2.9.2 RADIUS Overload Control

RADIUS may be used as an option, on a per APN basis, for a GGSN to use RADIUS authentication to authenticate a user and RADIUS accounting to provide information to a AAA server. There have been cases where RADIUS servers have become overloaded due to excessive traffic load and AAA networks have gone down.

With RADIUS there is no message defined for a server to tell a client that it is currently experiencing overload. Messages simply time out, and clients need to retransmit, which has a tendency to make the problem in the network worse and potentially spread to other servers.

To address this problem, a RADIUS router or proxy can be used between the clients and servers to control the amount of traffic presented to the servers and prevent server outages. Additionally, in the event there was an outage of one or more servers, such a centralized point of traffic control could help ensure a smooth re-introduction of active servers to the network.