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Multihomed ISPs and Policy Control &lt;draft-ohta-multihomed-isps-00&gt;. 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 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
slide4

| 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
slide6

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
slide9

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
slide11

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

slide12

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

slide13

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

slide14

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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