Cisco Systems Bell Labs Sun Microsystems Nortel Networks Current Internet Service Providers (ISPs) scale their networks by using the RADIUS protocol, which provides user Authentication, Authorization and Accounting (AAA) of Dial-up PPP clients. The recent work done in the Roaming Operations (ROAMOPS) Working Group was to investigate whether RADIUS could be used in a roaming network, and concluded that RADIUS was ill-suited for inter-domain purposes. The IETF has formed a new NAS Requirements Working Group, and part of their charter is to document the next generation NAS' AAA requirements. Recently, the Mobile-IP Working Group also documented their own AAA requirements that would help Mobile IP scale for Inter-Domain mobility. The DIAMETER protocol is a follow-on to the RADIUS protocol. DIAMETER addresses the known RADIUS deficiencies, and is intended for use with the NASREQ and Mobile IP application space.