Underst in addition to ing the Impact of Route Reflection in Internal BGPPh.D. Final Defensep

Underst in addition to ing the Impact of Route Reflection in Internal BGPPh.D. Final Defensep www.phwiki.com

Underst in addition to ing the Impact of Route Reflection in Internal BGPPh.D. Final Defensep

Lunden, Ingrid, Contributing Writer has reference to this Academic Journal, PHwiki organized this Journal Underst in addition to ing the Impact of Route Reflection in Internal BGPPh.D. Final Defensepresented by Jong Han (Jonathan) ParkJuly 15th, 20111Research Overview2Internal Border Gateway Protocol in addition to Route Reflection Underst in addition to ing the Impact of BGP Route Reflection – Underst in addition to ing BGP Next-hop Diversity (2nd author, Global Internet Symposium 2011) – A Comparative Study of Architectural Impact on Next-hop Diversity (under submission to IMC’11) – Quantifying i-BGP Convergence inside large ISPs (under submission to IMC’11) BGP Route Reflection Protocol Diagnosis – Investigating Occurrence of Duplicate Updates in BGP Announcements (PAM’10, Best Paper) Others (listed as 2nd author) on BGP Per as long as mance – Route Flap Damping with Assured Reachability (AINTEC’10) – Explaining Slow BGP Table Transfers: Implementing a TCP Delay Analyzer (under submission to IMC’11)MotivationRoute reflection was added to the routing architecture to fix a few critical problemsDespite the wide adoption of RR, a systematic evaluation in addition to analysis on the impact of route reflection is missing, which can be helpful in:Underst in addition to ing of the protocol per as long as mance in addition to enhancementsMore realistic simulationsDesigning the future routing protocols This work is to fill in the void3

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Outline4Introduction to Internal BGP in addition to Route ReflectionUnderst in addition to ing BGP Path Diversity in addition to the Impact of Route ReflectionUnderst in addition to ing BGP Convergence inside Large ISPsIntroduction to full-mesh i-BGPTotal number of sessions = N(N-1)/2Number of additional sessions as long as an additional i-BGP router = NTotal number of i-BGP routers in AS1 = 4 = NAS15Full-mesh i-BGP does not scaleCity 1City 2City 3Large ISPs have hundreds or even more than a thous in addition to routers internallyFull mesh leads to a high cost in provisioningAdding or removing a router requires reconfigurations of all other routers6

Addressing the scalability problem of full-mesh i-BGPTwo solutions are suggested in 1996AS confederations (RFC 1965)Route reflection (RFC 1966)This work focuses on route reflectionDominant solutionMain concerns shared with AS confederationPath diversity reductionConvergence delay7Route reflection solves scalability problemTotal number of sessions = 4Number of additional sessions as long as an additional i-BGP router = 1Total number of i-BGP routers = 5 = NAS1AS2route reflectorclient 1client 2client 3client 48Large ISP revisited with hierarchical RRRoute reflection substantially reduces the total number of sessionsRoute reflection can be deployed hierarchically to reduce even more9

Negative Impact of BGP route reflectionNegative side effects Routing per as long as mancePath diversity [Uhlig, Networking’06]ConvergenceOthersRobustness to failuresInternal update explosion [McPherson,APNIC talk, 2009]Optimal route selection [Vutukuru, Infocom’06]Routing correctnessData as long as warding loop [Griffin, Sigcomm’02]Route oscillations [McPherson, Internet Draft, 2000]10Outline11Introduction to Internal BGP in addition to Route ReflectionUnderst in addition to ing BGP Path Diversity in addition to the Impact of Route ReflectionUnderst in addition to ing BGP Convergence inside Large ISPsDefinitionsNext-hop POP in addition to ASNext-hop Point-of-Presence (i.e., city in which the next-hop router is located) in addition to AS that the ISP uses to reach a given external destinationBGP Next-hop DiversityNumber of distinct next-hops to reach a given external destination as used simultaneously inside a given ISP12

Why do we care about path diversityHigher path diversityMore flexibility in traffic engineering in addition to load balancingHigher availabilityCurrent IETF ef as long as ts to increase BGP diversityDiverse-path, Add-path, in addition to External-best13Path diversity reduction due to route reflectionAS1 RTR2 RTR3AS2, pp: NH = RTR1, ASPATH = AS2p: NH = RTR4, ASPATH = AS2RTR1 RTR4ALL14Main questions to answerWhat degree of BGP next-hop diversity do existing ISPs have nowDoes route reflection deployment reduce BGP next-hop diversity15

