Browsing by Author "Djamaa, Badis"
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Item Open Access Hybrid CoAP-based resource discovery for the Internet of Things(Springer, 2017-02-16) Djamaa, Badis; Yachir, Ali; Richardson, Mark A.Enabling automatic, efficient and scalable discovery of the resources provided by constrained low-power sensor and actuator networks is an important element to empower the transformation towards the Internet of Things (IoT). To this end, many centralized and distributed resource discovery approaches have been investigated. Clearly, each approach has its own motivations, advantages and drawbacks. In this article, we present a hybrid centralized/distributed resource discovery solution aiming to get the most out of both approaches. The proposed architecture employs the well-known Constrained Application Protocol (CoAP) and features a number of interesting discovery characteristics including scalability, time and cost efficiency, and adaptability. Using such a solution, network nodes can automatically and rapidly detect the presence of Resource Directories (RDs), via a proactive RD discovery mechanism, and perform discovery tasks through them. Nodes may, alternatively, fall back automatically to efficient fully-distributed discovery operations achieved through Trickle-enabled, CoAP-based technics. The effectiveness of the proposed architecture has been demonstrated by formal analysis and experimental evaluations on dedicated IoT platforms.Item Open Access The Trickle Algorithm: Issues and Solutions(2015-01-30) Djamaa, Badis; Richardson, Mark A.To manage the various multi-purpose Internet of Things applications brought about by low-power and lossy networks, efficient methods of network configuration and administration; firmware installation and updates; neighbourhood, route and resource discovery are required. These requirements can be reduced to a basic data consistency maintenance problem, making the Trickle algorithm a powerful candidate solution. Trickle is shaped by the so-called short-listen problem, hence the imposition of a listen-only period. Such a period allows Trickle to robustly address the short-listen problem at the expense of increased latency. In this report, we revisit the Trickle rules, the short-listen problem and interval-synchronisation, and hence introduce New-Trickle. New-Trickle is an optimisation to Trickle with virtually no extra cost in terms of communication overhead, computation demand and implementation effort, yet one that provides fast updates, yielding a propagation time more than 10 times faster than Trickle.