[nSLUG] Time services

Jamie Fifield jamie at fifield.ca
Wed Mar 19 19:18:25 AST 2003


That's cool to know that eastlink has a time server.  I knew dal had a
couple, but I think most people should only use the one (timeserver),
but to each his own.

What other NTP servers are in Nova Scotia and are intended for public
use?  Nslug is now running one too, just for the hell of it. :)
(time.nslug.ns.ca is now slowly drifting into alignment)


On Wed, Mar 19, 2003 at 05:54:41PM -0400, Peter Cordes wrote:
> On Wed, Mar 19, 2003 at 04:43:47PM -0400, Jamie Fifield wrote:
> > I'm going to include a bunch of replies in this one email. :)
> > 
> > 1. I believe timeserver.dal.ca is a tier 3 NTP server.  Frankly, for
> > most purposes, one don't need to load the tier 2 servers.
> 
>  That's correct, but dal has some stratum 2 servers.  Eastlink also has an
> NTP server.  There's really no need to go loading up the public timeservers
> if you're on eastlink, because eastlink has private peering with Dal, so
> traffic between you and Dal is very fast.  Besides that, you can keep your
> clocks accurate enough by just syncing up once a day, instead of constantly
> running ntpd.  /etc/cron.daily/set_clocks:
> #!/bin/sh
> # Set system clock from an NTP server
> 
> . /etc/default/rcS
> . /etc/default/ntp-servers
> 
> if /usr/sbin/ntpdate $NTPSERVERS ;then
> 	if [ yes = $UTC ];then /sbin/hwclock --utc --systohc
> 	   else			/sbin/hwclock --systohc
> 	fi
> fi	

For the list archives, what I use on my systems is probably a little
more portable:

wraith:~$ cat /etc/cron.daily/ntpdate
#! /bin/sh

/etc/init.d/ntpdate start


I know it's pretty much what yours does, but in the long run (where
conf files move, etc.) it might be saner.

> 
>  I use adjtimex to correct the clock drift so that the clock is only off by
> 0.1 seconds or so over a day.  Once you figure out your clock's drift rate,
> you can set /etc/adjtimex.conf, and /etc/init.d/adjtimex will load the
> correction at bootup, and you never have to worry about it.  It would be
> better if my ntpdate script kept fine-tuning the adjtimex parameters (so you
> didn't have to do it by hand in the first place), but it's ok the way it is.
> Of course, if you do run ntpd, don't use adjtimex.  ntpd takes care of
> tweaking the clock increment itself.
> 
> 
> llama]~$ ntpdate -q time.eastlink.ca timeserver.dal.ca spike.ucis.dal.ca
> lucy.ucis.dal.ca
> server 24.222.0.33, stratum 2, offset 0.051820, delay 0.04008
> server 129.173.1.10, stratum 3, offset 0.030925, delay 0.03267
> server 129.173.1.100, stratum 2, offset 0.034540, delay 0.04185
> server 129.173.1.40, stratum 2, offset 0.030438, delay 0.03391
> 19 Mar 17:33:39 ntpdate[12445]: adjust time server 129.173.1.40 offset
> 0.030438 sec
> 
> snoopy.ucis.d.c == timeserver.d.c, and z3.e.c == time.e.c.
> 
>  Eastlink's time server is stratum 2.  I recommend just using one of the Dal
> servers, and eastlink's server, and not adding traffic to any more than that.
> 
> 
> > 2. If network latency to ntp servers is an issue for you (I don't see
> > how it is, because the protocol takes into account latency and
> > compensates for it), run your own ntp server.  To do this on Debian:
> > apt-get install ntp
> 
> 
> z3's latency is jittery this time of day:
> 
> llama]~$ ping z3.eastlink.ca
> PING z3.eastlink.ca (24.222.0.33) from 24.222.156.67 : 56(84) bytes of data.
> 64 bytes from z3.eastlink.ca (24.222.0.33): icmp_seq=1 ttl=253 time=19.5 ms
> 64 bytes from z3.eastlink.ca (24.222.0.33): icmp_seq=2 ttl=253 time=39.0 ms
> 64 bytes from z3.eastlink.ca (24.222.0.33): icmp_seq=3 ttl=253 time=72.7 ms
> 64 bytes from z3.eastlink.ca (24.222.0.33): icmp_seq=4 ttl=253 time=14.2 ms
> 64 bytes from z3.eastlink.ca (24.222.0.33): icmp_seq=5 ttl=253 time=56.3 ms
> 64 bytes from z3.eastlink.ca (24.222.0.33): icmp_seq=6 ttl=253 time=34.7 ms
> 64 bytes from z3.eastlink.ca (24.222.0.33): icmp_seq=7 ttl=253 time=16.7 ms
> 
> --- z3.eastlink.ca ping statistics ---
> 7 packets transmitted, 7 received, 0% loss, time 6059ms
> rtt min/avg/max/mdev = 14.223/36.198/72.741/20.321 ms
> 
> (note mdev (mean or median deviation, I guess) of 20ms).
> 
>  I think later at night, when my set_clocks script runs, there is less
> jitter.  Of course, ntpdate detects the jitter and chooses one of the Dal
> servers instead :)
> 
> -- 
> #define X(x,y) x##y
> Peter Cordes ;  e-mail: X(peter at llama.nslug. , ns.ca)
> 
> "The gods confound the man who first found out how to distinguish the hours!
>  Confound him, too, who in this place set up a sundial, to cut and hack
>  my day so wretchedly into small pieces!" -- Plautus, 200 BC
> _______________________________________________
> nSLUG mailing list
> nSLUG at nslug.ns.ca
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-- 
Jamie Fifield
<jamie at fifield.ca>



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