| 1. |
- Allard, Christina, et al.
(author)
-
Rasbiologiskt språkbruk i statens rättsprocess mot sameby
- 2015
-
In: Dagens Nyheter. - 1101-2447.
-
Journal article (pop. science, debate, etc.)abstract
- Statens hantering av forskningsresultat i rättsprocessen med Girjas sameby utgör ett hot mot Sverige som rättsstat och kunskapsnation. Åratal av svensk och internationell forskning underkänns och man använder ett språkbruk som skulle kunna vara hämtat från rasbiologins tid. Nu måste staten ta sitt ansvar och börja agera som en demokratisk rättsstat, skriver 59 forskare.
|
|
| 2. |
- Allard, Christina, et al.
(author)
-
Rasbiologiskt språkbruk i statens rättsprocess mot sameby : DN Debatt 2015-06-11
- 2015
-
Other publication (pop. science, debate, etc.)abstract
- Statens hantering av forskningsresultat i rättsprocessen med Girjas sameby utgör ett hot mot Sverige som rättsstat och kunskapsnation. Åratal av svensk och internationell forskning underkänns och man använder ett språkbruk som skulle kunna vara hämtat från rasbiologins tid. Nu måste staten ta sitt ansvar och börja agera som en demokratisk rättsstat, skriver 59 forskare.
|
|
| 3. |
- Jacobsson, Krister, et al.
(author)
-
ACK-clock dynamics in network congestion control - An inner feedback loop with implications on inelastic flow impact
- 2006
-
In: PROCEEDINGS OF THE 45TH IEEE CONFERENCE ON DECISION AND CONTROL. - 9781424401710 ; , s. 1882-1887
-
Conference paper (peer-reviewed)abstract
- 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.
|
|
| 4. |
- Jacobsson, Krister, et al.
(author)
-
ACK-clocking dynamics: Modelling the interaction between windows and the network
- 2008
-
In: 27TH IEEE CONFERENCE ON COMPUTER COMMUNICATIONS (INFOCOM). - 9781424420254 ; , s. 181-185
-
Conference paper (peer-reviewed)abstract
- 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.
|
|
| 5. |
- Jacobsson, Krister, et al.
(author)
-
An Improved Link Model for Window Flow Control and Its Application to FAST TCP
- 2009
-
In: IEEE Transactions on Automatic Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 54:3, s. 551-564
-
Journal article (peer-reviewed)abstract
- 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.
|
|
| 6. |
- Jacobsson, Krister, et al.
(author)
-
Closed Loop Aspects of Fluid Flow Model Identification in Congestion Control
- 2006
-
In: 14th IFAC Symposium on System Identification. ; , s. 879-884
-
Conference paper (peer-reviewed)abstract
- 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.
|
|
| 7. |
- Jacobsson, Krister, 1976-
(author)
-
Dynamic modeling of Internet congestion control
- 2008
-
Doctoral thesis (other academic/artistic)abstract
- 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.
|
|
| 8. |
- Jacobsson, Krister, et al.
(author)
-
Estimation of RTT and bandwidth for congestion Control Applications in Communication Networks
- 2004
-
Conference paper (peer-reviewed)abstract
- 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.
|
|
| 9. |
- Jacobsson, Krister, et al.
(author)
-
Local analysis of structural limitations of network congestion control
- 2005
-
In: 2005 44th IEEE Conference on Decision and Control & European Control Conference. - 0780395670 ; , s. 6744-6749
-
Conference paper (peer-reviewed)abstract
- 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.
|
|
| 10. |
- Jacobsson, Krister, et al.
(author)
-
Round trip time estimation in communication networks using adaptive Kalman filtering
- 2004
-
Conference paper (peer-reviewed)abstract
- 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.
|
|
