261 research outputs found

    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

    Application Protocols enabling Internet of Remote Things via Random Access Satellite Channels

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    Nowadays, Machine-to-Machine (M2M) and Internet of Things (IoT) traffic rate is increasing at a fast pace. The use of satellites is expected to play a large role in delivering such a traffic. In this work, we investigate the use of two of the most common M2M/IoT protocols stacks on a satellite Random Access (RA) channel, based on DVB-RCS2 standard. The metric under consideration is the completion time, in order to identify the protocol stack that can provide the best performance level

    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

    An Experimental Evaluation of Constrained Application Protocol Performance over TCP

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    The Internet of Things (IoT) is the Internet augmented with diverse everyday and industrial objects, enabling a variety of services ranging from smart homes to smart cities. Because of their embedded nature, IoT nodes are typically low-power devices with many constraints, such as limited memory and computing power. They often connect to the Internet over error-prone wireless links with low or variable speed. To accommodate these characteristics, protocols specifically designed for IoT use have been designed. The Constrained Application Protocol (CoAP) is a lightweight web transfer protocol for resource manipulation. It is designed for constrained devices working in impoverished environments. By default, CoAP traffic is carried over the unreliable User Datagram Protocol (UDP). As UDP is connectionless and has little header overhead, it is well-suited for typical IoT communication consisting of short request-response exchanges. To achieve reliability on top of UDP, CoAP also implements features normally found in the transport layer. Despite the advantages, the use of CoAP over UDP may be sub-optimal in certain settings. First, some networks rate-limit or entirely block UDP traffic. Second, the default CoAP congestion control is extremely simple and unable to properly adjust its behaviour to variable network conditions, for example bursts. Finally, even IoT devices occasionally need to transfer large amounts of data, for example to perform firmware updates. For these reasons, it may prove beneficial to carry CoAP over reliable transport protocols, such as the Transmission Control Protocol (TCP). RFC 8323 specifies CoAP over stateful connections, including TCP. Currently, little research exists on CoAP over TCP performance. This thesis experimentally evaluates CoAP over TCP suitability for long-lived connections in a constrained setting, assessing factors limiting scalability and problems packet loss and high levels of traffic may cause. The experiments are performed in an emulated network, under varying levels of congestion and likelihood of errors, as well as in the presence of overly large buffers. For TCP results, both TCP New Reno and the newer TCP BBR are examined. For baseline measurements, CoAP over UDP is carried using both the default CoAP congestion control and the more advanced CoAP Simple Congestion Control/Advanced (CoCoA) congestion control. This work shows CoAP over TCP to be more efficient or at least on par with CoAP over UDP in a constrained setting when connections are long-lived. CoAP over TCP is notably more adept than CoAP over UDP at fully utilising the capacity of the link when there are no or few errors, even if the link is congested or bufferbloat is present. When the congestion level and the frequency of link errors grow high, the difference between CoAP over UDP and CoAP over TCP diminishes, yet CoAP over TCP continues to perform well, showing that in this setting CoAP over TCP is more scalable than CoAP over UDP. Finally, this thesis finds TCP BBR to be a promising congestion control candidate. It is able to outperform the older New Reno in almost all explored scenarios, most notably in the presence of bufferbloat

    A holistic approach to ZigBee performance enhancement for home automation networks

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    Wireless home automation networks are gaining importance for smart homes. In this ambit, ZigBee networks play an important role. The ZigBee specification defines a default set of protocol stack parameters and mechanisms that is further refined by the ZigBee Home Automation application profile. In a holistic approach, we analyze how the network performance is affected with the tuning of parameters and mechanisms across multiple layers of the ZigBee protocol stack and investigate possible performance gains by implementing and testing alternative settings. The evaluations are carried out in a testbed of 57 TelosB motes. The results show that considerable performance improvements can be achieved by using alternative protocol stack configurations. From these results, we derive two improved protocol stack configurations for ZigBee wireless home automation networks that are validated in various network scenarios. In our experiments, these improved configurations yield a relative packet delivery ratio increase of up to 33.6%, a delay decrease of up to 66.6% and an improvement of the energy efficiency for battery powered devices of up to 48.7%, obtainable without incurring any overhead to the network.Postprint (published version

    Facilitating the creation of IoT applications through conditional observations in CoAP

