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AAA Working Group Pat R. Calhoun
Internet-Draft Sun Microsystems, Inc.
Category: Standards Track Haseeb Akhtar
<draft-ietf-aaa-diameter-03.txt> Nortel Networks
Jari Arkko
Oy LM Ericsson Ab
Erik Guttman
Sun Microsystems, Inc.
Allan C. Rubens
Tut Systems, Inc.
Glen Zorn
Cisco Systems, Inc.
May 2001
Diameter Base Protocol
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at:
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at:
http://www.ietf.org/shadow.html.
Distribution of this memo is unlimited.
Copyright (C) The Internet Society 2001. All Rights Reserved.
Abstract
The Diameter base protocol is intended to provide a AAA framework for
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Mobile-IP, NASREQ and ROAMOPS. This draft specifies the message
format, transport, error reporting and security services to be used
by all Diameter extensions and MUST be supported by all Diameter
implementations.
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Table of Contents
1.0 Introduction
1.1 Diameter Protocol
1.2 Requirements language
1.3 Terminology
2.0 Protocol Overview
2.1 Transport
2.2 Securing Diameter Messages
2.3 Diameter Protocol Extensibility
2.3.1 Defining new AVP Values
2.3.2 Creating new AVPs
2.3.3 Creating a new Diameter extension
2.3.4 Extension authentication procedures
2.4 Diameter Extensions
2.5 Diameter Server Discovery
3.0 Diameter Header
3.1 Command Code Definitions
3.2 Command Code ABNF specification
3.3 Diameter Command Naming Conventions
3.3.1 Request/Answer
3.3.2 Query/Response
3.3.3 Indication
4.0 Diameter AVPs
4.1 AVP Header
4.2 Optional Header Elements
4.3 AVP Data Formats
4.4 Grouped AVP Values
4.4.1 Example AVP with a Grouped Data type
4.5 Diameter Base Protocol AVPs
5.0 Message Forwarding
5.1 Origin-FQDN AVP
5.2 Origin-Realm AVP
5.3 Destination-FQDN AVP
6.0 Capabilities Negotiation
6.2 Device-Reboot-Ind (DRI) Command
6.2.1 Vendor-Id AVP
6.2.2 Firmware-Revision AVP
6.2.3 Auth-Extension-Id AVP
6.2.4 Host-IP-Address AVP
6.2.5 Supported-Vendor-Id AVP
6.2.6 Product-Name AVP
6.2.7 Acct-Extension-Id AVP
7.0 Transport Failure Detection
7.1 Device-Watchdog-Request
7.2 Device-Watchdog-Answer
7.3 Failover/Failback Procedures
8.0 Peer State Machine
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8.1 States
8.2 Events
8.3 Actions
8.4 The Election Process
9.0 Per-Hop Error Signaling
9.1 Device-Status-Ind
9.1.1 DSI-Event AVP
9.1.1.1 Informational Events
9.1.1.2 Redirect Event
9.1.1.3 Transient Failure Events
9.1.1.4 Permanent Failure Events
10.0 End-to-End Error Signaling
10.1 Message-Reject-Ind (MRI) Command
10.1.1 Failed-AVP AVP
10.1.2 Failed-Command-Code AVP
10.1.3 Offending-Command-Code AVP
10.1.4 Offending-AVP AVP
10.1.5 Failed-Vendor-Id AVP
10.2 Result-Code AVP
10.2.1 Informational
10.2.2 Success
10.2.3 Transient Failures
10.2.4 Permanent Failures
10.3 Error-Message AVP
10.4 Error-Reporting-FQDN AVP
11.0 "User" Sessions
11.1 Authorization Session State Machine
11.2 Accounting Session State Machine
11.3 Session-Id AVP
11.4 Authorization-Lifetime AVP
11.5 Session-Timeout AVP
11.6 User-Name AVP
11.7 Max-Wait-Time AVP
11.8 Session Movement
11.8.1 Original-Session-Id AVP
11.9 Session Termination
11.9.1 Session-Termination-Ind
11.9.2 Session-Termination-Request
11.9.3 Session-Termination-Answer
12.0 Message Routing
12.1 Realm-Based Message Routing
12.1.1 Realm-Based Routing Table
12.2 Proxy and Redirect Server handling of requests
12.2.1 Proxy and Redirect Server handling of requests
12.3 Redirect Server
12.3.1 Redirect-Host AVP
12.3.2 Redirect-Host-Address AVP
12.3.3 Redirect-Host-Port AVP
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12.4 Proxy Server
12.4.1 Proxying Request, Query and Indication messages
12.4.2 Proxying Response and Answer messages
12.4.3 Route-Record AVP
12.4.4 Proxy-Info AVP
12.4.5 Proxy-Address AVP
12.4.6 Proxy-State AVP
12.4.7 Destination-Realm AVP
12.5 Applying Local Policies
12.6 Hiding Network Topology
12.7 Loop Detection
13.0 Accounting
13.1 Server Directed Model
13.2 Protocol Messages
13.3 Extension document requirements
13.4 Fault Resilience
13.5 Accounting Records
14.0 Accounting Command-Codes
14.1 Accounting-Request (ACR) Command
14.2 Accounting-Answer (ACA) Command
14.3 Accounting-Status-Ind (ASI) Command
14.4 Accounting-Poll-Ind (API) Command
15.0 Accounting AVPs
15.1 Accounting-Record-Type AVP
15.2 Accounting-Interim-Interval AVP
15.3 Accounting-Record-Number AVP
15.4 Accounting-State AVP
15.5 Accounting-Session-Id AVP
16.0 AVP Occurrence Table
16.1 Base Protocol Command AVP Table
16.2 Accounting AVP Table
17.0 IANA Considerations
17.1 AVP Header
17.1.1 AVP Code
17.1.2 AVP Flags
17.2 Diameter Header
17.2.1 Command Codes
17.2.2 Message Flags
17.3 Extension Identifier Values
17.4 Result-Code AVP Values
17.5 DSI-Event AVP Values
17.6 Accounting-State AVP Values
17.7 Accounting-Record-Type AVP Values
17.8 Diameter TCP/SCTP Port Numbers
18.0 Open Issues
19.0 Diameter protocol related configurable parameters
20.0 Security Considerations
21.0 References
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22.0 Acknowledgements
23.0 Authors' Addresses
24.0 Full Copyright Statement
Appendix A. Diameter Service Template
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1.0 Introduction
Historically, the RADIUS protocol has been used to provide AAA
services for dial-up PPP [42] and terminal server access. Over time,
routers and network access servers (NAS) have increased in complexity
and density, making the RADIUS protocol increasingly unsuitable for
use in such networks.
The Roaming Operations Working Group (ROAMOPS) has published a set of
specifications [20, 43, 44] that define how a PPP user can gain
access to the Internet without having to dial into his/her home
service provider's modem pool. This is achieved by allowing service
providers to cross-authenticate their users. Effectively, a user can
dial into any service provider's point of presence (POP) that has a
roaming agreement with his/her home Internet service provider (ISP),
the benefit being that the user does not have to incur a long
distance charge while traveling, which can sometimes be quite
expensive.
Given the number of ISPs today, ROAMOPS realized that requiring each
ISP to set up roaming agreements with all other ISPs did not scale.
Therefore, the working group defined a "broker", which acts as an
intermediate server, whose sole purpose is to set up these roaming
agreements. A collection of ISPs and a broker is called a "roaming
consortium". There are many such brokers in existence today; many
also provide settlement services for member ISPs.
The Mobile-IP Working Group has recently changed its focus to inter
administrative domain mobility, which is a requirement for cellular
carriers wishing to deploy IETF-based mobility protocols. The current
cellular carriers requirements [22, 23] are very similar to the
ROAMOPS model, with the exception that the access protocol is
Mobile-IP [45] instead of PPP.
The Diameter protocol was not designed from the ground up. Instead,
the basic RADIUS model was retained while fixing the flaws in the
RADIUS protocol itself. Diameter does not share a common protocol
data unit (PDU) with RADIUS, but does borrow sufficiently from the
protocol to ease migration.
The basic concept behind Diameter is to provide a base protocol that
can be extended in order to provide AAA services to new access
technologies. Currently, the protocol only concerns itself with
Internet access, both in the traditional PPP sense as well as taking
into account the ROAMOPS model, and Mobile-IP.
Although Diameter could be used to solve a wider set of AAA problems,
we are currently limiting the scope of the protocol in order to
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ensure that the effort remains focused on satisfying the requirements
of network access. Note that a truly generic AAA protocol used by
many applications might provide functionality not provided by
Diameter. Therefore, it is imperative that the designers of new
applications understand their requirements before using Diameter.
1.1 Diameter Protocol
The Diameter protocol allows peers to exchange a variety of messages.
The base protocol provides the following facilities:
- Delivery of AVPs (attribute value pairs)
- Capabilities negotiation, as required in [20]
- Error notification
- Extensibility, through addition of new commands and AVPs, as
required in [21]
All data delivered by the protocol is in the form of an AVP. Some of
these AVP values are used by the Diameter protocol itself, while
others deliver data associated with particular applications which
employ Diameter. AVPs may be added arbitrarily to Diameter messages,
so long as the required AVPs are included and AVPs which are
explicitly excluded are not included. AVPs are used by base Diameter
protocol to support the following required features:
- Transporting of user authentication information, for the
purposes of enabling the Diameter server to authenticate the
user.
- Transporting of service specific authorization information,
between client and servers, allowing the peers to decide whether
a user's access request should be granted.
- Exchanging resource usage information, which MAY be used for
accounting purposes, capacity planning, etc.
- Proxying and Re-directing of Diameter messages through a server
hierarchy.
The Diameter base protocol provides the minimum requirements needed
for an AAA transport protocol, as required by NASREQ [21], Mobile IP
[22, 23], and ROAMOPS [20]. The base protocol is not intended to be
used by itself, and must be used with an application-specific
extension, such as Mobile IP [10]. The Diameter protocol was heavily
inspired and builds upon the tradition of the RADIUS [1] protocol.
See section 2.4. for more information on Diameter extensions.
Any node can initiate a request. In that sense, Diameter is a peer to
peer protocol. In this document, a Diameter client is the device that
normally initiates a request for authentication and/or authorization
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of a user. A Diameter server is the device that either forwards the
request to another Diameter server (known as a proxy), or one that
performs the actual authentication and/or authorization of the user
based on some profile. Given that the server MAY send unsolicited
messages to clients, it is possible for the server to initiate such
messages. An example of an unsolicited message would be for a request
that the client issue an accounting update.
1.2 Requirements language
In this document, the key words "MAY", "MUST", "MUST NOT",
"optional", "recommended", "SHOULD", and "SHOULD NOT", are to be
interpreted as described in [13].
1.3 Terminology
Accounting
The act of collecting information on resource usage for the
purpose of trend analysis, auditing, billing, or cost allocation.
Authentication
The act of verifying the identity of an entity (subject).
Authorization
The act of determining whether a requesting entity (subject) will
be allowed access to a resource (object).
AVP
The Diameter protocol consists of a header followed by one or more
Attribute-Value-Pair (AVP). The AVP includes a header and is used
to encapsulation authentication, authorization or accounting
information.
Broker
A broker is a business term commonly used in AAA infrastructures.
A broker is either a proxy or redirect server, and MAY be operated
by roaming consortiums.
Diameter Client
A Diameter Client is a device at the edge of the network that
performs access control. An example of a Diameter client is a
Network Access Server (NAS) or a Foreign Agent (FA).
Diameter Server
A Diameter server is a device that is not acting as a NAS or FA.
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Servers can be proxy, redirect, or home servers
Downstream Server
Diameter Proxy servers identify an upstream server as one that is
providing routing services towards the Diameter client.
Home Domain
A Home Domain is the administrative domain with whom the user
maintains an account relationship.
Home Server
A Diameter Home Server is one that authenticates and/or authorizes
access for users of a particular realm. The same server MAY also
act as a proxy or redirect server for other realms, in which case
it is not acting as a Home Server for these realms.
Interim accounting
An interim accounting message provides a snapshot of usage during
a user's session. It is typically implemented in order to provide
for partial accounting of a user's session in the event of a
device reboot or other network problem that prevents the reception
of a session summary message or session record.
Local Domain
A local domain is the administrative domain providing services to
a user. An administrative domain MAY act as a local domain for
certain users, while being a home domain for others.
Network Access Identifier
The Network Access Identifier, or NAI [3], is used in the Diameter
protocol to extract a user's identity and realm. The identity is
used to identify the user during authentication and/or
authorization, while the realm is used for message routing
purposes.
Proxy Server
A proxy server ”ses the realm portion of the NAI to route Diameter
messages. Proxy servers are typically used to minimize the number
of security relationships that are required between Diameter
servers.
Realm
The string in the NAI that immediately follows the '@' character.
NAI realm names are required to be unique, and are piggybacked on
the administration of the DNS namespace. Diameter makes use of the
realm, also loosely referred to as domain, to determine whether
messages can be satisfied locally, or whether they must be
proxied.
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Real-time Accounting
Real-time accounting involves the processing of information on
resource usage within a defined time window. Time constraints are
typically imposed in order to limit financial risk.
Redirect Server
A Diameter redirect server provides realm to address translation,
by returning information necessary for Diameter peers to
communicate directly. Redirect servers are different from proxies
since they do not participate in the routing of messages between
end Diameter nodes.
Roaming Relationships
Roaming relationships include relationships between companies and
ISPs, relationships among peer ISPs within a roaming association,
and relationships between an ISP and a roaming consortia.
Together, the set of relationships forming a path between a local
ISP's authentication proxy and the home authentication server is
known as the roaming relationship path.
Session
The Diameter protocol is session based. When an authorization
request is initially transmitted, it includes a session identifier
that is used for the duration of the session. The Session-
Identifier AVP contains the identifier and must be globally
unique.
Session record
A session record represents a summary of the resource consumption
of a user over the entire session. Accounting gateways creating
the session record may do so by processing interim accounting
events or accounting events from several devices serving the same
user.
Upstream Server
Diameter Proxy servers identify a downstream server as one that is
providing routing services towards the home server for a
particular message.
2.0 Protocol Overview
The base Diameter protocol is never used on its own. It is always
extended for a particular application. Three extensions to Diameter
are defined by companion documents: NASREQ [7], Mobile IP [10],
Strong Security [11]. These options are introduced in this document
but specified elsewhere. Additional extensions to Diameter may be
defined in the future (see Section 17.3).
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Diameter servers MUST support the Base protocol, which includes
Accounting, and both the NASREQ and Mobile IP extensions. Diameter
Clients MUST support the Base protocol, including Accounting, and MAY
support any other extension that would be required to provide
service.
The base Diameter protocol concerns itself with capabilities
negotiation, and how messages are sent and how peers may eventually
be abandoned. The base protocol also defines certain rules which
apply to all exchanges of messages between Diameter peers.
Communication between Diameter peers begins with one peer sending a
message to another Diameter peer. The set of AVPs included in the
message is determined by a particular application of or extension to
Diameter. We will refer to this as the Diameter extension. One AVP
that is included to reference a user's session is the Session-Id.
The initial request for authentication and/or authorization of a user
would include the Session-Id. The Session-Id is then used in all
subsequent messages to identify the user's session (see section 11.0
for more information). The communicating party may accept the
request, or reject it by returning a response with Result-Code AVP
set to indicate an error occurred. The specific behavior of the
diameter server or client receiving a request depends on the Diameter
extension employed.
Session state (associated with a Session-Id) MUST be freed upon
receipt of the Session-Termination-Request, Session-Termination-
Answer, expiration of authorized service time in the Session-Timeout
AVP, and according to rules established in a particular
extension/application of Diameter.
Exchanges of messages are either request/reply oriented, or in some
special cases, do not require replies. All such messages that do not
require replies have names ending with '-Ind' (short for Indication).
The Diameter base protocol provides the Authorization-Lifetime AVP,
which MAY be used by extensions to specify the duration of a specific
authorized session.
2.1 Transport
The base Diameter protocol is run on port TBD of both TCP [27] and
SCTP [26] transport protocols (for interoperability test purposes
port 1812 will be used until IANA assigns a port to the protocol).
Diameter clients SHOULD support SCTP, but MUST support TCP if SCTP is
not available. future versions of this specification may mandate that
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clients support SCTP. Diameter servers MUST support both TCP and
SCTP.
A Diameter node MAY send packets from any source port, but MUST be
prepared to receive packets on port TBD. When a request is received,
the source and destination ports in the reply are reversed. Note that
the source and destination addresses used in request and replies MAY
any of a peer's valid IP addresses.
A given Diameter process SHOULD use the same port number to send all
messages to aid in identifying which process sent a given message.
More than one Diameter process MAY exist within a single host, so the
sender's port number is needed to discriminate them.
When no transport connection exists with a peer, an attempt to
connect SHOULD be periodically attempted. The recommended connection
interval is 30 seconds.
2.2 Securing Diameter Messages
All Diameter messages MUST be secured between peers, and both SSL
[38] and IP Security [37] are supported. Network Access Servers
(NASes) and Foreign Agents, commonly referred to as clients, MUST
support IP Security, while servers MUST support both SSL and IP
Security. The communication between a client and server MUST use IP
Security, while communication between servers MUST use SSL.
