I believe I've found a bug in the 6.0 implementation of PPP. Connecting to the Ricochet network (a standard PPP server) I couldn't send large packets. Pings worked fine, small web pages worked fine, but large packets couldn't get through. (Turning on kernel debugging showed that the large frames would arrive, but wouldn't "get through".) After struggling for 48 hours on the problem, I found that I could work around it by specifying "novj" (turn off Van Jacobson compression.) A quick search of the newsgroups shows that this problem affects many people.
This is in the kernel, not the ppp daemon. The ppp daemon merely sets up the connection; the kernel is in charge of the rest.
Ricochet does indeed have problems with VJ compression having reviewed some packet and byte traces. I've moved this bug to Michael because the only answer I see is to put Ricochet into RP3 and make RP3 know about VJ disable on some networks. Alan
Adding every possible option to rp3 will turn it into a user interface nightmare. I'd rather just explain how to work around ricochet's bugs until they get them fixed. linuxconf does have a way to set PPPOPTIONS so folks can use that to set PPPOPTIONS=novj to work around the problem in the meantime. AT&T chose the same kind of thing when they found a bug in their implementation that kept CCP negotiation going -- they preferred to tell people to set PPPOPTIONS=noccp to adding a bug-compat features to rp3 or some other tool.