On Sun, Nov 11, 2001 at 10:41:22AM +0100, Andi Kleen wrote:
> On Sun, Nov 11, 2001 at 12:29:34AM -0700, Ben Greear wrote:
> > The higher layers like TCP and UDP have their own checksums, so should catch
> > most bad packets there... (UDP may ignore it's checksum, btw)...
>
> The TCP/UDP checksum is much weaker than the CRC used by ethernet and
> does not detect many errors. It is mostly a protection against bugs, not
> about real bit errors as they could occur on the wire. I would not turn
> the ethernet CRC off.
Well, I'd assume disabling CRC and having the NIC forward all packets
(including the checksum) could be a useful feature for analyzing
network problems. If you see random CRC errors on the network and
your NIC drops packets with bad checksums, how can you find out what
machine sent it?
I don't know if any NICs support this. Best choice I can think
of is acenic with some firmware hacks. You can probably find copper-based
boards for pretty cheap ($150-200, not bad for a 1000baseT board. Will
work on 10/100baseT too)
--
Pekka Pietikainen
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