By default system reserves 20% of bandwidth of your internet connection


If you don't wanna be system resserve your speed then do the following

Go to run and type gpedit.msc



In local computer policy go to

Administrative templates\network\QoS packet scheduler



In the right pane you will see the option limit reservable bandwidth

by default it sets to not configured

double click on it and click enable set 20% to 0

All done

see the difference Enjoy