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Practice练习题

Networks and the Internet网络与互联网

Practice Questions · AP CSP-Feeder · US / ON / BC / AB Styles练习题集 · AP CSP 衔接 · 美 / 安 / 卑 / 阿省风格

EASY易 MEDIUM中 HARD难 🇺🇸 US美 🇨🇦 ON安 🇨🇦 BC卑 🇨🇦 AB阿 AP CSP-style MCQAP CSP 风格选择题 AP CSP-feeder FRQAP CSP 衔接简答题 ON Provincial-style安大略省考风格 BC Provincial-style卑诗省考风格 AB/Universal Applied阿省/通用应用题 Honors荣誉级
Name:姓名：Date:日期：
PART I  ·  SHORT RESPONSE第一部分  ·  短答题AP CSP-style MCQ + ON/BC short answer · 25 marksAP CSP 风格选择题 + 安/卑省考短答 · 共 25 分

Section A · Short ResponseA 部分 · 短答题

Questions mix multiple-choice and short-answer items. For MCQs, circle the letter and justify your choice in one sentence. For short-answer items, use precise technical vocabulary: packet, protocol, topology, client, server, DNS, firewall. Diagrams earn marks where specified.本部分包含选择题与短答题。选择题请圈出字母，并用一句话说明理由。短答题使用精确技术术语：数据包、协议、拓扑结构、客户端、服务器、DNS、防火墙。有要求时图示可得分。

Q1 EASY易 🇺🇸 US美 AP CSP-style MCQAP CSP 风格选择题 §1 Networks: LAN, WAN, Topology网络：LAN、WAN、拓扑 · CSTA 3A-NI-04 [3 marks][3 分]

A school has 40 computers all connected through one central switch inside a single building. Which statement BEST describes this network?一所学校有 40 台计算机，全部通过一栋楼内的一台中央交换机连接。哪项陈述最能描述该网络？

  1. (A) A WAN using mesh topology, because many devices are connected广域网，使用网状拓扑，因为连接了很多设备
  2. (B) A LAN using star topology, because all devices connect to one central switch局域网，使用星型拓扑，因为所有设备连接到一台中央交换机
  3. (C) A LAN using bus topology, because the switch carries all traffic on one cable局域网，使用总线拓扑，因为交换机通过一条电缆承载所有流量
  4. (D) A WAN using star topology, because the school connects to the Internet广域网，使用星型拓扑，因为学校连接到互联网
Q2 EASY易 🇺🇸 US美 AP CSP-style MCQAP CSP 风格选择题 §2 Packets and Packet Switching数据包与分组交换 · AP CSP CSN-1.A [3 marks][3 分]

A 4 MB image is sent over the Internet as 2,700 packets. Packet 1,430 is lost in transit. What happens next under TCP?一张 4 MB 的图片以 2,700 个数据包的形式通过互联网发送。数据包 1,430 在传输中丢失。在 TCP 协议下接下来会发生什么？

  1. (A) All 2,700 packets are resent from the beginning全部 2,700 个数据包从头重传
  2. (B) Only packet 1,430 is retransmitted; the other packets are unaffected仅重传数据包 1,430；其他数据包不受影响
  3. (C) The receiver reconstructs packet 1,430 from the surrounding packets接收方从相邻数据包重建数据包 1,430
  4. (D) The file transfer fails permanently and must be restarted文件传输永久失败，必须重新开始
Q3 MEDIUM中 🇨🇦 ON安 ON Provincial-style安大略省考风格 §3 IP Addresses and DNSIP 地址与 DNS · CSTA 3A-NI-04 [6 marks][6 分]

When a user types www.school.ca into their browser, a DNS lookup occurs before the page loads.当用户在浏览器中输入 www.school.ca 时，页面加载前会先进行 DNS 查找。

(a) State what DNS stands for and explain its purpose in one sentence.写出 DNS 的英文全称，并用一句话解释其作用。 [2]
(b) List, in correct order, the four entities contacted during a full DNS lookup for www.school.ca.按正确顺序列出完整 DNS 查找 www.school.ca 时依次联系的四个实体。 [2]
(c) Explain why the DNS resolver caches results and state one benefit of caching.解释为什么 DNS 解析器会缓存结果，并说明缓存的一个好处。 [2]
Q4 MEDIUM中 🇨🇦 BC卑 BC Provincial-style卑诗省考风格 §4 Protocols: TCP, UDP, HTTP/HTTPS协议：TCP、UDP、HTTP/HTTPS · BC CIS 11 [6 marks][6 分]

