21 research outputs found
Study, evaluation and contributions to new algorithms for the embedding problem in a network virtualization environment
Network virtualization is recognized as an enabling technology for the future Internet. It aims to overcome the resistance of the current Internet to architectural change and to enable a new business model decoupling the network services from the underlying infrastructure. The problem of embedding virtual networks in a substrate network is the main resource allocation challenge in network virtualization and is usually referred to as the Virtual Network Embedding (VNE) problem. VNE deals with the allocation of virtual resources both in nodes and links. Therefore, it can be divided into two sub-problems:
Virtual Node Mapping where virtual nodes have to be allocated in physical nodes and Virtual Link Mapping where virtual links connecting these virtual nodes have to be mapped to paths connecting the corresponding nodes in the substrate network. Application of network virtualization relies on algorithms that can instantiate virtualized networks on a substrate infrastructure, optimizing the layout for service-relevant metrics. This class of algorithms is commonly known as VNE algorithms. This thesis proposes a set of contributions to solve the research challenges of the VNE that have not been tackled by the research community. To do that, it performs a deep and comprehensive survey of virtual network embedding. The first research challenge identified is the lack of proposals to solve the virtual link mapping stage of VNE using single path in the physical network. As this problem is NP-hard, existing proposals solve it using well known shortest path algorithms that limit the mapping considering just one constraint. This thesis proposes the use of a mathematical multi-constraint routing framework called paths algebra to solve the virtual link mapping stage. Besides, the thesis introduces a new demand caused by virtual link demands into physical nodes acting as intermediate (hidden) hops in a path of the physical network. Most of the current VNE approaches are centralized. They suffer of scalability issues and provide a single point of failure. In addition, they are not able to embed virtual network requests arriving at the same time in parallel. To solve this challenge, this thesis proposes a distributed, parallel and universal virtual network embedding framework. The proposed framework can be used to run any existing embedding algorithm in a distributed way. Thereby, computational
load for embedding multiple virtual networks is spread across the substrate network Energy efficiency is one of the main challenges in future networking
environments. Network virtualization can be used to tackle this problem by sharing hardware, instead of requiring dedicated hardware for each instance. Until now, VNE algorithms do not consider energy as a factor for the mapping. This thesis introduces the energy aware VNE where the main objective is to switch off as many network nodes and interfaces as possible by allocating the virtual demands to a consolidated subset of active physical networking equipment. To evaluate and validate the aforementioned VNE proposals, this thesis helped in the development of a software framework called ALgorithms for Embedding VIrtual Networks (ALEVIN). ALEVIN allows to easily implement, evaluate and compare different VNE algorithms according to a set of metrics, which evaluate the algorithms and compute their results on a given scenario for arbitrary parameters
Software-Defined Networking: A Comprehensive Survey
peer reviewedThe Internet has led to the creation of a digital society, where (almost) everything is connected and is accessible from anywhere. However, despite their widespread adoption, traditional IP networks are complex and very hard to manage. It is both difficult to configure the network according to predefined policies, and to reconfigure it to respond to faults, load, and changes. To make matters even more difficult, current networks are also vertically integrated: the control and data planes are bundled together. Software-defined networking (SDN) is an emerging paradigm that promises to change this state of affairs, by breaking vertical integration, separating the network's control logic from the underlying routers and switches, promoting (logical) centralization of network control, and introducing the ability to program the network. The separation of concerns, introduced between the definition of network policies, their implementation in switching hardware, and the forwarding of traffic, is key to the desired flexibility: by breaking the network control problem into tractable pieces, SDN makes it easier to create and introduce new abstractions in networking, simplifying network management and facilitating network evolution. In this paper, we present a comprehensive survey on SDN. We start by introducing the motivation for SDN, explain its main concepts and how it differs from traditional networking, its roots, and the standardization activities regarding this novel paradigm. Next, we present the key building blocks of an SDN infrastructure using a bottom-up, layered approach. We provide an in-depth analysis of the hardware infrastructure, southbound and northbound application programming interfaces (APIs), network virtualization layers, network operating systems (SDN controllers), network programming languages, and network applications. We also look at cross-layer problems such as debugging and troubleshooting. In an effort to anticipate the future evolution of this - ew paradigm, we discuss the main ongoing research efforts and challenges of SDN. In particular, we address the design of switches and control platforms—with a focus on aspects such as resiliency, scalability, performance, security, and dependability—as well as new opportunities for carrier transport networks and cloud providers. Last but not least, we analyze the position of SDN as a key enabler of a software-defined environment
Dynamic Virtual Network Restoration with Optimal Standby Virtual Router Selection
Title form PDF of title page, viewed on September 4, 2015Dissertation advisor: Deep MedhiVitaIncludes bibliographic references (pages 141-157)Thesis (Ph.D.)--School of Computing and Engineering and Department of Mathematics and Statistics. University of Missouri--Kansas City, 2015Network virtualization technologies allow service providers to request partitioned,
QoS guaranteed and fault-tolerant virtual networks provisioned by the substrate network
provider (i.e., physical infrastructure provider). A virtualized networking environment
(VNE) has common features such as partition, flexibility, etc., but fault-tolerance requires
additional efforts to provide survivability against failures on either virtual networks or the
substrate network.
