ITU-T Rec. G.709 Y.1331 (06 2020) Interfaces for the optical transport network.pdf

I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n

ITU-T G.709/Y.1331

TELECOMMUNICATION

STANDARDIZATION SECTOR

OF ITU

(06/2020)

SERIES G: TRANSMISSION SYSTEMS AND MEDIA,

DIGITAL SYSTEMS AND NETWORKS

Digital terminal equipments – General

SERIES Y: GLOBAL INFORMATION

INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS,

NEXT-GENERATION NETWORKS, INTERNET OF

THINGS AND SMART CITIES

Internet protocol aspects – Transport

Interfaces for the optical transport network

Recommendation ITU-T G.709/Y.1331

ITU-T G-SERIES RECOMMENDATIONS

TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS

INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100–G.199

GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-

TRANSMISSION SYSTEMS

G.200–G.299

INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE

SYSTEMS ON METALLIC LINES

G.300–G.399

GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS

ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC

LINES

G.400–G.449

COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450–G.499

TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600–G.699

DIGITAL TERMINAL EQUIPMENTS G.700–G.799

General G.700–G.709

Coding of voice and audio signals G.710–G.729

Principal characteristics of primary multiplex equipment G.730–G.739

Principal characteristics of second order multiplex equipment G.740–G.749

Principal characteristics of higher order multiplex equipment G.750–G.759

Principal characteristics of transcoder and digital multiplication equipment G.760–G.769

Operations, administration and maintenance features of transmission equipment G.770–G.779

Principal characteristics of multiplexing equipment for the synchronous digital hierarchy G.780–G.789

Other terminal equipment G.790–G.799

DIGITAL NETWORKS G.800–G.899

DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900–G.999

MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-

RELATED ASPECTS

G.1000–G.1999

TRANSMISSION MEDIA CHARACTERISTICS G.6000–G.6999

DATA OVER TRANSPORT – GENERIC ASPECTS G.7000–G.7999

PACKET OVER TRANSPORT ASPECTS G.8000–G.8999

ACCESS NETWORKS G.9000–G.9999

For further details, please refer to the list of ITU-T Recommendations.

Rec. ITU-T G.709/Y.1331 (06/2020) i

Interfaces for the optical transport network

Summary

Recommendation ITU-T G.709/Y.1331 defines the requirements for the optical transport network (OTN) interface signals of the optical transport network, in terms of:

– OTN hierarchy

– functionality of the overhead in support of multi-wavelength optical networks

– frame structures

– bit rates

– formats for mapping client signals.

Edition 6.0 of this Recommendation includes the text of Amendments 1, 2, 3, Corrigendum 1 and 2 to Edition 5.0 of this

Recommendation, addition of 25 and 50 Gbit/s OTU, ODU and OPU frame formats and multiplexing of lower rate

ODUk/flex signals into these two OPUs, extension of the supported ODUflex(IMP) bit rates to any rate, specification of frequency synchronous OTU and ODU and addition of a new appendix with examples of ODUflex(GFP) and

ODUflex(IMP) clock generation methods. Edition 6.0 furthermore clarifies that the ODUflex(GFP) bit rate can be any rate and is not limited to the recommended bit rates, updates the OTN interface terminology, corrects the replacement signal definitions for some of the Ethernet client signals and restricts the FlexE aware sub-rate granularity to 25 Gbit/s.

History

Edition Recommendation Approval Study Group Unique ID*

1.0 ITU-T G.709/Y.1331 2001-02-09 15 11.1002/1000/5350

1.1 ITU-T G.709/Y.1331 (2001) Amd. 1 2001-11-29 15 11.1002/1000/5629

2.0 ITU-T G.709/Y.1331 2003-03-16 15 11.1002/1000/6265

2.1 ITU-T G.709/Y.1331 (2003) Amd. 1 2003-12-14 15 11.1002/1000/7060

2.2 ITU-T G.709/Y.1331 (2003) Cor. 1 2006-12-14 15 11.1002/1000/8982

2.3 ITU-T G.709/Y.1331 (2003) Amd. 2 2007-11-22 15 11.1002/1000/9155

2.4 ITU-T G.709/Y.1331 (2003) Cor.2 2009-01-13 15 11.1002/1000/9646

2.5 ITU-T G.709/Y.1331 (2003) Amd. 3 2009-04-22 15 11.1002/1000/9671

3.0 ITU-T G.709/Y.1331 2009-12-22 15 11.1002/1000/10398

3.1 ITU-T G.709/Y.1331 (2009) Cor. 1 2010-07-29 15 11.1002/1000/10875

3.2 ITU-T G.709/Y.1331 (2009) Amd. 1 2010-07-29 15 11.1002/1000/10874

3.3 ITU-T G.709/Y.1331 (2009) Amd. 2 2011-04-13 15 11.1002/1000/11115

4.0 ITU-T G.709/Y.1331 2012-02-13 15 11.1002/1000/11485

4.1 ITU-T G.709/Y.1331 (2012) Cor. 1 2012-10-29 15 11.1002/1000/11776

4.2 ITU-T G.709/Y.1331 (2012) Amd. 1 2012-10-29 15 11.1002/1000/11774

4.3 ITU-T G.709/Y.1331 (2012) Amd. 2 2013-10-22 15 11.1002/1000/11982

4.4 ITU-T G.709/Y.1331 (2012) Amd. 3 2014-12-05 15 11.1002/1000/12363

4.5 ITU-T G.709/Y.1331 (2012) Cor. 2 2015-01-13 15 11.1002/1000/12365

4.6 ITU-T G.709/Y.1331 (2012) Amd. 4 2015-01-13 15 11.1002/1000/12364

5.0 ITU-T G.709/Y.1331 2016-06-22 15 11.1002/1000/12789

5.1 ITU-T G.709/Y.1331 (2016) Amd. 1 2016-11-13 15 11.1002/1000/13080

5.2 ITU-T G.709/Y.1331 (2016) Cor. 1 2017-08-13 15 11.1002/1000/13298

5.3 ITU-T G.709/Y.1331 (2016) Amd. 2 2018-06-06 15 11.1002/1000/13520

5.4 ITU-T G.709/Y.1331 (2016) Amd. 3 2019-03-22 15 11.1002/1000/13742

5.5 ITU-T G.709/Y.1331 (2016) Cor. 2 2019-11-06 15 11.1002/1000/13995

6.0 ITU-T G.709/Y.1331 2020-06-06 15 11.1002/1000/14199

Keywords

Client mappings, frame formats, multiplexing, OTN.