Two applications use the Internet differently: an online banking website and a live video-streaming service.两种应用以不同方式使用互联网：一个在线银行网站和一个实时视频流服务。

(a) State which transport protocol (TCP or UDP) each application most likely uses. Justify each choice in one sentence.写出每种应用最可能使用的传输协议（TCP 或 UDP）。各用一句话说明理由。 [4]
(b) The banking site uses HTTPS. State what HTTPS adds over plain HTTP and identify the OSI layer responsible for the encryption.银行网站使用 HTTPS。写出 HTTPS 在 HTTP 基础上增加了什么，并指出负责加密的 OSI 层。 [2]
Q5 MEDIUM中 🇨🇦 BC卑 🇨🇦 AB阿 AB/Universal Applied阿省/通用应用题 §5 OSI Layered ModelOSI 分层模型 · BC CIS 11 [7 marks][7 分]

The OSI reference model organises network communication into seven layers.OSI 参考模型将网络通信组织为七层。

(a) Complete the table below. Fill in the missing layer names and give one protocol or hardware example for each row that needs it.补全下表。填写缺少的层名称，并为每个需要填写的行给出一个协议或硬件示例。 [4]
Layer #层编号Name名称Protocol / Hardware Example协议/硬件示例
7
6Presentation表示层
4TCP, UDPTCP、UDP
3Network网络层
1Fibre optic cable, radio waves光纤电缆、无线电波
(b) The TCP/IP model has four layers. State which TCP/IP layer combines OSI layers 5, 6, and 7.TCP/IP 模型有四层。写出哪个 TCP/IP 层合并了 OSI 第 5、6、7 层。 [1]
(c) Explain in two sentences why a layered model is useful for network design. (BC CIS 11 names "interoperability" as one benefit; include this in your answer.)用两句话解释分层模型对网络设计为何有用。（BC CIS 11 将"互操作性"列为优势之一；在回答中包含此点。） [2]
PART II  ·  EXTENDED RESPONSE第二部分  ·  简答题AP CSP-feeder FRQ + Honors · 30 marksAP CSP 衔接简答题 + 荣誉级 · 共 30 分

Section B · Extended ResponseB 部分 · 简答题

Show your reasoning fully. Use correct technical vocabulary. For justify/explain questions, two well-targeted sentences earn full marks. Labelled diagrams are encouraged where they add clarity.充分展示推理过程。使用正确技术术语。论证/解释题两句有针对性的话即可满分。有助于清晰表达时鼓励加标注图示。

Q6 EASY易 🇺🇸 US美 AP CSP-feeder FRQAP CSP 衔接简答题 §3 IP Addresses: IPv4 vs IPv6IP 地址：IPv4 与 IPv6 · CSTA 3A-NI-04 [6 marks][6 分]

Consider the two IP address formats below.考虑以下两种 IP 地址格式。

Address A:  192.168.1.105
Address B:  2001:0db8:85a3:0000:0000:8a2e:0370:7334
(a) Identify which address is IPv4 and which is IPv6. State the bit-length of each version.指出哪个地址是 IPv4，哪个是 IPv6。写出每种版本的位长度。 [2]
(b) Address A is a private IP address. Explain what "private" means in this context and state one way private addresses differ from public addresses in terms of routing.地址 A 是私有 IP 地址。解释"私有"在此语境下的含义，并从路由角度写出私有地址与公有地址的一个区别。 [2]
(c) State the primary reason the Internet moved from IPv4 to IPv6. Use the approximate address counts in your answer.写出互联网从 IPv4 迁移到 IPv6 的主要原因。在回答中使用大约的地址数量。 [2]
Q7 MEDIUM中 🇺🇸 US美 🇨🇦 ON安 AP CSP-feeder FRQAP CSP 衔接简答题 §4 + §6 HTTPS, TLS, and Security TradeoffsHTTPS、TLS 与安全权衡 · CSTA 3A-NI-07 [8 marks][8 分]

