This paper presents a model for designing wormhole routing algorithms, A unique

It is shown that wormhole routing in mesh-connected networks can be deadlock free and adaptive without the addition of channels to the basic topology. Several partially adaptive routing algorithms for 2-D and 3-D meshes are described and simulated for a variety of conditions. Simulations of policies for selecting input channels show that transmitting extra information in the header flits can reduce communication latencies at high network throughputs. Simulations of policies for selecting output channels show that avoiding turns reduces latencies at high throughputs. Unrestricted nonminimal routing is found to reduce latencies slightly at low throughputs but increase latencies significantly at high throughputs. For nonuniform traffic patterns, a partially adaptive routing algorithm performs better than a nonadaptive one.>

We present a model for designing wormhole routing algorithms that are deadlock free, livelock free, minimal or nonminimal, and maximally adaptive. A unique feature of this model is that it is not based on adding physical or virtual channels to network topologies (though it can be applied to networks with extra channels). Instead, the model is based on analyzing the directions in which packets can turn in a network and the cycles that the turns can form. Prohibiting just enough turns to break all of the cycles produces routing algorithms that are deadlock free, livelock free, minimal or nonminimal, and maximally adaptive for the network. In this paper, we focus on the two most common network topologies for wormhole routing, n-dimensional mesh, just a quarter of the turns must be prohibited to prevent deadlock. The remaining three quarters of the turns permit partial adaptiveness in routing. Partially adaptive routing algorithms are described for 2D meshes, n-dimensional meshes, k-ary n-cubes, and hypercubes. Simulations of partially adaptive and nonadaptive routing algorithms for 2D meshes and hypercubes show that which algorithm has the lowest latencies and highest sustainable throughput depends on the pattern of message traffic. For nonuniform traffic, partially adaptive routing algorithms perform better than non-adaptive ones.