1. John Doucette and Wayne D. Grover
Node-Inclusive Span Survivability in an Optical Mesh Transport Network
John Doucette and Wayne D. Grover
TRLabs and University of Alberta
Edmonton, AB, Canada
NFOEC 2003
Orlando, FL, USA
7-11 September 2003

2. Introduction Span Restoration End-to-End Path Restoration
Localized and shorter restoration paths
Faster and easier control of transmission effects
Less capacity efficient
No ability to recover from node failures
End-to-End Path Restoration
More capacity efficient
Inherent ability to recover from node failures
Operationally more complicated
Many nodes involved, and restoration paths are lengthy
Greater average delay
Can we modify span restoration to protect node failures?
Will this combine benefits of span and path restoration?

3. Node-Inclusive Span Survivability ConceptZ X B C D Y
custodial
nodes
Span Restoration A Z B C D X Y
custodial
node
Path Restoration A Z X B C D Y
custodial
regions
node-inclusive span entity NA NZ
Node-Inclusive Span Survivability

4. NISS Operational DetailsB C D E X A B C D E X
Span Failure Recovery:
Node Failure Recovery: A B C D E X

5. NISS Operational Details(2)
restoration route
custodial
node
custodial
regions A Z B Y X C O D X O D X
custodial
node
restoration route

6. Integer Linear Programming Model
Objective Function:
Minimize cost of spare capacity
Subject To:
Restoration flow for all span failure scenarios
Spare capacity allocation for span failures
including stub release
Restoration flow for all node failure scenarios
Spare capacity allocation for node failures

7. Computational Aspects
Test networks
Group A: Nine small test networks (9-node 17-span to 11-node 26-span)
Group B: Three families of networks of varying average nodal degree (15-node to 25-node)
Traffic demands
Group A: Various, as per networks’ sources
Group B: Uniform random demands from 1 to 10 wavelengths
Working capacity is shortest path routed
Eligible route enumeration
At least five eligible restoration routes per failure scenario
ILP solution method
Implemented in AMPL and solved using CPLEX 7.1 MIP
4-processor UltraSparc Sun Server, 450 MHz, 4 GB RAM
Solved to within 0.01% of optimality
Most problems solved in several seconds or minutes

8. Results
Test Networks: Group A

9. Results (2)
Test Networks:
Group B 15-node family

10. Results (3)
Test Networks:
Group B 20-node family

11. Results (4)
Test Networks:
Group B 25-node family

12. Concluding Remarks Node failure protection is inherent
and we can explicitly guarantee it
Spare capacity requirements are good
significantly below span restoration
approaching path restoration (within 0% to 10%)
Easily amenable to dynamic service provisioning
working capacity envelope can apply
Localized restoration paths make operational aspects much easier than path restoration