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RE: BFD WG adoption for draft-haas-bfd-large-packets

"Les Ginsberg (ginsberg)" <ginsberg@cisco.com> Mon, 29 October 2018 16:39 UTC

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From: "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>
To: Jeffrey Haas <jhaas@pfrc.org>, "Reshad Rahman (rrahman)" <rrahman@cisco.com>
CC: "Naiming Shen (naiming)" <naiming@cisco.com>, "rtg-bfd@ietf.org" <rtg-bfd@ietf.org>
Subject: RE: BFD WG adoption for draft-haas-bfd-large-packets
Thread-Topic: BFD WG adoption for draft-haas-bfd-large-packets
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Date: Mon, 29 Oct 2018 16:39:04 +0000
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Jeff/Albert -

Given the MTU issue is associated with a link coming up - and the use of Echo would allow the problem to be detected and prevent the BFD session from coming up - 
and you are acknowledging that the protocol allows padded Echo packets today ...

is there really a need to do anything more?

   Les

> -----Original Message-----
> From: Jeffrey Haas <jhaas@pfrc.org>
> Sent: Monday, October 29, 2018 8:36 AM
> To: Reshad Rahman (rrahman) <rrahman@cisco.com>
> Cc: Les Ginsberg (ginsberg) <ginsberg@cisco.com>; Naiming Shen (naiming)
> <naiming@cisco.com>; rtg-bfd@ietf.org
> Subject: Re: BFD WG adoption for draft-haas-bfd-large-packets
> 
> Reshad,
> 
> On Fri, Oct 26, 2018 at 06:32:26PM +0000, Reshad Rahman (rrahman) wrote:
> >On 2018-10-25, 11:38 AM, "Jeffrey Haas" <jhaas@pfrc.org> wrote:
> > >     The draft I had previously worked on with Xiao Min discussing probing
> using
> > >     BFD Echo had the concept of probes that would happen wherein the
> session is
> > >     not torn down.  The example carries similarly with the "send
> occasional".
> >
> > <RR> We discussed use of echo at IETF102. The large-packets draft
> mentions
> > that echo can only be used for single-hop, hence the need for padding the
> > control packets. But isn't single-hop Albert's main use-case?
> 
> It's Albert's primary use case.  And, I think a common related one is
> protecting tunnels of various flavors; e.g. GRE or IPsec.
> 
> > I believe we
> > should add the echo option in the large-packets draft, it has the benefit
> > that you get the desired functionality even if only 1 side of the WAN link
> > supports echo. I realize not all implementations support echo so they
> > might have to do pad control packets instead.
> 
> While I don't think Albert or I would have any objections to adding Echo
> discussion in the existing document, we perhaps risk running into one of the
> issues Xiao and I had briefly discussed.  Echo is intentionally
> under-specified in RFC 5880 et seq.  While it's possible that we can simply
> put in a discussion section that says "if you use Echo mode with similar
> padding, you can get similar benefit", I think that may be as far as we want
> to go.
> 
> The related observation is that nothing stops an Echo implementation from
> doing this with no changes to the protocol. :-)
> 
> -- Jeff

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