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Dual Homing Experiment

Dual Homing Experiment. Christian Huitema Architect Windows Networking & Communications Microsoft Corporation. Simple bridged network 2 routers, 2 ISP ingress filtering No ISP coordination Example 2 DSL modems DSL + cable Cable + WiFi mesh Several host Simple = IPv6 basic

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Dual Homing Experiment

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  1. Dual Homing Experiment Christian HuitemaArchitect Windows Networking & CommunicationsMicrosoft Corporation

  2. Simple bridged network 2 routers, 2 ISP ingress filtering No ISP coordination Example 2 DSL modems DSL + cable Cable + WiFi mesh Several host Simple = IPv6 basic Advanced = multi-homing aware It must work! Simple dual homing problem statement Internet (IPv6) ISP1 ISP2 R1 R2 Single link (bridge) H H H Dual homing experiment

  3. Define “it must work” • For the simple host • Can receive and send connection through either ISP • If an ISP is down, continue with other • For the advanced host • May choose the best connection based on some heuristic • May use MIPv6 to redirect connections • With MIPv6, connection survives loss of one ISP. Dual homing experiment

  4. First order issue: ingress filtering • Avoid the following failure scenario • Host choose source address A • Default route leads to router B • Router B forwards the packet to ISP B • Packet is dropped by ingress filtering. • Possible solutions • Exit router check source address, redirect packet to “right” router in case of problem • Host knows which router advertises what prefix, select default router that matches source address Dual homing experiment

  5. Second issue: avoid using dead router • Failure scenario • Router A is dead, or link to ISP A is dead • Host continue sending using source address A • Router B cannot forward the packets • Possible solutions • Dead router stops advertising, or advertise prefix as “deprecated” • Smart host detects that the router is dead, switches to other address Dual homing experiment

  6. Third issue: maintain connection • Failure scenario • Host has connection with peer P using address A • Router A or ISP A fails • Existing connections break • Solution • No solution for dumb host • Variation of MIPV6 for smart host Dual homing experiment

  7. Fourth issue: use the right exit/entrance • Failure mode • Peer picks address A rather than address B • Resulting traffic routed slow path • Performance looks terrible • Solution • Need information about which address will get best performance • Need MIPV6 to move connection to “better address” Dual homing experiment

  8. Further study • Large networks • Case 1: multilink subnet, all exit routers on same link. • Case 2: routed network, all exit routers on same link. • Case 3: routed network, exit routers at different location • PI addressing • Use a “virtual IP” solution, implemented with tunnels, as “a third connection” Dual homing experiment

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