Heuristic for the design of fault tolerant logical topology.

Wavelength division multiplexing (WDM) in optical fiber networks is widely viewed as the savior for its potential to satisfy the huge bandwidth requirement of network users. Optical cross connect (OCX) in WDM network facilitates the switching of signal on any wavelength from any input port to any output port. As a result, it is possible to establish ligthpaths between any pair of nodes. The set of lightpaths established over fiber links defines logical topology. In our thesis, we proposed a heuristic approach for the design of fault tolerant logical topology. Our design approach generalizes the design protection concept and enforces wavelength continuity constraint in a multi-hop optical network. In our work, we first designed logical topology for fault free state of the network. We, then, added additional lightpaths for each single link failure scenario. Numerical results clearly show that our approach outperforms Shared path protection and Dedicated path protection. Our simulation result shows that our approach is feasible for large networks. (Abstract shortened by UMI.) Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .S24. Source: Masters Abstracts International, Volume: 44-03, page: 1413. Thesis (M.Sc.)--University of Windsor (Canada), 2005

Robustness metrics for optical networks

Telecommunication networks are vulnerable towards single or simultaneous nodes/links failures, which may lead to the disruption of network areas. The failures may cause performance degradation, reduced quality of services, reduced nodes/links survivability, stability, and reliability. Therefore, it is important to measure and enhance the network robustness, via the use of robustness metrics. This paper gives an overview of several robustness metrics that are commonly used for optical networks, from the structural, centrality and functional perspectives

Efficiency Of Using Partial Path Protection Method In Optical Wdm Mesh Networks

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2006Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2006Bu çalışmada, dalga boyu bölümlemeli çoklama yöntemine dayalı optik ağlarda oluşan bağ aksaklıklarının önüne geçebilmek ve ağın kalımlığını sağlayabilmek için, her bir ana yolun her bir bağı için bir koruyucu onarım yolu belirleyen kısmi yol koruma yöntemi kullanılarak, korumanın etkinliğinin arttırılması sağlanmıştır. Bağlantıları koruyucu yolları oluşturan bağların dalga boylarının, farklı bağlantılar için oluşturulmuş koruyucu yollar ile paylaşılmasına izin verilip verilmemesine dayalı olan, adanmış ve paylaşımlı kısmi yol koruma yöntemleri de dikkate alınarak, paylaşımlı kısmi yol koruma yönteminin, adanmış kısmi yol koruma yöntemine olan üstünlüğü belirlenmiştir. Paylaşım oranı adı verilen, aynı linkte bulunan bir kaynağı paylaşabilen, aktif yolları koruma amaçlı kurulan koruyucu yolların sayısını belirleyen terimin de, başarımı nasıl etkilediği incelenmiştir. En yüksek paylaşım oranı değerine ve kaynağa sahip paylaşımlı kısmi yol korumanın en iyi başarıma sahip olduğu gözlemlenmiştir. Etkinlik başarım ölçüleri olarak, bağlantı isteklerine göre ağda kullanılan dalga boyu-link sayısı ve bağlantı isteklerinin bloke edilme oranı göz önünde bulundurulmuştur.In this study, the increase on the efficiency of protection, which is used to avoid link failures in Optical Wavelength-Division Multiplexed Networks and to ensure survivability for these networks, is provided by using the Partial Path Protection scheme, in which a different restoration path for every link of every primary path is determined. Dedicated Partial Path Protection and Shared Partial Path Protection, which are based on allowance of sharing the wavelengths of the links, which are used on the protection paths, by protection paths are considered. It is observed that Shared Partial Path Protection outperforms the Dedicated Partial Path Protection scheme. Sharing Ratio is the number of protection paths, which share the same resource of the link for protecting the active paths against failures is also analyzed. The simulations confirm that as the value of the sharing ratio increases, the performance of the network increases. Simulation results show that the Shared Partial Path Protection with the highest Sharing Ratio value and the number of wavelengths, has the best performance. The performance metrics used in simulations are, number of wavelength-links occupied per link and blocking probability, according to the number of connection requests in the network.Yüksek LisansM.Sc

Supporting differentiated classes of resilience in multilayer networks

Services provided over telecommunications networks typically have different resilience requirements and networks need to be able to support different levels of resilience in an efficient manner. This dissertation investigates the problem of supporting differentiated classes of resilience in multilayer networks, including the most stringent resilience class required by critical services. We incorporate an innovative technique of embedding a subnetwork, termed the spine, with comparatively higher availability values at the physical layer. The spine lays a foundation for differentiation between multiple classes of flows that can be leveraged to achieve both high resilience and differentiation. The aim of this research is mainly to explore, design, and evaluate the proposed spine concept model in multilayer networks. The dissertation has four major parts. First, we explore the spine concept through numerical analysis of simple topologies illustrating the potential benefits and the cost considerations of the spine. We develop heuristics algorithms to find suitable spines for a network based on the structural properties of the network topology. Second, an optimization problem is formulated to determine the spine. The problem encompasses estimates of link availability improvements, associated costs, and a total budget. Third, we propose a crosslayer mapping and spine-aware routing design problem with protection given mainly at the lower layer. The problem is designed to transfer lower layer differentiation capability to the upper layer network and flows. We provide two joint routing-mapping optimization formulations and evaluate their performance in a multilayer scenario. Fourth, the joint routing-mapping problem is redesigned with protection given in the upper network layer instead. This will create two isolated logical networks; one mapped to the spine and the other is mapped freely on the network. Flows are assigned a path or path-pair based on their class of resilience. This approach can provide more routing options yielding different availability levels. The joint routing-mapping design problems are formulated as Integer Linear Programming (ILP) models. The goal is to achieve a wider range of availability values across layers and high availability levels for mission-critical services without the need to use higher order protection configurations. The proposed models are evaluated with extensive numerical results using real network topologies

Software Defined Applications in Cellular and Optical Networks

abstract: Small wireless cells have the potential to overcome bottlenecks in wireless access through the sharing of spectrum resources. A novel access backhaul network architecture based on a Smart Gateway (Sm-GW) between the small cell base stations, e.g., LTE eNBs, and the conventional backhaul gateways, e.g., LTE Servicing/Packet Gateways (S/P-GWs) has been introduced to address the bottleneck. The Sm-GW flexibly schedules uplink transmissions for the eNBs. Based on software defined networking (SDN) a management mechanism that allows multiple operator to flexibly inter-operate via multiple Sm-GWs with a multitude of small cells has been proposed. This dissertation also comprehensively survey the studies that examine the SDN paradigm in optical networks. Along with the PHY functional split improvements, the performance of Distributed Converged Cable Access Platform (DCCAP) in the cable architectures especially for the Remote-PHY and Remote-MACPHY nodes has been evaluated. In the PHY functional split, in addition to the re-use of infrastructure with a common FFT module for multiple technologies, a novel cross functional split interaction to cache the repetitive QAM symbols across time at the remote node to reduce the transmission rate requirement of the fronthaul link has been proposed.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Data center network placement and data backup against region failures

指導教員：姜　暁