Showing papers on "Network topology published in 1983"

State of the Art-Location on Networks: A Survey. Part I: The p-Center and p-Median Problems

Abstract: Network location problems occur when new facilities are to be located on a network. The network of interest may be a road network, an air transport network, a river network, or a network of shipping lanes. For a given network location problem, the new facilities are often idealized as points, and may be located anywhere on the network; constraints may be imposed upon the problem so that new facilities are not too far from existing facilities. Usually some objective function is to be minimized. For single objective function problems, typically the objective is to minimize either a sum of transport costs proportional to network travel distances between existing facilities and closest new facilities, or a maximum of "losses" proportional to such travel distances, or the total number of new facilities to be located. There is also a growing interest in multiobjective network location problems. Of the approximately 100 references we list, roughly 60 date from 1978 or later; we focus upon work which deals directly with the network of interest, and which exploits the network structure. The principal structure exploited to date is that of a tree, i.e., a connected network without cycles. Tree-like networks may be encountered when having cycles is very expensive, as with portions of interstate highway systems. Further, simple distribution systems with a single distributor at the "hub" can often be modeled as star-like trees. With trees, "reasonable" functions of distance are often convex, whereas for a cyclic network such functions of distance are usually nonconvex. Convexity explains, to some extent, the tractability of tree network location problems.

Expressnet: A High-Performance Integrated-Services Local Area Network

Abstract: Expressnet is a local area communication network comprising an inbound channel and an outbound channel to which the stations are connected. Stations transmit on the outbound channel and receive on the inbound channel. The inbound channel is connected to the outbound channel so that all signals transmitted on the outbound channel are duplicated on the inbound channel, thus achieving broadcast communication among the stations. In order to transmit on the bus, the stations utilize a distributed access protocol which achieves a conflict-free round-robin scheduling. This protocol is more efficient than existing round-robin Schemes as the time required to switch control from one active user to the next in a round is minimized (on the order of a carrier detection time), and is independent of the end-to-end network propagation delay. This improvement is particularly significant when the channel data rate is so high, or the end-to-end propagation delay is so large, Or the packet size is so small as to render the end-to-end propagation delay a significant fraction of, or larger than, the transmission time of a packet. Moreover, some features of Expressnet make it particularly suitable for voice applications. In view of integrating voice and data, a simple access protocol is described which meets the bandwidth requirement and maximum packet delay constraint for voice communication at all times, while guaranteeing a minimum bandwidth requirement for data traffic. Finally, it is noted that the voice/data access protocol constitutes a highly adaptive allocation scheme of channel bandwidth, which allows data users to recover the bandwidth unused by the voice application. It can be easily extended to accommodate any number of applications, each with its specific requirements.

Classification Categories and Historical Development of Circuit Switching Topologies

Abstract: A broad tutorial survey is given of the various topologies available for use in circuit switching systems for tightly coupled parallel/distributed computer systems. Terminology and issues of circuit switching as related to parallel/distributed processing are first discussed. Circuit switching networks are then classified according to connection capability, topological geometry, and basis of development. Topological relationships of specific networks are addressed. 91 references.

The Principles and Performance of Hubnet: A 50 Mbit/s Glass Fiber Local Area Network

Abstract: The principles, some of the implementation details, and some performance results for Hubnet are given, Hubnet is a 50 Mbit/s local area network using glass fiber as a transmission medium. The performance of the network for different topologies and loads is analyzed. This analysis is supported by experience with prototype hardware. The network is shown to have excellent performance up to loads which are a large fraction of capacity. Hubnet uses a dual rooted tree structure with twin-fiber communications paths. This structure has not been reported previously in just this form. The network uses all seven layers of an early version of the proposed ISO Reference Model for Open Circuit Interconnection to implement its protocols. The protocols execute in 16 bit microprocessors embedded in the network access controllers within the network.

A token-ring network for local data communications

Abstract: Technical innovations such as large-scale integrated circuit technology and distributed operating systems have respectively reduced the cost of computing and provided a basis for large networks within the confines of a single building or cluster of buildings in close proximity to one another. Local area networks can provide a systematic approach for interconnecting personal workstations, control units, and central processing units, thereby providing a means for these machines to pass information from one to the other. This paper describes a local area network based on the fundamental concepts of a token-ring. Two main ideas are presented. The first idea concerns the physical topology of the wiring network and its star-ring organization. Next, the logical data flows are overlaid on the physical network to provide controlprocedures for exchanging data through the network. The resulting system has unique features that produce a local area network with good performance and reliability characteristics.

