Showing papers on "Network traffic simulation published in 1996"

Splitting for rare event simulation: analysis of simple cases

Abstract: An approach to rare event simulation uses the technique of splitting. The basic idea is to split sample paths of the stochastic process into multiple copies when they approach closer to the rare set; this increases the overall number of hits to the rare set for a given amount of simulation time. This paper analyzes the bias and efficiency of some simple cases of this method.

On the relevance of time scales in performance oriented traffic characterizations

Abstract: Efficient methods for congestion control in high-speed communication networks will be based on reasonable characterizations for traffic flows and time scale decompositions of the network dynamics. A key problem for modern network designers is to characterize/model the "bursty" traffic arising in broadband networks with a view to predicting and guaranteeing the performance. We attempt to unify several approaches ranging from histogram/interval based methods to "frequency domain" approaches by further investigating the asymptotic behavior of a multiplexer carrying a large number of streams. This analysis reveals the salient traffic/performance relationships which should guide us in selecting successful methods for traffic management and network dimensioning.

Experiences with network simulation

Abstract: Simulation is a critical tool in developing, testing, and evaluating network protocols and architectures. This paper describes x-Sim, a network simulator based on the x-kernel, that is able to fully simulate the topologies and traffic patterns of large scale networks. It also illustrates the capabilities and usefulness of the simulator with case studies. Finally, based on our experiences using x-Sim, we identify a set of principles (guidelines) for network simulation, and present concrete examples that quantify the value of these principles, along with the cost of ignoring them.

A gradient approach for smartly allocating computing budget for discrete event simulation

Abstract: Simulation plays a vital role in analyzing many discrete event systems. Usually, using simulation to solve such problems can be both expensive and time consuming. We present an effective approach to smartly allocate computing budget for discrete-event simulation. This approach can smartly determine the best simulation lengths for all simulation experiments and significantly reduce the total computation cost for obtaining the same confidence level. Numerical testing shows that our approach can obtain the same simulation quality with one-tenth the simulation effort.

Telecommunication traffic pricing control system

Abstract: Delay-tolerant calls access slack capacity in a telecommunications network under variable pricing controlled by the network so as to permit the network to pick up or stimulate background traffic loads as and when desired to gain revenue from background idle capacity.

Parallel real-time implementation of large-scale, route-plan-driven traffic simulation

Abstract: This work is part of our ongoing effort to design and implement a traffic simulation application capable of handling realistic problem sizes in multiple real-time. Our traffic simulation model includes multi-lane vehicular traffic and individual route-plans. On a 16-CPU SGI Power Challenger and a 12-CPU SUN workstation-cluster we have reached real-time for the whole German Autobahn network.

Water distribution network reliability: stochastic simulation

Abstract: Stochastic simulation is applied in a reliability analysis of a regional water distribution network. To complement the connectivity-based reliability analysis presented in the companion paper, the proposed stochastic simulation is aimed at evaluating the impacts of component failures on meeting demand at a certain quantity level. Simulation is conducted in a manner such that a sampling experiment of the system performance is repeated a sufficient number of times and the results are analyzed to obtain the desired reliability index. Given the mean time to failure and repair time of links, a large number of synthetic system conditions are generated and operations of system under the different conditions are simulated. Stochastic simulation of the system is conducted with a highly efficient embedded generalized network flow model (EMNET) to determine the optimal system operations for each scenario. The proposed reliability analysis method is applied to the water distribution network of the Metropolitan Water District of Southern California (MWDSC).

Traffic simulations using cellular automata: comparison with reality.

Abstract: In this article we summarize work concerned with the comparison between a cellular automaton (CA)-model 1 for traac ow and empirical data. The results presented here consist of two parts: comparing the fundamental diagrams and looking for a certain set of lane changing rules, which reproduce at least qualitatively the data measured on german motorways. These last results indicate, that it is possible to design microscopic lane changing rules that give the correct macroscopic behaviour regarding the lane-usage versus ow curves. To obtain such curves has been the problem in recent investigations using another microscopic model 2 .