All hosts running the Diameter protocol MUST have the necessary
security policies to ensure that unauthenticated Diameter packets are
not processed.
2.3 Diameter Protocol Extensibility
There are various ways the Diameter protocol can be extended. This
section is intended to assist protocol designers in selecting the
best method of using the Diameter protocol.
2.3.1 Defining new AVP Values
Defining a new AVP value is the best approach when a new application
needs to make use of an existing Diameter extension, but requires
that an existing AVP communicate different service-specific
information (e.g. NAS-Port-Type set to avian carriers).
When an existing AVP can be used to communicate the new information,
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this approach is preferred over creating new AVPs.
In order to allocate a new AVP value, a request MUST be sent to IANA,
with a detailed explanation of the value. Furthermore, if the command
code on which the AVP value is to be used would require a different
set of mandatory AVPs be present, the list of AVPs must accompany the
request.
2.3.2 Creating new AVPs
New AVPs may be created when a new application requiring Diameter
support can make use of an existing Diameter extension, but requires
new AVPs to communicate service-specific information.
Prior to defining the AVP, the AVP type MUST be one of the types
listed in section 4.3. In the event that a logical grouping of AVPs
is necessary, and multiple "groups" are possible in a given command,
it is highly recommended that a Grouped AVP be used (see Section
4.4).
In order to create a new AVP, a request MUST be sent to IANA, with a
detailed explanation of the AVP, its type and possible values.
Furthermore, the request MUST include the commands that would make
use of the AVP.
Note that new AVPS to be used with an existing extension MUST NOT be
defined to have the 'M'andatory bit set.
2.3.3 Creating new Diameter extensions
Should a new application require Diameter support, but it cannot fit
within an existing extension without requiring major changes to the
specification, it may be desirable to create a new Diameter
extension. Major changes to an extension include:
- Requiring a whole different set of mandatory AVPs to a command
- Requiring a command that has a different number of round trips
to satisfy a request (e.g. Extension foo has a command that
requires one round trip, but new extension bar has a command
that requires two round trips to complete).
- The method used to authenticate the user is drastically
different from any existing extension, and the authentication
information cannot be carried within the AVPs defined in the
extension.
Note that the creation of a new extension should be viewed as a last
resort.
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New Diameter extensions MUST define at least one Command Code, the
expected AVPs in an ABNF [31] grammar (see section 3.2), and MAY also
define new AVPs. If the Diameter extension has any accounting
requirements, it MUST also specify the AVPs that are to be present in
the Diameter Accounting messages (see section 13.3).
When possible, a new Diameter extension SHOULD attempt to re-use any
existing Diameter AVP, in order to reduce the possibility of having
multiple AVPs that carry similar information.
Every Diameter Extension specification MUST have an IANA assigned
Extension Identifier (see section 2.4).
2.3.4 Extension authentication procedures
When possible, extensions SHOULD be designed such that new
authentication methods MAY be added without requiring changes to the
extension. This MAY require that new AVP values be assigned to
represent the new authentication transform, or any other scheme that
produces similar results. When possible, authentication frameworks,
such as Extensible Authentication Protocol [25], SHOULD be used.
2.4 Diameter Extension Compliance
Extension Identifiers are advertised during the capabilities exchange
phase (see section 6.0). For a given extension, there are two
different ways of advertising support. First, advertising support of
the extension via the Auth-Extension-Id implies that the sender
supports all authentication and authorization command codes, and the
AVPs specified in the associated ABNFs, described in the
specification. Second, advertising support of the extension via the
Acct-Extension-Id implies that the sender supports the Accounting
command codes defined in this specification, as well as the
accounting AVPs defined in the extension's specification.
An implementation MAY add arbitrary AVPs to any command defined in an
extension, including vendor-specific AVPs. However, such AVPs MUST
NOT have the Mandatory ('M') bit set. An implementation that adds
AVPs not specified in a command's ABNF, and sets the AVP's Mandatory
bit MUST NOT advertise support of the extension.
An implementation MAY support both a proprietary version of an
extension by requesting an IANA extension identifier (see section
17.3), while supporting the original extension. During the
capabilities exchange, a Diameter node can determine whether to
exchange messages using the proprietary or standard version of the
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extension by inspecting the extensions advertised by the peer.
2.5 Diameter Server Discovery
Allowing for dynamic Diameter server discovery will make it possible
for simpler and more robust deployment of AAA services. In order to
promote interoperable implementations of Diameter server discovery,
the following mechanisms are described. These are based on existing
IETF standards.
There are two cases where Diameter server discovery may be performed.
The first is when a Diameter client needs to discover a first-hop
Diameter server. The second case is when a Diameter server needs to
discover another server - for further handling of a Diameter
operation. In both cases, the following 'search order' is
recommended:
1. The Diameter implementation consults its list of static
(manual) configured Diameter server locations. These will be
used if they exist and respond.
2. The Diameter implementation uses SLPv2 [28] to discover
Diameter services. The Diameter service template [32] is
included in Appendix A. It is recommended that SLPv2 security
be deployed (this requires distributing keys to SLPv2 agents.)
This is discussed further in Appendix A.
SLPv2 will allow Diameter implementations to discover the
location of Diameter servers in the local site, as well as
their characteristics. Diameter servers with specific
capabilities (say support for the Accounting extension) can be
requested, and only those will be discovered.
3. The Diameter implementation uses DNS to request the SRV RR [33]
for the '_diameter._sctp' and/or '_diameter._tcp' server in a
particular domain. The Diameter implementation has to know in
advance which domain to look for an Diameter server in. This
could be deduced, for example, from the 'realm' in a NAI that
an Diameter implementation needed to perform an Diameter
operation on.
Diameter allows AAA peers to protect the integrity and privacy
of communication as well as to perform end-point
authentication. Still, it is prudent to employ DNS Security as
a precaution when using DNS SRV RRs to look up the location of
a Diameter server. [34, 35, 36]
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3.0 Diameter Header
A summary of the Diameter header format is shown below. The fields
are transmitted in network byte order.
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|r r r r r r r r r r E I R| Ver | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop-by-Hop Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End-to-End Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Command-Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVPs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-
Flags
The Message Flags field is thirteen bits. The following bits are
assigned:
r(eserved) MUST be zero - this flag bit is reserved for
future use.
E(xpected Reply) - The message solicits a response.
I(nterrogation) - The message is a Query or a Response.
R(esponse) - The message is a response to another message.
These flags MUST be set depending on the command code used in a
Diameter message. This enables the type of message to be
interpreted, even if the specific command code is not recognized.
Command Type Flags Set
Indication - - -
Request E - -
Answer - - R
Query E I -
Response - I R
A Diameter node MUST NOT set these flags in any other combination.
A Diameter node receiving a message in which these flags are not
set appropriately MAY reject the message for this reason, but
SHOULD log the event for diagnosis.
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Version
This Version field MUST be set to 1 to indicate Diameter Version
1.
Message Length
The Message Length field is two octets and indicates the length of
the Diameter message including the header fields.
Hop-by-Hop Identifier
The Hop-by-Hop Identifier field is four octets, and aids in
matching requests and replies. The sender MUST ensure that the
Hop-by-Hop identifier in a request (*-Request or *-Query) or
indication (*-Ind) message is locally unique (to the sender) at
any given time, and MAY attempt to ensure that the number is
unique across reboots. The sender of a response (*-Answer or *-
Response) MUST ensure that the Hop-by-Hop Identifier field
contains the same value that was found in the corresponding
request. The Hop-by-Hop identifier is normally a monotonically
increasing number, whose start value was randomly generated. A
message of type Answer or Response that is received with an
unknown Hop-by-Hop Identifier MUST be discarded.
End-to-End Identifier
Unlike the Hop-by-Hop Identifier, the End-to-End Identifier is
used by servers to detect duplicate messages, and proxies MUST NOT
modify this field. The sender of a request, query, indication,
answer or response message MUST insert a locally unique value in
this field. The combination of the Session-Id AVP and this field
is used to detect duplicates. A message of type Answer or Response
which is received with a previously seen End-to-End Identifier,
and is to be locally consumed (meaning that the Destination-FQDN
AVP contains the local node's identity) SHOULD be silently
discarded.
Command-Code
The Command-Code field is four octets, and is used in order to
communicate the command associated with the message. The 32-bit
address space is managed by IANA (see section 17.2).
Vendor-ID
In the event that the Command-Code field contains a vendor
specific command, the four octet Vendor-ID field contains the IANA
assigned "SMI Network Management Private Enterprise Codes" [2]
value. If the Command-Code field contains an IETF standard
Command, the Vendor-ID field MUST be set to zero (0).
AVPs
AVPs are a method of encapsulating information relevant to the
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Diameter message. See section 4. for more information on AVPs.
3.1 Command Codes
Every Diameter message MUST contain a value in its header's Command-
Code field, which is used to determine the action that is to be taken
for a particular message. The following Command Codes are defined in
the Diameter base protocol:
Command-Name Abbrev. Code Reference
--------------------------------------------------------
Accounting-Answer ACA 272 14.2
Accounting-Poll-Ind API 273 14.4
Accounting-Request ACR 271 14.1
Accounting-Status-Ind ASI 279 14.3
Device-Reboot-Ind DRI 257 6.2
Device-Status-Ind DSI 282 9.1
Device-Watchdog-Req DWR 280 7.1
Device-Watchdog-Answer DWA 281 7.2
Message-Reject-Ind MRI 259 10.1
Session-Termination-Ind STI 274 11.9.1
Session-Termination- STR 275 11.9.2
Request
Session-Termination- STA 276 11.9.3
Answer
3.2 Command Code ABNF specification
Every Command Code defined MUST include a corresponding ABNF
specification, which is used to define the AVPs that MUST, MAY and
MUST NOT be present. The following format is used in the definition:
command-def = command-name "::=" diameter-message
diameter-name = ALPHA *(ALPHA / DIGIT / "-")
command-name = diameter-name
; The command-name has to be Command name,
; defined in the base or extended Diameter
; specifications.
diameter-message = header [ *fixed] [ *required] [ *optional] [ *fixed]
header = "<Diameter-Header:" command-id ">"
fixed = [qual] "<" avp-spec ">"
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required = [qual] "{" avp-spec "}"
optional = [qual] "[" avp-name "]"
; The avp-name in the 'optional' rule cannot
; evaluate to any AVP Name which is included
; in a fixed or required rule.
qual = [min] "*" [max]
; See ABNF conventions, RFC 2234 section 6.6.
; The absence of any qualifiers implies that one
; and only one such AVP MUST be present.
;
; NOTE: "[" and "]" have a different meaning
; than in ABNF (see the optional rule, above).
; These braces cannot be used to express
; optional fixed rules (such as an optional
; ICV at the end.) To do this, the convention
; is '0*1fixed'.
min = 1*DIGIT
; The minimum number of times the element may
; be present.
max = 1*DIGIT
; The maximum number of times the element may
; be present.
avp-spec = diameter-name
; The avp-spec has to be an AVP Name, defined
; in the base or extended Diameter
; specifications.
avp-name = avp-spec | "AVP"
; The string "AVP" stands for *any* arbitrary
; AVP Name, which does not conflict with the
; required or fixed position AVPs defined in
; the command code definition.
The following is a definition of a fictitious command code:
Example-Command ::= < Diameter-Header: 9999999 >
{ User-Name }
* { Origin-FQDN }
* [ AVP ]
3.3 Diameter Command Naming Conventions
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The following conventions are required for the naming of Diameter
messages. Diameter commands typically start with an object name, and
end with one of the following verbs:
3.3.1 Request/Answer
Request is used when the command is asking the peer to do something
for it, for example, authorize a user, or terminate a session. The
Answer MUST contain either a positive or negative result code,
telling the requester whether or not the request successfully
occurred. Other information can also be returned in the Answer.
For example, AA-Request asks the peer device to authorize and/or
authenticate a user in order to set up a session. The request may
fail, thus the answer may be positive or negative.
3.3.2 Query/Response
Query is used when the command is asking for information that it
expects the peer to have. An example would be querying for current
configuration information, or querying for information on resources
or sessions in use. The Response usually contains a positive result
code and the information, or a negative result code with the reason
for not completing the query.
For example, Resource-Query requests the peer device to return
specific information about one or more resources. The answer is
returned in a Resource-Response.
3.3.3 Indication
Indication is used either when the node wishes to inform the peer
that an event occurred, or is requesting that a particular function
be performed, but is not expecting a response. The transport level
acknowledgement is used to ensure that the message was reliably
delivered.
4.0 Diameter AVPs
Diameter AVPs carry specific authentication, accounting and
authorization information, security information as well as
configuration details for the request and reply.
Some AVPs MAY be listed more than once. The effect of such an AVP is
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specific, and is specified in each case by the AVP description.
Each AVP of type OctetString MUST be padded to align on a 32 bit
boundary, while other AVP types align naturally. NULL bytes are added
to the end of the AVP Data field till a word boundary is reached. The
length of the padding is not reflected in the AVP Length field.
4.1 AVP Header
The fields in the AVP header MUST be sent in network byte order. The
format of the header is:
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVP Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVP Length | Reserved |P|r|V|r|M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-ID (opt) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ...
+-+-+-+-+-+-+-+-+
AVP Code
The AVP Code identifies the attribute uniquely. The first 256 AVP
numbers are reserved for backward compatibility with RADIUS and
are to be interpreted as per NASREQ [7]. AVP numbers 256 and above
are used for Diameter, which are allocated by IANA (see section
17.1).
AVP Length
The AVP Length field is two octets, and indicates the length of
this AVP including the AVP Code, AVP Length, AVP Flags, Reserved,
the Vendor-ID field (if present) and the AVP data. If a message is
received with an invalid attribute length, the message SHOULD be
rejected.
AVP Flags
The AVP Flags field informs the Diameter host how each attribute
must be handled. Note that subsequent Diameter extensions MAY
define bits to be used within the AVP Header, and an unrecognized
bit should be considered an error. The 'r' and the reserved bits
are unused and should be set to 0 and ignored on receipt, while
the 'P' bit is defined in [11].
The 'M' Bit, known as the Mandatory bit, indicates whether support
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of the AVP is required. If an AVP is received by a Home server or
NAS with the 'M' bit enabled and the receiver does not support
the AVP, the message MUST be rejected. If such an AVP is received
by a Proxy or Redirect Server, the message MUST be forwarded to
its logical destination, and MUST NOT be rejected. It is the
responsibility of the originator of a message that is rejected for
this purpose to correct the error. AVPs without the 'M' bit
enabled are informational only and a receiver that receives a
message with such an AVP that is not supported MAY simply ignore
the AVP.
The 'V' bit, known as the Vendor-Specific bit, indicates whether
the optional Vendor-ID field is present in the AVP header. When
set the AVP Code belongs to the specific vendor code address
space.
Unless otherwise noted, AVPs will have the following default AVP
Flags field settings:
The 'M' bit MUST be set. The 'V' bit MUST NOT be set.
4.2 Optional Header Elements
The AVP Header contains one optional field. This field is only
present if the respective bit-flag is enabled.
Vendor-ID
The Vendor-ID field is present if the 'V' bit is set in the AVP
Flags field. The optional four octet Vendor-ID field contains the
IANA assigned "SMI Network Management Private Enterprise Codes"
[2] value, encoded in network byte order. Any vendor wishing to
implement a Diameter extension MUST use their own Vendor-ID along
with their privately managed AVP address space, guaranteeing that
they will not collide with any other vendor's extensions, nor with
future IETF extensions.
A vendor ID value of zero (0) corresponds to the IETF adopted AVP
values, as managed by the IANA. Since the absence of the vendor ID
field implies that the AVP in question is not vendor specific,
implementations SHOULD not use the zero (0) vendor ID.
4.3 AVP Data Formats
The Data field is zero or more octets and contains information
specific to the Attribute. The format and length of the Data field is
determined by the AVP Code and AVP Length fields. The format of the
Data field MAY be one of the following data types.
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The interpretation of the values depends on the specification of the
AVP. For example, an OctetString may be used to transmit human
readable string data and Unsigned32 may be used to transmit a time
value. Conventions for these common interpretations are described
below.
OctetString
The data contains arbitrary data of variable length. Unless
otherwise noted, the AVP Length field MUST be set to at least 9
(13 if the 'V' bit is enabled). Data used to transmit (human
readable) character string data uses the UTF-8 [24] character
set and is NOT NULL-terminated. The minimum Length field MUST
be 9, but can be set to any value up to 65504 bytes. AVP Values
of this type that do not align on a 32-bit boundary MUST have
the necessary padding.
Address
32 bit (IPv4) [17] or 128 bit (IPv6) [16] address, most
significant octet first. The format of the address (IPv4 or
IPv6) is determined by the length. If the attribute value is an
IPv4 address, the AVP Length field MUST be 12 (16 if 'V' bit is
enabled), otherwise the AVP Length field MUST be set to 24 (28
if the 'V' bit is enabled) for IPv6 addresses.
Integer32
32 bit signed value, in network byte order. The AVP Length
field MUST be set to 12 (16 if the 'V' bit is enabled).
