Introduction to Computer Networks

Main Idea

Computer networks connect devices so that they can communicate and share data, hardware, software, and services. They are classified by geographical coverage and depend on transmission media, networking devices, addressing systems, and protocols. The Internet is a worldwide network that supports services including the World Wide Web, email, file transfer, cloud computing, and online communication. Effective network use also requires security measures and responsible behaviour to protect devices, data, accounts, and communications.

Key Concepts and Definitions

• Computer Network: A group of interconnected computers and devices that communicate and share resources.
• Node: Any device connected to a network, such as a computer, printer, smartphone, or server.
• PAN: Personal Area Network, a small network around an individual, such as a phone connected to wireless earbuds.
• LAN: Local Area Network, a network covering a limited area such as a classroom, office, or building.
• MAN: Metropolitan Area Network, a network covering a city or a large campus.
• WAN: Wide Area Network, a network covering large geographical areas; the Internet is the largest example.
• Internet: A worldwide interconnection of computer networks that communicate using common protocols.
• Intranet: A private network used within an organization.
• Extranet: A private network that provides limited access to authorized external users.
• Network Topology: The physical or logical arrangement of devices and connections in a network.
• Bus Topology: A topology in which all devices share a single main communication cable.
• Star Topology: A topology in which all devices connect to a central hub or switch.
• Ring Topology: A topology in which each device is connected to two neighboring devices, forming a closed loop.
• Mesh Topology: A topology in which devices have multiple interconnections, providing high reliability.
• Transmission Media: The path through which data travels between devices.
• Twisted Pair Cable: A wired medium made of twisted copper wires, commonly used in LANs.
• Coaxial Cable: A cable with a central conductor and protective shielding, used for communication and cable television.
• Optical Fiber: A medium that transmits data as light through thin glass or plastic fibers; it offers high speed and low signal loss.
• Radio Wave: A wireless communication medium used by technologies such as Wi-Fi and mobile networks.
• Network Interface Card: Hardware that enables a device to connect to a network.
• Hub: A basic device that sends incoming data to all connected devices.
• Switch: A device that forwards data to the intended device using its hardware address.
• Router: A device that connects different networks and selects suitable paths for data packets.
• Modem: A device that converts signals between a computer or network and a communication service.
• Repeater: A device that regenerates or strengthens signals to extend network distance.
• Gateway: A device or system that connects networks using different communication methods.
• Access Point: A device that allows wireless devices to connect to a wired network.
• Protocol: A set of rules that governs communication between devices.
• TCP/IP: The main protocol suite used for communication over the Internet; TCP manages reliable delivery and IP handles addressing and routing.
• HTTP: A protocol used to transfer web pages and other web resources.
• HTTPS: A secure version of HTTP that encrypts communication between a browser and a web server.
• FTP: A protocol used to transfer files between computers over a network.
• SMTP: A protocol used to send email messages.
• POP3: A protocol used to download email messages from a mail server.
• IMAP: A protocol used to access and manage email while keeping messages on the mail server.
• DNS: Domain Name System, which converts domain names such as example.com into IP addresses.
• IP Address: A numerical address that identifies a device or network interface; IPv4 uses 32 bits and IPv6 uses 128 bits.
• MAC Address: A hardware address assigned to a network interface, generally used for communication within a local network.
• URL: Uniform Resource Locator, the address used to locate a resource on the web.
• Web Browser: Software used to access and display web pages.
• Web Server: A computer or software system that stores and delivers web resources to clients.
• World Wide Web: A collection of interlinked web pages and resources accessed through the Internet using web browsers.
• Search Engine: An online service that indexes web content and helps users find information.
• Cloud Computing: The use of computing resources such as storage, software, and processing through Internet-based services.
• Bandwidth: The maximum amount of data that can be transmitted through a communication channel per unit of time.
• Data Transfer Rate: The amount of data transmitted per second, commonly measured in bits per second, such as Mbps or Gbps.
• Latency: The time delay between sending data and receiving a response.
• Packet: A small unit into which data is divided for transmission across a network.
• Firewall: Hardware or software that monitors and controls network traffic according to security rules.
• Malware: Malicious software such as viruses, worms, spyware, ransomware, and trojans.
• Phishing: A fraud technique in which attackers use fake messages or websites to steal sensitive information.
• Authentication: The process of verifying the identity of a user or device.
• Encryption: The process of converting readable data into an unreadable form that can be restored using a key.
• Digital Certificate: An electronic credential used to verify the identity of a website or organization and support secure communication.
• Network Safety: Practices that protect systems and information, including strong passwords, updates, secure connections, backups, and careful online behaviour.

