System and method for scalable and redundant SIP message routing in an IP multimedia subsystem

1. For use in a telecommunication network, an Internet Protocol (IP) multimedia subsystem comprising:

an IP switch capable of receiving Session Initiation Protocol (SIP) messages from an external IP network; and

a plurality of call application nodes capable of executing a plurality of service application groups, wherein each of said service application groups comprises a primary application and a backup application associated with said primary application, wherein said IP switch distributes a first subset of said SIP messages without a group identifier to said plurality of call application nodes according to a load sharing algorithm, wherein each of a second subset of said SIP messages comprises a group identifier capable of identifying one of the service application groups, and wherein said IP switch distributes each SIP message comprising the group identifier to said plurality of call application nodes based on the group identifier, wherein if a group identifier is present the distribution of the SIP message is preformed on the basis of the group identifier, and if no group identifier is present, the distribution of the SIP message is preformed on the basis of the load sharing algorithm.

2. The IP multimedia subsystem as set forth in claim 1 , wherein a first one of said plurality of service application groups is executed on a first one of said plurality of call application nodes and is associated with a similar second one of said plurality of service application groups executed on a second one of said plurality of call application nodes separate from said first call application node.

3. The IP multimedia subsystem as set forth in claim 2 , wherein said first and second service application groups form a first load-sharing group.

4. The IP multimedia subsystem as set forth in claim 3 , wherein said first service application group comprises a first primary application executed on said first call application node and a first backup application associated with said first primary application.

5. The IP multimedia subsystem as set forth in claim 4 , wherein said first backup application resides on a call application node other than said first call application node.

6. The IP multimedia subsystem as set forth in claim 5 , further comprising a plurality of front-end nodes capable of executing a plurality of application level gateway (ALG) application groups, wherein said IP switch distributes said SIP messages to said plurality of front-end nodes for subsequent distribution to said plurality of call application nodes.

7. The IP multimedia subsystem as set forth in claim 6 , wherein a first of said plurality of ALG application groups comprises a first primary ALG application executed on a first front-end node and a first backup ALG application associated with said first primary ALG application.

8. The IP multimedia subsystem as set forth in claim 7 , wherein said first backup ALG application resides on a front-end node other than said first front-end node.

9. A telecommunication network comprising:

a plurality of end-user devices capable of communicating according to the Session Initiation Protocol (SIP);

a Internet protocol (IP) network coupled to said plurality of end-user devices; and

an IP multimedia subsystem coupled to said IP network and comprising:

an IP switch capable of receiving SIP messages from said end-user devices through said IP network, and

a plurality of call application nodes capable of executing a plurality of service application groups, wherein each of said service application groups comprises a primary application and a backup application associated with said primary application, wherein said IP switch distributes a first subset of said SIP messages without a group identifier to said plurality of call application nodes according to a load sharing algorithm, wherein each of a second subset of said SIP messages comprises a group identifier capable of identifying one of the service application groups, and wherein said IP switch distributes each SIP message comprising the group identifier to said plurality of call application nodes based on the group identifier, wherein if a group identifier is present the distribution of the SIP message is preformed on the basis of the group identifier, and if no group identifier is present, the distribution of the SIP message is preformed on the basis of the load sharing algorithm.

10. The telecommunication network as set forth in claim 9 , wherein a first one of said plurality of service application groups is executed on a first one of said plurality of call application nodes and is associated with a similar second one of said plurality of service application groups executed on a second one of said plurality of call application nodes separate from said first call application node.

11. The telecommunication network as set forth in claim 10 , wherein said first and second service application groups form a first load-sharing group.

12. The telecommunication network as set forth in claim 11 , wherein said first service application group comprises a first primary application executed on said first call application node and a first backup application associated with said first primary application.

13. The telecommunication network as set forth in claim 12 , wherein said first backup application resides on a call application node other than said first call application node.

14. The telecommunication network as set forth in claim 13 , further comprising a plurality of front-end nodes capable of executing a plurality of application level gateway (ALG) application groups, wherein said IP switch distributes said SIP messages to said plurality of front-end nodes for subsequent distribution to said plurality of call application nodes.

15. The telecommunication network as set forth in claim 14 , wherein a first of said plurality of ALG application groups comprises a first primary ALG application executed on a first front-end node and a first backup ALG application associated with said first primary ALG application.

16. The telecommunication network as set forth in claim 15 , wherein said first backup ALG application resides on a front-end node other than said first front-end node.

17. For use in an Internet Protocol (IP) multimedia subsystem comprising: i) an IP switch and ii) a plurality of call application nodes for executing a plurality of service application groups, a method of processing Session Initiation Protocol (SIP) messages comprising the steps of:

receiving SIP messages from an external IP network;

distributing a first subset of the SIP messages to the plurality of call application nodes according to a load sharing algorithm, wherein each of the service application groups comprises a primary application and a backup application associated with the primary application, and wherein each of a second subset of the SIP messages comprises a group identifier capable of identifying one of the service application groups; and

distributing each SIP message comprising the group identifier to the plurality of call application nodes based on the group identifier and the absence of the group identifier.

18. The method as set forth in claim 17 , wherein a first one of the plurality of service application groups is executed on a first one of the plurality of call application nodes and is associated with a similar second one of the plurality of service application groups executed on a second one of the plurality of call application nodes separate from the first call application node.

19. The method as set forth in claim 18 , wherein the first and second service application groups form a first load-sharing group.

20. The method as set forth in claim 19 , wherein the first service application group comprises a first primary application executed on the first call application node and a first backup application associated with the first primary application.