To work out what dizzying speeds they can offer you, ISPs have to use some simple math to predict how much the demand for delicious internet will vary at peak times. Only, they don't always get it right.
In this video, Dr Richard Mortier explains how statistical multiplexing allows ISPs to effectively gamble on their claims of how much bandwidth they can provide you with. And yes, it's why your internet always sucks just as you get home from work. [Computerphile]