Assume a scenario that your internet connectivity get fluctuating all the time so you can check is it a actual internet drop or some thing else, solution is ping to Google DNS and check the flow of data transferring(before that please chck whether y our network cable is properly connected :D)
Open command line
Type ping 184.108.40.206 -t
You will show how packets get flow
If this get disturb that means your internet connectivity going down.