Recommendation ITU-T G.709/Y.1331 (2020) Amd.2 (02/2022) Interfaces for the optical transport network
Summary
History
FOREWORD
Table of Contents
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
          6.1.1 OTN digital structure
          6.1.2 OTN optical 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=0,1,2,3,4,4-SC) frame structure
     11.2 Scrambling for OTUk (k=0,1,2,3,4)
     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
          12.2.1 ODU0, ODU1, ODU2, ODU3, ODU4, ODU25, ODU50, ODUCn
               12.2.1.1 ODUk (k=0,1,2,3,4), ODU25/50 and ODUCn transporting frequency synchronization information
          12.2.2 ODU2e
          12.2.3 ODUflex for CBR client signals
          12.2.4 ODUflex for PRBS and Null test signals
          12.2.5 ODUflex for GFP-F mapped packet client signals
          12.2.6 ODUflex for IMP mapped client signals
13 Optical payload unit (OPU)
14 Overhead information carried over the OSC and OCC
     14.1 OSC
     14.2 OCC
          14.2.1 OCh-O transport over OTN optical networking interface, type II
          14.2.2 OTSiG-O transport over OTN optical networking interface, type II
15 Overhead description
     15.1 Types of overhead
          15.1.1 Optical payload unit overhead (OPU OH)
          15.1.2 Optical data unit overhead (ODU OH)
          15.1.3 Optical transport unit overhead (OTU OH)
          15.1.4 OCh-O
          15.1.5 OMS-O
          15.1.6 OTS-O
          15.1.7 General management communications overhead (COMMS OH)
          15.1.8 OTSiG-O
     15.2 Trail trace identifier and access point identifier definition
     15.3 OTS-O description
          15.3.1 OTS trail trace identifier (TTI)
          15.3.2 OTS backward defect indication – Payload (BDI-P)
          15.3.3 OTS backward defect indication – Overhead (BDI-O)
          15.3.4 OTS payload missing indication (PMI)
     15.4 OMS-O description
          15.4.1 OMS forward defect indication – Payload (FDI-P)
          15.4.2 OMS forward defect indication – Overhead (FDI-O)
          15.4.3 OMS backward defect indication – Payload (BDI-P)
          15.4.4 OMS backward defect indication – Overhead (BDI-O)
          15.4.5 OMS payload missing indication (PMI)
          15.4.6 OMS multiplex structure identifier (MSI)
     15.5 OCh-O and OTSiG-O description
          15.5.1 OCh and OTSiA forward defect indication – Payload (FDI-P)
          15.5.2 OCh and OTSiA forward defect indication – Overhead (FDI-O)
          15.5.3 OCh and OTSiA open connection indication (OCI)
          15.5.4 Blank clause
          15.5.5 OTSiA backward defect indication – Payload (BDI-P)
          15.5.6 OTSiA backward defect indication – Overhead (BDI-O)
          15.5.7 OTSiA trail trace identifier (TTI)
          15.5.8 OTSiG transmitter structure identifier (TSI)
     15.6 OTU/ODU frame alignment OH description
          15.6.1 OTU/ODU frame alignment overhead location
          15.6.2 OTU/ODU frame alignment overhead definition
               15.6.2.1 Frame alignment signal (FAS)
               15.6.2.2 Multiframe alignment signal (MFAS)
     15.7 OTU OH description
          15.7.1 OTU overhead location
          15.7.2 OTU overhead definition
               15.7.2.1 OTU section monitoring (SM) overhead
                    15.7.2.1.1  OTU SM trail trace identifier (TTI)
                    15.7.2.1.2  OTU SM error detection code (BIP-8)
                    15.7.2.1.3  OTU SM backward defect indication (BDI)
                    15.7.2.1.4  OTU SM backward error indication and backward incoming alignment error (BEI/BIAE)
                    15.7.2.1.5  OTUk, OTU25 and OTU50 SM incoming alignment error overhead (IAE)
                    15.7.2.1.6  OTU SM reserved overhead (RES)
