85 research outputs found
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
Application of learning algorithms to traffic management in integrated services networks.
SIGLEAvailable from British Library Document Supply Centre-DSC:DXN027131 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Dynamic bandwidth allocation in multi-class IP networks using utility functions.
PhDAbstact not availableFujitsu Telecommunications Europe Lt
Quality-of-service management in IP networks
Quality of Service (QoS) in Internet Protocol (IF) Networks has been the subject of
active research over the past two decades. Integrated Services (IntServ) and
Differentiated Services (DiffServ) QoS architectures have emerged as proposed
standards for resource allocation in IF Networks. These two QoS architectures
support the need for multiple traffic queuing systems to allow for resource
partitioning for heterogeneous applications making use of the networks. There have
been a number of specifications or proposals for the number of traffic queuing
classes (Class of Service (CoS)) that will support integrated services in IF Networks,
but none has provided verification in the form of analytical or empirical investigation
to prove that its specification or proposal will be optimum.
Despite the existence of the two standard QoS architectures and the large volume of
research work that has been carried out on IF QoS, its deployment still remains
elusive in the Internet. This is not unconnected with the complexities associated with
some aspects of the standard QoS architectures. [Continues.
Application of an automatically designed fuzzy logic decision support system to connection admission control in ATM networks
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Performance analysis and improvement of InfiniBand networks. Modelling and effective Quality-of-Service mechanisms for interconnection networks in cluster computing systems.
The InfiniBand Architecture (IBA) network has been proposed as a new
industrial standard with high-bandwidth and low-latency suitable for constructing
high-performance interconnected cluster computing systems. This architecture
replaces the traditional bus-based interconnection with a switch-based network for
the server Input-Output (I/O) and inter-processor communications. The efficient
Quality-of-Service (QoS) mechanism is fundamental to ensure the import at QoS
metrics, such as maximum throughput and minimum latency, leaving aside other
aspects like guarantee to reduce the delay, blocking probability, and mean queue
length, etc.
Performance modelling and analysis has been and continues to be of great
theoretical and practical importance in the design and development of
communication networks. This thesis aims to investigate efficient and cost-effective
QoS mechanisms for performance analysis and improvement of InfiniBand
networks in cluster-based computing systems.
Firstly, a rate-based source-response link-by-link admission and congestion
control function with improved Explicit Congestion Notification (ECN) packet
marking scheme is developed. This function adopts the rate control to reduce
congestion of multiple-class traffic. Secondly, a credit-based flow control scheme is
presented to reduce the mean queue length, throughput and response time of the system. In order to evaluate the performance of this scheme, a new queueing
network model is developed. Theoretical analysis and simulation experiments show
that these two schemes are quite effective and suitable for InfiniBand networks.
Finally, to obtain a thorough and deep understanding of the performance attributes
of InfiniBand Architecture network, two efficient threshold function flow control
mechanisms are proposed to enhance the QoS of InfiniBand networks; one is Entry
Threshold that sets the threshold for each entry in the arbitration table, and other is
Arrival Job Threshold that sets the threshold based on the number of jobs in each
Virtual Lane. Furthermore, the principle of Maximum Entropy is adopted to analyse
these two new mechanisms with the Generalized Exponential (GE)-Type
distribution for modelling the inter-arrival times and service times of the input traffic.
Extensive simulation experiments are conducted to validate the accuracy of the
analytical models
A MAC protocol for IP-based CDMA wireless networks.
Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2005.The evolution of the intemet protocol (IP) to offer quality of service
(QoS) makes it a suitable core network protocol for next generation
networks (NGN). The QoS features incorporated to IP will enable future lP-based wireless networks to meet QoS requirements of various multimedia traffic. The Differentiated Service (Diffserv) Architecture is a promising QoS technology due to its scalability which arises from traffic flow aggregates. For this reason, in this dissertation a network infrastructure based on DiffServ is assumed. This architecture provides assured service (AS) and premium service (PrS) classes in addition to best-effort service (BE). The medium access control (MAC) protocol is one of the important design issues in wireless networks. In a wireless network carrying multimedia traffic, the MAC protocol is required to provide simultaneous support for a wide variety of traffic types, support traffic with delay and jitter bounds, and assign bandwidth in an efficient and fair manner among traffic classes. Several MAC protocols capable of supporting multimedia services have been proposed in the literature, the majority of which were designed for wireless A1M (Asynchronous Transfer Mode). The focus of this dissertation is on time division multiple access and code division multiple access (TDMAlCDMA)
based MAC protocols that support QoS in lP-based wireless networks. This dissertation begins by giving a survey of wireless MAC protocols. The survey considers MAC protocols for centralised wireless networks and classifies them according to their multiple access technology and as well as their method of resource sharing. A novel TDMAlCDMA based MAC protocol incorporating techniques from existing protocols is then proposed. To provide the above-mentioned services, the bandwidth is partitioned amongst AS and PrS classes. The BE class utilizes the remaining bandwidth from the two classes because it does not have QoS requirements. The protocol employs a demand assignment (DA) scheme to support traffic from PrS and AS classes. BE traffic is supported by a random reservation access scheme with dual multiple access interference (MAl) admission thresholds. The performance of the protocol, i.e. the AS or PrS call blocking probability, and BE throughput are evaluated
through Markov analytical models and Monte-Carlo simulations.
Furthermore, the protocol is modified and incorporated into IEEE 802.16 broadband wireless access (BWA) network
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