Web Proxy Autodiscovery (WPAD) definition

Web Proxy Autodiscovery (WPAD) is a proposed Internet protocol that allows a client, such as a Web browser or a streaming media application, to automatically locate and interface with cache services in a network so that information can be delivered more quickly to the user. A cache service stores copies of popular Web pages at a location closer to the users, usually on the outer edges of a network, for faster access. When a particular page is requested, the browser is directed to the cache service for that page instead of having to travel through the network to the originating site.

Cache services are maintained and offered by Internet service providers (ISPs) and special cache-providing services such as Akamai. The first WPAD-enabled browser was Internet Explorer 5.0. WPAD is a joint effort of Inktomi, Microsoft, Real Networks, and Sun Microsystems.

When an Internet session is started, the WPAD-enabled client automatically uses Dynamic Host Configuration Protocol (DHCP) to locate a cache service. If unsuccessful, WPAD then uses the Service Location Protocol (SLP). SLP is a protocol that allows network applications to discover the location and configuration of network services in an enterprise. If still unsuccessful, WPAD then searches through domain name system (DNS) records. Once a nearby cache service is located, WPAD automatically connects to that location for related page requests.

This was first published in September 2005

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