2,835 research outputs found
Network Virtualization Over Elastic Optical Networks: A Survey of Allocation Algorithms
Network virtualization has emerged as a paradigm for cloud computing services by providing key functionalities such as abstraction of network resources kept hidden to the cloud service user, isolation of different cloud computing applications, flexibility in terms of resources granularity, and onâdemand setup/teardown of service. In parallel, flexâgrid (also known as elastic) optical networks have become an alternative to deal with the constant traffic growth. These advances have triggered research on network virtualization over flexâgrid optical networks. Effort has been focused on the design of flexible and virtualized devices, on the definition of network architectures and on virtual network allocation algorithms. In this chapter, a survey on the virtual network allocation algorithms over flexibleâgrid networks is presented. Proposals are classified according to a taxonomy made of three main categories: performance metrics, operation conditions and the type of service offered to users. Based on such classification, this work also identifies open research areas as multiâobjective optimization approaches, distributed architectures, metaâheuristics, reconfiguration and protection mechanisms for virtual networks over elastic optical networks
Network-provider-independent overlays for resilience and quality of service.
PhDOverlay networks are viewed as one of the solutions addressing the inefficiency and slow
evolution of the Internet and have been the subject of significant research. Most existing
overlays providing resilience and/or Quality of Service (QoS) need cooperation among
different network providers, but an inter-trust issue arises and cannot be easily solved.
In this thesis, we mainly focus on network-provider-independent overlays and investigate
their performance in providing two different types of service. Specifically, this thesis
addresses the following problems:
Provider-independent overlay architecture: A provider-independent overlay
framework named Resilient Overlay for Mission-Critical Applications (ROMCA)
is proposed. We elaborate its structure including component composition and
functions and also provide several operational examples.
Overlay topology construction for providing resilience service: We investigate the topology design problem of provider-independent overlays aiming to provide resilience service. To be more specific, based on the ROMCA framework, we
formulate this problem mathematically and prove its NP-hardness. Three heuristics are proposed and extensive simulations are carried out to verify their effectiveness.
Application mapping with resilience and QoS guarantees: Assuming application mapping is the targeted service for ROMCA, we formulate this problem as
an Integer Linear Program (ILP). Moreover, a simple but effective heuristic is
proposed to address this issue in a time-efficient manner. Simulations with both
synthetic and real networks prove the superiority of both solutions over existing
ones.
Substrate topology information availability and the impact of its accuracy on overlay performance: Based on our survey that summarizes the methodologies available for inferring the selective substrate topology formed among a group
of nodes through active probing, we find that such information is usually inaccurate
and additional mechanisms are needed to secure a better inferred topology. Therefore, we examine the impact of inferred substrate topology accuracy on overlay
performance given only inferred substrate topology information
A Survey on the Path Computation Element (PCE) Architecture
Quality of Service-enabled applications and services rely on Traffic Engineering-based (TE) Label Switched Paths (LSP) established in core networks and controlled by the GMPLS control plane. Path computation process is crucial to achieve the desired TE objective. Its actual effectiveness depends on a number of factors. Mechanisms utilized to update topology and TE information, as well as the latency between path computation and resource reservation, which is typically distributed, may affect path computation efficiency. Moreover, TE visibility is limited in many network scenarios, such as multi-layer, multi-domain and multi-carrier networks, and it may negatively impact resource utilization. The Internet Engineering Task Force (IETF) has promoted the Path Computation Element (PCE) architecture, proposing a dedicated network entity devoted to path computation process. The PCE represents a flexible instrument to overcome visibility and distributed provisioning inefficiencies. Communications between path computation clients (PCC) and PCEs, realized through the PCE Protocol (PCEP), also enable inter-PCE communications offering an attractive way to perform TE-based path computation among cooperating PCEs in multi-layer/domain scenarios, while preserving scalability and confidentiality. This survey presents the state-of-the-art on the PCE architecture for GMPLS-controlled networks carried out by research and standardization community. In this work, packet (i.e., MPLS-TE and MPLS-TP) and wavelength/spectrum (i.e., WSON and SSON) switching capabilities are the considered technological platforms, in which the PCE is shown to achieve a number of evident benefits
Domain/Multi-Domain Protection and Provisioning in Optical Networks
LâĂ©volution rĂ©cente des commutateurs de sĂ©lection de longueurs dâonde (WSS -Wavelength Selective Switch) favorise le dĂ©veloppement du multiplexeur optique dâinsertionextraction reconfigurable (ROADM - Reconfigurable Optical Add/Drop Multiplexers) Ă plusieurs degrĂ©s sans orientation ni coloration, considĂ©rĂ© comme un Ă©quipement fort prometteur pour les rĂ©seaux maillĂ©s du futur relativement au multiplexage en longueur dâonde (WDM -Wavelength Division Multiplexing ). Cependant, leur propriĂ©tĂ© de commutation asymĂ©trique complique la question de lâacheminement et de lâattribution des longueur dâondes (RWA - Routing andWavelength Assignment). Or la plupart des algorithmes de RWA existants ne tiennent pas compte de cette propriĂ©tĂ© dâasymĂ©trie.
