draft-arkko-dual-stack-extra-lite-03.txt		draft-arkko-dual-stack-extra-lite.txt
	Network Working Group J. Arkko		Network Working Group J. Arkko
	Internet-Draft Ericsson		Internet-Draft Ericsson
	Intended status: Standards Track L. Eggert		Intended status: Standards Track L. Eggert
	Expires: April 28, 2011 Nokia		Expires: August 5, 2011 Nokia
	October 25, 2010		M. Townsley
			Cisco
			February 2011
	Scalable Operation of Address Translators with Per-Interface Bindings		Scalable Operation of Address Translators with Per-Interface Bindings
	draft-arkko-dual-stack-extra-lite-03		draft-arkko-dual-stack-extra-lite-05
	Abstract		Abstract
	This document explains how to employ address translation in networks		This document explains how to employ address translation in networks
	that serve a large number of individual customers without requiring a		that serve a large number of individual customers without requiring a
	correspondingly large amount of private IPv4 address space.		correspondingly large amount of private IPv4 address space.
	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
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	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 April 28, 2011.		This Internet-Draft will expire on August 5, 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.
	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
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
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	A Network Address Translator (NAT) is typically configured to connect		A Network Address Translator (NAT) is typically configured to connect
	a network domain that uses private IPv4 addresses to the public		a network domain that uses private IPv4 addresses to the public
	Internet. The NAT device - which is configured with a public IPv4		Internet. The NAT device - which is configured with a public IPv4
	address - creates and maintains a mapping for each communication		address - creates and maintains a mapping for each communication
	session from a device inside the domain it serves to devices in the		session from a device inside the domain it serves to devices in the
	public Internet. It does that by translating the packet flow of each		public Internet. It does that by translating the packet flow of each
	session such that the externally visible traffic uses only public		session such that the externally visible traffic uses only public
	addresses.		addresses.
	In most NAT deployments, the network domain connected by the NAT to		In many NAT deployments, the network domain connected by the NAT to
	the public Internet is a broadcast network sharing the same media,		the public Internet is a broadcast network sharing the same media,
	where each individual device must have a unique IPv4 address. In		where each individual device must have a private IPv4 address that is
	such deployments it is natural to also implement the NAT		unique within this network. In such deployments it is natural to
	functionality such that it uses this unique IPv4 address when looking		also implement the NAT functionality such that it uses the private
	up which mapping should be used to translate a given communication		IPv4 address when looking up which mapping should be used to
	session.		translate a given communication session.
	It is important to note, however, that this is not an inherent		It is important to note, however, that this is not an inherent
	requirement. When other methods of identifying the correct mapping		requirement. When other methods of identifying the correct mapping
	are available, and the NAT is not connecting a shared-media broadcast		are available, and the NAT is not connecting a shared-media broadcast
	network to the Internet, there is no need to assign each device in		network to the Internet, there is no need to assign each device in
	the domain a unique IPv4 address.		the domain a unique IPv4 address.
	This is the case, for example, when the NAT connects devices to the		This is the case, for example, when the NAT connects devices to the
	Internet that connect to it with individual point-to-point links. In		Internet that connect to it with individual point-to-point links. In
	this case, it becomes possible to use the same private addresses many		this case, it becomes possible to use the same private addresses many
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	small measure, which may aid NAT scalability. For other deployments,		small measure, which may aid NAT scalability. For other deployments,
	it is likely necessary to store both the user device IPv4 address and		it is likely necessary to store both the user device IPv4 address and
	the internal interface identifier, which slightly increases the size		the internal interface identifier, which slightly increases the size
	of the mapping entry.		of the mapping entry.
	This mode of operation is only suitable in deployments where user		This mode of operation is only suitable in deployments where user
	devices connect to the NAT over point-to-point links. If supported,		devices connect to the NAT over point-to-point links. If supported,
	this mode of operation SHOULD be configurable, and it should be		this mode of operation SHOULD be configurable, and it should be
	disabled by default in general-purpose NAT devices.		disabled by default in general-purpose NAT devices.
			All address translators make it hard to address devices behind them.
			The same is true of the particular NAT variant described in this
			document. An additional constraint is caused by the use of the same
			address space for different devices behind the NAT, which prevents
			the use of unique private addresses for communication between devices
			behind the same NAT.
	5. IPv6 Considerations		5. IPv6 Considerations
	Private address space conservation is important even during the		Private address space conservation is important even during the
	migration to IPv6, because it will be necessary to communicate with		migration to IPv6, because it will be necessary to communicate with
	the IPv4 Internet for a long time. This document specifies two		the IPv4 Internet for a long time. This document specifies two
	recommended deployment models for IPv6. In the first deployment		recommended deployment models for IPv6. In the first deployment
	model the mechanisms specified in this document are useful. In the		model the mechanisms specified in this document are useful. In the
	second deployment model no additional mechanisms are needed, because		second deployment model no additional mechanisms are needed, because
	IPv6 addresses are already sufficient to distinguish mappings from		IPv6 addresses are already sufficient to distinguish mappings from
	each other.		each other.
