LECTURE 12 IN COMPUTER SCIENCE ENGINEERING

Lecture 12: Computer Networks

In this lecture, we will study Computer Networks, which allow multiple computers and devices to communicate and share resources. Networking forms the backbone of the modern digital world, enabling the Internet, email, cloud computing, and distributed applications.

1. Introduction to Computer Networks

A computer network is a collection of interconnected devices (computers, servers, routers, etc.) that share data and resources through communication channels. Networks enable file sharing, messaging, remote access, and collaboration.

2. Components of a Network

Nodes: Devices such as computers, servers, printers.
Transmission Medium: Wired (Ethernet, fiber optic) or wireless (Wi-Fi, Bluetooth).
Network Devices: Routers, switches, hubs, modems, firewalls.
Protocols: Rules for communication (e.g., TCP/IP, HTTP, FTP).

3. Types of Networks

LAN (Local Area Network): Covers a small geographic area, like an office or building.
MAN (Metropolitan Area Network): Covers a city or campus.
WAN (Wide Area Network): Spans large areas, e.g., the Internet.
WLAN: Wireless LAN using Wi-Fi.
VPN (Virtual Private Network): Secure connection over the Internet.

4. Network Topologies

A topology defines the arrangement of devices in a network.

Bus: All devices connected to a single communication line.
Star: All devices connected to a central hub or switch.
Ring: Devices connected in a circular path.
Mesh: Every device connected to every other device.
Hybrid: Combination of two or more topologies.

5. Network Models

OSI Model (7 Layers): Physical, Data Link, Network, Transport, Session, Presentation, Application.
TCP/IP Model (4 Layers): Network Access, Internet, Transport, Application.

These models provide a framework for understanding and standardizing communication.

6. Common Network Protocols

HTTP/HTTPS: Web communication.
FTP: File transfer.
SMTP/IMAP/POP3: Email communication.
DNS: Domain name resolution.
DHCP: Automatic IP addressing.
TCP/IP: Core protocol suite of the Internet.

7. IP Addressing

An IP Address uniquely identifies devices in a network.

IPv4: 32-bit address (e.g., 192.168.1.1).
IPv6: 128-bit address for larger address space (e.g., 2001:0db8::1).

8. Wireless and Mobile Networking

Wi-Fi: Wireless LAN using radio signals.
Bluetooth: Short-range device communication.
Cellular Networks: 3G, 4G, 5G mobile communication.
Ad Hoc Networks: Temporary peer-to-peer connections.

9. Network Security

Ensuring safe data transmission is critical. Techniques include:

Encryption (SSL/TLS, VPNs).
Firewalls and Intrusion Detection Systems (IDS).
User authentication and access control.
Preventing attacks (DDoS, phishing, malware).

10. Applications of Networking

Internet access and web services.
Cloud computing and storage.
Email and instant messaging.
Online gaming and streaming.
IoT (Internet of Things) devices.

11. Summary

Computer networks connect devices to share data and resources.
Different types include LAN, MAN, WAN, and VPN.
Topologies define the physical or logical arrangement of devices.
OSI and TCP/IP models standardize communication layers.
Security is vital for protecting data against cyber threats.

Next Lecture (13): Database Systems

LECTURE 13 IN COMPUTER SCIENCE ENGINEERING