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    iSCSI: Nailing down CRC-32C



    
    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
    


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Last updated: Tue Sep 04 01:04:47 2001
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