Hm, 

technically, the first two questions should go to tech-net...

1) Its uniquely assigned to that interface by the hardware vendor from
a block of addresses uniquely assigned to them from the Ethernet
Address Block Committee (sorry, I forgot the real name of that :-)

2) In 4.4BSD derived systems, every network interface has a list of
addresses associated with it for the different addressing
families. One of them is the interfaces "hardware" or "link-level"
address, if applicable, and the 8.0.9.15.65.54 is simply the Ethernet
address of your interface.

3) depends on amount. The network software avoids big copies by
passing around linked lists of "mbufs"; the tty software passes around
linked lists of "clists". 

For big chunks of memory, this depends on operation mode. For a full
discussion of this issue, look at 4).

4) Besides simply looking at the source code, the man pages, and the
/usr/share/doc documents, you can look at "The Design and
Implementation of The 4.4BSD Operating System" by McKusick et al. ISBN
can be found on http://www.netbsd.org/, select Documentation, select
4.4BSD.

Regards,
	Ignatios Souvatzis