1

OTN NEWBIES

WHY OTN

• SDH/SONET • OAMP for a transparnet mixture for protocols

including ip,ethernet,generic frame procedure etc.• Single wavelength technology• DWDM• Served to increase the existing fibre bandwidth • Introduced new network elements like optical

amplifiers ,mux,demux ,switchs etc• Lacked the protection and management of sonet

WHY OTN CONTINUE

• OTN ----->HYBRID OF SONET AND DWDM• Combines the benefits of sonet with the bandwidth

expandabilty of dwdm• Applies oamp of sonet to the dwdm networks• Enables transparent and wave length manageability

multi wavelength networks to sonet networks

Foreword

• According to the ITU-T Recommendation G.709, an Optical Transport Network (OTN) is composed of a set of optical network elements connected by optical fiber links. The network provides functionality of transport, multiplexing, routing, management, supervision, and survivability of optical channels carrying client signals.

• This architecture can be seen as a combination of the advantages of SDH/SONET technology with the flexibility of DWDM. Using OTN, the OAM&P functionality of SDH/SONET is applied to DWDM optical networks.

• Compared to SDH/SONET, OTN has the following advantages:• • Stronger error correction mechanisms• • More levels of tandem connection monitoring• • Transparent transport of client signals• • Switching scalabilityIntroduction

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Contents

1. OTN Introduction 1.1 OTH1.2 OTN Port Structure1.3 Multiplexing/Mapping Principles and Bit Rates1.4 Overhead Description1.5 Maintenance Signals and Functions of Different

Layers1.6 Alarms and Performance Events

Page5

OTN

• Optical transport network (OTN)– An OTN network is composed of a set of optical

NEs connected by optical fiber links. These NEs are able to provide functions such as transport, multiplexing, routing, management, supervision, and protection (survivability) of client signals, according to the requirements specified in REC. G.872.

Page6

Features of OTN

• Compared with SDH and SONET networks, an OTN network

has the following features:– Ultra capacity with high accuracy, T-bit/second per fiber over

DWDM lines

– Service transparency for client signals

– Asynchronous mapping, powerful FEC function, simplified network

design, and reduced costs

• Compared with traditional WDM networks, an OTN network

has the following features:– Enhanced OAM and networking capabilities for all services

– Dynamic electrical/optical-layer grooming

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8

OTN Standard System

Structure

OTN

OTN network structureG.872

ASON network structureG.8080

Structure and

mappingGeneric frame protocol (GFP)G.7041

Link capacity adjustment scheme (LCAS) for virtual concatenation signalsG.7042

Ports on an OTN networkG.709

Equipmentfunctions

and features

Features of function blocks of equipment on an OTN networkG.798

Transport network equipment features: description methods and general functionsG.806

Physical-layer

featuresOptical ports for intra-office systemsG.693

Optical security rule and requirements in an optical transport systemG.664

Physical-layer ports on an OTN network G.959.1

Network

protection

Linear protection on an OTN networkG.873.1

Ring protection on an OTN networkG.873.2

Jitter and

performance

Jitter and shift control on an OTN networkG.8251Bit error performance parameters and specifications on

international channels of multiple carriers on an OTN networkG.8201

Equipment

management

Management features of NEs on an OTN networkG.874OTN network: Protocol-neutral management information model for the network element G.874.1

OTN Network Layers and Port Structure

• OPUk: optical channel payload unit-k• ODUk: optical channel data unit-k• OTUk: completely standardized optical

channel transport unit-k• OTUkV: functionally standardized Optical

channel transport unit-k• OCh: optical channel with full

functionality• OChr: optical channel with reduced

functionality• OMS: optical multiplex section• OTS: optical transmission section • OPS: optical physical section • OTM: optical transport module

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ODUk (ODUkP and ODUkT)OPUk

OTUk OTUkV OTUk OTUkV

OCh OChr

OMSnOTSn

OPSn

IP/MPLS ATM Ethernet STM-N

OTM-0.mOTM-nr.m

OTM-n.m

OTM-n.m Containment Relationships

• “n” represents the maximum number of wavelengths that can be supported at the lowest bit rate supported by the wavelengths. “m” equals 1, 2, 3, 12, 23, or 123.

• OTS_OH, OMS_OH, OCh_OH and COMMS OH information fields are contained in the OOS.• The optical supervisory channel (OSC) is used to transmit OOSs.

