Unit 1: Computer Network and Communication

Complete notes covering telecommunication basics, communication media, connectors, networking devices, topologies, network types, architecture, IP addressing, and internet/intranet/extranet, based on the CDC syllabus.

1.1 Concept of Telecommunication and Key Terminology

Telecommunication refers to the exchange of information over a distance using electronic means, such as cables, radio waves, or satellites. It’s the foundation that allows computers, phones, and other devices to communicate with each other, whether across a room or across the world.

Key Terminology

Bandwidth: the maximum amount of data that can be transmitted over a network connection in a given time, usually measured in bits per second (bps), such as Mbps (megabits per second) or Gbps (gigabits per second). A higher bandwidth means more data can pass through at once, similar to a wider road allowing more cars to travel side by side.

Throughput: the actual amount of data successfully transmitted over a network in real conditions. While bandwidth is the theoretical maximum, throughput is what you actually get, which is often lower due to network congestion, interference, or hardware limits.

Broadband: a high-speed, high-capacity internet connection that can carry large amounts of data at once, allowing multiple types of data (voice, video, text) to travel simultaneously. Common broadband types include DSL, cable, and fiber-optic connections.

3G/4G/5G: generations of mobile network technology, each offering faster speeds and better reliability than the last:

• 3G: introduced mobile internet browsing and video calling, but at relatively slow speeds
• 4G: significantly faster, enabling smooth video streaming and quicker downloads
• 5G: the newest generation, offering extremely high speeds, very low delay (latency), and support for many more connected devices at once

Data Packets: when information travels over a network, it’s broken down into small chunks called packets, sent separately, and reassembled at the destination. Each packet contains the actual data along with addressing information showing where it came from and where it’s going.

Frequency: the number of times a signal wave repeats per second, measured in Hertz (Hz). In wireless communication, different frequency bands are used to transmit signals; for example, common Wi-Fi routers operate on 2.4 GHz and 5 GHz frequency bands.

Communication Mode

Data communication is transferring data and information between computers and other electronic devices. The two types of data communication are simplex mode and duplex mode.

1.2 Communication Channel / Media

A communication channel (or medium) is the physical or wireless path through which data travels between devices. These are divided into wired and wireless media.

Wired Media

Wireless Media

Wi-Fi: a wireless technology that allows devices to connect to a network using radio waves, without physical cables, commonly used for home and office internet access.

Bluetooth: a short-range wireless technology used to connect nearby devices, such as connecting a phone to wireless earphones or a keyboard to a laptop.

RFID (Radio Frequency Identification): uses radio waves to identify and track tags attached to objects, commonly used in inventory systems, access cards, and toll payment systems.

Satellites: a method of sending information wirelessly worldwide using artificial satellites placed in outer space. It has been in use since 1965 for services like telecommunication, radio, television, and the Internet.

Guided Media	Unguided Media
Data and signals are sent through wires or cables.	Data and signals are sent through the air without wires.
Not affected by weather conditions like rain or wind.	Can be affected by weather conditions like rain or wind.
Used to connect close devices such as in a Local Area Network (LAN).	Used to connect devices far away such as in a Wide Area Network (WAN).
Provides a fixed path or direction for data.	No fixed path; data travels freely through the air.
Also called wired or guided media.	Also called wireless or unguided media.
Examples: CAT6 cable, Coaxial cable, Optical fiber.	Examples: Wi-Fi, Bluetooth, Microwave, Satellite, Infrared.

1.3 Connector: RJ45, Media Convertor

Media Converter: a device that converts one type of network signal into another, most commonly used to connect a fiber optic cable segment to a copper Ethernet cable segment (or vice versa). This allows networks using different types of cabling to communicate with each other without needing to replace the entire cabling system.

1.4 Networking Devices

Computer networks are used for the Internet, e-mail, chat, e-banking, etc. The hardware, software, and medium are components of computer network. Network Operating System (NOS) and application software are the software used as network software.

Repeater: a device that receives a network signal, strengthens (amplifies) it, and retransmits it, used to extend the range of a network when a signal would otherwise weaken over long distances.

Hub: a basic networking device that connects multiple computers together, but simply broadcasts any incoming data to all connected devices, regardless of which one it’s actually meant for. This makes hubs simple but inefficient, and they are largely outdated today.

Router: a device that connects different networks together, most commonly connecting a home or office network to the wider internet. A router directs (routes) data packets to their correct destination based on IP addresses, and often also assigns IP addresses to devices on the local network.

Device	Main Function
Repeater	Strengthens and extends a signal
Hub	Connects devices, broadcasts data to all
Switch	Connects devices, sends data only to the intended one
Bridge	Joins two network segments into one
Router	Connects different networks, directs data using IP addresses

1.5 Topologies

Network topology is the inter-connected pattern of network components. A network topology may be physical, mapping hardware configuration, or logical, mapping the path that the data must take to travel around the network. A LAN Topology is a cabling structure or pattern of computers in a local area.

Bus Topology

Features

• Simple design
• Requires less cable
• Relatively inexpensive
• Suitable for small networks
• Easy to understand

Disadvantage

• If the main cable fails, the network can be affected.

