- Source: IEEE 802.11 RTS/CTS
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 octets. 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 - RS-232 RTS/CTS flow control
Multiple Access with Collision Avoidance for Wireless
References
External links
"A New Channel Access Method for Packet Radio" Archived 2011-07-20 at the Wayback Machine
IEEE 802.11 frame format at the Wayback Machine (archived January 10, 2020)
Kata Kunci Pencarian:
- IEEE 802.11 RTS/CTS
- RTS/CTS
- IEEE 802.11
- IEEE 802.11g-2003
- IEEE 802.11n-2009
- Carrier-sense multiple access with collision avoidance
- IEEE 802.11e-2005
- Exposed node problem
- Hidden node problem
- Multiple Access with Collision Avoidance for Wireless
