draft-ietf-hip-rfc5206-bis-00.txt		draft-ietf-hip-rfc5206-bis-01.txt
	Network Working Group P. Nikander		Network Working Group P. Nikander
	Internet-Draft Ericsson Research NomadicLab		Internet-Draft Ericsson Research NomadicLab
	Obsoletes: 5206 (if approved) T. Henderson, Ed.		Obsoletes: 5206 (if approved) T. Henderson, Ed.
	Intended status: Standards Track The Boeing Company		Intended status: Standards Track The Boeing Company
	Expires: February 23, 2011 C. Vogt		Expires: April 21, 2011 C. Vogt
	J. Arkko		J. Arkko
	Ericsson Research NomadicLab		Ericsson Research NomadicLab
	August 22, 2010		October 18, 2010
	End-Host Mobility and Multihoming with the Host Identity Protocol		Host Mobility with the Host Identity Protocol
	draft-ietf-hip-rfc5206-bis-00		draft-ietf-hip-rfc5206-bis-01
	Abstract		Abstract
	This document defines mobility and multihoming extensions to the Host		This document defines mobility extensions to the Host Identity
	Identity Protocol (HIP). Specifically, this document defines a		Protocol (HIP). Specifically, this document defines a general
	general "LOCATOR" parameter for HIP messages that allows for a HIP		"LOCATOR" parameter for HIP messages that allows for a HIP host to
	host to notify peers about alternate addresses at which it may be		notify peers about alternate addresses at which it may be reached.
	reached. This document also defines elements of procedure for		This document also defines elements of procedure for mobility of a
	mobility of a HIP host -- the process by which a host dynamically		HIP host -- the process by which a host dynamically changes the
	changes the primary locator that it uses to receive packets. While		primary locator that it uses to receive packets. While the same
	the same LOCATOR parameter can also be used to support end-host		LOCATOR parameter can also be used to support end-host multihoming,
	multihoming, detailed procedures are left for further study.		detailed procedures are out of scope for this document.
	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 February 23, 2011.		This Internet-Draft will expire on April 21, 2011.
	Copyright Notice		Copyright Notice
	Copyright (c) 2010 IETF Trust and the persons identified as the		Copyright (c) 2010 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 33		skipping to change at page 3, line 13
	than English.		than English.
	Table of Contents		Table of Contents
	1. Introduction and Scope . . . . . . . . . . . . . . . . . . . . 4		1. Introduction and Scope . . . . . . . . . . . . . . . . . . . . 4
	2. Terminology and Conventions . . . . . . . . . . . . . . . . . 5		2. Terminology and Conventions . . . . . . . . . . . . . . . . . 5
	3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . . 6		3. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . . 6
	3.1. Operating Environment . . . . . . . . . . . . . . . . . . 6		3.1. Operating Environment . . . . . . . . . . . . . . . . . . 6
	3.1.1. Locator . . . . . . . . . . . . . . . . . . . . . . . 8		3.1.1. Locator . . . . . . . . . . . . . . . . . . . . . . . 8
	3.1.2. Mobility Overview . . . . . . . . . . . . . . . . . . 8		3.1.2. Mobility Overview . . . . . . . . . . . . . . . . . . 8
	3.1.3. Multihoming Overview . . . . . . . . . . . . . . . . . 9		3.2. Protocol Overview . . . . . . . . . . . . . . . . . . . . 8
	3.2. Protocol Overview . . . . . . . . . . . . . . . . . . . . 9		3.2.1. Mobility with a Single SA Pair (No Rekeying) . . . . . 9
	3.2.1. Mobility with a Single SA Pair (No Rekeying) . . . . . 10
	3.2.2. Mobility with a Single SA Pair (Mobile-Initiated		3.2.2. Mobility with a Single SA Pair (Mobile-Initiated
	Rekey) . . . . . . . . . . . . . . . . . . . . . . . . 12		Rekey) . . . . . . . . . . . . . . . . . . . . . . . . 11
	3.2.3. Host Multihoming . . . . . . . . . . . . . . . . . . . 12		3.2.3. Using LOCATORs across Addressing Realms . . . . . . . 11
	3.2.4. Site Multihoming . . . . . . . . . . . . . . . . . . . 14		3.2.4. Network Renumbering . . . . . . . . . . . . . . . . . 11
	3.2.5. Dual host multihoming . . . . . . . . . . . . . . . . 14		3.3. Other Considerations . . . . . . . . . . . . . . . . . . . 12
	3.2.6. Combined Mobility and Multihoming . . . . . . . . . . 15		3.3.1. Address Verification . . . . . . . . . . . . . . . . . 12
	3.2.7. Using LOCATORs across Addressing Realms . . . . . . . 15		3.3.2. Credit-Based Authorization . . . . . . . . . . . . . . 12
	3.2.8. Network Renumbering . . . . . . . . . . . . . . . . . 15		3.3.3. Preferred Locator . . . . . . . . . . . . . . . . . . 13
	3.2.9. Initiating the Protocol in R1 or I2 . . . . . . . . . 16		4. LOCATOR Parameter Format . . . . . . . . . . . . . . . . . . . 14
	3.3. Other Considerations . . . . . . . . . . . . . . . . . . . 17		4.1. Traffic Type and Preferred Locator . . . . . . . . . . . . 15
	3.3.1. Address Verification . . . . . . . . . . . . . . . . . 17		4.2. Locator Type and Locator . . . . . . . . . . . . . . . . . 16
	3.3.2. Credit-Based Authorization . . . . . . . . . . . . . . 17		4.3. UPDATE Packet with Included LOCATOR . . . . . . . . . . . 16
	3.3.3. Preferred Locator . . . . . . . . . . . . . . . . . . 19		5. Processing Rules . . . . . . . . . . . . . . . . . . . . . . . 16
	3.3.4. Interaction with Security Associations . . . . . . . . 19		5.1. Locator Data Structure and Status . . . . . . . . . . . . 16
	4. LOCATOR Parameter Format . . . . . . . . . . . . . . . . . . . 22		5.2. Sending LOCATORs . . . . . . . . . . . . . . . . . . . . . 18
	4.1. Traffic Type and Preferred Locator . . . . . . . . . . . . 24		5.3. Handling Received LOCATORs . . . . . . . . . . . . . . . . 19
	4.2. Locator Type and Locator . . . . . . . . . . . . . . . . . 24		5.4. Verifying Address Reachability . . . . . . . . . . . . . . 21
	4.3. UPDATE Packet with Included LOCATOR . . . . . . . . . . . 25		5.5. Changing the Preferred Locator . . . . . . . . . . . . . . 22
	5. Processing Rules . . . . . . . . . . . . . . . . . . . . . . . 25		5.6. Credit-Based Authorization . . . . . . . . . . . . . . . . 23
	5.1. Locator Data Structure and Status . . . . . . . . . . . . 25		5.6.1. Handling Payload Packets . . . . . . . . . . . . . . . 23
	5.2. Sending LOCATORs . . . . . . . . . . . . . . . . . . . . . 26		5.6.2. Credit Aging . . . . . . . . . . . . . . . . . . . . . 25
	5.3. Handling Received LOCATORs . . . . . . . . . . . . . . . . 28		6. Security Considerations . . . . . . . . . . . . . . . . . . . 26
	5.4. Verifying Address Reachability . . . . . . . . . . . . . . 30		6.1. Impersonation Attacks . . . . . . . . . . . . . . . . . . 27
	5.5. Changing the Preferred Locator . . . . . . . . . . . . . . 32		6.2. Denial-of-Service Attacks . . . . . . . . . . . . . . . . 28
	5.6. Credit-Based Authorization . . . . . . . . . . . . . . . . 32		6.2.1. Flooding Attacks . . . . . . . . . . . . . . . . . . . 28
	5.6.1. Handling Payload Packets . . . . . . . . . . . . . . . 33		6.2.2. Memory/Computational-Exhaustion DoS Attacks . . . . . 28
	5.6.2. Credit Aging . . . . . . . . . . . . . . . . . . . . . 34		6.3. Mixed Deployment Environment . . . . . . . . . . . . . . . 29
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 35		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
	6.1. Impersonation Attacks . . . . . . . . . . . . . . . . . . 36		8. Authors and Acknowledgments . . . . . . . . . . . . . . . . . 30
	6.2. Denial-of-Service Attacks . . . . . . . . . . . . . . . . 37		9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
	6.2.1. Flooding Attacks . . . . . . . . . . . . . . . . . . . 37		9.1. Normative references . . . . . . . . . . . . . . . . . . . 30
	6.2.2. Memory/Computational-Exhaustion DoS Attacks . . . . . 37		9.2. Informative references . . . . . . . . . . . . . . . . . . 30
	6.3. Mixed Deployment Environment . . . . . . . . . . . . . . . 38		Appendix A. Document Revision History . . . . . . . . . . . . . . 31
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38
	8. Authors and Acknowledgments . . . . . . . . . . . . . . . . . 39
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 39
	9.1. Normative references . . . . . . . . . . . . . . . . . . . 39
