Otc000005 Otn Introduction Issue1

OTN Introduction

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Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.

OTN Introduction

Optica l t ransport h ierarchy ………………………………………………Page4

OTN in te r face s t ructure…………………………………………………..Page8

Mult ip lexing/mapping pr inciples and bit rates……………...……….Page14

Overhead desc r ip t i on……………………………………………………Page19

Maintenance signals and function for different layers………………..Page39

Alarm and per formance events ……………………………………….Page50

OTN Introduction


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Page1Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.

Foreword

This course will introduce OTN, includes:

Optical transport hierarchy (OTH) , interface structure, overhead

Maintenance signals, function for different layers

Alarm and Performance events

This Course is mainly based on：ITU-T G.872 Architecture of optical transport networks

ITU-T G.709 Interfaces for the Optical Transport Network (OTN)

ITU-T G.874 Management aspects of the optical transport network element

ITU-T G.798 Characteristics of optical transport network hierarchy equipmentfunctional blocks

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Objectives

Upon completion of this course, you will be able to:

Describe OTN frame structure, maintenance signals and function

for different layers

Outline alarm and performance events generation mechanism

Analyze the alarm and performance events and locate the failures

in OTN

Reference:

ITU-T G.709

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Contents

1. Optical transport hierarchy

2. OTN interface structure

3. Multiplexing/mapping principles and bit rates

4. Overhead description

5. Maintenance signals and function for different layers

6. Alarm and performance events

Objectives for this chapter:

Describe the features of OTN

Outline the protocols which supports OTN system

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OTN

OTN（Optical Transport Network）

An Optical Transport Network (OTN) is composed of a set of Optical

Network Elements connected by optical fiber links, able to provide

functionality of transport, multiplexing, routing, management,

supervision and survivability of client signals.

One important feature of OTN is that the transmission setting of any digital customer signal is independent of specific features of the customer, that is, independence of customer.

According to the requirements given in Rec. G.872.

The optical transport network supports the operation and management aspects of optical networks of various architectures.

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Features of OTN

Compared with SDH and SONET ：

Ultra capacity with high accuracy, Terabit/second per fiber via

DWDM lines

Service transparency for client signals

Asynchronous mapping, powerful FEC function, predigest network

design and reduce the cost

Compared with traditional WDM

Enhanced OAM & networking functionality for all services

Dynamically electrical/optical layer grooming

Compared with SDH/SONET, the benefits of OTN are as follows:

Strong scalability of the capacity: The cross-connect capacity can be expanded to dozens of T bit/s.

The customer signal transparency covers payload and clock information.

The asynchronous mapping eliminates restriction on the synchronization in the whole network, with stronger FEC. The simplified system design can decrease the networking costs.

Up to 6-level TCM monitoring management capability.

Compared with the traditional WDM:

Effective monitoring capability: OAM&P and network survivability

Flexible optical/electrical grooming capability, carrier-class, manageable, and operable networking capability.

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OTN system

management

OTN

Jitter and

wander

Network protection

Equipment function and features

Structure and

mapping

Physic layer

featuresArchitecture

G.874G.874.1

G.8251G.8201

G.873.1G.873.2

G.798G.806

G.709G.7041G.7042

G.959.1G.693G.694

G.872G.8080

G.874, management features of optical transmission NE, describes the management feature of the OTN NE and transmission function of one or more network layers in the OTN. The management of the optical layer network is separated from the management of the customer layer network. Therefore, the same management method that is independent of the customer can be used. G.874 defines fault management, configuration management, billing management, and performance monitoring. G.874 describes the management network architecture model between the NE EMS and optical NE equipment management functions.

G.798, feature of equipment function block of the optical transport network, defines the function requirements of the optical transmission network in the NE equipment.

G.709, OTN interface, defines OTM-n signal requirements of OTN, including OTH, support of multi wavelength optical network overhead, frame structure, bit rate, and format of mapping customer signals.

G.872, OTN architecture, defines the relation between OTN hierarchical architecture, feature information and customer/service layer, and the function description of the network topology and layer network.

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Contents








Draw the frame structure of OTN;

Outline the function of each part in OTN frame;

Brief introduce the difference between OTM-n.m and OTM-0.m;

Describe how does a client signal are encapsulated to OTN frame.

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OTN network layers and interface structure

ODUk

OPUk

OTUk OTUkV OTUk OTUkV

OCh OChr

OMSn

OTSnOPSn

IP/MPLS ATM Ethernet STM-NOPUk: Optical channel Payload Unit-k

ODUk: Optical channel Data Unit-k

OTUk: completely standardizedOptical 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

OTM-0.mOTM-nr.m

OTM-n.m

Customer signals (for example, IP/MPLS, ATM, Ethernet, and SDH signals), served as OPU, plus the OPU payload are mapped to the OPUk, where, k is 1, 2, 3. k=1 indicates that the bit rate is about 2.5 Gbit/s, k=2 indicates that the bit rate is about 10 Gbit/s, and k=3 indicates that the bit rate is about 40 Gbit/s.

OPUk is added as the ODU payload. After ODUkP, ODUkT, frame alignment overhead, and all-zero OTU overhead are added, the ODUk is formed.

ODUk is combined into the OTU overhead and FEC region, and then mapped to the completely standardized optical channel transport unit k – OTUk, or standardized function optical channel transport unit k – OTUkV.

The OTUk is combined into OCh, and then mapped to the OCh with complete functions or, and simplified function optical channel OChr.

After the OCh is modulated to the optical channel carrier (OCC), n OCCs performs the Wavelength Division Multiplexing (WDM), and then are combined into the OMS overhead to form the OMSn interface.

After the OMSn is combined into the OTS overhead, the OTSn unit is formed.

The OChr is modulated to the OCCr. N OCCr perform the WDM to form the optical physical section OPSn. The OPSn is combined with the OMS without the monitoring information and the transport function of the OTS layer network.

To be continued in the next page

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OTN network layers and interface structure

ODUk（ODUkP,ODUkT）

OPUk

OTUk OTUkV OTUk OTUkV

OCh OChr

OMSn

OTSnOPSn

IP/MPLS ATM Ethernet STM-NOPUk: Optical channel Payload Unit-k

ODUk: Optical channel Data Unit-k

OTUk: completely standardizedOptical 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

OTM-0.mOTM-nr.m

OTM-n.m

As shown in the figure above, the OTM-n.m (n ≥1) is composed of OTSn, OMSn, OCh, OTUk/OTUkV, and ODUk.

“n” indicates the number of the maximum wavelength supported by the interface in case of the minimum bit rate supported by the wavelength. When n is 0, it indicates one wavelength.

“m” indicates the bit rate or bit rate set supported by the interface.

“r” indicates the reduced function. OTM-0.m need not label “r”, because one wavelength indicates the reduced function.

OTM-nr.m and OTM-0.m is composed of OPSn, OChr, OTUk/OTUkV, and ODUk.

The information structure that supports the OTN interface is called “OTM-n”, that is, the optical transport module-n. The OTM-n includes two structures: OTM with full functionality OTM-n.m, OTM with reduced functionality OTM-0.m and OTM-nr.m.

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OTM-n.m Containment Relationships

n represents the maximum number of wavelengths that can be supported at the lowest bit rate supported on the wavelength, m=1,2,3,12,23,123；OTS_OH, OMS_OH, OCh_OH and COMMS OH information fields are contained within the OOS

OSC：Optical Supervisory Channel used to transmit OOS

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

OC

Co

OChOH

OC

Co

OC

Co

OMU-n.m

Non

-ass

ocia

ted

OH

OOS

com

ms

OH

OTM

-n.m

OTM Overhead Signal (OOS)

λ2

λ1

λn

λOSC

The figure on the right shows the composition of the OTM-n.m signals of the OTM interface with complete function. The OTM-n.m is composed of up to n multiplexing wavelengths and OTM overhead signals that support the non-associated overhead, m can be 1, 2, 3, 12, 23, or 123.”m=1” indicates the signals are OTU1/OTU1V. m=2: indicate the signals are OTU2/OTU2V. “m=3” indicates the signals are OTU3/OTU3V. “m=12” indicates partial signals are OTU1/OTU1V and partial signals are OTU2/OTU2V. “m=23” indicates partial signals are OTU 2/OTU2V and partial signals are OTU3/OTU3V. “m=123” indicates partial signals are OTU 1/OTU1V, partial signals are OTU2/OTU2V, and partial signals are OTU3/OTU3V. The physical optical feature specifications of OTM-n.m signals are determined by the suppliers. The recommendations do not have specific specifications.

