C H A P T E R53
• Describe current network traffic overload issues.
• Describe how caching solves many of those issues.
• Describe how network caching works.
• Describe different caching technologies in use today.
Network Caching Technologies
Although the volume of Web traffic on the Internet is staggering, a large percentage of that traffic is
redundant–multiple users at any given site request much of the same content. This means that a
significant percentage of the WAN infrastructure carries the identical content (and identical requests for
it) day after day. Eliminating a significant amount of recurring telecommunications charges offers an
enormous savings opportunity for enterprise and service provider customers.
Web caching performs the local storage of Web content to serve these redundant user requests more
quickly, without sending the requests and the resulting content over the WAN.
Network caching is the technique of keeping frequently accessed information in a location close to the
requester. A Web cache stores Web pages and content on a storage device that is physically or logically
closer to the user–closer and faster than a Web lookup. By reducing the amount of traffic on WAN links
and on overburdened Web servers, caching provides significant benefits to ISPs, enterprise networks,
and end users. There are two key benefits:
• Cost savings due to WAN bandwidth reduction–ISPs can place cache engines at strategic points
on their networks to improve response times and lower the bandwidth demand on their backbones.
ISPs can station cache engines at strategic WAN access points to serve Web requests from a local
disk rather than from distant or overrun Web servers.
In enterprise networks, the dramatic reduction in bandwidth usage due to Web caching allows a
lower-bandwidth (lower-cost) WAN link to serve the same user base. Alternatively, the organization
can add users or add more services that use the freed bandwidth on the existi