Subject: LIB Table - LSR MIB v. LDP MIB

From: Adrian Farrel <[email-masked]>
Date: Wed, 15 Mar 2000 06:03:56 -0000

Tom, you wrote in response to Dave in response to Arun...

>>> I have the same objections to the current LDP MIB as Tom. The LIB
>>> and the FEC tables are not specific to LDP and do not belong here.
>>> The first one is part of the LSR MIB already and the second one
>>> should be in a separate packet classifier MIB. They should be removed
>>> before the LDP MIB goes to last call. 

>>I'd rather a little redundancy than the to use the new proposed 
>>MIB which hasn't had the scrutiny that the LDP MIB has had.

>That may be true in terms of the new MPLS Packet 
>Classifier MIB which deals most closely with the LDP
>FEC table. However, as Arun pointed out, the LIB Table 
>contained in the LDP MIB is redundant with the LSR MIB. 
>The LSR MIB has been out for quite a while now, and has been 
>under as much scrutiny as the LDP MIB.

It is true that some of the information contained in the LDP MIB's
LIB table is also contained in the LSR MIB, but consider
mplsLdpLibInLabelType, mplsLdpLibOutLabelType and 
mplsLdpLibLspLastChange.

Note also that to walk the 'LIB table' in the LSR MIB involves
walking the XC table and for each entry looking up the out
label and out interface in the Out Segment table.  This is,
perhaps, less graceful.

Did you consider putting a simple LIB table in the LSR MIB?

Adrian
--
Adrian Farrel  mailto:[email-masked]
ATM, MPLS and Telecoms Development Group
Data Connection Ltd., Chester, UK
http://www.datcon.co.uk/
Tel: +44 (0) 1244 313440  Fax: +44 (0) 1244 312422

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From: Joan Cucchiara <[email-masked]>
Date: Thu, 16 Mar 2000 16:00:46 -0500

Adrian has posed a good question, and I would
also like to see the response.

  Thanks, Joan

> -----Original Message-----
> From: Adrian Farrel [mailto:[email-masked]]
> Sent: Wednesday, March 15, 2000 1:04 AM
> To: Thomas D. Nadeau; [email-masked]
> Cc: [email-masked]; Arun Viswanathan (E-mail); Cheenu Srinivasan;
> [email-masked]
> Subject: LIB Table - LSR MIB v. LDP MIB
> 
>

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From: "Thomas D. Nadeau" <[email-masked]>
Date: Thu, 16 Mar 2000 17:10:26 -0500

Hi,

         See Arun's answers to your other questions.

> > label and out interface in the Out Segment table.

         I would recommend gathering this information by walking
the in/outSegment tables. The purpose of the XC tables is to tell
you how the labels are swapped and which ones are currently in
use (among other things).

>This is, perhaps, less graceful.

         The MIB does provide the information you seek,
and the NMS is then free to create a linear list of the
labels it discovers later if it so desires.

         --Tom

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From: Arun Viswanathan <[email-masked]>
Date: Thu, 16 Mar 2000 14:28:37 -0800

Joan,

> > mplsLdpLibInLabelType, mplsLdpLibOutLabelType and 

The LSR MIB supports all labels types but doesn't support an explicit
object for the label type. This approach is more generic in terms of
supporting currently existsing label type or others that may come up
in future. A LastChange object was not added because not sufficient
response was found from the list. I feel it is not a very useful
information either because often when the label mapping changes
it may be a new LSP.

> > Did you consider putting a simple LIB table in the LSR MIB?

First, what exists in the LSR MIB is the LIB. It supports all the
Arch requirements. The 'simple LIB' that is being alluded here is
simply inadequate. Do the excercise for yourself to see if the
various features listed (section 4) in the LSR document can be
supported. So making it look graceful should be the least of our
concerns, moreover it is a subjective matter. 

-arun

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From: Joan Cucchiara <[email-masked]>
Date: Thu, 16 Mar 2000 18:33:33 -0500

Hi Arun,

> concerns, moreover it is a subjective matter. 

I think what was being asked was if there was a way to make the
XC table more efficient not only for traversing but for easier
clean up on teardown.

Why is the indexing of the mplsOutSegmentTable mplsOutSegmentIndex,
and not (mplsOutSegmentIfIndex, mplsOutSegmentTopLabel) (also would
prefer to call this mplsOutSegmentLabel as the mplsOutSegmentPushTopLabel
tells you that whether it was pushed or not)?

Then the XC table could be mplsXCIndex, mplsInSegmentIfIndex,
mplsInSegmentLabel
and mplsOutSegmentLabel).  It seems this would be possible to do,
and also seems more efficient?

There is also a discussion of Terminating LSPs, but not sure it belongs
in an XC table...could you explain why this is here?  Wouldn't it be better
to just add something to the mplsInSegmentTable to indicate that the
insegment
was terminated?

Thanks, Joan

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From: Cheenu Srinivasan <[email-masked]>
Date: Thu, 16 Mar 2000 18:58:35 -0500

Joan,

> tells you that whether it was pushed or not)?

If you had been following the discussions and the evolution of this
MIB from the beginning, we addressed this specific proposal a couple of
times before by us on this mailing list.

This won't work for the case where we want to pop the top label and
forward the packet with whatever label is underneath, without knowing
or wanting to know the underlying labels.

As Arun mentioned, please do the exercise of going through the list of
features that MIB lists and ask whether there is a simpler way
to satisfy them all before proposing new solutions.

> to just add something to the mplsInSegmentTable to indicate that the

Again, the whole idea was to be able to represent originating, terminating
and
intermediate LSPs using the same cross-connect model. We have tried to
design the simplest possible cross-connect model that is unified yet
powerful
enough to represent all the features listed in the draft.

Cheenu

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From: Arun Viswanathan <[email-masked]>
Date: Thu, 16 Mar 2000 20:32:56 -0800

> From: [email-masked] [mailto:[email-masked]]On Behalf Of Joan
> Cucchiara
> Sent: Thursday, March 16, 2000 3:34 PM
> To: 'Arun Viswanathan'; Joan Cucchiara; 'Adrian Farrel'; 'Thomas D.
> Nadeau'; [email-masked]'
> Cc: [email-masked]'; 'Cheenu Srinivasan'
> Subject: RE: LIB Table - LSR MIB v. LDP MIB
> 
> 
> 
> 
> 
> 
> Hi Arun,
> 
> > 
> > > > 

I am sure you will always find better ways of doing anything
if you waited long enough. The MIB has been this away since Feb 1998!
I think in all fairess to all the folks who have worked on this draft
in this WG, its too late for this line of questioning at this time, IMHO.
We are into the mode 'if its not broken why fix it'.
-arun

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From: Arun Viswanathan <[email-masked]>
Date: Fri, 17 Mar 2000 09:56:35 -0800

> if you waited long enough. The MIB has been this away since Feb 1998!

Oops. That should have read 1999. But, almost the same MIB existed in
Dec 1998.
-arun