# Industrial IoT Monitoring: Technologies and Architecture Proposal
## 6 Related Work  
The solution presented in this paper proposes a multi-domain architecture that is able to monitor the condition of IWSNs from different perspectives. To the best of our knowledge, the proposed architecture is the first of its kind. The related work reviewed in this section also addresses the multi-domain nature of the architecture, by analysing the contributions in several domains. In Section 3, part of this multi-domain analysis was already made, in a detailed way, when different techniques to monitor the network, firmware and hardware were presented. On the other hand, this related work section will provide a broader overview, by analysing solutions from the Industry 4.0 perspective. Current related work in the Industry 4.0 topic is extensive. In general, most of the existing monitoring architectures target the prevention of security attacks in ICS systems, although without taking into consideration the IWSN technologies analysed in this paper [87]. Some of these solutions have been proposed because of the paradigm shift that occurs nowadays in the ICS core, with the introduction of IP networks. Additionally, more recent technologies such as Software Define Networks (SDN) [88] and Cloud-based platforms [89] are being considered in such architectures, due to the rich network metrics and flow control mechanisms that these technologies make available. However, this type of control and monitoring is specific for wired IP networks, that can work in a decentralised manner, and with different application requirements in mind (e.g., troughput). However, as presented before, applications in industrial process automation need deterministic latency, instead of pure throughput. This is, by way of example, the kind of requirement being considered by the Time-Sensitive Task Group (TSN). The group analyses the possibility of deterministic services in IEEE 802 based networks. As consequence, technologies like SDN cannot be applied to IWSN standards like WirelessHART, ISA100.11a, WIA-PA and ZigBee, at least inside the wireless network domain, at this stage, due to their centralized and deterministic nature. Solutions like [88] can only be used at gateway level, by virtualizing some of the non-deterministic features and roles in another device (e.g., the security manager in WirelessHART). Thus, in this section, only solutions proposed for the industrial standards addressed will be considered. From the first perspective, the authors of [90; 91] propose techniques that improve the reliability of the network at routing schedule-level: by using a finite-state Markov model [90], and by specifying scheduling emergency and recovery mechanisms when a path-down alarm occurs [91]. On the other hand, the work presented in [92; 93; 94] proposes several techniques and platforms that can be used to monitor some IWSN. In [92], the authors develop a passive monitoring tool for evaluation of the deployed WirelessHART networks using passive sniffers deployed in the network area. Additionally, in [93], the authors propose an hybrid monitoring technique to monitor wireless and wired industrial technologies in the scope of the project HiFlecs. Lastly, in [94], the authors present a debugging tool that is able to collect in the SensorLab2 environment routing topology information and end-to-end performance, by debugging the information using UART ports and then converting it to TCP/IP messages. Finally, some authors also show some concerns in the lack of integration solutions between the industrial standards [95; 96; 97]. In [95] the authors presented how the MQTT protocol can be used together with ISA S5.1 and ISA95/88 standards to represent the monitoring and control in topics