draft-ietf-6man-addr-select-opt-10.txt		draft-ietf-6man-addr-select-opt-11.txt
	6man Working Group A.M. Matsumoto		6man Working Group A. Matsumoto
	Internet-Draft T.F. Fujisaki		Internet-Draft T. Fujisaki
	Intended status: Standards Track NTT		Intended status: Standards Track NTT
	Expires: November 01, 2013 T.C. Chown		Expires: February 08, 2014 T. Chown
	University of Southampton		University of Southampton
	April 30, 2013		August 07, 2013
	Distributing Address Selection Policy using DHCPv6		Distributing Address Selection Policy using DHCPv6
	draft-ietf-6man-addr-select-opt-10.txt		draft-ietf-6man-addr-select-opt-11.txt
	Abstract		Abstract
	RFC 6724 defines default address selection mechanisms for IPv6 that		RFC 6724 defines default address selection mechanisms for IPv6 that
	allow nodes to select an appropriate address when faced with multiple		allow nodes to select an appropriate address when faced with multiple
	source and/or destination addresses to choose between. The RFC 6724		source and/or destination addresses to choose between. RFC 6724
	allowed for the future definition of methods to administratively		allows for the future definition of methods to administratively
	configure the address selection policy information. This document		configure the address selection policy information. This document
	defines a new DHCPv6 option for such configuration, allowing a site		defines a new DHCPv6 option for such configuration, allowing a site
	administrator to distribute address selection policy overriding the		administrator to distribute address selection policy overriding the
	default address selection parameters and policy table, and thus		default address selection parameters and policy table, and thus to
	control the address selection behavior of nodes in their site.		control the address selection behavior of nodes in their site.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on November 01, 2013.		This Internet-Draft will expire on February 08, 2014.
	Copyright Notice		Copyright Notice
	Copyright (c) 2013 IETF Trust and the persons identified as the		Copyright (c) 2013 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 25		skipping to change at page 2, line 25
	modifications of such material outside the IETF Standards Process.		modifications of such material outside the IETF Standards Process.
	Without obtaining an adequate license from the person(s) controlling		Without obtaining an adequate license from the person(s) controlling
	the copyright in such materials, this document may not be modified		the copyright in such materials, this document may not be modified
	outside the IETF Standards Process, and derivative works of it may		outside the IETF Standards Process, and derivative works of it may
	not be created outside the IETF Standards Process, except to format		not be created outside the IETF Standards Process, except to format
	it for publication as an RFC or to translate it into languages other		it for publication as an RFC or to translate it into languages other
	than English.		than English.
	1. Introduction		1. Introduction
	RFC 3484 [RFC3484] describes default algorithms for selecting an		[RFC6724] describes default algorithms for selecting an address when
	address when a node has multiple destination and/or source addresses		a node has multiple destination and/or source addresses to choose
	to choose from by using an address selection policy. In Section 2 of		from by using an address selection policy. In Section 2 of RFC 6724,
	RFC 6724, it is suggested that the default policy table may be		it is suggested that the default policy table may be administratively
	administratively configured to suit the specific needs of a site.		configured to suit the specific needs of a site. This specification
	This specification defines a new DHCPv6 option for such		defines a new DHCPv6 option for such configuration.
	configuration.
	Some problems have been identified with the default RFC 3484 address		Some problems were identified with the default address selection
	selection policy [RFC5220]. It is unlikely that any default policy		policy as originally defined in [RFC3484]. As a result, RFC 3484 was
	will suit all scenarios, and thus mechanisms to control the source		updated and obsoleted by [RFC6724]. While this update corrected a
	address selection policy will be necessary. Requirements for those		number of issues identifed from operational experience, it is
	mechanisms are described in [RFC5221], while solutions are discussed		unlikely that any default policy will suit all scenarios, and thus
	in [I-D.ietf-6man-addr-select-considerations]. Those documents have		mechanisms to control the source address selection policy will be
			necessary. Requirements for those mechanisms are described in
			[RFC5221], while solutions are discussed in
			[I-D.ietf-6man-addr-select-considerations]. Those documents have
	helped shape the improvements in the default address selection		helped shape the improvements in the default address selection
	algorithm [RFC6724] as well as the DHCPv6 option defined in this		algorithm in [RFC6724] as well as the requirements for the DHCPv6
	specification.		option defined in this specification.
