optical network planning - bme hálózati rendszerek …jakab/papers/1999/cost266_p709pre.pdf ·...

1“The Broadband Networks of Tomorrow” Roberto CLEMENTECSELT

P615 Evolution ... 1998 EURESCOM Participants in Project P709

Optical Network Planning



Outline

• Overview of planning processes

• What is new with WDM?

• Breakdown planning approach for single layer networks

• Planning multi-layer networks

• Incoherences among planning phases

• Conclusion



Long Term Planning Process

• based on experience• green-field approach• parametric models

strategic planning

• topology planning• allocation of functions

in network nodes• distribution of functions

to network layers• resource optimization

fundamental planning

generaltraffic

forecast • technology• network architecture• recovery mechanisms

cost models

technical constraints

detailed traffic

patterns

network structure



Medium Term Planning Process

T1 T2 T3 T4 T5

LTP plan T0

LTP demand

forecast T0

Installed plant T0

MTP demand

forecast T0

MTP plan T0

MTP plan T1

MTP plan T2

MTP plan T4

MTP plan T3



Long Term Planning Goals

• Location and technological evolution of the network nodes

• Partitioning into sub-network• Logical network structure for the single-

layer network• Dimensioning of network resources

• Location and technological evolution of the network nodes

• Partitioning into sub-network• Logical network structure for the single-

layer network• Dimensioning of network resources

LTP goals

• Single-period demand forecast• Greenfield non-capacitated network• Network architecture• Recovery scheme• Non-discounted cost of components and

transmission infrastructures

• Single-period demand forecast• Greenfield non-capacitated network• Network architecture• Recovery scheme• Non-discounted cost of components and


main inputs



Medium Term Planning Goals

• Detailed routing and groomig• Transmission systems to be installed or dismissed

in each period• Equipment to be installed, upgraded or dismissed

in each period • Scaling and possible delays in deploying new

network resources according to budget constraints

• Detailed routing and groomig• Transmission systems to be installed or dismissed

in each period• Equipment to be installed, upgraded or dismissed

in each period • Scaling and possible delays in deploying new

network resources according to budget constraints

MTP goals

• Multi-period demand forecast• Capacitated network• Network architecture & recovery scheme• Discounted cost of components and


• Multi-period demand forecast• Capacitated network• Network architecture & recovery scheme• Discounted cost of components and


main inputs



Several distributed functionality

Several distributed functionality

Several constraints to be considered

Several constraints to be considered

LTP Breakdown Approach

LTP is considered a very complicated task

LTP is considered a very complicated task

Several objects to be treated

Several objects to be treated

• sub-problems identification• separate sub-problem solution • identification of a information flow between

sub-problems

• sub-problems identification• separate sub-problem solution • identification of a information flow between

sub-problems

Several requirements to be respected

Several requirements to be respected

solution



A multi-period problem to be solved

A multi-period problem to be solved

Additional constraints (e.g. budget) to be considered

Additional constraints (e.g. budget) to be considered

MTP Breakdown Approach

MTP is even more complicated than LTPMTP is even more complicated than LTP

More detailed output to be obtained

More detailed output to be obtained

Additional requirements to be respected

Additional requirements to be respected

solution

Single-period

process

Installed resources

Unused resources

Demand matricesMTP

constraints

Installed resources

Unused resources

Single-period

process

Demand matricesMTP

constraints

Installed resources

Unused resources

time slot (j-1) time slot j time slot (j+1)

Time scale



Any change with WDM? (1)

• Network architecture (ring, mesh,…)• Available functionality (cross-connection, add-

drop,…)• Routing and recovery schemes• Resource allocation (cable, fibre)• Grooming/multiplexing policy• Technical constraints (regeneration step,…)

• Network architecture (ring, mesh,…)• Available functionality (cross-connection, add-

drop,…)• Routing and recovery schemes• Resource allocation (cable, fibre)• Grooming/multiplexing policy• Technical constraints (regeneration step,…)

SDH planning processes are influenced by...



