Reliable and efficient data transfer on the Internet is an important issue. Since late
70’s the protocol responsible for that has been the de facto standard TCP, which
has proven to be successful through out the years, its self-managed congestion
control algorithms have retained the stability of the Internet for decades. However,
the variety of existing new technologies such as high-speed networks (e.g. fibre
optics) with high-speed long-delay set-up (e.g. cross-Atlantic links) and wireless
technologies have posed lots of challenges to TCP congestion control algorithms.
The congestion control research community proposed solutions to most of these
challenges. This dissertation adds to the existing work by: firstly tackling the highspeed
long-delay problem of TCP, we propose enhancements to one of the existing
TCP variants (part of Linux kernel stack). We then propose our own variant:
TCP-Gentle. Secondly, tackling the challenge of differentiating the wireless loss
from congestive loss in a passive way and we propose a novel loss differentiation
algorithm which quantifies the noise in packet inter arrival times and use this
information together with the span (ratio of maximum to minimum packet inter
arrival times) to adapt the multiplicative decrease factor according to a predefined
logical formula. Finally, extending the well-known drift model of TCP to account
for wireless loss and some hypothetical cases (e.g. variable multiplicative decrease),
we have undertaken stability analysis for the new version of the model.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.