Adam Domański

The drop-from-front strategy in AQM

The article investigates the influence of the way packets are chosen to be dropped (end of the tail, head of the tail) on the performance, i.e. response time for in case of RED and DSRED queues - two representative active queue management mechanisms used in IP routers. In particular, the self-similar traffic is considered. The quantitative analysis is based on simulation and Markov chain models solved numerically.

A Choice of Optimal Packet Dropping Function for Active Queue Management

Algorithms of queue management in IP routers determine which packet should be deleted when necessary. The article investigates the influence of packet rejection probability function on the performance, i.e. response time for in case NLRED queues. For standard NLRED the linear packet dropping function is replaced by a quadratic function. Solution presented in this article based on orthogonal polynomials. Depending on a particular criterion of optimization a proper non-linear function may be chosen, but using averaged criterion leads up to choose the linear one as an optimal one.

Internet traffic source based on hidden Markov model

This article shows how to use Hidden Markov Models to generate self-similar traffic. The well-known Bellcore traces are used as a training sequence to learn HMM model parameters. Performance of trained model are tested on the remaining portions of the sequences. Then we can use the HMM trained with the Bellcore data as the traffic source model.

The Impact of Self-similarity on Traffic Shaping in Wireless LAN

IEEE 802.11 MAC protocol ist the de facto standard for wireless local area networks (WLANs). In todays Internet, the emerging widespread use of real-time voice, audio, and video applications makes QoS (Quality of Service) a key problem. At the MAC layer, 802.11e defines extensions to enhance the QoS performance of 802.11 WLAN. This MAC layer solution leaves such issues of QoS as QoS guarantee and admission control to the traffic control systems at the higher layers. This article tries to show that implementation of some mechanisms of traffic shaping causes some improvement of the level of QoS in WLANs. First we analyse the influence of the traffic shaping in WLANs stations by the mechanism of token bucket filter. Next the analysis of the behaviour of Access Point with AQM mechanism was carried out. The conducted research has shown that it is possible to achieve certain level of QoS thanks to the implementation of traffic shaping mechanisms. We make our experiments comparatively for the traffic sources with self-similarity and without it. Our results confirm the necessity of taking into account the self-similar character of wireless traffic.

Modeling Packet Traffic with the Use of Superpositions of Two-State MMPPs

The aim of this paper is to use the superposition of two-state Markov Modulated Poisson Processes to replicate the statistical nature of internet traffic over several time scales. This paper characterizes of network traffic using Bellcore data and LAN traces collected in IITiS PAN. The fitting procedure for matching second-order self-similar properties of real data traces to that of two-state MMPP’s has also been described.

Estimating the Intensity of Long-Range Dependence in Real and Synthetic Traffic Traces

This paper examines various techniques for estimating the intensity of Long-Range Dependence (LRD). Trial data sets with LRD are generated using Fractional Gaussian noise and Markov modulated Poisson process. The real data set collected in IITiS PAN is also used.

Comparison of AQM Control Systems with the Use of Fluid Flow Approximation

In the article we study a model of TCP/UDP connection with Active Queue Management in an intermediate IP router. We use the fluid flow approximation technique to model the interactions between the set of TCP/UDP flows and AQM. We model a system where RED or NLRED are the AQM policy. The obtained results confirm the advantage of our NLRED algorithm.

The Influence of Traffic Self-Similarity on QoS Mechanisms

We investigate the influence of stochastic features (self-similarity, long range autocorrelation) of the input traffic on the performance of some QoS mechanisms. We model the impact of input traffic characteristics on queue distributions and packet loss probability observed at leaky bucket mechanism, at fixed priority scheduling of packets and on the RED queue. The results confirm a strong influence of self-similarity on the behaviour of these mechanisms.

Fluid Flow Analysis of RED Algorithm with Modified Weighted Moving Average

We study with the use of fluid flow approximation the impact of a modified weighted moving average on the performance of RED mechanism. A model of TCP/UDP connection with RED implemented in an intermediate IP router is used, the weighted moving average is determined on the basis of a difference (recursive) equation. The fluid flow approximation technique is applied to model the interactions between the set of TCP/UDP flows and RED mechanism.

A RED modified weighted moving average for soft real-time application

Abstract The popularity of TCP/IP has resulted in an increase in usage of best-effort networks for real-time communication. Much effort has been spent to ensure quality of service for soft real-time traffic over IP networks. The Internet Engineering Task Force has proposed some architecture components, such as Active Queue Management (AQM). The paper investigates the influence of the weighted moving average on packet waiting time reduction for an AQM mechanism: the RED algorithm. The proposed method for computing the average queue length is based on a difference equation (a recursive equation). Depending on a particular optimality criterion, proper parameters of the modified weighted moving average function can be chosen. This change will allow reducing the number of violations of timing constraints and better use of this mechanism for soft real-time transmissions. The optimization problem is solved through simulations performed in OMNeT++ and later verified experimentally on a Linux implementation