What is Diameter?
Diameter was protocol was developed in 1998 as a direct response to overcome the limitations of RADIUS. The diameter of a circle is twice the radius, which is where the protocol derives its name. Diameter is a protocol for Authentication, Authorization and Accounting. It is frequently used in IMS architecture.
How Does Diameter Work?
Diameter is designed as a Peer-To-Peer architecture, and every host who implements the Diameter protocol can act as either a client or a server depending on network deployment. The Diameter node that receives the user connection request will act as the Diameter client. After collecting user credentials, such as username and password, it will send an access request message to another Diameter node. This Diameter node authenticates the user based on the information provided. If the information is accepted, the user will receive an access response by way of the corresponding Diameter client. Otherwise, an access reject message is sent.
Like RADIUS, Diameter provides AAA functionality, but uses TCP and SCTP instead of UDP, therefore delegating detection and handling of communication problems to those protocols. Diameter Applications extend the base protocol by adding new commands and/or attributes.