Configuring express pipes in emerging telecommunication networks

Abstract

Over the past few decades, telecommunication networks have been designed and implemented to support a wide variety of services, including the integration of a customer's voice, data and video communication requirements. Rapid advances in VLSI technology, coupled with declining costs of fiber-based transmission systems, have resulted in high speed, broadband digital networks capable of transporting hundreds of megabits per second. At the same time, a growing number of business customers have expressed the need for controlling and re-configuring their private networks themselves, to better match their business needs. In digital networks, a key component in allowing this flexibility is the establishment of intelligent Digital Cross-Connect Systems (DCS). With DCS, network re-configuration, including bandwidth allocation and topology changes, can be made on a near real time basis, or be scheduled on a reservation basis to take place once (or multiple times) in the future. In this paper, we study the application of digital cross-connect systems in packet switched networks. These systems allow the designer to configure express pipes or direct links between source--destination pairs that have high communication traffic requirements. Since express pipes are configured by borrowing channels from the underlying, leased, backbone network, establishing a direct link reduces the number of "free" channels available for regular switched traffic, and consequently have the potential of increasing queueing delays. We formulate the problem of judiciously selecting express pipes as a 0/1 nonlinear integer programming problem, that seeks to minimize overall network delay. An efficient Lagrangian relaxation based solution procedure is proposed. Results of computational experiments with the proposed solution technique are also reported.