Patent ID: 8650243

Claim:
A method for processing a session initiation protocol (SIP) request, comprising: receiving a SIP request from a user agent (UA) comprising an identifier of a different UA; obtaining lookup information of a plurality of different UAs related to the identifier based on a request to a registrar comprising the identifier; generating a routing header for the SIP request based at least in part on whether the lookup information for at least one UA in the plurality of different UAs includes a path header for the at least one UA; appending the routing header to an instance of the SIP request; and transmitting the instance of the SIP request based at least in part on an internet protocol (IP) address in the routing header, wherein the generating the routing header comprises including information regarding the at least one UA in the routing header where the lookup information for the at least one UA does not include the path header, wherein the appending comprises appending a plurality of routing headers to a plurality of instances of the SIP request, and wherein the transmitting comprises transmitting the plurality of instances of the SIP request to the plurality of different UAs.