Browsing by Subject "Optical packet switching"

Now showing 1 - 12 of 12

Open Access
Comparative analysis of power consumption in asynchronous wavelength modular optical switching fabrics
(Elsevier, 2011-04-02) Akar, N.; Eramo, V.; Raffaelli, C.
Next-generation optical routers will be designed to support the flexibility required by Future Internet services and, at the same time, to overcome the power consumption bottleneck which appears to limit throughput scalability in today routers. A model to evaluate average power consumption in asynchronous optical switching fabrics is here presented to compare these architectures with other synchronous and asynchronous solutions. The combination of wavelength modular switching fabrics with low spatial complexity and asynchronous operation is demonstrated to be the most power-efficient solution among those considered which employ wavelength converters, through presentation and discussion of a thorough set of numerical results.
Open Access
Dimensioning shared-per-node recirculating fiber delay line buffers in an optical packet switch
(Elsevier, 2013) Akar, N.; Gunalay, Y.
Optical buffering based on fiber delay lines (FDLs) has been proposed as a means for contention resolution in an optical packet switch. In this article, we propose a queuing model for feedback-type shared-per-node recirculating FDL optical buffers in asynchronous optical switching nodes. In this model, optical packets are allowed to recirculate over FDLs as long as the total number of recirculations is less than a pre-determined limit to meet signal loss requirements. Markov Modulated Poisson Process (MMPP)-based overflow traffic models and fixed-point iterations are employed to provide an approximate analysis procedure to obtain blocking probabilities as a function of various buffer parameters in the system when the packet arrival process at the optical switch is Poisson. The proposed algorithm is numerically efficient and accurate especially in a certain regime identified with relatively long and variably-sized FDLs, making it possible to dimension optical buffers in next-generation optical packet switching systems.
Open Access
Exact analysis of single-wavelength optical buffers with feedback markov fluid queues
(Optical Society of America, 2009-10-15) Kankaya H. E.; Akar, N.
Optical buffering via fiber delay lines is used for contention resolution in optical packet and optical burst switching nodes. This article addresses the problem of exactly finding the blocking probabilities in an asynchronous single-wavelength optical buffer. Packet lengths are assumed to be variable and modeled by phase-type distributions, whereas the packet arrival process is modeled by a Markovian arrival process that can capture autocorrelations in interarrival times. The exact solution is based on the theory of feedback fluid queues for which we propose numerically efficient and stable algorithms. We not only find the packet blocking probabilities but also the entire distribution of the unfinished work in this system from which all performance measures of interest can be derived.
Open Access
Optical core networks research in the e-Photon-ONe+ project
(2009) Callegati F.; Cugini F.; Ghobril P.; Gunreben, S.; López V.; Martini, B.; Pavón-Mariño P.; Perényi, M.; Sengezer, N.; Staessens, D.; Szigeti J.; Tornatore, M.
This paper reports a summary of the joint research activities on Optical Core Networks within the e-Photon-ONe+ project. It provides a reasonable overview of the topics considered of interest by the European research community and supports the idea of building joint research activities that can leverage on the expertise of different research groups. © 2009 IEEE.
Open Access
Packet loss analysis of synchronous buffer-less optical switch with shared limited range wavelength converters
(IEEE, 2007) Raffaelli, C.; Savi, M.; Akar, Nail; Karasan, Ezhan
Application of synchronous optical switches in Optical Packet/Burst switched networks is considered. The shared per node architectural concept, where wavelength converters are shared among all input and output channels, is applied for contention resolution in the wavelength domain. A semi-analytical traffic model suitable to represent the different contributions to packet loss is proposed and validated. Full and limited range wavelength conversion capabilities are considered, and loss results obtained to support switch design. An approximated fully analytical approach for the limited range case is also described and comparison with simulation results is presented to assess the capability to capture the main aspects of packet loss behavior.
Open Access
Performance modeling of QoS differentiation in optical packet switching via FDL access limitation
(Springer New York LLC, 2017) Yazici, M. A.; Akar, N.
We present an exact analytical model for single-wavelength quality of service (QoS) differentiation in a two-class optical packet switch. In this system, QoS differentiation is achieved by limiting the set of fiber delay lines (FDLs) to the low-priority class, whereas the high-priority class is allowed to access the entire FDL bank. The analytical model is based on multi-regime Markov fluid queues and is extensible to multi-class systems with more than two classes. Markovian arrival process packet arrivals and phase-type distributed packet sizes are considered for the purpose of generality. The proposed analytical model is validated through simulations. The numerical results provide insight into determining appropriate subsets of FDLs allowed for the access of the low-priority class. The results also show that it is possible to direct almost all the packet losses to the low-priority class under moderate loads.
