Showing papers on "Multipath routing published in 1990"

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. >

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.

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.

A gridless router for industrial design rules

Abstract: A point-to-point routing algorithm with three new features is presented. First, the router makes optimal use of oversized, rectangular contacts. Second, it allows different wire width on different layers, with the layers having complete freedom as to routing direction. These two features make the algorithm attractive for MOS layout applications. Finally, it is able to realize an all-angle routing and to accept all-angle obstacles, a feature interesting for hybrid and PCB routing. The router is gridless and guarantees a solution if one exists. Since it is based on computational geometry algorithms, it offers a low run-time complexity. The ideas have been implemented in a prototype version for 45 degrees routing. The results indicate that the router performs well, even on large designs. >

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.

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.

A unified approach to off-line permutation routing on parallel networks

Abstract: A unified framework for finding efficient permutation routes on parallel networks in an off-line setting is presented. If the underlying graph of a parallel network contains an appropriate “approximate” product structure then our method guarantees the existence of non-blocking near-optimal permutation routes. The routes in question can be determined in polynomial time. Furthermore, our results are extended to finding permutation routes among the remaining “live” nodes in a faulty network.

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%.

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. >

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.

Dynamic routing schemes for international networks

Abstract: Major issues that should be examined in evaluating the performance of networks with dynamic routing are reviewed The characteristics of international 24-h traffic profiles are examined, and proposed dynamic routing schemes are described Gain allocation principles are discussed, and results on circuit savings and fault tolerance of international dynamic routing networks are outlined >

Design and control of networks with dynamic nonhierarchical routing

Abstract: Dynamic routing concepts are described, and the design and control of dynamic routing networks is discussed. The vastly improved performance of the networks is illustrated with examples from operational experience. The evolution of dynamic routing with respect to several future directions is highlighted. These directions are extension to new networks and services, robust design and real-time adaptivity, and extension to interconnecting networks, including the Worldwide Intelligent Network. >

Composite routing protocols

Abstract: A novel routing protocol for computer networks is designed by combining two routing protocols that adapt to changes in the network topology. The first routing protocol is expensive to operate but yields shortest-paths in the networks; therefore, it is best used when changes in the network topology are rare. The second routing protocol is not as costly to operate, but may yield longer paths; hence, it is best used when changes in the network topology are frequent. By combining these two protocols, the resulting protocol has a wide domain of applicability that does not depend on the frequency of changes in the network topology. >

Markov decision algorithms for dynamic routing (telephone networks)

Abstract: The nature of the traffic-routing problem is described, and early studies of state-dependent routing are noted. A state-dependent scheme seeks to route each call so as to minimize the risk of blocking future calls, and thus responds to the current state of the network on the basis of certain assumptions about future traffic demands. State-dependent routing is considered as a Markov decision process. How the relative costs can be determined for the case of direct routing is shown. >

On bit-serial packet routing for the mesh and the torus

Abstract: The bit-serial routing problem wherein each packet consists of a sequence of k flits and is thus called a snake, is considered. On the basis of the properties of the snake during the routing, a formal definition is given for three different packet routing models, namely, the store-and-forward model, the cut-through model, and the wormhole model. The wormhole model, which is most commonly used in practice, is studied. The first algorithms (deterministic and probabilistic) based on the wormhole model for the permutation routing problem on a chain, on a square mesh, and on a square torus are given. A new lower bound is derived for distance-limited permutation routing on a ring of processors, and an algorithm that matches this lower bound if the packets are routed independently is given. >

Performance issues in the design of dynamically controlled circuit-switched networks

Abstract: The evolution of circuit-switched networks is analyzed with respect to the functional innovations that allowed for new traffic controls. The technical alternatives for routing techniques and their integration with congestion and flow control are considered. The performance of dynamically controlled networks is analyzed in the framework of research done at the Centre National d'Etudes des Telecommunications (CNET) together with studies carried out in other research laboratories. Comparisons are made of dynamic routing versus fixed hierarchical routing and time-dependent routing versus adaptive routing. For adaptive routing, centralized and isolated methods are compared. The benefits of advanced control methods are summarized. >

Network Routing Evolution

Abstract: In this paper we briefly examine some directions for evolution of routing in traffic networks of the future. General trends identified are the expected growth in ability to shift bandwidth both logically and physically. We identify four distinct stages in this evolution. The first stage we describe is the hierarchy that was the basis of virtually all networks just a few years ago. The next level of freedom, found in dynamic routing, allows logical shifts in routing to reallocate network bandwidth on, say, an hourly basis, or more rapidly, on a call-by-call basis. The third level we describe is robust routing for integrated networks, and this network implementation allows logical routing to shift network bandwidth rapidly among node pairs and services. Finally we describe integrated traffic/facility routing in which both physical and logical bandwidth are shifted in response to changing customer and network requirements.

