JayADee: What does DPI mean?
In simple terms, it means "Deep Packet Inspection". DPI is a method to inspect traffic down to each packet level to examine it's "contents", and based on that, the device (i.e. router) could then classify whether the traffic is high priority or not.
In theory by employing DPI, traffic could be classified, i.e. torrent trafiic could be prioritised to be the lowest priority, normal web/http traffic "medium" and delay sensitive data like voice could be high priority and always gets delivered/prossed first.
The downside of DPI is that as each packet has to be examined, it's very resource intensive (CPU, memory etc) on the processing device, and could potentially create a bottleneck and actually make things slower. You'll need fairly (and very very costly) grunty equipment to to be job...