SDH Principles

Part 2 Frame Structure & Multiplexing Methods Course Contents Part 1 SDH Overview Part 2 Frame Structure & Multiplexing Methods Part 3 Overheads & Pointers

Chapter 1 Emergence of SDH What is SDH? ---- Synchronous Digital Hierarchy ---- It defines frame structure, multiplexing method, digital rates hierarchy and interface code pattern. ---- Need for a system to process increasing amounts of information. ---- New standard that allows mixing equipment from different suppliers. Why did SDH emerge?

Plesiochronous Digital Hierarchy 1-1 Disadvantages of PDH Plesiochronous Digital Hierarchy interfaces Electrical interface :- Only regional standards. 3 PDH rate hierarchies for PDH: European (2.048 Mb/s), Japanese, North American (1.544 Mb/s). Optical interfaces:-No standards for optical line equipment, manufacturers develop at their will Multiplexing methods Asynchronous Multiplexing :- The location of low-rate signals in high-rate signals is not regular nor predictable. OAM function Weak Operation. Weak Administration. Weak Maintenance function. Capabilities to setup a TMN is limited. 140 Mb/s 34 Mb/s 8 Mb/s 2 Mb/s de-multiplexer multiplexer

synchronous Digital Hierarchy 1-1 Advantages of SDH synchronous Digital Hierarchy interfaces Electrical interfaces:-Can be connected to all existing PDH signals. Optical interfaces:-Can be connected to multiple vendors’ optical transmission equipment. Multiplexing methods Basic rate is STM-1, other rates are multiples of the basic rate Low level SDH to/from high level SDH PDH signal to/from SDH signal. ×4 WDM STM-1 155 Mb/s STM-4 622 Mb/s STM-16 2.5 Gb/s STM-64 10 Gb/s 10 Gb/s De-multiplexing 622 Mbit/s 2 Mbit/s Multiplexing

1-1-2 Advantages of SDH OAM function Compatibility Abundant overheads bytes for automation, network monitoring and maintenance Compatibility Working with all kinds of signals like PDH, SDH, ATM & FDDI package packing Processing transmit SDH network unpacking PDH, SDH, ATM, FDDI Signals receive STM-N Disadvantages of SDH Mechanism of pointer adjustment is complex. Large-scale application of software makes SDH system capable to receive viruses

Part 2 Frame Structure & Multiplexing Methods Course Contents Part 1 SDH Overview Part 2 Frame Structure & Multiplexing Methods Part 3 Overhead & Pointers

2- SDH Frame Structure From ITU-T G.707: Three parts: STM-1 is the basic transmission format One frame lasts for 125 microseconds (8000 frames/s Rectangular block structure 9 rows and 270 columns Each unit is one byte (8 bits) Transmission mode: Byte by byte, row by row, from left to right, from top to bottom Frame = 125 us 1 2 3 4 5 6 7 8 9 SOH Information Payload PTR 9 rows Three parts: Information Payload Section Overhead Pointer 9 270 Columns 1 byte = One 64 Kbit/s channel STM-N = 9 X 270 X N (N = 4, 16, 64) STM-1 rate = 9 X 270 X 8 X 8000 =155 Mb/s

Information Payload Information Payload Also known as Virtual Container level 4 (VC-4) Used to transport low speed tributary signals Contains low rate signals and Path Overhead (POH) Location: rows #1 ~ #9, columns #10 ~ #270 POH SOH Payload PTR package POH loading and aligning low rate signal 9 rows package POH Data package 9 1 270 Columns

Section Overhead Fulfills the section layer OAM functions 1 2 3 5 6 7 8 9 RSOH Information Payload PTR MSOH Types of Section Overhead Regenerator Section Overhead (RSOH), monitors the whole STM-N Multiplex Section Overhead (MSOH), monitors STM-1 in STM-N √ Location: RSOH: rows #1 ~ #3, columns #1 ~ #9 MSOH: rows #5 ~ #9, columns #1 ~ #9 9 rows 9 270 Columns