	1.1. Conventions Used in This Document		1.1. Conventions Used in This Document
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	1.2. Terminology		1.2. Terminology
	This document uses the terminology defined in [RFC2460] and the		This document uses the terminology defined in [RFC2460] and the
	DHCPv6 specification defined in [RFC3315]		DHCPv6 specification defined in [RFC3315]
	2. Address Selection options		2. Address Selection options
	The Address Selection option provides the address selection policy		The Address Selection option provides the address selection policy
	table, and some other configuration parameters.		table, and some other configuration parameters.
	An Address Selection option contains zero or more policy table		An Address Selection option contains zero or more policy table
	options. Multiple Policy Table options in an Address Selection		options. Multiple policy table options in an Address Selection
	option constitute a single policy table. When it does not contain		option constitute a single policy table. When an Address Selection
	policy table option, it is used to convey the A and P flags.		option does not contain a policy table option, it may be used to just
			convey the A and P flags.
	The format of the Address Selection option is given below.		The format of the Address Selection option is given below.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| OPTION_ADDRSEL | option-len |		| OPTION_ADDRSEL | option-len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Reserved |A|P| |		| Reserved |A|P| |
	+-+-+-+-+-+-+-+-+ POLICY TABLE OPTIONS |		+-+-+-+-+-+-+-+-+ POLICY TABLE OPTIONS |
	skipping to change at page 3, line 37		skipping to change at page 3, line 41
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 1: Address Selection option format		Figure 1: Address Selection option format
	option-code: OPTION_ADDRSEL (TBD).		option-code: OPTION_ADDRSEL (TBD).
	option-len: The total length of the Reserved field, A, P flags, and		option-len: The total length of the Reserved field, A, P flags, and
	POLICY TABLE OPTIONS in octets.		POLICY TABLE OPTIONS in octets.
	Reserved: Reserved field. Server MUST set this value to zero and		Reserved: Reserved field. The server MUST set this value to zero
	client MUST ignore its content.		and the client MUST ignore its content.
	A: Automatic Row Addition flag. This flag toggles the Automatic		A: Automatic Row Addition flag. This flag toggles the Automatic
	Row Addition flag at client hosts, which is described in the		Row Addition flag at client hosts, which is described in section
	section 2.1 in RFC 6724 [RFC6724]. If this flag is set to 1, it		2.1 of [RFC6724]. If this flag is set to 1, it does not change
	does not change client host behavior, that is, a client MAY		client host behavior, that is, a client MAY automatically add
	automatically add additional site-specific rows to the policy		additional site-specific rows to the policy table. If set to 0,
	table. If set to 0, the Automatic Row Addition flag is		the Automatic Row Addition flag is disabled, and a client SHOULD
	disabled, and a client SHOULD NOT automatically add rows to the		NOT automatically add rows to the policy table. If the option
	policy table.		contains a POLICY TABLE option, this flag is meaningless, and
			automatic row addition SHOULD NOT be performed against the
			distributed policy table.
	P: Privacy Preference flag. This flag toggles the Privacy		P: Privacy Preference flag. This flag toggles the Privacy
	Preference flag at client hosts, which is described in the		Preference flag on client hosts, which is described in section 5
	section 5 in RFC 6724 [RFC6724]. If this flag is set to 1, it		of [RFC6724]. If this flag is set to 1, it does not change
	does not change client host behavior, that is, a client will		client host behavior, that is, a client will prefer temporary
	prefer temporary addresses. If set to 0, the Privacy Preference		addresses [RFC4941]. If set to 0, the Privacy Preference flag
	flag is disabled, and a client will prefer public addresses.		is disabled, and a client will prefer public addresses.
	POLICY TABLE OPTIONS: Zero or more Address Selection Policy Table		POLICY TABLE OPTIONS: Zero or more Address Selection Policy Table
	options described below. This option corresponds to a row in		options, as described below. This option corresponds to a row
	the policy table defined in the section 2.1 in RFC 6724		in the policy table defined in section 2.1 of [RFC6724].
	[RFC6724].
