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Re: [Ntp] Antw: Re: Details of the fragmentation attacks against NTP and port randomization

Fernando Gont <fgont@si6networks.com> Mon, 08 July 2019 22:17 UTC

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To: Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de>, "ntp@ietf.org" <ntp@ietf.org>
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From: Fernando Gont <fgont@si6networks.com>
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Date: Mon, 08 Jul 2019 20:12:20 +0100
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Subject: Re: [Ntp] Antw: Re: Details of the fragmentation attacks against NTP and port randomization
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On 2/7/19 14:43, Ulrich Windl wrote:
> Hi!
> 
> Maybe the sentence "With changing port numbers there is a specific probability
> that the packet run times (transmission / reception) may change, having an
> effect on the accuracy of NTP that prefers fixed and symmetric packet run
> times." can make it into the document, making both parties happy; those for
> randomizing ports and those against ;-)
> 
> Note that in theory the effect on accuracy could be positive as well, but most
> likely not in the general case.

FWIW, the doc proposes the conservative approach of randomizing the
local port on a per-association basis, and leaves the analysis of
randomization on a per-transaction basis for future work.

Thanks!

Cheers,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492

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