Currently my four lines are running at downstream sync rates of 3.19, 3.02, 3.12, 3.11. My current modems, ZyXEL VMG 1312-B10As, are tweakable. I had rather an odd idea: Say I tweak the slowest to raise it to 3.11 Mbps, at some risk, or tweak three to raise them all to 3.19Mbps. That ought to give me another 320kbps. Question: would the benefit be actually more than that though, because the lines would then all be at an identical speed ?
Yes, I know, trying it is the answer.
Jitter, in a sense, variation in arrival times depending on which line a transmitted packet is allocated to would be non-existent if the lines were all at the same speed. (Assuming the system is not already smart enough to compensate for such timing variations by controlling the time of each packet-send appropriately depending on each line rate and the length of the ingress queue into each modem. Both should be knowable, provided line rate info is supplied.) Would elimination of jitter make a receiving TCP, or even both TCP entities, happier?
Actually getting the tweaking right though would not be easy. I have no idea what the tweak values need to be. Burrakucat has supplied me with the equation to convert dB of SNRM into the required parameter value for the appropriate magic Broadcom tweak command. That doesn’t help me without a knowledge of how to map dB SNRM into sync rates. And repeated attempts, groping to get the values correct, getting it wrong again and again, might upset the DLM Gods. Also, I would need to pick a time of day when noise levels are favourable.
An alternative plan would be to pick the time of day when SNR is at the lowest and then equalise speeds to some other speed that is attainable at that time. That way, I would not be pushing any line too hard, increasing risk of failure by raising the weakest line too much.
Most radical of all, would be to lower the faster lines by raising target SNRM, not by choosing time-of-day. If equality really dies give some extra benefit, I wonder if I could get back some of, or even more than, that which I lose.