Traffic Source Models Research Articles

Routing in ISL Networks Considering Empirical IP Traffic

Next-generation satellite networks are expected to provide a variety of applications with diverse performance requirements, which will call for the development of adaptive routing procedures supporting different levels of services. In this paper, we propose traffic class dependent (TCD) routing, which has the potential to differentiate between traffic classes using different optimization criteria in route calculation. The performance of TCD routing is evaluated for different traffic scenarios using an empirical traffic source model derived from the real backbone Internet traffic trace and compared with results obtained with equivalent Poisson traffic as a reference point. In addition, TCD routing is compared with a simple single service routing procedure, which does not make any distinction between traffic classes. Performance analysis, in terms of average packet delay, normalized data throughput, and normalized link load, reveals improved routing resulting from traffic class differentiation, regardless of the traffic scenario considered. The performance measures based of aggregate traffic flow show no significant difference between routing of empirical and equivalent Poisson traffic.

이동통신 네트워크 트래픽 모델을 위한 도시 지역 이동통신 트래픽 특성 분석

오래 전부터 이동통신 서비스를 위한 통신 프로토콜이나 기능 요소들의 성능을 평가하기 위해서는 분석적 방법, 시뮬레이션 및 평가적 방법이 이용되어 왔다. 이중 시뮬레이션을 통한 평가 방법은 시스템 내부 구성 요소들의 연관 관계가 매우 복잡한 시스템을 테스트하는데 유용하게 사용되고 있으며, 이를 위해서는 이동통신 통화 특성을 반영하는 텔레트래픽 모델을 제시하고 있어야 한다. 텔레트래픽 모델은 일반적으로 트래픽 소스 모델과 네트워크 트랙픽 모델로 구성되어 있으며, 본 네트워크 트래픽 모델을 정의하기 위해 요구되는 실제 기지국 통화량 자료를 수집하고 분석한 결과를 제공하기 위한 것이다. 본 논문에서는 서울시를 상업, 주거, 준공업, 그리고 녹지 지역으로 되어 있는 도시계획 용도지역으로 구분하고, 여기에 설치되어 있는 기지국으로부터 실제 데이터를 시간대별로 수집하였다. 수집된 자료를 이용하여 각 지역별 기지국의 시간대별 통화량 분포와 최대 및 최소 발생 호 수 등을 제시하였다. 분석 결과는 보다 더 정확한 이동통신 네트워크 트래픽 모델을 정의하거나, 기존 이동통신 시뮬레이션 과정에서의 입력 자료로 사용할 수 있다. Traditionally,, analysis, simulation and measurement have all been used to evaluate the performance of network protocols and functional entities that support mobile wireless service. Simulation methods are useful for testing the complex systems which have the very complicate interactions between components. To develop a mobile call simulator which is used to examine, validate, and predict the performance of mobile wireless call procedures must have the teletraffic model, which is to describe the mobile communication environments. Mobile teletraffic model is consists of 2 sub-models, traffic source and network traffic model. In this paper, we analyzed the network traffic data which are gathered from selected Base Stations (BSs) to define the mobile teletraffic model. We defined 4 types of cell location-Residential, Commercial, Industrial, and Afforest zone. We selected some Base Stations (BSs) which are represented cell location types in Seoul city, and gathered real data from them And then, we present the call rate per hour, cail distribution pattern per day, busy hours, loose hours, the maximum number of call, and the minimum number of calls based on defined cell location types. Those parameters are very important to test the mobile communication system´s performance and reliability and are very useful for defining the mobile network traffic model or for working the existed mobile simulation programs as input parameters.

Fluid-flow modelling of internet traffic in GSM/GPRS networks

In order to find an analytical solution for performance evaluation of Internet access over the General Packet Radio Service (GPRS), the packet-switched extension of the GSM mobile radio network, we evaluate the well-known Fluid-flow modelling (FFM) approach. Mobile Internet users are modeled by an ON/OFF source with exponentially distributed sojourn times in the ON and OFF state. We choose the IP datagram delay at the radio interface as quantity of interest. As Fluid-flow analysis only delivers the mean equilibrium buffer content, we present some additional methodology to calculate the sojourn time in the Fluid-flow model, taking specific characteristics of the GPRS into account. ON/OFF source parameters are determined representing the mean offered traffic in typical GPRS load scenarios by stochastic simulation, using the GPRS emulation system GPRSim. The GPRSim comprises load generators representing typical GPRS usage and a prototypical implementation of the GPRS protocols. Comparison of simulation results and analysis is performed using the same traffic source model for both simulation and analysis, eliminating approximation of WWW traffic characteristics as a reason for deviations between simulation results and analysis. Additionally analytical results are compared with results of the GPRSim using a detailed WWW model for traffic generation. The results illustrate the influence of accurate source modelling and the limitations of the FFM to model the GPRS system with elastic traffic. It is shown that the FFM is not able to depict the elastic property of TCP-based Internet traffic, but is capable of modelling the multiplexing of inelastic traffic like generated by streaming or real-time applications over the GPRS radio link in sufficient detail for performance estimations.

