Re: F-ckin Leap Seconds, how do they work?
On (2012-07-03 16:53 -0700), Owen DeLong wrote: Sure, but even with that, 99% of it has only a passing 'interesting' effect and then recovers. Inclusive you no longer know order of events based on your logs, and virtually none of your software are logging 60th second. What are only interesting and what can cause with luck (or bad luck) catastrophic failures is guess work, no one is going to review all the code written, and almost all of it assumes monotonic time. Quite. But it is not well known that unixtime travels backwards. In part because it shouldn't actually do so. It should simply chime 59 twice. Chiming 59 twice is traveling backwards. It goes to what ever precision you have between 59 and 00, then it goes back to 59 flat. -- ++ytti
Arbor network
Hi, Anybody using Arbor Peakflow? Can tell us about its efficiency? Any other DDoS detection and mitigation product ? Regards, WaseemÂ
Re: F-ckin Leap Seconds, how do they work?
Tyler Haske tyler.ha...@gmail.com writes: Someone running an NTP Server connected to a cesium clock could run the leap-second time code. Since its *their job* to have the correct time, they can do all the fancy rarely used things that make parts of the Internet die every couple of years. Ah, Tyler, I see the problem here. An NTP server is not like an XML-spitting web server which one consults each and every time one wants to know a piece of data (for instance a stock quote, the weather, or in this case, what time it is). NTP assumes a local clock, and the results of periodic queries to higher-than-or-equal-to-local-stratum servers are used to _discipline_ the local clock, steering it to have minimal error. Local clocks have to be consulted much too frequently (logging, timestamping, etc) for just put it in the cloud to work. You might want to read up on NTP (wikipedia provides a reasonable introduction). cheers, -r
Re: FYI Netflix is down
Tell that to people in the third world without utilities. On Jul 3, 2012 8:32 PM, Randy Bush ra...@psg.com wrote: Also, I don't think there is an acceptable level of downtime for water. coming soon to a planet near you randy
Re: F-ckin Leap Seconds, how do they work?
On 7/4/12, Robert E. Seastrom r...@seastrom.com wrote: [snip] Local clocks have to be consulted much too frequently (logging, timestamping, etc) for just put it in the cloud to work. You might want to read up on NTP (wikipedia provides a reasonable introduction). The NTP daemon could still provide a configuration option to not implement leap-seconds locally, or ignore the leap-second announcement received. So the admin can make a tradeoff favoring Stability over Correctness, of _allowing_ the local clock to become 1 second inaccurate for a short time after the rare occasion of a leap second; and step it or slew the local clock, eg include the leap second in the ordinary time correction, averaged over a period of time instead of a 1 second jump. The breakage doesn't occur for whatever reason when the time is stepped forward or backwards, or slewwed. So accept the inaccuracy and correct the clock in the normal way that NTP corrects clocks that have drifted. -- -JH
Re: F-ckin Leap Seconds, how do they work?
On 2012 Jul 4, at 08:50, Jimmy Hess wrote: So accept the inaccuracy and correct the clock in the normal way that NTP corrects clocks that have drifted. This is basically the leap smear that google instituted after the issues in 2005. It works nicely in cloud applications where real-time is not an issue. It does not work so well when precision calculations of real-time physics are important, nor in heterogeneous environments where not all devices pay attention to NTP or some handle the leap differently than others. Those are places where a kernel should never be asked to do what the combination of POSIX and leap seconds demand. -- Steve Allen s...@ucolick.org WGS-84 (GPS) UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99855 University of California Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m
Re: F-ckin Leap Seconds, how do they work?
On Wed, Jul 4, 2012 at 8:50 AM, Jimmy Hess mysi...@gmail.com wrote: The NTP daemon could still provide a configuration option to not implement leap-seconds locally, or ignore the leap-second announcement received. So the admin can make a tradeoff favoring Stability over Correctness, of _allowing_ the local clock to become 1 second inaccurate for a short time after the rare occasion of a leap second; and step it or slew the local clock, eg include the leap second in the ordinary time correction, averaged over a period of time instead of a 1 second jump. Unless I'm mis-reading things, it already does - of sorts. According to the ntpd website ( http://www.ntp.org/ntpfaq/NTP-s-algo-real.htm#AEN2499) : *The theory of leap seconds in explained in Q: 2.4.. In reality there are two cases to consider: If the operating system implements the kernel discipline described in Section 5.2, ntpd will announce insertion and deletion of leap seconds to the kernel. The kernel will handle the leap seconds without further action necessary. If the operating system does not implement the kernel discipline, the clock will show an error of one second relative to NTP's time immediate after the leap second. The situation will be handled just like an unexpected change of time: The operating system will continue with the wrong time for some time, but eventually ntpd will step the time. Effectively this will cause the correction for leap seconds to be applied too late. * Linux does implement the kernel discipline (via ntp_adjtime), so the first option is what normally happens. However you can disable this with an ntpd config option (disable kernel) or via ntpdc at which point I'm presuming it will fall back to the second option. The second option still gives you a step, but using the -x option to NTPD will slew this step, giving a gradual correction to the 1 second difference. Of course there would be side effects of this (the kernel implementation of NTP is there for a reason, and this disables it), but at least it's better than a server hang... Scott.
