SDH & PDH DIFF
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Transcript of SDH & PDH DIFF
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We bring Light to the Internet ™
SDH and SONET SDH and SONET
Transport TechnologiesTransport Technologies
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Introduction to Introduction to SDH and SONETSDH and SONET
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• Transmitter, Medium, Receiver
• Network
• Communication Rules – Protocol
Communication BasicsCommunication Basics
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• Voice
• Video & High quality video
• Data
Types of SignalsTypes of Signals
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• Copper - Electrical
• Wireless - Microwave / Radio
• Fiber - Optical
• Satellite*
MediumMedium
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• TDM
• FDM
• WDM
• STDM
Multiplexing TechniquesMultiplexing Techniques
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Transmission TypesTransmission Types
• Asynchronous
• Plesiochronous
• Synchronous
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Transmission ProtocolsTransmission Protocols
• ATM
• Frame Relay
• IP
• TCP
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Types of NetworksTypes of Networks
• LAN, WAN, MAN• GAN• Long Haul• Submarine• Metro• Access
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Network TopologiesNetwork Topologies
• Star Network• Hierarchical• Mesh• Bus• Ring• Hybrid• Private & Public
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Types of CircuitsTypes of Circuits
• Point-to-Point• Multi-Point• 2 and 4 Wire• Digital• Wire, Twisted Pair, Coaxial,
Optical,Wireless
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PDH – PDH – Plesiochronous Digital Plesiochronous Digital
HierarchyHierarchy
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COMPARISION OF SDH / PDH
SDH system has consistent frame structures throughout thehierarchy.
PDH system has different frame structures at different hierarchy levels.
SDHPDH
Digital cross- connections are provided at different signal levels and in different ways on NMS
Physical cross-connections on the same level on DDF are forced if any
The payload is transparentThe payload is not transparent.
The synchronous multiplexing results in simple access to SDH system has consistent frame structures throughout the hierarchy.
Multiplexing / Demultiplexing operations have to be performed from one level to the next level step by step.
The reference clock is synchronized throughout the network.
The reference clock is not synchronized throughout the network
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SDHPDH
G.707 specified the first level of SDH.That is, STM-1, Synchronous Transport Module 1st Order & higher. (STM-1,STM-4,STM-16, STM-64)
G.702 specifies maximum 45Mpbs & 140Mpbs & no higher order (faster) signal structure is not specified
SDH network is designed to be a transport medium for B-ISDN, namely ATM structured signal.
PDH system does not bear capacity totransport B-ISDN signals.
It will transport variety of services.Few services are available
It will transport service bandwidths Sufficient number of OHBs is available
Limited amount of extra capacity for user / management
Byte interleaved synchronous multiplexing.
Bit - by - bit stuff multiplexing
Comparison (Contd.)
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Synchronous Digital Hierarchy
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Contents• Introduction
• SDH frame format and structure
• Payload and Virtual container
• SDH multiplexing Technique
• Function of Section, Multiplex section over head and pointer bytes
• Operations (consolidation and grooming)
• Check your learning
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Bellcore originally proposed SONET - Synchronous Optical NETwork
1985ANSI T1X1 committee agreed the proposal
1986 CCITT SDH standards published: G.707, G.708, G.709
1987 Bellcore submitted SONET to CCITT - much European opposition
History
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History (Contd)
PDH Transmission Rates
Hierarchical Level
American DS-x
European CEPT-x
Japanese Inter-national
0
2
3
4
1
64 64 64 64
84486312
1544 204820481544
63126312
97728139264139264 139264
44736 4473634368 32064
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History (contd)
Note the various differences and hence the standardization problem Compromises Basic rate for SONET increased to 51.840 Mbs to permit more bandwidth for OAM - concession to Europeans - a good move.
Europeans dropped demand for level 2 and 3 rates to be directly supported.
SDH/SONET merged on DS-3 and CEPT-4 rates
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Summary • SONET is a digital hierarchy interface conceived by Bellcore and defined by ANSI for use in North America. • SDH is (a) a network node interface (NNI) defined by CCITT/ITU–TS for worldwide use and partly compatible with SONET; and (b) one of two options for the user-network interface (UNI) (i.e., the customer connection), and formally the U reference-point interface for support of BISDN.
