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Total 24 records

    Improving the Performance of Transport Layer Protocols in Cognitive Radio Networks

    , M.Sc. Thesis Sharif University of Technology Rahmani, Sajjad (Author) ; Hemmatyar, Ali Mohammad Afshin (Supervisor)
    Abstract
    The abstract is the most important section of the thesis because many readers limit most of their reading to abstracts, saving in-depth reading for specific theses. It should give the reader a "preview" of what's to come. The abstract should emphasize new and important aspects of the study or observations. The purpose of the abstract is to allow researchers to decide whether or not to read the whole thesis. The abstract is what researchers read first to decide if the thesis is important, interesting, and it allows them to assess the relevance of a thesis to their own research, without having to read the entire thesis. Thus, it is crucial that the abstract both summarize succinctly the key... 

    Estimation of Network Parameters for use in Congestion Control Algorithm

    , M.Sc. Thesis Sharif University of Technology Azimi, Arvin (Author) ; Jahangir, Amir Hossein (Supervisor)
    Abstract
    Many congestion control protocols proposed so far to alleviate the problems encountered by TCP protocol in high-speed networks and wireless links have to estimate the parameters of the network. For example, the TCP WESTWOOD congestion window is adjusted based on available bandwidth estimation, or TCP Vegas detects the congestion status based on RTT (Round Trip Time) estimation, and XCP protocol operates according to network traffic load. In this paper, we proposed a novel estimation algorithm that is based on burst identification techniques in router. we show through analysis and simulation that during burst periods this method can estimate the congestion window size of the specific flow... 

    On the better performance of ADMR versus ODMRP

    , Article 2012 6th International Symposium on Telecommunications, IST 2012 ; 2012 , Pages 621-625 ; 9781467320733 (ISBN) Aghdam, S. M ; Khansari, M ; Sharif University of Technology
    2012
    Abstract
    This paper presents a comparative performance analysis in more realistic scenario and more performance metrics of ADMR and ODMRP, two on-demand multicast routing protocols for Mobile Ad hoc Networks (MANETs) and Wireless Sensor Networks (WSNs). There are a few comparison works done between two multicast Ad hoc routing protocols, ADMR and ODMRP; these works are not complete in terms of both performance metrics and realistic scenarios. Simulation results show an unusual low number of control packets transmitted per data packet delivered in ADMR, this low number of control packet transmitted per data packet in ADMR has caused some comparison works to judge to better performance of ADMR than... 

    A novel transport agent for wireless routers to improve TCP and UDP performance over wireless links

    , Article 2005 IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2005, Berlin, 11 September 2005 through 14 September 2005 ; Volume 4 , 2005 , Pages 2201-2205 ; 3800729091 (ISBN); 9783800729098 (ISBN) Ghaboosi, K ; Hossein Khalaj, B ; Sharif University of Technology
    2005
    Abstract
    In this paper, by making slight modifications in protocol stack of wireless access points, the proposed CICADA scheme aims at isolating problems related to wireless section of a TCP connection from its wired portion, using IP spoofing and Virtual Protocol Stack scheme. As the simulation results for an 802.11 based system show, the proposed scheme improves the overall network throughput while reducing the mean and variance of end-to-end delay for voice and video flows due to smarter bandwidth allocation to elastic and real-time traffic. In addition, the proposed scheme uses a centralized NAT structure that prevents undesired disconnections during handovers and achieves a smaller handoff delay... 

    Adaptive generalized predictive control of active queue management in TCP networks

    , Article EUROCON 2005 - The International Conference on Computer as a Tool, Belgrade, 21 November 2005 through 24 November 2005 ; Volume I , 2005 , Pages 676-679 ; 142440049X (ISBN); 9781424400492 (ISBN) Firuzi, M. F ; Haeri, M ; Sharif University of Technology
    IEEE Computer Society  2005
    Abstract
    This paper develops methodology and technique tor the design, analysis, and impie mentation of an adaptive generalized predictive controller (AGPC) for Active Queue Management in TCP Networks. The TCP/AQM dynamic is modeled experimentally as a second-order system with a time delay where its parameters are estimated using the standard gradient algorithm. Based on this model, an AGPC is designed to gain the set-point tracking and robustness. AGPC, as a queue-based control mechanism, responds quickly to traffic changes, thus allowing for high utilization and small loss. We illustrate our results using ns-2 simulations and demonstrate the practical impact of adaptive model reference control on... 

