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QoS-Aware Path Protection for MPLS Networks

Learn about segment-based path protection schemes for MPLS networks, ensuring QoS guarantees and fault tolerance with efficient resource utilization. Explore algorithms for path segmentation, switch-over time analysis, end-to-end delay optimization, and reliability calculations. Discover a heuristic algorithm for reliability bounds and a visualization system for interactive simulations.

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QoS-Aware Path Protection for MPLS Networks

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  1. QoS Aware Path Protection Schemes for MPLS Networks Ashish GuptaAshish Gupta Under Guidance ofProf. B.N. Jain Department of Computer Science and Engineering Advanced Networking Laboratory

  2. 47.1 1 IP 47.1.1.1 2 IP 47.1.1.1 1 3 2 IP 47.1.1.1 1 47.2 3 47.3 2 IP 47.1.1.1 Routing - The IP Way All packets follow the same path Need for more control on routing

  3. IP 47.1.1.1 IP 47.1.1.1 Multiprotocol Label Switching 1 47.1 3 3 2 1 1 2 47.3 3 47.2 2 Gives explicit control over routing according to traffic requirements Concept of Label Switching and Label Switched Paths (LSPs)

  4. Need for Fault Tolerance 1 47.1 3 3 1 2 1 2 47.3 3 47.2 2 Modern delivery services need to be robust...

  5. BACKUP PATH Method of Path Protection 1 47.1 3 3 1 2 1 2 47.3 3 47.2 2 Using Dynamic Routing Algorithms, recovery may take order of seconds ! Enables faster recovery than Layer 3 Mechanisms Reserve an alternate path and use it in case of failure

  6. Major Concerns for Path Protection Should provide quick recovery after a failure Optimal Use of Backup Resources

  7. Backup Path Global Path Protection Primary Path

  8. Local Path Protection

  9. What's Missing ? • The solutions are fixed • No assurance for various QoS constraints We need guarantees that in case of failure, we will not lose packets for more than 50 ms Or even in case of failure, the end to end delay will not exceed 150 ms Fault Tolerance with QoS Guarantees

  10. Segment Based Approach to Path Protection

  11. Segment Based Path Protection The Main Idea Look at the path as a sequence of segments and protect each segment separately • Results in fewer backup paths – conserves resources • Can meet QoS constraints in a “tight” manner • Gives flexibility – How ?

  12. Main Focus An Example • A Segment is a set of nodes which consists of: • Segment Switch Router – protects the segment • Protected Nodes How to divide the path into segments such that ? If any segment fails, specified QoS constraints can be guaranteed

  13. + Algorithms have to use backup resources effectively Algorithms for segmenting the path • Various QoS constraints considered: • Bounded Switch-Over Time • End-to-End Delay • Jitter • Reliability • Combination of above

  14. Algorithms for bounded Switch over time Switch over time : The time for which the packets are lost between the failure and recovery Why do we lose packets ?

  15. Analysis for Bounded Switch over time Using Timing Analysis, we derived a limit to the possible segment size RTT( Ri , Rj ) + Ttest <

  16. The Algorithm Divide the path into minimum number of segments such that the inequality is satisfied for each segment • A new Adaptive Algorithm for Bounded Switch over time has been developed • Takes into account the topology and bandwidth reservation in the network • Intuitive choice: Greedy Algorithm • Problems with Greedy Algorithm

  17. The Adaptive Algorithm • Assures QoS satisfaction • Proved to be optimal • Robust • We have implemented it using the LSP Admission Control Simulator and tested it • Results indicate its efficiency

  18. In this analysis, we need to consider backup paths also. Max (T + ( T2 – T1 ) ) <  Analysis for End-to-End delay

  19. The Algorithm We need to satisfy the inequality for each possible path • For each segment (found using previous algorithm), find the shortest possible backup path • Will give the minimum value of end-to-end delay • Check if inequality is satisfied, otherwise reject the current segment

  20. More QoS constraints • Jitter – similar to End-to-End delay • Multiple QoS constraints • Bounded Switch Over time • End-to-End Delay • Jitter • Developed an algorithm using Dynamic Programming Approach

  21. Algorithm Developed for Reliability • Finding Reliability between two nodes : An NP complete problem • Earlier we were engaged in finding bounds • But turns out, Segment Based Approach allows for simpler analysis !

  22. Algorithm Developed for Reliability An O(No. of Links + (No. of Segments)2 ) Algorithm to find exact path reliability ! Algorithm for finding the most reliable backup path A heuristic Algorithm has been developed for meeting bounds on Reliability for the protection configuration

  23. 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

  24. The Visualization System • A visualization system developed for the Segment based Algorithms: based on POLKA • Closely Integrated with LSP Admission Control Simulator • Visualizations are Dynamic not Static • Aids in understanding how the algorithms work • Assists in establishing correctness of algorithms and simulations

  25. Topology Used

  26. Visualization Demonstration !

  27. Experimental Results Aim of the Experiments To evaluate the resource related advantages of Segment based Approach, while assuring QoS constraints

  28. Experimental Results • An LSP Admission Control Simulator has been developed in C++ • Simulates multiple networks with different reservation policies and compares results • We implement the Segment Based Algorithm for Bounded Switch over time for providing Protection to LSPs generated • BWSharing Mechanisms also implemented

  29. Experimental Results • Simulation Setup • Topology with 50 routers and 82 links • LSPs setup using Djiktra’s Algorithm • BW of each link: 3000 to 10000 units • Delay of each link : 8 to 12 ms • BW requirements of each LSP : 20 to 70 units LSP requests were generated with different QoS parameters

  30. Comparison of Different Schemes

  31. Variation of Switch over time bound

  32. Rejection Rate vs Bound on Switch over time

  33. Conclusion • Today major networking companies are quickly shifting towards MPLS-based networks • Major Players:Cisco , AT&T, Level 3, Hewlett Packard, UUNet, MCI World Com • “Within an MPLS-enabled network, even packet voice services such as voice over IP will benefit from reduced latency and congestion control” Ranjeet Sudan, MPLS product manager at Cisco Efficient Fault Tolerance in such services is a major concern

  34. Conclusion • For providing reliability to such services we now have Fault Tolerance Schemes which: • Guarantee satisfaction of various QoS constraints in case of failure • Use backup resources in an optimal manner

  35. Overview of BTP • Mechanisms for Detection and Notification • Algorithms for various QoS constraints • Bounded Switch over time • End-to-End delay • Jitter • Combination of above • Reliability • Issues relating to backup path – Sharing… • Admission Control Simulator developed for above • Visualization System

  36. Paper being submitted to Being held in Mumbai this year

  37. Thank You

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