Ubuntu 14.04 wired connection keep disconnecting

I was using Ubuntu 12.04 LTS on my Dell Vostro laptop. Yesterday I upgraded the same into Ubuntu 14.04 LTS, after upgrading my wired ethernet connection is getting automatically disconnected after connecting into wired net for 3 to 5 minutes, only unplugging and replugging ethernet cable reset the connection and I can access net (It showing it is "connected" in the network connection area, but i cant access internet till I unplug and reconnect it), the problem continue in every 3 to 5 minutes.

Output of lspci -knn | grep Eth -A2

07:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 0c)
Subsystem: Dell Device [1028:065c]
Kernel driver in use: r8168

This adapter [10ec:8168] does not need r8168 driver.

Default r8169 module supports it better.

You can test it by

sudo modprobe -r r8168
sudo modprobe r8169

If you installed r8168 from Ubuntu repositories, then run

sudo apt-get purge r8168-dkms

to make it permanent.