Lâinterruption des services causĂ©e par des dĂ©fauts dâĂ©quipements sur les chemins
optiques (résultat provenant de la résolution du problÚme RWA) a pour conséquence la
perte dâune grande quantitĂ© de donnĂ©es. Les recherches deviennent ainsi incontournables afin dâassurer la survie fonctionnelle des rĂ©seaux optiques, Ă savoir, le maintien des services, en particulier en cas de pannes dâĂ©quipement. La plupart des publications antĂ©rieures portaient particuliĂšrement sur lâutilisation dâun systĂšme de protection permettant de garantir le reroutage du trafic en cas dâun dĂ©faut dâun lien. Cependant, la conception de la protection contre le dĂ©faut dâun lien ne sâavĂšre pas toujours suffisante en termes de survie des rĂ©seaux WDM Ă partir de nombreux cas des autres types de pannes devenant courant de nos jours, tels que les bris dâĂ©quipements, les pannes de deux ou trois liens, etc. En outre, il y a des dĂ©fis considĂ©rables pour protĂ©ger les grands rĂ©seaux optiques multidomaines composĂ©s de rĂ©seaux associĂ©s Ă un domaine simple, interconnectĂ©s par des liens interdomaines, oĂč les dĂ©tails topologiques internes dâun domaine ne sont gĂ©nĂ©ralement pas partagĂ©s Ă lâextĂ©rieur.
La prĂ©sente thĂšse a pour objectif de proposer des modĂšles dâoptimisation de grande
taille et des solutions aux problĂšmes mentionnĂ©s ci-dessus. Ces modĂšles-ci permettent de gĂ©nĂ©rer des solutions optimales ou quasi-optimales avec des Ă©carts dâoptimalitĂ© mathĂ©matiquement prouvĂ©e. Pour ce faire, nous avons recours Ă la technique de gĂ©nĂ©ration de colonnes afin de rĂ©soudre les problĂšmes inhĂ©rents Ă la programmation linĂ©aire de
grande envergure.
Concernant la question de lâapprovisionnement dans les rĂ©seaux optiques, nous proposons
un nouveau modÚle de programmation linéaire en nombres entiers (ILP - Integer
Linear Programming) au problĂšme RWA afin de maximiser le nombre de requĂȘtes acceptĂ©es
(GoS - Grade of Service). Le modĂšle rĂ©sultant constitue celui de lâoptimisation
dâun ILP de grande taille, ce qui permet dâobtenir la solution exacte des instances RWA
assez grandes, en supposant que tous les noeuds soient asymétriques et accompagnés
dâune matrice de connectivitĂ© de commutation donnĂ©e. Ensuite, nous modifions le modĂšle
et proposons une solution au problĂšme RWA afin de trouver la meilleure matrice de
commutation pour un nombre donné de ports et de connexions de commutation, tout en
satisfaisant/maximisant la qualitĂ© dâĂ©coulement du trafic GoS.
