CS475: Computer Networks

[ Course Info | Course Objectives and Goals | Resources | Instructors | Textbooks | Schedule | Grading | Course Policies | Course Details ]

OSI Model v1
World map of submarine cables
Welcome to CS475!

Course Info

  • Course Number and Title: CS475 - Computer Networks
    • Section A
  • Credit Hours: 4 Semester Hours
    • Credit Hours include "contact time" in the classroom and outside course work. It is expected that the sum of classroom time and outside course work time should add up to three times the listed credit hours per week.
  • Course Webpage: https://BillJr99.github.io/Ursinus-CS475-Spring2021

  • LMS (Canvas): Canvas

  • Course Calendar: Import the course calendar into your favorite calendar app with this link!

  • Class Notebook: Access our class notebook here! If you are unable to access the notebook, please let me know and I will share the document with your account.

  • Help Room on Microsoft Teams: Click Here to Go to the Teams Help Room Channel on Microsoft Teams.

  • Academic Term: Spring 2020-21

  • Term Start and End: through

  • Course Prerequisites: CS274

  • Class Meeting Locations and Times:
    • Section A:
      • s from 10:00 AM to 10:50 AM in Kaleidoscope
      • s from 10:00 AM to 10:50 AM in Kaleidoscope
      • s from 10:00 AM to 10:50 AM in Kaleidoscope
  • Zoom Link for Class Sessions (see Canvas for password, and class recordings can be found on Panopto on Canvas):
  • Midterm Exam:
    • Section A: 2021/02/26 from 10:00 AM to 10:50 AM in Regular Class Period
  • Final Exam:
    • Section A: 2021/05/10 from 9:00 AM to 12:00 PM in REMOTE
  • Course Description: Architecture and protocols of computer networks. Protocol layers; network topology; data-communication principles, including circuit switching, packet switching and error control techniques; sliding window protocols, protocol analysis and verification; routing and flow control; local and wide area networks; network interconnection; client-server interaction; emerging networking trends and technologies; topicsin security and privacy. This course will satisfy the College requirement for a capstone experience in the major. Prerequisite or co-requisite: CS-274. Offered in the spring of odd years. Three hours per week. Four semester hours.

Course Learning Objectives and Learning Goals

Learning Objectives

  1. To comprehend the design of a network protocol suitable for implementation
  2. To select appropriate network protocols at each layer of abstraction
  3. To write multithreaded code capable of multiplexing simultaneous socket I/O requests

Learning Goals

  1. To articulate network privacy concerns with a global context, and to identify practices and techniques to improve online privacy
  2. To differentiate between various models of network security, including authentication, authorization, and non-repudiation
  3. To identify and differentiate between approaches to fairness and quality-of-service on the Internet

The Questions

Throughout the course, we will be thematically guided by the Ursinus Questions:
  • What should matter to me?
  • How should we live together?
  • How can we understand the world?
  • What will I do?



Ursinus College and your instructor are committed to ensuring equal access and providing reasonable accommodations for all students. If you have, or think you have, a disability in any area such as, mental health, attention, learning, chronic health, sensory, or physical, please contact the Director of Disability Services.

Ursinus College is committed to ensuring equal access and providing reasonable accommodations for students with disabilities. The Institute for Student Success works with students who have any kind of disability, whether apparent or non-apparent, learning, emotional, physical, or cognitive, and need accommodations to increase their access to this learning environment. I encourage you to reach out to the Director of Disability Services, Dr. Dolly Singley to discuss about supports and accommodations you may need. Dolly’s office is located in the Institute for Student Success in Lower Wismer. You can schedule a meeting with Dolly by using this link: https://dsingley.youcanbook.me/, by emailing her at dsingley@ursinus.edu or by calling her at 1-484-762-4329. Students can also review accessibility and disabilities services online at https://www.ursinus.edu/offices/institute-for-student-success/students-with-disabilities/.

Let's Talk

Let's Talk Poster
Mental health care is increasingly recognized as a crucial service for the undergraduate population. To decrease the barrier for entry, Ursinus college will be providing additional drop-in hours during the semester. Please refer to the flyer below for the awesome program. I am happy to discuss this in drop-in / office hours in more detail. Additionally, please know that the Wellness Center is available for students and includes a crisis hour at 2-3pm each weekday.

Peer Coaching

The Institute for Student Success offers Peer Coaching that you can sign up for anytime.

In addition, the Institute for Student Success has established specific tutoring sessions for students in our class. Please visit the tutoring site for the schedule and how to attend!

