My gut feeling says you have a 200/0.5Mbit/s connection at maximum, because just from watching some download monitor out of the corner of my eye while downloading something with 100Mbit/s requires about 250kbit/s ACK packets in the upstream.
No, I can still hit (almost) 1 Gigabit on the downlink. DOCSIS networks are so heavily asymmetric, they take special measures (ACK compression) to get around that!
That seems very atypical. As the link capacity ratio goes past 10:1, even for typical dowloads, speed starts to be limited by the ability to send requests, or even TCP ACKs.
I've seen 20:1 offers on cable providers, but it's mostly marketing BS, as you're unlikely to get full download speed in most circumstances due to upload limitations.
True - my nominal bandwidth (i.e. what I pay for) is 1000/50.
I do reach the full downlink speed though due to (presumably) ACK compression in the modem and ACK synthesis/reexpansion in the CMTS. You are right that otherwise such a high ratio would not be feasible with TCP.
Plain single-stream download-only TCP should fit without compression, probably even without Delayed ACKs.
IME, the line starts to choke when you actually want to send requests and they compete with ACKs and your internet stutters and crawls in both direction. Though that was with a slower connection - it's harder to fill a bigger pipe.
BTW, is the ACK compression counted for consumers benefit?
I live in Europe and I have a 1000/0.5 Mbit/s connection.