Change search
Refine search result
1 - 17 of 17
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Jacobsson, Krister
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Dynamic modeling of Internet congestion control2008Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    The Transmission Control Protocol (TCP) has successfully governed the Internet congestion control for two decades. It is by now, however, widely recognized that TCP has started to reach its limits and that new congestion control protocols are needed in the near future. This has spurred an intensive research effort searching for new congestion control designs that meet the demands of a future Internet scaled up in size, capacity and heterogeneity. In this thesis we derive network fluid flow models suitable for analysis and synthesis of window based congestion control protocols such as TCP.

    In window based congestion control the transmission rate of a sender is regulated by: (1) the adjustment of the so called window, which is an upper bound on the number of packets that are allowed to be sent before receiving an acknowledgment packet (ACK) from the receiver side, and (2) the rate of the returning ACKs. From a dynamical perspective, this constitutes a cascaded control structure with an outer and an inner loop.

    The first contribution of this thesis is a novel dynamical characterization and an analysis of the inner loop, generic to all window based schemes and formed by the interaction between the, so called, ACK-clocking mechanism and the network. The model is based on a fundamental integral equation relating the instantaneous flow rate and the window dynamics. It is verified in simulations and testbed experiments that the model accurately predicts dynamical behavior in terms of system stability, previously unknown oscillatory behavior and even fast phenomenon such as traffic burstiness patterns present in the system. It is demonstrated that this model is more accurate than many of the existing models in the literature.

    In the second contribution we consider the outer loop and present a detailed fluid model of a generic window based congestion control protocol using queuing delay as congestion notification. The model accounts for the relations between the actual packets in flight and the window size, the window control, the estimator dynamics as well as sampling effects that may be present in an end-to-end congestion control algorithm. The framework facilitates modeling of a quite large class of protocols.

    The third contribution is a closed loop analysis of the recently proposed congestion control protocol FAST TCP. This contribution also serves as a demonstration of the developed modeling framework. It is shown and verified in experiments that the delay configuration is critical to the stability of the system. A conclusion from the analysis is that the gain of the ACK-clocking mechanism dramatically increases with the delay heterogeneity for the case of an equal resource allocation policy. Since this strongly affects the stability properties of the system, this is alarming for all window based congestion control protocols striving towards proportional fairness. While these results are interesting as such, perhaps the most important contribution is the developed stability analysis technique.

  • 2.
    Jacobsson, Krister
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Andrew, Lachlan L. H.
    Tang, Ao
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Low, Steven H.
    California Institute of Technology.
    ACK-clocking dynamics: Modelling the interaction between windows and the network2008In: 27TH IEEE CONFERENCE ON COMPUTER COMMUNICATIONS (INFOCOM): VOLS 1-5, 2008, p. 181-185Conference paper (Refereed)
    Abstract [en]

    A novel continuous time fluid flow model of the dynamics of the interaction between ACK-clocking and the link buffer is presented.. A fundamental integral equation relating the instantaneous flow rate and the window dynamics is derived. Properties of the model, such as well-posedness and stability, are investigated. Packet level experiments verily that this new model is more accurate than existing models, correctly predicting qualitatively different behaviors, for example when round trill delays are heterogeneous.

  • 3. Jacobsson, Krister
    et al.
    Andrew, Lachlan L. H.
    Tang, Ao
    Low, Steven H.
    California Institute of Technology.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    An Improved Link Model for Window Flow Control and Its Application to FAST TCP2009In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 54, no 3, p. 551-564Article in journal (Refereed)
    Abstract [en]

    This paper presents a link model which captures the queue dynamics In response to a change in a transmission control protocol (TCP) source's congestion window. By considering both self-clocking and the link integrator effect, the model generalizes existing models and is shown to be more accurate by both open loop and closed loop packet level simulations. It reduces to the known static link model when flows' round trip delays are identical, and approximates the standard integrator link model when there is significant cross traffic. We apply this model to the stability analysis of fast active queue management scalable TCP (FAST TCP) Including its filter dynamics. Under this model, the FAST control law is linearly stable for a single bottleneck link with an arbitrary distribution of round trip delays. This result resolves the notable discrepancy between empirical observations and previous theoretical predictions. The analysis highlights the critical role of self-clocking in TCP stability, and the proof technique is new and less conservative than existing ones.

