I've transferred a file from one machine to anohter one. The md5sums
of the files didn't match. Investigation led me to find a bit error
in the destination file.
Source hd -> Ne2000 -> BNC ethernet -> Ne2000 -> harddisk ->
specialix IO8+ -> 1.5M serial cable -> Cable modem -> cable ->
internet -> cable -> cable modem -> 2M UTP -> HUB -> Tulip ethernet
card -> harddisk.
Somewhere the bit got flipped. At first I thought: Sure, no problem: a
bit probably got corrupted on my serial cable. However if I'm not
mistaken, the CRC should protect against that. And if I'm not mistaken,
the CRC should detect ALL single bit errors right?
Or was there something like "if (packet->crc != 0) check_crc
(packet)"? which means that my packet just happened to luck out with
a zero CRC.
I had about 50% packetloss on the transfer, so it could be that
biterrors were happening all the time, and that packets were getting
dropped due to CRC errors all the time. At 22Mb, 22k packets -> total
44k packets tranmitted -> about a 50/50 chance of a packet with a
zero CRC in there somewhere (if the CRC is indeed 16 bits).....
Comments anyone?
Oh, All linux boxes involved are still running 2.0.x kernels.
Roger.
-- ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 ** *-- BitWizard writes Linux device drivers for any device you may have! --* ------ Microsoft SELLS you Windows, Linux GIVES you the whole house ------
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