On Survivability in IP Networks

In this paper, we examine different aspects of the survivability in IP networks by experimentation on several current IP backbone network topologies. Maintaining service continuity even under failures requires redundancy in terms of connectivity and capacity. We analyze the cost of survivability for protection against single node failures for traditional OSPF based recovery as well as current MPLS based schemes using local or end-to-end recovery. We examine how link weight adjustments and careful introduction of a small number of new links in the network can significantly reduce the cost of network operation for survivability. The traffic matrix in the network can change significantly over time. However, our simulation results indicate that the benefits of weight adjustments and new link additions are robust to variations in the traffic matrix. We also investigate the relationship between load balancing and the cost of survivability and show that gaining a better degree of load balance in the network through the link weight adjustments may involve sacrificing the savings in the cost of operating the network and vice versa.