draft-ietf-v6ops-addr-select-ps-09.txt		rfc5220.txt
	IPv6 Operations Working Group A. Matsumoto		Network Working Group A. Matsumoto
	Internet-Draft T. Fujisaki		Request for Comments: 5220 T. Fujisaki
	Intended status: Informational NTT		Category: Informational NTT
	Expires: December 19, 2008 R. Hiromi		R. Hiromi
	Intec Netcore		Intec Netcore
	K. Kanayama		K. Kanayama
	INTEC Systems		INTEC Systems
	June 17, 2008		Problem Statement for Default Address Selection in Multi-Prefix
			Environments: Operational Issues of RFC 3484 Default Rules
	Problem Statement of Default Address Selection in Multi-prefix
	Environment: Operational Issues of RFC3484 Default Rules
	draft-ietf-v6ops-addr-select-ps-09.txt
	Status of this Memo
	By submitting this Internet-Draft, each author represents that any
	applicable patent or other IPR claims of which he or she is aware
	have been or will be disclosed, and any of which he or she becomes
	aware will be disclosed, in accordance with Section 6 of BCP 79.
	Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that
	other groups may also distribute working documents as Internet-
	Drafts.
	Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."
	The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt.
	The list of Internet-Draft Shadow Directories can be accessed at		Status of This Memo
	http://www.ietf.org/shadow.html.
	This Internet-Draft will expire on December 19, 2008.		This memo provides information for the Internet community. It does
			not specify an Internet standard of any kind. Distribution of this
			memo is unlimited.
	Abstract		Abstract
	A single physical link can have multiple prefixes assigned to it. In		A single physical link can have multiple prefixes assigned to it. In
	that environment, end hosts might have multiple IP addresses and be		that environment, end hosts might have multiple IP addresses and be
	required to use them selectively. RFC 3484 defines default source		required to use them selectively. RFC 3484 defines default source
	and destination address selection rules and is implemented in a		and destination address selection rules and is implemented in a
	variety of OS's. But, it has been too difficult to use operationally		variety of OSs. But, it has been too difficult to use operationally
	for several reasons. In some environment where multiple prefixes are		for several reasons. In some environments where multiple prefixes
	assigned on a single physical link, the host using the default		are assigned on a single physical link, the host using the default
	address selection rules will experience some trouble in		address selection rules will experience some trouble in
	communication. This document describes the possible problems that		communication. This document describes the possible problems that
	end hosts could encounter in an environment with multiple prefixes.		end hosts could encounter in an environment with multiple prefixes.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction ....................................................2
	1.1. Scope of this document . . . . . . . . . . . . . . . . . . 3		1.1. Scope of This Document .....................................3
	2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4		2. Problem Statement ...............................................4
	2.1. Source Address Selection . . . . . . . . . . . . . . . . . 4		2.1. Source Address Selection ...................................4
	2.1.1. Multiple Routers on Single Interface . . . . . . . . . 4		2.1.1. Multiple Routers on a Single Interface ..............4
	2.1.2. Ingress Filtering Problem . . . . . . . . . . . . . . 5		2.1.2. Ingress Filtering Problem ...........................5
	2.1.3. Half-Closed Network Problem . . . . . . . . . . . . . 6		2.1.3. Half-Closed Network Problem .........................6
	2.1.4. Combined Use of Global and ULA . . . . . . . . . . . . 7		2.1.4. Combined Use of Global and ULA ......................7
	2.1.5. Site Renumbering . . . . . . . . . . . . . . . . . . . 8		2.1.5. Site Renumbering ....................................8
	2.1.6. Multicast Source Address Selection . . . . . . . . . . 9		2.1.6. Multicast Source Address Selection ..................9
	2.1.7. Temporary Address Selection . . . . . . . . . . . . . 9		2.1.7. Temporary Address Selection .........................9
	2.2. Destination Address Selection . . . . . . . . . . . . . . 10		2.2. Destination Address Selection .............................10
	2.2.1. IPv4 or IPv6 prioritization . . . . . . . . . . . . . 10		2.2.1. IPv4 or IPv6 Prioritization ........................10
	2.2.2. ULA and IPv4 dual-stack environment . . . . . . . . . 11		2.2.2. ULA and IPv4 Dual-Stack Environment ................11
	2.2.3. ULA or Global Prioritization . . . . . . . . . . . . . 12		2.2.3. ULA or Global Prioritization .......................12
	3. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 13		3. Conclusion .....................................................13
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 14		4. Security Considerations ........................................14
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14		5. Normative References ...........................................14
	6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
	6.1. Normative References . . . . . . . . . . . . . . . . . . . 14
	6.2. Informative References . . . . . . . . . . . . . . . . . . 15
	Appendix A. Appendix. Revision History . . . . . . . . . . . . . 15
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
	Intellectual Property and Copyright Statements . . . . . . . . . . 17
	1. Introduction		1. Introduction
	In IPv6, a single physical link can have multiple prefixes assigned		In IPv6, a single physical link can have multiple prefixes assigned
	to it. In such cases, an end-host may have multiple IP addresses		to it. In such cases, an end host may have multiple IP addresses
	assigned to an interface on that link. In the IPv4-IPv6 dual stack		assigned to an interface on that link. In the IPv4-IPv6 dual-stack
	environment or in a site connected to both a ULA [RFC4193] and		environment or in a site connected to both a Unique Local Address
	Globally routable networks, an end-host typically has multiple IP		(ULA) [RFC4193] and globally routable networks, an end host typically
	addresses. These are examples of the networks that we focus on in		has multiple IP addresses. These are examples of the networks that
	this document. In such an environment, an end-host may encounter		we focus on in this document. In such an environment, an end host
	some communication troubles.		may encounter some communication troubles.
