usb--> serial converter--> external serial modem

works, connects, and all just seems a bit sluggish.
where the heck does it show baud rate on ubuntu.
any other settings I might check? I assume it would be running at usb2.0 speeds since its a 2.0 port?

umm, its a 56k modem, its always sluggish

hehe just kidding.

as for the baud rate, regardless of what port you plug it into, the modem will only ever be a 56k modem, even if it has a high-speed link to the pc. the maximum speed of the mdem is not defined by the link to the pc, but by the ability to transfer data over the telephone system, analogue modems are not very effecient.

you could try opening a serial console and just hammering down enough AT commands to dial your isp, then whatch the resulst, if you cant find the answer anywhere.

if you can hear your modems calling, you can use a little GeekPowa! to be uber impressive and tell 'by ear' what speed your modem is connecting at. if its a whistle-nnnergh-psssshhhh noise, usually fairly quick, then you probably have a good 56k connection, but it its a whistle-nnnergh-pssssshhhh-weirdbongynoise-pssshhhh-nnnneeeeeergh-pssshhhh then the modem has re-trained cause it cant get a good 56k connection, and usualy tries a slower 48k connection. i know, its a little "low tech", but its a modem, its fairly low tech as-is.

Not sure about Linux but in most Unix flavors you also set the connection to the modem at the /dev entry using a line /etc/inittab. You can see details about the connection from your Linux box to the modem itself by doing "stty -a </dev/device" where device is replaced by the tty device name of the modem. Its always possible you've set this connection to say 2400 baud and then eve if it is connecting 56 K on dial out you're being slowed down by the connection to your serial port.

Look at inittab and gettydefs for more info.

indeed ubuntu had set the modem up at 9600 baud
using
stty -F /dev/ttyS0 115200
was able to turn up the bits a bit