1. Network Survivability Against Region Failure Signal Processing, Communications and Computing (ICSPCC), 2011 IEEE International Conference on Ran Li, Xiaoliang Wang, Xiaohong Jiang Adviser: Frank, Yeong - Sung Lin Present by Jason Chang

2. Agenda INTRODUCTION Background Region failure model and SPM routing REGION-DISJOINT MULTI-PATH ROUTING Optimization of Traffic Throughput Complexity Analysis SPM AGAINST SINGLE REGION FAILURE Problem Formulation NETWORK UPGRADE PROBLEM NUMERICAL RESULT CONCLUSION

3. Agenda INTRODUCTION Background Region failure model and SPM routing REGION-DISJOINT MULTI-PATH ROUTING Optimization of Traffic Throughput Complexity Analysis SPM AGAINST SINGLE REGION FAILURE Problem Formulation NETWORK UPGRADE PROBLEM NUMERICAL RESULT CONCLUSION

4. Background Communication has been a tremendous success with significant impact on our daily life. people are increasingly relying on large-scale communications large-scale computer networks are now facing more and more potential threats It is essential for the large-scale computer networks to have the capability of guaranteeing mission-critical information change.

5. Background Previously work around network survivability mainly focuses on single link or node failure in a logical topology. link cut and router software/hardware error are the main failure modes Network scale is increasing and network robustness is becoming more stringent, the multiple simultaneous failure scenarios have been address in some recent research works. technique of providing protection if a second link fails before recovering from the first link failure resilient routing schemes SRLG(shared risk link group) Based on graph-theoretical optimization technique, the strategies for protection and restoration of optical paths against SLRG failures

6. Background In real networks some disruptive events which may simultaneously affect multiple network components confined to a specific area are so called region failure. Region failures may lead to catastrophic data loss and may take a long time to be recovered. Due to the fact that the network failures due to a region failure are geographically correlated, the geographical layout of network components needs to be carefully take into account in the region failure- related network survivability analysis.

7. Background Intuitively, the region failure can be considered as a highly localized event where the failed nodes and links are clustered in a geographical area.

8. Background In recent years, various methodologies have been proposed to evaluate the impact of region failure. identify the most vulnerable region to a region failure in real network physical topologies, where the region failures are modeled as line-segment cuts or circular cuts arbitrarily placed on network plane analyze network failures after randomly localized linear cut physical connectivity logical connectivity under physical link failure

9. Background The classical Menger’s theorem(i.e. the max-flow min-cut theorem) does not hold any more for region- based connectivity analysis.

10. Region failure model and SPM routing The region failure is modeled as a circular disk of radius r, which centers at a network node. Any network component intersecting with this region will be destroyed and removed from the network. Approach to dealing with network components failure is to provide both backup path and primary path for each traffic demand.

11. To improve the efficiency of protection : shared backup path protection self – protection multipath routing For simplicity, we assume that the cost effective self- protecting multipath routing is adopted and all routing paths are known in advance. Region failure model and SPM routing

12. Self-protecting multi-path routing (SPM) is based on the idea of traffic load-balance. In IP/MPLS networks, it is possible to setup two or more working path, and the spare capacity of these working path can be applied to provide backup for each other when network failure occurs. Region failure model and SPM routing

13. SPM consists of disjoint paths and the traffic is distributed over all of them according to a traffic distribution function. Due to the fact that two of the routing path may be covered by a single region, only one of them can be applied. Region failure model and SPM routing

14. Agenda INTRODUCTION Background Region failure model and SPM routing REGION-DISJOINT MULTI-PATH ROUTING Optimization of Traffic Throughput Complexity Analysis SPM AGAINST SINGLE REGION FAILURE Problem Formulation NETWORK UPGRADE PROBLEM NUMERICAL RESULT CONCLUSION

15. Optimization of Traffic Throughput NotationDescription G(N,E)a network with |N| nodes and |E| links Ra finite candidate regions e = (i,j)a link between two adjacent nodes i and j ueue the link capacity of e = (i,j) T sd the demand of connection requirement from node s to node d PB sd the set of routing paths illustrated in Figure 3(b) the path from s to d using link e the traffic throughput

16. Optimization of Traffic Throughput The optimization function aims at maximizing the traffic throughput ：

17. Optimization of Traffic Throughput Additionally, paths between a source-destination pair should be region-disjoint ：

18. Complexity Analysis As the number of connections is less than and the number of paths for one connection is less than the outdegree of the source node,,the number of variable is thus bounded by. The total number of equations in the constraint (1) is, while the number of equations in the constraint (2) is.