Integer64
64 bit signed value, in network byte order. The AVP Length
field MUST be set to 16 (20 if the 'V' bit is enabled).
Unsigned32
32 bit unsigned value, in network byte order. The AVP Length
field MUST be set to 12 (16 if the 'V' bit is enabled).
Unsigned32 values used to transmit time data contains the four
most significant octets returned from NTP [18], in network byte
order.
Unsigned64
32 bit unsigned value, in network byte order. The AVP Length
field MUST be set to 16 (20 if the 'V' bit is enabled).
Float32
This represents floating point values of single precision as
described by [30]. The 32 bit value is transmitted in network
byte order. The AVP Length field MUST be set to 12 (16 if the
'V' bit is enabled).
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Float64
This represents floating point values of double precision as
described by [30]. The 64 bit value is transmitted in network
byte order. The AVP Length field MUST be set to 16 (20 if the
'V' bit is enabled).
Float128
This represents floating point values of quadruple precision as
described by [30]. The 128 bit value is transmitted in network
byte order. The AVP Length field MUST be set to 24 (28 if the
'V' bit is enabled).
Grouped
The Data field is specified as a sequence of AVPs. Each of
these AVPs follows - in the order in which they are specified -
including their headers and padding. The AVP Length field is
set to 8 (12 if the 'V' bit is enabled) plus the total length
of all included AVPs, including their headers and padding.
4.4 Grouped AVP Values
The Diameter protocol allows AVP values of type 'Grouped.' This
implies that the Data field is actually a well defined sequence of
AVPs. It is possible to include an AVP with a Grouped type within a
Grouped type, that is, to nest them. AVPs within an AVP of type
Grouped have the same padding requirements as non-Grouped AVPs, as
defined in section 4.0.
Grouped type AVP specifications include an ABNF grammar [31]
specifying the required sequence of AVPs. Grouped AVP values MUST be
in the specified sequence and MUST NOT include other AVP values
besides those specified by the Grouped AVP grammar.
4.4.1 Example AVP with a Grouped Data type
The Example AVP (AVP Code 999999) is of type Grouped and is used to
clarify how Grouped AVP values work. The Grouped Data field has the
following ABNF grammar:
example-avp-val = Origin-FQDN Host-IP-Address
Origin-FQDN = ; See Section 5.1
Host-IP-Address = ; See Section 6.2.4
An Example AVP with the Grouped Data Origin-FQDN = "example.com",
Host-IP-Address = "10.10.10.10" would be encoded as follows:
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0 1 2 3 4 5 6 7
+-------+-------+-------+-------+-------+-------+-------+-------+
0 | Example AVP Header (AVP Code = 999999), Length = 40 |
+-------+-------+-------+-------+-------+-------+-------+-------+
8 | Origin-FQDN AVP Header (AVP Code = 264), Length = 19 |
+-------+-------+-------+-------+-------+-------+-------+-------+
16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' |
+-------+-------+-------+-------+-------+-------+-------+-------+
24 | 'c' | 'o' | 'm' |Padding| Host-IP-Addr AVP Header |
+-------+-------+-------+-------+-------+-------+-------+-------+
32 | (AVP Code = 257), Length = 12 | 0x0a | 0x0a | 0x0a | 0x0a |
+-------+-------+-------+-------+-------+-------+-------+-------+
4.5 Diameter Base Protocol AVPs
The following table describes the Diameter AVPs defined in the base
protocol, their AVP Code values, types, possible flag values and
whether the AVP MAY be encrypted.
+---------------------+
| AVP Flag rules |
|----+-----+----+-----|----+
AVP Section | | |SHLD| MUST|MAY |
Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr|
-----------------------------------------|----+-----+----+-----|----|
Accounting- 482 15.2 Unsigned32 | M | P | | V | Y |
Interim-Interval | | | | | |
Accounting- 485 15.3 Unsigned32 | M | P | | V | Y |
Record-Number | | | | | |
Accounting- 480 15.1 Unsigned32 | M | P | | V | Y |
Record-Type | | | | | |
Accounting- 44 15.5 OctetString| M | P | | V | Y |
Session-Id | | | | | |
Accounting-State 486 15.4 Unsigned32 | M | P | | V | Y |
Acct-Extension- 259 6.2.x Integer32 | M | | | | Y |
Id | | | | | |
Auth-Extension- 258 6.2.3 Integer32 | M | | | | Y |
Id | | | | | |
Authorization- 291 11.4 Unsigned32 | | | | | N |
Lifetime | | | | | |
Destination-FQDN 293 5.3 OctetString| | | | | Y |
Destination- 283 12.4.7 OctetString| M | | | V | N |
Realm | | | | | |
DSI-Event 297 9.1.1 Unsigned32 | M | | | | N |
Error-Message 281 10.3 OctetString| | | | | N |
-----------------------------------------|----+-----+----+-----|----|
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+---------------------+
| AVP Flag rules |
|----+-----+----+-----|----+
AVP Section | | |SHLD| MUST|MAY |
Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr|
-----------------------------------------|----+-----+----+-----|----|
Error-Reporting- 294 10.4 OctetString| | | | | Y |
FQDN | | | | | |
Failed-AVP 279 10.1.1 OctetString| | | | | Y |
Failed-Command- 270 10.1.2 Unsigned32 | | | | | Y |
Code | | | | | |
Failed-Vendor-Id 262 10.1.5 Unsigned32 | | | | | Y |
Firmware- 267 6.2.2 Unsigned32 | | | | V,M | Y |
Revision | | | | | |
Host-IP-Address 257 6.2.4 Address | M | | | V | N |
Max-Wait-Time 295 11.7 Unsigned32 | M | | | V | N |
Offending-AVP 271 10.1.4 OctetString| M | | | V | N |
Offending- 272 10.1.3 Unsigned32 | M | | | V | N |
Command-Code | | | | | |
Origin-FQDN 264 5.1 OctetString| M | | | V | N |
Origin-Realm 296 5.2 OctetString| M | | | V | N |
Original- 261 11.8.1 OctetString| M | | | V | N |
Session-Id | | | | | |
Product-Name 269 6.2.6 OctetString| | | | | N |
Proxy-Address 280 12.4.5 Address | M | | | V | N |
Proxy-Info 284 12.4.4 OctetString| M | | | V | N |
Proxy-State 33 12.4.6 Grouped | M | | | V | N |
Redirect-Host 292 12.3.1 Grouped | | | | | Y |
Redirect-Host- 278 12.3.2 Address | | | | | Y |
Address | | | | | |
Redirect-Host- 277 12.3.3 Unsigned32 | | | | | Y |
Port | | | | | |
Result-Code 268 10.2 Unsigned32 | M | | | | N |
Route-Record 282 12.4.3 OctetString| M | | | V | N |
Session-Id 263 11.3 OctetString| M | | | | Y |
Session-Timeout 27 11.5 Unsigned32 | | | | | Y |
Supported- 265 6.2.5 Unsigned32 | | | | | N |
Vendor-Id | | | | | |
User-Name 1 11.6 OctetString| | | | | Y |
Vendor-Id 266 6.2.1 Unsigned32 | | | | V,M | Y |
-----------------------------------------|----+-----+----+-----|----|
5.0 Message Forwarding
All Diameter messages MUST include the Origin-FQDN and Origin-Realm
AVPs. These AVPs are used to identify the source of the message.
When responding to a request or query message, the Origin-FQDN and
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Origin-Realm AVPs are replaced with the local node's information.
The Destination-FQDN AVP is used when the destination of the message
is fixed, such as:
- Authentication requests that span multiple round trips
- A Diameter message that uses a security mechanism that makes use
of a pre-established session key shared between the source and
the final destination of the message.
- Server initiated messages that MUST be received by a specific
Diameter client (e.g. access device), such as the Session-
Termination-Ind message, which is used to request that a
particular user's session be terminated.
Proxies receiving messages that contain the Destination-FQDN AVP MUST
verify whether they are able to forward Diameter messages to the host
specified in the AVP, and if so, MUST forward the message to the host
in question. Otherwise, the message routing procedures described in
section 12.0 MUST be followed.
Unless otherwise specified, this section defines the Diameter AVPs
that MUST be added in all messages originated by a Diameter node
(including nodes creating Response and Answer messages).
5.1 Origin-FQDN AVP
The Origin-FQDN AVP (AVP Code 264) is of type OctetString, encoded in
the UTF-8 [24] format. This AVP identifies the endpoint which
originated the Diameter message, i.e. the access device, home server,
or broker. Proxy servers do not modify this AVP. All Diameter
messages MUST include the Origin-FQDN AVP, which contains the host
name of the originator of the Diameter message and MUST follow the
Fully Qualified Domain Name naming conventions.
Note that the Origin-FQDN AVP may resolve to more than one address as
the Diameter peer may support more than one address.
5.2 Origin-Realm AVP
The Origin-Realm AVP (AVP Code 296) is of type OctetString, encoded
in the UTF-8 [24] format. This AVP contains the Realm of the
originator of any Diameter message.
5.3 Destination-FQDN AVP
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The Destination-FQDN AVP (AVP Code 293) is of type OctetString,
encoded in the UTF-8 [24] format, and contains the Fully Qualified
Domain Name (FQDN) of the intended recipient of the message. This AVP
MUST be present in all unsolicited server initiated messages, MAY be
present in messages of type Indication, Request or Query, and MUST be
present in messages of type Answer or Response. The value of the
Destination-FQDN AVP is set to the value of the Origin-FQDN AVP found
in a message from the intended target host.
6.0 Capabilities Exchange
When two Diameter peers establish a transport connection, they MUST
send the Device-Reboot-Ind message. This message has two purposes.
First it allows a peer's identity to be discovered, and allows for
capabilities exchange, such as the supported protocol version number,
and the locally supported extensions.
The receiver uses the extensions advertised in order to determine
whether it SHOULD send certain application-specific Diameter
commands. A Diameter node MUST retain the supported extensions in
order to ensure that unrecognized commands and/or AVPs are not sent
to a peer.
A receiver of a Device-Reboot-Ind message which does not have any
extensions in common with the sender MUST return a DSI message to the
peer with the DSI-Event AVP set to DIAMETER_NO_COMMON_EXTENSION, and
disconnect the transport layer connection.
The Device-Reboot-Ind message MUST NOT be proxied, or redirected.
Since the DRI cannot be proxied, it is still possible that a upstream
proxy receives a message for which it has no available peers to
handle the extension that corresponds to the Command-Code. In such
instances, the Device-Status-Ind message is used (see Section 9.1) to
inform the downstream to take action.
With the exception of the Device-Reboot-Ind message, a message of
type Request, Query or Indication that includes the Auth-Extension-Id
or Acct-Extension-Id AVPs, or a message with an extension-specific
command code, MAY only be forwarded to a host that has explicitly
advertised support for the extension (or has advertised the Wildcard
Extension).
6.1 Extension Identifiers
Each Diameter extension draft MUST have an IANA assigned Extension
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Identifier (see section 17.3). The base protocol does not require an
Extension Identifier since its support is mandatory.
Extension Identifiers are communicated via two separate AVPs; Auth-
Extension-Id and Acct-Extension-Id. The Auth-Extension-Id AVP is used
to communicate support for the authentication and authorization
portion of an extension. The Acct-Extension-Id AVP, on the other
hand, communicates support for the accounting portion of an
extension.
This separation of AVPs allows a server to communicate that it is
willing to accept only accounting messages for a given extension.
The following Extension Identifier values are defined:
NASREQ 1 [7]
End-to-End Security 2 [11]
Resource Management 3 [29]
Mobile-IP 4 [10]
Wildcard Extension 0xffffffff
Servers acting as Redirect or Proxy servers (see Section 12.0) MAY
wish to either advertise all supported extensions, or the wildcard
extension. The receiver of a wildcard extension MUST assume that the
sender supports all extensions.
Proxy servers are responsible for finding a downstream server that
supports the extension of a particular message. If none can be found,
a DSI message is returned with the DSI-Event AVP set to
DIAMETER_UNABLE_TO_DELIVER.
6.2 Device-Reboot-Ind (DRI) Command
The Device-Reboot-Ind (DRI), indicated by the Command-Code set to
257, is sent to inform a peer that a reboot has, or will, occur.
When Diameter is run over SCTP [26], which allows for connections to
span multiple interfaces, hence multiple IP addresses, the Device-
Reboot-Ind message MUST contain one Host-IP-Address AVP for each
potential IP address that MAY be locally used when transmitting
Diameter messages.
If a Diameter node receives a DRI message that results in an error, a
Message-Reject-Ind message MUST be returned.
Message Format
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<Device-Reboot-Ind> ::= < Diameter Header: 257 >
{ Origin-FQDN }
{ Origin-Realm }
1* { Host-IP-Address }
{ Vendor-Id }
{ Product-Name }
* { Supported-Vendor-Id }
* [ Auth-Extension-Id ]
* [ Acct-Extension-Id ]
[ Destination-FQDN ]
[ Firmware-Revision ]
* [ AVP ]
6.2.1 Vendor-Id AVP
The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains
the IANA "SMI Network Management Private Enterprise Codes" [2] value
assigned to the vendor of the Diameter device.
In combination with the Supported-Vendor-Id AVP (section 6.2.5), this
MAY be used in order to know which vendor specific attributes may be
sent to the peer. It is also envisioned that the combination of the
Vendor-Id, Product-Name (section 6.2.6) and the Firmware-Revision
(section 6.2.2) AVPs MAY provide very useful debugging information.
A Vendor-Id value of zero in the DRI is reserved and indicates that
the Diameter peer is in the experimental or concept stage and that an
IANA Private Enterprise Number has yet to be obtained by the
implementor.
6.2.2 Firmware-Revision AVP
The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 and is
used to inform a Diameter peer of the firmware revision of the
issuing device.
For devices that do not have a firmware revision (general purpose
computers running Diameter software modules, for instance), the
revision of the Diameter software module may be reported instead.
6.2.3 Auth-Extension-Id AVP
The Auth-Extension-Id AVP (AVP Code 258) is of type Unsigned32 and is
used in order to advertise support of the Authentication and
Authorization portion of an extension (see Section 6.1). The Auth-
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Extension-Id MUST also be present in all Authentication and/or
Authorization messages that are defined in a separate Diameter
specification and have an Extension ID assigned.
6.2.4 Host-IP-Address AVP
The Host-IP-Address AVP (AVP Code 257) is of type Address and is used
to inform a Diameter peer of the sender's IP address. All source
addresses that a Diameter node expects to use with SCTP [26] MUST be
advertised in the Device-Reboot-Ind message by including a Host-IP-
Address AVP for each address. This AVP MUST ONLY be used in the
Device-Reboot-Ind message.
6.2.5 Supported-Vendor-Id AVP
The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and
contains the IANA "SMI Network Management Private Enterprise Codes"
[2] value assigned to a vendor other than the device vendor. This is
used in the Device-Reboot-Ind message in order to inform the peer
that the sender supports a subset of the vendor-specific commands
and/or attributes defined by the vendor identified in this AVP.
6.2.6 Product-Name AVP
The Product-Name AVP (AVP Code 269) is of type OctetString, encoded
in the UTF-8 [24] format, and contains the vendor assigned name for
the product. The Product-Name AVP SHOULD remain constant across
firmware revisions for the same product.
6.2.7 Acct-Extension-Id AVP
The Acct-Extension-Id AVP (AVP Code 259) is of type Unsigned32 and is
used in order to advertise support of the Accounting portion of an
extension (see Section 6.1). The Acct-Extension-Id MUST also be
present in all Accounting messages that are defined in a separate
Diameter specification and have an Extension ID assigned.
7.0 Transport Failure Detection
Given the nature of the Diameter protocol, it is recommended that
transport failures be detected as soon as possible. Detecting such
failures will minimize the occurrence of messages sent to unavailable
servers, resulting in unnecessary delays, and will provide better
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failover performance.
In order to pro-actively detect such failures, the Diameter protocol
defines the Device-Watchdog-Request message, which is sent to an
inactive peer. A peer is considered inactive if no messages were sent
or received from the peer within the current watchdog interval period
(see Section 19.0), and no request or query messages are pending with
the peer.
For implementations that have access to the Retransmission Time-Out
(RTO) value of the underlying transport connection, a DWR SHOULD be
sent once per RTO of that connection, plus the watchdog interval
period, with a jittering of +/- 50%.
If the DWR is unanswered, the time until the next DWR is sent MUST be
recalculated after exponentially backing off the RTO portion. When
the value of the DWR's current watchdog interval period reaches the
maximum watchdog interval (Section 19.0), backoff is not continued,
and the peer is marked as failed. DWR messages continue to be sent
(jittered) at the final interval for detection for failover. The
current watchdog interval is returned to its starting point when a
DWA is received or the peer resumes activity.
Implementations that do not have access to the RTO SHOULD perform an
Round Trip Time (RTT) measurement for a given peer when a Device-
Watchdog-Answer message is received for a non-backed off DWR. The
fixed RTO base should be replaced by RTT-Multiplier (Section 19.0)
times the measured RTT.
An example of the backoff sequence, excluding jitter, would be:
30+RTO , 30+2*RTO , 30+4*RTO , 30+8*RTO, 60, 60, 60
Note that exponential backoff MUST be performed before the maximum is
reached.