SILK: An Implementation of a Buffer Insertion Ring

Abstract: Ring topology local area networks (LAN's) using the "buffer insertion" access method have as yet received relatively little attention. In this paper we present details of a LAN of this,type, called SILK-system for integrated local communication (in German, "Kommunikation"). Sections of the paper describe the synchronous transmission technique of the ring channel, the time-multiplexed access of eight ports at each node, the "braided" interconnection for bypassing defective nodes, and the role of interface transformation units and user interfaces, as well as some traffic characteristics and reliability aspects. SILK's modularity and open system concept are demonstrated by the already implemented applications such as distributed text editing, local telephone or teletex exchange, and process control in a TV studio.

Tradeoffs for selection in distributed networks (Preliminary Version)

Abstract: Algorithms are presented for selecting an element of given rank from a set of elements distributed among the nodes of a network. Network topologies considered are a ring, a mesh, and a complete binary tree. For the ring and the mesh, upper bound tradeoffs are identified between the number of messages transmitted and the total delay due to message transmission. For the tree, an algorithm is presented that uses an asymptotically optimal number of messages.

Completely-pipelined architectures for digital signal processing

Abstract: A class of completely-pipelined VLSI architectures is defined. Two topologies are then described: leaf-connected trees and mesh-connected trees. The leaf-connected tree structure is used to construct a completely-pipelined bit-serial multiplier and a completely-pipelined word-serial, bit-serial convolver. The mesh-connected tree structure is used to implement completely-pipelined bit-parallel multiplication and completely-pipelined word-parallel bit-parallel convolution. Layouts are described that are within log factors of asymptotic optimality. It is shown that, asymptotically, the area required for power distribution actually dominates the rest of the area for a wide class of structures. This illustrates the importance of studying the constants of proportionality in evaluating area, time, and energy requirements, and suggests that the choice of topologies may very well depend on the fabrication technology. The importance of parameterized and high-level design is stressed throughout. Also stressed is the idea of applying sound architectural technique at all levels of information organization, including, in particular, the bit level.

Design Of The Measurement System For State Estimation In The Norwegian High-Voltage Transmission Network

Abstract: A method proposed by Koglin has been used to find an optimal measurement system for static state estimation in the Norwegian high-voltage transmission network. The method is extended in order to obtain a more robust solution in situations with loss of measurements and bad data, and to reduce the computational effort required. The significance of choice of estimation method, load flow situation and network topology is discussed. In addition the optimal measurement system has been compared with manually designed and arbitrarily generated systems.

Network topology optimization for power system security enhancement.

Abstract: Up to now, preventive or corrective actions to improve power systems' operating states mainly concern power generation rescheduling, load-shedding and tap modifications of in-phase or phase-angle transformers. A method is proposed for relieving overloads by network topology modifications. The switching between busbars and feeders in substations is considered as a control variable. The optimization of the topology is a very difficult task due to the combinatorial nature of the problem and the nonlinearities inherent to networks. The method is based on the Maximal Flow Minimal Cost algorithm. All the possible switching actions are taken into account with, if desired, generation rescheduling and load-shedding. The power system is modelled so as to obtain the same power flow distribution as with a DC load flow. Final checks of security constraints (voltage magnitudes and short-circuit currents) are performed with AC load-flow and fast short-circuit programs. The method is very efficient considering the solution time (important for real time applications).

Multiport approach to multiple-fault location in analog circuits

Abstract: This paper deals with the multiport method for multiple-fault location in linear analog circuits. A hybrid multiport description of the linear network has been used in the presentation, which generalizes and explains proposals made by Biernacki and Bandler. The problem of consistency of the chosen set of equations used for fault identification is discussed. The restrictions of the method are explained on the basis of network topology.

Design of an Economical Multidrop Network Topology with Capacity Constraints

Abstract: This paper compares several algorithms for designing economical multidrop network topologies with capacity constraints. Sharma's algorithms, the outside-to-inside-city approach (OICCA, which happens to be a special case of the Esau-Williams algorithm) and the Exchange algorithm (predecessor of several "greedy" algorithms), are then compared to the Esau-Williams algorithm (EWA) and to EWA plus Sharma's exchange algorithm for some practical network applications.

