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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The Diameter protocol requires that relaying and proxying agents maintain transaction state, which is used for failover purposes. Application-ID is used to identify for which Diameter application the message is applicable. Obsolete RFCs are indicated with strikethrough text. If cleared, the message MUST be locally processed. Proxies MAY be used in call control centers or access ISPs that provide outsourced connections, they can monitor the number and types of ports in use, and make allocation and admission decisions according to their configuration.

The following Command Codes are defined in the Diameter base protocol: Packets may be filtered based on the following information that is associated with it: The supported TCP flags are: Messages with the “E” bit set are commonly referred to as error messages. Adding a new optional AVP does not require a new application.

Once the receiver has completed the request it issues the corresponding answer, which includes a result code that communicates one of the following: This scenario is advantageous since it does not require that the consortium provide routing updates to its members when changes are made to a member’s infrastructure.


A local realm may wish to limit this exposure, for example, by establishing credit limits for intermediate realms and refusing to accept responses which would violate those limits.

The Hop-by-Hop Identifier is an unsigned bit integer field in network byte order that is used to match the requests with their answers as the same value in the request is used in the response. Command Flags The Command Flags field is eight bits. Relaying of Diameter messages The example provided in Figure 2 depicts a request issued from NAS, which is an access device, for the user bob example. The Diameter protocol was initially developed by Pat R.

Due to space constraints, the short form DiamIdent is used to represent DiameterIdentity. This is known as the Realm Routing Table, as is defined further in Section 2. The example provided in Figure 3 depicts a request issued from the access device, NAS, for the user bob example.

Received answers that do not match a known Hop-by-Hop Identifier are ignored by the Diameter agent.

Diameter (protocol) – Wikipedia

The fields are transmitted in network byte order. The length of the padding is not reflected in the AVP Length field. Since redirect agents do not receive answer messages, they cannot maintain session state.

This does not affect the selection of port baase.

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. Role of Diameter Agents In addition to client and servers, the Diameter protocol introduces relay, proxy, redirect, and translation agents, each of which is defined in Section 1.

The Proxy-Info 358 allows stateless agents to add local state to a Diameter request, with the guarantee that the same state will be present in the answer.

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An example is a redirect agent that provides services to all members of a consortium, but does not wish to be burdened with relaying all messages between realms. Translation Agents A translation agent is a device that provides translation between two protocols e. Likewise, this reduces the configuration load on Diameter servers that would otherwise be necessary when NASes are added, changed or deleted.


Message Length The Message Length field is three octets and indicates the length of the Diameter message including the header fields. The ‘P’ bit indicates the need for encryption for end-to-end security. 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. Some common Diameter commands defined in the protocol base and applications are:.

For IPv4, a typical first rule is often “deny in ip! Diameter is used for many different interfaces defined by the 3GPP standards, with each interface typically defining new commands and attributes.

Diameter (protocol)

Only this exact IP number will match the rule. Both the request and the answer for a given command share the same command code.

An access device MAY apply deny rules of its own before the ptotocol rules, for example to protect the access device owner’s infrastructure. This requires that diajeter maintain the state of their downstream peers e. Additionally, application specific state machines can be introduced either later or at a higher abstraction layer.

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