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Local area network



Introduction

The local area network is naturally a regional network formed in a local area. It is characterized by a limited distribution area, which can be large or small, as large as between a building and adjacent buildings The connection is small enough to be a connection between offices. Compared with other networks, the local area network itself has faster transmission speed, more stable performance, simple framework, and closedness. This is why many organizations choose. The composition of the local area network itself is roughly composed of computer equipment, network connection equipment, and network transmission media. Computer equipment includes servers and workstations. Network connection equipment includes network cards, hubs, and switches. The network transmission medium is simply The network cable is composed of three major components: coaxial cable, twisted pair and optical cable.

A local area network is a private network, usually in 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, enabling them to share resources and exchange information. When local area networks are used in companies, they are called corporate networks.

The local area network connects various computers, external devices and databases in a certain area to form a computer communication network, and connects with other local local area networks or databases through dedicated data lines to form a larger-scale information processing system. The local area network connects network servers, network workstations, printers and other network interconnection equipment through network transmission media to realize system management of files, share application software, office equipment, and send communication services such as work schedules. The local area network is a closed network, which can prevent information leakage and external network virus attacks to a certain extent, and has high security. However, once hacker attacks and other incidents occur, it is very likely that the entire local area network will be paralyzed, and all work within the network will not be possible. And even leaked a large number of company secrets, causing serious damage to the company’s career development. In 2017, the State issued the "Cyber ​​Security Law of the People's Republic of China", which was formally implemented on June 1. It made clear provisions on network security and information security from a legal perspective, and put forward corresponding requirements for network operators and users. Improve the security of network usage.

Wireless Local Area Network

Wireless local area network, referred to as WLAN, is a computer network formed by connecting computers in company buildings or shopping malls within a few kilometers of each other, a wireless local area network Can support the use of several to several thousand computers. Nowadays, there are more and more applications of wireless local area network. Now campuses, shopping malls, companies and high-speed rail are all in use. The application of wireless local area network has brought great help to our lives and work, not only can quickly transmit the information that people need, but also make people's connections to the Internet more convenient and faster.

Wireless local area networks have been very popular recently, especially in homes, old office buildings, canteens, and other places where cable installation is too troublesome. In these systems, each computer has a wireless modem and an antenna to communicate with other computers. In most cases, each computer communicates with a device installed on the ceiling. This device becomes an access point, a wireless router or a base station. It is mainly responsible for relaying data packets between wireless computers, and it is also responsible for relaying data packets between wireless computers and the Internet.

A standard for wireless local area networks called IEEE 802.11, commonly known as WIFI, has been widely used.

The establishment of a local area network

Establishment goals

Wireless local area networks can transmit audio, video, and text. Many companies and campuses are now using wireless LAN. Not only can improve the efficiency of the office, but also quickly transmit information. The establishment, maintenance and management of the wireless local area network are very simple, and they are rarely disturbed. It can also save network expenses. There are two main standards for the establishment of wireless local area networks: First, flexibility and independence are strong. The placement of the components of the wireless local area network and related equipment is not subject to any space restrictions. After the user is connected to the wireless LAN. You can use your own mobile phone or laptop to connect to the system network, and it will not affect the normal use of the wireless LAN. Second, the scalability and advancement are good. The structure of the wireless local area network is very simple. It will be updated with the development of current technology and information technology, improve performance and upgrade the system, so as to make information transmission faster.

Wireless local area network application

Application in daily life

There are many implementation protocols of wireless local area network. It belongs to Wi-Fi, only one router is needed, that is, all devices with wireless functions can form a wireless local area network, which is very convenient and flexible. At present, most wireless local area networks are based on the IEEE 802.11 standard, and most wireless local area networks under this standard use 2.4 GHz or 5 GHz radio frequencies. A family generally only needs one router to form a small wireless local area network. A medium-sized enterprise can form a medium-sized wireless local area network covering the entire enterprise through multiple routers and switches, while a large-scale enterprise needs to pass some centralized wireless local area network. Controller to build a powerful large-scale wireless local area network with wide coverage.

Applications in different industries

The application of wireless local area networks in hospitals is of great help to medical work. Doctors need Check the patient's case at any time, and then check the patient's condition at that time under the doctor's order. After using the wireless network, the doctor can carry a tablet computer that can be connected to the wireless network during rounds, check the patient's case at any time, and record the patient's condition at the time. The wireless local area network can not only provide Internet service for doctors and patients, but also the patients' family members and visitors in the hospital can enjoy the speed and convenience of wireless network. The use of wireless network location services in hospital applications is also very helpful, doctors can locate the patient's location in time. When patients are in an emergency, they can get prompt treatment. In addition, the use of wireless positioning can also know the specific location of the medicine at any time, and the relevant personnel can be more precise and convenient in managing the inventory of the medicine.

There are many branches in the financial industry. It is recommended to adopt an AC+ thin AP networking architecture to facilitate unified management of the WLAN network. In the early stage of network deployment, cooperation with operators may be considered to reduce construction investment. The deployment of APs needs to be adjusted according to the actual environment, such as area, floor, etc., and the deployment scope should cover the e-banking service area, business hall, customer waiting area, VIP customer reception area, wealth management area, etc. All customers have the right to arrive At the same time, the wireless controller AC is deployed in the core computer room, and the wireless controller is deployed on the operator’s aggregation switch or core equipment through the N*GE link side-by-side or online deployment.

