I lose internet connectivity after waking up from sleep (MacBook Pro)

It does not always happen, but maybe in 90% of the times I send my computer to sleep and wake it up, I lose my internet connectivity and I have to restart it in order to get it back. The computer is still connected to Wi-Fi, but the internet doesn't work (both browser and mail).

I've had this problem on Yosemite as well and is something that just recently appeared from nowhere. I am a heavy user of "sleep" instead of shutting my computer down and I have been since 2012 when I bought the computer and never had this issue before. I hoped El Capitan will solve it, but it didn't.

Anyone who experienced the same?

My computer's configuration:

MacBook Pro (13-inch, Late 2011)

Processor: 2,8 GHz Intel Core i7

Memory: 8 GB 1333 MHz DDR3

Graphics: Intel HD Graphics 3000 512 MB

Running OS X El Capitan 10.11