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Diameter Overview


Diameter is an industry-standard protocol for providing AAA services for applications such as network access or IP mobility in both local and roaming situations. The Diameter protocol is widely used in the IP Multimedia Subsystem (IMS) and Long Term Evolution (LTE) architectures for LTE or IMS entities (such as Home Subscriber Server (HSS)) to exchange AAA-related information.

The Diameter protocol has the following benefits:

  • Acts as a reliable transport protocol (Transmission Control Protocol (TCP) or Stream Control Transmission Protocol (SCTP))

  • Satisfies network or transport layer security (IPsec or TLS)

  • Provides larger address space than RADIUS for attribute-value pairs (AVPs) and identifiers

  • Provides better roaming support

  • Enables dynamic discovery of peers

  • Supports additional extensions to add new command codes and AVPs to create new Diameter applications without modifying the existing code

  • Provides basic support for user-sessions and accounting

  • Supports server-initiated messages, such as a request to abort service to a particular user


SBR Carrier does not implement network or transport layer security, user-session management, or accounting. Also, the addition of new command codes and/or AVPs to create new Diameter applications is not supported.

A Diameter-based remote access environment typically involves the following types of components:

  • A Diameter node is a machine that performs the hosting process to implement the Diameter protocol. The Diameter node may act as a client, an agent, or a server.

  • The Diameter agent is a Diameter node that provides relay, proxy, redirect, or translation services.

  • The Diameter client is a Diameter node that supports Diameter client applications as well as the base protocol. Diameter clients are often implemented in devices situated at the edge of a network and provide access control services for the network. Typical examples of Diameter clients include the Network Access Device (NAD) and the mobile IP foreign agent.

  • Diameter peers represent two Diameter nodes sharing a direct TCP or SCTP transport connection.

  • The Diameter server is a Diameter node that handles AAA requests for a particular realm. The Diameter server must support Diameter server applications in addition to the base protocol.

Diameter Application

Diameter Application

A Diameter application is a protocol (not a software application) based on the Diameter base protocol. Each application is defined by an application identifier. You can add new command codes or new mandatory AVPs to the Diameter application. Adding a new optional AVP does not require a new application. Examples of Diameter application are:

  • Diameter Mobile IPv4 Application

  • Diameter Network Access Server Application

  • Diameter Session Initiation Protocol Application

  • Diameter Credit-Control Application