Wired LAN

Wired LAN uses a variety of different transmission technologies. Most of them use copper wire as the transmission medium, but some also use optical fiber. The size of the local area network is limited, which means that the worst-case transmission time is also bounded and can be known in advance. Understanding these boundaries helps the design of network protocols. Under normal circumstances, the operating speed of a wired LAN is between 100Mbps and 1Gbps, the delay is very low (microsecond or nanosecond level), and errors rarely occur. Newer LANs can work at speeds up to 10Gbps. Compared with wireless networks, wired LANs surpass them in all aspects of performance.

Many wired LAN topologies are based on point-to-point links. IEEE 802.3, commonly known as Ethernet, is by far the most common type of wired LAN. In switched Ethernet, each computer runs in the manner prescribed by the Ethernet protocol and is connected to a box through a point-to-point link. This box is called a switch. This is the origin of the name of the switched Ethernet.

Features and classifications

Local area networks are generally owned by a department or unit. Network construction, maintenance, and expansion are relatively easy, and the system is highly flexible. Its main features are:

  1. The geographical coverage is small, and it is only connected in a relatively independent local area, such as a cluster of buildings.

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

  3. The communication delay time is short and the reliability is high

  4. The local area network can support multiple transmission media

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, tree type, hybrid type, etc.; if according to the transmission medium used The classification of access control methods can be divided into Ethernet, token ring network, FDDI network and wireless local area network. Among them, Ethernet is currently the most commonly used local area network technology.

Topology structure

Local area network is usually a network system distributed in a limited geographic area, and the geographic area involved is usually only a few kilometers. The LAN is very specific and has a relatively stable and standardized topology. The common local area network topology structure is as follows:

Star type

The network of this structure is connected by the workstations in a star manner, and each node device in the network is centered The node is the center and is connected to the central node through a connecting line. If a workstation needs to transmit data, it must first pass through the central node. Because in the network system of this structure, the central node is the control center, and the communication between any two nodes only needs two steps at most, so the transmission speed is fast, and the network configuration is simple, the network is easy to build, and it is easy to control and manage. . However, this kind of network system has low network reliability and poor network sharing capabilities, and once the central node fails, the entire network will be paralyzed.

Tree type

The tree structure network is a natural hierarchical structure, also known as a hierarchical centralized network. It is characterized by low network cost and relatively simple structure. In the network, there is no loop between any two nodes, each link supports two-way transmission, and the nodes in the network are convenient and flexible to expand, and it is relatively simple to find the link path.

But in this structured network system, except for the leaf node and its connected links, failure of any workstation or link will affect the normal operation of the entire network system.

Bus type

The bus-shaped structure network connects each node device with a bus. All node workstations in the network transmit information through the bus. The communication connection as the bus can be a coaxial cable, a twisted pair, or a flat cable. In the bus structure, the load energy of the bus, which is necessary for data communication, is limited, which is determined by the physical performance of the communication medium itself. Therefore, the number of workstation nodes in a bus structure network is limited. If the number of workstation nodes exceeds the bus load energy, it is necessary to extend the length of the bus and add a considerable number of additional switching components to make the bus load meet the capacity requirements . The bus-shaped structure network is simple, flexible, and expandable. Therefore, it is very convenient to insert and remove the node equipment. In addition, the bus structure network has high reliability, fast response between network nodes, strong sharing of resources, low equipment input, low cost, and easy installation and use. When a workstation node fails, it will have little impact on the entire network system. Therefore, the bus structure network is the most commonly used network. But because all workstations communicate through a common bus, real-time performance is poor.

Ring type

The ring structure is a closed ring structure network in which the nodes in the network are connected by a communication link connected end to end. The structure of the ring structure network is also relatively simple, and the positions of the workstations in the system are equal. The communication equipment and lines in the system are relatively economical.

In the network, information flows in a fixed direction, and there is only one path between two workstation nodes. There is no channel selection problem in the system; a failure of a node will cause physical paralysis. In the ring network, because the loop is closed, it is not easy to expand, the system response delay is long, and the information transmission efficiency is relatively low.

Security issues

Servers have weaker protection capabilities

Compared with other networks, local area networks have faster information transmission and relatively simple transmission methods. If A computer in the local area network is invaded by a virus, and the virus will spread to all computers through the information in the local area network. Although there are some anti-virus software installed in some LANs, because the software patch update is not in place, or some computers do not have anti-virus software installed, the virus will use the vulnerabilities of the protection software to carry out network attacks, which will cause the operation of the LAN system to be paralyzed and cause the leakage of user information. , Theft of user property and other issues.

There are risks in network boundary access

The access risks in the LAN network boundary mainly include routing damage, eavesdropping of user information, unauthorized access and other network equipment attacks , And the spread of certain viruses. For the operation of the local area network, there are mainly denial of service attacks, which cause the host to crash and the network service to be suspended. However, 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 capacity or lack of memory, resulting in business interruption or service quality degradation of key equipment of the business server.

The user’s security awareness is weak

When local area network users use the network for data transmission, they sometimes use external storage devices, but users do not have the habit of detecting the security of external devices. Connect directly to the network for use. This causes external data and viruses to enter the local area network together. Through the spread of information in the local area network, the virus spreads in the local area network, resulting in the intrusion of the local area network virus. In addition, some users accidentally click on some pop-up windows or download virus-disguised software during website browsing, which can also cause computer poisoning, causing user information to leak, and threatening the safety of the entire local area network.

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