	9.2. Informative references . . . . . . . . . . . . . . . . . . 39
	Appendix A. Document Revision History . . . . . . . . . . . . . . 40
	1. Introduction and Scope		1. Introduction and Scope
	The Host Identity Protocol [RFC4423] (HIP) supports an architecture		The Host Identity Protocol [RFC4423] (HIP) supports an architecture
	that decouples the transport layer (TCP, UDP, etc.) from the		that decouples the transport layer (TCP, UDP, etc.) from the
	internetworking layer (IPv4 and IPv6) by using public/private key		internetworking layer (IPv4 and IPv6) by using public/private key
	pairs, instead of IP addresses, as host identities. When a host uses		pairs, instead of IP addresses, as host identities. When a host uses
	HIP, the overlying protocol sublayers (e.g., transport layer sockets		HIP, the overlying protocol sublayers (e.g., transport layer sockets
	and Encapsulating Security Payload (ESP) Security Associations (SAs))		and Encapsulating Security Payload (ESP) Security Associations (SAs))
	are instead bound to representations of these host identities, and		are instead bound to representations of these host identities, and
	the IP addresses are only used for packet forwarding. However, each		the IP addresses are only used for packet forwarding. However, each
	host must also know at least one IP address at which its peers are		host must also know at least one IP address at which its peers are
	reachable. Initially, these IP addresses are the ones used during		reachable. Initially, these IP addresses are the ones used during
	the HIP base exchange [RFC5201].		the HIP base exchange [RFC5201].
	One consequence of such a decoupling is that new solutions to		One consequence of such a decoupling is that new solutions to
	network-layer mobility and host multihoming are possible. There are		network-layer mobility and host multihoming are possible. There are
	potentially many variations of mobility and multihoming possible.		potentially many variations of mobility and multihoming possible.
	The scope of this document encompasses messaging and elements of		The scope of this document encompasses messaging and elements of
	procedure for basic network-level mobility and simple multihoming,		procedure for basic network-level host mobility, leaving more
	leaving more complicated scenarios and other variations for further		complicated scenarios and other variations for further study. More
	study. More specifically:		specifically:
	This document defines a generalized LOCATOR parameter for use in		This document defines a generalized LOCATOR parameter for use in
	HIP messages. The LOCATOR parameter allows a HIP host to notify a		HIP messages. The LOCATOR parameter allows a HIP host to notify a
	peer about alternate addresses at which it is reachable. The		peer about alternate addresses at which it is reachable. The
	LOCATORs may be merely IP addresses, or they may have additional		LOCATORs may be merely IP addresses, or they may have additional
	multiplexing and demultiplexing context to aid the packet handling		multiplexing and demultiplexing context to aid the packet handling
	in the lower layers. For instance, an IP address may need to be		in the lower layers. For instance, an IP address may need to be
	paired with an ESP Security Parameter Index (SPI) so that packets		paired with an ESP Security Parameter Index (SPI) so that packets
	are sent on the correct SA for a given address.		are sent on the correct SA for a given address.
	This document also specifies the messaging and elements of		This document also specifies the messaging and elements of
	procedure for end-host mobility of a HIP host -- the sequential		procedure for end-host mobility of a HIP host -- the sequential
	change in the preferred IP address used to reach a host. In		change in the preferred IP address used to reach a host. In
	particular, message flows to enable successful host mobility,		particular, message flows to enable successful host mobility,
	including address verification methods, are defined herein.		including address verification methods, are defined herein.
	However, while the same LOCATOR parameter is intended to support		However, while the same LOCATOR parameter is intended to support
	host multihoming (parallel support of a number of addresses), and		host multihoming (parallel support of a number of addresses), and
	experimentation is encouraged, detailed elements of procedure for		experimentation is encouraged, detailed elements of procedure for
	host multihoming are left for further study.		host multihoming are out of scope.
	While HIP can potentially be used with transports other than the ESP		While HIP can potentially be used with transports other than the ESP
	transport format [RFC5202], this document largely assumes the use of		transport format [RFC5202], this document largely assumes the use of
	ESP and leaves other transport formats for further study.		ESP and leaves other transport formats for further study.
	There are a number of situations where the simple end-to-end		There are a number of situations where the simple end-to-end
	readdressing functionality is not sufficient. These include the		readdressing functionality is not sufficient. These include the
	initial reachability of a mobile host, location privacy, simultaneous		initial reachability of a mobile host, location privacy, simultaneous
	mobility of both hosts, and some modes of NAT traversal. In these		mobility of both hosts, and some modes of NAT traversal. In these
	situations, there is a need for some helper functionality in the		situations, there is a need for some helper functionality in the
	network, such as a HIP rendezvous server [RFC5204]. Such		network, such as a HIP rendezvous server [RFC5204]. Such
	functionality is out of the scope of this document. We also do not		functionality is out of the scope of this document. We also do not
	consider localized mobility management extensions (i.e., mobility		consider localized mobility management extensions (i.e., mobility
	management techniques that do not involve directly signaling the		management techniques that do not involve directly signaling the
	correspondent node); this document is concerned with end-to-end		correspondent node); this document is concerned with end-to-end
	mobility. Finally, making underlying IP mobility transparent to the		mobility. Making underlying IP mobility transparent to the transport
	transport layer has implications on the proper response of transport		layer has implications on the proper response of transport congestion
	congestion control, path MTU selection, and Quality of Service (QoS).		control, path MTU selection, and Quality of Service (QoS).
	Transport-layer mobility triggers, and the proper transport response		Transport-layer mobility triggers, and the proper transport response
	to a HIP mobility or multihoming address change, are outside the		to a HIP mobility or multihoming address change, are outside the
	scope of this document.		scope of this document.
	2. Terminology and Conventions		2. Terminology and Conventions
	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 RFC 2119 [RFC2119].		document are to be interpreted as described in RFC 2119 [RFC2119].
	skipping to change at page 5, line 47		skipping to change at page 5, line 47
	The two most common examples are an IPv4 address and an IPv6		The two most common examples are an IPv4 address and an IPv6
	address. The set of possible addresses is a subset of the set of		address. The set of possible addresses is a subset of the set of
	possible locators.		possible locators.
	Preferred locator. A locator on which a host prefers to receive		Preferred locator. A locator on which a host prefers to receive
	data. With respect to a given peer, a host always has one active		data. With respect to a given peer, a host always has one active
	Preferred locator, unless there are no active locators. By		Preferred locator, unless there are no active locators. By
	default, the locators used in the HIP base exchange are the		default, the locators used in the HIP base exchange are the
	Preferred locators.		Preferred locators.
