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

[Geoff Huston <[e-mail]>]

> On 5 Jul 2024, at 10:37 AM, Tim Wicinski <[e-mail]> wrote:
> 
> 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.  
> 

I think you appear to be getting "requestor" and "responder" confused in your proposed text. Did you mean to say the following?

UDP responders should compose response response packets with a maximum UDP payload size that fits 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. 

Geoff