Introductory concepts HTTP/1.1 basics HTTP/1.1 is a request-reply based protocol - clients request a URL with headers describing the request, the server gives a reply with headers describing the reply /* request */ GET http://www.squid-cache.org/ HTTP/1.1 Host: www.squid-cache.org /* reply */ HTTP/1.1 200 OK Date: Fri, 15 Sep 2000 02:08:19 GMT Server: Apache/1.3.3 (Unix) Cache-Control: max-age=86400 Expires: Sat, 16 Sep 2000 02:08:19 GMT Last-Modified: Wed, 16 Aug 2000 22:43:04 GMT ETag: "30321b-1174-399b18f8" Accept-Ranges: bytes Content-Length: 4468 Content-Type: text/html ... /* More data */