Caller Preferences for the Session Initiation Protocol (SIP)

This document describes a set of extensions to the Session Initiation Protocol (SIP) which allow a caller to express preferences about request handling in servers.These preferences include the ability to select which Uniform Resource Identifiers (URI) a request gets routed to, and to specify certain request handling directives in proxies and redirect servers.It does so by defining three new request header fields, Accept-Contact, Reject-Contact, and Request-Disposition, which specify the caller's preferences.