Showing papers on "Static routing published in 1990"

A New Optimization Algorithm for the Vehicle Routing Problem with Time Windows

Abstract: The vehicle routing problem with time windows VRPTW is a generalization of the vehicle routing problem where the service of a customer can begin within the time window defined by the earliest and the latest times when the customer will permit the start of service. In this paper, we present the development of a new optimization algorithm for its solution. The LP relaxation of the set partitioning formulation of the VRPTW is solved by column generation. Feasible columns are added as needed by solving a shortest path problem with time windows and capacity constraints using dynamic programming. The LP solution obtained generally provides an excellent lower bound that is used in a branch-and-bound algorithm to solve the integer set partitioning formulation. Our results indicate that this algorithm proved to be successful on a variety of practical sized benchmark VRPTW test problems. The algorithm was capable of optimally solving 100-customer problems. This problem size is six times larger than any reported to date by other published research.

Split delivery routing

Abstract: This article examines a relaxed version of the generic vehicle routing problem. In this version, a delivery to a demand point can be split between any number of vehicles. In spite of this relaxation the problem remains computationally hard. Since only small instances of the vehicle routing problem are known to be solved using exact methods, the vehicle route construction for this problem version is approached using heuristic rules. The main contribution of this article to the existing body of literature on vehicle routing issues in (a) is presenting a new vehicle routing problem amenable to practical applications, and (b) demonstrating the potential for cost savings over similar “traditional” vehicle routing when implementing the model and solutions presented here. The solution scheme allowing for split deliveries is compared with a solution in which no split deliveries are allowed. The comparison is conducted on six sets of 30 problems each for problems of size 75, 115, and 150 demand points (all together 540 problems). For very small demands (up to 10% of vehicle's capacity) no significant difference in solutions is evident for both solution schemes. For the other five problem sets for which point demand exceeds 10% of vehicle's capacity, very significant cost savings are realized when allowing split deliveries. The savings are significant both in the total distance and the number of vehicles required. The vehicles' routes constructed by our procedure tend to cover cohesive geographical zones and retain some properties of optimal solutions.

A predictive access-controll and routing system for integrated services telecommunication networks

Abstract: A predictive access-control and routing system for a telecommunications network operating in uncertain environments and capble of handling heterogeneous traffic. The system is a real-time, state-dependent network traffic control system in which the control strategy is a function of both real-time congestion levels and real-time traffic profiles. At specific time epochs, the system, using real-time measurements of source-destination arrival dates and trunk group link occupancies, generates predictions of all network trunk group occupancy levels for the next epoch as a function of routing and access control. It then minimizes a projected cost function, such as blocking, to generate a traffic control policy to be implemented during the next time interval.

Method and system for routing packets in a packet communication network

Abstract: A packet network routing method and system based on geographic coordinate identifiers is described. Each node in a network is uniquely identified by absolute geographical coordinates or by a code indicating absolute location in an external coordinate-based reference system (node coordinates), and such absolute geographical coordinates or the equivalent are employed as part of a packet identifier for each packet generated for use in making routing decisions. The node coordinates of a local node and its neighboring nodes and the packet coordinates are used by means at each node through which a packet is routed for determining a desired forwarding route of a data packet. The routing may be prioritized according to preselected criteria, preferably achieving maximum forward progress using the least amount of power. The packet routing protocol according to the invention requires no routing directory or table to perform data routing.

Dynamic routing system for a multinode communications network

Abstract: A communication network having a multiplicity of nodes provides efficient exchange of messages between the nodes. The messages may be originated and received by the computers of a parallel computer system, the processors and associated memories of which are connected to each node. Each node includes a routing system which results in efficient system performance for the parallel computer system associated with the nodes. The messages have control information (a message tag) to which the routing system at each node is responsive. The tag contains data identifying the destination node of the message in the network and prioritization data which, when the message is generated, is initialized to have a value (weight) corresponding to the length (number of links) of the minimal path from the source node where the message originates to the destination node of the message. The routing system utilizes the weights to establish message priority. The routing system receives and sends messages not exceeding the number of links connected thereto on each cycle such that messages flow in and flow out of each routing node on each cycle without being held or stored in queues in the node. Messages of lesser priority are switched by the router to alternate links in accordance with their weights thereby dynamically routing and resolving conflicts among messages.

