Patent ID: 6876625

Claim:
A method for recovery from a failure which affects an active routing entity in a communications network, the active routing entity being associated with a network node of the communications network, the communications network comprising a routing protocol for intermittent advertisement of local state information throughout the network and further comprising an inactive routing entity to which network connections of the network node can be diverted from the active routing entity upon the said failure, the method comprising the steps of: (a) upon the failure, executing an activity switch between the active routing entity and the inactive routing entity, wherein network connections of the network node are diverted from the active routing entity to the inactive routing entity to thereby transform the inactive routing entity into a newly active routing entity; (b) following the activity switch, exchanging topology state information between the newly active routing entity and each immediately adjacent neighbour node of the network node associated with said failure such that the newly active routing entity and every said immediately adjacent neighbour node respectively possess synchronized topology state information; and wherein the exchange of topology slate information between the newly active routing entity and each said immediately adjacent neighbour node is performed without withdrawal, by the network node associated with said failure and by each said immediately adjacent neighbour node, of the said intermittent advertisement of local state information as it pertains respectively to the network node associated with said failure and to each said immediately adjacent neighbour node.