Patent ID: 6982977

Claim:
A packet routing/switching method comprising: defining a hierarchical plurality of label switched paths (LSP)/forwarding adjacency-label switched paths (FA-LSP) through a network of nodes from a lowest (least-nested) level to a highest (most-nested) level, each LSP/FA-LSP comprising a respective sequence of nodes comprising at least a source node and a destination node and possibly one or more transit nodes; to route/switch a packet flow from a first source node of said network of nodes to a first destination node of said network of nodes: a) maintaining at the first node a mapping between the packet flow and a first LSP of the hierarchical plurality of LSP/FA-LSPs defined between the first source node and the first destination node; b) at the first source node, for each packet of said packet flow, adding to the packet label switched routing information comprising an LSP label identifying the first LSP and sending the packet to subsequent node(s) in the sequence of nodes defined for the first LSP; c) at each node to which the packet is routed/switched other than said first source node: i) if the node is a source node of a higher level FA-LSP than the LSP/FA-LSP identified by the LSP label of the packet, changing the LSP label in the label switched routing information to indicate the source node of the higher level FA-LSP, and including in the label switched routing information hierarchy information in respect of all lower level LSP/FALSPs in the hierarchy leading up to the higher level FA-LSP and forwarding the packet to the next node in the sequence of nodes defined for the higher level FA-LSP; ii) if the node is only a transit node, forwarding the packet to the next node in the sequence of nodes defined for the LSP/FALSP identified by the LSP label; iii) if the node is a destination node of a higher level FA-LSP, changing the LSP label in the label switched routing information to indicate the source node of the next lower level LSP/FA-LSP indicated by the hierarchy information, and changing the hierarchy information to include only hierarchy information in respect of LSP/FA-LSPs in the hierarchy leading up to but not including the next lower level LSP/FA-LSP, and forwarding the packet to the next node in the sequence of nodes defined for the next lower level LSP/FA-LSP.