252 research outputs found

    Performance evaluation of an open distributed platform for realistic traffic generation

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    Network researchers have dedicated a notable part of their efforts to the area of modeling traffic and to the implementation of efficient traffic generators. We feel that there is a strong demand for traffic generators capable to reproduce realistic traffic patterns according to theoretical models and at the same time with high performance. This work presents an open distributed platform for traffic generation that we called distributed internet traffic generator (D-ITG), capable of producing traffic (network, transport and application layer) at packet level and of accurately replicating appropriate stochastic processes for both inter departure time (IDT) and packet size (PS) random variables. We implemented two different versions of our distributed generator. In the first one, a log server is in charge of recording the information transmitted by senders and receivers and these communications are based either on TCP or UDP. In the other one, senders and receivers make use of the MPI library. In this work a complete performance comparison among the centralized version and the two distributed versions of D-ITG is presented

    The design and analysis of a corporate data network supporting a real-time clinical data application

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    In this study a design is proposed for a corporate, data network supporting real-time data applications. The proposed network incorporates both Local Area Network and Wide Area Network technologies to form a system capable of supporting a variety of applications. Multimedia software, like desktop video conferencing, IP telephony, and video streaming are becoming more pervasive. Since multimedia applications depend on active human involvement and perception, they are commonly referred to as real-time. The content of real-time applications relies on the timely and consistent delivery of information. If real-time applications experience any variation in information delivery, usually referred to as jitter, the result is unacceptable application performance. However, real-time applications are not solely limited to traditional multimedia. Interactive client-server based data applications also fall into this category. This project will specifically focus on the performance of a real-time clinical application, which has become predominant in the healthcare industry. To support the implementation of the proposed network, empirical data was gathered from system testing. Testing involved comparing the performance of a real-time application on the proposed design, against the current architecture. The result found that the proposed data network design reduced transport latency, allowing the real-time application to perform more efficiently

    ACSys/RDN experiences with Telstra’s experimental broadband network, second progress report

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    This report addresses three issues relevant to DHPC network infrastructure requirements:. · Technically, what we can currently achieve with the EBN? · What are desirable qualities in future ATM networks? · What further development of the EBN would we like to see for other applications? In writing this report, we will briefly describe the EBN ATM experience of ACSys’ Distributed High Performance Computing Project and Digital Media Libraries project, explain some of the technology and networking issues we have dealt with and summarise what we have learned. We have also included some background material on the EBN and ATM networks in general

    Quality of service over ATM networks

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    PREDICTING INTERNET TRAFFIC BURSTS USING EXTREME VALUE THEORY

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    Computer networks play an important role in today’s organization and people life. These interconnected devices share a common medium and they tend to compete for it. Quality of Service (QoS) comes into play as to define what level of services users get. Accurately defining the QoS metrics is thus important. Bursts and serious deteriorations are omnipresent in Internet and considered as an important aspects of it. This thesis examines bursts and serious deteriorations in Internet traffic and applies Extreme Value Theory (EVT) to their prediction and modelling. EVT itself is a field of statistics that has been in application in fields like hydrology and finance, with only a recent introduction to the field of telecommunications. Model fitting is based on real traces from Belcore laboratory along with some simulated traces based on fractional Gaussian noise and linear fractional alpha stable motion. QoS traces from University of Napoli are also used in the prediction stage. Three methods from EVT are successfully used for the bursts prediction problem. They are Block Maxima (BM) method, Peaks Over Threshold (POT) method, and RLargest Order Statistics (RLOS) method. Bursts in internet traffic are predicted using the above three methods. A clear methodology was developed for the bursts prediction problem. New metrics for QoS are suggested based on Return Level and Return Period. Thus, robust QoS metrics can be defined. In turn, a superior QoS will be obtained that would support mission critical applications

    Traffic Management and Congestion Control in the ATM Network Model.

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    Asynchronous Transfer Mode (ATM) networking technology has been chosen by the International Telegraph and Telephony Consultative Committee (CCITT) for use on future local as well as wide area networks to handle traffic types of a wide range. It is a cell based network architecture that resembles circuit switched networks, providing Quality of Service (QoS) guarantees not normally found on data networks. Although the specifications for the architecture have been continuously evolving, traffic congestion management techniques for ATM networks have not been very well defined yet. This thesis studies the traffic management problem in detail, provides some theoretical understanding and presents a collection of techniques to handle the problem under various operating conditions. A detailed simulation of various ATM traffic types is carried out and the collected data is analyzed to gain an insight into congestion formation patterns. Problems that may arise during migration planning from legacy LANs to ATM technology are also considered. We present an algorithm to identify certain portions of the network that should be upgraded to ATM first. The concept of adaptive burn-in is introduced to help ease the computational costs involved in virtual circuit setup and tear down operations

    Comparative Analysis of Location Management Schemes in Wireless ATM Networks

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    Mobility is the cornerstone of wireless networks. Supporting mobility requires some form of tracking to locate mobile terminals within the network. In the wireline ATM network, the terminal is fixed and the terminal is located by identifying the terminal and following the routing information provided at each switch along the path. As terminals become mobile, the path to the mobile becomes dynamic; the terminal and the path are no longer synonymous. Signalling traffic incurred in tracking mobile users and delivering enhanced services causes an additional load in the Wireless ATM (WArM) network. Efficient database and location management schemes are needed to meet the challenges from high density and mobility of users, and various service scenarios. In this thesis the three "natural" Location Management Strategies, i.e., Timer-Based, Location Area Based and Movement Based are studied and analysed for a W ATM network. The model used for depicting user motion and call arrival is Brownian motion with drift process and Poisson arrival process, respectively. The Timer-Based location management strategy is one in which the user updates its location periodically after an "optimum" interval of time. This optimum interval of time is based upon the user's mobility and call arrival characteristics and is therefore best suited for that particular mobile. In the Adaptive Location Area Based strategy, the user updates its location on each LA boundary crossing. The size of the LA changes according to the user' s mobility characteristics. The objective is to minimise the combined average signalling cost of both paging and registration for each individual mobile user such that the overall system-wide signalling cost for location tracking can be minimised
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