World-Wide Web Proxies

A WWW proxy server, proxy for short, provides access to the Web for people on closed subnets who can only access the Internet through a firewall machine. The hypertext server developed at CERN, cern_httpd, is capable of running as a proxy, providing seamless external access to HTTP, Gopher, WAIS and FTP. cern_httpd has had gateway features for a long time, but only this spring they were extended to support all the methods in the HTTP protocol used by WWW clients. Clients don't lose any functionality by going through a proxy, except special processing they may have done for non-native Web protocols such as Gopher and FTP. A brand new feature is caching performed by the proxy, resulting in shorter response times after the first document fetch. This makes proxies useful even to the people who do have full Internet access and don't really need the proxy just to get out of their local subnet. This paper gives an overview of proxies and reports their current status. The primary use of proxies is to allow access to the Web from within a firewall (Fig. 1). A proxy is a special HTTP [HTTP] server that typically runs on a firewall machine. The proxy waits for a request from inside the firewall, forwards the request to the remote server outside the firewall, reads the response and then sends it back to the client. In the usual case, the same proxy is used by all the clients within a given subnet. This makes it possible for the proxy to do efficient caching of documents that are requested by a number of clients. The ability to cache documents also makes proxies attractive to those not inside a firewall. Setting up a proxy server is easy, and the most popular Web client programs already have proxy support built in. So, it is simple to configure an entire work group to use a caching proxy server. This cuts down on network traffic costs since many of the documents are retrieved from a local cache once the initial request has been made. Current proxy methodology is based on the earlier gateway code written by Tim Berners-Lee as part of libwww, the WWW Common Library [LIBWWW].