Post on 18-Dec-2015
updated 1/2002 1
SONET / SDH
Nirmala Shenoy
Information Technology Department
Rochester Institute Technology
updated 1/2002 2
SONET / SDH
• Scope– What is SONET/SDH – features– Signal hierarchy– Topologies– SONET components– Layers– Frames– Virtual tributaries
updated 1/2002 3
SONET / SDH
• What is SONET / SDH?– Synchronous Optical Network – ANSI (US)– Synchronous Digital Hierarchy –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)
updated 1/2002 4
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
updated 1/2002 5
SONET / SDH
• What is SONET / SDH?– Self healing ring topology– Consolidate and segregate traffic from different
end-points– Extensive integrated OAM&P– Backward compatibility
updated 1/2002 6
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
updated 1/2002 7
SONET / SDH• Sonet/SDH ratesSTS 1 OC-1 51.840STS-3 OC-3 155.520 STM-1STS-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-8STS-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
updated 1/2002 8
SONET / SDH
• Configuration
STS MUX STS MUX
regenerator regenerator
Add/drop mux
section section
line
path
updated 1/2002 9
SONET / SDH
• SONET topology
ADM
ADM
DCS
ADM
ADM
ADM
SMD
SMD
SMD SMD
SMD SA
SA
DS1
802.5
ADM – add drop multiplexer SMD- sts mu/demux DCS – digital cross connect switch SA – service adapter
Oc-n
Oc-n
Oc-n
Oc-n
Oc-n
Oc-n
updated 1/2002 10
SONET / SDH
• Multiplexing
MUX/DMUX
Service Adapters
Service Adapters
Service Adapters
DS1, CEPT1 etc
Maps into virtual tributaries
DS3 STS-1
STS-n
MAN, ATM, SMDS, others
STS-n
E/O
updated 1/2002 11
SONET / SDH
• SONET Devices
• STS Multiplexer– Multiplexes and de-multiplexes signals from
multiple sources– Path terminating equipment– Maps user payload into standard frame– Header goes end-to-end as part of Synchronous
Payload Envelope - SPE
updated 1/2002 12
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
updated 1/2002 13
SONET / SDH
• SONET Devices
• Regenerator– Repeater – improves signal quality– Operations – include layer 2
• Frame alignment, scrambling, error monitoring
– Section terminating equipment
updated 1/2002 14
SONET / SDH
• 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 / SDH
• SONET layers
PATH layer
LINE layer
SECTION layer
photonic layer
Data link
Physical
updated 1/2002 16
SONET / SDH
• Photonic layers – phy – Specs for optical fiber channel– NRZ encoding used
• Power level
• Wavelength
• Pulse shape
updated 1/2002 17
SONET / SDH
• Section layer– Frames – identifies beginning of frame– Scrambling – introducing 1’s to derive clock– error monitoring – section level– Adds 9 bytes to header – frame size 810 bytes– Provided at all devices
updated 1/2002 18
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
updated 1/2002 19
SONET / SDH
• 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
updated 1/2002 20
SONET / SDH
• SONET STS-1Frame
Frame1
Frame2
Frame8000
Frame = 810 octets * 8 = 6480bits 8000 frames/sec = 6480*8000 bits/sec = 51.84Mbps
updated 1/2002 21
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 Payload
Envelope – SPE – 9 bytes of path overheads
updated 1/2002 22
SONET / SDH
– first column in SPE – path overhead
STS SPE
Path overhead
Section overhead
line overhead
updated 1/2002 23
SONET / SDH
• 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 consecutive
frames – form a communication channel between regenerators
updated 1/2002 24
SONET / SDH
• Section overhead– User’s byte (F1)– bytes in consecutive frames
form a channel for user needs at the section level
– Management bytes (D1, D2 and D3)- 3 bytes per frame in consecutive frames = 192 kbps for OAM
updated 1/2002 25
SONET / SDH
• 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 kbps channel to detect problems in multiplexers
updated 1/2002 26
SONET / SDH
• 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
updated 1/2002 27
SONET / SDH
• 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
updated 1/2002 28
SONET / SDH
• 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–
updated 1/2002 29
SONET / SDH
• 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
updated 1/2002 30
SONET / SDH
• 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
updated 1/2002 31
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