How is LSA flooding controlled in OSPF?

In OSPF (Open Shortest Path First), Link State Advertisements (LSAs) are crucial for maintaining the network topology database. The control over LSA flooding is primarily handled through the use of sequence numbers and the age of LSAs.

The sequence number is an essential aspect that allows OSPF routers to identify whether an LSA is newer or older than the one they currently possess. When an LSA is received, the router examines the sequence number: if the received LSA has a higher sequence number, it indicates that this LSA is more current, and the router will update its information and propagate this new information. This ensures that all routers within an OSPF area have a synchronized view of the network.

The age of LSAs also plays a critical role in controlling flooding. Each LSA has an age field that indicates how long the LSA has been in existence. If the LSA becomes too old (usually exceeding 3600 seconds), it is considered stale and is purged from the routers' databases. This mechanism prevents outdated information from circulating within the network and ensures that all routers are working with up-to-date topology information.

Together, these mechanisms of sequence numbers and age effectively manage LSA flooding, ensuring