International Telecommunication Union   ITU
عربي  |  中文  |  Espa˝ol  |  Franšais  |  Русский
 Advanced Search Advanced Search Site Map Contact us Print Version
Home : ITU-T Home : Study Groups : Study Group 15
Question 13/15 – Network Synchronization and Time Distribution Performance
(Continuation of Question 13/15)


Network synchronization performance specifications are essential for successful operation and integration of digital transmission networks and associated switching and signalling systems. Network timing performance studies are needed to determine the feasibility and most effective means of implementing a time reference distribution service.

This Question has already studied the network synchronization issues related to PDH and SDH during Study Periods from 1988 until 2000, and to OTN during the 2001-2004 Study Period. This question has also started studying the network synchronization issues related to packet networks from 2004 until 2008.

Continuing effort needs to be put into the study of synchronization issues in packet based networks.

The following major Recommendations, in force at the time of approval of his Question, fall under its responsibility: G.810, G.811, G.812, G.813, G.822, G.823, G.824, G.825, G.8251, G.8261, G.8262, G.8264.


What are the requirements for jitter and wander for the future 100Gbit/s interface (HSSG related)?

What is the network functionality required to provide real-time distribution of absolute time-of-day reference services? What network capabilities are required to support the performance levels necessary to satisfy a selected set of time-of-day user applications?

How can network synchronization performance be enhanced through the use of synchronization status messages or other techniques?

What network synchronization characteristics, for both normal and degraded mode, should be recommended for services carried over packet networks? What is the dependence on synchronization of performance of various methods of service clock recovery with respect to service requirements (e.g. jitter, wander and slips etc)?

What network synchronization characteristics should be recommended for services carried over packet based networks?

What jitter and wander requirements are needed for wireless network applications (e.g., radio relay, satellite)?

What jitter and wander requirements are needed for access networks (e.g. DSL, PON)?

What jitter and wander specification requirements are needed in the evolution of OTN?

Study items to be considered include, but are not limited to:

  • Synchronization aspects (frequency, phase and time) of packet networks, e.g. Ethernet, MPLS, IP networks.
  • Synchronization aspects with regard to transport via satellite networks.


Tasks include, but are not limited to:

  • Possible revision to Recommendation G.810 – based on new terminology from packet networks and OTN areas.
  • Revisions to Recommendation G.825 (for the new 100G rate).
  • Continue development of recommendations related to packet networks, G.8261, G.8262, G.8264, G.pactiming-bis (G.8266), G.paclock-bis (G.8263) and G.pacmod-bis (G.8265).
  • Development of new Recommendations on packet networks to specify the need for synchronization in those networks plus the impact of packet technology on existing synchronization networks.
  • Revisions and enhancements to Recommendation G.8251.



  • Q551, G.781, G.783, G.798, Y.1731, Y.17tom


  • Q2/15, Q3/15, Q4/15, Q6/15, Q9/15, Q11/15, and Q15/15

Study Groups:

  • ITU-T SG2 on telecommunication management
  • ITU-T SG13 on MPLS, NGN and OAM
  • ITU-T SG9
  • ITU-R SG4 on satellites
  • ITU-R SG6 on broadcasting
  • ITU-R SG8 on mobile
  • ITU-R SG9 on radio relay

Standardization bodies, forums and consortia:

  • ATIS OPTXS SYNC on synchronization
  • IETF PWE3 on circuit over packet
  • MEF on circuit emulation over Ethernet and measurement delay
  • MEF mobile backhaul
  • IP/MPLS forum
  • IEEE 1588
  • IEEE 802.3
  • IEEE 802.1AS
  • IEEE 802.16 (Wireless MAN)
  • 3GPP
  • Broadband Forum


Top - Feedback - Contact Us -  Copyright ę ITU 2008 All Rights Reserved
Contact for this page : TSB EDH
Updated : 2008-12-23