[time-nuts] clock-block any need ?
Hal Murray
hmurray at megapathdsl.net
Sat Dec 29 03:18:06 UTC 2012
attila at kinali.ch said:
> From the data ntp gives me in the networks i manage. I hardly get any
> jitter number below 1ms, even with unloaded network and unloaded hosts. The
> 200us comes from the "usual" rtt time measurements on PCs.
What sort of networks are you talking about? Are you synchronizing over LAN
or WAN? Do you have a local refclock?
On LANs with non-ancient PCs, it's easy to get round trip times under 200
usec. That makes it hard to get jitter over 1 ms. Or, if the jitter is that
bad, how can you call the network unloaded?
Here are a couple of ntpq printouts:
$ ntpq -p tim
remote refid st t when poll reach delay offset jitter
==============================================================================
*glypnod .PPS. 1 u 194 256 377 0.145 0.186 0.018
-shuksan .PPS. 1 u 95 256 377 0.115 0.126 0.030
-mini-mon .PPS. 1 u 68 256 377 0.177 0.080 0.030
-tom 192.168.1.3 2 u 57 256 377 0.200 0.161 0.086
+bob .PPS. 1 u 117 256 377 0.146 0.199 0.045
+ted .PPS. 1 u 11 256 377 0.211 0.208 0.036
$ ntpq -p tom
remote refid st t when poll reach delay offset jitter
==============================================================================
*glypnod .PPS. 1 u 37 256 377 0.130 0.043 0.014
-shuksan .PPS. 1 u 91 256 377 0.139 -0.005 0.015
+mini-mon .PPS. 1 u 191 256 377 0.172 -0.006 0.023
-bob .PPS. 1 u 198 256 377 0.392 0.186 0.050
+ted .PPS. 1 u 206 256 377 0.319 0.127 0.038
-tim 192.168.1.3 2 u 34 256 377 0.243 -0.074 0.036
-jim 199.102.46.72 2 u 31 256 377 26.243 8.357 29.291
-xo-c2 155.101.3.113 3 u 126 256 377 28.335 10.815 23.143
The last two lines are from systems synchronizing out over the
big-bad-internet. The others systems are all local to my LAN. (Calling it a
LAN is stretching things. It's just one switch.)
--
These are my opinions. I hate spam.
More information about the time-nuts
mailing list