What a network is, and the types of network

What exactly is a network?

A network is built from three things and no more: nodes, meaning the devices that talk; links, meaning the cable or radio between them; and a protocol, meaning a shared language everyone follows plus one address per node. Two laptops with a cable between them are already a network.

Addressing is where most problems happen, not the cable. If two devices on one network do not take matching addresses, the link is healthy and nothing connects; that is exactly the case where the user says "the cable is plugged in but it does not work".

Something that gets said less often: a network has degrees. On our own server the site does not go through the network at all to talk to its database, because the setting is localhost and the connection goes through a socket on the same machine. Even when a program deliberately uses the network to talk to itself, the round trip on the machine takes 0.022 ms, while the same round trip to the first router, one cable away, is 0.252 ms. Ten times further, for a distance the eye cannot see.

So when something does not work, first decide which of those three parts is broken. Our support experience is that most "network outages" are really addressing problems or one specific device, and the cable and the antenna are innocent.

What is the difference between a LAN, a WAN and the internet?

The difference is scale and ownership, not technology. A LAN, a local network, is one place: a home, an office, one floor. You own it, its addresses are private, and you pay no rent for it. A WAN, a wide area network, connects several places and almost always runs on a line rented from an operator. The internet is the network of networks and has no single owner.

The practical border between the three is exactly where responsibility changes hands. Up to the home router it is yours and you fix it yourself; past the router it is something you rent and the only available move is to report it. That one sentence answers half of the arguments people have on the phone with support.

And the biggest household misunderstanding comes from here: wifi and the internet are not the same thing. A full signal icon only says the local network is healthy and your phone is talking to the router; it says nothing about the health of the operator line. That is why you can have full signal and no page opening, and why testing in the order given in the lesson on how the internet works, from near to far, gets you an answer.

What is actually sitting inside your home network?

Usually one box playing three roles at once. The modem turns the operator line into something your devices understand. The router decides what goes out and shares one public address among everyone. And the access point is the radio that makes the wifi. If there are network ports on the back of the box, there is a small switch inside it too.

Addresses inside the home are private, and deliberately so. Three ranges are set aside for exactly this and recorded in a document called RFC 1918: 10, 192.168, and the span from 172.16 to 172.31. Your router address is one of those. What is interesting is that our own public server has a default gateway in that same reserved span, which means even a machine that answers the world all day sits inside a local network first.

Outside the home, though, all of you are one address. The router passes the traffic of every device through a single public address, which is why a site you open cannot tell whether the request came from the phone or the laptop; they all look the same. The "my IP" you see on websites does not belong to any of your devices either, it belongs to the router.

A security consequence follows that few people notice: because devices inside the home have no direct address from outside, they are not reachable from the internet by default. That is free protection, and it is exactly what gets given away by "opening a port" or putting a device into DMZ mode.

Should you run a cable, or is wifi enough?

This question has no winner, and anyone who rules one out for you is selling something. A cable gives constant latency, is unaffected by walls and neighbours, and shares its capacity with nobody; in return it has to be run and plugged into a port. Wifi gives mobility and needs no cabling; in return it shares the air with every device around and its quality changes minute by minute.

One number is advertised everywhere and read correctly by few: the big figure on the router box is the radio rate under laboratory conditions, not the speed that reaches your device. Distance, walls, the number of devices and channel congestion each take something off it, and none of them is printed on the box.

Our position is simple: anything that is stationary and matters gets a cable. The desktop computer, the television that streams, and the machine you take video meetings on. Everything else stays wireless, and on the newer band where the device supports it, which is less crowded but passes through walls less well.

And the boundary of that advice: in a rented flat where you cannot drill, or for a laptop that moves constantly, a cable is the wrong answer. There the right work is improving the wifi itself, meaning where the router sits and which channel it uses, not pulling wire.

Which settings should you touch, and which not?

Three things are worth doing, and they are done once. Change the password for the router admin panel, which is not the wifi password and in most homes is still the factory value. Update the device firmware. And if your router offers a guest network, put visitors on it so they cannot reach the devices in the house.

And three things not to do merely because someone on the internet said so: opening a port, putting a device into DMZ mode, and switching off the router firewall. All three remove the free protection described in the previous section, and usually do not solve the problem they were suggested for.

A truth that security product advertising leaves out: for a home network the real danger is usually not a skilled attacker, it is the default panel password and firmware that has not been updated in years. The first takes a minute and the second takes ten, and both are more effective than anything you can buy.