The IMS AAA Server maintains routing rules for each type of request. When the IMS AAA Server receives a request, it examines the request to determine what type of request it is:
Once the server determines the type of request, it consults the respective routing rules to determine how to route the request.
Authentication Routing Rules — Routing rules for authentication requests. The functions associated with these routing rules are the HSS and the Diameter and RADIUS Downstream server functions. Note that for the RADIUS downstream server function, these routing rules include authentication/authorization requests, since in RADIUS both authentication and authorization are in the same request. For the Diameter "Downstream" (server) function, these routing rules apply only to authentication requests.
Authorization Routing Rules —Routing rules for authorization requests for the Diameter downstream server function.
Accounting Routing Rules — Routing rules for accounting requests. The only network element function associated with these rules is the Charging Data Function (CDF).
WAG Routing Rules — Routing rules for WAG requests.
Figure 89 summarizes the IMS AAA Server routing rules and their associated functions.
The IMS AAA Server supports both explicit and implicit routing.