* To access the Recommendation, type the URL http://handle.itu.int/ in the address field of your web browser, followed by the Recommendation's unique ID. For example, http://handle.itu.int/11.1002/1000/1

1830-en.

http://handle.itu.int/11.1002/1000/5350 http://handle.itu.int/11.1002/1000/5629 http://handle.itu.int/11.1002/1000/6265 http://handle.itu.int/11.1002/1000/7060 http://handle.itu.int/11.1002/1000/8982 http://handle.itu.int/11.1002/1000/9155 http://handle.itu.int/11.1002/1000/9646 http://handle.itu.int/11.1002/1000/9671 http://handle.itu.int/11.1002/1000/10398 http://handle.itu.int/11.1002/1000/10875 http://handle.itu.int/11.1002/1000/10874 http://handle.itu.int/11.1002/1000/11115 http://handle.itu.int/11.1002/1000/11485 http://handle.itu.int/11.1002/1000/11776 http://handle.itu.int/11.1002/1000/11774 http://handle.itu.int/11.1002/1000/11982 http://handle.itu.int/11.1002/1000/12363 http://handle.itu.int/11.1002/1000/12365 http://handle.itu.int/11.1002/1000/12364 http://handle.itu.int/11.1002/1000/12789 http://handle.itu.int/11.1002/1000/13080 http://handle.itu.int/11.1002/1000/13298 http://handle.itu.int/11.1002/1000/13520 http://handle.itu.int/11.1002/1000/13742 http://handle.itu.int/11.1002/1000/13995 http://handle.itu.int/11.1002/1000/14199 http://handle.itu.int/11.1002/1000/11830-en http://handle.itu.int/11.1002/1000/11830-en ii Rec. ITU-T G.709/Y.1331 (06/2020)

FOREWORD

The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication

Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis.

The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.

The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1.

In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.

NOTE

In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.

Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the

Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party.

INTELLECTUAL PROPERTY RIGHTS

ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.

As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http://www.itu.int/ITU-T/ipr/.

© ITU 2020

All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.

http://www.itu.int/ITU-T/ipr/

Rec. ITU-T G.709/Y.1331 (06/2020) iii

Table of Contents

Page

1 Scope

2 References

3 Definitions

3.1 Terms defined elsewhere

3.2 Terms defined in this Recommendation

4 Abbreviations and acronyms

5 Conventions

6 Optical transport network interface structure

6.1 Basic signal structure

6.2 Information structure for OTN interfaces

7 Multiplexing/mapping principles and bit rates

7.1 Mapping

7.2 Wavelength division multiplex

7.3 Bit rates and capacity

7.4 ODUk time-division multiplex

7.5 Interconnection of Ethernet UNI and FlexE Group UNI in two administrative domains in the OTN

8 OTN Interfaces

8.1 Point-to-point interface, type I

8.2 Point-to-point interface, type II

8.3 Optical networking interface, type II

8.4 Optical networking interface, type I

9 Media Element

10 OCh and OTSiA

10.1 OCh

10.2 Optical tributary signal assembly (OTSiA)

11 Optical transport unit (OTU)

11.1 OTUk (k=1,2,3,4,4-SC) frame structure

11.2 Scrambling for OTUk (k=1,2,3,4)

11.3 OTUCn frame structure

11.4 OTU25 and OTU50 frame structure

12 Optical data unit (ODU)

12.1 ODU frame structure

12.2 ODU bit rates and bit-rate tolerances

13 Optical payload unit (OPU)

14 Overhead information carried over the OSC and OCC

14.1 OSC

iv Rec. ITU-T G.709/Y.1331 (06/2020)

Page

14.2 OCC

15 Overhead description

15.1 Types of overhead

15.2 Trail trace identifier and access point identifier definition

15.3 OTS-O description

15.4 OMS-O description

15.5 OCh-O and OTSiG-O description

15.6 OTU/ODU frame alignment OH description

15.7 OTU OH description

15.8 ODU OH description

15.9 OPU OH description

16 Maintenance signals

16.1 OTS maintenance signals

16.2 OMS maintenance signals

16.3 OCh and OTiSA maintenance signals

16.4 OTU maintenance signals

16.5 ODU maintenance signals

16.6 Client maintenance signal

17 Mapping of client signals

17.1 OPU client signal fail (CSF)

17.2 Mapping of CBR2G5, CBR10G, CBR10G3 and CBR40G signals into

OPUk

17.3 Blank clause

17.4 Mapping of GFP frames into OPUk (k=0,1,2,3,4,flex)

17.5 Mapping of test signal into OPU

17.6 Mapping of a non-specific client bit stream into OPUk

17.7 Mapping of other constant bit-rate signals with justification into OPUk

17.8 Mapping a 1000BASE-X and FC-1200 signal via timing transparent transcoding into OPUk

17.9 Mapping a supra-2.488 Gbit/s CBR signal into OPUflex using BMP

17.10 Mapping of packet client signals into OPUk

17.11 Mapping of 64B/66B encoded packet client signals into OPUflex using

IMP

17.12 Mapping of FlexE aware signals into OPUflex

17.13 Mapping a 64B/66B PCS coded signal into OPUflex using BMP and 2-bit alignment of 66B code words

18 Blank clause

19 Mapping ODUj signals into the ODTU signal and the ODTU into the OPUk tributary slots

19.1 OPUk tributary slot definition

Rec. ITU-T G.709/Y.1331 (06/2020) v

19.2 ODTU definition

19.3 Multiplexing ODTU signals into the OPUk

19.4 OPUk multiplex overhead and ODTU justification overhead

19.5 Mapping ODUj into ODTUjk

19.6 Mapping of ODUj into ODTUk.ts

20 Mapping ODUk signals into the ODTUCn signal and the ODTUCn into the

OPUCn tributary slots

20.1 OPUCn tributary slot definition

20.2 ODTUCn definition

20.3 Multiplexing ODTUCn signals into the OPUCn

20.4 OPUCn multiplex overhead and ODTU justification overhead

20.5 Mapping ODUk into ODTUCn.ts

Annex A – Forward error correction using 16-byte interleaved RS(255,239) codecs

Annex B – Adapting 64B/66B encoded clients via transcoding into 513B code blocks

B.1 Transmission order

B.2 Client frame recovery

B.3 Transcoding from 66B blocks to 513B blocks

B.4 Link fault signalling

Annex C – Adaptation of OTU3 and OTU4 over multichannel parallel interfaces

Annex D – Generic mapping procedure principles

D.1 Basic principle

D.2 Applying GMP in OTN

D.3 Cm(t) encoding and decoding

D.4 CnD(t) encoding and decoding

Annex E – Adaptation of parallel 64B/66B encoded clients

E.1 Introduction

E.2 Clients signal format

E.3 Client frame recovery

E.4 Additions to Annex B transcoding for parallel 40GBASE-R clients

Annex F – Improved robustness for mapping of 40GBASE-R into OPU3 using 1027B code blocks

