comments on draft-kompella-mpls-multiarea-te-02.txt

[Francois Le Faucheur <flefauch@cisco.com>]

Kireeti, Yakov, Jean-Philippe,


A few suggestions on the Multi-Area TE draft for your consideration:

Independent per-area TE
=======================
The draft currently restricts its scope of multiple-area TE to only those 
scenarios using LSPs that span multiple areas.
Some SPs have/will deploy TE in multiple areas simply by running TE 
independently in each area. Although, this does not really require any 
specific new mechanisms, it is a valid scenario for doing TE in multi-area 
environments. So my suggestion would be to slightly broaden the scope of 
the draft (ie to not deliberately restrict it to the scenarios using 
inter-area LSPs) and include a section on the multiarea TE scenario where 
only intra-area LSPs are used.
You could then clarify that no new mechanisms are required for this (only 
require that routers at boundary may have to keep TED from two areas).
I think it would also be useful to highlight a few properties of such a 
deployment scenario (scalability/achieves kind of a natural "hierarchy" in 
the sense that you keep a small number of tunnels in the backbone area and 
packets from many leaf-area tunnels get aggregated into core-area tunnels, 
dynamic routing onto tunnels at Head-ends is somewhat simpler since 
Head-end IGP "sees" tail-end in its intra-area IGP Database, does not allow 
end-to-end control of smaller traffic trunks ie two traffic trunks from two 
head-end areas going to same tail-end cannot be "routed" separately in 
backbone area or tail-end area...).


Reoptimisation
==============
Since you discuss how "optimal" is the routing for each scenario of section 
4, I'd suggest a clarifying statement that handling reoptimisation on a 
per-area basis does not allow "globally optimum" reoptimisation.
I would also suggest adding a statement making it explicit that other 
methods of reoptimisation are possible which may reuse the mechanisms 
described earlier for initial path computation (e.g. Path Computation server).


Vocab
=====
in section 3, you clarify that you will be using OSPF terminology  to 
dicuss both OSPF and ISIS. You mention "backbone area" as one such term. 
You may want to mention ABR as another.

Typos/Editos
=============
	- 4.2: 2nd paragraph., last sentence. "LSR setup" should read "LSP setup".
	- 4.3: 2nd paragraph, 1st sentence . "in the tail-end area the head-end 
area)" should read  " in the tail-end area"
	- 4.4: paragraph 5 and 7 say the same thing and should be combined.

Hope this is useful

Francois