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Data Transmission Rates
A number of transmission rates are defined/possible:
• STS-1, STS-3, STS-9, STS-12, STS-18, STS-24, STS-36, STS-48, STS-192 , STS-768??
• STM-1, STM-3, STM-4, STM-6, STM-8, STM-12, STM-16, STM-64, STM-256??
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Data Transmission Rates(contd)
Optical CarrierOptical CarrierLevelLevel
ElectricalElectricalEquivalent / SDHEquivalent / SDH
Line RateLine Rate(Mb/s)(Mb/s)
OC-1
OC-3
OC-12
OC-24
OC-48
STS-1
STS-3/ STM1
STS-12/STM4
STS-24
STS-48/STM16
51.84
155.52
622.08
1,244.16
2,488.32
*
*
*
OC-192 STS-192/STM64 9,953.28*
OC-768 STS-768/STM256 39813.12
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STM-N Frame Format
• STM - "Synchronous Transport / Transmission Module"
• STM-N general format
• Basic frame STM-1 consists of • 270 x 9 = 2430 octets • 9 x 9 = 81 octets section overhead • 2349 octets payload
• Higher rate frames are derived from multiples of STM-1 according to value of N
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Frame Structure
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Payload details
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Elements of SDH• Container (C) • Virtual Container (VC)
• Tributary Unit (TU)
• Tributary Unit Group (TUG)
• Administrative Unit (AU)
• Administrative Unit Group (AUG)
• Synchronous Transport Module - N (STM – N)
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• Input signals are placed into the containers
• It adds stuffing bytes for PDH signals,which compensates for the permitted frequency deviation between the SDH system and the PDH signal
• C12 (2 Mbps – G.703)• C11 (1.5 Mbps)• C2 (6 Mbps)• C3 (34 / 45 Mbps)• C4 (140 Mbps)
Container
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Container(Contd)ALIGNMENT : It is a process of adopting the incoming PDH signals into containers i.e. PCM 30 or 2Mbps to C12.
ANALOGY
1. Putting 30 mobile phones in one polythene bag 2Mbps or PCM30
2. Packing the above polyethene bag in one carton box along with some packing material. Alignment
3. The above packing material called Stuffing bytes
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Virtual Container
=+POH PAYLOAD PAYLOADPOH
ANALOGY:
Packing C2 carton box with some more packing material and labeled as VC2 box
MAPPING : It is a process from Containers to Virtual containers.
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Mapping is a process used when tributaries are adapted into VCs by adding justification bits and Path overhead information
The 2 Mbps signals are not synchronized to the SDH signal.It imposes no signal structure requirements, so 2 Mbps signals using this mapping do not need to be framed.This allows easy interface with existing PDH systems as variable bit justification occurs as part of this type of 2Mbps mapping.
Mapping (Asynchronous)
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• The rate of 2Mbps signals are synchronized to the SDH signal, but the framing of the 2Mbps signal is not synchronized to SDH signal.It imposes no signal structure requirements, so no need to be framed.
• Variable bit justification does not take place, so 2 Mbps to be mapped must already be synchronized to SDH network.
• Generally used for national networks only.
Bit Synchronous Mapping
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•Here both rate and framing of 2Mbps signal are synchronized to SDH signal.
•Bit justification does not take place.
•Two types
Floating mode :- uses VC-12 pointers.
Locked mode :- avoids using VC-12 pointers. To reduce cost of VC-12 pointer processors.
Byte Synchronous Mapping
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• It adds overheads to a container or groups of tributary units, that provides facilities for supervision and maintenance of the end to end paths
• VCs carry information end to end between two path access points through the SDH system
• VCs are designed for transport and switching sub-SDH payloads• VC12 (C12 + POH)• VC11 (C11 + POH)• VC2 (C2 + POH)• VC3 (C3 + POH)• VC4 (C4 + POH)
Virtual Container
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Virtual Container (contd.)
• At each level, subdivisions of capacity can float individually between the payload areas of adjacent frames. Each subdivision can be readily located by its own pointer that is embedded in the overheads. • The pointer is used to find the floating part of the AU or TU, which is called a virtual container (VC).
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Virtual Container (contd.)
