Payload 4(Part2)

8/7/2019 Payload 4(Part2)

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Frequency Justification : NoJustification

� The frame rate of the STS SPE = the framerate of transport overhead ( OH; i.e., NE framerate)

� Then the alignment of the SPE is the same asthe previous frame.� NDF = 0110; I-bit / D-bit words are not

inverted.

� If pointer value = 0, the first byte of the data islocated next to the H3 byte;

� If pointer value = 10, the first byte starts on the11th byte after H3;

� Example=



STS-1: no frequency justification



Frequency Justification : PositiveJustification

� Frame rate of the STS SPE < the transport OH( i.e. NE frame rate )

� The alignment of the SPE is slipped back by a

byte.� H1, H2 incremtns and I-bits are inverted.� NDF = 0110� Example :

o I, D : value 00 0010 1010 = 40o First byte in SPE next to the H3 is 0o Positive justification is recognized quickly by

examining the bit next to the LSB of the H1 byte 1 : positive

0 : negative



STS-1 : positive-frequency justification



Frequency Justification :Negative Justification

� The frame rate of the STS SPE > thetransport OH (i.e., NE frame rate ).

� The alignment of the SPE is slipped back

by a byte� H1, H2 decrements� D-bit are inverted, NDF = 0110� Example :

o The I, D value is 00 0010 1000 = 40o H3 byte contains user payload in the current

frame.



STS-1 : negative frequency justification



New Data Found ( example )

� NDF = 1001� A resynchronization has taken place ( not

due to a positive or negative frequency

justification but because of some system or payload-type change .

� I-bit and D-bit are not inverted� New pointer value in H1 and H2� For another case, known as concatenation

indicaiton :o NDF=1001o

I-bit and D-bit = 11 1111 1111



STS-1 : new data found



Path Overhead

� The first column of the SPE ( 9 bytes )� Path bytes are directional.� J1 : the trace byte , is user programmable

o The receiving PTE collects 64 repeating J1 bytes to verify theconnectivity with the transmitting PTE.

o Default : 0x00� BIP-8 or B3 : error control.� C2 : indicates the construction of SPE, the asynchronous mapping,

ATM, etc.� G1 : path status to the originating PTE from the destination PTE.� F2 : for end-user communication use.

� H4 : multiframe, is used as an end-to-end generalized multiframeindicator for payloads.

� Z3, Z4, Z5 : user bytes, reserved for future use and undefined for now.



SONET STS-1 : pathoverhead



SDH VC-3/4 : path overhead



5.2 SONET and SDH

Virtual Tributaries



Virtual Tributaries

� VT ( virtual tributary ) : small container thatis used to transport user payloads.

� In SDH, they are called VC ( virtual

containers ).� Each VT arrives within a 125 s interval.� Several VTs with OH ( overhead ) will

constitute an SPE.



Fig. 5.38 VTs : what are they ?





Table 5.7 Virtual Tributariesand Payload Rates

6.9127110812VT6

3.456142546VT3

2.304213364VT2

1.728284273VT1.5

VT payloadrates (Mbps)

VTs/SPEVTs/GroupBytes/VTColumns/VTVT Type



Fig. 5.39 Virtual tributaries



SPE Groups

� An STS-1 SPE contains 87 columns, thereal user payload is 84 columns.

� The payload is partitioned in 7 groups,

each group has 12 columns in capacity.� Each group can fit in 4 VT1.5 or 3 VT2 or 2

VT3 or 1 VT4.� Different groups can have different types of

VTs� Each group can have only one type of VT.� In SDH, groups are called TUG-2 ( tributary

unit group ).



SPE Groups

� When VTs form one SPE group, they arebyte-interleaved.

� Each SPE group can have only one kind of

VT.� The 7 SPE groups form SPE by byte ( or

column ) interleaving� The fixed stuffs columns and the path

overhead column are also byte interleavedto construct the SPE.



Fig. 5.40 SONET ± VTs andgroup structures tributaries



Fig. 5.41 SONET ± groups andSPE structures



SDH Groups

� TU filled with user data are byte (or column) interleaved to construct TUG-2.

� Each TUG-2 can have only one type of TU.

� When all 7 TUGs are constructed, they arebyte ( or column ) interleaved and add twocolumns of fixed stuff to construct TUG-3.



