A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> D. SDN FOR I-IOT <s> The idea of programmable networks has recently re-gained considerable momentum due to the emergence of the Software-Defined Networking (SDN) paradigm. SDN, often referred to as a "radical new idea in networking", promises to dramatically simplify network management and enable innovation through network programmability. This paper surveys the state-of-the-art in programmable networks with an emphasis on SDN. We provide a historic perspective of programmable networks from early ideas to recent developments. Then we present the SDN architecture and the OpenFlow standard in particular, discuss current alternatives for implementation and testing of SDN-based protocols and services, examine current and future SDN applications, and explore promising research directions based on the SDN paradigm. <s> BIB001 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> D. SDN FOR I-IOT <s> With recent adoption of wireless sensor-actuator networks (WSANs) in industrial automation, industrial wireless control systems have emerged as a frontier of cyber-physical systems. Despite their success in industrial monitoring applications, existing WSAN technologies face significant challenges in supporting control systems due to their lack of real-time performance and dynamic wireless conditions in industrial plants. This article reviews a series of recent advances in real-time WSANs for industrial control systems: 1) real-time scheduling algorithms and analyses for WSANs; 2) implementation and experimentation of industrial WSAN protocols; 3) cyber-physical codesign of wireless control systems that integrate wireless and control designs; and 4) a wireless cyber-physical simulator for codesign and evaluation of wireless control systems. This article concludes by highlighting research directions in industrial cyber-physical systems. <s> BIB002 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> D. SDN FOR I-IOT <s> Software-Defined Networking (SDN) is a promising approach to build future industrial networks. The disruptive change of network architecture and management opens new possibilities in various application domains. While the approach is already deployed in several domains and was also initially examined to be used in the industrial area, many open questions arise when assessing the risks and improvements to be expected. The following work presents features of a potential future industrial network infrastructure and sets up requirements that are important for future communications. It reviews basics of SDN and correlates existing work to the specified requirements. Finally, it presents open questions and room for future research. <s> BIB003 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> D. SDN FOR I-IOT <s> The imminent arrival of the Internet of Things (IoT), which consists of a vast number of devices with heterogeneous characteristics, means that future networks need a new architecture to accommodate the expected increase in data generation. Software defined networking (SDN) and network virtualization (NV) are two technologies that promise to cost-effectively provide the scale and versatility necessary for IoT services. In this paper, we survey the state of the art on the application of SDN and NV to IoT. To the best of our knowledge, we are the first to provide a comprehensive description of every possible IoT implementation aspect for the two technologies. We start by outlining the ways of combining SDN and NV. Subsequently, we present how the two technologies can be used in the mobile and cellular context, with emphasis on forthcoming 5G networks. Afterward, we move to the study of wireless sensor networks, arguably the current foremost example of an IoT network. Finally, we review some general SDN-NV-enabled IoT architectures, along with real-life deployments and use-cases. We conclude by giving directions for future research on this topic. <s> BIB004 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> D. SDN FOR I-IOT <s> Industrial Wireless sensor networks (IWSNs) are emerging as a promising technique for industrial applications. With limited energy resources, prolonging the lifetime of IWSNs is a fundamental problem for industrial applications. At the same time, Software- Defined Networking (SDN) and Network Function Virtualization (NFV) are future network techniques which make the underlying networks and node functions programmable. SDN and NFV have inherent advantages to control topology and node mode in IWSNs. In this paper, we propose a mechanism improving energy efficiency in industrial wireless sensor networks using SDN and NFV named M-SEECH for industrial application. Firstly, we propose a new architecture based on traditional IWSNs and operation mechanism using SDN and NFV. In the architecture, the global view and central control properties of SDN are utilized to monitor IWSNs. Also, the programmability of SDN and instant deployment capability of NFV are utilized to control the topology of IWSNs and the modes of nodes in IWSNs. Thirdly, we propose advanced algorithms for controller in IWSNs taking the advantages of SDN and NFV. By this way, the average lifetimes of IWSNs are prolonged. Finally, the case study and evaluation show the advantages of the proposed energy efficient scheme comparing with traditional methods. <s> BIB005 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> D. SDN FOR I-IOT <s> The smart grid, as one of typical applications supported by Internet of Things, denoted as a re-engineering and a modernization of the traditional power grid, aims to provide reliable, secure, and efficient energy transmission and distribution to consumers. How to effectively integrate distributed (renewable) energy resources and storage devices to satisfy the energy service requirements of users, while minimizing the power generation and transmission cost, remains a highly pressing challenge in the smart grid. To address this challenge and assess the effectiveness of integrating