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Re: TOE brain dump

To: Andre Hedrick <andre@xxxxxxxxxxxxx>
Subject: Re: TOE brain dump
From: Lincoln Dale <ltd@xxxxxxxxx>
Date: Wed, 06 Aug 2003 18:20:06 +1000
Cc: Jeff Garzik <jgarzik@xxxxxxxxx>, netdev@xxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Werner Almesberger <werner@xxxxxxxxxxxxxxx>, Nivedita Singhvi <niv@xxxxxxxxxx>
In-reply-to: <Pine.LNX.4.10.10308060009130.25045-100000@xxxxxxxxxxxxxxxx .org>
References: <3F2CAE61.7070401@xxxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
At 05:12 PM 6/08/2003, Andre Hedrick wrote:
Do be sure to check that your data payload is correct.
Everyone knows that a router/gateway/switch with a sticky bit in its
memory will recompute the net crc16 checksum insure it pass the to the nic
regardless.  It is amazing how much data can be corrupted by a network
environment via all the NFS/NBD/etc wantabie storage products out there.

Andre, you are wrong.

firstly, do you REALLY think that most router(s)/switch(es) out there recompute IP checksums because they did a IP TTL decrement when routing an IP packet or NAT IP addresses?

no, they don't. just like netfilter or router-on-linux is smart enough to be able to re-code an IP checksum by unmasking and re-masking the old/new values in a header, so does the most router vendor's code.

secondly, why would a router or switch even be touching the data at layer-4 (TCP), let alone recalculating a CRC?

i know you really like your "we do ERL 2 in iSCSI" pitch, but lets stick to facts here eh?



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