RE: Last Call: <draft-ietf-6man-rfc1981bis-04.txt> (Path MTU Discovery for IP version 6) to Internet Standard

Hi,

> -----Original Message-----
> From: ipv6 [mailto:ipv6-bounces@ietf.org] On Behalf Of Brian E Carpenter
> Sent: Friday, February 03, 2017 11:33 AM
> To: ipv6@ietf.org
> Subject: Re: Last Call: <draft-ietf-6man-rfc1981bis-04.txt> (Path MTU Discovery for IP version 6) to Internet Standard
> 
> On 03/02/2017 23:52, otroan@employees.org wrote:
> ...
> > PLMTUD is better, and it is even better combined with PMTUD. But PLMTUD isn't deployed everywhere, nor used for UDP etc..
> > I don't see how that has any bearing on making 1981 an Internet standard.
> >
> > I would really encourage more work on the Path MTU discovery problem though. Possibly combined with removing fragmentation
> from the IP layer. But that's far outside of the context of taking 1981 to Internet standard.
> 
> Exactly. We aren't required to show that RFC1981 works in all circumstances. We're
> required to show that it works interoperably and is widely implemented.
> 
> Lars - nobody disagrees, I think, that we need to get RFC4821 widely implemented,
> but that is a separate thing entirely.

A note about RFC4821. We think it will work for end-to-end MTU determination and
black hole avoidance, but from discussions on intarea we now no longer think it will be
applicable to tunnel endpoints. That is because the tunnel ingress is not the source
of the original packets - it is only the source of the tunneled packets and the RFC4821
probes. And, if the original packets (once admitted into the tunnel) travel a different
path than the probes the system could black hole.

Is this worth an errata to RFC4821?

Thanks - Fred
fred.l.templin@boeing.com

>     Brian
> 
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