All optical multicasting in wavelength routing mesh networks with power considerations: design and operation

Wavelength routing Wavelength Division Multiplexing (WDM) are optical networks that support all-optical services. They have become the most appealing candidate for wide area backbone networks. Their huge available bandwidth provides the solution for the exponential growth in trayc demands that is due to the increase in the number of users and the surge of more bandwidth intensive network applications and services. A sizable fraction of these applications and services are of multi-point nature. Therefore, supporting multicast service in this network environment is very critical and unique. The all-optical support of various services has advantages, which includes achieving the signal transparency to its content. Nevertheless, the all-optical operational support comes with an associated cost and new issues that make this problem very challenging. In this thesis, we investigate the power-related issues for supporting multicast service in the optical domain, referred to as All-Optical Multicasting (AOM). Our study treats these issues from two networking contexts, namely, Network Provisioning and Connection Provisioning. We propose a number of optimal and heuristic solutions with a unique objective function for each context. In this regard, the objective function for the network provisioning problem is to reduce the network cost, while the solutions for the connection provisioning problem aim to reduce the connection blocking ratio. The optimal formulations are inherently non-linear. However, we introduce novel methods for linearizing them and formulate the problems as Mixed Integer Linear Programs. Also, the design of the heuristic solutions takes into account various optimization factors which results in efficient heuristics that can produce fast solutions that are relatively close to their optimal counterparts, as shown in the numerical results we present

IP multicast over WDM networks

Ph.DDOCTOR OF PHILOSOPH

Measurement-Driven Algorithm and System Design for Wireless and Datacenter Networks

The growing number of mobile devices and data-intensive applications pose unique challenges for wireless access networks as well as datacenter networks that enable modern cloud-based services. With the enormous increase in volume and complexity of traffic from applications such as video streaming and cloud computing, the interconnection networks have become a major performance bottleneck. In this thesis, we study algorithms and architectures spanning several layers of the networking protocol stack that enable and accelerate novel applications and that are easily deployable and scalable. The design of these algorithms and architectures is motivated by measurements and observations in real world or experimental testbeds. In the first part of this thesis, we address the challenge of wireless content delivery in crowded areas. We present the AMuSe system, whose objective is to enable scalable and adaptive WiFi multicast. AMuSe is based on accurate receiver feedback and incurs a small control overhead. This feedback information can be used by the multicast sender to optimize multicast service quality, e.g., by dynamically adjusting transmission bitrate. Specifically, we develop an algorithm for dynamic selection of a subset of the multicast receivers as feedback nodes which periodically send information about the channel quality to the multicast sender. Further, we describe the Multicast Dynamic Rate Adaptation (MuDRA) algorithm that utilizes AMuSe's feedback to optimally tune the physical layer multicast rate. MuDRA balances fast adaptation to channel conditions and stability, which is essential for multimedia applications. We implemented the AMuSe system on the ORBIT testbed and evaluated its performance in large groups with approximately 200 WiFi nodes. Our extensive experiments demonstrate that AMuSe can provide accurate feedback in a dense multicast environment. It outperforms several alternatives even in the case of external interference and changing network conditions. Further, our experimental evaluation of MuDRA on the ORBIT testbed shows that MuDRA outperforms other schemes and supports high throughput multicast flows to hundreds of nodes while meeting quality requirements. As an example application, MuDRA can support multiple high quality video streams, where 90% of the nodes report excellent or very good video quality. Next, we specifically focus on ensuring high Quality of Experience (QoE) for video streaming over WiFi multicast. We formulate the problem of joint adaptation of multicast transmission rate and video rate for ensuring high video QoE as a utility maximization problem and propose an online control algorithm called DYVR which is based on Lyapunov optimization techniques. We evaluated the performance of DYVR through analysis, simulations, and experiments using a testbed composed of Android devices and o the shelf APs. Our evaluation shows that DYVR can ensure high video rates while guaranteeing a low but acceptable number of segment losses, buffer underflows, and video rate switches. We leverage the lessons learnt from AMuSe for WiFi to address the performance issues with LTE evolved Multimedia Broadcast/Multicast Service (eMBMS). We present the Dynamic Monitoring (DyMo) system which provides low-overhead and real-time feedback about eMBMS performance. DyMo employs eMBMS for broadcasting instructions which indicate the reporting rates as a function of the observed Quality of Service (QoS) for each UE. This simple feedback mechanism collects very limited QoS reports which can be used for network optimization. We evaluated the performance of DyMo analytically and via simulations. DyMo infers the optimal eMBMS settings with extremely low overhead, while meeting strict QoS requirements under different UE mobility patterns and presence of network component failures. In the second part of the thesis, we study datacenter networks which are key enablers of the end-user applications such as video streaming and storage. Datacenter applications such as distributed file systems, one-to-many virtual machine migrations, and large-scale data processing involve bulk multicast flows. We propose a hardware and software system for enabling physical layer optical multicast in datacenter networks using passive optical splitters. We built a prototype and developed a simulation environment to evaluate the performance of the system for bulk multicasting. Our evaluation shows that the optical multicast architecture can achieve higher throughput and lower latency than IP multicast and peer-to-peer multicast schemes with lower switching energy consumption. Finally, we study the problem of congestion control in datacenter networks. Quantized Congestion Control (QCN), a switch-supported standard, utilizes direct multi-bit feedback from the network for hardware rate limiting. Although QCN has been shown to be fast-reacting and effective, being a Layer-2 technology limits its adoption in IP-routed Layer 3 datacenters. We address several design challenges to overcome QCN feedback's Layer- 2 limitation and use it to design window-based congestion control (QCN-CC) and load balancing (QCN-LB) schemes. Our extensive simulations, based on real world workloads, demonstrate the advantages of explicit, multi-bit congestion feedback, especially in a typical environment where intra-datacenter traffic with short Round Trip Times (RTT: tens of s) run in conjunction with web-facing traffic with long RTTs (tens of milliseconds)

