10-Synchron_OMSN_R4.6-5####### BITNO

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Alcatel University 3FL 40034 AGAA WB ZZA Ed.01 Page 10.1

Alcatel University - 3FL 40034 AGAA WBZZA Ed.0110.1

10 Synchronization


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10.2

10 SynchronizationSession presentation

Objective: to be able to configure synchronization parameters

Program:

z 10.1 Introduction

z 10.2 Operation


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10 Synchronization

10.1 Introduction


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10.4

10.1 IntroductionSynchronization hierarchical structure

PRC Level

SSU Level

SEC Level

PRC

SEC

SSU SSU

SSUSSU

SEC

SEC SEC

SEC

SECSEC

SEC

The clock signal is distributed throughout the entire network.A hierarchical structure is used for this.The signal is passed

on by the subordinate Synchronization Supply Unit (SSU) andSynchronous Equipment Clock(SECs)

To prevent Transmission errors in SDH network the internal clock of the network element must be synchronized to acentral clock, which is generated by an high-precision Primary Reference Clock (PRC) unit conforming to the ITU-TRecommendation G.811.This is the highest level of synchronization in a network.Normally there are two differentPRC in a network, one the main and one the spare.The PRC specifyan accuracy of:

z 10E-13 if it utilizes Cesiumradioactive sample

z 10E-11 if it utilizes Rubidiumradioactive sample

The second level of the hierarchical structure is represented bythe SSU(Synchronization Supply Unit), which isnormally a stand-alone piece of equipment in the network. In case of loss of the PRC reference, the SSU providesthe network with a high quality synchronization signal. The SSU filters the jitter out of the incoming reference, whichresults from phase noise on the synchronization links between the PRC and the SSU.

z SSUs with a Transit Node quality have a sufficient quality to be placed at each point of thesynchronization chain; thus each can be used as a reference for further SSUs.

z Local Node clocks, in contrast to Transit Node clocks, can only be placed as the last SSU in thesynchronization chain.

The third and last level of synchronization is represented by the SEC (SDH Equipment Clock) which is normally builtinto the SDH network elements. The SEC filters out jitter from the selected incoming timing reference and providesthe SDH network element with a holdover capability for at least 24 hours. The normal operating mode of the SEC is

to be slaved to an SSU.


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10.5

PRC

SEC

SEC

SSU

SSU

SSUSEC

SEC

SEC

SEC

SSU

SSU

SEC

SECSynchronization network reference chain

N = max 20

K = max 10

Synchronization link

10.1 IntroductionSynchronization diagram

The quality of timing will deteriorate as the number of synchronization links increases.

Therefore, the number of network elements in tandem should be minimized for reliability reasons.

The values for the worst case synchronization reference chain* (ITU recommendation G.803) are:

z K (maximum number of SSUs in a chain) =10

z N (maximum number of SECs between 2 SSUs) =20, with the total number of SDH network element clockslimited to 60

* Synchronization chain =an interconnection of synchronization nodes and links


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10.6

10.1 IntroductionQualitys Levels

PRC LEVEL

SSU LEVEL

SEC LEVEL SEC

SSUL

SSUT

PRCPrimary

Reference Clock

Synchronization Supply

Unit Transit Node

Synchronization Supply

Unit Local Node

G.811 10E-11

Long Term

Frequency departure

5*10E-9 Accuracy

G.812T 5* 10E-10 Offset

10E-9/Day Drift

5*10E-7 Accuracy

G.812L 10E-8 Offset

2*10E-8/Day Drif t

Synchronous

Equipment clock

4.6*10E-6 Accuracy

G.813 5*10E-8 Offset5*10E-7/Day Drif t

G.811 (ITU-T Recommendation) : Timing requirements at the outputs of primary reference clocks suitable forplesiochronous operation of international digital links.

G.812 (ITU-T Recommendation) :Timing requirements at the outputs of slave clocks suitable for plesiochronous

operation of international digital links. G.813 (ITU-T Recommendation) :Timing characteristics of SDH equipment slave clocks (SEC).

