Patent ID: 7756035
Filing Date: 2010-07-13
Classification: H04L

Abstract:
1. A method of planning routes and allocating route identifiers in a managed frame-forwarding network, the network comprising a set of nodes interconnected by links, with each node being arranged to forward data frames according to a combination of a route identifier and a network address carried by a received data frame and forwarding instructions stored at the node, the method comprising: identifying a sub-set of the nodes which are core nodes of the network, the remaining nodes being outlying nodes; building a spanning tree off each of the identified core nodes, with the spanning tree stopping one link short of any other core node, the spanning tree having a root, and the spanning tree defining a loop-free path between the core node at the root of the spanning tree and a set of outlying nodes; and, planning connections between roots of the spanning trees and allocating a different route identifier to each planned connection between a pair of spanning trees, wherein building the spanning tree off each of the identified core nodes is arranged such that where an outlying node is served by spanning trees rooted on two different core nodes, the paths of the two spanning trees are differently directed to that outlying node, wherein building the spanning tree uses a metric associated with each link and wherein, if the spanning trees provide paths which are co-directed, the value of the metric associated with the co-directed link is adjusted to ensure that on a subsequent iteration of building the spanning trees the paths of the two spanning trees are differently directed.