SONET. What is SONET? Synchronous Optical Network standard Defines a digital hierarchy of...

What is SONET?

• Synchronous Optical Network standard

• Defines a digital hierarchy of synchronous signals

• Maps asynchronous signals (DS1, DS3) to synchronous format

• Defines electrical and optical connections between equipment

• Allows for interconnection of different vendors’ equipment

• Provides overhead channels for interoffice OAM&P

SONETNetworkElement

SONETNetworkElement

DigitalTributaries

DigitalTributaries

Asynchronous Vs Synchronous

• Assume Maximum Clock Rate• Bit-Stuff As Required

• Assume Maximum Clock Rate• Bit-Stuff As Required

DS-M

DS-(M+1)

Asynchronous (aka Plesiochronous)

ooo

• Use Network Clock Rate• Use Pointers To Find Payload

• Use Network Clock Rate• Use Pointers To Find Payload

SONETVT1.5 OrSTS-M

STS-N(M < N)

ooo

Digital Signal HierarchiesMost Common Rates

Asynchronous

SONETVT1.5(1.7 Mb/s)

STS-3(156 Mb/s)

STS-12(622 Mb/s)

STS-48(2500 Mb/s)

28 84 336 1344Capacity

(DS-1 Equiv)

DS-1(1.544 Mb/s)

STS-1(52 Mb/s)

[Non-Standardized]

STM-1 STM-4 STM-16 SDH

DS-0(64 Kb/s)

VC-11 VC-3

DS: Digital SignalSONET: Synchronous Optical NETwork (US)SDH: Synchronous Digital Hierarchy (ITU)STS: Synchronous Transport SignalSTM: Synchronous Transfer ModeVC: Virtual ContainerVT: Virtual Tributary

DS-3(45 Mb/s)

SONET Rates

STS-1 OC-1 51.840

STS-3 OC-3 155.520

STS-12 OC-12 622.080

STS-48 OC-48 2,488.320

STS-192 OC-192 9,953.280

Level OpticalDesignation

Bit Rate(Mb/s)

STS = SYNCHRONOUS TRANSPORT SIGNALOC = OPTICAL CARRIER (“..result of a direct optical conversions of the STS after synchronous scrambling” - ANSI)

SONET Network Layers

DS3etc

DS3etc

Path • Map Services & POH Into SPE• Path Protection/Restoration • Other Path OA&M Functions

Line • Combine SPE & LOH• Sync & Mux For Path Layer• Line Protection/Restoration• Other Line OA&M Functions

Section • Add SOH & Create STS Signal• Framing, Scrambling• Section OA&M Functions

Physical(Photonic)

• E/O Conversion• Line Code• Physical Signal[No additional overhead]

MUX LTE Regen MUXLTELTERegen

ServicesDS3, DS1, etc

SONET ADM

Path

Line Line

SectionSection Section Section

Case Study: Two Path Layer Processors are Exchanging DS3s

SONETTerminal

STS-1OC-1

SONETTerminal

STS-1OC-1

RegenMux Mux

SectionSection

Line

Path

PTE PTE

LTE LTE

Map services & Path Over-Head into SPE

Map SPE & Line Over-Head into STS-N

Map STS-N & SectionOverhead into “Pulses”

Optical Conversion

Terminal TerminalRegen

Path

Line

Section

Photonic

Functional Description of SONET Layers

OH: Overhead

Path Layer

Line Layer

SectionLayer

PhotonicLayer

Information Payload

PathOH

LineOH

SectionOH

E/O Conversion

Transmission over OC-N

Function

Payload MappingError Monitoring

SynchronizationMultiplexingError MonitoringLine MaintenanceProtection SwitchOrder Wire

FramingScramblingError MonitoringSection MaintenanceOrderwire

E/O ConversionPulse ShapingPower LevelWavelenght

SONET STS-1 Frame Structure

SynchronousPayloadEnvelope

(SPE)

TOH

Ptr

87Bytes

3Bytes

SPE

87 Columns

POH

9Rows

87Bytes

3Bytes

t

t

FIxed

Stuff

FIxed

Stuff

Efficiencies

Mb/sec % STS1STS1 51.84 100%SPE (87 col) 50.11 96.67%SPE (84 col) 48.38 93.33%DS3 43.23 86.30%672 DS0’s 43.00 82.96%

