Wyniki wyszukiwania - Biblioteka Nauki

1

On the optimization of the inter - flow fairness in the Internet

100%

Adamczyk B. , Chydziński A.

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tom Vol. 24, No. 3

205-225

EN

All known active queue management algorithms invented to provide fair bandwidth allocation between TCP flows are designed to cooperate with the classic TCP congestion control (New Reno). However, some new congestion control schemes are becoming more and more popular nowadays (e.g. the Cubic algorithm). Therefore, the following question arises: will these fair queue management algorithms work well in the presence of a new congestion control scheme? To answer this questions, we present a comprehensive study of the performance of seven fair queue management algorithms in the presence of seven TCP variants. In particular, the fairness index, queue size and throughput were measured in scenarios with diversified RTTs, traffic patterns and congestion levels. Not only do the results allow us to answer the aforementioned question, but also to formulate recommendation on how to provide the best cross-layer fairness optimization in the Internet.

PL

Wszystkie znane z literatury algorytmy aktywnego zarządzania kolejkami (AQM) ukierunkowane na zapewnienie sprawiedliwego podziału pasma pomiędzy przepływy w Internecie były opracowywane z myślą o współpracy z (klasycznym dziś) algorytmem kontroli zatłoczenia TCP, tzn. New Reno. W ostatnich latach można zauważyć w Internecie istotne zwiększanie się udziału nowych algorytmów kontroli zatłoczenia TCP (jak np. algorytmu Cubic). Dlatego te˙z pojawia się naturalne pytanie: czy algorytmy sprawiedliwego podziału pasma zaprojektowane dla New Reno bedą równie dobrze działać w obecnosci tych nowych wariantów TCP? Aby uzyskać odpowiedź na to pytanie, przeprowadzone zostały szeroko zakrojone studia symulacyjne. Studia te uwzględniały siedem najważniejszych algorytmów AQM do sprawiedliwego podziału pasma, siedem wersji TCP (w tym najnowocześniejsze warianty), różne scenariusze zatłoczenia sieci oraz czasy RTT połączeń TCP. Uzyskane wyniki pozwoliły nie tylko udzielić odpowiedzi na sformułowane powyżej pytanie, ale także wskazać, które wersje TCP i AQM najlepiej realizują ideę optymalizacji międzywarstwowej w celu zapewnienia sprawiedliwego podziału pasma pomiędzy przepływy w Internecie.

2

Model Checking Optimisation Based Congestion Control Algorithms

100%

Lomuscio A. , Strulo B. , Walker N. G. , Wu P.

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tom Vol. 102, nr 1

77-96

EN

Model checking has been widely applied to the verification of network protocols. Alternatively, optimisation based approaches have been proposed to reason about the large scale dynamics of networks, particularly with regard to congestion and rate control protocols such as TCP. This paper intends to provide a first bridge and explore synergies between these two approaches. We consider a series of discrete approximations to the optimisation based congestion control algorithms. Then we use branching time temporal logic to specify formally the convergence criteria for the system dynamics and present results from implementing these algorithms on a state-of-the-art model checker. We report on our experiences in using the abstraction of model checking to capture features of the continuous dynamics typical of optimisation based approaches.

3

Quantity-based flow control strategy for connection-oriented communication networks

100%

Karbowańczyk M. , Żuk J.

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tom Vol. 60, nr 2

293-300

EN

In this paper a new flow control strategy for connection-oriented communication networks is presented. It utilises methods of control theory, in particular the Smith predictor and dead-beat control, to achieve desirable dynamics of the considered network. In contrast to a number of earlier proposals in which the controller command is interpreted as the rate transmission, in our solution it is interpreted as the quantity of data that the controlled node is expected to send. This allows us to model a single virtual connection with non-persistent data source as a time-delay system in which the delay may temporarily exceed its assumed boundary. Favourable properties of the proposed control strategy are formulated as mathematical theorems and thoroughly discussed.

4

Design of the state predictive model following control system with time-delay

88%

Wang D. , Wu S. , Okubo S.

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nr 2

247-254

EN

Time-delay systems exist in many engineering fields such as transportation systems, communication systems, process engineering and, more recently, networked control systems. It usually results in unsatisfactory performance and is frequently a source of instability, so the control of time-delay systems is practically important. In this paper, a design of the state predictive model following control system (PMFCS) with time-delay is discussed. The bounded property of the internal states for the control is given, and the utility of this control design is guaranteed. Finally, examples are given to illustrate the effectiveness of the proposed method, and state predictive control techniques are applied to congestion control synthesis problems for a TCP/AQM network.

5

Sared: self-adaptive active queue management scheme for improving quality of service in network systems

75%

Adamu A. , Surajo Y. , Jafar M. T.

Computer Science

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2021

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tom T. 22 (2)

251–266

EN

Considering the phenomenal growth of network systems, congestion remains a threat to the quality of the service provided in such systems; hence, research on congestion control is still relevant. The Internet research community regards active queue management (AQM) as an effective approach for addressing congestion in network systems. Most of the existing AQM schemes possess static drop patterns and lack a self-adaptation mechanism; as such they do not work well for networks where the traffic load fluctuates. This paper proposes a self-adaptive random early detection (SARED) scheme that smartly adapts its drop pattern based on a current network’s traffic load in order to maintain improved and stable performance. Under light- to moderate-load conditions, SARED operates in nonlinear modes in order to maximize utilization and throughput, while it switches to a linear mode in order to avoid forced drops and congestion under high-load conditions. Our conducted experiments revealed that SARED provides optimal performance regardless of the condition of the traffic load.

6

Congestion control in connection-oriented data transmission networks

63%

Ignaciuk P.

