Speaking of the role of LAN, let's first talk about the composition and characteristics of LAN, as well as its use in life:

The role of the local area network has shifted from the initial host connection, file and print services to services such as large data stream applications, Intranet, WWW browsing, and real-time audio/video transmission around the client/server model. The increasingly large and growing data streams continue to Increased network load. At the same time, due to the replacement of workgroup or department-level server solutions by enterprise-level servers, fundamental changes have taken place in the flow of data, and the status of the network backbone has been further improved. These have prompted the transition of LAN technology from bridge technology and backbone routing technology to LAN switching technology. The development of switching technology provides an unprecedented development opportunity for LAN switches, and also greatly promotes the upgrading of LAN switch technologies and products.
1 Definition of LAN
Intuitively speaking, a network is a collection of interconnected independent computers. The computers are connected through network cables, coaxial cables, optical fibers or wireless methods to share resources. Each computer is independent and has no affiliation with each other. .
By geographic location, we classify computer networks as Local Area Networks (LANs), Metropolitan Area Networks (MANs), and Wide Area Networks (WANs). The geographical extent of network coverage is a very important parameter for network classification, because networks of different sizes will use different technologies.
The so-called Local Area Network (LAN for short) refers to a computer network formed by interconnecting computers in office buildings or campuses within a range of tens of meters to several kilometers. A local area network can accommodate several to thousands of computers. According to the current characteristics of LAN, computer LAN is widely used in the networking of personal computers or workstations in campuses, factories, enterprises and institutions.
2 Features of LAN
As we all know, a LAN is a communication network that only provides communication functions. The local area network includes the functions of the physical layer and the data link layer, so the data communication equipment connected to the local area network must add high-level protocols and network software to form a computer network.
The LAN is connected to data communication equipment, including PCs, workstations, servers and other large, medium and small computers, terminal equipment and various computer peripheral equipment.
Due to the limited transmission distance of the LAN and the small coverage of the network, it has the following main characteristics: the geographical coverage of the LAN is small; the data transmission rate is high (up to 10000 Mbps); the transmission delay is small; the bit error rate is low; the price is cheap; general It is owned by a certain organization.
3 Classification by transmission medium
According to the classification of network transmission media, computer networks can be divided into two types: wired network and wireless network. A local area network usually uses a single transmission medium, such as twisted pair, which is currently popular, while a metropolitan area network and a wide area network can use multiple transmission media at the same time, such as optical fiber, coaxial thin cable, twisted pair, etc.
wired network
A wired network refers to a computer network connected by wired media such as coaxial cables, twisted pairs, and optical fibers. The use of twisted pair networking is currently the most common way of networking. It is cheap and easy to install, but it is susceptible to interference, has a lower transmission rate, and has a shorter transmission distance than coaxial cables. The optical fiber network uses optical fiber as the transmission medium, which has long transmission distance, high transmission rate and strong anti-interference, and is now developing rapidly.
Wireless networks Wireless networks use electromagnetic waves such as microwaves, infrared rays, and radios as transmission media. Because the networking method of the wireless network is flexible and convenient, and is not affected by geographical factors, it is a promising networking method. At present, many universities and companies are already using wireless networks. The development of wireless network depends on the support of wireless communication technology. At present, wireless communication systems mainly include: low-power cordless telephone system, Cellular System Simulator-CSS, digital cellular system, mobile satellite system, wireless LAN and wireless WAN, etc.
4 Classified by topology
The topology of a network refers to the geometry of the interconnection of communication lines and stations (computers or devices) in the network. According to different topologies, common computer network topologies include: bus topology, star topology, ring topology, etc.
bus topology
The bus-type structure means that all workstations and servers are connected to one bus, each workstation is equal, and there is no central node control. The information on the public bus is mostly transmitted serially in the form of baseband, and the transmission direction always starts from the node that sends the information. Diffusion to both ends, just like the information transmitted by radio stations, so it is also called broadcast computer network. Each node checks the address when receiving information to see if it matches the address of its own workstation, and if it matches, it receives the information on the Internet.
