DDN Network Application and Maintenance

Most DDN users are banking, securities, and communication lines between branches and their headquarters. Such users have high requirements on Network stability, high speed, and security, because DDN uses a physical point-to-point data link, once activated, this link is exclusive to the user. At the same time, the singularity of the physical line also guarantees the security requirements of the user. Currently, DDN users use the Mainstreet DTU series of Newbridge, which is mainly 2601, 2603, 2606, 2701, and 2703, when the External Loop of the entire user is less than 600 euros, 26 series can be used. If it is higher than 600, 27 series can be used, but the maximum length cannot exceed 800, therefore, the quality of the external line of the DDN line is high. It is best to measure the Ring Resistance of the user line when the new line is opened. During use, we found that this type of DTU also has high requirements on power supply grounding, And the protection field must be controlled below 3 V, A data link layer error, such as packet loss and slide Code, may occur during use, and may even cause damage to the DTU device. Therefore, it is recommended that the power supply of the user's home be powered by UPS to ensure the stable operation of the equipment. At the same time, as a communication electronic device, DTU also prohibits live insertion and removal of Data ports. When new devices are connected, the Data ports should be connected and then connected. Likewise, when removing the device, you must first unplug the data connector.
During routine maintenance of the line, when the user reports that the link is abnormal, The DTU status should be checked first. In the DTU of Mainstreet series, there is a line light specifically indicating the connection status of the line, if the light flashes, the physical line is disconnected and the line department should check the user's external line. If the light is always on, the line is normal, but line interference is not excluded, you can use the network management to view the DTU port Signal status. Under normal circumstances, the value should be 1. If there is 0 in the refresh, it indicates that the line has problems in insulation and grounding. Generally, a special error code tester is used to test the running status of the DDN line. When the DTU is correctly connected, the network administrator is used to build a software loop on the DTU port to be tested, and the error code tester is connected to the port for testing, before testing, you must first select the correct interface type based on different DTU types, such as the V.24 interface for 2601 and the V.35 interface for 2603. The error code meter is used as a self-collecting and spontaneous Data Testing Instrument, depending on the display of different software loops, you can basically determine the problem. The C loop is the loop of the Local Switch Port. If the C loop is normal, this ensures that the entire DDN line is normal. If no loop is detected or there is an error code or packet loss, you can ring E, that is, the device ring, this ring is directly used for DTU data interfaces. If this ring test is normal, DTU is normal and the quality of the line should be further checked; otherwise, DTU should be replaced first.
On the other hand, you can also use your device to determine the cause of the fault. The following uses a Cisco router as an example: After logging on to the router, first determine the serial number of the serial port associated with DTU, run the show interface serial */* command at the # prompt. The command displays the line and Data Link Protocol Status of the port. After the command is executed, the following information is displayed:
Serial */* is ** 1, line protocol is ** 2;
Where 1 is the line status of the interface. If it is up, it indicates that the interface has been correctly connected to the DCE device. If it is down, it indicates that the interface has not been connected to the control signal of the DCE, check whether the cable from the vrodtto DTU is correctly connected, or change a serial port. If it is set to administratively down, the port is forcibly disabled by the Administrator. You can execute the no shutdown command to reactivate the port. 2: indicates the Data Link Protocol Status of the port. If it is up, the Protocol is normal, and a data link is established between the local switch. The entire DDN data channel is normal. If it is down, it indicates that the layer-2 Data Link Protocol is not properly established. In this case, you can use the DDN network administrator to ring the user's DTU data port, which is usually a bidirectional C-loop, after the software ring is created, run the command again on the user router. If the loop is displayed after the line protocol, the router can access the loop. If no, it may be that the connection cable from the router to DTU is not properly inserted, and the data link layer protocol cannot be established. You can re-plug the cable or replace one. Note that this operation must be performed after the router is powered off, or the serial port of the router may be burned down.
As a transparent transmission network, DDN does not add any network protocols on the user's data link, so it can adapt to the transmission of various services, it also brings great convenience to daily network monitoring and management. At the same time, the end-to-end settings of the physical layer ensure the user's application bandwidth. Today, with the development of multi-service networks, familiar with DDN application and maintenance will provide users with better network services.