Internet DRAFT - draft-arifumi-ipv6-rfc3484-revise
draft-arifumi-ipv6-rfc3484-revise
Network Working Group A. Matsumoto
Internet-Draft T. Fujisaki
Intended status: Standards Track NTT
Expires: August 5, 2007 Feb 2007
Things To Be Considered for RFC 3484 Revision
draft-arifumi-ipv6-rfc3484-revise-00.txt
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Copyright (C) The IETF Trust (2007).
Abstract
RFC 3484 has several known descriptions to be modified mainly because
of the deprecation of IPv6 site-local unicast address and the coming
of ULA. This document covers these essential points to be modified
and also possible useful changes to be included in the revision of
RFC 3484.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Problem Example . . . . . . . . . . . . . . . . . . . . . . 3
2. Proposed Changes to RFC 3484 . . . . . . . . . . . . . . . . . 4
2.1. To remove site-local unicast address . . . . . . . . . . . 4
2.2. To change default policy table . . . . . . . . . . . . . . 4
2.3. To add ULA related considerations . . . . . . . . . . . . . 5
2.4. To make address type dependent control possible . . . . . . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Normative References . . . . . . . . . . . . . . . . . . . 6
5.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . . . 8
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1. Introduction
RFC 3484 [RFC3484] defines default address selection rules for IPv6
and partly for IPv4. Because of the deprecation of IPv6 site-local
unicast address and the coming of ULA, [RFC4193] these rules in RFC
3484 are known to cause serious communication failure problems.
1.1. Problem Example
When an enterprise has IPv4 Internet connectivity but does not yet
have IPv6 Internet connectivity, and the enterprise wants to provide
site-local IPv6 connectivity, ULA is the best choice for site-local
IPv6 connectivity. Each employee host will have both an IPv4 global
or private address and a ULA. Here, when this host tries to connect
to Host-C that has registered both A and AAAA records in the DNS, the
host will choose AAAA as the destination address and ULA for the
source address. This will clearly result in a connection failure.
+--------+
| Host-C | AAAA = 2001:db8::80
+-----+--+ A = 192.47.163.1
|
============
| Internet |
============
| no IPv6 connectivity
+----+----+
| Gateway |
+----+----+
|
| fd01:2:3::/48 (ULA)
| 192.0.2.0/24
++--------+
| Router |
+----+----+
| fd01:2:3:4::/64 (ULA)
| 192.0.2.240/28
------+---+----------
|
+-+----+ fd01:2:3:4::100 (ULA)
| Host | 192.0.2.245
+------+
[Fig. 1]
This problem can be solved by adding one entry to the default policy
table. The changed table looks like this.
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Prefix Pref Label
::1/128 50 0
::/0 40 1
2002::/16 30 2
fc00::/7 35 5 (added for ULA)
::/96 20 3
::ffff:0:0/96 10 4
This problem was mentioned at ipv6 mailing lists by Pekka Savola.
2. Proposed Changes to RFC 3484
2.1. To remove site-local unicast address
RFC3484 contains a few "site-local unicast" and "fec::" description.
It's better to remove examples related to site-local unicast address,
or change examples to use ULA. Possible points to be re-written are
below.
- 2nd paragraph in Section 3.1 describes scope comparison
mechanism.
- Section 10 contains examples for site-local address.
2.2. To change default policy table
The default rule today is:
Prefix Precedence Label
::1/128 50 0
::/0 40 1
2002::/16 30 2
::/96 20 3
::ffff:0:0/96 10 4
The changes we should consider for the default policy table are,
- IPv4-compatible IPv6 address is deprecated. [RFC4291] (However,
should we keep this entry for the sake of backward compatibility
?)
- Teredo [RFC4380] is defined and has 2001::/32. Teredo's
priority should be less or equal to 6to4, considering its
characteristic of tunnel mechanism. About Windows, this point is
already in the implementation.
- ULA should have less precedence than Global IPv6 unicast
address. As described in Section 1.1, ULA is a possible cause of
connection failure. Things will worsen as IPv6 deployment
proceeds and more FQDNs have both A and AAAA records.
When we apply these changes, the default policy table looks like
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this.
Prefix Precedence Label
::1/128 50 0
::/0 40 1
2002::/16 30 2
fc00::/7 20 3 (For ULA)
::ffff:0:0/96 10 4
2001::/32 5 5 (For Teredo)
Teredo has the worst precedence. This means that, for IPv4-IPv6
dual-stack host, Teredo address will be used only when the
destination host has an IPv6 address only.
ULA has its own label and higher precedence than IPv4 address. This
means ULA will be used when the destination host also uses ULA. If a
host has a ULA and a IPv4 address, the host will not use ULA when
connecting to a dual-stack host in the Internet.
2.3. To add ULA related considerations
For example, we have to pay attention to source address selection for
a multicast packet. By default, ULA will be chosen for a multicast
packet of any scope.
This issue cannot be solved by changing a RFC 3484 rule. THis is
because, multicast and unicast have different sets of scope and it is
site-dependent which unicast address scope is appropriate for the
site's multicast scope.
2.4. To make address type dependent control possible
It is hard to define default preferences for these address types, RA-
based, DHCP-based, manual-based, and privacy extention address,
because the appropriate preference value depends on the usage of
these addresses, but not on address types themselves. It is the
policy table where you can control host's address selection behavior.
For example, You can set priority on RFC 3041 [RFC3041] address by
putting a line in policy table specifying RFC 3041 address by 128-bit
prefixlen and continuing to update policy table according to RFC 3041
address re-generation. But, this is surely troublesome for users and
implementers.
One idea is to update RFC 3484 policy table definition so that it can
handle meta addresses like privacy, DHCPv6 generated, RA generated,
manually generated (and even Home Address ?)
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To prefer privacy address by default, and to prefer RA-generated
address for site internal, the policy table will look like this.
Prefix Pref Label
2001:db8:1234::(PRIVACY)/128 30 2
::/0 10 2
2001:db8:1234::(RA):/128 30 1
2001:db8::/48 20 1
3. Security Considerations
No security risk is found that degrades RFC 3484.
4. IANA Considerations
Address type number for the policy table may have to be assigned by
IANA.
5. References
5.1. Normative References
[RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.
5.2. Informative References
[RFC3041] Narten, T. and R. Draves, "Privacy Extensions for
Stateless Address Autoconfiguration in IPv6", RFC 3041,
January 2001.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through
Network Address Translations (NATs)", RFC 4380,
February 2006.
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Authors' Addresses
Arifumi Matsumoto
NTT PF Lab
Midori-Cho 3-9-11
Musashino-shi, Tokyo 180-8585
Japan
Phone: +81 422 59 3334
Email: arifumi@nttv6.net
Tomohiro Fujisaki
NTT PF Lab
Midori-Cho 3-9-11
Musashino-shi, Tokyo 180-8585
Japan
Phone: +81 422 59 7351
Email: fujisaki@syce.net
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