One document matched: draft-ietf-aaa-diameter-05.txt
Differences from draft-ietf-aaa-diameter-04.txt
AAA Working Group Pat R. Calhoun
Internet-Draft Sun Microsystems, Inc.
Category: Standards Track Haseeb Akhtar
<draft-ietf-aaa-diameter-05.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.
June 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.
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Abstract
The Diameter base protocol is intended to provide a AAA framework for
Mobile-IP, NASREQ and ROAMOPS. This draft specifies the message
format, transport, error reporting and security services to be used
by all Diameter applications and MUST be supported by all Diameter
implementations.
Table of Contents
1.0 Introduction
1.1 Diameter Protocol
1.2 Requirements language
1.3 Terminology
2.0 Protocol Overview
2.1 Transport
2.1.1 SCTP Guidelines
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 Applications
2.3.4 Application authentication procedures
2.4 Diameter Applications
2.5 Role of Diameter Agents
2.5.1 Relay Agents
2.5.2 Proxy Agents
2.5.3 Redirector Agents
2.5.4 Translation Agents
2.6 Diameter Server Discovery
2.7 Diameter Identity Encoding
3.0 Diameter Header
3.1 Command Code Definitions
3.2 Command Code ABNF specification
3.3 Diameter Command Naming Conventions
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 Diameter message processing
5.1 Processing Local Messages
5.2 Message Forwarding
5.2.1 Peer Table
5.3 Message Routing
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5.3.1 Realm-Based Routing Table
5.3.2 Redirecting requests
5.3.3 Relaying and Proxying Requests
5.3.4 Relaying and Proxying Answers
5.3.5 Hiding Network Topology
5.4 Origin-Host AVP
5.5 Origin-Realm AVP
5.6 Destination-Host AVP
5.7 Destination-Realm AVP
5.8 Routing AVPs
5.8.1 Route-Record AVP
5.8.2 Proxy-Info AVP
5.8.3 Proxy-Host AVP
5.8.4 Proxy-State AVP
5.9 Redirect-Host AVP
6.0 Capabilities Negotiation
6.1 Application Identifiers
6.2 Capabilities-Exchange-Request
6.3 Capabilities-Exchange-Answer
6.4 Vendor-Id AVP
6.5 Firmware-Revision AVP
6.6 Auth-Application-Id AVP
6.7 Host-IP-Address AVP
6.8 Supported-Vendor-Id AVP
6.9 Product-Name AVP
6.10 Acct-Application-Id AVP
6.11 Vendor-Specific-Application-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
8.1 States
8.2 Events
8.3 Actions
8.4 The Election Process
9.0 Error Handling
9.1 Result-Code AVP
9.1.1 Informational
9.1.2 Success
9.1.3 Protocol Errors
9.1.4 Transient Failures
9.1.5 Permanent Failures
9.2 Message-Reject-Answer
9.3 Error-Message AVP
9.4 Error-Reporting-Host AVP
9.5 Failed-AVP AVP
10.0 "User" Sessions
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10.1 Authorization Session State Machine
10.2 Accounting Session State Machine
10.3 Session-Id AVP
10.4 Authorization-Lifetime AVP
10.5 Session-Timeout AVP
10.6 User-Name AVP
10.7 Session Termination
10.7.1 Session-Termination-Request
10.7.2 Session-Termination-Answer
10.8 Aborting a Session
10.8.1 Abort-Session-Request
10.8.2 Abort-Session-Answer
10.9 Termination-Cause AVP
10.10 Inferring Session Termination from Origin-State-Id
10.11 Origin-State-Id AVP
11.0 Accounting
11.1 Server Directed Model
11.2 Protocol Messages
11.3 Application document requirements
11.4 Fault Resilience
11.5 Accounting Records
12.0 Accounting Command-Codes
12.1 Accounting-Request
12.2 Accounting-Answer
12.3 Accounting-Poll-Ind
13.0 Accounting AVPs
13.1 Accounting-Record-Type AVP
13.2 Accounting-Interim-Interval AVP
13.3 Accounting-Record-Number AVP
13.4 Accounting-Session-Id AVP
13.5 Accounting-Multi-Session-Id AVP
14.0 AVP Occurrence Table
14.1 Base Protocol Command AVP Table
14.2 Accounting AVP Table
15.0 IANA Considerations
15.1 AVP Header
15.1.1 AVP Code
15.1.2 AVP Flags
15.2 Diameter Header
15.2.1 Command Codes
15.2.2 Message Flags
15.3 Application Identifier Values
15.4 Result-Code AVP Values
15.5 Accounting-Record-Type AVP Values
15.6 Termination-Cause AVP Values
15.7 Diameter TCP/SCTP Port Numbers
16.0 Diameter protocol related configurable parameters
17.0 Security Considerations
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18.0 References
19.0 Acknowledgements
20.0 Authors' Addresses
21.0 Full Copyright Statement
22.0 Expiration Date
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.
- Relaying, 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 a Diameter application, 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 applications.
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.
Accounting 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
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 relay, proxy or redirect server, and MAY be
operated by roaming consortiums.
Diameter Agent
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A Diameter Agent is a host that is providing either server, relay,
proxy or redirector services.
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 Node
A Diameter node is a host that implements the Diameter protocol,
and acts either as a Client, or as a Proxy, Redirector, Server or
Translation agent.
Diameter Server
A Diameter Server is one that handles authentication,
authorization and accounting requests for a particular realm. By
its very nature, a Diameter Server MUST support Diameter
applications in addition to the base protocol.
Downstream Server
Diameter Proxy servers identify a downstream 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
See Diameter Server.
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.
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Proxy
In addition to forwarding requests and responses, proxies enforce
policies relating to resource usage and provisioning. This is
typically accomplished by tracking the state of NAS devices. While
proxies typically do not respond to client Requests prior to
receiving a Response from the server, they may originate Reject
messages in cases where policies are violated. As a result,
proxies need to understand the semantics of the messages passing
through them, and may not support all Diameter applications.
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.
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.
Relay
Relays forward requests and responses based on routing-related
AVPs and domain forwarding table entries. Since relays do not
enforce policies, they do not examine or alter non-routing AVPs.
As a result, relays never originate messages, do not need to
understand the semantics of messages or non-routing AVPs, and are
capable of handling any Diameter applications or message type.
Since relays make decisions based on information in routing AVPs
and domain forwarding tables they do not keep state on NAS
resource usage or conversations in progress.
Redirector
Rather than forwarding requests and responses between clients and
servers, Re-directs refer clients to servers and allow them to
communicate directly. Since Re-directs do not sit in the
forwarding path, they do not alter any AVPs transitting between
client and server. Re-direct proxies do not originate messages and
are capable of handling any message type, although they may be
configured only to re-direct messages of certain types, while
acting as Routing or Policy proxies for other types. As with
Routing proxies, re-directs do not keep state with respect to
conversations or NAS resources.
Roaming Relationships
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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. devices serving the same user.
Upstream Server
Diameter Proxy servers identify an upstream 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 Diameter applications
are defined by companion documents: NASREQ [7], Mobile IP [10],
End-to-End Security [11]. These options are introduced in this
document but specified elsewhere. Additional Diameter applications
MAY be defined in the future (see Section 15.3).
Diameter Clients MUST support the base protocol, which includes
accounting. In addition, they MUST fully support each Diameter
application which is needed to implement the client's service, e.g.
NASREQ and/or Mobile IP. A Diameter Client which does not support
both NASREQ and Mobile IP, MUST be referred to as "Diameter X Client"
where X is the application which it supports, and not a "Diameter
Client."
Diameter Servers must support the base protocol, which includes
accounting. In addition, they MUST fully support each Diameter
application which is needed to implement the intended service, e.g.
NASREQ and/or Mobile IP. A Diameter Server which does not support
both NASREQ and Mobile IP, MUST be referred to as "Diameter X Server"
where X is the application which it supports, and not a "Diameter
Server."
Diameter Relays and Redirectors are, by definition, protocol
transparent, and MUST transparently support the Diameter base
protocol, which includes accounting, and all Diameter applications.
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Diameter Proxies MUST suppport the base protocol, which includes
accounting. in addition, they MUST fully support each Diameter
application which is needed to implement proxied services, e.g.
NASREQ and/or Mobile IP. A Diameter Proxy which does not support also
both NASREQ and Mobile IP, MUST be referred to as "Diameter X Proxy"
where X is the application which it supports, and not a "Diameter
Proxy."
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 Diameter application. 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 10.0
for more information). The communicating party may accept the
request, or reject it by returning an answer message 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
application 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 Diameter
application.
The Diameter base protocol provides the Authorization-Lifetime AVP,
which MAY be used by applications 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).
When used with TLS [38], The Diameter protocol is run on port TBD of
both TCP and SCTP.
Diameter clients MUST support either TCP or SCTP, while agents and
servers MUST support both. Future versions of this specification MAY
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mandate that clients support SCTP.
A Diameter node MAY initiate connections from any source port, but
MUST be prepared to receive connections on port TBD. 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. This behavior is handled
via the Tc timer, whose recommended value is 30 seconds.
2.1.1 SCTP Guidelines
The following are guidelines for Diameter implementations that
support SCTP:
1. For interoperability: All Diameter nodes MUST be prepared to
receive Diameter messages on any SCTP stream in the
association.
2. To prevent blocking: All Diameter nodes SHOULD utilize all SCTP
streams available to the association to prevent head-of-the-
line blocking.
2.2 Securing Diameter Messages
Diameter clients, such as Network Access Servers (NASes) and Foreign
Agents MUST support IP Security [37], and MAY support TLS [38].
Diameter servers MUST support TLS, but the administrator MAY opt to
configure IPSec instead of using TLS. Operating the Diameter protocol
without any security mechanism is not recommended.
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
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Defining a new AVP value is the best approach when a new application
needs to make use of an existing Diameter application, 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,
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 application, 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 application MUST NOT
be defined to have the 'M'andatory bit set.
2.3.3 Creating new Diameter Applications
Should a new application require Diameter support, but it cannot fit
within an existing application without requiring major changes to the
specification, it may be desirable to create a new Diameter
application. Major changes to an application 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. application foo has a command that
requires one round trip, but new application bar has a command
that requires two round trips to complete).
- The method used to authenticate the user is drastically
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different from any existing application, and the authentication
information cannot be carried within the AVPs defined in the
application.
Note that the creation of a new application should be viewed as a
last resort.
New Diameter applications 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 application has any accounting
requirements, it MUST also specify the AVPs that are to be present in
the Diameter Accounting messages (see section 11.3).
When possible, a new Diameter application 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 application specification MUST have an IANA assigned
Application Identifier (see section 2.4).
2.3.4 Application authentication procedures
When possible, applications SHOULD be designed such that new
authentication methods MAY be added without requiring changes to the
application. 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 Application Compliance
Application Identifiers are advertised during the capabilities
exchange phase (see section 6.0). For a given application, there are
two different ways of advertising support. First, advertising support
of the application via the Auth-Application-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 application via the
Acct-Application-Id implies that the sender supports the Accounting
command codes defined in this specification, as well as the
accounting AVPs defined in the application's specification.
An implementation MAY add arbitrary AVPs to any command defined in an
application, including vendor-specific AVPs. However, implementations
that add such AVPs with the Mandatory 'M' bit set are not compliant,
and are at fault if the peer rejects the request. If the sender of
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such a message wishes to provide service, it MUST resend the message
with the offending AVPs removed.
