[ntp:questions] Re: Dopey selection of server
Christopher J. Burian
cburian at ll.mit.edu
Fri Jan 30 15:05:43 UTC 2004
"Richard B. Gilbert" <rgilbert88 at comcast.net> writes:
> I've experienced the same thing. I was told that NTP was working as
> designed. I guess I just don't understand the design! Intuitively, it
> would seem best to select the server with the lowest delay and jitter
> but that's not what it does. If cudns.cit.conrell.edu consistently
> shows high delay and jitter, you might want to look for another server.
I selected these three because they were all stratum 2 and all had good
offset and jitter, generally. At home, I ran that windows utility that
graphs ntp servers (mentioned a week ago here on the list) with 8
servers stratum 1 or stratum 2, and after a day (too short?) decided on
three stratum 2 servers. Because I don't feel entitled to stratum 1,
and because they seem less jumpy than stratum 1 servers.
I haven't bothered to do a traceroute to these machines, but they are
geographically in the northeast with me. filbert at Columbia is the
most stable according to logs, so I don't know why my ntpd prefers ntp0
at Cornell. tick (NAVOBS) down the road at MIT has a consistent bias
compared to everybody else (go figure), and other local stratum 1
servers are likewise unreliable for various reasons.
> I'm trying to get a stratum 1 server working in my home to avoid some of
> these problems. Unfortunately, my contract with Comcast appears to
> prohibit my making it publicly available.
The way I read my Comcast user agreement, I'm only barred from
use of my upstream connection. If you did go public, I'd publish it
here, and not to the whole world :-) I can view web pages served from
my home, but Google refuses to index them for some reason. Haven't
tried to use that machine as an NTP server (not that a Windows machine
can be reasonably used as a server anyway). I keep telling myself that
to get up to speed on embedded linux; maybe I should put a PC/104 (or
smaller) SBC with an Acutime2000 on my home network as my first learning
project. Trivial to do on a generic PC, but it appears to be a fun
challenge to do it with a customized minimalist kernel booting from a
tiny flash drive.
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