OSI 第 1–3 层简单详解 | AI生成和翻译
Question: In the OSI Reference Model, the physical layer, data link layer, and network layer are collectively called
A. End-to-end layers
B. Node-to-end layers
C. Node-to-node layers
D. Intermediate system layers
Your answer: D
Correct answer: C
Answer:
The correct answer is C. Node-to-node layers。
Explanation:
在 OSI Reference Model (OSI/RM) 中，七层结构根据其通信范围被分为两大组：
- Node-to-node layers（也称为 point-to-point layers 或 hop-by-hop layers）：
这些层负责相邻网络设备之间的通信（一次一跳）。- Physical layer (Layer 1)
- Data Link layer (Layer 2)
- Network layer (Layer 3)
→ 这三层统称为 node-to-node layers（或 point-to-point layers / 结点到结点层）。
- End-to-end layers（也称为 host-to-host layers）：
这些层负责从源主机到目标主机的通信，无论中间经过多少个设备（routers, switches）。- Transport layer (Layer 4)
- Session layer (Layer 5)
- Presentation layer (Layer 6)
- Application layer (Layer 7)
→ 这四层统称为 end-to-end layers（端到端层）。
Why not D (Intermediate system layer)?
“Intermediate system” 是 ISO 术语中主要用于指代 routers（工作在 Layer 3 — Network layer 的设备）的词汇。在 OSI 教学材料或教科书中，它不是 Layer 1–3 这一组层的标准名称。
Summary table:
| Group | Layers involved | Scope of responsibility | Chinese name |
|---|---|---|---|
| Node-to-node | Physical + Data Link + Network | Between adjacent nodes (one hop) | 结点到结点层 |
| End-to-end | Transport + Session + Presentation + Application | From source host to destination host | 端到端层 |
因此，physical layer, data link layer, 和 network layer 被正确地称为 node-to-node layers → 选项 C。
References:
- None (standard OSI model knowledge; widely consistent across textbooks and certification materials such as CCNA, CompTIA Network+, and Chinese computer network textbooks)