Knowledge points of Network Management in 2014: Chapter 4]

51cto college specially sorted out "network management knowledge points for the 2014 computer soft exam" in the soft exam preparation season to help schools pass smoothly! For more software proficiency test counseling and questions, please pay attention to the 51cto college-soft exam classification!

View summary:Summary of knowledge points in network management in 2014650) This. width = 650; "alt =" popular article "src =" http://www.exam8.com/images/hot.gif "style =" padding: 0px; margin: 0px; Vertical-align: middle; Border: 0px; "/>

Chapter 4 LAN system

☆The LAN system is a communication network that connects various communication devices in the residential area.

　　4.1 bus/tree network

(1) The bus/tree topology is a multi-point medium. Multiple devices share a single data path and only one device can send data at the same time.

(2) In the multi-point media transmission of the bus/tree topology, there are two issues that need special consideration:

A. Determine which station on the media can send the MAC Method of data;

B. Solve the Problem of signal balance.

(3) In order to meet the requirements of data transmission in Multi-Point media, the transmitter signal is not too weak, and the signal transmission requirements are not met in signal attenuation; or

Excessive signals lead to Circuit overload and generate harmonic and other false signals. Therefore, for systems with N sites, to meet the preceding requirements, consider

N * (n-1)/Two arrays.

(4) Two transmission technologies: baseband transmission (full-frequency transmission of two-way digital signal transmission) and broadband transmission (Radio modulation of analog signal)

, One-way transmission using the OFDM multiplexing technology)

4.1.1 baseband system

(1) The maximum transmission distance of the baseband transmission technology is 500 m, the maximum number of sites is 100, the data rate can reach 10 Mbps, And the repeater can be connected.

Connect each segment of the bus. & N bsp;

(2) five components of Ethernet:

A. Transceiver

Receives or sends signals, listens to signals on the bus, detects signal conflicts on the bus, and isolates the station and bus cables.

B. transceiver Cable

It consists of four pairs of cables connected to the Controller and transceiver. Its function is to transmit data and control signals to provide power to the transceiver.

C. 50 ohm coaxial cable

D. 50 ohm Terminal

Absorbs signals to prevent reflection.

E. controller.

(3) Three Ethernet structures of different sizes (see P49, figure 4.5)

(4) The baseband bus system can also use low-cost but low-performance twisted pair wires as transmission lines, which are composed of three parts: twisted pair buses and terminals.

And controller interfaces. The maximum length is 1 km, and the maximum data rate is 1 Mb/s. The number of connected sites reaches dozens.

4.1.2 broadband system

(1) broadband transmission technology is a one-way transmission technology, usually using a 75 ohm finite television cable as the transmission medium. And use

Analog signal transmission.

(2) Two Different broadband structures:

A. The single-cable structure uses different transmission frequencies to send and receive signals. The end is an active frequency converter;

B. The dual-cable structure uses the same frequency to send and receive signals in different channels.

C. disadvantages of a single cable structure: the use of complex components; the use of a frequency splitter.

(3) three standard splitters in a single cable system and their low and high frequency band ranges

A. subforking, with a low frequency band of 5 MHz ~ 30 MHz, the high frequency band is 54mhz ~ 300 MHz

B. Center forking. The low frequency band is 5 MHz ~ 116 MHz, with a high frequency band of MHz ~ 300 (400) MHz

C. High-score forks, with a low frequency band of 5 MHz ~ 174 MHz, the high-frequency band is 232mhz ~ 400 MHz

(4) The broadband system consists of five parts:

A. Cable:

A. trunk cable with a diameter of 0.75 inch ~ 1.0 inch, attenuation at MHz to 0.7db ~ per foot ~ 1.2db, up to dozens of kilometers;

B. distribution cable: the diameter is 0.4 inch ~ 0.5 inch, attenuation of 100 feet ~ 2.0db for short distance and Branch cables;

C. cables connecting to the LAN: the diameter is 0.25 inch 1.0 inch, and the attenuation is 4 dB to 100 feet ~ 6db.

B. Terminal Matching

C. amplifier: used to compensate for the attenuation of cables, which is not required for low-frequency systems. For a single-cable broadband system, the amplifier must be bidirectional

.

D. and foragger: The function is to divide an input into two outputs, or combine two inputs into one output;

E. Controller

4.1.3 comparison of baseband and broadband systems

(1) baseband system

Advantages: modem is not required and the price is low. The structure and technology are simple and easy to install;

Disadvantages: only one channel; limited capacity; limited distance;

(2) broadband system

Advantages: large capacity, multiple communication modes, flexible structure, large coverage, and mature CATV.

Disadvantages: modem is required, which is expensive; installation and maintenance are complicated; transmission delay is doubled.

