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Protection Routing in an MPLS Network using Bandwidth Sharing with Primary Paths Zartash Afzal Uzmi Computer Science and Engineering Lahore University of Management Sciences (LUMS) Visiting Professor – Chonbuk National University Jan 13, 2006 Lahore University of Management Sciences 1 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 Jan 13, 2006 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 Jan 13, 2006 Lahore University of Management Sciences 3 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) Jan 13, 2006 Lahore University of Management Sciences 4 QoS Requirements Bandwidth Guaranteed Primary Paths Bandwidth Guaranteed Backup Paths MPLS allows establishing bandwidth-guaranteed 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 Jan 13, 2006 Lahore University of Management Sciences 5 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 Primary Path Backup Path Jan 13, 2006 Lahore University of Management Sciences 6 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? Jan 13, 2006 YES: Try to share the bandwidth along backup paths Lahore University of Management Sciences 7 BW Sharing in backup Paths Example: LSP1 A BW: X Sharing is possible B IF X X E LSP2 G F X+Y Y C X max(X, Y) BW: Y Y Links (A,B) and (C,D) do not simultaneously fail! D Primary Path Backup Path Jan 13, 2006 Lahore University of Management Sciences 8 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 Jan 13, 2006 Lahore University of Management Sciences 9 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 Jan 13, 2006 Lahore University of Management Sciences 10 Protection Routing Framework Tasks related to backup paths in a protection routing framework: Objectives of protection routing framework Backup path computation Backup path signaling Incur scalable routing overhead Find optimal backup paths Maximize bandwidth sharing NPP++ framework achieves all of above Jan 13, 2006 Lahore University of Management Sciences 11 1.Scalable routing overhead More Information propagated More potential for BW sharing 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 Jan 13, 2006 Lahore University of Management Sciences 12 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 PFTLIM How much backup bandwidth will fall on a given link (u,v) if this element fails 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 Jan 13, 2006 Lahore University of Management Sciences 13 Path Computation in NPP++ The backup paths protecting against the failure of R2 cannot share bandwidth on any link. R 1 R2 Contains: a) BFTLIM b) PFTLIM But such backup paths may share bandwidth with primary paths originating or terminating at R2. R 5 R 2 R 3 R 4 Path computation is shifted to R2 because… Only R2 has full knowledge of its own Activation set Jan 13, 2006 Lahore University of Management Sciences 14 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 Jan 13, 2006 Lahore University of Management Sciences 15 NPP++ Summary Protecting R2 (1) Advertise aggregate link usage information only R 4 R 1 FTLIMs LTFIMs LTFIMs R 2 FTLIMs R 3 FTLIMs LTFIMs (2) Path computation is shifted to special nodes Results: Primary Path Backup Path Jan 13, 2006 •Path computation optimal (3) Nodes in primaryispath maintain “local data structures” •Bandwidth called sharingBFTLIM/PFTLIM on backup paths is maximum. (4) Nodes in backup paths maintain “local data •Advertisement overhead is minimum structures” called BLTFIM/PLTFIM Lahore University of Management Sciences 16 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 Jan 13, 2006 Lahore University of Management Sciences 17 Evaluation & Experimentation Traffic generation Rejected requests experiments Used existing traffic models 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 Jan 13, 2006 Lahore University of Management Sciences 18 Simulation Parameters Simulations performed on two networks Network 1: Network 2: 20-node homogenous topology (metros in the U.S.) Each link with capacity 120 units Ingress/Egress pairs chosen randomly 15-node heterogeneous topology Core links with capacity 480 units, other links 120 units LSP requests arrive one-by-one Bandwidth demand for each request is uniformly distributed between 1 and 6 100 experiments with different traffic matrices Jan 13, 2006 Lahore University of Management Sciences 19 Comparative Results: Network 1 Jan 13, 2006 Lahore University of Management Sciences 20 Comparative Results: Network 2 Jan 13, 2006 Lahore University of Management Sciences 21 Local Storage: Network 1 Jan 13, 2006 Lahore University of Management Sciences 22 Local Storage: Network 2 Jan 13, 2006 Lahore University of Management Sciences 23 Conclusions: NPP++ Optimal path computation Maximum sharing along computed path Scalable routing overhead Practically feasible 15% – 40% improvement over existing protection schemes Jan 13, 2006 Lahore University of Management Sciences 24 Last slide… Thank you! Questions? Jan 13, 2006 Lahore University of Management Sciences 25