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SDH OVERVIEW
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Limitation of PDH
INTERFACES:
Electrical interfaces
There are only regional standards, instead of universal standards
Optical interfaces
No unified standards for optical line equipments, manufacturers
develop equipment according to their own standards
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PDH: the electric interface is a standard interface, but the optical
interface is not a standard interface
Special PDH optical signal
Manufacturer
A
Manufacturer
B
Standard electric interface
2Mbit/s or 34Mbit/s
PDH Network
Manufacturer
B
Standardization of optical interface
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Limitations of PDH
MULTIPLEXING METHOD:
Asynchronous Multiplexing
Code rate justification is required for matching and
accepting clock difference
The locations of the low-rate signals in high-rate signals
are not regular nor fixed
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European Series
565Mb/s
139Mb/s
34Mb/s
8Mb/s
2Mb/s
4
4
4
4
Japanese Series North American Series
1.6Gb/s
400Mb/s
100Mb/s
32Mb/s
6.3Mb/s
1.5Mb/s
274Mb/s
45Mb/s
6.3Mb/s
44
4
4
6
7
3
5
64Kb/s
24 30
3
3
Limitations of PDH
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Limitations of PDH
OPERATION & MAINTENANCE (OAM)
PDH signal frame structure has very few overhead bytes
for Operation, Administration, and Maintenance (OAM)
NETWORK MANAGEMENT INTERFACE
No universal network management interface for PDH
network
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Advantages of SDH over PDH
INTERFACEElectrical interfaces
SDH provides a set of standard rate levels----STM-N.
(N= 4n =1, 4, 16, 64).The basic signal transmission structure level is STM-1, at a rate of
155Mb/s
Optical interfaces
Optical interfaces adopt universal standards. Line coding of SDH
signals involves scrambling, instead of inserting redundancy codes
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SDH Network
Standard optical interface
Uniform STM-N optical signal
Manufacturer
A
Manufacturer
B
Standardization of optical interface
SDH has standard optical interface
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Advantages of SDH over PDH
MULTIPLEXING METHOD
Low-rate SDH signals high-rate SDH
Signals via byte interleaved multiplexing method
PDH signals SDH
Synchronous multiplexing method and flexible mapping structure
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STM-256
STM-64
STM-16
STM-4
STM-1
4
4
4
4
STM-1, 2, 34, 140 Mb/s
STM-N
N
SDH Multiplexing
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SDH Signals Bit rate(Mb/s)
STM-1 155.520 or 155M
STM-4 622.080 or 622M
STM-16 2488.320 or 2.5G
STM-64 9953.280 or 10G
SDH higher-rate signal (STM-4,16,64) is exactly 4 times that
of the lower-rate signal (STM-1)
STM: Synchronous Transport Module
SDH Signals and Data Rates
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155Mbit/sOptical interface
155Mbit/sOptical interface
2Mbit/s
Electric signal
SDH: Economical and easy way for network!
Adding and dropping in SDH
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Advantages of SDH over PDH
OPERATION & MAINTENANCEAbundant overhead bits are used for OAM.
