This feature provides a mechanism for a system functioning as a Home Agent (HA) to communicate status information to a properly configured RADIUS server. The status information is used by the RADIUS server to determine the availability and readiness of the HA to accept Mobile IP (MIP) subscriber sessions. The RADIUS server\'s awareness of the HA status allows it to dynamically assign immediately available HAs to subscriber sessions.
When a RADIUS server assigns an HA to a Mobile Node (MN), it is very important that only active, or accessible, HAs are selected for the assignment. Therefore, it is necessary for the RADIUS server to detect the availability of each HA before assigning it to an MN. This feature allows the RADIUS server to gather and maintain a list of available HAs through a detection mechanism that provides frequent updates.
With this feature, bogus authentication messages, called probe authentication messages, are exchanged between the RADIUS server and the HA. The HA periodically sends Access-Request messages to the RADIUS server. The RADIUS server distinguishes the probe authentication request from other regular subscriber authentication messages, validates them, and sends proper response.
User-Name = Probe-User User-Password = 18 7F 88 02 82 1D B6 F6 70 48 B9 A1 4C 92 C3 3E NAS-IP-Address = 220.127.116.11 Service-Type = Authenticate_Only Event-Timestamp = 1255598429
User-Name and User-Password are configurable in the system.
If an Access-Accept message is sent in response to the probe authentication request, the RADIUS server updates the status of the HA as active. If an Access-Reject message is sent, the RADIUS server updates only the statistics without any further action. If the RADIUS server misses receiving a configured number of probe authentication requests, the HA, and all of its associated IP addresses, is marked as down, or inaccessible. When an HA is marked as down, a backup HA and its associated IP addresses are made active and used for assignment in the place of the inaccessible HA.
This feature is supported on system installations that are configured as Home Agents and are configured to communicate with a AAA Service Controller that supports the configuration of Active and Backup HAs. For more information on a compatible AAA Service Controller, contact your designated customer support engineer.