	Credit Based Authorization. A host must verify a mobile or		Credit Based Authorization. A host must verify a peer host's
	multihomed peer's reachability at a new locator. Credit-Based		reachability at a new locator. Credit-Based Authorization
	Authorization authorizes the peer to receive a certain amount of		authorizes the peer to receive a certain amount of data at the new
	data at the new locator before the result of such verification is		locator before the result of such verification is known.
	known.
	3. Protocol Model		3. Protocol Model
	This section is an overview; more detailed specification follows this		This section is an overview; more detailed specification follows this
	section.		section.
	3.1. Operating Environment		3.1. Operating Environment
	The Host Identity Protocol (HIP) [RFC5201] is a key establishment and		The Host Identity Protocol (HIP) [RFC5201] is a key establishment and
	parameter negotiation protocol. Its primary applications are for		parameter negotiation protocol. Its primary applications are for
	skipping to change at page 7, line 21		skipping to change at page 7, line 21
	| ---------		| ---------
	| |		| |
	---- ---------		---- ---------
	| MH |-> | HIP | {HIT_s, HIT_d, SPI} <-> {IP_s, IP_d, SPI}		| MH |-> | HIP | {HIT_s, HIT_d, SPI} <-> {IP_s, IP_d, SPI}
	---- ---------		---- ---------
	|		|
	---------		---------
	| IP |		| IP |
	---------		---------
	Figure 2: Architecture for HIP Mobility and Multihoming (MH)		Figure 2: Architecture for HIP Host Mobility (MH)
	Figure 2 depicts a layered architectural view of a HIP-enabled stack		Figure 2 depicts a layered architectural view of a HIP-enabled stack
	using the ESP transport format. In HIP, upper-layer protocols		using the ESP transport format. In HIP, upper-layer protocols
	(including TCP and ESP in this figure) are bound to Host Identity		(including TCP and ESP in this figure) are bound to Host Identity
	Tags (HITs) and not IP addresses. The HIP sublayer is responsible		Tags (HITs) and not IP addresses. The HIP sublayer is responsible
	for maintaining the binding between HITs and IP addresses. The SPI		for maintaining the binding between HITs and IP addresses. The SPI
	is used to associate an incoming packet with the right HITs. The		is used to associate an incoming packet with the right HITs. The
	block labeled "MH" is introduced below.		block labeled "MH" is introduced below.
	Consider first the case in which there is no mobility or multihoming,		Consider first the case in which there is no mobility or multihoming,
	skipping to change at page 7, line 43		skipping to change at page 7, line 43
	base exchange establishes the HITs in use between the hosts, the SPIs		base exchange establishes the HITs in use between the hosts, the SPIs
	to use for ESP, and the IP addresses (used in both the HIP signaling		to use for ESP, and the IP addresses (used in both the HIP signaling
	packets and ESP data packets). Note that there can only be one such		packets and ESP data packets). Note that there can only be one such
	set of bindings in the outbound direction for any given packet, and		set of bindings in the outbound direction for any given packet, and
	the only fields used for the binding at the HIP layer are the fields		the only fields used for the binding at the HIP layer are the fields
	exposed by ESP (the SPI and HITs). For the inbound direction, the		exposed by ESP (the SPI and HITs). For the inbound direction, the
	SPI is all that is required to find the right host context. ESP		SPI is all that is required to find the right host context. ESP
	rekeying events change the mapping between the HIT pair and SPI, but		rekeying events change the mapping between the HIT pair and SPI, but
	do not change the IP addresses.		do not change the IP addresses.
	Consider next a mobility event, in which a host is still single-homed		Consider next a mobility event, in which a host moves to another IP
	but moves to another IP address. Two things must occur in this case.		address. Two things must occur in this case. First, the peer must
	First, the peer must be notified of the address change using a HIP		be notified of the address change using a HIP UPDATE message.
	UPDATE message. Second, each host must change its local bindings at		Second, each host must change its local bindings at the HIP sublayer
	the HIP sublayer (new IP addresses). It may be that both the SPIs		(new IP addresses). It may be that both the SPIs and IP addresses
	and IP addresses are changed simultaneously in a single UPDATE; the		are changed simultaneously in a single UPDATE; the protocol described
	protocol described herein supports this. However, simultaneous		herein supports this. However, simultaneous movement of both hosts,
	movement of both hosts, notification of transport layer protocols of		notification of transport layer protocols of the path change, and
	the path change, and procedures for possibly traversing middleboxes		procedures for possibly traversing middleboxes are not covered by
	are not covered by this document.		this document.
	Finally, consider the case when a host is multihomed (has more than
	one globally routable address) and has multiple addresses available
	at the HIP layer as alternative locators for fault tolerance.
	Examples include the use of (possibly multiple) IPv4 and IPv6
	addresses on the same interface, or the use of multiple interfaces
	attached to different service providers. Such host multihoming
	generally necessitates that a separate ESP SA is maintained for each
	interface in order to prevent packets that arrive over different
	paths from falling outside of the ESP anti-replay window [RFC4303].
	Multihoming thus makes it possible that the bindings shown on the
	right side of Figure 2 are one to many (in the outbound direction,
	one HIT pair to multiple SPIs, and possibly then to multiple IP
	addresses). However, only one SPI and address pair can be used for
	any given packet, so the job of the "MH" block depicted above is to
	dynamically manipulate these bindings. Beyond locally managing such
	multiple bindings, the peer-to-peer HIP signaling protocol needs to
	be flexible enough to define the desired mappings between HITs, SPIs,
	and addresses, and needs to ensure that UPDATE messages are sent
	along the right network paths so that any HIP-aware middleboxes can
	observe the SPIs. This document does not specify the "MH" block, nor
	does it specify detailed elements of procedure for how to handle
	various multihoming (perhaps combined with mobility) scenarios. The
	"MH" block may apply to more general problems outside of HIP.
	However, this document does describe a basic multihoming case (one
	host adds one address to its initial address and notifies the peer)
	and leave more complicated scenarios for experimentation and future
	documents.
	3.1.1. Locator		3.1.1. Locator
	This document defines a generalization of an address called a		This document defines a generalization of an address called a
	"locator". A locator specifies a point-of-attachment to the network		"locator". A locator specifies a point-of-attachment to the network
	but may also include additional end-to-end tunneling or per-host		but may also include additional end-to-end tunneling or per-host
	demultiplexing context that affects how packets are handled below the		demultiplexing context that affects how packets are handled below the
	logical HIP sublayer of the stack. This generalization is useful		logical HIP sublayer of the stack. This generalization is useful
	because IP addresses alone may not be sufficient to describe how		because IP addresses alone may not be sufficient to describe how
	packets should be handled below HIP. For example, in a host		packets should be handled below HIP. For example, in a host
	skipping to change at page 9, line 28		skipping to change at page 8, line 49
	the host is able to receive packets that are protected using a HIP		the host is able to receive packets that are protected using a HIP
	created ESP SA from any address. Thus, a host can change its IP		created ESP SA from any address. Thus, a host can change its IP
	address and continue to send packets to its peers without necessarily		address and continue to send packets to its peers without necessarily
	rekeying. However, the peers are not able to send packets to these		rekeying. However, the peers are not able to send packets to these
	new addresses before they can reliably and securely update the set of		new addresses before they can reliably and securely update the set of
	addresses that they associate with the sending host. Furthermore,		addresses that they associate with the sending host. Furthermore,
	mobility may change the path characteristics in such a manner that		mobility may change the path characteristics in such a manner that
	reordering occurs and packets fall outside the ESP anti-replay window		reordering occurs and packets fall outside the ESP anti-replay window
	for the SA, thereby requiring rekeying.		for the SA, thereby requiring rekeying.
