Web Cache Communication Protocol (WCCP)

Purpose

To offset the load of edge router in http request. A http request sent by a host is redirected to local content cache engine (aka content engine), content engine will then send the content back to the requesting host.

Operation

Step 1: A host sends a http request.

Step 2: Router redirects the http request to local content engine.

Step 3a: If content engine has what the host needs, content engine will send the http content back to host that request it.

Step 3b: If content engine does not contain what the host needs, content engine will send http request to the destination web server to request for the http content.

Step 4: The web server replied the request, content engine cached the content onto its hard drive and send the content to host that requested for it.

Other things about WCCP

1. Only works with IPv4.

2. Has two versions.

3. WCCP version 1 – There can only be one router within a content engine cluster. A content engine cluster can contain up to 32 content engines. Supports http redirection only.

4. WCCP version 2 – Allows multiple routers to be attached to a content engine cluster. That is up to 32 content engines within a cluster, and up to 32 routers in a cluster. In other words multiple routers can participate in traffic redirection to content engines and hence offload the stress from a single router within one cluster.

Apart from supporting http, it supports other service ports in udp or tcp. Hence version 2 is more granular and flexible as compared to version 1.

WCCPv2 also supports MD5 password hashing.

5. WCCP uses udp 2048.

Enable WCCP globally

Router(config)#ip wccp version 2
Router(config)#ip access-list standard ce1
Router(config-std-nacl)#permit host 192.168.0.1
Router(config-std-nacl)#permit host 172.31.1.1
Router(config-std-nacl)#permit host 172.31.2.1
Router(config-std-nacl)#exit
Router(config)#ip access-list extended service-types
Router(config-ext-nacl)#permit tcp any any eq 80
Router(config-ext-nacl)#permit tcp any any eq 21
Router(config-ext-nacl)#permit tcp any any eq 8080
Router(config-ext-nacl)#exit
Router(config)#ip wccp web-cache group-list ce1 redirect-list service-types
Router(config)#

In this configuration, there are three content engines in the cluster which support ftp caching, proxy webserver caching and webserver caching traffic redirection. WCCPv2 is the default, hence user does not need to explicitly define version 2. Any service request that is within the redirection list will be redirected to the cache engine by the router.

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