Nortel Networks WEB OS 212777 - Manual (Page 159)

Web OS 10.0 Application Guide
Chapter 6: Server Load Balancing n 159
212777-A, February 2002
TPCP is Alteon’s proprietary protocol that is used to establish communication between the
RADIUS servers and the Alteon Web switch. It is UDP-based and uses ports 3121, 1812, and
1645.
Using TPCP, a static session entry is added or removed by the external devices, such as the
RADIUS servers. A regular session entry is usually added or removed by the switch itself. A
static session entry, like a regular session entry, contains information such as the client IP
address, the client port number, real port number, virtual (destination) IP address, virtual (des-
tination) port number.
A static session entry added via TPCP to the switch does not age out. The entry will only be
deleted by another TPCP
Delete Session request. If the user adds session entries using
the traditional server load balancing methods, the entries will continue to age out.
Since TPCP is UDP-based, the Add/Delete Session requests may get lost during trans-
mission. The WAP gateway issues another Add Session request on detecting that it has lost
a request. The WAP gateway detects this situation when it receives WAP traffic that does not
belong to that WAP gateway. If a
Delete Session request is lost, it will be overwritten by
another Add Session request.
How WAP SLB Works Using Static Session Entries
1. On dialing, the user is first authenticated by the Remote Access Server (RAS).
2. The RAS sends a RADIUS authentication request to one of the RADIUS servers, which
can be integrated with a WAP gateway.
3. If the user is accepted, the RADIUS server determines which WAP gateway is right for
this user and informs the switch of the decision via TPCP.
4. The switch receives an Add Session request from the RADIUS server and adds a ses-
sion entry to its session table to bind a WAP gateway with that user.
5. A response ( RADIUS Accept ) packet is sent back to the RAS by the RADIUS server.
6. The RAS receives a RADIUS A ccept packet and allows the WAP traffic for that user.
7. If the user disconnects, the RAS detects it and sends a RADIUS Accounting Stop
message to the RADIUS server.
8. The RADIUS server sends a Delete session message and removes the session entry
for that user.