	3.1.3. Multihoming Overview
	A related operational configuration is host multihoming, in which a
	host has multiple locators simultaneously rather than sequentially,
	as in the case of mobility. By using the LOCATOR parameter defined
	herein, a host can inform its peers of additional (multiple) locators
	at which it can be reached, and can declare a particular locator as a
	"preferred" locator. Although this document defines a basic
	mechanism for multihoming, it does not define detailed policies and
	procedures, such as which locators to choose when more than one pair
	is available, the operation of simultaneous mobility and multihoming,
	source address selection policies (beyond those specified in
	[RFC3484]), and the implications of multihoming on transport
	protocols and ESP anti-replay windows. Additional definitions of
	HIP-based multihoming are expected to be part of future documents.
	3.2. Protocol Overview		3.2. Protocol Overview
	In this section, we briefly introduce a number of usage scenarios for		In this section, we briefly introduce a number of usage scenarios for
	HIP mobility and multihoming. These scenarios assume that HIP is		HIP host mobility. These scenarios assume that HIP is being used
	being used with the ESP transform [RFC5202], although other scenarios		with the ESP transform [RFC5202], although other scenarios may be
	may be defined in the future. To understand these usage scenarios,		defined in the future. To understand these usage scenarios, the
	the reader should be at least minimally familiar with the HIP		reader should be at least minimally familiar with the HIP protocol
	protocol specification [RFC5201]. However, for the (relatively)		specification [RFC5201]. However, for the (relatively) uninitiated
	uninitiated reader, it is most important to keep in mind that in HIP		reader, it is most important to keep in mind that in HIP the actual
	the actual payload traffic is protected with ESP, and that the ESP		payload traffic is protected with ESP, and that the ESP SPI acts as
	SPI acts as an index to the right host-to-host context. More		an index to the right host-to-host context. More specification
	specification details are found later in Section 4 and Section 5.		details are found later in Section 4 and Section 5.
	The scenarios below assume that the two hosts have completed a single		The scenarios below assume that the two hosts have completed a single
	HIP base exchange with each other. Both of the hosts therefore have		HIP base exchange with each other. Both of the hosts therefore have
	one incoming and one outgoing SA. Further, each SA uses the same		one incoming and one outgoing SA. Further, each SA uses the same
	pair of IP addresses, which are the ones used in the base exchange.		pair of IP addresses, which are the ones used in the base exchange.
	The readdressing protocol is an asymmetric protocol where a mobile or		The readdressing protocol is an asymmetric protocol where a mobile
	multihomed host informs a peer host about changes of IP addresses on		host informs a peer host about changes of IP addresses on affected
	affected SPIs. The readdressing exchange is designed to be		SPIs. The readdressing exchange is designed to be piggybacked on
	piggybacked on existing HIP exchanges. The majority of the packets		existing HIP exchanges. The majority of the packets on which the
	on which the LOCATOR parameters are expected to be carried are UPDATE		LOCATOR parameters are expected to be carried are UPDATE packets.
	packets. However, some implementations may want to experiment with		However, some implementations may want to experiment with sending
	sending LOCATOR parameters also on other packets, such as R1, I2, and		LOCATOR parameters also on other packets, such as R1, I2, and NOTIFY.
	NOTIFY.
	The scenarios below at times describe addresses as being in either an		The scenarios below at times describe addresses as being in either an
	ACTIVE, VERIFIED, or DEPRECATED state. From the perspective of a		ACTIVE, VERIFIED, or DEPRECATED state. From the perspective of a
	host, newly-learned addresses of the peer must be verified before put		host, newly-learned addresses of the peer must be verified before put
	into active service, and addresses removed by the peer are put into a		into active service, and addresses removed by the peer are put into a
	deprecated state. Under limited conditions described below		deprecated state. Under limited conditions described below
	(Section 5.6), an UNVERIFIED address may be used. The addressing		(Section 5.6), an UNVERIFIED address may be used. The addressing
	states are defined more formally in Section 5.1.		states are defined more formally in Section 5.1.
	Hosts that use link-local addresses as source addresses in their HIP		Hosts that use link-local addresses as source addresses in their HIP
	skipping to change at page 12, line 32		skipping to change at page 11, line 32
	UPDATE(ESP_INFO, LOCATOR, SEQ, [DIFFIE_HELLMAN])		UPDATE(ESP_INFO, LOCATOR, SEQ, [DIFFIE_HELLMAN])
	----------------------------------->		----------------------------------->
	UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST)		UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST)
	<-----------------------------------		<-----------------------------------
	UPDATE(ACK, ECHO_RESPONSE)		UPDATE(ACK, ECHO_RESPONSE)
	----------------------------------->		----------------------------------->
	Figure 4: Readdress with Mobile-Initiated Rekey		Figure 4: Readdress with Mobile-Initiated Rekey
	3.2.3. Host Multihoming		3.2.3. Using LOCATORs across Addressing Realms
	A (mobile or stationary) host may sometimes have more than one
	interface or global address. The host may notify the peer host of
	the additional interface or address by using the LOCATOR parameter.
	To avoid problems with the ESP anti-replay window, a host SHOULD use
	a different SA for each interface or address used to receive packets
	from the peer host when multiple locator pairs are being used
	simultaneously rather than sequentially.
	When more than one locator is provided to the peer host, the host
	SHOULD indicate which locator is preferred (the locator on which the
	host prefers to receive traffic). By default, the addresses used in
	the base exchange are preferred until indicated otherwise.
	In the multihoming case, the sender may also have multiple valid
	locators from which to source traffic. In practice, a HIP
	association in a multihoming configuration may have both a preferred
	peer locator and a preferred local locator, although rules for source
	address selection should ultimately govern the selection of the
	source locator based on the destination locator.
	Although the protocol may allow for configurations in which there is
	an asymmetric number of SAs between the hosts (e.g., one host has two
	interfaces and two inbound SAs, while the peer has one interface and
	one inbound SA), it is RECOMMENDED that inbound and outbound SAs be
	created pairwise between hosts. When an ESP_INFO arrives to rekey a
	particular outbound SA, the corresponding inbound SA should be also
	rekeyed at that time. Although asymmetric SA configurations might be
	experimented with, their usage may constrain interoperability at this
	time. However, it is recommended that implementations attempt to
	support peers that prefer to use non-paired SAs. It is expected that
	this section and behavior will be modified in future revisions of
	this protocol, once the issue and its implications are better
	understood.
	Consider the case between two hosts, one single-homed and one
	multihomed. The multihomed host may decide to inform the single-
	homed host about its other address. It is RECOMMENDED that the
	multihomed host set up a new SA pair for use on this new address. To
	do this, the multihomed host sends a LOCATOR with an ESP_INFO,
	indicating the request for a new SA by setting the OLD SPI value to
	zero, and the NEW SPI value to the newly created incoming SPI. A
	Locator Type of "1" is used to associate the new address with the new
	SPI. The LOCATOR parameter also contains a second Type "1" locator,
	that of the original address and SPI. To simplify parameter
	processing and avoid explicit protocol extensions to remove locators,
	each LOCATOR parameter MUST list all locators in use on a connection
	(a complete listing of inbound locators and SPIs for the host). The
	multihomed host waits for an ESP_INFO (new outbound SA) from the peer
	and an ACK of its own UPDATE. As in the mobility case, the peer host
	must perform an address verification before actively using the new
	address. Figure 5 illustrates this scenario.
	Multi-homed Host Peer Host
	UPDATE(ESP_INFO, LOCATOR, SEQ, [DIFFIE_HELLMAN])
	----------------------------------->
	UPDATE(ESP_INFO, SEQ, ACK, [DIFFIE_HELLMAN,] ECHO_REQUEST)
	<-----------------------------------
	UPDATE(ACK, ECHO_RESPONSE)
	----------------------------------->
	Figure 5: Basic Multihoming Scenario
	In multihoming scenarios, it is important that hosts receiving
	UPDATEs associate them correctly with the destination address used in
	the packet carrying the UPDATE. When processing inbound LOCATORs
	that establish new security associations on an interface with
	multiple addresses, a host uses the destination address of the UPDATE
	containing the LOCATOR as the local address to which the LOCATOR plus
	ESP_INFO is targeted. This is because hosts may send UPDATEs with
	the same (locator) IP address to different peer addresses -- this has
	the effect of creating multiple inbound SAs implicitly affiliated
	with different peer source addresses.