QoS of internet access with GPRS

In this paper we examine the effects of Internet traffic on the Quality of Service (QoS) in GPRS wireless networks. With a stochastic source traffic model describing the user behavior, we will derive subjective and objective Quality of Service measures in terms of WWW downloading time and the transmission bandwidths on TCP and TBF level. Comparing the obtained values with wireline network modems and ISDN yields a slowdown factor which indicates the subjective degradation that the wireless user experiences.

Procedures and tools for analysis of network traffic measurements

We present procedures and tools for the analysis of network traffic measurements. The tools consist of stand-alone 1 The stand-alone software modules can be downloaded from http://www.ics.forth.gr/netgroup/msa; the web interface is available at http://trace.ucnet.uoc.gr 1 modules that implement advanced statistical analysis procedures and a flexible web-based interface through which a user can create, modify, save, and execute experiments using the statistical analysis modules. The tools do not assume a specific source traffic model, but rather process actual measurements of network traffic. Indeed, the theory that the tools are based on can identify the time-scales that affect a link’s performance, hence suggest the appropriate time granularity of traffic measurements. We present and discuss case studies that demonstrate the application of the tools for answering questions related to network management and dimensioning, such as the maximum link utilization when some quality of service is guaranteed, how this utilization is affected by the link buffer and traffic shaping, the acceptance region and the effects of the scheduling discipline, and the token (or leaky) bucket parameters of a traffic stream. The case studies involve actual traffic measurements obtained by a high performance measurement platform that we have deployed at the University of Crete network.

The superposition of discrete-time Markov renewal processes with an application to statistical multiplexing of bursty traffic sources

The main contribution in this paper is the introduction of a methodology for approximately characterizing the superposition process of N⩾2 arbitrary (and possibly heterogeneous) discrete-time Markov Renewal Processes (MRP). In this model, the superposition process is characterized by a MRP with a state space that grows exponentially with N. We consider an on/off traffic source model, where the distribution of the on and off periods is arbitrary, as a special case of the general MRP. Subsequently, a queueing model for a FIFO finite-buffer multiplexer with arbitrary on/off input sources is analyzed. We provide numerical results for testing the algorithms introduced in the paper. We also study the effect of some of the statistical properties of on/off input sources on the multiplexer's performance.

An adaptive call admission control in ATM networks using optimized measurements windows

We propose an adaptive measurement-based admission control algorithm that uses optimization procedure to choose an appropriate measurement window size dynamically. Previous designs on measurement-based admission control mainly focused on strategies that consider the worst case traffic source model to guarantee QoS bounds for all connections. In this paper, we develop a simple mechanism in which both statistical multiplexing gain and QoS are considered An accurate formula for the cell loss probability which is combined with measurements, is presented for refined on/off traffic model. Furthermore, more accurate measurements of traffic would be given to admission controller through optimized window size. The proposed adaptive control is an appealing alternative: not only does it offer adaptivity to changing traffic conditions, but supports a guarantee that loss QoS bound is not violated due to the admission of new calls into ATM network. Simulations were performed to test the performance of the proposed algorithm.

An integrated admission control based on measurements in ATM networks

We developed a novel scheme to maintain QoS (Quality of Service) requirement for different traffic classes in the dynamic environment through full utilization of statistical multiplexing. Previous designs on measurement-based admission control mainly focused on strategies that consider the worst case traffic source model to guarantee QoS bounds for all connections. This can result in overallocation of resources. The proposed mechanism not only allows statistical multiplexing gain to be exploited, it also simplifies the estimation process. An accurate formula for the cell loss probability which is combined with measurements, is presented for a new traffic model. Furthermore we enhance the performance of this mechanism through real-time measurements of traffic and monitoring of QoS.

