Hi Les,

> I am not yet overly enthused about approaches which promote non-hierarchical 
> network architectures. But it seems clear that there is interest in deploying 
> non-hierarchical solutions and both drafts present solutions
> which merit further evaluation.

I think that there’s some confusion here. The point is very much to have a 
hierarchical design.  The key point is that the IGP hierarchy must not require 
a hierarchical data plane.  While a hierarchical data plane may suffice in a 
WAN topology, imposing that restriction on mega-scale multi-dimensional Clos 
fabrics simply doesn’t fly.  

We want the hierarchy provided by the IGP.  We need tools for extreme scaling. 
We need the IGP abstractions decoupled from the data plane architecture.

Looked at sideways, we’re simply trying to generalize the IS-IS area mechanism. 
We need transit areas that do not impact the scale of L2.

Apologies if I’m simply restating what Tony P. has already said.


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