2.5 Role of Diameter Agents
In addition to client and servers, the Diameter protocol introduces
relays, redirectors, proxies and translation gateways, each of which
is defined in Section 1.3. These Diameter agents are useful for
several reasons:
- They can distribute administration of systems to a configurable
grouping, including the maintenance of security associations.
- They can be used for concentration of requests from an number of
co-located or distributed NAS equipment sets to a set of like
user groups.
- They can do value-added processing to the requests or responses.
- They can used for load balancing.
- A complex network will have multiple authentication sources,
they can sort requests and forward towards the correct target.
The Diameter protocol requires that agents maintain transaction
state, which is used for failover purposes. Transaction state implies
that upon forwarding a request, it's Hop-by-Hop identifier is saved,
the field is replaced with a locally unique identifier, which is
restored to its original value when the corresponding answer is
received. The request's state is released upon receipt of the answer.
A stateless agent is one that only maintains transaction state.
The Proxy-Info AVP allows stateless agent to add local state to a
Diameter request, with the guarantee that the same state will be
present in the answer. However, the protocol's failover procedures
requires that agents maintain a copy of pending requests.
A stateful agent is one that maintains session state information, by
keeping track of all authorized active sessions. Each authorized
session is bound to a particular service, and its state is considered
active either until it is notified otherwise, or by expiration. Each
authorized session has a expiration, which is communicated by
Diameter servers via the Authorized-Lifetime AVP.
Maintaining session state MAY be useful in certain applications, such
as:
- Protocol translation (e.g. RADIUS <-> Diameter)
- Limiting resources authorized to a particular user
- Per user or transaction auditing
A Diameter agent MAY act in a stateful manner for some requests,
while be stateless for others. A Diameter implementation MAY act as
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one type of agent for some requests, and as another type of agent for
others.
2.5.1 Relay Agents
Relay Agents are Diameter agents that accept requests and routes the
message to another Diameter agent based on information found in the
message (e.g. Destination-Realm). This routing decision is performed
using a list of supported domains, and known peers. This is known as
the Diameter Routing Table, as is defined further in section x.x.
Relays MAY be used to aggregate requests from multiple Network Access
Servers (NASes) within a common geographical area (POP). The use of
Relays is advantageous since it eliminates the need for NASes to be
configured with the necessary security information it would otherwise
require to communicate with Diameter servers in other realms.
Likewise, this reduces the configuration load on Diameter servers
that would otherwise be necessary when NASes are added, changed or
deleted.
Relays modify Diameter messages by inserting, and removing, routing
information, but do not modify any other portion of a message.
Further, Relays inherent simplicity implies that they are stateless,
and therefore SHOULD NOT maintain session state, but MUST maintain
transaction state.
+------+ ---------> +------+ ---------> +------+
| | 1. Request | | 2. Request | |
| NAS | | DRL | | HMS |
| | 4. Answer | | 3. Answer | |
+------+ <--------- +------+ <--------- +------+
mno.net mno.net abc.com
Figure 1: Relaying of Diameter messages
The example provided in Figure 1 depicts a request issued from NAS,
which is an access device, for the user bob@abc.com. Prior to issuing
the request, NAS performs a Diameter route lookup, using "abc.com" as
the key, and determines that the message is to be relayed to DRL,
which is a Diameter Relay. DRL performs the same route lookup as NAS,
and relays the message to HMS, which is abc.com's Home Diameter
Server. HMS identifies that the request can be locally supported (via
the realm), processes the authentication and/or authorization
request, and replies with an answer, which is routed back to NAS
using Diameter routing AVPs.
Since Relays do not perform any application level processing, they
provide relaying services for all Diameter applications, and
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therefore MUST advertise the Relay Application Identifier.
2.5.2 Proxy Agents
Similarly to Relays, Proxy agents route Diameter messages using the
Diameter Routing Table. However, they differ since they modify
messages to implement policy enforcement. This requires that proxies
maintain the state of their downstream peers (e.g. access devices) to
enforce resource usage, provide admission control, and provisioning.
It is important to note that although proxies MAY provide a value-add
function for NASes, they do not allow access devices to use the
Diameter End-to-End Security application, since modifying messages
breaks end-to-end authentication.
Proxies MAY be used in call control centers or access ISPs that
provide outsourced connections, they can monitor the number and types
of ports in use, and make allocation and admission decisions
according to their configuration.
Proxies that wish to limit resources MUST be stateful, and all
Proxies MUST maintain transaction state.
Proxy agents MUST NOT allow end-to-end security to be established
between two peers if it expects to modify ANY non-routing AVP in
messages exchanged between the peers. See [11] for more information.
Since enforcing policies requires an understanding of the service
being provided, Proxies MUST only advertise the Diameter applications
they support.
2.5.3 Redirector Agents
Redirector agents provide Realm to Server address resolution, and use
the Diameter routing table to determine where a given request should
be forwarded to. When a request is received by a Diameter redirector,
a special answer is created, which includes the identity of the
Diameter server(s) the originator of the request should contact
directly.
Redirectors are useful in scenarios where the Diameter routing
configuration needs to be centralized. An example is a redirector
that provides services to all members of a consortium, but does not
wish to be burdened with relaying all messages between domains. This
scenario is advantageous since it does not require that the
consortium provide routing updates to its members when changes are
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made to a member's infrastructure.
Since redirectors do not relay messages, and only return an answer
with the information necessary for Diameter agents to communicate
directly, they do not modify messages, and therefore MUST NOT
maintain session state. Further, since redirectors never relay
requests, they are not required to maintain transaction state.
+------+
| |
| DRD |
| |
+------+
^ |
2. Request | | 3. Redirection
| | Notification
| v
+------+ ---------> +------+ ---------> +------+
| | 1. Request | | 4. Request | |
| NAS | | DRL | | HMS |
| | 6. Answer | | 5. Answer | |
+------+ <--------- +------+ <--------- +------+
mno.net mno.net abc.com
Figure 2: Redirecting a Diameter Message
The example provided in Figure 2 depicts a request issued from the
access device, NAS, for the user bob@abc.com. The message is
forwarded by the NAS to its relay, DRL, which does not have a routing
entry in its Diameter Routing Table for abc.com. DRL has a default
route configured to DRD, which is a redirector that returns a
redirect notification to DLR, as well as HMS' contact information.
Upon receipt of the redirect notification, DRL establishes a
transport connection with HMS, if one doesn't already exist, and
forwards the request to it.
Since Redirectors do not perform any application level processing,
they provide relaying services for all Diameter applications, and
therefore MUST advertise the Relay Application Identifier.
2.5.4 Translation Agents
A Translation Agent is a device that provides translation between two
protocols (e.g. RADIUS<->Diameter, TACACS+<->Diameter). Translation
agents are likely to be used as aggregation servers to communicate
with a Diameter infrastructure, while allowing for the embedded
systems to be migrated at a slower pace.
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Given that the Diameter protocol introduces the concept of long-lived
authorized sessions, translation agents MUST be stateful and MUST
maintain transaction state.
Translation of messages can only occur if the agent recognizes the
application of a particular request, and therefore MUST only
advertise their locally supported applications.
+------+ ---------> +------+ ---------> +------+
| | RADIUS Request | | Diameter Request | |
| NAS | | TLA | | HMS |
| | RADIUS Answer | | Diameter Answer | |
+------+ <--------- +------+ <--------- +------+
mno.net mno.net abc.com
Figure 3: Translation of RADIUS to Diameter
2.6 Diameter Agent Discovery
Allowing for dynamic Diameter agent discovery will make it possible
for simpler and more robust deployment of AAA services. In order to
promote interoperable implementations of Diameter agent discovery,
the following mechanisms are described. These are based on existing
IETF standards.
There are two cases where Diameter agent discovery may be performed.
The first is when a Diameter client needs to discover a first-hop
Diameter agent. The second case is when a Diameter agent needs to
discover another agent - 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 agent 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 agents in the local site, as well as their
characteristics. Diameter agents with specific capabilities
(say support for the Mobile IP application) can be requested,
and only those will be discovered.
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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 agent 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 agent. [34, 35, 36]
2.7 Diameter Identity Encoding
Several Diameter AVPs are used to include a node's identity, such as
the Destination-Host, Origin-Host, Route-Record, etc. The contents of
such AVPs follow the Uniform Resource Identifiers (URI) syntax [29]
rules specified below:
Diameter-Identity = [protocol] fqdn [ port ]
[ transport ]
protocol-name = ( "diameter" | "radius" | "tacacs+" )
protocol = protocol-name "://"
; If absent, the default is "diameter://"
fqdn = Fully Qualified Host Name
port = ":" 1*DIGIT
; If absent, the default Diameter port (TBD) is assumed.
transport = ";transport=" ( "tcp" | "sctp" | "udp")
; If absent, the default SCTP [26] protocol is assumed.
; UDP is ONLY used when the protocol is set to RADIUS
The following are examples of valid Diameter host identities:
host.abc.com:6666;transport=tcp
diameter://host.abc.com
diameter://host.abc.com:6666
diameter://host.abc.com;transport=tcp
diameter://host.abc.com:6666;transport=tcp
radius://host.abc.com:1813;transport=udp
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ver | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R r r r r r r r| Command-Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop-by-Hop Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End-to-End Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVPs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-
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.
Command Flags
The Command Flags field is eight bits. The following bits are
assigned:
R(equest) - If set, the message is a request. If cleared, the
message is an answer.
r(eserved) - this flag bit is reserved for future use, and MUST
be set to zero.
Command-Code
The Command-Code field is three octets, and is used in order to
communicate the command associated with the message. The 24-bit
address space is managed by IANA (see section 15.2).
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
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Command, the Vendor-ID field MUST be set to zero (0). Any vendor
wishing to implement a vendor-specific Diameter command MUST use
their own Vendor-ID along with their privately managed Command-
Code address space, guaranteeing that they will not collide with
any other vendor's vendor-specific command, nor with future IETF
applications.
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 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 an Answer message
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. An answer message 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 to detect duplicate messages, and relay agents MUST NOT
modify this field. The sender of a request or answer message MUST
insert a locally unique value in this field. The combination of
the Origin-Host AVP and this field is used to detect duplicates.
An Answer message which is received with a previously seen End-
to-End Identifier, and is to be locally consumed (meaning that the
Destination-Host AVP contains the local node's identity) SHOULD be
silently discarded.
AVPs
AVPs are a method of encapsulating information relevant to the
Diameter message. See section 4. for more information on AVPs.
3.1 Command Codes
Each command Request/Answer pair is assigned a command code, and the
sub-type (e.g. request or answer) is identified via the 'R' bit in
the Command Flags field of the Diameter header.
Every Diameter message MUST contain a command code 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:
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Command-Name Abbrev. Code Reference
--------------------------------------------------------
Abort-Session-Request ASR 274 10.8.1
Abort-Session-Answer ASA 274 10.8.2
Accounting-Answer ACA 271 12.2
Accounting-Poll-Ind API 273 12.3
Accounting-Request ACR 271 12.1
Capabilities-Exchange- CER 257 6.2
Request
Capabilities-Exchange- CEA 257 6.3
Answer
Message-Reject-Answer MRA 282 9.2
Device-Watchdog-Answer DWA 280 7.2
Device-Watchdog-Request DWR 280 7.1
Session-Termination- STR 275 10.7.1
Request
Session-Termination- STA 275 10.7.2
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 [r-bit] ">"
command-id = 1*DIGIT
; The Command Code assigned to the command
r-bit = ", REQUEST"
; If present, the 'R' bit in the Command
; Flags is set, indicating that the message
; is a request, as opposed to an answer.
