Virgil Dobrota

REST Enabled Wireless Sensor Networks for Seamless Integration with Web Applications

The use of Internet Protocol (IP) technology in Wireless Sensor Network (WSN) is a key prerequisite for the realization of the Internet of Things (IoT) vision. The IPv6 over Low power Wireless Personal Area Networks (6LoWPAN) standard enables the use of IPv6 in networks of constrained devices. 6LowPAN enables the use of Service Oriented Architectures (SOAs) in WSN. The Internet Engineering Task Force (IETF) has defined the Constrained Application Protocol (CoAP), a web transfer protocol which provides several Hypertext Transfer Protocol (HTTP) functionalities, re-designed for constrained embedded devices. CoAP allows WSN applications to be built on top of Representational State Transfer (REST) architectures. This considerably eases the IoT application development and facilitates the integration of constrained devices with the Web. This work describes the prototype design and development of a Web platform which integrates a REST/CoAP WSN with a REST/HTTP Web application and allows a user to visualize WSN measurements in the Web browser. Since the WSN Web integration relies on a non-transparent gateway/server, we also show how to provide transparent cross-protocol resource access by means of an HTTP-CoAP proxy. The paper describes the major building blocks, functionalities and the implementation approach.

Evaluation of constrained application protocol for wireless sensor networks

IPv6 over Low power Wireless Personal Area Networks (6LoWPAN) and IPv6 Routing Protocol for Low-power and Lossy networks (RPL) have accelerated the integration of Wireless Sensor Networks (WSNs) and smart objects with the Internet. At the same time, the development of the Constrained Application Protocol (CoAP) has made it possible to provide resource constrained devices with web service functionalities. CoAP is an HTTP like web transfer protocol able to extend the REpresentational State Transfer (REST) architecture to LoWPANs. The major difference between CoAP and HTTP is the different transport layer protocol (UDP instead of TCP) and the header compression which makes the packet size significantly smaller. This work provides an evaluation of CoAP compared to HTTP. The performance is evaluated in terms of motes energy consumption and response time. The aim of the paper is to demonstrate, with a quantitative and qualitative analysis, that CoAP is more suited to REST based WSNs compared to HTTP. The results have been obtained by means of simulation as well as tests on real sensor motes.

Cross-layer QoS and its application in congestion control

The paper proposes a preliminary design of cross-layer quality of service applied to congestion control in future Internet. This is an alternative solution to QoS-aware routing, whenever the infrastructure operator cannot add new resources, and/or when re-routing is not possible. Dedicated software, running in each node, collects a list of local parameters such as available transfer rate and one-way delay between all neighbors. Then this real-time status information is distributed to all the in-network management enabled nodes that are allowed to be reached. Due to the statistics regarding individual link traffic, a minimal network coding scheme, triggered by cross-layer quality of service, is temporarily activated. This system presents an enhanced distributed routing that preserves the performances of the running services, despite the congestion which cannot be eliminated.

Evaluation of network traffic prediction based on neural networks with multi-task learning and multiresolution decomposition

Network traffic exhibits strong correlations which make it suitable for prediction. Real-time forecasting of network traffic load accurately and in a computationally efficient manner is the key element of proactive network management and congestion control. This paper compares predictions produced by different types of neural networks (NN) with forecasts from statistical time series models (ARMA, ARAR, HW). The novelty of our approach is to predict aggregated Ethernet traffic with NNs employing multiresolution learning (MRL) which is based on wavelet decomposition. In addition, we introduce a new NN training paradigm, namely the combination of multi-task learning with MRL. The experimental results show that nonlinear prediction based on NNs is better suited for traffic prediction purposes than linear forecasting models. Moreover, MRL helps to exploit the correlation structures at lower resolutions of the traffic trace and improves the generalization capability of NNs.

