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.
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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.