TCP flow control (sliding window) in Computer Networks - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the purpose of TCP sliding window

What is the main purpose of the sliding window mechanism in TCP flow control?

A To route packets through the shortest path in the network

B To encrypt data packets for secure transmission

C To assign IP addresses dynamically to devices

D To control the amount of data a sender can transmit before receiving an acknowledgment

💡 Hint

Think about how TCP manages data transmission to avoid overwhelming the receiver.

The sliding window controls how much data the sender can send before waiting for an acknowledgment, ensuring the receiver is not overwhelmed.

📋 Factual

intermediate

Sliding window size adjustment

In TCP flow control, what happens when the receiver advertises a window size of zero?

A The sender stops sending data until the window size increases

B The sender ignores the window size and continues sending data

C The sender increases its sending rate to fill the network

D The sender closes the connection immediately

💡 Hint

Consider what it means if the receiver cannot accept more data.

A window size of zero means the receiver's buffer is full, so the sender must pause sending until notified otherwise.

🔍 Analysis

advanced

Effect of window size on throughput

How does increasing the TCP sliding window size affect the throughput of a connection over a high-latency network?

A It causes the connection to reset frequently

B It increases throughput by allowing more data to be sent before waiting for acknowledgment

C It has no effect on throughput in high-latency networks

D It decreases throughput because larger windows cause more packet loss

💡 Hint

Think about how waiting times and data in transit relate to window size.

A larger window lets the sender transmit more data without waiting, improving throughput especially when delays are long.

❓ Comparison

advanced

Sliding window vs. congestion control

Which statement best distinguishes TCP flow control using sliding window from TCP congestion control?

A Flow control manages receiver buffer capacity; congestion control manages network traffic congestion

B Flow control encrypts data; congestion control compresses data

C Flow control assigns IP addresses; congestion control routes packets

D Flow control increases packet size; congestion control decreases packet size

💡 Hint

Consider what each mechanism is trying to protect or manage.

Flow control prevents overwhelming the receiver, while congestion control prevents network overload.

❓ Reasoning

expert

Interpreting sliding window behavior from sequence numbers

Given a TCP connection where the sender's current window size is 5000 bytes, the last acknowledged sequence number is 10000, and the next sequence number to send is 12000, how many bytes can the sender still send without receiving new acknowledgments?

A 5000 bytes

B 7000 bytes

C 3000 bytes

D 2000 bytes

💡 Hint

Calculate the difference between the window size and the amount of data already sent but not acknowledged.

The sender has sent 2000 bytes beyond the last acknowledgment (12000 - 10000). With a window of 5000 bytes, it can send 5000 - 2000 = 3000 more bytes.