Protection Routing in an MPLS Network using Bandwidth Sharing with Primary Paths

1. Protection Routing in an MPLS NetworkusingBandwidth Sharing with Primary Paths Zartash Afzal Uzmi Computer Science and Engineering Lahore University of Management Sciences (LUMS) Visiting Professor – Chonbuk National University Lahore University of Management Sciences

2. Outline • Background • Network Services and QoS Requirements • Protection Routing in MPLS • Backup Bandwidth Sharing • Sharing with Primary Paths • NPP++ Protection Routing Framework • Routing Overhead • Path Computation • Path Signaling • Simulation Results • Evaluation and Experimentation • Simulation Parameters • Comparative Results Lahore University of Management Sciences

3. Outline • Background • Network Services and QoS Requirements • Protection Routing in MPLS • Backup Bandwidth Sharing • Sharing with Primary Paths • NPP++ Protection Routing Framework • Routing Overhead • Path Computation • Path Signaling • Simulation Results • Evaluation and Experimentation • Simulation Parameters • Comparative Results Lahore University of Management Sciences

4. IP versus MPLS • In IP Routing, each router makes its own routing and forwarding decisions • In MPLS: • Only one router (source) makes the routing decision • Intermediate routers make forwarding decisions • A path is computed and a “virtual circuit” is established from ingress router to egress router • An MPLS path or virtual circuit from source to destination is called an LSP (label switched path) Lahore University of Management Sciences

5. QoS Requirements • Bandwidth Guaranteed Primary Paths • MPLS allows establishing bandwidth-guaranteed paths • Bandwidth Guaranteed Backup Paths • BW remains provisioned in case of network failure • Minimal “Recovery Latency” • Recovery latency is the time that elapses between: • “the occurrence of a failure”, and • “the diversion of network traffic on a new path” Preset backup paths needed for minimal latency Lahore University of Management Sciences

6. Primary Path Backup Path Types of Backup Paths LOCAL PROTECTION (showing one LSP only) All links and all nodes are protected! nnhop A B D C E nhop PLR: Point of Local Repair Lahore University of Management Sciences

7. Opportunity cost of backup paths • Protection requires that backup paths are setup in advance • Upon failure, traffic is promptly switched onto preset backup paths • Bandwidth must be reserved for all backup paths • This results in a reduction in the number of Primary LSPs that can otherwise be placed on the network • Can we reduce the amount of “backup bandwidth” but still provide guaranteed backups? • YES: Try to share the bandwidth along backup paths Lahore University of Management Sciences

8. Primary Path Backup Path BW Sharing in backup Paths • Example: LSP1 BW: X Sharing is possible IF Links (A,B) and (C,D) do not simultaneously fail! A B X X max(X, Y) X E G F X+Y Y Y C D BW: Y LSP2 Lahore University of Management Sciences

9. Sharing with Primary Paths • Can we do any sharing with primary paths? • Normally, the answer is NO because… • Traffic is always flowing on the primary paths • BUT… • Backup paths protecting a node N may share bandwidth with primary paths that originate or terminate at node N because… • Such backup will be active when: • node N fails, and in that condition… • No primary originates or terminates at node N Sharing with (some) primary paths is possible Lahore University of Management Sciences

10. Outline • Background • Network Services and QoS Requirements • Protection Routing in MPLS • Backup Bandwidth Sharing • Sharing with Primary Paths • NPP++ Protection Routing Framework • Routing Overhead • Path Computation • Path Signaling • Simulation Results • Evaluation and Experimentation • Simulation Parameters • Comparative Results Lahore University of Management Sciences

11. Protection Routing Framework • Tasks related to backup paths in a protection routing framework: • Backup path computation • Backup path signaling • Objectives of protection routing framework • Incur scalable routing overhead • Find optimal backup paths • Maximize bandwidth sharing • NPP++ framework achieves all of above Lahore University of Management Sciences

