88 research outputs found
Exact performance analysis of a single-wavelength optical buffer with correlated inter-arrival times
Providing a photonic alternative to the current electronic switching in the backbone, optical packet switching (OPS) and optical bursts witching (OBS) require optical buffering. Optical buffering exploits delays in long optical fibers; an optical buffer is implemented by routing packets through a set of fiber delay lines (FDLs). Previous studies pointed out that, in comparison with electronic buffers, optical buffering suffers from an additional performance degradation. This contribution builds on this observation by studying optical buffer performance under more general traffic assumptions. Features of the optical buffer model under consideration include a Markovian arrival process, general burst sizes and a finite set of fiber delay lines of arbitrary length. Our algorithmic approach yields instant analytic results for important performance measures such as the burst loss ratio and the mean delay
Burst switched optical networks supporting legacy and future service types
Focusing on the principles and the paradigm of OBS an overview addressing expectable performance and application issues is presented. Proposals on OBS were published over a decade and the presented techniques spread into many directions. The paper comprises discussions of several challenges that OBS meets, in order to compile the big picture. The OBS principle is presented unrestricted to individual proposals and trends. Merits are openly discussed, considering basic teletraffic theory and common traffic characterisation. A more generic OBS paradigm than usual is impartially discussed and found capable to overcome shortcomings of recent proposals. In conclusion, an OBS that offers different connection types may support most client demands within a sole optical network layer
A zero burst loss architecture for star OBS networks
Performance studies point to the fact that in an OBS network, the link utilization has to be kept very low in order for the burst loss probability to be within an acceptable level. Various congestion control schemes have been proposed, such as the use of converters, fiber delay lines, and deflection routing. However, these schemes do not alleviate this problem. It is our position that in order for OBS to become commercially viable, new schemes have to be devised that will either guarantee zero burst loss, or very low burst loss at high utilization. In a previous paper, we described effective zero burst loss schemes for OBS rings. In this paper, we present a zero burst loss scheme for star OBS topologies. Further research into the topic is required.5th IFIP International Conference on Network Control & Engineering for QoS, Security and MobilityRed de Universidades con Carreras en Informática (RedUNCI
Optical flow switched networks
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 253-279).In the four decades since optical fiber was introduced as a communications medium, optical networking has revolutionized the telecommunications landscape. It has enabled the Internet as we know it today, and is central to the realization of Network-Centric Warfare in the defense world. Sustained exponential growth in communications bandwidth demand, however, is requiring that the nexus of innovation in optical networking continue, in order to ensure cost-effective communications in the future. In this thesis, we present Optical Flow Switching (OFS) as a key enabler of scalable future optical networks. The general idea behind OFS-agile, end-to-end, all-optical connections-is decades old, if not as old as the field of optical networking itself. However, owing to the absence of an application for it, OFS remained an underdeveloped idea-bereft of how it could be implemented, how well it would perform, and how much it would cost relative to other architectures. The contributions of this thesis are in providing partial answers to these three broad questions. With respect to implementation, we address the physical layer design of OFS in the metro-area and access, and develop sensible scheduling algorithms for OFS communication. Our performance study comprises a comparative capacity analysis for the wide-area, as well as an analytical approximation of the throughput-delay tradeoff offered by OFS for inter-MAN communication. Lastly, with regard to the economics of OFS, we employ an approximate capital expenditure model, which enables a throughput-cost comparison of OFS with other prominent candidate architectures. Our conclusions point to the fact that OFS offers significant advantage over other architectures in economic scalability.(cont.) In particular, for sufficiently heavy traffic, OFS handles large transactions at far lower cost than other optical network architectures. In light of the increasing importance of large transactions in both commercial and defense networks, we conclude that OFS may be crucial to the future viability of optical networking.by Guy E. Weichenberg.Ph.D
Wavelength converter sharing in asynchronous optical packet/burst switching: An exact blocking analysis for markovian arrivals
Cataloged from PDF version of article.In this paper, we study the blocking probabilities
in a wavelength division multiplexing-based asynchronous
bufferless optical packet/burst switch equipped with a bank of
tuneable wavelength converters dedicated to each output fiber
line. Wavelength converter sharing, also referred to as partial
wavelength conversion, corresponds to the case of a number
of converters shared amongst a larger number of wavelength
channels. In this study, we present a probabilistic framework for
exactly calculating the packet blocking probabilities for optical
packet/burst switching systems utilizing wavelength converter
sharing. In our model, packet arrivals at the optical switch are
first assumed to be Poisson and later generalized to the more
general Markovian arrival process to cope with very general
traffic patterns whereas packet lengths are assumed to be exponentially
distributed. As opposed to the existing literature based
on approximations and/or simulations, we formulate the problem
as one of finding the steady-state solution of a continuous-time
Markov chain with a block tridiagonal infinitesimal generator. To
find such solutions, we propose a numerically efficient and stable
algorithm based on block tridiagonal LU factorizations. We show
that exact blocking probabilities can be efficiently calculated
even for very large systems and rare blocking probabilities, e.g.,
systems with 256 wavelengths per fiber and blocking probabilities
in the order of 10−40. Relying on the stability and speed of the
proposed algorithm, we also provide a means of provisioning
wavelength channels and converters in optical packet/burst
switching systems
Recommended from our members
Traffic and performance evaluation for optical networks. An Investigation into Modelling and Characterisation of Traffic Flows and Performance Analysis and Engineering for Optical Network Architectures.
