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
Layered Architecture in Computer Networks
Layered Architecture kya hoti hai?
Layered architecture ek aisa design hai jisme network communication ko alag-alag layers mein divide kiya gaya hai. Har layer ka apna specific kaam hota hai, aur wo sirf apni upar aur neeche wali layer se interact karti hai.
Ye system networking tasks ko asaani se manage karne aur samajhne ke liye banaya gaya hai.
Layers use karne ki zarurat kyun?
Sochiye aap ek courier bhej rahe ho:
Aap letter likhte ho
Usse envelope mein daalte ho
Label chipkaate ho
Courier waale ko dete ho
Wo deliver karta hai
Samne wala khol ke padhta hai
Yahan har step ek layer jaise kaam karta hai. Aapko har step ka detail nahi pata hona chahiye — bas sab sahi kaam karein. Network mein bhi har layer apna kaam karti hai aur next layer ko data pass karti hai.
OSI Model – Layered Architecture ka standard example
OSI ka full form hai Open Systems Interconnection. Isme total 7 layers hoti hain.
OSI ke 7 Layers (Top to Bottom):
| Layer No. | Layer Name | Kya karta hai (Simple Mein) |
|---|---|---|
| 7 | Application Layer | User aur software ka interface |
| 6 | Presentation Layer | Data ka format set karta hai (encoding, encryption) |
| 5 | Session Layer | Session (conversation) start/end karta hai |
| 4 | Transport Layer | Data delivery reliable banata hai (TCP/UDP) |
| 3 | Network Layer | IP address aur route decide karta hai |
| 2 | Data Link Layer | Data ko frames mein convert karta hai, MAC address use karta hai |
| 1 | Physical Layer | Bits ko cable ya signal ke form mein bhejta hai |
Real-Life Analogy: Letter bhejna
| OSI Layer | Letter ka example |
|---|---|
| Application | Aap letter likhte ho |
| Presentation | Aap language select karte ho (English, Hindi) |
| Session | Aap decide karte ho kab start/end karna hai |
| Transport | Courier fast/safe delivery ensure karta hai |
| Network | Courier best route select karta hai |
| Data Link | Courier package damage hone se bachata hai |
| Physical | Road aur vehicle letter deliver karte hain |
Layered Architecture ke Advantages
Easy to Understand – Har layer ka apna role hai
Modular – Har layer ko alag develop ya troubleshoot kiya ja sakta hai
Interoperability – Different devices ya systems easily connect ho sakte hain
Easy to Maintain – Agar problem ho to us layer mein dhundhna easy hai
Flexible – Ek layer badlo, baaki ko chhedne ki zarurat nahi
Real Example: Jab aap website visit karte ho
Application Layer: Browser kholta hai aur URL likhte ho
Presentation Layer: Data HTML, images format mein convert hota hai
Session Layer: Browser aur server ke beech session banta hai
Transport Layer: TCP ensure karta hai ki data complete aur correct ho
Network Layer: Data ko IP address ke according server tak bhejna
Data Link Layer: MAC address ke through data local network mein send hota hai
Physical Layer: Data as signals cable ya Wi-Fi se travel karta hai
Conclusion
Layered Architecture se networking simple, flexible aur reliable ban jaati hai. OSI model is approach ka perfect example hai jisme 7 layers hoti hain, aur har ek layer apna specific kaam karti hai.