Unnecessary to add redundancy bits to monitor line
performance during line coding
COMPATIBILITY
SDH network and the existing PDH network can work
together
SDH network can accommodate the signals of other hierarchies
such as ATM, FDDI, and Ethernet
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SDH FRAME STRUCTURE
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STM-N Frame Structure
For the convenience of signal analysis, the frame
structures of the signals are often illustrated as block
frame structures
The frame structure of PDH signals, ATM signals and
data packets of IP network are also block frames
The frame of E1 signals is a block frame of 1 Rows x32 Columns consisting of 32 Bytes
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RSOH
MSOH
1
3
4
5
9
STM-N payload
(including POH)
9 261
270 Columns
9 RowsAU-PTR
RSOH: Regenerator Section Overhead
MSOH: Multiplex Section Overhead
POH: Path Overhead
AUPTR: Administrative Unit Pointer
125 s
STM-1 Frame Structure
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RSOH
MSOH
1
3
4
5
9
STM-N payload
(including POH)
9 N 261 N
270 N
Columns
9 RowsAU-PTR
RSOH: Regenerator Section Overhead
MSOH: Multiplex Section Overhead
POH: Path Overhead
AUPTR: Administrative Unit Pointer
STM-N Frame Structure125 s
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SDH Frame Structure - ANATOMY
Transmission rate of single byte of STM-N frame:STM-N frame contains 2430xN Bytes and each frame is
transmitted every 125 s
That means a given byte is transmitted 8000 times a secondTransmission rate of a single byte:
8000 x 8 = 64 Kbps
Transmission rate of a STM-1 frame:
9 rows x 270 columns x 8000 frames/s x 8 bits = 15,55,20,000 bps
= 155.52 Mbps
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1
2161
270
2430
271 540
1st Byte of
STM frame # 1
Last byte of
STM frame # 1
STM-1 Frame # 1 1st Byte
STM Frame # 2
Transmission Mode: Byte-by-Byte,
From Left to right & top to bottom
Transmission Direction
1st
Byte
2430th
Byte
STM-1 Frame Transmission
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SDH Frame Structure
Payloadarea for services transmission in STM-N
2M, 34M, and 140M signals are packed and carried
in the payload of STM-N frame over SDH network
Path Overhead (POH) after packing low rate
signals, POH is added for OAM of every frame
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SDH Frame Structure
Section Overhead (SOH)monitors the whole STM-N frame
Regenerator Section Overhead (RSOH) monitors the
whole STM-N frame.
Multiplex Section Overhead (MSOH) monitors each
STM-1 of the STM-N frame.
RSOH, MSOH, and POH compose the integratedmonitoring system of SDH.
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SDH Network NE Types
Terminal Multiplexer (TM)
Add/Drop Multiplexer (ADM)
Regenerator (REG)
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Regenerator
Regenerator has the job of regenerating the clock and amplituderelationships of the incoming data signals that have attenuated
and distorted by dispersion
The regenerator replaces the RSOH bytes before re-transmittingthe signal
RegeneratorSTM-N STM-N
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Terminal Multiplexer
Terminal multiplexers are used to combine
plesiochronous and synchronous input signals into
higher bit rate STM-N signals
Terminal Multiplexer
PDH
SDH STM-N
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Add / Drop Multiplexer
PDH and SDH signals can be extracted from orinserted into high speed SDH bit streams by means of
ADMs
Add / Drop Multiplexer
PDHSDH
STM-N
Towards other NEs
Customers
IPATM
STM-N
Towards other NEs
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Sections in the SDH Network
There are three sections in the SDH
Path
Multiplex Section
Regenerator Section
The overheads are always generated at the beginning of asection and only evaluated at the end of a section
Terminal
MultiplexerAdd/Drop
MultiplexerTerminal
MultiplexerREG REG REG
Path
Multiplex Section
Regenerator Section
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Payload
Path
Section
Optical
Payload
Path
Section
OpticalOptical Fiber Cable
RSOH
MSOH
POH
Overhead Layer
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How to understand SOH and POH?
