draft-ietf-6man-addr-select-opt-00.txt		draft-ietf-6man-addr-select-opt-01.txt
	6man Working Group A. Matsumoto		6man Working Group A. Matsumoto
	Internet-Draft T. Fujisaki		Internet-Draft T. Fujisaki
	Intended status: Standards Track J. Kato		Intended status: Standards Track J. Kato
	Expires: June 9, 2011 NTT		Expires: December 30, 2011 NTT
	December 6, 2010		T. Chown
			University of Southampton
			June 28, 2011
	Distributing Address Selection Policy using DHCPv6		Distributing Address Selection Policy using DHCPv6
	draft-ietf-6man-addr-select-opt-00.txt		draft-ietf-6man-addr-select-opt-01.txt
	Abstract		Abstract
	This document describes a new DHCPv6 option for distributing address		RFC 3484 defines default address selection mechanisms for IPv6 that
	selection policy information defined in RFC3484 to a client. With		allow nodes to select appropriate address when faced with multiple
	this option, site administrators can distribute address selection		source and/or destination addresses to choose between. The RFC
	policy to control the node's address selection behavior.		allowed for the future definition of methods to administratively
			configure the address selection policy information. This document
			defines a new DHCPv6 option for such configuration, allowing a site
			administrator to distribute address selection policy, and thus
			control the address selection behavior of nodes in their site. While
			RFC 3484 is in the process of being updated, with a revised default
			policy table, that table may not suit every scenario, and thus the
			DHCPv6 option defined in this text may be used to override that
			policy where desired.
	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 June 9, 2011.		This Internet-Draft will expire on December 30, 2011.
	Copyright Notice		Copyright Notice
	Copyright (c) 2010 IETF Trust and the persons identified as the		Copyright (c) 2011 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	described in the Simplified BSD License.		described in the Simplified BSD License.
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			it for publication as an RFC or to translate it into languages other
			than English.
	1. Introduction		1. Introduction
	RFC3484 [RFC3484] describes algorithms for selecting a default		RFC 3484 [RFC3484] describes default algorithms for selecting an
	address when a node has multiple destination and/or source addresses		address when a node has multiple destination and/or source addresses
	by using an address selection policy. However, there are some		to choose between by using an address selection policy. In Section 2
	problems with the default address selection policy in RFC3484		of RFC 3484, it is suggested that the default policy table may be
	[RFC5220], and mechanisms to control a proper source address		administratively configured to suit the specific needs of a site.
	selection will be necessary. Requirements for those mechanisms are		This text defines a new DHCPv6 option for such configuration.
	described in [RFC5221]. Solutions are discussed in
			Some problems have been identified with the default address selection
			policy detailed in RFC 3484 [RFC5220], and as a result the RFC is in
			the process of being updated, as per [I-D.ietf-6man-rfc3484-revise].
			While this update provides a better default address selection policy,
			it is unlikely that such a default will suit all scenarios, and thus
			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-sol] and		[I-D.ietf-6man-addr-select-sol] and
	[I-D.ietf-6man-addr-select-considerations]. This document describes		[I-D.ietf-6man-addr-select-considerations]. Those documents have
	an option for distributing address selection policy information using		helped shape the improvements in [I-D.ietf-6man-rfc3484-revise] as
	DHCPv6, which is referred as `most proactive approach' in the		well as the DHCPv6 option defined here.
	solution document, and `preferable protocol to deliver RFC3848
	policies' in consideration document.
	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 [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 DHCP		This document uses the terminology defined in [RFC2460] and the
	specification defined in [RFC3315]		DHCPv6 specification defined in [RFC3315]
	2. Address Selection Policy Option		2. Address Selection Policy Option
	The Address Selection Policy Option provides policy information for		The Address Selection Policy Option provides the policy table for
	address selection rules. Specifically, it transmits a set of IPv6		address selection rules as described in RFC 3484 and updated in
	source and destination address prefixes and some parameters that are		[I-D.ietf-6man-rfc3484-revise].
	used to control address selection as described in RFC 3484.
