Transport Network Protection

TRAFFIC PROTECTION IN TRANSPORT NETWORKS

Alberto BellatoCTO Technology and architectureOptical Networks Division ALCATEL Vimercate

A. Bellato – CTO T&A Team - OND 2

ContentContent

> Transport Network Concept

> Need for traffic protection

> Methods for traffic protection: Protection & Restoration

> Basics for traffic protection

> Protection Schemes in Transport Networks

> APPENDIX: Protection schemes in SDH/ Sonet/ OTN


ContentContent








Transport network concept

Scope of a Transport Network is to

> Transparently carry a client signal over several nodes in the network

> Provide means for a service monitoring in order to guarantee an agreed quality of service

> Simplify maintenance operations


End users

End

users

End users

End

users

End users


Intermediate nodes



> Client signals to be carried are mapped over hierarchical transport entities in order to achieve an optimized network management

> I.e. no need to manage the client signal at intermediate nodes, but bundles of signals with larger granularity

End users

End

users

End users

End users

End

users

Intermediate

nodes

client

client

client

OH

OH

OH

OH clientOH clientOH clientOH OHOH

OH


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Need for traffic protection

> A transport network should provide a mean for a secure traffic delivery between different sites

> Need to provide a mechanism able to minimize as much as possible the impact of events that may cause the interruption of the service• Note that this is different from network security, where

there is the need to protect data from external attacks


Failures in the NetworkFailures in the Network

NODE FAILURE

• EQUIPMENT FAILURE

• POWER SUPPLY FAILURE

• OVERLOADS / SOFTWARE / PROCEDURAL

FIBRE DAMAGE• DIG UP• FIRE• HUMIDITY• MICRO-BENDING • RODENT• VIBRATION

CONNECTOR FAILURE • CONNECTOR DEFECT• TEMPERATURE CYCLING• DIRTHARDWARE FAILURE • OPTO-ELECTRONIC

DEVICE FAILURE• POWER SUPPLY FAILURE

SPLICE FAILURE • VIBRATION• CRAFT DEFECTS

OPTICAL LINK

FAILURE

N.E. SITE FAILURE


Why Traffic Protection in Transport Network?Why Traffic Protection in Transport Network?

IMPORTANT SOURCE OF COMPETITIVE ADVANTAGE.

SOURCE OF PROFITABILITY.

GAINS CUSTOMER LOYALTY.

REDUCES NETWORK MAINTENANCE COSTS.

MINIMISES BAD PRESS.


ESTIMATED BUSINESS LOSS DUE TO TELECOMS SERVICE FAILURE, AN FCA (US) REPORT:

$107000 PER MINUTE IN A BROKERAGE INSTITUTION

$47000 PER MINUTE IN A CREDIT CARD/SALES AUTHORISATION

$2500 PER MINUTE IN A PAY PER VIEW

$1800 PER MINUTE IN A HOME SHOPPING (TV)

$1500 PER MINUTE IN A CATALOG SALES

$1500 PER MINUTE IN AN AIRLINE RESERVATION BOOTH

User’s Dependency in TelecomsUser’s Dependency in Telecoms


Price Sensitivity in Public Telecom Operators SLAsPrice Sensitivity in Public Telecom Operators SLAs

EXAMPLES OF NATIONAL OPERATORS SERVICE LEVEL AGREEMENTS

GUARANTEED MAX UAT

GUARANTEED MAX MTTR

FINANCIAL PENALTY

PRICE PREMIUM

EU Premium: 1 – 2 Hour/Year

4 – 8 Hours 10% of a month 2 months

15 – 50%

EU Standard: 4 – 13 Hour/ Year

4 – 8 Hours 1 month - 1year revenue fees

10 – 15%


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Network TopologiesNetwork Topologies

Medium densityof population

High densityof population

Low densityof population

Ring Based

Ring Based

Mesh Based Linear

Eventualclosure

Eventualclosure

Linear

POPULATION IS CONSIDERED AS AMOUNT OF NETWORK

ELEMENTS TO BE CONNECTED


Protection is a method for the traffic recovery, considered as ‘high priority‘ traffic (‘Normal traffic‘) , usually associated to a fast process where the Network Elements (NE) autonomously decide when to act (selfhealing).

The protection algorithm is implemented and handled by NE‘s

The protection application makes use of preassigned capacity between nodes (protection transport entity)

The alternative path used for traffic recovery, has a either a predefined routing or it is allocated through predefined links

‘Protection‘ transport entity can carry ‘low priority‘ traffic (Extra Traffic) when not in switching condition

PROTECTIONPROTECTION


• Working circuit path: GFHIL

• Failure on section: HI

• Predefined alternative path (‘protection‘ path) on GEABL

• Protection transport entity can be used for the transport of ‘low riority‘ traffic (depending on the specific protection scheme)

G

F

E

A

H

I

L

D BC

Protection applicationProtection application

Switch time 50 300 ms


Restoration is a method for the traffic recovery, usually associated to a slower process, where the switching decision is taken by a Network Management System (NMS) which can be either centralized or distributed through the network.

The restoration application makes use of any capacity available between nodes, depending on failure

scenario and on traffic matrix

The restored path doesn't have a ‘unique‘ predefined routing.

RESTORATIONRESTORATION


Switch time 500 ms up to 10 s

• Working circuit path: GFHIL

• Failure on section: HI

• NMS decides optimum routing (e.g. GFABIL) among possible alternative paths (e.g. GEDCL or GFAIL or GFEABL)

G

F

E

A

H

I

L

D BC

Restoration ApplicationRestoration Application


Network TopologiesNetwork Topologies

PROTECTION

PROTECTION

RESTORATION

PROTECTION

PROTECTION

Medium densityof population

High densityof population

Low densityof population

Ring Based

Ring Based

Mesh Based Linear

Eventualclosure

Eventualclosure

LinearPROTECTIO

N


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> Basics for traffic protection• Definitions• Switching Criteria• Protection Architectures




A Trail is defined as the transfer of information validated by the overhead information between two ‘Access Points’ at whichever layer, (after terminating the overhead associated to that layer)

Scope of the Protection - Trail Scope of the Protection - Trail

Trail Protection

Sub-network

TCPAP TCP AP

Layer ‘a’ Trail

TCP AP TCPAP

Sub-network

Layer ‘a’ Trail

Layer ‘b’ Trail


End users

End

users

End users

End

users

End users


Intermediate nodes

Layer ‘b’ Trail Layer ‘b’ Trail

Layer ‘a’ Trail


A Sub-Network Connection (SNC) is defined as the transfer of information between ‘Connection Points’ or ‘Termination Connection Points’, (before terminating the overhead associated to that layer).

Scope of the Protection - SNC Scope of the Protection - SNC

SNC Protection

Sub-networkSub-network

TCPAP CP CP

Sub-network

TCP AP

‘End-to-End’ Path

‘Intermediate’ Path portion


End users

End

users

End users

End

users

End users


Intermediate nodes

Intermediate path portion


Architecture ModeArchitecture Mode

Normal Traffic

‘+’ (1 wk + 1 pr)

End 1 End 2Redundant: Normal Traffic is ‘bridged’ permanently on ‘working/protection’ resources Extra Traffic is not supported

Shared: Normal Traffic is usually connected to ‘working’ resource - ‘bridge’ occurs only when protection is required Extra Traffic may be carried by ‘protection’ resource (when no requested for protection)

‘Working’ (wk)

‘Protection’ (pr)

Normal Traffic

‘:’ (N1 wk : M pr)

End 1 End 2‘Working’ (wk)


Extra Traffic


Switching ModeSwitching Mode

‘Unidirectional’ (or single ended )

‘Bidirectional’ (or dual ended)

End 1 End 2

End 1 End 2

Each end switches independently on the base of ‘switching criteria’ locally detected

Both ends, on the base of ‘switching criteria’ detected, perform ‘bridge & switch’ triggered by protocol exchange message (Automatic Protection Switching signalling) over ‘protection’ transport entity

APS signaling over ‘protection’

‘Working’ (wk)



‘Working’ (wk)


Switching Mode and Path RoutingSwitching Mode and Path Routing

Bidirectional ‘Uniform’ routing

The traffic shares the same equipment and links

End 1 End 2

End 1 End 2

Unidirectional ‘Diverse’ routing

The traffic is routed on different equipment and links


Switching Mode – Possible AdvantagesSwitching Mode – Possible Advantages

Advantages of ‘unidirectional’ protection switching: simplicity of implementation: no protocol required

but double bandwidth used best ‘switch time’ performance, than ‘bidirectional’ protection switching, due to the lack of protocol message exchange greater chance of restoring traffic, than ‘bidirectional’ protection switching,

but ‘diverse’ routing

Advantages of ‘bidirectional’ protection switching: greater efficiency of bandwidth usage, than ‘unidirectional’ protection switching, due to the ability of supporting extra-traffic on ‘protection path when no switching is required chance to get easier maintenance operations due to ‘uniform’ routing: traffic travels in both directions either along the ‘working’ path or the ‘protection’ path, then, one path is ‘active’

the alternative path is ‘standby’ (reduced number of sites possibly interested)

equal delay for both directions of transmission, significant feature with transoceanic links and via-satellite links


Operation ModeOperation Mode

In revertive operation mode, the traffic signal always returns to the working transport entity, when it has recovered from the defect or the external request

is cleared (revertive operation is handled either ‘unidirectionally’ or ‘bidirectionally’ consistently to the ‘switching mode’ of the protection scheme)

Revertive ‘unidir’

End 1 End 2‘Working’

‘Protection’

In non‑revertive operation mode, the traffic signal does not return to the working transport entity, once the defect or the external request affecting working resource has been removed.

