Re: Re: fragmentation threshold support

I know that I'm not using the fragmentation threshold
as it's meant for; I'm trying to use fragmentation to
control the length depending on the bitrates.

I did change the dot11FragmentationThreshold but it
had no effect on the frames I could send...

any hint?

- laurent 



> Actually dot11RTSThreshold isn't what you want it's
> the 
> dot11FragmentationThreshold (Pizza: typo?)
> 
> The MAC will fragment the frames at the 802.11
> layer.  To see the 
> fragmentation, you will need to sniff the traffic in
> the air.  This 
> fragmentation has nothing to do with IP
> fragmentation.
> 
> It sounds like you may be trying to use 802.11
> fragmentation for some kind 
> of traffic control purposes, that's not what it's
> meant for.  802.11 
> fragmentation was added to the MAC behavior to
> mitigate the effect of 
> periodic inteferers on the medium.  The classic
> example of a periodic 
> interferer is a microwave oven, they transmit spikes
> of power with a 
> fairly long period.  The idea is to only do retries
> on the portion of the 
> frame that was lost rather than the whole frame.
> 
> -M
> 
> 
> 
> On Wed, 25 May 2005, P Laurent wrote:
> 
> > I forgot something: i'm using broadcasted frames
> so
> > RTS/CTS mechanism is not used and therefore
> setting
> > RTSThreshold does not help.
> >
> > Laurent
> >
> >> if I let the default mtu=1500 and I try to send
> >> fragments of 1800 bytes then it looks like no
> frame
> >> at
> >> all is transmitted.
> >>
> >> if I change the mtu with ifconfig wlan0 mtu=2000
> and
> >> then I try to send 1800 bytes long frames I get:
> >>  hfa384x_usbin_callback: wlan0 rx pipe stalled:
> >> requesting reset
> >>  hfa384x_usbin_ctlx: Could not match IN
> >> URB(0x0001,-75) to CTLX - ignored
> >>  wlan0 rx pipe reset complete.
> >>
> >> I set the RTSThreshold to 1000 but I could still
> >> send
> >> fragments of 1500 bytes as before. Actually I
> don't
> >> really understand why you mentionned this
> >> mibattribute. Thus I also set
> >> mibattribute=FragmentationThreshold=1000 but once
> >> again I could still send frames with 1500 bytes
> >> payload.
> >>
> >> I send frames using a SOCK_RAW socket.
> >>
> >> any idea?
> >>
> >> Laurent
> >>
> >>>> I'm using wlan-ng 0.2.1 pre26.
> >>>> I'd like to control the length of the frames I
> >>>> send(to set a fragmentation threshold).
> >>>
> >>> wlanctl wlan0 dot11req_mibset
> >>> mibattribute=dot11RTSThreshold=<whatever>
> >>>
> >>>> frames. But at the same time i can't send
> frames
> >>>> much longer than 1500 bytes.
> >>>
> >>> ifconfig wlan0 mtu <whatever>
> >>>
> >>> mtu is not the same thing as dot11
> fragmentation;
> >> if
> >>> you're bridging to
> >>> ethernet anywhere you'll want to leave it no
> >> greater
> >>> than 1500.
> >>>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >
>
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>
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> >>
> >
> >
> >
> >
> >
> >
> >
>
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> -- 
> 
> Mark S. Mathews
> 
> AbsoluteValue Systems      Web:   
> http://www.linux-wlan.com
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