IEEE 1588-2008

IEEE 1588 is a precision time standard. The goal is simply to give the internet a more precise time of day so that industries galore could all benefit. International Atomic Time (TAI) is the average of about 200 atomic clocks around the world. There are no leap seconds.

Coordinated Universal Time is presently 35 seconds behind the International Atomic time. The earth’s rotation is not as stable as an atomic clock. The average solar day is now 2 ms longer than it was in 1820, the year the Coordinated Universal Time is indexed to.

ytterbium lattice atomic clock
NIST Ytterbium Atomic Clocks Set Record for Stability

The NIST has developed several new clocks that are incredibly accurate.The contribution to the International Atomic Time has now become so precise that new standards were needed. A strontium clock operating at 430 THz now holds the accuracy record: it will gain or lose less than a second in 15 billion years, which is longer than the estimated age of the universe.

The first implementation of IEEE 1588 was in 2002 but it was revamped in 2008 with an incompatible new approach.

  • Apparent solar time varies ±16 minutes
  • Sidereal time (stellar) 23:56:04 day
  • NTP achieves 10 ms precision
  • PTP achieves 10 µs precision
  • GPS achieves 10 ns precision

IEEE 1588 is designed to fill a niche not well served by either of the two dominant protocols, NTP and GPS. GPS is comparatively expensive and it works best outside. An atomic clock is expensive to work to take better advantage has been ongoing for decades.

The epoch for IEEE 1588 is the same as Unix which is the number of seconds from January 1, 1970. Unix ignores leap seconds etc which can be a minor problem with precision time systems.

IEEE 1588 is defined to be the same as the International Atomic Time. GPS is presently 19 seconds behind the International Atomic Time.

IEEE 1558 uses the idea of clocks. Grandmaster clocks, master clock and slave clock are the roles used. Before the move to 64-bit there was been some concern of the 32-bit limitations. Every day is treated as if it contains exactly 86,400 seconds. The current time is 1.5 billion seconds so there is about 20 years to revise all of the 32-bit systems before the problem of rollover becomes apparent.

64-bit is now mainstream but much of the world is still not as modernized prices are falling rapidly so by the time 2038 rolls around that the rollover effect should be ancient history. Low cost android tablets are now manufactured with 64-bit processors. These low cost units easily achieved the $100 dream for a personal computer for internet use. By 2038, even entry level tablets will have more than 2048MB RAM and 32GB storage.

Windows 19 version 1809 added support for the precision time standard. Windows Server 2019 also added support. Universal adoption of the standard will take time as old systems are replaced etc. Older unshielded cat 5 cable can have varying lag with each pair. More recent cat 7 cable which is fully shielded is somewhat better. Fiber links are hard to replace so precision time analysis can help overcome bottlenecks etc.