Patent ID: 8886244

Claim:
A method for ensuring critical resource availability in a push-to-talk (PTT) communications environment comprising: identifying critical resources required for a group call that belong to a secondary PTT communications system by a controlling PTT communications system that is a home system for a subscriber group to which an originating PTT subscriber unit of the group call belongs, wherein the controlling and secondary PTT communications systems are members of a PTT communications environment, wherein the controlling and secondary PTT communications systems communicate using an expanded network-to-network interface (NNI), wherein said expanded NNI represents a NNI that has been modified to encompass messaging and procedural elements supporting management of critical resource availability; requesting allocation of the identified critical resources for the group call from the secondary PTT communications system using the expanded NNI; and in response to a successful allocation of the requested critical resources by the secondary PTT communications system, authorizing of the group call by the controlling PTT communications system, wherein the allocated critical resources of the secondary PTT communications system are used in establishing the group call.