Fig. 5.42 SDH ± TU and TUGstructures



Fig. 5.43 SDH -- TUGs



Fig. 5.44 VT1.5 mapping inSPE



VT Superframe

� VTs map data from different end users in theSPE payload.o End user data may also be out of phase with each

other and to the STS-N frame.o A pointer and a frequency justification scheme,

similar to the SPE level, applies on the VT level.

� Each VT is partitioned in a 1-byte VT overheadpart and in a VT envelope capacity ( depending

on the type of VT ).o VT1.5 : 26 bytes VT envelope capacityo VT6 : 107 bytes VT envelope capacity

� 4 consecutive VTs from one user¶s data form a

VT superframe.



VT Superframe

� Payloads below DS3 rates are mapped in andtrasported by VT structures.

� H4 in the SPE path overhead is used to

indicate the phase of V1-V4 ( bits B7 and B8 )as well as 6-, 16-, or 24-frame superframeindication ( bits B1 and B2 or B3 and B4 or B5and B6 )o

To comply with Bellcore ( AR-254-CORE ), thefollowing rules apply to H4 bits : X is set to ³1´ or Bits B1 and B2 count from 00 through 11 over 24 frames or Bits B3 and B4 count from 00 through 01 over 6 frames

and then repeat or Bits B5 and B6 countr from 00 through 11 over 16 frames



Fig. 5.45 VT superframe



Fig. 5.46 VT superframe ± H4byte

V4XXXXXX 1 1

V3XXXXXX 1 0

V2XXXXXX 0 1

V1XXXXXX 0 0

V1 ± V4H4 BYTE1 2 3 4 5 6 7 8







Fig. 5.48 VT payload pointer --NDF



Fig. 5.49 VT payload pointer --value



VT Payload Pointer

� Frequency adjustment is made by slippingby a byte forwand or back in time the VTenvelope.

o Similar to the STS SPE frequency justifications.� The increment or decrement amount is

indicated by inverting the I-bit or D-bit word,respectively.

� When the frame rate of the VT envelope isgreater than or less than that of the STSSPE, the alignment of the VT envelope is

periodically slipped forward or backward in



VT Overhead

� The first byte in the envelope.� Over four frames, or 500 s, the four

overhead bytes are V5, J2, Z6 and Z7.

� The remaining bytes in a VT are user payload.

� For VT1.5, the� user payload is 25 bytes.

� For VT6, the user payload is 106 bytes.� Each VT envelope contains four bytes of

VT POH ( V5, J2, Z6 and Z7 ), the

remaining bytes are VT payload capacity.

Fi 0 Vi l ib i



Fig. 5.50 Virtual tributariesoverhead



VT Overhead

� V5 : the first POH byte in the VT superframeo Error checking as a signal labelo Indicating the signal status

� Bits in V5 are :o BIP-2 (1) : set if parity of all odd-numbered bits of previous VT SPE

is eveno BIB-2 (2) : set if parity of all eveb-numbered bits of previous VT

SPE is eveno REI-V : VT remote error indication back to originating VT PTE.o RFI-V : VT path remote failure indication in byte-synchronous DS1

mapping.

o Signal label : indicates content of the VT SPE.o RDI-V : VT path remote defect indication.



Fig. 5.51 Virtual tributaries pathoverhead



Application : DS0 bytesynchronous Mapping For DS1

� In a DS1 frame, there are 24 time slots(bytes ).

� Mapping one DS1 in a VT1.5.

� User payload in a VT1.5 has 25 bytes, thefirst byte haso The phase of the signaling and the frame bits

(bits P0 and P1)

o Signaling for the 24 DS0 channels ( bits S1-S4 )o The framing bit ( bit F )o A bit not used ( or fixed stuff )

� The remaining 24 bytes map the 24 bytes

of the DS1 frame.



Fig. 5.52 VT1.5 DS0 byte ±synchronous mapping in Ds1

S



Application : DS0 Byte- Asynchronous Mapping for DS1

� A DS1 frame consists of 24 time slots� User payload in a VT1.5 has 25 bytes, the

first byte has

o Fixed stuff ( bits R )o Information bits ( bit 1 )o Stuff control bits ( bits C1 and C2 )o Overhead bits ( bit O )o

Stuff opportunity ( bits S )� The remaining 24 bytes map the 24 bytesof the DS1 frame.