Center for Writing and Speaking

The Center for Writing and Speaking is available for one-on-one and group appointments to advise you as you revise your writing projects and presentations. They will even support your personal projects and extracurricular activities! Please feel free and encouraged to review any and all writing and speaking work from this class with them.


The Bear2Bear fund is a student emergency fund established to assist with temporary emergency financial circumstances.

Help Room

The Math Help Room (Pfahler 102) is a great place to go if you are struggling and is managed by the Institute for Student Success. Students who have previously taken the course will be there to help you with the assignments.

Course Instructors and Drop-In / Office Hours

Role Name and Contact Information Drop-In / Office Hours
Professor William Mongan
Picture of Professor William Mongan

Phone: 610-409-3410
E-Mail: wmongan@ursinus.edu
Office: Pfahler Hall 101L
  • s from 5:00 PM to 6:00 PM in Virtual Office Hours on Microsoft Teams Help Room
  • s from 9:00 AM to 10:50 AM in Virtual Office Hours on Microsoft Teams Help Room
  • s from 2:00 PM to 3:00 PM in Virtual Office Hours on Microsoft Teams Help Room
  • s from 5:00 PM to 6:00 PM in Virtual Office Hours on Microsoft Teams Help Room
  • s from 9:00 AM to 10:00 AM in Virtual Office Hours on Microsoft Teams Help Room
  • s from 11:00 AM to 12:00 PM in Virtual Office Hours on Microsoft Teams Help Room
  • s from 1:30 PM to 3:30 PM in Virtual Office Hours on Microsoft Teams Help Room
Drop-In / office hours are certainly available for asking questions about the course, about your assignments, and other academic questions you may have. You do not need an appointment to come to drop-in hours, and you do not even need to have an agenda or set questions! You can come and just have a general chat about things with us. If you cannot make it to drop-in hours, you can contact us for an appointment as well. Drop-In hours are also for non-instructional topics of conversation: you can talk with me about your adjustments to college life, your long-term goals, advice about your academic journey, and most other things. If I don't know the answer to something or if I don't feel I am the best person to offer you advice about it, I will be happy to help connect you with the right people. In other words, don't be afraid to ask me things that you think are "off topic" - I love teaching because I love to be a resource for you on your journey. I'll be happy to see you there.


Required? Title Author Edition ISBN Freely Available?
Required An Introduction to Computer Networks Peter L Dordal 2nd Edition 978-0133594140 Online Version
Required TCP/IP Tutorial and Technical Overview Lydia Parziale et al IBM Redbook N/A Online Version
Recommended / Supplemental Computer Networking: A Top Down Approach Jim Kurose and Keith Ross 8th Edition N/A
Please Note: The cost of the book may be prohibitive for some students, so please note that renting the book is much cheaper. Please communicate as early as possible if you are having trouble obtaining the book, rather than keeping this to yourself, so that we can work on a solution together. If you are experiencing a financial hardship, please consider the Bear2Bear Emergency Fund for temporary relief applications.

Course Schedule

Week Date Title Readings Deliverables
Week 1 Course Overview
Week 1 Sending Packets
Week 2 Motivating Examples: nslookup, HTTP, Traceroute
Week 2 Networking: A Layered Approach
Week 2 The Physical Layer: Considerations
  • Dordal Ch. 2
Week 3 TDMA with CSMA and ALOHA
Week 3 CSMA and ALOHA
Week 3 Ethernet
Week 4 Wi-Fi with FDMA and CDMA Wireless Protocols
  • Dordal Ch. 4
Week 4 The Link Layer
  • Dordal Ch. 5
Week 4 Switching
Week 5 From Bits to Packets
Week 5 The Network Layer and IPv4
Week 5 IPv4 Addressing and Subnets
Week 6 IPv4 Addressing and Subnets
Week 6 IP Multiplexing with NAT
  • Midterm Exam: Midterm Handed Out
Week 6 Outside Address Lookups with DNS
Week 7 Inside Address Lookups with ARP
Week 7 Dynamic Configuration with DHCP
Week 8 ICMP and Ping
Week 8 IPv6
  • Dordal Ch. 11
Week 8 VPN and Tunneling
Week 9 Routing
Week 9 Distance Vector Algorithms
Week 9 Hierarchical Routing
  • Dordal Ch. 14
Week 10 Routing at Scale: BGP
Week 10 The Transport Layer: Considerations
Week 10 Basic Transport Services with UDP
Week 11 UDP
Week 11 Coordinating Transport Services with TCP
Week 12 TCP
Week 12 TCP Sliding Window Protocols
  • Dordal Ch. 8
Week 12 Congestion Management with TCP
Week 13 Application Layer Protocols
Week 13 HTTP and SMTP
Week 13 Socket Programming
Week 14 Socket Programming
Week 14 Multithreaded Socket Programming
Week 14 Security and Privacy
  • Redbook Ch. 22
Week 15 Security and Privacy
Week 15 Security and Privacy with Public Key Cryptosystems
Week 16 Review
Please note the following holidays this term:
Please note the following key calendar dates:
  • Add Deadline:
  • Drop with a W Deadline:
  • Designated Tuesday Schedule:
  • Designated Wednesday Schedule:
  • Designated Thursday Schedule:

