Interfaces and Services in Computer Networks 

 Interface aur Service kya hote hain?

Jab hum computer networks ke layers ki baat karte hain (jaise OSI model ya TCP/IP model), toh har layer doosri layer ke saath interact karti hai.

• Service = Ek layer doosri layer ko kya kaam de rahi hai

• Interface = Upar wali layer, neeche wali layer ke service ko kaise use karti hai

 Ek simple example:

Agar layers ek building ke floors hain:

• Service = Lift ka kaam (aapko upar le jaana)

• Interface = Lift ke buttons (jinse aap service use karte ho)

 Layered Architecture Reminder

Har layer:

• Sirf apne upar wali layer ko service provide karti hai

• Aur neeche wali layer se service leti hai

Isse system modular aur easy to manage ban jaata hai.

 Networking mein Service kya hoti hai?

Service ek kaam ya feature hai jo ek layer doosri (upper) layer ko deti hai.

 Service ke Types:

1. Connection-Oriented Service

   • Jaise phone call: Pehle connection banta hai, data send hota hai, phir disconnect hota hai

   • Example: TCP

2. Connectionless Service

   • Jaise postcard: Direct bhej do, koi connection banane ki zarurat nahi

   • Example: UDP

3. Reliable Service

   • Data safe aur sahi order mein pahuchta hai

   • Example: TCP

4. Unreliable Service

   • Data lost ho sakta hai, lekin fast hota hai

   • Example: UDP

 Interface kya hota hai?

Interface ek point of interaction hota hai — jahan ek layer apne neeche wali layer ke service ko use karti hai.

• Ye define karta hai ki ek layer doosri layer ke functions ko kaise call karegi

• Jaise browser socket function ka use karta hai TCP service ke liye

 Layer, Interface, Service

 example:

 Example – Browser se Website Access

Jab aap browser me www.google.com open karte ho:

1. HTTP request banata hai (Application Layer)

2. HTTP, TCP layer se data bhejne ke liye socket interface use karta hai

3. TCP reliable delivery service deta hai

4. TCP, IP layer se packets bhejne ke liye service use karta hai

Har layer sirf apni neeche wali layer se service leti hai using its interface

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 Important Baaten

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 Summary

• Services define karte hain kya kaam diya jaa raha hai

• Interfaces define karte hain kaise wo kaam use kiya jaa raha hai

• Is design se network communication modular aur reliable hota hai

• Example: HTTP uses TCP service via socket interface