After upgrading from RH5.2 to RH6.1, I had intermittent
failures with ppp. That is, I could connect every time,
but on some connections TCP connections did not work.
Control packets (i.e., ping) and DNS always worked.
At the suggestion of someone on comp.os.linux.networking,
I disabled the "VJ header compression" with the "novj"
option in /etc/ppp/options, and this *seems* to have solved
the problem (can't be 100% sure, since the problem was
While this could be a problem at the server end, it seems
unlikely, since ppp was working fine with RH5.2, without
using "novj". If someone can explain to me how to log the
kernel ppp activity, I can perhaps provide better
information on what's going wrong (I tried using the pppd
"debug" option, but that seems to show only the protocol
startup, and doesn't show any IP traffic).
Quite a few servers get vj compression with options wrong. You may
find disabling sack and time stamps has a similar #fixing'
effect. For real world use SACK is worth more than VJ except on very