Why OSPF is in the broadcast network, DD and LSR are unicast, and LSU Hello is multicast-based.

A: Hello is used to keep a neighbor and does not require each neighbor to replicate a single unicast packet. LSU is the link state with the new, a network segment generally has the DR and Bdr, both of which need to establish a neighbor with R-other and monitor the multicast address of the 224.0.0.6. If LSU sends it out from Drother, not sending it to the multicast address, sending it to unicast will result in a waste of bandwidth and a burden on the device.

DD is sent when a neighboring relationship is established between two devices. Therefore is unicast, the LSR is with the new request, directly requests the DR without requesting the BDR. So unicast.

Why OSPF is in the broadcast network, DD and LSR are unicast, and LSU Hello is multicast-based.