Web Caching

Being Cache-Friendly

This section is directed to content providers: I want to convince you to engineer a cache-friendly web site. If you stick with me through the motivation section, I’ll give you some practical advice and even show you how to implement many of the tips on the Apache server.

Why?

Why should you, as a content provider, care about web caching? For at least the following three reasons:

• When people access your web site, pages will load faster.

• Caches isolate clients from network failures.

• Caches reduce the load placed on your servers and network connections.

Let’s examine each of these reasons in more detail.

Latency

It should be pretty obvious that caching objects close to web clients can greatly reduce the amount of time it takes to access those objects. This is the reason why web browsers have their own built-in cache. Retrieving an object from the browser cache is almost always faster than retrieving it over the network. When considering how your web site interacts with caches, don’t forget browser caches!

What if the requested objects are not in the browser cache but might be stored in a proxy cache? Now the benefits of caching are strongly correlated to relative proximity of the client, cache, and origin server. Here, proximity refers to network topology rather than geography. Both latency and throughput characterize network proximity. As an example, let’s consider two different users accessing the www.cnn.com home page. The first user is connected to a U.S. ...