draft-ietf-mext-rfc3775bis-01.txt   draft-ietf-mext-rfc3775bis-02.txt 
IETF Mobile IP Working Group D. Johnson IETF Mobile IP Working Group D. Johnson
Internet-Draft Rice University Internet-Draft Rice University
Obsoletes: 3775 (if approved) C. Perkins (Ed.) Obsoletes: 3775 (if approved) C. Perkins (Ed.)
Expires: January 15, 2009 WiChorus Inc. Expires: April 4, 2009 WiChorus Inc.
J. Arkko J. Arkko
Ericsson Ericsson
July 14, 2008 October 1, 2008
Mobility Support in IPv6 Mobility Support in IPv6
draft-ietf-mext-rfc3775bis-01.txt draft-ietf-mext-rfc3775bis-02.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware 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 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. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
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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."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
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This Internet-Draft will expire on January 15, 2009. This Internet-Draft will expire on April 4, 2009.
Abstract Abstract
This document specifies a protocol which allows nodes to remain This document specifies a protocol which allows nodes to remain
reachable while moving around in the IPv6 Internet. Each mobile node reachable while moving around in the IPv6 Internet. Each mobile node
is always identified by its home address, regardless of its current is always identified by its home address, regardless of its current
point of attachment to the Internet. While situated away from its point of attachment to the Internet. While situated away from its
home, a mobile node is also associated with a care-of address, which home, a mobile node is also associated with a care-of address, which
provides information about the mobile node's current location. IPv6 provides information about the mobile node's current location. IPv6
packets addressed to a mobile node's home address are transparently packets addressed to a mobile node's home address are transparently
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11.3.3. Receiving Packets While Away from Home . . . . . . . 116 11.3.3. Receiving Packets While Away from Home . . . . . . . 116
11.3.4. Routing Multicast Packets . . . . . . . . . . . . . . 117 11.3.4. Routing Multicast Packets . . . . . . . . . . . . . . 117
11.3.5. Receiving ICMP Error Messages . . . . . . . . . . . . 119 11.3.5. Receiving ICMP Error Messages . . . . . . . . . . . . 119
11.3.6. Receiving Binding Error Messages . . . . . . . . . . 119 11.3.6. Receiving Binding Error Messages . . . . . . . . . . 119
11.4. Home Agent and Prefix Management . . . . . . . . . . . . 120 11.4. Home Agent and Prefix Management . . . . . . . . . . . . 120
11.4.1. Dynamic Home Agent Address Discovery . . . . . . . . 120 11.4.1. Dynamic Home Agent Address Discovery . . . . . . . . 120
11.4.2. Sending Mobile Prefix Solicitations . . . . . . . . . 121 11.4.2. Sending Mobile Prefix Solicitations . . . . . . . . . 121
11.4.3. Receiving Mobile Prefix Advertisements . . . . . . . 122 11.4.3. Receiving Mobile Prefix Advertisements . . . . . . . 122
11.5. Movement . . . . . . . . . . . . . . . . . . . . . . . . 123 11.5. Movement . . . . . . . . . . . . . . . . . . . . . . . . 123
11.5.1. Movement Detection . . . . . . . . . . . . . . . . . 123 11.5.1. Movement Detection . . . . . . . . . . . . . . . . . 123
11.5.2. Forming New Care-of Addresses . . . . . . . . . . . . 125 11.5.2. Home Link Detection . . . . . . . . . . . . . . . . . 125
11.5.3. Using Multiple Care-of Addresses . . . . . . . . . . 126 11.5.3. Forming New Care-of Addresses . . . . . . . . . . . . 126
11.5.4. Returning Home . . . . . . . . . . . . . . . . . . . 127 11.5.4. Using Multiple Care-of Addresses . . . . . . . . . . 127
11.5.5. Returning Home . . . . . . . . . . . . . . . . . . . 127
11.6. Return Routability Procedure . . . . . . . . . . . . . . 129 11.6. Return Routability Procedure . . . . . . . . . . . . . . 129
11.6.1. Sending Test Init Messages . . . . . . . . . . . . . 129 11.6.1. Sending Test Init Messages . . . . . . . . . . . . . 129
11.6.2. Receiving Test Messages . . . . . . . . . . . . . . . 130 11.6.2. Receiving Test Messages . . . . . . . . . . . . . . . 130
11.6.3. Protecting Return Routability Packets . . . . . . . . 131 11.6.3. Protecting Return Routability Packets . . . . . . . . 132
11.7. Processing Bindings . . . . . . . . . . . . . . . . . . . 131 11.7. Processing Bindings . . . . . . . . . . . . . . . . . . . 132
11.7.1. Sending Binding Updates to the Home Agent . . . . . . 132 11.7.1. Sending Binding Updates to the Home Agent . . . . . . 132
11.7.2. Correspondent Registration . . . . . . . . . . . . . 134 11.7.2. Correspondent Registration . . . . . . . . . . . . . 135
11.7.3. Receiving Binding Acknowledgements . . . . . . . . . 137 11.7.3. Receiving Binding Acknowledgements . . . . . . . . . 138
11.7.4. Receiving Binding Refresh Requests . . . . . . . . . 139 11.7.4. Receiving Binding Refresh Requests . . . . . . . . . 140
11.8. Retransmissions and Rate Limiting . . . . . . . . . . . . 140 11.8. Retransmissions and Rate Limiting . . . . . . . . . . . . 141
12. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 142 12. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 143