Re: F-ckin Leap Seconds, how do they work?
On Tue, Jul 03, 2012 at 04:54:24PM -0400, valdis.kletni...@vt.edu wrote: On Tue, 03 Jul 2012 21:49:40, Peter Lothberg said: Leapseconds can be both positive and negative, but up to now, the earth has only slowed down, so we have added seconds. That's what many people believe, but it's not exactly right. Leap seconds are added for the exact same reason leap days are - the earth's rotation isn't a clean multiple of the year. We know we need to stick in an entire leap day every 4 years or so, then add the 400 hack to get it closer. At that point, it's *really* close, to the point where just shimming in a second every once in a while is enough to get it back in sync. The earth's slowdown (or speedup) is measured by *how often* we need to add leap seconds. If we needed to add one every 3 years, but the frequency rises to once every 2.5 years, *that* indicates slowing. In other words, the slowdown or speedup is the first derivative of the rate that UT and TAI diverge - if the earth rotated at constant speed, the derivative would be zero, and we'd insert leap seconds on a nice predictable schedule. Leap Seconds and Leap Years are completely unrelated and solve two completely different problems. Leap Seconds exist to adjust time to match the Earth's actual rotation. They exist because the solar day is not exactly 24 hours. Leap Years exist to adjust time to match the Earth's actual revolution around the Sun. They exist because the that time period isn't exactly 365 days. Without leap seconds, the sun stops being overhead at noon. Without leap years, the equinozes and solstices start drifting to different days. -- Brett
Re: F-ckin Leap Seconds, how do they work?
On Wed, 04 Jul 2012 12:44:40 -0500, Brett Frankenberger said: Leap Seconds and Leap Years are completely unrelated and solve two completely different problems. Leap Seconds exist to adjust time to match the Earth's actual rotation. They exist because the solar day is not exactly 24 hours. Leap Years exist to adjust time to match the Earth's actual revolution around the Sun. They exist because the that time period isn't exactly 365 days. Actually, it's the same exact problem - an astronomical value isn't exactly conformant to the civil value, and thus adjustments are needed. And you missed the bigger point - that leap seconds aren't needed because the earth is slowing any more than leap days are needed because the year is getting longer. If an actual siderial day was a fixed unchanging 86400.005 seconds long, you'd still need a leap second every 200 days. *SLOWING* would be indicated by the every 200 days changing to every 175 or every 150. For bonus points - at the current rate of slowing, in what year will the day be of sufficient length that the current rule of 400 for leap days requires changing? You may assume that the orbital parameters of the Earth do not also change. :) pgpOsreuTOR8f.pgp Description: PGP signature
Re: F-ckin Leap Seconds, how do they work?
On Wed, Jul 4, 2012 at 1:44 PM, Brett Frankenberger rbf+na...@panix.com wrote: Without leap seconds, the sun stops being overhead at noon. But that's ridiculous. The sun *isn't* overhead at noon except at one particular longitude within each time zone. Everywhere else time synch to local noon is +/- half an hour. IMO, leap seconds are a really bad idea. Let the vanishingly few people who care about a precision match against the solar day keep track of the deviation from clock time and let everybody else have a *simple* clock year after year. When the deviation increases to an hour every what, thousand years? Then you can do a big, well publicized correction where everybody is paying attention to making it work instead of being caught by surprise. Regards, Bill Herrin -- William D. Herrin her...@dirtside.com b...@herrin.us 3005 Crane Dr. .. Web: http://bill.herrin.us/ Falls Church, VA 22042-3004
Re: F-ckin Leap Seconds, how do they work?
