The answer given is 5 which we get when we solve it using the formula **2*a**.

**My doubt is when do we use the formula** *(1 + 2*a)* **to find the optimal window size ?**

# Sliding window protocol

**Anmol_Binani**#1

propagation : 10^6/(2*10^8)sec = 5 mSec
round trip time : 10millisec
number of bytes we can transmit in 10millisec : 10*10^(-3) * 128 * (10^3)*(1/8) = 160Bytes

number packets is 160B/32B = 5packets.

It is optimal window

But i dont know about that formula how to use .

**Anmol_Binani**#3

go to this link and see, for max utilisation the window size should be

**(1 + 2a)**

but here we are only considering

**2a**