Computer Networks

A system of connecting computers together

What is Computer Network?

A computer network is a group of devices connected through a transmission medium such as wires, cables etc. These devices can be computers, printers, scanners, Fax machines etc.

A computer network is a collection of two or more computer systems that are linked together. A network connection can be established using either cable or wireless media. Hardware and software are used to connect computers and tools in any network.

A computer network consists of various kinds of nodes. Servers, networking hardware, personal computers, and other specialized or general-purpose hosts can all be nodes in a computer network. Hostnames and network addresses are used to identify them.

How Does a Computer Network Work?

Basics building blocks of a Computer network are Nodes and Links. A Network Node can be illustrated as Equipment for Data Communication like a Modem, Router, etc., or Equipment of a Data Terminal like connecting two computers or more. Link in Computer Networks can be defined as wires or cables or free space of wireless networks.

The working of Computer Networks can be simply defined as rules or protocols which help in sending and receiving data via the links which allow Computer networks to communicate. Each device has an IP Address, that helps in identifying a device.

Criteria of a Good Network

1. Performance: It can be measured in many ways, including transmit time and response time. Transit time is the amount of time required for a message to travel from one device to another. Response time is the elapsed time between an inquiry and a response. The performance of the network depends on a number of factors, including the number of users, the type of medium & Hardware
2. Reliability: In addition to accuracy is measured by frequency of failure, the time it takes a link to recover from failure, and the network’s robustness in catastrophe.
3. Security: Network security issues include protecting data from unauthorized access, protecting data from damage and development, and implementing policies and procedures for recovery from breaches and data loss.

Basic Terminologies of Computer Networks

• Network: A network is a collection of computers and devices that are connected together to enable communication and data exchange.
• Nodes: Nodes are devices that are connected to a network. These can include computers, Servers, Printers, Routers, Switches, and other devices.
• Protocol: A protocol is a set of rules and standards that govern how data is transmitted over a network. Examples of protocols include TCP/IP, HTTP, and FTP.
• Topology: Network topology refers to the physical and logical arrangement of nodes on a network. The common network topologies include bus, star, ring, mesh, and tree.
• Service Provider Networks: These types of Networks give permission to take Network Capacity and Functionality on lease from the Provider. Service Provider Networks include Wireless Communications, Data Carriers, etc.
• IP Address: An IP address is a unique numerical identifier that is assigned to every device on a network. IP addresses are used to identify devices and enable communication between them.
• DNS: The Domain Name System (DNS) is a protocol that is used to translate human-readable domain names (such as www.google.com) into IP addresses that computers can understand.
• Firewall: A firewall is a security device that is used to monitor and control incoming and outgoing network traffic. Firewalls are used to protect networks from unauthorized access and other security threats.

Components Of Computer Network

NIC(Network interface card)

NIC is a device that helps the computer to communicate with another device. The network interface card contains the hardware addresses, and the data-link layer protocol uses this address to identify the system on the network so that it transfers the data to the correct destination.

There are two types of NIC: wireless NIC and wired NIC.

• Wireless NIC: All modern laptops use the wireless NIC. In Wireless NIC, a connection is made using the antenna that employs radio wave technology.
• Wired NIC: Cables use the wired NIC to transfer the data over the medium.

Hub

Hub is a central device that splits the network connection into multiple devices. When a computer requests information from a computer, it sends the request to the Hub. Hub distributes this request to all the interconnected computers.

Switches

The switch is a networking device that groups all the devices over the network to transfer the data to another device. A switch is better than Hub as it does not broadcast the message over the network, i.e., it sends the message to the device to which it belongs. Therefore, we can say that switch sends the message directly from the source to the destination.

Cables and connectors

A cable is a transmission media that transmits the communication signals. There are three types of cables:

• Twisted pair cable: It is a high-speed cable that transmits data over 1Gbps or more.
• Coaxial cable: Coaxial cable resembles a TV installation cable. Coaxial cable is more expensive than twisted pair cable, but it provides a high data transmission speed.
• Fibre optic cable: Fibre optic cable is a high-speed cable that transmits data using light beams. It provides high data transmission speed as compared to other cables. It is more expensive compared to other cables, so it is installed at the government level.

Router

The router is a device that connects the LAN to the internet. The router is mainly used to connect distinct networks or connect the internet to multiple computers.