Open Access
Performance study of asynchronous/ synchronous optical burst/ packet switching with partial wavelength conversion
(2006) Doğan, Kaan
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.
Open Access
Retrial queuing models of multi-wavelength FDL feedback optical buffers
(Institute of Electrical and Electronics Engineers, 2011) Akar, N.; Sohraby, K.
Optical buffers based on Fiber Delay Lines (FDL) have been proposed for contention resolution in optical packet/burst switching systems. In this article, we propose a retrial queuing model for FDL optical buffers in asynchronous optical switching nodes. In the considered system, the reservation model employed is of post-reservation type and optical packets are allowed to re-circulate over the FDLs in a probabilistic manner. We combine the MMPP-based overflow traffic models of the classical circuit switching literature and fixed-point iterations to devise an algorithmic procedure to accurately estimate blocking probabilities as a function of various buffer parameters in the system when packet arrivals are Poisson and packet lengths are exponentially distributed. The proposed algorithm is both accurate and fast, allowing one to use the procedure to dimension optical buffers in next-generation optical packet switching systems.
Open Access
Shared-per-wavelength asynchronous optical packet switching: a comparative analysis
(Elsevier, 2010-03-23) Akar, N.; Rafaelli, C.; Savi, M.; Karasan, E.
This paper compares four different architectures for sharing wavelength converters in asynchronous optical packet switches with variable-length packets. The first two architectures are the well-known shared-per-node (SPN) and shared-per-link (SPL) architectures, while the other two are the shared-per-input-wavelength (SPIW) architecture, recently proposed as an optical switch architecture in synchronous context only, which is extended here to the asynchronous scenario, and an original scheme called shared-per-output-wavelength (SPOW) architecture that we propose in the current article. We introduce novel analytical models to evaluate packet loss probabilities for SPIW and SPOW architectures in asynchronous context based on Markov chains and fixed-point iterations for the particular scenario of Poisson input traffic and exponentially distributed packet lengths. The models also account for unbalanced traffic whose impact is thoroughly studied. These models are validated by comparison with simulations which demonstrate that they are remarkably accurate. In terms of performance, the SPOW scheme provides blocking performance very close to the SPN scheme while maintaining almost the same complexity of the space switch, and employing less expensive wavelength converters. On the other hand, the SPIW scheme allows less complexity in terms of number of optical gates required, while it substantially outperforms the widely accepted SPL scheme. The authors therefore believe that the SPIW and SPOW schemes are promising alternatives to the conventional SPN and SPL schemes for the implementation of next-generation optical packet switching systems.
Open Access
State aggregation-based model of asynchronous multi-fiber optical switching with shared wavelength converters
(Elsevier, 2013) Akar, N.; Raffaelli, C.; Savi, M.
This paper proposes new analytical models to study optical packet switching architectures with multi-fiber interfaces and shared wavelength converters. The multi-fiber extension of the recently proposed Shared-Per-Input-Wavelength (SPIW) scheme is compared against the multi-fiber Shared-Per-Node (SPN) scheme in terms of cost and performance for asynchronous traffic. In addition to using Markov chains and fixed-point iterations for modeling the mono-fiber case, a novel state aggregation technique is proposed to evaluate the packet loss in asynchronous multi-fiber scenario. The accuracy of the performance models is validated by comparison with simulations in a wide variety of scenarios with both balanced and imbalanced input traffic. The proposed analytical models are shown to remarkably capture the actual system behavior in all scenarios we tested. The adoption of multi-fiber interfaces is shown to achieve remarkable savings in the number of wavelength converters employed and their range. In addition, the SPIW solution allows to save, in particular conditions, a significant number of optical gates compared to the SPN solution. Indeed, SPIW allows, if properly dimensioned, potential complexity and cost reduction compared to SPN, while providing similar performance.
Open Access
Stochastic analysis of finite population bufferless multiplexing in optical packet/burst switching systems
(Denshi Jouhou Tsuushin Gakkai,Institute of Electronics Information and Communication Engineers, 2007) Akar, N.; Gunalay, Y.
In this letter, we study the blocking probabilities in an asynchronous optical packet/burst switching system with full wavelength conversion. Most of the existing work use Poisson traffic models that is well-suited for an infinite population of users. In this letter, the optical packet traffic arriving at the switching system is modeled through a superposition of a finite number of identical on-off sources. We propose a block tridiagonal LU factorization algorithm to efficiently solve the two dimensional Markov chain that arises in the modeling of the switching system.
Open Access
Wavelength converter sharing in asynchronous optical packet/burst switching: an exact blocking analysis for markovian arrivals
(IEEE, 2006-12-11) Akar, N.; Karasan, E.; Doğan, K.
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.