164 research outputs found
A Low-Power CoAP for Contiki
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
Enhancing Block-Wise Transfer with Network Coding in CoAP
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
Securing name resolution in the IoT: DNS over CoAP
In this paper, we present the design, implementation, and analysis of DNS
over CoAP (DoC), a new proposal for secure and privacy-friendly name resolution
of constrained IoT devices. We implement different design choices of DoC in
RIOT, an open-source operating system for the IoT, evaluate performance
measures in a testbed, compare with DNS over UDP and DNS over DTLS, and
validate our protocol design based on empirical DNS IoT data. Our findings
indicate that plain DoC is on par with common DNS solutions for the constrained
IoT but significantly outperforms when additional, CoAP standard features are
used such as block-wise transfer or caching. With OSCORE for end-to-end
security, we can save more than 10 kBytes of code memory compared to DTLS while
enabling group communication without compromising the trust chain when using
intermediate proxies or caches. We also discuss a scheme for very restricted
links that compresses redundant or excessive information by up to 70%.Comment: 12 pages, 13 figures, 4 table
Application Protocols enabling Internet of Remote Things via Random Access Satellite Channels
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
Using SCHC for an optimized protocol stack in multimodal LPWAN solutions
Low Power Wide Area Networks (LPWANs) are formed out of cheap, small, interconnected devices which operate in the sub-GHz domain. The last couple of years, many communication technologies arose in this domain, each with its own characteristics. In order to satisfy more diverse requirements, devices are now equipped with multiple LPWAN radio technologies, which requires the use of a unified protocol stack independent of the underlying LPWAN technology. With its 2128 addresses available and its ability to operate over different link layer technologies, the IPv6 protocol stack would be the ideal candidate. However, many LPWAN configurations do not allow standardized IP/UDP communication, sometimes acquiring more header overhead than there is room for the actual payload. Recently, a new initiative to directly connect constrained devices over IP was initiated by the LPWAN working group of the Internet Engineering Task Force (IETF). This work resulted in the Static Context Header Compression or SCHC mechanism. This header compression mechanism is able to compress the overhead of these internet protocols up to 95%. In order to comply with the IPv6 Maximum Transfer Unit (MTU) of 1280 bytes, a fragmentation mechanism is also included. In this work, we validate the benefits of using SCHC for multimodal LPWAN solutions and show its implementation feasibility on such constrained devices
IoT Content Object Security with OSCORE and NDN: A First Experimental Comparison
The emerging Internet of Things (IoT) challenges the end-to-end transport of
the Internet by low power lossy links and gateways that perform protocol
translations. Protocols such as CoAP or MQTT-SN are degraded by the overhead of
DTLS sessions, which in common deployment protect content transfer only up to
the gateway. To preserve content security end-to-end via gateways and proxies,
the IETF recently developed Object Security for Constrained RESTful
Environments (OSCORE), which extends CoAP with content object security features
commonly known from Information Centric Networks (ICN).
This paper presents a comparative analysis of protocol stacks that protect
request-response transactions. We measure protocol performances of CoAP over
DTLS, OSCORE, and the information-centric Named Data Networking (NDN) protocol
on a large-scale IoT testbed in single- and multi-hop scenarios. Our findings
indicate that (a) OSCORE improves on CoAP over DTLS in error-prone wireless
regimes due to omitting the overhead of maintaining security sessions at
endpoints, and (b) NDN attains superior robustness and reliability due to its
intrinsic network caches and hop-wise retransmissions
A Framework for Handling Heterogeneous M2M Traffic
Sensors, actuators and devices that compose the Internet of Things (IoT) world are becoming more diverse every day in terms of capabilities and amount of generated traffic. Current Machine-to-Machine (M2 M) communication standardization efforts try to formalize the interfaces between M2 M nodes based on the perspective of exchanging uniform small data size with low sampling rate only. However, many devices will require support for more heterogeneous traffic patterns, with different network capacity. This paper introduces a communication concept for supporting gracefully a heterogeneous set of devices. This paper analyses the effect of traffic size in M2 M transactions and propose a concept to adapt gracefully to support heterogeneous traffic patterns in M2 M systems. To prove its feasibility, the concept is exemplified on top of oneM2 M architecture and implemented as part of the Fraunhofer FOKUS OpenMTC toolkit. Additionally, the concept was applied to a deployment in an E-Health pilot and practical measurements during functional evaluation are reported
An Experimental Evaluation of Constrained Application Protocol Performance over TCP
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
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