WAN Packetloss when Traffic Shaping is activated



  • Last weekend I setup a small test environment for a LAN Party before the real event next month.

    The uplink at the test location was not ideal: 10Mbps Down, 1Mbps Up.

    It was do-able, however when someone started downloading something heavy like a game server, it was immediately noticeable that any other download was (even more) frustratingly slow.

    At this point, I decided to set up traffic shaping using the wizard.

    I selected the Multi-Wan setup (effectively only used 1) and chose HFSC. I set the bandwidth limits to be slightly less than the actual speed test measurements when the line was not in use (~95% with the idea to counter buffer bloat).

    With regard to the priorities of applications I made some sane decisions: limit torrents, chat, email protocols etc.... and increased priority for games, HTTP, HTTPS and DNS.

    Before all that, the line was actually perfectly fine: no packet loss.

    After the traffic shaping was enabled, I noticed immediately that everything was more lively.
    However, I did notice the WAN connection getting some pretty severe packet drops, peaking to 70% even.

    Under normal default settings, pfsense would have considered the interface as down after +20% packet loss and reset all the firewall states, but I've disabled that action.

    Interestingly, I've seen this happen before on a much beefier connection: 240Mbps Down 30Mbps Up

    My instincts tell me that dropping packets is essential to doing any kind of traffic shaping, but what seems counter-intuitive is for me to see the packet loss in the wan monitoring screen and pfsense acting upon it by resetting the firewall states (if I left the default behavior on of taking action up +20% loss).

    After removing packet shaping, no packet loss anymore.

    My questions essentially are: is this normal? Are there some better suggestions for dealing with generally sane traffic shaping adequate for a Lan party?