Advanced techniques for multicast service provision in core transport networks

Although the network-based multicast service is the optimal way to support of a large variety of popular applications such as high-definition television (HDTV), videoon- demand (VoD), virtual private LAN service (VPLS), grid computing, optical storage area networks (O-SAN), video conferencing, e-learning, massive multiplayer online role-playing games (MMORPG), networked virtual reality, etc., there are a number of technological and operational reasons that prevents a wider deployment. This PhD work addresses this problem in the context of core transport network, by proposing and analyzing new cost-effective and scalable techniques to support multicast both at the Optical layer and at the Network layer (MPLS-IP networks). In the Optical layer, in particular in Wavelength Division Multiplexing (WDM) Optical Circuit Switched networks, current multicast-capable OXC node designs are of a great complexity and have high attenuation levels, mainly because of the required signal splitting operation plus the traversal of a complex switching stage. This makes multi-point support rarely included in commercial OXC nodes. Inspired in previous works in the literature, we propose a novel architecture that combines the best of splitting and tap-and-continue (TaC), called 2-STC (2-split-tap-and-continue) in the framework of integrated optics. A 2-STC OXC node is a flexible design capable of tapping and splitting over up to two outgoing links in order to obtain lower end-to-end latency than in TaC and an improved power budget distribution over split-and-delivery (SaD) designs. Another advantage of this architecture is its simplicity and the reduced number of components required, scaling well even for implementations of the node with many input/output ports. Extensive simulations show that the binary split (2-split) is quite enough for most real-life core network topologies scenarios, since the average node degree is usually between 3 and 4. A variant of this design, called 2-STCg, for making the node capable of optical traffic grooming (i.e. accommodation of low-speed demands into wavelength-links) is also presented. At the Network layer, one of the main reasons that hinder multicast deployment is the high amount of forwarding state information required in core routers, especially when a large number of medium/small-sized multicast demands arrive to the core network, because the state data that needs to be kept at intermediate core routers grows proportionally to the number of multicast demands. In this scenario, we study the aggregation of multicast demands into shared distribution trees, providing a set of techniques to observe the trade-off between bandwidth and state information. This study is made in the context of MPLS VPN-based networks, with the aggregation of multicast VPNs in different real network scenarios and using novel heuristics for aggregation. Still, the main problem of aggregation is the high percentage of wasted bandwidth that depends mainly on the amount of shared trees used. On the other hand, recent works have brought back Bloom filters as an alternative for multicast forwarding. In this approach the packet header contains a Bloom filter that is evaluated at each hop for matching with the corresponding outgoing link ID. Although this approach is claimed to be stateless, it presents serious drawbacks due to false positives, namely important forwarding anomalies (duplicated flows, packet storms and loops) and the header overhead. In order to solve these drawbacks we propose D-MPSS (Depth-Wise Multi-Protocol Stateless Switching). This technique makes use of a stack of Bloom filters instead of a single one for all the path/tree, each one including only the links of a given depth of the tree. Analytical studies and simulations show that our approach reduces the forwarding anomalies present in similar state-of-the-art techniques, achieving in most network scenarios a forwarding efficiency (useful traffic) greater than 95%. Finally, we study the possibility of using tree aggregation and Bloom filters together, and propose a set of techniques grouped as H-ABF techniques (hybrid aggregation - Bloom filter-based forwarding), which improve D-MPSS and other previously proposed techniques, practically eliminating the forwarding loops and increasing the forwarding efficiency up to more than 99% in most network scenarios. -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Aunque el servicio de multidifusión (multicast) basado en redes es la mejor manera de dar soporte a una gran variedad de aplicaciones populares como la televisión de alta definición (HDTV), el video bajo demanda (VoD), el servicio de LAN privadas virtuales (VPLS), la computación grid, las redes de área de