What is LAN

A local area network is a regional network formed in a local area. Its characteristic is that the distribution area is limited and can be large or small. It can be as large as the connection between a building and an adjacent building, or as small as an office. connections between. Local area networks are widely used to connect personal computers and consumer electronic devices, allowing them to share resources and exchange information. When LANs are used in companies, they are called enterprise networks. Compared with other networks, the LAN itself has faster transmission speed, more stable performance, simple framework, and closed nature, which is why many organizations choose it.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

What is a local area network?

# A local area network is a regional network formed in a local area. Its characteristic is that the distribution area is limited and can be large or small. It can be as large as the connection between a building and an adjacent building, or as small as the connection between offices.

A LAN is a private network, typically within or near a building, such as a home, office, or factory. Local area networks are widely used to connect personal computers and consumer electronic devices, allowing them to share resources and exchange information. When LANs are used in companies, they are called enterprise networks.

Compared with other networks, the LAN itself has faster transmission speed, more stable performance, simple framework, and closed nature, which is why many organizations choose it.

The local area network itself is generally composed of three major parts: computer equipment, network connection equipment, and network transmission media. Among them, computer equipment includes servers and workstations, and network connection equipment includes network cards, hubs, switches, and networks. The transmission medium is simply a network cable, which is composed of three major components: coaxial cable, twisted pair and optical cable.

A local area network connects various computers, external devices and databases in a certain area to form a computer communication network, and connects to local area networks or databases in other places through dedicated data lines to form a larger information processing system.

LAN connects network servers, network workstations, printers and other network interconnection devices through network transmission media to realize system management files, share application software, office equipment, send work schedules and 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 security. However, once an incident such as a hacker attack occurs, it is very likely to cause the entire LAN to be paralyzed. All work within the network cannot be carried out, and a large number of company secrets may even be leaked, causing serious damage to the company's business development.

Characteristics of local area networks

Local area networks are generally owned by one department or unit. They are easier to build, maintain and expand, and have high system flexibility. Its main characteristics are:

• covers a small geographical range and is only connected within a relatively independent local range, such as one or a concentrated building group.

• Use specially laid transmission media for networking, with high data transmission rate (10Mb/s~10Gb/s)

• Short communication delay time , higher reliability

• LAN can support a variety of transmission media

Types of LAN

There are many types of local area networks. If classified according to the transmission medium used by the network, it can be divided into wired network and wireless network; if classified according to the network topology, it can be divided into bus type, star type, ring type, and tree type. Type, mixed type, etc.; if classified according to the access control method used in the transmission medium, it can be divided into Ethernet, Token Ring network, FDDI network and wireless LAN, etc. Among them, Ethernet is the most commonly used LAN technology currently.

Security issues

• The server protection capability is weak

  Compared with other networks, LAN The information spreads quickly and the transmission method is relatively simple. If a computer in the LAN is invaded by a virus, the virus will spread to all computers through the information in the LAN. Although some anti-virus software is installed in some LANs, because the software patches are not updated in place, or some computers do not have anti-virus software installed, viruses will exploit vulnerabilities in the protection software to carry out network attacks, resulting in paralysis of the LAN system and leakage of user information. , stealing user property and other issues.

• There are risks in network boundary access

  The access risks that exist at the LAN network boundary mainly include the destruction of routes, the eavesdropping of user information, and unauthorized access. and other network device attacks, as well as the spread of certain viruses, etc. For the operation of local area networks, there are mainly denial of service attacks, which cause host crashes, network service suspension, etc. A large number of junk data packets generated after a large number of SYNFlood, ACKFlooding, UDPFlood and other attacks make the CPU of the attacked party run at full load or the memory is insufficient, causing business interruption of key equipment of the business server or a decline in service quality.

• User’s security awareness is weak

  When LAN users use the network for data transmission, they sometimes use external storage devices. However, users do not have the habit of security detection of external devices, but directly connect to the network for use. This causes external data and viruses to enter the LAN together. Through the spread of information in the LAN, the virus spreads in the LAN, thus causing LAN virus invasion. In addition, some users accidentally click on some pop-up windows or download virus-disguised software while browsing the website, which can also lead to computer poisoning, leakage of user information, and threat to the security of the entire local area network.

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