A student accesses their school's grade portal on a public Wi-Fi network. The portal uses HTTPS. A classmate says this is unnecessary because "the school controls the Wi-Fi anyway."一名学生在公共 Wi-Fi 网络上访问学校成绩门户网站。该门户使用 HTTPS。一位同学说这没必要，因为"反正学校控制着 Wi-Fi"。

(a) Explain what TLS (used by HTTPS) does to the data in transit and why this matters even on a school-controlled network.解释 TLS（HTTPS 使用）对传输中数据做了什么，以及为什么即使在学校控制的网络上这也很重要。 [3]
(b) The school's IT department considers requiring HTTPS for all internal systems but some staff say it adds "unnecessary overhead." Describe one security benefit and one usability tradeoff of enforcing HTTPS universally. (CSTA 3A-NI-07)学校 IT 部门考虑对所有内部系统强制使用 HTTPS，但部分员工认为这增加了"不必要的开销"。描述强制全面使用 HTTPS 的一个安全优势和一个可用性权衡。（CSTA 3A-NI-07） [2]
(c) The TCP 3-way handshake occurs before the TLS handshake when a browser connects to an HTTPS site. List the three steps of the TCP handshake in order, using the correct signal names (SYN, SYN-ACK, ACK), and state which party initiates each step.浏览器连接到 HTTPS 站点时，TCP 三次握手发生在 TLS 握手之前。按顺序列出 TCP 握手的三个步骤，使用正确的信号名称（SYN、SYN-ACK、ACK），并写出每步由哪方发起。 [3]
Q8 HARD难 🇨🇦 BC卑 🇺🇸 US美 AP CSP-feeder FRQAP CSP 衔接简答题 §4 + §5 Protocol Stack and Encapsulation协议栈与封装 · BC CIS 11 / CSTA 3A-NI-04 [8 marks][8 分]

A browser sends an HTTPS request to a web server. The message passes down through each layer of the OSI model on the sender's side, travels across the network, and passes back up the layers on the receiver's side.浏览器向 Web 服务器发送一个 HTTPS 请求。消息在发送方侧从上到下经过 OSI 模型的每一层，穿越网络，然后在接收方侧从下到上经过各层。

(a) Match each protocol or action in the list below to its correct OSI layer number. Write the layer number next to each item.将下列每个协议或动作与正确的 OSI 层编号对应。在每项旁写出层编号。 [4]
  • HTTP GET request                     Layer ___HTTP GET 请求                     第 ___ 层
  • TLS encryption / decryption           Layer ___TLS 加密/解密                       第 ___ 层
  • IP routing between networks           Layer ___网络间 IP 路由                      第 ___ 层
  • Ethernet frame delivery on local link    Layer ___本地链路以太网帧传送               第 ___ 层
(b) Explain the concept of encapsulation: what does each layer add when a message travels downward (sending side), and what does each layer do when a message travels upward (receiving side)?解释封装的概念：消息向下传输（发送侧）时每层添加什么？消息向上传输（接收侧）时每层做什么？ [2]
(c) BC CIS 11 names "interoperability" as a key function of the Internet. Explain what interoperability means in the context of open networking standards, and give one consequence of having open rather than proprietary protocols.BC CIS 11 将"互操作性"列为互联网的关键功能。在开放网络标准的语境下解释互操作性的含义，并说明开放协议（而非专有协议）带来的一个结果。 [2]
Q9 HARD难 Honors荣誉级 🇺🇸 US美 AP CSP-feeder FRQAP CSP 衔接简答题 §1 + §2 Fault Tolerance and Packet Routing容错性与数据包路由 · AP CSP CSN-1.C / CSTA 3A-NI-04 [8 marks][8 分]

AP CSP CSN-1.C states that the Internet is "fault tolerant" because it uses packet switching with redundant paths. Consider the simplified network diagram below:AP CSP CSN-1.C 指出互联网因使用具有冗余路径的分组交换而具有"容错性"。考虑以下简化网络图：

