Executive Summary, SG15, March 2025

​​​​​​Geneva, 17-28 March 2025
ITU-T Study Group 15
Networks, Technologies and Infrastructures for Transport, Access and Home
Study Group 15 Chair: Glenn Parsons

Study Group 15 held its first meeting of the 2025 study period in-person in Geneva from 17 – 28 March 2025, had more than 400 registrations and was attended by 369 delegates representing 37 countries.
The meeting received 384 contributions and 413 TDs.  The meeting observed the 12-day contribution deadline of Recommendation ITU-T A.1, and almost all of the contributions to this meeting were submitted using Direct Document Posting (DDP).
SG15 approved one Amendment, consented 48 texts (5 new and 17 revised Recommendations, 24 Amendments, and 2 Corrigenda), and agreed 7 supplements.
Interim activities prior to the next SG15 plenary have been planned as virtual or in-person, consisting of 32 single-day or multiple-day meetings.

In fulfilling its lead study group responsibilities, SG15 revised the Access Network Transport (ANT) standards overview and work plan, the Home Network Transport (HNT) Standards Overview and Work Plan, and the Optical Transport Networks and Technologies (OTNT) standardization work plan. In addition, web-based versions are available at
https://www.itu.int/itu-t/landscape?topic=tx356&group=g&search_text= , https://www.itu.int/itu-t/landscape?topic=tx153&group=g&search_text= , and https://www.itu.int/itu-t/landscape?topic=tx401&group=g&search_text= , respectively.

SG15 generated 38 Liaison Statements.  These included an update to the JCA IMT-2020 concerning the IMT-2020 roadmap, and a request to ITU-R regarding existing and proposed work on free space optics.

WP1/15 – Transport aspects of access, home and smart grid networks

WP1/15 Chair: Ian Horsley, Vice-Chair: Frank Van der Putten
WP1/15 approved 1 Recommendation, consented 9 Recommendations, agreed 3 Supplements, agreed 1 technical paper and initiated 6 new work items.

Q2/15 met for 5 days at ITU-T in Geneva (March 20-21, 24-26). All the consent and agreement documents were progressed to decision. A joint meeting was held with Q6 and Q12 (regarding ION2030). Several face-to-face and teleconference interim meetings were planned, and outgoing liaisons were prepared. The work program was updated, and new work on low-latency over TDM-PON was started, as well as several revision and amendment projects.
Significant work progressed Passive Optical Networks (PON) towards Very High Speed PON (VHSP), targeting October 2025 consent.   The meeting consented three Recommendations and agreed one Supplement to improve PON transmission convergence (TC-layer) consistency.  Updated the OMCI (ONU M&C Interface) to capture new service features, and HSP requirements to capture coexistence aspects. 

Q3/15 met for 4 days (24 – 27 March 2025) in Geneva, addressed 38 contributions and reviewed four incoming liaison statements and prepared one outgoing liaison.
The work progressed on the various families of Recommendations under the group responsibilities (G.hn, G.vlc, G.iot, G.fin,G.p2pf,G.Sup.Edge4Home, G.sg, G.uvs, etc…).
At the end of the meeting, one draft Recommendation was forwarded for approval after finishing the last call comments, four draft Recommendations were forwarded for consent and one appendix to a Recommendation was forwarded for agreement.

Q4/15 met for half a day in Geneva. One contribution and one liaison were received and reviewed. Both were for information only. The BAIN draft was reviewed and considered mature by Q4. The work programme was reviewed and confirmed. Contributions are invited for the next meeting to progress the work.

A joint session including Q2, Q3, and Q4/15 was held to finalise the technical paper, agreed by the plenary, on broadband access and in premise networks (BAIN) that provides an overview of the WP1 body of work.

​WP2/15 – Optical technologies and physical infr​astructures

WP2/15 Chair: Paul Doolan; Vice-Chair: Sudipta Bhaumik
WP2/15 consented 10 Recommendations, 3 supplements and initiated 15 new work items.
In addition, WP2 prepared 8 outgoing liaisons.

