In-operation planning in flexgrid optical core networks

New generation applications, such as cloud computing or video distribution, can run in a telecom cloud infrastructure where the datacenters (DCs) of telecom operators are integrated in their networks thus, increasing connections' dynamicity and resulting in time-varying traffic capacities, which might also entail changes in the traffic direction along the day. As a result, a flexible optical technology able to dynamically set-up variable-capacity connections, such as flexgrid, is needed. Nonetheless, network dynamicity might entail network performance degradation thus, requiring re-optimizing the network while it is in operation. This thesis is devoted to devise new algorithms to solve in-operation network planning problems aiming at enhancing the performance of optical networks and at studying their feasibility in experimental environments. In-operation network planning requires from an architecture enabling the deployment of algorithms that must be solved in stringent times. That architecture can be based on a Path Computation Element (PCE) or a Software Defined Networks controller. In this thesis, we assume the former split in a front-end PCE, in charge of provisioning paths and handling network events, and a specialized planning tool in the form of a back-end PCE responsible for solving in-operation planning problems. After the architecture to support in-operation planning is assessed, we focus on studying the following applications: 1) Spectrum fragmentation is one of the most important problems in optical networks. To alleviate it to some extent without traffic disruption, we propose a hitless spectrum defragmentation strategy. 2) Each connection affected by a failure can be recovered using multiple paths to increase traffic restorability at the cost of poor resource utilization. We propose re-optimizing the network after repairing the failure to aggregate and reroute those connections to release spectral resources. 3) We study two approaches to provide multicast services: establishing a point-to-multipoint connections at the optical layer and using multi-purpose virtual network topologies (VNT) to serve both unicast and multicast connectivity requests. 4) The telecom cloud infrastructure, enables placing contents closer to the users. Based on it, we propose a hierarchical content distribution architecture where VNTs permanently interconnect core DCs and metro DCs periodically synchronize contents to the core DCs. 5) When the capacity of the optical backbone network becomes exhausted, we propose using a planning tool with access to inventory and operation databases to periodically decide the equipment and connectivity to be installed at the minimum cost reducing capacity overprovisioning. 6) In multi-domain multi-operator scenarios, a broker on top of the optical domains can provision multi-domain connections. We propose performing intra-domain spectrum defragmentation when no contiguous spectrum can be found for a new connection request. 7) Packet nodes belonging to a VNT can collect and send incoming traffic monitoring data to a big data repository. We propose using the collected data to predict next period traffic and to adapt the VNT to future conditions. The methodology followed in this thesis consists in proposing a problem statement and/or a mathematical formulation for the problems identified and then, devising algorithms for solving them. Those algorithms are simulated and then, they are experimentally assessed in real test-beds. This thesis demonstrates the feasibility of performing in-operation planning in optical networks, shows that it enhances the performance of the network and validates the feasibility of its deployment in real networks. It shall be mentioned that part of the work reported in this thesis has been done within the framework of several research projects, namely IDEALIST (FP7-ICT-2011-8) and GEANT (238875) funded by the EC and SYNERGY (TEC2014-59995-R) funded by the MINECO.Les aplicacions de nova generació, com ara el cloud computing o la distribució de vídeo, es poden executar a infraestructures de telecom cloud (TCI) on operadors integren els seus datacenters (DC) a les seves xarxes. Aquestes aplicacions fan que incrementi tant la dinamicitat de les connexions, com la variabilitat de les seves capacitats en el temps, arribant a canviar de direcció al llarg del dia. Llavors, cal disposar de tecnologies òptiques flexibles, tals com flexgrid, que suportin aquesta dinamicitat a les connexions. Aquesta dinamicitat pot degradar el rendiment de la xarxa, obligant a re-optimitzar-la mentre és en operació. Aquesta tesis està dedicada a idear nous algorismes per a resoldre problemes de planificació sobre xarxes en operació (in-operation network planning) per millorar el rendiment de les xarxes òptiques i a estudiar la seva factibilitat en entorns experimentals. Aquests problemes requereixen d’una arquitectura que permeti desplegar algorismes que donin solucions en temps restrictius. L’arquitectura pot estar basada en un Element de Computació de Rutes (PCE) o en un controlador de Xarxes Definides per Software. En aquesta tesis, assumim un PCE principal encarregat d’aprovisionar rutes i gestionar esdeveniments de la xarxa, i una eina de planificació especialitzada en forma de PCE de suport per resoldre problemes d’in-operation planning. Un cop validada l’arquitectura que dona suport a in-operation planning, estudiarem les següents aplicacions: 1) La fragmentació d’espectre és un dels principals problemes a les xarxes òptiques. Proposem reduir-la en certa mesura, fent servir una estratègia que no afecta al tràfic durant la desfragmentació. 2) Cada connexió afectada per una fallada pot ser recuperada fent servir múltiples rutes incrementant la restaurabilitat de la xarxa, tot i empitjorar-ne la utilització de recursos. Proposem re-optimitzar la xarxa després de reparar una fallada per agregar i re-enrutar aquestes connexions tractant d’alliberar recursos espectrals. 3) Estudiem dues solucions per aprovisionar serveis multicast: establir connexions punt-a-multipunt sobre la xarxa òptica i utilitzar Virtual Network Topologies (VNT) multi-propòsit per a servir peticions de connectivitat tant unicast com multicast. 4) La TCI permet mantenir els continguts a prop dels usuaris. Proposem una arquitectura jeràrquica de distribució de continguts basada en la TCI, on els DC principals s’interconnecten per mitjà de VNTs permanents i els DCs metropolitans periòdicament sincronitzen continguts amb els principals. 5) Quan la capacitat de la xarxa òptica s’exhaureix, proposem utilitzar una eina de planificació amb accés a bases de dades d’inventari i operacionals per decidir periòdicament l’equipament i connectivitats a instal·lar al mínim cost i reduir el sobre-aprovisionament de capacitat. 6) En entorns multi-domini multi-operador, un broker per sobre dels dominis òptics pot aprovisionar connexions multi-domini. Proposem aplicar desfragmentació d’espectre intra-domini quan no es pot trobar espectre contigu per a noves peticions de connexió. 7) Els nodes d’una VNT poden recollir i enviar informació de monitorització de tràfic entrant a un repositori de big data. Proposem utilitzar aquesta informació per adaptar la VNT per a futures condicions. La metodologia que hem seguit en aquesta tesis consisteix en formalitzar matemàticament els problemes un cop aquests son identificats i, després, idear algorismes per a resoldre’ls. Aquests algorismes son simulats i finalment validats experimentalment en entorns reals. Aquesta tesis demostra la factibilitat d’implementar mecanismes d’in-operation planning en xarxes òptiques, mostra els beneficis que aquests aporten i valida la seva aplicabilitat en xarxes reals. Part del treball presentat en aquesta tesis ha estat dut a terme en el marc dels projectes de recerca IDEALIST (FP7-ICT-2011-8) i GEANT (238875), finançats per la CE, i SYNERGY (TEC2014-59995-R), finançat per el MINECO.Postprint (published version

