The Internet Chapter Notes | AP Computer Science Principles - Grade 9 PDF Download

Introduction

The Internet is a fundamental topic in AP Computer Science Principles, shaping how we connect and share information globally. This chapter explains what the Internet is, how it connects devices and networks, and the protocols that make communication possible. It covers concepts like data packets, routing, bandwidth, and the World Wide Web, highlighting the Internet’s scalability and its role in modern life. Understanding the Internet helps us appreciate the technology behind everyday activities like browsing websites or streaming videos.

Computing Devices, Systems, and Networks

• Computing Device: A physical device that runs programs, like laptops, smartphones, servers, routers, or even smart sensors like a digital thermometer.
• Computing System: Formed when devices connect, enabling data sharing. The most common type is a computer network.
• Computer Network: A group of devices that exchange data. This could be as simple as a computer and printer or as complex as all devices in an office or city.

The internet unites these networks into a massive global system, allowing any device worldwide to connect with another, spanning billions of users across continents.

Data Streams, Packets, and Routing

• Data travels over the Internet in data streams, made up of bits (basic units of data).
• Data is broken into packets, small chunks with headers containing metadata (e.g., source, destination, and reassembly instructions).
• Packets travel through paths, sequences of connected devices (mostly routers), from sender to receiver.
• Routing is the process of choosing a path for packets, decided by routers as packets move, not pre-planned.
• Packets may arrive out of order or not at all, but devices reassemble them correctly at the destination.
  • Example: On a website, text may load before images due to packet arrival order.

Bandwidth

• Bandwidth is the maximum amount of data a network can transfer in a given time.
• It measures the speed of data transfer between devices.
• Originally measured in bits per second, now typically in megabits per second (1 megabit = 1 million bits).
• Higher bandwidth means faster data transfer, impacting how quickly packets reach their destination.

Internet Protocols

• Protocols are standard rules that devices follow to communicate over the Internet.
• Internet protocols are open (nonproprietary), meaning they are freely accessible and not owned by any company.
• Major protocols:
  • TCP/IP (Transmission Control Protocol/Internet Protocol), from the 1970s:
    • TCP manages packet creation and reassembly.
    • IP handles packet delivery and assigns IP addresses to devices.
  • UDP (User Datagram Protocol), from the 1980s:
    • Faster than TCP/IP by skipping some error checks.
    • Used for rapid connections, like online gaming or live video streaming.
• HTTP (Hypertext Transfer Protocol):
  • Governs the World Wide Web, controlling how web page data is sent.
  • Built on TCP/IP to transmit data between web browsers and servers.

The World Wide Web

• The World Wide Web (WWW) is a system of web pages, programs, and files accessed via the Internet.
• It is not the same as the Internet, which is the underlying network of devices.
• The WWW runs on the Internet, using HTTP to transmit data.
• Users navigate the WWW through hyperlinks connecting websites.

Scalability

• Scalability is a system’s ability to handle increased size or data volume without significant performance loss.
• The Internet is designed to be scalable, supporting billions of devices and growing data traffic.
• Scalability ensures the Internet can adapt to new devices and demands, maintaining connectivity for users worldwide.

Key Terms to Review

• Bandwidth: The maximum data transferable over a network in a set time, usually in megabits per second (Mbps)
• Computing Devices: Machines like computers, tablets, or smart sensors that process data.
• Computing Systems: Hardware and software combinations that process data together.
• Computer Network: Interconnected devices sharing resources and data.
• HTTP: Protocol for client-server communication, defining web requests and responses.
• Internet Protocols: Rules ensuring reliable data transmission across the internet.
• Internet: A global network of networks enabling worldwide device communication.
• IP Address: A unique identifier for devices on a network.
• Megabits per Second (Mbps): A measure of network data transfer speed.
• Networks: Systems of devices communicating via wired or wireless connections.
• Routing: Selecting paths for data packets based on speed and reliability.
• Scalability: A system’s ability to handle growth without performance loss.
• TCP/IP: Protocols ensuring reliable, ordered data delivery.
• UDP: A faster, connectionless protocol for data transmission without delivery guarantees.
• World Wide Web (WWW): A system of internet-accessed resources navigated via hyperlinks.