Re: [Ntp] Antw: [EXT] [Errata Verified] RFC5905 (5020)

I don't get it.

Theta is "the offset of B relative to A". The proposed revision is
   1/2 * [(T2-T1) + (T4-T3)]
Example: Let's assume that B and A are exactly synced to UTC and that the
network delay is 50msec in each direction.
    T2-T1 is the NTP mode 3 request delay (including network delay).
This gives 50 msec
    T4-T3 is the NTP mode 4 response delay (including network delay).
 This gives 50 msec.
The proposed revision gives 100msec/2 = RTT/2, not the expected offset of
zero.

The RFC5905 formula seems correct.

    theta = T(B) - T(A) = 1/2 * [(T2-T1) + (T3-T4)]

but might have been clearer had it been written:

    theta = T(B) - T(A) = 1/2 * [(T2-T1) - (T4-T3)]

On Thu, Jul 28, 2022 at 4:54 AM Ulrich Windl <
Ulrich.Windl@rz.uni-regensburg.de> wrote:

> >>> RFC Errata System <rfc-editor@rfc-editor.org> schrieb am 27.07.2022 um
> 17:06 in
> Nachricht <20220727150611.170A66AB09@rfcpa.amsl.com>:
> > The following errata report has been verified for RFC5905,
> > "Network Time Protocol Version 4: Protocol and Algorithms
> Specification".
> >
> > --------------------------------------
> > You may review the report below and at:
> > https://www.rfc-editor.org/errata/eid5020
> >
> > --------------------------------------
> > Status: Verified
> > Type: Technical
> >
> > Reported by: Ferenc Wágner <wferi@niif.hu>
> > Date Reported: 2017-05-15
> > Verified by: Erik Kline (IESG)
> >
> > Section: 8
> >
> > Original Text
> > -------------
> > theta = T(B) - T(A) = 1/2 * [(T2-T1) + (T3-T4)]
> >
> > Corrected Text
> > --------------
> > theta = T(B) - T(A) = 1/2 * [(T2-T1) + (T4-T3)]
>
> If that's wrong, RFC 1305 would be just as wrong, because it says (page 25
> in
> PDF):
> ((Ti−2 − Ti−3) + (Ti−1 − Ti)) / 2
> ,
>
> >
> > Notes
> > -----
> > The corresponding code line in A.5.1.1. agrees with this correction:
> >
> > offset = (LFP2D(r->rec - r->org) + LFP2D(r->dst - r->xmt)) / 2;
> >
> > taking Figure 7 into account:
> >
> > | org       | T1         | origin timestamp      |
> > | rec       | T2         | receive timestamp     |
> > | xmt       | T3         | transmit timestamp    |
> > | dst       | T4         | destination timestamp |
> >
> > --------------------------------------
> > RFC5905 (draft-ietf-ntp-ntpv4-proto-13)
> > --------------------------------------
> > Title               : Network Time Protocol Version 4: Protocol and
> > Algorithms Specification
> > Publication Date    : June 2010
> > Author(s)           : D. Mills, J. Martin, Ed., J. Burbank, W. Kasch
> > Category            : PROPOSED STANDARD
> > Source              : Network Time Protocols
> > Area                : Internet
> > Stream              : IETF
> > Verifying Party     : IESG
> >
> > _______________________________________________
> > ntp mailing list
> > ntp@ietf.org
> > https://www.ietf.org/mailman/listinfo/ntp
>
>
>
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