Originating endpoints may obtain reachability information from a directory service, which collects contact and related information from available users. When initiating a peer-to-peer communication session to an endpoint of a destination user, the originating endpoint will access the directory service to obtain reachability information for the destination user. The reachability information may contain one or more addresses, one of which will be a peer-to-peer communication session address. From the reachability information, the originating terminal will determine an appropriate address to initiate communications with the destination user. The reachability information may identify multiple addresses, where only certain of the addresses may be peer-to-peer communication addresses and other addresses may be used to establish other types of sessions through disparate types of networks.