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Performing Gateway Load Balancing in MANETs PhD Dissertation February 10 th 2012 Vinh Pham

Performing Gateway Load Balancing in MANETs PhD Dissertation February 10 th 2012 Vinh Pham. Vinh Pham, PhD Dissertation 2012. Outline. Introduction Motivation MANET Challenges Main focus of the Thesis Thesis overview Contributions Part I: Mobility

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Performing Gateway Load Balancing in MANETs PhD Dissertation February 10 th 2012 Vinh Pham

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  1. Performing Gateway Load Balancing in MANETs PhD Dissertation February 10th 2012 Vinh Pham Vinh Pham, PhDDissertation 2012

  2. Outline • Introduction • Motivation • MANET • Challenges • Main focusoftheThesis • Thesisoverview • Contributions • Part I: Mobility • Part II: Loadbalancing for Intradomain • Part III: Loadbalancing for Interdomain • Concludingremarks

  3. Motivation Improvingtheinformationflow in emergency and rescueoperations • Today • Mainly low bandwidth, single-hop, voice-only • Tomorrow • Based on MANET • Broadband multihop • Voice, data, video • Situationalawareness, e.g. positionsharing • Access criticalinformation: victim info, maps, • constructiondrawings

  4. MANET – What is it?Mobile Ad Hoc Network B Transmission range A C • Infrastructureless • Dynamic: mobility, join/leavethenetwork • Rapid deployment • Costeffective

  5. Challenges • Medium access: Contention-basedrandomaccess • Interference and collisions • Distributedrouting • Inconsistency and overhead • Link quality • Varying, affected by topography, weather etc. • Node mobility • Link breaks, packet loss, loss ofconnectivity • Network Capacity • Lowcapacity, limited scalability Need to overcomethesechallenges to achieve highernetworkperformance!

  6. Main FocusoftheThesis • Mobility • Rerouting time due to mobility and link break • Loadbalancing • Intradomaintraffic • Interdomaintraffic

  7. Overview of the work Part I Part II Part III

  8. Contributions Part I

  9. Mobility • Paper A • “Rerouting Time and Queueing in Proactive Ad Hoc Networks” • V. Pham, E. Larsen, K. Øvsthus, P. Engelstad and Ø. Kure, In proceedingsofthePerformance, Computing, and Communications Conference 2007 (IPCCC 2007), New Orleans, USA, April 11-13, 2007, pp. 160-169.

  10. Motivation • Discovery: Rerouting due to mobility exceeds the expected 4-6 seconds. B A C

  11. The contributions • Analysingthererouting time • Proposedsolution: Adaptive Retry Limit

  12. Analysing a Link Break Last Hello from C received at A New routeto C. Link is broken. A’squeuebeingfilled up. Last successfull data transmission from A directly to C Garbagepacketsarediscarded from A’squeue A transmits data to C B A C I II III QueueReductionPhase QueueAccumulationPhase Last Hello from C te td t2 t3 t t1 t0

  13. Solution – Adaptive Retry Limit Node A’sInterfaceQueue Packet 7 is transmitted 1 time and discarded Packet 2 is transmitted 6 times and discarded Packet 1 is transmitted 7 times and discarded 9 8 9 8 7 7 7 1 8 2 9 9 8 2 3 3 In Out • Assumption: • Retry limit = 7 • All packetsto the same destination

  14. Results Gain

  15. Conclusion - Part I • Rerouting time is affected by: • Packetsize and rate • MAC layerqueuesize • MAC layerretries • Adaptingthe MAC layerretriesreducesthererouting time.

  16. Contributions Part II

  17. LoadBalancing for IntradomainTraffic Paper B “RoutingofInternalMANET Traffic over External Networks” V. Pham, E. Larsen, K. Øvsthus, Ø. Kure and P. Engelstad, Mobile InformationSystems Journal, iiWAS/MoMM special issue, Volume 5, Number 3, 2009

  18. Motivation • Transit routing → Load balancing for intradomain traffic • Alleviatetrafficload in the MANET • Improveperformanceofintradomaintraffic: • Throughput • E2E delay • Packetdeliveryprobability 650 kbps 300 kbps

  19. Contributions • Analysis and simulationoftransitrouting • Proposedsolution: Costmetricalgorithm for transitrouting

  20. Solution: The CostMetricAlgorithm Cost for ad hoc path Ci = k Cost for wiredpath, nointerference Cii = max(m,n)+c Cost for wiredpath, withinterference Cii = sum(m,n)+c c = constantbetween 0 and 1

  21. Evaluation B C A 4 11 10 5 2 9 1 12 6 3 7 8 Transitroutingenabled Transitrouting not enabled

  22. Results Averageenhancement = 40.3 %

  23. Conclusion - Part II • Enablingtransitroutingcan be beneficial • Reduceload in MANET • Increase E2E throughput • Reduce E2E delay • Increaseprobability for packetdelivery