• The AU pointer locates a higher-order VC, and the TU pointer locates a lower-order VC. For example, an AU–3 contains a VC–3 plus a pointer, and a TU–2 contains a VC–2 plus a pointer.
• A VC is the payload entity that travels across the network, being created and dismantled at or near the service termination point.
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• It adds pointers to the VCs
• This pointer permits the SDH system to compensate for phase differences within the SDH network and also for the frequency deviations between the SDH networks
• TUs acts as a bridge between the lower order path layer and higher order path layer
• TU12 (VC12 + pointer)• TU2 (VC2 + pointer) • TU3 (VC3 + pointer)
Tributary Unit
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• It defines a group of tributary units that are multiplexed together
• As a result, a TU group could contain one of the following combinations
• Three TU-12s (TUG – 2)
• Seven TUG-2s (TUG – 3)
Tributary Unit Group
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• It adds pointer to the HO Virtual containers(similar to the tributary unit) • AU - 3 (VC-3 + pointer)• AU - 4 (VC-4 + pointer)
Administrative Unit Group
• It defines a group of administrative units that are multiplexed together to form higher order STM signal
Administrative Unit
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Synchronous Transport Module – n• It adds section overhead (RSOH & MSOH) to a number of AUGs that adds facilities for supervision & maintenance of the multiplexer & regenerator sections
• This is the signal that is transmitted on the SDH line
• The digit “n” defines the order of the STM signal
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STM-1 frame structure
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SDH Multiplexing ProcessSDH Multiplexing Process
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• As indicated in the figure, the STM – n signal is multiples of frames consisting of 9 rows with 270 bytes in each row
• The order of transmission of information is first from left to right and then from top to bottom
• The first 9 bytes in each row are for information and used by the SDH system itself.This area is divided into 3 parts
Regenerator Section Overhead(RSOH) Multiplex Section Overhead(MSOH) Pointers
STM-1 frame structure (contd..)
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SDH Generalised Multiplexing Structure
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Mapping of 2Mbps into STM – N signal
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• Stuffing bytes are added in the container one at the head and the other at the tail of each frame
• The lower order POHs are added at the head of each frame in the VC12
• Adding of pointers takes place at the head of each frame in the TU12
• Three parallel TU12s are multiplexed to form a TUG-2
• Seven TUG-2s are multiplexed to form a TUG-3
• Multiplexing of three TUG3s with stuffing bytes at the header forms the input to VC4
Mapping of 2Mbps into STM – N signal
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• Higher order path over heads are added at this level, which is the input to AU4
• The location of the starting byte J1(VC-4) is written in pointer bytes H1 and H2. This process is defined as pointer processing
• AUG, performs the function of concatenation in case of higher order STMs
• In STM-1,virtually there is no difference between AUG and AU-4
• AUG is attached with SOH, to form an STM-1 (1st order of Synchronous Transport module)
Mapping of 2Mbps into STM – N signal
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2.048 Mbps(E1)
1 2 3 32
32 Bytes
1 2 3 32VC-1235 Bytes
POH (Lower Order)
1 2 3 32C-1234 Bytes
Stuffing Bytes
Mapping of 2Mbps into STM – N signal
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TU-12
36 Bytes
Pointer
9 Rows
4 Columns
TU 12 is arranged Into Matrix of 9 X 4
Mapping of 2Mbps into STM – N signal
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TUG-2 9 Rows
12 Columns
9 Rows
4 Columns 4 Columns 4 Columns
TU-12 TU-12 TU-12
Multiplexing
Mapping of 2Mbps into STM – N signal
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7 TUG-2s
Stuffing Bytes
86 Columns 84 Columns
TUG 3
X 7 TUG-2 TUG-3(multiplexing)
Mapping of 2Mbps into STM – N signal
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HOPOH
VC - 4
258 Columns
Stuffing Bytes
261 Columns
TUG - 3 TUG - 3 TUG - 3
86 Columns
X 3 TUG–3
Mapping of 2Mbps into STM – N signal
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261 Columns
AU – 4 (Adding Pointer)
PO
H Pay LoadAU Pointer
9 Columns
4 th Row
Pay LoadP
OH
VC - 4
261 Columns
9 rows
Mapping of 2Mbps into STM – N signal
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PAY LOAD
RSOH
MSOH
AU Pointer
261 Columns
270 Columns
9 Columns
1-3 rows
5-9 rows
4th row
STM-1 frame structure
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SDH Over HeadsSDH Over Heads
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STM-1 Section Overhead
Y Y 1 1
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A1 & A2 – Framing Bytes
• These two bytes indicate the beginning of the STM-N frame
J0 – Regenerator Section Trace
• It’s used to transmit a Section Access Point Identifier so that a section receiver can verify its continued connection to the intended transmitter
• Identifies by a number in the individual STM – 1s of a higher order STM - n
Regenerator Section Overhead
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• This is a parity code (even parity), used to check for transmission errors over a regenerator section
• Its value is calculated over all bits of the previous STM-N frame after scrambling, then placed in the B1 byte of STM-1 before scrambling E1 – Engineering Order wire • This byte is allocated to be used as a local order wire channel for voice communication between regenerators
• This byte functionality is available at both multiplexers and Regenerators
B1- Bit Interleaved parity (BIP-8)
RSOH (contd.)
