Wireshark-users: [Wireshark-users] Acp 142 checksum algorithm
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From: Ricardo Cristian Ramirez <r.cristian.ramirez@xxxxxxxxx>
Date: Wed, 10 Dec 2014 23:10:57 +0200
ACP 142 (PMul) protocol has two versions. The first one [1] was
released at 2001 and the second one [2] was released at 2008. The
first version suggests to use 8-bit Fletcher's algorithm, which
produces 16 bit checksum. And, an implementation of this algorithm is
provided in the specification. Current PMul dissector [3] of the
Wireshark uses this provided algorithm.

The checksum description in the second version was changed: Provided
algorithm was removed and below statement is given without an
algorithm:
" The checksum field is the 16 bit one's complement of the one's
complement sum of all 16 bit words in the header. "

As far as I know, this statement decribes the TCP/IP checksum and an
update is needed for PMul dissector.


[1] jcs.dtic.mil/j6/cceb/acps/acp142/ACP142.pdf
[2] jcs.dtic.mil/j6/cceb/acps/acp142/ACP142A.pdf
[3] https://code.wireshark.org/review/gitweb?p=wireshark.git;a=blob;f=epan/dissectors/packet-p_mul.c;h=a03e69f10825e6dacb82f3aacb33b465adeb721a;hb=HEAD