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OMSn payload

OCCp OCCp OCCp

OCh payload

ODUk FECOH

OPUkOH

Client signal

OPUk payloadOHOPUk

ODUk

OTUk[V]

OCh

OCG-n.m

OTM-n.m OTSn payloadOTSn OH

OMSn OH

OCC

o

OChOH

OCC

o

OCC

o

OMU-n.m

Non-

asso

ciat

ed O

H

OOS

Com

mon

m

anag

emen

t O

H

OTM

-n.

m

OTM overhead signal (OOS)

l 2

l 1

l n

l OSC

OTN Ports

• User to network interface (UNI)• Network node interface (NNI)

– Inter-domain interface (IrDI)– Intra-domain interface (IaDI)

– Between equipment provided by different vendors (IrVI)– Within subnet of one vendor (IaVI)

• The completely standardized OTUk is used at OTM IrDIs and OTM IaDIs.• The partly standardized OTUk is used at OTM IaDIs.

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OTMUNI

OTM NNIIaDI-IrVI

OTM NNIIaDI-IaVI

OTM NNIIaDI-IaVI

Network Operator B

Vendors X Vendors Y

OTMNNIIrDI

Network Operator

C

USER A

Contents

1. OTN introduction 1.1 Optical transport hierarchy 1.2 OTN interface structure1.3 Multiplexing/mapping principles and bit rates1.4 Overhead description1.5 Maintenance signals and function for different

layers1.6 Alarm and performance events

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13Page13

OTN Frame Formats (k = 1, 2, or 3)

3825

40801 7 8 14 15 16 17 3824

1

2

3

4

OPU k payloadO

PUk

OH

OPUk - optical channel payload unit

ODUk OH

ODUk - Optical Channel Data Unit

Client signal mapped in

OPUk payload

Client signal

OTUKFEC

OTUk OH

OTUk - Optical Channel Transport Unit

Alignment

Alignment

K:1 - 2.5G2 - 10G3 - 40G

OTN Electrical Overhead Overview

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ODUk OH TCMACT: tandem connection monitoring

activation/deactivation control channel TCMi: tandem connection monitoring i FTFL: fault type and fault location reporting

channel PM: path monitoring EXP: experimental GCC1/2: general communication channel 1/2 APS/PCC: automatic protection switching

coordination channel/protection communication control channel

Alignment OHFAS: frame alignment signalMFAS: multiframe alignment signal

OTUk OH SM: section monitoring GCC0: general communication channel 0 RES: reserved for future international

standardization

OPUk OH PSI: payload structure identifierJC: justification control NJO: negative justification opportunity

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2 TCM1

TCM4

PM

TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS MFAS SM GCC0 RES JCRES17

Frame Alignment Signal

Page15

Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6

1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8

OA1 OA1 OA1 OA2 OA2 OA2

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2 TCM1

TCM4

PM

TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS MFAS SM GCC0 RES JCRES

17

Frame alignment signal (FAS) A six-byte OTUk-FAS signal is defined in row 1 and columns 1 to 6 of the OTUk

overhead.

OA1 is 0xF6 (1111 0110) and OA2 is 0x28 (0010 1000).

Multiframe Alignment Signal

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MFAS OH byte

MFAS sequence

1 2 3 4 5 6 7 8

0 0 0 0 0 0 0 00 0 0 0 0 0 0 10 0 0 0 0 0 1 00 0 0 0 0 0 1 10 0 0 0 0 1 0 0

....

..

1 1 1 1 1 1 1 01 1 1 1 1 1 1 10 0 0 0 0 0 0 00 0 0 0 0 0 0 1..

Multiframe alignment signal (MFAS) It is defined in row 1 and column 7.

The value of the MFAS byte is increased by OTUk/ODUk

frame and the MFAS byte provides a maximum of 256

multiframes.

Individual OTUk/ODUk overhead signals may use this

central multiframe to lock their 2, 4, 8, 16, or 32

multiframes to the main frame.

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2 TCM1

TCM4

PM

TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS SM GCC0 RES JCRES

17

MFAS

OTUk Section Monitoring Overhead

Page17

Trail trace identifier (TTI) A one-byte overhead is defined to transport 64-byte TTI

signals.

The 64-byte TTI signal should be aligned with the OTUk

multiframe and transmitted four times per multiframe.

TTI structure: 16-byte SAPI: source access point identifier

16-byte DAPI: destination access point identifier

32-byte operator specified information

Operatorspecified

TTI BIP-8

BEI/BIAE BDI

RES

1 2 3 4 5 6 7 8

1 2 3IA

E

63

32

0

1516

31

SAPI

DAPI

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2 TCM1

TCM4

PM

TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS GCC0 RES JCRES

17

MFAS SM

OTUk Section Monitoring Overhead

• Bit interleaved parity-8 (BIP-8)– For section monitoring and a one-byte error detection code signals are defined. – This byte provides a bit interleaved parity-8 (BIP-8) code.– OTUk BIP-8 is computed over bits in the OPUk (columns 15 to 3824) area of OTUk frame i,

and inserted in the OTUk BIP-8 overhead location in OTUk frame i+2.

