Showing papers on "Destination-Sequenced Distance Vector routing published in 1984"

Second Derivative Algorithms for Minimum Delay Distributed Routing in Networks

Abstract: We propose a class of algorithms for finding an optimal quasi-static routing in a communication network. The algorithms are based on Gallager's method [1] and provide methods for iteratively updating the routing table entries of each node in a manner that guarantees convergence to a minimum delay routing. Their main feature is that they utilize second derivatives of the objective function and may be viewed as approximations to a constrained version of Newton's method. The use of second derivatives results in improved speed of convergence and automatic stepsize scaling with respect to level of traffic input. These advantages are of crucial importance for the practical implementation of the algorithm using distributed computation in an environment where input traffic statistics gradually change.

A heuristic algorithm for the period vehicle routing problem

Abstract: In this paper we consider the period vehicle routing problem, which is the problem of designing routes for delivery vehicles to meet customer service level requirements (not all customers require delivery on every day in the period). A heuristic algorithm, based upon the daily vehicle routing algorithm of Fisher and Jaikumar, is presented and computational results are given for test problems drawn from the literature.

Three-Layer Channel Routing

Abstract: With the advent of VLSI technology, multiple-layer routing becomes feasible. Two special types of three-layer channel routing, VHV and HVH, are introduced in this paper. The merging algorithm and the left edge algorithm used in two-layer routing can be extended to three layers. Attempts are made to compare the lower bounds of channel width of three types of routing--two-layer, VHV, and HVH. The algorithms were coded in PASCAL and implemented on VAX 11/780 computer. The computational results are satisfactory, since all the results lead to a further reduction in routing area.

Optimal dynamic routing in communication networks with continuous traffic

Abstract: New characterizations of optimal state-dependent routing strategies are obtained for the continuous traffic network model proposed by Segall for linear cost with unity weighting at each node and for constant inputs. The concept of flow relaxation is introduced and is used to transform the optimal routing problem into an initial flow optimization problem with convex cost and linear constraints. Three algorithms are given for open-loop computation of the optimal initial flow. The first is a simple iterative algorithm based on gradient descent with bending and it is well suited for decentralized computation. The second algorithm reduces the problem to a series of max-flow problems and it computes the exact optimal flow in O (mod N to the fourth) computations, where mod N is the number of nodes in the network. The third algorithm is based on a search for successive bottlenecks in the network. (Author/TRRL)

A new look at fault tolerant network routing

Abstract: Consider a communication network G in which a limited number of link and/or node faults F might occur. A routing r for the network (a fixed path between each pair of nodes) must be chosen without any knowledge of which components might become faulty. Choosing a good routing corresponds to bounding the diameter of the surviving route graph R(G,r)/F, where two nonfaulty nodes are joined by an edge if there are no faults on the route between them. We prove a number of results concerning the diameter of surviving route graphs. We show that if r is a minimal length routing, then the diameter of R(G,r)/F can be on the order of the number of nodes of G, even if F consists of only a single node. However, if G is the n-dimensional cube, the diameter of R(G,r)/F≤3 for any minimal length routing r and any set of faults F with |F|

A Global Routing Algorithm for General Cells

Abstract: An algorithm is presented which accomplishes the global routing for a building block or general cell routing problem. A line search technique is employed and therefore no grid is assumed either for the module placements or the pin locations. Instead of breaking the routing surface up into channels, a maze search finds acceptable global routes while avoiding the blocks. Both multi-pin terminals and multi-terminal nets are accomodated. It is shown that the Lee-Moore grid-based approach is actually a special case of the general search algorithm presented. This algorithm is borrowed from the field of artificial intelligence where it has been applied to many state-space search problems.

An Efficient Channel Router

Abstract: In the LSI chip layout design, channel routing is one of the key problems. The problem is to route a spcified net list between two rows of terminals across a two layer channel. This paper presents a new routing algorithm, which is an improved version of the classical "left edge algorithm". The new algorithm uses a row by row approach, calculating an optimum net assignment to each row. The algorithm was implemented for examples in previously published papers. Experimental results show that the new algorithm produces optimum solutions in most cases.

An Efficient Single-Row Routing Algorithm

Abstract: In this paper, we present a heuristic algorithm for single-row routing. Our approach is based on the interval graphical representation of the given net list. The objective function for minimization is the street congestion. The problem is known to be intractable in the sense of NP-completeness, thus a polynomial-time heuristic algorithm is proposed. It has been implemented and tested with various examples. So far it has always produced optimal solutions.

Updating routing tables after resource failure in a distributed computer network

Abstract: This paper is an analysis of overhead required by the MERIT routing table update algorithm after failure of a single network resource. The number of update messages sent by each node during the update process is used as the measure of update overhead. Both synchronous behavior and asynchronous behavior of the MERIT algorithm are considered. The number of messages required for synchronous update is shown to be an upper bound for the number of messages required if update occurs asynchronously. The effect of network topology on update overhead is discussed. Finally, some implementation suggestions aimed at minimizing looping of messages during routing table update are presented.

Sequencial Routing Optimization for Circuit Switched Networks

Abstract: Nonhierarchical alternate routing is the simplest extension to the hierarchical routing currently used in telephone networks. In order to evaluate the merits of such a technique, it is necessary to be able to optimize some performance measure over the routing variables. In a first step, a short discussion is presented of the evaluation algorithms used for computing the end-to-end blocking probabilities in networks operating under nonhierarchicai alternate routings. Then the results of a statistical sampling of the routing space for a small network are presented, to illustrate important characteristics of the routing problem. Next, two heuristic optimization techniques are discussed, one based on classical steepest descent and the other inspired from classical routing optimization of traffic flows in transportation and communication networks. Acceleration techniques are discussed in both cases, and the convergences rates of the alorgithms are presented for a number of networks. A brief discussion is finally given of the usefulness of nonhierarchical alternate routing in reducing the blocking probability in already existing networks, and in decreasing the number of trunks required to maintain a prespecified grade of service, both in real and artificially generated networks.

Distributed asynchronous optimal routing in data networks

Abstract: We prove convergence of a distributed gradient projection method for optimal routing in a data communication network. The analysis is carried out without any synchronization assumptions and takes into account the possibility of transients caused by updates in the routing strategy being used.

An algorithm of loss and profit analysis of tracks for channel routing

Abstract: A new algorithm based on the concept of track competition is presented in this paper for channel routing. In order to minimize the number of tracks a quantitative analysis method of effective covering is proposed. By using this method, the precision, the stability with respect to initial conditions and the processing efficiency of the results are very satisfactory, and optimal solutions are obtained for the 16 routing cases shown in Ref. [6, 7]. Finally the optimalization of complete routing is discussed.