The convergence of multiservice heterogeneous networks and ever increasing Internet applications, like peer to peer networking and the increased number of users and services, demand a more efficient bandwidth allocation in optical networks. In this context, new architectures and protocols are needed in conjuction with cost effective quantitative methodologies in order to provide an insight into the performance aspects of the next and future generation Internets.
This thesis reports an investigation, based on efficient simulation methodologies, in order to assess existing high performance algorithms and to propose new ones. The analysis of the traffic characteristics of an OC-192 link (9953.28 Mbps) is initially conducted, a requirement due to the discovery of self-similar long-range dependent properties in network traffic, and the suitability of the GE distribution for modelling interarrival times of bursty traffic in short time scales is presented. Consequently, using a heuristic approach, the self-similar properties of the GE/G/¿ are being presented, providing a method to generate self-similar traffic that takes into consideration burstiness in small time scales. A description of the state of the art in optical networking providing a deeper insight into the current technologies, protocols and architectures in the field, which creates the motivation for more research into the promising switching technique of ¿Optical Burst Switching¿ (OBS). An investigation into the performance impact of various burst assembly strategies on an OBS edge node¿s mean buffer length is conducted. Realistic traffic characteristics are considered based on the analysis of the OC-192 backbone traffic traces. In addition the effect of burstiness in the small time scales on mean assembly time and burst size distribution is investigated. A new Dynamic OBS Offset Allocation Protocol is devised and favourable comparisons are carried out between the proposed OBS protocol and the Just Enough Time (JET) protocol, in terms of mean queue length, blocking and throughput. Finally the research focuses on simulation methodologies employed throughout the thesis using the Graphics Processing Unit (GPU) on a commercial NVidia GeForce 8800 GTX, which was initially designed for gaming computers. Parallel generators of Optical Bursts are implemented and simulated in ¿Compute Unified Device Architecture¿ (CUDA) and compared with simulations run on general-purpose CPU proving the GPU to be a cost-effective platform which can significantly speed-up calculations in order to make simulations of more complex and demanding networks easier to develop
Performance study of asynchronous/ synchronous optical burst/ packet switching with partial wavelength conversion
Cataloged from PDF version of article.Wavelength conversion is known to be one of the most effective methods for
contention resolution in optical packet/burst switching networks. In this thesis,
we study various optical switch architectures that employ partial wavelength
conversion, as opposed to full wavelength conversion, in which a number of converters
are statistically shared per input or output link. Blocking is inevitable
in case contention cannot be resolved and the probability of packet blocking is
key to performance studies surrounding optical packet switching systems. For
asynchronous switching systems with per output link converter sharing, a robust
and scalable Markovian queueing model has recently been proposed by Akar and
Karasan for calculating blocking probabilities in case of Poisson traffic. One of
the main contributions of this thesis is that this existing model has been extended
to cover the more general case of a Markovian arrival process through
which one can study the impact of traffic parameters on system performance.
We further study the same problem but with the converters being of limited range type. Although an analytical model is hard to build for this problem, we
show through simulations that the so-called far conversion policy in which the
optical packet is switched onto the farthest available wavelength in the tuning
range, outperforms the other policies we studied. We point out the clustering
effect in the use of wavelengths to explain this phenomenon. Finally, we study a
synchronous optical packet switching architecture employing partial wavelength
conversion at the input using the per input line converter sharing. For this architecture,
we first obtain the optimal wavelength scheduler using integer linear
programming and then we propose a number of heuristical scheduling algorithms.
These algorithms are tested using simulations under symmetric and asymmetric
traffic scenarios. Our results demonstrate that one can substantially reduce the
costs of converters used in optical switching systems by using share per input
link converter sharing without having to sacrifice much from the low blocking
probabilities provided by full input wavelength conversion. Moreover, we show
that the heuristic algorithm that we propose in this paper provides packet loss
probabilities very close to those achievable using integer linear programming and
is also easy to implement.Doğan, KaanM.S
Comparative study of limited-range wavelength conversion policies for asynchronous optical packet switching
We study an asynchronous optical packet (OP)-switching node equipped with a number of limited range (LR) wavelength converters shared per output link. We study both circular and noncircular LR-wavelength-conversion schemes. A wavelength conversion policy governs the selection of the outgoing wavelength for an OP if the incoming wavelength is in use. Through simulations, we show that the so-called far-conversion policy for which the OP is switched onto the farthest available wavelength in the tuning range, outperforms the other policies we studied. We point out the clustering effect in the use of wavelengths to explain this phenomenon. We also provide an approximate analytical method to find the packet-blocking probability in circular-type LR-wavelength-conversion systems. Based on the simulation results, the approximate method appears to lead to a lower bound for blocking probabilities for all the conversion policies we study. © 2007 Optical Society of America
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