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Course 116 · Digital course 23

Understand Computer Networks

See how a request crosses local links and routers, and explain what supplied network evidence does and does not show.

Before you start

Know basic device/file concepts and whole-number arithmetic.

See everything you’ll need

Practice materials and a worked example · Free download. Download the starter pack

What you’ll leave with

A labeled network model, packet journey, transport comparison, transfer calculation and evidence-based failure explanations.

Start course Start without an account. Sign in to save lesson progress across devices.

Your project

Start with the practice files. Build your project one lesson at a time.

Practice files are free without an account. Sign in to save your project record in My Proof: a description, checklist, and optional work link. Keep the original files in your own app or notebook; saving a project record does not upload them.

  1. Get your materialsDownload practice filesStart with the supplied materials, follow the lessons, and compare your work with the annotated example.
  2. Make your projectView the project checklist Work in your own notebook, document, or software. Use the supplied practice examples when you prefer.
  3. Keep a private recordSave a project record Sign in to save a description and checklist, then return to update them.
Optional course overview

Watch an introduction.

This overview from CrashCourse introduces ideas you’ll practice in the lessons.

Watch directly on YouTube
CrashCourseComputer Networks: Crash Course Computer Science #28YouTube
Course handbook

Know the route before you begin.

Here’s what you’ll need and what you’ll make. You can return to this guide during any lesson.

Who this is for

Learners age 14+ who meet the stated prerequisites.

Prepare before lesson one
  • Know basic device/file concepts and whole-number arithmetic.
  • Use paper or a text editor; no network equipment, account or live-system access is required.
  • Reading and core practice include the three checks. Initial software setup and optional video viewing take extra time.
Your final project

Finish with proof you can use.

A labeled network model, packet journey, transport comparison, transfer calculation and evidence-based failure explanations.

Save a project record in My Proof
See project checklist and review criteria

Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.

What to include

  • Labeled two-subnet network model.
  • Name/address/gateway explanation.
  • Packet and hop-limit trace.
  • Transport comparison and unit-checked delay calculation.
  • Two failure-card interpretations with limits.

Review and revise

Use these criteria to check your work and choose what to improve.

  • Device roles and paths are correct.
  • Addresses and prefixes are used consistently.
  • Calculations use stated units and assumptions.
  • Evidence supports the conclusions without live-system claims.
Three ideas to help you along the way
Three useful ideas

The rules behind the steps.

01

Separate layers

Names, addresses, forwarding and applications answer different questions.

02

Keep units explicit

Rate, size and delay need compatible units.

03

Reason from evidence

Distinguish a supported next check from a proven root cause.

What do these words mean?
Key words

Key terms worth knowing.

Subnet
An IP network defined by an address prefix.
Router
A device that forwards IP packets between networks.
DNS
The system for looking up domain-name records.
Gateway
The next router used for destinations beyond a local route.
Latency
Delay in communication.
Throughput
The achieved rate of data transfer.
Your route

6 lessons.
One useful project.

Work in order the first time. Each lesson makes something the next lesson can use.

  1. 1
    Up next

    Model local links and routed networks

    Distinguish a switch’s local-link role from a router’s network-to-network role.

  2. 2
    18 min

    Separate names, addresses and local assignments

    Explain DNS, IP addresses and the default gateway as different information.

  3. 3
    22 min

    Trace a packet across a router

    Follow source/destination IPs and next-hop forwarding without changing the intended destination.

  4. 4
    22 min

    Compare transport needs

    Distinguish reliable ordered delivery from application goals that tolerate loss.

  5. 5
    18 min

    Reason about delay and capacity

    Calculate a simplified transfer bound and distinguish it from latency.

  6. 6
    26 min

    Explain the complete network journey

    Use a supplied evidence card to identify which stage is known and which remains uncertain.

Use the tools

Tools to help you practice.

See all tools
ZIP · practice files

Understand Computer Networks practice files

Start with the supplied materials, follow the lessons, and compare your work with the annotated example.

Text worksheet

Your course project worksheet

A downloadable text worksheet with each lesson’s working output, space for your answers, and the shared final-project checklist. Save your own copy.

Source transparency

Sources and further study.

Explore the references behind the lessons and take your learning further. Source notes explain access and reuse.

Loyola University Chicago: An Overview of Networks
Source & access notes · checked 2026-09-12

Opened and inspected on 2026-09-12: Layers, packets, forwarding and capacity.

Access: Free public web page; no paid enrollment required.

Reuse: BY-NC-ND with additional electronic-use terms; link only, no copied diagrams or adapted book text.

Loyola: IP version 4
Source & access notes · checked 2026-09-12

Opened and inspected on 2026-09-12: Interfaces and IP delivery.

Access: Free public web page; no paid enrollment required.

Reuse: Same textbook terms; independent exercises only.

Loyola: IPv4 Companion Protocols
Source & access notes · checked 2026-09-12

Opened and inspected on 2026-09-12: DNS, ARP and DHCP roles.

Access: Free public web page; no paid enrollment required.

Reuse: Same textbook terms; independent exercises only.

Computer Networks: Crash Course Computer Science #28
Source & access notes · checked 2026-09-12

Metadata retrieved and inspected on 2026-09-12: exact title and channel confirmed through YouTube oEmbed. Playback and full video content were not tested. Optional overview; the written lesson and supplied practice stand alone.

Access: Free public web page; no paid enrollment required.

Reuse: Link or provider embed only; do not copy video, audio or transcript.

Ready when you are

Start with the first useful move.

You’ll always know what to do, what to make, and where to go next.

Start lesson one