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BIP8

OPUk

1 14 15 3824

Frame i

Frame i+1

Frame i+2

OTUk Section Monitoring Overhead

• Backward error indication/backward incoming alignment error (BEI/BIAE)

– A four-bit BEI and BIAE signal is defined.

– This signal is used to transmit in the upstream direction the count of interleaved-bit blocks and incoming alignment error (IAE) conditions.

– During an IAE condition the code "1011" is inserted into the BEI/BIAE field and the error count is ignored. Otherwise the error count (0-8) is inserted into the BEI/BIAE field.

Page19

Operatorspecified

TTI BIP-8

BEI/BIAE BDI

RES

1 2 3 4 5 6 7 8

1 2 3IA

E

63

32

0

1516

31

SAPI

DAPI

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2 TCM1

TCM4

PM

TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS GCC0 RES JCRESMFAS SM

OTUk Section Monitoring Overhead

• Backward defect indication (BDI)

– A single-bit BDI signal is defined to transmit the signal

failure status detected by the section termination sink

function in the upstream direction.

– BDI is set to "1" to indicate an OTUk backward defect

indication; otherwise, it is set to "0".

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Operatorspecified

TTI BIP-8

BEI/BIAE BDI

RES

1 2 3 4 5 6 7 8

1 2 3IA

E

63

32

0

1516

31

SAPI

DAPI

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2 TCM1

TCM4

PM

TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS GCC0 RES JCRES

17

MFAS SM

OTUk Section Monitoring Overhead

• Incoming alignment error (IAE)

– A single-bit IAE signal is defined to allow the S-CMEP

ingress point to inform its peer S-CMEP egress point

that an alignment error in the incoming signal has been

detected.

– IAE is set to "1" to indicate a frame alignment error;

otherwise it is set to "0".

• RES (reserved)

– Two bits are reserved (RES) for future international

standardization. They are set to "00".

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Operatorspecified

TTI BIP-8

BEI/BIAE BDI

RES

1 2 3 4 5 6 7 8

1 2 3IA

E

63

32

0

1516

31

SAPI

DAPI

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2 TCM1

TCM4

PM

TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS GCC0 RES JCRES

17

MFAS SM

OTUk GCC0 and RES Overhead

• General communication channel (GCC0)

– Two bytes are allocated in the OTUk overhead to support a general communications

channel between OTUk termination points.

– A clear channel is located in row 1 and columns 11 and 12.

• RES (reserved)

– Two bytes of the OTUk overhead are reserved for future international

standardization.

– They are located in row 1 and columns 13 and 14.

– They are set to all “0”s.

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RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2 TCM1

TCM4

PM

TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS RES JCRES

17

MFAS SM GCC0

ODUk Path Monitoring Overhead

Page23

TTI / BIP-8 / BEI / BDI For path monitoring, this overhead’s functions are the

same as those of the OTUk SM signal, except that BEI

signals do not support the BIAE function.

They are located in row 3 and columns 10 to 12.

Operatorspecified

TTI BIP-8

BEI BDI

STAT

1 2 3 4 5 6 7 8

1 2 3

63

32

0

1516

31

SAPI

DAPI

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2 TCM1

TCM4TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS RES JCRES

17

MFAS SM GCC0

PM

ODUk Path Monitoring Overhead

Page24

Operatorspecified

TTI BIP-8

BEI BDI

STAT

1 2 3 4 5 6 7 8

1 2 3

63

32

0

1516

31

SAPI

DAPI

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2 TCM1

TCM4TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS RES JCRES

17

MFAS SM GCC0

PM

Bit 678 Status

000 Reserved for future international standardization

001 Normal path signal

010 Reserved for future international standardization

011 Reserved for future international standardization

100 Reserved for future international standardization

101 Maintenance signal: ODUk - LCK

110 Maintenance signal: ODUk - OCI

111 Maintenance signal: ODUk - AIS

Status (STAT) For path monitoring, three bits are defined as status bits. They indicate the presence of a maintenance signal.

ODUk PM delay measurement (DMp)

• For ODUk path monitoring, a one-bit path delay measurement (DMp) signal is defined to convey the start of the delay measurement test.

• DMp signal is inserted by the DMp originating P-CMEP and sent to the far-end P-CMEP, This far-end P-CMEP loops back the DMp signal towards the originating P-CMEP

ODUk TCM Overhead

Page26

TTIi/BIP-8i/BEIi/BIAEi/BDIi For each tandem connection monitoring field,

this overhead’s functions are the same as those

of OTUk SM signals.

Six fields of the ODUk TCM overhead are defined

in row 2 and columns 5 to 13, and row 3 and

columns 1 to 9 of the ODUk overhead.

