which a node communicates (or remembers
3897 communicating) a different nonce value MUST be used and the counter
3898 is initiated at zero and increases by one each time this AVP is
3899 emitted to that peer.
3901 7. Error Handling
3903 There are two different types of errors in Diameter; protocol and
3904 application errors. A protocol error is one that occurs at the base
3905 protocol level, and MAY require per hop attention (e.g., message
3906 routing error). Application errors, on the other hand, generally
3907 occur due to a problem with a function specified in a Diameter
3908 application (e.g., user authentication, Missing AVP).
3910 Result-Code AVP values that are used to report protocol errors MUST
3911 only be present in answer messages whose 'E' bit is set. When a
3912 request message is received that causes a protocol error, an answer
3913 message is returned with the 'E' bit set, and the Result-Code AVP is
3914 set to the appropriate protocol error value. As the answer is sent
3915 back towards the originator of the request, each proxy or relay agent
3916 MAY take action on the message.
3918 1. Request +---------+ Link Broken
3919 +-------------------------->|Diameter |----///----+
3920 | +---------------------| | v
3921 +------+--+ | 2. answer + 'E' set | Relay 2 | +--------+
3922 |Diameter |<-+ (Unable to Forward) +---------+ |Diameter|
3923 | | | Home |
3924 | Relay 1 |--+ +---------+ | Server |
3925 +---------+ | 3. Request |Diameter | +--------+
3926 +-------------------->| | ^
3927 | Relay 3 |-----------+
3928 +---------+
3930 Figure 7: Example of Protocol Error causing answer message
3932 Figure 7 provides an example of a message forwarded upstream by a
3933 Diameter relay. When the message is received by Relay 2, and it
3934 detects that it cannot forward the request to the home server, an
3935 answer message is returned with the 'E' bit set and the Result-Code
3936 AVP set to DIAMETER_UNABLE_TO_DELIVER. Given that this error falls
3937 within the protocol error category, Relay 1 would take special
3938 action, and given the error, attempt to route the message through its
3939 alternate Relay 3.
3941 +---------+ 1. Request +---------+ 2. Request +---------+
3942 | Access |------------>|Diameter |------------>|Diameter |
3943 | | | | | Home |
3944 | Device |<------------| Relay |<------------| Server |
3945 +---------+ 4. Answer +---------+ 3. Answer +---------+
3946 (Missing AVP) (Missing AVP)
3948 Figure 8: Example of Application Error Answer message
3950 Figure 8 provides an example of a Diameter message that caused an
3951 application error. When application errors occur, the Diameter
3952 entity reporting the error clears the 'R' bit in the Command Flags,
3953 and adds the Result-Code AVP with the proper value. Application
3954 errors do not require any proxy or relay agent involvement, and
3955 therefore the message would be forwarded back to the originator of
3956 the request.
3958 There are certain Result-Code AVP application errors that require
3959 additional AVPs to be present in the answer. In these cases, the
3960 Diameter node that sets the Result-Code AVP to indicate the error
3961 MUST add the AVPs. Examples are:
3963 o An unrecognized AVP is received with the 'M' bit (Mandatory bit)
3964 set, causes an answer to be sent with the Result-Code AVP set to
3965 DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the
3966 offending AVP.
3968 o An AVP that is received with an unrecognized value causes an
3969 answer to be returned with the Result-Code AVP set to
3970 DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the
3971 AVP causing the error.
3973 o A command is received with an AVP that is omitted, yet is
3974 mandatory according to the command's ABNF. The receiver issues an
3975 answer with the Result-Code set to DIAMETER_MISSING_AVP, and
3976 creates an AVP with the AVP Code and other fields set as expected
3977 in the missing AVP. The created AVP is then added to the Failed-
3978 AVP AVP.
3980 The Result-Code AVP describes the error that the Diameter node
3981 encountered in its processing. In case there are multiple errors,
3982 the Diameter node MUST report only the first error it encountered
3983 (detected possibly in some implementation dependent order). The
3984 specific errors that can be described by this AVP are described in
3985 the following section.
3987 7.1. Result-Code AVP
3989 The Result-Code AVP (AVP Code 268) is of type Unsigned32 and
3990 indicates whether a particular request was completed successfully or
3991 whether an error occurred. All Diameter answer messages defined in
3992 IETF applications MUST include one Result-Code AVP. A non-successful
3993 Result-Code AVP (one containing a non 2xxx value other than
3994 DIAMETER_REDIRECT_INDICATION) MUST include the Error-Reporting-Host
3995 AVP if the host setting the Result-Code AVP is different from the
3996 identity encoded in the Origin-Host AVP.
3998 The Result-Code data field contains an IANA-managed 32-bit address
3999 space representing errors (see Section 11.4). Diameter provides the
4000 following classes of errors, all identified by the thousands digit in
4001 the decimal notation:
4003 o 1xxx (Informational)
4005 o 2xxx (Success)
4007 o 3xxx (Protocol Errors)
4009 o 4xxx (Transient Failures)
4011 o 5xxx (Permanent Failure)
4013 A non-recognized class (one whose first digit is not defined in this
4014 section) MUST be handled as a permanent failure.
4016 7.1.1. Informational
4018 Errors that fall within this category are used to inform the
4019 requester that a request could not be satisfied, and additional
4020 action is required on its part before access is granted.
4022 DIAMETER_MULTI_ROUND_AUTH 1001
4024 This informational error is returned by a Diameter server to
4025 inform the access device that the authentication mechanism being
4026 used requires multiple round trips, and a subsequent request needs
4027 to be issued in order for access to be granted.
4029 7.1.2. Success
4031 Errors that fall within the Success category are used to inform a
4032 peer that a request has been successfully completed.
4034 DIAMETER_SUCCESS 2001
4036 The Request was successfully completed.
4038 DIAMETER_LIMITED_SUCCESS 2002
4040 When returned, the request was successfully completed, but
4041 additional processing is required by the application in order to
4042 provide service to the user.
4044 7.1.3. Protocol Errors
4046 Errors that fall within the Protocol Error category SHOULD be treated
4047 on a per-hop basis, and Diameter proxies MAY attempt to correct the
4048 error, if it is possible. Note that these and only these errors MUST
4049 only be used in answer messages whose 'E' bit is set. To provide
4050 backward compatibility with existing implementations that follow
4051 [RFC3588], some of the error values that have previously been used in
4052 this category by [RFC3588] will not be re-used. Therefore the error
4053 values enumerated here maybe non-sequential.
4055 DIAMETER_UNABLE_TO_DELIVER 3002
4057 This error is given when Diameter can not deliver the message to
4058 the destination, either because no host within the realm
4059 supporting the required application was available to process the
4060 request, or because Destination-Host AVP was given without the
4061 associated Destination-Realm AVP.
4063 DIAMETER_REALM_NOT_SERVED 3003
4065 The intended realm of the request is not recognized.
4067 DIAMETER_TOO_BUSY 3004
4069 When returned, a Diameter node SHOULD attempt to send the message
4070 to an alternate peer. This error MUST only be used when a
4071 specific server is requested, and it cannot provide the requested
4072 service.
4074 DIAMETER_LOOP_DETECTED 3005
4076 An agent detected a loop while trying to get the message to the
4077 intended recipient. The message MAY be sent to an alternate peer,
4078 if one is available, but the peer reporting the error has
4079 identified a configuration problem.
4081 DIAMETER_REDIRECT_INDICATION 3006
4083 A redirect agent has determined that the request could not be
4084 satisfied locally and the initiator of the request should direct
4085 the request directly to the server, whose contact information has
4086 been added to the response. When set, the Redirect-Host AVP MUST
4087 be present.
4089 DIAMETER_APPLICATION_UNSUPPORTED 3007
4091 A request was sent for an application that is not supported.
4093 DIAMETER_INVALID_BIT_IN_HEADER 3011
4095 This error is returned when an unrecognized bit in the Diameter
4096 header is set to one (1).
4098 DIAMETER_INVALID_MESSAGE_LENGTH 3012
4100 This error is returned when a request is received with an invalid
4101 message length.
4103 7.1.4. Transient Failures
4105 Errors that fall within the transient failures category are used to
4106 inform a peer that the request could not be satisfied at the time it
4107 was received, but MAY be able to satisfy the request in the future.
4108 Note that these errors MUST be used in answer messages whose 'E' bit
4109 is not set.
4111 DIAMETER_AUTHENTICATION_REJECTED 4001
4113 The authentication process for the user failed, most likely due to
4114 an invalid password used by the user. Further attempts MUST only
4115 be tried after prompting the user for a new password.
4117 DIAMETER_OUT_OF_SPACE 4002
4119 A Diameter node received the accounting request but was unable to
4120 commit it to stable storage due to a temporary lack of space.
4122 ELECTION_LOST 4003
4124 The peer has determined that it has lost the election process and
4125 has therefore disconnected the transport connection.
4127 7.1.5. Permanent Failures
4129 Errors that fall within the permanent failures category are used to
4130 inform the peer that the request failed, and should not be attempted
4131 again. Note that these errors SHOULD be used in answer messages
4132 whose 'E' bit is not set. In error conditions where it is not
4133 possible or efficient to compose application specific answer grammar
4134 then answer messages with E-bit set and complying to the grammar
4135 described in 7.2 MAY also be used for permanent errors.
4137 To provide backward compatibility with existing implementations that
4138 follow [RFC3588], some of the error values that have previously been
4139 used in this category by [RFC3588] will not be re-used. Therefore
4140 the error values enumerated here maybe non-sequential.
4142 DIAMETER_AVP_UNSUPPORTED 5001
4144 The peer received a message that contained an AVP that is not
4145 recognized or supported and was marked with the Mandatory bit. A
4146 Diameter message with this error MUST contain one or more Failed-
4147 AVP AVP containing the AVPs that caused the failure.
4149 DIAMETER_UNKNOWN_SESSION_ID 5002
4151 The request contained an unknown Session-Id.
4153 DIAMETER_AUTHORIZATION_REJECTED 5003
4155 A request was received for which the user could not be authorized.
4156 This error could occur if the service requested is not permitted
4157 to the user.
4159 DIAMETER_INVALID_AVP_VALUE 5004
4161 The request contained an AVP with an invalid value in its data
4162 portion. A Diameter message indicating this error MUST include
4163 the offending AVPs within a Failed-AVP AVP.
4165 DIAMETER_MISSING_AVP 5005
4167 The request did not contain an AVP that is required by the Command
4168 Code definition. If this value is sent in the Result-Code AVP, a
4169 Failed-AVP AVP SHOULD be included in the message. The Failed-AVP
4170 AVP MUST contain an example of the missing AVP complete with the
4171 Vendor-Id if applicable. The value field of the missing AVP
4172 should be of correct minimum length and contain zeroes.
4174 DIAMETER_RESOURCES_EXCEEDED 5006
4176 A request was received that cannot be authorized because the user
4177 has already expended allowed resources. An example of this error
4178 condition is a user that is restricted to one dial-up PPP port,
4179 attempts to establish a second PPP connection.
4181 DIAMETER_CONTRADICTING_AVPS 5007
4183 The Home Diameter server has detected AVPs in the request that
4184 contradicted each other, and is not willing to provide service to
4185 the user. One or more Failed-AVP AVPs MUST be present, containing
4186 the AVPs that contradicted each other.
4188 DIAMETER_AVP_NOT_ALLOWED 5008
4190 A message was received with an AVP that MUST NOT be present. The
4191 Failed-AVP AVP MUST be included and contain a copy of the
4192 offending AVP.
4194 DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009
4196 A message was received that included an AVP that appeared more
4197 often than permitted in the message definition. The Failed-AVP
4198 AVP MUST be included and contain a copy of the first instance of
4199 the offending AVP that exceeded the maximum number of occurrences
4201 DIAMETER_NO_COMMON_APPLICATION 5010
4203 This error is returned by a Diameter node that is not acting as a
4204 relay when it receives a CER which advertises a set of
4205 applications that it does not support.
4207 DIAMETER_UNSUPPORTED_VERSION 5011
4209 This error is returned when a request was received, whose version
4210 number is unsupported.
4212 DIAMETER_UNABLE_TO_COMPLY 5012
4214 This error is returned when a request is rejected for unspecified
4215 reasons.
4217 DIAMETER_INVALID_AVP_LENGTH 5014
4219 The request contained an AVP with an invalid length. A Diameter
4220 message indicating this error MUST include the offending AVPs
4221 within a Failed-AVP AVP. In cases where the erroneous avp length
4222 value exceeds the message length or is less than the minimum AVP
4223 header length, it is sufficient to include the offending AVP
4224 header and a zero filled payload of the minimum required length.
4226 DIAMETER_NO_COMMON_SECURITY 5017
4228 This error is returned when a CER message is received, and there
4229 are no common security mechanisms supported between the peers. A
4230 Capabilities-Exchange-Answer (CEA) MUST be returned with the
4231 Result-Code AVP set to DIAMETER_NO_COMMON_SECURITY.
4233 DIAMETER_UNKNOWN_PEER 5018
4235 A CER was received from an unknown peer.
4237 DIAMETER_COMMAND_UNSUPPORTED 5019
4239 The Request contained a Command-Code that the receiver did not
4240 recognize or support. This MUST be used when a Diameter node
4241 receives an experimental command that it does not understand.
4243 DIAMETER_INVALID_HDR_BITS 5020
4245 A request was received whose bits in the Diameter header were
4246 either set to an invalid combination, or to a value that is
4247 inconsistent with the command code's definition.
4249 DIAMETER_INVALID_AVP_BITS 5021
4251 A request was received that included an AVP whose flag bits are
4252 set to an unrecognized value, or that is inconsistent with the
4253 AVP's definition.
4255 7.2. Error Bit
4257 The 'E' (Error Bit) in the Diameter header is set when the request
4258 caused a protocol-related error (see Section 7.1.3). A message with
4259 the 'E' bit MUST NOT be sent as a response to an answer message.
