Operation and Maintenance Xiaobai's Growth Diary Day 4 - Basic Network Building OSI Seven-layer Model - Basic Knowledge of Physical Layer

Operation and Maintenance Xiaobai's Growth Diary Day 4-

 

Basic network construction OSI seven-layer model - basic knowledge of physical layer

Xiaobai of network operation and maintenance and friends who want to join network operation and maintenance are worth seeing ~

Today is the fourth day of the first time I learned about network operation and maintenance. I hope that like-minded friends can discuss and learn together, and I also hope that the great gods of network operation and maintenance can help guide me on the road of network operation and maintenance, and I can make more progress by giving more opinions.

 

Today, I will share with you the basic knowledge of the physical layer in the OSI seven-layer model.

1. Physical medium

1. The physical media for data transmission are: twisted pair, optical fiber, coaxial cable (cable TV), wireless, power line, infrared, bluetooth, microwave

2. Signal

( 1 ) Analog signals: such as sound waves (water ripples)

( 2 ) Digital signal: 1 and 0

3. If there is only one signal in the medium, it is called baseband transmission; if there can be multiple signals in the medium, it is called broadband transmission.

 

 

ADSL -> Internet access and phone calls at the same time. The telephone line medium transmits network signals and telephone signals at the same time, with low frequency running voice and high frequency running network.

 

4. Twisted pair: 4 pairs of 8 cores. The maximum transmission distance of twisted pair is theoretically 100 meters

5、双绞线分类：屏蔽双绞线(STP)、非屏蔽双绞线(UTP)。UTP用得多

5、标准双绞线一箱305米，价格正品好线（安普永生）五六百，但是假线只有200以内。

6、光纤理论最大距离可以2-3km

（1）光纤利用光的全反射原理

（2）光纤分为单模和多模

（3）单模光纤，只传一束激光

（4）多模光纤，可以传多束光

 

7、网线上的水晶头名称为RJ45接头，电话线的叫RJ11

8、双绞线的线序：

568B：白橙 橙 白绿 蓝 白蓝 绿 白棕 棕

568B在我国应用广泛。568A的线序是1和3对调，2和6对调

9、如果线的两头用相同标准是直通线，两头不同标准是交叉线。

10、同种设备用交叉线，不同设备用直通线。

11、现实情况下，两台主之间、两台交换机之间插什么线都行。因为现在多数设备支持自动翻转。

12、双绞线实际上只用了1236四根线。其余四根线没有使用。

 

二、物理层的设备

1、网络接口卡其实就是我们电脑中的网卡

                                                                连接计算机和网络硬件

                                                                有一个唯一的网络节点地址

                                                                按照速度可分为10M、10/100M自适应和千兆网卡

                                                                按照总线程类型可分为ISA网卡和PCI网卡等

                                                                按照提供的线缆接口类型可分为RJ-45 、光纤网卡等

                                                                便携式电脑可使用PCMCIA网络接口卡

1、中继器：实现除噪放大功能。早期使用同轴电缆时代使用，两个口。

      

2、集线器HUB：2000年初被淘汰，相当于是多端口的中继器。

3、中继器没有任何智能，收到数据包后，向除接收端口以外的所有其他端口发送。所以中继器共享带宽，如100Mb/s的HUB，连10台主机，每主机带宽10Mb/s，如果连20台主机，每主机带宽5Mb/s。