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 the session request from a calling party to a called party, wherein said called party uses a registered user endpoint (UE) device;
• querying an tElephone NUmbering Mapping (ENUM) server for said called party of said session request;
• determining if at least one Naming Authority Pointer (NAPTR) resource record associated with said called party is received from said ENUM server;
• determining if a Session Initiation Protocol Universal Resource Identifier (SIP URI) is returned in said NAPTR resource record, if said at least one NAPTR resource record associated with said called party is received;
• processing said session request using said SIP URI, if said SIP URI is returned;
• determining if said processing of said session request using said SIP URI resulted in a successful call completion;
• and
• processing said session request using a telephone URI, if said telephone URI is returned and said processing of said session request using said SIP URI resulted in an unsuccessful call completion.

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

• means for receiving the session request from a calling party to a called party, wherein said called party uses a registered user endpoint (UE) device;
• means for querying an tElephone NUmbering Mapping (ENUM) server for said called party of said session request;
• means for determining if at least one Naming Authority Pointer (NAPTR) resource record associated with said called party is received from said ENUM server;
• means for determining if a Session Initiation Protocol Universal Resource Identifier (SIP URI) is returned in said NAPTR resource record, if said at least one NAPTR resource record associated with said called party is received;
• means for processing said session request using said SIP URI, if said SIP URI is returned;
• means for determining if said processing of said session request using said SIP URI resulted in a successful call completion;
• and
• means for processing said session request using a telephone URI, if said telephone URI is returned and said processing of said session request using said SIP URI resulted in an unsuccessful call completion.