Decentralized control of traffic networks

Abstract: An arbitrary interconnected network of intersecting streets with one-way traffic flow is considered in which some or all intersections are assumed to be operating at maximum capacity. In this case, it is desired to find a robust decentralized controller at each traffic intersection, so that for all perturbed external traffic flow sources/sinks, the resulting perturbed queues at each intersection are asymptotically “balanced”. The only local knowledge required of the controllers at each intersection is that re the queue lengths of the intersection. It is shown that the necessary and sufficient conditions for a solution to the problem to exist depend solely on the topology of the network and the percentage of vehicles turning at each intersection, and are identical to the conditions required for a solution to exist for the centralized controller case. In particular, it is shown that if turns always occur at an intersection, then a solution to the problem always exists. A characterization of controllers which solve the problem are then given. In particular, it is shown that the local controllers which solve the problem are identical to each other, which implies that if the network is expanded (assuming a solution exists) then one can use the same local controllers to solve the problem. It is also shown that the local controllers can, in principle, give “perfect control” to the problem. Some examples are included to illustrate the results.

Optimal Network Bus Ordering in Power System State Estimation --- Its Consistency with that in Load Flow

Abstract: This paper presents a basic rule of making network bus ordering for state estimation by taking into consideration both circuit topology and measurement set information. In order to unify these two different kinds of reference information, measurement information is translated into its topological equivalent and annexed to the system topology representation. Therefore, the ordering can be done by referring only to the modified network topology information. The translation rule is found through the investigation of the topological property of the coefficient matrix of a normal equation in state estimation calculation.

Interconnection of Local Computer Networks: Modeling and Optimization Problems

Abstract: We study problems of optimization of the topology of interconnected local computer networks using random access to a single channel. An approach to modeling of the system by a queueing network is proposed: the analytical solution of the model allows us to obtain global performance measures, which may be used as evaluation criteria in network topology optimization problems. A heuristic is proposed for the latter aspect for one class of problems. We also derive from the model the time needed, for a new user which joins the network, to transmit its number of messages.

Performance based design and analysis of multimicrocomputer networks

Abstract: A new paradigm for parallel computation based on large numbers of interconnected microcomputer nodes has recently emerged. Each network node, fabricated as one or two VLSI chips would contain a processor with some local memory, a communication controller that routes messages without delaying the processor, and a few connections to other network nodes. The cooperating tasks of a parallel algorithm would execute asynchronously on different nodes and communicate via message passing. This approach to parallel processing poses several new and interesting problems in network performance evaluation, distributed task scheduling, and parallel algorithm design. The absence of shared memory makes the evaluation and design of an interconnection network capable of efficiently supporting internode communication patterns crucial. A network model based on the asymptotic properties of closed queueing networks representing the effects of the network topology, node and communication link speeds, and the internode communication patterns is developed. With this model, it is possible to compare the performance of different network topologies processing the same workload, determine the range of network sizes over which a given topology can meet specified performance requirements, and calculate the size of computation quanta below which communication delays negate possible gains due to increased parallelism. Because of communication delays, no node can possess an exact description of the entire network state; all scheduling decisions must be made using incomplete and possibly inaccurate status information. The efficacy of distributed scheduling heuristics as a function of network topology, status information accuracy, and the amount of computation represented by each task are examined. Knowledge of a small area surrounding each node is shown to be sufficient to make acceptable scheduling decisions. Finally, the importance of partial differential equations as models of many phenomena has motivated the search for solution algorithms suited to multimicrocomputer networks. This work has sought to relax the severe synchronization constraints imposed by most algorithms and to determine an appropriate number of discretization points to place in each network node. This has led to a class of solution algorithms spanning the spectrum from completely sequential and synchronous to completely parallel and fully asynchronous.

Incorporation of multiaccess links into a routing protocol

Abstract: Conventional routing protocols and algorithms work most efficiently on sparsely connected networks. Network topologies today include multiaccess links which include hundreds of nodes, all of which are capable of direct communication with each other. Some of these multiaccess links have broadcasting ability. This paper presents protocols and algorithms for efficiently dealing with the characteristics of various types of multiaccess links, when they are included as links in a general topology net.