	3.2.4. Site Multihoming
	A host may have an interface that has multiple globally routable IP
	addresses. Such a situation may be a result of the site having
	multiple upper Internet Service Providers, or just because the site
	provides all hosts with both IPv4 and IPv6 addresses. The host
	should stay reachable at all or any subset of the currently available
	global routable addresses, independent of how they are provided.
	This case is handled the same as if there were different IP
	addresses, described above in Section 3.2.3. Note that a single
	interface may experience site multihoming while the host itself may
	have multiple interfaces.
	Note that a host may be multihomed and mobile simultaneously, and
	that a multihomed host may want to protect the location of some of
	its interfaces while revealing the real IP address of some others.
	This document does not presently specify additional site multihoming
	extensions to HIP; further alignment with the IETF shim6 working
	group may be considered in the future.
	3.2.5. Dual host multihoming
	Consider the case in which both hosts would like to add an additional
	address after the base exchange completes. In Figure 6, consider
	that host1, which used address addr1a in the base exchange to set up
	SPI1a and SPI2a, wants to add address addr1b. It would send an
	UPDATE with LOCATOR (containing the address addr1b) to host2, using
	destination address addr2a, and a new set of SPIs would be added
	between hosts 1 and 2 (call them SPI1b and SPI2b -- not shown in the
	figure). Next, consider host2 deciding to add addr2b to the
	relationship. Host2 must select one of host1's addresses towards
	which to initiate an UPDATE. It may choose to initiate an UPDATE to
	addr1a, addr1b, or both. If it chooses to send to both, then a full
	mesh (four SA pairs) of SAs would exist between the two hosts. This
	is the most general case; it often may be the case that hosts
	primarily establish new SAs only with the peer's Preferred locator.
	The readdressing protocol is flexible enough to accommodate this
	choice.
	-<- SPI1a -- -- SPI2a ->-
	host1 < > addr1a <---> addr2a < > host2
	->- SPI2a -- -- SPI1a -<-
	addr1b <---> addr2a (second SA pair)
	addr1a <---> addr2b (third SA pair)
	addr1b <---> addr2b (fourth SA pair)
	Figure 6: Dual Multihoming Case in Which Each Host Uses LOCATOR to
	Add a Second Address
	3.2.6. Combined Mobility and Multihoming
	It looks likely that in the future, many mobile hosts will be
	simultaneously mobile and multihomed, i.e., have multiple mobile
	interfaces. Furthermore, if the interfaces use different access
	technologies, it is fairly likely that one of the interfaces may
	appear stable (retain its current IP address) while some other(s) may
	experience mobility (undergo IP address change).
	The use of LOCATOR plus ESP_INFO should be flexible enough to handle
	most such scenarios, although more complicated scenarios have not
	been studied so far.
	3.2.7. Using LOCATORs across Addressing Realms
	It is possible for HIP associations to migrate to a state in which		It is possible for HIP associations to migrate to a state in which
	both parties are only using locators in different addressing realms.		both parties are only using locators in different addressing realms.
	For example, the two hosts may initiate the HIP association when both		For example, the two hosts may initiate the HIP association when both
	are using IPv6 locators, then one host may loose its IPv6		are using IPv6 locators, then one host may loose its IPv6
	connectivity and obtain an IPv4 address. In such a case, some type		connectivity and obtain an IPv4 address. In such a case, some type
	of mechanism for interworking between the different realms must be		of mechanism for interworking between the different realms must be
	employed; such techniques are outside the scope of the present text.		employed; such techniques are outside the scope of the present text.
	The basic problem in this example is that the host readdressing to		The basic problem in this example is that the host readdressing to
	IPv4 does not know a corresponding IPv4 address of the peer. This		IPv4 does not know a corresponding IPv4 address of the peer. This
	may be handled (experimentally) by possibly configuring this address		may be handled (experimentally) by possibly configuring this address
	information manually or in the DNS, or the hosts exchange both IPv4		information manually or in the DNS, or the hosts exchange both IPv4
	and IPv6 addresses in the locator.		and IPv6 addresses in the locator.
	3.2.8. Network Renumbering		3.2.4. Network Renumbering
	It is expected that IPv6 networks will be renumbered much more often		It is expected that IPv6 networks will be renumbered much more often
	than most IPv4 networks. From an end-host point of view, network		than most IPv4 networks. From an end-host point of view, network
	renumbering is similar to mobility.		renumbering is similar to mobility.
	3.2.9. Initiating the Protocol in R1 or I2
	A Responder host MAY include a LOCATOR parameter in the R1 packet
	that it sends to the Initiator. This parameter MUST be protected by
	the R1 signature. If the R1 packet contains LOCATOR parameters with
	a new Preferred locator, the Initiator SHOULD directly set the new
	Preferred locator to status ACTIVE without performing address
	verification first, and MUST send the I2 packet to the new Preferred
	locator. The I1 destination address and the new Preferred locator
	may be identical. All new non-preferred locators must still undergo
	address verification once the base exchange completes.
	Initiator Responder
	R1 with LOCATOR
	<-----------------------------------
	record additional addresses
	change responder address
	I2 sent to newly indicated preferred address
	----------------------------------->
	(process normally)
	R2
	<-----------------------------------
	(process normally, later verification of non-preferred locators)
	Figure 7: LOCATOR Inclusion in R1
	An Initiator MAY include one or more LOCATOR parameters in the I2
	packet, independent of whether or not there was a LOCATOR parameter
	in the R1. These parameters MUST be protected by the I2 signature.
	Even if the I2 packet contains LOCATOR parameters, the Responder MUST
	still send the R2 packet to the source address of the I2. The new
	Preferred locator SHOULD be identical to the I2 source address. If
	the I2 packet contains LOCATOR parameters, all new locators must
	undergo address verification as usual, and the ESP traffic that
	subsequently follows should use the Preferred locator.
	Initiator Responder
	I2 with LOCATOR
	----------------------------------->
	(process normally)
	record additional addresses
	R2 sent to source address of I2
	<-----------------------------------
	(process normally)
	Figure 8: LOCATOR Inclusion in I2
	The I1 and I2 may be arriving from different source addresses if the
	LOCATOR parameter is present in R1. In this case, implementations
	simultaneously using multiple pre-created R1s, indexed by Initiator
	IP addresses, may inadvertently fail the puzzle solution of I2
	packets due to a perceived puzzle mismatch. See, for instance, the
	example in Appendix A of [RFC5201]. As a solution, the Responder's
	puzzle indexing mechanism must be flexible enough to accommodate the
	situation when R1 includes a LOCATOR parameter.
	3.3. Other Considerations		3.3. Other Considerations
	3.3.1. Address Verification		3.3.1. Address Verification
	When a HIP host receives a set of locators from another HIP host in a		When a HIP host receives a set of locators from another HIP host in a
	LOCATOR, it does not necessarily know whether the other host is		LOCATOR, it does not necessarily know whether the other host is
	actually reachable at the claimed addresses. In fact, a malicious		actually reachable at the claimed addresses. In fact, a malicious
	peer host may be intentionally giving bogus addresses in order to		peer host may be intentionally giving bogus addresses in order to
	cause a packet flood towards the target addresses [RFC4225].		cause a packet flood towards the target addresses [RFC4225].
	Likewise, viral software may have compromised the peer host,		Likewise, viral software may have compromised the peer host,
	skipping to change at page 18, line 20		skipping to change at page 13, line 11
	amplification could be obtained this way.		amplification could be obtained this way.