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	[I-D.ietf-behave-v6v4-xlate-stateful]. In this deployment model		[I-D.ietf-behave-v6v4-xlate-stateful]. In this deployment model
	there is no IPv4 in the internal network at all. This model is		there is no IPv4 in the internal network at all. This model is
	applicable only in situations where all relevant devices and		applicable only in situations where all relevant devices and
	applications are IPv6-capable. In this situation, per-interface		applications are IPv6-capable. In this situation, per-interface
	mappings could be employed as specified above, but they are generally		mappings could be employed as specified above, but they are generally
	unnecessary as the IPv6 address space is large enough to provide a		unnecessary as the IPv6 address space is large enough to provide a
	sufficient number of mappings.		sufficient number of mappings.
	6. Security Considerations		6. Security Considerations
	This practices outlined in this document do not affect the security		The practices outlined in this document do not affect the security
	properties of address translation.		properties of address translation. The binding method specified in
			this document is not observable to a device that is on the outside of
			the NAT; i.e., a regular NAT and a NAT specified here cannot be
			distinguished. However, the use of point-to-point links implies
			naturally that the devices behind the NAT cannot communicate with
			each other directly without going through the NAT (or a router). The
			use of same address space for different devices implies in addition
			that a NAT operation must occur between two devices in order for them
			to communicate.
			The security implications of address translation in general have been
			discussed in many previous documents, including [RFC2663] [RFC2993]
			[RFC4787], and [RFC5382].
	7. IANA Considerations		7. IANA Considerations
	This document has no IANA implications.		This document has no IANA implications.
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	skipping to change at page 6, line 42		skipping to change at page 7, line 17
	BCP 5, RFC 1918, February 1996.		BCP 5, RFC 1918, February 1996.
	[RFC2516] Mamakos, L., Lidl, K., Evarts, J., Carrel, D., Simone, D.,		[RFC2516] Mamakos, L., Lidl, K., Evarts, J., Carrel, D., Simone, D.,
	and R. Wheeler, "A Method for Transmitting PPP Over		and R. Wheeler, "A Method for Transmitting PPP Over
	Ethernet (PPPoE)", RFC 2516, February 1999.		Ethernet (PPPoE)", RFC 2516, February 1999.
	[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address		[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
	Translator (NAT) Terminology and Considerations",		Translator (NAT) Terminology and Considerations",
	RFC 2663, August 1999.		RFC 2663, August 1999.
			[RFC2993] Hain, T., "Architectural Implications of NAT", RFC 2993,
			November 2000.
	[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms		[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
	for IPv6 Hosts and Routers", RFC 4213, October 2005.		for IPv6 Hosts and Routers", RFC 4213, October 2005.
	[RFC4787] Audet, F. and C. Jennings, "Network Address Translation		[RFC4787] Audet, F. and C. Jennings, "Network Address Translation
	(NAT) Behavioral Requirements for Unicast UDP", BCP 127,		(NAT) Behavioral Requirements for Unicast UDP", BCP 127,
	RFC 4787, January 2007.		RFC 4787, January 2007.
	[RFC5382] Guha, S., Biswas, K., Ford, B., Sivakumar, S., and P.		[RFC5382] Guha, S., Biswas, K., Ford, B., Sivakumar, S., and P.
	Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142,		Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142,
	RFC 5382, October 2008.		RFC 5382, October 2008.
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	Appendix A. Contributors		Appendix A. Contributors
	The ideas in this draft were first presented in		The ideas in this draft were first presented in
	[I-D.ietf-softwire-dual-stack-lite]. This document also in debt to		[I-D.ietf-softwire-dual-stack-lite]. This document also in debt to
	[I-D.arkko-townsley-coexistence] and [I-D.miles-behave-l2nat].		[I-D.arkko-townsley-coexistence] and [I-D.miles-behave-l2nat].
	However, all of these documents focused on additional components,		However, all of these documents focused on additional components,
	such as tunneling protocols or the allocation of special IP address		such as tunneling protocols or the allocation of special IP address
	ranges. We wanted to publish a specification that just focuses on		ranges. We wanted to publish a specification that just focuses on
	the core functionality of a per-interface NAT mappings. However,		the core functionality of a per-interface NAT mappings. However,
	Mark Townsley, David Miles, and Alain Durand should be credited with		David Miles, and Alain Durand should be credited with coming up with
	coming up with the ideas discussed in this memo.		the ideas discussed in this memo.
	Appendix B. Acknowledgments		Appendix B. Acknowledgments
	The authors would also like to thank Randy Bush, Fredrik Garneij, Dan		The authors would also like to thank Randy Bush, Fredrik Garneij, Dan
	Wing, Christian Vogt, Marcelo Braun, Joel Halpern, Wassim Haddad,		Wing, Christian Vogt, Marcelo Braun, Joel Halpern, Wassim Haddad,
	Alan Kavanaugh and others for interesting discussions in this problem		Alan Kavanaugh and others for interesting discussions in this problem
	space.		space.
	Lars Eggert is partly funded by the Trilogy Project [TRILOGY], a		Lars Eggert is partly funded by the Trilogy Project [TRILOGY], a
	research project supported by the European Commission under its		research project supported by the European Commission under its
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	Lars Eggert		Lars Eggert
	Nokia Research Center		Nokia Research Center
	P.O. Box 407		P.O. Box 407
	Nokia Group 00045		Nokia Group 00045
	Finland		Finland
	Phone: +358 50 48 24461		Phone: +358 50 48 24461
	Email: lars.eggert@nokia.com		Email: lars.eggert@nokia.com
	URI: http://research.nokia.com/people/lars_eggert/		URI: http://research.nokia.com/people/lars_eggert/
			Mark Townsley
			Cisco
			Paris 75006
			France
			Email: townsley@cisco.com
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