Pointer Information Payload Indicates the first byte of the payload container Pointers permit phase and frequency differences of the VCs Location: row #4, columns #1 ~ #9 RSOH Information Payload AU-PTR MSOH 4 9 rows 9 270 Columns Two stage alignment operation: TU-PTR 1st alignment AU-PTR 2nd alignment 2 M 34 M

SDH Multiplexing Structure Mapping A process used when tributaries are adapted into VCs by adding justification bits and POH information Aligning This process takes place when a pointer is included in a Tributary Unit (TU) or an Administrative Unit (AU), to allow the 1st byte of the VC to be located Multiplexing This process is used when multiple low-order path signals are adapted into a higher-order path signal, or when high-order path signals are adapted into a Multiplex Section Stuffing As the tributary signals are multiplexed and aligned, some spare capacity has been designed into the SDH frame to provide enough space for all various tributary rates. Therefore, at certain points in the multiplexing hierarchy, this space capacity is filled with “fixed stuffing” bits that carry no information, but are required to fill up the particular frame SDH Multiplexing Structure Legend TUG = Tributary Unit Group AUG = Administrative Unit Group STM = Synchronous Transfer Module

SDH Multiplexing Structure ×1 Mapping AUG-64 STM-64 Aligning ×4 Multiplexing ×1 AUG-16 STM-16 Pointer processing ×4 ×1 AUG-4 STM-4 Add AU pointer ×4 ×1 ×1 Add POH Packing AU-4 VC-4 C-4 STM-1 AUG-1 139264 kbit/s Add SOH Filling Gabs ×3 Add AU pointer Add POH Multiplexing Packing TU-3 VC-3 C-3 TUG-3 ×1 34368 kbit/s Filling Gabs ×7 TUG-2 Add AU pointer Add POH Multiplexing TU-12 Packing VC-12 C-12 2048 kbit/s ×3 Multiplexing

Part 2 Frame Structure & Multiplexing Methods Course Contents Part 1 SDH Overview Part 2 Frame Structure & Multiplexing Methods Part 3 Overhead & Pointers

Part 3 Section Overheads 1 A1 A2 J0 2 B1 ∆ E1 F1 3 D1 D2 D3 AU-PTR M S O H 5 B2 K1 K2 6 D4 D5 D6 7 D7 D8 D9 8 D10 D11 D12 9 S1 M1 E2 ∆ = Media dependent bytes

A1 and A2 Bytes Framing Bytes Indicate the beginning of the STM-N frame The A1, A2 bytes are unscrambled A1 = f6H (11110110), A2 = 28H (00101000) In STM-N: (3XN) A1 bytes, (3XN) A2 bytes Framing Next process Find A1,A2 OOF LOF N Y AIS over 3ms stream STM-N Finding frame head

D1 ~ D12 Bytes Data Communications Channels (DCC) Bytes – Message-based Channel for OAM between NEs and NMS RS-DCC – D1 ~ D3 – 192 Kbit/s (3X64 Kbit/s) MS-DCC – D4 ~ D12 – 576 Kbit/s (9X64kbit/s) NE NE NE NE – TMN DCC channel OAM Information: Control, Maintenance, Remote Provisioning, Monitoring (Alarm & Performance), Administration

E1 and E2 Bytes Orderwire Bytes Provides one 64 Kbit/s each for voice communication E1 –RS Order wire Byte – RSOH order wire message E2 –MS Order wire Byte – MSOH order wire message NE NE NE NE E1 and E2 Digital telephone channel E1-RS, E2-MS

B1 & B2 Bytes B1:- Bit interleaved Parity Code (BIP-8) Byte A parity code (even parity), used to check the transmission errors over the RS B1 BBE is represented by RS-BBE B2:- Bit interleaved Parity Code (MS BIP-24) Byte – This bit interleave parity NX24 code is used to determine transmission errors occurred over the MS B2 BBE is represented by MS-BBE BIP-8 Tx 2#STM-N Rx 1#STM-N Calculate B1, B2 Verify B1 B2 STM-N