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-Request ::= < Diameter-Header: 9999999, REQUEST >
{ User-Name }
* { Origin-Host }
* [ 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 either the Request or Answer verb.
The Request/Answer message pair is used when a Diameter node requests
that some action be performed by a peer (e.g. authorize a user,
terminate a session). The corresponding answer MUST contain either a
positive or negative result code, informing the requester whether the
request was successful or not. Other information MAY also be returned
in the Answer message.
Request and Answer messages share the same command code, and the
R(equest) bit in the Diameter header is used to identify whether a
message is the request or answer.
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
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V M P r r r r r| AVP Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-ID (opt) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ...
+-+-+-+-+-+-+-+-+
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AVP Code
The AVP Code, combined with the Vendor-Id field, 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 15.1).
AVP Flags
The AVP Flags field informs the receiver how each attribute must
be handled. Note that subsequent Diameter applications 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
of the AVP is required. If an unrecognized AVP with the 'M' bit
set is received by a Diameter node, the message MUST be rejected.
Diameter Relay and Redirector agents MUST NOT reject messages with
unrecognized AVPs.
A Diameter node that sets the 'M' bit in an AVP that is not
defined in a given message's ABNF is at fault if the message is
rejected. In order to provide service to the user, the node at
fault MUST re-issue a request either without the AVP, or without
setting its 'M' bit.
A Diameter node that rejects a message due to an unrecognized AVP
with the 'M' bit set, and the AVP in question is defined in the
message's ABNF is at fault. In most cases the initiator of the
failing request will not provide service to the user.
AVPs with the 'M' bit cleared 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.
AVP Length
The AVP Length field is three octets, and indicates the length of
this AVP including the AVP Code, AVP Length, AVP Flags, Reserved,
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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.
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 vendor-specific Diameter AVP 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
vendor-specific AVP, nor with future IETF applications.
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.
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 8
(12 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.
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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
64 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).
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 including their headers and padding. The
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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 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.
Every Grouped AVP defined MUST include a corresponding grammar, using
ABNF [31] (with modifications), as defined below.
avp-def = name "::=" avp
name-fmt = ALPHA *(ALPHA / DIGIT / "-")
name = name-fmt
; The name has to be the name of an AVP,
; defined in the base or extended Diameter
; specifications.
avp = header [ *fixed] [ *required] [ *optional]
[ *fixed]
header = "<AVP-Header:" avpcode ">"
avpcode = 1*DIGIT
; The AVP Code assigned to the Grouped AVP
fixed = [qual] "<" avp-spec ">"
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.
;
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; 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 = name-fmt
; 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.
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 ::= < AVP Header: 999999 >
{ Origin-Host }
1*{ Session-Id }
*[ AVP ]
An Example AVP with Grouped Data follows.
The Origin-Host AVP is required. In this case:
Origin-Host = "example.com".
One or more Session-Ids must follow. Here there are two:
Session-Id =
"grump.example.com:33041;23432;893;0AF3B81"
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Session-Id =
"grump.example.com:33054;23561;2358;0AF3B82"
optional AVPs included are
Recovery-Policy = <binary>
2163bc1d0ad82371f6bc09484133c3f09ad74a0dd5346d54195a7cf0b35
2cabc881839a4fdcfbc1769e2677a4c1fb499284c5f70b48f58503a45c5
c2d6943f82d5930f2b7c1da640f476f0e9c9572a50db8ea6e51e1c2c7bd
f8bb43dc995144b8dbe297ac739493946803e1cee3e15d9b765008a1b2a
cf4ac777c80041d72c01e691cf751dbf86e85f509f3988e5875dc905119
26841f00f0e29a6d1ddc1a842289d440268681e052b30fb638045f7779c
1d873c784f054f688f5001559ecff64865ef975f3e60d2fd7966b8c7f92
Futuristic-Acct-Record = <binary>
fe19da5802acd98b07a5b86cb4d5d03f0314ab9ef1ad0b67111ff3b90a0
57fe29620bf3585fd2dd9fcc38ce62f6cc208c6163c008f4258d1bc88b8
17694a74ccad3ec69269461b14b2e7a4c111fb239e33714da207983f58c
41d018d56fe938f3cbf089aac12a912a2f0d1923a9390e5f789cb2e5067
d3427475e49968f841
The data for the optional AVPs is represented in hex since the format
of these AVPs is neither known at the time of definition of the
Example-AVP group, nor (likely) at the time when the example instance
of this AVP is interpreted - except by Diameter implementations which
support the same set of AVPs. The encoding example illustrates how
padding is used, how length fields are calculated and how AVPs do not
have to begin on 8 byte boundaries. Also note that AVPs may be
present in the Grouped AVP value which the receiver cannot interpret
(here, the Recover-Policy and Futuristic-Acct-Record AVPs).
This AVP 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 = 468 |
+-------+-------+-------+-------+-------+-------+-------+-------+
8 | Origin-Host AVP Header (AVP Code = 264), Length = 19 |
+-------+-------+-------+-------+-------+-------+-------+-------+
16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' |
+-------+-------+-------+-------+-------+-------+-------+-------+
24 | 'c' | 'o' | 'm' |Padding| Session-Id AVP Header |
+-------+-------+-------+-------+-------+-------+-------+-------+
32 | (AVP Code = 263), Length = 50 | 'g' | 'r' | 'u' | 'm' |
+-------+-------+-------+-------+-------+-------+-------+-------+
. . .
+-------+-------+-------+-------+-------+-------+-------+-------+
64 | 'A' | 'F' | '3' | 'B' | '8' | '1' |Padding|Padding|
+-------+-------+-------+-------+-------+-------+-------+-------+
68 | Session-Id AVP Header (AVP Code = 263), Length = 51 |
+-------+-------+-------+-------+-------+-------+-------+-------+
72 | 'g' | 'r' | 'u' | 'm' | 'p' | '.' | 'e' | 'x' |
+-------+-------+-------+-------+-------+-------+-------+-------+
. . .
+-------+-------+-------+-------+-------+-------+-------+-------+
104 | '0' | 'A' | 'F' | '3' | 'B' | '8' | '2' |Padding|
+-------+-------+-------+-------+-------+-------+-------+-------+
112 | Recovery-Policy Header (AVP Code = 8341), Length = 223 |
+-------+-------+-------+-------+-------+-------+-------+-------+
120 | 0x21 | 0x63 | 0xbc | 0x1d | 0x0a | 0xd8 | 0x23 | 0x71 |
+-------+-------+-------+-------+-------+-------+-------+-------+
. . .
+-------+-------+-------+-------+-------+-------+-------+-------+
320 | 0x2f | 0xd7 | 0x96 | 0x6b | 0x8c | 0x7f | 0x92 |Padding|
+-------+-------+-------+-------+-------+-------+-------+-------+
328 | Futuristic-Acct-Record Header (AVP Code = 15930), Length = 137|
+-------+-------+-------+-------+-------+-------+-------+-------+
336 | 0xfe | 0x19 | 0xda | 0x58 | 0x02 | 0xac | 0xd9 | 0x8b |
+-------+-------+-------+-------+-------+-------+-------+-------+
. . .
+-------+-------+-------+-------+-------+-------+-------+-------+
464 | 0x41 |Padding|Padding|Padding|
+-------+-------+-------+-------+
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.
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+---------------------+
| AVP Flag rules |
|----+-----+----+-----|----+
AVP Section | | |SHLD| MUST|MAY |
Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr|
-----------------------------------------|----+-----+----+-----|----|
Accounting- 482 13.2 Unsigned32 | M | P | | V | Y |
Interim-Interval | | | | | |
Accounting- 50 13.5 OctetString| M | P | | V | Y |
Multi-Session-Id | | | | | |
Accounting- 485 13.3 Unsigned32 | M | P | | V | Y |
Record-Number | | | | | |
Accounting- 480 13.1 Unsigned32 | M | P | | V | Y |
Record-Type | | | | | |
Accounting- 44 13.4 OctetString| M | P | | V | Y |
Session-Id | | | | | |
Acct- 259 6.10 Integer32 | M | | | V | N |
Application-Id | | | | | |
Auth- 258 6.6 Integer32 | M | | | V | N |
Application-Id | | | | | |
Authorization- 291 10.4 Unsigned32 | M | | | V | N |
Lifetime | | | | | |
Destination-Host 293 5.6 OctetString| M | | | V | N |
Destination- 283 5.7 OctetString| M | | | V | N |
Realm | | | | | |
Error-Message 281 9.3 OctetString| | | | V | N |
Error-Reporting- 294 9.4 OctetString| | | | V | N |
Host | | | | | |
Failed-AVP 279 9.5 OctetString| M | | | V | Y |
Firmware- 267 6.5 Unsigned32 | | | | V,M | N |
Revision | | | | | |
Host-IP-Address 257 6.7 Address | M | | | V | N |
Origin-Host 264 5.4 OctetString| M | | | V | N |
Origin-Realm 296 5.5 OctetString| M | | | V | N |
Product-Name 269 6.9 OctetString| | | | | N |
Proxy-Host 280 5.8.3 Address | M | | | V | N |
Proxy-Info 284 5.8.2 Grouped | M | | | V | N |
Proxy-State 33 5.8.4 OctetString| M | | | V | N |
Redirect-Host 292 5.9 OctetString| M | | | V | Y |
Result-Code 268 9.1 Unsigned32 | M | | | V | N |
Route-Record 282 5.8.1 OctetString| M | | | V | N |
Session-Id 263 10.3 OctetString| M | | | V | Y |
Session-Timeout 27 10.5 Unsigned32 | M | | | V | N |
Origin-State-Id 278 10.11 Unsigned32 | M | | | V | N |
Supported- 265 6.8 Unsigned32 | M | | | V | N |
Vendor-Id | | | | | |
-----------------------------------------|----+-----+----+-----|----|
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+---------------------+
| AVP Flag rules |
|----+-----+----+-----|----+
AVP Section | | |SHLD| MUST|MAY |
Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr|
-----------------------------------------|----+-----+----+-----|----|
Termination- 295 10.9 Unsigned32 | M | | | V | N |
Cause | | | | | |
User-Name 1 10.6 OctetString| M | | | V | Y |
Vendor-Id 266 6.4 Unsigned32 | M | | | V,M | N |
Vendor-Specific- 260 6.11 Grouped | M | | | V,M | N |
Application-Id
-----------------------------------------|----+-----+----+-----|----|
5.0 Diameter message processing
All Diameter messages MUST include the Origin-Host and Origin-Realm
AVPs, which are used to identify the source of the message. The
Destination-Host AVP MAY be present in requests, and MUST be present
in answers. The Destination-Host AVP is used when the destination of
the message is fixed, which includes:
- 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 Abort-
Session-Request message, which is used to request that a
particular user's session be terminated.
The Destination-Realm AVP MUST be present if the message is routable.
A message that MUST NOT be relayed, proxied or redirected MUST NOT
include the Destination-Realm in its ABNF. The value of the
Destination-Realm AVP MAY be extracted from the User-Name AVP, or
other application-specific methods.
When a message is received, the message is processed in the following
order:
1. If the message is destined for the local host, the procedures
listed in section 5.1 are followed.
