RTNR application in the AT&T network

Summary form only given, substantially as follows. The introduction of real-time network routing (RTNR) into the AT&T switched network was completed in July 1991, and completely replaced dynamic nonhierarchical routing (DNHR). RTNR provides the platform for the dynamic class-of-service routing features for emerging new services, and also a provides an ingress/egress routing arrangement to ensure reliability and flexibility for international and access networks. 10 virtual networks have been established to serve major classes-of-service, which share the facilities of the network but provide individual control and monitoring of traffic as well as new priority service capabilities. RTNR allows a marked improvement in network reliability by providing for the selection of over 135 routes between every pair of cities for every call. RTNR performance improvements are illustrated across various network conditions, which include: a) high day loads on the Monday after Thanksgiving, b) peak day loads on Thanksgiving and Christmas, c) a cable cut near Austin, Indiana, in which the combination of RTNR and automatic facility restoration provided excellent recovery from the failure, and d) the international network performance to Taiwan during the Chinese New Year three-day holiday calling period. We conclude that RTNR improves network performance under all network conditions, that it simplifies the operations environment and lowers operations cost, and that it enables the sharing of voice and data network capacity