K1 and K2 Bytes K1 & K2(b1 ~ b5) bytes K2 (b6 ~ b8) Transmitting APS signaling (Automatic Protection Switching ) Implement equipment self-healing function Used for network multiplex protection switch function K2 (b6 ~ b8) Multiplex Section Remote Defect Indication (MS-RDI): K2 (b6-b8) Rx detects K2 (b6-b8)="111" generate MS-AIS alarm after 5 consecutive frames Rx detects K2 (b6-b8)="110" generate MS-RDI alarm Generate MS-AIS Start Detect K2(b6-b8) Return MS-RDI 111 MS-RDI 110

S1& M1 Bytes S1 byte:- M1 byte:- Synchronization Status Message Byte (SSMB): S1 (b5~ b8) Value indicates the sync. level Used to implement the clock source protection function bits 5 ~ 8 Meaning 0000 Quality unknown 0010 G.811 PRC 0100 SSU-A (G.812 transit) 1000 SSU-B (G.812 local) 1011 G.813 (Sync. Equipment ) 1111 Do not use for sync. M1 byte:- Multiplex Section Remote Error Indication（MS-REI）Byte A return message from Rx to TX ,when RX find MS-BBE A count of the number of BIP-24xN (B2) errors TX generate corresponding performance event MS-REI Tx Rx Traffic Return M1

Higher Order Path Overhead Path Overheads 1 2 3 4 5 6 7 8 9 10 J1 VC-n Path Trace Byte B3 Path BIP-8 C2 Path Signal Label G1 Path Status F2 Path User Channel H4 TU Multi frame Indi F3 K3 AP Switching N1 Network Operator Higher Order Path Overhead

Path Overheads Path BIP-8 Byte: B3 Path trace byte: J1 Path bit interleaved parity code byte (even parity code) Used to detect transmission errors(Performance Monitoring) Calculated over all bits of the previous VC before scrambling and placed in the B3 of the current frame Next process Verify B3 correct HP-BBE Y N Next process Detect J1 Match HP-TIM Insert AIS downward Y N Path trace byte: J1 The first byte of VC-4 User-programmable Required match

Path Overheads Signal label byte: C2 Path Status Byte: G1 Specifies the mapping type in the VC-N 00 H  Unequipped 02 H  TUG structure 13 H  ATM mapping Requires matching Detect C2 00H HP-UNEQ Match HP-SLM Next process Insert AIS downward N Y Detect receiving VC4 HP-UNEQ HP-TIM HP-SLM Return HP-RDI HP-BBE Return HP-REI Next process N Y Path Status Byte: G1 Return performance message from Rx to TX HP-REI  b1 ~ b4 HP-RDI  b5

Path Overheads Error checking, Signal Label and Path Status of VC-12 V5 First byte of the multi frame Indicated by TU-PTR b1 ~ b2  Error Performance Monitoring (BIP-2) b3  Return Error detected in VC-12 (LP-REI) b4  Return Failure declared in VC-12 (LP-RFI) b5 ~ b7  Signal Label for VC-12 b8  Indicate Defect in VC-12 path (LP-RDI) Low Order Path Overhead V5 J2 N2 K4 Verify b1 b2 match LP-BBE Y N Detect V5 Return LP-REI b3 Detect b5-b7 000 LP-UNEQ Match LP-SLM Return LP-RDI b8 Next process

Pointers AU-Pointer H1 & H2 Bytes  Pointer bytes: Payload pointers permit differences in phase and frequency of the VC-N Indicates the offset between VC payload & STM-N frame by pointing to 1st byte in VC Divide the VC-4 payload bytes into 3 *783 units each unit is given an address  0 ~ 782 H1 & H2 Bytes  Pointer bytes: VC pointer bytes specify the VC frame location Used to align the VC and STM-1 SOHs in an STM-N Perform frequency justification H3 Byte  Pointer action byte Depending on the pointer value, the bytes are used as buffers for positive or negative pointer justifications If receiver side cannot interpret the PTR value, AU-LOP then AIS alarms are inserted downwards “Receiving H1H2H3H3H3 all 1s, insert AU-AIS downwards” 此页标题禁止有多级标题，更不要出现所在章节的名称。 此页标题要简练，能直接表达出本页的内容。 内容页可以除标题外的任何版式，如图、表等。 该页在授课和胶片＋注释中都要使用。 H1 H2 H3 3 x AU-3 1 = All 1s Y = 1001ss11 (S bits unspecified) H1 Y H2 1 H3 1 x AU-4

