I have just bought a usb modem, aztech 56k usb um9800-u. They have are also providing the usb drivers for this modem as rpms. the usual modems are configures as ttysx but how can I configure this one.

following is some additional information regarding the modem I have just described. There are two rpms avaliable at their website named "slmdm-2.04-00_20mdk.i386.rpm" and "slmdm-usb-2.04-00_20mdk.i386.rpm". I have installed them both and they have been installed properlly. but the problem is that I cannot access them through /dev/usb/acmx where x is the number of usb device. on giving this command on the command line "/dev/usb/acm0" or "/dev/usb/ttyUSBx" it says that no such file found, although in the /dev/usb folder I can see ttyUSBx names being displayed in yellow. even in the kppp visual configuration utility under modems it does show usb ports but when I try to query the modem through the same visual utility it does respond. Please help or direct me towards any good usb modem resource on the web as i cannot find one.

Your best bet would be to check out http://www.linux-usb.org and see what they have to offer.