Routing and Wavelength Assignmentin All-Optical DWDM Transport Networks

with Sparse Wavelength Conversion Capabilities

Ala I. Al-Fuqaha, Ph.D.

2

Overview

•Transport Network Architectures: Current Vs. IP over DWDM

•Introduce Routing and Wavelength Assignment (RWA) problemin networks with Sparse wavelength conversion (RWA-SWC)

•Propose Integer Linear Programming (ILP) formulation for RWA-SWC

•Propose OSPF Extension (new LSAs) in support of all-optical

DWDM networks with sparse wavelength conversion

•Propose new OSPF LSA origination Policies (Immediate/Fuzzy)

3

Will not talk about

•Propose new Most-Contiguous Wavelength Assignment Heuristic

•Propose new fuzzy-based approach for route selection

Part 1 4

Today’s Transport Network - ArchitectureVoice Switches

Services Overlay

W-DCS Overlay

B-DCS Overlay

Sonet ADM Overlay

IP Routers

W-DCS

W-DCS W-DCS

B-DCS

B-DCS B-DCS

ADM

ADM ADM

DS-3, OC-3, OC-12, OC-48

OC-3, OC-12

DS-3

DS-3, OC-3, OC-12

ATM

ATM ATM

OC-12, OC-48

Part 1 5

Today’s Transport Network Architecture - Disadvantages

•Functional Overlap: Each overlay tries to perform protection

•Inefficient: IP over ATM over SONET over WDM ≈ 22%

•Overlays do not often work in concert:every overlay runs at its own speed slower devices cannot fill the bandwidth

•No automated provisioning at the optical overlaythe architecture does not scale well with increasing demand

•SONET Add and Drop Multiplexers:- Inflexible: Bit rate and signal format dependent- Costly: Introducing new OC-level requires new equipment

Part 1 6

New Transport Network Architecture + Motivations

All-Optical DWDM Transport NetworksIntroduces concurrency to unlockThe 50 Tbps potential capacityof single-mode fiber(i.e., bridging the opto-electronic bandwidth mismatch)

Signal Format Independent (OC/STS/STM/Ethernet)

Signal Bit Rate Independent (OC-Level Independent)

Automatic Provisioning of light-paths

Part 1 7

IP R outers Voice Switches

W-DC S

W-DC S W-DCS

B-DC S

B-DC S B-DC S

ADM

ADM ADM

OT S

OT S OT S

Services Layer

W-DCS Layer

B-DCS Layer

Sonet ADM Layer

Phtonic Layer(All-Optical DWDM transport Switches)

DS-3, OC-3, OC-12

OC-48, OC-19 2, OC-768

DS-3

DS-3, OC-3, OC-12OC-12

New Transport Network : Architecture (IP over DWDM)

Part 1 8

New Transport Network Architecture : Advantages

•Reduce the functional overlap between the overlays

•Independence from the signal formats and data rates

•Automatic provisioning of optical circuits

•More efficient transport of services (specially IP-based)

Part 1 9

Types of Services:

• Permanent Optical Circuits (POC)

• Switched Optical Circuits (SOC)

DWDM

All-Optical DWDM Transport Networks

General Characteristics:• Optical-Optical-Optical (O-O-O) Switches.• No optical-electrical-optical (O-E-O) within the network.• Dense Wavelenegth Division Multiplexing (DWDM Links).