Pointers TU-Pointer TU payload PTR allows dynamic alignment of the L-O VC-12 within the Multi frame Payload PTR value is located in bits 7~ 16 of V1 & V2 Bytes VC-12 Multi frame is divided into 140 units, each unit is 1 Byte. Each Byte has an address, Range 0~ 139, Unit 1 (Add = 0) is located after V2 Byte in the Multi frame Indication of Multi frame in H4 Byte If receiver side cannot interpret the PTR value, TU-LOP then AIS alarms are inserted downwards ”Receiving V1, V2, V3, V4 all 1s, insert TU-AIS downwards” 此页标题禁止有多级标题，更不要出现所在章节的名称。 此页标题要简练，能直接表达出本页的内容。 内容页可以除标题外的任何版式，如图、表等。 该页在授课和胶片＋注释中都要使用。 TU Pointer V1 V2 V3 V4

SDH Networking Application

Chapter 1 Common SDH Network Topologies Course Contents Chapter 1 Common SDH Network Topologies Chapter 2 Common Network Elements Chapter 3 Introduction to SDH Network Protection Chapter 4 Synchronization of SDH networks Chapter 5 ECC Networking Application

1- Chain Network 2- Star Network 3- Tree Network 4- Ring Network Chapter 1 Common SDH Network Topologies 1- Chain Network 2- Star Network 3- Tree Network 4- Ring Network 5- Mesh Network

1-1 Chain Network Features of chain network: All the nodes are connected one after the other Both ends open Advantages of chain network: Cheap to build Easy to operate , administrate and maintain Disadvantages of chain network: Services are difficult to protect Applications of chain network Railway Lines Power Supply Lines

1-2 Star Network Features of star network A special node connected directly with other nodes No direct connections between other nodes Advantages of star network: Capable of managing bandwidth Disadvantages of star network: Potential bottle neck Equipment failure at the hub node Applications of star network: Access Networks Rural Telephone Networks

1-3 Tree Network Features of star network Combination of chain network and star network Advantages of star network: Capable of managing bandwidth Disadvantages of star network: Potential bottle neck Equipment failure at the hub node Applications of star network: Broadcast Services

1-4 Ring Network Features of star network All nodes are connected together Connect the two end nodes of a chain network to form a ring network Advantages of star network: Highly-reliable Highly-survivable Disadvantages of star network: Complicated Applications of star network: The most common network- -of modern SDH system

1-5 Mesh Network Features of star network Many nodes are interconnected together via direct routes Advantages of star network: No bottle neck Very reliable Disadvantages of star network: Expensive Complicated Difficult to manage Applications of star network: Regions with large traffic High hierarchy communication networks

Chapter 1 Common SDH Network Topologies Course Contents Chapter 1 Common SDH Network Topologies Chapter 2 Common Network Elements Chapter 3 Introduction to SDH Network Protection Chapter 4 Synchronization of SDH networks Chapter 5 ECC Networking Application

1- Terminal Multiplexer(TM) Chapter 2 Common Network Elements 1- Terminal Multiplexer(TM) 2 - Add/Drop Multiplexer (ADM) 3 - Regenerators (REG)

2-1 TM Functions and Features: PDH low rate signals <->STM-N SDH signals<->STM-N Electrical signals<-> Optical signals Applications: Point-to-point Network Chain Network Ring-chain Combination

2-2 ADM Functions and Features: PDH low rate signals <->STM-N SDH signals<->STM-N Electrical signals<-> Optical signals Cross connections: Tributary unit<->Eastward Line unit; Tributary unit<-> Westward Line unit; Eastward Line unit<->Westward Line unit Applications: Hub Network Chain Network Ring Network

