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Ring Architecture and Switching

SDH

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Path protection switch (PPS) / Line protection switch (LPS)

1+1 protection switch / 1:N (1:1) protection switch

Stand-by Line Access (SLA)

Unidirectional switch / Bidirectional switch

Unidirectional ring / Biderectional ring

Revertive switch / Non-revertive switch

Manual switch operation

Wait to restore (WTR) time

Protection Switch Architecture

(Basics)

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Path protection switch Line protection switch

Line Protection Switch (LPS)

Working

Protection

Path SW

Path SW

Path SW

Path (VC-n) Line (STM-n)

Path Protection Switch (PPS)

Working

Protection

Line SW (equivalent)

Path SW

equivalent

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Note : only one direction is shown.

TX

TX

RX

RX

1+1Protection

Switch

TX

TX

RX

RX1:1Protection

Switch

TX

TX

TX

TX

RX

RX

RX

RX1:N

ProtectionSwitch

Working

Protection

Working

Protection

Working 1

Working 2

Working N

Protection

1+1, 1:1 and 1:N Protection Switch

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TX RX

TX RX

TX RX

TX RX

Working

Protection

Working

Protection

Extra Traffic

Normal Traffic

Extra Traffic

Normal Traffic

Extra Traffic service

is stopped.Note : only one direction is shown.

Stand-by Line Access (SLA)

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TX

RX

TX

RX

RX

TX

RX

TX

Working

Protection

TX

RX

TX

RX

RX

TX

RX

TX

Working

Protection

Unidirectional Switch

Bidirectional Switch

Unidirectional Switch and Bidirectional Switch

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Unidirectional Ring Bidirectional Ring

The drawing shows the traffic routing under normal (no failure) condition.

Unidirectional Ring and Bidirectional Ring

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Working Line normal failure

Protection Line

normal

normal failure


Protection Line

normal

normal failure

Non-reverteve Switch

Reverteve Switch

Revertive Switch and Non-reverteve Switch

Traffic flow

Revertive Switch and Non-reverteve Switch

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1. MSW Manual Switch

2. (SF) Signal Failure

3. FSW Forced Switch

4. LKOW Lock Out of Working

4. LKOP Lock Out of Protection

Note: Larger number has higher priority.

Manual Switch Operation

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Protection Line

normal

normal

WTR time

Traffic flow

Hold-Off & Wait to Restore (WTR) times

HOLD OFF time

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Ring Architecture

Node B Node A

Node C

East West

East

WestEast

West

STM-N

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1

Ring System

Unidirectional

Ring / Switch

Bidirectional

Ring / Switch

PPS

LPS

PPS

LPS

2-fiber

2-fiber

2-fiber

4-fiber

2-fiber

Subnetwork Connection Protection Ring (SNCP-ring)(2F-UPSR)

MS Dedicated Protection Ring(2F-ULSR) (for further study, G.841)

Subnetwork Connection Protection Ring (SNCP-ring)

(2F-BPSR) (for further study, G.841)

4F MS Shared Protection Ring (MS-SP ring)(4F-BLSR)

2F MS Shared Protection Ring (MS-SP ring)(2F-BLSR)

Types of Ring System

LPS:Line Protection Switch (MS protection)PPS:Path Protection Switch (VC trail protection)

MS:Multiplex Section

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1

Subnetwork Connection Protection (SNCP) Ring

(2 Fiber Uni-directional Path Switch Ring - UPSR)

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1

SNCP(Unidirectional Ring) / 2F-UPSR (1)

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1

SNCP(Unidirectional Ring) / 2F-UPSR (2)

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1

Any Physical Structure

(Mesh,Ring or Mixed)

TCP

PPS PPS

TCP

Path

Case 1


(Mesh,Ring or Mixed)PPS PPSTCPTCP CP

PathSNC-P SNC

Case 2


(Mesh,Ring or Mixed)PPS PPSTCPTCP CP CP

PathSNC-P SNCSNC

Case 3

Aggrega

te

1

Aggrega

te

Aggrega

te

1

Aggrega

te

2

Aggrega

te

2

Tributary

Tributary

Tributary 1 Tributary 2

Aggregate - Aggregate

PPS

Aggregate - Tributary

PPS

Trubutary - Tributary

PPS

TCP : Termination Connection Point

CP : Connection Point

Subnetwork Connection Protection (SNCP)

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1

4 Fiber

Multiplex Section Shared Protection (MS-SP) Ring

(4 Fiber Bi-directional Line Switch Ring - BLSR)

- Terrestrial Application -

4 Fib MS SPRi / 4F BLSR (1)

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1

4 Fiber MS-SPRing / 4F-BLSR (1)


4 i S S i / 4 S (2)

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1



4 Fib MS SPRi / 4F BLSR (3)

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2



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2

2 FiberMultiplex Section Shared Protection (MS-SP) Ring

(2 Fiber Bi-directional Line Switch Ring - BLSR)



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2

2 Fiber MS SPRing / 2F BLSR (1)



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2

2 Fiber MS SPRing / 2F BLSR (2)- Terrestrial Application -

N d ID M f 4F/2F MS SPRi

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2

Node ID Map of 4F/2F MS-SPRing

MS SPRi Mi ti d S l h C t l

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2

A/D

at C ?

yes

no

TU AIS

no AU AIS

A/D

at C ?

