Re: Netgear WPN824v2 (MIMO) router...

["Darren Albers" <dalbers gmail com>]

On 7/3/06, Robert G. Brown <rgb phy duke edu> wrote:
> I run a set of system monitor panels at the top of my screen that
> includes the network.  I noticed that my network load (which was zero a
> lot of the time before as I work on local files etc) starts off at zero
> but then creeps up over time to end up in a range anywhere from 4% to
> 100%, sustained, when I'm not typing and nothing at all is happening on
> the system.  This is enough that the system load average sometimes bumps
> up to a few percent when nothing is happening, and the system fan kicks
> on as heat is generated from the load.
>
> I used tcpdump/top to try to figure out just what was happening.  top is
> unremarkable -- hald accumulates a bit of time, NM accumulates a minute
> or so a day, X of course accumlates time, but nothing looks like it is
> running away or unreasonable.
>
> tcpdump is interesting, though.  I see a steady stream of packets like
> the one below -- typically 3-5 almost-full-MTU frames/sec.  Note that
> they are "from" the router and "to" the wireless interface on my laptop.
> Note also that they are completely empty past the ethernet header itself
> (or if there ever was data, it was stripped off upstream by the wireless
> interface).
> I'm wondering if this is an artifact of netgear's implementation of MIMO
> -- perhaps what is making it through to the OS from a "sounding frame".
> In order to tune the multiple antennae dynamically, tuning frames are
> (supposedly) periodically sent with some complex encoded information.
> It MAY be that these frames are supposed to be isolated by the wireless
> client device and not passed back to the recipient network interface --
> if you have a MIMO compliant device receiving, which is of course pretty
> much impossible at this point.  Perhaps the radio pulls off the tuning
> information correctly but is still forwarding the packet headers and an
> empty frame to the bus, I don't know.  Does anybody on this list know
> what's going on ?  Is this perhaps an artifact instead of a NM feature,
> perhaps in response to these odd no-protocol packets?  Is there any way
> to shut them off or regulate them to drop the network "load" back down
> to sane idle levels?

I would connect to your AP by stopping NM and starting WPA_Supplicant
manually and see if you observe the same behavior.  I haven't
witnessed what you are describing personally but I wonder if what you
are seeing is just noise caused by the MIMO router hopping channels...