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How the Internet works

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Let’s “connect” the dots

The Internet is a fantastic tool. It truly is the “information highway”. With it, we can connect to people on different continents. Have you ever wondered how we can connect to any website from anywhere in the world? You’ve come to the right place to learn how it all works!

In this lesson, we will discuss the main hardware used, what computer use to speak to one another, and everything else in between that gets you the information or entertainment you’re looking for!

For this lesson, we will focus on your at-home Internet connection and network.

The Hardware

Modems

For you to visit a website, you need some hardware to connect to the Internet. The most important device you have in your home is the modem. Modem stands for modulator/demodulator. The modem is what allows you to see web pages, download files, and stream all your shows.

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Your modem connects to your Internet Service Provider (ISP). Once you power up the modem, it will start getting data sent to it from your ISP. The modem will then translate the data into what you see on the screen.

The modem “translates” data because while computers only understand binary (1s and 0s), the data that goes to and from the modem are analog signals. An example of an analog signal would be radio waves or sound waves. As you see below, the sound wave from a voice recording dips up and down in a continuous pattern. In electronics, these waves are either positive voltage (when the wave is moving up) or negative voltage (when the wave is moving down).

An analog wave of a voice recording.

Once your modem receives these analog signals from your ISP, it will turn them into bits that are either a 1 or a 0 so computers can understand the data received. This is known as demodulation.

A modem “translates” these analog signals to digital via “sampling”. During the sampling process, chunks of the analog signal (wave) are taken and the computer turns those chunks into 1s and 0s based on the voltage from the analog signal.

A “digital” signal.

When your home network is ready to send data to your ISP, it will reach the modem as the digital signal, and your modem will take the digital signals and turn them into analog signals to go to the ISP. This is known as modulation.

A modem converts the digital signals to analog ones by using a Digital-to-Analog Converter (DAC for short). This converter takes in the digital signals from your computer and converts them into one continuous analog wave.

Routers

You most likely have a wireless router at home. This router gives you the freedom to connect to any Internet based service, such as video streaming or checking social media apps on your smartphone. Think of the router as a bridge for all your devices to the Internet.

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Having a router at home allows you to create a Local Area Network, commonly known as a LAN. In a LAN, multiple devices within a short range can connect and communicate with one another. Your wireless router allows you to connect smartphones, streaming devices, and desktop/laptops to your Internet connection. It’s important to know that the router doesn’t create the Internet connection but is rather the “gateway” to the Internet since the router is directly connected to the modem.

You can see what your gateway address is at home by running the following steps (note: this is for computers running Windows):

  1. Open the Start Window
  2. Type “cmd”. This will give you the “Command Prompt” app as “Best Match”. Click this to open the command prompt.
  3. Once the command prompt is open, type “ipconfig”. This command will show you the basic networking information for your computer.
    1. If you would like to see more information, add /all. This command would be ipconfig /all.
  4. The output from this command will show you the following
    1. Ethernet adapter Ethernet.
    2. Wireless LAN adapter Wi-Fi
    3. Ethernet adapter vEthernet (this won’t show on all computers. This will show if your computer can run virtual machines. We’ll explain those another time).
  5. The IP address of your router, which acts as the gateway, is found on the line labeled “Default Gateway”.
Output of ipconfig command in Windows

Wait, where am I going?

Whenever you want to go somewhere you haven’t been before, you’ll likely use a GPS to help with directions. Of course, you’ll need an address to enter into the GPS to tell it where you’re going. Like a GPS, the Internet needs an address as well, so it knows where requests and responses are going. When dealing with the Internet, we have Internet Protocol (IP) addresses and Media Access Control (MAC) addresses.

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MAC addresses are six sets of two characters each. These characters can be 0-9 and A-F. If you added the /all flag in the ipconfig example above, you’ll see a line labeled “Physical Address”. This is the MAC address of either a wireless card if you are using Wi-Fi to connect to the Internet, or an Ethernet card if you are using a wired connection.

This is an example of a MAC address. The first three sets of characters are specific to who made the hardware,
while the second sets of characters are specific to the example device only.

The first six characters are specific the networking hardware manufacturer, and the last six characters are specific to each device create by the manufacturer. MAC addresses don’t change as they are “burned” into the device. MAC addresses are used to help direct traffic within the same network (LAN). In the event the destination machine is within the same LAN as the source machine, the MAC address will be used instead of an IP address, since the traffic doesn’t need to go over the Internet.

IP addresses are four sets of numbers that are 8 bits each, separated by a period. Each set of numbers is called an octet. IP addresses are usually given by a Dynamic Host Configuration Protocol (DHCP) server. We will go over DHCP in another lesson. IP addresses help computers speak to one another through the Internet. Think of IP addresses as phone numbers for computers. The IP address can help find the destination computer in the event it exists in a different network.

An IP address.