Q5/15 obtained consent for a revision of L.104, and agreement for new G.Suppl.G.65x and revised G.Suppl.47. The new supplement, G.Suppl.G.65x -Standardization framework for optical fibres for space division multiplexing (SDM) – is an important milestone in the standardization of SDM fibres where Q5/15 is leading industry activities for multi-core fibre.
Q5/15 agreed to start work on three new Recommendations and on one new Supplement:

• L.ocwp.1 “Aerial Optical fibre cables along electrical power lines applications with lower voltage".
  
• L.ocwp.2 “Aerial optical fibre cables along electrical power lines applications with higher voltage".
• G.smmcf "Characteristics of a single-mode weakly-coupled multi-core optical fibre and cable".
• L.Suppl.ne "National experiences with respect to ITU-T L.1xx-series optical fibre cables, installation methods, and test methods".

Three Interim E-meeting and correspondence activities are planned to progress revision work on multiple Recommendations and on new Recommendation G.smmcf which will be the first standard in the industry for this technology.

Q6/15 obtained consent for revisions to Recommendations: G.698.4; G.672; G.671; G.661; G.695 and amendment G.959.1 Amd.2, in addition, a revision of G Suppl. 39 was agreed.  Of note, the revision of bi-di DWDM (G.698.4) included self-tuning and remote performance monitoring (based on MOPA).
Progress continues on 800G DWDM, FSO and DFOS.  In addition, Q6/15 agreed to begin work on a Revision of G.665 and on a new technical report:

• ​TR.fsc "Technical Report on feed-forward sensing in optical communication networks "
  
  Q6/15 will hold an RGM (face to face with remote participation), hosted by Huawei in Paris from 9-13 June 2025.
  

Q7/15 obtained consent for revisions to Recommendations L.341 and L.360 (overhead infrastructure to include inspection and maintenance procedures) and agreed to start development of a new Recommendation:

• L.mct "Maintenance of conduits for telecommunication"
  

In addition to its normal meeting business Q7/15 prepared Flyers on newly revised L.250 and L.341.
Q7/15 will conduct two correspondence activities (to Prepare draft L.391 and L.pcc for consent and make progress on revision L.361, new L.nis and L.mct) before the October meeting.

Q8/15 obtained consent for a revision to G.978 (Characteristics of optical fibre submarine cables – notably to include fibre sensing) and agreed to begin work on a Corrigendum to ITU‑T G.971 (General features of optical fibre submarine cable systems).
Q8/15 will conduct correspondence activities (on Revision of G.976 and G.979 and the Corrigendum to G.971) before the October meeting.

WP3/15 – Transport network characteristics

WP3/15 Chair: Tom Huber; Vice-Chair: Silvana Rodrigues
WP3/15 consented 22 Recommendations, agreed 1 Supplement, and initiated 30 new work items.

• ​Q10/15 has initiated the approval process on new Recommendation G.8020.3 that will simplify referencing of the IEEE 802.3 LAN/MAN Standards from other ITU Recommendations.
  
• Q11 has continued to refine and enhance the suite of OTN Recommendations and has initiated two new work items on the definition of beyond 1 Tbit/s OTN. (B1T)
• Q12/15 is continuing to work on the application of SDN to the transport network and the interfaces to AI/ML and Digital Twin applications and has initiated work on a Technical Report on International Optical Networks towards 2030 and Beyond.
• Q12/15 updated the OTNT SWP
• Q13/15 continued its work to enhance the accuracy and robustness of time and frequency distribution.
• Q13/15 is continuing work on extending the ITU defined synchronization frameworks and profiles to apply to synchronization in data centres. This work is being undertaken in cooperation with IEEE P1588, IEEE P1952, IEEE P3335, IEEE IC Timing in Datacentre and OCP.
• Q14/15 is continuing to extend the suite of management Recommendations to allow management of the new functions recently defined by Q10, Q11 and Q13.
• Q14/15 is continuing to work in cooperation with IEEE 802.1, IEEE 1588, IEEE 802.3, Linux Foundation ONMI, MEF, BBF, and IETF to provide consistent information models and YANG data models for transport networks; the current focus of this work is on the management of network synchronization and Ethernet.
• Q14/15 has added the necessary legal text to the YANG-related Recommendations that will allow the YANG modules to be made available via the IETF git repository where other SDOs working on YANG publish their modules.

