Subject: [6lo] Alissa Cooper's Discuss on draft-ietf-6lo-deadline-time-04: (with DISCUSS and COMMENT)

From: Alissa Cooper via Datatracker <[email-masked]>
Date: Wed, 15 May 2019 12:59:21 -0700

Alissa Cooper has entered the following ballot position for
draft-ietf-6lo-deadline-time-04: Discuss

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DISCUSS:
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The Gen-ART reviewer made the following observation, which I'd like to discuss:

There is a serious problem with the last 5 paragraphs of section 8,
"Synchronization Aspects":  they seem to assume that the time
representation for the Deadline Time and Origination Time values will
wrap around, that is, that the representation is the absolute value
modulo the size of the field.  In addition, there is a lack of clarity
how the new epoch point will be chosen after the value wraps around.
This seems to contradict the earlier sections of the document which
speak of the values as if they are always to be considered as absolute
values on a time scale selected by the TU field, viz., either the NTP
time scale (in seconds) or the network's ASN numbering.

It's possible that four of these paragraphs are intended to only apply
to the use of TU = 00, the NTP time scale, and perhaps that usage of
the header is understood not to be completely specified yet.

However, the final paragraph discusses TU = 10 (the ASN time scale),
and claims that wrapping of the DT value is intended.  This is
relevant to current implementations.

Some sort of resolution of this is needed; as the document stands it
is self-inconsistent.  One possible resolution would be to omit these
paragraphs.

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COMMENT:
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Please respond to the rest of the Gen-ART review.