Re: [ippm] Magnus Westerlund's Discuss on draft-ietf-ippm-stamp-07: (with DISCUSS and COMMENT)

Greg Mirsky <gregimirsky@gmail.com> Wed, 11 September 2019 15:25 UTC

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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Wed, 11 Sep 2019 08:25:06 -0700
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To: Magnus Westerlund <magnus.westerlund@ericsson.com>
Cc: "hnydell@accedian.com" <hnydell@accedian.com>, "draft-ietf-ippm-stamp@ietf.org" <draft-ietf-ippm-stamp@ietf.org>, "iesg@ietf.org" <iesg@ietf.org>, "tal.mizrahi.phd@gmail.com" <tal.mizrahi.phd@gmail.com>, "ippm-chairs@ietf.org" <ippm-chairs@ietf.org>, "ippm@ietf.org" <ippm@ietf.org>
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Subject: Re: [ippm] Magnus Westerlund's Discuss on draft-ietf-ippm-stamp-07: (with DISCUSS and COMMENT)
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Hi Magnus,
thank you for the clarification of the question. As Henrik already noted,
in an effort to characterize the source of ingress and egress timestamps at
the Session-Reflector we've introduced the Timestamp Information TLV
(Section 4.3 in draft-ietf-ippm-stamp-option-tlv). It does not provide the
name/location of the clock master/synchronization source, only a clock
synchronization protocol and the method by which the timestamp is obtained.
Much appreciate your comments, suggestions to make that TLV more useful.

Regards,
Greg

On Wed, Sep 11, 2019 at 2:36 AM Magnus Westerlund <
magnus.westerlund@ericsson.com>; wrote:

> Hi Henrik,
>
> On Wed, 2019-09-11 at 10:30 +0200, Henrik Nydell wrote:
> > See below for PTP/NTP comment
> >
> > On Wed, Sep 11, 2019 at 9:53 AM Magnus Westerlund <
> > magnus.westerlund@ericsson.com>; wrote:
> > >
> > > On Tue, 2019-09-10 at 12:43 -0700, Greg Mirsky wrote:
> > >
> > > > >         3.  Section 4.1.1.:
> > > > >         Timestamp is eight octets long field.  STAMP node MUST
> > > > > support
> > > > >       Network Time Protocol (NTP) version 4 64-bit timestamp
> > > format
> > > > >       [RFC5905], the format used in [RFC5357].  STAMP node MAY
> > > > > support
> > > > >       IEEE 1588v2 Precision Time Protocol truncated 64-bit
> > > > > timestamp
> > > > >       format [IEEE.1588.2008], the format used in [RFC8186].
> > > > >
> > > > >         Is the clock source here something that may be relevant
> > > or
> > > > > simply
> > > > >         information the management functions should capture. I
> > > > > think there is a
> > > > >         similar issue to that of RTP faced when it comes to
> > > > > understand what the
> > > > >         timestamp actually represent and thus be used
> > > correctly.
> > > > > RTP clock
> > > > >         source specification is RFC 7273
> > > > >         (https://datatracker.ietf.org/doc/rfc7273/)
> > > >
> > > > GIM>> NTP and PTP encodings have a different interpretation of
> > > the
> > > > Fraction field of the Timestamp field. In my experience, PTP
> > > format
> > > > is native for the data plane, while NTP is more used at the
> > > control
> > > > plane. Original extension to TWAMP has been described in RFC
> > > 8186.
> > >
> > > I think you missunderstood. When I talk about clock source, I am
> > > actually referring to identifying the particular clock that the
> > > node
> > > use to derive the included timestamp from.
> > >
> > > And likely this is a moot point in this document where the clock
> > > source
> > > information belongs in the management layer, e.g. in the YANG data
> > > model.
> >
> >
> > In section 4.1.1 of draft-ietf-ippm-stamp there is a definition of
> > the Z-bit in the error correction field that denotes if the clock
> > source is NTP or PTP
> >
>
> Yes, to be clear I have no issue with if the format is NTP or PTP. That
> was not my comment. It was a comment if the protocol should identify
> which particular NTP or PTP server the node is using. For example for a
> node on my network having NTP based clock it matters if that NTP server
> is sth1.ntp.se which is a stratum 1 server distributing certified
> swedish time, or if I use europe.pool.ntp.org where I would use any NTP
> server part of the pool indicating that they are in europe.
>
>
> However, I am convinced that information is of interest the information
> should be in the management layer.
>
>
> Cheers
>
> Magnus Westerlund
>
>
> ----------------------------------------------------------------------
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