AU A IS

MS-SP switch

no

y e s

yes

no

Squelch Control

VC-4

path ?

The ring-switch is applied afterAU AIS insertion at B and D.For VC-12/3, AU AIS is insertedat B and D first, then it is

stopped after TU AIScompletion, in order to avoidshort term misconnections.

A

B

C

D

E

FA- E

A - E

E-F

E-F

A

B

C

D

E

FA- C

A - F

with AIS

A- C C-F

C-FA - F

with AIS

misconnection no misconnection

working channel

protection channel

on the same channel

of the STM-N.

on the same channel

of the STM-N.

for individual AUat B and D

for individual TUat A, E and F

no TU AIS

MS-SPRing Misconnection and Squelch Control

Sq elch Table of MS SPRing

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2

AU-4 #m

AU-4 #n

VC-3/VC-12

in AU-4

VC-3/VC-12

Add/Dro p

VC-3/VC-12

all through

VC-4 (VC organized AU)

through

VC-4 (VC organized AU) through

(at intermediate nodes)

AU-4

?1 k

West East

?2

AU-4 #m

AU-4 #n j

-*

W est East

AU-4 #m

AU-4 #n

West East

?4

AU-4 #m

AU-4 #n ji k

i ?3Squelch Table

AU-4 through node : The node where VC-4 cross connect level is applied to the AU-4.

AU-4 termination node :The node where VC-3/VC-12 cross connect level is applied to the AU-4 in question,

regardless cross connections, either all through or several add/drop connections.

* VC-4 cross connect level requires

no squelch table.

-*

AU-4 #m

AU-4 #n

AU-4 #m

AU-4 #n AU-4 #n

AU-4 #m

AU-4 #n

AU-4 Path (i) (j) (k)

Node ID No.

i

Node ID No.

j

Node ID No.

k

STM-N STM-NSTM-NMS-SP

Ring

West East West East West East

Squelch Table of MS-SPRing

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2

4/2 FiberMultiplex Section Shared Protection (MS-SP) Ring

(4/2 Fiber Bi-directional Line Switch Ring - BLSR)

- Transoceanic Application -

4/2 Fiber MS-SPRing / 4/2F-BLSR

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2

g- Transoceanic Application -

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2

Inter Locked Ring (ILR)


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3

Primary

node

Secondary

node

Primary

node

Secondary

node

No. 1 Ring No. 2 Ring

ring failurelink failure


Inter Locked MS-SPRing (1)

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3

g(P-S Connection: on working channel)

SSSS

Secondary node

Primary node

A

B

C

D

E

F

G

MS-SP Ring No.2 MS-SP Ring No.1

SSSS


Secondary node

Primary node

A

B

C

D

E

F

G

normal

ring failure

working

protection

working

protection


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3

(P-S Connection: on working channel)

SSSS

Secondary node

Primary node

A

B

C

D

E

F

G


working

protection


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3

(P-S Connection: on protection channel)

SS

Secondary node

Primary node

A

B

C

D

E

F

G

MS-SP Ring No.2 MS-SP Ring No.1MS-SP Ring No.2 MS-SP Ring No.1

Secondary node

A

B

C

D

E

F

G

normal

ring failure

SSSS

protection

working

SS

transferworking

Primary node

protection

SS


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3

SS

Secondary node

Primary node

A

B

C

D

E

F

G


SS

SS

transferprotection

working

(P-S Connection: on protection channel)

Inter Locked MS-SPRing

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3

(SNCP Ring - SNCP Ring)

SN-CP Ring No.1 SN-CP Ring No.2

Double Failure on Link and Ring (SNCP/ILR)

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3

Primary

node

Secondary

node

Primary

node

Secondary

node

SNCP ring

or

MS-SP ring

SNCP ring PPS

unprotected bouble failure

protected bouble failure

Double Failure on Link and Ring (SNCP/ILR)

Inter Locked Ring

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3

SS

SN-CP Ring MS-SP Ring

(SNCP - MS-SP)

Review Questions

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3

Fill up the space enclosed in parentheses in the following sentence with correct words.

1. For the 1+1 line system, only the failure line is transferred to the protection line, this

transfer is called ( a ). Even if failure is only on one direction, both lines are

transferred to the protection lines. This transfer is called ( b ).

2. For the 1+1 linear system, the protection line can be used to transport an ( a )

traffic. This system is called ( b ) ( c ) access system.

3. For the APS of the ring, the maximum number of nodes on a ring is ( a ). The

node number start from ( b ) to ( c ). The number assignment is not

necessarily in ( d ).

4. For linear APS, there are various switching priority, the top of the list of switchpreemption priority is ( a ).

5. Both line and path switched rings can be implemented by either as a ( a )-

directional ring, or as a ( b )-directional ring.

6. What stands for ILR( a ) ( b )( c )?

Q

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5.SDH Ring