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• Each bit in BIP will indicate the parity of all respective bits in the previous frame.
Ex :
Transmitted signal = 01100100
10000110
10100100
BIP calculation = 01000110
Bit Interleaved parity (BIP)
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• Regenerator section BIP is calculated over the entire signal including all RSOH,MSOH,VC-4 POH and payload of the previous frame..The result is placed in B1 for a STM-1.
• MS BIPs are calculated over the previous STM-1 frame,minus RSOH, and placed in the B2 bytes.
• Path BIP’ are calculated over the previous frame, minus RSOH and MSOH and are found in the B3 byte of every STM-1.
BIP (contd…)
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F1 – User Channel
• This byte is set aside for the user’s purposes
D1 to D3 – Data Communication Channel
• These three bytes form a 192 kbps DCC for Operation & management of the SDH System
• Network management system sends / receives provisioning, security, status / control alarm and performance monitoring command / response by way of DCC
RSOH (contd.)
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• This is used to determine if a transmission error has occurred over a multiplex section. It is even parity, and is calculated over all bits of the MS Overhead and the STM-N frame (except the regenerator section) of the previous STM-N frame before scrambling
• The value is placed in the three B2 bytes of the MS Overhead before scrambling. These bytes are provided for all STM-1 signals in an STM-N signal
B2 – Bit Interleaved parity (BIP – 24)
Multiplex Section Overhead
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D4 to D12 – Data Communication Channel• These nine bytes form a 576 kbps DCC for Operation & management of the multiplexers on a SDH line
• Network management system sends / receives provisioning, security, status / control alarm and performance monitoring command / response by way of DCC
K1 & K2 – Multiplex Section Protection
• These two bytes are used for MSP signaling between multiplex level entities for bi-directional automatic protection switching and for communicating Alarm Indication Signal (AIS) and Remote Defect Indication (RDI) conditions
MSOH (contd.)
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K1 Byte Allocation
..Unused1001
..Manual switch1000
..Signal degrade, low priority1010
..Signal degrade, high priority1011
..Signal fail, low priority1100
..Signal fail, high priority1101
..Forced switching1110
HighLockout of protection1111
PriorityCondition,state or external request
Bits
1234
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..Do not revert0001
..Reverse request0010
LowNo request0000
..Unused0011
..Exercise0100
..Unused0101
..Wait to restore0110
..Unused0111
PriorityCondition,state or external request
Bits
1234
K1 Byte Allocation
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K1 Byte Allocation
Working channel091001
Working channel081000
Working channel101010
Working channel111011
Working channel121100
Working channel131101
Working channel141110
Extra Traffic channel151111
Requesting switch actionChannel no.
Bits
5678
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Working channel010001
Working channel020010
Null channel000000
Working channel030011
Working channel040100
Working channel050101
Working channel060110
Working channel070111
Requesting switch actionChannel no.
Bits
5678
K1 Byte Allocation
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6708
09
10
11
12
13
14
15
Channel no.
1000
1001
1010
1011
1100
1101
1110
1111
Bits
1234
Working channel
Working channel
Working channel
Working channel
Working channel
Working channel
Working channel
Extra traffic channel
Requesting switch action
K2 Byte Allocation
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Working channel010001
Working channel020010
Null channel000000
Working channel030011
Working channel040100
Working channel050101
Working channel060110
Working channel070111
Requesting switch actionChannel no.