Optical Networks and Interconnects

The rapid evolution of communication technologies such as 5G and beyond, rely on optical networks to support the challenging and ambitious requirements that include both capacity and reliability. This chapter begins by giving an overview of the evolution of optical access networks, focusing on Passive Optical Networks (PONs). The development of the different PON standards and requirements aiming at longer reach, higher client count and delivered bandwidth are presented. PON virtualization is also introduced as the flexibility enabler. Triggered by the increase of bandwidth supported by access and aggregation network segments, core networks have also evolved, as presented in the second part of the chapter. Scaling the physical infrastructure requires high investment and hence, operators are considering alternatives to optimize the use of the existing capacity. This chapter introduces different planning problems such as Routing and Spectrum Assignment problems, placement problems for regenerators and wavelength converters, and how to offer resilience to different failures. An overview of control and management is also provided. Moreover, motivated by the increasing importance of data storage and data processing, this chapter also addresses different aspects of optical data center interconnects. Data centers have become critical infrastructure to operate any service. They are also forced to take advantage of optical technology in order to keep up with the growing capacity demand and power consumption. This chapter gives an overview of different optical data center network architectures as well as some expected directions to improve the resource utilization and increase the network capacity

Design and implementation of a fault-tolerant multimedia network and a local map based (LMB) self-healing scheme for arbitrary topology networks.

by Arion Ko Kin Wa.Thesis (M.Phil.)--Chinese University of Hong Kong, 1997.Includes bibliographical references (leaves 101-[106]).Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Overview --- p.1Chapter 1.2 --- Service Survivability Planning --- p.2Chapter 1.3 --- Categories of Outages --- p.3Chapter 1.4 --- Goals of Restoration --- p.4Chapter 1.5 --- Technology Impacts on Network Survivability --- p.5Chapter 1.6 --- Performance Models and Measures in Quantifying Network Sur- vivability --- p.6Chapter 1.7 --- Organization of Thesis --- p.6Chapter 2 --- Design and Implementation of A Survivable High-Speed Mul- timedia Network --- p.8Chapter 2.1 --- An Overview of CUM LAUDE NET --- p.8Chapter 2.2 --- The Network Architecture --- p.9Chapter 2.2.1 --- Architectural Overview --- p.9Chapter 2.2.2 --- Router-Node Design --- p.11Chapter 2.2.3 --- Buffer Allocation --- p.12Chapter 2.2.4 --- Buffer Transmission Priority --- p.14Chapter 2.2.5 --- Congestion Control --- p.15Chapter 2.3 --- Protocols --- p.16Chapter 2.3.1 --- Design Overview --- p.16Chapter 2.3.2 --- ACTA - The MAC Protocol --- p.17Chapter 2.3.3 --- Protocol Layering --- p.18Chapter 2.3.4 --- "Segment, Datagram and Packet Format" --- p.20Chapter 2.3.5 --- Fast Packet Routing --- p.22Chapter 2.3.6 --- Local Host NIU --- p.24Chapter 2.4 --- The Network Restoration Strategy --- p.25Chapter 2.4.1 --- The Dual-Ring Model and