7.1 Device-Watchdog-Request
The Device-Watchdog-Request (DWR), indicated by the Command-Code set
to 280, is sent to a peer when no traffic has been exchanged between
two peers as defined in Section 7.0, and no requests are pending with
the peer.
Message Format
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<Device-Watchdog-Request> ::= < Diameter Header: 280 >
{ Origin-FQDN }
{ Origin-Realm }
[ Destination-FQDN ]
7.2 Device-Watchdog-Answer
The Device-Watchdog-Answer (DWA), indicated by the Command-Code set
to 281, is sent as a response to the Device-Watchdog-Request message.
A receiver of the DWA SHOULD perform RTT calculation in the event
that the transport RTO information is not available.
Message Format
<Device-Watchdog-Answer> ::= < Diameter Header: 281 >
{ Result-Code }
{ Origin-FQDN }
{ Origin-Realm }
{ Destination-FQDN }
7.3 Failover/Failback Procedures
In the event that a transport failure is detected with a peer, it is
necessary for all pending request, query and indication messages to
be forwarded to an alternate server, if possible. This is commonly
referred to as failover.
In order for a Diameter node to perform failover procedures, it is
necessary for the node to maintain a pending message queue for a
given peer. When a response is received, the message is removed from
the queue. The Hop-by-Hop Identifier field MAY be used to match the
corresponding response with the queued request.
When a transport failure is detected, all messages in the queue are
sent to an alternate server, if possible. An example of a case where
it is not possible for forward the message to an alternate server is
when the message has a fixed destination, and the unavailable peer is
the message's final destination (see Destination-FQDN AVP). Such an
error requires that the server return an DSI with the DSI-Event AVP
set to DIAMETER_UNABLE_TO_DELIVER.
It is important to note that multiple identical request or responses
MAY be received as a result of a failover. The End-to-End Identifier
field in the Diameter header MUST be used to identify duplicate
messages.
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As described in section 2.1, a connection request should be
periodically attempted with the failed peer in order to re-establish
the transport connection. Once a connection has been successfully
established, messages can once again be forwarded to the peer. This
is commonly referred to as failback.
8.0 Peer State Machine
This section contains a finite state machine, that MUST be observed
by all Diameter implementations. Each Diameter node MUST follow the
state machine described below when communicating with each peer.
Multiple actions are separated by commas, and may continue on
succeeding lines as space requires. Similarly, state and next state
may also span multiple lines as space requires.
There may be at most one transport connection between any two peers
over which Diameter messages may be passed. This state machine is
intended to handle both the simple case, in which one peer initiates
a connection to the other, and the complex case, in which each peer
simultaneously initiates a connection to the other. In the complex
case, an election occurs to determine which transport connection will
survive.
I- is used to represent the initiator (connecting) connection, while
the R- is used to represent the responder (listening) connection. The
lack of a prefix indicates that the event or action is the same
regardless of the connection on which the event occurred.
The stable states that a state machine may be in are Closed, I-Open
and R-Open; all other states are intermediate. Note that I-Open and
R-Open are equivalent except for whether the initiator or responder
transport connection is used for communication.
A DRI message is always sent on the responder connection immediately
after accepting the connection request. The non-elected connection
will close down. All subsequent messages are sent on the elected
connection.
The state machine constrains only the behavior of a Diameter
implementation as seen by Diameter peers through events on the wire.
Any implementation that produces equivalent results is considered
compliant.
state event action next state
-----------------------------------------------------------------
Closed Start I-Snd-Conn-Req Wait-Conn-Ack
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R-Rcv-Conn-Req R-Snd-Conn-Ack Wait-R-DRI
Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-DRI Wait-I-DRI
I-Rcv-Conn-Nack Cleanup Closed
R-Rcv-Conn-Req R-Snd-Conn-Ack Wait-Conn-Ack/
Wait-R-DRI
Timeout Error Closed
Wait-I-DRI I-Rcv-DRI Process-DRI I-Open
R-Rcv-Conn-Req R-Snd-Conn-Ack Wait-R-DRI/
Elect
I-Peer-Disc I-Disc Closed
Timeout Error Closed
Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-DRI Wait-R-DRI/
Wait-R-DRI Elect
I-Rcv-Conn-Nack Cleanup Wait-R-DRI
R-Rcv-DRI Process-DRI Wait-Conn-Ack/
Elect
Timeout Error Closed
Wait-R-DRI/ R-Rcv-DRI Process-DRI, Wait-Returns
Elect Elect
I-Peer-Disc I-Disc Wait-R-DRI
Timeout Error Closed
Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-DRI,Elect Wait-Returns
Elect I-Rcv-Conn-Nack R-Snd-DRI R-Open
R-Peer-Disc R-Disc Wait-Conn-Ack-2
Timeout Error Closed
Wait-Returns Win-Election I-Disc,R-Snd-DRI R-Open
I-Peer-Disc I-Disc,R-Snd-DRI R-Open
I-Rcv-DRI R-Disc I-Open
R-Peer-Disc R-Disc Wait-I-DRI-2
Timeout Error Closed
Wait-Conn-Ack-2 I-Rcv-Conn-Ack I-Snd-DRI Wait-I-DRI-2
I-Rcv-Conn-Nack Cleanup Closed
R-Rcv-Conn-Req R-Snd-Conn-Nack Wait-Conn-Ack-2
Timeout Error Closed
Wait-I-DRI-2 I-Rcv-DRI Process-DRI I-Open
I-Peer-Disc I-Disc Closed
R-Rcv-Conn-Req R-Snd-Conn-Nack Wait-I-DRI-2
Timeout Error Closed
Wait-R-DRI R-Rcv-DRI R-Snd-DRI R-Open
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Timeout Error Closed
R-Open Send-Message R-Snd-Non-DRI R-Open
R-Rcv-Non-DRI Process R-Open
R-WatchDog-Timer R-Snd-DWR R-Open
R-Rcv-DWA Process-DWA R-Open
Stop R-Snd-Disc Closed
R-Peer-Disc R-Disc Closed
R-Rcv-DRI Error Closed
I-Open Send-Message I-Snd-Non-DRI I-Open
I-Rcv-Non-DRI Process I-Open
I-WatchDog-Timer I-Snd-DWR I-Open
I-Rcv-DWA Process-DWA I-Open
Stop I-Disc Closed
I-Peer-Disc I-Disc Closed
I-Rcv-DRI Error Closed
R-Rcv-Conn-Req R-Snd-Conn-Nack I-Open
8.1 States
Following is a more detailed description of each automaton state.
Closed A peer is initially in the closed state, and no
transport connection exists with the peer.
Wait-Conn-Ack A transport connection has been initiated with the
peer, and an acknowledgement is pending.
Wait-I-DRI The local Diameter node is waiting for the peer to
issue a DRI.
Wait-Conn-Ack/Wait-R-DRI
A transport connection indication from the peer was
received, while a transport connection has already
been locally initiated.
Wait-R-DRI/Elect
Two transport connections have been established
with the peer, and a DRI is pending on the
responder connection.
Wait-Conn-Ack/Elect
A transport connection exists on the responder
connection, while an acknowledgment has yet to be
received on the initiator connection.
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Wait-Returns Multiple transport connections caused an election
to occur.
Wait-Conn-Ack-2
While an acknowledgement to a locally initiated
transport connection hasn't been received, an
election has failed and the initiator connection
will be used between the peers.
Wait-I-DRI-2 Following an election, the initiator connection
won, and a DRI has yet to be received by the peer.
Wait-R-DRI A transport connection indication has been received
from the peer, and a DRI has yet to be received by
the peer.
R-Open The responder connection will be used to
communicate with the peer.
I-Open The initiator connection will be used to
communicate with the peer.
8.2 Events
Transitions and actions in the automaton are caused by events. In
this section we will ignore the -I and -R prefix, since the actual
event would be identical, but would occur on one of two possible
connections.
Start The Diameter application has signaled that a
connection should be initiated with the peer.
Rcv-Conn-Req A transport connection indication from the peer has
been received.
Rcv-Conn-Ack A positive acknowledgement was received to a
locally initiated transport connection.
Rcv-Conn-Nack A negative acknowledgement was received to a
locally initiated transport connection.
Timeout An application-defined timer has expired while
waiting for some event.
Rcv-DRI A DRI message from the peer was received.
Peer-Disc A disconnection indication from the peer was
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received.
Win-Election An election was held, and the local node was the
winner.
Send-Message A Non-DRI message is to be sent.
Rcv-Non-DRI A Non-DRI message was received.
WatchDog-Timer The Watchdog timer expired, indicating that a DWR
message is to be sent to the peer.
Rcv-DWA A DWA message was received.
Stop The Diameter application has signaled that a
connection should be terminated (e.g., on system
shutdown).
8.3 Actions
Actions in the automaton are caused by events and typically indicate
the transmission of packets and/or an action to be taken on the
connection. In this section we will ignore the -I and -R prefix,
since the actual action would be identical, but would occur on one of
two possible connections.
Snd-Conn-Req A transport connection is initiated with the peer.
Snd-Conn-Ack an acknowledgement is sent in response to a connect
request, confirming that the transport layer
connection is open.
Snd-Conn-Nack A negative acknowledgement is sent in response to a
connect request, indicating that the request was
refused.
Snd-DRI A DRI message is sent to the peer.
Cleanup If necessary, the connection is shutdown, and any
local resources are freed.
Error The transport layer connection is disconnected,
either politely or abortively, in response to an
error condition. Local resources are freed.
Process-DRI A received DRI is processed.
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Disc The transport layer connection is disconnected, and
local resources are freed.
Elect An election occurs (see Section 8.4 for more
information).
Snd-Non-DRI A non-DRI message is sent.
Snd-DWR A DWR message is sent.
Process-DWA The DWA message is serviced.
Process A non-DRI Diameter message is serviced.
8.4 The Election Process
The election is performed on the responder. The responder compares
the Origin-FQDN received in the DRI sent by its peer with its own
Origin-FQDN (which it may or may not have actually sent). The
transport layer connection with the higher value of Origin-FQDN is
the one that survives. The comparison proceeds by considering the
shorter OctetString to be null-padded to the length of the longer,
then performing an octet by octet unsigned comparison with the first
octet being most significant. Hanging octets are assumed to have
value 0x80, but dimpled octets are ignored.
9.0 Per-Hop Error Signaling
There are many instances where error conditions occur on a Diameter
node, that needs to be signaled to the downstream server, and not
necessarily to the Diameter client. Examples of such error conditions
are inability to forward a message to a particular domain, etc. In
these cases, returning the error back to the Diameter client will
only cause delay, and perhaps confusion in roaming networks.
Therefore, when such errors occur, it is necessary for the error to
be handled by the downstream next hop, and some local action be taken
to rectify the problem, such as forwarding to a different next hop.
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Request +--------+ Link Broken
+-------------------------->|Diameter|----///----+
| +---------------------| | v
+-----+---+ | DSI | Server | +--------+
|Diameter |<-+ (Unable to Forward) +--------+ |Diameter|
|Client or| | |
| Server |--+ +--------+ | Server |
+---------+ | Request |Diameter| +--------+
+-------------------->| | ^
| Server |-----------+
+--------+
Figure 1 - Example of Per-Hop Error Condition
9.1 Device-Status-Ind
The Device-Status-Ind (DSI), indicated by the Command-Code set to
282, is sent to inform a peer that an event has occurred.
When a Diameter node issues a DSI message downstream, the target peer
MUST attempt to rectify the problem, or issue a similar message
downstream. The Device-Status-Ind message MUST NOT be proxied, but
MAY be forwarded, as long as the Origin-FQDN and Origin-Realm AVPs
are replaced to include the local node's identity.
The Device-Status-Ind message MUST contain the same Hop-by-Hop
Identifier value in the header as the message which motivated sending
the DSI. If the Session-Id AVP was present in the original message,
the same AVP MUST be present in the DSI.
Message Format
<Device-Status-Ind> ::= < Diameter Header: 282 >
{ Origin-FQDN }
{ Origin-Realm }
{ DSI-Event }
[ Destination-FQDN ]
[ Session-Id ]
* [ AVP ]
9.1.1 DSI-Event AVP
The DSI-Event AVP (AVP Code 297) is of type Unsigned32 and indicates
that an event occurred which requires attention from a Diameter peer.
The DSI-Event contains an IANA-managed 32-bit address space
representing events (see section 17.5). Diameter provides the
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following classes of event notification, all identified by the
thousands digit:
- 1xxx (Informational Events)
- 3xxx (Redirect Notification)
- 4xxx (Transient Failure Events)
- 5xxx (Permanent Failure Events)
A non-recognize class (one whose first digit is not defined in this
section) MUST be handled as a permanent failure.
9.1.1.1 Informational Events
Events that fall within the Informational category are used to inform
a peer that a request cannot be immediately satisfied, and a further
response will be issued in the near future.
DIAMETER_STILL_WORKING 1001
A request's Max-Wait-Time has expired, and the request is still
being serviced. This event MAY be sent prior to the Max-Wait-
Time expiration, to inform the peer that the request is not
expected to be serviced in the allotted time, but the request
is not being abandoned. It is important to note that receiving
this event will result in another Diameter message being
received with the same Hop-by-Hop and End-to-End identifiers.
9.1.1.2 Redirect Event
Errors that fall within the Redirect Event category are used to
inform a peer that the request cannot be satisfied locally and should
instead be forwarded to another server.
DIAMETER_REDIRECT_INDICATION 3001
A proxy or redirect server has determined that the request
could not be satisfied locally and the initiator of the request
should direct the request directly to the server, whose contact
information has been added to the response.
9.1.1.3 Transient Failure Events
Errors that fall within the transient failures category are used to
inform a peer that the request could not be satisfied at the time it
was received, but MAY be able to satisfy the request if the error is
corrected.
DIAMETER_UNSUPPORTED_TRANSFORM 4001
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A message was received that included an CMS-Data AVP [11] that
made use of an unsupported transform.
9.1.1.4 Permanent Failure Events
Errors that fall within the permanent failures category are used to
inform the peer that the request failed, and cannot be satisfied by
the originator of the Device-Status-Ind. The receiver of a DSI
message with the DSI-Event set to a value that falls within this
event class SHOULD forward the message to an alternate peer, if one
is available.
DIAMETER_INVALID_ROUTE_RECORD 5001
The last Route-Record AVP in the message is not set to the
identity of the sender of the message. See Section 12.0 for
more information.
DIAMETER_COMMAND_UNSUPPORTED 5002
The Request contained a Command-Code that the receiver did not
recognize or support. The Device-Status-Ind message MUST also
contain an Failed-Command-Code AVP containing the unrecognized
Command-Code.
DIAMETER_UNABLE_TO_DELIVER 5003
The request could not be delivered to a host that handles the
realm, and extension, requested at this time.
DIAMETER_REALM_NOT_SERVED 5004
The originator of the DSI message could not deliver the message
since the realm requested is unknown.
DIAMETER_TOO_BUSY 5005
When returned, a Diameter node SHOULD attempt to sent the
message to an alternate peer. This value MAY also be used to
inform a peer that the request is not expected to be processed
within the Max-Wait-Time value, and is giving up on the
request.
DIAMETER_CANNOT_PROCESS_IN_TIME 5006
The time limit in a request's Max-Wait-Time AVP has expired,
and no response is available.
DIAMETER_NO_COMMON_EXTENSION 5007
This event is returned when a DRI message is received, and
there are no common extensions supported between the peer.
DIAMETER_UNSUPPORTED_VERSION 5008
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This event is returned when a DRI message is received, and the
Diameter message is unsupported.
10.0 End-to-End Error Signaling
There are several different types of error conditions that can occur
within Diameter.
The first occurs when a Diameter message is poorly formatted, and
unrecognizable, indicated in the figure below as "Bad Message". This
error condition applies if a received message is less than the length
of the Diameter header. Messages that generate such an error are
ignored.
A second case occurs when a Command-Code field is set to an
unsupported value, which is shown as "Unknown Command" in the figure.
Such errors generate a Device-Status-Ind message, and require per-hop
behavior.
A third case occurs when an AVP is received, marked as Mandatory ('M'
bit is set), and is unknown by the receiver. This error condition is
labeled as "Unknown AVP" in the figure below, and causes a Message-
Reject-Ind message to be sent.
The fourth case occurs when a message is received that contains an
AVP with either an unknown or illegal value. This is labeled as "Bad
AVP Value", and requires that a Message-Reject-Ind message be sent.
The last two cases require that a Message-Reject-Ind message be
generated to ensure that such errors are identified in both request
and response messages.
The last error condition occurs when an extension specific error is
identified in a request or response message. In a message of type
request or query, the natural corresponding answer or response
message MUST be used. However, if an error occurs while processing an
indication, answer or response message, a Message-Reject-Ind is used
to inform the peer that an error occurred while processing the
message.
