SDH BasicsSDH Basics

Objectives

> Introduction to SDH> Multiplexing

> STM-1 frame

> Virtual Containers (VCs)

> TU coordinates

> STM-N frame

> SDH layers and trails

> SDH network elements

> SDH overhead

> Mapping

IntroductionIntroduction

What is SDH?

> SDH = Synchronous Digital Hierarchy

> It is a transport network> synchronous

> fully standardized

> with high bandwidth

> for synchronous and asynchronous signals

> for future broadband signals and new services

> with standardized network management capabilities

> with traffic protection

> with a flexible multiplexing structure> direct access to tributaries

> cross-connections without demultiplexing

Network ElementsNetwork Elements

Digital Transmission System

> Regenerator> Recreates the signal.

> Multiplexer (MUX)> Multiplexer combines data from

several lines and transmits itover a higher-capacity data link.

No signal

100 km

R

100 km

Regenerator

MUX MUX

> Add-Drop Multiplexer (ADM)> Part of the traffic is terminated.

> Part of the traffic goes transparently through.

Multiplexer Naming Conventions

> Terminal Multiplexer (TM)> All traffic is terminated here.> m: aggregate level> n: lowest tributary level

TMm/n

aggregate

trib uta ri e s

ADM

m/n

aggregateaggregate

tributaries

> No traffic is terminated.

> Cross-connection matrix connects tributary signals of one aggregate to another aggregate.

Digital Cross-connect (DXC m/n)

MUX

MUX

MU

X

MUX

MUX

MUX

MUX

MU

X

MU

X

MU

X

MUX

MUXM

UX

MU

X

MU

X

MU

X

PDH vs. SDHPDH vs. SDH

PDH vs. SDH — Bit Rates

• E1 (2.048 Mbit/s)

• T1 (1.544 Mbit/s)

• DS-2 (6.312 Mbit/s)

• E3 (34.368 Mbit/s)

• DS-3 (44.736 Mbit/s)

• E4 (139.264 Mbit/s)

• ATM

• etc.

PDH

SDHTM STM-1

TM STM-4

TM STM-16

E1E0

E2

E3E4

plesiochronous

plesiochronous

plesiochronous

synchronous

PDH vs. SDH — Add & Drop Function

Six TMs needed

to drop E1

One ADM is enough to

drop E1

PDH SDH

E3

E3

E3

E2

E2

E1

E1

E1

E4 E4

E1 (2.048 kbit/s)

E2

TM4/3

TM3/2

TM2/1

TM2/1

TM3/2

TM4/3

ADM STM-4STM-4

STM-1 FrameSTM-1 Frame

STM-1 Frame

2430 bytes/frame × 8 bit/byte × 8000 frame/s = 155.52 Mbit/s

transmitted from left to right and top to bottom

9 ro

ws

(byt

es)

9

5

261

270 columns (bytes)

3 RSOH

AU-4 pointers

MSOH

Payload VC-4 (HO-VC)

C4 4. level 140 Mbit/s

C3 3. level 34/45 Mbit/s

C2 2. level 6 Mbit/s

C1.2 1. level 2 Mbit/s

C1.1 1. level 1.55 Mbit/s

Virtual Containers (VCs)

VC-3

VC-4

VC-12VC-11

VC-2

E1 (2.048 Mbit/s)T1 (1.544 Mbit/s)

DS-2 (6.312 Mbit/s)

E3 (34.368 Mbit/s)

DS-3 (44.736 Mbit/s)

ATM cells

Mapping

E4 (139.264 Mbit/s)

VC-4STM-N× N

× 3× 1

× 3

× 7

139 264 kbit/s

44 736 kbit/s34 368 kbit/s

6312 kbit/s

2048 kbit/sPointer processing

Multiplexing

Aligning

Mapping

1544 kbit/s

CTPPassing connectionContains: payload pointer...

