What is diameter protocol? Explain

The RADIUS protocol (Remote Access Dial In User Services) has been widely and successfully deployed to provide authentication, authorization, and accounting (AAA) services for dial-up PPP/IP and Mobile IP access. However, inherent shortcomings of the RADIUS protocol have limited its ability to adapt to the ever-increasing capabilities of routers and network access servers, and the ever-expanding set of desired AAA services. A number of working groups have specified their requirements for AAA protocols, and these requirements drove the design of the Diameter protocol. The Roaming Operations (ROAMOPS) Working Group of the IETF published a set of requirements for roaming networks. The NAS Requirements (NASREQ) Working Group of the IETF documented the next generation NAS AAA requirements. The Mobile IP Working Group of the IETF documented AAA requirements that would help Mobile IP scale for Inter-Domain mobility. The Telecommunication Industry Association (TIA) TR-45.6 Adjunct Wireless Packet Data Technology working group documented the CDMA2000 Wireless Data Requirements for AAA. Based on the work of TR-45.6, 3GPP2 has specified a two phased architecture for supporting Wireless IP networking based on IETF protocols;the second phase requiring AAA functionality not supportable in RADIUS. Diameter was specifically designed to meet the requirements indicated by these various groups.Diameter is currently focused on, and limited to, supporting access to IP networks. The Diameter protocol was designed as an improved version of the RADIUS protocol. A goal was to maximize compatibility and ease migration from RADIUS to Diameter.For example, a Diameter message, like a RADIUS message, conveys a collection of attribute value pairs. Diameter is defined in terms of a base protocol and a set of applications. This design allows the protocol to be extended to new access technologies. The base protocol provides basic mechanisms for reliable transport, message delivery, and error handling.