Configuring the WSM using Device Manager # Go back one pageGo to the next page#Go to this book's Index

How WAP SLB works using RADIUS snooping

RADIUS snooping examines RADIUS accounting packets for client information. to update static session entries. The WSM session table uses these to maintain persistency for load balancing. If a static session entry is added using RADIUS snooping, it must also be deleted using RADIUS snooping, instead of aging out. The WSM load balances both the RADIUS and WAP gateway traffic using the same virtual server IP address.

The following is a step-by-step description of how RADIUS snooping works:

  1. The user is authenticated on dialing.
  2. The RAS establishes a session with the client and sends a RADIUS Accounting Start message to the RADIUS server which includes the client IP address. Before a session entry is recorded on the WSM, WAP packets for a user can go to any of the real WAP gateways.
  3. The WSM snoops on the RADIUS accounting packet and adds a session entry only if it finds required information (type of RADIUS Accounting message, client IP address, caller ID, and user's name) in the packet.
    4. If any information is missing, the WSM will not add the session entry.
    If a session entry for a client cannot be added because of resource constraints, the subsequent WAP packets for that client will not be load balanced correctly; and the client must drop the connection and reconnect to his wireless service.
  4. The WSM load balances the WAP traffic to a specific WAP gateway.
    5. The WSM maintains persistency during the session, however, session persistence cannot be maintained if the number of healthy real WAP gateways changes during the session, for example, if a new WAP server comes into service or existing WAP servers are down.
    Persistence cannot be maintained if the user moves from one ISP to another, or if the base of the user's session changes (that is, from CALLING_STATION_ID to USER_NAME, or vice versa). For example, if a user moves out of a roaming area, it is possible that his/her CALLING_STATION_ID is not available in the RADIUS Accounting packets. If not, the WSM uses USER_NAME to choose a WAP server instead of CALLING_STATION_ID, and persistence cannot be maintained.
  5. When the client terminates the session, the RAS sends an Accounting Stop message to the RADIUS server, and the session entry is deleted from the WSM.

See also:

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