How does the GUID algorithms handle the "clock sequence"?

Question

The GUID algorithms produces algorithms starting from 3 value:

the MAC address of your network card
the current timestamp with a resolution of 100 nanoseconds
something called "clock sequence": based on the RFC of GUID this value is incremented when the clock is set backward or if the timestamp is not changed from the last GUID generation.

So, how does the GUID algorithms handle the "clock sequence"? Is it maybe a hardware mechanism? Is it a tread and process safe software routine? What happen when computer will have the computational power to produce so many GUID per 100 nanoseconds to reset the "code sequence"? Maybe is not so far the day when the GUIDs become obsoletes..

The [RFC 4122](https://tools.ietf.org/html/rfc4122) states only "clock sequence", not "code sequence". Where did you get that reference? — Stefan M, Mar 02 '18 at 08:10
Possible duplicate of [What does "clock sequence" mean?](https://stackoverflow.com/questions/41475842/what-does-clock-sequence-mean) — Stefan M, Mar 02 '18 at 08:14
Yes. If you would look into the answer you'd see that it's commonly implementated as RANDOM. — Stefan M, Mar 02 '18 at 08:22
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/166080/discussion-between-optimusfrenk-and-stefan-m). — optimusfrenk, Mar 02 '18 at 08:31

score 0 · Accepted Answer · edited Oct 07 '21 at 13:28

The implementation is free to anyone who writes it. You won't get an answer on SO for every language/compiler/library which provides GUIDs.

From RFC4122:

If the previous value of the clock sequence is known, it can just be incremented; otherwise it should be set to a random or high-quality pseudo-random value.

So the most developers just choose the latter.

The clock-is-set-backward is just the reason for the clock sequence. The clock sequence isn't linked to the hardware clock or anything like it.

How does the GUID algorithms handle the "clock sequence"?

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