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12. MAC address

The lMAC address is commonly referred to as the physical address or hardware address of the network card.

The lMAC address is 48 bits, often expressed in hexadecimal as 6 bytes, and is an address that cannot be changed. L where the first 24 bits represent the supplier code. The remaining 24 bits are serial numbers assigned by the manufacturer itself.

If all 48 bits are 1, the address is a broadcast address. (FF-FF-FF-FF-FF-FF)

13. UTP unshielded twisted pair

STP shielded twisted pair

14. LT568B: orange white, orange, green white, blue, blue white, green, brown white, brown

LT568A: green and white, green, orange and white, blue, blue and white, orange, brown and white, brown

15. Three different wiring methods: straight-through line, cross line and reverse line

16. Conflict domain (in the same conflict domain, one terminal sends data and the other terminal can only receive data passively, but can not send data at the same time. If it is sent, it will cause conflict) (HUB does not divide the conflict domain, switch and bridge to divide the conflict domain)

Broadcast domain: can receive broadcasts in a broadcast domain (router divides broadcast domain)

17. Working principle of lCSMA/CD

LCS: carrier sense.

-monitor before sending data to ensure that the line is idle and reduce the chance of conflict.

LMA: multiple access.

-the data sent by each site can be received by multiple sites at the same time.

LCD: collision detection.

-detect while sending, stop sending when you find a conflict, and then continue sending after delaying for a random time.

18. Ethernet frame structure (packet with MAC address)

International Organization for Standardization (ISO)

The contribution is the establishment of the reference model of open systems interconnection, the famous OSI/RM model.

L Association of Electrical and Electronic Engineers (IEEE)

The contribution is 802.3 and other industry standards (802.3 is also the standard of Ethernet)

The bandwidth of Ethernet is 10m 802.3.

The bandwidth of Fast Ethernet is 100m 802.3U

L INTERNET Engineering Task Committee (IETF)

Contribution is RFC (request for comments)

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