Re: [Ntp] Roughtime time resolution and timestamp format

Hi,

In my opinion it is always best to reuse an existing timestamp format,
preferably one of the NTP timestamp formats or a derivative (for
example a subset of the bits of the NTP format).
Note that the number of bits in the timestamp defines the resolution,
which is not necessarily the accuracy of the protocol.

Anyway it is important to define the timestamp format in a clear way:
https://datatracker.ietf.org/doc/rfc8877/

Cheers,
Tal.

On Tue, Apr 2, 2024 at 10:42 PM Marcus Dansarie <marcus@dansarie.se> wrote:
>
> Dear all,
>
> I looked over the latest Roughtime draft this weekend. One of the things
> that struck me was that the protocol's time resolution has changed three
> or four times in the nine drafts so far. I discussed this off-list with
> Watson and he suggested that we check with the list what people think is
> appropriate.
>
> In the current draft, resolution in both time and accuracy is one
> second. This means that the lowest possible interval reported by a
> Roughtime server will be two seconds (i.e. plus/minus one second). The
> midpoint can be off by as much as half a second from the server's best
> time estimate. The resolution in previous drafts has been microseconds.
>
> Related to this is the question of how time should be formatted in the
> protocol. In the current draft, time is transferred as the "count of
> seconds since the Unix epoch in UTC". Previous drafts have used either
> microseconds since the Unix epoch or modified Julian date and
> microseconds since midnight.
>
> Personally, I think that single-second resolution is too low. Indeed, a
> user could look at two devices that have successfully used Roughtime to
> get time and visibly see that they do not match. Also, a second is eons
> in computer time. At the very least, we should specify decisecond
> resolution and preferably millisecond. I am also hesitant towards using
> the Unix epoch, considering the history of problems involving
> conversions to and from it, not to mention leap seconds. The time
> transferred with Roughtime should be clear and unambiguous. For that
> reason, I prefer the date and time-since-midnight format. The date could
> be either days since an epoch or year-month-day.
>
> To summarize, these are the two questions that we would like to hear
> your opinions (and eventually reach consensus) on:
>
> * What resolution of time and time accuracy should Roughtime use?
>
> * What should the Roughtime timestamp format look like?
>
> Kind regards,
> Marcus
>
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