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| OPTION_ADDRSEL_TABLE | option-len |		| OPTION_ADDRSEL_TABLE | option-len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| label | precedence | prefix-len | |		| label | precedence | prefix-len | |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
	| |		| |
	| prefix (variable length) |		| prefix (variable length) |
	skipping to change at page 5, line 7		skipping to change at page 4, line 43
	Figure 2: Address Selection Policy Table option format		Figure 2: Address Selection Policy Table option format
	option-code: OPTION_ADDRSEL_TABLE (TBD).		option-code: OPTION_ADDRSEL_TABLE (TBD).
	option-len: The total length of the label field, precedence field,		option-len: The total length of the label field, precedence field,
	prefix-len field, and prefix field.		prefix-len field, and prefix field.
	label: An 8-bit unsigned integer; this value is for correlation of		label: An 8-bit unsigned integer; this value is for correlation of
	source address prefixes and destination address prefixes. This		source address prefixes and destination address prefixes. This
	field is used to deliver a label value in RFC 6724 policy table.		field is used to deliver a label value in the [RFC6724] policy
			table.
	precedence: An 8-bit unsigned integer; this value is used for		precedence: An 8-bit unsigned integer; this value is used for
	sorting destination addresses. This field is used to to deliver		sorting destination addresses. This field is used to to deliver
	a precedence value in RFC 6724 policy table.		a precedence value in [RFC6724] policy table.
	prefix-len: An 8-bit unsigned integer; the number of leading bits in		prefix-len: An 8-bit unsigned integer; the number of leading bits in
	the prefix that are valid. The value ranges from 0 to 128.		the prefix that are valid. The value ranges from 0 to 128.
	prefix: A variable-length field containing an IP address or the		prefix: A variable-length field containing an IP address or the
	prefix of an IP address. An IPv4-mapped address [RFC4291] must		prefix of an IP address. An IPv4-mapped address [RFC4291] must
	be used to represent an IPv4 address as a prefix value. This		be used to represent an IPv4 address as a prefix value. This
	field is padded with zeros up to the nearest octet boundary when		field is padded with zeros up to the nearest octet boundary when
	prefix6-len is not divisible by 8. This can be expressed using		prefix-len is not divisible by 8. This can be expressed using
	the following equation: (prefix-len+7)/8 So the length of this		the following equation: (prefix-len + 7)/8 So the length of this
	field should be between 0 and 16 bytes. For example, the prefix		field should be between 0 and 16 bytes. For example, the prefix
	2001:db8::/60 would be encoded with an prefix-len of 60, the		2001:db8::/60 would be encoded with an prefix-len of 60, the
	prefix would be 8 octets and would contains octets 20 01 0d b8		prefix would be 8 octets and would contains octets 20 01 0d b8
	00 00 00 00.		00 00 00 00.
	3. Processing the Policy Table option		3. Processing the Address Selection option
	This section describes how to process received Policy Table option at		This section describes how to process a received Address Selection
	the DHCPv6 client.		option at the DHCPv6 client.
	This option's concept is to serve as a hint for a node about how to		This option's concept is to serve as a hint for a node about how to
	behave in the network. Ultimately, it can be controlled by the		behave in the network. Ultimately, while the node's administrator
	node's administrator how to deal with the received policy		can control how to deal with the received policy information, the
	information, but the implementation SHOULD follow the way described		implementation SHOULD follow the method described below uniformly, to
	below uniformly to ease diagnose brokenness and to reduce operational		ease troubleshooting and to reduce operational costs.
	costs.
	3.1. Handling of the local policy table		3.1. Handling local configurations
	RFC 6724 defines the default policy table. Also, users are usually		[RFC6724] defines two flags (A, P) and the default policy table.
	able to configure the policy table to satisfy their own requirements.		Also, users are usually able to configure the flags and the policy
			table to satisfy their own requirements.
	The client implementation SHOULD provide the following choices to the		The client implementation SHOULD provide the following choices to the
	user. The choice a SHOULD be default, as far as the policy table is		user.
	not configured by the user.
	a) replace the existing active policy table with the DHCPv6		(a) replace the existing flags and active policy table with the
	distributed policy table.		DHCPv6 distributed flags and policy table.
	b) preserve the existing active policy table, whether this be the		(b) preserve the existing flags and active policy table, whether
	default policy table, or user configured policy.		this be the default policy table, or user configured policy.
	3.2. Handling of the stale policy table		Choice (a) SHOULD be the default, i.e. that the policy table is not
			explictly configured by the user.
			3.2. Handling stale policy tables
	When the information from the DHCP server goes stale, the policy		When the information from the DHCP server goes stale, the policy
	received form the DHCP server SHOULD be deprecated.		received from the DHCP server SHOULD be deprecated.
	The received information can be considered stale in several cases,		The received information can be considered stale in several cases,
	such as, when the interface goes down, the DHCP server does not		e.g., when the interface goes down, the DHCP server does not respond
	respond for a certain amount of time, and the Information Refresh		for a certain amount of time, and the Information Refresh Time is
	Time is expired.		expired.