Both SOH and POH are OAM bytes added to ensure correct and
flexible transmission of signals
SOH and POH are used in different layers to supervise and
administrate the signals. RSOH and MSOH are used in RS and MS
separately, but HPOH and LPOH are used for VC-3/VC4 and VC12LPOH----used to supervise small package (VC-12)
HPOH----used to supervise big package (VC-3 / VC-4)
MSOH----used to supervise the carriage(STM-1) of the truck
RSOH----used to supervise the motorcade formed by trucks (STM-4/16/64)
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SDH Frame Structure
AU Pointer (AU-PTR)Used for alignment of lower rate signals in the payload of STM-N
frame to accurately locate the payload
AU-PTR is added in transmitting end, when the signal is packed
into the payload of STM-N frame
At receiving end, the low rate signal is dropped from STM-N
frame according to the AU-PTR value
Low-rate signals in the STM frame are arranged obeying some
rules byte interleave; so only have to locate the first low-rate
signal in the STM frame
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SDH MULTIPLEXING
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SDH Multiplexing
SDH Multiplexing includes:Low to high rate SDH signals (STM-1 STM-N)
PDH to SDH signals (2M, 34M & 140M STM-N)
Other hierarchy signals to SDH Signals (ATM STM-N)
SDH Multiplexing Structure
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SDH Multiplexing Structure
STM-1 AU-4
TU-3
AUG-1
TUG-3 VC-3 C-3
VC-4 C-4
TU-12 VC-12 C-12
TUG-2
1 1
3
1
7
3
139264 kbit/s
34368 kbit/s
2048 kbit/s
Pointer processing
Multiplexing
Mapping
Aligning
AUG-4
AUG-16
AUG-64
STM-4
STM-16
STM-64
1
1
1
4
4
4
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Mapping, Aligning and Multiplexing
Low-rate tributaries are multiplexed into STM-N signals through three procedures:
Mapping
Aligning
Multiplexing.
MAPPING
SDH mapping is a procedure by which tributaries are adapted into virtual containers at the
boundary of an SDH network, for example, E1 into VC-12, E3 into VC-3, E4 into VC-4.ALIGNING
SDH aligning is a procedure by which the frame-offset information is incorporated into the
tributary unit, by adding a pointer
The pointer value constantly locates the start point of the VC frame within the payload, so that
the receiving end can correctly separate the corresponding VC
MULTIPLEXING
SDH multiplexing is the procedure by which multiple lower order path layer signals are adapted
into a higher order path
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Multiplexing Structure
C: Container
VC: Virtual Container
TU: Tributary Unit
TUG: Tributary Unit GroupAU: Administrative Unit
AUG: Administrative Unit Group
2 Mb Si l M i P d
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2 Mb Signal Mapping Procedure
C12
Rate
Adaptation
2 Mbps Signal
1 4
1
9125 s
1 Byte Path
Overhead
(POH)
1 4
1
9
VC12
C-12 Size: (9 Rows x 4 Columns) 2 = 34 Bytes
C12
POH
VC-12 Size: (9 Rows x 4 Columns) 1 = 35 Bytes
125 s
VC-12 = C-12 + (1 Byte POH)
C-12 Frame Duration = 125 s
VC-12 Frame Duration = 125 s
There can be four different POH
bytes for one C-12 V5, J2, N2, K4
MAPPING
2 Mb Si l M i P d
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2 Mb Signal Mapping Procedure
