Internet of Things (IoT) devices are widely used in many industries including smart cities, smart agriculture, smart medical, smart logistics, etc. However, Distributed Denial of Service (DDoS) attacks pose a serious threat to the security of IoT. Attackers can easily exploit the vulnerabilities of IoT devices and control them as part of botnets to launch DDoS attacks. This is because IoT devices are resource-constrained with limited memory and computing resources. As an emerging technology, Blockchain has the potential to solve the security issues in IoT. Therefore, it is important to analyse various Blockchain-based solutions to mitigate DDoS attacks in IoT. In this survey, a detailed survey of various Blockchain-based solutions to mitigate DDoS attacks in IoT is carried out. First, we discuss how the IoT networks are vulnerable to DDoS attacks, its impact over IoT networks and associated services, the use of Blockchain as a potential technology to address DDoS attacks, in addition to challenges of Blockchain implementation in IoT. We then discuss various existing Blockchain-based solutions to mitigate the DDoS attacks in the IoT environment. Then, we classify existing Blockchain-based solutions into four categories i.e., Distributed Architecture-based solutions, Access Management-based solutions, Traffic Control-based solutions and the Ethereum Platform-based solutions. All the solutions are critically evaluated in terms of their working principles, the DDoS defense mechanism (i.e., prevention, detection, reaction), strengths and weaknesses. Finally, we discuss future research directions that can be explored to design and develop better Blockchain-based solutions to mitigate DDoS attacks in IoT.

The Internet of Things (IoT) is aimed to provide efficient and seamless connectivity to a large number of low-power and low-cost embedded devices, consequently, the routing protocols play a fundamental role in achieving these goals. The IETF has recently standardized the IPv6 Routing Protocol for Low Power and Lossy Networks (RPL) for LLNs (i.e., Low-power and Lossy Networks) and is well-accepted among the Internet community. However, RPL was proposed for static IoT devices and suffers from many issues when IoT devices are mobile. In this paper, we first present various issues that are faced by the RPL when IoT devices are mobile. We then carry out a detailed survey of various solutions that are proposed in the current literature to mitigate the issues faced by RPL. We classify various solutions into five categories i.e., ‘Trickle-timer based solutions’, ‘ETX based solutions’, ‘RSSI based solutions’, ‘Position-based solutions’, and ‘Miscellaneous solutions’. For each category of these solutions, we illustrate their working principles, issues addressed and make a thorough assessment of their strengths and weaknesses. In addition, we found several flaws in the performance analysis done by the authors of each of the solutions, e.g., nodes mobility, time intervals, etc., and suggest further investigations for the performance evaluations of these solutions in order to assess their applicability in real-world environments. Moreover, we provide future research directions for RPL supporting various real-time applications, mobility support, energy-aware, and privacy-aware routing.

Address Resolution Protocol (ARP) is a widely used protocol that provides a mapping of Internet Protocol (IP) addresses to Media Access Control (MAC) addresses in local area networks. This protocol suffers from many spoofing attacks because of its stateless nature and lack of authentication. One such spoofing attack is the ARP Cache Poisoning attack, in which attackers poison the cache of hosts on the network by sending spoofed ARP requests and replies. Detection and mitigation of ARP Cache Poisoning attack is important as this attack can be used by attackers to further launch Denial of Service (DoS) and Man-In-The Middle (MITM) attacks. As with traditional networks, an ARP Cache Poisoning attack is also a serious concern in Software Defined Networking (SDN) and consequently, many solutions are proposed in the literature to mitigate this attack. In this paper, a detailed survey on various solutions to mitigate ARP Cache Poisoning attack in SDN is carried out. In this survey, various solutions are classified into three categories: Flow Graph based solutions; Traffic Patterns based solutions; IP-MAC Address Bindings based solutions. All these solutions are critically evaluated in terms of their working principles, advantages and shortcomings. Another important feature of this survey is to compare various solutions with respect to different performance metrics, e.g., attack detection time, ARP response time, calculation of delay at the Controller etc. In addition, future research directions are also presented in this survey that can be explored by other researchers to propose better solutions to mitigate the ARP Cache Poisoning attack in SDN.

