WDIFF

draft-ietf-aaa-diameter-01.txt --> draft-ietf-aaa-diameter-02.txt

AAA Working Group Pat R. Calhoun
Internet-Draft Sun Microsystems, Inc.
Category: Standards Track Allan C. Rubens
<draft-ietf-aaa-diameter-01.txt> Tut Systems, Inc. Haseeb Akhtar
<draft-ietf-aaa-diameter-02.txt> Nortel Networks
Jari Arkko
Oy LM Ericsson Ab
Erik Guttman
Sun Microsystems, Inc.
March
Allan C. Rubens
Tut Systems, Inc.
Glen Zorn
Cisco Systems, Inc.
April 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.

Abstract

The Diameter base protocol is intended to provide a AAA framework for

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Mobile-IP, NASREQ and ROAMOPS. This draft specifies the message
format, transport, error reporting and security services to be used
by all Diameter extensions and MUST be supported by all Diameter
implementations.

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Table of Contents

1.0 Introduction
1.1 Diameter Protocol
1.2 Requirements language
1.2
1.3 Terminology
2.0 Protocol Overview
2.1 Transport
2.2 Securing Diameter Messages
2.3 Diameter Extensions
2.4 Diameter Server Discovery
2.4 Mandatory Accounting Support
3.0 Diameter Header
3.1 Command Code Definitions
3.2 Command Code ABNF specification
3.3 Diameter Command Naming Conventions
3.3.1 Request/Answer
3.3.2 Query/Response
3.3.3 Indication
4.0 Diameter AVPs
4.1 AVP Header
4.2 Optional Header Elements
4.3 AVP Data Formats
4.4 Grouped AVP Values
4.4.1 Example AVP with a Grouped Data type
4.5 Diameter Base Protocol AVPs
5.0 Message Forwarding
5.1 Origin-FQDN AVP
5.2 Origin-Realm AVP
5.3 Destination-FQDN AVP
6.0 Capabilities Negotiation
6.1 Device-Reboot-Ind (DRI) Command
6.1.1 Vendor-Id AVP
6.1.2 Firmware-Revision AVP
6.1.3 Extension-Id AVP
6.1.4 Host-IP-Address AVP
6.1.5 Supported-Vendor-Id AVP
6.1.6 Product-Name 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 Per-Hop Error Signaling
9.1 Device-Status-Ind

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9.1.1 Device-Error DSI-Event AVP
9.1.1.1 Informational Events
9.1.1.2 Redirect Event
9.1.1.3 Transient Failure Events
9.1.1.4 Permanent Failure Events
10.0 End-to-End Error Signaling
10.1 Message-Reject-Ind (MRI) Command
10.1.1 Failed-AVP AVP
10.1.2 Failed-Command-Code AVP
10.1.3 Failed-Vendor-Id AVP
10.2 Result-Code AVP
10.2.1 Informational
10.2.2 Success

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10.2.3 Redirect Notification
10.2.4 Transient Failures
10.2.5 Permanent Failures
10.3 Error-Message AVP
10.4 Error-Reporting-FQDN AVP
11.0 "User" Sessions
11.1 Session State Machine
11.2 Session-Id AVP
11.3 Authorization-Lifetime AVP
11.4 Session-Timeout AVP
11.5 User-Name AVP
11.6 Max-Wait-Time AVP
11.7 Original-Session-Id AVP
11.8 Session Termination
11.7.1
11.8.1 Session-Termination-Ind
11.7.2
11.8.2 Session-Termination-Request
11.7.3
11.8.3 Session-Termination-Answer
12.0 Message Routing
12.1 Realm-Based Message Routing
12.1.1 Realm-Based Routing Table
12.2 Proxy and Redirect Server handling of requests
12.2.1 Proxy and Redirect Server handling of requests
12.3 Redirect Server
12.3.1 Redirect-Host AVP
12.3.2 Redirect-Host-Address AVP
12.3.3 Redirect-Host-Port AVP
12.4 Proxy Server
12.4.1 Proxying Requests
12.4.2 Proxying Responses
12.4.3 Route-Record AVP
12.4.4 Proxy-State AVP
12.4.5 Proxy-Address AVP
12.4.6 Proxy-Info AVP
12.4.7 Destination-Realm AVP
12.5 Applying Local Policies

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12.6 Hiding Network Topology
12.7 Loop Detection
13.0 Diameter Message Security Accounting
13.1 Hop-by-Hop Security
13.1.1 Integrity-Check-Value AVP
13.1.1.1 Authentication-Transform-Id AVP
13.1.1.2 Digest AVP
13.1.2 Encrypted-Payload Authorization-Server Directed Model
13.2 Protocol Messages
13.3 Extension document requirements
13.4 Fault Resilience
13.5 Session Records
14.0 Accounting Command-Codes
14.1 Accounting-Request (ACR) Command
14.2 Accounting-Answer (ACA) Command
14.3 Accounting-Status-Ind (ASI) Command
14.4 Accounting-Poll-Ind (API) Command
15.0 Accounting AVPs
15.1 Accounting-Record-Type AVP
13.1.2.1 Encryption-Transform-Id
15.2 Accounting-Interim-Interval AVP
13.1.2.1.1 MD5 Payload Hiding
13.1.2.2 Plaintext-Data-Length
15.3 Accounting-Record-Number AVP
13.1.2.3 Encrypted-Data
15.4 Accounting-State AVP
13.2 Nonce
15.5 Accounting-Session-Id AVP
13.3 Timestamp
16.0 AVP

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13.4 Key-Id Occurrence Table
16.1 Base Protocol Command AVP
14.0 Table
16.2 Accounting AVP Table
15.0
17.0 IANA Considerations
15.1
17.1 AVP Attributes
15.2
17.2 Command Code AVP Values
15.3
17.3 Extension Identifier Values
15.4
17.4 Result-Code AVP Values
15.5 Integrity-Check-Value AVP Transform Values
15.6 Encryption-Transform-Id AVP Values
15.7
17.5 Message Header Bits
15.8
17.6 AVP Header Bits
15.9
17.7 DSI-Event AVP Values
16.0
18.0 Open Issues
17.0
19.0 Diameter protocol related configurable parameters
18.0
20.0 Security Considerations
19.0
21.0 References
20.0
22.0 Acknowledgements
21.0
23.0 Authors' Addresses
22.0
24.0 Full Copyright Statement
Appendix A. Diameter Service Template

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1.0 Introduction

The Diameter

Historically, the RADIUS protocol allows peers has been used 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 provide AAA
services for dial-up PPP [42] and AVPs, as
required terminal server access. Over time,
routers and network access servers (NAS) have increased in [21]

All data delivered by complexity
and density, making the RADIUS protocol is increasingly unsuitable for
use in the form of an AVP. Some such networks.

The Roaming Operations Working Group (ROAMOPS) has published a set 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
specifications [20, 43, 44] that define how a PPP user can gain
access to Diameter messages,
so long as the required AVPs are included and AVPs which are
explicitly excluded are not included. AVPs are used Internet without having to dial into his/her home
service provider's modem pool. This is achieved by base Diameter
protocol allowing service
providers to support the following required features:

- Transporting of cross-authenticate their users. Effectively, a user authentication information, for the
purposes of enabling the Diameter server to authenticate the
user.
- Transporting can
dial into any service provider's point of presence (POP) that has a
roaming agreement with his/her home Internet service specific authorization information,
between client and servers, allowing provider (ISP),
the peers benefit being that the user does not have to decide whether incur a user's access request should be granted.
- Exchanging resource usage information, long
distance charge while traveling, which MAY can sometimes be used for
accounting purposes, capacity planning, etc.
- Proxying and Re-directing of Diameter messages through a server
hierarchy.
- Providing application-level security, through quite
expensive.

Given the use number of ISPs today, ROAMOPS realized that requiring each
ISP to set up roaming agreements with all other ISPs did not scale.
Therefore, the
Integrity-Check-Value (ICV) and Encrypted-Payload AVPs.

The Diameter base protocol provides the minimum requirements needed
for an AAA transport protocol, working group defined a "broker", which acts as required by NASREQ [21], Mobile IP
[22, 23], and ROAMOPS [20]. The base protocol an
intermediate server, whose sole purpose is not intended to be
used by itself, set up these roaming
agreements. A collection of ISPs and must be used with an application-specific
extension, such as Mobile IP [10]. The Diameter protocol was heavily
inspired and builds upon the tradition of the RADIUS [1] protocol.

Any node can initiate a request. In that sense, Diameter broker is called a peer "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
peer protocol. In this document, a Diameter client inter
administrative domain mobility, which is the device that
normally initiates a request requirement for authentication and/or authorization 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 a user. A PPP.

The Diameter server is protocol was not designed from the device that either forwards ground up. Instead,
the
request 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 another ease migration.

The basic concept behind Diameter server (known as is to provide a proxy), or one base protocol that
performs
can be extended in order to provide AAA services to new access
technologies. Currently, the actual authentication and/or authorization of protocol only concerns itself with
Internet access, both in the user
based on some profile. Given that traditional PPP sense as well as taking
into account the server MAY send unsolicited
messages ROAMOPS model, and Mobile-IP.

Although Diameter could be used to clients, it is possible for solve a wider set of AAA problems,
we are currently limiting the server to initiate such
messages. An example scope of an unsolicited message would be for a request the protocol in order to

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ensure that the client issue an accounting update.

Diameter services require sequenced in-order reliable delivery of
data, with congestion control (receiver windowing). Timely detection effort remains focussed on satisfying the
requirements of failed or unresponsive peers is also required, allowing for robust
operation. TCP is insufficient for this second requirement.
Diameter SHOULD be transported over SCTP [26].

1.1 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].

1.2 Terminology

Refer to [9] for terminology used in this document.

2.0 Protocol Overview

The base Diameter network access. Note that a truly generic AAA
protocol is never used on its own. It is always
extended for a particular application. Four extensions to Diameter
are defined by companion documents: NASREQ [7], Mobile IP [10],
Accounting Extension [15], Strong Security [11]. These options are
introduced in this document but specified elsewhere. Additional
extensions to Diameter may be defined in many applications might provide functionality not
provided by Diameter. Therefore, it is imperative that the future (see Section
15.3). designers
of new applications understand their requirements before using
Diameter.

1.1 Diameter Protocol

The base Diameter protocol concerns itself with capabilities
negotiation, and how messages are sent and how allows peers may eventually
be abandoned. The base protocol also defines certain rules which
apply to all exchanges exchange a variety of messages between Diameter peers. It is
important to note that the messages.
The base protocol provides optional
application-level security the following facilities:

- Delivery of AVPs (Integrity-Check-Value) which MAY be
used (attribute value pairs)
- Capabilities negotiation, as required in absence of an underlying security protocol (e.g. IP
Security).

Communication between Diameter peers begins with one peer sending a
message to another Diameter peer. The set [20]
- Error notification
- Extensibility, through addition of AVPs included new commands and AVPs, as
required in [21]

All data delivered by the
message protocol is determined in the form of an AVP. Some of
these AVP values are used by a the Diameter protocol itself, while
others deliver data associated with particular application of or extension to applications which
employ Diameter. We will refer AVPs may be added arbitrarily to this Diameter messages,
so long as the Diameter extension. One AVP
that is required AVPs are included and AVPs which are
explicitly excluded are not included. AVPs are used by base Diameter
protocol to reference 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 session is the Session-Id.

The initial access request should be granted.
- Exchanging resource usage information, which MAY be used for authentication and/or authorization
accounting purposes, capacity planning, etc.
- Proxying and Re-directing of Diameter messages through a user
would include server
hierarchy.

The Diameter base protocol provides the Session-Id. minimum requirements needed
for an AAA transport protocol, as required by NASREQ [21], Mobile IP
[22, 23], and ROAMOPS [20]. The Session-Id base protocol is then not intended to be
used in all by itself, and must be used with an application-specific
extension, such as Mobile IP [10]. The Diameter protocol was heavily
inspired and builds upon the tradition of the RADIUS [1] protocol.
See section 2.3. for more information on Diameter extensions.

Any node can initiate a request. In that sense, Diameter is a peer to
peer protocol. In this document, a Diameter client is the device that

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subsequent messages to identify the user's session (see section 11.0
for more information). The communicating party may accept the
request, or reject it by returning

normally initiates a response with Result-Code AVP
set to indicate an error occurred. The specific behavior request for authentication and/or authorization
of the
diameter server or client receiving a request depends on the user. A Diameter
extension employed.

Session state (associated with a Session-Id) MUST be freed upon
receipt of server is the Session-Termination-Request, Session-Termination-
Answer, expiration of authorized service time in device that either forwards the Session-Timeout
AVP, and according
request to rules established in another Diameter server (known as a particular
extension/application of Diameter.

Exchanges of messages are either request/reply oriented, proxy), or in one that
performs the actual authentication and/or authorization of the user
based on some
special cases, do not require replies. All such messages profile. Given that do not
require replies have names ending with '-Ind' (short for Indication).

The Diameter base protocol provides the Authorization-Lifetime AVP,
which server MAY be used by extensions send unsolicited
messages to specify clients, it is possible for the duration server to initiate such
messages. An example of an unsolicited message would be for a specific
authorized session.

2.1 Transport

The base request
that the client issue an accounting update.

Diameter protocol is run on port TBD services require sequenced in-order reliable delivery of both
data, with congestion control (receiver windowing). Timely detection
of failed or unresponsive peers is also required, allowing for robust
operation. TCP [27] and
SCTP [26] transport protocols (for interoperability test purposes
port 1812 will is insufficient for this second requirement.
Diameter SHOULD be used until April 2001). Diameter clients [9] MUST
support TCP, but are warned that future versions of this
specification may mandate transported over SCTP support. Diameter servers MUST support
both TCP and SCTP.

A Diameter node MAY sent packets from any source port, but MUST be
prepared to receive packets on port TBD. When a request is received, [26].

1.2 Requirements language

In this document, the source key words "MAY", "MUST", "MUST NOT",
"optional", "recommended", "SHOULD", and destionation ports "SHOULD NOT", are to be
interpreted as described in [13].

1.3 Terminology

Accounting
The act of collecting information on resource usage for the reply are reversed. Note
that
purpose of trend analysis, auditing, billing, or cost allocation.

Authentication
The act of verifying the source and destination addresses used in request and replies
MAY any identity of an entity (subject).

Authorization
The act of determining whether a peer's valid IP addresses.

A given Diameter process SHOULD use the same port number to send all
messages requesting entity (subject) will
be allowed access to aid in identifying which process sent a given message.
More than one resource (object).

AVP
The Diameter process MAY exist within protocol consists of a single host, so the
sender's port number header followed by one or more
Attribute-Value-Pair (AVP). The AVP includes a header and is needed used
to discriminate them.

When no transport connection exists with encapsulation authentication, authorization or accounting
information.

Broker
A broker is a peer, an attempt to
connect SHOULD be periodically attempted. The recommended connection
interval business term commonly used in AAA infrastructures.
A broker is 30 seconds.

2.2 Securing Diameter Messages either a proxy or redirect server, and MAY be operated
by roaming consortiums.

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All

Diameter messages MUST be secured between peers, and both SSL
[28] and IP Security [37] are supported. Network Access Servers
(NASes) and Foreign Agents, commonly referred to as clients, MUST
support IP Security, while servers MUST support both SSL and IP
Security. The communication between Client
A Diameter Client is a client and server MUST use IP
Security, while communication between servers MUST use SSL.

All hosts running device at the Diameter protocol MUST have edge of the necessary
security policies to ensure network that unauthenticated Diameter packets are
not processed.

2.3
performs access control. An example of a Diameter client is a
Network Access Server Discovery

Allowing for dynamic Diameter server discovery will make it possible
for simpler and more robust deployment of AAA services. In order to
promote interoperable implementations of (NAS) or a Foreign Agent (FA).

Diameter server discovery,
the following mechanisms are described. These are based on existing
IETF standards.

There are two cases where Server
A Diameter server discovery may be performed.
The first is when a Diameter client needs to discover a first-hop
Diameter server. The second case device that is when not acting as a NAS or FA.
Servers can be proxy, redirect, or home servers

Downstream Server
Diameter Proxy servers identify a downstream server needs to
discover another as one that is
providing routing services towards the home server - for further handling of a Diameter
operation. In both cases, the following 'search order'
particular message.

Home Domain
A Home Domain is
recommended:

1. The the administrative domain with whom the user
maintains an account relationship.

Home Server
A Diameter implementation consults its list Home Server is one that authenticates and/or authorizes
access for users of static
(manual) configured Diameter a particular realm. The same server locations. These will be
used if they exist and respond.

2. The Diameter implementation uses SLPv2 [28] to discover
Diameter services. The Diameter service template [32] is
included MAY also
act as a proxy or redirect server for other realms, in Appendix A. It which case
it is recommended that SLPv2 security
be deployed (this requires distributing keys to SLPv2 agents.)
This not acting as a Home Server for these realms.

Integrity Check Value (ICV)
An Integrity Check Value is discussed further in Appendix A.

SLPv2 will allow Diameter implementations to discover the
location an unforgeable or secure hash of Diameter servers in the local site, as well as
their characteristics. Diameter servers
message with specific
capabilities (say support for the Accounting extension) can be
requested, and only those will be discovered.

3. The Diameter implementation uses DNS to request the SRV RR [33]
for the '_diameter._sctp' and/or '_diameter._tcp' server in a
particular domain. The Diameter implementation has to know shared secret.

Interim accounting
An interim accounting message provides a snapshot of usage during
a user's session. It is typically implemented in
advance which domain order to look for an Diameter server in. This
could be deduced, provide
for example, from the 'realm' partial accounting of a user's session in the event of a NAI
device reboot or other network problem that

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an Diameter implementation needed to perform an Diameter
operation on.

Diameter allows AAA peers to protect prevents the integrity and privacy reception
of communication as well as to perform end-point
authentication. Still, it a session summary message or session record.

Local Domain
A local domain is prudent the administrative domain providing services to employ DNS Security
a user. An administrative domain MAY act as a precaution when using DNS SRV RRs to look up the location of
a Diameter server. [34, 35, 36]

2.4 Mandatory Accounting Support

All Diameter implementations MUST support the Diameter Accounting
Extension [15]. An implementation that does not support [15] does NOT
comply with the Diameter base protocol.

3.0 Diameter Header

A summary of the Diameter header format is shown below. The fields
are transmitted in network byte order.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|r r r r r r r r r r E I R| Ver | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop-by-Hop Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| End-to-End Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Command-Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVPs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-

Flags
The Message Flags field is thirteen bits. The following bits are
assigned:

r(eserved) MUST be zero - this flag bit is reserved local domain for
future use.
E(xpected Reply) - The message solicits
certain users, while being a response.
I(nterrogation) - home domain for others.

Network Access Identifier
The message is a Query Network Access Identifier, or NAI [3], is used in the Diameter
protocol to extract a Reply.
R(esponse) - user's identity and realm. The message identity is a response
used to another message. identify the user during authentication and/or
authorization, while the realm is used for message routing
purposes.

Proxy Server

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These flags are set depending on

A proxy server �ses the command code used in a
Diameter message. This enables realm portion of the type NAI to route Diameter
messages. Proxy servers are typically used to minimize the number
of message security relationships that are required between Diameter
servers.

Realm
The string in the NAI that immediately follows the '@' character.
NAI realm names are required to be
interpreted, even if unique, and are piggybacked on
the specific command code is not recognized.

Command Type Flags Set
Indication - - -
Request E - -
Answer - - R
Query E I -
Reply - I R

A administration of the DNS namespace. Diameter node MUST NOT set these flags 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 any other combination. order to limit financial risk.

Redirect Server
A Diameter node receiving a message in which these flags redirect server provides realm to address translation,
by returning information necessary for Diameter peers to
communicate directly. Redirect servers are different from proxies
since they do not
set appropriately SHOULD NOT reject the message for this reason,
but MAY log participate in the event for diagnosis.

Version
This Version field MUST be set to 1 to indicate routing of messages between
end Diameter Version
1.

Message Length
The Message Length field is two octets nodes.

Roaming Relationships
Roaming relationships include relationships between companies and indicates
ISPs, relationships among peer ISPs within a roaming association,
and relationships between an ISP and a roaming consortia.
Together, the length set of relationships forming a path between a local
ISP's authentication proxy and the Diameter message including home authentication server is
known as the header fields.

Hop-by-Hop Identifier roaming relationship path.

Session
The Identifier field Diameter protocol is four octets, and aids in matching requests
and replies. The sender MUST ensure that the identifier in a session based. When an authorization
request (*-Request or *-Query) or indication (*-Ind) message is
locally unique (to the sender) at any given time, and MAY attempt
to ensure initially transmitted, it includes a session identifier
that the number is unique across reboots. The sender used for the duration of
a response (*-Answer or *-Response) MUST ensure that the session. The Session-
Identifier field AVP contains the same Identifier value that was found
in the corresponding request. For The identifier is normally a
monotonically increasing number, whose start value was randomly
generated. Diameter servers should consider a message to be unique
by examining the source address, source port, Session-Id and
Identifier field must be globally
unique.

