WCCP

Web Cache Communication Protocol (WCCP):


WCCP provides for the communication between routers and web
caches as well as load balancing and fault tolerance.WCCP is supported on various models of Cisco routers and Layer 3 switches. WCCPv2 requires the equipment to have at least IOS version 12.0(3).


WCCP v2 can be used for various protocols; HTTP, HTTPS and FTP over HTTP are
all common choices, because they can make use of caching and proxying. WCCP does
not support IPv6, so it should not be used in IPv6 deployments.

WCCP Data Flow:


Client requests get redirected to the proxy. The proxy makes a connection to the
requested server and then sends the results back to the client.
The steps involved are as follows:

1. Client sends traffic via the router to some destination (no proxies are
configured on the client).

2. WCCP v2 router depending on its configuration sends some traffic (such as
HTTP, HTTPS, FTP, and DNS) to appropriate service group, so it may reach
proxy server or cluster of servers in that service group.

3. The Adaptive Redirection Module (ARM) readdresses traffic. For example,
HTTP traffic on port 80 is readdressed to Content Gateway port 8080. The
proxy processes the request as usual, then the traffic hits the router again.

4. Request is sent to the destination.

5. Return traffic reaches the WCCP router and is redirected based on return rules
in the router.

6. The ARM readdresses the proxy port in the response header to port 80
(undoing the readdressing it did on the way to the proxy). As a result, the user
sees the response as if it had been sent directly from the origin server.


The ARM (steps 3 and 6) can make two changes to the address of an incoming packet:
its destination IP address and its destination port. For example, the destination IP
address of an HTTP packet is readdressed to the IP address of the proxy and the
destination HTTP port is readdressed to the Websense Content Gateway HTTP proxy
port (default port 8080). On the way back to the client, the ARM changes the source
IP address to the origin server IP address and the source port to the origin server po