[smw]

"Traditional" cable, even digital cable, is broadcast, not streamed.

There are no acks to be sent, a consumer endpoint just tunes to a channel and reads transport stream [1] video off the wire.

[1] http://en.wikipedia.org/wiki/MPEG_transport_stream

[toast0]

With switched video [1], there is some upstream, as the set-top box requests a channel, and may need to send some sort of heartbeat. For video on demand, there's some amount of upstream for program selection and control as well. But that should be extremely low bandwidth, just control information, not acks for content (although, sending quality feedback to the headend could be very useful to solve delivery issues before customers notice)

[1] http://en.wikipedia.org/wiki/Switched_video