[ntp:questions] Thoughts on KOD

Magnus Danielson magnus at rubidium.dyndns.org
Mon Jul 7 15:24:04 UTC 2014


On 07/07/2014 04:00 PM, Danny Mayer wrote:
> 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.

Which would make sense if the client has multiple sources and is a 
relatively decent NTP client. Issues we have seen is outside of the NTP 
client realm.


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