Data collection settingsISPFM: Tier-1 ISP with full-mesh i-BGP backbone routing infrastructureISPRR: Tier-1 ISP with route reflection i-BGP backbone routing infrastructurei-BGP full-meshISPFMbackbone sub-ASSubASAS1SubASSubASASiISPRRASiiAS11AS22AS2CollectorCollectorBGP routerNode type: confederation BGP1st level reflector2nd level reflector3rd level reflectorSession type: i-BGP reflector to client i-BGP peer e-BGP peer16BGP next-hop diversity of the 2 ISPsISPFMISPRRCommon observationsA small number of prefixes with a very high degree of next-hop diversityPrefixes with very low degree (diversity=1) of next-hop diversityA few large groups of prefixes with the same moderate degree of next-hop diversityA significant number of prefixes (more than 90% in addition to 65% respectively) have multiple next-hop POPs in addition to ASesOverall, ISPRR has relatively lower next-hop diversity, compared to ISPFM17Inferring external connectivity18AS1 R2 R1AS2, pR3 R4AS3In the absence of failures, the reachability through R2 is not visibleIf the current best path fails, the path through R2 will be explored

Inferred external connectivity vs. next-hop POPsThe external connectivity is not the main reason as long as the differenceISPFM (during 1st week of June 2010)19ISPRR (during 1st week of June 2010)Paths can be hidden due to path preference7 BGP path attribute values used by a BGP router in BGP best path selectionFirst 4 are independent from the i-BGP topological location of the given routerLOCAL-PREFAS-PATH lengthORIGINMEDThe rest 3 attribute values change depending on the i-BGP topological location of the given routerPrefer e-BGP over i-BGP IGP costRouter ID20Diversity reduction by the first 4 BGP path attributesThe first 2 criteria of BGP path selection hides the majority of the path diversityAbout 16% in addition to 10% reduction as long as ISPFM in addition to 34% in addition to 7.6% reduction as long as ISPRR by (1) LOCAL-PREF in addition to (2) AS-PATH length respectively 21ISPFM (during 1st week of June 2010)ISPRR (during 1st week of June 2010)

SummaryThe overall next-hop diversity varies widely, depending on the topological location of origin AS as long as a given prefixThe difference in the overall next-hop diversity is due to i-BGP topology-independent factors More specifically, the first 2 BGP best selection criteria hides up to 42%Next-hop diversity reduction by ISPRR’s hierarchical RR is less than 3.3%Main reason. significant reduction by the i-BGP topology-independent factors already22Outline23Introduction to internal BGP in addition to Route ReflectionUnderst in addition to ing BGP Path Diversity in addition to the Impact of Route ReflectionUnderst in addition to ing BGP Convergence inside Large ISPsDefinitionsEventChange in routing in as long as mation to reach a given external prefixMonitorRouter from which i-BGP data is collected within a given ISPi-BGP convergenceConvergence of all monitors inside a given ISP as long as a given event24

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Why do we care about i-BGP convergenceBGP suffers from slow convergenceMay cause severe per as long as mance problems in data delivery [TON’01, Labovitz] [Infocom’01,Labovitz] [IMC’03,Mao] [Sigcomm’06,Wang] at inter-AS levelVirtually no measurement studies exist on BGP convergence inside an ISP25Increased convergence delay in i-BGP RRAS1RTR 1RR1RTR 2RR2AS2, pUpdate pathRR2->RTR1RR1->RTR1RR2->RR1->RTR1RR1->RR2->RTR1Not reachableThere is no path to prefix p!1. Delay due to hierarchy – additional path distance – additional processing delays2. Delay due to route reflector redundancy – increased of control paths26RTR 3RTR 4Main questions to answerWhat does i-BGP convergence look likeWhat is the impact of route reflection convergence delay27

Data collection settingsISPFM: the collector is a member of the i-BGP full-meshISPRR: the collector is a client of the 2nd level route reflectorsi-BGP full-meshISPFMbackbone sub-ASSubASAS1SubASSubASASiISPRRASiiAS11AS22AS2CollectorCollector28BGP routerNode type: confederation BGP1st level reflector2nd level reflector3rd level reflectorSession type: i-BGP reflector to client i-BGP peer e-BGP peerInferring best path selection as long as peers in i-BGP full-meshQ: Best path used by RTR3 to reach prefix pA: Use geographical in as long as mation of the routers to approximate IGP cost in the BGP best path selection29AS1RTR1Path1 to prefix pRTR2RTR3Path2 to prefix pWhich path does RTR3 useCollectorHigh-level view of quantifying i-BGP convergencemonitornmonitor1collectorEvent Identification(update clustering)event eevent eT = 60 secondspath preferenceTS30METRICS1. Duration(e)2. NumUpdates(e)3. NumPaths(e)Event Classification(Determine Type & Scale)

Increased convergence time in i-BGP HRRSettingData: Level3 i-BGP data from 20100603Apply different MRAI timers to the monitor-collector session in addition to calculate the convergence duration as long as beacon prefixesObservationThe increased convergence time is proportional to the MRAI timer used in Iup52

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