163 research outputs found

    Enhancing Block-Wise Transfer with Network Coding in CoAP

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    CoAP (Constrained Application Protocol) with block-wise transfer (BWT) option is a known protocol choice for large data transfer in general lossy IoT network environments. Lossy transmission environments on the other hand lead to CoAP resending multiple blocks, which creates overheads. To tackle this problem, we design a BWT with network coding (NC), with the goal to reducing the number of unnecessary retransmissions. The results show the reduction in the number of block retransmissions for different values of blocksize, implying the reduced transfer time. For the maximum blocksize of 1024 bytes and total probability loss of 0.5, CoAP with NC can resend up to 5 times less blocks.Comment: 4 pages, 2 figures, submitted to Euro-Par 201

    Publish/subscribe protocol in wireless sensor networks: improved reliability and timeliness

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    The rapidly-evolving demand of applications using wireless sensor networks in several areas such as building and industrial automation or smart cities, among other, makes it necessary to determine and provide QoS support mechanisms which can satisfy the requirements of applications. In this paper we propose a mechanism that establishes different QoS levels, based on Publish/Subscribe model for wireless networks to meet application requirements, to provide reliable delivery of packet and timeliness. The first level delivers packets in a best effort way. The second one intends to provide reliable packet delivery with a novel approach for Retransmission Timeout (RTO) calculation, which adjusts the RTO depending on the subscriber Packet Delivery Ratio (PDR). The third one provides the same reliable packet delivery as the second one, but in addition, it provides data aggregation trying to be efficient in terms of energy consumption and the use of network bandwidth. The last one provides timeliness in the packet delivery. We evaluate each QoS Level with several performance metrics such as PDR, Message Delivery Ratio, Duplicated and Retransmitted Packet Ratio and Packet Timeliness Ratio to demonstrate that our proposal provides significant improvements based on the increase of the PDR obtained.Peer ReviewedPostprint (author's final draft

    A Low-Power CoAP for Contiki

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    Internet of Things devices will by and large be battery-operated, but existing application protocols have typically not been designed with power-efficiency in mind. In low-power wireless systems, power-efficiency is determined by the ability to maintain a low radio duty cycle: keeping the radio off as much as possible. We present an implementation of the IETF Constrained Application Protocol (CoAP) for the Contiki operating system that leverages the ContikiMAC low-power duty cycling mechanism to provide power efficiency. We experimentally evaluate our low-power CoAP, demonstrating that an existing application layer protocol can be made power-efficient through a generic radio duty cycling mechanism. To the best of our knowledge, our CoAP implementation is the first to provide power-efficient operation through radio duty cycling. Our results question the need for specialized low-power mechanisms at the application layer, instead providing low-power operation only at the radio duty cycling layer

    CoAP congestion control for the Internet of Things

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    “© © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.” August Betzler, Javier Isern, Carles Gomez, Ilker Demirkol, Josep Paradells, "Experimental evaluation of congestion control for CoAP communications without end-to-end reliability", Ad Hoc Networks, pp. , 2016, ISSN 15708705. DOI: 10.1109/MCOM.2016.7509394CoAP is a lightweight RESTful application layer protocol devised for the IoT. Operating on top of UDP, CoAP must handle congestion control by itself. The core CoAP specification defines a basic congestion control mechanism, but it is not capable of adapting to network conditions. However, IoT scenarios exhibit significant resource constraints, which pose new challenges on the design of congestion control mechanisms. In this article we present CoCoA, an advanced congestion control mechanism for CoAP being standardized by the Internet Engineering Task Force CoRE working group. CoCoA introduces a novel round-trip time estimation technique, together with a variable backoff factor and aging mechanisms in order to provide dynamic and controlled retransmission timeout adaptation suitable for the peculiarities of IoT communications. We conduct a comparative performance analysis of CoCoA and a variety of alternative algorithms including state-of-the-art mechanisms developed for TCP. The study is based on experiments carried out in real testbeds. Results show that, in contrast to the alternative methods considered, CoCoA consistently outperforms the default CoAP congestion control mechanism in all evaluated scenarios.Peer ReviewedPostprint (author's final draft

    A Survey on Congestion Control Protocols for CoAP

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    The Internet of things (IoT) comprises things interconnected through the internet with unique identities. Congestion management is one of the most challenging tasks in networks. The Constrained Application Protocol (CoAP) is a low-footprint protocol designed for IoT networks and has been defined by IETF. In IoT networks, CoAP nodes have limited network and battery resources. The CoAP standard has an exponential backoff congestion control mechanism. This backoff mechanism may not be adequate for all IoT applications. The characteristics of each IoT application would be different. Further, the events such as unnecessary retransmissions and packet collision caused due to links with high losses and packet transmission errors may lead to network congestion. Various congestion handling algorithms for CoAP have been defined to enrich the performance of IoT applications. Our paper presents a comprehensive survey on the evolution of the congestion control mechanism used in IoT networks. We have classified the protocols into RTO-based, queue-monitoring, and rate-based. We review congestion avoidance protocols for CoAP networks and discuss directions for future work