TTPEnd of trailContains: path trace, signal label, error detection…

AUG AU-4

TUG-3

TUG-2

TU-3

TU-2

TU-12

VC-2

VC-3

VC-12

VC-11

C-4

C-3

C-2

C-12

C-11

× 1

C-n Container-n

SDH Multiplexing Structure (ETSI)× 1

ITU-T

VC-4STM-N× N

× 3× 1

× 3

× 7

139 264 kbit/sGb Ethernet

44 736 kbit/s34 368 kbit/s

2048 kbit/sFast Ethernet

Pointer processing

Multiplexing

Aligning

Mapping

AUG AU-4

TUG-3

TUG-2

TU-3

TU-12

VC-3

VC-12

C-4

C-3

C-12

C-n Container-n

Tellabs 6300 SDH Multiplexing Structure

× 1

VC-4STM-N× N

× 3

× 3

× 7

n x 8, n x 64 kbit/s

2048 kbit/sn x 8, n x 64 kbit/s

Pointer processing

Multiplexing

Aligning

Mapping

AUG AU-4

TUG-3

TUG-2TU-2

TU-12

VC-2

VC-12

C-2

C-12

× 1

C-n Container-n

Tellabs 8100 SDH Multiplexing Structure

× 1

RSOH

AU-4 pointers

MSOH

PayloadVC-4 (HO-VC)

KLM Coordinates

VC-4 POH

VC-2

VC-12

K

L

TU12-1 TU12-2 TU12-3

TUG3-1 TUG3-2 TUG3-3

TUG2-6

TUG2-7

TUG2-5

TUG2-4

TUG2-3

TUG2-1

TUG2-2

TUG-3 number (values 1-3)TUG-2 number (values 0-7)TU-12 number (values 0-3)

KLM: 170KLM: 152 KLM: 300

VC-3

STM-N FrameSTM-N Frame

STM-N Frame

T1518000-95

4

3

1

9

5

270 N columns (bytes)

9 N 261 N

STM-N payload9 rows

Section overheadSOH

Section overheadSOH

Administrative unit pointer(s)

> One SOH> AU pointers for every VC-4> N VC-4s

Synchronous Transport Module

Line RateMbit/s

STM-1 155.520

STM-4 622.080

STM-16 2488.320

STM-64 9953.280

Multiplexing of AU into STM-N

> AU-4 is placed directly in the AUG.

> N AUGs are one-byte interleaved into STM-N with fixed phase.

Figure 7-1/G.707

1 9

1 261

1 9

1 261

N × 9 N × 261

123...N123...N

T1518050-95123 ... N

123...N123...N

AUG AUG

RSOH

MSOH

STM-N

#1 #N

SDH TrailsSDH Trails

SDH Layers

PSTN ISDN ATM IP

Lower-Order

Higher-Order

Multiplex

Regenerator

Physical

Client

Server

OS, ES

RS

MS

HOP (VC-4)

LOP (VC-12, VC-2, VC-3)

R R

LO Path

MS trail MStrail

RStrail

RStrail

RStrail

RStrail

MS trail

TM LO TM LOADM HO DXC LO

HO Path HO Path

SDH Trails 1(2)

> Trail: Route between two Trail Termination Points (TTP)

> TTP: Point where signal is terminated

> RS trail: Regenerator Section trail (or just RS) is between regenerators

> MS trail: Multiplex Section trail (or just MS) is between multiplexers

> Path (P): Trail in path layer (HOP or LOP)

RStrail

SDH Trails 2(2)

H O

LO

M S

R S R S R SR S R S R S R S

M S M S M S M S

H O H O

R S R S R S

M S

H O

LO

RS tra il RS tra il RS tra il RS tra il RS tra il

M S tra il M S tra ilM S tra il

HO path HO path

LO path

LO matrix LO matrix

HO matrix

> Regenerates the optical signal.

> Terminates RSOH.

REG

STM-N STM-N

Regenerator

Terminal Multiplexer

TMSTM-N

orPDH

STM-M

> Terminates RSOH and MSOH.

> May terminate HOP and LOP overhead.

> Multiplexes/maps tributary signals

> Includes timing and management functions.

STM-N or PDH

STM-MSTM-M

ADM

Add/drop Multiplexer

> Terminates RSOH and MSOH.> May terminate HOP and LOP overhead.> Includes connection function between the two aggregates.> Multiplexes/maps tributary signals.> Includes a connection function for allocation of TUs within the

STM frame. > Includes timing and management functions.

