Executive Summary December 2023

​​​20 November – 1 December 2023
ITU-T Study Group 15
Networks, Technologies and Infrastructures for Transport, Access and Home

Study Group 15 held its third meeting of the 2023 study period in-person in Geneva from 20 November to 1 December 2023, had more than 400 registrations and was attended by 345 delegates representing 32 countries.   The in-person meeting was welcomed as a rapid means to build consensus on new work items.
The meeting received 282 contributions and 431 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 new and two revised Recommendations, consented 49 texts (10 new and 14 revised Recommendations, 23 Amendments, and 2 Corrigenda), and agreed 6 supplements.  SG15 agreed to delete Recommendation ITU-T L.106.
Interim activities prior to the next SG15 plenary have been planned as virtual or in-person, consisting of 31 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 generated 36 Liaison Statements.  These included 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.

WP1/15 – Transport aspects of access, home and smart grid networks
WP1/15 Chair: Tom Starr, Vice Chair: Ian Horsley
WP1/15 approved 3 Recommendations, consented 9 Recommendations, agreed 3 Supplements and initiated 8 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 documents were revised. The list of certification and interoperability activities for WP1/15 Recommendations was updated.
Q2/15 met for four days, working on Passive Optical Networks (PON).  Four texts for consent and three Supplements were prepared. Q2/15 plans to hold five interim meetings including two joint virtual meeting with Q3/15 on coordinated management of access PON and fibre in the premises.  One A.1 and three A.13 statements were prepared for new projects.
Q3/15 met for four days, working on fibre indoor networks (G.fin) and other aspects of home networking. Five draft Recommendations were prepared for consent and two were prepared for approval.  G.9942, specifying the G.fin data link layer was provided for consent at this SG15 meeting even though it was not on the initial list of candidate texts for consent.  Q3/15 plans to hold two interim F2F meeting and two virtual meetings jointly with Q2/15. Three A.1 and two A.13 statements were prepared for new projects.
Q4/15 met for one day addressing broadband access over metallic conductors. Q4 updated its terms of reference in preparation of WTSA2024.  Q4/15 plans to hold one interim virtual meeting. 

WP2/15 – Optical technologies and physical infrastructures

WP2 Chair: Paul Doolan; WP2 Vice-Chair: Sudipta Bhaumik
WP2/15 consented 8 Recommendations, agreed 1 Supplement and initiated 15 new work items.

​Q5/15 agreed to start a discussion on space division multiplexing (SDM) optical fibre cable to clarify the application area and deployment roadmap for this new technology. A Revision of ITU-T Recommendation G.652 was initiated to cover the statistical design approach for chromatic dispersion and polarization mode dispersion particularly for short links.
 The Q6/15 meeting resulted in the consent of two new ITU-T Recommendations (G.698.5, formerly G.owdm and G.698.6, formerly G.owdm2) and of revised Recommendation (G.959.1). Q6 also approved eight new work items: 100G per lane 400G applications in G.695, updates of optical signals definitions in G.959.1, optical switching systems based on NxN arrayed waveguide grating routers in G.671, remote optically pumped amplifiers in G.661, reconfigurable optical add drop multiplexers architectures in G.672, remote performance monitoring and self-tuning in G.698.4, 800G DWDM optical interfaces in G.698.2 and development of a new ITU-T Recommendation on distributed optical fibre sensing (G.dfos).
Q7/15 agreed to begin a revision of technical paper LSTP-GLSR, and to continue discussion for creating a new ITU-T Recommendation “Technical and functional requirements for sharing network infrastructures," with focus on the technical perspective. Revised ITU-T Recommendations L.250 and L.312 were consented and the new L Suppl. 58 (ex. L.Suppl.fttx) was agreed during the meeting.
Q8/15 made a progress on editing new ITU-T Recommendations G.smart and G.dsssc as well as on revisions of G.971 and G.972. A contribution from the Ministry of Posts and Telecommunications of Cameroun proposing the use of G.smart sensing capabilities for strengthening submarine cables was discussed and existing solutions like DAS (Distributed Acoustic Sensing) were proposed. The revision of Supplement G Suppl. 41 has been stabilized but no consensus was reached in the joint meeting with Q5 on the main topic of the revision “fibre colour identification" and so the work continues. During the meeting Q8 prepared a draft G.977.1 flyer and agreed to send it for publication; it is available here.

