cc513 computing systems
DESCRIPTION
CC513 Computing Systems. Interconnection Networks Ω Network. Omega Network. The omega network is another example of a banyan multistage interconnection network that can be used as a switch fabric - PowerPoint PPT PresentationTRANSCRIPT
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CC513 Computing SystemsInterconnection Networks Network
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Omega NetworkThe omega network is another example of a banyan multistage interconnection network that can be used as a switch fabricThe omega differs from the delta network in the pattern of interconnections between the stagesThe omega MIN uses the perfect shuffle
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Perfect ShuffleThe interconnections between stages are defined by the logical rotate left of the bits used in the port idsExample: 000 ---> 000 ---> 000 ---> 000Example: 001 ---> 010 ---> 100 ---> 001Example: 011 ---> 110 ---> 101 ---> 011Example: 111 ---> 111 ---> 111 ---> 111
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8 x 8 OMEGA NETWORK1234675001234567
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Self RoutingOmega network has self-routing propertyThe path for a cell to take to reach its destination can be determined directly from its routing tag (i.e., destination port id)Stage k of the MIN looks at bit k of the tagIf bit k is 0, then send cell out upper portIf bit k is 1, then send cell out lower portWorks for every possible input port (really!)
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Path ContentionThe omega network has the problems as the delta network with output port contention and path contentionAgain, the result in a buffer less switch fabric is cell loss (one cell wins, one loses)Path contention and output port contention can seriously degrade the achievable throughput of the switch
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12346750012345674Path Contention5
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1234675001234567Path Contention
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Performance Degradation1234675001234567104673
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Performance Degradation1234675001234567147063
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Performance Degradation12346750012345673
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A Solution: Batcher SorterOne solution to the contention problem is to sort the cells into monotonically increasing order based on desired destination portDone using a bitonic sorter called a BatcherPlaces the M cells into gap-free increasing sequence on the first M input portsEliminates duplicate destinations
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Batcher-Banyan Example1234675001234567104673
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Batcher-Banyan Example1234675001234567061734
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Batcher-Banyan Example1234675001234567061734
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Batcher-Banyan Example1234675001234567036174
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Batcher-Banyan Example1234675001234567013467