An efficient exact algorithm for finding two link-disjoint paths with related path cost and QoS constraint

We consider here a problem of QoS routing in survivable networks which provides protection against link failures. In this problem, a pair of link-disjoint paths between the source and the destination has to be established in which they satisfy the total delay path constraint and a related paths cost is optimal (the SNOP-D problem). Although this is a complex problem, the NP-hard behavior seems only to occur in specially constructed graphs, which are unlikely to occur in realistic communication networks. That is the main reason to consider exact multi-constrained routing algorithms. We propose in this paper an efficient exhaustive search algorithm SNOP-D for solving it which is based on the brach-and-bound technique. The major contribution of this paper is an efficient algorithm for finding a primal upper bound of the optimal objective value of this problem. Based on this primal bound, the brach-and-bound search can then perform efficiently. Simulation results show the feasibility of the proposed technique.