High-Performance Adaptive Routing in Multicomputers Using Dynamic Virtual Circuits

A message transport mechanism which provides highbandwidth low-latency interprocessor communication is the key to the ability of multicomputers to achieve high performance. The system should adapt to changing conditions by routing packets around congested areas and failed links or nodes. We introduce a new message transport mechanism, called Dynamic Virtual Circuits, that combines the best features of circuit switching, packet switching, and static virtual circuits. Routing through intermediate nodes usually requires only a single lookup in a small table, packets include minimal control information, and are delivered in FIFO order. Nodes in the middle of a Dynamic Virtual Circuit can break it and later reestablish it through a different physical path, thus supporting adaptive routing while maintaining the semantics of virtual circuits. We present the basic algorithms for Dynamic Virtual Circuits and the required hardware support in the context of a VLSI communication coprocessor for multicomputers.