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Since 1976 the 4ESSTM switch and its 1A processor had been the workhorse of the network. As technology advanced and customers required new services, the capacity of the 4ESS switch came close to being exhausted, making it necessary to develop a successor to the 1A processor. Developers of the 1B processor were presented with the challenge of designing and implementing a system that could accommodate the new network demands, that would be “like a 1A, only better.” This paper describes several problems encountered during that project and how they were solved.

This paper describes the dramatic changes taking place in the architecture and capabilities of the wide area network as it evolves from a collection of several servicespecific networks, each typically supporting only one transport protocol, to a single multiprotocol network supporting a variety of services. The paper also discusses the technological forces driving this evolution and considers its practical implications.