Re: Why recalculation from scratch?

[Jing Shen <[e-mail]>]

Bin Liu,

The first, router does not maintains all information as human does.
the second, each router computes its routing table on its view of network.
When state of some links varies, the logical view of network changes
and the shortest path tree of the graph may become a totally new one;
the third, as link state propagates by relaying hop by hop, it can not
be expected that every router update their routing table simulataneously,
so each time a new link state is received the routing table must be
recomputed
to guarantee the convergence.

Of course, in a network with thousands of prefix such computing need a lot
of
CPU time but it's just one of the key reasons. IMO, Route flapping and
looping is
the factors attracting more attention.

Cheers

Jing Shen