DDN status quo in China

The construction of DDN in China began in early 1990s. As of the beginning, DDN has covered most of the country and showed a good development. The newly opened China Public Digital Data Network DHINADDN is easy to describe) it is widely welcomed by all sectors of the society, especially for customers with high transmission requirements and a large amount of information. It provides customers with services such as circuits, frame relay, voice/G3 fax, and virtual private network, it has connected 21 provincial capitals and expanded to the provincial capitals of the People's Armed Forces in Tongda by the end of 1995. In addition, all provinces and cities are actively planning to build DDN and even some provinces and cities). DDN has been developed to the county.
China's DDN network is large in size and large in quantity. In order to make the network flexible, easy to expand, and clear business organization and management, DDN is divided into three layers: core layer, access layer, and user interface layer, as shown in Figure 1.2. The core layer consists of Large and Medium-capacity network devices, which are connected by digital circuits of 2048kb/s or higher speed. The layer consists of Medium and Small-capacity network devices, connect a digital circuit of 2048kb/s to the core layer and provide access for various DDN Services; the user interface layer consists of a variety of frame mounting/dismounting devices that require devices, BRIDGE/router devices, and frame relay services. You can also set small-capacity network devices on the user interface layer, provides sub-rate multiplexing and analog voice/G3 Fax Service Access.

　

Figure 1.2 DDN functional hierarchy

China's DDN can also be divided into the national backbone network, provincial DDN and domestic network by geographical region, as shown in Figure 1.3. The national backbone network is composed of network devices deployed in provinces, autonomous regions, and municipalities directly under the Central Government. It provides inter-province long-distance DDN Services and network equipment is located in the central city of the province; the provincial DDN is composed of network devices in the provinces and autonomous regions. It provides DDN Services for long-distance and inbound and outbound provinces in the province. The network equipment is generally deployed in the city center of each region. The provincial DDN is the end network of the DDN, it provides local and long-distance DDN Services for local customers. The network equipment is installed in the local telephone Bureau, and the local network is the link between the DDN business department and the customer.

Figure 1.3 DDN by geographical region

With the development of the economy and the popularization of computers, the society's demand for computer networking and high-speed and high-quality data services is increasing. The public DDN people have become the information technology of the national economy, the Golden Bridge of the National three gold projects, the golden card, and the golden customs) main communication platform.