Relativement Ă la protection des rĂ©seaux dâun domaine simple, nous proposons des
solutions favorisant la protection contre les pannes multiples. En effet, nous développons
la protection dâun rĂ©seau dâun domaine simple contre des pannes multiples, en utilisant
les p-cycles de protection avec un chemin indépendant des pannes (FIPP - Failure Independent
Path Protecting) et de la protection avec un chemin dépendant des pannes
(FDPP - Failure Dependent Path-Protecting). Nous proposons ensuite une nouvelle formulation
en termes de modĂšles de flots pour les p-cycles FDPP soumis Ă des pannes
multiples. Le nouveau modĂšle soulĂšve un problĂšme de taille, qui a un nombre exponentiel
de contraintes en raison de certaines contraintes dâĂ©limination de sous-tour. Par
conséquent, afin de résoudre efficacement ce problÚme, on examine : (i) une décomposition
hiérarchique du problÚme auxiliaire dans le modÚle de décomposition, (ii) des
heuristiques pour gérer efficacement le grand nombre de contraintes.
à propos de la protection dans les réseaux multidomaines, nous proposons des systÚmes
de protection contre les pannes dâun lien. Tout dâabord, un modĂšle dâoptimisation
est proposé pour un systÚme de protection centralisée, en supposant que la gestion du
réseau soit au courant de tous les détails des topologies physiques des domaines. Nous
proposons ensuite un modĂšle distribuĂ© de lâoptimisation de la protection dans les rĂ©seaux
optiques multidomaines, une formulation beaucoup plus réaliste car elle est basée
sur lâhypothĂšse dâune gestion de rĂ©seau distribuĂ©. Ensuite, nous ajoutons une bande pasiv
sante partagée afin de réduire le coût de la protection. Plus précisément, la bande passante
de chaque lien intra-domaine est partagée entre les p-cycles FIPP et les p-cycles
dans une premiĂšre Ă©tude, puis entre les chemins pour lien/chemin de protection dans une
deuxiÚme étude. Enfin, nous recommandons des stratégies parallÚles aux solutions de
grands réseaux optiques multidomaines.
Les rĂ©sultats de lâĂ©tude permettent dâĂ©laborer une conception efficace dâun systĂšme
de protection pour un trÚs large réseau multidomaine (45 domaines), le plus large examiné
dans la littérature, avec un systÚme à la fois centralisé et distribué.Recent developments in the wavelength selective switch (WSS) technology enable
multi-degree reconfigurable optical add/drop multiplexers (ROADM) architectures with
colorless and directionless switching, which is regarded as a very promising enabler for
future reconfigurable wavelength division multiplexing (WDM) mesh networks. However,
its asymmetric switching property complicates the optimal routing and wavelength
assignment (RWA) problem, which is NP-hard. Most of the existing RWA algorithms
do not consider such property.
Disruption of services through equipment failures on the lightpaths (output of RWA
problem) is consequential as it involves the lost of large amounts of data. Therefore,
substantial research efforts are needed to ensure the functional survivability of optical
networks, i.e., the continuation of services even when equipment failures occur. Most
previous publications have focused on using a protection scheme to guarantee the traffic
connections in the event of single link failures. However, protection design against single
link failures turns out not to be always sufficient to keep the WDM networks away from
many downtime cases as other kinds of failures, such as node failures, dual link failures,
triple link failures, etc., become common nowadays. Furthermore, there are challenges
to protect large multi-domain optical networks which are composed of several singledomain
networks, interconnected by inter-domain links, where the internal topological
details of a domain are usually not shared externally.
The objective of this thesis is to propose scalable models and solution methods for
the above problems. The models enable to approach large problem instances while producing
optimal or near optimal solutions with mathematically proven optimality gaps.
For this, we rely on the column generation technique which is suitable to solve large
scale linear programming problems.
