Deflection Routing Strategies for Optical Burst Switching Networks: Contemporary Affirmation of the Recent Literature

A promising option to raising busty interchange in system communication could be Optical Burst Switched (OBS) networks among scalable and support routing effective. The routing schemes with disputation resolution got much interest, because the OBS network is buffer less in character. Because the deflection steering can use limited optical buffering or actually no buffering thus the choice or deflection routing techniques can be critical. Within this paper we investigate the affirmation of the current literature on alternate (deflection) routing strategies accessible for OBS networks

Performance evaluation of slotted optical burst switching systems with quality of service differentiation

Slotted optical burst switching (SOBS) has recently caught the attention of the optical networking community due to performance gains achievable with synchronous infrastructures. In this paper, we study the loss probabilities in a slotted optical burst switching node fed with Poisson burst traffic where the fixed burst size is an integer multiple of the slot length. We develop a discrete-time Markov chain (DTMC) based framework to obtain the loss probabilities in systems with and without quality of service (QoS) differentiation. In particular, we focus on analytical modeling of 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 distribution approximation for the discrete Poisson distribution leading to an accurate approximation for the loss probabilities. A hybrid QoS mechanism which jointly utilizes offset-based differentiation together with priority scheduling is also analyzed. © 2009 IEEE

Quality of service analysis for slotted optical burst switching networks

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

Mécanismes de résolution et de prévention de la contention pour les réseaux optiques à commutation de rafales

L'explosion actuelle de l'utilisation des applications en temps réel, telles que la téléphonie et la vidéo haute définition, fait en sorte qu'une demande croissante en bande passante existe. Or, la fibre optique offre un très grand potentiel en termes de bande passante allant physiquement jusqu'à 50 terabits par seconde par fibre optique en utilisant un multiplexage en longueurs d'onde. La commutation de rafales en optique est une nouvelle technique de commutation permettant de tirer profit des avantages de la commutation de paquets et de la commutation de circuits. Une problématique majeure est le taux de perte élevé à cause du problème de la contention. Plusieurs techniques de résolution de la contention existent, notamment la déflexion et la retransmission. Dans la première partie de ce travail, on s'intéresse à combiner dynamiquement la déflexion et la retransmission d'une manière adaptative en tenant compte de l'état du réseau. L'algorithme proposé permet d'effectuer le plus de déflexions possibles tant que celles-ci ne déstabilisent pas le réseau. Les résultats démontrent également, avec des topologies fortement connectées telles que COST239, que l'algorithme proposé permet de diminuer radicalement les pertes en utilisant un ratio de déflexion très grand. La deuxième partie de ce travail porte sur la prévention de la contention en utilisant des tables de routage optimisées. Ces tables de routage sont optimisées en utilisant un modèle graphique probabiliste utilisé en intelligence artificielle, soit un réseau bayésien. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Fibre optique, WDM, Commutation de rafales, Contention, Déflexion, Retransmission

Selected topics in optical burst switched networks Performance analysis

Projecte final de carrera realitzat en col.laboració amb École Polytechnique Fédérale de Lausanne (EPFL)English: This report is the result of the final year project carried out at the Laboratoire des telecommunications (TCOM), École Polytechnique Fédérale de Lausanne (EPFL) between March and October 2010 under the supervision of Dr. Christian Gaumier and the assistance of Sébastien Rumley. The work presented in this thesis is based on the JAVOBS simulator, which was presented for Oscar Pedrola in [31]. This OBS network simulator has been built on top of the JAVANCO framework developed for Sébastien Rumley and other collaborators in TCOM laboratory. The report starts presenting the basics of OBS paradigm in order to situate the lector in context and to present the operation possibilities of OBS networks and its problem of burst contention. It continues in chapter 2 with the explanation of network modeling and specifically for the particular model of JAVOBS. In the different sections in chapter 3, the selected topics are presented and treated in detail. Each section of chapter 3 is divided in a presentation of the topic and the reason why it is interesting to work on it, the necessary implementation to introduce it in the Javobs tool, some simulation tests to validate and check the correct functionality of the component developed and some results and conclusions by simulation comparison. Mainly, the selected topics are the following: ‐ The routing topic is treated with the purpose to define a proactive routing protocol based on load balanced-algorithm which operates as a contention resolution technique. ‐ The virtual topology design is treated in order to also alleviate and reduce the contention problem by the establishment of a particular set of dedicated lightpaths on the physical network. ‐ To provide new models of traffic for JAVOBS simulator, the traffic generation topic is raised. Traffic characteristics and self-similar properties are presented and a Markov-modulated traffic generator and a Self-Similar traffic generator are implemented and validated. Then, its impact in the network performance is evaluated and compared

Stabilizing deflection routing in optical burst switched networks

This paper studies the blocking performance of optical burst switching (OBS) networks using a sequential office control (SOC) state-independent deflection routing policy. We show that unprotected deflection routing may destabilize OBS resulting in higher blocking probabilities than if bursts were not deflected but simply blocked. This study was motivated by the well-known destabilizing effect that alternative routing has on circuit switching in classical telephony networks. We propose two forms of protection to guard against destabilization: 1) wavelength reservation, which is analogous to trunk reservation in circuit switching; and, 2) preemptive priority, which is a new form of protection where bursts that have not been deflected are given preemptive priority over bursts that have been deflected. Our main contribution is a one-moment reduced-load approximation to evaluate the blocking performance of OBS networks using deflection routing protected by either wavelength reservation or preemptive priority. Our reduced-load approximation relies on the usual assumptions of link independence and Poisson distributed link arrivals. We quantify the error admitted in making these two assumptions via simulation. Using our reduced-load approximation, we evaluate the blocking performance of protected and unprotected deflection routing in several randomly generated networks. The chief conclusion of our study is that deflection routing in OBS should be given some form of protection to avoid destabilization resulting from upward load variations, and in terms of blocking performance, preemptive priority is the best form of protection for OBS. We use simulation to verify that our conclusions remain valid for a realistic traffic scenario