Networking

Network Topologies & Scope

Every network so far in this domain has been described by protocol — Ethernet, IP, TCP. This page classifies networks along two completely different axes instead: how big they are (LAN, WAN, PAN), and what shape their connections form (star, bus, mesh) — vocabulary that shows up constantly in job descriptions and hardware documentation without ever being tied to one specific protocol.

Quick reference

What it is: Two independent classification systems: network scope (how far it reaches) and network topology (how its connections are physically/logically arranged).
Mental model: Scope is like "neighborhood vs. city vs. country" — a size classification. Topology is like a city's road layout — a shape classification, independent of the city's actual size.
Key numbers: A typical home router sits at the exact boundary between a LAN and a WAN.
Reach for it when: Describing a network's reach and physical layout, independent of which specific protocols happen to run over it.

Scope: PAN, LAN, WAN

PAN: Personal Area Network — the smallest scope, typically one person's immediate devices: a phone talking to a Bluetooth earbud or a smartwatch, usually just a few meters.
LAN: Local Area Network — one site: a home, an office floor, a single building. Everything this domain's Ethernet and Wi-Fi pages describe operates within a LAN.
WAN: Wide Area Network — connects LANs across real distance: the internet itself is the largest WAN there is, but a company linking two office LANs together (see VPN's site-to-site section) is running a smaller, private WAN.

A home router is, structurally, the device sitting exactly on the LAN/WAN boundary — everything on the inside is your LAN, everything reachable through its internet connection is the WAN.

Topology: star, bus, mesh

How a network's connections are actually arranged, independent of its size:

Modern wired LANs are almost always star topology in practice (every device to a switch) — bus and mesh survive mostly in older wiring and specialized/wireless-mesh setups.

Star: Every device connects to one central point — the shape a modern switch-based LAN actually is. Simple to wire and to add devices to; the central point is also a single point of failure.
Bus: Every device shares one single line — early Ethernet's original physical form. A break anywhere on the line takes down every device past that point; almost entirely obsolete in wired LANs today.
Mesh: Devices connect directly to several others, giving multiple paths between any two points — more resilient to a single link failing, at the cost of much more complex wiring/configuration as the network grows. Modern Wi-Fi mesh systems implement this logically over radio, not physical cabling.

Real-world applications

Home/office LANs — star topology around one or more switches, almost universally, today.
The internet — the canonical WAN, itself built from a mesh of interconnected networks at the BGP level.
Wi-Fi mesh systems — consumer mesh routers use a logical mesh topology over radio to extend coverage without a single access point being a hard bottleneck.
Bluetooth/IoT device pairing — a phone-to-earbud or phone-to-sensor connection is a PAN, the smallest scope this page covers.

Gotchas

Field notes

Scope and topology are independent — a WAN can be arranged as a mesh (the internet) or a LAN can be (an office wired in a legacy bus layout); don't assume one implies the other.
A star topology's central switch is a real single point of failure worth taking seriously in any network where uptime actually matters — redundant switching exists specifically to address this.
"Mesh Wi-Fi" as a marketing term describes the logical topology, not the physical scope — a mesh Wi-Fi system still typically covers one LAN, not a WAN.