Routing and Wavelength Assignment in All-Optical DWDM networks...
Transcript of Routing and Wavelength Assignment in All-Optical DWDM networks...
Routing and Wavelength Assignmentin All-Optical DWDM Transport Networks
with Sparse Wavelength Conversion Capabilities
Ala I. Al-Fuqaha, Ph.D.
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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)
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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
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Lightpaths
Coun
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Variables Constraints
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ILP Formulation: Problem Size ( Cont’d)
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1000015000200002500030000350004000045000
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ILP Formulation: Problem Size ( Cont’d)
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ILP Formulation: Problem Size ( Cont’d)
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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
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Traffic Load (Erlang)
Blo
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obab
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No Advertisements Advertisements
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Degree of Wavelength Conversion (%)
Blo
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obab
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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
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Traffic Load (Erlangs)
Num
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of e
xcha
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essa
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Immediate Flooding Fuzzy FLooding
Part 4 37
Origination Policies : Results (Cont’d)
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Traffic Load (Eralngs)
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Immediate Flooding Fuzzy Flooding
Part 4 38
Origination Policies : Results (Cont’d)
0
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Degree of Wavelength Conversion (%)
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Immediate flooding Fuzzy flooding
Part 4 39
Origination Policies : Results (Cont’d)
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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.