19. Agenda INTRODUCTION Background Region failure model and SPM routing REGION-DISJOINT MULTI-PATH ROUTING Optimization of Traffic Throughput Complexity Analysis SPM AGAINST SINGLE REGION FAILURE Problem Formulation NETWORK UPGRADE PROBLEM NUMERICAL RESULT CONCLUSION

20. The SPM consist of multiple paths over which the traffic is distributed according to a load balancing function. The backup capacities may be shared by different flows in various failure scenario. Our target is maximize network throughput under any single region failure. Problem Formulation

21. NotationDescription G(N,E)a network with |N| nodes and |E| links Ra finite candidate regions e = (i,j)a link between two adjacent nodes i and j ueue the link capacity of e = (i,j) PB sd the set of routing paths illustrated in Figure 3(b) link e is covered by region r k, r k R r0r0 the normal scenario (no failure) R’R r 0

22. We useas the traffic spilt ration of path P for demand from s to d in case of a region failure The throughput of this demand can be expressed as: Problem Formulation

23. The function of LP model can then be expressed as:

24. Agenda INTRODUCTION Background Region failure model and SPM routing REGION-DISJOINT MULTI-PATH ROUTING Optimization of Traffic Throughput Complexity Analysis SPM AGAINST SINGLE REGION FAILURE Problem Formulation NETWORK UPGRADE PROBLEM NUMERICAL RESULT CONCLUSION

25. For a network can not accommodate all the traffic with regard to any single region failure, we may need to upgrade the network by providing additional link capacity. To realize a minimum capacity for a upgrade for a given network such that it can serve all traffic matrix in case of any single region failure. Network Upgrade Problem

26. We denote the additional capacity require by link as, then we have : Network Upgrade Problem

27. Agenda INTRODUCTION Background Region failure model and SPM routing REGION-DISJOINT MULTI-PATH ROUTING Optimization of Traffic Throughput Complexity Analysis SPM AGAINST SINGLE REGION FAILURE Problem Formulation NETWORK UPGRADE PROBLEM NUMERICAL RESULT CONCLUSION

28. Two real network topologies are adopted in our simulation, the USA network and the NFSNET network. Set capacity as 1 for all the links. The demands are generated randomly with equal probability between any pair of nodes. Bandwidth requirements are over provided in the interval of 0 – 50 with uniform distribution. Numerical Result

29. USA network : 26 nodes 41 links Max distance : 187 Average distance : 111 Minimum distance : 66 Numerical Result

30. NFSNET network : 79 nodes 109 links Max distance : 154 Average distance : 175 Minimum distance : 36 Numerical Result

31. The throughput decreases as the region size increase :

32. The worst region failure in the network that results in the maximum throughput degradation : (in USA network) Numerical Result

33. The worst region failure in the network that results in the maximum throughput degradation : (in NFSNET network) Numerical Result

34. Agenda INTRODUCTION Background Region failure model and SPM routing REGION-DISJOINT MULTI-PATH ROUTING Optimization of Traffic Throughput Complexity Analysis SPM AGAINST SINGLE REGION FAILURE Problem Formulation NETWORK UPGRADE PROBLEM NUMERICAL RESULT CONCLUSION

35. Evaluate the impact of region failures on network survivability. Apply the region – disjoint self – protecting multi – path routing. The existing networks are actually very vulnerable to the region failure. It is critical to design a fault – tolerant network against region failure. Conclusion

36. Thanks for your listening