Switch-to-Computer Networking in the Nineties: The Evolution of AT&T's Switch-Computer Interfaces

Abstract

This paper highlights AT&T's role in the evolution of ISDN switch‐to‐computer interfaces. Initially, the digital multiplexed interface (DMI) provided a multiplexed channel for data communications between a computer and a private branch exchange (PBX). DMI evolved to the Integrated Services Digital Network (ISDN) primary rate interface (PRI) that forms the backbone of many customers' networks. While PRI and DMI provided data transport applications based on higher performance, speed, and economy, these applications addressed only part of the potential power of an ISDN‐computer link. In telecommunications, the term “switch‐computer applications interface” (SCAI) is applied to linking computers and switches on an application (as opposed to a connectivity) basis. SCAI combines switches and computers in a client/server arrangement that provides new applications to integrate communications and computing functions. This paper describes the architecture, capabilities, and applications of AT&T's SCAI, the adjunct/switch application interface (ASAI). It addresses the requirements for marketing ASAI, specifically the need to conformance‐test ASAI interface implementations and test the interoperability of switch and computer applications. Finally, it identifies future trends for SCAI standards activities.