Two common survivability paradigms are protection (proactive) and restoration
(reactive). In the protection scheme, the substrate network provider (SNP) allocates redundant
resources (e.g., nodes, paths, bandwidths, etc) to protect against potential failures
in the VNE. In the restoration scheme, the SNP dynamically allocates resources to restore
the networks, and it usually occurs after the failure is detected.
In this dissertation, we design a restoration scheme that can be dynamically implemented
in a centralized manner by an SNP to achieve survivability against node failures
in the VNE. The proposed restoration scheme is designed to be integrated with a protection
scheme, where the SNP allocates spare virtual routers (VRs) as standbys for the
virtual networks (VN) and they are ready to serve in the restoration scheme after a node
failure has been identified. These standby virtual routers (S-VR) are reserved as a sharedbackup
for any single node failure, and during the restoration procedure, one of the S-VR
will be selected to replace the failed VR. In this work, we present an optimal S-VR selection
approach to simultaneously restore multiple VNs affected by failed VRs, where
these VRs may be affected by failures within themselves or at their substrate host (i.e.,
power outage, hardware failures, maintenance, etc.). Furthermore, the restoration scheme
is embedded into a dynamic reconfiguration scheme (DRS), so that the affected VNs can
be dynamically restored by a centralized virtual network manager (VNM).
We first introduce a dynamic reconfiguration scheme (DRS) against node failures
in a VNE, and then present an experimental study by implementing this DRS over a
realistic VNE using GpENI testbed. For this experimental study, we ran the DRS to
restore one VN with a single-VR failure, and the results showed that with a proper S-VR
selection, the performance of the affected VN could be well restored. Next, we proposed
an Mixed-Integer Linear Programming (MILP) model with dual–goals to optimally select
S-VRs to restore all VNs affected by VR failures while load balancing. We also present a
heuristic algorithm based on the model. By considering a number of factors, we present
numerical studies to show how the optimal selection is affected. The results show that
the proposed heuristic’s performance is close to the optimization model when there were
sufficient standby virtual routers for each virtual network and the substrate nodes have
the capability to support multiple standby virtual routers to be in service simultaneously.
Finally, we present the design of a software-defined resilient VNE with the optimal S-VR
selection model, and discuss a prototype implementation on the GENI testbed.Introduction -- Literature survey -- Dynamic reconfiguration scheme in a VNE -- An experimental study on GpENI-VNI -- Optimal standby virtual router selection model -- Prototype design and implementation on GENI -- Conclusion and future work -- Appendix A. Resource Specification (RSpec) in GENI -- Appendix B. Optimal S-VR Selection Model in AMP
Network virtualisation from an operator perspective
Doutoramento em Engenharia EletrotécnicaNetwork virtualisation is seen as a promising approach to overcome the so-called
“Internet impasse” and bring innovation back into the Internet, by allowing easier
migration towards novel networking approaches as well as the coexistence of complementary
network architectures on a shared infrastructure in a commercial context.
Recently, the interest from the operators and mainstream industry in network
virtualisation has grown quite significantly, as the potential benefits of virtualisation
became clearer, both from an economical and an operational point of view. In the
beginning, the concept has been mainly a research topic and has been materialized
in small-scale testbeds and research network environments. This PhD Thesis aims
to provide the network operator with a set of mechanisms and algorithms capable
of managing and controlling virtual networks. To this end, we propose a framework
that aims to allocate, monitor and control virtual resources in a centralized and
efficient manner. In order to analyse the performance of the framework, we performed
the implementation and evaluation on a small-scale testbed. To enable the
operator to make an efficient allocation, in real-time, and on-demand, of virtual
networks onto the substrate network, it is proposed a heuristic algorithm to perform
the virtual network mapping. For the network operator to obtain the highest
profit of the physical network, it is also proposed a mathematical formulation that
aims to maximize the number of allocated virtual networks onto the physical network.