Revertive ‘bidir’

End 1 End 2‘Working’

‘Protection’

‘bidirectional’ revert switch triggered by APS signaling


Operation Mode ApplicationOperation Mode Application

The ‘not revertive’ operation mode is applicable only where a working transport resource has a dedicated protection resource (e.g. protection scheme with ‘unidirectional’ switching mode).

Advantage: glitch on traffic, due to ‘revert switch’, avoided, then traffic performance increased.

The ‘revertive’ operation mode is applicable both in case of protection resource dedicated to a working resource and in case of protection resourceshared among different working transport entities. The ‘revertive’ mode is appropriate when:

the protection resource capacity is required to restore other traffic signal, due to more urgent need (e.g., protection scheme with ‘shared’ protection transport entity) the protection resource may be subject to frequent re-arrangement (e.g. where a network has limited capacity and protection routes are frequently re-arranged to maximize network efficiency when changes occur in the network) the protection resource is of significantly lower performance than the working resource (e.g. where the protection transport entity has a worse error performance or longer delay than the working transport entity) an operator needs to know which transport entities are carrying normal traffic in order to simplify the management of the network


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Protection Algorithm ControllerProtection Algorithm Controller

PROTECTION ALGORITHMCONTROLLER

INPUTSParameters able to

produce a state machine evolution

OUTPUTSActions produced

by the state machine evolution

EXTERNALLYINITIATED

COMMANDS

AUTOMATICALLYINITIATED

COMMANDS

PROTOCOLMESSAGES

(in ‘dual-ended’ sw.)

MATRIXRE-CONFIGURATION

(e.g. Bridge/Switch)

UPDATEDPROTOCOLMESSAGES

(in ‘dual-ended’ sw.)

Hardware (fpga usually) or Software tasks resident into the Network Elementable to process input parameters and providing output actions according to the specific protection algorithm

SWITCHING CRITERIA


Switching Initiation Criteria…Switching Initiation Criteria…

AUTOMATICALLYINITIATED

COMMANDS

EXTERNALLYINITIATED

COMMANDS

Fault conditions affecting the traffic to be protected at the specific layer

Available commands allowing the operator to control protection algorithm, by forcing, pre-empting or testing the switching status

…are, those conditions able to START (initiate), at a Network Element, a protection activity (i.e. a state machine evolution). Specifically:

IN DETAILS…


……Automatically Initiated Commands…Automatically Initiated Commands…

Signal Fail

All the defect conditions producing the ‘unavailability’ of the traffic to be protected at the interested layer

Signal Degrade

Error condition affecting traffic to be protected at the interested layer, over a specific threshold set by operator (not necessarily producing a ‘unavailability’)


……Externally Initiated Commands…Externally Initiated Commands…

Configuration modification and maintenance

Lockout of Protection makes the protection transport entity ‘unavailable’ for (all) the Normal Traffic(s) to be protected

Forced Switch (#n) forces Normal Traffic (#n) to be routed over the protection transport entity

Manual Switch (#n) routes Normal Traffic (#n) over the protection transport entity unless a fault condition (SF, SD) requires another signal to be routed over this transport entity

Control Commands

Lockout of Working (#n) disables the access to the protection transport entity for the (specific) Normal Traffic

Clear Lockout of Working (#n) clears the Lockout of Working (#n) command


……Externally Initiated Commands…Externally Initiated Commands…

In ‘bidirectional’ switching mode systems, testing of APS protocol

Exercise (#n) emulates a switch request (for Normal Traffic #n) without performing any actual switch action, unless the protection transport entity is being used

Clearing previous external command (not addressable by other specific clear command)

Clear clears all the switch commands

Freeze the protection process (commands under standardization)

Freeze the current state of the ‘Protection Algorithm Controller’ (mainly thought for checking the APS protocol exchange for APS Controller)

Clear Freeze clears the Freeze command and allows the ‘Protection Algorithm Controller to evolve on the base of current inputs state


Hold-Off TimeTime interval after the detection of a SF or SD

and its confirmation as a condition requiring the protection switching

procedure

Protection Switching PerformanceProtection Switching Performance

Switch Completion Time

The interval from the decision to switch

(including time needed to achieve this decision) to the

completion of the bridge and switch operation at a

switching node initiating the ‘bridge request’

Switch Initiation Time

(or Detection Time)Time interval between the occurrence of a network

impairment and the detection of a signal fail

(SF) or signal degrade (SD) triggered by that network

impairment

Network Impairment SF – SD trigger Start of protection Switching operations(SF-SD confirmation)

Protected traffic restored

Time


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Protection Architecture Protection Architecture Linear Linear

N.T.

NE 1

NE 2

NE 3

N.T.

NE 1

NE 2

NE 4

N.T.N.T.

NE 3

NE 4

‘Linear’ network topology ‘Ring’ network topology

(Wk)

(Wk)

(Pr)

(Pr)

P.A.C.

P.A.C.

P.A.C.

P.A.C.

Linear protection architecture is applicable to both linear and ring network topology: only ‘End’ nodes performs a protection activity, due to the resident ‘Protection Algorithm Controller’

‘Intermediate’ node performing traffic cross-connection and alarm (defects / errors) propagation

‘Intermediate’ node performing traffic cross-connection and alarm (defects / errors) propagation


Protection Architecture Protection Architecture Linear Linear

N.T.‘Meshed’ network topology

Linear protection architecture is also applicable to meshed network topology, whenever two separated paths (working and protection) can be identified through the network: again, only ‘End’ nodes performs a protection activity, due to the resident ‘Protection Algorithm Controller’

‘Intermediate’ nodes performing traffic cross-connection and alarm (defects / errors) propagation

N.T.

(Wk)

(Pr)


Protection Architecture Protection Architecture SPRing SPRing

N.T.

NE 1

NE 2

NE 4

N.T.

P.A.C.

P.A.C. P.A.C.

P.A.C.

SPRing (Shared Protected Ring) protection architecture is applicable only to ring network topology: every node of the ring performs a protection activity due to the resident ‘Protection Algorithm Controller’ (APS controller)

‘2F’ (fiber) ring’ network topology

NE 3

N.T.

NE 1

NE 2

NE 4

N.T.

P.A.C.

P.A.C. P.A.C.

P.A.C.

NE 3

‘4F’ (fiber) ring’ network topology

‘Working’ and Protection’ resources carried into the same transmission mean (e.g. fiber / )(Wk)

(Pr)

‘Working’ and ‘Protection’ resources carried into dedicated transmission means (e.g. fiber / )


Protection Architecture Protection Architecture SPRing SPRing

SPRing protection architecture is also applicable to meshed network topology, whenever a ‘closed’ connection of NE’s (i.e. a ring) is identified through the network: again, every node of the ring, performs a protection activity, due to the resident ‘Protection Algorithm Controller’

N.T.

‘Meshed’ network topology

N.T.