STAR TOPOLOPY
The star structure means that each workstation is connected into a network in a star manner. The network has a central node, and other nodes (workstations, servers) are directly connected to the central node. This structure centers on the central node, so it is also called a centralized network.
RING TOPOLOGY
The ring structure consists of several nodes in the network connected end to end through point-to-point links to form a closed ring. This structure makes the public transmission cable form a ring connection, and data is transmitted between nodes along one direction in the ring. Information is passed from one node to another. The signal passes through each computer, which acts like a repeater, boosting that signal and sending it on to the next computer.
CELLULAR TOPOLOGY
Cellular topology is a commonly used structure in WLAN. It is characterized by point-to-point and point-to-multipoint transmission of wireless transmission media (microwave, satellite, infrared, wireless transmitter, etc.), and is a wireless network, suitable for urban networks, campus networks, enterprise networks, and more suitable for mobile communication.
There are other types of topologies in computer networks, such as mixed bus and star, bus and ring mixed connected networks. In the local area network, the most used is the star structure.
Development Trend of Local Area Network
The future LAN will integrate a complete set of server programs, client programs, firewalls, development tools, upgrade tools, etc., to provide a comprehensive solution for enterprises to transfer to the LAN. The LAN will further strengthen the combination with E-mail and groupware, bring Web technology into E-mail and groupware, and shift from information release-based applications to information exchange and collaboration. The local area network will provide an increasingly solid security defense and guarantee system, and the local area network is also an open information platform that can integrate new applications at any time.
With the rapid development and maturity of wireless local area network (WLAN) products, many enterprises have begun to deploy wireless networks in order to improve the work efficiency of employees. Many schools, including middle schools and universities, have also begun to implement wireless networks. With the popularization of home computers and the gentrification of housing decoration, home wireless networks have also become a potential market.
The above is the composition and characteristics of the local area network. The following summarizes the functions of some local area networks:
1. Share files
In the state of stand-alone operation, the information on each computer cannot directly access each other. If everyone needs the same file on the same computer, they have to use a floppy disk to copy the file, and then copy it to everyone. on their respective computers. It is very cumbersome to do so, but with the network, this file can be shared and let everyone access it directly.
2. Shared hardware
On the network, not only files can be shared, but resource devices on computers can also be shared, such as shared printers. With the network, if your computer does not have a printer installed, if you want to print a file on your computer, you can directly use the shared printer on the network instead of copying the file to a floppy disk, and then get the printer installed. computer to print. In addition, CD-ROMs, hard disks, floppy disks, modems, scanners, etc. can be shared.
3. Shared database
With the Internet, you can store data in a database on a network server, and through specially written application programs, each user on the Internet can easily and conveniently manipulate the data on their own computers.
4. Information transmission
Computer network is an important channel for information dissemination and exchange. You can look up valuable information for you from the Internet, and you can also publish your information. You can also easily send and receive emails on the Internet, which is simple and fast.
5. Save information
In a stand-alone environment, information is stored on a single computer, it is difficult to effectively back up data, and important data will be lost due to operational errors or accidental factors. However, in a network environment, data can be backed up to a central location, and once data is lost, it can also be restored, effectively preserving information.
6. protect information
In a stand-alone environment, users only need to access the computer to manipulate the data in it. In the network environment, it provides a more secure environment for important data. It can assign a different user name and password to each network user, and give them different permissions, so that different users can be distinguished to access different information. Protect information from unauthorized users.
7. Internet function
After the LAN is connected to the Internet through a router or proxy server, LAN users can access the Internet through the proxy server, browse online resources, query information, send and receive external e-mails, etc., just like going online directly.
8. Remote access function
When users are away from the office due to business trips or at home, they can log in to the LAN through a dial-up connection. Remote users work in the same LAN environment as LAN users, but the connection speed is relatively slow.