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Week 1: Introduction (Part 1) 第 1 周：引言（第一部分）

Core Concepts 核心概念

1. Data Communications & Networking in Business (1.1)

Data communication is the exchange of data between devices via transmission media. Key components include senders, receivers, messages, transmission media, and protocols.

Role of Protocols: A protocol is a set of rules that governs data communications. It defines what is communicated, how it is communicated, and when it is communicated. It has three key elements:

  • Syntax: Refers to the structure or format of the data (e.g., the first 8 bits define the address).
  • Semantics: Refers to the meaning of each section of bits (e.g., how to interpret the address).
  • Timing: Refers to when data should be sent and how fast it can be sent.

2. De Facto vs. De Jure Standards (1.2)

  • De Facto Standard: Standards that have been widely adopted through common usage and market dominance without formal approval by any regulatory body (e.g., TCP/IP).
  • De Jure Standard: Standards that have been formally approved and legislated by an officially recognized regulatory body (e.g., OSI model, IEEE 802.3).

3. Distributed Processing & Convergence (1.3)

Distributed Processing: Processing tasks are distributed among multiple computers connected via a network rather than relying on a single mainframe. Advantage: Higher system reliability (if one local processor fails, remaining processors continue normally).

Convergence: Merging voice, data, and video onto a single IP-based infrastructure. Unified Communications (UC) integrates these tools (VoIP, video, instant messaging) into a single interface.

1. 商业中的数据通信与网络 (1.1)

数据通信是设备之间通过传输介质进行的数据交换。关键组件包括发送方、接收方、消息、传输介质和协议。

协议的作用：协议是管理数据通信的一套规则。它定义了通信的内容、通信方式和通信时间。它有三个关键要素：

  • 语法 (Syntax)：指数据的结构或格式（例如，前 8 位定义地址）。
  • 语义 (Semantics)：指每部分比特的含义（例如，如何解释该地址）。
  • 时序 (Timing)：指何时发送数据以及发送速度有多快。

2. 事实标准与法定标准 (1.2)

  • 事实标准 (De Facto)：未经任何监管机构正式批准，但通过共同使用和市场主导地位而被广泛采用的标准（例如，TCP/IP）。
  • 法定标准 (De Jure)：经官方认可的监管机构正式批准并立法的标准（例如，OSI 模型、IEEE 802.3）。

3. 分布式处理与网络融合 (1.3)

分布式处理：处理任务分布在通过网络连接的多台计算机上，而不是依赖单个主机。优势：系统可靠性高（如果一个本地处理器发生故障，其余处理器仍能正常运行）。

网络融合：将语音、数据和视频合并到单一基于 IP 的基础设施中。统一通信 (UC) 将这些工具（VoIP、视频、即时消息）集成到一个界面中。

Concept Visualization: Network Convergence 概念可视化：网络融合

Voice Data Video Converged IP Net Unified Comms

Tips 提示

  • Wireshark Capture: Always select the correct physical network interface card (NIC) (e.g. Ethernet or Wi-Fi) from the startup list to start capturing actual packets. Use filters to remove background noise.
  • Packet Tracer Cabling: Use straight-through cables (solid line) to connect different layers (PC to Switch, Switch to Router). Use crossover cables (dotted line) to connect similar layers (PC to PC, Switch to Switch).
  • Wireshark 捕获：始终从启动列表中选择正确的物理网卡（如以太网或 Wi-Fi）以开始捕获实际数据包。使用过滤器过滤背景噪音。
  • Packet Tracer 接线：使用直通线（实线）连接不同层设备（PC 到交换机，交换机到路由器）。使用交叉线（虚线）连接同层设备（PC 到 PC，交换机到交换机）。

Practical Exercises & Step-by-Step Guide 实践练习与分步指南

Exercise 1: Cisco Packet Tracer - Two-Node Connection Setup 练习 1：Cisco Packet Tracer - 双节点连接设置

Steps to complete:

  1. Open Cisco Packet Tracer. In the bottom-left corner, click on End Devices, then drag two Generic PCs (PC0 and PC1) into the workspace.
  2. Click on Network Devices -> Switches, and drag a 2960 Switch between the PCs.
  3. Click the Connections icon (lightning bolt). Select the solid black cable (Copper Straight-Through).
  4. Click PC0 -> select FastEthernet0. Connect the cable to the Switch -> select FastEthernet0/1. Repeat this for PC1 (connect to FastEthernet0/2).
  5. Double-click PC0 -> click Desktop tab -> select IP Configuration. Enter IP 192.168.1.10 and Subnet Mask 255.255.255.0.
  6. Double-click PC1 -> configure IP 192.168.1.11 and Subnet Mask 255.255.255.0.
  7. On PC0 Desktop, open the Command Prompt. Run command ping 192.168.1.11 to verify connectivity.