(Wk)

(Pr)


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> Protection Schemes in Transport Networks• Linear• Ring



Basic Linear Protection SchemesBasic Linear Protection Schemes

Protection Architecture

Network Topology

Protection Algorithm

Switching Operation

LINEAR

Linear / Ring / Meshed 1 + 1 unidir / bidir

Linear / Ring / Meshed 1 : N unidir / bidir

Linear / Ring / Meshed M : N bidir


Linear ‘1 + 1’ protection schemeLinear ‘1 + 1’ protection scheme

NE 1 NE 2Cross-connection matrix

Linear / ring protected network

Working (Wk)

Protection (Pr)

Normal Traffic(High Priority)

Normal Traffic(High Priority)

1+1 scheme

1 ‘protection’ resources dedicated to 1 ‘working’ resource

only Normal Traffic connected (Extra Traffic on ‘protection’ res. NOT supported) through permanent ‘bridge’ on the two communication resources (wk/pr)

traffic data ‘switched’ (selected) on the base of switching criteria detected

Permanent ‘bridge’ Selector


1 + 1 ‘unidir’ algorithm - I1 + 1 ‘unidir’ algorithm - I

N.T. (Wk)

(Pr)

NE 1 NE 2

N.T. (Wk)

(Pr)

NE 1 NE 2

SwitchNo Action

Unidirectional Switch completed

NE 1 NE 2

Switching criterion declaration

[Time][Time]

TAL

TAL – algorithm evolution time

Protection activity

Switch

In ‘non-revertive’ systems, new switch status is kept also after

failure/degrade/command removalfrom ‘working’ resource


1 + 1 ‘unidir’ algorithm - II1 + 1 ‘unidir’ algorithm - II

N.T. (Wk)

(Pr)

NE 1 NE 2

Switch

No Action

Revert switch on main performed

NE 1 NE 2Failure / Degrade removal

[Time][Time]

W.T.R.

W.T.R.– timer expiring

Protection activityN.T. (Wk)

(Pr)

NE 1 NE 2

Switch present until WTR timer expiring

Failure/Degrade condition removedfrom ‘working’ resource – WTR timer starts

At WTR timer expired, starting connectivity re-established (revert switch on ‘working’ main resource)

(Switch)

Revert


1 + 1 ‘bidir’ algorithm - I1 + 1 ‘bidir’ algorithm - I

N.T. (Wk)

(Pr)

NE 1 NE 2

N.T. (Wk)

(Pr)

NE 1 NE 2

Protocol message along ‘protection’ resource(‘No Request’ code)

Switch

Switch

(Bridge)

(Bridge)

Bidirectional Switch completed

NE 1 NE 2


Request Type, Channel ‘identifier’

Reverse Request, Channel ‘bridged

Request Type, Channel ‘bridged’

Switch

Switch

[Time][Time]


TAL

TAL

TAL

TAL

Protection activity

In ‘non-revertive’ systems, new switch status is kept also after failure/degrade/command removalfrom ‘working’ resource, ‘Do Not Revert’ code is signaled


1 + 1 ‘bidir’ algorithm - II1 + 1 ‘bidir’ algorithm - II

N.T. (Wk)

(Pr)

NE 1 NE 2

N.T. (Wk)

(Pr)

NE 1 NE 2

Failure/Degrade condition removed from ‘working’ resource – WTR timer starts at ‘tail’ end

Switch present at both ends until WTR timer expiring

(Bridge)Switch

(Bridge)Switch

NE 1Head end

NE 2Tail end

Wait To Restore, Channel ‘bridged’

No Request, Channel ‘bridged’

[Time][Time]

Protection activity

Failure / Degrade removal

W.T.R.


Revert switch on main ‘bidirectionally’perfor

med

Revert

Revert


No Request

As soon as WTR timer is expired, starting connectivity is re-established on both ends through, ‘No Request’ code.


Linear ‘1 : N’ protection schemeLinear ‘1 : N’ protection scheme

NE 1

Normal Traffic #1(High Priority)

Normal Traffic #n(High Priority)

Extra Traffic(Low Priority)

NE 2

1:N scheme

1 ‘protection’ resource shared among N (1) ‘working’ resources

implicitly ‘bidirectional’; protocol exchange along the ‘protection’ resource

the amount of ‘working’ resources (N) handled, and, consequently, of the Normal Traffics protected, depends on the characteristics of protocol supported (nr of bits/bytes dedicated into signaling)

both ‘bridge’ and ‘switch’ connections performed on the base of protocol algorithm activation

either Null Signal (no meaningful traffic connected) or Extra Traffic (low priority traffic) can be connected to ‘protection’ resource when protection activity is not required

Protection (Pr)

Working (Wk)

Normal Traffic #1(High Priority)

Normal Traffic #n(High Priority)

Extra Traffic(Low Priority)


1 : N ‘bidir’ algorithm - I1 : N ‘bidir’ algorithm - I

Protection (Pr)

Working (Wk)

Protection (Pr)

Working (Wk)

Bridge Switch

N. T. #1 recovered

N. T. #n not interested by protection activity

N. T. #1

N. T. #n

E. T.

‘No Request’ code on protocol and E.T./ Null Signal connected on ‘pr’)

E. T. squelched

‘Squelching’(AIS injection)



1 : N ‘bidir’ algorithm - II1 : N ‘bidir’ algorithm - II

Protection (Pr)

Working (Wk)

N. T. #1

N. T. #n

E. T.

Protection (Pr)

Working (Wk)

N. T. #1 recovered

N. T. #n not interested by protection activity

E. T. squelched

Br&Sw and E.T. squelching present at both ends until WTR timer expiring

Failure/Degrade condition removed from ‘working’ resourceWTR timer starts at ‘tail’ end

As soon as WTR timer is expired, starting connectivity is re-established on both ends through protocol


1 : N ‘bidir’ algorithm - III1 : N ‘bidir’ algorithm - III

E.T. sq.

E.T. sq.Bridge

Bidirectional Switch completed

NE 1 NE 2


Request Type, Channel Identifier


Request Type, Channel ‘bridged’

Bridge&

Switch

Switch

[Time][Time]


TAL

TAL

TAL

TAL

Protection activity for single Degrade/Failure/Command

Bridge&

Switch

Bridge&

Switch

NE 1Head end

NE 2Tail end

Wait To Restore, Channel ‘bridged’

No Request, E.T/N.S. Ch. Ident.

[Time][Time]

Failure / Degrade removal

W.T.R.


Revert on main ‘bidirectionally’perfor

med

Release Switch

Release SwitchBridge E.T. / N.S.

on protection


No RequestE.T./N.S. Ch. bridge

No RequestE.T./N.S. Ch. bridge

Bridge & Switch E.T. / N.S.

on protectionSwitch

E.T. / N.S.on protection


Linear APS channel contentLinear APS channel content

Protocol Parameters

• Request Type i.e. the request (failure / degrade / command) or state (‘No Request’ / ‘Do Not Revert’ / WTR) to be signalled / acknowledged by each end of the protection group

• Requesting Channel Identifier i.e. the identifier of ‘working’ / ‘protection’ resource for which the request type is issued

• Bridged Channel Identifier (bridge status) i.e. the identifier of ‘working’ / ‘protection’ resource for which the ‘bridge’ / ’switch’ matrix configuration is performed

• Architecture mode i.e. the ‘redundant’ configuration, “+”, or the ‘shared’ configuration, “:”

• Switching mode i.e. the locally provisioned ‘unidirectional’ / ‘bidirectional’ switching modesignalled to remote end for possible ‘provisioning mismatch’ detection (supported in OTH, optional in SDH)

• Operation mode i.e. the locally ‘revertive’ / ‘not revertive’ operation mode signalled to remote end for possible ‘provisioning mismatch’ detection (supported in OTH)


Squelching in linear schemesSquelching in linear schemes

Extra Traffic squelchingThis type of squelching is needed in every type of scheme, linear or ring,

supporting traffic configuration on the ‘Low Priority’ channels (Protection channels). This traffic, called ‘extra’ with respect that one configured on ‘High Priority’

channels called ‘normal’, is pre-empted when the ‘Low Priority’ channels are required for

protecting ‘normal’ traffic. The access to the ‘Low Priority’ by Normal Traffic might lead to traffic

misconnected, if no specific mechanism was implemented: Extra Traffic squelching performed before

any matrix re-configuration (Bridge/Switch) avoids this potential problem.

In linear 1:N schemes, Extra Traffic squelching implies that ‘end’ nodes forces a defined alarm signal (AIS) towards the Extra Traffic user.


N.T.NE 2

E.T.

N.T.NE 1

E.T.

Squelching in linear schemes - ISquelching in linear schemes - I

(Wk)

(Pr)


N.T.NE 2

E.T.

N.T.NE 1

E.T.

(Wk)

(Pr)

(No E.T. sq.)Bridge

(No E.T. sq.)


‘Request Type’ from NE2 processed - ‘Bridge’ performed at NE1 (but ‘Switch’ not performed yet at NE2) transient misconnection between N.T. and E.T. in the direction NE1 > NE2


Squelching in linear schemes - IISquelching in linear schemes - II

N.T.NE 2

E.T.

N.T.NE 1

E.T.