	3.3. Multi-interface situation		3.3. Handling multiple interfaces
	The policy table, and other parameters specified in this document are		The policy table, and other parameters specified in this document,
	node-global information by their nature. One reason being that the		are node-global information by their nature. One reason being that
	outbound interface is usually chosen after destination address		the outbound interface is usually chosen after destination address
	selection. So, a host cannot make use of multiple address selection		selection. So a host cannot make use of multiple address selection
	policies even if they are stored per interface.		policies even if they are stored per interface.
	Even if the received policy from one source is merged with one from
	another source, the effect of both policy are more or less changed.
	The policy table is defined as a whole, so the slightest addition/		The policy table is defined as a whole, so the slightest addition/
	deletion from the policy table brings a change in semantics of the		deletion from the policy table brings a change in the semantics of
	policy.		the policy.
	It also should be noted that absence of the distributed policy from a		It also should be noted that the absence of a DHCP-distributed policy
	certain network interface should not be treated as absence of policy		from a certain network interface should not infer that the network
	itself, because it may mean preference for the default address		administrator does not care about address selection policy at all,
	selection policy.		because it may mean there is a preference to use the default address
			selection policy. So, it should be safe to assume that the default
			address selection policy should be used where no overriding policy is
			provided.
	Under the above assumptions, how to handle received policy is		Under the above assumptions, we can specify how to handle received
	specified below.		policy as follows.
	A node SHOULD use Address Selection options by default in any of the		In the absence of distributed policy for a certain network interface,
	following two cases:		the default address selection policy SHOULD be used. A node should
			use Address Selection options by default in any of the following two
			cases:
	1: The host is single-homed, where the host belongs to one		1: A single-homed host SHOULD use default address selection options,
	administrative network domain exclusively usually through one		where the host belongs exclusively to one administrative network
	active network interface.		domain, usually through one active network interface.
	2: The host implements some advanced heuristics to deal with multiple		2: Hosts that use advanced heuristics to deal with multiple received
	received policy, which is outside the scope of this document.		policies that are defined outside the scope of this document
			SHOULD use Address Selection options.
	The above restrictions do not preclude implementations from providing		Implementations MAY provide configuration options to enable this
	configuration options to enable this option on a certain network		protocol on a per interface basis.
	interface.
	Nor, they do not preclude implementations from storing distributed		Implementations MAY store distributed address selection policies per
	address selection policies per interface. They can be used		interface. They can be used effectively on implementations that
	effectively on such implementations that adopt per-application		adopt per-application interface selection.
	interface selection.
	4. Implementation Considerations		4. Implementation Considerations
	o The value 'label' is passed as an unsigned integer, but there is		o The value 'label' is passed as an unsigned integer, but there is
	no special meaning for the value, that is whether it is a large or		no special meaning for the value, that is whether it is a large or
	small number. It is used to select a preferred source address		small number. It is used to select a preferred source address
	prefix corresponding to a destination address prefix by matching		prefix corresponding to a destination address prefix by matching
	the same label value within the DHCP message. DHCPv6 clients		the same label value within the DHCP message. DHCPv6 clients
	SHOULD convert this label to a representation appropriate for the		SHOULD convert this label to a representation appropriate for the
	local implementation (e.g., string).		local implementation (e.g., string).
	o Currently, the label and precedence values are defined as 8-bit
	unsigned integers. In almost all cases, this value will be
	enough.
	o The maximum number of address selection rules that may be conveyed		o The maximum number of address selection rules that may be conveyed
	in one DHCPv6 message depends on the prefix length of each rule		in one DHCPv6 message depends on the prefix length of each rule
	and the maximum DHCPv6 message size defined in RFC 3315. It is		and the maximum DHCPv6 message size defined in [RFC3315]. It is
	possible to carry over 3,000 rules in one DHCPv6 message (maximum		possible to carry over 3,000 rules in one DHCPv6 message (maximum
	UDP message size). However, it should not be expected that DHCP		UDP message size). However, it should not be expected that DHCP
	clients, servers and relay agents can handle UDP fragmentation.		clients, servers and relay agents can handle UDP fragmentation.
	Network adiministrators SHOULD consider local limitations to the		Network adiministrators SHOULD consider local limitations to the
	maximum DHCPv6 message size that can be reliably transported via		maximum DHCPv6 message size that can be reliably transported via
	their specific local infrastructure to end nodes; and therefore		their specific local infrastructure to end nodes; and therefore
	they SHOULD consider the number of options, the total size of the		they SHOULD consider the number of options, the total size of the
	options, and the resulting DHCPv6 message size, when defining		options, and the resulting DHCPv6 message size, when defining
	their Policy Table.		their policy table.
