Delivering a guarantee of 1000Mbps is not possible on a gigabit ethernet network, due to hardware limitations
We only guarantee 900Mbps and not 1000Mbps on our Hypersonic plan even though this is the speed we supply, because it is difficult to achieve more than this without expensive specialist equipment.
Another reason why most users can't achieve >900Mbps is because of data overhead.
When data is sent over a connection, extra information or data overhead has to be sent. This takes up some of your bandwidth and will decrease speeds.