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

From: [email-masked]
Date: Tue, 6 Mar 2001 04:21:59 +0200

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

[email-masked] on 05/03/2001 23:27:49

Please respond to [email-masked]

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)
>

---

From: "Douglas Otis" <[email-masked]>
Date: Mon, 5 Mar 2001 20:39:32 -0800

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