In this thesis we provide a model for a bufferless optical burst switching (OBS) and an optical packet switching (OPS) network. The thesis is divided in three parts. In the first part we introduce the basic functionality and structure of OBS and OPS networks. We identify the blocking probability as the main performance parameter of interest. In the second part we study the statistical properties of the traffic that will likely run through these networks. We use for this purpose a set of traffic traces obtained from the Universidad Politécnica de Catalunya. Our conclusion is that traffic entering the optical domain in future OBS/OPS networks will be long-range dependent (LRD). In the third part we present the model for bufferless OBS/OPS networks. This model takes into account the results from the second part of the thesis concerning the LRD nature of traffic. It also takes into account specific issues concerning the functionality of a typical bufferless packet-switching network. The resulting model presents scalability problems, so we propose an approximative method to compute the blocking probability from it. We empirically evaluate the accuracy of this method, as well as its scalability.

Optical packet switching (OPS) is the most prominent candidate transport solution that can seamlessly integrate electrical and optical layers by transferring certain switching functionality from electronics to optics, thus alleviating unnecessarily slow and expensive optical-electrical-optical conversions and signal processing at the switching node. Optical Label Switching (OLS) is an important aspect of the optical packet switched network that enables very low-latency forwarding of ultra-high bit-rate, protocol-independent packets entirely in the optical domain. The objective of the proposed research is to develop novel, efficient techniques to realize several key enabling technologies such as optical label generation and encoding, optical label swapping, all-optical buffering, and spectral efficient transmission system for optical label switched based OPS networks. A novel scheme of generating optical label at the ingress node using optical carrier suppression and separation (OCSS) technique is proposed. This scheme does not suffer from any unavoidable interference, limited extinction ratio or strict synchronization requirements between payload and label as observed by the currently available other label generation methods. One of the primary challenges to realize optical label swapping at the core node of scalable OLS network is the insertion of new optical labels without any wavelength conversion for same wavelength packet routing. A novel mechanism to realize same wavelength packet switching without using any conventional wavelength converter in the OLS network carrying differential phase-shift keying (DPSK) modulated payload and on-off keying (OOK) modulated optical label is demonstrated. Also a new dense wavelength division multiplexing (DWDM) optical buffer architecture using optical fiber delay lines that can provide wavelength selective reconfigurable variable delays is proposed. Optical packet switching provides automated, reconfigurable, and faster provision of both wavelength and bandwidth with finer granularity in the optical layer. However, a newer, cost-effective, and spectrally efficient optical transmission technology is essential to support the explosive bandwidth demand expected by the future optical packet switched networks. To meet this challenge, a spectrally efficient solution for transporting 40 Gbps per channel data over 50 GHz spaced DWDM system is developed by exploiting optical carrier suppression and separation technique and optical duobinary modulation.

Orientadores: Edson Moschim, Felipe Rudge Barbosa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-07T06:09:06Z (GMT). No. of bitstreams: 1 Nascimento_LuizHenriqueBonanido_D.pdf: 2297657 bytes, checksum: b04918af9ef98f4cae4bd6c3d6d4c0ca (MD5) Previous issue date: 2006 / Resumo: Hoje em dia, como uma multiplicidade muito grande de tecnologias converge para as redes fotônicas, a demanda por vazão cresce. Os protocolos para acesso múltiplo e simultâneo às portas de entrada da rede, bem como a abordagem do formato dos pacotes fotônicos e a arquitetura das redes, são considerados como alternativas tecnológicas para a melhora do desempenho das redes fotônicas. Deste modo, apresenta-se aqui uma proposta para a arquitetura de redes fotônicas,utilizando topologias em malha otimizadas para que os pacotes atinjam seus respectivos nós de destino no menor número de hops possível, com nós de rede 2x2. Além disso, utiliza-se o roteamento por deflexão para a resolução de contenda entre pacotes ópticos, bem como buffers eletrônicos na entrada da rede óptica para evitar problemas de perdas de inserção. Além disso, a estrutura de rede permite hierarquização e também se propõe um modelo para o funcionamento do nó que faz a ligação entre hierarquias diferentes dentro da rede óptica. Esta arquitetura de rede