TTIi BIP-8i

BEIi/BIAEi BDIi

STATi

1 2 3 4 5 6 7 8

1 2 3

63

32

0

1516

31

SAPI

DAPI

Operatorspecific

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS RES JCRESMFAS SM GCC0

PMTCM1TCM2TCM3

TCM6 TCM5 TCM4

ODUk TCM Overhead

Page27

TTIi BIP-8i

BEIi/BIAEi BDIi

STATi

1 2 3 4 5 6 7 8

1 2 3

63

32

0

1516

31

SAPI

DAPI

Operatorspecified

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIGCC2 APS/PCC RES

EXP

FAS RES JCRES

17

MFAS SM GCC0

PMTCM1

Bit 678 Status

000 No source TC

001 In use without IAE

010 In use without IAE

011 Reserved for future international standardization

100 Reserved for future international standardization

101 Maintenance signal: ODUk -LCK

110 Maintenance signal: ODUk -OCI

111 Maintenance signal: ODUk -AIS

TCM2TCM3

TCM6 TCM5 TCM4

STAT (status) For each tandem connection monitoring field, three

bits are defined as status bits. They indicate the presence of a maintenance signal if

there is an incoming alignment error at the source TC-CMEP, or if there is no source TC-CMEP active.

Nested and Cascaded ODUk Monitored Connections

Page28

A1 B1 C1 C2 B2 B3 B4 A2

A1 - A2

B1 - B2

C1 - C2

B3 - B4

TCM1 TCM1

TCM2

TCM1

TCM2

TCM3

TCM1

TCM2

TCM1 TCM1

TCM2

TCM1

TCM2

TCM3

TCM4

TCM5

TCM6

TCMi TCM OH field not in use TCMi TCM OH field in use

TCM2

TCM3

TCM4

TCM5

TCM6

TCM2

TCM3

TCM4

TCM5

TCM6

TCM3

TCM4

TCM5

TCM6

TCM3

TCM4

TCM5

TCM6

TCM3

TCM4

TCM5

TCM6

TCM4

TCM5

TCM6

Overlapped ODUk Monitored Connections

Page29

A1 B1 C1 C2B2 A2

A1 - A2

B1 - B2

C1 - C2

TCM1 TCM1

TCM2

TCM1

TCM2

TCM3

TCM1

TCM2

TCM1

TCMi TCM OH field not in use TCMi TCM OH field in use

TCM2

TCM3

TCM4

TCM5

TCM6

TCM2

TCM3

TCM4

TCM5

TCM6

TCM3

TCM4

TCM5

TCM6

TCM3

TCM4

TCM5

TCM6

TCM4

TCM5

TCM6

ODUk TCM ACT Coordination Protocol

Page30

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2

TCM4TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIAPS/PCC RES

EXP

FAS RES JCRES

17

MFAS SM GCC0

PMTCM1

GCC2

TCM activation/deactivation (TCMACT)

A one-byte TCM activation/deactivation field is located in row 2 and

column 4.

Its definition is to be defined in future.

ODUk GCC1/GCC2

Page31

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2

TCM4TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIAPS/PCC RES

EXP

FAS RES JCRES

17

MFAS SM GCC0

PMTCM1

GCC2

General communication channel (GCC1/GCC2) Two fields of the two bytes are allocated in the ODUk overhead to support two

general communication channels between any two NEs with access to the ODUk

frame structure (for example, at 3R regeneration points).

The bytes for GCC1 are located in row 4 and columns 1 and 2, and the bytes for

GCC2 are located in row 4 and columns 3 and 4 of the ODUk overhead.

ODUk APS/PCC Channel

Page32

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2

TCM4TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIRES

EXP

FAS RES JCRES

17

MFAS SM GCC0

PMTCM1

GCC2 APS/PCC

Automatic protection switching/protection communication control

(APS/PCC) A four-byte ODUk-APS/PCC signal is defined in row 4 and columns 5 to 8 of the ODUk

overhead.

For linear protection schemes, bit assignments for these bytes and the bit oriented protocol

are given in ITU-T G.873.1. Bit assignment and byte oriented protocol for ring protection

schemes are to be defined in future.

A maximum of eight levels of nested APS/PCC signals may be present in this field.

ODUk FTFL Channel

• Fault Type & Fault Location (FTFL)

– One byte is allocated in the ODUk overhead to transport a 256-byte FTFL message.

– The byte is located in row 2 and column 14 of the ODUk overhead.

– The 256-byte FTFL message consists of two 128-byte fields. The forward field is

allocated in bytes 0 to 127 of the FTFL message. The backward field is allocated in

bytes 128 to 255 of the FTFL message.

Page33

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2

TCM4TCMACT

GCC1

RES JC

RES JC

NJOPSIAPS/PCC RES

EXP

FAS RES JCRES

17

MFAS SM GCC0

PMTCM1

GCC2

FTFL

ODUk Experimental and Reserved Overhead

• Experimental (EXP)– Two bytes are allocated in the ODUk overhead for experimental use.

