CS 4700 / CS 5700 - Network Fundamentals

General Information

Professor:David Choffnes
Room:Knowles Center 010
Time:Wednesdays, 6-9pm
Office Hours:Tuesdays 10-11am
Location: 613 ISEC
Teaching Assistants:Archit Mathur, Salim Ali Siddiq, Prathameth Kirloskar
TA Email:cs5700sp17-staff@ccs.neu.edu
Lab Hours:Monday, Friday 2-4pm (location in WVH to be posted on Piazza)
Class Forum:On Piazza
Paper List:Click here

Course Description

Computer networking is a rapidly advancing field, and the Internet is already an integral part of society. It is therefore important for computer scientists and computer engineers to be familiar with the fundamentals of computer networking. This course will focus on the architecture, algorithms, and protocols of the Internet. Topics include local area networking, routing, congestion control, network security, and applications such as peer-to-peer and content distribution networks. 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 3650 and 3700 (or equivalents). 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 also essential. You should know how to write code using emacs/vim, write a makefile, compile/debug code, check for running processes, kill runaway processes, and create compressed archives.

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. If you have questions while in lecture feel free to post to folders for the lecture. 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.

Schedule, Lecture Slides, and Assigned Readings

Meeting DateSlidesPiazza FolderTextbookReadingsComments
Jan. 11 Welcome: Intro, History, Architecture #lecture1 §1.1-1.5 Proj. 1 out Join Piazza
Jan. 18 Moving bits and bytes: Physical Layer,
Data Link Layer
#lecture2 §2.1-2.8, 3.1 Cla88, SRC84
Jan. 25 Multihopping: Bridging, Network Layer #lecture3 §3.2, 3.3, 4.1.3 P85, SG04 Proj. 1 due, Proj. 2 out
Feb. 1 The Gentlemen's Agreement:
Intradomain routing
Interdomain routing
#lecture4 §4.1-4.4 CR04, KSC+12
Feb. 8 Playing Nicely: Transport Layer,
Congestion Control
#lecture5 §2.5, 5.1, 5.2, 6.3 CK74, Jac88, WB13 Proj. 2 due, Proj. 3 out
Feb. 15 Review BGP/TCP
Glue and Duct Tape: DNS, NAT
#lecture6 §6.5, 9.3.1 KWNP10, CAR13,
Feb. 22 Flattening of the Internet: CDNs, IXPs #lecture7 §9.4 SCKB+06, LIMOJ+06,
Mar. 1 Midterm #midterm Proj. 3 due, Proj. 4 out
Mar. 8 No Lecture: Spring Break
Mar. 15 Volatile and Decentralized: P2P, BitTorrent, Other Overlay Networks #lecture8 §6.5, 9.3.1 LLSB08, KN10, SMK+01, GM+04
Mar. 22 (Overlays) #lecture9
Mar. 29 (Big) Data Centers: DCN architectures and protocols #lecture10 Read papers WBKR11, AGM+10 Proj. 4 Due, Proj. 5 Out
Apr. 5 Bleeding Hearts and Tinfoil Hats: TLS and Anonymity #lecture11 Read papers ReCon, Heartbleed, Herd
Apr. 12 Generation Next: Mobile Networks and SDNs
For those interested, check out this great talk about SDNs: An attempt to motivate and clarify Software-Defined Networking (SDN)

Read papers FRZ+13, QWG+10, JST+09
Apr. 19 Final exam (in class) Proj. 5 due


The focus of this course will be on lectures, in-class exercises and reading important papers from the networking research community. Thus, I do not require that you get a textbook. However, a textbook may be useful if you are not totally comfortable with network fundamentals, or if you just want to have a handy reference book. Officially, the textbook for the course is:

Computer Networks: A Systems Approach, 4th Edition by Larry Peterson and Bruce Davie, Morgan Kaufmann.

There is also a supplement:

TCP/IP Sockets in C by Jeff Donahoo and Ken Calvert, Morgan Kaufmann.

Also recommended, for reference:

Computer Networking: A Top-Down Approach Featuring the Internet. by Jim Kurose and Keith Ross, Addison-Wesley.

Reading and Participation

As previously mentioned, a large component of this course will be reading important papers from the networking research community. Some of these papers are classics: older, but intrumental in guiding the design of today's networks. Other papers will be more contemporary, and focus on improving existing networks, or even replacing them entirely. All the papers can be found here.

Several papers will be assigned as reading before each lecture. A discussion thread will be opened on Piazza for each paper, and each student must post 1) a summary of the paper in three senteneces or less, and 2) the strengths (at least 3) and weaknesses (at least 3) of the paper before Tuesday at 9am of the week it is assigned. You are also encouraged to ask questions about the paper and respond to other students' questions.

