# Approaches and Challenges in Internet of Robotic Things
## 2 IoRT: An Overview
### IoRT Architectures
#### 2.6.3 Five-Tier Architecture  
According to [1], IoRT has a five-tier architecture, which can be further subdivided for a better understanding of IoRT functionalities, thereby minimizing modification requirements to the underlying hardware and software logic: (i) hardware/ robotic things layer, (ii) network layer, (iii) Internet layer, (iv) infrastructure layer, and (v) application layer. The five-tier architecture layers are summarized below.  
**Network layer:** The network layer and transport layer are in charge of transmitting data from one end of a network to the other. Both layers are closely linked and are commonly mentioned collectively. Figure 7 depicts a five-tier design, with the network layer referred to as the transport layer.  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Layers** & **Domain** \\ \hline \multirow{2}{*}{**Services and application layer**} & Smart environments \\  & Installation and execution of programs are \\  & carried out here by interconnected IoRT \\ \hline \multirow{2}{*}{**Network and control layer**} & Routers, switches, local and cloud servers, and \\  & network and management protocols \\ \hline \multirow{2}{*}{**Physical/hardware layer**} & Sensors, robots, actuators, robot-to-robot \\  & communication, and multi-robotic systems \\ \hline \hline \end{tabular}
\end{table}
Table 4: An illustration of various components in a three-tier IoRT architecture.  
**Internet layer:** Network connectivity is an option for facilitating device connectivity and the right to use information from wherever in the world. Internet connectivity provides connectivity for systems and access to data anywhere and anytime. Internet connectedness is regarded as the core part of communication in the IoRT architecture. As the IoRT is constructed on the basis of robotic things, it uses a variety of IoT-defined communication protocols to enable M2M and M2H communication, as well as lightweight processing of information in robotic systems [1, 49].  
**Infrastructure layer:** The robotic cloud stack transforms this portion of the architecture into the maximum managed service-centric methods for the cloud, middleware, business processes, and big data. The infrastructure layer is made up of five different but connected modules, including robotic cloud infrastructure, M2M2A cloud infrastructure support, IoT business cloud facilities, big data facilities, and IoT cloud robotics structure. All of these layers are well outlined in the architecture diagram (Figure 8) of IoRT [1, 51].  
Figure 7: Five-layered IoRT infrastructural architecture.  
**Application layer:** The application layer is the uppermost layer in the IoRT architecture. The physical layer aims to distribute the client experience by investigating the offered sample of robotics-based applications. IoT-connected robots can actively participate in solving a variety of problems in fields [53].  
A conceptual diagram of the detailed architecture of robotic things and cloud computing is given in Figure 8. This architecture gives an overview of how the robotic platform support gives robot-specific service technologies such as middleware, robotic operating systems, service network protocol, and network interfaces. The M2M2A exchanges the data to the network with resource utilization in the Internet of things business cloud services [1].