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计算机网络参考模型

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• 路由器：帮助设备高速转发数据
• 交换机：提供更多的网络接口（网口）） ，让更多的机器加入局域网中来

分层思想 osi七层参考模型

定义：“OSI模型，即开放式通信系统互联参考模型（Open System Interconnection Reference Model），是国际标准化组织（ISO）提出的一个试图使各种计算机在世界范围内互连为网络的标准框架，简称OSI。

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| 层级 | osi模型7层 | 5层模型 |常用协议 | | ------ | ------ | ------ | ------ | | 7 | 应用层 | 应用层 | !!#ff0000 http!! https ftp tftp| | 6 | 表示层 | 应用层| .. | | 5 | 会话层 | 应用层 | ..| | 4 | 传输层 | 传输层 | !!#ff0000 tcp!!/dup| | 3 | 网络层 | 网络层 | icmp !!#ff0000 ip!! ARP| | 2 | 数据链路层 |数据链路层 | | | 1 |物理层 | 物理层 | 光纤 等| ::: ::: center ::: 通俗表达：

• A发起方

• 应用层：输入高级语言的指令 （打开微信 输入聊天的话语 人和程序之间的交流平台）

• 表示层： 将人类使用的高级语言编译成二进制语言

• 会话层：管理多个会话 保证消息正确到达 指定主机

• 传输层： tcp ：传数据的时候慢 但是很稳定 udp：传数据的时候很快 但是不稳定 直播 作用：确定传输协议 端口号 （在网络传输中通过端口号的不同 来区分应用）

• 网络层：选择数据的最佳传输路线 （ip地址）

• 数据链路层： 二次确认数据是否正确到达 mac地址 （全球唯一）

• 物理层 ：插上网线 定义了一些物理接口的标准 将二进制数据转换成电信号

• B接收方

• 物理层 ：将电信号转换成二进制

• 数据链路层： 对比自己的mac地址 和数据包mac地址 一致则接收 否则丢弃

• 网络层： 再次对比ip地址

• 传输层： 通过端口号找对应的程序

• 会话层： 通过特定的会话通道 到达表达层

• 表示层： 将二进制语言转换为高级语言

• 应用层： 显示在应用程序中

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常用协议说明： :::

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|协议 |说明 | | ------ | ------ | | http | 超文本传输协议 明文传输 | |https | http+ssl协议 超文本加密版 | | ftp | 文件传输协议 | | tftp | 简单文件 默认使用udp协议 | | icmp | ping trcert 检测主机双向联通性 | |ARP |地址解析 将IP地址 转换成mac地址的协议 | |ip|
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!!#ff0000 数据封装过程!!

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多层原理的典型设备 :::

• 2层原理 -----交换机-----数据链路层------根据mac地址转发数据
• 3层原理-----路由器------网络层------------根据IP地址转发数据
• 4层原理-----防火墙------传输层------------根据协议和端口号