Missiora
Network+ Domain 1: Networking Concepts

IT & Cyber Certifications

Network+ Domain 1: Networking Concepts

1 min readPublished 22 Jul 2026

Track your progress. Sign in to mark this guide complete and build your Job Readiness Score.

Domain 1 lays the conceptual groundwork for everything else in Network+. It's the largest domain on the exam, so it's worth getting rock-solid here.

The OSI model

Every network conversation and every troubleshooting session references the seven layers. Know what each layer does and which devices and protocols live where.

Interactive explainer

The OSI Model

The seven-layer map every networking technician uses to troubleshoot.

17. Application26. Presentation35. Session44. Transport53. Network62. Data Link71. Physical

Tap or hover a part to learn more.

7. Application

User-facing protocols.

Where apps interact with the network — HTTP, HTTPS, DNS, SMTP. This is what users and applications actually 'see'.

Check your understanding

1. Which layer do IP addresses and routers operate at?

2. TCP and UDP live at which layer?

Keep learning

Networking FundamentalsCompTIA A+ CompTIA A+
Practise this in AI Interview™

Ports and protocols

You will be expected to recall common port numbers instantly — in both multiple-choice and performance-based questions.

Interactive explainer

Common Ports & Protocols

The port numbers every network professional must know by heart.

Web80HTTP443HTTPSEmail25SMTP587Submit143IMAP110POP3Remote22SSH3389RDP23TelnetCore53DNS67/68DHCP123NTP161SNMP

Tap or hover a part to learn more.

Web

80, 443

HTTP runs on TCP 80 and HTTPS on TCP 443. HTTPS (443) is encrypted with TLS and is the modern default — plain HTTP on 80 usually just redirects to it.

Check your understanding

1. Which port does HTTPS use?

2. Which is the SECURE remote-access protocol?

Keep learning

Networking Concepts (Network+)TCP/IP & Encapsulation CompTIA Network+
Practise this in AI Interview™

TCP vs UDP

Understand when a protocol chooses reliability over speed — it explains a huge amount of network behaviour.

Interactive explainer

TCP vs UDP

Reliable and ordered versus fast and connectionless.

TCPSYN →← SYN-ACKACK →reliable · orderedUDPdatagram →fast · connectionless

Tap or hover a part to learn more.

TCP

Reliable & ordered.

TCP is connection-oriented: it guarantees delivery, keeps data in order and retransmits anything lost. The cost is extra overhead and latency from acknowledgements.

Check your understanding

1. Which protocol uses a three-way handshake?

2. Which is better for live video and VoIP?

Keep learning

TCP/IP & EncapsulationNetworking Fundamentals CompTIA Network+
Practise this in AI Interview™

Network types and topologies

Know LAN, WAN, WLAN, PAN and the star/mesh/hybrid topologies, plus modern additions: cloud networking (IaaS/PaaS, VPCs, cloud gateways) and software-defined networking (SDN), which separates the control plane from the data plane so networks can be managed centrally and programmatically. SD-WAN applies the same idea across wide-area links.

Why this domain matters

Concepts are the shared language of networking. When something breaks, engineers say "it's a Layer 2 issue" or "check port 443" — and everyone knows exactly what that means. Master this domain and the rest of Network+ becomes far easier.

Interview Intelligence

How this topic actually shows up in interviews — and how to demonstrate you understand it.

Why employers ask about this

Concepts are the foundation interviewers test first, because a candidate who's shaky on the OSI model or common ports will struggle with everything downstream. Fluency here signals you can communicate and reason about networks precisely.

Junior questions
Walk me through the OSI model.+

Name each layer bottom to top with a one-line function and an example (e.g. Layer 3 Network = routing/IP, Layer 4 Transport = TCP/UDP). Being able to map devices and protocols to layers is what interviewers want.

What's the difference between TCP and UDP?+

TCP is connection-oriented, reliable and ordered (uses a handshake); UDP is connectionless, fast and best-effort. Give examples: HTTPS uses TCP, DNS and VoIP use UDP.

Mid-level questions
A colleague says 'it's a Layer 2 problem'. What are they implying?+

The issue is at the Data Link layer — MAC addressing, switching, VLANs or a switching loop — rather than IP/routing (Layer 3). Show you can localise a fault to a layer.

Senior questions
How does SDN change how you operate a network?+

It centralises control so policy is defined once and pushed programmatically, improving consistency and automation. Discuss the trade-offs: agility and central visibility versus a new central dependency to secure and make highly available.

Real-world scenarios
“A web service is unreachable but you can ping the server.”+

Expected answer: Ping proves Layers 1–3 are fine, so move up: check the Transport/Application layers — is port 443 listening and open through the firewall? Demonstrates layered reasoning.

Common candidate mistakes
  • •Memorising the OSI layers as words but not knowing what actually happens at each.
  • •Mixing up port numbers (e.g. HTTP 80 vs HTTPS 443, SSH 22 vs Telnet 23).
Practise in AI Interview™Rehearse these questions, scored.Plan with Career Coach™A personalised path to your goal.Evidence it in Career Passport™Prove this skill to employers.

Employability Intelligence

Where this knowledge takes you — the jobs, skills and certifications it feeds into.

Relevant roles
Network Support TechnicianNetwork AdministratorNOC Technician
Skills you're proving
OSI modelPorts & protocolsTCP/IPCloud & SDN concepts
Recommended certifications
Networking FundamentalsCompTIA Network+
Career progression

This is the vocabulary foundation for every networking, cloud and security role.

What employers expect

That you can describe how traffic flows through a network and speak precisely about layers, ports and protocols.

Frequently asked questions

How many layers does the OSI model have?

Seven: Physical, Data Link, Network, Transport, Session, Presentation and Application.

What port does HTTPS use?

TCP 443. Plain HTTP uses TCP 80 and usually redirects to 443.

What is SDN?

Software-Defined Networking separates the control plane (decisions) from the data plane (forwarding), allowing networks to be managed centrally and programmatically.

Related guides

CompTIA Network+ (N10-009): The Complete GuideNetwork+ Domain 2: Network ImplementationNetwork+ Domain 3: Network OperationsNetwork+ Domain 4: Network Security

Practise what you've learned

Turn this guide into real, evidenced progress

Missiora helps you measure, improve and evidence the capabilities employers actually value — start with the tools best suited to this topic.

M
Published by
Missiora

Missiora is an AI Employability Intelligence platform. Our resources are researched and reviewed by the Missiora team to help you measure, improve and prove your career readiness.

All resources