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Re: TR : I-D ACTION:draft-ietf-tewg-interarea-mpls-te-req-00.txt



hi jl, here below several comments on this updated version of the document:

1) section 5.3.1 mentions:

"The solution MUST entirely preserve the concept of IGP hierarchy. In
   other words, flooding of TE link information across areas MUST be
   precluded."

section 5.3.2 mentions:

"The solution MUST also not increase IGP load which could compromise
   IGP scalability. In particular, a solution satisfying those
   requirements MUST not require for the IGP to carry some unreasonable
   amount of extra information and MUST not unreasonably increase the
   IGP flooding frequency."

but section 7.12 tells:

"The discovery mechanism SHOULD
   be applicable across multiple IGP areas, and SHOULD not impact the
   IGP scalability, provided that IGP extensions are used for such a
   discovery mechanism."

-> would it be possible to align these requirements, i get the impression (please confirm) that you preclude TE link information but you would allow for node information (auto-mesh) ? note also that the section 7.12 doesn't tell us a lot about the expected distribution of the mesh

2) section 7.3

"   In the context of this requirement document, an optimal path is
   defined as the shortest path across multiple areas taking into
   account either the IGP or TE metric. "

are you referring here to
<http://www.ietf.org/internet-drafts/draft-ietf-tewg-te-metric-igp-02.txt>

would you clarify ?

3) section 7.3

it is not clear for me what is behind the last part of the following sentence

"So a solution should support both mechanisms, and SHOULD allow
   the operator to select by configuration, and on a per-LSP basis, the
   required level of optimality. "

what is meant by "level of optimality" ? is it simply "optimal - sub-optimal" or do you have something else in mind ?

4) section 7.4

"Another example is the requirement to set up multiple TE LSPs between
   a pair of LSRs residing in different IGP areas in case a single TE
   LSP satisfying the set of requirements could not be found. "

why in such a case diversity would be desirable ? got the impression that if a single path would have been feasible it would have been selected in this case - isn't it ?

5) section 7.7

"This may reduce the recovery delay, but with the risk of
   multiple crankbacks, and sub-optimality.  "

i agree, but this is valid iff the head-end has initially computed an end-to-end optimal path, also unclear if you refer also here to the provisioning delay ?

editorially speaking it is also a bit unclear why you've splitted section 7.7 and section 7.8 both refers to inter-area lsp recovery

6) section 7.11

would it be possible to mention what's expected (or not expected) in terms also of hard preemption ?

7) section 8.2

what's meant by stability ? ie stability of what ? (for instance, as i read the document, but please correct me, stability and re-optimization are imho two features that are going in somehow opposite directions so a trade-off has to be found here)

thanks in advance,
- dimitri.

LE ROUX Jean-Louis FTRD/DAC/LAN wrote:

Hi all,

Thanks in advance for your comments on this new revision of inter-area
TE requirements.

Regards,

JL


A New Internet-Draft is available from the on-line Internet-Drafts directories. This draft is a work item of the Internet Traffic Engineering Working Group of the IETF.

Title : Requirements for Inter-area MPLS Traffic

Engineering


       Author(s)       : J. Le Roux, et al.
       Filename        : draft-ietf-tewg-interarea-mpls-te-req-00.txt
       Pages           : 20
       Date            : 2004-3-26

This document lists a detailed set of functional requirements for the
support of inter-area MPLS Traffic Engineering (inter-area MPLS TE) which could serve as a guideline to develop the required set of protocol extensions.


A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-tewg-interarea-mpls-te-r

eq-00.txt


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-- Papadimitriou Dimitri E-mail : dimitri.papadimitriou@alcatel.be E-mail : dpapadimitriou@psg.com Webpage: http://psg.com/~dpapadimitriou/ Address: Fr. Wellesplein 1, B-2018 Antwerpen, Belgium Phone : +32 3 240-8491