Showing papers on "Network traffic simulation published in 1998"

Self-similarity and heavy tails: structural modeling of network traffic

Abstract: High-resolution traac measurements from modern communications networks provide unique opportunities for developing and validating mathematical models for aggregate traac. To exploit these opportunities, we emphasize the need for structural models that take into account spe-ciic physical features of the underlying communication network structure. This approach is in sharp contrast to the traditional black box modeling methodology from time series analysis that ignores, in general, speciic physical structures. We demonstrate, in particular, how the proposed structural modeling approach provides a direct link between the observed self-similarity characteristic of measured aggregate network traac, and the strong empirical evidence in favor of heavy-tailed, innnite variance phenomena at the level of individual network connections.

Method and system for adaptive network security using intelligent packet analysis

Abstract: A method and system for adaptive network security using intelligent packet analysis are provided. The method comprises monitoring network data traffic. The network data traffic is analyzed to assess network information. A plurality of analysis tasks are prioritized based upon the network information. The analysis tasks are to be performed on the monitored network data traffic in order to identify attacks upon the network.

Phase transition in a computer network traffic model

Abstract: We propose and study here a simple model of computer network traffic that can exhibit a phase transition from a low to high congestion state measured in terms of average travel time of packets as a function of the packet creation rate in the network. In the model, packets are generated with destination addresses, and are transferred from one router to another toward their destinations. The routers are capable of queuing packets and autonomously selecting a path to the next router for a packet. Through simulations on a two-dimensional lattice model network, we found that the phase transition point into the congestion phase depends on how each router chooses a path for the packets in its queue. In particular, an appropriate randomness in path selection can shift the onset of traffic congestion to accommodate more packets in the model network.

Apparatus and method for network capacity evaluation and planning

Abstract: Network capacity evaluation and planning is performed based upon the traffic across the links of the network Once a link's traffic volume has been measured, it is compared with the link's traffic capability, and the resulting parameters compared with the traffic and capability of other links of the network to create measures of network capacity and balance Then, simulated changes to the network configuration may be made by substituting simulated traffic volume amounts and capabilities for selected link traffic measurements and capabilities, and the resulting measures of network capacity and balance may then be compared to determine whether the simulated changes represent a preferred network configuration

Simulation of traffic systems : an overview

Abstract: In this paper, the author presents an overview of the growth in the use of computer simulation in traffic systems. The history behind the growth is described, followed by a discussion of application areas. New trends and applications in traffic simulation are described including demand analysis, parallel computing, cellular automata, and rule based simulation.

Traffic engineering technique for routing inter-class traffic in a computer network

Abstract: A technique is provided for routing traffic in an integrated services network which supports a plurality of different service classes including a relative low priority class (e.g. best-effort) and a relative high priority class (e.g. guaranteed sessions). The technique of the present invention improves inter-class resource sharing efficiency and achieves high network throughput of each class of service in the network. The technique discourages guaranteed (high priority) traffic from using links that are already loaded with best-effort (low priority) traffic. This is achieved by using, in the link cost for high priority traffic, a concept of “virtual residual bandwidth”, derived from the link residual bandwidth by taking into account of the congestion condition of low priority traffic. The proposed mechanism is simple in the sense that no changes are needed to the path selection algorithms employed for individual service classes the only change is in the link cost. The distribution of network resources across traffic classes adapts dynamically and automatically to the mix of traffic in the traffic classes, even if the traffic distribution is uneven across the network. When the traffic load is concentrated, significant performance improvements are achieved for low priority sessions without penalizing high priority sessions.