é então avaliada quanto à sua capacidade de prover requisitos para QoS em termos de perdas de pacotes, atrasos e inversão de ordem de pacotes, para a qual é proposta uma heurística para uma avaliação quantitativa. Os resultados mostram que uma arquitetura nos moldes apresentados é capaz de prover ganhos de desempenho, oferecendo condições para a garantia de QoS, provida por protocolos de rede em nível superior, até cerca de 70% de carga / Abstract: Nowadays, as a multiplicity of technologies converges upon the optical network, the demand for throughput increases. The protocols for multiple and simultaneous access to network ports, as well as the optical packet approach should be considered as technological alternatives to optical network performance upgrade. Thus, we present here a new proposal to the architecture of optical packet networks, using mesh topologies optimized in such a way that the packets reach their respective destination nodes with the smaller possible number of hops, and using 2x2 network nodes. Besides, we use deflection routing to solve the contention between optical packets, as well as electronical buffers at the optical network input to prevent problems with insertion losses. The structure of the network also allows hierarchization, performing the link between different hierarchies on the optical network. The performance of the proposed architecture is evaluated by the capacity of providing requirements of QoS, in terms of packet losses, delays and the amount of out of order packets, for which is presented a heuristic to get a quantitative estimation. The results show that the proposed architecture is able to provide performance gains, giving conditions to guarantee some levels of QoS, which is done by the specific protocols of superior network layers, up to 70% of network load / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica

A tecnologia de chaveamento de pacotes ópticos comumente utiliza componentes muito complexos, relegando sua viabilidade para o futuro. A utilização de pacotes ópticos, entretanto, é uma boa opção para melhorar a granularidade dos enlaces ópticos, bem como para tornar os processos de distribuição de banda muito mais eficientes e flexíveis. Esta tese propõe simplificações nas chaves ópticas que além de tornarem o pacote óptico viável para um futuro mais próximo, permitem montar redes ópticas complexas, com muitos nós, que operam de maneira auto-organizada. A rede proposta nesta tese não possui sinalização para reserva ou estabelecimento de caminho. As rotas são definidas pacote a pacote, em tempo real, durante o seu percurso, utilizando roteamento por deflexão. Com funções muito simples realizadas localmente, a rede ganha características desejáveis como: alta escalabilidade e eficiente sistema de proteção de enlace. Estas características desejáveis são tratadas como funções da rede que emergem de funções realizadas em cada um dos nós de rede individualmente. A tese apresenta um modelo analítico estatístico, validado por simulação, para caracterização da rede. No sistema de proteção contra falhas, os cálculos realizados para redes com até 256 nós mostram que o aumento do número médio de saltos ocorre apenas para destinos localizados no entorno da falha. Para demonstrar a viabilidade de construção de chave óptica rápida simplificada utilizando somente componentes já disponíveis no mercado foi montado um protótipo, que mostrou ter um tempo de chaveamento inferior a dois nanossegundos, sendo compatível com as operações de chaveamento de pacotes ópticos. / The Optical Packet Switching (OPS) technology usually involves complex and expensive components relegating its application viability to the future. Nevertheless the OPS utilization is a good option for improving the granularity at high bit rate transmissions, as well as for operation involving flexibility and fast bandwidth distribution. This thesis proposes simplifications on optical switching devices that besides getting closer future viability enable the deployment of highly scalable and self-organized complex network architecture. The proposed network operates without resources reservation or previous path establishment. The routes are defined packet-by-packet in a real time deflection routing procedure. With simple local functions the network starts to operate with desirable performance characteristics such as high scalability and automatic protection system. Those desirable performance characteristics are treated as Emerging Functions. For the network characterization it is presented a statistical analytical model validated by simulation. In the automatic protection functions investigation the results for a 256 nodes network showed that the mean number of hops enhancement occurs only around the failure neighborhood. To demonstrate the switch viability, a prototype was fabricated utilizing components already available in the market. The switching time obtained was below two nanoseconds showing compatibility with the optical packet switching technology.

