[ntp:questions] what happens when sys.peer turns stratum 16?

Kalle Pokki kalle.pokki at iki.fi
Mon May 31 08:57:50 UTC 2010

On Mon, May 31, 2010 at 06:42, unruh <unruh at wormhole.physics.ubc.ca> wrote:
> Note, that this is one of the reasons why your customers should never
> use 2 servers. You have no way to know which one is crazy. Use 3 or 5.
> (4 can be as bad as 2 if two of the servers go nuts in exactly the same
> way-- eg they are both tied to a single server which has gone nuts).

The concept of configuring lots of servers in case some of them go
crazy comes up often in the mailing list. Is this really a common
problem with NTP? How often are there really crazy servers whose time
is off by more than milliseconds?

What are the usual reasons for servers going crazy? From Mr. Mills'
book I get the impression that he feels the NTP algorithms itself are
stable. Using random internet servers is of course risky, as anyone
could easily e.g. misconfigure a server to stratum 1 using only the
LCL reference clock driver.

If we assume there is a private subnet that has two GPS reference
clocks to synchronize the rest of the machines, what would be the
expected failure mode where one of the stratum 1 servers go crazy, and
having three GPS clocks actually makes a difference?

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