Grade Breakdown

Letter grades will be assigned on the scale below at the end of the course. "Grade grubbing" is not conducive to professional practice; every assignment has or will have very precise expectations and point breakdowns, and I will evaluate submitted work carefully according to these standards. I will also return assignments in a timely manner, and the running weighted grades will be updated frequently. Therefore, I expect a commensurate level of respect from you. In sum, you should know where you stand at all times, there will be plenty of opportunities to improve your standing, and there should be no surprises at the end of the course.

Grading Table

Item Weight
Programming Assignments 25%
Labs 40%
Midterm Exam 15%
Final Project 10%
Class Participation and Quizzes 10%

Letter Grades

Letter Grade Range
A+ 96.9-100
A 93-96.89
A- 89.5-92.99
B+ 87-89.49
B 83-86.99
B- 79.5-82.99
C+ 77-79.49
C 73-76.99
C- 69.5-72.99
D+ 67-69.49
D 63-66.99
D- 59.5-62.99
F 0-59.49

Course Policies

Netiquette in Online Discussion Boards infographic
Courtesy of the Online Education Blog of Touro College.

Classroom Environment and Inclusivity Standards

My goal is to foster a environment in which students across all axes of diversity feel welcome and valued, both by me and by their peers. Axes of diversity include, but are not limited to, age, background, beliefs, race, ethnicity, gender/gender identity/gender expression (please feel free to tell me in person or over e-mail which pronouns I should use), national origin, religious affiliation, and sexual orientation. Discrimination of any form will not be tolerated. Furthermore, I want all students to feel comfortable expressing their opinions or confusion at any point in the course, as long as they do so respectfully. As I will stress over and over, being confused is an important part of the process of learning computer science. Therefore, I will not tolerate any form of put-downs by one student towards another about their confusion or progress in the class. Learning computer science and struggling to grow is not always comfortable, but I want it to feel safe. Much of this material is probably new to everyone, and those with some prior experience likely recall a time when it was new to them, too. Remember that this is not a competition: helping others to grow is itself a richly rewarding professional development opportunity. In order to allow for equitable access to class for students who may be attend and participating remotely, I may record our class sessions. These recordings will only be available on our Canvas site. I will announce that we are recording in the beginning of any classes of this kind; out of respect and privacy for me and all class members, please do not download, copy, or redistribute class recordings.

Online Communication Policy

Since this is a class-wide communication, the following rules apply to message groups and electronic communications:
  1. Students are expected to be respectful and mindful of the classroom environment and inclusivity standards.
  2. They are equally applicable to a virtual environment as they are in class.
  3. Students are not permitted to share direct answers or questions which might completely give away answers to any homework problems or labs publicly on Microsoft Teams. When in doubt, please send me a direct message there.
  4. I will attempt to answer questions real time during my virtual drop-in / office hours. Otherwise, I will make every attempt to respond within 24 hours. Of course, students can and should still respond to each other outside of these intervals, when appropriate!
  5. Students may ask anonymous questions.

Course Management Systems: Canvas, Microsoft OneNote, and Microsoft Teams

We will be using Canvas to post all of the grades. For the most part, we will submit work using Canvas as well. For class activities and notes, we will be using OneNote, and for other discussions and announcements for the course, including messaging me directly with questions, we will use Microsoft Teams. OneNote and Teams are linked to your Office suite through Ursinus, so you are automatically enrolled. There you can ask and answer questions about the lecture content and assignments.

Since it is likely that students will have similar questions, it is much more efficient for me to answer them there so the whole class can see the answer, so it is possible that I will ask you to re-send a question on the forum that I get in e-mail (please do not be shy or take it personally if I do so; it means it was a great question and worth sharing with everyone!). There will be an anonymous option at the top of every chatroom to help facilitate this.

Collaboration Policy and Academic Integrity Policy

Communication between students is allowed (and encouraged!), but it is expected that every student's code or writeups will be completely distinct! Please do not copy code off of the Internet (repurposing code from the Internet will probably make it harder anyway because the assignments are so specialized). Please cite any sources in addition to materials linked from the course website that you used to help in crafting your code and completing the assignment.

