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BGP FlowSpec in 2019: operational experience and future developments

BGP FlowSpec in 2019: operational experience and future developments a.k.a. “yet another FlowSpec talk”. Alessandro Bulletti Kirill Kasavchenko. Volumetric DDoS attacks 2018-2019.

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BGP FlowSpec in 2019: operational experience and future developments

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  1. BGP FlowSpec in 2019: operational experienceandfuturedevelopments a.k.a. “yet another FlowSpec talk” Alessandro Bulletti Kirill Kasavchenko

  2. Volumetric DDoS attacks 2018-2019 Source: Rapporto Clusit 2019 sulla Sicurezza ICT in Italia - Tipologie di attacchi DDoS (Dati Fastweb relativi all’anno 2018) Source: Netscout Threat Report 2018

  3. The needforcollaboration • Ideally, large DDoSattacksshouldbemitigatedasclosetothesourceaspossible. • Practically, thegoodfirststepwouldbe: • Customer asksupstreamprovidertomitigate • Peer asksanotherpeers • As time goesbyandtrustisbuilt, wemightexpectmitigationtonaturallypropagateclosertothesource.

  4. Wait... This is not a newidea! Someof initiatives in thisarea: • Fingerprint Sharing Alliance (Arbor, 2005) • BGP FlowSpec (IETF, 2009) • M3AAWG DDoS Info Sharing (2017) • I2NSF (IETF, 2017) • Stellar: advancedblackholing (DE-CIX/TU Berlin/Max Planck Institute, 2018) • DOTS (IETF, work in progress)

  5. Wait... This is not a newidea! Someof initiatives in thisarea: • Fingerprint Sharing Alliance (Arbor, 2005) • BGP FlowSpec (IETF, 2009) • M3AAWG DDoS Info Sharing (2017) • I2NSF (IETF, 2017) • Stellar: advancedblackholing (DE-CIX/TU Berlin/Max Planck Institute, 2018) • DOTS (IETF, work in progress) • Vendorsupport • Open-sourcetools • Operational experience • User groups

  6. FlowSpec: vendorsand open-source Controllers and BGP FlowSpecspeakers: • Arbor (Netscout) • ExaBGP • FastNetMon • Nokia • Radware Routers: • Cisco IOS-XR (ASR9K, NCS5K) and IOS-XE • Juniper MX/PTX • Alcatel/Nokia 7x50 • Huawei NE routers • 6WIND • Arista FlowSpec Telemetry

  7. FlowSpec: operational experience & usergroups Deployments (based on publicinformation): • Cloudflare, Level3, Rostelecom, Orange Poland DDoSPeering initiative: • AT&T, Century Link, Charter • See slides at NANOG 71 and 75 (links in the end ofthispresentation) FlowSpecmultivendortestsby T-Mobile Austria andNextLayer : • Cisco, Juniper, Huawei, Nokia • Focus on Inter-AS applicabilityand operational needs

  8. Whatworkswell • FlowSpecisextensivelyusedagainstDDoSAmplificationattacks: • Wesee operational communityisautomatingFlowSpecgenerationtostopattackswithout human involvement: • Not just hyperscalers • WeseeadoptionofFlowSpecasthewaytoredirecttraffic on demand: • Redirect to Route Target • Redirect to Next-Hop

  9. Whatcouldbeimproved • Scale on routerside: • NumberofconcurrentlysupportedFlowSpecrules • Speed ofFlowSpecrulesimportandprocessing • Various „safetynets“: • PreventtoomanyFlowSpecrulesfromimpactingrouterforwardingperformance • Lack ofgranularity in importpolicies: • Itisimpossibletoallow/rejectFlowSpecrulesbased on action • Therefore, possibleforcustomertochange DSCP oftheirtrafficto „network-critical“ • These areimplementation-specificimprovements. They do not requireindustryconsensus in a form of IETF documentor BCP.

  10. Whatisimpossibleto do withFlowSpectoday • Match trafficbased on random L3-L4 fieldorbased on payload • Example: IP TTL, TCP Window Size • Report trafficstatisticsacross administrative boundaries • ISP1 sends a FlowSpecruleto ISP2 • How ISP1 getsvisibilityintodroppedtraffictoestimatetheefficacyofFlowSpec? • Thereis a lack ofcommonapproachtotheseproblems. • Weneedstandards (think RFC documents) orsome well-defined Best Current Practices

  11. Flexible Payload Matching: problemstatement • MajorityofvolumetricDDoSattacksareamplificationattacks. Theycanbesuccessfullymitigatedusing „standard“ FlowSpec, matchingsource UDP port: • However, thereexistmorecomplexcases: • Bittorentamplification • SSDP diffraction • These attacksresult in packetswithrandomsource UDP port, so it‘s not possibletocreate a classifierusingFlowSpec. • At the same time, theseattacksgeneratespecificpatterns in payload. • Andsomeroutersareabletomatchpacketsbased on payload.

