Patent ID: 8055262

Claim:
A communications network, comprising: a plurality of dispatch application servers (DAS); a serving call session control function (S-CSCF) device located in a first IP multimedia subsystem (IMS) core, the S-CSCF device adapted to: receive an IMS registration request from a subscriber unit; authenticate said IMS registration request; send an IMS registration confirmation to said subscriber unit; and send a notification indicating said IMS registration to an event notification server; and an event notification server coupled to the S-CSCF device, coupled to another S-CSCF device located in a second IMS core, and coupled to the plurality of dispatch application servers, the event notification server adapted to: receive said registration notification from said S-CSCF device; select from among one of said plurality of dispatch application servers (DAS) a first DAS associated with the first IMS core or a second DAS associated with the second IMS core based on information related to the location domain, location and address associated with said subscriber unit in said registration notification; and send an assignment notification to said selected dispatch application server (DAS) indicating an assignment to provide dispatch service to said subscriber unit; wherein said event notification server is adapted to use a look up table to determine said selected dispatch application server based on said location domain, location and address information.