	5. Security Considerations		5. Security Considerations
	A rogue DHCPv6 server could issue bogus address selection policies to		A rogue DHCPv6 server could issue bogus address selection policies to
	a client. This might lead to incorrect address selection by the		a client. This might lead to incorrect address selection by the
	client, and the affected packets might be blocked at an outgoing ISP		client, and the affected packets might be blocked at an outgoing ISP
	because of ingress filtering, incur additional network charges, or be		because of ingress filtering, incur additional network charges, or be
	misdirected to an attacker's machine. Alternatively, an IPv6		misdirected to an attacker's machine. Alternatively, an IPv6
	transition mechanism might be preferred over native IPv6, even if it		transition mechanism might be preferred over native IPv6, even if it
	is available. To guard against such attacks, a legitimate DHCPv6		is available. To guard against such attacks, a legitimate DHCPv6
	server should communicate through a secure, trusted channel, such as		server should communicate through a secure, trusted channel, such as
	a channel protected by IPsec, SEND and DHCP authentication, as		a channel protected by IPsec, SEND and DHCP authentication, as
	described in section 21 of RFC 3315,		described in section 21 of [RFC3315]. A commonly used alternative
			mitigation is to employ DHCP snooping at Layer 2.
	Another threat is about privacy concern. As in the security		Another threat surrounds the potential privacy concern as described
	consideration section of RFC 6724, at least a part of, the address		in the security considerations section of [RFC6724], whereby an
	selection policy stored in a host can be leaked by a packet from a		attacker can send packets with different source addresses to a
	remote host. This issue will not be modified by the introduction of		destination to solicit different source addresses in the responses
	this option, regardless of whether the host is multihomed or not.		from that destination. This issue will not be modified by the
			introduction of this option, regardless of whether the host is
			multihomed or not.
	6. IANA Considerations		6. IANA Considerations
	IANA is requested to assign option codes to OPTION_ADDRSEL and		IANA is requested to assign option codes to OPTION_ADDRSEL and
	OPTION_ADDRSEL_TABLE from the "DHCP Option Codes" registry (http://		OPTION_ADDRSEL_TABLE from the "DHCP Option Codes" registry (http://
	www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xml).		www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xml).
	7. References		7. References
	7.1. Normative References		7.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,		[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
	and M. Carney, "Dynamic Host Configuration Protocol for		and M. Carney, "Dynamic Host Configuration Protocol for
	IPv6 (DHCPv6)", RFC 3315, July 2003.		IPv6 (DHCPv6)", RFC 3315, July 2003.
	[RFC3484] Draves, R., "Default Address Selection for Internet
	Protocol version 6 (IPv6)", RFC 3484, February 2003.
	[RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown,		[RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
	"Default Address Selection for Internet Protocol Version 6		"Default Address Selection for Internet Protocol Version 6
	(IPv6)", RFC 6724, September 2012.		(IPv6)", RFC 6724, September 2012.
	7.2. Informative References		7.2. Informative References
	[I-D.ietf-6man-addr-select-considerations]		[I-D.ietf-6man-addr-select-considerations]
	Chown, T. and A. Matsumoto, "Considerations for IPv6		Chown, T. and A. Matsumoto, "Considerations for IPv6
	Address Selection Policy Changes", draft-ietf-6man-addr-		Address Selection Policy Changes", draft-ietf-6man-addr-
	select-considerations-05 (work in progress), April 2013.		select-considerations-05 (work in progress), April 2013.
	[RFC2460] Deering, S.E. and R.M. Hinden, "Internet Protocol, Version		[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
	6 (IPv6) Specification", RFC 2460, December 1998.		(IPv6) Specification", RFC 2460, December 1998.
	[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.		[RFC3484] Draves, R., "Default Address Selection for Internet
	Stevens, "Basic Socket Interface Extensions for IPv6", RFC		Protocol version 6 (IPv6)", RFC 3484, February 2003.
	3493, February 2003.
	[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing		[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
	Architecture", RFC 4291, February 2006.		Architecture", RFC 4291, February 2006.
	[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy		[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
	Extensions for Stateless Address Autoconfiguration in		Extensions for Stateless Address Autoconfiguration in
	IPv6", RFC 4941, September 2007.		IPv6", RFC 4941, September 2007.
