[ntp:questions] What exactly does "Maximum Distance Exceded" mean?

Joseph Gwinn joegwinn at comcast.net
Sat Mar 14 04:34:54 UTC 2009

In article <eNydnX61waj9gSbUnZ2dnUVZ_tjinZ2d at giganews.com>,
 "Richard B. Gilbert" <rgilbert88 at comcast.net> wrote:

> Joseph Gwinn wrote:
> > I have been debugging some system problems.  The main system is too 
> > complicated, with too many people doing too many things, so I sought 
> > quiet refuge in an isolated test system consisting of a NTP timeserver 
> > connected by a point-to-point ethernet cable to a computer running NTP, 
> > which generates peerstats and loopstats data.  This test system is 
> > air-gap isolated from the rest of everything.  Only one timeserver is 
> > available to a given computer at a time.
> > 
> > The timeserver can be either a Symmetricom ET6010 GPS receiver feeding 
> > an IRIG-B002 time signal to a Symmetricom TS2100 Network Time Server, or 
> > a Spectracom 9383 NTP timeserver with built-in GPS receiver.  The GPS 
> > receivers are driven from a common antenna via a splitter.
> > 
> > The computer can be a Sun Ultra 10 or a Sun Ultra 60, in both cases 
> > running Solaris 9.  Solid boxes, but old.  The OS version reply is SunOS 
> > 5.9 Generic May 2002.  This was clean installed from CD a week ago, so 
> > has not had time to collect too many barnicles.
> > 
> > NTP version 3 is running.  I've been trying to find the command to give 
> > me the full version, including dot (like 3.4y), and I get answers, but 
> > don't know which one to believe, and if the version given is that of the 
> > NTP daemon itself, or of ntpq, or of ntpdate.
> > 
> > The full grid of four tests, being two timeservers by two computers, has 
> > been run.  Many odd things are seen, but the question for today is about 
> > status codes in peerstats file records.
> > 
> > Most of the replies that NTP is using to update the time have a status 
> > code of 9514, which translates to the following:
> > 
> > Configured, reachability OK; Current sync source - max distance 
> > exceeded; Count is 1; Peer now reachable.
> > 
> > The part that has me most perplexed is the "max distance exceeded" part, 
> > as this is a direct wired connection, with zero hops, zero delay, and no 
> > interfering traffic.  Obviously, they are not talking about physical 
> > distance or hops or the like, so the "distance" has to have units of 
> > time.
> > 
> I think that, perhaps, "maximum distance" refers to "synchronization 
> distance" q.v.  Once upon a time, I knew the definition but my memory 
> has failed me.

The other answers didn't use this exact term, but it sounds like the 
same idea.

Joe Gwinn

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