Hat tip to Richard Bennett at the Original Blog.
I’ll say this loud and clear; QoS is a reordering of packets that is an essential part of network traffic engineering. Take the following example where A represents VoIP packets and b represents webpage packets.
No enhanced QoS policy
With enhanced QoS policy
Now note that there are only 5 A packets in the entire stream for either scenario and you still get the exact same throughput for the b packets with or without prioritization for the VoIP A packets. The difference is that the A packets are now a lot more uniform which makes sound quality go up and the webpage b packets don’t really care about uniformity since all they care is that they get there at all intact. With this QoS example, you can improve VoIP without affecting the average throughput of web surfing. More precisely, QoS has ZERO throughput effect on non-prioritized when there is zero congestion on the pipe. If it had been a congested network, then QoS will have minimal effect on non-prioritized traffic.
Also see Dave Siegel on QoS and net neutrality.