Wireless Access

At what rate are control frames sent?  I'm seeing most sent at 24Mbps on  5 GHz, but I can't determine which setting (if any) dictates this speed.

"Control" frames?  In the Air?  In the Advanced SSID profile look at your a-basic-rates and your a-beacon-rates.

24 Mbps is the highest basic rate supported.

12 Mbps is the beacon rate.

The best I can figure is that control frames are sent at the highest basic rate supported, but I haven't been able to confirm that with any documentation.

Exactly what type of frame are you talking about?  Control is only a class of frames.  In addition, if you have Broadcast/Multicast Optimization enabled in the SSID profile, it will attempt to send broadcast/mgmt  frames at a max of 24 meg.

From the captures I've done, all of the control frames are being sent at 24 Mbps: ACK, Block ACK, RTS, CTS, etc.

Yes, bc/mc optimization is configured.  This must be what's doing it as you stated.

The reason I've been looking at control frames is that I'm seeing what seems to be a disproportinate amount of control frames to data and management frames.  RTS/CTS is making up about 50% of the frames at times.  If considering air time, they're consuming about 1/3 of the air time.  So at any given time, the majority of traffic captured is running at 24 Mbps, but that's considering Block ACK, ACK, the stuff that is expected.  I'm not sure if I should be alarmed by this or not.

There is no way to determine the appropriate percentage of control frames to data.  The way wifi works it is typically 50%.  In all environments, it varies.  Since it is all being sent at 24 megs, I would not worry about it.

As a follow up to this, I found that my wifi tools are not working properly resulting in skewed data frame ratios.  After figuring that out and getting a different tool, the ratio of control frames to data frames looks correct.

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@thecompnerd wrote:

At what rate are control frames sent?  I'm seeing most sent at 24Mbps on  5 GHz, but I can't determine which setting (if any) dictates this speed.

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Wanted to provide some supplemental information that sort of addresses my question.

According to Ben Miller's blog,  RTS/CTS frames will be sent at a data rate which all legacy devices can understand when the WLAN is operating in mixed mode:

"An AP or device using the protection mechanism will precede its data frame transmissions with the transmission of a non-data carrying frame called a request to send (RTS) or a clear to send (CTS).  The RTS and CTS frames are always sent at a data rate that the legacy devices can understand.  For example, a WiFi network with a mix of 802.11a and 802.11ac devices would see 802.11a (24 Mbps, typically) RTS and/or CTS frames sent in advance of data that would be sent using VHT rates (up to 1,300 Mbps with today's gear)."

I think we need to focus on what you are seeing.  You should post the frame that you see and we can say exactly what it is.  "Control" frames are something more general that require more explanation.  Let's start with what you are seeing..

Sorry, I was not very clear when I posted the original question.  I was referring to seeing RTS/CTS frames at 24 Mbps and was curious as to why they were not transmitted at the highest rate possible.  Based on your replies and what I found on the blog I referenced earlier, I'm satisfied with the answers.