On Wed, Jul 04, 2012 at 06:10:45PM -0400, William Herrin wrote: On Wed, Jul 4, 2012 at 1:44 PM, Brett Frankenberger rbf+na...@panix.com wrote: Without leap seconds, the sun stops being overhead at noon. But that's ridiculous. The sun *isn't* overhead at noon except at one particular longitude within each time zone. Everywhere else time synch to local noon is +/- half an hour. IMO, leap seconds are a really bad idea. Let the vanishingly few people who care about a precision match against the solar day keep track of the deviation from clock time and let everybody else have a *simple* clock year after year. When the deviation increases to an hour every what, thousand years? Then you can do a big, well publicized correction where everybody is paying attention to making it work instead of being caught by surprise. Yeah but what you don't understand is that manual navigation after a certain point of difference becomes inaccurate to a degree that is unacceptable by most military standards. 100 or a 1000 years the difference is too big. Someone somewhere at some point evaluated this need in the range of 0.3 - 0.9? in order for nauticle and other means of direction to not be impacted. It would be easy to disagree and say Well! we have GPS and other such digital devices to tell where you are now!... and if those go out just like all these failing Java Apps ?. I would not want to be the guy that would have to calculate all possible differences just to attempt to get a accurate location and then find out the math was wrong and you are 100 miles off target. Just sayin! -- - (2^(N-1))
Re: FYI Netflix is down
Tell that to people in the third world without utilities. Also, I don't think there is an acceptable level of downtime for water. coming soon to a planet near you i work there regularly. the typical nanog kiddie does not. randy
Re: F-ckin Leap Seconds, how do they work?
On Jul 4, 2012, at 3:29 PM, Jason Hellenthal jhellent...@dataix.net wrote: Yeah but what you don't understand is that manual navigation after a certain point of difference becomes inaccurate to a degree that is unacceptable by most military standards. Manual navigation (sextant, etc) is dead. It's not taught for new pilots or mariners / navigators. A few hobbyists still learn that, but they can easily keep a solar-true time clock around if they wish. Maintaining any time standard for that purpose is not supported. It's no reason for the timekeepers, nothing we need to care about. The few navigation systems that look at the sun and stars have - and inherently need - better time reference than the allowed 0.9 sec before we leap. They already handle this internally. That 0.9 sec max error comes to up to about 400 meters for equitorial surface nav or 6500 for orbital objects (or suborbital - cough). Already unacceptable... George William Herbert Sent from my iPhone
Re: F-ckin Leap Seconds, how do they work?
On Wed, Jul 04, 2012 at 05:02:02PM -0400, valdis.kletni...@vt.edu wrote: On Wed, 04 Jul 2012 12:44:40 -0500, Brett Frankenberger said: Leap Seconds and Leap Years are completely unrelated and solve two completely different problems. Leap Seconds exist to adjust time to match the Earth's actual rotation. They exist because the solar day is not exactly 24 hours. Leap Years exist to adjust time to match the Earth's actual revolution around the Sun. They exist because the that time period isn't exactly 365 days. Actually, it's the same exact problem - an astronomical value isn't exactly conformant to the civil value, and thus adjustments are needed. No. Leap Years arise because the solar year is not an integral multiple of the solar day. Yes, you can argue that leap years exist because the Earth doesn't revolve around the sun in 86400*365 seconds, but that missed the underlying point that since well before civil time differed from solar time, people have defined a year in terms of days, preferring not to have years starting a midnight, then dawn, then noon, then dusk, and so on. Leap years have existed since well before civil time and solar time were any different. And you missed the bigger point - that leap seconds aren't needed because the earth is slowing any more than leap days are needed because the year is getting longer. If an actual siderial day was a fixed unchanging 86400.005 seconds long, you'd still need a leap second every 200 days. *SLOWING* would be indicated by the every 200 days changing to every 175 or every 150. I assume you meant solar instead of [sidereal] -- the sidereal day hasn't been 86400.anything seconds ever. And if the mean solar day were unchanging, then it would be 86400 civil seconds today, just like it was (by definition) in 1900. The civil second was initially defined as 1/86400 of the mean solar day in 1900 (then later redefined based on radiation from the cesium atom, but the redefinition didn't change the length of the second by enough to matter for the purposes of this discission). The only reason the mean solar day today isn't 86400 is because the Earth's rotation has slowed since 1900 and we've elected to not redefine the length of a second. Yes, technically, you're right that if the Earth's rotation rate were constant and were such that the mean solar day were 86400.005 seconds long, we'd still need leap sections. But that's a highly unlikely counterfactual hypothetical, because, again, if the Earth weren't slowing, then 1/86400-of-mean-solar-day defintion of the second would still hold. There's virtually no chance that on a hypothetical Earth that wasn't slowing, that population would have decided that the second should be 1/86400.005 of a solar day. -- Brett
Re: F-ckin Leap Seconds, how do they work?
