OSI 结构

OSI ： Open systems Interconnection 开放系统互联，由ISO定义的互联网模型（Internet model），分为七层

 

7,Application Layer

 

    provide user interface to internet

    http,ftp,dns,telnet...

 

6,Presentation Layer

 

   Code and encode,compress and uncropress

 

5,Session Layer

 

   estblishment and termination of a link

 

4,Transportation Layer

 

   end to end

 

3,Network layer

 

    router choose, error and flow control

    ip address

 

2,Data Link Layer

 

   Frame of data

   MAC address

 

1,Physics Layer

 

   To transfer data between different physics media 

 

MAC(Media Ascess Control)由48bit组成，具有全球唯一性

ARP协议用来将IP映射到MAC地址

交换机工作在数据链路层