[ntp:questions] All my servers rejected

David Moerman (dot at dot) david.m at advmeas.com
Wed Jan 7 20:14:00 UTC 2004

I've got a situation where I'm trying to synchronize through a modem
connection (115200 bps through a satellite).  Ping delays are between 2 to
3.5 seconds, and jitter is often above 1 second.  I've tried between 3 and 5
different servers;  I've tried using just NIST servers;  I've tried just
stratum 2 servers with varying NTP version (3 or 4) support;  no difference.
BTW, I'm using ntpq version 4.1.2 on linux 2.4 kernel (redhat 9).

Actually, I *have* had success *once*:  it took between 60 and 90 minutes to
synchronize (not sure how long it took because I had given up and forgot
about it, then checked again, surprise!).  Also, I checked my bandwidth
usage, and it was in the hundreds of kilobytes.  This is definitely not
acceptable.  ntpq reports that all the servers are connected, but the
_space_ tally code shows "reject".

My situation is this:  my modem connection is usually off (could be for an
hour or more), then connects for about a minute (PPP connection) and then
goes off again.  I would like my time sync to happen within that period, and
sync regardless of my offset (I have verified it is using ntpd -g).  Also, I
don't want high bandwidth usage, because that drives up my satellite
air-time costs.  I tried using ntpdate, and it works fine, and used only
about 1KB total.  ntpd version 4 claims to be able to duplicate this with
the 'iburst' flag, but this does not seem to work (do all the servers need
to be NTPv4?).  Why shouldn't I just use ntpdate?  That would be fine, but I
also have a client sub-net connected which will be using my ntpd as a
server, so it will be running anyway.  I'd like to get it to work and not
use ntpdate if possible.

One last thing:  this is an automated, headless system.  It must run with no
administration for long periods.  I absolutely require reliability.



David Moerman
Advanced Measurements Inc

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