When you download a file, it is broken into many packets of data before it is sent over the World Wide Web to your computer (where it is then reassembled). The size of these packets is called your MTU value, or the Maximum Transfer Unit. Your downloads will be slow and disappointing if this value is not set correctly.

Each packet that is sent over the Internet contains a header which contains a variety of information about the packet, source, and destination. Setting your computer's MTU value too low would make downloading less efficient because a greater percentage of the packet is taken up by the packet header.