Diameter Protocol

The Diameter base protocol provides authentication, authorization, and accounting (AAA) services in 3G, IMS, and 4G networks for applications such as network access and data mobility. AAA protocols form the basis for service administration within the telecommunications industry, such as deciding which services a user can access, at what quality of service (QoS), and at what cost.

Since the introduction of IP-based technology in a telecommunications network, Diameter protocol has been chosen as the AAA protocol for all fixed and mobile networks. Diameter has the competitive edge over legacy AAA solutions and is a foundation of EPS (Evolved Packet System), the new core network that supports LTE technology.

The Diameter name is a play on words from its predecessor RADIUS protocol (Remote Authentication Dial-In User Service). Diameter has been embraced by the many standards bodies, such as the 3GPP and ETSTI, as the foundation for all AAA functionalities in next-generation networks (NGN).

Diameter was developed as AAA grew to support additional needs, such as policy control, dynamic rules, quality of service, bandwidth allocation, and new charging schemes. It is also possible for Diameter base protocol to be extended for use in new applications, via the addition of new commands or AVPs. Other upgrades in 4G, such as real-time functionality for transactions, can only be handled with Diameter protocol.

Some of Diameter protocol’s advantages over its predecessor RADIUS include:

  • Unlimited scalability to enable growth
  • Fault tolerance to guarantee message delivery
  • Agent support to clearly define proxy, redirect, relay, or translation agents
  • Secure transmission of Diameter message packets
  • Reliable transmission over TCP or SCTP


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