Since the power consumption of the physical network is very significant in
the operating costs, it is important to make the allocation of virtual networks in
fewer physical resources and onto physical resources already active. To address
this challenge, we propose a mathematical formulation that aims to minimize the
energy consumption of the physical network without affecting the efficiency of the
allocation of virtual networks. To minimize fragmentation of the physical network
while increasing the revenue of the operator, it is extended the initial formulation
to contemplate the re-optimization of previously mapped virtual networks, so that
the operator has a better use of its physical infrastructure. It is also necessary to
address the migration of virtual networks, either for reasons of load balancing or
for reasons of imminent failure of physical resources, without affecting the proper
functioning of the virtual network. To this end, we propose a method based on
cloning techniques to perform the migration of virtual networks across the physical
infrastructure, transparently, and without affecting the virtual network. In order to
assess the resilience of virtual networks to physical network failures, while obtaining
the optimal solution for the migration of virtual networks in case of imminent
failure of physical resources, the mathematical formulation is extended to minimize
the number of nodes migrated and the relocation of virtual links. In comparison
with our optimization proposals, we found out that existing heuristics for mapping
virtual networks have a poor performance. We also found that it is possible to
minimize the energy consumption without penalizing the efficient allocation. By
applying the re-optimization on the virtual networks, it has been shown that it
is possible to obtain more free resources as well as having the physical resources
better balanced. Finally, it was shown that virtual networks are quite resilient to
failures on the physical network.A virtualização de rede é vista como uma abordagem promissora para ultrapassar
o “Impasse da Internet” e permitir inovação na Internet, possibilitando assim
uma migração fácil para novas abordagens de redes, bem como a coexistência
de arquiteturas de redes complementares numa infraestrutura compartilhada e em
ambiente comercial. Recentemente tem crescido de forma bastante significativa o
interesse pela virtualização de rede por parte dos operadores e dos grandes fabricantes,
desde que os potenciais benefícios da virtualização se tornaram claros, tanto
de ponto de vista económico como operacional. No início, o conceito foi versado
pelo meio académico, onde foram realizadas provas de conceito de pequena escala,
e em que a virtualização de rede foi considerada como forma de investigação de
novos protocolos. Esta Tese de Doutoramento tem como objetivo geral dotar uma
rede de operador de um conjunto de mecanismos e algoritmos capazes de gerir e
controlar redes virtuais. Para este fim, é proposta uma framework que visa alocar,
monitorizar e controlar recursos virtuais de uma forma centralizada e eficiente. De
forma a analisar o desempenho da framework, procedeu-se à sua implementação
e avaliação numa rede de pequena dimensão. De forma a permitir que se possa
efetuar uma alocação eficiente, em tempo real, e a pedido, de redes virtuais numa
rede física, é proposta uma heurística para efetuar o mapeamento na rede física.
Para que o operador de rede possa rentabilizar ao máximo a sua infraestrutura de
rede, é ainda proposta uma formulação matemática que, através de programação
linear, visa maximizar o número de redes alocadas na infraestrutura de rede. Dado
que o consumo energético de uma infraestrutura de rede começa a ter significância
nos custos de operação, é importante que se faça a alocação das redes virtuais
no menor número de recursos físicos e também em recursos físicos ativos. Para
endereçar este desafio é proposta uma formulação matemática que visa minimizar o
consumo energético da rede física sem afetar a eficiência da alocação de redes virtuais.
