[HN Gopher] The Thorny Problem of Keeping the Internet's Time
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The Thorny Problem of Keeping the Internet's Time
Author : mitchbob
Score : 116 points
Date : 2022-10-08 10:28 UTC (12 hours ago)
(HTM) web link (www.newyorker.com)
(TXT) w3m dump (www.newyorker.com)
| adamgordonbell wrote:
| I had written David and NTP down as a podcast episode idea. Never
| expected to get scooped by the New Yorker.
| htopg wrote:
| An intricate topic like this works better as a written article.
| Podcasts are more for people who want to listen to some lowbrow
| stuff while driving.
| one_more_q wrote:
| Sorry but this is just your opinion. I Listen to tons of very
| technical podcasts and it works great. If you are interested
| in technology, check out the omega tau podcast for example.
| psYchotic wrote:
| Or, ironically, the podcast of the guy he responded to,
| adamgordonbell: https://corecursive.com/
|
| It's a podcast I've really been enjoying for a few years
| now. It used to be a little more technical (as the name,
| corecursive, kinda implies), but found a niche in
| interviewing people more about the people than the tech
| they're knowledgeable about, which is also very pleasant.
| Anyway, I encourage you to listen to both an early and a
| recent episode to find out if you like it.
| someguydave wrote:
| This article is pretty lowbrow, not much technical meat and
| lots of ephemeral kibitzing.
| whoibrar wrote:
| This quote hits hard Coders who contribute to
| it, she said, should feel proud enough to declare, "Everyone uses
| the software, it's in everything, and I wrote it!" It's striking
| how few people know Mills's name, given how many know the
| pseudonym of whoever created Bitcoin."
|
| I never heard of Mill before, and am just glad to have read and
| known this critical man and technology to internet
| infrastructure.
| mdbauman wrote:
| Relevant xkcd: https://xkcd.com/2347
|
| I was a little sad to read that Mills in fact lives in
| Delaware, not Nebraska. I always had a sneaking suspicion that
| this comic was NTP-related.
| Maursault wrote:
| To be fair, that's only off by 0.0069625621 seconds. Since
| time advances at the speed of light, you could say everyone
| lives in Nebraska and still be correct well within the margin
| of error.
| Sniffnoy wrote:
| I mean, I think Satoshi Nakamoto is notorious precisely
| _because_ of his pseudonymous nature. If he 'd used his real
| name, I doubt he'd get nearly as much attention.
| photochemsyn wrote:
| Computerphile has a really amusing (sort of) video on the related
| issue of how to translate between internet time and local time
| zones (though they have a different opinion about the wisdom of
| 'leap smears' vs 'leap seconds'):
|
| https://www.youtube.com/watch?v=-5wpm-gesOY
|
| Note that the common-sense notion that time intervals are fixed
| fails when relativistic concepts are introduced. Atomic clocks
| get out of sync due to being in different relativistic frames
| (satellites vs. ground, for example). Hence designating a
| 'universal time' is always going to be somewhat arbitrary.
|
| https://blog.swiftnav.com/relativistic-correction/
| seanc wrote:
| Found this on a deep man page, but I can't remember which one:
|
| Our units of temporal measurement, from seconds on up to months,
| are so complicated, asymmetrical and disjunctive so as to make
| coherent mental reckoning in time all but impossible. Indeed, had
| some tyrannical god contrived to enslave our minds to time, to
| make it all but impossible for us to escape subjection to sodden
| routines and unpleasant surprises, he could hardly have done
| better than handing down our present system. It is like a set of
| trapezoidal building blocks, with no vertical or horizontal
| surfaces, like a language in which the simplest thought demands
| ornate constructions, useless particles and lengthy
| circumlocutions. Unlike the more successful patterns of language
| and science, which enable us to face experience boldly or at
| least level-headedly, our system of temporal calculation silently
| and persistently encourages our terror of time. ... It is as
| though architects had to measure length in feet, width in meters
| and height in ells; as though basic instruction manuals demanded
| a knowledge of five different languages. It is no wonder then
| that we often look into our own immediate past or future, last
| Tuesday or a week from Sunday, with feelings of helpless
| confusion. ... --Robert Grudin, 'Time and the Art of Living'.
| manv1 wrote:
| Talk to any developer who's been around for any period of time,
| and they'll tell you that dealing with time is a PITA.
|
| What's bad is that there's no real thought given to
| interplanetary time. It's alluded to occasionally in SF, but
| there are no RFCs etc about it.
|
| Earth has UTC. Mars will presumably have MTC. What about things
| wandering about? How will that be mapped?
|
| More importantly, what happens to timestamps, GUIDs, etc?
| vageli wrote:
| Real thought has indeed been given to interplanetary time (even
| by the subject of TFA). You may find this of interest:
|
| https://webcache.googleusercontent.com/search?q=cache:pyKjMo...
| (forgive the cache but a postscript file is more easily viewed
| this way in the browser).