POH

STS-1 Payloads1

VT1.5(1.7 Mb/sec)

DS-1(1.544 Mb/sec)

27

3 Columns

4 columns

VT Group(12 Columns)

x 4

VT2(2.3 Mb/sec)

6 columnsVT3(3.5 Mb/sec)

12 columnsVT4(6.9 Mb/sec)




x 3

x 2

SPE(84 Usable Columns)

SubSTS-1

Mappings

90 Total Columns

POH

Ctl&

StuffInformation

Stuff

Ctl&

StuffInformation

Stuff

Ctl&

StuffInformation

3 2528 Columns

3 2528 Columns

3 2528 Columns

DS-3

STS-1 Overhead Structure

SectionOH

A1 A2 J0

B1 E1 F1

D1 D2 D3

H1 H2 H3

D4 D5 D6

D7 D8 D9

D10 D11 D12

Z1 Z2 E2

B2 K1 K2

Framing STS1 ID

BIP-8(previous frame)

Orderwire(64 kb/sec) User Channel

DataComm ( 192 kb/sec)

Pointer Action

BIP-8(previous LOH+SPE)

ProtSwitching

DataCom(576 kb/sec)

NESync

FEBE Orderwire(64 kb/sec)

LineOH

Transport Overhead(3 Columns)

J1

B3

C2

G1

F2

H4

Z3

Z4

Z5

Path Overhead(1 Column)

Path Trace(multi-frame)

BIP-8

Signal Label

Path Status

User Channel

Indicator(multi-frame)

Growth

Growth

0 - 2 BytesFor Sync

IdentifiesSource of Sync

Eg, CLLI Code

BIP-8: Bit Interleaved Parity-8 (each bit set to give even parity over same-positioned bits)

SPE Type:• DS3• ATM• VT-Structured• Unequipped• Etc

• Path FEBE (4 bits)• RDI-P (4 bits) showing

• AIS-P• LOP-P

SPE Type-Dependent

Growth

FEBE: Far End Block Error (Count of BIP-8 Errors On Reverse Channel)

AIS-L

STS-N And STS-Nc(N = 3, 12, 48)

• STS-N• Formed By Byte-Interleaving N STS-N Signals• 3N Columns of Transport Overhead

• Frame Aligned• Redundant Fields Not Used - eg APS, Datacomm

• N Distinct Payloads (87N Bytes)• NOT Frame Aligned• N Columns Of Path Overhead - All Used• 2N Columns Of Fixed Stuff Bytes• 84N Columns Of Information

• STS-Nc• 3N Columns of Transport Overhead

• Frame Aligned• Redundant Fields Not Used - eg APS, Datacomm

• Single Payload• 1 Column Of Path Overhead• 3/N - 1 Columns Of Fixed Stuff Bytes• 87N - 3/N Columns Of Information

STS-1, STS-3, & STS-3c

TOH

POH

125 sec

TOH

POH

125 sec

TOH

POH

125 sec

POH

POH

POH

TOH

125 sec

POH

TOH

125 sec

STS-1

STS-3c

STS-3

Layering Application Bellcore Approach

A

B

C D

E

Trunks(DS1 = 24 Trunks)4E 4E

4E 4E

A

B

CD

DS3 or OC3

A

D

E

OC-48

A

B

C D

E

Switched

Cross-Connect

Multiplex

Photonic

LAYER

B

C

DCSDCS

DCS

DCS

DCS

ADMADM

ADM

ADM

ADM

ADM ADM

DS1

DS3/OC3

OC48

CustomerService Requests

Pt-Pt Traffic(Erlangs)

DS1 Private Line

DS3/OC3/OC12Private Line

[OC48Private Line]

Generic SONET Network Elements

ooo

ooo

STS-NPorts

STS-NPorts

STS-MFabric(M<N)

o o o

STS-MPorts

M:NDigital Cross-Connect System

(DCS)

STS-MFabric(M<N)

o o o

STS-MPorts

M:NAdd/Drop

Multiplexer(ADM)

STS-N

o o o

STS-MPorts

W E

STS-N

STS-N

M:NMultiplexer

(aka “End Terminal”)

SONET Configurations

Key SONET Configurations

48 S

48 P

PointTo

Point

• Compatible With OLS• 2 Nodes Per System• All T3’s Use DACS III• 1x1 Protection Switching

