#ptp — Public Fediverse posts

[Перевод] Синхронизация часов — это кошмар

Кажется, что время — это просто. Но мы, инженеры, теряем сон из-за такой простой задачи, как синхронизация часов. Причина этого в том, что не существует каких-то глобальных часов. У нас есть тысячи машин, распределённых по дата-центрам, континентам и часовым поясам; каждая из них работает независимо от других, поэтому ответ на простой вопрос «сколько сейчас времени?» оказывается на удивление сложным. Синхронизация часов становится основой самых сложных задач в распределённых системах, она влияет на всё, от согласованности баз данных и отладки до финансовых транзакций.

https://habr.com/ru/companies/ruvds/articles/1030464/

#синхронизация_времени #ntp #ptp #атомные_часы #ruvds_перевод

Blogged: My public NTP Server, one year later: Hardware upgrades, better RF, and OSNMA

https://www.tabsoverspaces.com/id/233969

#time #ntp #cm4 #raspberrypi #ptp

As well as the obvious implications to navigation both at sea and in the air, this is a timely reminder not to rely only on satellite-based signals for network time synchronisation.

#GPS #GNSS #jamming #NTP #PTP #time

https://www.france24.com/en/middle-east/20260306-surge-gps-interference-strait-hormuz-increases-shipping-risks

My overnight tests finished!

In my environment, I get the best #NTP accuracy with #Chrony when using `minpoll -2 maxpoll -2` and not applying any filtering. That is, have the client poll the NTP server 4 times per second. Anything between `minpoll -4` (16x/second) and `minpoll 0` (1x/second) should have similar offsets, but the jitter increases with fewer than 4 polls per second.

https://scottstuff.net/posts/2025/06/03/measuring-ntp-accuracy-with-an-oscilloscope-2/

Chrony has a `filter` option that applies a median filter to measurements; the manual claims that it's useful for high-update rate local servers. I don't see any consistent advantage to `filter` in my testing and larger filter values (8 or 16) consistently make everything worse.

When polling 4x/second on a carefully constructed test network, NTP on the client machine is less than 2 ns away from #PTP with 20 ns of jitter. I know that PTP on the client is 4 ns away from PTP on the server (w/ 2 ns of jitter), as measured via oscilloscope.

So, you could argue that this counts as single-digit nanosecond NTP error, although with 20 ns of jitter that's probably a bit optimistic. In any case, that's *well* into the range where cable lengths are a major factor in accuracy. It's a somewhat rigged test environment, but it's still much better than I'd have expected from NTP.

On the other hand, using #PTP to sync time to my web servers is a big win. They're behind a software router and using PTP with Intel NICs drops the sync error from ~10 us to ~5 ns, according to #Chrony. This is mostly because time is bypassing the firewall entirely and being distributed directly by the switch, so there's far less jitter.

I'm not quite sure what a 5 ns time error means when devices are more than 2.5 feet apart, but lets ignore that for now.

David Groves' (https://www.fibrecat.org/) talk at #NetMCR about measuring and calculating the current time was really interesting, explaining crazy timezones, how DST has changed over the years, leap years and seconds, and then how computers sync time to each other via #NTP and #PTP.

I learnt that you can even get expansion cards that have mini atomic clocks on them! (https://www.opencompute.org/products/319/ocp-time-card-made-by-time-beat)

Sadly I couldn't stay and chat afterwards as I had to get my train ☹️

Work4LuV --> https://hearthis.at/emuziek/work4luv/ -

A trainwreck of a show for lovers & other strangers.
#80s #newwave & #postpunk to make your 🧡 beat faster. 😍

#P1E #dj #valentines #TheAssociates #PIL #EM #Security #Klaxons #SigloXX #PrimalScream #PTP #Ministry #dj #Dive #ThrobbingGristle #FanTan #DuranDuran #GeneralPublic #TheCure #PetShopBoys #Tuxedomoon #MartinDupont #SadLoversandGiants #MastodonMusic #MastoMusic #MastoRadio #Music #MusicHistory #Musodon #vinyl #Nowstreaming #music

#Greenpeace Stands Up Against #SLAPPs And Wins

By Joe Mullin
April 26, 2023

"The U.S. litigation system is meant to resolve serious disputes. Unfortunately, the high cost of litigation can be weaponized as a means of #harassment and #censorship. That’s become all too common, and the last few decades have seen the rise of what’s known as a #StrategicLawsuitAgainstPublicParticipation, or #SLAPP.

"At #EFF, as more speech of all types has moved online, we’ve seen SLAPPs proliferate over #DigitalSpeech. SLAPPs get filed against #protesters who oppose #OilPipelines, and regular people doing everyday things like sending #emails to local officials, or even posting an online review.

"Five years ago, together with Greenpeace and other environmental nonprofits, EFF helped create the #ProtectTheProtest coalition, or #PTP. It’s a group of nonprofits that supports its members and others in their fights against SLAPP lawsuits.

"One of the lawsuits that spurred the formation of PTP was #ResoluteForestryProducts v. Greenpeace. In this case, a #logging company claimed that Greenpeace’s advocacy for #CanadianForests amounted to a 'global #fraud' that should be punished under civil #RICO laws—U.S. federal laws that were originally intended to go after organized crime.

"Following a summary judgment hearing last week, the Resolute v. Greenpeace case has finally been put to rest, with a complete victory for Greenpeace. This baseless lawsuit, which lasted seven years, should never have been brought in the first place. We hope Greenpeace’s victory against #Resolute sends a strong message to corporate SLAPP plaintiffs—you won’t win, and your targets won’t stay silent."

Read more:
https://www.eff.org/deeplinks/2023/04/greenpeace-stands-against-slapps-and-wins

#DigitalFreeSpeech #DirectAction #Fascism #CriminalizingDissent #WaterProtectors #ForestDefenders #EnvironmentalActivists #ClimateActivists #ClimateJustice #SilencingDissent #CorporateColonialism #EcoActivists #Censorship #HumanRightsViolations #Article20 #RightToProtest #SlowMarch #BigOilAndGas