Session record
A session record represents a summary of the message.

End-to-End Identifier
Unlike resource consumption
of a user over the Hop-by-Hop Identifier, entire session. Accounting gateways creating
the End-to-End Identifier is
used session record may do so by servers to detect duplicate messages, and proxies MUST NOT
modify this field. The sender of a request, query, indication,
answer processing interim accounting
events or response message MUST insert a locally unique value in
this field. The combination of accounting events from several devices serving the Session-Id AVP and this field
is used to detect duplicates.

Command-Code same
user.

Upstream Server

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The Command-Code field is four octets, and

Diameter Proxy servers identify an upstream server as one that is used in order to
communicate the command associated with
providing routing services towards the message. Diameter client.

2.0 Protocol Overview

The 32-bit
address space base Diameter protocol 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
Command, the Vendor-ID field MUST be set never used on its own. It is always
extended for a particular application. Four extensions to zero (0).

AVPs
AVPs Diameter
are a method of encapsulating information relevant defined by companion documents: NASREQ [7], Mobile IP [10],
Strong Security [11]. These options are introduced in this document
but specified elsewhere. Additional extensions to Diameter may be
defined in the future (see Section 17.3).

The base Diameter message. See section 4. for more information on AVPs.

3.1 Command Codes

Every 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 message MUST contain peers.

Communication between Diameter peers begins with one peer sending a value
message to another Diameter peer. The set of AVPs included in its header's Command-
Code field, which the
message is used determined by a particular application of or extension to determine
Diameter. We will refer to this as the action Diameter extension. One AVP
that is included to be taken reference a user's session is the Session-Id.

The initial request for authentication and/or authorization of a particular message. user
would include the Session-Id. The following Command Codes are defined Session-Id is then used in all
subsequent messages to identify the Diameter base protocol:

Command-Name Abbrev. Code Reference
--------------------------------------------------------
Device-Reboot-Ind DRI 257 6.1
Device-Status-Ind DSI 282 9.1
Device-Watchdog-Req DWR 280 7.1
Device-Watchdog-Answer DWA 281 7.2
Message-Reject-Ind MRI 259 10.1
Session-Termination-Ind STI 274 11.7.1
Session-Termination- STR 275 11.7.2
Request
Session-Termination- STA 276 11.7.3
Answer

Every Command Code defined MUST include user's session (see section 11.0
for more information). The communicating party may accept the
request, or reject it by returning a corresponding ABNF
specification, which is used response with Result-Code AVP
set to define indicate an error occurred. The specific behavior of the AVPs that MUST, MAY and
diameter server or client receiving a request depends on the Diameter
extension employed.

Session state (associated with a Session-Id) MUST NOT be present. The following format is used freed upon
receipt of the Session-Termination-Request, Session-Termination-
Answer, expiration of authorized service time in the definition:

command-def = command-name "::=" diameter-message

diameter-name = ALPHA *(ALPHA / DIGIT / "-")

command-name = diameter-name
; The command-name has Session-Timeout
AVP, and according to be Command name,
; defined rules established in the base a particular
extension/application of Diameter.

Exchanges of messages are either request/reply oriented, or extended in some
special cases, do not require replies. All such messages that do not
require replies have names ending with '-Ind' (short for Indication).

The Diameter
; specifications. base protocol provides the Authorization-Lifetime AVP,
which MAY be used by extensions to specify the duration of a specific
authorized session.

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diameter-message = header [ *fixed] [ *required] [ *optional] [ *fixed]

header = "<Diameter-Header:" command-id ">"

fixed = [qual] "<" avp-spec ">"

required = [qual] "{" avp-spec "}"

optional = [qual] "[" avp-name "]"
;

2.1 Transport

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 base Diameter protocol is run on port TBD of any qualifiers implies both TCP [27] and
SCTP [26] transport protocols (for interoperability test purposes
port 1812 will be used until April 2001). Diameter clients [9] MUST
support TCP, but are warned that one
; future versions of this
specification may mandate SCTP support. Diameter servers MUST support
both TCP and only one such AVP SCTP.

A Diameter node MAY send packets from any source port, but MUST be present.
;
; NOTE: "[" and "]" have
prepared to receive packets on port TBD. When a different meaning
; than in ABNF (see request is received,
the optional rule, above).
; These braces cannot be used to express an
; optional fixed rules (such as an optional
; ICV at source and destionation ports in the end.) To do this, reply are reversed. Note
that the convention
; is '0*1fixed'.

min = 1*DIGIT
; The minimum number source and destination addresses used in request and replies
MAY any of times a peer's valid IP addresses.

A given Diameter process SHOULD use the element may
; be present.

max = 1*DIGIT
; The maximum same port number of times the element may
; be present.

avp-spec = diameter-name
; The avp-spec has to be an AVP Name, defined
; send all
messages to aid in the base or extended identifying which process sent a given message.
More than one Diameter
; specifications.

avp-name = avp-spec | "AVP"
; The string "AVP" stands for *any* arbitrary
; AVP Name, which does not conflict process MAY exist within a single host, so the
sender's port number is needed to discriminate them.

When no transport connection exists with a peer, an attempt to
connect SHOULD be periodically attempted. The recommended connection
interval is 30 seconds.

2.2 Securing Diameter Messages

All Diameter messages MUST be secured between peers, and both SSL
[38] and IP Security [37] are supported. Network Access Servers
(NASes) and Foreign Agents, commonly referred to as clients, MUST
support IP Security, while servers MUST support both SSL and IP
Security. The communication between a client and server MUST use IP
Security, while communication between servers MUST use SSL.

All hosts running the
; required Diameter protocol MUST have the necessary
security policies to ensure that unauthenticated Diameter packets are
not processed.

2.3 Diameter Extensions

As previously mentioned, the Diameter base protocol does not operate
on its own, but requires appplication-specific extensions, commonly
referred to as Diameter extensions. A Diameter extension is a
specification that defines one or fixed position more Diameter Command-Codes, the
expected AVPs defined in
; an ABNF [31] grammar (see section 3.2), and MAY also
define new AVPs. If the command code definition.

The following is a definition of a fictitious command code:

Example-Command ::= < Diameter-Header: 9999999 >
{ User-Name } Diameter extension has any accounting
requirements, it MUST also specify the AVPs that are to be present in

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* { Origin-FQDN }
* [ AVP ]
0*1< Integrity-Check-Vector >

4.0

the Diameter AVPs Accounting messages (see section 13.3).

Every Diameter AVPs carry specific authentication, accounting and
authorization information, security information as well as
configuration details for Extension specification MUST have an IANA assigned
Extension-Id value (see section 6.1.3). This Extension-Id is
advertised during the request capabilities exchange phase (see section 6.0).
Advertising support of a particular extension implies that the sender
support all of the Command Codes, and reply.

Some the AVPs specified in the
associated ABNF, described in the specification.

An implementation MAY be listed more than once. The effect of such add arbitrary AVPs to any command defined in an AVP is
specific, and is
extension, including vendor-specific AVPs. However, such AVPs MUST
NOT have the M(andatory) bit set. An implementation that adds AVPs
not specified in each case by a command's ABNF, and sets the AVP description.

Each AVP of type OctetString AVP's M(andatory) bit
MUST be padded to align on NOT advertise support of the extension.

An implementation MAY support both a 32 bit
boundary, proprietary version of an
extension by requesting an IANA extension identifier (see section
17.3), while other AVP types align naturally. NULL bytes are added
to supporting the end of original extension. During the AVP Data field till
capabilities exchange, a word boundary is reached. The
length of Diameter node could know whether it should
send the padding is not reflected in prorietary version, or the AVP Length field.

4.1 AVP Header

The fields in standards one, by inspecting the AVP header MUST be sent in network byte order. The
format
extensions advertised by the peer.

2.4 Diameter Server Discovery

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVP Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVP Length | Reserved |P|r|V|r|M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-ID (opt) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ...
+-+-+-+-+-+-+-+-+

AVP Code
The AVP Code identifies the attribute uniquely. The first 256 AVP
numbers are reserved for backward compatibility with RADIUS and following mechanisms are to be interpreted as per NASREQ [7]. AVP numbers 256 and above described. These are used for Diameter, which based on existing
IETF standards.

There are allocated by IANA (see section
15.1).

AVP Length two cases where Diameter server discovery may be performed.
The AVP Length field first is two octets, and indicates the length when a Diameter client needs to discover a first-hop
Diameter server. The second case is when a Diameter server needs to
discover another server - for further handling of
this AVP including the AVP Code, AVP Length, AVP Flags, Reserved, a Diameter
operation. In both cases, the Vendor-ID field (if present) following 'search order' is
recommended:

1. The Diameter implementation consults its list of static
(manual) configured Diameter server locations. These will be
used if they exist and the AVP data. If a message 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.

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received with an invalid attribute length, the message SHOULD be
rejected.

AVP Flags
The AVP Flags field informs

SLPv2 will allow Diameter implementations to discover the
location of Diameter host how each attribute
must be handled. Note that subsequent servers in the local site, as well as
their characteristics. Diameter extensions MAY
define bits to be used within servers with specific
capabilities (say support for the AVP Header, and an unrecognized
bit should Accounting extension) can be considered an error. The 'r' and the reserved bits
are unused
requested, and should only those will be set discovered.

3. The Diameter implementation uses DNS to 0 and ignored on receipt, while request the 'P' bit is defined SRV RR [33]
for the '_diameter._sctp' and/or '_diameter._tcp' server in [11]. a
particular domain. The 'M' Bit, known as the Mandatory bit, indicates whether support
of the AVP is required. If Diameter implementation has to know in
advance which domain to look for an AVP is received by a Home Diameter server or
NAS with the 'M' bit enabled and the receiver does not support
the AVP, the message MUST in. This
could be rejected. If such an AVP is received
by a Proxy or Redirect Server, deduced, for example, from the message MUST be forwarded 'realm' in a NAI that
an Diameter implementation needed to
its logical destination, and MUST NOT be rejected. It is perform an Diameter
operation on.

Diameter allows AAA peers to protect the
responsibility 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 originator location of
a message that is rejected for
this purpose to correct the error. AVPs without Diameter server. [34, 35, 36]

3.0 Diameter Header

A summary of the 'M' bit
enabled are informational only and a receiver that receives a
message with such an AVP that Diameter header format is not supported MAY simply ignore
the AVP. shown below. The 'V' bit, known as the Vendor-Specific bit, indicates whether
the optional Vendor-ID field is present fields
are transmitted in the AVP header. When
set the AVP Code belongs to the specific vendor code address
space.

Unless otherwise noted, network byte order.

Flags
The Message Flags field settings: is thirteen bits. The 'M' bit following bits are
assigned:

r(eserved) MUST be set. The 'V' zero - this flag bit MUST NOT be set.

4.2 Optional Header Elements

The AVP Header contains one optional field. This field is only
present if the respective bit-flag reserved for
future use.

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E(xpected Reply) - The message solicits a response.
I(nterrogation) - The message is enabled.

Vendor-ID a Query or a Reply.
R(esponse) - The Vendor-ID field is present if the 'V' bit message is a response to another message.

These flags MUST be set in the AVP
Flags field. The optional four octet Vendor-ID field contains depending on the
IANA assigned "SMI Network Management Private Enterprise Codes"
[2] value, encoded command code used in network byte order. Any vendor wishing to
implement a
Diameter extension MUST use their own Vendor-ID along
with their privately managed AVP address space, guaranteeing that
they will message. This enables the type of message to be
interpreted, even if the specific command code is not collide with recognized.

Command Type Flags Set
Indication - - -
Request E - -
Answer - - R
Query E I -
Reply - I R

A Diameter node MUST NOT set these flags in any other vendor's extensions, nor with
future IETF extensions.

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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 Diameter node receiving a message in question is which these flags are not vendor specific,
implementations
set appropriately MAY reject the message for this reason, but
SHOULD not use log the zero (0) vendor ID.

4.3 AVP Data Formats event for diagnosis.

Version
This Version field MUST be set to 1 to indicate Diameter Version
1.

Message Length
The Data Message Length field is zero or more two octets and contains information
specific to indicates the Attribute. The format and length of
the Data field is
determined by Diameter message including the AVP Code and AVP Length header fields.

Hop-by-Hop Identifier
The format of the
Data Hop-by-Hop Identifier field MAY be one of the following data types. is four octets, and aids in
matching requests and replies. The interpretation of the values depends on sender MUST ensure that the specification of
Hop-by-Hop identifier in a request (*-Request or *-Query) or
indication (*-Ind) message is locally unique (to the
AVP. For example, an OctetString may be used to transmit human
readable string data sender) at
any given time, and Unsigned32 may be used MAY attempt to transmit a time
value. Conventions for these common interpretations are described
below.

OctetString ensure that the number is
unique across reboots. The data contains arbitrary data sender of variable length. Unless
otherwise noted, a response (*-Answer or *-
Response) MUST ensure that the AVP Length Hop-by-Hop Identifier field MUST be set to at least 9
(13 if
contains the 'V' bit 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.

End-to-End Identifier
Unlike the Hop-by-Hop Identifier, the End-to-End Identifier is enabled). Data
used by servers to transmit (human
readable) character string data uses the UTF-8 [24] character
set detect duplicate messages, and is proxies MUST NOT NULL-terminated.
modify this field. The minimum Length field MUST
be 9, but can be set to any value up to 65527 bytes. AVP Values sender of this type that do not align on a 32-bit boundary MUST have
the necessary padding.

Address
32 bit (IPv4) [17] request, query, indication,
answer or 128 bit (IPv6) [16] address, most
significant octet first. response message MUST insert a locally unique value in
this field. The format combination 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 Session-Id AVP Length and this 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 used to 12 (16 if the 'V' bit is enabled). detect duplicates.

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Unsigned32 values

Command-Code
The Command-Code field is four octets, and is used in order to transmit time data
communicate the command associated with the message. The 32-bit
address space is managed by IANA (see section 17.2).

Vendor-ID
In the event that the Command-Code field contains a vendor
specific command, the four
most significant octets returned from NTP [18], in network byte
order.

Unsigned64
32 bit unsigned value, in network byte order. The AVP Length octet Vendor-ID field contains the IANA
assigned "SMI Network Management Private Enterprise Codes" [2]
value. If the Command-Code field contains an IETF standard
Command, the Vendor-ID field MUST be set to 16 (20 if the 'V' bit is enabled).

Float32
This represents floating point values zero (0).

AVPs
AVPs are a method of single precision as
described by [30]. The 32 bit value is transmitted in network
byte order. The AVP Length field MUST be set encapsulating information relevant 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
Diameter message. See section 4. for more information on AVPs.

3.1 Command Codes

Every Diameter message 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 contain a value is transmitted in network
byte order. The AVP Length field MUST be set its header's Command-
Code field, which is used to 24 (28 if determine the
'V' bit is enabled).

Grouped
The Data field action that is specified as to be taken
for a sequence of AVPs. Each of
these AVPs follows - particular message. The following Command Codes are defined in
the order in Diameter base protocol:

Command-Name Abbrev. Code Reference
--------------------------------------------------------
Accounting-Answer ACA 272 14.2
Accounting-Poll-Ind API 273 14.4
Accounting-Request ACR 271 14.1
Accounting-Status-Ind ASI 279 14.3
Device-Reboot-Ind DRI 257 6.1
Device-Status-Ind DSI 282 9.1
Device-Watchdog-Req DWR 280 7.1
Device-Watchdog-Answer DWA 281 7.2
Message-Reject-Ind MRI 259 10.1
Session-Termination-Ind STI 274 11.8.1
Session-Termination- STR 275 11.8.2
Request
Session-Termination- STA 276 11.8.3
Answer

3.2 Command Code ABNF specification

Every Command Code defined MUST include a corresponding ABNF
specification, which they are specified -
including their headers and padding. The AVP Length field is
set used to 8 (12 if define the 'V' bit AVPs that MUST, MAY and
MUST NOT be present. The following format is enabled) plus used in the total length
of all included AVPs, including their headers.

4.4 Grouped AVP Values

The Diameter protocol allows AVP values of type 'Grouped.' This
implies that the Data field is actually a well defined sequence of
AVPs. It is possible to include an AVP with a Grouped type within a
Grouped type, that is, to nest them. AVPs within an AVP of type
Grouped have the same padding requirements as non-Grouped AVPs, as
defined in section 4.0.

Grouped type AVP specifications include an ABNF grammar [31]
specifying the required sequence of AVPs. Grouped AVP values MUST be
in the specified sequence and MUST NOT include other AVP values
besides those specified by the Grouped AVP grammar. definition:

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4.4.1 Example AVP with a Grouped Data type

The Example AVP (AVP Code 999999) is of type Grouped and is used to
clarify how Grouped AVP values work. The Grouped Data field has the
following ABNF grammar:

example-avp-val

command-def = Origin-FQDN Host-IP-Address
Origin-FQDN command-name "::=" diameter-message

diameter-name = ; See Section 5.1
Host-IP-Address ALPHA *(ALPHA / DIGIT / "-")

command-name = diameter-name
; See Section 6.1.4

An Example AVP with The command-name has to be Command name,
; defined in the Grouped Data Origin-FQDN = "example.com",
Host-IP-Address base or extended Diameter
; specifications.

diameter-message = "10.10.10.10" would be encoded as follows:

0 1 2 3 4 5 6 7
+-------+-------+-------+-------+-------+-------+-------+-------+
0 | Example AVP Header (AVP Code header [ *fixed] [ *required] [ *optional] [ *fixed]

header = 999999), Length "<Diameter-Header:" command-id ">"

fixed = 40 |
+-------+-------+-------+-------+-------+-------+-------+-------+
8 | Origin-FQDN AVP Header (AVP Code [qual] "<" avp-spec ">"

required = 265), Length [qual] "{" avp-spec "}"

optional = 19 |
+-------+-------+-------+-------+-------+-------+-------+-------+
16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' |
+-------+-------+-------+-------+-------+-------+-------+-------+
24 | 'c' | 'o' | 'm' |Padding| Host-IP-Addr [qual] "[" avp-name "]"
; The avp-name in the 'optional' rule cannot
; evaluate to any AVP Header |
+-------+-------+-------+-------+-------+-------+-------+-------+
32 | (AVP Code Name which is included
; in a fixed or required rule.

qual = 257), Length [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 = 12 | 0x0a | 0x0a | 0x0a | 0x0a |
+-------+-------+-------+-------+-------+-------+-------+-------+

4.5 Diameter Base Protocol AVPs 1*DIGIT
; The following table describes minimum number of times the Diameter AVPs 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
protocol, their AVP Code values, types, possible flag values and
whether the AVP MAY be encrypted.

+---------------------+
| AVP Flag rules or extended Diameter
; specifications.

avp-name = avp-spec |
|----+-----+----+-----|----+ "AVP"

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; The string "AVP" stands for *any* arbitrary
; AVP Section | | |SHLD| MUST|MAY |
Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr|
-----------------------------------------|----+-----+----+-----|----|
Authentication- 285 13.1.1.1 Unsigned32 | | | | | N |
Transform-Id | | | | | |
Authorization- 291 11.3 Unsigned32 | | | | | N |
Lifetime | | | | | |
Destination-FQDN 293 5.3 OctetString| | | | | Y |
Digest 287 13.1.1.2 OctetString| | | | | N |
DSI-Event 297 9.1.1 Unsigned32 | M | | | | N |
-----------------------------------------|----+-----+----+-----|----|

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+---------------------+
| AVP Flag rules |
|----+-----+----+-----|----+ Name, which does not conflict with the
; required or fixed position AVPs defined in
; the command code definition.

The following is a definition of a fictitious command code:

Example-Command ::= < Diameter-Header: 9999999 >
{ User-Name }
* { Origin-FQDN }
* [ AVP Section | | |SHLD| MUST|MAY |
Attribute Name Code Defined Data Type |MUST| MAY | NOT| NOT|Encr|
-----------------------------------------|----+-----+----+-----|----|
Encrypted-Data 290 13.1.2.3 OctetString| | | | | N |
Encrypted- 260 13.1.2 Grouped | M | | | | N |
Payload | | | | | |
Encryption- 288 13.1.2.1 Unsigned32 | | | | | N |
Transform-Id | | | | | |
Error-Message 281 10.3 OctetString| | | | | N |
Error-Reporting- 294 10.4 OctetString| | | | | Y |
FQDN | | | | | |
Extension-Id 258 6.1.3 Integer32 | M | | | | Y |
Failed-AVP 279 10.1.1 OctetString| | | | | Y |
Failed-Command- 270 10.1.2 Unsigned32 | | | | | ]

3.3 Diameter Command Naming Conventions

The following conventions are required for the naming of Diameter
messages. Diameter commands typically start with an object name, and
end with one of the following verbs:

3.3.1 Request/Answer

Request is used when the command is asking the peer to do something
for it, for example, authorize a user, or terminate a session. The
Answer MUST contain either a positive or negative result code,
telling the requester whether or not the request successfully
occurred. Other information can also be returned in the Answer.

