The Thread specification defines a distributed mesh network topology based on IPv6.
It provides the framework for a resilient network with no single point of failure, including self-healing and self-extending capabilities.
A typical Thread network will have a Leader node which is in charge with network management and maintenance services. If for any reason the current Leader goes offline, another Router will assume the Leader role.
A Thread network may also include multiple Router nodes as well as one or more Border Routers which provide the network with connectivity to the rest of the home IP infrastructure or to the wider Internet.
Router nodes are responsible for packet routing within the Thread network as well as facilitating network attachment of other devices.
The number of active Routers in the mesh at a given time is adjusted dynamically based on network topology requirements and on how many available devices are Router Eligible.
Finally, some Thread nodes are characterized by a low duty cycle and require some periods of being in a low-power sleep state in order to extend battery life.
Such nodes are usually not eligible to become active Routers and will always play an End Device (Host only) role.