Fi 5 53 VT1 5 DS0 b



Fig. 5.53 VT1.5 DS0 byte ±synchronous mapping in Ds1



5.2 SONET and SDH

STS-N/STM-N Frames



Single-Step Multiplexer

� A multiplexer that receives N STS-1 SPEswithin a time window and then in one singlestage to multiplex them to produce an STS-

N.� The basic building block ( signal ) for STS-

N frames are STS-1 SPE when N > 1.� Multiplexing is on the byte level.

Fi 5 54 STS N i l t



Fig. 5.54 STS-N single-stageinterleaving.



Two-Step Multiplexer

� Two-step multiplexing : K STS-1 SPEs maybe received and multiplexed in an STS-Kand then N/K STS-Ks multiplexed to

produce an STS-N.� Multiplexing is on the byte level.� Two-step multiplexing is more complicated

than one-step multiplexing.

� Two-step multiplexing also creates moredelay ( because there are more steps inmultiplexing ) than one-step multiplexing.

Fig 5 55 STS N t o stage



Fig. 5.55 STS-N two-stageinterleaving.



STS-N Frame Structure

� Each STS-N frame has Nx90 columns and 9rows.

� Overhead ( line, section ) : the first Nx3columns

� Each STS-N SPE has Nx783 bytes� The first N columns of an STS-N SPE are the

path overhead

� For exampleo For an STS-3 frame, has a total of 3x90 = 270

columns by 9 rows.o Line & section overhead are the first 3x3 = 9

columnso Each STS-3 SPE has 3x783 = 2249 bytes

Fig 5 56 STS N frame



Fig. 5.56 STS-N framestructure.



STS-N Floating Frame

� The component STS-1 SPE in an STS-Nframe may be floating.

� Each component STS-1 SPE may start

from a different location in the STS-N SPE.� The pointers H1, H2 and H3 for each

component STS-1 SPE are still in the STS-N section overhead and each identifies the

starting location of its corresponding STS-1SPE as well as makes frequencyadjustments individually.

Fig 5 57 STS N example N =



Fig. 5.57 STS-N example, N =3.



Concatenation or Super-Rate

� For example of STS-3� If 3 STS-1 SPEs are from different sources and

each one may be in different phases with eachother and with the node, each will keep its own

ponter H1-H3 and frequency justification.� If 3 SPS-1 SPEs are belong to the SAME signal

source, and they arrive in a specific order and insynchronism ( which must be maintained throughout

the end-to-end path .), these will be processed intoconcatenated SPEs.

� The 3 SPEs are mapped in a known sequence andthus only one overhead pointer is required to pointto the first SPE.

� The remainin ointers contain a fixed code set to a



Concatenation or Super-Rate

� Also, only one path overhead is needed.� At the receiving end, all 3 SPEs are

received in the same order they were

transmitted.� The STS that transports concatenated

SPEs is called concatenated STS, denotedby STS-Nc ( in this case, STS-3c ).

� Similar case for N > 3.

Fig 5 58 STS Nc example N



Fig. 5.58 STS-Nc example, N = 3.

Contiguous Concatenation in



Contiguous Concatenation inSDH

� Allows bit rates in excess of the capacity of theC-4 container.

� Concatenation implies that payload should notbe split up

� A virtually contiguous container within an STM-4 ( for example ).

� Then the payload of several consecutive AU-

4¶s are mapped in a fixed order.� The first pointer is set to its value and the restpointers are set to a fixed CI value.

� This VC-4 is identified as a VC-4-4c.



Virtual Concatenation

� Some network (switching) nodes are notcapable of switching complete STS-3c or VC-4-4c with contiguously concatenated

payload in them.� Then these payload will be split into

payloads of lower rate, like STS-1 andeach STS-1 will be switched independently.

� The responsibility of reconstruct the STS-1¶s back to the original STS-3c is on thenetwork elements.



Fig 5 59 STM N frame



Fig. 5.59 STM-N framestructure.



STS-Nc Frame Structure

� The major difference between STS-N andSTS-Nc payload : then number of pathoverhead column in the SPE.o

For STS-N : N columnso For STS-Nc : 1 column

� The difference in the fixed-stuff columnso For STS-N : 2N columnso

For STS-Nc : N/3 -1 columns� STS-Nc has more bandwidth for dedicateduser payload and more efficient.