(Wk)

(Pr)

Reverse Request, Channel ‘bridged Bridge & Switch

‘Reverse Request’ from NE1 processed - ‘Switch’ performed at NE2 initial misconnection removed;‘Bridge’ performed at NE2 (and ‘Switch’ not performed yet at NE1) new transient misconnection between N.T. and E.T. in the direction NE2 > NE1

N.T.NE 2

E.T.

N.T.NE 1

E.T.

(Wk)

(Pr)

SwitchRequest Type,

Channel ‘bridged’

‘Request Type’ from NE2 processed - ‘Switch’ performed at NE1 new misconnection removed;


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> Protection Schemes in Transport Networks• Linear• Ring



Basic SPRing Protection SchemesBasic SPRing Protection Schemes

Protection Architecture

Network Topology

Protection Algorithm

Switching Operation

SPRING

Ring / Meshed1 : 1

2F/4F ‘classic’bidir

Ring / Meshed1 : 1

4F ‘transoceanic’

bidir


2F/4F SPRing protection scheme2F/4F SPRing protection scheme

NE 1

NE 2

NE 3

NE 4

Working (Wk) Protection (Pr)

N.T. E.T.

N.T. E.T.

E.T.

E.T.

2F/4F scheme

In ‘2F’ topology, same transmission mean (fiber / ) carries both working and protection resources. If N is total number of resources (channels) available as ring line capacity, then:

- ‘working’ resources are 1 N/2 - ‘protection’ resources are N/2 + 1 N

In ‘4F’ topology, dedicated transmission mean (fiber / ) carries either working or protection resources. If N is total number of resources (channels) available as ring line capacity, then:

- ‘working’ resources are N - ‘protection’ resources are N

Each side of a node interfacing the ring is conventionally named ‘West’/’East

Each node of the ring is involved in protection activity (protocol handling, matrix configuration). Protocol message exchange always occurs between adjacent nodes along ‘protection’ resources

In Idle state (no protection required through the ring), N.T. is on working resources, E.T. may be configured on protection resources. Protocol signaling carries ‘No request’ code from each node to the adjacent one

‘IDLE’ state

W E

E

W

WE

W

E

‘Protection’ resources

‘Working’ resources


2F ‘classic’ SPRing – Ring Switch2F ‘classic’ SPRing – Ring Switch

NE 1

NE 2

NE 3

NE 4

E.T. squelched

E.T. squelched

N.T. recovered

E.T. squelchedN.T. recovered ‘Bridge’ to ‘x+N/2’ Protection resources

Bridge

Switch


‘Protection’ resources ‘N/2+1 N’

Pass-through

PATH‘S

HO

RT

’

‘LONG’

PA

TH

‘Switch’ to ‘x+N/2’ Protection resources

P.T.

‘Working’ resourcex





‘Ring Switch’ recovers Normal Traffic through ‘protection’ resources on the ‘LONG’ path, when both ‘working’ and ‘protection’ resources of a span are failure/degrade affected or when a ring command (Force / Manual)is applied.

- In 2F topology this scenario occurs anytime a failure/degrade affects at least one out of two transmission means of a span, or when a ring command is applied on that span.

During ‘ring switch’ all the Extra Traffics configured through the ring are ‘squelched’ (regardless of the actual use of that channel for Normal Traffic protection).

The following node macro-states are entered during protection activity:

Switching Macro-state entered by ‘end’ nodes of the span interested with switching criteria, both initiating a ‘ring switch’ by sending (tail end) to the adjacent ‘switching’ node, both on the ‘LONG’ and on the ‘SHORT’ path of the ring a ‘ring bridge request’, or acknowledging (head end), both on LONG / SHORT path a ‘ring bridge request’ destined to itself. In ‘classic’ application, only ‘switching’ nodes performs ring ‘Bridge&Switch’, on the base of APS signaling exchanged through the ‘LONG’ path(see yellow nodes in previous example)

‘Full’ Pass-through Macro-state entered by each node of the ring (not ‘switching’), by-passing ‘bridge request’ not destined to itself; performing also the ‘bidirectional’ by-pass (EW, W E) of ‘protection’ resources (Low Priority channels). ‘Pass-through’ nodes are also called ‘intermediate’ nodes.(see grey nodes in previous example)




NE 1

NE 2

NE 3

NE 4

E.T. squelched

E.T. squelched

N.T. recovered

E.T. squelchedN.T. recovered

Bridge

Bridge

Switch

Switch

P.T.

PATH

‘SH

OR

T’

‘LONG’

PA

TH

In ‘classic’ application (2F/4F) the protection path corresponds always to the ‘LONG’ path of the scheme: the propagation delay for the protected traffic is, then, always maximized. When applied to huge rings including ‘transoceanic’ links or ‘via satellite’ links, and depending on the type of service transported, this delay can lead to a final performance degradation of the service



P.T.


4F ‘transoceanic’ SPRing – Ring Switch4F ‘transoceanic’ SPRing – Ring Switch

NE 1

NE 2

NE 3

NE 4

E.T. squelched

E.T. squelched

N.T. recovered


Bridge

BridgeSwitch

Switch

Pass-through

PATH

‘SH

OR

T’

‘LONG’

PA

TH

In ‘transoceanic’ application (4F) the protection path in ‘ring switch’ condition, corresponds to the ‘LONG’ path of the scheme only when the protected Normal Traffic is configured between adjacent nodes.

With different traffic distribution (where node pass-through occurs) the protection path is limited to the portion of the ring, not fault affected, between nodes terminating the protected Normal Traffic.

Temporary squelching, if associated LP channels are not required for ‘ring switch’ connectivity


4F SPRing – Ring Switch - I4F SPRing – Ring Switch - I

‘Ring Switch’, in 4F topology occurs anytime a failure/degrade affects at least two out of four transmission means of a span, in such a way that both one ‘working’ and one

‘protection’ resources results fault affected or when a ring command is applied on that span. As for ‘2F ring’, Normal Traffic is recovered through ‘protection’ resources on the ‘LONG’ path.

In ‘classic’ (also called ‘terrestrial’) application, same behaviour already described about ‘2F’ ring’, same E.T. squelching policy and same node macro-states apply.

In ‘transoceanic’ application, current standard reference (SDH) states that during ‘ring switch’ all the Extra Traffics configured through the ring are ‘squelched’; after the ‘ring switch’ is performed, those Low Priority channels not used for Normal Traffic protection are re-connected to Extra Traffic.

This is a slow process possibly using ‘communication channels’ between the nodes of the ring, i.e. control plane, for E.T. re-configuration (protection protocol independent).

Both ‘distributed’ ring switch and Extra Traffic recovery is applicable, due to the knowledge of the whole ring connectivity at each node of the ring (see ‘Traffic Map’).



4F SPRing – Ring Switch - II4F SPRing – Ring Switch - II

Switching Macro-state entered by ’end’ node of the span interested with switching criteria, initiating a ‘ring switch’ by sending (tail end) to the adjacent ‘switching’ node, both on the ‘LONG’ and on the ‘SHORT’ path of the ring a ‘ring bridge request’, or acknowledging (head end), both on LONG/SHORT path a ‘ring bridge request’ destined to itself. Switching nodes performs ring ‘Bridge&Switch’ only when adding/dropping (terminating) Normal Traffic to be protected on the base of APS signaling exchanged through the ‘LONG’ path (see yellow nodes in previous example).

‘Full’ Pass-through Macro-state entered by each node of the ring (not ‘switching’), by-passing ‘bridge request’ not destined to itself. The same protocol specified in ‘classic’ application is used. ‘Pass-through’ nodes performs ring ‘Bridge&Switch’ only when adding/dropping (terminating) Normal Traffic to be protected on the base of APS signaling received by both switching nodes; otherwise, they realize the ‘bidirectional by-pass (EW, W E) of ‘protection’ resources (Low Priority channels). ‘Pass-through’ nodes are also called ‘intermediate’ nodes (see grey nodes in previous example).


SPRing APS channel contentSPRing APS channel content

Protocol parameters

• Request Type i.e. the request (failure / degrade / command) or state (‘No Request’ / WTR) to be signalled / acknowledged by opposite end of the span interested

• Destination Node i.e. the adjacent node addressed by APS signalling

• Source Node i.e. the node sourcing the APS signaling

• Path i.e. the portion of the ring interested by APS signaling, ‘short’ ,(span fault affected), or ‘long’, (the remaining spans of the ring)

• Bridge status i.e. ‘idle’, ‘bridge’ , ’bridge & switch’ matrix configuration


4F SPRing – Span switch4F SPRing – Span switch

NE 1

NE 2

NE 3

NE 4

E.T. kept

E.T. kept

N.T. recovered


Bridge

Switch

K - pass-through

PATH

‘SH

OR

T’

‘LONG’

PA

TH

The protection path corresponds always to the ‘SHORT’ path of the scheme: i.e. Normal Traffic is recovered through the same span along protection resource.

