Hal Murray wrote: > In article <[email protected]>, > Andy Yates <[email protected]> writes: >> 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. > >> 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. > > What sort of accuracy are you interested in? 1 ms? 10 ms? 100 ms?
Hi Hal Its up to us to specify what we think the SLA should be - the guide is "as accurate as possible"! > > How stable is your temperature? (Both the room and the CPU load.) Temperature will be very stable, the DC is the very well specified and scrupulously engineered - no cables blocking air flow etc. Generally speaking the CPU is over specified. > > What is the load on the LAN between the clients and servers? > (Delay is not a problem. Variation in delay is a problem.) The NTP will be on a separate management LAN to the production traffic so not subject to the variances that application load has on the network. > > > I suggest you measure it. Start with your current system. > > Setup a box as a ntpd system and tell it to use several target boxes > as servers and turn on logging. peerstats will tell you the difference > between your local clock and the target system. > I'll look at the current NTP infrastructure however its completely different to the new. The old has 3 geographically diverse GPS receivers plus a GPS and radio source on the roof of the data centre and we use network components to provide the intermediate strata between stratum one and client - and have not really had many issues after almost 10 years of use. However, requirements are changing and we will probably be using dedicated stratum 2/3 servers as required. Regards Andy _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
