Abstract: (seminar) World Wide Web technology (HTTP publishing and browsing)
has become so popular that the increasing traffic volume threatens to overwhelm the networking capacity in place within corporate Intranets
and on the Internet. Web caching products are a key solution to this
problem.Caches diminish the need for network bandwidth, typically by
reducing the traffic from browsers to content servers.Caches can make even more dramatic improvements in the Quality of Service (QoS) for browser users by delivering content at higher bandwidth and reducing transmission delays (latency).Caches gather superior network management information that allows for smarter network management.A Web cache exploits some inalienable facts of life on an HTTP network. There are billions of Web pages out there, but only a small fraction of those pages (or objects on pages) are requested frequently. Many users request the same popular pages and objects. A simple example is the logo image at the top of most Amazon.com pages. This image must be delivered to a browser user every time the browser accesses one of Amazon’s pages, and these pages are requested tens of thousands of times a day.A Web cache is a dedicated computer system within the Internet that monitors Web object requests and stores objects it retrieves form a server. On subsequent requests for the same object, the cache delivers the object from its storage rather than passing the request on to the origin server. Every object changes over time, so each Web object has a useful life or “freshness”. Caches determine whether or not their copy an object is still “fresh,” or whether they need to retrieve a new copy from the origin server. The higher the number of people requesting the same object during its useful life, the more upstream traffic the cache eliminates.By handling object requests rather than passing them upstream to the origin server, caches reduce network traffic and improver the browser experience for users. Caches can be located anywhere on a network, and each cache will store a different set of objects based on the needs of the users it serves.Caches come in all sizes. Caches for individual LAN servers cost as little as $1800, while the largest “carrier class” products for network peering points can run above $100,000.