6 research outputs found
Performance of TCP over ABR with Long-Range Dependent VBR Background Traffic over Terrestrial and Satellite ATM networks
Compressed video is well known to be self-similar in nature. We model VBR
carrying Long-Range Dependent (LRD), multiplexed MPEG-2 video sources. The
actual traffic for the model is generated using fast-fourier transform of
generate the fractional gaussian noise (FGN) sequence. Our model of compressed
video sources bears similarity to an MPEG-2 Transport Stream carrying video,
i.e., it is long-range dependent and generates traffic in a piecewise-CBR
fashion. We study the effect of such VBR traffic on ABR carrying TCP traffic.
The effect of such VBR traffic is that the ABR capacity is highly variant. We
find that a switch algorithm like ERICA+ can tolerate this variance in ABR
capacity while maintaining high throughput and low delay. We present simulation
results for terrestrial and satellite configurations.Comment: Proceedings of LCN `9
Methods of Congestion Control for Adaptive Continuous Media
Since the first exchange of data between machines in different locations in early 1960s,
computer networks have grown exponentially with millions of people now using the
Internet. With this, there has also been a rapid increase in different kinds of services offered
over the World Wide Web from simple e-mails to streaming video. It is generally accepted
that the commonly used protocol suite TCP/IP alone is not adequate for a number of
modern applications with high bandwidth and minimal delay requirements. Many
technologies are emerging such as IPv6, Diffserv, Intserv etc, which aim to replace the onesize-fits-all approach of the current lPv4. There is a consensus that the networks will have
to be capable of multi-service and will have to isolate different classes of traffic through
bandwidth partitioning such that, for example, low priority best-effort traffic does not cause
delay for high priority video traffic. However, this research identifies that even within a
class there may be delays or losses due to congestion and the problem will require different
solutions in different classes.
The focus of this research is on the requirements of the adaptive continuous media
class. These are traffic flows that require a good Quality of Service but are also able to
adapt to the network conditions by accepting some degradation in quality. It is potentially
the most flexible traffic class and therefore, one of the most useful types for an increasing
number of applications.
This thesis discusses the QoS requirements of adaptive continuous media and
identifies an ideal feedback based control system that would be suitable for this class. A
number of current methods of congestion control have been investigated and two methods
that have been shown to be successful with data traffic have been evaluated to ascertain if
they could be adapted for adaptive continuous media. A novel method of control based on
percentile monitoring of the queue occupancy is then proposed and developed. Simulation
results demonstrate that the percentile monitoring based method is more appropriate to this
type of flow. The problem of congestion control at aggregating nodes of the network
hierarchy, where thousands of adaptive flows may be aggregated to a single flow, is then
considered. A unique method of pricing mean and variance is developed such that each
individual flow is charged fairly for its contribution to the congestion
Uma abordagem para adaptação de QoS baseada em controle nebuloso
Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Tecnológico. Programa de Pós-Graduação em Engenharia ElétricaDurante a execução de uma aplicação multimídia distribuída, os parâmetros de qualidade de serviço (QoS) podem sofrer variações bruscas e descontroladas em seus valores em virtude de perturbações externas ao sistema multimídia distribuído. O usuário percebe essa variação na forma de lapsos no som, distorção e estagnação do vídeo e falta de sincronismo entre imagem e som. O objetivo desta tese é propor um mecanismo para adaptação de QoS baseado em controle nebuloso que minimize os efeitos dessas perturbações, aumentando a satisfação do usuário. O uso de controle nebuloso deve-se ao fato desse tipo de abordagem ter sido pouco explorada por mecanismos de adaptação de QoS, apesar de ser uma abordagem que tem sido usada com sucesso para o controle de sistemas com características similares àquelas de um sistema multimídia distribuído. O mecanismo proposto representa a qualidade através combinações de valores de parâmetros de QoS da aplicação com uma métrica associada e obtida a partir da opinião dos usuários. Os resultados obtidos mostraram a adequação do uso de controle nebuloso, no sentido de proporcionar uma adaptação mais ajustada à dinâmica do sistema multimídia distribuído, e da representação de qualidade utilizada, que permitiu um melhor uso da largura de banda disponível, sob o ponto de vista do usuário final