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
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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.
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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
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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
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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.
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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 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
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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
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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
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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
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
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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
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.
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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
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