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Error Type Ignore Send Send Send
Message MRI DSI Response
Bad Message X
Unknown Command X
Unknown AVP X
Bad AVP Value X
Request,Query Error X
Answer,Response,Ind Error X
"Ignore Message" indicates that the message is simply dropped. "Send
MRI" means that a Message-Reject-Ind message is sent to report the
error condition, while "Send DSI" requires that a Device-Status-Ind
message is sent (see Section 9.1). "Send Response" means that the
response message for a request or query message is returned.
10.1 Message-Reject-Ind (MRI) Command
The Message-Reject-Ind (MRI), indicated by the Command-Code set to
259, provides a generic means of completing transactions by
indicating errors in the messages that initiated them. The Message-
Reject-Ind command is sent in response:
1. An error is found in a message of type Ind, Answer and Response
2. A Unknown AVP, marked as Mandatory, is received
3. An AVP was received with an unknown, or illegal, value.
The Message-Reject-Ind message MUST contain the same Hop-by-Hop
Identifier value in the header as the message that caused the error
condition. If the Session-Id AVP was present in the original message,
the same AVP MUST be present in the MRI.
Message Format
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<Message-Reject-Ind message> ::= < Diameter Header: 259 >
[ Session-Id ]
{ Result-Code }
{ Origin-FQDN }
{ Origin-Realm }
{ Destination-FQDN }
{ Error-Reporting-FQDN }
[ Error-Message ]
[ Failed-Command-Code ]
* [ Failed-AVP ]
[ Failed-Vendor-Id ]
[ Destination-Realm ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
where the Result-Code AVP indicate the nature of the error causing
rejection, and the Failed-AVP AVP provides some minimal debugging
data by indicating a specific AVP type which caused the problem.
See the description of the Result-Code AVP for indication of when
the Failed-AVP AVP MUST be present in the message.
10.1.1 Failed-AVP AVP
The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides
debugging information in cases where a request is rejected or not
fully processed due to erroneous information in a specific AVP. The
value of the Result-Code AVP will provide information on the reason
for the Failed-AVP AVP.
Failed-AVP = Offending-AVP Failed-Vendor-Id
Offending-AVP = ; See Section 10.1.4
Failed-Vendor-Id = ; See Section 10.1.5
A Diameter message MAY contain one or more Failed-AVP AVPs, each
containing a complete AVP that could not be processed successfully.
The possible reasons for this AVP are the presence of an improperly
constructed AVP, an unsupported or unrecognized AVP, an invalid AVP
value, the omission of a required AVP, the presence of an explicitly
excluded AVP (see table 14.0), or the presence of two or more
occurrences of an AVP which table 16.1 restricts to 0, 1, or 0-1
occurrences.
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+---------------------------------------------------------------+
| AVP Header (AVP Code = 279) |
+---------------------------------------------------------------+
| Offending-AVP AVP |
+---------------------------------------------------------------+
| Failed-Vendor-Id AVP |
+---------------------------------------------------------------+
10.1.2 Failed-Command-Code AVP
The Failed-Command-Code AVP (AVP Code 270) is of type Grouped and
provides and contains the offending Command-Code that resulted in
sending the Message-Reject-Ind message.
Failed-Command-Code = Offending-Command-Code Failed-Vendor-Id
Offending-Command-Code = ; See Section 10.1.3
Failed-Vendor-Id = ; See Section 10.1.5
+---------------------------------------------------------------+
| AVP Header (AVP Code = 270) |
+---------------------------------------------------------------+
| Offending-Command-Code AVP |
+---------------------------------------------------------------+
| Failed-Vendor-Id AVP |
+---------------------------------------------------------------+
10.1.3 Offending-Command-Code AVP
The Failed-Command-Code AVP (AVP Code 272) is of type Unsigned32 and
contains the offending Command-Code that resulted in sending the
Message-Reject-Ind message.
10.1.4 Offending-AVP AVP
The Failed-Command-Code AVP (AVP Code 271) is of type OctetString and
contains the offending AVP.
10.1.5 Failed-Vendor-Id AVP
The Failed-Vendor-Id AVP (AVP Code 262) is of type Unsigned32 and
contains the Vendor-Id of the Command-Code or AVP that caused the
error.
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10.2 Result-Code AVP
The Result-Code AVP (AVP Code 268) is of type Unsigned32 and
indicates whether a particular request was completed successfully or
whether an error occurred. All Diameter messages of type *-Response
or *-Answer MUST include one Result-Code AVP, while messages of type
-Ind MAY include the Result-Code AVP. A non-successful Result-Code
AVP (one containing a non 2001 value) MUST include the Error-
Reporting-FQDN AVP.
The Result-Code data field contains an IANA-managed 32-bit address
space representing errors (see section 17.4). Diameter provides the
following classes of errors, all identified by the thousands digit:
- 1xxx (Informational)
- 2xxx (Success)
- 4xxx (Transient Failures)
- 5xxx (Permanent Failure)
A non-recognize class (one whose first digit is not defined in this
section) MUST be handled as a permanent failure.
10.2.1 Informational
Errors that fall within the Informational category are used to inform
a requester that the request cannot be immediately satisfied and a
further response will be issued in the near future. There are
currently no errors that fall within this class.
10.2.2 Success
Errors that fall within the Success category are used to inform a
peer that a request has been successfully completed.
DIAMETER_SUCCESS 2001
The Request was successfully completed.
10.2.3 Transient Failures
Errors that fall within the transient failures category are used to
inform a peer that the request could not be satisfied at the time it
was received, but MAY be able to satisfy the request in the future.
DIAMETER_AUTHENTICATION_REJECTED 4001
The authentication process for the user failed, most likely due
to an invalid password used by the user. Further attempts MUST
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only be tried after prompting the user for a new password.
DIAMETER_END_2_END_SECURITY 4002
A proxy has detected that end-to-end security has been applied
to portions of the Diameter message, and the proxy does not
allow this security mode since it needs to alter the message by
applying some local policies.
DIAMETER_OUT_OF_SPACE 4003
A Diameter node received the accounting request but was unable
to commit it to stable storage due to a temporary lack of
space.
10.2.4 Permanent Failures
Errors that fall within the permanent failures category are used to
inform the peer that the request failed, and should not be attempted
again.
DIAMETER_USER_UNKNOWN 5001
A request was received for a user that is unknown, therefore
authentication and/or authorization failed.
DIAMETER_AVP_UNSUPPORTED 5002
The peer received a message that contained an AVP that is not
recognized or supported and was marked with the Mandatory bit.
A Diameter message with this error MUST contain one or more
Failed-AVP AVP containing the AVPs that caused the failure.
DIAMETER_UNKNOWN_SESSION_ID 5003
The request or response contained an unknown Session-Id.
DIAMETER_AUTHORIZATION_REJECTED 5004
A request was received for which the user could not be
authorized. This error could occur if the service requested is
not permitted to the user.
DIAMETER_INVALID_AVP_VALUE 5005
The request contained an AVP with an invalid value in its data
portion. A Diameter message indicating this error MUST include
the offending AVPs within a Failed-AVP AVP.
DIAMETER_MISSING_AVP 5006
The request did not contain an AVP that is required by the
Command Code definition. If this value is sent in the Result-
Code AVP, a Failed-AVP AVP SHOULD be included in the message.
The data portion of the Failed-AVP MUST only contain the AVP
Code of the missing AVP.
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DIAMETER_INVALID_CMS_DATA 5007
The Request did not contain a valid CMS-Data [11] AVP.
DIAMETER_LOOP_DETECTED 5008
A Proxy or Redirect server detected a loop while trying to get
the message to the Home Diameter server. The message MAY be
sent to an alternate peer, if one is available, but the peer
reporting the error has identified a configuration problem.
DIAMETER_AUTHORIZATION_FAILED 5009
A request was received for which the user could not be
authorized at this time. This error could occur when the user
has already expended allowed resources, or is only permitted to
access services within a time period.
DIAMETER_CONTRADICTING_AVPS 5010
The Home Diameter server has detected AVPs in the request that
contradicted each other, and is not willing to provide service
to the user. One or more Failed-AVP AVPs MUST be present,
containing the AVPs that contradicted each other.
DIAMETER_AVP_NOT_ALLOWED 5011
A message was received with an AVP that MUST NOT be present.
The Failed-AVP AVP MUST be included and contain the AVP Code of
the offending AVP.
DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5012
A message was received that included an AVP that appeared more
often than permitted in the message definition. The Failed-AVP
AVP MUST be included and contain the AVP Code of the offending
AVP.
DIAMETER_VENDOR_ID_UNSUPPORTED 5013
The Home Diameter server has detected vendor-specific AVPs in
the message, and the vendor dictionary is not supported. One or
more Failed-AVP MUST be present, containing the offending AVPs.
10.3 Error-Message AVP
The Error-Message AVP (AVP Code 281) is of type OctetString. It is a
human readable UTF-8 character encoded string. It MAY accompany a
Result-Code AVP as a human readable error message. The Error-Message
AVP is not intended to be useful in real-time, and SHOULD NOT be
expected to be parsed by network entities.
10.4 Error-Reporting-FQDN AVP
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The Error-Reporting-FQDN AVP (AVP Code 294) is of type OctetString,
encoded in the UTF-8 [24] format. This AVP contains the FQDN of the
Diameter host that set the Result-Code AVP to a value other than 2001
(Success). This AVP is intended to be used for troubleshooting
purposes, and MUST be set when the Result-Code AVP indicates a
failure.
11.0 "User" Sessions
Diameter can provide two different type of services to applications.
The first involves authentication and authorization, and can
optionally make use of accounting. The second only makes use of
accounting.
When a service makes use of the authentication and/or authorization
portion of an extension, and a user requests access to the network,
the Diameter client issues an auth request to its local server. The
auth request is defined in a service specific Diameter extension
(e.g. NASREQ). The request contains a Session-Id AVP, which is used
in subsequent messages (e.g. subsequent authorization, accounting,
etc) relating to the user's session. The Session-Id AVP is a means
for the client and servers to correlate a Diameter message with a
user session.
When a Diameter server authorizes a user to use network resources, it
SHOULD add the Authorization-Lifetime AVP to the response. The
Authorization-Lifetime AVP defines the maximum amount of time a user
MAY make use of the resources before another authorization request is
to be transmitted to the server. If the server does not receive
another authorization request before the timeout occurs, it SHOULD
release any state information related to the user's session. Note
that the Authorization-Lifetime AVP implies how long the Diameter
server is willing to pay for the services rendered, therefore a
Diameter client SHOULD NOT expect payment for services rendered past
the session expiration time.
The base protocol does not include any authorization request
messages, since these are largely application-specific and are
defined in a Diameter protocol extension document. However, the base
protocol does define a set of messages that are used to terminate
user sessions. These are used to allow servers that maintain state
information to free resources.
When a service only makes use of the Accounting portion of the
Diameter protocol, even in combination with an extension, the
Session-Id is still used to identify user sessions. However, the
session termination messages are not used, since a session is
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signaled as being terminated by issuing an accounting stop message.
11.1 Authorization Session State Machine
This section contains a finite state machine, representing the life
cycle of Diameter sessions, and MUST be observed by all Diameter
implementations that makes use of the authentication and/or
authorization portion of a Diameter extension. The term Service-
Specific below refers to a message defined in a Diameter extension
(e.g. Mobile IP, NASREQ).
The following table contains the authorization session state machine.
State Event Action New State
-------------------------------------------------------------
Idle Client or Device Requests send serv. Pending
access specific
auth req
Idle Service-Specific authorization send serv. Open
request received, and specific
successfully processed response
Pending Successful Service-Specific Grant Open
Authorization response Access
received
Open Authorization-Lifetime expires send serv. Open
specific
auth req
Open Successful Service-Specific Extend Open
Authorization response Access
received
Open Accounting message sent or process Open
received
Open Failed Service-Specific Discon. Closed
Authorization response user/device
received.
Open Session-Timeout Expires on send STR Discon
Access Device
Open STI Received send STR Discon
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Open Session-Timeout Expires on send STI Discon
home AAA server
Discon STI Received ignore Discon
Discon STR Received Send STA Closed
Discon STA Received Discon. Closed
user/device
Closed Transition to state Cleanup
When the Cleanup action is invoked, the Diameter node MAY attempt to
release all resources for the particular session. Any event not
listed above MUST be considered as an error condition, and a
response, if applicable, MUST be returned to the originator of the
message.
11.2 Accounting Session State Machine
For applications that only require accounting services, the following
state machine MUST be supported.
State Event Action New State
-------------------------------------------------------------
Idle Client or device requests send Pending
access accounting
start req.
Idle Accounting start request send Open
received, and successfully accounting
processed. start
answer
Pending Successful accounting grant Open
start answer received access
Open User service terminated send Discon
accounting
stop req.
Open Accounting stop request send Closed
received, and successfully accounting
processed stop answer
Discon Successful accounting discon. Closed
stop answer received user/device
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11.3 Session-Id AVP
The Session-Id AVP (AVP Code 263) is of type OctetString and is used
to identify a specific session (see section 11.0). The Session-Id
data uses the UTF-8 [24] character set. All messages pertaining to a
specific session MUST include only one Session-Id AVP and the same
value MUST be used throughout the life of a session. When present,
the Session-Id SHOULD appear immediately following the Diameter
Header (see section 3.0).
For messages that do not pertain to a specific session, multiple
Session-Id AVPs MAY be present as long as they are encapsulated
within an AVP of type Grouped.
The Session-Id MUST be globally unique at any given time since it is
used by the server to identify the session (or flow). The format of
the session identifier SHOULD be as follows:
<Sender's Origin-FQDN><sender's port number> <monotonically
increasing 32 bit value><optional value>
The monotonically increasing 32 bit value SHOULD NOT start at zero
upon reboot, but rather start at a random value. This will minimize
the possibility of overlapping Session-Ids after a reboot.
Alternatively, an implementation MAY keep track of the increasing
value in non-volatile memory. The optional value is implementation
specific but may include a modem's device Id, a layer 2 address,
timestamp, etc.
The session Id is created by the Diameter device initiating the
session, which in most cases is done by the client. Note that a
Session-Id MAY be used by more than one extension (e.g.
authentication for a specific service and accounting, both of which
have separate extensions).
11.4 Authorization-Lifetime AVP
The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32
and contains the maximum number of seconds of service to be provided
to the user before the user is to be re-authenticated and/or re-
authorized. Great care should be taken when the Authorization-
Lifetime value is determined, since a low value could create
significant Diameter traffic, which could congest both the network
and the servers.
This AVP MAY be provided by the client as a hint of the maximum
duration that it is willing to accept. However, the server DOES NOT
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have to observe the hint, and MAY return a value that is smaller than
the hint. A value of zero means that no re-authorization is required.
11.5 Session-Timeout AVP
The Session-Timeout AVP (AVP Code 27) [1] is of type Unsigned32 and
contains the maximum number of seconds of service to be provided to
the user before termination of the session. A value of zero means
that this session has an unlimited number of seconds before
termination.
This AVP MAY be provided by the client as a hint of the maximum
duration that it is willing to accept. However, the server DOES NOT
have to observe the hint, and MAY return a value that is smaller than
the hint.
11.6 User-Name AVP
The User-Name AVP (AVP Code 1) [1] is of type OctetString, which
contains the User-Name. The value is represented as a UTF-8
character encoded string in a format consistent with the NAI
specification [8].
11.7 Max-Wait-Time AVP
The Max-Wait-Time AVP (AVP Code 295) is of type Unsigned32, and
contains the maximum amount of time the downstream server is willing
to wait for a response. A server that determines that it cannot
satisfy a request within the requested time MUST issue a DSI message
with the DSI-Event set to DIAMETER_STILL_WORKING or
DIAMETER_CANNOT_PROCESS_IN_TIME.
11.8 Session Movement
There are applications that over the course of a session a user MAY
receive service from different access servers. While the service is
relocated, it MAY be desirable for the AAA infrastructure to view
this as a persistent session, as opposed to a new session each time a
user is relocated. In order to support these applications, when an
AAA server identifies that a request is the continuation of an
existing session, it MUST include the original session identifier in
the Original-Session-Id AVP in the corresponding response message to
the access device.
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11.8.1 Original-Session-Id AVP
The Original-Session-Id AVP (AVP Code 261) is of type OctetString and
MAY be sent in a message of type Response or Answer if a AAA server
already has a session identifier for the user, and wishes to keep the
existing Session-Id. All further messages from the Access Device for
this session MUST use the session identifier in this AVP. This
shouldn't be viewed as a new session, but rather renaming the old
session. Any further messages not using the Session Id in this AVP
will be treated as an unrecognized Session Id.
11.9 Session Termination
The Diameter Base Protocol provides a set of messages that MUST be
used by any peer to explicitly request that a previously
authenticated and/or authorized session be terminated. Since the
Session-Id is typically tied to a particular service (i.e. Mobile IP,
NASREQ, etc), the session termination messages are used to request
that the service tied to the Session Id be terminated.
Session Termination MAY be initiated by a Diameter server, by issuing
a Session-Termination-Ind (STI) message to the access device. An
access device MUST issue a Session-Termination-Request (STR) message
either upon receipt of an STI, or when service to a particular user
is terminated.
A Diameter server MUST be prepared to clean up resources if a
session's authorization lifetime has expired, and no STR was
received. This event could occur if an access device was to
unexpectedly reboot.
