Congestion window based adaptive burst assembly for TCP traffic in optical burst switching networks
Author(s)
Advisor
Date
2008Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Burst assembly is one of the key factors affecting the TCP performance in Optical
Burst Switching (OBS) networks. Timer based burst assembly algorithm generates
bursts independent of the rate of TCP flows. When TCP congestion window
is small, the fixed-delay burst assembler waits unnecessarily long, which increases
the end-to-end delay and decreases the TCP goodput. On the other hand, when
TCP congestion window becomes larger, the fixed-delay burst assembler may
unnecessarily generate a large number of small-sized bursts, which increases the
overhead and decreases the correlation gain, resulting in a reduction in the TCP
goodput. Using simulations, we show that the usage of the congestion window
(cwnd) size of TCP flows in the burst assembly algorithm consistently improves
the TCP goodput (by up to 38.4%) compared with the fixed-delay timer based
assembly even when the timer based assembler uses the optimum assembly period
threshold value. One limitation of this proposed method is the assumption
that the exact value of the congestion window is available at the burst assembler.
We then extend the adaptive burstification algorithm such that the burst
assembler uses estimated values of the congestion winpassive measurements at the ingress node. It is shown through simulations that
even when estimated values are used, TCP goodput can achieve values close to
the results obtained by using exact values of the congestion window.
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