Stop and Wait Protocol

 Stop-and-Wait Protocol kya hota hai?

Stop-and-Wait Protocol ek basic flow control technique hai jo Data Link Layer mein use hoti hai.

Is protocol mein sender ek time par sirf ek frame bhejta hai, aur phir receiver se uska acknowledgment (ACK) aane ka wait karta hai. Jab tak ACK nahi milta, next frame send nahi hota.

 Kaise kaam karta hai – Step by Step

1. Sender Frame 0 send karta hai Receiver ko.

2. Sender ACK 0 ka wait karta hai.

3. Jab ACK milta hai, tabhi next Frame 1 bheja jaata hai.

4. Ye process repeat hoti rehti hai.

 Diagram: Stop-and-Wait Protocol

• Ek samay mein sirf ek frame bheja jaata hai.

• Sender hamesha ACK milne ka wait karta hai.

 Example:

Maan lo sender ko message “ABC” bhejna hai.

Toh ye teen frames mein divide hoga:

• Frame 0: A

• Frame 1: B

• Frame 2: C

Communication aise hoga:

 Agar Acknowledgement (ACK) lost ho jaaye toh?

Agar ACK ya data frame lost ho jaye, toh sender kuch time wait karta hai (timeout hota hai) aur phir dobara same frame bhejta hai.

 Lost ACK ka Example:

 Timeout ka kya role hai?

Sender har frame bhejne ke baad ek fixed time tak ACK ka wait karta hai. Agar us time tak ACK nahi aata, toh sender assume karta hai ki frame ya ACK lost ho gaya aur same frame dobara send karta hai.

  Advantages

• Simple aur reliable protocol hai.

• Data correct order mein receiver tak pahuchta hai.

  Disadvantages

• Bahut slow hota hai agar distance zyada ho.

  • Sender har frame ke baad idle ho jaata hai jab tak ACK nahi aata.

• Bandwidth ka full use nahi hota, kyunki ek baar mein sirf ek frame send hota hai.

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 Kahan use hota hai?

Ye protocol directly zyada use nahi hota aaj ke time mein, lekin yahi base banata hai advance protocols ke liye, jaise:

• Go-Back-N Protocol

• Selective Repeat Protocol