Path Protection in MPLS Networks

1. Path Protection in MPLS Networks Using Segment Based Approach

2. Overview • Short Intro to MPLS • Introduction to Our work – Protection and the segment Based approach • Algorithms for QoS constraints • Switch Over time Algorithm • Greedy Approach • Consideration of Backup Paths • Conserving protection resources – sharing bw • End-to-End delay and Jitter • Combining the above constraints • Reliability • Visualization System • Experimental Results • Conclusion and work done

3. Introduction to MPLS Request: 47.1 Request: 47.1 Mapping: 0.50 Mapping: 0.40 1 47.1 3 3 1 2 1 2 47.3 3 47.2 2

4. Label Switched Path (LSP) IP 47.1.1.1 IP 47.1.1.1 1 47.1 3 3 1 2 1 2 47.3 3 47.2 2

5. Introduction to Path Protection 1 47.1 3 3 1 2 1 2 47.3 3 47.2 2

6. Introduction to Path Protection BACKUP PATH 1 47.1 3 3 1 2 1 2 47.3 3 47.2 2

7. Requirements of Path Protection • Should Reroute the traffic satisfying certain QoS constraints • Should aim to conserve the amount of protection resources reserved

8. Global Path Protection Backup Path

9. Local Path Protection

10. Segment Based Path Protection • Look at the path as a group of segments – protect each segment separately • Results in fewer backup paths – conserves resources • Meets QoS constraints in a “tight” manner • Gives flexibility Issue : How to segment the path ?

11. Algorithms for QoS constraints

12. QoS Constraints • Important parameters • Switch-Over Time • End-to-End Delay • Jitter • Reliability • Combination of above • Have to conserve protection resources

13. Bounded Switch Over Time • Definition of Switch Over Time

14. An expression for switch over time Analysis for switch over time RTT( Ri , Rj ) + Ttest <

15. Example for Segment Based Approach

16. Example for Segment Based Approach Here we are able to meet the Switch Over time constraint with 3 backup paths as compared to 7 backup paths in LPP A simple algorithm for segmentation: Greedy Approach

17. The Resource advantage

18. Problem with Greedy Approach Need to consider the topology of the network as well

19. An adaptive Algorithm for segmentation Start from the egress and look for longest possible segment

20. End-to-End Delay An important parameter

21. Analysis Max (T + ( t2 – t1 ) ) < EED Bound

22. Algorithm for end-to-end delay • For each backup path, we need to make sure that the end-to-end constraint is satisfied • Use shortest path approach for finding a backup path – minimizes end-to-end delay

23. Algorithm for end-to-end delay d1 d2 d3 d2 + d3 d3 d1 + d2 + d3 0 Searching for a backup path

24. Jitter • Jitter can be treated as a link property • Path Jitter = Σ Link Jitter • Algorithm similar to end-to-end delay

25. Combination of above constraints A combined Algorithm for Approach Dynamic Programming Switch Over Time End-to-End Delay Jitter

26. Algorithm based on Dynamic Programming Ri Rk Rj Artificial Node

27. Reliability • An important QoS parameter in Computer Networks. • Path Reliability : Probability of a path to be in a working state at some instant of time. • Link Reliability (p) : Probability of a link to be in working state at some instant of time.

28. Reliability - Objectives • Effect of Path Protection on Reliability • Effect of Segment Size on Reliability • An O(No. of Links + (No. of Segments)2 ) Algorithm to find exact path reliability ! • Algorithm for Finding most reliable Backup Path • Heuristics for SBPP with reliability bounds

29. Effect of Path Protection on Reliability n links n links B A • Total number of links in primary path = n • Reliability of a link : p • Path Reliability from A to B = pn Path Reliability from A to B with backup path = 2pn – p2n

30. Effect of Path Protection on Reliability

31. Effect of Segment Size on Reliability • Total number of links in primary path = n • Reliability of a link : p • Size of Segments = k • Number of Segments = n/k • Size of Backup Path = Size of Segment • Reliability of the path = (2pk – p2k)n/k

32. Effect of Segment Size on Reliability

33. Algorithm to find path reliability Theoretically a path exists between ingress and egress nodes : R1 -> R2 -> R4 -> R5 -> R6 -> R7 No path between ingress and egress nodes in our path switching approach !

34. Algorithm to find path reliability Probability of Primary path for a particular segment Si to be working Probability of Backup path for Segment Si to be working Probability of Sito Sj-1 segments’s primary path to be working & segment Sj primary path to have an error

35. Algorithm for Finding most reliable Backup Path Ri Rj Artificial Node

36. Heuristics for SBPP with reliability bounds • Find the Segmentation with least number of segments • Divide any segment into two till the reliability bound is met

37. Visualization System

38. Visualization of Algorithms • A visualization system developed based on POLKA – an algorithm animation toolkit • Closely Integrated with the simulator • Aids in understanding how the algorithms work • Assists in establishing correctness of algorithms and simulations • Dynamic Nature of Visualizations

39. Visualization • Two categories of Visualization: • Animation for Adaptive Bounded Switch Over Time Algorithm • Rerouting of packets by SSR in case of failure (packet flow animation) – demonstrates various cases

40. Topology for Visualization

41. Visualization Demo

42. Experimental Results

43. Implementation • Simulator developed in C++ for implemented some algorithms • Size of model graph : 100 nodes , 1000 edges • RTT of each link = 10 ms • BW – 50 to 100 • Generated large number of random LSP requests and observed various parameters • Results indicate advantages of SBPP

44. Segment Size vs BW reserved

45. Segment Size vs Rejection Rate ( for 250 LSPs )

46. No. of Requested LSPs vs Rejection Rate

47. Effect of Backup Path Sharing

48. Crossover - Effects of backup path sharing

49. Effect of additional constraint

50. Effect of additional constraint