Fig 5 60 STS Nc frame



Fig. 5.60 STS-Nc framestructure.



Fig 5 61 STS-3c transport



Fig. 5.61 STS-3c transportoverhead.

Transport Overhead : SOH for



Transport Overhead : SOH for SDH

� A1, A2 : frame alignment; fixed framing pattern set at the hexadecimalvalue 0xF628 [ 1111 0110 0010 1000 ].o A1, A2 are NOT scrambled.

� B1, B2 : parity bytes for quality monitoring ( or error monitoring inSONET ).o The parity is calculated over ALL bytes of the previous frame before

scrambling and is placed in the current frame before scrambling.� D1 ± D3 : for network management for the regenerator section

o An 192 Kbps communication channels for alarms, maintenance,control, monitoring, administration, and other needs.

� D4 ± D12 : for network management as the D1 ± D3 but for themultiplex section.

� E1, E2 : a 64 Kbps voice communication channel for craft personnel.� F1 : a maintenance byte� J0 ( C1 ) : trace identifier

Transport Overhead : SOH for



Transport Overhead : SOH for SDH

� K1, K2 : for automatic protection switching ( APS ) control

� S1 : clock quality indicator

� M1 : transmission error acknowledgement

Fig 5 62 STM-1 section



Fig. 5.62 STM-1 sectionoverhead.



Scrambling

� When the complete frame has beenassembled, the bytes in it are scrambled.

� Purpose : to assure the receiver that a

density of 1¶s is maintained in the signal.� A1, A2, C1 bytes are not scrambledo A1 and A2 are used to locate the beginning of

the frame, so no scrambling are applied



Fig. 5.63 Frame scrambled.



STS-N Scrambler

� The scrambling code is generated by thepolynomial 1 + x6 + x7

� The scrambler is frame synchronous at the linerate ( STS-N ), and it has a sequence length of 127 bits that repeats itself.

� The scrambler is set to 1111111 on the mostsignificant bit ( MSB ) of the byte following theNth STS-1 C1 byte ( of an STS-N )

� The framing bytes A1, A2 and C1 from the firstSTS-1 through the Nth STS-1 are NOTscrambled.

� The scrambler runs continuously throughout

S S



Fig. 5.64 STS-N scrambler.

Layered Overhead and Transport



Layered Overhead and TransportFunction

� How to transport traditional signals, such as DS1, E1, etc. with aSONET signal ?

� To transport a DS1 signal to a SONET signal :o The incoming DS1 signal at the path layer is mapped onto a VT.o The VT is mapped onto the SPE, and the SPE path overhead is

also constructed.o The SPE is mapped onto the SONET signal, and the line overhead

information is added.o The signal is mapped onto the STS-N signal, and the section

overhead information is added. Now the complete STS SONET signal is formed, and the signal is

scrambled.

o The signal passed through the electrical-to-optical transducer ( thetransmitter ), and the optical signal ( with an NRZ optical coding ) iscoupled into the optical fiber and transmitted at the speed of light.

Fig. 5.65 Conversion of a legacy signal to a



SONET, layered overhead and transportfunctions.

I t ti B t L



Interaction Between Layers

� SONET signal is transmitted between NEs� Similar layers of the SONET signal, as

viewed between the transmitting and

receiving NEs, interact at thecorresponding layers.

. . ²OC N l d h d d



OC-N, layered overhead andtransport functions.

. .l l d h d d



layers, layered overhead andtransport functions.

SDH M lti l i



SDH Multiplexing

� SDH follows a very similar hierarchicalmultiplexing scheme to SONET

� Traditional signals are mapped onto

containers, the containers are multiplexedinto groups, and overhead is added toconstruct an STM-N signal. ( CCITTRecommendation G.907 )

Fig. 5.68 SONET multiplexing



Fig. 5.68 SONET multiplexingscheme.

Fig. 5.69 SDH multiplexing



Fig. 5.69 SDH multiplexingscheme.



5.2 SONET and SDH

Synchronization and Timing

N t k S h i ti



Network Synchronization

� On a network, from a receiving node pointof reference, all signals are received atdifferent phases with its clock and frame

synchronization.� The phase difference could be easilyengineered if it would remian fixed or bounded;o Received signals can be aligned if the phase

difference is fixed.o A fixed phase also implies all nodes are exactly

operate at the same frequency.

