A wired local area network is a local area network where the connectivity between different components or elements of the LAN is done using wires and cable. Well to implement the wired LANs various technologies were introduced such as token ring, token bus, FDDI, ATM LANs, and Ethernet.
Among all these technologies only Ethernet survived the market as it has the capability to update itself to meet the increasing requirements. So, in this context, we will discuss wired local area networks in brief and how the ethernet technology succeeded in implementing wired LANs.
Content: Wired Local Area Network
Essential Components of Wired LAN
To establish a wired local area network, we require some essential components. We will discuss those elements or components in the section below:
The network adaptor we use in wired LANs is also referred to as Ethernet adaptor, network controller or network interface card (NIC), or LAN adapter. It is mounted on the computer’s motherboard which helps the computer to connect with other computers on the LAN network.
For wired LAN the network adaptor has an RJ 45 port. To these ports, the Ethernet cables that have RJ 45 connectors are inserted. This allows the computer to transmit and receive information over the LAN network.
Medium of Network
In wired LAN the medium of network or the communication channel that that connects two computers is the Ethernet cable. The Ethernet cables can be a coaxial cable, twisted pair cable, or a fiber optic cable.
The most used cable is the twisted pair cable which has evolved with time. The first Category cable CAT 1 has a data transfer rate of 1Mbps and the recent CAT 8 has a data transfer rate of 40 Gbps.
May the LAN network be wired or wireless it requires a power supply to send and receive the information over the network. The wireless LAN requires power to generate the radio waves that will carry information from one computer to another.
The wired LAN requires a power supply to generate the electronic signals which are interpreted as data.
Hub, switches, and routers all are the connecting devices that connect computers in a network or connect multiple networks together.
What is Ethernet?
Ethernet is one of the dominant technologies that is used to implement the wired LAN. Don’t get confused with the term Ethernet as a physical connection between the components in LAN. Instead, Ethernet is a communication standard that was standardized to the standard of IEEE 802.
This IEEE standard of 802 defines first the two layers of the OSI model i.e., the physical layer and data link layer.
The physical layer defines cables and devices involved in the network. The ethernet cable can be a coaxial cable, twisted pair cable, or a fiber optic cable. The most commonly used cable is twisted pair cable CAT 6 with the speed of 1 Gbps and CAT 7 with the speed of 10 Gbps.
The ethernet devices are computers, printers, or any other devices that have an inbuilt network adaptor or network interface card (NIC) or external USB or PCI based. The other devices include switches and router that directs the network whereas gateways and bridges connect two ethernet networks.
Data Link Layer
The Ethernet standards have divided the data link layer into two subsections media access control (MAC) and logical link control (LLC).
The role of MAC is to identify the source and destination Ethernet devices on the network among which data is being transmitted, using the hardware addresses assigned to their network interface card (NIC).
The role of LLC is to set up a path between the source and destination ethernet devices for data transmission.
Evolution of Ethernet
The standards of Ethernet were introduced in the year 1976 at Xerox’s Palo Alto Research Center in the year 1983 it was standardized into IEEE standard 802. Over a period of time, Ethernet has evolved to its fourth generation as you can see in the figure below.
1. Standard Ethernet
Standard Ethernet is the first generation of Ethernet which has a data transfer speed of 10 Mbps. The Ethernet uses the CSMA/CD access method. In the CSMA/CD method the computer that wants to transmit data first senses the network and if the network is idle then only it will transmit data.
2. Fast Ethernet
Fast Ethernet is a second-generation Ethernet that was evolved to compete with FDDI or fiber channel. The Fast Ethernet is compatible with the older Standard Ethernet. It transmits data at the speed of 100 Mbps.
Fast Ethernet has an additional feature of auto-negotiation which allows two devices to negotiate and select the common transmission parameters such as data transfer speed, flow control, mode of operation half-duplex or full-duplex.
3. Gigabit Ethernet
Further evolution in the Ethernet standard resulted in the evolution of Gigabit. The data transmission speed of Gigabit Ethernet is 1 Gbps. It is compatible with both the older version Standard and Faster Ethernet.
Gigabit Ethernet also supports auto-negotiation, the feature introduced in Fast Ethernet.
4. Ten-Gigabit Ethernet
The Ten-Gigabit Ethernet is the fourth generation of Ethernet and it transmits data at the rate of 10 Gbps. It is compatible with Standard, Faster, and Gigabit Ethernet. It is also compatible with other technologies such as Frame Relay and ATM.
How CSMA/CD Works?
CSMA/CD is a carrier sense media access with collision detection. Let us see the working of the CSMA/CD protocol.
Step 1: A node in a network that wants to transmit the data to some other node first checks whether the network is idle or not.
Step 2: If the node senses that the network is busy it then waits for some time till the network becomes idle.
Step 3: If the node sense that the network is idle then the node starts transmitting the frames and along with that it also keeps on monitoring that if there occurs a collision.
Step 4: If in between the data transmission the collision occurs then the collision resolution algorithm is activated.
Step 5: If no collision is detected then the node completes the data transmission and resets the retransmission counters.
Collision Resolution Algorithm
Step 1: If the node detects the collision in between the transmission then the node continues transmitting the current frame and along with that the node alerts the collision signals to alert all other nodes in the network.
Step 2: Further the node increments the retransmission counter.
Step 3: If the node finishes off the retransmission attempts then the node aborts that corresponding transmission.
Step 4: Or the node waits for a random amount of time and starts the data transmission again.
The CSMA/CD algorithm is able to determine the collision and resolves the collision but it does not have an appropriate method to reduce the collision. This will be problematic for large networks.
So, this is all about the wired local area network. To implement the wired LAN usually the Ethernet communication standard is used as it is cheap to install and maintain.