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Self-Healing Network

ZTE UniversityTransmission Course Group


Self-Healing Network Overview

Chain Protection

Ring Protection

Course Objectives


Self-Healing Network Overview


What is Self-Healing Network?

Self-Healing Network:

It is a network which can automatically resume its loaded services within a very short time in case of fault.

Its terminal users do not notice any service interruption.

* Self-healing can only recover the failed services through the standby channel, but it can not correct or replace the components and the lines with fault.


Self-Healing Network Basic Principle

When the working route fails or experience problems, services will be switched to the protecting route automatically within a very short time (


Self-Healing Network Classification

Classification

Based on Topology Train or Chain Network Service Protection Ring Network Service Protection Inter-Ring Service Protection

Based on Protection Method Multiplex Section Protection (MSP) Path Protection (PP) Logical Subnet Protection


Chain Network Protection Types

1+1 Path Protection

1+1 Multiplex Section Protection

1:1 Multiplex Section Protection


Chain Network 1+1 Path Protection

OL

OL

TR OL

OL

TR

At sending end, the STM-N signal is sent simultaneously over both segments of the work and protect.At receiving side, only one (work or protect) path is selected based on quality.Send Together Receive One.

work route

protect routework or protect

CS CS


Chain Network 1+1 Multiplex Section Protection

OL

OL

TR OL

OL

TR

At sending end, the STM-N signal is sent simultaneously over both segments of the work and protect.At receiving side, only one (work or protect) path is selected based on quality.Send Together Receive One.

work route

protect routework or protect

CS CS


Chain Network 1:1 Multiplex Section Protection

OL

OL

Work CSOL

OL

CS

Protection

Work

ProtectionThe 1:1 structure is the subset of the 1:N (where N=1) structure.It has the capacity to work in the 1+1 structure and to interconnect with the 1+1 structure of the other end.


Self-Healing Networks

Multiplexing segment 1:1 protection is different from multiplexing segment 1+1 protection. The working payload is transmitted through the working path while the protection path can be used to carry extra payload which is of inferior class.

When the working path fails, the extra payload on the protection path will be superseded by the working payload according to APS protocol. Thus the working payload is protected.

In normal working 1:1 comes up to 2+0.


Automatic Protection Switch

source end

source end

PS

PS

WORK

PROTECT

K1

K1,K2

K2

5a

5b

WORKING PATH

PROTECTION PATH

2

3

4

1

7 6


Ring Network Protection


Basic Ring Network Protection Types

2-fiber Unidirectional Path Protection Ring

2-fiber Bidirectional Multiplex Section Protection Ring

4-fiber Bidirectional Multiplex Section Protection Ring


2-Fiber Unidirectional Path Protection Ring

It adopts 1+1 protection mode, the switching criteria is PATH-AIS, & APS protocol is not needed.

At the source NE, the payload is send to the working path and protection path simultaneously. The destination NE detect and compare the coming signal from both paths , then determine to receive the payload of better quality.

AC

CA AC

AB

CD

CA

W1

W1

P1

P1

CA AC

AB

CD

W1

P1

P1

W1

CA AC

switching



CS

OL OL

EP

R

RT

T

CS

OL OLEPR

RT

T



OL OLR

RT

T

Receive One

Send TogetherEP

CS

Protection Path

Working Path


2-Fiber Bidirectional MS Protection Ring

Definitions:

2 fiber: Two fibers between a pair of nodes

Bi-direction: Service between two NEs use the same section of the network and are transmitted by reverse direction

Multiplexing Section: Protection based on MS, protect the payload part, use APS to start the protection.


Working Principle

S1/P2

S2/P1A

C

BD

Working pathS1 & S2; in normal situations, service is transmitted along the working path. The first half of one fiber is working path. Taking STM-16 as an example, 1-8 AU4 are used for working path.


Working Principle

S1/P2

S2/P1A

C

BD

Protecting PathP1 & P2, Services transmits along the protection path after switch over. The last half part of the fiber is used as protecting path. Taking STM-16 as example, 9-16 AU4 are used as protecting path.


Working Principle

S1/P2

S2/P1A

C

BDRelationship between working & protecting pathsThe protecting path of one direction protect the working path of the other direction, i.e, P1 protects S1, & P2 protects S2.


Working Principle

Use S1 and S2 to transmit services.

Service AC is sent in S1 through path A->B->C

Service CA is sent in S2 through path C->B->A

P1 and P2 can be used to send extra service now.

AC TxS1/P2

S2/P1A

C

BD

AC RxCA Tx

CA Rx


Switching Conditions

Auto Switch Conditions:

LOS, LOF, MS-AIS, Signal Degrade


Switching Procedure

SwitchIf the fiber between B and C is broken, switch occurs in B and C

B node: service AC crosses from S1 to P1, and sent through A->B->A->D->C

C node: service CA crosses from S2 to P2, and sent through C->D->A->B->A

AC TxS1/P2

S2/P1

BD

A

C

AC RxCA Tx

CA Rx


Features of 2 Fiber Bidirectional MSP Ring

Advantages: time slot protection, Time slots between two nodes can be reused, increasing the transmission capacity. Standby path P1 and P2 can be used to transmit extra service.

Disadvantages: longer switching time due to APS protocol & adopt cross connection. Numbers of nodes is limited to 16.

Transmission capacity: (k/2) x STM-N (k=no. of nodes).

Note: Suitable for distribution services


4-fiber Bidirectional MS Protection Ring

CA AC

CA AC

A

C

D B

W1P1W2P2

P2W2P1W1

CA AC switchingCA AC

A

CD B

W1P1W2P2

P2W2P1W1

CA AC

Two working fibers (W1 & W2) and two protection fibers (P1 & P2)W1 is clockwise and W2 is counter clockwise

P1 & P2 are in the opposite directions to W1 and W2 respectively. Each node has its own changeover switch.

Self-Healing Network OverviewWhat is Self-Healing Network?Self-Healing Network Basic PrincipleSelf-Healing Network ClassificationChain Network Protection TypesChain Network 1+1 Path ProtectionChain Network 1+1 Multiplex Section ProtectionChain Network 1:1 Multiplex Section ProtectionSelf-Healing NetworksAutomatic Protection SwitchRing Network ProtectionBasic Ring Network Protection Types2-Fiber Unidirectional Path Protection Ring2-Fiber Unidirectional Path Protection Ring2-Fiber Unidirectional Path Protection Ring2-Fiber Bidirectional MS Protection RingWorking PrincipleWorking PrincipleWorking PrincipleWorking PrincipleSwitching ConditionsSwitching ProcedureFeatures of 2 Fiber Bidirectional MSP Ring4-fiber Bidirectional MS Protection Ring

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