Showing papers on "Equal-cost multi-path routing published in 1981"

Provably Good Channel Routing Algorithms

Abstract: In this paper we present three new two-layer channel routing algorithms that are provably good in that they never require more than 2d-1 horizontal tracks where d is the channel density, when each net connects just two terminals. To achieve this result, we use a slightly relaxed (but still realistic) wiring model in which wires may run on top of each other for short distances as long as they are on different layers. Two of our algorithms will never use such a “parallel run” of length greater than 2d-1 and our third algorithm will require overlap only at jog points or cross points. Since in this wiring model at least d/2 horizontal tracks are required, these algorithms produce a routing requiring no more than four times the best possible number of horizontal tracks. The second algorithm also has the property that it uses uses at most 4n contacts, where n is the number of nets being connected.

Servicing and real-time control of networks with dynamic routing

Abstract: The design of a network for dynamic routing is made using the forecasted network loads. Load uncertainties arising from errors in the forecast and from daily variations in network load give rise to reserve or idle network capacity not immediately needed by current network demands. The reserve capacity can be reduced by the use of more flexible dynamic routing methods, which allow routing flexibility to help control network flow under load uncertainties. We illustrate techniques for changing network routing patterns in planned and demand servicing to counteract the effects of forecast errors. Included in the benefits are a reduction in both reserve capacity, estimated to be about 5 percent of network first cost, and in trunk rearrangements. We also present call-by-call simulation results for real-time routing enhancements to the basic routing algorithms. The real-time routing algorithms use dynamic trunk reservation techniques, and the simulation results illustrate the improvement in network efficiency and performance under normal daily load variations, network overloads, and network failures.

A Technique for Adaptive Routing in Networks

Abstract: A two-level adaptive routing scheme for packet-switched computer communication networks is proposed and investigated. The first level is quasi-static and based on the global network status. The second level is dynamic with decisions being made at each node in an attempt to obtain the savings in average delay predicted by a multiserver model of the node. Simulations confirm the predicted improvement.

Optimal Routing in Rectilinear Channels

Abstract: Programs for integrated circuit layout typically have two phases: placement and routing. The router should produce as efficient a layout as possible, but of course the quality of the routing depends heavily on the quality of the placement. On the other hand, the placement procedure would like to know how good a routing it can expect without actually routing the wires. This paper presents fast algorithms for optimal routing and for accurately estimating the area cost of such routings without actually laying them out.

TWIGY A Topological Algorithm Based Routing System

Abstract: A two-level approach to routing is described, in which a multi-layer printed circuit board routing problem is broken down into a set of single-layer ones. A topological transformation is then applied to accomplish single-layer routing. A solution found for each layer by a search in this new domain is then translated back into physical space by means of a deterministic drawing algorithm. The algorithms are independent of specific technological parameters, affording their use on a variety of board routing grids, pad diameters and wire sizes.

Delay Analysis of Broadcast Routing in Packet-Switching Networks

Abstract: Broadcast addressing is the capability to send a packet from a source node to all other nodes in the network. Store-and-forward, packet-switching networks are not inherently designed to carry broadcast packets, and broadcasting has to be implemented by some sort of routing algorithm. In this paper, the source based forwarding algorithm is considered. With this algorithm, a spanning tree is defined for each node, and broadcast packets are sent along the branches of these trees. Approximation methods are presented to obtain a lower bound and estimates of the mean broadcast time. The accuracy of these methods is evaluated by comparison with simulation.

Incorporation of service classes into a network architecture

Abstract: This paper defines a service class and describes how a completely general service class structure can be provided by a packet switched network. It describes the difference between a handling directive and a routing metric, and defines a service class as an arbitrary collection of handling directives and routing metrics. It describes what types of distributed routing algorithms make it possible to provide for a completely general service class concept in a network, and describes the special problems to be encountered when providing for a general service class capability in a hierarchical network.

A distributed minimum hop routing algorithm

Abstract: A two-part distributed algorithm for minimum hop routing in message-switched networks subject to end-to-end average message delay constraints is developed. The first part of the algorithm provides for unconstrained minimum hop routing, while the second corrects this routing to satisfy the delay constraints. Both parts are implemented nodewise via low-order linear programs wherein the information exchange required for each node to carry out its computations involves only adjacent neighbor nodes. The algorithm is illustrated via an example of an 8- node, 14-link network with 7 commodities, and directions for future research to enhance present results are indicated.

Aiming at a General Routing Strategy

Abstract: A general method for automatic routing, based on a channel splitting approach, is presented. A weighted graph depicting multilayer partitions and allowing expected channel occupancy estimation is introduced. Problems and algorithms related to the detailed routing phase are briefly reviewed.

A Preprocessor for Channel Routing

Abstract: This paper presents a "preprocessor" which separates a channel routing problem into two subproblems. One is a specialized channel routing problem where no two nodes of two different nets are of the same y-grid position. The other is a problem of connecting pairs of nodes where each pair of nodes has a path reserved for it. The use of a "preprocessor" in channel routing [5] is justified by the comparison of routing results.

A Responsive Distributed Routing Algorithm for Computer Networks.

Abstract: A new distributed algorithm is presented for dynamically determining weighted shortest paths used for message routing in computer networks. The major features of the algorithm are that the paths defined do not form transient loops when weights change and the number of steps required to find new shortest paths when network links fail is less than for previous algorithms. Specifically, the worst case recovery time is proportional to the largest number of hops h in any of the weighted shortest paths. For previous loop-free distributed algorithms this recovery time is proportional to h2.

Adaptive routing in large communication networks: Probabilistic study

Abstract: A network model is presented and conditions for stochastic stability of the network system are given. For adaptation algorithms which change the routing probabilities slowly (small stepsize), expressions for steady-state variances are derived; usimg these, guidelines for the selection of algorithm parameters are discussed.

Routing in Networks

Abstract: : This report is concerned with routing protocols in networks. The major result is a low bound for any oblivious routing strategy where the route of a packet depends only on the source and destination of the packet. We show that for any oblivious routing protocol for a network of n processors in which the maximum number of processors directly connected to any processor is d, there exists a permutation that requires time (sq. root of n) d (to the 3/2). For specific networks such as an n-cube we give an oblivious routing algorithm whose performance is close to this lower bound. (Author)