    Performance analysis of CDM as an AQM congestion controller in dynamic networks

    , Article EUROCON 2005 - The International Conference on Computer as a Tool, Belgrade, 21 November 2005 through 24 November 2005 ; Volume I , 2005 , Pages 680-683 ; 142440049X (ISBN); 9781424400492 (ISBN) Bigdeli, N ; Haeri, M ; Sharif University of Technology
    IEEE Computer Society  2005
    Abstract
    The performance of a new robust AQM strategy for dynamically varying TCP/AQM networks is proposed. Network variations include in both network topology and traffic variations. The developed AQM is designed based on Coefficient Diagram Method (CDM), which is a new indirect pole placement method that considers the speed, stability and robustness of the closed loop system in terms of time domain specifications. Simulation results show different features of the proposed method. ©2005 IEEE  

    A compensated PID active queue management controller using an improved queue dynamic model

    , Article International Journal of Communication Systems ; Vol. 27, issue. 12 , 2014 , pp. 4543-4563 Kahe, G ; Jahangir, A. H ; Ebrahimi, B ; Sharif University of Technology
    Abstract
    Beside the major objective of providing congestion control, achieving predictable queuing delay, maximizing link utilization, and robustness are the main objectives of an active queue management (AQM) controller. This paper proposes an improved queue dynamic model while incorporating the packet drop probability as well. By applying the improved model, a new compensated PID AQM controller is developed for Transmission Control Protocol/Internet Protocol (TCP/IP) networks. The non-minimum phase characteristic caused by Padé approximation of the network delay restricts the direct application of control methods because of the unstable internal dynamics. In this paper, a parameter-varying dynamic... 

    Encountering to DDoS Attack

    , M.Sc. Thesis Sharif University of Technology Razian, Mohammad Reza (Author) ; Kharrazi, Mehdi (Supervisor) ; Movaghar Rahimabadi, Ali (Co-Advisor)
    Abstract
    Distributed Denial of Service (DDoS) is one of the more important attacks in computer networks. DDoS attacks can be categorized in to two categories: high rate and low rate. In the high rate DDoS category, the attacker tries to fill up all the link’s bandwidth capacity by flooding the link with packets. On the other hand, in the low rate DDoS category (i.e. LDDoS), the attacker executes a DDoS attack while keeping a low average transmission rate. TCP LDDoS is a low rate DDoS attack in which the attacker exploits the TCP congestion control behavior.
    In this thesis, we investigate a system for defending against the TCP LDDoS attack and propose a novel method for doing so. We present some... 

    CPM: A congestion control method for interplanetary network

    , Article Canadian Conference on Electrical and Computer Engineering ; 2014 Ravandi, M. G ; Mortazavi, M ; Ghorshi, S ; Sharif University of Technology
    Abstract
    The vision of future space exploration includes missions to deep space that require communication among ground stations on ground and another planets such as mars, moons, satellites in different orbiters, asteroids, robotic spacecrafts, and specially for crewed vehicles for delivering information. These communications requires high bit rate for autonomous operations and also have several different limitations. These type of communications set as a network that is called Interplanetary Network (IPN). There are difference challenges in space communication that TCP and UDP are not able to address them such as Long propagation delay, asymmetric bandwidth, etc. In this work, a congestion method... 

    Incorporating fault-proneness estimations into coverage-based test case prioritization methods

    , Article Information and Software Technology ; Volume 121 , May , 2020 Mahdieh, M ; Mirian Hosseinabadi, S. H ; Etemadi, K ; Nosrati, A ; Jalali, S ; Sharif University of Technology
    Elsevier B. V  2020
    Abstract
    Context: During the development process of a software program, regression testing is used to ensure that the correct behavior of the software is retained after updates to the source code. This regression testing becomes costly over time as the number of test cases increases and it makes sense to prioritize test cases in order to execute fault-detecting test cases as soon as possible. There are many coverage-based test case prioritization (TCP) methods that only use the code coverage data to prioritize test cases. By incorporating the fault-proneness estimations of code units into the coverage-based TCP methods, we can improve such techniques. Objective: In this paper, we aim to propose an... 

