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CS 4594 CS 4594 Broadband CommunicationsBroadband Communications

SONETSONET

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Synchronous Optical NetworkSynchronous Optical Network

• SONET = SONET = Synchronous Optical NetworkSynchronous Optical Network• First standardized by ANSI/ECSA, now SDH by ITU-T.First standardized by ANSI/ECSA, now SDH by ITU-T.

• SONET is Time Division Multiplexing (TDM)SONET is Time Division Multiplexing (TDM)..• SONET encompasses optical and electrical specifications.SONET encompasses optical and electrical specifications.• SONET uses octet multiplexing.SONET uses octet multiplexing.• SONET uses extremely precise timing.SONET uses extremely precise timing.• SONET provides support for operation, maintenance, and SONET provides support for operation, maintenance, and

administration (OAM).administration (OAM).

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SONET is superior to T-3 and T-4SONET is superior to T-3 and T-4

• with improved (over T-carrier)with improved (over T-carrier)• transport performancetransport performance

• ability to identify substreamsability to identify substreams

• international connectivityinternational connectivity

• enhanced control and administrative functionsenhanced control and administrative functions

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SONET electrical signal hierarchySONET electrical signal hierarchy

• STS-1 = Synchronous transport signal level 1STS-1 = Synchronous transport signal level 1• speed = 51.84 Mbit/sspeed = 51.84 Mbit/s

• designed to carry DS-3 or a combination of DS-1, DS-designed to carry DS-3 or a combination of DS-1, DS-1C, and DS-2 signals that are equivalent to DS-31C, and DS-2 signals that are equivalent to DS-3

• STS-N = Synchronous transport signal level NSTS-N = Synchronous transport signal level N• speed = N x 51.84 Mbit/sspeed = N x 51.84 Mbit/s

• designed to carry multiple STS-1designed to carry multiple STS-1

• octet multiplexed STS-1octet multiplexed STS-1

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SONET optical signal hierarchySONET optical signal hierarchy

• OC-1 = Optical carrier level 1 (caries STS-1)OC-1 = Optical carrier level 1 (caries STS-1)• OC-N = Optical carrier level N (caries STS-N)OC-N = Optical carrier level N (caries STS-N)

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Sections, Lines, and PathsSections, Lines, and Paths

• Sections are bounded by repeaters or Sections are bounded by repeaters or multiplexers that terminate the line.multiplexers that terminate the line.

• Lines may carry several tributary signals.Lines Lines may carry several tributary signals.Lines are bounded by multiplexers.are bounded by multiplexers.

• A path goes end to end (between terminating A path goes end to end (between terminating multiplexers).multiplexers).

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SECTION, LINE, and PATHSECTION, LINE, and PATH

M1

MPX

M1

MP

X

repeater repeater

sectionsection section

line

path

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STS-1 FrameSTS-1 Frame

• Each STS frame lasts 125 microseconds (8000 Each STS frame lasts 125 microseconds (8000 types a second)types a second)

• STS-1 frame has 6480 bits = 810 octetsSTS-1 frame has 6480 bits = 810 octets• The octets are understood in terms of a table of The octets are understood in terms of a table of

9 rows of 90 columns9 rows of 90 columns

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SONET FrameSONET Frame

3 Columns

9 rows

87 Columns

SonetFrame

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STS-1 Frame - ColumnsSTS-1 Frame - Columns

• The first three columns contain TOH = The first three columns contain TOH = Transport Overhead: Transport Overhead: • TOH has 9 rows by 3 columns (27 octets) which is TOH has 9 rows by 3 columns (27 octets) which is

subdivided intosubdivided into

• SOH = Section Overhead: 9 octets (3 rows of 3 SOH = Section Overhead: 9 octets (3 rows of 3 columns)columns)

• LOH = Line Overhead:18 octets (6 rows of 3 LOH = Line Overhead:18 octets (6 rows of 3 columns)columns)

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SECTION, LINE, and PATHSECTION, LINE, and PATH

M1

MPX

M1

MP

X

repeater repeater

sectionsection section

line

path

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Overhead patterns - Section and LineOverhead patterns - Section and Line

A A CB E FD D DH H HB K KD D DD D DD D DZ Z Z

A - framingB - error monitoringC - identificationD - data communications channelsE - orderwireF - network useG - receiver statusH - pointerJ - path indicatorK - data communications channelZ - future growth

SectionOverhead

LineOverhead

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Overhead StreamsOverhead Streams

• Section Overhead (SOH) defines and identifies frames, Section Overhead (SOH) defines and identifies frames, and monitors section errors and communication between and monitors section errors and communication between section terminating equipmentsection terminating equipment

• Line Overhead (LOH) locates first octet of SPE and Line Overhead (LOH) locates first octet of SPE and monitors line errors and communication between monitors line errors and communication between terminating equipmentterminating equipment

• Path Overhead (POH) verifies connection, and monitors Path Overhead (POH) verifies connection, and monitors path errors, receiver status, and communication between path errors, receiver status, and communication between path terminating equipmentpath terminating equipment

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STS-1 Frame - ColumnsSTS-1 Frame - Columns

• The last 87 columns hold SPEs = The last 87 columns hold SPEs = Synchronous Payload EnvelopeSynchronous Payload Envelope• SPE has 9 rows by 87 columns which are divided intoSPE has 9 rows by 87 columns which are divided into

• POH = Path OverheadPOH = Path Overhead

• payloadpayload

• The SPE does not necessarily start in column 4.The SPE does not necessarily start in column 4.• The SPE does not necessarily stay within one The SPE does not necessarily stay within one

frame.frame.

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Two SONET FramesTwo SONET Frames

3 Columns

9 rows

87 Columns

SonetFrame

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SPE = Synchronous Payload EnvelopeSPE = Synchronous Payload Envelope

SPE

3 Columns

9 rows

87 Columns

SonetFrame

Path overhead