Dimensioning of play-out buffers for real-time services in a B-ISDN

A large fraction of traffic that the future B-ISDN will probably transport is made up of real-time services with stringent delay and delay jitter requirements. Since ATM networks do not provide time transparent links (i.e. constant delay links), a delay equalisation has to be provided in the adaptation layer or in user equipments. In this paper, we first present a source model analysis and then propose an analytical model that allows the evaluation of the end-to-end delay and of the relevant jitter; finally, we focus on the dimensioning of play-out buffers. The proposed model is validated with simulation results and we found a good agreement between analytical and simulation results. To make the study analytically tractable we use rather simple traffic source models and we make suitable simplifying assumptions. These assumptions are fairly general but the source models are still far from representing accurately certain kinds of real traffic. For this reason, we also carry out an additional simulation study (supported by some analytical arguments), by using real experimental MPEG and LAN traffic traces, to assess the system performance in real scenarios.

A Source traffic model and its transient analysis for network control

Traffic measurements from communication networks have shown that network traffic is quite complex, exhibiting phenomena such as long-tail probability distributions, long-range dependence and self similarity. Thus, in order to design and control new communication networks, we are motivated to consider new source traffic models and new ways to analyze network performance when there are many independent sources each with traffic that can be described by such models. We present a candidate source traffic model: The required bandwidth (arrival rate) as a function of time for each source is represented as the sum of two stochastic processes: (1) a macroscopic (longer-time-scale) level process and (2) a microscopic (shorter-time-scale) within-level variation process. We let the level process be a finite-state semi-Markov process (SMP), allowing general (possibly long-tail) level holding-time distributions, and we let the within-level variation process be a zero-mean piecewise-stationary process. To cope with the added model complexity, we suggest making design and control decisions based on the likelihood that aggregate demand (the input rate from a set of sources) will exceed capacity (the maximum possible output rate). This approach to model analysis avoids the customary queue-ing detail (focus on buffer content and overflow). We propose using transient analysis for control, conditioning on the level and elapsed level holding time of each source. In doing so, we exploit asymptotics associated with multiplexing a large number of sources

Comparative analysis of wireless ATM channel access protocols supporting multimedia traffic

Extension of multimedia services and applications offered by ATM networks to wireless and mobile users has captured a lot of recent research attention. Research prototyping of wireless ATM networks is currently underway at many leading research and academic institutions. Various architectures have been proposed depending on the intended application domain. Successful implementation of wireless connectivity to ATM services is significantly dependent on the medium access control (MAC) protocol, which has to provide support for multimedia traffic and for quality-of-service (QoS) guarantees. The objective of this paper is to investigate the comparative performance of a set of access protocols, proposed earlier in the literature, with more realistic source traffic models. Data traffic is modeled with self-similar (fractal) behavior. Voice traffic is modeled by a slow speech activity detector (SAD). Video traffic is modeled as a H.261 video teleconference, where the number of ATM cells per video frame is described by a gamma distribution and a first-order discrete autoregressive process model. A comparison of the protocols based on simulation data is presented. The goal of the paper is to identify appropriate techniques for effectively and efficiently supporting multimedia traffic and QoS. Simulation results show that boundaries between different types of services are necessary for multimedia traffic. Reservation for certain traffic type especially video can significantly improve its quality. Reducing the number of collisions is an important issue for wireless networks since contentions lead not only to potentially high delay but also result in high power consumption.

Reminder on queueing theory for ATM networks

Queueing theory is a very useful means for performance prediction during the system design phase, for resource dimensioning and for planning of networks according to load andquality of service figures. In this paper, an overview is given about traffic models for ATM traffic sources, generic ATM traffic control models and performance evaluation methods.

A multiservice user descriptive traffic source model

The asynchronous transfer mode (ATM)-based broadband integrated services digital network (B-ISDN) dominates the research interest in telecommunications. Traffic and network modeling are the techniques used for performance evaluation and assessment of B-ISDN design alternatives and planning. The specific nature of the ATM technique requires new approaches for traffic modeling. Selecting appropriate traffic source models is an important issue, since it is closely related to the successful design and efficient performance of the networks to be built in the future. The source (multilevel, multiservice structured Markovian) model presented provides a simple way for characterizing the behavior of a telecommunication user recognizing the multilevel discipline of a telecommunication session. The traffic model is general enough to fit a variety of different services by appropriately varying the values of the parameters defining it, but also it is simple enough because it is described by a small number of parameters and the defining parameters make a good intuitive sense by being closely related to actual physical quantities.