An access device MUST issue Session-Termination-Request messages for
all active session prior to an orderly reboot.
11.9.1 Session-Termination-Ind
The Session-Termination-Ind (STI), indicated by the Command-Code set
to 274, MAY be sent by any Diameter entity to the access device to
request that a particular session be terminated. This message MAY be
used when a server detects that a session MUST be terminated, which
is typically done as a policy decision (e.g. local resources have
been expended, etc). The Destination-FQDN AVP MUST be present, and
contain the fully qualified domain name of the access device that
initiated the session (see section 11.0).
Upon receipt of the STI message, the access device MUST issue a
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Session-Terminate-Request message.
Message Format
<Session-Termination-Ind> ::= < Diameter Header: 274 >
< Session-Id >
{ Origin-FQDN }
{ Origin-Realm }
{ User-Name }
{ Destination-Realm }
{ Destination-FQDN }
* [ AVP ]
* [ Proxy-Info ]
11.9.2 Session-Termination-Request
The Session-Termination-Request (STR), indicated by the Command-Code
set to 275, is sent by the access device to inform the Diameter
Server that an authenticated and/or authorized session is being
terminated.
Message Format
<Session-Termination-Request> ::= < Diameter Header: 275 >
< Session-Id >
{ Origin-FQDN }
{ Origin-Realm }
{ User-Name }
{ Destination-Realm }
{ Destination-FQDN }
* [ AVP ]
* [ Proxy-Info ]
* [ Route-Record ]
11.9.3 Session-Termination-Answer
The Session-Termination-Answer (STA), indicated by the Command-Code
set to 276, is sent by the Diameter Server to acknowledge that the
session has been terminated. The Result-Code AVP MUST be present, and
MAY contain an indication that an error occurred while servicing the
STR.
Upon sending or receipt of the STA, the Diameter Server MUST release
all resources for the session indicated by the Session-Id AVP. Any
intermediate server in the Proxy-Chain MAY also release any
resources, if necessary.
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Message Format
<Session-Termination-Answer> ::= < Diameter Header: 276 >
< Session-Id >
{ Result-Code }
{ Origin-FQDN }
{ Origin-Realm }
{ Destination-FQDN }
{ User-Name }
* [ AVP ]
* [ Proxy-Info ]
* [ Route-Record ]
12.0 Message Routing
This section describes the expected behavior of a Diameter server
acting as a proxy or redirect server.
12.1 Realm-Based Message Routing
Diameter request, query and indication message routing is done
through the use of the realm portion of the Network Access Identifier
(NAI) or via a realm encoded in an AVP (e.g. Origin-Realm,
Destination-Realm), and an associated realm routing table (see
section 12.1.1).
When an NAI is used, the realm portion of the user@realm is used to
perform the realm lookup. Diameter servers have a list of locally
supported realms, and MAY have a list of externally supported realms.
When a request, query or indication message is received that includes
a realm that is not locally supported, the message is proxied to the
Diameter entity configured in the "route" table.
Figure 2 depicts an example where DIA1 is an access device and
receives a request for network access from jow@abc.com. DIA1 looks up
"abc.com" in its local realm route table and determines that the
message must be proxied to DIA2. DIA2 does the same check, and
proxies the message to DIA3. DIA3 checks its realm route table, and
determines that the realm is locally supported, and processes the
authentication request, and returns the response. How the response
actually makes it back to the sender of the original request is
described in the next section.
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(Origin-FQDN=dia1.mno.net) (Origin-FQDN=dia1.mno.net)
(Origin-Realm=mno.net) (Origin-Realm=mno.net)
(Destination-Realm=abc.com) (Destination-Realm=abc.com)
(Route-Record=dia2.xyz.com)
+------+ ------> +------+ ------> +------+
| | (Request) | | (Request) | |
| DIA1 +-------------------+ DIA2 +-------------------+ DIA3 |
| | | | | |
+------+ <------ +------+ <------ +------+
mno.net (Response) xyz.com (Response) abc.com
(Origin-FQDN=dia3.abc.com) (Origin-FQDN=dia3.abc.com)
(Origin-Realm=abc.com) (Origin-Realm=abc.com)
(Destination-FQDN=dia1.mno.net) (Destination-FQDN=dia1.mno.net)
(Route-Record=dia2.xyz.com)
Figure 2: Realm-Based Routing
Note the processing rules contained in this section are intended to
be used as general guidelines to Diameter developers. Certain
implementations MAY use different methods than the ones described
here, and still be in compliance with the protocol specification.
12.1.1 Realm-Based Routing Table
All Realm-Based routing lookups are performed against what is
commonly known as the Domain Routing Table (see section 19.0). A
Domain Routing Table Entry contains the following fields:
- Domain Name. The Domain Name is analogous to the realm portion
of the NAI. This is the field that is typically used as a
primary key in the routing table lookups. Note that some
implementations perform their lookups based on longest-match-
from-the-right on the realm rather than requiring an exact
match.
- Extension Id. It is possible for a routing entry to have a
different destination based on the extension identifier of the
message. This field is typically used as a secondary key field
in routing table lookups.
- Local Action. The Local Action field is used to identify how a
message should be treated. The following actions are supported:
1. LOCAL - Diameter messages that resolve to a routing entry
with the Local Action set to Local can be satisfied
locally, and do not need to be forwarded to another
server.
2. PROXY - All Diameter messages that fall within this
category MUST be forwarded to a next hop server. The local
server MAY apply its local policies to the message by
including new AVPs to the message prior to forwarding.
See section 12.4 for more information.
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3. REDIRECT - Diameter messages that fall within this
category MUST have the identity of the home Diameter
server(s) appended, and returned to the sender of the
message. See section 12.3 for more information.
- Server Identifier - One or more servers the message is to be
forwarded to. When the Local Action is set to PROXY, this field
contains the identities of the server(s) the message must be
forwarded to. When the Local Action field is set to REDIRECT,
this field contains the Home Diameter server(s) for the realm.
It is important to note that Diameter servers MUST support at least
one of the PROXY, REDIRECT, or LOCAL modes of operation. Servers do
not need to support all modes of operation in order to conform with
the protocol specification. Servers MUST NOT reorder AVPs with the
same AVP Code.
When a message is being proxied, the servers in a given domain
routing entry MUST have advertised the Extension Identifier (see
section 6.1) for the given message, or have advertised the Wildcard
Extension.
12.2 Proxy and Redirect Server handling of requests
When a message of type request, query or indication is received by a
proxy or redirect server, and it is determined that the request
cannot be locally handled, the next hop for the request is determined
in the following order:
1. If the Destination-FQDN AVP is present, and the host specified
in the AVP can be directly contacted, the message is forwarded
to the host (see section 5.1 for more information), or
2. If the Destination-Realm AVP is present, a routing table lookup
is performed using the domain specific in the AVP.
A message that does not contain any of the above AVPs MUST NOT be
routed. If the message in question cannot be handled locally, a
Message-Reject-Ind is sent with the Result-Code AVP set to an
appropriate error condition.
12.3 Redirect Server
A Redirect Server is one that provides Realm to Diameter Home Server
address resolution. When a message is received by a peer, the
Destination-Realm AVP (or the User-Name AVP if the Destination-Realm
AVP is not present) is extracted from the message, and is used to
perform a lookup in the domain routing table. Implementations MAY
also use the Extension Identifiers as a secondary key in the domain
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routing table lookup.
Successful routing table lookups will return one or more home
Diameter servers that could satisfy the message. The home servers are
encoded in one or more Redirect-Host AVPs, and the Command-Code field
is set to Device-Status-Ind.
+------------------+
| Diameter |
| Redirect Server |
+------------------+
^ |
Request | | DSI +
joe@xyz.com | | DSI-Event = Redirect +
| | Redirect-Host AVP(s)
| v
+----------+ Request +----------+
| abc.net |------------->| xyz.net |
| Diameter | | Diameter |
| Server |<-------------| Server |
+----------+ Response +----------+
Figure 3: Diameter Redirect Server
Lastly, the DSI-Event AVP is added with the Data field of the AVP set
to DIAMETER_REDIRECT_INDICATION, and the message is returned to the
sender of the request. Redirect servers MAY also include the
certificate of the Home server(s). These certificates are
encapsulated in a CMS-Cert AVP [11]. When this occurs, the server
forwarding the request directly to the Home Diameter server SHOULD
include its own certificate in the message.
12.3.1 Redirect-Host AVP
The Redirect-Host AVP (AVP Code 292) is of type Grouped and is found
in Device-Status-Ind messages that include the DSI-Event AVP set to
DIAMETER_REDIRECT_INDICATION. This AVP only needs to be used if the
host the message is to be redirected to is not listening on the
standard Diameter port. Its Data field has the following ABNF
grammar:
Redirect-Host = Redirect-Host-Address Redirect-Host-Port
Redirect-Host-Address = ; See Section 12.3.2
Redirect-Host-Port = ; See Section 12.3.3
The Redirect-Host-Address AVP Data field contains the IP Address of
the Diameter host to which the request MUST be redirected. The
Redirect-Host-Port contains the port number to which the request
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should be sent. Upon receipt of such a event, and this AVP, the
receiving host SHOULD send the request directly to the host
identified by the Redirect-Host-Address AVP.
+---------------------------------------------------------------+
| AVP Header (AVP Code = 292) |
+---------------------------------------------------------------+
| Redirect-Host-Address AVP |
+---------------------------------------------------------------+
| Redirect-Host-Port AVP |
+---------------------------------------------------------------+
12.3.2 Redirect-Host-Address AVP
The Redirect-Host-Address AVP (AVP Code 278) is of type Address. Its
use is described in Section 12.3.1.
12.3.3 Redirect-Host-Port AVP
The Redirect-Host-Port AVP (AVP Code 277) is of type Unsigned32. Its
use is described in Section 12.3.1.
12.4 Proxy Server
This section outlines the processing rules for Diameter proxy
servers. A proxy server can either be stateful or stateless. A Proxy
server MAY act in a stateful manner for some requests, and be
stateless for others. There are two types of states that servers MAY
wish to maintain; transaction and session.
Maintaining transaction state implies that a server keeps a copy of a
request or query messages, which is then used when the corresponding
response is received. Maintaining transaction state also requires
that the Hop-by-Hop identifier MUST be saved, and restored to its
original value when the corresponding response message is received. A
Proxy server MAY also add a Proxy-Info AVP to request and query
message, but MUST remove the AVP in the corresponding response.
Maintaining session state implies that a server keeps track of all
"active" users. An active user is one that has been authorized for a
particular service, and the server has not received any indication
that the user has relinquished access.
A stateless proxy is one that does not maintain session state, but
MUST maintain transaction state. Transaction state SHOULD be released
after a request's corresponding response has been forwarded towards
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the recipient, and has been acknowledged by the underlying transport.
A stateful proxy is one that maintains both transaction and session
state, the latter being done by observing request and responses.
Session state SHOULD be released once it is informed that a user
and/or device has relinquished access. A stateful server MAY provide
the following features:
- Protocol translation (e.g. RADIUS <-> Diameter)
- Limiting resources authorized to a particular user
- Per user or transaction auditing
Home servers processing requests that include the Route-Record and/or
the Proxy-Info AVPs MUST return these AVPs in the same order in the
corresponding response.
12.4.1 Proxying Request, Query and Indication messages
In addition to the rules defined in section 12.2, the following
procedures MUST be handled by proxy servers handling messages of type
request, query or indication.
A proxy server MUST check for forwarding loops before proxying a
message of type Request, Query or Indication. Such as message has
been looped if the server finds its own address in a Route-Record
AVP.
A Diameter server that proxies a message of type Request, Query or
Indication MUST append a Route-Record AVP, which includes its
identity. Diameter Servers that receive messages MUST validate the
last Route-Record AVP in the message and ensure that the host
identified in the AVP is the same as the sender of the message.
A Proxy Server MAY also include the Proxy-Info AVP in a message of
type Request or Query, which is used to encode local state
information. The Proxy-Info AVP is guaranteed to be present in the
corresponding response.
The message is then forwarded to the downstream Diameter server, as
identified in the Domain Routing Table.
Proxy Server MUST save the Hop-by-Hop Identifier in request messages,
if the value of the field is changed, with a locally unique value.
The saved identifier MAY be encoded in the Proxy-Info AVP, and will
be required in the processing of the corresponding response.
12.4.2 Proxying Response and Answer messages
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A proxy server MUST only process messages of type Response or Answer
whose last Route-Record AVP matches one of its identities. Any
responses that do not conform to this rule MUST be dropped. The last
Route-Record AVP MUST be removed from the message before it is
forwarded to the next hop, which is identified by the second to last
Route-Record AVP.
If the last Proxy-Info AVP in the message is targeted to the local
Diameter server, the AVP MUST be removed.
If a proxy server receives a response with a Result-Code AVP
indicating a failure, it MUST NOT modify the contents of the AVP. Any
additional local errors detected SHOULD be logged, but not reflected
in the Result-Code AVP.
Prior to forwarding the response, proxy servers MUST restore the
original value of the Diameter header's Hop-by-Hop Identifier field.
12.4.3 Route-Record AVP
The Route-Record AVP (AVP Code 282) is of type OctetString, encoded
in the UTF-8 [24] format, and contains the Fully Qualified Domain
Name of the Proxy appending this AVP to a Diameter message. The FQDN
added in this AVP MUST be the same as the FQDN sent in the Origin-
FQDN in the Device-Reboot-Ind message.
12.4.4 Proxy-Info AVP
The Proxy-Info AVP (AVP Code = 284) is of type Grouped. The Grouped
Data field has the following ABNF grammar:
Proxy-Info = Proxy-Address Proxy-State
Proxy-Address = ; See Section 12.4.5
Proxy-State = ; See Section 12.4.6
The Proxy-Address AVP Data field contains one of the IP addresses of
the system that created the AVP. This assists hosts in determining
whether a Proxy-Info AVP is intended for the local host. The Proxy-
State AVP contains state information, and MUST be treated as opaque
data.
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+---------------------------------------------------------------+
| AVP Header (AVP Code = 284) |
+---------------------------------------------------------------+
| Proxy-Address AVP |
+---------------------------------------------------------------+
| Proxy-State AVP |
+---------------------------------------------------------------+
12.4.5 Proxy-Address AVP
The Proxy-Address AVP (AVP Code = 280) is of type Address. Its use
is described in Section 12.4.4.
12.4.6 Proxy-State AVP
The Proxy-State AVP (AVP Code = 33) is of type OctetString. Its use
is described in Section 12.4.4.
12.4.7 Destination-Realm AVP
The Destination-Realm AVP (AVP Code 283) is of type OctetString,
encoded in the UTF-8 [24] format, and contains the realm the message
is to be routed to. The Destination-Realm AVP MUST NOT be present in
messages of type Answer or Response. Diameter Clients insert the
realm portion of the User-Name AVP. Home servers initiating a message
of type Request, Query or Indication use the value of the Origin-
Realm AVP from a previous message received from the intended target
host (unless it is known a priori). When present, the Destination-
Realm AVP is used to perform message routing decisions.
12.5 Applying Local Policies
Proxies MAY apply local access policies to Diameter requests, or
responses, by adding, changing or deleting AVPs in the messages.
Proxies that apply local policies MUST NOT allow end-to-end security
on any messages that traverse through it, unless security is
terminated locally.
A proxy wishing to modify a Diameter message to enforce some local
policy that detects that end-to-end security has been applied to the
message MUST return a response to the originator with the Result-Code
set to DIAMETER_NO_END_2_END_SECURITY. The originator of the request
MAY re-issue the request with no end-to-end security if it falls
within its local policy.
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In the event that the Home Diameter server receives a request with
contradictory information (possibly due to some proxy adding a local
policy), it MAY accept the latest AVP, or MAY return the response
with the Result-Code AVP set to DIAMETER_CONTRADICTING_AVPS. However,
an access device receiving a response that contains contradictory
information SHOULD reject service to the user.
12.6 Hiding Network Topology
Stateful proxies forwarding requests to servers outside of their
administrative domain MAY hide the internal network topology. Servers
perform this by removing all Route-Record AVPs in the message, and
maintains the Route-Record AVPs to add to the corresponding response.
Such servers MUST still add their own Route-Record AVP to the request
prior to forwarding.
12.7 Loop Detection
When a Diameter Proxy or Redirect server receives a message of type
Request, Query or Indication, it MUST examine all Route-Record AVPs
in the message to determine whether such an AVP already exists with
the local server's identity. If an AVP with the local host's identity
is found in the request, it is an indication that the message is
being looped through the same set of proxies. When such an event
occurs, the Diameter server that detects the loop returns a response
(or MRI if no response is possible) with the Result-Code AVP set to
DIAMETER_LOOP_DETECTED.
13.0 Accounting
This accounting protocol is based on an authorization-server directed
model with capabilities for real-time delivery of accounting
information. Several fault resilience methods [40] have been built in
to the protocol in order minimize loss of accounting data in various
fault situations and under different assumptions about the
capabilities of the used devices.
13.1 Server Directed Model
The server directed model means that the device generating the
accounting data gets information from either the authorization server
(if contacted) or the accounting server regarding the way accounting
data shall be forwarded. This information includes accounting record
timeliness requirements.
