RE: ISCSI: found the constant for divide-only circuit!

[Paul Koning <ni1d@arrl.net>]

>>>>> "Vince" == A-Roseville,ex1  <CAVANNA> writes:

 Vince> Added iSCSI prefix to subject line.  Actually both "example"
 Vince> and "preferred" seem inappropriate. How about "reference" or
 Vince> "assumed" implementation? 

That suggest you have to do it (or at least SHOULD do it) the way that
is being described, which is not the right thing to say.  The thing
that has to be stated is the mathematical statement of the CRC value,
and the rules of bit order.  That and only that is required for
interoperability.

All else is implementation detail that can certainly be helpful but is
in no way normative, and anyone is entirely free to do something
completely different so long as the PDUs come out the same.

 Vince> For the claims and examples in the
 Vince> iSCSI spec to be correct we must refer to an implementation
 Vince> that performs the following transformations (responses), after
 Vince> n input bits are applied, on an initial state I(x) and an
 Vince> input M(x):

 Vince> 1. when I(x) is zero, multiplies the input, M(x), by x^32 and
 Vince> divides by G(x).  2. when M(x) is zero, multiplies the initial
 Vince> state, I(x), by x^n and divides by G(x).

 Vince> ... In contrast, the divide-only serial circuit that I have also
 Vince> provided performs the following transformations on an initial
 Vince> state I(x) and an input M(x) and iSCSI should not refer to it
 Vince> unless it changed some of its claims and examples:

 Vince> 1. when I(x) is zero, divides the input, M(x), by G(x) 2. when
 Vince> M(x) is zero, multiplies the initial state, I(x), by x^n and
 Vince> divides by G(x)

Those are four example implementations, I think.  I'm not sure if
giving four examples is better than giving just one, or more
confusing.  (Perhaps the right answer is to give no examples, as Pat
suggested, retaining only the formal mathematical definition; that
would match the practice of all other datacomm specs other than
Ethernet that I know of.)

      paul