I am guessing that you have limited bandwidth, or there is something consuming a fair amount of your upstream bandwidth. That is why the quality of service idea was suggested.
Here is another idea. The OBi 202 has a built in router. You can plug the OBI into your modem, and plug the WAN port of the router to the LAN port of the OBi202. That way, if it works as I suspect, the OBi gets first crack at the bandwidth.
If you decide to try that, you may want to set your router to not do the DHCP serving, so as to avoid double NAT. There are different opinions about that topic. Anyway, if you decide to try this, experiment. I have not done this myself, because I have not run into a problem. Plus, right now I am using a combo router and modem, so it would complicate things to try that. Since you use a separate router, this could be easy to implement.