[DNSOP] Re: [v6ops] Re: Fwd: New Version Notification - draft-ietf-dnsop-avoid-fragmentation-18.txt

[Tim Wicinski <[e-mail]>]

Paul

On Thu, Jul 4, 2024 at 6:41 PM Paul Vixie <paul=[e-mail]>
wrote:

> On Thursday, July 4, 2024 7:05:22 AM PDT Tim Wicinski wrote:
>
> > On Tue, Jul 2, 2024 at 9:26 PM David Farmer <[e-mail]> wrote:
>
> > > 2. Also, maybe R5 should have text similar to R3 with "...the minimum
>
> > > of...the interface MTU, the network MTU...and 1400 bytes..." Instead of
>
> > > "It should use a limit of 1400 bytes, but a smaller limit MAY be used."
>
> >
>
> > Something like this:
>
> >
>
> > "UDP requestors should limit the requestor's maximum UDP payload size  to
>
> > use the RECOMMENDED size of 1400 bytes, but a smaller limit MAY be used."
>
> As before, I'd like to future-proof this document. 1400 may not survive
> and should not be a hard limit. If someone ever gets PLPMTUD working, or if
> local knowledge includes MTU over a topology as a static configuration,
> then the recommended value should be ignored, and the measured or locally
> defined limit should be the operational maximum for that datagram.
>
> Thus, not only a smaller limit, but also a larger limit, may be sometimes
> used. This document need not enumerate all such cases, but should not
> require revision if 1400 turns out to be like 640KB -- not a sensible limit
> for all possible futures.
>

I agree with you on future proofing, and I did not seem to craft that in my
suggestion.

David mentions R5 should have similar text 'flow' (my word) as R3.

Here is R3

   R3.  UDP responders should compose response packets that fit in the
   minimum of the offered requestor's maximum UDP payload size
   [RFC6891], the interface MTU, the network MTU value configured by the
   knowledge of the network operators, and the RECOMMENDED maximum DNS/
   UDP payload size 1400.  (See Appendix A for more information.)

Here is R5

   R5.  UDP requestors should limit the requestor's maximum UDP payload
   size.  It should use a limit of 1400 bytes, but a smaller limit MAY
   be used.  (See Appendix A for more information.)


Me trying (and perhaps failing again) :

UDP requestors should limit requestor's maximum UDP payload size that fit
in the minimum
of the offered requestor's maximum UDP payload size, [RFC6891],
the interface MTU, the network MTU value configured by the knowledge of the
network operators,
and the RECOMMENDED maximum DNS/UDP payload size 1400.



tim

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> P Vixie
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