Any change with WDM? (2)

WDM networks can be described like SDH one WDM networks can be described like SDH one

WDM SDHdemands OCH connection VC-4functionality x-connection (OXC) x-connection (DXC)

add-drop (OADM) add-drop (ADM)regeneration (O/E/O, 3Rreg) regeneration

architectures OXC-based mesh DXC-based meshOCH-DPRing SNCP-DPRingOMS-SPRing MSP-SPRING

multiplexing w OCH connections on a n VC-4s on aw-wavelength OMS STM-n MS

It is possible to adapt the SDH planning processes to WDM networks

It is possible to adapt the SDH planning processes to WDM networks



Maximum re-use of experience

Always re-use all the knowledge, experience, processes, algorithms, models

and tools matured with SDH networks

Always re-use all the knowledge, experience, processes, algorithms, models

and tools matured with SDH networks

The breakdown approach can be defined for WDM network planning as well

The breakdown approach can be defined for WDM network planning as well

to obtain the maximum advantage (in terms of

reusability) from the breakdown approach, atomic sub-problems

must be identified



Atomic Breakdown

• network partitioning or clustering • routing of transmission demands• demand grooming • stand-by network planning• wavelength allocation• transmission system allocation• equipment allocation and evaluation

• network partitioning or clustering • routing of transmission demands• demand grooming • stand-by network planning• wavelength allocation• transmission system allocation• equipment allocation and evaluation

Atomic Sub-Problems

Atomic relationship

it is the planning method that

solves an atomic sub-problem

it is the planning method that

solves an atomic sub-problem

Atomic sub-function

Atomic sub-function A

Atomic sub-function B

moving



merging



interleaving



Planning processes

• It is a series of consecutive steps and iterations to elaborate a network plan (otherwise stated to solve a network problem)

• Its complexity suggest to divide it in atomic sub-functions• To obtain the network plan sub-functions must be solved in

an ordered way, depending on the relationship among them• Relationship among atomic sub-functions are generally fully

meshed

• It is a series of consecutive steps and iterations to elaborate a network plan (otherwise stated to solve a network problem)

• Its complexity suggest to divide it in atomic sub-functions• To obtain the network plan sub-functions must be solved in

an ordered way, depending on the relationship among them• Relationship among atomic sub-functions are generally fully

meshedsimplification

Planning process

decompositiongradual

simplificationmixed

methodology



• a model is a mathematical description of a problem

• an algorithm is a finite sequence of steps to obtain solutions to the problem

• a model is a mathematical description of a problem

• an algorithm is a finite sequence of steps to obtain solutions to the problem

Algorithms & models

A simple example: OMS-SPRing

optical demand routing

transmission allocation

stand-by resources

wavelength allocation

equipment allocation

planning process (decomposition approach)

dimension an OMS-SPRing minimising its cost


Planning problem

atomic planning sub-problem

atomic planning relationship (moving)

atomic planning relationship (merging)

Thank to the breakdown approach, models and

algorithms must be onlyapplied to atomic sub-problems



A simple example: OMS-SPRing



Planning problem

1 2 3 4 51 - 3 4 1 32 3 - 1 2 33 4 1 - 3 14 1 2 3 - 45 3 3 1 4 -

5

1

4

3

2

40 km

35 km20 km

25 km

15 km

Topology andtraffic demands

• Minimum hop • Minimum distance• Minimum load• Minimum load with

random scrambling• Minimum load with

intelligent scrambling

Routing algorithmsMinimum hop algorithm

5

1

4

3

2

d14 d15 d15 d15d25 d25 d25

d14 d35 d45 d45d45 d45

d24 d24 d34 d34d34 d35

d13 d13 d13 d13d23 d24 d24

d12 d12 d12 d13d13 d13 d13 d25

d25 d25



024681012

wav

elen

gths

per

spa

n

a1 a2 a3 a4 a5

Example results

024681012

wav

elen

gths

per

spa

n

Minimum load with random

scrambling

Minimum load

Minimum distance

Minimum hop

Minimum load with intelligent

scrambling

Non adaptiveMinimum load with random scrambling

Non adaptiveMinimum load

Non adaptiveMinimum hop

Non adaptiveMinimum load with intelligent

scrambling

AdaptiveMinimum load with random scrambling

AdaptiveMinimum load

AdaptiveMinimum load with intelligent

scrambling

a1 a2 a3 a4 a5



Multi-layer networks

WDM technology represent a good opportunity to improve the overall network behaviour…

