[Bloat] Ethernet PAUSE frames, concatenated buffers

[grenville armitage]

So, Dave Taht suggested this might be of interest to some on
this list -- keep an eye out for consumer devices helpfully
using Ethernet PAUSE frames for layer 2 flow control.

We recently stumbled across this when exploring the behaviour of
a certain Netgear HomePlugAV (Ethernet over home powerline) device.
It was fun enough that the devices had a few thousand packets of
internal buffering. But when their buffer came close to full they'd
push-back with Ethernet PAUSE frames, forcing the next NIC upstream
(e.g. a host OS stack) to begin OS-specific buffering of outbound
Ethernet frames for a short while. This essentially concatenated the
HomePlugAV device's buffering with the sending host's NIC driver
buffering. Bufferbloat++

More details of our specific experiments can be found here,
http://caia.swin.edu.au/reports/130121A/CAIA-TR-130121A.pdf

cheers,
gja