!!! Overview
[{$pagename}] is an [authentication], [authorization], and [accounting] [protocol] for [networks]. 

[{$pagename}] evolved from and replaces the much less capable [RADIUS] [protocol]. 

[{$pagename}] belongs to the [Application Layer] [protocols] in the [Internet Protocol Suite].

[{$pagename}] [Applications] extend the base [protocol] by adding new commands and/or attributes, such as those for use with the [Extensible Authentication Protocol ]([EAP]).


The name is a play on words, derived from the [RADIUS] [protocol], which is the predecessor (a [{$pagename}] is twice the radius). Diameter is not directly backwards compatible but provides an upgrade path for [RADIUS]. 

The main features provided by Diameter but lacking in RADIUS are:
* Support for [SCTP]
* Capability negotiation
* [Application Layer] acknowledgements, Diameter defines failover methods and [State] machines ([RFC 3539])
* Extensibility; new commands can be defined
* Aligned on 32 bit boundaries
* intended to work in both local and roaming AAA situations. 
* uses [TCP] or [SCTP] and __NOT__ [UDP]. 
* uses [Transport Layer Security] ([IPSEC] or [TLS]). 
* supports [stateless] as well as [stateful] modes. 
* uses AVPs. Diameter allows defining new commands and attributes. It is easy to extend.

!! More Information
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