Computer Networks and Applications COMP3331/COMP9331 25T1

Final Exam + myExperience

Posted by Salil Kanhere Saturday 26 April 2025, 03:13:58 PM, last modified Saturday 26 April 2025, 05:40:17 PM.

The assignment deadline has passed. I hope everyone has completed it and enjoyed the experience. However, you can submit it after the deadline, subject to the late penalty outlined in the specification.

Please complete the myExperience surveys . The response rate so far is low (only 26% ). I am sure we can do better. We would appreciate your feedback.

The final exam is scheduled as follows:

• COMP3331 - Thursday , 15th May, from 09:45 am to 12:00 noon.
• COMP9331 - Thursday, 8th May, from 1:45 pm to 4:00 pm.

The exam is in-person, invigilated and closed-book. You must bring your own laptop and install the Safe Exam Browser on it . Please check all the information for the exam here . There is a practice exam available that uses the safe exam browser. Make sure you try it out. Details are here .

I have created a final exam information page . Please read all the information provided here carefully, and be sure to check which content is examinable and which is excluded.

A practice final exam is available in Inspera. The Moodle link is posted on the Final Exam page. You can only sit this exam once, which will close in 2 hours + 15 minutes after you start the attempt. Please keep this in mind before attempting the exam. You should be able to view the correct answers in Inspera after you submit your attempt. I strongly encourage you to try the practice exam in Inspera to ensure that you are comfortable with the Inspera platform so that there are no surprises in the final exam.

I have also posted 2 PDF files of the exam (one with just questions, the other with questions and answers) on the Final Exam page.

Everyone is strongly encouraged to solve all the homework questions and engage in discussions on the forum.

I have arranged 5 exam consultation slots leading up to the exam dates. The schedule is here .

Have a good weekend, and good luck with your exam preparation.

Week 10: Final Week !!

Posted by Salil Kanhere Friday 18 April 2025, 03:44:03 PM.

Here are a few important announcements for next week, which will be the last teaching week of this term:

• In the lectures, we will wrap up the Wireless Network discussions we started last week and then move on to Network Security. The lecture slides are available.
• Lab 5 is due by 10 am on Tuesday, 22nd April . Next week, a tutorial will replace the lab (in your usual labs or online). This will serve as helpful practice for the final exam. Please look through the questions beforehand and try to solve them by yourself. All questions on the tutorial are from past exams, so effectively, it is a sample exam.
• We have two public holidays next week: Monday, 21st April (Easter Monday) and Friday, 25th April (ANZAC day). Alternate arrangements have been made for the Monday and Friday tutorials. Check the schedule here .
• Please complete the myExperience surveys . The response rate so far is very low (only about 10 % ). I am sure you all can do better. We would appreciate your feedback.
• Information about the final exam is now available on the Final Exam page. I will discuss the exam in the lecture on Wednesday. It is an invigilated on-campus exam and Inspera-based . You will need to bring your own device and install the Safe Exam Browser on it. Instructions are here .
• The assignment is due by noon on Thursday, 24 April . This is a hard deadline. Assignment consults are running, so seek help if you need it. Please test your code in VLAB before submitting it to avoid angst later. If your code does not run as expected in VLAB, then there isn't much we can do about it.

I know next week will be busy for everyone, but don't overwhelm yourself. Good luck with everything.

Reliability Testing for Assignment

Posted by Tim Arney Tuesday 15 April 2025, 01:37:48 PM.

We've made a proxy available on the CSE servers to simulate UDP packet loss.

Running the Proxy

To run the proxy, the basic usage is:

3331 lossy_proxy <request_port> <forward_port>

Here’s what those ports mean:

• <request_port> is the port that your clients should send their messages to, i.e. the "server_port" you give to your clients.
• <forward_port> is the port that your server should be listening on, i.e. the "server_port" you give to your server.

Important: These two ports must be different — the proxy needs to sit between the clients and the server so it can forward (or drop!) messages appropriately — and the proxy must be running on the same host as your server and clients.

Example

Say you run:

3331 lossy_proxy 49283 54923

That means:

• Clients should send messages to port 49283.
• The server should expect messages on port 54923.

Packet Loss

By default, the proxy simulates a 10% chance of dropping messages in both directions (client → server and server → client). You can change this using the `-f` (forward drop rate) and `-r` (reverse drop rate) flags:

3331 lossy_proxy 49283 54923 -f 0.0 -r 1.0

This configures the proxy to:

• Drop no packets from client to server (`-f 0.0`)
• Drop all packets from server to client (`-r 1.0`)

Don't worry too much — the marking won't aggressively test extreme loss scenarios. As long as your system can handle the occasional dropped packet (1–2 per interaction), you’ll be fine.

TCP Support

The proxy also tunnels TCP connections , so you can still use it to test commands like `UPD` and `DWN`. Note that TCP traffic is not made unreliable — the proxy passes it through without simulating loss.