– They are located in row 3 and columns 13 and 14 of the ODUk overhead.

– There is no requirement for forwarding the EXP overhead over different (sub)networks.

• RES– 9 bytes are reserved in the ODUk overhead for future international standardization.

– They are located in row 2 and columns 1 to 3, and row 4 and columns 9 to 14 of the ODUk

overhead.

– They are set to all “0”s.

Page34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2

TCM4TCMACT

GCC1

FTFL RES JC

RES JC

NJOPSIAPS/PCC

FAS RES JCRES

17

MFAS SM GCC0

PMTCM1

GCC2

EXP

RES

RES

OPUk Payload Structure Identifier

• Payload structure identifier (PSI)– One byte is allocated in the OPUk overhead to

transport a 256-byte payload structure

identifier (PSI) signal.

– It is aligned with the ODUk multiframe.

– PSI[0] contains a one-byte payload type.

PSI[1] to PSI[255] are mapping and

concatenation specific.

Page35

255

0

1

PT

Mapping and concatenation specific

RES

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

1

2

3

4

TCM3

TCM6 TCM5

TCM2

TCM4TCMACT

GCC1

RES JC

RES JC

NJOAPS/PCC RES

EXP

FAS RES JCRES

17

MFAS SM GCC0

PMTCM1

GCC2

FTFL

PSI

Payload Type Code Points

MSB 1234 LSB 1234 Hex CodeMeaning

0000 0001 01 Experimental mapping

0000 0010 02 Asynchronous CBR mapping

0000 0011 03 Bit synchronous CBR mapping

0000 0100 04 ATM mapping

0000 0101 05 GFP mapping

0000 0110 06 Virtual Concatenated signal

0001 0000 10 Bit stream with octet timing mapping

0001 0001 11 Bit stream without octet timing mapping

0010 0000 20 ODU multiplex structure

0101 0101 55 Not available

0110 0110 66 Not available

1000 xxxx 80-8F Reserved codes for proprietary use

1111 1101 FD NULL test signal mapping

1111 1110 FE PRBS test signal mapping

1111 1111 FF Not availablePage36

OPUk Mapping Specific Overhead

• Justification control/negative justification opportunity/reserved (JC/NJO/RES)

– Seven bytes are reserved in the OPUk overhead for the mapping and concatenation specific overhead.

– These bytes are located in rows 1 to 3 and columns 15 and 16, and row 4 and column 16.

– 255 bytes in the PSI are reserved for mapping and concatenation specific purposes.

Page37

RES

1

2

3

4

TCM3

TCM6 TCM5

TCM2

TCM4TCMACT

GCC1

RES JC

JC

APS/PCC RES

EXP

FAS RES JCRESMFAS SM GCC0

PMTCM1

GCC2 PSI

FTFL

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

RES

NJO

Forward Error Correction (FEC)• Forward Error Correction (FEC)

• Add redundancy to a message through encoding prior to transmission to enable the receiver (decoder) to correct errors induced in the communication channel

• Roughly 7%-25% of each OTN frame is dedicated to an error correcting code • Resulting in (choice of) lower error rates, lower transmission power, greater transport distance• Standardized G.975 (Reed-Solomon) code and also proprietary enhanced codes

• Reed-Solomon Code (RS) 255/239• 239 base data bits• 16 added overhead bits: (6.7% overhead)• Corrects for 8 or less bit errors in 239 bits

• 8 x 16 x 4 = 512 bits per OTU frame• Anything over 8 bits is completely uncorrected• Typical gain (NCG) is ~6.5 dB at 1e-12 BER

• Enhanced FEC schemes are defined in ITU-T G975.1• Defines super FEC codes that have higher correction ability than RS (255, 239)• G.975.1 - I.4 and I.7 are popular OSNR (dB)

LogBER

10-12 ~6.5dB Gain @ 10-12 BER

With FEC

No FEC

FEC• The OTUk (k=1,2,3,4) forward error correction (FEC) contains the Reed-

Solomon RS(255,239) FEC codes. Transmission of the OTUk FEC is mandatory for k=4 and optional for k=1,2,3. If no FEC is transmitted, fixed stuff bytes (all-0s pattern) are to be used

• For interworking of equipment supporting FEC, with equipment not supporting FEC (inserting fixed stuff all-0s pattern in the OTUk (k=1,2,3) FEC area), the FEC supporting equipment shall support the capability to disable the FEC decoding process (ignore the content of the OTUk (k=1,2,3) FEC)

