Re: [Ntp] Robert Wilton's No Objection on draft-ietf-ntp-port-randomization-06: (with COMMENT)

Miroslav Lichvar <mlichvar@redhat.com> Wed, 02 June 2021 11:42 UTC

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Date: Wed, 2 Jun 2021 13:42:14 +0200
From: Miroslav Lichvar <mlichvar@redhat.com>
To: Robert Wilton <rwilton@cisco.com>
Cc: The IESG <iesg@ietf.org>, draft-ietf-ntp-port-randomization@ietf.org, ntp-chairs@ietf.org, ntp@ietf.org, odonoghue@isoc.org
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Subject: Re: [Ntp] Robert Wilton's No Objection on draft-ietf-ntp-port-randomization-06: (with COMMENT)
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On Wed, Jun 02, 2021 at 03:54:03AM -0700, Robert Wilton via Datatracker wrote:
> Like Ben's comment, I was wondering why the document doesn't give a stronger
> recommendation as to which of the two approaches to follow.  It looks like all
> the implementations that the document lists already take the per-association
> approach, and that approach seems to be sufficient.   Hence, would it not be
> simpler to make that the RECOMMENDED approach, and then say that
> implementations MAY do per request randomization, but need to be aware that
> individual requests are more likely to take different paths with different
> latencies?

Both approaches have some disadvantages, which may have a different
impact depending on the implementation (e.g. it's filtering
capabilities), so it's difficult to make a general recommendation. 

The implementations mentioned in the document don't use the same
approach. OpenNTPD and nwtime.org sntp seem to use the per-session
approach, but chrony by default uses the per-request approach. Another
widely used client using the per-request approach is the busybox ntpd.

-- 
Miroslav Lichvar