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ITU-T G.8264 (11/2025)

Distribution of timing information through packet networks

Recommendation ITU-T G.8264 outlines aspects of distribution of timing information through packet networks and initially focuses on Ethernet networks. A number of methods may be used to transfer frequency which may be physical-layer based or protocol-layer based. This Recommendation provides information on architectural aspects of timing flows in Ethernet networks which will form the basis for future work related to time and phase transfer.
This Recommendation specifies the synchronization status message (SSM) protocol and formats for use with synchronous Ethernet. Adherence to the SSM formats specified in this Recommendation is required in order to ensure interoperability between synchronous Ethernet equipment involved in frequency transfer.
This revision of Recommendation ITU-T G.8264:
•Moves the contents of clauses 11.3.1.2 and 11.3.1.3 to Recommendation ITU-T G.781 and adds a reference to Recommendation ITUT G.781.
•Moves the contents of clause 11.6 to Recommendation ITU-T G.781 and adds a reference to Recommendation ITU-T G.781.
•Moves the contents of clause A.7 to Recommendation ITU-T G.781 and adds a reference to Recommendation ITU-T G.781.
•Replaces the reference of IEEE 802.3 with Recommendation ITU-T G.8020.3.
•Adds clarification in clause 11.1.1 on synchronization over link aggregation (LAG).

Citation:	https://handle.itu.int/11.1002/1000/16546
Series title:	G series: Transmission systems and media, digital systems and networks G.8000-G.8999: Packet over Transport aspects G.8200-G.8299: Synchronization, quality and availability targets
Approval date:	2025-11-29
Provisional name:	G.pacmod
Approval process:	AAP
Status:	In force
Maintenance responsibility:	ITU-T Study Group 15
Further details:	Patent statement(s) Development history [14 related work items in progress]

Ed.	ITU-T Recommendation	Status	Summary	Table of Contents	Download
4	G.8264 (11/2025)	In force	here	here	here
3.2	G.8264/Y.1364 (2017) Amd. 2 (01/2024)	Superseded	here	here	here
3.1	G.8264/Y.1364 (2017) Amd. 1 (03/2018)	Superseded	here	here	here
3	G.8264/Y.1364 (08/2017)	Superseded	here	here	here
2.2	G.8264/Y.1364 (2014) Amd. 2 (04/2016)	Superseded	here	-	here
2.1	G.8264/Y.1364 (2014) Amd. 1 (01/2015)	Superseded	here	-	here
2	G.8264/Y.1364 (05/2014)	Superseded	here	here	here
1.4	G.8264/Y.1364 (2008) Amd. 2 (02/2012)	Superseded	here	-	here
1.3	G.8264/Y.1364 (2008) Cor. 2 (02/2012)	Superseded	here	-	here
1.2	G.8264/Y.1364 (2008) Amd. 1 (09/2010)	Superseded	here	-	here
1.1	G.8264/Y.1364 (2008) Cor. 1 (11/2009)	Superseded	here	here	here
1	G.8264/Y.1364 (10/2008)	Superseded	here	here	here


