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Capacity Comparison of Mesh Capacity Comparison of Mesh Network Restoration and Protection Network Restoration and Protection
Schemes Under Varying Graph Schemes Under Varying Graph ConnectivityConnectivity
John DoucetteJohn Doucette
Wayne D. GroverWayne D. GroverTRLabs and University of Alberta
Edmonton, Canada
Copyright © W. Grover (TRLabs) November 2001
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 20012
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
OutlineOutline
• Background• Restoration / Protection Schemes• Test Network Families with Varying Nodal Degree• Computational Aspects• Results• Interpretations and Summary• Further Reading
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 20013
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
BackgroundBackground
• Growing number of restoration and protection mechanisms and design schemes– we identify six alternatives
to compare
• How does graph connectivity affect mesh-survivable capacity design?– Not widely studied aspect of
mesh networks– greater understanding can
guide topology planning– research method can vary
nodal degree as a parameter
d = 2.3
TORINO
GENOVA
ALESSANDRIA
PISA
MILANOBRESCIA
SAVONA
BOLOGNA
VERONA
VICENZA
VENEZIA
FIRENZEANCONA
PESCARA
PIACENZA
MILANO2
PERUGIA
L’AQUILA
ROMA
ROMA2
NAPOLI SALERNO
CATANZARO
POTENZA
BARI
TARANTO
CAGLIARI
SASSARI
FOGGIA
PALERMOMESSINA
REGGIO C.
d = 4.4
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 20014
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
Restoration/Protection Schemes ComparedRestoration/Protection Schemes Compared
• RestorationRestoration– Span-Restorable Spare Capacity Assignment
(SCASCA)– Span-Restorable Joint Capacity Assignment
(JCAJCA)– Meta-Mesh (M-MM-M)
– Path-Restorable Spare Capacity Assignment (PathPath)
• ProtectionProtection– Non-Shared Backup Path Protection
(1+1 APS1+1 APS)– Shared Backup Path Protection (SBPPSBPP)
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 20015
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
1+1 APS1+1 APS
• shortest path working route and shortest disjoint backup path (if it exists)
• at least 100% redundancy– no sharing of protection
capacity
• no optimization required– global solution is sum of
individual 1 +1 routing problems
Select(tail endtransfer)
2 diverse paths, full signal feed2 diverse paths, full signal feed
2 diverse paths, full signal feed2 diverse paths, full signal feed
Select(tail endtransfer)
2 12 2
1
SpareNeeded
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 20016
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
Span-Restorable Schemes (Span-Restorable Schemes (SCASCA and and JCAJCA))
SCASCA• working paths first routed
via shortest path
JCAJCA• working paths optimized
jointly with spare capacity for minimum total capacity
• conceptual mesh counter-part to BLSR multi-ring networks
• can use “self-healing” distributed protocol or centralized control for KSP-type re-routing
• amenable to distributed pre-planning for fast restoration
W = 4
W = 6 multiple restoration
paths
2
4
1
3
3
13
4reuse of sparecapacity
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 20017
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
Meta-MeshMeta-Mesh
add/dropadd/drop
add/dropadd/drop
add/dropadd/drop
expressbypass
localflow
Meta-Mesh (M-M)Meta-Mesh (M-M)
• span restoration method with logically bypassed chain subnetworks– span restoration operates on
the meta-mesh abstraction– chain subnetworks use line
loop-back for intra-chain flows
– express flows on chains fail back to meta-mesh nodes
• as JCA span-restorable capacity design but with added logical bypass spans
• especially targeted to improve mesh efficiency on sparse transport graphs
restorationflow into
meta-mesh
restorationflow into
meta-mesh
loopback
loopback
failback
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 20018
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
Shared Backup Path Shared Backup Path ProtectionProtection (SBPP) (SBPP)
• as 1+1 APS but with sharing of spare capacity
• motivated by IETF deliberations for MPλS, etc.
