📚 GCSE WJEC Computer Science: Network Fundamentals | GCSE WJEC 计算机：网络基础考点精讲
Networks form the backbone of modern computing, enabling devices to communicate, share resources and access the internet. In WJEC GCSE Computer Science, you must understand the hardware, protocols, topologies and security concepts that keep networks running. This revision guide breaks down every key topic in clear, exam-focused language.
网络构成了现代计算的骨架，使设备能够通信、共享资源并访问互联网。在 WJEC GCSE 计算机科学中，你必须掌握让网络保持运行的硬件、协议、拓扑结构和安全概念。本复习指南用清晰、贴近考试的语言拆解每一个关键主题。
1. What Is a Network? | 什么是网络？
A network is a collection of two or more interconnected computing devices that can exchange data and share resources.
网络是由两个或多个相互连接的计算设备组成的集合，它们可以交换数据并共享资源。
Networks allow users to share hardware, such as printers and storage drives, reducing costs.
网络允许用户共享打印机和存储驱动器等硬件，从而降低成本。
They enable software and data sharing, letting multiple people work on the same files from different locations.
它们支持软件和数据共享，使多人可以在不同位置处理同一个文件。
Communication is greatly enhanced through email, instant messaging, VoIP and video conferencing.
通过电子邮件、即时消息、VoIP 和视频会议，通信得到了极大的增强。
Centralised management simplifies tasks like installing updates, backing up data and monitoring security.
集中管理简化了安装更新、备份数据和监控安全等任务。
2. Types of Network: LAN and WAN | 网络类型：局域网和广域网
A Local Area Network (LAN) covers a small geographical area, such as a single building or school, and is usually owned by one organisation.
局域网 (LAN) 覆盖一个小的地理区域，例如一栋建筑或一所学校，通常由一个组织拥有。
LANs offer high data transfer speeds (up to 10 Gbps with modern standards) and low latency because devices are close together and use high‑quality cabling or Wi‑Fi.
局域网提供高数据传输速度（现代标准最高 10 Gbps）和低延迟，因为设备距离很近并使用高质量电缆或 Wi‑Fi。
A Wide Area Network (WAN) spans large geographical distances, often connecting LANs across cities or countries. The internet is the largest WAN.
广域网 (WAN) 跨越较大的地理距离，通常连接不同城市或国家的局域网。互联网是最大的广域网。
WANs rely on leased telecommunication lines or satellite links; they are slower than LANs and have higher latency, but enable global communication.
广域网依赖租用的电信线路或卫星链路；它们比局域网慢且延迟更高，但实现了全球通信。
WANs are typically not owned by a single user but are maintained by multiple service providers.
广域网通常不归单个用户所有，而是由多个服务提供商维护。
3. Client‑Server and Peer‑to‑Peer Networks | 客户端‑服务器与对等网络
In a client‑server network, one or more powerful computers (servers) provide resources, files and services to many client devices.
在客户端‑服务器网络中，一台或多台功能强大的计算机（服务器）向许多客户端设备提供资源、文件和服务。
Servers handle centralised authentication, file storage, email and print services. Clients request data and rely on the server.
服务器处理集中式身份验证、文件存储、电子邮件和打印服务。客户端请求数据并依赖服务器。
Advantages include better security, easier backups and centralised management. Disadvantages are higher cost and reliance on the server – if the server fails, the whole network can go down.
优点包括更好的安全性、更容易备份和集中管理。缺点是成本较高且依赖服务器——如果服务器发生故障，整个网络可能瘫痪。
In a peer‑to‑peer (P2P) network, all computers have equal status and can share resources directly without a central server.
在对等 (P2P) 网络中，所有计算机地位平等，无需中央服务器即可直接共享资源。
P2P networks are cheaper to set up and work well for small groups, but they are harder to manage, less secure and lack centralised backup.
对等网络安装成本较低，适合小团体使用，但较难管理、安全性较差且缺乏集中备份。
4. Network Topologies | 网络拓扑结构
A topology describes the physical or logical layout of devices in a network. Common topologies include star, mesh, bus and ring.
拓扑结构描述了网络中设备的物理或逻辑布局。常见的拓扑结构包括星形、网状、总线和环形。
In a star topology, all devices connect to a central switch or hub. If one cable fails, only that device is affected, making it very reliable and easy to troubleshoot.
在星形拓扑中，所有设备都连接到一个中央交换机或集线器。如果一条电缆出现故障，只有该设备受影响，因此非常可靠且易于故障排除。
However, the central device is a single point of failure – if the switch stops working, the entire network goes down. Star networks require more cable than bus topologies.
然而，中央设备是单点故障——如果交换机停止工作，整个网络就会瘫痪。星形网络比总线拓扑需要更多的电缆。
A mesh topology connects every device to every other device (full mesh) or provides multiple redundant paths (partial mesh). It offers exceptional reliability because data can travel alternative routes if a link fails.
