LAN, network type,CoverageIt is generally within a radius of several thousand meters. Its features such as convenient installation, cost saving, and easy expansion make it easy toofficeIt is widely used internally.LAN can realizefile management, application software sharingPrinter SharingAnd other functions, through the maintenance of the LANnetwork security, which can effectively protect data security and ensure the normal and stable operation of the LAN network.[1]
LAN is naturallyLocal areasA regional network formed is characterized by its limited distribution area, which can be large or small, from the connection between a building and adjacent buildings to the connection between offices.The LAN itself is relative to other networkstransmission speed Faster, more stable performance, simple framework, andClosureThis is also the reason why many institutions choose.The LAN itself consists of computer equipmentNetwork connection device、Network transmission medium3. Most of them are composed of computer equipment including server and workstation, and network connection equipment including network cardHubSwitch, network transmission medium is simply network cable, which is composed ofCoaxial cable、Twisted pairAnd optical cable.[2]
LAN connects various computers, external devices and databases in a certain areaComputer communication network, connect with other local area networks or databases through special data lines, and form a larger range ofinformation processing system 。The LAN willNetwork server、network station, printer, etcNetwork interconnection equipmentConnect to realize the systemManage files, sharing application softwareoffice equipment , sending workScheduleAnd other communication services.The LAN is a closed network, which can prevent information leakage and external network virus attacks to a certain extent, and has high securityHacker attackIt is very likely that the whole LAN will be paralyzed, all work in the network will not be carried out, and even a large number of company secrets will be leaked, which will cause heavy damage to the company's career development.In 2017, the People's Republic of China issuednetwork securityLaw of the People's Republic of China, which was officially implemented on June 1, provides a legal perspective on network security andinformation safetyHas made clear provisions onnetwork operators Users have put forward corresponding requirements to improve the security of network use.[4]
Wireless LAN
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Wireless LAN, or WLAN for short, is formed by connecting computers in company buildings or shopping malls within several thousand meterscomputer networkOne WLAN can support several to thousands of computers.NowApplication of WLANMore and more.Today's campus, shopping malls, companies and high-speed railways are all in use.The application of WLAN has brought great help to our life and work. It not only can quickly transmit the information that people need, but also can make people's contact with the Internet faster and more convenient.[5]
WLAN has been very popular recently, especially in homes, old office buildings, canteens and other places where it is too troublesome to install cables.In these systems, each computer has a wirelessModemAnd an antenna for communication with otherelectronic communication。In most cases, each computer is installed withceilingA device on the communicates.This device becomesAccess point、wireless routerOr the base station, which is mainly responsible forrelayData packets between wireless computers are also responsible for relaying data packets between wireless computers and the Internet.[3]
One standard of WLAN is calledIEEE 802.11, commonly known asWIFI, has been widely used.[3]
Establishment of LAN
Organization goal
WLAN can transmit audio, video and text.Now many companies and campuses are using WLAN.It can not only improve the efficiency of office work, but also quickly transmit information.The establishment, maintenance and management of WLAN are very simple and rarely interfered with.It can also save the cost of network.There are two main standards for the establishment of WLAN: first, strong flexibility and independence.The placement of WLAN components and related equipment is not limited by any space.After the user is connected to the WLAN.You can use your own mobile phone or laptop to connect to the system network, without affecting the normal use of wireless LAN.Second, scalability andprogressivenessOK.The structure of WLAN is very simple.It will follow the current technologyDevelopment of information technologyTo update, improve performance and upgrade the systeminformation transmissionFaster.[5]
Wireless LAN application
Application in daily life
There are many implementation protocols of WLAN, among which the most widely used one isWi-FiOnly one router is needed to make all devices with wireless functions form a wireless LAN, which is very convenient and flexible.At present, most wireless LANs are based on the IEEE802.11 standard, and most wireless LANs under this standard use 2.4GHz or 5GHz RF.Households generally need only one router to build small wireless local area networks. Medium sized enterprises can build medium-sized wireless local area networks covering the entire enterprise through multiple routers and switches, while large enterprises need to build some centralized wireless local area networksWireless controllerTo build a powerfulCoverageA large wireless local area network.[6]
Application in different industries
The application of wireless LAN in hospitals is very helpful for medical work. Doctors need to check patients' cases at any time during ward rounds, and then check patients' conditions at that timeDoctor's order。After using the wireless network, doctors can carry the wireless networktablet PC, check the patient's case at any time, and record the patient's condition at that time.Wireless LAN can not only provide doctors and patients with Internet access services, but also provide patients' families and visitors in the hospital with fast and convenient wireless network.WirelessLocation serviceThe application in hospitals is also very helpful, and doctors can locate patients in time.When patients have an emergency, they can get timely treatment.In addition, usingWireless locationThe specific location of drugs can also be known at any time, so that relevant personnel can manage the inventory of drugs more accurately and conveniently.[5]
There are many outlets in the financial industry, AC is recommended+Thin APTo facilitate WLAN networkunified management 。In the early stage of network deployment, cooperation with operators can be considered to reduceConstruction investment。APThe deployment of shall be adjusted according to the actual environment, such as area, floor, etc. The deployment scope shall coverE-bankingservice area, business hall, customer waiting areaVIPCustomer reception area, wealth management area and other areas that all customers have the right to reach. At the same time, the wireless controller AC is deployed in the core machine room, and the wireless controller is attached by the N * GE link or deployed online on the operator convergence switch or core equipment.[7]
Wired LAN
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Wired LANVariousTransmission technology。Most of them use copper wire as transmission medium, but some use optical fiber.The size of the LAN is limited, which means that the transmission time in the worst case is bounded and can be known in advance.Understanding these boundaries helpsNetwork ProtocolDesign.In general, wired LANrunning speed Very low latency between 100Mbps and 1Gbps（MicrosecondOr nanosecond), and errors rarely occur.Newer LANs can work at speeds up to 10Gbps.andwireless networkIn contrast, wired LANs outperform them in all aspects of performance.[3]
Many wired LANtopological structure It is based on the point-to-point link.Commonly known as EthernetIEEE 802.3It is by far the most common kind of wired LAN.staySwitched EthernetEach computer inEthernet protocolThe specified mode of operation is connected to a box through a point-to-point link. This box is called a switch, which is the origin of the name of switched Ethernet.[3]
Features and classification
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The LAN is generally owned by a department or unit, which is easy to build, maintain and expand, and has high system flexibility.Its main characteristics are:
one
It covers a small geographical area and is only connected within a relatively independent local area, such as one or a concentrated building group.
