GPS timing system (network timing instrument) application of e-government system
Beijing Zhun electronic technology official micro enterprise — ahjzsz
Abstract: with the continuous development of e-government, many provinces have set up their own government network, using more and more network equipment and servers. These devices have their own clocks, which can be adjusted. Therefore, the time of all devices and hosts in the network can not be guaranteed to be synchronized. After long-term operation, the time difference will become larger and larger, and this deviation is reflected in a single machine Not too loud, but with the continuous development of various network applications, the requirement for time is also higher and higher. Time synchronization will cause many unexpected problems. Next, we will discuss the solution of NTP in government affairs network based on the actual network architecture.
What is network time service?
Clock synchronization is also called “clock synchronization”. In the field of communication, “synchronization” refers to the synchronization of frequency, that is, the clock frequency and phase synchronization of each node in the network, and its error shall comply with the provisions of relevant standards. Time synchronization refers to that the time and time interval of the clocks of each node in the network and the clocks of each application interface connected through the network are synchronized with coordinated universal time (UTC), at least in a local area network or metropolitan area network to synchronize with Beijing time. Time synchronization network is the basis of time synchronization. The time synchronization network can be wired or wireless.
In TCP / IP protocol, NTP protocol is used for network synchronization time. It is designed and implemented by Professor of Delaware University in the United States. It makes computers on the network keep time synchronization. Its transmission is based on UDP with port number of 123 reserved. NTP protocol can estimate the round-trip delay of data packets on the network, and independently estimate the computer clock deviation To achieve reliable and accurate time synchronization between computers, NTP is a dynamic, stable and fault-tolerant protocol, which is used to ensure that the clock accuracy error of all devices in the network is within 1ms. This protocol is defined in rfc958. After that, NTP protocol is constantly modified to add more redundancy and security features. Other RFCs related to time synchronization are rfc1128, rfc1129, rfc1165, rfc1305, rfc2030.
Some people may think that the clock deviation of the computer has little effect. In fact, this is very wrong. In computer system, file saving, file transmission and time stamp in e-mail are all based on the computer clock. If you want to search files and log in the future, if the system clock is not accurate, or the computer time in the same network is not synchronized, it will bring a lot of follow-up work Trouble, now many backup software, translation software, FTP tools are based on the file save time for comparison, if the time is not unified, it will be difficult for these software to work normally.
In network management, when we check the operation of various network management software systems or server logs, we find that due to the different system time on different devices, it is not convenient to observe the influence and sequence of an event on each device through log information (console output or syslog record). This problem can also be solved by configuring NTP NTP provides a time synchronization mechanism among routers, switches and workstations. The time is synchronized, and the relevant time records on multiple network devices can be viewed together, which is more clear and convenient to analyze complex faults and security events. In addition, the application of authentication, maintenance, management and backup system in government affairs network requires high accuracy of time. For example, the time accuracy requirement of switch and billing is 1s, and that of network management system is accurate The degree requirement is 500s.
There are three working modes of NTP service, namely client / server mode, broadcast mode and symmetric module.
In the client / server mode, the client sends NTP packets periodically. According to the label, the client can directly view the working status, event results, and timely feedback.
After a period of operation, there are 24589 general hidden danger data records in the database, of which 24077 have been rectified, with a rectification rate of 97.91%; 145 major hidden danger data have been rectified, of which 144 have been rectified, with the rectification rate of 99.3%. The system provides accurate safety hazard data for decision makers, and the work results of safety investigation are mainly reflected in production safety accidents, fire and traffic accidents Based on the statistical data, according to the survey data of two months, the occurrence rate of various accidents, casualties and direct economic losses in the city have decreased significantly, and the city’s carrying capacity, emergency handling capacity, safety prevention and control capacity, and disaster prevention and mitigation capacity have also been greatly improved. A large number of hidden dangers that have not been found in the past have been found and solved. A large number of outstanding problems discovered in the past have been rectified, and some long-term problems left over from history have been properly handled, which has played a positive role in effectively curbing the occurrence of hidden dangers and accidents and creating a safe, stable and harmonious urban environment.