Syllabus
CS 438: Computer Networks (formerly "Communication Networks") is an introductory course on computer networks at the University of Illinois Urbana-Champaign (UIUC). The course examines the fundamental principles, architectures, and protocols that enable networked systems to communicate reliably and efficiently.
As computer networks form the backbone of modern computing — supporting the Internet, cloud services, mobile applications, large-scale distributed systems, and AI systems — this course provides essential conceptual and practical foundations for understanding how today's networked systems are designed, implemented, and evaluated. Modern AI workloads rely heavily on computer networks for large-scale data collection, distributed training, and the deployment of intelligent services, making a solid understanding of networking fundamentals increasingly important.
CS 438 also serves as the prerequisite for CS 538: Advanced Computer Networks, a research-oriented seminar course, and is generally suitable for students considering systems, networking, or AI infrastructure as a potential career focus.
Grading Policy
The overall score for the course will be computed as a weighted sum of the following components:
Note that students enrolled for 4 credit hours (as opposed to 3) are required to complete a mini project in addition to the standard coursework. Their overall score, with a maximum of 133%, will be normalized to 100% for final grade computation.
Bonus points may be awarded throughout the semester and will be added on top of the (normalized) overall score at the end of the course. Additionally, a grading curve may be applied prior to converting the scores to letter grades.
Regrading policy: Students may request a regrade for any problem set, programming assignment, or exam within one week of the grade being posted. Requests must be made on Campuswire through posts private to the course staff, clearly specifying the justification for the regrade.
Late Policy
You have a total of 7 grace days (rounded up to the nearest 24-hour period) that may be applied to any problem set or programming assignment without penalty.
Example: 23h 50m is considered 1 day, but 24h 10m will be counted as 2 days.
At the end of the course, grace days will be applied automatically in a way that maximizes your score. You do not have to specify which assignments to apply them to when submitting your work.
When grace days are not applied (during the score maximization), late submissions will incur a penalty of 10% per day (rounded up to the nearest 24-hour period) of the assignment's total points.
Example: 25 hours late will incur a penalty of 20%, i.e., your final score for the assignment will be multiplied by 80%.
⚠️ Late work will not be accepted after 72 hours past the original deadline.
Problem Sets
- There will be four problem sets (PS1, PS2, PS3, PS4) throughout the semester, each worth 3%.
- Due dates will be announced on the course schedule.
- Submit your solutions on Campuswire.
Programming Assignments
- There will be four programming assignments worth a total of 48%: 3% MP0, 11% MP1, 17% MP2, 17% MP3.
- Due dates will be announced on the course schedule.
- Submit your solutions on Campuswire.
- You can discuss very general concepts with others, but if you find yourself looking at a screenful/whiteboard of pseudocode (let alone actual code), you have gone too far.
- MPs solutions can be in C or C++. However only C will be officially supported by the staff (meaning we may not always be able to answer code-related questions on C++). If you choose to use C++, you may not use any socket programming libraries; all the networking should be implemented using the standard C API covered in class.
- If you wish to use a library for data structures, you must first obtain approval from the course staff and then acknowledge the source in your README file. However, all algorithms (e.g. Dijkstra's) must be implemented by yourself.
Exams
Midterm and final exams will be announced on the course schedule.
Exams will be closed-book and closed-notes. You are only allowed to bring pens and empty sheets of paper.
Make-up exams: We offer accommodations for legitimate conflicts with the exams, but you must submit a formal request via email to both instructors — including supporting documentation — at least a week before the exam. Emergencies will be handled on a case-by-case basis. If your request is approved, you will be allowed to take a make-up exam, typically scheduled within a week of the original date.
Mini Project
The mini project is required only for students enrolled for 4 credit hours. It could be either a research-oriented exploration of a networking topic of your choice, or an engineering project involving the design and implementation of a networked system.
By Week 5 (the exact date will be announced on the course schedule), you must submit a few paragraphs on Campuswire outlining your proposed idea. This brief "proposal" will not be graded but must be approved by the course staff before you proceed with the project. You are strongly encouraged to attend office hours to discuss and refine your project plans.
The mini project consists of two deliverables:
- Poster presentation: You will present your project during a poster session to be held near the end of the course. External guests will also be invited to attend the session. More details will be shared later in the semester.
- Project report: You must submit a short written report summarizing your work. Format: 5 pages (excluding references), 11pt Times New Roman, single space, single column, with 1 inch margins. You may use our LaTeX template if you prefer.
Course Communication
Please post all general questions regarding lectures, problem sets, programming assignments, exams, or course logistics on Campuswire rather than emailing the course staff, so that all students can benefit from the discussion. You may choose to post anonymously to your classmates; however, the instructors will always be able to see the author of a post.
Exceptions: Do not post complete or partial solutions to any assignments on Campuswire. If in doubt, contact the course staff first. For personal or sensitive matters, please email both instructors.
You are expected to regularly monitor Campuswire for course announcements, as well as responses to your classmates' questions since repeated Q&A will be a waste of shared resources. The course staff will also regularly monitor Campuswire and aim to respond within 24 hours (excluding weekends).
That said, the class benefits greatly when students help answer each other's questions. A 1% bonus point will be awarded to selected students at the end of the course based on overall contributions on Campuswire (considering statistics and quality).
Textbooks
There is no required textbook. The primary reference for this course is:
- Computer Networks: A Systems Approach (open source), by Peterson and Davie.
Other recommended textbooks include:
- Computer Networking: A Top-Down Approach, by Kurose and Ross.
- Computer Networks, by Tanenbaum and Wetherall (and Feamster).
For the Unix network programming portion of the course, we recommend:
- UNIX Network Programming, Volume 1: The Sockets Networking API, by Stevens, Fenner, and Rudoff.
Academic Honesty
- You must adhere to the CS Honor Code.
- All submitted work must be your own.
- Please refer to the GenAI policies above regarding the use of GenAI tools for problem sets and programming assignments.
- We may use similarity-detection tools to compare submitted code and binaries against other submissions, including those from previous semesters.
- Academic dishonesty — including, but not limited to, copying or sharing answers during exams, plagiarizing homework solutions, sharing project code, or using code found online — will result in a grade of zero on the first offense.
- Subsequent violations will lead to failure in the course and/or a recommendation for dismissal from the university.
Sexual Misconduct Policy and Reporting
The University of Illinois is committed to combating sexual misconduct. Faculty and staff members are obligated to report any instances of sexual misconduct — which also includes harassment, sexual assault, sexual exploitation, dating violence, domestic violence, and stalking — to the University's Title IX Office. What this means is that as your professor, I am required to report any incidents of sexual misconduct that are directly reported to me, or of which I am somehow made aware. When a report is received, an individual with the Title IX Office reaches out to provide information about rights and options, including accommodations, support services, the campus disciplinary process, and law enforcement options.
There is an exception to this reporting requirement about which you should be aware. A list of the designated University employees who, as counselors, confidential advisors, and medical professionals, do not have this reporting responsibility and can maintain confidentiality, can be found here: wecare.illinois.edu/resources/students/#confidential.
Other information about resources and reporting is available here: wecare.illinois.edu.