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4.1 The Internet

6 min readβ€’march 13, 2023

Minna Chow

Minna Chow


AP Computer Science Principles ⌨️

80Β resources
See Units

It's difficult to imagine the world today without the internet and all of the wonderful and horrible things it does. We can all name things we do on the internet: watch funny cat videos, connect with our friends, read Fiveable articles... However, defining the internet itself is a tricky thing.
The College Board defines the Internet as "a computer network consisting of interconnected networks that use standardized, open (nonproprietary) communication protocols." The word, "internet," comes from the combination of two words: interconnection and networks.
What does any of this mean? In this guide, we'll break down the definition of the Internet and explain what it means to be a part of it.

Computing Devices, Systems, and Networks

The internet connects computer networks, which are systems of computing devices. Let's start small and work our way up.
A computing device is a physical machine that can run a program. Examples include computers, tablets, servers, and routers (which we'll discuss more later in this guide). A computing device can also be a smart sensor such as a smart thermometer.
When computing devices connect to each other, they form computing systems. The primary type of computing system that we'll talk about is a computer network. A computer network is a group of computing devices that can share data with each other.
A computer network can be a simple connection between two devices, such as the connection between your printer and your computer. It can also be a more complex connection, such as one that links all the computing devices in your workspace or city.
The internet takes all of these computer networks and connects them to one another. This creates the digital world we know today, one where any computer in the world can connect to any other it chooses. In this sense, it is the very largest of computer networks, covering billions of users and multiple continents.

Data Streams, Packets, and Routing

Information goes through the internet in data streams. (Remember from Big Idea 2 that data is a collection of facts that computers store in bits.) When you send or receive data from the internet, you have to get this data from one place to another. Oftentimes, a photo, video or website is made up of too much data for it all to be sent in one transaction. The data is therefore broken up into packets.
Packets contain a section of the data you want to send out. They come with a header that contains metadata (data about data) used to tell the routers where this packet is from, where it's going, and how it should be reassembled once it gets to its final destination. Computing devices create these packets, then send them out through paths. Paths are sequences of connected computing devices, primarily known as routers, that begin at the sender and end at the receiver.
There are many different paths that a packet could take to get from one device to another. The process of finding a path to take is known as routing. Routing paths aren't usually planned out in advance. The routers moving data along make their path decisions as packets are sent to them.
Due to this method of breaking up and sending information, packets can arrive at their destination in order or out of order (or even not at all if something goes wrong.) If you've ever clicked on a website where the text loads before the photos do as you scroll down it, you've seen how the data doesn't always come together in exactly the right order.
If everything's working correctly, the packets of data will be reassembled in the correct order once they get to their final destination, and you'll be good to go!
Here's a visual example of how packets go through the internet:
https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-qlFRLhgHPiLe.gif?alt=media&token=2f259315-45b3-4b56-8025-d63fd483a34b

Image source: Oddbodz / CC BY-SA

How fast you get these packets depends on your computer network's bandwidth.

Bandwidth

The bandwidth of a computer network is the rate of data transfer it allows from one device to another. In other words, it's the maximum amount of data a network connection can move in a certain amount of time. Although bandwidth was once measured in bits per second, these days it's usually measured in megabits per second, where one megabit is a million bits. This illustrates just how fast the internet is growing!
(For those of you physics nerds out there, the relationship between bandwidth and data is a little like the relationship between power and work. Power is the amount of work done over a given time and Bandwidth refers to the amount of data transferred over a given time.)

Internet Protocols

In order for computing devices to communicate with each other over the internet, they all have to use the same protocols.
A protocol is a standard set of rules that everyone agrees on. The protocols used to communicate on the internet are open, which means that they're not tied to a certain company. Everyone has access to them. Another word for open, in this case, is nonproprietary.
Two major protocols for transporting information over the internet are known as TCP/IP and UDP.
TCP/IP is the older of the protocols, designed in the 1970s. It stands for Transmission Control Protocol/Internet Protocol. The TCP governs how packets are created and reassembled, while the IP moves packets to their destinations. It also dictates how devices are given addresses to communicate with each other (which is where the name IP address comes from.)
The UDP is newer by about ten years and functions as an alternative to TCP/IP. It offers a way to deliver a faster stream of information by eliminating a lot of the error checking that TCP/IP does. Therefore, it's often used for connections that need to happen rapidly, such as those used by online games and live videos.

The World Wide Web

One of the main ways we use the internet is through the World Wide Web, a system of web-pages, programs, and files. Take care to note that the World Wide Web is not the same thing as the internet, which is a network of computing devices. The World Wide Web runs on the internet. The World Wide Web is governed by the HTTP protocol, which controls how web page data is transmitted.
While TCP/IP and UDP from above are protocols used to transmit data over a variety of networks, HTTP is a specific protocol used to transmit data over the World Wide Web. HTTP is built on top of the TCP/IP protocol and uses it to transmit data between devices.
πŸ”— Check out this website for more information about the World Wide Web!

Scalability

Finally, it's important to know that the Internet was designed to be scalable. The scalability of a system is defined by College Board as "the capacity for the system to change in size and scale to meet new demands." If a computer system gets larger because more devices are connected to it or a greater volume of data is sent over it, we would say it is scalable if it's able to handle that change without a significant decrease in performance.
With billions of devices using the internet each day, and new devices connecting all the time, the scalability of the internet is crucial to keep it running and us connected to the world, each other, and those funny cats.
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