What is Half Duplex and Full Duplex ?

What is Half Duplex and Full Duplex?

Hello everyone in this article we're going to talk about a couple of different transmission types that are used in networking.
Those types are half-duplex and full-duplex.

Half-Duplex
Let's talk about half-duplex first
In a half-duplex network, you have a point-to-point system where two devices are connected to each other using a network cable and these devices can communicate with each other in both directions, but in a half-duplex, they can only communicate in one direction at a time they cannot communicate in both directions at the same time.
If computer "A" is sending data to computer "B", computer B has to wait until computer "A" is done before it can send data to computer "A" so data flows in one direction at a time.
The two computers have to take turns when they send data to each other.

Half-Duplex Explanation Example
Half-duplex is just like how walkie-talkies work.
With walkie-talkies, a person has to press a button if they want to talk to transmit their voice to the other person and while the button is
pressed information is only going in one direction so they can't hear the other person while they're transmitting their voice.
They would have to release the button in order to receive the other person's transmission.

Full-Duplex
A full-duplex is better than a half-duplex.
In a full-duplex, the two devices can also communicate in both directions with each other, but the difference is that they can communicate in both directions at the same time which gives a full-duplex advantage over half-duplex devices that can send and receive data simultaneously.
As a result, it sends and receives data at the same time, a full-duplex system has double the bandwidth of a half-duplex.

Full-Duplex Explanation Example
A good example of a full-duplex would be telephone communication.
When you talk to somebody on the phone you can talk to and hear the other person at the same time, so you don't have to wait to do one or the other.
you can talk and listen simultaneously.

Comparison Between Half-Duplex and Full Duplex & also CSMA/CD Concept
As a comparison between half-duplex and full-duplex, you can use an analogy of cars on a highway where you have cars that travel across an area.
When a half-duplex, the cars would all have to share a single lane on the highway and that lane only allows traffic in one direction at a time.
The cars on the opposite sides of the highway would have to wait their turn to use that lane to get to their destination and since it only has one lane collisions do happen from time to time and that's why in a half-duplex network it needs a traffic cop to regulate that lane to tell cars to wait their turn and in networking this traffic cop is called CSMA/CD or carrier sense multiple access with collision detection and this is an access method that's used to help avoid collisions and to also respond correctly if a collision does happen.
But in a full-duplex, the cars don't have to wait because you can compare a full-duplex as having a two lane highway each Lane is dedicated for a direction the cars that are traveling in the opposite directions have their own dedicated lane as they travel to their destination.
As a result, since each direction has its own dedicated Lane it avoids collisions and there is no need for a traffic cop (CSMA/CD)
now today we use full-duplex networks the main reason why you would see, a half-duplex network today is for older (legacy) equipment that can only be used in half-duplex mode.
For example, if a network is still using hubs instead of switches because hubs can only operate in half-duplex mode and not full-duplex (switches use full-duplex) which is the main reason why hubs are obsolete today and you can't even buy them anymore.