13. Protocol Configuration Variables . . . . . . . . . . . . . . 143 13. Protocol Configuration Variables . . . . . . . . . . . . . . 144
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 144 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 145
15. Security Considerations . . . . . . . . . . . . . . . . . . . 147 15. Security Considerations . . . . . . . . . . . . . . . . . . . 148
15.1. Threats . . . . . . . . . . . . . . . . . . . . . . . . . 147 15.1. Threats . . . . . . . . . . . . . . . . . . . . . . . . . 148
15.2. Features . . . . . . . . . . . . . . . . . . . . . . . . 149 15.2. Features . . . . . . . . . . . . . . . . . . . . . . . . 150
15.3. Binding Updates to Home Agent . . . . . . . . . . . . . . 150 15.3. Binding Updates to Home Agent . . . . . . . . . . . . . . 151
15.4. Binding Updates to Correspondent Nodes . . . . . . . . . 153 15.4. Binding Updates to Correspondent Nodes . . . . . . . . . 154
15.4.1. Overview . . . . . . . . . . . . . . . . . . . . . . 153 15.4.1. Overview . . . . . . . . . . . . . . . . . . . . . . 154
15.4.2. Achieved Security Properties . . . . . . . . . . . . 154 15.4.2. Achieved Security Properties . . . . . . . . . . . . 155
15.4.3. Comparison to Regular IPv6 Communications . . . . . . 155 15.4.3. Comparison to Regular IPv6 Communications . . . . . . 156
15.4.4. Replay Attacks . . . . . . . . . . . . . . . . . . . 157 15.4.4. Replay Attacks . . . . . . . . . . . . . . . . . . . 158
15.4.5. Denial-of-Service Attacks . . . . . . . . . . . . . . 157 15.4.5. Denial-of-Service Attacks . . . . . . . . . . . . . . 158
15.4.6. Key Lengths . . . . . . . . . . . . . . . . . . . . . 158 15.4.6. Key Lengths . . . . . . . . . . . . . . . . . . . . . 159
15.5. Dynamic Home Agent Address Discovery . . . . . . . . . . 159 15.5. Dynamic Home Agent Address Discovery . . . . . . . . . . 160
15.6. Mobile Prefix Discovery . . . . . . . . . . . . . . . . . 159 15.6. Mobile Prefix Discovery . . . . . . . . . . . . . . . . . 161
15.7. Tunneling via the Home Agent . . . . . . . . . . . . . . 160 15.7. Tunneling via the Home Agent . . . . . . . . . . . . . . 161
15.8. Home Address Option . . . . . . . . . . . . . . . . . . . 160 15.8. Home Address Option . . . . . . . . . . . . . . . . . . . 162
15.9. Type 2 Routing Header . . . . . . . . . . . . . . . . . . 161 15.9. Type 2 Routing Header . . . . . . . . . . . . . . . . . . 162
16. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 163 16. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 164
17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 164 17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 165
18. References . . . . . . . . . . . . . . . . . . . . . . . . . 165 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 166
18.1. Normative References . . . . . . . . . . . . . . . . . . 165 18.1. Normative References . . . . . . . . . . . . . . . . . . 166
18.2. Informative References . . . . . . . . . . . . . . . . . 166 18.2. Informative References . . . . . . . . . . . . . . . . . 167
Appendix A. Future Extensions . . . . . . . . . . . . . . . . . 168 Appendix A. Future Extensions . . . . . . . . . . . . . . . . . 170
A.1. Piggybacking . . . . . . . . . . . . . . . . . . . . . . 168 A.1. Piggybacking . . . . . . . . . . . . . . . . . . . . . . 170
A.2. Triangular Routing . . . . . . . . . . . . . . . . . . . 168 A.2. Triangular Routing . . . . . . . . . . . . . . . . . . . 170
A.3. New Authorization Methods . . . . . . . . . . . . . . . . 168 A.3. New Authorization Methods . . . . . . . . . . . . . . . . 170
A.4. Dynamically Generated Home Addresses . . . . . . . . . . 168 A.4. Dynamically Generated Home Addresses . . . . . . . . . . 170
A.5. Remote Home Address Configuration . . . . . . . . . . . . 168 A.5. Remote Home Address Configuration . . . . . . . . . . . . 170
A.6. Neighbor Discovery Extensions . . . . . . . . . . . . . . 169 A.6. Neighbor Discovery Extensions . . . . . . . . . . . . . . 171
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 171 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 173
Intellectual Property and Copyright Statements . . . . . . . . . 172 Intellectual Property and Copyright Statements . . . . . . . . . 174
1. Introduction 1. Introduction
This document specifies a protocol which allows nodes to remain This document specifies a protocol which allows nodes to remain
reachable while moving around in the IPv6 Internet. Without specific reachable while moving around in the IPv6 Internet. Without specific
support for mobility in IPv6 [8], packets destined to a mobile node support for mobility in IPv6 [8], packets destined to a mobile node
would not be able to reach it while the mobile node is away from its would not be able to reach it while the mobile node is away from its
home link. In order to continue communication in spite of its home link. In order to continue communication in spite of its
movement, a mobile node could change its IP address each time it movement, a mobile node could change its IP address each time it
moves to a new link, but the mobile node would then not be able to moves to a new link, but the mobile node would then not be able to
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o Service Discovery. o Service Discovery.
o Distinguishing between packets lost due to bit errors vs. network o Distinguishing between packets lost due to bit errors vs. network
congestion. congestion.
