if you use single Desktop then go for Type-1 ADSL modem provided by BSNL...
(works with your USB even if u don't have Network Port)
and if you use Laptop or more than one desk top then go for Type-2 ADSL Modem...
(as type-2 modem has 4 Ethernet + 1 Wi-Fi port.. )
and now, BSNL is providing ADSL2+ Modems...