PDHSDH.ppt

7/22/2019 PDHSDH.ppt

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PDH & SDH


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PDH

PLESIOCHRONOUS DIGITAL HIERARCHY.A TECHNOLOGY USED IN TELECOMMUNICATIONS

NETWORK TO TRANSPORT LARGE QUANTITY OFDATA OVER DIGITAL TRANSPORT EQUIPMENTSUCH AS FIBRE OPTIC AND MICROWAVE RADIO

WAVE SYSTEMS.

THE TERM PLESIOCHRONOUS IS DERIVED FROMGreekplesio which means near, and chronous, time.

IT MEANS THAT PDH NETWORKS RUN IN A STATE

WHERE DIFFERENT PARTS OF THE NETWORK AREALMOST, BUT NOT QUITE PERFECTLYSYNCHRONISED.


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PDH

SENDING A LARGE QUANTITY OF DATA ON FIBREOPTIC TRANSMISSION SYSTEM.

TRANSMISSION AND RECEPTION ARESYNCHRONIZED BUT TIMING IS NOT.

THE CHANNEL CLOCKS ARE DERIVED FROMDIFFERENT MASTER CLOCKS WHOSE RANGE ISSPECIFIED TO LIE WITHIN CERTAIN LIMITS. THEMULTIPLEXED SIGNAL IS CALLED A

PLESIOCHRONOUS SIGNAL.

PDH SIGNALS ARE NEITHER SYNCHRONOUS NORASYNCHRONOUS.


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PDH

PDH ALLOWS TRANSMISSION OF DATA STREAMSTHAT ARE NOMINALLY RUNNING AT THE SAMERATE, BUT ALLOWING SOME VARIATION ON THESPEED AROUND A NOMINAL RATE.

BY ANALOGY, ANY TWO WATCHES ARENOMINALLY RUNNING AT THE SAME RATE,CLOCKING UP 60 SECONDS EVERY MINUTE.

HOWEVER, THERE IS NO LINK BETWEENWATCHES TO GUARANTEE THEY RUN AT EXACTLYTHE SAME RATE.

IT IS HIGHLY LIKELY THAT ONE IS RUNNINGSLIGHTLY FASTER THAN THE OTHER.


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VERSIONS OF PDH

THERE ARE TWO VERSIONS OF PDH NAMELY

1) THE EUROPEAN AND 2 ) THE AMERICAN.

THEY DIFER SLIGHTLY IN THE DETAIL OF THEIRWORKING BUT THE PRINCIPLES ARE THE SAME.

EUROPEAN PCM = 30 CHANNELS

NORTH AMERICAN PCM = 24 CHANNELS

JAPANESE PCM = 24 CHANNELS

IN INDIA WE FOLLOW THE EUROPEAN PCM OF 30

CHANNELS SYSTEM WORKING.


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EUROPEAN DIGITAL HIERARCHY

30 Channel PCM = 2 Mbps

2 Mbps x 4 = 8 Mbps

8 Mbps x 4 = 34 Mbps 34 Mbps x 4 = 140 Mbps

140 Mbps x 4 = 565 Mbps


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EUROPEAN PDH HIERARCHY WITH BIT

RATES

MUX BIT RATE PARTS PERMILLION

CHANNELS

2 Mbps 2.048 Mbps +/- 50 ppm 30

8 Mbps 8.448 Mbps +/- 30 ppm 120

34 Mbps 34.368 Mbps +/- 20 ppm 480

140 Mbps 139.264 Mbps +/- 15 ppm 1920


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DESCRIPTION OF EUROPEAN E-CARRIER SYSTEM

THE BASIC DATA TRANSFER RATE IS A STREAM OF 2048 KBPS.

FOR SPEECH TRANSMISSION, THIS IS BROKEN DOWN INTO 30 X64 KBIT/S CHANNELS PLUS 2 X 64 KBPS CHANNELS USED FORSIGNALLING AND SYNCHRONIZATION.

ALTERNATIVELY, THE WHOLE 2 MB/S MAY BE USED FOR NON

SPEECH PURPOSES, FOR EXAMPLE, DATA TRANSMISSION.

THE EXACT DATA RATE OF THE 2 MBPS DATA STREAM ISCONTROLLED BY A CLOCK IN THE EQUIPMENT GENERATING THEDATA.

