Cisco Systems This document proposes an extension to the Session Initiation Protocol (SIP) Reason Header [1] to include in a BYE Method Request [2] as a result of a session preemption event either at a user agent (UA), or somewhere in the network using RSVP [3]. This document does not attempt to address routers failing in the packet path; but a deliberate event of tearing down a flow between UAs.