almacenamiento óptico (O-SAN), la videoconferencia, la educación a distancia, los juegos masivos de rol en línea de múltiples jugadores (MMORPG), la realidad virtual en red, etc., hay varias razones tecnológicas y operacionales que le impiden un mayor despliegue. Esta tesis doctoral aborda este problema en el contexto de las redes troncales de transporte, proponiendo y analizando técnicas de bajo coste y escalables para dar soporte al multicast tanto para la capa óptica como para la capa de red (redes MPLS-IP). En la capa óptica, en particular en las redes ópticas conmutadas por circuitos con multiplexación de longitud de onda (WDM), los diseños de nodos OXC con capacidades multicast muestran una gran complejidad y altos niveles de atenuación, principalmente debido a la necesaria operación de división de la señal, además del paso de ella a través de una compleja fase de conmutación. Esto hace que el soporte multi-punto sea raramente incluido en los nodos OXC comerciales. Inspirados en trabajos previos de la literatura, proponemos una novedosa arquitectura que combina lo mejor de dividir (splitting) y tap-y-continuar (TaC), llamado 2-STC (2-split-tapand- continue) en el marco de trabajo de la óptica integrada. Un nodo OXC 2-STC es un diseño flexible capaz de hacer tapping (tomar una pequeña muestra de la señal) y dividir la señal hacia un máximo de dos enlaces de salida, con el fin de obtener una menor latencia terminal-a-terminal que en TaC y una mejorada distribución de la disponibilidad de potencia por encima de los diseños split-and-delivery (SaD). Otra ventaja de esta arquitectura es su simplicidad y el número reducido de componentes requerido, escalando bien para las implementaciones del nodo con muchos puertos de entrada/salida. Extensas simulaciones muestran que la división binaria (2-split) es prácticamente suficiente para la mayoría de las topologías de redes de transporte en la vida real, debido a que el grado promedio de los nodos es usualmente 3 y 4. Una variante de este diseño, llamada 2-STCg, para hacer el nodo capaz de realizar grooming (es decir, la capacidad de acomodar demandas de menor velocidad en longitudes de onda - enlaces) de tráfico óptico, es también presentada. En la capa de red, una de las principales razones que obstaculizan el despliegue del multicast es la gran cantidad de información del estado de reenvío requerida en los enrutadores de la red de transporte, especialmente cuando un gran número de demandas multicast de tamaño mediano/pequeño llegan a la red de transporte, ya que los datos de estado a ser almacenados en los enrutadores crecen proporcionalmente con el número de demandas multicast. En este escenario, estudiamos la agregación de demandas multicast en árboles de distribución, proporcionando un conjunto de técnicas para observar el equilibrio entre el ancho de banda y la información de estado. Este estudio está hecho en el contexto de las redes basadas en redes privadas virtuales (VPN) MPLS, con la agregación de VPNs multicast en distintos escenarios de redes reales y utilizando nuevos heurísticos para la agregación. Aún así, el principal problema de la agregación es el alto porcentaje de ancho de banda desperdiciado que depende principalmente de la cantidad de árboles compartidos usados. Por otro lado, trabajos recientes han vuelto a traer a los filtros de Bloom como una alternativa para realizar el reenvío multicast. En esta aproximación la cabecera del paquete contiene un filtro de Bloom que es evaluado en cada salto para emparejarlo con el identificador del enlace de salida correspondiente. Aunque se afirma que esta solución no utiliza información de estado, presenta serias desventajas debido a los falsos positivos, esto es, anomalías de reenvío importantes (flujos duplicados, tormentas de paquetes y bucles) y gasto de ancho de banda por la cabecera de los paquetes. Para poder resolver estos problemas proponemos D-MPSS (Depth- Wise Multi-Protocol Stateless Switching). Esta técnica hace uso de una pila de filtros de Bloom en lugar de uno sólo para todo el camino/árbol, incluyendo cada uno sólo los enlaces de una determinada profundidad del árbol. Estudios analíticos y simulaciones demuestran que nuestra propuesta reduce los anomalías de reenvío presentes en otras técnicas similares del estado del arte, alcanzando en la mayoría de escenarios reales una eficiencia de reenvío (tráfico útil) mayor que 95%. Finalmente, estudiamos la posibilidad de usar agregación de árboles y filtros de Bloom juntos, y proponemos un conjunto de técnicas agrupadas como técnicas HABF (hybrid aggregation - Bloom filter-based forwarding), que mejoran D-MPSS y las otras técnicas propuestas previamente, eliminando prácticamente los bucles e incrementando la eficiencia de reenvío hasta más de un 99% en la mayoría de los escenarios de redes

