Subject: [mpls] P2MP LSP Ping

From: "Adrian Farrel" <[email-masked]>
Date: Fri, 18 Mar 2005 21:53:50 -0000

Hi Rahul,

In Minneapolis you raised a question about the P2MP LSP Ping draft.
This is captured in the minutes as...

      Rahul:   The draft tries to limit the ping to a subset of
               the recipients?

      Adrian:  Sub-set permitted in sub-set 1 or all (target
               individual recipient or whole tree)

      Rahul:   If I have a tree with a thousand egresses then I am not
               sure that that solves my problem.

The previous version of the draft had three options...
- ping one
- ping a list
- ping all

After discussion with several people (including you and Yakov in
Washington), we removed the ability to ping a list. In part, this was felt
to be reasonable because pinging a list introduced significant additional
processing at all egresses.

In Minneapolis I wasn't sure whether you were speaking in favor or against
the ability to ping a list of leaves.

We agreed that there was clearly a need to understand the requirements and
that's what I'd like to do now. Could you look at the current draft and
let me know whether it captures all of the requirements (perhaps we need
to add some more requirements text), and then we can see whether the
proposed solution addresses all of the requirements.

Thanks,
Adrian

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From: Erblichs <[email-masked]>
Date: Sat, 19 Mar 2005 03:44:20 -0800

Guys,

	This maybe totally stupid, but what about a walking
	ping when dealing with "a subset". Only the ping reciepents
	respond if the TLL is decremented to 0, or the equiv.

	Or only the respondents within the walking radius
	responds..

	So, it would be something like:

		ping walk 5 : where 5 is the radius of the ping

	This way you can build a explicit source route, if
	the ping reciepents are somewhat stable, and/or...

	And gives you a different subset of responders.

	Mitchell Erblich
	--------------------

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From: "Adrian Farrel" <[email-masked]>
Date: Mon, 21 Mar 2005 21:21:31 -0000

Hi Mitchell

> And gives you a different subset of responders.

I'm not completely clear about what you are suggesting.
There are two possiblities in what you are saying.

1. We send echo requests to the tree with TTL 1, then 2, then 3, etc.
When the TTL expires for any single request, every LSR that is processing
the request responds.
This is the technique described in the LSP Ping draft and extended in the
P2MP LSP Ping for traceroute function. As you suggest it can be used to
build an "explicit source route" or ERO.

2. OTOH you might be suggesting that we send echo requests to the tree
with TTL 1, then 2, then 3, etc.
When the TTL expires for any single request, every LSR that is processing
the request responds if and only if it is a leaf of the tree.
Such a technique might help stagger the responses from multiple leaves,
but I suspect that the problem of managing "silent" hops in the tree would
make this unworkable.

Cheers,
Adrian

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From: Rahul Aggarwal <[email-masked]>
Date: Mon, 21 Mar 2005 17:36:24 -0800 (PST)

Hi Adrian,

> that's what I'd like to do now.

Agreed.

> Could you look at the current draft and
> let me know whether it captures all of the requirements

It will be great if you could point me to the text that describes the
requirements for P2MP OAM ?

Thanks,
rahul

> (perhaps we need

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From: "Adrian Farrel" <[email-masked]>
Date: Tue, 22 Mar 2005 18:00:51 -0000

> requirements for P2MP OAM ?

:-)

I guess there is as yet no draft that covers all of the requirements for
OAM for P2MP (TE) LSPs.
As I recall this was also the case for P2P when the LSP Ping work started,
but no matter.

The requirements for P2MP LSP Ping are covered in the P2MP LSP Ping draft.
Wider scoped OAM requirements will be in a draft that Tom and I plan to
write just as soon as we have a few spare cycles.

Cheers,
Adrian

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From: "Thomas D. Nadeau" <[email-masked]>
Date: Tue, 22 Mar 2005 14:22:04 -0500

> write just as soon as we have a few spare cycles.

	Yes, indeed we planed on doing this as one of our actions
from comments on the MPLS OAM requirements document's WG last
call.

	--Tom

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From: Rahul Aggarwal <[email-masked]>
Date: Wed, 30 Mar 2005 12:05:27 -0800 (PST)

Hi Adrian,

Sorry for the delay.

> write just as soon as we have a few spare cycles.

I also think we need some more input from providers on this to understand the
requirements better.

rahul