The Domain Name System is a global network of servers that translate host names into IP addresses. Most DNS servers are UNIX machines running BIND (Berkely Internet Name Domain) software; other platforms and software are available. The software is composed of two elements: the name server and a resolver. The name server responds to browser requests by supplying name-to-address conversions. This information is cached (saved for a predefined period of time). When/if it doesn’t know the answer, the resolver will ask another name server for the information. It continues to look up the ‘tree’ of name servers until it finds a name server that knows the answer. Occasionally browsers can timeout waiting for this process even when the propagation has taken place.