draft-ietf-6man-addr-select-opt-06.txt		draft-ietf-6man-addr-select-opt-07.txt
	6man Working Group A. Matsumoto		6man Working Group A. Matsumoto
	Internet-Draft T. Fujisaki		Internet-Draft T. Fujisaki
	Intended status: Standards Track NTT		Intended status: Standards Track NTT
	Expires: March 25, 2013 T. Chown		Expires: May 18, 2013 T. Chown
	University of Southampton		University of Southampton
	September 21, 2012		November 14, 2012
	Distributing Address Selection Policy using DHCPv6		Distributing Address Selection Policy using DHCPv6
	draft-ietf-6man-addr-select-opt-06.txt		draft-ietf-6man-addr-select-opt-07.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 appropriate address when faced with multiple		allow nodes to select 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. The RFC 6724
	allowed for the future definition of methods to administratively		allowed 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
	skipping to change at page 1, line 40		skipping to change at page 1, line 40
	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 March 25, 2013.		This Internet-Draft will expire on May 18, 2013.
	Copyright Notice		Copyright Notice
	Copyright (c) 2012 IETF Trust and the persons identified as the		Copyright (c) 2012 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 3, line 15		skipping to change at page 3, line 15
	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.
	A 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 a Policy Table option		options. Multiple Policy Table options in an Address Selection
	constitute a single policy table.		option constitute a single policy table.
	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 48		skipping to change at page 3, line 48
	Reserved: Reserved field. Server MUST set this value to zero and		Reserved: Reserved field. Server MUST set this value to zero and
	client MUST ignore its content.		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 the
	section 2.1 in RFC 6724 [RFC6724]. If this flag is set to 1, it		section 2.1 in RFC 6724 [RFC6724]. If this flag is set to 1, it
	does not change client host behavior, that is, a client MAY		does not change client host behavior, that is, a client MAY
	automatically add additional site-specific rows to the policy		automatically add additional site-specific rows to the policy
	table. If set to 0, the Automatic Row Addition flag is		table. If set to 0, the Automatic Row Addition flag is
	disabled, and a client MAY NOT automatically add rows to the		disabled, and a client SHOULD NOT automatically add rows to the
	policy table.		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 at client hosts, which is described in the
	section 5 in RFC 6724 [RFC6724]. If this flag is set to 1, it		section 5 in RFC 6724 [RFC6724]. If this flag is set to 1, it
	does not change client host behavior, that is, a client SHOULD		does not change client host behavior, that is, a client will
	prefer temporary addresses. If set to 0, the Privacy Preference		prefer temporary addresses. If set to 0, the Privacy Preference
	flag is disabled, and a client SHOULD prefer public addresses.		flag 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.		options described 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_TABLE | option-len |		| OPTION_ADDRSEL_TABLE | option-len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| label | precedence | prefix-len | |		| label | precedence | prefix-len | |
	skipping to change at page 4, line 46		skipping to change at page 4, line 46
	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.		sorting destination addresses.
	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. The		be used to represent an IPv4 address as a prefix value. The
	prefix should be zero padded up to the next octet boundary. So		prefix should be left aligned, big-endian, and zero padded on
	the length of this field should be between 0 and 16 bytes.		the right up to the next octet boundary. So the length of this
			field should be between 0 and 16 bytes.
	3. Appearance of the Address Selection options		3. Appearance of the Address Selection options
	The Address Selection options MUST NOT appear in any messages other		The Address Selection options MUST NOT appear in any DHCPv6 messages
	than the following ones: Solicit, Advertise, Request, Renew, Rebind,		other than the following ones: Solicit, Advertise, Request, Renew,
	Reconfigure, Information-Request, and Reply.		Rebind, Reconfigure, Information-Request, and Reply.
	4. Processing the Policy Table option		4. Processing the Policy Table option
	This section describes how to process received Policy Table option at		This section describes how to process received Policy Table option at
	the DHCPv6 client.		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. So, basically, it should be up to the node's		behave in the network. So, basically, it should be up to the node's
	administrator how to deal with the received policy information in the		administrator how to deal with the received policy information in the
	way described below.		way described below.
	4.1. Handling of the local policy table		4.1. Handling of the local policy table
	RFC 6724 defines the default policy table. Also, a user is usually		RFC 6724 defines the default policy table. Also, users are usually
	able to configure the policy table to satisfy his requirement.		able to configure 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:		user:
	a) It receives distributed policy table, and replaces the existing		a) replace the existing active policy table with the DHCPv6
	policy tables with that.		distributed policy table.
	b) It preserves the default policy table, or manually configured		b) preserve the existing active policy table, whether this be the
	policy.		default policy table, or user configured policy.
	4.2. Handling of the stale policy table		4.2. Handling of the stale policy table
	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 removed and the default		received form the DHCP server should be deprecated.
	policy should be restored.
	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		such as, when the interface goes down, the DHCP server does not
	respond for a certain amount of time, and the Information Refresh		respond for a certain amount of time, and the Information Refresh
	Time is expired.		Time is expired.
	4.3. Multi-interface situation		4.3. Multi-interface situation
	The policy table, and other parameters specified in this document are		The policy table, and other parameters specified in this document are
	node-global information by its nature. One of the reason is that the		node-global information by their nature. One reason being that the
	outbound interface is usually chosen after destination address		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
	policy 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		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.		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 semantics of the
	policy.		policy.