Part 1 10

All-Optical Transport Network : Protocols

… … …

UNI …A

ATM Switch ATM Switch

B… …

CNNI NNIUNI

• Signaling protocol: OIF-LDP or OIF-RSVP on UNI side

• GMPLS signaling for NNI

• Routing: GMPLS Routing

Part 1 11

Routing and Wavelength Assignment : RWA Problem

• Optical Paths that need to be established on O-O-O DWDM networks have to be assigned:

Route: Path from source to destination thru intermediate nodes

Wavelength(s): The lambda(s) assigned on each link thru the path

• Two variations of the RWA problem have been studied in the literature:

• We focus on RWA problem in networks with Sparse wavelength conversion capabilities (because wavelength converters are expensive)

With wavelength continuity constraintWithout wavelength continuity constraint

(Wavelength Conversion expensive)

Part 1 12

RWA Example : Wavelength Continuity

Part 1 13

RWA Example : Wavelength Conversion

Part 2 14

ILP Formulation : Approach

•RWA problem is an NP-Complete problem

•The RWA problem has been formulated as an Integer Linear Programming (ILP) problem in the literature

•Our objective is to relax some of the constraints presented in previous literature to introduce an ILP that handles networks with Sparse and Limited Wavelength Conversion Capabilities

•We also introduce a pruning strategy that minimizes the number of variables and constraints in the ILP problem

ILP can be applied to larger networks

Part 2 15

ILP Formulation: RWA-SWC

•The objective function of this formulation is to minimize the total cost of all lightpaths that need to be established in the optical network.

subject to the following constraints:

⎥⎦

⎤⎢⎣

⎡∑Π

=

i

i

Ti SYMinimize1

)(

)1(111 iij rjiS ≤≤Π≤≤∀≤

)2(11

Π≤≤∀≤∑=

iSQir

j

ij

i

)3(1)( Π≤≤∀≤ iWUS iTi

)4(1)( Π≤≤∀≤ iVXS iiTi

)5(11)( Π≤≤∀≤ iZS iTi

Part 2 16

ILP Formulation: Pruning Strategy

•In order to use our ILP formulation with larger networksWe need to reduce the search space (non-optimal solutions)

•Pruning Strategy:(1) Limit the possible routes between source-destination pairs(2) Limit the possible wavelengths according to used tunable-lasers(3) Limit the possible wavelengths according to used wavelength

converters(4) Limit the possible wavelengths to be the same before and after

any node that does not support wavelength conversion(5) Limit the possible wavelengths to be a subset of the wavelengths

that the DWDM links can support

Part 2 17

Number of Variables =

Number of Constraints =

[ ]HWPPK *)1(*)1(** 21 −−∏[ ]HWPPK *)1(*)1(**4 21 −−∏+∏

• ∏ Number of lightpath requests•K Average number of possible routes •W Number of wavelengths per DWDM Link•H Average number of hops•P1 Percentage of wavelength options pruned

due to technology limitations•P2 Percentage of wavelength options pruned

due to user’s educated decision to use subsetof the DWDM wavelengths

ILP Formulation: Problem Size

Part 2 18

ILP Formulation: Problem Size (Cont’d)

0

500

1000

1500

2000

2500

0 5 10 15 20 25 30

Lightpaths

Coun

t

Variables Constraints

Part 2 19

ILP Formulation: Problem Size ( Cont’d)

05000

1000015000200002500030000350004000045000

0 20 40 60 80 100 120 140

W

Coun

t

Variables Constraints

Part 2 20

ILP Formulation: Problem Size ( Cont’d)

0

500

1000

1500

2000

2500

0 0.2 0.4 0.6 0.8 1

P1

Coun

t

Variables Constraints

Part 2 21

ILP Formulation: Problem Size ( Cont’d)

0

500

1000

1500

2000

2500

0 0.2 0.4 0.6 0.8 1

P2

Cou

nt

Variables Constraints

Part 2 22

A F

E

D

C

B

c = 1

c = 2

c = 2

c = 0

c = 3

c = 1

1

1

1

1

1

1

1

1

C : Number of wavelength converters installed on the nodeNumber of wavelengths = 3 (per each bi-directional link)

Scenario

Source Destination

Route

Wavelengths

Converters

A F AB BD

DF 3 3 3 0 0

A F AC CE EF

3 3 3 0 0

E A EC CA 1 1 0 E A EC CA 2 2 0 E B ED DB 2 2 0

A

C D CB BD 1 1 0 E A EC CA 3 3 0 E B ED DB 1 1 0 E B ED DB 2 2 0 E B ED DB 3 3 0 E B EC CB 1 1 0 E B EC CB 3 3 0 A B AB 1 0 A B AB 2 0 A B AB 3 0

