Ethernet Layer 1: wiring, speed, and duplex

 

RJ45 pin leads and Class 5 Wiring

 

RJ45 is a common Ethernet interface with eight copper wires. A network cable has two headers. The two ends are called a direct line, and the two ends are called a cross line. The full image is called an inverted line and is mainly used for configuration ports.

 

Generally, it uses a four-core network cable, which is 1236. The student name is T568A (B)

 

Auto-MDIX

 

(Medium-dependent interface crossover) automatically converts the send and receive data PIN, so that you do not need to change the network cable.

 

Automatic negotiation, speed and duplex

 

Automatic negotiation means that the Ethernet port can work in an adaptive and random way. Only three 10 Mbps, 1000 Mbps, and Mbps are supported. There are two types of duplex: Half duplex and full duplex. Half duplex is like a bpserver, one-way, full duplex is like a mobile phone, two-way. CSMA/CD, Niang xipi. I see this abbreviation every day. I can't tell the full name after I close the book. CD is collision detection. Ethernet is a way of working, for fear that every computer in a collision domain sends messages together, messy sets. When a computer sends a message, it will notify other computers that Lao Tzu is sending the message. Do not change it. How to play it? I will ask Wendell later. Said Wendell: Carrier Sense Multiple Access, the Carrier detects Multiple accesses. Wendell: 1. a device with a frame to be sent should first listen to whether there is any blank Ethernet, that is to say, there is no carrier signal on the Ethernet, just like the person who wants to go to the toilet, first check whether there is anyone in the toilet. 2. If the Ethernet is idle, the device is ready to send frames. No one is in the restroom. You are about to take a shit. 3. check whether there is a collision, that is, whether there is a dry frame for this position, although no one is pulling shit. 3. If there is a collision, all frame sending sites send a Jamming signal to let all sites know. When someone came across, he shouted to the outside, saying that someone in the restroom had to fight for a location. 4. After the Jamming signal is sent, all the collision frames will be resold after a random wait time. If a conflict occurs, you can find a time to pull it again. Other people do not have to wait.

 

Collision domain and exchange Buffer

 

The collision domain is where the host may conflict, just like a cell is a collision domain. The collision domain allows a device to send frames in conflict with another device. For example, if two devices connect to the hub and send frames at the same time, the carrier signals are stacked to affect each other, the original meaning is lost. The exchange buffer, I think, is put in the cache before the message is sent. The switch does not conflict with each other because it has a caching mechanism, that is, there is a chair and newspaper next to the toilet. People who pull shit can endure it for a while. If the switch receives three different frames from three different ports and must exit from the same port, the switch can first put the two frames in the memory and then queue them out.

 

Basic switch port configuration

 

Three aspects: auto-negotiation, speed, and duplex. Why is there a half-duplex collision? Because a frame is generated when a port is sent, it will crash. If it is full duplex, no. Like a one-way street, a car is driving, and a collision will occur when the car comes on the way. In the two-way road, the car that meets the face will not collide.

 

Use Fast Link Pulse (latency) to detect the speed.

From muziyiwu's BLOG