Para minimizar a fragmentação da infraestrutura de rede e ao mesmo tempo
aumentar as receitas do operador, é também estendida a formulação inicial para
contemplar a re-otimização de redes virtuais previamente mapeadas, fazendo com
que o operador tenha um melhor aproveitamento da sua infraestrutura física. Será
ainda necessário endereçar a migração de redes virtuais, quer por motivos de balanceamento
de carga, quer por motivos de falha iminente de recursos físicos, sem
afetar o bom funcionamento da rede virtual. Para este fim, é proposto um método
baseado em técnicas de clonagem, para efetuar a migração de redes virtuais entre
recursos da infraestrutura física de forma transparente e sem impacto para a rede
virtual. De forma a avaliar a resiliência das redes virtuais a falhas na rede física,
e ao mesmo tempo obter a solução ótima de migração de redes virtuais em caso
de falha iminente dos recursos físicos, a formulação matemática é estendida para
minimizar o número de nós migrados em simultâneo com a realocação de ligações
virtuais. Em comparação com as nossas propostas de otimização verificou-se que
as heurísticas existentes para mapeamento de redes virtuais têm um desempenho
muito baixo. Verificou-se ainda que é possível efetuar a redução do consumo energético
sem a penalização da alocação eficiente. Com a re-otimização das redes
virtuais mostrou-se que é possível obter mais recursos livres, assim como obter
uma melhor distribuição dos recursos. Por último, demonstrou-se que as redes
virtuais são bastante resilientes a falhas na rede física
Implementation of New Multiple Access Technique Encoder for 5G Wireless Telecomunication Networks
RÉSUMÉ Les exigences de la connectivité mobile massive de différents appareils et de diverses applications déterminent les besoins des prochaines générations de technologies mobiles (5G) afin de surmonter les demandes futures. L'expansion significative de la connectivité et de la densité du trafic caractérisent les besoins de la cinquième génération de réseaux mobiles. Par conséquent, pour la 5G, il est nécessaire d'avoir une densité de connectivité beaucoup plus élevée et une plus grande
portée de mobilité, un débit beaucoup plus élevé et une latence beaucoup plus faible. En raison de l'exigence d'une connectivité massive, de nombreuses nouvelles technologies
doivent être améliorées: le codage des canaux, la technique d'accès multiple, la modulation et la diversité, etc. Par conséquent, compte tenu de l'environnement 5G, surcoût de signalisation et de la latence devrait être pris en compte [1]. En outre, l'application de la virtualisation des accès sans fil (WAV) devrait également être considérée et, par conséquent, il est également nécessaire de concevoir la plate-forme matérielle prenant en charge les nouvelles normes pour la mise en œuvre des émetteurs-récepteurs virtuels. L'une des nouvelles technologies possibles pour la 5G est l'accès multiple pour améliorer
le débit. Par conséquent, au lieu d'OFDMA utilisé dans la norme LTE (4G), l'application d'une nouvelle technique d'accès multiple appelée Sparse Code Multiple Access (SCMA) est investiguée dans cette dissertation. SCMA est une nouvelle technique d'accès multiple non orthogonale du
domaine fréquentiel proposée pour améliorer l'efficacité spectrale de l'accès radio sans fil [2]. L'encodage SCMA est l'un des algorithmes les plus simples dans les techniques d'accès multiple qui offre l'opportunité d'expérimenter des méthodes génériques de mise en oeuvre. En outre, la nouvelle méthode d'accès multiple est supposée fournir un débit plus élevé. Le choix du codage
SCMA avec moins de complexité pourrait être une approche appropriée. La cible fixée pour cette recherche était d'atteindre un débit d’encodage de plus de 1 Gbps pour le codeur SCMA. Les implémentations de codage SCMA ont été effectuées à la fois en logiciel et en matériel
pour permettre de les comparer. Les implémentations logicielles ont été développées avec le langage de programmation C. Parmi plusieurs conceptions, la performance a été améliorée en utilisant différentes méthodes pour augmenter le parallélisme, diminuer la complexité de calcul et par conséquent le temps de traitement.----------ABSTRACT The demands of massive mobile connectivity of different devices and diverse applications
at the same time set requirments for next generations of mobile technology (5G). The significant expansion of connectivity and traffic density characterize the requirements of fifth generation mobile. Therefore, in 5G, there is a need to have much higher connectivity density, higher mobility ranges, much higher throughput, and much lower latency. In pursuance of the requirement of massive connectivity, numerous technologies must be
improved: channel coding, multiple access technique, modulation and diversity, etc. For instance,
with 5G, the cost of signaling overhead and latency should be taken into account [1]. Besides, applying wireless access virtualization (WAV) should be considered and there is also a need to have effective implementations supporting novel virtual transceiver. One of the possible new technologies for 5G is exploiting multiple access techniques to improve throughput. Therefore, instead of OFDMA in LTE (4G), applying a new multiple access
