Diameter
Diameter is a set of commands and processes that can receive identification information from a potential user of a network service, authenticates the identity of the user, validates the authorization to use the requested service and creates event information for accounting purposes. Diameter protocol is an evolution of Radius protocol. Diameter protocol was originally a provisioning protocol, which was expanded to include authentication, authorization and accounting capability when it was determined that evolving the Radius protocol would be impractical. While diameter protocol is not backward compatible to Radius protocol, it can provide Radius capabilities along with many new features. Diameter protocol features include the ability to use reliable transport protocols (such as TCP or SCTP), transport security (e.g. IPSEC or TLS), a large number of attribute value pairs (AVPs), both client side and service side service request ability, dynamic recovery, service negotiation capability, error notification, extensibility, and application layer acknowledgements.