So a little info for you.
So here are my tests.
Running APs in mixed mode, and I have performed over 180 individual tests in the last two days. Using IXIA tools.
I see an average thruput when loading up the APs of approx 12 M/Bits ps over the 180 tests on different APs. I transfer 800 Mbits to every AP.
Some reach 17-18 Mbps, and some (only a couple) reach 5 Mbps, the majority between 10 and 13 Mbps.
*** How do the stats above sound to you experts out there? ****
I know what I have tested in the last two days may not be the same tomorrow, but thats the nature of it right? I wanted to get a benchmark.
The one thing I am thinking about is turning off 802.11b across all 300 APs, but there is no gaurenttee that this will make things better right? It may be SNR ratios that bring the performance down, and not CTS/RTS phy controls right?
These stats look very good for a b/g deployment. I'm guessing the the AP's that only provided 5Mbps may have had a "B" client associated to them. If you can get away with turning off the "B" data rates, I would move ahead.
As you nicely noted, this does not guarantee better performance, but things will likely improve :) The other statement that you made about the "nature of wireless" is most correct! You have to keep on top of your deployment, due to the fluid nature of the medium itself.
Your statement :
When 802.11b clients are **associated to an 802.11g access point, the access point will turn on a protection mechanism called Request to Send/Clear to Send (RTS/CTS)."
What about when you see on the WLCs lots of clients probing using protocol 802.11b.
Does that turn on mixed mode protection?
Yes, that would be the case my friend :)
Page 302 of the excerpt you linked in another thread really tells it all;
Hope this helps! It sounds like you are making great progress with this!
Man, you are most helpful.
I am turning off B tonight on one area and will retest with IXIA. Will update you tomorrow mate :)
Also, one thing I have heard on the grapevine :) is that even if you turn off 802.11b and run G only under the WLAN, client laptops can still use B rates if they are a fair distance away? and the only real way to stop that from happening is set the 11b rates to disabled.
How does that sound to you?
Good stuff my friend! I have never heard of that anomaly (I have my doubts....but I guess anything is possible ;-).
Just to finish this off in terms of test results.
I have performed some further tests, and the maximum I can get on 802.11g thruput is an avarage throughput of 19.5Mbps
This is running the following:
THE WLAN in radio policy G only
All Wireless B rates disabled withe the following
Also, please note that when all rates are left enabled and you run your WLAN in Radio policy G-Only, you see that frames still set the protection ERP information element but one thing I did not test was a packet capture when all the B rates were disabled to see if any beacons/probes had the bit set?
Any ideas on that would be good.
That is right... The radio policy in the wlan is just a policy and you will see logs generated if the policy is not meet. Data Rates specifically tells the radio what is the rates to be used. This is where you need to disable 1,2,5.5 & 11 if you don't want 802.11b clients.
Yes this is all good stuff. What we have done just because we still have clients using the legacy b rates. On the controller we don't require the 1 and 2 Mbps basic rates, instead we require the higher rates of 5.5 and 11 Mbps. This just to keep those customers connected and happy.
It is the l and 2 Mbps that really seems slow. If you have deployed a dense, well overlapped AP environment, you may want to require only the 11 Mbps for the b clients.
Word of Warning: Reducing your rate will reduce the AP coverage cell size and may isolate the clients on the far edges of the network. I advise migrating to this with that in mind. Some devices may need the lower rates to perform at their peak.
Then again, everybody just go purchase the new 1140 and call it a day! :-)
The ClientLink technology in the 1140 is reported by Cisco to enhance the throughput of the legacy a/g clients . Note not b clients bit A/G.. If you can migrate away from the legacy b , it would be ideal.
Hope all is well!
I thought you might enjoy this reference that we found recently (Thanks Simon!). It's pretty good :)
Here's the reference to protection mode from Matthew Gast's Definitive Guide Book (2nd Edition, Page 302):
"Only the protection frames are required to be transmitted at the 802.11b-compatible data rates. Protection does not require 802.11g stations to use a slower data rate for the payload data, as is commonly asserted."
The link below documents Gast's testing on this issue and his chart shows that "g" technology working in protected mode still experiences between 1.6 and 2.3 times the throughput of the "b" technology depending on which type of protection mechanism is used.