On Wed, 04 Jul 2012 21:01:50 -0500, Brett Frankenberger said: No. Leap Years arise because the solar year is not an integral multiple of the solar day. And leap seconds arise because the astronomical day is not an integral multiple of the hour, minute, or second. Same problem. still hold. There's virtually no chance that on a hypothetical Earth that wasn't slowing, that population would have decided that the second should be 1/86400.005 of a solar day. Look up the *original* definition of the meter, and think about the phrase measurement error. pgp0bwEdWYPVB.pgp Description: PGP signature
Re: F-ckin Leap Seconds, how do they work?
On 7/4/12, William Herrin b...@herrin.us wrote: IMO, leap seconds are a really bad idea. Let the vanishingly few people who care about a precision match against the solar day keep track of the deviation from clock time and let everybody else have a *simple* clock year after year. When the deviation increases to an hour every what, thousand years? Then you can do a big, well publicized correction where everybody is paying attention to making it work instead of being caught by surprise. [snip] Instead of having leap seconds; redraw the world timezone map, so that the boundaries of every time zone are shifted by a distance in feet that corresponds to one second; and such that after a thousand years and an hour's worth of leap seconds, the physical locations of the timezones will have shifted just so far, that there is a 1 hour adjustment. :) -- -JH
Re: F-ckin Leap Seconds, how do they work?
On Jul 4, 2012, at 8:39 PM, Jimmy Hess wrote: On 7/4/12, William Herrin b...@herrin.us wrote: IMO, leap seconds are a really bad idea. Let the vanishingly few people who care about a precision match against the solar day keep track of the deviation from clock time and let everybody else have a *simple* clock year after year. When the deviation increases to an hour every what, thousand years? Then you can do a big, well publicized correction where everybody is paying attention to making it work instead of being caught by surprise. [snip] Instead of having leap seconds; redraw the world timezone map, so that the boundaries of every time zone are shifted by a distance in feet that corresponds to one second; and such that after a thousand years and an hour's worth of leap seconds, the physical locations of the timezones will have shifted just so far, that there is a 1 hour adjustment. :) -- -JH Given that we don't seem to be able to eliminate the absurdity of DST, I doubt that either of those proposals is likely to fly. Owen
ACTA rejected by EU Parliment
http://www.bbc.com/news/technology-18704192 This is very good news, IMHO. And operationally relevant, even to North American operators. -- TTFN, patrick
Re: F-ckin Leap Seconds, how do they work?
Rather than discussing the pros and cons of UTC and leap seconds, just create your own time system. You could call it OpenTime. OpenTime will use NTP servers where the Stratum 1 servers are synced to some time standard that doesn't care about leap seconds. That way the consumer can chose to connect his machines to UTC or OpenTime.
Re: F-ckin Leap Seconds, how do they work?
On 7/5/2012 12:47 AM, Roy wrote: Rather than discussing the pros and cons of UTC and leap seconds, just create your own time system. You could call it OpenTime. OpenTime will use NTP servers where the Stratum 1 servers are synced to some time standard that doesn't care about leap seconds. That way the consumer can chose to connect his machines to UTC or OpenTime. Oblig: http://xkcd.com/927/ - Pete smime.p7s Description: S/MIME Cryptographic Signature
Re: F-ckin Leap Seconds, how do they work?
On 7/4/2012 10:06 PM, Peter Kristolaitis wrote: On 7/5/2012 12:47 AM, Roy wrote: Rather than discussing the pros and cons of UTC and leap seconds, just create your own time system. You could call it OpenTime. OpenTime will use NTP servers where the Stratum 1 servers are synced to some time standard that doesn't care about leap seconds. That way the consumer can chose to connect his machines to UTC or OpenTime. Oblig: http://xkcd.com/927/ - Pete Right on!
Re: F-ckin Leap Seconds, how do they work?
On 7/4/12 8:48 PM, Owen DeLong wrote: Given that we don't seem to be able to eliminate the absurdity of DST, I doubt that either of those proposals is likely to fly. Owen Before we had timezones your clock offset was forward or backward 4 minutes every-time you crossed a meridian.
