IETF standardization in the field of the Internet of Things (IoT): a survey

Smart embedded objects will become an important part of what is called the Internet of Things. However, the integration of embedded devices into the Internet introduces several challenges, since many of the existing Internet technologies and protocols were not designed for this class of devices. In the past few years, there have been many efforts to enable the extension of Internet technologies to constrained devices. Initially, this resulted in proprietary protocols and architectures. Later, the integration of constrained devices into the Internet was embraced by IETF, moving towards standardized IP-based protocols. In this paper, we will briefly review the history of integrating constrained devices into the Internet, followed by an extensive overview of IETF standardization work in the 6LoWPAN, ROLL and CoRE working groups. This is complemented with a broad overview of related research results that illustrate how this work can be extended or used to tackle other problems and with a discussion on open issues and challenges. As such the aim of this paper is twofold: apart from giving readers solid insights in IETF standardization work on the Internet of Things, it also aims to encourage readers to further explore the world of Internet-connected objects, pointing to future research opportunities

Layered Label Propagation: A MultiResolution Coordinate-Free Ordering for Compressing Social Networks

We continue the line of research on graph compression started with WebGraph, but we move our focus to the compression of social networks in a proper sense (e.g., LiveJournal): the approaches that have been used for a long time to compress web graphs rely on a specific ordering of the nodes (lexicographical URL ordering) whose extension to general social networks is not trivial. In this paper, we propose a solution that mixes clusterings and orders, and devise a new algorithm, called Layered Label Propagation, that builds on previous work on scalable clustering and can be used to reorder very large graphs (billions of nodes). Our implementation uses overdecomposition to perform aggressively on multi-core architecture, making it possible to reorder graphs of more than 600 millions nodes in a few hours. Experiments performed on a wide array of web graphs and social networks show that combining the order produced by the proposed algorithm with the WebGraph compression framework provides a major increase in compression with respect to all currently known techniques, both on web graphs and on social networks. These improvements make it possible to analyse in main memory significantly larger graphs

Doctor of Philosophy

dissertationIn the past few years, we have seen a tremendous increase in digital data being generated. By 2011, storage vendors had shipped 905 PB of purpose-built backup appliances. By 2013, the number of objects stored in Amazon S3 had reached 2 trillion. Facebook had stored 20 PB of photos by 2010. All of these require an efficient storage solution. To improve space efficiency, compression and deduplication are being widely used. Compression works by identifying repeated strings and replacing them with more compact encodings while deduplication partitions data into fixed-size or variable-size chunks and removes duplicate blocks. While we have seen great improvements in space efficiency from these two approaches, there are still some limitations. First, traditional compressors are limited in their ability to detect redundancy across a large range since they search for redundant data in a fine-grain level (string level). For deduplication, metadata embedded in an input file changes more frequently, and this introduces more unnecessary unique chunks, leading to poor deduplication. Cloud storage systems suffer from unpredictable and inefficient performance because of interference among different types of workloads. This dissertation proposes techniques to improve the effectiveness of traditional compressors and deduplication in improving space efficiency, and a new IO scheduling algorithm to improve performance predictability and efficiency for cloud storage systems. The common idea is to utilize similarity. To improve the effectiveness of compression and deduplication, similarity in content is used to transform an input file into a compression- or deduplication-friendly format. We propose Migratory Compression, a generic data transformation that identifies similar data in a coarse-grain level (block level) and then groups similar blocks together. It can be used as a preprocessing stage for any traditional compressor. We find metadata have a huge impact in reducing the benefit of deduplication. To isolate the impact from metadata, we propose to separate metadata from data. Three approaches are presented for use cases with different constrains. For the commonly used tar format, we propose Migratory Tar: a data transformation and also a new tar format that deduplicates better. We also present a case study where we use deduplication to reduce storage consumption for storing disk images, while at the same time achieving high performance in image deployment. Finally, we apply the same principle of utilizing similarity in IO scheduling to prevent interference between random and sequential workloads, leading to efficient, consistent, and predictable performance for sequential workloads and a high disk utilization

RESTful Wireless Sensor Networks

Sensor networks have diverse structures and generally employ proprietary protocols to gather useful information about the physical world. This diversity generates problems to interact with these sensors since custom APIs are needed which are tedious, error prone and have steep learning curve. In this thesis, I present RESThing, a lightweight REST framework for wireless sensor networks to ease the process of interacting with these sensors by making them accessible over the Web. I evaluate the system and show that it is feasible to support widely used and standard Web protocols in wireless sensor networks. Being able to integrate these tiny devices seamlessly into the global information medium, we can achieve the Web of Things

Web browsing optimization over 2.5G and 3G: end-to-end mechanisms vs. usage of performance enhancing proxies

