[e2e] use of MAC addresses

David P. Reed dpreed at reed.com
Tue Apr 18 14:26:16 PDT 2006

John Day wrote:
> I have always thought it peculiar that MAC addresses had a larger 
> address space than IP addresses.
Yup, we have always known that IP address space was too small to be 
correct.  To be specific, we includes, without being limited to, Xerox 
PARC and the Saltzer, Clark, Reed group at MIT.
> This confusion of IEEE 802 universal serial numbers with addresses 
> always seemed a little strange to me.
This goes back to Xerox PARC, whose researchers recognized the very low 
cost and very high value of guaranteed unique identifiers as the base 
name space for networking, given the fact that networks are transient 
collections of devices, so binding naming to the particular topology 
merely made the system architecture more complex than necessary.

A simple way to realized that this is not strange is that the integers 
are the same mathematical objects, no matter whether you choose to 
represent them in decimal, hex or floating point ternary.   Same with 
endpoints.  They are the same no matter what network they are 
temporarily attached to.

Only people who thought that the wires and topology are more 
conceptually important than the endpoints would have decided that 
mobility was of such little importance that they would bind addressing 
to topological happenstance.  In other words, in IP, the  "routerheads" 
won - rather than the "internetworkers".

48-bits was chosen by the Xerox-DEC-Intel group as a compromise.  Most 
of us researchers were convinced that 64 bits would have been more 
easily allocated.

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