  24. Contributions Part III

  25. LoadBalancing for InterdomainTraffic Paper C-E “PerformanceAnalysis of Gateway Load Balancing in Ad Hoc Networks with Random Topologies” V. Pham, E. Larsen, K. Øvsthus, P. Engelstad and Ø. Kure and, Proceedings of The 7th ACM International Symposium on Mobility Management and Wireless Access (Mobiwac09), Tenerife, Canary Islands October 26-30, 2009 “GatewayLoadBalancing in Future Tactical Networks”, V. Pham, E. Larsen, K. Øvsthus, Ø. Kure and P. Engelstad, IEEE Military Communications Conference 2010 (MILCOM 2010), San Jose, CA, USA, October 31 - November 3, 2010 “A Radio Load Based Gateway Load Balancing Scheme with Admission Control” V. Pham, E. Larsen, Q. Le-Trung, P. Engelstad and Ø. Kure, Proceedings of the International Symposium on Wireless and Pervasive Computing (ISWPC 2011), Hong Kong, China, February 23-25, 2011

  26. Motivation Global Internet GW0 Bottleneck GW1 Addressgatewayloadbalancing → Loadbalancing for interdomaintraffic Focusonoutboundtraffic! Howevertheresult is anticipated to be applicable for inboundtraffic as well!

  27. Contributions • Analysing the nature of gateway load balancing (LB) • Explorefactorsthatimpacttheperformanceof LB • Proposedsolutions: • RLLB (Radio Load Based Load Balancing) • RLAC (Radio Load Based Load Balancing with Admission Control)

  28. Analysis

  29. Factorsthataffect LB • Shortcoming in previous work: • Simple and smalltopologies • Grid or constructedtopologies • Fewtopologies used in evaluation • Needs many random topologies to statistically explore factors affecting the benefit of LB • ~200 randomtopologies and thousandsofsimulations • Factorsthataffectperformanceof LB: • Offeredload – Gatewaydistance • Asymmetrylevel – Levelof spatial reuse/sensing range • Network shape and size • However, thesefactorsalonecannotexplainwhythebenefitof LB is high for certaintopologieswhile it is poor for others. The layout ofthetopology is a crucialfactor!

  30. CongestionMap # transmissions The congested area represents an obstaclepreventingefficientreroutingoftraffic! The efficiencyof LB dependsonwhere nodes arelocated relative to thecongestedcentre area The centreofthe area is most congested, not the area aroundtheGWs!

  31. Load BalancingSolution

  32. Overview RLAC ArchitectureRadio Load Based Load Balancing Scheme with Admission Control

  33. Radio LoadMetric Tbusy time (sec) Twindow • RL metric provides a measure for the condition in the network • Pros: The RL info is FREE! RL does not dependonactiveprobingsuch as in ETX, Packet Pair, RTT

  34. GatewaySelection L0 L1 GW0 GW1 ? h0 h1 B0 B1 Gatewayselectionalgorithmneeds to consider: The loadL at theGWs The distanceh to theGWs The bottleneckcapacityB to theGWs Condition at theGWs The propertiesofthepathtowards a specific GW

  35. SynchronizedRerouting • Problem: • A groupof nodes maysimultaneously and repeatedlyreroutetheirtraffic back and forth from one GW to another. • Solution: • Use a randomizedratherthan a deterministic • gatewayselectionapproach!

  36. RandomizedGatewaySelection Deterministic: IfGWn is leastcongestedthenselect it as default GW Randomized: 1. Draw a randomnumberR∈ [0,1], and let theoutcomedecide 2.

  37. RandomizedGatewaySelectionExample R5 R3 R4 0 1 P0=1/3 P1=2/3

  38. Admission Control (AC) • AC prevents traffic load from reaching a critical high level • AC is enabled/disabled using: L, B and h • When the network load is high: • Preempt nodes fartherawaywhilegivingpriority to nodes closer to theGWs • Cost is higher to send packets for nodes farther away • Reasonable to enable AC on nodes that have very low packet delivery ratio • Disadvantage: Unfairness

  39. Results

  40. StaticTopologies (1) TS1 TS2

  41. StaticTopologies (2)

  42. Mobile Topologies

  43. Performanceof LB in Mobile Topologies The performanceof LB is lower in mobile topologiescompared to statictopologiesbecause: • More challenging to perform LB in mobile topologies: • Link breaks, shorter link life time and lowereffectivecapacity • Cannotcapturethechanges in thetopology fast enough due to the inherent delay in theroutingprotocol. • The solution in paper A can be used to improveperformance • Condition for evaluation not same. LB is onlyfeasible/ beneficial for a certainamountofthesimulation time: • Lowasymmetrylevel or theload is evenlydistributed • Partitioning

  44. Conclusion - Part III Performanceof LB is affected by: • Asymmetrylevel, offeredload, sensing range,… • Layout oftopology Staticasymmetrictopologies • LB canimproveperformance Mobile topologies • More challenging • Lowmobility: moderate enhancement • Highmobility: low/noenhancement

  45. Concluding Remarks • We are not there yet: • Challenges need to be solved before we can realize a communication system of tomorrow • Challenges addressed in this thesis: • Mobility – rerouting time • Load balancing – Intradomain and interdomain traffic • Increased understanding has been provided through this work • Proposed solutions that increase the network performance

  46. Thank You!

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