sdh principles sdh principles. course contents chapter 1 emergence of sdh what is sdh? ----...

SDH PrinciplesSDH Principles

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.

Why did SDH emerge?

---- Need for a system to process increasing amounts of information.---- New standard that allows mixing equipment from different suppliers.

1-1 Disadvantages of PDH

interfacesElectrical 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.

Plesiochronous Digital Hierarchy

140 Mb/s

34 Mb/s 34 Mb/s

8 Mb/s 8 Mb/s

2 Mb/s

140 Mb/s

de-multiplexer multiplexer

1-1 Advantages of SDH

interfacesElectrical 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.

synchronous Digital Hierarchy

Multiplexing

De-m

ultiplexing

622 Mbit/s 622 Mbit/s

2 Mbit/s

×4

WDM

STM-1 155 Mb/s

STM-4 622 Mb/s

STM-16 2.5 Gb/s

×4

×4STM-64 10

Gb/s

10 Gb/s

1-1-2 Advantages of SDH

OAM function 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

SDHnetwork

unpacking

PDH, SDH, ATM, FDDI Signals

receive Processing

STM-N STM-N package

PDH, SDH, ATM, FDDI Signals

Disadvantages of SDH Mechanism of pointer adjustment is complex.Large-scale application of software makes SDH system capable to receive viruses

Course Contents

Part 1 SDH Overview


Part 3 Overhead & Pointers

2- SDH FRAME STRUCTURE

Three parts:

Information Payload Section Overhead Pointer

Frame = 125 us

9

SOH

Information

Payload

PTR

SOH1 2 3 4 5 6 7 8 9

270 Columns

9 rows

From ITU-T G.707: 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

1 byte = One 64 Kbit/s channelSTM-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

9

SOH

PayloadPTR

SOH

270 Columns

PO

H

1

package

package

low rate signal

POH

POH

9 rowsloading andaligning

Data package

SECTION OVERHEAD

Fulfills the section layer OAM functions

9

RSOH

Information

Payload

PTR

MSOH

270 Columns

9 rows

Types of Section Overhead

1. Regenerator Section Overhead (RSOH), monitors the whole STM-N

2. Multiplex Section Overhead (MSOH), monitors STM-1 in STM-N

√ Location:3. RSOH: rows #1 ~ #3, columns #1 ~ #94. MSOH: rows #5 ~ #9, columns #1 ~ #9

1 2 3 5 6 7 8 9

POINTER

9

RSOH

Information

Payload

AU-PTR

MSOH

270 Columns

9 rows4

Indicates the first byte of the payload container

Pointers permit phase and frequency differences of the VCs

Location: row #4, columns #1 ~ #9

2 M

34 M

TU-PTR1st alignment

AU-PTR2nd alignment

Two stage alignment operation:

SDH MULTIPLEXING STRUCTURE

Mapping A process used when tributaries are adapted into VCs by adding justification bits and

POH informationAligning 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 locatedMultiplexing 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 SectionStuffing 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

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

Add POH

Add SOH

Add AU pointer

Filling Gabs

Add POHAdd AU pointer

Add POHAdd AU pointer

Packing

Packing

Packing

Multiplexing

Multiplexing

Multiplexing

Filling Gabs

Course Contents

Part 1 SDH Overview


Part 3 Overhead & Pointers

PART 3 SECTION OVERHEADS

R

S

O

H

1 A1 A1 A1 A2 A2 A2 J0

2 B1 ∆ ∆ E1 ∆ F1

3 D1 ∆ ∆ D2 ∆ D3

AU-PTR

M

S

O

H

5 B2 B2 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

stream

STM-N STM-N STM-N STM-N STM-N STM-N

Finding frame head

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

Nextprocess

FindA1,A2

OOF

LOF

N

Y

AIS

over 3ms

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 NMS RS-DCC – D1 ~ D3 – 192 Kbit/s (3X64 Kbit/s) MS-DCC – D4 ~ D12 – 576 Kbit/s (9X64kbit/s)

E1 AND E2 BYTES

Digital telephone channelE1-RS, E2-MS

E1 and E2

NE NE NENE

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

B1 & B2 BYTES

BIP-8

Tx

2#STM-N

Rx

1#STM-N CalculateB1, B2

1#STM-N

2#STM-N

Verify B1 B2

STM-N

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

K1 AND K2 BYTES

K1 & K2(b1 ~ b5) bytes 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

GenerateMS-AIS

Start

DetectK2(b6-b8)

