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SONET / SDH

Nirmala Shenoy

Information Technology DepartmentRochester Institute Technology

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SONET / SDH

Scope What is SONET/SDH features

Signal hierarchy Topologies SONET components Layers Frames Virtual tributaries

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What is SONET / SDH? S ynchronous O ptical Net work ANSI (US) S ynchronous D igital H ierarchy ITU-T Europe Similar and compatible A standard to be used for fibre optics

Recommendation for FOTS equipment Fibre Optic Transmission Systems

Can carry incompatible DS-0, DS1 (Asyn)

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SONET / SDH

What is SONET / SDH? Single reference clock

synchronize transmissions

Predictability Powerful frame Transmission envelope

Multiplex channels Multiplexed transport mechanism

Optical based Carrier System

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What is SONET / SDH? Self healing ring topology Consolidate and segregate traffic from different

end-points Extensive integrated OAM&P

Backward compatibility

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SONET / SDH

Signal Hierarchy STS Synchronous Transport Signals

support a certain base data rate- 51.84Mbps STS 1 STS 192 different hierarchies

Corresponding carrier System

Optical Carrier OC-1, OC-3, OC-12, OC-48 SDH STM Synchronous Transport Module

STM 1 = STS 3

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SONET / SDH Sonet/SDH ratesSTS 1 OC-1 51.840STS-3 OC-3 155.520 STM-1

STS-9 OC-9 466.560 STM-3STS-12 OC-12 622.080 STM-4STS-18 OC-18 933.120 STM-6STS-24 OC-24 1244.160 STM-8

STS-36 OC-36 1866.230 STM-12STS-48 OC-48 2488.320 STM-16STS-96 OC-96 4976.640 STM-32STS-192 OC-192 9953.280 STM-64

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Configuration

STS MUX STS MUX

regenerator regenerator

Add/drop mux

sectionsection

line

path

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SONET topology

ADM

ADM

DCS

ADM

ADM

ADM

SMD

SMD

SMDSMD

SMD

SA

SA

DS1

802.5

ADM add dropmultiplexerSMD- sts mu/demuxDCS digital crossconnect switchSA service adapter

Oc-n

Oc-n

Oc-n

Oc-n

Oc-n

Oc-n

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Multiplexing

MUX/DMUX

ServiceAdapters

ServiceAdapters

ServiceAdapters

DS1, CEPT1

etc

Maps into virtualtributaries

DS3 STS-1

STS-n

MAN, ATM,SMDS, others

STS-n

E/O

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SONET / SDH

SONET Devices STS Multiplexer

Multiplexes and de-multiplexes signals frommultiple sources

Path terminating equipment

Maps user payload into standard frame Header goes end-to-end as part of Synchronous

Payload Envelope - SPE

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SONET / SDH

SONET Devices Add /Drop Multiplexer

Adds signals from different sources/removes Uses header address information to identify

stream and remove

Line terminating Equipment Performs multiplexing, synchronization, APS

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SONET Devices Regenerator

Repeater improves signal quality Operations include layer 2

Frame alignment, scrambling, error monitoring

Section terminating equipment

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Section Connects two neighboring devices

Line Connects two multiplexers (STS , Add/Drop)

Path Connects two STS Mux/demux

Layers likewise path, line, section

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SONET layers

PATH layer

LINE layer

SECTION layer

photonic layer

Data link

Physical

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Photonic layers phy Specs for optical fiber channel

NRZ encoding used Power level Wavelength

Pulse shape

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Section layer Frames identifies beginning of frame

Scrambling introducing 1s to derive clock error monitoring section level Adds 9 bytes to header frame size 810 bytes

Provided at all devices

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SONET / SDH

Line layer Locates partial payload virtual tributaries

Provides frequency justification, bit stuffing To adjust to clocking from different systems

Does APS

Adds 18 bytes to header Provided at the STS Mux and Add/Drop Mux

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Path layer Converts to optical signals and back to

electromagnetic Adds 9 bytes to header - is part of SPE Defines the payload being carried

End-to-end path control Support virtual tributaries Provided at the STS Mux

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SONET STS-1Frame

Frame1 Frame2 Frame8000

Frame = 810 octets * 8 = 6480bits8000 frames/sec = 6480*8000 bits/sec = 51.84Mbps

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SONET Frame Matrix of nine rows 90 octets each

First 3 columns (octets) three rows section overhead 9 bytes

Next 6 rows line overheads 18 bytes

Rest of the frame Synchronous PayloadEnvelope SPE 9 bytes of path overheads

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first column in SPE path overhead

STS SPE

Path overhead

Sectionoverhead

lineoverhead

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Section overhead Alignment bytes (A1 & A2) framing and

synchronization pattern F628hex Identification byte (C1) unique id for the STS-1 frame

Parity byte (B1)

Order-wire byte (E1) bytes in consecutiveframes form a communication channel

between regenerators

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Section overhead Users byte (F1) bytes in consecutive frames

form a channel for user needs at the sectionlevel

Management bytes (D1, D2 and D3)- 3 bytes per frame in consecutive frames = 192 kbps forOAM

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Line Overhead Pointer bytes (H1, H2, H3) 3 bytes identify

location of the payload Line Parity byte (B2) Automatic Protection Switching bytes 2 bytes

(K1, K2) consecutive frames- 128 kbpschannel to detect problems in multiplexers

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Line Overhead Data communication channel bytes (D4-D12)

consecutive frames 576 kbps OAM at the line Growth bytes (Z1, Z2) future use Orderwire byte (E2) line level

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Path Overhead Path trace byte (J1) bytes in consecutive

frames path tracking verify connection Path parity byte (B3) Path signal label byte (C2) path id gives the

construction details of the SPE Path Status byte (G1) receiver communicates

its status

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Path Overhead Path user channel byte (F2) user needs at path

level Virtual tributary indicator (H4) multi-frame

indicator payload not fitting into a frame

Growth byte (Z3, Z4, Z5) reserved

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Virtual Tributaries Partial payload share a frame

The SPE has a number of tributaries VT1.5 = 8000 frames * 3 columns * 9 rows * 8

bits = 1.728 Mbps DS-1 service

VT2 = 8000 frames*4 columns*9 rows * 8 bits= 2.304 Mbps CEPT-1

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Virtual Tributaries VT3 = 8000 frames * 6 columns * 9 rows * 8

bits = 3.456 Mbps DS-1C VT6 = 8000 frames*12 columns*9 rows * 8

bits = 6.912 Mbps DS-2

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Summary A carrier system optical carriers

Synchronous transmission - faster Time Division multiplexing High speed backbone Support for high bit rate applications? Add/Drop multiplexers Self healing rings