Re: [AVTCORE] Working Group Last Call on draft-ietf-avtcore-leap-second-03

Kevin Gross <kevin.gross@avanw.com> Mon, 26 August 2013 16:25 UTC

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Date: Mon, 26 Aug 2013 10:23:12 -0600
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From: Kevin Gross <kevin.gross@avanw.com>
To: Colin Perkins <csp@csperkins.org>
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Cc: Magnus Westerlund <magnus.westerlund@ericsson.com>, IETF AVTCore WG <avt@ietf.org>
Subject: Re: [AVTCORE] Working Group Last Call on draft-ietf-avtcore-leap-second-03
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Thanks for the review. See responses below.

Kevin Gross

On Mon, Aug 26, 2013 at 6:57 AM, Colin Perkins <csp@csperkins.org> wrote:

> On 15 Aug 2013, at 08:46, Magnus Westerlund <
> magnus.westerlund@ericsson.com> wrote:
> > This starts the WG last call on RTP and Leap Seconds with the intended
> > status of Proposed Standard. Please provide any comments by 1st of
> > September.
> >
> > https://datatracker.ietf.org/doc/draft-ietf-avtcore-leap-second
>
>
> Section 5 says that: "No special treatment with respect to RTP timestamps
> is required in the presence of a negative leap second". This might be
> clearer written "No special treatment is needed to avoid ambiguity with
> respect to RTP timestamps in the presence of a negative leap second". I
> think some special treatment is needed, as noted in Section 5.2, to avoid
> jumps in the playout time.
>

That looks like a good improvement.

>
> Section 5 also says NTP includes leap seconds, and that implementations
> working to a leap-second-bearing reference need "a working communications
> channel to receive notification of leap-second scheduling". Is having an
> NTP-synchronised clock a sufficient channel to receive the necessary
> notification, or is something more needed?
>

NTP includes a mechanism for leap-second notification. That's a good start
but what we're trying to capture here is the entire communications chain
from IERS to the slaved clocks. In addition to these protocol mechanisms
for delivering leap-second notifications, master clocks must have access to
an up-to-date leap second schedule through some other communications
channel (e.g. FTP leap-seconds.list from a NIST server).

I can revise to emphasize that time protocol notifications are not
sufficient but I don't think we want to try and describe the whole
communications channel for this information. Or we can leave it as it is.
The current text is terse but correct.

>
> Typos:
> - Section 3, 1st paragraph: "synchronized with with the rotation"
> - Section 6, 2nd paragraph: "leap-seocnd-bearing"
>

Thanks. I will fix these.

>
>
> Cheers,
> Colin
>
>
>
> --
> Colin Perkins
> http://csperkins.org/
>
>
>
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