> Out of curiosity, since you monitor NIST Gaithersburg, if you were to average > over the offsets for a whole month, what kind of value would you get? Surely > it is close to zero but I am curious how close. Within 1ms?
It depends. Mostly on the routing between you and NIST. If you are closer, the routing is more likely to be symmetric. >From my experience, routing is generally stable on the scale of months. There are short (hours) changes when a fiber gets cut or a router gets busted. There are long term changes as people add fibers and/or change business deals. There are some cases where a stable routing will produce 2 answers: x% of the packets will be slightly faster/slower than most of them. I think what's going on is that the routers are doing load sharing on multiple paths, hashing on the address+port. Or something like that. So it's a roll of the dice which path you get. -------- I'm in California. NIST has NTP servers at 3 locations in the Boulder CO area: NIST, WWV, and Univ of Colorado. (Google maps says WWV is 60 miles north of Bouler. Univ of Colorado is a few miles from NIST.) >From a cheap cloud server (Digital Ocean) in San Francisco, the RTT to NIST is 31.5 ms, to WWV is 32.1 ms, to Univ of Colorado is 54.5 ms. The time offsets are about 1 ms for NIST and WWV and 12 ms for Univ of Colorado. >From my home (AT&T via Sonic), 30 miles south of San Francisco, the RTTs are 61 ms for NIST and WWV and 81-82 for Univ of Colorado. Offsets are 6-7 ms for NIST and WWV and 4-5 ms in the other direction for Univ of Colorado. -- These are my opinions. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