	Inappropriate source address selection at the end-host causes		Inappropriate source address selection at the end host causes
	unexpected asymmetric routing, filtering by a router or discarding of		unexpected asymmetric routing, filtering by a router, or discarding
	packets because there is no route to the host.		of packets because there is no route to the host.
	Considering a multi-prefix environment, destination address selection		Considering a multi-prefix environment, destination address selection
	is also important for correct or better communication establishment.		is also important for correct or better communication establishment.
	RFC 3484 [RFC3484] defines default source and destination address		RFC 3484 [RFC3484] defines default source and destination address
	selection algorithms and is implemented in a variety of OS's. But,		selection algorithms and is implemented in a variety of OSs. But, it
	it has been too difficult to use operationally for several reasons,		has been too difficult to use operationally for several reasons, such
	such as lack of autoconfiguration method. There are some problematic		as lack of an autoconfiguration method. There are some problematic
	cases where the hosts using the default address selection rules		cases where the hosts using the default address selection rules
	encounter communication troubles.		encounter communication troubles.
	This document describes such possibilities of incorrect address		This document describes the possibilities of incorrect address
	selection which leads to dropping packets and communication failure.		selection that lead to dropping packets and communication failure.
	1.1. Scope of this document		1.1. Scope of This Document
	As other mechanisms already exist, the multi-homing techniques for		As other mechanisms already exist, the multi-homing techniques for
	achieving redundancy are basically out of our scope.		achieving redundancy are basically out of our scope.
	We focus on an end-site network environment and unmanaged hosts in		We focus on an end-site network environment and unmanaged hosts in
	such an environment. This is because address selection behavior at		such an environment. This is because address selection behavior at
	this kind of hosts is difficult to manipulate owing to the users'		these kinds of hosts is difficult to manipulate, owing to the users'
	lack of knowledge, hosts' location, or massiveness of the hosts.		lack of knowledge, hosts' location, or massiveness of the hosts.
	The scope of this document is to sort out problematic cases related		The scope of this document is to sort out problematic cases related
	to address selection. It includes problems that can be solved in the		to address selection. It includes problems that can be solved in the
	framework of RFC 3484 and problems that cannot. For the latter, RFC		framework of RFC 3484 and problems that cannot. For the latter, RFC
	3484 might be modified to meet their needs, or another address		3484 might be modified to meet their needs, or another address
	selection solution might be necessary. For the former, an additional		selection solution might be necessary. For the former, an additional
	mechanism that mitigates the operational difficulty might be		mechanism that mitigates the operational difficulty might be
	necessary.		necessary.
	This document also includes simple solution analysis for each		This document also includes simple solution analysis for each
	problematic case. This analysis basically just focuses on whether		problematic case. This analysis basically just focuses on whether or
	the case can be solved in the framework of RFC 3484 or not. If not,		not the case can be solved in the framework of RFC 3484. If not,
	some possible solutions are described. Even if a case can be solved		some possible solutions are described. Even if a case can be solved
	in the framework of RFC 3484, as mentioned above, it does not		in the framework of RFC 3484, as mentioned above, it does not
	necessarily mean that there is no operational difficulty. For		necessarily mean that there is no operational difficulty. For
	example, in the environment stated above, it is not a feasible		example, in the environment stated above, it is not a feasible
	solution to configure each host's policy table by hand. So, for such		solution to configure each host's policy table by hand. So, for such
	an solution, configuration pain is yet another common problem.		a solution, the difficulty of configuration is yet another common
			problem.
	2. Problem Statement		2. Problem Statement
	2.1. Source Address Selection		2.1. Source Address Selection
	2.1.1. Multiple Routers on Single Interface		2.1.1. Multiple Routers on a Single Interface
	==================		==================
	| Internet |		| Internet |
	==================		==================
	| |		| |
	2001:db8:1000::/36 | | 2001:db8:8000::/36		2001:db8:1000::/36 | | 2001:db8:8000::/36
	+----+-+ +-+----+		+----+-+ +-+----+
	| ISP1 | | ISP2 |		| ISP1 | | ISP2 |
	+----+-+ +-+----+		+----+-+ +-+----+
	| |		| |
	skipping to change at page 4, line 40		skipping to change at page 4, line 33
	+-------+-+ +-+-------+		+-------+-+ +-+-------+
	| |		| |
	2001:db8:1000:1::/64 | | 2001:db8:8000:1::/64		2001:db8:1000:1::/64 | | 2001:db8:8000:1::/64
	| |		| |
	-----+-+-----+------		-----+-+-----+------
	|		|
	+-+----+ 2001:db8:1000:1::100		+-+----+ 2001:db8:1000:1::100
	| Host | 2001:db8:8000:1::100		| Host | 2001:db8:8000:1::100
	+------+		+------+
	[Fig. 1]		Figure 1
	Generally speaking, there is no interaction between next-hop		Generally speaking, there is no interaction between next-hop
	determination and address selection. In this example, when a host		determination and address selection. In this example, when a host
	starts a new connection and sends a packet via Router1, the host does		starts a new connection and sends a packet via Router1, the host does
	not necessarily choose address 2001:db8:1000:1::100 given by Router1		not necessarily choose address 2001:db8:1000:1::100 given by Router1
	as the source address. This causes the same problem as described in		as the source address. This causes the same problem as described in
	the next section 'Ingress Filtering Problem'.		the next section, "Ingress Filtering Problem".
