Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03 / Extension fields
Miroslav Lichvar <mlichvar@redhat.com> Thu, 02 December 2021 08:59 UTC
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Date: Thu, 02 Dec 2021 09:59:24 +0100
From: Miroslav Lichvar <mlichvar@redhat.com>
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Subject: Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03 / Extension fields
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On Wed, Dec 01, 2021 at 10:26:11PM -0600, Dan Drown wrote: > Quoting Miroslav Lichvar <mlichvar@redhat.com>: > > I have no idea if anyone is actually willing to implement the > > correction field. In any case, it will still be more difficult to > > implement than the PTP correction field as NTP works with timestamps > > corresponding to the end of the reception instead of beginning. > > Wouldn't the middle boxes just need to measure queue latency from RX(first > byte) to TX(first byte)? The gist you linked had the correction factor just > adding latency in the request packet and subtracting latency in the response > packet to result in the asymmetric latency that the client can use as a > correction. That assumes the correction field is supported on all network devices between the server and client, or at least that all network links have the same speed and the packet length doesn't change (e.g. due to adding and removing VLAN tags). If that is not the case, the correction will have an error due to the asymmetric link speed or length. In the NTPv5 draft this specific case is mentioned, but in general it is required that the correction works with the end of the reception to support networks where not all devices support the correction field. This is in contrast to PTP which requires the support everywhere. That is ok as PTP was specifically designed for full hardware support. But in NTP I think it would be nice if switches in a network could be upgraded only one at a time without breaking the assumptions. -- Miroslav Lichvar
- [Ntp] comments on draft-mlichvar-ntp-ntpv5-03 Dan Drown
- [Ntp] Antw: [EXT] comments on draft‑mlichvar‑ntp‑… Ulrich Windl
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03 Miroslav Lichvar
- Re: [Ntp] Antw: [EXT] comments on draft‑mlichvar‑… Miroslav Lichvar
- [Ntp] Antw: Re: Antw: [EXT] comments on draft‑mli… Ulrich Windl
- Re: [Ntp] Antw: Re: Antw: [EXT] comments on draft… Miroslav Lichvar
- Re: [Ntp] Antw: Re: Antw: [EXT] comments on draft… Ulrich Windl
- Re: [Ntp] Antw: Re: Antw: [EXT] comments on draft… Miroslav Lichvar
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Miroslav Lichvar
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Miroslav Lichvar
- Re: [Ntp] comments on draft‑mlichvar‑ntp‑ntpv5‑03 Dan Drown
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Dan Drown
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Harlan Stenn
- Re: [Ntp] comments on draft‑mlichvar‑ntp‑ntpv5‑03 Steven Sommars
- Re: [Ntp] comments on draft‑mlichvar‑ntp‑ntpv5‑03 Dan Drown
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Dan Drown
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Dan Drown
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Dan Drown
- [Ntp] Antw: [EXT] Re: comments on draft‑mlichvar‑… Ulrich Windl
- [Ntp] Antw: [EXT] Re: comments on draft‑mlichvar‑… Ulrich Windl
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Dan Drown
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Miroslav Lichvar
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Miroslav Lichvar
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Dan Drown
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Dan Drown
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Miroslav Lichvar
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Miroslav Lichvar
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Miroslav Lichvar
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Danny Mayer
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Dan Drown
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Dan Drown
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Dan Drown
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Miroslav Lichvar
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Danny Mayer
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Doug Arnold
- Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03… Miroslav Lichvar