RE: I-D ACTION:draft-cavanna-iscsi-crc-vs-cksum-00.txt

["Douglas Otis" <dotis@sanlight.net>]

Julian,

As there are already selectors in place for checking schemes, what reason is
there for excluding Adler-32?  It is not code size, speed of execution nor
difficulty in hardware implementation.  Excluding this alternative ensures
potential loss of a competitive software solution.  You wish to build a
bridge to carry trucks, but there is a height barrier that prevents such
trucks.  Is a serial burst error high on the list of probable errors if CRC
checks prevent these already?

Doug

> Pat,
>
> I did not run a check. That is very expensive.
> With CRCs there are methods that enable you to run a check on the
> complement code
> (that has only 2**32 different patterns for any block length) and derive
> from there the distances (Fujiwara has done this in 1989 for the IEEE
> CRC-32 and about some more recent experiments I'll get back to the list).
>
> And that is the trouble with this whole line of argument.
> There are no numbers to prove Adler32 or Fletcher32 and there are plenty
> for CRCs.
>
> The big question is then is there anybody out there that wants to build a
> modern bridge based only on its beauty?
>
> Regards,
> Julo
>
>
> pat_thaler@agilent.com on 05/03/2001 23:27:49
>
> Please respond to pat_thaler@agilent.com
>
> To:   Julian Satran/Haifa/IBM@IBMIL
> cc:
> Subject:  RE: I-D ACTION:draft-cavanna-iscsi-crc-vs-cksum-00.txt
>
>
>
>
> Julian,
>
> I know that Hamming distance gets down to 2 for errors that are separated
> by
> the modulus (or a multiple of it). Is there another case?
>
> Pat
>
> > - Adler and Fletcher are weak and there is no theory behind your
> > distribution statements, nor any simulation results as far as I
> know.  We
> > found that on very simple sequences the Hamming distance gets
> > down to 2 (or
> > lower) and the burst protection is probably not better than 16 bit.
> There
> > is even a simple formula for what sequences will get you false
> codes (see
> > bellow for a reference)
> >
>
>
>
>