网状拓扑将每台设备彼此直接连接（全网状）或提供多条冗余路径（部分网状）。它具有出色的可靠性，因为如果某条链路发生故障，数据可以通过备用路由传输。
Mesh networks are expensive and complex to install due to the high number of cables and interfaces, so they are mainly used for backbone connections and critical systems.
网状网络由于电缆和接口数量众多，安装成本高且复杂，因此主要用于骨干连接和关键系统。
Bus and ring topologies are older designs. In a bus, all devices share a single cable; in a ring, data travels in one direction around a loop. Both have largely been replaced by star and mesh in modern networks.
总线和环形拓扑是较老的设计。在总线中，所有设备共享一条电缆；在环形中，数据沿环单向传输。在现代网络中，这两者大多已被星形和网状取代。
5. Key Network Hardware | 关键网络硬件
A Network Interface Card (NIC) is built into every networked device and provides a unique MAC address. It can be wired (Ethernet) or wireless (Wi‑Fi).
网络接口卡 (NIC) 内置于每个联网设备中，并提供唯一的 MAC 地址。它可以是有线的（以太网）或无线的（Wi‑Fi）。
A switch connects devices within a LAN and forwards data only to the specific destination device using MAC addresses. This reduces unnecessary traffic and improves security over older hubs.
交换机连接局域网内的设备，并使用 MAC 地址仅将数据转发到特定目标设备。与老式集线器相比，这减少了不必要的流量并提高了安全性。
A router connects different networks together, typically joining a LAN to the internet. It forwards data packets based on IP addresses and often includes firewall and DHCP functions.
路由器将不同的网络连接在一起，通常将局域网连接到互联网。它基于 IP 地址转发数据包，通常还包含防火墙和 DHCP 功能。
A wireless access point (WAP) allows Wi‑Fi‑enabled devices to connect to a wired network. It acts as a bridge between wireless clients and the wired infrastructure.
无线接入点 (WAP) 允许支持 Wi‑Fi 的设备连接到有线网络。它充当无线客户端与有线基础设施之间的桥梁。
Other hardware includes modems (converting digital signals to analogue for telephone lines), firewalls (hardware‑based) and powerline adapters, which use existing electrical wiring to extend networks.
其他硬件包括调制解调器（将数字信号转换为电话线路的模拟信号）、硬件防火墙以及利用现有电线扩展网络的电力线适配器。
6. Network Protocols and Standards | 网络协议与标准
Protocols are sets of rules that govern how data is transmitted and received between devices. Standards ensure equipment from different manufacturers can work together.
协议是管理设备之间如何传输和接收数据的一组规则。标准确保来自不同制造商的设备能够协同工作。
Ethernet is the dominant standard for wired LANs. It defines how data is framed and sent over copper (twisted‑pair) or fibre‑optic cables, typically using the TCP/IP suite.
以太网是有线局域网的主要标准。它定义了数据如何通过铜缆（双绞线）或光纤电缆进行组帧和发送，通常使用 TCP/IP 协议族。
Wi‑Fi (based on IEEE 802.11 standards) enables wireless communication within a local area. It uses radio waves on 2.4 GHz or 5 GHz bands and supports encryption like WPA3.
Wi‑Fi（基于 IEEE 802.11 标准）实现了局部区域内的无线通信。它使用 2.4 GHz 或 5 GHz 频段的无线电波，并支持 WPA3 等加密。
TCP/IP is a suite of protocols that underpins the internet. IP handles addressing and routing of packets, while TCP ensures reliable, ordered delivery and checks for errors.
TCP/IP 是支撑互联网的一组协议。IP 处理数据包的寻址和路由，而 TCP 确保可靠、有序的传递并检查错误。
Other important protocols include HTTP/HTTPS (web traffic), FTP (file transfer), SMTP (email sending) and DNS (converting domain names to IP addresses).
其他重要协议包括 HTTP/HTTPS（网页流量）、FTP（文件传输）、SMTP（电子邮件发送）和 DNS（将域名转换为 IP 地址）。
7. IP Addresses and MAC Addresses | IP 地址与 MAC 地址
An Internet Protocol (IP) address is a logical address assigned to a device on a network. It can change when a device moves to a different network (dynamic) or be fixed (static).
互联网协议 (IP) 地址是分配给网络设备的逻辑地址。当设备移动到不同网络时它可以更改（动态），也可以是固定的（静态）。
IPv4 addresses are 32‑bit numbers written as four decimal octets (e.g. 192.168.1.10). IPv6 uses 128‑bit addresses to overcome address exhaustion.
IPv4 地址是 32 位数字，写为四个十进制八位字节（例如 192.168.1.10）。IPv6 使用 128 位地址以解决地址枯竭问题。
A Media Access Control (MAC) address is a physical, hardware‑embedded identifier burnt into a device’s NIC by the manufacturer. It is usually permanent.
媒体访问控制 (MAC) 地址是制造商烧录在设备网卡中的物理硬件标识符。它通常是永久的。
MAC addresses are 48 bits long, shown as 12 hexadecimal digits (e.g. 00:1A:2B:3C:4D:5E). Switches use MAC addresses to forward frames within a LAN.
