A comprehensive addressing scheme

The HTTP protocol uses the concept of reference provided by the Universal Resource Identifier (URI) as a location (URL) or name (URN), for indicating the resource on which a method is to be applied. When an HTML hyperlink is composed, the URL (Uniform Resource Locator) is of the general form http://host:port-number/path/file.html. More generally, a URL reference is of the type service://host/file.file-extension and in this way, the HTTP protocol can subsume the more basic Internet services. HTTP/1.0 is also used for communication between user agents and various gateways, allowing hypermedia access to existing Internet protocols like SMTP, NNTP, FTP, Gopher, and WAIS. HTTP/1.0 is designed to allow communication with such gateways, via proxy servers, without any loss of the data conveyed by those earlier protocols.