Consider a TCP connection between a client and a server with the following specifications: the round trip time is 6 ms, the size of the receiver advertised window is 50 KB, slow-start threshold at the client is 32 KB, and the maximum segment size is 2 KB. The connection is established at time $t = 0$. Assume that there are no timeouts and errors during transmission. Then the size of the congestion window (in KB) at time $t + 60\text{ ms}$ after all acknowledgements are processed is ________.

Given parameters:

• Round Trip Time (RTT) = $6\text{ ms}$

• Maximum Segment Size (MSS) = $2\text{ KB}$

• Slow-start threshold (ssthresh) = $32\text{ KB}$

• Receiver advertised window (rwnd) = $50\text{ KB}$

• Total time elapsed = $60\text{ ms} = \frac{60}{6} = 10\text{ RTTs}$

Congestion Window Progression:

At $t = 0$, the initial congestion window is:

Phase 1: Slow-Start (cwnd doubles each RTT until it reaches ssthresh = $32\text{ KB}$):

• After $1^{\text{st}}$ RTT ($t = 6\text{ ms}$): $\text{cwnd} = 2 \times 2 = 4\text{ KB}$

• After $2^{\text{nd}}$ RTT ($t = 12\text{ ms}$): $\text{cwnd} = 2 \times 4 = 8\text{ KB}$

• After $3^{\text{rd}}$ RTT ($t = 18\text{ ms}$): $\text{cwnd} = 2 \times 8 = 16\text{ KB}$

• After $4^{\text{th}}$ RTT ($t = 24\text{ ms}$): $\text{cwnd} = 2 \times 16 = 32\text{ KB} = \text{ssthresh}$

Phase 2: Congestion Avoidance (cwnd increases linearly by $1\text{ MSS} = 2\text{ KB}$ per RTT):

• After $5^{\text{th}}$ RTT ($t = 30\text{ ms}$): $\text{cwnd} = 32 + 2 = 34\text{ KB}$

• After $6^{\text{th}}$ RTT ($t = 36\text{ ms}$): $\text{cwnd} = 34 + 2 = 36\text{ KB}$

• After $7^{\text{th}}$ RTT ($t = 42\text{ ms}$): $\text{cwnd} = 36 + 2 = 38\text{ KB}$

• After $8^{\text{th}}$ RTT ($t = 48\text{ ms}$): $\text{cwnd} = 38 + 2 = 40\text{ KB}$

• After $9^{\text{th}}$ RTT ($t = 54\text{ ms}$): $\text{cwnd} = 40 + 2 = 42\text{ KB}$

• After $10^{\text{th}}$ RTT ($t = 60\text{ ms}$): $\text{cwnd} = 42 + 2 = 44\text{ KB}$

Since $\text{cwnd} = 44\text{ KB} \le \text{rwnd} = 50\text{ KB}$, the congestion window size is 44 KB.