Patent attributes
A routing algorithm has particular advantage in sparsely connected networks in which nodes have a ranked set of alternative routes to a destination node, these routes being node-disjoint. Setup messages have an additional information element for the identity of a virtual source node, and a source node inserts its own identity in the virtual source information element. Unless a node is the destination for a message, it examines the content of the virtual source information element of a message, and if there is no match with its own identity it selects from its routing table a predetermined alternative route for the destination node. If that route is unavailable, the node replaces the content of the virtual source information element with its own identity, performs routing on the basis that there is now a match with its own identity, i.e. it behaves as if it had generated the message. It selects from its routing table the highest ranking of the set for the destination node, and in the event of a fault on the highest ranking route, tries one or more lower ranking routes. If no route is available, the node replaces the content of the virtual source information element with the identity of the node from which it was received, and sends the message back to the node from which it was received.