B

A B AC CB 1 3 1

ILP Formulation: Problem Size ( Cont’d)

Part 2 23

ILP Formulation: Summary

• Our ILP can handle networks with Sparse and Limitedwavelength conversion capabilities

•Our ILP can be used to solve SLE problem(Typically : 6,000 variables and 6,000 constraints)

•Our Pruning strategy can be used to minimizethe number of variables and constraints involvedin the ILP problem handling bigger SLE problems

Part 3 24

OSPF Extension : Introduction

•K. Kompella, Y. Rekhter, "Routing Extensions in Supportof Generalized MPLS," Internet Draft, Work in Progress,August 2002

•K. Kompella, Y. Rekhter, "OSPF Extensions in Supportof Generalized MPLS," Internet Draft, Work in Progress,August 2002.

Our stand on GMPLS:Generic signaling and routing approach forPSC, TSC, LSC, FSC equipment. This introducesunnecessary complexities while ignoring the overlaymodel

Did not address many of the details of all-opticalDWDM transport networks (Advertising wavelengths,converters, origination policies, RWA techniques)

Part 3 25

OSPF Extension : Our Approach

•We need to know the availability of the wavelength and converter resourcesin order to perform SMART RWA or we will crankback or block the calls.

•Overlay-specific protocols are more efficient than generic ones.

•Overlay-specific protocols are less complex than generic ones.

•Having protocols that handle all the particularities of a specificswitching technology efficiently is better than having a protocolthat handles all switching technologies inefficiently.

In this research we address the issues that GMPLS routingdid not handle:

(1) Advertising resource availabilities: Wavelengths and converters(2) Origination policies convenient for the dynamic nature of

all-optical DWDM networks(3) RWA heuristics to conserve resource usage and minimize blocking

Part 3 26

OSPF Extension : New Wavelength LSALS Age Option

Advertising Router

LS Type=10TE Type TE LSA ID LSA#

LS Sequence NumberLS checksum Length=108

Type=2 Length=84

Link IDType=2 Length=4

Type=3 Length=4Local Interface IP Address

Type=4 Length=4Remote Interface IP Address

Type=11 Length=4Outgoing Interface Identifier

Type=12 Length=4Incoming Interface Identifier

Type=32775

Type=32773 Length=4

Type=32774 Length=8Shared Risk Link Group (SRLG1)Shared Risk Link Group (SRLG2)

Link Protocetion Type Not Used

Length=20

Wavelength Availability Mask

Length of Mask

Not Used

LinkTLV

LSAHeader

Remote Interfacesub-TLV

Local Interfacesub-TLV

Link IDsub-TLV

Outgoing Interfacesub-TLV

Outgoing Interfacesub-TLV

Protection Typesub-TLV

SRLGsub-TLV

WavelengthAvailabilitysub-TLV

Wavelength Resource availability Opaque LSA

Part 3 27

OSPF Extension : New Conversion LSA

Converter Type(1)

Type=32776 Length=12

LS Age Option

Advertising Router

LS Type=10TE Type TE LSA ID LSA#

LS Sequence NumberLS checksum Length=36

LSAHeader

Total Used Not Used

Converter Type(2) Total Used Not Used

Converter Type(3) Total Used Not Used

ConverterAvailability

TLV

Wavelength-Conversion Resource availability Opaque LSA

Part 3 28

OSPF Extension : DWDM Simulation

Typical 16-node Motro-core/ Long-haul network

Part 3 29

OSPF Extension : Protocol Simulation

Part 3 30

OSPF Extension : Results

0.00E+005.00E-021.00E-011.50E-012.00E-012.50E-013.00E-013.50E-014.00E-014.50E-015.00E-01

0 2 4 6 8 10 12 14

Traffic Load (Erlang)

Blo

ckin

g Pr

obab

ility

No Advertisements Advertisements

Part 3 31

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 0.2 0.4 0.6 0.8 1

Degree of Wavelength Conversion (%)

Blo

ckin

g Pr

obab

ility

No Advertisements Advertisements

OSPF Extension : Results (Cont’d)

Part 4 32

Origination Policies: Immediate

•Strategy: Advertise changes in wavelength and conversionavailabilities as soon as they happen.