	Solution analysis:		Solution analysis:
			As this case depends on next-hop selection, controlling the
	As this case depends on next hop selection, controling the address		address selection behavior at the Host alone doesn't solve the
	selection behavior at Host alone doesn't solve the entire problem.		entire problem. One possible solution for this case is adopting
	One possible solution for this case is adopting source address		source-address-based routing at Router1 and Router2. Another
	based routing at Router1 and Router2. Another solution may be		solution may be using static routing at Router1, Router2, and the
	using static routing at Router1, Router2 and Host, and using the		Host, and using the corresponding static address selection policy
	corresponding static address selection policy at Host.		at the Host.
	2.1.2. Ingress Filtering Problem		2.1.2. Ingress Filtering Problem
	==================		==================
	| Internet |		| Internet |
	==================		==================
	| |		| |
	2001:db8:1000::/36 | | 2001:db8:8000::/36		2001:db8:1000::/36 | | 2001:db8:8000::/36
	+----+-+ +-+----+		+----+-+ +-+----+
	| ISP1 | | ISP2 |		| ISP1 | | ISP2 |
	skipping to change at page 5, line 35		skipping to change at page 5, line 28
	| Router |		| Router |
	+----+----+		+----+----+
	| 2001:db8:1000:1::/64		| 2001:db8:1000:1::/64
	| 2001:db8:8000:1::/64		| 2001:db8:8000:1::/64
	------+---+----------		------+---+----------
	|		|
	+-+----+ 2001:db8:1000:1::100		+-+----+ 2001:db8:1000:1::100
	| Host | 2001:db8:8000:1::100		| Host | 2001:db8:8000:1::100
	+------+		+------+
	[Fig. 2]		Figure 2
	When a relatively small site, which we call a "customer network", is		When a relatively small site, which we call a "customer network", is
	attached to two upstream ISPs, each ISP delegates a network address		attached to two upstream ISPs, each ISP delegates a network address
	block, which is usually /48, and a host has multiple IPv6 addresses.		block, which is usually /48, and a host has multiple IPv6 addresses.
	When the source address of an outgoing packet is not the one that is		When the source address of an outgoing packet is not the one that is
	delegated by an upstream ISP, there is a possibility that the packet		delegated by an upstream ISP, there is a possibility that the packet
	will be dropped at the ISP by its Ingress Filter. Ingress filtering		will be dropped at the ISP by its ingress filter. Ingress filtering
	is becoming more popular among ISPs to mitigate the damage of DoS		is becoming more popular among ISPs to mitigate the damage of
	attacks.		denial-of-service (DoS) attacks.
	In this example, when the Router chooses the default route to ISP2		In this example, when the router chooses the default route to ISP2
	and the Host chooses 2001:db8:1000:1::100 as the source address for		and the host chooses 2001:db8:1000:1::100 as the source address for
	packets sent to a host (2001:db8:2000::1) somewhere on the Internet,		packets sent to a host (2001:db8:2000::1) somewhere on the Internet,
	the packets may be dropped at ISP2 because of Ingress Filtering.		the packets may be dropped at ISP2 because of ingress filtering.
	Solution analysis:		Solution analysis:
			One possible solution for this case is adopting source-address-
	One possible solution for this case is adopting source address		based routing at the Router. Another solution may be using static
	based routing at Router. Another solution may be using static		routing at the Router, and using the corresponding static address
	routing at Router, and using the corresponding static address		selection policy at the Host.
	selection policy at Host.
	2.1.3. Half-Closed Network Problem		2.1.3. Half-Closed Network Problem
	You can see a second typical source address selection problem in a		You can see a second typical source address selection problem in a
	multihome site with global-closed mixed connectivity like in the		multi-homed site with global half-closed connectivity, as shown in
	figure below. In this case, Host-A is in a multihomed network and		the figure below. In this case, Host-A is in a multi-homed network
	has two IPv6 addresses, one delegated from each of the upstream ISPs.		and has two IPv6 addresses, one delegated from each of the upstream
	Note that ISP2 is a closed network and does not have connectivity to		ISPs. Note that ISP2 is a closed network and does not have
	the Internet.		connectivity to the Internet.
