Diameter is specified primarily as a base protocol by the IETF in RFC and then DIAMETER base protocol must be used in conjunction with DIAMETER. Diameter is an authentication, authorization, and accounting protocol for computer networks. It evolved from the earlier RADIUS protocol. It belongs to the application layer protocols in the internet protocol suite. Diameter Applications extend the base protocol by adding new commands The Diameter base protocol is defined by RFC (Obsoletes: RFC ). RFC Diameter Base Protocol, September Canonical URL: Discuss this RFC: Send questions or comments to [email protected] Other actions: View.

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In order to preserve interoperability, a Diameter implementation MUST be able to exclude from a Diameter message any Mandatory AVP which is neither defined bas the base Diameter protocol nor in any of the Diameter Application specifications governing the message in which it appears.

The following format is used in the definition: Relay Agents Relay Agents are Diameter agents that accept protocool and route messages to other Diameter nodes based on information found in the messages e.

Transaction state implies that upon forwarding a request, its Hop-by-Hop Identifier is saved; the field is replaced with a locally unique identifier, which is restored to its original value when the corresponding answer is received.

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This requires that proxies maintain the state of their downstream peers e. However, the protocol’s failover procedures require that agents maintain a copy of pending requests. The definition contains a list of valid values and their interpretation and is described in the Diameter application introducing the AVP. As ofthe only value supported is 1.

End-to-End Identifier The End-to-End Identifier is an unsigned bit integer field in network byte order and is used to detect duplicate messages. The AddressType is used to discriminate the content and format of the remaining octets. The AVP contains the identity of the peer the request was received from. This is part of the basic protocol functionality and all stacks should support it and as such abstract from the connectivity related operations.


A Command Code is used to determine the action that is to be taken for a particular message. Diameter Applications can extend the base protocol by adding new commands, attributes, or both.

Upon receipt of the redirect notification, DRL establishes a transport connection with HMS, if one doesn’t already exist, and forwards the request to it. One or more Session-Ids must follow. In case of redirecting agents, the Hop-by-Hop Identifier is maintained in the header as the Diameter agent responds with an answer message. The Diameter protocol requires that relaying and proxying agents maintain transaction state, which is used for failover purposes.

However, they differ since they modify messages to implement policy enforcement.

Retrieved 30 April Diameter implementations are required to support all Mandatory AVPs which are allowed by the message’s formal syntax and defined either in the base Diameter standard or in one of the Diameter Application specifications governing the message. Hop-by-Hop Identifier The Hop-by-Hop Identifier is an unsigned bit integer field in network byte order and aids in matching requests and replies. Here there are two: By vase this site, you agree to the Terms of Use and Privacy Policy.

Obsolete RFCs are indicated with strikethrough text. The default value is zero. Since Relays do not perform any application level processing, they provide relaying services for all Diameter applications, and therefore MUST advertise the Relay Application Identifier.

Translation Agents A translation agent is a device that provides translation between two protocols e. This scenario is advantageous since it does not require that prtocol consortium provide routing updates to its members when changes are made to a member’s infrastructure. A stateless agent is one that only maintains transaction state.

This allows a single server to handle policies for many services. OctetString The data contains arbitrary data of variable length.


Further, since redirect agents never relay requests, they are not required to maintain transaction state. If cleared, the message MUST be locally processed. These services are provided by supporting AVP integrity and confidentiality between two peers, communicating through agents. The ” E ” Error bit — If set, the message contains a protocol error, and the message will not conform to the CCF described for this command.

The keyword “assigned” is the address or set of addresses assigned to the terminal. The format of the Data field MUST be one of the following base data types or a data type derived from the base data types. See Section 4 for more information on AVPs. Diameter is an authentication, authorization, and accounting protocol for computer networks. Integer32 32 bit signed value, in network byte order.

Thus an administrator could change the configuration to avoid interoperability problems. See the frag option for details on matching fragmented packets.

It is set when resending requests not yet acknowledged, as an indication of a possible duplicate due to a link failure. Received answers that do not match a known Hop-by-Hop Identifier are ignored by the Diameter agent. Diameter Command Naming Conventions Diameter command names typically includes one or more English words followed by the verb Request or Answer.

Diameter (protocol)

A home realm may also wish to check that each accounting request message corresponds to a Diameter response authorizing the session. The name is a play on words, derived from the RADIUS protocol, which is the predecessor a diameter is twice the radius. The Message Length field indicates the length of the Diameter message in bytes, including the header fields and the padded AVPs.