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Re: [Ntp] NTS Pools

"Windl, Ulrich" <u.windl@ukr.de> Thu, 29 February 2024 07:16 UTC

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From: "Windl, Ulrich" <u.windl@ukr.de>
To: Miroslav Lichvar <mlichvar@redhat.com>, "martin.langer=40ptb.de@dmarc.ietf.org" <martin.langer=40ptb.de@dmarc.ietf.org>
CC: David Venhoek <david@venhoek.nl>, NTP WG <ntp@ietf.org>, "Dieter.Sibold@ptb.de" <Dieter.Sibold@ptb.de>, "Kristof.Teichel@ptb.de" <Kristof.Teichel@ptb.de>, Rainer Bermbach <r.bermbach@ostfalia.de>
Thread-Topic: [Ntp] NTS Pools
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Date: Thu, 29 Feb 2024 07:16:36 +0000
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Subject: Re: [Ntp] NTS Pools
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Hi!

While it may "work", there are some issues/comments:
1) If you use the pool like a plain server, one would add the same name multiple times (to get multiple servers). However there's no guarantee that different servers will be selected
2) The special pool directive handles these issues (automatically "pull" some servers from the pool, and once some seem 
dead, pull new ones). I guess it will also avoid duplicate IPs (which may mean duplicate servers unless those are multi-homed or use multiple IPs on one interface)
3) The mechanism relies on the fact that a server specified as FQDN is resolved to an IP only once by NTP; if it would resolve once per poll, you could get a different server each poll, breaking the synchronization.

Kind regards,
Ulrich

-----Original Message-----
From: ntp <ntp-bounces@ietf.org> On Behalf Of Miroslav Lichvar
Sent: Monday, February 26, 2024 12:21 PM
To: martin.langer=40ptb.de@dmarc.ietf.org
Cc: David Venhoek <david@venhoek.nl>; NTP WG <ntp@ietf.org>; Dieter.Sibold@ptb.de; Kristof.Teichel@ptb.de; Rainer Bermbach <r.bermbach@ostfalia.de>
Subject: [EXT] Re: [Ntp] NTS Pools

[...]

This DNS-based concept of a pool works with plain NTP and it works
also with NTS. There can be multiple NTS servers available under the
[...]

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