For example, AA-Request asks the peer device to authorize and/or
authenticate a user in order to set up a session. The request may
fail, thus the answer may be positive or negative.

3.3.2 Query/Response

Query is used when the command is asking for information that it
expects the peer to have. An example would be querying for current
configuration information, or querying for information on resources
or sessions in use. The Response usually contains a positive result
code and the information, or a negative result code with the reason
for not completing the query.

For example, Resource-Query requests the peer device to return
specific information about one or more resources. The answer is
returned in a Resource-Response.

3.3.3 Indication

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Indication is used either when the node wishes to inform the peer
that an event occured, or is requesting that a particular function be
performed, but is not expecting a response. The transport level
acknowledgement is used to ensure that the message was reliably
delivered.

4.0 Diameter AVPs

Diameter AVPs carry specific authentication, accounting and
authorization information, security information as well as
configuration details for the request and reply.

Some AVPs MAY be listed more than once. The effect of such an AVP is
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:

AVP Code
The AVP Code identifies the attribute uniquely. The first 256 AVP
numbers are reserved for backward compatibility with RADIUS and
are to be interpreted as per NASREQ [7]. AVP numbers 256 and above
are used for Diameter, which are allocated by IANA (see section
17.1).

AVP Length
The AVP Length field is two octets, and indicates the length of

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this AVP including the AVP Code, AVP Length, AVP Flags, Reserved,
the Vendor-ID field (if present) and the AVP data. If a message is
received with an invalid attribute length, the message SHOULD be
rejected.

AVP Flags
The AVP Flags field informs the Diameter host how each attribute
must be handled. Note that subsequent Diameter extensions MAY
define bits to be used within the AVP Header, and an unrecognized
bit should be considered an error. The 'r' and the reserved bits
are unused and should be set to 0 and ignored on receipt, while
the 'P' bit is defined in [11].

The 'M' Bit, known as the Mandatory bit, indicates whether support
of the AVP is required. If an AVP is received by a Home server or
NAS with the 'M' bit enabled and the receiver does not support
the AVP, the message MUST be rejected. If such an AVP is received
by a Proxy or Redirect Server, the message MUST be forwarded to
its logical destination, and MUST NOT be rejected. It is the
responsibility of the originator of a message that is rejected for
this purpose to correct the error. AVPs without the 'M' bit
enabled are informational only and a receiver that receives a
message with such an AVP that is not supported MAY simply ignore
the AVP.

The 'V' bit, known as the Vendor-Specific bit, indicates whether
the optional Vendor-ID field is present in the AVP header. When
set the AVP Code belongs to the specific vendor code address
space.

Unless otherwise noted, AVPs will have the following default AVP
Flags field settings:
The 'M' bit MUST be set. The 'V' bit MUST NOT be set.

4.2 Optional Header Elements

The AVP Header contains one optional field. This field is only
present if the respective bit-flag is enabled.

Vendor-ID
The Vendor-ID field is present if the 'V' bit is set in the AVP
Flags field. The optional four octet Vendor-ID field contains the
IANA assigned "SMI Network Management Private Enterprise Codes"
[2] value, encoded in network byte order. Any vendor wishing to
implement a Diameter extension MUST use their own Vendor-ID along
with their privately managed AVP address space, guaranteeing that
they will not collide with any other vendor's extensions, nor with

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future IETF extensions.

A vendor ID value of zero (0) corresponds to the IETF adopted AVP
values, as managed by the IANA. Since the absence of the vendor ID
field implies that the AVP in question is not vendor specific,
implementations SHOULD not use the zero (0) vendor ID.

4.3 AVP Data Formats

The Data field is zero or more octets and contains information
specific to the Attribute. The format and length of the Data field is
determined by the AVP Code and AVP Length fields. The format of the
Data field MAY be one of the following data types.

The interpretation of the values depends on the specification of the
AVP. For example, an OctetString may be used to transmit human
readable string data and Unsigned32 may be used to transmit a time
value. Conventions for these common interpretations are described
below.

OctetString
The data contains arbitrary data of variable length. Unless
otherwise noted, the AVP Length field MUST be set to at least 9
(13 if the 'V' bit is enabled). Data used to transmit (human
readable) character string data uses the UTF-8 [24] character
set and is NOT NULL-terminated. The minimum Length field MUST
be 9, but can be set to any value up to 65504 bytes. AVP Values
of this type that do not align on a 32-bit boundary MUST have
the necessary padding.

Address
32 bit (IPv4) [17] or 128 bit (IPv6) [16] address, most
significant octet first. The format of the address (IPv4 or
IPv6) is determined by the length. If the attribute value is an
IPv4 address, the AVP Length field MUST be 12 (16 if 'V' bit is
enabled), otherwise the AVP Length field MUST be set to 24 (28
if the 'V' bit is enabled) for IPv6 addresses.

Integer32
32 bit signed value, in network byte order. The AVP Length
field MUST be set to 12 (16 if the 'V' bit is enabled).

Integer64
64 bit signed value, in network byte order. The AVP Length
field MUST be set to 16 (20 if the 'V' bit is enabled).

Unsigned32

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32 bit unsigned value, in network byte order. The AVP Length
field MUST be set to 12 (16 if the 'V' bit is enabled).
Unsigned32 values used to transmit time data contains the four
most significant octets returned from NTP [18], in network byte
order.

Unsigned64
32 bit unsigned value, in network byte order. The AVP Length
field MUST be set to 16 (20 if the 'V' bit is enabled).

Float32
This represents floating point values of single precision as
described by [30]. The 32 bit value is transmitted in network
byte order. The AVP Length field MUST be set to 12 (16 if the
'V' bit is enabled).

Float64
This represents floating point values of double precision as
described by [30]. The 64 bit value is transmitted in network
byte order. The AVP Length field MUST be set to 16 (20 if the
'V' bit is enabled).

Float128
This represents floating point values of quadruple precision as
described by [30]. The 128 bit value is transmitted in network
byte order. The AVP Length field MUST be set to 24 (28 if the
'V' bit is enabled).

Grouped
The Data field is specified as a sequence of AVPs. Each of
these AVPs follows - in the order in which they are specified -
including their headers and padding. The AVP Length field is
set to 8 (12 if the 'V' bit is enabled) plus the total length
of all included AVPs, including their headers and padding.

4.4 Grouped AVP Values

Grouped type AVP specifications include an ABNF grammar [31]
specifying the required sequence of AVPs. Grouped AVP values MUST be
in the specified sequence and MUST NOT include other AVP values

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besides those specified by the Grouped AVP grammar.

4.4.1 Example AVP with a Grouped Data type

The Example AVP (AVP Code 999999) is of type Grouped and is used to
clarify how Grouped AVP values work. The Grouped Data field has the
following ABNF grammar:

example-avp-val = Origin-FQDN Host-IP-Address
Origin-FQDN = ; See Section 5.1
Host-IP-Address = ; See Section 6.1.4

An Example AVP with the Grouped Data Origin-FQDN = "example.com",
Host-IP-Address = "10.10.10.10" would be encoded as follows:

0 1 2 3 4 5 6 7
+-------+-------+-------+-------+-------+-------+-------+-------+
0 | Example AVP Header (AVP Code = 999999), Length = 40 |
+-------+-------+-------+-------+-------+-------+-------+-------+
8 | Origin-FQDN AVP Header (AVP Code = 264), Length = 19 |
+-------+-------+-------+-------+-------+-------+-------+-------+
16 | 'e' | 'x' | 'a' | 'm' | 'p' | 'l' | 'e' | '.' |
+-------+-------+-------+-------+-------+-------+-------+-------+
24 | 'c' | 'o' | 'm' |Padding| Host-IP-Addr AVP Header |
+-------+-------+-------+-------+-------+-------+-------+-------+
32 | (AVP Code = 257), Length = 12 | 0x0a | 0x0a | 0x0a | 0x0a |
+-------+-------+-------+-------+-------+-------+-------+-------+

4.5 Diameter Base Protocol AVPs

The following table describes the Diameter AVPs defined in the base
protocol, their AVP Code values, types, possible flag values and
whether the AVP MAY be encrypted.

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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 15.2 Unsigned32 | M | P | | V | Y |
Interim-Interval | | | | | |
Accounting- 485 15.3 Unsigned32 | M | P | | V | Y |
Record-Number | | | | | |
Accounting- 480 15.1 Unsigned32 | M | P | | V | Y |
Record-Type | | | | | |
Accounting- 44 15.5 OctetString| M | P | | V | Y |
Session-Id | | | | | |
Accounting-State 486 15.4 Unsigned32 | M | P | | V | Y |
Authorization- 291 11.3 Unsigned32 | | | | | N |
Lifetime | | | | | |
Destination-FQDN 293 5.3 OctetString| | | | | Y |
Destination- 283 12.4.7 OctetString| M | | | V | N |
Realm | | | | | |
DSI-Event 297 9.1.1 Unsigned32 | M | | | | N |
Error-Message 281 10.3 OctetString| | | | | N |
Error-Reporting- 294 10.4 OctetString| | | | | Y |
FQDN | | | | | |
Extension-Id 258 6.1.3 Integer32 | M | | | | Y |
Failed-AVP 279 10.1.1 OctetString| | | | | Y |
Failed-Command- 270 10.1.2 Unsigned32 | | | | | Y |
Code | | | | | |
Failed-Vendor-Id 262 10.1.3 Unsigned32 | | | | | Y |
Firmware- 267 6.1.2 Unsigned32 | | | | V,M | Y |
Revision | | | | | |
Host-IP-Address 257 6.1.4 Address | M | | | V | N |
Max-Wait-Time 295 11.6 Unsigned32 | M | | | V | N |
Origin-FQDN 264 5.1 OctetString| M | | | V | N |
Origin-Realm 296 5.2 OctetString| M | | | V | N |
Original- 261 11.7 OctetString| M | | | V | N |
Session-Id | | | | | |
Product-Name 269 6.1.6 OctetString| | | | | N |
Proxy-Address 280 12.4.5 Address | M | | | V | N |
Proxy-Info 284 12.4.6 OctetString| M | | | V | N |
Proxy-State 33 12.4.4 Grouped | M | | | V | N |
Redirect-Host 292 12.3.1 Grouped | | | | | Y |
Redirect-Host- 278 12.3.2 Address | | | | | Y |
Address | | | | | |
Redirect-Host- 277 12.3.3 Unsigned32 | | | | | Y |
Port | | | | | |
Result-Code 268 10.2 Unsigned32 | M | | | | N |
-----------------------------------------|----+-----+----+-----|----|

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5.0 Message Forwarding

All Diameter messages MUST include the Origin-FQDN and Origin-Realm
AVPs. These AVPs are used to identify the source of the message.
When responding to a request or query message, the Origin-FQDN and
Origin-Realm AVPs are replaced with the local node's information.

When a Diameter entity receives a Diameter message of type Request,
Query or Indication that includes a Destination-FQDN AVP, and the
host specified in the AVP can be contacted directly, the message MUST
be forwarded to the host in question.

The Destination-FQDN AVP is used when the destination of the message
is fixed, such as:

- Authentication requests that span multiple round trips
- A Diameter message that uses a security mechanism that makes use
of a pre-established session key shared between the source and
the final destination of the message.
- Server initiated messages that MUST be received by a specific
Diameter client (e.g. NAS), such as the Session-Termination-Ind
message, which is used to request that a particular user's
session be terminated.

Proxies receiving messages that contain the Destination-FQDN AVP MUST
verify whether they are able to forward Diameter messages to the host
specified in the AVP, and if so, MUST forward the message to the host
in question. Otherwise, the message routing procedures described in
section 12.0 MUST be followed.

This section defines the Diameter AVPs that MUST be added in all
messages originated by a Diameter node (including nodes creating

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Response and Answer messages).

5.1 Origin-FQDN AVP

The Origin-FQDN AVP (AVP Code | | | | | |
Firmware 267 6.1.2 Unsigned32 | | | | V,M | Y |
-Revision | | | | | |
Host-IP-Address 257 6.1.4 Address | M | | | V | N | 264) is of type OctetString, encoded in
the UTF-8 [24] format. This AVP identifies the endpoint which
originated the Diameter message, i.e. the NAS, home server, or
broker. Proxy servers do not modify this AVP. All Diameter messages
MUST include the Origin-FQDN AVP, which contains the host name of the
originator of the Diameter message and MUST follow the Fully
Qualified Domain Name naming conventions.

Note that the Origin-FQDN 264 5.1 OctetString| M | | | V | N |
Integrity-Check 259 13.1.1 Grouped | M | | | | N |
-Value | | | | | |
Key-Id 286 13.4 Unsigned32 | | | | | N |
Max-Wait-Time 295 11.6 Unsigned32 | M | | | V | N |
Nonce 261 13.2 OctetString| | | | | N |
Origin-Realm 296 AVP may resolve to more than one address as
the Diameter peer may support more than one address.

5.2 OctetString| M | | | V | N |
Plaintext-Data- 289 13.1.2.2 Unsigned32 | | | | | N |
Length | | | | | |
Proxy-Address 280 12.4.5 Address | M | | | V | N |
Proxy-Info 284 12.4.6 OctetString| M | | | V | N |
Proxy-State 33 12.4.4 Grouped | M | | | V | N |
Redirect-Host 292 12.3.1 Grouped | | | | | Y |
Redirect-Host- 278 12.3.2 Address | | | | | Y |
Address | | | | | |
Redirect-Host- 277 12.3.3 Unsigned32 | | | | | Y |
Port | | | | | |
Result-Code 268 10.2 Origin-Realm AVP

The Origin-Realm AVP (AVP Code 296) is of type OctetString, encoded
in the UTF-8 [24] format. This AVP contains the Realm of the
originator of any Diameter message.

5.3 Destination-FQDN AVP

The Destination-FQDN AVP (AVP Code 293) is of type OctetString,
encoded in the UTF-8 [24] format, and contains the Fully Qualified
Domain Name (FQDN) of the intended recipient of the message. This AVP
MUST be present in all unsolicited server initiated messages. The
value of the Destination-FQDN AVP is set to the value of the Origin-
FQDN AVP found in a message from the intended target host.

6.0 Capabilities Exchange

When two Diameter peers establish a transport connection, they MUST
send the Device-Reboot-Ind message. This message has two purposes.
First it allows a peer's identity to be discovered, and allows for
capabilities exchange, such as the supported protocol version number,
and the locally supported extensions.

The receiver uses the extensions advertised in order to determine
whether it SHOULD send certain application-specific Diameter
commands. A Diameter node MUST retain the supported extensions in
order to ensure that unrecognized commands and/or AVPs are not sent
to a peer.

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The Device-Reboot-Ind message MUST NOT be proxied, or redirected.

Since the DRI cannot be proxied, it is still possible that a upstream
proxy receives a message for which it has no available peers to
handle the extension that corresponds to the Command-Code. In such
instances, the Device-Status-Ind message is used (see Section 9.1) to
inform the downstream to take action.

With the exception of the Device-Reboot-Ind message, a message of
type Request, Query or Indication that includes the Extension-Id AVP,
or a message with an extension-specific command code, MAY only be
forwarded to a host that has explicitely advertised support for the
extension (or has advertised the Wildcard Extension).

6.1 Device-Reboot-Ind (DRI) Command

The Device-Reboot-Ind (DRI), indicated by the Command-Code set to
257, is sent to inform a peer that a reboot has, or will, occur.

When Diameter is run over SCTP [26], which allows for connections to
span multiple interfaces, hence multiple IP addresses, the Device-
Reboot-Ind message MUST contain one Host-IP-Address AVP for each
potential IP address that MAY be locally used when transmitting
Diameter messages.

If a Diameter node receives a DRI message that results in an error, a
Message-Reject-Ind message MUST be returned.

Message Format

<Device-Reboot-Ind> ::= < Diameter Header: 257 >
{ Origin-FQDN }
{ Origin-Realm }
1* { Host-IP-Address }
{ Vendor-Id }
{ Product-Name }
* { Supported-Vendor-Id }
* { Extension-Id }
[ Firmware-Revision ]
* [ AVP ]

6.1.1 Vendor-Id AVP

The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 | M | | | | N |
Route-Record 282 12.4.3 OctetString| M | | | V | N |
Destination- 283 12.4.7 OctetString| M | | | V | N |
Realm | | | | | |
Session-Id 263 11.2 OctetString| M | | | | Y |
Session-Timeout 27 11.4 and contains
the IANA "SMI Network Management Private Enterprise Codes" [2] value
assigned to the vendor of the Diameter device.

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In combination with the Supported-Vendor-Id AVP (section 6.1.5), this
MAY be used in order to know which vendor specific attributes may be
sent to the peer. It is also envisioned that the combination of the
Vendor-Id, Product-Name (section 6.1.6) and the Firmware-Revision
(section 6.1.2) AVPs MAY provide very useful debugging information.

A Vendor-Id value of zero in the DRI is reserved and indicates that
the Diameter peer is in the experimental or concept stage and that an
IANA Private Enterprise Number has yet to be obtained by the
implementor.

6.1.2 Firmware-Revision AVP

The Firmware-Revision AVP (AVP Code 267) is of type Unsigned32 | | | | | Y |
Timestamp 262 13.3 and is
used to inform a Diameter peer of the firmware revision of the
issuing device.

For devices that do not have a firmware revision (general purpose
computers running Diameter software modules, for instance), the
revision of the Diameter software module may be reported instead.

6.1.3 Extension-Id AVP

The Extension-Id AVP (AVP Code 258) is of type Unsigned32 | | | | | N |
User-Name and is used
in order to identify a specific Diameter extension. This AVP is used
in the Device-Reboot-Ind message in order to inform the peer what
extensions are locally supported. The Extension-Id MUST also be
present in all messages that are defined in a separate Diameter
specification and have an Extension ID assigned.

Each Diameter extension draft MUST have an IANA assigned extension
Identifier (see section 17.3). The base protocol does not require an
Extension-Id since its support is mandatory.

There MAY be more than one Extension-Id AVP within a Diameter
Device-Reboot-Ind message. The following values are recognized:

NASREQ 1 11.5 OctetString| | | | | Y |
Vendor-Id 266 6.1.1 Unsigned32 | | | | V,M | Y |
-----------------------------------------|----+-----+----+-----|----| [7]
Strong Security 2 [11]
Resource Management 3 [29]
Mobile-IP 4 [10]
Wildcard Extension 0xffffffff

Servers acting as Redirect or Proxy servers (see Section 12.0) MAY
wish to either advertise all supported extensions, or the wildcard
extension. The receiver of a wildcard extension MUST assume that the

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5.0 Message Forwarding

All Diameter messages MUST include the Origin-FQDN and Origin-Realm
AVPs. These AVPs

sender supports all extensions.

Proxy servers are used to identify the source of the message.
When responding to responsible for finding a request or query message, the Origin-FQDN and
Origin-Realm AVPs are replaced with downstream server that
supports the local node's information.

When a Diameter entity receives a Diameter message extension of type Request,
Query or Indication that includes a Destination-FQDN AVP, and the
host specified in the AVP particular message. If none can be contacted directly, the found,
a DSI message MUST
be forwarded to is returned with the host in question. DSI-Event AVP set to
DIAMETER_UNABLE_TO_DELIVER.

6.1.4 Host-IP-Address AVP

The Destination-FQDN Host-IP-Address AVP (AVP Code 257) is used when the destination of the message
is fixed, such as:

- Authentication requests that span multiple round trips
- A Diameter message that uses a security mechanism that makes use of a pre-established session key shared between the source type Address and
the final destination of the message.
- Server initiated messages that MUST be received by a specific
Diameter client (e.g. NAS), such as the Session-Termination-Ind
message, which is used
to request that inform a particular user's
session be terminated.

Proxies receiving messages that contain Diameter peer of the Destination-FQDN AVP MUST
verify whether they are able to forward sender's IP address. All source
addresses that a Diameter messages node expects to use with SCTP [26] MUST be
advertised in the host
specified Device-Reboot-Ind message by including a Host-IP-
Address AVP for each address. This AVP MUST ONLY be used in the AVP,
Device-Reboot-Ind message.

