## 4 Thread vs. Competitors  
Several wireless communication technologies are used for IoT deployment, depending upon the application requirements [9; 12]. These communication technologies can also be classified as long and short-range. The most commonly used short-range communication technologies are, Wireless Fidelity (Wi-Fi), ZigBee, and Bluetooth. The common features among most applications are low cost, low processing, low power, low storage, and a low bit rate. Wi-Fi is a wireless protocol from the IEEE 802.11 family that operates over unlicensed bands of 2.4 GHz and 5 GHz. Its basic purpose was to replace wired Ethernet with wireless. Wi-Fi is a strong choice for IoT deployments, but due to its higher power consumption, is not suitable for power-constrained and battery-powered IoT networks [28]. On the other side, communication technologies like Bluetooth, Zigbee, and Thread require considerably low power and are more practical for applications like smart cities, health care, home automation, etc. [29; 30]. These applications are not bandwidth-hungry and require a small number of sensors to provide some parametric data; hence, low-bandwidth technologies are suitable for such systems. These three short-range communication technologies have a common characteristic, they all use the 2.4 GHz ISM band. Zigbee is particularly developed to fulfill the needs of machine-to-machine and IoT networks, providing low-cost and low-power wireless connectivity, while Bluetooth is short-range wireless and very low-power but a high-bandwidth connectivity option [12]. As mentioned earlier, the Thread protocol connects different existing technologies like IEEE 802.15.4, 6 LoWPAN, and IETF IPv6 while providing mesh networking and distinguishing itself from its peers. Some of its distinguishing characteristics are described below  
* **IPv6 support (highly scalable in terms of connectivity, compatible with existing IP-based systems)** Resource-constrained devices can achieve device-device, device-mobile, and device-cloud communication via IPv6. It can employ several IP-based concurrent applications and ecosystems. End-to-end IP support facilitates customized applications and services. It also unifies convergence across PHY/MAC networks [31]. * **Highly resilient (auto-configuring and self-healing, no central hub)** The network automatically adapts to changing conditions. The number of routers in the network can be increased or decreased as REEDs can act both ways. Thread is robust and has a self-healing mesh network. Every Thread network has a leader node that is responsible for network management, in the event of failure of this leader node, another router is elected as a leader without compromising the network performance [14]. * **Reliable (mesh network, no single point of failure)** Thread is a mesh network where each router node is connected to all available router nodes. If a connection breaks down between any two nodes, these nodes can still communicate as the network reroutes the traffic through another route. Another distinguishing feature of the Thread network is that it can support multiple border routers. As described before, these border routers provide connectivity from local mesh to the global internet, so multiple border routers guarantee connectivity to the internet and make the network more reliable with no single point of failure [20; 24]. * **Scalable (suitable for small and large networks)** Thread supports 32 routers, and each router can connect up to 511 devices, reaching over 16 thousand devices. Multiple border routers also make it more scalable [20]. The Thread has 15 channels for radio communication, which can help achieve smooth performance in situations with high node density. * **Secure (AES encryption, and secure commissioning)** Thread employs link-layer security, encrypts all network communication, and only permits authorized nodes to connect to the network. Datagram Transport Layer Security (DTLS) encryption technology is used for authentication in order to prevent tamperingand message forging.