Showing papers on "Static routing published in 1980"

A simple dynamic routing problem

Abstract: As jobs arrive they have to be routed to one of two similar exponential servers. It is shown that if the queue lengths at both servers are observed then the Optimal decision is to route jobs to the shorter queue, whereas if the queue lenths are not observed then it is best to alternate between queues, provided the initial distribution of the two queue sizes is the same. The optimality of these routing strategies is independent of the statistics of the job arrivals.

Routing Techniques Used in Computer Communication Networks

Abstract: An overview is provided in this paper of the routing procedures used in a number of operating networks, as well as in two commercial network architectures. The networks include TYMNET, ARPANET, and TRANSPAC. The network architectures discussed are the IBM SNA and the DEC DNA. The routing algorithms all tend to fall in the shortest path class. In the introductory sections, routing procedures in general are discussed, with specialization to shortest path algorithms. Two shortest path algorithms, one appropriate for centralized computation, the other for distributed computation, are described. These algorithms, in somewhat modified form, provide the basis for the algorithms actually used in the networks discussed.

An optimal routing algorithm for mesh-connected Parallel computers

Abstract: An opUmal algorithm to route data in a mesh-connected parallel computer is presented This algorithm can be used to perform any data routing that can be specified by the permutation and complementing of the bits in a PE address Matrix transpose, bit reversal, vector reversal, and perfect shuffle are examples of data permutations that can be specified in this way The algorithm presented uses the minimum number of unit distance routing steps for every data permutation that can be specified as above K~EV WORDS ANY PrmASES parallel algorithm, mesh-connected computer, ILLIAC IV, permutation, complexity, data routing CR CATEGORIES 5 25, 5 31, 6 22

Method for traffic determination in a routing and information system for individual motor vehicle traffic

Abstract: In a method for traffic determination, a routing and information system for individual motor vehicle traffic is used, in which by way of stationary routing station poles, route information and local information are transmitted to the passing vehicles. For the determination of the traffic situation, the traveling times between two routing station poles are measured in individual vehicles with timing units. These traveling times are transmitted, together with the local information of the first routing station pole passed by a vehicle, to the second routing station pole and are considered in determining new route recommendations.

Queuing Network Models with State-Dependent Routing

Abstract: A model of a closed queuing network within which customer routing between queues may depend on the state of the network is presented. The routing functions allowed may be rational functions of the queue lengths of various downstream queues which reside within special subnetworks called p-subnetworks. If a network with no state-dependent routing has a product-form joint equilibrium distribution of the queue lengths, then the introduction of these routing functions will preserve the product form of the equilibrium distribution. An example to illustrate the applicability of the model to the problem of analyzing a load balancing strategy is presented. It is also indicated how the parametric analysis of a network with routing functions can be simplified through the analysis of a simpler “equivalent” network.

Applied Network Optimization

Abstract: Contents: Network flows Network synthesis Network construction Vehicle routing Vehicle routing in urban transportation

Dynamic, non-hierarchical arrangement for routing traffic

Abstract: In a network for routing traffic from an originating node to a terminating node, it is common to provide alternate routes in order to increase the number of route choices between the originating and terminating nodes. The Bell System toll network employs a hierarchical alternate routing arrangement wherein various nodes, or control switching points (CSPs), are rank ordered for defining a process of routing calls through the network, whereby some CSPs are prohibited from routing traffic through other CSPs. Hence, known hierarchical alternate routing arrangements tend to inhibit route choices, which tends toward longer, and hence more costly, routes. Such problems tend to arise from the limited capability of electromechanical switching equipment. But with the increasing use of electronic stored program controlled CSPs, they can be solved with our alternate routing method which allows route choices without regard to network hierarchy. A plurality of routing sequences is generated, each route sequence including a plurality of route choices and being time sensitive to traffic demands, subject to a grade of service constraint and used for some predetermined time interval during which the sequence tends to mitigate network cost. An appropriate routing sequence is selected and in response thereto a signal is generated to identify a route choice. The route choice signal is then extended, perhaps on a call-by-call basis, to a node which is intermediate to the originating and terminating nodes for identifying the route to be followed in completing the call. In the event a link on the route choice is unavailable, a crankback signal is returned to the originating node. Responsive to the crankback signal, a second route choice from the routing sequence may be attempted from the originating node. This flexible, time sensitive arrangement tends toward increasing the number of route choices and toward mitigating or reducing route length and hence route cost.

Flow Control and Routing Algorithms for Data Networks

Abstract: : We consider flow control algorithms consisting of two parts: quasi- static flow control and dynamic flow control. The quasi-static part uses short term average information on network utilization to allocate maximum data rates and to determine routes for each user. The rates are allocated to achieve an optimal trade-off between assigned priority cost functions for each user and the cost of congestion in the network. This optimization can be done by a distributed algorithm and is essentially no more complicated than optimizing routing alone. The dynamic flow control has the function of admitting or rejecting individual units of traffic into the network so as to enforce the maximum allocated rates and to prevent congestion by smoothing out the fluctuations in buffer occupancy. (Author)

A Line-Expansion Algorithm for the General Routing Problem with a Guaranteed Solution

Abstract: A new routing algorithm is presented which is based on the expansion of a line in the direction perpendicular to the line The line-expansion principle is first applied to the single layer routing problem For the routing on two layers only some minor modifications have to be made An important extension is added in which the search for an interconnection from a given point is initiated in more than one direction at the same time The major advantage of the line-expansion algorithm over the well-known line-search algorithm is the guarantee that always a solution will be found if one exists

Processor Interconnection Strategies

Abstract: In this paper, we describe four families of topologies for interconnecting many identical processors into a computer network. Each family extends to arbitrarily many processors while keeping the number of neighbors of any one processor fixed. These families are investigated with respect to bus load, routing algorithms, and the relation between the average interprocessor distance and the size of the network.

