5 ms·
UT1 NTP Time Dissemination
- toast0 5y ago> The reply will have no special indication that the transmitted time is UT1 and not UTC. And this is how really terrible time situations occur.
- amluto 5y agoLike when Google’s smeared leap second leaked into the general NTP pool?
- encoderer 5y agoWait what?
- snypher 5y agohttps://developers.google.com/time/smear https://developers.google.com/time/smear
- aidenn0 5y agoFor me at least the "wait what" was "when did the google smear leek into general NTP pools," not "what is the google leap second smear"
- jeffbee 5y agoI think the question wasn't about whether Google smears leap seconds on their time service, which has debatable benefits and drawbacks, but rather about your use of "leaked" and "the pool". You should not mix smearing and non-smearing NTP services. I don't believe Google intentionally participates in any NTP pool projects.
- toast0 5y agoI also don't believe google intentionlly participates in pool.ntp.org, but it would be easy for some of the pool servers to have one of google's public ntp servers in their static configuration. On days without a leap second, they're pretty good ntp servers. Personally, I had servers configured with google and some other semi-public servers during the last leap second, and (traditional) ntpd did lots of weird stuff, so I ended up with pretty mushy time that day.
- brian_cunnie 5y agoI have six servers in the pool, and I definitely leaked the Google time smear into the pool. It's hard to get reliable upstream NTP servers--it was easier to point to Google. Google smeared, so my servers smeared, so all my downstream clients smeared. I don't know how much my servers currently handle, but at one point they carried 1% of the North American pool NTP traffic.
- mhio 5y agoDo you have any more detail of the leak event? My google-fu is failing me
- amluto 5y agoOne of my servers was incorrectly fed the Google smeared time via the NTP pool. Diagnosing it was delightful.
- petee 5y agoAs I read, only two specific servers provide this -- ut1-wwv.nist.gov for example, is well labeled too. Its not clear if its part of the standard round-robin but the wording gives me the impression that it is not.
- toast0 5y agoI wouldn't expect anyone to unintentionally use these two servers. But traditional ntp also publishes time, so it would be easy to propigate. Since it's not identified as an alternate time scheme on the wire, there's no way for downstream ntpds to know and refuse ut1. Falseticker checks help, but don't eliminate the possibility of following the wrong clock.
- contravariant 5y agoHow bad an idea would it be to just use UT1 everywhere and forget about leap seconds? It'd probably break something but I can't for the life of me figure out what.
- phaker 5y agoTAI is the 'UTC without leap seconds'. UT1 is an evolution of solar time, and wobbles when Earth does because it's using the Earth and Sun (and other bodies) as a clock. UTC is TAI with leap seconds added when UT1 drifts too far away.
- LeoPanthera 5y ago"UT1R" is a smoothed version of UT1 with the wobble removed.
- jws 5y agoI wrote an OS that used TAI as it’s time. All in all I was pleased with the outcome. UTC conversion happened at parsing and formatting, but those are relatively uncommon compared to comparison and interval addition so it works well performance wise.
- aidenn0 5y agoGiven that UTC is always within 0.9s of UT1, either TAI or UT1 can be considered "UTC without leap seconds" since the leap seconds in UTC are an attempt to reconcile the two.
- LeoPanthera 5y agoIt would be quite bad. See this page: https://www.ucolick.org/~sla/leapsecs/dutc.html https://www.ucolick.org/~sla/leapsecs/dutc.html And scroll down to "Implementing the plan outlined at Torino", taking note of the "Notable event" column. Edit: I think I misunderstood your question. This table shows the results of what would happen if we just stopped adding leap seconds.
- aidenn0 5y ago
- ape4 5y agoIn case you're like me and don't know what UT1 is https://en.wikipedia.org/wiki/Universal_Time#Versions https://en.wikipedia.org/wiki/Universal_Time#Versions
- aidenn0 5y agontpdate shows ~120ms difference from UTC, though from the docs it looks like there is a table to calculate the exact difference.