In this paper we develop a general approach to global reactive congestion control in multicomputer networks. The approach uses timeout mechanism to detect congestion, and exploits control lines such as those used for handshaking in the flit-level flow control of wormhole routers to distribute information about congestion. It is also based on a mechanism that limits the demands placed by the network interface and the processing element. The approach is described in detail and evaluated through simulation experiments. We show that the proposed congestion control can provide network stability and predictable network performance. By choosing the right timeout, we can provide bounds on average delay and worst-case delay. Furthermore, with appropriate timeouts the network can be kept out of saturation. Other attributes of the approach include fairness and applicability to a wide range of network architectures.

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Algorithms for traversing and marking the nodes of a directed graph have applications in many fields, for instance search inethods in artificial intelligence and garbage collection schemes. In this paper, a general nonrecursive algorithm for the purpose is formulated and proved, and some if its properties are investigated. A second general nonrecursive algorithm is also discussed. Then two implementations of the general algorithms with valuable properties are described. Finally a recursive version is given.

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