# Wireless Mesh Networking: An IoT-Oriented Perspective Survey on Relevant Technologies
## 5 Mesh Networking with IEEE 802.15.4
### Other solutions
#### 5.2.1 Thread  
Thread has been designed to address several challenges of the IoT, such as, for example, interoperability, architecture, and security. Thread is an open and proven standard-based low-power and battery-operated wireless mesh networking protocol, based on IP (both IPv4 and IPv6), allowing devices to talk to other IoT nodes (even mobile devices) and directly to the Cloud. Moreover, it allows to reliably connect a large number of IEEE 802.15.4-based products (more than 250) and includes mandatory security features, thus having no single point of failure-on the basis of the concept of border router, which will be explained in the following, a Thread-based network can involve multiple border routers in it and being self-healing and reconfigurable when a device is added or removed [61; 62].  
From a protocol stack perspective, Thread refers to the networking layer only, as shown in Figure 5, allowing both unicast (routed) and multicast (flooding) messaging, and providing scalability and reliability. Since Thread-based nodes are authenticated, using MAC encryption, before joining the network [63], then security is built-in at the networking layer, thus exploiting an IEEE 802.15.4 data link layer on top of which an IPv6-based transport is deployed, together with a 6 LoWPAN adaptation layer in-between, implementing IPv6 header compression for maximizing the efficiency of network communications.  
Since one of the main features of Thread is that similar devices do not need proprietary gateways, proxies or translators among them, this reduces infrastructure needs and maintenance burdens, while, in the case of devices using other technologies, the interconnection may carried out through a gateway or a hub, as shown in Figure 5. Hence, this allows to support and integrate several IoT nodes (through IP), in turn provided with different application layers (i.e., allowing the execution of Weave [64], OWA LWM2M [65; 66], Dotdot [67], or OCF [68]).  
Figure 5: Protocol stack and network architecture representation of an infrastructure handled with Thread protocol. **(a)** Thread networking protocol stack [69]; **(b)** Thread network architecture example [70].  
Summarizing, Thread offers the following technological advantages over other wireless technology protocols.  
* Thread presents a small and low-consumption footprint, interoperable and scalable up to a huge number of devices, thus being reliable and secure, avoiding single bottlenecks and failure points.
* Thread presents a flexible intermediate layer allowing the device-to-device communication across all networks.
* Thread provides a security layer admitting to join a Thread-based network only to authenticated devices, thus encrypting the traffic flowing inside the network and including built-in link-layer authorization policies.
* Thread is able to expand its controlled network (composed by low-power nodes) to external networks (e.g., either based on IEEE 802.11 or IEEE 802.3) or to the Internet, through the adoption of border routers.
* Thread allows the inclusion of battery-powered nodes into a Thread-handled network, avoiding frequent coin-cell changes and, in this way, allowing those that people use every day--such as thermostats and lighting controls.