Methods and apparatus for planning and managing a communications network

Abstract: A method for automatically planning and managing the performance of a communications network comprising a propagation forecasting step where propagation forrecast algorithms form a propagation forecast from weather inputs and a traffic forecasting step where traffic forecast algorithms form a traffic forecast from traffic data inputs and a network planning step where planning algorithms display an automated network model. During a forecast updating step, meteorological measurements and radio traffic measurements are continuously provided, resulting in adjusted propagation and traffic forecasts, which are then followed by a network realignment step to adjust the network. During a model comparison step, an artificial intelligence program continuously compares the model, the model adjustments, the realigned network and the network performance parameters with each other. A coefficient adjustment step adjusts the propagation, traffic and planning algorithms. In a reconfiguration instructions step, taking into account the meteorological and radio traffic measurements, the adjusted propagation forecast, the adjusted traffic forecast and network performance parameters, reconfiguration instructions are developed and transmitted to network operators. Also provided is an automated communications network planning apparatus for converting meteorological data and traffic data into a network model, capable of adjustment and updating, shown on a network terminal display.

Route optimization and traffic management in an ATM network using neural computing

Abstract: Neural computing techniques are used to optimize route selection in a communication network, such as an ATM network. Output measurements of the network are used to provide optimal routing selection and traffic management. Specifically, link data traffic is monitored in the network to obtain traffic history data. An autoregressive backpropagation neural network is trained using the traffic history data to obtain respective predicted traffic profiles for the links. Particular links are then selected for carrying data based on the predicted traffic profiles. A cost function, limits on network parameters such as link cost and cell rate, and other quality of service factors are also considered in selecting the optimal route.

Application and evaluation of large deviation techniques for traffic engineering in broadband networks

Abstract: Accurate yet simple methods for traffic engineering are important for efficient dimensioning of broadband networks. The goal of this paper is to apply and evaluate large deviation techniques for traffic engineering. In particular, we employ the recently developed theory of effective bandwidths, where the effective bandwidth depends not only on the statistical characteristics of the traffic stream, but also on a link's operating point through two parameters, the space and time parameters, which are computed using the many sources asymptotic. We show that this effective bandwidth definition can accurately quantify resource usage. Furthermore, we estimate and interpret values of the space and time parameters for various mixes of real traffic demonstrating how these values can be used to clarify the effects on the link performance of the time scales of burstiness of the traffic input, of the link parameters (capacity and buffer), and of traffic control mechanisms, such as traffic shaping. Our approach relies on off-line analysis of traffic traces, the granularity of which is determined by the time parameter of the link, and our experiments involve a large set of MPEG-1 compressed video and Internet Wide Area Network (WAN) traces, as well as modeled voice traffic.

Distributed simulation with javagpss based on the high level architecture

Abstract: This paper focuses on the High Level Architecture for reusable and interoperable distributed simulation, platform independence, and how classical simulation tools can fit into this new arena. The current integration efforts focus on GPSS/H and SLX; in this paper the GPSS/H track is described. The experiences using the standard GPSS/H version and the reasons for a Java implementation of GPSS/H, JavaGPSS, are sketched. The introduction of JavaGPSS and the incorporation of distributed simulation mechanisms based on HLA into this tool build the main issue of the remainder of this paper. New application areas are mentioned as an outlook on this new dynamic technology. 1 DISTRIBUTED SIMULATION In the past few years, the field of distributed simulation, driven by the rapid expansion and acceptance of the Internet and its multimedia front-end, the WWW, has become one of the most promising and challenging technologies in modeling and simulation. The large number of different approaches to distribute and interoperate simulations (e.g. Aggregate Level Simulation Protocol ALSP, Distributed Interactive Simulation DIS) has now lead to a unifying approach, the High Level Architecture (HLA), which has the challenging vision to support its predecessors and different time regimes. 2 HIGH LEVEL ARCHITECTURE The High Level Architecture is a simulation interoperability standard currently being developed by the US Department of Defense (DMSO 1997). The architecture is defined by : 1. rules which govern the behavior of the overall distributed simulation (Federation) and their members (Federates) (DoD 1996). 2. an interface specification, which prescribes the interface between each federate and the Runtime Infrastructure (RTI), which provides communication and coordination services to the federates. Federation communication only takes place between each federate and the RTI, not between federates themselves. The RTI as the central coordination software component as well as the federates can be located on any networked computer on an Intranet or the Internet (DoD 1997). 3. an Object Model Template (OMT) which defines the way how federations and federates have to be documented (using the Federation Object Model, FOM and the Simulation Object Model, SOM, resp.). The OMT uses a tabular approach which is well suited for automated tools and conversion into the OMT data interchange format (OMT DIF). OMTs promote the reuse of single federates or federations as a whole. Federations can be viewed as a contract between federates on how a common federation execution is intended to be run (DoD 1997a). The time management services provided by HLA allow the transparent running of federates under different time regimes (e.g. real time, time stepped, event driven) (DMSO 1997a). Even though it originates from military application surrounding, the architecture seems to be very well suited for civilian applications, too. Together with web-enabled simulation and animation components, an exciting new variety of applications and collaboration modes could be developed (Picture 1). RTI Interface Other Federates Simulation Federates Animation Federates Runtime Infrastructure (RTI) Picture 1 HLA-based Simulation and Animation

