Thread (network protocol)

Thread is a low-power, mesh network protocol which has been developed by a consortium of competing companies in the smart home industry. Thread uses IP version 6 over wireless networks, and it is a protocol designed specifically for IoT devices, allowing them to communicate more quickly, using less power, with fewer points of failure, than previous solutions using IEEE 802.15.4 radio technology. For examples, Thread is a lot like existing smart home protocols Zigbee and Z-Wave, except that no central hub or bridge is needed. Instead, Thread devices talk directly to each other in a wireless mesh network and can connect directly to any other IP-based device, including smart phones, tablets, computers, and Wi-Fi routers.

Thread is the first low-power, wireless mesh networking protocol to allow low-power devices to use IP. And with a mesh network, there is no single point of failure.

There are two kinds of devices on a Thread network--those plugged into power (such as, a light bulb or smart plug) and those that are battery-powered (such as a motion sensor or a smart lock). Thread considers an always-powered device on its network to be a "Router", and a battery-powered device to be an "End Device". Thread consider an always-powered device that also connects to the internet (such as a smart speaker or Wi-Fi router) to be a "Border Router".

A Thread network can support more the 250 devices, and of those, as many as 64 can be Routers (always-powered), with at most 32 Routers active simultaneously. Among the Routers, multiple instances of Border Routers may exist.

The new smart home standard, Matter, is an application that runs on top of a Thread network. Matter supports both Wi-Fi and Thread for connecting its devices, and its use of Thread means that there is no single point of failure in the home network--any one device may fail or be unplugged, but the rest of the network can continue to work normally. Other applications that may run over Thread include HomeKit, Google/Weave, or Open Thread, etc. Because it's an IP-based network, a Thread network could support multiple of these application laters running simultaneously.

Unlike earlier technologies, Thread has been optimized from its inception to run on low-power devices that require near real-time access to rapidly changing data, and thus to handle a high volume of data messages with minimal delay (latency). Early benchmarking of Thread, as compared with Zigbee and Bluetooth networks, show Thread networks to have much less delay, especially when scaled to large numbers of devices, and the quicker activity of Thread translates into less power usage, which is especially important for battery-driven devices.

A smart home will usually want to have at least one Thread-capable Border Router in order for any of its Thread-capable devices to reach the internet, and any Thread-capable device should be able to use any Border Router to reach the internet, regardless of manufacturer.

Finally, unlike with a bridge of hub, a Border Router cannot read the traffic that it passes along, because all communications in a Thread network are encrypted.

A Thread Border Router is not usually going to be a dedicated device like a hub or bridge; instead, it is a feature that can be integrated into any powered device that has access to the internet.

The one kind of smart home device currently in use that does not work well on Thread is security cameras, because those require high-bandwidth internet connections, whereas Thread is designed for much lower-bandwidth applications. Thread is specifically intended to do well for small, low-powered devices such as leak detectors, CO detectors, and motion sensors. Such devices may be left untouched and unused for months but need to spring into action reliably when required and need still to have battery life left when that happens. In addition to sensors, Thread is designed to perform actions on devices such as door locks, window shades, light bulbs, water valves, thermostats, and so on.

Thread, and the Matter application layer which can run over it, are both emerging standards in 2023. The latest release of Thread as of April 2023 is version 1.3.0.