E.T. squelched

Temporary squelching in ‘transoceanic’ application, if associated LP channels are not required for ‘span switch’ connectivity

K - pass-through

‘Working’ resourcex ‘Bridge’ to ‘Protection’

resource x

‘Switch’ to ‘Protection’ resource x


4F SPRing – Span switch4F SPRing – Span switch ‘Span Switch’, in 4F topology (both ‘classic’ and ‘transoceanic’ applications) occurs anytime a failure/degrade affects only the ‘working’ transmission mean of a span in one or both directions or a span command is applied. Normal Traffic is recovered through the associated ‘protection’ resource of that span by using the same algorithm already described for ‘linear’ 1:N scheme.

During ‘span switch’ (both ‘classic’ and ‘transoceanic’ applications) all the Extra Traffics configured in the span fault affected are ‘squelched’; while remaining E.T. allocated in different spans of the ring are kept. In ‘transoceanic’ application, those L.P. channels not required for ‘span switch’ connectivity, then the associated E.T., are restored after ‘span switch’ is performed (same way already described for ‘ring switch’).


Switching Macro-state entered by ’end’ node of the span interested with switching criteria, initiating a ‘span switch’ by sending (tail end) to the adjacent ‘switching’ node, both on the ‘LONG’ and on the ‘SHORT’ path of the ring a ‘span bridge request’, or acknowledging (head end) , both on LONG/SHORT path, a ‘span bridge request’ destined to itself. Only switching nodes performs span ‘Bridge&Switch’ (see yellow nodes in the example).

‘K byte’ Pass-through Macro-state entered by each node of the ring (not ‘switching’), by-passing ‘bridge request’ sent on the ’LONG’ path by ‘switching’ node. The same protocol specified in ‘classic’ application is used.

‘K byte’ Pass-through nodes do not perform any reconfiguration of local connectivity. ‘K-byte Pass-through nodes are also called ‘intermediate’ nodes. (see grey nodes in the example)


Squelching in ring schemesSquelching in ring schemes

Extra Traffic squelchingThe same considerations already reported for linear schemes apply: the access to the ‘Low Priority’ by Normal Traffic might lead to traffic misconnected, if no specific mechanism was implemented: Extra Traffic squelching performed before any matrix re-configuration (Bridge/Switch/Pass-Through) avoids this potential problem.

In ring schemes, Extra Traffic squelching implies that nodes ‘dropping’ Extra Traffic forces a defined alarm signal (AIS) towards the Extra Traffic user, both in case they enter the ‘switching’ (due to a ring/span switch) or the ‘pass-through’ state.

Besides, nodes performing ‘span switch’ have also to insert the alarm signal (AIS) towards the ring, on ‘Low Priority’ channels carrying possible E.T. passing from the ‘protected’ span through the node.



NE 1

NE 2

NE 3

NE 4

N.T. recovered


Span Br&Sw

E.T. squelched on adjacent span

Span Br&Sw

E.T. squelched (by NE 4)

‘4F’ topology



Ring squelchingThis type of squelching is needed in 2F/4F ‘classical’ SPRing, when a node of the ring becomes ‘isolated’ either for node failure or for multiple failures requiring ‘ring switch’ at both sides.In this case, due to the ring switch action performed by nodes adjacent the isolated one (i.e. ‘switching’ nodes), possible traffics terminated into isolated node and allocated on same ‘High Priority’ channels for both sides (West/East), would be misconnected by accessing the same ‘Low Priority’ channels.

This condition is avoided by inserting at the ‘switching’ nodes AIS signal on ‘protection channels’, making them unavailable through the ring (the AIS insertion is performed bidirectionally).



NE 1

NE 2

NE 3

NE 4

N.T. #1

N.T. #2

N.T. #1

N.T. #2

W E

E

W

WE

W

E

Wk Ch. #x

Wk Ch. #x

Pr Ch. #x+ N/2

Pr Ch. #x+ N/2

Same ‘Protection’ channel accessed by switching nodes (NE1-NE3) through Ring Br&Sw with no squelching policy, permanent misconnection produced between N.T. #1 and N.T. #2



NE 1

NE 2

NE 3

NE 4

N.T. #1

N.T. #2

N.T. #1

N.T. #2

W E

E

W

WE

W

E

Wk CH. #x

Wk CH. #x

Pr CH. #x+ N/2

Pr CH. #x+ N/2

Misconnection avoided through Low Priority channel squelching (AIS injection) at switching nodes


Total N paths

N/2 ‘wk‘ resources

SNC vs SPRingSNC vs SPRing

N/2 ‘wk‘ resources

N/2

‘w

k‘ r

eso

urc

es

N/2

‘wk‘ re

sou

rces

N ‘wk‘ resourcesUp to 2xN paths Up to N paths

WITH ‘ADJACENT’ TRAFFIC ALLOCATIONTHE PROTECTION SCHEME WITH MOST PROFITABLE BANDWIDTH

OCCUPATIONIS…

WITH ‘ADJACENT’ TRAFFIC ALLOCATIONTHE PROTECTION SCHEME WITH MOST PROFITABLE BANDWIDTH

OCCUPATIONIS…

SPRING

WITH ‘HUBBED’ TRAFFIC ALLOCATIONTHE PROTECTION SCHEME WITH MOST PROFITABLE BANDWIDTH

OCCUPATIONIS…

WITH ‘HUBBED’ TRAFFIC ALLOCATIONTHE PROTECTION SCHEME WITH MOST PROFITABLE BANDWIDTH

OCCUPATIONIS…

SNC


SNC vs SPRingSNC vs SPRing

Access networ

k

Accessnetwork

e2e protection

Ring protection


ContentContent





> Protection Schemes in Transport Networks• Restoration



Centralized RestorationCentralized Restoration

Operating System

Transport Network

Centralized restoration is historically an application of network management in Transport Network (i.e. SDH), where the amount of operators was very limited and a complete geographical network (e.g. country) used to be configured and controlled by a single(few) manager(s).

Centralized Restoration is an application provided to an operator by a ‘single’ vendor.

Centralized Restoration is a network application not standardized, i.e. proprietary applications are provided by each vendor.

Network

Element

ECC

Generic Path

DCN Network


System Evolution - Distributed RestorationSystem Evolution - Distributed Restoration

Distributed Restoration is historically an application coming from Data Network survivability , where the amount of ‘Private Networks’ (i.e. Data) is unlimited and it becomes unfeasible to configure and control different networks connected to each other through a single (few) manager(s).

Distributed Restoration is an application thought for a ‘multi’ vendor enviroment.The de-regulation in ‘Public Networks’, has made ‘distributed management’, then ‘distributed restoration’ attractive also for Transport Network. This implies a standard activity in order to align applications from different vendors.

Transport Network

ECC

Generic Path

DCN NetworkDCN Network

Distributed Manger

NE from vendor ‘a’

NE from vendor ‘b’


ContentContent






> APPENDIX: Protection schemes in SDH/ Sonet/ OTN• Layering• Network• Frame Structure• Schemes• Network Applications• Reference Standards


SDH layeringSDH layering

MSTSk

MSASk

HPOMHSUT

HTCMHTCT

MSPC

HPC

LO PATH/TRAIL

HO PATH/TRAIL

MS TRAIL

LAYERS

RSTSk

PHYSk

MSASo

MSTSo

RSTSo

PHYSo

RS TRAIL

PHYSICAL

HPTSoHPTSk

CLIENT CLIENT

HOTrail

HPASk

LPOMLSUT

LTCMLTCT

LPC

LPASo

LPTSoLPTSkLO

Trail


SDH NetworkSDH Network

2R 3R

ADM

ADM ADM

STM-N

MS trail

RS trail RS trail

STM-N STM-N

RS trail

MS trail

HO / LO PATH (TRAIL)

KEYTM Terminal MultiplexerLE (2R) Line Equipment: repeater (no Ck recovery)LE (3R) Line Equipment: regenerator (Ck recovery)DXC Digital Cross-ConnectADM Add Drop Multiplex

DXC

DXCTM

TM

STM-

NRS trail

MS trail

DXCTM

TM


STM-N Frame Structure

RSOH AUG

MSOH

VC4POH

VC3POH

VC12POH

VC3POH

Administrative pointers Two ways of SDH multiplexing

High OrderHigh Order

Low OrderLow Order

Low OrderLow Order


STM-N

KEYRSOH Regenerator Section OverHeadMSOH Multiplex Section OverHead AUG Administrative Unit GroupVC Virtual ContainerPOH Path OverHead