System and method for network optimization using code blocking

Abstract: A fast and efficient system and method for network management under traffic overload conditions is described. The technique uses an algorithm to automatically generate a close approximation of the optimum working state of a telecommunications network when the actual traffic is found to be greater than network capacity. The algorithm uses traffic blockage measurements obtained from distributed network switches and generates code blocking parameters that can be applied to the distributed network switches to enhance total revenue. The described technique provides additional revenue gains over that obtainable by partially rerouting traffic away from congested network links. The use of the described code blocking technique may be discontinued when the conditions causing the network overload are determined to have disappeared.

Can Self-Similar Traffic Be Modeled by Markovian Processes?

Abstract: In this paper, we compare high time resolution local area network (LAN) traffic with three different traffic models: Poisson, ON-OFF and 5-state Markov process. Due to the measured data's extreme variability on time scales ranging from milliseconds to days, it is difficult to find a model for it, especially a Markovian one. Recent studies show that conventional models do not capture the characteristics of the observed traffic. Fractal-based models have already been built to characterize such a traffic but they are not easily tractable tractability of them is not great. Through a new method which integrates different time scales in the model, we have tried to find a quite simple Markovian process having the same behavior as the measured traffic on the LAN. We show in particular that a simple 5-state Markov process integrating different time scales can reasonably model the behavior of measured traffic up to a certain time interval.

A Model for Real-Time Traffic Coordination Using Simulation Based Optimization

Abstract: An approximate traffic model, APRES-NET, is proposed for a simulation-based optimization approach for real-time network coordination of traffic flows. The objective of APRES-NET is twofold: to provide network-wide prediction of traffic movements and to evaluate, approximately but quickly, the performance of any signal timing strategy. To make a prediction, it uses the observed network vehicular traffic and signal data for a period of time, a future signal plan, and statistical information on vehicle movement, to predict the traffic for some future time period. The APRES-NET simulation consists of propagating into the future the movement of the vehicles detected in the network during the “last detection period”. To quickly, and approximately, simulate the vehicle movement through the whole network, a simplified queuing mechanism is implemented at the intersections. At an intersection, a turn is assigned to each vehicle based on turning probabilities. Performance measures are calculated continuously as the simulation run is being conducted. APRES-NET is being used for real-time coordination of signal phase timings by making it behave as a “function evaluator” in an iterative optimization scheme. The paper discusses the basic structure and the algorithms used by APRES-NET.

Design and evaluation of an Ethernet-based residential network

Abstract: When the information superhighway arrives at the neighborhood, a residential network will connect home appliances to the community access network. These appliances include personal computers, printers, and video clients. Among all local-area network (LAN) protocols, Ethernet is the most economic and the most popular. The unique characteristics of residential networks call for new performance studies. A residential network typically has few nodes and runs different applications than business and academic LANs. Consequently, residential networks have traffic characteristics different from the subject of existing studies. We constructed a residential network testbed to collect typical application traffic statistics. Additional live traffic characterization was obtained from campus networks. Also, we investigated the suitability of Ethernet for video distribution through simulation. This paper discusses the design issues for residential networks and presents a network design that is based on Ethernet technology. Traffic models are established from the actual traffic traces and used for the performance evaluation of residential networks. Furthermore, several future data traffic scenarios are considered with bandwidth up to 6 Mb/s by scaling up current data traffic. The simulation results of the performance suggest that Ethernet can be used as a cost-effective residential network for video and data communications.

Synopsis of Traffic Simulation Models

Abstract: Computer simulation modeling is an established tool for assessing traffic operations. Over the past three decades, a variety of traffic simulation models have been developed, and many experiments and applications of these traffic simulation models to imaginary and real traffic operations have been conducted. This paper is intended to review widely used and newly developed models, in terms of modeling mechanisms, characteristics, and applications. Traffic simulation theories and approaches are briefly described. Simulation models developed for different traffic systems are then reviewed, including those for urban networks, freeways and integrated urban street/freeway systems. Important issues on model application are discussed.

