Design of Time Synchronization System in Telecom Network
The following introduces a specific design method of the telecommunication network time synchronization system. 1. Local network independent construction plan The local network time synchronization system is composed of 3 parts: master-slave GPS receiving equipment, switch timing subsystem, intelligent network, and value-added service platform time synchronization subsystem, as shown in Figure 7.20. The master-slave GPS receiver as the time source of the local time synchronization network provides UTC standard time signals to the master-slave backup time server; the master-slave backup time server provides time signals to devices that support the protocol through NTP; for those that do not support NTP Switch equipment, need to design and develop the time calibration server software to initiate the MML instruction to read the time to each switch through the local network management interface API, calculate the deviation of the switch from the standard time, and then initiate the MML instruction to the time calibration to correct the switch time . Second, the provincial time center + local network school time program The time-saving center system includes a master-slave GPS receiver as the time source of the time-saving synchronization network. The master-slave time server serves as a time application server to provide time service to other local networks through NTP. The time center can be equipped with a rubidium clock oscillator as GPS When the time is lost, the accuracy of the time can be maintained for a long time, as shown in Figure 7.21. In the local network, only a secondary time server and a school time server need to be established. The secondary time server of the master-slave backup obtains the standard time signal from NTP through the provincial network DCN. At the same time, the time server of the master-slave backup provides the time signal to the device supporting the protocol through NTP; for switch devices that do not support NTP, a design and development school is required. The time server software initiates an MML command to read time to each switch through the local network management interface API, calculates the deviation of the switch from the standard time, and then initiates an MML command to calibrate the time to calibrate the clock of the switch. For the UNIX server, two methods are used to achieve NTP time synchronization: The first method: start the ntpd time synchronization process on the UNIX host, and configure the secondary time server as the reference clock source of the host. The second method: configure cron plan parameters on the UNIX host, regularly start the time synchronization script, automatically correct the host system time within the allowed correction range, and configure the secondary time server as the reference clock source of the host in the script. Flexible, convenient, with time threshold control function, with time fine-tuning instructions, it has high time security, and takes up less host resources, supporting time server redundancy backup. (1) Safety control requirements of time synchronization system In this system, the accuracy and stability of the standard time are of the utmost importance. The master-slave GPS time server is used for redundant backup in the time synchronization source to provide the system with a reliable, stable and uninterrupted GPS clock to ensure the continuity of the system timing With stability. The master-slave GPS time server provides time to the system time server when each second pulse (PPS) arrives. The system monitors whether the GPS satellite is tracking normally to confirm whether the current time of the time server is normal. The task of correcting the time of the switch is stopped, and an alarm message is sent to the monitoring and management system, and the operation and maintenance personnel handle the fault. When the fault is removed, the system returns to normal working condition. (2) System security / protection against viruses NTP security: The message encryption mechanism provided by NTP is used to ensure that NTP time messages are not modified during network transmission and to ensure the security of time synchronization of intelligent network devices. Network security: Configure each service subnet through the three-layer exchange mechanism, enable the server firewall function, and close the ports not used by the system to achieve safe isolation between each service network. Anti-virus: Linux and Solaris operating systems have high security and anti-virus capabilities. By installing software firewalls and closing ports not used by the system, viruses and hackers can be further prevented from attacking. Real-time antivirus software is installed in the Windows 2000 operating system to prevent virus infection. At the same time, the system installs a software firewall to close unused ports of the system to prevent viruses and hacker attacks.
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