A. Grue, W. D. Grover, J. Doucette, B. Forst, D. Onguetou, D. Baloukov TRLabs

HHigh-igh-AvaAvailability ilability NNetwork etwork AArchitectures (HAVANA):rchitectures (HAVANA):

Comparative Study of Fully Pre-Cross-Connected Protection Architectures for

Transparent Optical Networks

Contact: [email protected]. Grue, W. D. Grover, J. Doucette, B. Forst, D. Onguetou, D. Baloukov

TRLabs(Network Systems Group)7th Floor, 9107 – 116 StreetEdmonton, Alberta, Canada T6G 2V4

M. Clouqueur, D. Schupke

Nokia Siemens Networks(Network Control-Plane and

Transport)Otto-Hahn-Ring 6

81730 Munich, Germany

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July 9, 2007Confidential to TRLabs and Nokia-Siemens Networks

Pre-Cross-Connection: A Design ConstraintPre-Cross-Connection: A Design ConstraintNon-Pre-Cross-Connected• Shared “pool” of spare

capacity• Backup paths cross-connected

at failure time• Examples: SBPP, span-

restorable mesh

Pre-Cross-Connected• Cross-connections for backup

paths formed in advance of failure

• Resulting chains of pre-cross-connected capacity coalesce into protection “structures”

• Examples: BLSR, p-cycles

2

64

8

7

1

11

3 4

55

912

1

10

x3

x2

x5

-1

-1

-1 -1-1

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OutlineOutline

• Architectures

• Project Overview

• Methods and Results

• Conclusions

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pp-Cycles-Cycles

Straddling span

On-cycle span

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Failure Independent Path Protecting Failure Independent Path Protecting pp-Cycles-Cycles

Straddling path

On-cycle path

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PXTs (Pre-Cross-Connected Trails)PXTs (Pre-Cross-Connected Trails)

Understanding PXTs: Behave like FIPP cycles, only the structures are not closed

As a consequence, they are not able to provide two protection paths for failed working paths

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DSP (Demand-Wise Shared Protection)DSP (Demand-Wise Shared Protection)

Understanding DSP: It is essentially 1:N APS over N+1 disjoint routes between end nodes

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OutlineOutline

• Architectures



• Conclusions

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Project HAVANA Outline/Objectives Project HAVANA Outline/Objectives

• Objective: To characterize and compare many different pre-cross-connected protection architectures on a single network, under real-world constraints to network intelligence and flexibility

• Project Phases1. Basic architecture design (capacity for single span failure restorability)

2. Dual failure analysis of basic designs

3. Wavelength assignment: feasibility and methods

4. Optical path length constraints: analysis and enhancement

• Outputs1. A set of “best feasible” network designs

2. Theoretical insights into architectural properties

3. Design methods and insights

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OutlineOutline

• Architectures


• Methods and Results– Basic architecture design

• Conclusions

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““TestSet0” NetworkTestSet0” Network

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Working Routing: ConstraintsWorking Routing: Constraints

• Models for FIPP, PXTs, and p-cycles are SCP (spare capacity placement) only; working routing is static

• Both FIPP and PXTs require a working routing such that at least one path, disjoint from the working path, exists between the end nodes

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Results: Spare Capacity RedundancyResults: Spare Capacity Redundancy

• p-Cycles are the most capacity efficient• DSP has capacity efficiencies just slightly lower than that

of 1+1 APS

60%

80%

100%

120%

140%

160%

180%

DSP PXTs p-Cycles FIPP p-Cycles

Re

du

nd

an

cy

1+1 APS 173%

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OutlineOutline

• Architectures


• Methods and Results– Basic architecture design– Dual failures

• Conclusions

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Dual Failures: Network IntelligenceDual Failures: Network Intelligence

• The response to a first failure cannot change as a result of a second failure; failure responses are independent

1

2

2

1

2 paths restored 1 path restored

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Results: Dual FailuresResults: Dual Failures

DSP: ~85%

PXTs and p-cycles: ~66%

FIPP p-cycles: ~50%

100% …of all failed paths restored over all dual failure scenarios

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OutlineOutline

• Architectures


• Methods and Results– Basic architecture design– Dual failures– Wavelength assignment

• Conclusions

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Wavelength Assignment in Wavelength Assignment in pp-Cycles-Cycles

• p-Cycles require either wavelength conversion or at least 2 fibres on every span in order to support wavelength continuity

Wavelength conversion required for break-in

Different wavelengths for 2 different working paths

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Results: Wavelength AssignmentResults: Wavelength Assignment

• Wavelengths are allocated to the network in bands of 20

• 40-wavelength (2 bands) assignment found for all architectures

• 20-wavelength (1 band) assignments found for:– PXTs (modified SCP model)– FIPP p-cycles (JCP model necessary)

• Not found for:– DSP (impossible)– p-cycles (perhaps possible using JCP?)

