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

Ah, yes, I think was not paying sufficient attention to the sign of various
expressions.

I can ask for the erratum to be reopened so that I can revise that.  May I
copy from your explanation here to prepare the rejection explanation?

On Thu, Jul 28, 2022 at 10:19 AM Steven Sommars <stevesommarsntp@gmail.com>
wrote:

> 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
>> >
>> > _______________________________________________
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>> > ntp@ietf.org
>> > https://www.ietf.org/mailman/listinfo/ntp
>>
>>
>>
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