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
Network Layer and Design Issues in Computer Networks
Network Layer kya hai? (What is Network Layer?)
Network Layer OSI Model ki Layer 3 hoti hai, jo different networks ke beech Host-to-Host (End-to-End) data delivery ke liye responsible hoti hai.
Data Link Layer sirf ek local physical link ya same LAN ke do padosi devices ke beech frames transfer karti hai. Lekin agar Source computer Delhi mein hai aur Destination server New York mein, toh packets ko hazaron alag-alag networks aur routers se hokar guzarna padta hai. Yeh kaam Network Layer manage karti hai.
Network Layer par data unit ko Packet (ya Datagram) kaha jaata hai.
Is layer ka primary device Router hota hai, jo logical addressing (IP addresses) ko check karke best path decide karta hai.
Key Functions of Network Layer
-> Routing: Source se destination tak packet bhejne ke liye sabse best, shortest aur efficient path select karna (using routing algorithms jaise Dijkstra, Bellman-Ford).
-> Logical Addressing: Har device ko globally unique IP Address provide karna taaki packets worldwide sahi device tak deliver ho sakein.
-> Internetworking: Alag-alag tarah ke networks (Ethernet, Wi-Fi, Fiber, Token Ring) ko aapas mein seamlessly connect karna.
-> Packetizing: Transport layer ke segments ko receive karke unpe Network layer headers lagana aur Destination par unpack karna.
-> Fragmentation & Reassembly: Agar koi intermediate network bada packet carry nahi kar sakta (MTU limit), toh packet ko chote fragments mein todna aur destination par jodna.
Major Design Issues in Network Layer
Network layer ko design karte waqt engineers ke saamne 4 major challenges aate hain:
| Design Issue | Problem Statement | Solution / Mechanism |
|---|---|---|
| 1. Store-and-Forward Packet Switching | Packet aane par router ko pehle pure packet ko buffer mein store karna padta hai, CRC check karke verify karna hota hai, fir aage forward karna hota hai. Isse queuing delay hota hai. | High-speed router memory, hardware routing engines aur specialized ASIC chips. |
| 2. Connection-Oriented vs Connectionless Service | Kya data bhejne se pehle dedicated circuit banana chahiye (Virtual Circuit) ya har packet ko independently route karna chahiye (Datagram)? | Internet ne Datagram (Connectionless) model apnaya (IP protocol), jabki ATM aur X.25 Virtual Circuits use karte the. |
| 3. Routing & Scalability | Millions of routers ke beech optimal path kaise calculate kiya jaye bina routing tables ko overload kiye? | Hierarchical Routing aur Autonomous Systems (AS) with intra-domain (OSPF) aur inter-domain (BGP) routing. |
| 4. Congestion Control & Quality of Service (QoS) | Jab network par aane wala traffic router ke buffer aur bandwidth capacity se zyada ho jaye, toh packets drop hone lagte hain aur network freeze ho jaata hai. | Leaky Bucket, Token Bucket algorithms, Choke packets, aur ECN (Explicit Congestion Notification). |
Virtual Circuit vs Datagram Subnet (Exam High-Yield!)
| Parameter | Datagram Subnet (Connectionless) | Virtual Circuit Subnet (Connection-Oriented) |
|---|---|---|
| Setup Phase | No setup phase. Data turant transmit hota hai. | Transmission se pehle dedicated VC setup karna padta hai. |
| Addressing | Har packet mein complete Source aur Destination IP address hota hai. | Packets mein sirf ek chota VC ID (Virtual Circuit Identifier) hota hai. |
| Packet Ordering | Packets alag-alag raaste se jaa sakte hain, isliye out-of-order pahunch sakte hain. | Sabhi packets ek hi fixed path follow karte hain, isliye in-order deliver hote hain. |
| Router Failure | Robust! Agar koi router fail ho jaye, packets naya rasta dhund lete hain. | Fragile! Agar path ka ek bhi router fail hua toh poora connection terminate ho jaata hai. |
| Real Example | The Internet (IP Protocol) | ATM (Asynchronous Transfer Mode), X.25, MPLS |
Summary Table
| Network Layer Aspect | Key Concept |
|---|---|
| Scope | Host-to-Host (End-to-End) logical packet delivery across multiple interconnected networks. |
| Primary Device | Router (Layer 3 device that maintains routing tables). |
| Internet Approach | Datagram connectionless model (IP), prioritizing fault tolerance and simplicity. |