12. 1.Scalable routing overhead • Aggregate Information Scenario (AIS) • Fij: Bandwidth reserved on link (i, j) for all primary LSPs • Gij: Bandwidth reserved on link (i, j) for all backup LSPs • Rij: Bandwidth remaining on link (i, j) • Extended NPP (NPP++) relies on AIS • Low routing overhead More Information propagated  More potential for BW sharing Lahore University of Management Sciences

13. 2.Optimal backup paths • Backup path computation is moved to a node that has maximal information about the activation set of protected element • Node that computes backup paths maintains two local maps: • BFTLIM • How much backup bandwidth will fall on a given link (u,v) if this element fails • PFTLIM • How much primary bandwidth will be available on a given link (u,v) if this element fails • FTLIMs keep historical information about bandwidth reserved for protecting an element • Leads to the computation of backup paths that are optimal Lahore University of Management Sciences

14. Path Computation in NPP++ R2 Contains: a) BFTLIM b) PFTLIM The backup paths protecting against the failure of R2 cannot share bandwidth on any link. R1 But such backup paths may share bandwidth with primary paths originating or terminating at R2. R5 R2 R3 R4 Path computation is shifted to R2 because… Only R2 has full knowledge of its own Activation set Lahore University of Management Sciences

15. 3.Maximum Bandwidth Sharing • Optimal path is signaled with requirements for FULL bandwidth • All nodes (along the backup path) maintain two local data structures: • BLTFIM • How much backup bandwidth will fall on this link if a given element fails • PLTFIM • How much primary bandwidth will be released on this link if a given element fails • LTFIMs help nodes reserve only what is needed • Leading to maximum sharing along backup paths Lahore University of Management Sciences

16. NPP++ Summary Protecting R2 (1) Advertise aggregate link usage information only LTFIMs R4 R1 R2 R3 FTLIMs FTLIMs FTLIMs LTFIMs LTFIMs (2) Path computation is shifted to special nodes • Results: • Path computation is optimal • Bandwidth sharing on backup paths is maximum. • Advertisement overhead is minimum (3) Nodes in primary path maintain “local data structures” called BFTLIM/PFTLIM Primary Path (4) Nodes in backup paths maintain “local data structures” called BLTFIM/PLTFIM Backup Path Lahore University of Management Sciences

17. Outline • Background • Network Services and QoS Requirements • Protection Routing in MPLS • Backup Bandwidth Sharing • Sharing with Primary Paths • NPP++ Protection Routing Framework • Routing Overhead • Path Computation • Path Signaling • Simulation Results • Evaluation and Experimentation • Simulation Parameters • Comparative Results Lahore University of Management Sciences

18. Evaluation & Experimentation • Traffic generation • Used existing traffic models • Rejected requests experiments • Generate a set of LSP requests • Measure the number of rejected requests • Simulate on various topologies • Scalability of local state information • How do the average number of entries in locally stored maps grow with the number of requests Lahore University of Management Sciences

19. Simulation Parameters • Simulations performed on two networks • Network 1: • 15-node heterogeneous topology • Core links with capacity 480 units, other links 120 units • Network 2: • 20-node homogenous topology (metros in the U.S.) • Each link with capacity 120 units • LSP requests arrive one-by-one • Ingress/Egress pairs chosen randomly • Bandwidth demand for each request is uniformly distributed between 1 and 6 • 100 experiments with different traffic matrices Lahore University of Management Sciences

20. Comparative Results: Network 1 Lahore University of Management Sciences

21. Comparative Results: Network 2 Lahore University of Management Sciences

22. Local Storage: Network 1 Lahore University of Management Sciences

23. Local Storage: Network 2 Lahore University of Management Sciences

24. Conclusions: NPP++ • Optimal path computation • Maximum sharing along computed path • Scalable routing overhead • Practically feasible • 15% – 40% improvement over existing protection schemes Lahore University of Management Sciences

25. Last slide… Thank you! Questions? Lahore University of Management Sciences