SDH Protection Schemes - Summary

LAYER SCHEME TRIGGERING FAULT

SWITCH COM. TIME

REFERENCE STANDARDS

MS Trail

Linear 1+1 MSP (uni/bid)

MS layer defects (SF/SD)

50 ms

ITU-T G.841

ITU-T G.783

ITU-T G.808.1

Linear 1:N MSP (uni/bid)


50 ms

2F/4F ‘classic’ MS-SPRing (bid)


50 ms

4F ‘transoceanic’ MS-SPRing (bid)


300 ms

HO/LO Path

Linear 1+1 SNCP/I (uni)

MSA/HPA defects (SF AIS/LOP)

50 ms

Linear 1+1 SNCP/N (uni)

MSA/HPA defects + HPOM/LPOM defects (SF/SD)

50 ms

Linear 1+1 SNCP/S (uni)

HTCM/LTCM defects (N1/N2 byte SF/SD)

50 ms

HO/LO Trail

Linear 1+1 VC Trail (uni/bid)

SNCP/N defects (SF/SD)

50 ms


SDH Multiplex Section Protection SDH Multiplex Section Protection

Protection Scheme

Linear 1+1 MSP - Linear 1:N MSP

Layer MS Trail

Switching Mode Unidirectional / Bidirectional

Operation Mode Revertive / Not Revertive

W.T.R. timer (Revertive mode)

5 12 min

APS channel (Bidirectional Mode)

K1 – K2 byte of MSOH

Switching Criteria/ States (decreasing priority level)

Clear SF on Protection Lockout – Pr FS SF High Priority SF Low Priority SD High Priority SD Low Priority MS WTR EX NR

N x Clear N x Lockout – Wk (in 1:N scheme only)


50 ms (line/NE propagation delay not included)

Hold-Off timer NOT DEFINED by ITU-T G.841


SDH Multiplex Section Protection SDH Multiplex Section Protection Protection Scheme

2/4F ‘classic’ MS-SPRing - 4F ‘transoceanic’ MS-SPRing (ring)

Layer MS Trail

Switching Mode Bidirectional

Operation Mode Revertive


NOT DEFINED


K1 – K2 bytes of MSOH

Switching Criteria/ States* (decreasing priority level)

Clear LP-S (or SF-P) FS-S FS-R SF-S SF-R SD-P SD-S SD-R MS-S MS-R WTR EX-S EX-R NR

Clear LW-S

Clear LW-R


50 ms for ‘classic’ application (1200 Km/16 NE’s propagation delay included)

300 ms for ‘transoceanic’ application

Hold-Off timer NOT REQUIRED by ITU-T G.841

* - S span / P protection / R ring


SDH Multiplex Section Protection – SDH Multiplex Section Protection – SF / SD SF / SD

RSOH

MSOH

Administrative pointers

STM-N

• K2 byte (bits 5-8) MS-AIS (due to LOS, LOF) (SF)• B2 bytes B2 Exber (SF) / B2 Signal Degrade (SD)


APS channel in SDH MSP schemesAPS channel in SDH MSP schemes

RSOH

Pointers

STM-N

K1 K2

MSOH

bits 1-4

Request Type Req. Ch. Id. Br. Ch. Id. (Bridge Status)

Arch. Mode

RSOH

Pointers

STM-N

K1 K2

MSOH

bits 1-4

Request Type Source Node ID

Destination Node ID Path

Bridge Status


SDH MS Protection ApplicationsSDH MS Protection Applications

2R 3R

ADM

ADM ADM

MS trail MS trail

DXC

DXCTM

TMDXC

TM

TM

MS trail

Linear 1+1 MSP Linear 1:N MSP

2/4 FMS-SPRing

Working

Protection


SDH SNC ProtectionSDH SNC Protection

Protection Scheme

Linear 1+1 SNCP/I - ‘Inherent’ based on MSA (HO) or HPA defects (LO)

Layer HO / LO Path

Switching Mode Unidirectional



5 12 min; 1 sec step


NOT APPLICABLE


Clear Lockout-Pr Forced Switch SF (SSF) Manual Switch WTR NR


50 ms (due to the lack of APS protocol, line propagation delay not applicable)

Hold-Off timer 0 10 sec; 100 ms step


SDH SNC Protection – SDH SNC Protection – SF (SNCP/I)SF (SNCP/I)

RSOH

MSOH

STM-N • H1, H2 bytes AUAIS / AULOP (HO VC3/VC4 SSF SF)• H1, H2 bytes TUAIS / TULOP (LO VC3 SSF SF)

H1 H2 H3

V5

K4

Stuff byte

V1

V2

V3

V4

• V1, V2 bytes TUAIS / TULOP (LO VC12 SSF SF)

VC 12



Protection Scheme

Linear 1+1 SNCP/N - ‘Not Intrusive’ based on MSA / HPA defects + POH defects (HPOM / LPOM)

Layer HO / LO Path






NOT APPLICABLE


Clear Lockout-Pr Forced Switch SF SD Manual Switch WTR NR





SDH SNC protection – SF / SD (SNCP/N)SDH SNC protection – SF / SD (SNCP/N)

V5

J2

N2

K4

Stuff byte

VC 12 POH

• J1 Trace Identifier Mismatch (SF)• B3 B3 Exber (SF) / B3 Signal Degrade (SD)• C2 Signal Label Mismatch (SF) / UNEQ (SF)

• V5 Bip2 Exber (SF) / Bip2 Signal Degrade (SD) / Signal Label Mismatch (SF) / UNEQ (SF)• J2 Trace Identifier Mismatch (SF)• K4 (bit 1) ‘Extended’ Signal Label Mismatch (SF)

140bytes

VC 3/4 POH

J1B3C2G1F2

K3N1

H4F3

HO / LO SSF (SF) (AUAIS / TUAIS

AULOP / TULOP)+


SDH SNC Protection ApplicationSDH SNC Protection Application

2R 3R

ADM

ADM ADM

HO/LO Sub-NetworkHO/LO

Sub-Net.

DXC

DXCTM

TMDXC

TM

TM

HO/LO SNCP N

HO/LOSNCP N

Working

Protection

HO/LO Sub-Network

HO/LO SNCP I



Protection Scheme

Linear 1+1 SNCP/S - ‘Subsystem’ based on N1 byte (HO-POH) and N2 byte (LO-POH) monitoring through HTCM block or LTCM block

Layer HO / LO Path






NOT APPLICABLE


Clear Lockout-Pr Forced Switch SF SD Manual Switch WTR NR





SDH SNC Protection – SF / SD (SNCP/S)SDH SNC Protection – SF / SD (SNCP/S)

VC 3/4 POH

V5

J2

N2

K4

Stuff byte

VC 12 POH

J1

K3N1

• N1 Bip8 Signal Degrade (SD) / UNEQ (SF) / Loss of Tandem Connection (SF) / Trace Identifier Mismatch (SF)

HO / LO SSF (SF) (AUAIS / TUAIS

AULOP / TULOP)+

• N2 Bip2 Signal Degrade (SD) / UNEQ (SF) / Loss of Tandem Connection (SF) / Trace Identifier Mismatch (SF)


SDH SNCP/S ApplicationSDH SNCP/S Application

DXC

DXC DXC

DXC

DXC

DOMAIN A

DOMAIN B

DOMAIN C

Protection

Working

HTCT/LTCT

HTCT/LTCT

HO / LO VC TC(intermediate monitoring)

HO / LO VC trail (end-to-end monitoring)


SDH Trail ProtectionSDH Trail ProtectionProtection Scheme

Linear 1+1 HO / LO VC Trail (linear 1:1 f.f.s.)

Layer HO / LO Trail

Switching Mode Unidirectional / Bidirectional f.f.s.





K3 (bits 1-4; APS protocol T.B.D.) (HO)

K4 (bits 3-4; APS protocol T.B.D.) (LO)


Clear Lockout-Pr Forced Switch SF* SD* Manual Switch WTR NR


50 ms (line/NE’s propagation delay is T.B.D.)


* - As for SNCP/N


SONET Layering (Bellcore GR-253)SONET Layering (Bellcore GR-253)

Map Payloadand Path OH

into SPE

Map SPEand Line

OHinto

internal signalMap

internal signal and Section OH

into STS-N signal

Optical Conversion

STS-NSignal

Light Pulses

Payload and Path Overhead

SPE and Line Overhead

STE RegeneratorTerminal Terminal

PHYSICAL

SECTION

LINE

HO/LO PATH

LAYERS

Payload (DS1, DS2, DS3DS4NA, Video, etc.)


