LECTURE 7 IN COMPUTER SCIENCE ENGINEERING

Lecture 7: Computer Networks

In today’s interconnected world, Computer Networks form the foundation of communication between systems. From browsing the internet to sending emails, from streaming videos to cloud computing, networking makes it all possible. This lecture covers the fundamentals, architecture, types, and protocols of computer networks.

1. Definition of Computer Networks

A Computer Network is a collection of interconnected computers and devices that can communicate, share resources, and exchange data using transmission media (wired or wireless).

2. Components of a Network

Nodes – Computers, printers, or any device connected to the network.
Transmission Media – Cables, optical fibers, or wireless signals.
Network Devices – Routers, switches, hubs, and access points.
Protocols – Rules governing communication (e.g., TCP/IP).
Software – Network Operating Systems and applications.

3. Types of Networks

LAN (Local Area Network) – Covers a small geographical area like an office or school.
WAN (Wide Area Network) – Covers large areas; the Internet is the largest WAN.
MAN (Metropolitan Area Network) – Spans a city or large campus.
WLAN (Wireless LAN) – Uses Wi-Fi for wireless connectivity.
PAN (Personal Area Network) – Connects personal devices (Bluetooth, hotspot).

4. Network Topologies

Network topology defines the arrangement of devices in a network.

Bus Topology – All devices connected to a single backbone cable.
Star Topology – All nodes connected to a central hub or switch.
Ring Topology – Each node connects to two others, forming a circle.
Mesh Topology – Every device connects directly to others (high redundancy).
Hybrid Topology – Combination of two or more topologies.

5. OSI Model (Open Systems Interconnection)

The OSI Model is a conceptual framework that standardizes how data is transmitted across a network in 7 layers:

Physical Layer – Transmission of raw bits (cables, signals).
Data Link Layer – Error detection, MAC addressing.
Network Layer – Routing (IP addresses).
Transport Layer – Reliable delivery (TCP, UDP).
Session Layer – Manages sessions between applications.
Presentation Layer – Data translation, encryption.
Application Layer – Interfaces with user applications (HTTP, FTP, SMTP).

6. TCP/IP Model

The TCP/IP Model is the practical model used in the Internet today. It has 4 layers:

Network Access Layer – Physical hardware and data link protocols.
Internet Layer – IP addressing and routing.
Transport Layer – Ensures reliability (TCP) or speed (UDP).
Application Layer – Protocols like HTTP, FTP, SMTP, DNS.

7. Common Networking Devices

Router – Connects multiple networks and directs data packets.
Switch – Connects devices in a LAN and forwards data intelligently.
Hub – Basic device that broadcasts data to all connected devices.
Access Point – Provides wireless connectivity.
Firewall – Monitors and filters network traffic for security.

8. Network Security

Since networks are prone to cyber threats, security measures are critical:

Encryption – Protects data in transit.
Authentication – Ensures only authorized users access resources.
Firewalls – Block malicious traffic.
Antivirus and IDS/IPS – Detect and prevent intrusions.
VPN (Virtual Private Network) – Secures remote connections.

9. Applications of Computer Networks

Internet Browsing – Accessing websites and online services.
Email & Messaging – Fast global communication.
Cloud Computing – Remote storage and services.
Video Conferencing – Remote meetings and education.
IoT (Internet of Things) – Connecting smart devices.

“Computer Networks are the nervous system of the digital world — connecting people, devices, and systems across the globe.”

10. Summary of Key Points

A computer network enables communication and resource sharing between devices.
Networks are classified into LAN, WAN, MAN, WLAN, and PAN.
Topologies define physical and logical arrangements of networks.
The OSI and TCP/IP models standardize data transmission.
Routers, switches, hubs, and firewalls are essential networking devices.
Network security ensures safe communication.
Applications include internet browsing, cloud services, and IoT.

✦ Lecture 7 prepared under the authority of English Master Institute (EMI) Worldwide ✦

LECTURE 8 IN COMPUTER SCIENCE ENGINEERING