Re: "TCPv4 bad checksum" errors: a little more debugging

Jamie Lokier (lkd@tantalophile.demon.co.uk)
Sat, 5 Dec 1998 20:58:00 +0000

On Sat, Dec 05, 1998 at 08:16:29PM +0000, Shaw Carruthers wrote:
> It is believed that there is a problem with the Ascends that Demon use
> which leads to checksum errors. The Ascends have a fixed buffer of about
> 16k per connected user. If you advertise a large receive window, the
> buffer can overrun and packets get dropped which screws the VJ
> compression. I use a window of 7k which reduces the problem.

The VJ compression bugs are quite well known. It's the first thing
people suspect when there are checksum errors.

> There is also another problem as I get checksum errors with novj, but far
> less often.

This problem was the focus of my mail. Looks a routing problem, as the
erroneous packets appear to be ones I shouldn't be receiving.

-- Jamie

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