Multiplexing
x 31 12
1
9
TUG2
T
U
-
12
125 s
1 4
1
9
VC12
C12
POH
125 s
1 Byte Tributary
Unit Pointer
(TU-PTR)1 4TU12
C12
POH
125 s
PTR
T
U
-
12
T
U
-
12
TUG-2 size: (9 Rows x 12 Columns) = 108 Bytes
TU-12 Size : (9 Rows x 12 Columns) = 36 Bytes
TU-12 = VC-12 + (1 Byte TU-PTR)
TUG-2 = TU-12 + TU-12 + TU-12
TU-12 and TUG-2 Frame Duration = 125 s
ALIGNING MULTIPLEXING
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RR
2 Mb Signal Mapping Procedure
1 12
1
9
TUG2
T
U
-
12
125 s
T
U
-
12
T
U
-
12
Multiplexing
x 71 86
1
9
TUG3
125 s
T
U
G
-2
T
U
G
-2
T
U
G
-2
T
U
G
-2
T
U
G
-2
T
U
G
-2
T
U
G
-2
TUG-3 Size = (TUG-2) x 7 + R (2 Columns)
TUG-3 Frame Duration = 125 s
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2 Mb Signal Mapping Procedure
1 86
1
9
TUG3
125 s
Multiplexing
x 3
R
P
O
H
1 261
1
9
VC4
125 s
T
U
G
-3
T
U
G
-3
T
U
G
-3
R
VC-4 = TUG-3 + TUG-3 + TUG-3 + R (2 Columns) + POH (1 Column)
VC-4 Frame Size = 9 Rows x 261 Columns = 2349 Bytes
VC-4 Frame Duration = 125 s
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VC4
2 Mb Signal Mapping Procedure
1 2611
9
125 s
AU-PTR
AU4
VC4
1 2701
9
125 s
AUG1 270
1
9
125 s
STM-11 270
1
9
125 s
Multiplexing
x 1
RSOH and
MSOH
AU-PTR
VC4AU-PTR
VC4AU-PTR
MSOH
RSOH
2 Mb Multiplexing Route
2 Mb C-12 VC-12 TU-12 TG-2 TG-3 VC-4 AU-4 AUG STM-1
34 Mb Signal Mapping Procedure
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34 Mb Signal Mapping Procedure
C3
Rate
Adaptation
34 Mbps Signal
1 84
1
9
125 s
Path
Overhead
(POH)
C3
1 85
1
9
125 s
P
O
H
VC3
C-3 Frame Size: 9 rows x 84 columns = 756 Bytes
C-3 Frame Duration: 125 s
VC-3 = C-3 + (POH) POH = 9 Rows x 1 Column = 9 Byte
VC-3 Frame Size: 9 Rows x 85 Columns = 765 Bytes
VC-3 Frame Duration: 125 s
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34 Mb Signal Mapping Procedure
VC3
TributaryUnit Pointer
1 86
1
9
125 s
FixedStuffing Bits
1 86
1
9
125 s
TU3
H1
H2
H3
R
TUG3TU3H1
H2
H3
TU-3 = VC-3 + TU-PTR TU-PTR = 3 Byte Pointer (H1, H2 and H3)
TUG-3 = TU-3 + R (Fixed StuffingBits)
R (Fixed Stuffing Bits) = 6 Bytes (Fixed Stuffing Bits)
TU-3 and TUG-3 Frame Duration = 125 s
STUFFING
b l d
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34 Mb Signal Mapping Procedure
T
U
G
3
1 261
1
9
125 s
P
O
H
R R
VC4Multiplexing
x 3
TU3
1 86
1
9
125 s
H1
H2
H3
R
TUG3
VC-4 = TUG-3 + TUG-3 + TUG-3 + R (2 Columns) + POH (1 Column)VC-4 Frame Size = 9 Rows x 261 Columns = 2349 Bytes
VC-4 Frame Duration = 125 s
T
U
G
3
T
U
G
3
34 Mb Si l M i P d
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VC4
34 Mb Signal Mapping Procedure
1 2611
9
125 s
AU-PTR
AU4
VC4
1 2701
9
125 s
AUG1 270
1
9
125 s
STM-11 270
1
9
125 s
Multiplexing
x 1
RSOH and
MSOH
AU-PTR
VC4AU-PTR
VC4AU-PTR
MSOH
RSOH
34 Mb Multiplexing Route
34 Mb C-3 VC-3 TU-3 TUG-3 VC-4 AU-4 AUG STM-1
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VC-4 = C-4 + (POH) POH = 9 Rows x 1 Column = 9 Byte
VC-4 Frame Size: 9 Rows x 261 Columns = 2349 Bytes
140 Mb Signal Mapping Procedure
C4
Rate
Adaptation
140 Mbps Signal
1 260
1
9
125 s
C-4 Frame Size: 9 rows x 260 columns = 2340 Bytes
C-4 Frame Duration: 125 s
Path
Overhead
(POH)
C4
1 261
1
9
125 s
P
O
H
VC4
Rate Adaptation: The process of Bit stuffing, to account for different
