Avaya P330 User Manual page 19

Avaya P330 Load Balancing Manager User Guide
The following figure illustrates Cache Redirection.
In this figure, the sequence of events is as follows:
1. The user issues an HTTP request. The source IP address is the
user's IP address and the destination IP address is the Web server's
IP address.
2. The load balancer routes the packet to the local cache. The packet
still has the Web server's IP address as its destination IP address.
3. If the cache has the required page, the cache returns the page to
the load balancer with the destination IP address of the client and
the source IP address of the Web server. If the cache does not
have the required page, the cache returns the packet to the load
balancer, and the load balancer routes the packet to the Web
server.
4. On the way back from the Web server, the load balancer routes
the packet to the cache.
5. The cache saves the packet and routes it back to the load balancer.
6. The load balancer sends the page to the user.
A client's request for a Web page and the cache's request for a Web page
have the same source and destination IP addresses. To distinguish
between them, the load balancer uses separate VLANs for clients and the
cache. If the request is on the clients' VLAN, the load balancer forwards
the request to the cache. If the request is on the cache's VLAN, the load
balancer forwards the request to the WAN.
Similarly, the WAN's return of a Web page and the cache's forwarding of
a Web page to a client have the same source and destination IP
addresses. To distinguish between them, the load balancer uses separate
VLANs for clients and the cache. If the response is on the cache's VLAN,
the load balancer forwards the response to the cache. If the response is
on the clients' VLAN, the load balancer forwards the response to the
client.
Figure 1-7. Cache Redirection
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