CS 3700 – Networks and Distributed Systems


Instructor: Long Lu and Christo Wilson
Location: Lu: Behrakis 325
Wilson: West Village G 104
Meeting Times: Lu: Tuesday/Friday 3:25 – 5:05pm
Wilson: Monday/Wednesday 2:50 – 4:30pm
Office Hours: Thursday 2 – 4pm (or by appointment)


  • Course Description

    The Internet has become an integral part of modern society. We are constantly connected by smart, mobile devices backed by large-scale, cloud-based infrastructure. Thus, it has become critically important for computer scientists to be familiar with the fundamentals of computer networking, and the design principals behind distributed systems that leverage the network. This course will focus on the architecture, algorithms, and protocols of the Internet, as well as key design principals of distributed systems. Topics include local area networking, routing, congestion control, the domain name system, network security, and applications such as distributed key-value stores, peer-to-peer and content distribution networks, and crypto-currencies. This course will be systems oriented, and students will work on hands-on projects to learn how to build and understand Internet applications. .


    The official prerequisites for this course are CS 3600 or CS 3650. This course is systems oriented, so I expect you to understand the basics of computer architecture and operating systems, and to have experience implementing non-trivial systems-type projects. Basic knowledge of the Unix command line is essential. You should know how to write code using emacs/vim, write a makefile, compile code using makefiles, check for running processes, kill runaway processes, and create compressed archives. Experience with a debugger is recommended.

    Class Forum

    The class forum is on Piazza. Why Piazza? Because they have a nice web interface, as well as iPhone and Android apps. Piazza is the best place to ask questions about projects, programming, debugging issues, exams, etc. To keep things organized, please tag all posts with the appropriate hashtags, e.g. #lecture1, #project3, etc. I will also use Piazza to broadcast announcements to the class. Bottom line: unless you have a private problem, post to Piazza before writing me/the TA an email.

    Projects and Groups

    There will be five programming projects throughout the semester. Programming projects are due at 11:59:59pm on the specified date. You will use a turn-in script to create a compressed archive of the project files, timestamp them, and submit them for grading. These projects require significant design and coding, hence students are recommended to start early!

    You will form groups of two people (possibly three, if necessary) to do the projects. I will allow you to form your own groups; if you are having trouble finding a partner, post a notice to Piazza. As you are free to choose your partner(s), I will not be sympathetic to complaints at the end of the semester about how your group-mates did not do any work. If you are having problems with your teammate(s), tell me about it sooner rather than later. You may switch groups between programming projects. All group members should be involved in all major design decisions, and groups should develop a programming plan that can be effectively parallelized. The course projects are hard, so you will want to distribute work between yourself and your teammate.

    Most projects can be programmed in a language of your choice. The only universal requirement is that your projects must compile and run on an unmodified CCIS Linux machine. Notice the stress on unmodified: if you’re relying on libraries or tools that are only available in your home directory, then we will not be able to run your code and you will fail the assignment. You are welcome to develop and test code on your home machines, but in the end everything needs to work on the CCIS Linux machines. If you have any questions about the use of particular languages or libraries, post them to Piazza.


    This course will have ten homework assignments reviewing concepts in class. Homework assignments are to be done by each student individually. The homework assignments will be graded and handed back to you within a week. Links to the homeworks can be found in the above schedule.

    Homework assignments are due at the beginning of lecture on the specified date. Late homework assignments will not be accepted, and slip days may not be used for homeworks (see the late policy, below).


    There will be one midterm and one final. All exams will be closed book and closed notes, and computers are not allowed nor is any access to the Internet via any device. The exams will cover material from lectures, readings, and the projects. The final will be cumulative, so review everything!

    Participation and Attendance

    I do not require students to attend class, and I won’t be taking attendance. If you need to miss class for any reason, you don’t need to tell me beforehand. That said, I like teaching and interacting with students, so please attend class and speak up. I welcome questions and discussion!


    • Projects (5): – 4%, 14%, 10%, 8%, 14%
    • Homeworks (11): – 2% each
    • Midterm and Final: – 14% each

  • Schedule

    Students should check this schedule regularly as changes may happen without separate announcements.
    Last update: 11/30/2018

