This assignment has two parts. The first is a required one and the other is a bonus research question. You should submit your answers to the required questions in ONE PDF.

If you will do the bonus question, please submit this as a separate PDF file.

Note on grading: We randomly select some questions (and/or parts of questions) and grade them. You need to answer all questions, since you do not know which questions we will grade. You get credits only on the graded questions. We include more questions for you to practice and understand the materials.

Required Questions

The following problems are from Chapter 3 of the textbook [Kurose and Ross, 7th edition]. For quick access, a screenshot of these problems can be found here.

• Problem 40
• Problem 41
• Problem 44
• Problem 46
• Problem 48

• True or False Question:

Please write your answers to the following questions in a 2-column table, with the question number (no text) in the first column and either True or False in the second column. While it is indeed important to understand the reason behind your answer and you should do it, it is not required for this question to justify your answer.

1. TCP CUBIC does not use a slow start phase because it employs a cubic function that can grow the congestion window quickly.

2. Under the simple periodic loss model, the throughput of TCP Reno is inversely proportional to the packet loss rate p.

3. Unlike CUBIC and Reno, TCP Vegas uses a delay-based congestion control algorithm.

4. In TCP BBR, a sender transmits data immediately after receiving ACKs. That is, BBR is a self-clocking algorithm.

5. In TCP BBR, the sender periodically measures the bottleneck bandwidth and RTT, and uses them in determining the sending rate.

6. In Explicit Congestion Control (ECN), a router observing congestion will directly send notification packets to all senders of the flows passing through it so that they can reduce their sending rates.

7. Switches in data centers have large buffers because they use high-speed links.

8. DCTCP (Data Center TCP) reduces the CongWin in proportion to the congestion level at routers using the equation CongWin = CongWin * (1- 𝛂/2), where 𝛂 is the fraction of segments in which the ECN-Echo (ECE) bit is set to 1.

9. Random Early Detection (RED) is a mechanism used by TCP receivers to randomly drop packers if their queues are getting full.

10. In Random Early Detection (RED), a router maintains two thresholds MinThresh and MaxThresh. When the average queue length at the router exceeds MaxThresh, the router will drop packets with probability equals 1.

Bonus: Research Question

This is an optional question. Its weight will be 2% of the total course grade. Thus, you can use it (and other bonus questions in future assignments) to improve your grade, in addition of course to learning more.

QUIC is a protocol originally developed by Google to mitigate some of the TCP inefficiencies. It has been recently standardized by the IEFT in RFC 9000, which is supported by a few other RFCs: RFC 8999, RFC 9001, and RFC 9002.

Write a 2-3 page report summarizing QUIC and its operation and main features.

Your writing must be your own, no copying. You get no credits if you copy any text. You should provide the list of references you used at the end of your report. Use 12-point font, 1.5 line spacing, with 1-inch margins.

Your report should start with an Overview of QUIC section (0.5 page), mentioning the high-level operation of QUIC and summarizing its main features. The overview should also mention applications that QUIC supports and the ones that may not be suitable for it.

Then, the report should cover some/most of the following issues in a few sections:

• QUIC short latency. How connections are established, how data can quickly start to flow (e.g., 0-RTT transmission).

• QUIC parallel streams, and how it handles addressing head-of-line blocking in TCP.

• QUIC and security, and how it works with TLS (Transport Layer Security).

• How QUIC supports reliability and congestion control.

• Describe similarities and differences between QUIC and TCP. Mention whether new variations of TCP (e.g., TCP BBR) will coexist with or replace QUIC.

• QUIC limitations and future.