The time information of various communication devices or computer devices on the communication local area network is limited to a sufficiently small range based on the UCT time deviation. This synchronization process is called network time synchronization.
Active synchronization and passive synchronization.
Any time application system should have a sustained time increase. In fact, the only way for users of this application system to obtain time has become the basic and only way for most time application systems in the world to access the system’s time retention system. Time keeping time standard, so the research holding system is the internal time reference of the application system. Obviously, the time synchronization of the user's computer network must study active synchronization, that is, the process of accessing the system time holding system is the user putting his time into the GPS. The time signal appears to have absolute meaning. Here, the process of synchronizing my clock with the internal time reference. Since the internals of the system regard the computer network to maintain time growth and maintain the time reference with no relation to external time, the synchronization process is limited to the internal stable system called the time server. Therefore, we can call it passive synchronization or relative synchronization.
Coordinated Universal Time is consistent with the International Atomic Time. Because TAI is the weighted average time obtained by the International Time Administration of more than 10 atomic time scales distributed in 25 countries around the world, and all official standard time systems in the world follow Jumping seconds from UTC.
So UTC is called absolute time, and it is also called natural physical time when used for research. The high-precision time signal in the GPS signal is mainly maintained by two brilliant atomic clocks and two rivet atomic clocks mounted on each satellite, and is synchronized with UTC through the ground control station. GPS time signal has in fact become the basic time standard of most time application systems in the world. Therefore, to study the time synchronization of computer networks, active synchronization must be studied. That is, GPS time signal must be introduced to have absolute meaning. Here, We call the system of computer networks that can maintain time growth and maintain time stability as time servers.
Time transfer method transfer
from GPS to time server
To transfer the PTS signal from the GPS to the network time client unit through the computer network time server, two steps must be taken: direct time transfer from the GPS to the time server, and network protocol transfer from the time server to the time client unit.
The direct time transfer technology mainly includes 3 types and 6 methods. The first type is the encoding type, which mainly includes serial port RS232C time encoding and IRIG-B time system encoding.
Its common feature is that time information such as year, month, day, hour, minute, second and millisecond is defined in binary, BCD or A SCll encoding to the level and byte to be transmitted, usually in an asynchronous manner, and the connection uses a standard interface, which is relatively convenient to use. concise.
SYN2136 Beidou NTP network time server
The second type is pulse type, mainly 1pps, lppm, lpph, they are all periodic pulse timing signals, these pulse signals have fixed rising edge width and pulse width requirements, and their rising edges are strictly maintained with UTC Synchronization accuracy better than lus.
The third type is a frequency reference signal, which is often an accompanying modulation signal.
Time Service Protocol Analysis The
network time code protocol is defined by a series of documents called Requests for Comments (RFCs). There are three main time code protocols currently in use: they are Daytime (RFC-867), Time (RFC-868) and Network Time Protocol. The network time protocol is currently the most complex, most advanced, and most accurate time code protocol. Among them, SNMP and TNMP are two widely used network time code protocols. Install the network time server software on the time server, and install the NTP client software on other computers in the local area network. The client software can be used as a background task to run continuously and periodically to continuously get the server's updated information. The GPS system itself is equipped with high-precision timing equipment, which can output high-precision time and frequency information, and provides a convenient and practical clock source for the computer time synchronization of the range, which can maximize the use of these resources and improve the quality of the test tasks. Use the high-precision time information output by the time system equipment to synchronize the clocks of the entire range computer through the network time server. On the basis of the original basic clock server, the
gps network time server product The
network clock server greatly improves the performance indicators of the clock server, which reduces the failure rate and improves work efficiency. Basically, it can be compared with advanced foreign network clock servers.
The network clock server receives time signals from GPS satellites and Beidou satellites, and transmits standard UTC time information through the network to provide network equipment with accurate, standard, safe, reliable and multifunctional ntp time calibration services. The front panel displays the year, month, day, hour, minute and second. , Received stars, system working status, power status and other information. It is a network time synchronization server with extremely high cost performance.
The clock system consists of a GPS antenna and a GPS clock server, which are connected by a coaxial cable with a prefabricated BNC connector. It adopts SYN2151 clock server, which has two 10/100/1000Mb/s adaptive Ethernet interfaces, and different network segments can be set respectively for network time synchronization of field devices.
Product function
1) Establish time reference with GPS Beidou satellite timing signal;
2) Provide up to 4 NTP/SNTP network time calibration interfaces;
3) Serial TOD time service, sending hour, minute, second, year, month, and day every second Time information;
4) Output timing synchronization pulse signal (1PPS), TTL interface output;
5) The front panel displays the year, month, day, hour, minute, second, number of satellites and working status;
6) Support windows, LINUX, UNIX, SUN SOLARIS, IBM AIX Wait for operating system time synchronization;
7) Support redundant seamless switching dual power supply.
Problems encountered in the use of network synchronization clock and solutions
1. Question: If the antenna is not long enough, how to deal with it?
Answer: Finally, measure the length of the wiring in advance and report to the sales, so that you can order a suitable antenna length, and cut/connect the cable privately. There is no guarantee of receiving the satellite.
2. How to consider antenna lightning protection?
Answer: Under normal circumstances, high-rise buildings will take lightning protection measures. The white mushroom heads erected on the roof/windows/balconies/balconies will not exceed the highest lightning protection measures of the building. If you are still worried about lightning strikes, you can add lightning arresters and lightning arresters. Installed between the host and the antenna, does not affect the effect of receiving stars.
3. How to install the antenna?
Answer: Under normal circumstances, the standard accessories will be equipped with mounting brackets, mounting screws and other accessories. The connection between the mounting bracket and the antenna is threaded, and it can be tightened once it is screwed. There are 3 fixing holes under the mounting bracket. Install expansion screws at the place, drill holes on the roof and fix them with screws.
4. It is recommended to test the receiving effect of all antennas after receiving the goods.
Conclusion
With the development of modern science and technology, both the quality and breadth of network time service have continuously put forward new requirements for time service. Therefore, the networked time service system needs to be continuously improved and perfected to improve the accuracy of time transmission, and the use of network time service has a wider range of applications.