[c-nsp] IS-IS question

[Oliver Boehmer (oboehmer)]

> Of course any feedbacks on the following are more than welcome .

Saku has already replied (and I agree with everything he has mentioned),
but I'd like to add some minor comments:
 
> Basically why we choose IsIs compare to Ospf :
> 
> - Partial Route Calculation (PRC):  SPF (Dijkstra) is run
> when topology has to be calculated (SPF tree) but when only IP routing
> information has to be calculated IS-IS performs a Partial Route
Calculation (PRC)
> which consumes less CPU.

Well, OSPF also doesn't run SPF when Type 3 or 5 updates arrive. IOS
still does full-SPF even when stub networks are added to Type-1, but
iSPF also changes this, as Saku has mentioned.
 
> The scalability of IS-IS might drives our choice of this IGP
> for the MPLS backbone versus OSPF.

You can build large, scalable networks with either protocol. It's a myth
that ISIS is more scalable than OSPF per se.

	oli