Per Question highlights:

Q10/15 consented new ITU-T G.8020.3 “Ethernet" incorporating IEEE Std 802.3 (as amended) by reference thereby extending the global reach of Ethernet and simplifying work on other Recommendations by providing referencing conventions avoiding the need for ITU-T A.5 qualification. Q10/15 also consented amendments to ITU-T G.8013/Y.1731 (OAM for Ethernet-based networks) and ITU-T G.8021 (Ethernet equipment) to improve alignment with IEEE 802 standards, facilitate interpretation, and address editorial issues, as well as an amendment to ITU-T G.8121 (MPLS-TP equipment) adding support for reporting the state of linear and ring protection processes to equipment management functionality and addressing editorial issues. Q10/15 proposed two new work items agreed at this meeting toward consents in October 2025 of revised ITU-T G.8020.3 and in July 2026 of revised G.8011 (Ethernet services characteristics), to align with the evolution of IEEE Std 802.3 and carrier Ethernet-centric MEF standards, respectively.

Q11/15 made significant progress on all of its agenda topics, with seven consented Recommendations and approving a total of nine new formal work items.  Q11 continued its work associated with OTN for rates beyond 1 Tbit/s (B1T).  Other work topics related to fine grain MTN (fgMTN), fine grain OTN (fgOTN), and FlexO.
The consented Recommendations include the following:  A G.709 amendment with terminology updates and additional fgOTN information; a G.798 amendment with several updates and minor corrections; G.8312 and G.8321 amendments with information related to mapping CBR clients into fgMTN, with G.8321 also adding information related to hitless resizing; a G.8023 amendment with clarification of the meaning of “[IEEE 802.3] processes," a G.709.20 amendment with additional function definitions, and a G.709.5 corrigendum aligning the lane skew tolerance requirement with the IEEE 802.3df value and correcting some typos.
The B1T discussions resulted in significant progress on common understandings and further narrowing and clarification of the key remaining open questions.  These results should enable further significant progress at the upcoming Q11/15 interim meeting.  New B1T-work items were added for FlexO Recommendations G.709.1 (common elements), G.709.5 (short reach interfaces), and G.709.6 (B400G long reach interfaces).
Due to the maintenance challenges associated with current G.798 due to its size and breadth, it was agreed to restructure the content into new Recommendations G.798.odu, G.798.flexo, G.798.media and revised G.798, which will provide an overview and pointers to the other G.798.x Recommendations to indicate where the current information has been moved.
With the growing importance of multi-vendor interface between equipment and optical module vendors, it was agreed that module-to-framer (MFI) FOIC lane rates ≥100 Gbit/s, should be defined in new Recommendation G.709.mfi, leaving the lower rates in G.Sup58 where they are currently defined.
A new work item was also added for a G.806 revision.
​Q11/15 plans to hold a face-to-face interim meeting in June 2025 in Geneva.

Q12/15 consented Amendment 2 to G.8310 to support additional fgMTN clients. Discussions on AI/ML/DT topics with Q14/15 resulted in a new work item that is a technical report on enhanced network operations for transport networks. It expands the management-control architecture with interfaces to applications that may use AI/ML/DT techniques.
In a joint meeting with Q2/15 and Q6/15, new technical report was initiated that covers the future development of optical network to support IMT-2030, AI, data centre interconnection, and broadband access etc.
The OTNT Standardization Work Plan was updated and Issue 35 will be liaised to other SDOs.
A liaison was generated to ITU-R to inquire about their scope of satellite-to-satellite communication using free space optics. Existing SG15 free space optics work is terrestrial.
A joint face-to-face interim meeting is planned with Q14/15 for 9-13 June 2025 in Paris.