4260 Note that a message with the 'E' bit set is still subjected to the
4261 processing rules defined in Section 6.2. When set, the answer
4262 message will not conform to the ABNF specification for the command,
4263 and will instead conform to the following ABNF:
4265 Message Format
4267 ::= < Diameter Header: code, ERR [PXY] >
4268 0*1< Session-Id >
4269 { Origin-Host }
4270 { Origin-Realm }
4271 { Result-Code }
4272 [ Origin-State-Id ]
4273 [ Error-Reporting-Host ]
4274 [ Proxy-Info ]
4275 * [ AVP ]
4277 Note that the code used in the header is the same than the one found
4278 in the request message, but with the 'R' bit cleared and the 'E' bit
4279 set. The 'P' bit in the header is set to the same value as the one
4280 found in the request message.
4282 7.3. Error-Message AVP
4284 The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY
4285 accompany a Result-Code AVP as a human readable error message. The
4286 Error-Message AVP is not intended to be useful in real-time, and
4287 SHOULD NOT be expected to be parsed by network entities.
4289 7.4. Error-Reporting-Host AVP
4291 The Error-Reporting-Host AVP (AVP Code 294) is of type
4292 DiameterIdentity. This AVP contains the identity of the Diameter
4293 host that sent the Result-Code AVP to a value other than 2001
4294 (Success), only if the host setting the Result-Code is different from
4295 the one encoded in the Origin-Host AVP. This AVP is intended to be
4296 used for troubleshooting purposes, and MUST be set when the Result-
4297 Code AVP indicates a failure.
4299 7.5. Failed-AVP AVP
4301 The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides
4302 debugging information in cases where a request is rejected or not
4303 fully processed due to erroneous information in a specific AVP. The
4304 value of the Result-Code AVP will provide information on the reason
4305 for the Failed-AVP AVP. A Diameter message SHOULD contain only one
4306 Failed-AVP that corresponds to the error indicated by the Result-Code
4307 AVP. For practical purposes, this Failed-AVP would typically refer
4308 to the first AVP processing error that a Diameter node encounters.
4310 The possible reasons for this AVP are the presence of an improperly
4311 constructed AVP, an unsupported or unrecognized AVP, an invalid AVP
4312 value, the omission of a required AVP, the presence of an explicitly
4313 excluded AVP (see tables in Section 10), or the presence of two or
4314 more occurrences of an AVP which is restricted to 0, 1, or 0-1
4315 occurrences.
4317 A Diameter message SHOULD contain one Failed-AVP AVP, containing the
4318 entire AVP that could not be processed successfully. If the failure
4319 reason is omission of a required AVP, an AVP with the missing AVP
4320 code, the missing vendor id, and a zero filled payload of the minimum
4321 required length for the omitted AVP will be added. If the failure
4322 reason is an invalid AVP length where the reported length is less
4323 than the minimum AVP header length or greater than the reported
4324 message length, a copy of the offending AVP header and a zero filled
4325 payload of the minimum required length SHOULD be added.
4327 AVP Format
4329 ::= < AVP Header: 279 >
4330 1* {AVP}
4332 7.6. Experimental-Result AVP
4334 The Experimental-Result AVP (AVP Code 297) is of type Grouped, and
4335 indicates whether a particular vendor-specific request was completed
4336 successfully or whether an error occurred. Its Data field has the
4337 following ABNF grammar:
4339 AVP Format
4341 Experimental-Result ::= < AVP Header: 297 >
4342 { Vendor-Id }
4343 { Experimental-Result-Code }
4345 The Vendor-Id AVP (see Section 5.3.3) in this grouped AVP identifies
4346 the vendor responsible for the assignment of the result code which
4347 follows. All Diameter answer messages defined in vendor-specific
4348 applications MUST include either one Result-Code AVP or one
4349 Experimental-Result AVP.
4351 7.7. Experimental-Result-Code AVP
4353 The Experimental-Result-Code AVP (AVP Code 298) is of type Unsigned32
4354 and contains a vendor-assigned value representing the result of
4355 processing the request.
4357 It is recommended that vendor-specific result codes follow the same
4358 conventions given for the Result-Code AVP regarding the different
4359 types of result codes and the handling of errors (for non 2xxx
4360 values).
4362 8. Diameter User Sessions
4364 In general, Diameter can provide two different types of services to
4365 applications. The first involves authentication and authorization,
4366 and can optionally make use of accounting. The second only makes use
4367 of accounting.
4369 When a service makes use of the authentication and/or authorization
4370 portion of an application, and a user requests access to the network,
4371 the Diameter client issues an auth request to its local server. The
4372 auth request is defined in a service specific Diameter application
4373 (e.g., NASREQ). The request contains a Session-Id AVP, which is used
4374 in subsequent messages (e.g., subsequent authorization, accounting,
4375 etc) relating to the user's session. The Session-Id AVP is a means
4376 for the client and servers to correlate a Diameter message with a
4377 user session.
4379 When a Diameter server authorizes a user to use network resources for
4380 a finite amount of time, and it is willing to extend the
4381 authorization via a future request, it MUST add the Authorization-
4382 Lifetime AVP to the answer message. The Authorization-Lifetime AVP
4383 defines the maximum number of seconds a user MAY make use of the
4384 resources before another authorization request is expected by the
4385 server. The Auth-Grace-Period AVP contains the number of seconds
4386 following the expiration of the Authorization-Lifetime, after which
4387 the server will release all state information related to the user's
4388 session. Note that if payment for services is expected by the
4389 serving realm from the user's home realm, the Authorization-Lifetime
4390 AVP, combined with the Auth-Grace-Period AVP, implies the maximum
4391 length of the session the home realm is willing to be fiscally
4392 responsible for. Services provided past the expiration of the
4393 Authorization-Lifetime and Auth-Grace-Period AVPs are the
4394 responsibility of the access device. Of course, the actual cost of
4395 services rendered is clearly outside the scope of the protocol.
4397 An access device that does not expect to send a re-authorization or a
4398 session termination request to the server MAY include the Auth-
4399 Session-State AVP with the value set to NO_STATE_MAINTAINED as a hint
4400 to the server. If the server accepts the hint, it agrees that since
4401 no session termination message will be received once service to the
4402 user is terminated, it cannot maintain state for the session. If the
4403 answer message from the server contains a different value in the
4404 Auth-Session-State AVP (or the default value if the AVP is absent),
4405 the access device MUST follow the server's directives. Note that the
4406 value NO_STATE_MAINTAINED MUST NOT be set in subsequent re-
4407 authorization requests and answers.
4409 The base protocol does not include any authorization request
4410 messages, since these are largely application-specific and are
4411 defined in a Diameter application document. However, the base
4412 protocol does define a set of messages that is used to terminate user
4413 sessions. These are used to allow servers that maintain state
4414 information to free resources.
4416 When a service only makes use of the Accounting portion of the
4417 Diameter protocol, even in combination with an application, the
4418 Session-Id is still used to identify user sessions. However, the
4419 session termination messages are not used, since a session is
4420 signaled as being terminated by issuing an accounting stop message.
4422 Diameter may also be used for services that cannot be easily
4423 categorized as authentication, authorization or accounting (e.g.,
4424 certain 3GPP IMS interfaces). In such cases, the finite state
4425 machine defined in subsequent sections may not be applicable.
4426 Therefore, the applications itself MAY need to define its own finite
4427 state machine. However, such application specific statemachines MUST
4428 comply with general Diameter user session requirements such co-
4429 relating all message exchanges via Session-Id AVP.
4431 8.1. Authorization Session State Machine
4433 This section contains a set of finite state machines, representing
4434 the life cycle of Diameter sessions, and which MUST be observed by
4435 all Diameter implementations that make use of the authentication
4436 and/or authorization portion of a Diameter application. The term
4437 Service-Specific below refers to a message defined in a Diameter
4438 application (e.g., Mobile IPv4, NASREQ).
4440 There are four different authorization session state machines
4441 supported in the Diameter base protocol. The first two describe a
4442 session in which the server is maintaining session state, indicated
4443 by the value of the Auth-Session-State AVP (or its absence). One
4444 describes the session from a client perspective, the other from a
4445 server perspective. The second two state machines are used when the
4446 server does not maintain session state. Here again, one describes
4447 the session from a client perspective, the other from a server
4448 perspective.
4450 When a session is moved to the Idle state, any resources that were
4451 allocated for the particular session must be released. Any event not
4452 listed in the state machines MUST be considered as an error
4453 condition, and an answer, if applicable, MUST be returned to the
4454 originator of the message.
4456 In the case that an application does not support re-auth, the state
4457 transitions related to server-initiated re-auth when both client and
4458 server sessions maintains state (e.g., Send RAR, Pending, Receive
4459 RAA) MAY be ignored.
4461 In the state table, the event 'Failure to send X' means that the
4462 Diameter agent is unable to send command X to the desired
4463 destination. This could be due to the peer being down, or due to the
4464 peer sending back a transient failure or temporary protocol error
4465 notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the
4466 Result-Code AVP of the corresponding Answer command. The event 'X
4467 successfully sent' is the complement of 'Failure to send X'.
4469 The following state machine is observed by a client when state is
4470 maintained on the server:
4472 CLIENT, STATEFUL
4473 State Event Action New State
4474 -------------------------------------------------------------
4475 Idle Client or Device Requests Send Pending
4476 access service
4477 specific
4478 auth req
4480 Idle ASR Received Send ASA Idle
4481 for unknown session with
4482 Result-Code
4483 = UNKNOWN_
4484 SESSION_ID
4486 Idle RAR Received Send RAA Idle
4487 for unknown session with
4488 Result-Code
4489 = UNKNOWN_
4490 SESSION_ID
4492 Pending Successful Service-specific Grant Open
4493 authorization answer Access
4494 received with default
4495 Auth-Session-State value
4497 Pending Successful Service-specific Sent STR Discon
4498 authorization answer received
4499 but service not provided
4501 Pending Error processing successful Sent STR Discon
4502 Service-specific authorization
4503 answer
4505 Pending Failed Service-specific Cleanup Idle
4506 authorization answer received
4508 Open User or client device Send Open
4509 requests access to service service
4510 specific
4511 auth req
4513 Open Successful Service-specific Provide Open
4514 authorization answer received Service
4516 Open Failed Service-specific Discon. Idle
4517 authorization answer user/device
4518 received.
4520 Open RAR received and client will Send RAA Open
4521 perform subsequent re-auth with
4522 Result-Code
4523 = SUCCESS
4525 Open RAR received and client will Send RAA Idle
4526 not perform subsequent with
4527 re-auth Result-Code
4528 != SUCCESS,
4529 Discon.
4530 user/device
4532 Open Session-Timeout Expires on Send STR Discon
4533 Access Device
4535 Open ASR Received, Send ASA Discon
4536 client will comply with with
4537 request to end the session Result-Code
4538 = SUCCESS,
4539 Send STR.
4541 Open ASR Received, Send ASA Open
4542 client will not comply with with
4543 request to end the session Result-Code
4544 != SUCCESS
4546 Open Authorization-Lifetime + Send STR Discon
4547 Auth-Grace-Period expires on
4548 access device
4550 Discon ASR Received Send ASA Discon
4552 Discon STA Received Discon. Idle
4553 user/device
4555 The following state machine is observed by a server when it is
4556 maintaining state for the session:
4558 SERVER, STATEFUL
4559 State Event Action New State
4560 -------------------------------------------------------------
4561 Idle Service-specific authorization Send Open
4562 request received, and successful
4563 user is authorized serv.
4564 specific
4565 answer
4567 Idle Service-specific authorization Send Idle
4568 request received, and failed serv.
4569 user is not authorized specific
4570 answer
4572 Open Service-specific authorization Send Open
4573 request received, and user successful
4574 is authorized serv. specific
4575 answer
4577 Open Service-specific authorization Send Idle
4578 request received, and user failed serv.
4579 is not authorized specific
4580 answer,
4581 Cleanup
4583 Open Home server wants to confirm Send RAR Pending
4584 authentication and/or
4585 authorization of the user
4587 Pending Received RAA with a failed Cleanup Idle
4588 Result-Code
4590 Pending Received RAA with Result-Code Update Open
4591 = SUCCESS session
4593 Open Home server wants to Send ASR Discon
4594 terminate the service
4596 Open Authorization-Lifetime (and Cleanup Idle
4597 Auth-Grace-Period) expires
4598 on home server.
4600 Open Session-Timeout expires on Cleanup Idle
4601 home server
4603 Discon Failure to send ASR Wait, Discon
4604 resend ASR
4606 Discon ASR successfully sent and Cleanup Idle
4607 ASA Received with Result-Code
4609 Not ASA Received None No Change.
4610 Discon
4612 Any STR Received Send STA, Idle
4613 Cleanup.
4615 The following state machine is observed by a client when state is not
4616 maintained on the server:
4618 CLIENT, STATELESS
4619 State Event Action New State
4620 -------------------------------------------------------------
4621 Idle Client or Device Requests Send Pending
4622 access service
4623 specific
4624 auth req
4626 Pending Successful Service-specific Grant Open
4627 authorization answer Access
4628 received with Auth-Session-
4629 State set to
4630 NO_STATE_MAINTAINED
4632 Pending Failed Service-specific Cleanup Idle
4633 authorization answer
4634 received
4636 Open Session-Timeout Expires on Discon. Idle
4637 Access Device user/device
4639 Open Service to user is terminated Discon. Idle
4640 user/device
4642 The following state machine is observed by a server when it is not
4643 maintaining state for the session:
4645 SERVER, STATELESS
4646 State Event Action New State
4647 -------------------------------------------------------------
4648 Idle Service-specific authorization Send serv. Idle
4649 request received, and specific
4650 successfully processed answer
4652 8.2. Accounting Session State Machine
4654 The following state machines MUST be supported for applications that
4655 have an accounting portion or that require only accounting services.
4656 The first state machine is to be observed by clients.
4658 See Section 9.7 for Accounting Command Codes and Section 9.8 for
4659 Accounting AVPs.
4661 The server side in the accounting state machine depends in some cases
4662 on the particular application. The Diameter base protocol defines a
4663 default state machine that MUST be followed by all applications that
4664 have not specified other state machines. This is the second state
4665 machine in this section described below.
4667 The default server side state machine requires the reception of
4668 accounting records in any order and at any time, and does not place
4669 any standards requirement on the processing of these records.
