Showing papers on "Dynamic Source Routing published in 1990"

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 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.

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.

Admission control and routing in ATM networks

Abstract: Different approaches for effective bandwidth allocation in an ATM link are investigated. The results can be useful in constructing some simple admission models. A framework for flow control and routing in ATM networks is proposed. It is based on methods developed for circuit-switched networks.

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. >

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. >

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. >

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.

Automated interconnect routing system

Abstract: A method of manufacturing a multiple element circuit interconnect substrate is provided which provides an optimized routing plan. The routing plan is based upon a multi-dimensional binary data structure having nodes representing each terminal interconnect requirement which is preprocessed to order the required interconnects according to density.

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. >

An extended least-hop distributed routing algorithm

Abstract: A routing strategy called NELHNET has been developed for networks with multiprecedence traffic and operating under dynamic traffic and topological conditions. An adaptive distributed algorithm that uses least-hop and least-hop-plus-1 routes in a table of routing vectors, as opposed to the usual table of routing scalars, is described. Current delays are passed backward and forward with the packets to allow development of expected delays to each node via all acceptable routes. The route then selected is the acceptable route with the least expected delay. For speedier recovery, a node returning to service receives the current network status from an adjoining node as soon as the link connecting them is operational. The resultant algorithms show far greater than the marginal improvements originally expected over Arpanet simulations. NELHENET strategies also permit the network to function stably under more heavily loaded conditions than do the Arpanet strategies. >

Routing logic means for a communication switching element

Abstract: Routing logic (RL) for a communication switching element (ISE) of a self-routing multi-stage switching network and able to transfer cells or packets of information from any of its inlets (I1/32) to any of its outlets (O1/32). The outlets of the switching element are arranged in routing groups containing one or more of them and of which the identity is derived by the routing logic from an output-port-address (OPA) identifying an output of the switching network and contained in the self-routing-tag (SRT) associated to the cell. This cell is then transferred to one of the outlets belonging to the selected routing group. The routing logic (RL) is also able to control the transfer of a cell through the switching element according to the execution of a predetermined routing function selected amongst a plurality of routing functions (RS, DI, MC, BH, IS). This routing function to be executed is selected by the routing logic according to a routing-control-code (RCC) also contained in the self-routing-tag (SRT) and each value thereof identifies a specific transfer pattern constituted by a predetermined sequence of routing functions to be executed in the switching elements (ISE) through the switching network (SN).

Optimal routing to parallel heterogeneous servers-small arrival rates

Abstract: Consider a set of k(>or=2) heterogeneous and exponential servers that operate in parallel. Customers arrive into a single infinite capacity buffer according to a Poisson process, and are routed to available servers in accordance with some routing policy. It is shown that for arrival rates in some possible interval (0, lambda /sub 0/), ever routing policy which minimizes the long-run expected holding cost is contained in the set of routing policies that minimize the expected flow time for a system with fixed initial population and no new arrivals. >

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. >

A multi-layer router utilizing over-cell areas

Abstract: A new methodology is presented for the solution of the multilayer routing problem that has the potential to outperform channel based multi-layer routing algorithms by expanding the routing regions to include areas over the cells. It is assumed that four routing layers are available. Routing is completed in two steps; a selected group of nets is routed in the between-cell areas using existing channel routing algorithms and the first two routing layers. Then the remaining nets are routed over the entire layout area, between-cell and over-cell areas, using a new two-dimensional router and the next two routing layers. The router used for over-cell routing recognizes arbitrarily sized obstacles, for example, due to power and ground routing or sensitive circuits in the underlying cells. The proposed router was tested on a number of macro-cell layout examples. Advantages of dedicating two routing layers for over-cell routing is illustrated. Results show a significant reduction in total layout area, wire length and number of via when compared to results obtained using two-layer or multi-layer channel routing methods.

A decentralized discrete-time controller for dynamic routing

Abstract: A 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 assumed that the rate of messages being sent out from one node to another (the control signals) is updated at discrete time instants, which is the usual case in practice. 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 an LP optimization problem; there is no solution to the routing problem if these rates are exceeded). >

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.

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. >