said by sef5:said by SMC_QoS :In your case the problem sounds as if it is directly caused by the asymmetric (not asynchronous) nature of an HFC connection
Note that I said it's behaving AS IF it is synchronous instead of asynchronous.
The asymmetric nature is irrelevant; you can have this particular class of problem with a fully symmetric connection. If it's a synchronous communication, however, then data can only be transmitted in one direction at a time. And that's how it's behaving.
I know IP and above rather well.
In that case, possibly what you really meant to say was half vs full duplex, not asynchronous vs synchronous (and neither of those terms are directly related to IP networking).
And FWIW, the symptom you describe is a classic asymmetric upstream capacity problem, and is a more likely explanation than either a half/full duplex or asynchronous/synchronous misconfiguration in the SMC gateway firmware (although it might not hurt to check the SMC gateway's switch port interface status/settings).
And good luck resolving your problem.