With the large-scale deployment of IEEE1588 in the PTN network of China Mobile Communications Corporation, the use of IEEE1588 technology to replace GPS to achieve time synchronization is actively advancing, and it is increasingly important to provide a stable and reliable time and clock synchronization source for the PTN network.
PTP time synchronization server is a set of high-precision master clock technology and secure network timing synchronization solutions that combine to provide users with a powerful time and frequency reference system. The quality of the PTP time synchronization server, the accuracy and long-term stability of time and clock output, provide a strong guarantee for the normal and stable operation of the communication network. At present, the main domestic manufacturers of PTP time synchronization servers include Huawei Technologies, Datang Telecom, Beijing Guozhiheng, and American Symmetricom.
XG7010 IEEE1588 time analyzer is the first dedicated instrument in China that supports mobile IEEE1588 time-frequency synchronization launched by Shenzhen Xiaguang Communication Technology Co., Ltd. Measure and evaluate the time, clock accuracy and long-term stability of the PTP time synchronization server.
In June 2011, the XG7010 IEEE1588 time analyzer provided by Shenzhen Xiaguang Communication Technology Co., Ltd. was used in the Communication Standards Research Institute of the Telecommunications Research Institute of the Ministry of Industry and Information Technology. The PTP time synchronization server provided by the company has been tested comprehensively for 3 weeks, and has achieved good results. At the same time, it has been compared with similar foreign time testers, and all indicators are qualified, which proves that the XG7010 IEEE1588 time analyzer function can be used. Meet the test of various indicators of the PTP time synchronization server.
Below, we propose XG7010 test solution for PTP time synchronization server based on the functional characteristics of XG7010 and the performance of PTP time synchronization server
Test item and purpose
The PTP Time Synchronization Server Test Assessment includes the following:
PTP time synchronization server clock synchronization deviation;
PTP time synchronization server time synchronization deviation;
PTP time synchronization server PTP synchronization situation;
PTP time synchronization server clock, time keeping ability;
PTP time synchronization server GPS, Beidou switching time.
The main purpose is to verify the time, clock output accuracy and long-term stability of the PTP time synchronization server, and to verify the performance changes of the PTP time synchronization server when the PTP time synchronization server is abnormal.
XG7010 is directly connected to the corresponding output interface of the PTP time synchronization server, which can effectively measure the output time of the PTP time synchronization server, the deviation of the clock signal, and whether the data transmission of the PTP protocol is normal, and can measure the time of the PTP time synchronization server and the drift of the clock signal. characteristics (MTIE and TDEV) are evaluated.
In addition, it is necessary to conduct a long-term stability test on the time and clock of the PTP time synchronization server to observe the deviation; it is also necessary to change the GPS timing mode to the Beidou timing mode to observe the changes in the time output switching process and the long-term stability test after the switching.
XG7010’s test solution for PTP time synchronization server mainly includes clock test and time test, which are described as follows:
The XG7010 clock test includes clock deviation measurement and clock drift test. It mainly tests the output indicators of the 2Mb/s clock interface or FE interface of the PTP time synchronization server. XG7010 selects the clock test or clock drift test function item, and sets the corresponding interface and other related parameters. The test connection is shown in Figure 1.
Figure 1 Clock test connection diagram
XG7010 is directly connected to the 1PPS or 1PPS+TOD time synchronization interface to measure the time offset, or set the XG7010 to PTP (Slave) mode, directly receive IEEE1588 data from the Ethernet interface of the PTP time synchronization server, parse out the relevant time information, and calculate the time offset .
XG7010 selects the time test function item, and sets relevant parameters according to the interface of the PTP time synchronization server under test. The test connection is shown in Figure 2.
Figure 2 Time Test Connection Diagram
When doing the 1PPS test, pay attention to the selection of the interface type. In general, if the RJ45 interface is RS422, the BNC interface is TTL.
When testing 1PPS+TOD, in addition to the interface type and other settings, it is also necessary to pay attention to the protocol type, baud rate, parity bit, stop bit and other settings, which must be consistent with the PTP time synchronization server.
During the PTP test, as shown in Figure 2, connect the PTP interface of the PTP time synchronization server to the PTP interface of the instrument. Before the PTP test, the technicians of the PTP time synchronization server manufacturer (or mobile company technicians) should be familiar with PTP. Some settings of the time synchronization server, pay special attention to the following points:
Whether the PTP message is Layer 2 or Layer 3, if it is Layer 3, PTP network settings are required;
Whether VLAN is set;
The settings of parameters such as delay mechanism, delay mode, and frequency synchronization must be consistent with the settings of the time server.
Clock, time keeping ability test
Connect the XG7010 to the PTP time synchronization server according to Figure 1 or Figure 2, and unplug the GPS antenna of the PTP time synchronization server. The test method is the same as the clock test, time test and PTP test.
Test time server in GPS and Beidou switching time mode
This test is mainly to observe whether the time of the PTP time synchronization server will jump during the process of GPS and Beidou handover. The test is shown in Figure 3. The switch between GPS and Beidou is mainly completed by the PTP time synchronization server, and the instrument only needs to be connected to the clock or time interface for testing.
Figure 3 GPS, Beidou handover test
Test Process Notes
XG7010 should first set the GPS antenna compensation value, and then perform GPS positioning and locking.
After the XG7010 is locked to the GPS and the working state is normal, the relevant tests can be carried out.
Test cable delay compensation (the cable between the test interface of the device under test and the test interface of the instrument).
When the test result appears 9999999, it means that the test exceeds the measurement range, which is displayed in red.
The test time deviation of the PTP time synchronization server should be no less than 24 hours. Generally, a 72-hour test is required in the acceptance link, so as to observe the long-term stability of the time output of the PTP time synchronization server.
The PTP time synchronization server provides a stable and reliable synchronization source for the communication network, and plays a pivotal role in the normal operation of the business in the future. The PTP time synchronization server test requires a long time to analyze the test results, so as to effectively evaluate the PTP time synchronization server. performance.
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