Lecture 7: Internet Applications #3.3: HTTP/1.1

Support for Caching in HTTP/1.1

The World Wide Web has been spectacularly successful -- so successful that a huge proportion of Internet traffic is HTTP, ie Web pages and related objects (eg, images). Caching is a technique whereby copies of popular objects are kept in strategic locations, and supplied in lieu of the originals, saving huge amounts of traffic on the "backbone networks".

The Conditional-GET operation seen earlier allows support for caching at the browser level -- that is, the browser can keep a local copy of an object and check if it's up to date before displaying it.

HTTP/1.1 adds support for proxy server caches. A proxy server is an HTTP server which fetches Web objects (pages, images, etc) on behalf of its clients. Requested objects are always specified as full URLs in HTTP/1.1, so the first line of a GET request now looks like:

GET http://www.bendigo.latrobe.edu.au/index.html HTTP/1.1
....other request headers...

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