Description
输层的功能如IP的传输协议（TCP）、单位是段（segment）。会话层处理两个或多个系统之间连接的建立和维护。它保证正确完成具体的服务请求。如果系统正在运行多个网络应用程序，会话层负责保持正确通信顺序，保证进入的数据引到正确的应用程序。表示层保证数据可以用于应用程序的形式接收。它的任务是编码和解码。应用层的任务是确定何时要求访问网络资源。
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