Showing papers on "Network traffic simulation published in 1991"

A unifying framework for distributed simulation

Abstract: A theory of distributed simulation applicable to both discrete-event and continuous simulation is presented. It derives many existing simulation algorithms from the theory and describes an implementation of a new algorithm derived from the theory. A high-level discrete-event simulation language has been implemented, using the new algorithm, on parallel computers; performance results of the implementation are also presented.

A novel algorithm for discrete-event simulation: asynchronous distributed discrete-event simulation algorithm for cyclic circuits using a dataflow network

Abstract: Distributed simulation of circuits in which the process interactions form a cyclic graph is addressed. The method described uses a dataflow network synthesized on the basis of the connectivity of the circuit components. The algorithm, called Yaddes (which stands for yet another asynchronous distributed discrete-event simulation algorithm), computes for each component a quantity time of next event, which permits the corresponding model to execute asynchronously as far ahead in simulation time as possible. The network ensures that a simulation process executing in a distributed processing environment will not deadlock. The algorithm, which also offers acceptable performance and provable correctness, is compared with the two other principal algorithms proposed to avoid deadlocks: the deadlock recovery algorithm and the exception-mode algorithm. Performance results for Yaddes are presented. >

Robust traffic design for dynamic routing networks

Abstract: The authors present traffic restoration design algorithms to attain a robust network for any facility link or node failure. Some of these algorithms were implemented on network models to compute the cost for doing traffic restoration for different traffic restoration level objectives. From their simulation studies, the authors found that with efficient use of trunk group diversity and at a reasonable incremental cost, one can obtain a robust network to respond to a major facility link or a node failure and still meet the network objectives. A similar approach based on the algorithms presented in this work has been proposed for design of the worldwide intelligent network. >

Evaluation of control strategies through a doubly dynamic assignment model

Abstract: A within-day and day-to-day dynamic assignment model for a general network has been proposed recently. The model follows a nonequilibrium approach, in which flow fluctuations are modeled as a stochastic process. It includes a model of dynamic network loading for computing within-day variable arc flows from path flows. In this paper, the sensitivity and the operational characteristics of the model are tested by analyzing some effects of control measures on a small realistic network. The results of these applications show that the proposed model is a valid tool to estimate the effectiveness of some traffic engineering measures and informative systems. It also appears that some control measures cannot be assessed correctly without the explicit simulation of the demand elasticity over departure times and of the day-to-day adjustment process determined by users' memory and forecasting.

Aggregate Approach for Specification, Validation, Simulation and Implementation of Computer Network Protocols

Abstract: The application of aggregate approach for the formal description, validation, simulation and implementation of computer networks protocols is considered in the paper. With this approach the above mentioned design stages can be executed using a single mathematical scheme. The method of reachability states is used for the validation of protocol general properties, while individual characteristics are analysed by the invariant method which enables to verify the correctness of the invariant by protocol formal description. Aggregative mathematical schemes are used in the specification languages AGREGAT-84 and ESTELLE/AG applied in creating protocol analysing systems simulation and validation of protocols. Protocol automated implementation method based on the specification language ESTELLE/AG is presented. Formal description and results of alternating -bit protocol validation and simulation as its speciffication in AGREGAT 84 and Estelle/Ag are presented for illustration.

A new definition of survivability of communication networks

Abstract: It is suggested that the most important and reasonable parameter of a communication network is the traffic capacity, which might be selected to measure the survivability. It is concluded that the definition of survivability based on traffic flow can be used to evaluate or design a military communication network conveniently. It includes the old definition based on connectivity and is broader in concept. There will be no problem in calculation, because the program is already available. A design of a military communication network using this concept has been performed, showing that the definition is correct. >

Network management using database discovery tools

Abstract: As the volume of network traffic increases due to the proliferation of distributed systems and the growth of real-time applications, a good understanding of traffic distribution and patterns becomes critical in network control and performance management. The authors upgrade the facilities of network management from traditional file systems to database and knowledge base systems and apply machine learning techniques to discover traffic patterns which are difficult to discern by human operators among a large volume of measurements. An experiment on interconnected LANs is conducted where some interesting patterns are found. The results show a strong traffic locality and some cyclic traffic patterns. The discovered rule base can describe the traffic distribution and patterns which need to be captured for any sophisticated performance management. The experiment has shown the high applicability of induction techniques to network management. >

