US Patent 7471669 Routing of protocol data units within a communication network

A protocol data unit is routed along a path between a first node and a second node within a communication network. The protocol data unit carries routing information which specifies the path in the form of a list of identifiers of the links to be followed towards the second node. At each intermediate node, the link identifier for the link just traversed with a link identifier for the corresponding link in the reverse direction towards the first node. At any point along the path the protocol data unit carries information which allows it to be carried towards the second node, or to follow a reverse path towards the first node. This reverse path can be used to report a fault to the first node.