The optical layer signal OCh is composed of OCh payload and OCh overhead. After the OCh is modulated to the OCC, multiple OCC time division multiplexes (TDM) constitute the OCG-n.m unit. OMSn payload and OMSn overhead constitute the OMU-n.m. OTSn payload and OTSn overhead constitute the OTM-n.m unit.

The overhead and generic management information of the optical layer units constitute the OTM overhead signal (OOS), which is transmitted by 1-channel independent OSC in the non-associated overhead.

The overhead of electrical layer units such as OPUk, ODUk, and OTUk are the associated channel overheads, which are transmitted together with the payload.

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OTM-nr.m Containment Relationships

Fixed channel spacing, irrespective of signal level

1<n≤16, m=1,2,3,12,23,123

Without optical supervisory channel

OPSn

OCCp OCCp OCCp

OCh payload

ODUk FECOH

OPUkOH

Client signal

OPUk payloadOHOPUk

ODUk

OTUk[V]

OChr

OCG-nr.m

OTM-nr.m

OTM

-16r

.m

λ2

λ1

λ16

The OTM-nr.m signals are composed of up to n optical channel multiplexing, and does not support the non-associated overhead. At present, m of OTM-16r.m can be 1, 2, 3, 12, 23, or 123, where, the physical optical feature specifications of OTM-16r.1 and OTM-16r.2 are defined in G959.1 of ITU-T. The physical optical feature specifications of other four signals are in need of the further study.

The electrical layer signal structures of OTM-nr.m and OTM-n.m are the same. The optical layer signals do not support the non-associated overhead OOS, without the optical monitor channel. Therefore, it is called the OTM interface with the reduced function.

This OTM-16r.m supports 16 optical channels on a single optical span with 3R regeneration at each end. The OTM-16r.m signal is an OTM-nr.m signal with 16 optical channel carriers (OCCr) numbered OCCr #0 to OCCr #15. An optical supervisory channel (OSC) is not present and there is no OOS either.

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OTM-0.m Containment Relationships

The OTM 0.m supports a non colored optical channel on a single optical span with 3R

regeneration at each end.

m=1,2,3

Without optical supervisory channel

OCh payload

ODUk FECOH

OPUkOH

Client signal

OPUk payloadOHOPUk

ODUk

OTUk[V]

OChr

OTM-0.m OPS0

OTM

-0.m

The OTM-0.m supports a non-coloured optical channel on a single optical span with 3R regeneration at each end.

OTM-0.m is composed of the single optical channel. It does not support the associated overhead OOS and is without specific wavelength configuration. Only one optical channel is contained; therefore, m can be 1, 2, or 3 only. The physical optical feature specifications of OTM-0.1, OTM-0.2, and OTM-0.3 are defined in G.959.1 and G.693.

The electrical layer signal structure of three OTM interfaces are the same, the electrical layer signals are monitored through the associated overhead. The difference is: The OTM-n.m optical layer signals supports the transmission of the non-associated overhead through 1-channel OSC. The OTM-nr.m and OTM-0.m do not support the optical layer overhead.

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Contents








Draw the mapping route of OTM;

List the rate of all types of OTUk,ODUk and OPUk signals;

Describe how does a lower rate ODUk multiplex to a higher rate ODUk.

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OTM multiplexing and mapping structure

Mapping

Multiplexing

ODTUG3

ODTUG2

OChr

OChr

OChr

OCh

OCh

OCh

OTU3[V]

OTU2[V]

OTU1[V]

Client signal

Client signal

OPU3ODU3

OCCr

OCCr

OCCr

OCC

OCC

OCC

OCG-nr.m

1 ≤ i+j+k ≤ n

OCG-n.m

1 ≤ i+j+k ≤ n

OPU2ODU2

×1OPU1ODU1

OTM-nr.m

OTS, OMS, OCh, COMMSOSC OOS

OTM-n.m

×4

×1

×1×4

×16×1

×1×1

×1

×1

×1

×1

×1

×1

×1

×1

×1

×1

×1

×1

×1

×1

× i

× j

× k

× i

× j

× 1

Client signal

×1

OTM-0.m

× k

Customer signals or ODTUGk is mapped to OPUk; OPUk is mapped to ODUk; ODUk is mapped to OTUk or OTUkV; OTUk or OTUkV is mapped to OCh or OChr. Finally, OCh or OChr is modulated to OCC or OCCr.

The multiplexing includes the TDM from low-level ODU to high-level ODU and the WDM from up to n OCC or OCCr to one OCG-n.m or OCG-r.m (here, n ≥1).

The TDM is used to transmit multiple low-rate optical channel signals on one high-rate optical channel, and to perform the end-to-end path maintenance for these low-rate channels. Through the TDM, up to four ODU1 signals can be multiplexed to one ODTUG2. Then, the ODTUG2 is mapped to the OPU2. Meanwhile, j ODU2 and 16-4j ODU1 signals can be multiplexed to one ODTUG3, where j≤4. ODTUG3 is mapped to OPU3. OPU2 and OPU3 can be multiplexed to the corresponding large granularity customer signals.

For the WDM, the OCC or OCCr unit of OCG-n.m or OCG-r.m can adopt various rates. OTM-n.m or OTM-r.m transmits OCG-n.m or OCG-r.m. In addition, OTM-n.m interface can multiplex the OSC to the OTM-n.m through the WDM.

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Types and capacity

40 150 519.322 kbit/sOPU3

9 995 276.962 kbit/sOPU2

2 488 320 kbit/sOPU1

40 319 218.983 kbit/sODU3

10 037 273.924 kbit/sODU2

2 498 775.126 kbit/sODU1

43 018 413.559 kbit/sOTU3

10 709 225.316 kbit/sOTU2

±20 ppm

2 666 057.143 kbit/sOTU1

bit rate tolerancenominal bit rateTypes

As we know,the size of OTUk is fixed, that is, OTU1, OTU2, and OTU3 are 4-line and 4080-column. For OTU1 frames, from Column 1 to Column 16, there are OTU1, ODU1, and OPU1 overhead. From Column 17 to Column 3824 (with 3808 columns in total), there are customer signals. From column 3825 to column 4080 (with 256 columns in total), there are FEC areas. Assume the customer signals are STM-16 SDH signals, the rate is 2 488 320kbit/s, the calculations are as follows:

Customer signal /OTU frame = Customer signals rate / nominal OTU frame rate

3808/4080 = 2 488 320 / nominal OTU1 frame rate

That is, nominal OTU1 frame rate = 255/238 x 2 488 320 kbit/s

For OTU2 frames, four ODU1s are combined to ODTUG2 through the TDM. Four ODU1s operate as the OPU2 payload, occupying 3808 columns. In OPU2 payload, there are 16 columns of OTU1, ODU1, and OPU1 overhead. Therefore, the customer signals are 3792 columns. The calculation is as follows:

3792/4080 = 2 488 320 x 4 / nominal OTU2 frame rate

That is, nominal OTU2 frame rate = 255/237 x 9 953 280 kbit/s

The nominal OTU3 frame rate = 255/236 x 39 813 120 kbit/s

For OTU1/2/3 frame rate, the conclusion is as follows:

OTUk rate = 255/(239-k) x STM-N frame rate , k=1, 2, 3 correspond to the frame rate of STM-16, STM-64, and STM-256 respectively.