A detailed router for field-programmable gate arrays

Abstract: A detailed routing algorithm, called the coarse graph expander (CGE), that has been designed specifically for field-programmable gate arrays (FPGAs) is described. The algorithm approaches this problem in a general way, allowing it to be used over a wide range of different FPGA routing architectures. It addresses the issue of scarce routing resources by considering the side effects that the routing of one connection has on another, and also has the ability to optimize the routing delays of time-critical connections. CGE has been used to obtain excellent routing results for several industrial circuits implemented in FPGAs with various routing architectures. The results show that CGE can route relatively large FPGAs in very close to the minimum number of tracks as determined by global routing, and it can successfully optimize the routing delays of time-critical connections. CGE has a linear run time over circuit size. >

Depth-first search approach for fault-tolerant routing in hypercube multicomputers

Abstract: Using depth-first search, the authors develop and analyze the performance of a routing scheme for hypercube multicomputers in the presence of an arbitrary number of faulty components. They derive an exact expression for the probability of routing messages by way of optimal paths (of length equal to the Hamming distance between the corresponding pair of nodes) from the source node to an obstructed node. The obstructed node is defined as the first node encountered by the message that finds no optimal path to the destination node. It is noted that the probability of routing messages over an optimal path between any two nodes is a special case of the present results and can be obtained by replacing the obstructed node with the destination node. Numerical examples are given to illustrate the results, and they show that, in the presence of component failures, depth-first search routing can route a message to its destination by means of an optimal path with a very high probability. >

Method for providing an efficient and adaptive management of message routing in a multi-platform and apparatus communication system

Abstract: The method for providing an efficient and adaptive management of message routing in a multi-platform, communication system having dynamically changing platform populations and dynamically changing connectivities between platforms where each of the platforms are capable of performing the steps of recognizing at least certain ones of the platforms in the system, deriving from at least one of the recognized platforms the quality of interconnectivities of the recognized platforms and certain others of the platforms in the system; and employing the derived quality of interconnectivities to make connectivity-based routing decisions using a selective one of a point-to-point routing algorithm, a point-to-multipoint routing algorithm and a broadcast routing algorithm.

Routing method and routing system for switching system having a plurality of paths

Abstract: A routing method routes cells which are transferred through one of a plurality of paths within an asynchronous transfer mode (ATM) switching system (50, 10) selected by routing information. The routing method includes the steps of adding first routing information to incoming cells at an input stage of the ATM switching system when supplying the cells to the ATM switching system, generating a route switching confirmation cell in response to a route switching instruction and for adding second routing information to incoming cells thereafter so as to supply the route switching confirmation cell and the cells added with the second routing information to the ATM switching system, where the second routing information is different from the first routing information and is determined by the route switching instruction, comparing routing information of the cells with the second routing information at an output stage of the ATM switching system in response to the route switching instruction, outputting each cell from the ATM switching system having routing information different from the second routing information as it is, and temporarily storing each cell from the ATM switching system having routing information identical to the second routing information and reading out and outputting the stored cell after the route switching confirmation cell is output from the ATM switching system.

Routing and scheduling on a shoreline with release times

Abstract: In this paper we examine computational complexity issues and develop algorithms for a class of "shoreline" single-vehicle routing and scheduling problems with release time constraints. Problems in this class are interesting for both practical and theoretical reasons. From a practical perspective, these problems arise in several transportation environments. For instance, in the routing and scheduling of cargo ships, the routing structure is "easy" because the ports to be visited are usually located along a shoreline. However, because release times of cargoes at ports generally complicate the routing structure, the combined routing and scheduling problem is nontrivial. For the straight-line case a restriction of the shoreline case, our analysis shows that the problem of minimizing the maximum completion time can be solved exactly in quadratic time by dynamic programming. For the shoreline case we develop and analyze heuristic algorithms. We derive data-dependent worst-case performance ratios for these heuristics that are bounded by constant. We also discuss how these algorithms perform on practical data.

