Intro to Networking: LANs, WANs, the Internet, and the Web
This is the first module in a series covering networking fundamentals. It assumes zero previous knowledge of networking and minimal knowledge of computers.
So, what is a network? I know this may seem like a silly question, but it can be helpful to start off with a clear definition of the subject at hand. To wit:
A network is two or more connected devices that communicate and share data using established protocols.
Now, this may sound like an oversimplified definition, but on a very high level, it truly encompasses what networking is all about: devices communicating with each other and sharing data. Granted, there’s plenty to learn in terms of how these devices accomplish those tasks (you’ll be knee-deep in protocols soon enough). However, you might be surprised at how fast you will grasp the underlying concepts. And why wouldn’t you? You deal with networks everyday.
The whole world’s a network
All the devices connected to your WiFi at home are on a network. Your mobile phone is connected to your service provider’s data and cellular networks. Your router allows your home network to access the Web, which uses an Internet protocol (HTTP) to access resources and data in a fraction of a second. And the Internet itself is a global network of… you guessed it, networks!
As you’re surely beginning to see, you can’t do much of anything without connecting to a network these days. With that in mind, its a good time to gently introduce some fundamental networking terms that you will be building upon from here on out:
Node: Any device that is connected to a network
Host: A node that actively participates on a network. Some examples include desktop PCs, laptops, servers, printers, phones, tablets, TVs, etc. NOTE: All hosts are nodes, but not all nodes are hosts.
Network Interface: Hardware or software that connects a device to a network. Sometimes seen as a Network Interface Card (NIC) on a PC or laptop. Connections on an interface can be wired (commonly using Ethernet cable) or wireless.
Ethernet: A networking protocol that controls how data is sent, received, and processed on a local area network (LAN).
Internet Protocol (IP) Address: A number associated with a node or host on a network. Required for all network devices. Think of it like your mailing address. If another device wants to send data to you, it needs to know your “mailing address” (IP).
Fun Fact: You’re already a part-time Network Administrator
All that jargon aside, this networking business is old news to you. You’ve been at it for a while. I’d venture to say that you have, at some point, power cycled your router at home in order to reset the connection to your Internet Service Provider (ISP). You are the master of your WiFi password and have the authority to control who joins your network. So that makes you an administrator over your home’s local area network (LAN)… whether you like it or not.
A LAN (Local Area Network) is a group of networked devices within a small geographical area — such as a home, an office, etc.
LANs are small, typically private networks with nodes connected via Ethernet cable or Wireless Access Point (WAP). At home, your wireless access point is likely built in to the router you got from your internet service provider. When you enter your WiFi password into your phone, that device is automatically assigned an IP address (a process called Dynamic Host Configuration Protocol or DHCP) and becomes a node on the LAN. At this point, the device can communicate with other devices on your LAN.
But your phone can’t connect directly to the internet or web. That’s where your router comes in.
A router is a network device that moves (or “routes”) data from one network to another.
In order to visit websites — or even conduct a Google search — the data sent from your phone needs to make a pit stop at your router. This is because websites are hosted on remote web servers, and these servers are not a part of your LAN. I think you would notice if Google’s web servers were in your living room.
The issue is, your phone doesn’t know how to reach any device that isn’t on your LAN. But, thankfully your router is a part of your LAN, and its job is to find routes and send data to other networks. Essentially, any time a web request is sent, all of your home devices think to themselves: “If I want to connect to an IP address that isn’t local, I need to go through my router”.
Your router has, at the very least, two major network interfaces. One interface is connected to your LAN. The other is connected to your ISP’s Wide Area Network (WAN). So, when a device on your LAN makes a web request, your router facilitates the flow of data, acting as the gatekeeper between your LAN and the open internet (WAN).
A WAN is a network that extends over a large geographical region, and is commonly associated with the publicly-accessible internet.
Okay, so what’s the deal with making a distinction between the internet and the web?
The terms “Internet” and “Web” are often used interchangeably. While I can understand why this happens, it’s very much incorrect. The internet and the web are two distinct things. And now that you’re learning about networking, it’s time you find out why!
Commonly referred to as a “network of networks”, the Internet as we know it is a global infrastructure of interconnected networks, computers, etc. You can think of the internet as a highway. And The World Wide Web (or Web) is a utility that uses the Internet to transfer and link data and resources. If the Internet is a highway, then you can consider the Web a vehicle using that highway.
The Web is based on the Hyper Text Transport Protocol (HTTP), which is invoked when you open a browser and click on a link or type in a Uniform Resource Identifier (URI) — that’s why web addresses are preceded by “http://”. However, in this day and age, we should hope the websites you visit are using be the secure form of the protocol: HTTPS
To sum it up: the Internet provides the infrastructure that allows the Web to do its thing.
Whew! We covered a lot here, so congratulations for getting through it! Now that we’ve seen a high level overview of some major networking concepts, lets get our hands dirty and start building some networks — virtually, that is.
The modules that follow will be utilizing free software from Cisco called PacketTracer (available for Windows and Mac). This will allow us to set up a virtual networking lab where you can immediately apply the knowledge you’re gaining.
You can find PacketTracer here: https://www.netacad.com/courses/packet-tracer
FYI, you will need to create an Cisco Network Academy account in order to download the software. Its easy… and did I mention free?
That’s all for now. Hope to see you in the next module: Network Components