The development of various standards is closely related to the evolution of technology, and there is no exception for synchronous standards. Since the 1980s, in order to meet the needs of communication networks development, synchronization technology has undergone many evolutions. Correspondingly the synchronization standards have been developed from nothing, from imperfection to gradual improvement, and from frequency synchronization to time synchronization. Based on different development stages, standardization organizations from different industries have successively promulgated corresponding technical profiles and test specifications of time and frequency synchronization in accordance with the practical situation.
Some international standardization organizations involved in the field of synchronization standards mainly include ITU-T, IETF and IEEE, etc. These standardization organizations have their own emphasis on synchronization research as follows: ITU-T is the most comprehensive, covering frequency synchronization, time synchronization, services synchronization and other aspects; while IETF and IEEE mainly focus on the research of time synchronization.
In addition, CCSA, Power Systems, Railway Systems have also formulated some time and frequency synchronization standards to meet the needs of relevant industries.
I ITU-T Recommendations
• ITU-T G.801
i. Frequency Synchronization In PDH Networks
• ITU-T G.823
• ITU-T G.824
• ITU-T O.171-
ii. Frequency Synchronization In SDH Networks
• ITU-T G.781
• ITU-T G.783
• ITU-T G.803
• ITU-T G.811
• ITU-T G.812
• ITU-T G.813
• ITU-T G.825
• ITU-T O.172
• ITU-T O.173
iii. In Packet-Based Networks
• ITU-T G.8260
i） Frequency Synchronization
• ITU-T G.8261
• ITU-T G.8262
• ITU-T G.8261.1
• ITU-T G.8263
• ITU-T G.8264
• ITU-T G.8265
• ITU-T G.8265.1
• ITU-T G.8266
• ITU-T O.174
ii） Time Synchronization
• ITU-T G.8271
• ITU-T G.8271.1
• ITU-T G.8271.2
• ITU-T G.8272
• ITU-T G.8272.1
• ITU-T G.8273.1
• ITU-T G.8273.2
• ITU-T G.8273.3
• ITU-T G.8273.4
• ITU-T G.8275
• ITU-T G.8275.1
• ITU-T G.8275.2
II IETF Standards
• RFC-958（NTPv0）
• RFC-1059（NTPv1）
• RFC-1119（NTPv2）
• RFC-1305（NTPv3）
• RFC-1589 （A Kernel Model for Precision Time keening）
• RFC-5905（NTPv4）
III IEEE Standards
• IEEE1588（v2）——IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems
IV CCSA Standards
i. Frequency Synchronization In PDH/SDH Networks
• GB/T5837-2008
• YDN117-1999
• YDN121-1999
• YDN123-1999
• YD/T1267-2003
• YD/T1299-2004
• YD/T1420-2005
• GB12048-1989
• GB/T3158-1991
• YDN118-1999
• YD/T900-1997
• YD/T1011-1999
• YD/T1012-1999
• YD/T1355-2005
• YD/T1479-2006
• YD/T1811-2008
• YD/T1750-2008
• YD/T1751-2008
ii. Frequency Synchronization In Packet-Based Networks
• YD/T2551-2013
• YDT 3074-2016
iii. Time Synchronization In Packet-Based Networks
• YD/T2375-2011
• YD/T2879-2015
• YD/T2022-2009
• YD/T2550-2013
• YDT 3075-2016
• QB-B-018-2010
• QB-B-016-2010
• QB-B-017-2010
V Standards in Power Systems
i. Frequency Synchronization
• QGDWZ11394.1-2015
• QGDWZ11394.2-2015
• QGDW11394.3—2016
• QGDW11394.4—2016
• QGDW11394.5—2016
• QGDW11640—2016
ii. Time Synchronization
• DLT 1100.1-2009
• DLT 1100.1
• DLT 1100.2-2013
• DLT 1405.1-2015
• GBT 26866-2011
VI Standards In Railway Systems
• TBT 3283-2015
