- the router update timer expiring
- a link to a neighbor router has become congested
- a change in the topology
- the initial startup of the routing protocol process
- the requirement to periodically flood link-state packets to all neighbors
Explanation: An LSP (link-state packet) is only sent during initial startup of the routing protocol process on a router; and whenever there is a change in the topology, including a link going down or coming up, or a neighbor adjacency being established or broken. Data traffic congestion does not directly influence routing protocol behavior. LSPs are not flooded periodically, and update timers are not relevant to LSPs.