Subject Re: [Firebird-Architect] Digest Number 964
Author David Johnson
On Wed, 2005-03-30 at 06:53 +0000,
> This is a point I didn't understand how do you get an unique ID based
> on
> MAC or IP Address for unconnected DB's that is guaranteed unique,
> it's
> made with human intervention ?

MAC (Media Access Controller) address is guaranteed unique for any
network media device. It is encoded in the EPROM or an electronic
serial number chip on every network controller device built.

It is a requirement for the functioning of the ethernet CS/CD system,
and any other networking system for that matter. If you MAC address is
not unique, then you will get crosstalk at the network hardware level.
This is a really bad thing - it's even worse than two machines on the
same network having the same IP address.

Systems without a MAC often use the serial number of the BIOS or CPU as
the starting point. They are not guaranteed to be as unique, but they
are the source of the "sufficiently unique" comment that non-MAC based
methods of computing UUID's are constrained by.

To be fair, Jim's mechanism looks to me like a variant of the MAC based
UUID, without the randomization code that adds a level of safety to the
uniqueness of the UUID for global scale applications.