Scouting: fully adaptive, deadlock-free routing in faulty pipelined networks

Adaptive routing protocols based on message pipelining using wormhole routing (WR) can provide superior performance. However, the occurrence of faults can lead to situations that may produce deadlock. Variants of adaptive WR have been introduced (P.T. Gaughan and S. Yalamanchili, 1992) that employ backtracking and misrouting to first establish a path, followed by message pipelining (pipelined circuit switching, or PCS). This scheme avoids deadlock due to faults, but is overly conservative leading to reduced performance. The paper introduces a new family of flow control mechanisms ranging from WR to PCS that offers a compromise by only decoupling the routing probe and the data fits the minimal extent required to provide deadlock-free routing in the presence of faults.