How Computer Networks Move Data
Bridge the gap between everyday network terms and how traffic actually moves through the internet. Learn to trace packets across switches, routers, and firewalls while demystifying transport protocols and the models that govern them.
Like Duolingo, but for How Computer Networks Move Data. Tomo turns the whole topic into a game you play five minutes a day, until it actually sticks.
21 levels across 3 sections, about 42 minutes end to end, roughly 8 days at five minutes a day. It moves through Diagnosing Traffic and Transport, Hardware in the Physical and Logical Path, and Conceptual Models and Packet Anatomy. It assumes you already know the basics.
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Key ideas in How Computer Networks Move Data
- ICMP echo is handled by the operating system kernel, not by application processes.
- A host can reply to ping even when its web server daemon is dead or uninstalled.
- Ping operates at the Internet layer and does not query application TCP or UDP ports.
- Traceroute starts with TTL=1 and increments by 1 for each successive probe.
- Each intermediary router decrements the TTL and sends back an ICMP Time Exceeded message.
- The router's ICMP Time Exceeded reply reveals its IP address and round-trip delay.
- Many security firewalls drop ICMP ping while allowing TCP connections through.
- Netcat or curl attempts a TCP three-way handshake to verify a specific port.
- A successful TCP handshake confirms both IP routing and transport listening status.
- Testing the hostname first reproduces whether the application layer can find the target.
- Querying DNS tools like dig or nslookup checks if the name resolves to an IP address.
- Testing the raw numeric IP bypasses DNS to isolate basic Layer 3 reachability.
- Loss at hop 1 indicates an issue with the local LAN cable, Wi-Fi, or default gateway.
- Loss starting in intermediate hops points to transit links managed by the ISP.
- Reaching all intermediate hops but failing only at the end indicates destination firewalling.
- A host IP delivers packets to the OS, but port numbers route payloads to specific running services.
You've tried the other tabs
Thirty open tabs. Four facts you actually kept.
You watched. You nodded. By Sunday it was gone.
One answer, then back to scrolling.
Eight weeks. You meant to finish. You didn't.
Tomo gives How Computer Networks Move Data the Duolingo treatment: levels, streaks, and quick quizzes that test what you just learned. That game loop is what the tabs above never had, so it's the one you actually finish.
Here's what playing it feels like
A real question from this course. Take your best guess.
When you ping a server, what component actually receives and answers that ICMP echo?
Get it right to open this lesson and 20 more in the app.
Where How Computer Networks Move Data takes you
- 1
Diagnosing Traffic and Transport
- Isolating Network Faults Along the Path
- Transport Mechanics: Ports, Multiplexing, and Reliability
- 2
Hardware in the Physical and Logical Path
- Layer 2 Switching and Local Delivery
- Layer 3 Routing and Network Boundaries
- Middleboxes, Firewalls, and Edge Appliances
- 3
Conceptual Models and Packet Anatomy
- Reconciling the OSI Reference Model with Real TCP/IP
- Encapsulation, Framing, and Packet Dissection
3 sections · 7 units · 21 levels. Built to play, not to enroll.
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Add Tomo to ChatGPT- What to ask
- “Make me a Tomo course on black holes.” “Turn this chat into a Tomo course.”
- What you get
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- No sign-up to start. Connect your Tomo account and your streak carries on in the app.
You pick the voice
How Computer Networks Move Data is taught in the Bestie style: your friend who just gets it. Want a different feel? In the app you can spin up the same topic in any of Tomo's teaching styles. Same facts, totally different vibe.
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