[ntp:questions] NTP - best practice if there is a local stratum 2 server

Rich Wales richw at richw.org
Sun Jul 5 18:42:20 UTC 2009

[Summary:  One of my servers ended up synching on a pool server of
questionable quality at stratum 1.  How to protect against this?]

A few days ago, "Rob" wrote the following in this discussion thread:

> What you get from the pool may be a stratum-1 server locked to GPS
> time on a fast unloaded connection, or it may be a slow box on a
> saturated ADSL line and synchronized to time.windows.com.  Your
> local server will be better to depend on.  You at least know what
> you get, and/or you can ask the department it belongs to what
> quality you can expect.  You can never do that with the pool.

Is there any general way to avoid stratum-1 servers from a pool?

I recently had a situation where one of my three boxes grabbed onto a
stratum-1 server from the US pool, even though this server was about
8 msec off in relation to closer (Stanford campus) stratum-2 servers,
and even though my other two boxes (I have my three peering with each
other) were marked with "prefer" in the afflicted box's ntp.conf.

"tos floor 2" would seem to preclude synching directly to any stratum-1
server, but this could present its own problems if I were ever to want
to set up my own local stratum-1 server.  What I would prefer would be
some way to make a stratum floor apply only to a single pool -- not to
the entire configuration (as appears to be the case with "tos floor").

Or is there a better solution to this overall issue -- short of simply
shunning pools entirely, even as a backup strategy?

Rich Wales  /  richw at richw.org  /  richw at stanford.edu
Wikipedia:  http://en.wikipedia.org/wiki/User:Richwales
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