While computers are fantastic tools, what takes them to the next level is their ability to communicate. By itself, a computer is a fancy typewriter, calculator, and (limited) gaming system. But when we connect computers to other computers, we get the glory and grandeur of the internet!
The word internet is a shortened form of the U.S. Defense Department's internetwork, where inter- means "between." So, our beloved internet means between networks. And it is that magic that happens between all our networks. But part of those networks is our networks. Our phone providers' cellular networks. Our work networks. Our home networks.
Today, we are going to look at our networks and the infrastructure that makes these possible. Since we all use computers, understanding how these devices connect to each other and the internet affects us all. Since you are reading these words, you must be on a network right now. So, let's explore how these words entered into your network and ended up on your screen.
For this journey, we'll start with the modem. Then we'll move on to the router, switch, access point, and (finally) your computer. Of course, we'll touch on all the wires in-between, as well as how data travels wirelessly. We will also explore all-in-one versions and even firewalls. Along the way, you will learn about what you can do to maintain a network properly or even upgrade your network infrastructure.
Before diving into our network infrastructure, let's take a moment to talk about these abstractly. What is a net? No, not The Net, the 1995 Sandra Bullock classic film. A net. Like a fishing net. A net is a collection of interlocking threads, strands, ropes, etc. Together these form a mesh. In the context of the network, the word -work is used like in the phrase "a work of art." Work here means a creation. As such, a network is a mesh-like creation.
That is what computer networks are: They are these net-like structures formed by various wires running between several points. These can be the telephone wires of our DSL provider or the coaxial wires from our cable-internet provider. They can even be fiberoptic lines. And these are just external networks. Our home and business networks are filled with ethernet cables running from one device to the next. This crisscrossing of our patch cables forms the net of our network.
And what is the largest network? The world wide web! And why is it a web? Because it's a network and networks resemble spider-webs. Hence why the bots Google uses to explore and index the internet are called spiders: They crawl all over the web.
But what about that infrastructure part? Infra- means "below," and structure is an organization or construction. As such, the infrastructure is the underlying organization. It is the unseen foundation that allows everything on top of it to function. Think about government infrastructure like roads. This foundation allows us to get to and from our works, homes, store, and more. Furthermore, it facilitates our goods to go from production to the warehouse to the store. Without the foundational support of infrastructure, nothing could go anywhere.
This web-like substructure in our homes and businesses is how our computers connect to one another. It is from this interconnection that something wonderful happens! From this connection, we can shop at Amazon, learn from Wikipedia, and watch videos on YouTube. It's not the devices themselves but the connection between them—much like our brains. As Neuroscientist Kimberley McAllister explains, "That’s because it’s the connections between those cells that make the brain so amazing."
Alright, let's talk about core network components. We'll start with the internet side coming through our internet service provider. And we will finish with the device you are using now to read this now.
The internet enters our residences and businesses via telephone line, coaxial cable, fiberoptic, or something else. Those wires then go to a device that we tend to call a modem. The word modem is an abbreviation of MOdulate DEModulate, the process of converting from digital to analog and back again. As such, we only have an actual modem if we are using telephone-based technologies such as DSL. For coaxial and fiberoptic, what we call a modem is instead a media converter. It takes the digital signal from one medium and transforms it into another.
But for simplicity's sake, let's just call all of these modems. The modem receives the signal from the internet, converts it, and pushes it out to the router.
Router's divide up our networks. Often, a router separates the external wide area network (WAN), the internet, from our internal local area network (LAN). However, it is possible to divide up internal networks into separate LANs using multiple routers. Similarly, the internet itself is divided up into various networks via routers. In all of these cases, because they set the border between two networks, routers have two ports.
Across these networks, routers communicate with one another via internet protocol (IP) packets. Because they use IP addresses, routers operate on the network layer (or layer 3) of the Open Systems Interconnection (OSI) model. These packets have both a receiver and a sender's IP address. These addresses tell all the routers along the way where a packet is coming from and where it is trying to go. Routers know where to send these packets by using routing tables.
The routers on the internet use public IP addresses to send information, while our private networks use private IP addresses. As such, one of the coolest tricks a router can do is to convert a public address to a private one and vice versa. Once converted, the router can then pass this information off to a switch.
Switches (and Hubs)
While a router has two ports, a switch often has four, eight, 16, 24, or more. It is common to find one or more 48-port switches in many businesses—and all of these ports are in use! Regardless of the number of ports, a switch creates links between devices on the network. For example, one workstation sends an email, which the switch will route to the router. The switch directs another workstation to the server to access a shared file. The switch creates a link between a third workstation and the network printer to print off a document. All at the same time. A 48-port switch could simultaneously make 24 connections between 48 different devices. And when one device needs to switch to another, the switch switches the connection.
Switches function like telephone operators. They create links between different devices and then create new links between other devices. In this way, any device on a network can communicate with any other device on the same network. While routers use IP addresses, switches know which device is which because of their media access control (MAC) address. Since they use MAC addresses, switches operate on the data link layer (layer 2) of the OSI model. Once they have switched to the right device, the switch forwards the signal down patch cables to its destination.
