because local forwarding decisions are based on the contents of a routing
table that contains a list of destinations, combined with one or more next-hop neighbors
that lead toward these destinations and costs associated with each next hop option. While
table-driven protocols eliminate the route discovery delays, they may be overly aggressive
in that routes are established that may never be needed. Further, the time interval between
route discovery and actual use of the route can be very large, potentially leading to outdated
routes (e.g., a link along the route may have broken in the meantime). Finally, the
cost of establishing a routing table can be significant, for example, in some protocols it
involves propagating a node’s local information (such as its list of neighbors) to all other
nodes in the network