4670 Implementations of Diameter MAY perform checking, ordering,
4671 correlation, fraud detection, and other tasks based on these records.
4672 Both base Diameter AVPs as well as application specific AVPs MAY be
4673 inspected as a part of these tasks. The tasks can happen either
4674 immediately after record reception or in a post-processing phase.
4675 However, as these tasks are typically application or even policy
4676 dependent, they are not standardized by the Diameter specifications.
4677 Applications MAY define requirements on when to accept accounting
4678 records based on the used value of Accounting-Realtime-Required AVP,
4679 credit limits checks, and so on.
4681 However, the Diameter base protocol defines one optional server side
4682 state machine that MAY be followed by applications that require
4683 keeping track of the session state at the accounting server. Note
4684 that such tracking is incompatible with the ability to sustain long
4685 duration connectivity problems. Therefore, the use of this state
4686 machine is recommended only in applications where the value of the
4687 Accounting-Realtime-Required AVP is DELIVER_AND_GRANT, and hence
4688 accounting connectivity problems are required to cause the serviced
4689 user to be disconnected. Otherwise, records produced by the client
4690 may be lost by the server which no longer accepts them after the
4691 connectivity is re-established. This state machine is the third
4692 state machine in this section. The state machine is supervised by a
4693 supervision session timer Ts, which the value should be reasonably
4694 higher than the Acct_Interim_Interval value. Ts MAY be set to two
4695 times the value of the Acct_Interim_Interval so as to avoid the
4696 accounting session in the Diameter server to change to Idle state in
4697 case of short transient network failure.
4699 Any event not listed in the state machines MUST be considered as an
4700 error condition, and a corresponding answer, if applicable, MUST be
4701 returned to the originator of the message.
4703 In the state table, the event 'Failure to send' means that the
4704 Diameter client is unable to communicate with the desired
4705 destination. This could be due to the peer being down, or due to the
4706 peer sending back a transient failure or temporary protocol error
4707 notification DIAMETER_OUT_OF_SPACE, DIAMETER_TOO_BUSY, or
4708 DIAMETER_LOOP_DETECTED in the Result-Code AVP of the Accounting
4709 Answer command.
4711 The event 'Failed answer' means that the Diameter client received a
4712 non-transient failure notification in the Accounting Answer command.
4714 Note that the action 'Disconnect user/dev' MUST have an effect also
4715 to the authorization session state table, e.g., cause the STR message
4716 to be sent, if the given application has both authentication/
4717 authorization and accounting portions.
4719 The states PendingS, PendingI, PendingL, PendingE and PendingB stand
4720 for pending states to wait for an answer to an accounting request
4721 related to a Start, Interim, Stop, Event or buffered record,
4722 respectively.
4724 CLIENT, ACCOUNTING
4725 State Event Action New State
4726 -------------------------------------------------------------
4727 Idle Client or device requests Send PendingS
4728 access accounting
4729 start req.
4731 Idle Client or device requests Send PendingE
4732 a one-time service accounting
4733 event req
4735 Idle Records in storage Send PendingB
4736 record
4738 PendingS Successful accounting Open
4739 start answer received
4741 PendingS Failure to send and buffer Store Open
4742 space available and realtime Start
4743 not equal to DELIVER_AND_GRANT Record
4745 PendingS Failure to send and no buffer Open
4746 space available and realtime
4747 equal to GRANT_AND_LOSE
4749 PendingS Failure to send and no buffer Disconnect Idle
4750 space available and realtime user/dev
4751 not equal to
4752 GRANT_AND_LOSE
4754 PendingS Failed accounting start answer Open
4755 received and realtime equal
4756 to GRANT_AND_LOSE
4758 PendingS Failed accounting start answer Disconnect Idle
4759 received and realtime not user/dev
4760 equal to GRANT_AND_LOSE
4762 PendingS User service terminated Store PendingS
4763 stop
4764 record
4766 Open Interim interval elapses Send PendingI
4767 accounting
4768 interim
4769 record
4770 Open User service terminated Send PendingL
4771 accounting
4772 stop req.
4774 PendingI Successful accounting interim Open
4775 answer received
4777 PendingI Failure to send and (buffer Store Open
4778 space available or old record interim
4779 can be overwritten) and record
4780 realtime not equal to
4781 DELIVER_AND_GRANT
4783 PendingI Failure to send and no buffer Open
4784 space available and realtime
4785 equal to GRANT_AND_LOSE
4787 PendingI Failure to send and no buffer Disconnect Idle
4788 space available and realtime user/dev
4789 not equal to GRANT_AND_LOSE
4791 PendingI Failed accounting interim Open
4792 answer received and realtime
4793 equal to GRANT_AND_LOSE
4795 PendingI Failed accounting interim Disconnect Idle
4796 answer received and realtime user/dev
4797 not equal to GRANT_AND_LOSE
4799 PendingI User service terminated Store PendingI
4800 stop
4801 record
4802 PendingE Successful accounting Idle
4803 event answer received
4805 PendingE Failure to send and buffer Store Idle
4806 space available event
4807 record
4809 PendingE Failure to send and no buffer Idle
4810 space available
4812 PendingE Failed accounting event answer Idle
4813 received
4815 PendingB Successful accounting answer Delete Idle
4816 received record
4818 PendingB Failure to send Idle
4820 PendingB Failed accounting answer Delete Idle
4821 received record
4823 PendingL Successful accounting Idle
4824 stop answer received
4826 PendingL Failure to send and buffer Store Idle
4827 space available stop
4828 record
4830 PendingL Failure to send and no buffer Idle
4831 space available
4833 PendingL Failed accounting stop answer Idle
4834 received
4836 SERVER, STATELESS ACCOUNTING
4837 State Event Action New State
4838 -------------------------------------------------------------
4840 Idle Accounting start request Send Idle
4841 received, and successfully accounting
4842 processed. start
4843 answer
4845 Idle Accounting event request Send Idle
4846 received, and successfully accounting
4847 processed. event
4848 answer
4850 Idle Interim record received, Send Idle
4851 and successfully processed. accounting
4852 interim
4853 answer
4855 Idle Accounting stop request Send Idle
4856 received, and successfully accounting
4857 processed stop answer
4859 Idle Accounting request received, Send Idle
4860 no space left to store accounting
4861 records answer,
4862 Result-Code
4863 = OUT_OF_
4864 SPACE
4866 SERVER, STATEFUL ACCOUNTING
4867 State Event Action New State
4868 -------------------------------------------------------------
4870 Idle Accounting start request Send Open
4871 received, and successfully accounting
4872 processed. start
4873 answer,
4874 Start Ts
4876 Idle Accounting event request Send Idle
4877 received, and successfully accounting
4878 processed. event
4879 answer
4881 Idle Accounting request received, Send Idle
4882 no space left to store accounting
4883 records answer,
4884 Result-Code
4885 = OUT_OF_
4886 SPACE
4888 Open Interim record received, Send Open
4889 and successfully processed. accounting
4890 interim
4891 answer,
4892 Restart Ts
4894 Open Accounting stop request Send Idle
4895 received, and successfully accounting
4896 processed stop answer,
4897 Stop Ts
4899 Open Accounting request received, Send Idle
4900 no space left to store accounting
4901 records answer,
4902 Result-Code
4903 = OUT_OF_
4904 SPACE,
4905 Stop Ts
4907 Open Session supervision timer Ts Stop Ts Idle
4908 expired
4910 8.3. Server-Initiated Re-Auth
4912 A Diameter server may initiate a re-authentication and/or re-
4913 authorization service for a particular session by issuing a Re-Auth-
4914 Request (RAR).
4916 For example, for pre-paid services, the Diameter server that
4917 originally authorized a session may need some confirmation that the
4918 user is still using the services.
4920 An access device that receives a RAR message with Session-Id equal to
4921 a currently active session MUST initiate a re-auth towards the user,
4922 if the service supports this particular feature. Each Diameter
4923 application MUST state whether service-initiated re-auth is
4924 supported, since some applications do not allow access devices to
4925 prompt the user for re-auth.
4927 8.3.1. Re-Auth-Request
4929 The Re-Auth-Request (RAR), indicated by the Command-Code set to 258
4930 and the message flags' 'R' bit set, may be sent by any server to the
4931 access device that is providing session service, to request that the
4932 user be re-authenticated and/or re-authorized.
4934 Message Format
4936 ::= < Diameter Header: 258, REQ, PXY >
4937 < Session-Id >
4938 { Origin-Host }
4939 { Origin-Realm }
4940 { Destination-Realm }
4941 { Destination-Host }
4942 { Auth-Application-Id }
4943 { Re-Auth-Request-Type }
4944 [ User-Name ]
4945 [ Origin-State-Id ]
4946 * [ Proxy-Info ]
4947 * [ Route-Record ]
4948 * [ AVP ]
4950 8.3.2. Re-Auth-Answer
4952 The Re-Auth-Answer (RAA), indicated by the Command-Code set to 258
4953 and the message flags' 'R' bit clear, is sent in response to the RAR.
4954 The Result-Code AVP MUST be present, and indicates the disposition of
4955 the request.
4957 A successful RAA message MUST be followed by an application-specific
4958 authentication and/or authorization message.
4960 Message Format
4962 ::= < Diameter Header: 258, PXY >
4963 < Session-Id >
4964 { Result-Code }
4965 { Origin-Host }
4966 { Origin-Realm }
4967 [ User-Name ]
4968 [ Origin-State-Id ]
4969 [ Error-Message ]
4970 [ Error-Reporting-Host ]
4971 * [ Failed-AVP ]
4972 * [ Redirect-Host ]
4973 [ Redirect-Host-Usage ]
4974 [ Redirect-Host-Cache-Time ]
4975 * [ Proxy-Info ]
4976 * [ AVP ]
4978 8.4. Session Termination
4980 It is necessary for a Diameter server that authorized a session, for
4981 which it is maintaining state, to be notified when that session is no
4982 longer active, both for tracking purposes as well as to allow
4983 stateful agents to release any resources that they may have provided
4984 for the user's session. For sessions whose state is not being
4985 maintained, this section is not used.
4987 When a user session that required Diameter authorization terminates,
4988 the access device that provided the service MUST issue a Session-
4989 Termination-Request (STR) message to the Diameter server that
4990 authorized the service, to notify it that the session is no longer
4991 active. An STR MUST be issued when a user session terminates for any
4992 reason, including user logoff, expiration of Session-Timeout,
4993 administrative action, termination upon receipt of an Abort-Session-
4994 Request (see below), orderly shutdown of the access device, etc.
4996 The access device also MUST issue an STR for a session that was
4997 authorized but never actually started. This could occur, for
4998 example, due to a sudden resource shortage in the access device, or
4999 because the access device is unwilling to provide the type of service
5000 requested in the authorization, or because the access device does not
5001 support a mandatory AVP returned in the authorization, etc.
5003 It is also possible that a session that was authorized is never
5004 actually started due to action of a proxy. For example, a proxy may
5005 modify an authorization answer, converting the result from success to
5006 failure, prior to forwarding the message to the access device. If
5007 the answer did not contain an Auth-Session-State AVP with the value
5008 NO_STATE_MAINTAINED, a proxy that causes an authorized session not to
5009 be started MUST issue an STR to the Diameter server that authorized
5010 the session, since the access device has no way of knowing that the
5011 session had been authorized.
5013 A Diameter server that receives an STR message MUST clean up
5014 resources (e.g., session state) associated with the Session-Id
5015 specified in the STR, and return a Session-Termination-Answer.
5017 A Diameter server also MUST clean up resources when the Session-
5018 Timeout expires, or when the Authorization-Lifetime and the Auth-
5019 Grace-Period AVPs expires without receipt of a re-authorization
5020 request, regardless of whether an STR for that session is received.
5021 The access device is not expected to provide service beyond the
5022 expiration of these timers; thus, expiration of either of these
5023 timers implies that the access device may have unexpectedly shut
5024 down.
5026 8.4.1. Session-Termination-Request
5028 The Session-Termination-Request (STR), indicated by the Command-Code
5029 set to 275 and the Command Flags' 'R' bit set, is sent by the access
5030 device to inform the Diameter Server that an authenticated and/or
5031 authorized session is being terminated.
5033 Message Format
5035 ::= < Diameter Header: 275, REQ, PXY >
5036 < Session-Id >
5037 { Origin-Host }
5038 { Origin-Realm }
5039 { Destination-Realm }
5040 { Auth-Application-Id }
5041 { Termination-Cause }
5042 [ User-Name ]
5043 [ Destination-Host ]
5044 * [ Class ]
5045 [ Origin-State-Id ]
5046 * [ Proxy-Info ]
5047 * [ Route-Record ]
5048 * [ AVP ]
5050 8.4.2. Session-Termination-Answer
5052 The Session-Termination-Answer (STA), indicated by the Command-Code
5053 set to 275 and the message flags' 'R' bit clear, is sent by the
5054 Diameter Server to acknowledge the notification that the session has
5055 been terminated. The Result-Code AVP MUST be present, and MAY
5056 contain an indication that an error occurred while servicing the STR.
5058 Upon sending or receipt of the STA, the Diameter Server MUST release
5059 all resources for the session indicated by the Session-Id AVP. Any
5060 intermediate server in the Proxy-Chain MAY also release any
5061 resources, if necessary.
5063 Message Format
5065 ::= < Diameter Header: 275, PXY >
5066 < Session-Id >
5067 { Result-Code }
5068 { Origin-Host }
5069 { Origin-Realm }
5070 [ User-Name ]
5071 * [ Class ]
5072 [ Error-Message ]
5073 [ Error-Reporting-Host ]
5074 * [ Failed-AVP ]
5075 [ Origin-State-Id ]
5076 * [ Redirect-Host ]
5077 [ Redirect-Host-Usage ]
5078 ^
5079 [ Redirect-Max-Cache-Time ]
5080 * [ Proxy-Info ]
5081 * [ AVP ]
5083 8.5. Aborting a Session
5085 A Diameter server may request that the access device stop providing
5086 service for a particular session by issuing an Abort-Session-Request
5087 (ASR).
