Subject: Re: Is anyone seeing lots of TCP checksum errors?
To: John F. Woods <email@example.com>
From: Dennis Ferguson <firstname.lastname@example.org>
Date: 11/08/1997 15:13:09
> The incorrect checksum value for the first curdled packet turns out to be
> the CORRECT checksum value for the next curdled packet, whose incorrect
> checksum value was the correct checksum value for the 3rd curdled packet,
> whose incorrect checksum value was the correct checksum value for the 5th
> curdled packet (whoops, there goes the SIMPLE theory), and so on. In short,
> the packets' checksum fields appear to the the checksum of some *other*
> packet (two bad checksums were the valid checksums of the two most recent
> acknowledgements my system sent!).
This very probably isn't a bug, it is what happens when you lose a
packet on a circuit running VJ header compression. The decompressor
stays out of sync with the compressor until the far end retransmits,
which tells the compressor to reset the session state. See the
section on error handling in RFC 1144.