Introduction

The pool.ntp.org project is a big virtual cluster of timeservers striving to provide reliable easy to use NTP service for millions of clients without putting a strain on the big popular timeservers.

Adrian von Bidder created this project after a discussion about resource consumption on the big timeservers, with the idea that for everyday use a DNS round robin would be good enough, and would allow spreading the load over many servers. The disadvantage is, of course, that you may occasionally get a bad server and that you usually won't get the server closest to you. The workarounds for this is respectively to make sure you configure at least three servers in your ntp.conf and to use the country zones (for example 0.us.pool.ntp.org) rather than the global zone (for example 0.pool.ntp.org). Read more on using the pool.

The pool is now enormously popular, being used by millions of systems around the world. It's the default "time server" for most of the major Linux distributions (see information for vendors).

The pool project has since 2005 been maintained by Ask Bjørn Hansen and a great group of contributors on the mailing lists. Hosting and bandwidth for the "hub" servers are currently provided by Develooper, Phyber Communications and Internap.

News

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• May 25, 2009

  "The pool is one hour off"

  As mentioned a few months ago, NTP operates exclusively with UTC time. If your system is (typically) one hour off after syncing with the NTP Pool then it's because your operating system needs to be configured with the correct timezone and daylight saving time setting. If you live in a place that recently changed rules for daylight saving time you need to make sure you have the latest system updates installed.

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• May 5, 2009

  Dynect DNS services

  The goal of the NTP Pool is to provide accurate time to everybody. Though internally it's really about serving DNS requests. Quite a lot of them, and ideally fast.

  Through history we've ended up with using the 'pool.ntp.org' domain for client access which for performance isn't really optimal, but it's what we have. Through a bit of administrative division it ends up that just to find out who to ask for the IP of '1.fedora.pool.ntp.org' you have to send a whole lot of DNS requests out.

  While the DNS system is resilient in handling failures, to get decent performance it's important that each "layer" has fast and highly available servers. To that end we're fortunate that Dynect are providing Anycast DNS services for the NTP Pool (about 300 million requests a month right now, and we're just getting started).

  For now we're just using Dynect for the ntpns.org zone, but in the future we're looking forward to also using their failover system to help make sure the pool website is always available.

  Permalink | 2 Comments
• March 11, 2009

  How many requests does the pool handle?

  Due to the distributed nature of the pool system we don’t know exactly; but based on some sample measurements we estimate that the overall pool system on average handles somewhere between 40 and 120 thousand NTP requests per second.

  If we assume it’s 50,000 a second, that makes a bit over 4300 million requests a day!

  In a year that’s about 1500 trillion (american) / billion (other countries) requests a day. (1576800000000, if I’m counting the zeroes right).

  That’s a lot of accurate time distributed; and yet triains, planes and meetings run late. :-)

  Permalink | 2 Comments
• March 9, 2009

  Happy Daylight Saving Time!

  In many places around the world March is the month of changing clocks as daylight saving time comes and goes.

  Usually a number of users write to tell me that the NTP Pool is an hour off during this time and in the fall when clocks change the other way. Happily it isn’t so; because NTP is based on the almost stable Coordinated Universal Time (aka UTC).

  If you use NTP and your clock is an hour off, you either need to update your operating system with the latest patches for the time zone information or you need to check that your time zone is configured correctly and “adjust automatically for daylight saving time” is enabled if that option is provided.

  For people in the Northern Hemisphere: Enjoy spring and the increasing daylight!

  For those of you on the other side: Sorry, but it’s our turn to have longer days now. :-)

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• January 6, 2009

  IPv6 status

  Happy New Year everyone! Please take a moment to remind your fellow sysadmins about registering their servers in the pool if they have servers meeting the requirements (~100% uptime and a static and stable IP address).

  As mentioned earlier the pool system now has partial support for IPv6 servers.

  It's currently limited to just getting the servers registered though! They are not monitored and the pool DNS system does not give out AAAA records.

  The plan is to start testing various approaches to IPv6 support during 2009. Stay tuned.

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Links

• NTP home - the website about ntp
• Meinberg, makers of incredibly fine time server systems.
• The Public servers abuse and the Fixing the NTP server abuse problem threads on the comp.protocols.time.ntp newsgroup have caused this project to be started.
• Federico Sevilla III also has a mailing list archive of the timekeepers list - this one is searchable.