5089 For example, the Diameter server that originally authorized the
5090 session may be required to cause that session to be stopped for
5091 credit or other reasons that were not anticipated when the session
5092 was first authorized. On the other hand, an operator may maintain a
5093 management server for the purpose of issuing ASRs to administratively
5094 remove users from the network.
5096 An access device that receives an ASR with Session-ID equal to a
5097 currently active session MAY stop the session. Whether the access
5098 device stops the session or not is implementation- and/or
5099 configuration-dependent. For example, an access device may honor
5100 ASRs from certain agents only. In any case, the access device MUST
5101 respond with an Abort-Session-Answer, including a Result-Code AVP to
5102 indicate what action it took.
5104 Note that if the access device does stop the session upon receipt of
5105 an ASR, it issues an STR to the authorizing server (which may or may
5106 not be the agent issuing the ASR) just as it would if the session
5107 were terminated for any other reason.
5109 8.5.1. Abort-Session-Request
5111 The Abort-Session-Request (ASR), indicated by the Command-Code set to
5112 274 and the message flags' 'R' bit set, may be sent by any server to
5113 the access device that is providing session service, to request that
5114 the session identified by the Session-Id be stopped.
5116 Message Format
5118 ::= < Diameter Header: 274, REQ, PXY >
5119 < Session-Id >
5120 { Origin-Host }
5121 { Origin-Realm }
5122 { Destination-Realm }
5123 { Destination-Host }
5124 { Auth-Application-Id }
5125 [ User-Name ]
5126 [ Origin-State-Id ]
5127 * [ Proxy-Info ]
5128 * [ Route-Record ]
5129 * [ AVP ]
5131 8.5.2. Abort-Session-Answer
5133 The Abort-Session-Answer (ASA), indicated by the Command-Code set to
5134 274 and the message flags' 'R' bit clear, is sent in response to the
5135 ASR. The Result-Code AVP MUST be present, and indicates the
5136 disposition of the request.
5138 If the session identified by Session-Id in the ASR was successfully
5139 terminated, Result-Code is set to DIAMETER_SUCCESS. If the session
5140 is not currently active, Result-Code is set to
5141 DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the
5142 session for any other reason, Result-Code is set to
5143 DIAMETER_UNABLE_TO_COMPLY.
5145 Message Format
5147 ::= < Diameter Header: 274, PXY >
5148 < Session-Id >
5149 { Result-Code }
5150 { Origin-Host }
5151 { Origin-Realm }
5152 [ User-Name ]
5153 [ Origin-State-Id ]
5154 [ Error-Message ]
5155 [ Error-Reporting-Host ]
5156 * [ Failed-AVP ]
5157 * [ Redirect-Host ]
5158 [ Redirect-Host-Usage ]
5159 [ Redirect-Max-Cache-Time ]
5160 * [ Proxy-Info ]
5161 * [ AVP ]
5163 8.6. Inferring Session Termination from Origin-State-Id
5165 Origin-State-Id is used to allow rapid detection of terminated
5166 sessions for which no STR would have been issued, due to
5167 unanticipated shutdown of an access device.
5169 By including Origin-State-Id in CER/CEA messages, an access device
5170 allows a next-hop server to determine immediately upon connection
5171 whether the device has lost its sessions since the last connection.
5173 By including Origin-State-Id in request messages, an access device
5174 also allows a server with which it communicates via proxy to make
5175 such a determination. However, a server that is not directly
5176 connected with the access device will not discover that the access
5177 device has been restarted unless and until it receives a new request
5178 from the access device. Thus, use of this mechanism across proxies
5179 is opportunistic rather than reliable, but useful nonetheless.
5181 When a Diameter server receives an Origin-State-Id that is greater
5182 than the Origin-State-Id previously received from the same issuer, it
5183 may assume that the issuer has lost state since the previous message
5184 and that all sessions that were active under the lower Origin-State-
5185 Id have been terminated. The Diameter server MAY clean up all
5186 session state associated with such lost sessions, and MAY also issues
5187 STRs for all such lost sessions that were authorized on upstream
5188 servers, to allow session state to be cleaned up globally.
5190 8.7. Auth-Request-Type AVP
5192 The Auth-Request-Type AVP (AVP Code 274) is of type Enumerated and is
5193 included in application-specific auth requests to inform the peers
5194 whether a user is to be authenticated only, authorized only or both.
5195 Note any value other than both MAY cause RADIUS interoperability
5196 issues. The following values are defined:
5198 AUTHENTICATE_ONLY 1
5200 The request being sent is for authentication only, and MUST
5201 contain the relevant application specific authentication AVPs that
5202 are needed by the Diameter server to authenticate the user.
5204 AUTHORIZE_ONLY 2
5206 The request being sent is for authorization only, and MUST contain
5207 the application specific authorization AVPs that are necessary to
5208 identify the service being requested/offered.
5210 AUTHORIZE_AUTHENTICATE 3
5212 The request contains a request for both authentication and
5213 authorization. The request MUST include both the relevant
5214 application specific authentication information, and authorization
5215 information necessary to identify the service being requested/
5216 offered.
5218 8.8. Session-Id AVP
5220 The Session-Id AVP (AVP Code 263) is of type UTF8String and is used
5221 to identify a specific session (see Section 8). All messages
5222 pertaining to a specific session MUST include only one Session-Id AVP
5223 and the same value MUST be used throughout the life of a session.
5224 When present, the Session-Id SHOULD appear immediately following the
5225 Diameter Header (see Section 3).
5227 The Session-Id MUST be globally and eternally unique, as it is meant
5228 to uniquely identify a user session without reference to any other
5229 information, and may be needed to correlate historical authentication
5230 information with accounting information. The Session-Id includes a
5231 mandatory portion and an implementation-defined portion; a
5232 recommended format for the implementation-defined portion is outlined
5233 below.
5235 The Session-Id MUST begin with the sender's identity encoded in the
5236 DiameterIdentity type (see Section 4.4). The remainder of the
5237 Session-Id is delimited by a ";" character, and MAY be any sequence
5238 that the client can guarantee to be eternally unique; however, the
5239 following format is recommended, (square brackets [] indicate an
5240 optional element):
5242 ;;[;]
5244 and are decimal representations of the
5245 high and low 32 bits of a monotonically increasing 64-bit value. The
5246 64-bit value is rendered in two part to simplify formatting by 32-bit
5247 processors. At startup, the high 32 bits of the 64-bit value MAY be
5248 initialized to the time, and the low 32 bits MAY be initialized to
5249 zero. This will for practical purposes eliminate the possibility of
5250 overlapping Session-Ids after a reboot, assuming the reboot process
5251 takes longer than a second. Alternatively, an implementation MAY
5252 keep track of the increasing value in non-volatile memory.
5254 is implementation specific but may include a modem's
5255 device Id, a layer 2 address, timestamp, etc.
5257 Example, in which there is no optional value:
5259 accesspoint7.acme.com;1876543210;523
5261 Example, in which there is an optional value:
5263 accesspoint7.acme.com;1876543210;523;mobile@200.1.1.88
5265 The Session-Id is created by the Diameter application initiating the
5266 session, which in most cases is done by the client. Note that a
5267 Session-Id MAY be used for both the authorization and accounting
5268 commands of a given application.
5270 8.9. Authorization-Lifetime AVP
5272 The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32
5273 and contains the maximum number of seconds of service to be provided
5274 to the user before the user is to be re-authenticated and/or re-
5275 authorized. Great care should be taken when the Authorization-
5276 Lifetime value is determined, since a low, non-zero, value could
5277 create significant Diameter traffic, which could congest both the
5278 network and the agents.
5280 A value of zero (0) means that immediate re-auth is necessary by the
5281 access device. This is typically used in cases where multiple
5282 authentication methods are used, and a successful auth response with
5283 this AVP set to zero is used to signal that the next authentication
5284 method is to be immediately initiated. The absence of this AVP, or a
5285 value of all ones (meaning all bits in the 32 bit field are set to
5286 one) means no re-auth is expected.
5288 If both this AVP and the Session-Timeout AVP are present in a
5289 message, the value of the latter MUST NOT be smaller than the
5290 Authorization-Lifetime AVP.
5292 An Authorization-Lifetime AVP MAY be present in re-authorization
5293 messages, and contains the number of seconds the user is authorized
5294 to receive service from the time the re-auth answer message is
5295 received by the access device.
5297 This AVP MAY be provided by the client as a hint of the maximum
5298 lifetime that it is willing to accept. However, the server MAY
5299 return a value that is equal to, or smaller, than the one provided by
5300 the client.
5302 8.10. Auth-Grace-Period AVP
5304 The Auth-Grace-Period AVP (AVP Code 276) is of type Unsigned32 and
5305 contains the number of seconds the Diameter server will wait
5306 following the expiration of the Authorization-Lifetime AVP before
5307 cleaning up resources for the session.
5309 8.11. Auth-Session-State AVP
5311 The Auth-Session-State AVP (AVP Code 277) is of type Enumerated and
5312 specifies whether state is maintained for a particular session. The
5313 client MAY include this AVP in requests as a hint to the server, but
5314 the value in the server's answer message is binding. The following
5315 values are supported:
5317 STATE_MAINTAINED 0
5319 This value is used to specify that session state is being
5320 maintained, and the access device MUST issue a session termination
5321 message when service to the user is terminated. This is the
5322 default value.
5324 NO_STATE_MAINTAINED 1
5326 This value is used to specify that no session termination messages
5327 will be sent by the access device upon expiration of the
5328 Authorization-Lifetime.
5330 8.12. Re-Auth-Request-Type AVP
5332 The Re-Auth-Request-Type AVP (AVP Code 285) is of type Enumerated and
5333 is included in application-specific auth answers to inform the client
5334 of the action expected upon expiration of the Authorization-Lifetime.
5335 If the answer message contains an Authorization-Lifetime AVP with a
5336 positive value, the Re-Auth-Request-Type AVP MUST be present in an
5337 answer message. The following values are defined:
5339 AUTHORIZE_ONLY 0
5341 An authorization only re-auth is expected upon expiration of the
5342 Authorization-Lifetime. This is the default value if the AVP is
5343 not present in answer messages that include the Authorization-
5344 Lifetime.
5346 AUTHORIZE_AUTHENTICATE 1
5348 An authentication and authorization re-auth is expected upon
5349 expiration of the Authorization-Lifetime.
5351 8.13. Session-Timeout AVP
5353 The Session-Timeout AVP (AVP Code 27) [RFC2865] is of type Unsigned32
5354 and contains the maximum number of seconds of service to be provided
5355 to the user before termination of the session. When both the
5356 Session-Timeout and the Authorization-Lifetime AVPs are present in an
5357 answer message, the former MUST be equal to or greater than the value
5358 of the latter.
5360 A session that terminates on an access device due to the expiration
5361 of the Session-Timeout MUST cause an STR to be issued, unless both
5362 the access device and the home server had previously agreed that no
5363 session termination messages would be sent (see Section 8.9).
5365 A Session-Timeout AVP MAY be present in a re-authorization answer
5366 message, and contains the remaining number of seconds from the
5367 beginning of the re-auth.
5369 A value of zero, or the absence of this AVP, means that this session
5370 has an unlimited number of seconds before termination.
5372 This AVP MAY be provided by the client as a hint of the maximum
5373 timeout that it is willing to accept. However, the server MAY return
5374 a value that is equal to, or smaller, than the one provided by the
5375 client.
5377 8.14. User-Name AVP
5379 The User-Name AVP (AVP Code 1) [RFC2865] is of type UTF8String, which
5380 contains the User-Name, in a format consistent with the NAI
5381 specification [RFC4282].
5383 8.15. Termination-Cause AVP
5385 The Termination-Cause AVP (AVP Code 295) is of type Enumerated, and
5386 is used to indicate the reason why a session was terminated on the
5387 access device. The following values are defined:
5389 DIAMETER_LOGOUT 1
5391 The user initiated a disconnect
5393 DIAMETER_SERVICE_NOT_PROVIDED 2
5395 This value is used when the user disconnected prior to the receipt
5396 of the authorization answer message.
5398 DIAMETER_BAD_ANSWER 3
5400 This value indicates that the authorization answer received by the
5401 access device was not processed successfully.
5403 DIAMETER_ADMINISTRATIVE 4
5405 The user was not granted access, or was disconnected, due to
5406 administrative reasons, such as the receipt of a Abort-Session-
5407 Request message.
5409 DIAMETER_LINK_BROKEN 5
5411 The communication to the user was abruptly disconnected.
5413 DIAMETER_AUTH_EXPIRED 6
5415 The user's access was terminated since its authorized session time
5416 has expired.
5418 DIAMETER_USER_MOVED 7
5420 The user is receiving services from another access device.
5422 DIAMETER_SESSION_TIMEOUT 8
5424 The user's session has timed out, and service has been terminated.
5426 8.16. Origin-State-Id AVP
5428 The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a
5429 monotonically increasing value that is advanced whenever a Diameter
5430 entity restarts with loss of previous state, for example upon reboot.
5431 Origin-State-Id MAY be included in any Diameter message, including
5432 CER.
5434 A Diameter entity issuing this AVP MUST create a higher value for
5435 this AVP each time its state is reset. A Diameter entity MAY set
5436 Origin-State-Id to the time of startup, or it MAY use an incrementing
5437 counter retained in non-volatile memory across restarts.
5439 The Origin-State-Id, if present, MUST reflect the state of the entity
5440 indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST
5441 either remove Origin-State-Id or modify it appropriately as well.
5442 Typically, Origin-State-Id is used by an access device that always
5443 starts up with no active sessions; that is, any session active prior
5444 to restart will have been lost. By including Origin-State-Id in a
5445 message, it allows other Diameter entities to infer that sessions
5446 associated with a lower Origin-State-Id are no longer active. If an
5447 access device does not intend for such inferences to be made, it MUST
5448 either not include Origin-State-Id in any message, or set its value
5449 to 0.
5451 8.17. Session-Binding AVP
5453 The Session-Binding AVP (AVP Code 270) is of type Unsigned32, and MAY
5454 be present in application-specific authorization answer messages. If
5455 present, this AVP MAY inform the Diameter client that all future
5456 application-specific re-auth messages for this session MUST be sent
5457 to the same authorization server. This AVP MAY also specify that a
5458 Session-Termination-Request message for this session MUST be sent to
5459 the same authorizing server.