	Each end node is expected to configure its policy table, as described		Each end node is expected to configure its policy table, as described
	in RFC 3484, using the Address Selection Policy option information as		in RFC 3484, using the Address Selection Policy option information as
	an reference.		described in the section below on processing the option.
	The format of the Address Selection Policy option is given below:		The format of the Address Selection Policy 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_DASP | option-len |		| OPTION_DASP | option-len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| label | precedence |z|n| reserved | prefix-len |		| label | precedence |z| reserved | prefix-len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| zone-index (if present (z = 1)) |		| zone-index (if present (z = 1)) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |		| |
	| Prefix (Variable Length) |		| Prefix (Variable Length) |
	| |		| |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| label | precedence |z|n| reserved | prefix-len |		| label | precedence |z| reserved | prefix-len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| zone-index (if present (z = 1)) |		| zone-index (if present (z = 1)) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |		| |
	| Prefix (Variable Length) |		| Prefix (Variable Length) |
	| |		| |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	. .		. .
	. .		. .
	. .		. .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| label | precedence |z|n| reserved | prefix-len |		| label | precedence |z| reserved | prefix-len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| zone-index (if present (z = 1)) |		| zone-index (if present (z = 1)) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |		| |
	| Prefix (Variable Length) |		| Prefix (Variable Length) |
	| |		| |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	[Fig. 1]		[Fig. 1]
	skipping to change at page 4, line 24		skipping to change at page 5, line 24
	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.
	z bit: 'zone-index' bit. If z bit is set to 1, 32 bit zone-index		z bit: 'zone-index' bit. If z bit is set to 1, 32 bit zone-index
	value is included right after the "prefix-len" field, and		value is included right after the "prefix-len" field, and
	"Prefix" value continues after the "zone-index" field. If z bit		"Prefix" value continues after the "zone-index" field. If z bit
	is 0, "Prefix" value continues right after the "prefix-len"		is 0, "Prefix" value continues right after the "prefix-len"
	value.		value.
	n bit: 'no privacy iid' bit. If n bit is set to 1, RFC 4941
	[RFC4941] privacy extensions MUST NOT be used for this prefix.
	If n bit is 0, interface ID may use RFC4941.
	reserved: 6-bit reserved field. Initialized to zero by sender, and		reserved: 6-bit reserved field. Initialized to zero by sender, and
	ignored by receiver.		ignored by receiver.
	zone-index: If z-bit is set to 1, this field is inserted between		zone-index: If the z-bit is set to 1, this field is inserted between
	"prefix-len" field and "Prefix" field. Zone-index field is an		"prefix-len" field and "Prefix" field. The zone-index field is
	32-bit unsigned integer and used to specify zones for scoped		an 32-bit unsigned integer and used to specify zones for scoped
	addresses. This bit length is defined in RFC3493 [RFC3493] as		addresses. This bit length is defined in RFC3493 [RFC3493] as
	'scope ID'.		'scope ID'.
	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		the prefix that are valid. The value ranges from 0 to 128. The
	Prefix field is 0, 4, 8, 12, or 16 octets, depending on the		Prefix field is 0, 4, 8, 12, or 16 octets, depending on the
	length.		length.
	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. IPv4-mapped address [mapped] must be		prefix of an IP address. An IPv4-mapped address [RFC4291] must
	used to represent an IPv4 address as a prefix value.		be used to represent an IPv4 address as a prefix value.
	3. Appearance of this Option		3. Appearance of this Option
	The Address Selection Policy option MUST NOT appear in any messages		The Address Selection Policy option MUST NOT appear in any messages
	other than the following ones : Solicit, Advertise, Request, Renew,		other than the following ones: Solicit, Advertise, Request, Renew,
	Rebind, Information-Request, and Reply.		Rebind, Information-Request, and Reply.
	4. Implementation Considerations		4. Processing the Address Selection Policy Option
			This section describes how to process received Address Selection
			Policy Options at the DHCPv6 client.
			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
			administrator how to make use of or even ignore the received policy
			information.
