Showing papers on "Link-state routing protocol 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.

Datagram routing for internet multicasting

Abstract: We present a solution to the problem of multidestination routing in internetworks. The component subnets of these internets share a common datagram internet layer, and the gateways and hosts can determine the next gateway en route to a foreign net. Our datagram routing offers high resilience to network failures, major reductions in network traffic, and no changes whatsoever to the subnetwork routing. The routing follows “shortest” paths as defined by the distance criteria of an internet. We intend to use the algorithm as an option of the DoD Internet Protocol with only minor changes to IP while preserving interoperability with IP modules not supporting multidestination.

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.

Alternate paths in a self-routing packet switching network

Abstract: A packet switching architecture in which switching network nodes (200-206) automatically determine alternate routes through a switching network (107) so as to increase reliability and distribute traffic. The switching network comprises stages of distribution (D) and routing nodes (R). The routing nodes are responsive to physical addresses associated with the packets to communicate those packets to address designated downstream nodes. The distribution switching nodes statistically communicate packets to downstream switching nodes on the basis of an alternate routing algorithm and availability of downstream nodes. The initial network stages are alternate distribution and routing stages followed by only routing stages for the remaining stages of the network. Both the routing and the distributing nodes are identical in design and are responsive to an input signal from the network to assume either routing or distributing functions.

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.

A k-SHORTEST PATHS ROUTING HEURISTIC FOR STOCHASTIC NETWORK EVACUATION MODELS

Abstract: Stochastic-network evacuation models require an optimization process to determine the best evacuation routes for a building's occupants. The optimization process developed and applied below is a heuristic based on the K-th Shortest Path Algorithm.

Routing Strategies in Computer Networks

Abstract: A principal function of distributed computer networks is message routing in which a data unit is moved along a network path from where it is first accepted (source node) to where it is to be delivered (destination node), through possibly one or more network nodes. In the OS1 protocol architecture, routing is the principal function of Level 3, the Network Layer. 1 In most operational networks, the network automatically generates the routes used to forward data units. To use network resources efficiently, selected routes must involve minimum cost, according to some specific cost criteria, such as the number and type of communications channels on the route, the utilization levels of the channels, and the average delay incurred in transporting a data unit along the route. The cost of a route is the sum of the costs of the constituent links. Once we know the cost of the network links, we can calculate the minimum-cost path for any source-destination pair using algorithms developed in operations research. Major issues related to routing include

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.

Topological Routing of Multi-Bit Data Buses

Abstract: In LSI and VLSI layout, certain categories of signal nets, e.g. critical nets, power buses and data buses, require special attention during routing. In data bus routing the goal is to maximize the commonality of the routing paths comprising the bus, without unnecessarily lengthening individual routing paths. A topological data bus router has been implemented in the Hughes Automated Layout system and is the subject of this paper.

Routing of telephone traffic as a controlled Markov process

Abstract: In a modern stored-program-controlled telephone network, a considerable amount of information regarding the state of the network can be made available for operational decisions such as traffic routing. This paper is an attempt to obtain a computable solution to the problem of optimum traffic routing with state information, in the framework of the theory of Markov decision processes.

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.

Two algorithms for three-layer channel routing

Abstract: A channel router is an important design aid in the design automation of VLSI circuit layout. Many algorithms have been developed based on various wiring models with routing done on two layers. With the recent advances in VLSI process technology, it is possible to have three independent layers for interconnection. In this paper two algorithms are presented for three-layer channel routing. The first assumes a very simple wiring model. This enables the routing problem to be solved optimally in a time of O ( n log n ) . The second algorithm is for a different wiring model and has an upper bound of O( n 2 ) for its execution time. It uses fewer horizontal tracks than the first algorithm. For the second model the channel width is not bounded by the channel density.

Control algorithms for out-of-chain routing in a telephone network

Abstract: When part of a telephone network is congested because a different traffic pattern from that designed is offered, attempts are made to improve the network throughput by utilizing other vacant facilities. One such control method is out-of-chain routing, which permits calls which overflow from the final in-chain route under the existing routing scheme (far to near rotation) to be offered to out-of-chain routes. Out-of-chain routing is expected to improve the network throughput but, on the contrary, it could degrade the network throughput by increasing the traffic toward the alternate route. Therefore a control algorithm for out-of-chain routing becomes necessary. This paper first models the switching machine which affects the network overload performance and clarifies the traffic characteristics of three-node triangle network model when out-of-chain routing is permitted unconditionally. As a result, it is clarified that the algorithm which stops routing to the out-of-chain routes with office congestion is important. Also, the algorithm which permits out-of-chain routing when there is no trunk congestion on out-of-chain routes may decrease the throughput compared with the case of no out-of-chain routing. the results presented here are confirmed by computer simulation of a laeger network.

Layout Automation Based on Placement and Routing Algorithms

Abstract: The advent of VLSI has necessitated the use of layout automation to generate the masks. Whereas in earlier small and medium scale circuits, automatic layout merely served to shorten the layout process from months to days, it now has become a real necessity to cope with the ever increasing complexity of VLSI.