A tecnologia de chaveamento de pacotes ópticos comumente utiliza componentes muito complexos, relegando sua viabilidade para o futuro. A utilização de pacotes ópticos, entretanto, é uma boa opção para melhorar a granularidade dos enlaces ópticos, bem como para tornar os processos de distribuição de banda muito mais eficientes e flexíveis. Esta tese propõe simplificações nas chaves ópticas que além de tornarem o pacote óptico viável para um futuro mais próximo, permitem montar redes ópticas complexas, com muitos nós, que operam de maneira auto-organizada. A rede proposta nesta tese não possui sinalização para reserva ou estabelecimento de caminho. As rotas são definidas pacote a pacote, em tempo real, durante o seu percurso, utilizando roteamento por deflexão. Com funções muito simples realizadas localmente, a rede ganha características desejáveis como: alta escalabilidade e eficiente sistema de proteção de enlace. Estas características desejáveis são tratadas como funções da rede que emergem de funções realizadas em cada um dos nós de rede individualmente. A tese apresenta um modelo analítico estatístico, validado por simulação, para caracterização da rede. No sistema de proteção contra falhas, os cálculos realizados para redes com até 256 nós mostram que o aumento do número médio de saltos ocorre apenas para destinos localizados no entorno da falha. Para demonstrar a viabilidade de construção de chave óptica rápida simplificada utilizando somente componentes já disponíveis no mercado foi montado um protótipo, que mostrou ter um tempo de chaveamento inferior a dois nanossegundos, sendo compatível com as operações de chaveamento de pacotes ópticos. / The Optical Packet Switching (OPS) technology usually involves complex and expensive components relegating its application viability to the future. Nevertheless the OPS utilization is a good option for improving the granularity at high bit rate transmissions, as well as for operation involving flexibility and fast bandwidth distribution. This thesis proposes simplifications on optical switching devices that besides getting closer future viability enable the deployment of highly scalable and self-organized complex network architecture. The proposed network operates without resources reservation or previous path establishment. The routes are defined packet-by-packet in a real time deflection routing procedure. With simple local functions the network starts to operate with desirable performance characteristics such as high scalability and automatic protection system. Those desirable performance characteristics are treated as Emerging Functions. For the network characterization it is presented a statistical analytical model validated by simulation. In the automatic protection functions investigation the results for a 256 nodes network showed that the mean number of hops enhancement occurs only around the failure neighborhood. To demonstrate the switch viability, a prototype was fabricated utilizing components already available in the market. The switching time obtained was below two nanoseconds showing compatibility with the optical packet switching technology.

A unique all-optical 1x2 self-routed switch is introduced. This switch routes an optical packet from one input to one of two possible outputs. The header and payload are transmitted separately in the system, and the header bits are processed in parallel thus increasing the switching speed as well as reducing the amount of buffering required for the payload. A 1x2 switching operation is analysed and a switching ratio of up to 14dB is obtained. The objective of the research was to investigate a unique all-optical switch. The switch works by processing the optical bits in a header packet which contains the destination address for a payload packet. After the destination address is processed the optical payload packet gets switched to one of two outputs depending on the result of the optical header processing. All-optical packet switching in the optical time domain was accomplished by making use of all-optical parallel processing of an optical packet header. This was demonstrated in experiments in which a three bit parallel processing all-optical switching node was designed, simulated and used to successfully demonstrate the concept. The measure of success that was used in the simulated experiments was the output switching ratio, which is the ratio between the peak optical power of a high bit at the first output and the peak optical power of a high bit at the second output. In all experimental results the worst case scenario was looked at, which means that if there was any discrepancy in the peak value of the output power then the measurement’s minimum/maximum value was used that resulted in a minimum value for the switching ratio. The research resulted in an optical processing