Extended timeout

The worst-case transmission timeout when you are sending data to an end device is a larger issue than when transmitting to a router or coordinator. As described in Parent operation, RF data packets are sent to the parent of the end device, which buffers the packet until the end device wakes to receive it. The parent buffers an RF data packet for up to (1.2 * SP) time.

To ensure the end device has adequate time to wake and receive the data, the extended transmission timeout to an end device is:

(50 * NH) + (1.2 * SP)

This timeout includes the packet buffering timeout (1.2 * SP) and time to account for routing through the mesh network (50 * NH).

If no acknowledgment is received within this time, the sender resends the transmission up to two more times. With retries included, the longest transmission timeout when sending data to an end device is:

3 * ((50 * NH) + (1.2 * SP))

The SP value in both equations must be entered in millisecond units. The SP command setting uses 10 ms units and must be converted to milliseconds to be used in this equation.

For example, suppose a router is configured with NH=30 (0x1E) and SP=0x3E8 (10,000 ms), and that it is either trying to send data to one of its end device children, or to a remote end device. The total extended timeout to the end device is approximately:

3 * ((50 * NH) + (1.2 * SP)) or one of the following: