Patent ID: 7027453
Filing Date: 2006-04-11
Classification: H04L

Abstract:
1. Apparatus for determining paths for forwarding frames among end stations in a system of interconnected local area networks, comprised of: first and second groups of frame forwarding devices known as bridges, which are used to interconnect local area networks; a spanning tree cooperating with said groups of bridges for providing loop-free frame forwarding; said first and second groups of bridges having means for determining tree paths for loop-free frame forwarding to an end station; said second group of bridges having further means cooperating with said first group of bridges to determine an alternate path for loop-free forwarding of a frame to the end station, which alternate path is shorter than any tree path to said end station wherein bridges of said second group are respectively arranged upstream and downstream of an intervening bridge of said first group in a common tree path and said bridges of said second group including means for encapsulating a received frame with a source address and a destination address enabling transfer through the intervening bridge, wherein (a) wherein a cross-link incident on a said downstream bridge is a segment on said alternate path, said transfer through the intervening bridge is in the downstream direction, and (b) wherein a cross-link incident on said upstream bridge is a segment on said alternate path, said transfer through the intervening bridge is in the upstream direction.