[e2e] use of MAC addresses

John Day day at std.com
Tue Apr 18 11:00:11 PDT 2006

At 9:58 -0700 2006/04/18, Bob Braden wrote:
>That line of reasoning (Saltzer plus) does not seem to clarify
>a central distinction: media-dependent addressing vs.
>media dependent addressing.  No one thought about building one
>universal address space for media addresses, because we assumed
>that each distinct medium would naturally have its own form
>of addressing.  (Today, there is a tendency for (almost) all
>media to look like Ethernets, so perhaps one exploit that
>fact).  IP addresses were built to provide a universal
>address space, with essentially an indirection linking to the
>corresponding media-dependent addresses of connection points.

I am sorry, Bob, but I don't have a clue what you are talking about. 
I fail to see how medium affects addressing.

Any medium has limited scope and hence a limited address space.  As I 
commented earlier, I have always thought it peculiar that MAC 
addresses had a larger address space than IP addresses.  By my 
calculation, they are about 3 - 4 times larger than they need to be, 
i.e. the maximum number of devices one would reasonably expect on a 
single LAN segment.  This confusion of IEEE 802 universal serial 
numbers with addresses always seemed a little strange to me.

It is also a little strange that *IP* addresses name a *subnet* point 
of attachment.  ;-)

Take care,

More information about the end2end-interest mailing list