TCP congestion control in Computer Networks - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main goal of TCP congestion control?

The main goal of TCP congestion control is to prevent network congestion by controlling the rate at which data is sent, ensuring efficient use of network resources and avoiding packet loss.

beginner

Name the four key phases of TCP congestion control.

The four key phases are: Slow Start, Congestion Avoidance, Fast Retransmit, and Fast Recovery.

intermediate

Explain the Slow Start phase in TCP congestion control.

In Slow Start, TCP begins sending data slowly, increasing the congestion window exponentially each round-trip time until it detects packet loss or reaches a threshold called the slow start threshold (ssthresh).

intermediate

What happens during the Fast Retransmit phase?

Fast Retransmit triggers retransmission of lost packets quickly after receiving three duplicate acknowledgments, without waiting for a timeout.

intermediate

How does TCP adjust its congestion window during Congestion Avoidance?

During Congestion Avoidance, TCP increases the congestion window linearly to probe for available bandwidth carefully and avoid congestion.

Which TCP phase increases the congestion window exponentially?

A Fast Retransmit

B Congestion Avoidance

C Slow Start

D Fast Recovery

Slow Start increases the congestion window exponentially to quickly find the network capacity.

What triggers the Fast Retransmit phase in TCP?

A Three duplicate ACKs

B Window size reaching zero

C Timeout expiration

D Receiving a SYN packet

Fast Retransmit is triggered when TCP receives three duplicate acknowledgments indicating packet loss.

During Congestion Avoidance, TCP increases the congestion window:

A Linearly

B Exponentially

C Randomly

D Not at all

TCP increases the congestion window linearly during Congestion Avoidance to avoid congestion.

What is the purpose of the congestion window in TCP?

A To route packets through the network

B To encrypt data packets

C To establish a connection

D To limit the number of packets sent without acknowledgment

The congestion window limits how many packets TCP can send before receiving an acknowledgment.

Which TCP phase immediately follows Slow Start?

A Fast Retransmit

B Congestion Avoidance

C Connection Termination

D Handshake

After Slow Start, TCP enters Congestion Avoidance to increase the window more cautiously.

Describe the four main phases of TCP congestion control and their roles.

Think about how TCP adjusts sending rate to avoid congestion.

Explain how TCP detects and responds to network congestion.

Focus on signals TCP uses and its reaction steps.