Star Topology

Features

• Easy to install
• Easy to troubleshoot
• Easy to expand
• Fast performance
• Failure of one node normally does not affect other nodes

Disadvantage

• If the central switch or hub fails, the connected network can be affected.

Ring Topology

Features

• Devices form a closed loop
• Data is transferred sequentially
• Each computer has an active role in communication
• Repeaters may be used when there are many nodes

Hybrid Topology

Features

• Flexible
• Scalable
• Can combine advantages of different topologies
• Suitable for large networks

1.6 Overview of Networks Based on Coverage

A computer network is a group of two or more computers and devices connected through wire or wireless media to exchange data and information and share hardware, software, and other resources. the interconnection of many computers to share information is called a computer network. It can share resources like scanners, printers, hard disks, operating system software, application software, etc.

Networks are also classified by how large an area they cover.

PAN (Personal Area Network)

It is used for connecting devices close to an individual, typically within a range of a few meters. The PANs are designed for personal use and facilitate communication and data sharing between devices such as smartphones, tablets etc

LAN (Local Area Network)

It is a network limited to small areas like a room, a building, a school, a college, etc. It is generally connected through wire media. It can cover up to one kilometer for transferring data and information between the computers.

Features

• Small coverage area
• High data transfer speed
• Low transmission error
• Can use wired or wireless connections

MAN (Metropolitan Area Network)

MAN covers within an area like a valley, city, metropolitan, etc. connected through wire or wireless technology or media. It covers more area than the LAN and less area than the WAN. It has a higher data transfer capacity than the WAN and is slower than the LAN.

WAN (Wide Area Network)

A Wide Area Network is a network that is extended to a large geographical area in which computers are connected through wireless technology or media as satellite communication. It is the largest computer network. Internet, 4G Mobile Broadband Systems, and satellite communication are the best examples of the WAN.

Network Type	Typical Coverage
PAN	A few meters (around one person)
LAN	A single building or school
MAN	A city or large campus
WAN	Countries or continents (e. g. the internet)

1.7 Network Architecture

Network architecture defines how the computer communicates and interact with each other on the network. It is the combined form of topologies and data transmission modes between the different computers in the network. The two types of network architecture are:

Client-Server Architecture

Features

• Centralized control
• Centralized backup is possible
• Better management
• Better security through centralized administration
• Suitable for larger networks

Peer-to-Peer (P2P) Architecture

Features

• Simple to set up
• Low cost
• No dedicated server required
• Suitable for small networks
• Each user can control their shared resources

Network Protocols

A set of rules followed for interconnection and communication between computers in a network is called a protocol.

1. TCP/IP (Transmission Control Protocol/Internet Protocol) is used on the Internet.
2. HTTP (Hypertext Transfer Protocol) is used to transfer HTML documents in WWW.
3. HTTPS (Hypertext Transfer Protocol Secure) is a secure way to send and receive information on websites, protecting your data from hackers.
4. DHCP (Dynamic Host Configuration Protocol) is a system that automatically gives devices on a network an IP address so they can connect to the internet.
5. SMTP (Simple Mail Transfer Protocol) is used in sending e-mail.
6. FTP (File Transfer Protocol) is used to transmit files between computers

1.8 Concept of IP Addressing

An IP address (Internet Protocol address) is a unique numerical label assigned to every device connected to a network, allowing devices to identify and communicate with each other, similar to how a house address allows mail to reach the correct destination.

IPv4

IPv4 is the older and still widely used version of IP addressing, written as four numbers (each from 0 to 255) separated by dots. E.g 192.168.1.1 IPv4 can support around 4.3 billion unique addresses, which sounded like a huge number when it was designed, but has become insufficient given the massive growth in internet-connected devices worldwide.

IPv6

IPv6 is the newer version, designed to solve IPv4’s address shortage. It uses a much longer format, written as eight groups of hexadecimal numbers separated by colons. E.g 2001:0db8:85a3:0000:0000:8a2e:0370:7334 IPv6 provides an enormously larger number of possible addresses, ensuring that every device in the world, now and in the future, can have its own unique address.

IPv4	IPv6
32-bit address	128-bit address
Written in decimal, separated by dots	Written in hexadecimal, separated by colons
About 4.3 billion addresses	Vastly larger address space

1.9 Concept of Internet, Intranet, and Extranet

Internet: a global network connecting millions of smaller networks and devices worldwide, open and accessible to the public.

Intranet: a private network, based on the same technology as the internet, but restricted for use within a single organization, such as a school or company. It’s used to share internal resources, documents, or announcements only among authorized members, and is not accessible to the general public.

Extranet: an extension of an intranet that allows limited, controlled access to selected outside parties, such as suppliers, business partners, or specific clients, while still keeping the rest of the network private. It sits between a fully private intranet and the fully open internet.

Network	Who Can Access It
Internet	Everyone, worldwide
Intranet	Only members of one organization
Extranet	Organization members plus select outside partners

Here we have compariosn table of Internet, Intranet and Extranet

Published July 2026. Last verified and updated: September 2026.