Web Caching

Web Caching Overview

Web caching is the temporary storage of web objects (such as HTML documents) for later retrieval. There are three significant advantages to web caching: reduced bandwidth consumption (fewer requests and responses that need to go over the network), reduced server load (fewer requests for a server to handle), and reduced latency (since responses for cached requests are available immediately, and closer to the client being served). Together, they make the web less expensive and better performing.

Caching can be performed by the client application, and is built in to most web browsers. There are a number of products that extend or replace the built-in caches with systems that contain larger storage, more features, or better performance. In any case, these systems cache net objects from many servers but all for a single user.

Caching can also be utilized in the middle, between the client and the server as part of a proxy. Proxy caches are often located near network gateways to reduce the bandwidth required over expensive dedicated internet connections. These systems serve many users (clients) with cached objects from many servers. In fact, much of the usefulness (reportedly up to 80% for some installations) is in caching objects requested by one client for later retrieval by another client. For even greater performance, many proxy caches are part of cache hierarchies, in which a cache can inquire of neighboring caches for a requested document to reduce the need to fetch the object directly.

Finally, caches can be placed directly in front of a particular server, to reduce the number of requests that the server must handle. Most proxy caches can be used in this fashion, but this form has a different name (reverse cache, inverse cache, or sometimes httpd accelerator) to reflect the fact that it caches objects for many clients but from (usually) only one server.

Cache Now!

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Last modified: Sat Feb 9 13:40:19 EST 2008
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