Web Caching and Replication

5.11. Summary

This chapter introduces the most important HTTP features used in the context of caching and replication. One such feature is conditional requests, which retrieve objects only if a certain condition is true. An HTTP request is made conditional by including in the request special request headers, such as if-modified-since.

Another group of headers is used to specify which objects can be cached, how long they can be cached, whether they can be shared among different clients, and so on. In particular, the expires and age response headers are used by caches to expire cached Web objects. The complex cache-control header can be used by either requests or responses to control cache behavior in a variety of ways. Perhaps the most important ...