Introduction
Hi, welcome to the first lesson of Unit 4 for AP CSP.
The main purpose of this article is to cover the material in the AP CSP CED.
- CSN-1.A: Explain how computing devices work together in a network.
- CSN-1.B: Explain how the Internet works.
- CSN-1.C: Explain how data is sent through the Internet via packets.
- CSN-1.D: Describe the differences between the Internet and the World Wide Web.
Computing Devices, Systems, and Networks
At the heart of everything is a computing device. A computing device is simply a physical object that can run a program, like a computer, tablet, or router.
When multiple computing devices are joined together for a common goal or objective, they become a computing system. The primary type of computing system discussed in this unit is a computer network. This is a group of interconnected devices that are able to transmit (send and receive) data to one another.
A path between two computing devices in the same computing system is made of lots of directly connected computing devices, beginning at the sender and ending with the receiver. This process of creating a path from start to end for data is known as routing, with the maximum amount of data that can be transmitted at a time being called the bandwidth, usually measured in bits per second.
For example, your home may have a bandwidth of 100 MBps (Megabytes per second.*) This means that the maximum amount of data that can be transferred per second is 100 MB, but it does not necessarily mean it performs consistently at this rate.
*Note:
- “b” → bits
- “B” → bytes
- “Mbps” → “megabits per second”
- “MB/s” or “MBps” → “megabytes per second”
The Internet
The Internet is a large computer network that uses standardized and open communication protocols. These protocols are a readily agreed-upon set of rules that determines the operations of the computing system. Because they are open protocols, it makes it easy for new devices to access the Internet. Two major protocols used to transmit information on the Internet are TCP/IP and UDP.
TCP (Transmission Control Protocol), is the older set of protocols, created in the 1970s. TCP governs how data packets are created and reassembled, while IP (Internet Protocol) helps with moving packets. Each device is given a unique name to signal it as a receiver or sender. This is what we commonly know as an “IP address”.
UDP (User Datagram Protocol) is a newer alternative to TCP/IP, created in the 1980s. It serves the same purpose as TCP, transmitting data. However, unlike TCP, which rechecks for lost packets and retransmits what was missed, UDP does not in order to transmit in a quicker and more efficient manner.
On the Internet, there is no set path or route for data to take; it is determined at each computing device. In addition, the Internet was built to be scalable. The scalability of a system is defined as its ability to change in size and scale to match demand. When the Internet first started, it had few users, and according to statistics as of early 2026, almost 3 quarters of the world are now online- meaning more than 6 billion users. This goes to show how the Internet has been able to sustain large amounts of data transfer without a significant dip in performance, being a major example of the importance of scalability in our modern world!
Data Packets
Information is passed through the Internet through data streams, which are contained in packets.
Packets contain a section of the data that is transmitted, along with some metadata (data of data), used to rebuild packets when they reach their final destination. This metadata includes the sender address, the destination address, and instructions for how it should be reassembled.
Paths are determined through routing and stopping at connected computing devices, or routers. Because routing is not predetermined, packets can end up out of order or not even arrive at their destination. They are rebuilt based on metadata at their final location. The speed at which you receive these packets depends on your bandwidth.
The World Wide Web
A common misconception someone might have is that “the web” and “the internet” are the same, and can be used interchangeably.
The Internet refers to the physical hardware of interconnected computing devices, while the World Wide Web, or “www” (what you see before your URLs) is a system of interconnected pages, programs, and files.
The World Wide Web is governed by the HTTP protocol and runs on the Internet. TCP and UDP are used to transmit information over many different network systems, but HTTP is specific to the World Wide Web.
Practice Questions
Free Response:
For the following question, match each description with its respective protocol.
- This protocol is somewhat “slower”, but it guarantees that all your information will arrive, leaving no gaps in data.
- This is the most efficient protocol, especially good for video streaming and video games.
- This protocol is loading the article you are reading on fivehive.org.
Free Response Answer:
- TCP (Transmission Control Protocol): This protocol is somewhat “slower” but guarantees that all your information will arrive, leaving no gaps in data.
- UDP (User Datagram Protocol): This is the most efficient protocol, especially good for video streaming and video games.
- HTTP (Hypertext Transfer Protocol): This protocol is loading the article you are reading on fivehive.org.