• Compatible With OLS• 2 To 16 Nodes• Add/Drop Multiplexing (“Tributary Add/Drop”) - Only DS3’s Changing Routes Or Terminating Use DACS III• 1x1 Protection Switching

48 S

48 P

DACSIII

DCSIII

ADM

ADM ADM ADM

ADM ADM

48 S

48 P

All DS3’s All DS3’s

48 S

48 P

ET: End TerminalADM: Add/Drop Multiplexer

ET

ET ET

ET

ET ET

ET ET

Key SONET ConfigurationsLinear Office Sequences

ET IIIPoint

ToPoint

LinearAdd/Drop

(“Open Ring”)

o o o IIIET ET IIIET ETIII ET IIIET ETETIII

N Offices• 2 End Offices• N-2 Interior Offices

ET

IIIIII ETADM ADMET ADM ADM o o o

Key SONET Configurations

III III III

IIIIII

PointTo

Point

ClosedRing

S

P

• Compatible With OLS• 2 Nodes Per System• 1x1 Protection Switching, • DACS III - Based Restoration

• Compatible With OLS• 2 To 16 Nodes - End Terminals At Ends, ADM’s Elsewhere• Add/Drop Multiplexing (“Tributary Add/Drop”)• 1x1 Protection Switching,• DACS III-Based Restoration At Ends & Add/Drop Points Only

• Compatible With OLS• 2 To 16 Nodes• Add/Drop Multiplexing (“Tributary Add/Drop”)• 1x1 Protection Switching• Ring Loopback Protection Switching• Must Be Of Uniform Size Around Entire Loop

DACSIII

ET ET ET ET

“MESH”“RING”

LinearAdd/Drop

(“Open Ring”)

DACSIII ADMET ET DACS

III

ADM ADM

ADM ADMADM

ET: End TerminalADM: Add/Drop Multiplexer

III

S

P

S

P

S P SP

S

P

S

P

S

P

S

P

SONET Network Management

SONET Ring APS (Automatic Protection Switching)

• Uni-directional Vs. Bi-directional Rings

• Two-Fiber Vs. Four Fiber Rings

• Ring Switching Vs. Span Switching

Applications of:• Bi-directional Line Switched Ring (BLSR)• Uni-directional Path Switched Ring (UPSR)

Definition of a RingA Ring is a collection of nodes (NE1, NE2, ….)

forming a closed loop. Each node is connected to two adjacent nodes

via a duplex communications facility.

A SONET Ring will provide:• Redundant Bandwidth

• Redundant Network Equipment• or both.

Ring Classification

• A Unidirectional Line Switched Ring (ULSR)• A Bidirectional Line Switched Ring (BLSR)• A Unidirectional Path Switched Ring (UPSR)• A Bidirectional Path Switched Ring (BPSR)

Any of the above type can be a two-fiber or a four fiber ring. Therefore, for all practical applications, SONET/SDH standards provide eight types of ring for network node interconnections.

Unidirectional Vs. Bidirectional Rings

C

BA

D

A B : 1

B A : 2 3 4

1

2

3

4

5

6

7

8

A - Unidirectional Ring

C

BA

D

A B : 1

B A : 5

1

2

3

4

5

6

7

8

B - Bidirectional Ring

Two-Fiber Vs. Four-Fiber Rings

C

BA

D

A

BWorking 1

Protection 2

Working 2

Protection 1

A - Two-Fiber Ring/Span

C

BA

D

A

BWorking 1

Protection 1

Working 2

Protection 2

B - Four-Fiber Ring/Span

Ring Switching 2-Fiber Ring

C

BA

D

Failure

Route before PS (Protection Switching)

A: Ring Switching: Two-fiber ring

50%

50%

50% - original+

50% - additional

50% - original+

50% - additional

Ring Switching 4-Fiber Ring

B: Ring Switching: Four-fiber ring

C

BA

D

Route before PS

Span Switching - 4-fiber Rings only

C

BA

D

Route before PS

B: Ring Switching: Four-fiber ring

A B

Route before PS

Route after PS

Bi-directional Line Switched RingNo Failures

CB

A

F

S

S

S

S

S

P

P

P

P

P

D

E

S

P

Original Circuit

A

B

C C

B

A

BidirectionalTraffic

UnidirectionalTraffic

SONET Add-Drop Multiplexer (ADM)Lucent FT-2000 LCT Example

)