Assumptions --- p.26Chapter 2.4.2 --- Scenarios of Network Failure and Remedies --- p.26Chapter 2.4.3 --- Distributed Fault-Tolerant Algorithm --- p.26Chapter 2.4.4 --- Distributed Auto-Healing Algorithm --- p.28Chapter 2.4.5 --- The Network Management Signals --- p.31Chapter 2.5 --- Performance Evaluation --- p.32Chapter 2.5.1 --- Restoration Time --- p.32Chapter 2.5.2 --- Reliability Measures --- p.34Chapter 2.5.3 --- Network Availability During Restoration --- p.41Chapter 2.6 --- The Prototype --- p.42Chapter 2.7 --- Technical Problems Encountered --- p.45Chapter 2.8 --- Chapter Summary and Future Development --- p.46Chapter 3 --- A Simple Experimental Network Management Software - NET- MAN --- p.48Chapter 3.1 --- Introduction to NETMAN --- p.48Chapter 3.2 --- Network Management Basics --- p.49Chapter 3.2.1 --- The Level of Management Protocols --- p.49Chapter 3.2.2 --- Architecture Model --- p.51Chapter 3.2.3 --- TCP/IP Network Management Protocol Architecture --- p.53Chapter 3.2.4 --- A Standard Network Management Protocol On Internet - SNMP --- p.54Chapter 3.2.5 --- A Standard For Managed Information --- p.55Chapter 3.3 --- The CUM LAUDE Network Management Protocol Suite (CNMPS) --- p.56Chapter 3.3.1 --- The Architecture --- p.53Chapter 3.3.2 --- Goals of the CNMPS --- p.59Chapter 3.4 --- Highlights of NETMAN --- p.61Chapter 3.5 --- Functional Descriptions of NETMAN --- p.63Chapter 3.5.1 --- Topology Menu --- p.64Chapter 3.5.2 --- Fault Manager Menu --- p.65Chapter 3.5.3 --- Performance Meter Menu --- p.65Chapter 3.5.4 --- Gateway Utility Menu --- p.67Chapter 3.5.5 --- Tools Menu --- p.67Chapter 3.5.6 --- Help Menu --- p.68Chapter 3.6 --- Chapter Summary --- p.68Chapter 4 --- A Local Map Based (LMB) Self-Healing Scheme for Arbitrary Topology Networks --- p.70Chapter 4.1 --- Introduction --- p.79Chapter 4.2 --- An Overview of Existing DCS-Based Restoration Algorithms --- p.72Chapter 4.3 --- The Network Model and Assumptions --- p.74Chapter 4.4 --- Basics of the LMB Scheme --- p.75Chapter 4.4.1 --- Restoration Concepts --- p.75Chapter 4.4.2 --- Terminology --- p.76Chapter 4.4.3 --- Algorithm Parameters --- p.77Chapter 4.5 --- Performance Assessments --- p.78Chapter 4.6 --- The LMB Network Restoration Scheme --- p.80Chapter 4.6.1 --- Initialization - Local Map Building --- p.80Chapter 4.6.2 --- The LMB Restoration Messages Set --- p.81Chapter 4.6.3 --- Phase I - Local Map Update Phase --- p.81Chapter 4.6.4 --- Phase II - Update Acknowledgment Phase --- p.82Chapter 4.6.5 --- Phase III - Restoration and Confirmation Phase --- p.83Chapter 4.6.6 --- Phase IV - Cancellation Phase --- p.83Chapter 4.6.7 --- Re-Initialization --- p.84Chapter 4.6.8 --- Path Route Monitoring --- p.84Chapter 4.7 --- Performance Evaluation --- p.84Chapter 4.7.1 --- The Testbeds --- p.84Chapter 4.7.2 --- Simulation Results --- p.86Chapter 4.7.3 --- Storage Requirements --- p.89Chapter 4.8 --- The LMB Scheme on ATM and SONET environment --- p.92Chapter 4.9 --- Future Work --- p.94Chapter 4.10 --- Chapter Summary --- p.94Chapter 5 --- Conclusion and Future Work --- p.96Chapter 5.1 --- Conclusion --- p.95Chapter 5.2 --- Future Work --- p.99Bibliography --- p.101Chapter A --- Derivation of Communicative Probability --- p.107Chapter B --- List of Publications --- p.11