Supporting Arguments and Evidence

• Purpose and benefits of networking: A network enables resource sharing, communication, centralized management, reliability, and access to shared services. Its basic communication process is:

sender → transmission medium → receiver

Protocols control addressing, formatting, timing, and error handling during this process.

• Classification by geographical coverage: Networks are mainly categorized as PAN, LAN, MAN, or WAN according to geographical area. A PAN operates around an individual, a LAN covers a classroom, office, or building, a MAN covers a city or large campus, and a WAN covers large geographical areas. The Internet is the largest example of a WAN.

• Topologies and reliability: Common topologies include bus, star, ring, and mesh. In a bus topology, all devices share one main cable. In a star topology, devices connect to a central hub or switch. In a ring topology, devices form a closed loop, while a mesh topology provides multiple interconnections and high reliability. Star topology is widely used because failure of one individual cable usually affects only one device; however, failure of the central device can affect the entire network.

• Transmission media: Wired media, including twisted pair cable, coaxial cable, and optical fiber, generally provide stable and fast communication. Wireless media, such as radio waves used by Wi-Fi and mobile networks, offer mobility and easier installation but may be affected by interference and security risks.

• Roles of networking devices: A hub broadcasts incoming data to all ports, whereas a switch generally forwards data only to the destination device using its hardware address. A router connects separate networks and forwards packets using IP addresses. A modem converts signals between a computer or network and a communication service. Repeaters regenerate or strengthen signals, gateways connect networks using different communication methods, and access points allow wireless devices to connect to a wired network. A Network Interface Card enables a device to connect to a network.

• Protocols and Internet communication: Protocols ensure that devices follow common rules for formatting, addressing, transmitting, receiving, and interpreting data. TCP provides reliable, ordered delivery of data, while IP provides logical addressing and routing. Common protocols and their usual ports include HTTP on port 80, HTTPS on port 443, FTP on ports 20 and 21, SMTP on port 25, and DNS on port 53. HTTP transfers web pages and other web resources, HTTPS encrypts browser–web server communication, FTP transfers files, SMTP sends email, POP3 downloads email, and IMAP manages email while retaining messages on the mail server.

• Addressing and naming: IPv4 addresses contain 32 bits and are commonly written in dotted-decimal form, for example 192.168.1.10. IPv6 addresses contain 128 bits and are written in hexadecimal groups. A MAC Address identifies a network interface for communication within a local network, whereas an IP Address identifies a device or network interface for logical addressing and routing. A domain name is easier for people to remember, while DNS converts names such as example.com into the IP addresses required by network devices. A URL identifies the location of a web resource.

• The Web and Internet services: The Internet is the global network infrastructure, whereas the World Wide Web is one service operating on it. Web browsers access and display web pages, web servers store and deliver web resources, and search engines index web content. Internet-based services include email, web browsing, video conferencing, online banking, e-learning, cloud storage, and file sharing. Cloud computing provides storage, software, and processing through Internet-based services.

• Network performance: A packet is a small unit into which data is divided for transmission. The relevant relationship is:

Data transfer rate = amount of data transferred / time taken

One byte equals eight bits:

1 byte = 8 bits

Network speeds are commonly expressed in bits per second, including Kbps, Mbps, and Gbps. Bandwidth describes the maximum capacity of a channel, whereas throughput is the actual data rate achieved in practice. Latency measures delay and is distinct from bandwidth.

• Security threats and controls: Network security protects devices, data, accounts, and communication from unauthorized access, malware, fraud, and other threats. Malware includes viruses, worms, spyware, ransomware, and trojans. Phishing uses fraudulent messages or websites to obtain sensitive information. Firewalls monitor and control traffic according to security rules, authentication verifies identity, encryption protects readable data by converting it into an unreadable form, and digital certificates help verify websites or organizations and support secure communication.

• Safe and responsible network use: Important safety measures include using long, unique passwords; enabling multi-factor authentication; installing security updates; using antivirus protection; checking HTTPS and website addresses; avoiding suspicious links and attachments; and maintaining backups. Public Wi-Fi may be unsafe, so sensitive activities should use trusted networks and secure connections. Confidentiality prevents unauthorized viewing, integrity prevents unauthorized change, and availability ensures that authorized users can access information when required. Responsible Internet use also involves respecting privacy, following cyber laws and institutional policies, avoiding plagiarism, verifying sources, protecting personal data, and reporting harmful or suspicious activity.

What to Remember

Computer networks connect devices and provide communication and resource sharing through suitable media, devices, addresses, and protocols. For examinations, distinguish the network types, topologies, device functions, TCP/IP roles, protocol ports, IPv4 and IPv6, bandwidth, throughput, and latency. Network security depends on both technical controls such as firewalls and encryption and responsible user behaviour, including authentication, safe browsing, secure connections, backups, and ethical Internet use.