网络七层(OSI model)、以及常见的telnet、Http、Socket分别属于第几层

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。