[ntp:questions] Re: What's different about these (S)NTP servers?

gabriel rosenkoetter grosen at cc3.com
Thu Oct 30 00:58:03 UTC 2003

On Thu, Oct 30, 2003 at 12:31:41AM +0000, Harlan Stenn wrote:
> I have a vague recolleciton that the "reference" time on the response from
> the misbehaving server was 0, while it was nonzero in the response from the
> behaving server.

Yes, you're right. I apologize for not reproducing that text:

mix:~# ntpdate -d -q forest
reference time:    00000000.00000000  Thu, Feb  7 2036  1:28:16.000
originate timestamp: c34a63a0.00000000  Wed, Oct 29 2003 11:04:48.000
transmit timestamp:  c34a631b.ea52bd3c  Wed, Oct 29 2003 11:02:35.915
29 Oct 11:02:35 ntpdate[2160]: no server suitable for synchronization found
mix:~# ntpdate -d -q bkupserv
reference time:    c34a19e1.019d89e9  Wed, Oct 29 2003  5:50:09.006
originate timestamp: c34a6104.9916872a  Wed, Oct 29 2003 10:53:40.598
transmit timestamp:  c34a6105.1e612839  Wed, Oct 29 2003 10:53:41.118
29 Oct 10:53:41 ntpdate[2143]: step time server A.B.C.160 offset -0.520515 sec

> I also have a vague recollection that a 0 reference time means "I'm not
> sync'd".

Yes, I see that in RFC 958 now that I know to look for it:

   Reference Timestamp

      This is a 64-bit timestamp established by the server or client
      host as the timestamp (presumably obtained from a reference clock)
      most recently used to update the local clock.  If the local clock
      has never been synchronized, the value is zero.

So it would be a safe bet that, presuming Microsoft's SNTP
implementation updates its reference timestamp when it's done
synchronizing, ntpdate (and ntpd) will then believe this is a valid
server. Thanks, that's exacty what I was looking for!

I think that it would be useful for ntpdate (and ntpd's) "no
suitable server" messages to be a bit more verbose, especially if
I've asked for verbose (debugging) output. Something like "server is
not synchronized" doesn't seem like much to ask. Perhaps such a
message is present in a more recent version of NTP?

gabriel rosenkoetter / grosen at cc3.com / CC3 Unix & Linux sysadmin

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