SONET NetworkSONET Network

3R

ADM

ADM ADM

Line

Section

OC-M OC-M

Section

Line

STS path / VT PATH

KEYTM Terminal MultiplexerRGTR Regenerator (3R)DCS Digital Cross-ConnectADM Add Drop Multiplex

DCS

DCSTM

TM

OC-MSection

Line

DCSTM

TM

Section

OC-M

The following matches may be considered between SDH and SONET technology:STM-N OC-M (where M=3N)RS SectionMS LineHO PATH STS pathLO PATH VT path


VT6POH

Low OrderLow Order

VT3POH

Low OrderLow Order

SONET Frame StructureSONET Frame Structure

SectionOverhead

LineOverhead

STS1POH

STS1 pointers


OC-N / STS-N

Transport Overhead

VT2POH

Low OrderLow Order

VT

1.5POH

Low OrderLow Order


SONET Protection Schemes - Summary


SWITCH COM. TIME

REFERENCE STANDARDS

Line Linear 1+1 APS (uni/bid)

Line layer defects (SF/SD)

50 ms

Bellcore GR-253 (linear APS)

Bellcore GR- 1400 (UPSR)

Bellcore GR-1230 (BLSR)

Linear 1:N APS (uni/bid)


50 ms

2F/4F ‘classic’ MS-SPRing (bid)


50 ms

HO/LO Path

Linear 1+1 UPSR (uni)

STS/VT pointer processing defects (AIS/LOP) + STS/VT POH defects

50 ms


SONET Line Protection SONET Line Protection

Protection Scheme

Linear 1+1 APS - Linear 1:N APS

Layer Line




5 12 min; 1 min step


K1 – K2 byte of Line Overhead


Clear SF on Protection Lockout – Pr FS SF High Priority SF Low Priority SD High Priority SD Low Priority MS WTR EX NR

N x Clear N x Lockout – Wk (in 1:N scheme only)



Hold-Off timer NOT DEFINED by Bellcore GR-253


SONET Line Protection SONET Line Protection Protection Scheme

2/4F Bidirectional Line Self–healing Ring (BLSR)

Layer Line

Switching Mode Bidirectional

Operation Mode Revertive


5 12 min; step 1 min (optionally, lower bound of 0 min)


K1 – K2 bytes of MSOH

Switching Criteria/ States* (decreasing priority level)

Clear LP-S (or SF-P) FS-S FS-R SF-S SF-R SD-P SD-S SD-R MS-S MS-R WTR EX-S EX-R NR

Clear LW-S

Clear LW-R


50 ms for ‘classic’ application (1200 Km/16 NE’s propagation delay included)


* - S span / P protection / R ring


SONET Line Protection – SONET Line Protection – SF / SD SF / SD

SectionOverhead

LineOverhead

STS1 pointers

OC-N

Transport Overhead

• K2 byte (bits 5-8) AIS-L (SF)• B2 bytes B2 Exber (SF) / B2 Signal Degrade (SD)

LOS (Loss of Signal) and LOF (Loss of Frame) are considered as direct triggers (both as SF) for Line protection scheme

OPTICAL SIGNAL ONLY


APS channel in SONET Line schemesAPS channel in SONET Line schemes

SectionOH

Pointers

OC-N

K1 K2

bits 1-4

Request Type Source Node ID

Destination Node ID Path

Bridge Status

SectionOH

Pointers

OC-N

K1 K2

LineOH

bits 1-4


Arch. Mode

LineOH


SONET Path ProtectionSONET Path ProtectionProtection Scheme

Linear 1+1 Unidirectional Path Self-healing Ring (UPSR) - based on STS / VT pointer processing defects + STS POH / VT POH defects

Layer HO / LO Path




5 12 min; 1 min step


NOT APPLICABLE


Clear Lockout-Pr Forced Switch AIS;LOP;UNEQ* Ex BER** PDI-P^ SD+ Manual Switch WTR NR




* - ‘P’ for STS path (HO) / ‘V’ for VT path (LO)** - Excessive STS path BER (HO) / Excessive VT path BER (LO)

^ - Applicable only to STS path+ - STS Signal Degrade (HO) / VT Signal Degrade (LO)


SONET Path Protection – SF / SD SONET Path Protection – SF / SD

V5

J2

Z6

Z7

Stuff byte

VT POH

• V5 Bip2 Exber (SF) Bip2 Signal Degrade

(SD) Uneq (SF)

STS1 POH

J1B3C2G1F2

Z4Z5

H4Z3

SectionOverhead

LineOverhead

OC-N / STS-N

STS1 pointers

• H1, H2 bytes AIS-P / LOP-P (SF)

V1

V2

V3

V4

VT pointer

VT

STS1

• V1, V2 bytes AIS-V / LOP-V (SF)

• B3 B3 Exber (SF)B3 Signal Degrade

(SD)• C2 UNEQ (SF)


OTH LayeringOTH Layering

OMSSk

OCHSk

OCHPOM

OMSnP

OCH_C

ODUk_CDIGITAL

PATH

ELECTRO/OPTICALCONVERSION

OPTICAL CHANNEL (ASSIGNMENT & MULTIPLEXING

LAYERS

OTSSk

OCHSo

OMSSo

OTSSo

MULTIPLEXED SIGNALTRANSMISSION

OTUkSk ODUkSo OTUkSoODUPOM

ODUkSk

OPUkSkOPUkSo

CLIENT CLIENT

TCTTCM

OMS/OCH_A OMS/OCH_A


OTH NetworkOTH Network

3R

OADM

STM-N

OCH, OTUk trailOMSn trailOTSn trail

ODUk path (trail)

OXCLT

LTOXC

LT

LT

KEYLT Line Terminal (optical channel multiplexing)OADM Optical Channel Add/Drop MultiplexerOXC ODU Cross-Connect3R Wavelength assignment/regeneration (O/E/O, w/ clock recovery)R repeater (Optical Amplifier)

DXC

IP

LT

IP data

R

OMSn trailOTSn trail OTSn trail

OCH, OTUk trail

LT

3R

OCH, OTUk trail

LT

OMSn trailOTSn trail

LT

3R

OMSn trailOTSn trail

DXC

STM-N OSn


OTH Frame StructureOTH Frame Structure

Optical Transport Module

OPSn

OTUk

Optical Channel (OCh)

Optical Channel Carrier (OCC)

ODUk FECOH

OCh Transport Unit (OTUk)

OPUkOH

OCh Data Unit (ODUk)

ClientOH

OCh Payload Unit (OPUk)

Dig

ital dom

ain

Associa

ted

overh

ead

Optical Supervisory Channel OSC

Non

-associa

ted

overh

ead

OMSn

OTSn

Optical Multiplex Section

Optical Transmission Section

OPS0 Optical Physical Section

Op

tica

l d

om

ain

SDH/SONET

FDDI ATM IP GbE clear channel

OTS OH

OMS OH

OCh OH OCH

2.5 Gb/s K=1 10 Gb/s K=2 40 Gb/s K=3

OCC OCC


OTH Protection Schemes - Summary


SWITCH COM. TIME

REFERENCE STANDARDS

OMS Trail

Linear 1+1 OMS (uni)

OMS layer LOS + OMS OH OOS defects (SF/SD)

50 ms

ITU-T G.873.1 (Linear protection)

ITU-T G.798

ITU-T G.808.1 (under definition)

OCH Trail

Linear 1+1 OCH SNC/N (uni)

OCH layer LOS (through OCH POM) + OCH OH OOS defects (SF/SD)

50 ms

ODUk Path

Linear 1+1/1:N ODUk SNCP/I (uni/bid)

OTUk defects (SF/SD)

50 ms

Linear 1+1/1:N ODUk SNCP/N (uni/bid)

ODUk defects (through ODUk POM) (SF/SD)

50 ms

Linear 1+1 SNCP/S (uni/bid)

TCMi defects (up to six TC independent levels in ODUk OH)

50 ms


OTH OMS ProtectionOTH OMS Protection

Protection Scheme

Linear 1+1 OMS (scheme under definition - based on OMS LOS detection and OMS-OH OOS defects detection)

Layer OMS trail




5 12 min; (T.B.D. step)


Not Required (since ‘unidir’ switching mode)


Clear SF on Protection (TSF-P) Lockout – Pr FS SF (TSF-P) SD (TSF-O)* MS WTR NR




* - TSF-O may be disabled by provisioning


OTH OMS Protection – OTH OMS Protection – SF / SD SF / SD

OSC

OTM

Overh

ead

Sig

nal (O

OS

)

