Thanks guys.. in particular Alien tech

Previously I tried deleting the bridge protocol and leaving only the pppoe in the ADV-> WAN option. But today I tried changing all the protocol to the pppoe mode and it works really well..
I don't know how or whats the technical explanation for that..
Anyway this is what I've done( Explanation for those who have the same problem ):
* Used 192.168.1.1 in url to login to my modem( the default username and password is admin)
* Advanced setup-> Wan-> edit
Click next-> select ppp over ethernet(pppoe) -> fill in ur username and password given to you by ur ISP(internet service provider)
*service name( for bsnl->dataone, for tataindicom-> VSNL or TATA)
* Enable NAT, FIREWALL AND IGMP
Do this for all the seven options. Usually by default, you will have the first protocol to be pppoe and the rest be bridge. So change everything to pppoe.
This method is for always connected mode(pppoe), you only need to power on the modem and you can surf your way to internet.
But as Alien tech said, there will be some data transfer happening even if you don't download or browse. I don't advise this method for limited plans.. I changed this mode to bridge when I was using bsnl home 500c paln, cos during my 1st month of usage, I went beyond the limit of 1.5GB by 300MB. I probably would've used only about 1GB or 1.1GB..The rest were just data transfer ( i don't know why it happens ), both upload and download, even when my pc was turned off, but my modem wasn't.
PPPoe -> recommended for unlimited plans