2-3 REG Functions and Features: Signal regeneration Amplification Relaying Applications: Long-distance Transmission

Course Contents Chapter 1 Common SDH Network Topologies Chapter 2 Common Network Elements Chapter 3 Introduction to SDH Network Protection Chapter 4 Synchronization of SDH networks Chapter 5 ECC Networking Application

1-Types of Survivable Network Chapter 3 Introduction to SDH Network Protection 1-Types of Survivable Network 2- Linear MS Protection 3- Protection Rings

3- 1 Types of Survivable Network A network that is capable of restoring traffic in the event of a failure. Automatically restore services Within very short time (50ms) Without manual intervention Types of Survivable Network Linear Multiplex Section Protection: 1+1 Linear MS Protection 1:N Linear MS Protection Protection Rings 2-fiber Unidirectional Path Protection Ring 2-fiber Bidirectional Path Protection Ring 2-fiber Bidirectional Multiplex Section Shared Protection Ring 2-fiber Unidirectional Multiplex Section Dedicated Protection Ring 4-fiber Bidirectional Multiplex Section Shared Protection Ring

3-1 Types of Survivable Network Unidirectional Traffic Traffic flow direction along the ring Clockwise and counter-clockwise Bidirectional Traffic Traffic flow direction along the ring Clockwise or counter-clockwise

3-2 Linear MS Protection Switching modes of 1+1 linear MS protection system: Unidirectional switching or Bidirectional switching Revertive mode or Non-revertive mode As a result: Unidirectional switching in revertive mode Unidirectional switching in non-revertive mode Bidirectional switching in revertive mode Bidirectional switching in non-revertive mode APS protocol necessity Unidirectional switching in non-revertive mode unnecessary Other modes necessary

3-2-1 1+1 Linear MS Protection Structure of 1+1 Linear MS Protection System Protection mechanism of 1+1linear MS protection system: Concurrent sending is permanent bridging Selective receiving is switching

3-2-2 1:1 Linear MS Protection Structure of 1:1 Linear MS Protection System Protection mechanism of 1+1linear MS protection system: Normal traffic flow

3-2-3 Linear MS Protection criteria Linear MS protection is based on the MS (STM-1 within STM-N) Protection switching criteria are SF and SD SF (Signal Fail) includes RLOS, RLOF, MS-AIS, etc. SD (Signal Degrade) includes B2-EXC, B2-SD Those requiring the APS protocol 1:N linear MS protection uni- or bi-directional 1+1 linear MS protection in revertive modes bidirectional 1+1 linear MS protection in non-revertive mode This not requiring the APS protocol unidirectional 1+1 linear MS protection

Classifications of Protection Rings 3- 3 Types of ring protection Classifications of Protection Rings Protected Traffic Path protection ring Multiplex section protection ring Traffic Direction Unidirectional protection ring Bidirectional protection ring Number of Optical Fibers Two-fiber protection ring Four-fiber protection ring

3- 3-1 Two-fiber bidirectional path protection ring network is normal: Protection switching mechanism:

3- 3-2 Two-fiber bidirectional Multiplex Section protection ring Structure: No active ring or standby ring First half time slots are to carry normal traffic The other half time slots are to protect the normal traffic on another fiber

3- 3-3 Sub Network connection protection (SNCP) Structure: Concurrent sending (transmit end) Selective receiving (receive end)

3- 3-3 Comparison between protection rings Protected Traffic PP: protects locally dropped paths (VC12) tributaries. MSP: protects line traffic at the level of MS SNCP: protects the Sub Network Connection, which is applicable to all the protections. APS necessity PP: unnecessary MSP: necessary SNCP: dependent Revertive - necessary Non-revertive - unnecessary

3- 3-3 Comparison between protection rings Switching Completion Time About 15ms for PP ring About 25ms for MSP ring Less than 50ms for SNCP The more traffic, the longer the switching completion time Network capacity STM-N for PP 1/2  NSTM-N for 2-fiber bidirectional MS shared protection ring NSTM-N for 4-fiber bidirectional MS shared protection ring SNCP has no limitation

Thanks