Obtaining and Using Globally Routable User Agent (UA) URIs (GRUU) in the Session Initiation Protocol (SIP)
Several applications of the Session Initiation Protocol (SIP) require a user agent (UA) to construct and distribute a URI that can be used by anyone on the Internet to route a call to that specific UA instance. A URI that routes to a specific UA instance is called a Globally Routable UA URI (GRUU). This document describes an extension to SIP for obtaining a GRUU from a server and for communicating a GRUU to a peer within a dialog.