� But NEs are not exactly using the SAME

N t k S h i ti



Network Synchronization

� In practical, a small difference between theclocks from node to node may result in asubstantial frequency variation as the

signal passed through many nodes.� The problem can be solved if a commontiming source can be established

� The network uses a frequency of extremely

high accuracy from a timing service knownas Building Information Timing Supply (BITS ) in North America

� In Europe, the similar standard to BITS is

Fig. 5.70 Network



gsynchronization²a model.

Timing Accuracy : Strata




� The timing architecture in the communicationsnetwork is hierarchical.

� Each node in the network is required to main afrequency accuracy and depends on its major function in the network for timing accuracy ( if other nodes in the network depend on it for timing accuracy).

� The highest possible frequency accuracy is 10x 10-11

o Highly accurate atomic clockso The clock will be the PRS and the accuracy is

referred as stratum 1.o Stratum 1 accuracy allows a slip up to 2.523





� Stratum 2 : 1.6 x 10-8

� Stratum 3 : 4.6 x 10-6

� Stratum 4 : 3.2 x 10-5

o

For example, the digital PRX

s, central officeterminals, and digital channel banks.

� In SDH, PRS is called primary referenceclock ( PRC )o

Accuracy 1.0 x 10-11

o The clock is distributed throughout the entirenetwork

o Regenerated at the NEs by a synchronization

supply unit ( SSU ) and also by a synchronous

Table 5 8 Timing Accuracy



Table 5.8 Timing Accuracy

DCB/COT/DPBX15.36 / minute3.2×10-54

e.g. 5ESS/DCS132.48 / hour 4.6×10-63

e.g., 4ESS/5ESS11.06 / day1.6×10-82

PRS2.523 / year 10×10-111

NotesSkip RateMinimum Accuracy

Stratum

Timing Stability



Timing Stability

� Since signal may pass through parts of networkowned by more than one provider

� SONET NEs must be synchronized with astratum 3 or better quality clock.

� Or, SONET NEs can equipped with an internalclock ( oscillator ) that has a minimum accuracyof 20 parts per million ( ppm ).o This is required to support operation,

administration, maintenance, and provisioning (OAM&P ) functionality of all nodes in the network.

o Network providers must also supply a timingreference signal that meets the recommended

stability requirements.



BITS Timing Model



BITS Timing Model

� Where BITS ( or SASE ) is available, the NEsare externally timed from it.o The same quality reference clock over two paths,

the active and the alternate, are supplied by BITS.o The NE receives both signals, but it operates from

the active path.o If the active path goes down, the NE selects the

alternate clock.o

NE¶s time unit ( TU ) Receiving the two clocks from BITS Monitoring the incoming clocks for faults Selecting the correct ones Distributes the clock to all functional units in the NE

Fig. 5.71 BITS network



gsynchronization.



Fig. 5.72 OC-N Line (DS1)



g ( )timing model.

OC-M Single DS1 Line Timing



Model

� The NE extracts an 8-KHz clock from anincoming signal, typically a DS1 that isembedded in an incoming OC-M ( N > M)

signal.� The extracted 8 KHz is sent to TU, thensent to BITS over two separate paths.

� The BITS retimed and sent it back to the

NE over the active and alternate paths.� The TU distributes the retimed reference

clock to all functional units in the NE.

Fig. 5.73 OC-M Line (DS1)



timing model.

OC-N Dual-DS1 Line Timing



Model

� The NE extracts two independent clocksfrom two OC-N incoming signals.

� The two incoming OC-Ns are used to

extract from DS1¶s two 8-KHzsynchronization signals.� The extracted 8 KHz is sent to TU, then

sent to BITS over two separate paths.

� The BITS retimed and sent it back to theNE over the active and alternate paths.

� The TU distributes the retimed referenceclock to all functional units in the NE.

Fig. 5.74 OC-N Line (two DS1)



timing model.

