[ntp:questions] Query about NTP accuracy

Andy Yates andyy1234 at gmail.com
Thu May 21 23:13:05 UTC 2009

Does anybody have any figures that shows the effect on accuracy of an
NTP v3 client using a stratum 1 server rather than a stratum 2 or 3
server? It's all in a GE LAN based scenario, commercial stratum 1
servers connected to GPS and stratum 2 and 3 servers are typically
dedicated Linux boxes.

The reasons is that I would rather scale by adding strata - its a very
big data center with thousands of clients and has several "zones" that
are isolated. However some opinion is suggesting we run IRIG-B between
the GPS receiver and a bunch of stratum 1 servers and clients access
these directly. Much more expensive and any increase in accuracy from a
client experience may be negligible.

However I'm been pressed to supply an SLA for accuracy. My argument is
that although you can get your stratum one server to synchronize to
microseconds of UTP, as soon as the client uses NTP v3 over the LAN,
even a GE LAN, then the accuracy degrades and putting well designed well
specified stratum between the boxes is not going to decrease accuracy
sufficiently to warrant purchasing many stratum one appliances.



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