The variable bandwidth virtual path ATM network and its self-healing performance

This paper discusses the self-healing performance of the new network environment: "variable bandwidth virtual path ATM network", which is suitable for realizing cost-effective B-ISDN and providing various low-cost multimedia services. This network environment is based on the VP-based ATM network architecture and employs bandwidth-resizing technologies for adjusting the bandwidth of VP connections corresponding to changes of their traversing traffic. In this paper, self-healing algorithms are categorized into the pre-plan algorithm and real-time algorithm, whose performances are affected by the variation of the VP's bandwidth in the network. We have developed a simple evaluation model of the variable bandwidth VP network environment for evaluating the pre-plan and real-time algorithms. These 2 algorithms are evaluated based on: (a) the required spare capacities, (b) the restoration time and (c) the robustness to unexpected wide area failure. The simulation results suggests that the real-time restoration algorithm is more suitable for the variable bandwidth VP network environment than the pre-plan restoration algorithm. This is due to it requiring less spare capacity and having greater robustness against wide area failures or topological changes. In addition, the priority-based restoration function is also essential to the self-healing algorithm since it can keep the restoration ratio of the high priority failed VP's at a high value even in a severe situation such as wide-area unexpected failures.