Telephone switching systems software architecture: where have we been-where are we going?

Some of the history of telephone switching systems architecture is reviewed, and an overview of the directions being taken in this area is given. The switching software architecture envisioned for the future would allow an operating company to rapidly deploy new services in response to customers´ needs. The open interface between call processing and service processing would permit the company to make deployment decisions based on business and operational considerations, in order to optimize service offerings. In fact, it should be possible to migrate service programs from one platform (e.g. the switch) to another (e.g. a centralized control point) and back again as needs dictate. All this could be done without the need for reprogramming call processing or service processing. With the standard program language used for application programming, every switch (independent of supplier) would have the same application software. That software could be acquired, module by module, from many diverse sources