WP3/15 – Transport network characteristics

WP3 Chair: Malcolm Betts; WP3 Vice-Chair: Tom Huber
WP3/15 consented 32 Recommendations, agreed 2 Supplements, and initiated 22 new work items. 

WP3 chair summary
Q11 consented a restructured set of Flexible OTN (FlexO) Recommendations that address 800Gb/s interfaces and interfaces optimized for Ethernet. This restructuring will simplify the evolution of FlexO to bitrates beyond 1Tbit/s. The FlexO Recommendations have been used as the basis for specifications in the OIF, OpenZR+ MSA, and the OpenROADM MSA. The restructured Recommendations make it simpler for other SDOs or MSAs to reference the parts of the base specifications that are relevant to their target application.
Q13/15 continued its work to enhance the accuracy and robustness of time and frequency distribution.
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 with a focus on the management of network synchronization and Ethernet.

Per Question highlights:
Q10/15 consented amendments to G.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. Q10/15 also consented a corrigendum to G.8013/Y.1731 (OAM for Ethernet-based networks) clarifying how the Length field of the Test ID TLV for one-way delay measurement is specified. Q10/15 drafted five technical flyers covering the Recommendations and Supplements under its responsibility.
Q11/15 made significant progress on all the topics on its agenda, with ten consented Recommendations and agreed a Supplement in addition to approving a total of seven new work items. Q11 also began work associated with optimizing OTN for rates beyond 1 Tbit/s (B1T).
The consented Recommendations included a reorganization of the FlexO specifications with revised G.709.1 containing the common elements of FlexO interfaces that are used in the other FlexO Recommendations. New G.709.5 containing the short reach interfaces (that had previously been in G.709.1), revised G.709.3 continues to specify long reach FlexO interfaces for 100G-400Gbit/s and new G.709.6 specifies a long reach interface for 400G-800Gbit/s rates. Revised G Suppl. 58 (Optical transport network module framer interfaces) includes the specification of multiple new FOIC FlexO interfaces, including several using of Ethernet PHY rates.
A new amendment to G.709 OTN includes the specification of a new mapping for 800Gbit/s Ethernet into OTN and an update to the GMP specification in Annex D to make it more convenient to reference from other ITU-T Recommendations and by standards organizations outside ITU-T (e.g., OIF, IEEE 802.3, and OpenROADM).  The primary focus of the G.798 (Characteristics of optical transport network hierarchy equipment functional blocks) amendment is FlexO equipment functional blocks associated with the G.709.x restructuring.
Sub-1Gbit/s (fine grain) support was added for OTN (fgOTN) as part of the G.709 amendment and for MTN (fgMTN) in a new G.8312 amendment. 
New Recommendations G.709.20 and G.8312.20 provide overviews for fgOTN and fgMTN, respectively.
An amendment to G.8023 (Characteristics of equipment functional blocks supporting Ethernet physical layer and Flex Ethernet interfaces) includes the addition of 800 Gbit/s PHYs recently specified in IEEE 802.3df.
The new work items included defining equipment functional blocks for fgMTN and fgOTN in G.8321 and G.798, respectively, adding new fgMTN functionality in G.8312, and adding support for 4FOIC1.2 in G.709.5 and G Suppl. 58.
Q11/15 plans to hold an in person interim meeting in April 2024.
Q12/15 consented two architecture Recommendations related to OTN and MTN that complement work progressed in Q11/15 on FlexO, fgOTN, and fgMTN. These are:
-Revision to G.872 “Architecture of the optical transport network"
-Amendment 1 to G.8310 “Architecture of the metro transport network"
Work continued in collaboration with Q14/15 on management and control Recommendations and related topics including digital twin and AI/ML based applications.
Work progressed in media architecture in G.807. Discussions across Q2/15, Q6/15, and Q12/15 on point-to-multipoint optical topologies that started after the September 2022 plenary came to some decisions at this meeting. The topic of distributed fibre optical sensing was raised and the media constructs in G.807 could be helpful in discussions across multiple Questions.