DNU: Do Not Use. This signal should not be used for synchronization.

The Unknown quality level was defined to characterize the quality of existing SDH networks. This quality level is nolonger supported by the hardware. Today, in SDH it indicates an invalid timing quality. The quality unknown is acommonly used quality in SONET networks. It is the highest quality in those networks except for PRC quality which ishigher. SDH networks should never(!) use quality unknown.


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10.8

Does onlyone sourcehave the

highest qualitycriterion?

10.1 IntroductionSSM algorithm

Selection of the sourcewith thebest criterion

Analysis of thepriorities table

Lockingof thesync board

Selection of the clockswith the highestquality criterion

Is the SSMmanaged?

YES NO

YES

NO

Selection of the clockwith the highest priority

The SSM is an algorithm that allows the NE to choose the best possibility for the synchronisation of a NE.In particular :

z If in a NE there are two different ports with two different signals the system choose the port with the best

quality of signal.z If in a NE there are two different ports with the same quality of signal the system choose the port that has

the highest priority.


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10.9

Selector

A

Selector

B

Squelch

A SelectorC

SETG

SquelchB

SETG

osc

T0

(Internal Clk)

T4/T5(External Clk)

To SERVICE/SERGI

T3/T6

T1/T2 6

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FromSERVICE/SERGI

SETS

10.1 IntroductionSETS Functions

The SETS function (Synchronous equipment timing source) is a subsystem of an SDH Network Element and itsimplemented within the MATRIX unit in the 1660SM and the SYNTH in the 1650SM-C

The SDH Equipment accepts up to 6 synchronization inputs from the following types of sources:

z T1 is the clock derived from STM-N line signalz T2 is a clock derived from the 2Mbit/s signal

z T3 is a 2MHz signal

z T6 is a 2Mbit/s signal without data information but with SSM information (not available on 1640FOX)

z internal oscillator (VCO Voltage Controlled Oscillator)

z T3 and T6 share the same connector on the front panel of SERVICE(for 1660SM and /SERG I(for1650SM-C) card; the selection between the two signals is made via software.

z Automatic selection of one of these input sources is achieved by a selector using quality criteria(SSMalgorithm) or priority criteria.

z Also manual selection is possible.


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10.10

The SETG (Synchronous equipment timing generation) generates the following synchronizationsignals

z for internal use:

a system clock T0(at 622.08MHz)locked to the selected reference(T1,T2,T3 orT6)and distributed to the equipment;

CK38MHz: it is derived from the system clock(T0)and is distributed to all the ports.Its frequency is 38.88MHz.

MFSY: it is the multiframe synchronism at 500Hz, obtained from the ck38MHz. It isdistributed to all the ports.

SY1S: it is a one second synchronism used on the MATRIX for the 1660SM and onthe SYNTH for the 1650SM-C for performance monitoring calculation

z for external use:

T4 is a 2MHz signal

T5 is a 2Mbit/s signal

T4 and T5 share the same connector on the front panel of SERVICE card for the1660SM, of SERGI card for the 1650SM-C; the selection between the two signals ismade via software.

10.1 IntroductionSETG Functions


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10.11

MATRIX a HCMATRIX aCOMPACT ADM main

MATRIX b HCMATRIX bCOMPACT ADM spare

From SERVICE/SERGI

Notes:The 1640FOX has only the SYNTH main and there arent the T3/T6 signals.

10.1 IntroductionSynchronization function block diagram

The working modes:

z locked

z holdover

z free running

are compliant to the ITU-T G.810, G.812 and G.813 Recommendations.

Theholdovermode requires at least 30 minutes of locked condition before loosing the reference.

There is a PLL that maintains locked the System clock to the one selected as input in case the equipment works in"locked" mode.

As the MATRIX /HCMATRIX and SYNTH are redundant, the synchronization function is redundant as well.

