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Projeto de investigação
Institute for Systems Engineering and Computers at Coimbra - INESC Coimbra
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Publicações
Fundamental schemes to determine disjoint paths for multiple failure scenarios
Publication . Gomes, Teresa; Jorge, Luisa; Girão-Silva, Rita; Yallouz, Jose; Babarczi, Péter; Rak, Jacek
Disjoint path routing approaches can be used to cope with multiple failure cenarios. This can be achieved using a set of k (k>2) link- (or node-) disjoint path pairs (in single-cost and multi-cost networks). Alternatively, if Shared Risk Link Groups (SRLGs) information is available, the calculation of an SRLG-disjoint path pair (or of a set of such paths) can protect a connection against the joint failure of the set of links in any single SRLG. Paths traversing disaster-prone regions should be disjoint, but in safe regions it may be acceptable for the paths to share links or even nodes for a quicker recovery. Auxiliary algorithms for obtaining the shortest path from a source to a destination are also presented in detail, followed by the illustrated description of Bhandari’s and Suurballe’s algorithms for obtaining a pair of paths of minimal total additive cost. These algorithms are instrumental for some of the presented schemes to determine disjoint paths for multiple failure scenarios.
Failure simulation in software-defined networks with differential link availability
Publication . Melo, Paulo; Jorge, Luisa; Gomes, Teresa
In Software-Defined Networks (SDN) the placement
of controllers is an important factor for overall network reliability.
Whereas most studies assume that all links have similar link
failure rates/availability, placing controllers taking into account
differences in link availability can yield advantages. This is even
more relevant if the network is designed with a particular subset
of high availability links (a spine). After presenting integer linear
programming formulations to support controller placement
considering differential link availability, we propose a simulation
approach to verify the reliability change due to that placement.
From a simulational study using 2 networks, 30 different link
availability configurations we found a definite advantage in
overall reliability in using the knowledge of high availability
links to place the controllers. However, while there were also
advantages to using certain spines for individual networks, these
advantages were not uniform, and varied according to networks,
the number of controllers placed and link availability ratio.
Further work is suggested to check whether fault patterns may
influence the reliability advantage of individual spines.
Multiclass data plane recovery using different recovery schemes in SDN: a simulation analysis
Publication . Jorge, Luisa; Melo, Paulo; Gomes, Teresa
To provide dependable services SDN networks need to be resilient to link or switching node failures. This entails, when faults occur, ensuring differentiated types of recovery, according to carried traffic, to routing paths. However, the choice of the recovery scheme best suited to each traffic class is not direct, nor is obvious the impact of the combination of various recovery schemes, according to traffic classes. We explore the usage of different recovery schemes for traffic with distinct requirements Simulation analysis confirms that using different recovery schemes for distinct types of traffic does create differentiated effects in terms of traffic carried and bandwidth usage.
Modelling with NGSI-LD: the VALLPASS project case study
Publication . Ribeiro, Tiago; Coelho, João Paulo; Jorge, Luísa; Sardão, Joaquim; Gonçalves, José; Rosse, Higor
The smart cities paradigm covers multiple domains which span from citizens' accessibility and mobility to general infrastructures and services. Hence, smart cities can be seen as an excellent showcase of heterogeneity, namely at the data level. For this reason, they are a perfect candidate for linked data and semantic web concept applications. This powerful combination leads to interoperability at the data level which is one of the ultimate goals of the Internet of Things (IoT). In this reference frame, NGSI-LD is an open framework for context information processing consisting of both a semantic information model and a RESTful Application Programming Interface (API). This paper proposes a methodology for creating semantic data models in the context of IoT, namely to represent and describe data associated with digital twins. The methodology is presented in a practical way, through the process of creating an NGSI-LD semantic data model for the VALLPASS project, inserted in the traffic domain, which is one of the most popular in smart cities.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UIDB/00308/2020