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

"Templin, Fred L" <Fred.L.Templin@boeing.com> Tue, 07 February 2017 19:58 UTC

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From: "Templin, Fred L" <Fred.L.Templin@boeing.com>
To: Joe Touch <touch@isi.edu>, "otroan@employees.org" <otroan@employees.org>, "Eggert, Lars" <lars@netapp.com>
Subject: RE: Last Call: <draft-ietf-6man-rfc1981bis-04.txt> (Path MTU Discovery for IP version 6) to Internet Standard
Thread-Topic: Last Call: <draft-ietf-6man-rfc1981bis-04.txt> (Path MTU Discovery for IP version 6) to Internet Standard
Thread-Index: AQHSgW+yaUQDcUzHwUaWWd7FFympqaFd8O5wgACJwID//3pYkA==
Date: Tue, 7 Feb 2017 19:57:53 +0000
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Hi Joe,

> -----Original Message-----
> From: Joe Touch [mailto:touch@isi.edu]
> Sent: Tuesday, February 07, 2017 11:53 AM
> To: Templin, Fred L <Fred.L.Templin@boeing.com>om>; otroan@employees.org; Eggert, Lars <lars@netapp.com>
> Cc: tsv-area@ietf.org; 6man-chairs@ietf.org; 6man WG <ipv6@ietf.org>rg>; ietf@ietf.org; draft-ietf-6man-rfc1981bis@ietf.org
> Subject: Re: Last Call: <draft-ietf-6man-rfc1981bis-04.txt> (Path MTU Discovery for IP version 6) to Internet Standard
> 
> Hi, Fred,
> 
> This is a separate issue with RFC4821, though.

Agreed. Fred Baker and I were discussing about whether an erratum
should be filed.

> My point for 1981bis is that it needs to be more clear that ICMP
> blocking renders this technique ineffective for the most part. I'm not
> saying that PLPMTUD is perfect or the only alternative, but this doc
> should be more clear about its own viability.

I could agree if suitable language could be adopted.

Thanks - Fred

> Joe
> 
> 
> On 2/7/2017 11:45 AM, Templin, Fred L wrote:
> > Hi Joe,
> >
> > In my understanding, RFC4821 does not adequately address scenarios where the
> > probe packets may (for legitimate reasons) take a different path than the data
> > packets, e.g., when Equal-Cost Multi Path (ECMP) is present. This is not only a
> > consideration for tunnels, but also for path MTU sharing between transport layer
> > sessions where an MTU learned by a first session is shared with a second session
> > bound for the same destination. In that case, the probes of the first session may
> > take a different path than the data packets of the second session, and a black
> > hole is possible.
> >
> > Thanks - Fred
> > fred.l.templin@boeing.com
> >
> >> -----Original Message-----
> >> From: tsv-area [mailto:tsv-area-bounces@ietf.org] On Behalf Of Joe Touch
> >> Sent: Tuesday, February 07, 2017 10:26 AM
> >> To: otroan@employees.org; Eggert, Lars <lars@netapp.com>
> >> Cc: tsv-area@ietf.org; 6man-chairs@ietf.org; 6man WG <ipv6@ietf.org>rg>; ietf@ietf.org; draft-ietf-6man-rfc1981bis@ietf.org
> >> Subject: Re: Last Call: <draft-ietf-6man-rfc1981bis-04.txt> (Path MTU Discovery for IP version 6) to Internet Standard
> >>
> >>
> >>
> >> On 2/4/2017 10:40 AM, otroan@employees.org wrote:
> >>> Lars,
> >>>
> >>>>> My apologies: my comments were probably misleading. Certainly, this
> >>>>> document is simply RFC1981 to Std, and hence recommending RFC4821 would
> >>>>> be kind of ou of scope, here.
> >>>>>
> >>>>> That say, one might wonder to what extent, and for the general Internet,
> >>>>> RFC1981 can be considered succesful (given the filtering of ICMP
> >>>>> messages). -- i.e., at this point in time you wouldn't rely on RFC1981
> >>>>> (icmp-based pmtud) for path-mtu discovery.
> >>>> What Fernando said: I'm certainly not opposed to lifting this to Standard, but it is painting an incorrect picture - PLPMTUD is de
> facto
> >> mandatory these days, and has been for years.
> >>> While I'm all in favour of PLMTUD. It doesn't seem like a complete solution.
> >>> PMTUD on the other hand supports all protocols on top of IP.
> >> If by "supports" you mean "doesn't work", then yes. That's why we now
> >> have PLPMTUD.
> >>
> >>> Looking just at our specifications, we cannot state that PLMTUD can replace PMTUD. Take RFC2473 (IPv6 tunnelling) for example.
> >> See draft-ietf-intarea-tunnels, esp. v03 Section 5.5.2
> >>
> >> (yes, that doc has expired while we're preparing the 04 update, which
> >> should be issued shortly)
> >>
> >> Joe
> >>
> >
>