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Abstract

A system for rapidly switching at least one virtual local area network (VLAN) from a first loop-free topology to a second loop-free topology in response to a failure within the first loop-free topology. Each VLAN has one 'logical' VLAN which represents the network entities organized into the VLAN and a set of 'physical' VLANs each having its own VLAN designation. For each physical VLAN, a different loop-free topology is defined, although only one physical VLAN is 'active' at any given time. Messages associated with the logical VLAN are tagged with the designation of the currently active physical VLAN, and forwarded along its loop-free topology. Upon detecting a failure in the loop-free topology, the logical VLAN is rapidly switched to the loop-free topology defined by a second, back-up physical VLAN. Following the switch messages associated with the logical VLAN are tagged with the designation of this back-up VLAN and are forwarded along its loop-free topology.

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First Claim