![](https://codelido.com/assets/files/2023-01-01/1672569388-568886-ethernet.png)
Ethernet LAN
A local area network (LAN) is a collection of devices connected together in one physical location, such as a building, office, or home.
The term Ethernet refers to a family of LAN standards that together define the physical and data-link layers of the world’s most popular wired LAN technology.
The most fundamental cabling choice has to do with the materials used inside the cable for the physical transmission of bits that is either copper wires or glass fibers. Devices using UTP (Unshielded Twisted Pair) cabling transmit data over electrical circuits via the copper wires inside the cable. Fiber-optic cabling, the more expensive alternative, allows Ethernet nodes to send light over glass fibers in the center of the cable. Although more expensive, optical cables typically allow longer cabling distances between nodes.
Building Physical Ethernet LANs with UTP
Transmitting Data Using Twisted Pairs
While it is true that Ethernet sends data over UTP cables, the physical means to send the data uses electricity that flows over the wires inside the UTP cable. To better understand how Ethernet sends data using electricity, break the idea down into two parts: how to create an electrical circuit and then how to make that electrical signal communicate 1s and 0s.
To send data, the two devices follow some rules called an encoding scheme. The idea works a lot like when two people talk using the same language: The speaker says some words in a particular language, and the listener, because she speaks the same language, can understand the spoken words. With an encoding scheme, the transmitting node changes the electrical signal over time, while the other node, the receiver, using the same rules, interprets those changes as either 0s or 1s.
Breaking Down a UTP Ethernet Link
The term Ethernet link refers to any physical cable between two Ethernet nodes. To learn about how a UTP Ethernet link works, it helps to break down the physical link into those basic pieces as shown in figure.
![](https://codelido.com/assets/files/2023-01-01/1672578059-121418-1.png)
The cable holds some copper wires, grouped as twisted pairs. Each wire has a color-coded plastic coating, with
the wires in a pair having a color scheme. Many Ethernet UTP cables use an RJ-45 connector on both ends. The RJ-45 connector has eight physical locations into which the eight wires in the cable can be inserted, called pin
positions, or simply pins. These pins create a place where the ends of the copper wires can touch the electronics inside the nodes at the end of the physical link so that electricity can flow.
![](https://codelido.com/assets/files/2023-01-01/1672578081-554136-ethernetport-custom.jpg)
PCs often include this RJ-45 Ethernet port as part of a network interface card (NIC), which can be an expansion card on the PC or can be built in to the system itself. Switches typically have many RJ-45 ports because switches give user devices a place to connect to the Ethernet LAN.
Building Physical Ethernet LANs with Fiber
An engineer might prefer to use fiber cabling for some links in an Ethernet LAN, first to reach greater distances.
Fiber Cabling Transmission Concepts
Fiber-optic cables use fiberglass, which allows a manufacturer to spin a long thin string (fiber) of flexible glass. A fiber-optic cable holds the fiber in the middle of the cable, allowing the light to pass through the glass—which is a very important attribute for the purposes of sending data. The glass could break, so the glass fiber needs some protection and strengthening.
![](https://codelido.com/assets/files/2023-01-01/1672579101-846059-optic-fibre.png)
The three outer layers of the cable protect the interior of the cable and make the cables easier to install and manage, while the inner cladding and core work together to create the environment to allow transmission of light over the cable.
Using Fiber with Ethernet
To use fiber with Ethernet switches, you need to use a switch with either built-in ports that support a particular optical Ethernet standard, or a switch with modular ports that allow you to change the Ethernet standard used on the port.
![](https://codelido.com/assets/files/2023-01-01/1672579190-618902-fiber-optics-ethernet-cable-custom.jpg)
Although distance might be the first criterion to consider when thinking about whether to use UTP or fiber cabling, a few other tradeoffs exist as well. UTP wins again on cost also. UTP has some negatives, however. First, UTP might work poorly in some electrically noisy environments such as factories, because UTP can be affected by electromagnetic interference (EMI). Also, UTP cables emit a faint signal outside the cable, so highly secure networks may choose to use fiber, which does not create similar emissions, to make the network more secure.