QoS in IP Networks
What can Linux systems do?

Bandwidth limiting at the sender application
not many applications support it
server often out of control (on Internet, ...)
server doesn't know what's between him and the client

Bandwidth control on intermediate router before bottleneck
Ideal case because this is where packet loss would occurr
Sophisticated queue scheduling on the outgoing queue
Variety of different queue scheduling algorithms

Flow throttling at the Receiver
Worst case, because influence is limited
Theoretically possible for TCP, no implementation yet.
Ingress qdisc might help