Subject: Re: CRC-32 Checksum for IPv6

From: [email-masked] (Hal Sandick)
Date: Fri, 25 Sep 1998 14:29:56 -0400

I couldn't find the article at the dr. dobbs web site but I was wondering
if this is suppose to work like the IP checksum.  That is, when the IP
checksum is re-calculated including the the one's compliment of the
checksum the result is zero ("TCPIP illustrated," Stevens). 

regards,

Hal

> Garry wrote:
>For RP hashing, the PIM-SM spec states that one should use the IPv4
address for
>IPv6 IPv4-compatible addresses and the CRC-32 checksum for all other IPv6
>addresses.  The specification then references an article by Mark R. Nelson in
>the Dr. Dobb's Journal, May 1992 issue.
>
>I obtained the Dr. Dobb's article code and found a DOS/UNIX application for
>calculating CRC-32 for files in a directory.  Knowing that the most important
>PIM-SM goal here is calculating a crc value that is the same throughout the
>network, I got a little nervous.  Mark calculates crc for an entire file
>buffer, keeping an accumulative crc.  When done, the resultant crc is
returned
>for the file crc, but undergoes a final one's complemented on return.
>
>Question I have is with respect to the final XOR operation.  Is this
>required/desired?  I just want to ensure that no matter how I apply the
CRC-32
>checksum to obtain the hash value, I'm doing it the same way as everyone
else.
>Thanks,
>Garry