OC-48 OC-48

OC-48 OC-48

STS-3Fabric

STS-3 Terminations (<= 4x16 = 64)

STS-3 STS-3STS-1/DS3

OC-48TerminatingEquipment




SERVICEWEST

PROTECTIONWEST

SERVICEEAST

PROTECTIONEAST

Bi-directional Line Switched RingSpan Switch

S

F

CB

S

S

S

S

P

P

P

P

P

D

E

S

P

X

A

Original Circuit

Protection Switch

SONET ADM Automatic Protection Switching

Lucent FT-2000 LCT Example

)

OC-48 OC-48

OC-48 OC-48

STS-3Fabric(60 msswitchtime)







SERVICEWEST

PROTECTIONWEST

SERVICEEAST

PROTECTIONEAST

Bi-directional Line Switched RingRing Switch

S

E

CB

A

F

S

S

S

S

P

P

P

P

P

D

S

P

Original CircuitRing Switch

X

SONET ADM Ring Protection SwitchingLucent FT-2000 LCT Example

)

OC-48 OC-48

OC-48 OC-48

STS-3Fabric(60 msswitchtime)







SERVICEWEST

PROTECTIONWEST

SERVICEEAST

PROTECTIONEAST

Ring Restoration Protocol

Reference: GR-1230-COREIssue 1, 12/93

1-4 5-8

Bridge Request Priority Destination Node ID

K1 K2

Sourcing Node ID

1-4 5S / L Completed Action

1111 LP-S Protection Lockout (span) or Signal Fail Of Protection(span)1110 FS-S Forced Switch (Span)1101 FS-R FS (Ring)1100 SF-S Signal Failure (Span)1011 SF-R Signal Failure (Ring)1010 SD-P Signal Degrade (Protection)1001 SD-S Signal Degrade (Span)1000 SD-R Signal Degrade (Ring)0111 MS-S Manual Switch (Span)0110 MS-R Manual Switch (Ring)0101 WTR Wait To Restore0100 EX-S Exerciser (Span)0011 EX-R Exerciser (Ring)0010 RR-S Reverse Request (Span)0001 RR-R Reverse Request (Ring)0000 NR No Request

0 Short Path1 Long Path

111 Line AIS110 Line RDI :010 Bridged and Switched)001 Bridged000 Idle

AIS = Alarm Indication SignalFS = Forced SwitchRDI = Remote Defect Indication

SF = Signal FailureSD = Signal DegradeFS = Forced Switch

4 bits 4 bits

Route Failure In Ring

F AD EP

RingBridge& Switch

XX

XS

P

X

RingBridge& Switch

SF-R/EF/L/Br&Sw

XSF-R/FE/L/Br&Sw

Detect Failureon Working & Protection

Detect Failureon Working & Protection

SF-R/EF/L/Idle

SF-R/FE/L/Idle

SF-R/EF/L/Idle SF-R/F

E/L/Idle

1

1

2

2

Bi-directional Line Switched RingRing Switch - Node Failure

F

CB

A

S

S

S

S

S

P

P

P

P

P

D

S

P

E xOriginal Circuit

Ring Switch

Bi-directional Line Switched RingNo Failures

CB

A

F

S

S

S

S

S

P

P

P

P

P

D

E

S

P

Original Circuits (Both Slot 2)

Bi-directional Line Switched RingNeed For Squelching

CB

A

F

S

S S

S

P

P

P

P

P

D

E

S

P

Original Circuits (Both Slot 2)x

• Requires Sharing of State Information• Significant Software Complexity

Bi-directional Line Switched RingDouble Ring Failure (No Recovery)

Original Circuit

Ring Switch

CB

A

F

S

S

S

S

S

P

P

P

P

P

D

E

S

P

X

X

SONET Rings will fail -- The question is “When?”

• Initial estimates of DWDM hardware show that it is 8 times more reliable than WDM equipment. – POEs not included

• Ring reliability is dependent upon ring mileage.– Ring sizes vary from 200 miles to 2800 miles.

• Ring Failures:– Given 100, 1000-mile perimeter rings:

• Current optimistic estimation is 1 network ring failure every 5 yrs.

