Chair of Network Architectures and Services Department of Informatics Technical University of Munich Influence of BGP Community Attributes on Routing and Internet Traffic Final talk for the IDP by Fabian Raab B.Sc. advised by Oliver Gasser, Quirin Scheitle, Minoo Rouhi Monday 18 th February, 2019 Chair of Network Architectures and Services Department of Informatics Technical University of Munich
Chair of Network Architectures and Services Department of Informatics Technical University of Munich BGP communities introduction • The Border Gateway Protocol (BGP) is used for exchanging routing information • A BGP Community can optimize routing decisions and is a simple integer: ASN val For example AS1273 (Vodafone): • Informational • Tagging (ex. geographic) 1273:12276 Route learned from a customer in Germany • • Action • Routes redistribution (ex. backup routes) Informational Provider AS 1273:90 Sets local preference value • within AS1273 to 90 R Action • Export control (ex. blackholing) 1273:666 Discard any traffic to • the announced prefix (blackhole) R R R Customer AS Customer AS Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 2
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Communities Taxonomy Tree usage category informational action tagging action relic BGP attribute manipulation export control attach link-tags pass-tags prepend localpref announce blackhole legend application class inbound outbound routes redistribution attack mitigation process category unspecified peertype IXP geographic scope AS IPv4 IPv6 Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 3
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Goals • Better understand dynamics of routing networks with BGP Communities • Identify BGP Communities announcement characteristics • Stable behaviour • Parallel announcements (Community Flapping) • For impact, correlate BGP Community changes with • BGP routing changes • traffic changes • Hopefully leads to better and more stable BGP configuration since effects are known Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 4
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Path types AS64501 BR4 BR3 BGP Router AS64502 TR3 TR2 BR1 TR1 Traffic Router C Collector-AS64504 Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 5
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Path types AS64501 BR4 BR3 AS64502 TR3 TR2 BR1 TR1 AS path C Collector-AS64504 Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 5
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Path types AS64501 BR4 BR3 AS64502 IP path TR3 TR2 BR1 TR1 AS path C Collector-AS64504 Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 5
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Path types Communities Ruter path AS64501 BR4 BR3 AS64502 IP path TR3 TR2 BR1 TR1 AS path C Collector-AS64504 Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 5
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Research questions • Routing • How detailed are Communities, and therefore influence the route? (path, AS configuration) • In which cases do changed Communities replace an older one, in which remain both valid in parallel? (Router and AS behaviour) → Can Communities improve routing? Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 6
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Research questions • Routing • How detailed are Communities, and therefore influence the route? (path, AS configuration) • In which cases do changed Communities replace an older one, in which remain both valid in parallel? (Router and AS behaviour) → Can Communities improve routing? • Normal behaviour • How stable are Communities? • Can regular Community changes be a stable condition? • Should they cause like intended traffic/routing changes? → Can instabilities/problems be identified? Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 6
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Case study 1 (Single switch) Prefix Peer-IP AS-Path Diego Cassio (Brasilia) ↓ 138.117.146.0/24 193.178.185.65 286 7738 8167 53062 262607 264242 Announce Time BGP Community set 11.11.2017 14:07:33 286:286, 286:3001, 286:4502 BR1 , 286:4991, 7738:51448 BR3 11.11.2017 22:01:12 286:286, 286:3001, 286:4510 BR2 , 286:4991, 7738:51448 BR3 value Description 286:4502 US - nyk-s2 (New York, Switch and Data / 8th Avenue 111) 286:4510 US - miaf-s1 (Miami, Terremark) 286:286 own or customer prefix 286:3001 Unites States 286:4991 North America BR2 AS7738 AS286 • Replacement route CR BR3 • Second route VP BR1 AS3856 • Wrong community / misconfiguration • Effectless Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 7
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Case study 2 (Community Flapping Set change) lower local preference to 94, Asia, Turkey, itb-s3 Istanbul lower local preference to 97, Asia, Turkey, itb-s3 Istanbul Europe, Germany, ffm-s1 Frankfurt lower local preference to 97, Europe, Germany, ffm-s1 Frankfurt, some unknown Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 8
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Community change detection — primitive approach [2] α Base β γ • Base: For 48h only one Community set allowed (here definition of stable) • Other behaviour does not work Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 9
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Community change detection — primitive approach [2] α Changes Base β γ • Base: For 48h only one Community set allowed (here definition of stable) • Other behaviour does not work • Any other Community set is a change Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 9
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Community changes detection — Own approach α β γ Announcement is a change iff: The same Community set is not seen 24h before OR after (= ✓ ) Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 10
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Community changes detection — Own approach α β γ Announcement is a change iff: The same Community set is not seen 24h before OR after (= ✓ ) • Begin of new Comm set can be detected Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 10
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Community changes detection — Own approach α β γ Announcement is a change iff: The same Community set is not seen 24h before OR after (= ✓ ) • Begin of new Comm set can be detected • Flapping is not a change Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 10
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Community changes detection — Own approach α β γ Announcement is a change iff: The same Community set is not seen 24h before OR after (= ✓ ) • Begin of new Comm set can be detected • Flapping is not a change • Begin/End of Sequence within Flapping can be detected Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 10
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Community change detection — Summary • Approach: • Simple • Detects changes in relation to direct previous/next announcements • Works with many announcement characteristics • Supports permanent changes • Community Flapping are not changes • Challenging parametrization: • Announcement frequency varies • Duration compare back/forth → Jumping back/forth n announcements → But still many change hits Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 11
Chair of Network Architectures and Services Department of Informatics Technical University of Munich Traffic analysis: outage — Communities Europe, Germany, ffm-s1 Frankfurt, Kleyerstr. 90 Europe, Germany, hmb-s2 Hamburg, Wendenstr. 251 Europe, Germany, mchn-s1 Munich, Seibelstr./Arnulfstr. Fabian Raab — Influence of BGP Community Attributes on Routing and Internet Traffic 12
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