Virtual path routing for survivable ATM networks

Abstract

The advent of high-capacity optical fiber has increased the impact of a network failure in high-speed networks since a large volume of data can be lost even in a short outage. Self-healing algorithms have previosly been proposed to achieve fast restoration from a failure, but their success greatly depends on how traffic is distributed and how spare capacity is dimensioned over the network when a failure happens. Thus, in order to offer better network survivability, it is crucial that a network manager realizes a restorable traffic assignment in response to changing traffic demand and facility network configuration. The authors address the problem of virtual path routing for survivable asynchronous transfer mode (ATM) networks. An algorithm is developed to find a virtual path configuration and bandwidth assignment that minimizes the expected amount of lost flow upon restoration from a network failure. The concept of two-step restoration is introduced to achieve fast restoration as well as optimal reconfiguration. The problem can be formulated as a nonlinear, nonsmooth multicommodity flow problem with linear constraints. A modified flow deviation method is developed to obtain a near-optimal solution, where premature convergence to a nonsmooth point could be avoided by adjusting an optimization parameter. The result of the performance evaluation indicates that the proposed routing scheme can detect the links that are vulnerable to a failure under the current traffic demand pattern and adjust a flow so as to improve the network survivability level.