Executive Summary - April 2023

As a result of resignations, SG15 appointed several Working Party chairs and rapporteurs. SG15 also agreed a minor revision to our long-standing guidelines for carrying out the work of the study group.

The meeting received 287 contributions and 367 TDs, about the same as contributions from our previous plenary. The meeting observed the 12-day contribution deadline of Recommendation ITU-T A.1, and all of the contributions to this meeting were submitted using Direct Document Posting (DDP).

SG15 approved one Amendment (by TAP) and one revised Recommendation (by AAP), determined one revised Recommendation, consented 22 texts (2 new and 10 revised Recommendations, 7 Amendments, and 3 Corrigenda), agreed one Corrigendum, two questionnaires, one revised Supplement. 

Future SG15 plenary meeting have been confirmed with in-person facilities for 2023, despite the challenges associated with the new building project.  Interim activities prior to the next SG15 plenary have been planned as virtual or in-person, consisting of 28 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.

SG15 also provided an update to the JCA IMT-2020 concerning the IMT-2020 roadmap, and an update to ITU-T SG2 regarding the Telecommunication Management and OAM project plan.

SG15 generated 26 Liaison Statements. 

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

WP1/15 Chairman: Tom Starr, Vice Chairman: Ian Horsley
WP1/15 consented 9 Recommendations and 2 Corrigenda and initiated 4 new work items. 

Q1/15 met for one day, updating the web-based Access Network Transport (ANT) Standards Overview and Work Plan documents. The web-based Home Network Transport (HNT) Standards Overview and Work Plan document were revised. The list of certification and interoperability activities for WP1/15 Recommendations was updated. 
Q2/15 met for three days, working on Passive Optical Networks (PON), preparing five texts for consent and agreeing to start work on Supplements addressing PON security and operational aspects of PON. Q2/15 is joining the joint correspondence activity studying deployed G.652/657 fibres.  Q2/15 will hold face-to-meetings on 14-16 June and 5-8 September 2023, as well as two virtual meetings.
Q3/15 met for four days, working on G.hn, G.fin (G.9940-3), G.uvs-XR, and G.9991 enhancements for visible light communications.  A new project G.p2pf was started. Four draft Recommendations were prepared for consent, two for approval, and one for Determination.  Q3 will hold face-to-face meetings 27-29 June and 19-21 September, as well as one virtual meeting.
Q4/15 met for one day, producing Corrigenda for G.9701 and G.9711.  Q4 will hold two virtual meetings: 27 June and 10 October.​

WP2/15 – Optical technologies and physical infrastructures

WP2 Chairman: Paul Doolan; WP2 Vice-Chairman: Sudipta Bhaumik
WP2/15 consented 3 Recommendations, reviewed 2 Questionnaires and initiated 10 new work items.

Q5/15 agreed to start revision work on Recommendation G.657 to clarify the application area of each fibre type considering the possible new application spaces, the revised Recommendation is expected to consent in 2024. Q5/15 also agreed to update the L-series cable Recommendations by the end of 2025. A new flyer on Space Division Multiplexing (SDM ) was published and is available here. A more detailed description is of SDM is provided in GSTR-SDM and is available at https://www.itu.int/pub/T-TUT-HOME-2022-1.
Q6/15 progressed new revisions of Recommendations ITU-T G.698.1 and G.698.4, now including 25G application codes, which were consented. Draft Recommendations G.owdm and G.owdm2 were progressed and are now mature enough to be considered for consent at the next SG15 Plenary Meeting, this is a remarkable achievement, considering that no baseline document existed before the Q6 Interim meeting in Feb 2023. A joint meeting with Q11/15 allowed progress to be made on the definition of the application space for 400G (and beyond) DWDM applications. Q6 will hold an interim meeting in Pisa, in July 2023 to progress this and other topics under study and will conduct four correspondence activities in preparation for that meeting.
Q7/15 's revision of Recommendation L.340 was consented. A Questionnaire on optical infrastructure sharing was revised and reviewed and will now be sent to sector members. Q7 agreed to develop revisions of Recommendations L.341 and L.360 and to begin work on a new supplement (L.Suppl.fttx) on 'National Experiences for FTTx Network Architectures' and a new Recommendation (L.pcc) describing 'Pre-connectorised cabling components for FTTx infrastructures'.  Work on a revision of Recommendation L.250 progressed with the intent to obtain consent during the November meeting.
Q8/15 worked on optical fiber submarine cable systems and made a progress for the revision of G suppl.41. Q8/15 also discussed a new reference model and generic information for submarine cable systems with sensing capabilities and made a progress on the revision of G.971.  In addition Q8/15 discussed and made a progress on the new Recommendations G.dsssc (Dedicated scientific sensing submarine cable system) and G.smart (Scientific monitoring and telecommunication submarine systems).

