Computer Networks · Quiz 2 · Jan 2026

A TCP receiver has a buffer size of 24 KB. The sender transmits data at 9 KB/s, while the receiver’s application reads data from the buffer at 5 KB/s. Assuming the buffer is initially empty, after how many seconds will the receiver buffer become full? Note: Give your answer to two decimal places.

A TCP connection achieves a maximum throughput of 500 KB/s. The Round Trip Time (RTT) of the connection is 100 ms. Ignoring congestion effects, compute the advertised window size (in KB) required to achieve this throughput based only on flow control.

Given the IP address A = 192.168.45.130 and netmask 255.255.240.0, compute the **network** **address** of A (expressed in dotted-decimal form).

An organization has been assigned an address block of 10.25.4.0/27. How many usable host addresses can be assigned to devices in this network?

An organization has 1,000 devices connected in a private network. Each NAT router can handle up to 80,000 simultaneous connections and can serve 300 devices comfortably. If the organization uses NAT (one public IP address per NAT router), how many public IP addresses are required?

A 20 Mbps link has a propagation delay of 400 s. The transmitter employs the Stop- and-Wait protocol. Assuming each frame is 100 bytes long, what is the maximum data rate possible? Note: Write in Mbps

At the start of an RTT, the congestion window (CWND) is 18 MSS, where the Maximum Segment Size (MSS) is 1000 bytes. TCP is operating in the congestion avoidance phase, and there is one ACK per segment. What will be the new value of CWND (in bytes) after receiving 18 ACKs (i.e., one RTT worth of ACKs)?

A bottleneck link has a total capacity of 120 Mbps and is shared by three flows: • Flow 1 (TCP AIMD): x1 = 60 Mbps • Flow 2 (TCP AIMD): x2 = 40 Mbps • Flow 3 (UDP): x3 = 30 Mbps What is the Jain’s Fairness Index (JFI) for these three flows? **Note:** Give your answer to two decimal places.

A TCP connection starts with CW N D = 1 MSS = 4 KB and ssthresh = 32 KB. There is no packet loss during the first 4 RTTs. Once slow start ends at CW N D = 64 KB and congestion avoidance begins, what is the CW N D after 3 additional RTTs assuming additive increase of 1 MSS (2 KB) per RTT? **Note:** Answer in KB.

A TCP connection has a round-trip time (RTT) of 100 ms and a maximum segment size (MSS) of 1300 bytes. If the steady-state congestion window is 50 MSS, what is the maximum achievable throughput (in Mbps)? Note: Give your answer to two decimal places.

A TCP flow has a Maximum Segment Size (MSS) of 4 KB. The current flight size is 80 KB. The flow detects a loss through 3 duplicate ACKs. What is the value of CW N D(in KB) immediately after the fast retransmit, during the Fast Recovery phase (i.e., CW N D = ssthresh + 3 × MSS)?