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ITU-T Study Group 15 List of Questions Under Study (Study Period 2005-2008) |
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ITU-T SG 15 Question 13/15 |
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Network Synchronization and Time Distribution Performance (Continuation of Question 13/15)
- Motivation
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.
Continuing effort needs to be put into the study of synchronization
issues in packet based networks. This area had only been discussed
briefly toward the end of the 2001-2004 Study Period and will require
significant additional attention during the 2005-2008 Study Period.
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.
- Question
- What are the requirements for jitter and wander at STM-256
interfaces (to be added in Recommendation G.825)?
- 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?
- What network synchronization characteristics, for both
normal and degraded mode, should be recommended for services
carried over ATM? 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)?
Study items to be considered include, but are not limited to:
- Synchronization aspects of Ethernet, MPLS, ATM, IP networks
- Synchronization aspects with regard to transport via satellite networks
- Tasks
Tasks include, but are not limited to:
- Possible revision to Recommendation G.810 – based on new terminology
from ATM, IP and OTN areas.
- Revisions to Recommendation G.825 as required
- 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
Note: An up-to-date status of work under this Question is contained in
the SG 15 Work Programme.
- Relationships
- Recommendations:
- Q551, G.781, G.783, G.798
- Questions:
- Study Groups:
- ITU-T SG 4 on TMN and test equipment
- ITU-T SG 13 on MPLS and NGN
- 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 T1X1.3 on synchronization
- IETF PWE-3 on circuit over packet
- MEF on circuit emulation over Ethernet
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