Day 1: Network Fundamentals — Network Types & the OSI Model (N10-009)
Introduction to Networking Fundamentals
Welcome aboard. Today is the “set the table” day: what a network actually is, how we classify different network types, and the seven-layer OSI model that CompTIA loves to test. Keep this close—everything you do on later days builds on these two ideas. (You’ll feel this immediately in Day 2: Exploring Network Topologies and Types and again when IP addressing shows up in Day 4: Subnetting Part 1.)
Make sure you make it all the way to the end to check out our mastery notes.
Objectives (N10-009)
Compare and contrast common network types (LAN, WAN, MAN, PAN, CAN, WLAN, SAN).
Explain the functions of the OSI model layers (1–7) and where common devices/protocols live.
What is a “network,” really?
A network is just devices agreeing on rules so they can talk—sharing data, internet access, or printers. At home that’s your router + Wi-Fi; at work it’s switches, routers, access points, and services playing nicely. For the exam, define it simply: connected devices + shared resources + agreed protocols.
Network Types (know the names, scope, and common examples)
Think of network types like maps with different zoom levels—street, city, region, world.
Exam cue: SAN ≠ “wireless.” It’s a storage network (often Fibre Channel). WLAN is your wireless LAN. That distinction shows up a lot.
You’ll revisit these categories when you study topologies tomorrow in Day 2: Topologies & Types, and again when we place devices in Day 8: Network Devices & CLI.
Analogy:
PAN = your personal bubble.
LAN/WLAN = your house.
CAN = your neighborhood of buildings.
MAN = the city grid.
WAN = highways between cities.
SAN = a private express lane just for storage traffic.
The OSI Model (7 layers, top to bottom & bottom to top)
OSI is a mental map for where things happen. CompTIA wants you to:
know what each layer does,
place common devices/protocols at the right layer, and
follow encapsulation (how data gets wrapped/unwrapped).
One-glance cheat table
When we dive into media and connectors on Day 11: Cables & Connectors, you’ll anchor those details to Layer 1. Wireless specs on Day 12 land at Layer 1/2. When protocols and ports show up in Day 6: Protocols, that’s Layer 4 territory.
A conversational walkthrough (down then up)
7 → 5 (App/Pres/Session): Your browser forms an HTTPS request (Application), TLS encrypts it (Presentation), and a session gets tracked (Session).
4 (Transport): TCP gives it port numbers and reliability (think: “address + tracking number”).
3 (Network): IP adds source/destination IPs so routers can move it between networks.
2 (Data Link): Your NIC wraps it in a frame with source/dest MAC to cross the local LAN/WLAN.
1 (Physical): Bits go out as voltage/light/radio on cable or Wi-Fi.
Reverse on the way back up at the destination: unwrap → check → hand off to the app.
Analogy:
Layer 1 roads, Layer 2 neighborhood mailperson (MAC), Layer 3 city-to-city routing (IP), Layer 4 shipping service with tracking (TCP/UDP), Layers 5–7 the storefront/cashier/register finishing the transaction.
Mnemonic you’ll see everywhere:
Please Do Not Throw Sausage Pizza Away
(1–7: Physical, Data Link, Network, Transport, Session, Presentation, Application)
This framework is the backbone for packet flow you’ll practice in Day 9: Map Your Network with CLI and for placing devices in Day 10: Mastering Network Devices. App-layer services resurface in Day 14: Network Services & Applications.
Quick “exam traps” to avoid
WLAN vs. LAN: WLAN is a LAN (wireless flavor). Don’t treat it as a WAN.
SAN: Storage network (Fibre Channel/iSCSI). Not “wireless” and not the same as “LAN.”
Layers vs. Devices: Switches = Layer 2 (MAC/VLANs). Routers = Layer 3 (IP/routing).
(Yes, there are Layer-3 switches, but default switch ≈ L2 for exam.)Ports live at Layer 4, not Layer 7. HTTP is an app-layer protocol, but TCP/UDP ports are transport-layer details.
Encapsulation terms: Frames (L2), Packets (L3), Segments (TCP at L4), Datagrams (UDP at L4).
Tiny look-ups you’ll use all month
Common pairings:
Switch ↔ MAC/VLAN ↔ Layer 2
Router ↔ IP/routing ↔ Layer 3
TLS/SSL ↔ Layer 6 (encryption/format)
HTTP/HTTPS/DNS client behaviors ↔ Layer 7, but ports for them are at Layer 4
Where to study next: Topology names and diagrams flow straight into Day 2; addressing and routing logic get real in Day 4 and Day 23: Advanced Routing & Infrastructure.
Watch (solid, free explanations)
Professor Messer — Understanding the OSI Model (N10-009). If you’re taking Network+, this is home base for OSI. YouTube
PowerCert Animated — OSI Model Explained (animated). Clean visuals; great for locking in each layer. YouTube
PowerCert Animated — Network Types: LAN, WAN, PAN, CAN, MAN, SAN, WLAN. Quick refresh on scope and examples.
Fast recap
You can now name and classify PAN/LAN/WLAN/CAN/MAN/WAN/SAN by scope and examples.
You can place devices/protocols at the correct OSI layer and follow encapsulation.
You’ve set up the context for topologies (Day 2), protocols & ports (Day 6), devices (Day 8/10), media (Day 11/12), and services (Day 14)—so Day 1 keeps paying dividends.
That’s the foundation. On to Day 2: Exploring Network Topologies and Types to put shapes and diagrams to these networks.
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