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Multihomed ISPs and Policy Control <draft-ohta-multihomed-isps-00>. Masataka Ohta Tokyo Institute of Technology [email protected] 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

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Multihomed isps and policy control draft ohta multihomed isps 00

Multihomed ISPs andPolicy Control<draft-ohta-multihomed-isps-00>

Masataka Ohta

Tokyo Institute of Technology

[email protected]


All the hosts should have full default free routing table

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


Ip version 6 addressing architecture rfc237 34

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


Multihomed isps and policy control draft ohta multihomed isps 00

| 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


Multihomed isps

Multihomed ISPs

  • Why multihoming is necessary?

    • Robustness!

  • May NLIs be not so robust?

    • No!

  • NLIs MUST be multihomed to TLIs


Multihomed isps and policy control draft ohta multihomed isps 00

TLI

NLI

Subscribers

Typical Scenario of IPv6 ISPs with Multihoming


The question

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


Can nlis control policy

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


Multihomed isps and policy control draft ohta multihomed isps 00

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


Ingress control

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


Multihomed isps and policy control draft ohta multihomed isps 00

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


Multihomed isps and policy control draft ohta multihomed isps 00

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


Multihomed isps and policy control draft ohta multihomed isps 00

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


Multihomed isps and policy control draft ohta multihomed isps 00

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


How much is the limit

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?


Conclusion

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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