Method and system for dynamically balancing network traffic using address resolution protocol

Abstract: This invention provides dynamic balance of the traffic among data processing devices interconnecting networks and thereby improve the networking performance. For network traffic flowing between a first network and a second network, the traffic is distributed among the data processing devices that act as routers according to the traffic amount. An algorithm for balancing the traffic is used to select appropriate data processing devices as routers.

Computing budget allocation for simulation experiments with different system structures

Abstract: Simulation plays a vital role in analyzing discrete event systems, particularly in comparing alternative system designs with a view to optimize system performance. Using simulation to analyze complex systems, however, can be both prohibitively expensive and time consuming. We present effective algorithms to intelligently allocate computing budget for discrete event simulation experiments with different system structures. These algorithms dynamically determine the best simulation lengths for all simulation experiments and thus significantly reduce the total computation cost for a desired confidence level. Numerical illustrations are included. We also compare our algorithms with our earlier approach in which different system structures are not considered. Numerical testing shows that we can further improve simulation efficiency.

A real-time traffic simulation system

Abstract: This article studies the usefulness of parallel processing in real-time traffic-flow simulation based on continuum modeling of traffic dynamics. Computational fluid dynamics (CFDs) methods for solving simple macroscopic traffic-flow continuum models have been studied and efficiently implemented in traffic simulation codes (on serial computers) in the past. We designed a traffic-flow simulation code and mapped it onto a parallel computer architecture. This traffic simulation system is capable of simulating freeway traffic flow in real time. Tests with real traffic data collected from the freeway network in the metropolitan area of Minneapolis, MN, were used to validate the accuracy and computational rate of the parallel simulation system. The execution time for a 2-h traffic-flow simulation of about 200 619 vehicles in an 18-mi freeway, which takes 2.35 min of computer time (on a single-processor computer simulator), took only 5.25 s on the parallel traffic simulation system. This parallel system has a lot of potential for real-time traffic engineering applications.

Simulation optimization of air traffic delay cost

Abstract: The cost of delay is a serious and increasing problem in the airline industry. Air travel is increasing, and already domestic airports incur thousands of hours of delay daily, costing the industry $2 billion a year. One strategy for reducing total delay costs is to hold planes for a short time at the gate in order to reduce costly airborne congestion. In a network of airports involving thousands of flights, it is difficult to determine the amount to hold each flight at the gate. This paper discusses how the optimization procedure simultaneous perturbation stochastic approximation (SPSA) can be used to process delay cost measurements from air traffic simulation packages and produce an optimal gate holding strategy. As a test case, the SIMMOD air traffic simulation package was used to model a simple four-airport network.

