Conclusions on Diameter's business prospects
AAA roaming management for PPP and Mobile IP services

At present, RADIUS is the protocol routinely used whenever a network device such as a NAS, VPN device, Wi-Fi device or router needs to authenticate and authorize a user, or even collect connection information. However, the Diameter protocol offers a number of advantages over RADIUS: it provides cross-domain AAA service; it allows a user to be authorized to connect without requiring authentication; it is possible to re-authenticate and/or re-authorize a user during a connection. For all these reasons, Diameter is seen as the AAA protocol of the future.

It's almost certain that Diameter will be used for remote dial-up connections, replacing RADIUS. Thanks to Diameter, ISPs will no longer need to place access points to their network all over the world. Diameter will enable them to benefit from the access point of other ISPs, and thus increase their geographical coverage...