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From: mark@hyper.UUCP (Mark Mendel)
Newsgroups: net.micro.mac
Subject: crc errors: Death to Checksums!
Message-ID: <66@hyper.UUCP>
Date: Tue, 8-Jul-86 11:02:51 EDT
Article-I.D.: hyper.66
Posted: Tue Jul  8 11:02:51 1986
Date-Received: Fri, 11-Jul-86 06:27:02 EDT
References: <229@ndsuvax.UUCP>
Organization: Network Systems Corp., Mpls., Mn.
Lines: 20

> 
>      Sometimes when I binhex a file that has come over the net I get
> a message about a crc error.  Can anyone save me a lot of time by explaining

I, too, have experienced these errors.  I believe they are caused by the file
being transferred at some point using a CHECKSUM instead of a CRC.

I know of at least one case where this must have been the problem.  The BOSTON 
II font distribution had a CRC error.  I looked at the fonts, and LO!, several
characters had double bit errors.  That is, a localized burst of errors where
in nearby bytes the same bit was wrong s.t. a checksum will not detect the 
error. These are precisely the types of errors that CRCs are designed to catch.

I have read articles where people say "checksums have always worked for me...".
Well, 99% IS NOT GOOD ENOUGH for a transfer protocol!  If you are going to be
posting stuff, please try to use an terminal package that supports CRC.
-- 
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Mark G. Mendel, Network Systems Corporation
ihnp4!umn-cs!hyper!mark