RE: Optical Link Interface - LMP-WDM comments

[Jonathan Lang <jplang@calient.net>]

 Bala,
  Please see inline.

Thanks,
Jonathan 

>-----Original Message-----
>From: Bala Rajagopalan
>To: Andre Fredette
>Cc: 'ccamp@ops.ietf.org'
>Sent: 7/30/2001 7:38 AM
>Subject: Optical Link Interface - LMP-WDM comments
>
>Andre:
>
>I'm attaching specific comments on LMP-WDM. Top level issues are
>as follows:
>
>1. Layer mix-up: In some places, the WDM system is required to
>send information which is not native to OLS to the OXCs. In fact, 
>this is very strange, because this information must originate from
>the OXC domain, get configured in WDM, and then go back to OXCs. This
>is a problem with OLI definition, not LMP-WDM itself. This requires
>some discussion and clean up. 
What specific information are you talking about here?  As you say, this is
an issue with OLI definition itself and the parameters were discussed at
quite length among both LMP-WDM authors and NTIP authors.  (I do notice that
you are also listed as an OLI author...).  Certainly we can revisit these
issues if they need to be addressed...

>2. Rather than tailoring the procedures for the particular requirements
>(OLI), the draft seems to be written with the goal of maximal reuse of
>LMP. This sometimes adds to the complexity of the proposal.  
LMP-WDM was written to satisfy the OLI requirements and reuse the LMP
protocol.  This is similar to the approach taken for GMPLS RSVP-TE and
CR-LDP.

>Specifically, LMP-WDM has many "extensions" to LMP, giving the impression
>that LMP-WDM is a superset of LMP. I think there are differences in the
>situations where LMP is applied as compared to LMP-WDM and these aspects
>are not discussed sufficiently. I think a meticulous examination of the
>OLI requirements and LMP procedures is necessary to just carve out a set 
>of procedures for OLI, rather than the superset approach. The maximal
>"re-use" argument doesn't make any sense on the WDM side where there is
>no LMP. Or, for that matter, where OXCs don't implement LMP. (This is
>where NTIP makes a good point).
Which LMP-WDM procedures are not required for OLI?

>3. I'm afraid the current LMP link verification definition (and as a
>corollary, LMP-WDM link verification) has only a marginal value
>considering the investment on hardware and protocol implementation. This 
>is an area that requires more work.
If you believe link verification has marginal value, you don't have to
implement it (remember it's optional).  We have heard otherwise from
customers.

>4. Some of the procedures in the draft must be more explicitly described
>rather than saying that they are same as LMP's.
Please clarify which procedures you are referring to.

>As you noted, a more careful examination of LMP itself is in order.
This is greatly encouraged.

I also think it would be useful for you to do a similar analysis of NTIP.

Thanks,
Jonathan

>Regards,
>
>Bala
>
>Bala Rajagopalan
>Tellium, Inc.
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