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From: jbvb@VAX.FTP.COM (James B. Van Bokkelen)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Zero manufacturer code in SNAP?
Message-ID: <9007181417.AA15116@vax.ftp.com>
Date: 18 Jul 90 14:17:31 GMT
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    From: agate!shelby!portia.stanford.edu!jessica.stanford.edu!morgan@ucbvax.Berkeley.EDU  (RL "Bob" Morgan)
    Subject: Zero manufacturer code in SNAP?
    
    The 40-bit SNAP extension to IEEE 802.2 specifies a 24-bit
    "organizationally unique identifier" that is apparently supposed to be
    the same 24 bits that a manufacturer uses to form the upper part of a
    48-bit unique IEEE 802 MAC address.  The other 16 bits are assigned by
    the organization in any way it sees fit.

The IEEE 802.2 document actually specifies the SNAP extension header as
the 3-byte OIU only.  RFC 1042 is where the extra two bytes come from,
and the authors chose to put a DIX Ethertype there.  They could have put
the beginning of an IP packet there instead, or their initials...
    
    The question is, has the all-zeros SNAP id been assigned by IEEE to
    DoD, or the IAB, or some IP authority, to be administered by that
    authority?  Or is the all-zeros id just a general purpose format for
    translating Ethernet frames to 802.2/SNAP, to be used by anyone?

They way I've heard it (I hope I'm right enough that Jon is saved a
post) the "all zeroes" OUI was owned by Xerox from the beginning.
When RFC 1042 was being worked out, the SNAP header was the only way
to run IP on 802.2 networks, because of our inability to obtain a SAP
value for ARP (one has been assigned for IP).  So, the authors went
looking for an OUI, and Xerox was forthcoming.

Yes, you can put Ethertype 809b into those two bytes and Appletalk away.
You might want to look at a paper by Roger Pfister, "Bridging Ethernet
Frames - Which OUI?", which can be found as pub/msb_vs_lsb/661-062.txt
on vax.ftp.com.

James B. VanBokkelen		26 Princess St., Wakefield, MA  01880
FTP Software Inc.		voice: (617) 246-0900  fax: (617) 246-0901