WP3/15 – Transport network characteristics

WP3 Chairman: Malcolm Betts; WP3 Vice-Chairman: Tom Huber
WP3/15 consented 7 Recommendations and 1 corrigendum, agreed 1 supplement and 1 corrigendum reviewed the OTNT SWP and initiated 26 new work items.

• ​Q10/15 continued to evolve the Ethernet and MPLS-TP Recommendations
• Q11/15 updated the OTN Recommendations to support 800G FlexO
• Q12/15 continued to evolve the Management and Control Recommendations including the application of ML in the control of transport networks.
• Q13/15 has taken the first steps to remove non-inclusive terminology from the Synchronization Recommendations.
• Q13/15 is continuing to enhance the performance defined in a suite of Time and Frequency synchronization Recommendations.
• Q13/15 and Q14/15 are continuing to work, in cooperation with IEEE 1588, on the management of the synchronization network and equipment.
• ​​​Q14/15 is continuing to work in cooperation with IEEE 1588, IEEE 802.1, IEEE 802.3, ONF, MEF, BBF, and IETF to provide industry wide consistent information models and YANG data models to support the management of transport networks including network synchronization and Ethernet.

Q10/15 consented draft revised G.8013/Y.1731 (OAM for Ethernet-based networks) primarily updated for consistency and improved readability. Q10/15 also prepared, toward December 2023 consent, draft amendments to both Gtom.8021 (Ethernet equipment) and G.8121 (MPLS-TP equipment) adding support for mapping Ethernet frames or MPLS-TP packets to OTN by leveraging G.798 adaptation functions using the idle mapping procedure. To support Q14/15's management work, the use of multicast addresses with G.8013/Y.1731 performance monitoring messages and specifics of Ethernet and MPLS‑TP linear protection switching mechanisms were discussed. ​Q11/15 continued to extend the OTN Recommendations. A revision to G.798 on OTN equipment was consented, and an amendment to FlexO Recommendation G.709.1 that adds a new 800 Gbit/s FlexO interface. This interface includes definition of a direct Ethernet mapping into FlexO and extends the overhead to support new FlexO applications and it is expected that other standards organizations (including OIF and OpenROADM) will reference this Recommendation. Q11 agreed to undertake a reorganization of the G.709.x FlexO-related Recommendations at the next meeting to simplify the evolution of these Recommendations (e.g., address higher bitrates) and provide better separation between the basic frame format (and multiplexing structure) and the application specific FECs.
A revision to the OTN module‑framer interface defined in supplement G.Sup58 included the addition of a new FOIC4.4 interface carried over four 112 Gbit/s electrical lanes.
Significant progress was made on the sub1G topic, which provides TDM channelization to carrying sub-1 Gbit/s clients over OTN (fine grain OTN (fgOTN)) and MTN (fine grain MTN (fgMTN)). Many key agreements were made, which allowed the approval of a set of new work items to develop a suite of sub1G Recommendations for consent at the next SG15 meeting.
An interim meeting is planned for the last week of June to further progress the work on OTN/FlexO topics for beyond 400 Gbit/s (B400G) and sub1G. 
Q12/15 made progress on media modelling to extend the model to support multipoint topologies and, in cooperation with Q6/15, on the refinement of definitions (esp. network media channel and OTSi) to support these topologies. 
In response to new Q11/15 work on FlexO, fgOTN, and fgMTN corresponding architecture work was initiated in G.872 and G.8310.
Collaborative work with Q14/15 continued on management and control to continue the extension of the G.770x series of Recommendations (G.7701 on common aspects; G.7702 on SDN and G.7703 on ASON). This work included the study of how AI and ML can be used to support the control of transport networks.