	On this basis, rather than eliminating malicious packet redirection		On this basis, rather than eliminating malicious packet redirection
	in the first place, Credit-Based Authorization prevents		in the first place, Credit-Based Authorization prevents
	amplifications. This is accomplished by limiting the data a host can		amplifications. This is accomplished by limiting the data a host can
	send to an unverified address of a peer by the data recently received		send to an unverified address of a peer by the data recently received
	from that peer. Redirection-based flooding attacks thus become less		from that peer. Redirection-based flooding attacks thus become less
	attractive than, for example, pure direct flooding, where the		attractive than, for example, pure direct flooding, where the
	attacker itself sends bogus packets to the victim.		attacker itself sends bogus packets to the victim.
	Figure 9 illustrates Credit-Based Authorization: Host B measures the		Figure 5 illustrates Credit-Based Authorization: Host B measures the
	amount of data recently received from peer A and, when A readdresses,		amount of data recently received from peer A and, when A readdresses,
	sends packets to A's new, unverified address as long as the sum of		sends packets to A's new, unverified address as long as the sum of
	the packet sizes does not exceed the measured, received data volume.		the packet sizes does not exceed the measured, received data volume.
	When insufficient credit is left, B stops sending further packets to		When insufficient credit is left, B stops sending further packets to
	A until A's address becomes ACTIVE. The address changes may be due		A until A's address becomes ACTIVE. The address changes may be due
	to mobility, multihoming, or any other reason. Not shown in Figure 9		to mobility, multihoming, or any other reason. Not shown in Figure 5
	are the results of credit aging (Section 5.6.2), a mechanism used to		are the results of credit aging (Section 5.6.2), a mechanism used to
	dampen possible time-shifting attacks.		dampen possible time-shifting attacks.
	+-------+ +-------+		+-------+ +-------+
	| A | | B |		| A | | B |
	+-------+ +-------+		+-------+ +-------+
	| |		| |
	address |------------------------------->| credit += size(packet)		address |------------------------------->| credit += size(packet)
	ACTIVE | |		ACTIVE | |
	|------------------------------->| credit += size(packet)		|------------------------------->| credit += size(packet)
	skipping to change at page 19, line 28		skipping to change at page 13, line 44
	|<-------------------------------| credit -= size(packet)		|<-------------------------------| credit -= size(packet)
	| |		| |
	|<-------------------------------| credit -= size(packet)		|<-------------------------------| credit -= size(packet)
	| X credit < size(packet)		| X credit < size(packet)
	| | => do not send packet!		| | => do not send packet!
	+ address verification concludes |		+ address verification concludes |
	address | |		address | |
	ACTIVE |<-------------------------------| do not change credit		ACTIVE |<-------------------------------| do not change credit
	| |		| |
	Figure 9: Readdressing Scenario		Figure 5: Readdressing Scenario
	3.3.3. Preferred Locator		3.3.3. Preferred Locator
	When a host has multiple locators, the peer host must decide which to		When a host has multiple locators, the peer host must decide which to
	use for outbound packets. It may be that a host would prefer to		use for outbound packets. It may be that a host would prefer to
	receive data on a particular inbound interface. HIP allows a		receive data on a particular inbound interface. HIP allows a
	particular locator to be designated as a Preferred locator and		particular locator to be designated as a Preferred locator and
	communicated to the peer (see Section 4).		communicated to the peer (see Section 4).
	In general, when multiple locators are used for a session, there is
	the question of using multiple locators for failover only or for
	load-balancing. Due to the implications of load-balancing on the
	transport layer that still need to be worked out, this document
	assumes that multiple locators are used primarily for failover. An
	implementation may use ICMP interactions, reachability checks, or
	other means to detect the failure of a locator.
	3.3.4. Interaction with Security Associations
	This document specifies a new HIP protocol parameter, the LOCATOR
	parameter (see Section 4), that allows the hosts to exchange
	information about their locator(s) and any changes in their
	locator(s). The logical structure created with LOCATOR parameters
	has three levels: hosts, Security Associations (SAs) indexed by
	Security Parameter Indices (SPIs), and addresses.
	The relation between these levels for an association constructed as
	defined in the base specification [RFC5201] and ESP transform
	[RFC5202] is illustrated in Figure 10.
	-<- SPI1a -- -- SPI2a ->-
	host1 < > addr1a <---> addr2a < > host2
	->- SPI2a -- -- SPI1a -<-
	Figure 10: Relation between Hosts, SPIs, and Addresses (Base
	Specification)
	In Figure 10, host1 and host2 negotiate two unidirectional SAs, and
	each host selects the SPI value for its inbound SA. The addresses
	addr1a and addr2a are the source addresses that the hosts use in the
	base HIP exchange. These are the "preferred" (and only) addresses
	conveyed to the peer for use on each SA. That is, although packets
	sent to any of the hosts' interfaces may be accepted on the inbound
	SA, the peer host in general knows of only the single destination
	address learned in the base exchange (e.g., for host1, it sends a
	packet on SPI2a to addr2a to reach host2), unless other mechanisms
	exist to learn of new addresses.
	In general, the bindings that exist in an implementation
	corresponding to this document can be depicted as shown in Figure 11.
	In this figure, a host can have multiple inbound SPIs (and, not
	shown, multiple outbound SPIs) associated with another host.
	Furthermore, each SPI may have multiple addresses associated with it.
	These addresses that are bound to an SPI are not used to lookup the
	incoming SA. Rather, the addresses are those that are provided to
	the peer host, as hints for which addresses to use to reach the host
	on that SPI. The LOCATOR parameter is used to change the set of
	addresses that a peer associates with a particular SPI.
	address11
	/
	SPI1 - address12
	/
	/ address21
	host -- SPI2 <
	\ address22
	\
	SPI3 - address31
	\
	address32
	Figure 11: Relation between Hosts, SPIs, and Addresses (General Case)
	A host may establish any number of security associations (or SPIs)
	with a peer. The main purpose of having multiple SPIs with a peer is
	to group the addresses into collections that are likely to experience
	fate sharing. For example, if the host needs to change its addresses
	on SPI2, it is likely that both address21 and address22 will
	simultaneously become obsolete. In a typical case, such SPIs may
	correspond with physical interfaces; see below. Note, however, that
	especially in the case of site multihoming, one of the addresses may
	become unreachable while the other one still works. In the typical
	case, however, this does not require the host to inform its peers
	about the situation, since even the non-working address still
	logically exists.
	A basic property of HIP SAs is that the inbound IP address is not
	used to lookup the incoming SA. Therefore, in Figure 11, it may seem
	unnecessary for address31, for example, to be associated only with
	SPI3 -- in practice, a packet may arrive to SPI1 via destination
	address address31 as well. However, the use of different source and
	destination addresses typically leads to different paths, with
	different latencies in the network, and if packets were to arrive via
	an arbitrary destination IP address (or path) for a given SPI, the
	reordering due to different latencies may cause some packets to fall
	outside of the ESP anti-replay window. For this reason, HIP provides
	a mechanism to affiliate destination addresses with inbound SPIs,
	when there is a concern that anti-replay windows might be violated.
	In this sense, we can say that a given inbound SPI has an "affinity"
	for certain inbound IP addresses, and this affinity is communicated
	to the peer host. Each physical interface SHOULD have a separate SA,
	unless the ESP anti-replay window is loose.
	Moreover, even when the destination addresses used for a particular
	SPI are held constant, the use of different source interfaces may
	also cause packets to fall outside of the ESP anti-replay window,
	since the path traversed is often affected by the source address or
	interface used. A host has no way to influence the source interface
	on which a peer sends its packets on a given SPI. A host SHOULD
	consistently use the same source interface and address when sending
	to a particular destination IP address and SPI. For this reason, a
	host may find it useful to change its SPI or at least reset its ESP
	anti-replay window when the peer host readdresses.