Sender --[Router A]--[Router B]--[Router C]-- Receiver
              |                       |
              +------[Router D]-------+
(a) List all distinct paths a packet could take from Sender to Receiver. (Count each unique sequence of routers as one path.)列出数据包从发送方到接收方可能经过的所有不同路径。（将每条唯一的路由器序列算作一条路径。） [2]
(b) Router B fails. Explain why packets can still reach the Receiver, state which path they now take, and relate your answer to the definition of "fault tolerance."路由器 B 故障。解释为什么数据包仍能到达接收方，写出它们现在走的路径，并将你的回答与"容错性"的定义联系起来。 [3]
(c) Three packets from the same file arrive at the Receiver in the order: Packet 3, Packet 1, Packet 2. Explain how the Receiver reconstructs the file in the correct order and name the field in the packet header that makes this possible.同一文件的三个数据包以以下顺序到达接收方：数据包 3、数据包 1、数据包 2。解释接收方如何按正确顺序重建文件，并命名数据包头部中使这成为可能的字段。 [2]
(d) Contrast the Internet's mesh-like routing with a star topology LAN in terms of fault tolerance. State the single point of failure in a star topology.在容错性方面，对比互联网的网状路由与星型拓扑局域网。写出星型拓扑中的单点故障。 [1]
PART III  ·  MODELING / APPLIED第三部分  ·  建模与应用Universal / multi-region applied · 25 marks通用/多地区应用题 · 共 25 分

Section C · Modeling and ApplicationsC 部分 · 建模与应用

Read each scenario carefully before answering. Use precise technical terms throughout. Where a diagram is requested, label all components clearly. Conclude each question with a one-sentence answer that directly addresses the scenario.作答前仔细阅读每个场景。全程使用精确技术术语。要求画图时，清晰标注所有组件。每题以一句直接回答场景核心问题的总结句结束。

Q10 MEDIUM中 🇺🇸 US美 🇨🇦 ON安 AP CSP-feeder FRQAP CSP 衔接简答题 §1 + §2 Network Design and Packet Switching网络设计与分组交换 · CSTA 3A-NI-04 / BC CS10 [8 marks][8 分]

A new public library is designing its network. Requirements: (1) 20 desktop computers on the ground floor must all connect through one central device; (2) the network must remain functional if any single desktop fails; (3) the library's network must connect to the Internet (a WAN). A consultant proposes a star-topology LAN connected through a router to the Internet.一座新图书馆正在设计其网络。要求：（1）一楼 20 台台式机必须全部通过一台中央设备连接；（2）任意一台台式机故障时网络仍须正常运行；（3）图书馆网络必须连接到互联网（广域网）。一位顾问建议采用星型拓扑局域网，通过路由器连接到互联网。

(a) Draw a labelled ASCII diagram of the proposed network. Your diagram must clearly show: the central device (name its type), at least 3 desktop computers (label as PC1, PC2, ...), the router, and the Internet.画出所提议网络的带标注的 ASCII 图示。图示必须清晰包含：中央设备（标出类型）、至少 3 台台式机（标注为 PC1、PC2、...）、路由器和互联网。 [3]
(b) Explain why a star topology satisfies requirement (2) that the network stays functional when one desktop fails. Also state the single weakness of a star topology with respect to requirement (2).解释为什么星型拓扑满足要求（2），即任意一台台式机故障时网络仍正常运行。同时写出星型拓扑与要求（2）相关的唯一弱点。 [2]
(c) When a patron searches the library catalogue online, the request travels as packets. State three advantages of packet switching over sending one continuous stream. (CSTA 3A-NI-04)当读者在线搜索图书馆目录时，请求以数据包形式传输。写出分组交换相比发送一个连续流的三个优势。（CSTA 3A-NI-04） [3]
Q11 MEDIUM中 🇨🇦 ON安 🇨🇦 BC卑 ON Provincial-style安大略省考风格 §6 Network Security Basics网络安全基础 · ICS3U C2.2 / CSTA 3A-NI-05 / 3A-NI-06 [9 marks][9 分]

Ontario ICS3U C2.2 asks students to "devise a thorough system protection plan." A high school network experienced three security incidents: (i) a student downloaded a program disguised as a game that secretly transmitted the student's files to an external server; (ii) a piece of software spread from computer to computer across the school network without being attached to any file; (iii) an external attacker accessed the staff Wi-Fi by guessing a weak password.安大略 ICS3U C2.2 要求学生"制定全面的系统保护计划"。某高中网络遭受了三起安全事件：（i）一名学生下载了一个伪装成游戏的程序，该程序秘密将学生文件发送到外部服务器；（ii）一段软件无需附着于任何文件，在校内网络中从一台计算机传播到另一台；（iii）外部攻击者通过猜测弱密码访问了教职工 Wi-Fi。