THE EXACT RATE IS ALLOWED TO VARY SOME PERCENTAGE (+/-

50 PPM) EITHER SIDE OF AN EXACT 2.048 MBPS. DIFERENT 2 MBPS DATA STREAMS CAN BE RUNNING AT SLIGHTLY

DIFERENT RATES TO ONE ANOTHER.


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MULTIPLEXING TECHNIQUE

IN ORDER TO MOVE MULTIPLE 2 MBPS DATA STREAMSFROM ONE PLACE TO ANOTHER, THEY ARE COMBINEDTOGETHER OR MULTIPLEXED IN GROUPS OF FOUR.

THIS IS DONE BY TAKING 1 BIT FROM STREAM #1,

FOLLOWED BY 1 BIT FROM STREAM #2, THEN #3, THEN #4. THE TRANSMITTING MULIPLEXER ALSO ADDS ADDITIONAL

BITS IN ORDER TO ALLOW THE FAR END RECEIVINGMULTIPLEXER TO DECODE WHICH BITS BELONG TO WHICH2 MBPS DATA STREAM, AND SO CORRECTLY RECONSTITUTETHE ORIGINAL DATA STREAMS.

THESE ADDITIONAL BITS ARE CALLED JUSTIFICATION

BITS OR STUFFING BITS


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30 Chl Digital Hierarchy

III OrderMux

480 Chls

IV Order

Mux

1920 Chls

Primary

Mux

30 ChlsII orderMux120 Chls

X 4 X 4

2.048 Mbps 8.448 Mbps 34.368 Mbps 139.264 Mbps


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DIGITAL MUX CONCEPTS

BIT INTERLEAVING:

ALTERNATELY EACH CHANNEL CODE

CAN BE SCANNED ONE DIGIT AT A TIME.

THE MULTIPLEXED SIGNAL IS CALLED A

BIT INTERLEAVED SIGNAL. BIT INTERLEAVING IS USED IN HIGHER

ORDER MULTIPLEXING.

A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3 C4 D1 D2 D3 D4


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DIGITAL MUX CONCEPTS

BYTE INTERLEAVING

WORD / BYTE / BLOCK INTERLEAVING:

IF THE CHANNEL TIME SLOT IS LONG

ENOUGH TO ACCOMMODATE A GROUPOF BITS THEN THE MULTIPLEXEDSIGNAL IS CALLED A BYTE

INTERLEAVED OR WORD INTERLEAVEDSIGNAL.

A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3 A4 B4 C4 D4


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SLIP, JUSTIFICATION AND JITTER

SLIP THIS OCCURS WHEN THE INCOMING BITRATE DOES NOT MATCH WITH THE DIVIDED

MUX/DEMUX CLOCK RATE. SAME BIT MAY BE

READ TWICE OR LOSS OF BITS WILL OCCUR.

JUSTIFICATION:-IT IS A PROCESS OF ADDINGADDITIONAL BITS TO SOLVE THE PROBLEM OF

SLIP.

JITTER:- DISPLACE MENT OF A PULSE FROM ITSNORMAL SIGNIFICANT INSTANT IS CALLED JITTER.


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JUSTIFICATION -TYPES

JUSTIFICATION

POSITIVE JUSTIFICATION

NEGATIVE JUSTIFIATION

POSITIVE-NEGATIVEJUSTIFICATION


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JUSTIFICATION

IF MUX CLOCK RATE IS HIGHER THAN TRIBUTARY

RATE, IT IS KNOWN AS POSITIVE JUSTIFICATION.

THIS IS USED UPTO 140 MBPS SYSTEMS.

IF MUX CLOCK RATE IS LOWER THAN TRIBUTARY

RATE, IT IS KNOWN AS NEGATIVE JUSTIFICATION.

IF ON AN AVERAGE, MUX CLOCK RATE AND

TRIBUTARY BIT RATE ARE EQUAL, IT IS CALLED

POSITIVE-NEGATIVE JUSTIFICATION.


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PROBLEMS INVOLVED IN HIGHER ORDER

MULTIPLEXING AND SOLUTIONS FOR THEM

1. MUX CLOCK SPEEDS SHOULD BE SAME AT BOTH THEENDS.SOLUTION :- THIS PROBLEM IS SOLVED BYUSING P L L CIRCUIT AT TERMINAL B TO RECOVER THE

CLOCK.

