Re: Offtopic? Windows 7 Virtual Wifi adapter.

[Dan Williams <dcbw redhat com>]

On Mon, 2009-05-18 at 18:40 +0100, Stuart Ward wrote:
> Isn't this just mesh networking without the auto configuration bits.

You mean the Windows thing?  I don't think so...  could be wrong, but
when I first read about this, I thought it actually was radio
timeslicing.

Dan

> -- Stuart Ward M +44 7782325143
> 
> 
> 
> 2009/5/18 Dan Williams <dcbw redhat com>:
> > On Mon, 2009-05-18 at 11:44 -0400, Darren Albers wrote:
> >> On Mon, May 18, 2009 at 11:00 AM, John W. Linville
> >> <linville tuxdriver com> wrote:
> >> > On Mon, May 18, 2009 at 10:57:05AM -0400, Tom Sutherland wrote:
> >> >> Ran across this article today:
> >> >>
> >> >> http://www.engadget.com/2009/05/18/microsofts-virtual-wifi-will-make-windows-7-wireless-adapters-d/
> >> >>
> >> >>
> >> >> >From the article...
> >> >> "The tech lets one piece of WiFi hardware be represented in Windows as
> >> >> two separate adapters, meaning you can connect to two hotspots
> >> >> simultaneously if you like, or turn your virtual device into an access
> >> >> point that others can connect to."
> >> >>
> >> >> In the long term, would something like that be relevant to
> >> >> networkmanager?
> >> >
> >> > You have to make it work in the kernel first...
> >> >
> >> > John
> >> > --
> >> > John W. Linville                Someday the world will need a hero, and you
> >> > linville tuxdriver com                  might be all we have.  Be ready.
> >>
> >> Don't some wireless drivers support this already with multiple
> >> subinterfaces that correspond to a VLAN?
> >
> > They dont' really correspond to a VLAN, they appear as separate
> > "wiphy" (aka wireless phy) devices which can be configured separately.
> >
> > Note that by doing this "splitting", you're effectively time-sharing the
> > adapter, and your transfer rate will go down by more than half, since
> > the adapter has to be on one channel for 1/2 the time, and the other
> > channel for the other 1/2 the time.  It's actually more than 50% because
> > there's channel switch time involved, and probably null-packet exchanges
> > when jumping to a channel to notify the AP that you're coming back from
> > sleep.
> >
> > Yes, it can work, and yes, some mac80211 drivers support this type of
> > functionality, but something that *also* should be done is figuring out
> > how to tell users that little Elves didn't magically replace the single
> > radio in their wifi card with two separate radios, and about the
> > inherent limitations thereof.
> >
> > You could of course do a STA + AP with the same card on the same
> > channel, where for instance the STA was connected to an existing AP, and
> > you were connection-sharing the traffic out over the your own
> > just-created AP to friends or something.  But of course there you'll
> > also be increasing contention of the medium (since you're effectively
> > broadcasting the same traffic on the same channel twice, once from
> > friend -> you, then you -> real AP).  There is no silver bullet here of
> > course, unless you really do have two wifi cards in your machine.
> >
> > Dan
> >
> >
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