2. If the message is intended for a Diameter peer with whom the
local host is able to directly communicate with, the procedures
listed in section 5.2 are followed. This is known as Message
Forwarding.
3. The procedures listed in section 5.3 are followed, which is
known as Message Routing.
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4. If none of the above are successful, an answer is returned with
the Result-Code set to DIAMETER_UNABLE_TO_DELIVER.
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.
5.1 Processing Local Messages
A request is known to be for local comsumption when one of the
following conditions occur:
- The Destination-Host AVP contains the local host's identity,
- The Destination-Host AVP is not present, the Destination-Realm
AVP contains a realm the server is configured to process
locally, and the Diameter application is locally supported, or
- The Destination-Realm AVP is not present.
When a request is locally processed, the following procedures MUST be
applied, in addition to any additional procedures that MAY be
discussed in the Diameter application defining the command:
- The same Hop-by-Hop identifier in the request is used in the
answer.
- The local host's identity is encoded in the Origin-Host and
Origin-Host AVPs.
- The value of the Origin-Host AVP in the request is included in
the answer's Destination-Host AVP.
- The Result-Code AVP is added with its value indicating success
or failure.
- If the Session-Id is present in the request, it MUST be included
in the answer.
- Any Route-Record or Proxy-Info AVPs in the request MUST be added
to the answer message, in the same order they were present in
the request.
When the local message is an answer, no additional procedures beyond
those listed in the specific Diameter application are to be followed.
5.2 Message Forwarding
Message forwarding is done using the Diameter Peer Table. The
Diameter peer table contains all of the peers that the local node is
able to directly communicate with.
When a request is received, and the host encoded in the Destination-
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Host AVP is one that is present in the peer table, the message SHOULD
be forwarded to the peer.
If the message received is an answer, the host in the Destination-
Host AVP is in the peer table, and there are no Route-Record AVPs in
the message, the message MUST be forwarded to the peer.
5.2.1 Peer Table
The Diameter Peer Table is used in message forwarding, and referenced
by the Domain Routing Table. A Peer Table entry contains the
following fields:
- Peer name. The Fully Qualified Domain Name of the peer. This MAY
be resolved locally, or known via the CER or CEA message.
- Port Number. The port number the peer may be contacted on.
- Protocol. Specifies whether TCP or SCTP is the protocol to use
to communicate with the peer.
- TLS Enabled. Specifies whether TLS is to be used when
communicating with the peer.
5.3 Message Routing
Diameter request message routing is done via realms. A Diameter
message that is proxyable MUST include the target realm in the
Destination-Realm AVP. The realm MAY be retrieved from the User-Name
AVP, which is in the form of a Network Access Identifier (NAI). The
realm portion of the NAI is inserted in the Destination-Realm AVP.
Diameter agents have a list of locally supported realms, and MAY have
a list of externally supported realms. When a request is received
that includes a realm that is not locally supported, the message is
routed to the peer configured in the Domain Routing Table table (see
section 5.3.1).
5.3.1 Realm-Based Routing Table
All Realm-Based routing lookups are performed against what is
commonly known as the Domain Routing Table (see section 16.0). 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.
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- Application Identifier. It is possible for a routing entry to
have a different destination based on the Acct-Application-Id
(for accounting messages) or Auth-Application-Id (for non-
accounting messages) 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 routed to another server.
2. RELAY - All Diameter messages that fall within this
category MUST be routed to a next hop server, without
modifying any non-routing AVPs. See sections 5.3.3 and
5.3.4 for relaying guidelines
3. PROXY - All Diameter messages that fall within this
category MUST be routed 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 routing. See
sections 5.3.3 and 5.3.4 for relaying guidelines.
4. 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 5.3.2 for redirect guidelines.
- Server Identifier - One or more servers the message is to be
routed to. These servers MUST also be present in the Peer
table. When the Local Action is set to RELAY or PROXY, this
field contains the identity of the server(s) the message must be
routed to. When the Local Action field is set to REDIRECT, this
field contains the identity of one or more servers the message
should be redirected to.
It is important to note that Diameter agents MUST support at least
one of the LOCAL, RELAY, PROXY or REDIRECT modes of operation. Agents
do not need to support all modes of operation in order to conform
with the protocol specification, but MUST follow the protocol
compliance guidelines in section 2.0. Relay agents MUST NOT reorder
AVPs, and proxies SHOULD NOT reorder AVPs.
When a request is routed, the target server MUST have advertised the
Application Identifier (see section 6.1) for the given message, or
have advertised itself as a relay or proxy agent.
5.3.2 Redirecting requests
When a redirector agent receives a request whose routing entry is set
to REDIRECT, it MUST answer the request with Message-Reject-Answer,
while maintaining the Hop-by-Hop Identifier in the header, and
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include the Result-Code AVP to DIAMETER_REDIRECT_INDICATION. Each of
the servers associated with the routing entry are added in separate
Redirect-Host AVP.
+------------------+
| Diameter |
| Redirector Agent |
+------------------+
^ |
1. Request | | 2. MRA +
joe@xyz.com | | Result-Code = DIAMETER_REDIRECT_INDICATION +
| | Redirect-Host AVP(s)
| v
+---------+ 3. Request +----------+
| abc.net |------------->| xyz.net |
| Relay | | Diameter |
| Agent |<-------------| Server |
+---------+ 4. Answer +----------+
Figure 7: Diameter Redirect Server
Redirector agents MAY also include the certificate of the servers in
the Redirect-Host AVP(s). These certificates are encapsulated in a
CMS-Cert AVP [11].
The receiver of the MRA message with the Result-Code AVP set to
DIAMETER_REDIRECT_INDICATION uses the hop-by-hop field in the
Diameter header to identify the request in the pending message queue
(see Section 7.3) that is to be redirected. If no transport
connection exists with the new agent, one is created, and the request
is sent directly to it.
5.3.3 Relaying and Proxying Requests
A relay or proxy agent MUST check for forwarding loops before
forwarding requests. A loop is detected if the server finds its own
address in a Route-Record AVP. When such an event occurs, the agent
MUST answer with the Result-Code AVP set to DIAMETER_LOOP_DETECTED.
A relay or proxy agent MUST append a Route-Record AVP that includes
its identity to all requests forwarded. The last Route-Record AVP in
all requests received MUST be validated, by ensuring that the host
encoded in the AVP is the same as the peer the message was received
from.
The Hop-by-Hop identifier in the request is saved, and replaced with
a locally unique value.
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Relay and Proxy agents MAY include the Proxy-Info AVP in requests if
it requires access any local state information when the corresponding
response is received. Alternatively, it MAY simply use local storage
to store state information.
The message is then forwarded to the next hop, as identified in the
Domain Routing Table.
Figure 6 provides an example of message routing using the procedures
listed in these sections.
(Origin-Host=nas.mno.net) (Origin-Host=nas.mno.net)
(Origin-Realm=mno.net) (Origin-Realm=mno.net)
(Destination-Realm=abc.com) (Destination-Realm=abc.com)
(Route-Record=drl.mno.net)
+------+ ------> +------+ ------> +------+
| | (Request) | | (Request) | |
| NAS +-------------------+ DRL +-------------------+ HMS |
| | | | | |
+------+ <------ +------+ <------ +------+
mno.net (Answer) mno.net (Answer) abc.com
(Origin-Host=hms.abc.com) (Origin-Host=hms.abc.com)
(Origin-Realm=abc.com) (Origin-Realm=abc.com)
(Destination-Host=nas.mno.net) (Destination-Host=nas.mno.net)
(Route-Record=drl.mno.net)
Figure 6: Routing of Diameter messages
5.3.4 Relaying and Proxying Answers
A relay or proxy agent MUST only process Answers whose last Route-
Record AVP matches one of its identities. Any answers 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 relay or proxy agent receives an answer 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. If the agent receives an answer message with
a Result-Code AVP indicating success, and it wishes to modify the AVP
to indicate an error, it MUST issue an STR on behalf of the access
device.
Prior to forwarding the answer, the agent MUST restore the original
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value of the Diameter header's Hop-by-Hop Identifier field.
5.3.5 Hiding Network Topology
A Relay or Proxy agent routing messages outside of their
administrative domain MAY need to hide the internal Diameter
topology. This is done by removing all Route-Record AVPs in a
request, and later adding them back into the corresponding answer, in
the same order. Such agents MUST take care to not assume that the
absence of any Route-Record AVPs implies the message is for local
comsumption.
5.4 Origin-Host AVP
The Origin-Host AVP (AVP Code 264) is of type OctetString, encoded in
the UTF-8 [24] format, according to the Diameter identity rules
defined in section 2.7, and MUST be present in all Diameter messages.
This AVP identifies the endpoint which originated the Diameter
message, i.e. the access device, home server, or broker. Relay agents
MUST NOT modify this AVP.
Note that the Origin-Host AVP may resolve to more than one address as
the Diameter peer may support more than one address.
This AVP SHOULD be placed as close to the Diameter header as
possible.
5.5 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 and MUST be present in all
messages
This AVP SHOULD be placed as close to the Diameter header as
possible.
5.6 Destination-Host AVP
The Destination-Host AVP (AVP Code 293) is of type OctetString,
encoded in the UTF-8 [24] format, according to the Diameter identity
rules defined in section 2.7. This AVP MUST be present in all
unsolicited agent initiated messages, MAY be present in request
messages, and MUST be present in Answer messages. The value of the
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Destination-Host AVP is set to the value of the Origin-Host AVP found
in a message from the intended target host.
This AVP SHOULD be placed as close to the Diameter header as
possible.
5.7 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
Answer messages. Diameter Clients insert the realm portion of the
User-Name AVP. Diameter servers initiating a request message 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.
Request messages whose ABNF does not list the Destination-Realm AVP
as a mandatory AVP are inherently non-routable messages.
This AVP SHOULD be placed as close to the Diameter header as
possible.
5.8 Routing AVPs
The AVPs defined in this section are Diameter AVPs used for routing
purposes. These AVPs change as Diameter messages are processed by
agents, and therefore MUST NOT be protected using the Diameter CMS
Security application [11].
5.8.1 Route-Record AVP
The Route-Record AVP (AVP Code 282) is of type OctetString, encoded
in the UTF-8 [24] format, according to the Diameter identity rules
defined in section 2.7. The identity added in this AVP MUST be the
same as the identity sent in the Origin-Host of the Capabilities-
Exchange-Request message.
5.8.2 Proxy-Info AVP
The Proxy-Info AVP (AVP Code = 284) is of type Grouped. The Grouped
Data field has the following ABNF grammar:
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Proxy-Info ::= < AVP Header: 284 >
{ Proxy-Host }
{ Proxy-State }
* [ AVP ]
5.8.3 Proxy-Host AVP
The Proxy-Host AVP (AVP Code = 280) is of type OctetString, encoded
in the UTF-8 [24] format, according to the Diameter identity rules
defined in section 2.7. This AVP contains the identity of the host
that added the Proxy-Info AVP.
5.8.4 Proxy-State AVP
The Proxy-State AVP (AVP Code = 33) is of type OctetString, and
contains state local information, and MUST be treated as opaque data.
5.9 Redirect-Host AVP
The Redirect-Host AVP (AVP Code 292) is of type OctetString, encoded
in the UTF-8 [24] format, according to the Diameter identity rules
defined in section 2.7. This AVP MUST be present in Message-Reject-
Answer messages that include the Result-Code AVP set to
DIAMETER_REDIRECT_INDICATION.
