Computer Networking

Transport Layer

CSMA With Collision Avoidance (CSMA/CA)

CSMA/CA is used in wireless (Wi-Fi) network. CSMA/CA is just similar to CSMA/CD but difference is that, the CSMA/CA detects collision instead of detection. So, CSMA/CA is just use for collision avoidance.

Working of CSMA/CA

In CSMA CA, whenever a station sends a frame to a channel

  • First, it checks the status of medium (idle or busy). If the medium is busy, the station waits until the medium becomes idle.
  • Second, if the channel is idle then station waits for an Inter-frame gap (IFG) amount of time and then sends the frame.
  • Third, after sending the data frame, CSMA/CA sets a timer.
  • In the end, station waits for positive acknowledgement from the receiver. If positive ACK receives before expiry of timer, then it is a successful transmission. Otherwise, station waits for a back-off time period and restarts the transmission.

Flow Chart

Descriptive flow chart of CSMA/CA is given below

Difference Between CSMA/CD and CSMA/CA

1.  It detects the collision on a shared medium. CSMA CA is used to avoid collision on a shared channel.
2. It is the collision detection protocol. It is the collision avoidance protocol.
4. It works in wired networks i.e. (802.3 Ethernet network cable) It works in wireless networks (i.e. Wi-fi).
6. It use the collision signals to resend the data. It uses the timer to resend the data.
7. It minimizes the recovery time. It minimizes the risk of collision.
8. The efficiency of CSMA/CD is high than CSMA. The efficiency of CSMA/CA is similar to CSMA but less than CSMA/CD.
9. It is more popular than CSMA/CA It is less popular than CSMA/CD.


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