[Cbor] Paywalled IEEE standards referenced in draft-bormann-cbor-time-tag

[Emile Cormier <[e-mail]>]

The IETF draft for cbor tags 1001 thru 1003 reference the IEEE1588-2008
standard for the clock quality keys.

Are there no other public domain or open-source standards that would serve
the same purpose as IEEE1588-2008 for the clock quality keys? I ask that
without any expertise on the subject, but merely as a C++ CBOR library
implementer who wants to support these CBOR tags (they are better for
transmitting std::chrono::time_point values losslessly).

At the very least, can the descriptions be more explicit about the data
types needed for the clock quality keys? ClockClass and ClockAccuracy
specify "one-byte integer", but it's not clear if it's signed or unsigned.
Also, "octet" would be a better word than "byte", since there are
architectures (such as DSPs) where a byte is 16 bits.

The OffsetScaledLogVariance key does not mention the value's data type(s)
or its physical units.

My motivation is to create an intermediate extended_time struct in my C++
library that contains all the possible fields of a CBOR extended time. If
an application wants to deserialize it into a std::chrono::time_point, my
library would discard the clock quality stuff. If some sort of scientific
application really wants the clock quality information, then they just
deserialize into an extended_time destination object and my library copies
all the available information.

It would be preferable if the numeric clock quality fields in my
extended_time struct were of a known static type, such as a double. But
since I don't have access to IEEE1588, I don't know if double is of
sufficient accuracy. I would appreciate it if an expert could illuminate me
on the required numeric precision, or point me in the right direction for
my own research on the subject.

Cheers,
Emile Cormier