5461 This field is a bit mask, and the following bits have been defined:
5463 RE_AUTH 1
5465 When set, future re-auth messages for this session MUST NOT
5466 include the Destination-Host AVP. When cleared, the default
5467 value, the Destination-Host AVP MUST be present in all re-auth
5468 messages for this session.
5470 STR 2
5472 When set, the STR message for this session MUST NOT include the
5473 Destination-Host AVP. When cleared, the default value, the
5474 Destination-Host AVP MUST be present in the STR message for this
5475 session.
5477 ACCOUNTING 4
5479 When set, all accounting messages for this session MUST NOT
5480 include the Destination-Host AVP. When cleared, the default
5481 value, the Destination-Host AVP, if known, MUST be present in all
5482 accounting messages for this session.
5484 8.18. Session-Server-Failover AVP
5486 The Session-Server-Failover AVP (AVP Code 271) is of type Enumerated,
5487 and MAY be present in application-specific authorization answer
5488 messages that either do not include the Session-Binding AVP or
5489 include the Session-Binding AVP with any of the bits set to a zero
5490 value. If present, this AVP MAY inform the Diameter client that if a
5491 re-auth or STR message fails due to a delivery problem, the Diameter
5492 client SHOULD issue a subsequent message without the Destination-Host
5493 AVP. When absent, the default value is REFUSE_SERVICE.
5495 The following values are supported:
5497 REFUSE_SERVICE 0
5499 If either the re-auth or the STR message delivery fails, terminate
5500 service with the user, and do not attempt any subsequent attempts.
5502 TRY_AGAIN 1
5504 If either the re-auth or the STR message delivery fails, resend
5505 the failed message without the Destination-Host AVP present.
5507 ALLOW_SERVICE 2
5509 If re-auth message delivery fails, assume that re-authorization
5510 succeeded. If STR message delivery fails, terminate the session.
5512 TRY_AGAIN_ALLOW_SERVICE 3
5514 If either the re-auth or the STR message delivery fails, resend
5515 the failed message without the Destination-Host AVP present. If
5516 the second delivery fails for re-auth, assume re-authorization
5517 succeeded. If the second delivery fails for STR, terminate the
5518 session.
5520 8.19. Multi-Round-Time-Out AVP
5522 The Multi-Round-Time-Out AVP (AVP Code 272) is of type Unsigned32,
5523 and SHOULD be present in application-specific authorization answer
5524 messages whose Result-Code AVP is set to DIAMETER_MULTI_ROUND_AUTH.
5525 This AVP contains the maximum number of seconds that the access
5526 device MUST provide the user in responding to an authentication
5527 request.
5529 8.20. Class AVP
5531 The Class AVP (AVP Code 25) is of type OctetString and is used to by
5532 Diameter servers to return state information to the access device.
5533 When one or more Class AVPs are present in application-specific
5534 authorization answer messages, they MUST be present in subsequent re-
5535 authorization, session termination and accounting messages. Class
5536 AVPs found in a re-authorization answer message override the ones
5537 found in any previous authorization answer message. Diameter server
5538 implementations SHOULD NOT return Class AVPs that require more than
5539 4096 bytes of storage on the Diameter client. A Diameter client that
5540 receives Class AVPs whose size exceeds local available storage MUST
5541 terminate the session.
5543 8.21. Event-Timestamp AVP
5545 The Event-Timestamp (AVP Code 55) is of type Time, and MAY be
5546 included in an Accounting-Request and Accounting-Answer messages to
5547 record the time that the reported event occurred, in seconds since
5548 January 1, 1900 00:00 UTC.
5550 9. Accounting
5552 This accounting protocol is based on a server directed model with
5553 capabilities for real-time delivery of accounting information.
5554 Several fault resilience methods [RFC2975] have been built in to the
5555 protocol in order minimize loss of accounting data in various fault
5556 situations and under different assumptions about the capabilities of
5557 the used devices.
5559 9.1. Server Directed Model
5561 The server directed model means that the device generating the
5562 accounting data gets information from either the authorization server
5563 (if contacted) or the accounting server regarding the way accounting
5564 data shall be forwarded. This information includes accounting record
5565 timeliness requirements.
5567 As discussed in [RFC2975], real-time transfer of accounting records
5568 is a requirement, such as the need to perform credit limit checks and
5569 fraud detection. Note that batch accounting is not a requirement,
5570 and is therefore not supported by Diameter. Should batched
5571 accounting be required in the future, a new Diameter application will
5572 need to be created, or it could be handled using another protocol.
5573 Note, however, that even if at the Diameter layer accounting requests
5574 are processed one by one, transport protocols used under Diameter
5575 typically batch several requests in the same packet under heavy
5576 traffic conditions. This may be sufficient for many applications.
5578 The authorization server (chain) directs the selection of proper
5579 transfer strategy, based on its knowledge of the user and
5580 relationships of roaming partnerships. The server (or agents) uses
5581 the Acct-Interim-Interval and Accounting-Realtime-Required AVPs to
5582 control the operation of the Diameter peer operating as a client.
5583 The Acct-Interim-Interval AVP, when present, instructs the Diameter
5584 node acting as a client to produce accounting records continuously
5585 even during a session. Accounting-Realtime-Required AVP is used to
5586 control the behavior of the client when the transfer of accounting
5587 records from the Diameter client is delayed or unsuccessful.
5589 The Diameter accounting server MAY override the interim interval or
5590 the realtime requirements by including the Acct-Interim-Interval or
5591 Accounting-Realtime-Required AVP in the Accounting-Answer message.
5592 When one of these AVPs is present, the latest value received SHOULD
5593 be used in further accounting activities for the same session.
5595 9.2. Protocol Messages
5597 A Diameter node that receives a successful authentication and/or
5598 authorization messages from the Home AAA server MUST collect
5599 accounting information for the session. The Accounting-Request
5600 message is used to transmit the accounting information to the Home
5601 AAA server, which MUST reply with the Accounting-Answer message to
5602 confirm reception. The Accounting-Answer message includes the
5603 Result-Code AVP, which MAY indicate that an error was present in the
5604 accounting message. A rejected Accounting-Request message MAY cause
5605 the user's session to be terminated, depending on the value of the
5606 Accounting-Realtime-Required AVP received earlier for the session in
5607 question.
5609 Each Diameter Accounting protocol message MAY be compressed, in order
5610 to reduce network bandwidth usage. If TLS is used to secure the
5611 Diameter session, then TLS compression [RFC2246] MAY be used.
5613 9.3. Accounting Application Extension and Requirements
5615 Each Diameter application (e.g., NASREQ, MobileIP), MUST define their
5616 Service-Specific AVPs that MUST be present in the Accounting-Request
5617 message in a section entitled "Accounting AVPs". The application
5618 MUST assume that the AVPs described in this document will be present
5619 in all Accounting messages, so only their respective service-specific
5620 AVPs need to be defined in this section.
5622 Applications have the option of using one or both of the following
5623 accounting application extension models:
5625 Split Accounting Service
5627 The accounting message will carry the application identifier of
5628 the Diameter base accounting application (see Section 2.4).
5629 Accounting messages maybe routed to Diameter nodes other than the
5630 corresponding Diameter application. These nodes might be
5631 centralized accounting servers that provide accounting service for
5632 multiple different Diameter applications. These nodes MUST
5633 advertise the Diameter base accounting application identifier
5634 during capabilities exchange.
5636 Accounting messages which uses the Diameter base accounting
5637 application identifier in its header MUST include the application
5638 identifier of the Diameter application it is providing service for
5639 in the Acct-Application-Id AVP. This allows the accounting server
5640 to determine which Diameter application the accounting records are
5641 for.
5643 Coupled Accounting Service
5645 The accounting messages will carry the application identifier of
5646 the application that is using it. The application itself will
5647 process the received accounting records or forward them to an
5648 accounting server. There is no accounting application
5649 advertisement required during capabilities exchange and the
5650 accounting messages will be routed the same as any of the other
5651 application messages.
5653 In cases where an application does not define its own accounting
5654 service, it is preferred that the split accounting model be used.
5656 9.4. Fault Resilience
5658 Diameter Base protocol mechanisms are used to overcome small message
5659 loss and network faults of temporary nature.
5661 Diameter peers acting as clients MUST implement the use of failover
5662 to guard against server failures and certain network failures.
5663 Diameter peers acting as agents or related off-line processing
5664 systems MUST detect duplicate accounting records caused by the
5665 sending of same record to several servers and duplication of messages
5666 in transit. This detection MUST be based on the inspection of the
5667 Session-Id and Accounting-Record-Number AVP pairs. Appendix C
5668 discusses duplicate detection needs and implementation issues.
5670 Diameter clients MAY have non-volatile memory for the safe storage of
5671 accounting records over reboots or extended network failures, network
5672 partitions, and server failures. If such memory is available, the
5673 client SHOULD store new accounting records there as soon as the
5674 records are created and until a positive acknowledgement of their
5675 reception from the Diameter Server has been received. Upon a reboot,
5676 the client MUST starting sending the records in the non-volatile
5677 memory to the accounting server with appropriate modifications in
5678 termination cause, session length, and other relevant information in
5679 the records.
5681 A further application of this protocol may include AVPs to control
5682 how many accounting records may at most be stored in the Diameter
5683 client without committing them to the non-volatile memory or
5684 transferring them to the Diameter server.
5686 The client SHOULD NOT remove the accounting data from any of its
5687 memory areas before the correct Accounting-Answer has been received.
5688 The client MAY remove oldest, undelivered or yet unacknowledged
5689 accounting data if it runs out of resources such as memory. It is an
5690 implementation dependent matter for the client to accept new sessions
5691 under this condition.
5693 9.5. Accounting Records
5695 In all accounting records, the Session-Id AVP MUST be present; the
5696 User-Name AVP MUST be present if it is available to the Diameter
5697 client.
5699 Different types of accounting records are sent depending on the
5700 actual type of accounted service and the authorization server's
5701 directions for interim accounting. If the accounted service is a
5702 one-time event, meaning that the start and stop of the event are
5703 simultaneous, then the Accounting-Record-Type AVP MUST be present and
5704 set to the value EVENT_RECORD.
5706 If the accounted service is of a measurable length, then the AVP MUST
5707 use the values START_RECORD, STOP_RECORD, and possibly,
5708 INTERIM_RECORD. If the authorization server has not directed interim
5709 accounting to be enabled for the session, two accounting records MUST
5710 be generated for each service of type session. When the initial
5711 Accounting-Request for a given session is sent, the Accounting-
5712 Record-Type AVP MUST be set to the value START_RECORD. When the last
5713 Accounting-Request is sent, the value MUST be STOP_RECORD.
5715 If the authorization server has directed interim accounting to be
5716 enabled, the Diameter client MUST produce additional records between
5717 the START_RECORD and STOP_RECORD, marked INTERIM_RECORD. The
5718 production of these records is directed by Acct-Interim-Interval as
5719 well as any re-authentication or re-authorization of the session.
5720 The Diameter client MUST overwrite any previous interim accounting
5721 records that are locally stored for delivery, if a new record is
5722 being generated for the same session. This ensures that only one
5723 pending interim record can exist on an access device for any given
5724 session.
5726 A particular value of Accounting-Sub-Session-Id MUST appear only in
5727 one sequence of accounting records from a DIAMETER client, except for
5728 the purposes of retransmission. The one sequence that is sent MUST
5729 be either one record with Accounting-Record-Type AVP set to the value
5730 EVENT_RECORD, or several records starting with one having the value
5731 START_RECORD, followed by zero or more INTERIM_RECORD and a single
5732 STOP_RECORD. A particular Diameter application specification MUST
5733 define the type of sequences that MUST be used.
5735 9.6. Correlation of Accounting Records
5737 The Diameter protocol's Session-Id AVP, which is globally unique (see
5738 Section 8.8), is used during the authorization phase to identify a
5739 particular session. Services that do not require any authorization
5740 still use the Session-Id AVP to identify sessions. Accounting
5741 messages MAY use a different Session-Id from that sent in
5742 authorization messages. Specific applications MAY require different
5743 a Session-ID for accounting messages.
5745 However, there are certain applications that require multiple
5746 accounting sub-sessions. Such applications would send messages with
5747 a constant Session-Id AVP, but a different Accounting-Sub-Session-Id
5748 AVP. In these cases, correlation is performed using the Session-Id.
5749 It is important to note that receiving a STOP_RECORD with no
5750 Accounting-Sub-Session-Id AVP when sub-sessions were originally used
5751 in the START_RECORD messages implies that all sub-sessions are
5752 terminated.
5754 Furthermore, there are certain applications where a user receives
5755 service from different access devices (e.g., Mobile IPv4), each with
5756 their own unique Session-Id. In such cases, the Acct-Multi-Session-
5757 Id AVP is used for correlation. During authorization, a server that
5758 determines that a request is for an existing session SHOULD include
5759 the Acct-Multi-Session-Id AVP, which the access device MUST include
5760 in all subsequent accounting messages.
5762 The Acct-Multi-Session-Id AVP MAY include the value of the original
5763 Session-Id. It's contents are implementation specific, but MUST be
5764 globally unique across other Acct-Multi-Session-Id, and MUST NOT
5765 change during the life of a session.
5767 A Diameter application document MUST define the exact concept of a
5768 session that is being accounted, and MAY define the concept of a
5769 multi-session. For instance, the NASREQ DIAMETER application treats
5770 a single PPP connection to a Network Access Server as one session,
5771 and a set of Multilink PPP sessions as one multi-session.
5773 9.7. Accounting Command-Codes
5775 This section defines Command-Code values that MUST be supported by
5776 all Diameter implementations that provide Accounting services.
5778 9.7.1. Accounting-Request
5780 The Accounting-Request (ACR) command, indicated by the Command-Code
5781 field set to 271 and the Command Flags' 'R' bit set, is sent by a
5782 Diameter node, acting as a client, in order to exchange accounting
5783 information with a peer.
