[lug] NTP question

[Neal McBurnett]

I like that idea.  I did the same thing, also from AT&T/Comcast.
My first traceroute hop is 10.157.192.1

 $ ntpq -p 10.157.192.1
      remote           refid  st t when poll reach   delay   offset jitter
 =========================================================================
 *199.37.175.40   .TRUE.       1 -  678 1024  377   43.690    1.251  2.870

That looks like a good source - it is just one hop away from a stratum
1 NTP clock, a TRUETIME receiver (could be GPS, GOES or OMEGA, etc).
It is as close to me as possible, and its time is (at least currently)
in sync with my other clocks.

Like Bear, I also can't reach the stratum 1 server that it is synced
to (199.37.175.40), but I see no problem with that, since the ntpq
data shows that 10.157.192.1 has no problem reaching it.  That sounds
like a good system design, in fact - preventing the world from getting
to your stratum one clocks and potentially hacking them.

So my first hop seems like a reasonable server to put in my mix of
servers.  It is not advertised, and may go away, but with at least 2
or 3 other likely possibilities for redundancy, it sounds like a good
choice.

I found the other clocks I use with this little script I wrote, to
find the closest ones from the "stratum 2" list that are keeping good
time right now.  I choose manually from the handful of servers
with the lowest (but non-zero) delay.

 lynx -source http://www.eecis.udel.edu/~mills/ntp/clock2a.html |
      sed -n -e 's,).*,,' -e' /([0-9.]*$/s/.*(//p' |
      xargs ntpdate -q |
      sort -n +7 > /tmp/ntp-close

Unfortunately, no one very nearby is on the list - the closest for me
are about 76 ms away.  Perhaps tummy.com would like to put their
server on the list?  International fame and forture!  Of a sort....

I've talked to the NIST folks, and have experience myself, and have
never actually seen servers that are overloaded.

Cheers,

Neal McBurnett                 http://bcn.boulder.co.us/~neal/
GPG/PGP signed and/or sealed mail encouraged.  Keyid: 2C9EBA60

On Wed, Mar 19, 2003 at 05:34:27PM -0700, Bear Giles wrote:
> D. Stimits wrote:
> > I called the tech support at AT&T/Comcast yesterday, and asked if they 
> > had any official ntp server. The guy said no, and he is probably right, 
> > but I doubt the tech people know enough there to actually be certain. 
> 
> The support people, you mean.  Although there are days I think the 
> same about the true techs.
> 
> After some other comments I decided to go NTP hunting - traceroute 
> to some site, then ntptrace each host in turn.  The neighborhood 
> switch has NTP (but the upstream stratum is non-responsive)... and 
> no other blather.att.net site is running NTP.  (Or responding to 
> the likes of me.)  Meanwhile the first non-AT&T site does respond 
> with a Stratum 4 time server that traces back to a GPS, and about 
> 2/3 of the remaining sites trace their time back to various 
> sources (e.g., I saw a USNO in there).
> 
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