[ntp:questions] Thoughts on KOD

Danny Mayer mayer at ntp.org
Mon Jul 7 14:00:16 UTC 2014


On 7/6/2014 2:42 AM, Rob wrote:
> Harlan Stenn <stenn at ntp.org> wrote:
>> Discussion appreciated.
> 
> I think it is best to remove KOD from ntpd.
> It does not serve a useful purpose, because precisely the kind of
> clients that you want to say goodbye to, do not support it.
> 
> In real life it has either no effect at all, or it even has a negative
> effect because the client does not understand it and re-tries the
> request sooner than it would when no reply was sent at all.

You haven't read the code. Any client that ignores the KOD flag will
find (if they ever looked) that their clock will be drifting away
further and further from the proper time. When KOD is set the value of
the received and sent timestamps are the same as the initial client sent
timestamp. It doesn't use the system time for the returned packet.
Calculate what this does to the resulting clock.

Please also note that there is more than one type of KOD packet. See RFC
5905 Section 7.4. See also Figure 13. You need to clearly distinguish
the different ones when talking about them. Most of this discussion
seems to be about action a. As discussed above this is an extremely
useful feature because any client ignoring the KOD flag and using the
packet any way will get pushed way of the actual time that they would
normally expect regardless of the client software used.

Danny


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