I honestly don't understand why traffic shaping by ISPs is necessary.
My mental model is:
* their pipes are such that they can support N units of simultaneous traffic (MB/s or whatever that may be)
* they have m subscribers
* therefore each subscriber is entitled to N/m units (or whatever the calculation is, if some subscribers pay for more bandwidth)
* a subscriber may transmit more than N/m units IFF the total number of units being transmitted is less than N (i.e. they get to use some other subscriber's allocation if that subscriber doesn't need it)
* so, as a subscriber your theoretical maximum rate is N and your actual minimum is N/m
* what application the subscriber is using their allocation for is irrelevant
Why is it not so? I assume I'm completely wrong about how traffic works, given that QoS is a thing.