72 research outputs found
Benchmarking and viability assessment of optical packet switching for metro networks
Optical packet switching (OPS) has been proposed as a strong candidate for future metro networks. This paper assesses the viability of an OPS-based ring architecture as proposed within the research project DAVID (Data And Voice Integration on DWDM), funded by the European Commission through the Information Society Technologies (IST) framework. Its feasibility is discussed from a physical-layer point of view, and its limitations in size are explored. Through dimensioning studies, we show that the proposed OPS architecture is competitive with respect to alternative metropolitan area network (MAN) approaches, including synchronous digital hierarchy, resilient packet rings (RPR), and star-based Ethernet. Finally, the proposed OPS architectures are discussed from a logical performance point of view, and a high-quality scheduling algorithm to control the packet-switching operations in the rings is explained
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
Packet Loss Rate Differentiation in slotted Optical Packet Switching OCDM/WDM
We propose a multi-class mechanism for Optical Code Division Multiplexing (OCDM), Wavelength Division Multiplexing (WDM) Optical Packet Switch (OPS) architecture capable of supporting Quality of Service (QoS) transmission. OCDM/WDM has been proposed as a competitive hybrid switching technology to support the next generation optical Internet. This paper addresses performance issues in the slotted OPS networks and proposed four differentiation schemes to support Quality of Service. In addition, we present a comparison between the proposed schemes as well as, a simulation scheduler design which can be suitable for the core switch node in OPS networks. Using software simulations the performance of our algorithm in terms of losing probability, the packet delay, and scalability is evaluated
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
Architecture, design, and modeling of the OPSnet asynchronous optical packet switching node
An all-optical packet-switched network supporting multiple services represents a long-term goal for network operators and service providers alike. The EPSRC-funded OPSnet project partnership addresses this issue from device through to network architecture perspectives with the key objective of the design, development, and demonstration of a fully operational asynchronous optical packet switch (OPS) suitable for 100 Gb/s dense-wavelength-division multiplexing (DWDM) operation. The OPS is built around a novel buffer and control architecture that has been shown to be highly flexible and to offer the promise of fair and consistent packet delivery at high load conditions with full support for quality of service (QoS) based on differentiated services over generalized multiprotocol label switching
Benchmarking and viability assessment of optical packet switching for metro networks
Optical packet switching (OPS) has been proposed as a strong candidate for future metro networks. This paper assesses the viability of an OPS-based ring architecture as proposed within the research project DAVID (Data And Voice Integration on DWDM), funded by the European Commission through the Information Society Technologies (IST) framework. Its feasibility is discussed from a physical-layer point of view, and its limitations in size are explored. Through dimensioning studies, we show that the proposed OPS architecture is competitive with respect to alternative metropolitan area network (MAN) approaches, including synchronous digital hierarchy, resilient packet rings (RPR), and star-based Ethernet. Finally, the proposed OPS architectures are discussed from a logical performance point of view, and a high-quality scheduling algorithm to control the packet-switching operations in the rings is explained
Optical Packet Switching Contention Resolution Based On A Hybrid Wavelength Conversion-Fiber Delay Line Scheme
Due to the convergence of computer communication and telecommunication technology,
data traffic exceeds the telephony traffic. Thus, existing connection oriented and circuit
switched network will need to be upgraded toward optical packet switched network.
Optical packet switching has characteristics like high speed, data rate/data format
transparency and configurable. Wavelength Division Multiplexing is the technology of
combining a number of wavelengths in a single fiber. It is a tremendous trend to harness
larger bandwidth for enormous delivery. WDM optical devices for multiplexing and
switching in simple configuration are now available at a reasonable cost. It is a very
appealing solution for development of optical packet switching.
The issue of contention arises when two or more packets contend for the same output
port in a switch with the same wavelength, which results to packet loss. The packet loss
probability is addressed as the most inevitable and significant measurable performance
parameter with QoS provisioning that is dominated by wavelength contention in optical packet switches. In electronic domain packet switched network, the contention is
resolved by store and forward technique using the available electronic random access
memory (RAM). Due to the immaturity of optical memory storage technology, there is
no available ready-to-use optical random access memory.
In order to overcome this bottleneck, several approaches have been adopted to resolve
the contention problem from three domains: time, space and wavelength as stated: fiber
delay line (time), deflection routing (space) and wavelength conversion (wavelength).
Consequently, contention resolution in wavelength domain has attracted considerable
interest among the optical communications community instead of implementing optical
buffering and deflection routing that have been studied previously.
This thesis proposes a bufferless, single stage, non-blocking fully connected optical
packet switch for synchronous optical packet switching network, followed by a
prioritized scheduling algorithm in association with hybrid contention resolution
schemes. This iterative prioritized scheduling comprises of a set of preemptive selective
policies for contention resolution. It is a hybrid technique that integrates wavelength
conversion with feedback mechanism realized by fiber delay lines (FDL).
By means of simulation, the proposed scheme has been investigated and compared with
the conventional baseline scheme. A sensitive description of the satisfied packet loss
probability and average packet delay as a function of main design parameters such as
switch size, number of wavelengths, traffic load, degree of conversion and number of
fiber delay lines have been carried out with significant improvement.Simulation results proved that the proposed scheme is an efficient approach in resolving
packet contention with less complexity in execution. Relatively, number of wavelength,
traffic load and degree of conversion has significant impact to packet loss ratio. The
implementation of fiber delay lines results on average packet delay. Simulation results
demonstrated that the switch size mildly affect the performance parameter.
Respectively, packet loss ratio below 10-10 is obtained via simulation by the means of
wavelength conversion without conventional buffering delay. The packet loss ratio is
further reduced with the method as aforementioned with the insertion of fiber delay lines
where PLR below 10-13 is achieved, which is much lower than the benchmark value.
Furthermore, the obtained simulation results show that by classifying packet priority, the
proposed scheduling scheme and architecture are able to offer differentiated class of
service
Analytic modelling and resource dimensioning of optical burst switched networks
The realisation of optical network architectures may hold the key to delivering the enormous bandwidth demands of next generation Internet applications and services. Optical
Burst Switching (OBS) is a potentially cost-effective switching technique that can satisfy these demands by offering a high bit rate transport service that is bandwidth-efficient under dynamic Internet traffic loads. Although various aspects of OBS performance have been extensively investigated, there remains a need to systematically assess the cost/performance trade-offs involved in dimensioning OBS switch resources in a network. This goal is essential in enabling the future deployment of OBS but poses a significant challenge due to the complexity of obtaining tractable mathematical models applicable to OBS network optimisation. The overall aim of this thesis lies within this challenge.
This thesis firstly develops a novel analytic performance model of an OBS node where burst contention is resolved by combined use of Tuneable Wavelength Converters (TWCs)
and Fibre Delay Lines (FDLs) connected in an efficient share-per-node configuration. The model uses a two-moment traffic representation that gives a good trade-off between accuracy and complexity, and is suitable for extension to use in network modelling.
The OBS node model is then used to derive an approximate analytic model of an OBS network of switches equipped with TWCs and FDLs, again maintaining a two-moment traffic model for each end-to-end traffic path in the network. This allows evaluation of link/route loss rates under different offered traffic characteristics, whereas most OBS network
models assume only a single-moment traffic representation.
In the last part of this thesis, resource dimensioning of OBS networks is performed by solving single and multi-objective optimisation problems based on the analytic network model. The optimisation objectives relate to equipment cost minimisation and throughput maximisation under end-to-end loss rate constraints. Due to non-convexity of the network performance constraint equations, a search heuristic approach has been taken using a constraint-handling genetic algorithm
- …