Virtual Topology Reconfrigation of WDM Optical Network with Minimum Physical Node

This paper review the reconfiguration of high capacity WDM optical Network, messages are carried in all optical form using light paths. The set of semi-permanent light paths which are set up in the network may be viewed as a virtual topology by higher layers such as SONET, ATM and IP. Reconfiguration is to charge in virtual topology to meet traffic pattern in high layers. It provides a trade off between objective value and the no. of changes to the virtual topology. In another study Objective is to design the logical topology & routing Algorithm on physical topology, so as to minimize the net work congestion while constraining the average delay seen by source destination pair and the amount of processing required at the nodes. Failure handling in WDM Networks is of prime importance due to the nature and volume of traffic, these network carry, failure detection is usually achieved by exchanging control messages among nodes with time out mechanism. Newer and more BW thirsty applications emerging on the horizon and WDM is to leveraging the capabilities of the optical fiber Wavelength  routing  is  the  ability  to  switch  a  signal  at intermediate  nodes  in  a  WDM  network  based  on  their wavelength. Virtual topology can be reconfigured when necessary to improve performance. To create the virtual topology different from the physical topology of the underlying network, is the ability of wavelength routing WDM. Keywords: WDM, Physical Topology, Virtual Topology and Reconfiguratio

On the Conditions that Justify Dynamic Reconfigurability in WDM-TDMA Optical Access Networks

[EN] In a passive optical network with a hybrid wavelength division multiplexing time division multiple-access scheme, implementing reconfigurable wavelength assignment is complex; hence the need to determine the conditions for which the capacity improvements justify requiring reconfigurability over adopting a more inexpensive fixed wavelength assignment. Fixed and reconfigurable approaches to wavelength assignment are modeled and evaluated under nonstationary traffic conditions. The performance improvement is obtained in terms of bit rate gain relative to the nominal bandwidth and depends on the number of wavelength channels as well as the magnitude of the load offered by the optical network units. In addition, frame delay and frame loss in relation to the bit rate performance are obtained for Pareto and exponentially distributed traffic. Simulations show that when introducing reconfigurability, typical peak bit rate gains with respect to the fixed case are 17%, and maxima of 175% are potentially possible when traffic demands are particularly uneven.This work was supported by the EC 7th Framework Program: Architectures for fLexible Photonic Home and Access networks (ALPHA), under contract ICT CP-IP 212 352, from the Generalitat of Valencia under contract ACOMP/2010/196. The authors thank the Performability Engineering Research Group (PERFORM) at the University of Illinois at Urbana-Champaign for developing the software tool Mobius.García Roger, D.; Artundo Martínez, I.; Ortega Tamarit, B. (2011). On the Conditions that Justify Dynamic Reconfigurability in WDM-TDMA Optical Access Networks. Journal of Optical Communications and Networking. 3(4):259-271. https://doi.org/10.1364/JOCN.3.000259S25927134A highly flexible and efficient passive optical network employing dynamic wavelength allocation. (2005). 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Wavelength reconfigurability for next generation optical access networks

Next generation optical access networks should not only increase the capacity but also be able to redistribute the capacity on the fly in order to manage larger variations in traffic patterns. Wavelength reconfigurability is the instrument to enable such capability of network-wide bandwidth redistribution since it allows dynamic sharing of both wavelengths and timeslots in WDM-TDM optical access networks. However, reconfigurability typically requires tunable lasers and tunable filters at the user side, resulting in cost-prohibitive optical network units (ONU). In this dissertation, I propose a novel concept named cyclic-linked flexibility to address the cost-prohibitive problem. By using the cyclic-linked flexibility, the ONU needs to switch only within a subset of two pre-planned wavelengths, however, the cyclic-linked structure of wavelengths allows free bandwidth to be shifted to any wavelength by a rearrangement process. Rearrangement algorithm are developed to demonstrate that the cyclic-linked flexibility performs close to the fully flexible network in terms of blocking probability, packet delay, and packet loss. Furthermore, the evaluation shows that the rearrangement process has a minimum impact to in-service ONUs. To realize the cyclic-linked flexibility, a family of four physical architectures is proposed. PRO-Access architecture is suitable for new deployments and disruptive upgrades in which the network reach is not longer than 20 km. WCL-Access architecture is suitable for metro-access merger with the reach up to 100 km. PSB-Access architecture is suitable to implement directly on power-splitter-based PON deployments, which allows coexistence with current technologies. The cyclically-linked protection architecture can be used with current and future PON standards when network protection is required