• PCIs not included

– Most probable cause of a complete ring failure is an equipment failure and a fiber cut.

• Physical diversity violations in some rings (single-pt-of-failure).

Restoration Alternatives

Target Failure ModesRoute(Ring)

1 Fiber(Ring or

Pt-Pt)

Span Protection Switch

Ring Protection Switch

NominalResponse

Time

Yes

No

No

Yes

50 ms

100 ms

No

No

No

No

No

No

Total Ring

Ring Interconnect

Node

Access/EgressNode or ADM

MultipleRings

No

No

RingNode

No

Yes

Route(Pt-Pt)

No

No

Ring InterworkingInterconnect Problem (No Recovery)

A

C

BD

Z

E

D

S

S

S

S

S

P

P

P

P

P

Office X

S

S

S

S

S

P

P

P

P

PRing1

Ring2

X

Original Circuit

Failure

Dual Ring Interworking(Unidirectional A => Z Circuit)

No Failure

A

C

B

Z

E

D

S

S

S

S

S

P

P

P

P

P

Office X

Office Y

S

S

S

S

S

P

P

P

P

P

SS

Ring1

Ring2

v

v

v

v

v

v

v

Original CircuitSecondary (Inactive)

v

v

Dual Ring Interworking(Unidirectional A => Z Circuit)

ADM Failure

A

C

B

Z

E

D

S

S

S

S

S

P

P

P

P

P

Office X

Office Y

S

S

S

S

S

P

P

P

P

P

SS

Ring1

Ring2

v

v

v

v

XOriginal CircuitSecondary CircuitRing Switch

Dual Ring Interworking(Unidirectional A => Z Circuit)Office Or Double ADM Failure

E

v

A

C

B

Z

D

S

S

S

S

S

P

P

P

P

P

Office X

Office Y

S

S

S

S

S

P

P

P

P

PRing1

Ring2

SSXXOriginal CircuitSecondary CircuitRing Switch

DRI Capacity ImpactAll Transit Traffic Example

X

Y24

DS-3s Z

X

Y Z

48DS3s

48DS3s

48DS3s

(a) No DRI (b) With DRI (Secondary Channel On Service Capacity)

24DS3s

24DS3s

Restoration Alternatives

* If restoration capacity is available** Can help in a limited number of specific failure situations

Target Failure ModesRoute(Ring)

1 Fiber(Ring or

Pt-Pt)

Span Protection Switch

Ring Protection Switch

DRI

NominalResponse

Time

Yes

No

No

No

Yes

No

50 ms

100 ms

100 ms

No

No

Yes**

No

No

No

No

No

Yes

Total Ring

Ring Interconnect

Node

Access/EgressNode or ADM

MultipleRings

No

No

No

RingNode

No

Yes

No

Route(Pt-Pt)

No

No

No

Ring/Mesh Example - 1

40 T3

40 T3

40T3

40T3

BalancedDemands

1 OC48 (1x1)

1 OC48 (1x1)

1OC48(1x1)

1OC48(1x1)

1 OC48 (1x1)

1 OC48 (1x1)

1OC48(1x1)

1OC48(1x1)

ADM/DWDM $2.0M $2.0M $2.0MProtection Access 0 0.8 0.4

TOTAL $2.0 $2.8 $2.4

Ring/Mesh Ratio 0.72 0.83

RING Restn Restn 100% PMO

MESH

Ring Mesh

ADM

DACS III

ADM

DACS III

Svce Svce Prot

Note: DWDM Costs Prorated Per OC-48. No OA’s.


40 T3

40 T3

40T3

40T3

60 T3

40 T3

40T3

40T3

BalancedDemands

UnbalancedDemands

1 OC48 (1x1)

2 OC48 (1x1)

1OC48(1x1)

1OC48(1x1)

1 OC48 (1x1)

1 OC48 (1x1)

1OC48(1x1)

1OC48(1x1)

2 OC48 (1x1)

2 OC48 (1x1)

2OC48(1x1)

2OC48(1x1)

1 OC48 (1x1)

1 OC48 (1x1)

1OC48(1x1)

1OC48(1x1)


TOTAL $2.0 $2.8 $2.4



TOTAL $4.0 $3.8 $3.5



MESH


MESH

Ring Mesh

Note: DWDM Costs Prorated Per OC-48. No OA’s.


