[ILUG-BOM] switching off internet when not in use in Ubuntu

[BombayNews]

Dear all,

I think my Internet usage (MTNL Triband) has increased ever since I
switched over to Ubuntu! Earlier when I had Windows XP I could disable
Triband by right clicking the Internet connectivity icon on the bottom
right of the screen. There is no such blinking icon on Ubuntu and the
net stays on even while I want to work offline. How to get this so that I can switch off
Internet when I want to work offline?

regards
shiv kumar