1, local area network (LAN): generally confined to a very small area, less than 10km, generally wired connection. Local area network is generally owned by a department or unit, so it is easy to build, maintain and expand the network, and the system has high flexibility. Its main features are:
(1) covers a very small geographical area and is only connected in a relatively independent local area, such as a building or a concentrated building complex.
(2) Using specially paved transmission media for networking, the data transmission rate is high (10MB/s ~ 10GB/s).
(3) Short communication delay time and high reliability.
(4) LAN can support a variety of transmission media.
There are many types of LAN, which can be divided into wired network and wireless network according to the transmission medium used in the network. According to the classification of network topology, it can be divided into bus type, star type, ring type, tree type and hybrid type. According to the access control mode adopted by transmission media, it can be divided into Ethernet, token ring network, FDDI network and wireless local area network. Among them, Ethernet is the most widely used LAN technology at present.
2. Metropolitan Area Network (MAN): The scale is limited to one city, with an area of 10 ~ 100 km.
(1) transmission rate
Broadband MAN adopts large-capacity packet Over SDH transmission technology to provide transmission guarantee for high-speed routing and switching. With the wide application of Gigabit Ethernet technology in broadband metropolitan area network, the ports of backbone routers can be extended to distribution layer switches at high speed and effectively. Optical fiber and network cable to the user's desktop, so that the data transmission speed can reach 100M and 1000 m.
(2) Less investment and simplicity
Broadband MAN client devices are cheap and popular, and routers, hubs and even ordinary network cards can be used. Users only need to connect the optical fiber and network cable correctly and simply configure the relevant parameters of the user network card or router to access the broadband metropolitan area network.
Individual users only need to install an Ethernet card on their own computers and plug the interface of broadband metropolitan area network into the network card to connect to the network. The installation process is the same as the previous telephone, except that the network cable replaces the telephone line and the computer replaces the telephone.
(3) Advanced technology
Technically, it provides users with a highly secure service guarantee. Broadband MAN provides the second layer VLAN isolation in the network, which ensures the security. Because of the security of VLAN, only computers in the user's LAN can access each other, and computers in the non-user LAN cannot access the user's computer through abnormal channels.
If you want to access from outside the network, you must go through the normal routing and security system. Therefore, it is impossible for hackers to use the underlying vulnerabilities to destroy. Ordinary users with virtual dialing access the Internet through broadband access server, and can access the Internet only after verifying their account numbers and passwords. Users can easily control the time and place of surfing the Internet by themselves.
3. Wide Area Network (WAN): The network crosses national boundaries, continental boundaries and even the global scope. The transmission medium of WAN mainly uses telephone line or optical fiber, and ISP connects enterprises. These lines are embedded under the road by ISP. Because the project is huge, it is not easy to maintain and the bandwidth can be guaranteed, so the cost will be more expensive.
Generally speaking, the Internet belongs to the public wide area network. The cost of public network WAN will be lower, which is a cheaper online environment. But compared with WAN, there is no way to manage the bandwidth, and the public network system can't guarantee any bandwidth.
Extended data:
Main uses of metropolitan area network:
1, Internet TV
Net TV)-Breaking through the traditional TV mode, transcending the limitations of time and space, and realizing TV viewing with unlimited channels on the Internet. Watching TV programs directly from the internet through a web browser overcomes the disadvantages of the existing TV channels being restricted by various factors such as region and climate, and is conducive to the production and playback of a new type of interactive TV series "network TV series".
2. Telemedicine
Telemedicine-Using advanced digital processing technology and broadband communication technology, medical personnel can diagnose and treat patients hundreds or thousands of kilometers away. Telemedicine is a new medical method developed with the rise of broadband multimedia communication.
Conference call-you don't have to travel or go to different places for meetings. In the video conference system on the high-speed information network, the feeling of "God never shuts one door but he opens another" has been perfectly interpreted.
3. Distance education
Distance education-fundamentally overcomes the shortcomings of one-way broadcasting based on TV technology, text query based on web pages and meeting TV which is too expensive to enter the home, and integrates multimedia information such as images, texts and sounds by using the latest products and technologies of broadband network.
Entering ordinary families, schools, enterprises and institutions in an interactive way, students can watch teaching programs at home through broadband networks and interact with teachers in real time; You can check information online, assign homework, hand in homework and answer questions by email. If you are absent from class, you can search the course database and play the teacher's lecture video in VOD mode.
4. Remote monitoring
Remote monitoring (webcam)-Monitor remote systems or other things, and authorize users to freely perform lens rotation, focusing and other operations through the Web to realize real-time monitoring and management functions.
The monitoring system adopts digital monitoring mode. Digital monitoring mode is well combined with computer network to give full play to the bandwidth advantage of broadband metropolitan area network. This is the development trend of monitoring system in the future.
5. Trading system
Family securities trading system-online stock trading in the form of a large securities room can be carried out interactively at home. Not only can you consult the Shenzhen and Shanghai stock markets in real time to obtain comprehensive and timely financial information, but you can also use various analytical tools for real-time analysis, and you can place orders online in real time, referring to expert stock reviews.
6. Broadband service
Broadband services can also provide internet information browsing, information inquiry, e-mail, online games, multimedia online education, video and audio on demand and other services for users. 、
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