Incrematal SPF (ATTN: Narbik and Marko, et al)

*NB*
*Disclaimer*
The goal of this is not to stimulate rivalry or competiton between the
parties addressed. Rather it is an effort by a soldier that has been fallen
twice but not detered, a soldier whose sole goal is the medal of honor that
awaits him at the finish line. One who wants to take advantage of the battle
strategies, knowlege and wisdom of generals who have trod this path before.

I have the decided to engage them, 'cos since i have been following this
group they have been very consistent at sharing great insights on members'
study and even real life challenges in this field . I just want you guys to
make a general out of me, be part of my success story.
.....................

Enough on the story ...

I said i was going to post some clarification questions by COB... but i just
came across this some minutes ago and i thought i should ask.

OSPF uses Dijkstra's SPF algorithm to compute the shortest path tree (SPT).
During the computation of the SPT, the shortest path to each node is
discovered. The topology tree is used to populate the routing table with
routes to IP networks. When changes to a Type-1 or Type-2 link-state
advertisement (LSA) occur in an area, the entire SPT is recomputed. In many
cases, the entire SPT need not be recomputed because most of the tree
remains unchanged. Incremental SPF allows the system to recompute only the
affected part of the tree. Recomputing only a portion of the tree rather
than the entire tree results in faster OSPF convergence and saves CPU
resources. Note that if the change to a Type-1 or Type-2 LSA occurs in the
calculating router itself, then the full SPT is performed.

*From the areas i highlighted, my understanding of how ISPF work is that it
is only usefull when you have mutiple areas and there are changes to the
LSA's outside the calculating router's area... Is this correct?*

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Received on Thu Mar 25 2010 - 11:48:20 ART