distributed energy resources and storage devices, in this paper, we develop a theoretical framework to model and analyze three types of power grid systems: 1) the power grid with only bulk energy generators; 2) the power grid with distributed energy resources; and 3) the power grid with both distributed energy resources and storage devices. Based on the metrics of the power cumulative cost and the service reliability to users, we formally model and analyze the impact of integrating distributed energy resources and storage devices in the power grid. We also use the concept of network calculus, which has been traditionally used for carrying out traffic engineering in computer networks, to derive the bounds of both power supply and user demand to achieve a high service reliability to users. Through an extensive performance evaluation, our evaluation results show that integrating distributed energy resources conjointly with energy storage devices can reduce generation costs, smooth the curve of bulk power generation over time, reduce bulk power generation and power distribution losses, and provide a sustainable service reliability to users in the power grid. <s> BIB006 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> D. SDN FOR I-IOT <s> With the rapid development of digital and network technologies, Industry 4.0 is having a huge impact on commerce. In the manufacturing sector, enterprises that produce many customized products, and those that produce a few and different of products, have the opportunity to achieve the same production standards and costs as each other. In an intelligent factory, workers and operators are shifting from traditional machine operators to production process controllers, and staff who make adjustments to management and decisions, to optimize production processes. This work proposes a software-defined infrastructure, which is then deployed in an Industry 4.0 network environment. This infrastructure improves the overall operations of the network environment, the rate of data transmission and the quality of services provided. <s> BIB007 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> D. SDN FOR I-IOT <s> Recent standardization efforts in IEEE 802.15.4-2015 Time Scheduled Channel Hopping (TSCH) and the IETF 6TiSCH Working Group (WG), aim to provide deterministic communications and efficient allocation of resources across constrained Internet of Things (IoT) networks, particularly in Industrial IoT (IIoT) scenarios. Within 6TiSCH, Software Defined Networking (SDN) has been identified as means of providing centralized control in a number of key situations. However, implementing a centralized SDN architecture in a Low Power and Lossy Network (LLN) faces considerable challenges: not only is controller traffic subject to jitter due to unreliable links and network contention, but the overhead generated by SDN can severely affect the performance of other traffic. This paper proposes using 6TiSCH tracks, a Layer-2 slicing mechanism for creating dedicated forwarding paths across TSCH networks, in order to isolate the SDN control overhead. Not only does this prevent control traffic from affecting the performance of other data flows, but the properties of 6TiSCH tracks allows deterministic, low-latency SDN controller communication. Using our own lightweight SDN implementation for Contiki OS, we firstly demonstrate the effect of SDN control traffic on application data flows across a 6TiSCH network. We then show that by slicing the network through the allocation of dedicated resources along a SDN control path, tracks provide an effective means of mitigating the cost of SDN control overhead in IEEE 802.15.4-2015 TSCH networks. <s> BIB008 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> D. SDN FOR I-IOT <s> In recent years, smart factory in the context of Industry 4.0 and industrial Internet of Things (IIoT) has become a hot topic for both academia and industry. In IIoT system, there is an increasing requirement for exchange of data with different delay flows among different smart devices. However, there are few studies on this topic. To overcome the limitations of traditional methods and address the problem, we seriously consider the incorporation of global centralized software defined network (SDN) and edge computing (EC) in IIoT with EC. We propose the adaptive transmission architecture with SDN and EC for IIoT. Then, according to data streams with different latency constrains, the requirements can be divided into two groups: 1) ordinary and 2) emergent stream. In the low-deadline situation, a coarse-grained transmission path algorithm provided by finding all paths that meet the time constrains in hierarchical Internet of Things (IoT). After that, by employing the path difference degree (PDD), an optimum routing path is selected considering the aggregation of time deadline, traffic load balances, and energy consumption. In the high-deadline situation, if the coarse-grained strategy is beyond the situation, a fine-grained scheme is adopted to establish an effective transmission path by an adaptive power method for getting low latency. Finally, the performance of proposed strategy is evaluated by simulation. The results demonstrate that the proposed scheme outperforms the related methods in terms of average time delay, goodput, throughput, PDD, and download time. Thus, the proposed method provides better solution for IIoT data transmission. <s> BIB009 </s> A Survey on Industrial Internet of Things: A Cyber-Physical Systems Perspective <s> D. SDN FOR I-IOT <s> Software-defined networking (SDN) is a key enabling technology of industrial Internet of Things (IIoT) that provides dynamic reconfiguration to improve data network robustness. In the context of smart grid infrastructure, the strong demand of seamless data transmission during critical events (e.g., failures or natural disturbances) seems to be fundamentally shifting energy attitude toward emerging technology. Therefore, SDN will play a vital role on energy revolution to enable