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As discussed in [40], real-time transfer of accounting records is a
requirement, such as the need to perform credit limit checks and
fraud detection. Note that batch accounting is not a requirement, and
is therefore not supported by this extension. Should Batched
Accounting be required in the future, a new Diameter extension will
need to be created, or it could be handled using another protocol.
The authorization server (chain) directs the selection of proper
transfer strategy, based on its knowledge of the user and
relationships of roaming partnerships. The server (or proxies in
between) uses the Accounting-Interim-Interval AVP to control the
operation of the Diameter peer operating as a client. The
Accounting-Interim-Interval AVP, when present, instructs the Diameter
node acting as a client to produce accounting records continuously
even during a session.
The Diameter accounting server MAY override the interim interval by
including an Accounting-Interim-Interval AVP in the Accounting-Answer
message. When the AVP is present, the latest value received SHOULD be
used in the generation of interim accounting messages.
13.2 Protocol Messages
A Diameter node that receives a successful authentication and/or
authorization messages from the Home AAA Server, MUST collect
accounting information for the session. The Accounting-Request
message is used to transmit the accounting information to the Home
AAA server, which MUST reply with the Accounting-Answer message to
confirm reception. The Accounting-Answer message includes the
Result-Code AVP, which MAY indicate that an error was present in the
accounting message. A rejected Accounting-Request message SHOULD
cause the user's session to be terminated.
Each Diameter Accounting protocol message MAY be compressed using
IPComp [41] in order to reduce the used network bandwidth, which MAY
use IKE [15] to negotiate the compression parameters.
13.3 Extension document requirements
Each Service-Specific Diameter extension (e.g. NASREQ, MobileIP),
MUST define their Service-Specific AVPs that MUST be present in the
Accounting-Request message in a section entitled "Accounting AVPs".
The extension MUST assume that the AVPs described in this document
will be present in all Accounting messages, so only their respective
service-specific AVPs need to be defined in this section.
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13.4 Fault Resilience
Diameter Base protocol mechanisms are used to overcome small message
loss and network faults of temporary nature.
Diameter peers acting as clients MUST implement the use of failover
to guard against server failures and certain network failures.
Diameter peers acting as servers or related off-line processing
systems MUST detect duplicate accounting records caused by the
sending of same record to several servers and duplication of messages
in transit. This detection MUST be based on the inspection of the
Session-Id and Accounting-Record-Number AVP pairs.
Diameter clients MAY have non-volatile memory for the safe storage of
accounting records over reboots or extended network failures, network
partitions, and server failures. If such memory is available the
client SHOULD store new accounting records there as soon as the
records are created and until a positive acknowledgement of their
reception from the Diameter Server has been received. Upon a reboot,
the client MUST starting sending the records in the non-volatile
memory to the accounting server with appropriate modifications in
termination cause, session length, and other relevant information in
the records.
A further extension of this protocol may include AVPs to control how
many accounting records may at most be stored in the Diameter client
without committing them to the non-volatile memory or transferring
them to the Diameter server.
The client SHOULD NOT remove the accounting data from any of its
memory areas before the correct Accounting-Answer has been received.
The client MAY remove oldest, undelivered or yet unacknowledged
accounting data if it runs out of resources such as memory. It is an
implementation dependent matter for the client to accept new sessions
under this condition.
13.5 Accounting Records
In all accounting records the Session-Id and User-Name AVPs MUST be
present. If strong authentication is required, as described in [11],
the CMS-Data AVP may be used to authenticate the Accounting Data and
Service Specific AVPs. It is not typically necessary, nor
recommended, that the strong authentication cover any additional AVPs
since the Data and Service Specific AVP, and associated CMS-Data, MAY
need to be submitted to a third party.
Different types of accounting records are sent depending on the
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actual type of accounted service and the authorization server's
directions for interim accounting. If the accounted service is a
one-time event, meaning that the start and stop of the event are
simultaneous, then the Accounting-Record-Type AVP MUST be present and
set to the value EVENT_RECORD.
If the accounted service is of a measurable length, then the AVP MUST
use the values START_RECORD, STOP_RECORD, and possibly,
INTERIM_RECORD. If the authorization server has directed interim
accounting to be enabled for the session, but no interim interval was
specified, two accounting records MUST be generated for each service
of type session. When the initial Accounting-Request is sent for a
given session is sent, the Accounting-Record-Type AVP MUST be set to
the value START_RECORD. When the last Accounting-Request is sent, the
value MUST be STOP_RECORD.
If a specified interim interval exists, the Diameter client MUST
produce additional records between the START_RECORD and STOP_RECORD,
marked INTERIM_RECORD. The production of these records is directed
both by Accounting-Interim-Interval as well as any re-authentication
or re-authorization of the session. The Diameter client MUST
overwrite any previous interim accounting records that are locally
stored for delivery, if a new record is being generated for the same
session. This ensures that only one pending interim record can exist
on an access device for any given session.
14.0 Accounting Command-Codes
This section defines new Command-Code values that MUST be supported
by all Diameter implementations that provide Accounting services.
14.1 Accounting-Request (ACR) Command
The Accounting-Request command, indicated by the Command-Code field
set to 271, is sent by a Diameter node, acting as a client, in order
to exchange accounting information with a peer.
When the Accounting-Request is being submitted to a broker, and
includes the CMS-Data AVP [11], the CMS-Data AVP MUST be signed by
both the local and home Diameter server using the countersignature
procedures described in [11].
The AVP listed below SHOULD include service specific accounting AVPs,
as described in section 13.3.
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Message Format
<Accounting-Request> ::= < Diameter Header: 271 >
< Session-Id >
{ Acct-Extension-Id }
{ User-Name }
{ Origin-FQDN }
{ Origin-Realm }
{ Destination-Realm }
{ Accounting-Record-Type }
{ Accounting-Record-Number }
[ Accounting-Interim-Interval ]
{ Accounting-Session-Id }
* [ AVP ]
[ CMS-Data ]
* [ Proxy-Info ]
* [ Route-Record ]
14.2 Accounting-Answer (ACA) Command
The Accounting-Answer command, indicated by the Command-Code field
set to 272, is used to acknowledge an Accounting-Request command. The
Accounting-Answer command contains the same Session-Id and MAY
contains the same Accounting Description and Usage AVPs that were
sent in the Accounting-Request command. If the CMS-Data AVP was
present in the Accounting-Request, the corresponding ACA message MUST
include the CMS-Data AVP signed by the responder to provide strong
AVP authentication, which MAY be used for the purposes of
repudiation.
Only the target Diameter Server, known as the home Diameter Server,
SHOULD respond with the Accounting-Answer command.
The AVP listed below SHOULD include service specific accounting AVPs,
as described in section 13.3.
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Message Format
<Accounting-Answer> ::= < Diameter Header: 272 >
< Session-Id >
{ Acct-Extension-Id }
{ User-Name }
{ Result-Code }
{ Origin-FQDN }
{ Origin-Realm }
{ Destination-FQDN }
{ Accounting-Record-Type }
{ Accounting-Record-Number }
{ Accounting-Session-Id }
[ Error-Reporting-FQDN ]
[ Accounting-Interim-Interval ]
* [ AVP ]
[ CMS-Data ]
* [ Proxy-Info ]
* [ Route-Record ]
14.3 Accounting-Status-Ind (ASI) Command
The Accounting-Status-Ind command, indicated by the Command-Code
field set to 279, is sent by a Diameter node in order to inform its
peer of whether Accounting messages will be sent in the future. A
Diameter node that is about to be taken out of service SHOULD issue
an Accounting-Status-Ind message, with the Accounting-State AVP set
to DISABLED. Prior to sending such a message, every attempt SHOULD be
made to transmit any pending accounting messages.
A Diameter node that detected that it is able to issue Accounting
messages MUST issue an Accounting-Status-Ind message, with the
Accounting-State AVP set to ENABLED.
Message Format
<Accounting-Status-Ind> ::= < Diameter Header: 279 >
{ Acct-Extension-Id }
{ Origin-FQDN }
{ Origin-Realm }
{ Destination-Realm }
{ Accounting-State }
* [ AVP ]
* [ Proxy-Info ]
* [ Route-Record ]
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14.4 Accounting-Poll-Ind (API) Command
The Accounting-Poll-Ind command, indicated by the Command-Code field
set to 273, is sent by a Diameter Server in order to force the peer
to send current accounting data. This data MUST include not yet sent
accounting records from completed sessions, as well as INTERIM_RECORD
records from all ongoing sessions.
Diameter implementations MAY support the Accounting-Poll-Ind command.
An implementation still conforms to this specification if API is not
supported.
The receiver MUST use the Accounting-Request command to send the
accounting data.
The use of Accounting-Poll-Ind is useful in situations where a
Diameter server comes up after an unscheduled downtime, and wishes to
synchronize with the client(s) sooner than at the end of the next
INTERIM_RECORD or at the end of a session.
Warning: The use of the Accounting-Poll-Ind message is discouraged in
roaming networks, since it is unfeasible for a server to attempt to
poll all of it's roaming partner's Diameter peers.
Message Format
<Accounting-Poll-Ind> ::= < Diameter Header: 273 >
< Session-Id >
{ Acct-Extension-Id }
{ Destination-FQDN }
{ Origin-FQDN }
{ Origin-Realm }
{ Destination-Realm }
{ Accounting-Session-Id }
[ Destination-FQDN ]
* [ AVP ]
* [ Proxy-Info ]
* [ Route-Record ]
15.0 Accounting AVPs
This section contains AVPs that describe accounting usage information
related to a specific session.
15.1 Accounting-Record-Type AVP
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The Accounting-Record-Type AVP (AVP Code 480) is of type Unsigned32
and contains the type of accounting record being sent. The following
values are currently defined for the Accounting-Record-Type AVP:
EVENT_RECORD 1
An Accounting Event Record is used to indicate that a one-time
event has occurred (meaning that the start and end of the event
are simultaneous). This record contains all information
relevant to the service, and is the only record of the service.
START_RECORD 2
An Accounting Start, Interim, and Stop Records are used to
indicate that a service of a measurable length has been given.
An Accounting Start Record is used to initiate an accounting
session, and contains accounting information that is relevant
to the initiation of the session.
INTERIM_RECORD 3
An Interim Accounting Record contains cumulative accounting
information for an existing accounting session. Interim
Accounting Records SHOULD be sent every time a re-
authentication or re-authorization occurs. Further, additional
interim record triggers MAY be defined by application-specific
Diameter extensions. The selection of whether to use
INTERIM_RECORD records is directed by the Accounting-Interim-
Interval AVP.
STOP_RECORD 4
An Accounting Stop Record is sent to terminate an accounting
session and contains cumulative accounting information relevant
to the existing session.
15.2 Accounting-Interim-Interval AVP
The Accounting-Interim-Interval AVP (AVP Code 482) is of type
Unsigned32 and is sent from the Diameter authenticating/authorizing
server to the Diameter client. The client uses information in this
AVP to decide how and when to produce accounting records. With
different values in this AVP, service sessions can result in one,
two, or two+N accounting records, based on the needs of the home-
organization. The following accounting record production behavior is
directed by the inclusion of this AVP:
1. The omission of the Accounting-Interim-Interval AVP or its
inclusion with Value field set to 0 means that EVENT_RECORD,
START_RECORD, and STOP_RECORD are produced, as appropriate for
the service.
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2. The inclusion of the AVP with Value field set to a non-zero
value means that INTERIM_RECORD records MUST be produced
between the START_RECORD and STOP_RECORD records. The Value
field of this AVP is the nominal interval between these records
in seconds. The Diameter node that originates the accounting
information, known as the client, MUST produce the first
INTERIM_RECORD record roughly at the time when this nominal
interval has elapsed from the START_RECORD, the next one again
as the interval has elapsed once more, and so on until the
session ends and a STOP_RECORD record is produced.
The client MUST ensure that the interim record production times
are randomized so that large accounting message storms are not
created either among records or around a common service start
time.
15.3 Accounting-Record-Number AVP
The Accounting-Record-Number AVP (AVP Code 485) is of type Unsigned32
and identifies this record within one session. As Session-Id AVPs are
globally unique, the combination of Session-Id and Accounting-
Record-Number AVPs is also globally unique, and can be used in
matching accounting records with confirmations. An easy way to
produce unique numbers is to set the value to 0 for records of type
EVENT_RECORD and START_RECORD, and set the value to 1 for the first
INTERIM_RECORD, 2 for the second, and so on until the value for
STOP_RECORD is one more than for the last INTERIM_RECORD.
15.4 Accounting-State AVP
The Accounting-State AVP (AVP Code 486) is of type Unsigned32 and is
used to communicate to a peer whether Accounting messages will be
sent in the future. A node that issues an ASI with the Accounting-
State AVP set to DISABLED is informing its peer that it will no
longer be transmitting Accounting messages until a subsequent ASI
message is sent with the Accounting-State AVP set to ENABLED.
The following values have been defined:
1 ENABLED
2 DISABLED
15.5 Accounting-Session-Id AVP
The Accounting-Session-Id AVP (AVP Code 44) is of type OctetString,
and SHOULD be encoded in UTF-8 format [13]. The Accounting-Session-Id
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is not used by the Diameter protocol, since the Session-Id defined in
[1] is used for both authentication/authorization and accounting
purposes. However, a RADIUS/Diameter gateway MAY need to include the
Accounting-Session-Id in Diameter accounting messages.
16.0 AVP Occurrence Table
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 table uses the following symbols:
0 The AVP MUST NOT be present in the message.
0+ Zero or more instances of the AVP MAY be present in the
message.
0-1 Zero or one instance of the AVP MAY be present in the
message. It is considered an error if there are more than
once instance of the AVP.
1 One instance of the AVP MUST be present in the message.
1+ At least one instance of the AVP MUST be present in the
message.
16.1 Base Protocol Command AVP Table
The table in this section is limited to the non-accounting Command
Codes defined in this specification.
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+-------------------------------+
| Command-Code |
|---+---+---+---+---+---+---+---+
Attribute Name |DRI|DSI|DWR|DWA|MRI|STI|STR|STA|
------------------------------|---+---+---+---+---+---+---+---|
Auth-Extension-Id |1+ |0 |0 |0 |0 |0 |0 |0 |
Authorization-Lifetime |0 |0 |0 |0 |0 |0 |0 |0 |
Destination-FQDN |0-1|0-1|0-1|1 |1 |1 |0-1|1 |
Destination-Realm |0 |0 |0 |0 |1 |1 |1 |0 |
DSI-Event |0 |1 |0 |0 |0 |0 |0 |0 |
Error-Message |0 |0 |0 |0 |0-1|0 |0 |0 |
Error-Reporting-FQDN |0 |0 |0 |0 |1 |0 |0 |0 |
Failed-AVP |0 |0 |0 |0 |0-1|0 |0 |0 |
Failed-Command-Code |0 |0 |0 |0 |0-1|0 |0 |0 |
Firmware-Revision |0-1|0 |0 |0 |0 |0 |0 |0 |
Host-IP-Address |1+ |0 |0 |0 |0 |0 |0 |0 |
Max-Time-Wait |0 |0 |0 |0 |0 |0 |0 |0 |
Origin-FQDN |1 |1 |1 |1 |1 |1 |1 |1 |
Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |
Original-Session-Id |0 |0 |0 |0 |0 |0 |0 |0 |
Product-Name |1 |0 |0 |0 |0 |0 |0 |0 |
Proxy-Info |0 |0 |0 |0 |0+ |0+ |0+ |0+ |
Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0 |
Result-Code |0 |0 |0 |1 |1 |0 |0 |1 |
Route-Record |0 |0 |0 |0 |0+ |0+ |0+ |0+ |
Session-Id |0 |0-1|0 |0 |0-1|1 |1 |1 |
Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |
Supported-Vendor-Id |0+ |0 |0 |0 |0 |0 |0 |0 |
User-Name |0 |0 |0 |0 |0 |1 |1 |1 |
Vendor-Id |1 |0 |0 |0 |0 |0 |0 |0 |
------------------------------|---+---+---+---+---+---+---+---|
16.2 Accounting AVP Table
The table in this section is used to represent which AVPs defined in
this document are to be present in the Accounting messages.
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+-----------------------+
| Command-Code |
|-----+-----+-----+-----+
Attribute Name | ACR | ACA | API | ASI |
------------------------------|-----+-----+-----+-----+
Accounting-Interim-Interval | 0-1 | 0-1 | 0 | 0 |
Accounting-Record-Number | 1 | 1 | 0 | 0 |
Accounting-Record-Type | 1 | 1 | 0 | 0 |
Accounting-Session-Id | 1 | 1 | 0 | 1 |
Accounting-State | 0 | 0 | 1 | 0 |
Destination-FQDN | 0+ | 1 | 0+ | 0-1 |
Destination-Realm | 1 | 0 | 1 | 1 |
Error-Reporting-FQDN | 0 | 0+ | 0 | 0 |
Acct-Extension-Id | 1 | 1 | 1 | 1 |
Origin-FQDN | 1 | 1 | 1 | 1 |
Origin-Realm | 1 | 1 | 1 | 1 |
Proxy-Info | 0+ | 0+ | 0+ | 0+ |
Route-Record | 0+ | 0+ | 0+ | 0+ |
Result-Code | 0 | 1 | 0 | 0 |
Session-Id | 1 | 1 | 0 | 1 |
------------------------------|-----+-----+-----+-----+
17.0 IANA Considerations
This document defines a number of assigned numbers to be maintained
by the IANA. This section explains the criteria to be used by the
IANA to assign additional numbers in each of these lists. The
following subsections describe the assignment policy for the
namespaces defined elsewhere in this document.
