Wireless Sensor Networks and Software Defined ...

Wireless Sensor Networks and Software Defined Networks Integration Abdel Nasser Zaied, Ehab Rushdy Mohamed, Mohamed Nosseir Hemdan

Wireless Sensor Networks and Software Defined Networks Integration 1

Abdel Nasser Zaied, 1Ehab Rushdy Mohamed, 1,2Mohamed Nosseir Hemdan 1

Faculty of Computers and Informatics, Zagazig University Faculty of Information Technology and Computer Sciences, Sinai University

2

[email protected], [email protected], [email protected]

Abstract Use of Wireless Sensor Networks has been extended late to cover a wide range of different fields such as home automation, smart city, health care monitoring, environmental sensing, etc. Sensor nodes send the collected data to the gateway which ,in turn, links the Wireless Sensor Networks with other networks so that storing, visualizing, and analyzing data can be easily achieved. With the release of Software Defined Networks that separate the control and the data planes, the complexity of networks configuration and management is reduced relatively. Required network services run as applications that manage data flow and control network devices. This would be the first step to integrate Wireless Sensor Networks with Software Defined Networks implementing them both in a unified system. This integration could ease the process of analyzing data, monitoring data flows, redirecting the traffic automatically if it is needed, enhancing security and Quality of Service, and aggregating various Wireless Sensor Networks. Experimentally, this integration is done through three phases. In the first phase, a physical Wireless Sensor Network is implemented by using an open source Raspberry Pi and Arduino. In the second phase, a virtual Software Defined Network is designed by using an open source network emulator Mininet, an OpenDayLight controller and a web server. And in the last phase, the physical Wireless Sensor Network and a virtual Software Defined Network are interlaced together. The integrated network topology and the design of hardware and software components are provided in details in this work. A web application is developed to display the stored data and real-time readings of sensors. Samples of measurement results are also presented in this work to show how useful o the integrated network may be.

Keywords: Wireless Sensor Networks, Software Defined Networks, integration, Raspberry pi, Arduino, Mininet, OpenDayLight.

1. Introduction For The sensor node is one of the main parts of a Wireless Sensor Networks (WSN). Sensors are attached to a lot of objects such as smart phones, vehicles, robots and so on. A sensor is placed where we need to monitor and interact with the environment [1]. Sensor node contains simple processing, storage, sensing, and communication capabilities as shown in figure 1.

Figure 1 The sensor node hardware components

International Journal of Digital Content Technology and its Applications(JDCTA) Volume11, Number4, Dec. 2017

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WSN consists of two components; a generic sensor node and a gateway. A generic sensor node is responsible for measuring different physical parameters such as temperature, light, humidity, pressure, velocity, acceleration, acoustics, etc. Gateway node is responsible for collecting data from generic sensors and for sending them to the base station [2]. WSN is deployed in structured and in unstructured way. In a structured WSN, the sensor nodes are deployed in a pre-planned manner. In unstructured WSN, the sensor nodes are deployed randomly by placing them into the field in an ad hoc manner. WSN is classified according intended application. The most popular network topologies in WSN are star, tree, and chain network topology as shown in figure 2.

