1. A method of determining forwarding information for use in forwarding packets at a first node of a packet-forwarding network, each node of the network having a unique node identifier, the method comprising: determining, by a network node having a processor, shortest paths between the first node and a second node of the network; determining, by the network node, when a plurality of shortest paths have substantially equal-cost; forming, by the network node for each substantially equal-cost path, a set of node identifiers which define the set of nodes in the path; ordering, by the network node, each set of node identifiers using a first ordering criterion to form a path identifier, wherein the first ordering criterion is independent of an order in which node identifiers appear in the path; selecting, by the network node, between the plurality of equal-cost paths by comparing the path identifiers.