    Advanced Congestion Control Mechanisms for Internet of Things

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    The number of IoT devices is growing at high speed, around 18 billion devices are forecast by 2022. Many of these devices are implemented with simple hardware, with low specifications and low resources. Taking into account the limited hardware resources and the huge network formed by IoT devices, CoAP was born as a lighter application protocol than HTTP. One important task for this scenario is the congestion control of huge networks using simple hardware devices. CoAP implements a simple congestion control solution, but many research articles show that this solution is not very efficient and it could be improved using other congestion control algorithms. CoCoA was born with the aim of being the standard congestion control algorithm for CoAP and has been proven through many studies, that it improves CoAP default performance in several scenarios. However, some research articles show that CoCoA offers low performance in bufferbloat scenarios. This thesis evaluates CoCoA in bufferbloat scenarios and introduces changes on CoCoA algorithm, achieving an improvement on its performance

    FASOR Retransmission Timeout and Congestion Control Mechanism for CoAP

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    The Constrained Application Protocol (CoAP) has been designed to be used on constrained devices such as Internet of Things (IoT) devices. The existing congestion control algorithms for CoAP have known shortcomings in addressing congestion and retaining a good level of performance when link errors occur. In this paper, we propose Fast-Slow RTO (FASOR) mechanism that takes into account special needs in wireless environments while still properly addressing congestion. We run a series of experiments to confirm that FASOR is able to successfully cope with challenging network conditions such as bufferbloat, high level of congestion, and high link-error rates unlike the default and CoCoA congestion control that have severe problems with bufferbloated congestion.Peer reviewe

    End to End Reliability without Unicast Acknowledgements over Vehicular Networks

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    The Future Cities Project (http://futurecities.up.pt/) has turned the city of Porto (Portugal) into an urban-scale living lab, where researchers, companies and startups can develop and test technologies, products and services. One of its largest infrastructures is the UrbanSense testbed, consisting of 25 environmental sensing units installed around the city, and another the BusNet, a vehicular ad-hoc network installed in over 400 STCP buses together with 55 Road Side Units (RSU), operated by the UP spin-off Veniam. The data gathered by UrbanSense is carried by BusNet to a storage facility. Because BusNet does not support unicast addressing, there i currently on means to provide end-to-end reliability to the communication, leading to data losses. The goal of this thesis is to explore possibilities to address this problem, designing an application level protocol that provides reliability to the data transfer without requiring unicast addressing. Instead, the protocol should leverage the knowledge about bus routes and geographic location of sensing nodes to target the delivery of the acknowledgements

    CoAP Infrastructure for IoT

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    The Internet of Things (IoT) can be seen as a large-scale network of billions of smart devices. Often IoT devices exchange data in small but numerous messages, which requires IoT services to be more scalable and reliable than ever. Traditional protocols that are known in the Web world does not fit well in the constrained environment that these devices operate in. Therefore many lightweight protocols specialized for the IoT have been studied, among which the Constrained Application Protocol (CoAP) stands out for its well-known REST paradigm and easy integration with existing Web. On the other hand, new paradigms such as Fog Computing emerges, attempting to avoid the centralized bottleneck in IoT services by moving computations to the edge of the network. Since a node of the Fog essentially belongs to relatively constrained environment, CoAP fits in well. Among the many attempts of building scalable and reliable systems, Erlang as a typical concurrency-oriented programming (COP) language has been battle tested in the telecom industry, which has similar requirements as the IoT. In order to explore the possibility of applying Erlang and COP in general to the IoT, this thesis presents an Erlang based CoAP server/client prototype ecoap with a flexible concurrency model that can scale up to an unconstrained environment like the Cloud and scale down to a constrained environment like an embedded platform. The flexibility of the presented server renders the same architecture applicable from Fog to Cloud. To evaluate its performance, the proposed server is compared with the mainstream CoAP implementation on an Amazon Web Service (AWS) Cloud instance and a Raspberry Pi 3, representing the unconstrained and constrained environment respectively. The ecoap server achieves comparable throughput, lower latency, and in general scales better than the other implementation in the Cloud and on the Raspberry Pi. The thesis yields positive results and demonstrates the value of the philosophy of Erlang in the IoT space

    Is CoAP Congestion Safe?

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    A huge number of Internet of Things (IoT) devices are expected to be connected to the Internet in the near future. The Constrained Application Protocol (CoAP) has been increasingly deployed for wide-area IoT communication. It is crucial to understand how the specified CoAP congestion control algorithms perform. We seek an answer to this question by performing an extensive evaluation of the existing IETF CoAP Congestion Control proposals. We find that they fail to address congestion properly, particularly in the presence of a bufferbloated bottleneck buffer. We also fix the problem with a few simple modifications and demonstrate their effectiveness.Peer reviewe
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