Private data network refers to the data network established, owned, managed and used by enterprises, organizations or departments to meet their own needs. Although the utilization rate is not as high as public network, it is suitable for some departments with special needs, such as military, public security and railway.
Private data network refers to the data network established, owned, managed and used by enterprises, organizations or departments to meet their own needs.
The so-called private data network refers to the network designed for the needs of one or several large groups or departments, and the ownership also belongs to this group or department. For example, the weather network is a typical example. Private data network has strong pertinence, good transmission quality, strong confidentiality and short construction period. Although the utilization rate is not as high as public network, it is suitable for some departments with special needs, such as military, public security and railway. In a word, public data network and private data network complement each other and should be developed coordinately.
Private data network (PDN) first appeared in the period when minicomputers and microcomputers have not yet developed. It is mainly composed of a host computer connecting many data terminals with telephone lines or special communication lines to realize data transmission within enterprises or industries. Today, with the popularity of microcomputers, private data network still has a wide range of applications, such as bank centralized accounting system, train, civil aviation booking system and so on.
In order to achieve its construction goal, the following principles should be followed in the establishment of industry specific data communication network:
(1) we should design the network according to the scale, organizational structure, business characteristics and other industries, and pay attention to the unity of practicality and advanced nature.
(2) Data flow direction and flow analysis should be carried out, and the selected scheme should meet the current needs and medium and long-term development goals, and have scalability and easy management functions;
(3) It has the safety and reliability to meet the special requirements of the industry;
(4) It can be compatible with the existing private network and facilitate the access or smooth transition of various private systems.
Private data network access to the Internet
The principle of Internet access
Generally speaking, the private data network is mainly a data transmission network. Through the data network
Data network access to the Internet
Installation, configuration and test of data network
（1）在 Windows 系统下点击“开始——控制面板——网络任务/创建一个新的连接”项；
(1) Click “start – control panel – network task / create a new connection” under Windows system;
(2) Select “connect with broadband connection requiring user name and password” to connect to the network;
(3) Set the user name and password to be entered;
(4) Log in to the data network to connect and access to the Internet;
（5）如果不能上网，可以用 ping 命令测试，ping 指定地址，以查看网络是否逻辑连通。
(5) If you can’t access the Internet, you can use the ping command to test and Ping the specified address to check whether the network is logically connected.
In the private data network, the connection between the computer and the data terminal is shown in the right figure.
Connection mode of private data network
1. Point to point connection
Point to point connection is the simplest. The computer and the terminal are connected by a dedicated direct line without special communication control signal. However, the point-to-point mode uses a large number of lines and interfaces, so it is only suitable for the situation where the number of terminals is small and the distribution area of terminals is small.
2. Polling multipoint mode
In the polling multipoint mode, multiple terminals are connected to the computer by a common circuit, so the cost of the circuit is economical. However, in the aspect of communication control and management, polling multipoint mode needs special control software and unified communication protocol, which increases the complexity of computer programming.
3. Multiplex network
Multiplexing network adopts time division multiplexing technology, so it is more economical in line cost. The transmission line between multiplexers is high speed. Generally, the communication rate of high-speed line should be at least equal to the sum of the communication rates of each terminal. This kind of connection is especially suitable for the situation where the multiplexer is needed and each terminal needs to have an independent interface with the computer.
4. Software multiplex network
The software multiplex network enables the computer to automatically identify the data format on the high-speed line through software, and thus distinguish which terminal the data comes from. This method saves the cost of hardware, but increases the cost of software programming, storage capacity and computer time.
5. Hub network
A hub network is formed by using a hub to concentrate data transmission services from many terminals on a few lines without a multiplexer. The capability of this method is between polling and multiplexing.
6. Software control hub network
The number of communication lines and computer interfaces can be further reduced by adding the function of data buffer storage to the hub to make it have the ability of data processing. The hub with the ability of data storage and processing usually uses a small general-purpose computer to complete the data processing function through the control program.