After the adjacencies are established, the routers may begin sending out LSAs. As the term flooding
implies, the advertisements are sent to every neighbor. In turn, each received LSA is copied and
forwarded to every neighbor except the one that sent the LSA. This process is the source of one of link
state's advantages over distance vector. LSAs are forwarded almost immediately, whereas distance vector
must run its algorithm and update its route table before routing updates, even the triggered ones, can be
forwarded. As a result, link state protocols converge much faster than distance vector protocols converge
when the topology changes.
The flooding process is the most complex piece of a link state protocol. There are several ways to make
flooding more efficient and more reliable, such as using unicast and multicast addresses, checksums, and
positive acknowledgments. These topics are examined in the protocol-specific chapters, but two
procedures are vitally important to the flooding process: sequencing and aging.