Loop Timing Model



Loop Timing Model

� The NE is not connected to a BITS.� The NE is connected to only one OC-N and to

lower bit rate OC-M ( N > M ) and DS-N.� The NE extracts the clock from incoming

signals of the loop, typically a DS1.� An incoming OC-N is used to extract an 8-KHz

synchronization signal.� The extracted 8 KHz is sent to TU, .� The TU retimed the clock based on an

accurate phase-locked loop oscillator, locatedon the TU and then distributes it to allfunctional units in the NE.

Fig 5 75 Loop timing model



Fig. 5.75 Loop timing model.

Through-Timing Model



Through-Timing Model

� This model applies to regenerator elements.

� Each direction has its own TU and timing is

extracted from each direction.� This model is not recommended for add-drop multiplexers.

Fig. 5.76 Through-timing



model.

Clock Applications



Clock Applications

� The minimum free-running accuracy of a SONET minimum clock (SMC ) shall be 20 ppm.

� An ADM could be timed from a clock extracted from a line or from anexternal clock sources, or though-timed.o A holdover : when the reference clock fails, then for a specified

limited period of time, it enters a free-running state with a specified

tolerance.� A switched digital module in terminal mode ( TM ) configuration and

loop-timed may be required to provide holdover.� A digital cross-connect system with external timing is required with a

minimum accuracy of 4.6 ppm.� Entry into holdover and restoration from holdover shall be error free.



5.2 SONET and SDH

Maintenance

Maintenance



Maintenance

� Anomaly : a discrepancy between the actualand desired characteristics of an item.

� Defect : a limited interruption in the ability of anitem to perform a required function.

� Failure : a persistent defect. An NE enters afailure state when a failure condition has beendetected, and it exits a failure state when thecondition has been corrected.

� Maintenance of a system defineso The functions to be monitoredo The requirementso The criteriao Their parameters

Maintenance



Maintenance

� Performance of a function :o Acceptableo Unacceptable ( failed )o Degraded

� Main objectives of maintenance :o Trouble detectiono Trouble sectionalizationo Trouble or repair verificationo Trouble isolationo Restoration

Maintenance



Maintenance

� Maintenance requirementso Alarm surveillanceo Performance monitoring ( PM )o Control

Alarm Surveillance



Alarm Surveillance

� Alarm surveillance deals with the detection andreporting of certain failures and degradedconditions in the network.

� NE alarm surveillance takes place on different

levels, at :o Section terminating equipment ( STE )o Line terminating equipment ( LTE )o STS path terminating equipment ( STS PTE )

o VT path terminating equipment ( VT PTE )� A VT PTE contains all functionality of an STE,

LTE and STS PTE.� An STS PTE has all the functionality of an LTE

and STE.

Fig. 5.77 Maintenance: layeredl ill



alarm surveillance.

Alarm Indications



Alarm Indications

� A change of state may cause an alarmindication immediately as it occurs or after some period of time.

� When a failure state is detected, an alarmindication signal ( AIS ) is constructed andit is sent to the next NE on the downstreampath.o AIS is to alert downstream equipment of an

upstream failure.o The response to a received AIS is a remote

defect indication ( RDI ) signal in the upstream

direction

Alarm States, Declarations, andI di ti



Indications

� Loss of signal ( LOS ) : no light pulses persistfor 100 s.o If light pulses are lost for less than 2.3 s, then no

LOS is declared.

o However, if they persist for a period longer than 2.5sec, then an alarm message is sent to theoperating system ( OS ).

� Loss of frame ( LOF ) : a severely erroneous

frame ( SEF ) persists for a period longer than3 ms.o If at least four consecutive frameshave incorrect

framing patterns, then an alarm message is sent tothe OS.




Indications

� Equipment failures :o Service affecting ( SA )o Non-service affecting ( NSA )o Classified as critical, major, and minor.

o When equipment failure is detected, a message issent to OS.

� Loss of synchronization : loss of primary or secondary timing reference. A message is sent

to the OS stating the reason ( LOS, LOF, etc )� Automatic protection switching ( APS ) troubles: related to channel mismatch, K1 with unusedcode, K2 with APS mode mismatch, etc.




Indications

� DCC failure : any failed hardware or failure tocarry a data communications channel ( DCC ).o When this occurs, then the switch moves to

standby DCC and a report is sent to the OS.

� Signal label mismatch : related to signal labels.o Payload label mismatch ( PLM )o Unequipped ( ENEQ )o Signal label mismatch is performed by monitoring

the C2 byte for STS signal labels and for STSpayload label mismatch ( PLM-P).o Also performed by monitoring the V5 byte for VT

PLM and VT path unequipped.





