Do you want to maximize your bandwidth? Here are few important settings you should do to speed up your internet and it works in Ubuntu and all Linux operating system via sysctl.
First open a Terminal via Applications->Accessories->Terminal
Type:

sudo gedit /etc/sysctl.conf

Then Paste the Following at the end of the file:

# increase TCP max buffer size setable using setsockopt()
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
# increase Linux autotuning TCP buffer limits
# min, default, and max number of bytes to use
# set max to at least 4MB, or higher if you use very high BDP paths
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216
# don’t cache ssthresh from previous connection
net.ipv4.tcp_no_metrics_save = 1
net.ipv4.tcp_moderate_rcvbuf = 1
# recommended to increase this for 1000 BT or higher
net.core.netdev_max_backlog = 2500
# for 10 GigE, use this, uncomment below
# net.core.netdev_max_backlog = 30000
# Turn off timestamps if you’re on a gigabit or very busy network
# Having it off is one less thing the IP stack needs to work on
#net.ipv4.tcp_timestamps = 0
# disable tcp selective acknowledgements.
net.ipv4.tcp_sack = 0
#enable window scaling
net.ipv4.tcp_window_scaling = 1

Press Ctrl-S to save, then alt-F4 to exit and then type:

sudo sysctl -p

to apply the settings.

Now, check your speed using speed-test site or download files in the net.

You can disable all these settings by removing these lines you added via:

sudo gedit /etc/sysctl.conf