Reliability constrained routing in QoS networks

The issue of handling network failures is becoming increasingly important. In this paper, we address the problem of constrained routing by treating reliability as one of the QoS requirements. The problem is to create a feasible path from a given node to the destination such that the bandwidth and reliability requirements of the path are satisfied and the cost of the path is minimized (Reliability Constrained Least Cost Routing Problem). To solve the problem, we propose an approach which employs a novel concept, called partial protection, wherein backup paths are created for a selected set of domains in the network so as to meet the reliability constraints. The Partial Protection Approach (PPA) has two steps: Primary Path Creation and Backup Path Creation if necessary. To implement PPA, we propose three scalable two-pass resource reservation schemes, viz., Conservative, Optimistic, and Hybrid schemes. These schemes differ depending on whether the backup paths are created during the forward pass, reverse pass, or both. We evaluate the performance of the proposed schemes for dynamic multicast groups with different bandwidth and reliability requirements using average call acceptance rate and average tree cost as performance metrics. Our studies show that group dynamics and reliability requirements have significant impact on the performance of the schemes.