Ethernet networking

Ethernet is a way to access media in which all hosts on a network share same bandwidth of a link. Ethernet is comparatively popular, easy to integrate to new technologies , simple to implement with easy troubleshooting methods.

  It uses Carrier sense multiple access with collision detection ( CSMA/CD) protocol  facilitating even sharing of bandwidth.

CSMA/CD Working:

In this transmitting host checks digital signal on wire. If no other host is transmitting it starts sending its data and along with this also detect the digital signal if any other hosts begin data transmission and therefore sends out  a jam signal so as  to stop other hosts to send data so as to protect collision.

Now when collision occurs in Ethernet LAN :

1. A jam signal is sent over the wire.
2. A random back-off algorithm is run through collision occured.
3. Every ither host stops transmitting data for a particular time set by timers.
4. After the timer expires other hosts can transmit there data 

CSMA/CD network have some drawbacks of sustaining collisions :

1. Delay
2. Low throughput
3. Congestion

Half- duplex and Full-duplex Ethernet:

As the name indicated Half-duplex network which is capable of transmitting or recieving data in one direction  at a time and Full-Duplex network is capable of transmitting or receiving data simultaneously in both directions.

Half-duplex originally known as 802.3 Ethernet uses only one pair of wire 10baseT which is only 30 to 40% efficient and usually gives 3 to 4Mbps,at most also uses CSMA/CD protocol  to help prevent collision and facilitate retransmission  of data if collision occurs.

Full-Duplex uses Two pairs of wires and point to point connection between transmitter of transmitting device and receiver  of receiving device. It has following charachteristics:

1. Faster data transmission.
2. No collision occurs.
3. A dedicated port is required for each duplex node.
4. Both host netwok card and switch port must be capable of operating in full-duplex mode
5. It gives 100% efficiency in both directions.

Full -Duplex Ethernet is used in following  three conditions:

1. For connecting switch to host.
2. For connecting switch to switch.
3. for connecting host to host using a crossover cable.