Routers in the Internet core exchange between three and
six million routing prefixes each day, and the fluctuation
of network topology can have a direct impact on a
router’s performance.? A router that has not yet reached
convergence in its internal routing tables may drop
packets or deliver packets to the wrong next-hop router.?
Topology changes in the Internet must be reflected in
both the routing and forwarding tables within routers.?
The router architecture illustrated in Figure 1 indicates
that the routing table and the forwarding table are likely
to be implemented in separate hardware modules within
routers.? In fact, in modern carrier-class routers, the
forwarding table is often duplicated on each line card.?
The operations by which changes propagate from the
routing table to the forwarding tables are potentially
complex, and certainly very time-critical.? These
databases must remain closely synchronized or routing
loops and packet loss are likely.