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114 Intel NetStructure Cache Appliance Administrator’s Guide
Web proxy caching
The Intel NetStructure Cache Appliance is a high-performance caching proxy
server. It is designed to efficiently handle multiple client connections
simultaneously and supports HTTP, FTP, NNTP, ICP, and WCCP 2.0 protocols.
Caching The idea behind Web caching is to store copies of frequently accessed documents
close to users and serve this information to them on demand. Users get their
information faster, and Internet bandwidth is freed up for other tasks.
Proxy server Users direct their requests to Web servers all over the Internet. For a caching
server to serve these requests, it must act as a Web proxy server. A Web proxy
server fields user requests to arbitrary Web servers and either serves the requests,
or forwards them on to the origin server (the Web server that contains the original
copy of the requested information).
Transparent
and explicit
proxy caching
The proxy supports both transparent proxy caching, where the user’s client
software is unaware that it is communicating with a proxy, and explicit proxy
caching, where client software (typically a browser) must be expressly pointed at
the proxy. Transparent proxy caching is discussed in more detail on page 120.
A day in the life of a cache request
Here is an overview of the steps that take place as the appliance acts as a proxy
cache and serves a user request.
Step 1 The appliance receives a user request for a document, image, news article, or
other Web object.
Step 2 With the object address in hand, the appliance looks up the requested object in its
object database (cache).
Step 3 If the object is in the cache, the appliance checks to see if the object is fresh
enough to serve. (See Ensuring cached object freshness‚ on page 115 for details.)
If the object is fresh, the appliance serves it to the user as a cache hit (Figure 1).
Figure 1 A cache hit
cache
local
request
a cache hit
returned document
Intel NetStructure Cache Appliance
hit
1
2
3
client