Analysis of Routing Issues in the Design of Packet Networks

Abstract

An analysis of several routing issues that have an impact on the topological design of nonhierarchical packet networks is presented. Routing constraints that arise due to the limits on maximum number of hops and maximum number of paths and due to the virtual circuit mode of operation have an impact on critical network design parameters such as trunk costs, topological connectivity, and average packet delay. The analysis is conducted through a design algorithm that configures cost-effective networks subject to an end-to-end mean delay constraint and specified routing constraints. The analysis indicates that significant savings in trunk costs can be realized when the hop and path constraints are relaxed from one to three. Beyond these limits, however, the reduction in network cost is marginal. Furthermore, it is more cost effective to allow flow bifurcation over multiple paths than to allow longer paths. Virtual circuit routing constraints have a significant impact on network costs under highly unbalanced loads; however, their impact is minimal under more realistk traffic patterns. The analysis also shows that network designs based solely on a network average delay constraint may lead to high end-to-end delays for some node pairs. The algorithm described here is capable of controlling the end-to-end delays for all node pairs at little or no additional costs.