technique called Sparse Code Multiple Access (SCMA) is an approach considered in this dissertation. SCMA is a new frequency domain non-orthogonal multiple access technique proposed to improve spectral efficiency of wireless radio access [2]. SCMA encoding is one of the simplest
multiple access technique that offers an opportunity to experiment generic implementation methods. In addition, the new multiple access method is supposed to provide higher throughput, thus choosing SCMA encoding with less complexity could be an appropriate approach. The target
with SCMA was to achieve an encoding throughput of more that 1Gbps. SCMA encoding implementations were done both in software and hardware to allow comparing them. The software implementations were developed with the C programing language. Among several designs, the performance was improved by using different methods to increase
parallelism, decrease the computational complexity and consequently the processing time. The best achieved results with software implementations offer a 3.59 Gbps throughput, which is 3.5 times more that the target. For hardware implementation, high level synthesis was experimented. In order to do that, the C based functions and testbenches which were developed for software implementations, were
used as inputs to Vivado HLS
Interoperabilidade e mobilidade na internet do futuro
Research on Future Internet has been gaining traction in recent years,
with both evolutionary (e.g., Software Defined Networking (SDN)-
based architectures) and clean-slate network architectures (e.g., Information
Centric Networking (ICN) architectures) being proposed. With
each network architectural proposal aiming to provide better solutions
for specific Internet utilization requirements, an heterogeneous Future
Internet composed by several architectures can be expected, each targeting
and optimizing different use case scenarios. Moreover, the increasing
number of mobile devices, with increasing capabilities and
supporting different connectivity technologies, are changing the patterns
of traffic exchanged in the Internet.
As such, this thesis focuses on the study of interoperability and mobility
in Future Internet architectures, two key requirements that need to be
addressed for the widely adoption of these network architectures. The
first contribution of this thesis is an interoperability framework that,
by enabling resources to be shared among different network architectures,
avoids resources to be restricted to a given network architecture
and, at the same time, promotes the initial roll out of new network
architectures. The second contribution of this thesis consists on the
development of enhancements for SDN-based and ICN network architectures
through IEEE 802.21 mechanisms to facilitate and optimize
the handover procedures on those architectures. The last contribution
of this thesis is the definition of an inter-network architecture mobility
framework that enables MNs to move across access network supporting
different network architectures without losing the reachability to
resources being accessed. All the proposed solutions were evaluated
with results highlighting the feasibility of such solutions and the impact
on the overall communication.A Internet do Futuro tem sido alvo de vários estudos nos últimos anos,
com a proposta de arquitecturas de rede seguindo quer abordagens
evolutionárias (por exemplo, Redes Definidas por Software (SDN))
quer abordagens disruptivas (por exemplo, Redes Centradas na Informação (ICN)). Cada uma destas arquitecturas de rede visa providenciar
melhores soluções relativamente a determinados requisitos de
utilização da Internet e, portanto, uma Internet do Futuro heterogénea
composta por diversas arquitecturas de rede torna-se uma possibilidade,
onde cada uma delas é usada para optimizar diferentes casos
de utilização. Para além disso, o aumento do número de dispositivos
móveis, com especificações acrescidas e com suporte para diferentes
tecnologias de conectividade, está a mudar os padrões do tráfego na
Internet.
Assim, esta tese foca-se no estudo de aspectos de interoperabilidade e
mobilidade em arquitecturas de rede da Internet do Futuro, dois importantes
requisitos que necessitam de ser satisfeitos para que a adopção
destas arquitecturas de rede seja considerada. A primeira contribuição
desta tese é uma solução de interoperabilidade que, uma vez que permite
que recursos possam ser partilhados por diferentes arquitecturas
de rede, evita que os recursos estejam restringidos a uma determinada
arquitectura de rede e, ao mesmo tempo, promove a adopção de novas
arquitecturas de rede. A segunda contribuição desta tese consiste
no desenvolvimento de extensões para arquitecturas de rede baseadas
em SDN ou ICN através dos mecanismos propostos na norma IEEE
802.21 com o objectivo de facilitar e optimizar os processos de mobilidade
nessas arquitecturas de rede. Finalmente, a terceira contribuição
desta tese é a definição de uma solução de mobilidade envolvendo diferentes
arquitecturas de rede que permite a mobilidade de dispositivos
móveis entre redes de acesso que suportam diferentes arquitecturas de
rede sem que estes percam o acesso aos recursos que estão a ser acedidos.