A high-speed self-similar ATM VBR traffic generator

Abstract: Analysis of real network traffic has shown that a large number of traffic sources produces a traffic stream that is self-similar over several time scales. Motivated by this observation a high-speed asynchronous transfer mode (ATM) traffic generator based on fractional Brownian motion is presented. The traffic simulator generates call arrivals as well as the desired traffic parameters for each call. It is therefore an ideal tool to analyze a wide spectrum of networking functions such as switch performance, routing, and call admission control algorithms. The presented algorithm can be highly parallelized, thus generating traffic logs in a period several orders of magnitude below the actual simulated time period.

Traffic management of a satellite communication network using stochastic optimization

Abstract: The performance of nonhierarchical circuit switched networks at moderate load conditions is improved when alternate routes are made available. Alternate routes, however, introduce instability under heavy and overloaded conditions, and under these load conditions network performance is found to deteriorate. To alleviate this problem, a control mechanism is used where, a fraction of the capacity of each link is reserved for direct routed calls. In this work, a traffic management scheme is developed to enhance the performance of a mesh-connected, circuit-switched satellite communication network. The network load is measured and the network is continually adapted by reconfiguring the map to suit the current traffic conditions. The routing is performed dynamically. The reconfiguration of the network is done by properly allocating the capacity of each link and placing an optimal reservation on each link. The optimization is done by using two neural network-based optimization techniques: simulated annealing and mean field annealing. A comparative study is done between these two techniques. The results from the simulation study show that this method of traffic management performs better than the pure dynamic routing with a fixed configuration.

Comparison of NETSIM, NETFLO I, and NETFLO II Traffic Simulation Models for Fixed-Time Signal Control

Abstract: This paper documents a comparative analysis of the NETSIM, NETFLO I, and NETFLO II traffic simulation models when simulating traffic networks with fixed-time signal control. The objective was to find out whether the results of simulating the same traffic network with the three models were compatible. The three models employ different approaches to simulate traffic flow on urban street networks. Four different scenarios with varying network configurations and intersection geometries were simulated for three volume levels. The average speed and delay measures of effectiveness generated by the three models were compared for each scenario. Analysis of variance techniques were used for statistical analyses of the simulation output data. The execution speeds of the models were also compared. The quickness of simulation will be very important in the ITS applications, real-time traffic adaptive systems, and so forth. The results of this study indicated that the estimated measures of effectiveness from the three m...

A New Scheduling Method for Parallel Discrete-Event Simulation

Abstract: In this paper we introduce a new conservative and non blocking algorithm for discrete event simulation on parallel computers with distributed memory. The new approach, called critical process first (CPF) algorithm, is especially well suited for simulating complex VLSI designs consisting of many logical processes. The algorithm avoids deadlocks by repeatedly sending lookahead information about critical processes to other computation nodes. Processes are called critical if they may directly influence processes of another computation node. To hide the communication latency of the parallel computer the CPF method gives priority to the execution of events which may affect critical processes. Simulation results show the superiority of the CPF algorithm over approaches without priority handling.

Development of a Road Traffic Simulator by an Autonomous Vehicle Movement Model

Abstract: Increasing vehicular traffic are causing traffic jam and social economic loss in recent years. Dynamic traffic management systems based on actual traffic conditions are expected to reduce these problems. Computer simulation is a powerful tool to evaluate the system performance of new traffic management system, since it is difficult to evaluate it under various traffic conditions in the real world due to huge costs and safety concerns.In this paper, we propose a new microscopic traffic simulation model by object-oriented programming style. In this model, the street network is composed of nodes and links and vehicles run autonomously in the street network. The autonomous vehicle movement model is composed of decision model that depends on the driver's character and vehicle motion model that depends on the attribution of the vehicle. Then, we analyze the quality of our proposed model and show the effectiveness for evaluating the performance of the traffic management systems.