6.1.5 Supported-Vendor-Id AVP

The Supported-Vendor-Id AVP (AVP Code 265) is of type Unsigned32 and if so, MUST forward
contains the message IANA "SMI Network Management Private Enterprise Codes"
[2] value assigned to a vendor other than the host device vendor. This is
used in question. Otherwise, the Device-Reboot-Ind message routing procedures described in
section 12.0 MUST be followed.

This section defines order to inform the Diameter AVPs peer
that MUST be added in all
messages originated by the sender supports a Diameter node (including nodes creating
Response and Answer messages).

5.1 Origin-FQDN subset of the vendor-specific commands
and/or attributes defined by the vendor identified in this AVP.

6.1.6 Product-Name AVP

The Origin-FQDN Product-Name AVP (AVP Code 264) 269) is of type OctetString, encoded
in the UTF-8 [24] format. This AVP identifies the endpoint which
originated the Diameter message, i.e. the NAS, home server, or
broker. Proxy servers do not modify this AVP. All Diameter messages
MUST include the Origin-FQDN AVP, which [25] format, and contains the host vendor assigned name of for
the
originator product. The Product-Name AVP SHOULD remain constant across
firmware revisions for the same product.

7.0 Transport Failure Detection

Given the nature of the Diameter message and MUST follow the NAI [8] naming
conventions.

Note protocol, it is recommended that
transport failures be detected as soon as possible. Detecting such
failures will minimize the Origin-FQDN AVP may resolve occurrence of messages sent to more than one address as unavailable
servers, resulting in unnecessary delays, and will provide better
failover performance.

In order to pro-actively detect such failures, the Diameter protocol
defines the Device-Watchdog-Request message, which is sent to an
inactive peer. A peer is considered inactive if no messages were sent
or received from the Diameter peer may support more than one address. within the current watchdog interval period

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5.2 Origin-Realm AVP

The Origin-Realm AVP (AVP Code 296) is of type OctetString, encoded
in the UTF-8 [24] format. This AVP contains the Realm of the
originator of any Diameter message.

5.3 Destination-FQDN AVP

The Destination-FQDN AVP (AVP Code 293) is of type OctetString,
encoded in the UTF-8 [24] format,

(see Section 19.0), and contains the Fully Qualified
Domain Name (FQDN) of the intended recipient of the message. This AVP
MUST be present in all unsolicited server initiated messages. The
value of no request or query messages are pending with
the Destination-FQDN AVP is set peer.

For implementations that have access to the Retransmission Time-Out
(RTO) value of the Origin-
FQDN AVP found in a message from the intended target host.

6.0 Capabilities Exchange

When two Diameter peers establish a underlying transport connection, they MUST
send the Device-Reboot-Ind message. This message has two purposes.
First it allows a peer's identity to DWR SHOULD be discovered, and allows for
capabilities exchange, such as
sent once per RTO of that connection, plus the supported protocol version number,
and watchdog interval
period, with a jiterring of +/- 50%.

If the locally supported extensions.

The receiver uses DWR is unanswered, the extensions advertised in order to determine
whether it SHOULD send certain application-specific Diameter
commands. A Diameter node MUST retain time until the supported extensions in
order to ensure that unrecognized commands and/or AVPs are not next DWR is sent
to a peer.

The Device-Reboot-Ind message MUST NOT be proxied, or redirected.

Since
recalculated after exponentially backing off the DRI cannot be proxied, it is still possible that a upstream
proxy receives a message for which it has no available peers to
handle RTO portion. When
the extension that corresponds to value of the Command-Code. In such
instances, DWR's current watchdog interval period reaches the Device-Status-Ind message
maximum watchdog interval (Secton 19.0), backoff is used (see Section 9.1) not continued,
and the peer is marked as failed. DWR messages continue to
inform be sent
(jittered) at the downstream final interval for detection for failover. The
current watchdog interval is returned to take action.

With its starting point when a
DWA is received or the exception of peer resumes activity.

Implementations that do not have access to the Device-Reboot-Ind message, RTO SHOULD perform an
Round Trip Time (RTT) measurement for a given peer when a Device-
Watchdog-Answer message is received for a non-backed off DWR. The
fixed RTO base should be replaced by RTT-Multiplier (Section 19.0)
times the measured RTT.

An example of
type Request, Query or Indication that includes the Extension-Id AVP
MAY only backoff sequence, excluding jitter, would be:
30+RTO , 30+2*RTO , 30+4*RTO , 30+8*RTO, 60, 60, 60

Note that exponential backoff MUST be forwarded performed before the maximum is
reached.

7.1 Device-Watchdog-Request

The Device-Watchdog-Request (DWR), indicated by the Command-Code set
to 280, is sent to a host that has explicitely advertised
support for the extension (or peer when no traffic has advertised the Wildcard Extension).

6.1 Device-Reboot-Ind (DRI) Command 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 >
{ Origin-FQDN }
{ Origin-Realm }

7.2 Device-Watchdog-Answer

The Device-Reboot-Ind (DRI), Device-Watchdog-Answer (DWA), indicated by the Command-Code set
to 281, is sent as a response to the Device-Watchdog-Request message.

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257, is sent to inform a peer that a reboot has, or will, occur.

When Diameter is run over SCTP [26], which allows for connections to
span multiple interfaces, hence multiple IP addresses,

A receiver of the Device-
Reboot-Ind message MUST contain one Host-IP-Address AVP for each
potential IP address that MAY be locally used when transmitting
Diameter messages.

If a Diameter node receives a DRI message that results DWA SHOULD perform RTT calculation in an error, a
Message-Reject-Ind message MUST be returned. the event
that the transport RTO information is not available.

Message Format

<Device-Reboot-Ind>

<Device-Watchdog-Answer> ::= < Diameter Header: 257 281 >
{ Origin-FQDN }
{ Origin-Realm }
1* { Host-IP-Address Result-Code }
{ Vendor-Id Origin-FQDN }
*
{ Extension-Id Origin-Realm }
[ Firmware-Revision ]
* [ AVP ]
0*1< Integrity-Check-Value >

6.1.1 Vendor-Id AVP

The Vendor-Id AVP (AVP Code 266) is of type Unsigned32 and contains
the IANA assigned "SMI Network Management Private Enterprise Codes"
[2] value of the Diameter device.

This MAY be used in order to know which vendor specific attributes
may be sent to

7.3 Failover/Failback Procedures

In the peer. It is also envisioned event that the combination
of the Vendor-Name and the Firmware-Revision (section 6.1.2) AVPs MAY
provide very useful debugging information.

6.1.2 Firmware-Revision AVP

The Firmware-Revision AVP (AVP Code 267) a transport failure is of type Unsigned32 detected with a peer, it is
necessary for all pending request, query and indication messages to
be forwarded to an alternate server, if possible. This is
used commonly
referred to inform a Diameter peer of the firmware revision of the
issuing device.

For devices that do not have as failover.

In order for a firmware revision (general purpose
computers running Diameter software modules, node to perform failover procedures, it is
necessary for instance), the
revision of the Diameter software module may be reported instead.

6.1.3 Extension-Id AVP

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The Extension-Id AVP (AVP Code 258) is of type Unsigned32 and is used
in order node to identify maintain a specific Diameter extension. This AVP pending message queue for a
given peer. When a response is used
in received, the Device-Reboot-Ind message in order to inform is removed from
the peer what
extensions are locally supported. queue. The Extension-Id MUST also be
present in all messages that are defined in a separate Diameter
specification and have an Extension ID assigned.

Each Diameter extension draft MUST have an IANA assigned extension Hop-by-Hop Identifier (see section 15.3). The base protocol does not require an
Extension-Id since its support is mandatory.

There field MAY be more than one Extension-Id AVP within a Diameter
Device-Reboot-Ind message. The following values are recognized:

NASREQ 1 [7]
Strong Security 2 [11]
Resource Management 3 [29]
Mobile-IP 4 [10]
Accounting 5 [15]
Wildcard Extension 0xffffffff

Servers acting as Redirect or Proxy servers (see Section 12.0) MAY
wish used to either advertise all supported extensions, or match the wildcard
extension. The receiver of a wildcard extension MUST assume that
corresponding response with the
sender supports queued request.

When a transport failure is detected, all extensions.

Proxy servers messages in the queue are responsible for finding
sent to an alternate server, if possible. An example of a downstream case where
it is not possible for forward the message to an alternate server that
supports is
when the extension of a particular message. If none can be found,
a DSI message has a fixed destination, and the unavailable peer is returned
the message's final destination (see Destination-FQDN AVP). Such an
error requires that the server return an DSI with the DSI-Event AVP
set to DIAMETER_UNABLE_TO_DELIVER.

6.1.4 Host-IP-Address AVP

The Host-IP-Address AVP (AVP Code 257) is of type Address and

It is used important to inform note that multiple identical request or responses
MAY be received as a Diameter peer result of the sender's IP address. All source
addresses that a Diameter node expects to use with SCTP [26] MUST be
advertised failover. The End-to-End Identifier
field in the Device-Reboot-Ind message by including a Host-IP-
Address AVP for each address. This AVP Diameter header MUST ONLY be used to identify duplicate
messages.

As described in section 2.1, a connection request should be
periodically attempted with the
Device-Reboot-Ind message.

7.0 Transport Failure Detection

Given the nature of failed peer in order to re-establish
the Diameter protocol, it is recommended that transport failures connection. Once a connection has been successfully
established, messages can once again be detected as soon as possible. Detecting such
failures will minimize forwarded to the occurrence of messages sent peer. This
is commonly referred to unavailable
servers, resulting in unnecessary delays, and will provide better 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

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failover performance.

In order to pro-actively detect such failures, the Diameter protocol
defines the Device-Watchdog-Request message, which is sent to an
inactive peer. A peer is considered inactive if no messages were sent
or received from the peer within the current watchdog interval period
(see Section 17.0), and no request or query messages are pending

state machine described below when communicating with
the each peer.

For implementations that have access to the Retransmission Time-Out
(RTO) value of the underlying
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, a DWR SHOULD connection between any two peers
over which Diameter messages may be
sent once per RTO of that connection, plus the watchdog interval
period, with a jiterring of +/- 50%.

If the DWR is unanswered, the time until the next DWR passed. This state machine is sent MUST be
recalculated after exponentially backing off the RTO portion. When
the value of
intended to handle both the DWR's current watchdog interval period reaches simple case, in which one peer initiates
a connection to the
maximum watchdog interval (Secton 17.0), backoff is not continued, other, and the complex case, in which each peer is marked as failed. DWR messages continue
simultaneously initiates a connection to be sent
(jittered) at the final interval for detection for failover. The
current watchdog interval is returned other. In the complex
case, an election occurs to its starting point when a
DWA determine which transport connection will
survive.

I- is received or the peer resumes activity.

Implementations that do not have access used to represent the RTO SHOULD perform an
Round Trip Time (RTT) measurement for a given peer when a Device-
Watchdog-Answer message initiator (connecting) connection, while
the R- is received for a non-backed off DWR. used to represent the responder (listening) connection. The
fixed RTO base should be replaced by RTT-Multiplier (Section 17.0)
times
lack of a prefix indicates that the measured RTT.

An example event or action is the same
regardless of the backoff sequence, excluding jitter, would be:
30+RTO , 30+2*RTO , 30+4*RTO , 30+8*RTO, 60, 60, 60

Note connection on which the event occured.

The stable states that exponential backoff MUST a state machine may be performed before 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 maximum initiator or responder
transport connection is
reached.

7.1 Device-Watchdog-Request used for communication.

A DRI message is always sent on the responder connection immediately
after accepting the connection request. The Device-Watchdog-Request (DWR), indicated non-elected connection
will close down. All subsesquent 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 Command-Code set
to 280, 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 I-Snd-Conn-Ack Wait-R-DRI

Wait-Conn-Ack I-Rcv-Conn-Ack I-Snd-DRI Wait-I-DRI
I-Rcv-Conn-Nack Cleanup Closed
R-Rcv-Conn-Req R-Snd-Conn-Ack Wait-Conn-Ack/
Wait-R-DRI
Timeout Error Closed

Wait-I-DRI I-Rcv-DRI Process-DRI I-Open
R-Rcv-Conn-Req R-Snd-Conn-Ack Wait-R-DRI/
Elect

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I-Peer-Disc I-Disc Closed
Timeout Error Closed

Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-DRI Wait-R-DRI/
Wait-R-DRI Elect
I-Rcv-Conn-Nack Cleanup Wait-R-DRI
R-Rcv-DRI Process-DRI Wait-Conn-Ack/
Elect
Timeout Error Closed

Wait-R-DRI/ R-Rcv-DRI Process-DRI, Wait-Returns
Elect Elect
I-Peer-Disc I-Disc Wait-R-DRI
Timeout Error Closed

Wait-Conn-Ack/ I-Rcv-Conn-Ack I-Snd-DRI,Elect Wait-Returns
Elect I-Rcv-Conn-Nack R-Snd-DRI R-Open
R-Peer-Disc R-Disc Wait-Conn-Ack-2
Timeout Error Closed

Wait-Returns Win-Election I-Disc,R-Snd-DRI R-Open
I-Peer-Disc I-Disc,R-Snd-DRI R-Open
I-Rcv-DRI R-Disc I-Open
R-Peer-Disc R-Disc Wait-I-DRI-2
Timeout Error Closed

Wait-Conn-Ack-2 I-Rcv-Conn-Ack I-Snd-DRI Wait-I-DRI-2
I-Rcv-Conn-Nack Cleanup Closed
R-Rcv-Conn-Req R-Snd-Conn-Nack Wait-Conn-Ack-2
Timeout Error Closed

Wait-I-DRI-2 I-Rcv-DRI Process-DRI I-Open
I-Peer-Disc I-Disc Closed
R-Rcv-Conn-Req R-Snd-Conn-Nack Wait-I-DRI-2
Timeout Error Closed

Wait-R-DRI R-Rcv-DRI R-Snd-DRI R-Open
Timeout Error Closed

R-Open Send-Message R-Snd-Non-DRI R-Open
R-Rcv-Non-DRI Process R-Open
R-WatchDog-Timer R-Snd-DWR R-Open
R-Rcv-DWA Process-DWA R-Open
Stop R-Snd-Disc Closed
R-Peer-Disc R-Disc Closed
R-Rcv-DRI Error Closed

I-Open Send-Message I-Snd-Non-DRI R-Open

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I-Rcv-Non-DRI Process I-Open
R-WatchDog-Timer R-Snd-DWR R-Open
R-Rcv-DWA Process-DWA R-Open
Stop I-Disc Closed
I-Peer-Disc I-Disc Closed
I-Rcv-DRI Error Closed
R-Rcv-Conn-Req R-Snd-Conn-Nack I-Open

8.1 States

Following is sent to a more detailed description of each automaton state.

Closed A peer when no traffic has been exchanged between
two peers as defined is initially in Section 7.0, the closed state, and no requests are pending
transport connection exists with the peer.

Message Format

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<Device-Watchdog-Request> ::= < Diameter Header: 280 >
{ Origin-FQDN }
{ Origin-Realm }
0*1< Integrity-Check-Value >

7.2 Device-Watchdog-Answer

Wait-Conn-Ack A transport connection has been initiated with the
peer, and an acknowledgement is pending.

Wait-I-DRI The Device-Watchdog-Answer (DWA), indicated by local Diameter node is waiting for the Command-Code set peer to 281, is sent as
issue a response to the Device-Watchdog-Request message. DRI.

Wait-Conn-Ack/Wait-R-DRI
A receiver of the DWA SHOULD perform RTT calculation in the event
that the transport RTO information is not available.

Message Format

<Device-Watchdog-Answer> ::= < Diameter Header: 281 >
{ Result-Code }
{ Origin-FQDN }
{ Origin-Realm }
0*1< Integrity-Check-Value >

7.3 Failover/Failback Procedures

In connection indication from the event that peer was
received, while a transport failure is detected connection has already
been locally initiated.

Wait-R-DRI/Elect
Two transport connections have been established
with a the peer, it and a DRI is
necessary for all pending request, query and indication messages on the
responder connection.

Wait-Conn-Ack/Elect
A transport connection exists on the responder
connection, while an acknowlegement has yet to be forwarded
received on the initiator connection.

Wait-Returns Multiple transport connections caused an election
to occur.

Wait-Conn-Ack-2
While an alternate server, if possible. This is commonly
referred acknowledgement to as failover.

In order for a Diameter node to perform failover procedures, it is
necessary for locally initiated
transport connection hasn't been received, an
election has failed and the node to maintain a pending message queue for a
given peer. When initiator connection
will be used between the peers.

Wait-I-DRI-2 Following an election, the initiator connection
won, and a response is received, DRI has yet to be received by the message is removed peer.

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Wait-R-DRI A transport connection indication has been received
from the queue. peer, and a DRI has yet to be received by
the peer.

R-Open The Hop-by-Hop Identifier field MAY responder connection will be used to match
communicate with the
corresponding response peer.

I-Open The initiator connection will be used to
communicate with the queued response.

When a transport failure is detected, all messages peer.

8.2 Events

Transitions and actions in the queue automaton are
sent to an alternate server, if possible. An example 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 a case where
it is not two possible
connections.

Start The Diameter application has signalled that a
connection should be initiated with the peer.

Rcv-Conn-Req A transport connection indication from the peer has
been received.

Rcv-Conn-Ack A positive acknowlegement 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 forward some event.

Rcv-DRI A DRI 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 an alternate server be sent.

Rcv-Non-DRI A Non-DRI message was received.

WatchDog-Timer The Watchdog timer expired, indicating that a DWR
message is
when to be sent to the peer.

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Rcv-DWA A DWA message was received.

Stop The Diameter application has signalled that a fixed destination, and the unavailable peer is
connection should be terminated (e.g., on system
shutdown).

8.3 Actions

Actions in the message's final destination (see Destination-FQDN AVP). Such an
error requires that automaton are caused by events and typically indicate
the server return transmission of packets and/or an DSI with the DSI-Event AVP
set action to DIAMETER_UNABLE_TO_DELIVER.

As described in be taken on the
connection. In this section 2.1, a connection request should we will ignore the -I and -R prefix,
since the actual action would be
periodically attempted identical, but would occur on one of
two possible connections.

Snd-Conn-Req A transport connection is initiated with the failed peer peer.

Snd-Conn-Ack an acknowledgement is sent in order response to re-establish a connect
request, confirming that the transport connection. Once a layer
connection has been successfully
established, messages can once again be forwarded to the peer. This is commonly referred open.

Snd-Conn-Nack A negative acknowledgement is sent in response to as failback.

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8.0 Peer State Machine

This section contains a finite state machine,
connect request, indicating that MUST be observed
by all Diameter implementations. Each Diameter node MUST follow the
state machine described below when communicating with each peer.

State Event Action New State
----- ----- ------ ---------
Initial Local request was
refused.

Snd-DRI A DRI message is sent to establish SCTP/TCP Idle
communication with a Diameter Connect
peer with which there the peer.

Cleanup If necessary, the connection is no
existing shutdown, and any
local resources are freed.

Error The transport level layer connection established.

Initial Receive transport level Send is disconnected,
either politely or abortively, in response to an
error condition. Local resources are freed.

Process-DRI A received DRI Wait-DRI is processed.

Disc The transport layer connection request from a
Diameter peer.

Idle Connection Established Send DRI Wait-DRI

Idle Receive DRI Send DRI + Open
Reset Watchdog
Timer

Wait-DRI Receive DRI Reset Watchdog Open
Timer

Open Receive other messages Process Open
Message +
Reset Watchdog
Timer

Open Idle link, is disconnected, and no pending Send DWR Open
requests

Open Receive
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 Send DWA Open

Open Receive DWA Calculate RTT Open

Open Receive DRI Cleanup Closed

Open Transport level failure Cleanup Closed

Closed Diameter Entity shutdown or Close Initial
close connection with peer connection message is sent.

Process-DWA The Initial and Idle states MAY be merged if the local SCTP
implementation DWA message is able to implement the piggyback of data during the serviced.

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Process A non-DRI Diameter message is serviced.

8.4 The Election Process

The election is performed on the responder. The responder compares
the Origin-FQDN received in the DRI sent by its peer with its own
Origin-FQDN (which it may or may not have actually sent). The
transport layer connection phase.

When with the Cleanup action higher value of Origin-FQDN is invoked,
the failover procedures 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
executed (see Section 7.3 for more information). assumed to have
value 0x80, but dimpled octets are ignored.

9.0 Per-Hop Error Signaling

There are many instances where error conditions occur on a Diameter
node, that needs to be signalled to the downstream server, and not
necessarily to the Diameter client. Examples of such error conditions
are invalid time synchronization, inability to forward a message to a particular domain, etc. In
these cases, returning the error back to the Diameter client will
only cause delay, and perhaps confusion in roaming networks.

