1) Discuss the CSMA/CD and CSMA/CA protocols?
CSMA/CD is the acronym for carrier sense multiple access with collision detection. It is a media access control method which is used mostly in early ethernet or LAN technology. It uses a carrier sensing scheme in whic a transmiting station detects collision by sensing transmissions from other stations when it is transmitting a frame.
When a collision is detected the station that is transmitting stops transmitting that frame and transmits a jam signal and then waits for a random time interval before trying to resend the fraame.
It is modification of CSMA . CSMA/CD is used to improve CSMA performance by terminating transmission as soon as a collision is detected.It also helps in shortening the time required before a retry is attempted.
it is important to note that it is the collision detection capablity that imposes a distance limitation.that is why it is not effective beyond 2500 meters. The segments cannot sense sinals beyond this distance.The data collision will take place when more than one computer transmit data into the network at the same time.
CSMA/CA is acronym for carrier sense multiple access with collision avoidance. it is the least popular of the access methods.In this protocol computer will signal its intention to transmit before it actually sends or transmits the data. This way computers will sense when a collision may occur which allows them to avoid collisions in the transmissions.
Unfortunately this broadcast of the intention to transmit data increases the amount of trafion the cable and slows the network performance. this method was once very popular in MAC and it is now used with WLAN’s.