technique which took an optical bit sequence and delivered a single output result which was then used to switch an optical payload packet. The packet switch node had two optical fibre inputs and two optical fibre outputs. The one input fibre carried the header packet and the other input fibre carried the payload packet. The aim was to switch the payload packet to one of the two output fibres depending on the bit sequence within the header packet. Also only one unique address (header bit sequence) caused the payload packet to exit via one of the outputs and all the other possible addresses caused the payload packet to exit via the other output. The physical configuration of the all-optical switches in the parallel processing structure of the switching node determined for which unique address the payload packet would exit via a different output than when the address was any of the other possible combinations of sequences. Only three Gaussian shaped bits were used in the header packet at a data rate of 10 Gbps and three Gaussian shaped bits in the payload packet at a data rate of 40 Gbps, but in theory more bits can be used in the payload packet at a decreased bit length to increase throughput. More bits can also be used in the header packet to increase the number of addresses that can be reached. In the simulated experiments it was found that the payload packet would under most circumstances exit both outputs, and at one output it would be much larger than at the other output (where it was normally found to be suppressed when compared to the other output’s optical power). The biggest advantage of this method of packet-switching is that it occurs all-optically, meaning that there is no optical to electronic back to optical conversions taking place in order to do header processing. All of the header processing is done optically. One of the disadvantages is that the current proposed structure of the all-optical switching node uses a Cross-Gain Modulator (XGM) switch which is rather expensive because of the Semiconductor Optical Amplifier (SOA). In this method of packet-switching the length of the payload packet cannot exceed the length of one bit of the header packet. This is because the header processing output is only one header bit length long and this output is used to switch the payload packet. Thus any section of the payload packet that is outside this header processing output window will not be switched correctly / Dissertation (MEng (Electronic Engineering))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted

[pt] Redes Manhattan Street (MS) têm sido descritas como um arranjo linear bidimensional de nós, semelhante à configuração de ruas e avenidas de Manhattan. O roteamento por deflexão é implementado encaminhando os pacotes que atingem um determinado nó a uma de suas saídas de forma síncrona ou assíncrona. O principal objetivo deste trabalho consiste na simulação e análise de redes totalmente ópticas configuradas segundo a topologia MS. O roteamento por deflexão e o assincronismo são considerados, para evitar complexidade eletrônica e armazenamento de pacotes no domínio óptico. Serão apresentadas as características das redes MS, suas propriedades estruturais e os parâmetros utilizados para analisar seu desempenho. Uma metodologia analítica dedicada a obtenção teórica destes parâmetros será introduzida. Serão apresentados alguns conceitos básicos sobre simulação de redes;diversas simulações da rede proposta utilizando os protocolos UDP e TCP; uma descrição do software que foi utilizado para realizar as simulações; uma comparação entre os resultados obtidos através da simulação e os obtidos através da metodologia analítica; e uma análise do efeito da latência na vazão do protocolo TCP. / [en] Manhattan Street (MS) Networks are bidimensional linear node sets arranged as the avenues and streets of Manhattan. The simulation and analysis of all-optical MS networks is the central target of this paper. In order to avoid using complex electronics and/or optical domain buffers, the deflection routing and the asynchronism are taken into account in the analysis. Deflection routing is performed by conveying incoming packets towards one of the two outputs. The characteristics of MS Networks are presented, along with their structural properties and the parameters used for performance analysis. An analytical methodology for the theoretical obtaining of these parameters is described. Some basic concepts on network simulation are discussed. Several simulations of the proposed network are presented, using both UDP and TCP protocols, and the software used for simulations is also described. The obtained results are compared and discussed with respect to the previously described analytic methodologies. Finally, the effect of network latency on the TCP-protocol throughput is assessed.