An integrated methodology for supporting network planning and traffic engineering with considerations to SMDS service

Abstract: The integrated network planning system (INPLANS) is introduced. It was developed to provide a single environment to support regional network planning and traffic engineering across different networking technologies. There are four main capabilities in INPLANS: integrated network monitoring (INM), which supports planning and engineering monitoring studies; integrated network servicing (INS), which provides an integrated and interactive environment for the network servicing process; integrated capacity expansion (ICE), which provides a 1-5 year view of network demands and requirements; and integrated technology planning (ITP), which provides cost effective backbone and network access design plans. The overall network planning and traffic engineering process and how it is supported and implemented in INPLANS are described. The switched multimegabit data service (SMDS) is considered, and the impact of SMDS on the planning and engineering process is described. >

Demonstration of TRAF-NETSIM for traffic operations management

Abstract: The utility of the simulation package TRAF-NETSIM to the traffic engineer is assessed and demonstrated by means of a case study. The methodology employed in performing the analysis is presented in a way that will aid future users of TRAF-NETSIM. The advantages and disadvantages of TRAF-NETSIM are documented along with the human resource requirements for a first-time application of the program. TRAF-NETSIM permits the engineer to compare alternative control and design strategies for a traffic intersection, corridor, or network and allows the user to design and test within the office environment the simulation of many traffic options. TRAF-NETSIM attempts to be as realistic as possible. Lanes can be channelized for turns only or designated for carpool or bus activity. Pedestrian activity, long- and short-term events, and bus routes can be simulated as well. Creativity permits the engineer to evaluate unusual networks when required. The output of TRAF-NETSIM provides the user with a host of measures of effectiveness to compare traffic options. Delay time/vehicle, number of phase failures, speed, vehicle miles, stops/vehicle trip are some of the measures of effectiveness that can be used to evaluate networks.

A provably correct, non-deadlocking parallel event simulation algorithm

Abstract: This paper first summarizes and then presents a formal proof to a new conservative deadlock-free algorithm, YADDES, for asynchronous discrete event simulation. The proof not only makes the algorithm complete but helps better understand the seemingly complicated algorithm. YADDES constructs a special acyclic data-flow network from the network of simulation models to keep track of the run time data dependencies, which permits a model to be correctly executed as far ahead in time as possible. The data-flow network also uses the asynchronous parallel discrete event driven technique and runs concurrently with the network of simulation models. This paper also reports a preliminary implementation of the algorithm and discusses the algorithm's limitations. >

A neural network model for traffic controls in multistage interconnection networks

Abstract: Summary form only given. A neural network model for data traffic controls in multistage interconnection networks is discussed. The goal of the neural network model is to find conflict-free traffic flows to be transmitted among given I/O traffic demands in order to maximize the network throughput. The model requires n/sup 2/ processing elements for the traffic control in an n*n multistage interconnection network. The model runs not only on a sequential machine but also on a parallel machine with maximally n/sup 2/ processors. The model was verified by solving ten 32*32 network problems. >

An effective synchronization network for large multiprocessor systems

Abstract: The authors propose a single-stage combining network to handle synchronization traffic, which is separated from the regular memory traffic. A single-stage combining network has several advantages: (1) It is very cost effective because only one stage is needed (instead of logN stages). (2) Only one network is needed to handle both forward and returning requests. (3) All synchronization traffic is confined to a single stage; hence, packets have more opportunities to combine. (4) Combined requests are distributed evenly through the network; the wait buffer size is reduced. (5) Fast-finishing algorithms can be used to shorten the network delay. Because of all these advantages, the authors show that a single-stage combining network gives good performance at a lower cost than a multistage combining network. >

