Fedora Hardware :: Prolific Pl2303 + Serial Modem - Dials But PPP Won't Authenticate

Background info

1) Compaq laptop, legacy free (no COM or LPT ports, USB only)

2) The laptop owner has dial-up and can't get broadband right now.

3) The laptop is running F12 with the PAE kernel.

4) Internal modem is a Conexant modem masquerading as Intel ICHxxx chipset. All attempts at getting a driver to work for this so far have failed.

5) I downloaded a Linuxant RPM but this failed to work.

So my only option that will get the computer back to its owner is an external modem using a Prolific PL2303 USB to SERIAL adaptor cable. When using the PL2303 cable my external modem appears as /dev/ttyUSB0 For the most part this works fine. I used the steps in the solution from the following thread

[URL]

The only problem I have is getting PPP to work THROUGH the cable. I have verified the cable is the issue. HOW?

1) I have tested all the modems on another machine with F12 through the onboard COM port. All modems dial, connect, then authenticate and maintain connection until I manually disconnect.

2) I have tested all modems used on the other machine with the PL2303 and can replicate the problem on that machine.

3) I have used more than one PL2303 cable and get the same behaviour.

Using the network configuration utility / wvdial / modem lights OR kppp produces the same results when controlling the modem located at /dev/ttyUSB0 So do I

1) have to make some configuration changes to relating to /dev/ttyUSB0

OR

2) is the something in ppp that needs configuring

OR

3) is it something else altogether that I am not aware of?