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Two-Stage Switch. High-Performance Networking Group Isaac Keslassy, Nick McKeown. Scheduler. inputs. outputs. Input-Queued Packet Switch. Crossbar. 1. N. 1. N. Round-Robin Scheduling. Uniform & non-bursty traffic => 100% throughput Problem: traffic is non-uniform & bursty. 1. 1. - PowerPoint PPT Presentation
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High PerformanceSwitching and RoutingTelecom Center Workshop: Sept 4, 1997.
Two-Stage Switch
High-Performance Networking Group
Isaac Keslassy, Nick McKeown
Input-Queued Packet Switch
Crossbar
Scheduler
inputs
outputs
1
N
1 N
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Round-Robin Scheduling
• Uniform & non-bursty traffic => 100% throughput
• Problem: traffic is non-uniform & bursty
Two-Stage Switch (I)
1
N
1
N
1
N
External Outputs
Internal Inputs
External Inputs
First Round-Robin Second Round-Robin
[C.S.Chang et al.: http://www.ee.nthu.edu.tw/~cschang/PartI.pdf]
Two-Stage Switch (I)
1
N
1
N
1
N
External Outputs
Internal Inputs
External Inputs
First Round-Robin Second Round-Robin
Load Balancing
[C.S.Chang et al.: http://www.ee.nthu.edu.tw/~cschang/PartI.pdf]
Two-Stage Switch (I)
1
N
1
N
1
N
External Outputs
Internal Inputs
External Inputs
First Round-Robin Second Round-Robin
• No scheduling• Problem: unbounded mis-sequencing
Two-Stage Switch (II)
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F ik
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FlowSplitter
LoadBalancer VOQs First-Stage Round-Robin Second-Stage Round-RobinVOQs
External inputs Internal outputs Internal inputs External outputs
1 1 1
N N N
1
N
1
N
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[Infocom’02 paper: http://klamath.stanford.edu/~keslassy/tmp/two-stage.pdf]
New
N3 instead of N2
Current Work
• Practical implementation of this scheme
• Statistical bounds on mis-sequencing• Queue length distributions• TCP properties
An optical two-stage switch
1
2
3
Phase 2
Phase 1