[ntp:questions] Re: peer trouble ? reach going down

David J Taylor david-taylor at blueyonder.co.uk
Thu Aug 7 11:34:56 UTC 2003


> > Can you explain to me why peer exchange are slow ? (and sometime
> > one-way,
> > because they are not the same stratum 2/3 ?)  and my reach not 377 ?
>
>     Because peering relationships do not consist of queries and replies.
> Your reachability is probably due to packet loss. By the way, I don't
> recommend setting 'maxpoll'. You may force the servers to talk to each
other
> too often and the newer data will push older data out of the averaging
> window. This will mean averaging over a smaller window, which can be
less
> accurate.

Interesting - I have seen something similar on my own LAN, where there is
most unlikely to be packet loss (or so I would have thought....).  None of
the other network stuff shows any problems - although perhaps the fact
that NTP uses UDP matters?  The internal stuff is polling at 64s
intervals.

Externally, through my router, cable modem, ISP, Internet etc. I hardly
ever see reaches other than 377, and I would have thought the likelihood
of packet loss to be far greater externally than internally.  Mind you
external stuff is on 1024s polling.

There's something here which seems counter-intuitive.

Cheers,
David





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