[Ntp] Robert Wilton's Discuss on draft-ietf-ntp-interleaved-modes-05: (with DISCUSS and COMMENT)

Robert Wilton via Datatracker <noreply@ietf.org> Mon, 28 June 2021 15:55 UTC

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Date: Mon, 28 Jun 2021 08:55:52 -0700
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Subject: [Ntp] Robert Wilton's Discuss on draft-ietf-ntp-interleaved-modes-05: (with DISCUSS and COMMENT)
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Robert Wilton has entered the following ballot position for
draft-ietf-ntp-interleaved-modes-05: Discuss

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Disclaimer, I don't know NTP.

Thanks for this document, and whilst I agree with Eric that the mechanism is
clever, I am less convinced that it is wise.  Specifically, I have a deep
concern with repurposing fields to have a different meaning with no indication
other than heuristics on the field to deduce their true meaning.  It feels to
me that this pseudo-extension will operationally make NTP harder to manage and
to debug issues.

I note that Daniel Franke suggested that this extra information be carried in
extension fields, but the authors are concerned with the increase in packet
size causing problems.  I didn't really understand the explanation as to why
this would be a problem, in that it is comparing the length between basic and
extended packets, but if the extension was negotiated then could all packets
use the extension fields and be of the same length?  Or is it simply the
increase in packet length that is an issue?

Alternatively, would it at least be possible to use an extension field to flag
that the fields now have a different meaning?  Would that allow receivers to
discard the packets with an "unknown extension" warning rather than a "the peer
seems to be sending me garbage" error.



Note, it looks like the wrong shepherd writeup has been uploaded on the datatracker page.