Higher education for sustainable development (HESD) plays a key role in achieving the United Nations’ 17 Sustainable Development Goals (SDGs). This research study specifically examined HESD in terms of eLearning initiatives in Australian private higher education providers from the perspective of teachers. A qualitative structured interview method was adopted wherein 10 teachers were interviewed in order to gain an understanding of their general knowledge of HESD, their attitudes and experience towards HESD, their teaching practices related to HESD, and their understandings of strategy as well as planning initiatives for their institution. The main findings suggest that (1) teachers in private higher education providers tend to have a limited knowledge of sustainability concepts and limited experience in teaching sustainability; (2) eLearning can be a valuable approach in teaching sustainability, but this approach presents teachers with challenges such as student engagement; and (3) private higher education providers require proper resources and governance frameworks in order for any sustainability initiative to be successful. This research highlights the resourcing aspect of private higher education providers in training staff, developing learning materials, and developing practical guidelines to achieve the SDGs by 2030.

IEEE 802.11ac is an emerging standard that operates in 5GHz frequency band and provides high data rate as compared to IEEE 802.11n. In this paper we carry out experiments in a real indoor environment and quantify the gain in average throughput provided by IEEE 802.11ac compared to IEEE 802.11n in the presence of interference caused by other IEEE 802.11n sources. The experiments are performed for both Line of Sight (LoS) and Non-Line of Sight (NLoS) conditions. We note that IEEE 802.11n (2.4GHz) provides the worst average throughput due to the highly congested 2.4GHz frequency band in our experimental environment. We find that IEEE 802.11n (5GHz) with 40MHz channel width provides a gain of 36% in average throughput compared to 20MHz channel width at a distance of 20m from the wireless router in LoS conditions. Our experimental results reveal that IEEE 802.11ac achieves 42% better average throughput when compared to the IEEE 802.11n (5GHz) at a distance of 5m in LoS conditions. Similarly, IEEE 802.11ac provides 55% improvement over IEEE 802.11n (5GHz) at a distance of 15m in NLoS conditions. We conclude that IEEE 802.11ac can effectively handle interference caused by other IEEE 802.11n (5GHz) sources and provides higher throughput than IEEE 802.11n for both LoS and NLoS conditions.

In differentiated learning, the teacher needs to be aware of the learning styles of students in the classroom to accommodate specific learning preferences, e.g., the Felder–Silverman learning style model. The corresponding instrument, i.e., the Felder–Silverman Index of Learning Style (ILS), was designed to assess learning styles, specifically for engineering students. The ILS has been tested at the middle school level to identify the learning styles; however, validity/reliability had not been established in earlier studies with large samples. The focus of this study was to identify the validity and reliability of an ILS instrument for middle school students ($N=450$) by investigating the factor structure through factor analysis. This includes internal consistency reliability and constructing validity report of the ILS. An exploratory and confirmatory factor analysis was undertaken to investigate the factor structure to establish validity. As a result of the study, the reliability of the instrument was established. Five-factors emerged through exploratory factor analysis (EFA), which were subjected to confirmatory factor analysis (CFA). The outcome provided five-factors (i.e., Comparative Fit Index (CFI), Tucker–Lewis Index (TLI), Root Mean Square Error of Approximation (RMSEA), Standardized Root Mean Residual (SRMR), and Goodness of Fit (GFI)), out of which four factors were related to the four dimensions of the Felder–Silverman model, and the fifth factor was related to the association of sensing/intuitive and sequential/global dimensions of the model, which is in agreement with the theoretical construct of ILS. As a result of CFA, ILS entailing 24 items indicates a good fit with five-factor structure. $CFI=0.922;TLI=0.927$; $RMSEA=0.026$; $SRMR=0.585;GFI=0.911;X2=277;df=42;p=0.60$. This study suggests that the ILS for the secondary-grade students needs to be revised with fewer items to improve the reliability, as supported by empirical evidence through the EFA and CFA.