The status ahd evolution of ISDN in the united states

Abstract

ISDN is being rapidly deployed in the United States. Each of the Regwnal Bell Operating Companies as well as several independent telephone companies currently offer ISDN commercial service through use of the basic rate interface. AT&T has been leading the way for intererchange carrier implementation of ISDN by providing primary-rate-interface-based services via direct connections to the AT&T service node. The major interexchange carriers have ako deployed Signaling System No. 7 throughout their networks. Equipment for ISDN implementation i s predominantly supplied by AT&T and Northern Telecom; however, European and Japanese vendors are ako active in the United States market.. The local exchange carrier 'sprimary motivation for centralofice based ISDN has been to provide business sewices which are competitive with digital PBX's. There are several impediments to residential ISDN which make it unlikely that it wit1 be common in the United States for several years. One of the most common configurations for deploying central ofice based ISDN is the use of remote vehicles. Remoting strategies have reduced cost through pair gain and, in some installotionst the ability to use T (rather than relatively erpensive U) line carakandeliminate NT1 's. One of the Iorgest drawbacks for ISDN Cenaer today is that it mists in ishnds where end-to-end ISDN functionality i s only available to subscribers on the same switch. Increasing deployment of Signaling System No. 7 by the local erchange carriers and interconnection with intererchange carrier SS7 networks should remedy this situation. Interexchange carriers are deploying the ISDNprimary rate interface to provide more attroctiw service oferings for customers who connect directly to their service node. Customer demand for the ATdiTprimary rate interface has been very strong. The single most sought after function on the primary rate has been delivery of calling party number which is usedpredominantly in telemarketing applicatwns. Other functions such as more eficient trunk usage, the use of switched HO and H l l channels and message associated user to user information are also drawing increasing attention. PBX vendors are placing initial emphasis on the primary rate interface in order to gain access to the nationwide ISDN capabilities offered by AT&T There has been less emphasis on the basic rate because PBX's already support sophisticated voice telephone functionality via proprietary intetfaces. These pmprietary solutions are generally lower cost than basic rate and support a wide range of supplementary services. However, these pmprietary interfaces do not currently support either passive bus or D-channel data finctionality. There is a very limited availobility of ISDN trunk arrangements, all of which are based on the primary rate, by which PBX's can access the h a 1 uchnnge cawier ISDN networks.