Default Address Selection for IPv6

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Default Address Selection for IPv6
draft-ietf-ipngwg-default-addr-select-02

• Richard DravesDecember 13, 2000
• San Diego IETF Meeting

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Source Address Selection and Destination Address
Ordering

• Minimal requirement for all implementations
• Automatically pick reasonablesource and
  destination addresses
• Configuration/policy is possible
• NOT just for multi-homing
• Complement other multi-homing approaches

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Not Just for Multi-Homing

• Consider a singly-homed IPv6 host
• Loopback, link-local, site-local addresses
• Global address, temporary address
• v4-compatible address, 6to4 address
• Home address
• IPv4 address
• 90 of the complexity due to considerations other
  than multi-homing.

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Whats Changed?

• Toned down requirement strength. Remaining MUSTs
  for inter-operability
• Candidate set what is a legal source address?
• Prefer appropriate scope when choosing source
  addresses.
• Simplified default policy table.
• Added more destination ordering rules.
• Added examples.

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Default Policy Table

• Implementations SHOULD be configurable. If not
  configured, then they SHOULD operate according to
  the default policy table

IPv4 destinations are represented as v4-mapped
addresses.
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Source Address Selection Rules

• Selecting IPv6 source for IPv6 destination
• Prefer same address (for loopback).
• Prefer appropriate scope.
• Avoid deprecated addresses.
• Prefer home addresses over care-of addresses.
• Prefer source assigned to originating interface.
• Prefer matching label from policy table.
• Prefer temporary addresses.
• Use longest-matching-prefix.

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Destination Address Ordering

• First, select best source for each
  destination,IPv6 and IPv4
• Avoid unusable destinations.
• Prefer matching scope.
• Avoid deprecated source addresses.
• Prefer home source addresses.
• Prefer matching label from policy table.
• Prefer destinations with higher precedence.
• Prefer smaller scope destinations.
• Use longest-matching-prefix.
• Otherwise, leave order from DNS unchanged

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Configuration Examples

• Prefer IPv4 over IPv6
• Prefer global destinations over link-local or
  site-local destinations.
• Control address selection in multi-homed sites.

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Remaining Issues

• API (socket options?) for controlling mobility
  privacy preferences
• Home vs care-of addresses
• Temporary vs public addresses
• Consolidate SrcLabel/DstLabel?
• Last call?