[ntp:questions] Compensating for asymmetric delay on a per-peer/server basis?
Rich Wales
richw at richw.org
Sat Sep 13 05:46:43 UTC 2014
Replying to Charles Elliott:
> The offset may be a function of distance. Try this experiment:
> Set up your ntp.conf file to have three servers . . . :
> 1. A relatively unused stratum 1 or 2 server as close to you as possible
> 2. A relatively unused stratum 1 or 2 server about 1,000 miles away
> 3. A relatively unused stratum 1 or 2 server more than 2,000 miles away
OK, here is information taken from two local servers under my control.
==============================================================================
This first machine (171.67.203.16) is on the Stanford University campus. The
first two peers listed below are located on the Stanford campus; the third
peer is also run by Stanford but is about 50 miles east of the campus.
+171.64.7.105 .PPS. 1 u 1012 1024 377 0.465 -0.045 0.076
+171.64.7.67 .PPS. 1 u 217 1024 377 0.584 -0.043 0.081
*204.63.224.70 .PPS. 1 u 737 1024 377 1.803 -0.031 0.252
This next peer is my home machine (the one I described earlier as being
connected to the Internet via a cable modem), with its own local GPS clock.
-68.65.164.12 .PPS. 1 u 13 16 372 8.168 -2.126 4.585
Finally, these two servers are in Utah (Xmission) and Poland.
-198.60.22.240 .GPS. 1 u 721 1024 377 18.931 0.239 0.045
-213.222.200.99 .PPS. 1 u 833 1024 377 172.099 -4.083 1.167
==============================================================================
Now, here is the info from my home machine (68.65.164.12). First, my local
GPS reference clock:
*127.127.28.1 .PPS. 0 l 14 16 377 0.000 -0.003 0.025
x127.127.28.0 .GPS. 8 l 7 16 377 0.000 -37.762 13.399
Next, my campus machine (see above for details):
-171.67.203.16 204.63.224.70 2 u 2 16 333 9.689 2.146 3.930
And finally, the same two remote servers (in Utah and Poland) that I used on
my campus machine:
+198.60.22.240 .GPS. 1 u 45 64 377 35.222 6.542 2.864
+213.222.200.99 .PPS. 1 u 18 64 377 191.192 4.890 8.968
==============================================================================
Any thoughts?
Rich Wales
richw at richw.org
More information about the questions
mailing list