Default Address Selection for IPv6

1
Default Address Selection for IPv6
draft-ietf-ipngwg-default-addr-select-03

• Richard DravesMarch 19, 2001
• Minneapolis IETF Meeting

2
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

3
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 addresses
• 90 of the complexity due to considerations other
  than multi-homing.

4
Whats Changed?

• Further simplified default policy table.
• Tweaked home/care-of address treatment,favoring
  addresses that are both.
• 6to4 and v4-compatible addresses are treated as
  global scope.

5
Default Policy Table

• Implementations SHOULD be configurable, via
  mechanisms at least as powerful as these policy
  tables. If not configured, then they SHOULD
  operate according to the default policy table

IPv4 destinations are represented as v4-mapped
addresses.
6
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.

7
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

8
Controversial Issues

• Configuration mechanisms and default treatment
  for mobility privacy preferences
• Home vs care-of addresses
• Temporary vs public addresses
• Current draft says
• Prefer home address over care-of address
• Prefer temporary address over public address
• Configure via socket option (but does not
  preclude other approaches)