Flow control (stop-and-wait, sliding window) in Computer Networks - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the flow control method where the sender waits for an acknowledgment after sending each frame.

Computer Networks

if sender_waits_for_ack == [1]:
    method = "Stop-and-Wait"

Drag options to blanks, or click blank then click option'

ATrue

BFalse

CMaybe

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing False because they think the sender sends frames continuously.

Selecting None or Maybe as they are not boolean values.

In Stop-and-Wait flow control, the sender waits for an acknowledgment (True) after sending each frame before sending the next.

2fill in blank

medium

Complete the code to calculate the window size in sliding window flow control given the sequence number bits.

Computer Networks

window_size = 2[1] - 1

Drag options to blanks, or click blank then click option'

A**2

B**3

C**5

D**4

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of exponentiation.

Forgetting to subtract 1 from the power of 2.

The window size in sliding window flow control is calculated as 2 to the power of the number of sequence bits minus 1. For example, if sequence bits = 2, window size = 2² - 1 = 3.

3fill in blank

hard

Fix the error in the code that checks if the sender can send more frames in sliding window protocol.

Computer Networks

if frames_sent < [1]:
    can_send = True
else:
    can_send = False

Drag options to blanks, or click blank then click option'

Awindow_size - 1

Bwindow_size + 1

Cwindow_size

Dwindow_size * 2

Attempts:

3 left

💡 Hint

Common Mistakes

Adding or subtracting 1 incorrectly from window size.

Multiplying window size by 2 which is not correct.

The sender can send frames as long as the number sent is less than the window size. Using 'window_size' directly is correct.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps frame numbers to their acknowledgment status if the frame number is less than the window size.

Computer Networks

{frame_num: status for frame_num, status in frames.items() if frame_num [1] window_size and status [2] 'sent'}

Drag options to blanks, or click blank then click option'

A<

B==

C!=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' for frame number comparison.

Using '!=' instead of '==' for status comparison.

The comprehension filters frames where the frame number is less than the window size and the status is exactly 'sent'.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps sequence numbers (mod window size) to frame data for frames with status 'acknowledged'.

Computer Networks

{(frame_num [1] window_size): data for frame_num, (data, status) in frames.items() if status [2] 'acknowledged' and frame_num [3] window_size}

Drag options to blanks, or click blank then click option'

A%

B==

C<

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction (-) instead of modulo (%).

Using '!=' instead of '==' for status check.

Using '>' instead of '<' for frame number filtering.

The comprehension uses modulo (%) to wrap sequence numbers, checks if status equals 'acknowledged', and filters frame numbers less than window size.