A WAN or "Wide Area Network" is a computer network designed to connect multiple local area networks (LAN). Your home network is your LAN, and it is connected to your neighbors over a WAN, which is often handled by your ISP. You can think of the internet itself as a giant WAN.
Although the Internet itself is a WAN, it is possible for a smaller WAN to exist that runs over the Internet, as 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 regard it as a separate WAN. The US government uses a WAN to secure communications between different branches across the country. In fact, the Internet started as a government WAN called ARPANET.
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WAN and LAN Differences
WAN and LAN are based on many of the same technology and appear to be separated only by the scale, but in practice they go on very different hardware.
While WANs are not really slow, they often do not have the same speed as your local network can. They are built to carry as much bandwidth as possible, with speed as a secondary to their function.
On a LAN, because the connection distance is much smaller, you can equip all computers with 10Gbps network cards and transfer files and data between them at great speeds, even up to 100Gbps on specialty networking products like Infiniband.
Compare it to WANs, which even when connected to fiber cables usually does not reach more than 1 Gbps (systems slower than LAN speeds) because WAN has to be connected over hundreds of miles. But if you do not do much internets, you usually use your LAN to access the internet and the gigabit internet is still very fast. The average Internet speed for the United States is a moderate 18 Mbit / s (55 times slower than gigabit).
Cables and Connectors
You are probably familiar with the Ethernet cable standard used to connect wired computers to your router. While Ethernet is very fast, manages gigabit or even 10 gigabits of throughput, it can not carry data very far, peaked at about 100 meters (about the length of the football). These cables are called patch cables and are used to connect connections over short distances, such as within a data center or home.
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This is an obvious problem for WAN that needs to be connected over hundreds of miles would not get there over Ethernet. The Internet used to run over copper phone lines until it was switched to run on fiber optic cables primarily. Fiber optic cables use light to transfer data and are extremely fast compared to dial-up. They are typically bundled to increase bandwidth, which forms a fiber optic "root cable" cable. These are the most important cables that form the backbone of the internet.  Switching Hardware
Driving the internet on fiber optics comes at a cost, and the cost comes up at the end of the line – the actual hardware that has to handle routing of millions of different signals many times per second. Your home router is quite simple: it manages a data line that comes in and directs it to a handful of devices in your house. Now imagine that you take thousands of them, shoot them into a large system, the size of a warehouse, and connect them to every house in the city. It easily increases the complexity of the operation.
These facilities are called "Internet Exchange Points" or IXPs. To drive the internet, thousands of these switching and routing stations are connected worldwide, usually with fiber optic cable. However, when coming to IXP, they often switch to traditional copper cable (and sometimes bundled with your TV signal). When someone says they have "fiber internet", it means that the IXP terminal cable to their house is fiber, which gives them instant access to the speeds of IXP connections. Your internet is just as fast as the weakest link in the chain, so while everyone uses fiber cables at some point in time, do not get all the full speed.
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