	+--------+		+--------+
	| Host-C | 2001:db8:a000::1		| Host-C | 2001:db8:a000::1
	+-----+--+		+-----+--+
	|		|
	============== +--------+		============== +--------+
	| Internet | | Host-B | 2001:db8:8000::1		| Internet | | Host-B | 2001:db8:8000::1
	============== +--------+		============== +--------+
	| |		| |
	2001:db8:1000:/36 | | 2001:db8:8000::/36		2001:db8:1000:/36 | | 2001:db8:8000::/36
	skipping to change at page 6, line 44		skipping to change at page 6, line 39
	| Router |		| Router |
	+----+----+		+----+----+
	| 2001:db8:1000:1::/64		| 2001:db8:1000:1::/64
	| 2001:db8:8000:1::/64		| 2001:db8:8000:1::/64
	------+---+----------		------+---+----------
	|		|
	+--+-----+ 2001:db8:1000:1::100		+--+-----+ 2001:db8:1000:1::100
	| Host-A | 2001:db8:8000:1::100		| Host-A | 2001:db8:8000:1::100
	+--------+		+--------+
	[Fig. 3]		Figure 3
	You do not need two physical network connections here. The		You do not need two physical network connections here. The
	connection from the Router to ISP2 can be a logical link over ISP1		connection from the Router to ISP2 can be a logical link over ISP1
	and the Internet.		and the Internet.
	When Host-A starts the connection to Host-B in ISP2, the source		When Host-A starts the connection to Host-B in ISP2, the source
	address of a packet that has been sent will be the one delegated from		address of a packet that has been sent will be the one delegated from
	ISP2, that is 2001:db8:8000:1::100, because of rule 8 (longest		ISP2 (that is, 2001:db8:8000:1::100) because of rule 8 (longest
	matching prefix) in RFC 3484.		matching prefix) in RFC 3484.
	Host-C is located somewhere on the Internet and has IPv6 address		Host-C is located somewhere on the Internet and has IPv6 address
	2001:db8:a000::1. When Host-A sends a packet to Host-C, the longest		2001:db8:a000::1. When Host-A sends a packet to Host-C, the longest
	matching algorithm chooses 2001:db8:8000:1::100 for the source		matching algorithm chooses 2001:db8:8000:1::100 for the source
	address. In this case, the packet goes through ISP1 and may be		address. In this case, the packet goes through ISP1 and may be
	filtered by ISP1's ingress filter. Even if the packet is not		filtered by ISP1's ingress filter. Even if the packet is not
	filtered by ISP1, a return packet from Host-C cannot possibly be		filtered by ISP1, a return packet from Host-C cannot possibly be
	delivered to Host-A because the return packet is destined for 2001:		delivered to Host-A because the return packet is destined for 2001:
	db8:8000:1::100, which is closed from the Internet.		db8:8000:1::100, which is closed from the Internet.
	The important point is that each host chooses a correct source		The important point is that each host chooses a correct source
	address for a given destination address. To solve this kind of		address for a given destination address. To solve this kind of
	network policy based address selection problems, it is likely that		network-policy-based address selection problem, it is likely that
	delivering additional information to a node fits better than		delivering additional information to a node provides a better
	algorithmic solutions that are local to the node.		solution than using algorithms that are local to the node.
	Solution analysis:		Solution analysis:
	This problem can be solved in the RFC 3484 framework. For		This problem can be solved in the RFC 3484 framework. For
	example, configuring some address selection policies into Host-A's		example, configuring some address selection policies into Host-A's
	RFC 3484 policy table can solve this problem.		RFC 3484 policy table can solve this problem.
	2.1.4. Combined Use of Global and ULA		2.1.4. Combined Use of Global and ULA
	============		============
	| Internet |		| Internet |
	skipping to change at page 7, line 50		skipping to change at page 7, line 45
	+-+-----+-+		+-+-----+-+
	| | 2001:db8:a:100::/64		| | 2001:db8:a:100::/64
	fd01:2:3:200:/64 | | fd01:2:3:100:/64		fd01:2:3:200:/64 | | fd01:2:3:100:/64
	-----+--+- -+--+----		-----+--+- -+--+----
	| |		| |
	fd01:2:3:200::101 | | 2001:db8:a:100::100		fd01:2:3:200::101 | | 2001:db8:a:100::100
	+----+----+ +-+----+ fd01:2:3:100::100		+----+----+ +-+----+ fd01:2:3:100::100
	| Printer | | Host |		| Printer | | Host |
	+---------+ +------+		+---------+ +------+
	[Fig. 4]		Figure 4
	As RFC 4864 [RFC4864] describes, using a ULA may be beneficial in		As RFC 4864 [RFC4864] describes, using a ULA may be beneficial in
	some scenarios. If the ULA is used for internal communication,		some scenarios. If the ULA is used for internal communication,
	packets with ULA need to be filtered at the Router.		packets with the ULA need to be filtered at the Router.
	This case does not presently create an address selection problem		This case does not presently create an address selection problem
	because of the dissimilarity between the ULA and the Global Unicast		because of the dissimilarity between the ULA and the global unicast
	Address. The longest matching rule of RFC 3484 chooses the correct		address. The longest matching rule of RFC 3484 chooses the correct
	address for both intra-site and extra-site communication.		address for both intra-site and extra-site communication.
	In the future, however, there is a possibility that the longest		In the future, however, there is a possibility that the longest
	matching rule will not be able to choose the correct address anymore.		matching rule will not be able to choose the correct address anymore.
