Introduction of Computer Networks

By Anand Pandey|Updated : December 3rd, 2021
  • Computer Network is a collection of computers that are able to communicate with each other through some medium, using hardware and software.
  • Two computers are said to be connected if they are able to exchange information or able to communicate.
  • The network is connected by the set of nodes via communication links where a node can be any device capable of sending &/or receiving data to &/or from other nodes in the network.
  • Data Source: Provides the data to transmit.
  • Sender (Transmitter): Converts data to signals for transmission.
  • Data Transmission System: Transmits the data i.e., converted in signals.
  • Receiver: Converts received signals to data.
  • Destination: Receives and uses incoming data.
  • Node: A device with independent communication ability and a unique network address.
  • Protocol: A formal description, comprising rules and conventions defines the method of communication between networking devices.

Components of a Network: There are five basic components of a network. Clients, Servers, Channels, Interface Devices, and Operating Systems.

Methods of Message Delivery: A message can be delivered in the following ways

  • Unicast: One device sends a message to the other to its address.
  • Broadcast: One device sends messages to all other devices on the network. The message is sent to an address reserved for this goal.
  • Multicast: One device sends messages to a certain group of devices on the network.

Types of Networks: Mainly three types of networks based on their coverage areas: LAN, MAN, and WAN.

  • LAN : It is a local area network typically interconnects hosts that are up to a few or maybe a few tens of kilo meters apart.
  • MAN : It is a metropolitan area network typically interconnects devices that are up to a few hundred kilo meters apart
  • WAN : It is a wide area network interconnect hosts that can be located anywhere on Earth
LAN (Local Area Network)
  • LAN is privately owned network within a single building or campus.
  • LANs can be small, linking as few as three computers, but often link hundreds of computers used by thousands of people (like in some IT office, etc.)
  • Examples of LAN technology: Ethernet, Token Ring, and Fibber Distributed Data Interconnect (FDDI).

MAN (Metropolitan Area Network)
  • A MAN covers a city.
  • An example of MAN is cable television network in city.
  • It may be a single network such as cable TV network by means of connecting a number of LANs into a larger network.
  • Resources may be shared LAN to LAN as well as device to device.
  • A MAN can be owned by a private company or it may be a service provided by a public company such as local telephone company.
  • Telephone companies provide a popular MAN service called (SMDS) Switched Multi-megabit Data Services.

WAN (Wide Area Network)
  • A wide area network or WAN spans a large geographical area often a country.
  • Internet It is also known as network of networks.
  • The Internet is a system of linked networks that are world wide in scope and facilitate data communication services such as remote login, file transfer, electronic mail, World Wide Web and newsgroups etc.

Characteristics of Networking:
  • Topology: The geometrical arrangement of the computers or nodes.
  • Protocols: How they communicate.
  • Medium: Through which medium.
Network Topology
  • Network topology is the arrangement of the various elements of a computer or biological network.
  • Essentially it is the topological structure of a network, and may be depicted physically or logically.
  • Physical topology refers to the placement of the network's various components, inducing device location and cable installation, while logical topology shows how data flows within a network, regardless of its physical design.
  • Network topology can be classified as Bus topology, Star topology, Ring topology, Mesh topology, and Tree topology.

Bus Topology: In bus topology, each node is directly connected to a common cable. 
  • In bus topology at the first, the message will go through the bus then one user can communicate with other.
  • The drawback of this topology is that if the network cable breaks, the entire network will be down.

Star Topology: In this topology, each node has a dedicated set of wires connecting it to a central network hub. Since, all traffic passes through' the hub, it becomes a central point for isolating network problems and gathering network statistics.


Ring Topology: A ring 'topology features a logically closed loop. Data packets travel in a single direction around the ring from one network device to the next. Each network device acts as a repeater to keep the signal strong enough as it travels.
Mesh Topology: In mesh topology, each system is connected to all other systems in the network.
  • In bus topology at the first, the message will go through the bus then one user can communicate with other.
  • In star topology, first the message will go to the hub then that message will go to other user.
  • In ring topology, user can communicate as randomly.
  • In mesh topology, any user can directly communicate with other users.
Tree Topology: In this type of network topology, in which a central root is connected to two or more nodes that are one level lower in hierarchy.


Hardware/Networking Devices: Networking hardware may also be known as network equipment computer networking devices.
  • Network Interface Card (NIC):
    • NIC provides a physical connection between the networking cable and the computer's internal bus.
    • Each computer on a network must have a network card.
    • NICs come in three basic varieties 8 bit, 16 bit and 32 bit.
    • The larger number of bits that can be transferred to NIC, the faster the NIC can transfer data to network cable.
  • Repeater:
    • Repeaters are used to connect together two Ethernet segments of any media type.
    • In larger designs, signal quality begins to deteriorate as segments exceed their maximum length.
    • Signal transmission is always attached with energy loss. So, a periodic refreshing of the signals is required.
  • Hubs:
    • A hub is a device used to connect a PC to the network
    • Hubs are actually multiport repeaters.
    • A hub takes any incoming signal and repeats it out all ports.
  • Bridges:
    • When the size of the LAN is difficult to manage, it is necessary to breakup the network.
    • The function of the bridge is to connect separate networks together.
    • Bridges do not forward bad or misaligned packets.
  • Switch:
    • Switches are an expansion of the concept of bridging.
    • Switches are used to connect multiple devices on the same network within a building or campus. 
    • Cut through switches examine the packet destination address, only before forwarding it onto its destination segment, while a store and forward switch accepts and analyzes the entire packet before forwarding it to its destination.
    • It takes more time to examine the entire packet, but it allows catching certain packet errors and keeping them from propagating through the network.
  • Routers: 
    • Routers are used to tie multiple networks together.
    • Router forwards packets from one LAN (or WAN) network to another.
    • It is also used at the edges of the networks to connect to the Internet. 
    • Routers analyze the data being sent over a network, change how it is packaged, and send it to another network, or over a different type of network. 
  • Gateway:
    • Gateway acts like an entrance between two different networks.
    • Gateway in organisations is the computer that routes the traffic from a work station to the outside network that is serving web pages.
    • ISP (Internet Service Provider) is the gateway for Internet service at homes.