Todas as soluções propostas foram avaliadas com os resultados
a demonstrar a viabilidade de cada uma das soluções e o impacto que
têm na comunicação.Programa Doutoral em Informátic
Improving the performance of software-defined networks using dynamic flow installation and management techniques
As computer networks evolve, they become more complex, introducing several challenges in the areas of performance and management. Such problems can lead to stagnation in network innovation. Software Defined Networks (SDN) framework could be one of the best candidates for improving and revolutionising networking by giving the full control to the network administrators to implement new management and performance optimisation techniques.
This thesis examines performance issues faced in SDN due to the introduction of the SDN Controller. These issues include the extra delay due to the round-trip time between the switch and the controller as well as the fact that some packets arrive at the destination out-of-order.
We propose a novel dynamic flow installation and management algorithm (OFPE) using the SDN protocol OpenFlow, which preserves the controller to a non-overloaded CPU state and allow it to dynamically add and adjust flow table rules to reduce packet delay and out-of-order packets. In addition, we propose OFPEX, an extension to OFPE algorithm that includes techniques for managing multi-switch environments as well as methods that make use of the packets interarrival time in categorising and serving packet flows. Such techniques allow topology awareness, helping the controller to install flow table rules in such a way to form optimal routes for high priority flows thus increasing network performance. For the performance evaluation of the proposed algorithms, both hardware testbed as well as emulation experiments have been conducted. The performance results indicate that OFPE algorithm achieves a significant enhancement in performance in the form of reduced delay by up to 92.56% (depending on the scenario), reduced packet loss by up to 55.32% and reduced out-of-order packets by up to 69.44%.
Furthermore, we propose a novel placement algorithm for distributed Mininet implementations which uses weights in order to distribute the experiment components to the appropriately distributed machines. The proposed algorithm uses static code analysis in order to examine the experimental code as well as it measures the capabilities of physical components in order to create a weights table which is then used to distribute the experiment components properly. The performance results of the proposed algorithm evaluation indicated reductions in delay and packet loss of up to 65.51% and 86.35% respectively, as well as a decrease in the standard deviation of CPU usage by up to 88.63%. These results indicate that the proposed algorithm distributes the experiment components evenly across the available resources.
Finally, we propose a series of Benchmarking tests that can be used to rate all the available SDN experimental platforms. These tests allow the selection of the appropriate experimental platform according to the scenario needs as well as they indicate the resources needed by each platform
Self-managed resources in network virtualisation environments
Network virtualisation is a promising technique for dealing with the resistance of the Internet to architectural changes, enabling a novel business model in which infrastructure management is decoupled from service provision. It allows infrastructure providers (InPs) who own substrate networks (SNs) to lease chunks of them out to service providers who then create virtual networks (VNs), which can then be re-leased out or used to provide services to end-users.
However, the different VNs should be initialised, in which case virtual links and nodes must be mapped to substrate nodes and paths respectively. One of the challenges in the initialisation of VNs is the requirement of an efficient sharing of SN resources. Since the profitability of InPs depends on how many VNs are able to be allocated simultaneously onto the SN, the success of network virtualisation will depend, in part, on how efficiently VNs utilise physical network resources. This thesis contributes to efficient resource sharing in network virtualisation by dividing the problem into three sub-problems: (1) mapping virtual nodes and links to substrate nodes and paths i.e. virtual network embedding (VNE), (2) dynamic managing of the resources allocated to VNs throughout their lifetime (DRA), and (3) provisioning of backup resources to ensure survivability of the VNs.
The constrained VNE problem is NP-Hard. As a result, to simplify the solution, many existing approaches propose heuristics that make assumptions (e.g. a SN with infinite resources), some of which would not apply in practical environments. This thesis proposes an improvement in VNE by proposing a one-shot VNE algorithm which is based on column generation (CG). The CG approach starts by solving a restricted version of the problem, and thereafter refines it to obtain a final solution. The objective of a one-shot mapping is to achieve better resource utilisation, while using CG significantly enhances the solution time complexity.
In addition current approaches are static in the sense that after the VNE stage, the resources allocated are not altered for the entire lifetime of the VN. The few proposals that do allow for adjustments in original mappings allocate a fixed amount of node and link resources to VNs throughout their life time. Since network load varies with time due to changing user demands, allocating a fixed amount of resources based on peak load could lead to an inefficient utilisation of overall SN resources, whereby, during periods when some virtual nodes and/or links are lightly loaded, SN resources are still reserved for them, while possibly rejecting new VN requests. The second contribution of this thesis are a set of proposals that ensure that SN resources are efficiently utilised, while at the same making sure that the QoS requirements of VNs are met. For this purpose, we propose self-management algorithms in which the SN uses time-difference machine learning techniques to make autonomous decisions with respect to resource allocation.