The OTU bit rate tolerance is ± 20 ppm.

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ODUk（TDM）

Low rate ODUk signals are multiplexed into high rate ODUk

signals using time-division multiplexing :

Up to 4 ODU1 signals are multiplexed into an ODU2 using

time-division multiplexing

A mixture of j (j ≤ 4) ODU2 and 16-4j ODU1 signals can be

multiplexed into an ODU3 using time-division multiplexing.

Two customer/service relationships are defined:

One ODU2 transmits four ODU1.

One ODU3 transmits 16 ODU1, or four ODU2, or other combinations in this range, where, one ODU2 is equivalent to four ODU1.

TDM includes two cases: ODU1 multiplexing to ODU2, and ODU1/ODU2 multiplexing to ODU3.

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ODU1 into ODU2 multiplexing methodODU1floats in ¼ of the OPU2 payload area.

An ODU1 frame will cross multiple ODU2 frame boundaries.

OTU2 OTU2FEC

Client layer signal(e.g., STM-16, ATM, GFP)

ODU1ODU1OH

Alignm

ODU2

x4

Client Layer Signal(e.g. STM-16)ODU1 OH O

PU

1 O

H


PU

1 O

H


PU

1 O

H

Client layer signal(e.g., STM-16, ATM, GFP)ODU1 OHODU2 OH

OP

U2 O

H

OPU2 PayloadODU2 OH

Alignm

OP

U2 O

H

OTU2OH


PU

1 O

H


PU

1 O

H


PU

1 O

H

Client layer signal(e.g., STM-16, ATM, GFP)ODU1 OH

OP

U1 O

H

Alignm

Alignm

OP

U1 O

H

OP

U1 O

H

ODU1floats in ¼ of the OPU2 payload area. An ODU1 frame will cross multiple ODU2 frame boundaries.

A complete ODU1 frame(15296 bytes) requires the bandwidth of (15296/3808 =) 4.017 ODU2 frame

The figure shows the ODU1 frame, including the frame alignment overhead and all-zero OTUk overhead. The ODU1 adapts to the clock synchronization of the ODU2 signal through the asynchronous mapping.

As shown in the frame structure in the figure, four ODU1 after adaptation is multiplexed to the OPU2 payload area in the byte interleaved mode; JC and NJO are inserted to OPU2 overhead area.

After ODU2 overhead is added, ODU2 is mapped to OTU2 (or OTU2V). After OTU2 (or OTU2V) overhead, frame alignment overhead, and FEC area are added, the OTU2 signals transmitted through the OTM are formed.

The frame size of ODU1 and ODU2 are the same, that is, 4 lines and 3824 columns, where, the payload is 3808 column. How can OPU2 take four ODU1 frames? The ODU1 frame must cross one ODU2 frame border, occupying 3824/3808, that is, 1.004 ODU2 frame. The frame frequency of the ODU1 differs from that of ODU2. The frame frequency of the ODU2 is higher than ODU1. Therefore, it is feasible when ODU1 is multiplexed to ODU2 with occupying one ODU2 frame.

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Contents








List the overheads in OTN frame;

Describe the function of each overhead.

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OTN frame formats (k=1,2,3)

3825

40801 7 8 14 15 16 17

3824

1

2

3

4

OPU k payload

OP

Uk

OH

OPUk - Optical Channel Payload Unit

ODUkOH

ODUk – Optical Channel Data Unit

Client signal mapped in

OPUk payload

Client signal

OTUKFEC

OTUkOH

OTUk – Optical Channel Transport Unit

Alignm

Alignment

k :1 － 2.5G2 － 10G3 － 40G

The OPUk is in the area from row 15 to row 3824, where, OPUk overhead area is from column 15 to column 16, OPUk payload area is from column 17 to column 3824, customer signals are in the OPUk payload area.

The ODUk is in the block structure with 4 lines and 3824 columns, which is composed of ODUk overhead and OPUk, where ODUk overhead area is from row 1 to row 4 and from column 1 to column 14. The frame alignment overhead area is from column 1 to column 7 in the first line. Column 8 to 14 in the first line are all-zero.

The OTUk overhead area is from column 8 to column 14 in the first line, and the FEC area is from column 3825 to column 4084 (256 columns in total) on the right of the frame. The frame alignment overhead area is from Column 1 to column 7 of the first line in the frame header.

The customer signal rate corresponding to OTU1/2/3 is respectively 2.5G/10G/40Gbits/s. The OTUk frame structure of each level is the same. The OTUk signals at the ONMI must have the sufficient bit timing information. Therefore, the OTUk provides the scramble function, to construct an appropriate bit pattern by using a scrambler, with the avoidance of long “1” or long “0” series. With the consideration of the framing, the OTUk overhead FAS should not be scrambled. The scrambling operation is performed after FEC calculation and insertion of OTUk signals.

The transmission sequences of the bytes in the OTUk frame is from left to right, from top down

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OTN electrical overhead overview

ODUk OHTCMACT: Tandem Connection Monitoring

Activation/deactivation control channel

TCMi:Tandem Connection Monitoring i

FTFL:Fault Type & Fault Location reporting

channel

PM: Path Monitoring

EXP:Experimental

GCC1/2: General Communication Channel 1/2

APS/PCC:Automatic Protection Swiching

coordination channel/Protection Communication

Control channel

Alignment OHFAS: Frame Alignment Signal

MFAS: multi-frame Alignment SignalOTUk OH

SM: Section Monitoring

GCC0:General Communication Channel0

RES: Reserved for future international

standardisation

OPUk OH PSI: Payload Structure Identifier

JC: 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 JCRES

The figure shows the overall electrical layer overhead, include frame alignment overhead, OTUk layer overhead, ODUk layer overhead, and OPUk layer overhead.

The frame alignment overhead is used for the framing. It is composed of 6-byte frame alignment signal overhead FAS and 1-byte multi-frame alignment overhead MFAS.

OTUk layer overhead supports the transmission operation function connected through one or more optical channel. It is composed of 3-byte SM, 2-byte GCC0, and 2-byte RES. It is terminated at the OTUk signal assembly and dissemble places.

ODUk layer overhead is used to support the operation and maintenance of the optical channel. It is composed of 3-byte PM for end-to-end ODUk channel monitoring, 6-level TCM1-TCM6 with 3 bytes respectively, 1-byte TCMACT, 1-byte FTFL, 2-byte EXP, 2-byte GCC1, 2-byte GCC2, 4-byte APS/PCC, and 6-byte reservation overhead. The ODUk overhead is terminated at the ODUK assembly and disassemble places. TC overhead is added at the source, and is terminated at the sink.

OPUk overhead is used to support the customer signal adaptation. It is composed of 1-byte PSI, 3-byte JC, 1-byte NJO, and 3-byte reservation overhead. It is terminated at the OPUk assembly and disassemble places.

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Frame Alignment Signal

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


EXP

FAS MFAS SM GCC0 RES JCRES

17

FAS (Frame Alignment Signal)

A six byte OTUk-FAS signal is defined in row 1, columns 1 to 6 of the OTUk

overhead.

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

Frame Alignment Signal (FAS) is used for the frame alignment and positioning, with the length of six bytes. It is located in Column 1 to Column 6 of Line 1. The contents are shown in the figure: three OA1 plus three OA2 series. The value of OA1 is 0xF6, and the value of OA2 is 0x28.

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Multi-Frame Alignment Signal

MFAS OH Byte

MFA

S sequen

ce

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

..

MFAS (Multi-Frame Alignment Signal)

defined in row 1, column 7；

The value of the MFAS byte will be incremented each

OTUk/ODUk frame and provides as such a 256 frame

multi-frame.

