RE: iSCSI: CRC description

[Bill Studenmund <wrstuden@wasabisystems.com>]

On Wed, 12 Jun 2002, Julian Satran wrote:

> The thing about this text that is going on and on is very frustrating.
> First Vince insisted on emphasis.
> Now you find it confusing.
>
> I gave it as a quiz to a undergraduate class and no one made a mistake.
>
> How much effort do you think I will spend on it? And who are the people
> that are confused?

I'm not sure how much effort you need to spend on this. I'll admit I was
one of the people confused, but that was more about CRC methods and the
bit reflection we have happening than anything else.

The only thing I might suggest would be to include parameters appropriate
for one of the CRC libraries. For instance including settings for Ross
Williams's CRC discussion could be quite useful, and remove much
ambiguity.

If there still is confusion and size becomes a concern, perhaps we should
generate an ID covering the CRC process. Something like
draft-ietf-tsvwg-sctpcsum-07.txt but for iSCSI.

> pat_thaler@agilent.com
> 06/12/2002 09:24 PM
> Please respond to pat_thaler
>
>
>         To:     Julian Satran/Haifa/IBM@IBMIL
>         cc:     ips@ece.cmu.edu, owner-ips@ece.cmu.edu
>         Subject:        RE: iSCSI: CRC description
>
>
>
> Julian,
>
> The changes to the text on CRC are a step down rather than up in clarity.
>
> In particular:
>  " - In the bit stream mentioned above the CRC bits are appended   to the message bits with x^31 first followed by x^30 etc. In   the examples provided in Appendix B.4 - CRC Examples, the   value is outlined as a word sent or received and therefore   the CRC bits are mapped into the CRC word according to Section   1.3.4 Bit Rule - i.e., the x^31 coefficient in bit 7 of   the first byte of the digest continuing to through the byte the x^24
> coefficient in bit 0 of the first byte, continuing with the x^23
> coefficient in bit 7 of second byte through x^0 in bit 7 of the last byte.

Shouldn't that be "x^0 in bit 0 of the last byte"?

> Replace, "The CRC should be calculated as follows:" with "The CRC MUST be
> calculated using a method that produces the same result as the following
> process:"
> Regards,
> Pat

Take care,

Bill