    Adaptive model predictive TCP delay-based congestion control

    , Article Computer Communications ; Volume 29, Issue 11 , 2006 , Pages 1963-1978 ; 01403664 (ISSN) Haeri, M ; Mohsenian Rad, A. H ; Sharif University of Technology
    2006
    Abstract
    Adaptive Model Predictive Transmission Control Protocol (AMP-TCP) as a new TCP delay-based congestion control algorithm is introduced. Both aspects of design and implementation of the algorithm are described using simulations on the ns-2 network simulator. The design stage is composed of two steps. First, a recursive system identification approach is proposed to capture the network delay dynamics from TCP source view. Second, the proposed modeling is employed to develop an adaptive model predictive TCP congestion control strategy in the absence of any explicit congestion notification. The characteristics and performance of AMP-TCP are investigated using several network simulations. Finally a... 

    Modeling of Interference Control in Wireless Ad-Hoc Networks in the Base of Transmission Rate Control in TCP

    , M.Sc. Thesis Sharif University of Technology Naseri Samaghcheh, Zeynab (Author) ; Haeri, Mohammad (Supervisor)
    Abstract
    An Ad-Hoc wireless network consists of a collection of geographically distributed nodes that communicate with each other over a wireless medium. These networks don’t use any infrastructure or base station to channel allocation. The important difference between wireless networks and wired networks is the broadcast nature of wireless communications. In these networks, each node transmits data to all of the nodes in the transmission range which may cause an increase in interference and data loss. On the other hand, due to mobility of users, fading the channel between them and change of routing, the probability of data loss increases. The extensive and successful employment of TCP variants in... 

    AQM controller design for TCP networks based on a new control strategy

    , Article Telecommunication Systems ; Volume 57, Issue 4 , December , 2013 , Pages 295-311 ; 10184864 (ISSN) Kahe, G ; Jahangir, A. H ; Ebrahimi, B ; Sharif University of Technology
    Kluwer Academic Publishers  2013
    Abstract
    When the network suffers from congestion, the core or edge routers signal the incidence of congestion through the active queue management (AQM) to the sources. The time-varying nature of the network dynamics and the complex process of retuning the current AQM algorithms for different operating points necessitate the development of a new AQM algorithm. Since the non-minimum phase characteristics of the network dynamics restrict direct application of the proportional-integral-derivative (PID) controller, we propose a compensated PID controller based on a new control strategy addressing the phase-lag and restrictions caused by the delay. Based on the unstable internal dynamics caused by the... 

    Microstructure and mechanical properties of an Al-Mg-Si tube processed by severe plastic deformation and subsequent annealing

    , Article Materials Science and Engineering A ; Volume 640 , July , 2015 , Pages 42-50 ; 09215093 (ISSN) Farshidi, M. H ; Kazeminezhad, M ; Miyamoto, H ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    This study is aimed to realize evolution of microstructure and mechanical properties of aluminum 6061 alloy tube subjected to Severe Plastic Deformation (SPD) and subsequent annealing. For this purpose, the tube is initially processed by different passes of an SPD process called Tube Channel Pressing (TCP) and then subjected to a subsequent annealing at 473. °K for 2. h. Afterwards, tension test is used for the evaluation of mechanical properties while Electron Back-Scattered Diffraction (EBSD) equipped Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) are utilized for the microstructural characterizations. Results show that the Continuous Static Recrystallization... 

    Vulnerability analysis of networks to detect multiphase attacks using the actor-based language Rebeca

    , Article Computers and Electrical Engineering ; Volume 36, Issue 5 , 2010 , Pages 874-885 ; 00457906 (ISSN) Shahriari, H. R ; Makarem, M. S ; Sirjani, M ; Jalili, R ; Movaghar, A ; Sharif University of Technology
    2010
    Abstract
    Increasing use of networks and their complexity make the task of security analysis more and more complicated. Accordingly, automatic verification approaches have received more attention recently. In this paper, we investigate applying of an actor-based language based on reactive objects for analyzing a network environment communicating via Transport Protocol Layer (TCP). The formal foundation of the language and available tools for model checking provide us with formal verification support. Having the model of a typical network including client and server, we show how an attacker may combine simple attacks to construct a complex multiphase attack. We use Rebeca language to model the network... 

