1. A method of providing a group of reachable nodes of a communications environment, said communications environment including a plurality of networks, and said method comprising: dynamically determining a group of reachable nodes of said communications environment, said group of reachable nodes including one or more nodes of the communications environment that can communicate with one another via a same network of the plurality of networks; and making available to one or more nodes of the communications environment an indication of the group of reachable nodes.