Editing Diameter (protocol) (section)

== Comparison with RADIUS ==
The name is a play on words, derived from the [[RADIUS]] protocol, which is the predecessor (a diameter is twice the radius). Diameter is not directly [[backward compatibility| backward compatible]] but provides an upgrade path for RADIUS. The main features provided by Diameter but lacking in RADIUS are:
* Support for [[Stream Control Transmission Protocol|SCTP]]
* Capability negotiation
* [[Application layer]] acknowledgements; Diameter defines [[failover]] methods and state machines (RFC 3539)
* Extensibility; new commands can be defined
* Aligned on 32&nbsp;bit boundaries

Also:
Like RADIUS, it is intended to work in both local and roaming AAA situations.
It uses TCP or SCTP, unlike RADIUS which uses UDP.
Unlike RADIUS it includes no encryption but can be protected by transport-level security (IPSEC or TLS).
The base size of the AV identifier is 32&nbsp;bit unlike RADIUS which uses 8&nbsp;bit as the base AV identifier size.
Like RADIUS, it supports stateless as well as stateful modes.
Like RADIUS, it supports application-layer acknowledgment and defines failover.
Diameter is used for many different interfaces defined by the [[3GPP]] standards, with each interface typically defining new commands and attributes.