Re: [Bier] draft-ietf-bier-oam-requirements-00: PMTUD requirement in BIER OAM Requirements

Gregory Mirsky <gregory.mirsky@ericsson.com> Fri, 06 November 2015 10:48 UTC

From: Gregory Mirsky <gregory.mirsky@ericsson.com>
To: "eckert@cisco.com" <eckert@cisco.com>
Thread-Topic: draft-ietf-bier-oam-requirements-00: PMTUD requirement in BIER OAM Requirements
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Date: Fri, 06 Nov 2015 10:48:08 +0000
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Subject: Re: [Bier] draft-ietf-bier-oam-requirements-00: PMTUD requirement in BIER OAM Requirements
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Hi Toerless,
perhaps I wasn't clear at the mike today. PMTUD is clearly not for OAM but it is OAM service to determine OAM on particular path (the same as PMTUD in p2p, right?). I believe that the fact that PMTUD over multicast in MPLS or IPv4/IPv6 doesn't scale is another indication of advantage BIER technology presents us with.
I'll be glad to continue our discussion on the list.

	Regards,
		Greg

-----Original Message-----
From: eckert@cisco.com [mailto:eckert@cisco.com] 
Sent: Friday, November 06, 2015 1:29 PM
To: Gregory Mirsky
Cc: BIER (bier@ietf.org)
Subject: draft-ietf-bier-oam-requirements-00: PMTUD requirement in BIER OAM Requirements

Thanks, Greg.

I was looking just for PMTU or MTU in the text and could not find it.

I do not agree to this requirement in the OAM requirement draft as of now.

Why is it needed for BIER ? AFAIK, there is no PMTUD for OAM in any of the prior IP multicast transport options - native IP or MPLS. True ?
Any reason why BIER would need this more than those prior options ?
Any reason why BIER would make it a lot easier  than the prior options ?

This should IMHO be discussed in the draft.

If we get PMTUD, would it only be for OAM and only for the BIER path, eg:
not the end-to-end path ? If so, it should be called different (BP-MTUD or the like). 

If someone proposes that it should be end-to-end, then this needs to go back to MBoned, because it would ask to introduce PMTUD into eg: PIM path segments.

Wrt. the protocols proposed in your PMTUD draft proposal: I would like to understand why we would not want to proactively signal MTU intead of probing it. There seems to have been some work in the past around this in unicast, not sure how successful.

Cheers
    Toerless

On Fri, Nov 06, 2015 at 01:02:10AM +0000, Gregory Mirsky wrote:
> Hi Toerless,
> I'd like to bring requirement #9 in the BIER WG document OAM Requirements for BIER<https://tools.ietf.org/html/draft-ietf-bier-oam-requirements-00>:
> BIER OAM MUST support Path Maximum Transmission Unit discovery.
> Hope that addresses your question why are we doing PMTUD.
> 
>                 Regards,
>                                 Greg

[Bier] PMTUD requirement in BIER OAM Requirements Gregory Mirsky
[Bier] draft-ietf-bier-oam-requirements-00: PMTUD… eckert@cisco.com
Re: [Bier] draft-ietf-bier-oam-requirements-00: P… Gregory Mirsky
Re: [Bier] draft-ietf-bier-oam-requirements-00: P… eckert@cisco.com
Re: [Bier] draft-ietf-bier-oam-requirements-00: P… Antoni Przygienda
Re: [Bier] draft-ietf-bier-oam-requirements-00: P… Gregory Mirsky
Re: [Bier] draft-ietf-bier-oam-requirements-00: P… eckert@cisco.com
Re: [Bier] draft-ietf-bier-oam-requirements-00: P… eckert@cisco.com