Analysis of routing table update activity after resource failure in a distributed computer network

Abstract: In a distributed computer network each node participates in the routing process, making routing decisions based on information about network topology which is stored in tables in the node. To maintain the accuracy of these tables without interrupting the functionality of the network, they must be dynamically updated whenever there is a topology change in the network. The purpose of this paper is to analyze update activity required by a topology information maintenance scheme which has been implemented on the three-node MERIT Computer Network in Michigan. The main theorem gives upper and lower bounds on the number of update messages required after failure of a single network resource, either a node or a link.

A model of interprocessor communication for parallel image processing

Abstract: Conflict-free communication in large networks of processors with particular application to image processing is discussed. A general network model and a general class of communication tasks are defined, and algorithms are given for carrying out such tasks on an arbitrary network. Specific types of communication tasks (e.g., one-to-many, many-to-one, and one-to-one) are then considered; these tasks are found to be sufficient for implementing the standard image processing operations. Next, various specific networks topologies are treated, including hypercubes, rings, arrays, and trees. Finally, these results are applied to defining algorithms for performing basic types of image processing operations on both general and specific types of networks.

Queueing network models of multimicrocomputer networks

Abstract: Recent developments in very large scale integration have made it feasible to construct a highly parallel computer composed of large numbers of interconnected microcomputers. The modeling problems posed by this approach to parallel processing differ in several significant respects from those associated with traditional queueing network models of computer systems. Among them are the size of the models, the varied interconnection network topologies, and algorithm dependent internode communication patterns. We extend queueing theoretic models to include multimicrocomputer networks with primary emphasis on two areas: characterizing interconnection network workloads and finding efficient solution techniques for the resulting models.

Application of Local Area Networks to Accelerator Control Systems at the Stanford Linear Accelerator

Abstract: The history and current status of SLAC's SDLC networks for distributed accelerator control systems are discussed. These local area networks have been used for instrumentation and control of the linear accelerator. Network topologies, protocols, physical links, and logical interconnections are discussed for specific applications in distributed data acquisition and control sytems, computer networks and accelerator operations.

Bus, ring, star and tree local area networks

Abstract: This paper examines some of the relative merits of Bus, Ring and Star topologies for Local Area Networks, and describes a new structure - the dual rooted tree. The latter produces superior performance for heavy loads and for impulse loads, while avoiding the message length limitations associated with CSMA LAN's. A 50 Mbit/s fibre-optic prototype network has been constructed and tested. A large (250 port) 50 Mbit/s fibre-optic field trial network is now being installed at the University of Toronto.

Configuring Computation Tree Topologies on a Distributed Computing System.

Abstract: The authors describe an approach to connecting hardware resources for high-performance computation. Two basic algorithms are designed for configuring binary tree topologies. The configuring command can be issued from any processing mode. The algorithms can select proper modes for connection while maintaining good utilization of processing nodes. 7 references.

Large scale network architecture synthesis: interactive strategy

Abstract: Large scale network architecture design problems are described in this paper. The networking cost study is provided and the difficulties of analysis or the problem under consideration are discussed. The idea of continuous parameterization of a combinatorial problem and the notion of pretopology are introduced. Quantitative methods of transmission optimization and transmission-awitching analysis are studied from different points of view. Many other aspects of large scale network architecture design problems (capacities and reliabilities improvement, detailed algorithms, etc) are beyond the scope of this paper. Some of them will be described, analyzed and discussed in forthcoming papers.

A methodology for the design of reliable communication networks in distributed processing systems

Abstract: The combined problem of the communication network design and resource allocation is studied for Distributed Data Processing (DDP) networks. The reliability measure for a distributed data processing system is used in order to enhance network reliability.A model is proposed to determine an optimal DDP network and to allocate resources that maximize the reliability measure of the network, The model takes into consideration network topology, resource avaliability and channel capacity. It is shown that the model may be represented by a linear programming model.

Impact Of Fiber Optics On Local Area Networking

Abstract: The cross impact of key standard access protocols on fiber-optic-configured topologies for local area network (LAN) applications is examined. A taxonomy of topologies and access techniques for fiber optic local area networks is developed. Network performance criteria and the key parameters affecting fiber optic networks are identified. These parameters are used to develop a methodology to enable the selection of an optimum fiber optic topology for a particular access protocol and application. Critical components required for the realization of a fiber-optic-based LAN are discussed.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.