[Ntp] [Errata Rejected] RFC5905 (5020)

RFC Errata System <rfc-editor@rfc-editor.org> Mon, 29 August 2022 22:39 UTC

To: wferi@niif.hu, mills@udel.edu, jrmii@isc.org, jack.burbank@jhuapl.edu, william.kasch@jhuapl.edu
From: RFC Errata System <rfc-editor@rfc-editor.org>
Cc: ek.ietf@gmail.com, iesg@ietf.org, ntp@ietf.org, rfc-editor@rfc-editor.org
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Message-Id: <20220829223908.75BE36AAEB@rfcpa.amsl.com>
Date: Mon, 29 Aug 2022 15:39:08 -0700
Archived-At: <https://mailarchive.ietf.org/arch/msg/ntp/_8rrfe-Wa4IYRT7-GEvNOGWZWis>
Subject: [Ntp] [Errata Rejected] RFC5905 (5020)
Precedence: list

The following errata report has been rejected for RFC5905,
"Network Time Protocol Version 4: Protocol and Algorithms Specification".

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You may review the report below and at:
https://www.rfc-editor.org/errata/eid5020

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Status: Rejected
Type: Technical

Reported by: Ferenc Wágner <wferi@niif.hu>
Date Reported: 2017-05-15
Rejected 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)]

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 |
 --VERIFIER NOTES-- 
As noted this thread:

    https://mailarchive.ietf.org/arch/msg/ntp/AR7k0IP2PMgXdq2bknx6Eiz4upE/

'''
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)]
'''

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RFC5905 (draft-ietf-ntp-ntpv4-proto-13)
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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] [Errata Rejected] RFC5905 (5020) RFC Errata System