4.1 The Internet 互联网

Computer systems and networks facilitate the transfer of data.

• 计算机系统和网络促进数据的传输。

核心要点 Core Points

1. A computing device is a physical artifact that can run a program, such as computers, tablets, servers, routers, and smart sensors.

   • 计算设备是可以运行程序的物理制品，如计算机、平板电脑、服务器、路由器和智能传感器。

2. A computing system is a group of computing devices and programs working together for a common purpose.

   • 计算系统是为共同目的而协同工作的一组计算设备和程序。

3. A computer network is a group of interconnected computing devices capable of sending or receiving data.

   • 计算机网络是能够发送或接收数据的相互连接的计算设备组。

4. A computer network is a type of computing system.

   • 计算机网络是计算系统的一种类型。

5. A path between two computing devices on a computer network is a sequence of directly connected computing devices that begins at the sender and ends at the receiver.

   • 计算机网络上两个计算设备之间的路径是从发送方开始到接收方结束的直接连接的计算设备序列。

6. Routing is the process of finding a path from sender to receiver.

   • 路由是寻找从发送方到接收方路径的过程。

7. The bandwidth of a computer network is the maximum amount of data that can be sent in a fixed amount of time.

   • 计算机网络的带宽是在固定时间内可以发送的最大数据量。

8. Bandwidth is usually measured in bits per second.

   • 带宽通常以每秒位数来测量。

9. The Internet is a computer network consisting of interconnected networks that use standardized, open (nonproprietary) communication protocols.

   • 互联网是由使用标准化、开放（非专有）通信协议的相互连接网络组成的计算机网络。

10. Access to the Internet depends on the ability to connect a computing device to an Internet-connected device.

    • 访问互联网取决于将计算设备连接到互联网连接设备的能力。

11. A protocol is an agreed-upon set of rules that specify the behavior of a system.

    • 协议是规定系统行为的商定规则集。

12. The protocols used in the Internet are open, which allows users to easily connect additional computing devices to the Internet.

    • 互联网中使用的协议是开放的，这允许用户轻松地将额外的计算设备连接到互联网。

13. Routing on the Internet is usually dynamic; it is not specified in advance.

    • 互联网上的路由通常是动态的；它不是预先指定的。

14. Scalability is the capacity for the system to change in size and scale to meet new demands.

    • 可扩展性是系统改变大小和规模以满足新需求的能力。

15. The Internet was designed to be scalable.

    • 互联网被设计为可扩展的。

16. Information is sent through the Internet as a data stream. Data streams contain chunks of data, which are encapsulated in packets.

    • 信息通过互联网作为数据流发送。数据流包含数据块，这些数据块被封装在数据包中。

17. A packet contains a chunk of data and metadata used for routing the packet along the Internet (from source to destination) and for data reassembly.

    • 数据包包含数据块和用于在互联网上路由数据包（从源到目的地）以及数据重组的元数据。

18. Packets may arrive at their destination in order, out of order, or not at all.

    • 数据包可能按顺序、不按顺序到达目的地，或者根本不到达。

19. IP, TCP, and UDP are common protocols used on the Internet.

    • IP、TCP和UDP是互联网上使用的常见协议。

20. The World Wide Web is a system of linked pages, programs, and files.

    • 万维网是链接页面、程序和文件的系统。

21. HTTP is a protocol used by the World Wide Web.

    • HTTP是万维网使用的协议。

22. The World Wide Web uses the Internet.

    • 万维网使用互联网。

学生活动 Student Activities

1. Explain how computing devices work together in a network.

   • 解释计算设备如何在网络中协同工作。

2. Explain how the Internet works.

   • 解释互联网如何工作。

3. Explain how data is sent through the Internet via packets.

   • 解释数据如何通过数据包通过互联网发送。

4. Describe the differences between the Internet and the World Wide Web.

   • 描述互联网和万维网之间的差异。

相关资源 Related Resources

• The Computer and the Internet: TCP/IP: How Messages Get Delivered Across the Internet from College Board

  • 计算机与互联网：TCP/IP：消息如何通过互联网传递 来自大学理事会

• Routing and Deadlock from CS Unplugged

  • 路由与死锁 来自CS Unplugged

• Network Protocols from CS Unplugged

  • 网络协议 来自CS Unplugged

• Blown to Bits: Appendix - Understanding the Digital World

  • Blown to Bits：附录 - 理解数字世界