17.1 AVP
As defined in section 4.0, the AVP header contains two fields that
requires IANA namespace management; the AVP Code and Flags field.
17.1.1 AVP Code
the AVP Code namespace is used to identify attributes. When the
Vendor ID value is set to zero (0), IANA will maintain a registry of
assigned AVP codes, and in some cases also their values. AVP Codes
0-254 are managed separately as RADIUS Attribute Types [46], while
the remaining namespace is available for assignment through
Designated Expert [12].
Vendor-Specific AVP Codes, where the Vendor-Id field in the AVP
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header is set to a non-zero value, is for Private Use.
This document defines the AVP Codes 257-259, 260-272, 277-284, 291-
297, 480, 482 and 485-486. See section 4.5 for the assignment of the
namespace in this specification.
17.1.2 AVP Flags
There are 16 bits in the AVP Flags field of the AVP header, defined
in section 4.0. This document assigns bit 1 ('M'andatory), bit 3
('V'endor Specific) and bit 5 ('P'rotected). The remaining bits
should only be assigned via a Standards Action [12].
17.2 Diameter Header
As defined in section 3.0, the Diameter header contains two fields
that require IANA namespace management; Command Code and Message
Flags.
17.2.1 Command Codes
The Command Code namespace is used to identify Diameter commands.
The values 0-255 are reserved for RADIUS backward compatibility, and
are defined as "RADIUS Packet Type Codes" in [46]. The remaining
values are available via Standards Action [12].
Vendor-Specific Command Codes, where the Vendor-Id field in the
Diameter header is set to a non-zero value, is for Private Use.
This document defines the Command Codes 257, 259, 271-276, 279-282.
See section 3.1 for the assignment of the namespace in this
specification.
17.2.2 Message Flags
There are thirteen bits in the Flags field of the Diameter header.
This document assigns bit 1 ('R'esponse), bit 2 ('I'nterrogation) and
bit 3 ('E'xpected Reply). Bits 4 through 13 should only be assigned
via a Standards Action [12].
17.3 Extension Identifiers
As defined in section 6.1, the Extension Identifier is used to
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identify a specific Diameter Extension. All values, other than zero
(0) are available for assignment via Standards Action [12].
Note that the Diameter protocol is not intended to be extended for
any purpose. Any extensions defined MUST ensure that they fit within
the existing framework, and that no changes to the base protocol are
required.
17.4 Result-Code AVP Values
As defined in Section 10.2, the Result-Code AVP (AVP Code 268)
defines the values 2001, 4001-4003 and 5001-5013.
All remaining values are available for assignment via IETF Consensus
[12].
17.5 DSI-Event AVP Values
As defined in Section 9.1.1, the DSI-Event AVP (AVP Code 297) defines
the values 1001, 3001, 4001 and 5001-5008. All remaining values are
available for assignment via IETF Consensus [12].
17.6 Accounting-State AVP Values
As defined in Section 15.4, the Accounting-State AVP (AVP Code 486)
defines the values 1-2. All remaining values are available for
assignment via IETF Consensus [12].
17.7 Accounting-Record-Type AVP Values
As defined in Section 15.1, the Accounting-Record-Type AVP (AVP Code
480) defines the values 1-4. All remaining values are available for
assignment via IETF Consensus [12].
17.8 Diameter TCP/SCTP Port Numbers
An IANA request has been placed for TCP and SCTP port numbers. The
IANA has informed the authors that "TBD" should be used in section
2.1 this document, and will be updated by the RFC editor during the
RFC publication process.
18.0 Open Issues
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The following are the open issues that SHOULD be addressed in future
versions of the Diameter protocol:
- AVPs with time values are represented by Unsigned32 type data.
This value is a timestamp consistent with NTP [18]. This field
is expected to expire sometime in 2038. Future investigation
SHOULD be done to determine if a 64 bit time format could be
used.
19.0 Diameter protocol related configurable parameters
This section contains the configurable parameters that are found
throughout this document:
Diameter Peer
A Diameter entity MAY communicate with peers that are
statically configured. A statically configured Diameter peer
would require that either the IP address or the fully qualified
domain name (FQDN) be supplied, which would then be used to
resolve through DNS.
Realm Routing Table
A Diameter Proxy server routes messages based on the realm
portion of a Network Access Identifier (NAI). The server MUST
have a table of Realms Names, and the address of the peer to
which the message must be forwarded to. The routing table MAY
also include a "default route", which is typically used for all
messages that cannot be locally processed.
RTT-Multiplier
The Round Trip Time Multiplier is used to determine when a DWR
message is to be sent to an inactive peer. The recommended
valus is 4.
Watchdog Interval Period
The Watchdog Interval Period is the frequency at which DWR
messages are sent to inactive peers. The recommended value is
30 seconds.
20.0 Security Considerations
The Diameter base protocol assumes that messages are secured by using
either IP Security, or TLS. This security model is acceptable in
environments where there are no untrusted third party Diameter
brokers, or redirect servers.
Calhoun et al. expires October 2001 [Page 80]
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When third party brokers or redirect servers are used, strong
application level security SHOULD be required, such as non-
repudiation. When the communicating peers do require this level of
security either for legal or business purposes, the extension defined
in [11] MAY be used. This security model provides AVP-level
authentication, and the encryption mechanism is designed such that
only the target host has the keying information required to decrypt
the information.
21.0 References
[1] C. Rigney, A. Rubens, W. Simpson, S. Willens, "Remote Authenti-
cation Dial In User Service (RADIUS)", RFC 2865, June 2000.
[2] Reynolds, Postel, "Assigned Numbers", RFC 1700, October 1994.
[3] Postel, "User Datagram Protocol", RFC 768, August 1980.
[4] Rivest, "The MD5 Message-Digest Algorithm", RFC 1321, April
1992.
[5] Kaufman, Perlman, Speciner, "Network Security: Private Communi-
cations in a Public World", Prentice Hall, March 1995, ISBN 0-
13-061466-1.
[6] Krawczyk, Bellare, Canetti, "HMAC: Keyed-Hashing for Message
Authentication", RFC 2104, January 1997.
[7] P. Calhoun, W. Bulley, A. Rubens, J. Haag, "Diameter NASREQ
Extension", draft-ietf-aaa-diameter-nasreq-03.txt, IETF work in
progress, May 2001.
[8] Aboba, Beadles "The Network Access Identifier." RFC 2486. Janu-
ary 1999.
[10] P. Calhoun, C. Perkins, "Diameter Mobile IP Extensions", draft-
ietf-aaa-diameter-mobileip-03.txt, IETF work in progress, May
2001.
[11] P. Calhoun, W. Bulley, S. Farrell, "Diameter End-2-End Security
Extension", draft-ietf-aaa-diameter-e2e-sec-01.txt (work in pro-
gress), May 2001.
[12] Narten, Alvestrand,"Guidelines for Writing an IANA Considera-
tions Section in RFCs", BCP 26, RFC 2434, October 1998
Calhoun et al. expires October 2001 [Page 81]
Internet-Draft May 2001
[13] S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[14] Myers, Ankney, Malpani, Galperin, Adams, "X.509 Internet Public
Key Infrastructure Online Certificate Status Protocol (OCSP)",
RFC 2560, June 1999.
[15] D. Harkins, D. Carrel, "The Internet Key Exchange (IKE)", RFC
2409, November 1998.
[16] Hinden, Deering, "IP Version 6 Addressing Architecture", RFC
2373, July 1998.
[17] ISI, "Internet Protocol", RFC 791, September 1981.
[18] Mills, "Simple Network Time Protocol (SNTP) Version 4 for IPv4,
IPv6 and OSI, RFC 2030, October 1996.
[19] Housley, Ford, Polk, Solo, "Internet X.509 Public Key Infras-
tructure Certificate and CRL Profile", RFC 2459, January 1999.
[20] B. Aboba, G. Zorn, "Criteria for Evaluating Roaming Protocols",
RFC 2477, January 1999.
[21] M. Beadles, D. Mitton, "Criteria for Evaluating Network Access
Server Protocols", draft-ietf-nasreq-criteria-05.txt, IETF work
in progress, June 2000.
[22] T. Hiller and al, "CDMA2000 Wireless Data Requirements for AAA",
draft-hiller-cdma2000-aaa-02.txt, IETF work in progress, Sep-
tember 2000.
[23] S. Glass, S. Jacobs, C. Perkins, "Mobile IP Authentication,
Authorization, and Accounting Requirements". RFC 2977. October
2000.
[24] F. Yergeau, "UTF-8, a transformation format of ISO 10646", RFC
2279, January 1998.
[25] L. J. Blunk, J. R. Vollbrecht, "PPP Extensible Authentication
Protocol (EAP)." RFC 2284, March 1998.
[26] R. Stewart et al., "Stream Control Transmission Protocol". RFC
2960. October 2000.
[27] Postel, J. "Transmission Control Protocol", RFC 793, January
1981.
Calhoun et al. expires October 2001 [Page 82]
Internet-Draft May 2001
[28] E. Guttman, C. Perkins, J. Veizades, M. Day. "Service Location
Protocol, Version 2", RFC 2165, June 1999.
[29] P. Calhoun, "Diameter Resource Management", draft-calhoun-
diameter-res-mgmt-06.txt, IETF Work in Progress, February 2001.
[30] Institute of Electrical and Electronics Engineers, "IEEE Stan-
dard for Binary Floating-Point Arithmetic", ANSI/IEEE Standard
754-1985, August 1985.
[31] D. Crocker, P. Overell, "Augmented BNF for Syntax Specifica-
tions: ABNF", RFC 2234, November 1997.
[32] E. Guttman, C. Perkins, J. Kempf, "Service Templates and Ser-
vice: Schemes", RFC 2609, June 1999.
[33] A. Gulbrandsen, P. Vixie, L. Esibov, "A DNS RR for specifying
the location of services (DNS SRV)", RFC 2782, February 2000.
[34] D. Eastlake, "Domain Name System Security Extensions", RFC 2535,
March 1999.
[35] D. Eastlake, "DNS Security Operational Considerations", RFC
2541, March 1999.
[36] D. Eastlake, "DNS Request and Transaction Signatures ( SIG(0)s
)", RFC 2931, September 2000.
[37] S. Kent, R. Atkinson, "Security Architecture for the Internet
Protocol", RFC 2401, November 1998.
[38] A. Frier, P. Karlton, and P. Kocher, "The SSL 3.0 Protocol",
Netscape Communications Corp., Nov 18, 1996.
[39] "The Communications of the ACM" Vol.33, No.6 (June 1990), pp.
677-680.
[40] B. Aboba, J. Arkko, D. Harrington. "Introduction to Accounting
Management", RFC 2975, October 2000.
[41] A. Shacham, R. Monsour, R. Pereira, M. Thomas, "IP Payload
Compression Protocol (IPComp)", RFC 2393, December 1998.
[42] W. Simpson, "The Point-to-Point Protocol (PPP)", RFC 1661, STD
51, July 1994.
[43] B. Aboba, J. Lu, J. Alsop, J. Ding, W. Wang, "Review of Roaming
Implementations", RFC 2194, September 1997.
Calhoun et al. expires October 2001 [Page 83]
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[44] B. Aboba, J. Vollbrecht, "Proxy Chaining and Policy Implementa-
tion in Roaming", RFC 2607, June 1999.
[45] C. Perkins, Editor. IP Mobility Support. RFC 2002, October
1996.
[46] IANA, "RADIUS Types", http://www.isi.edu/in-
notes/iana/assignments/radius-types
22.0 Acknowledgements
The authors would like to thank Nenad Trifunovic, Tony Johansson and
Pankaj Patel for their participation in the pre-IETF Document Reading
Party. Allison Mankin's assistance was invaluable in working out
transport issues, and similarly with Steven Bellovin's help in the
security area.
Paul Funk and David Mitton were instrumental in getting the Peer
State Machine correct, and our deep thanks go to them for their time.
The authors would also like to acknowledge the following people for
their contribution in the development of the Diameter protocol:
Bernard Aboba, William Bulley, Mark Eklund, David Frascone, Daniel C.
Fox, Lol Grant, Ignacio Goyret, Nancy Greene, Peter Heitman, Fredrik
Johansson, Mark Jones, Martin Julien, Paul Krumviede, Fergal Ladley,
Ryan Moats, Victor Muslin, Kenneth Peirce, Stephen Farrell, Sumit
Vakil, John R. Vollbrecht, Jeff Weisberg and Jonathan Wood
23.0 Authors' Addresses
Questions about this memo can be directed to:
Pat R. Calhoun
Network and Security Research Center, Sun Laboratories
Sun Microsystems, Inc.
15 Network Circle
Menlo Park, California, 94025
USA
Phone: +1 650-786-7733
Fax: +1 650-786-6445
E-mail: pcalhoun@eng.sun.com
Calhoun et al. expires October 2001 [Page 84]
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Haseeb Akhtar
Wireless Technology Labs
Nortel Networks
2221 Lakeside Blvd.
Richardson, TX 75082-4399
USA
Phone: +1 972-684-8850
E-Mail: haseeb@nortelnetworks.com
Jari Arkko
Oy LM Ericsson Ab
02420 Jorvas
Finland
Phone: +358 40 5079256
E-Mail: Jari.Arkko@ericsson.com
Erik Guttman
Solaris Advanced Development
Sun Microsystems, Inc.
Eichhoelzelstr. 7
74915 Waibstadt
Germany
Phone: +49-7263-911-701
E-mail: erik.guttman@germany.sun.com
Allan C. Rubens
Tut Systems, Inc.
220 E. Huron, Suite 260
Ann Arbor, MI 48104
USA
Phone: +1 734-995-1697
E-Mail: arubens@tutsys.com
Glen Zorn
Cisco Systems, Inc.
500 108th Avenue N.E., Suite 500
Bellevue, WA 98004
USA
Phone: +1 425 438 8218
Calhoun et al. expires October 2001 [Page 85]
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24.0 Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this docu-
ment itself may not be modified in any way, such as by removing the
copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of develop-
ing Internet standards in which case the procedures for copyrights
defined in the Internet Standards process must be followed, or as
required to translate it into languages other than English. The lim-
ited permissions granted above are perpetual and will not be revoked
by the Internet Society or its successors or assigns. This document
and the information contained herein is provided on an "AS IS" basis
and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DIS-
CLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE.
25.0 Expiration Date
This memo is filed as <draft-ietf-aaa-diameter-03.txt> and expires in
October 2001.
Calhoun et al. expires October 2001 [Page 86]
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Appendix A. Diameter Service Template
The following service template describes the attributes used by Diam-
eter servers to advertise themselves. This simplifies the process of
selecting an appropriate server to communicate with. A Diameter
client can request specific Diameter servers based on characteristics
of the Diameter service desired (for example, an AAA server to use
for accounting.)
Name of submitter: "Erik Guttman" <Erik.Guttman@sun.com>
Language of service template: en
Security Considerations:
Diameter clients and servers use various cryptographic mechanisms
to protect communication integrity, confidentiality as well as
perform end-point authentication. It would thus be difficult if
not impossible for an attacker to advertise itself using SLPv2 and
pose as a legitimate Diameter peer without proper preconfigured
secrets or cryptographic keys. Still, as Diameter services are
vital for network operation it is important to use SLPv2 authenti-
cation to prevent an attacker from modifying or eliminating ser-
vice advertisements for legitimate Diameter servers.
Template text:
-------------------------template begins here-----------------------
template-type=service:diameter
template-version=0.0
template-description=
The Diameter protocol is defined by draft-ietf-aaa-diameter-03.txt
template-url-syntax=
url-path= ; The standard service URL syntax is used.
; For example: 'service:diameter://aaa.example.com:1812
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supported-extensions= string L M
# This attribute lists the Diameter extensions supported by the
# AAA implementation. The extensions currently defined are:
# Extension Name Defined by
# --------------- -----------------------------------
# NASREQ draft-ietf-aaa-diameter-nasreq-03.txt
# MobileIP draft-ietf-aaa-diameter-mobileip-03.txt
# Strong Security draft-ietf-aaa-diameter-e2e-sec-00.txt
# Resource Management draft-calhoun-diameter-res-mgmt-06.txt
#
# Notes:
# . Diameter implementations support one or more extensions.
# . Additional extensions may be defined in the future.
# An updated service template will be created at that time.
#
NASREQ,MobileIP,Accounting,Strong Security,Resource Management
supported-transports= string L M
SCTP
# This attribute lists the supported transports that the Diameter
# implementation accepts. Note that a compliant Diameter
# implementation MUST support SCTP, though it MAY support other
# transports, too.
SCTP,TCP
-------------------------template ends here-----------------------
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