[ntp:questions] Thoughts on KOD

Harlan Stenn stenn at ntp.org
Tue Jul 8 09:31:14 UTC 2014


Rob writes:
> Harlan Stenn <stenn at ntp.org> wrote:
> > Rob writes:
> >> 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.
> >
> > What are these "many broken and inconsistent bits" of which you speak?
> 
> Strange stratum, both leap bits set, etc.

The definition of a KoD packet is that the Stratum field is 0, which *by
definition* is unspecified/invalid.  Neither broken nor inconsistent.

If the system sending the KoD sets both leap bits, again, *by
definition* that means the sending system is saying "my clock is invalid
- don't believe it."  Neither broken nor inconsistent.

If somebody chooses to implement an NTP client that blows past these
core definitions in the NTP RFCs that's their fault.  We're talking
about definitions that are unchanged since NTPv1.

I'm not buying your assertion, but I could be missing something. Also,
you did say "etc" and there might be some other cases there that would
change my mind.  But I doubt it, as S0 is a showstopper, as is LI=3.

H


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