2. SYNCHRONIZATION:- SOLUTION- THIS IS SOLVED BYFRAME ALIGNMENT WORD (FAW).

3. TRIBUTARY BIT RATE AND MUX CLOCK (DIVIDED)SHOULD BE THE SAME:- SOLUTION - SOLVED BY PULSESTUFFING OR BIT STUFFING OR JUSTIFICATION

PROCESS. THISMEANS ADDING ADDITIONAL BITS.


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FOTS

FIBRE OPTIC TRANSMISSION SYSTEM.

SUB SYSTEMS

DIGITAL MULTIPLEX SUB SYSTEM.

OPTICAL LINE TRANSMISSION SUBSYSTEM.

CENTRAL SUPERVISORY SUB SYSTEM

POWER SUB SYSTEM ALARM SUB SYSTEM


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Fiber Optic Cable

Fig 6.6


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FIBRE OPTIC CABLE

Fiber Optic Cable

Consists of many extremely thin strands of solidglass or plastic bound together in a sheathing

Transmits signals with light beams

No risk of sparks, safe for explosive environments

More expensive than coaxial, but more bandwidth

Different colors of light are used to simultaneouslysend

Multiple signals


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OPTICAL LINE TRANSMISSION SUB SYSTEM

OPTICAL LINE TERMINATINGEQUIPMENT.

LINE SWITCHING EQUIPMENTS

LINE SUPERVISORY EQUIPMENTS

ORDERWIRE EQUIPMENTS.

SUPERVISORY SERVICE DATA REMOTE SERVICE DATA


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LIMITATIONS

LOWER CAPACITY.

ADD AND DROP DIFFICULT.

COMPLEX MULTIPLEXING ANDDEMULTIPLEXING.

NO UNIVERSAL STANDARD

INTERWORKING BETWEENHIERARCHIES COMPLEX.


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DISADVANTAGES OF PDH SYSTEM

PDH IS NOT IDEALLY SUITED TO THE EFFICIENT DELIVERYAND MANAGEMENT OF HIGH BANDWIDH CONNECTIONS.

PDH IS NO LONGER EFFICIENT TO MEET THE DEMANDSPLACED ON IT.

TO ACCESS THE LOWER ORDER TRIBUTARY, THE WHOLE

SYSTEM SHOULD BE DEMULTIPLEXED. BANDWIDTH LIMITATIONS MAX CAPACITY IS 566 MBPS

ONLY.

NO COMMON STANDARDS AMONG VENDORS.

TOLERANCE IS ALLOWED IN BIT RATES.

POINT TO POINT CONFIGURATION ( LINEAR WORKING )ONLY IS POSSIBLE.

IT DOES NOT SUPPORT HUB.

NO PROVISIONING FOR NMS.


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EVOLUTION OF SDH

FIBER OPTIC BANDWIDTH:Bandwidth of the optical fibercan be increased and there is no limit

TECHNICAL SOPHISTICATION:Using VLSI techniques whichis also cost effective

INTELLIGENCE:Availability of cheaper memory opens newpossibilities

CUSTOMER SERVICE NEEDS:Requirement of customerservices can be easily met w/o much additional equipments


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EVOLUTION OF SDH

TOTALLY SYNCHRONOUS SYSTEM.

INTERNATIONAL STANDARD/SYSTEM MULTIPLEXINGSTANDARD.

IN 1988, (ITU-T) 18TH STUDY GROUP FORMULATED

CERTAIN STANDARDS FOR MULTIPLEXING. THE MAIN AIM IS TO ACCOMMODATE THE EXISTING PDH

SIGNALS ALSO.

ADOPTING THE DIFFERENT VENDORS EQUIPMENTS.

DISADVANTAGES OF PDH LED TO THE INVENTION OF SDH.


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DIFFERENT SERVICES

LOW/HIGH SPEED DATA

VOICE

INTERCONNECTION OF LAN

COMPUTER LINKS FEATURE SERVICES LIKE HDTV

BROAD BAND ISDN TRANSPORT


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EXISTING NETWORK

4 RTH ORDER

3RD ORDER

2 ND ORDER

5 TH ORDER

2 Mbps

8 Mbps

34 Mbps

140 Mbps

5

6

5

mb

/

s

565 Mbps


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SYNCHRONOUS :ONE MASTER CLOCK & ALL ELEMENTS

SYNCHRONISE WITH IT.

DIGITAL:INFORMATION IN BINARY.

HIERARCHY:

SET OF BIT RATES IN A HIERARCHIAL

ORDER.

WHAT IS S D H ?


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WHAT IS SDH?