Apparatus and method for detecting and eliminating call looping in a node-by-node routing network

Abstract: An apparatus and method for effectively managing a switched virtual circuit network by detecting and resolving call routing problems occurring in the routing pattern of the network is provided. Detecting the call routing problems is advantageously achieved by a first process contained in a network management center which has access to all nodes in the network and performs routing table verification for each node whenever there are changes in the routing tables caused by changes in the network, such as an addition of nodes, links and the like. Otherwise, call looping may occur during call set-up as a result of any undiscovered or uncorrected errors in one or more routing tables in the network. Detection of call loops is achieved by the first process through use of a plurality of processing modules that recognizes and excludes in their analysis of the network certain network components that can not be involved in call looping. Identified routing problems are resolved by a second process which provides alternative recommendations as to how best to modify the routing tables in the nodes of the network. A selected one of the alternative recommendations is coupled from the network management center to the nodes in the network for changing the routing tables located at the respective nodes.

Routing system to interconnect local area networks

Abstract: A transmission system transmits data among interconnected local area networks using a bridge coupled between local area networks which senses whether the data originating node transmitted the data using transparent routing or source routing. The bridges provide interconnection at the MAC-layer and based upon information contained in the MAC-layer header, automatically perform either transparent routing or source routing, depending upon the type of routing used by the data originating node. In addition, the bridge provides source routing over multiple wide area channels to those nodes which use source routing.

Routing and flow control in high-speed wide-area networks

Abstract: The routing and flow control techniques developed for wide-area, local-area, and metropolitan-area networks are surveyed. A classification that shows the characteristics that are desirable for high-speed wide-area networks is developed. On the basis of the classification, techniques that should and should not be considered for future high-speed networks are identified. In particular, an attempt is made to determine the effect of increasing transmission rates on the routing and flow control algorithms that are used in packet-switched networks. >

Shortest path first with emergency exits

Abstract: Under heavy and dynamic traffic, the SPF routing algorithm often suffers from wild oscillation and severe congestion, and results in degradation of the network performance. In this paper, we present a new routing algorithm (SPF-EE) which attempts to eliminate the problems associated with the SPF algorithm by providing alternate paths as emergency exits. With the SPF-EE algorithm, traffic is routed along the shortest-paths under normal condition. However, in the presence of congestion and resource failures, the traffic can be dispersed temporarily to alternate paths without route re-computation. Simulation experiments show that the SPF-EE algorithm achieves grater throughput, higher responsiveness, better congestion control and fault tolerance, and substantially improves the performance of routing in a dynamic environment.

Locally-optimal deflection routing in the Bidirectional Manhattan Network

Abstract: A class of shortest-path distributed-routing techniques is presented, and the authors show a locally optimal solution under uniform traffic assumptions. It is argued that, as the number of nodes grows to infinity, the throughput tends to the limit represented by the maximum throughput attainable with the store-and-forward technique and infinite queueing storage. The results obtained show the suitability, as far as the throughput is concerned, of meshed networks using packet switching without storing packets at nodes. The routing techniques investigated perform similarly. At least one of these is simple enough to be implemented with very-fast circuitry, able to cope with the speed foreseen in future metropolitan-area networks (MANs). >

Communication circuit switching or parallel operation system

Abstract: The communication system has a plurality of sub-networks, for example composed of transmission communication nodes, PBX communication notes, application communication nodes, and the like, respectively. Each of these sub-networks is managed by a management system, and all of the management systems are managed by an integrated management system. Each communication node is autonomously provided with the function of establishing an emergency routing as a first stage routing control on the occurrence of a failure in a circuit affecting the communication node. The autonomous routing is heirarchial with respect to node types. Failure and the influences of failure are reported to the sub-network management systems, which in turn can report to the integrated management system. As a second stage of routing control, one or more of the management systems establishes a global routing to replace the emergency local routing. The global routing may take effect if the managment system determines that the failure cannot be corrected within a substantially fixed period of time.