	It also should be noted that absence of the distributed policy from a		It also should be noted that absence of the distributed policy from a
	certain network interface should not be treated as absence of policy		certain network interface should not be treated as absence of policy
	itself, because it may mean preference for the default address		itself, because it may mean preference for the default address
	skipping to change at page 6, line 43		skipping to change at page 6, line 43
	address selection policies per interface. They can be used		address selection policies per interface. They can be used
	effectively on such implementations that adopt per-application		effectively on such implementations that adopt per-application
	interface selection.		interface selection.
	5. Implementation Considerations		5. 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 need		the same label value within the DHCP message. DHCPv6 clients
	to convert this label to a representation specified by each		SHOULD convert this label to a representation appropriate for the
	implementation (e.g., string).		local implementation (e.g., string).
	o Currently, the label and precedence values are defined as 8-bit		o Currently, the label and precedence values are defined as 8-bit
	unsigned integers. In almost all cases, this value will be		unsigned integers. In almost all cases, this value will be
	enough.		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 RFC 3315. 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.
	So, the number of the options and the total size of the options		Network adiministrators SHOULD consider local limitations to the
	should be taken care of.		maximum DHCPv6 message size that can be reliably transported via
			their specific local infrastructure to end nodes; and therefore
			they SHOULD consider the number of options, the total size of the
			options, and the resulting DHCPv6 message size, when defining
			their Policy Table.
	o Since the number of selection rules could be large, an		o Since the number of selection rules could be large, an
	administrator configuring the policy to be distributed should		administrator configuring the policy to be distributed should
	consider the resulting DHCPv6 message size.		consider the resulting DHCPv6 message size.
	6. Security Considerations		6. 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. Alternatively, an IPv6 transition		because of ingress filtering, incur additional network charges, or be
	mechanism might be preferred over native IPv6, even if it is		misdirected to an attacker's machine. Alternatively, an IPv6
	available. To guard against such attacks, a legitimate DHCPv6 server		transition mechanism might be preferred over native IPv6, even if it
	should be communicated through a secure, trusted channel, such as a		is available. To guard against such attacks, a legitimate DHCPv6
	channel protected by IPsec, SEND and DHCP authentication, as		server should communicate through a secure, trusted channel, such as
			a channel protected by IPsec, SEND and DHCP authentication, as
	described in section 21 of RFC 3315,		described in section 21 of RFC 3315,
	Another threat is about privacy concern. As in the security		Another threat is about privacy concern. As in the security
	consideration section of RFC 6724, at least a part of, the address		consideration section of RFC 6724, at least a part of, the address
	selection policy stored in a host can be leaked by a packet from a		selection policy stored in a host can be leaked by a packet from a
	remote host. This issue will not be degraded regardless of the		remote host. This issue will not be modified by the introduction of
	introduction of this option, or regardless of whether the host is		this option, regardless of whether the host is multihomed or not.
	multihomed or not.
	7. IANA Considerations		7. IANA Considerations
	IANA is requested to assign option codes to OPTION_ADDRSEL ,		IANA is requested to assign option codes to OPTION_ADDRSEL and
	OPTION_ADDRSEL_TABLE, and OPTION_ADDRSEL_ZONE from the option-code		OPTION_ADDRSEL_TABLE from the option-code space as defined in section
	space as defined in section "DHCPv6 Options" of RFC 3315.		"DHCPv6 Options" of RFC 3315.
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[I-D.ietf-6man-stable-privacy-addresses]
	Gont, F., "A method for Generating Stable Privacy-Enhanced
	Addresses with IPv6 Stateless Address Autoconfiguration
	(SLAAC)", draft-ietf-6man-stable-privacy-addresses-00
	(work in progress), May 2012.
	[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		[RFC3484] Draves, R., "Default Address Selection for Internet
	Protocol version 6 (IPv6)", RFC 3484, February 2003.		Protocol version 6 (IPv6)", RFC 3484, February 2003.
	skipping to change at page 9, line 15		skipping to change at page 9, line 13
	Default Rules", RFC 5220, July 2008.		Default Rules", RFC 5220, July 2008.
	[RFC5221] Matsumoto, A., Fujisaki, T., Hiromi, R., and K. Kanayama,		[RFC5221] Matsumoto, A., Fujisaki, T., Hiromi, R., and K. Kanayama,
	"Requirements for Address Selection Mechanisms", RFC 5221,		"Requirements for Address Selection Mechanisms", RFC 5221,
	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, and the members of 6man's address selection design team for		Anipko, Ray Hunter, Rui Paulo, Brian E Carpenter, Tom Petch, and the
	their invaluable contributions to this document.		members of 6man's address selection design team for their invaluable
			contributions to this document.
	Appendix B. Past Discussion		Appendix B. Past Discussion
	o The 'zone index' value is used to specify a particular zone for		o The 'zone index' value is used to specify a particular zone for
	scoped addresses. This can be used effectively to control address		scoped addresses. This can be used effectively to control address
	selection in the site scope (e.g., to tell a node to use a		selection in the site scope (e.g., to tell a node to use a
	specified source address corresponding to a site-scoped multicast		specified source address corresponding to a site-scoped multicast
	address). However, in some cases such as a link-local scope		address). However, in some cases such as a link-local scope
	address, the value specifying one zone is only meaningful locally		address, the value specifying one zone is only meaningful locally
	within that node. There might be some cases where the		within that node. There might be some cases where the
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