Cross-Layer Platform for Dynamic, Energy-Efficient Optical Networks

The design of the next-generation Internet infrastructure is driven by the need to sustain the massive growth in bandwidth demands. Novel, energy-efficient, optical networking technologies and architectures are required to effectively meet the stringent performance requirements with low cost and ultrahigh energy efficiencies. In this thesis, a cross-layer communications platform is proposed to enable greater intelligence and functionality on the physical layer. Providing the optical layer with advanced networking capabilities will facilitate the dynamic management and optimization of optical switching based on performance monitoring measurements and higher-layer attributes. The cross-layer platform aims to create a new framework for networks to incorporate packet-scale measurement subsystems and techniques for monitoring the health of the optical channel. This will allow for quality-of-service- and energy-aware routing schemes, as well as an enhanced awareness of the optical data signals. This thesis first presents the design and development of an optical packet switching fabric. Leveraging a networking test-bed environment to validate networking hypotheses, advanced switching functionalities are demonstrated, including the support for quality-of-service based routing and packet multicasting. The investigated cross-layering is based on emerging optical technologies, enabling packet protection techniques and packet-rate switching fabric reconfiguration. Coupled with fast performance monitoring, the platform will achieve significant performance gains within the endeavor of all-optical switching. Allowing for a more intelligent, programmable optical layer aims to support greater flexibility with respect to bandwidth allocation and potentially a significant reduction in the network's energy consumption. The ultimate deliverable of this work is a high-performance, cross-layer enabled optical network node. The experimental demonstration of an initial prototype creates a dynamic network element with distributed control plane management, featuring fast packet-rate optical switching capabilities and embedded physical-layer performance monitoring modules. The cross-layer box enables an intelligent traffic delivery system that can dynamically manipulate optical switching on a packet-granular scale. With the goal of achieving advanced multi-layer routing and control algorithms, the network node requires an intelligent co-optimization across all the layers. The proposed cross-layer design should drive optical technologies and architectures in an innovative way, in order to fulfill the void between the design of basic photonic devices and the networking protocols that use them. The performance of the entire network -- from the optical components, to the routing algorithms and user applications -- should be optimized in concert. This contribution to the area of cross-layer network design creates an adaptable optical pipe that is extremely flexible and intelligent aware of both the physical optical signals and higher-layer requirements. The impact of this work will be seen in the realization of dynamic, energy-efficient optical communication links in future networking infrastructures

