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

Damon Buckwalter (
Sun, 06 Dec 1998 04:19:42 -0800

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.
> Note: the single Ascend buffer has to handle multiple TCP streams to you.
> There is also another problem as I get checksum errors with novj, but far
> less often.

This sounds very possible to me, as we use Ascends as well, and I've
been experiencing the same problems. I get lots of RX frame errors on
my PPP connection as well -- this causes/is related to the TCP checksum
errors, yes?

We're using an Ascend MAX 4048 firmware v6.1.7 here, BTW.

/me has found another reason to dislike Ascend, besides the fact that
configuring one is a PITA.

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