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OutlineOutline

• Architectures


• Methods and Results– Basic architecture design– Dual failures– Wavelength assignment– Optical path lengths

• Conclusions

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Results: Optical Path LengthsResults: Optical Path Lengths

• Only DSP design satisfied reach constraints with the original design

• PXTs and FIPP p-cycle designs easily found by modifying the pre-processing step

• Compliant p-cycle design found by using a new ILP model altogether

60%

80%

100%

120%

140%

160%

180%

DSP PXTs p-Cycles FIPP p-Cycles

Red

un

dan

cy

Path Length Controlled Design Costs

Original Design Costs

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OutlineOutline

• Architectures



• Conclusions

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ConclusionsConclusions

Dual Failure Restorability

Wavelength Assignment

Optical Reach

Cost of Design

p-Cycles

FIPP p-Cycles, PXTs

DSP

Best

Worst

DSP

PXTs, p-Cycles

FIPP p-Cycles

PXTs

FIPP p-Cycles

DSP, p-Cycles

DSP

p-Cycles

FIPP p-Cycles, PXTs

• Architecture Scorecard:

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To Find Out More…To Find Out More…

• References on PXTs, FIPP p-Cycles, DSP (listed in paper)

A. Kodian, W.D. Grover, “Failure Independent Path-Protecting p-Cycles: Efficient and Simple Fully Pre-connected Optical-path Protection,” IEEE Journal of Lightwave Technology, vol. 23, no.10, October 2005.

T. Y. Chow, F. Chudak, A. M. Ffrench. “Fast Optical Layer Mesh Protection Using Pre-Cross-Connected Trails,” IEEE/ACM Trans. Networking, vol. 12, no. 3, pp. 539-547, June 2004.

Koster, A. Zymolka, M. Jager, R. Hulsermann, “Demand-wise Shared Protection for Meshed Optical Networks,” Journal of Network and Systems Management, vol. 13, no. 1, pp. 35-55, March 2005.

A. Grue, W.D. Grover, “Characterization of pre-cross-connected trails for optical mesh network protection,” OSA Journal of Optical Networking, May 2006, pp.493-508

HHigh-igh-AvaAvailability ilability NNetwork etwork AArchitectures (HAVANA):rchitectures (HAVANA):

Comparative Study of Fully Pre-Cross-Connected Protection Architectures for

Transparent Optical Networks

Contact: [email protected]. Grue, W. D. Grover, J. Doucette, B. Forst, D. Onguetou, D. Baloukov

TRLabs(Network Systems Group)7th Floor, 9107 – 116 StreetEdmonton, Alberta, Canada T6G 2V4

M. Clouqueur, D. Schupke

Nokia Siemens Networks(Network Control-Plane and

Transport)Otto-Hahn-Ring 6

81730 Munich, Germany

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Some InsightsSome Insights

• DSP:

- Why isn't it more efficient than it is ? (Turns out almost identical to 1+1 APS)

- Amenability to exact design with ILP (design ease)

• PXTs:

- High design and conceptual complexity

- Good flexibility for wavelength assignment, optical path length constraints

• p-Cycles

-Surprise that plain p-Cycles still have the best spare capacity efficiency

-Not inherently end-to-end path-protecting

-Optical Reach design control developed

-FIPP p-Cycles

- Offer a simple end-to-end “protected path tunnel” operating paradigm

- Exact ILP design possible, heuristics under development

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Project HAVANA: Ongoing WorkProject HAVANA: Ongoing Work

1. Node Failure restorability analysis (and enhanced design)

2. Detailed minimum-cost mapping of designs into nodal equipment models

3. Costs associated with design for 100% node failure restorability

4. Implications / feasibility of “same wavelength” protection options in each architecture

5. Finding a good heuristic for FIPP p-Cycle design.

6. Design for 100% R2 and/or to support multi-QoP classes involving an ultra high availability (R2=1) priority service.

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pp-Trees / -Trees / pp-Cycles: Computationally Distinct-Cycles: Computationally Distinct

p-Cycles Span p-Trees

PXTs/FIPP p-Cycles

Path p-Trees

100s or 1,000s of structures

10,000s or 100,000s of structures

Model Input Size

Mod

el C

ompl

exity Unified span-

protecting structure model

Unified path-protecting structure model

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The “Z” Case in FIPP The “Z” Case in FIPP pp-Cycle Design-Cycle Design• Protection paths are pre-connected, but the protection path to be used will

depend on the failure scenario

• For the purpose of this study, the network was deemed not intelligent enough to handle this degree of failure dependency

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The “Z” Case in FIPP The “Z” Case in FIPP pp-Cycle Design-Cycle Design• Protection paths are pre-connected, but the protection path to be used will

depend on the failure scenario

• For the purpose of this study, the network was deemed not intelligent enough to handle this degree of failure dependency

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Optical Path Lengths for Optical Path Lengths for pp-Cycles-Cycles• In a path-protecting architecture, protection paths are completely substituted

for working paths during failure, meaning that the lengths of the restored state paths are not in question

• In a span-protecting architecture (p-Cycles, span p-Trees), protection paths are only substituted for the failed span, which may be used by many working paths with different lengths

Too long?

Documents

A. Grue, W. D. Grover, J. Doucette, B. Forst, D. Onguetou, D. Baloukov TRLabs