	That is the moment when the assignment of those Global Unicast		That is the moment when the assignment of those global unicast
	Addresses starts, where the first bit is 1. In RFC 4291 [RFC4291],		addresses starts, where the first bit is 1. In RFC 4291 [RFC4291],
	almost all address spaces of IPv6, including those whose first bit is		almost all address spaces of IPv6, including those whose first bit is
	1, are assigned as Global Unicast Addresses.		1, are assigned as global unicast addresses.
	Namely, when we start to assign a part of the address block 8000::/1		Namely, when we start to assign a part of the address block 8000::/1
	as the global unicast address and that part is used somewhere in the		as the global unicast address and that part is used somewhere in the
	Internet, the longest matching rule ceases to function properly for		Internet, the longest matching rule ceases to function properly for
	the people trying to connect to the servers with those addresses.		the people trying to connect to the servers with those addresses.
	For example, when the destination host has an IPv6 address 8000::1,		For example, when the destination host has an IPv6 address 8000::1,
	and the originating host has 2001:db8::1 and fd0:1::1, the source		and the originating host has 2001:db8:a:100::100 and
	address will be fd00:1::1, because the longest matching bit length is		fd01:2:3:100::100, the source address will be fd01:2:3:100::100,
	0 for 2001:db8::1 and 1 for fd0:1::1 respectively.		because the longest matching bit length is 0 for 2001:db8:a:100::100
			and 1 for fd01:2:3:100::100, respectively.
	Solution analysis:		Solution analysis:
	This problem can be solved in the RFC 3484 framework. For		This problem can be solved in the RFC 3484 framework. For
	example, configuring some address selection policies into Host's		example, configuring some address selection policies into the
	RFC 3484 policy table can solve this problem. Another solution is		Host's RFC 3484 policy table can solve this problem. Another
	to modify RFC 3484 and define ULA's scope smaller than the global		solution is to modify RFC 3484 and define ULA's scope smaller than
	scope.		the global scope.
	2.1.5. Site Renumbering		2.1.5. Site Renumbering
	RFC 4192 [RFC4192] describes a recommended procedure for renumbering		RFC 4192 [RFC4192] describes a recommended procedure for renumbering
	a network from one prefix to another. An autoconfigured address has		a network from one prefix to another. An autoconfigured address has
	a lifetime, so by stopping advertisement of the old prefix, the		a lifetime, so by stopping advertisement of the old prefix, the
	autoconfigured address is eventually invalidated.		autoconfigured address is eventually invalidated.
	However, invalidating the old prefix takes a long time. You cannot		However, invalidating the old prefix takes a long time. You cannot
	stop routing to the old prefix as long as the old prefix is not		stop routing to the old prefix as long as the old prefix is not
	removed from the host. This can be a tough issue for ISP network		removed from the host. This can be a tough issue for ISP network
	administrators.		administrators.
	There is a technique of advertising the prefix with the preferred		There is a technique of advertising the prefix with the preferred
	lifetime zero, however, RFC 4862 [RFC4862] 5.5.4 does not absolutely		lifetime zero; however, RFC 4862 [RFC4862], Section 5.5.4, does not
	prohibit the use of a deprecated address for a new outgoing		absolutely prohibit the use of a deprecated address for a new
	connection due to limitations relating to what applications are		outgoing connection due to limitations on the capabilities of
	capable of doing."		applications.
	+-----+---+		+-----+---+
	| Router |		| Router |
	+----+----+		+----+----+
	| 2001:db8:b::/64 (new)		| 2001:db8:b::/64 (new)
	| 2001:db8:a::/64 (old)		| 2001:db8:a::/64 (old)
	------+---+----------		------+---+----------
	|		|
	+--+---+ 2001:db8:b::100 (new)		+--+---+ 2001:db8:b::100 (new)
	| Host | 2001:db8:a::100 (old)		| Host | 2001:db8:a::100 (old)
	+------+		+------+
	[Fig. 5]		Figure 5
	Solution analysis:		Solution analysis:
	This problem can be mitigated in the RFC 3484 framework. For		This problem can be mitigated in the RFC 3484 framework. For
	example, configuring some address selection policies into Host's		example, configuring some address selection policies into the
	RFC 3484 policy table can solve this problem.		Host's RFC 3484 policy table can solve this problem.
	2.1.6. Multicast Source Address Selection		2.1.6. Multicast Source Address Selection
	This case is an example of site-local or global unicast		This case is an example of site-local or global unicast
	prioritization. When you send a multicast packet across site-		prioritization. When you send a multicast packet across site
	borders, the source address of the multicast packet should be a		borders, the source address of the multicast packet should be a
	globally routable address. The longest matching algorithm, however,		globally routable address. The longest matching algorithm, however,
	selects a ULA if the sending host has both a ULA and a Global Unicast		selects a ULA if the sending host has both a ULA and a Global Unicast
	Address.		Address.
	Solution analysis:		Solution analysis:
	This problem can be solved in the RFC 3484 framework. For		This problem can be solved in the RFC 3484 framework. For
	example, configuring some address selection policies into the		example, configuring some address selection policies into the
	sending host's RFC 3484 policy table can solve this problem.		sending host's RFC 3484 policy table can solve this problem.