Controller interface device

Abstract: An interface device between a computer running a traffic simulation program and any number of traffic signal controllers. The traffic simulation program simulates traffic in a road network including signal-controlled intersections. There are many signal manufacturers and they do not release the details of the control algorithms used in their controllers, hence it is impractical if not impossible to merely insert the control algorithm for a given controller into the program. The interface of the present invention allows any controller from any manufacturer to be used with the simulation program so that traffic flow in any network including signal-controlled intersections can be simulated. An assumed traffic network and demand traffic is input into the program; the program sends detector actuations to the signal controllers via the interface device and the controllers's phase indication states are sent back into the program also via the controller. The program then integrates this feedback into its operation and simulates the way traffic will flow through the road network having intersections with these particular signal controllers.

Distributed Traffic Simulation based on the High Level Architecture

Abstract: Although originating from the military simulation domain, the High Level Architecture also addresses the needs of the civil simulation community asking for software interoperability and reusability As a joint industry/academic effort, a traffic simulation prototype has been developed by CCI and ISG which is composed of heterogeneous software components It serves as a testbed for interoperability and performance issues and will provide a framework for future enhancements The prototype, its federates and the development process are described as well as the special viewpoint of the civil simulation community A summary of lessons learned and ongoing work concludes the paper

The impact of self-similar traffic on network delay

Abstract: The effect of self-similar traffic on the delay of a single queue system is first studied through the use of the measured traffic and models as input process. A model-driven simulation-based method is then proposed for the computation of mean line delay in a network routing design. Both the hybrid-FGN and the FARIMA algorithms have been used to synthesize self-similar sample paths. The comparison results with real-traffic data sets firmly establish the usefulness of our model-driven simulation-based method. We have proposed a practical database method that helps the designer to determine the parameters in network design. This approach may likely play an important role in network design and analysis.

Network traffic management system

Abstract: A traffic management system includes a traffic monitor and a traffic manager. The traffic monitor monitors traffic at a reference point T of user network interface to produce traffic information for each connection established. The traffic-manager manages network traffic of the wide-area network based on the traffic information received from the traffic monitor. The traffic information is produced for each permanent virtual connection (PVC) or for each dedicated line.

Predicting network traffic for collaborative virtual environments

Abstract: We introduce a method for predicting the network traffic that will be generated by collaborative virtual environment applications with varying numbers of participants. Statistical analysis of event logs from user trials results in a user behaviour model. Controlled traffic measurements combined with an analysis of the application architecture and network topology results in a system behaviour model. These two models are combined to produce a network traffic model. We describe the application of this method to a business game application that has been developed as part of the COVEN project. Finally, we make some general observations concerning the network traffic generated by CVEs including its bursty nature and the potential use of techniques such as multicasting and statistical multiplexing to reduce network load.

The traffic measurement and the empirical studies for the Internet

Abstract: The traffic engineering for a packet switched network such as the Internet is important for the network management and the future network plan. The investigation method for the traffic measurement should be build to understand the characteristics of the network. This paper describes the measurement system for the Internet traffic and shows some aspects of the Internet with the system. The results show some aspects of TCP sessions such as the number of packets, amount for transmission, connection time, the starting time, connection interval and retransmission of packets. The self-similar test for the traffic of the TCP and UDP were also done with the variance time plot and they were self-similar traffic.

Evaluations of traffic safety improvement using an autonomous traffic flow simulator including inter-vehicle communications

Abstract: In ITS (intelligent transport systems), it is very important to evaluate the effectiveness of inter-vehicle communication systems Unfortunately, few studies on traffic flow simulators that can evaluate the effectiveness of inter-vehicle communication systems for improving the traffic safety have been reported In this paper, we evaluate the effectiveness of inter-vehicle communication systems using the traffic flow simulator including inter-vehicle communications developed by the authors Simulation results show that the inter-vehicle communication system is effective in improving the traffic safety