AIS and RDI



AIS and RDI

� AIS ± Lo Generated when a line LOS / LOF is detectedo An STE forms an OC-N signal with a valid section overhead and

generates a line AIS by sending an all ± 1¶s pattern ( after scrambling ) for the remainder of the OC-N signal.

o The signal is sent downstream.o When the LTE detects AIS-L, an RDI signal is sent upstream.

� AIS ± Po Generated when a path LOS / LOF / LOP is detectedo An LTE forms a STS path AIS by filling the entire STS SPE with all

1¶s including H1 ± H3 bytes ( after scrambling).o The signal is sent downstream to the STS-LTE.o An RDI signal is sent upstream if the AIS is for LOS / LOF only.

AIS and RDI



S a d

� AIS ± Vo Generated when a VT LOS / LOF / LOP is

detected.o An STS PTE generates a VT path AIS by filling

the entire VT with all 1¶s ( after scrambling ).o The signal is sent downstream to the VT PTE.o An RDI signal is sent upstream if the AIS is for

LOS or LOF.

� Embedded DS-N with failures ( LOS, LOF,or LOP ) will cause an AIS depending onthe composition.

� RDI alarm signals are sent upstream to

Types of RDI



yp

� STS path RDI : alerts the upstream STSPTE that an AIS has been received in thedownstream STS path.

� VT path RDI : alerts the upstream VT PTEthat an AIS has been received in thedownstream VT path.

� DS-N RDI : when this signal is detected, it

is converted to a VT path RDI signal if aDS-N is mapped into its associated VT.

AIS ± RDI Summary



y

� When an STE receives an invalid signal, it sends an AIS-L alarmdownstream.

� When an LTE receives an invalid signal or an AIS-L and it is unable toprotect the line, it sends an STS path AIS downstream.

� When an STS PTE receives either an invalid signal or an STS path AIS, it propagates the appropriate AIS downstream.

� When a VT PTE receives either a VT path AIS or an invalid signal, itgenerates the appropriate AIS downstream.

� Upon detection at a terminal of a service affecting failure, a local REDalarm is declared and an RDI signal is returned upstream to the far-end NE that terminates the service.

� Automatic service management processes are initiated at each NE and

they are maintained for the duration of th failure.� Alarm states and RDI are coordinated between source and sink to

restore service.

Performance Monitoring



g

� Performance monitoring ( PM ) : a set of rules for the in-service monitoring of thetransmission quality.

� Difference between SONET and SDH PMphilosophy :o SDH : PM is based on counting erroneous

blocks within a period of a second.o

SONET : based on counting code violationswithin a period of a second.

� SONET PM functions :o Detection of transmission degradationo Detection of performance parameter deviation

Performance Monitoring



g

� NE gathers PM from the values of :o Section BIP ( B1 )o Line BIP ( B2 )o STS path BIP ( B3 )o VT path BIP ( bits 1 and 2 of V5 : BIP ± 2 )

� PM stores information collected over a period of time in some

registers. Information related too The current periodo The previous periodo The recent periodo Threshold value

� Two types of registerso Current-second register ( CSR ) : contains defects or anomalies

that have occurred within a second.o Current-period register ( CPR ) : contains cumulative defects or

anomalies detected and stored in the CSR.



PM Inhibition Registers



g

� Inhibition registers are positive andnegative adjustment registers that are usedto add or subtract one of the following to acurrent period register o Coding violation ( CV )o Erroneous second ( ES )o Severely erroneous second ( SES )o Unavailable second ( UAS )o Line pointer justification ( PJ ), STS path PJ,

and VT path PJ

� All of the above have a negativeadjustment register, a positive adjustment



PM at the Section Layer



y

� Severely erroneous framing seconds ( SEFS-Ss ) : a count of secondsduring which an SEF defect was present

� Coding violations ( CV-Ss ) : a count of BIP errors detected at thesection layer ( using the B1 byte ).

� Erroneous seconds ( ES-Ss ) : a count of the number of secondsduring which

o at least one section layer BIP error was detected or o an SEF or o LOS defect was present

� Severely erroneous seconds ( SES-Ss ) : a count of the secondsduring whicho K or more section layer BIP errors was detected or o an SEF or o LOS defect was present.

