Halfduplex and Fullduplex

Simplex:-
One way Communication
Example:- RADIO, TV receiver, SMS, etc.


HALF DUPLEX:-
++can send and receive but not at a time.
++this was originally used on coaxial cables(10BASE5, 10Base2)
and For ethernet HUBS. because these cannot use fullduplex.
++it uses CSMA/CD method.
CSMA/CD:-
Rule1)Computer has to listen to Ethernet if any hosts are sending any frame, if no one then it will send
Rule2)After sending the frame also it will still continiously listen if there is any collisions.
Rule3)If collision heard, Both senders send JAM signals to all Hosts telling not to send any packets.
and a BACKOFF algorithm is calculated
backoff algorithm:- telling other computers not to transmit new data for a random amount of time..
When BACKOFF TIMER is expired then it willl again send the data.process is  REPEATED...

FULL DUPLEX:-
++can send and receive at same time.
++copper twisted pair used in Full duplex.
++NO need of CSMA/CD
++No COLLISION.

HUB(half)-------(full)Switch====>HALF-DUPLEX

 
T” stands for Twisted Pair.
2 and -5 which indicate Coaxial wiring with maximum ranges of 200~ and 500 meters,

100 BASE-T4:-
8 wires= 4 pairs
1st pair=TX signals
2nd pait=RX signals
remaining 2=either TX or RX to negotialte which wire to use TX and RX

100 BASE-TX:- commonly used for Fast ethernet.
8 wires= 4 pairs
1st pair=TX signals 
2nd pait=RX signals 
remaining 2=UNUSED

1000 BASE-TX:- commonly used for Fast ethernet.
8 wires= 4 pairs
2 pairs=TX signals 
2 pairs=RX signals 

FOR MDI-NIC CARDS(Media dependent interface)
---------------------------------------------
uses opposite
PC1_TX(pin 1&2)
PC1_RX(pin 3&6)

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