Client Signal Mapping Methods

o Mapping methods provide a means for rate adapting a client signal into a server layer container (ODUj or ODUflex)• Three methods: Asynchronous Mapping Procedure (AMP), Bit-synchronous Mapping Procedure (BMP)

and Generic Mapping Procedure (GMP)• Mapping may also utilize client signal transcoding (e.g., GFP, 1024B/1027B, etc)

o Bit-synchronous Mapping Procedure (server rate synchronous to client rate)• Bit synchronously maps client signal into server layer payload area

o Asynchronous Mapping Procedure (client and server rates asynchronous)• Monitors client rate relative to server rate (derived from local oscillator) and performs stuffing operations

once per lower rate container frame (negative and positive justification operations)• Signals stuffing operations through justification control bits to far end (demux)

o Generic Mapping Procedure (client and server rates synchronous or asynchronous)• Monitors client rate relative to server rate, adjusts number of bytes sent per server frame, and distributes

bytes evenly throughout server frame• Signals bytes (and residual bits) per frame via Cm and CnD control bits to far end (demux)

41

OH

Payload Area

client data

stuff

server frame or multi-frame

0

memory

Pserver?

Pserver

client data

indication =

read/write enable

payload area

frame start

clock

Cm(t)

enable

GMP can automatically adapt CBR services to an OTN container. It is the key technology

for an OTN network to bear multiple services. Service rate information transmitted in overheads Sigma-delta algorithm M byte bit width Separation of data and clocks

GMP Mapping

42

ODUflex

OH

OHServices with a fixed bit rate

Client signals

Packet services

Client services

OHGMP

TSi TSj

ODUflex

OHBMP

TSi TSjGMP

GFP

Map CBR services to ODUflex services using synchronized packet encapsulation. Map packet services to ODUflex services using GFP. Map ODUflex services to HO OPUk services using GMP.

ODUflex

OTN Mapping Procedure Summary

Mapping method Application

Asynchronous MappingProcedure (AMP)

Mapping SONET/SDH client signals into OTN

Bit-synchronous MappingProcedure (BMP)

Alternative method for mapping SONET/SDH client signals into OTN

Mapping CBR clients into ODUflex(CBR)

Generic Mapping Procedure(GMP)

Mapping non-SONET/SDH CBR clients into ODUk (k = 0, 1, 2, 3, 4) and low rate TDM clients into ODU0

Timing Transparent Transcoding (TTT) using a combination of GFP and GMP

Transcoding the native client signal into a lower bit rate CBR stream in order to increase bandwidth efficiency, and maintain client character and timing information transparency

GFP frames or ATM cells into an OPU payload container

Mapping packet clients into ODUk (k = 0, 1, 2, 3, 4) with GFP (Generic Framing Procedure) encapsulation

Mapping packet clients into an ODUflex(GFP) with GFP encapsulation

Mapping ATM (Asynchronous Transfer Mode) cells into OTN

Overclocked OTNo OTN line rates were originally defined to match SONET/SDH signals. Unfortunately, the 10 GigE

LAN PHY signal (10.3125 Gbit/s) does not fit into a standard OPU2 (9.995 Gbit/s) payload rate.

o Overclocking enables the transport of 10 GbE LAN signals transparently over OTN networks as per ITU-T series G supplement 43. Offers real bit transparency of 10GbE LAN signals.

o Compensates for rate mismatch between 10GbE LAN and the OPU2 payload by raising the overall OTU2 data rate from the standard 10.709 Gbit/s to fit the 10GbE LAN client signal.

o Over-clocked OTN supports the following optical line rates for mapping and multiplexing 10GigE LAN signals (10G FC is also an overclocked rate, i.e. OTU1f and OTU2f):

• OTU2e: 11.0957 Gbits/s ±100 ppm• OTU1e: 11.0491 Gbits/s ±100 ppm• OTU3e1: 44.569 Gbits/s ±100 ppm (for multilpexing ODU1e)• OTU3e2: 44.583 Gbits/s ±100 ppm (for multilpexing ODU2e)

o The transparent transportation of 10 GigE LAN signals means that the full 10 Gigabit Ethernet data rate (10.3125 Gbit/s) is transported over OTN, including PCS 64B/66B coded information, inter-frame filler (IPG), MAC FCS, preamble, start-of-frame delimiter (SFD) and ordered sets (remote fault indication).

Client Signal Mapping Summary

Client Signal OPUk Justification Method

Comment

1GE OPU0 GMP Uses GFP-T CBR clients: ≤ 1.238 Gbit/s OPU0 GMP Includes STM-1,

STM-4, FC-100 CBR clients: 1.238 Gbit/s < client ≤ 2.488 Gbit/s

OPU1 GMP Includes FC-200

STS-48 OPU1 AMP or BMP STS-192 OPU2 AMP or BMP 10GE LAN PHY OPU2e BMP Fiber Channel FC-1200 OPU2e BMP Uses TTT/GFP-T STS-768 OPU3 AMP or BMP 40GE OPU3 GMP Transcoded 100GE OPU4 GMP CBR clients: client > 2.488 Gbit/s OPUflex(CBR) BMP Includes FC-400,

