Transport network architectures in an IP world

Abstract

We develop a telecommunications architecture based on IP routers and compare it empirically to the current TDM hierarchy. The study is based on two premises: first that data traffic will continue to grow much faster than voice traffic and will be mostly IP, and second, that IP routers and networks will soon achieve the scalability and dependability necessary to provide the service quality expected of telecommunications networks. The IP architecture exploits a number of mechanisms to improve network efficiency: mesh restoration requires less spare bandwidth than SONET rings; private line services are carried as virtual leased lines, enabling more fine-grained bandwidth offerings; a voice subnetwork uses OC-48 links rather than DS-1 trunk groups, so it requires less total bandwidth to achieve the same blocking probability; and the multiplying inefficiencies of layer-by-layer routing in the TDM hierarchy are avoided. We find that an all-IP architecture could offer much greater network efficiency and considerable capital savings. We examine how technology must evolve to support such an architecture.