Dave, Not really strange. The Ct is an old design from EndRun that is very small and allows the server to run additional software. The latter is the reason we continue to deploy the Ct. (Just bought 10 more and are about to order another 10.)
The systems to which these clocks are connected need to also run OWAMP <http://e2epi.internet2.edu/owamp/>, a one-way ping tool. It is only as accurate as the times on the client and server, so we need single digit usec. sync between the systems which are scattered all over the country. It's quite nice to have a tool that tells you that a circuit has moved from working to protect because you can see the propagation time increase by 40 usec. and we can do exactly that. It is a key part of our high performance network monitoring system. That is why we have found the Ct to be the ideal unit for our purposes. It can emulate several different clocks including TrueTime and Trimble Palisade, but, in our testing, we concluded that Either TrueTime or Spectracom emulation with PPS kernel support provided the most accurate and stable time. In any case, thank you for the information. While I've been working with NTP since at least V2 days, I won't claim to really understand all of the gory details and some of the non-intuitive behaviors. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: [EMAIL PROTECTED] Phone: +1 510 486-8634 Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751 > From: "David L. Mills" <[EMAIL PROTECTED]> > Date: Thu, 08 May 2008 03:21:49 +0000 > Sender: [EMAIL PROTECTED] > > > Kevin, > > Strange. I have an EndRun Cntp, bu it has an Ethernet interface. If 4 > works for you use it. That's a pretty grotty driver with all kinds of > bandaids to deal with long forgotten radios; I wonder why EndRun chose > that driver... > > Dave > > Kevin Oberman wrote: > > Dave, > > > > Thanks for the quick response, but I guess I failed to make one point > > clear. > > > > EndRun supplies only the hardware. It is the Ct which as only a serial > > interface which is plugged into a standard COM port on the server. They > > don't provide any software at all. The clock just provides the time > > string every second (with an offset of about 10 ms. and jitter in the > > area of 3-5 ms.) and a very accurate PPS which allows us sync within > > about three usec. (The clock spec is better than ten usec, but three > > seems the norm.) > > > > I am running 4.2.0-a using the stock TrueTime and PPS drivers. The > > FreeBSD kernel has PPS support included, so any filtering in the > > TrueTime driver should be of little or no impact. > > > > I am assuming than as long as I am using PPS and training the TrueTime > > source, a minpoll of 4 is reasonable and I just wanted to make sure that > > I am not wrong in doing this. > > _______________________________________________ > questions mailing list > [email protected] > https://lists.ntp.org/mailman/listinfo/questions >
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