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Multihomed ISPs and Policy Control <draft-ohta-multihomed-isps-00>

Multihomed ISPs and Policy Control <draft-ohta-multihomed-isps-00>. Masataka Ohta Tokyo Institute of Technology mohta@necom830.hpcl.titech.ac.jp. All the Hosts Should have Full (Default Free) Routing Table. Best locator of a peer from multiple ones absence of a TLA in the table means

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Multihomed ISPs and Policy Control <draft-ohta-multihomed-isps-00>

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  1. Multihomed ISPs andPolicy Control<draft-ohta-multihomed-isps-00> Masataka Ohta Tokyo Institute of Technology mohta@necom830.hpcl.titech.ac.jp

  2. All the Hosts Should haveFull (Default Free) Routing Table • Best locator of a peer from multiple ones • absence of a TLA in the table means • routing system has detected the TLA is unreachable • metric entry of the table gives preference • Metric can be set according to the policy of a site • Source address selection for ingress filtering • no forwarding or source address based routing! • use source address entry (new!) of the table • selection is hard, unless routing system is involved

  3. IP Version 6 Addressing Architecture (RFC237[34]) • IPv6 addresses has STRONG hierarchy • 13 bits of TLA (Top Level Aggregator) • 24 bits of NLA (Next Level Aggregator) • Hierarchy of ISPs is assumed • TLIs (Top Level ISPs) get globally unique TLAs • NLIs (Next Level ISPs) get NLAs unique within TLA

  4. | 3| 13 | 8 | 24 | 16 | 64 bits | +--+-----+---+--------+--------+--------------------------------+ |FP| TLA |RES| NLA | SLA | Interface ID | | | ID | | ID | ID | | +--+-----+---+--------+--------+--------------------------------+ <--Public Topology---> Site <--------> Topology <------Interface Identifier-----> IP Version 6 Addressing Architecture

  5. Multihomed ISPs • Why multihoming is necessary? • Robustness! • May NLIs be not so robust? • No! • NLIs MUST be multihomed to TLIs

  6. TLI NLI Subscribers Typical Scenario of IPv6 ISPs with Multihoming

  7. The Question • Can the number of TLAs limited? • Can NLIs be happy enough that not all ISPs require TLAs • Can NLIs control policy? • How much is the limit? • No question: how the limit is imposed • to be determined by global/regional/country NICs

  8. Can NLIs Control Policy? • ISPs are identified by AS#s • An NLI must peer with its TLI • the NLI may peer with any other ISP • Full egress control by NLIs possible • Ingress control? • Already limited today • locally possible if compatible with egress control

  9. ISP B ISP C ISP D ISP E ISP A ISP F ISP G ISP H ISP I policy essentially determined as egress ones (local arrangement negotiable) Propagation of Prefix of ISP A

  10. Ingress Control • Possible as long as NLA is propagated • An NLI can ask neighbor ISPs for the propagation • The NLA will be filtered by other ISPs • the NLI can still receive packets to NLA from corresponding TLA • not really a limitation

  11. ISP B (TLI of A) ISP C ISP D ISP E ISP A (NLI) ISP F ISP G ISP H ISP I arrangements with D, H, E and I necessary for ingress control Propagation of Prefix of ISP A

  12. ISP B (TLI of A) ISP C ISP D ISP E ISP A (NLI) ISP F ISP G ISP H (filter NLA) ISP I arrangement with H fail Propagation of Prefix of ISP A

  13. ISP B (TLI of A) ISP C ISP D ISP E ISP A (NLI) ISP F ISP G ISP H (pass NLA) ISP I Propagation of Prefix of ISP A

  14. ISP B (TLI of A) ISP C ISP D ISP E ISP A (NLI) ISP F ISP G ISP H (filter NLA) ISP I Propagation of Prefix of ISP A

  15. How Much is the Limit? • A lot larger than the number of those ISPs which claims to be global (tier1) • Much larger than the number of NICs • Better to be compatible with RFC237[34] • 1024~8192?

  16. Conclusion • NLIs must be multihomed to TLIs • NLIs policy can still be controlled • The number of TLAs should be limited below 1024~8192

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