Individual OTUk/ODUk overhead signals may use this

central multi-frame to lock their 2-frame, 4 frame, 8-

frame, 16-frame, 32-frame, etc., multi-frames to the

principal 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


EXP

FAS SM GCC0 RES JCRES

17

MFAS

Multi-Frame Alignment Signal (MFAS) follows the FAS. Some OTUk and ODUk overheads, for example, TTI, should cross multiple OTUk/ODUk frames. These overheads must implement the OTUk/ODUk frame alignment and multi-frame alignment processing. The MFAS is used for the multi-frame alignment.

The length of the overhead is one byte, and is located in Line 1 Column 7.

The value of the MFAS bytes increases with the increase of the OTUk/ODUk basic frame number, from 0 to 255 (with up to 256 basic frames). For the overhead of each multi-frame structure, the length can be adjusted. For example, if an overhead uses the multi-frame structure with 16 basic frames, bit1-bit4 are not calculated when the multi-frame signals are extracted.

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OTUk section monitoring overhead

TTI (Trail Trace Identifier)

a one-byte overhead is defined to transport the 64 byte TTI

signal

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

multi-frame and transmitted four times per multi-frame.

TTI struture：16 bytes SAPI:Source Access Point Identifier

16 bytes DAPI:Destination Access Point Identifier

32 bytes operator specific

Operatorspecific

TTI BIP-8

BEI/BIAE BDI

RES

1 2 3 4 5 6 7 8

1 2 3

IAE

63

32

0

15

16

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


EXP

FAS GCC0 RES JCRES

17

MFAS SM

The SM overhead is composed of three bytes.

The trail trace identifier (TTI), with the length of one byte, is located in the first byte of the SM overhead. It is used to transmit 64-byte OTUk-level trail trace identifier signals. The content sequence of 64 bytes are:

Byte 0 includes SAPI[0] character, with the fixed value of all zeroes.

Byte 1-byte5 include 15-character SAPI.

Byte 16 includes DAPI[0] character, with the fixed value of all zeroes.

Byte 17-byte 31 include 15-character DAPI.

Byte 32- byte 63 are the contents designated by the operator.

The 64-byte TTI signal should align with the OTUk multi-frame. Transmit for four times in each multi-frame. Each multi-frame contains 256 frames.

OTN Introduction


P-24


OTUk section monitoring overheadBIP-8 (Bit Interleaved Parity-8)

For section monitoring, a one-byte error detection code signal is defined.

This byte provides a bit interleaved parity-8 (BIP-8) code ；

The OTUk BIP-8 is computed over the 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

BIP8

OPUk

1 14 15 3824

Frame i

Frame i+1

Frame i+2

Bit Interleaved Parity-8 (BIP-8) byte is used for the detection of the OTUk-level bit error detection. The code is in the even parity inserted among bits. Its length is one byte, located in the second byte of the SM overhead. For BIP8 parity, calculate the bit in the whole OPUK frame area of the No.i OTUk frame to obtain the OTUk BIP-8. Insert the results to No.(i+2) OTUk frame OTUk BIP-8 overhead position. In No.(i+2) frame, as shown in the figure, compare this value with the DIP8 calculation results of the current frame. If both values mismatch, detect the bit error block of the near end.

OTN Introduction


P-25


OTUk section monitoring overhead

BEI/BIAE (Backward Error Indication/ Backward

Incoming Alignment Error)

BDI (Backward Defect Indication)

IAE (Incoming Alignment Error)

RES (Reserved)

Operatorspecific

TTI BIP-8

BEI/BIAE BDI

RES

1 2 3 4 5 6 7 8

1 2 3

IAE

63

32

0

15

16

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


EXP

FAS GCC0 RES JCRESMFAS SM

Backward Error Indication (BEI) and Backward Incoming Alignment Error (BIAE) are used to return the detected bit errors to the upstream of the OTUk-level and to introduce the IAE. The length is four bits. It is located in the most significant four bits of the third byte of the SM overhead. In the IAE status, the field is set to 1011. The bit error number and non IAE state is omitted, insert the bit error number (0-8). Other six values may be caused by some irrelevant status. It should be explained as 0 bit error and BIAE inactivation.

The backward defect indication (BDI) is used for OTUk-level to return the signal invalidity status detected in the terminal sink function. The length is one bit. It is located in Bit5 of byte3 of the SM overhead. When the BDI is set to 1, it indicates OTUk backward defect. Otherwise, it is set to 0.

The Incoming Alignment Error (IAE) is used for the OTUk-level S-CMEP at the ingress point to notify the peer S-CMEP at the egress point that the alignment error is detected in the introduction signals. The S-CMEP egress point can use this information to stress the bit error number. These bit error may be caused by the ODUk frame phase change at the TC ingress point. The IAE length is one bit. It is located in bit6 of byte 3 of the SM overhead. The IAE bit is set to 1 to indicate the frame alignment error. Otherwise, it is set to 0.

The last two bits of the SM is reserved, and is set to “00”.

S-Connection Monitoring End Point (CMEP): Section-Connection monitoring end-points represent end points of trails and correspond as such with the trail termination functions.

OTN Introduction


P-26


GCC0 (General Communication Channel)

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

communications channel between OTUk termination points

A clear channel which are located in row 1, columns 11 and 12

RES (Reserved)

Two bytes of OTUk overhead are reserved for future international standardization

Located in row 1, columns 13 and 14

Set to all ZEROs

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


EXP

FAS RES JCRES

17

MFAS SM GCC0

OTUk GCC0 and RES overhead

General Communication Channel 0 (GCC0) is used to support the general communication between OTUk terminals. The length is two bytes. It is located in Column 11 to Column 12 of line 1. The GCC0 is the transparent channel. The format specification is not discussed here in this course.

Then, it is the 2-byte OTUk reserved overhead, for the international standardization. It is located in column 13-column 14 of line 1. The reserved overhead is set to all zeroes.

OTN Introduction


P-27


ODUk path monitoring overhead

TTI / BIP-8 / BEI / BDI

For path monitoring, this overheads’ function are the

same as OTUk SM signal, except BEI signal which

doesn’t support BIAE function.

In row 3, columns 10 to 12

Operatorspecific

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


EXP

FAS RES JCRES

17

MFAS SM GCC0

PM

The PM is similar to the SM.

The PM overhead is composed of three bytes. It is located in column 10-column 12 of line 3. The PM is composed of 1-byte TTI, 1-byte BIP-8, 4-bit BDI, 1-bit BEI, and 3-bit STAT. The definitions of TTI / BIP-8 / BEI / BDI are similar to those in SM. These parts support the channel monitor.

The PM overhead does not support IAE and BIAE function. In addition, BIP-8 of the PM overhead is parity of the whole OPUk frame (column 15- 3824). But, the parity position is in the PM overhead, which differs from the BIP regenerated node in the BIP8.The BEI field needs not to support the BIAE function. Therefore, one value is less that of the SM overhead to indicate the return of the IAE state. Four bits of BEI fields in the PM overhead have nine effective values in total. 0-8 indicates 0-8 bit errors respectively. The other seven values are caused by some irrelevant status, which can be interpreted as 0 bit error.

OTN Introduction


P-28


ODUk path monitoring overhead

Operatorspecific

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


EXP

FAS RES JCRES

17

MFAS SM GCC0

PM

Maintenance signal: ODUk - AIS 1 1 1

Maintenance signal: ODUk - OCI 1 1 0

Maintenance signal: ODUk - LCK 1 0 1

Reserved for future international standardization 1 0 0



Normal path signal0 0 1


statusBit 6 7 8

STAT (Status)

For path monitoring, three bits are defined as status bits

They indicate the presence of a maintenance signal

The STAT field is used for the maintenance signals of ODUk channel level. The length is 3 bits. It is located in the least significant 3 bits of Column 12 of Line 3.

The table describes the meaning of the STAT field.

