Executive Summary - April 2021

Study Group 15 held its seventh meeting of the 2017 study period as a fully virtual meeting from 12-23 April 2021, attended by 350 delegates representing 28 countries. Study Group 15 operated according to the revised question texts endorsed by TSAG in January 2021.

The meeting received 324 contributions and 375 TDs, a slight increase in contributions from the virtual meeting held in a similar format in September 2020. 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 5 texts (2 new Recommendations and 3 Amendments), consented 28 texts (8 new and 5 revised Recommendations, 12 Amendments, and 3 Corrigenda), and agreed three technical papers, two new Supplements, and one revised Implementers' Guide.

Given the current COVID-19 situation, all interim activities prior to the next SG15 plenary have been planned as virtual, consisting of 47 single-day or multiple-day virtual meetings. A procedure for authorizing the conversion of some of these virtual meetings to physical meetings, which had been defined at the September 2020 SG15 meeting, is available should face-to-face meetings become feasible prior to the next plenary of SG15.
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. No update was needed to the Smart Grid standards overview and work plan, which no longer requires active coordination.
​​SG15 generated 24 Liaison Statements.

Executive reports from WP Chairmen
WP1/15 – Transport aspects of access, home and smart grid networks
WP1 Chairman: Tom Starr; WP1 Vice-Chairman: Ian Horsley 

Q1/15 met for one day, updating the Access Network Transport (ANT) Standards Overview and Work Plan documents. The Home Network Transport (HNT) Standards Overview and Work Plan document was revised. The list of certification and interoperability activities for WP1/15 Recommendations was updated.

Q2/15 met for seven days, working on Passive Optical Networks (PON), preparing eight texts for consent and one for agreement.  The Recommendations for consent include the PMD and TC layers for the 50 Gbit/s PON.

Q4/15 met for eight days, working on access via metallic conductors.  Two texts on MGFAST were prepared for approval, addressing transmission of up to eight Gbit/s over metallic conductors.

Q18/15 met for four days, working on the Recommendations and Technical Papers related to G.hn, narrow-band PLC, free space optical communication, and fiber in the premises.  Three texts were prepared for approval, two for consent, and two Technical Papers for agreement. Q18/15 requested the appointment of Mr. Tony Zeng (Huawei) as Liaison Rapporteur to ETSI ISG F5G, which was approved by the SG15 meeting.

WP2/15 – Optical technologies and physical infrastructures
WP2 Chairman: Noriyuki Araki; WP2 Vice-Chairman: Peter Stassar 

WP2/15 made good progress on the development of a number of Recommendations and produced two revised Recommendations and one technical paper. WP2 produced four Liaisons and updated its work programme. WP2 also scheduled four interim e-meetings and a number of correspondence activities to progress the work.

Q5/15 worked on characteristics and test methods of optical fibres and cables, and installation guidance, and consented the revised L.100, which was revised to be consistent with the IEC cable standards for outdoor application. Q5 made progress on new Recommendation L.oehc, which deals with optical/electrical hybrid cables for access points, and the new Technical Report on optical fibre, cable and components for space division multiplexing transmission.​

Q6/15 made progress on draft revised G.698.2 and its extensions for 200 & 400 Gbit/s applications. Q6/15 decided to adopt CFEC based mapping for those application codes for 80 km distances and OFEC based mapping for 200 – 450 km distances. Q6/15 discussed definition of maximum spectral excursion for 25G NRZ applications in the revision of G.698.1, G.698.2 and G.698.4 and also discussed many proposals on the new Recommendation G.owdm “Multichannel WDM applications with single-channel optical interfaces in the O-band".

Q8/15 worked on optical fibre submarine cable systems, and discussed the revision of G.suppl.41 for including information about OSNR measurement methods, GAWBS (guided acoustic-wave Brillouin scattering) coefficient and fibre colour identification for high fibre pairs count cable. Q8/15 also agreed to start studying scientific monitoring submarine cable system as two new work items, which focused on the characteristics and requirements for both of telecommunication and dedicated sensing submarine cable systems.

Q16/15 was merged with former Q17/15 and part to former Q7/15, and worked on connectivity, operation and maintenance of optical physical infrastructures. Q16/15 consented the revised L.201“Performance requirements for passive optical nodes: sealed closures for outdoor environments". Q16/15 also made progress on new Recommendations L.cid (cable identification), L.font (network terminal box) and the revision of L.400 (Optical fibre splices). It was agreed to consent these work items at the next SG15 meeting in December 2021.​

Furthermore, the revised ITU-T Technical Paper "Guide on the use of ITU-T L-series Recommendations related to optical technologies for outside plant" was agreed.

WP3/15 – Transport network characteristics
WP3 Chairman: Malcolm Betts; WP3 Vice-Chairman: Glenn Parsons​

• Q10/15 is continuing to work revisions to G.8012 (Ethernet UNI and NNI) and G.8021 (Ethernet equipment) to simplify and align the Recommendations with the work in external standards.
• Q11/15 is continuing work to evolve and enhance the OTN Recommendations including the addition of a new work item to add an OTU0 (1.25Gbit/s) interface. Discussion has been initiated on the support for the beyond 400Gbit/s interfaces being defined in IEEE 802.3. Work is continuing on G.osu to provide support for clients at rates below 1Gbit/s.
• Q11/15 is also continuing to work on MTN Recommendations for protection and equipment.
• Q12/15 has consented a new Recommendation G.7703 on the ASON architecture. This will supersede G.8080 and aligns the description of ASON architecture with the SDN architecture in G.7702 and the common control components in G.7701.
• Q12/15 and Q14/15 are continuing to discuss how AI/ML capabilities fit into the management and control architecture with a focus on the interfaces to the transport network.
• Q13/15 Has continued to enhance the set of Recommendations on frequency synchronization and precision time distribution. This included incorporating the enhancements defined in IEEE1588-2019.
• Q13/15 and Q6/15 will hold a short interim meeting to discuss the measurement of fibre delay, including any asymmetry.
• 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 work on the management of the transport network and has consented a Recommendation (G.876) on the management of the media network.
• 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 Ethernet and network synchronization.
  

