IEEE1588 (2008) is an enormous standard, 269 pages long. It defines the Precision Time Protocol (PTP), a protocol for distributing time across a packet network. The problem is that nowadays there are about ten types of packet networks. There are industrial networks, power grids, telecommunications networks, audio networks, video networks, automotive networks, to name just a few. They all have subtly different requirements and so IEEE1588 contains lots of different options and features that simply are not appropriate for all networks.
For this reason, the members of the 1588 committee created profiles. A profile is “a set of required options, prohibited options, and ranges and default values of configurable attributes”. The idea was to allow other organizations (such as industry bodies or other standards bodies) to define which parts of the PTP protocol their sector would use. For example, the ITU defined the G.8265.1 profile specifically to distribute exact frequency (but not time) to mobile base stations.
The problem is that profiles have proliferated. The ITU has defined 3 of them, IEEE itself has at least 3, the IETF tried to define one but never finished it, the IEC has one that is almost the same as one of the IEEE profiles but not quite, SMPTE has one, and there are probably others out there too.
It is as if everyone claimed to speak English, but each had a different dialect: one speaks Geordie, another speaks American, another speaks Scottish, and another speaks the Queen’s English. Each is different enough that they don’t fully understand each other.
So the next time someone says: “All these clocks are PTP, they must talk to each other”, you should ask what profile they have before answering.
Want to know about our synchronization products?
Microsemi
https://www.tecnous.com/productos/timeprovider-4100/
Other synchronization notes