• optimization chooses shared backup routes for minimum total spare capacity
• a compromise over true path-restoration to avoid signaling for stub-release
1 11 1
1
SpareNeeded
1+1 APS: 8 spare1+1 APS: 8 spareSBPP: 5 spareSBPP: 5 spare
Working path
Working path
spare capacity spare capacity reusereuse
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 20019
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
Dynamic Path Dynamic Path RestorationRestoration
• theoretically most capacity efficient class of scheme (MCMF-like recovery)
• failure-specific re-routing of all affected demand pairs with no pre-planned disjoint backup routes
• stub-releasestub-release: surviving stubs of failed working paths released for re-use as spare capacity
• centralized control or self-organizing path restoration protocol options
• distributed pre-planning an option for very fast restoration
3 affected end-node pairs3 affected end-node pairsstub-releasestub-releaseMCMF-like recoveryMCMF-like recovery
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 200110
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
d = 3.29d = 3.29
Making Nodal Degree a Study Parameter:Making Nodal Degree a Study Parameter:Using Families of Test NetworksUsing Families of Test Networks
• family of 18 related networks of varying average nodal degree– derived by reduction from 32-node 51-span master
network– each successively sparser network created by a random
span removal subject to retaining bi-connectivity
d = 3.23d = 3.23d = 3.16d = 3.16d = 3.10d = 3.10d = 3.03d = 3.03d = 2.97d = 2.97d = 2.90d = 2.90d = 2.84d = 2.84d = 2.77d = 2.77d = 2.71d = 2.71d = 2.65d = 2.65d = 2.58d = 2.58d = 2.52d = 2.52d = 2.45d = 2.45d = 2.39d = 2.39d = 2.32d = 2.32d = 2.26d = 2.26d = 2.19d = 2.19
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 200111
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
Computational AspectsComputational Aspects
• full-mesh pattern of demand pairs for master network– generated by mutual attraction model (no inverse distance
effects)– average of 5.8 demands units per O-D pair
• eligible route enumeration– SCA, Path: 20 distinct eligible restoration routes per span
failure– JCA: as SCA plus 10 distinct eligible working routes per O-D
pair– SBPP: 5 distinct eligible restoration routes per O-D pair– Meta-Mesh: 20+20, 10+10
• design solutions– implemented in AMPL and solved with Parallel CPLEX 7.1 MIP– SBPP: solved within 1% of optimality (CPLEX mipgap 0.01)– All Others: solved within 0.01% of optimality (mipgap
0.0001)
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 200112
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
500 000
600 000
700 000
800 000
900 000
1 000 000
1 100 000
1 200 000
1 300 000
1 400 000
1 500 000
2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4
Tota
l C
apac
ity
(dis
tan
ce-w
eig
hte
d)
SCA
JCA
M-M
Path
SBPP
1+1 APS
Network Average Nodal Degree, d
Results: Total Capacity vs. Nodal DegreeResults: Total Capacity vs. Nodal Degree
x2x230%30%
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 200113
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
100 000
200 000
300 000
400 000
500 000
600 000
700 000
800 000
900 000
2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4
Wo
rkin
g a
nd
Sp
are
Cap
acit
y (d
ista
nce
-wei
gh
ted
)
SCASpare
JCA Spare
M-M Spare
PathSpare
SBPPSpare
M-M Working
JCA Working
Shortest Path Working
Network Average Nodal Degree, d
Results: Capacity Breakdown vs. Nodal DegreeResults: Capacity Breakdown vs. Nodal Degree
x3x3
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 200114
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
40%
60%
80%
100%
120%
140%
160%
180%
200%
220%
2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4
Dis
tan
ce-C
apac
ity
Red
un
dan
cy
SCA
JCA
M-M
Path
SBPP
1+1 APS
Network Average Nodal Degree, d
40%
60%
80%
100%
120%
140%
160%
180%
200%
220%
2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4
Dis
tan
ce-C
apac
ity
Red
un
dan
cy
SCA
JCA
M-M
Path
SBPP
1+1 APS
Network Average Nodal Degree, d
1 ( -1)d
Results: Redundancy vs. Nodal DegreeResults: Redundancy vs. Nodal Degree
x2x2
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 200115
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
Interpretations and Summary (1)Interpretations and Summary (1)
• capacity differences between mesh schemes come essentially all from spare capacity difference, not working
• tends to confirm that when going from ring to mesh, benefit is obtained simply by the change to mesh, regardless of type (working routing benefits greatly)
• dynamic path restoration with stub-release outperforms all other schemes in capacity efficiency
• meta-mesh and SBPP are almost as efficient as path restoration but simpler to implement
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 200116
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
Interpretations and Summary (2)Interpretations and Summary (2)
• 1/(d-1) redundancy bound explains how span-restorable schemes react to graph connectivity (path curves are steeper)
• meta-mesh uses a span-restoration mechanism but nonetheless does better than 1/(d-1) bound
• there exists a point in the graph connectivity scale where capacity requirements level out (2.6 for this network)– helpful from a network topology planning point of view
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 200117
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
Further ReadingFurther Reading
• J. Doucette, W. D. Grover, “Comparison of Mesh Protection and Restoration Schemes and the Dependency on Graph Connectivity,” Proc. 3rd International Workshop on Design of Reliable Communication Networks (DRCN 2001), Budapest, Hungary, pp. 121-128, October 2001.
