Recall from Chapter 2 that flooding is the mechanism by which the topological information originated by an OSPF or IS-IS router is received by all other routers in an area, so that the routers can add the information to their link state databases. Also recall from Chapter 2 that for a link state protocol to operate correctly, the link state databases of every router in an area must be identical. Therefore, flooding requires not just a transport mechanism but also reliability features. Given these requirements, both OSPF and IS-IS flooding use the following components:
A “container” packet or PDU for transporting information from one router to the next
A means of acknowledging ...