JWarp: a Java library for parallel discrete‐event simulations

Abstract: SUMMARY Java is a very promising language for use in the simulation of physical models due to its objectoriented nature, portability, robustness and support for multithreading. This paper presents JWarp, a Java library for discrete-event parallel simulations. It is based on an optimistic model for synchronization of the simulation entities: the Time Warp mechanism. We introduce the main features of the library and discuss some of the implementation details. ©1998 John Wiley & Sons, Ltd. In several areas like engineering, computer science, economics and military applications, simulation is used to study the behaviour of complex models. The execution of some of these simulation models can be a very time-consuming task. For statistical reasons, it might be necessary to simulate a model for quite a long time, or to perform the same simulation several times with different parameter values. A possible solution to reduce the execution times of long-running simulations is by using multiple processors operating in parallel[ 1]. A typical simulation model involves several components or entities. By exploiting this inherent model of parallelism, it would be possible to speed up the performance of the simulations by decomposing these components through several processors. Every simulation model is a specification of the corresponding physical model and is composed of a set of states and events. In a discrete event simulation, the state of the system only changes at discrete points in simulated time. A natural decomposition strategy can result in an object-oriented system design, where an object corresponds to some component of the real system and is represented by a computational task that is assigned to a processor for execution. In this way, every component of the model is simulated by a logical process (LP). A discrete-event simulation requires the existence of multiple LP entities, a time-ordered event list holding time stamped events to be processed in the future, a global discrete clock that indicates the current simulation time and a set of state variables that define the state of the simulation. The simplest way to manage the event list would be based on a centralized strategy. The list of events would be managed by a single process (master), and there would be a pool of slave processes running on the parallel system that would execute those events in a concurrent way. However, the existence of a centralized queue of events would represent a bottleneck to the simulation, thereby clearly reducing the potential for parallelism.

Coordination of local adaptive traffic signal controllers

Abstract: We consider that freeway traffic flows out onto surface streets and surface street traffic flows into freeways and thus the combined performance of both freeway and surface street portions of a network are interrelated. We analyze a control architecture to improve surface street flow using adaptive signal controllers and introduce an important component towards coordinating control of surface street networks with freeway control. The contribution of this paper relates to the use of a particular adaptive signal control scheme at each intersection called ALLONS-D and a description of how to impart directives from a higher level controller to these local controllers such that traffic performance on the whole is maximized. Our result is a multi-layer approach for controlling the infrastructure in an urban street network. Simulations on an arterial network and a grid network are performed to test the coordination procedure that is presented.

Estimating all-terminal network reliability using a neural network

Abstract: The exact calculation of all-terminal network reliability is an NP-hard problem, with computational effort growing exponentially with the number of nodes and links in the network. Due to the impracticality of calculating all-terminal network reliability for networks of moderate to large size, Monte Carlo simulation methods have been used to estimate the network reliability and reliability upper and lower bounds. This paper puts forth an alternative to the estimation of all-terminal network reliability by using artificial neural network predictive models. Neural networks are constructed, trained and validated using alternative network topologies, a network reliability upper bound and the exact network reliability as a target. A hierarchical approach is used: a general neural network screens all network designs for reliability followed by a specialized neural network for highly reliable network designs. Results on a ten node problem are given using a grouped cross validation approach.

Network test system

Abstract: A network test system for monitoring and simulating a network and for testing the performance of a network device. The network test system comprising a computer in communications with the network, simulation software for emulating the network, formatting messages and emulating protocols, and a clock in substantial synchronization to a remote clock which is in communications with a remote computer and simulation software. The network test system allows for the accumulation of network performance data which can be used to test the performance characteristics of a device under test and to monitor and recommend to a network switch alternative switching patterns.

Network Management and Realtime Traffic FlowMeasurement

Abstract: An understanding of the traf® c ̄ ows in a network is vital for network management. One needs to collect traf® c ̄ ow data from many points throughout the network for performance monitoring and capacity planning, and be able to analyze it in terms of users and traf® c types for security and congestion management. The Realtime Traf® c Flow Measurement (RTFM) Architecture provides an effective method for obtaining traf® c ̄ ow data, and for these purposes it offers some advantages over current remote monitoring (RMON) techniques. The IETF’ s RTFM Working Group has developed the architecture and is re® ning it within the IETF Standards process [1±4].