Method and apparatus for completing a circuit switched service call in an internet protocol network

A computer-readable medium having stored thereon a plurality of instructions, the plurality of instructions including instructions which, when executed by a processor, cause the processor to perform steps of a method for processing a session request in an Internet Protocol (IP) network, comprising:

• receiving by a Proxy-Call Session Control Function (P-CSCF) the session request from a calling party;
• determining if a Session Description Protocol (SDP) value of said session request is for a service provided over the IP network or a circuit switched network;
• forwarding said session request towards a Serving-Call Session Control Function (S-CSCF) of said calling party, if said SDP value of said session request indicates a service that is provided over said IP network;
• and
• forwarding said session request to said circuit switched network, if said SDP value of said session request indicates a service that is provided over said circuit switched network.

An apparatus for processing a session request in an Internet Protocol (IP) network, comprising:

• means for receiving by the session request from a calling party;
• means for determining if a Session Description Protocol (SDP) value of said session request is for a service provided over the IP network or a circuit switched network;
• means for forwarding said session request towards a Serving-Call Session Control Function (S-CSCF) of said calling party, if said SDP value of said session request indicates a service that is provided over said IP network;
• and
• means for forwarding said session request to said circuit switched network, if said SDP value of said session request indicates a service that is provided over said circuit switched network.