1. History Since created in 1995, RADIUS has been used to provide authentication, authorization and generate accounting information for dial-in users. However, it does not support roaming users efficiently, and is not designed to support emerging QoS (RSVP, IntServ, DiffServ) services. In March 1998, the IESG decided to close the RADIUS WG to open the way for a more flexible protocol for AAA services. In August 1998, a new BOF is created to design a new AAA protocol.

2. DIAMETER Designed by Pat Calhoun in 1996, it provides AAA for roaming users. Today, DIAMETER can also provide policy support for VPN (Virtual Private Service), Voice over IP, Fax over IP, Mobile IP, and resource management (or Bandwidth Broker). DIAMETER protocol consists of two potions: –Base Protocol: provide secure communication among DIAMETER entities, feature discovery, and version negotiation. –Extensions: Build on top of the base protocol to provide specific services.

3. DIAMETER Network Architecture S2 C1 C3 C4C2 S1 Servers: S1, S2 Clients: C1, C2, C3, C4 Communications: Peer-to-peer: Client-Server:

4. IP Telephony Service Network User Accounting (DIAMETER Extension) Resource Management Real-time Data Policy Server A Router Router SIP Proxy Caller Regional ISP B Regional ISP A Policy Server B Transit ISPs Inter-carrier Accounting SIP Proxy Callee

5. DIAMETER / SIP Extension SIP Client DIAMETER Client SIP Proxy Server DIAMETER Server DIAMETER Messages SIP Messages SIP Messages

6. … Mechanism Caller ProxyPolicy Server Callee Proxy Allow? Yes SIP INVITE Accept? Yes SIP 200 (Success) Register SIP ACK Register SIP BYE Release