Types of Internet Connections

  • Broadband: 
    • Broadband internet connections provide high-speed internet that is always on and allows for more data to be transmitted than the traditional dial-up connections.
    • Unlike dial-up services, it does not block phone lines and you do not have to reconnect to the network each time you log off.
    • There are various types of broadband technologies, including digital subscriber line (DSL), cable modems, fibers, wireless broadband connections, and Satellite connections.
  • Wi-Fi:
    • Wi-Fi is a play on the term Hi-Fi and represents a wireless internet connection.
    • More specifically, it is a wireless local area network (WLAN) that allows devices to connect wirelessly to the internet.
    • It utilizes 2.4 GHz and 5.0 GHz radio waves to connect Wi-Fi enabled gadgets (computers, gaming systems, mobile phones, and even some cameras) to the internet without the need for cumbersome wires.
  • WiMAX:
    • WiMAX is a more advanced form of wireless internet technology than Wi-Fi.
    • It aims to provide the high speeds of broadband connections, the large coverage of phone networks, and the convenience of Wi-Fi into one package.
    • The implementation of WiMAX would allow DSL and cable modem users to ditch their wired internet connections in favor of a high-speed, wireless alternative.

Data Transfer Modes: There are mainly three modes of data transfer.

  • Simplex: Data transfer only in one direction e.g., radio broadcasting.
  • Half Duplex: Data transfer in both direction, but not simultaneously e.g., talk back radio.
  • Full Duplex or Duplex: Data transfer in both directions, simultaneously e.g., telephone

Data representation: Information comes in different forms such as text, numbers, images, audio and video.

  • Text: Text is represented as a bit pattern. The number of bits in a pattern depends on the number of symbols in the language.
  • ASCII: The American National Standards Institute developed a code called the American Standard code for Information Interchange .This code uses 7 bits for each symbol.
  • Extended ASCII: To make the size of each pattern 1 byte (8 bits), the ASCII bit patterns are augmented with an extra 0 at the left.
  • Unicode: To represent symbols belonging to languages other than English, a code with much greater capacity is needed. Unicode uses 16 bits and can represent up to 65,536 symbols.
  • ISO: The international organization for standardization known as ISO has designed a code using a 32-bit pattern. This code can represent up to 4,294,967,296 symbols.
  • Numbers: Numbers are also represented by using bit patterns. ASCII is not used to represent numbers. The number is directly converted to a binary number.
  • Images: Images are also represented by bit patterns. An image is divided into a matrix of pixels, where each pixel is a small dot. Each pixel is assigned a bit pattern. The size and value of the pattern depends on the image. The size of the pixel depends on what is called the resolution.
  • Audio: Audio is a representation of sound. Audio is by nature different from text, numbers or images. It is continuous not discrete
  • Video: Video can be produced either a continuous entity or it can be a combination of images.
Classification of Networks: Networks are classified into the following types.
  1. Peer-to-peer networks:
    • All computers on a peer-to-peer network can be considered equal.
    • Peer-to-peer networks are popular as home networks and for use in small companies because they are inexpensive and easy to install.
    • Most operating systems (the software that runs the basic computer functionality) come with peer-to-peer networking capability built in.
  2. Server-based networks:
    • A dedicated server is one that, for all practical purposes, operates solely as a server.
    • A dedicated server on a server-based network services its network clients by storing data, applications, and other resources, and then providing access to those resources when called for by a client.
    • When a client requests a resource such as a document, the server sends the whole resource (the document) over the network to the client, where it is processed and later returned to the server for continued storage.
    • Server-based networks offer central control and are designed for secured operations.
  3. Client-based networks:
    • A client-based network takes better advantage of the server’s powerful processors and of the increasingly powerful computers used in typical workstations.
    • A clientbased network utilizes a client workstation’s power in processing some functions locally while requesting additional processing from a server whenever it is needed for increased speed.
  • It define the rules that govern the communications between two computers connected to the network.
  • Roles include addressing and routing of messages, error detection and recovery, sequence and flow controls etc.
  • A protocol specification consists of the syntax, which defines the kinds and formats of the messages exchanged, and the semantic, which specifies the action taken by each entity when specific events occur.
  • Protocols are designed based on a layered architecture such as the OSI reference model.
  • Example: HTTP protocol for communication between web browsers and servers.

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