Session initiation from application servers in an ip multimedia subsystem

Abstract

The present invention provides a technique where application servers can initiate sessions within the IMS network by initially sending session initiation messages to the I-CSCF. By routing the session initiation messages to the I-CSCF, the application servers need not directly access the HSSs in order to initiate sessions. Upon receiving a session initiation message from an application server, the I-CSCF may access the HSS to identify an S-CSCF to use for session control and then route the session initiation message to that S-CSCF. The S-CSCF may then access the same or different HSS to determine how to further route the session initiation message to establish the session. The session initiation message may be routed toward other S-CSCFs en route to the appropriate user elements. The session may be a session established between user elements or between the application server and a user element.

What is claimed is: 
     
         1 . A method of initiating sessions through an Internet Protocol multimedia subsystem (IMS) from an application server, the method comprising:
 at the application server, creating a session initiation message configured to initiate a session through the IMS between a designated originating element and a terminating element;   from the application server, sending the session initiation message directly to an interrogating call/session control function (I-CSCF) in the IMS to initiate the session;   at the I-CSCF, receiving the session initiation message;   determining a first serving call/session control function, S-CSCF, to which the session initiation message should be routed; and   from the I-CSCF, routing the session initiation message to the first S-CSCF.   
     
     
         2 . The method of  claim 1 , wherein the I-CSCF is identified in route information provided in the session initiation message. 
     
     
         3 . The method of  claim 1 , wherein the designated originating element is the application server, the terminating element is a user element, and the session is established between the application server and the user element. 
     
     
         4 . The method of  claim 1 , wherein the designated originating element is a first user element, the terminating element is a second user element, and the session is established between the first user element and the second user element. 
     
     
         5 . The method of  claim 1 , wherein the application server is outside of the IMS. 
     
     
         6 . The method of  claim 1 , wherein the I-CSCF is adapted to determine the first S-CSCF to which the session initiation message should be routed, and to route the session initiation message to the first S-CSCF. 
     
     
         7 . The method of  claim 1 , wherein the first S-CSCF is determined based on the designated originating element. 
     
     
         8 . The method of  claim 7 , wherein determining the first S-CSCF comprises:
 sending a request to identify the first S-CSCF to a home subscriber server; and   receiving information identifying the first S-CSCF.   
     
     
         9 . The method of  claim 7 , further comprising:
 at the first S-CSCF, receiving the session initiation message;   determining a terminating S-CSCF associated with the terminating element; and   from the first S-CSCF, routing the session initiation message to the terminating element to effect establishment of the session.   
     
     
         10 . The method of  claim 1 , further comprising, at the I-CSCF, relaying session messages between the designated originating element and the terminating element. 
     
     
         11 . The method of  claim 1 , wherein the I-CSCF and the S-CSCF are implemented on separate service nodes. 
     
     
         12 . The method of  claim 1 , wherein the I-CSCF and the S-CSCF are implemented on a common service node. 
     
     
         13 . A method of supporting at a serving call/session control function (S-CSCF) initiation of sessions through an Internet Protocol multimedia subsystem (IMS) from an application server, the method comprising:
 at the S-CSCF, receiving a session initiation message from an interrogating call/session control function (I-CSCF), the session initiation message being configured to initiate a session through an IMS between a designated originating element and a terminating element;   determining a terminating S-CSCF associated with the terminating element; and   from the first S-CSCF, routing the session initiation message to the terminating element to effect establishment of the session.   
     
     
         14 . The method of  claim 13 , wherein the I-CSCF is identified in route information provided in the session initiation message. 
     
     
         15 . The method of  claim 13 , wherein the designated originating element is the application server, the terminating element is a user element, and the session is established between the application server and the user element. 
     
     
         16 . The method of  claim 13 , wherein the designated originating element is a first user element, the terminating element is a second user element, and the session is established between the first user element and the second user element. 
     
     
         17 . The method of  claim 13 , wherein the I-CSCF and the S-CSCF are implemented on separate service nodes. 
     
     
         18 . The method of  claim 13 , wherein the I-CSCF and the S-CSCF are implemented on a common service node.