Chapter 2 OSI Model & TCP/IP Protocol Suite The OSI/RM Layers in the OSI/RM TCP/IP protocol suite Addressing in TCP/IP TCP/IP versions ******@uestc. 1 The OSI/RM An ISO standard Open System Interconnection/ Reference Model 开放系统互连/参考模型 Released in 1984 Ensured patibility and interoperability 7 layers, each of which illustrates a work function ISO is anization, OSI is the model OSI is not a protocol, but a conceptual model ******@uestc. 2 OSI Model Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1 应用层 表示层 会话层 传输层 网络层 数据链路层 物理层 网络支持层 (软/硬件) 应用支持层 (软件) ******@uestc. 3 Why Layered? Advantages plexity Standardizes interfaces Facilitates modular engineering Ensures interoperable technology Accelerates evolution Simplifies teaching and learning Disadvantages Strict layered architecture makes its software not so efficient. … N+1 N N-1 … ******@uestc. 4 The Features of Layering Each layer concerns on its own details Each layer provides a service to the layer above Each municates with its peer layer in another node through the use of a corresponding protocol ******@uestc. 5 Peer-to-munication 对等进程/对等实体 (Peer Entity) Peer Entity 对等进程/对等实体 对等层 Peer Layer Peer Layer 对等层 Interface 接口 对等层协议 Peer-to-Peer Protocol Peer-to-Peer Protocol 对等层协议 Service 服务 ******@uestc. 6 Peer Layer vs. Peer Entity Multiple entities in one layer Peer entity:存在通信关系的对等层实体 Multiple protocols in one layer Protocol:对等实体间的通信规则 CutFTP FTP Server Outlook Mail Server IE Layer 7 Layer 7 Outlook IE CutFTP FTP Server Mail Server FTP HTTP SMTP ******@uestc. 7 Data Exchange: Encapsulation Source Destination A P S T N DL Ph PDU:Protocol Data Unit 协议数据单元 帧 Frame 分组 Packet 数据段 Segment 数据 Data ******@uestc. 8 Postal Delivery 信件 邮局 分拣邮包 邮政网络 邮政运输 交通运输 信件 邮局 分拣邮包 邮政网络 邮政运输 信件格式 寄信方式 分拣邮包规则 邮路选择 运输方式 同层间需要约定规则——协议 ******@uestc. 9 Layers in the OSI/RM Application Presentation Session Transport Ne
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