… however they are still deploying their SDH transmission networks and they are not likely to leave the “SHD way” in the next years

WDM technology represent a good opportunity to improve the overall network behaviour…

… however they are still deploying their SDH transmission networks and they are not likely to leave the “SHD way” in the next years

Multi-layer transmission networks

Physical

WDM

That leads to multi-layer transmission network

SDH



Multi-layer planning strategies

Two general strategies for multi-layer planning

Two general strategies for multi-layer planning

solution solution

WDM

SDH

WDM

SDH

Single multi-layer planning

Multi single-layer planning



Multi single-layer planning

Physical

WDM

SDH

Physical topology

Other inputs

WDM planning

tool• WDM network

dimensioning and costs• wavelength routing

WDM demand matrixSDH

logical topology

SDH planning

tool

Other inputs

• SDH network dimensioning and costs

• VC-4 routing

SDH demand matrixPhysical

topology

Other inputs

SDH planning

tool• SDH network

dimensioning and costs• VC-4 routing

WDM planning

tool

Other inputs

• WDM network dimensioning and costs

• wavelength routing

WDM demand matrix

SDH demand matrixSDH

logical topology

Two pure sequential multi single-layer planning strategies

Two pure sequential multi single-layer planning strategies



Bottom-up approachBottom-up approach

WDM-layer

planning tool

• WDM network dimensioning and costs

• wavelength routing

Cost model

SDH-layer

planning tool

• SDH network dimensioning and costs

• VC-4 routing

Demand matrix

Top-down approachTop-down approach

Single-layer

planning tool

• network dimensioning and costs

• routing

Cost model

Demand matrix

WDM

SDH

Iterative sequential approach

solution

For further work: EURESCOM 2000

“WDM-based multi-layer networks”

Single-layer

planning tool

• network dimensioning and costs

• routing

Cost model

Demand matrix



STP, MTP and LTP coherence

• LTP defines the long term evolution of the network• MTP schedules the needed network upgrade (node and

systems)• STP uses provided resources to support demands

• LTP defines the long term evolution of the network• MTP schedules the needed network upgrade (node and

systems)• STP uses provided resources to support demands

Ideally LTP, MTP and STP act coherently

• higher and higher uncertainty• budget limitation• different optimisation criteria in different planning

phases• resource utilisation rules

• higher and higher uncertainty• budget limitation• different optimisation criteria in different planning

phases• resource utilisation rules

Actually LTP, MTP and STP are incoherent



Two classes of countermeasures against incoherence

Two classes of countermeasures against incoherence

Incoherence countermeasures

• Improved forecast• Reduced time-scale• Demand reconfiguration • Improvement of the

network creation process• Simpler network

architectures and structures

• Improved forecast• Reduced time-scale• Demand reconfiguration • Improvement of the

network creation process• Simpler network

architectures and structures

Preventive

• Risk analysis• Studies on dynamic

demand evolution

• Risk analysis• Studies on dynamic

demand evolution

Reactive

For further work: EURESCOM 2000

“Risk analysis, dynamic demand evolution and churning in transport networks”



Conclusions

• Planning is a complex task: a decomposition approach is suggested

• Identifying a set of atomic sub-functions which solve layer-independent planning sub-problems, we get a high degree of re-usability of the already matured experience

• Multi-layer planning is going to become more and more important: a general framework has been presented

• Additional objectives are likely to be added to the planner work in order to cope with incoherent network evolution

optical network planning - bme hálózati rendszerek …jakab/papers/1999/cost266_p709pre.pdf ·...

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