Many standards groups require payment for their published standards: the ISO and most national standards bodies (ANSI, etc) are maybe the most prominent examples.
This is their business model. You pay for access to the standards documents, and that money funds the development and maintenance process. It's supported by governments requiring adherence to these standards, so implementors are obliged to purchase them.
Gratis access to standards is a newer model which relies on a different funding stream. The IETF is one such example.
I once made the shocking discovery, that most ISO and IEEE documents can be found on chinese PDF dump sites. Since this is obviously against all copyright laws, i would recommend to explicitly exclude such domains from your google search. Just to be safe.
Yes almost anything to do with Industrial Ethernet type standards are all over the place. 1588 PTP mixes with IETF TICTOC workgroup output. Synchronous data also gets used in Psuedowire backhaul for low level circuit emulation signaling like from SCADA or GSM towers etc. And that's without going into IECxxxxx's for powerplant comms.
Certifiable Precision Timeing over anything is not trivial.
This is their business model. You pay for access to the standards documents, and that money funds the development and maintenance process. It's supported by governments requiring adherence to these standards, so implementors are obliged to purchase them.
Gratis access to standards is a newer model which relies on a different funding stream. The IETF is one such example.