2. Comparison with Mobile IP for IPv4 2. Comparison with Mobile IP for IPv4
The design of Mobile IP support in IPv6 (Mobile IPv6) benefits both The design of Mobile IP support in IPv6 (Mobile IPv6) benefits both
from the experiences gained from the development of Mobile IP support from the experiences gained from the development of Mobile IP support
in IPv4 (Mobile IPv4) [28] [22] [23], and from the opportunities in IPv4 (Mobile IPv4) [33] [27] [28], and from the opportunities
provided by IPv6. Mobile IPv6 thus shares many features with Mobile provided by IPv6. Mobile IPv6 thus shares many features with Mobile
IPv4, but is integrated into IPv6 and offers many other improvements. IPv4, but is integrated into IPv6 and offers many other improvements.
This section summarizes the major differences between Mobile IPv4 and This section summarizes the major differences between Mobile IPv4 and
Mobile IPv6: Mobile IPv6:
o There is no need to deploy special routers as "foreign agents", as o There is no need to deploy special routers as "foreign agents", as
in Mobile IPv4. Mobile IPv6 operates in any location without any in Mobile IPv4. Mobile IPv6 operates in any location without any
special support required from the local router. special support required from the local router.
o Support for route optimization is a fundamental part of the o Support for route optimization is a fundamental part of the
protocol, rather than a nonstandard set of extensions. protocol, rather than a nonstandard set of extensions.
o Mobile IPv6 route optimization can operate securely even without o Mobile IPv6 route optimization can operate securely even without
pre-arranged security associations. It is expected that route pre-arranged security associations. It is expected that route
optimization can be deployed on a global scale between all mobile optimization can be deployed on a global scale between all mobile
nodes and correspondent nodes. nodes and correspondent nodes.
o Support is also integrated into Mobile IPv6 for allowing route o Support is also integrated into Mobile IPv6 for allowing route
optimization to coexist efficiently with routers that perform optimization to coexist efficiently with routers that perform
"ingress filtering" [25]. "ingress filtering" [30].
o The IPv6 Neighbor Unreachability Detection assures symmetric o The IPv6 Neighbor Unreachability Detection assures symmetric
reachability between the mobile node and its default router in the reachability between the mobile node and its default router in the
current location. current location.
o Most packets sent to a mobile node while away from home in Mobile o Most packets sent to a mobile node while away from home in Mobile
IPv6 are sent using an IPv6 routing header rather than IP IPv6 are sent using an IPv6 routing header rather than IP
encapsulation, reducing the amount of resulting overhead compared encapsulation, reducing the amount of resulting overhead compared
to Mobile IPv4. to Mobile IPv4.
o Mobile IPv6 is decoupled from any particular link layer, as it o Mobile IPv6 is decoupled from any particular link layer, as it
uses IPv6 Neighbor Discovery [18] instead of ARP. This also uses IPv6 Neighbor Discovery [20] instead of ARP. This also
improves the robustness of the protocol. improves the robustness of the protocol.
o The use of IPv6 encapsulation (and the routing header) removes the o The use of IPv6 encapsulation (and the routing header) removes the
need in Mobile IPv6 to manage "tunnel soft state". need in Mobile IPv6 to manage "tunnel soft state".
o The dynamic home agent address discovery mechanism in Mobile IPv6 o The dynamic home agent address discovery mechanism in Mobile IPv6
returns a single reply to the mobile node. The directed broadcast returns a single reply to the mobile node. The directed broadcast
approach used in IPv4 returns separate replies from each home approach used in IPv4 returns separate replies from each home
agent. agent.
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router router
A node that forwards IP packets not explicitly addressed to A node that forwards IP packets not explicitly addressed to
itself. itself.
unicast routable address unicast routable address
An identifier for a single interface such that a packet sent to it An identifier for a single interface such that a packet sent to it
from another IPv6 subnet is delivered to the interface identified from another IPv6 subnet is delivered to the interface identified
by that address. Accordingly, a unicast routable address must by that address. Accordingly, a unicast routable address must
have either a global or site-local scope (but not link-local). either be global IPv6 address or a unique local IPv6 address.
host host
Any node that is not a router. Any node that is not a router.
link link
A communication facility or medium over which nodes can A communication facility or medium over which nodes can
communicate at the link layer, such as an Ethernet (simple or communicate at the link layer, such as an Ethernet (simple or
bridged). A link is the layer immediately below IP. bridged). A link is the layer immediately below IP.