Finally, while some scientific research has already studied multi-domain VNE, the available approaches to survivable VNs have focused on the single InP environment. Since in the more practical situation a network virtualisation environment will involve multiple InPs, and because an extension of network survivability approaches from the single to multi domain environments is not trivial, this thesis proposes a distributed and dynamic approach to survivability in VNs. This is achieved by using a multi-agent-system that uses a multi-attribute negotiation protocol and a dynamic pricing model forming InPs coalitions supporting SNs resource backups. The ultimate objective is to ensure that virtual network operators maximise profitability by minimising penalties resulting from QoS violations.La virtualització de xarxes es una tècnica prometedora per afrontar la resistència d'Internet als canvis arquitectònics, que permet un nou model de negoci en el que la gestió de la infraestructura de xarxa es desacobla de la provisió del servei. Això permet als proveïdors de infraestructura (InPs), propietaris de la xarxa física substrat (SN), llogar segments d'aquesta als proveïdors dels serveis, que crearan xarxes virtuals (VNs) que a l'hora poden re-llogar-se o utilitzar-se per donar servei a usuaris finals.
No obstant això, les diferents VNs s'han d'inicialitzar assignant els seus nodes i enllaços als del substrat. Un dels reptes d'aquest procés es el requisit de fer un ús eficient dels recursos de la SN. Donat que el benefici d'un InP depèn del nombre de xarxes virtuals que puguin allotjar-se simultàniament en la SN, l'èxit de la virtualització de xarxes depèn en part de quan eficient es l’ús dels recursos de la xarxa física per part de les VNs. Aquesta Tesi contribueix a la millora de l’eficiència en la compartició de recursos en la virtualització de xarxes dividint el problema en tres sots problemes: (1) assignació de nodes i enllaços virtuals a nodes i enllaços del substrat (VNE), (2) gestió dinàmica dels recursos assignats a les VNs al llarg de la seva vida útil (DRA) i (3) aprovisionament de recursos de backup per assegurar la supervivència de les VNs.
La naturalesa del problema VNE el fa “NP-Hard". En conseqüència, per simplificar la solució, moltes de les propostes son heurístiques que es basen en hipòtesis (per exemple, SN amb recursos il•limitats) de difícil compliment en escenaris reals.
Aquesta Tesi proposa una millora al problema VNE mitjan_cant un algorisme “one-shot VNE" basat en generació de columnes (CG). La solució CG comena resolent una versió restringida del problema, per tot seguit refinar-la i obtenir la solució final.
L'objectiu del “one-shot VNE" es aconseguir millorar l’ús dels recursos, mentre que CG redueix significativament la complexitat temporal del procés.
D'altre banda, les solucions actuals son estàtiques, ja que els recursos assignats en la fase VNE no es modifiquen durant tot el temps de vida útil de la VN. Les poques propostes que permeten reajustar l’assignació inicial, es basen en una assignació fixe de recursos a les VNs. No obstant això, degut a que la càrrega de la xarxa varia a conseqüència de la demanda canviant dels usuaris, assignar una quantitat fixe de recursos basada en situacions de càrrega màxima esdevé en ineficiència per infrautilització en períodes de baixa demanda, mentre que en tals períodes de demanda baixa, el tenir recursos reservats, pot originar rebutjos de noves VNs. La segona contribució
d'aquesta Tesi es un conjunt de propostes que asseguren l’ús eficient dels recursos de la SN, garantint a la vegada els requeriments de qualitat de servei de totes les VNs. Amb aquesta finalitat es proposen algorismes d’autogestió en els que la SN utilitza tècniques d'aprenentatge de màquines per a materialitzar decisions autònomes en l’assignació dels recursos.