			However, we need to define the default behavior of the receiving node
			in order to reduce operational complexity.
			4.1. Handling the local policy table
			RFC3484 defines the default policy for the policy table. Also, a
			user is usually able to configure the policy table to satisfy his
			requirement.
			The client node SHOULD provide the following choices:
			a) It receives distributed policy table, and replaces the existing
			policy tables with that.
			b) It preserves the default policy table, or manually configured
			policy.
			4.2. Processing multiple received policy tables
			The policy table is node-global information by its nature. So, the
			node cannot use multiple received policy tables at the same time.
			It should be noted that adopting a received policy table as the node-
			global information can cause security problems, such as DOS attack,
			and leak of privacy information.
			Moreover, it also should be noted that, when a node is single-homed
			and has only one upstream line, adopting a received policy table does
			not degrade the security level.
			Under the above assumptions, we specify how to handle multiple
			received policy tables below.
			A node MAY use OPTION_DASP in any of the following two cases:
			1: The address selection option is delivered across a secure, trusted
			channel.
			2: The address selection option is not secured, but the node is
			single-homed.
			In other cases the node MUST NOT use OPTION_DASP unless the node is
			specifically configured to do so.
			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 this DHCP message. DHCPv6 clients		the same label value within the DHCP message. DHCPv6 clients need
	need to convert this label to a representation specified by each		to convert this label to a representation specified by each
	implementation (e.g., string).		implementation (e.g., string).
	o Currently, the value label, precedence 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 in one DHCPv6		o The maximum number of address selection rules that may be conveyed
	message depend on the prefix length of each rules and maximum		in one DHCPv6 message depends on the prefix length of each rule
	DHCPv6 message size defined in RFC3315. It is possible to carry		and the maximum DHCPv6 message size defined in RFC 3315. It is
	over 3,000 rules (e.g. default policy table defined in RFC3484		possible to carry over 3,000 rules in one DHCPv6 message (maximum
	contains 5 rules) in one DHCPv6 message (maximum UDP message		UDP message size), but the usual number would be much smaller,
	size).		e.g. the default policy table defined in RFC 3484 contains 5
			rules.
	o Since the number of selection rules would be large, policy
	distributer should be care about the DHCPv6 message size.
	o If there are multiple DHCPv6 servers (e.g. a node with multiple
	interface), a node may have multiple address selection policies.
	Since RFC3484 policy table is one and global for a node, the node
	have to decide how to process multiple policies. This policy
	conflict is discussed in
	[I-D.ietf-6man-addr-select-considerations].
	5. Discussion
	o The 'zone index' value is used to specify a particular zone for
	scoped addresses. This can be used effectively to control address
	selection in the site scope (e.g., to tell a node to use a
	specified source address corresponding to a site-scoped multicast
	address). However, in some cases such as a link-local scope
	address, the value specifying one zone is only meaningful locally
	within that node. There might be some cases where the
	administrator knows which clients are on the network and wants
	specific interfaces to be used though. However, in general case,
	it is hard to use this value.
	o Since we got a comment that some implementations use 32-bit
	integers for zone index value, we extended the bit length of the
	'zone index' field. However, as described above, there might be
	few cases to specify 'zone index' in policy distribution, we
	defined this field as optional, controlled by a flag.
	o There may be some demands to control the use of special address		o Since the number of selection rules could be large, an
	types such as the temporary addresses described in RFC4941		administrator configuring the policy to be distributed should
	[RFC4941], address assigned by DHCPv6 and so on. (e.g., informing		consider the resulting DHCPv6 message size.
	not to use a temporary address when it communicate within the an
	organization's network). It is possible to indicate the type of
	addresses using reserved field value.
	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.		because of ingress filtering. Alternatively, an IPv6 transition
			mechanism might be preferred over native IPv6, even if it is
			available.
	To guard against such attacks, both DCHP clients and servers SHOULD		To guard against such attacks, both DCHP clients and servers SHOULD
	use DHCP authentication, as described in section 21 of RFC 3315,		use DHCP authentication, as described in section 21 of RFC 3315,
	"Authentication of DHCP messages."		"Authentication of DHCP messages."
