SQM QoS OpenWrt OpenMPTCProuter

Doing QoS with OpenMPTCProuter

I’m at the countryside so no fiber/FTTH but only FTTD (Fiber To The DSLAM)… Being a remote worker I need a quite stable connection, so I’m currently using 3 ADSL connections aggregated via OpenMPTCProuter. Thus not only if one link fail it will be transparent but the upload and download links are aggregated, it’s not only a failover on the links. Initially I was an OverTheBox user, but that’s another story

OpenMPTCProuter is based on OpenWrt and includes Smart Queue Management (SQM) allowing to do traffic shaping. Due to this it’s possible to use the standard SQM documentation, basically it involves:

  • measuring the current speed of the setup
  • computing the download and upload caps
  • configuring SQM appropriately

Measuring the current speed of the setup

Various convenient online services are available to test your connection. I’m using https://nperf.com with a free registered account as they provide an history of the checks, so it’s quite convenient.

Be sure to do multiple test to have a propre idea of the speed.

With my 3 ADSL connections I measured:

  • average download around 33/34 megabits/s
  • average upload around 1.5/1.7 megabits/s
  • average ping around 27/33 ms

My ADSL connections are around 10-12 Mb each, so it’s coherent.

Measuring speed from the CLI

In order to measure the download time you could also just download some files from the CLI and see the speed, OVH provides some convenient files for this.

wget -O /dev/null http://proof.ovh.net/files/10Mb.dat

For the upload it’s not as easy as you will need service listening on the internet, nc can be used for this.

# On the remote server, be sure to have port 4444 open
 nc -v -l 4242 > /dev/null
# From a local computer
dd if=/dev/zero bs=1024K count=512 | nc -v $SERVER_IP 4242
# Then you will be able to check dd's output

Computing the download and upload caps

For the download and upload caps SQM Documentation recommends using a max value between 80 and 95 % of the measured value.

To be a bit conservative I selected 85%:

  • 33000 * 0.85 = 28050
  • 1.600 * 0.85 = 1360

Configuring SQM in OpenMPTCProuter

Assuming OpenMPTCProuter will be reachable at, the configuration should be done at S (so under Network->SQM QoS).

As I want to do QoS on the aggregated MPTCP link it’s on the tun0 (omrvpn) interface, be sure to configure SQM for this specific interface.

In the Basic Settings tab:

  • Ensure that this SQM instance is enabled
  • Download speed: 28050
  • Upload speed: 1360

In the Queue Discipline tab:

  • Queuing disciplines usable: cake
  • Queue setup script: piece_of_cake.qos

In the Link Layer Adapation tab:

  • Which link layer to account for: ATM (as I’m using 3 ADSL connections)
  • Per packet Overhead: 44

Then save an apply!