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

Mike K Smith mks-usenet at dsl.pipex.com
Fri Mar 13 09:04:55 UTC 2009


On 13 Mar, 04:31, Joseph Gwinn <joegw... at comcast.net> wrote:
> 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.
I'm familiar with the Spectracom 9383, but not the other equipment.

What does the NTP status page show?

What does the GPS Signal Status show?

How many satellites are you seeing?

Is the device reporting 'Position Hold'?

> 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.
>
> Although most received replies have status 9514, they are nonetheless
> used to update the loop filter and so appear in the loopstats file.  
You say most are 9514, are there any 96xx values?

> When I co-plot loopstats and peerstats, the loopstats dots land on top
> of the peerstats dots.
I've never seen a device come up as status 5, but since the RFC1305
text treats it as "current synchronization source; max distance
exceeded (if limit check implemented)" then I guess it makes sense
that it will use it as the sync source and will update loopstats
appropriately.




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