Q10/15 agreed an Implementers' Guide for G.8001 (Ethernet terms and definitions) to reflect the incorporation in G.8010 Amd.3 of a subset of the G.8001 terms and definitions. Work advanced on revising G.8012 (Ethernet UNI and NNI) and G.8021 (Ethernet equipment) to update them as needed, simplify them (via direct referencing of relevant mechanisms specified in non-ITU-T standards), and also supersede G.8012.1 and G.8021.1. Progress was made towards planned consent in December 2021 and a series of three E-meetings was approved to continue this work in the interim. Future work is also planned towards September 2022 consent of G.8121 Amd.1 (MPLS-TP equipment) to allow MPLS-TP packets to be encapsulated into OPUflex using Idle Mapping Procedure.

Q11/15 consented an amendment to G.703 that defines the requirements for a high accuracy (one pulse-per-second) synchronization interface.  Significant progress was made on a range of topics, with new work items approved for amendments to four Recommendations at the next meeting, including adding an OTN OTU0 interface to G.709 and CRC test vectors for the MTN Path overhead to G.8312.  While OTN already has the flexibility to carry clients with rates over 400 Gbit/s, there was significant discussion at this meeting around new potential OTN optimizations associated with these higher rates, especially as they relate to the new “B400G" Ethernet client signals that IEEE 802.3 is beginning to consider.  Agreement was reached to create a Q11/15 Living List to capture and organize the topics to consider, which will lead to one or more formal new work items at a future meeting.  Due to the very large number of incoming contributions, it was necessary to defer contributions not addressed at this meeting to be the subjects of the first of three Q11/15 interim meetings.  While the deferred contributions cover a range of topics, the largest blocks are associate with developing the new Recommendations for G.8321 MTN equipment and the G.osu switched path layer network for carrying sub-1G clients over OTN.  Q11/15 intends to hold two additional interim meetings to continue work on these and other topics.

Q12/15 consented G.7703 (ASON architecture) which will supersede G.8080. ASON and SDN control of transport networks (in G.7702) share many functions and architecture in common as described in G.7701 (Common control aspects). Work continues on Revisions to G.7701 and G.7702. Also consented was G.8010 Amendment 3 (Architecture of Ethernet layer networks). Discussions continued on how AI/ML capabilities fit into management and control architecture, and what data they need from transport networks.

Q13/15 consented several Recommendations at this meeting. Revision to G.8265.1 (PTP profile for frequency sync), Amendment 2 to G.8275.1 and G.8275.2 (PTP profiles for time sync) to address, among other things, the use of recently released standard IEEE 1588-2019. G.8273.4 Amendment 1, clock for partial timing support, with several improvements and the addition of Noise Tolerance Testing details. G.8271.2 revision with improvements on the definition of the network limits for partial timing support. G.8275 Amendment 1 (time sync architectures) addresses alignment with the updated PTP profiles, including guidelines on the use of IEEE1588-2019.
Good progress was made also on recommendation G.781.1, Synchronization layer functions for packet-based synchronization that is planned for consent at the next SG15 plenary.  To mention initial discussions held on the new sync requirements defined by 3GPP related to the use of 5G in Industrial automation applications. This may trigger some future studies in Q13/15.
Initial discussions have been held with Q11/15 on new topics: synchronization for MTN and timing aspects related to the transport of CBR over OSU. Further discussion will be required at future meetings.
Q13/15 plans to hold one correspondence activity on simulations required for some time sync scenarios not addressed yet; e-meetings are planned to make progress on various topics, and address the contributions that could not be discussed at this meeting due to lack of time. One special e-meeting is planned with Q6/15 to discuss solutions for fiber delay measurements. This is an important topic for Q13/15 as it concerns control of asymmetries that can impact time sync performance. Q13/15 experts also plan to work with Q14/15 on PTP and SyncPhy YANG data modelling.  ​

Q14/15 made good progress at this meeting. It consented four Recommendations: new G.876 (Optical media network management and IM), G.7714.1 (Transport network automatic discovery) amendment, new G.7719 (Management IM for MC components), new G.8052.2 (Ethernet resilience IM/DM), and agreed on G.Suppl.media-im-ex. Progress was made on the other active work items. It also initiated two new work items: amendment to G.876 and amendment to G.7721 (Synchronization management and IM).
Q14/15 plans to hold four tracks of correspondence activities (each of which includes a series of 5 to 6 virtual meetings) on modeling coordination (with invited modelling experts from IEEE 1588, IEEE 802.1, IEEE 802.3, ONF, MEF, BBF, IETF, TM Forum), MC management & operation, MTN management & ECC, and OTN & Optical media management.

Decisions (ITU-T SG15, April 2021)
AAP Approval

WP1/15 – AAP Approval

Consent

WP1/15 - Consent

* 30-day editing period was requested before initiating last call.

​WP2/15 - Consent

WP3/15 - Consent

* 30-day editing period was requested before initiating last call.

Agreement

WP1/15 - Agreement

WP2/15 - Agreement

​WP3/15 - Agreement

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