Patent ID: 8228900

Claim:
A method of routing a Session Initiation Protocol (SIP) message within an IP Multimedia Subsystem (IMS), the message originating at an IMS/SIP client attached to a visited network and containing as its destination address, a Telephone Uniform Resource Indicator (TEL URI) including a local telephone number, the method comprising: at the IMS/SIP client, specifying whether the telephone number is a local number of the visited network or a local number of a home network of the client; determining one of a global number digit set or a domain name of the network specified in the specifying step, wherein the IMS/SIP client resides in a mobile wireless terminal, and the global number digit set or domain name identifying the home network is preconfigured into an IP Multimedia Services Identity Module (ISIM) or Universal Subscriber Identity Module (USIM) of the terminal, and wherein the IMS/SIP client obtains at radio protocol layers of the terminal, the global number digit set or domain name identifying the visited network; including at the IMS/SIP client, a phone-context within the TEL URI, said phone-context containing the determined global number digit set or domain name; delivering the message from the IMS/SIP client to the home network; and routing the message by the home network according to the phone-context contained within the TEL URI.