Modem

The modem connects the computer to the internet over the existing telephone line. A modem is not integrated with the computer motherboard. A modem is a separate part of the PC slot found on the motherboard.

Types of Computer Networks

• Local Area Network (LAN): A LAN is a network that covers an area of around 10 kilometres. For example, a college network or an office network. Depending upon the needs of the organization, a LAN can be a single office, building, or Campus. We can have two PCs and one printer in-home office or it can extend throughout the company and include audio and video devices. Each host in LAN has an identifier, an address that defines hosts in LAN. A packet sent by the host to another host carries both the source host’s and the destination host’s address.
• Metropolitan Area Network (MAN): MAN refers to a network that covers an entire city. For example: consider the cable television network.
• Wide Area Network (WAN): WAN refers to a network that connects countries or continents. For example, the Internet allows users to access a distributed system called www from anywhere around the globe.WAN interconnects connecting devices such as switches, routers, or modems. A LAN is normally privately owned by an organization that uses it.

Types of Computer Network Architecture

1. Client-Server Architecture: Client-Server Architecture is basically the architecture where the clients and the server are connected as two clients can communicate with each other and the devices present work as servers in the network.

2. Peer-to-Peer Architecture: Peer-to-Peer Architecture, computers are connected to each other and each computer is equally capable of working as there is no central server here. Each device present here can be used as a client or server.

Network Topology

The Network Topology is the layout arrangement of the different devices in a network. Common examples include Bus, Star, Mesh, Ring, and Daisy chain.

Bus Topology

Every computer and network device is connected to a single cable in a bus topology network. Linear Bus topology is defined as having exactly two terminals.

Ring Topology

The topology is named ring topology because one computer is connected to another, with the final one being connected to the first. Exactly two neighbours for each device. A signal is passed along the ring in one direction. Each ring incorporates a repeater.

Star Topology

Each device in a star topology has a dedicated point-to-point link to a central controller, which is commonly referred to as the HUB. There is no direct connection between the devices. Traffic between the devices is not allowed in this topology. As an exchange, the controller is used.

Mesh Topology

Every device in a mesh topology has dedicated point-to-point connectivity to every other device. The term “dedicated” refers to the fact that the link exclusively transports data between the two devices it links. To connect n devices, a fully connected mesh network contains n *(n-1)/2 physical channels.

Tree Topology

The topology of a tree is similar to that of a star. Nodes in a tree, like those in a star, are connected to a central hub that manages network traffic. It has a root node, which is connected to all other nodes, producing a hierarchy. Hierarchical topology is another name for it. The number of Star networks is connected via Bus in Tree Topology.

OSI Model

OSI stands for Open Systems Interconnection. It is a reference model that specifies standards for communications protocols and also the functionalities of each layer. The OSI has been developed by the International Organization For Standardization and it is 7 layer architecture. Each layer of OSI has different functions and each layer has to follow different protocols. The 7 layers are as follows:

• Physical Layer
• Data link Layer
• Network Layer
• Transport Layer
• Session Layer
• Presentation Layer
• Application Layer

Protocol

A protocol is a set of rules or algorithms which define the way how two entities can communicate across the network and there exists a different protocol defined at each layer of the OSI model. A few such protocols are TCP, IP, UDP, ARP, DHCP, FTP, and so on.

Internet

The Internet is a larger network that allows computer networks controlled by enterprises, governments, colleges, and other organizations all over the world to communicate with one another. As a result, there is a tangle of cables, computers, data centres, routers, servers, repeaters, satellites, and Wi-Fi towers that allow digital data to go around the world.

The Internet is a vast network of networks that functions as a networking infrastructure. It links millions of computers throughout the world, creating a network in which any computer can talk with any other computer as long as they are both linked to the Internet.

The Internet is a global network of interconnected computers that communicate and share information using a standardized Internet Protocol Suite.

Uses Of Computer Network

• Resource sharing: Resource sharing is the sharing of resources such as programs, printers, and data among the users on the network without the requirement of the physical location of the resource and user.
• Server-Client model: Computer networking is used in the server-client model. A server is a central computer used to store the information and maintained by the system administrator. Clients are the machines used to access the information stored in the server remotely.
• Communication medium: The computer network behaves as a communication medium among the users. For example, a company that contains more than one computer has an email system which the employees use for daily communication.
• E-commerce: A computer network is also important in businesses. We can do business over the Internet. For example, amazon.com is doing their business over the internet, i.e., they are doing their business over the internet.