| dc.description.abstract | The TCP congestion control algorithm is used to minimise the congestion in a network
and to improve the performance of TCP. The TCP congestion control algorithm is
originally designed to operate in wired network. When the TCP congestion control
algorithm is implemented in a wireless network, the TCP congestion control algorithm
assumptions are violated and result in performance degradation in a wireless network.
This thesis presents the enhanced-TCP Vegas congestion control algorithm to optimise
the performance of TCP in a wireless IPv6 network. Three enhancements are proposed
in the enhanced-TCP Vegas algorithm. The first enhancement is to minimise the bursty
traffic flow at the TCP sender network. The first enhancement is called Packet Spacing.
The second enhancement is to optimise the probing of the transmission rate into the
network. The second enhancement is called Progressive CWND. The third enhancement
is to differentiate between the real congestion and the spurious congestion in the
wireless network. The third enhancement is called Congestion Measure. The proposed
algorithm is implemented in ns-2. The simulation experiment is conducted in two
scenarios. The first scenario investigates the performance of TCP Vegas algorithms in
single TCP connection network. The results of simulation experiment show that the
enhanced-TCP Vegas algorithm, which combines the packet spacing, progressive
CWND and congestion measure methods performs compared with the other TCP
congestion control algorithms that are used in this research. The second scenario
investigates the performance of the enhanced-TCP Vegas in multiple TCP connections.
The results of simulation experiment show that: (i) as the number of TCP connection in
a network increases, the packet delay, network throughput and network efficiency
increases; (ii) the throughput fairness increases as the packet size increases. However,
as the number of TCP connection increases, the variation of the throughput fairness for
all the packet sizes decreases. The proposed algorithm shows poor throughput fairness
against standard TCP Vegas algorithm; (iii) as the number of TCP connections in
network increase, the handover recovery time increases accordingly. The proposed
algorithm exhibits lesser handover recovery time compared to the standard TCP Vegas
algorithm; (iv) the appropriate packet size of FTP file is inversely proportional to the
number of TCP connection in a network; (v) as the buffer size in a network increases,
packet delay, network throughput and network efficiency increases. Additionally, this
research presents the appropriate packet size and buffer size to be used over the multiple
TCP connections network by using the proposed algorithm. | en_US |
