Link state advertisement It is a message that communicates the router's local routing topology to all other local routers in the same OSPF area. This LSA has types depend on the type of router and has also sequence number.
Every OSPF router maintains a Link state database (LSDB). Each router stores the received LSA packets in the link-state database (LSDB). After LSDBs are synced between the routers, OSPF uses the shortest path first (SPF) algorithm to calculate the best routes. (full version of the database)
Database description packets (also referred as DDPs) These packets are exchanged when an adjacency is being initialized. They describe the contents of the topological database. It does not include full LSAs but would include LSA headers in the link-state database of the sender..
After exchanging Database Description packets with a neighboring router, a router may find that parts of its topological database are out of date. The Link State Request packet is used to request the pieces of the neighbor's database that are more up to date. The sending of Link State Request packets is the last step in bringing up an adjacency
What other have (DBDs) – What I have (LADB) = What I need to order (LSR)
A packet that contains fully detailed LSAs, typically sent in response to an LSR message
- Link-State Acknowledgment (LSAck)
Sent to confirm receipt of an LSU message