Published version on Wiley's platform: https://onlinelibrary.wiley.com/doi/abs/10.1002/wcm.4562.5 Generation (2.5G) and Third Generation (3G) cellular wireless networks allow mobile Internet access withbearers specifically designed for data communications. However, Internet protocols under-utilize wireless widearea network (WWAN) link resources, mainly due to large round trip times (RTTs) and request–reply protocolpatterns. Web browsing is a popular service that suffers significant performance degradation over 2.5G and 3G. Inthis paper, we review and compare the two main approaches for improving web browsing performance over wirelesslinks: (i) using adequate end-to-end parameters and mechanisms and (ii) interposing a performance enhancingproxy (PEP) between the wireless and wired parts. We conclude that PEPs are currently the only feasible way forsignificantly optimizing web browsing behavior over 2.5G and 3G. In addition, we evaluate the two main currentcommercial PEPs over live general packet radio service (GPRS) and universal mobile telecommunications system(UMTS) networks. The results show that PEPs can lead to near-ideal web browsing performance in certain scenarios.Postprint (published version

Towards a neonatal brain stethoscope: a framework for quantifying the accuracy of subjective and objective detection of neonatal brain injuries, and integration of a bluetooth communication system

Increasing and quantifying the accuracy of perceptual discrimination of brain injuries through auditory images. Appropriate conversion of a neonate EEG signal to an audio signal that is discriminative and sounds natural.The goal of this project is to work in different aspects of the development of a neonatal brain stethoscope. This tool is expected to be an alternative to the current devices, which are expensive and require a very specific training to be used. First, an interactive web interface has been developed to assess the detection of neonatal brain injuries by the users using an alternative interpretation method framework. The webpage presents the currently-used visual method, based on visualisation of electroencephalogram (EEG) traces, and an alternative way that also includes a sonification output and an AI-assisted decision support. Secondly, a connection has been established between an acquisition board and a portable device using Bluetooth Low Energy (BLE). This allows to wirelessly receive and store in real time the EEG signals that come from the electrodes through the acquisition board.La finalidad de este proyecto es trabajar en diferentes aspectos del desarrollo de un estetoscopio cerebral para recién nacidos. Esta herramienta está pensada como alternativa a los sistemas actuales, que generalmente son caros y cuyo uso requiere un entrenamiento muy específico. En primer lugar, se ha desarrollado una interfaz web interactiva para poder analizar y valorar la detección de daño cerebral en neonatos por parte de los usuarios utilizando un método alternativo de interpretación. La página web incluye el método gráfico actual, que corresponde a la visualización de señales electroencefalográficas (EEG), así como una forma alternativa de interpretar las señales, utilizando una representación acústica de éstas y un soporte de decisiones haciendo uso de un sistema asistido por inteligencia artificial. En segundo lugar, se ha establecido una conexión entre la placa de adquisición y una tableta táctil, utilizando la tecnología Bluetooth Low Energy. Esto permite, sin necesidad de cables, recibir y almacenar las señales EEG que provienen de los electrodos a través de la placa de adquisición.La finalitat d'aquest projecte es treballar en diferents aspectes del desenvolupament d'un estetoscopi cerebral per a nounats. Aquesta eina està concebuda com a alternativa als sistemes actuals, que resulten cars i el seu ús requereix un entrenament molt específic. Primer de tot, s'ha desenvolupat una interfície web interactiva per a analitzar i valorar la detecció per part dels usuaris de dany cerebral en neonats emprant un mètode alternatiu d?interpretació. La pàgina web inclou el mètode gràfic actual, que correspon a la visualització de senyals electroencefalogràfics (EEG), i també una forma alternativa d'interpretar les senyals, fent ús tant de la seva representació acústica com d'un suport de decisions emprant un sistema assistit per intel·ligència artificial. En segon lloc, s'ha establert la connexió entre una placa d'adquisició i una tauleta tàctil, fent ús de la tecnologia Bluetooth Low Energy. Això permet, sense necessitat de cables, rebre i emmagatzemar en temps real els senyals EEG que provenen dels elèctrodes a través de la placa d'adquisició

Is the Web ready for HTTP/2 Server Push?

HTTP/2 supersedes HTTP/1.1 to tackle the performance challenges of the modern Web. A highly anticipated feature is Server Push, enabling servers to send data without explicit client requests, thus potentially saving time. Although guidelines on how to use Server Push emerged, measurements have shown that it can easily be used in a suboptimal way and hurt instead of improving performance. We thus tackle the question if the current Web can make better use of Server Push. First, we enable real-world websites to be replayed in a testbed to study the effects of different Server Push strategies. Using this, we next revisit proposed guidelines to grasp their performance impact. Finally, based on our results, we propose a novel strategy using an alternative server scheduler that enables to interleave resources. This improves the visual progress for some websites, with minor modifications to the deployment. Still, our results highlight the limits of Server Push: a deep understanding of web engineering is required to make optimal use of it, and not every site will benefit.Comment: More information available at https://push.netray.i