Cross-connect

> Terminates RSOH and MSOH.

> Includes connection function between the aggregates.

> Can have tributary ports, for which it may terminate HOP and LOP overhead.

> Includes timing and management functions.

STM-N or PDH

STM-MSTM-M DXC

STM-16

STM-4

STM-1

STM-16

STM-4

STM-1

SDXC 4/1

Example of Cross-connect (XC)

16 x

4 x

1 x

16 x

4 x

1 x

SDH multiplexer

AUG

VC-4

34 (45) Mbit/s2(1.5) Mbit/s

VC-12 VC-3

HOXC

LOXC

SDH OverheadSDH Overhead

SDH Overhead

> Overheads carry information for monitoring, maintaining and controlling the operation of network.

> Overhead types> POH for end-to-end monitoring of payload signal

(VC-12, VC-3 and VC-4)> Block errors, far end alarms, trace and payload type

> SOH is used for monitoring of signal between SDH equipment. > RSOH: block errors, trace and TMN communication

> MSOH: block errors, synchronization, TMN communication and far-end alarms

POH

RSOH

MSOH

POINTER

9 260

270

3

5

9

RSOH

> A1, A2 framing patterns (F6H), (28H)> J0 regenerator section Trail Trace Identifier (TTI)> B1 BIP-8 parity byte> E1 RS orderwire channel (service telephone)> F1 user (network operator) data channel> D1, D2, D3 regenerator section Data Communication

Channel (DCCR)> NU1, NU2, NU3, NU4 bytes reserved for national use> R1, R2, R3, R4, R5, R6 media specific bytes (e.g. radio link)> U1, U2, U3, U4 bytes with no defined use

MSOH

> B2 BIP-24 parity bytes> K1, K2 Automatic Protection Switching (APS) channel, bit oriented

protocol (bits 1-5), Remote Defect Indication (RDI) (bits 6-8)

> D4 to D12 multiplex section Data Communication Channel (DCCM)> S1 synchronization status (bits 5-8)> M1 Remote Error Indication (REI)> E2 MS orderwire channel (service telephone)> NU5, NU6 bytes reserved for national use> U5 to U26 bytes with no defined use> Z12, Z13, Z21, Z22 bytes with no defined use

VC-4 and VC-3 POH

POHJ1B3C2G1F2H4F3K3N1

J1 Trail Trace IdentifierB3 Parity BIP-8C2 Signal label (C2), used for payload type identificationG1 Path status

REI Remote Error Indication

RDI Remote Defect Indication

F2 Network operator (user) channelH4 Multiframe indicator, a sequence indicating

TU-multiframe phase (position of VC-12/VC-2)F3 Network operator (user) channelK3 Automatic Protection Switching (bits 1-4)N1 Tandem Connection Monitoring TCM, optional use in

multioperator environments

REI RDI Reserved Spare

1 2 3 4 5 6 7 8

VC-2 and VC-12 POH

J2 Trail Trace IdentifierN2 Tandem Connection Monitoring TCM, optional use in

multioperator environmentsK4 Automatic Protection Switching (bits 1-4), additional

information for RDI (bits 5-7) (optional)V5 Signal monitoring

Parity BIP-2 Remote Error Indication (REI) Remote Failure Indication (RFI), only for

VC-11 (not in ETSI) Signal label (SL) Remote defect indication (RDI)

POHV5 J2 N2 K4

V51 2 3 4 5 6 7 8BIP-2 BIP-2 REI RFI SL SL SL RDI

PDH over SDHPDH over SDH

PDH over SDH

2 Mbit/s plesiochronous stream

Justification bytes

C12POH

Path OverheadVC12

Container

POH

TU PointerTU12

Virtual Container

> Container (C)> Basic payload unit

> Virtual Container (VC)> C + POH (path

overhead)

> Tributary Unit (TU)> VC + pointer

> The pointer indicates the start of the VC and allows dynamic alignment of the VC within the TU frame.

MappingMapping

Mapping

> Mapping is a process where tributaries (Containers) are adapted to VC at boundary of SDH network.