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    With the advent of IPv6, the world is getting ready to incorporate smart objects to the current Internet to realize the idea of Internet of Things. The biggest challenge faced is the resource constraint of the smart objects to directly utilize the existing standard protocols and applications. A number of initiatives are currently witnessed to resolve this situation. One of such initiatives is the introduction of Constrained Application Protocol. This protocol is developed to fit in the resource-constrained smart object with the ability to easily translate to the prominent representational state transfer implementation, hypertext transfer protocol (and vice versa). The protocol has several optional extensions, one of them being, resource observation. With resource observation, a client may ask a server to be notified every state change of the resource. However, in many applications, all state changes are not significant enough for the clients. Therefore, the client will have to decide whether to use a value sent by a server or not. This results in wastage of the already constrained resources (bandwidth, processing power,aEuro broken vertical bar). In this paper, we introduced an alternative to the normal resource observation function, named Conditional Observation, where clients tell the servers the criteria for notification. We evaluated the power consumption and number of packets transmitted between clients and servers by using different network sizes and number of servers. In all cases, we found out that the existing observe option results in excessive number of packets (most of them unimportant for the client) and higher power consumption. We also made an extensive theoretical evaluation of the two approaches which give consistent result with the results we got from experimentation

    Improvements to end-to-end performance of low-power wireless networks

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    Over the last decades, wireless technologies have become an important part of our daily lives. A plentitude of new types of networks based on wireless technologies have emerged, often replacing wired solutions. In this development, not only the number and the types of devices equipped with wireless transceivers have significantly increased, also the variety of wireless technologies has grown considerably. Moreover, Internet access for wireless devices has paved the way for a large variety of new private, business, and research applications. Great efforts have been made by the research community and the industry to develop standards, specifications, and communication protocols for networks of constrained devices, we refer to as Wireless Sensor Networks (WSNs). The Institute of Electrical and Electronics Engineers (IEEE) defined the 802.15.4 standard for Personal Area Networks (PANs). With the introduction of an adaptation layer which makes IEEE 802.15.4 networks IPv6-capable, interconnecting billions of constrained devices has become possible and is expected to become a reality in the near future. The vision that embraces the idea of interweaving Internet technology with any type of smart objects, such as wearable devices or sensors of a WSN, is called the Internet of Things (IoT). The main goal of this thesis is the improvement of the performance of low-power wireless networks. Given the wide scope of application scenarios and networking solutions proposed for such networks, the development and optimization of communication protocols for wireless low-power devices is a challenging task: The hardware restrictions of constrained devices, specific application scenarios that may vary from one network to another, and the integration of WSNs into the IoT require new approaches to the design and evaluation of communication protocols. To face these challenges and to find solutions for them, research needs to be carried out. Mechanisms and parameter settings of communication protocol stacks for WSNs that are crucial to the network performance need to be identified, optimized, and complemented by adding new ones. The first contribution of this thesis is the improvement of end-to-end performance for IEEE 802.15.4-based PANs, where default parameter settings of common communication protocols are analyzed and evaluated with regard to their impact on the network performance. Physical evaluations are carried out in a large testbed, addressing the important question of whether the default and allowed range settings defined for common communication protocols are efficient or whether alternative settings may yield a better performance. The second contribution of this thesis is the improvement of end-to-end performance for ZigBee wireless HA networks. ZigBee is an important standard for low-power wireless networks and the investigations carried out address the crucial lack of investigation the ZigBee HA performance evaluations through physical experiments and potential ways to improve the network performance based on these experiments. Eventually, this thesis focuses on the improvement of the congestion control (CC) mechanism applied by the Constrained Application Protocol (CoAP) used in IoT communications. For the handling of the possible congestion in the IoT produced by the plethora of the devices and/or link errors innate to low-power radio communications, the default CC mechanism it lacks an advanced CC algorithm. Given CoAP's high relevance for IoT communications, an advanced CC algorithm should be capable of adapting to these particularities of IoT communications. This thesis contributes to this topic with the design and optimization of the CoAP Advanced Congestion Control/Simple (CoCoA) protocol, an advanced CC mechanism for CoAP.The investigations of advanced CC mechanisms for CoAP involve extensive performance evaluations in simulated networks and physical experiments in real testbeds using different communication technologies.En les últimes dècades, les tecnologies sense fils s'han convertit en una part important de la nostra vida quotidiana. Una àmplia varietat de nous tipus de xarxes basades en tecnologies sense fils han sorgit, sovint reemplaçant solucions cablejades. En aquest desenvolupament, no només el nombre i els tipus de dispositius equipats amb transceptors sense fils han augmentat significativament, també la varietat de tecnologies sense fils ha crescut de manera considerable. D'altra banda, l'accés a Internet per als dispositius sense fils ha donat pas a una gran varietat de noves aplicacions privades, comercials i d'investigació. La comunitat científica i la indústria han fet grans esforços per desenvolupar normes, especificacions i protocols de comunicació per a xarxes de sensors sense fils (WSNs). L'Institut d'Enginyeria Elèctrica i Electrònica (IEEE) defineix l'estàndard 802.15.4 per a xarxes d'àrea personal (PAN). Amb la introducció d'una capa d'adaptació que possibilita les IEEE 802.15.4 xarxes compatibles amb IPv6, la interconnexió de milers de milions de dispositius restringits s'ha fet possible. La idea d'entreteixir la tecnologia d'Internet amb qualsevol tipus d'objectes intel·ligents, com els dispositius o sensors d'una WSN és coneguda com la Internet de les Coses (IoT). L'objectiu principal d'aquesta tesi és la millora del rendiment de les WSNs. Donada l'àmplia gamma d'escenaris d'aplicacions i solucions de xarxes proposats per a aquest tipus de xarxes, el desenvolupament i l'optimització dels protocols de comunicació per a dispositius de WSNs és una tasca difícil: les limitacions de capacitats dels dispositius restringits, escenaris d'aplicació específics que poden variar d'una xarxa a l'altra, i la integració de les WSNs a la IoT requereixen nous enfocaments per al disseny i avaluació de protocols de comunicació. Cal identificar mecanismes i configuracions de paràmetres de les piles de protocols de comunicació per a WSNs que són elementals per al rendiment de la xarxa, optimitzar-los, i complementar-los amb l'addició d'altres de nous. La primera contribució d'aquesta tesi és la millora del rendiment extrem a extrem per PANs basat en IEEE 802.15.4, on s'analitza la configuració de paràmetres que es fan servir per defecte en protocols de comunicació comuns i s'avalua el seu impacte en el rendiment de la xarxa. Avaluacions físiques en una xarxa de sensors permeten fer front a la important qüestió de si els valors estàndards dels paràmetres són eficients o si ajustant-los es pot proporcionar un millor rendiment. La segona contribució d'aquesta tesi és l'optimització del rendiment extrem a extrem de xarxes ZigBee domòtiques (HA) sense fils. ZigBee és un estàndard important per a WSNs. Els estudis duts a terme cobreixen la important falta d'investigació d'avaluacions de rendiment de xarxes HA de ZigBee mitjançant experiments físics i mostrant formes per millorar el rendiment de la xarxa en base d'aquests experiments. Finalment, aquesta tesi es centra en la millora del mecanisme bàsic de control de congestió (CC) aplicada pel Constrained Application Protocol (CoAP) utilitzat en les comunicacions de la IoT. És necessari un algoritme de CC avançat per al control de la possible congestió en la IoT produïda per la plètora de dispositius i/o errors d'enllaç naturals per a les comunicacions de ràdio de baixa potencia. Donada l'alta rellevància de CoAP per a les comunicacions en la IoT, un algoritme CC avançat ha de ser capaç d'adaptar-se a les particularitats de les comunicacions de la IoT. Aquesta tesi contribueix al problema amb el disseny i l'optimització Control de Congestió Avançat / Simple del CoAP (CoCoA), un mecanisme de CC avançat per CoAP. Les investigacions de mecanismes de CC avançats per CoAP impliquen avaluacions extenses en xarxes simulades i experiments físics en xarxes reals utilitzant diferents tecnologies de comunicacions

    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

    A survey of communication protocols for internet of things and related challenges of fog and cloud computing integration

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    The fast increment in the number of IoT (Internet of Things) devices is accelerating the research on new solutions to make cloud services scalable. In this context, the novel concept of fog computing as well as the combined fog-to-cloud computing paradigm is becoming essential to decentralize the cloud, while bringing the services closer to the end-system. This article surveys e application layer communication protocols to fulfill the IoT communication requirements, and their potential for implementation in fog- and cloud-based IoT systems. To this end, the article first briefly presents potential protocol candidates, including request-reply and publish-subscribe protocols. After that, the article surveys these protocols based on their main characteristics, as well as the main performance issues, including latency, energy consumption, and network throughput. These findings are thereafter used to place the protocols in each segment of the system (IoT, fog, cloud), and thus opens up the discussion on their choice, interoperability, and wider system integration. The survey is expected to be useful to system architects and protocol designers when choosing the communication protocols in an integrated IoT-to-fog-to-cloud system architecture.Peer ReviewedPostprint (author's final draft
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