Upon receiving the above, the receiving Diameter node SHOULD forward
the request directly to the host identified in this AVP.
6.0 Capabilities Exchange
When two Diameter peers establish a transport connection, they MUST
exchange the Device Reboot messages, as specified in the peer state
machine (see section 8.0). 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,
the locally supported Diameter applications, etc.
The receiver only issues commands to its peers that have advertised
support for the Diameter application that defines the command. A
Diameter node MUST cache the supported applications in order to
ensure that unrecognized commands and/or AVPs are not unnecessarily
sent to a peer.
A receiver of a Capabilities-Exchange-Req message which does not have
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any applications in common with the sender MUST return a
Capabilities-Exchange-Answer with the Result-Code AVP set to
DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport
layer connection.
The Capabilities-Exchange-Request and Capabilities-Exchange-Answer
messages MUST NOT be proxied, or redirected.
Since the CER/CEA messages cannot be proxied, it is still possible
that an upstream proxy receives a message for which it has no
available peers to handle the application that corresponds to the
Command-Code. In such instances, the Message-Reject-Answer message is
used (see Section 9.2.1) to inform the downstream to take action
(e.g. re-routing request to an alternate peer).
With the exception of the Capabilities-Exchange-Request message, a
message of type Request that includes the Auth-Application-Id or
Acct-Application-Id AVPs, or a message with an application-specific
command code, MAY only be forwarded to a host that has explicitly
advertised support for the application (or has advertised the Relay
Application Identifier).
6.1 Application Identifiers
Each Diameter application MUST have an IANA assigned Application
Identifier (see section 15.3). The base protocol does not require an
application Identifier since its support is mandatory.
Application Identifiers are communicated via two separate AVPs;
Auth-Application-Id and Acct-Application-Id. The Auth-Application-Id
AVP is used to communicate support for the authentication and
authorization portion of an application. The Acct-Application-Id AVP,
on the other hand, communicates support for the accounting portion of
an application.
This separation of AVPs allows a server to communicate that it is
willing to accept only accounting messages for a given application.
The following Application Identifier values are defined:
NASREQ 1 [7]
End-to-End Security 2 [11]
Mobile-IP 4 [10]
Relay 0xffffffff
Relay and redirect agents MUST advertise the Proxy application
identifier, while all other Diameter nodes MUST advertise locally
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supported applications. The receiver of a Device Reboot message
advertising Relay service MUST assume that the sender supports all
current and future applications.
Diameter relay and proxy agents are responsible for finding a
downstream server that supports the application of a particular
message. If none can be found, a MRA message is returned with the
Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER.
6.2 Capabilities-Exchange-Request
The Capabilities-Exchange-Request (CER), indicated by the Command-
Code set to 257 and the Command Flags' 'R' bit set, is sent to inform
a peer that a reboot has occurred.
When Diameter is run over SCTP [26], which allows for connections to
span multiple interfaces, hence multiple IP addresses, the
Capabilities-Exchange-Request message MUST contain one Host-IP-
Address AVP for each potential IP address that MAY be locally used
when transmitting Diameter messages.
Message Format
<Capabilities-Exchange-Req> ::= < Diameter Header: 257, REQUEST >
{ Origin-Host }
{ Origin-Realm }
1* { Host-IP-Address }
{ Vendor-Id }
{ Product-Name }
[ Origin-State-Id ]
* [ Supported-Vendor-Id ]
* [ Auth-Application-Id ]
* [ Acct-Application-Id ]
[ Destination-Host ]
[ Firmware-Revision ]
* [ AVP ]
6.3 Capabilities-Exchange-Answer
The Capabilities-Exchange-Request (CEA), indicated by the Command-
Code set to 257 and the Command Flags' 'R' bit cleared, is sent in
response to a CER message.
When Diameter is run over SCTP [26], which allows for connections to
span multiple interfaces, hence multiple IP addresses, the
Capabilities-Exchange-Answer message MUST contain one Host-IP-Address
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AVP for each potential IP address that MAY be locally used when
transmitting Diameter messages.
Message Format
<Capabilities-Exchange-Answer> ::= < Diameter Header: 257 >
{ Result-Code AVP }
{ Origin-Host }
{ Origin-Realm }
1* { Host-IP-Address }
{ Vendor-Id }
{ Product-Name }
[ Origin-State-Id ]
* [ Supported-Vendor-Id ]
* [ Auth-Application-Id ]
* [ Acct-Application-Id ]
[ Destination-Host ]
[ Firmware-Revision ]
* [ AVP ]
6.4 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 6.8), 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 6.9) and the Firmware-Revision
(section 6.5) AVPs MAY provide very useful debugging information.
A Vendor-Id value of zero in the CER or CEA messages 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.
6.5 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.
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6.6 Auth-Application-Id AVP
The Auth-Application-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 application (see Section 6.1). The Auth-
Application-Id MUST also be present in all Authentication and/or
Authorization messages that are defined in a separate Diameter
specification and have an Application ID assigned.
This AVP SHOULD be placed as close to the Diameter header as
possible.
6.7 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 CER and CEA messages by including a Host-IP-Address
AVP for each address. This AVP MUST ONLY be used in the CER and CEA
messages.
6.8 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 CER and CEA messages in order to inform the peer that the
sender supports a subset of the vendor-specific commands and/or AVPs
defined by the vendor identified in this AVP.
6.9 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.
6.10 Acct-Application-Id AVP
The Acct-application-Id AVP (AVP Code 259) is of type Unsigned32 and
is used in order to advertise support of the Accounting portion of an
application (see Section 6.1). The Acct-Application-Id MUST also be
present in all Accounting messages that are defined in a separate
Diameter specification and have an Application ID assigned.
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This AVP SHOULD be placed as close to the Diameter header as
possible.
6.11 Vendor-Specific-Application-Id AVP
The Vendor-Specific-Application-Id AVP (AVP Code 260) is of type
Grouped and is used to advertise support of a vendor-specific
Diameter Application. Either the Auth-Application-Id or the Acct-
Application-Id AVP MAY be present. Both AVPs MAY be present if they
both contain the same value.
This AVP MUST also be present in all vendor-specific commands defined
in the vendor-specific application.
This AVP SHOULD be placed as close to the Diameter header as
possible.
AVP Format
<Vendor-Specific-Application-Id> ::= < AVP Header: 260 >
1* [ Vendor-Id ]
0*1{ Auth-Application-Id }
0*1{ Acct-Application-Id }
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
failover performance. The Device-Watchdog-Request and Device-
Watchdog-Answer messages, defined in this section, are used to pro-
actively detect transport failures.
The watchdog behavior is controlled by the Tw timer, which ranges
between 30 and 60 seconds. In order to avoid synchronization
behaviors that can occur with fixed timers among distributed systems,
each time the watchdog interval is calculated with a jitter by using
the Tw value (which defaults to 30 seconds) and randomly adding or
subtracting a random value drawn between 0.5 and 2 seconds.
Alternative calculations to create jitter MAY be used. These MUST be
pseudo-random and not cyclic.
When a response is received, Tw is reset. Receiving a watchdog from a
peer constitutes activity, and Tw should be reset. On sending a
message, if the queue is empty, then Tw is reset. If the watchdog
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timer expires and the queue is empty, then a watchdog packet is sent.
7.1 Device-Watchdog-Request
The Device-Watchdog-Request (DWR), indicated by the Command-Code set
to 280 and the Command Flags' 'R' bit set, 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
<Device-Watchdog-Request> ::= < Diameter Header: 280, REQUEST >
{ Origin-Host }
{ Origin-Realm }
{ Destination-Host }
7.2 Device-Watchdog-Answer
The Device-Watchdog-Answer (DWA), indicated by the Command-Code set
to 280 and the Command Flags' 'R' bit cleared, 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: 280 >
{ Result-Code }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Host }
7.3 Failover/Failback Procedures
In the event that a transport failure is detected with a peer, it is
necessary for all pending request messages to be forwarded to an
alternate agent, 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 an answer message is received, the corresponding
request is removed from the queue. The Hop-by-Hop Identifier field
MAY be used to match the answer with the queued request.
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When a transport failure is detected, all messages in the queue are
sent to an alternate agent, 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-Host AVP). Such an
error requires that the agent return an MRA with the Result-Code AVP
set to DIAMETER_UNABLE_TO_DELIVER.
It is important to note that multiple identical request or answer MAY
be received as a result of a failover. The End-to-End Identifier
field in the Diameter header along with the Origin-Host AVP MUST be
used to identify duplicate messages.
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 CER message is always sent on the initiating connection immediately
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after the connection request is successfully completed. 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
R-Rcv-Conn-Req R-Snd-Conn-Ack Wait-R-CER
Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA
I-Rcv-Conn-Nack Cleanup Closed
R-Rcv-Conn-Req R-Snd-Conn-Ack Wait-Conn-Ack/
Wait-R-CER
Timeout Error Closed
Wait-I-CEA I-Rcv-CEA Process-CEA I-Open
R-Rcv-Conn-Req R-Snd-Conn-Ack Wait-R-CER/
Elect
I-Peer-Disc I-Disc Closed
Timeout Error Closed
Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER Wait-R-CER/
Wait-R-CER Elect
I-Rcv-Conn-Nack Cleanup Wait-R-CER
R-Rcv-CER Process-CER Wait-Conn-Ack/
Elect
Timeout Error Closed
Wait-R-CER/ R-Rcv-CER Process-CER, Wait-Returns
Elect Elect
I-Peer-Disc I-Disc Wait-R-CER
Timeout Error Closed
Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-CER,Elect Wait-Returns
Elect I-Rcv-Conn-Nack R-Snd-CEA R-Open
R-Peer-Disc R-Disc Wait-Conn-Ack-2
Timeout Error Closed
Wait-Returns Win-Election I-Disc,R-Snd-CEA R-Open
I-Peer-Disc I-Disc,R-Snd-CEA R-Open
I-Rcv-CEA R-Disc I-Open
R-Peer-Disc R-Disc Wait-I-CEA-2
Timeout Error Closed
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Wait-Conn-Ack-2 I-Rcv-Conn-Ack I-Snd-CER Wait-I-CEA-2
I-Rcv-Conn-Nack Cleanup Closed
R-Rcv-Conn-Req R-Disc Wait-Conn-Ack-2
Timeout Error Closed
Wait-I-CEA-2 I-Rcv-CEA Process-CEA I-Open
I-Peer-Disc I-Disc Closed
R-Rcv-Conn-Req R-Disc Wait-I-CEA-2
Timeout Error Closed
Wait-R-CER R-Rcv-CER Process_CER, R-Open
R-Snd-CEA
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-CER 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-Disc 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-CEA The local Diameter node is waiting for the peer to
issue a DRI.
Wait-Conn-Ack/Wait-R-CER
A transport connection indication from the peer was
received, while a transport connection has already
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been locally initiated.
Wait-R-CER/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.
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-CEA-2 Following an election, the initiator connection
won, and a DRI has yet to be received by the peer.
Wait-R-CER 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.
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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-CER A CER message from the peer was received.
Rcv-CEA A CEA message from the peer was received.
Peer-Disc A disconnection indication from the peer was
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-CER A CER message is sent to the peer.
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Snd-CEA A CEA 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-CER A received CER is processed.
Process-CEA A received CEA is processed.