4.1.4 IEEE 802.3 Local Area Network

(1) IEEE 802.3 is a LAN that supports the CSMA/CD algorithm. The most common baseband IEEE 802.3 lan has four types: & n bsp;

A. 10base5 (backbone network, crude cable)

B. 10base2 (cheap, thin cable)

C. 10base-t (easy to maintain)

D. 10base-f (optical fiber network, suitable for interconnection between buildings)

E. See P52-P53 for detailed graphics

　　4.2 Ring Network

4.2.1 working principle of the Ring Network

(1) The repeater provides three basic functions of the Ring Network: inserting data into the ring, receiving data, and deleting data from the ring.

(2) how to delete a message in the ring:

A. After the target station receives the message, it removes the message from the ring;

B. The destination site receives a greeting and the message is still in the ring. The message is not deleted until the sending site is returned. This method has three advantages:

A. Compared with the first method, the latency generated to identify an address can be reduced to one delay;

B. The receiving site changes a flag of the message and sends it back to the sending site for response;

C. Multi-Point broadcast is allowed.

(3) Four statuses of relay in the Environment Network

A. Listener status:

B. Sending status

C. receiving status

D. Bypass status

4.2.2 labeling Media Access Control

(1) three different labeling schemes

A. The number of packets that can be sent after the site receives the control mark;

B. control whether the situation and position of the tag are included in the information frame or outside the information frame;

C. When will the sender site release the tag to the next site.

(2) Three labeled Ring Networks: DCs, ESM, and prime

(3) The biggest advantage of the ring topology is that the signal transmitted is regenerated at each node due to the point-to-point communication link. Therefore,

The transfer error can be minimized, and the entire network transmission distance can be long. The Ring Structure of point-to-point communication can use optical fiber as the transmission medium,

It has the advantages of high speed and strong anti-interference ability. The biggest drawback is reliability.

　　4.3 FDDI (Optical Fiber Distribution Data Interface) Network

(1) FDDI network performance indicators

It is a high-performance Optical Fiber labeling ring LAN with a running speed of 100 Mbps, a maximum distance of 200 km, and a maximum of 1000 sites.

Point.

(2) FDDI contains two optical fiber rings, which are transmitted clockwise and counterclockwise. If either of the Rings fails

One can be used as a backup. If two rings fail at the same point, the two rings can be merged into a single ring, and the length is almost doubled.

It has the function of adding two rings or bypassing sites.

(3) FDDI defines sites A and B. A can connect to two rings, and B can only connect to one of them.

(4) FDDI uses the 4b/5b encoding technology. Compared with Manchester Coding, this encoding method does not have the advantage of clock self-synchronization.

The cost of components is reduced.

　　4.4 Fast Ethernet

4.4.1 Fast Ethernet

(1) Comparison Between Fast Ethernet and Ethernet

High speed and low cost (for more information, see P58)

(2) Three Types of transmission receivers supported by Fast Ethernet

Two types are used for twisted pair wires (100base-t4 and 100base-tx), and one type is used for optical fiber (100base-fx)

(3) Glossary

UTP --------- unshielded twisted pair wires r> STP ---------- shielded twisted pair wires

4.4.2 Fast Ethernet products

(1) Fast Ethernet products are divided into adapters and hub

A. Adapter

The structure is simple. One side is a bus structure that transmits data to a host, repeater, or hub. The other side is connected to the selected media.

B. Hub

A) Repeater of the Sharing Mechanism

B) switch value Switch

4.4.3 Fast Ethernet Technology

(1) Two main application forms of exchange technology are fold-over backbone network and high-speed server connection.

(2) to support the gradual downward transition of switches, manufacturers that produce fast Ethernet have developed the following features:

A. More ports;

B. A larger buffer;

C. Better address filtering;

D. management tools;

Recommended high-quality articles:

Preparing for the 2014 soft exam! Recommendation of high-quality video tutorials (Comprehensive review + experience sharing + pre-test Sprint)

Testing Questions of the soft exam over the years (Network Management + programmers + Information Technology + expert prediction questions)

Soft exam intermediate exam self-testing over the years and the latest video summary (network workers + software + database + expert prediction questions)

Exercise questions and answers for the 2014 soft exam Network Administrator examination [summary]

For online soft test video tutorials, click:

Http://edu.51cto.com/course/courseList/id-44.html

650) This. width = 650; "src =" http://s3.51cto.com/wyfs02/M02/3D/9F/wKioL1PE_n3z629yAACXIHScsJM092.jpg "alt =" wkiol1pe_n3z629yaacxihscsjm092.jpg "style =" padding: 0px; margin: 0px; Vertical-align: Top; Border: none; "/>

This article is from the "51cto college official blog" blog, please be sure to keep this source http://51edu.blog.51cto.com/8899635/1539295