OTN Introduction


P-29


ODUk TCM overhead

TTIi / BIP-8i / BEIi/BIAEi / BDIi

For each tandem connection monitoring field,

this overheads’ function are the same as OTUk

SM signal

Six fields of ODUk TCM overhead are defined in

row 2, columns 5 to 13 and row 3, 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


EXP

FAS RES JCRESMFAS SM GCC0

PMTCM1TCM2TCM3

TCM6 TCM5 TCM4

The ODUk overhead defines TCM1-TCM6 of six domains. The Tandem Connection Monitoring (TCM) overhead supports the monitoring of the ODUk connection. It is used to the scenarios such as one or more optical UNI to UNI, NNI to NNI serial line connection monitoring, linear and ring protection switch sub-layer monitoring, the fault location of the optical channel serial line connection, and the service delivery quality acceptance. TCM6-TCM1 are located in Column 5-Column 13 of line 2, Column 1-Column 9 of Line 3. Its format is similar to the SM of the OTUk overhead and the PM of the ODUk overhead.

TTIi / BIP-8i / BEIi / BIAEi / BDIi support the TCMi sub-layer monitoring, where, i ranges from 1 to 6. The definitions and functions of these parts are the same as the corresponding parts in SM. But, only the monitoring levels are different.

OTN Introduction


P-30


ODUk TCM 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


EXP

FAS RES JCRES

17

MFAS SM GCC0

PMTCM1

Maintenance signal: ODUk -AIS 1 1 1

Maintenance signal: ODUk -OCI 1 1 0

Maintenance signal: ODUk -LCK 1 0 1

Reserved for future international standardization1 0 0

Reserved for future international standardization0 1 1

In use with IAE0 1 0

In use without IAE0 0 1

No source TC 0 0 0

statusBit 6 7 8

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.

STAT is used for the maintenance signal of TCMi sub layer, whether the IAE error exists in the source TC-CMEP, whether the source TC-CMEP is activated. The length is 3 bits. It is located in the least significant 3 bits of the TCMi field.

It indicates the meaning of the STAT field.

TCMi overhead has more BIAE function than PM overhead. In the maintenance signals in the STAT field, there are more two meanings: No source TC, and TC in use but with IAE error.

OTN Introduction


P-31


Nested and Cascaded ODUk monitored connections

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

Along one ODUk trail, the monitored connections range from 0 to 6. The monitored multi-level connections can be overlay, nesting, or cascading. At present, the overlay mode is applicable to the test only. Each TC-CMEP inserts or extracts the TCM overhead from six TCMi overhead domains. The corresponding network operator, network management system or switching control platform provides the TCMi overhead domain contents.

As shown in the figure, the monitored connects A1-A2, B1-B2, and C1-C2 are nested, A1-A2 and B3-B4 are nested, B1-B2 and B3-B4 are cascaded.

OTN Introduction


P-32


Overlapping ODUk monitored connections

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

As shown in the figure, the monitored connects B1-B2 and C1-C2 are overlaid, A1-A2 and B1-B2 are nested, A1-A2 and C1-C2 are nested.

OTN Introduction


P-33


ODUk GCC1/GCC2

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

GCC1 / GCC2 (General Communication Channel)

Two fields of two bytes are allocated in the ODUk overhead to support two

general communications channels between any two network elements with

access to the ODUk frame structure (i.e., at 3R regeneration points).

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

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

GCC1 and GCC2 can be used to access to the ODUk frame structure (that is, located in 3R regeneration points) between any two NEs. The length is 2 bytes, respectively located in Column 1-2 and Column 3-4 of Line 1. It is the transparent channel. Its function is similar to OTUk overhead GCC0. The ESC function can be applied to the product.

OTN Introduction


P-34


Other overheads 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 PSI

FAS RES

17

MFAS SM GCC0

PMTCM1

GCC2

TCMACT (TCM Activation/Deactivation)

APS/PCC (Automatic Protection Switching/Protection Communication

Control)

EXP (Experimental)

FTFL (Fault Type & Fault Location)

EXP

FTFL

APS/PCC

RES JC

RES JC

NJO

RES JC

RES

RES

TCM Activation/Deactivation (TCMACT) overhead is 1-byte long, and is located in Column 4 of Line 2. Its definition is not determined yet.

Automatic Protection Switching (APS)/Protection Communication Control (PCC) overhead is applicable to the protection protocol communication, with the length of four bytes. This field can appear in up to 8-level nested APS/PCC signals. It can be used by multiple protection mechanisms. In the multi-frame, the first eight basic frames (for MFAS, it is 0-7) APS/PCC are sequentially allocated to ODUk channel layer, ODUk TCM1-TCM6 sub layers, and OTUk section layer.

The ODUk overhead defines 2-byte EXP, which allows the equipment supplier or network operator to use the extra ODUk overhead on the subnet. The specific function of the EXP is not limited to the standard, which is not defined within G.709 range.

The ODUk overhead is allocated with one byte to transmit total 256-byte Fault Type & Fault Location (FTFL). The FTFL message is composed of forward area and backward area, with 128 bytes in each area, respectively containing the forward and backward fault type, operator identifier, and operator designated domain.

OTN Introduction


P-35


OPUk payload structure identifier

PSI (Payload Structure Identifier)

One byte is allocated in the OPUk overhead

to transport a 256-byte payload structure

identifier (PSI) signal

Aligned with the ODUk multi-frame.

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

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

concatenation specific .

255

0

1

PT

Mapping& 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

The OPUk overhead defines 1-byte payload structure identifier (PSI) overhead to transmit the 256-byte PSI to indicate the OPUk signal type. The PSI overhead is in Column 15 of Line 4. The 256-byte PSI signal aligns with the ODUk multi-frame. PSI[0] is a 1-byte payload type (PT); PSI[1]-PSI[255] are used for the mapping and cascading; PSI[1] is reserved, and PSI[2]-PSI[17] is the multiplex structure identifier (MSI). The MSI includes the ODU type and transmitted ODU tributary port number information. For OPU2, there are only four ODU1 tributary port number. Therefore, only four bytes PSI[2]-PSI[5] are needed, and the last 12 bytes of the MSI are set to 0.

OTN Introduction


P-36


OOS

TTI: Trail Trace IdentifierPMI: Payload Missing Indication OCI: Open Connection Indication BDI-O: Backward Defect Indication –OverheadBDI-P: Backward Defect Indication – PayloadFDI-O: Forward Defect Indication –OverheadFDI-P: Forward Defect Indication – Payload

OTSn

n

32

OC

h

1

General Management Communications

OM

Sn

FDI-O

FDI-P

OCI

BDI-O

BDI-P

PMI

FDI-P

FDI-O

BDI-O

BDI-P

PMI

TTI

The OOS is the non-associated overhead, which is transmitted through the OSC. The optical layer overhead function should comply with the standard. The recommendation defines overheads and corresponding functions contained in the optical layer, and does not define the frame rate or frame structure. The optical layer overhead include OTS, OMS, OCh overheads, and generic management information overhead defined by the supplier, where,

The OTS overhead is used to support the maintenance and operation function of the optical transmission section, and is terminated at the OTM signal assembly and dissemble places, including:

TTI: Transmit the TTI consisting of 64-byte character string. The TTI includes the source access point indication, destination access point indication, and information designated by the operator.

BDI-P: Transmit the OTSn payload signal invalidity status detected from the OTSn terminal sink function to the upstream.

BDI-O: Transmit the OTSn overhead signal invalidity status detected from the OTSn terminal sink function to the upstream.

PMI: It is used to transmit the status of payload that is not added at the upstream of the OTS signal source terminal to the downstream, to suppress subsequent reporting of loss of signal.

