Alternate routing of communications in a packet-based network

Abstract

A method for performing alternate and therefore least cost routing in distributed H.323 Voice over IP (VoIP) networks is provided. With this method, the VoIP network consists of a hierarchy of gatekeeper (GK) functions to provide alternate routing, network element redundancy, and scalability. The alternate routing function is performed by a directory gatekeeper with route selection advancing from a first route to a second route by either of two conditions: (1) there are no resources available to terminate the call in the first zone; and (2) a lack of response to the directory GK request for such resources.

What is claimed is: 
     
         1 . A method for performing alternate routing comprising:
 receiving a request to initiate a session for communicating data;   in response,
 selecting a route from a list of possible routes by querying a resource management gatekeeper to determine availability of outbound gateway resources associated with the selected route based on outbound gateway resource availability reported to the resource management gatekeeper; 
 if a route is available, sending a response to the received request indicating the selected route; and 
 if a route is not available, sending a response to the received request indicating that the request cannot be completed. 
   
     
     
         2 . The method as recited in  claim 1 , further comprising:
 in response to the querying act, if the resource management gateway indicates that no outbound gateway resources associated therewith are available, selecting a route from the list of possible routes by querying a second resource management gatekeeper to determine availability of outbound gateway resources associated with the selected route based on outbound gateway resource availability reported to the second resource management gatekeeper.   
     
     
         3 . The method as recited in  claim 1 , wherein the list of possible routes comprises routes corresponding to a numbering plan area (NPA) associated with the session. 
     
     
         4 . The method as recited in  claim 1 , wherein the data is voice data. 
     
     
         5 . The method as recited in  claim 1 , wherein each route in the list of possible routes is associated with a particular resource management gatekeeper. 
     
     
         6 . The method as recited in  claim 5 , wherein the act of selecting a route from the list of possible routes further comprises:
 selecting a candidate route from the list of possible routes; and   determining if the selected candidate route is available by querying the resource management gatekeeper.   
     
     
         7 . The method as recited in  claim 6 , wherein the candidate route is the least cost route from the list of possible routes. 
     
     
         8 . The method as recited in  claim 6 , wherein the candidate route is selected in accordance with a predetermined ratio. 
     
     
         9 . The method as recited in  claim 8 , wherein the likelihood of selecting each of the one or more candidate routes is substantially equal in accordance with the predetermined ratio. 
     
     
         10 . The method as recited in  claim 6 , wherein the selecting acts are performed by a directory gatekeeper, and wherein if each resource management gatekeeper accessible to the directory gatekeeper indicates that no outbound gateway resources are available for the selected candidate route, the method further comprising:
 selecting a second candidate route from the list of possible routes; and   determining if the selected candidate route is available by querying the resource management gatekeeper.   
     
     
         11 . The method as recited in  claim 1 , wherein the request to initiate the session is received by an inbound gatekeeper, the method further comprising:
 receiving, by a directory gatekeeper, a routing request from the inbound gatekeeper to determine a route for initiating the session.