Default Address Selection for IPv6 Richard Draves March 19, 2001 Minneapolis IETF Meeting draft-ietf-ipngwg-default-addr-select-03

Source Address Selection and Destination Address Ordering Minimal requirement for all implementations Automatically pick “reasonable” source and destination addresses Configuration/policy is possible NOT just for multi-homing Complement other multi-homing approaches

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.

What’s 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.

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: PrefixPrecedenceLabel ::1/ ::/ ::/16302 ::/96203 ::ffff:0:0/96104 IPv4 destinations are represented as v4-mapped addresses. …

Source Address Selection Rules Selecting IPv6 source for IPv6 destination: 1.Prefer same address (for loopback). 2.Prefer appropriate scope. 3.Avoid deprecated addresses. 4.Prefer home addresses over care-of addresses. 5.Prefer source assigned to originating interface. 6.Prefer matching label from policy table. 7.Prefer temporary addresses. 8.Use longest-matching-prefix.

Destination Address Ordering First, select best source for each destination, IPv6 and IPv4: 1.Avoid unusable destinations. 2.Prefer matching scope. 3.Avoid deprecated source addresses. 4.Prefer home source addresses. 5.Prefer matching label from policy table. 6.Prefer destinations with higher precedence. 7.Prefer smaller scope destinations. 8.Use longest-matching-prefix. 9.Otherwise, leave order from DNS unchanged

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)