VC-3

VC-4VC-12

VC-11

VC-2

GMX, GMU(-A/M)

> VC-12 mapping method

> 63x0 2M: asynchronous > GMX & GMU-A: byte synchronous and

asynchronous> GMU & GMU-M: byte synchronous> SBU: asynchronous

SBU 63x0 2M

Virtual Containers (VCs)

63x0 34/45M

63x0 140M

V5

32 bytes

R R R R R R R RJ2

R R R R R R R R

C1 C2 O O O O R R

32 bytes

R R R R R R R RN2

C1 C2 O O O O R R

32 bytes

R R R R R R R RK4

C1 C2 R R R R R S1

S2 D D D D D D D

31 bytes

R R R R R R R R

140octets

1st fram

e2

nd fram

e3

rd frame

4th fram

e

Asynchronous 2048 kbit/s

> Four VC-12 POH bytes (V5, J2, N2 and K4)

> 1023 data bits

> Six justification control bits> C1C1C1=111

S1 is a justification bit (data bit).

> C2C2C2=111 S2 is a justification bit (data bit).

> Majority vote should be used.

> Eight overhead communication channel bits (0)

> 49 fixed stuff bits (R)

Byte Synchronous 2048 kbit/s

> Four VC-12 POH bytes(V5, J2, N2 and K4)

> No justification opportunities

> 2 R-bytes per frame

R

R

R

R

R

V5

R500 µs

R

J2

N2

K4

R

Time Slot 0Time Slots 1 to 15

Time Slot 16

Time Slots 17 to 31

Time Slot 0

Time Slots 1 to 15

Time Slot 16

Time Slots 17 to 31

Time Slot 0

Time Slots 1 to 15

Time Slot 16

Time Slots 17 to 31

Time Slot 0

Time Slots 1 to 15

Time Slot 16

Time Slots 17 to 31

140

bytes

R Fixed stuff byte

11stst fram

e fram

e22

nd

nd fram

e fram

e33

rdrd frame

frame

44thth fram

e fram

e

GMX/GMU(-A/M) R-bytes

> R-bytes: reserved bytes

> VC-12 payload: 2 R-bytes

> VC-2 payload: 10 R-bytes

> R-bytes can be used for:> control channel

> traffic

> R-bytes cannot have CAS capacity.

V5

TS 0 - 31

R R R R R R R RJ2

R R R R R R R R

R R R R R R R RN2

R R R R R R R RK4

R R R R R R R R

140octets

11stst fram

e fram

e22

nd

nd fram

e fram

e33

rdrd frame

frame

44thth fram

e fram

eTS 0 - 31

TS 0 - 31

TS 0 - 31

R R R R R R R R

R R R R R R R R

R R R R R R R R

byte sync 2048 kbit/s

> Use VC-12s when going over Tellabs 63x0 nodes on lower order level, because they do not support VC-2s

Byte synchronous Asynchronous

PDH synchronized with SDHBit rate adaptation

Yes 4.6 ppm

No 50 ppm

Justification needed No Yes

Direct access to 64 kbit/s 2048 kbit/s

R-bytes (long buffer) for data 2 —

Concatenation possible Yes No

CAS (TS-16) Yes No

VC-12

P12s Layer

> P12s generates or/and monitors G.704 frame with or without CAS (G.826 performance statistics).

TS0 TS31

POH R bytes

TS1 TS31

FAS

POH Stuff

User data from XBUS

POH Stuff

2048 kbit/s (G.704)

FAS

FAS

GMX/GMU-A

VC-12 P12s MonitoringP12s TTP

Locks to FAS Locks to FAS

P12s ApplicationsIs the other end of the connection

in GMX/GMU-A /GMU/GMU-

M?

Yes

Do you have full 2048 kbit/s or n x 64 kbit/s connections?

No

n x 64 kbit/s

Yes

Are you transporting

G.704 frame?

2048 kbit/s

No

Byte synchronous

P12s transparent

AsynchronousP12s TTP

AsynchronousP12s

transparent

AsynchronousP12s

monitoring

ReviewReview