The ACK field is 2-bits long. It contains the ACK slot and ACK delimiter. In the ACK slot, the transmitting station sends 2 recessive bits. Every receiver that has received a valid message reports the accurate reception to the transmitting node by placing a dominant bit in the ACK slot. Any receiving node that disagrees – that is , any that did not receive an accurate Data Frame – votes ‘NO’ after the delimiter by sending an error flag, six consecutive dominant bits. Incidentally, because every node acknowledges message felids, the round-trip propagation delay is the primary distance limitation of CAN.