14,470 research outputs found
Survivability aspects of future optical backbone networks
In huidige glasvezelnetwerken kan een enkele vezel een gigantische hoeveelheid data dragen, ruwweg het equivalent van 25 miljoen gelijktijdige telefoongesprekken. Hierdoor zullen netwerkstoringen, zoals breuken van een glasvezelkabel, de communicatie van een groot aantal eindgebruikers verstoren. Netwerkoperatoren kiezen er dan ook voor om hun netwerk zo te bouwen dat zulke grote storingen automatisch opgevangen worden. Dit proefschrift spitst zich toe op twee aspecten rond de overleefbaarheid in toekomstige optische netwerken. De eerste doelstelling die beoogd wordt is het tot stand brengen vanrobuuste dataverbindingen over meerdere netwerken. Door voldoende betrouwbare verbindingen tot stand te brengen over een infrastructuur die niet door een enkele entiteit wordt beheerd kan men bv. weredwijd Internettelevisie van hoge kwaliteit aanbieden. De bestudeerde oplossing heeft niet enkel tot doel om deze zeer betrouwbare verbinding te berekenen, maar ook om dit te bewerkstelligen met een minimum aan gebruikte netwerkcapaciteit. De tweede doelstelling was om een antwoord te formuleren om de vraag hoe het toepassen van optische schakelsystemen gebaseerd op herconfigureerbare optische multiplexers een impact heeft op de overleefbaarheid van een optisch netwerk. Bij lagere volumes hebben optisch geschakelde netwerken weinig voordeel van dergelijke gesofistikeerde methoden. Elektronisch geschakelde netwerken vertonen geen afhankelijkheid van het datavolume en hebben altijd baat bij optimalisatie
Markov Decision Processes with Applications in Wireless Sensor Networks: A Survey
Wireless sensor networks (WSNs) consist of autonomous and resource-limited
devices. The devices cooperate to monitor one or more physical phenomena within
an area of interest. WSNs operate as stochastic systems because of randomness
in the monitored environments. For long service time and low maintenance cost,
WSNs require adaptive and robust methods to address data exchange, topology
formulation, resource and power optimization, sensing coverage and object
detection, and security challenges. In these problems, sensor nodes are to make
optimized decisions from a set of accessible strategies to achieve design
goals. This survey reviews numerous applications of the Markov decision process
(MDP) framework, a powerful decision-making tool to develop adaptive algorithms
and protocols for WSNs. Furthermore, various solution methods are discussed and
compared to serve as a guide for using MDPs in WSNs
Survivable mesh-network design & optimization to support multiple QoP service classes
Every second, vast amounts of data are transferred over communication systems around the world, and as a result, the demands on optical infrastructures are extending beyond the traditional, ring-based architecture. The range of content and services available from the Internet is increasing, and network operations are constantly under pressure to expand their optical networks in order to keep pace with the ever increasing demand for higher speed and more reliable links
Understanding the role of mobile ad hoc networks in non-traditional contexts
With the rapid development of short-range wireless technology new venues to apply it in more sophisticated, complex, and dynamic environments have been opened. Nevertheless, the applicability of such technology in nontraditional settings like face-to-face encounters and disaster relief environments, remains unclear. This article describes a research effort aimed to narrow that gap by means of using two non-traditional settings as case studies; face-to-face encounters among unacquainted people and first responders in urban disaster relief environments. Among the results obtained are: a) interactions among unacquainted people may be promoted, though the level of interaction becomes easily constrained due to the current state of RF technology and the design of the experiments, and b) it is feasible to obtain a reliable communication platform for first responders operating in disaster relief missions. These results supports the idea that short-range wireless technology may play both a facilitator and a promoter role in face-to-face contexts, and at least a facilitator role in the case of users co-located in highly dynamic contexts.8th IFIP/IEEE International conference on Mobile and Wireless CommunicationRed de Universidades con Carreras en Informática (RedUNCI
Segment Routing: a Comprehensive Survey of Research Activities, Standardization Efforts and Implementation Results
Fixed and mobile telecom operators, enterprise network operators and cloud
providers strive to face the challenging demands coming from the evolution of
IP networks (e.g. huge bandwidth requirements, integration of billions of
devices and millions of services in the cloud). Proposed in the early 2010s,
Segment Routing (SR) architecture helps face these challenging demands, and it
is currently being adopted and deployed. SR architecture is based on the
concept of source routing and has interesting scalability properties, as it
dramatically reduces the amount of state information to be configured in the
core nodes to support complex services. SR architecture was first implemented
with the MPLS dataplane and then, quite recently, with the IPv6 dataplane
(SRv6). IPv6 SR architecture (SRv6) has been extended from the simple steering
of packets across nodes to a general network programming approach, making it
very suitable for use cases such as Service Function Chaining and Network
Function Virtualization. In this paper we present a tutorial and a
comprehensive survey on SR technology, analyzing standardization efforts,
patents, research activities and implementation results. We start with an
introduction on the motivations for Segment Routing and an overview of its
evolution and standardization. Then, we provide a tutorial on Segment Routing
technology, with a focus on the novel SRv6 solution. We discuss the
standardization efforts and the patents providing details on the most important
documents and mentioning other ongoing activities. We then thoroughly analyze
research activities according to a taxonomy. We have identified 8 main
categories during our analysis of the current state of play: Monitoring,
Traffic Engineering, Failure Recovery, Centrally Controlled Architectures, Path
Encoding, Network Programming, Performance Evaluation and Miscellaneous...Comment: SUBMITTED TO IEEE COMMUNICATIONS SURVEYS & TUTORIAL
p-Cycle Based Protection in WDM Mesh Networks
Abstract
p-Cycle Based Protection in WDM Mesh Networks
Honghui Li, Ph.D.
Concordia University, 2012
WDM techniques enable single fiber to carry huge amount of data. However, optical WDM
networks are prone to failures, and therefore survivability is a very important requirement
in the design of optical networks. In the context of network survivability, p-cycle based
schemes attracted extensive research interests as they well balance the recovery speed and
the capacity efficiency. Towards the design of p-cycle based survivableWDM mesh networks,
some issues still need to be addressed. The conventional p-cycle design models and solution
methods suffers from scalability issues. Besides, most studies on the design of p-cycle
based schemes only cope with single link failures without any concern about single node
failures. Moreover, loop backs may exist in the recovery paths along p-cycles, which lead
to unnecessary stretching of the recovery path lengths.
This thesis investigates the scalable and efficient design of segment p-cycles against single
link failures. The optimization models and their solutions rely on large-scale optimization
techniques, namely, Column Generation (CG) modeling and solution, where segment pcycle
candidates are dynamically generated during the optimization process. To ensure full
node protection in the context of link p-cycles, we propose an efficient protection scheme,
called node p-cycles, and develop a scalable optimization design model. It is shown that,
depending on the network topology, node p-cycles sometimes outperform path p-cycles in
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terms of capacity efficiency. Also, an enhanced segment p-cycle scheme is proposed, entitled
segment Np-cycles, for full link and node protection. Again, the CG-based optimization
models are developed for the design of segment Np-cycles. Two objectives are considered,
minimizing the spare capacity usage and minimizing the CAPEX cost. It is shown that
segment Np-cycles can ensure full node protection with marginal extra cost in comparison
with segment p-cycles for link protection. Segment Np-cycles provide faster recovery speed
than path p-cycles although they are slightly more costly than path p-cycles. Furthermore,
we propose the shortcut p-cycle scheme, i.e., p-cycles free of loop backs for full node and
link protection, in addition to shortcuts in the protection paths. A CG-based optimization
model for the design of shortcut p-cycles is formulated as well. It is shown that, for full node
protection, shortcut p-cycles have advantages over path p-cycles with respect to capacity
efficiency and recovery speed. We have studied a whole sequence of protection schemes
from link p-cycles to path p-cycles, and concluded that the best compromise is the segment
Np-cycle scheme for full node protection with respect to capacity efficiency and recovery
time. Therefore, this thesis offers to network operators several interesting alternatives to
path p-cycles in the design of survivable WDM mesh networks against any single link/node
failures
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