Advantages Simple, good for not very dynamic networksDisadvantages Generates a lot of advertisements (overhead)

if (One of the neighboring routers changes to/from the FULL state) then Originate a new Router LSA

if (LS-age field of the one of router’s self-originated advertisement > LSRefreshTime)

then Originate a new instance of the LSA that just expired if (wavelength availability on one or more of the outgoing links changes)

then Originate new wavelength availability opaque LSA if (wavelength-conversion resource availability on the switch changes)

then Originate new wavelength-conversion availability opaque LSA

Part 5 33

Advantages of Using Fuzzy-Logic

• Rule-Based Fuzzy Inference Systems (FIS) employ linguisticvariables that can be easily understood and so modified orextended by others.

• Many criteria can be incorporated to make smarter routingdecisions.

• Fuzzy Inference Systems (FIS) can easily incorporatethe different heuristic algorithms employed in OperatingSystems field (e.g., First-Fit, Last-Fit, Best-fit, etc.)

Part 4 34

Origination Policies: Fuzzy-Based

•Strategy: Even if we do not advertise resource availabilities when the wavelength and conversion resources areNot highly utilized, the blocking probability willnot increase.

Advantages Simple, extensible approach that can handlevery dynamic networks with less overhead.

Rule-base for Fuzzy-Based LSA Origination

if (Bandwidth Utilization is low) and (Converter Utilization is low)then Update Frequency is slow(Bandwidth Utilization is high) or (Converter Utilization is high)then Update Frequency is fast

if

Part 4 35

Origination Policies: Fuzzy-Based (Example)

Part 4 36

Origination Policies : Results

0100000020000003000000400000050000006000000700000080000009000000

0 2 4 6 8 10 12 14

Traffic Load (Erlangs)

Num

ber

of e

xcha

nged

M

essa

ges

Immediate Flooding Fuzzy FLooding

Part 4 37

Origination Policies : Results (Cont’d)

00.05

0.10.15

0.20.25

0.30.35

0.40.45

0.5

0 2 4 6 8 10 12 14

Traffic Load (Eralngs)

Cal

l Blo

ckin

g Pr

obab

ility

Immediate Flooding Fuzzy Flooding

Part 4 38

Origination Policies : Results (Cont’d)

0

2000000

4000000

6000000

8000000

10000000

12000000

14000000

0 20 40 60 80 100

Degree of Wavelength Conversion (%)

Num

ber o

f Mes

sage

s

Immediate flooding Fuzzy flooding

Part 4 39

Origination Policies : Results (Cont’d)

00.1

0.20.30.4

0.50.6

0.70.8

0 20 40 60 80 100

Degree of wavelength conversion (%)

Cal

l blo

ckin

g pr

obab

ility

Immediate flooding Fuzzy flooding

Conclusions

• Proposed an ILP formulation and pruning-strategy for RWAproblem in networks with sparse wavelength conversioncapabilities.

• Proposed OSPF extension that enhances the blockingperformance of networks with sparse wavelength conversioncapabilities.

•Proposed fuzzy-based LSA origination policy that drasticallyreduces the number of messages exchanged over the controlplane without hindering the blocking performance.

Future Extensions

•Evaluate the performance of the proposed OSPF extensionand fuzzy origination policy for optical packet switching (OPS)and Optical Burst Switching (OBS) networks.

•Use Neuro-Fuzzy approach to dynamically learn and tunethe parameters of the membership functions used in our fuzzyorigination policy.