[ntp:questions] Thoughts on KOD

Rob nomail at example.com
Sun Jul 6 09:23:39 UTC 2014

Jan Ceuleers <jan.ceuleers at computer.org> wrote:
> I recommend providing motivation for the undesired clients to stop using
> the server, by the server sending a regular response indicating that it
> is not synchronised or replying in some other way that has no
> timekeeping value to the offending client.

Well, that is what KOD actually is.
However, it has so many broken and inconsistent bits that some clients
believe that they have received a corrupted packet and decide to re-try
the request to see if that results in a better response.

(of course a programmer that would even try that, will not be clever
enough to put a retry limit or an increasing delay in the code.  so
those badly written clients just start to hammer on the server)

> Another way would be to use a
> bogus fixed timestamp that is in the past (i.e. one that suggests that
> there is no passage of time on the server).

Probably that would be better, but of course KOD has already been defined
and changing its definition yet again would be risky as well.

> My recommendation is based on the assumption, yet to be verified in
> practice, that this server behaviour won't result in worse client
> behaviour than would be the case if the server just served the client's
> request as normal.

This has to be tested very well.  When I was still in the IPv4 NTP pool
I had some very bad experiences with KOD.  And I was not the only one.

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