Multi-Granular Optical Cross-Connect: Design, Analysis, and Demonstration

A fundamental issue in all-optical switching is to offer efficient and cost-effective transport services for a wide range of bandwidth granularities. This paper presents multi-granular optical cross-connect (MG-OXC) architectures that combine slow (ms regime) and fast (ns regime) switch elements, in order to support optical circuit switching (OCS), optical burst switching (OBS), and even optical packet switching (OPS). The MG-OXC architectures are designed to provide a cost-effective approach, while offering the flexibility and reconfigurability to deal with dynamic requirements of different applications. All proposed MG-OXC designs are analyzed and compared in terms of dimensionality, flexibility/reconfigurability, and scalability. Furthermore, node level simulations are conducted to evaluate the performance of MG-OXCs under different traffic regimes. Finally, the feasibility of the proposed architectures is demonstrated on an application-aware, multi-bit-rate (10 and 40 Gbps), end-to-end OBS testbed

A Novel QoS provisioning Scheme for OBS networks

This paper presents Classified Cloning, a novel QoS provisioning mechanism for OBS networks carrying real-time applications (such as video on demand, Voice over IP, online gaming and Grid computing). It provides such applications with a minimum loss rate while minimizing end-to-end delay and jitter. ns-2 has been used as the simulation tool, with new OBS modules having been developed for performance evaluation purposes. Ingress node performance has been investigated, as well as the overall performance of the suggested scheme. The results obtained showed that new scheme has superior performance to classical cloning. In particular, QoS provisioning offers a guaranteed burst loss rate, delay and expected value of jitter, unlike existing proposals for QoS implementation in OBS which use the burst offset time to provide such differentiation. Indeed, classical schemes increase both end-to-end delay and jitter. It is shown that the burst loss rate is reduced by 50% reduced over classical cloning

Design And Analysis Of Effective Routing And Channel Scheduling For Wavelength Division Multiplexing Optical Networks

Optical networking, employing wavelength division multiplexing (WDM), is seen as the technology of the future for the Internet. This dissertation investigates several important problems affecting optical circuit switching (OCS) and optical burst switching (OBS) networks. Novel algorithms and new approaches to improve the performance of these networks through effective routing and channel scheduling are presented. Extensive simulations and analytical modeling have both been used to evaluate the effectiveness of the proposed algorithms in achieving lower blocking probability, better fairness as well as faster switching. The simulation tests were performed over a variety of optical network topologies including the ring and mesh topologies, the U.S. Long-Haul topology, the Abilene high-speed optical network used in Internet 2, the Toronto Metropolitan topology and the European Optical topology. Optical routing protocols previously published in the literature have largely ignored the noise and timing jitter accumulation caused by cascading several wavelength conversions along the lightpath of the data burst. This dissertation has identified and evaluated a new constraint, called the wavelength conversion cascading constraint. According to this constraint, the deployment of wavelength converters in future optical networks will be constrained by a bound on the number of wavelength conversions that a signal can go through when it is switched all-optically from the source to the destination. Extensive simulation results have conclusively demonstrated that the presence of this constraint causes significant performance deterioration in existing routing and wavelength assignment (RWA) algorithms. Higher blocking probability and/or worse fairness have been observed for existing RWA algorithms when the cascading constraint is not ignored. To counteract the negative side effect of the cascading constraint, two constraint-aware routing algorithms are proposed for OCS networks: the desirable greedy algorithm and the weighted adaptive algorithm. The two algorithms perform source routing using link connectivity and the global state information of each wavelength. Extensive comparative simulation results have illustrated that by limiting the negative cascading impact to the minimum extent practicable, the proposed approaches can dramatically decrease the blocking probability for a variety of optical network topologies. The dissertation has developed a suite of three fairness-improving adaptive routing algorithms in OBS networks. The adaptive routing schemes consider the transient link congestion at the moment when bursts arrive and use this information to reduce the overall burst loss probability. The proposed schemes also resolve the intrinsic unfairness defect of existing popular signaling protocols. The extensive simulation results have shown that the proposed schemes generally outperform the popular shortest path routing algorithm and the improvement could be substantial. A two-dimensional Markov chain analytical model has also been developed and used to analyze the burst loss probabilities for symmetrical ring networks. The accuracy of the model has been validated by simulation. Effective proactive routing and preemptive channel scheduling have also been proposed to address the conversion cascading constraint in OBS environments. The proactive routing adapts the fairness-improving adaptive routing mentioned earlier to the environment of cascaded wavelength conversions. On the other hand, the preemptive channel scheduling approach uses a dynamic priority for each burst based on the constraint threshold and the current number of performed wavelength conversions. Empirical results have proved that when the cascading constraint is present, both approaches would not only decrease the burst loss rates greatly, but also improve the transmission fairness among bursts with different hop counts to a large extent