For the provisioning problem in optical networks, we propose a new ILP (Integer
Linear Programming) model for RWA problem with the objective of maximizing the
Grade of Service (GoS). The resulting model is a large scale optimization ILP model,
which allows the exact solution of quite large RWA instances, assuming all nodes are
asymmetric and with a given switching connectivity matrix. Next, we modify the model
and propose a solution for the RWA problem with the objective of finding the best switching
connectivity matrix for a given number of ports and a given number of switching
connections, while satisfying/maximizing the GoS.
For protection in single domain networks, we propose solutions for the protection
against multiple failures. Indeed, we extent the protection of a single domain network
against multiple failures, using FIPP and FDPP p-cycles. We propose a new generic
flow formulation for FDPP p-cycles subject to multiple failures. Our new model ends
up with a complex pricing problem, which has an exponential number of constraints due
to some subtour elimination constraints. Consequently, in order to efficiently solve the
pricing problem, we consider: (i) a hierarchical decomposition of the original pricing
problem; (ii) heuristics in order to go around the large number of constraints in the
pricing problem.
For protection in multi-domain networks, we propose protection schemes against
single link failures. Firstly, we propose an optimization model for a centralized protection
scheme, assuming that the network management is aware of all the details of the
physical topologies of the domains. We then propose a distributed optimization model
for protection in multi-domain optical networks, a much more realistic formulation as it
is based on the assumption of a distributed network management. Then, we add bandwidth
sharing in order to reduce the cost of protection. Bandwidth of each intra-domain
link is shared among FIPP p-cycles and p-cycles in a first study, and then among paths
for link/path protection in a second study. Finally, we propose parallel strategies in order
to obtain solutions for very large multi-domain optical networks.
The result of this last study allows the efficent design of a protection scheme for a
very large multi-domain network (45 domains), the largest one by far considered in the
literature, both with a centralized and distributed scheme
SoftwareâDefined Optical Networking (SDON): Principles and Applications
Featured by the advantages of high capacity, long transmission distance, and low energy consumption, optical network has been deployed widely as the most important infrastructure for backbone transport network. With the development of Internet, datacenter has become the popular infrastructure for cloud computing, which needs to be connected with high bitrate transport network to support heterogeneous applications. In this case, optical network also becomes a promising option for intra and interâdatacenter networking. In the networking field, softwareâdefined networking (SDN) has gained a lot of attention from both academic and industry, and it aims to provide a flexible and programmable control plane. SDN is applicable to optical network, and the optical network integrated with SDN, namely softwareâdefined optical network (SDON), are expected as the future transport solutions, which can provide both high bitrate connectivity and flexible network applications. The principles and applications of SDON are introduced in this chapter
Progressive introduction of network softwarization in operational telecom networks: advances at architectural, service and transport levels
Technological paradigms such as Software Defined Networking, Network Function
Virtualization and Network Slicing are altogether offering new ways of providing services.
This process is widely known as Network Softwarization, where traditional operational
networks adopt capabilities and mechanisms inherit form the computing world, such as
programmability, virtualization and multi-tenancy.
This adoption brings a number of challenges, both from the technological and operational
perspectives. On the other hand, they provide an unprecedented flexibility opening
opportunities to developing new services and new ways of exploiting and consuming telecom
networks.
This Thesis first overviews the implications of the progressive introduction of network
softwarization in operational networks for later on detail some advances at different levels,
namely architectural, service and transport levels. It is done through specific exemplary use
cases and evolution scenarios, with the goal of illustrating both new possibilities and existing
gaps for the ongoing transition towards an advanced future mode of operation.
This is performed from the perspective of a telecom operator, paying special attention on
how to integrate all these paradigms into operational networks for assisting on their evolution
targeting new, more sophisticated service demands.Programa de Doctorado en IngenierĂa TelemĂĄtica por la Universidad Carlos III de MadridPresidente: Eduardo Juan Jacob Taquet.- Secretario: Francisco Valera Pintor.- Vocal: Jorge LĂłpez VizcaĂn
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