overly timid congestion control with amazon prime live video

[Daniel Sterling <sterling.daniel () gmail com>]

While streaming football last night from AT&T fiber (AS7018), I
noticed the video quality went way down when I did a large download on
another system. I have gigabit fiber but I'm using Linux tc to
throttle my network traffic. I've configured cake with a 200mbit
limit, and I also use a low BQL setting to further ensure low latency
for low-bandwidth traffic.

IOW, my Linux router will drop packets across the board rather
liberally in the face of large downloads, but I've always seen streams
fight back for their share of the bandwidth -- except for amazon's.

The live stream appears to use UDP on a non-standard port (not 443).
Does anyone know what amazon has done to cause their congestion
control algorithms to yield so much bandwidth and not fight for their
fair share?

Thanks,
Dan