Unlike MAC addresses, IP addresses can change. For example, think of having a land line at home for your phone service. You receive a number with an area code, and then your home number. If you were to move, while your actual phone stays the same, you would expect that your number would change, especially if you move to another state. This is the same with moving into another network. Your MAC address stays the same since you are using the same computer, but your IP address will change since you moved into a different network.

So, why do we have two different types of addresses? Simply, we use MAC addresses so computers within the same network can speak to each other without having to go over the Internet, while we use IP addresses to speak to computers in different networks (this is where the Internet comes into play).

Time to hit the road

Now that you’ve requested to go to a website, or you want to start streaming your favorite show, your request starts its journey to its destination. The Internet comprises of multiple ISPs in different tier levels. The most common tiers are Tier 1, 2 and 3.

Tier 1 ISPs help connect networks throughout the entire world. They span the longest distances to help countries connect to one another. Tier 1 ISPs connect to each other through peering agreements. Think of peering agreements as two competitors who agree to connect with each other for exchanging information.

Tier 1 ISPs are known as the backbone of the Internet. They also can connect to one-another on more than one continent, and manage major infrastructure, such as the Atlantic sea cabling system. It’s important to note that Tier 1 ISPs don’t sell directly to customers. Instead, they sell to Tier 2 ISPs. AT&T and Verizon are well known Tier 1 ISPs.

Tier 2 ISPs are the regional providers of the Internet. Tier 2 ISPs can provide connectivity to states or even an entire country. Like Tier 1 providers, Tier 2 ISPs also use peering agreements so data can be exchanged between one another. Tier 2 ISPs also purchase transit from Tier 1 ISPs so they can reach networks outside the regions they provide service to. Tier 2 providers aren’t as fast as Tier 1, and they don’t have as robust infrastructure as well.

Tier 2 providers sell to Tier 2 providers, as well as offer their services to large enterprises and governments that require faster speeds and more robust infrastructure that Tier 3 ISPs provide. Comcast is a well-known Tier 2 ISP.

Tier 3 ISPs are the “last mile” providers. These are the ISPs that connect you to the Internet at home. Tier 3 ISPs only purchase Internet transit, meaning they purchase from Tier 2 ISPs to connect to the Internet. Tier 3 providers are solely focused on providing Internet access to their customers, who are either local businesses or consumers. Tier 3 providers use cable, DSL or fiber optics as the mediums to help you connect to the Internet.

Putting it all together via an example

So, we threw a lot of information at you. To have it all make sense, let’s use an example to put all the pieces of the puzzle together. For you to read this fascinatingly wonderful article, you make a request through your web browser to read this page. Your device will start creating something called a packet with the information as to what you’re looking for.

This packet includes the source IP and MAC address, which is your computer, and the destination IP and MAC address. To get all the requested information, your computer will create multiple packets.

Your router sees that the information you requested is on a computer that is outside of your own network, so it sends the data to your modem. In order for your request to reach the right destination, it needs to get the IP address of the machine that holds the data.

To get this information, your network will use something called the Domain Name Service (DNS). DNS is the phone book of the Internet, as it matches a web address (www.google.com, for example) to an IP address. While enterprises and large networks have their own DNS server, your ISP provides you their DNS servers. The request for the IP address from the DNS server is called a DNS query.

Once the destination IP address is known, your computer will pass the packets over to your router to begin the data transit. The packet from your router will reach your Tier 3 ISP router, which will pass it on to the Tier 2 network. The Tier 2 network will pass it onto the Tier 1 network so it can reach locations that are outside of the Tier 2 coverage if necessary.

As data moves from place to place, each movement becomes a “hop”. Each individual router is a hop until the request reaches the end network and destination machine.

Once your request makes it to the destination machine, the machine will start creating a response and send over the requested information in the same process as listed above.

But what about MAC addresses? Where do they come into play throughout the entire process?

When the packets are created, they include the destination IP address grabbed from the DNS query response and a destination MAC address. Your computer will have the MAC address of your router as the destination MAC address when the packets begin their journey. As the packets move along the path, the destination IP address will stay the same, but the destination MAC address will change to the next router’s MAC address.

While there is a lot more in play throughout the process, this should give you a basic understanding of how the Internet works. We will look at all the pieces in granular detail, including protocols used, in additional lessons.

Sources

“A/D Basics.” A/D Conversion, The McGill Physiology Virtual Lab, http://www.medicine.mcgill.ca/physio/vlab/biomed_signals/atodvlab.htm.

Rivenes, Logan. “Tier 1 ISP, Tier 2 ISP, Tier 3 ISP – Learn What That Means in Detail.” Datapath.io, 12 July 2016, datapath.io/resources/blog/what-is-an-internet-service-provider/.

“What Is DAC? Digital to Analog Converter Basics, Types & Working.” Components101, 2019, components101.com/articles/digital-to-analog-converters-dac.

Cannon, Kelly, et al. CCNA Guide to Cisco Networking. Course Technology, 2009.

Source: https://tech-summary.com/2019/10/08/how-the-internet-works/

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