LAN, WAN and Internet
Networks are classified by their physical scope — from a single room to an entire planet. The same packets travel the same protocols; only how far they travel changes.
01Three scopes, one logic
Each scope is not a different technology — it is the same IP model applied to a different geographic boundary. Smallest to largest:
Devices connected within a single physical location — a room, a house, a floor, or a campus building. Usually clustered around a single switch or Wi-Fi router.
- High speed — 1–10 Gbps
- Low latency — < 1 ms
- Limited area — < 1 km
- Single administrative domain
A network that connects multiple geographically separate LANs. A company's offices in two different cities can communicate over a private WAN — via leased lines, VPN tunnels, or MPLS.
- Medium speed — 10 Mbps–1 Gbps
- Higher latency — 10–80 ms
- Wide geographic area
- Depends on a service provider
The global public network where millions of autonomous networks interconnect via shared protocols — primarily IP. No single entity owns it; thousands of ISPs announce their address blocks via BGP and peer with each other.
- Variable speed — depends on ISP
- Variable latency — 20–300 ms
- Global scope
- No owner — belongs to everyone
02How a packet travels across scopes
LANs sit inside WANs, WANs sit inside the Internet. A single packet can cross all three in one trip.
When a user in London sends a file to the New York server, the packet first crosses the LAN to the local switch, then reaches the edge router (gateway). The router forwards it onto the WAN link — a leased line or VPN tunnel. If the WAN link is down, the same packet exits via 0.0.0.0/0 onto the Internet and attempts to reach its destination via public routes.
03Side-by-side comparison
| LAN | WAN | Internet | |
|---|---|---|---|
| Scope | Room / building | City / country | Global |
| Speed | 1–10 Gbps | 10 Mbps–1 Gbps | Variable |
| Latency | < 1 ms | 10–80 ms | 20–300 ms |
| Owner | You | Company / ISP | Nobody |
| Cost | Low (own hardware) | High (leased lines) | Subscription |
| Protocol | Ethernet / Wi-Fi | MPLS, VPN | BGP / IP |
04Summary
- LAN = devices in one physical space, fast and cheap
- WAN = multiple LANs bridged across geography, you lease the link
- Internet = every WAN and LAN on Earth, stitched together by BGP and IP
- A packet may cross all three scopes in a single round-trip