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limited support for the reconfiguration of the home network. In limited support for the reconfiguration of the home network. In
these cases, the mobile node may not know the IP address of its own these cases, the mobile node may not know the IP address of its own
home agent, and even the home subnet prefixes may change over time. home agent, and even the home subnet prefixes may change over time.
A mechanism, known as "dynamic home agent address discovery" allows a A mechanism, known as "dynamic home agent address discovery" allows a
mobile node to dynamically discover the IP address of a home agent on mobile node to dynamically discover the IP address of a home agent on
its home link, even when the mobile node is away from home. Mobile its home link, even when the mobile node is away from home. Mobile
nodes can also learn new information about home subnet prefixes nodes can also learn new information about home subnet prefixes
through the "mobile prefix discovery" mechanism. These mechanisms through the "mobile prefix discovery" mechanism. These mechanisms
are described starting from Section 6.5. are described starting from Section 6.5.
This document assumes that the mobile node is configured with the
home prefix for the mobile node to be able to discover a home agent
and configure a home address. This might be limiting in deployments
where the home agent and the home address for the mobile node needs
to be assigned dynamically. Additional mechanisms have been
specified for the mobile node to dynamically configure a home agent,
a home address and the home prefix. These mechanisms are described
in "Mobile IPv6 Bootstrapping in Split Scenario" [25] and "MIP6
bootstrapping for the Integrated Scenario" [37].
4.2. New IPv6 Protocol 4.2. New IPv6 Protocol
Mobile IPv6 defines a new IPv6 protocol, using the Mobility Header Mobile IPv6 defines a new IPv6 protocol, using the Mobility Header
(see Section 6.1). This Header is used to carry the following (see Section 6.1). This Header is used to carry the following
messages: messages:
Home Test Init Home Test Init
Home Test Home Test
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A Binding Refresh Request is used by a correspondent node to A Binding Refresh Request is used by a correspondent node to
request a mobile node to re-establish its binding with the request a mobile node to re-establish its binding with the
correspondent node. This message is typically used when the correspondent node. This message is typically used when the
cached binding is in active use but the binding's lifetime is cached binding is in active use but the binding's lifetime is
close to expiration. The correspondent node may use, for close to expiration. The correspondent node may use, for
instance, recent traffic and open transport layer connections as instance, recent traffic and open transport layer connections as
an indication of active use. an indication of active use.
Binding Error Binding Error
The Binding Error is used by the correspondent node to signal an The Binding Error is used by the correspondent node or the home
error related to mobility, such as an inappropriate attempt to use agent to signal an error related to mobility, such as an
the Home Address destination option without an existing binding. inappropriate attempt to use the Home Address destination option
without an existing binding, or when an unrecognized Mobility
Header is received.
4.3. New IPv6 Destination Option 4.3. New IPv6 Destination Option
Mobile IPv6 defines a new IPv6 destination option, the Home Address Mobile IPv6 defines a new IPv6 destination option, the Home Address
destination option. This option is described in detail in destination option. This option is described in detail in
Section 6.3. Section 6.3.
4.4. New IPv6 ICMP Messages 4.4. New IPv6 ICMP Messages
Mobile IPv6 also introduces four new ICMP message types, two for use Mobile IPv6 also introduces four new ICMP message types, two for use
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Home agents need to know which other home agents are on the same Home agents need to know which other home agents are on the same
link. This information is stored in the Home Agents List, as link. This information is stored in the Home Agents List, as
described in more detail in Section 10.1. The list is used for described in more detail in Section 10.1. The list is used for
informing mobile nodes during dynamic home agent address informing mobile nodes during dynamic home agent address
discovery. discovery.
4.6. Unique-Local Addressability 4.6. Unique-Local Addressability
This specification requires that home and care-of addresses MUST be This specification requires that home and care-of addresses MUST be
unicast routable addresses. Site-local addresses may be usable on unicast routable addresses. Unique-local IPv6 unicast addresses
networks that are not connected to the Internet, but this RFC4193 [22] may be usable on networks that use such non-globaly
specification does not define when such usage is safe and when it is routable addresses but this specification does not define when such
not. Mobile nodes may not be aware of which site they are currently usage is safe and when it is not. Mobile nodes may not be aware of
in, it is hard to prevent accidental attachment to other sites, and which site they are currently making it hard to prevent accidental
ambiguity of site-local addresses can cause problems if the home and attachment to other sites, resulting in possible unrechability
visited networks use the same addresses. Therefore, site-local between the MN and the HA, when unique-local IPv6 routable addresses
addresses SHOULD NOT be used as home or care-of addresses. are used as care-of addresses. Also, CNs outside the MN's own site
are not going to be reachable when unique-local IPv6 routable
addresses are used as home addresses. Therefore, unique-local IPv6
unicast addresses SHOULD NOT be used as home or care-of addresses.
If such addresses are used, however, according to RFC4193 [22], they
are treated as any global unicast IPv6 address so, for the remainder
of this specification, use of unique-local IPv6 unicast addresses is
not differentiated from other globally unique IPv6 addresses.
