Note: The instructions for setting QoS below were relevant for CeroWrt prior to the Modena build (February 2013). We have preserved them here for historical reasons.
Note: These have been superseded by the Setting up AQM page.
CeroWrt has the ability to solve latency using a number of mechanisms. One is our major focus: decreasing bufferbloat. Another technique is AQM (active queue management) and bandwidth shaping: enabling AQM with sane values will make it more possible for you and your family to do more work simultaneously - doing uploads while your son is downloading and your daughter is making phone calls and your spouse is playing games, with fewer complaints from everyone.
AQM set to good values is best. Getting good values automatically is hard. We’re working on it.
Since it’s hard to determine good values automatically, CeroWrt ships with QoS (Quality of service) turned OFF by default. This will make your router and network connection seem slow until you use these steps to manually measure your network’s speed and set good values:
To set up QoS for CeroWrt:
A HUGE problem with most network tests is that they don’t run for long
enough. Over a minute is required in order to get a reasonable value,
most run for less than 20 seconds, and many ISPs are now gaming that. We
netperf to various sites supporting it to get a reasonable value.
Decrease the Upload and Download speeds somewhat in the web GUI until you can do both. You should make adjustments in 256kb increments (or do a binary search between 60% and 100% of your provisioned bandwidth).
The values can be approximate, in the range suggested in the previous question. AQM is “bandwidth” shaping, and attempts to limit the filling of queues in the broadband equipment. Unfortunately, this can miss out on the advantages of Comcast’s PowerBoost, and it cannot take into account other dynamic changes in availability of bandwidth caused by your neighbors or even the temperature. We note that SPEEDTEST reports misleading results on broad band service which provides temporary bandwidth boosts such as Comcast’s PowerBoost, and we are working on a better test.
It’s important to set some AQM speed settings. Although disabling AQM can (sometimes) make single stream downloads run nearly as fast as possible, it occurs at the expense of other activities. And it may not always work.