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-Host received in the DRI sent by its peer with its own
Origin-Host (which it may or may not have actually sent). The
transport layer connection with the higher value of Origin-Host 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 Error Handling
There are two different types of errors in Diameter; protocol and
applications. A protocol error is one that occurs at the base
protocol level, and MAY require per hop attention (e.g. message
routing error). Application errors, on the other hand, are generally
occur due to a problem with a function specified in a Diameter
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application (e.g. user authentication, Missing AVP).
Result-Code AVP values that are used to report protocol errors MUST
be used in the Message-Reject-Answer command. Unlike most Diameter
commands, the Message-Reject-Answer does not have a corresponding
request.
When a request message is received that causes a protocol error, the
command code is changed to Message-Reject-Answer, and the Result-Code
AVP is set to the appropriate protocol error value. As the answer is
sent back towards the originator of the request, each proxy or relay
agent MAY take action on the message.
1. Request +---------+ Link Broken
+-------------------------->|Diameter |----///----+
| +---------------------| | v
+------+--+ | 2. MRA | Relay 2 | +--------+
|Diameter |<-+ (Unable to Forward) +---------+ |Diameter|
| | | Home |
| Relay 1 |--+ +---------+ | Server |
+---------+ | 3. Request |Diameter | +--------+
+-------------------->| | ^
| Relay 3 |-----------+
+---------+
Figure 4 - Example of Protocol Error causing MRA message
Figure 4 provides an example of a message forwarded upstream by a
Diameter relay. When the message is received by Relay 2, and it
detects that it cannot forward the request to the home server, an MRA
message is returned with the Result-Code AVP set to
DIAMETER_UNABLE_TO_DELIVER. Given that this error falls within the
protocol error category, Relay 1 would take special action, and given
the error, attempt to route the message through its alternate Relay
3.
+---------+ 1. Request +---------+ 2. Request +---------+
| Access |------------>|Diameter |------------>|Diameter |
| | | | | Home |
| Device |<------------| Relay |<------------| Server |
+---------+ 4. Answer +---------+ 3. Answer +---------+
(Missing AVP) (Missing AVP)
Figure 5 - Example of Application Error Answer message
Figure 5 provides an example of a Diameter message that caused an
application error. When application errors occur, the Diameter entity
reporting the error clears the 'R' bit in the Command Flags, and adds
the Result-Code AVP with the proper value. Application errors do not
require any proxy or relay agent involvement, and therefore the
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message would be forwarded back to the originator of the request.
There are certain Result-Code AVP application errors that require
additional AVPs to be present in the answer, such as:
- An unrecognized AVP is received with the 'M' bit (Mandatory bit)
set, causes an answer to be sent with the Result-Code AVP set to
DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the
offending AVP.
- An AVP that is received with an unrecognized value causes an
answer to be returned with the Result-Code AVP set to
DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing
the AVP causing the error.
- A command is received with an AVP that is ommitted, yet is
mandatory according to the command's ABNF. The receiver issues
an answer with the Result-Code set to DIAMETER_MISSING_AVP, and
creates an AVP with the AVP Code and other fields set to the
missing AVP's. The created AVP is then added to the Failed-AVP
AVP.
The Result-Code AVP contains additional errors conditions, and
defines the expected behavior of each.
9.1 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 answer messages MUST include
one Result-Code AVP. A non-successful Result-Code AVP (one containing
a non 2xxx value) MUST include the Error-Reporting-Host AVP if the
host setting the Result-Code AVP is different from the identity
encoded in the Origin-Host AVP.
The Result-Code data field contains an IANA-managed 32-bit address
space representing errors (see section 15.4). Diameter provides the
following classes of errors, all identified by the thousands digit:
- 1xxx (Informational)
- 2xxx (Success)
- 3xxx (Protocol Errors)
- 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.
9.1.1 Informational
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Errors that fall within this category are used to inform the
requester that a request could not be satisfied, and additional
action is required on its part before access is granted.
DIAMETER_MULTI_ROUND_AUTH 1001
This informational error is returned by a Diameter server to
inform the access device that the authentication mechanism
being used required multiple round trip, and a subsequent
request needs to be issued in order for access to be granted.
9.1.2 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.
9.1.3 Protocol Errors
Errors that fall within the Protocol Error category SHOULD be treated
on a per-hop basis, and Diameter proxies MAY attempt to correct the
error, if it is possible. Note that these errors MUST only be used in
the Message-Rejected-Answer message, therefore a Diameter entity that
wishes to return an error in this category MUST change the command
code to Message-Rejected-Answer message.
DIAMETER_INVALID_ROUTE_RECORD 3001
The last Route-Record AVP in the message is not set to the
identity of the sender of the message. See Section 11.0 for
more information.
DIAMETER_COMMAND_UNSUPPORTED 3002
The Request contained a Command-Code that the receiver did not
recognize or support.
DIAMETER_UNABLE_TO_DELIVER 3003
The request could not be delivered to a host that handles the
realm, and application, requested at this time.
DIAMETER_REALM_NOT_SERVED 3004
The intended realm of the offending message is unknown.
DIAMETER_TOO_BUSY 3005
When returned, a Diameter node SHOULD attempt to sent the
message to an alternate peer.
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DIAMETER_INVALID_CMS_DATA 3006
The Request did not contain a valid CMS-Data [11] AVP.
DIAMETER_LOOP_DETECTED 3007
An agent 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_END_2_END_SECURITY 3008
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.
9.1.4 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
only be tried after prompting the user for a new password.
DIAMETER_OUT_OF_SPACE 4002
A Diameter node received the accounting request but was unable
to commit it to stable storage due to a temporary lack of
space.
9.1.5 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.
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DIAMETER_UNKNOWN_SESSION_ID 5003
The request 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 contain an AVP header
containing the AVP Code and vendor-Id.
DIAMETER_AUTHORIZATION_FAILED 5007
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 5008
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 5009
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 5010
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 5011
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.
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DIAMETER_UNSUPPORTED_TRANSFORM 5012
A message was received that included an CMS-Data AVP [11] that
made use of an unsupported transform.
DIAMETER_NO_COMMON_APPLICATION 5013
This error is returned when a CEA message is received, and
there are no common applications supported between the peer.
DIAMETER_UNSUPPORTED_VERSION 5014
This error is returned when a CEA message is received, and the
Diameter message is unsupported.
DIAMETER_UNABLE_TO_COMPLY 5015
This error is returned when a request is rejected for
unspecified reasons.
9.2 Message-Reject-Answer
The Message-Reject-Answer (MRA), indicated by the Command-Code set to
282, and the Command Flags' 'R' bit cleared, is sent in response to a
request that has caused a protocol error.
Although the command code is different from the one found in the
request, the same procedures used in issuing an answer message is
followed. The Result-Code AVP MUST be present, and include a value in
the "Protocol Error" category.
Proxies receiving an MRA message MAY attempt to rectify the error
reported, if possible. In the event that no proxy is able to correct
the problem, the MRA will be returned to the originator of the
request message.
Message Format
<Message-Reject-Answer> ::= < Diameter Header: 282 >
< Session-Id >
{ Origin-Host }
{ Origin-Realm }
{ Result-Code }
{ Destination-Host }
[ Origin-State-Id ]
* [ AVP ]
9.3 Error-Message AVP
The Error-Message AVP (AVP Code 281) is of type OctetString. It is a
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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.
9.4 Error-Reporting-Host AVP
The Error-Reporting-Host AVP (AVP Code 294) is of type OctetString,
encoded in the UTF-8 [24] format, according to the Diameter identity
rules defined in section 2.7. This AVP contains the identity of the
Diameter host that set the Result-Code AVP to a value other than 2001
(Success), only if the host setting the Result-Code is different from
the one encoded in the Origin-Host AVP. This AVP is intended to be
used for troubleshooting purposes, and MUST be set when the Result-
Code AVP indicates a failure.
9.5 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.
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 12.0), or the presence of two or more
occurrences of an AVP which table 14.1 restricts to 0, 1, or 0-1
occurrences.
A Diameter message MAY contain one Failed-AVP AVP, containing the
entire AVP that could not be processed successfully. If the failure
reason is omission of a required AVP, an AVP with the missing AVP
code, the missing vendor id, and a zero filled payload of the minimum
required length for the ommitted AVP will be added.
AVP Format
<Failed-AVP> ::= < AVP Header: 279 >
1* {AVP}
10.0 "User" Sessions
Diameter can provide two different type of services to applications.
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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 application, 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 application
(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 answer message. 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 application 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 application, the
Session-Id is still used to identify user sessions. However, the
session termination messages are not used, since a session is
signaled as being terminated by issuing an accounting stop message.
10.1 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 application. The term Service-
Specific below refers to a message defined in a Diameter application
(e.g. Mobile IP, NASREQ).
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The following table contains the authorization session state machine.
State Event Action New State
-------------------------------------------------------------
Idle Client or Device Requests send Pending
access service
specific
auth req
Idle Service-Specific authorization send serv. Open
request received, and specific
successfully processed answer
Pending Successful Service-Specific Grant Open
Authorization answer Access
received
Pending Successful Service-Specific Sent STR Discon
authorization answer received
but service not provided
Pending Error processing successful Sent STR Discon
Service-Specific authorization
answer
Open Authorization-Lifetime about send Open
to expire on access device service
specific
auth req
Open Successful Service-Specific Extend Open
Authorization answer Access
received
Open Accounting message sent or process Open
received
Open Failed Service-Specific Discon. Closed
Authorization answer user/device
received.
Open Session-Timeout Expires on send STR Discon
Access Device
Open SKR Received send SKA, Discon
STR
Open Session-Timeout or Cleanup Discon
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Authorization-Lifetime
expires on home AAA server
Open SKA Received Cleanup Closed
Discon SKR 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 an answer,
if applicable, MUST be returned to the originator of the message.
10.2 Accounting Session State Machine
For applications that only require accounting services, the following
state machine MUST be supported.
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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 Receive Interim Record send Open
accounting
answer
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
10.3 Session-Id AVP
The Session-Id AVP (AVP Code 263) is of type OctetString and is used
to identify a specific session (see section 10.0). 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 and eternally unique, as it is meant
to uniquely identify a user session without reference to any other
information, and may be needed to correlate historical authentication
information with accounting information. The Session-Id includes a
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mandatory portion and an implementation-defined portion; a
recommended format for the implementation-defined portion is outlined
below.
The Session-Id MUST begin with the sender's identity (see section
2.7). The remainder of the Session-Id MAY be any sequence that the
client can guarantee to be eternally unique; however, the following
format is recommended, (square brackets [] indicate an optional
element):
<client FQDN>[:<port>];<high 32 bits>;<low 32 bits>[;<optional
value>]
<high 32 bits> and <low 32 bits> are decimal representations of the
high and low 32 bits of a monotonically increasing 64-bit value. The
64-bit value is rendered in two part to simplify formatting by 32-bit
processors. At startup, the high 32 bits of the 64-bit value MAY be
initialized to the time, and the low 32 bits MAY be initialized to 0.
This will for practical purposes eliminate the possibility of
overlapping Session-Ids after a reboot, assuming the reboot process
takes longer than a second. Alternatively, an implementation MAY keep
track of the increasing value in non-volatile memory.
<optional value> is implementation specific but may include a modem's
device Id, a layer 2 address, timestamp, etc.
