A WAN or "Wide Area Network" is a computer network designed to connect to several smaller Local Area Networks (LANs). Your home network is your LAN and it's connected to your neighbors via a WAN, which is often managed by your Internet service provider. You could imagine the Internet itself as a gigantic WAN.
Although the Internet itself is a WAN, there may be a smaller WAN that runs over the Internet, like a company that wants to connect multiple offices. It would be too expensive to run the cables themselves, so they use the internet, but we can still consider it a separate WAN. The US government uses a WAN to ensure communication between different offices across the country. In fact, the Internet began as a government WAN called ARPANET.
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The differences between WANs and LANs
WANs and LANs are built on many of the same technologies and seem to be separated by scale, but in practice they run on very different hardware.
Although WANs are certainly not slow, they often do not reach the speed that your local area network can offer. They are built to carry as much bandwidth as possible, with speed playing only a minor role.
Because the connection distance is much lower, you can equip all computers in a LAN with 10 Gbps network cards and transfer data between them at breathtaking speeds and even up to 100 Gbps on special network hardware such as Infiniband.
Compare that to WANs that typically do not reach more than 1 Gbps even when connected to fiber-optic cable (orders of magnitude slower than LAN speeds) because WANs need to be interconnected over hundreds of miles. However, if you do not do much in-house networking, most of the time you use your LAN to access the Internet, and gigabit Internet is still very fast. The average Internet speed for the US is only 18 Mbps (55 times slower than Gigabit).
Cables and Connections
You are probably familiar with Ethernet – the cable standard used to connect wired computers to your router. Although Ethernet is very fast and handles gigabit or even 10 gigabit throughput, it can not transport data and reaches about 100 meters (about the length of a soccer field). These cables are called patch cables and are used to connect short-distance connections, such as a cable. In a data center or at home.
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This is an obvious problem for WANs that span over hundreds of kilometers must be connected. the signal would not get there via ethernet. The Internet ran over copper telephone lines until it switched to fiber optic cable. Fiber optic cables use light to transmit data and are extremely fast compared to dial-up. They are usually bundled to increase bandwidth and form a fiber optic "trunk" cable. These are the main cables that form the backbone of the Internet.
However, running the Internet with fiber optic cables is costly, and these costs end up falling at the end of the line – the actual hardware that handles the routing of millions of different signals many times per second. Your home router is pretty simple: it processes an incoming data line and forwards it to a handful of devices in your house. Imagine taking thousands of them in a large, warehouse-sized system and connecting them to every house in the city. It easily increases the complexity of the operation.
These facilities are referred to as "Internet Exchange Points" or IXPs. To power the Internet, thousands of these switching and routing stations are typically connected by fiber optic cable. However, the IXP is often converted to a traditional copper cable (and sometimes bundled with your television signal). When someone says they have "fiber optic internet," they mean that the last cable from the IXP to their home is fiber, giving them direct access to the speed of the connections between the IXPs. Their Internet is only as fast as the weakest link in the chain, so everyone uses fiber optic cable during the process, but not everyone reaches full speed.
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