Therefore, when such errors occur, it is necessary for the error to
be handled by the downstream next hop, and some local action be taken
to rectify the problem, such as forwarding to a different next hop.

Request +--------+ Link Broken
+-------------------------->|Diameter|----///----+
| +---------------------| | v
+-----+---+ | DSI | Server | +--------+
|Diameter |<-+ (Unable to Forward) +--------+ |Diameter|
|Client or| | |
| Server |--+ +--------+ | Server |
+---------+ | Request |Diameter| +--------+
+-------------------->| | ^
| Server |-----------+
+--------+
Figure 1 - Example of Per-Hop Error Condition

9.1 Device-Status-Ind

The Device-Status-Ind (DSI), indicated by the Command-Code set to
282, is sent to inform a peer that an event has occurred.

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When a Diameter node issues a DSI message downstream, the target peer
MUST attempt to rectify the problem, or issue a similar message
downstream. The Device-Status-Ind message MUST NOT be proxied, but
MAY be forwarded, as long as the Origin-FQDN AVP is and Origin-Realm AVPs
are replaced to include the local node's identity.

The Device-Status-Ind message MUST contain the same Hop-by-Hop
Identifier value in the header as the message which motivated sending
the DSI. If the Session-Id AVP was present in the original message,
the same AVP MUST be present in the DSI.

Message Format

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<Device-Status-Ind> ::= < Diameter Header: 282 >
{ Origin-FQDN }
{ Origin-Realm }
[ DSI-Event ]
* [ AVP ]
0*1< Integrity-Check-Value >

9.1.1 DSI-Event AVP

The Result-Code DSI-Event AVP (AVP Code 297) is of type Unsigned32 and indicates
that an event occurred which requires attention from a Diameter peer.
The DSI-Event contains an IANA-managed 32-bit address space
representing events (see section 15.9). 17.7). Diameter provides four
different classes of event notification, all identified by the
thousands digit:
- 1xxx (Informational Events)
- 3xxx (Redirect Notification)
- 4xxx (Transient Failure Events)
- 5xxx (Permanent Failure Events)

A non-recognize class (one whose first digit is not defined in this
section) MUST be handled as a permanent failure.

9.1.1.1 Informational Events

Events that fall within the Informational category are used to inform
a peer that a request cannot be immediately satisfied, and a further
response will be issued in the near future.

DIAMETER_STILL_WORKING 1001
A request's Max-Wait-Time has expired, and the request is still
being serviced. This event MAY be sent prior to the Max-Wait-
Time expiration, to inform the peer that the request is not

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expected to be serviced in the alloted time, but the request is
not being abandoned. It is important to note that receiving
this event will result in another Diameter message being
received with the same Hop-by-Hop and End-to-End identifiers.

9.1.1.2 Redirect Event

Errors that fall within the Redirect Notification category are used
to inform a peer that the request cannot be satisfied locally and
should instead be forwarded to another server.

DIAMETER_REDIRECT_INDICATION 3001
A proxy or redirect server has determined that the request
could not be satisfied locally and the initiator of the request

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should direct the request directly to the server, whose contact
information has been added to the response.

9.1.1.3 Transient Failure Events

Errors that fall within the transient failures category are used to
inform a peer that the request could not be satisfied at the time it
was received, but MAY be able to satisfy the request is the error is
corrected.

DIAMETER_TIME_INVALID 4001
The originator of the Device-Status-Ind message detected a time
synchronization error, and a able to satisfy the request for time synchronization if the error is being requested.
corrected.

DIAMETER_UNSUPPORTED_TRANSFORM 4002 4001
A message was received that included an Integrity-Check-Value
or CMS-Data AVP [11] that
made use of an unsupported transform.

DIAMETER_INVALID_ICV 4003
The Request did not contain a valid Integrity-Check-Value AVP.

9.1.1.4 Permanent Failure Events

Errors that fall within the permanent failures category are used to
inform the peer that the request failed, and cannot be satified by
the originator of the Device-Status-Ind. The receiver of a DSI
message with the DSI-Event set to a value that falls within this
event class SHOULD forward the message to an alternate peer, if one
is available.

DIAMETER_INVALID_RECORD_ROUTE 5001
The last Record-Route Route-Record AVP in the message is not set to the
identity of the sender of the message. See Section 12.0 for
more information.

DIAMETER_COMMAND_UNSUPPORTED 5002
The Request contained a Command-Code that the receiver did not
recognize or support. The Device-Status-Ind message MUST also

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contain an Failed-Command-Code AVP containing the unrecognized
Command-Code.

DIAMETER_UNABLE_TO_DELIVER 5003
The request could not be delivered to a host that handles the
realm, and extension, requested at this time.

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DIAMETER_REALM_NOT_SERVED 5004
The originator of the DSI message could not deliver the message
since the realm requested is unknown.

DIAMETER_ERROR_TOO_BUSY 5005
When returned, a Diameter node SHOULD attempt to sent the
message to an alternate peer.

DIAMETER_CANNOT_PROCESS_IN_TIME 5006
The time limit in a request's Max-Wait-Time AVP has expired,
and no response is available. This value MAY also be used to
inform a peer that the request is not expected to be processed
within the Max-Wait-Time value.

10.0 End-to-End Error Signaling

There are five six different types of error conditions that can occur
within Diameter.

The first occurs when a Diameter message is poorly formatted, and
unrecognizable, indicated in the figure below as "Bad Message". This
error condition applies if a received message is less than the length
of the Diameter header. Messages that generate such an error are
ignored.

A second case occurs when a Command-Code field is set to an
unsupported value, which is shown as "Unknown Command" in the figure.
Such errors generate a Device-Status-Ind message, and require per-hop
behavior.

A third case occurs when an AVP is received, marked as Mandatory ('M'
bit is set), and is unknown by the receiver. This error condition is
labelled as "Unknown AVP" in the figure below, and causes a Message-
Reject-Ind message to be sent.

The fourth case occurs when a message is received that contains an
AVP with either an unknown or illegal value. This is labelled as "Bad
AVP Value", and requires that a Message-Reject-Ind message be sent.

The last two cases require that a Message-Reject-Ind message be

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generated to ensure that such errors are identified in both request
and response messages.

The last error condition occurs when an extension specific error is
identified in a request or response message. In a message of type
request or query, the natural corresponding answer or response
message MUST be used. However, if an error occurs while processing an

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indication, answer or response message, a Message-Reject-Ind is used
to inform the peer that an error occurred while processing the
message.

Error Type Ignore Send Send Send
Message MRI DSI Response
Bad Message X
Unknown Command X
Unknown AVP X
Bad AVP Value X
Request,Query Error X
Answer,Response,Ind Error X

"Ignore Message" indicates that the message is simply dropped. "Send
MRI" means that a Message-Reject-Ind message is sent to report the
error condition, while "Send DSI" requires that a Device-Status-Ind
message is sent (see Section 9.1). "Send Response" means that the
response message for a request or query message is returned.

10.1 Message-Reject-Ind (MRI) Command

The Message-Reject-Ind (MRI), indicated by the Command-Code set to
259, provides a generic means of completing transactions by
indicating errors in the messages that initiated them. The Message-
Reject-Ind command is sent in response:

1. An error is found in a message of type Ind, Answer and Response
2. A Unknown AVP, marked as Mandatory, is received
3. An AVP was received with an unknown, or illegal, value.

The Message-Reject-Ind message MUST contain the same Hop-by-Hop
Identifier value in the header as the message that caused the error
condition. If the Session-Id AVP was present in the original message,
the same AVP MUST be present in the MRI.

Message Format

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<Message-Reject-Ind message> ::= < Diameter Header: 259 >
[ Session-Id ]
{ Result-Code }
{ Origin-FQDN }
{ Origin-Realm }
{ Error-Reporting-FQDN }
[ Failed-Command-Code ]
[ Failed-AVP ]
* [ AVP ]
* [ Proxy-State ]
* [ Route-Record ]
* [ Destination-Realm ]
0*1< Integrity-Check-Value >

where the Result-Code AVP indicate the nature of the error causing
rejection, and the Failed-AVP AVP provides some minimal debugging
data by indicating a specific AVP type which caused the problem.
See the description of the Result-Code AVP for indication of when
the Failed-AVP AVP MUST be present in the message. See [25] for
more information.

10.1.1 Failed-AVP AVP

The Failed-AVP AVP (AVP Code 279) is of type OctetString 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.

A Diameter message MAY contain one or more Failed-AVP AVPs, each
containing a complete AVP that could not be processed successfully.
The possible reasons for this AVP are the presence of an improperly
constructed AVP, an unsupported or unrecognized AVP, an invalid AVP
value; or
value, the omission of a required AVP. AVP, the presence of an explicitly
excluded AVP (see table 14.0), or the presence of two or more
occurances of an AVP which table 14.0 restricts to 0, 1, or 0-1
occurances.

10.1.2 Failed-Command-Code AVP

The Failed-Command-Code AVP (AVP Code 270) is of type Unsigned32 and
contains the offending Command-Code that resulted in sending the
Message-Reject-Ind message.

10.1.3 Failed-Vendor-Id AVP

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The Failed-Command-Code-Vendor-Id AVP (AVP Code 262) is of type
Unsigned32 and MUST be present if a vendor-specific Command-Code or
AVP caused the error.

10.2 Result-Code AVP

The Result-Code AVP (AVP Code 268) is of type Unsigned32 and
indicates whether a particular request was completed successfully or

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whether an error occurred. All Diameter messages of type *-Response
or *-Answer MUST include one Result-Code AVP, while messages of type
-Ind MAY include the Result-Code AVP. A non-successful Result-Code
AVP (one containing a non 2001 value) MUST include the Error-
Reporting-FQDN AVP.

The Result-Code data field contains an IANA-managed 32-bit address
space representing errors (see section 15.4). 17.4). Diameter provides four
different classes of errors, all identified by the thousands digit:
- 1xxx (Informational)
- 2xxx (Success)
- 4xxx (Transient Failures)
- 5xxx (Permanent Failure)

A non-recognize class (one whose first digit is not defined in this
section) MUST be handled as a permanent failure.

10.2.1 Informational

Errors that fall within the Informational category are used to inform
a requester that the request cannot be immediately satisfied and a
further response will be issued in the near future. There are
currently no errors that fall within this class.

10.2.2 Success

Errors that fall within the Success category are used to inform a
peer that a request has been successfully completed.

DIAMETER_SUCCESS 2001
The Request was successfully completed.

10.2.4 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

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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_NO_END_2_END_SECURITY 4002
A proxy has detected that end-to-end security has been applied

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to portions of the Diameter message, and the proxy does not
allow this security mode since it needs to alter the message by
applying some local policies.
DIAMETER_OUT_OF_SPACE 4003
A Diameter node received the accounting request but was unable
to commit it to stable storage due to a temporary lack of
space.

10.2.5 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.

DIAMETER_UNKNOWN_SESSION_ID 5003
The request or response contained an unknown Session-Id.

DIAMETER_AUTHORIZATION_REJECTED 5004
A request was received for which the user could not be
authorized. This error could occur if the service requested is
not permitted to the user.

DIAMETER_INVALID_AVP_VALUE 5005
The request contained an AVP with an invalid value in its data
portion. A Diameter message indicating this error MUST include
the offending AVPs within a Failed-AVP AVP.

DIAMETER_MISSING_AVP 5006

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The request did not contain an AVP that is required by the
Command Code definition. If this value is sent in the Result-
Code AVP, a Failed-AVP AVP SHOULD be included in the message.
The data portion of the Failed-AVP MUST only contain the AVP
Code of the missing AVP.

DIAMETER_INVALID_CMS_DATA 5007
The Request did not contain a valid CMS-Data [11] AVP.

DIAMETER_LOOP_DETECTED 5008
A Proxy or Redirect server detected a loop while trying to get
the message to the Home Diameter server. Further attempts
should not be attempted until the loop has been fixed.

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DIAMETER_AUTHORIZATION_FAILED 5009
A request was received for which the user could not be
authorized at this time. This error could occur when the user
has already expended allowed resources, or is only permitted to
access services within a time period.

DIAMETER_CONTRADICTING_AVPS 5010
The Home Diameter server has detected AVPs in the request that
contradicted each other, and is not willing to provide service
to is not willing to provide service
to the user. One or more Failed-AVP AVPs MUST be present,
containing the AVPs that contradicted each other.

DIAMETER_AVP_NOT_ALLOWED 5011
A message was received with an AVP that MUST NOT be present.
The Failed-AVP AVP MUST be included and contain the user. One or AVP Code of
the offending AVP.

DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5012
A message was received that included an AVP that appeared more
often than permitted in the message definition. The Failed-AVP AVPs
AVP MUST be present,
containing included and contain the AVPs that contradicted each other. AVP Code of the offending
AVP.

10.3 Error-Message AVP

The Error-Message AVP (AVP Code 281) is of type OctetString. It is a
human readable UTF-8 character encoded string. It MAY accompany a
Result-Code AVP as a human readable error message. The Error-Message
AVP is not intended to be useful in real-time, and SHOULD NOT be
expected to be parsed by network entities.

10.4 Error-Reporting-FQDN AVP

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The Error-Reporting-FQDN AVP (AVP Code 294) is of type OctetString,
encoded in the UTF-8 [24] format. This AVP contains the Network
Access Identifier of the Diameter host that set the Result-Code AVP
to a value other than 2001 (Success). This AVP is intended to be used
for troubleshooting purposes, and MUST be set when the Result-Code
AVP indicates a failure.

11.0 "User" Sessions

When a user requests access to the network, a Diameter client issues
an authentication and authorization request to its local server. The
request contains a Session-Id AVP, which is used in subsequent
messages (e.g. subsequent authorization, accounting, etc) relating to
the user's session. The Session-Id AVP is a means for the client and
servers to correlate a Diameter message with a user session.

When a Diameter server authorizes a user to use network resources, it
SHOULD add the Authorization-Lifetime AVP to the response. The
Authorization-Lifetime AVP defines the maximum amount of time a user
MAY make use of the resources before another authorization request is
to be transmitted to the server. If the server does not receive
another authorization request before the timeout occurs, it SHOULD
release any state information related to the user's session. Note

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that the Authorization-Lifetime AVP implies how long the Diameter
server is willing to pay for the services rendered, therefore a
Diameter client SHOULD NOT expect payment for services rendered past
the session expiration time.

The base protocol does not include any authorization request
messages, since these are largely application-specific and are
defined in a Diameter protocol extension document. However, the base
protocol does define a set of messages that are used to terminate
user sessions. These are used to allow servers that maintain state
information to free resources.

11.1 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. The term Service-Specific below refers to a message
defined in a Diameter extension (e.g. Mobile IP, NASREQ).

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State Event Action New State
----- ----- ------ ---------
-------------------------------------------------------------
Idle Client or Device Requests send serv. Pending
access specific
auth req

Idle Service-Specific authorization send serv. Open
request received, and specific
successfully processed response

Pending Successful Service-Specific Grant Open
Authorization response Access
received

Open Authorization-Lifetime expires send serv. Open
specific
auth req

Open Successful Service-Specific Extend Open
Authorization response Access
received

Open Failed Service-Specific Discon. Closed
Authorization response user/device
received.

Open Session-Timeout Expires on send STR Discon
NAS

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Access Device

Open STI Received send STR Discon

Open Session-Timeout Expires on send STI Discon
home AAA server

Discon STI Received ignore Discon

Discon STR Received Discon. Send STA Closed
user/device

Discon STA Received Discon. Closed
user/device

Closed Transition to state Cleanup

When the Cleanup action is invoked, the Diameter node MAY attempt to
release all resources for the particular session. Any event not
listed above MUST be considered as an error condition, and a
response, if applicable, MUST be returned to the originator of the
message.

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11.2 Session-Id AVP

The Session-Id AVP (AVP Code 263) is of type OctetString and is used
to identify a specific session (see section 11.0). The Session-Id
data uses the UTF-8 [24] character set. All messages pertaining to a
specific session MUST include only one Session-Id AVP and the same
value MUST be used throughout the life of a session. When present,
the Session-Id SHOULD appear immediately following the Diameter
Header (see section 3.0).

For messages that do not pertain to a specific session, multiple
Session-Id AVPs MAY be present as long as they are encapsulated
within an AVP of type Grouped.

The Session-Id MUST be globally unique at any given time since it is
used by the server to identify the session (or flow). The format of
the session identifier SHOULD be as follows:

<Sender's Origin-FQDN><sender's port number> <monotonically
increasing 32 bit value><optional value>

The monotonically increasing 32 bit value SHOULD NOT start at zero
upon reboot, but rather start at a random value. This will minimize
the possibility of overlapping Session-Ids after a reboot.
Alternatively, an implementation MAY keep track of the increasing
value in non-volatile memory. The optional value is implementation

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specific but may include a modem's device Id, a layer 2 address,
timestamp, etc.

The session Id is created by the Diameter device initiating the
session, which in most cases is done by the client. Note that a
Session-Id MAY be used by more than one extension (e.g.
authentication for a specific service and accounting, both of which
have separate extensions).

11.3 Authorization-Lifetime AVP

The Authorization-Lifetime AVP (AVP Code 291) is of type Unsigned32
and contains the maximum number of seconds of service to be provided
to the user before the user is to be re-authenticated and/or re-
authorized. Great care should be taken when the Authorization-
Lifetime value is determined, since a low value could create
significant Diameter traffic, which could congest both the network
and the servers.

This AVP MAY be provided by the client as a hint of the maximum
duration that it is willing to accept. However, the server DOES NOT

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have to observe the hint, and MAY return a value that is smaller than
the hint. A value of zero means that no re-authorization is required.

11.4 Session-Timeout AVP

The Session-Timeout AVP (AVP Code 27) [1] is of type Unsigned32 and
contains the maximum number of seconds of service to be provided to
the user before termination of the session. A value of zero means
that this session has an unlimited number of seconds before
termination.

This AVP MAY be provided by the client as a hint of the maximum
duration that it is willing to accept. However, the server DOES NOT
have to observe the hint, and MAY return a value that is smaller than
the hint.

11.5 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].

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11.6 Max-Wait-Time AVP

The Max-Wait-Time AVP (AVP Code 295) is of type Unsigned32, and
contains the maximum amount of time the downstream server is willing
to wait for a response. A server that determines that it cannot
satisfy a request within the requested time MUST issue a DSI message
with the DSI-Event set to DIAMETER_STILL_WORKING or
DIAMETER_CANNOT_PROCESS_IN_TIME.

11.7 Original-Session-Id AVP

The Original-Session-Id AVP (AVP Code 261) is of type OctetString and
MAY be sent in a message of type Response or Answer if the Home AAA
server already has a session identifier for the user, and wishes to
keep the existing Session-Id. All further messages from the Access
Device for this session MUST use the session identifier in this AVP.
This shouldn't be viewed as a new session, but rather renaming the
old session.

11.8 Session Termination

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The Diameter Base Protocol provides a set of messages that MUST be
used by any peer to explicitly request that a previously
authenticated and/or authorized session be terminated. Since the
Session-Id is typically tied to a particular service (i.e. Mobile IP,
NASREQ, etc), the session termination messages are used to request
that the service tied to the Session Id be terminated.

11.7.1

11.8.1 Session-Termination-Ind

The Session-Termination-Ind (STI), indicated by the Command-Code set
to 274, MAY be sent by any Diameter entity to the access device to
request that a particular session be terminated. This message MAY be
used when a server detects that a session MUST be terminated, which
is typically done as a policy decision (e.g. local resources have
been expended, etc). The Destination-FQDN AVP MUST be present, and
contain the NAI fully qualified domain name of the access device that
initiated the session (see section 11.0).

Upon receipt of the STI message, the access device SHOULD issue a
Session-Terminate-Request message.

Message Format

<Session-Termination-Ind> ::= < Diameter Header: 274 >
< Session-Id >
{ Origin-FQDN }
{ Origin-Realm }
{ User-Name }
{ Destination-Realm }
{ Destination-FQDN }
* [ AVP ]
* [ Proxy-State ]
0*1< Integrity-Check-Value >

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11.7.2

11.8.2 Session-Termination-Request

The Session-Termination-Request (STR), indicated by the Command-Code
set to 275, is sent by the access device to inform the Diameter
Server that an authenticated and/or authorized session is being
terminated.

Message Format

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<Session-Termination-Request> ::= < Diameter Header: 275 >
< Session-Id >
{ Origin-FQDN }
{ Origin-Realm }
{ User-Name }
{ Destination-Realm }
{ Destination-FQDN }
* [ AVP ]
* [ Proxy-State ]
* [ Route-Record ]
0*1< Integrity-Check-Value >

11.7.3

11.8.3 Session-Termination-Answer

The Session-Termination-Answer (STA), indicated by the Command-Code
set to 276, is sent by the Diameter Server to acknowledge that the
session has been terminated. The Result-Code AVP MUST be present, and
MAY contain an indication that an error occurred while servicing the
STR.