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2009

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tom z. 117

5-12

EN

In this paper formal, control-theoretic methods are applied to design an efficient congestion control algorithm for modern connection-oriented data transmission networks. The design is based on the principles of discrete-time sliding-mode control and linear-quadratic optimal control. The asymptotic stability of the closed-loop system with the designed controller implemented is demonstrated, and the conditions for achieving the maximum throughput in the networks are defined.

PL

W pracy zaprojektowano nowy algorytm sterowania przepływem danych dla połączeniowych sieci teleinformatycznych. Do tego celu wykorzystano zaawansowane metody teorii sterowania - dyskretne sterowanie ślizgowe oraz dyskretne sterowanie optymalne z kwadratowym wskaźnikiem jakości. Pokazano, że zaproponowany algorytm pozwala wyeliminować ryzyko gubienia danych przy jednoczesnym pełnym wykorzystaniu dostępnego pasma.

7

Problemy wdrażania szerokopasmowych usług multimedialnych w heterogenicznych sieciach IP

63%

Chodorek A. , Chodorek R. R. , Krempa A. , Pach A. R.

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tom T. 10

10--18

PL

Przez ponad 30 lat swojego istnienia, sieć Internet wyewoluowała z klasycznej sieci transmisji danych w największą z sieci wielousługowych. Część usług internetowych tworzona była od podstaw (jak np. poczta elektroniczna), część z nich (np. telewizja, czy telefonia internetowa) stanowi przeniesienie do Internetu usług realizowanych dotychczas w sieciach specjalizowanych (telewizyjnej, telefonicznej). Wdrażanie nowych usług jest zagadnieniem złożonym. Nowe usługi mogą spowodować problemy z funkcjonowaniem aplikacji już istniejących. Problemy mogą wystąpić także z usługami przeniesionymi z sieci specjalizowanych - w sieci Internet mogą one źle funkcjonować, np. ze względu na dużo niższą jakość transmisji niż wymagana. W niniejszym artykule dokonano analizy współczesnych usług, m.in. z punktu widzenia wymagań, jakie stawiają one dla sieci transmisyjnej. Przeanalizowano najistotniejsze elementy heterogenicznych sieci IP pod kątem współpracy z różnego typu usługami. Określono, jakie problemy występują podczas współistnienia wielu różnych aplikacji w sieci heterogenicznej. Wskazano również, jak te problemy rozwiązywać.

EN

For over 30 years of its existence, the Internet has evolved from traditional data networks in the largest multiservice networks. Some Internet service has been created from scratch (like e-mail), some of them (eg. television, or Internet telephony) is the adaptation of services previously implemented in specialized networks (broadcast television network, Plain Old Telephone Service - POTS, etc.). Implementation of new services is a complex issue. New services may interact with existing applications. Problems can also occur with services adapted from specialized networks - for example, due to much lower transmission quality than required. In this paper an analysis of contemporary services and requirements is described. We show problems, which occur due to the heterogeneity of multiservice network, as well as how to solve these problems.

8

ABR traffic control over multi-source single-bottleneck ATM networks

63%

Bartoszewicz A. , Molik T.

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2004

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tom Vol. 14, no 1

43-51

EN

The problem of flow control in fast, connection-oriented communication networks supporting the traffic generated by multiple sources is considered. A novel sampled time strategy governing the behaviour of the sources is proposed. The strategy combines the Smith principle with the conventional sampled time proportional controller. It guarantees an equal resource allocation between various users, full bottleneck link utilisation and no cell loss in the controlled network. Consequently, the need for cell retransmission is eliminated and a high throughput is ensured. Furthermore, transmission rates generated by the algorithm are limited. This property permits a direct implementation of the proposed strategy in the network environment. A simulation example confirms favourable performances of the proposed control scheme.

9

Design of the state predictive model following control system with time-delay

63%

Wang D. , Wu S. , Okubo S.

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tom Vol. 19, no 2

247-254

EN

Time-delay systems exist in many engineering fields such as transportation systems, communication systems, process engineering and, more recently, networked control systems. It usually results in unsatisfactory performance and is frequently a source of instability, so the control of time-delay systems is practically important. In this paper, a design of the state predictive model following control system (PMFCS) with time-delay is discussed. The bounded property of the internal states for the control is given, and the utility of this control design is guaranteed. Finally, examples are given to illustrate the effectiveness of the proposed method, and state predictive control techniques are applied to congestion control synthesis problems for a TCP/AQM network.

10

Approximation models for the evaluation of TCP/AQM networks

51%

Marek D. , Domański A. , Domańska J. , Szyguła J. , Czachórski T. , Klamka J. , Filus K.

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tom Vol. 70, nr 4

art. no. e141986

EN

The article proposes a model in which Diffusion Approximation is used to analyse the TCP/AQM transmission mechanism in a multinode computer network. In order to prevent traffic congestion, routers implement AQM (Active Queue Management) algorithms. We investigate the influence of using RED-based AQM mechanisms and the fractional controller PIγ on the transport layer. Additionally, we examine the cases in which the TCP and the UDP flows occur and analyse their mutual influence. Both transport protocols used are independent and work simultaneously. We compare our solution with the Fluid Flow approximation, demonstrating the advantages of Diffusion Approximation.

11

Exact and approximation algorithms for joint routing and flow rate optimization

44%

Junosza-Szaniawski K. , Nogalski D.

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tom Vol. 20

29--36

EN

This paper addresses comparison of algorithms for a version of the NUM problem. The joint formulation of routing and transmission rate control within the multi-user and single-path setting is assumed within the NUM. Since problem is NP-hard, the efficient heuristics are designed, implemented and compared experimentally with other existing heuristics and exact linear programming solver. The linear approximation is applied for nonlinear utility function. The results of experiments demonstrate a trade-off between computing time and precision of goal value.