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SONET/SDH

Synchronous Optical Network/Synchronous Digital Hierarchy

SONET was developed by ANSISDH was developed by ITU-T

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SONET/SDH RatesSTS OC Rate (Mbps) STM

STS-1 OC-1 51.840

STS-3 OC-3 155.520 STM-1

STS-9 OC-9 466.560 STM-3

STS-12 OC-12 622.080 STM-4

STS-18 OC-18 933.120 STM-6

STS-24 OC-24 1244.160 STM-8

STS-36 OC-36 1866.23 STM-12

STS-48 OC-48 2488.320 STM-16

STS-96 OC-96 4976.640 STM-32

STS-192 OC-192 9953.28 STM-64

STS- synchronous Transport Signal STM – Synchronous Transport ModulesOC- optical carriers

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Figure 20-1

A SONET System

STS Mux/Demux – beginning & end pointsRegenerator – repeater that regenerates the optical signalsAdd/drop mux – add signals into a given path or remove a desired signal from a path

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Figure 20-2

An Example of a SONET Network

Section – optical link connecting 2 neighbor devicesLine – portion of a network between 2 muxesPath - end to end portion of the network between 2 STS muxes

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Figure 20-3

SONET Layers

Photonic Layer-Specs for optical fiber channel, sensitivity of the receiver-NRZ – 1-presence of light

Section layer -Responsible for the movement of a signal across a physical section-Framing, scrambling, error control

Line layer- STS mux and add/drop mux provide line layer functions

Path layer-Responsible for the movement of signal from its optical source to its optical destination-Transformation of signals-STS mux provides path layer functions

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Figure 20-4

Device-Layer Relationship in SONET

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Figure 20-5

Data Encapsulation in SONET

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Figure 20-6

STS-1 Frame

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Figure 20-7

STS-1 Frame Overhead

SPE – Synchronous payload envelope- Contains user data and details about charges (if any)

Path overhead - end-to-end tracking information

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Figure 20-8

STS-1 Frame Section Overhead

A1 & A2 – for framing & synchronization, F6 & 28 in hexC1 – Frame idB1 – LRCE1 –used for communication bet. regenerators or bet. terminals & regeneratorsF1 reserved for user needsD1, D2, D3 – for operation, administration and maintenance signaling

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Figure 20-9

STS-1 Frame Line Overhead

H1, H2, H3 – identify the location of the payload in the frame

K1, K2 – used for automatic detection of problems in line-terminating equipment (mux)

Z1, Z2 – reserved for future use

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Figure 20-10

Payload Pointers

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Figure 20-11

STS-1 Frame Path Overhead

J1 – used for tracking the pathC2 – path identification byte, used to identify different protocols used at higher levelsG1- sent by the receiver to communicate its status to the senderF2 – reserved for user needsH4 – multiframe indicator

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Figure 20-12

Virtual Tributaries

- Partial payload that can be inserted into STS-1 and combined with other partial payloads to fill out the frames

SONET – backward compatible with the current digital hierarchy (DS-1 to DS-3

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Figure 20-13

VT Types

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Figure 20-14

STS-n

Multiplexing STS Frames

3 STS-1s = 1 STS-34 STS-3s = 1 STS-12

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Figure 20-15

STS Multiplexing

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Figure 20-16

ATM in an STS-3 Envelope

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Applications

• Can replace T-1 or T-3 lines

• Can be the carrier for ISDN and B-ISDN

• Can be the carrier for ATM cells

• Can support bandwidth on demand

• Can be used as the backbone or totally replace other networking protocols such as FDDI.