Optical burst switching (OBS) has been paid increasing attention as an attractive alternative for building future photonic Internet. Besides pure theoretical research, experimental prototype and proof-of-concept demonstration are also significant parts toward practical burst switched WDM optical networks. This paper describes hardware architecture, software module and experimental results of optical burst switching nodes using a just-enough-time (JET) protocol and contention resolutions. The core node forwards bursts in the optical domain with deflection routing resolution. It is designed to be transparent to the format, the protocol and the bit rate of traffic. The edge node performs burst assembly/disassembly, as well as burst forwarding, which makes it flexible to be applied to various topologies. The related control protocols and algorithms are implemented taking into account characteristics of being used commercial off-the-shelf devices. By the experiments, the basic function of optical burst switching is demonstrated, the delay measurement result is analyzed, and the effort direction is given.
Contention resolution has been a major concern in the design of burst photonic networks. Previous researches have proven that wavelength conversion is an effective technique for contention resolution. However, it is not realistic under the current technology to assume that all nodes of the network have conversion capabilities. Therefore, burst photonic networks with limited wavelength conversion lead to more practical solutions. Efficient wavelength assignment algorithm is required for such networks. As a simple but effective approach, PWA (Priority-based Wavelength Assignment) tries to avoid contentions beforehand by assigning different wavelengths to bursts sharing one or more common links, using a wavelength priority database where every wavelength is prioritized for each destination based on the history of prior transmissions. In this paper, we extend PWA to be suitable for burst photonic networks with sparse conversion or limited-range conversion and show the validation of our algorithm through simulation results.
In WDM wavelength routed networks, prior to a data transfer, a call setup procedure is required to reserve a wavelength path between the source-destination node pairs. A distributed approach to a connection setup can achieve a very high speed, while improving the reliability and reducing the implementation cost of the networks. However, along with many advantages, several major challenges have been posed by the distributed scheme in how the management and allocation of wavelength could be efficiently carried out. In this thesis, we apply a distributed wavelength assignment algorithm named priority based wavelength assignment (PWA) that was originally proposed for the use in burst switched optical networks to the problem of reserving wavelengths of path reservation protocols in the distributed control optical networks. Instead of assigning wavelengths randomly, this approach lets each node select the “safest” wavelengths based on the information of wavelength utilization history, thus unnecessary future contention is prevented. The simulation results presented in this paper show that the proposed protocol can enhance the performance of the system without introducing any apparent drawbacks.
Photonic networks using Optical Burst Switching (OBS) emerged as an attractive choice for building the next generation Photonic Internet. In burst switched photonic networks, contentions caused by multiple bursts intending to use the same wavelength of the same link at the same time, remarkably increase burst dropping probability and degrade network throughput. As efficient contention resolution methods, the previously presented deflection routing and priority-based wavelength assignment (PWA) work individually but are not compatible with each other. It is therefore desirable to combine these two methods together to make further performance improvement. In this work, we revamped PWA to support deflection routing and show the improved performance of deflection routing-compatible PWA through simulation results.
Given the significant progress made and the continuing advances expected in the optical networking technology, it becomes attractive to build a future Optical Internet that natively supports bursty IP datagrams. Burst switching WDM optical networks are touted as suitable network architectures for future Optical Internet backbones. However, the lack of optical processing capabilities results in increased burst blocking probability, which in turn leads to very limited network performance. Efficient contention resolution method is therefore necessary. Based on discussions of the state of the art of recent optical technologies, a deflection routing protocol for burst switching WDM mesh networks is proposed. The idea of this approach is to use idle optical links as fiber delay lines for contention resolution. Simulation results show that the proposed protocol is available solution for effectively reducing the blocking probability and increasing the performance of burst switching WDM optical networks.
Given the significant progress made and the continuing advances expected in the optical networking technology, it becomes attractive to build a future Optical Internet that natively supports bursty IP datagrams. Burst switching WDM optical networks are touted as suitable network architectures for future Optical Internet backbones. However, the lack of optical processing capabilities results in increased burst blocking probability, which in turn leads to very limited network performance. Efficient contention resolution method is therefore necessary. Based on discussions of the state of the art of recent optical technologies, a burst optical deflection routing protocol is proposed. The idea of this approach is to use idle optical links as fiber delay lines for contention resolution. Simulation results show that the proposed protocol is available solution for effectively reducing the blocking probability and increasing the performance of burst switching WDM optical networks.
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