Subject: Re: [v6ops] TCP and IPV6_USE_MINMTU

From: Mark Andrews <[email-masked]>
Date: Mon, 19 Oct 2015 09:58:06 +1100

In message <[email-masked]>, Brian E Carpenter writes:
> I think that
> (a) This draft should not be Informational, it should become a BCP.
> (b) I suspect it belongs in v6ops rather than 6man, since it doesn't
> change anything in the standards.

Isn't this similar to RFC6691 which was only informational?

That said I don't care which w.g. processes this so long as it gets
processed.  Similarly w.r.t. to the category.  Lets let the chairs
decide which w.g.

For v6ops this is
https://datatracker.ietf.org/doc/draft-andrews-tcp-and-ipv6-use-minmtu/

Mark

> (c) I think it doesn't say quite enough about how this is a very serious
> and recurrent operational problem which causes real damage to IPv6 deployment
> .
> 
> Also - it's not OK that POSIX hasn't yet picked up the advanced socket API
> and that it isn't available in all programming languages with socket calls.
> We, for some value of "we", need to campaign to get this fixed.
> 
>     Brian
> 
> 
> On 17/10/2015 11:56, Mark Andrews wrote:
> > In message <[email-masked]>, Brian E Carpenter writes:
> >> On 17/10/2015 09:31, Mark Andrews wrote:
> >>>
> >>> In message <20151016202620.GI1442@verdi>, John Leslie writes:
> >>>> Mark Andrews <[email-masked]> wrote:
> >>>>>
> >>>>> Please see
> >>>>> https://www.ietf.org/id/draft-andrews-tcp-and-ipv6-use-minmtu-00.txt
> >>>>>
> >>>>> It addresses what should be obviously done but isn't by many
> >>>>> implementations.
> >>>>
> >>>>    Alas, this draft gives no clue _how_ to check IPV6_USE_MINMTU ...
> >>>> (or, for that matter, how to set it).
> >>>>
> >>>>    One could reasonably guess that s/he should look through RFC3542 to
> >>>> find how to check this; but RFC3542 contains no such string. (It does
> >>>> contain the string IPV6_USE_MIN_MTU; but I don't feel justified in
> >>>> guessing that far astream...
> >>
> >> Incidentally, it recently came to my attention that standard Python
> >> doesn't support RFC3542. I don't know how widespread that issue is, but
> >> it may be behind some of these broken MSS deployments.
> >>
> >>     Brian
> > 
> > The entire advanced socket API is poorly supported because POSIX
> > didn't pick it up.
> > 
> > That said I've updated the document based on the feedback received
> > to date.
> > 
> > https://tools.ietf.org/html/draft-andrews-tcp-and-ipv6-use-minmtu-03
> > 
> >>> Yes, I typo'd that, repeatedly.
> >>>  
> >>>>    Perhaps adding a citation to the specific section of a particular
> >>>> RFC would help?
> >>>>
> >>>> --
> >>>> John Leslie <[email-masked]>
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: [email-masked]

---

From: Brian E Carpenter <[email-masked]>
Date: Mon, 19 Oct 2015 12:17:33 +1300

> Isn't this similar to RFC6691 which was only informational?

IMHO that's an error and 6691 should be standards track, but I wasn't
involved in that discussion so there may be a reason.

> processed.  Similarly w.r.t. to the category.  Lets let the chairs

Sure. I would argue for BCP because it really is an operational requirement
to get this fixed in all implementations.

   Brian

---

From: Mark Smith <[email-masked]>
Date: Mon, 19 Oct 2015 10:18:31 +1100

> Isn't this similar to RFC6691 which was only informational?

I think Bob is saying this is an important enough issue that it should be
given BCP status.