FC-800, IB-SDR, IB-DDR, IB-QDR

Packet clients OPUk, k=0,1,2,3,4 GFP Idles GFP-F Packet client streams OPUflex(GFP) GFP Idles GFP-F

ODU Definitions

ODU0 Definition

o Smallest container defined in G.709 (OTN Standard)• 1.25G container size (specifically 1.244160 Gbit/s, +/- 20ppm)• Established in October 2009 for transport of Gigabit Ethernet

o Sized to fit existing OTN hierarchy• x 2 into ODU1• x 8 into ODU2• x 32 into ODU3• x 80 into ODU4

o ODU0 can carry:• 1GbE• OC-3• OC-12• 1G-FC

o No OTU0 physical layer• Only a lower order wrapper for 1GbE mapped into standardized physical layers• OTU1 and above

ODU1 Definition

o Original tier of the hierarchy to transport 2.5G signals• ODU1 = 2.498775Gbit/s• OTU1 = 2.666057Gbit/s• Can be used as a higher order ODU to carry lower order ODU0s

o Divided into 2 x 1.25G tributary slots:• ODU0 maps into 1 tributary slot

o OPU1 can carry:• OC-48• 2G-FC

ODU2 Definition

o Original tier of the hierarchy to transport 10G signals• ODU2 = 10.037273Gbit/s• OTU2 = 10.709224Gbit/s• Can be used as a higher order ODU to carry lower order ODUs

o Divided into 4 x 2.5G or 8 x 1.25G tributary slots:• ODU0 maps into 1 tributary slot• ODU1 maps into 1 x 2.5G or 2 x 1.25G tributary slot(s)• ODUflex maps into 1-8 x 1.25G tributary slots

o OPU2 can carry:• OC-192

ODU2e Definition

o Newer Low Order (LO) tier of the hierarchy (Oct 2009) to transport “proprietary” 10G signals

• Serves as a logical wrapper for 10GbE when carried over a standardized physical layer of OTU3 or OTU4

• Part of compromise made to enable standards progress - most commonly deployed “proprietary” transparent mapping of 10GbE

• Over-clocked physical OTU2e signal remains in G.sup43

o Can map 10 into OPU4 (which is sized to carry 100GBASE-R)

o Can map as ODUflex in 9 x 1.25G OPU3 tributary slots (up to 3 ODU2e per OPU3)

o OPU2e can carry:• 10GbE• Transcoded 10GFC

ODU3 Definition

o Original tier of the hierarchy to transport 40G signals• ODU3 = 40.319218Gbit/s• OTU3 = 43.018410Gbit/s• Can be used as a higher order ODU to carry lower order ODUs

o Divided into 16 x 2.5G or 32 x 1.25G tributary slots:• ODU0 maps into 1 tributary slot• ODU1 maps into 1 x 2.5G or 2 x 1.25G tributary slot(s)• ODU2 maps into 4 x 2.5G or 8 x 1.25G tributary slot(s)• ODU2e maps into 9 x 1.25G tributary slots• ODUflex maps into 1-32 x 1.25G tributary slots

o OPU3 can carry:• OC-768• Transcoded 40GbE

ODU4 Definition

o Newer tier of the hierarchy (Oct-09)• ODU4 = 104.794445Gbit/s• OTU4 = 111.809973Gbit/s• Can be used as a higher order ODU to carry lower order ODUs

o Divided into 80 x 1.25G tributary slots:• ODU0 maps into 1 tributary slot• ODU1 maps into 2 tributary slots• ODU2 or ODU2e maps into 8 tributary slots• ODU3 maps into 32 tributary slots• ODUflex maps into 1-80 tributary slots

o OPU4 can carry:• 100GBase-R

Based on support for 100GE or (10 × OC192/STM64 × 239/227)

ODUflex Description

Client mapped to ODU2 then to 8 x 1.25Gbps HO Tributary Slots

Client mapped to ODUflex then to 5 x 1.25Gbps HO Tributary Slots

Wasted Capacity

Re-usable Capacity~6G

ODUFlex6 GbpsClient

10G ODU2

o Flexible ODU rate for transport of arbitrary client rates to improve HO ODUk bandwidth utilization (transport efficiency, basically replaces VCAT)

o Provides a single variable size container for client mapping

o Two forms of client signal to ODUflex mapping:

• Constant Bit Rate (CBR) client signals• ODUflex Rate = 239/238 x CBR rate with up to ± 100ppm clock tolerance (bit-

synchronous to client clock, BMP)• Ex. ODUflex (CBR) carrying FC-400 is 4.268Gbit/s (239/238 x 4.250Gbit/s) ±100 ppm

• GFP-F mapped packet client signals• Chosen to be multiples of tributary slot (TS) rate• ODUflex Rate = N × TS with ± 100ppm clock tolerance

Multiplexing

• HO ODU: Higher Order ODU. The HO ODUk (k can be 1, 2, 2e, 3, or 4) represents the entity transporting a multiplex of LO ODUj tributary signals in its OPUk area. Essentially, an ODUk that directly becomes an OTUk is referred to as a HO ODU. ODUk is often used to refer to ODU entities used as an HO ODU.