                    15.7.2.1.7  OTUCn SM status (STAT)
               15.7.2.2 OTU general communication channel 0 (GCC0)
               15.7.2.3 OTU reserved overhead (RES)
               15.7.2.4 OTU OTN synchronisation message channel (OSMC)
                    15.7.2.4.1  Generation of event message timestamps
                         15.7.2.4.1.1 OTN interface event message timestamp point
                         15.7.2.4.1.2 Event timestamp generation
          15.7.3 OTUkV overhead
     15.8 ODU OH description
          15.8.1 ODU OH location
          15.8.2 ODU OH definition
               15.8.2.1 ODU path monitoring (PM) overhead
                    15.8.2.1.1  ODU PM trail trace identifier (TTI)
                    15.8.2.1.2  ODU PM error detection code (BIP-8)
                    15.8.2.1.3  ODU PM backward defect indication (BDI)
                    15.8.2.1.4  ODU PM backward error indication (BEI)
                    15.8.2.1.5  ODU PM status (STAT)
                    15.8.2.1.6  ODU PM delay measurement (DMp)
                    15.8.2.1.7  ODU PM reserved overhead (RES)
               15.8.2.2 ODU tandem connection monitoring (TCM) overhead
                    15.8.2.2.1  ODU TCM trail trace identifier (TTI)
                    15.8.2.2.2  ODU TCM error detection code (BIP-8)
                    15.8.2.2.3  ODU TCM backward defect indication (BDI)
                    15.8.2.2.4  ODU TCM backward error indication (BEI) and backward incoming alignment error (BIAE)
                    15.8.2.2.5  ODU TCM status (STAT)
                    15.8.2.2.6  TCM overhead field assignment
                    15.8.2.2.7  Blank clause
                    15.8.2.2.8  ODU TCM delay measurement (DMti, i=1 to 6)
                    15.8.2.2.9  ODU TCM reserved overhead (RES)
               15.8.2.3 ODU general communication channels (GCC1, GCC2)
               15.8.2.4 ODU automatic protection switching and protection communication channel (APS/PCC)
               15.8.2.5 Blank clause
               15.8.2.6 ODU experimental overhead (EXP)
               15.8.2.7 ODU reserved overhead (RES)
     15.9 OPU OH description
          15.9.1 OPU OH location
          15.9.2 OPU OH definition
               15.9.2.1 OPU payload structure identifier (PSI)
                    15.9.2.1.1  OPU payload type (PT)
               15.9.2.2 OPU mapping specific overhead
16 Maintenance signals
     16.1 OTS maintenance signals
          16.1.1 OTS payload missing indication (OTS-PMI)
     16.2 OMS maintenance signals
          16.2.1 OMS forward defect indication – Payload (OMS-FDI-P)
          16.2.2 OMS forward defect indication – Overhead (OMS-FDI-O)
          16.2.3 OMS payload missing indication (OMS-PMI)
     16.3 OCh and OTiSA maintenance signals
          16.3.1 OCh and OTiSA forward defect indication – Payload (OCh-FDI-P, OTSiA-FDI-P)
          16.3.2 OCh and OTiSA forward defect indication – Overhead (OCh-FDI-O, OTSiA-FDI-O)
          16.3.3 OCh and OTiSA open connection indication (OCh-OCI, OTSiA-OCI)
     16.4 OTU maintenance signals
          16.4.1 OTUk (k=1,2,3) alarm indication signal (OTUk-AIS)
          16.4.2 OTUCn alarm indication signal (OTUCn-AIS)
     16.5 ODU maintenance signals
          16.5.1 ODU alarm indication signal (ODU-AIS)
          16.5.2 ODUk open connection indication (ODUk-OCI)
          16.5.3 ODU locked (ODU-LCK)
     16.6 Client maintenance signal
          16.6.1 Generic AIS for constant bit rate signals
17 Mapping of client signals
     17.1 OPU client signal fail (CSF)
     17.2 Mapping of CBR2G5, CBR10G, CBR10G3 and CBR40G signals into OPUk
          17.2.1 Mapping a CBR2G5 signal (e.g., STM-16, CMGPON_D/CMGPON_U2) into OPU1
          17.2.2 Mapping a CBR10G signal (e.g., STM-64, CMXGPON_D/CMXGPON_U2) into OPU2