Solving a maximum flow problem using backpropagation

Abstract: One of the most commonly used methods to quantify traffic in terms of flow and speed is generally known as the Greenberg model. The authors propose to relate some of the parameters that are used to compute the Greenberg equations by mapping them by means of a neural network. It is noted that many different aspects of the relationship between the traffic flow and the traffic density as expressed in the Greenberg model can be mapped by means of the neural net. In the case considered, the authors choose to relate the maximum traffic flow (vehicles/minute) for different traffic densities. As input for the net they used the traffic density (number of vehicles/unit length) and the space mean speed; the output will be the maximum possible traffic flow. The simulation discussed indicates that the relations between different traffic parameters can be adequately learned by a neural network. >

A new method for evaluating lightwave network architectures

Abstract: Presents a novel analytical technique for evaluating a lightwave network architecture for two different traffic distribution patterns, viz., uniform traffic distributions (UTDs) and zonal traffic distributions (ZTDs). Evaluating an architecture in the context of interest calls for determining the internode distance (IND) distribution, the mean IND (MIND), the topology z-transform, and the penalty per deflection en route to destination for a prespecified version of the network structure. It is shown that the architectural properties of a network are very much dependent on the traffic distribution patterns. >

SNA route generation using traffic patterns

Abstract: This paper describes a procedure used by the IBM Information Network to generate optimum routes for a complex Systems Network Architecture (SNA) network by utilizing communication traffic patterns. The Route Table Generator and an understanding of customer locations and available facilities had been the basis for route generation. However, this approach became overwhelming as the network grew. The lack of flexibility required an increasing need to manually override generated routes. The resulting approach could not ensure that network delay had been minimized. The Network Design and Analysis (NETDA) tool developed at the IBM Yorktown Research Center was used as a solution. NETDA orders routes based on static indicators such as number of hops, route distance, and speed of the path components. However, NETDA also selects optimal routes based on network traffic patterns. Traffic data were easily incorporated into NETDA, and the IBM Information Network has optimized its SNA routing using NETDA and actual traffic data. The process was challenging because of the number of network components involved and the difficulty in obtaining portions of the traffic data. The use of NETDA for route generation is discussed, and the data collection methodology is described. Network component utilization and network delay changes are reviewed as a means of showing the benefits of such optimizations.

NEMACS: the NEtwork MAnagement and Control Simulator

Abstract: The Network Management and Control Simulator (NEMACS) is a software tool for developing, testing, integrating and evaluating different network management (NM) techniques for multiservice circuit switched networks. NEMACS is designed to provide the modeling detail and flexibility required for research and development work in NM. NEMACS models network elements, signaling protocols, and exogenous network events to a level of detail sufficient for capturing network behavior pertinent to NM. Logical layering of call transport, call control, and network control functions in NEMACS provides flexibility in composition of both network scenarios and their respective NM strategies. >

Traffic analysis for high speed networks

Abstract: A description is presented of the use of time series analysis techniques to characterize aspects of traffic patterns in high-speed wide-area communication networks. One aspect relates to the possible periodic behavior of the traffic; another aspect relates to the bursts or spikes characteristic of traffic approaching the maximum load. It is found that a time-of-day periodicity exists at several levels of network traffic and should be considered regardless of the analytical technique used to estimate traffic load. The authors have confirmed that a composite or average day model is not precise enough for modeling network traffic in their environment. >

Real Time Network Load Estimation in Packet Switched Networks

Abstract: In this paper we consider the problem of real-time traffic load estimation in a packet-switched network environment. In emerging highspeed packet-switched networks, many control functions such as bandwidth management, dynamic route selection and rate-based traffic control depend on real-time characterization of traffic load in the network. In order to perform these functions properly, the traffic parameters have to be continuously monitored and an accurate estimate of traffic parameters must be obtained. Since the traffic parameters are generally time varying, the filtering mechanism must distinguish between a real change in traffic level and a temporary fluctuation of the measured data. Also, the estimator must have the capability to react quickly and trace fast changes in traffic level. To achieve this objective, we propose a time-varying adaptive bi-modal filtering technique which on one hand is very responsive to fast variations of traffic level, and on the other hand, less sensitive to measurement fluctuations. This objective is also desirable in order to limit the number of unnecessary updates and reports for various network control functions.