Return MS-RDI

111

GenerateMS-RDI

110

S1& M1 BYTESS1 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-BBEA count of the number of BIP-24xN (B2) errors TX generate corresponding performance event MS-REI

Tx RxTraffic

Return M1

PATH OVERHEADS

1 2 3 4 5 6 7 8 9 10

1 J1 VC-n Path Trace Byte

2 B3 Path BIP-8

3 C2 Path Signal Label

4 G1 Path Status

5 F2 Path User Channel

6 H4 TU Multi frame Indi

7 F3 Path User Channel

8 K3 AP Switching

9 N1 Network Operator

Higher Order Path Overhead

Path trace byte: J1

Next process

Detect J1

Match

HP-TIM

Insert AIS downward

YN

Path OverheadsPath BIP-8 Byte: B3 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

YN

The first byte of VC-4 User-programmable Required match

Detect C2

00H

HP-UNEQMatch

HP-SLMNext process

Insert AIS downward

N Y

NY

Path Overheads Signal label byte: C2 Specifies the mapping type in the VC-N 00 H Unequipped 02 H TUG structure 13 H ATM mapping Requires matching

Path Status Byte: G1 Return performance message from Rx to TX HP-REI b1 ~ b4 HP-RDI b5

Detect receiving VC4

HP-UNEQ

HP-TIMHP-SLM Return HP-

RDIHP-BBE

ReturnHP-REI

Next process

N Y

N Y

Low Order Path Overhead

Path Overheads

V5

J2

N2

K4

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)

Verify b1 b2

match

LP-BBE

YN

Detect V5

Return LP-REI b3

Detect b5-b7

000

LP-UNEQMatch

LP-SLM

N Y

NY

Return LP-RDI b8

Next process

Next process

POINTERS AU-Pointer

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”

H1 Y Y H2 1 1 H3 H3 H3

3 x AU-3

1 x AU-4

1 = All 1sY = 1001ss11(S bits unspecified)

H1 H1 H1 H2 H2 H2 H3 H3 H3

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”

TU Pointer

V1

V2

V3

V4

Pointers

SDH Networking ApplicationSDH Networking Application

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

5- Mesh Network


1-1 Chain Network Features of chain network:

All the nodes are connected one after the otherBoth ends open

Advantages of chain network:Cheap to buildEasy to operate , administrate and maintain

Disadvantages of chain network:Services are difficult to protect

Applications of chain networkRailway LinesPower Supply Lines

A C DB E

Features of star networkA special node connected directly with other nodesNo direct connections between other nodes

Advantages of star network:Capable of managing bandwidth

Disadvantages of star network:Potential bottle neckEquipment failure at the hub node

Applications of star network:Access NetworksRural Telephone Networks

A C

D

B

E

1-2 Star Network

Features of star networkCombination of chain network and star network

Advantages of star network:Capable of managing bandwidth

Disadvantages of star network:Potential bottle neckEquipment failure at the hub node

Applications of star network:Broadcast Services

1-3 Tree Network

A

C

D

B

E

Features of star networkAll nodes are connected togetherConnect the two end nodes of a chain network to form a ring network

Advantages of star network:Highly-reliableHighly-survivable

Disadvantages of star network:Complicated

Applications of star network:The most common network-

-of modern SDH system

1-4 Ring Network

A

C D

B E

Features of star networkMany nodes are interconnected together via direct routes

Advantages of star network:No bottle neckVery reliable

Disadvantages of star network:ExpensiveComplicatedDifficult to manage

Applications of star network:Regions with large trafficHigh hierarchy communication networks

1-5 Mesh Network

A

C

DBE

Course Contents






1- Terminal Multiplexer(TM)

2 - Add/Drop Multiplexer (ADM)

3 - Regenerators (REG)


TM TM

ADM TMTM

ADM

ADM

ADM ADM TM

2-1 TM

Functions and Features:PDH low rate signals <->STM-NSDH signals<->STM-NElectrical signals<-> Optical signals

Applications:Point-to-point NetworkChain NetworkRing-chain Combination

2-2 ADM

Functions and Features:PDH low rate signals <->STM-NSDH signals<->STM-NElectrical signals<-> Optical signalsCross connections:

• Tributary unit<->Eastward Line unit;• Tributary unit<-> Westward Line unit;• Eastward Line unit<->Westward Line unit