Survivable network design with stepwise incremental cost function

Modern society has become more and more dependent on information services, transferred in both public and private network, than ever before. The use of integration of computers with telecommunications has created a so-called “Information Age”. The advent of high capacity digital telecommunication facilities has made it possible for the huge amount of traffic to be carried in an economical and efficient method, in recent years. These facilities, which are used to carry much higher capacities than the traditional ones, also result in the network’s vulnerability to the failure of network facilities, i.e. a single link failure. This thesis is concerned with the technology by which the spare capacity on the link of mesh networks is placed in order to protect the active traffic from network failure with a minimal cost. Although there have been many works to address the issue all of these works have been developed based on the assumption that the link cost with its capacity is linear. In fact, the linear cost functions does not reflect the reality that optic fiber cables with the specific amount of capacities are only available, in other words, the link cost function is stepwise rather than linear. Therefore, all existing algorithms developed for the linear assumption may not be applicable properly for the stepwise case. A novel heuristic algorithm is proposed to solve the problem in this thesis. The algorithm is composed of two parts as follows. In part one, a maximum flow algorithm is employed to work out the maximal amount of feasible spare paths consisting of spare capacities in the network to re-route the disrupted traffic at the event of network failure. In part two, a newly proposed algorithm is used to find an alternative path on which to place the non-rerouted traffic on the failed link with the minimum network cost increment. The superiority of the algorithm is presented over other algorithms published in this area

Single-Layer versus Multilayer Preplanned Lightpath Restoration

Special Issue on ”Optical Networks” October 200