Upon sending or receipt of the STA, the Diameter Server MUST release
all resources for the session indicated by the Session-Id AVP. Any
intermediate server in the Proxy-Chain MAY also release any
resources, if necessary.

Message Format

<Session-Termination-Answer> ::= < Diameter Header: 276 >
< Session-Id >
{ Result-Code }
{ Origin-FQDN }
{ Origin-Realm }
{ Destination-FQDN }
{ User-Name }
{ Destination-Realm }
* [ AVP ]
* [ Proxy-State ]
* [ Route-Record ]
0*1< Integrity-Check-Value >

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12.0 Message Routing

This section describes the expected behavior of a Diameter server
acting as a proxy or redirect server.

12.1 Realm-Based Message Routing

Diameter request, query and indication message routing is done

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through the use of the realm portion of the Network Access Identifier
(NAI),
(NAI) or via a realm encoded in an AVP (e.g. Origin-Realm,
Destination-Realm), and an associated realm routing table (see
section 12.1.1).
The

When an NAI has a format is used, the realm portion of user@realm, and the user@realm is used to
perform the realm lookup. Diameter servers have a list of locally
supported realms, and MAY have a list of externally supported realms.
When a request, query or indication message is received that includes
a realm that is not locally supported, the message is proxied to the
Diameter entity configured in the "route" table.

Figure 2 depicts an example where DIA1 receives a request to
authenticate user "joe@abc.com". DIA1 looks up "abc.com" in its local
realm route table and determines that the message must be proxied to
DIA2. DIA2 does the same check, and proxies the message to DIA3. DIA3
checks its realm route table, and determines that the realm is
locally supported, and processes the authentication request, and
returns the response. How the response actually makes it back to the
sender of the original request is described in the next section.

(Origin-FQDN=dia1.mno.net) (Origin-FQDN=dia1.mno.net)
(Origin-Realm=mno.net) (Origin-Realm=mno.net)
(Destination-Realm=abc.com) (Destination-Realm=abc.com)
(Record-Route=dia2.xyz.com)
(Route-Record=dia1.mno.net) (Route-Record=dia1.mno.net)
(Route-Record=dia2.xyz.com)
+------+ ------> +------+ ------> +------+
| | (Request) | | (Request) | |
| DIA1 +-------------------+ DIA2 +-------------------+ DIA3 |
| | | | | |
+------+ <------ +------+ <------ +------+
mno.net (Response) xyz.com (Response) abc.com
(Destination-Realm=mno.net) (Destination-Realm=abc.net)
(Origin-Realm=abc.com) (Origin-Realm=abc.com)
(Destination-FQDN=dia1.mno.net) (Destination-FQDN=dia1.mno.net)
(Record-Route=dia2.xyz.com)
(Route-Record=dia2.xyz.com)
Figure 2: Realm-Based Routing

Note the processing rules contained in this section are intended to
be used as general guidelines to Diameter developers. Certain
implementations MAY use different methods than the ones described
here, and still be in compliance with the protocol specification.

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12.1.1 Realm-Based Routing Table

All Realm-Based routing lookups are performed against what is
commonly known as the Domain Routing Table (see section 17.0). 19.0). A
Domain Routing Table Entry contains the following fields:

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- Domain Name. The Domain Name is analogous to the realm portion
of the NAI. This is the field that is typically used as a
primary key in the routing table lookups. Note that some
implementations perform their lookups based on longest-match-
from-the-right on the realm rather than requiring an exact
match.
- Extension Id. It is possible for a routing entry to have a
different destination based on the extension identifier of the
message. This field is typically used as a secondary key field
in routing table lookups.
- Local Action. The Local Action field is used to identify how a
message should be treated. The following actions are supported:
1. LOCAL - Diameter messages that resolve to a routing entry
with the Local Action set to Local can be satisfied
locally, and do not need to be forwarded to another
server.
2. PROXY - All Diameter messages that fall within this
category MUST be forwarded to a next hop server. The local
server MAY apply its local policies to the message by
including new AVPs to the message prior to forwarding.
See section 12.4 for more information.
3. REDIRECT - Diameter messages that fall within this
category MUST have the identity of the home Diameter
server(s) appended, and returned to the sender of the
message. See section 12.3 for more information.
- Server Identifier - One or more servers the message is to be
forwarded to. When the Local Action is set to PROXY, this field
contains the identities of the server(s) the message must be
forwarded to. When the Local Action field is set to REDIRECT,
this field contains the Home Diameter server(s) for the realm.

It is important to note that Diameter servers MUST support at least
one of the PROXY, REDIRECT, or LOCAL modes of operation. Servers do
not need to support all modes of operation in order to conform with
the protocol specification. Servers MUST NOT reorder AVPs with the
same AVP Code.

When a message is being proxied, the servers in a given domain
routing entry MUST have advertised the Extension Identifier (see
section 6.1.3) for the given message, or have advertised the Wildcard
Extension.

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12.2 Proxy and Redirect Server handling of requests

When a message of type request, query or indication is received by a
proxy or redirect server, and it is determined that the request
cannot be locally handled, the next hop for the request is determined

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in the following order:
1. If the Destination-FQDN AVP is present, and the host specified
in the AVP can be directly contacted, the message is forwarded
to the host (see section 8.1 5.1 for more information), or
2. If the Destination-Realm AVP is present, a routing table lookup
is performed using the domain specific in the AVP.

A message that does not contain any of the above AVPs MUST NOT be
routed. If the message in question cannot be handled locally, a
Message-Reject-Ind is sent with the Result-Code AVP set to an
appropriate error condition.

12.3 Redirect Server

A Redirect Server is one that provides NAI Realm to Diameter Home Server
address resolution. When a message is received by a peer, the
Destination-Realm AVP (or the User-Name AVP if the Destination-Realm
AVP is not present) is extracted from the message, and is used to
perform a lookup in the domain routing table. Implementations MAY
also use the Extension Id Extension-Id as a secondary key in the domain routing
table lookup.

Successful routing table lookups will return one or more home
Diameter servers that could satisfy the message. The home servers are
encoded in one or more Redirect-Host AVPs, and the Command-Code field
is set to Device-Status-Ind.

+------------------+
| Diameter |
| Redirect Server |
+------------------+
^ |
Request | | DSI +
joe@xyz.com | | DSI-Event = Redirect +
| | Redirect-Host AVP(s)
| v
+----------+ Request +----------+
| abc.net |------------->| xyz.net |
| Diameter | | Diameter |
| Server |<-------------| Server |
+----------+ Response +----------+
Figure 3: Diameter Redirect Server

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Lastly, the DSI-Event AVP is added with the Data field of the AVP set
to DIAMETER_REDIRECT_INDICATION, and the message is returned to the
sender of the request. Redirect servers MAY also include the
certificate of the Home server(s). These certificates are

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encapsulated in a CMS-Data AVP [11]. When this occurs, the server
forwarding the request directly to the Home Diameter server SHOULD
include its own certificate in the message.

12.3.1 Redirect-Host AVP

The Redirect-Host AVP (AVP Code 292) is of type Grouped and is found
in Device-Status-Ind messages that include the DSI-Event AVP set to
DIAMETER_REDIRECT_REQUEST. This AVP only needs to be used if the host
the message is to be redirected to is not listening on the standard
Diameter port. Its Data field has the following ABNF grammar:

Redirect-Host = Redirect-Host-Address Redirect-Host-Port
Redirect-Host-Address = ; See Section 12.3.2
Redirect-Host-Port = ; See Section 12.3.3

The Redirect-Host-Address AVP Data field contains the IP Address of
the Diameter host to which the request MUST be redirected. The
Redirect-Host-Port contains the port number to which the request
should be sent. Upon receipt of such a event, and this AVP, the
receiving host SHOULD send the request directly to the host
identified by the Redirect-Host-Address AVP.

+---------------------------------------------------------------+
| AVP Header (AVP Code = 292) |
+---------------------------------------------------------------+
| Redirect-Host-Address AVP |
+---------------------------------------------------------------+
| Redirect-Host-Port AVP |
+---------------------------------------------------------------+

12.3.2 Redirect-Host-Address AVP

The Redirect-Host-Address AVP (AVP Code 278) is of type Address. Its
use is described in Section 12.3.1.

12.3.3 Redirect-Host-Port AVP

The Redirect-Host-Port AVP (AVP Code 277) is of type Unsigned32. Its
use is described in Section 12.3.1.

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12.4 Proxy Server

This section outlines the processing rules for Diameter proxy
servers. A proxy server can either be stateful or stateless. A Proxy

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server MAY act in a stateful manner for some requests, and be
stateless for others. There are two types of states that servers MAY
wish to maintain; transaction and session.

Maintaining transaction state implies that a server keeps a copy of a
request, which is then used when the corresponding response is
received. This could be done to apply local policies to the message,
or simply for auditing purposes. Maintaining session state implies
that a server keeps track of all "active" users. An active user is
one that has been authorized for a particular service, and the server
has not received any indication that the user has relinquished
access.

A stateless proxy is one that does not maintain transaction, nor session state, but
MUST maintain transaction state. It frees Transaction state SHOULD be released
after a request's corresponding response has been forwarded towards
the messages sent once acknowledgements are
received recipient, and has been acknowledged by the transport layer. underlying transport.

A stateful proxy can be viewed as a Diameter Server upon receiving a
request, is one that maintains both transaction and as a Client when forwarding session
state, the message. For all intents
and purposes, stateful servers terminate an upstream "session", latter being done by observing request and
initiates responses.
Session state SHOULD be released once it is informed that a downstream "session" (see Figure 4), and user
and/or device has relinquished access. A stateful server MAY provide
the following features:
- Protocol translation (e.g. RADIUS <-> Diameter)
- Limiting resources authorized to a particular user
- Per user or transaction auditing

+--------+ +-----------------+ +--------+
| Client | --------> | Server | Client | -------> | Server |
+--------+ +-----------------+ +--------+
Figure 4 - Example

Home servers processing requests that include the Route-Record and/or
the Proxy-State AVPs MUST return these AVPs in the same order in the
corresponding response.

12.4.1 Proxying Requests

In addition to the rules defined in section 12.2, the following
procedures MUST be handled by proxy servers handling messages of Stateful Proxy type
request, query or indication.

A stateful proxy that maintains transaction state SHOULD release
transaction information after server MUST check for forwarding loops before proxying a request's corresponding response
message of type Request, Query or Indication. Such as message has
been forwarded towards looped if the recipient, server finds its own address in a Route-Record
AVP.

A Diameter server that proxies a message or type Request, Query or
Indication MUST append a Route-Record AVP, which includes its
identity. Diameter Servers that receive messages MUST validate the
last Route-Record AVP in the message and has been acknowledged by ensure that the host
identified in the AVP is the same as the sender of the message.

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A Proxy Server MAY also include the Proxy-State AVP in a message of
type Request or Query, which is used to encode local state
information. The Proxy-State AVP is guaranteed to be present in the
corresponding response.

The message is then forwarded to the downstream Diameter server, as
identified in the Domain Routing Table.

Proxy Server MUST save the Hop-by-Hop Identifier in request messages,
if the underlying transport.

A stateful proxy that maintains session state SHOULD release value of the
session state once it field is informed that changed, with a user and/or device has
relinquished access.

Home servers processing requests that include the Route-Record and/or locally unique value.
The saved identifier MAY be encoded in the Proxy-State AVPs MUST return these AVPs AVP, and will
be required in the same order in processing of the corresponding response.

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12.4.1

12.4.2 Proxying Requests

In addition to the rules defined in section 12.2, the following
procedures MUST be handled by proxy servers handling messages of type
request, query or indication. Responses

A proxy server MUST check for forwarding loops before proxying a
message only process messges of type Request, Query Response or Indication. Such as Answer
whose last Route-Record AVP matches one of its addresses. Any
responses that do not conform to this rule MUST be dropped. The last
Route-Record AVP MUST be removed from the message has
been looped if before it is
forwarded to the server finds its own address in a next hop, which is identified by the second to last
Route-Record AVP.

If the last Proxy-State AVP in the message is targeted to the local
Diameter server, the AVP MUST be removed.

If a proxy server that proxies receives a message or type Request, Query or
Indication MUST append response with a Route-Record AVP, which includes its
identity. Diameter Servers that receive messages Result-Code AVP
indicating a failure, it MUST NOT modify the contents of the AVP. Any
additional local errors detected SHOULD be logged, but not reflected
in the Result-Code AVP.

Prior to forwarding the response, proxy servers MUST validate restore the
last
original value of the Diameter header's Hop-by-Hop Identifier field.

12.4.3 Route-Record AVP

The Route-Record AVP (AVP Code 282) is of type OctetString, encoded
in the message UTF-8 [24] format, and ensure that contains the host
identified in Fully Qualified Domain
Name of the Proxy appending this AVP is to a Diameter message. The FQDN
added in this AVP MUST be the same as the sender of FQDN sent in the message.

A Proxy Server MAY also include Origin-
FQDN in the Device-Reboot-Ind message.

12.4.4 Proxy-State AVP in a message of
type Request or Query, which is used to encode local state
information.

The Proxy-State AVP (AVP Code = 33) is guaranteed to be present in of type Grouped. The Grouped
Data field has the
corresponding response. following ABNF grammar:

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Proxy-State = Proxy-Address Proxy-Info
Proxy-Address = ; See Section 12.4.5
Proxy-Info = ; See Section 12.4.6

The message is then forwarded to Proxy-Address AVP Data field contains one of the downstream Diameter server, as
identified in IP addresses of
the Domain Routing Table.

Proxy Server MUST save system that created the Hop-by-Hop Identifier AVP. This assists hosts in request messages,
if determining
whether a Proxy-State AVP is intended for the value local host. The Proxy-
Info AVP contains state information, and MUST be treated as opaque
data.

+---------------------------------------------------------------+
| AVP Header (AVP Code = 33) |
+---------------------------------------------------------------+
| Proxy-Address AVP |
+---------------------------------------------------------------+
| Proxy-Info AVP |
+---------------------------------------------------------------+

12.4.5 Proxy-Address AVP

The Proxy-Address AVP (AVP Code = 280) is of type Address. Its use
is described in Section 12.4.4.

12.4.6 Proxy-Info AVP

The Proxy-Info AVP (AVP Code = 284) is of the field type OctetString. Its use
is changed, with a locally unique value. described in Section 12.4.4.

12.4.7 Destination-Realm AVP

The saved identifier MAY be Destination-Realm AVP (AVP Code 283) is of type OctetString,
encoded in the Proxy-State AVP, UTF-8 [24] format, and will contains the realm the message
is to be required routed to. The Destination-Realm AVP MUST NOT be present in
messages of type Answer of Reply. Diameter Clients insert the processing realm
portion of the corresponding response.

12.4.2 Proxying Responses

A proxy server MUST only process messges User-Name AVP. Home servers initiating a message of
type Response Request, Query or Answer
whose last Route-Record AVP matches one Indication use the value of its addresses. Any
responses that do not conform to this rule MUST be dropped. The last
Route-Record the Origin-Realm
AVP MUST be removed from the a previous message before received from the intended target host
(unless it is
forwarded to known a priori). When present, the next hop, which Destination-Realm
AVP is identified used to perform message routing decisions.

12.5 Applying Local Policies

Proxies MAY apply local access policies to Diameter requests, or
responses, by adding, changing or deleting AVPs in the second messages.

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Proxies that apply local policies MUST NOT allow end-to-end security
on any messages that traverse through it, unless security is
terminated locally.

A proxy wishing to modify a Diameter message to enforce some local
policy that detects that end-to-end security has been applied to last
Route-Record AVP.

If the last Proxy-State AVP in the
message is targeted MUST return a response to the originator with the Result-Code
set to DIAMETER_NO_END_2_END_SECURITY. The originator of the request
MAY re-issue the request with no end-to-end security if it falls
within its local
Diameter server, policy.

In the AVP MUST be removed.

If a proxy event that the Home Diameter server receives a response request with
contradictory information (possibly due to some proxy adding a Result-Code AVP
indicating a failure, local
policy), it MUST NOT modify MAY accept the contents of latest AVP, or MAY return the AVP. Any
additional local errors detected SHOULD be logged, but not reflected
in response
with the Result-Code AVP.

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Prior AVP set to DIAMETER_CONTRADICTING_AVPS. However,
a NAS receiving a response that contains contradictory information
SHOULD reject service to forwarding the response, proxy user.

12.6 Hiding Network Topology

Stateful proxies forwarding requests to servers MUST restore the
original value outside of their
administrative domain MAY hide the Diameter header's Hop-by-Hop Identifier field.

12.4.3 Route-Record AVP

The internal network topology. Servers
perform this by removing all Route-Record AVP (AVP Code 282) is of type OctetString, encoded AVPs in the UTF-8 [24] format, message, and contains
maintains the Fully Qualified Domain
Name of Route-Record AVPs to add to the Proxy appending this corresponding response.
Such stateful servers MUST still add their own Route-Record AVP to
the request prior to forwarding.

12.7 Loop Detection

When a Diameter message.

12.4.4 Proxy-State AVP

The Proxy-State AVP (AVP Code = 33) is Proxy or Redirect server receives a message of type Grouped. The Grouped
Data field has
Request, Query or Indication, it MUST examine all Route-Record AVPs
in the following ABNF grammar:

Proxy-State = Proxy-Address Proxy-Info
Proxy-Address = ; See Section 12.4.5
Proxy-Info = ; See Section 12.4.6

The Proxy-Address message to determine whether such an AVP Data field contains one of already exists with
the IP addresses local server's identity. If an AVP with the local host's identity
is found in the request, it is an indication that the message is
being looped through the same set of proxies. When such an event
occurs, the system Diameter server that created detects the AVP. This assists hosts in determining
whether loop returns a Proxy-State AVP is intended for response
with the local host. The Proxy-
Info AVP contains state information, and MUST be treated as opaque
data.

12.4.5 Proxy-Address AVP

The Proxy-Address Result-Code AVP (AVP Code = 280) set to DIAMETER_LOOP_DETECTED.

13.0 Accounting

This accounting protocol is based on an authorization-server directed
model with capabilities for real-time delivery of type Address. Its use
is described accounting
information. Several fault resilience methods [40] have been built in Section 12.4.4.

12.4.6 Proxy-Info AVP

The Proxy-Info AVP (AVP Code = 284) is
to the protocol in order minimize loss of type OctetString. Its use
is described accounting data in Section 12.4.4.

12.4.7 Destination-Realm AVP various
fault situations and under different assumptions about the

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capabilities of the used devices.

13.1 Authorization-Server Directed Model

The authorization-server directed model means that at authorization
time, the device generating the accounting data gets information from
the authorization 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 this extension. Should Batched
Accounting be required in the future, a new Diameter extension will
need to be created, or it could be handled using another protocol.

The Destination-Realm AVP (AVP Code 283) is authorization server (chain) directs the selection of proper
transfer strategy, based on its knowledge of type OctetString,
encoded in the UTF-8 [24] format, user and contains the realm
relationships of roaming partnerships. The server (or proxies in
between) uses the message
is Accounting-Interim-Interval AVP to be routed to. Diameter Clients insert control the realm portion
operation of the
User-Name Diameter peer operating as a client. The
Accounting-Interim-Interval AVP, while home servers insert when present, instructs the value of Diameter
node acting as a client to produce accounting records continuously
even during a session.

13.2 Protocol Messages

A Diameter node that receives a successful authentication and/or
authorization messages from the Origin-
Realm AVP into this AVP. When present, Home AAA Server, MUST collect
accounting information for the Destination-Realm AVP session. The Accounting-Request
message is used to perform message routing decisions.

12.5 Applying Local Policies

Proxies MAY apply local access policies transmit the accounting information to Diameter requests, or
responses, by adding, changing or deleting AVPs in the messages.
Proxies that apply local policies Home
AAA server, which MUST NOT allow end-to-end security
on any messages reply with the Accounting-Answer message to
confirm reception. The Accounting-Answer message includes the
Result-Code AVP, which MAY indicate that traverse through it, unless security is
terminated locally. an error was present in the
accounting message. A proxy wishing rejected Accounting-Request message SHOULD
cause the user's session to modify a be terminated.

Each Diameter Accounting protocol message MAY be compressed using
IPComp [41] in order to enforce some local
policy that detects reduce the used network bandwidth, which MAY
use IKE [15] to negotiate the compression parameters.

13.3 Extension document requirements

Each Service-Specific Diameter extension (e.g. NASREQ, MobileIP),

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MUST define their Service-Specific AVPs that end-to-end security has been applied to MUST be present in the
Accounting-Request message MUST return in a response to the originator with section entitled "Accounting AVPs".
The extension MUST assume that the Result-Code
set AVPs described in this document
will be present in all Accounting messages, so only their respective
service-specific AVPs need to DIAMETER_NO_END_2_END_SECURITY. The originator be defined in this section.