    A self-tuning controller for queuing delay regulation in TCP/AQM networks

    , Article Telecommunication Systems ; 2018 ; 10184864 (ISSN) Kahe, G ; Jahangir, A. H ; Sharif University of Technology
    Springer New York LLC  2018
    Abstract
    AQM router aims primarily to control the network congestion through marking/dropping packets which are used as congestion feedback in traffic sources to balance their flow rate. However, stabilizing queuing delay and maximizing link utilization have been considered as the main control objectives, especially in media dominated networks. Usually, most of the AQM algorithms are designed for a nominal operating point. However, time-varying nature of network parameters frequently violates their robustness bounds. In this paper, a self-tuning compensated PID controller is proposed to address the time-varying nature of network conditions caused by parameter variations and unresponsive connections.... 

    Calibration of parallel kinematic machine tools using mobility constraint on the tool center point

    , Article International Journal of Advanced Manufacturing Technology ; Volume 45, Issue 5-6 , 2009 , Pages 531-539 ; 02683768 (ISSN) Abtahi, M ; Pendar, H ; Alasty, A ; Vossoughi, G. R ; Sharif University of Technology
    2009
    Abstract
    In the application of parallel kinematic machine tools (PKM), because of errors in the geometric parameters, it is necessary to calibrate the PKM to improve the positioning accuracy. In existing self-calibration methods, either some redundant sensors on passive joints or some mobility constraints on the kinematic chains are used. However, the mobility constraints imposed on kinematic chains might apply large forces during the test on legs and passive joints. Also, these kinds of calibrating are applicable only on PKMs in which their actuated joints can be used as passive joints. To overcome weaknesses of existing methods, a novel approach to calibration based on imposing position constraints... 

    A self-tuning controller for queuing delay regulation in TCP/AQM networks

    , Article Telecommunication Systems ; Volume 71, Issue 2 , 2019 , Pages 215-229 ; 10184864 (ISSN) Kahe, G ; Jahangir, A. H ; Sharif University of Technology
    Springer New York LLC  2019
    Abstract
    AQM router aims primarily to control the network congestion through marking/dropping packets which are used as congestion feedback in traffic sources to balance their flow rate. However, stabilizing queuing delay and maximizing link utilization have been considered as the main control objectives, especially in media dominated networks. Usually, most of the AQM algorithms are designed for a nominal operating point. However, time-varying nature of network parameters frequently violates their robustness bounds. In this paper, a self-tuning compensated PID controller is proposed to address the time-varying nature of network conditions caused by parameter variations and unresponsive connections.... 

    Direct-DMC for AQM computational complexity reduction in TCP/IP networks

    , Article International Conference on Control, Automation and Systems, ICCAS 2007, Seoul, 17 October 2007 through 20 October 2007 ; December , 2007 , Pages 1270-1273 ; 8995003871 (ISBN); 9788995003879 (ISBN) Ostadabbas, S ; Haeri, M ; Sharif University of Technology
    2007
    Abstract
    Active queue management (AQM) mechanisms are designed to provide better support for end-to-end congestion control mechanisms of transmission control protocol (TCP) in TCP/IP networks. This paper introduces Direct Dynamic Matrix Control (D-DMC) as a new AQM method in dynamic TCP networks. Ability of the controller in handling system delay along with its simplicity and low computational loads makes D-DMC a privileged AQM method in high speed networks. The controller is designed based on a small signal linearized fluid-flow model of TCP/AQM networks. The computational complexity analysis as well as the MATLAB simulation results shows the out-performance of the developed controller for both... 

    Neural network approximation of model predictive controller for congestion control of TCP/AQM networks

    , Article International Conference on Control, Automation and Systems, ICCAS 2007, Seoul, 17 October 2007 through 20 October 2007 ; 2007 , Pages 2591-2596 ; 8995003871 (ISBN); 9788995003879 (ISBN) Marami, B ; Haeri, M ; Sharif University of Technology
    IEEE Computer Society  2007
    Abstract
    Due to the excellent properties of the model predictive controllers (MPC) in implementing on nonlinear and time varying systems, utilizing these controllers as Active Queue Management (AQM) strategy is proposed for congestion control of computer networks. However, high computational demand to solve the optimization problem exist in these controllers is a major obstacle when they are applied on fast large-scale constrained systems such as the computer networks. Small signal linearized model of the nonlinear TCP/AQM network is used to design MPC controller and then a neural network is trained to approximate the model predictive control strategy. Using this approach, due to the parallel...