• LO ODU: Lower Order ODU. The LO ODUj (j can be 0, 1, 2, 2e, 3, 4, or flex) represents the container transporting a client of the OTN that is either directly mapped into an OTUk (k = j) or multiplexed into a server HO ODUk (k > j) container. When an ODUk is being discussed in terms of carrying a client signal, it is referred to as a LO ODUk. For example, client signals are mapped into the OPU of a LO ODU. ODUj is often used to refer to ODU entities acting as LO ODU.

The terminology Low Order ODU (LO ODU) and High Order ODU (HO ODU) were introduced to distinguish the function being served by the ODU in that application:

High and Low Order ODUs

High and Low Order ODUs

OPU1

OPU2 ODU2 (H)

OPU2Client

OPU3 ODU3 (H)

OPU3Client ODU3 (L)

OTU1

OTU2

OTU3

Client

OCh

OCh

OChODU1 (L)

ODTU12

ODU2 (L)

ODTU13ODTU23

x4

x16x4

2.666G

10.709G

43.018Gor

or

10.037G

2.499G

40.319G

The concepts of lower order and high order ODU are specific to the role that the ODU plays within a single domain. The same ODU can be both LO and HO, depending on the functional context. For example, a client signal is mapped into a LO ODUk, but if that ODUk is transmitted directly within an OTUk, then the ODUk is also a HO ODU.

Intermediate carrier applications create a similar situation. The HO ODUk transmitted by the end carrier may have multiple LO ODU signals multiplexed into it. When the intermediate carrier multiplexes this ODUk into a higher rate HO ODUj for transparent transport, the intermediate carrier is treating the ODUk as a LO ODU. High and Low order ODUs can also be referred to simply by using (L) or (H) as in the example below.

Multiplexing

Mapping ODUk (L) = Low Order ODUODUk (H) = High Order ODU

ODU Multiplexing

OP

U2

OH

ODU2 OH

Alignm

ODU1 OH OPU Client Signal

Align

ODU1 OH OPU Client Signal

Align

ODU1 OH OPU Client Signal

Align

OP

U1

OH

ODU1 OH OPU Client Signal

Align

OPU k PayloadOP

U1

OH

ODU1 OH OPU Client Signal

Align

ODU1

OP

U1

OH

ODU2 OH

OTU2 OHAlignm

ODU1 OH OPU Client Signal

Align

ODU1 OH OPU Client Signal

Align

ODU1 OH OPU Client Signal

Align

OP

U1

OH

ODU1 OH OPU Client Signal

Align OTU2FEC

ODU2

OTU2

SONET OC-48

OTN standards have evolved to include a standard multiplexing hierarchy, defining exactly how the lower-rate signals map into higher-rate payloads. This allows any OTN switch and WDM platform to electronically groom and switch lower-rate services within 10 Gbps, 40 Gbps, or 100 Gbps wavelengths.

As an example, a 2.5 Gbps signal (OC-48) is mapped into an ODU1 frame. Four of these 2.5 Gbps containers can be mapped into an OPU2 frame and then wrapped with additional OH and FEC for transport in an OTU2. This is single-stage multiplexing (ODU1 ODU2), but multistage multiplexing is defined as well, e.g. ODU1 ODU2 ODU3.

Standard G.709 Mapping and Multiplexing Structure

Multiplexing

Mapping ODUk (L) = Low Order ODUODUk (H) = High Order ODU

OPU0

OPU1 ODU1 (H)

ODTU01

OPU1

OPU2 ODU2 (H)

OPU2Client

OPU3 ODU3 (H)

OPU3Client ODU3 (L)

OTU1

OTU2

OTU3

OPU4 ODU4 (H)

OPU4Client ODU4 (L)OTU4

Client

Client

OCh

OCh

OCh

OCh

ODU0 (L)

ODU1 (L)

ODTU2.tsODTU12

ODU2 (L)

ODTU3.tsODTU13ODTU23

ODTU4.ts

x2

x8

x32

x80

x4

x16

x40

x4

x10x2

or

or

or

or 2.666G

10.709G

43.018G

111.809G

10.037G

2.499G

40.319G

104.794G

1.244G

OPU2e10GbE ODU2e (L)

x10

x3

OPUflex ClientODUflex (L)

x80/ts

x32/ts

x8/ts

Non-standard rates not shown

59

OTN Multiplexing and Mapping Structure

60

OTN Multiplexing and Mapping Structure