TOPS: An architecture for telephony over packet networks

Packet telephony is of increasing interest in both the telecommunications a nd internet communities. The emergence of packet telephony mill a create ne w services, and presents an opportunity to rethink how conventional telepho ny services are implemented, In this paper, we present an architecture for telephony over packet networks (TOPS), TOPS allows users to move between te rminals or to use mobile terminals while being reachable by the same name. TOPS users can have multiple terminals and control how calls are routed to them, TOPS allows for terminals with a range of capabilities such as suppor t for video, whiteboard, and other media with a variety of coding formats. TOPS retains the necessary information on terminal capabilities to determin e the appropriate type of communication to be established with the remote t erminal. The architecture assumes that the underlying network supports the establishment of end-to-end connectivity between terminals, with an appropr iate quality of service, The components of TOPS are a directory service, an application layer signal ing protocol, and a logical channel abstraction for communication between e nd-systems, The directory service maps a user's name to a set of terminals where the user may be reached. A user can control the translation operation by specifying profiles that customize how his name is mapped to a set of t erminals where he can be reached. Terminal capabilities are also stored in the directory service. The application layer signaling protocol establishes and maintains call state between communicating terminals, The logical chan nel abstraction provides a shared end-to-end contest for a call's constitue nt media and control streams, while isolating the applications from the det ails of the network transport mechanisms. In addition to supporting simple point-to-point calls! the architecture supports both centralized and decent ralized conferencing. We also introduce a simple encapsulation format for v oice.