[OpenWireless Tech] OpenWRT: traffic prioritization between WLANs

[Dan Auerbach]

Hi everyone,

This question is about OpenWRT, but I'd also be interested to know if
others have solutions for dd-wrt or Tomato or other firmware.

I'm looking into how to best to traffic prioritization beyond simple QoS
between two wireless networks: let's say, "home" and "guest". I
understand there are out-of-the-box ways to do bandwidth limiting
(wshaper, qos-scripts, etc). But the behavior I'm seeking is for the
"home" network to be first in line no matter what, and for the "guest"
network to have maximum bandwidth otherwise (although I understand this
is not quite optimal -- see #3 below). I have a series of questions
along these lines that maybe folks on the list can help me with.

1. AFAICT the ability to achieve this type of traffic prioritization
does NOT exist out of the box. Am I missing something? If it does not
exist out of the box, is there anyone else here who would be interested
in working on this?
2. I'm looking at trying to achieve this with tc and a Qdisc.
Unfortunately, Qdiscs are attached to an interface, and in this case
there will be two virtual interfaces corresponding to the different
WLANs. Is there a way to use the physical interface underlying both
virtual interfaces to create a Qdisc that prioritizes based on the
virtual interface (or something like the ssid)? I hope that this is
doable and if anyone has pointers, that would be fantastic.
3. I understand that my description above might be suboptimal. For
example, a guest using SSH might have their connection break as soon as
someone on the home network downloads a video file, even though the home
network user couldn't notice the difference in download speed if the SSH
connection TCP packets got enough priority to maintain the connection
(supposing a normal SSH session, not using SSH to tunnel
bandwidth-intensive traffic). Ideally, the guest should be able to use
SSH while the video file download still gets the lion's share of the
bandwidth. I think a more advanced approach would be to guarantee a
small portion of bandwidth for the guest connection if needed. My rough
understanding is that I can achieve this using the htb Qdisc, but
wondered if others have experience doing this / pointers to good
resources about it.

Thanks,
Dan

-- 
Dan Auerbach
Staff Technologist
Electronic Frontier Foundation
dan at eff.org
415 436 9333 x134