Question QOS bufferbloat question?


Feb 28, 2016
So when I play FPS games, I noticed that sometimes when someone else is using a device on my network I get micro-stuttering in-game when shooting or moving.. My FPS is above 200 at all times. My internet connection is 400mb/s. When I ran a test on bufferbloating, I got an F. I adjusted my bandwidth to 250mb/s and 10mb/s upload, and it seems to have disappeared. My question is, is the microstuttering associated with bufferbloat, and where does the rest of the 150mb/s go if I only set my max bandwidth to 250?

First the buffbloat test is mostly bogus. It intentionally causes bufferbloat on any connection. What it is suppose to be used for is testing after you have configured some form of QoS....which is what you ended up doing.

It is actually very hard to get real bufferbloat on a 400mbps connection. You only get bufferbloat if the connection is fully used. Data is placed in buffers rather than drop it which is where the name comes from. When a connection is not overloaded no data is placed in buffers. It is very hard to overload a large internet connection, mostly someone would have to be doing large file downloads a lot. Even 4k netflix only uses about 25mbps.

What is more likely is you are overloading your upload speed. This used to be very uncommon but now people are doing video chat/conference stuff. I can add up pretty quickly.

You need to try to determine what other people are doing on your network. That more than anything else is going to tell you if you potentially are overloading the network. Again if you are not overload the upload or download you do not have real bufferbloat.

2 major issues with using QoS to solve bufferbloat. First is it takes a lot of cpu power to do this. You will cap your speed well below the 400mbps you pay for. The best forms of QoS for bufferbloat on most routers cap you out just over 100mbps. Running the router cpu at 100% can also cause microstutters by itself.

The second problem is related to your question about what happens to the extra 150mbps. To work well you must cap the rates below the full speed, the recommended number is between 80-90%. This is related to how bandwidth is calculated. One key factor to remember is data circuits are either running 100% used or 0%. Not a very useful that way so the usage is averaged over time. So lets say you have a giabit ethernet. It transmit 1gbit of data in 1 second and then does nothing for 9 seconds. The second case it transmits 100mbps of data in .1 seconds but does this every second for 10 seconds. Both have a 10 second average rate of 100mbps but the traffic is very different. To avoid problems with burst of data the maximum rate is reduced so you have less chance to get data buffered. In effect this extra bandwidth is do not care about bandwidth though it is other applications that will be affected.

It is not very likely it is bufferbloat causing your stutter problems when you have a very large connection. It is much more common on a connection say less than 50mbps and the bufferbloat solutions work very well on smaller connections.

You need to try to determine what is running on your network and if you are exceeding your bandwidth. Stuttering is caused by many things, most times video settings.

Note if you are using wifi then that can easily cause this problem.