SDH IS A HIERARCHICAL SET OF INFORMATIONSTRUCTURE (DIGITAL TRANSPORT STRUCTURE) TO CARRYPAY LOAD.

SDH MULTIPLEXING:- A PROCEDURE BY WHICH MULTIPLELOWER ORDER PATH LAYER SIGNALS ARE ADAPTED INTOHIGHER ORDER PATH OR MULTIPLE HIGHER PATH LAYERSIGNALS ARE ADAPTED INTO MUX SECTION LAYER.

POINTER DEFINES FRAME OFFSET VALUE OF A VIRTUALCONTAINER.

SDH MAPPING:- THE PROCEDURE BY WHICH THETRIBUTARY ARE ADAPTED INTO VIRTUAL CONTAINERS ATTHE BOUNDARY OF THE SDH NETWORK.


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ADVANTAGES OF SDH

1. SIMPLIFIED MULTIPLEXING/DEMULTIPLEXING TECHNIQUES.

2. DIRECT ACCESS TO LOWER ORDER TRIBUTARIES.

3. ACCOMMODATES EXISTING PDH SIGNALS.

4. CAPABLE OF TRANSPORTING BROADBAND SIGNALS.

5. MULTI-VENDOR, MULTI OPERATOR ENVIRONMENT.

6. PROTECTION SWITCHING TO TRAFFIC IS OFFERED BY RINGS.

7. ENHANCED BANDWIDTH.

8. NMS FACILITY.

9. UNLIMITED BANDWIDTH

10. GROWTH OF THE EXISTING TO THE HIGHER ORDER SYSTEM ISSIMPLE.


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The Container (C)

Basic packaging unit for tributary signals (PDH)

Synchronous to the STM-1

Bitrate adaptation is done via a positive stuffing

procedure

Adaptation of synchronous tributaries by fixed stuffingbits

Bit by bit stuffing

The Virtual Container (VC) Formation of the Container by adding of a POH (Path

Overhead)

Transport as a unit through the network (SDH)

A VC containing several VCs has also a pointer area

The Tributary Unit (TU)


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The Tributary Unit (TU)

Is formed via adding a pointer to the VC

The Tributary Unit Group (TUG)

Combines several TUs for a new VC

The Administrative Unit (AU) Is shaped if a pointer is allocated to the VC formed at last

The Syncronous Transport Module Level 1(STM-1)

Formed by adding a Section Overhead (SOH) to AUs

Clock justification through positive-zero-negativestuffing in the AU pointer area

byte by byte stuffing


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STM1 Frames


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RSOH: Regenerator section overhead

MSOH: Multiplex section overheadPayload: Area for information transport

Transport capacity of one Byte: 64 kbit/s

Frame capacity: 270 x 9 x 8 x 8000 = 155.520 Mbit/s

Frame repetition time: 125 s

1

3

5

9

4

270

270 Columns (Bytes)

1 9transmit

row by row

RSOH

MSOH

AU Pointer Payload

(transport capacity)


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(MATRIX REPRESENTATION)

1ST ROW 2ND ROW 3RD ROW

9 261 9 261 9 261 9 261

I I I

9 261

PAY LOADS

O

H

I I270

9TH ROW

FRAME REPRESENTATION


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STM-N AUG AU-4 VC-4

TUG-3 TU-3 VC-3

C-4

C-3

TUG-2

TU-1 VC-1 C-1

140Mbps

34Mbps

2Mbps

(REDUCED DIAGRAM FOR SDH-MULTIPLEXING)

REDUCED MUX STRUCTURE


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Containers: C-3, C-2, C-12 and C-11

Container Carries signals at

C-11 1.544 Mbit/s

C-12 2.048 Mbit/s

C-2 6.312 Mbit/s

C-3 34.368 Mbit/s and 44.736 Mbit/s

C-4 139.264 Mbit/s


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TERMINOLOGY & DEFINITIONS

SDH:Set of hierarchical structures,standardized for the

transport of suitably adapted pay load over physical

transmission network

STM:Synchronous transport module

It is the information structure used to support section

layer connections in SDH

VIRTUAL CONTAINER :used to support path layer connections

in the SDH

LOWER ORDER VC ( VC1,VC2,VC3) HIGHER ORDER VC (VC3 ,VC4)


