I can't understand this question. If Airtel gives you Wifi modem in Rs500 than why you will take Dlink or netlink at Rs2000+ ????
Is the Dlink or netlink ones a modem or a router?
normally, ppl used to purchase a router in addition to the modem for enhanced security. router features are all not available in modem.
for 500 bucks airtel gives normal wired modem. their wifi router cum modem price is 1000 bucks and the are not readily available.