Fault Tolerant Design for Multistage Routing Networks

Abstract: As the size of digital systems increases, the mean time between single component failures diminishes. To avoid component related failures, large computers must be fault-tolerant. In this paper, we focus on methods for achieving a high degree of fault-tolerance in multistage routing networks. We describe a multipath scheme for providing end-to-end fault-tolerance on large networks. The scheme improves routing performance while keeping network latency low. We also describe the novel routing component, RN1, which implements this scheme, showing how it can be the basic building block for fault-tolerant multistage routing networks.

Empirical evaluation of randomly-wire multistage networks

Abstract: Experimental data are presented indicating that multistage interconnection networks with randomly positioned wires are likely to be substantially better for message routing applications than traditional multistage networks, such as the butterfly. The data are presented for a variety of routing models, including store-and-forward routing, cut-through routing, and circuit switching, as well as for scenarios in which a potentially large number of switches are faulty. In most cases, the differences are dramatic, particularly when several switches in the network are faulty. The data provide empirical confirmation of recent theoretical work. >

Flow control models for multi-service networks with delayed call set up

Abstract: Admission control and routing in circuit-switched networks are investigated with two types of traffic: wideband with delayed call set up and narrowband operating in loss mode. Markov decision theory is used to construct a state-dependent routing policy. Optimality conditions for a load sharing routing are derived from the first-order Kuhn-Tucker equations. These models together with a direct routing scheme are used in a simulation study to determine the best approach for control of traffic with delayed call setup. State-dependent routing is found to be superior to direct routing and load sharing routing, although its operation is much more complex. >

Distributed and fail-safe routing algorithms in toroidal-based metropolitan area networks

Abstract: A two-dimensional toroidal network is simply a rectangular mesh where opposite nodes on the left and right boundaries are connected to each other and opposite nodes on the upper and lower boundaries are also connected to each other. Examples of toroidal based metropolitan area networks are HR 4 -NET and Manhattan Street Network (MSN). The original routing algorithm for HR 4 -NET proposed by Borgonovo and Cadorin, however, does not direct packets through shortest paths. This paper presents shortest path routing algorithms for HR 4 -NET, which are distributed and fail-safe. These algorithms can also be applied to multiple traffic types. Simple routing rules that use of the regular structure of the network are compared to MSN.

Neural network controller for adaptive routing in survivable communications networks

Abstract: An isolated routing algorithm for adaptive dynamic routing in communications networks that is based on a neural network approach has been developed. A neural network is located within each site of a communications network, and it uses the patterns of incoming traffic to maintain and dynamically update an internal representation of the global topology of the communications network. The information stored in the neural network models is updated using various routing paradigms, including Hebbian learning. The scheme has been implemented in a software simulation running on a Sun workstation

Via minimization with associated constraints in three-layer routing problem

Abstract: Via minimization is the same as the layer assignment problem in VLSI or PCB routing. It consists of determining which layers can be used for routing the wire segments such that the number of vias can be minimized. A heuristic algorithm is presented to globally eliminate the vias in the three-layer channel routing. Some associated constraints, such as restricted terminals and adjacent limitation, are addressed extensively. According to the results, the algorithm is fast and efficient, thus generating very good results. >

Decentralized routing, teams and neural networks in communications

Abstract: A communication network with stochastic input flows is considered. The nodes which route the traffic are required: (i) to react instantaneously to the variations of their incoming flows so as to minimize an aggregate transmission cost, and (ii) to compute or adapt their routing strategies online on the basis of the measured values of the incoming flows and of some local information. Owing to the first requirement, the routing nodes must be considered as the cooperating decision makers of a team organization. The second requirement calls for a computationally distributed algorithm. This fact and the intractability, under general conditions, of team functional optimization problems were the reasons to assign each routing node a multilayer feedforward neural network, which generates the routing variables. For these neural networks the stochastic input flows play the role of training patterns. The weights of the routing neural networks are then adjusted by means of an efficient algorithm based on backpropagation and stochastic approximation. >

Routing of voice and data in burst-switched networks

Abstract: The static and centralized routing of voice and data traffic in burst switched networks is addressed. It is assumed that the routing allows random bifurcation in voice and data paths and preemptive priorities for voice requirements. A study is made of routing of voice only, by using a multicommodity flow model with linearized link losses and average network loss as a minimization objective. Solving the resulting linear program, it is observed that optimal routing strategies prefer to freeze a requirement at an early stage of its path rather than those requirements that are close to their destinations. A study is made of the voice-data interaction at the link level using an available fluid-flow model, and the combined link performance is translated as a maximum flow constraint on a link. This constraint may have undesirable effects on the voice, such as introducing routes with flow absorbing loops, and unfair freezing of some requirements. All conflicting multiple objectives and constraints are included in a linear programming formulation, and it is shown how parameters can be tuned to produce desirable voice and data paths. >