To be continued in the next page

OTN Introduction


P-37


OOS

TTI: Trail Trace IdentifierPMI: Payload Missing Indication OCI: Open Connection Indication BDI-O: Backward Defect Indication –OverheadBDI-P: Backward Defect Indication – PayloadFDI-O: Forward Defect Indication –OverheadFDI-P: Forward Defect Indication – Payload

OTSn

n

32

OC

h

1

General Management Communications

OM

Sn

FDI-O

FDI-P

OCI

BDI-O

BDI-P

PMI

FDI-P

FDI-O

BDI-O

BDI-P

PMI

TTI

The OMS overhead is used to support the maintenance and operation function of the optical MS, and is terminated at the OMU signal assembly and dissemble places, including:

FDI-P: Transmit OMSn payload signal status to the downstream direction.

FDI-O: Transmit OMSn overhead signal status to the downstream direction.

BDI-P: Transmit the OMSn payload signal invalidity status detected from the OMSn terminal sink function to the upstream.

BDI-O: Transmit the OMSn overhead signal invalidity status detected from the OMSn terminal sink function to the upstream.

PMI: Transmit the information with a OCCp containing optical channel signal information at the upstream of OMS signal source terminal to the downstream, to suppress subsequent reporting of signal invalidity status.

The OCh overhead is used to support the maintenance function of the fault management in the optical channel, and is terminated at the OCh signal assembly and dissemble places, including:

FDI-P: Transmit OCh payload signal status to the downstream direction.

FDI-O: Transmit OCh overhead signal status to the downstream direction.

OCI: It is the OCh open connection indication. The OCI is the signal sent to the downstream. It indicates that the matrix connection is opened when the upstream delivers the management commands in the connection function. Then, at the OCh terminal point, detect that the OCh signal loss status may be related to the open matrix.

OTN Introduction


P-38


Contents








List the maintenance signals type;

Describe the function and application of maintenance signals.

OTN Introduction


P-39


OTN Maintenance LayersOChn

TTIBDI-PBDI-OPMI

FDI-OBDI-PBDI-OPMI

FDI-POTS OMS

FDI-PFDI-OOCI

OCh1

OCh2

General management communications (OSC)

1

2

3

4

FAS

EXP

TCMACT TCM4

TCM3 TCM2

TCM6

GCC1 GCC2

FTFL

PM

RES

RESAPS/PCC

SM RESGCC0MFAS JC

JC

JC

NJO PJO

RES

RES

RES

TCM5

TCM1

1 167 8 14 15

PSI

OTS OTS OTS OTS OTS OTS OTS

OMS OMS OMS OMS

OTM OADM/ROADM

Och OchOch

TCM1 (UNI to UNI)

OTN XC

OEO

OLA OLA OTM OTM OTMOLA

OTN boundaryOTN boundary

OTUk SMOTUk SM OTUk SM

PM

(NNI to NNI) TCM2(NNI to NNI)－ TCM2

Electrical layer Optical layer

OTS, OMS, OCh are all optical layer trails and OTUk, ODUk, Client are all electrical layer trails.

OSC trail is independent, which is related to supervisory signal.

OTUK use SM section to send maintenance signals.

ODUK use PM and TCM to send maintenance signals.

OTS,OMS,OCh ,OSC send different optical layer maintenance signals.

OTN Introduction


P-40


OTN Layer Network Trail

OTU OTU

OM OA OA OD

OTSOTSOTS

OMS

OCH

OTUk

ODUk

Client

OSC

OSC

OSC

OCh client trail sets the source/sink port at the client side of OTU. LQG, as an example, it is GE service trail of the client port.

OCh trail sets the source/sink port at the WDM side of OTU. LQG, as an example, it is the wavelength trail.

OMS trail sets the source/sink port at the OUT/IN port of MUX/DeMUX. It is a trail of the multiplex signal.

OTS trail is the fiber connection between adjacent OM/OD/OA in the main path.

OSC trail is independent, which is related to supervisory signals.

OTN Introduction


P-41


Maintenance signals

FDI（forward defect indication）FDI is a signal sent downstream as an indication that an upstream defect has

been detected.

An FDI signal is detected in a trail termination sink function to suppress defects

or failures that would otherwise be detected as a consequence of the

interruption of the transport of the original signal at an upstream point..

AIS and FDI are similar signals. AIS is used as term when the signal is in the

digital domain. FDI is used as the term when the signal is in the optical domain.

FDI is transported as non associated overhead in the OTM overhead signal

(OOS).

The FDI is the signal sent to the downstream in OMS and OCh layers, to indicate the detected upstream defects. FDI-P indicates the payload forward defect, and FDI-O indicates the overhead forward defect.

OMS-FDI-P indicates the OMS servcie layer dfect of the OTS network layer.

OMS-FDI-O indicates that the transmission of the OMS overhead transmitted through the OOS is interrupted owing to the signal invalidity status of the OOS.

OCh-FDI-P indicates the OCh service layer defect in the OMS network layer. When the OTUk is terminated, OCh-FDI-P serves as the ODUk-AIS signal to continue.

OCh-FDI-O indicates that the transmission of the OCh overhead transmitted through the OOS is interrupted owing to the signal invalidity status of the OOS.

The FDI signal is generated in the adaptation sink function. In the trail terminal sink function, it is generated to suppress the downstream defects and invalidities detected owing to the transmission interruption of the upstream signals.

The FDI is similar to AIS. When the signal is in the optical domain, use the FDI. When the signal is in the digital domain, use the AIS. The FDI served as the non-associated overhead is transmitted in the OTM overhead signal (OOS)

OTN Introduction


P-42


Maintenance signals

AIS（alarm indication signal）

AIS is a signal sent downstream as an indication that an upstream

defect has been detected. An AIS signal is generated in an

adaptation sink function

An AIS signal is detected in a trail termination sink function to

suppress defects or failures that would otherwise be detected as a

consequence of the interruption of the transport of the original

signal at an upstream point.

AIS is the electrical layer OTUk, ODUkP, ODUkT, and customer layer CBR sent to downstream to indicate the detected upstream defect, to suppress the downstream defects and invalidities detected due to the interruption of upstream signal transmission. The AIS of ODUkP and ODUkT layer uses the ASI with all-1 pattern.

Note:

OTUk-AIS supports the new service layer in future. At present, only the signal is required to be detected, instead of the generation of this signal. According to this recommendation, Huawei equipment only supports the detection of the OTUk-AIS, instead of inserting OTUk_AIS. CBR AIS is generated in the the ODUk/CBRx adaptation sink function. If the SDH receives this signal, it is detected as the LOF.

OTN Introduction


P-43


Maintenance signals

AIS（alarm indication signal）

ODUk-AIS is specified as all "1"s in the entire ODUk signal, excluding

the frame alignment overhead (FA OH), OTUk overhead (OTUk OH)

and ODUk FTFL

The presence of ODUk-AIS is detected by monitoring the ODUk STAT

bits in the PM and TCMi overhead fields

1

2

3

4

1 17 3824

All-1s pattern

87 14

FTFL

FA OH OTUk OH

STA

T

STA

T

STA

T

STA

T

STA

T

STA

T

STA

T

The AIS of ODUkP and ODUkT level uses the all-1 pattern, as shown in the figure.

When we introduce the PM and TCMi overhead, we have learnt that the value 111 of STAT field of PM or TCMi indicates the detected ODUk_AIS signals. When ODUkP or ODUkT detects the AIS, it only concerns about the value of the STAT of the corresponding level. For example, to detect the AIS of the TCM1, check whether the STAT corresponding bit of the TCM1 is 111; To check the AIS of the PM, check whether the STAT corresponding bit of the PM is 111.

To insert the AIS, the ODUkP or ODUkT is not distinguished. For either of them, insert to PM or 6-level PCM overhead area or all payloads (excluding FTFL byte). Therefore, it is called the insertion of ODUk-AIS signals. The ODUk_AIS may be generated in the adaptation sink function from OTU to ODU or in the ODUkT termination sink function. For the adaptation sink function from OTU to ODT, insert the ODUk_AIS owing to the invalidity of the service layer. For the ODUkT termination sink function, when the TCM is in the operation mode, insert ODUk_AIS owing to the detection of the LCK, OCI, and TIM. Whether the TIM is inserted with the AIS can be set.

