Introduction to Computer Networks

Understanding the Digital Battlefield

Tuesday, January 6, 2026

Instructor Introduction

Introduce Yourself!

• Your Name + Name you like to be called
• Company
• Hometown
• Major + Branch preference
• What do you hope to get out of this course?
• What have you heard about the course?
• Anything else you would like to share?
  • Interesting fact about you
  • Something you are passionate about
  • Any activities you are involved in

Course Overview

1. Understand and apply the five-layer network model.
2. Compare and contrast network protocols and architectures.
3. Develop network applications using the socket application programming interface.
4. Understand fundamental network vulnerabilities and associated mitigation techniques.

Lesson Objectives

• Explain why networking is critical terrain in modern warfare and civilian life.
• Identify real-world cyber disruptions to critical services and their broader societal effects.
• Describe the organization of the Internet (end hosts, ISPs, IXPs, CDNs, governments).
• Understand the unique challenges of cyberspace operations across the physical, logical, and persona layers.
• Verify VSCode setup and access to EECSNet and VMs.

Why Care?

• Cyber Domain: Software at all levels of computing devices is where the big opportunities are for exploitation and defense.
• The Army: Communication is critical. All military branches use data networks to communicate.
• Elsewhere: Amazon, Google, Apple, Meta, NSA, the list goes on…

Syllabus at a Glance

• Canvas = source of truth (schedule, readings, rubrics, submissions)
• In-Class Labs, 5-20 points each \(= 100\) points total
• \(10\) Problem Sets, \(30\) points each \(= 300\) points total
• \(2\) WPRs, \(100\) points each \(= 200\) points total
  • closed‑book; one handwritten double‑sided page of notes permitted
• Programming Project, \(3\) milestones, \(= 400\) points total
  • Python 3 & sockets; incremental feedback

Point to Canvas navigation * Stress incremental progress on project; encourage early Q&A and AI‑usage boundaries.

Policies

• Late policy: −10% per 24h; hard stop after 120 hours
• Extension requests: at least 48h in advance
• Start early, ask questions, and get help!
• Academic Use Agreement
  • with great power comes great responsibility
  • no unauthorized use of tools on production networks
  • acknowledge / sign in Problem Set 1

• Require signature/ack in PS1 (Usage Agreement). early = 48 hours

Additional Instruction

1. Send me a calendar invitation
2. Find me before/after class
3. Email me directly
4. Drive by! (TH106)

Resources

• Textbook: Computer Networking by Kurose & Ross, 8th Edition
  • Companion website
• Check Canvas modules for additional readings
• Read before class; come prepared to discuss!

Assistance or Collaboration?

• Getting a verbal explanation of a specific point of confusion
• Working jointly on a problem set to produce a solution
• Working on parts of homework separately and then combining them
• Using AI tools to help debug code or explain concepts
• Using AI tools to generate code
• Copying from a source considered common knowledge
• Copying from another student
• Looking at another student’s code

Always document assistance or collaboration!

• ✅ verbal explanation of a specific point of confusion
• ❌ working jointly on a problem set to produce a solution
• ❌ working on parts of homework separately and then combining them
• ✅ using AI tools to help debug code or explain concepts
• ❌ using AI tools to generate code
• ✅ copying from a source considered common knowledge
• ❌ copying from another student
• ❌ looking at another student’s code

Measure of Software Similarity (MOSS)

• This course uses MOSS to compare student solutions
  • detects similarities in code
  • looks for similarities in structure and logic

Classroom Standards

• Exhibit peer leadership
• Attendance -> Inspection -> Call Attention
• No food or backpacks
• If you see ⭐, call class to attention!

Introduction to Networking

TCP/IP Model

Network Layers

What is EECSNet?

• External network provided by EECS Department
• Supports networking labs and virtual machines for classes and research
• Outside of normal USMA network security protections and restrictions
  • Must be accessed via VPN or direct connection (WiFi or Ethernet)
  • Carries a little more risk to participating machines

Quick Linux Network Commands

# Find interfaces & addresses
ip addr
ip route

# DNS & connectivity checks
ping -c 3 8.8.8.8
dig www.example.com

• Explain why IP/route helps pick the right interface in captures.

Quick Windows Network Commands

# Find interfaces & addresses
ipconfig
route print

# DNS & connectivity checks
ping 1.1.1.1
nslookup www.example.com

In-Class Exercise

When you just logged into the VM, where do you think those packets actually went?