5. Overview of Mobile IPv6 Security 5. Overview of Mobile IPv6 Security
This specification provides a number of security features. These This specification provides a number of security features. These
include the protection of Binding Updates both to home agents and include the protection of Binding Updates both to home agents and
correspondent nodes, the protection of mobile prefix discovery, and correspondent nodes, the protection of mobile prefix discovery, and
the protection of the mechanisms that Mobile IPv6 uses for the protection of the mechanisms that Mobile IPv6 uses for
transporting data packets. transporting data packets.
Binding Updates are protected by the use of IPsec extension headers, Binding Updates are protected by the use of IPsec extension headers,
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careful treatment of the addresses used for transporting IKE. This careful treatment of the addresses used for transporting IKE. This
is necessary to ensure that a Binding Update is not needed before the is necessary to ensure that a Binding Update is not needed before the
IKE exchange which is needed for securing the Binding Update. IKE exchange which is needed for securing the Binding Update.
When IKE version 1 is used with preshared secret authentication When IKE version 1 is used with preshared secret authentication
between the mobile node and the home agent, aggressive mode MUST be between the mobile node and the home agent, aggressive mode MUST be
used. used.
The ID_IPV6_ADDR Identity Payload MUST NOT be used in IKEv1 phase 1. The ID_IPV6_ADDR Identity Payload MUST NOT be used in IKEv1 phase 1.
Reference [14] contains a more detailed description and examples on Reference [15] contains a more detailed description and examples on
using IPsec to protect the communications between the mobile node and using IPsec to protect the communications between the mobile node and
the home agent. the home agent.
5.2. Binding Updates to Correspondent Nodes 5.2. Binding Updates to Correspondent Nodes
The protection of Binding Updates sent to correspondent nodes does The protection of Binding Updates sent to correspondent nodes does
not require the configuration of security associations or the not require the configuration of security associations or the
existence of an authentication infrastructure between the mobile existence of an authentication infrastructure between the mobile
nodes and correspondent nodes. Instead, a method called the return nodes and correspondent nodes. Instead, a method called the return
routability procedure is used to assure that the right mobile node is routability procedure is used to assure that the right mobile node is
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A correspondent node MAY generate a fresh node key at any time; this A correspondent node MAY generate a fresh node key at any time; this
avoids the need for secure persistent key storage. Procedures for avoids the need for secure persistent key storage. Procedures for
optionally updating the node key are discussed later in optionally updating the node key are discussed later in
Section 5.2.7. Section 5.2.7.
5.2.2. Nonces 5.2.2. Nonces
Each correspondent node also generates nonces at regular intervals. Each correspondent node also generates nonces at regular intervals.
The nonces should be generated by using a random number generator The nonces should be generated by using a random number generator
that is known to have good randomness properties [15]. A that is known to have good randomness properties [17]. A
correspondent node may use the same Kcn and nonce with all the correspondent node may use the same Kcn and nonce with all the
mobiles it is in communication with. mobiles it is in communication with.
Each nonce is identified by a nonce index. When a new nonce is Each nonce is identified by a nonce index. When a new nonce is
generated, it must be associated with a new nonce index; this may be generated, it must be associated with a new nonce index; this may be
done, for example, by incrementing the value of the previous nonce done, for example, by incrementing the value of the previous nonce
index, if the nonce index is used as an array pointer into a linear index, if the nonce index is used as an array pointer into a linear
array of nonces. However, there is no requirement that nonces be array of nonces. However, there is no requirement that nonces be
stored that way, or that the values of subsequent nonce indices have stored that way, or that the values of subsequent nonce indices have
any particular relationship to each other. The index value is any particular relationship to each other. The index value is
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Home and care-of keygen tokens are produced by the correspondent node Home and care-of keygen tokens are produced by the correspondent node
based on its currently active secret key (Kcn) and nonces, as well as based on its currently active secret key (Kcn) and nonces, as well as
the home or care-of address (respectively). A keygen token is valid the home or care-of address (respectively). A keygen token is valid
as long as both the secret key (Kcn) and the nonce used to create it as long as both the secret key (Kcn) and the nonce used to create it
are valid. are valid.
5.2.4. Cryptographic Functions 5.2.4. Cryptographic Functions
In this specification, the function used to compute hash values is In this specification, the function used to compute hash values is
SHA1 [13]. Message Authentication Codes (MACs) are computed using SHA1 [14]. Message Authentication Codes (MACs) are computed using
HMAC_SHA1 [24] [13]. HMAC_SHA1(K,m) denotes such a MAC computed on HMAC_SHA1 [29] [14]. HMAC_SHA1(K,m) denotes such a MAC computed on
message m with key K. message m with key K.
