Combining distributed and centralized arbitration schemes for combined input-crosspoint buffered packet switches

Combined input-crosspoint buffered (CICB) packet switches perform input and output arbitrations separately. This arbitration separation permits distributed selection for both inputs and outputs. While input arbitrations are implemented in a distributed manner because inputs are located in different physical locations, output arbitrations can be implemented in either distributed or centralized manner since output arbiters are placed in the buffered crossbar. An advantage of using a centralized output arbitration approach is that more complex schemes can be executed without completely sacrificing the timing efficiency that CICB switches are known to have. In this paper, we introduce a hybrid arbitration approach that combines a distributed selection scheme at the inputs and a centralized selection scheme at the outputs. By using this hybrid approach, we show that a CICB switch with the minimum crosspoint-buffer size provides 100% throughput under admissible traffic that follows the strong law of large numbers, without using speedup.