[ntp:questions] tool to collect statistics on round trip delay offset?

joe blow someone at msn.com
Wed Oct 25 23:07:54 UTC 2006

Are there any monitoring tools that allow you to collect statistics on the 
round trip delay, and offset without using the data.

On a small, self contained network, (using no routers, just cisco switches), 
I have multiple servers that I want to be in sync to  < 1ms (200-300 usec 
ideally). It is not so important how well these match to GMT, but it is very 
important that they agree with each other.  They are used to time tag event 
data that needs to be correlated across servers.

I want to take some statistics on the measurement jitter (both offset and 
round trip delay) of a typical NTP packet.  I envision a utility that would 
send the UPD NTP packets, and be able to calculate delay and offset from a 
specific server (but not use the data), but just collect them for analysis 

I'm trying to assess how much variation there is in the NTP measurements.

The standard out of the box NTP takes way too long to stabalize to 1 ms 
offset.  I suspect that this is due to the time constants used to be able to 
sync to typical NTP servers on the internet. Since my network will be closed 
(and small - all in the same room), with only 2 NTP servers (one for 
backup),  I'm expecting very small variations in measurements, and thus only 
a small amount of filtering should be required.  This should result in 
faster converging times, and the ability to respond quickly to server clock 
frequency changes (for example, room temperature changes quickly due to AC 
cooling loss).


More information about the questions mailing list