Editing IEEE 802.11 RTS/CTS

{{Short description|Computer network protocol}}
{{More citations needed|article|date=May 2010}}

'''IEEE 802.11 RTS/CTS''' (request to send/clear to send) is the optional mechanism used by the [[802.11]] wireless networking protocol to reduce frame collisions introduced by the [[hidden node problem]]. Originally the protocol fixed the [[exposed node problem]] as well, but later RTS/CTS does not, but includes ACKs.

== Frame format ==
The RTS, CTS and ACK frame headers all contain

* frame control (two bytes of metadata flags)
* duration
* receiver MAC address
* [[frame check sequence]]. 
* RTS frames contain the transmitter's MAC address.

== Exposed terminal problem ==
This protocol was designed under the assumption that all nodes have the same transmission ranges. RTS/CTS frames can cause the exposed terminal problem in which a wireless node that is nearby, but is associated with another access point, overhears the exchange and then is signaled to back off and cease transmitting for the time specified in the RTS.

== Carrier sensing ==
RTS/CTS is an additional method to implement virtual carrier sensing in [[carrier sense multiple access with collision avoidance]] (CSMA/CA). By default, [[802.11]] relies on physical carrier sensing only.

== Frame size ==
The RTS/CTS packet size threshold is 0–2347 [[octet (computing)|octet]]s. Typically, sending RTS/CTS frames does not occur unless the packet size exceeds this threshold. If the packet size that the node wants to transmit is larger than the threshold, the RTS/CTS handshake gets triggered. Otherwise, the data frame gets sent immediately.

== See also ==
* [[RS-232 RTS/CTS#RTS, CTS, and RTR|RS-232 RTS/CTS]] - RS-232 RTS/CTS flow control
* [[Multiple Access with Collision Avoidance for Wireless]]

==References==
{{Reflist}}

== External links ==
* [http://www.ece.rice.edu/~camp/MAC/maca.pdf "A New Channel Access  Method for Packet Radio"] {{Webarchive|url=https://web.archive.org/web/20110720002102/http://www.ece.rice.edu/~camp/MAC/maca.pdf |date=2011-07-20 }}
* {{webarchive |url=https://web.archive.org/web/20200110083327/http://www.studioreti.it:80/slide/802-11-Frame_E_C.pdf |date=January 10, 2020 |title=IEEE 802.11 frame format}}

{{DEFAULTSORT:IEEE 802.11 RTS CTS}}
[[Category:IEEE 802.11|RTS CTS]]

[[de:Carrier Sense Multiple Access/Collision Avoidance#RTS/CTS Koordination]]