Patent ID: 7403484

Claim:
A network unit for use in a switching fabric comprising a plurality of network units each having ports for the reception and forwarding of data packets, each unit having at least one fabric port connected to a partner port on another one of the network units by at least one of a multiplicity of links which interconnect the network units; wherein said network unit is organized: (a) to store a table which for each network unit in the switching fabric indicates a respective change identification number; (b) on the detection of a change in operational status relating to the unit to increment the unit's change identification number; (c) to broadcast protocol packets which indicate the incremented change identification number; (d) to receive corresponding packets from the other units; (e) to updates said table in accordance with incremented values; (f) to determine when the last change identification numbers in said are the same for all the units; and wherein said network unit maintains an indication of a fabric state for all the units, the fabric states including a first ‘stable’ state denoting normal operation and a second ‘unstable’ state indicating lack of match of change identification numbers.