13.4 Fault Resilience

Diameter Base protocol mechanisms are used to overcome small message
loss and network faults of temporary nature.

Diameter peers acting as clients MUST implement the request
MAY re-issue use of failover
to guard against server failures and certain network failures.
Diameter peers acting as servers or related off-line processing
systems MUST detect duplicate accounting records caused by the request with no end-to-end security if it falls
within its local policy.

In
sending of same record to several servers and duplication of messages
in transit. This detection MUST be based on the event that inspection of the Home
Session-Id and Accounting-Record-Number AVP pairs.

Diameter server receives a request with
contradictory information (possibly due to some proxy adding a local
policy), it clients MAY accept have non-volatile memory for the latest AVP, safe storage of
accounting records over reboots or MAY return extended network failures, network
partitions, and server failures. If such memory is available the response
with
client SHOULD store new accounting records there as soon as the Result-Code AVP set to DIAMETER_CONTRADICTING_AVPS. However,
records are created and until a NAS receiving positive acknowledgement of their
reception from the Diameter Server has been received. Upon a response that contains contradictory information
SHOULD reject service to reboot,
the user.

12.6 Hiding Network Topology

Stateful proxies forwarding requests client MUST starting sending the records in the non-volatile
memory to servers outside of their
administrative domain MAY hide the internal network topology. Servers
perform this by removing all Route-Record AVPs accounting server with appropriate modifications in the message,
termination cause, session length, and
maintains other relevant information in
the Route-Record records.

A further extension of this protocol may include AVPs to add to control how
many accounting records may at most be stored in the corresponding response.
Such stateful servers MUST still add their own Route-Record AVP Diameter client
without committing them to the request prior non-volatile memory or transferring
them to forwarding.

12.7 Loop Detection

When a the Diameter Proxy or Redirect server receives a message server.

The client SHOULD NOT remove the accounting data from any of type
Request, Query its
memory areas before the correct Accounting-Answer has been received.
The client MAY remove oldest, undelivered or Indication, yet unacknowledged
accounting data if it MUST examine all Route-Record AVPs
in the message to determine whether runs out of resources such as memory. It is an AVP already exists with
implementation dependent matter for the local server's identity. If an AVP with client to accept new sessions
under this condition.

13.5 Session Records

In all accounting records the local host's identity Session-Id and User-Name AVPs MUST be
present. If strong authentication is found required, as described in the request, it is an indication that the message is [11],

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being looped through

the same set CMS-Data AVP may be used to authenticate the Accounting Data and
Service Specific AVPs. It is not typically necessary, nor
recommended, that the strong authentication cover any additional AVPs
since the Data and Service Specific AVP, and associated CMS-Data, MAY
need to be submitted to a third party.

Different types of proxies. When such an session 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
occurs, are simultaneous, then
the Accounting-Record-Type AVP MUST be present and set to the Diameter server that detects value
EVENT_RECORD.

If the loop returns accounted service is of a response
with measurable length, then the Result-Code AVP set MUST
use the values START_RECORD, STOP_RECORD, and possibly,
INTERIM_RECORD. If the authorization server has directed interim
accounting to DIAMETER_LOOP_DETECTED.

13.0 Diameter Message Security

The Diameter Base protocol MAY be secured in one of three ways. The
first method does not involve any security mechanisms in enabled for the Diameter
protocol, session, but relies on an underlying security mechanism, such as IP
Security. The second method is hop-by-hop security, which SHOULD no interim interval was
specified, two accounting records MUST be
supported by all Diameter implementations. The third method generated for each service
of type session. When the initial Accounting-Request is
optional and requires sent for a Public Key Infrastructure [14], and
given session is
documented in [11].

13.1 Hop-by-Hop Security

Diameter Hop-by-Hop security provides message integrity and per sent, the Accounting-Record-Type AVP
encryption, and requires that MUST be set to
the communicating entities have a pre-
configured shared secret. Hop-by-Hop security value START_RECORD. When the last Accounting-Request is very difficult to
deploy and administer in large scale networks and involves symmetric
trust, unlike security based on sent, the
value MUST be STOP_RECORD.

If a public key infrastructure (PKI).
PKI is used for specified interim interval exists, the Diameter End-to-End security, client MUST
produce additional records between the START_RECORD and STOP_RECORD,
marked INTERIM_RECORD. The production of these records is defined in [11].
Hop-by-Hop security may be desirable in environments where symmetric
cryptography is sufficient directed
both by Accounting-Interim-Interval as well as any re-authentication
or when re-authorization of the session. The Diameter client MUST
overwrite any previous interim accounting records that are locally
stored for delivery, if a PKI new record is not available.

Figure 5 below provides an example of hop-by-hop security in being generated for the same
session. This ensures that only one pending interim record can exist
on a proxy
chain. Assuming NAS for any given session.

14.0 Accounting Command-Codes

This section defines new Command-Code values that MUST be supported
by all Diameter implementations that the packet was received provide Accounting services.

14.1 Accounting-Request (ACR) Command

The Accounting-Request command, indicated by DIA2 from DIA1, and
was the Command-Code field
set to be proxied 271, is sent by a Diameter node, acting as a client, in order
to DIA3, the following steps would be taken:

1. Validating the message's integrity using the shared secret with
DIA1, and removing the authenticated security AVPs.

2. Decrypting any encrypted AVPs using the secret shared with DIA1.

3. Re-encrypting AVPs using the secret shared exchange accounting information with DIA3.

4. Computing the message hash using a peer.

When the secret shared with DIA3,
and adding it Accounting-Request is being submitted to a broker, and
includes the ICV CMS-Data AVP in [11], the Diameter message.

(Shared-Secret-1) (Shared-Secret-2)
+------+ -----> +------+ ------> +------+
| | |1 3| | |
| DIA1 +------------------>+ DIA2 +------------------>+ DIA3 |
| | |2 4| | |
+------+ +------+ +------+
Figure 5: Hop-by-Hop Security in Proxy Environments CMS-Data AVP MUST be signed by

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The above steps that each proxy MUST perform in a proxy chain clearly
describes

both the security issues associated with hop-by-hop security in
a proxy environment. Since local and home Diameter server using the message integrity is re-computed at
each node countersignature
procedures described in the chain, it is not possible to detect if a proxy
modified information [11].

The AVP listed below SHOULD include service specific accounting AVPs,
as described in section 13.3.

Message Format

<Accounting-Request> ::= < Diameter Header: 271 >
< Session-Id >
{ Extension-Id }
{ User-Name }
{ Origin-FQDN }
{ Origin-Realm }
{ Destination-Realm }
{ Accounting-Record-Type }
{ Accounting-Record-Number }
[ Accounting-Interim-Interval ]
{ Accounting-Session-Id }
* [ AVP ]
[ CMS-Data ]
* [ Proxy-State ]
* [ Route-Record ]

14.2 Accounting-Answer (ACA) Command

The Accounting-Answer command, indicated by the message (e.g. session time). Furthermore,
any sensitive information would be known Command-Code field
set to all proxies in 272, is used to acknowledge an Accounting-Request command. The
Accounting-Answer command contains the chain,
since each node must decrypt AVPs. Therefore, Any same Session-Id and MAY
contains the same Accounting Description and Usage AVPs that contain
data that MUST NOT be seen by intermediate Diameter nodes MUST be
protected via were
sent in the mechanism described Accounting-Request command. If the CMS-Data AVP was
present in the strong security
extension [11].

It is highly recommended that Accounting-Request, the size of corresponding ACA message MUST
include the shared secrets used be
sufficiently long (e.g. 128 bits), and that different shared secrets
be used for both authentication and encryption.

13.1.1 Integrity-Check-Value CMS-Data AVP

The Integrity-Check-Value signed by the responder to provide strong
AVP (AVP Code 259) is of type Grouped and
is authentication, which MAY be used for hop-by-hop message authentication and integrity.

The the purposes of
repudiation.

Only the target Diameter header as well Server, known as all AVPs (including padding) up to the
Digest home Diameter Server,
SHOULD respond with the Accounting-Answer command.

The AVP is protected listed below SHOULD include service specific accounting AVPs,
as described in section 13.3.

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Message Format

<Accounting-Answer> ::= < Diameter Header: 272 >
< Session-Id >
{ Extension-Id }
{ User-Name }
{ Result-Code }
{ Origin-FQDN }
{ Origin-Realm }
{ Accounting-Record-Type }
{ Accounting-Record-Number }
{ Accounting-Session-Id }
[ Error-Reporting-FQDN ]
[ Accounting-Interim-Interval ]
* [ AVP ]
[ CMS-Data ]
* [ Proxy-State ]
* [ Route-Record ]

14.3 Accounting-Status-Ind (ASI) Command

The Accounting-Status-Ind command, indicated by the Integrity-Check-Value AVP. Note that
the Message Length Command-Code
field in the Diameter header MUST be set to zero
(0) prior 279, is sent by a Diameter node in order to inform its
peer of whether Accounting messages will be sent in the ICV calculation. The Timestamp AVP provides replay
protection and future. A
Diameter node that is about to be taken out of service SHOULD issue
an Accounting-Status-Ind message, with the Nonce Accounting-State AVP provides randomness. If present, any
AVPs in a message set
to DISABLED. A Diameter node that detected that it is not succeeded by able to issue
Accounting messages MUST issue an Accounting-Status-Ind message, with
the Integrity-Check-Value Accounting-State AVP MUST be ignored.

All set to ENABLED.

Message Format

<Accounting-Status-Ind> ::= < Diameter implementations SHOULD support this AVP.

The Integrity-Check-Value Header: 279 >
{ Extension-Id }
{ Origin-FQDN }
{ Origin-Realm }
{ Destination-Realm }
{ Accounting-State }
* [ AVP (AVP Code = 259) is of type Grouped. ]
* [ Proxy-State ]
* [ Route-Record ]

14.4 Accounting-Poll-Ind (API) Command

The grammar for Accounting-Poll-Ind command, indicated by the grouped Data Command-Code field
set to 273, is defined is:

Integrity-Check-Value = Nonce Time Auth-Trans-Id Key-ID Digest
Nonce = ; Nonce, See Section 13.2
Timestamp = ; Timestamp, See Section 13.3
Auth-Trans-Id = ; Authentication-Transform-Id, /
; See Section 13.1.1.1
Key-ID = ; Key-ID, See Section 13.4
Digest = ; Digest, See Section 13.1.1.2 sent by a Diameter Server in order to force the peer

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+---------------------------------------------------------------+
| AVP Header (AVP Code = 259) |
+---------------------------------------------------------------+
| Nonce AVP |
+---------------------------------------------------------------+
| Timestamp AVP |
+---------------------------------------------------------------+
| Authentication-Transform-Id AVP |
+---------------------------------------------------------------+
| Key-ID AVP |
+---------------------------------------------------------------+
| Digest AVP |
+---------------------------------------------------------------+

13.1.1.1 Authentication-Transform-Id AVP

The Transform-Id AVP (AVP Code = 285) is of type Unsigned32. This
value identifies the transform that was used

to compute the ICV. The
following values are defined in this document:

HMAC-MD5-96[6] 1
The ICV is computed using the HMAC-MD5 algorithm, and the first
12 bytes of the hash output is included in the Digest AVP. All send current accounting data. This data MUST include not yet sent
accounting records from completed sessions, as well as INTERIM_RECORD
records from all ongoing sessions.

Diameter implementations supporting this AVP MUST MAY support this
transform. Using the example code provided in [6], the
following call would be used Accounting-Poll-Ind command.
An implementation still conforms to generate the Digest AVP:

hmac_md5(DiameterMessage, MessageLength, Secret,
Secretlength, Output)

where the DiameterMessage this specification if API is not
supported.

The receiver MUST use the complete message up Accounting-Request command to send the
Digest AVP.

13.1.1.2 Digest AVP
accounting data.

The Digest AVP (AVP Code = 287) is use of type OctetString. This value
contains the output from the hashing algorithm, covering all AVPs Accounting-Poll-Ind is useful in situations where a
Diameter server comes up after an unscheduled downtime, and wishes to
synchronize with the message, including all AVPs in client(s) sooner than at the Integrity-Check-Value AVP up
to, but not including, end of the Digest AVP.

13.1.2 Encrypted-Payload AVP next
INTERIM_RECORD or at the end of a session.

Warning: The Encrypted-Payload AVP (AVP Code 260) is use of type Grouped and the Accounting-Poll-Ind message is
used to encapsulate encrypted AVPs for privacy during transmission.

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Hop-by-Hop confidentiality discouraged in
roaming networks, since it is achieved by encapsulating all AVPs
which are unfeasible for a server to be encrypted into an Encrypted-Payload AVP. This
feature SHOULD be supported by attempt to
poll all of it's roaming partner's Diameter implementations.

The grammar for the grouped Data field is defined is:

Encrypted-Payload = Enc-Trans-Id Key-ID ptextlen data
Enc-Trans-Id = ; Encryption-Transform-Id, /
; See Section 13.1.2.1
Key-ID = ; See Section 13.4
ptextlen = ; Plaintext-Data-Length, See Section 13.1.2.2
data = ; Encrypted-Data, See Section 13.1.2.3

+---------------------------------------------------------------+
| AVP Header (AVP Code = 260) |
+---------------------------------------------------------------+
| Encryption-Transform-Id AVP |
+---------------------------------------------------------------+
| Key-ID AVP |
+---------------------------------------------------------------+
| Plaintext-Data-Length AVP |
+---------------------------------------------------------------+
| Encrypted-Data peers.

Message Format

<Accounting-Poll-Ind> ::= < Diameter Header: 273 >
< Session-Id >
{ Extension-Id }
{ Destination-FQDN }
{ Origin-FQDN }
{ Origin-Realm }
{ Destination-Realm }
{ Accounting-Session-Id }
[ Destination-FQDN ]
* [ AVP |
+---------------------------------------------------------------+

13.1.2.1 Encryption-Transform-Id ]
* [ Proxy-State ]
* [ Route-Record ]

15.0 Accounting AVPs

This section contains AVPs that describe accounting usage information
related to a specific session.

15.1 Accounting-Record-Type AVP

The Encryption-Transform-Id Accounting-Record-Type AVP (AVP Code = 288) 480) is of type
Unsigned32. This AVP identifies the transform that was used to
encrypt the data contained in Unsigned32
and contains the Encrypted-Data AVP. type of accounting record being sent. The following
values are currently defined in this document:

MD5 1
See section 13.1.2.1.1 for more information.

13.1.2.1.1 MD5 Payload Hiding

The plain text (which is a buffer containing one or more AVPs) the Accounting-Record-Type AVP:

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EVENT_RECORD 1
An Accounting Event Record is
first padded used to indicate that a sixteen (16) byte boundary with 0 bytes. Since one-time
event has occurred (meaning that the
encapsulated AVPs have length fields, it start and end of the event
are simultaneous). This record contains all information
relevant to the service, and is possible the only record of the service.

START_RECORD 2
An Accounting Start, Interim, and Stop Records are used to detect their
boundaries, whether or not padding
indicate that a service of a measurable length has been done.

One or more Nonce AVPs MUST precede an Encrypted-Payload AVP. given.
An MD5
hash Accounting Start Record is performed on the:

- last Nonce AVP which precedes used to initiate an accounting
session, and contains accounting information that is relevant
to the Encrypted-Payload AVP

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- initiation of the shared 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 secret

This MD5 hash value or re-authorization occurs. Further, additional
interim record triggers MAY be defined by application-specific
Diameter extensions. The selection of whether to use
INTERIM_RECORD records is then XORed with directed by the first 16 octet segment Accounting-Interim-
Interval AVP.

STOP_RECORD 4
An Accounting Stop Record is sent to terminate an accounting
session and contains cumulative accounting information relevant
to the existing session.

15.2 Accounting-Interim-Interval AVP

The Accounting-Interim-Interval AVP (AVP Code 482) is of type
Unsigned32 and is sent from the Diameter authenticating/authorizing
server to the buffer Diameter client. The client uses information in this
AVP to encrypt. The resulting 16 octet decide how and when to produce accounting records. With
different values in this AVP, service sessions can result is saved as in one,
two, or two+N accounting records, based on the
first 16 octets needs of the encrypted buffer. home-
organization. The result following accounting record production behaviour is also used to
calculate a new value using MD5:

- the shared authentication secret
-
directed by the 16 byte result inclusion of this AVP:

1. The omission of the previous XOR

This value is then XORed Accounting-Interim-Interval AVP or its
inclusion with the next 16 bytes. This is done Value field set to 0 means that EVENT_RECORD,
START_RECORD, and STOP_RECORD are produced, as appropriate for
each 16 bytes successively in
the buffer to encrypt, producing an
equal sized encrypted buffer. service.

2. The receiver inclusion of a Diameter message with an Encrypted-Payload the AVP with Value field set to a non-zero
value means that INTERIM_RECORD records MUST
first check be produced
between the integrity START_RECORD and STOP_RECORD records. The Value

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field of the message, either through the ICV, or
the CMS-Data AVP [11] if it protects the Encrypted-Payload AVP. Then
the Encrypted-Payload this AVP is decrypted, by reversing the above
procedure, which applied to nominal interval between these records
in seconds. The Diameter node that originates the buffer will reproduce accounting
information, known as the plain text
version. The decapsulated AVPs are then used to process client, MUST produce the Diameter
message in first
INTERIM_RECORD record roughly at the normal manner.

13.1.2.2 Plaintext-Data-Length AVP

The Plaintext-Data-Length AVP (AVP Code = 289) is of type Unsigned32,
and contains time when this nominal
interval has elapsed from the length of START_RECORD, the plaintext data. This AVP is necessary
in order to not treat any possible padded data, added next one again
as part of the
encryption transform, as part of interval has elapsed once more, and so on until the plaintext.

13.1.2.3 Encrypted-Data AVP

The Encrypted-Data AVP (AVP Code = 290)
session ends and a STOP_RECORD record is of type OctetString. This
AVP contains produced.

The client MUST ensure that the encrypted AVPs.

13.2 Nonce interim record production times
are randomized so that large accounting message storms are not
created either among records or around a common service start
time.

15.3 Accounting-Record-Number AVP

The Nonce Accounting-Record-Number AVP (AVP Code 261) 485) is of type OctetString Unsigned32
and is present in identifies this record within one session. As Session-Id AVPs are
globally unique, the Integrity-Check-Value AVP combination of Session-Id and Accounting-
Record-Number AVPs is also globally unique, and can be used in
matching accounting records with confirmations. An easy way to ensure randomness within
a message. The content of this AVP MUST be a random
produce unique numbers is to set the value to 0 for records of at least
128 bits.

13.3 Timestamp type
EVENT_RECORD and START_RECORD, and set the value to 1 for the first
INTERIM_RECORD, 2 for the second, and so on until the value for
STOP_RECORD is one more than for the last INTERIM_RECORD.

15.4 Accounting-State AVP

The Timestamp Accounting-State AVP (AVP Code 262) 486) is of type Unsigned32 and is
used to

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add replay protection communicate to the Diameter protocol. The Data field of
this AVP is the most significant four octets returned from an NTP
[18] server that indicates the number of seconds expired since Jan.
1, 1900.

Messages that are older than a configurable maximum age SHOULD be
rejected (see section 17.0) and a response SHOULD peer whether Accounting messages will be returned with
the Result-Code AVP Data field set to DIAMETER_TIMEOUT. Note that the
larger the configurable value, the more susceptible one is to a
replay attack. However, one does have to take into account the
possibility for clock drift, and the latency involved
sent in the
transmission of the message over the network. The timestamp AVP
SHOULD be updated prior to retransmission. future. A Diameter node that receives a message issues an ASI with the Result-Code Accounting-
State AVP set to DIAMETER-TIMEOUT MAY use the time found in the Timestamp AVP
within the reply in order to synchronize its clock with its peer.
When time synchronization DISABLED is done, the sender MUST NOT change informing its
local time, but SHOULD adjust the time delta for all outgoing
messages to the peer, and require peer that its local time be used in
received messages.

Implementations must it will no
longer be prepared to wrap at transmitting Accounting messages until a subsequent ASI
message is sent with the epochal 2038 where
Time Accounting-State AVP set to ENABLED.

The following values are used, and 0,1,... MUST be considered greater than
2^32-1 at that time.

13.4 Key-Id have been defined:
1 ENABLED
2 DISABLED

15.5 Accounting-Session-Id AVP

The Key-Id Accounting-Session-Id AVP (AVP Code = 286) 44) is of type Unsigned32. This value
contains a key identifier, which OctetString,
and SHOULD be encoded in UTF-8 format [13]. The Accounting-Session-Id
is not used to identify by the keying
information 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 generate the Digest AVP or include the Encrypted-Data
AVP.