Performance of cellular packet CDMA in an integrated voice/data network

This paper presents a simulation-based study of cellular packet CDMA systems operating in an integrated voice/data traffic scenario. Spread-spectrum CDMA provides a suitable framework for resource-shared packet transport capable of combining isochronous (voice, ISDN) and bursty data services. In this work, a general network model for cellular packet CDMA with mixed voice/data traffic is described and used to evaluate the capacity/performance impact of several key system parameters. First, the effect of spreading factor (N) and forward error correction (FEC) rate are studied, confirming earlier work indicating a weak dependence onN and a well-defined optimum code rate in the range of 0.5–0.7 (with BCH coding). Next, the effect of propagation loss coefficient (γ) on network capacity is investigated over a range of possible assumptions forγ, including both constant and distance-dependent models. The results show that system capacity depends strongly onγ, varying by as much as a factor of 2 over the range of parameters considered. For a given distance-dependentγ assumption, performance results are also obtained for different cell sizes in order to understand the overall spatial reuse efficiency achievable in different cellular and microcellular scenarios. This is followed by an investigation of traffic source model effects: first the capacity improvement from voice activity detection VAD) is presented, showing the expected ∼2∶1 gains. Results for varying proportions of voice and data traffic intensities indicate that the operating efficiency does not change significantly as the proportion of bursty data relative to voice is varied.

Operational departmentwide picture archiving communication system analysis using discrete event-driven block-oriented network simulation

The accurate prediction of image throughput is a critical issue in planning for and acquisition of any successful picture archiving and communication system (PACS). Simulation plays an important role in this effort. The PACS image management chain is decomposed into eight subsystems. These subsystems include network transfers over three different networks and five software programs and/or queueing structures. This decomposition is used to create a simulation model that was effectuated using commercially available block-oriented network simulation software. From the PACS database, the traffic generation patterns of the imaging modality devices are used to drive the simulation. The simulation models the image file flow through the PACS for a 24-hour period. The behavior of the simulated traffic generators agreed well with the values derived from the PACS database. The mean delay for the simulated PACS is found to be 225 +/- 59 seconds. The delay time was found to vary during the simulated 24-hour cycle in a consistent manner with observations. This simulation provides estimates on what a radiological department can expect from a PACS in terms of throughput, utilization, and delay. The block-oriented network simulator (BONeS, Comdisco Systems Inc, Foster City, CA) simulation model of the modeled PACS is highly accurate. The models for the imaging modality traffic sources are validated with a high degree of accuracy. The simulation model allows for the study of what happens to the delay time under various loads. In this simulation, the reformatting process was determined to be the bottleneck causing a large increase in delay time under heavy loads.

Overview of ATM networks: functions and procedures

The purpose of this paper is to present an overview of the ATM technique. The basic principles of the ATM transfer technique, the B-ISDN layered protocol reference model, as well as the architecture and the main functions of the ATM network, are described in this tutorial. In particular, we present the main characteristics of the ATM technique, the structure of the ATM cell, the functions which deal with the protection from errored cells (HEC procedure) and the identification of the boundaries of the ATM cells (cell delineation and scrambling). The VP/VC concept is explained in detail, and the main principles and functions of the three lowest layers (Physical, ATM and Adaptation) of the B-ISDN layered protocol reference model are surveyed. The issue of Quality of Service parameters in ATM networks is reviewed, and the problem of the allocation of the network resources in response to user demands, as well as the problems of congestion control, Usage Parameter Control (UPC) and traffic modelling in ATM networks, are assessed. Finally, we present ‘possible’ sets of traffic characterization parameters, and show how possible B-ISDN sources can be modelled according to the basic on-off ATM traffic source model.

Simulation models for performance evaluation of satellite multiple access protocols

Simulation models are described for the performance evaluation of satellite multiple-access protocols used in VSAT (very small aperture terminal) data networks. Since the design of VSAT-based wide-area networks for interactive applications is critically dependent on the delay-throughput characteristics of the channel access protocol used, detailed simulation models have been developed to augment analytical performance-evaluation methods. Simulation models for several candidate VSAT access protocols, including random-access techniques such as Aloha, selective reject Aloha and slotted Aloha and demand-assignment multiple-access based techniques, are discussed in terms of traffic-source models, access algorithms, and performance-evaluation criteria. Numerical results for a realistic interactive data VSAT network environment are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>