Advanced devices based on fibers, integrated optics and liquid crystals for WDM networks

The increment of bandwidth required for new services offered to users make necessary the use of optical fibres in data transmission. Glass optical fibres are widely used in long distance communications, and there are many devices implemented for using in these networks, but these technologies are sometimes expensive for their used in local loops. Different systems implemented over the established technology are used for increasing local loops bandwidth, but more services are demanded at home. Those applications require more bandwidth than the offered by the usual twisted copper pair. Multimode fibres (both silica and polymer) with larger core diameters and numerical aperture, allows for large tolerance on axial misalignments, which results in cheaper connectors as well as associated equipment, but with a bandwidth penalty with regards to their singlemode counterparts, mainly due to the introduction of modal dispersion. On the other hand, polymer optical fibre (POF) offers several advantages over conventional multimode optical fibre over short distances (ranging from 100m to 1000m) such as the even potential lower cost associated with its easiness of installation, splicing and connecting. This is due to the fact that POF is more flexible and ductile, making it easier to handle. Consequently, POF termination can be realized faster and cheaper than in the case of multimode silica fibre. Therefore, the number of applications that use POF is quickly increasing. POF is being used in video transmission in medical equipment, or in multimedia applications for civil aviation and high range cars, in-home and access networks, wireless LAN backbone or office LAN, and in intrinsic optical sensor networks among others. Even greater channel capacity can be available using a specific type of POF, perfluorinated Graded-Index POF (PF GIPOF), having low attenuation and large bandwidth from 650nm to 1300nm. Link lengths for in-building/home scenarios are short (less than 1 km), and thus the loss per unit length is of less importance. Transmission of 10Gbps data over 100m and transmission of 1.25Gbps Ethernet over 1 km have been experimentally demonstrated with PF GIPOF. On the other hand, combiners and multiplexers are basic elements in POF networks using Wavelength Division Multiplexing (WDM) and there are not that many already developed. It is important to have low losses devices and reconfiguration can be an additional feature in those networks. On the other hand, reconfigurable optical networks in critical applications demand devices able to have different functionalities, including switching. This work has focused in the development of different optical switches for a wide range of optical networks. Different switching technologies are available. Liquid crystals are widely used as displays, but they are also employed in telecommunications. Other common technology used in data routing is integrated optics. In this case, light propagates by means of a waveguide and the modification of its parameters makes possible switching operation. Micro-Electromechanical Mechanisms, MEMs, based in small mobile mirrors that can change the direction of the incident light when required are an important optical switching technology. The objective of the present work is the proposal of several optical switches using different technologies depending on the final application. Some of these structures have been experimentally tested whereas others have been simulated. Most of the presented switches use liquid crystals, having different functionalities and broadband operation range, so allowing wavelength division multiplexing. To these respect it has been developed an optical multiplexer/combiner and an advanced multifunctional optical switch (AMOS), both implemented with Nematic Liquid Crystal technology. It has also been developed a multiplexer/combiner based on Polymer Dispersed Liquid Crystals. The third kind of switches proposed are micro ring-resonators combined with liquid crystals. Micro ring-resonators consist of a circular waveguide attached to one or two straight waveguides acting like input and output ports. Light that passes through the structure can be filtered according to the ring resonator characteristics: ring length, coupling ratio, losses… The use of liquid crystal makes possible the tuning of the ring resonator filtering properties. The last proposed switch is made of a passive splitter and a Mach-Zehnder Interferometer. This kind of devices makes use of integrated optics and interference for switching purposes. The variation of the optical properties influencing the two light beam interference can be done in different ways: thermally, electrically… Finally, an automated optical characterization bench has been implemented in order to make easy the measurements. It is composed by a three axis translation stage with three actuators, several linear translation stages that allows the user to modify the bench structure for adapting it to his experiment, and different machinery for mounting the optics.The present research work has been supported by the following Spanish projects: TIC2003-038783 (DISFOTON), TEC2006-13273-C03-03-MIC (FOTOCOMIN) and TEC2009-14718-C03-03-MCI (DEDOS) of the Spanish Interministerial Commission on Science and Technology (CICYT), FACTOTEM-CM: S-005/ESP/000417, and FACTOTEM-II-CM: S2009/ESP-1781 and FENIS-CCG06-UC3M/TIC-619 of Comunidad Autónoma de Madrid. Additional financial support has been obtained form European Thematic Network SAMPA: Synclinic and Anticlinic Mesophases for Photonic Applications (HPRNCT- 2002-00202), carried out during the V Framework Program of the European Union, COST Action 299 FIDES: Optical Fibres Dedicated to Society, and from the European Network of Excellence: ePhoton/ONe+ (FP6-IST-027497), both carried out during the VI Framework Program of the European Union, and BONE: Building the Future Optical Network in Europe (FP7-ICT-216863) carried out during the VII Framework Program of the European Union