Figure 2 Wireless Sensor Networks topologies Sensor nodes send the collected data to the gateway. The gateway links the WSN with other networks so that visualizing and analyzing data can be easily achieved. Dir ect (single-hop) communication between the gateway and all sensor nodes may become feasible in small sensor networks where sensor nodes and a gateway are in close proximity. On the other hand, an indirect (multi-hop) communication approach may be applicable in large sensor networks. That is, sensor nodes must not only generate and disseminate their own information, but also, they serve as relays or forwarding nodes for other sensor nodes. The process of establishing paths from a source to a specific destination (e.g., a gateway device) across one or more relays is called routing [3]. WSN may be store the collected data in local or remote servers. Combining WSN technology with Cloud environments helps in managing remotely connected sensor nodes and the data generated by these sensor nodes. For security and easy access of data, cloud computing is widely used in distributed/mobile computing environment [4]. WSN is the key technology for Internet of Things (IoT) applications. WSN also has many useful applications in agriculture such as smart irrigation system that is used to improve kiwi production in Italy, smart city such as snow and ice monitoring in UK winter highways and smart environment such as flood prevention [5]. All of these applications generate a hug e amount of data and this data can serve many purposes. Software Defined Networks (SDN) is an emerging networking paradigm that seeks to change the limitations of traditional network infrastructures by decoupling the control and data planes. This separation produces a more flexible, innovative, cost-efficient and programmable network architecture. The network switches become simple forwarding devices and the control logic is implemented in a logically centralized controller, simplifying policy enforcement a nd network (re) configuration and evolution [6]. SDN consists of SDN controller that represents the control logic, SDN switches that instructed by the controller to handle packets, and end devices that is the ordinary personal computer or laptop, as shown in figure 3 [6].


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Figure 3 Software Defined Networks architecture SDN controller is the core of the SDN network. It uses protocols such as OpenFlow to control network devices. It provides a set of Application Programing Interfa ces (APIs) that simplifies the implementation of common network services as routing, access control, traffic engineering, QoS, etc. [7]. SDN controllers may be open source or commercial controllers. The open source controllers are such as Pox [8], Floodlight [9], Ryu [10] and OpenDayLight [11], and the commercial controllers are available by different manufactures such as NEC, IBM and HP [12]. OpenDaylight Controller is an open source SDN controller hosted by Linux Foundation. It is used for building programmable networks and it is mainly supported by community. It enables developers to observe and manage the controller via web applications and to write their applications using Java programming language [11]. SDN switches are considered as forwarding devices. They have well-defined instruction sets (e.g., flow rules) used to take actions on the incoming packets (e.g., forward to specific ports, drop, forward to the controller, rewrite some header). These instructions are defined by southbound interfaces (e.g., OpenFlow [13], ForCES [14]) and are installed in the forwarding devices by the SDN controllers. SDN switches may be an open source software switch or a commercial hardware switch. The open source software switches such as Open vSwitch (OVS), Indigo, LIN C, and Pantou. The commercial hardware switches are available by different manufactures such as Pica8, Cisco, Juniper, NEC, HP, Extreme, Brocade, Arista, and IBM. Open vSwitch is a production quality and a multilayer virtual switch. OVS is designed to meet the requirements of the open source community. It supports standard management interfaces and protocols (e.g. OpenFlow, 802.1ag, CLI, NetFlow, sFlow) [15]. It can operate as a software switch running within hypervisor such as VMware, and as the control st ack for switching silicon. OVS can be managed and controlled by third party controllers (e.g. OpenDaylight, POX, Ryu). OVS can be integrated with SDN and has many deployments in data centers [16]. SDN has many deployed applications such as network optimizer, network visualizer and network protector [17]. The rest of this paper is organized as follows. The main approaches for WSN and SDN are discussed in Section 2. Then, system architecture is presented in Section 3. The design of hardware and software components is described in Section 4. The experimental results are presented in Section 5. Finally, in Section 6, the conclusions are drawn.


