content. Assuming a web cache server is deployed, when a user accesses a web site, the
content that is downloaded is cached on the cache server. Subsequent access to the same
content is then delivered from the local cache server versus downloading the content
from the original server.
The Web Cache Communications Protocol (WCCP) allows the security appliances to
interact with external web cache and/or filtering servers.
WCCP Process
To understand the benefits that WCCP provides, I’ll go through the process that the
appliance goes through when using WCCP:
1. The user opens a web page, where the connection (or connections) makes its
way to the appliance.
2. The appliance intercepts the web connection request, encapsulates it in a Generic
Routing Encapsulation (GRE) packet to prevent modification by intermediate
devices, and forwards it to the web cache server.
3. If the content is cached in the server, it responds to the user directly with the
content.
4. If the content is not cached in the server, a response is sent to the appliance,
and the appliance allows the user’s connection to proceed to the original
web server.
Some of the benefits of WCCP include
· Users don’t have to change their web browser settings.
· The web caching server can perform optional content filtering.
· Bandwidth is optimized if the content the user is requesting has been previously cached on the web cache server.
· The web cache server can log and report web requests by your users.
Cisco created the protocol, and it has two versions: 1 and 2. Some enhancements of
WCCPv2 include support for other protocols besides HTTP, multicasting of requests
to the web cache servers, multiple cache servers, load distribution among multiple
cache servers, MD5 authentication of information between the redirector and the
web cache server, and many others. Of the two versions, the appliances support only
WCCPv2; however, some features are not supported by the appliances, like multicast
WCCP.
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