	2.1.7. Temporary Address Selection		2.1.7. Temporary Address Selection
	RFC 3041 [RFC3041] defines a Temporary Address. The usage of a		RFC 3041 [RFC3041] defines a Temporary Address. The usage of a
	Temporary Address has both pros and cons. That is good for viewing		Temporary Address has both pros and cons. It is good for viewing web
	web pages or communicating with the general public, but that is bad		pages or communicating with the general public, but it is bad for a
	for a service that uses address-based authentication and for logging		service that uses address-based authentication and for logging
	purposes.		purposes.
	If you could turn the temporary address on and off, that would be		If you could turn the temporary address on and off, that would be
	better. If you could switch its usage per service (destination		better. If you could switch its usage per service (destination
	address), that would also be better. The same situation can be found		address), that would also be better. The same situation can be found
	when using HA (home address) and CoA (care-of address)in a Mobile		when using an HA (home address) and a CoA (care-of address) in a
	IPv6 [RFC3775] network.		Mobile IPv6 [RFC3775] network.
	The Future Work section in RFC 3041 discusses that an API extension		Section 6 ("Future Work") of RFC 3041 discusses that an API extension
	might be necessary to achieve a better address selection mechanism		might be necessary to achieve a better address selection mechanism
	with finer granularity.		with finer granularity.
	Solution analysis:		Solution analysis:
	This problem can not be solved in the RFC 3484 framework. A		This problem can not be solved in the RFC 3484 framework. A
	possible solution is to make applications to select desirable		possible solution is to make applications to select desirable
	addresses by using the IPv6 Socket API for Source Address		addresses by using the IPv6 Socket API for Source Address
	Selection defined in RFC 5014 [RFC5014].		Selection defined in RFC 5014 [RFC5014].
	2.2. Destination Address Selection		2.2. Destination Address Selection
	2.2.1. IPv4 or IPv6 prioritization		2.2.1. IPv4 or IPv6 Prioritization
	The default policy table gives IPv6 addresses higher precedence than		The default policy table gives IPv6 addresses higher precedence than
	IPv4 addresses. There seem to be many cases, however, where network		IPv4 addresses. There seem to be many cases, however, where network
	administrators want to control the address selection policy of end-		administrators want to control the address selection policy of end
	hosts the other way around.		hosts so that it is the other way around.
	+---------+		+---------+
	| Tunnel |		| Tunnel |
	| Service |		| Service |
	+--+---++-+		+--+---++-+
	| ||		| ||
	| ||		| ||
	===========||==		===========||==
	| Internet || |		| Internet || |
	===========||==		===========||==
	skipping to change at page 11, line 4		skipping to change at page 11, line 33
	| Router |		| Router |
	+----+----+		+----+----+
	| 2001:db8:a:1::/64		| 2001:db8:a:1::/64
	| 192.0.2.0/28		| 192.0.2.0/28
	|		|
	------+---+----------		------+---+----------
	|		|
	+-+----+ 2001:db8:a:1::100		+-+----+ 2001:db8:a:1::100
	| Host | 192.0.2.2		| Host | 192.0.2.2
	+------+		+------+
	[Fig. 6]
	In the figure above, a site has native IPv4 and tunneled-IPv6		Figure 6
			In the figure above, a site has native IPv4 and tunneled IPv6
	connectivity. Therefore, the administrator may want to set a higher		connectivity. Therefore, the administrator may want to set a higher
	priority for using IPv4 than using IPv6 because the quality of the		priority for using IPv4 than for using IPv6 because the quality of
	tunnel network seems to be worse than that of the native transport.		the tunnel network seems to be worse than that of the native
			transport.
	Solution analysis:		Solution analysis:
	This problem can be solved in the RFC 3484 framework. For		This problem can be solved in the RFC 3484 framework. For
	example, configuring some address selection policies into Host's		example, configuring some address selection policies into the
	RFC 3484 policy table can solve this problem.		Host's RFC 3484 policy table can solve this problem.
	2.2.2. ULA and IPv4 dual-stack environment		2.2.2. ULA and IPv4 Dual-Stack Environment
	This is a special form of IPv4 and IPv6 prioritization. When an		This is a special form of IPv4 and IPv6 prioritization. When an
	enterprise has IPv4 Internet connectivity but does not yet have IPv6		enterprise has IPv4 Internet connectivity but does not yet have IPv6
	Internet connectivity, and the enterprise wants to provide site-local		Internet connectivity, and the enterprise wants to provide site-local
	IPv6 connectivity, a ULA is the best choice for site-local IPv6		IPv6 connectivity, a ULA is the best choice for site-local IPv6
	connectivity. Each employee host will have both an IPv4 global or		connectivity. Each employee host will have both an IPv4 global or
	private address and a ULA. Here, when this host tries to connect to		private address and a ULA. Here, when this host tries to connect to
	Host-B that has registered both A and AAAA records in the DNS, the		Host-B that has registered both A and AAAA records in the DNS, the
	host will choose AAAA as the destination address and the ULA for the		host will choose AAAA as the destination address and the ULA for the
	source address. This will clearly result in a connection failure.		source address. This will clearly result in a connection failure.