F.1 Introduction

F.2 513B code block framing and flag bit protection

F.3 66B block sequence check

Annex G – Mapping ODU0 into a low latency OTU0 (OTU0LL)

G.1 Introduction

G.2 Optical transport unit 0 low latency (OTU0LL)

Annex H – OTUCn sub rates (OTUCn-M)

H.1 Introduction vi Rec. ITU-T G.709/Y.1331 (06/2020)

H.2 OTUCn-M frame format

Annex I

Annex J – Recovery of 64B/66B encoded clients from parallel 256B/257B interfaces

Annex K – Transporting 200GbE and 400GbE am_sf<2:0> information through a single optical link between two Ethernet/OTN transponder entities in the OTN

K.1 Introduction

K.2 Client Degrade Indication (CDI) overhead

Annex L – OTU25u and OTU50u interfaces

L.1 Introduction

L.2 Bit rates

Appendix I – Range of stuff ratios for asynchronous mappings of CBR2G5, CBR10G, and CBR40G clients with 20 ppm bit-rate tolerance into OPUk, and for asynchronous multiplexing of ODUj into ODUk (k > j)

Appendix II – Examples of functionally standardized OTU frame structures

Appendix III – Example of ODUk multiplexing

Appendix IV – Blank appendix

Appendix V – ODUk multiplex structure identifier (MSI) examples

Appendix VI – Parallel logic implementation of the CRC-9, CRC-8, CRC-5 and CRC-6

Appendix VII – OTL4.10 structure

Appendix VIII – CPRI into ODU mapping

Appendix IX – Overview of CBR clients into OPU mapping types

Appendix X – Overview of ODUj into OPUk mapping types

Appendix XI – Derivation of recommended ODUflex(GFP) bit-rates based on n ×

ODUk.ts clock and examples of ODUflex(GFP,n,k) clock generation

XI.1 Introduction

XI.2 Tributary slot sizes

XI.3 Example methods for ODUflex(GFP,n,k) clock generation

Appendix XII – Terminology changes between ITU-T G.709 Edition 4, Edition 5 and

Edition 6

Appendix XIII – OTUCn sub rates (OTUCn-M) Applications

XIII.1 Introduction

XIII.2 OTUCn-M frame format and rates

XIII.3 OTUCn-M fault condition

Appendix XIV – Examples of interconnection of Ethernet UNI and FlexE Group UNI in two administrative domains in the OTN for the case that these UNIs deploy different mapping methods

Appendix XV – Examples of ODUflex(GFP) and ODUflex(IMP) clock generation methods

Bibliography

Rec. ITU-T G.709/Y.1331 (06/2020) 1

Interfaces for the optical transport network

1 Scope

The optical transport network (OTN) supports the operation and management aspects of optical networks of various architectures, e.g., point-to-point, ring and mesh architectures.

This Recommendation defines the interfaces of the OTN to be used within and between subnetworks of the optical network, in terms of:

– OTN hierarchy;

– functionality of the overhead in support of multi-wavelength optical networks;

– frame structures;

– bit rates;

– formats for mapping client signals.

Functions and process flows associated with the defined interfaces are specified in [ITU-T G.798].

The interfaces defined in this Recommendation can be applied at user-to-network interfaces (UNI) and network node interfaces (NNI) of the OTN.

2 References

The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision;

users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this

Recommendation does not give it, as a stand-alone document, the status of a Recommendation.

[ITU-T G.652] Recommendation ITU-T G.652 (2016), Characteristics of a single-mode optical fibre and cable.

[ITU-T G.693] Recommendation ITU-T G.693 (2009), Optical interfaces for intra-office systems.

[ITU-T G.695] Recommendation ITU-T G.695 (2018), Optical interfaces for coarse wavelength division multiplexing applications.

[ITU-T G.698.1] Recommendation ITU-T G.698.1 (2009), Multichannel DWDM applications with single-channel optical interfaces.

[ITU-T G.698.2] Recommendation ITU-T G.698.2 (2018), Amplified multichannel dense wavelength division multiplexing applications with single channel optical interfaces.

[ITU-T G.698.3] Recommendation ITU-T G.698.3 (2012), Multichannel seeded DWDM applications with single-channel optical interfaces.

[ITU-T G.707] Recommendation ITU-T G.707/Y.1322 (2007), Network node interface for the synchronous digital hierarchy (SDH).

[ITU-T G.709.1] Recommendation ITU-T G.709.1/Y.1331.1 (2018), Flexible OTN short-reach interfaces.

2 Rec. ITU-T G.709/Y.1331 (06/2020)

[ITU-T G.709.3] Recommendation ITU-T G.709.3/Y.1331.3 (2018), Flexible OTN long-reach interfaces.

[ITU-T G.709.4] Recommendation ITU-T G.709.4/Y.1334.4 (2020), OTU25 and OTU50 short-reach interfaces.

[ITU-T G.780] Recommendation ITU-T G.780/Y.1351 (2010), Terms and definitions for synchronous digital hierarchy (SDH) networks.

[ITU-T G.798] Recommendation ITU-T G.798 (2017), Characteristics of optical transport network hierarchy equipment functional blocks.

[ITU-T G.805] Recommendation ITU-T G.805 (2000), Generic functional architecture of transport networks.

[ITU-T G.806] Recommendation ITU-T G.806 (2012), Characteristics of transport equipment – Description methodology and generic functionality.

[ITU-T G.807] Recommendation ITU-T G.807 (2020), Generic functional architecture of the optical media network.

[ITU-T G.870] Recommendation ITU-T G.870/Y.1352 (2016), Terms and definitions for optical transport networks (OTN).

[ITU-T G.872] Recommendation ITU-T G.872 (2019), Architecture of optical transport networks.

[ITU-T G.873.1] Recommendation ITU-T G.873.1 (2014), Optical Transport Network

(OTN): Linear protection.2017

[ITU-T G.873.2] Recommendation ITU-T G.873.2 (2015), ODUk shared ring protection

(SRP).

[ITU-T G.959.1] Recommendation ITU-T G.959.1 (2018), Optical transport network physical layer interfaces.

[ITU-T G.984.6] Recommendation ITU-T G.984.6 (2008), Gigabit-capable passive optical networks (GPON): Reach extension.

[ITU-T G.987.4] Recommendation ITU-T G.987.4 (2012), 10 Gigabit-capable passive optical networks (XG-PON): Reach extension.

[ITU-T G.7041] Recommendation ITU-T G.7041/Y.1303 (2016), Generic framing procedure (GFP).

[ITU-T G.7044] Recommendation ITU-T G.7044/Y.1347 (2011), Hitless Adjustment of

ODUflex(GFP).