clock rates of the signals coming from different sources
140 Mb Signal Mapping Procedure
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140 Mb Signal Mapping Procedure
VC4
AU-PTR
10 270
1
9
125 s
Multiplexing x 1
AU-PTR
AU-PTR: A 9 byte pointer is inserted at Row No 4
AU4 Size: (1x9)+(9x261) = 2358 Bytes
1 9
A U 4
10 270
1
9
125 s
1 9
AU4 AUG4
In case of 140 Mb signal mapping in STM-1, AU-4 and AUG are identical
AU-4 and AUG Frame Duration: 125 s
4
140 Mb Signal Mapping Procedure
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140 Mb Signal Mapping Procedure
STM-1
RSOH and
MSOH
1 270
1
9
125 s
A U 4
10 2701
9
125 s
1 9
RSOH
MSOH
AUG4
RSOH Size: 3 Rows x 9 Columns = 27 Bytes
MSOH Size: 5 Rows x 9 Columns = 45 Bytes
STM-1 Size: 9 Rows x 270 Columns = 2430 Bytes
STM-1 Frame Size: 125 s
3
5
A U 4
270
125 s
1AUG4
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OVERHEADS
Overhead Bytes
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Overhead Bytes
270
1
9
STM-1 Frame Structure
RSOH
MSOH
AU-PTR
P
O
H
OVERHEAD
1
PAYLOAD
S ti O h d (SOH)
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Section Overhead (SOH)
Overhead in SDH frame structure are classified as:Section Overhead SOH
Path Overhead POH
SOH is further divided into RSOH and MSOH
RSOH can be accessed in the regenerator or at the terminal
equipment
MSOH can be processed at the terminal equipment
R t S ti O h d RSOH
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Regenerator Section Overhead RSOH
A1 A1 A1 A2 A2 A2 J0 X X
B1 E1 F1 X X
D1 D2 D3
: Media dependent bytes
X: Bytes reserved for national use
A1 d A2 B t
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A1 and A2 Bytes
Frame Alignment (Framing) BytesIndicate the beginning of the STM-N frameA1 = F6H (11110110), A2 = 28H (00101000)In STM-N: (3XN) A1 bytes, (3XN) A2 bytes
stream
STM-N STM-N STM-N STM-N STM-N STM-N
Finding frame head
Frame # 1 Frame # 2 Frame # 3 Frame # 4 Frame # 5 Frame # 6
A1 d A2 B t
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A1 and A2 Bytes
Framing
Next
process
Find
A1,A2
OOF
LOF
N
Y
AIS
over 3ms
625 s
OOF: Out Of Frame
LOF: Loss Of Frame
AIS: Alarm Indication Signal
R t S ti T J0 B t
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Regenerator Section Trace J0 Byte
Regenerator Section Trace Byte: J0Its used to transmit repetitively a Section Access Point
Identifier so that a section receiver can verify its continued
connection to the intended transmitter
Another usage of the J0 byte is that J0 byte in each STM-N
frame is defined as an STM identifier C1 i.e., to identify
individual STM-1 inside a multiplexed STM-N
Within the domain of a single operator, this byte may use
any character
B1 B t
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B1 Byte
Tx
2#STM-N
Rx
1#STM-N
Calculate
B1 of STM-N #1
1#STM-N
2#STM-N
Verify B1 B2
STM-NA1 00110011
A2 11001100
A3 10101010
A4 00001111
B 01011010
BIP-8
Bit interleaved Parity Code (BIP-8) Byte
A parity code (even parity), used to check the transmissionerrors over the RS
Place the resultof BIP in B1 ofSTM-N #2
F1 B te
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F1 Byte
User Channel Byte: F1Provides a 64 kb/s data/voice channel for special
maintenance purposes.
