DFZ, pTLAs and the 6bone

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DFZ, pTLAs and the 6bone

• Michel Py
• michel_at_arneill-py.sacramento.ca.us
• Iljitsch van Beijnum
• iljitsch_at_muada.com
• ipv6mh mailing list
• http//arneill-py.sacramento.ca.us/ipv6mh

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Goals of this presentation

• Semantics clarifications.
• Provoke thoughts about the future of the IPv6
  Internet backbone.

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Semantics

• Problem at hand define IPv6 DFZ.
• What does it mean?
• Default-Free Zone
• But what is it exactly?

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Semantics

• IPv4 DFZ
• The subset of routers that do not have a default
  route and do not receive a full routing table
  from a single peer.
• In the current IPv4 tiered system, the DFZ is the
  inter-connected full mesh of tier-1 providers.
  Tier-1 ISPs do not pay anyone for transit,
  resulting in them being fully meshed.

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Semantics

• There is a difference between the IPv4 DFZ and
  the IPv4 DFZs routing table.
• The IPv4 DFZs routing table extends beyond the
  DFZs boundaries (for example, to multihomed
  customers).
• One of todays IPv4 issues is the size of the
  DFZs routing table.

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Semantics

• Several things have contributed to the large size
  of the routing table.
• Due to the shortage of v4 addresses, allocation
  policies tend to allocate barely what is needed
  at a given time, resulting in relatively poor
  aggregation.
• Multihoming has little influence on the size of
  the v4 DFZs routing table, since only 12k ASes
  are currently in use.

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Semantics

• Then, what is the IPv6 DFZ?
• If the v4 definition is to be used for v6, there
  is no such thing as an IPv6 DFZ today.
• The definition of the IPv6 DFZ is based on our
  guess of the evolution of the IPv6 Internet.

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Semantics

• We see three possible scenarios
• 1. Centralized backbone, Arpanet / NSFnet style.
  Unlikely.
• 2. Competing but interconnected backbones. This
  is the current tier-1 system. Likely.
• 3. No major backbone(s) but large scale direct
  interconnection between smaller networks.
• Is this a realistic possibility?

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Semantics

• Consequences on semantics
• _IF_ scenario 2 is what happens
• The term TLA and the derived 8k DFZ are used
  as described in RFC2373. The authors understand
  that draft-ietf-ipngwg-addr-arch-v3-07.txt
  obsoletes this model.
• As soon as RFC2373 is becomes obsolete or
  historic, we will need a definition for what
  used to be called a TLA.

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Semantics

• Consequences on semantics
• _IF_ scenario 2 is what happens
• Most TLAs (there could be 8,189 of them with
  2001, 2002 and 3FFE taken, the so-called 8K DFZ
  ) will be tier-2 ISPs. Note that here, 8K DFZ
  does not make any sense because only tier-1 are
  part of the DFZ. It should be 8K DFZs routing
  table.
• There is no direct relation between being a
  Top-Level Aggregator and being a tier-1 ISP.

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Semantics

• _IF_ scenario 3 is what happens
• Then what is the definition of IPv6 DFZ ?
  (because the v4 definition does not match
  anything).
• A possible definition is that the DFZ will be a
  backup only localized at one or more exchanges.

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Relation to the 6bone

• The question is not how to transform the 6bone
  into the IPv6 backbone.
• The question is not whether or not tunnelling v6
  in v4 is bad. We know it is. But guess what? The
  flexibility and price are right.
• The question is what 6bone participants think
  about the future IPv6 Internet.

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Food for thought

• The 6bone and the production v6 Internet are
  connected.
• How many 6bone pTLAs are we planning on and what
  is the impact of the 6bone on the DFZs routing
  table?
• IPv4 style multihoming depends on not
  aggregating, so doing this in IPv6 will either
  lead to an exploding routing table or to
  multihoming being restricted to a happy few.

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Food for thought

• Is scenario 2 the only one?
• If yes, does the 6bone / IETF have a role in
  recommendations, or do we just accept the fact
  the current v4 tier-1 will become v6 tier-1 as
  well?
• If not, please speak up about what you think the
  peering structure should be.

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Thank you for your time and attention