An analysis of 'hot-potato' routing in a fiber optic packet switched hypercube

Abstract: Two implementations of a fiber-optic packet-switched hypercube are proposed. In the first, each directed link is implemented with a fixed wavelength laser and photodetector, and all optical transmissions are wavelength multiplexed onto one or more fibers. In the second, the electronic crosspoint matrices within the nodes are eliminated by allowing each laser to be tunable over a range of log N wavelengths. Assume that a hot potato, or deflection, routing algorithm is used; as soon as a packet is received at a node, a routing decision is made and the packet is sent out. The node attempts to send the packet towards its destination. The analysis indicates that a hypercube, hot-potato routing offers essentially optimal performance for random traffic, regardless of how large the hypercube grows, and it significantly outperforms traditional shortest-path routing with buffering and flow control. A few variations, including an algorithm which gives priority to packets closer to their destinations and one which gives priority to various classes of traffic, are also proposed and analyzed. >

The chaos router: a practical application of randomization in network routing

Abstract: We present the chaos router, an asynchronous adaptive router, which under certain circumstances can send messages farther from their destinations. The chaos router greatly simplifies the routing logic by removing the livelock protection of previous schemes. Through an effective use of randomness, whose sources include that due to the adaptively processed load, the natural timing differences of selftimed circuitry and explicitly injected randomization, the chaos router avoids long message routes with high probability. In this paper the router is described, it is argued that the chaos router is deadlock free and probabilistically live-lock and starvation free, and simulation results are presented showing that the chaos router performs well.

General models and algorithms for over-the-cell routing in standard cell design

Abstract: When an over-the-cell routing layer is available for standard cell layout, efficient utilization of routing space over the cells can significantly reduce layout area. In this paper, we present three physical models to utilize the area over the cells for routing in standard cell designs. We also present efficient algorithms to choose and to route a planar subset of nets over the cells so that the resulting channel density is reduced as much as possible. For each of the physical models, we show how to arrange inter-cell routing, over-the-cell routing and power/ground busses to achieve valid routing solutions. Each algorithm exploits the particular arrangement in the corresponding physical model and produces provably good results in polynomial time. We tested our algorithms on several industrial standard cell designs. In our tests, this method reduces total channel density as much as 21%.

Distributed algorithms for shortest-path, deadlock-free routing and broadcasting in arbitrarily faulty hypercubes

Abstract: The authors present a distributed table-filling algorithm for point-to-point routing in a degraded hypercube system. This algorithm finds the shortest length existing path from each source to each destination in the faulty hypercube and fills the routing tables so that messages are routed along these paths. A novel scheme for broadcast routing with tables is proposed, and the algorithm required to fill the broadcast tables, given the point-to-point routing tables, is presented. In addition, the modifications necessary to make these algorithms ensure deadlock-free routing are given. A quantitative and equalitative comparison of previously proposed reroute strategies with table routing, where the tables are filled by the authors' algorithms, are presented. >

Hybrid routing

Abstract: A general-purpose routing algorithm for very-large-scale integrated (VLSI) circuits and printed circuit board (PCB) designs is proposed. Ideas behind the maze-running algorithm and the hierarchical routing algorithm are combined into a powerful algorithm called hybrid routing. The new algorithm demonstrates a speed compatible to a hierarchical router and produces routings with quality equivalent to that obtained by a maze router. Hybrid routing is based on the maze-running method with a third search dimension added. The extra search space is built by recursively constructing a hierarchy of coarser grid meshes. By means of a parameter-controlled expansion into the coarser meshes, the hybrid router is able to find the preferred search region very quickly and will not miss local information as a hierarchical router does. A user-given parameter can turn the algorithm into a pure maze router, a pure hierarchical router, or a wide spectrum of hybrid routers with different speed/quality characteristics between the extremes. The algorithm has been implemented and integrated into a global router that can handle large-scale routing, such as that encountered in the sea-of-gates layout. >

