Table of Contents - G.8264 (11/2025) - Distribution of timing information through packet networks

1	Scope
2	References
3	Definitions
	3.1	Terms defined elsewhere
	3.2	Terms defined in this Recommendation
4	Abbreviations and acronyms
5	Conventions
6	Packet network architectures
	6.1	Network layers and synchronization
	6.2	Layer network performance impacts on synchronization
7	Timing flows
8	Functional blocks
9	Next generation timing architectures
	9.1	Current synchronization based on SDH
	9.2	Synchronization performance
	9.3	Network evolution
	9.4	Next generation synchronization networks
10	Frequency transfer using synchronous Ethernet
	10.1	Synchronous Ethernet: General
	10.2	Operation modes
11	SSM for synchronous Ethernet
	11.1	Packet-level SSM
	11.2	Sync selection based on SSM
	11.3	SSM for synchronous Ethernet: Format and protocol
	11.4	ESMC PDU extensions
	11.5	Interworking with existing synchronization networks
	11.6	SSM for clocks with enhanced holdover
12	Use of synchronous Ethernet in a multi-operator context
	12.1	Timing transparent transport of synchronous Ethernet client signals
	12.2	Synchronization service provided by the carrier operator based on an interface providing a physical timing reference (generation of synchronous Ethernet interface)
13	Synchronization management aspects
Annex A – Reference source selection mechanism
	A.1	Requirements
	A.2	Inputs
	A.3	Internal oscillator
	Page
	A.4	Internal physical timing flows – Frequency ETY
	A.5	Selection mechanism
	A.6	Synchronization status message selection
	A.7	Hybrid equipment selection function
Appendix I – Examples of timing flows
Appendix II – Functional models based on ITU-T G.805 and ITU-T G.809
	II.1	Background
	II.2	Application of ITU-T G.805 to the IWF
	II.3	Timing information transported over layer networks
	II.4	Functional model of Ethernet physical layer timing
	II.5	Functional model for differential and adaptive methods
Bibliography