Jan 13, 2006Lahore University of Management Sciences1 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, 2006Lahore University of Management Sciences2 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, 2006Lahore University of Management Sciences3 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, 2006Lahore University of Management Sciences4 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, 2006Lahore University of Management Sciences5 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

Jan 13, 2006Lahore University of Management Sciences6 Types of Backup Paths Primary Path Backup Path All links and all nodes are protected! AB C D E PLR: Point of Local Repair nnhop nhop LOCAL PROTECTION (showing one LSP only)

Jan 13, 2006Lahore University of Management Sciences7 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

Jan 13, 2006Lahore University of Management Sciences8 BW Sharing in backup Paths Example: max(X, Y) BW: Y AB CD E F G LSP1 LSP2 BW: X Primary Path Backup Path X X X YY X+YX+Y Sharing is possible IF Links (A,B) and (C,D) do not simultaneously fail!

Jan 13, 2006Lahore University of Management Sciences9 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, 2006Lahore University of Management Sciences10 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, 2006Lahore University of Management Sciences11 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

Jan 13, 2006Lahore University of Management Sciences12 1.Scalable routing overhead Aggregate Information Scenario (AIS) F ij : Bandwidth reserved on link (i, j) for all primary LSPs G ij : Bandwidth reserved on link (i, j) for all backup LSPs R ij : Bandwidth remaining on link (i, j) Extended NPP (NPP++) relies on AIS Low routing overhead More Information propagated  More potential for BW sharing

Jan 13, 2006Lahore University of Management Sciences13 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

Jan 13, 2006Lahore University of Management Sciences14 Path Computation in NPP++ R1R1 R2R2 R3R3 R4R4 R5R5 The backup paths protecting against the failure of R2 cannot share bandwidth on any link. R2 Contains: a) BFTLIM a) BFTLIM b) PFTLIM b) PFTLIM Path computation is shifted to R2 because… Only R2 has full knowledge of its own Activation set But such backup paths may share bandwidth with primary paths originating or terminating at R2.

Jan 13, 2006Lahore University of Management Sciences15 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, 2006Lahore University of Management Sciences16 NPP++ Summary Primary Path Backup Path R1R1 R2R2 R3R3 R4R4 (2) Path computation is shifted to special nodes (3) Nodes in primary path maintain “local data structures” called BFTLIM/PFTLIM (4) Nodes in backup paths maintain “local data structures” called BLTFIM/PLTFIM (1) Advertise aggregate link usage information only Results: Path computation is optimalPath computation is optimal Bandwidth sharing on backup paths is maximum.Bandwidth sharing on backup paths is maximum. Advertisement overhead is minimumAdvertisement overhead is minimum FTLIMs LTFIMs FTLIMs FTLIMs LTFIMs LTFIMs Protecting R2

Jan 13, 2006Lahore University of Management Sciences17 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, 2006Lahore University of Management Sciences18 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

Jan 13, 2006Lahore University of Management Sciences19 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 experiments with different traffic matrices

Jan 13, 2006Lahore University of Management Sciences20 Comparative Results: Network 1

Jan 13, 2006Lahore University of Management Sciences21 Comparative Results: Network 2

Jan 13, 2006Lahore University of Management Sciences22 Local Storage: Network 1

Jan 13, 2006Lahore University of Management Sciences23 Local Storage: Network 2

Jan 13, 2006Lahore University of Management Sciences24 Conclusions: NPP++ Optimal path computation Maximum sharing along computed path Scalable routing overhead Practically feasible 15% – 40% improvement over existing protection schemes

Jan 13, 2006Lahore University of Management Sciences25 Last slide… Thank you! Questions?