[ITU-T G.7712] Recommendation ITU-T G.7712/Y.1703 (2019), Architecture and specification of data communication network.

[ITU-T G.7714.1] Recommendation ITU-T G.7714.1/Y.1705.1 (2010), Protocol for automatic discovery in SDH and OTN networks.

[ITU-T G.8260] Recommendation ITU-T G.8260 (2015), Definitions and terminology for synchronization in packet networks.

[ITU-T G.8262] Recommendation ITU-T G.8262/Y.1362 (2018), Timing characteristics of a synchronous equipment slave clock.

[ITU-T G.8264] Recommendation ITU-T G.8264 (2017), Distribution of timing information through packet networks.

Rec. ITU-T G.709/Y.1331 (06/2020) 3

[ITU-T M.1400] Recommendation ITU-T M.1400 (2001), Designations for interconnections among operators' networks.

[ITU-T M.3100] Recommendation ITU-T M.3100 (2004), Generic network information model.

[ITU-T O.150] Recommendation ITU-T O.150 (1996), General requirements for instrumentation for performance measurements on digital transmission equipment.

[ITU-T T.50] Recommendation ITU-T T.50 (1992), International Reference Alphabet

(IRA) (Formely International Alphabet No. 5 or IA5) – Information technology – 7-bit coded character set for information interchange.

[IEEE 802.3] IEEE Std. 802.3:2018, Standard for Ethernet.

[IEEE 802.3cd] IEEE Std 802.3cd-2018, Standard for Ethernet Amendment 3: Media

Access Control Parameters for 50 Gb/s and Physical Layers and

Management Parameters for 50 Gb/s, 100 Gb/s, and 200 Gb/s Operation

[OIF FlexE IA] OIF, Flex Ethernet 2.0 Implementation Agreement (2018).

3 Definitions

3.1 Terms defined elsewhere

This Recommendation uses the following terms defined elsewhere:

3.1.1 Terms defined in [ITU-T G.780]:

– BIP-X

– network node interface

3.1.2 Terms defined in [ITU-T G.805]:

– adapted information (AI)

– characteristic information (CI)

– network

– subnetwork

3.1.4 Terms defined in [ITU-T G.872]:

– optical multiplex section (OMS)

– optical transmission section (OTS)

3.1.5 Terms defined in [ITU-T G.959.1]:

– optical tributary signal (OTSi).

3.1.6 Terms defined in [OIF FlexE IA]:

– FlexE Client

3.1.7 Terms defined in [ITU-T G.807]:

– optical signal maintenance entity (OSME)

4 Rec. ITU-T G.709/Y.1331 (06/2020)

3.2 Terms defined in this Recommendation

This Recommendation defines the following terms:

3.2.1 ODUk.ts: The ODUk.ts is an increment of bandwidth which when multiplied by a number of tributary slots gives the recommended size of an ODUflex(GFP,n,k) optimized to occupy a given number of tributary slots of an OPUk.

3.2.2 OTU0 low latency: The OTU0 low latency (OTU0LL) is the information structure used for transport of an ODU0 over a multi-vendor optical network interface in one administrative domain at the edge of the optical transport network.

3.2.3 optical tributary signal assembly (OTSiA): The OTSiG together with the non-associated overhead (OTSiG-O).

3.2.4 optical tributary signal group (OTSiG): The set of OTSi signals that supports an OTU.

3.2.5 optical tributary signal overhead (OTSiG-O): The non-associated overhead for an OTSiG.

3.2.6 connection monitoring end-point (CMEP): Connection monitoring end-points represent end-points of trails and correspond as such with the trail termination functions. Connection monitoring overhead (CMOH) is inserted and extracted at the CMEPs.

For the ODU and OTU the CMEPs are categorized in three classes:

– OTU section CMEP (OS_CMEP), which represents the end-points of the OTUk/OTUCn trail. The SM overhead field contains the related CMOH.

– ODU tandem connection CMEP (TC_CMEP), which represents the end-points of

ODUkT/ODUCnT trails. The TCM1..6 overhead fields contain the related CMOH.

– ODU path CMEP (P_CMEP), which represents the end-points of the ODUkP/ODUCnP trail.

The PM overhead field contains the related CMOH.

3.2.7 non-associated overhead: Supervisory information transported in an optical supervisory signal, overhead communication channel or other means.

3.2.8 optical data unit (ODU): The ODU is an information structure consisting of the information payload (OPU) and ODU related overhead, either as ODUk or ODUCn.

3.2.9 optical payload unit (OPU): The OPU is the information structure used to adapt client information for transport over the OTN, either as an OPUk or an OPUCn. It comprises client information together with any overhead needed to perform rate adaptation between the client signal rate and the OPU payload rate, and other OPU overheads supporting the client signal transport. The index k or Cn (see clause 5) is used to identify the approximate bit rate and different versions.

3.2.10 optical transport unit (OTU): The OTU is the information structure used for transport of an ODU over an OTSiA or OCh, either as an OTUk or an OTUCn.

For OCh and OTN point-to-point interface cases, the OTU overhead is used as overhead for the transport over the optical layer, and the OTU must terminate where the OCh and OTN point-to-point interface is terminated. For an OTSiA, the OTU overhead may or may not be terminated where the

OTSiA is terminated.

Three versions of the OTUk are defined: completely standardized OTUk (OTUk), functionally standardized OTUk (OTUkV) and an OTUk with completely standardized overhead and functionally standardized FEC (OTUk-v). The completely standardized OTUk is used on OTN IrDIs and may be used on OTN IaDIs. The other two are used on OTN IaDIs.

3.2.11 OCh: The OCh is an information structure consisting of the information payload (OTSiG) with a certain bandwidth and non-associated overhead (OCh-O) for management of the OCh.

Rec. ITU-T G.709/Y.1331 (06/2020) 5

3.2.12 optical transport network: An optical transport network (OTN) is composed of a set of optical network elements connected by optical fibres, that provide functionality to encapsulate, transport, multiplex, route, manage, supervise and provide survivability of client signals. The information of the client signals is processed in the digital domain and carried across the media, according to the requirements given in [ITU-T G.872].

3.2.13 optical transport network node interface (ONNI): The interface at an optical transport network node which is used to interconnect with another optical transport network node.

3.2.14 ODUflex(GFP): ODUflex for GFP-F mapped client signals with user configured bit rate.

3.2.15 ODUflex(GFP,n,k): ODUflex for GFP-F mapped client signals with user configured bit rate of n × ODUk.ts in which n = number of 1.25G tributary slots and k = ODUk.ts representative.

ODUflex(GFP,n,k) is a subset of ODUflex(GFP).

