A Working Research Prototype of an ISDN Central Office

This paper describes a working research prototype of an ISDN central office which demonstrates the key hardware and software elements needed for ISDN services. As such, it does not include all the normal trappings of a central office such as maintenance or non-ISDN interfaces and there is no attempt to cope with heavy traffic conditions. Details are included on the prototype central office architecture which is a distributed system, the call processing procedure´s and the necessary data structures which provide basic circuit switching and a small number of advanced capabilities. These include the ability to suspend and resume calls at different line appearances, the ability of users to set their own line restrictions and move their services from one line to another, and the allowance of multiple directory number listings for terminals. Also discussed are security aspects of such line controls and commonplace call scenarios which must be considered to avoid deadlocks or incorrect processing by the call processor. Detailed presentations consider all of these aspects within the context of a real-time distributed central office software architecture.