          17.2.3 Mapping a CBR40G signal (e.g., STM-256) into OPU3
          17.2.4 Mapping a CBR10G3 signal (e.g., 10GBASE-R) into OPU2e
     17.3 Blank clause
     17.4 Mapping of GFP frames into OPUk (k=0,1,2,3,4,flex)
          17.4.1 Mapping of GFP frames into an extended OPU2 payload area
     17.5 Mapping of test signal into OPU
          17.5.1 Mapping of a NULL client into OPU
          17.5.2 Mapping of PRBS test signal into OPU
     17.6 Mapping of a non-specific client bit stream into OPUk
          17.6.1 Mapping bit stream with octet timing into OPUk
          17.6.2 Mapping bit stream without octet timing into OPUk
     17.7 Mapping of other constant bit-rate signals with justification into OPUk
          17.7.1 Mapping a sub-1.238 Gbit/s CBR client signal into OPU0
               17.7.1.1 1000BASE-X transcoding
               17.7.1.2  FC-100
               17.7.1.3 SBCON/ESCON
          17.7.2 Mapping a supra-1.238 to sub-2.488 Gbit/s CBR client signal into OPU1
               17.7.2.1 FC-200
          17.7.3 Mapping CBR client signals into OPU2
          17.7.4 Mapping CBR client signals into OPU3
               17.7.4.1 40GBASE-R multi-lane processing and transcoding
          17.7.5 Mapping CBR client signals into OPU4
               17.7.5.1 100GBASE-R multi-lane processing
     17.8 Mapping a 1000BASE-X and FC-1200 signal via timing transparent transcoding into OPUk
          17.8.1 Mapping a 1000BASE-X signal into OPU0
          17.8.2 Mapping an FC-1200 signal into OPU2e
     17.9 Mapping a supra-2.488 Gbit/s CBR signal into OPUflex using BMP
          17.9.1 FC-400 and FC-800
          17.9.2 FC-1600
          17.9.3 FC-3200
     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
          17.13.1 25GBASE-R
          17.13.2 200GBASE-R and 400GBASE-R
          17.13.3 50GBASE-R
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
          19.1.1 OPU2 tributary slot allocation
          19.1.2 OPU3 tributary slot allocation
          19.1.3 OPU1 tributary slot allocation
          19.1.4 OPU4 tributary slot allocation
          19.1.5 OPU25 tributary slot allocation
          19.1.6 OPU50 tributary slot allocation
     19.2 ODTU definition
     19.3 Multiplexing ODTU signals into the OPUk
          19.3.1 ODTU12 mapping into one OPU2 tributary slot
          19.3.2 ODTU13 mapping into one OPU3 tributary slot
          19.3.3 ODTU23 mapping into four OPU3 tributary slots
          19.3.4 ODTU01 mapping into one OPU1 1.25G tributary slot
          19.3.5 ODTU2.ts mapping into ts OPU2 1.25G tributary slots
          19.3.6 ODTU3.ts mapping into ts OPU3 1.25G tributary slots
          19.3.7 ODTU4.ts mapping into ts OPU4 1.25G tributary slots
          19.3.8 ODTU25.ts mapping into ts OPU25 1.25G tributary slots
          19.3.9 ODTU50.ts mapping into ts OPU50 1.25G tributary slots
     19.4 OPUk multiplex overhead and ODTU justification overhead
          19.4.1 OPUk multiplex structure identifier (MSI)
               19.4.1.1 OPU2 multiplex structure identifier (MSI) – Payload type 20
               19.4.1.2 OPU3 multiplex structure identifier (MSI) – Payload type 20
               19.4.1.3 OPU1 multiplex structure identifier (MSI) – Payload type 20
               19.4.1.4 OPU4 multiplex structure identifier (MSI) – Payload type 21
               19.4.1.5 OPU2 multiplex structure identifier (MSI) – Payload type 21
               19.4.1.6 OPU3 with 1.25G tributary slots (payload type 21) multiplex structure identifier (MSI)
               19.4.1.7 OPU25 multiplex structure identifier (MSI) – Payload type 21
               19.4.1.8 OPU50 multiplex structure identifier (MSI) – Payload type 21