Dynamic Routing and Flow Control

Abstract: This is an expanded version of an earlier report, adding, new results. The first part introduces a simple analytic model showing that dynamic routing may increase network throughput or lower delay when trunks are moderately loaded, but will reduce throughput or increase delay at heavy trunk loads. The second part of the paper presents simulation results characterizing: 1) the operation of a network "protected" by end-to-end flow control, 2) the operation of an "unprotected" network, 3) the transition between these two modes, 4) the effect of changing the update interval for the routing algorithms, 5) the effect of slow local loops, and 6) the effect of increasing the number of alternate paths available for dynamic routing. Overall, the results show that dynamic routing improves network performance only over a small parameter range, and should dynamic routing be used at all, it must be implemented with great care.

A Generalized Channel Router

Abstract: A "generalized" channel router operates on horizontal and vertical channels generated from an irregular cell structure, and is free of a routing grid. Such a router can solve virtually any routing problem. It has two major phases: the global routing phase and the channel routing phase. This paper describes both phases as they have been implemented at TI. It concludes with a demonstration of the versatility of the router (it is used to solve the Hampton Court Maze) and with applications of the router in TI's I2L (Integrated Injector Logic) / STL (Schottky Transistor Logic) Automatic Layout System.

A note on determining operating strategies for probabilistic vehicle routing

Abstract: The stochastic vehicle routing problem is a problem of current importance and research interest. Applications include schoolbus routing, municipal waste collection, subscription bus scheduling, daily delivery of dairy goods, and a host of related transportation and distribution activities. In this paper, we assume that routes for vehicles have already been generated and we focus on determining operating strategies. That is, under what conditions should a driver return to the central depot in order to replenish his supply? We present a dynamic programming recursion which addresses this question and we show that the optimal policy is of a rather simple form. Finally, an algorithm and example illustrate the policy.

Recursive Algorithms for Computing End-to-End Blocking in a Network with Arbitrary Routing Plan

Abstract: This paper presents three recursive algorithms for computing end-to-end blocking probabilities in a network with alternate routing, based on link blocking probabilities. The only assumption made is the statistical independence of link blocking probabilities. The first algorithm applies to arbitrary routing plans. The second algorithm applies to single-loss-route routing plans which include predictive routing plans used in advanced private networks. The second algorithm is also applicable to solving the terminal-pair reliability problem. The third algorithm applies to tandem-node-matrix-generated routing plans which include hierarchical routing plans similar to those used in North American public toll network, AT&T's CCSA, EPSCS, and ETN networks. These three algorithms are progressively more efficient.

A Fast Maze Router with Iterative Use of Variable Search Space Restriction

Abstract: This paper describes a new method of restricting search space for maze routing, to achieve a higher routing completion ratio and shorter machine time. The router is applied iteratively, expanding the width of L-shaped search space restriction from narrow one to wider ones successively. Using this method, machine time was reduced to one-fourth and the routing completion ratio was more than 10% higher in experimental comparison with singly restricted routers of no iteration. This paper also discusses an analysis to help to decide the iteration number and L-shaped path width.

A Hierarchical Routing and Flow Control Policy (HRFC) for Packet Switched Networks

Abstract: A new policy that can effectively handle message routing and flow control simultaneously in a packet switched computer network is presented. In such a policy, a traffic threshold level is assigned for each channel in the network. If all the channels along the preassigned primary route from current node to its destination do not exceed the predetermined traffic threshold, then the primary route is used. Otherwise, alternative route(s) are used to share the traffic load. When all the alternative routes from a source to a destination become unavailable, then the input traffic from that source to that destination is temporarily rejected. Simulation results of the behavior and performance of such a routing and flow control policy are presented. The implementation of the policy is also discussed. Simulation results reveal that this new policy is simpler to implement and yields better performance than that of distributed routing algorithm and buffer allocation flow control policy, which are currently being used in many packet switched networks.

Routing and Flow Control in Virtual Circuit Networks

Abstract: The concept of available bandwidth to each destination is used to establish routes and flow-control data in a virtual circuit network in which traffic requirements are relatively steady with time A distributed algorithm to evaluate available bandwidth between any two nodes in the network is presented

Minimum hop flow assignment and routing in computer-communication networks

Abstract: The problem of minimum hop flow assignment and routing in computer-communication networks subject to an average message delay constraint or to a set of end-to-end average message delay constraints is formulated, and a simple algorithm for solution of the problem is developed. The algorithm is illustrated via an example, and directions for future research are indicated.

Learning routing applied to large scale packet–switched communication networks

Abstract: Learning routing is introduced to large-scale communication network to compensate the lack of a priori information on the network behavior. Learning routing consists of learning automaton as a learning controller placed at each network node. This learning automaton makes decision on routes for packets which are the basic unit of data to be transmitted through the network. Using learning automaton we propose two routing methods, LRI and LRI, which are basically reinforcement methods for the learning automaton. The effectiveness of these proposed methods is shown by means of simulation on a concrete network topology.

Application Note Local Congestion Control In Computercommunication Networks With Random Routing

Abstract: A queueing model for the analysis of a local congestion control scheme is presented. Analytic study of the model shows that local congestion control witb random routing is superior to similar control with deterministic routing at least for the particular example considered here.