Question

Explain the difference between communication access techniques:

- CSMA/CD

- CSMA/CA

- Token ring

(5 marks)

Answer 1

CSMA/CD

• It is nothing but the Carrier Sense Multiple Access/ Collision Detection.
• It is media access control(MAC) method which is most commonly used in the LAN technology.
• It is one type of technique where a variety of stations which follows this protocol gives the green signal or acceptance on some rules and regulations which measures for the data transmission.
• This protocol will determine which station and when the station will transmit the data so that it can reach the destination in less time without any data loss and collision.
• It retransmits the data packets or data frames whenever the collision occurred.
• It gets affected more after the collision as compared to CSMA/CA.
• It minimizes the recovery time after the occurrence of any collision.

CSMA/CA

• It is Carrier Sense Multiple Access/ Collision Avoidance.
• It is mainly developed to reduce the probability of collisions when two or more stations begin sending their data from the source to the destination over the data link layer.
• It first checks the current state of the medium before sending the data from the source station to the destination station.
• It is most commonly used in wireless networks whereas CSMA/CD in wired networks like LAN.
• The main idea behind this technique is that the station should be able to receive while transferring the data in order to detect the collision.
• It reduces the probability of the collision more than the probability of CSMA/CD.
• It takes the effect before the occurrence of a collision whereas CSMA/CD takes the effect before the collision occurs.

Token Ring

   It is one type of Local Area Network in which all the computers or systems are connected in the form of a ring topology. By connecting like this each system passes the tokens from one host system to another host system. Whatever the host holding the token could be able to send the data and the tokens should get relief when the receipt of the data is accepted or confirmed. The tokens number is not fixed but less number of tokens are used. So that data can be sent only by the token holder. so network rings prevent the data packets from colliding with each other.