完成步骤：

  1. 打开 Cisco Packet Tracer。在左下角点击 End Devices（终端设备），然后拖入两台 Generic PC（PC0 和 PC1）到工作区。
  2. 点击 Network Devices -> Switches（交换机），拖入一台 2960 交换机 放在两台 PC 之间。
  3. 点击 Connections（连接）图标（闪电）。选择黑色实线（铜直通线）。
  4. 点击 PC0 -> 选择 FastEthernet0。连接至交换机 -> 选择 FastEthernet0/1。对 PC1 重复此操作（连接至交换机 FastEthernet0/2）。
  5. 双击 PC0 -> 点击 Desktop（桌面）选项卡 -> 选择 IP Configuration。输入 IP 192.168.1.10 和子网掩码 255.255.255.0。
  6. 双击 PC1 -> 配置 IP 192.168.1.11 和子网掩码 255.255.255.0。
  7. 在 PC0 的桌面上打开 Command Prompt（命令提示符）。运行命令 ping 192.168.1.11 验证连通性。

Exercise 2: Wireshark - Capture and Follow plain TCP stream 练习 2：Wireshark - 捕获并跟踪纯 TCP 流

Steps to complete:

  1. Open Wireshark. Double-click your active network card (e.g. Wi-Fi) to start capturing.
  2. Open your command prompt or browser. To trigger test traffic, run ping 8.8.8.8.
  3. In Wireshark, enter icmp in the display filter bar and press Enter. You will see the echo request/reply packets.
  4. To capture application traffic, visit a plaintext site (e.g., `http://neverssl.com`).
  5. Filter by http. Right-click on the HTTP packet (e.g. GET) -> select Follow -> TCP Stream to see the decoded plaintext headers.

完成步骤：

  1. 打开 Wireshark。双击您的活动网卡（例如 Wi-Fi）开始捕获。
  2. 打开命令提示符或浏览器。要触发测试流量，运行 ping 8.8.8.8。
  3. 在 Wireshark 的显示过滤器栏输入 icmp 并按回车。您将看到 ping 请求/回复数据包。
  4. 为了捕获应用层流量，访问一个明文 HTTP 站点（如 `http://neverssl.com`）。
  5. 在过滤器栏输入 http。右键点击 HTTP 数据包 (例如 GET) -> 选择 Follow -> TCP Stream，即可查看解码后的明文包头内容。

Self-Check Practice Questions 自测练习题

1. Identify the standard-making body that defines internet communication protocols. 识别定义互联网通信协议的标准制定机构。

2. Describe the main function of a protocol in data communications. 描述协议在数据通信中的主要功能。

3. Classify a network standard created by an official regulatory body. 对官方监管机构创建的网络标准进行分类。

4. Identify the standard body that defines electrical and electronics standard configurations. 识别定义电气和电子标准配置的标准机构。

5. Describe the timing element of a communication protocol. 描述通信协议的“时序”要素。

6. Classify a network standard that has become popular without formal approval. 对未经正式批准但已变得流行的网络标准进行分类。

Review Questions 复习问答题

Q1. Explain the role of 'Protocols' in data communication and describe THREE (3) key elements of a protocol.

Q2. Explain the difference between a 'De facto' standard and a 'De jure' standard in networking, providing one example for each.

Vocabulary Matching Game 词汇配对游戏

Match the term on the left with its definition on the right. (Click a term, then click its matching definition). 将左侧的术语与右侧的定义进行配对。（点击术语，然后点击匹配的定义）。

Syntax
Semantics
Timing
De Facto Standard
De Jure Standard
When data should be sent and how fast it can be sent 数据何时发送以及发送的速度有多快
Structure or format of the data (e.g. first 8 bits as address) 数据的结构或格式（例如前 8 位表示地址）
Standards formally approved by an officially recognized body (e.g. OSI, IEEE) 由官方认可机构正式批准的标准（如 OSI、IEEE）
Meaning of each section of bits (how to interpret it) 各比特段 of 含义（如何进行解释）
Standards adopted through usage without formal approval (e.g. TCP/IP) 未经正式批准但通过使用被采纳的标准（如 TCP/IP）