	7. IANA Considerations		7. IANA Considerations
	IANA is requested to assign option codes to OPTION_DASP from the		IANA is requested to assign option codes to OPTION_DASP from the
	option-code space as defined in section "DHCPv6 Options" of RFC 3315.		option-code space as defined in section "DHCPv6 Options" of RFC 3315.
	skipping to change at page 7, line 10		skipping to change at page 8, line 30
	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.
	8.2. Informative References		8.2. Informative References
	[I-D.ietf-6man-addr-select-considerations]		[I-D.ietf-6man-addr-select-considerations]
	Chown, T., "Considerations for IPv6 Address Selection		Chown, T., "Considerations for IPv6 Address Selection
	Policy Changes",		Policy Changes",
	draft-ietf-6man-addr-select-considerations-02 (work in		draft-ietf-6man-addr-select-considerations-03 (work in
	progress), July 2010.		progress), March 2011.
	[I-D.ietf-6man-addr-select-sol]		[I-D.ietf-6man-addr-select-sol]
	Matsumoto, A., Fujisaki, T., and R. Hiromi, "Solution		Matsumoto, A., Fujisaki, T., and R. Hiromi, "Solution
	approaches for address-selection problems",		approaches for address-selection problems",
	draft-ietf-6man-addr-select-sol-03 (work in progress),		draft-ietf-6man-addr-select-sol-03 (work in progress),
	March 2010.		March 2010.
			[I-D.ietf-6man-rfc3484-revise]
			Matsumoto, A., Kato, J., and T. Fujisaki, "Update to RFC
			3484 Default Address Selection for IPv6",
			draft-ietf-6man-rfc3484-revise-03 (work in progress),
			June 2011.
	[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6		[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
	(IPv6) Specification", RFC 2460, December 1998.		(IPv6) Specification", RFC 2460, December 1998.
	[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.		[RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
	Stevens, "Basic Socket Interface Extensions for IPv6",		Stevens, "Basic Socket Interface Extensions for IPv6",
	RFC 3493, February 2003.		RFC 3493, February 2003.
			[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
			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-
	Prefix Environments: Operational Issues of RFC 3484		Prefix Environments: Operational Issues of RFC 3484
	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. Past Discussion
			o The 'zone index' value is used to specify a particular zone for
			scoped addresses. This can be used effectively to control address
			selection in the site scope (e.g., to tell a node to use a
			specified source address corresponding to a site-scoped multicast
			address). However, in some cases such as a link-local scope
			address, the value specifying one zone is only meaningful locally
			within that node. There might be some cases where the
			administrator knows which clients are on the network and wants
			specific interfaces to be used though. However, in general case,
			it is hard to use this value.
			o Since we got a comment that some implementations use 32-bit
			integers for zone index value, we extended the bit length of the
			'zone index' field. However, as described above, there might be
			few cases to specify 'zone index' in policy distribution, we
			defined this field as optional, controlled by a flag.
			o There may be some demands to control the use of special address
			types such as the temporary addresses described in RFC4941
			[RFC4941], address assigned by DHCPv6 and so on. (e.g., informing
			not to use a temporary address when it communicate within the an
			organization's network). It is possible to indicate the type of
			addresses using reserved field value.
	Authors' Addresses		Authors' Addresses
	Arifumi Matsumoto		Arifumi Matsumoto
	NTT SI Lab		NTT SI 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
	skipping to change at line 327		skipping to change at page 10, line 33
	Email: fujisaki@nttv6.net		Email: fujisaki@nttv6.net
	Jun-ya Kato		Jun-ya Kato
	NTT SI Lab		NTT SI 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 2939		Phone: +81 422 59 2939
	Email: kato@syce.net		Email: kato@syce.net
			Tim Chown
			University of Southampton
			Southampton, Hampshire SO17 1BJ
			United Kingdom
			Email: tjc@ecs.soton.ac.uk
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