OTNT Standardization Work Plan was updated and Issue 33 will be liaised to other SDOs.
Q12/15 and Q14 plans to hold an in person joint interim meeting in April 2024.
Q13/15 continued the work on requirements and solutions for time and frequency synchronization. Actions to update the terminology to meet the requirements for inclusive language continued at this meeting in alignment with IEEE Std 1588g™-2022.  
Several Recommendations were consented.
G.8272.1 (enhanced Primary Reference Time Clock) with enhanced holdover.
A new clock G.8272.2 to support the coherent PRTC network (i.e., a network of ePRTCs) which provides enhanced resiliency to the synchronization network. G.8272.1 and G.8272.2 together can address the important issue of GNSS vulnerability.
The time sync architecture and PTP profiles (G.8275, G.8275.1, and G.8275.2) have been updated to address, amongst other things, a new option for a standardized way to monitor the performance of PTP in networks. G.781 (synchronization layer functions for synchronization over the physical layer) was revised to support the work on Sync management done in Q14. G.8271.1 (network limits for time synchronization over full timing support) was amended with further details on performance objectives based on the latest technology and with initial analysis of network scenarios integrating sync over 5G.
Other documents consented at this meeting were G.8260 Amd1 (time sync terminology) and G.8264 Amd2 (related to physical layer sync).  A revision of G Suppl. 68 dealing with synchronization OAM was agreed.  Progress was also made on time sync clocks (G.8262, G.8273.2 and G.8273.3) adding new interfaces that can be used to carry timing (FlexE, PAM4).
A new work item to enhance partial timing support (“ePTS") was created. The target is to distribute accurate timing from a network segment that has access to PRTC / ePRTC references, towards a remote network segment that does not have local access to a PRTC/ePRTC reference.
A joint meeting was held with Q14 on the topic of synchronization management.
A joint meeting was also held with Q11 on the topic of fgOTN and fgMTN.
A liaison was sent to O-RAN on the topic of providing security for PTP messages.
Q13/15 plans to hold an in person interim meeting in April 2024.
Q14/15 consented 8 documents including: G.874 (2020) Amd.2 “Management aspects of optical transport network elements - Amendment 2", G.876 (2021) Amd.1 “Management Requirement and Information Model for the optical media network – Amendment 1", G.8051 Cor.1 “Management aspects of the Ethernet transport (ET) capable network element - Corrigendum 1", G.8052 “Protocol-neutral management information model for the Ethernet Transport capable network element", G.8052.1 (2021) Amd.2 “Operation, administration, maintenance (OAM) Management Information and Data Models for the Ethernet-Transport Network Element -Amendment 2", G.8151 (2020) Amd.1 “Management aspects of the MPLS-TP network element - Amendment 1", G.8152 “Protocol-neutral management information model for the MPLS-TP network element", and G.8350 (2022) Amd.1 “Management and Control for metro transport network - Amendment 1". 
Five new work items were started, including: Revision to G.8051 “Management aspects of the Ethernet transport (ET) capable network element", Revision to G.8052.1 “Operation, administration, maintenance (OAM) Management Information and Data Models for the Ethernet-Transport Network Element", Revision to G.8151 “Management aspects of the MPLS-TP network element", Revision to Recommendation ITU-T G.7716 “Architecture of management and control operations", and Amendment 2 to Recommendation ITU-T G.876 “Management Requirement and Information Model for the optical media network".
Q14/15 progressed work on the other Recommendations under its responsibility including G.875 “Optical transport network: Protocol-neutral management information model for the network element view".
Q14/15 is continuing to work in cooperation with IEEE 802.1, IEEE 1588, IEEE 802.3, ONF, MEF, Broadband Forum, and IETF to provide consistent information models and YANG data models for transport networks including Ethernet and network synchronization.
Q12/15 and Q14 plan to hold an in person joint interim meeting in April 2024.

Decisions

Approval

WP1/15 - TAP 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

Deletion