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
Protocol Hierarchy in Computer Networks
Protocol kya hota hai?
Protocol ka matlab hota hai rules ka set jo define karta hai ki computers ya devices network par kaise baat karenge.
Example:
Jaise do log Hindi ya English mein baat karte hain, waise hi computers protocols ka use karke ek dusre se data share karte hain — jaise HTTP, FTP, TCP/IP.
Protocol Hierarchy kya hoti hai?
Protocol Hierarchy ka matlab hota hai protocols ka layer-wise arrangement — jahan har layer ka apna kaam hota hai.
Har layer:
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Neeche wali layer se services leta hai
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Upar wali layer ko services deta hai
Isse communication simple, clear, aur manageable ban jaata hai.
Protocol Hierarchy ki zarurat kyun hai?
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Networking tasks ko chhote-chhote parts mein divide karna
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Communication ko standard aur reliable banana
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Debugging aur maintenance ko easy banana
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Alag-alag devices (chahe kisi bhi company ke ho) easily connect ho sakein
OSI Model – Protocol Hierarchy ka Example
OSI ka full form hai Open Systems Interconnection. Ye ek standard model hai jisme 7 layers hoti hain:
| Layer No. | Layer Name | Kaam (Simple Explanation) |
|---|---|---|
| 7 | Application | User ke software se data lena (browser, email) |
| 6 | Presentation | Data ko format karna (encryption, JPEG etc.) |
| 5 | Session | Session banana, maintain karna, end karna |
| 4 | Transport | Reliable delivery ensure karna (TCP/UDP) |
| 3 | Network | IP address aur routing handle karna |
| 2 | Data Link | MAC address, framing, error detect karna |
| 1 | Physical | Bits ko wires ya wireless se bhejna |
Example – Website Access karna
Jab aap apne browser mein www.google.com open karte ho:
Sender (Aapka system):
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Application Layer: Browser request banata hai
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Presentation Layer: Data ko readable format mein convert karta hai
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Session Layer: Session start hota hai server ke saath
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Transport Layer: Data chhote packets mein divide hota hai (TCP use hota hai)
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Network Layer: IP address add hota hai (source aur destination)
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Data Link Layer: MAC address add hota hai
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Physical Layer: Bits cable ya Wi-Fi ke through bheje jaate hain
Receiver (Server):
Wahin steps reverse order mein follow hote hain — bits ko packet me convert kiya jata hai, phir message banaya jaata hai aur website ka response diya jaata hai.
Real-Life Analogy – Courier ka Example
| Layer | Courier Wala Example |
|---|---|
| Application | Aap letter likhte ho |
| Presentation | Language select karte ho (Hindi/English) |
| Session | Decide karte ho kab bhejna hai |
| Transport | Express ya normal courier select karte ho |
| Network | Best route courier wala decide karta hai |
| Data Link | Parcel label karta hai (barcode, ID) |
| Physical | Truck/road use karke parcel bhejta hai |
Protocol Hierarchy ke Advantages
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Modular Design: Har layer ka kaam alag hota hai
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Troubleshooting Easy: Khaali problem wali layer fix karni hoti hai
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Compatibility: Different devices aasani se connect ho jaate hain
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Global Standard: Har jagah ek jaise rules use hote hain
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Upgrade Friendly: Ek layer badalne se dusri par asar nahi padta
Conclusion
Protocol hierarchy ek layered design hai jisse complex communication ko simple steps mein break kiya jaata hai. Har layer ka ek specific role hota hai, aur sab ek dusre ke saath milkar kaam karti hain — isse hi bolte hain network stack ya protocol hierarchy.