Bought a brand new 2850n yesterday from dabs.com to replace our 2820n and BT Openreach modem setup. I configured the 2850n exactly how the 2820n is set but there's a problem.

Under QoS, WAN1 is enabled only. Under WAN1 I have set Class 1, 2 and 3 to 1% reserved bandwidth which leaves "others" with 97%. When I run a speed test, instead of getting 37/8 (without QoS), I get 30/6. If I change one of the classes to say 50%, leaving "others" with 48%, the speed test results are the same. By "reserved bandwidth" I would expect the bandwidth for that particular class to be reserved but it seems regardless what settings we use, 25% of the bandwidth is being reserved.

In comparison, the 2820n never did this, which leads me to believe this is a firmware bug.

Has anyone else encountered this or have any suggestions what I could try?

Two points:

1) enabling QOS does slow the connection slightly but that is just the price you pay for prioritising certain types of traffic.

2) the QOS will only kick in when the connection is saturated. At any other time traffic will flow unrestricted.

Does that explain what you've found? Which class does your speed test traffic come under? 1, 2, 3, or other?

Hi. The speed test comes under "other" and the bandwidth limit occurs whether there is traffic under the VoIP class or not. I have a 2820n setup the exact same way and this issue does not occur with that model.

This is a standard feature. When QoS is turned on, the router reserves a certain amount of bandwidth in order for it to function properly. You can only change this using the Telnet or SSH interface.

The commands you need to look at are "adsl txpct" and "adsl rxpct". Issue the commands without a number after them to see the current settings. Set to 100 to maximise throughput (although I presume this compromises the QoS prioritisation, otherwise I can't see why you'd want to set it any lower).

HTH

Dave Robinson,
Malvern