Example, in which the standard port is used and there is no optional
value:
accesspoint7.acme.com;1876543210;523
Example, in which a non-standard port is used and there is an
optional value:
accesspoint7.acme.com:831;1876543210;523;mobile@200.1.1.88
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 for both the authorization and accounting
commands of a given application.
10.4 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-
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Lifetime value is determined, since a low value could create
significant Diameter traffic, which could congest both the network
and the agents.
If both this AVP and the Session-Timeout AVP are present in a
message, the value of the latter MUST NOT be smaller than the
Authorization-Lifetime AVP.
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. A value of zero means that no re-authorization is required.
10.5 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 session terminated due
to the Session-Timeout expiration MUST NOT generate a re-
authentication and/or re-authorization.
A value of zero, or the absence of this AVP, 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.
10.6 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].
10.7 Session Termination
It is necessary for a Diameter server that authorized a session to be
notified when that session is no longer active, both for tracking
purposes as well as to allow stateful agents to release any resources
that they may have provided for the user's session.
When a user session that required Diameter authorization terminates,
the access device that provided the service MUST issue a Session-
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Termination- Request (STR) message to the Diameter server that
authorized the service, to notify it that the session is no longer
active. An STR MUST be issued when a user session terminates for any
reason, including user logoff, expiration of Session-Timeout,
administrative action, termination upon receipt of an Abort-Session-
Request (see below), orderly shutdown of the access device, etc.
The access device also MUST issue an STR for a session that was
authorized but never actually started. This could occur, for example,
due to a sudden resource shortage in the access device, or because
the access device is unwilling to provide the type of service
requested in the authorization, or because the access device does not
support a mandatory AVP returned in the authorization, etc.
It is also possible that a session that was authorized is never
actually started due to action of a proxy. For example, a proxy may
modify an authorization answer, converting the result from success to
failure, prior to forwarding the message to the access device. A
proxy that causes an authorized session not to be started MUST issue
an STR to the Diameter server that authorized the session, since the
access device has no way of knowing that the session had been
authorized.
A Diameter server that receives an STR message MUST clean up
resources (e.g., session state) associated with the Session-Id
specified in the STR, and return a Session-Termination-Answer.
A Diameter server also MUST clean up resources when the Session-
Timeout expires, or when the Authorization-Lifetime expires without
re-authorization, regardless of whether an STR for that session is
received. The access device is not expected to provide service beyond
the expiration of these timers; thus, expiration of either of these
timers implies that the access device may have unexpectedly shut
down.
10.7.1 Session-Termination-Request
The Session-Termination-Request (STR), indicated by the Command-Code
set to 275 and the Command Flags' 'R' bit set, is sent by the access
device to inform the Diameter Server that an authenticated and/or
authorized session is being terminated.
Message Format
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<Session-Termination-Request> ::= < Diameter Header: 275, REQUEST
>
< Session-Id >
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Destination-Host }
{ User-Name }
{ Termination-Cause }
[ Origin-State-Id ]
* [ AVP ]
* [ Proxy-Info ]
* [ Route-Record ]
10.7.2 Session-Termination-Answer
The Session-Termination-Answer (STA), indicated by the Command- Code
set to 275 and the message flags' 'R' bit clear, is sent by the
Diameter Server to acknowledge the notification 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.
Message Format
<Session-Termination-Answer> ::= < Diameter Header: 275 >
< Session-Id >
{ Result-Code }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Host }
{ User-Name }
[ Origin-State-Id ]
* [ AVP ]
* [ Proxy-Info ]
* [ Route-Record ]
10.8 Aborting a Session
A Diameter server may request that the access device stop providing
service for a particular session by issuing an Abort-Session-Request
(ASR).
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For example, the Diameter server that originally authorized the
session may be required to cause that session to be stopped for
credit or other reasons that were not anticipated when the session
was first authorized. Or, an operator may maintain a management
server for the purpose of issuing ASRs to administratively remove
users from the network.
An access device that receives an ASR with Session-ID equal to a
currently active session MAY stop the session. Whether the access
device stops the session or not is implementation- and/or
configuration- dependent. For example, an access device may honor
ASRs from certain agents only. In any case, the access device MUST
respond with an Abort-Session-Answer, including a Result-Code AVP to
indicate what action it took.
Note that if the access device does stop the session upon receipt of
an ASR, it issues an STR to the authorizing server (which may or may
not be the agent issuing the ASR) just as it would if the session
were terminated for any other reason.
10.8.1 Abort-Session-Request
The Abort-Session-Request (ASR), indicated by the Command-Code set to
274 and the message flags' 'R' bit set, may be sent by any server to
the access device that is providing session service, to request that
the session identified by the Session-Id be stopped.
Message Format
<Abort-Session-Request> ::= < Diameter Header: 274, REQUEST >
< Session-Id >
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Destination-Host }
[ Origin-State-Id ]
* [ AVP ]
* [ Proxy-Info ]
* [ Route-Record ]
10.8.2 Abort-Session-Answer
The Abort-Session-Answer (ASA), indicated by the Command-Code set to
274 and the message flags' 'R' bit clear, is sent in response to the
ASR. The Result-Code AVP MUST be present, and indicates the
disposition of the request.
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If the session identified by Session-Id in the ASR was successfully
terminated, Result-Code is set to DIAMETER_SUCCESS. If the session is
not currently active, Result-Code is set to
DIAMETER_UNKNOWN_SESSION_ID. If the access device does not stop the
session for any other reason, Result-Code is set to
DIAMETER_UNABLE_TO_COMPLY.
Message Format
<Abort-Session-Answer> ::= < Diameter Header: 274 >
< Session-Id >
{ Result-Code }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Host }
[ Origin-State-Id ]
* [ AVP ]
* [ Proxy-Info ]
* [ Route-Record ]
10.9 Termination-Cause AVP
The Termination-Cause AVP (AVP Code 295) is of type Unsigned32, and
is used to indicate the reason why a session was terminated on the
access device. The following values are defined:
DIAMETER_LOGOUT 1
The user initiated a disconnect
DIAMETER_SERVICE_NOT_PROVIDED 2
This value is used when the user disconnected prior to the
receipt of the authorization answer message.
DIAMETER_BAD_ANSWER 3
This value indicates that the authorization answer received by
the access device was not processed successfully.
DIAMETER_ADMINISTRATIVE 4
The user was not granted access, or was disconnected, due to
administrative reasons, such as the receipt of a Session-Kill-
Request message.
DIAMETER_LINK_BROKEN 5
The communication to the user was abruptly disconnected.
10.10 Inferring Session Termination from Origin-State-Id
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Origin-State-Id is used to allow rapid detection of terminated
sessions for which no STR would have been issued, due to
unanticipated shutdown of an access device.
By including Origin-State-Id in CER/CAA messages, an access device
allows a next-hop server to determine immediately upon connection
whether the device has lost its sessions since the last connection.
By including Origin-State-Id in request messages, an access device
also allows a server with which it communicates via proxy to make
such a determination. However, a server that is not directly
connected with the access device will not discover that the access
device has been restarted unless and until it receives a new request
from the access device. Thus, use of this mechanism across proxies is
opportunistic rather than reliable, but useful nonetheless.
When a Diameter server receives a Origin-State-Id that is greater
than the Origin-State-Id previously received from the same issuer, it
may assume that the issuer has lost state since the previous message
and that all sessions that were active under the lower Origin-State-
Id have been terminated. The Diameter server MAY clean up all session
state associated with such lost sessions, and MAY also issues STRs
for all such lost sessions that were authorized on downstream
servers, to allow session state to be cleaned up globally.
10.11 Origin-State-Id AVP
The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a
monotonically increasing value that is advanced whenever a Diameter
entity restarts with loss of previous state, for example upon reboot.
Origin-State-Id MAY be included in any Diameter message, including
CER.
A Diameter entity issuing this AVP MUST create a higher value for
this AVP each time its state is reset. A Diameter entity MAY set
Origin-State-Id to the time of startup, or it MAY use an incrementing
counter retained in non-volatile memory across restarts.
The Origin-State-Id, if present, MUST reflect the state of the entity
indicated by Origin-Host. If a proxy modifies Origin-Host, it MUST
either remove Origin-State-Id or modify it appropriately as well.
Typically, Origin-State-Id is used by an access device that always
starts up with no active sessions; that is, any session active prior
to restart will have been been lost. By including Origin-State-Id in
a message, it allows other Diameter entities to infer that sessions
associated with a lower Origin-State-Id are no longer active. If an
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access device does not intend for such inferences to be made, it MUST
either not include Origin-State-Id in any message, or set its value
to 0.
11.0 Accounting
This accounting protocol is based on a 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.
11.1 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.
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 Diameter. Should Batched Accounting be
required in the future, a new Diameter application 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 agents) 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.
11.2 Protocol Messages
A Diameter node that receives a successful authentication and/or
authorization messages from the Home AAA Server, MUST collect
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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.
11.3 Application document requirements
Each Diameter application (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 application 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.
11.4 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 agents 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 application of this protocol may include AVPs to control
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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.
11.5 Accounting Records
In all accounting records the Session-Id and User-Name AVPs MUST be
present. If end-to-end 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 end-to-end 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
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.
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A particular value of Accounting-Session-Id MUST appear only in one
sequence of accounting records from a DIAMETER client, except for the
purposes of retransmission. Note that sometimes such sequence of
records is related to a higher-level session, possibly spanning
several DIAMETER clients. The linking of such record sequences
together lies, however, outside DIAMETER and is typically performed
by postprocessing systems. It is the responsibility of the particular
Diameter application specification to define a sufficient set of AVPs
so that this correlation can be done based on, for instance, IP
addresses. Likewise, the application specifications MUST also define
the exact concept of a session that is being accounted. For
instance, the NASREQ DIAMETER application treats a single PPP
connection to a Network Access Server as one session.
The one sequence that is sent MUST be either one record with
Accounting-Record-Type AVP set to the value EVENT_RECORD, or several
records starting with one having the value START_RECORD, followed by
zero or more INTERIM_RECORD, and a single STOP_RECORD. That is, it is
not allowed to mix record types, such as sending interim records
followed by an event record. A particular Diameter application
specification MUST define which kind of sequences should be used.
12.0 Accounting Command-Codes
This section defines new Command-Code values that MUST be supported
by all Diameter implementations that provide Accounting services.
12.1 Accounting-Request
The Accounting-Request command, indicated by the Command-Code field
set to 271 and the Command Flags' 'R' bit set, 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 third party (e.g.
settlement service), 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 11.3.
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Message Format
<Accounting-Request> ::= < Diameter Header: 271, REQUEST >
< Session-Id >
{ Acct-Application-Id }
{ User-Name }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Accounting-Record-Type }
{ Accounting-Record-Number }
{ Accounting-Session-Id }
[ Accounting-Interim-Interval ]
[ Origin-State-Id ]
* [ AVP ]
* [ Proxy-Info ]
* [ Route-Record ]
12.2 Accounting-Answer
The Accounting-Answer command, indicated by the Command-Code field
set to 271 and the Command Flags' 'R' bit cleared, 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 11.3.
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Message Format
<Accounting-Answer> ::= < Diameter Header: 271, A >
< Session-Id >
{ Acct-Application-Id }
{ User-Name }
{ Result-Code }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Host }
{ Accounting-Record-Type }
{ Accounting-Record-Number }
{ Accounting-Session-Id }
[ Error-Reporting-Host ]
[ Accounting-Interim-Interval ]
[ Origin-State-Id ]
* [ AVP ]
* [ Proxy-Info ]
* [ Route-Record ]
12.3 Accounting-Poll-Ind
The Accounting-Poll-Ind command, indicated by the Command-Code field
set to 273 and the message flags' 'I' bit set, 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.
