Date of Award


Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy


Electronic Engineering

First Advisor

Dr. Oliver Gough

Second Advisor

Dr. John Barrett


The deployment of Quality of Service (QoS) in high speed networks is vital to successful application delivery, especially those that are data-intensive. Continuous efforts have been made to develop infrastructures for enhancing QoS capabilities to manage available bandwidth through the use of traffic conditioners. However, research shows that these techniques distribute bandwidth in an unfair manner. This thesis addresses the failings of traffic conditioning techniques for bandwidth QoS provisioning. Traffic conditioners are comprised of two components, a traffic meter that is responsible for measuring transient characteristics of a traffic stream through a rate estimation technique and a traffic marker that is responsible for marking a packet’s compliance with respect to a set of parameters defined by the Service Level Agreement (SLA). This should allow for the fairer distribution of bandwidth in the network. In this work, a rate estimation technique is presented for use as a traffic metering component of a traffic conditioner. In addition a traffic marking mechanism is developed and presented.

A traffic rate estimator needs to be accurate, stable and agile, however, as agility and stability are somewhat in conllict, a single rate estimation technique is incapable of being agile and stable simultaneously. Hence, in this thesis I propose a metering algorithm that uses two rate estimation techniques and a controller to allow it to satisfy the requirements of being accurate, agile and stable. Simulation analysis validates that the proposed algorithm produces accurate estimated rates and is capable of ignoring short term changes in traffic behaviour while also tracking changes in the actual rate of traffic.

The second part of the work presented in this thesis focuses on a traffic marking technique. For bandwidth QoS requirements, traffic marking techniques should allocate bandwidth to subscribers according to their agreed contracted rate as defined by their SLA. To ensure fairness in the network, excess bandwidth should be shared in proportion to this agreed rate when the network is over or well provisioned. For under provisioned networks the allocated bandwidth should degrade in proportion to its agreed rate. This work proposes a provision aware, proportional, fair sharing, three colour marker to ensure these fairness criteria are fulfilled for aggregated flows. Its main achievements are in achieving fairness in under provisioned networks and in the presence of UDP traffic whilst being insensitive to the number of flows in an aggregate. This is demonstrated through quantitative simulation analysis. The scheme also shows improved performance over other aggregated approaches.

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