Connection between user network and DDN

Connection between user network and DDN

As a Data Service bearer network, DDN can not only access user terminals, but also interconnect user networks and expand information exchange and application scope. The user network can be a LAN, a dedicated digital data network, a group exchange network, a user switch, and other user networks.
DDN Interconnection

The LAN uses DDN to interconnect devices through bridges or routers. The interfaces are ITU-TG.703 or V.35, X.21 standard. This connection is essentially the connection between LAN and LAN, as shown in figure 8.

Figure 8 LAN interconnection through DDN

The bridge stores and forwards packets received on one network to other networks. DDN is used to interconnect local networks. The function of a bridge is to convert the LAN protocol on the link layer to connect it.

A vro provides the Internet routing function. The router selects and forwards the packets of different subnets. The vrodddn enables interconnection between multiple local networks.

Connection between dedicated DDN and public DDN

Private DDN and public DDN are essentially no different, it is a useful supplement to public DDN. The geographical regions covered by the dedicated DDN are limited. Generally, the region is dedicated to a single organization. The structure is simple and managed by the private network. Due to the limitations of dedicated DDN, its function implementation and data exchange breadth are not as good as that of public DDN. Therefore, the connection between dedicated DDN and public DDN has far-reaching significance.

The connection between a dedicated DDN and a public DDN varies by V.24, V.35, and X.21, or G.703 2048kb/s, as shown in figure 9. The specific requirements on the channel transmission rate, interface standards, and routes can be determined according to the dedicated DDN.

Figure 9 connection between dedicated DDN and public DDN

Because DDN uses synchronization to ensure the normal operation of the network, the dedicated DDN should obtain the timing synchronous signal from the public DDN.

Interconnect a group exchange network with DDN

The group exchange network can provide high-quality data communication services at different rates and is suitable for short messages and low-density data communication. DDN has a high transmission rate and is suitable for data communication with high real-time requirements, the group exchange network and DDN can complement each other in the business.

Customers on DDN and customers on the group exchange network communicate with each other. Therefore, we must adopt the X.25 or X.28 interface procedures for the two networks. The DDN terminal here is equivalent to a remote direct access customer of the group exchange network, as shown in figure 10, the transmission rate meets the requirements of the group exchange network.

Figure 10 remote clients access the group-based network through DDN

DDN not only provides data transmission channels for remote customers in the group exchange network, but also provides transmission channels for the inter-Bureau trunk lines of the group switch, which provides good conditions for group switch interconnection. The interconnection interfaces between DDN and the group exchange network are G.703, V.35, and 11.

Figure 11 Group switch interconnection through DDN

Connection between user switches and DDN

The connection between the user exchange network and DDN can be divided into two aspects, as shown in Figure 12.

Figure 12 connection between user switches and DDN

First, the DDN voice function is used to solve the remote customer transmission problem for the user switch. If the traditional analog line is used for transmission, the transmission failure limit will be exceeded, affecting the call quality ), connect to DDN using the second-line audio interface;

Second, the transmission capability of DDN is used to provide the required inter-Bureau trunk lines for the user switch. At this time, the G.703 or the second-line/Fourth-line audio interface is used for interconnection with DDN.