[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.  

<off topic>
> 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
commercial
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
I need 
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.
</off topic>

Regards,
Chris



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