什么是OSI

OSI(Open System Interconnect),即开放式系统互联。 一般都叫OSI参考模型,是ISO(国际标准化组织)组织在1985年研究的网络互连模型。ISO为了更好的使网络应用更为普及,推出了OSI参考模型。其含义就是推荐所有公司使用这个规范来控制网络。这样所有公司都有相同的规范,就能互联了。
OSI定义了网络互连的七层框架(物理层、数据链路层、网络层、传输层、会话层、表示层、应用层),即ISO开放互连系统参考模型。

 

每一层实现各自的功能和协议,并完成与相邻层的接口通信。OSI的服务定义详细说明了各层所提供的服务。某一层的服务就是该层及其下各层的一种能力,它通过接口提供给更高一层。各层所提供的服务与这些服务是怎么实现的无关。

众所周知,OSI参考模型是学术上和法律上的国际标准,是完整的权威的网络参考模型。而TCP/IP参考模型是事实上的国际标准,即现实生活中被广泛使用的网络参考模型。

 

OSI七层和TCP/IP四层的关系

OSI引入了服务、接口、协议、分层的概念,TCP/IP借鉴了OSI的这些概念建立TCP/IP模型。

OSI先有模型,后有协议,先有标准,后进行实践;而TCP/IP则相反,先有协议和应用再提出了模型,且是参照的OSI模型。

OSI是一种理论下的模型,而TCP/IP已被广泛使用,成为网络互联事实上的标准。

 

  • TCP:transmission control protocol 传输控制协议
  • UDP:user data protocol 用户数据报协议

OSI七层和TCP/IP的区别

  • TCP/IP他是一个协议簇;而OSI(开放系统互联)则是一个模型,且TCP/IP的开发时间在OSI之前。
  • TCP/IP是由一些交互性的模块做成的分层次的协议,其中每个模块提供特定的功能;OSi则指定了哪个功能是属于哪一层的。
  • TCP/IP是五层结构,而OSI是七层结构。OSI的最高三层在TCP中用应用层表示。

Jinming

95后典型金牛座,强迫症。

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