Types of networks: PAN, LAN, MAN and WAN
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Networks are named by how much ground they cover. Zoom out from the phone, watch and earbuds around you (a PAN) to your home (a LAN), a school campus (a CAN), a city fibre ring (a MAN) and the long links between cities (a WAN). Then see why the internet is the biggest WAN, and how a VPN builds a private network on top of it.
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01Your phone, smartwatch and wireless earbuds talk to each other over Bluetooth. What kind of network is that?
A PAN covers a few metres around one person. Bluetooth reaches about 10 m, which is the right size.
02What is a WLAN?
W stands for wireless. It still covers a home or office like any LAN; only the links are radio instead of cables.
03Signals in fibre travel at about two-thirds of the speed of light. Roughly how long does a signal take to cross 1,000 km of fibre?
Two-thirds of light speed is about 200 km per millisecond, so 1,000 km takes about 5 ms one way, and a round trip about 10 ms.
04Which of these is usually true of a WAN, but not of your home LAN?
You own your LAN. Long-distance links belong to carriers, the big telecom companies, and are rented by the organisations that use them.
05How does a VPN make a laptop at home act as if it were on the office network in another city?
A VPN is a virtual network: its links are tunnels through another network, here the internet, rather than cables of its own.
المسرد
- PAN
- Personal area network: a few devices around one person, joined by Bluetooth or USB. About 10 m across.
- LAN
- Local area network: the devices in one home, office or building, on equipment the owner runs, joined by Ethernet or Wi-Fi.
- WLAN
- Wireless LAN: a LAN whose links are radio, such as Wi-Fi.
- CAN
- Campus area network: the LANs of several buildings, such as a school or company site, joined by the organisation's own fibre.
- MAN
- Metropolitan area network: a network across a city, such as a provider's fibre ring, tens of kilometres wide.
- WAN
- Wide area network: links between cities and countries, usually leased from carriers. The internet is the biggest one.
- Carrier
- A large telecom company that owns long-distance links and rents capacity on them to others.
- VPN
- Virtual private network: a private network built from encrypted tunnels through a shared network such as the internet.
الملاحظات والمصادر
- The sizes are typical, not hard limits: names describe roughly how much ground a network covers. A Bluetooth class 2 radio reaches about 10 m; Ethernet over copper (IEEE 802.3, 1000BASE-T) is specified up to 100 m per cable.
- Signal times use the same rule of thumb as the "Bits on the wire" lesson: about two-thirds of the speed of light, 200 km per millisecond, so 1,000 km takes about 5.0 ms. Real paths are longer than a straight line and add waiting in routers.
- Who owns the links is the big practical difference: you own your PAN and LAN, an organisation its campus, while city and long-distance links are rented from providers and carriers.
- 192.168.1.0/24 and 10.20.0.0/16 are private ranges (RFC 1918); 203.0.113.5 and 198.51.100.0/24 are RFC 5737 documentation addresses. Distances are illustrative.
- A VPN is one example of a virtual network: its links are tunnels through another network rather than cables of its own (RFC 4026). The tunnel's outer packets cross the internet like any others.
- IEEE 802 LAN/MAN Standards Committee
- IEEE Std 802-2014: Overview and Architecture (LANs and MANs)
- IEEE 802.3 Ethernet Working Group
- IEEE 802.11 Wireless LAN (Wi-Fi) Working Group
- IEEE 802.15 Wireless Personal Area Network Working Group
- Bluetooth Core Specification (Bluetooth SIG)
- RFC 4026: Provider Provisioned VPN Terminology
- RFC 4301: Security Architecture for IP (IPsec)
- RFC 1930: Autonomous systems (the networks that make up the internet)
- RFC 1918: Private address ranges
- RFC 5737: IPv4 address blocks reserved for documentation
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