Performance evaluation of bursty traffic using neural networks

Abstract: We investigate the application of neural networks to evaluate the performance, packet loss probability, of a bursty traffic stream. We show, that in a bursty multimedia environment, performance is a function of burstiness, Hurst parameter, traffic intensity and buffer size. In a closed loop traffic control system each source uses this reported measure to regulate their traffic to the destination queue. A multilayer neural network is used to capture the functional relationship between the loss probability and the traffic descriptor (Hurst parameter and traffic intensity) for a fixed value of buffer size. The neural network approach makes practical real-time performance measurement and hence the control of traffic in an adaptive environment.

Statistical Characterization of Wide-Area Self-Similar Network Traffic

Abstract: Background traffic models are fundamental to packet-level network simulation since the background traffic impacts packet drop rates, queuing delays, end-to-end delay variation, and also determines available network bandwidth. In this paper, we present a statistical characterization of wide-area traffic based on a week-long trace of packets exchanged between a large campus network, a state-wide educational network, and a large Internet service provider. The results of this analysis can be used to provide a basis for modeling background load in simulations of wide-area packet-switched networks such as the Internet, contribute to understanding the fractal behavior of wide-area network utilization, and provide a benchmark to evaluate the accuracy of existing traffic models. The key findings of our study include the following: (1) both the aggregate and its component substreams exhibit significant long-range dependencies in agreement with other recent traffic studies, (2) the empirical probability distributions of packet arrivals are log-normally distributed, (3) packet sizes exhibit only short-term correlations, and (4) the packet size distribution and correlation structure are independent from both network utilization and time of day.

Applying the transport network relational database to a turning flows study and a traffic noise model

Abstract: The Transport Network Relational Database is a set of rational tables for storing details of road transport networks. It is an effort to address the need for a common data format to aid those organizations involved with transportation modeling and analysis. The relational database approach is used due to its advantages of increased flexibility, the current emphasis on client/server computing and the ever-increasing power of the desktop PC.

A restoration system for ATM networks

Abstract: This paper describes a restoration system for ATM networks that is built on top of a pre-planned hop-by-hop routing system in the network and operates on a connection-by-connection basis Unlike most of the existing proposals that use dedicated spare facilities to protect network traffic against network fault conditions, this scheme simply takes advantage of unused network capacity to redirect traffic from the problem area Given that ATM switches are being deployed in the network to support switched broadband services, the additional development cost and operations overhead associated with this restoration system is relatively insignificant The performance of the proposed restoration system is discussed based on simulation studies for video on demand (VoD) applications

A simulation algorithm for source-terminal communication network reliability

Abstract: In order to evaluate the capacity of a communication network architecture to resist faults of some of its components, several reliability models are extensively used. We consider the source-terminal network reliability parameter. The exponential time complexity of exact methods for its evaluation leads to the use of simulation schemes. We present a new simulation algorithm, which recursively changes the original problem into the reliability problem for a smaller network obtained from the previous one by conditioning out one of its paths. This algorithm results in a more efficient (accurate) estimator than the standard one; it is easy to implement, and has good overall performance, as shown by experimental results.

Validation of a ca-model for traffic simulation of the northrhine- westphalia motorway network

Abstract: This paper describes a project which has as it first aim to get an instrument for the simulation of traffic flow on a road network in Germany and the resulting impact on the environment. A second aim is to use this model for complex scenarios such as changes in traffic demand, modal split, or financial restrictions. The final aim of the project is to use the model for traffic control. The first part of the paper presents an introduction to the topic of traffic simulation of large areas. The next section introduces the microscopic model designed to perform road-network simulations for large areas in faster than real-time. The final part of the paper describes efforts towards calibrating the model.

Simulation of traffic characteristics of non-geostationary satellite systems

Abstract: Based on the data generated for traffic volume estimation for satellite mobile systems, and by utilising computer simulations, the general statistical characteristics of non-geostationary (non-GEO) satellite beam traffic are presented. Simulation results show that the traffic level in a non-GEO satellite beam varies dramatically and with a wide dynamic range. This is significantly different from the case of geostationary satellite and terrestrial cellular networks.