QoS , Qudloty of Service, us sbout how packets are treated when there is contention. Your home network will rarely have contention since ut us fast ethernet or Gigabit speed. Contention occyrs on the link between your home netwotk and the ISP.
Your DSL router msy be sble to prioritise packets from uour router to the ISP accirding to packet markings (DSCP at IP level, or dot1p at frame level, or by source or destination subnet for a very poor implementation). However, you have no control over the traffic arriving from the internet. The woS mechanidms for that at in the ISP equipment (Broadband Network Gateway). At leadt you can help contention in your uplink, but people streaming are not causing contention there (they are mostly receiving, not sending).
One day an ISP will offer full control to their subscribers (by a web gui I expect) for QoS and traffic shaping in their downlink direction. So we could describe inbound traffic (this is called classification) snd how to handle it in terms iof queuring/policing/shaping/dropping at tgeir end. This is very advanced though, and I never saw it offered so far.
