[ntp:questions] NTP Loses sync over time.

Brian Szmyd brian.szmyd at adic.com
Fri May 12 17:02:15 UTC 2006

Sorry about the generic subject...but I'm not familiar enough with the
NTP protocol to describe the issue I'm having any other way.

We have a customer using our product running SNTP v4 and they have
having trouble keeping the machine in sync with their v3 NTP server.
They are seeing a drift of about a minute a day...and I really have no
idea about where to start to debug the problem. I have collected a days
worth of Ethernet Frames between the two machines and have a couple of
questions about the data held within them.

If I look at the Frames under Ethereal I see:

Clock Dispersion:	10.2222 sec
Reference Clock ID: uncalibrated local clock
Reference Clock Update Time: May  4, 2006 08:52.53.0510 UTC
Originate Time Stamp: May  4, 2006 13:50:18.8941 UTC
Receive Time Stamp: May  4, 2006 13:50:18.3950 UTC
Transmit Time Stamp: May  4, 2006 13:50:18.3950

Clock Dispersion: What is this?
Ref. Clock ID: "
Ref. Clock Update Time: I assume this is the time that this server was
last updated?
Originate Time Stamp: Meaning?
Receive Time Stamp: "
Transmit Time Stamp: Time the packet was transmitted?

Do these fields have different meanings in the context of Client to
Server and vice-versa? Which fields should be closing the gap and what
does it mean to have them actually drifting apart? The Polling Interval
is 6 seconds if that is of any value.

Thanks in advance for any advice!

brian szmyd
advanced digital information corporation
firmware engineer  |  720.249.5827  |  brian.szmyd at adic.com

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