Finalment, malgrat que diversos estudis han tractat ja el problema VNE en entorn multi-domini, les propostes actuals de supervivència de xarxes virtuals s'han limitat a contexts d'aprovisionament per part d'un sol InP. En canvi, a la pràctica, la virtualització de xarxes comportarà un entorn d'aprovisionament multi-domini, i com que l’extensió de solucions de supervivència d'un sol domini al multi-domini no es trivial, aquesta Tesi proposa una solució distribuïda i dinàmica per a la supervivència de VNs. Això s'aconsegueix amb un sistema multi-agent que utilitza un protocol de negociació multi-atribut i un model dinàmic de preus per formar coalicions d'InPs que proporcionaran backups als recursos de les SNs. L'objectiu últim es assegurar que els operadors de xarxes virtuals maximitzin beneficis minimitzant les penalitzacions per violació de la QoS.La virtualización de redes es una técnica prometedora para afrontar la resistencia de Internet a cambios arquitectónicos, que permite un nuevo modelo de negocio en el que la gestión de la infraestructura está desacoplada del aprovisionamiento del servicio. Esto permite a los proveedores de infraestructuras (InPs), propietarios de la red física subyacente (SN), alquilar segmentos de la misma a los proveedores de servicio, los cuales crearán redes virtuales (VNs), que a su vez pueden ser realquiladas o usadaspara proveer el servicio a usuarios finales.
Sin embargo, las diferentes VNs deben inicializarse, mapeando sus nodos y enlaces en los del substrato. Uno de los retos de este proceso de inicialización es el requisito de hacer un uso eficiente de los recursos de la SN. Dado que el benecio de los InPs depende de cuantas VNs puedan alojarse simultáneamente en la SN, el éxito de la virtualización de redes depende, en parte, de cuan eficiente es el uso de los recursos de red físicos por parte de las VNs. Esta Tesis contribuye a la compartición eficiente de recursos para la virtualización de redes dividiendo el problema en tres sub-problemas:
(1) mapeo de nodos y enlaces virtuales sobre nodos y enlaces del substrato (VNE), (2) gestión dinámica de los recursos asignados a las VNs a lo largo de su vida útil (DRA), y (3) aprovisionamiento de recursos de backup para asegurar la supervivencia de las VNs.
La naturaleza del problema VNE lo hace “NP-Hard". En consecuencia, para simplificar la solución, muchas de las actuales propuestas son heurísticas que parten de unas suposiciones (por ejemplo, SN con recursos ilimitados) de difícil asumir en la práctica. Esta Tesis propone una mejora al problema VNE mediante un algoritmo “one-shot VNE" basado en generación de columnas (CG). La solución CG comienza resolviendo una versión restringida del problema, para después refinarla y obtener la solución final. El objetivo del “one-shot VNE" es mejorar el uso de los recursos, a la vez que con CG se reduce significativamente la complejidad temporal del proceso.
Por otro lado,las propuestas actuales son estáticas, ya que los recursos asignados en la fase VNE no se alteran a lo largo de la vida útil de la VN. Las pocas propuestas que permiten reajustes del mapeado original ubican una cantidad fija de recursos a las VNs.
Sin embargo, dado que la carga de red varía con el tiempo, debido a la demanda cambiante de los usuarios, ubicar una cantidad fija de recursos basada en situaciones de pico conduce a un uso ineficiente de los recursos por infrautilización de los mismos en periodos de baja demanda, mientras que en esta situación, al tener los recursos reservados, pueden rechazarse nuevas solicitudes de VNs. La segunda contribución de esta Tesis es un conjunto de propuestas para el uso eficiente de los recursos de la SN, asegurando al mismo tiempo la calidad de servicio de las VNs.
Para ello se proponen algoritmos de auto-gestión en los que la SN usa técnicas de aprendizaje de máquinas para materializar decisiones autónomas en la asignación de recursos.
Finalmente, aunque determinadas investigaciones ya han estudiado el problema multi-dominio VNE, las propuestas actuales de supervivencia de redes virtuales se han limitado a un entorno de provisión de infraestructura de un solo InP. Sin embargo, en la práctica, la virtualización de redes comportará un entorno de aprovisionamiento con múltiples InPs, y dado a que la extensión de las soluciones de supervivencia de un entorno único a uno multi-dominio no es trivial, esta Tesis propone una solución distribuida y dinámica a la supervivencia de VNs. Esto se consigue mediante un sistema multi-agente que usa un protocolo de negociación multi-atributo y un modelo dinámico de precios para conformar coaliciones de InPs para proporcionar backups a los recursos de las SNs. El objetivo último es asegurar que los operadores de VNs maximicen su beneficio minimizando la penalización por violación de la QoS