	skipping to change at page 12, line 30		skipping to change at page 12, line 35
	| Router |		| Router |
	+----+----+		+----+----+
	| fd01:2:3:4::/64 (ULA)		| fd01:2:3:4::/64 (ULA)
	| 192.0.2.240/28		| 192.0.2.240/28
	------+---+----------		------+---+----------
	|		|
	+-+------+ fd01:2:3:4::100 (ULA)		+-+------+ fd01:2:3:4::100 (ULA)
	| Host-A | 192.0.2.245		| Host-A | 192.0.2.245
	+--------+		+--------+
	[Fig. 7]		Figure 7
	Solution analysis:		Solution analysis:
	This problem can be solved in the RFC 3484 framework. For		This problem can be solved in the RFC 3484 framework. For
	example, configuring some address selection policies into Host-A's		example, configuring some address selection policies into Host-A's
	RFC 3484 policy table can solve this problem.		RFC 3484 policy table can solve this problem.
	2.2.3. ULA or Global Prioritization		2.2.3. ULA or Global Prioritization
	Differentiating services by the client's source address is very		Differentiating services by the client's source address is very
	common. IP-address-based authentication is an typical example of		common. IP-address-based authentication is a typical example of
	this. Another typical example is a web service that has pages for		this. Another typical example is a web service that has pages for
	the public and internal pages for employees or involved parties. Yet		the public and internal pages for employees or involved parties. Yet
	another example is DNS zone splitting.		another example is DNS zone splitting.
	However, a ULA and IPv6 global address both have global scope, and		However, a ULA and an IPv6 global address both have global scope, and
	RFC3484 default rules do not specify which address should be given		RFC3484 default rules do not specify which address should be given
	priority. This point makes IPv6 implementation of address-based		priority. This point makes IPv6 implementation of address-based
	service differentiation a bit harder.		service differentiation a bit harder.
	+--------+		+--------+
	| Host-B |		| Host-B |
	+-+--|---+		+-+--|---+
	| |		| |
	===========|==		===========|==
	| Internet | |		| Internet | |
	skipping to change at page 13, line 31		skipping to change at page 13, line 36
	| Router ||		| Router ||
	+---+-----|+		+---+-----|+
	| | 2001:db8:a:100::/64		| | 2001:db8:a:100::/64
	| | fc12:3456:789a:100::/64		| | fc12:3456:789a:100::/64
	--+-+---|-----		--+-+---|-----
	| |		| |
	+-+---|--+ 2001:db8:a:100::100		+-+---|--+ 2001:db8:a:100::100
	| Host-A | fc12:3456:789a:100::100		| Host-A | fc12:3456:789a:100::100
	+--------+		+--------+
	[Fig. 7]		Figure 8
	Solution analysis:		Solution analysis:
	This problem can be solved in the RFC 3484 framework. For		This problem can be solved in the RFC 3484 framework. For
	example, configuring some address selection policies into Host-A's		example, configuring some address selection policies into Host-A's
	RFC 3484 policy table can solve this problem.		RFC 3484 policy table can solve this problem.
	3. Conclusion		3. Conclusion
	We have covered problems related to destination or source address		We have covered problems related to destination or source address
	selection. These problems have their roots in the situation where		selection. These problems have their roots in the situation where
	end-hosts have multiple IP addresses. In this situation, every end-		end hosts have multiple IP addresses. In this situation, every end
	host must choose an appropriate destination and source address, which		host must choose an appropriate destination and source address; this
	cannot be achieved only by routers.		choice cannot be achieved only by routers.
	It should be noted that end-hosts must be informed about routing		It should be noted that end hosts must be informed about routing
	policies of their upstream networks for appropriate address		policies of their upstream networks for appropriate address
	selection. A site administrator must consider every possible address		selection. A site administrator must consider every possible address
	false-selection problem and take countermeasures beforehand.		false-selection problem and take countermeasures beforehand.
	4. Security Considerations		4. Security Considerations
	When an intermediate router performs policy routing (e.g. source		When an intermediate router performs policy routing (e.g., source-
	address based routing), inappropriate address selection causes		address-based routing), inappropriate address selection causes
	unexpected routing. For example, in the network described in 2.1.3,		unexpected routing. For example, in the network described in Section
	when Host-A uses a default address selection policy and chooses an		2.1.3, when Host-A uses a default address selection policy and
	inappropriate address, a packet sent to VPN can be delivered to a		chooses an inappropriate address, a packet sent to a VPN can be
	location via the Internet. This issue can lead to packet		delivered to a location via the Internet. This issue can lead to
	eavesdropping or session hijack. However, sending the packet back to		packet eavesdropping or session hijack. However, sending the packet
	the correct path from the attacker to the node is not easy, so these		back to the correct path from the attacker to the node is not easy,
	two risks are not serious.		so these two risks are not serious.
	As documented in the security consideration section in RFC 3484,		As documented in the Security Considerations section of RFC 3484,
	address selection algorithms expose a potential privacy concern.		address selection algorithms expose a potential privacy concern.