  • 4.
    Jacobsson, Krister
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Closed Loop Aspects of Fluid Flow Model Identification in Congestion Control2006In: 14th IFAC Symposium on System Identification / [ed] Brett Ninness, Håkan Hjalmarsson, 2006, p. 879-884Conference paper (Refereed)
    Abstract [en]

    Fluid flow models have turned out to be instrumental for analysis and synthesis of primal/dual congestion control algorithms which rely on aggregated information from a network path. In particular stability has been analyzed using such models. In network congestion control, validation experiments will with necessity be performed in closed loop since the communication protocol has to be active. Guidelines on how such experiments should be carried out in practice has until now been lacking in the literature. Departing from the theory of modeling for control, we refine a fluid flow model by augmenting the customary model of transport latencies, link price and source control with estimator dynamics and sampling properties. The impact of cross-traffic and changes in network configuration is incorporated as well. Furthermore, we analyze, from a closed-loop perspective, how the network should be excited when validating such models. The resulting identification framework is used for validating the derived model using packet-level experimental data from NS-2 simulations.

  • 5.
    Jacobsson, Krister
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Local analysis of structural limitations of network congestion control2005In: 2005 44th IEEE Conference on Decision and Control & European Control Conference: Vols 1-8, 2005, p. 6744-6749Conference paper (Refereed)
    Abstract [en]

    Recently there have been a number of interesting contributions to the stability analysis of network congestion control based on fluid models. Here, we further this emerging analysis by studying the structural limitations that so called primal/dual congestion control algorithms impose. Such algorithms rely on aggregated information from a network path, e.g. TCP-Vegas use the aggregated queuing delay. We show through local analysis that this imposes certain limitations of feedback control. Viewed from the source side, the complementary sensitivity and the sensitivity functions are severely restricted when many sources share the same bottleneck. This impose that source control must be small enough to achieve suitable noise rejection. In addition, a specialized congestion control paradigm where all sources share a common time-base is analyzed. For this scenario the analysis facilitates significantly and robustness limitations towards configuration changes is observed.

  • 6.
    Jacobsson, Krister
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Towards accurate congestion control models: validation and stability analysis2006Conference paper (Refereed)
  • 7.
    Jacobsson, Krister
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Unbiased bandwidth estimation in communication protocols2005In: Proceedings of the 16th IFAC World Congress, 2005, IFAC , 2005Conference paper (Refereed)
    Abstract [en]

    Heterogeneous communication networks with their variety of application demands, uncertain time-varying trafc load, and mixture of wired and wireless links pose several challenging problem in modeling and control. In this paper we focus on bandwidth estimation and elucidate why estimates based directly on bandwidth samples are biased. Previously, this phenomenon has been observed but not properly explained, it seems. Standard techniques for bandwidth estimation are based on measurements of inter-arrival times of packets as the bandwidth is proportional to the inverse of the  nterarrival time. Two main classes of bandwidth estimators are analyzed wrt how variations in the inter-arrival times affect the estimates. It is shown that linear time-invariant ltering of instantaneous bandwidth estimates does not change the bias. In contrast to this, smoothing the inter-arrival-time samples does give a bias reduction which depends on the properties of the smoothing lter. Hence, with such approach, noise attenuation can be traded against tracking ability wrt changes in the actual bandwidth.

  • 8.
    Jacobsson, Krister
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Möller, Niels
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    ACK-clock dynamics in network congestion control - An inner feedback loop with implications on inelastic flow impact2006In: PROCEEDINGS OF THE 45TH IEEE CONFERENCE ON DECISION AND CONTROL: VOLS 1-14, 2006, p. 1882-1887Conference paper (Refereed)
    Abstract [en]

    The focus of this paper is the window mechanism in network congestion control, whereby packet acknowledgments control when new packets are being sent This constitutes an inner control loop that so far has received little attention. We provide a novel model of this loop that bridges between the standard integrator link model and the more recent static link model. The model is in validation experiments shown to be accurate. It is also shown that as the amount of inelastic cross-traffic increases the dynamics of this inner loop becomes slower. This may influence overall performance and stability in scenarios with heavy inelastic flows.

