Call processing and signaling in a desktop multimedia conferencing system

The design and implementation of the user-network signaling protocol and call processing software in a desktop multimedia conferencing system are described. The system is built on an EXPANSE broadband network prototype and aims at supporting multimedia and multiparty services such as videophone, video mail, video-on-demand, and video conferencing. A message-based, common-channel signaling protocol is used. It supports multiple connections and multiple parties within a call. The call processing software has a layered structure and is implemented in C++ using an object-oriented approach. The inheritance and virtual function mechanisms of C++ also ease the introduction of new services to the system