[ntp:questions] Re: Architecture / best practice for small/medium company setups

Maarten Wiltink maarten at kittensandcats.net
Sat Jul 1 12:49:31 UTC 2006

"David Woolley" <david at djwhome.demon.co.uk> wrote in message
news:T1151748999 at djwhome.demon.co.uk...
> In article <44a52073$1$31653$e4fe514c at news.xs4all.nl>,
> Maarten Wiltink <maarten at kittensandcats.net> wrote:0

>> [The spiral of doom] is caused by having a number of peers all at
>> the same local-clock stratum. If one of them is put at a lower stratum
> Isn't the real problem caused by the use of the local clock driver.
> Distributors like including this and users don't understand that ntpd
> will maintain frequency even without any servers, so a lot of people
> include them without really understanding them.

Note that even while a peer cluster is descending into a spiral,
one is in no worse a situation than letting all clients coast by

But there are gains to be had by configuring the local clock into
a server. The server will still drift away from UTC, but now all
the clients will stay close to it and therefore to each other.

Unfortunately, if local clocks are configured incorrectly into a
peer cluster, new and exciting problems may be introduced. With
local clocks all at the same stratum, arguably the worst outcome
of all is likely to happen: the servers drifting confidently apart,
with some clients following one and some another, hopping and
stepping until the servers have drifted too far apart to remain
believable. All the while believing that nothing is the matter,
because they're still synchronised to something.

> The other problem is that many people think that ntpd is designed to
> negotiate a consensus time under such circumstances, when except
> possibly for the new isolated networks option, it isn't and one
> should use timed, or similar, instead.

This is a problem. But it is a problem of misunderstanding and can be
cured by education.

Maarten Wiltink

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