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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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SONET / SDH
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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SONET / SDH
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 / SDH
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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SONET / SDH
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 / SDH
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 / SDH
SONET STS-1Frame
Frame1 Frame2 Frame8000
Frame = 810 octets * 8 = 6480bits8000 frames/sec = 6480*8000 bits/sec = 51.84Mbps
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SONET / SDH
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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SONET / SDH
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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SONET / SDH
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