Re: why 0xFFFE is used in the modified EUI-64 format

[Bob Hinden <[e-mail]>]

Before submitting the new text, I went back and tried to find out  
what the difference is between an MAC-48 and an EUI-48.  In the  
document:

    http://standards.ieee.org/regauth/oui/tutorials/UseOfEUI.html

I found the following:
   "The (obsolete label) MAC-48 is a concatenation of a 24-bit OUI  
assigned by the IEEE Registration Authority and a 24-bit extension  
identifier assigned by the organization with that OUI assignment.

The EUI-48™ is a concatenation of a 24-bit OUI value assigned by the  
IEEE Registration Authority and a 24-bit extension identifier  
assigned by the organization with that  OUI assignment."

and:

   "The use of the MAC-48 identifier is obsolete; the EUI-48 or  
EUI-64 should be used in current and future applications requiring  
the use of unique 48-bit identifiers."

My reading of this is that from a technical point of view MAC-48 and  
EUI-48 are equivalant.  They are both have the same definition:

   Mac-48:  "a concatenation of a 24-bit OUI assigned by the IEEE  
Registration Authority and a 24-bit extension identifier assigned by  
the organization with that OUI assignment"

   EUI-48:  "a concatenation of a 24-bit OUI value assigned by the  
IEEE Registration Authority and a 24-bit extension identifier  
assigned by the organization with that OUI assignment"

They both use the same 24-bit OUI values.  It looks to me like IEEE  
decided to deprecate the name MAC-48.  Why IEEE choose to have two  
different ways to create EUI-64 from these 48-bit identifiers is a  
mystery to me.  As far as bits on the wire, EUI-48 and MAC-48 appear  
to be exactly the same.  The link in Jinmei's email that started this  
discussion confirms this:

"The distinction between EUI-48 and MAC-48 identifiers is purely  
semantic: MAC-48 is used for network hardware; EUI-48 is used to  
identify other sorts of devices and software. (Thus, by definition,  
an EUI-48 is not in fact a "MAC address", although it is  
syntactically indistinguishable from one and assigned from the same  
numbering space.)"

I will still plan to submit the new text as it clarifies our use of  
these identifiers.

Bob











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