Due to the tremendous growth of traffic volume caused by both exponential increase of number of Internet users and continual emergence of new bandwidth demanding applications, high capacity networks are required in order to satisfactorily handle the extremely large amount of traffic. Hence, optical fiber communication is the key technology for the network infrastructure. This thesis addresses design, analysis and simulation of access and core networks targeting important research problems, which need to be tackled for the effective realization of next generation optical networks. Among different fiber access architectures, passive optical network (PON) is considered as the most promising alternative for the last mile connection due to its relatively low cost and resource efficiency. The inherent bursty nature of the user generated traffic results in dynamically changing bandwidth demand on per subscriber basis. In addition, access networks are required to support differentiated quality of service and accommodate multiple service providers. To address these problems we proposed three novel scheduling algorithms to efficiently realize dynamic bandwidth allocation in PON, along with guaranteeing both the priority and fairness of the differentiated services among multiple users and/or service providers. Meanwhile, because of the increasing significance of reliable access to network services, an efficient fault management mechanism needs to be provided in PON. In addition, access networks are very cost sensitive and the cost of protection should be kept as low as possible. Therefore, we proposed three novel cost-effective protection architectures keeping in mind that reliability requirement in access networks should be satisfied at the minimal cost. Regarding the optical core networks, replacing electronic routers with all-optical switching nodes can offer significant advantages in realizing high capacity networks. Because of the technological limitations for realizing all-optical nodes, the focus is put on the ingenious architecture design. Therefore, we contributed on novel switching node architectures for optical circuit and packet switching networks. Furthermore, we addressed different aspects of routing and wavelength assignment (RWA) problem, which is an important and hard task to be solved in wavelength routed networks. First, we proposed an approach based on the information summary protocol to reduce the large amount of control overhead needed for dissemination of the link state information in the case of adaptive routing. In addition, transparency in optical networks may cause vulnerability to physical layer attacks. To target this critical security related issue, we proposed an RWA solution to minimize the possible reachability of a jamming attack. Finally, in order to evaluate our ideas we developed two tailor-made simulators based on discrete event driven system for the detailed studies of PON and switched optical networks. Moreover, the proposed tabu search heuristic for our RWA solution was implemented in C++. / QC 20100707

Optical packet switching (OPS) is one of the more promising solutions for meeting the diverse needs of broadband networking applications of the future. By virtue of its small data traffic granularity as well as its nanoseconds switching speed, OPS can be used to provide connection-oriented or connectionless services for different groups of users with very different networking requirements. The optical buffer and the switch fabric are two of the most important components in an OPS router. In this research, novel designs for the optical buffer and switch fabric are proposed and experimentally demonstrated. In particular, an optical buffer that is based on a folded-path delay-line tree architecture will be discussed. This buffer is the most compact non-recirculating optical delay line buffer to date, and it uses an array of high-speed ON-OFF optical reflectors to dynamically reconfigure its delay within several nanoseconds. A major part of this research is devoted to the design and performance optimization of these high-speed reflectors. Simulations and measurements are used to compare different reflector designs as well as to determine their optimal operating conditions. Another important component in the OPS router is the switch fabric, and it is used to perform space switching for the optical packets. Optical switch fabrics are used to overcome the limitations imposed by conventional electronic switch fabrics: high power consumption and dependency on the modulation format and bit-rate of the signals. Currently, only those fabrics that are based on the broadcast-and-select architecture can provide truly non-blocking multicast services to all input ports. However, a major drawback of these fabrics is that they are implemented using a large number of optical gates based on semiconductor optical amplifiers (SOA). This results in large component count and high energy consumption. In this research, a new multicast-capable switch fabric which does not require any SOA gates is proposed. This fabric relies on a passive all-optical gate that is based on the Four-wave mixing (FWM) wavelength conversion process in a highly-nonlinear fiber. By using this new switch architecture, a significant reduction in component count can be expected.