Applications:Hub NetworkChain NetworkRing Network

TM ADM ADM TM

ADM

ADM

ADM ADM

TM TM

TM TM

ADM

2-3 REG

Functions and Features:Signal regenerationAmplificationRelaying

Applications:Long-distance Transmission

orderwire

REGENERATORSSTM-N STM-N

power alarm TMN interface

Course Contents







1-Types of Survivable Network

2- Linear MS Protection

3- Protection Rings

3- 1 Types of Survivable Network

Survivable NetworkA network that is capable of restoring traffic in the event of a failure. Automatically restore servicesWithin very short time (50ms)Without manual intervention

Types of Survivable NetworkLinear 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 TrafficTraffic flow direction along the

ringClockwise and counter-

clockwise

T1516670-94

The traffic shares the sameequipment and link

B

A

a) Uniformly routed

B

b) Diversely routed

The traffic is ondifferent equipment

and links

A

T1516670-94

The traffic shares the sameequipment and link

B

A

a) Uniformly routed

B

b) Diversely routed

The traffic is ondifferent equipment

and links

A

Bidirectional Traffic Traffic flow direction along

the ringClockwise or counter-

clockwise

3-2 Linear MS ProtectionSwitching modes of 1+1 linear MS protection system:

Unidirectional switching or Bidirectional switchingRevertive mode or Non-revertive mode

As a result:Unidirectional switching in revertive modeUnidirectional switching in non-revertive modeBidirectional switching in revertive modeBidirectional switching in non-revertive mode

APS protocol necessityUnidirectional switching in non-revertive mode unnecessaryOther modes necessary

3-2-1 1+1 Linear MS ProtectionStructure of 1+1 Linear MS Protection System

DoubleTM

DoubleTM

Working

Protection

Protection mechanism of 1+1linear MS protection system:Concurrent sending is permanent bridgingSelective receiving is switching

selective receiving

concurrentsending

TU traffic TU traffic

concurrentsending

selective receivingswitch

switch

3-2-2 1:1 Linear MS ProtectionStructure of 1:1 Linear MS Protection System

Protection mechanism of 1+1linear MS protection system:Normal traffic flow

Working

Protection

switch

switch

TU traffic TU traffic

Working

Protection

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 SDSF (Signal Fail) includes RLOS, RLOF, MS-AIS, etc.SD (Signal Degrade) includes B2-EXC, B2-SD

Those requiring the APS protocol1:N linear MS protectionuni- or bi-directional 1+1 linear MS protection in revertive modesbidirectional 1+1 linear MS protection in non-revertive mode

This not requiring the APS protocolunidirectional 1+1 linear MS protection

3- 3 Types of ring protection

Classifications of Protection Rings

Protected TrafficPath protection ringMultiplex section protection ringTraffic DirectionUnidirectional protection ringBidirectional protection ringNumber of Optical FibersTwo-fiber protection ringFour-fiber protection ring

A

B D

C

3- 3-1 Two-fiber bidirectional path protection ring

network is normal:

Protection switching mechanism:

A

B

C

D

S1

P1

A

B

C

D

switch

S1

P1

3- 3-2 Two-fiber bidirectional Multiplex Section protection ring

Structure:No active ring or standby ringFirst half time slots are to carry normal trafficThe other half time slots are to protect the normal traffic on another

fiber

C A

C A

A C

A C

S 1 / P 2

S 2 / P 1

A

C

D B

S 2 / P 1

S 1 / P 2

3- 3-3 Sub Network connection protection (SNCP)

Structure:

Concurrent sending (transmit end)Selective receiving (receive end)

Switch Bridge

Traffic out Traffic in

a) Normal condition – Transmitted traffic bridgeda) to working and protection paths –a) Received traffic switch selects working channel

Working Protection

Failure

b) Failure in working channel of incoming traffic –a) Receiver switch selects protection path

Working Protection

Switch Bridge

Traffic out Traffic in

Working Protection

Working Protection

3- 3-3 Comparison between protection rings

Protected TrafficPP: protects locally dropped paths (VC12) tributaries.MSP: protects line traffic at the level of MSSNCP: protects the Sub Network Connection, which is applicable to all

the protections.

APS necessityPP: unnecessaryMSP: necessarySNCP: dependent

• Revertive - necessary• Non-revertive - unnecessary

3- 3-3 Comparison between protection rings

Switching Completion Time

About 15ms for PP ringAbout 25ms for MSP ringLess than 50ms for SNCP

• The more traffic, the longer the switching completion time

Network capacity STM-N for PP1/2 NSTM-N for 2-fiber bidirectional MS shared protection ringNSTM-N for 4-fiber bidirectional MS shared protection ringSNCP has no limitation

Thanks

sdh principles sdh principles. course contents chapter 1 emergence of sdh what is sdh? ----...

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