draft-ietf-ipngwg-default-addr-select-05.txt

bind-3.2.

   following behavior: 
   Sources: 2001:aaaa:aaaa::a or 2007:0:aaaa::a or fe80::a 
   Destinations: 2001:bbbb:bbbb::b vs 2007:0:bbbb::b 
  
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   Result: 2007:0:bbbb::b (src 2007:0:aaaa::a) then 2001:bbbb:bbbb::b 
   (src 2001:aaaa:aaaa::a) (longest matching prefix) 
   In other words, when a host in site A initiates a connection to a 
   host in site B, the traffic does not take advantage of their 
   connections to the high-performance ISP. This is not their desired 
   behavior. 
   Sources: 2001:aaaa:aaaa::a or 2007:0:aaaa::a or fe80::a 
   Destinations: 2001:cccc:cccc::c vs 2006:cccc:cccc::c 
   Result: 2001:cccc:cccc::c (src 2001:aaaa:aaaa::a) then 
   2006:cccc:cccc::c (src 2007:0:aaaa::a) (longest matching prefix) 
   In other words, when a host in site A initiates a connection to a 
   host in some other site C, the reverse traffic may come back through 
   the high-performance ISP. Again, this is not their desired behavior. 
   This situation demonstrates the limitations of the longest-matching-
   prefix heuristic in multi-homed situations. 
   However, the administrators of sites A and B can achieve their 
   desired behavior via policy table configuration. For example, they 
   can use the following policy table: 
          Prefix              Precedence Label 
          ::1                         50     0 
          2001:aaaa:aaaa::/48         45     5 
          2001:bbbb:bbbb::/48         45     5 
          ::/0                        40     1 
          2002::/16                   30     2 
          ::/96                       20     3 
          ::ffff:0:0/96               10     4 
 
   This policy table produces the following behavior: 
   Sources: 2001:aaaa:aaaa::a or 2007:0:aaaa::a or fe80::a 
   Destinations: 2001:bbbb:bbbb::b vs 2007:0:bbbb::b 
   New Result: 2001:bbbb:bbbb::b (src 2001:aaaa:aaaa::a) then 
   2007:0:bbbb::b (src 2007:0:aaaa::a) (prefer higher precedence) 
   In other words, when a host in site A initiates a connection to a 
   host in site B, the traffic uses the high-performance ISP as 
   desired. 
   Sources: 2001:aaaa:aaaa::a or 2007:0:aaaa::a or fe80::a 
   Destinations: 2001:cccc:cccc::c vs 2006:cccc:cccc::c 
   New Result: 2006:cccc:cccc::c (src 2007:0:aaaa::a) then 
   2001:cccc:cccc::c (src 2007:0:aaaa::a) (longest matching prefix) 
   In other words, when a host in site A initiates a connection to a 
   host in some other site C, the traffic uses the normal ISP as 
   desired. 
  
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References 
 
   1  S. Bradner, "The Internet Standards Process -- Revision 3", BCP 
      9, RFC 2026, October 1996. 
   2  R. Hinden, S. Deering, "IP Version 6 Addressing Architecture", 
      RFC 2373, July 1998. 
   3  S. Thompson, T. Narten, "IPv6 Stateless Address Autoconfig-
      uration", RFC 2462 , December 1998. 
   4  T. Narten, R. Draves, "Privacy Extensions for Stateless Address 
      Autoconfiguration in IPv6", RFC 3041, January 2001. 
   5  D. Johnson, C. Perkins, "Mobility Support in IPv6", draft-ietf-
      mobileip-ipv6-13.txt, November 2000. 
   6  S. Cheshire, B. Aboba, "Dynamic Configuration of IPv4 Link-local 
      Addresses", draft-ietf-zeroconf-ipv4-linklocal-02.txt, March 
      2001. 
   7  S. Bradner, "Key words for use in RFCs to Indicate Requirement 
      Levels", BCP 14, RFC 2119, March 1997. 
   8  R. Gilligan, S. Thomson, J. Bound, W. Stevens, "Basic Socket 
      Interface Extensions for IPv6", RFC 2553, March 1999. 
   9  S. Deering et. al, "IP Version 6 Scoped Address Architecture", 
      draft-ietf-ipngwg-scoping-arch-02.txt, March 2001. 
   10 Y. Rekhter et. al, "Address Allocation for Private Internets", 
      RFC 1918, February 1996. 
   11 F. Baker, Editor, "Requirements for IP Version 4 Routers", RFC 
      1812, June 1995. 
   12 B. Carpenter, K. Moore, "Connection of IPv6 Domains via IPv4 
      Clouds", RFC 3056, February 2001. 
   13 T. Narten, E. Nordmark, and W. Simpson, "Neighbor Discovery for 
      IP Version 6", RFC 2461, December 1998. 
Acknowledgments 
   The author would like to acknowledge the contributions of the IPng 
   Working Group, particularly Marc Blanchet, Brian Carpenter, Matt 
   Crawford, Steve Deering, Robert Elz, Jun-ichiro itojun Hagino, Tony 
   Hain, M.T. Hollinger, JINMEI Tatuya, Erik Nordmark, Ken Powell, 
   Markku Savela, Dave Thaler, Ole Troan, and Mauro Tortonesi. Please 
   let the author know if you contributed to the development of this 
   draft and are not mentioned here. 
  