	An address may appear on more than one SPI. This creates no
	ambiguity since the receiver will ignore the IP addresses during SA
	lookup anyway. However, this document does not specify such cases.
	When the LOCATOR parameter is sent in an UPDATE packet, then the
	receiver will respond with an UPDATE acknowledgment. When the
	LOCATOR parameter is sent in an R1 or I2 packet, the base exchange
	retransmission mechanism will confirm its successful delivery.
	LOCATORs may experimentally be used in NOTIFY packets; in this case,
	the recipient MUST consider the LOCATOR as informational and not
	immediately change the current preferred address, but can test the
	additional locators when the need arises. The use of the LOCATOR in
	a NOTIFY message may not be compatible with middleboxes.
	4. LOCATOR Parameter Format		4. LOCATOR Parameter Format
	The LOCATOR parameter is a critical parameter as defined by		The LOCATOR parameter is a critical parameter as defined by
	[RFC5201]. It consists of the standard HIP parameter Type and Length		[RFC5201]. It consists of the standard HIP parameter Type and Length
	fields, plus zero or more Locator sub-parameters. Each Locator sub-		fields, plus zero or more Locator sub-parameters. Each Locator sub-
	parameter contains a Traffic Type, Locator Type, Locator Length,		parameter contains a Traffic Type, Locator Type, Locator Length,
	Preferred locator bit, Locator Lifetime, and a Locator encoding. A		Preferred locator bit, Locator Lifetime, and a Locator encoding. A
	LOCATOR containing zero Locator fields is permitted but has the		LOCATOR containing zero Locator fields is permitted but has the
	effect of deprecating all addresses.		effect of deprecating all addresses.
	skipping to change at page 23, line 32		skipping to change at page 14, line 44
	| Traffic Type | Locator Type | Locator Length | Reserved |P|		| Traffic Type | Locator Type | Locator Length | Reserved |P|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Locator Lifetime |		| Locator Lifetime |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Locator |		| Locator |
	| |		| |
	| |		| |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 12: LOCATOR Parameter Format		Figure 6: LOCATOR Parameter Format
	Type: 193		Type: 193
	Length: Length in octets, excluding Type and Length fields, and		Length: Length in octets, excluding Type and Length fields, and
	excluding padding.		excluding padding.
	Traffic Type: Defines whether the locator pertains to HIP signaling,		Traffic Type: Defines whether the locator pertains to HIP signaling,
	user data, or both.		user data, or both.
	Locator Type: Defines the semantics of the Locator field.		Locator Type: Defines the semantics of the Locator field.
	Locator Length: Defines the length of the Locator field, in units of		Locator Length: Defines the length of the Locator field, in units of
	4-byte words (Locators up to a maximum of 4*255 octets are		4-byte words (Locators up to a maximum of 4*255 octets are
	skipping to change at page 27, line 41		skipping to change at page 19, line 4
	host moves to another link. In any case, link-local addresses MUST		host moves to another link. In any case, link-local addresses MUST
	NOT be announced to a peer unless that peer is known to be on the		NOT be announced to a peer unless that peer is known to be on the
	same link.		same link.
	Once the host has decided on the groups and assignment of addresses		Once the host has decided on the groups and assignment of addresses
	to the SPIs, it creates a LOCATOR parameter that serves as a complete		to the SPIs, it creates a LOCATOR parameter that serves as a complete
	representation of the addresses and affiliated SPIs intended for		representation of the addresses and affiliated SPIs intended for
	active use. We now describe a few cases introduced in Section 3.2.		active use. We now describe a few cases introduced in Section 3.2.
	We assume that the Traffic Type for each locator is set to "0" (other		We assume that the Traffic Type for each locator is set to "0" (other
	values for Traffic Type may be specified in documents that separate		values for Traffic Type may be specified in documents that separate
	the HIP control plane from data plane traffic). Other mobility and		the HIP control plane from data plane traffic). Other mobility cases
	multihoming cases are possible but are left for further		are possible but are left for further experimentation.
	experimentation.
	1. Host mobility with no multihoming and no rekeying. The mobile		1. Host mobility with no multihoming and no rekeying. The mobile
	host creates a single UPDATE containing a single ESP_INFO with a		host creates a single UPDATE containing a single ESP_INFO with a
	single LOCATOR parameter. The ESP_INFO contains the current		single LOCATOR parameter. The ESP_INFO contains the current
	value of the SPI in both the OLD SPI and NEW SPI fields. The		value of the SPI in both the OLD SPI and NEW SPI fields. The
	LOCATOR contains a single Locator with a "Locator Type" of "1";		LOCATOR contains a single Locator with a "Locator Type" of "1";
	the SPI must match that of the ESP_INFO. The Preferred bit		the SPI must match that of the ESP_INFO. The Preferred bit
	SHOULD be set and the "Locator Lifetime" is set according to		SHOULD be set and the "Locator Lifetime" is set according to
	local policy. The UPDATE also contains a SEQ parameter as usual.		local policy. The UPDATE also contains a SEQ parameter as usual.
	This packet is retransmitted as defined in the HIP protocol		This packet is retransmitted as defined in the HIP protocol
	skipping to change at page 28, line 22		skipping to change at page 19, line 32
	single LOCATOR parameter (with a single address). The ESP_INFO		single LOCATOR parameter (with a single address). The ESP_INFO
	contains the current value of the SPI in the OLD SPI and the new		contains the current value of the SPI in the OLD SPI and the new
	value of the SPI in the NEW SPI, and a KEYMAT Index as selected		value of the SPI in the NEW SPI, and a KEYMAT Index as selected
	by local policy. Optionally, the host may choose to initiate a		by local policy. Optionally, the host may choose to initiate a
	Diffie Hellman rekey by including a DIFFIE_HELLMAN parameter.		Diffie Hellman rekey by including a DIFFIE_HELLMAN parameter.
	The LOCATOR contains a single Locator with "Locator Type" of "1";		The LOCATOR contains a single Locator with "Locator Type" of "1";
	the SPI must match that of the NEW SPI in the ESP_INFO.		the SPI must match that of the NEW SPI in the ESP_INFO.
	Otherwise, the steps are identical to the case in which no		Otherwise, the steps are identical to the case in which no
	rekeying is initiated.		rekeying is initiated.
	3. Host multihoming (addition of an address). We only describe the
	simple case of adding an additional address to a (previously)
	single-homed, non-mobile host. The host SHOULD set up a new SA
	pair between this new address and the preferred address of the
	peer host. To do this, the multihomed host creates a new inbound
	SA and creates a new SPI. For the outgoing UPDATE message, it
	inserts an ESP_INFO parameter with an OLD SPI field of "0", a NEW
	SPI field corresponding to the new SPI, and a KEYMAT Index as
	selected by local policy. The host adds to the UPDATE message a
	LOCATOR with two Type "1" Locators: the original address and SPI
	active on the association, and the new address and new SPI being
	added (with the SPI matching the NEW SPI contained in the
	ESP_INFO). The Preferred bit SHOULD be set depending on the
	policy to tell the peer host which of the two locators is
	preferred. The UPDATE also contains a SEQ parameter and
	optionally a DIFFIE_HELLMAN parameter, and follows rekeying
	procedures with respect to this new address. The UPDATE message
	SHOULD be sent to the peer's Preferred address with a source
	address corresponding to the new locator.
	The sending of multiple LOCATORs, locators with Locator Type "0", and		The sending of multiple LOCATORs, locators with Locator Type "0", and
	multiple ESP_INFO parameters is for further study. Note that the		multiple ESP_INFO parameters is for further study. Note that the
	inclusion of LOCATOR in an R1 packet requires the use of Type "0"		inclusion of LOCATOR in an R1 packet requires the use of Type "0"
	locators since no SAs are set up at that point.		locators since no SAs are set up at that point.
