What is a router ?

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• Nibodhika@lemmy.world ⁨30⁩ ⁨minutes⁩ ago

  Let’s get into very basic things.

  You have two computers you want to connect, you grab a cable, plug it in both and voila!

  You now need to connect a third computer, you could have a three way cable, but that makes it hard to replace things. Instead you have a box that has multiple connectors and internally it just connects all of them, essentially making a multi-end cable ok demand, this is what’s called a Hub because it’s just a centralized location where every package goes in/out.

  But now your machines need to know how to send messages to one or another, so you implement a protocol where each machine has a number, and every message sent you encapsulate in a header saying something like “For X”, and computers know their own number so they can discard messages that are not for them.

  Cool, but as you add more computers and longer cables the signal might become weak, you could add a very small chip to that box and some electricity so it can now act as a repeater. Most hubs were also repeaters, it was a small extra cost but a lot of extra functionality so it was an easy choice.

  As you add more computers you start to have an issue, whenever two computers send a message at the same time they collide and no one receives it. Now, this is silly, you have computer 1 sending a message to computer 2 and computer 3 sending a message to computer 4, there’s no reason these should collide, but because of the Hub they do (because both messages are actually sent to all computers and they just discard what’s not for them).

  It’s time to make your box a bit smarter. Instead of naively sending all messages everywhere, you add a computer there, it can understand the protocol we described before, and instead of just being a blind signal repeater. This box now knows which port each computer is plugged in, and so when 1 sends a message to 2 the signal only goes from the port 1 to the port 2, all other ports are free and can send messages at the same time. This is what’s called a Switch, because it switches what output the message goes to.

  Cool, but now we have two separate networks, which means there are two Computer 1. You can’t just put one cable between the two switches because they won’t know where computer 1 is. Each switch needs to have it’s own number, and you need to wrap the message twice, e.g. Computer 1 connected to switch 1 wants to send a message to computer 2 connected to switch 2. Switch 2 is connected on port 5 to switch 1, so you wrap your message with something like “For 5, For 2”. The first switch sends to 5, the second switch receives it, notices it’s for himself, discards the first wrapper, and sends to 2.

  Magic, right? Well, not quite, you need to know where computer 2 is located, and know all of the path to it. That’s not feasible for users to manage. What if we gave each computer a unique number across networks? It would be a sort of an Inter-Network Protocol address, or an Internet Protocol address for short, or even shorter IP. So now each computer has a unique number, and computer one can just send a message to computer 10 and not have to worry where it is.

  But how does the message actually get to computer 10? Well, it’s time to add some extra logic to our Switch, and have it store a table of routes, so it knows that computer 10 is on port 5. Because they now not only know what’s on their ports but what route a package needs to take to reach its destination between networks this device is called a Router.

  And there you go. A short introduction to network to explain what a router is and how it works. Obviously I simplified a lot of stuff and the real thing is a lot more complex, but this should give you a good ELI5 version of routers and networking.

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  • LoveEspresso@retrofed.com ⁨10⁩ ⁨minutes⁩ ago

    Lovely !! Thanks for taking the time to explain it so nicely.

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• RustyNova@lemmy.world ⁨3⁩ ⁨hours⁩ ago

  Routers are multiple things in one box:

  • Network gateway: this is the exit point for your home network. All the traffic going to the internet is routed here, then sent towards the internet. Traffic coming from the internet is also pass through here, and is directed towards the switch

  • Network switch: this is the “intersection” of your network. Each device, the gateway, wifi, tv, etc… Is connected to it. It directs traffic where it wants to go

  • wifi module: this turns regular wired internet into wifi, handles connections, etc…

  • tv module: this is especially a device that connects to the internet and get the tv stream from it

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  • ohulancutash@feddit.uk ⁨1⁩ ⁨hour⁩ ago

    Also increasingly a VoIP module to replace conventional phonelines.

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• ProfessorScience@lemmy.world ⁨3⁩ ⁨hours⁩ ago

  If the postman is your ISP, and the people in your house are computers, then the person who picks up your mail at the mailbox and hands it out is the router.

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• roguelazer@lemmy.world ⁨3⁩ ⁨hours⁩ ago

  Technically, a router is any device which routes traffic at the IP layer (layer 3; based on IP addresses like 10.1.2.3 or fe80::abcd:1234), as opposed to some other later (e.g., a device which routes at layer 2 is a switch; a device which routes at layer 7 is a load balancer).

  In colloquial usage, “router” usually refers to a home internet gateway, which is a device that does a few things:

  • serves as a masquerading gateway for your local network (allowing multiple devices inside your home to share a single IP address provided by your ISP)
  • serves as a traditional router for IPv6 if your ISP provides such access
  • contains an Ethernet switch allowing you to connect multiple Ethernet devices
  • often contains a WiFi access point, allowing you to connect WiFi devices and bridge them into your main network
  • has firewall/ACL systems to prevent the outside world from getting into your network

  It usually does this by being a single box containing a small Linux or BSD computer running some custom software, dedicated WiFi and Ethernet chips, and some antennas. No magic there; you can do the same thing with any computer if you put enough elbow grease into it.

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  • abbadon420@sh.itjust.works ⁨1⁩ ⁨hour⁩ ago

    Also, all the devices in your home network (pc, tv, phone, thermostat, whatever) can talk to each other via broadcast. They just frequently yell out “I am here! See me!”. The router stops those broadcasts from going into your neighbour’s network or even the internet.

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• e0qdk@reddthat.com ⁨3⁩ ⁨hours⁩ ago

  Assuming you mean in the computer sense, it’s a device that forwards messages from one network connection to another. e.g. between ethernet connections and/or WiFi in home use, typically, or sometimes other kinds of networks in industry.

  Messages on the internet are usually transferred as IP packets (Internet Protocol packets). The router looks at the destination address on each packet that arrives, consults a table (“routing table”) to determine which connection to use to forward the message out on, and then it actually copies the message onto that connection. The basic idea is pretty straightforward, but it can get complicated in real world situations when you have multiple networks, redundant links, etc.

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