Q13/15 important actions have been taken with respect to update the terminology to meet the requirements for inclusive language on the documents consented at this meeting. This initiative is aligned with the recently published IEEE Std 1588g™-2022, similar actions have been taken with respect to the synchronization over the physical layer technologies. Work on this topic will continue at the next meetings on other documents that are planned for consent.
Work continued on requirements and solutions for time and frequency synchronization. Several Recommendations were consented: G.8271.1 (network limits for time synchronization over full timing support) Amd.1 that included new performance objectives based on the latest technology: G.8273.2 Amd2 (Timing characteristics of telecom boundary clocks and telecom time slave clocks): A revision of G.8273 (framework for time clocks) that included additional requirements and guidance for testing clocks.
Work was progressed on several other topics: G.8260 (time synchronization terminology and definitions) with further clarification on the terminology for UTC traceability; G.8272.1 (enhanced Primary Reference Time Clock) with enhanced holdover. The time sync architecture and PTP profiles (G.8275, G.8275.1, and G.8275.2) drafts have been updated among other things with a new option for performance monitoring based on IEEE1588-2019 Annex J.
G.Suppl-FTS, that describes the use of the options in PTP profile with full timing support from the network, has been updated adding the specification for the Enhanced Accuracy TLV which provides information on the expected network performance to the receiving time clocks.
Progress has been made on the topic of coherent PRTC (i.e., a network of PRTCs) The related clock Recommendation(G.8272.2) is planned for consent at the next SG15 plenary.
A joint meeting was held with Q14 on the topic of synchronization management. Progress was made on the specification of dataset members to support the management of the distribution of frequency synchronization over the physical layer. The plan is to complete this work by 2023 as part of a new Appendix in G.781 (synchronization layer functions for synchronization over the physical layer).
A Joint meeting was held with Q11 on the topic of fgOTN (with the analysis of the related synchronization solutions).
Q13/15 plans to hold a face-to-face interim meeting in September 2023 and a virtual joint meeting with Q14 in June 2023.
Q14/15 consented Amendment 1 to G.8051 “Management aspects of the Ethernet transport (ET) capable network element" and agreed to a Corrigendum 1 to G.8052.2 “Resilience information/data models for the Ethernet transport network element".
New work was started on a revision to G.875, a revision to G.7710 and Amendment 2 of G.874.  Q14/15 progressed the other Recommendations under Q14/15 responsibility, including: OTN management information model G.875, Optical media management G.876, Synchronization management requirements and model G.7721, Ethernet management model G.8052.x, MPLS-TP management G.8151 and G.8152.x, MTN management G.8350, MC component/function management information model G.7718 and G.7719, and Common equipment management function requirements in G.7710.
Q14/15 is continuing to work in cooperation with IEEE 802.1, IEEE 1588, IEEE 802.3, ONF, MEF, BBF, and IETF to provide consistent information models and YANG data models for transport networks including Ethernet and network synchronization.​

Approval

WP1/15 - TAP Approval

WP1/15 - AAP Approval

Note: Although this was consented as G.9962 Amd.2, it was approved as a revision to G.9962.​

Determination

WP1/15 - Determination

​ ​

Consent

WP1/15 - Consent

WP2/15 – Consent

​​​WP3/15 – Consent

Agreement

WP3/15 – Agreement