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2. Related Work There are many efforts did in designing Wireless Sensor Network systems. For example, in [18] a development for low-cost WSN system using Raspberry Pi and Arduino is introduced. The research integrates the gateway, database server, and web server into one single low-power computer Raspberry Pi. With advent of Software Defined Networks, some of network emulation tools is presented. In [19] Mininet is discussed as an open source Network emulation software whose switches are programmed using the Open-Flow protocol. Software Defined Network design that run on Mininet can be easily transferred to hardware Open-Flow Switches for line rate packet forwarding. The program that run on Mininet can send packet with a given link speed and delay through an interface which look like a real Ethernet interface. Packets get processed by an interface which looks similar to actual Ethernet switch, router or middlebox. Mininet’s virtual hosts, switches, links, and controllers are programmable items which look like real hardware items. Recently, many researches have been proposed to extend the OpenFlow approach to the wireless sensor networks domain. In [20] the first initiative to apply the SDN concept to WSN, a novel idea is presented to exploit the OpenFlow technology by proposing Flow-sensor which is OpenFlow based sensor claimed to be much more reliable in comparison to typical sensor nodes since data packets, control packets and the sensor nodes themselves can be easily monitored, regulated and routed whenever required. In [21] Sensor OpenFlow (SOF) is discussed to make the underlying network (i.e., data plane) programmable by manipulating a user-customizable flow table on each sensor via SOF to solve the inherit problems in WSN. The researchers introduce solutions as redefine a flow table to suitable for the special addressing scheme in WSN or augment WSN with IP. In [22] TinySDN is presented to enable multiple controllers within the WSN. Experiments were conducted on COOJA simulator, and results concerning delay and memory footprint are also presented. In [23] the first real implementation of an OpenFlow-like solution for WSNs is presented. A prototype of SDNWISE, SDN solution for WIreless SEnsor networks has been implemented. Such implementation contains the modules that allow a real SDN Controller to manage an OMNeT++ simulated network. Finally, the paper illustrates the results obtained through an experimental testbed which has been developed to evaluate the performance of SDN-WISE.

3. System Architecture Many of the discussed solutions deal with the WSN as an individual network. With time passing, we may have more and more WSN networks, so the data could be difficult to be analyzed and the sensor nodes may be difficult to be managed. With the advent of SDN, many of the discussed solutions adopt the SDN approach and apply OpenFlow-like solutions to sensor nodes. This work suggests applying some of the SDN features to WSN by integrating them. This integration will open a window toward innovation in many fields by using centralized management. It centralizes data store to facilitate retrieving and analyzing data, builds various security applications to secure the WSN data, allows Big Data analytics to simplify the work by centralization of data store, eases the integration with Cloud and builds a new road towards integrating IoT applications with SDN networks. Overall system architecture is a WSN network that consists of two sensor nodes and a gateway, and SDN network consists of SDN switch, SDN controller, and server as shown in figure 4. The sensor nodes sense the environment parameters and send it to the gateway, so it sends data to server that is located in the SDN network. The data pass through an Open Vswitch before accessing the server. In turn, Open Vswitch sends data to the destination according to flow rules that is installed in the switch by SDN controller.


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App

App

SDN Controller SDN Network Devices

SDN Network

App

Server

Sensor Node 1

Sensor Node 2

WSN Network

WSN Gateway

Figure 4 Overall system architecture

4. Design of Hardware and Software Components The proposed network consists of two parts; the first is designed physically using real WSN network devices (e.g. Arduino, Raspberry Pi), and the second is conducted virtually on the SDN network emulator Mininet [24] to emulate the SDN network. The two networks have been integrated together as shown in figure 5. The simulation has been run on laptop (1) whose specifications is presented in table 1.

Remote Controller

SDN Network Web Server Open vSwitch

GW

WSN Network

Temp. Sensor

Humidity Sensor

Figure 5 WSN and SDN integrated topology


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Table 1

Laptop (1) specifications

Specifications

Laptop (1)

Processor Hard Drive RAM

2.3 GHz Intel Core i5-4200 500 GB 4 GB

4.1 Design of WSN Network WSN network consists of two sensors and a gateway. Sensors are prepared using an open source Arduino Uno R3 [25] that enables researchers to create intelligent electronic objects. Arduino Uno R3 specifications is presented in table 2. Gateway is a Raspberry Pi 3 Model B [26] that is a series of low-cost computers developed by the Raspberry Pi Foundation to help in developing countries. Raspberry Pi 3 Model B specifications is presented in table 3. Table 2

Arduino Uno R3 specifications

Specifications

Arduino Uno R3

Microcontroller Clock Speed Flash Memory SRAM EEPROM Analog Input Pins Digital I/O Pins

