1. Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity John Doucette Wayne D. Grover TRLabs and University of Alberta Edmonton, Canada Copyright © W. Grover (TRLabs) November 2001

2. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 1 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Outline Background Restoration / Protection Schemes Test Network Families with Varying Nodal Degree Computational Aspects Results Interpretations and Summary Further Reading

3. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 2 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Background 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 d = 4.4

4. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 3 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Restoration/Protection Schemes Compared RestorationRestoration SCA –Span-Restorable Spare Capacity Assignment (SCA) JCA –Span-Restorable Joint Capacity Assignment (JCA) M-M –Meta-Mesh (M-M) Path –Path-Restorable Spare Capacity Assignment (Path) ProtectionProtection 1+1 APS –Non-Shared Backup Path Protection (1+1 APS) SBPP –Shared Backup Path Protection (SBPP)

5. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 4 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity 1+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 end transfer) 2 diverse paths, full signal feed Select (tail end transfer) 21 22 1 Spare Needed

6. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 5 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Span-Restorable Schemes (SCA and JCA) SCA working paths first routed via shortest pathJCA 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 1 3 4 reuse of spare capacity

7. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 6 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Meta-Mesh add/drop add/drop add/drop express bypass local flow 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 restoration flow into meta-mesh restoration flow into meta-mesh loop back loop back fail back

8. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 7 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Shared Backup Path Protection (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 11 11 1 Spare Needed 1+1 APS: 8 spare SBPP: 5 spare Working path spare capacity reuse spare capacity reuse

9. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 8 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Dynamic Path Restoration 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 pairs stub-release MCMF-like recovery

10. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 9 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity d = 3.29 Making Nodal Degree a Study Parameter: Using 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 = 3.23 d = 3.16 d = 3.10 d = 3.03 d = 2.97 d = 2.90 d = 2.84 d = 2.77 d = 2.71 d = 2.65 d = 2.58 d = 2.52 d = 2.45 d = 2.39 d = 2.32 d = 2.26 d = 2.19

11. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 10 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Computational 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)

12. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 11 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Results: Total Capacity vs. Nodal Degree x2 30%

13. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 12 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Results: Capacity Breakdown vs. Nodal Degree x3

14. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 13 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Results: Redundancy vs. Nodal Degree x2

15. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 14 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity 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

16. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 15 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity 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

17. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 16 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Further 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.

18. Overview and Evaluation of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity John Doucette Wayne D. Grover TRLabs and University of Alberta Edmonton, Canada TRLabs Smartboard Presentation 01/November/2001

19. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 18 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity Span-Restorable Bound on Redundancy W1W1 W2W2 WdWd W3W3... W1W1 W2W2 WdWd W3W3 W1W1 S 2 S d S 3 An isolated node: Best case for efficiency: W 1 = W i for all i & S 1 = S i for all i

20. John Doucette, Wayne D. Grover Copyright © W. Grover (TRLabs) November 2001 19 Capacity Comparison of Mesh Network Restoration and Protection Schemes Under Varying Graph Connectivity SBPP 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 D C B U V T S