	When a malicious host can make a target host perform address		When a malicious host can make a target host perform address
	selection, for example by sending a anycast or a multicast packet,		selection (for example, by sending an anycast or multicast packet),
	the malicious host can get knowledge multiple addresses attached to		the malicious host can get knowledge of multiple addresses attached
	the target host. In a case like 2.1.4, if an attacker can make Host		to the target host. In a case like Section 2.1.4, if an attacker can
	to send a multicast packet and Host performs the default address		make the Host to send a multicast packet and the Host performs the
	selection algorithm, the attacker may be able to determine the ULAs		default address selection algorithm, the attacker may be able to
	attached to the Host.		determine the ULAs attached to the host.
	These security risks have roots in inappropriate address selection.		These security risks have roots in inappropriate address selection.
	Therefore, if a countermeasure is taken, and hosts always select an		Therefore, if a countermeasure is taken, and hosts always select an
	appropriate address that is suitable to a site's network structure		appropriate address that is suitable to a site's network structure
	and routing, these risks can be avoided.		and routing, these risks can be avoided.
	5. IANA Considerations		5. Normative References
	This document has no actions for IANA.
	6. References
	6.1. Normative References
	[RFC3041] Narten, T. and R. Draves, "Privacy Extensions for		[RFC3041] Narten, T. and R. Draves, "Privacy Extensions for
	Stateless Address Autoconfiguration in IPv6", RFC 3041,		Stateless Address Autoconfiguration in IPv6", RFC 3041,
	January 2001.		January 2001.
	[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.
	[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support		[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
	in IPv6", RFC 3775, June 2004.		in IPv6", RFC 3775, June 2004.
	skipping to change at page 15, line 24		skipping to change at page 16, line 5
	Address Autoconfiguration", RFC 4862, September 2007.		Address Autoconfiguration", RFC 4862, September 2007.
	[RFC4864] Van de Velde, G., Hain, T., Droms, R., Carpenter, B., and		[RFC4864] Van de Velde, G., Hain, T., Droms, R., Carpenter, B., and
	E. Klein, "Local Network Protection for IPv6", RFC 4864,		E. Klein, "Local Network Protection for IPv6", RFC 4864,
	May 2007.		May 2007.
	[RFC5014] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6		[RFC5014] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6
	Socket API for Source Address Selection", RFC 5014,		Socket API for Source Address Selection", RFC 5014,
	September 2007.		September 2007.
	6.2. Informative References
	Appendix A. Appendix. Revision History
	01:
	IP address notations changed to documentation address.
	Description of solutions deleted.
	02:
	Security considerations section rewritten according to comments
	from SECDIR.
	03:
	Intended status changed to Informational.
	04:
	This version reflects comments from IESG members.
	05:
	This version reflects comments from IESG members and Bob Hinden.
	06:
	This version reflects comments from Thomas Narten.
	07:
	This version reflects comments from Alfred Hoenes.
	08:
	Solution analysis for the section 2.1.6 was added.
	09:
	Typos were fixed, thanks to Jari Arrko.
	Authors' Addresses		Authors' Addresses
	Arifumi Matsumoto		Arifumi Matsumoto
	NTT PF Lab		NTT PF Lab
	Midori-Cho 3-9-11		Midori-Cho 3-9-11
	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
	Tomohiro Fujisaki		Tomohiro Fujisaki
	NTT PF Lab		NTT PF Lab
	Midori-Cho 3-9-11		Midori-Cho 3-9-11
	Musashino-shi, Tokyo 180-8585		Musashino-shi, Tokyo 180-8585
	Japan		Japan
	Phone: +81 422 59 7351		Phone: +81 422 59 7351
	Email: fujisaki@nttv6.net		EMail: fujisaki@nttv6.net
	Ruri Hiromi		Ruri Hiromi
	Intec Netcore, Inc.		Intec Netcore, Inc.
	Shinsuna 1-3-3		Shinsuna 1-3-3
	Koto-ku, Tokyo 136-0075		Koto-ku, Tokyo 136-0075
	Japan		Japan
	Phone: +81 3 5665 5069		Phone: +81 3 5665 5069
	Email: hiromi@inetcore.com		EMail: hiromi@inetcore.com
	Ken-ichi Kanayama		Ken-ichi Kanayama
	INTEC Systems Institute, Inc.		INTEC Systems Institute, Inc.
	Shimoshin-machi 5-33		Shimoshin-machi 5-33
	Toyama-shi, Toyama 930-0804		Toyama-shi, Toyama 930-0804
	Japan		Japan
	Phone: +81 76 444 8088		Phone: +81 76 444 8088
	Email: kanayama_kenichi@intec-si.co.jp		EMail: kanayama_kenichi@intec-si.co.jp
	Full Copyright Statement		Full Copyright Statement
	Copyright (C) The IETF Trust (2008).		Copyright (C) The IETF Trust (2008).
	This document is subject to the rights, licenses and restrictions		This document is subject to the rights, licenses and restrictions
	contained in BCP 78, and except as set forth therein, the authors		contained in BCP 78, and except as set forth therein, the authors
	retain all their rights.		retain all their rights.
	This document and the information contained herein are provided on an		This document and the information contained herein are provided on an
End of changes. 63 change blocks.
	210 lines changed or deleted		154 lines changed or added
This html diff was produced by rfcdiff 1.35. The latest version is available from http://tools.ietf.org/tools/rfcdiff/