Acknowledgement packets are sent unreliably over the network, and there is no guaranteed delivery of acknowledgement packets between neighboring routers.

Acknowledgement packets are a special type of hello packets that do not contain data and have a non-zero acknowledgement number. These are sent as a unicast.

Update, Query, and Reply packets use Reliable Transport Protocol (RTP), which ensures guaranteed delivery of packets between neighboring devices. The RTP mechanism ensures loop-free synchronized network.