3.2.16 ODUflex(IMP): ODUflex for IMP mapped client signals with user configured bit rate.

3.2.17 ODUflex(IMP,s): ODUflex for IMP mapped client signals with bit rate of s × 239/238 ×

5 156 250 kbit/s ± 100 ppm in which s = 2, 8, n × 5 with n ≥ 1.

ODUflex(IMP,s) is a subset of ODUflex(IMP).

4 Abbreviations and acronyms

This Recommendation uses the following abbreviations and acronyms:

16FS 16 columns with Fixed Stuff

3R Reamplification, Reshaping and Retiming

AI Adapted Information

AIS Alarm Indication Signal

AMP Asynchronous Mapping Procedure

API Access Point Identifier

APS Automatic Protection Switching

ASI Asynchronous Serial Interface for DVB

BDI Backward Defect Indication

BDI-O Backward Defect Indication Overhead

BDI-P Backward Defect Indication Payload

BEI Backward Error Indication

BI Backward Indication

BIAE Backward Incoming Alignment Error

BIP Bit Interleaved Parity

BMP Bit-synchronous Mapping Procedure

CAUI (Chip to) 100 Gb/s Attachment Unit Interface

CB Control Block

CBR Constant Bit Rate

CI Characteristic Information

CM Connection Monitoring

6 Rec. ITU-T G.709/Y.1331 (06/2020)

Cm number of m-bit Client data entities

CMEP Connection Monitoring End Point

CMGPON_D Continuous Mode GPON Downstream

CMGPON_U2 Continuous Mode GPON Upstream 2

CMOH Connection Monitoring Overhead

CMXGPON_D Continuous Mode XGPON Downstream

CMXGPON_U2 Continuous Mode XGPON Upstream 2

Cn number of n-bit client data entities

CnD difference between Cn and (m/n x Cm)

CPRI Common Public Radio Interface

CRC Cyclic Redundancy Check

CS Client Specific

CSF Client Signal Fail

CTRL Control word sent from source to sink

DAPI Destination Access Point Identifier

DDR Double Data Rate

DMp Delay Measurement of ODUk path

DMti Delay Measurement of TCMi

DNU Do Not Use

DVB Digital Video Broadcast

EDC Error Detection Code

EOS End Of Sequence

ESCON Enterprise Systems Connection eSSM enhanced Synchronization Status Message

EXP Experimental

ExTI Expected Trace Identifier

FA Frame Alignment

FAS Frame Alignment Signal

FC Fibre Channel

FC Flag Continuation

FDI Forward Defect Indication

FDI-O Forward Defect Indication Overhead

FDI-P Forward Defect Indication Payload

FEC Forward Error Correction

FlexO Flexible OTN information structure

FlexO-x FlexO interface information structure of order x

FlexO-x-<fec> FlexO interface signal of order x with a FEC

Rec. ITU-T G.709/Y.1331 (06/2020) 7

FlexO-x-<fec>-m Group of m × FlexO-x-<fec> interfaces

GCC General Communication Channel

GID Group Identification

GMP Generic Mapping Procedure

GPON Gigabit-capable Passive Optical Networks

IAE Incoming Alignment Error

IB InfiniBand

IMP Idle Mapping Procedure

IP Internet Protocol

JC Justification Control

JOH Justification Overhead

LF Local Fault

LLM Logical Lane Marker

LSB Least Significant Bit

MFAS MultiFrame Alignment Signal

MFI Multiframe Indicator

MPLS Multi Protocol Label Switching

MPLS-TP Multi Protocol Label Switching – Transport Profile

MS Maintenance Signal

MSB Most Significant Bit

MSI Multiplex Structure Identifier

NJO Negative Justification Opportunity

NNI Network Node Interface

NOS Not_Operational Sequence

OCC Overhead Communication Channel

OCI Open Connection Indication

OCN Overhead Communication Network

ODTUG Optical Data Tributary Unit Group

ODTUGk/Cn Optical Data Tributary Unit Group-k/Cn

ODTUjk Optical Data Tributary Unit j into k

ODTUk/Cn.ts Optical Data Tributary Unit k/Cn with ts tributary slots

ODU Optical Data Unit

ODUk/Cn Optical Data Unit-k/Cn

ODUk/Cn.ts Optical Data Unit k/Cn fitting in ts tributary slots

ODUk/CnP Optical Data Unit-k/Cn Path monitoring level

ODUk/CnT Optical Data Unit-k/Cn Tandem connection monitoring level

OH Overhead

8 Rec. ITU-T G.709/Y.1331 (06/2020)

OMFI OPU Multi-Frame Identifier

OMS Optical Multiplex Section

OMS-O Optical Multiplex Section Overhead

OMS-P Optical Multiplex Section Payload

ONNI Optical Network Node Interface

OPS Optical Physical Section

OPSM Optical Physical Section Multilane

OPU Optical Payload Unit

OPUk/Cn Optical Payload Unit-k/Cn

OSC Optical Supervisory Channel

OSMC OTN synchronization messaging channel

OSME Optical Signal Maintenance Entity

OTL Optical Transport Lane

OTLk.n group of n Optical Transport Lanes that carry one OTUk

OTLC.n group of n Optical Transport Lanes that carry one OTUC of an OTUCn

OTN Optical Transport Network

OTS Optical Transmission Section

OTS-O Optical Transmission Section Overhead

OTS-P Optical Transmission Section Payload

OTSi Optical Tributary Signal

OTSiA Optical Tributary Signal Assembly

OTSiG Optical Tributary Signal Group

OTSiG-O Optical Tributary Signal Group – Overhead

OTU Optical Transport Unit

OTU0LL Completely standardized Optical Transport Unit-0 Low Latency

OTU4-SC Optical Transport Unit 4 with Stair Case FEC

OTUCn-M Optical Transport Unit-Cn with n OxUC overhead instances and M 5G tributary slots