The synchronization sub-system guarantees the Hitless switch because the two MATRIX/HCMATRIX and SYNTHboards work in a Master-Slave mode. In order to maintain locked and in phase conditions the two GAs some signals

are exchanged on the SYNC BUS.This function isnt implemented in the 1640FOX because it hasnt the Master-Slavemode.


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10.12

10.1 IntroductionTiming Loop

A reuse of signal for synchronization purpose must be deeply investigated since timing loops

might be generated through a lot of PDH and SDH pieces of equipment. Next figure gives an

example of timing loop.

SEC SECSEC SECSEC

This port mustnot be a sync port

SSU SSU

B

SSU

DNU

B

direction of timing

SSU

squelched

Risk of timing loop No risk of timing loop


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10.13

Time allowed :

15 minutes

10.1 IntroductionTest

9 1. What is the PRC? And what does the acronymPRC mean?______________________________________________________________________________________________________________

9 2. Which is the byte in the STM-N frame in which the quality of asignal is inserted?

M1 S1 D12

9 3. Flag the signals that can be used as synchronisation source.

2Mbit/s 140Mbit/s STM-N 2MHz 34Mbit/s

9 4. How many external sources could a NE have at maximum?

3 2 6

9 5. When does a NE go in holdover state?______________________________________________________________________________________________________________


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10.14


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10 Synchronization

10.2 Operation


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10.16

10.2 OperationConfiguration start up

The selector for T4 output is displayedonly if Service (in the 1660SM and1670SM) or Sergi (in the 1650SM-C)card is configured! Not availablein the 1640FOX.

This option is shown only whenthere is inserted and selected a

2 MHz source

To start the synchronization management

z Select views in the bar menu ofEML main window.

z Select synchronization option in the views pull down menu, opened by clicking on views.

z Thesynchronization view window opens and synchronization menu will appear in the bar-menu

Synchronization view window shows the functional scheme ofSETS (Synchronous equipment Timing Source)according to ITU-T Rec. G.783.

The input clock can be selected from6 different inputs, separately for T0 (internal reference ) and for T4 (externaloutput).

The free running indication is changed into holdover, when the NE looses the external clock reference (it is necessaryto maintain the reference for at least 30 minutes, to get holdover when removing the reference)


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10.17

10.2 OperationTiming Source Configuration

1st - Click on an input block

2nd- Select Synchronization in the bar

menu

3rd - Select the Timing Source

Configuration option in thebarmenu

4th -The Timing SourceConfiguration window will open

5th - Click on Chooseto open TPSearch window

To configure the timing inputs:

Select Synchronization menu in thebarmenu

Select Timing Source Configuration option in the pulldown menu

Timing Source Configuration window opens, with the following parameters to be configured:

Input Source: must be a physical port (select Choose to open TP Search)

Input quality Configuration: possible values are displayed i the pulldown menu open by the arrow ( )on the right of the entry box. G.811, G812/T, G.812/L, G813, Dont use, Extracted

Priority: from 1 to 6.

z Criteria for automatic selection is, in the order:

Signal present

Quality (determined by SSM, if enabled)

Priority (determined by the Operator)

N.B. Quality is not taken into account if SSM is disabled.


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10.18

10.2 OperationTiming Source Configuration

1-This window is opened by Choose button inTiming Source Configuration window

4- Select thetermination ( in thiscase only one) andclick on OK or double

click on it.

3- Select the ClassOpS (for optical SDHport), EIS (for electricalSDH port), PPI (for the2Mbit/s port) and Ignore(for the 2MHz signals)and click on Search.

5- Insert Quality andPriority and click on OKin order to activate theclock source.

2- Click in sequence onto retrieve theequipment details andselect an SDH or PDHport.

Within TP Search window the operator has to select the port which is considered as clock input.