A Failed API would contain the same Command-Code, but would require
that only be 'F' bit be set.
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.
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Message Format
<Accounting-Poll-Ind> ::= < Diameter Header: 273, I >
< Session-Id >
{ Acct-Application-Id }
{ Destination-Host }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Accounting-Session-Id }
[ Origin-State-Id ]
* [ AVP ]
* [ Proxy-Info ]
* [ Route-Record ]
13.0 Accounting AVPs
This section contains AVPs that describe accounting usage information
related to a specific session.
13.1 Accounting-Record-Type AVP
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 applications. The selection of whether to use
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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.
13.2 Accounting-Interim-Interval AVP
The Accounting-Interim-Interval AVP (AVP Code 482) is of type
Unsigned32 and is sent from the Diameter home authorization 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.
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.
13.3 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
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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.
13.4 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], following the format
specified in section 10.3. The Accounting-Session-Id 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.
13.5 Accounting-Multi-Session-Id AVP
The Accounting-Multi-Session-Id AVP (AVP Code 50) is of type
OctetString and SHOULD be encoded in UTF08 format [13], following the
format specified in section 10.3. The Accounting-Multi-Session-Id AVP
is used to link together multiple related accounting sessions, where
each session would have a unique Accounting-Session-Id, but the same
Acounting-Multi-Session-Id AVP. This AVP MAY be returned by the
Diameter server in an authorization answer, and MUST be used in all
accounting messages for the given session.
14.0 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.
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14.1 Base Protocol Command AVP Table
The table in this section is limited to the non-accounting Command
Codes defined in this specification.
+-----------------------------------+
| Command-Code |
|---+---+---+---+---+---+---+---+---+
Attribute Name |CER|CEA|MRA|DWR|DWA|ASR|ASA|STR|STA|
------------------------------|---+---+---+---+---+---+---+---+---|
Acct-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |
Auth-Application-Id |0+ |0+ |0 |0 |0 |0 |0 |0 |0 |
Authorization-Lifetime |0 |0 |0 |0 |0 |0 |0 |0 |0 |
Destination-Host |0-1|0-1|1 |0-1|1 |1 |1 |0-1|1 |
Destination-Realm |0 |0 |0 |0 |0 |1 |0 |1 |0 |
Error-Message |0 |0 |0 |0 |0 |0 |0-1|0 |0 |
Error-Reporting-Host |0 |0 |0 |0 |0 |0 |0-1|0 |0 |
Failed-AVP |0 |0+ |0+ |0 |0+ |0 |0+ |0 |0+ |
Firmware-Revision |0-1|0-1|0 |0 |0 |0 |0 |0 |0 |
Host-IP-Address |1+ |1+ |0 |0 |0 |0 |0 |0 |0 |
Origin-Host |1 |1 |1 |1 |1 |1 |1 |1 |1 |
Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |1 |
Product-Name |1 |1 |0 |0 |0 |0 |0 |0 |0 |
Proxy-Info |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |
Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0 |0 |
Result-Code |0 |1 |1 |0 |1 |0 |0 |0 |1 |
Route-Record |0 |0 |0 |0 |0 |0+ |0+ |0+ |0+ |
Session-Id |0 |0 |1 |0 |0 |1 |1 |1 |1 |
Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 |0 |
Origin-State-Id |0-1|0-1|0-1|0-1|0-1|0-1|0-1|0-1|0-1|
Supported-Vendor-Id |0+ |0 |0 |0 |0 |0 |0 |0 |0 |
Termination-Cause |0 |0 |0 |0 |0 |0 |0 |1 |0 |
User-Name |0 |0 |0 |0 |0 |1 |1 |1 |1 |
Vendor-Id |1 |1 |0 |0 |0 |0 |0 |0 |0 |
Vendor-Specific-Application-Id|0+ |0+ |0 |0 |0 |0 |0 |0 |0 |
------------------------------|---+---+---+---+---+---+---+---+---|
14.2 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 |
------------------------------|-----+-----+-----+
Accounting-Interim-Interval | 0-1 | 0-1 | 0 |
Accounting-Multi-Session-Id | 0-1 | 0-1 | 0 |
Accounting-Record-Number | 1 | 1 | 0 |
Accounting-Record-Type | 1 | 1 | 0 |
Accounting-Session-Id | 1 | 1 | 1 |
Acct-Application-Id | 1 | 1 | 1 |
Destination-Host | 0+ | 1 | 0-1 |
Destination-Realm | 1 | 0 | 1 |
Error-Reporting-Host | 0 | 0+ | 0 |
Max-Time-Wait | 0+ | 0 | 0 |
Origin-Host | 1 | 1 | 1 |
Origin-Realm | 1 | 1 | 1 |
Proxy-Info | 0+ | 0+ | 0 |
Route-Record | 0+ | 0+ | 0+ |
Result-Code | 0 | 1 | 0 |
Session-Id | 1 | 1 | 1 |
------------------------------|-----+-----+-----+
15.0 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.
15.1 AVP
As defined in section 4.0, the AVP header contains two fields that
requires IANA namespace management; the AVP Code and Flags field.
15.1.1 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 via Specification
Required [12].
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Vendor-Specific AVP Codes, where the Vendor-Id field in the AVP
header is set to a non-zero value, is for Private Use.
This document defines the AVP Codes 257-260, 263-269, 278-284, 291-
297, 480, 482 and 485-486. See section 4.5 for the assignment of the
namespace in this specification.
15.1.2 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].
15.2 Diameter Header
As defined in section 3.0, the Diameter header contains two fields
that require IANA namespace management; Command Code and Command
Flags.
15.2.1 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, 271, 273-275, 280 and
282. See section 3.1 for the assignment of the namespace in this
specification.
15.2.2 Command Flags
There are eight bits in the Command Flags field of the Diameter
header. This document assigns bit 8 ('R'equest). Bits 1 through 7
MUST only be assigned via a Standards Action [12].
15.3 Application Identifiers
As defined in section 6.1, the Application Identifier is used to
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identify a specific Diameter Application. 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 applications defined MUST ensure that they fit
within the existing framework, and that no changes to the base
protocol are required.
15.4 Result-Code AVP Values
As defined in Section 9.1, the Result-Code AVP (AVP Code 268) defines
the values 1001, 2001, 4001-4003 and 5001-5015.
All remaining values are available for assignment via IETF Consensus
[12].
15.5 Accounting-Record-Type AVP Values
As defined in Section 13.1, the Accounting-Record-Type AVP (AVP Code
480) defines the values 1-4. All remaining values are available for
assignment via IETF Consensus [12].
15.6 Termination-Cause AVP Values
As defined in Section 10.9, the Termination-Cause AVP (AVP Code 295)
defines the values 1-5. All remaining values are available for
assignment via IETF Consensus [12].
15.7 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.
IANA should also replace "TBD" in section 2.7 with the port number
assigned in section 2.1
16.0 Diameter protocol related configurable parameters
This section contains the configurable parameters that are found
throughout this document:
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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.
Tc timer
The Tc timer controls the frequency that transport connection
attempts are done to a peer with whom no active transport
connection exists. The recommended value is 30 seconds.
Tw timer
The Tw timer controls the frequency the watchdog messages are
to be sent to inactive peers. The recommended value is 30
seconds.
17.0 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 relay, proxy,
or redirect servers.
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 Diameter
application 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.
18.0 References
[1] C. Rigney, A. Rubens, W. Simpson, S. Willens, "Remote Authenti-
cation Dial In User Service (RADIUS)", RFC 2865, June 2000.
Calhoun et al. expires December 2001 [Page 87]
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[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
Application", draft-ietf-aaa-diameter-nasreq-05.txt, IETF work
in progress, June 2001.
[8] Aboba, Beadles "The Network Access Identifier." RFC 2486. Janu-
ary 1999.
[10] P. Calhoun, C. Perkins, "Diameter Mobile IP Application",
draft-ietf-aaa-diameter-mobileip-05.txt, IETF work in progress,
June 2001.
[11] P. Calhoun, W. Bulley, S. Farrell, "Diameter CMS Security appli-
cation", draft-ietf-aaa-diameter-cms-sec-00.txt (work in pro-
gress), June 2001.
[12] Narten, Alvestrand,"Guidelines for Writing an IANA Considera-
tions Section in RFCs", BCP 26, RFC 2434, October 1998
[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,
Calhoun et al. expires December 2001 [Page 88]
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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.
[28] E. Guttman, C. Perkins, J. Veizades, M. Day. "Service Location
Protocol, Version 2", RFC 2165, June 1999.
[29] T. Berners-Lee, R. Fielding, U.C. Irvine, L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax". RFC 2396, August
1998.
[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.
Calhoun et al. expires December 2001 [Page 89]
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[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] T. Dierks, C. Allen, "The TLS Protocol Version 1.0", RFC 2246,
January 1999.
[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.
[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
19.0 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, Jonathan Wood and Bernard Aboba's assistance
Calhoun et al. expires December 2001 [Page 90]
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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.
Text in this document was also provided by Paul Funk, Mark Eklund,
Mark Jones and Dave Spence.
The authors would also like to acknowledge the following people for
their contribution in the development of the Diameter protocol:
William Bulley, 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 Mus-
lin, Kenneth Peirce, Stephen Farrell, Sumit Vakil, John R. Vollbrecht
and Jeff Weisberg
20.0 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
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
Calhoun et al. expires December 2001 [Page 91]
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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
21.0 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
Calhoun et al. expires December 2001 [Page 92]
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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.
22.0 Expiration Date
This memo is filed as <draft-ietf-aaa-diameter-05.txt> and expires in
December 2001.
Calhoun et al. expires December 2001 [Page 93]
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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-04.txt
template-url-syntax=
url-path= ; The diameter URL format is described in section 2.7.
; Example: 'diameter://aaa.example.com:1812;transport=tcp
Calhoun et al. expires December 2001 [Page 94]
Internet-Draft June 2001
supported-auth-applications= string L M
# This attribute lists the Diameter applications supported by the
# AAA implementation. The applicationss currently defined are:
# Application Name Defined by
# ---------------- -----------------------------------
# NASREQ draft-ietf-aaa-diameter-nasreq-04.txt
# MobileIP draft-ietf-aaa-diameter-mobileip-04.txt
# CMS Security draft-ietf-aaa-diameter-cms-sec-00.txt
#
# Notes:
# . Diameter implementations support one or more applications.
# . Additional applications may be defined in the future.
# An updated service template will be created at that time.
#
NASREQ,MobileIP,CMS Security
supported-acct-applications= string L M
# This attribute lists the Diameter applications supported by the
# AAA implementation. The applicationss currently defined are:
# Application Name Defined by
# ---------------- -----------------------------------
# NASREQ draft-ietf-aaa-diameter-nasreq-04.txt
# MobileIP draft-ietf-aaa-diameter-mobileip-04.txt
# CMS Security draft-ietf-aaa-diameter-cms-sec-00.txt
#
# Notes:
# . Diameter implementations support one or more applications.
# . Additional applications may be defined in the future.
# An updated service template will be created at that time.
#
NASREQ,MobileIP,CMS Security
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-----------------------
Calhoun et al. expires December 2001 [Page 95]
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