  Link state routing protocols such as OSPF or IS-IS currently use only best
paths to forward IP packets throughout a domain. The optimality of sub-paths
ensures consistency of hop by hop forwarding although paths, calculated using
Dijkstra algorithm, are recursively composed. According to the link metric, the
diversity of existing paths can be underestimated using only best paths. Hence,
it reduces potential benefits of multipath applications such as load balancing
and fast rerouting. In this paper, we propose a low time complexity multipath
computation algorithm able to calculate at least two paths with a different
first hop between all pairs of nodes in the network if such next hops exist.
Using real and generated topologies, we evaluate and compare the complexity of
our proposition with several techniques. Simulation results suggest that the
path diversity achieved with our proposition is approximatively the same that
the one obtained using consecutive Dijsktra computations, but with a lower time
complexity.
