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 URIs a request gets routed to, and to specify certain request handling directives in proxies and redirect servers. It does so by defining four new request headers, Accept-Contact, Reject- Contact, Require-Contact and Request-Disposition, which specify the caller's preferences. The extension also defines new parameters for the Contact header that describe the capabilities and characteristics of a UA.