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Re: [Ntp] Symmetric mode

Miroslav Lichvar <mlichvar@redhat.com> Mon, 03 October 2022 07:55 UTC

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Date: Mon, 03 Oct 2022 09:55:20 +0200
From: Miroslav Lichvar <mlichvar@redhat.com>
To: Doug Arnold <doug.arnold@meinberg-usa.com>
Cc: Hal Murray <halmurray@sonic.net>, "ntp@ietf.org" <ntp@ietf.org>
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Subject: Re: [Ntp] Symmetric mode
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On Fri, Sep 30, 2022 at 02:23:22PM +0000, Doug Arnold wrote:
> Please enlighten me. I’ve been reading the discussion on symmetric ntp, and I don’t understand the purpose. An ntp server can ask other servers for time using client server ntp, and use that information to examine its own time and that of the peer it is looking at.  Why is a different over-the-wire version of the protocol needed?

You can push time to the server using the symmetric mode, without the
server having to know your IP address in advance. This has a major
impact on security. When NTP started, I guess very few people cared
about that, but now I don't think it's acceptable.

-- 
Miroslav Lichvar

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