[ns] periodic updates

["Prasad V. Boddupalli" <bprasad@sie.arizona.edu>]

Hello,
    When I use rtModels to simulate the link failures, the rtObject at
each node triggers the exchange of routing information. After all the
nodes propagated their changes, the rtObject selects the best routes at
each node and installs in the routing table.
    But what is the effect of periodic updates as initiated by the routing
protocols themselves. They just seem to access the metrics present in
the rtObject tables and propagate them. What is the use of that ?
Moreover, I don't see rtObject computing the new routes after periodic
updates. Can someone please explain this ?

- Prasad.