  • 9.
    Jacobsson, Krister
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Hjalmarsson, Håkan
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Möller, Niels
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Johansson, Karl Henrik
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Estimation of RTT and bandwidth for congestion Control Applications in Communication Networks2004Conference paper (Refereed)
    Abstract [en]

    Heterogeneous communication networks with their variety of application demands, uncertain time-varying traffic load, and mixture of wired and wireless links pose several challenging problem in modeling and control. In this paper we focus on the round-trip time (RTT), which is a particularly important variable for efficient end-to-end congestion control, and on bandwidth estimation. Based on a simple aggregated model of the network, an algorithm combining a Kalman filter and a change detection algorithm is proposed for RTT estimation. It is illustrated on real data that this algorithm provides estimates of significantly better accuracy as compared to the RTT estimator currently used in TCP, especially in scenarios where new cross-trafficflows cause bottle-neck queues to rapidly build up which in turn induces rapid changes of the RTT.

    Standard techniques for bandwidth estimation is based on measurements of inter-arrival times of packets as the bandwidth is proportional to the inverse of the inter-arrival time. Two main classes of bandwidth estimators are analyzed wrt how variations in the inter-arrival times affect the estimates. It is shown that linear time-invariant filtering of instantaneous bandwidth estimates does not change the bias. In contrast to this, smoothing the inter-arrival-time samples, does give a bias reduction which depends on the smoothing filter. Hence, with such approach, noise attenuation can be traded against tracking ability wrt changes in the actual bandwidth.

  • 10.
    Jacobsson, Krister
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Hjalmarsson, Håkan
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Möller, Niels
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Johansson, Karl Henrik
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Round trip time estimation in communication networks using adaptive Kalman filtering2004Conference paper (Refereed)
    Abstract [en]

    Heterogeneous communication networks with their variety of application demands, uncertain time-varying traffic load, and mixture of wired and wireless links pose several challenging problem in modeling and control. In this paper we focus on the roundtrip time (RTT), which is a particularly important variable for efficient end-to-end congestion control. Based on a simple aggregated model of the network, an algorithm combining a Kalmanfilter and a change detection algorithm is proposed for RTT estimation. It is illustrated on real data that this algorithm provides estimates of significantly better accuracy as compared to the RTT estimator currently used in TCP, especially in scenarios where new cross-trafficflows cause a bottle-neck link to rapidly build up a queue, which in turn induces rapid changes of the RTT.

  • 11.
    Jacobsson, Krister
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Möller, Niels
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Johansson, Karl Henrik
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Hjalmarsson, Håkan
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Some modeling and estimation issues in control of heterogeneous networks2004Conference paper (Refereed)
    Abstract [en]

    Heterogeneous communication networks with their variety of application demands, uncertain time-varying trafc load, and mixture of wired and wireless links pose several challenging problem in modeling and control. In this paper we focus on the round-trip time (RTT), which is a particularly important variable for efficient end-to-end congestion control. Based on a simple aggregated model of the network, an algorithm combining a Kalman lter and a change detection algorithm is proposed for RTT estimation. It is illustrated on real data that this algorithm provides estimates of significantly better accuracy as compared to the RTT estimator currently used in TCP.We also analyze how wireless links affect the RTT distribution. Link re-transmissions induce delays which do not conform to the assumptions on which the transport protocol is based. This causes undesired TCP control actions which reduce throughput. A link layer solution based on adding carefully selected delays to certain packets is proposed to counteract this problem.

  • 12.
    Möller, Niels
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jacobsson, Krister
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Stability of window-based queue control with application to mobile terminal download2006In: Proceedings of the 17th International Symposium on Mathematical Theory of Networks and Systems, 2006, p. 683-694Conference paper (Refereed)
  • 13. Suchara, M.
    et al.
    Andrew, L. L. H.
    Witt, R.
    Jacobsson, Krister
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Wydrowski, B. P.
    Low, S. H.
    Implementation of provably stable MaxNet2008Conference paper (Refereed)
    Abstract [en]

    MaxNet TCP is a congestion control protocol that uses explicit multi-bit signalling from routers to achieve desirable properties such as high throughput and low latency. In this paper we present an implementation of an extended version of MaxNet. Our contributions are threefold. First, we extend the original algorithm to give both provable stability and rate fairness. Second, we introduce the MaxStart algorithm which allows new MaxNet connections to reach their fair rates quickly. Third, we provide a Linux kernel implementation of the protocol. With no overhead but 24-bit price signals, our implementation scales from 32bit/s to lpeta-bit/s with a 0.001% rate accuracy. We confirm the theoretically predicted properties by performing a range of experiments at speeds up to 1 Gbit/sec and delays up to 180 ms on the WAN-in-Lab facility.