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Author's Address 
   Richard Draves 
   Microsoft Research 
   One Microsoft Way 
   Redmond, WA 98052 
   Phone: [phone] 
   Email: [e-mail] 
Revision History 
Changes from draft-ietf-ipngwg-default-addr-select-04 
   Clarified candidate set formation for routers. 
   Added some explanatory discussion to the candidate set section. 
   Replaced usages of scope id with zone index. 
   Augmented the first destination-address selection rule, to avoid 
   destination addresses for which the current next-hop neighbor is 
   known to be unreachable. 
Changes from draft-ietf-ipngwg-default-addr-select-03 
   Reversed the treatment of temporary addresses, so that unless an 
   application specifies otherwise public addresses are preferred over 
   temporary addresses. 
   Added text clarifying our expectation that applications should 
   iterate through the list of possible destination addresses until 
   finding a working address. 
   Removed references to getipnodebyname(). 
Changes from draft-ietf-ipngwg-default-addr-select-02 
   Changed scope treatment of IPv4-compatible and 6to4 addresses, so 
   they are always considered to be global. Removed mention of IPX 
   addresses. 
   Changed home address rules to favor addresses that are 
   simultaneously home and care-of addresses, over addresses that are 
   just home addresses or just care-of addresses. 
   Combined SrcLabel & DstLabel in the policy table into a single Label 
   attribute. 
   Added mention of the invalidation counter technique in the 
   implementation section. 
  
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Changes from draft-ietf-ipngwg-default-addr-select-01 
   Added Examples section, demonstrating default behavior and some 
   policy table configuration scenarios. 
   Removed many uses of MUST. Remaining uses concern the candidate set 
   of source addresses and the source address selection rule that 
   prefers source addresses of appropriate scope. 
   Simplified the default policy table. Reordered the source address 
   selection rules to reduce the influence of policy labels. Added more 
   destination address selection rules. 
   Added scoping of v4-compatible and 6to4 addresses based on the 
   embedded IPv4 address. 
   Changed references to anonymous addresses to use the new term, 
   temporary addresses. 
   Clarified that a user-level implementation of destination address 
   ordering, which does not have knowledge of the outgoing interface 
   for each destination, may use a looser definition of the candidate 
   set. 
   Clarified that an implementation should prevent an application or 
   upper-layer from choosing a source address that is not in the 
   candidate set and not prevent an application or upper-layer from 
   choosing a source address that is in the candidate set. 
   Miscellaneous editorial changes, including adding some missing 
   references. 
Changes from draft-ietf-ipngwg-default-addr-select-00 
   Changed the candidate set definition so that the strong host model 
   is recommended but not required. Added a rule to source address 
   selection to prefer addresses assigned to the outgoing interface. 
   Simplified the destination address selection algorithm, by having it 
   use source address selection as a subroutine. 
   Added a rule to source address selection to handle anonymous/public 
   addresses. 
   Added a rule to source address selection to handle home/care-of 
   addresses. 
   Changed to allow destination address selection to sort both IPv6 and 
   IPv4 addresses. Added entries in the default policy table for IPv4-
   mapped addresses. 
   Changed default precedences, so v4-compatible addresses have lower 
   precedence than 6to4 addresses. 
  
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Changes from draft-draves-ipngwg-simple-srcaddr-01 
   Added framework discussion. 
   Added algorithm for destination address ordering. 
   Added mechanism to allow the specification of administrative policy 
   that can override the default behavior. 
   Added section on routing interactions and TBD section on mobility 
   interactions. 
   Changed the candidate set definition for source address selection, 
   so that only addresses assigned to the outgoing interface are 
   allowed. 
   Changed the loopback address treatment to link-local scope. 
Changes from draft-draves-ipngwg-simple-srcaddr-00 
   Minor wording changes because DHCPv6 also supports "preferred" and 
   "deprecated" addresses. 
   Specified treatment of other format prefixes; now they are 
   considered global scope, "preferred" addresses. 
   Reiterated that anycast and multicast addresses are not allowed as 
   source addresses. 
   Recommended that source addresses be taken from the outgoing 
   interface. Required this for multicast destinations. Added analogous 
   requirements for link-local and site-local destinations. 
   Specified treatment of the loopback address. 
   Changed the second selection rule so that if both candidate source 
   addresses have scope greater or equal than the destination address 
   and only of them is preferred, the preferred address is chosen. 
  
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