Should I set all data rates on WLC4400 to 'Supported'?

[limtohsoon]

Hi Sir,

On a WLC4404, the default data rates on the 802.11b/g Global Parameters are as follows:

1 Mbps - Mandatory

2 Mbps - Mandatory

5.5 Mbps - Mandatory

6 Mbps - Supported

9 Mbps - Supported

11 Mbps - Mandatory

12 Mbps - Supported

18 Mbps - Supported

24 Mbps - Supported

36 Mbps - Supported

48 Mbps - Supported

54 Mbps - Supported

** Data Rate 'Mandatory' implies that clients who do not support that specific rate will not be able to associate. Data Rate 'Supported' implies that any associated client that also supports that same rate may communicate with the AP using that rate. But it is not required that a client be able to use the rates marked supported in order to associate **

Is it recommended to set all data rates to 'Supported'? Many clients (a mixture of b & g) occasionally face a lot of disconnections and I received many syslog messages as follows:

2007-01-25 11:58:31 Local0.Critical 10.0.0.10 [ERROR] apf_utils.c 198: Missing Supported Rate.

2007-01-25 11:58:31 Local0.Notice 10.0.0.10 [WARNING] apf_80211.c 2408: Received a message with an invalid supported rate from station 00:13:ce:11:89:b6.

Is the above syslog message has any implication on the client?

Thank you.

B.Rgds,

Lim TS

[sbilgi]

Yes, if your wireless network comprises both of 802.11b and 802.11g clients, it is better to use supported than the mandatory option.

[johnruffing]

Actually, the answer may not be that cut and dry.

Supporting lower data rates also results in the increase of AP radio receiver sensitivity.

This means that when lower data rates are enabled, one side effect is that the AP will receive more background noise.

In high-density environments (i.e.: where lots of APs that are close together and can then "hear" one another), supporting lower data rates can mean more co-channel interference.

From listening to Cisco's Neil Reid, a 15+ year vetran of 802.11, one of the first things that he says he does is to disable 1Mbit and 2Mbit data rates (for the RF advantages).

So it is important to understand the RF impact of any data rate settings.

- John

[sbhadrav@cisco.com]

Step 1 Choose Wireless > 802.11a/n or 802.11b/g/n > High Throughput (802.11n) to open the 802.11n (5 GHz or 2.4 GHz)
High Throughput page.
Step 2 Select the 11n Mode check box to enable 802.11n support on the network. The default value is enabled.
Step 3 Select the check boxes of the desired rates to specify the modulation and coding scheme (MCS) rates at which data can
be transmitted between the access point and the client. These data rates, which are calculated for a 20-MHz channel
width using a short guard interval, are available:
• 0 (7 Mbps)
• 1 (14 Mbps)
• 2 (21 Mbps)
• 3 (29 Mbps)
• 4 (43 Mbps)
• 5 (58 Mbps)
• 6 (65 Mbps)
• 7 (72 Mbps)
• 8 (14 Mbps)
• 9 (29 Mbps)
• 10 (43 Mbps)
• 11 (58 Mbps)
• 12 (87 Mbps)
• 13 (116 Mbps)
• 14 (130 Mbps)
• 15 (144 Mbps)
Any associated clients that support the selected rates may communicate with the access point using those rates.
However, the clients are not required to be able to use this rate in order to associate. The MCS settings determine
the number of spatial streams, the modulation, the coding rate, and the data rate values that are used.
Step 4 Click Apply.
Step 5 Use the 802.11n data rates that you configured by enabling WMM on the WLAN as follows:
a) Choose WLANs to open the WLANs page.
b) Click the ID number of the WLAN for which you want to configure WMM mode.
c) When the WLANs > Edit page appears, choose the QoS tab to open the WLANs > Edit (Qos) page.
d) From the WMM Policy drop-down list, choose Requiredor Allowedto require or allow client devices to use WMM.
Devices that do not support WMM cannot join the WLAN.
If you choose Allowed, devices that cannot support WMM can join the WLAN but will not benefit from the 802.11n
rates.
e) Click Apply.
Step 6 Click Save Configuration.
To determine if an access point supports 802.11n, look at the 11n Supported text box on either the 802.11a/n
(or 802.11b/g/n) Cisco APs > Configure page or the 802.11a/n (or 802.11b/g/n) AP Interfaces.