See the Course Management page in the Faculty Handbook for an explanation of college policies on plagiarism and other academic honesty violations.

To encourage collaboration, students will be allowed to choose one "buddy" to work "near" during the assignment. Students are still expected to submit their own solutions, but they are allowed to provide substantial help to their designated buddy, and even to look at the buddy's code during the process. Students must indicate their buddies in the README upon assignment submission. Please let me know if you would like a buddy but are having trouble finding one.

Below is a table spelling out in more detail when and how you are allowed to share code with people (table style cribbed from Princeton CS 126).

Please Note: The terms "exposing" and "viewing" exclude sending or ingesting electronically, which would be considered copying. Exposing and viewing are normally done in the context of in-person working or in the help room. In addition, "Other People" includes internet sources!
Your Buddy Course Staff Course Grads Classmates Others
Discuss Concepts With OK OK OK OK OK
Acknowledge Collaboration With OK OK OK OK OK
Expose Your Code/Solutions To ALL EXCEPT
View the Code/Solutions Of ALL EXCEPT
Copy Code/Solutions From NO NO NO NO NO

If the work you submit appears to be copied from previous work or the collaboration policy has been violated in any way (including working with more collaborators or "buddies" than the course deliverable specifies) according to the College Academic Honesty policy, regardless of intent, then it may be an academic dishonesty case, and it will be referred to the Associate Dean for Academic Affairs. I am required to make this report in every occurrence, so it is best to speak with me first if there are any questions about the policy or expectations. You should feel free to have these conversations with me anytime prior to making your submission without fear of penalty. Finally, aside from the collaboration policy here, it is expected that your work is your original work. You must cite any collaborations or references that you use. You may have a friend or relative with computing experience, but they should not do your assignments, labs, etc., for you.

Flexible Submission Policy

In the absence of accommodations arranged in advance with the instructor or college, all assignments are due at 11:59PM Eastern Time on the date(s) stated on the schedule. Assignments will be accepted without prior permission following this time with a points deduction of 3% per day if submitted before 11:59 PM Eastern Time on the day submitted. Late work cannot be accepted after the final class meeting, nor during final exams week, nor after the exam.

Title IX

Title IX is a federal law, under which it is prohibited to discriminate, harass, or commit misconduct on the basis of gender or sex. The Title IX Coordinator is available to receive inquiries and to investigate allegations in this regard.

Inclement Weather and Class Cancellation Policy

In the event that the College closes due to inclement weather or other circumstances, our in-person class sessions, drop-in / office hours, labs, or other meetings will not be held. I will contact you regarding our plan with regard to rescheduling the class or the material, any assignments that are outstanding, and how we can move forward with the material (for example, any readings or remote discussions that we can apply). If necessary, I may schedule online virtual sessions in lieu of class sessions, and will contact you with information about how to participate in those. I will communicate this plan to the department so that it can be posted on my office door if it is feasible to do so. This policy and procedure will also apply in the event that the College remains open but travel conditions are hazardous or not otherwise conducive to holding class as normal. Should another exigent circumstance arise (for example, illness), I will follow this policy and procedure as well.

Miscellaneous Policies

  • COVID-19 Requirements/Policy: For in person sessions, you are required to wear a mask and you will be asked to leave the classroom if you are not properly wearing a mask. If you forget your face mask, disposable masks will be available in all buildings. DO NOT attend class if you do not feel well; you are always welcome to attend remotely, but just contact me if you are unable to attend class at all. In the event our course must go fully remote, we will continue towards achieving the course learning goals, but there may be adjustments to the schedule, content, assessments etc. My drop-in / office hours will mainly be conducted remotely to maintain physical distancing.

Student Perception of Teaching Questionnaire (SPTQ)

I will be soliciting student feedback through the SPTQ and possibly through other forms of commentary. This feedback greatly assists me and the department as we develop our courses and overall curriculum for this program. This course has benefitted from the feedback of those students who took the course before you, and your feedback will help maintain and improve the course for those to follow. I strongly encourage you to participate in this important and valuable process.

Syllabus Subject to Change

I will do my best to provide all relevant information about the course on this syllabus. Sometimes, exigent circumstances, the pace of the class, or other circumstances will warrant minor revisions to the syllabus. For example, inclement weather or other campus closure might affect the course schedule and assignment deadlines; in addition, I may find that the class benefits from spending more time on a particular topic, and adjust accordingly. Although I try to avoid rescheduling drop-in / office hours, it may become necessary from time to time to accommodate other events in the College. Should any revisions be necessary, I commit to making any revisions in my estimation of the best interests of the class, and commit to communicating those changes to you as soon as I make them.

