Showing papers on "Network planning and design published in 1981"

Delay Related Issues in Integrated Voice and Data Networks

Abstract: This paper focuses on network delays as they apply to voice traffic. First the nature of the delay problem is discussed and this is followed by a review of enhanced circuit, packet, and hybrid switching techniques: these include fast circuit switching (FCS), virtual circuit switching (VCS), buffered speech interpolation (SI), packetized virtual circuit (PVC), cut-through switching (CTS), composite packets, and various frame management strategies for hybrid switching. In particular, the concept of introducing delay to resolve contention in SI is emphasized, and when applied to both voice talkspurts and data messages, forms a basis for a relatively new approach to network design called transparent message switching (TMS). This approach and its potential performance advantages are reviewed in terms of packet structure, multiplexing scheme, network topology, and network protocols. The paper then deals more specifically with the impact of variable delays on voice traffic. In this regard the importance of generating and preserving appropriate length speech talkspurts in order to mitigate the effects of variable network delay is emphasized. The results indicate that a desirable length of talkspurt "hangover" of about 200 ms will accomplish this without unduly affecting speech activity, and that, under these circumstances, the perceptable threshold of variable talkspurt delay can be as high as about 200 ms average. As such, the results provide a useful guideline for integrated services system designers. Finally, suggestions are made for further studies on performance analysis and subjective evaluation of advanced integrated services systems.

Congestion Control of Packet Communication Networks by Input Buffer Limits—A Simulation Study

Abstract: An experimental study was conducted using a network simulator to investigate the performance of packet communication networks as a function of: the network resource capacities (channels, buffers), the network load (number of virtual channels, virtual channel loads), protocols (flow control, congestion control, routing), and protocol parameters (virtual channel window size, input buffer limits). Performance characteristics are shown and the design of input buffer limits for network congestion control, virtual channel window size, and nodal buffer capacity addressed. Network design strategies for the control of load fluctuations are proposed and discussed.

A multi-commodity flow network design problem

Abstract: There exist systems which can be usefully described by a network containingarcs through which a commodity of one type flows. This paper is concerned with finding a solution procedure for a particular multi-commodity flow network design problem. The problem is to identify a set of arcs in the network such that if travel is prohibited in them all flow travels by feasible paths and its total cost is minimal. The total flow in each arc may not exced its capacity, which is a known constant. Each arc and each node of the network has a non-negative constant unit traversal cost. Between each pair of distinct nodes there is a given non-negative rate of flow from the first vertex to the second which may be split up among a number of paths according to some constant traversal cost flow assignment process. The optimality criterion is the total traversal cost of all flow, which is to be minimized. Previous work on network design problems of this type is surveyed. The principal contribution of this paper is the presentation of a solution procedure for the above problem based on branch and bound enumeration. An illustrative numerical example is included. Computational experience gained in using the procedure with a FORTRAN IV program on an IBM 370 is favourable.

Analysis and Design of Hybrid Switching Networks

Abstract: This paper presents a methodology for the design of hybrid switching systems. Hybrid switching enables both circuit and packet-switched services to be provided in the same communication network. A model for the analysis of blocking and delay of a hybrid switching link is developed. The capacity assignment problem for hybrid-switched networks is also formulated and solution techniques developed. These models are incorporated into an overall hybrid switching network design methodology, and applied to study alternative system operations.

Multiobjective Optimization in Transportation: The Case of Equilibrium Network Design

Abstract: In this paper we offer a statement of the continuous multiobjective equilibrium network design problem and discuss how it may be solved by an adaptation of Geoffrion’s interactive method. The formulation is fully multimodal and employs no symmetry restrictions.

Air Monitoring Network Design: Case Study

Abstract: This paper addresses the problem of air monitoring network design in the metropolitan Atlanta area. Use of a quantitative location model is described as part of a general solution procedure using diffusion modeling and statistical modeling. The case study is presented in detail, and issues of data base manipulation, computer resource requirements and solution interpretation are explored.

Network planning of projects comprising repetitive activities

Abstract: The paper introduces a method to analyse networks comprising repetitive activities Resource constraints are considered when computing the durations of the repetitive activities The method is very useful for large multiple design housing projects where the major activities are repetitive The resource constraints in non-repetitive activities are not considered in this paper Linear programming is used in the computations

Network flow models for heat exchanger network synthesis.

Abstract: Using the fact that the lowest cost heat exchanger network nearly always possesses the highest possible degree of energy recovery and comprises the least number of positive stream/stream matches, a new mathematical formulation for the network design synthesis problem is proposed. The new representation accounts for the problem thermodynamic constraints, and its solution space only includes networks with maximum energy recovery. Neither cyclic nor split networks are ignored as long as they are thermodynamically feasible. The new model admits an efficient solution procedure and each of its solutions represents at least a low cost network design. A near-optimum solution of the model is found by solving a much simpler mathematical relaxation of it. Frequently, it already comprises a minimum number of positive matches. If not so, a modified version of the Stepping Stone Algorithm commonly used to solve linear transportation problems permits one to derive an optimal solution. Another simple mathematical relaxation of the network synthesis problem formulation is proposed to help the searching for all the other feasible networks comprising a minimum number of matches. A very" well defined and efficient search technique is presented and applied to two example problems.