5785 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs
5786 MUST be present. If the Vendor-Specific-Application-Id grouped AVP
5787 is present, it must have an Acct-Application-Id inside.
5789 The AVP listed below SHOULD include service specific accounting AVPs,
5790 as described in Section 9.3.
5792 Message Format
5794 ::= < Diameter Header: 271, REQ, PXY >
5795 < Session-Id >
5796 { Origin-Host }
5797 { Origin-Realm }
5798 { Destination-Realm }
5799 { Accounting-Record-Type }
5800 { Accounting-Record-Number }
5801 [ Acct-Application-Id ]
5802 [ Vendor-Specific-Application-Id ]
5803 [ User-Name ]
5804 [ Accounting-Sub-Session-Id ]
5805 [ Acct-Session-Id ]
5806 [ Acct-Multi-Session-Id ]
5807 [ Acct-Interim-Interval ]
5808 [ Accounting-Realtime-Required ]
5809 [ Origin-State-Id ]
5810 [ Event-Timestamp ]
5811 * [ Proxy-Info ]
5812 * [ Route-Record ]
5813 * [ AVP ]
5815 9.7.2. Accounting-Answer
5817 The Accounting-Answer (ACA) command, indicated by the Command-Code
5818 field set to 271 and the Command Flags' 'R' bit cleared, is used to
5819 acknowledge an Accounting-Request command. The Accounting-Answer
5820 command contains the same Session-Id as the corresponding request.
5822 Only the target Diameter Server, known as the home Diameter Server,
5823 SHOULD respond with the Accounting-Answer command.
5825 One of Acct-Application-Id and Vendor-Specific-Application-Id AVPs
5826 MUST be present. If the Vendor-Specific-Application-Id grouped AVP
5827 is present, it must have an Acct-Application-Id inside.
5829 The AVP listed below SHOULD include service specific accounting AVPs,
5830 as described in Section 9.3.
5832 Message Format
5834 ::= < Diameter Header: 271, PXY >
5835 < Session-Id >
5836 { Result-Code }
5837 { Origin-Host }
5838 { Origin-Realm }
5839 { Accounting-Record-Type }
5840 { Accounting-Record-Number }
5841 [ Acct-Application-Id ]
5842 [ Vendor-Specific-Application-Id ]
5843 [ User-Name ]
5844 [ Accounting-Sub-Session-Id ]
5845 [ Acct-Session-Id ]
5846 [ Acct-Multi-Session-Id ]
5847 [ Error-Reporting-Host ]
5848 [ Acct-Interim-Interval ]
5849 [ Accounting-Realtime-Required ]
5850 [ Origin-State-Id ]
5851 [ Event-Timestamp ]
5852 * [ Proxy-Info ]
5853 * [ AVP ]
5855 9.8. Accounting AVPs
5857 This section contains AVPs that describe accounting usage information
5858 related to a specific session.
5860 9.8.1. Accounting-Record-Type AVP
5862 The Accounting-Record-Type AVP (AVP Code 480) is of type Enumerated
5863 and contains the type of accounting record being sent. The following
5864 values are currently defined for the Accounting-Record-Type AVP:
5866 EVENT_RECORD 1
5868 An Accounting Event Record is used to indicate that a one-time
5869 event has occurred (meaning that the start and end of the event
5870 are simultaneous). This record contains all information relevant
5871 to the service, and is the only record of the service.
5873 START_RECORD 2
5875 An Accounting Start, Interim, and Stop Records are used to
5876 indicate that a service of a measurable length has been given. An
5877 Accounting Start Record is used to initiate an accounting session,
5878 and contains accounting information that is relevant to the
5879 initiation of the session.
5881 INTERIM_RECORD 3
5883 An Interim Accounting Record contains cumulative accounting
5884 information for an existing accounting session. Interim
5885 Accounting Records SHOULD be sent every time a re-authentication
5886 or re-authorization occurs. Further, additional interim record
5887 triggers MAY be defined by application-specific Diameter
5888 applications. The selection of whether to use INTERIM_RECORD
5889 records is done by the Acct-Interim-Interval AVP.
5891 STOP_RECORD 4
5893 An Accounting Stop Record is sent to terminate an accounting
5894 session and contains cumulative accounting information relevant to
5895 the existing session.
5897 9.8.2. Acct-Interim-Interval
5899 The Acct-Interim-Interval AVP (AVP Code 85) is of type Unsigned32 and
5900 is sent from the Diameter home authorization server to the Diameter
5901 client. The client uses information in this AVP to decide how and
5902 when to produce accounting records. With different values in this
5903 AVP, service sessions can result in one, two, or two+N accounting
5904 records, based on the needs of the home-organization. The following
5905 accounting record production behavior is directed by the inclusion of
5906 this AVP:
5908 1. The omission of the Acct-Interim-Interval AVP or its inclusion
5909 with Value field set to 0 means that EVENT_RECORD, START_RECORD,
5910 and STOP_RECORD are produced, as appropriate for the service.
5912 2. The inclusion of the AVP with Value field set to a non-zero value
5913 means that INTERIM_RECORD records MUST be produced between the
5914 START_RECORD and STOP_RECORD records. The Value field of this
5915 AVP is the nominal interval between these records in seconds.
5916 The Diameter node that originates the accounting information,
5917 known as the client, MUST produce the first INTERIM_RECORD record
5918 roughly at the time when this nominal interval has elapsed from
5919 the START_RECORD, the next one again as the interval has elapsed
5920 once more, and so on until the session ends and a STOP_RECORD
5921 record is produced.
5923 The client MUST ensure that the interim record production times
5924 are randomized so that large accounting message storms are not
5925 created either among records or around a common service start
5926 time.
5928 9.8.3. Accounting-Record-Number AVP
5930 The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32
5931 and identifies this record within one session. As Session-Id AVPs
5932 are globally unique, the combination of Session-Id and Accounting-
5933 Record-Number AVPs is also globally unique, and can be used in
5934 matching accounting records with confirmations. An easy way to
5935 produce unique numbers is to set the value to 0 for records of type
5936 EVENT_RECORD and START_RECORD, and set the value to 1 for the first
5937 INTERIM_RECORD, 2 for the second, and so on until the value for
5938 STOP_RECORD is one more than for the last INTERIM_RECORD.
5940 9.8.4. Acct-Session-Id AVP
5942 The Acct-Session-Id AVP (AVP Code 44) is of type OctetString is only
5943 used when RADIUS/Diameter translation occurs. This AVP contains the
5944 contents of the RADIUS Acct-Session-Id attribute.
5946 9.8.5. Acct-Multi-Session-Id AVP
5948 The Acct-Multi-Session-Id AVP (AVP Code 50) is of type UTF8String,
5949 following the format specified in Section 8.8. The Acct-Multi-
5950 Session-Id AVP is used to link together multiple related accounting
5951 sessions, where each session would have a unique Session-Id, but the
5952 same Acct-Multi-Session-Id AVP. This AVP MAY be returned by the
5953 Diameter server in an authorization answer, and MUST be used in all
5954 accounting messages for the given session.
5956 9.8.6. Accounting-Sub-Session-Id AVP
5958 The Accounting-Sub-Session-Id AVP (AVP Code 287) is of type
5959 Unsigned64 and contains the accounting sub-session identifier. The
5960 combination of the Session-Id and this AVP MUST be unique per sub-
5961 session, and the value of this AVP MUST be monotonically increased by
5962 one for all new sub-sessions. The absence of this AVP implies no
5963 sub-sessions are in use, with the exception of an Accounting-Request
5964 whose Accounting-Record-Type is set to STOP_RECORD. A STOP_RECORD
5965 message with no Accounting-Sub-Session-Id AVP present will signal the
5966 termination of all sub-sessions for a given Session-Id.
5968 9.8.7. Accounting-Realtime-Required AVP
5970 The Accounting-Realtime-Required AVP (AVP Code 483) is of type
5971 Enumerated and is sent from the Diameter home authorization server to
5972 the Diameter client or in the Accounting-Answer from the accounting
5973 server. The client uses information in this AVP to decide what to do
5974 if the sending of accounting records to the accounting server has
5975 been temporarily prevented due to, for instance, a network problem.
5977 DELIVER_AND_GRANT 1
5979 The AVP with Value field set to DELIVER_AND_GRANT means that the
5980 service MUST only be granted as long as there is a connection to
5981 an accounting server. Note that the set of alternative accounting
5982 servers are treated as one server in this sense. Having to move
5983 the accounting record stream to a backup server is not a reason to
5984 discontinue the service to the user.
5986 GRANT_AND_STORE 2
5988 The AVP with Value field set to GRANT_AND_STORE means that service
5989 SHOULD be granted if there is a connection, or as long as records
5990 can still be stored as described in Section 9.4.
5992 This is the default behavior if the AVP isn't included in the
5993 reply from the authorization server.
5995 GRANT_AND_LOSE 3
5997 The AVP with Value field set to GRANT_AND_LOSE means that service
5998 SHOULD be granted even if the records can not be delivered or
5999 stored.
6001 10. AVP Occurrence Table
6003 The following tables presents the AVPs defined in this document, and
6004 specifies in which Diameter messages they MAY, or MAY NOT be present.
6005 Note that AVPs that can only be present within a Grouped AVP are not
6006 represented in this table.
6008 The table uses the following symbols:
6010 0 The AVP MUST NOT be present in the message.
6012 0+ Zero or more instances of the AVP MAY be present in the
6013 message.
6015 0-1 Zero or one instance of the AVP MAY be present in the message.
6016 It is considered an error if there are more than one instance of
6017 the AVP.
6019 1 One instance of the AVP MUST be present in the message.
6021 1+ At least one instance of the AVP MUST be present in the
6022 message.
6024 10.1. Base Protocol Command AVP Table
6026 The table in this section is limited to the non-accounting Command
6027 Codes defined in this specification.
6029 +-----------------------------------------------+
6030 | Command-Code |
6031 +---+---+---+---+---+---+---+---+---+---+---+---+
6032 Attribute Name |CER|CEA|DPR|DPA|DWR|DWA|RAR|RAA|ASR|ASA|STR|STA|
6033 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+
6034 Acct-Interim- |0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 |
6035 Interval | | | | | | | | | | | | |
6036 Accounting-Realtime-|0 |0 |0 |0 |0 |0 |0-1|0 |0 |0 |0 |0 |
6037 Required | | | | | | | | | | | | |
6038 Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6039 Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 |
6040 Auth-Grace-Period |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6041 Auth-Request-Type |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6042 Auth-Session-State |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6043 Authorization- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6044 Lifetime | | | | | | | | | | | | |
6045 Class |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0+ |0+ |
6046 Destination-Host |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |0-1|0 |
6047 Destination-Realm |0 |0 |0 |0 |0 |0 |1 |0 |1 |0 |1 |0 |
6048 Disconnect-Cause |0 |0 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6049 Error-Message |0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|0 |0-1|
6050 Error-Reporting-Host|0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
6051 Failed-AVP |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |0 |0+ |
6052 Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6053 Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6054 Inband-Security-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6055 Multi-Round-Time-Out|0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6056 Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |
6057 Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |1 |
6058 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|
6059 Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6060 Proxy-Info |0 |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |0+ |0+ |
6061 Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |
6062 Redirect-Host-Usage |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
6063 Redirect-Max-Cache- |0 |0 |0 |0 |0 |0 |0 |0-1|0 |0-1|0 |0-1|
6064 Time | | | | | | | | | | | | |
6065 Result-Code |0 |1 |0 |1 |0 |1 |0 |1 |0 |0 |0 |1 |
6066 Re-Auth-Request-Type|0 |0 |0 |0 |0 |0 |1 |0 |0 |0 |0 |0 |
6067 Route-Record |0 |0 |0 |0 |0 |0 |0+ |0 |0+ |0 |0+ |0 |
6068 Session-Binding |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6069 Session-Id |0 |0 |0 |0 |0 |0 |1 |1 |1 |1 |1 |1 |
6070 Session-Server- |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6071 Failover | | | | | | | | | | | | |
6072 Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6073 Supported-Vendor-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6074 Termination-Cause |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |1 |0 |
6075 User-Name |0 |0 |0 |0 |0 |0 |0-1|0-1|0-1|0-1|0-1|0-1|
6076 Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6077 Vendor-Specific- |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |0 |0 |0 |
6078 Application-Id | | | | | | | | | | | | |
6079 --------------------+---+---+---+---+---+---+---+---+---+---+---+---+
6081 10.2. Accounting AVP Table
6083 The table in this section is used to represent which AVPs defined in
6084 this document are to be present in the Accounting messages. These
6085 AVP occurrence requirements are guidelines, which may be expanded,
6086 and/or overridden by application-specific requirements in the
6087 Diameter applications documents.
6089 +-----------+
6090 | Command |
6091 | Code |
6092 +-----+-----+
6093 Attribute Name | ACR | ACA |
6094 ------------------------------+-----+-----+
6095 Acct-Interim-Interval | 0-1 | 0-1 |
6096 Acct-Multi-Session-Id | 0-1 | 0-1 |
6097 Accounting-Record-Number | 1 | 1 |
6098 Accounting-Record-Type | 1 | 1 |
6099 Acct-Session-Id | 0-1 | 0-1 |
6100 Accounting-Sub-Session-Id | 0-1 | 0-1 |
6101 Accounting-Realtime-Required | 0-1 | 0-1 |
6102 Acct-Application-Id | 0-1 | 0-1 |
6103 Auth-Application-Id | 0 | 0 |
6104 Class | 0+ | 0+ |
6105 Destination-Host | 0-1 | 0 |
6106 Destination-Realm | 1 | 0 |
6107 Error-Reporting-Host | 0 | 0+ |
6108 Event-Timestamp | 0-1 | 0-1 |
6109 Origin-Host | 1 | 1 |
6110 Origin-Realm | 1 | 1 |
6111 Proxy-Info | 0+ | 0+ |
6112 Route-Record | 0+ | 0+ |
6113 Result-Code | 0 | 1 |
6114 Session-Id | 1 | 1 |
6115 Termination-Cause | 0-1 | 0-1 |
6116 User-Name | 0-1 | 0-1 |
6117 Vendor-Specific-Application-Id| 0-1 | 0-1 |
6118 ------------------------------+-----+-----+
6120 11. IANA Considerations
6122 This section provides guidance to the Internet Assigned Numbers
6123 Authority (IANA) regarding registration of values related to the
6124 Diameter protocol, in accordance with BCP 26 [RFC2434]. The
6125 following policies are used here with the meanings defined in BCP 26:
6126 "Private Use", "First Come First Served", "Expert Review",
6127 "Specification Required", "IETF Consensus", "Standards Action".