Bits
1234
K2 Byte Allocation
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1: n architecture
1+ 1 architecture
1
0
MSP switch architectureBit 5
K2 Byte Allocation
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Future use000
Future use001
Future use010
Future use011
Future use100
Future use101
MS FERF110
MS AIF111
StatusBits 678
K2 Byte Allocation
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Automatic Protection Switching•APS is the capability of a transmission system to detect a failure on a working facility and to switch to a standby facility to recover the traffic.
•Only the Multiplex Section in SDH is protected in this automatic fashion.
•MS protection mechanism is coordinated by K1 and K2 bytes.
•Path protection is managed at a higher level by network management functions
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Protection Switching is initiated due to :
• Signal failure
• Signal degradation
• In response to commands from a local craft terminal or a remote network manager.
Two modes of APS are provided
• 1+1 Protection
• 1:N protection
APS (contd…)
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1+1 Protection switching
Normal condition
One signal is chosen per
pair
Failure condition
The best signal is chosen
Near End Far End
DestinationSource
Working
Protection
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1: N Protection switching
Normal condition
Protection on channel empty
Failure condition
Protection channel
contains failed line
Near End Far End
Source Destination
Working
Protection
Protection
Near End Far End
Working
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E2 – Engineering Order wire
• This byte is allocated to be used as a local order wire channel for voice communication between multiplexers• This byte is not accessible at the regenerators
M1 - Remote Error indication
• It is used to indicate the MS layer remote error indication (MS-REI)
MSOH (contd.)
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S1 Synchronization status message byte (SSMB)• Bits 5 to 8 of this S1 byte are used to carry the synchronization messages
0000 Quality unknown (existing sync. network)
0010 G.811 PRC (Primary Reference Clock)
0100 G.812 transit SSU-A (Synchronisation Supply Unit - A)
1000 G.812 local SSU-B (Synchronisation Supply Unit – B)
1011 G.813 Option 1 SEC (Synchronous Equipment Timing Clock)
1111 Do not use for synchronization. This message may be emulated by equipment failures and will be emulated by
Multiplex Section AIS signal.
MSOH (contd.)
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H1 Y Y H2 1 1 H3 H3 H3
H1 & H2 = VC payload pointer
H3 = Negative Justification
1 = All 1’s
Y = 1001SS11 (S bits unspecified)
SDH Pointers Use of Pointers• It indicates the starting position of VC• It is also used for justification• AU pointer is also used for concatenation• SDH provides payload pointers to permit differences in the phase and frequency of the Virtual Containers (VC-n) with respect to the STM-N frame
• Lower-order pointers are also provided to permit phase
differences between VC-12/VC-2 and the higher-order
VC-3/VC-4
To accomplish this, a process known as byte stuffing is used
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• The value of the pointer has a range of 0 to 782
For example, • If the VC-4 Payload Pointer has a value of 0, then the VC-4 begins in the byte adjacent to the H3 byte of the Overhead;
• If the Payload Pointer has a value of 87 (since each row of the payload has 86 positions), then the VC-4 begins in the byte adjacent to the K2 byte of the overhead in the byte of the next row
• The pointer value, which is a binary number, is carried in bits 7 through 16 of the H1-H2 pointer word.
Pointers (contd.)
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Positive Pointer Justification• When the data rate of the VC is too slow in relation to the rate of the STM-1 frame, positive stuffing must occur. An additional byte is stuffed in, allowing the alignment of the container to slip back in time. This is known as positive stuffing
Negative Pointer Justification• Conversely, when the data rate of the VC is too fast in relation to the rate of the STM-1 frame, that negative stuffing must occur. Because the alignment of the container advances in time, the payload capacity must be moved forward. Thus, actual data is written in the H3 byte, the negative stuff opportunity within the Overhead; this is known as negative stuffing
Pointers (contd.)