  • 14. Tang, A.
    et al.
    Jacobsson, Krister
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Andrew, L. L. H.
    Low, S. H.
    An accurate link model and its application to stability analysis of FAST TCP2007In: INFOCOM 2007, IEEE , 2007, p. 161-169Conference paper (Refereed)
    Abstract [en]

    This paper presents a link model which captures the queue dynamics when congestion windows of TCP sources change. By considering both the self-clocking and the link integrator effects, the model is a generalization of existing models and is shown to be more accurate by both open loop and closed loop packet level simulations. It reduces to the known static link model when flows' round trip delays are similar, and approximates the standard integrator link model when the heterogeneity of round trip delays is significant. We then apply this model to the stability analysis of FAST TCP. It is shown that FAST TCP flows over a single link are always linearly stable regardless of delay distribution. This result resolves the notable discrepancy between empirical observations and previous theoretical predictions. The analysis highlights the critical role of self-clocking in TCP stability and the scalability of FAST TCP with respect to delay. The proof technique is new and less conservative than the existing ones.

  • 15. Tang, A.
    et al.
    Jacobsson, Krister
    KTH, School of Electrical Engineering (EES).
    Andrew, L. L. H.
    Low, S. H.
    Linear stability analysis of FAST TCP using a new accurate link model2006In: 44th Annual Allerton Conference on Communication, Control, and Computing 2006, 2006, p. 599-606Conference paper (Refereed)
    Abstract [en]

    A link model which captures the queue dynamics when congestion windows of TCP sources change was recently proposed. By considering both the self-clocking and the link integrator effects, the model is a generalization of the known extreme cases and is more accurate in general. In this paper, we apply this model to the stability analysis of FAST TCP. It is shown that FAST TCP flows over a single link are always linearly stable regardless of delay distribution. This result resolves the notable discrepancy between empirical observations and previous theoretical predictions. The analysis highlights the critical role of self-clocking in TCP stability and the scalability of FAST TCP with respect to delay. The proof technique is new and much less conservative than existing ones.

  • 16.
    Tang, Ao
    et al.
    Cornell University.
    Andrew, Lachlan L. H.
    Swinburne University of Technology.
    Jacobsson, Krister
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Low, Steven H.
    California Institute of Technology.
    Queue Dynamics With Window Flow Control2010In: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 18, no 5, p. 1422-1435Article in journal (Refereed)
    Abstract [en]

    This paper develops a new model that describes the queueing process of a communication network when data sources use window flow control. The model takes into account the burstiness in sub-round-trip time (RTT) timescales and the instantaneous rate differences of a flow at different links. It is generic and independent of actual source flow control algorithms. Basic properties of the model and its relation to existing work are discussed. In particular, for a general network with multiple links, it is demonstrated that spatial interaction of oscillations allows queue instability to occur even when all flows have the same RTTs and maintain constant windows. The model is used to study the dynamics of delay-based congestion control algorithms. It is found that the ratios of RTTs are critical to the stability of such systems, and previously unknown modes of instability are identified. Packet-level simulations and testbed measurements are provided to verify the model and its predictions.

  • 17.
    Tang, Ao
    et al.
    Cornell University.
    Andrew, Lachlan L. H.
    Swinburne University of Technology.
    Jacobsson, Krister
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Low, Steven H.
    California Institute of Technology.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Window flow control: Macroscopic properties from microscopic factors2008In: 27TH IEEE CONFERENCE ON COMPUTER COMMUNICATIONS (INFOCOM), 2008, p. 538-546Conference paper (Refereed)
    Abstract [en]

    This paper studies window flow control focusing on bridging the gap between microscopic factors such as burstiness in sub-RTT timescales, and observable macroscopic properties such as steady state bandwidth sharing and flow level stability. Using new models, we analytically capture notable effects of microscopic behavior on macroscopic quantities. For loss-based protocols, we calculate the loss synchronization rate for different flows and use it to quantitatively explain the unfair bandwidth sharing between paced and unpaced TCP flows. For delay-based protocols, we show that the ratios of round trip delays are critical to the stability of the system. These results deepen the fundamental understanding of congestion control systems. Packet level simulations are used to verify our theoretical claims.

1 - 17 of 17
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf