2 - ota000006 sdh networking and protection issue 1.20

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Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.

SDH Networking and Protection

Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page2

Objectives

Upon completion of this course, you will be able to:

Describe the common SDH network topology and

features

Explain the protection mechanism


Contents

1. SDH Network Topologies

2. Survivable networks and their protection

mechanisms


Contents


1.1 Optical networking introduction

1.2 Classification of topologies

1.3 Sub-networks


Optical Networking Introduction An SDH network consists of Network Elements (NE)

interconnected with optical fiber.

The geometrical layout of the NEs and optical

transmission lines is called the network topology.

The efficiency, reliability and the cost performance

of a network highly depend on its topology.


Classification of Topologies

Chain

Star

Tree

Ring

Mesh


Classification of Topologies (Cont.)

Chain network is used when the networks nodes are

arranged in a long line.

e. g. along railway lines, highways, power supply lines,

etc.

NE A NE B NE C NE D

Chain network (Point-to-point or point-to-multi-point network)

In a chain network, all nodes are connected one after another

on a line with both ends open.



Star network is mainly used in access networks or rural telephone networks in which nodes are scattered here and there and the traffics are not important.

Star network

In a star network there is a central node to which the

other nodes are directly connected. There are no direct

links between other nodes.

NE A

NE B

NE C

NE D

NE E


Tree network is mostly used for broadcasted services like CATV.

Classification of Topologies (Cont.) Tree network

A tree network can be considered as a combination of the chain

and star topologies.

NE ANE B

NE C NE D

NE E


Ring network is widely used in SDH networking due to

its high survivability.

Classification of Topologies (Cont.) Ring network

Ring network is such a structure in which all nodes are

connected one after another to form a circle.NE A

NE B

NE C NE D

NE E


Mesh network is suitable for the regions with large

amount of traffic and for high hierarchy

communication networks.

Classification of Topologies (Cont.) Mesh network

Mesh network is such a structure in which many nodes are

interconnected together via direct links.

NE ANE A

NE B

NE C NE D

NE E


Other possible combination networks



A sub-network functions as a container. It can

include NEs, links and even lower level sub-networks.

Sub-network

Sub-network

In backbone networks or large region networks, there are a large number of NEs and links. In order to simplify the network management, a large network can be divided into several sub-networks according to the administrative regions.


Sub-network (Cont.)

Sub-network A

Sub-network B Sub-network C

Sub-network D

Subnet


Contents



mechanisms


Contents


mechanisms

2.1 Survivable networks introduction

2.2 Types of protection


Survivable Networks Introduction Causes of network failures

Accidents: Cable/fiber cuts

Human errors: Incorrect maintenance, installation, …

Environmental hazards: Floods, fire, …

Sabotages: Physical, electronic, …

Operational disruptions: Schedule upgrade,

maintenance, power outage, …

Hardware/software failures: Line unit failure, faulty

laser, software crash


Survivable Networks Introduction (Cont.)

Survivable networks can restore traffic in the event of a

failure

Requirements for survivability of network includes…

Robust equipment (Strong cross-connect capability, intelligent

nodes)

Security (Physical, electronic)

Design networks with enough resource

Redundant routes as standby routes

Fast failure detection and fast traffic rerouting to redundant

routes

No human intervention


Types of Protection

Line

Ring

Node

1+1 linear MSM:N linear MS

Path protection （ PP）2-fiber unidirectional Path Protection Ring2-fiber bidirectional Path Protection Ring

4-fiber bidirectional MSP Ring (4f-MS SPRing)

Multiplex section protection (MSP)

2-fiber bidirectional MSP Ring (2f-MS SPRing)2-fiber unidirectional MSP Ring (2f-MS SPRing)

Sub-network connection protection (SNCP)


Line Protection

Working Channels

Protection Channels

NE A NE B NE C NE D

Use in point-to-point or chain networks

Switch is within two interconnected nodes


Linear 1+1 MS Traffic source node sends the traffic on both working and

protection channels (Concurrent sending).

Traffic sink node receives the traffic from working channel (Selective receiving).

When the working channel fails, traffic sink node switches to receive the traffic from protection channel

NE A NE B


Linear 1+1 MS (Cont.)

Switching Modes

Single-ended (Unidirectional)

Dual-ended (Bidirectional)

Restoration Modes

Revertive (WTR Default: 600 sec)

Non-revertive

Automatic Protection Switch (APS) protocol is not

required when Single-ended and Non-revertive are

selected.


Linear M:N MS

Protection Channel

Working Channel 1

Working Channel 2

Working Channel N

NE A NE B

Extra trafficNormal traffic

SwitchingSwitching Switching Switching

M Protection channels N Working channels


Linear M:N MS (Cont.)

Switching mode:

Bidirectional switching

Restoration mode:

Revertible mode


Line Protection Line protection types

Linear 1+1 MS

Linear M:N (M=1)

Protection switch criteria:

Signal Fail (SF): R_LOS, R_LOF, MS_AIS, B2_EXC.

Signal Degrade (SD): B2_SD.

Externally initiated protection switching command

Network Capacity:

1+1 linear MS: 1 x STM-N.

1:N linear MS without extra traffic: N x STM-N.

1:N linear MSP system with extra traffic: (1+N) x STM-N.


Questions

Which linear protection type switches the fastest?

Which type can carry extra traffic?


Ring Protection

Ring protection types:

Path protection (PP)

Multiplex section protection (MSP)

Traffic directions:

Unidirectional (PP Diversely routed, MSP

Dedicated)

Bidirectional (PP Uniformly routed, MSP Shared)

Number of fiber:

2 fiber

4 fiber


Two-fiber Multiplex Section Shared Protection Ring (2f-MS SPRing) Fiber connection and slots

requirements:

2 fibers

Line boards must be inserted

in dual slots

Left line board W

Right line board E

A

C

B

OUT

IN


S1S2

2f-MS SPRing (Cont.)

NE B

NE C

NE D

NE A

2f-MSSPRing2f-MSSPRing

STM-16STM-16

P1

Protection channel (P): VC4 #9 ~ VC4 #16

P2

Working channel (S): VC4 #1 ~ VC4 #8



Exploded view of one fiber for STM-16 in 2f-

MSSPRing

VC-4 #1VC-4 #2VC-4 #3VC-4 #4VC-4 #5VC-4 #6VC-4 #7VC-4 #8VC-4 #9VC-4 #10VC-4 #11VC-4 #12VC-4 #13VC-4 #14VC-4 #15VC-4 #16

Working channels (S)

Protection channels (P)

FiberFiber

Section overheads



Normal traffic flow between NE A & NE C

NE B

NE C

NE D

NE A

2f-MS SPRing2f-MS SPRing

STM-16STM-16

S1

S2



Switched traffic flow between NE A & NE C

NE C

NE D

NE A


STM-16STM-16NE B

S1

P1

S2

P2

P2

Bridge &

Switch

Pass-throughPass-through



When fiber is repaired, traffic switches back to working

channels after WTR time

NE B

NE C

NE D

NE A


STM-16STM-16

S1

S2


2f-MS SPRing (Cont.) Protection switching trigger conditions:

APS Signal Failure (SF): R_LOS, R_LOF, MS_AIS, B2_EXC (Default) Signal Degrade (SD): B2_SD (Optional)

Externally initiated protection switching command Forced switch Manual switch Exercise switch

Protection switching restoration: APS

Clearing of SF: R_LOS, R_LOF, MS_AIS, B2_EXC Clearing of SD: B2_SD WTR (Wait to Restore): 10 minutes (5-12 minutes provisionable)

External commands Clearing of Forced switch Clearing of Manual switch



APS controller: Processes APS protocol, which is carried in the K1, K2 bytes.

Transition of APS controller status

P

WTR

WTR P

I

I

I I

P

S

S P

I = IdleP = Pass-throughS = SwitchingWTR = Wait to Restore


2f-MS SPRing (Cont.) Features of 2f-MSSPRing:

Advantages:

Time slots can be reused

High network capacity: ½ x M x STM-N

M is the number of nodes on the ring, STM-N is the STM

level

Disadvantages:

Mechanism is complicated

Maximum number of nodes on one ring is limited to 16

Application:

Mainly for STM-4 and STM-16 or above systems

Scattered traffic distribution


Four-fiber Multiplex Section Shared Protection Ring (4f-MS SPRing) Structure:

4 fibers

Working channels (fibers) S1, S2, carry normal traffic

Protection channels (fibers) P1, P2, protect normal traffic

A

DC

EF

B

S1S2P1P2



Traffic flow when network is normal:

Working channels = S1, S2

Protection channels = P1, P2

A

DC

EF

B

A D

D A

A D

D A

S1

S2

P1P2



Traffic flow after only the working channel (s) is (are)

broken :

Span switching

A

DC

EF

B

S1

S2

P1

P2

A D

D A

A D

D A



Traffic flow after the working and protection

channels are broken:

Ring switching

A

DC

EF

B

S1

S2

P1

P2

A D

D A

A D

D A



Protection switching trigger conditions:

Automatic protection switching: Ring or Span

SF (Signal Failure): R_LOS, R_LOF, MS_AIS, B2_EXC

SD (Signal Degrade): B2_SD

External initiated protection switching: Ring or Span

Forced switch

Manual switch

Exercise switch


4f-MS SPRing (Cont.) Protection switching restoration:

Automatic protection switching: Ring or Span Clear of SF (Signal Failure): R_LOS, R_LOF, MS_AIS, B2_EXC

Clear of SD (Signal Degrade): B2_SD

WTR (Wait to Restore): 10 minutes (5-12 minutes provisionable)

External command: Ring or Span Clear of Forced switch

Clear of Manual switch

APS controller status: Idle

Switching

Pass-through

WTR


4f-MS SPRing (Cont.) Features of 4f_MSSPRing:

Advantages: Time slots can be reused

High network capacity: M*STM-N

Disadvantages: Maximum number of nodes on one ring is limited to 16

Mechanism is complicated

Expensive

Application: Mainly STM-16 or above system

Scattered traffic distribution

Backbone system


Summary

MSP

ring

2f_MSSPRing 4f_MSSPRing

Similarit

y

APS protocol necessary

Nodes number on MSP ring ≤16

SCC unit configures MSP protocol

Dual slots

Bidirectional and dispersed traffics

Differenc

e

M*STM-N/2

capacity

(without extra

traffic)

M*STM-N capacity

(without extra traffic)

Unique span switch

K1 & K2 bytes are in the protection

fiber


Traffic transmit and

receive conditions in

normal situation.A

B

C

D

in

out

out

out

out

out

out

out

in

in

in

in

in

in

in

PP Ring

2M

2M

Concurrent sending

Selective receiving

out

Two-fiber Unidirectional Path Protection Ring (Diversely Routed PP Ring)


Diversely routed pp ring



fiber failure situation. A

B

C

D

in

out

out

out

out

out

out

out

in

in

in

in

in

in

in

PP Ring

2M

2M

Concurrent sending

Selective receivingSwitching

out


Diversely routed pp ring

Protection switching trigger conditions

TU_AIS, TU_LOP, BIP_EXC

Features:

Every path (2M) switches independently.

Restoration mode is revertive.


Questions

Can the services

between stations

A and E be

protected?

A

B

C

D

in

out

out

out

out

out

out

out

in

in

in

in

in

in

in

PP

2M

2M

STM-N

Concurrent sending

Will the services be selectively received here?

out

E


Node protection Node protection type:

Subnetwork connection protection (SNCP)

Protection features:

Traffic transmit end sends concurrently, receive end receives

selectively

2 fiber unidirectional traffic (Diversely routed)

1 + 1 single-ended protection

Protection switching criteria:

Signal fail (SF)

Signal degrade (SD)

Externally initiated command


SNCP Protección de la conexión de Subred (Subnetwork connection protection )

Nodo Inicio de la Conexión de Subred

Nodo Terminal de la Conexión de Subred

Conexión de Subred de Protección

Conexión de Subred de Trabajo

Sub-Red1

Sub-Red 2 NE A NE B

Selector

Selector

Tráfico Saliente Tráfico entrante

Condición Normal

Canal de Trabajo

Canal de Protección

Conmutación

Puenteo PuenteoConmutación Tráfico entranteTráfico Saliente

Canal de Trabajo fallanfo


SNCP (cont.)



normal situation.A

B

C

D

in

out

out

out

out

out

out

out

in

in

in

in

in

in

in

SNCP Ring

2M

2M

STM-N

Sub-Network 1 Sub-Network

2

Concurrent sending

Selective receiving

out


SNCP (cont.)


receive conditions

in fiber failure

situation.

A

B

C

D

Entrada

Salida

Salida

out

out

Salida

Salida

Entrada

in

in

Entrada

Entrada

AnilloSNCP

2M

2M

STM-N

Sub-Red 1

Envío de forma constante

Recepción selectivaConmutación

Salida

Entrada

Salida

Entrada

Sub-Red 2

E


SNCP (cont.)

Protection switching trigger conditions :

Default AU_AIS, AU_LOP, TU_AIS, TU_LOP, HP_LOM, HP_UNEQ

B3_EXC, Unplug the line card

Optional HP_TIM, HP_SLM, B3_SD


SNCP (cont.)

Protection Restoration:

Wait to restore time 10 minutes (5-12 minutes

provisionable)

10 minutes later

A

B

C

D

switching

S1

P1A

B

C

D

S1

P1


Questions

What is the difference between unidirectional (diverse)

and bidirectional (uniform) traffics?

What is the difference between SNCP and MSP protection

schemes?

Which type of network protection can carry extra traffic?


Summary A survivable network is capable of restoring services within

a very short time and without any human intervention in

the event of a failure.

Linear protection networks can be classified into 1+1 linear

MS and 1:N linear MS.

Ring protection networks can be classified into Path

Protection (PP) ring, Multiplex Section Protection (MSP) ring.

Sub-Network Protection (SNCP) is used for node protection.


Item 2f_MSSPRing SNCP

APS protocol Necessary Unnecessary

Typical services Bidirectional and distributedUnidirectional and

centralized

Switch level (objective) MS SNC services

Suitable networking Only ring Any topology

Switching implementing

boardsLU, XC LU, XC

Switch time ≤50ms ≤50ms

Network Capacity (without

extra service)K*STM-N/2 STM-N

Extra traffic Supported Not supported

Summary (cont.)


Summary (cont.)

EquipmentLinear

MS

2f-MS

SPRing

4f-MS

SPRingPP SNCP

Metro 100Suppor

tNo No No

Suppor

t

Metro 200/500Suppor

tNo No Support

Suppor

t

Metro 1000V2Suppor

tSupport No Support

Suppor

t

Metro 1000V3/1050Suppor

tSupport No No

Suppor

t

Metro 2050/3000Suppor

tSupport

Suppor

tSupport

Suppor

t

Metro 5000, OSN

1500/2500/3500/7500/9

500

Suppor

tSupport

Suppor

tNo

Suppor

t

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