Warning! The selected TP must be a physical port, e.g.:

z a physical port at 2Mbit/s (not available in the 1670SM);

z a physical port at STM-N in an SDH module

z one of the two external synchronization sources, T3#A,T3#B, T6#A orT6#B physically available on connectorson Service card of the 1660SM and 1670SM or Sergi of the 1650SM-C. Not available on the 1640FOX.

Input Quality Configuration box is used to assign a quality level to the reference source: choose Extracted if thesignal carries quality information (SSM), otherwise select a specific value according to the synchronization networkorganization

Constraints for 1670SM: if an interface managed by P16OS1 or P16S1N must be set as synchronization source, theinterface must belong to Group 1 and must be configured as A, B or C.

P16OS1

A12OS1

Group 1

Group 2

Group 2

Group 1

P16S1N

A16ES1

Group 1

Group 2

P16S1N

REMEP16

A4S1

Group 2Group 1

A4S1

A4S1

A4S1

A

B

C

D

E

F


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10.19

10.2 OperationResult of Timing Source Configuration

STM-N port configuredas clock source and

selected asreference clock

LOS at 2Mbit/s external clock

The sources ofT4 areshowed only if there isconfigured the Servicecard in the 1660SMand the Sergi card inthe 1650SM-C

The SETS is working in lockedmode that means that the NE hasan external source.

Result of Source configuration

DRIFT alarm

In this example:

z Synchronization view window was modified, by clicking on OK within Timing Source Configuration window,

after selecting a 2Mbit/s port :

The selected port is automatically inserted into the input block.

The 2Mbit/s port is not selected due to LOS.

The selected reference is the STM-N port.

DRIFT : is an alarm appearing when the Clock frequency offset is larger then 15 ppm; it is cleared when the offset is

less than 7 ppm(roughly).


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10.20

10.2 OperationChange 2MHz/2Mbit

The firs t feature allows to change

T4(2MHz)in T5(2Mbit/s).

The second feature allows to

change

the T3 (2MHz source) in T6 (2Mbit/s

source.) This opt ion is displayed

only if there is a 2MHz source.

This menu is enabled only if the operator selects a protection unit which has as source a 2 MHz

When you change the source the TP changes from

z 2MhT3#A to 2MbpsT6#A

z 2MhT3#B to 2MbpsT6#B

In case of T6 setting (2Mbps), the SSM algorithm is supported:

z choose Extracted in Input Quality Configuration

z choose a specific SaBit, which will be used to transport the SSM information

In case of T5 setting, the SSM information is transmitted and one

bit in the SaSSMBit field has to be used to transport the

SSM information.It is possible to set this field going into the

T4 configuration.


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10.21

10.2 OperationT0 Configuration

TheSSM algorithm implements the choice among the sources of synchronization, according to the best qualityindicated in SSM byte. The use of SSM algorithm allows also the automatic restoration of the synchronization in anetwork in case of failure.

When SSM algorithm is enabled:

z SSM is extracted by the incoming signal and used as criteria toselect the clock reference

z NE inserts SSM=Dont use in the opposite direction from where the clock is received (in case of SDH

reference clock)

z Internal clock is assumed SSM=G.813; you have the same quality in the Holdover condition

z IfInserted is selected in Transmitted SSM Quality Configuration window, the system internal T0 clock

quality is transmitted towards the external interface


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10.22

10.2 OperationT4 Configuration

When an input reference is selectedto generate T4

It is used to enable the SSM algorithm in the T4output clock.

When T0 is selected to generate T4

Different squelch criteria may be applied:

z when T0 is selected to generate T4:

T0 may be squelched if all the allowable timing references ofSelector B have Quality Level lower thanthe programmable threshold.

z When an input reference is selected to generate T4:

the output ofselector A may be squelched if the Quality Level of selected source is lower than theprogrammable threshold or if it becomes unavailable.

