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
HDLC (High-Level Data Link Control) Protocol
HDLC kya hai?
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HDLC ek bit-oriented protocol hai jo ISO (International Organization for Standardization) ne develop kiya.
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Yeh OSI Model ke Data Link Layer (Layer 2) par kaam karta hai.
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Iska kaam hai reliable aur efficient data transfer provide karna over point-to-point ya multipoint links.
HDLC IBM ke SDLC protocol par based hai, lekin ye ek standardized version hai.
Features of HDLC
-> Bit-oriented protocol – Data ko bits ke continuous stream mein bhejta hai
-> Error detection ke liye CRC (Cyclic Redundancy Check) use hota hai
-> Flow control aur error control ke liye acknowledgments hoti hain
-> Half-duplex aur full-duplex communication dono support karta hai
-> Teen tarah ke frames use karta hai (I, S, U Frames)
HDLC Frame Format
Ek HDLC frame ke parts:
| Field | Kaam |
|---|---|
| Flag | Frame ke start aur end ko batata hai (01111110) |
| Address | Bataata hai kaunsa receiver station hai |
| Control | Frame ka type aur control info batata hai |
| Information | Actual data jo bhejna hai |
| FCS (CRC) | Error checking ke liye bits |
| Flag | Frame end ka indicator (same as start flag) |
HDLC Frame Structure
Types of Frames
1. Information Frames (I-Frames)
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Data bhejne ke liye use hota hai
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Flow control aur error control info bhi hoti hai
2. Supervisory Frames (S-Frames)
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Flow control aur error control ke liye
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Example: RR (Receive Ready), REJ (Reject)
3. Unnumbered Frames (U-Frames)
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Control aur management kaam ke liye
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Link establish ya terminate karne ke liye use hota hai
Modes of HDLC
Normal Response Mode (NRM)
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Primary station control karta hai.
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Secondary station tabhi data bhej sakta hai jab primary allow kare.
Asynchronous Balanced Mode (ABM)
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Dono stations equal hote hain, dono kabhi bhi data bhej sakte hain.
Asynchronous Response Mode (ARM)
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NRM jaisa hi hai, par secondary kabhi-kabhi bina permission ke bhi data bhej sakta hai.
Example
Station A (Primary) ko Station B (Secondary) ko “HELLO” bhejna hai.
Frame kuch aisa banega:
Receiver (B) frame check karega (error ke liye FCS se) aur ACK (S-Frame) bhej dega.
Communication Diagram
Advantages
-> Reliable aur error-free data transfer
-> Half-duplex aur full-duplex dono links ke liye kaam karta hai
-> Flow control aur error control ka support hai
Disadvantages
-> Frame structure thoda bada hone se overhead zyada hota hai
-> Simple protocols ke comparison mein thoda complex hai
Summary Table
| Feature | HDLC |
|---|---|
| Developed By | ISO |
| Type | Bit-oriented protocol |
| Layer | Data Link Layer |
| Modes | NRM, ABM, ARM |
| Frame Types | I-Frame, S-Frame, U-Frame |
| Error Detection | CRC |
| Based On | IBM SDLC |