flexible interfacing between smart utility domains and facilitate the integration of mix renewable energy resources to deliver efficient power of sustainable grid. In this regard, we propose a new SDN platform based on IIoT technology to support resiliency by reacting immediately whenever a failure occurs to recover smart grid networks using real-time monitoring techniques. We employ SDN controller to achieve multifunctionality control and optimization challenge by providing operators with real-time data monitoring to manage demand, resources, and increasing system reliability. Data processing will be used to manage resources at local network level by employing SDN switch segment, which is connected to SDN controller through IIoT aggregation node. Furthermore, we address different scenarios to control packet flows between switches on hub-to-hub basis using traffic indicators of the infrastructure layer, in addition to any other data from the application layer. Extensive experimental simulation is conducted to demonstrate the validation of the proposed platform model. The experimental results prove the innovative SDN-based IIoT solutions can improve grid reliability for enhancing smart grid resilience. <s> BIB010
Existing network infrastructures are often statically deployed and application-specific, unable to support increasing numbers and types of industrial applications with diversified requirements. In addition, it is not cost-effective and efficient to deploy dedicated network infrastructures for massive industrial applications. This calls for a cost-effective and VOLUME 6, 2018 efficient network infrastructure that can enable dynamic configuration and interoperability for different industrial applications BIB002 . SDN, as a networking technique, can play a critical role in enabling the scalability and programmability of networks while coping with increasingly diverse and complex networking functions BIB001 . The key concept of SDN is to separate the control plane (algorithms, protocols, etc.) and the data plane (packet routing, forwarding, etc.). In this way, the implementation and configuration of network controls for individual applications can be deployed, modified, and updated. Several efforts have been made to adopt SDN for I-IoT. For example, Henneke et al. BIB003 reviewed the applicability of SDN in networks for industrial systems and pointed out that the interoperability enabled by SDN could improve the network performance to satisfy the I-IoT requirements in heterogeneous and complex industrial systems. In particular, they identified the network challenges for industrial systems from the network perspectives (e.g., heterogeneity, QoS, reliability, and security, among others). In addition, toward implementing SDN in I-IoT, Baddeley et al. BIB008 evaluated the performance of lightweight SDN with the layer-2 slicing mechanism defined in the IEEE 802.15.4 networks for I-IoT scenarios. In this case, SDN control slices are created for the controlling traffic, which prevents interference with network traffic. In addition, the recently standardized IEEE 802.15.4 -2015 Time Scheduled Channel Hopping (TSCH) improved reliability and latency of communication paths in the lossy industrial environment  . Furthermore, leveraging SDN has been demonstrated to improve network performance with different delay requirements in heterogeneous I-IoT settings. For example, Li et al. BIB009 proposed an adaptive transmission architecture and algorithms, which adapts to different traffic flows. Particularly, an adaptive routing scheme was proposed to compute optimal routes for non-urgent and urgent data streams. This work can be mapped to <Control, PA/FA, Reliability> in Figure 7 . As a typical application in the utility industry, the smart gird will integrate a variety of energy resources, including traditional energy, renewable energy, electrical vehicles, and others BIB006 . The complex energy generation integration requires frequent information exchange, which poses a challenge to the traditional communication infrastructure. In response, Al-Rubaye et al. BIB010 utilized the SDN platform to improve the resiliency of power grid communications for enabling real-time monitoring and controlling capabilities. The proposed SDN platform includes an infrastructure layer, control layer, and application layer. The SDN controller plays a critical role in carrying out optimization and control. For instance, the SDN controller can reschedule traffic flows when failures occur. This work maps to <Control, PA/FA, Reliability> in Figure. 7. SDN can be further integrated with network virtualization (NV) to provide service to I-IoT BIB004 , BIB007 . For instance, Bizanis and Kuipers BIB004 surveyed techniques in radio access networks (RANs) and core networks (CNs). The technique in RAN first uses network function virtualization (NFV) to effectively manage network resources in 5G  . Then, the concept of SDN is leveraged to create virtual network ''slices'' over the same physical network. The virtual network ''slices'' support different wireless technologies and standards to improve interoperability in heterogeneous networks. Towards the integration of SDN and NV for I-IoT, Ma et al. BIB007 proposed an SDN and NV integrated network architecture for the industrial environment. Their integrated architecture consists of software-defined infrastructure (SDI), virtualized network, control plane management, and network function virtualization in four different layers. The architecture was shown to improve the efficiency of network resource utilization, reduce the complexity of network design, and satisfy the requirements of various production processes. In addition, as a use case in the embryonic stage of I-IoT, Luo et al. BIB005 used SDN and NFV to improve the energy efficiency of industrial wireless sensor networks. In particular, the SDN controller was introduced to control and optimize the topology of sensor networks. The NFV was leveraged to enable functional replaceability of industrial devices.