The authors describe efforts to develop the Q.931 protocol software for the 5ESS Central Office Switch. Q.931 is a layer-3 message-based, user/network interface protocol for the integrated services digital network (ISDN). The approach uses a single formal specification written in the Augmented Protocol Specification Language to model the 1.931 protocol as a set of communicating extended finite state machines. From this specification, tools validate the protocol and generate the bulk of a C language implementation. The authors successfully integrated this code, along with other handwritten code, into a working system in the lab. Their results demonstrate that protocol tools can be used effectively to develop high quality protocol software quickly from formal specifications.>

The software architecture of a multimedia workstation connected to an experimental packet switching network which is capable of switching voice, data, and video simultaneously is described. The user of a multimedia workstation may engage in several multimedia calls, each using multiple information streams consisting of voice, data, and images. The network interface software in the workstation maintains the temporal relationship among a given call's information streams. For each call, the network interface provides a multiple information channel interface to upper layer software supporting the notion of a multimedia virtual circuit. A connector mechanism is provided to control the information exchange among the network interface, the various voice, data, and image peripherals, and the computer programs used in a multimedia application. These information sources and sinks share a common abstraction called active devices.>