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SubjectRe: "TCPv4 bad checksum" errors: a little more debugging
On Sun, Dec 06, 1998 at 04:19:42AM -0800, Damon Buckwalter wrote:

> 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?

FWIW, I see plenty of failed checksums with my PPP connection to my
school through an Annex 4000... no frame errors, though.

I'm also seeing problems with packets from the network on the other side
of the Annex, which seems to point to problems with the Annex, and not
Cisco or any other routers...

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

annex: stat
S/W Version: ANNEX3-UX R9.2.7 Build #2: Wed Mar 15 17:13:22 EST 1995
H/W: Remote Annex 4000 H/W Rev: 37. ROM Rev 0813.

Aaron J. Grier | Staff Programmer, OGI |
"Windows is the one true OS. MS invented the GUI. MS invented the 32
bit OS. MS is open and standard. MS loves you. We have always been
at war with Oceania." -- Tracy Reed

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