# Modeling and Fault Tolerance Analysis of ZigBee Protocol in IoT Networks
## 4 Analysis of the Simulation Results Concerning the Fault Tolerance Issues in ZigBee Protocol
This fault tolerance mechanism in IEEE 802.15.4/ Zigbee is also called orphaned device realignment. This recovery/repair routine is triggered whenever there are recurring traffic errors in data requests (e.g., data frames sent without receiving the requested acknowledgment that occur either when a device and its parent or when a device drops out of sync with its parent). Once a unit is deemed orphaned, a resignment or channel rescan process is triggered [43]. Devices in IoT are very diverse in terms of communication, the computation performed, memory and capacity for stored data, and transmission capability. An Internet of Things application consists of various devices, but typically there is a main coordinating node (gateway), a few intermediate nodes (routers), and most end nodes. The number of nodes in the network can take values from a few to several hundred, but in order to visualize the different processes occurring in the network, the research was limited to 17 nodes, which were assigned in proportion to the number used in IoT systems. It was assumed that in the ideal case all devices should be properly organized by the network and should be accessible. The Internet of Things can be an aggregation of heterogeneous networks such as wireless sensor networks, mobile networks, and Wireless Local Area Networks (WLANs). By using these networks, many complex activities, such as data exchange, computation, and decision-making, can be performed. Reliable communication between the gateway and the objects is essential for the management process in the Internet of Things. The gateway is able to locally run an optimization algorithm. It does this by leveraging its knowledge of the network. The computational complexity is transferred from the object to the gateway. A global optimal route and parameter values for the gateway can be obtained in this way. The deployment of nodes allows for a more accurate location of events. Many WSN implementations use battery-powered sensors because charging or replacing them may not be practical. Disposable sensors are used. Improving the lifetime and performance of disposable nodes should reduce potential failure, which is the primary concern. The values obtained in the simulations represent averaged numbers from several runs of experiments. For the initial state, tests were performed 10 times, while for the post-failure states, the number decreased proportionally as the results were reproducible. The IoT network was assumed to have full coverage in a given area. To this end, end nodes were randomly \"scattered\", but so in each case, the number of nodes was the same. Due to the nature of the network operation, each end node must be connected to the coordinating node through an intermediate node (router). The number of routers depends on the distance from the coordinating node. This condition has been satisfied for each node. Additionally, in order to demonstrate the changes in the network and traffic statistics (management traffic, control traffic, rejected data, etc. ), both the case of nodes that connect through a single router and the case where the farthest node is connected to the coordinator through several routers have been selected for failure.