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

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

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TLIs (Top Level ISPs) get globally unique TLAs ... NLIs policy can still be controlled. The number of TLAs should be limited below 1024~8192 ... – PowerPoint PPT presentation

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


1
Multihomed ISPs andPolicy Controlltdraft-ohta-mul
tihomed-isps-00gt
  • Masataka Ohta
  • Tokyo Institute of Technology
  • mohta_at_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 (RFC23734)
  • 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
-------------------------------------------
--------------- lt--Public Topology---gt
Site lt--------gt
Topology
lt------Interface
Identifier-----gt
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 ASs
  • 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 RFC23734
  • 10248192?

16
Conclusion
  • NLIs must be multihomed to TLIs
  • NLIs policy can still be controlled
  • The number of TLAs should be limited below
    10248192
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