When the AIS is cleared, 111 of the STAT of the local area is cleared also. For example, for the TCM1 source function, change the STAT of the TCM1 from 111 to 001.

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Maintenance signals

BDI (Backward Defect Indication)

Backward Defect Indication Payload defect (dBDI-P) is

monitored at the OTS and OMS layers. The purpose of

monitoring this parameter is to allow for single ended

supervision of the trail

During signal fail conditions of the overhead signal, dBDI-P

shall be set to false

The Backward Defect Indication (BDI) includes the OTS of the optical layer, the BDI of the OMS layer, OTUk and ODUkP of the electrical layer, and the BDI of the ODUkT layer.

The BDI-P indicates the payload backward defect. The BDI-O indicates the overhead backward defect. If the remote defect of the BDI inserting the OOS detected consecutively in X ms, the BDI is generated. If the BDI-P upstream defect inserted by OOS detected within the consecutive Y ms is cleared, clear the BDI-P. The values of X and Y needs the further study.

For the electrical layer OTUk, ODUkP and ODUkT layer’s BDI, we have learnt the electrical layer overhead part. If the BDI bit of the SM/PM/TCMi overhead domain of the consecutive five frames (bit 5 of byte 3) is 1, generate the dBDI. If the BDI bit of the SM/PM/TCMi overhead domain of the consecutive five frames (bit 5 of byte 3) is 0, clear the dBDI.

If the signal is invalid, the BDI should be cleared.

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Maintenance signals

OCI (open connection indication)

A signal sent downstream as an indication that upstream the signal is not

connected to a trail termination source

The presence of ODUk-OCI is detected by monitoring the ODUk STAT bits

in the PM and TCMi overhead fields.

The repeating "0110 0110" pattern is the default pattern; other patterns

are also allowed as long as the STAT bits in the PM and TCMi overhead

fields are set to "110".

1

2

3

4

1 17 382487 14

FTFL

FA OH OTUk OH

STA

T

STA

T

STA

T

STA

T

STA

T

STA

T

STA

T Repeating “0110 0110” pattern

The Open connection indication (OCI) is used for the optical layer OCh, electrical layer ODUkP, and ODUkT to indicate that the upstream signal does not connect to the trail terminal source signals. The OCI signal is generated in the connection function. Through the connection function, output at any output connection point that is not connected to any input connection point. The OCI signals are detected in the trail terminal sink function.

For the OCh layer, if the input and output is detected in the consecutive X ms, generate the OCI. If the input and output connection is normal or the overhead signal is invalid in the consecutive Y ms, clear OCI. The values of X and Y are still under the research.

As shown in the figure, it is the OCI pattern of the ODUkP and ODUkT layer. Detect the OCI, which is similar to the detection of the AIS. Check whether the corresponding bit of the STAT is 110. For example, check the OCI of the TCM1 to check whether the STAT corresponding bit of the TCM1 is 110. Detect the OCI of the PM, to check whether the STAT corresponding bit of the PM is 110.

Insert the OCI, and insert to PM and 6-level TCM area and all payloads. Clear the OCI to clear 110 of this area STAT. For example, for TCM1, it means to change the STAT of the TCM1 from 110 to 001. If the data signal is invalid, the OCI should be cleared.

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Maintenance signals

LCK (locked)

A signal sent downstream as an indication that upstream the connection is

"locked", and no signal is passed through.

The presence of ODUk-LCK is detected by monitoring the ODUk STAT bits in

the PM and TCMi overhead fields.

dLCK shall be declared if the accepted STAT information (AcSTAT) is “101”.

dLCK shall be cleared if the accepted STAT information is not equal to “101”.

During signal fail conditions of the data signal, dLCK shall be set to false.

1

2

3

4

1 17 382487 14

FTFL

FA OH OTUk OH

STA

T

STA

T

STA

T

STA

T

STA

T

STA

T

STA

T Repeating “0101 0101”pattern

To support the operator's requirement of locking the user access point signal, ODUkP and PDUkT layer provide the LCK maintenance signals to indicate the upstream connection is the locked signal, without signals passing.

When the operator performs sets up the test, the customer signals are replaced by the locked (LCK) fixed digital signals. It is generated through the service layer adaptation sink and source function, and is sent to the downstream. The downstream termination sink function allows the report of the LCK alarm, indicating that the upstream connection is locked and no signals pass.

As shown in the figure, it is the LCK pattern of the ODUkP and ODUkT layer. Detect the LCK, and check whether the corresponding bit of the STAT is 101. For example, check the LCK of the TCM1 to check whether the STAT corresponding bit of the TCM1 is 101. Detect the LCK of the PM, to check whether the STAT corresponding bit of the PM is 101.

Insert the LCK, and insert to PM and 6-level TCM area and all payloads. Clear the LCK to clear 101 of this area STAT. For example, for TCM1 source function, change the STAT of the TCM1 from 101 to 001.

The priority of inserting the LCK is higher than that of the AIS. That is, if a user sets the insertion of the LCK and meets the condition of automatic insertion of the ASI, the result is insertion of the LCK.

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Maintenance signals

IAE (Incoming Alignment Error)

IAE at the OTUk layer: dIAE shall be declared/cleared if the IAE bit in the SM

overhead field (byte 3, bit 6) is “1”/ “0” for X consecutive frames. X shall be 5.

IAE at the ODUkT layer: dIAE shall be declared/cleared if the accepted STAT

information (AcSTAT) is/is not “010”.

During signal fail conditions of the data signal, dIAE shall be set to false .

BIAE (Backward Incoming Alignment Error)

dBIAE shall be declared/cleared if the BEI/BIAE bits in the SM/TCM overhead

field (byte 3, bit 1 to 4) are/are not “1011” for X consecutive frames. X shall

be 3.

During signal fail conditions of the data signal, dBIAE shall be set to false .

Incoming Alignment Error (IAE) and Backward Incoming Alignment Error (BIAE). The electrical layer OTUk and ODUkT provide the maintenance signals of IAE and BIAE. IAE and BIAE are not the fault reasons. The IAE is used to suppress the near end performance of the OTUk and ODUkT (EBC and DS). The BIAE is used to suppress the remote performance of the OTUk and ODUkT.

For the IAE of the OTUk, if the IAE bit in the consecutive 5-frame SM overhead domain (bit 6 of byte 3) is 1, generate the dIAE. If the IAE bit in the consecutive 5-frame SM overhead domain (bit 6 of byte 3) is 0, clear the dIAE. For the IAE of the ODUkT, if the received STAT information is 010, generate the dIAE. If the received STAT information is not 010, clear the dIAE.

If the signal is invalid, the dIAE and dBIAE should be cleared.

For the signals sent to the upstream by the BIAE, if the BEI/BIAE bit of the consecutive 3-frame SM/TCMi overhead domain (bit1-bit4 of byte 3) is 1011, generate dBIAE. If the BEI/BIAE bit of the consecutive 3-frame SM/TCMi overhead domain (bit1-bit4 of byte 3) is 1011, clear dBIAE.

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Maintenance and management signal

Y––LTC

YYYBEI

Maintenance

Signal

YYYBIP-8Signal quality

Y–YIAE/BIAE

YYYBDI

YY–LCK

YY–OCI

YYYAIS

YYYTTIConnectivity

–YYLOF/LOMAlignment

ODUkTODUkPOTUk

Network layerssignal

Management

function

For the framing and monitoring, the OTUk and ODUkP support to obtaining the LOF and LOM through the detection of the FAS and MFAS. The ODUkP is applicable to the scenario from the low-level ODU multiplexing to the high-level ODU signals.

