HTTP

A Web page (also called a document) consists of objects. An object is simply a file—such as HTML file, a JPEG image, a Java applet, or a video clip—that is addressable by a single URL.

Each URL has two components: the hostname of the server that houses the object and the objects path name.

Because an HTTP server maintains no information about the clients, HTTP is said to be a stateless protocol.

Non-Persistant connections; parallel TCP connections; The default mode of HTTP uses persistent connections with pipelining.

Application developers often use the HEAD method for debugging. The PUT method is also often used in conjunction with Web publishing tool: upload.

Cookie technology has four components. Cookies can be used to identify a user. Cookies can thus be used to create a user session layer on top of stateless HTTP.

A Web cache—also called a proxy server—is a network entity that satisfies HTTP requests on the behalf of an origin Web server.

Conditional GET: the object housed in the Web server may have been modified since the copy was cached at the client.