It has a long history and has to do with our topic today, Ethernet.

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Ethernet is a communication standard

that was developed in the early '80s to network computers and other devices

in a local environment such as a home or a building.

This local environment is defined as a LAN (Local Area Network)

and it connects multiple devices so that they can create,

store and share information with others in the location.

Ethernet is a wired system

that started with using coaxial cable

and has successfully progressed to now using twisted pair copper wiring

and fiber optic wiring.

Let's break for a trivia question.

Who invented twisted pair wiring?

Alexander Graham Bell invented twisted pair wiring in 1881.

In 1983, Ethernet was standardized

into the standard IEEE 802.3

by the Institute of Electrical and Electronic Engineers (IEEE).

This standard defined the physical layer

and the MAC (media access control) portion of the data link layer of wired Ethernet.

These two layers are defined as the first two layers

in the OSI (Open Systems Interconnection) model

The “physical” layer consists of the following components:

Cabling and Devices.

First, let's take a look at Ethernet Cabling;

As stated previously, Ethernet cables come as coaxial cable,

which is not very common except in older installations,

twisted pair, and fiber optic.

The most common cable is twisted pair cables,

with the latest being Category 6 with speeds up to 1 Gbps

and Cat6a and Cat 7 with speeds up to 10 Gbps.

Category 5 and 5e cables are both still used in many existing applications

but handle the lower speeds between 10 Mbps

to 100 Mbps but are more susceptible to noise.

The Ethernet twisted pair utilizes RJ-45 eight-pin connectors

at either end of the cable that is pinned for transmitting

and receiving data in either half or full-duplex mode.

Half-duplex transmits data in one direction at a time

while “full-duplex” allows data to be transmitted

in both directions at the same time.

Full-duplex in Ethernet can be achieved by using two pairs of wires

to allow data to travel both directions simultaneously.

Fiber optic cable uses glass or plastic optical fiber

as a conduit for light pulses to transmit data.

It has allowed Ethernet to travel farther distances at higher speeds.

Fiber optic cables use several different types of connectors

that vary depending on your application needs.

Some of the different types are SFP

(Small Form Pluggable or Small Factor Pluggable)

and SC (Subscriber Connector, also known as Square Connector or Standard Connector).

In order to use fiber optic in an Ethernet network

that utilizes twisted pair Ethernet cabling,

you need to use an Ethernet to fiber converter

that will allow your network to take advantage of the higher speeds of fiber optic

and lengthen the distance that the Ethernet network can reach.

How about the Ethernet devices?

Ethernet devices are consist of computers,

printers or any device which either have an internal NIC

(Network Interface Card)

or an external one that is USB or PCI based.

“Switches” and “Routers” that act as the director of the network

and connect multiple computers

or even networks together to enable communication

between all the different devices.

“Gateways” or “Bridges” are used to connect multiple Ethernet networks together

and allow communication across them.

Gateways connect two dissimilar networks together

while a bridge connects two similar networks together

so that you only see one network.

Now that we have discussed the basic physical components of Ethernet,

let's move into the second layer of the OSI model, the “data link” layer.

The data link layer can be split into two sections;

the Logical Link Control (LLC)

and the Media Access Control (MAC).

The Logical Link Control establishes paths for data

on the Ethernet to transmit between devices.

The Media Access Control uses hardware addresses

that are assigned to Network Interface Cards (NIC)

to identify a specific computer or device

to show the source and destination of data transmissions.

Ethernet transmits data packets in this data link layer

by using an algorithm called CSMA/CD

(Carrier Sense Multiple Access with Collision Detection).

CSMA/CD is used as a standard for Ethernet

to reduce data collisions and increase successful data transmission.

The algorithm first checks to see if there is traffic on the network.

If it does not find any,

it will send out the first bit of information to see if a collision will occur.

If this first bit is successful,

then it will send out the other bits while still testing for collisions.

If a collision occurs, the algorithm calculates a waiting time

and then starts the process all over again

until the full transmission is complete.

When you use the faster Ethernets in full-duplex modes

and incorporate switches,

then you are utilizing a star topology

between the switch ports and the devices.

This allows for more direct transmission paths and fewer collisions

as compared to a bus topology where all devices share the same paths.

Ethernet capabilities are quickly changing with new technologies emerging every day.

And while we are currently on the brink of successfully moving into speeds higher

than the current 1 Gbps with 10 Gbps emerging over the last few years,

these new Ethernet technologies will be costly.

Also, your possibilities for the information world

can seem endless when you connect this Ethernet local area network

to the internet to create a very large WAN (Wide Area Network).

But that is a story for another day.

All in all, Ethernet is popular

because it strikes a good balance between speed,

cost, and ease of installation.

These benefits, combined with wide acceptance in the computer marketplace

and the ability to support virtually all popular network protocols.

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