Maximum free circuit routing in circuit-switched networks

Abstract: An analysis is made of an alternate-path routing rule called maximum free circuit routing (MFCR). In the use of MFCR, a call is routed to the alternate path that has the maximum number of free circuits when the direct path is blocked. Analytical results show that in conjunction with trunk reservation, this routing rule can offer a stable throughput at high traffic conditions and can increase the call carrying capacity by about 20% (compared to direct path routing) under a blocking requirement of 10/sup -2/ on a fully connected symmetrical nonhierarchical network. >

Distributed dynamic routing schemes

Abstract: Schemes that do not explicitly use much information about the state of networks are briefly surveyed, with the focus on dynamic alternative routing (DAR), a simple but highly effective routing method currently planned for the British Telecom Network. State-dependent routing and how some of the methodology also has bearing on the control issue are discussed. The problem of dimensioning a network that uses dynamic routing (i.e. how much capacity is needed and where it should be put to provide an acceptable performance) is addressed. A practical example, which refers to routing in an international access network, is discussed. Some conclusions are drawn on the benefits and drawbacks of distributed routing. >

A new metric for dynamic routing algorithms

Abstract: A dynamic routing algorithm that has as its goal the control of congestion in a packet switching network is presented. The algorithm is based in part on the ARPANET SPF algorithm. However, instead of employing a delay metric, the authors make use of a combination of link and buffer utilizations. A detailed simulation model of the ARPANET was constructed to compare the performance of the congestion-based algorithm to the traditional delay-based (SPF) routing algorithm. The results indicate a substantial improvement in the delay and throughput of the network with the congestion-based routing algorithm. >

Topology distribution cost vs. efficient routing in large networks

Abstract: Routing a message in a network is efficient (in terms of weight of the path used to carry the message) when nodes know the full topology of the network. This may not be the case in large networks since a network may be composed of smaller autonomous pieces by design or by requirements on performance, with each piece having less than complete information about other pieces. We present a trade-off between the amount of topology information exchanged among these pieces and the efficiency of routing in the network. The large network that we study is a collection of networks connected by boundary nodes. Each boundary node knows the topology of its network and the connectivity of networks to each other. The question addressed here is how much topology information about each network should be distributed to other networks in order to achieve reasonably efficient routing.

Decentralized Robust Control for Dynamic Routing of Large Scale Networks

Abstract: A variable structure decentralized controller for dynamic routing in multi-destination large-scale data communication networks is presented. A dynamic model, which can incorporate different processing delays at different nodes, is developed to describe the network dynamics. It is shown that the proposed controller guarantees stability and clears the queues of the system in the absence of external input flows. The controller also keeps the queue lengths bounded in the presence of external flow rates, which do not exceed a certain maximum flow rate (obtained by solving a LP optimization problem - there is no solution to the routing problem if these rates are exceeded). Furthermore, the controller is also robust with respect to variations in the processing delay constants. Some simulation results are presented to illustrate the controller's performance in a number of practical cases.

Design of inter-administrative domain routing protocols

Abstract: Policy Routing (PR) is a new area of development that attempts to incorporate policy related constraints on inter-Administrative Domain (AD) communication into the route computation and forwarding of inter-AD packets.Proposals for inter-AD routing mechanisms are discussed in the context of a design space defined by three design parameters: location of routing decision (i.e., source or hop-by-hop), algorithm used (i.e., link state or distance vector), and expression of policy in topology or in link status. We conclude that an architecture based upon source routing, a link state algorithm, and policy information in the link state advertisements, is best able to address the long-term policy requirements of inter-AD routing. However, such an architecture raises several new and challenging research issues related to scaling.