OTS OH

OMS OH

OCh OH

OPSnOMSn

OTSn

OCH

OCC OCC

OTU

Logical content for protection purposeForward Defect Indication Overhead TSF-O (SD)(FDI-O due to ‘Loss of Signal Overhead’ or ‘Trace Identifier Mismatch’ detected, locally or remotely, at OTS OH level)Forward Defect Indication Payload TSF-P (SF)(FDI-P due to ‘Loss of Signal Payload’ / ‘Trace Identifier Mismatch’ / ‘Payload Missing Indication’ detected, locally or remotely, at OTS OH level)

Loss of Signal Payload TSF-P (SF) (LOS-P)


OTH OMS Protection ApplicationOTH OMS Protection Application

3R

OADM

STM-N

OMSn trail

OXCLT

LTOXC

LT

LT

DXC

IP

LT

IP data

R

OMSn trail

LT

3R

LT LT

3R

OMSn trail

DXC

STM-N

Linear 1+1 OMS

OSC (OMS-OH OOS)

Same ’s bundle

Wk 1 N

OSC

Linear 1+1 OMS

Pr 1 N

x2

x2

WK ’s

PR ’s

Wavelengthaccomodation


OTH OCH ProtectionOTH OCH Protection

Protection Scheme

Linear 1+1 OCH SNC/N - ‘Not Intrusive’ based on OCH LOS detection through POM and OCH-OH OOS defects

Layer OCH trail






Not Applicable


Clear Lockout-Pr Forced Switch SF (TSF-P) SD (TSF-O)* Manual Switch WTR NR




* - TSF-O may be disabled by provisioning


OTH OCH Protection – OTH OCH Protection – SF / SD SF / SD

OSC

OTM

Overh

ead

Sig

nal (O

OS

)

OTS OH

OCH OH

OMS OH

OPSnOMSn

OTSn

OCC OCC

OTU

Logical content for protection purposeForward Defect Indication Overhead TSF-O (SD)(FDI-O due to ‘Loss of Signal Overhead’ or ‘Trace Identifier Mismatch’ detected, locally or remotely, at OTS OH level and confirmed at OMS level)Forward Defect Indication Payload TSF-P (SF)(FDI-P due to ‘Loss of Signal Payload’ / ‘Trace Identifier Mismatch’ / ‘Payload Missing Indication’ detected, locally or remotely, at OTS OH level or due to ‘Loss of Signal Payload detected at OMS level)

OCHLoss of Signal Payload TSF-P (SF) (LOS-P)


OTH OCH Protection ApplicationOTH OCH Protection Application

3R

OADM

STM-N

OCH trail

OXCLT

LTOXC

LT

LT

DXC

IP

LT

IP data

R

OCH trail

LT

3R

LT

Linear 1+1 OCH

OSC (OCH OH-OOS)

Same ’s bundle

OXC

Linear 1+1 OCH

Wk 1 N

Pr 1 N

OSC (OCH OH-OOS)

x2

x2x2

WK ’s

PR ’s

WK ’s

PR ’s

x1WK ’s

PR ’s

Optical Fiber

Possible wavelengthaccomodation


OTH ODUk ProtectionOTH ODUk Protection

Protection Scheme

Linear 1+1 – Linear 1:N ODUk SNC/I - ‘Inherent’ based on ‘server’ OTUk defects driving ODUk matrix re-configuration

Layer ODUk path






APS / PCC bytes of ODUk Overhead


Clear Lockout-Pr Forced Switch SF (SSF) SD (SSD) Manual Switch WTR NR





OTH ODUk SNC/I protection – OTH ODUk SNC/I protection – SF / SD SF / SD

OTUk

ODUk FECOH

OCH

FEC

1

2

3

4

1 2 3 4 5 6 7 8

FAS

Column #

MFAS SM

9 10 11 12 13 14

Row

#

ODU Overhead

RESGCC0

• FAS LOF (SF)• MFAS LOM (SF)• TTI Trace Identifier Mismatch (SF)• BIP-8 DEG (SD) TTI BIP8

1 2 3SM

BEI/BIAE BD

I

RES

1 2 3 4 5 6 7 8

IAE

KEYFAS: Frame Alignment Signal (3xF6h,

3x28h)MFAS: Multi-frame alignment signal

(0..255)SM: Section Monitoring overhead

15…………..3824 3825…………4080


APS channel in OTN linear protectionAPS channel in OTN linear protection


Arch. Mode

1

2

3

4

1 2 3 4 5 6 7

RES

Row

#

EXP

TCMACT TCM6

TCM3 TCM2 TCM1

GCC1 GCC2 RES

FTFL

PM

OPUkoverhead

Frame Alignment Overhead

APS/PCC

8 10 11 12 13 14 15

OTUk Overhead

169

TCM5 TCM4

Bytes 5-6-7 Automatic Protection Switching / Protection Communication ChannelByte 8 reserved for future use

ODUk


OTH ODUk SNC/I Protection ApplicationOTH ODUk SNC/I Protection Application

OADM

OXCLT

LTOXC

LT

LT

IP

LT

IP data

R

OTUk trail

3RLinear 1+1 ODUk SNC/I

OXCSTM-N

DXC

LT LT

x2

x2x2

WK ’s

PR ’s

WK ’s

PR ’s

x1WK ’s

PR ’s

Optical Fiber


OTUk trail

Linear 1+1 ODUk SNC/I



Protection Scheme

Linear 1+1 – Linear 1:N ODUk SNC/N - ‘Not Intrusive’ based on ODUk defects monitored through ODUk POM

Layer ODUk path






APS / PCC bytes of ODUk OH


Clear Lockout-Pr Forced Switch SF (TSF) SD (TSD) Manual Switch WTR NR





OTH ODUk SNC/N Protection – OTH ODUk SNC/N Protection – SF / SD SF / SD

1

2

3

4

1 2 3 4 5 6 7

RES

Row

#

EXP

TCMACT TCM6

TCM3 TCM2 TCM1

GCC1 GCC2 RES

FTFL

PM

OPUkoverhead


APS/PCC

OPUkOH

OTUk

ODUk FECOH

• STAT Locked Defect (SF) / ODUkAIS (SF)• TTI Trace Identifier Mismatch (SF)• BIP-8 DEG (SD)

TTI BIP81 2 3

PM

BEI BD

I

STAT

1 2 3 4 5 6 7 8

8 10 11 12 13 14 15

OTUk Overhead

169

TCM5 TCM4

KEYPM: Path

Monitoring

STAT: Status


OTH ODU SNC/N Protection ApplicationOTH ODU SNC/N Protection Application

OADM

ODUk path

OXCLT

LTOXC

LT

LT

IP

LT

IP data

R

3R

OXCSTM-N

DXC

LT LT

Linear 1+1 ODUk SNC/N

x2

x2x2

WK ’s

PR ’s

WK ’s

PR ’s

x1WK ’s

PR ’s

Optical Fiber




Protection Scheme

Linear 1+1 – Linear 1:N ODUk SNC/S - based on TCMi defects monitored at ODUk OH

Layer ODUk path






APS / PCC bytes of ODUk OH


Clear Lockout-Pr Forced Switch SF (TSF) SD (TSD) Manual Switch WTR NR





OTH ODUk SNC/S Protection – OTH ODUk SNC/S Protection – SF / SD SF / SD

1

2

3

4

1 2 3 4 5 6 7

RES

Row

#

EXP

TCMACT TCM6

TCM3 TCM2 TCM1

GCC1 GCC2 RES

FTFL

PM

OPUkoverhead


APS/PCC

OPUkOH

OTUk

ODUk FECOH

• STAT Locked Defect (SF) / AIS (SF) / LTC (SF)• TTI Trace Identifier Mismatch (SF)• BIP-8 DEG (SD) TTI BIP8

1 2 3

TCMi

BEI/BAEI BD

I

STAT

1 2 3 4 5 6 7 8

8 10 11 12 13 14 15

OTUk Overhead

169

TCM5 TCM4

KEYTCM: Tandem Connection MoniitoringSTAT: Status

Up to six independent TC

levels monitored/termin

ated


OTH ODUk SNC/S Protection ApplicationOTH ODUk SNC/S Protection Application

Operator A

Operator B

User

Working

Protection

End-to-End path supervision (PM)

User QoS supervision (TCM1)

User

Border of the OTNClient mapping into ODU

Border of the OTNClient mapping into ODU

TCM3 trail

Linear 1+1 ODUk SNC/S (B)

TCM2 trail

Linear 1+1 ODUk SNC/S (A)

Documents

Transport Network Protection