I bought a Docsis 3.0 cable modem (Motorola SB6121) that's compatible with cox cable. I was looking to upgrade from an old Arris modem and hoped to get an increase in my internet speed. Surprisingly there was no change in my down speed which remains at about 23Mbps. The shocker is the upload speed which basically quadrupled since it was about 5.5Mbps before, but now I get 18-21Mbps upload whether I try it wired or wireless with the SB6121. So I am curious, why the big increase in the upload speed but no difference in the download speed? Now I know it most likely it has to do with the internet package I have with cox which is the preferred package that gives about 15Mbps down and 4-5Mbps up so there is of course a limit to the speed I can get but I was just curious if there could be something else going on here that I could take a look at. Any info appreciated