OTUk/Cn completely standardized Optical Transport Unit-k/Cn

OTUkV functionally standardized Optical Transport Unit-k

OTUk-v Optical Transport Unit-k with vendor specific OTU FEC

PCC Protection Communication Channel

P-CMEP Path-Connection Monitoring End Point

PCS Physical Coding Sublayer

PJO Positive Justification Opportunity

PKT Packet

PLD Payload

Rec. ITU-T G.709/Y.1331 (06/2020) 9

PM Path Monitoring

PMA Physical Medium Attachment sublayer

PMI Payload Missing Indication

PMOH Path Monitoring Overhead

PN Pseudo-random Number

POS Position field ppm parts per million

PRBS Pseudo Random Binary Sequence

PSI Payload Structure Identifier

PT Payload Type

QDR Quad Data Rate

RES Reserved for future international standardization

RF Remote Fault

RS Reed-Solomon

RS-Ack Re-sequence Acknowledge

SAPI Source Access Point Identifier

SBCON Single-Byte command code sets Connection

SDI Serial Digital Interface

SDR Single Data Rate

Sk Sink

SM Section Monitoring

SMOH Section Monitoring Overhead

SNC Subnetwork Connection

SNC/I Subnetwork Connection protection with Inherent monitoring

SNC/N Subnetwork Connection protection with Non-intrusive monitoring

SNC/S Subnetwork Connection protection with Sublayer monitoring

So Source

SSM Synchronization Status Message

TC Tandem Connection

TC-CMEP Tandem Connection-Connection Monitoring End Point

TCM Tandem Connection Monitoring

TCMOH Tandem Connection Monitoring Overhead

TS Tributary Slot

TSI Transmitter Structure Identifier

TSOH Tributary Slot Overhead

TTI Trail Trace Identifier

TTT Timing Transparent Transcoding

10 Rec. ITU-T G.709/Y.1331 (06/2020)

TxTI Transmitted Trace Identifier

UNI User-to-Network Interface

XC Cross Connect

XGPON 10 Gigabit-capable Passive Optical Networks

5 Conventions

This Recommendation uses the following conventions:

– k or Cn: The index "k" is used to represent a supported bit rate and the different versions of

OPUk, OPUCn, ODUk, ODUCn, OTUk and OTUCn. Examples for k are "1" for an approximate bit rate of 2.5 Gbit/s, "2" for an approximate bit rate of 10 Gbit/s, "3" for an approximate bit rate of 40 Gbit/s, and "4" for an approximate bit rate of 100 Gbit/s. When the "Cn" index is used the approximate bit rate is n*100 Gbit/s. For example for Cn = C4 the approximate bit rate is 400 Gbit/s.

– x: The index x gives the approximate bit rate for a CBR signal. It is used in the form "unit value, unit, [fractional unit value]". The currently defined unit value is "G" for Gbit/s.

Examples for x are "40G" for 40 Gbit/s and "2G5" for 2.5 Gbit/s.

– -P: The suffix -P is used to identify the payload element of the signal.

– -O: The suffix -O is used to identify the non-associated overhead element of the signal.

– ODUj: When two different ODUk information structures are involved, ODUj is used to denote the lower rate ODUk information structure (e.g., for ODUk multiplexing).

The functional architecture of the optical transport network as specified in [ITU-T G.872] is used to derive the ONNI. The ONNI is specified in terms of the adapted and characteristic information present in each layer as described in [ITU-T G.805].

Transmission order: The order of transmission of information in all the diagrams in this

Recommendation is first from left to right and then from top to bottom. Within each byte the most significant bit is transmitted first. The most significant bit (bit 1) is illustrated at the left in all the diagrams.

Mapping order: The serial bit stream of a constant bit rate signal is inserted into the OPU payload so that the bits will be transmitted on the OPU/ODU in the same order that they were received at the input of the AMP, BMP or GMP mapper function. If m bits ba, bb, bc up to bm are client signal bits of which ba is the bit that is received first and bm is the bit that is received last, then ba will be mapped into bit 1 of a first OPU byte and bm will be mapped into bit 8 of an nth OPU byte (with n = m/8).

Value of reserved bit(s): The value of an overhead bit, which is reserved or reserved for future international standardization shall be set to "0".

Value of non-sourced bit(s): Unless stated otherwise, any non-sourced bits shall be set to "0".

OTUk (k=1,2,3,4), OTUCn, OTU25, OTU50, ODUk (k=0,1,2,2e,3,4,flex,25,50), ODUCn, OPUk

(k=0,1,2,2e,3,4,flex,25,50) and OPUCn overhead assignment: The assignment of an overhead in the optical transport/data/payload unit signal to each part is defined in Figure 5-1. OTUk, OTU25, OTU50, ODUk, OPUk contain one instance of OTU, ODU, OPU overhead. OTUCn, ODUCn and

OPUCn contain n instances of OTU, ODU, OPU overhead, numbered 1 to n.

Interleaved versions of the OTU, ODU and OPU overhead may be present on OTUCn interfaces.

This interleaving is interface specific and specified for OTN interfaces with standardized application codes in the interface specific Recommendations (ITU-T G.709.x series). Within the other clauses of this Recommendation an OTUCn, ODUCn and OPUCn are presented in an interface independent manner, by means of n OTUC, ODUC and OPUC instances that are marked #1 to #n.

Rec. ITU-T G.709/Y.1331 (06/2020) 11

Figure 5-1 − OTU, ODU and OPU overhead

6 Optical transport network interface structure

The optical transport network as specified in [ITU-T G.872] provides for two OTN interface types:

point-to-point interfaces and optical networking interfaces. Both OTN interface types consist of one or more optical tributary signals.

The OTN point-to-point interfaces are defined with 3R processing at each end of the interface

(terminating the optical tributary signals) and do not provide for optical layer overhead.

The OTN optical networking interfaces are defined with optical layer overhead and may not provide for 3R processing at each end of the interface, which allow optical tributary signals to be forwarded beyond the interface.

These two types of OTN interfaces consist of digital and management information defined in this

Recommendation as carried by a physical interface, the specifications of which are outside the scope of this Recommendation.

Each OTN interface may be associated with one or more application identifiers. Each application identifier represents either a standardized application code or a vendor specific identifier. An interface with one or more application codes may be used to interconnect (OTN) equipment from different vendors. An interface with one or more vendor specific identifiers is to be used to interconnect (OTN) equipment from the same vendor. When considering interconnection over an interface between user and provider administrations or provider to provider administrations, 3R termination shall be used on either side of the interface, unless mutually agreed otherwise.

6.1 Basic signal structure

The basic structure is shown in Figures 6-1 and 6-2 and consists of a digital and an optical structure.

6.1.1 OTN digital structure

The OTN digital structure (see Figure 6-1) is based on three classes of optical transport units (OTU);

the OTUk, OTU25 and OTU50 and OTUCn.

– The OTUk signal consists of a 4080 column by 4 row frame, which includes 256 columns allocated to contain a forward error correction code (FEC) and is operated at various bit rates that are represented by the value of k.

– The OTU25 and OTU50 signals consist of a 3824 column by 4 row frame, which do not include a FEC area and are operated at 25 Gbit/s and 50 Gbit/s bit rates that are represented by the values 25 and 50. FEC for the OTU25 and OTU50 signals are interface specific and not included in the OTU25 and OTU50 definition.

– The OTUCn signal consists of n interleaved 3824 columns by 4 row frames, which do not include a FEC area and is operated at n times a basic rate that is represented by OTUC. FEC for the OTUCn signal is interface specific and not included in the OTUCn definition.