ATmega328P 16 MHz quartz crystal 32 KB 2KB 1KB 6 pins 14 pins

Table 3

Raspberry Pi Model B specifications

Specifications

Raspberry Pi 3 Model B

Processor Chipset RAM Storage USB 2.0 Ethernet Port Wireless LAN Bluetooth GPIO Power Draw/Voltage

1.2GHz 64-bit quad core ARMv8 1GB Micro SD 4 Ports Yes 802.11n Yes 40 pins 1.8A at 5V

4.1.1 Design of Sensor Nodes Arduino Uno R3 boards are attached to two types of sensors. The first sensor is an analog sensor named LM35DZ temperature sensor, and the second sensor is a digital sensor named DH11 temperature humidity sensor module. Breadboard and different jumper wires are used to attach sensors with Arduino boards. Arduino Uno supports ZigBee, XBeePro S2b from Digi [27], which operates at 2.4 GHz ISM band for a wireless communication. Using Arduino IDE, two applications have been developed using ArduinoC programming language to collect different parameters from the environment and send the gathered data to the gateway so that it can be sent to data store.


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Each sensor node senses the environment physical parameter and send the data to gateway at periodic time interval of 5 seconds. The transmitted data include sensor ID, type of measurement data (Temperature or Humidity), and the value of measurement. LM35DZ Temperature sensor is programmed to sense temperature parameter and it is given ID number 4009. DH11 is programmed to sense humidity parameter and it is given ID number 4010.

4.1.2 Design of Gateway Raspberry Pi 3 Model B represents the gateway. It supports different Linux distributions (e.g. OpenElec, Raspbian, Kali Linux, ROS and NOOBS). In this case, Raspbian OS is installed. An application on Raspberry Pi is developed using Python programming language to receive data from the sensor nodes and send it through an Ethernet cable to the database that located in the virtual SDN network on a laptop as shown in figure 6. Raspberry Pi is prepared to login remotely to the desktop using Virtual Network Computing (VNC) viewer. It i s given a static IP 192.168.0.111 and subnet mask 255.255.255.0.

Figure 6 Physical WSN network

4.2 Design of SDN Network SDN network topology is emulated on Mininet. It is created to be a multilayer Open Virtual Switch (Open vSwitch) connected to a remote SDN controller, a web server, and a physical WSN as shown in figure 7.


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Figure 7 Virtual SDN topology

4.2.1 Design of Switch Open vSwitch runs OpenFlow protocol. It can be instructed by the controller and it has one or more flow tables to handle packets.

4.2.2 Design of Controller The SDN controller is an OpenDaylight controller which is used to manage flow control. It is hosted on laptop (2) which is located on LAN. Laptop (2) specifications is presented in table 4. The SDN controller is given an IP 192.168.1.9 and subnet mask 255.255.255.0. Layer 2 switching feature is enabled. Table 4

Laptop (2) specifications

Specifications

Laptop (2)

Processor

2.5 GHz Intel Core i5

Hard Drive

500 GB

RAM

4 GB

4.2.3 Design of Web Interface The web server was simulated as a virtual machine on Oracle Virtualbox hypervisor. It includes a relational database management system MYSQL used to store the collected data from sensors. Database is prepared to hold an incremental unique ID for each data record, sensor ID, type of data measurement, value of measurement, and date and time of measurement. The server is given a static IP 192.168.0.125 and subnet mask 255.255.255.0 so it can be reached by WSN sink node (Gateway) and other devices in the network such as personal computer, laptop or smart phone. A web application is developed to preview sensor data and statistics. It presents the data collected in tables, charts and real-time display. The client-side web interface is developed using HTML, CSS, JavaScript, Ajax, jQuery, and Flot. The web services of the server-side are written in PHP.


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A web application includes Sensor Data tab that is prepared to preview all the data that inserted into the database, Chart tab that is prepared to preview the measured values from database according to the record ID, and Real-Time tab that is prepared to preview real-time data updates according to time change. The user has to choose between different measurements temperature or humidity- from Chart tab and Real-Time tab as shown in figure 8.

