What I understand is:
- A LAN is connecting two or more computers to form a cable network between them.
- A WAN is connecting two or more computers over a broad area to form a cable network between them.
So, is the difference the length of cable used to form a network or does it depend if it's formed in a city, state or between countries?
Best Answer
Many Answers here have given textbook-like definitions that have touched on this, but there are certain practical, real-world distinctions worth underscoring:
A LAN is typically something completely within your own premises (your organization's campus, or building, or office suite, or your home), so it's something you build and own yourself, all the way down to the physical cabling. In contrast, a WAN is something that connects between geographically separated locations, so you generally have to lease access to lines or data transmission services from telecommunications carriers to create your WAN.
Because of the shorter distances needed for on-premises networks, and because of the focus on connecting PCs and servers, LANs tend to be built on Ethernet and other 802.3-family (and 802.11-family) physical layers and data links. 1000BASE-T, 1000BASE-SX, 1000BASE-LX, etc.
Because off-premises network links usually need to go longer distances and work over the telecommunication carriers' existing infrastructure, they tend to use physical and data-link standards that are more common in the telecom industry. Then again, for your convenience, telecom carriers usually hand off to you using an 802.3-family link, even if what they're using behind the scenes is, say, OC-3 and SONET/SDH.
Because of the technical hurdles associated with moving lots of data long distances reliably, WAN links tend to be lower bandwidth and higher latency than LAN links. Also, because you're usually paying a separate telecom carrier for the service, to keep costs down, most organizations try to limit (or at least not go crazy with) how much data they move over WAN links.
The differences between LANs and WANs tend to be at the physical and data-link layers. At the network layer (Layer 3 in the old-but-still-helpful-for-some-discussions OSI layering model), most people use IP (Internet Protocol) nowadays. Because it all uses IP, applications that use IP don't have to know what physical and data-link layers are in use, so anything you can do on a LAN you can potentially do on a WAN as well, if you have high enough bandwidth and low enough latency for whatever it is you're trying to do, and as long as you haven't blocked it at your firewall (or via the accidentally firewall-like properties of a NAT).