I assume that you are using the ethernet connection and have proved that there are no problems with the cable, wall socket, router, network generally,etc.
If so the first thing I would do is to go to the link below, select your product from the lists given and check the driver you have installed is the correct one for your operating system, as there is only one listed for your machine. The simplest way may be to simply download this driver and install it to see if this cures your problem.
Drivers and Manuals
Alternatively if you are using a wireless access point you will need to check which wireless adaptor you have and then down load the appropriate driver and install it.
If these both fail to correct the problem, and all the rest of the network components are fine, you may be looking at a gradual deterioration of the LAN hardware, in whci case you should consider repair, or just to check, obtain a USB wireless LAN adaptor and driver and try that. They are relatively cheap, and if the problems continue even after that then the cause must be outside of your laptop and its hardware.
Hope this helps