Any card supporting 802.11b supports the nominal
11Mbps "burst" data rate, which can usually come close
to 6Mbps for good links.  Time duplexing does not
necessarily cut the rate in half because traffic can
be asymmetric (especially for streaming video), but
there is overhead for header information at the
physical, link, and IP layers for every data packet
and there are also transmitted packets that maintain
the network but do not contain application data (the
video, in this case).

The Cisco statistics (and also the Orinoco, I'm pretty
sure) can be very useful, and you want to see how many
packet errors occurred compared to total number of
packets received.  If you lose half of your packets
(this should never happen) then your data rate will
only be half what it could have been.  You also need
to check how many duplicate packets were received,
because these are also taking up potential throughput.

If your packet error rate is high (over 10%), you are
probably experiencing interference.  If duplicate
pakcets received is high, your AP is experiencing
interference, because it isn't recognizing your
acknowledgements and hence is retransmitting data you
already received.  Turn off your microwave, cordless
phones, bluetooth devices, or whatever else.  (Some
cordless phones have a range of close to a block, so
if your neighbors have them there might not be much
you can do.)  The signal strength indicator will still
be high under interference, and signal quality may
even report as ok, since interference may be bursty. 
(It is possible for interference to be so bad that you
don't see high packet error rates because you don't
even recognize incoming packets.  Compare the number
of packets sent by the AP to the number received by
your card.)

The reason that Qcheck and similar utilities don't
tell you anything about your raw data rate is that
they operate at the TCP level of the network, while
the 802.11b raw data rate is at the physical level of
the network.  These are insulated from each other by
design.  I would think that programs could be written
(and may already exist) which report all of the data,
but they would be specific to your 802.11b driver and
your TCP implementation.  If anyone is thinking about
writing this, please report packet error rates in a
meaningful way!  I don't fully understand the Cisco
statistics---they don't always add up the way that I
expect them to (I have the Xircom implementation, so
I'm not sure how different that is).

John


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