Matching Output Queueing with Combined Input and Output Queueing

At very high aggregate bandwidths, output queueing is impractical because of insufficient memory bandwidth. This problem is getting worse: memory bandwidth is improving slowly, whereas the demand for network bandwidth continues to grow exponentially. The difficulty is that outputqueued switches require memories that run at a speedup of N, where N is equal to the number of switch ports. This paper addresses the following question: Is it possible for a switch to exactly match outputqueueing with a reduced speedup? We prove that if virtual output queueing is used, a combined input-output queued switch is always work-conserving if its speedup is greater than . This result is proved using a novel scheduling algorithm the Home Territory Algorithm (HTA).