[e2e] use of MAC addresses

Charles M. Hannum mycroft at netbsd.org
Thu Apr 13 17:13:48 PDT 2006

On Fri, Apr 14, 2006 at 09:13:34AM +1000, grenville armitage wrote:
> Charles M. Hannum wrote:
> 	[..]
> >I'm still trying to figure out where this notion of IP addresses being
> >"globally unique" came from.  IP addresses are *not* globally unique.
> >Even if we ignore NAT, they are still ephemeral due to DHCP, ND, etc.
> Being ephemeral, and being unique while assigned, seem orthogonal to me.

I saw no qualifier of "while assigned".  For many of the uses of MAC
addresses -- e.g. DHCP -- the permanance of the uniqueness actually
matters (in several different ways).

For that matter, consider 802.11.  An AP may not even have an IP
address, if it's bridging, so the *only* identifier is a MAC address.
Like an Ethernet switch, it's specifically designed to be transparent
to IP and blend in with the Ethernet switch architecture.  What's the
advantage of changing that?  (Besides screwing all the cable users who
can't get more than one IP address, and forcing them to use NAT even
if they have a single machine!  Now there's a good goal.)

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