Definition of Canonical

George Penokie gop at us.ibm.com
Thu May 28 09:59:10 PDT 1998


* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
* George Penokie <gop at us.ibm.com>
*
OK so someone had to ask!! Here is the way IEEE uses the term when referring to
OUIs (Organizationally Unique Identifier). IEEE defines two forms of hex data;
the MSB hex form and the Canonical form. The difference between the two is in
the order the bits in a byte are sent over a serial link (e.g., token ring,
ethernet). The MSB hex form transmits the most significant bit of a byte first
and least significant bit of a byte last. The Canonical form transmits the
least significant bit of a byte first and the most significant bit of a byte
last. That means 00h 06h 29h is equivalent to 00h 60h 94h.

So what does this have to do this us we don't care how the data is transferred
as long as it is the same when it gets to the other side. The problem is that
is we do not define which form is used then a company has no idea which form to
use when putting the three bytes into the VDP page. It turns out when you look
at the IEEE OUI database the company IDs are given in the Canonical form. This
by the way is not obvious when looking at that data base. Because of this
someone could think they need to use the MSB form and place that in the VDP
page which means they would be using ID not assigned to them.

Bye for now,
George Penokie

Dept EGB  114-2 N212
E-Mail:    gop at us.ibm.com
Internal:  553-5208
External: 507-253-5208   FAX: 507-253-5208
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