Ethereal-users: RE: [Ethereal-users] Sniffing 801.11 packets

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From: Biot Olivier <Olivier.Biot@xxxxxxxxxxx>
Date: Tue, 6 Jan 2004 11:18:44 +0100
| -----Original Message-----
| From: Guy Harris
| 
| I'm not a radio expert, but I think that an 802.11 device can only
| receive on one channel - the manual for Sniffer Wireless 
| indicates that
| it implements a "channel surfing" mode, but in that mode it appears to
| listen on a given channel for some number of seconds, and 
| then switch to
| the next enabled channel and listen on that for some number 
| of seconds,
| and so on - if you've configured it to look for a particular BSSID,
| it'll stop if it detects that BSSID on a given channel and will, I
| infer, capture traffic on that channel.  You can also specify "trigger
| events" (particular types of packets to look for) and, if it gets a
| trigger event in channel surfing mode, it'll capture on the channel on
| which it saw that packet.  That seems to imply that you can 
| only capture traffic on one channel at a time.
| 
| (I don't know whether that's an intrinsic limitation of 
| 802.11; it might
| be possible to have an 802.11 card that taps multiple 
| channels, although
| that card might require multiple DSPs to handle multiple channels.  I
| suspect no cards do so.)

I suspect the "boosted" 802.11 equipment providing multiples of 11Mbps
from using more than one channel at a time.

Regards,

Olivier