128 research outputs found
Congestion control mechanisms within MPLS networks
PhDAbstract not availabl
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 multidifusiĂłn (multicast) basado en redes es la mejor manera
de dar soporte a una gran variedad de aplicaciones populares como la televisiĂłn de
alta definiciĂłn (HDTV), el video bajo demanda (VoD), el servicio de LAN privadas
virtuales (VPLS), la computaciĂłn grid, las redes de ĂĄrea de almacenamiento Ăłptico
(O-SAN), la videoconferencia, la educaciĂłn a distancia, los juegos masivos de rol en
lĂnea de mĂșltiples jugadores (MMORPG), la realidad virtual en red, etc., hay varias
razones tecnolĂłgicas 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 Ăłptica como para la capa de red (redes MPLS-IP).
En la capa Ăłptica, en particular en las redes Ăłpticas 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 atenuaciĂłn,
principalmente debido a la necesaria operación de división de la señal, ademås 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 Ăłptica 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 måximo de dos enlaces de salida, con el fin de obtener una
menor latencia terminal-a-terminal que en TaC y una mejorada distribuciĂłn de la
disponibilidad de potencia por encima de los diseños split-and-delivery (SaD). Otra
ventaja de esta arquitectura es su simplicidad y el nĂșmero reducido de componentes
requerido, escalando bien para las implementaciones del nodo con muchos puertos
de entrada/salida. Extensas simulaciones muestran que la divisiĂłn binaria (2-split)
es prĂĄcticamente suficiente para la mayorĂa de las topologĂas 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 tråfico 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 informaciĂłn del estado de reenvĂo requerida en los
enrutadores de la red de transporte, especialmente cuando un gran nĂșmero 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 nĂșmero de demandas multicast. En este escenario, estudiamos la agregaciĂłn
de demandas multicast en ĂĄrboles de distribuciĂłn, proporcionando un conjunto de
técnicas para observar el equilibrio entre el ancho de banda y la información de estado.
Este estudio estĂĄ hecho en el contexto de las redes basadas en redes privadas
virtuales (VPN) MPLS, con la agregaciĂłn de VPNs multicast en distintos escenarios
de redes reales y utilizando nuevos heurĂsticos para la agregaciĂłn. AĂșn asĂ, el principal
problema de la agregaciĂłn es el alto porcentaje de ancho de banda desperdiciado
que depende principalmente de la cantidad de ĂĄrboles compartidos usados.
Por otro lado, trabajos recientes han vuelto a traer a los filtros de Bloom como una
alternativa para realizar el reenvĂo multicast. En esta aproximaciĂłn 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 soluciĂłn no utiliza informaciĂłn de estado, presenta serias desventajas debido
a los falsos positivos, esto es, anomalĂas de reenvĂo 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 sĂłlo para todo el camino/ĂĄrbol, incluyendo cada
uno sĂłlo los enlaces de una determinada profundidad del ĂĄrbol. Estudios analĂticos
y simulaciones demuestran que nuestra propuesta reduce los anomalĂas de reenvĂo
presentes en otras tĂ©cnicas similares del estado del arte, alcanzando en la mayorĂa
de escenarios reales una eficiencia de reenvĂo (trĂĄfico Ăștil) mayor que 95%.
Finalmente, estudiamos la posibilidad de usar agregaciĂłn de ĂĄrboles 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 pråcticamente los bucles e
incrementando la eficiencia de reenvĂo hasta mĂĄs de un 99% en la mayorĂa de los
escenarios de redes
Optimal Design Strategies for Survivable Carrier Ethernet Networks
Ethernet technologies have evolved through enormous standardization efforts over the past two decades to achieve carrier-grade functionalities, leading to carrier Ethernet. Carrier Ethernet is expected to dominate next generation backbone networks due to its low-cost and simplicity. Ethernet's ability to provide carrier-grade Layer-2 protection switching with SONET/SDH-like fast restoration time is achieved by a new protection switching protocol, Ethernet Ring Protection (ERP). In this thesis, we address two important design aspects of carrier Ethernet networks, namely, survivable design of ERP-based Ethernet transport networks together with energy efficient network design. For the former, we address the problem of optimal resource allocation while designing logical ERP for deployment and model the combinatorially complex problem of joint Ring Protection Link (RPL) placements and ring hierarchies selection as an optimization problem. We develop several Mixed Integer Linear Programming (MILP) model to solve the problem optimally considering both single link failure and concurrent dual link failure scenarios. We also present a traffic engineering based ERP design approach and develop corresponding MILP design models for configuring either single or multiple logical ERP instances over one underlying physical ring. For the latter, we propose two novel architectures of energy efficient Ethernet switches using passive optical correlators for optical bypassing as well as using energy efficient Ethernet (EEE) ports for traffic aggregation and forwarding. We develop an optimal frame scheduling model for EEE ports to ensure minimal energy consumption by using packet coalescing and efficient scheduling
NETWORK DESIGN UNDER DEMAND UNCERTAINTY
A methodology for network design under demand uncertainty is proposed in this dissertation. The uncertainty is caused by the dynamic nature of the IP-based traffic which is expected to betransported directly over the optical layer in the future. Thus, there is a need to incorporate the uncertainty into a design modelexplicitly. We assume that each demand can be represented as a random variable, and then develop an optimization model to minimizethe cost of routing and bandwidth provisioning. The optimization problem is formulated as a nonlinear Multicommodity Flow problemusing Chance-Constrained Programming to capture both the demand variability and levels of uncertainty guarantee. Numerical work ispresented based on a heuristic solution approach using a linear approximation to transform the nonlinear problem to a simpler linearprogramming problem. In addition, the impact of the uncertainty on a two-layer network is investigated. This will determine how theChance-Constrained Programming based scheme can be practically implemented. Finally, the implementation guidelines for developingan updating process are provided
Security of Electrical, Optical and Wireless On-Chip Interconnects: A Survey
The advancement of manufacturing technologies has enabled the integration of
more intellectual property (IP) cores on the same system-on-chip (SoC).
Scalable and high throughput on-chip communication architecture has become a
vital component in today's SoCs. Diverse technologies such as electrical,
wireless, optical, and hybrid are available for on-chip communication with
different architectures supporting them. Security of the on-chip communication
is crucial because exploiting any vulnerability would be a goldmine for an
attacker. In this survey, we provide a comprehensive review of threat models,
attacks, and countermeasures over diverse on-chip communication technologies as
well as sophisticated architectures.Comment: 41 pages, 24 figures, 4 table
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