A feedback-based hybrid OBS/OCS architecture with fast-over-slow capability

Dynamic bandwidth allocation in response to the bandwidth requirements of new emerging applications is an essential demand for future optical networks. Hybrid switching architectures combining the benefits of different switching technologies in a single node are key elements to support wavelength and sub-wavelength granularities. This paper proposes a novel feedback-based hybrid OBS/OCS node architecture that integrates slow (ms regime) and fast (ns regime) switching elements, aiming at flexible bandwidth allocation while reducing the related costs. Such a node utilizes the pre-transmission idle periods of slow elements in order to send those contending fast bursts, thus improving the overall network performance. The obtained simulation results illustrate significant improvement in terms of Burst Loss Rate (BLR), and lower related network costs when compared to previously proposed hybrid OBS/OCS node architectures.Postprint (author’s final draft

Performance issues in optical burst/packet switching

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-01524-3_8This chapter summarises the activities on optical packet switching (OPS) and optical burst switching (OBS) carried out by the COST 291 partners in the last 4 years. It consists of an introduction, five sections with contributions on five different specific topics, and a final section dedicated to the conclusions. Each section contains an introductive state-of-the-art description of the specific topic and at least one contribution on that topic. The conclusions give some points on the current situation of the OPS/OBS paradigms

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

New contention resolution techniques for optical burst switching

Optical burst switching (OBS) is a technology positioned between wavelength routing and optical packet switching that does not require optical buffering or packet-level parsing, and it is more efficient than circuit switching when the sustained traffic volume does not consume a full wavelength. However, several critical issues still need to be solved such as contention resolution without optical buffering which is a key determinant of packet-loss with a significant impact on network performance. Deflection routing is an approach for resolving contention by routing a contending packet to an output port other than the intended output port. In OBS networks, when contention between two bursts cannot be resolved through deflection routing, one of the bursts will be dropped. However, this scheme doesn’t take advantage of all the available resources in resolving contentions. Due to this, the performance of existing deflection routing scheme is not satisfactory. In this thesis, we propose and evaluate three new strategies which aim at resolving contention. We propose a new approach called Backtrack on Deflection Failure, which provides a second chance to blocked bursts when deflection failure occurs. The bursts in this scheme, when blocked, will get an opportunity to backtrack to the previous node and may get routed through any deflection route available at the previous node. Two variants are proposed for handling the backtracking delay involved in this scheme namely: (a) Increase in Initial Offset and (b) Open-Loop Reservation. Furthermore, we propose a third scheme called Bidirectional Reservation on Burst Drop in which bandwidth reservation is made in both the forward and the backward directions simultaneously. This scheme comes into effect only when control bursts get dropped due to bandwidth unavailability. The retransmitted control bursts will have larger offset value and because of this, they will have lower blocking probability than the original bursts. The performance of our schemes and of those proposed in the literature is studied through simulation. The parameters considered in evaluating these schemes are blocking probability, average throughput, and overall link utilization. The results obtained show that our schemes perform significantly better than their standard counterparts

Effective preemptive scheduling scheme for optical burst-switched networks with cascaded wavelength conversion consideration

We introduce a new preemptive scheduling technique for next-generation optical burst switching (OBS) networks considering the impact of cascaded wavelength conversions. It has been shown that when optical bursts are transmitted all optically from source to destination, each wavelength conversion performed along the lightpath may cause certain signal-to-noise deterioration. If the distortion of the signal quality becomes significant enough, the receiver would not be able to recover the original data. Accordingly, subject to this practical impediment, we improve a recently proposed fair channel scheduling algorithm to deal with the fairness problem and aim at burst loss reduction simultaneously in OBS environments. In our scheme, the dynamic priority associated with each burst is based on a constraint threshold and the number of already conducted wavelength conversions among other factors for this burst. When contention occurs, a new arriving superior burst may preempt another scheduled one according to their priorities. Extensive simulation results have shown that the proposed scheme further improves fairness and achieves burst loss reduction as well