Before we had switches that could intelligently direct signals, we had hubs. Hubs didn't care about MAC addresses. Instead, they took a signal in and then rebroadcast it to every port. Every device connected to the hub gets the signal, but unless it is directed to this device, they ignore it. As such, with a hub, there could only be one message at a time. The message comes in one port and is rebroadcast to every port. The next message comes in and goes to every port. So, while a switch can have any number of ports, a hub would just be more and more bogged down with every additional port.
Patch Cables and Patch Panels
The net part of our internal network is overwhelmingly made up of patch cables. Most patch cables are made up of four sets of twisted-pair copper wires. Sometimes these twisted pairs are shielded from magnetic interference (STP). More often though, they left unshielded because of the cost (UTP). These are then numerically rated based on their technological capabilities, from 5 (or lower) to 8 (or higher).
Our homes may have only a few of these wires. However, our works are often overflowing with them. The plug, known as an RJ45 port, looks like (and is) a fat phone jack. The modem has one of these RJ45 ports, which is connected to one of the two RJ45 ports on the router. The router's other RJ45 connects to one of the switches via another patch cable. And then several or even dozens of patch cables explode out of every RJ45 port on the switch.
To bring some semblance of organization to all these wires, the ports on the switch are often connected to a patch panel. Attaching patch cables to a patch panel is a relatively easy task. And then, patch cables of any length can be run throughout the ceiling, floors, and walls. These will then often wind up terminating at a wall plug throughout the building. It is from here, that we will plug in our computers, VOIP phones, printers, access points, etc. Because they connect physically everything, patch cables are on the physical layer (layer 1) of the OSI model. If your computer is hardwired to the internet, then these words have traveled this path to your screen.
While it is possible to have an entirely wired network, many of us like the convivence of wireless technology. Like a modem converting from one medium to another, an access point (AP) converts from copper wires to radio waves. The signal comes in via the patch cables and is then broadcast to nearby wireless computers, tablets, smartphones, etc.
Unlike a switch, which knows what device should be receiving a message, APs are more like hubs. They simply send the signal out to everything. And like a hub, each device receives all the signals, but just ignores anything not addressed to it.
You may recognize most or all of these devices from your work. However, many of you might be saying that you don't have most of these at home. Instead, you have a router. To you, I say, your "router" is much more than a router. Like a modem (which is rarely actually a modem), a router is only a router if it has two ports. Any more, and it's a router/switch. And if it has built-in WIFI, it's a router/switch/AP.
These all-in-one devices can be fantastic. They do it all. But they do it all, so you can't upgrade them. You can't add more ports to this device. And if the built-in AP is using an old wireless standard, you aren't going to be able to make it new.
That said, it doesn't matter. The great thing about networks is that they are expandable. If you have even a single port, you can add a switch to it. And you can add a switch to that switch. I've gone into businesses where they have racks with three 48-port switches. Remember that each of these has to end up at the singular router port, so one switch plugs into another. And you know what's really cool about switches? They're intelligent! You can plug anything into any port on any switch and it will just know what it is. So yes, a switch knows when it is plugged into another switch and will behave accordingly. (Just don't be tempted to plug in two or more ports from one switch into another unless you turn on spanning tree protocol.)
Now, let's say you want to upgrade your AP, just add another AP to your switch. Done. Not only does this work for upgrading the wireless technologies that are available to your network, but this also works when you want to increase the coverage to your home network. Is WIFI not great in a part of your space? Just run some patch cable out toward that area and place an AP nearby, preferably attached to the ceiling.
If you have to set up two APs though, take the time to ensure that they are not interfering with one another. WIFI is broadcast over radio waves. So, if two or more devices try to use the same or similar channels, they will both interfere with one another. This issue isn't a big deal in the 5.0 GHz range but can be a real problem with 2.4 GHz. By the way, this is also true if you live in a place with multiple competing wireless networks, such as apartments or condos. If you live in such a place, you need to get ahold of a wireless spectrum analyzer and see which channels are being used the most.
And on the off chance you are still using a hub, you've got to replace that with a switch now.
We spend so much of our time trying to fortify our computers. However, we often forget to protect our network infrastructure. While our systems are set up to not trust anything outside, they blindly trust everything on our private network. So, if any element of our network is compromised, everything in our network is compromised.
As such, here are some ways to secure our network infrastructure:
For those wanting to dive deeper into networking infrastructure, there are many opportunities to learn more.
Network infrastructure is composed of the same elements. Information comes in from the internet comes into our house or business via a modem. This information crosses from one network to another via a router. It then travels over a switch toward a particular endpoint. And if the endpoint is using WIFI, the information will head out via an AP. At our work, each of these steps will be through distinct devices. At our homes, some or all of these might be combined into one device.
Knowing this, you are now armed with ways to improve both the quality and security of your network. Whether it is your home or business, you know how to recognize what you have. Furthermore, you should have some ideas on where you'd like to go next.
And if you want some help with your journey into a network that is better, stronger, faster, we're here for you.
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 Some devices are referred to as a Layer 3 switch because they function on both the network and data link layers of the OSI model. However, this is really a misnomer. As James "Professor" Messer explains, inside these devices are separate routers and switches that are combined in the same chassis. As we'll talk about later, it's possible to have one device that combines these with a modem and AP, and more.