For the continuity monitoring, three layers support the TTI signals of the corresponding level.

For the information maintenance, three layers support AIS, BDI, and BEI signals. The ASI of the OTUk layer is the generic AIS signal. In ODUkP and ODUkT, there are all-1 AIS signals.

ODUkP and ODUkT layers support OCI and LCK signals.

The ODUkT layer supports the LTC signals. Note: LTC indicates there is no TCM source.

OTUk and ODUkT support the IAE/BIAE signals.

For the monitoring of the signal quality, three layers support the performance detection based on the BIP-8 calculation. That is, check the OPUk frames. But the check location and layers are different.

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Contents






6. Alarms and performance events


Classify the alarms into the corresponding layer;

Outline the suppression mechanism of alarms.

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Alarms

OPUk_PLM,OPU2_MSIM,OPU3_MSIMOPUk

ODUk_TCMi_TIM,ODUk_TCMi_DEG ,ODUk_TCMi_EXC ,ODUk_TCMi_BDI,

ODUk_TCMi_LCK,ODUk_TCMi_OCI, ODUk_TCMi_AIS,ODUk_TCMi_LTC

ODUk_TCMi

ODUk_PM_TIM,ODUk_PM_DEG,ODUk_PM_EXC,

ODUk_PM_BDI,ODUk_PM_LCK,ODUk_PM_OCI,ODUk_PM_AIS,ODUk_L

OFLOM

ODUk_PM

OTUk_LOF,OTUk_AIS,OTUk_LOM,OTUk_TIM,OTUk_DEG,

OTUk_EXC,OTUk_BDI,BEFFEC_EXC

OTUk

Alarms Layer

Remark: k=1,2,3,5G, i=1～6.

Firstly,about the OTN alarm of each electrical layer, for the alarms of OTUk layer, except the BEFFEC_EXC alarm related to the FEC, other alarm names start with “OTUk”. For the ODUkP layer, except ODUk_LOFLOM, other alarms start with “ODUk_PM”. For ODUkT layer alarms, the name starts with “ODUk_TCMi”. The OPUk layer alarm starts with “OPUk”.

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Performance events

ODUk_TCMi_BBE,ODUk_TCMi_BBER,ODUk_TCMi_BIAES,ODUk_TCMi_ES,ODUk_TCMi_F

EBBE,ODUk_TCMi_FEBBER,ODUk_TCMi_FEES,ODUk_TCMi_FESES,ODUk_TCMi_FESESR,

ODUk_TCMi_FEUAS,ODUk_TCMi_IAES,ODUk_TCMi_SES,ODUk_TCMi_SESR,ODUk_TCMi

_UAS

ODUk_TCMi

ODUk_PM_BBE,ODUk_PM_BBER,ODUk_PM_ES,ODUk_PM_FEBBE,ODUk_PM_FEBBER,O

DUk_PM_FEES,ODUk_PM_FESES,ODUk_PM_FESESR,ODUk_PM_FEUAS,ODUk_PM_SES,

ODUk_PM_SESR,ODUk_PM_UAS

ODUk_PM

OTUk_BBE ,OTUk_BBER,OTUk_BIAES,OTUk_ES,OTUk_FEBBE,OTUk_FEBBER,OTUk_FEES,

OTUk_FESES,OTUk_FESESR,OTUk_FEUAS,OTUk_IAES,OTUk_SES,OTUk_SESR,OTUk_UAS,

FEC_AFT_COR_ER

OTUk

Performance eventslayer

K=1,2,3,5G i=1～6.

This table lists OTN performance events in the OTUk, ODUk_PM, and ODUk_TCMi layers. For definitions related to the performances, see ITU-T G.8201.ES: Errored Second: When one or more bit error blocks are found in one second, it is called ES. FEES: far end ES.SES: Severely Errored Second: In one second period, include ≥ 15% bit error blocks, or, there is at least one defect (OCI/AIS/LCK/IAE/LTC/TIM/PLM). FESES: far end severely errored second.SESR: Severely Eroded Second Ratio: It indicates the ratio between the SES and total seconds in the available time within the fixed test interval. FESESR: far end Severely Eroded Second Ratio.BBE: Background Block Error: It indicates the bit error block beyond the severely eroded second. FEBBE: far end background block error.BBER: Background block error ratio. It indicates the ratio between the BBE and total blocks in the available time within the fixed test interval. The total number of the blocks excludes the number of the blocks in the SES. FEBBER: far end background block error ratio.UAS: Unavailable second: It starts from 10 consecutive SES events. The 10 seconds are considered as a part of the unavailable second. The new available time period starts from 10 consecutive non-SES events. Ten seconds can be considered as one part of the available time. FEUAS: Far end unavailable second.IAES: Incoming Alignment Error Second: When the IAE error exists in one second, the second is the incoming alignment error second. BIAES: backward Incoming Alignment Error Second.After the FEC is used, the definitions of all performance events are after the FEC. That is, the detection of the performance event (for example, BBE and SES) is after all error corrections.

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Questions

Which kinds of the components does the OTM-n.m have?

What’s the difference between SM and PM?

Which kinds of the components does the OTM-n.m have?

OTSn, OMSn, OCh, OTUk/OTUkV, ODUk, OPUk

What’s the difference between SM and PM?

SM is in the OTUk OH,PM is in the ODUk OH.

SM contains TTI/BIP-8/BEI/BIAE/BDI/IAE/RES,PM contains TTI/BIP-8/BEI/BDI/STAT.

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Summary

Optical transport hierarchy

OTN interface structure

Multiplexing/mapping principles and bit rates

Overhead description

Maintenance signals and function for different layers

Alarms and performance events

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P-54


Abbreviations and AcronymsAIS Alarm Indication Signal

APS Automatic Protection Switching

BDI Backward Defect Indication

BEI Backward Error Indication

BIAE Backward Incoming Alignment Error

BIP Bit Interleaved Parity

CBR Constant Bit Rate

CMEP Connection Monitoring End Point

DAPI Destination Access Point Identifier

EXP Experimental

ExTI Expected Trace Identifier

FAS Frame Alignment Signal

FDI Forward Defect Indication

FEC Forward Error Correction

GCC General Communication Channel

IAE Incoming Alignment Error

IrDI Inter-Domain Interface

JOH Justification Overhead

MFI Multi-frame Indicator

MSI Multiplex Structure Identifier

NNI Network Node Interface

OCC Optical Channel Carrier

OCG Optical Carrier Group

OCGr Optical Carrier Group with reduced functionality

OCh Optical channel with full functionality

OChr Optical channel with reduced functionality

OCI Open Connection Indication

ODTUG Optical channel Data Tributary Unit Group

ODTUjk Optical channel Data Tributary Unit j into k

ODU Optical Channel Data Unit

ODUk Optical Channel Data Unit-k

OMS Optical Multiplex Section

OMU Optical Multiplex Unit

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P-55


Abbreviations and AcronymsONNI Optical Network Node Interface

OOS OTM Overhead Signal

OPS Optical Physical Section

OPU Optical Channel Payload Unit

OPUk Optical Channel Payload Unit-k

OSC Optical Supervisory Channel

OTH Optical Transport Hierarchy

OTM Optical Transport Module

OTN Optical Transport Network

OTS Optical Transmission Section

OTU Optical Channel Transport Unit

OTUk completely standardized Optical Channel Transport Unit-k

OTUkV functionally standardized Optical Channel Transport Unit-k

PCC Protection Communication Channel

PLD Payload

PMI Payload Missing Indication

PRBS Pseudo Random Binary Sequence

PSI Payload Structure Identifier

PT Payload Type

RES Reserved for future international standardization

SAPI Source Access Point Identifier

Sk Sink

SM Section Monitoring

So Source

TCM Tandem Connection Monitoring

TS Time Slot

TxTI Transmitted Trace Identifier

UNI User-to-Network Interface

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