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H1 Y Y H2 1 1
H2 1 1H1 Y Y
H1 Y Y H2 1 1
H3 H3 H3
H3 H3 H3
H3 H3 H3
Points outStart of VC-4 VC-4 Boundary
AU-4 Pointer Positive justification
Points outStart of VC-4
Points outStart of VC-4 VC-4 Boundary
VC-4 Boundary
To next RowTo next Row
Positive justification opportunity
AU – 4 Positive Pointer Justification
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Points outStart of VC-4
Points outStart of VC-4 VC-4 Boundary
VC-4 Boundary
From next row
From next row
Negative justification opportunity
AU-4 Pointer Negative justification
H1 Y Y H2 1 1
H2 1 1H1 Y Y
H1 Y Y H2 1 1
H3 H3 H3
H3 H3 H3
Points outStart of VC-4 VC-4 Boundary
AU – 4 Positive Pointer Justification
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Path OverHead
TCM – Tandem Connection Monitoring
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J1- Path trace
• Starting point of VC• It is used to transmit repetitively a path access
point identifier, similar to J0
B3 – Path Bit Interleaved Parity – BIP- 8
• Error Monitoring over the previous VC-4 frame.• Even parity is used to monitor path errors
Path Overhead
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C2 – Signal Label• It is defined to indicate the composition or the maintenance of the VC-4
POH (contd.)
FDDI150001 0101
MAN (DQDB)140001 0100
ATM130001 0011
140 Mbps into C4 (async)120001 0010
34 / 45 Mbps into C3 (async)040000 0100
Locked TU030000 0011
TUG structure020000 0010
Equipped,non specific010000 0001
Unequipped000000 0000
MappingHexBinary
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G1- Path status
• It is defined to send back the path status and performance to where the path is generated
F2,F3 – Path User Channels
• It is assigned for user communication purposes between path elements by the network operator
H4 – Multi frame Indicator
• H4 byte provides the multiframe information
POH (contd.)
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K3 – Automatic protection switching(APS) channel
• (b1-b4) are assigned for APS signaling for protection at the VC-4/3 path labels
N1 – Network operator Byte
• The tandem connection monitoring function is currently not used
POH (contd.)
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Benefits of SDHBenefits of SDH
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Pointers, Mux/Demux
Reduced back to back multiplexing
Optical Interconnect
Multi Point Configuration
Grooming
Enhanced OAM
Enhanced Performance monitoring
Benefits of SDH
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Operations
Managing capacity in the network involves such operations as the following:
a. protection, for circuit recovery in milliseconds
a. restoration, for circuit recovery in seconds or minutes
a. provisioning, for the allocation of capacity to preferred routes destinations for each type of traffic
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Operations ( contd)
a. consolidation, or the funneling of traffic from unfilled bearers onto fewer bearers in order to reduce waste of traffic capacity
b. grooming, or the sorting of different traffic types from mixed payloads into separate
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Consolidation and Grooming
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Routing Function of a Typical ADM
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SDH Network ElementsSDH Network Elements
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SDH Network elements
Terminal multiplexer
Regenerator
Add / Drop Multiplexer
Cross – connect
Wide-band Digital cross connect
Broad band Digital cross connect
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Terminal Multiplexer STM –1
E1 VC STM-N
E3 STM-1
STM-1
E1
E3
STM-N
STM-N STM-N
Regenerator
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STM-N
STM-N STM-N
STM-N TU AU-4
STM-N E1 E4
STM-N 2 Mbps 140 Mbps
STM-N STM-N
Add / Drop Multiplexer
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TU – 12 Switch Matrix
TU-12 TU-12 TU-12 ` TU-12
STM-N STM-1 E1 E4
STM-N STM-1 2 Mbps 140 MbpsSTM-N
Wide Band Digital Cross Connect
Transparent Switch Matrix
AU-4 AU-4 AU-4 ` AU-4
STM-N STM-N E1 E4
STM-N STM-1 2 Mbps 140 MbpsSTM-N
Broad Band Digital Cross Connect
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TopologiesTopologies
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Network Configurations
Point to Point
Point to Multipoint
Mesh Architecture
Ring Architecture
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PTE PTERegen
Point to Point
Point to Multi point
PTE ADM PTERegenRegen
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ADM
ADM
ADM
ADM
Ring Architecture
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Mesh Topology
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G.811
G.812
G.812
Under definition (G.81s)
Primary Reference Clock (PRC)
Slave clock (transit node)
Slave clock (local node)
SDH network-element clock
Related CCITT recommendation
Clock type
Synchronization