14.0

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Accounting-Session-Id in Diameter accounting messages.

16.0 AVP Occurrence Table

The following table 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.

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once instance of the AVP.
1 One instance of the AVP MUST be present in the message.
1+ At least one instance of the AVP MUST be present in the
message.

16.1 Base Protocol Command AVP Table

The table in this section is limited to the non-accounting Command
Codes defined in this specification.

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+-------------------------------+
| Command-Code Command-Code |
|---+---+---+---+---+---+---+---+
Attribute Name |DRI|DSI|DWR|DWA|MRI|STI|STR|STA|
------------------------------|---+---+---+---+---+---+---+---|
Authorization-Lifetime |0 |0 |0 |0 |0 |0 |0 |0 |
Destination-FQDN |0 |0 |0 |1 |0+ |1 |0+ |1 |
Destination-Realm |1 |1 |0 |0 |1 |1 |1 |0 |
DSI-Event |0 |1 |0 |0 |0 |0 |0 |0 |
Error-Message |0 |0 |0 |0 |0 |0 |0 |0 |
Error-Reporting-FQDN |0 |0 |0 |0 |1 |0 |0 |0 |
Extension-Id |1+ |0 |0 |0 |0 |0 |0 |0 |
Failed-AVP |0 |0 |0 |0 |0-1|0 |0 |0 |
|---+---+---+---+---+---+---+---+
Attribute Name |DRI|DSI|DWR|DWA|MRI|STI|STR|STA|
------------------------------|---+---+---+---+---+---+---+---|
Authorization-Lifetime
Failed-Command-Code |0 |0 |0 |0 |0-1|0 |0 |0 |
Failed-Vendor-Id |0 |0 |0 |0 |0-1|0 |0 |0 |
Destination-FQDN
Firmware-Revision |0-1|0 |0 |0 |0 |0 |0 |0 |
Host-IP-Address |1+ |0 |0 |0 |0 |0 |0 |0 |
Max-Time-Wait |0 |0 |0 |0 |0 |0 |0 |0 |
Origin-FQDN |1 |1 |1 |1 |1 |1 |0+ |1 |0+ |1 |
Destination-Realm
Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 |
DSI-Event
Original-Session-Id |0 |1 |0 |0 |0 |0 |0 |0 |
Encrypted-Payload |0 |
Product-Name |1 |0 |0 |0 |0 |0 |0 |0 |
Error-Message |0
Proxy-State |0 |0 |0 |0 |0+ |0+ |0+ |0+ |
Redirect-Host |0 |0 |0 |
Error-Reporting-FQDN |0 |0 |0 |0 |1 |0 |
Result-Code |0 |0 |
Extension-Id |1+ |0 |1 |1 |0 |0 |1 |
Route-Record |0 |0 |0 |0 |0+ |0+ |0+ |0+ |
Failed-AVP
Session-Id |0 |0 |0 |0 |0-1|0 |0-1|1 |1 |1 |
Session-Timeout |0 |0 |
Failed-Command-Code |0 |0 |0 |0 |0-1|0 |0 |0 |
Firmware-Revision |0-1|0 |0
Supported-Vendor-Id |0+ |0 |0 |0 |0 |0 |
Host-IP-Address |1+ |0 |0 |
User-Name |0 |0 |0 |0 |0 |1 |1 |1 |
Integrity-Check-Value |0-1|0-1|0-1|0-1|0-1|0-1|0-1|0-1|
Max-Time-Wait |0
Vendor-Id |1 |0 |0 |0 |0 |0 |0 |0 |
------------------------------|---+---+---+---+---+---+---+---|

16.2 Accounting AVP Table

The table in this section is used to represent which AVPs defined in
this document are to be present in the Accounting messages.

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+-----------------------+
| Command-Code |
|-----+-----+-----+-----+
Attribute Name | ACR | ACA | API | ASI |
------------------------------|-----+-----+-----+-----+
Accounting-Interim-Interval | 0-1 | 0-1 | 0 | 0 |
Accounting-Record-Number | 1 | 1 | 0 | 0 |
Accounting-Record-Type | 1 | 1 | 0 | 0 |
Accounting-Session-Id | 1 | 1 | 0 | 1 |
Accounting-State | 0 | 0 | 1 | 0 |
Destination-FQDN | 0+ | 1 | 0+ | 0-1 |
Destination-Realm | 1 | 0 | 1 | 1 |
Error-Reporting-FQDN | 0 | 0+ | 0 | 0 |
Extension-Id | 1 | 1 | 1 | 1 |
Integrity-Check-Value | 0-1 | 0-1 | 0-1 | 0-1 |
Origin-FQDN |1 |1 |1 |1 |1 |1 |1 |1 | 1 | 1 | 1 | 1 |
Origin-Realm |1 |1 |1 |1 |1 |1 |1 |1 | 1 | 1 | 1 | 1 |
Proxy-State |0 |0 |0 |0 |0+ |0+ |0+ |0+ |
Redirect-Host |0 |0 |0 |0 |0 |0 |0 |0 0+ |
Result-Code |0 |0 |0 |1 |1 |0 |0 |1 0+ | 0+ | 0+ |
Route-Record |0 |0 |0 |0 |0+ |0+ |0+ |0+ | 0+ | 0+ | 0+ | 0+ |
Result-Code | 0 | 1 | 0 | 0 |
Session-Id |0 |0 |0 |0 |0-1|1 |1 |1 |
Session-Timeout |0 |0 |0 |0 |0 |0 |0 |0 1 |
Timestamp |0 |0 |0 |0 |0 |0 |0 |0 1 |
User-Name |0 |0 |0 |0 |0 |1 |1 |1 0 |
Vendor-Id |1 |0 |0 |0 |0 |0 |0 |0 1 |
------------------------------|---+---+---+---+---+---+---+---|

15.0
------------------------------|-----+-----+-----+-----+

17.0 IANA Considerations

This document defines a number of assigned numbers to be maintained
by the IANA. This section explains the criteria to be used by the
IANA to assign additional numbers in each of these lists. The
following subsections describe the assignment policy for the
namespaces defined elsewhere in this document.

15.1

17.1 AVP Attributes

As defined in section 4.0, AVPs contain vendor ID, attribute and Data
fields. For vendor ID value of 0, IANA will maintain a registry of

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assigned AVP codes and in some case also values. Attribute 0-254 are
assigned from the RADIUS protocol [1], whose attributes are also
maintained through IANA. AVP Codes 256-280 256-284, 480, 482, 485 and 486 are
assigned within this document. The remaining values are available for
assignment through Designated Expert [12].

15.2

17.2 Command Code Values

As defined in section 3.0, the Command Code field has an associated
value maintained by IANA. Values 0-255 are reserved for backward

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RADIUS compatibility, and values 257, 259, 271, 272, 273, 274, 275 275,
276, 279, 280, 281, and 276 282 are
defined in this specification. The remaining
values are available for assignment via Designated Expert [12].

15.3

17.3 Extension Identifier Values

As defined in section 6.1.3, the Extension Identifier is used to
identify a specific Diameter Extension. All values, other than zero
(0) are available for assignment via Standards Action [12].

Note that the Diameter protocol is not inteded to be extended for any
purpose. Any extensions added to the protocol 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 10.2, the Result-Code AVP (AVP Code 268)
defines the values 2001, 4001-4002 and 5001-5010. All remaining
values are available for assignment via IETF Consensus [12].

15.5 Authentication-Transform-Id AVP Values

Section 13.1.1.1 defines the Authentication-Transform-Id AVP (AVP
Code 285) which is used to identify the authentication algorithm used
to generate the contents of the Digest AVP. This document reserves
the value 1. All remaining values are available for assignment via
Designated Expert [12].

15.6 Encryption-Transform-Id to the base
protocol are required.

17.4 Result-Code AVP Values

As defined in Section 13.1.2.1 defines 10.2, the Encryption-Transform-Id Result-Code AVP (AVP Code
288) which is used to identify the encryption algorithm used to

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generate the contents of the Encrypted-Data AVP. This document
reserves 268)
defines the value 1. values 2001, 4001-4003 and 5001-5012. All remaining
values are available for assignment via Designated Expert IETF Consensus [12].

15.7

17.5 Message Header Bits

There are thirteen bits in the Flags field of the Diameter header.
This document assigns bit 1 ('R'esponse), bit 2 ('I'nterrogation) and
bit 3 ('E'xpected Reply). Bits 4 through 13 should only be assigned
via a Standards Action [12].

15.8

17.6 AVP Header Bits

There are 16 bits in the 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].

15.9

17.7 DSI-Event AVP Values

As defined in Section 9.1.1, the DSI-Event AVP (AVP Code 297) defines
the values 1001, 3001, 4001-4003 4001 and 5001-5006. All remaining values are
available for assignment via IETF Consensus [12].

16.0

18.0 Open Issues

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The following are the open issues that SHOULD be addressed in future
versions of the Diameter protocol:

- AVPs with time values are represented by Unsigned32 type data.
This value is a timestamp consistent with NTP [18]. This field
is expected to expire sometime in 2038. Future investigation
SHOULD be done to determine if a 64 bit time format could be
used.

- The fact that the Sender's IP Address is used in the
construction of the Session-Id means that the introduction of
Network Address Translation MAY cause two hosts to represent the
same Session Identifier. This area needs to be investigated
further to be able to support Diameter hosts on a private
network.

17.0

19.0 Diameter protocol related configurable parameters

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This section contains the configurable parameters that are found
throughout this document:

Diameter Peer
A Diameter entity MAY communicate with peers that are
statically configured. A statically configured Diameter peer
would require that either the IP address or the fully qualified
domain name (FQDN) be supplied, which would then be used to
resolve through DNS.

Realm Routing Table
A Diameter Proxy server routes messages based on the realm
portion of a Network Access Identifier (NAI). The server MUST
have a table of Realms Names, and the address of the peer to
which the message must be forwarded to. The routing table MAY
also include a "default route", which is typically used for all
messages that cannot be locally processed.

Maximum Age of an outstanding message
Messages older than the maximum age SHOULD be rejected, as
described in section 13.3. The recommended value is 4 seconds.

RTT-Multiplier
The Round Trip Time Multiplier is used to determine when a DWR
message is to be sent to an inactive peer. The recommended
valus is 4.

Shared Secret
The shared secret is a value that is known by two communicating
peers, and is used to generate the Integrity-Check-Value and
the Encryption-Payload AVP. There is no default.

Watchdog Interval Period
The Watchdog Interval Period is the frequency at which DWR
messages are sent to inactive peers. The recommended value is
30 seconds.

18.0

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20.0 Security Considerations

The Diameter base protocol requires assumes that two communicating peers
exchange messages in a secure fashion. This document describes two
security methods that can be used. The first requires no security at
the application layer, but rather relies on an underlying security
mechanism, such as IP Security.

When are secured by using
either IP Security is not available, Security, or desirable, the Diameter
protocol MAY use hop-by-hop security, which requires communicating

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peers to negotiate a symmetric key through some out of band
mechanism. Hop-by-Hop TLS. This security provides replay protection by
requiring that the communicating peers share a time source, such as
an NTP server. Information of a sensitive nature, which MUST NOT be
seen by any intermediate model is acceptable in
environments where there are no untrusted third party Diameter node MUST NOT be encrypted using
hop-by-hop encryption.
brokers, or redirect servers.

When the Diameter protocol is used in an inter-domain network, third party brokers or redirect servers are used, strong
application level security MAY SHOULD be required, such as non-repudiation. non-
repudiation. When the communicating peers do require this level of
security either for legal or business purposes, the extension defined
in [11] MAY be used. This security model provides AVP-level
authentication, and the encryption mechanism is designed such that
only the target host has the keying information required to decrypt
the information.

19.0

21.0 References

[1] Rigney, et alia, "RADIUS", RFC-2138, April 1997.

[2] Reynolds, Postel, "Assigned Numbers", RFC 1700, October 1994.

[3] Postel, "User Datagram Protocol", RFC 768, August 1980.

[4] Rivest, "The MD5 Message-Digest Algorithm", RFC 1321, April
1992.

[5] Kaufman, Perlman, Speciner, "Network Security: Private Communi-
cations in a Public World", Prentice Hall, March 1995, ISBN 0-
13-061466-1.

[6] Krawczyk, Bellare, Canetti, "HMAC: Keyed-Hashing for Message
Authentication", RFC 2104, January 1997.

[7] P. Calhoun, W. Bulley, A. Rubens, J. Haag, "Diameter NASREQ
Extension", draft-ietf-aaa-diameter-nasreq-01.txt, IETF work in
progress, March 2001.

[8] Aboba, Beadles "The Network Access Identifier." RFC 2486. Janu-
ary 1999.

[9] Calhoun, Zorn, Pan, Akhtar, "Diameter Framework", draft-ietf-
aaa-diameter-framework-01.txt, IETF work in progress, March
2001.

[10] P. Calhoun, C. Perkins, "Diameter Mobile IP Extensions", draft-
ietf-aaa-diameter-mobileip-01.txt, IETF work in progress, March

Calhoun et al. expires August September 2001 [Page 58] 73]

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ietf-aaa-diameter-mobileip-01.txt, IETF work in progress, March
2001.

[11] P. Calhoun, W. Bulley, S. Farrell, "Diameter Strong Security
Extension", draft-calhoun-diameter-strong-crypto-06.txt (work in
progress), February 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] Arkko, Calhoun, Patel, Zorn, "Diameter Accounting Extension",
draft-ietf-aaa-diameter-accounting-01.txt, IETF work in pro-
gress, March 2001. D. Harkins, D. Carrel, "The Internet Key Exchange (IKE)", RFC
2409, November 1998.

[16] Hinden, Deering, "IP Version 6 Addressing Architecture", RFC
2373, July 1998.

[17] ISI, "Internet Protocol", RFC 791, September 1981.

[18] Mills, "Simple Network Time Protocol (SNTP) Version 4 for IPv4,
IPv6 and OSI, RFC 2030, October 1996.

[19] Housley, Ford, Polk, Solo, "Internet X.509 Public Key Infras-
tructure Certificate and CRL Profile", RFC 2459, January 1999.

[20] B. Aboba, G. Zorn, "Criteria for Evaluating Roaming Protocols",
RFC 2477, January 1999.

[21] M. Beadles, D. Mitton, "Criteria for Evaluating Network Access
Server Protocols", draft-ietf-nasreq-criteria-05.txt, IETF work
in progress, June 2000.

[22] T. Hiller and al, "CDMA2000 Wireless Data Requirements for AAA",
draft-hiller-cdma2000-aaa-02.txt, IETF work in progress, Sep-
tember 2000.

[23] S. Glass, S. Jacobs, C. Perkins, "Mobile IP Authentication,
Authorization, and Accounting Requirements". RFC 2977. October
2000.

[24] F. Yergeau, "UTF-8, a transformation format of ISO 10646", RFC
2279, January 1998.

Calhoun et al. expires August September 2001 [Page 59] 74]

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[25] P. Calhoun, A. Rubens, H. Akhtar, E. Guttman, W. Bulley, J.
Haag, "Diameter Implementation Guidelines", draft-ietf-aaa-
diameter-impl-guide-00.txt, IETF work in progress, June 2000.

[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] P. Calhoun, "Diameter Resource Management", draft-calhoun-
diameter-res-mgmt-06.txt, IETF Work in Progress, February 2001.

[30] Institute of Electrical and Electronics Engineers, "IEEE Stan-
dard for Binary Floating-Point Arithmetic", ANSI/IEEE Standard
754-1985, August 1985.

[31] D. Crocker, P. Overell, "Augmented BNF for Syntax Specifica-
tions: ABNF", RFC 2234, November 1997.

[32] E. Guttman, C. Perkins, J. Kempf, "Service Templates and Ser-
vice: Schemes", RFC 2609, June 1999.

[33] A. Gulbrandsen, P. Vixie, L. Esibov, "A DNS RR for specifying
the location of services (DNS SRV)", RFC 2782, February 2000.

[34] D. Eastlake, "Domain Name System Security Extensions", RFC 2535,
March 1999.

[35] D. Eastlake, "DNS Security Operational Considerations", RFC
2541, March 1999.

[36] D. Eastlake, "DNS Request and Transaction Signatures ( SIG(0)s
)", RFC 2931, September 2000.

[37] S. Kent, R. Atkinson, "Security Architecture for the Internet
Protocol", RFC 2401, November 1998.

[38] A. Frier, P. Karlton, and P. Kocher, "The SSL 3.0 Protocol",
Netscape Communications Corp., Nov 18, 1996.

[39] "The Communications of the ACM" Vol.33, No.6 (June 1990), pp.
677-680.

[40] B. Aboba, J. Arkko, D. Harrington. "Introduction to Accounting

Calhoun et al. expires August September 2001 [Page 60] 75]

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20.0

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.

22.0 Acknowledgements

The authors would like to thank Nenad Trifunovic, Tony Johansson and
Pankaj Patel for their participation in the pre-IETF Document Reading
Party. Allison Mankin's assistance was invaluable in working out
transport issues, and similarly with Steven Bellovin's help in the
security area.

Paul Funk and David Mitton were instrumental in getting the Peer
State Machine correct, and our deep thanks go to them for their time.

The authors would also like to acknowledge the following people for
their contribution in the development of the Diameter protocol:

Bernard Aboba, Jari Arkko, William Bulley, Mark Eklund, David Frascone, Daniel C.
Fox, Lol Grant, Ignacio Goyret, Nancy Greene, Peter Heitman, Fredrik
Johansson, Mark Jones, Paul Krumviede, Fergal Ladley, Ryan Moats,
Victor Muslin, Kenneth Peirce, Stephen Farrell, Sumit Vakil, John R.
Vollbrecht, Jeff Weisberg, Jon Wood Weisberg and Glen
Zorn

21.0 Jonathan Wood

23.0 Authors' Addresses

Questions about this memo can be directed to:

Calhoun et al. expires September 2001 [Page 76]

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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

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

Haseeb Akhtar
Wireless Technology Labs
Nortel Networks
2221 Lakeside Blvd.

Calhoun et al. expires August 2001 [Page 61]

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Richardson, TX 75082-4399
USA

Phone: +1 972-684-8850
E-Mail: haseeb@nortelnetworks.com

Jari Arkko
Oy LM Ericsson Ab
02420 Jorvas
Finland

Phone: +358 40 5079256
E-Mail: Jari.Arkko@ericsson.com

Erik Guttman
Solaris Advanced Development
Sun Microsystems, Inc.
Eichhoelzelstr. 7
74915 Waibstadt
Germany

Phone: +49-7263-911-701
E-mail: erik.guttman@germany.sun.com

22.0

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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

24.0 Full Copyright Statement

This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this docu-
ment itself may not be modified in any way, such as by removing the
copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of develop-
ing Internet standards in which case the procedures for copyrights
defined in the Internet Standards process must be followed, or as
required to translate it into languages other than English. The lim-
ited permissions granted above are perpetual and will not be revoked
by the Internet Society or its successors or assigns. This document
and the information contained herein is provided on an "AS IS" basis
and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DIS-
CLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE.

23.0

25.0 Expiration Date

This memo is filed as <draft-ietf-aaa-diameter-01.txt> <draft-ietf-aaa-diameter-02.txt> and expires in
August

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September 2001.

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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-00.txt

template-url-syntax=
url-path= ; The standard service URL syntax is used.
; For example: 'service:diameter://aaa.example.com:1812

Calhoun et al. expires August September 2001 [Page 63] 80]

Internet-Draft March April 2001

supported-extensions= string L M
# This attribute lists the Diameter extensions supported by the
# AAA implementation. The extensions currently defined are:
# Extension Name Defined by
# --------------- -----------------------------------
# NASREQ draft-ietf-aaa-diameter-nasreq-00.txt
# MobileIP draft-ietf-aaa-diameter-mobileip-00.txt
# Accounting draft-ietf-aaa-diameter-accounting-00.txt
# Strong Security draft-calhoun-diameter-strong-crypto-05.txt
# Resource Management draft-calhoun-diameter-res-mgmt-06.txt
#
# Notes:
# . Diameter implementations support one or more extensions.
# . Additional extensions may be defined in the future.
# An updated service template will be created at that time.
#
NASREQ,MobileIP,Accounting,Strong Security,Resource Management

supported-transports= string L M
SCTP
# This attribute lists the supported transports that the Diameter
# implementation accepts. Note that a compliant Diameter
# implementation MUST support SCTP, though it MAY support other
# transports, too.
SCTP,TCP

-------------------------template ends here-----------------------

Calhoun et al. expires August September 2001 [Page 64] 81]

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