Effect Of Reconfiguration On Ip Packet Traffic In Wdm Networks

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2007Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2007Günümüzde iletişim ağlarına erişen insan sayısı ve iletişim uygulamalarının ihtiyaç duyduğu band genişliği ihtiyacı hızla artmaya devam etmektedir. Artan trafik istekleri daha geniş band genişliği kullanımına olanak verebilen optik iletişim ağlarının tasarımını tetiklemektedir. Bir veya daha fazla sayıda optik fiberi kapsayabilen bir ışıkyolu alt katmanda yer alan optik altyapının üzerinde iletişim kanalları sağlamaktadır. Sanal topoloji tasarımı, verilen bir trafik matrisine göre bir grup ışık yolunun kurulması olarak tanımlanabilir. Trafikte meydana gelecek bir değişiklik yeniden konfigürasyon kararının alınmasına neden olabilir. Sanal topoloji yeniden konfigürasyonu, hem yeni sanal topolojinin belirlenmesini hem de bu yeni topolojiye geçişi içermektedir. Bu tez çalışmasında IP/WDM ağlarda sanal topoloji yeniden konfigürasyonunun IP paket trafiği üzerindeki etkileri incelenmiştir. Çalışma kapsamında, çeşitli yeniden kofigürasyon algoritmaları gerçeklenmiş ve Fishnet tabanlı bir IP simülatörü üzerinde test edilmiştir. Gerçeklenen sanal topoloji tasarım algoritmalarına ait paket gecikmeleri/kayıpları incelenmiş ve algoritmaların başarımları karşılaştırılmıştır.Today, both the amount of people accessing communication networks and new communication applications which require high data transfer rates are exponentially increasing. Growing traffic demands triggered the design of optical communication networks which will be able to provide larger bandwidth utilization. A lightpath, which can span multiple fiber links, provides communication channels over the underlying optical communication infrastructure. Virtual Topology Design (VTD) means establishment of a set of lightpaths under a given traffic pattern. A change in traffic pattern may trigger reconfiguration decision. Virtual Topology Reconfiguration (VTR) contains determination of a new virtual topology and migration between the old and new virtual topologies. In this thesis, the effects of virtual topology reconfiguration on Internet Protocol (IP) packet traffic on IP over WDM networks were studied. Various reconfiguration algorithms were implemented and tested on a Fishnet based IP simulator. Packet delays/losses are investigated during reconfiguration procedure for performance comparison of implemented reconfiguration algorithms.Yüksek LisansM.Sc

Topology Reconfiguration with Successive Approximations

Recent technologies have enabled the formation of point-to-point directional wireless networks that are capable of dynamic changes in the network topology. The process of changing this topology in response to changes in available link capacities and load demands of various nodes is called topology control. One example of the type of communication network studied in this context is a Free Space Optical (FSO) network. Topology control consists of computing new topologies to dynamically optimize the network under changing traffic conditions and then carrying out the reconfiguration process to achieve the target topology. This thesis considers the process of topology reconfiguration and use the packet drops that happen during this process as a cost metric for this process. It is shown that by implementing the topology reconfiguration as a series of smaller steps (successive approximation), the number of packets that are dropped during the reconfiguration are reduced. Using this knowledge, the topology computation algorithm can be refined to also minimize the reconfiguration cost along with the typical objective of minimizing congestion