• W. D. Grover, J. Doucette, M. Clouqueur, D. Leung, D. Stamatelakis, “New Options and Insights for Survivable Transport Networks,” IEEE Communications Magazine, vol. 40, no. 1, in press, January 2002.
• W. D. Grover, J. Doucette, “Design of a Meta-Mesh of Chain Sub-Networks: Enhancing the Attractiveness of Mesh-Restorable WDM Networking on Low Connectivity Graphs,” IEEE Journal on Selected Areas in Communications, Special Issue on WDM-based Network Architectures, in press, 1st Quarter 2002.
• W. D. Grover, J. Doucette, “Topological design of span-restorable mesh transport networks,” Annals of Operations Research, Special Issue on Topological Design of Telecommunication Networks, in press, 2001.
• W. D. Grover, J. Doucette, “A Novel Heuristic for Topology Planning and Evolution of Optical Mesh Networks,” Proc. IEEE Global Telecommunications Conference (GlobeCom 2001), San Antonio, TX, in press, November 2001.
• M. Herzberg, S. J. Bye, A. Utano, “The hop-limit approach for spare-capacity assignment in survivable networks,” IEEE/ACM Transactions on Networking, vol. 3, no. 6, pp. 775-784, December 1995.
• B. Van Caenegem, W. Van Parys, F. De Turck, P. M. Demeester, “Dimensioning of Survivable WDM Networks,” IEEE Journal on Selected Areas in Communications, vol. 16, no. 7, pp. 1146-1157, September 1998.
• R. R. Iraschko, W. D. Grover, “A highly efficient path-restoration protocol for management of optical network transport integrity,” IEEE Journal on Selected Areas in Communications, vol. 18, no. 5, pp. 779-793, May 2000.
• R. R. Iraschko, M. H. MacGregor, W. D. Grover, “Optimal Capacity Placement for Path Restoration in STM or ATM Mesh-Survivable Networks,” IEEE/ACM Transactions on Networking, vol. 6, no. 3, pp. 325-336, June 1998.
• W. D. Grover, “Self-organizing Broad-band Transport Networks,” Proceedings of the IEEE, vol. 85, no. 10, pp. 1582-1611, October 1997.
• Y. Xiong; L. G. Mason, “Restoration strategies and spare capacity requirements in self-healing ATM networks," IEEE/ACM Transactions on Networking, vol. 7, no. 1, pp. 98-110, February 1999.
Overview and Evaluation of Mesh Overview and Evaluation of Mesh Network Restoration and Protection Network Restoration and Protection
Schemes Under Varying Graph Schemes Under Varying Graph ConnectivityConnectivity
John DoucetteJohn Doucette
Wayne D. GroverWayne D. GroverTRLabs and University of Alberta
Edmonton, Canada
TRLabs Smartboard Presentation01/November/2001
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 200119
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
Span-Restorable Bound on RedundancySpan-Restorable Bound on Redundancy
W1
W2
Wd
W3
...
W1
W2
Wd
W3
W1
S2
Sd
S3
An isolated node:An isolated node:
Best case for efficiency:Best case for efficiency:
WW11 = W = Wii for all for all ii
&&SS11 = S = Sii for all for all ii
John Doucette, Wayne D. GroverCopyright © W. Grover (TRLabs) November 200120
Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity
SBPP Routing InfeasibilitiesSBPP Routing Infeasibilities
• all node-pairs in (A, B, C, D) with (S, T, U, V) are unable to find a disjoint backup path if use shortest path work routing
• frequent in sparse networks
• several solutions– Suurballe’s algorithm– shortest cycle– iteration– joint capacity design
A DCB
U
V
TS