HCIA - data link layer

Data link layer and Ethernet

Now contact the network equipment , For example, switches are generally called Ethernet switches ,Windows The network card in the system is directly called Ethernet .WLAN It is also generally called wireless Ethernet . So what is Ethernet ？

What is Ethernet （Ethernet）

Ethernet : Today's dominant LAN networking technology . Now we need to set up a local area network , Almost all the technologies used in layer 2 technology are Ethernet Technology . Ethernet is not a protocol , It's just a standard .

A LAN , Use switch 、 Routers and wireless AP. The switch outlet is connected to the router gateway , The router outlet is connected to broadband （ Internet ）. The following figure shows an enterprise network , Networking technology is Ethernet .（ The second layer determines the networking technology , The upper layer is the same ）

The development of Ethernet

• 20 century 70 years , from Xerox The company United Intel and DEC The company developed Ethernet
• 1973 year , Transmission rate 3Mb/s（ laboratory ）
• 1980 year , Transmission rate 10Mb/s
• 1990 year , Ethernet with twisted pair media
• 1992 year , Transmission rate 100Mb/s
• 1998 year , Transmission rate 1000Mb/s
• 2010 year ,IEEE Release 40G/100G standard （ Cloud computing 、 Data center use ）
• 2013 year ,400G The standard work of Ethernet is officially launched

The classification of Ethernet

UTP： Twisted pair
Fiber： Optical fiber

The standard of Ethernet

Packet structure and encapsulation

Hierarchical design of data link layer

Sublayer	remarks
LLC	Logic Link Cotrol, Logical link control Responsible for identifying the protocol type of the network layer , After receiving the upper data packet and encapsulating it into a frame , Pass down
MAC	Media Access Cotrol, Media access control Responsible for controlling and connecting the physical media of the physical layer Dealing with physical addressing of hardware devices 、 Define the network topology and the transmission order of data frames

Tips ： Here you can add the general content to be recorded in this article ：
for example ： With the development of artificial intelligence , Machine learning is becoming more and more important , A lot of people have turned on learning machine learning , This paper introduces the basic content of machine learning .

The term	remarks
Protocol type	Agreement on behalf of the upper level , Such as 0x0800 representative IPv4
data	All upper layer protocol data
MTU	Maximum transmission unit , Default 1500 byte , The maximum value of data sent each time
Frame check	The value obtained by calculating the data packet through a certain calculation formula
MAC Address	48bit, Hexadecimal representation , Represents the physical address of the Ethernet interface , The only global

---