[c-nsp] Unified MPLS - Discrete area or separate IGP in Access Layer

[Adam Vitkovsky]

> There has been quite a bit of talk about this in past posts on this list. 
Now that you mentioned it I recall the discussions. 

> Generally, I'd recommend IS-IS because as a single Level IGP, it scales
very well.  
And I did support this. However now facing real world restrictions of 12K
routes per ME (app template) or ASR901 I could probably use some separation
for future proofing the network. 

> You also want a single Level because some MPLS-TE features don't work well

> across Levels (although I know those restrictions are being lifted with
SR, 
> but that's still a while away). 
Way back when I haven't had any major problems with inter-area or inter-as
MPLS-TE, or MVPN for that matter -but that wasn't on ME :). 


> What Saku, I and others have loosely agreed on for the way forward 
> for deploying large scale IP/MPLS networks, edge-to- edge, is:
> - IS-IS L2-only in the core
> - IS-IS L2-only in the edge
> - IS-IS L2-only in the Metro-E Access
> - BGP-LS between Metro-E rings and edge
> - SR within IGP domains

So ISIS L2 everywhere though Edge and Metro-E Access rings are not
continuous L2 but rather separate domains interconnected with BGP-LS please?

-Which I would now accomplish with RFC3107 in the meantime. 

adam