Suse network installation via ISDN impossible?

Hello, I have a couple of question about SuSE network installation. I am not connected to internet via network. I am usin ISDN modem (Aethra NT-IP, 128kbps) and it is connected to computer via rs232. I've burned ISO boot network image, but i am unable to select module that will allow me to dial-up the internet (there's no such module). There are only network-cards modules. Is it possible to perform installation using ISDN external modem? What shall I do? maybe i shouldn't download and burn iso image, but use boot-diskette? I have no idea, what can i do now. Ich hoffe dass Sie veranworten meine fragen. Kind regards, Krzysztof Kruszynski