Re: Netgear WPN824v2 (MIMO) router...

[Dan Williams <dcbw redhat com>]

On Mon, 2006-07-03 at 18:46 -0400, Darren Albers wrote:
> 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

Probably a good idea.

> witnessed what you are describing personally but I wonder if what you
> are seeing is just noise caused by the MIMO router hopping channels...
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