    Date Topic & Slides Readings & References Note
    9/7 Intro, History, Network Programming Beej’s Guide Proj. 1 Out (Slides)
    9/11 Network Architecture, Physical Layer §1.1-1.6, 2.1-2.3
    9/14 Data Link Layer §2.4-2.8
    9/18 Data Link Layer §2.4-2.8
    9/21 Bridging and Switching §3.1, 3.4 Hw. 1 Due
    Proj. 1 Due
    Proj. 2 Out
    9/25 Network Layer §3.2
    9/28 Intra-domain Routing, Inter-domain Routing §3.3 4.1 Hw. 2 Due
    10/2 Transport Layer §5.1-5.2
    10/5 Transport Layer §6.1-6.4 Hw. 3 Due
    10/9 No class
    Midterm: 6-9pm, Wed. Oct. 10 in ISEC 102
    10/12 NAT, DNS §9.3 Hw. 4 Due
    Proj. 2 Due
    10/16 Distributed Systems Overview, Web Architecture †5; §9.1 Proj. 3 Out (Slides)
    10/19 Web Architecture Hw. 5 Due
    10/23 P2P and BitTorrent (with audio) †10.1-10.3, 20.6 Hw. 6 Due
    10/26 Overlay Networks §9.4; †10.4-10.7 Proj. 3 Due
    10/30 Overlay Networks, Time and Logical Clocks †14 Proj. 4 Out
    11/2 Fault Tolerance and Consensus
    11/6 Fault Tolerance and Consensus
    11/9 Fault Tolerance and Consensus Hw. 7 Due
    11/13 Network Security, Transport Layer Security §8
    11/16 No class Proj. 4 Due
    Proj. 5 Out
    11/20 Transport Layer Security Hw. 8 Due
    11/23 No class: Turkey Day
    11/27 Bitcoin Hw. 9 Due
    11/30 Bitcoin, Anonymous Communication
    12/4 Anonymous Communication Hw. 10 Due
    Proj. 5 Due (12/5)
    12/12 Final Exam 1:00 pm – 3:00 pm, Richards Hall 300


  • Requests for Regrading

    In this class, we will use the Coaches Challenge to handle requests for regrading. Each student is allotted two (2) challenges each semester. If you want a project or a test to be regraded, you must come to the professors office hours and make a formal challenge specifying (a) the problem or problems you want to be regraded, and (b) for each of these problems, why you think the problem was misgraded. If it turns out that there has been an error in grading, the grade will be corrected, and you get to keep your challenge. However, if the original grade was correct, then you permanently lose your challenge. Once your two challenges are exhausted, you will not be able to request regrades. You may not challenge the use of slip days, or any points lost due to lateness.

    Note that, in the case of projects, all group members must have an available challenge in order to contest a grade. If the challenge is successful, then all group members get to keep their challenge. However, if the challenge is unsuccessful, then all group members permamently lose one challenge.

    Late Policy

    For programming projects, we will use flexible slip days. Each student is given four (4) slip days for the semester. You may use the slip days on any project during the semester in increments of one day. For example, you can hand in one project four days late, or one project two days late and two projects one day late. You do not need to ask permission before using slip days; simply turn in your assignment late and the grading scripts will automatically tabulate any slip days you have used.

    Slip days will be deducted from each group member’s remaining slip days. Keep this stipulation in mind: if one member of a group has zero slip days remaining, then that means the whole group has zero slip days remaining.

    After you have used up your slip days, any project handed in late will be marked off using the following formula:

    Original_Grade * (1 – ceiling(Seconds_Late / 86400) * 0.2) = Late_Grade

    In other words, every day late is 20% off your grade. Being 1 second late is exactly equivalent to being 23 hours and 59 minutes late. Since you will be turning-in your code on the CCIS machines, their clocks are the benchmark time (so beware clock skew between your desktop and CCIS if you’re thinking about turning-in work seconds before the deadline). My late policy is extremely generous, and therefor I will not be sympathic to excuses for lateness.

    Cheating Policy

    It’s ok to ask your peers about the concepts, algorithms, or approaches needed to do the assignments. We encourage you to do so; both giving and taking advice will help you to learn. However, what you turn in must be your own, or for projects, your group’s own work. Looking at or copying code or homework solutions from other people or the Web is strictly prohibited. In particular, looking at other solutions (e.g., from other groups or prior CS 3700 students) is a direct violation. Projects must be entirely the work of the students turning them in, i.e. you and your group members. If you have any questions about using a particular resource, ask the course staff or post a question to the class forum.

    All students are subject to the Northeastern University’s Academic Integrity Policy. Per CCIS policy, all cases of suspected plagiarism or other academic dishonesty must be referred to the Office of Student Conduct and Conflict Resolution (OSCCR). This may result is deferred suspension, suspension, or expulsion from the university.

    Accomodations for Students with Disabilities

    If you have a disability-related need for reasonable academic accommodations in this course and have not yet met with a Disability Specialist, please visit www.northeastern.edu/drc and follow the outlined procedure to request services. If the Disability Resource Center has formally approved you for an academic accommodation in this class, please present the instructor with your “Professor Notification Letter” at your earliest convenience, so that we can address your specific needs as early as possible.

    Title IX

    Title IX makes it clear that violence and harassment based on sex and gender are Civil Rights offenses subject to the same kinds of accountability and the same kinds of support applied to offenses against other protected categories such as race, national origin, etc. If you or someone you know has been harassed or assaulted, you can find the appropriate resources here.