Hello packets are used for neighbor discovery. These are sent as multicasts and do not require an acknowledgement.

Update packets are sent to communicate the routes used by a router to converge. When a new route is discovered or the convergence process is completed, updates are sent as multicast. During topology table synchronization, updates are sent as unicasts to neighboring peers.

Query packets are sent when a router performs route computation and cannot find a feasible successor. These packets are sent to neighboring peers asking if they have a feasible successor to the destination network.

Reply packets are sent in response of a query packet. These are unicast and sent to the originator of the query.