F1
TM REG TMADM
E1 and E2 Bytes
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E1 and E2 Bytes
Digital telephone channel
E1-RS, E2-MS
E1 and E2
TM ADM TMREG
Orderwire Bytes: Provides one 64 kbps each for voice
communicationE1: RS Orderwire Byte RSOH orderwire messageE2: MS Orderwire Byte MSOH orderwire message
Quiz
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Quiz
If only E2 byte is used as order wire byte, then orderwire voice communication is provided between:
A and B
B and C
C and D
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D1 ~ D12 Bytes
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D1 ~ D12 Bytes
TMN
DCC channel
NE NE NENE
OAM Information: Control, Maintenance,Remote Provisioning, Monitoring (Alarm &
Performance), Administration
Data Communications Channels (DCC) Bytes
Message-based Channel for OAM between NEs and NMSRS-DCC D1 ~ D3 192 kbit/s (3X64 kbit/s)
MS-DCC D4 ~ D12 576 kbit/s (9X64kbit/s)
Multiplex Section Overhead MSOH
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Multiplex Section Overhead MSOH
B2 B2 B2 K1 K2
D4 D5 D6
D7 D8 D9
D10 D11 D12
S1 M1 E2 X X
X: Bytes reserved for national use
B2 Bytes
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B2 Bytes
The B1 byte monitors the transmission error of thecomplete STM-N frame signal
The B2 bytes monitor the error performance status for
each STM-1 frame within the STM-N frame
There are N*3 B2 bytes in an STM-N frame with
every three B2 bytes corresponding to an STM-1 frame
B2 Bytes
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ytes
B2 Byte Principle
At transmitting end, the BIP-Nx24 is computed over all bits of the STM-
N frame except for the first three rows of SOH, and the result is placedin 3 bytes B2 of the preceding frame before scrambling.
At receiving end, the BIP- Nx24 is computed over all bits of the frameexcept for the first three rows of SOH, and then Exclusive OR with theB2 bytes of the later arrived frame.
If the value of Exclusive OR operation is zero, there is no bit block error.Any mismatch in result indicates transmission errors.
For example
BIP-N24 is computed over
a frame of signal composed
of 9 bytes.
11001100 11001100 11001100
01011101 01011101 01011101
11110000 11110000 11110000BIP24
01100001 01100001 01100001
K1 and K2 (b1 ~ b5)
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K1 and K2 (b1 b5)
Automatic Protection Switching (APS) channel
bytes
Used for transmitting APS signaling to implement
equipment self-healing function
The K1 byte and K2(b1~b5) are used forautomatic switchover to a standby path
K1 and K2 (b1 ~ b5)
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K1 and K2 (b1 b5)
NE-A NE-BWorking path
Standby path
Working path
Standby path
NE-B detects a transmission error on the line and informs NE-A via K1 byte
to switchover
NE-A switches to the standby channel
NE-A via K2 byte indicates the switchover in NE-B
NE-B switches to the standby channel
K1
K2
S1 Byte
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y
bits 5 ~ 8 Meaning0000 Quality unknown (existing sync. Network)
0010 G.811 PRC
0100 G.812 transit
1000 G.812 local
1011G.813 SETS (Synchronous Equipment
Timing Clock)
1111 Do not use for sync.
Synchronization Status Message Byte (SSMB)This byte is used for synchronizationof network
Bits 5 to 8 of S1 byte indicate the quality of the incoming clockThe smaller the value of S1 (b5-b8), the higher the level of clock qualityThis helps to determine whether or not to switch the clock source, i.e.
