How Fragmentation does ?
It sending a request to the destination and if the destination said it is too large . It will reply back to your router and then your router fragment a packets such as My mtu is : 1400 bytes but I'm sending at 2000 bytes. It will fragmented by a byte range 0 - 1400 and 1400 - 2000 which can cause a delay time which slow down your internet connection. This setting and how to find out MTU Size can be increase your internet speed.