	[RFC5220] Matsumoto, A., Fujisaki, T., Hiromi, R., and K. Kanayama,		[RFC5220] Matsumoto, A., Fujisaki, T., Hiromi, R., and K. Kanayama,
	"Problem Statement for Default Address Selection in Multi-		"Problem Statement for Default Address Selection in Multi-
	skipping to change at page 9, line 29		skipping to change at page 9, line 22
	July 2008.		July 2008.
	Appendix A. Acknowledgements		Appendix A. Acknowledgements
	Authors would like to thank to Dave Thaler, Pekka Savola, Remi Denis-		Authors would like to thank to Dave Thaler, Pekka Savola, Remi Denis-
	Courmont, Francois-Xavier Le Bail, Ole Troan, Bob Hinden, Dmitry		Courmont, Francois-Xavier Le Bail, Ole Troan, Bob Hinden, Dmitry
	Anipko, Ray Hunter, Rui Paulo, Brian E Carpenter, Tom Petch, and the		Anipko, Ray Hunter, Rui Paulo, Brian E Carpenter, Tom Petch, and the
	members of 6man's address selection design team for their invaluable		members of 6man's address selection design team for their invaluable
	contributions to this document.		contributions to this document.
			Appendix B. Examples
			[RFC5220] gives several cases where address selection problems
			happen. This section contains some examples for solving those cases
			by using the DHCP option defined in this text to update the hosts'
			policy table in a network accordingly. There is also some discussion
			of example policy tables in sections 10.3 to 10.7 of RFC 6724.
			B.1. Ingress Filtering Problem
			In the case described in section 2.1.2 of [RFC5220], the following
			policy table should be distributed, when Router performs static
			routing and directs the default route to ISP1 as per Figure 2. By
			putting the same label value to all IPv6 addresses (::/0) and the
			local subnet (2001:db8:1000:1::/64), a host picks a source address in
			this subnet to send a packet via the default route.
			Prefix Precedence Label
			::1/128 50 0
			::/0 40 1
			2001:db8:1000:1::/64 45 1
			2001:db8:8000:1::/64 45 14
			::ffff:0:0/96 35 4
			2002::/16 30 2
			2001::/32 5 5
			fc00::/7 3 13
			::/96 1 3
			fec0::/10 1 11
			3ffe::/16 1 12
			B.2. Half-Closed Network Problem
			In the case described in section 2.1.3 of [RFC5220], the following
			policy table should be distributed. By splitting the closed network
			prefix (2001:db8:8000::/36) from all IPv6 addresses (::/0) and giving
			different labels, the closed network prefix will only be used when
			packets are destined for the closed network.
			Prefix Precedence Label
			::1/128 50 0
			::/0 40 1
			2001:db8:8000::/36 45 14
			::ffff:0:0/96 35 4
			2002::/16 30 2
			2001::/32 5 5
			fc00::/7 3 13
			::/96 1 3
			fec0::/10 1 11
			3ffe::/16 1 12
			B.3. IPv4 or IPv6 Prioritization
			In the case described in section 2.2.1 of [RFC5220], the following
			policy table should be distributed to prioritize IPv6. This case is
			also described in [RFC6724]
			Prefix Precedence Label
			::1/128 50 0
			::/0 40 1
			::ffff:0:0/96 100 4
			2002::/16 30 2
			2001::/32 5 5
			fc00::/7 3 13
			::/96 1 3
			fec0::/10 1 11
			3ffe::/16 1 12
			B.4. ULA or Global Prioritization
			In the case described in section 2.2.3 of [RFC5220], the following
			policy table should be distributed, or Automatic Row Addition flag
			should be set to 1. By splitting the ULA in this site
			(fc12:3456:789a::/48) from all IPv6 addresses (::/0) and giving it
			higher precendence, the ULA will be used to connect to servers in the
			same site.
			Prefix Precedence Label
			::1/128 50 0
			fc12:3456:789a::/48 45 14
			::/0 40 1
			::ffff:0:0/96 35 4
			2002::/16 30 2
			2001::/32 5 5
			fc00::/7 3 13
			::/96 1 3
			fec0::/10 1 11
			3ffe::/16 1 12
	Authors' Addresses		Authors' Addresses
	Arifumi Matsumoto		Arifumi Matsumoto
	NTT NT Lab		NTT NT Lab
	3-9-11 Midori-Cho		3-9-11 Midori-Cho
	Musashino-shi, Tokyo 180-8585		Musashino-shi, Tokyo 180-8585
	Japan		Japan
	Phone: +81 422 59 3334		Phone: +81 422 59 3334
	Email: arifumi@nttv6.net		Email: arifumi@nttv6.net
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