The optimal design of distributed computer control systems.

Abstract: The control of a modem power generating station is a complex task involving the acquisition and processing of a large amount of data. This involves the processing of data from transducers or other inputs which then produce the desired outputs for actuators and displays etc. The advent of small cheap digital data processing systems has made it economically desirable and indeed feasible to implement distributed computer control schemes. The overall control of the station can be achieved by an interconnected set of such computer systems, each computer being at the node of a communications network. The actual control functions are implemented as a number of co-operating modular programs resident in each of the control nodes. It is assumed that the computers will be functionally similar ( hardware and software ) and that the characteristics of each module (task) such as the CPU loading and the inter-task communication requirements are known a priori. This work investigates the assignment of these tasks such that the distributed computer network uses the minimum number of computers and that the overall inter-computer communication is minimised. However, this overall objective is influenced by a number of technical and operational constraints which are used to formulate a series of mathematical models that progressively include more aspects of the problem. The application of various linear and non-linear optimisation techniques to the solution of these models is investigated. Three independant methods of optimisation are investigated to solve the computer control network problem. In each case, the aim is to construct a simple model based on certain aspects of the problem and then extend the model to include all other aspects. A complete mathematical model which applies the standard methods of optimisation is presented. It is claimed that these formulations are original. It is shown that the complete network design problem is difficult to solve efficiently using standard methods of optimisation, because of the size and the complexity of a practical problem. Hence, the central component of this research has been the development of an algorithm to solve practical network design problems. This algorithm is claimed to be original and is computationally more efficient than the standard methods of optimisation for this type of problems. The basic steps of this algorithm are to decompose the problem and then interactively solve the less complex subproblems. It is shown that this algorithm used interactively will provide a feasible solution. This work contributes to the research into the design of distributed computing systems for process control applications, undertaken by the Central Electricity Research Laboratory (C.E.R.L., Leatherhead, Surrey). In particular it makes a major contribution to the objective of producing a design aid for such computing systems.

A computer-aided methodology for the design and analysis of data communication networks

Abstract: The increase in the interconnection of computers has led to a corresponding increase in the complexity of effective network design. This increase is partly to the size and diversity of computer networks, but also is due to the proliferation of available network hardware and software. As with any system, computer networks are made up of various interrelated components, all of which are essential to the network design process. Some of these components are physical in nature, that is, they specify a piece of hardware or software with certain perfomance properties. Other components are considered to be logical elements of network design. The problem of designing, implementing and controlling present and planned data communication networks is rapidly exceeding manual planning and design capabilities. Network managers and designers are looking more and more to computer resources to manage the volume of traffic information, to develop and evaluate network configurations, and to assist in allocating and placing control functions among network processors. The number of network alternatives is increasing so fast that the demand for network optimization--both in private network design and in the interface to, and use of, public network facilities--can be satisfied only through computer aids. These aids range from simple scratch-pad systems that store and compile network statistics to complete traffic emulators, design configurators, and software for data-distribution modelling. Network design generates a set of performance/cost tradeoffs for an existing or proposed network. The network design process generates and regenerates these performance curves in response to changes in critical design parameter such as protocols, line capacity, concentration points, host processor capability and message routing techniques. This dissertation considers the development of a generalized model of the network design process. This model proposes that the physical and logical network components can be described using a set of objects, properties and relationships. Objects are used to describe network physical and logical components. These components are given properties, thus associating with each object a set of network descriptions. Linkages between objects or classes of objects are provided by object-object relationships. The prototype system provides a generalized network design tool which allows a concise and explicit statement of network requirements providing a network planning and design model which is independent of any particular network or application.

A model for investigating the introduction of digital techniques based on a decomposition into elementary networks: methodology and first results *

Abstract: This paper concerns the definition of general rules for planning and decision making in the digitalization of a long distance telecommunications network. It is shown that, under some hypotheses, a network built around a transit centre may be decomposed into elementary triangular networks for which traffic routing and circuit routing are treated at the same time. In the proposed method the evolution in time of the existing network is optimized by minimizing the discounted cost and taking into account modularity constraints. In particular, using simple examples, the dependence of the transit threshold on the immediate environment is studied. Finally we show how the model may be used for setting up a network configurator.

Traffic securization in «Ile-de-France»

Abstract: After having describing the Paris area telephonic network, the authors examine the appropriate methods of network structuring, to protect from breakdowns due to outs in transmission lines and failures in transit switching centres whereas the disturbance should not affect more than 5% of the traffic and should not hinder priority traffic at all. The setting-up of a last choice network based on a specialized transit centre to deal with traffic overloads in normal conditions and with call routing in case of breakdown is recommended. The network design should provide means for directing the communications towards the above mentioned centre.