Figure 8 Web interface displays sensor’s data

4.3 Technical Challenges Some of the technical challenges that face preparing this architecture are: ▪ SDN is a new technology that is very limited materials, since no previous solutions are presented to achieve such integration. ▪ An open source SDN network emulator is required while SDN devices are costly. ▪ There is no integrated software can support SDN and WSN together to achieve this simulation. ▪ The difficulty of integrating two different networks that are simulated in differen t simulators. ▪ Various electronic boards to build a WSN are available in the market, so the researcher has to choose materials carefully regarding cost and power. ▪ It is difficult to connect the virtual switch of SDN network to the real gateway of WSN network. This connection transfers the data gathered from WSN network to the data store located in SDN network. ▪ Each electronic board requires a different application using a different programming language [25] [26].

5. Experimental Results 5.1 Test Scenario Description OpenDayLight controller is used to manage and control the network. Figure 9 shows the topology displayed on the controller using the OpenDaylight User Interface (DLUX). The topology displayed is an Open vSwitch connected to three hosts, the p hysical gateway of WSN, the virtual web server, and the physical laptop (1). Figure 10 shows the statistics of sending packets between gateway and database on the controller window.


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Figure 9 The displayed topology on OpenDayLight controller

Figure 10 Node Connector statistics on OpenDayLight controller

The data collected by sensor nodes is stored in a relational database management system MYSQL as shown in figure 11. The database includes a number of fields; ID field that is an incremental unique ID for each data record, MoteID field that represents sensor ID (4009 for temperature sensor and 4010 for humidity sensor), Des field that represents the type of measurement such as temperature or humidity, Value field that represents the value of measurement, and Time field that represents time and date of measurement. Each sensor node sends a data packet to database every 5 seconds.


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Figure 11 WSN MYSQL database The web application shows the data stored in database. The data is represented in a table that shows serial number of packet, sensor ID, type of measurement, value of measurement, and date and time of measurement as shown in figure 12.

Figure 12 WSN web interface

The web application shows the data of the temperature and humidity sensors represented in chart and real-time readings as shown in figure 13.


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Figure 13 Web application shows sensor’s data

5.2 Results The system operates for 10 minutes and the results are measured as the following: ▪ Each sensor node is programmed to send one data packet to the gateway e very 5 seconds. ▪ Total number of packets = simulation time in seconds / time elapsed to send one packet in seconds. This means that each sensor node sends (10 * 60)/5=120 packets. ▪ According to the measurements, the total number of packets that is stored i n the database is 237 packets. This takes 10 minutes. ▪ Two sensor nodes operate. So, each sensor node has 237/2 ≈ 118 packets. This means that the reliability of this system is 99%.

6. Conclusion Wireless Sensor Networks have become very popular recently. It has many applications in different fields such as home automation, health care monitoring, environmental sensing, etc. Data collected from Wireless Sensor Networks may be stored, monitored and visualized easily. Software Defined Networks introduce new solutions challenging the traditional networks limitations by decoupling the control and data planes. Software Defined Networks allow us to control network devices via an application that is running on a controller. In this work, the first integration between WSN and SDN has been implemented to apply the features of them both. This integration could ease analyzing data, monitoring the data flow, redirecting the traffic automatically, enhancing security and Quality of Service, and aggregating various Wireless Sensor Networks. The integrated system consists of real WSN and virtual SDN; real WSN with two sensor nodes and one gateway, virtual SDN with a controller, SDN switch, and a web server. The two sensor nodes sense temperature and humidity parameters from the environment and send data via the gateway which sends the data collected to the web server through SDN switch. A web application is developed to display the stored data or real -time readings of sensors. Samples of measurement results are presented to show how useful the integrated network is. Future work is destined to increase the number of sensor nodes to check the stability of this system in large networks and to develop a security application on the top of controller to protect WSN from possible attacks.


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