Whenever clients on the network are downloading from hosting sites (particularly megaupload) qos completely stops functioning but otherwise works perfectly for normal downloads. Not sure what's going on.
For example, the basic config below works perfectly to distribute bandwidth equally among clients but completely fails with mega.
/queue simple
add max-limit=2M/25M name=wlan queue=pcq-upload-default/pcq-download-default target=192.168.1.0/24
edit: Just wanted to give an update for anyone else who's struggling with this problem. The way that megaupload overwhelms qos is by flooding both the download AND upload with multiple streams. By flooding the upload, ack packets from other downloads get dropped, resulting in having to resend again creating a feedback loop that limits everything else. The way I ended up solving the upload problem is to mark all upload ack packets in mangle and giving them their own high priority queue so they don't get dropped. This way other downloads don't slow down as severely from having to resend multiple times.
Managing downloads is not as straight forward. As mentioned in a later post, setting pcq to dst-address-only doesn't work to handle multiple streams. The only way to prevent those downloads from having such a high contention ratio is to set a max limit and/or pcq rate for those clients. Aside from slowing them down, the only other reliable way I found to distribute bandwidth perfectly is to have the clients route there traffic through a tcp vpn tunnel when downloading from mega. This way it's just a single tcp connection that's easy handle.