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Performance analysis of priority queueing systems in an ATM environment


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Pieloor, Jason 1996 , 'Performance analysis of priority queueing systems in an ATM environment', PhD thesis, University of Tasmania.

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Current and future digital telecommunication networks are facing ever increasing bandwidth
and service demands. One scheme aimed at meeting these demands is the broadband
integrated services digital network (B-ISDN). The B-ISDN is based on the asynchronous
transfer mode (ATM) which provides flexible and dynamic transport and
routing functions. One of the main challenges for designers and managers of these
networks is to provide a guaranteed quality of service (QoS) for each connection, while
still achieving a high network utilisation overall.
To provide a guaranteed QoS, the network must have a mechanism for deciding whether
it can support a requested quality of service for a new connection, whilst still maintaining
the QoS of existing connections. This decision process is called connection
admission control (CAC). Mechanisms for implementing CAC must be acceptably accurate,
while executing in as the shortest time as possible. Most CAC mechanisms are
based on the application of queueing theory to the network - the accuracy of which is
largely dependent on the models of the network traffic used, and the solution method
chosen for the queue analysis.
B-ISDN connections can be generally classified as either loss sensitive or delay sensitive.
Unfortunately, the requirements for transporting both these types of connections within
the same network appear to be at odds with each other. Small internal buffers in ATM
switching nodes result in small transmission delays but potentially high loss rates, while
the use of large buffer sizes favours small loss rates with long transmission delays. To
accommodate both types of connections, a dual buffer approach can be used within the
network switches, wherein one buffer receives priority access to the output line over the
other. Delay sensitive traffic can then be served ahead of loss sensitive traffic, and a
large buffer space can be used to accommodate low loss requirements. The difficulty
with the dual buffer approach for the purposes of CAC, is that analysis of the loss queue
is complicated due to service interruptions caused by the delay traffic. Fortunately, a
relationship between single buffer and dual buffer analyses exists, allowing some of the
more important results for the loss queue to be obtained using single buffer analysis.

This thesis considers the modelling of traffic both at the edges of the network, and at
intermediate stages within the network. Several models are proposed, with a particular
concern that the bursty nature of actual network traffics be adequately captured. In
order to apply these descriptions of the network traffic to connection admission, the
population analysis of infinite buffer queueing problems is carried out using the proposed
models. Queueing delays are then obtained directly from the queue population
results. Although the traffic models are not particularly complicated, closed form solutions
for the average and variance of the queue population are obtained only for one
type of bursty traffic model. For the other traffic models, exact numerical solutions
are discussed, and some simple approximations examined. To overcome limitations in'
these solutions, a new approximation technique is proposed, which achieves extremely
high accuracy for a modest computational cost. In addition to these infinite buffer
results, consideration is also given to obtaining the loss probabilities of the finite buffer.
The developed queueing theory is lastly applied to a dual buffer example problem to
highlight the role of correlations between arrival processes, and to the modelling of
queue outputs for the purpose of describing networks of switching elements.

Item Type: Thesis - PhD
Authors/Creators:Pieloor, Jason
Keywords: Asynchronous transfer mode, Broadband communication systems, Queuing theory
Copyright Holders: The Author
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Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1999. Includes bibliographical references

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