MPLS Local Restoration using Optimized Aggregate Information Zartash Afzal Uzmi Computer Science and Engineering Lahore University of Management Sciences

May 18, 2005Lahore University of Management Sciences2 Outline Introduction QoS Requirements Local Restoration: Types of Backup Paths Local Restoration: Fault Models Backup Bandwidth Sharing Activation sets The new model for bandwidth sharing Optimized aggregate information scenario (oAIS) Experiments, simulations, and results

May 18, 2005Lahore University of Management Sciences3 QoS Requirements Bandwidth Guaranteed Primary Paths Bandwidth Guaranteed Backup Paths BW remains provisioned in case of network failure Minimal “Restoration Latency” Restoration latency is the time that elapses between the occurrence of a failure and the diversion of network traffic on a new path Path Restoration  More Latency Local Restoration  Less Latency

May 18, 2005Lahore University of Management Sciences4 Types of Backup Paths A next hop (nhop) path that spans a link (i, j) is a backup path which: originates at node i, and provides restoration for a primary LSP that traverses (i, j), if (i, j) fails. i j PLR: Point of Local Repair nhop path that spans (i, j)

May 18, 2005Lahore University of Management Sciences5 Types of Backup Paths A next next hop (nnhop) path that spans a link (i, j) is a backup path which: originates at node i, and provides restoration for a primary LSP that traverses (i, j), if either (i, j) or node j fails. i j PLR: Point of Local Repair nnhop path that spans (i, j)

May 18, 2005Lahore University of Management Sciences6 Local Restoration: Fault Models ABCD Link Protection ABCD ABCD Node Protection Element Protection

May 18, 2005Lahore University of Management Sciences7 nhop and nnhop paths Primary Path Backup Path All links and all nodes are protected! AB C D E PLR: Point of Local Repair nnhop nhop

May 18, 2005Lahore University of Management Sciences8 Opportunity cost of backup paths Local 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?

May 18, 2005Lahore University of Management Sciences9 BW Sharing in backup Paths Example: max(X, Y) BW: Y AB CD E F G L1 L2 BW: X Primary Path Backup Path X X X YY X+YX+YSharing

May 18, 2005Lahore University of Management Sciences10 Activation Sets A B C D E Activation set for node BActivation set for link (A,B) A B C D E

May 18, 2005Lahore University of Management Sciences11 Extent of BW Sharing: oAIS 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 Optimized AIS (oAIS) – (H ij instead of F ij ) Hij : Maximum bandwidth reserved on any one link by all backup paths spanning link (i, j) More Information propagated  More potential for BW sharing

May 18, 2005Lahore University of Management Sciences12 oAIS versus AIS: Example LSP Request-1 (src, dst, bw) = (A, C, 4) A F D E BC G F AB =4 H AB =4 G AF =4

May 18, 2005Lahore University of Management Sciences13 oAIS Example LSP Request-2 (src, dst, bw) = (A, C, 5) A F D E BC G F AB =9 H AB =5 G AF =4 G AG =5 F AB =4 H AB =4

May 18, 2005Lahore University of Management Sciences14 oAIS Example LSP Request-3 (src, dst, bw) = (D, E, 7) A F D E BC G F AB =9 H AB =5 G AF =4 G AG =5 F DE =7 G AF =7

May 18, 2005Lahore University of Management Sciences15 oAIS Example LSP Request-4 (src, dst, bw) = (A, C, 6) A F D E BC G F AB =9 H AB =5 G AF =7 G AG =5 F DE =7 Need to Evaluate cost of all possible backup paths? How much BW is shareable on (A, F)? AIS: Shareable = max(0, G AF - F AB ) = G AF - min(G AF, F AB ) = 0 Additional resv = 6 oAIS: (H AB ≤ F AB ) Shareable = G AF - min(G AF, H AB ) = 2 Additional resv = = 4 CIS: (link (A,B) knows BW red ) Shareable = G AF - BW red = = 3 Additional resv = = 3

May 18, 2005Lahore University of Management Sciences16 Bandwidth Sharing Model Previous: A ij := Set of all primaries traversing through (i, j) B ij := Set of all backups traversing through (u, v) Our definition (for link protection case): A ij := Set of all primaries traversing through (i, j) B ij := Set of all nhop paths traversing through (u, v) µ ij := Set of all nhop paths that span (i, j)  ij uv := B uv ∩ µ ij

May 18, 2005Lahore University of Management Sciences17 Bandwidth Sharing Model i uv j k RED=7 BLU=2 3 OLD MODEL: A ij = {R, B} B uv = {R, B, …} A ij ∩ B uv = {R, B} || A ij ∩ B uv || = 2+7 = 9 Un-shareable = 9 Shareable = = 1 GRN=3 (New Request) Guv = 10 NEW MODEL: A ij = {R, B} B uv = {nh ij r, nh ij b, …}(nhops through (u, v)) µ ij = {nh ij r, nh ij b, …}(nhops spanning (i, j))  ij uv = µ ij ∩ B uv = {nh ij r } ||  ij uv || = = 9(Un-shareable) Shareable = G uv - ||  ij uv || = = 1

May 18, 2005Lahore University of Management Sciences18 Bandwidth Sharing Model i uv j k RED=7 BLU=2 3 OLD MODEL: A ij = {R, B} B uv = {R, B, …} A ij ∩ B uv = {R, B} || A ij ∩ B uv || = 2+7 = 9 Un-shareable = 9 Shareable = = 1 NEW MODEL: A ij = {R, B} B uv = {nh ij r, nh jk b, …}(nhops through (u, v)) µ ij = {nh ij r, nh ij b, …}(nhops spanning (i, j))  ij uv = µ ij ∩ B uv = {nh ij r } ||  ij uv || = 7(Un-shareable) Shareable = G uv - ||  ij uv || = = 3 GRN=3 (New Request) Guv = 10

May 18, 2005Lahore University of Management Sciences19 Simulation Experiments Rejected Requests Experiments Simulated on two topologies Measure the number of rejected LSPs for each information scenario Network Loading Experiments Simulated on two topologies Link capacities set to infinity Measure the total bandwidth required to service a given set of LSPs for each information scenario

May 18, 2005Lahore University of Management Sciences20 Single Link Protection: Network 1

May 18, 2005Lahore University of Management Sciences21 Single Link Protection: Network 1

May 18, 2005Lahore University of Management Sciences22 Single Link Protection: Network 2

May 18, 2005Lahore University of Management Sciences23 Single Link Protection: Network 2

May 18, 2005Lahore University of Management Sciences24 Single Node Protection: Network 1

May 18, 2005Lahore University of Management Sciences25 Single Element Protection: Network 1

May 18, 2005Lahore University of Management Sciences26 Questions & Answers

May 18, 2005Lahore University of Management Sciences27 Restoration in MPLS Primary Path Backup Path Path Protection MPLS path Protection may take 100s of ms, whereas MPLS Local protection takes less than 10 ms. AB CDE