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网络七层(OSI model)、以及常见的telnet、Http、Socket分别属于第几层
Open System Interconnection model是一个对计算机连接交互的总结出来的一个标准模型。 它制定了不同系统之间的交互的标准协议。模型分为7层。
以下是wiki上的模型:
| OSI Model | |||
| Layer | Protocol data unit (PDU) | Function[3] | |
| Host layers | 7. Application | Data | High-level APIs, including resource sharing, remote file access |
| 6. Presentation | Translation of data between a networking service and an application; including character encoding, data compression and encryption/decryption | ||
| 5. Session | Managing communication sessions, i.e. continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes | ||
| 4. Transport | Segment (TCP) / Datagram (UDP) | Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing | |
| Media layers | 3. Network | Packet | Structuring and managing a multi-node network, including addressing, routing and traffic control |
| 2. Data link | Frame | Reliable transmission of data frames between two nodes connected by a physical layer | |
| 1. Physical | Bit | Transmission and reception of raw bit streams over a physical medium | |
socket是基于tcp/rtp/pptp的会话层, http是应用层, telnet是应用层。
但是并非所有的都能够完全适应于这个7层模型，比如http session层，并对应不上7层协议的session。所以7层只能是一个标准模型，并非完全适用。