(a) Identify the specific type of malware in each incident (i), (ii), and (iii). Justify each identification in one sentence. (ICS3U C2.2)指出事件（i）、（ii）和（iii）中各自具体的恶意软件类型。各用一句话说明理由。（ICS3U C2.2） [3]
(b) For each of the three incidents, recommend one specific security measure to prevent recurrence and state one tradeoff (a cost or usability impact). Present your answer using the table format below.针对三起事件中的每一起，推荐一项具体的安全措施以防止再次发生，并写出一个权衡（成本或可用性影响）。使用以下表格格式作答。 [6]
Incident事件Security Measure安全措施Tradeoff权衡
(i)
(ii)
(iii)
Q12 HARD难 🇺🇸 US美 🇨🇦 ON安 🇨🇦 BC卑 AP CSP-feeder FRQAP CSP 衔接简答题 §7 Web vs Internet, Client-Server, URL Anatomy万维网与互联网、客户端-服务器、URL 解析 · AP CSP / AB CSE1210 [8 marks][8 分]

A student clicks a link and their browser loads the page at this URL:一名学生点击了一个链接，浏览器加载了该 URL 处的页面：

https://library.school.ca:443/catalogue?subject=science#results
(a) Identify and explain the role of each of the following components of the URL: the scheme (https), the domain (library.school.ca), the port (443), the path (/catalogue), the query string (subject=science), and the fragment (#results).识别并解释该 URL 中以下各组成部分的作用：协议方案（https）、域名（library.school.ca）、端口（443）、路径（/catalogue）、查询字符串（subject=science）和片段（#results）。 [3]
(b) Describe the full client-server interaction when this URL is loaded: (1) what DNS step occurs first, (2) what the browser (client) sends to the server, (3) what the server sends back, and (4) what the browser does with the response. Use correct HTTP terminology.描述加载此 URL 时完整的客户端-服务器交互：（1）首先发生什么 DNS 步骤，（2）浏览器（客户端）向服务器发送什么，（3）服务器返回什么，（4）浏览器如何处理响应。使用正确的 HTTP 术语。 [3]
(c) A classmate says "the Internet and the Web are the same thing." Correct this misconception in exactly two sentences: define the Internet, then define the Web and clarify the relationship. Name one Internet service that is NOT the Web.一位同学说"互联网和万维网是同一件事"。用恰好两句话纠正这个误解：定义互联网，然后定义万维网并阐明两者关系。举一个不属于万维网的互联网服务。 [2]
🇺🇸 US CSTA / AP CSP美国 CSTA / AP CSP3A-NI-04 · 3A-NI-05 · 3A-NI-06 · 3A-NI-07 · CSN-1.A/C
🇨🇦 Ontario安大略ICS3U C2.2 · malware types, system protection plan恶意软件类型、系统保护计划
🇨🇦 British Columbia不列颠哥伦比亚BC CS10: wired/wireless networks, routers, switches. BC CIS 11: OSI 7 layers, TCP/IP 4 layers, LAN/WAN, interoperabilityBC CS10：有线/无线网络、路由器、交换机。BC CIS 11：OSI 7 层、TCP/IP 4 层、LAN/WAN、互操作性
🇨🇦 Alberta阿尔伯塔CSE1210 / CSE1220: Internet computing, client-server, web markup. CS has no AB standalone diploma exam.CSE1210 / CSE1220：互联网计算、客户端-服务器、Web 标记语言。CS 无独立 AB 毕业考。

Full Syllabus Map in Study Guide: ../Study Guides/Unit_11_Networks_and_the_Internet.html. CS has no AB standalone diploma exam; AB framing uses CSE1210/CSE1220 outcomes.完整大纲对照见学习指南：../Study Guides/Unit_11_Networks_and_the_Internet.html。CS 无独立 AB 毕业考；AB 题使用 CSE1210/CSE1220 结果框架。