5.2.5. Return Routability Procedure 5.2.5. Return Routability Procedure
The Return Routability Procedure enables the correspondent node to The Return Routability Procedure enables the correspondent node to
obtain some reasonable assurance that the mobile node is in fact obtain some reasonable assurance that the mobile node is in fact
addressable at its claimed care-of address as well as at its home addressable at its claimed care-of address as well as at its home
address. Only with this assurance is the correspondent node able to address. Only with this assurance is the correspondent node able to
accept Binding Updates from the mobile node which would then instruct accept Binding Updates from the mobile node which would then instruct
the correspondent node to direct that mobile node's data traffic to the correspondent node to direct that mobile node's data traffic to
skipping to change at page 46, line 23 skipping to change at page 46, line 23
136 Expired home nonce index 136 Expired home nonce index
137 Expired care-of nonce index 137 Expired care-of nonce index
138 Expired nonces 138 Expired nonces
139 Registration type change disallowed 139 Registration type change disallowed
Up-to-date values of the Status field are to be specified in the Up-to-date values of the Status field are to be specified in the
IANA registry of assigned numbers [12]. IANA registry of assigned numbers [13].
Sequence # Sequence #
The Sequence Number in the Binding Acknowledgement is copied from The Sequence Number in the Binding Acknowledgement is copied from
the Sequence Number field in the Binding Update. It is used by the Sequence Number field in the Binding Update. It is used by
the mobile node in matching this Binding Acknowledgement with an the mobile node in matching this Binding Acknowledgement with an
outstanding Binding Update. outstanding Binding Update.
Lifetime Lifetime
skipping to change at page 57, line 31 skipping to change at page 57, line 31
routing headers. routing headers.
6.5. ICMP Home Agent Address Discovery Request Message 6.5. ICMP Home Agent Address Discovery Request Message
The ICMP Home Agent Address Discovery Request message is used by a The ICMP Home Agent Address Discovery Request message is used by a
mobile node to initiate the dynamic home agent address discovery mobile node to initiate the dynamic home agent address discovery
mechanism, as described in Section 11.4.1. The mobile node sends the mechanism, as described in Section 11.4.1. The mobile node sends the
Home Agent Address Discovery Request message to the Mobile IPv6 Home- Home Agent Address Discovery Request message to the Mobile IPv6 Home-
Agents anycast address [10] for its own home subnet prefix. (Note Agents anycast address [10] for its own home subnet prefix. (Note
that the currently defined anycast addresses may not work with all that the currently defined anycast addresses may not work with all
prefix lengths other than those defined in RFC 4291 [16] [32].) prefix lengths other than those defined in RFC 4291 [18] [38].)
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum | | Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier | Reserved | | Identifier | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Type
144 144
Code Code
0 0
Checksum Checksum
The ICMP checksum [17]. The ICMP checksum [19].
Identifier Identifier
An identifier to aid in matching Home Agent Address Discovery An identifier to aid in matching Home Agent Address Discovery
Reply messages to this Home Agent Address Discovery Request Reply messages to this Home Agent Address Discovery Request
message. message.
Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
skipping to change at page 59, line 14 skipping to change at page 59, line 14
Type Type
145 145
Code Code
0 0
Checksum Checksum
The ICMP checksum [17]. The ICMP checksum [19].
Identifier Identifier
The identifier from the invoking Home Agent Address Discovery The identifier from the invoking Home Agent Address Discovery
Request message. Request message.
Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
sender and MUST be ignored by the receiver. sender and MUST be ignored by the receiver.
skipping to change at page 60, line 41 skipping to change at page 60, line 41
Type Type
146 146
Code Code
0 0
Checksum Checksum
The ICMP checksum [17]. The ICMP checksum [19].
Identifier Identifier
An identifier to aid in matching a future Mobile Prefix An identifier to aid in matching a future Mobile Prefix
Advertisement to this Mobile Prefix Solicitation. Advertisement to this Mobile Prefix Solicitation.
Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
sender and MUST be ignored by the receiver. sender and MUST be ignored by the receiver.
The Mobile Prefix Solicitation messages may have options. These The Mobile Prefix Solicitation messages may have options. These
options MUST use the option format defined in RFC 4861 [18]. This options MUST use the option format defined in RFC 4861 [20]. This
document does not define any option types for the Mobile Prefix document does not define any option types for the Mobile Prefix
Solicitation message, but future documents may define new options. Solicitation message, but future documents may define new options.
Home agents MUST silently ignore any options they do not recognize Home agents MUST silently ignore any options they do not recognize
and continue processing the message. and continue processing the message.
6.8. ICMP Mobile Prefix Advertisement Message Format 6.8. ICMP Mobile Prefix Advertisement Message Format
A home agent will send a Mobile Prefix Advertisement to a mobile node A home agent will send a Mobile Prefix Advertisement to a mobile node
to distribute prefix information about the home link while the mobile to distribute prefix information about the home link while the mobile
node is traveling away from the home network. This will occur in node is traveling away from the home network. This will occur in
skipping to change at page 62, line 24 skipping to change at page 62, line 24
Type Type
147 147
Code Code
0 0
Checksum Checksum
The ICMP checksum [17]. The ICMP checksum [19].
Identifier Identifier
An identifier to aid in matching this Mobile Prefix Advertisement An identifier to aid in matching this Mobile Prefix Advertisement
to a previous Mobile Prefix Solicitation. to a previous Mobile Prefix Solicitation.