Course Details


Computer Networks study interconnected computing systems at scale from many different perspectives. Moving a bit from one computer to another over the Internet is a complex process. The bit must travel to its destination from one computer to another, which must have some way of knowing where that bit is trying to go so that it can be moved along the right path. Wireless communications (and even wired connections) are subject to noise and interference that may corrupt the bit as it transits between any two of those computers. We need ways to manage these destination addresses, optimal pathways, and mechanisms to detect corrupted messages. Sometimes, computers might become too overworked to forward your message, and they can be lost: worse yet, we cannot communicate this situation back to the sender (after all, if we had the resources to do so, we could have just forwarded the message properly!). The sender, then, needs a way to ensure that their message was received, and received in-tact. Ideally, we would do so efficiently: if new, faster paths to the destination appear (sort of like new expressways on the interstate highway system), we’d like to find out about them and utilize them, traffic permitting. Even then, we need to define what those bits represent: an e-mail, a webpage, a function call, or data like a shopping cart. And beyond all this, we need a mechanism to enable these communications to occur privately and securely: we want to ensure that the sender and receiver can validate one another’s identity and privilege. To facilitate all of this, we organize the study of computer networks into a “layered” model, in which we investigate each of these concepts independently of the others. In fact, networks are implemented according to this layered model, which greatly simplifies the apparent complexity of the network as a whole: we implement an independent algorithm for each concept, and they interact only as much as is required (typically, only with one or two neighboring algorithms, which, in turn interact with their immediately adjacent layers).



Every week, we will have a lab session where students get a chance to practice concepts we just learned in a safe and collaborative environment. Tasks will be given that serve as warm-ups for the larger assignments, and final submissions will be graded on a scale from 0 to 2. Students will have a chance to refine their submissions until the Friday of every week, and there will be help from the Lab T.A.s listed above.


The bulk of the grade in the course will be earned by completing individual programming assignments. Be sure to start them early! Note that collaboration and sharing rules differ slightly for labs and assignments.

Classroom Participation

Group Work [1]

In addition to ordinary participation that follows the natural rhythm of a lecture, most days there will be at least one followup problem, which is a question that follows on the heels of newly presented material. Students will split into groups of 2 and try to write some code to address a particular problem. When a group of students believe they have figured out the answer, they raise their hand. The other students can continue to work while I verify that the answer is correct. If the answer is correct, the students present the answer to the class. If the group is not correct upon my checking, then the groups continue this process until one gets it correct.

Other ways to help your fellow classmates in class are as follows:

  • Helping to teach a student a topic during office hours.
  • Certain calls for participation in class
  • Particularly helpful or insightful messages on Microsoft Teams
  • Finding mistakes in the book or on the assigned homework and labs

Class Participation and Classroom Etiquette [1]

For classroom attendance, the following rules apply:

  • Please be attentive during class. There will be class exercises that involve coding, but class time should be used for learning computer science. It is imperative that technology be used for this purpose during our class time together. Alternatively, please try to think of this as a safe space away from social media. We could all use a break, and we are fortunate to have a good excuse to make that space.
  • Please follow common courtesy. For instance, you can bring food and drink as long as it’s not distracting, but please clean up after yourself if you do. Our janitorial staff deserves the utmost respect and help with their job.
  • In-class exercises and “low stakes” activities will take place individually and in groups to assess our progress together. These exercises will be given both synchronously (for example, in-class activities, pair programming exercises) and asynchronously (for example, pre-lab exercises, peer code reviews, book surveys) and will be graded on a participation basis. These are given equal weight and form the basis of the class participation score.
  • If a class session is remote, please feel free to make choices that make you most comfortable. For example, I will record these sessions for students who cannot make the session or for those who would benefit from a review of the material. I’d encourage you to enable your video feed if it is available, but if you need leave your video off, you feel free to do so; however, if you find that this becomes necessary on a prolonged basis, please see me to discuss. Please keep your microphone on mute to avoid background noises while others are speaking; however, please do not feel “mic fright” about unmuting to speak up and participate anytime. If, however, you would prefer to communicate via the chat interface (either exclusively or in combination with your audio/video), you should feel free to do that. Whether in-person or remote, all I ask is that you engage as best you can; the material is challenging but fun, and we’re all here to learn new things together.
  1. This introduction is adapted from Dr. Tralie’s CS173 Course Syllabus 2