Re: iSCSI: Nailing down CRC-32C

[Mark Bakke <mbakke@cisco.com>]

BTW, I just ran the algorithm from the paper with these parameters.
If they are specified correctly, the CRC of the string "123456789"
should be 0xe3069283.  Note that's without padding, which we have
to unambiguously specify as well.

--
Mark

Mark Bakke wrote:
> 
> At the interim meeting, it was stated that iSCSI has selected
> the CRC-32C polynomial as its required iSCSI-level header and
> data CRC.  Now that we have it, it's time to move on and make
> sure we can implement it.
> 
> In the interest of interoperability, we need to not only specify
> the polynomial, but also the initial values, bit and byte
> ordering, etc.
> 
> "A Painless Guide to CRC Error Detection Algorithms"
> (http://www.ross.net/crc/crcpaper.html) specifies a
> method to unambiguously characterize these parameters
> (sections 15 and 16).  Has anyone taken a shot at defining
> these yet?  Otherwise, here is what it might look like:
> 
> Name   : "CRC-32C"
> Width  : 32
> Poly   : 1EDC6F41   (note that the leading "1" is implied)
> Init   : FFFFFFFF
> RefIn  : True
> RefOut : True
> XorOut : FFFFFFFF
> Check  : ?
> 
> I haven't attempted to create check data based on these yet.  As
> soon as the other parameters are nailed down, we need to do this.
> 
> Anyway, I am not a CRC expert, and can't make any statement about
> the above values being the "best" way to do this, but instead just
> copied them (except the polynomial itself) from the Ethernet CRC,
> since that is likely the easiest for everyone implementing hardware
> to deal with.
> 
> If someone else is already doing this, let me know; I just wanted
> to start this thread so we can get closure.
> 
> Regards,
> 
> Mark
> 
> --
> Mark A. Bakke
> Cisco Systems
> mbakke@cisco.com
> 763.398.1054

-- 
Mark A. Bakke
Cisco Systems
mbakke@cisco.com
763.398.1054