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...