@Isha_99 @Vishal_kumar98

**optimal window size is when link utilization is 100% …**

**To find optimal window size for sender , **

**we consider N=1+2a**

**=>( N/1+2a) **

**= 1 ..…**

**where N = sender window size and a = Tp / Tt ..**

**Given, RTT between x and y as 60 ms **

**= (60 * 10-3 ) seconds**

**and**

**bandwidth of link between X and Y is 512 KBps **

**= (512 * 103 ) Bytes/seconds…. **

**It is Full duplex channel, so total data send from x to y is **

**= (2* Tp) * Band Width **

**= RTT * band width **

**=( 60 * 10-3) * ( 512 * 103) **

**= 60 * 512 **

**= 30720 Bytes….**

## **packet size = 64 bytes... **

**### Number of window require = 30720 / 64 = 480 ...**

**@@@ So optimal window size is N = 1+2a **

**= 1+480 **

**= 481.... **

**In case optimal window size, we can indirectly say that maximum throughput should be achieved. It means link utilization is 100% in case of optimal window... **

**And as you said , window size is defined as number of frames sent in 1 RTT--> This is window size in terms of packets .... **

**we can say , optimal window size is 1 greater than number of frames send in 1 RTT .**

**See this thread also https://gateoverflow.in/107261/optimal-window-size …**