M M
1-bit Managed Address Configuration flag. When set, hosts use the 1-bit Managed Address Configuration flag. When set, hosts use the
administered (stateful) protocol for address autoconfiguration in administered (stateful) protocol for address autoconfiguration in
addition to any addresses autoconfigured using stateless address addition to any addresses autoconfigured using stateless address
autoconfiguration. The use of this flag is described in [18] autoconfiguration. The use of this flag is described in [20]
[19]. [21].
O O
1-bit Other Stateful Configuration flag. When set, hosts use the 1-bit Other Stateful Configuration flag. When set, hosts use the
administered (stateful) protocol for autoconfiguration of other administered (stateful) protocol for autoconfiguration of other
(non-address) information. The use of this flag is described in (non-address) information. The use of this flag is described in
[18] [19]. [20] [21].
Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
sender and MUST be ignored by the receiver. sender and MUST be ignored by the receiver.
The Mobile Prefix Advertisement messages may have options. These The Mobile Prefix Advertisement messages may have options. These
options MUST use the option format defined in RFC 4861 [18]. This options MUST use the option format defined in RFC 4861 [20]. This
document defines one option which may be carried in a Mobile Prefix document defines one option which may be carried in a Mobile Prefix
Advertisement message, but future documents may define new options. Advertisement message, but future documents may define new options.
Mobile nodes MUST silently ignore any options they do not recognize Mobile nodes MUST silently ignore any options they do not recognize
and continue processing the message. and continue processing the message.
Prefix Information Prefix Information
Each message contains one or more Prefix Information options. Each message contains one or more Prefix Information options.
Each option carries the prefix(es) that the mobile node should use Each option carries the prefix(es) that the mobile node should use
to configure its home address(es). Section 10.6 describes which to configure its home address(es). Section 10.6 describes which
prefixes should be advertised to the mobile node. prefixes should be advertised to the mobile node.
The Prefix Information option is defined in Section 4.6.2 of RFC The Prefix Information option is defined in Section 4.6.2 of RFC
4861 [18], with modifications defined in Section 7.2 of this 4861 [20], with modifications defined in Section 7.2 of this
specification. The home agent MUST use this modified Prefix specification. The home agent MUST use this modified Prefix
Information option to send home network prefixes as defined in Information option to send home network prefixes as defined in
Section 10.6.1. Section 10.6.1.
If the Advertisement is sent in response to a Mobile Prefix If the Advertisement is sent in response to a Mobile Prefix
Solicitation, the home agent MUST copy the Identifier value from that Solicitation, the home agent MUST copy the Identifier value from that
message into the Identifier field of the Advertisement. message into the Identifier field of the Advertisement.
The home agent MUST NOT send more than one Mobile Prefix The home agent MUST NOT send more than one Mobile Prefix
Advertisement message per second to any mobile node. Advertisement message per second to any mobile node.
The M and O bits MUST be cleared if the Home Agent DHCPv6 support is The M and O bits MUST be cleared if the Home Agent DHCPv6 support is
not provided. If such support is provided then they are set in not provided. If such support is provided then they are set in
concert with the home network's administrative settings. concert with the home network's administrative settings.
7. Modifications to IPv6 Neighbor Discovery 7. Modifications to IPv6 Neighbor Discovery
7.1. Modified Router Advertisement Message Format 7.1. Modified Router Advertisement Message Format
Mobile IPv6 modifies the format of the Router Advertisement message Mobile IPv6 modifies the format of the Router Advertisement message
[18] by the addition of a single flag bit to indicate that the router [20] by the addition of a single flag bit to indicate that the router
sending the Advertisement message is serving as a home agent on this sending the Advertisement message is serving as a home agent on this
link. The format of the Router Advertisement message is as follows: link. The format of the Router Advertisement message is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum | | Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O|H| Reserved| Router Lifetime | | Cur Hop Limit |M|O|H| Reserved| Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time | | Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer | | Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ... | Options ...
+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-
This format represents the following changes over that originally This format represents the following changes over that originally
specified for Neighbor Discovery [18]: specified for Neighbor Discovery [20]:
Home Agent (H) Home Agent (H)
The Home Agent (H) bit is set in a Router Advertisement to The Home Agent (H) bit is set in a Router Advertisement to
indicate that the router sending this Router Advertisement is also indicate that the router sending this Router Advertisement is also
functioning as a Mobile IPv6 home agent on this link. functioning as a Mobile IPv6 home agent on this link.
Reserved Reserved
Reduced from a 6-bit field to a 5-bit field to account for the Reduced from a 6-bit field to a 5-bit field to account for the
addition of the above bit. addition of the above bit.
7.2. Modified Prefix Information Option Format 7.2. Modified Prefix Information Option Format
Mobile IPv6 requires knowledge of a router's global address in Mobile IPv6 requires knowledge of a router's global address in
building a Home Agents List as part of the dynamic home agent address building a Home Agents List as part of the dynamic home agent address
discovery mechanism. discovery mechanism.
However, Neighbor Discovery [18] only advertises a router's link- However, Neighbor Discovery [20] only advertises a router's link-
local address, by requiring this address to be used as the IP Source local address, by requiring this address to be used as the IP Source
Address of each Router Advertisement. Address of each Router Advertisement.