PM at the Line Layer



y

� The line layer performance parameters aredivided into near end ( NE ) and the far end( FE )

� For the near-end line layer, performanceparameters are :o NE line coding violations ( CV-Ls ) : a count of

BIP errors detected at the line layer.o NE line erroneous seconds ( ES-Ls ) : a counter

in seconds during which at least one line layer BIP error was detected or an AIS-L defect waspresent

o NE line severely erroneous seconds ( SES-Ls )




y

� NE line unavailable seconds ( UAS-Ls ) : a count in seconds duringwhich the line was considered unavailable.

� NE line failure counts ( FC-L ) : a count of the number of near-end linefailure events.o A failure event begins when an AIS-L is declared and ends when an AIS-L

is cleared.

� Protection switching count ( PSC ) : relates to systems that areequipped with two switching fabrics, the working and the protectiono For working line : a count of the times that service switched from the

monitored line to the protection line + the times it switched back to theworking line.

o For protection line : a count of the times that service switched from anyworking line to the protection line + the times it switched back to theworking line.




y

� Protection switching duration ( PSD ) : a count insecondso For working line : a count in seconds that indicates the

duration of time service was carried on the protectionline.

o For protection line : a count in seconds that indicatesthe duration of time the protection line was used tocarry service.

� STS pointer justification ( STS-PJ ) : a count of the

STS pointer adjustments created or absorbed byan NE due to differences in the frame rates of incoming and outgoing SONET signals.o The STS-PJ parameter is accumulated for a non-

terminated STS path.




� FE line erroneous seconds ( ES-LFEs ) : a countin seconds during which at least one line BIP error was reported by the FE LTE using the REI-L or anRDI-L defect was present.

� FE line severely erroneous seconds ( SES-LFEs ): a count of the seconds during which K or moreline BIP errors were reported by the FE LTE or anRDI-L defect was present.

� FE line unavailable seconds ( UAS-LFE ) : a countin seconds during which the line was consideredunavailable at the FE.

� FE line failure counts ( FC-LFEs ) : a count of thenumber of FE line failure events.

PM STS Path Layer



� STS path layer performance parameters are divided into STS and VT.� Each failure divided into near end and far end� The near end STS path layer performance parameters are :

o NE STS path coding violations ( CV-Ps ) : a count of BIP errorsdetected at the STS path layer.

o NE STS path erroneous seconds ( ES-Ps ) : a count in seconds

during which at least one STS path BIP error was detected or an AIS-P defect was present.

o NE STS path severely erroneous seconds ( SES-Ps ) : a count of the seconds during K or more STS path BIP errors were detected or an AIS-P or LOP-P was present.

o NE STS path unavailable seconds ( UAS-P ) : a count of the

seconds during which the STS path was unavailable.o NE STS path failure counts ( FC-Ps ) : a count of the number of NE

STS path failure events. A failure event begins when an AIS-P or LOP-P is declared and it ends

when it is cleared.

Fig. 5.78 Performancemonitoring: intermediate path



monitoring: intermediate path.

Fig. 5.79 Maintenance: facilityloopbacks



loopbacks.

Fig. 5.80 Maintenance: DS-Nloopbacks



loopbacks.



5.2 SONET and SDH

IP over SONET

IP over SONET



� Mapping IP over SONET takes 4 steps1.The IP packet consists of a header and a

variable-length data field, known as a datagram2.There is a protocol known as point-to-point

protocol ( PPP ). The IP datagram isencapsulated ina PPP packet; that is , a header is attached to it.

3.The PPP-encapsulated IP datagram is framed

using high-level data link control ( HDLC ).4.The end result is mapped row-wise and byte-

wise in the SPE. That is, VTs and bytemultiplexing is not applicable in this case.

IP over SONET



� PPP provides multiprotocol encapsulation,error control, and link initialization controlfeatures.

� HDLC is primarily used for frame delineation.

That is, to identify the start and the end of theIP/PPP/HDLC frame.

� Each HDLC frame stars and ends with thehexadecimal byte 7E or 0x7E.

� Other 0x7E, if not in the start or the endposition of the frame, it is replaced by the

0 7D f ll d b 0 5E

Documents

Payload 4(Part2)