220BX is both a modem as well as a router(running on linux). It can be connected via USB or through ethernet. Mine is configured through ethernet and it is completely trouble free option. You do not even need to install any drivers in that case.
@Udit: In what way are you facing problems with ethernet connection? It should be the most trouble free option. If you got some other modem, then get the Airtel people to change it to a 220BX instead of purchasing a new modem.