What is a Network?
Definition and Fundamentals

Definition:
A network is a collection of two or more computing devices (such as computers, servers, printers, smartphones, etc.) interconnected using communication links and protocols to share resources, exchange data, and enable communication.

What Constitutes a Computer Network?

At least two devices (nodes) capable of communicating.
Devices connected via physical media (cables, fiber) or wireless media (Wi-Fi, Bluetooth).
Protocols define how communication and data exchange occur.

class="highlight"> Example:
In an office, five computers are connected to a central switch using Ethernet cables. These computers share files and a printer, forming a simple Local Area Network (LAN).

Components Involved

Category	Examples	Description
Devices (Hosts)	Computers, servers, laptops, printers, phones	Endpoints that generate, receive, or store data
Networking Devices	Switches, routers, hubs, APs, firewalls, modems	Connect and manage network traffic
Links	Ethernet cables, fiber optics, Wi-Fi, infrared	Physical or wireless channels for data transfer
Protocols	TCP/IP, HTTP, FTP, DHCP, DNS	Rules for data exchange and communication

Purpose of Networking

Sharing Resources: Access shared printers, files, software, and Internet connections.
Communication and Collaboration: Email, chat, video conferencing, VoIP.
Centralized Management: Backups, updates, and security controls are streamlined.

Example:

  In a university, students submit assignments via a network file server accessible to all.

Types of Data Transmitted

Data: Text, spreadsheets, code, etc.
Voice: VoIP calls, telephony
Video: Streaming, video conferencing
Multimedia: Images, audio, and video combined

Example:

  A video call (Zoom/Teams) transmits voice and video data over the network.

Network Architecture

Model	Description	Example
Client-Server	Clients request resources/services from central servers	Workstations access files from a file server
Peer-to-Peer (P2P)	All devices act as both clients and servers	File sharing between two laptops
Centralized	Control/resources managed centrally	Traditional enterprise network
Decentralized	Control is distributed among devices	P2P applications, blockchain

Physical and Logical Connections

Physical Topology: How devices are physically connected (star, bus, ring, mesh).
Logical Topology: How data flows, may differ from physical layout.
Media Types: Wired (twisted pair, coax, fiber optic), wireless (Wi-Fi, Bluetooth).

Example:

  A star physical topology uses a central switch, but logically, all communication is between end devices through the switch.

Key Network Elements

Element	Role
Host	Generates/receives data (PCs, servers, phones)
Switch	Connects devices in LAN; forwards frames based on MAC
Router	Connects multiple networks, forwards packets based on IP
Access Point	Provides wireless connectivity
Firewall	Enforces security, controls access

Example:

  A home network might have a router (for internet), a switch (wired PCs), and Wi-Fi APs (wireless devices).

Network Protocols

Protocols are sets of rules for transmitting and receiving data.
Common Examples:
- TCP/IP: Core of Internet & LANs
- HTTP: Web browsing
- FTP: File transfers
- SMTP: Email
- DHCP: Dynamic IP assignment
- DNS: Name resolution

Example:

  When you open a website, your computer uses HTTP to talk to the web server and DNS to resolve the domain name.

Benefits of Networking

Efficiency: Share resources, reduce duplication
Scalability: Easily add more devices and users
Flexibility: Access data and applications anywhere
Cost-effectiveness: Share expensive resources
Centralized Security: Simpler to implement/manage

Network Boundaries

Internal Networks: Inside a company, home, or organization
External Networks: Connected to outside world (Internet)
Scope & Scale: Small (LAN/PAN), Medium (MAN/CAN), Large (WAN/Internet)

Evolution of Networks

Era	Milestone	Impact
1960s	ARPANET	First network, Internet foundation
1980s–1990s	Ethernet, LANs, client-server	PC networking becomes mainstream
2000s–Now	Wireless, cloud, IoT	Always-on, everywhere connectivity

Exam Tips & Key Points

Understand network definitions and purposes
Identify key components: devices, media, protocols
Understand switch, router, AP, firewall roles
Differentiate client-server vs. peer-to-peer
Distinguish physical vs. logical topology
Know protocol functions and examples
Connect scenarios to real-world networks

Practical Example

Scenario:

  A small business has 10 computers, a shared printer, a file server, and Wi-Fi for mobile devices.

  The computers and printer connect to a switch.

  The switch connects to a router for Internet.

  The router provides Wi-Fi via an integrated AP.

  This enables resource sharing, Internet access, and centralized security—a classic network in practice.

1. What is the basic definition of a network?

A. A single device connected to the Internet B. A software program for sharing files C. Two or more devices connected to share resources and communicate D. A type of server that manages email

Correct answer is C. A network connects multiple devices to share resources and enable communication.

2. Which device is commonly used to connect multiple devices in a Local Area Network (LAN)?

A. Switch B. Router C. Modem D. Firewall

Correct answer is A. Switches connect devices within the same LAN.

3. What is a key function of a router?

A. Forward frames based on MAC addresses B. Provide wireless access C. Encrypt data packets D. Connect different networks and forward packets based on IP addresses

Correct answer is D. Routers connect multiple networks and route packets by IP.

4. Which protocol is fundamental for the Internet and most modern networks?

A. FTP B. TCP/IP C. SMTP D. HTTP

Correct answer is B. TCP/IP is the core protocol suite for Internet communications.

5. What is the difference between Client-Server and Peer-to-Peer models?

A. Client-server networks do not use servers B. Peer-to-peer networks require centralized servers C. Client-server has dedicated servers, peer-to-peer has equal devices acting as clients and servers D. Peer-to-peer networks are always faster

Correct answer is C. Client-server uses centralized servers, peer-to-peer devices are equal.

6. What type of physical media is commonly used in wired LANs?

A. Copper Ethernet cables B. Infrared signals C. Bluetooth D. Wi-Fi

Correct answer is A. Copper Ethernet cables are widely used wired media in LANs.

7. What is the primary purpose of network protocols?

A. Encrypt data for security B. Define rules for data transmission and communication C. Assign IP addresses D. Provide physical connections

Correct answer is B. Protocols establish how data is transmitted and received.

8. Which of the following is NOT a typical benefit of networking?

A. Sharing expensive resources B. Centralized security management C. Flexibility to access data anywhere in the network D. Guaranteed elimination of all network errors

Correct answer is D. Networking improves many areas but cannot guarantee elimination of all errors.

9. What kind of network boundary is defined by a company’s internal network?

A. External network B. Internet C. Internal network D. WAN

Correct answer is C. The internal network is within an organization or company.

10. What model describes a network where all devices are equal and can act as both clients and servers?

A. Client-server model B. Peer-to-peer model C. Centralized model D. Distributed model

Correct answer is B. Peer-to-peer networks have equal devices acting as clients and servers.

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What is a Network? Definition and Fundamentals