Repeater Node - Must Sensors use ACK to detect "3 failed" messages?

[Spanners]

I have a clarification question on this text in "The Sensor Network".

If the sensor node later loses contact with the gateway or a repeater-sensor node, it will automatically repeat this procedure to determine the best path to the gateway - a sensor node considers contact with the gateway to be lost if it fails to send 3 consecutive messages.

For messages to be detected as failed (and therefore the sensor tries to find a new gateway/repeater) must messages be sent with ACK requested as true?

eg: send(msg1valve.setSensor(i).set(true), true);

This question is for NRF24 radio in case that's significant.

[mfalkvidd]

@Spanners no, there is no need to request ack.

[Spanners]

Thanks @mfalkvidd

Unfortunately that ruins my theory as to what I’m observing. I will keep experimenting.