DCC Checksums: How are they determined?

Vernon Schryver vjs@calcite.rhyolite.com
Sun Nov 17 04:14:04 UTC 2002

> From: Peter Beckman <beckman@purplecow.com>

> I've noticed that the From: Message-ID: and Received: checksums are no
> longer attached to my mail, and usually show up blank in the dccproc -C.  

Dccm and dccproc try to guess the counts for each checksum that the
server had before the current report was added to the totals.  When
their guess is 0, they display blanks.  When the server is not recording
a checksum, every report of that checksum will have a previous total
of 0 and so be displayed by dccm and dccproc as blank.

The only way that a checksum itself will be blank is if dccproc does
not compute it for some reason.  A message without any Received headers
will not have a Received checksum in the result of `dccproc -C`.
However, a missing Message-ID is treated as if it were present but blank.

>                                                                           I
> read through the change log looking for "header" and "from" but was unable
> to find any note about no longer keeping the header checksums on the
> server.  Is this a per-server basis or now legacy tags?

By default, the DCC servers store only body checksums since version
1.0.44, which was released Feb. 2, 2002.  That default can be
overridden with `dccd -Kwhatever`.  See the dccd man page or

Vernon Schryver    vjs@rhyolite.com

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