switch to higher quality clock source
M1 Byte
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M1 Byte
Tx Rx
Traffic
Multiplex Section Remote Error Indication
MS-REI
ByteThis byte is used to report back the number of error blocksdetected by the receiver by evaluating three B2 bytes
Tx generate corresponding performance event MS-REI
B2 B2 B2
Report no. of
errors detected
Evaluate B2 and
detect bit errors
M1
Generate MS-REIMS-REI
Path Overheads
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Path Overheads
J1
B3
C2
G1
F2
H4
F3
K3
N1
12
3
4
5
6
7
89
VC-n Path Trace BytePath BIP-8
Path Signal Label
Path Status
Path User Channel
TU Multiframe Indicatio
Path User Channel
AP Switching
Network Operator
Higher Order Path Overhead
1 2 3 4 5 6 7 8 9 10
Path Signal Label : C2 Byte
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Path Signal Label : C2 Byte
C2 byte is used to indicate the type and compositionof the VC-4 tributary information
Path Status : G1 Byte
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Path Status : G1 Byte
Path status byte
This byte is used to report back the fault from path sink to path
source and is set in the POH of the opposite direction
HP-REI HP-RDI Reserved
87654321
HP-REI: High order Path Remote Error Indication
HP-RDI: High order Path Remote Defect Indication
HP-REI and HP-RDI
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HP-REI and HP-RDI
Higher order Path Remote Error Indication
The SDH NE (sink end) checks B3 bytes
If error blocks are detected, the number of error blocks detected
is sent to the remote terminal in HP-REI signal
Higher order Path Remote Defect Indication
The SDH NE (sink end) checks J1 and C2 bytes
If J1 and C2 fail to be consistent, HP-TIM (Higher order path
Trace Identifier Mismatch) and HP-SLM (Higher order Path
Signal Label Mismatch) alarms are generated
HP-RDI is sent back to the remote end
Multiframe Indication : H4 Byte
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Multiframe Indication : H4 Byte
This byte indicates the framelabel for a multiframe in the next
VC-4 payload
The value of this byte ranges
from 00H to 03H
Path Overheads
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Path Overheads
V5 J2 N2 K4
VC-12 VC-12 VC-12 VC-12
1
9
1 4
500s VC-12 multiframe
Low Order Path Overhead
Path Status and Signal Label : V5 Byte
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g y
BIP-2
Parity code of VC-12
LP-REI
Low order Path Remote Error Indication
LP-REI is set to "1" and returned to the opposite direction if one or more errors are detected via BIP-2
LP-RFI
Low order Path Remote Failure Indication
If a defect condition persists beyond the maximum allowed time, it becomes a failure, then LP-RFI is set to "1"
and sent back to the source
Signal Label
Indicates type and composition of VC-12 tributary information
LP-RDI
Low order Path Remote Defect Indication
If sink end detects a TU-12 AIS, it sets LP-RDI to "1" and sends back to the source
BIP-2 LP-REI LP-RFI Signal Label LP-RDI
87654321
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POINTERS
Pointers
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Pointers
Pointers
AU-PTR TU-PTR
AU-PTR
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AU PTR
RSOH
AU-PTR
MSOH
4
1
9
AU-PTR
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AU PTR
Y: Fixed value 1001SS11
F: Fixed value 11111111
H3: Additional transmission capacity during negative
justification
H1 and H2: Pointer value is contained in the last ten bits of H1
and H2
H1 Y Y H2 F F H3 H3 H387654321 9
AU-PTR
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AU PTR
N: New data flag bits
A notification to the receiver about the change in pointer value and pointer
justification operation
AU/TU type:
For AU-4 and TU-3, SS=10
I/D: Increment/Decrement bits
D bits are inverted to decrement next AU-PTR address (-ve justification)
I bits are inverted to increment next AU-PTR address (+ve justification)
N N N N S S I D I D I D I D I D
H1 and H2
TU-PTR
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TU PTR
The tributary unit pointer is used to indicate thespecific location of the first byte (V5) of the VC-12
within the TU-12 payload
TU-PTR
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VC-12 VC-12 VC-12 VC-12
V1 V2 V3 V4
1
9
500s VC-12 multiframe
TU POINTERS
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THANK YOU
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