METHODS TO ROUTE A BEARER VIA CIRCUIT SWITCHING TO AN INTERNET PROTOCOL MULTIMEDIA SYSTEM NODE USING SESSION INITIATION PROTOCOL CONTACT HEADER

摘要

A method of call routing is pro-vided. The method comprises receiving a ses-sion initiation protocol (SIP) INVITE message that contains a uniform resource identifier (URI) of a called party and that identifies that a bearer for a call to the called party is to be set--up at least in part over the circuit switching do-main. The method also comprises determining a digit string associated with the URI. The method also comprises sending a SIP informa-tional response message having a contact head-er that contains information based on the digit string.