Locate the 'Receive Window Auto-Tuning Level' value under TCP Global Parameters. Run the command netsh interface tcp show global.Tap on the Windows-key, type cmd.exe, hold down Shift and Ctrl keys, and hit enter.Note: you don't need administrative privileges for running the command above, but you will need them for modifying the Window Auto-Tuning parameter. If it is turned off for instance, it is likely that it is not the case for the slow downs, but if it is set, it may very well be the culprit. The first thing you may want to do is check the status of Window Auto-Tuning. Managing Window Auto-Tuning in Windows 10

While data transfers should be more efficient as a general rule, users may experience slower than usual data transfer speeds under certain conditions or even connectivity issues.

Set to on by default, it is designed to improve performance for programs that receive TCP data over a network. Microsoft introduced a feature called Window Auto-Tuning back in Windows Vista, and has made it part of any newer version of Windows as well. It may be particularly useful if the Internet speed was fine on previous versions of Windows, and is no longer after the upgrade to Windows 10 Anniversary Update edition.