Method and Apparatus for Exchanging Routing Information and the Establishment of Connectivity Across Multiple Network Areas

Abstract

Routes may be installed across multiple link state protocol controlled Ethernet network areas by causing ABBs to leak I-SID information advertised by BEBs in a L1 network area into an L2 network area. ABBs will only leak I-SIDs for BEBs where it is the closest ABB for that BEB. Where another ABB on the L2 network also leaks the same I-SID into the L2 network area from another L1 network area, the I-SID is of multi-area interest. ABBs will advertise I-SIDs that are common to the L1 and L2 networks back into their respective L1 network. Within each L1 and L2 network area, forwarding state will be installed between network elements advertising common interest in an ISID, so that multi-area paths may be created to span the L1/L2/L1 network areas. The L1/L2/L1 network structure may recurse an arbitrary number of times.

What is claimed is: 
     
         1 - 21 . (canceled) 
     
     
         22 . A method of associating a set of boundary edge bridges (BEBs) of a layer X network area with a first of a plurality of area boundary bridges (ABBs) interfacing the layer X network area with a layer X+1 network area, the method comprising:
 receiving, by backbone core bridges (BCBs) of the layer X network area, advertisements indicating an ability of the ABBs to reach a virtual BEB representing the layer X+1 network area into the layer X network area; and   installing, by the BCBs, shortest path connectivity between the virtual BEB advertised by the ABBs and the BEBs in the layer X network area, wherein if a shortest path from a BEB to the virtual BEB passes through the first of the ABBs, the BEB is in the set of BEBs associated with that first ABB.   
     
     
         23 . The method of  claim 22 , wherein the virtual BEB is advertised into the layer X network area by all ABBs interfacing between the layer X network area and the layer X+1 network area. 
     
     
         24 . The method of  claim 23 , wherein the ABBs all advertise the virtual BEB as being connected via equal cost links. 
     
     
         25 . The method of  claim 22 , further comprising:
 receiving, by the first of the ABBs, link state advertisements containing community of interest identifiers from all BEBs in the layer X network area; and   selectively leaking, by the first of the ABBs into the layer X+1 network area, community of interest identifiers received from the set of BEBs by the first of the ABBs.   
     
     
         26 . The method of  claim 22 , further comprising leaking at least some of the community of interest identifiers received from the set of BEBs into the layer X network area.