Module Review

In this module, we explored the logic of end-to-end communication:

  1. TCP Header: The complex 20-byte structure that enables reliability, including sequence numbers, ACKs, and flags.
  2. UDP Header: The minimal 8-byte alternative for when speed matters more than certainty.
  3. Flow Control: Using the Sliding Window to ensure the sender doesn’t drown the receiver in data.
  4. Congestion Control: Managing network health through Slow Start and AIMD algorithms.
  5. Reliability: How TCP uses checksums, timers, and cumulative ACKs to guarantee a perfect stream of bits.

1. Flash Quiz

1. How long is the standard UDP header?

  • 8 Bytes.

2. What is the difference between SYN and ACK in the 3-way handshake?

  • SYN (Synchronize) is a request to open a connection; ACK (Acknowledge) confirms receipt of a previous segment.

3. Which mechanism prevents a fast sender from overwhelming a slow receiver?

  • Flow Control (Sliding Window).

4. What does AIMD stand for in the context of congestion control?

  • Additive Increase, Multiplicative Decrease.

5. Why is UDP preferred for online gaming?

  • It has lower latency because it doesn’t require a 3-way handshake or retransmissions, which would cause significant “lag” if a single packet was lost.

2. What’s Next?

In the next module, we reach the top of the stack: the Application Layer. We’ll explore HTTP, DNS, SMTP, and how your favorite apps talk to the world.