LAN stands for Local Area Network.
A LAN is just a network of devices connected locally, hence the Local Area part. This local area can be something as small as a house, or as big as a university. LANs are used for a number of things! The first Halo games are sort of famous for encouraging LAN parties, because the internet during that era just wasn’t good enough to prevent lag when the players were physically distant. LAN cut out the middle man and allowed the computers to communicate with each other directly over a much shorter distance.
LAN’s primary advantage here is clear: it’s speedy! Accessing computers within the LAN usually has a speed advantage over trying to access outside computers with the internet. When it was first being used and really put to the test, LAN also allowed users to share storage space and printers, keeping costs down while still keeping information within reach.
It’s sort of like New York’s subway vs it’s surface streets: as long as what you need is at one of the stops (one of the computers in the network), it’s much faster than trying to cross the upper streets if the traffic is bad. If you need something from Milwaukee, though, the subways can’t get you there.
With that in mind, remember that just because it’s local doesn’t mean it’s ‘insulated’ or ‘more secure’. LANs that have things like smart thermometers and remote controlled lightbulbs can leave gaps in security where there shouldn’t be and allow outsiders to get on the network.
WLANs (Wireless Local Area Networks) are just LANs, but wireless – the connection is made with encrypted channels instead of physical wires.
Meanwhile, WAN
WANs, or Wide Area Networks, are generally used to connect LANs together across distances (although it doesn’t have to be just LANs – singular computers can also be connected via WAN). Where LANs work with a bunch of close-together computers, and don’t necessarily need access to the outside internet for them to function as a LAN, WANs connect computers over very large distances, miles, states, or countries away. The first versions of a WAN connected US Air Force bases together with a series of dedicated telephones, hard phone lines, and modems, followed closely by universities doing something similar to connect research labs. Now, we use two kinds of routers to do the same: core routers work inside the network (for the LAN) and boundary routers work to connect inside and outside (for the WAN). Not every system will have two separate routers to perform these functions – the router that connects your printer to your computer wirelessly while also connecting that computer to Netflix is doing both!
WAN, for certain organizations, still functions on wires connecting to routers – if the company has a couple of offices in different states, the home-base organization can be connected via a dedicated line to the flagship one. Boundary routers on either end of the line allow them to share LANs as though they were together! Whether or not this line is leased out exclusively to the company often depends on budget – other methods, like circuit-switching (which works sort of like an old-fashioned phone operator board, but for the internet) allow the company to treat the relevant line like it is their dedicated line when they need to send or retrieve something, but once that thing has traveled, it’s someone else’s turn to use it for data transfer. The info is only allowed to travel once the circuit is connected, which in theory prevents illegitimate access to the network.
SD-WAN
Software-Defined Wide Area Networks skip the designated line entirely and use encryption to simulate a line over regular internet service. This is also cheaper than a designated leased line. The original WANs weren’t designed with things like server clouds in mind, so they often had inefficient or unoptimized policies in place, which doesn’t matter on smaller scales but does on larger ones. Similarly, old-fashioned WANs often didn’t have to worry too hard about things like load balancing and redirecting, something that becomes increasingly important the more connections there are on a WAN. SD-WANs can compensate in ways that physical-line WANs could not.
And as previously said, WANs depend on a physical line. If that line gets damaged, then there’s no data transfer happening on it until it’s repaired. This doesn’t happen very often, but when it does, it can be devastating, grinding business to a halt. However, SD-WANs have their drawbacks too. Firstly, they’re not necessarily automatically secured – they’re just connected. SD-WANs are a networking solution, not a security one. The old-fashioned line system limits the WAN’s ability to load-balance, but it does provide secure access via a physical cable that would have to be tampered with; SD-WAN can self-balance, but it requires a security solution as well, and that can be difficult to navigate in a world where things like the Solar Winds or Kesaya hack happened with seemingly no warning. If you’re shopping for an SD-WAN, make sure you get the kind that comes with a security solution built in – many do!
Sources:
https://www.cisco.com/c/en/us/products/switches/what-is-a-wan-wide-area-network.html#~what-it-is
https://www.cloudflare.com/learning/network-layer/what-is-a-wan/
https://www.silver-peak.com/sd-wan/sd-wan-explained
https://www.riverbed.com/faq/what-is-sd-wan.html
https://www.checkpoint.com/cyber-hub/network-security/what-is-sd-wan/sd-wan-vs-vpn/