Linux operation and maintenance of the road network basic Learning 1.2

Network Fundamentals 1.2

Physical Layer Parsing

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Physical Layer-the foundation of the network

------Physical layer is the lowest level of the TCP/IP model

------Physical layer provides a reliable environment for data transmission

the physical layer functions :

1: To provide the data-terminal equipment to transmit data access;

2: Transmission of data;

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Issues of concern to the physical layer:

Signal:

Information is a kind of cognition about the existence way or movement state of things in the real world;

Data is a specific measure used to describe certain properties of a thing;

Signal is the medium of information transmission;

Analog and digital signals:

Analog signal is the signal parameter size continuous change of electromagnetic waves can be transmitted at different frequencies in the media;

The digital signal is a discontinuous physical quantity, and the signal parameters are not continuously changed;

The signal generates distortion, noise and attenuation during transmission;

----in the transmission of the signal. Signals not related to the input signal due to the equipment itself, environmental disturbances, etc. during processing

----Signal-to-noise ratio (S/n) refers to the ratio of the original component to the noise, often expressed in decibels of db

The attenuation of----signal decreases with the transmission of the signal.

Advantages of digital signals:

----strong anti-jamming ability;

----long-distance transmission can still guarantee quality;

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Ethernet interface:

RJ-45

---RJ is the interface of public telecommunication network, commonly used RJ11 and RJ45;

Fiber:

--for stable but not permanent connection two or more passive components;

FC: Round with threaded fiber connector

ST: Snap-in circular fiber connector

SC: Square Fiber connector

LC: Narrow-body square fiber connector

MT-RJ: Transceiver-Integrated square fiber connector

Transport media for the physical layer:

Wired Media:

Twisted pair wire, fiber optic;

Wireless Media:

--radio, microwave, laser, infrared;

Twisted pair Wire:

Twisted-pair TP is the most widely used and relatively inexpensive transmission medium at present.

Consists of two insulated copper conductors which are wound together to reduce electrical disturbance to the adjacent line pairs;

A plurality of twisted pair cables are called twisted-pair cables;

Unshielded twisted pair UTP and shielded twisted pair stp;

Standard for twisted-pair Wire:

Type transfer Rate

CAT5 100mbps

CAT5e 100mbps

Cat6 1000mbps (1Gbps)

CAT7 10000mbps (10Gbps)

Cable:

T568A: White green green white orange blue white blue orange white brown

T568B: White orange orange white green blue white blue green white brown brown

Cable Type : Standard network cable, crossover cable, all anti-network cable

Network interface card:

--Connecting computer and network hardware;

--There is a unique network node address;

--according to the rate can be divided into 10m network card, 10/100m Adaptive network card and Gigabit network card

--according to the type of bus can be divided into ISA network card, PCI network card;

--according to the type of cable provided can be divided into RJ-45 interface card, fiber optic card, etc.

--portable computer can use PCMCIA network interface card;

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Physical layer of equipment:

Repeater:

-Can amplify the signal;

--Extend the network transmission distance;

--Contains only one input port and output port, so it can only send and receive data stream;

-Low cost;

Hubs:

--Initially a multi-port repeater that can be used for star topologies;

-can support a variety of different transmission media and data transmission rate;

-Some hubs have internal processing power;

-Replaced by the switch;

This article is from the "13391400" blog, please be sure to keep this source http://13401400.blog.51cto.com/13391400/1975720

Linux operation and maintenance of the road network basic Learning 1.2