6129 This section explains the criteria to be used by the IANA for
6130 assignment of numbers within namespaces defined within this document.
6132 Diameter is not intended as a general purpose protocol, and
6133 allocations SHOULD NOT be made for purposes unrelated to
6134 authentication, authorization or accounting.
6136 For registration requests where a Designated Expert should be
6137 consulted, the responsible IESG area director should appoint the
6138 Designated Expert. For Designated Expert with Specification
6139 Required, the request is posted to the AAA WG mailing list (or, if it
6140 has been disbanded, a successor designated by the Area Director) for
6141 comment and review, and MUST include a pointer to a public
6142 specification. Before a period of 30 days has passed, the Designated
6143 Expert will either approve or deny the registration request and
6144 publish a notice of the decision to the AAA WG mailing list or its
6145 successor. A denial notice must be justified by an explanation and,
6146 in the cases where it is possible, concrete suggestions on how the
6147 request can be modified so as to become acceptable.
6149 11.1. AVP Header
6151 As defined in Section 4, the AVP header contains three fields that
6152 requires IANA namespace management; the AVP Code, Vendor-ID and Flags
6153 field.
6155 11.1.1. AVP Codes
6157 The AVP Code namespace is used to identify attributes. There are
6158 multiple namespaces. Vendors can have their own AVP Codes namespace
6159 which will be identified by their Vendor-ID (also known as
6160 Enterprise-Number) and they control the assignments of their vendor-
6161 specific AVP codes within their own namespace. The absence of a
6162 Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA
6163 controlled AVP Codes namespace. The AVP Codes and sometimes also
6164 possible values in an AVP are controlled and maintained by IANA.
6166 AVP Code 0 is not used. AVP Codes 1-255 are managed separately as
6167 RADIUS Attribute Types [RADTYPE]. This document defines the AVP
6168 Codes 257-274, 276-285, 287, 291-300, 480, 483 and 485-486. See
6169 Section 4.5 for the assignment of the namespace in this
6170 specification.
6172 AVPs may be allocated following Designated Expert with Specification
6173 Required [RFC2434]. Release of blocks of AVPs (more than 3 at a time
6174 for a given purpose) should require IETF Consensus.
6176 Note that Diameter defines a mechanism for Vendor-Specific AVPs,
6177 where the Vendor-Id field in the AVP header is set to a non-zero
6178 value. Vendor-Specific AVPs codes are for Private Use and should be
6179 encouraged instead of allocation of global attribute types, for
6180 functions specific only to one vendor's implementation of Diameter,
6181 where no interoperability is deemed useful. Where a Vendor-Specific
6182 AVP is implemented by more than one vendor, allocation of global AVPs
6183 should be encouraged instead.
6185 11.1.2. AVP Flags
6187 There are 8 bits in the AVP Flags field of the AVP header, defined in
6188 Section 4. This document assigns bit 0 ('V'endor Specific), bit 1
6189 ('M'andatory) and bit 2 ('P'rotected). The remaining bits should
6190 only be assigned via a Standards Action [RFC2434].
6192 11.2. Diameter Header
6194 As defined in Section 3, the Diameter header contains two fields that
6195 require IANA namespace management; Command Code and Command Flags.
6197 11.2.1. Command Codes
6199 The Command Code namespace is used to identify Diameter commands.
6200 The values 0-255 are reserved for RADIUS backward compatibility, and
6201 are defined as "RADIUS Packet Type Codes" in [RADTYPE]. Values 256-
6202 16,777,213 are for permanent, standard commands, allocated by IETF
6203 Consensus [RFC2434]. This document defines the Command Codes 257,
6204 258, 271, 274-275, 280 and 282. See Section 3.1 for the assignment
6205 of the namespace in this specification.
6207 The values 16,777,214 and 16,777,215 (hexadecimal values 0xfffffe -
6208 0xffffff) are reserved for experimental commands. As these codes are
6209 only for experimental and testing purposes, no guarantee is made for
6210 interoperability between Diameter peers using experimental commands,
6211 as outlined in [IANA-EXP].
6213 11.2.2. Command Flags
6215 There are eight bits in the Command Flags field of the Diameter
6216 header. This document assigns bit 0 ('R'equest), bit 1 ('P'roxy),
6217 bit 2 ('E'rror) and bit 3 ('T'). Bits 4 through 7 MUST only be
6218 assigned via a Standards Action [RFC2434].
6220 11.3. Application Identifiers
6222 As defined in Section 2.4, the Application Identifier is used to
6223 identify a specific Diameter Application. There are standards-track
6224 application ids and vendor specific application ids.
6226 IANA [RFC2434] has assigned the range 0x00000001 to 0x00ffffff for
6227 standards-track applications; and 0x01000000 - 0xfffffffe for vendor
6228 specific applications, on a first-come, first-served basis. The
6229 following values are allocated.
6231 Diameter Common Messages 0
6232 NASREQ 1 [RFC4005]
6233 Mobile-IP 2 [RFC4004]
6234 Diameter Base Accounting 3
6235 Relay 0xffffffff
6237 Assignment of standards-track application IDs are by Designated
6238 Expert with Specification Required [RFC2434].
6240 Both Auth-Application-Id and Acct-Application-Id AVPs use the same
6241 Application Identifier space. A diameter node advertising itself as
6242 a relay agent MUST set either Application-Id or Acct-Application-Id
6243 to 0xffffffff.
6245 Vendor-Specific Application Identifiers, are for Private Use. Vendor-
6246 Specific Application Identifiers are assigned on a First Come, First
6247 Served basis by IANA.
6249 11.4. AVP Values
6251 Certain AVPs in Diameter define a list of values with various
6252 meanings. For attributes other than those specified in this section,
6253 adding additional values to the list can be done on a First Come,
6254 First Served basis by IANA.
6256 11.4.1. Result-Code AVP Values
6258 As defined in Section 7.1, the Result-Code AVP (AVP Code 268) defines
6259 the values 1001, 2001-2002, 3001-3012, 4001-4003 and 5001-5021.
6261 All remaining values are available for assignment via IETF Consensus
6262 [RFC2434].
6264 11.4.2. Accounting-Record-Type AVP Values
6266 As defined in Section 9.8.1, the Accounting-Record-Type AVP (AVP Code
6267 480) defines the values 1-4. All remaining values are available for
6268 assignment via IETF Consensus [RFC2434].
6270 11.4.3. Termination-Cause AVP Values
6272 As defined in Section 8.15, the Termination-Cause AVP (AVP Code 295)
6273 defines the values 1-8. All remaining values are available for
6274 assignment via IETF Consensus [RFC2434].
6276 11.4.4. Redirect-Host-Usage AVP Values
6278 As defined in Section 6.13, the Redirect-Host-Usage AVP (AVP Code
6279 261) defines the values 0-5. All remaining values are available for
6280 assignment via IETF Consensus [RFC2434].
6282 11.4.5. Session-Server-Failover AVP Values
6284 As defined in Section 8.18, the Session-Server-Failover AVP (AVP Code
6285 271) defines the values 0-3. All remaining values are available for
6286 assignment via IETF Consensus [RFC2434].
6288 11.4.6. Session-Binding AVP Values
6290 As defined in Section 8.17, the Session-Binding AVP (AVP Code 270)
6291 defines the bits 1-4. All remaining bits are available for
6292 assignment via IETF Consensus [RFC2434].
6294 11.4.7. Disconnect-Cause AVP Values
6296 As defined in Section 5.4.3, the Disconnect-Cause AVP (AVP Code 273)
6297 defines the values 0-2. All remaining values are available for
6298 assignment via IETF Consensus [RFC2434].
6300 11.4.8. Auth-Request-Type AVP Values
6302 As defined in Section 8.7, the Auth-Request-Type AVP (AVP Code 274)
6303 defines the values 1-3. All remaining values are available for
6304 assignment via IETF Consensus [RFC2434].
6306 11.4.9. Auth-Session-State AVP Values
6308 As defined in Section 8.11, the Auth-Session-State AVP (AVP Code 277)
6309 defines the values 0-1. All remaining values are available for
6310 assignment via IETF Consensus [RFC2434].
6312 11.4.10. Re-Auth-Request-Type AVP Values
6314 As defined in Section 8.12, the Re-Auth-Request-Type AVP (AVP Code
6315 285) defines the values 0-1. All remaining values are available for
6316 assignment via IETF Consensus [RFC2434].
6318 11.4.11. Accounting-Realtime-Required AVP Values
6320 As defined in Section 9.8.7, the Accounting-Realtime-Required AVP
6321 (AVP Code 483) defines the values 1-3. All remaining values are
6322 available for assignment via IETF Consensus [RFC2434].
6324 11.4.12. Inband-Security-Id AVP (code 299)
6326 As defined in Section 6.10, the Inband-Security-Id AVP (AVP Code 299)
6327 defines the values 0-1. All remaining values are available for
6328 assignment via IETF Consensus [RFC2434].
6330 11.5. Diameter TCP/SCTP Port Numbers
6332 The IANA has assigned TCP and SCTP port number 3868 to Diameter.
6334 11.6. NAPTR Service Fields
6336 The registration in the RFC MUST include the following information:
6338 Service Field: The service field being registered. An example for a
6339 new fictitious transport protocol called NCTP might be "AAA+D2N".
6341 Protocol: The specific transport protocol associated with that
6342 service field. This MUST include the name and acronym for the
6343 protocol, along with reference to a document that describes the
6344 transport protocol. For example - "New Connectionless Transport
6345 Protocol (NCTP), RFC 5766".
6347 Name and Contact Information: The name, address, email address and
6348 telephone number for the person performing the registration.
6350 The following values have been placed into the registry:
6352 Services Field Protocol
6354 AAA+D2T TCP
6355 AAA+D2S SCTP
6357 12. Diameter protocol related configurable parameters
6359 This section contains the configurable parameters that are found
6360 throughout this document:
6362 Diameter Peer
6364 A Diameter entity MAY communicate with peers that are statically
6365 configured. A statically configured Diameter peer would require
6366 that either the IP address or the fully qualified domain name
6367 (FQDN) be supplied, which would then be used to resolve through
6368 DNS.
6370 Routing Table
6372 A Diameter proxy server routes messages based on the realm portion
6373 of a Network Access Identifier (NAI). The server MUST have a
6374 table of Realm Names, and the address of the peer to which the
6375 message must be forwarded to. The routing table MAY also include
6376 a "default route", which is typically used for all messages that
6377 cannot be locally processed.
6379 Tc timer
6381 The Tc timer controls the frequency that transport connection
6382 attempts are done to a peer with whom no active transport
6383 connection exists. The recommended value is 30 seconds.
6385 13. Security Considerations
6387 The Diameter base protocol assumes that messages maybe secured by
6388 using TLS. As an alternative, IPSec can be also be used to secure
6389 Diameter peer connections but its usage is transparent from the
6390 Diameter node and Diameter protocol perspective. These security
6391 mechanism is acceptable in environments where there is no untrusted
6392 third party agent.
6394 Diameter clients, such as Network Access Servers (NASes) and Mobility
6395 Agents MAY support TLS [RFC2246]. Diameter servers MUST support TLS.
6396 Diameter implementations SHOULD use transmission-level security of
6397 some kind (IPsec or TLS) on each connection.
6399 If a Diameter connection is to be protected via TLS, then the CER/CEA
6400 exchange MUST include an Inband-Security-ID AVP with a value of TLS.
6401 For TLS usage, a TLS handshake will begin when both ends are in the
6402 open state, after completion of the CER/CEA exchange. If the TLS
6403 handshake is successful, all further messages will be sent via TLS.
6404 If the handshake fails, both ends move to the closed state. See
6405 Sections 13.1 for more details.
6407 13.1. TLS Usage
6409 A Diameter node that initiates a connection to another Diameter node
6410 acts as a TLS client according to [RFC2246], and a Diameter node that
6411 accepts a connection acts as a TLS server. Diameter nodes
6412 implementing TLS for security MUST mutually authenticate as part of
6413 TLS session establishment. In order to ensure mutual authentication,
6414 the Diameter node acting as TLS server must request a certificate
6415 from the Diameter node acting as TLS client, and the Diameter node
6416 acting as TLS client MUST be prepared to supply a certificate on
6417 request.
6419 Diameter nodes MUST be able to negotiate the following TLS cipher
6420 suites:
6422 TLS_RSA_WITH_RC4_128_MD5
6423 TLS_RSA_WITH_RC4_128_SHA
6424 TLS_RSA_WITH_3DES_EDE_CBC_SHA
6426 Diameter nodes SHOULD be able to negotiate the following TLS cipher
6427 suite:
6429 TLS_RSA_WITH_AES_128_CBC_SHA
6431 Diameter nodes MAY negotiate other TLS cipher suites.
6433 13.2. Peer-to-Peer Considerations
6435 As with any peer-to-peer protocol, proper configuration of the trust
6436 model within a Diameter peer is essential to security. When
6437 certificates are used, it is necessary to configure the root
6438 certificate authorities trusted by the Diameter peer. These root CAs
6439 are likely to be unique to Diameter usage and distinct from the root
6440 CAs that might be trusted for other purposes such as Web browsing.
6441 In general, it is expected that those root CAs will be configured so
6442 as to reflect the business relationships between the organization
6443 hosting the Diameter peer and other organizations. As a result, a
6444 Diameter peer will typically not be configured to allow connectivity
6445 with any arbitrary peer. With certificate authentication, Diameter
6446 peers may not be known beforehand and therefore peer discovery may be
6447 required.
