Do we need ack frequency control per path?

[yfmascgy]

In our testing, one thing worth noticing is that for different sim cards, the uplink/downlink ratio can be quite different. For example, with a China Mobile 4G card, we measured a downlink at 35Mbps and an uplink at 3Mbps, while with a China Telecom 4G card, we measured a downlink at 45Mbps and an uplink at 23Mbps at the same time in the same spot.

If we want to measure RTT more precisely, we let ACK return from the same path. However, because some sim cards are more asymmetrical than the others, it introduced a question, do we want ack frequency control per path?

In the QUIC ack-frequency draft, one of the motivations is to handle link asymmetry such that the link throughput won't be constraint by ack packets in the reverse direction. My understanding is that some 5G IoT cards can be more asymmetrical, so do we want to add a mechanism to address this issue? What do you think?

[mirjak]

I think this is likely rather a separate extension. There are actually two questions here: 1) the per-path ack frequency and 2) guidance on which path to use for acks.

[qdeconinck]

I think that 1) should be an extension of the draft-ietf-quic-ack-frequency. 2) probably deserves some further discussion in the current draft (maybe track this in #33?).

[mirjak]

Might be best to open a new separate issue on guidance for sending acks.

[mirjak]

opened issue #123 now for ACK guidance.