ITU-T Supplement	Title	Status	Summary	Table of contents	Download
G Suppl. 4 (12/1972)	Certain methods of avoiding the transmission of excessive noise between interconnected systems	In force	-	-	here
G Suppl. 5 (10/1984)	Measurement of the load of telephone circuits under field conditions	In force	-	-	here
G Suppl. 7 (12/1972)	Loss-frequency response of channel-translating equipment used in some countries for international circuits	In force	here	here	here
G Suppl. 8 (12/1972)	Method proposed by the Belgian telephone administration for interconnection between coaxial and symmetric pair systems	In force	-	-	here
G Suppl. 17 (10/1984)	Group-delay distortion performance of terminal equipment	In force	-	-	here
G Suppl. 19 (10/1984)	Digital crosstalk measurement (method used by the Administrations of France, the Netherlands and Spain)	In force	-	-	here
G Suppl. 22 (10/1984)	Mathematical models of multiplex signals	In force	-	-	here
G Suppl. 26 (10/1984)	Estimating the signal load margin of FDM wideband amplifier equipment and transmission systems	In force	-	-	here
G Suppl. 27 (10/1984)	Interference from external sources	In force	-	-	here
G Suppl. 28 (10/1984)	Application of transmultiplexers, FDM codecs, data-in-voice (DIV) systems and data-over-voice (DOV) systems during the transition from an analogue to a digital network	In force	-	-	here
G Suppl. 32 (11/1988)	Transfer of alarm information on 60-channel transmultiplexing equipment	In force	-	-	here
G Suppl. 34 (11/1988)	Temperature in underground containers for the installation of repeaters	In force	-	-	here
G Suppl. 35 (11/1988)	Guidelines concerning the measurement of wander	In force	-	-	here
G Suppl. 36 (11/1988)	Jitter and wander accumulation in digital networks	In force	-	-	here
G Suppl. 39 (10/2025)	Optical system design and engineering considerations	In force	here	here	here
G Suppl. 40 (07/2024)	Optical fibre and cable Recommendations and standards guideline	In force	here	here	here
G Suppl. 41 (07/2024)	Design guidelines for optical fibre submarine cable systems	In force	here	here	here
G Suppl. 42 (10/2018)	Guide on the use of the ITU-T Recommendations related to optical fibres and systems technology	In force	here	here	here
G Suppl. 43 (02/2011)	Transport of IEEE 10GBASE-R in optical transport networks (OTN)	In force	here	here	here
G Suppl. 44 (06/2007)	Test plan to verify B-PON interoperability	In force	here	here	here
G Suppl. 45 (09/2022)	Power conservation in optical access systems	In force	here	here	here
G Suppl. 46 (05/2009)	G-PON interoperability test plan between optical line terminations and optical network units	In force	here	here	here
G Suppl. 47 (03/2025)	General aspects of optical fibres and cables	In force	here	here	here
G Suppl. 48 (06/2010)	10-Gigabit-capable passive optical networks: Interface between media access control with serializer/deserializer and physical medium dependent sublayers	In force	here	here	here
G Suppl. 49 (09/2020)	Rogue optical network unit (ONU) considerations	In force	here	here	here
G Suppl. 50 (09/2011)	Overview of digital subscriber line Recommendations	In force	here	here	here
G Suppl. 51 (06/2017)	Passive optical network protection considerations	In force	here	here	here
G Suppl. 52 (09/2012)	Ethernet ring protection switching	In force	here	here	here
G Suppl. 53 (12/2014)	Guidance for Ethernet OAM performance monitoring	In force	here	here	here
G Suppl. 54 (07/2015)	Ethernet linear protection switching	In force	here	here	here
G Suppl. 55 (10/2025)	Radio-over-fibre (RoF) technologies and their applications	In force	here	here	here
G Suppl. 56 (02/2016)	OTN transport of CPRI signals	In force	here	here	here
G Suppl. 57 (07/2015)	Smart home profiles for 6LoWPAN devices	In force	here	here	here
G Suppl. 59 (02/2018)	Guidance on optical fibre and cable reliability	In force	here	here	here
G Suppl. 60 (09/2016)	Ethernet linear protection switching with dual node interconnection	In force	here	here	here
G Suppl. 62 (02/2018)	Gfast certification	In force	here	here	here
G Suppl. 64 (02/2018)	PON transmission technologies above 10 Gb/s per wavelength	In force	here	here	here
G Suppl. 65 (10/2018)	Simulations of transport of time over packet networks	In force	here	here	here
G Suppl. 66 (09/2020)	5G wireless fronthaul requirements in a passive optical network context	In force	here	here	here
G Suppl. 67 (07/2019)	Application of optical transport network Recommendations to 5G transport	In force	here	here	here
G Suppl. 68 (10/2025)	Synchronization operations, administration and maintenance requirements	In force	here	here	here
G Suppl. 69 (09/2020)	Migration of a pre-standard network to a metro transport network	In force	here	here	here
G Suppl. 70 (09/2020)	Supplement on sub 1 Gbit/s services transport over optical transport network	In force	here	here	here
G Suppl. 71 (12/2023)	Optical line termination capabilities for supporting cooperative dynamic bandwidth assignment	In force	here	here	here
G Suppl. 72 (03/2025)	Modelling consideration for optical media networks	In force	here	here	here
G Suppl. 73 (10/2021)	Influencing factors on quality of experience for multiview video (MVV) services	In force	here	here	here
G Suppl. 74 (12/2021)	Network slicing in a passive optical network context	In force	here	here	here
G Suppl. 75 (12/2021)	5G small cell backhaul/midhaul over TDM-PON	In force	here	here	here
G Suppl. 76 (12/2021)	Optical transport network security	In force	here	here	here
G Suppl. 77 (06/2022)	Supplement 77 to ITU-T G-series of Recommendations - Influencing factors on quality of experience (QoE) for video customized alerting tone (CAT) and video customized ringing signal (CRS) services	In force	here	here	here
G Suppl. 78 (09/2022)	Use case and requirements of fibre-to-the-room for small business applications	In force	here	here	here
G Suppl. 79 (12/2023)	Latency control and deterministic capability over a PON system	In force	here	here	here
G Suppl. 80 (07/2024)	Use case and requirements of fibre-based in-premises networking for home application (FIP4H)	In force	here	here	here
G Suppl. 81 (10/2025)	Practical aspects of PON security - Revision 1	In force	here	here	here
G Suppl. 82 (07/2024)	Enhanced optical line termination with information technology functions	In force	here	here	here
G Suppl. 83 (10/2025)	Supplement on the use of options in the precision time protocol profile with full timing support from the network	In force	here	here	here
G Suppl. 84 (03/2025)	Operational aspects of optical access	In force	here	here	here
G Suppl. 85 (03/2025)	FgODUflex over point-to-multipoint networks	In force	here	here	here
G Suppl. 86 (03/2025)	Fibre to the power grid (FTTGrid) use cases and network requirements	In force	here	here	here
G Suppl. 87 (03/2025)	Standardization framework for optical fibres for space division multiplexing	In force	here	here	here
G Suppl. 88 (10/2025)	Point to multipoint passive optical access system requirements and transmission technologies above 50 Gbit/s per wavelength	In force	here	here	here
G Suppl. 89 (10/2025)	Coordinated management of access and fibre in premises networks	In force	here	here	here
G Suppl. 90 (10/2025)	Coexistence between G.fin and G.Xfin systems	In force	here	here	here
G Suppl. 91 (10/2025)	Use cases and requirements of fibre-in-premises for small and medium enterprise applications	In force	here	here	here
G Suppl. 93 (07/2026)	Low layer split mobile fronthaul over T(W)DM PON	In force	here	-	here
G Suppl. 94 (07/2026)	Enhanced in-premises networking with computing functions	In force	here	-	here

Title	Approved on	Download
Roadmap for QoS and QoE in the ITU-T Study Group 12 context (TR-RQ)	2023	here
Considerations on the use of GNSS as a primary time reference in telecommunications	2020	here
Use of G.hn in industrial applications	2020	here
Transport network support of IMT-2020/5G (October 2018)	2018	here

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ITU-T G.8264 (11/2025)