Problems with Quality of Service on DD-WRT (and a fix)

Following up on my previous DD-WRT post, I’ve had some problems with Quality of Service on my upgraded router. I am using an Asus WL-500G Premium which has tons of memory and processor power for the job, but occasionally QoS won’t work properly when I’m on a phone call.

DD-WRT ships with two implementations of Quality of Service: HTB and HTSC (known to be buggy). My experience with each over time has been that they both kind of work and then fail miserably. Part of the problem might just be that QoS really complicated, and DD-WRT hasn’t had a release in two years.

However, a few weeks ago, I came across something new to me called TCP Vegas. A lot of people have had QoS problems with DD-WRT, and one poster suggested I enter several commands in the Administration section of my DD-WRT router.

echo 0 > /proc/sys/net/ipv4/tcp_westwood
echo 1 > /proc/sys/net/ipv4/tcp_vegas_cong_avoid
echo 3 > /proc/sys/net/ipv4/tcp_vegas_alpha
echo 3 > /proc/sys/net/ipv4/tcp_vegas_beta

I turned QoS completely off, removed the Up & Down limits on my Internet connection, and just used the four commands above. It worked! I can now download podcasts, stream video, surf the net and take phone calls without worrying about my VoIP connection occasionally messing up. Of course, my speedy DSL provider (Sonic.net) helps, too.