two
Use specially laid transmission media for networking, with high data transmission rate (10Mb/s~10Gb/s)
LAN is usually distributed in a limited geographical areaNetwork systemGenerally, it covers only a few kilometers.The LAN has strong specificity, and is relatively stable and standardtopological structure 。Common LAN topologies are as follows:
Star type
Star structure
The network with this structure is connected by workstations in a star mode. Each node equipment in the network is connected to the central node through the connection line with the central node as the center. If a workstation needs to transmit data, it must first pass through the central node.In the network system with this structure, the central node iscontrol centerThe communication between any two nodes only needs two steps at most. Therefore, the transmission speed is fast, and the network configuration is simple, easy to build, easy to control and manage.But this network system has low reliability,Network sharingThe capability is poor, and once the central node fails, the whole network will be paralyzed.
Treelike
tree structureNetwork is naturalHierarchy, also known as gradedCentralized network。Its characteristics are low network cost and simple structure.In the network, there is no loop between any two nodes, and each link supportsBidirectional transmissionIn addition, the nodes in the network are easy to expand and flexible, and it is relatively simple to find the link path.
But in this kind of network system, exceptLeaf nodeThe failure of any workstation or link will affect the normal operation of the entire network system.
Bus type
Bus structure
Bus structureThe network is to connect each node device with a bus.All node workstations in the network transmit information through the bus.The communication line as the bus can beCoaxial cable、Twisted pair, orFlat cable。stayBus structureMedium asdata communicationThe load energy of the required bus is limited, which is determined byCommunication mediaOf itselfphysical property Determined.Therefore, the number of workstation nodes in the bus structure network is limited. If the number of workstation nodes exceeds the bus load energy, it is necessary to extend the bus length and add a considerable number of additional switching components to make the bus load meet the capacity requirements.The bus structure network is simple and flexible with good expandability.Therefore, it is very convenient to insert and disassemble node equipment.In addition, the bus structure network has high reliabilitynetwork nodeIt has fast response speed, strong ability to share resources, less equipment investment, low cost, and convenient installation and use. When a workstation node fails, it has little impact on the entire network system.Therefore, the bus structure network is the most commonly used network.However, since all workstations communicate through a common bus,Real timePoor.
Annular type
Annular structureThe nodes in the network are connected end-to-endcommunication linkA closed ring structure network connected together.The structure of the ring structure network is also relatively simple, and the status of each workstation in the system is equal.The communication equipment and lines in the system are relatively economical.
The information in the network has a fixed direction one-way flow, and there is only one channel between two workstation nodes, so there is no channel selection problem in the system;The failure of a node will lead to physical paralysis.In the ring network, because the ring is closed, it is not easy to expand,system response Long delay and informationtransmission efficiency Relatively low.
safety problem
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Weak server protection capability
Compared with other networks, LANpropagation velocityIt is fast and the transmission mode is relatively simple. If a computer in the LAN is affected byVirusesThe virus will pass through theInformation disseminationSpread to all computers.Although there are some LANsChina CouncilInstall someanti-virus softwareHowever, because the software patches are not updated properly, or some computers do not have anti-virus software installed, the virus will take advantage of the vulnerability of the protection softwarenetwork attack , resulting in the paralysis of the LAN system and usersInformation leakage, stealing user property, etc.[8]
Risk of network boundary access
On LANNetwork boundaryThe existing access risks mainly include route destruction, user information eavesdropping, unauthorized access, etcnetwork equipment Attack, and the spread of some viruses.In the operation of LANDenial of service attackMore, which causes the host to crashnetwork servicePause, etc.A large amount of garbage generated after a large number of SYNFlood, ACKFlooding, UDP Flood and other attacksdata packet, making the target partyCPUFull load operation orinsufficient memory, causingKey equipmentBusiness interruption orService qualityDown.[8]
The user's security awareness is weak
LAN usersUsing the networkdata transmissionSometimes externalstorage device, but the user did notperipheralThe habit of safety inspection, butDirect connectionNetwork.causeExternal dataIt enters the LAN together with the virus, and spreads the virus in the LAN through the spread of information in the LAN, resulting in the LANVirus invasionThe situation.In addition, some users accidentally click on some pop-up windows or download virus disguised software during the process of browsing the website, which will also lead to computer poisoning, user information leakage and threaten the security of the entire LAN.[8]
