A fundamental unsolved challenge in multipath
routing is to provide disjoint end-to-end paths, each one satisfying
certain operational goals (e.g., shortest possible), without overwhelming
the data plane with prohibitive amount of forwarding
state. In this paper, we study the problem of finding a pair
of shortest disjoint paths that can be represented by only two
forwarding table entries per destination. Building on prior work
on minimum length redundant trees, we show that the underlying
mathematical problem is NP-complete and we present heuristic
algorithms that improve the known complexity bounds from
cubic to the order of a single shortest path search. Finally, by
extensive simulations we find that it is possible to very closely
attain the absolute optimal path length with our algorithms (the
gap is just 1–5%), eventually opening the door for wide-scale
multipath routing deployments
