time.windows.com NTP server seems to be sending out wrong time

[Geoff]

time.windows.com seems to be sending garbage to clients.

 

ntpdate[32691]: ntpdate [email protected] Fri Apr 10 19:04:04 UTC 2015 (1) server 40.68.115.144, stratum 16, offset -0.335147, delay 0.03069

 

Confirmed by twitter:

 

https://twitter.com/search?f=tweets&vertical=default&q=time.windows.com&src=typd

 

 

I'd suggest using uk.pool.ntp.org on your DCs for time sync as a replacement.

 

w32tm /config /syncfromflags:manual /manualpeerlist:"0.uk.pool.ntp.org 1.uk.pool.ntp.org 2.uk.pool.ntp.org 3.uk.pool.ntp.org"

Edited April 3, 2017 by Geoff

[Arthur]

Hasn't the general consensus always been not to use time.windows.com since it isn't reliable? I remember reading something years ago about it and have always used other NTP servers.

[caffrey]

Ooh thanks for the reminder completely forgot to set the NTP service on the PDC, now set to time.google.com

[Geoff]

time.google.com should not be used for production systems (Google said as much themselves).

 

It's also not RFC compliant as it fudges leap seconds.

 

https://github.com/systemd/systemd/issues/437

[caffrey]

Weird, didn't know that either thanks - you would think that Googles time service would be reliable...

[Arthur]

Google said as much themselves.

I thought Google simply said that you shouldn't use their time servers in combination with non-smearing time servers?

 

www.edugeek.net/forums/news/177604-google-makes-its-ntp-servers-public.html

 

It's also not RFC compliant as it fudges leap seconds.

The last time there was a leap second wasn't it RFC compliant systems that had the most issues?

 

www.wired.com/2012/07/leap-second-glitch-explained/

 

WHEN SATURDAY NIGHT’S leap second glitch hit Reddit, Jason Harvey didn’t realize it was the leap second glitch. He thought it was some sort of internet slowdown related to the massive Amazon cloud outage that brought down some of the web’s most popular services less than 24 hours earlier.

 

“It looked like the network was just moving really poorly,” says Harvey, one of the system administrators who oversee the operation of Reddit, the popular news aggregation and discussion site. “With Amazon going down, a network problem just made sense.”

 

But after about half an hour, Harvey and his team traced the problem to a group of their own machines running the open source Linux operating system. These servers had almost ground to a halt after failing to properly accommodate the “leap second” that was added to the world’s atomic clocks on Saturday night, as June turned into July.

 

In Reddit’s case, the problem could be traced to a glitch in the Linux kernel, the core of the open source operating system. A Linux subsystem called “hrtimer” — short for high-res timer — got confused by the time change, and suddenly sparked some hyperactivity on those servers, which locked up the machines’ CPUs.

 

Reddit was just one of several web outfits that were hit by leap second glitches just after midnight Greenwich Mean Time on Saturday, including Gawker Media and Mozilla, and these sorts of problems tend to pop up with every time there’s a leap second adjustment. In January 2009, for instance, the leap second reportedly caused problems with Sun Microsystems’ Solaris operating system and an Oracle software package.

 

“Almost every time we have a leap second, we find something,” Linux’s creator, Linus Torvalds, tells Wired. “It’s really annoying, because it’s a classic case of code that is basically never run, and thus not tested by users under their normal conditions.”

 

[...]

 

While Reddit was struggling with its Cassandra servers, Gawker had issues with its Tomcat servers, and Mozilla had trouble with Hadoop. Both Hadoop and Tomcat also depend on Linux and Java, and it would seem they were hit by the same glitch.

 

Other systems, however, experienced problems a day before the leap second arrived. Systems such as Linux use the Network Time Protocol, or NTP, to plug into the world’s atomic clocks and check the time. On Friday, NTP began warning servers that this year’s leap second was on the way, and according to Opera Software system admin Marco Marongiu, at least some Opera servers started locking up when they received the announcement. This issued is discussed on a Linux mailing list here, and it’s unclear how closely this issue is tied to the hrtimer problem experienced by Reddit.

 

[...]

 

Some have called for an end to leap second — so that these problems can be avoided. But in the meantime, others have proposed master fixes that seek to hide the sudden time changes from systems such as Linux. Opera’s Marongiu suggests pausing a system’s NTP system for a second, rather than actually moving a system’s clock back.

 

“Basically, you trick NTP, so it won’t take that sudden step back, but still adds the extra second,” says Marongiu.

 

But he calls this a “poor man’s workaround.” The better solution, he says, is the one used by Google. Last fall, with a blog post, Google described a method it calls “leap smear.” Rather than add the extra second all at once, Google has modified NTP so that it adds milliseconds to clocks over a relatively long period of time.

 

It’s a clever fix. But don’t expect it to become the norm. When the next leap second hits, someone somewhere will go down.

 

you would think that Googles time service would be reliable...

All of Google's services sync time with time.google.com so it must be reliable?

Edited April 3, 2017 by Arthur

[caffrey]

Geoff's link to git was 2015, iirc Google released their NTP servers to public in December 2016 - I think that's where I was getting it from https://developers.google.com/time/ from your post back on Dec 1st http://www.edugeek.net/forums/news/177604-google-makes-its-ntp-servers-public.html

[MatthewL]

Interesting post, my computer gained an hour this morning using the Google one. I am now using uk.pool.ntp.org

[Geoff]

Googles time service is reliable if you only use it (not in a combination with other NTP servers) and that all OS and applications are aware of the time smearing (obviously something Google can support on its platform for itself).

 

Standard *nix NTP can handle leap seconds just fine.

 

https://www.eecis.udel.edu/~mills/leap.html

 

In the case of Linux NTP doesn't have to do anything other than tell the kernel there is a leap second. It is handled by the OS rather than the daemon. (The issue in the past with Linux, e.g. in the Reddit case, is because you are not supposed to use the hires timer on a server).

Edited April 3, 2017 by Geoff