SYSTEM AND METHOD OF CONTROLLING DISCOVERY OF A CALL-CONTROL SERVER IN A PACKET DATA NETWORK

摘要

A system and method for directing a Gatekeeper Request Query (GRQ) message or a SIP discovery message to a preferred call control server in a General Packet Radio Service (GPRS (25, 32, 41)), Universal Mobile Telecommunication System (UMTS), or Code Division Multiple Access (CDMA) network. The network may operate with the Session Initiation Protocol (SIP) or the H.323 protocol. A mobile terminal sends the GRQ message to a Gateway GPRS Service Node (GGSN(22)) which is modified with a Server Discovery Agent (SDA(23)). The SDA includes a lookup table (55) comprising a list of preferred gatekeepers, and selects the preferred gatekeeper from the list and unicasts (26) the GRQ message to the selected preferred gatekeeper. The gatekeeper then responds to the mobile terminal. The gatekeeper may send a confirmation message to the SDA. If the SDA does not receive the confirmation message within a predetermined time period, the SDA may select another gatekeeper, or may multicast (33) the GRQ message to a plurality of gatekeepers. Alternatively, the SDA may multicast (42) the GRQ message over a predefined area which is controlled by modifying the Time-to-Live (TTL(46)) field in the header of the packets in the GRQ message.