          19.4.2 OPUk payload structure identifier reserved overhead (RES)
          19.4.3 OPUk multiplex justification overhead (JOH)
               19.4.3.1 Asynchronous mapping procedures (AMP)
               19.4.3.2 Generic mapping procedure (GMP)
          19.4.4 OPU multiframe identifier overhead (OMFI)
     19.5 Mapping ODUj into ODTUjk
          19.5.1 Mapping ODU1 into ODTU12
          19.5.2 Mapping ODU1 into ODTU13
          19.5.3 Mapping ODU2 into ODTU23
          19.5.4 Mapping ODU0 into ODTU01
     19.6 Mapping of ODUj into ODTUk.ts
          19.6.1 Mapping ODUj into ODTU2.M
          19.6.2 Mapping ODUj into ODTU3.M
          19.6.3 Mapping ODUj into ODTU4.M
          19.6.4 Mapping ODUj into ODTU25.M
          19.6.5 Mapping ODUj into ODTU50.M
20 Mapping ODUk signals into the ODTUCn signal and the ODTUCn into the OPUCn tributary slots
     20.1 OPUCn tributary slot definition
          20.1.1 OPUCn tributary slot allocation
     20.2 ODTUCn definition
     20.3 Multiplexing ODTUCn signals into the OPUCn
          20.3.1 ODTUCn.ts mapping into ts OPUCn 5G tributary slots
     20.4 OPUCn multiplex overhead and ODTU justification overhead
          20.4.1 OPUCn multiplex structure identifier (MSI)
               20.4.1.1 OPUCn multiplex structure identifier (MSI) – Payload type 22
          20.4.2 OPUCn payload structure identifier reserved overhead (RES)
          20.4.3 OPUCn multiplex justification overhead (JOH)
               20.4.3.1 Generic mapping procedure (GMP)
          20.4.4 OPUCn multiframe identifier overhead (OMFI)
     20.5  Mapping ODUk into ODTUCn.ts
          20.5.1 Mapping ODUk into ODTUCn.M
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.3.1 Errors detected before 512B/513B encoder
          B.3.2 Errors detected by 512B/513B decoder
     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
          D.4.1 (CnD(t) encoding and decoding for OPUk
          D.4.2 (CnD(t) encoding and decoding for OPUCn
Annex E  Adaptation of parallel 64B/66B encoded clients
     E.1 Introduction
     E.2 Clients signal format
     E.3 Client frame recovery
          E.3.1 40GBASE-R client frame recovery
          E.3.2 100GBASE-R client frame recovery
     E.4 Additions to Annex B transcoding for parallel 40GBASE-R clients
          E.4.1 40GBASE-R BIP-8 transparency
          E.4.2 Errors detected by 40GBASE-R to OPU3 mapper
          E.4.3 Errors detected by 40GBASE-R to OPU3 de-mapper
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
          F.3.1 State diagram conventions
          F.3.2 State variables
               F.3.2.1  Constants
               F.3.2.2 Variables
               F.3.2.3 Functions
               F.3.2.4  Counters
          F.3.3 State diagrams
Annex G  Mapping ODU0 into a low latency OTU0 (OTU0LL)
     G.1 Introduction
     G.2 Optical transport unit 0 low latency (OTU0LL)
          G.2.1 OTUk frame structure
          G.2.2 Scrambling
Annex H  OTUCn sub rates (OTUCn-M)
     H.1 Introduction
     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
          XI.3.1 Generating ODUflex(GFP,n,k) clock from OPUk clock
          XI.3.2 Generating ODUflex(GFP,n,k) clock from system clock
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
     XV.1 Client timing based
     XV.2 Local clock based
Appendix XVI   Implications of OTSiG (de)modulator processes and OCh|OTSiG overhead trail termination functions being located in adjacent network elements
     XVI.1 Introduction
     XVI.2 Black link deployment without co-location of OTSiG (de)modulator and OTSiG-O_TT/OCh-O_TT function
     XVI.3 Failure correlation for black link deployment without colocation of OTSiG (de)modulator and OTSiG-O_TT/OCh-O_TT function
Bibliography
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