Re: Van J compression?
Andi Kleen (ak@muc.de)
Sun, 27 Dec 1998 22:47:34 +0100
In muc.lists.linux-kernel, you wrote:
>Hi Jack.
>
> > The search for TCPv4 bad checksums continues. adding novj to the
> > ppp options seems to have fixed the problem. Still doing more
> > testing to ensure that the router (the remote point of my point to
> > point) has a bad ppp implementation and not me. Since it has a bad
> > finger implementation, and ppp works fine over null modems and
> > telnet sessions, I dare say the problem is with the router.
>
>Probably a useful check is to find out if the "bad Van J compression"
>problem is bad in the same way each time. If so, then it could be an
>idea to include some sort of workaround for it in the PPP routines,
>similar to the way we've worked round the F00F bug rather than insist
>that users upgrade...
"We" didn't have a VJ compression problem. Some terminal servers (e.g.
Ascend?) seem to have buggy VJ compression functions in some firmware
releases that can't deal with the extended TCP options used by Linux 2.1:
TCP timestamp, TCP sack and TCP window scaling.
Workaround is to turn them off:
echo 0 > /proc/sys/net/ipv4/tcp_{window_scaling,timestamps,sack}
-Andi
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