Congestion and flow control in private wide area ATM network-a simulation study

Abstract: ATM is a promising technology for private network such as in business environment that requires wideband and multimedia communications In private wide area ATM network various types of information (voice, video and data) can be statistically multiplexed onto high speed transmission streams with high efficiency A fundamental challenge in the design of a robust B-ISDN architecture is the structuring of a comprehensive strategy for congestion and flow controls, which will be essential during those instances of resource overloads due to unforeseen traffic focussing and peaking Unfortunately, the multi-megabit-per-second speeds that is responsible for the high performance/capacity of B-ISDN networks will also severely limit the number of implementable and stable congestion control strategies A preventive congestion control strategy is discussed The aim is to have a simple, effective, fair control that is not optimized for any specific service types >

Traffic shaping in asynchronous transfer mode networks

Abstract: Attention in performance engineering studies of ATM (asynchronous transfer mode) networks is beginning to focus on high level issues such as specification of the contract between network and customer, and management of bandwidth in the network. The paper deals with one aspect of the contract between network and customer, namely charging. It describes a means by which customers may reduce the burstiness of their traffic streams (this process is referred to as traffic shaping, or simply shaping) and quantifies the benefit which shaping can bring to the traffic capacity of the network. Such results are a necessary precursor to the definition of a charging and operations policy for the ATM network.< >

BTS (version 1.0): Bottleneck Traffic Simulator User's Manual

Abstract: Describes the computer program BTS which is a macroscopic tool for simulating the performance of freeway bottlenecks

An approach to generating network requirements

Abstract: A formal technique is presented for generating traffic matrices for distributed data networks Traffic matrices are used by engineers to design new networks or, more typically, plan for changes in an existing network The technique combines measured data from proposed design changes to calculate a set of traffic matrices Network hardware and applications are defined by a weighted connection matrix Traffic is estimated using a set of statistics for different types of applications >

Determining maximum traffic flow using backpropagation

Abstract: Summary form only given, as follows. The backpropagation model, a neural network model, was used to relate the traffic flow and the traffic density parameters used in the Greenberg equations to design traffic and highway constructions. After simulation, the relations between the different traffic parameters can be adequately learned by the neural network. >

HF communications network modeling

Abstract: To ascertain a comprehensive picture of high-frequency (HF) communications network performance through each of the physical, data link, and network layers, a suite of computer simulations was developed to support network development and operational deployment support. The author describes a case study where a number of operational constraints were considered to determine the impact on HF network operational feasibility. For this case study, the signaling techniques and protocol interactions used for a HF network were simulated vertically as well as horizontally across the three layers to determine the performance attributes under varying ambient and threat conditions. A comparison between two different network architectures assessed the performance once all the operational constraints were satisfied. >

Modeling and performance analysis of an integrated digital communications network in a military environment

Abstract: An internet environment which offers an integrated communications service will be emerging in the future, and part of it exists now. The author presents a methodology for modeling and performance analysis and addresses the simulation and performance evaluation of the proposed digital communications network from the user's perspective. The network case study for integration and analysis spans the Pacific Ocean, providing geographic connectivity as illustrated. The study describes the development of the model, gives a network system description, and discusses and analyzes the results of some of the simulation experiments. It is shown that a commercially available software package was usefully employed to model and simulate an integrated multimedia command and control communications network. >

Communications network design and planning

Abstract: An overview of the key topics discussed at the 13th International Teletraffic Congress (ITC13) held in Copenhagen, Denmark, in June 1991, particularly the sessions on network design and planning, is given. Nineteen papers were presented at these sessions. Four issues that are of particular importance to ISDN design and planning are emphasized: design of networks with digital information transfer capabilities; design of networks with advanced network/traffic control techniques; use of GOS and reliability objectives for network design and planning; and design of intelligent networks. >