MAC 地址长度为 48 位，显示为 12 个十六进制数字（例如 00:1A:2B:3C:4D:5E）。交换机使用 MAC 地址在局域网内转发帧。
While IP addresses are used for routing between networks, MAC addresses are essential for delivery on the local segment. Both are needed for data to reach its final destination.
虽然 IP 地址用于网络间的路由，但 MAC 地址对于本地网段的传递至关重要。两者都是数据到达最终目的地所必需的。
8. Factors Affecting Network Performance | 影响网络性能的因素
Bandwidth is the maximum amount of data that can be transmitted in a given time, measured in bits per second (bps). Higher bandwidth allows more data to flow simultaneously.
带宽是指在给定时间内可以传输的最大数据量，以比特每秒 (bps) 为单位。更高的带宽允许同时传输更多数据。
Available bandwidth is often shared between users; if many devices stream video or download large files, each receives a smaller share, slowing down the network.
可用带宽通常由用户共享；如果许多设备同时传输视频或下载大文件，每个设备获得的份额就会减少，导致网络速度下降。
Latency is the delay between sending a data packet and it reaching its destination. High latency causes noticeable lags, especially in real‑time applications like online gaming or VoIP.
延迟是指从发送数据包到其到达目的地之间的时延。高延迟会导致明显的滞后，尤其是在在线游戏或 VoIP 等实时应用中。
The number of devices connected to a network directly impacts performance. Each additional device generates traffic and competes for bandwidth and processing resources.
连接到网络的设备数量直接影响性能。每增加一台设备都会产生流量，并争夺带宽和处理资源。
Error rates and transmission media also matter. Fibre‑optic cables offer far lower error rates and higher bandwidth over long distances than copper, while wireless signals can suffer from interference and walls.
错误率和传输介质也很重要。光纤电缆在长距离上比铜缆的错误率低得多且带宽更高，而无线信号可能会受到干扰和墙壁的影响。
9. Network Security Measures | 网络安全措施
Encryption scrambles data so that only authorised parties with the correct key can read it. Protocols like HTTPS, WPA3 and VPNs all use encryption to protect data in transit.
加密对数据进行加扰，只有拥有正确密钥的授权方才能读取。HTTPS、WPA3 和 VPN 等协议都使用加密保护传输中的数据。
Firewalls monitor incoming and outgoing network traffic, blocking unauthorised access based on a set of security rules. They can be hardware appliances or software installed on devices.
防火墙监控传入和传出的网络流量，根据一组安全规则阻止未经授权的访问。它们可以是硬件设备或安装在设备上的软件。
User authentication methods, such as strong passwords, two‑factor authentication and biometrics, ensure that only legitimate users can access the network and its resources.
用户身份验证方法，如强密码、双因素认证和生物识别技术，确保只有合法用户才能访问网络及其资源。
A Virtual Private Network (VPN) creates an encrypted tunnel between a device and a private network over the public internet, securing data from eavesdropping.
虚拟专用网络 (VPN) 通过公共互联网在设备与私有网络之间创建一个加密隧道，保护数据免受窃听。
Physical security is equally important: locking server rooms, using cable locks and restricting access to networking equipment prevent tampering and theft.
物理安全同样重要：锁上服务器机房、使用电缆锁并限制对网络设备的访问可以防止篡改和盗窃。
Regular software updates and patches close vulnerabilities, and network policies should include regular backups and user training to avoid social engineering attacks.
定期的软件更新和补丁可以修复漏洞，而网络策略应包括定期备份和用户培训以避免社会工程攻击。
10. The Internet and the World Wide Web | 互联网与万维网
The internet is a global network of interconnected networks that uses the TCP/IP protocol suite to link devices worldwide. It is the physical and logical infrastructure.
互联网是一个由相互连接的网络组成的全球网络，使用 TCP/IP 协议族将全球设备连接起来。它是物理和逻辑基础设施。
The World Wide Web (WWW) is a collection of webpages and multimedia content accessed via the internet using HTTP/HTTPS. It is a service that runs on top of the internet.
万维网 (WWW) 是通过互联网使用 HTTP/HTTPS 访问的网页和多媒体内容的集合。它是运行在互联网之上的一种服务。
Other services that use the internet include email (SMTP), file transfer (FTP) and voice calls (VoIP) – none of these are the World Wide Web, even though they rely on the same network.
使用互联网的其他服务包括电子邮件 (SMTP)、文件传输 (FTP) 和语音通话 (VoIP)——这些都不是万维网，尽管它们依赖同一个网络。
When you browse the web, you use a browser to request pages from web servers; the internet routes those requests and delivers the data back.
当你浏览网页时，使用浏览器向 Web 服务器请求页面；互联网路由这些请求并将数据传回。
Key exam tip: remember that the internet is the hardware and connections; the WWW is just one of many applications using it.
关键考试提示：记住互联网是硬件和连接；万维网只是使用它的众多应用程序之一。
Published by TutorHao | Computer Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导