Walter Colitti

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.

Comparison of two lightweight protocols for smartphone-based sensing

Smartphones are equipped with numerous sensors and have become sophisticated sensing platforms. However, several sensing applications running on a smartphone can degrade the device performance. This can be overcome by using lightweight application protocols which improve the smartphone performance in terms of bandwidth consumption, battery lifetime and communication latency. This work focuses on two emerging application protocols: the Message Queuing Telemetry Transport (MQTT) and the Constrained Application Protocol (CoAP). Although both protocols have been designed for highly constrained environments such as sensors, they are also appropriate to be adopted in smartphone applications. We provide a qualitative and quantitative comparison between MQTT and CoAP when used as smartphone application protocols and we give preliminary indications on the application scenarios in which either protocol should be adopted. While MQTT has already been adopted in smartphone applications, CoAP is relatively new and has up to now mainly been considered for sensors and actuators. Our comparison shows that CoAP can be a valid alternative to MQTT for certain application scenarios.

Satellite based wireless sensor networks: global scale sensing with nano- and pico-satellites

Space and Earth monitoring is the next step for sensor networks. Distributed systems of small sensor-equipped satellites improve the cost efficiency and the missions performance. This abstract discusses the characteristics of satellite Wireless Sensor Networks (WSNs) and the challenges they introduce.

Comparative performance study of RPL in Wireless Sensor Networks

In order to enable the interoperability of the IP-based WSNs with the Internet, the Internet Engineering Task Force (IETF) chartered the IPv6 over Low power Wireless Personal Area Networks (6LoWPAN) and Routing Over Low power and Lossy networks (RoLL) working groups. The working group has been standardizing an IPv6 routing protocol for Low-power and Lossy Networks (RPL). This paper presents a comprehensive study of the performance of RPL when compared with Collection Tree Protocol (CTP). The aim of this work is to show the superiority of RPL in network scalability. Our results describe the benefit of RPL in terms of high Packet Reception Ratio (PRR) and low energy consumption. We also highlight the advantages in the design of the protocol, which can be used in further investigation of RPL.

Integrated routing in GMPLS-based IP/WDM networks

The Internet traffic evolution has forced network operators to migrate toward an integrated infrastructure which brings the IP and optical layers under a unified model. The integration between the two technologies has been facilitated by the development of the Generalized Multi Protocol Label Switching. In the integrated scenario, Multilayer Traffic Engineering can be reinforced with integrated routing techniques. Integrated IP/WDM routing facilitates the routing decision phase by allowing a node to have a complete knowledge of the IP and WDM domains when accommodating traffic. This study focuses on integrated IP/WDM routing. We analyze two basic policies widely discussed in literature: one policy prioritizes the traffic accommodation on the virtual topology, while the other prioritizes the traffic accommodation on the physical topology. We show that both the mechanisms do not lead to efficient resource utilization because they tend to congest one layer more than the other one. We propose an adaptive heuristic which combines the advantages of both the policies. When accommodating traffic, the proposed approach selects the appropriate layer depending on the resource utilization being experienced in the virtual and the physical topologies. We demonstrate via simulations that the cross-layer resource optimization executed by the proposed scheme achieves significant improvements in terms of blocking ratio.

Adaptive multilayer routing in the next generation GMPLS Internet

The Automatically Switched Optical Networks (ASONs) and the Generalized Multi Protocol Label Switching (GMPLS) control plane are envisaged to play an important role in the next generation Internet. They provide optical networks with intelligence and automation and they enable the Multilayer Traffic Engineering (MTE) paradigm which facilitates the IP/optical adaptive integrated routing. This paper proposes an adaptive strategy for integrated routing. The routing decision is based on the network state. The strategy either sets up a new lightpath or grooms traffic on the existing virtual topology depending on the resource utilization level experienced on the IP and optical layers. To reduce the quantity of control information, we also propose and evaluate a heuristic that overcomes scalability problems at the expenses of less optimal performance. The proposed strategies are evaluated by means of simulation and they are compared with two non adaptive routing policies widely investigated in literature.

Maximum flow based Routing and Wavelength Assignment in all-optical networks

This paper presents a new routing and wavelength assignment (RWA) strategy for WDM optical networks. This new strategy is based on a maximum flow computation and it is particularly useful when we consider optical networks with limited wavelength conversion capability. We use a simple topology transformation combined with a flow-network representation to solve the RWA problem without decoupling routing from wavelength assignment. Results and comparisons show that the max-flow based RWA strategy outperforms, in terms of blocking probability, other state-of-the-art strategies.

Applying routing policy differentiation for diverse QoS degrees in multi-domain optical networks

IP/MPLS based ASON/GMPLS networks enable the interaction between the IP layer and the optical WDM layer. Furthermore, it decouples the physical topology from the dynamically created IP topology, which is called Virtual Topology. In this network architecture, there are two known routing policies, they are the Physical Topology First (PTF) and Virtual Topology First (VTF). PTF and VTF are different in the order of actions taken to accommodate a new connection request. PTF will first try to set up a new lightpath in the optical plane while VTF will first try to groom the traffic imposed by the new connection on the virtual plane. The combination of both routing policies provides the opportunity for multilayer traffic engineering (MTE). Additionally the incorporation of both routing policies improves the Quality of Service (QoS) in both IP and WDM optical layers. The challenge being that both routing policies have been applied in the single domain network scenario, while the application of both routing policies in the optical multilayer multi-domain networks scenario has not been deeply investigated. In this paper we try to combine these routing policies VTF/PTF with the traffic priority level to support a degree of QoS differentiation in an integrated routing scheme. We use PTF routing policy to accommodate High Priority (HP) traffic and VTF to accommodate the Low Priority (LP) traffic. The Internet consists of more than 29.000 domains, therefore applying a multilayer routing methodology in a multi-domain scenario is required. In this work we apply a two level hierarchical routing scheme, which adapts the Full Mesh (FM) topology abstraction algorithm in order to support multilayer routing in optical multi-domain networks.

Service differentiation in IP/MPLS over ASON/GMPLS networks

There is a general agreement that the future infrastructure for broadband communications will consist of Automatically Switched Optical Networks (ASONs) controlled by the Generalized Multi-Protocol Label Switching (GMPLS) control plane. Due to the convergence of most services on the Internet Protocol (IP) layer, ASON/GMPLS networks need to provide transport for a variety of applications having different Quality of Service (QoS) requirements. This implies that the Differentiated Service paradigm, which improves the QoS in pure IP networks, needs to be extended to the new underlying infrastructure. This article proposes and compares three schemes for the service differentiation in IP/MPLS over ASON/GMPLS networks. Simulation results demonstrate that a fair trade-off between QoS and resource utilization is achieved when combining routing policy differentiation (RPD), virtual topology differentiation (VTD), and virtual topology sharing (VTS) techniques. The RPD technique decides on the multilayer routing policy to apply depending on the Class of Service (CoS). The VTD technique transports different CoS over different independent virtual topologies. The VTS technique introduces a certain degree of resource sharing among the different virtual topologies.