Wireshark Primer

What is Wireshark?

• GUI packet analyzer for sniffing packets to/from your system
• Parses protocol stacks; shows headers and payloads
• Save/share captures as PCAP files
• Powerful display filters to focus on the traffic you care about

Check out the web version: Wireview

Now: Download any PCAP file from Wireshark Sample Captures

Interface Tour

• Packet List (top): one row per packet

• Packet Details (middle): protocol tree (L2→L7)

• Packet Bytes (bottom): hex + ASCII view

• Filter bar: type display filters (e.g., http, dns, tcp.port==443)

• Common Menu Options

  • File → Open/Save PCAPs
  • Edit → Preferences
  • View → Time Display Format
  • Go → Next/Previous Packet
  • Analyze → Follow TCP Stream

• Live demo: open a small PCAP and narrate the panes.

Filters & Tips

# Display filter examples
ip.addr == 10.0.0.5
(tcp.port == 80 or tcp.port == 443) and ip.addr == 192.168.1.10
dns and !icmp
http.request.method == "GET"

• Change Time Display Format to absolute if helpful
• Stop capture before saving; annotate packets when answering questions
• Ensure that you are capturing on the correct host / computer!
• For non-GUI headless captures, use tcpdump or tshark

# Headless capture → PCAP for Wireshark
sudo tcpdump -i eth0 -w web.pcap 'tcp port 80 or 443'
# Quick CLI analysis with tshark
sudo tshark -r web.pcap -Y 'http.request' -T fields -e http.host -e http.request.uri | head

• Show difference between capture and display filters.

Common Pitfalls

• Capturing on the wrong interface (VPN vs non‑VPN)
• Not using capture filters to limit data
• Forgetting to clear old capture or display filters
• Looking at unrelated IPs/ports

• Teach method: identify app’s IP/port first → then filter.

Problem Set Standards

• Prove your answer!
  • Wireshark portions: If the question is what version of HTTP is run, show it in a Wireshark capture (pdf) by highlighting answer and labelling highlight as to which question is being answered.
  • Computational portion: On a separate piece of paper, answer each question and upload to appropriate question on Canvas problem set.
  • This will help with partial credit.
• Answer all the questions!

Review

Question 1

What best describes the Internet?

1. A single global router that forwards all packets
2. A network of networks using standardized protocols
3. A social media platform for sharing content
4. A private military communications backbone

Answer: B. The Internet is a network of networks interconnected by protocols (notably IP) enabling end systems to communicate.

Question 2

Which Wireshark pane displays the protocol tree for a selected packet?

1. Packet List pane
2. Packet Details pane
3. Packet Bytes pane
4. Capture Options pane

Answer: B. The Packet Details pane shows the hierarchical protocol fields for the selected packet.

Question 3

Problem sets are submitted via Canvas and are typically due at…

1. 2359 on the posted date
2. 1700 the day before the posted date
3. 0730 on the posted date
4. Rolling deadline; no specific time

Question 4

Which of the following is a display filter example in Wireshark?

1. tcpdump -i eth0 port 80
2. udp and (dns or quic)
3. host 10.6.7.8 and port 53
4. net 10.0.0.0/8

Answer: B. udp and (dns or quic) matches Wireshark display filter syntax. Other options resemble capture filters/libpcap syntax.

Question 5

On a headless Linux VM, which tool is best to capture packets for later analysis in Wireshark?

1. top
2. curl
3. tcpdump
4. ping

Answer: C. Use tcpdump (or tshark) to write PCAPs you can open in Wireshark.

Question 6

Which statement about EECSNet is TRUE?

1. It’s the same as the USMA production network and requires no VPN
2. It’s an instructional/research network accessed via VPN/Wi‑Fi with fewer enterprise restrictions
3. It provides free public internet to the entire Hudson Valley
4. It only supports Windows clients

Answer: B. EECSNet is a separate instructional network typically accessed via VPN or direct EECSNet Wi‑Fi/Ethernet.

What’s Next?

• Readings before next class
  • Chapter 1
• Assigned
  • PS0 - Usage Agreement & Basic Programming (due Sunday)
• Upcoming
  • PS1 - Python Primer

Parting Advice

• Start early, ask questions, and get help!
• Read before class; come prepared to discuss!
• Be proactive about academic integrity and use of AI tools!
• Embrace challenges and stay curious!