Computer Networks
CN Part-1
- What is a Computer Network?
- Goals and Applications of Computer Networking
- Computer Network Components
- Types of Computer Networks
- Network Topology
- Difference between Client Server and Peer to Peer Network
- Layered Architecture in Computer Networks
- Protocol Hierarchy in Computer Networks
- Interfaces and Services in Computer Networks
- Connection Oriented and Connectionless Services
- Service Primitives
- OSI Model
- TCP/IP Model
- Difference between OSI Model and TCP/IP Model
- Encapsulation and Decapsulation in Computer Networks
- Queueing Models in Computer Network
CN Part-2
- Physical Layer in Computer Networks
- Transmission Media in Computer Networks
- Analog and Digital Signals
- Data Rate and Bandwidth
- Encoding Techniques
- Multiplexing in Computer Networks
- Transmission Modes in Computer Networks
- Data Link Layer
- Framing in Data Link Layer
- Flow Control in Data Link Layer
- Error Control in Data Link Layer
- Error Detection and Correction in Computer Networks
- Stop and Wait Protocol
- Sliding Window Protocol
- SDLC(Synchronous Data Link Control) Protocol
- High-Level Data Link Control (HDLC) Protocol
- Point-to-Point Protocol (PPP)
CN Part-3
- MAC Sublayer and MAC Addressing
- Channel Allocation Methods
- ALOHA Protocol (Pure and Slotted ALOHA)
- CSMA/CD and CSMA/CA in Computer Networks
- Ethernet (IEEE 802.3)
- Wireless LANs (IEEE 802.11, Wi-Fi, and Bluetooth Basics)
- Network Layer and Design Issues
- IPv4 and IPv6 Protocols
- Addressing: IP Address, Subnetting, and Supernetting
- Routing Algorithms: Static vs Dynamic, Distance Vector, and Link State
- Routing Protocols: RIP, OSPF, and BGP
- Packet Switching and IP Fragmentation
- Network Layer Protocols: ICMP, ARP, RARP, DHCP, and NAT
CN Part-4
- Transport Layer and Functions
- Process-to-Process Delivery, Ports, and Sockets
- TCP Segment and Three-Way Handshake Connection Establishment
- UDP (User Datagram Protocol): Format and Features
- Flow Control and Error Control in Transport Layer
- Congestion Control: Leaky Bucket, Token Bucket, and TCP Congestion Control
CN Part-5
- Application Layer Architecture and Principles
- Domain Name System (DNS)
- Email Protocols: SMTP, POP3, and IMAP
- File and Web Protocols: FTP, HTTP, and HTTPS
- Remote Access Protocols: Telnet and SSH
- World Wide Web (WWW) and Web Architecture
- Network Security Basics: SSL, TLS, and Cryptography Fundamentals
Application Layer Architecture and Principles in Computer Networks
Application Layer kya hai? (What is Application Layer?)
Application Layer OSI Model ki sabse top layer (Layer 7) hoti hai. Yeh akeli aisi layer hai jo directly human users aur software applications (jaise web browsers, email clients, file sharing tools) ke saath interact karti hai.
Niche ki 6 layers (Physical se lekar Transport tak) ka saara kaam sirf ek hi maqsad ke liye hota hai: Application Layer ke data ko safely aur reliably transmit karna.
Application Layer define karti hai ki do computers par chal rahe network applications aapas mein kis language, messages, aur syntax ke zariye baat karenge.
Network Application Architectures
Network applications ko design karne ke do primary architectures hote hain:
1. Client-Server Architecture 2. Peer-to-Peer (P2P) Architecture
[ Central Server ] [ Peer A ] <-----> [ Peer B ]
/ | \ \ /
/ | \ \ /
[Client1] [Client2] [Client3] [ Peer C ] <--> [ Peer D ]
1. Client-Server Architecture
Ek Server hota hai jo hamesha on (Always-on host) rehta hai aur jiska ek fixed, permanent IP address hota hai.
Multiple Clients (jaise aapka smartphone ya laptop) server ko request bhejte hain aur server reply karta hai.
Clients aapas mein directly communicate nahi karte (sirf server se baat karte hain).
Examples: Web browsing (Web Server & Chrome Client), Email (Gmail Server & App), Database servers.
2. Peer-to-Peer (P2P) Architecture
Isme koi central dedicated server nahi hota. Sabhi connected computers (Peers) equal status rakhte hain.
Har peer simultaneously Client bhi hota hai aur Server bhi (data download bhi karta hai aur baakiyo ko upload karke serve bhi karta hai).
Self-Scalability: Naye peers aane se network par load nahi badhta, balki file sharing capacity aur bandwidth badhti hai!
Examples: BitTorrent, Blockchain networks (Bitcoin, Ethereum), Skype (initial versions).
Client-Server vs Peer-to-Peer (P2P) Comparison
| Feature | Client-Server Architecture | Peer-to-Peer (P2P) Architecture |
|---|---|---|
| Central Coordinator | Dedicated Central Server mandatory hai. | No central server (Distributed system). |
| Single Point of Failure | High (Agar central server crash hua, poora network down). | Zero (Agar 5 peers offline bhi ho jayein, network chalta rehta hai). |
| Scalability | Limited (Users badhne par server overload ho jaata hai). | High (Har naya user apni bandwidth contribute karta hai). |
| Security & Management | Easy to manage, secure, central backup possible. | Difficult to manage, security aur copyright concerns. |
Summary Table: Application Layer Protocols
| Application | Application Protocol | Underlying Transport | Default Port |
|---|---|---|---|
| Web Browsing | HTTP / HTTPS | TCP | Port 80 / 443 |
| Domain Name Resolution | DNS | UDP (queries), TCP (zone) | Port 53 |
| Email Delivery | SMTP | TCP | Port 25 |
| File Transfer | FTP | TCP | Port 20, 21 |
| Remote Command Line | SSH / Telnet | TCP | Port 22 / 23 |