> <https://datatracker.ietf.org/doc/draft-andrews-tcp-and-ipv6-use-minmtu/>
https
<https://datatracker.ietf.org/doc/draft-andrews-tcp-and-ipv6-use-minmtu/>://
<https://datatracker.ietf.org/doc/draft-andrews-tcp-and-ipv6-use-minmtu/>
datatracker.ietf.org
<https://datatracker.ietf.org/doc/draft-andrews-tcp-and-ipv6-use-minmtu/>
/doc/
<https://datatracker.ietf.org/doc/draft-andrews-tcp-and-ipv6-use-minmtu/>
draft-andrews-tcp-and-ipv6-use-minmtu
<https://datatracker.ietf.org/doc/draft-andrews-tcp-and-ipv6-use-minmtu/>/
<https://datatracker.ietf.org/doc/draft-andrews-tcp-and-ipv6-use-minmtu/>
> > >>>> Mark Andrews <[email-masked]> wrote:
<https://www.ietf.org/id/draft-andrews-tcp-and-ipv6-use-minmtu-00.txt>https
<https://www.ietf.org/id/draft-andrews-tcp-and-ipv6-use-minmtu-00.txt>://
<https://www.ietf.org/id/draft-andrews-tcp-and-ipv6-use-minmtu-00.txt>
www.ietf.org
<https://www.ietf.org/id/draft-andrews-tcp-and-ipv6-use-minmtu-00.txt>/id/
<https://www.ietf.org/id/draft-andrews-tcp-and-ipv6-use-minmtu-00.txt>
draft-andrews-tcp
<https://www.ietf.org/id/draft-andrews-tcp-and-ipv6-use-minmtu-00.txt>
-and-ipv6-use-minmtu-00.txt
<https://www.ietf.org/id/draft-andrews-tcp-and-ipv6-use-minmtu-00.txt>
> > > <https://tools.ietf.org/html/draft-andrews-tcp-and-ipv6-use-minmtu-03>
https <https://tools.ietf.org/html/draft-andrews-tcp-and-ipv6-use-minmtu-03>
:// <https://tools.ietf.org/html/draft-andrews-tcp-and-ipv6-use-minmtu-03>
tools.ietf.org
<https://tools.ietf.org/html/draft-andrews-tcp-and-ipv6-use-minmtu-03>/
<https://tools.ietf.org/html/draft-andrews-tcp-and-ipv6-use-minmtu-03>html
<https://tools.ietf.org/html/draft-andrews-tcp-and-ipv6-use-minmtu-03>/
<https://tools.ietf.org/html/draft-andrews-tcp-and-ipv6-use-minmtu-03>
draft-andrews-tcp-and-ipv6-use-minmtu-03
<https://tools.ietf.org/html/draft-andrews-tcp-and-ipv6-use-minmtu-03>
> PHONE: +61 2 9871 4742                 INTERNET: marka@ <[email-masked]>
isc.org <[email-masked]>
>
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---

From: Tomoyuki Sahara <[email-masked]>
Date: Mon, 19 Oct 2015 11:00:35 +0900

> I think Bob is saying this is an important enough issue that it should be given BCP status.

I agree that this is an important issue, but what practice can we
recommend?

As is written in the draft, current TCP implementations ignore
IPv6_USE_MIN_MTU when they send TCP SYNs with MSS options (I have
tested and confirmed it on FreeBSD 10, NetBSD 6.1 and OpenBSD 5.7).
Linux distributions (CentOS/Ubuntu) don't support IPv6_USE_MIN_MTU
at all, even on raw IPv6 sockets.

Thanks,
Tomoyuki

---

From: Brian E Carpenter <[email-masked]>
Date: Mon, 19 Oct 2015 15:55:50 +1300

> at all, even on raw IPv6 sockets.

Well, the recommendation is to fix that, and the first step to
fix that is for all stacks to support the Advanced Socket API.
It is not unknown for the IETF to make implementation recommendations,
and sometimes vendors follow them.

   Brian

---

From: Dave Thaler <[email-masked]>
Date: Mon, 19 Oct 2015 17:35:06 +0000

The IETF isn't the right standards org for APIs per se (hence API RFCs are
usually informational).   The Austin Group (ISO+IEEE+OpenGroup)
standardizes POSIX APIs, W3C standardizes JavaScript APIs, etc.

If the IETF wants APIs to become standards, then the IETF should be
sending liaison statements to those organizations.

Dave

-----Original Message-----
From: ipv6 [mailto:[email-masked]] On Behalf Of Brian E Carpenter
Sent: Sunday, October 18, 2015 7:56 PM
To: Tomoyuki Sahara <[email-masked]>; [email-masked]
Cc: [email-masked]
Subject: Re: [v6ops] TCP and IPV6_USE_MINMTU

On 19/10/2015 15:00, Tomoyuki Sahara wrote:
>>>> (b) I suspect it belongs in v6ops rather than 6man, since it 
>>>> doesn't change anything in the standards.
>>>
> Linux distributions (CentOS/Ubuntu) don't support IPv6_USE_MIN_MTU at 
> all, even on raw IPv6 sockets.

Well, the recommendation is to fix that, and the first step to fix that is for all stacks to support the Advanced Socket API.
It is not unknown for the IETF to make implementation recommendations, and sometimes vendors follow them.

   Brian

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---

From: Brian E Carpenter <[email-masked]>
Date: Tue, 20 Oct 2015 07:58:51 +1300

> sending liaison statements to those organizations.

Indeed, and I believe we should do that. I hadn't realised until recently
how big a hole this is in terms of IPv6 deployment glitches. It's a more
general problem than just the current draft.

   Brian