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SDH BIT RATES

SDH Levels Bit rates in Kbps

STM-1 155520

STM-4 622080

STM-16

STM-64

2488320

9953.28


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SOH BYTE ALLOCATION

A1A2 Frame alignment

B1B2 Error monitoring

D1..D3 Data comm channel for RSOH

D4..D12 Data comm channel for MSOH

E1-E2 Order wire channel

F1 Maintenance

J0 STM Identifier

K1 K2 Automatic protection switching

S1 SYNCHRONISATION STATUS

M1 Txmn Error acknowledgement

Media dependent bytes


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2 Mbps mapping

E1: 2.048Mb/s

STM-1 AU-4 VC-4

C-12VC-12

TUG-3

TUG-2

TU-12

x3

x7

x3

VC-n

AU-n

AUG

STM-n Synchronous Transport Module

Administrative Unit Group: One or

more AU(s)

Administrative Unit: VC + pointers

Virtual Container: payload + path

overhead

AUG


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The following are the different steps in the

mapping of 2Mbps stream

Formation of containerC12 Formation of virtual containerVC12

Formation of tributary unit TU12

Multiplexing of TU12 s to form TUG3

Multiplexing of TUG3s to form VC4

Formation of administrative unit AU4 Formation of administrative unit group AUG

Adding SOH to form STM1


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SDH NETWORK ELEMENTS

The different network elements are

SYNCHRONOUS MULTIPLEXER

SYNCHRONOUS DIGITAL CROSS

CONNECT

REGENERATOR

NMS


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NETWORK ELEMENTS

SYNCHRONOUS MULTIPLEXER

As per ITU-T Rec. synchronousmultiplexer performs both

multiplexing and live line terminatingfunctions.

synchronous multiplexer replaces a

bank of plesiochronous multiplexersand associated line terminatingequipment.


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SYNCHRONOUS MUX

Types ofsynchronousmultiplexers

TERMINAL MULTIPLEXER(TM)ADD DROP MULTIPLEXER(ADM)


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TM

TERMINAL MULTIPLEXER(TM)

TM Accepts a no. Of tributary

signals and multiplex them toappropriate optical/electricalaggregate signal viz

STM1,STM4,STM16 etc.


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TERMINAL MULTIPLEXER(TM)


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ADD DROP MULTIPLEXER(TM)

ADM is designed for THRU mode

of operation. Within ADM its possible to ADD

channels or DROP channels from

THROUGH CHANNELS


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At an ADM site ,only those signals that

need to be accessed are dropped or

inserted

The remaining traffic continues thru

the NE without requiring special pass

thru units or other signal processing


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ADM


AGGREGATE SIGNAL AGGREGATE SIGNALSDH(E/O) SDH(E/O)

ADM

TRIBUTARY SIGNALS (PDH/SDH)


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ADD DROP MULTIPLEXER(ADM)

ADD DROP MULTIPLEXER(ADM)


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CROSS CONNECT EQUIPMENT

Cross connect equipment functions as asemi permanent switch for varying

bandwidth control it can pick out one ormore lower order channels fortransmitting signal without transmissionchannels

Channels can be 64Kbps up to STM1 Under software program the need of

demultiplexing

TYPES OF NETWORK


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TYPES OF NETWORK

TOPOLOGY

STRING/BUS/LINEAR Topology

RING Topology

STAR Topology MESH Topology


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STRING/BUS/LINEAR

TOPOLOGY

TMADM ADM ADMREG

Aggregate signal

Tributarysignal

(STM1/STM4/STM16)

(2/34/140Mbps/STM1(e)/ STM1(o))

TM


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RING TOPOLOGY

Ring is a linear network looped back toitself

Network elements are ADMs or

REGENERATORS

Every node on a ring has two

communication paths to each other node

via the two directions around the ring.


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RING TOPOLOGY

ADM

ADM

Aggregate signal(STM1/STM4/STM16)

Tributarysignal (2/34/140Mbps/STM1(e)/ STM1(o))


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RING TOPOLOGY

Ring network is self healing type(allowingrerouting of traffic when a link fails).

The simple topology of a ring facilitates

the implementation of protocols that candetect failure of a fiber segment or node

and rapidly reestablish communications,

typically in timeframes on the order ofmilliseconds. This is referred to as

protection or protection switching


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RING TOPOLOGY

Rings gives greater flexibility in theallocation of band width to the

different users. Normally used in LAN,WAN, Core

Network,Regional Network etc.


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STAR TOPOLOGY

Traffic passes thru a central nodecalled HUB.

The HUB is a DXC. If HUB fails ,total traffic fails.

Documents

PDHSDH.ppt