Ankara : The Department of Electrical and Electronics Engineering and Sciences of Bilkent University, 2008.Thesis (Master's) -- Bilkent University, 2008.Includes bibliographical references leaves 70-76.Optical burst switching (OBS) is proposed as the switching paradigm of nextgeneration
optical Internet. In OBS, IP packets from access networks are assembled
into longer units of bursts allowing a lower level of switching granularity
offered by the readily available optical technology. Although OBS was asynchronous
in the earlier work, slotted OBS (SOBS) has recently caught the attention of
the researchers due to performance gains achievable with synchronous infrastructures.
In this thesis, we study the blocking probabilities in a slotted optical burst
switching node fed with independent and identically distributed Poisson burst
traffic and for which the burst sizes are a fixed integer multiple of the slot length.
We develop a discrete time Markov chain based framework to obtain the blocking
probabilities in systems with and without QoS differentiation. In particular,
we study priority scheduling and offset-based QoS differentiation mechanisms
for SOBS networks. The latter problem suffers from the curse of dimensionality,
which we address by a discrete phase type approximation for the discrete
Poisson distribution. The results obtained by using the moment-matched phase
type distribution are shown to provide a very accurate approximation for the blocking probabilities. Finally, we extend our framework to analyze the hybrid
priority scheduling with unity-offset based differentiation scheme which proves to
outperform the others in the degree of class isolation. We show that increasing
burst length has an adverse affect on the attained QoS level. We also give a
quantitative discussion of the trade off between the burst blocking probability
and the slot granularity. As the slot duration is decreased, burst transmissions
can be initiated in an earlier time decreasing the end-to-end delay in an SOBS
network with a penalty of increased burst loss probability. We evaluate the burst
blocking probabilities of a classless and two-class SOBS nodes as a function of
the slot length, number of wavelengths and traffic load.Öztürk, OnurM.S