The OTUCn signal may be carried via a FlexO-x-<fec>-m interface group with m = n/x FlexO-x-

<fec> interfaces; refer to [ITU-T G.709.1] and [ITU-T G.709.3].

G.709-Y.1331(12)_F5-1

R o w

Column #

Frame alignment area OTU specific overhead area

ODU specific overhead area O P

U sp ec if ic o v er h ea d a re a1

1 167 14 158

12 Rec. ITU-T G.709/Y.1331 (06/2020)

The OTU25 and OTU50 signals are carried via OTU25-RS and OTU50-RS interfaces; refer to

[ITU-T G.709.4].

The OTU contains an optical data unit (ODU), which contains an optical payload unit (OPU). The

OTUk, OTU25, OTU50, OTUCn and ODUCn are digital section layers. The ODUk (and ODUj) is a path layer.

The OTUk (k {1,2,3,4,4-SC}) is fully standardized. There are two functionally standardized alternatives: OTUk-v and OTUkV. In all cases, these provide supervision and condition the signal for transport between 3R regeneration points in the OTN.

The OTUCn, OTU25 and OTU50 provide supervision for transport between 3R regeneration points in the OTN. Note that the OTUCn, OTU25 and OTU50 do not condition the signal for transport between 3R regeneration points because encapsulation and forward error correction are not included in the OTUCn, OTU25 and OTU50 definition.

The ODU provides:

– Tandem connection monitoring (ODUjT, ODUkT, ODUCnT);

– end-to-end section supervision (ODUjP, ODUkP, ODUCnP);

– adaptation of client signals via the OPUk and OPUj (j {0, 1, 2, 2e, 3, 4, flex}, k {0, 1, 2, 2e, 3, 4, flex});

– adaptation of client ODUj signals via the OPUk (j {0, 1, 2, 2e, 3, 4, flex}, k {1, 2, 3, 4, 25, 50}, the bit rate of the ODUj is less than the OPUk payload bit rate);

– adaptation of client ODUk signals via the OPUCn (k {0, 1, 2, 2e, 3, 4, flex}).

Figure 6-1 − Digital structure of the OTN interfaces

6.1.2 OTN optical structure

The OTN optical structure (see Figure 6-2) is based on the presence of one or more optical tributary signals combined with three classes of optical overhead deployment:

– Absence of optical overhead in the case of OTN point-to-point interfaces.

– Optical overhead carried in the same fibre as the one or more optical tributary signals in the case of OTN optical networking interfaces, type I.

– Optical overhead carried via the overhead communication network (OCN) outside the fibre with one or more optical tributary signals in the case of OTN optical networking interfaces, type II.

Rec. ITU-T G.709/Y.1331 (06/2020) 13

The optical overhead is divided into three digital layers that coincide with the maintenance entities defined in [ITU-T G.872], as shown in Figure 6-2:

– Overhead to monitor the optical path maintenance entity (OCh-O and OTSiG-O), which extends between two OTSiG modulators and demodulators.

– Overhead to monitor the optical multiplex section maintenance entity, which extends between two points of optical multiplexing (OMS-O).

– Overhead to monitor the optical transmission section maintenance entity, which extends between two optical amplifiers, or between an optical multiplexer (without an amplifier) and the next optical amplifier (OTS-O).

The OTN optical networking interfaces may support optical layer overhead (represented by the entities described above). Such overhead may be transported within the optical supervisory channel

(OSC), the overhead communication channel (OCC) that is provided by the overhead communication network (OCN) (refer to [ITU-T G.7712]) or an alternative communication channel. Interfaces that support OCh-O and/or OTSiG-O support switching in the optical layer of the OCh and/or OTSiA signals which carry one optical transport unit or FlexO-x-<fec>-m group signal between 3R regeneration points. Interfaces that support OTS-O and OMS-O also support deployment of in-line optical amplifiers between optical layer switching points.

The OTN point-to-point interfaces do not support optical layer overhead and are designed to transport the optical transport unit or FlexO-x-<fec>-m group signals over a single optical span with 3R regeneration points at each end. For such cases there is no optical path layer present in the interface stack.

OTN point-to-point interfaces carry one or more OTUk or OTUCn or FlexO-x-<fec> of an

OTUCn/FlexO-x-<fec>-m group, which are monitored by means of OTUk or OTUCn or FlexO-x-

<fec>-m group overhead.

OTN optical networking interfaces carry one or more optical tributary signals, each transporting an

OTUk or an OTUCn or an OTUCn or one FlexO-x-<fec> out of an OTUCn/FlexO-x-<fec>-m group or a non-OTN client signal.

Figure 6-2 − Optical structure of the OTN interfaces

6.2 Information structure for OTN interfaces

The information structure for OTN interfaces is represented by information containment relationships and flows. The principal information containment relationships of the digital structure of the OTUk and OTUCn are described in Figures 6-3 and 6-4.

For supervision purposes in OTN optical networking interfaces, the OTU signal is terminated whenever the OCh signal is terminated and the OTU signal may be terminated when the OTSiA signal

14 Rec. ITU-T G.709/Y.1331 (06/2020) is terminated. For supervision purposes in OTN point-to-point interfaces, the OTU signals are terminated whenever the interface signal is terminated.

Figure 6-3 – Principal information containment relationship of digital structure of OTUk

Figure 6-4 – Principal information containment relationship of digital structure of OTUCn

Rec. ITU-T G.709/Y.1331 (06/2020) 15

7 Multiplexing/mapping principles and bit rates

Figures 7-1A and 7-1B show the relationship between various information structure elements and illustrates the multiplexing structure and mappings for the OTU. In the multi-domain OTN any combination of the ODU multiplexing layers may be present at a given OTN NNI. The interconnection of and visibility of ODU multiplexing layers within an equipment or domain is outside the scope of this Recommendation. Figures 7-1A and 7-1B show that a (non-OTN) client signal is mapped into an OPU. This OPU signal is mapped into the associated ODU. This ODU signal is either mapped into the associated OTU[V] signal, or into an ODTU. This ODTU signal is multiplexed into an ODTU Group (ODTUG). The ODTUG signal is mapped into an OPU. This OPU signal is mapped into the associated ODU, etc.

The OPUk (k=0,1,2,2e,3,4,flex,25,50) are the same information structures, but with different client signals. The OPUCn has a different information structure than the OPUk; the OPUCn information structure consists of n times the information structure of the OPU while the OPUk contain a single instance of the OPU information structure.

Figure 7-1A – OTN multiplexing and mapping structures

16 Rec. ITU-T G.709/Y.1331 (06/2020)

NOTE – Implementations should support the multiplexing of up to 10n ODUk (k=0,1,2,2e,3,4,flex) signals into an OPUCn.