La consommation d'énergie des centres de données est un enjeu majeur. Leurs communications internes représentent près du quart de cette consommation. Les technologies de commutation optique ont en principe une meilleure efficacité énergétique que les solutions actuelles. Ce travail porte sur les réseaux optiques en mode paquet pour des centres de données de petite et moyenne taille. Il s'est déroulé dans le cadre du projet EPOC (Energy Proportional and Opportunistic Computing) qui s'intéresse à la réduction de la consommation d'énergie d'un centre de données alimenté partiellement par des sources renouvelables. Une hypothèse clé est l'absence d'un réseau de stockage dédié réduisant ainsi la consommation des interconnexions. Par contre, afin de pouvoir éteindre certains serveurs selon la charge de travail et l'énergie disponible, le débit doit être de l'ordre de 100 Gbit/s. Après un état de l'art des réseaux optiques pour centre de données nous choisissons une solution reposant sur une infrastructure entièrement passive et des émetteurs rapidement accordables en longueur d'onde, proposée récemment dans la littérature (POPI).Nous étudions les limitations dues aux composants (pertes d'insertion, plage d'accord et espacement des canaux). Nous proposons une extension (E-POPI) qui permet d'augmenter le nombre de serveurs connectés en utilisant plusieurs plages de longueurs d'onde. Pour les centres de données de plus grande taille nous proposons un réseau à deux étages (intra- et inter-racks) opérant respectivement dans les bandes C et L, POPI+. La connexion entre étages se fait via une passerelle transparente dans un sens et opaque dans l'autre. Différentes solutions de contrôle des deux étages sont détaillées.Un des éléments essentiels de faisabilité de ces architectures est de concilier la montée en débit avec les pertes du réseau passif d'interconnexion. Les techniques cohérentes des transmissions longue distance ne sont pas actuellement envisageables pour un centre de données. Nous avons donc étudié les formats PAM 4 et 8, par simulation avec différents débits (jusqu'à 112 Gbit/s et récepteurs (PIN, APD et SOA-PIN) et aussi, expérimentalement, à 12 et 18 Gbit/s. Nous avons développé une méthode de compensation des distorsions générées par les différents composants qui procure un compromis entre précision de correction et temps de calcul.Ces résultats nous permettent de déterminer les pertes d'insertion tolérables. Nous les combinons avec les limitations liées à la plage d'accord des émetteurs et à l'encombrement spectral des canaux occupant des fenêtres multiples de 12,5 GHz pour dimensionner les différentes architectures. Les réseaux POPI, E-POPI et POPI+ permettent respectivement la connexion de 48, 99 et 2352 entités à 112 Gbit/s. Nos évaluations tiennent compte d'une possible dispersion des caractéristiques des principaux composants. / Data-center energy consumption is nowadays a major issue. Intra-data-center networking accounts almost for a quarter of the data-center total power consumption. Optical switching technologies could provide higher power efficiency than current solutions based on electrical-packet switching. This work focuses on optical-packet-switched networks for small- and medium-size data centers. It takes part of the EPOC (Energy-Proportional and Opportunistic Computing) project, which main interest consists on reducing the overall power consumption of a data center partially powered by renewable sources. A key assumption is that our data center does not rely on a dedicated storage network, in order to reduce the consumption of those interconnections. In addition, with the aim of being able to turn off some servers according to the workload and the available energy, the bit rate must be close to 100 Gbit/s. We have chosen, after studying the state of the art of data-center interconnects, a purely passive network architecture based on fast-wavelength-tunable transmitters under the name of POPI.We study POPI's limitations due to its components (insertion loss, tuning range and channel spacing). We then propose an extension called E-POPI that allows to increase the number of connected servers by using several transmission bands. For larger data centers, we propose POPI+, a two-stage infrastructure for intra- and inter-rack communications operating in the C and L bands, respectively. The connection between both stages is done via a transparent gateway in one direction and an opaque one in the other. We discuss different control solutions for both stages.The feasibility of these architectures depends on, among other factors, dealing with bit-rate increasing and power losses of a passive interconnect. Coherent long-distance-transmission techniques are not currently suited to data centers. We therefore studied PAM 4 and 8 modulation formats with direct detection. On one hand, by simulation, with different bit rates (up to 112 Gbit/s) and receivers (PIN, APD and SOA-PIN) and, on the other hand, experimentally, at 12 and 18 Gbit/s. We have developed a method for compensating the distortions generated by the different network components. Our method takes into account a good tradeoff between correction accuracy and computation time.Simulation results allow us to determine the amount of insertion loss that may be supported. We then combine these results with the limitations of transmitters-tuning range and channel spacing using multiple of 12.5 GHz slots for dimensioning the proposed architectures. POPI, E-POPI and POPI+ interconnects allow the connection of 48, 99 and 2352 entities, respectively, at 112 Gbit/s. Our assessments take into account a potential dispersion of the characteristics of the main architecture components.