MPP: Optimal Multi-Path Routing with Protection

Multi-path routing routes the upcoming demand over multiple paths. This is feasible in networks where the demand can be split into multiple parallel flows, i.e., the network is capable to perform inverse multiplexing (e.g., ngSDH and OTN via VCat) and where the connectivity of the topology also allows it. In this paper we propose the MPP (Multi-Path Protection) scheme, where the demand is not only routed, but also protected using multiple parallel paths. We give a Linear Programming (LP) formulation of the problem that finds the globally optimal solution. The main features of our approach are twofold. First, it always finds a trade-off between the number of parallel paths to be used and the total length of these paths while it balances the traffic optimally between them. Second, we use LP with real variables that is solvable in polynomial time instead of Integer LP (ILP) and still we are able to avoid branching of the flows in nodes different than the source and the target of the considered demand.