Figure 7-1B – OTN multiplexing and mapping structures

7.1 Mapping

The client signal or an optical data tributary unit group (ODTUG) is mapped into the OPU. The OPU is mapped into an ODU and the ODU is mapped into an OTU. The OTU is mapped into an OTSiG.

The OTUk may also be mapped into an OTLk.n and an OTLk.n is then mapped into an OTSiG.

Rec. ITU-T G.709/Y.1331 (06/2020) 17

7.2 Wavelength division multiplex

Wavelength division multiplexing is used to multiplex the OTSi of one or more OTSiG for transport over an OTN interface.

For the case of the OTN optical networking interfaces, type I, the OTSi of the OSC is multiplexed for transport over the interface using wavelength division multiplexing.

7.3 Bit rates and capacity

The bit rates and tolerance of the OTU signals are defined in Table 7-1.

The bit rates and tolerance of the ODU signals are defined in clause 12.2 and Table 7-2.

The bit rates and tolerance of the OPU payload are defined in Table 7-3.

The OTU, ODU and OPU frame periods are defined in Table 7-4.

The types and bit rates of the OTL signals are defined in Table 7-5.

The 2.5G and 1.25G tributary slot related OPUk multiframe periods and 5G tributary slot OPUCn multiframe periods are defined in Table 7-6.

The ODTU payload area bandwidths are defined in Table 7-7. The bandwidth depends on the OPU type and the mapping procedure (AMP or GMP). The AMP bandwidths include the bandwidth provided by the NJO overhead byte. GMP is defined without such NJO bytes.

The bit rates and tolerance of the ODUflex(GFP,n,k) are defined in Table 7-8.

The number of OPU tributary slots required by a client ODU are summarized in Table 7-9 and specified in clauses 19.6 and 20.5.

Table 7-1 − OTU types and bit rates

OTU type OTU nominal bit rate OTU bit-rate tolerance

OTU1 255/238 × 2 488 320 kbit/s

20 ppm

(Note 5)

OTU2 255/237 × 9 953 280 kbit/s

OTU3 255/236 × 39 813 120 kbit/s

OTU4 255/227 × 99 532 800 kbit/s

OTUCn n × 239/226 × 99 532 800 kbit/s

OTU25 61677/58112 × 24 883 200 kbit/s

OTU50 61677/58112 × 49 766 400 kbit/s

NOTE 1 – The nominal OTU rates are approximately: 2 666 057.143 kbit/s (OTU1), 10 709 225.316 kbit/s (OTU2), 43 018 413.559 kbit/s (OTU3), 111 809 973.568 kbit/s (OTU4), 26 409 711.013 kbit/s (OTU25), 52 819 422.026 kbit/s (OTU50) and n × 105 258 138.053 kbit/s (OTUCn).

NOTE 2 – OTU0, OTU2e and OTUflex are not specified in this Recommendation. ODU0 signals are to be transported over ODU1, ODU2, ODU3, ODU4, ODU25, ODU50 or ODUCn signals, ODU2e signals are to be transported over ODU3, ODU4, ODU25, ODU50 and ODUCn signals and ODUflex signals are transported over

ODU2, ODU3, ODU4, ODU25, ODU50 and ODUCn signals.

NOTE 3 – The OTUk (k=1,2,3,4) signal bit rates include the FEC overhead area. The OTUCn signal bit rates do not include a FEC overhead area.

NOTE 4 – The OTU25 [OTU50] bit rate can be based on the OTU25-RS [OTU50-RS] bit rate as follows: 514/544 ×

41118/41120 × OTU25-RS [OTU50-RS] bit rate = 514/544 × 41118/41120 × 255/227 × 24 883 200 [49 766 400] kbit/s.

NOTE 5 – Refer to clause 12.2.1.1 for the bit rate tolerance of synchronous OTUk (k=1,2,3,4), OTU25/50 and

OTUCn.

18 Rec. ITU-T G.709/Y.1331 (06/2020)

Table 7-2 − ODU types and bit rates

ODU type ODU nominal bit rate ODU bit-rate tolerance

ODU0 1 244 160 kbit/s

20 ppm

(Note 4)

ODU1 239/238 × 2 488 320 kbit/s

ODU2 239/237 × 9 953 280 kbit/s

ODU3 239/236 × 39 813 120 kbit/s

ODU4 239/227 × 99 532 800 kbit/s

ODU25 61677/58112 × 24 883 200 kbit/s

ODU50 61677/58112 × 49 766 400 kbit/s

ODUCn n × 239/226 × 99 532 800 kbit/s

ODU2e 239/237 × 10 312 500 kbit/s 100 ppm

ODUflex for CBR client signals

239/238 × client signal bit rate 100 ppm

(Notes 2, 3)

ODUflex for GFP-F mapped client signals

(ODUflex(GFP))

239/238 × OPUflex(GFP) payload signal rate

100 ppm

ODUflex for GFP-F mapped client signals based on

ODUk.ts and n 1.25G tributary slots

(ODUflex(GFP,n,k))

Configured bit rate (see Table 7-8)

ODUflex for IMP mapped client signals

(ODUflex(IMP))

239/238 × OPUflex(IMP) payload signal rate

ODUflex for IMP mapped

FlexE Client signals

(ODUflex(IMP,s)) s × 239/238 × 5 156 250 kbit/s s = 2, 8, n × 5 with n ≥ 1 (refer to clause 12.2.6)

ODUflex for FlexE-aware client signals

103 125 000 × 240/238 × n/20 kbit/s

(n = n1 + n2 + .. + np)

NOTE 1 – The nominal ODU rates are approximately: 2 498 775.126 kbit/s (ODU1), 10 037 273.924 kbit/s (ODU2), 40 319 218.983 kbit/s (ODU3), 104 794 445.815 kbit/s (ODU4), 26 409

711.013 kbit/s (ODU25), 52 819 422.026 kbit/s (ODU50), 10 399 525.316 kbit/s (ODU2e), n × 105 258

138.053 kbit/s (ODUCn).

NOTE 2 – The bit-rate tolerance for ODUflex(CBR) signals is specified as 100 ppm. This value may be larger than the tolerance for the client signal itself (e.g., 20 ppm). For such case, the tolerance is determined by the ODUflex(CBR) maintenance signals, which have a tolerance of 100 ppm.

NOTE 3 – For ODUflex(CBR) signals with nominal bit rates close to the maximum ODTUk.ts payload bit rate and client rate tolerances less than 100 ppm (e.g., 10 ppm), the ODUflex(CBR) maintenance signal bit rates may exceed the ODTUk.ts payload bit rate.