On Jun 19, 2007, at 14:36, Jorge Bodden wrote:
James,
I've tested this theory with a B client and a G client on the same
AP and the B client works at B speeds and the G client works at G
speeds. We tested on both Cisco Aironet and Cisco LWAPP and both
yielded the same results. Someone out there may have had different
results, but it worked fine for us.
we did this test when we did our cisco vs meru testing in the fall of
'05. this was the newly aquired (then) thin airespace APs for
cisco. here's the info for just that from the writeup I did at the
time:
b/g interaction -- Meru said they had impressive b/g inter-
operability. To test this we setup an iperf client on a "g"
connected laptop, and attempted to send 40 Mbps (udp). For Meru,
when the "g" client was alone on the AP, iperf recorded the BW as
being typically around 30 Mbps, when the "b" client associated with
the AP doing a ping, it dropped by about 3-4 Mbps to about 27 Mbps.
When the "b" client ping flooded something, it dropped to about 20
Mbps, and went back up when the ping flood was stopped almost
immediately. With Cisco the "g" user was getting 25-30 Mbps BW, and
as soon as the "b" client associated it dropped to 15 Mbps, and
ranged as far down as 6 Mbps when the "b" client was actively doing
things. During this test we made sure all other "b" clients were off
in the room to be sure that it was a single "b" station connection
causing the problem. Once the "b" client was turned off it took one
to two minutes for the "g" client's speed to get back to the mid-20
Mbps.
now the reason it works for meru (my understanding anyhow) is they
take turns for the b and g users, and like David said the g data can
go fast. I don't think there's been a change to require this in the
standard recently, or the vendors would make a much bigger deal about
it.
Also, while I wouldn't put too much money in the absolute BW numbers
from iperf, I think that the relative changes should be reasonably
correct.
but then I drank too much meru kool-aid too.
Jorge
David Gillett wrote:
If there's a B user in the cell, the *control* traffic needs to
be at B rates.
During time slices given to G clients, it's not necessary that the
*data* traffic
be understandable by the B client....
David Gillett
---------------------------------------------------------------------
---
*From:* Jamie Savage [mailto:[EMAIL PROTECTED]
*Sent:* Tuesday, June 19, 2007 12:18 PM
*To:* [email protected]
*Subject:* [WIRELESS-LAN] B user in a G cell
I always understood that 802.11G provides connection rates of 54
meg. but realistically has usable throughput of ~24meg. Also, if
a B radio associates to a G AP then the usable throughput
drops to
~8 meg. I was advised today that, due to recent enhancements
(within the last year?), a B user in a G cell no longer lowers
the
bandwidth <24meg. for all G users in the cell. It doesn't sound
right to me.....can anyone comment on these 'enhancements' (if
they do exist?)
..........thx.................J
James Savage York
University Senior Communications Tech. 108
Steacie Building
[EMAIL PROTECTED] 4700 Keele Street
ph: 416-736-2100 ext. 22605 Toronto, Ontario
fax: 416-736-5701 M3J 1P3, CANADA
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-debbie
Debbie Fligor, n9dn Network Engineer, CITES, Univ. of Il
email: [EMAIL PROTECTED] <http://www.uiuc.edu/ph/www/fligor>
"My turn." -River
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