​Q13/15 continued the work on requirements and solutions for time and frequency synchronization and updates to several Recommendations have been consented at this meeting.

New Recommendation G.8371 addresses synchronization aspects in MTN networks.
G.8275 Amendment 2, finalizes the parameters required to monitor performance of PTP networks.
The G.781 (synchronization layer functions for synchronization over the physical layer) was amended with further enhancements on the sync PHY dataset. These updates have allowed Q14 to complete work on synchronization data modeling for syncPHY (Joint meeting was also held with Q14 on this topic).
G.781.1 was revised including updates related to Synchronization layer functions for packet-based synchronization.
G.8271.1 Amd3 includes details related to the transport of timing over 5G.
Recommendations on Primary Reference Clocks (G.8272, G.8272.1 and G.8272.2) have been revised or amended including new functions and clarifications.
G.8273 has been amendment among other things, with further details on testing methodology for the physical layer frequency clock transients.
Work has also been done on other recommendations planned to be consented in future SG15 plenaries.
Good progress was made on the new work item dealing with synchronization in Data centres with initial definition of requirements, architectures and solutions.  Work will continue in coordination with other groups in IEEE and OCP dealing with related items.
Updated have been agreed for clock recommendations on some important aspects that were under study (e.g., variable temperature related requirements in G.8262.1, holdover requirements for class C clocks in G.8273.2). Enhancements to PTP profiles (G.8275.1 and G.8275.2) have also been agreed at this meeting.
Various new work items have been approved to continue the work on most of the Recommendations consented at this meeting.
Q13/15 plans to hold an Interim meeting in presence in June 2025 and virtual meetings on the work item dealing with enhancements to Partial Timing Support (ePTS) and synchronization in data centres.
Liaison has been exchanged with O-RAN to on updates on the synchronization recommendations relevant to O-RAN, and with IEEE P1588 on items relevant to the PTP telecom profiles.

Q14/15 continued the work on common transport management requirements, and technology-specific (including OTN, MTN, Ethernet, MPLS-TP, Synchronization and Media) information models and YANG models. Eight Recommendations were consent and one Supplement was agreed.

Seven new work items were created in total to amend the work on the information model of Synchronization, media, Ethernet and MPLS-TP, and the general procedure enhancement for distributed control plane to support hybrid SDN and ASON architecture. Based on the guidance from the SG15 and WP3 management team and targeting to upload all YANG modules defined in Q14 into IETF GitHub repository at the same time, two work items on G.8052.2 amd.1 and G.8152.1 amd.3 were created emergently and meanwhile the draft of these two Recommendations adding the legal text into the YANG modules were consented in this meeting.
G.7716 MC operations architecture, G.7719 MC component/function management information model, G.7710 common equipment management function requirements, G.874/G.875 OTN management and G.8350 MTN management were made good progress and the editor drafts of those Recommendations were updated.
Q14/15 plans to hold one in person interim meeting with Q12/15 from 9 to 13 June 2025 and four tracks of correspondence activities, including e-Meetings, to progress the work items.
Two spontaneous liaisons on consented/agreed Recommendations and coordination on IM/DM with IEEE 802.1, IEEE PNCS (P1588), IEEE 802.3, MEF, IETF, BBF, TM Forum, Linux Foundation ONMI, O-RAN WG9 were agreed. Q14/15 flyer was created for promotion.​

Decisions (ITU-T SG15, March 2025)
Approval

WP1/15 - AAP Approval

​Consent

WP1/15 - Consent

WP2/15 - Consent

WP3/15 - Consent

 Agreement

WP1/15 - Agreement

WP2/15 - Agreement

 WP3/15 - Agreement