Distributed control schemes for fast arbitration in large crossbarnetworks

摘要

In a large nonblocking crossbar switch, the controller oftennbecomes a bottleneck in terms of both performance and reliability. Wenpresent a number of schemes for distributing the setup function amongnmultiple controllers, thus improving both the performance and thenreliability of the switch. The controllers are symmetric and operate innparallel. We present four distributed control schemes that provide anrange of tradeoffs in controller complexity, speed, and hardwarenoverhead for nonblocking operation. We derive a lower bound of N(1-1/K)nfor the number of buses required for nonblocking operation of a crossbarnswitch with N ports and K controllers under certain constraints. We thenndescribe a scheme that actually achieves this lower bound. Results fromnsimulation indicate that the hardware overhead in terms of the extranbuses needed is small for all the schemes if a small probability ofnblocking is acceptable