Wavelengths switching and allocation algorithms in multicast technology using m-arity tree networks topology

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University London.In this thesis, the m-arity tree networks have been investigated to derive equations for their nodes, links and required wavelengths. The relationship among all parameters such as leaves nodes, destinations, paths and wavelengths has been found. Three situations have been explored, firstly when just one server and the leaves nodes are destinations, secondly when just one server and all other nodes are destinations, thirdly when all nodes are sources and destinations in the same time. The investigation has included binary, ternary, quaternary and finalized by general equations for all m-arity tree networks. Moreover, a multicast technology is analysed in this thesis to transmit data carried by specific wavelengths to several clients. Wavelengths multicast switching is well examined to propose split-convert-split-convert (S-C-S-C) multicast switch which consists of light splitters and wavelengths converters. It has reduced group delay by 13% and 29% compared with split-convert (S-C) and split-convert-split (S-C-S) multicast switches respectively. The proposed switch has also increased the received signal power by a significant value which reaches 28% and 26.92% compared with S-C-S and S-C respectively. In addition, wavelengths allocation algorithms in multicast technology are proposed in this thesis using tree networks topology. Distributed scheme is adopted by placing wavelength assignment controller in all parents’ nodes. Two distributed algorithms proposed shortest wavelength assignment (SWA) and highest number of destinations with shortest wavelength assignment (HND-SWA) algorithms to increase the received signal power, decrease group delay and reduce dispersion. The performance of the SWA algorithm was almost better or same as HND-SWA related to the power, dispersion and group delay but they are always better than other two algorithms. The required numbers of wavelengths and their utilised converters have been examined and calculated for the researched algorithms. The HND-SWA has recorded the superior performance compared with other algorithms. It has reduced number of utilised wavelengths up to about 19% and minimized number of the used wavelengths converters up to about 29%. Finally, the centralised scheme is discussed and researched and proposed a centralised highest number of destinations (CHND) algorithm with static and dynamic scenarios to reduce network capacity decreasing (Cd) after each wavelengths allocation. The CDHND has reduced (Cd) by about 16.7% compared with the other algorithms