6449 14. References
6451 14.1. Normative References
6453 [FLOATPOINT]
6454 Institute of Electrical and Electronics Engineers, "IEEE
6455 Standard for Binary Floating-Point Arithmetic, ANSI/IEEE
6456 Standard 754-1985", August 1985.
6458 [IANAADFAM]
6459 IANA,, "Address Family Numbers",
6460 http://www.iana.org/assignments/address-family-numbers.
6462 [RADTYPE] IANA,, "RADIUS Types",
6463 http://www.iana.org/assignments/radius-types.
6465 [IPV4] Postel, J., "Internet Protocol", RFC 791, September 1981.
6467 [TCP] Postel, J., "Transmission Control Protocol", RFC 793,
6468 January 1981.
6470 [RFC3539] Aboba, B. and J. Wood, "Authentication, Authorization and
6471 Accounting (AAA) Transport Profile", RFC 3539, June 2003.
6473 [RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and
6474 P. McCann, "Diameter Mobile IPv4 Application", RFC 4004,
6475 August 2005.
6477 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
6478 "Diameter Network Access Server Application", RFC 4005,
6479 August 2005.
6481 [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
6482 Loughney, "Diameter Credit-Control Application", RFC 4006,
6483 August 2005.
6485 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
6486 Authentication Protocol (EAP) Application", RFC 4072,
6487 August 2005.
6489 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M.,
6490 Canales-Valenzuela, C., and K. Tammi, "Diameter Session
6491 Initiation Protocol (SIP) Application", RFC 4740,
6492 November 2006.
6494 [RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
6495 Specifications: ABNF", RFC 2234, November 1997.
6497 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by
6498 an On-line Database", RFC 3232, January 2002.
6500 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
6501 Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
6503 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
6504 "Definition of the Differentiated Services Field (DS
6505 Field) in the IPv4 and IPv6 Headers", RFC 2474,
6506 December 1998.
6508 [RFC2284] Blunk, L. and J. Vollbrecht, "PPP Extensible
6509 Authentication Protocol (EAP)", RFC 2284, March 1998.
6511 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
6512 IANA Considerations Section in RFCs", BCP 26, RFC 2434,
6513 October 1998.
6515 [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
6516 (IKE)", RFC 2409, November 1998.
6518 [RFC2373] Hinden, R. and S. Deering, "IP Version 6 Addressing
6519 Architecture", RFC 2373, July 1998.
6521 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
6522 Requirement Levels", BCP 14, RFC 2119, March 1997.
6524 [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
6525 Network Access Identifier", RFC 4282, December 2005.
6527 [RFC2915] Mealling, M. and R. Daniel, "The Naming Authority Pointer
6528 (NAPTR) DNS Resource Record", RFC 2915, September 2000.
6530 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
6531 A., Peterson, J., Sparks, R., Handley, M., and E.
6532 Schooler, "SIP: Session Initiation Protocol", RFC 3261,
6533 June 2002.
6535 [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
6536 Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
6537 Zhang, L., and V. Paxson, "Stream Control Transmission
6538 Protocol", RFC 2960, October 2000.
6540 [RFC2030] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
6541 for IPv4, IPv6 and OSI", RFC 2030, October 1996.
6543 [RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
6544 RFC 2246, January 1999.
6546 [RFC2396] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
6547 Resource Identifiers (URI): Generic Syntax", RFC 2396,
6548 August 1998.
6550 [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO
6551 10646", RFC 2279, January 1998.
6553 14.2. Informational References
6555 [RFC2989] Aboba, B., Calhoun, P., Glass, S., Hiller, T., McCann, P.,
6556 Shiino, H., Zorn, G., Dommety, G., C.Perkins, B.Patil,
6557 D.Mitton, S.Manning, M.Beadles, P.Walsh, X.Chen,
6558 S.Sivalingham, A.Hameed, M.Munson, S.Jacobs, B.Lim,
6559 B.Hirschman, R.Hsu, Y.Xu, E.Campell, S.Baba, and E.Jaques,
6560 "Criteria for Evaluating AAA Protocols for Network
6561 Access", RFC 2989, November 2000.
6563 [RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction to
6564 Accounting Management", RFC 2975, October 2000.
6566 [RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
6567 Aboba, "Dynamic Authorization Extensions to Remote
6568 Authentication Dial In User Service (RADIUS)", RFC 3576,
6569 July 2003.
6571 [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,
6572 RFC 1661, July 1994.
6574 [RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy
6575 Implementation in Roaming", RFC 2607, June 1999.
6577 [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.
6579 [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS
6580 Extensions", RFC 2869, June 2000.
6582 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
6583 "Remote Authentication Dial In User Service (RADIUS)",
6584 RFC 2865, June 2000.
6586 [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6",
6587 RFC 3162, August 2001.
6589 [RFC2194] Aboba, B., Lu, J., Alsop, J., Ding, J., and W. Wang,
6590 "Review of Roaming Implementations", RFC 2194,
6591 September 1997.
6593 [RFC2477] Aboba, B. and G. Zorn, "Criteria for Evaluating Roaming
6594 Protocols", RFC 2477, January 1999.
6596 [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
6597 Internet Protocol", RFC 2401, November 1998.
6599 [RFC1492] Finseth, C., "An Access Control Protocol, Sometimes Called
6600 TACACS", RFC 1492, July 1993.
6602 [IANA-EXP]
6603 Narten, T., "Assigning Experimental and Testing Numbers
6604 Considered Useful, Work in Progress.".
6606 Appendix A. Acknowledgements
6608 The authors would like to thank the following people that have
6609 provided proposals and contributions to this document:
6611 To Vishnu Ram and Satendra Gera for their contributions on
6612 Capabilities Updates, Predictive Loop Avoidance as well as many other
6613 technical proposals. To Tolga Asveren for his insights and
6614 contributions on almost all of the proposed solutions incorporated
6615 into this document. To Timothy Smith for helping on the Capabilities
6616 Updates and other topics. To Tony Zhang for providing fixes to loop
6617 holes on composing Failed-AVPs as well as many other issues and
6618 topics. To Jan Nordqvist for clearly stating the usage of
6619 application ids. To Anders Kristensen for providing needed technical
6620 opinions. To David Frascone for providing invaluable review of the
6621 document.
6623 Special thanks also to people who have provided invaluable comments
6624 and inputs especially in resolving controversial issues:
6626 Glen Zorn, Yoshihiro Ohba, Marco Stura, and Pasi Eronen.
6628 Finally, we would like to thank the original authors of this
6629 document:
6631 Pat Calhoun, John Loughney, Jari Arkko, Erik Guttman and Glen Zorn.
6633 Their invaluable knowledge and experience has given us a robust and
6634 flexible AAA protocol that many people have seen great value in
6635 adopting. We greatly appreciate their support and stewardship for
6636 the continued improvements of Diameter as a protocol. We would also
6637 like to extend our gratitude to folks aside from the authors who have
6638 assisted and contributed to the original version of this document.
6639 Their efforts significantly contributed to the success of Diameter.
6641 Appendix B. NAPTR Example
6643 As an example, consider a client that wishes to resolve aaa:ex.com.
6644 The client performs a NAPTR query for that domain, and the following
6645 NAPTR records are returned:
6647 ;; order pref flags service regexp replacement
6648 IN NAPTR 50 50 "s" "AAA+D2S" ""
6649 _diameter._sctp.example.com IN NAPTR 100 50 "s" "AAA+D2T"
6650 "" _aaa._tcp.example.com
6652 This indicates that the server supports SCTP, and TCP, in that order.
6653 If the client supports over SCTP, SCTP will be used, targeted to a
6654 host determined by an SRV lookup of _diameter._sctp.ex.com. That
6655 lookup would return:
6657 ;; Priority Weight Port Target
6658 IN SRV 0 1 5060 server1.example.com IN SRV 0
6659 2 5060 server2.example.com
6661 Appendix C. Duplicate Detection
6663 As described in Section 9.4, accounting record duplicate detection is
6664 based on session identifiers. Duplicates can appear for various
6665 reasons:
6667 o Failover to an alternate server. Where close to real-time
6668 performance is required, failover thresholds need to be kept low
6669 and this may lead to an increased likelihood of duplicates.
6670 Failover can occur at the client or within Diameter agents.
6672 o Failure of a client or agent after sending of a record from non-
6673 volatile memory, but prior to receipt of an application layer ACK
6674 and deletion of the record. record to be sent. This will result
6675 in retransmission of the record soon after the client or agent has
6676 rebooted.
6678 o Duplicates received from RADIUS gateways. Since the
6679 retransmission behavior of RADIUS is not defined within [RFC2865],
6680 the likelihood of duplication will vary according to the
6681 implementation.
6683 o Implementation problems and misconfiguration.
6685 The T flag is used as an indication of an application layer
6686 retransmission event, e.g., due to failover to an alternate server.
6687 It is defined only for request messages sent by Diameter clients or
6688 agents. For instance, after a reboot, a client may not know whether
6689 it has already tried to send the accounting records in its non-
6690 volatile memory before the reboot occurred. Diameter servers MAY use
6691 the T flag as an aid when processing requests and detecting duplicate
6692 messages. However, servers that do this MUST ensure that duplicates
6693 are found even when the first transmitted request arrives at the
6694 server after the retransmitted request. It can be used only in cases
6695 where no answer has been received from the Server for a request and
6696 the request is sent again, (e.g., due to a failover to an alternate
6697 peer, due to a recovered primary peer or due to a client re-sending a
6698 stored record from non-volatile memory such as after reboot of a
6699 client or agent).
6701 In some cases the Diameter accounting server can delay the duplicate
6702 detection and accounting record processing until a post-processing
6703 phase takes place. At that time records are likely to be sorted
6704 according to the included User-Name and duplicate elimination is easy
6705 in this case. In other situations it may be necessary to perform
6706 real-time duplicate detection, such as when credit limits are imposed
6707 or real-time fraud detection is desired.
6709 In general, only generation of duplicates due to failover or re-
6710 sending of records in non-volatile storage can be reliably detected
6711 by Diameter clients or agents. In such cases the Diameter client or
6712 agents can mark the message as possible duplicate by setting the T
6713 flag. Since the Diameter server is responsible for duplicate
6714 detection, it can choose to make use of the T flag or not, in order
6715 to optimize duplicate detection. Since the T flag does not affect
6716 interoperability, and may not be needed by some servers, generation
6717 of the T flag is REQUIRED for Diameter clients and agents, but MAY be
6718 implemented by Diameter servers.
6720 As an example, it can be usually be assumed that duplicates appear
6721 within a time window of longest recorded network partition or device
6722 fault, perhaps a day. So only records within this time window need
6723 to be looked at in the backward direction. Secondly, hashing
6724 techniques or other schemes, such as the use of the T flag in the
6725 received messages, may be used to eliminate the need to do a full
6726 search even in this set except for rare cases.
6728 The following is an example of how the T flag may be used by the
6729 server to detect duplicate requests.
6731 A Diameter server MAY check the T flag of the received message to
6732 determine if the record is a possible duplicate. If the T flag is
6733 set in the request message, the server searches for a duplicate
6734 within a configurable duplication time window backward and
6735 forward. This limits database searching to those records where
6736 the T flag is set. In a well run network, network partitions and
6737 device faults will presumably be rare events, so this approach
6738 represents a substantial optimization of the duplicate detection
6739 process. During failover, it is possible for the original record
6740 to be received after the T flag marked record, due to differences
6741 in network delays experienced along the path by the original and
6742 duplicate transmissions. The likelihood of this occurring
6743 increases as the failover interval is decreased. In order to be
6744 able to detect out of order duplicates, the Diameter server should
6745 use backward and forward time windows when performing duplicate
6746 checking for the T flag marked request. For example, in order to
6747 allow time for the original record to exit the network and be
6748 recorded by the accounting server, the Diameter server can delay
6749 processing records with the T flag set until a time period
6750 TIME_WAIT + RECORD_PROCESSING_TIME has elapsed after the closing
6751 of the original transport connection. After this time period has
6752 expired, then it may check the T flag marked records against the
6753 database with relative assurance that the original records, if
6754 sent, have been received and recorded.
6756 Authors' Addresses
6758 Victor Fajardo (editor)
6759 Toshiba America Research
6760 One Telcordia Drive, 1S-222
6761 Piscataway, NJ 08854
6762 USA
6764 Phone: 1 908-421-1845
6765 Email: vfajardo@tari.toshiba.com
6767 Jari Arkko
6768 Ericsson Research
6769 02420 Jorvas
6770 Finland
6772 Phone: +358 40 5079256
6773 Email: jari.arkko@ericsson.com
6775 John Loughney
6776 Nokia Research Center
6777 Itamerenkatu 11-13
6778 Helsinki, 00180
6779 Finland
6781 Phone: +358 50 483 6242
6782 Email: john.loughney@nokia.com
6784 Full Copyright Statement
6786 Copyright (C) The IETF Trust (2007).
6788 This document is subject to the rights, licenses and restrictions
6789 contained in BCP 78, and except as set forth therein, the authors
6790 retain all their rights.
6792 This document and the information contained herein are provided on an
6793 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
6794 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
6795 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
6796 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
6797 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
6798 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
6800 Intellectual Property
6802 The IETF takes no position regarding the validity or scope of any
6803 Intellectual Property Rights or other rights that might be claimed to
6804 pertain to the implementation or use of the technology described in
6805 this document or the extent to which any license under such rights
6806 might or might not be available; nor does it represent that it has
6807 made any independent effort to identify any such rights. Information
6808 on the procedures with respect to rights in RFC documents can be
6809 found in BCP 78 and BCP 79.
6811 Copies of IPR disclosures made to the IETF Secretariat and any
6812 assurances of licenses to be made available, or the result of an
6813 attempt made to obtain a general license or permission for the use of
6814 such proprietary rights by implementers or users of this
6815 specification can be obtained from the IETF on-line IPR repository at
6816 http://www.ietf.org/ipr.
6818 The IETF invites any interested party to bring to its attention any
6819 copyrights, patents or patent applications, or other proprietary
6820 rights that may cover technology that may be required to implement
6821 this standard. Please address the information to the IETF at
6822 ietf-ipr@ietf.org.
6824 Acknowledgment
6826 Funding for the RFC Editor function is provided by the IETF
6827 Administrative Support Activity (IASA).