During class, students may be called at random to briefly summarize papers. Thus, although attendance in lectures is not required, if you get called and you are not present (or you haven't read the paper), then you are busted. I also may hand out in-class exercises, and you will receive points only if you attend class to complete them.

5% of your final grade will be based on participation. If you post on Piazza when you are the assigned discussion leader for a paper, and summarize papers when called in class, then you will receive full marks for participation.


There will be five programming projects throughout the semester (three for undergraduates). Programming projects are due at 11:59:59pm on the specified date. We 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!

AssignmentDescriptionDue DatePiazza Folder
Project 1 (MS only)Socket BasicsJan 25#project1
Project 2 (MS only)Web CrawlerFeb 7#project2
Project 3TCP Simulation in NS-2Feb 27 (MS)
Feb 13 (UG)
Project 4Raw SocketsMar 27 (MS)
Mar 20 (UG)
Project 5Roll Your Own CDNApr 21 (MS and UG)#project5

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. All group members should be involved in all major design decisions, and groups should develop a programming plan that can be effectively parallelized. You may switch groups between programming projects.

Groups must be either all undergraduates or all graduate students.


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!


When answering exam questions, you cannot reproduce a figure from lecture slides or other sources in textbooks or the Web. Doing so is plagiarism. Even when answering exam questions your work must be your own. Answers violating this rule will be given an automatic zero. If any group of students have the exact same answer to a question, it will be treated as if you copied from each other during the exam.

I do not want to discourage studying for exams in groups. However, regurgitation of facts without being able to use your own words shows that you don't truly understand the material.

If you do not know the answer to an exam question and leave it blank, you will automatically receive 10% of the points for the question. If you answer a question incorrectly, you get zero points.


Projects:4%, 8%, 12%, 16%, 20%
Midterm and Final:15% and 20%

Each project will include a breakdown of how it will be graded. Some projects may include extra credit components that can boost your grade above the maximum score :)

To calculate final grades, I simply sum up the points obtained by each student (the points will sum up to some number x out of 100) and then use the following scale to determine the letter grade: [0-60] F, [60-62] D-, [63-66] D, [67-69] D+, [70-72] C-, [73-76] C, [77-79] C+, [80-82] B-, [83-86] B, [87-89] B+, [90-92] A-, [93-100] A. I do not curve the grades in any way.

Regrading and Challenges

New policy!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 homework, project, or a test to be regraded, you must visit during office hours with a challenge in writing 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.

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.

Any requests for grade changes must be made within seven days of when the work was returned.

Late Policy

For programming projects, we will use flexible slip dates. Each student is given four 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. The slip time will be deducted from each group member's remaining slip time. 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 time, 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. My late policy is extremely generous, and therefore I will not be sympathetic to excuses for lateness. Late penalties cannot be challenged.

Cheating Policy

Projects must be entirely the work of the students turning them in, i.e. you and your group members. Copying code from other students (past or present) or websites is strictly prohibited. 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 Academic Integrity Policy. All cases of suspected plagiarism or other academic dishonesty will be referred to the Office of Student Conduct and Conflict Resolution (OSCCR).

Consequences of Violating Academic Integrity Policy

  1. All students who are caught cheating will be referred to the Office of Student Conduct and Conflict Resolution (OSCCR). Students who have been referred to OSCCR will be given the opportunity to accept responsibility for their infraction or to request a hearing before a student conduct board. If a student accepts responsibility for a minimum sanction of deferred suspension will follow. A second violation will meet with expulsion from the University.
  2. All students who are caught cheating will receive a -100% for the item on which cheating occurred. Cheating is worse than not turning in the item.

Someone may already have written a program that does part of what you'll need to do for your assignments. For your assignments, however, you are expected to write all of the source code yourself, without copying source code from any other program, even if there are programs out there that would allow you to copy their source code. You also should not post your work for others to obtain.

You may discuss problems with other students, but you should not share or show code to anyone other than your assigned partner.

You are responsible for keeping your code hidden from all other students. If you keep your local repository on our CCS servers, make sure that it is protected 600. Leaving it group- or world- readable means that anyone can steal your work. Your home directory includes, by default, a directory called classes that is readable only by you. Put all your class work here. If you put class material in some unprotected directory, and somebody else copies it, you will be held responsible.

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: http://www.northeastern.edu/oidi/titleix/

Support for this class

The CDN project for this class is supported by an AWS in Education Grant award. Many thanks to Amazon for this!