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 Veat) and where the connectivity of the topology also allows it.We propose LP (Linear Programming) formulation of the MPP (Multi-Path Protection) problem, where the demand is not only routed, but also protected using multiple parallel paths. Instead of the simplest edge-disjointness we generalise our method to the general SRLG-disjointness that includes node-disjointness as well (SRLG: Shared Risk Link Group).We give a Linear Programming (LP) formulation of the problem that finds the globally optimal solution. The main features of our approach are threefold.First, 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.Second, we present our network transformation model which helps to handle a part of SRLG scenarios in the LP without integer variables.Finally, we generalise and reuse the idea that was developed for MPP, for dedicated path protection (DPP) and show that LP can be used in practice to achieve disjointness of paths. Even if disjointness is not guaranteed, it is achieved with high probability.
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