	5.3. Handling Received LOCATORs		5.3. Handling Received LOCATORs
	A host SHOULD be prepared to receive a LOCATOR parameter in the		A host SHOULD be prepared to receive a LOCATOR parameter in the
	following HIP packets: R1, I2, UPDATE, and NOTIFY.		following HIP packets: R1, I2, UPDATE, and NOTIFY.
	skipping to change at page 31, line 26		skipping to change at page 22, line 16
	Note that in the case of receiving a LOCATOR in an R1 and replying		Note that in the case of receiving a LOCATOR in an R1 and replying
	with an I2 to the new address in the LOCATOR, receiving the		with an I2 to the new address in the LOCATOR, receiving the
	corresponding R2 is sufficient proof of reachability for the		corresponding R2 is sufficient proof of reachability for the
	Responder's preferred address. Since further address verification of		Responder's preferred address. Since further address verification of
	such an address can impede the HIP-base exchange, a host MUST NOT		such an address can impede the HIP-base exchange, a host MUST NOT
	separately verify reachability of a new Preferred locator that was		separately verify reachability of a new Preferred locator that was
	received on an R1.		received on an R1.
	In some cases, it MAY be sufficient to use the arrival of data on a		In some cases, it MAY be sufficient to use the arrival of data on a
	newly advertised SA as implicit address reachability verification as		newly advertised SA as implicit address reachability verification as
	depicted in Figure 13, instead of waiting for the confirmation via a		depicted in Figure 7, instead of waiting for the confirmation via a
	HIP packet. In this case, a host advertising a new SPI as part of		HIP packet. In this case, a host advertising a new SPI as part of
	its address reachability check SHOULD be prepared to receive traffic		its address reachability check SHOULD be prepared to receive traffic
	on the new SA.		on the new SA.
	Mobile host Peer host		Mobile host Peer host
	prepare incoming SA		prepare incoming SA
	NEW SPI in ESP_INFO (UPDATE)		NEW SPI in ESP_INFO (UPDATE)
	<-----------------------------------		<-----------------------------------
	switch to new outgoing SA		switch to new outgoing SA
	data on new SA		data on new SA
	----------------------------------->		----------------------------------->
	mark address ACTIVE		mark address ACTIVE
	Figure 13: Address Activation Via Use of a New SA		Figure 7: Address Activation Via Use of a New SA
	When address verification is in progress for a new Preferred locator,		When address verification is in progress for a new Preferred locator,
	the host SHOULD select a different locator listed as ACTIVE, if one		the host SHOULD select a different locator listed as ACTIVE, if one
	such locator is available, to continue communications until address		such locator is available, to continue communications until address
	verification completes. Alternatively, the host MAY use the new		verification completes. Alternatively, the host MAY use the new
	Preferred locator while in UNVERIFIED status to the extent Credit-		Preferred locator while in UNVERIFIED status to the extent Credit-
	Based Authorization permits. Credit-Based Authorization is explained		Based Authorization permits. Credit-Based Authorization is explained
	in Section 5.6. Once address verification succeeds, the status of		in Section 5.6. Once address verification succeeds, the status of
	the new Preferred locator changes to ACTIVE.		the new Preferred locator changes to ACTIVE.
	skipping to change at page 33, line 22		skipping to change at page 24, line 9
	status ACTIVE is available, the host checks whether it can send the		status ACTIVE is available, the host checks whether it can send the
	packet to the UNVERIFIED locator. The packet SHOULD be sent if the		packet to the UNVERIFIED locator. The packet SHOULD be sent if the
	value of the credit counter is higher than the size of the outbound		value of the credit counter is higher than the size of the outbound
	packet. If the credit counter is too low, the packet MUST be		packet. If the credit counter is too low, the packet MUST be
	discarded or buffered until address verification succeeds. When a		discarded or buffered until address verification succeeds. When a
	packet is sent to a peer at an UNVERIFIED locator, the peer's credit		packet is sent to a peer at an UNVERIFIED locator, the peer's credit
	counter MUST be reduced by the size of the packet. The peer's credit		counter MUST be reduced by the size of the packet. The peer's credit
	counter is not affected by packets that the host sends to an ACTIVE		counter is not affected by packets that the host sends to an ACTIVE
	locator of that peer.		locator of that peer.
	Figure 14 depicts the actions taken by the host when a packet is		Figure 8 depicts the actions taken by the host when a packet is
	received. Figure 15 shows the decision chain in the event a packet		received. Figure 9 shows the decision chain in the event a packet is
	is sent.		sent.
	Inbound		Inbound
	packet		packet
	|		|
	| +----------------+ +---------------+		| +----------------+ +---------------+
	| | Increase | | Deliver |		| | Increase | | Deliver |
	+-----> | credit counter |-------------> | packet to |		+-----> | credit counter |-------------> | packet to |
	| by packet size | | application |		| by packet size | | application |
	+----------------+ +---------------+		+----------------+ +---------------+
	Figure 14: Receiving Packets with Credit-Based Authorization		Figure 8: Receiving Packets with Credit-Based Authorization
	Outbound		Outbound
	packet		packet
	| _________________		| _________________
	| / \ +---------------+		| / \ +---------------+
	| / Is the preferred \ No | Send packet |		| / Is the preferred \ No | Send packet |
	+-----> | destination address |-------------> | to preferred |		+-----> | destination address |-------------> | to preferred |
	\ UNVERIFIED? / | address |		\ UNVERIFIED? / | address |
	\_________________/ +---------------+		\_________________/ +---------------+
	|		|
	skipping to change at page 34, line 43		skipping to change at page 25, line 43
	|		|
	| Yes		| Yes
	|		|
	v		v
	+---------------+ +---------------+		+---------------+ +---------------+
	| Reduce credit | | Send packet |		| Reduce credit | | Send packet |
	| counter by |----------------> | to preferred |		| counter by |----------------> | to preferred |
	| packet size | | address |		| packet size | | address |
	+---------------+ +---------------+		+---------------+ +---------------+
	Figure 15: Sending Packets with Credit-Based Authorization		Figure 9: Sending Packets with Credit-Based Authorization
	5.6.2. Credit Aging		5.6.2. Credit Aging
	A host ensures that the credit counters it maintains for its peers		A host ensures that the credit counters it maintains for its peers
	gradually decrease over time. Such "credit aging" prevents a		gradually decrease over time. Such "credit aging" prevents a
	malicious peer from building up credit at a very slow speed and using		malicious peer from building up credit at a very slow speed and using
	this, all at once, for a severe burst of redirected packets.		this, all at once, for a severe burst of redirected packets.
	Credit aging may be implemented by multiplying credit counters with a		Credit aging may be implemented by multiplying credit counters with a
	factor, CreditAgingFactor (a fractional value less than one), in		factor, CreditAgingFactor (a fractional value less than one), in
	skipping to change at page 40, line 21		skipping to change at page 31, line 21
	in Progress, February 2006.		in Progress, February 2006.
	Appendix A. Document Revision History		Appendix A. Document Revision History
	To be removed upon publication		To be removed upon publication
	+----------+-------------------------------------------------------+		+----------+-------------------------------------------------------+
	| Revision | Comments |		| Revision | Comments |
	+----------+-------------------------------------------------------+		+----------+-------------------------------------------------------+
	| draft-00 | Initial version from RFC5206 xml (unchanged). |		| draft-00 | Initial version from RFC5206 xml (unchanged). |
			| draft-01 | Remove multihoming-specific text; no other changes. |
	+----------+-------------------------------------------------------+		+----------+-------------------------------------------------------+
	Authors' Addresses		Authors' Addresses
	Pekka Nikander		Pekka Nikander
	Ericsson Research NomadicLab		Ericsson Research NomadicLab
	JORVAS FIN-02420		JORVAS FIN-02420
	FINLAND		FINLAND
	Phone: +358 9 299 1		Phone: +358 9 299 1
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