40 T3

40 T3

40 T3

40 T3

40 T3

40 T3

40 T3

Ring Mesh

OneExtra

1x1 OC-48

40T3

40T3

40T3

40T3

40T3

40T3

40T3

40T3

40T3

40T3

40 T3

40 T3

40 T3


Ring MeshNewRoute

Hybrid Network Concept

• Both Ring & Mesh Restoration Architectures Would Be Used

• Each OC-48 Would Be Either Ring Or Mesh Protected, But Not Both

• DWDMU Network Would Be Shared

• An Office Would Have A Mix Of Ring & Mesh OC-48’s, Depending On

Service Mix & Economics

Sample SONET Architecture

P

Circuit

DCS

DCS

48 S

48 S

48 P

48 P

48 P48 P

48 S

48 S

ADMADM

DCS

P

S

Circuit

DCS

DCS

SP

S

ADM ADM

DCS

Light Terminatingequipment

Restoration of DS-3 Services DS-3s services can be routed on all rings, all mesh, or

hybrid ring/mesh. Ring portion of DS-3:

– Restored by self-healing ring for multiple electrical or single optical/fiber failures, including fiber cuts.

– Backed up using DCS for multiple failure scenarios. Restoral is semi-manual and expected to take at least 20 min.

Mesh portion of DS-3:

– Restored via some “restoration platform”.

– Future restoration via the SONET DCS.

Sample T3 Architecture

T3

ADM

DCS

LGX

48 S

48 P

48 P48 P

48 S

48 S

48 S

48 P

ADM

ADMADM

DCS

DCS

ADM

P

S

LGX

DCS

P

S

P

S

T3Normal Service PathRing Restoration PathRestoration

DCS: Digital Cross Connect System

Sample SONET Architecture

P

Circuit

DCS

DCS

48 S

48 S

48 P

48 P

48 P48 P

48 S

48 S

ADMADM

DCS

P

S

Circuit

DCS

DCS

SP

S

Light Terminating Equipment

ADM ADM

DCS

P

Circuit

DCS

DCS

48 S

48 S

48 P

48 P

48 P48 P

48 S

48 S

ADMADM

DCS

P

S

Circuit

DCS

DCS

SP

S

Light Terminating

ADM ADM

DCS

P

Circuit

DCS

DCS

48 S

48 S

48 P

48 P

48 P48 P

48 S

48 S

ADMADM

DCS

P

S

Circuit

DCS

DCS

SP

S

ADM ADM

DCS

Other Types Of SONET Self-Healing Rings(2-Fiber Unidirectional Line-Switched Ring)

ADMA

ADMA

ADMADM ADMZ

ADMZ

ADMADM

Notes: Each Link Is Just 1 (1-Way) Fiber Transmission Directions Routed Differently

Ser

vice

Service

Ser

vice

Service

Pro

tect

ion

Pro

tect

ion

Protection

Protection

A=>Z

Z=>A

Z=>A

A=>Z

A=>Z

Z=>A

Other Types Of SONET Self-Healing Rings(2-Fiber Unidirectional Line-Switched Ring)

ADMA

ADMA

ADMADM ADMZ

ADMZ

ADMADM

Ser

vice

Service

Ser

vice

Service

Pro

tect

ion

Pro

tect

ion

Protection

ProtectionZ=>A

A=>Z

Z=>A

A=>Z

Z=>A

A=>Z

Other Types Of SONET Self-Healing Rings(2-Fiber Bi-directional Line-Switched Ring)

ADMA

ADMA

ADMADM ADMZ

ADMZ

ADMADM

Note: Each Link Uses 1 (1-way) Fiber Capacity On Each Fiber Divided Equally Between Service & Protection (2 “Logical Fibers”)

Serv

ice/

Pro

tect

ion

Service/Protection

Serv

ice/

Pro

tect

ion

Service/Protection

Serv

ice/

Pro

tect

ion

Serv

ice/

Pro

tect

ion

Service/Protection

Service/Protection

SONET. What is SONET? Synchronous Optical Network standard Defines a digital hierarchy of...

Documents

Transcript of SONET. What is SONET? Synchronous Optical Network standard Defines a digital hierarchy of...