MetaRouters
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Fault Tolerance

A Banyan or Butterfly network can be made fault tolerant.

• The topology can be made redundant by doubling the number of links.

• The path-based routing algorithm has to be modified to handle the redundant topology.

A MetaRouter can be made fault tolerant.

• The topology can be made redundant by adding a another row of hardware.

• The destination-based routing algorithm can handle the redundant topology without modification.

A fault tolerant Banyan or Butterfly network requires more hardware by a factor of 4 than a fault tolerant MetaRouter. A fault tolerant MetaRouter based on 12 port routers will survive 5 simutaneous faults, while a fault tolerant Banyan or Butterfly network will only survive a single fault.