You can use the Squelching Criteria to define the lowest quality in the T4/T5 output clock

Force Squelch enables both the squelches for T4

TheSSM algorithm implements the choice among the synchronizations sources, according to the best qualityindicated in SSM byte. The use of SSM algorithm allows also the automatic restoration of the synchronization in anetwork in case of failure


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10.23

10.2 OperationTransmitted SSM Quality Configuration

The Transmitted SSM Quality Configuration window permits to define the value of SSM byte in the signal outgoingfrom the selected port.

z open the window by selecting Synchronization Transmission SSM Quality

z choose the quality level selecting among the different values: Inserted allows to transmit the system internal

T0 clock quality towards the external interface

N.B. to use the Inserted option, the SSU algorithm must be enabled

It is possible to configure the Transmitted SSM quality also from the Port View as in the picture below.

1- Select MST in the Port View of the STM-N Port

2- Select Port / Physical Media /Tx

Quality Conf.


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10.24

10.2 OperationClock Protection Command

This indication describes thecurrent synchronization status.It can be:

lockout manual switch force switch automatic switch no request fail.

The automatic selection algorithm overrules the manual selection

To perform or release a T0 or T4/T5 lockout or a force or manual selection:

z Select the T0 or T4/T5 source

z Select Synchronization/ Protection Commands

z Select Invoke/release within Lockout orForce orManual

Click on Apply to confirm the command

Remember:

Force has the priority on alarms

Manual has not the priority on alarms, and not priority on automatic SSM algorithm

Lockout means to exclude the object.


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10.25

10.2 OperationSSU Configuration

Selecting the SSU box, the SSU Configuration option, from

Synchronization pull down menu, is available:

z Single NE: means that the NE receives the clock from ports

or from external 2 MHz.

z NE with SSU: means that the ADM is connected to anexternal SSU and uses the 2MHz coming from the SSU, for

internal synchronization (T0): in this case T4 is T0.

NE

SSU

2 MHzfrom SSU

Clock fromSTM-1,traced fromPRC

2 MHz from NE

T4T3

21

SSUPRC SSU

N SEC

SSU

3

In case ofNE with SSU,NE with SSU, the SSU quality is thevalue transmitted on all the interfaces when T3

clock reference source is selected

The SSU is used to filter the phase noise of the

received clock.


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10.26

10.2 OperationSet/Remove T0 Equal T4

The connection between T0 and T4 will pass from a shaped to a continue line as in the picture.


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10.27

10.2 OperationRemove Timing Reference

This command is used in order to remove one source.


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10.28

10.2 OperationShow Timing Source

Select any reference source in the synchronization view hence Show Timing Source.

This selection opens the Port View of the selected reference source allowing to analyse the input source considering its

payload structure and the related alarms.


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10.29

10.2 OperationFrame Mode Configuration

See session 7 Configuration


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10.30

Time allowed :

See nextpage

10.2 OperationTest

Using as support the attached Synchronisation view window,answer the following questions :

9 1. How many reference sources have been configured inthe equipment?

2 3 4

9 2. Which priority has the selected timing reference? Priority 1 Priority 2 Priority 3

9 3. Is the SSM algorithm enabled or not? Yes No

9 4. Describe the criteria for that reference has beenautomatically selected by the equipment:

__________________________________________

9 5. Which signal is provided as Timing Output? 2Mbit/s None 2MHz


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10.31

Time allowed :

15 minutes

10.2 OperationTest


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10.32

Time allowed :

50 minutes

10.2 OperationExercise

9 Objective of this exercise is to synchronize the following three network

elements ring avoiding the timing loop

LEGENDA:

Eq=equipment

INS=inserted

EX=extracted

Q=quality

PORT

PORT

Eq 1PORT

PORT

PORT

Eq 2

POR

T

POR

T

Eq 3

2MHzMAIN

EX

EX

EX

EX

INS

INS

Q=G811PORT


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10.33

Thank you for answering

the self-assessment

of the objectives sheet

10 SynchronizationEvaluation

Objective: to be able to configuresynchronization parameters

Documents

10-Synchron_OMSN_R4.6-5####### BITNO