Ethernet in Local Area Networks

- Local Area Network

A Local Area Network (LAN) is a network of computers and other electronic devices that covers a small area such as a room, office, or building. It is used in contrast to a wide area network (WAN), which spans a large geographical area. Ethernet is a network protocol that controls how data is transmitted over a LAN and is referred to as the IEEE 802.3 protocol. The protocol has evolved and improved over time to transfer data at the speed of a gigabit per second.

A LAN uses the same network access protocol and usually the same transmission medium (e.g., Ethernet), allowing message delivery without the need to route messages through different networks. Devices that send and receive messages on the network are called hosts or nodes. These devices are peers, meaning that no device has more control or coordination of the network than any other device. Any host can initiate a data transfer with any other host on the LAN. LANs usually exhibit very low latency and a high data rate: typically 10s to a gigabit per second (Gbps) for wireless networks and a 1 gigabit per second (Gbps) or more for wired connections (although speeds as high as 10 and 100 Gbps are available). 

Ethernet networks can also be wireless. Rather than using Ethernet cable to connect the computers, wireless NICs (Network Interface Cards) use radio waves for two-way communication with a wireless switch or hub. It consists of Ethernet ports, wireless NICs, switches and hubs. Wireless network technology can be more flexible to use, but also require extra care in configuring security. Ethernet and Wi-Fi are the two most common technologies in use for local area networks.

- How Ethernet LAN Works

Nodes (machines) connect to a LAN (Ethernet) with an adapter. These are usually integrated onto the main circuit board but may be separate components, such as a USB ethernet adapter. Another term for these is NIC, which stands for Network Interface Controller. When a machine (node) on the network (LAN) wants to send data to another, it senses the carrier, which is the main wire connecting the devices. If it is free, meaning no one is sending anything, it sends the data packet on the network, and the other devices check the packet to see whether they are the recipient. The recipient consumes the packet. If there is a packet on the highway, the device that wants to send holds back for some thousandths of a second to try again until it can send. 

The physical data communication links that the adapter uses to send and receive data are called media. Common examples are unshielded twisted pair (UTP) copper wire (e.g., ethernet cable), radio frequency (e.g., the 5 GHz frequency bands used by 802.11ac), coaxial cable (e.g., used by cable TV in the home and the MoCA standard, multimedia over coax), and optical fiber (which is not commonly used in the home).  

The Gigabit Ethernet is a type of Ethernet network capable of transferring data at a rate of 1000 Mbps based on a twisted-pair or fiber optic cable, and it is very popular. The type of twisted-pair cables that support Gigabit Ethernet is Cat 5e cable, where all the four pairs of twisted wires of the cable are used to achieve high data transfer rates. The 10 Gigabit Ethernet is a latest generation Ethernet capable of transferring data at a rate of 10 Gbps using twisted-pair or fiber optic cable.

- Ethernet Switch

A LAN uses the same network access protocol and usually the same transmission medium (e.g., Ethernet), allowing message delivery without the need to route messages through different networks. Devices that send and receive messages on the network are called hosts or nodes. These devices are peers, meaning that no device has more control or coordination of the network than any other device. Any host can initiate a data transfer with any other host on the LAN. LANs usually exhibit very low latency and a high data rate: typically 10s to a gigabit per second (Gbps) for wireless networks and a 1 gigabit per second (Gbps) or more for wired connections (although speeds as high as 10 and 100 Gbps are available).

The other end of the media (i.e., the physical data communication link) terminates at a switch or hub. A hub is a device that acts as a central point for multiple LAN cables. It takes any data that comes in one port and sends it to all the other ports. A switch is similar to a hub but smarter. It looks at incoming data and determines the port or ports on which to transmit it. Switches have largely replaced hubs. They provide scalable bandwidth in that they do not introduce more network congestion as you add more hosts onto your LAN. Switches and hubs are link-layer devices (more on that later). That is, they move ethernet packets to their destination as opposed to relaying data between networks. They are responsible for creating the physical network. For wireless networks, a wireless access point serves as link-layer switch. 

(Geneva Lake, Switzerland - Alvin Wei-Cheng Wong)

- To Set Up A Wired Ethernet LAN

Nodes connect to a LAN with an adapter. These are usually integrated onto the main circuit board but may be separate components, such as a USB ethernet adapter. Another term for these is NIC, which stands for Network Interface Controller.

The physical data communication links that the adapter uses to send and receive data are called media. Common examples are unshielded twisted pair (UTP) copper wire (e.g., ethernet cable), radio frequency (e.g., the 5 GHz frequency bands used by 802.11ac), coaxial cable (e.g., used by cable TV in the home and the MoCA standard, multimedia over coax), and optical fiber (which is not commonly used in the home).

A computer network interface card (NIC) is installed in each computer, and is assigned to a unique address. An Ethernet cable runs from each NIC to the central switch or hub. The switch and hub act as a relay though they have significant differences in the manner in which they handle network traffic - receiving and directing packets of data across the LAN. Thus, Ethernet networking creates a communications system that allows sharing of data and resources including printers, fax machines and scanners.

• Computers and devices to connect: Ethernet connects any computer or other electronic device to its network as long as the device has an Ethernet adapter or network card.
• Network interface cards (NICs) in the devices: A network interface card is either integrated into the motherboard of the computer or installed separately in the device. There are also USB versions of Ethernet cards, such as external dongles. An Ethernet card is known as a network card. It has ports where you connect cables. There may be two ports, one for an RJ-45 jack that connects unshielded twisted pair (UTP) cables and one for a coaxial jack on the network card.
• A router, hub, or gateway to connect devices: A hub is a device that acts as a connecting point between devices on a network. It consists of several RJ-45 ports to which you plug the cables.
• Cables: UTP cables are commonly used in Ethernet LANs. This cable is similar to the cable used for landline telephone sets but fatter, with eight twisted pairs of wires of different colors inside. The end is crimped with an RJ-45 jack, which is a larger version of the RJ-11 jack that plugs into a landline phone. When the Ethernet spans beyond a room to a greater distance, coaxial cable is used. This is the same cable with a round single-core jack you use for a TV.
• Software to manage the network: Modern operating systems like recent versions of Windows, Linux and macOS are more than sufficient to manage Ethernet LANs. Third-party software that gives more features and better control is available

Ethernet supports different types of networks or topologies such a bus topology, ring topology, star topology, tree topology, and so on. These topologies can be used for transferring and receiving data using different types of cables like coax, twisted pair, fiber optic, etc.

- Wireless Ethernet

Wi-Fi is the wireless counterpart to Ethernet, which is the universal standard for local area networks (LANs). In both homes and offices, networks are generally a mix of Wi-Fi and Ethernet. Most stationary machines are cabled together via Ethernet, because there is an Ethernet port on every modern computer. Wi-Fi networks (Wi-Fi hotspots) are set up for laptops, smartphones and tablets. However, any desktop machine can be made wireless with an adapter (see wireless adapter). 

Wi-Fi is achieved with a wireless base station, called an "access point." Its antennas transmit and receive a radio frequency within a range of 30 to 150 feet through walls and other non-metal barriers.