Practical evaluation of H.264 video streaming over IEEE 802.11e devices by cross-layer signaling

Recent years have seen a growing demand for high quality multimedia traffic over wireless links. Due to the strong demands imposed to all the involved actors, several optimization techniques have been proposed and studied, mostly through theoretical analysis and simulation. In this article we focus on the practical evaluation of H.264 video streaming performance over IEEE 802.11e wireless devices. Measurement results present the effects of employing several key mechanisms which aim to improve the transmission quality over the wireless medium. A cross-layer signaling solution between the application and the MAC layers is implemented, in order to account for the different QoS characteristics of video and elastic traffic. In addition, network support for efficient multiqueue transmission is enabled in the Linux wireless card driver. Measurements also illustrate the effects of changing several H.264 and IEEE 802.11e parameters in the player and driver software.

Steps towards native IPv6 multicast: CastGate router with PIM-SM support

The paper presents a testbed for native IPv6 multicast and tries to evaluate the available routing protocols such as PIM-DM and PIM-SM. From an objective perspective we can measure the join latency, as well as multicast forwarding delay, its jitter and the control overhead. Having a calibrated software tool, we can evaluate later the existing alternative solution towards IPv6 multicast: CastGate and CastGate router. The proposed enhancements are referring to PIM-SM support and to the possibility of migrating from IPv4 to IPv6 on CastGate architectures

An OpenNetInf-based cloud computing solution for cross-layer QoS: Monitoring part using iOS terminals

This paper presents a monitoring application for quality of service parameters, called iQoSStats, dealing with Available Transfer Rate and One-Way Delay. The tool is running on iOS5-based iPad terminal. Due to the lack of Java support, a proxy server is needed to allow the connection to the cloud computing solution based on OpenNetInf. It relies on an information-centric communication paradigm and provides large-scale information dissemination. The intention was to use this infrastructure to support cross-layer QoS for the Future Internet.

fHA: A flexible and distributed Home Agent architecture for Mobile-IP based networks

Home Agents (HAs) represent a single point of failure in Mobile IP-based networks. In order to address this issue, researchers have proposed the deployment of redundant HAs on each sub-network. Although these approaches effectively mitigate this problem, they do not take into consideration the requirements of large networks with dozens of sub-networks. Both deploying and managing several HAs on each sub-network could prove to be too expensive. In this paper we present a novel HA architecture that only requires one set of HAs for the whole network. Our basic idea is that the location of mobile nodes can be announced to exit routers. This way, forwarding packets can be done without involving the HA. Our solution provides the same level of reliability as existing ones, while improving overall performance. We validate the proposed architecture by comparing its performance with that of a standard HA, using three network traffic traces collected in different networks. Our results show that, besides the architectural benefits, the proposed architecture would forward roughly 90% less traffic in a Mobile IPv4/NEMO network, and 15% less in a Mobile IPv6 one, when compared to a standard HA.

The Management Infrastructure of a Network Measurement System for QoS Parameters

The paper presents the designing principles of a management infrastructure for monitoring the capabilities of different network interface cards (gigabit Ethernet, Endace), both for traffic generation and capturing at reception. This evaluation is useful to asses the goodness of captured traffic analysis and QoS performance measurements, using PC based platforms. The idea was to implement the communication of the management information between an administration console and a set of distributed SNMP-based software measurement agents for GNU/Linux platforms that enable to perform QoS measurement sessions

On the impact of indirect WAN routing on geo-replicated storage

Micro-clouds infrastructures allow supporting applications on local and energy-efficient resources. Communication between micro-clouds takes place on shared and non-dedicated Internet links. Network control and optimization can only happen at the edge. For availability and persistence, the storage of application data must be geo-replicated. Maintaining strong data consistency under concurrent accesses requires delay-sensitive coherence protocols, linking the performance of the storage to that of the network between micro-clouds. We evaluate if the use of network control at the edge of a European-wide multi-site testbed, together with appropriate network monitoring, can allow improving the performance of ZooKeeper, a strongly-consistent replicated store. Our approach leverages the indirect routing of coherence protocol traffic in the presence of network triangle equality violations. We analyze the impact on storage of variations in WAN performance, and show how the use of traffic redirection can help reducing it.