Effect of burst assembly over TCP performance in optical burst switching networks
Author
Gürel, Güray
Advisor
Karaşan, Ezhan
Date
2006Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Optical Burst Switching (OBS) is proposed as a short-term feasible solution
that is capable of efficiently utilizing the optical bandwidth of the future Internet
backbone. Performance evaluation of TCP traffic in OBS networks has been
under intensive study, as TCP constitutes the majority of Internet traffic. Since
burst assembly mechanism is one of the fundamental factors that determine the
performance of an OBS network, we focus our attention on burst assembly and
specifically, we investigate the influence of the number of burstifiers on TCP performance
for an OBS network. We start with a simple OBS network scenario
where very large flows are considered and losses resulting from the congestion
in the core OBS network are modeled using a burst independent Bernoulli loss
model. Then, a background burst traffic is generated in order to create contention
at a core node realizing burst-length dependent losses. Finally, simulations are
repeated for Internet flows where flow sizes are modeled using a Bounded Pareto
distribution. Simulation results show that for an OBS network employing timerbased
assembly algorithm, TCP goodput increases as the number of burst assemblers
is increased for each loss model. The improvement from one burstifier
to moderate number of burst assemblers is significant, but the goodput difference
between moderate number of buffers and per-flow aggregation is relatively
small, implying that a cost-effective OBS edge switch implementation should use
moderate number of assembly buffers per destination. The numerical studies are
carried out using nOBS, which is an ns2 based OBS simulation tool, built within
this thesis for studying the effects of burst assembly, scheduling and contention
resolution algorithms in OBS networks.