Theory

A computer network is a collection of interconnected devices that communicate and share resources.

Goals: Resource sharing, high reliability, cost efficiency, scalability, communication.

Types of Networks

• LAN (Local Area Network): Covers small area (Ex: office)

• MAN (Metropolitan Area Network): Covers city-wide

• WAN (Wide Area Network): Covers large geographic areas (Ex: internet)

Network Topologies

• Bus, Star, Ring, Mesh, Hybrid

• Star is most widely used due to simplicity and fault tolerance.

OSI Reference Model

Seven layers: Physical, Data Link, Network, Transport, Session, Presentation, Application

• Each layer serves a specific function in the data transmission process.

TCP/IP Model

4 Layers: Network Interface, Internet, Transport, Application

• Protocols: IP, TCP, UDP, FTP, HTTP, DNS, etc.

Transmission Media

• Guided: Twisted pair, Coaxial, Fiber optic

• Unguided: Radio waves, Microwaves, Infrared

Networking Devices

• Hub: Broadcasts to all ports

• Switch: Forwards based on MAC address

• Router: Forwards based on IP

• Bridge: Connects LAN segments

• Modem: Converts digital to analog

IP Addressing

• IPv4: 32-bit, e.g., 192.168.0.1

• IPv6: 128-bit, e.g., 2001:0db8::1

• Public vs Private addresses

Protocols and Services

• HTTP/HTTPS, FTP, SMTP, POP3, IMAP

• DNS: Resolves domain names to IP addresses

• DHCP: Assigns IP addresses dynamically

Switching Techniques

• Circuit Switching: Reserved path

• Packet Switching: Data in packets

• Message Switching: Store and forward

Error Detection and Correction

• Techniques: Parity bits, Checksum, CRC

• Used at Data Link Layer to ensure integrity

Congestion and Flow Control

• Congestion: Network overload

• Flow control: Prevent fast sender from overwhelming receiver (e.g., TCP sliding window)

Networking Models

• Client-Server Model: Centralized

• Peer-to-Peer Model: Decentralized

Future Trends in Networking

• Internet of Things (IoT)

• 5G Networks

• Software Defined Networking (SDN)

• Network Function Virtualization (NFV)

Unit-1

Important Questions 

“Every failed connection is a lesson in layers.”