| zokier wrote:
| Few other relevant pointers:
| https://en.wikipedia.org/wiki/Deep_Space_Atomic_Clock and
| https://en.wikipedia.org/wiki/Barycentric_Coordinate_Time
| Maursault wrote:
| > Earth has UTC. Mars will presumably have MTC.
|
| If UTC doesn't work on Mars, it's false advertising, and we
| should really change the name.
| wrycoder wrote:
| There is an implementation: _Martian Time in Hare_ [0], which
| is based on the _Martian Business Calendar_ [1]
|
| [0] https://harelang.org/blog/2022-08-01-martian-time-in-hare/
|
| [1] http://www.bdm.id.au/calendar/mars_calendar.html
| amdelamar wrote:
| https://www.nwtime.org/current-members-donors/
| neilv wrote:
| > _Mills wrote, in a 2003 paper. "Today, the Sun never sets or
| even gets close to the horizon on NTP."_
|
| I'd guess the capitalized "Sun" was a pun, for the Sun
| Microsystems computers that still ran much of the Internet. For
| example: https://www.sunmanagers.org/1992/1188.html
| andylynch wrote:
| It's a play on a well-known description of the extent of the
| British Empire in its time. And which still, if you squint a
| bit, remains true today, at least according to Randall Munroe*
|
| * https://what-if.xkcd.com/48/
| imglorp wrote:
| Sun definitely advanced the state of the art. They had a well
| written set of three Blue Papers on timekeeping in SunOS, if
| you can find them after Oracle ate everything. Their
| implementation was mostly Mills ntpd but had to tweak it for
| their motherboard realtime clocks. Both ntpd and the Sun RTC
| were the source of much debugging amusement. But that's another
| story :-)
| snailmailman wrote:
| I've recently gotten curious about how accurate my computers
| clock is, and the answer is "usually, only vaguely accurate down
| to one second"
|
| I check via time.gov, and it's often off by .5-.8s which just
| seems kinda insane to me. On my phone it's always accurate to
| around .01s.
|
| I think I have a guess as to why though. The bios clock might not
| save milliseconds[0]. So whenever I turn the computer on in the
| morning, it's _always_ not synced to the second. And windows just
| doesn't care? Even if it's off by 900ms and I manually go in and
| try to resync it often won't bother. I have to manually change it
| to something blatantly wrong, then resync. And only then will it
| will finally be accurate to to .01s.
|
| This seemingly default level of imprecision to nearly 1 full
| second is very surprising to me. I'm curious if that affects
| anything.
|
| [0] not 100% certain about this. Maybe I just have insane second-
| per-day drift. I've seen the computer be off by as much as 1.3s,
| which doesn't quite match my theory, but that error is enough to
| resync on its own.
| adrian_b wrote:
| I have not checked if in recent versions of Windows there has
| been any change, but previously by default the computer clock
| was synchronized with a time server only once per day, so until
| the next synchronization it is normal to accumulate a time
| difference up to one or two seconds.
|
| I do not know how many Linux distributions enable by default a
| ntpd daemon, but I have always enabled it on any computer
| running Linux or FreeBSD.
|
| When a ntpd is active, it adjusts continuously the local clock
| based on comparisons with NTP servers, so the time cannot be
| wrong by more than a few milliseconds. Therefore the error
| becomes 100 to 1000 times less than without ntpd.
|
| The time differences between computers using NTP on the same
| LAN are smaller, usually of a few hundred microseconds. For
| even better synchronization within a LAN, the Precision Time
| Protocol must be used.
| djbusby wrote:
| If you have systemd it enables a timesyncd service which is
| NTP.
| jwilk wrote:
| To be precise, it's SNTP, not full-fledged NTP:
|
| > _The systemd-timesyncd service implements SNTP only. This
| minimalistic service will step the system clock for large
| offsets or slowly adjust it for smaller deltas. Complex use
| cases that require full NTP support (and where SNTP is not
| sufficient) are not covered by systemd-timesyncd._
| mitchbob wrote:
| Archived: https://archive.ph/tmbk6
| geerlingguy wrote:
| Time has been on my mind a lot lately, testing the OCP's Time
| Card, working with bringing up PTP on the Raspberry Pi CM4, and
| most recently interviewing Dr. Demetrios Matsakis, who was one of
| the people who coordinated UTC for many years (and now works as
| chief scientist at a local clock/timing company).
|
| It's always fascinating how certain individuals can really push
| things forward in a much greater way than you'd think. NTP
| changed a lot of what's possible online and in software, by
| giving a reliable more centralized timing solution for much of
| the world (still to this day).
|
| But talking to some actual experts in the field (like Dr.
| Matsakis), it's fascinating some of the additional problems you
| encounter when Internet, LAN, and even GPS connectivity can't be
| guaranteed, but you still need many devices with microsecond-
| level accuracy for long periods of time.
| rzimmerman wrote:
| This is a really great article that doesn't shy away from
| technical aspects while putting a human face on NTP. It's really
| cool to learn the history behind something we take for granted.
| amdelamar wrote:
| I also really enjoyed reading this; the mix of computer science
| & history was well balanced and kept my interest.
|
| It makes me think there should be a CompSci history class
| taught in college.
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