  12. Flexible Payload Matching: solution (1/2) • ExtendFlowSpecwith „flexible matchconditions“ component type: • draft-khare-idr-bgp-flowspec-payload-match Type X – Flexible Match Conditions

  13. Flexible Payload Matching: solution (2/2) • Usenewcomponent type tomatchanywhere in the packet: • In anyfield • Acrossfieldsregardlessoffieldboundaries • In payload • Match using: • Bit patternwithbitmask • Numericpattern • Regular expressions • draft-khare-idr-bgp-flowspec-payload-match

  14. FlowSpecand Reporting: problemstatement • How do youknowifFlowSpecruleiseffective? • NostandardizedwaytoreporttrafficthatmatchesFlowSpecpolicy: • SNMP counters • XML/Netconf • draft-wu-idr-flowspec-yang-cfg-02 • Goodnews: mostroutersgenerateflowtelemetryfortraffic, droppedbyFlowSpec:

  15. FlowSpecand Reporting: solution • CorellateFlowSpec NLRI and Flow records: • Vendor-independent approach • Noneedto parse proprietary SNMP or XML datamodels Flow Record Src IP Dest IP Src Port Dst Port Proto Input Intf Output Intf = 0 ToS Flags Packet length Etc… Dest Prefix Source Prefix IP Protocol Port Dst Port Src Port ICMP type ICMP code TCP flags FlowSpec NLRI

  16. FlowSpecand Reporting: Inter-AS? • Reporting based on NetflowandFlowSpeccorrelationwon‘tworkbetween ASNs • Nowayfor ISP1 toreceiveflowtelemetryfrom ISP2 • Other approaches (SNMP, Netconf, streamingtelemetry) won‘tworkeither • Wewouldneedsomethingtotallynew: • Most likelysomemediationtoolthatmakessureonly relevant informationisreportedbetween ASNs • Orsomeconceptof „administrative domains“ in flow / SNMP / streamingtelemetry • Whateverthesolutionwouldbe, havingvisibilityintoFlowSpecrulespropagatedbetween ASNs isgoingtobe an essential factorforadoption

  17. FlowSpecevolution: RFC5575bis • Defines all traffic action extended communities as transitive extended communities. RFC5575 defined the traffic- rate action to be non-transitive and did not define the transitivity of the other action communities at all. • Introduces a new traffic filtering action traffic-rate-packets: • Instead of ”rate-limit to 100 bps” you can now “rate-limit to 100 pps” • Introduces rules how updates of Flow Specifications shall be handled in case they contain interfering actions • A full list of changes can be found in the references section of this slide deck • Major changes

  18. Other interestingFlowSpecdevelopments • FlowSpec interface set (draft-ietf-idr-flowspec-interfaceset) • Use BGP communities to signal to which interfaces (interface-set) should a FlowSpec action be applied • Supported in Cisco IOS-XE

  19. Summary • FlowSpecis a matureDDoSmitigationtechnology • No, it‘s not perfectandaloneis not enoughtostop all typesofDDoSattacks • itis not applicableagainst TCP SYN floodsandapplicationlayerDDoS • but itmitigatesthemostimpactingDDoStypes in ISP networks – amplificationattacks • Check with $your_router_vendorwhattheplatformlimitsare: • Scale • Policies • Don‘tbeafraidtoautomateFlowSpec. Ifyoudon‘tknowhow – talktous. • Work with IETF andvendorstogetnewFlowSpecideasimplemented • A.k.a Last Slide

  20. References • Stellar, advancedblackholing: https://www.de-cix.net/Files/2731074c857497be3827ac9537b6e486f27aa57c/Research-paper-Stellar-Network-Attack-Mitigation-using-Advanced-Blackholing.pdf • NANOG71 DDoSpeering: https://www.youtube.com/watch?v=Aj8EKYVSTtk • NANOG75 eBGPFlowSpecpeering: https://www.youtube.com/watch?v=rKEz8mXcC7o • InteropFlowSpectestsby T-Mobile and Next Layer: https://www.nextlayer.at/wp-content/uploads/2018/06/loibl-bacher-bgp-flowspec-interop-012017.pdf • FlowSpecpayloadmatching: https://datatracker.ietf.org/doc/draft-khare-idr-bgp-flowspec-payload-match/ • SSDP DiffractionAttack: https://www.netscout.com/blog/asert/new-twist-ssdp-attacks • FlowSpec at CloudFlare: https://meetings.ripe.net/see4/files/RIPE%20SEE4%20Belgrade%20Serbia%20-%20CloudFlare%20-%20DDoS%20mitigation%20-%20Martin%20Levy.pdf • FlowSpec at Level3: https://www.capacitymedia.com/articles/3585228/Level-3-launches-BGP-Flowspec-on-global-backbone • FlowSpec at Rostelecom: https://habr.com/ru/company/rostelecom/blog/325138/ • FlowSpec in Orange Poland: https://cert.orange.pl/aktualnosci/ddos-w-naszej-sieci-coraz-silniej-coraz-wiecej • RFC5575bis changescomparedto RFC5575: https://tools.ietf.org/html/draft-ietf-idr-rfc5575bis-14#appendix-A • The last slide, really

  21. alessandro.bulletti@netscout.com kirill.kasavchenko@netscout.com

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