802.11a/g/n optimizing for compatibility

Unanswered Question
Oct 1st, 2010
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How to ensure maximum client compatibility and stability in 802.11a/b/g/n networks?


I am running a Wireless network based on the WLC 5508 6 SW version, (with WCS mgmt) and 1142 APs. I would like a broad variety of clients, old G clients and new N clients to experience a stable connection to the network. I see Apple Macbooks, Lenovo-, Dell- and HP laptops in addition to HTC smartphones and iPhones on this network.


I am having issues with some types of clients experiencing "unstable" connections. They are able to get a link for a variable ammount of time, then suddenly loose connection for a short period of time before reconnecting. These clients mostly use a third party SSL-VPN link over my wireless, therefore the loss of connection can be quite annoying. From time to time some of these clients seem to be flapping between access points but not seamless like roaming should be, rather with a short stop in connectivity before reconnecting.


Previously we had a 802.11g Aruba wireless network in the same location. It had no such difficulties. This points me toward the config parametres in the controller.


Which 802.11 b/g/n and WLAN parameters can affect this? I am looking for a document describing a best practice for setting up these parameters, or if someone here has input to a successful stable setup as the configuration guide only says e.g. "Enable if you want Aironet Information Elements"  does not help in deciding if I want this


My WLAN is set up with WPA2/AES PSK

and a guest network with web auth


Examples of parameters:


which Radio policy (bgn or gn)

Aironet IE?

MFP (disabled or enabled)

QoS profile?


can CCX location measurement affect performance?

Which Data rates should be set mandatory/enabled/disabled?


MCS (data rate) settings for 802.11n


anything I have forgotten?


The goal is:

A simple, no hassle network providing maximum compatibility with different clients with a plus of 802.11n speeds for compatible clients



wbr

-LA

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JOHN SAINATO Fri, 10/01/2010 - 05:32
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LA


I am having the exact same issues with connectivity.  We wer told to upgrade to 7.0.98, but we still have the problem.  Let me know if you get anywhere.  I am presently waiting on Cisco for some support, I will let you know if we get this resolved

larsaschim Fri, 10/01/2010 - 06:01
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Thanx!


I am running 6.0.199.4


Hopefully someone can shed some light on this issue for us!

b.garczynski Fri, 10/01/2010 - 08:23
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Regarding web authentication I always disable the session timeout under advanced on the SSID. This will prevent the annoying disconnection and re-auth via web. QOS profiles will not provide much of a benefit unless you have QOS fully deployed in your infrastructure. I would also verify that you have WMM enabled on your SSIDs. Without WMM enabled you will not get 802.11n data rates on your SSID. As far as RF settings go for 802.11A I typically disable 6 and 9 Mbps data rates, make 12 Mbps mandatory and all the other data rates supported. For 802.11b/g/n I typically disable all data rates through 11Mbps (assuming no 802.11b clients) make 12Mbps mandatory and all the rest supported.

a.frollano Mon, 10/18/2010 - 02:22
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So I'm not the only one with this issue! We have two SSID, an internal and a guest one. No probs with the internal, or at least no one complained, but frequent drops with the guest SSID.Current firmware is the 6.0.199.4 which we recently updated from the 6.0.196.0 with the hope it would resolve it.

I noticed that sometimes the nslookup times out, do you have this same behaviour? We also use QoS just to limit the bandwith so that each guest user can't use more than 1024 kb, I'm wondering if this could be a problem. Initially we thought there was an issue with Win7 clients since they were the only ones complaining, now also XP seems to suffer the same problem.

larsaschim Mon, 10/18/2010 - 02:54
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Hi!


This is interesting, then you should compare the configuration on both your WLANs and see which parameter is different.


Unfortunately I have this problem on both the internal and the external WLAN.


I am not sure of how to export the configuration of the WLANs to a text file, this would be really helpfull to enlighten this issue as we could have compared each and every property to see which one differed, anyone know how?
-LA

larsaschim Wed, 11/17/2010 - 04:12
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Hey! I implemented your suggested improvements and the first impression is good!


on 802.11a and b/g I disabled lower datarates, set 12Mbps to mandatory and the higher ones to supported. The instant improvement was the RTT measurements I made (previously they averaged at about 13ms (to an internet site) after the change they dropped to about 3-4 ms on average! I would say this is a very significant improvement!


I have not been able to get any feedback from the user community yet :), but it sounds promising...



I am still looking for some more insight into these issues, so if someone still has some ideas, please let us know!


-LA

larsaschim Mon, 10/18/2010 - 03:00
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Hi! thank you for sharing,


WMM is set to enabled, and clients report 144Mbps or sometimes as high as 300 Mbps (from the windows/ MAC wireless property page)


QoS I left with the default values that came with the controller, I think it was "best effort" so no, I do not wish to enable QoS, as it is not implemented in the rest of my infrastructure.


I have not touched the 802.11 speed parameters, I will try that in the next available service window.



wbr


-LA


PS: if possible, could you post all of your WLAN / SSID configuration so that I could compare it to mine?

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