[c-nsp] vs isis routing levels

[Mark Tinka]

On Friday, December 20, 2013 08:38:16 PM Saku Ytti wrote:

> I think this is backwards. If it's small enough to be
> single area, it does not matter what it is.
> If maybe sometime in future you might need more areas,
> make your network level-2, i.e. core, to which you can
> attach say metro areas.
> 
> level-2 is always correct answer when you start ISIS
> network, because you don't lose anything, and you gain
> ability to add areas later on, if you need to.

Agree. L2-only is quite scalable, especially if you're 
running routers developed in the last 5 - 8 years which can 
handle it.

I'd recommend running L2-only because if you're messing with 
MPLS-TE, you don't have to worry about inter-area TE.

> We're right now rocking about 1500 nodes flat l2 core.
> But we are in situation where we're going to replace
> L2/LAN metro networks with MPLS, and this is good
> situation to look into our alternatives

Glad to hear you're going MPLS in the Access :-). I've never 
regretted that decision since it became possible back in 
2010.

More networks should do this.

> a) keep flat L2
> b) make each metro L1, and metro<->core border routers
> L1L2 c) make metro L2 and core L2, but don't connect IGP
> domains. Capitalize BGP-LS and Segment Routing for
> end-to-end MPLS with MPLS-TE capabilities, without
> combining IGP.

Do you have access to pre-production BGP-LS code?

I know there is SR code in the wild, but if BGP-LS is 
starting to make an appearance, that would be great!

I'll probably give BGP-LS and SR another 3x years before I 
begin considering it. I've just built enough trust for 
(r)LFA, so bit by bit :-).

But yes, I certainly agree as a future operator roadmap:

	- L2-only in the core
	- L2-only in the edge
	- L2-only in the Metro-E Access
	- BGP-LS between Metro-E rings and edge
	- SR within IGP domains

This is why I think moving route reflection to servers will 
be helpful, if BGP-LS is deployed, among other things.

Cheers,

Mark.
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