Tuesday, 2 June 2009

Disabling CTS Protection Mode

I've been twiddling my Access Point (AP) settings and discovered that disabling CTS protection mode significantly increases Wifi throughput in a low transmission error network. CTS (Clear-To-Send) protection mode should be enabled when your Wireless-G devices are experiencing problems, for example, not being able to transmit to the Router in an environment with heavy 802.11b traffic.

The theory is as follows:  When there are many devices connected to an AP they can sometimes transmit to the AP at the same time. This can occur when a client cannot detect the other client to determine if it is transmitting on the same channel. In the case of this collision, the AP discards the colliding data and the error rate is increased. 

CTS protection helps by choosing which device gets to transmit at each moment. The client has to send a request to send (RTS) to the AP. The AP then replies with a CTS packet and then only listens to that client until the client has completed transmitting.  This overhead decreases throughput.

Most APs also allow one to change the RTS threshold. This specifies the packet size  requiring an RTS. On a very noisy network where there are a lot of transmission errors one can bring the RTS threshold right down making clients send RTS packets for smaller packet.s, but this will decrease performance.

With CTS enabled it should help 802.11B/G devices to have a chance to transmit to the AP.  If your network error rate is low, disable CTS protection to get better performance. 

Hope that helps!


  1. Very helpful info. Thanks.

  2. Thanks for info, it helped me out a lot!

  3. Gracias, necesitaba saber la funciĆ³n de eso en el DD-WRT. :)

    1. which translates to: Thanks, I needed to know the function of that in the DD-WRT. :)

  4. What is considered a "low" error rate?

  5. Don't disable cts protection if you have 3 or more devices connected

  6. Thanks, very helpful!

  7. This may be the key to my problem: my cell phone is able to connect to the AP router, but sometimes my laptop does not detect it; probably this is because one or more cell phones may be already connected to it at that time. The CTS is 'Auto'.