Mobile IPv6 extends Neighbor Discovery to allow a router to advertise Mobile IPv6 extends Neighbor Discovery to allow a router to advertise
its global address, by the addition of a single flag bit in the its global address, by the addition of a single flag bit in the
format of a Prefix Information option for use in Router Advertisement format of a Prefix Information option for use in Router Advertisement
messages. The format of the Prefix Information option is as follows: messages. The format of the Prefix Information option is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
skipping to change at page 65, line 29 skipping to change at page 65, line 29
| | | |
+ + + +
| | | |
+ Prefix + + Prefix +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This format represents the following changes over that originally This format represents the following changes over that originally
specified for Neighbor Discovery [18]: specified for Neighbor Discovery [20]:
Router Address (R) Router Address (R)
1-bit router address flag. When set, indicates that the Prefix 1-bit router address flag. When set, indicates that the Prefix
field contains a complete IP address assigned to the sending field contains a complete IP address assigned to the sending
router. The indicated prefix is the first Prefix Length bits of router. The indicated prefix is the first Prefix Length bits of
the Prefix field. The router IP address has the same scope and the Prefix field. The router IP address has the same scope and
conforms to the same lifetime values as the advertised prefix. conforms to the same lifetime values as the advertised prefix.
This use of the Prefix field is compatible with its use in This use of the Prefix field is compatible with its use in
advertising the prefix itself, since Prefix Advertisement uses advertising the prefix itself, since Prefix Advertisement uses
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Reserved1 Reserved1
Reduced from a 6-bit field to a 5-bit field to account for the Reduced from a 6-bit field to a 5-bit field to account for the
addition of the above bit. addition of the above bit.
In a Router Advertisement, a home agent MUST, and all other routers In a Router Advertisement, a home agent MUST, and all other routers
MAY, include at least one Prefix Information option with the Router MAY, include at least one Prefix Information option with the Router
Address (R) bit set. Neighbor Discovery specifies that, if including Address (R) bit set. Neighbor Discovery specifies that, if including
all options in a Router Advertisement causes the size of the all options in a Router Advertisement causes the size of the
Advertisement to exceed the link MTU, multiple Advertisements can be Advertisement to exceed the link MTU, multiple Advertisements can be
sent, each containing a subset of the options [18]. Also, when sent, each containing a subset of the options [20]. Also, when
sending unsolicited multicast Router Advertisements more frequently sending unsolicited multicast Router Advertisements more frequently
than the limit specified in RFC 4861 [18], the sending router need than the limit specified in RFC 4861 [20], the sending router need
not include all options in each of these Advertisements. However, in not include all options in each of these Advertisements. However, in
both of these cases the router SHOULD include at least one Prefix both of these cases the router SHOULD include at least one Prefix
Information option with the Router Address (R) bit set in each such Information option with the Router Address (R) bit set in each such
advertisement, if this bit is set in some advertisement sent by the advertisement, if this bit is set in some advertisement sent by the
router. router.
In addition, the following requirement can assist mobile nodes in In addition, the following requirement can assist mobile nodes in
movement detection. Barring changes in the prefixes for the link, movement detection. Barring changes in the prefixes for the link,
routers that send multiple Router Advertisements with the Router routers that send multiple Router Advertisements with the Router
Address (R) bit set in some of the included Prefix Information Address (R) bit set in some of the included Prefix Information
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Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
sender and MUST be ignored by the receiver. sender and MUST be ignored by the receiver.
Advertisement Interval Advertisement Interval
32-bit unsigned integer. The maximum time, in milliseconds, 32-bit unsigned integer. The maximum time, in milliseconds,
between successive unsolicited Router Advertisement messages sent between successive unsolicited Router Advertisement messages sent
by this router on this network interface. Using the conceptual by this router on this network interface. Using the conceptual
router configuration variables defined by Neighbor Discovery [18], router configuration variables defined by Neighbor Discovery [20],
this field MUST be equal to the value MaxRtrAdvInterval, expressed this field MUST be equal to the value MaxRtrAdvInterval, expressed
in milliseconds. in milliseconds.
Routers MAY include this option in their Router Advertisements. A Routers MAY include this option in their Router Advertisements. A
mobile node receiving a Router Advertisement containing this option mobile node receiving a Router Advertisement containing this option
SHOULD utilize the specified Advertisement Interval for that router SHOULD utilize the specified Advertisement Interval for that router
in its movement detection algorithm, as described in Section 11.5.1. in its movement detection algorithm, as described in Section 11.5.1.
This option MUST be silently ignored for other Neighbor Discovery This option MUST be silently ignored for other Neighbor Discovery
messages. messages.
skipping to change at page 69, line 13 skipping to change at page 69, line 13
This option MUST be silently ignored for other Neighbor Discovery This option MUST be silently ignored for other Neighbor Discovery
messages. messages.
If both the Home Agent Preference and Home Agent Lifetime are set to If both the Home Agent Preference and Home Agent Lifetime are set to
their default values specified above, this option SHOULD NOT be their default values specified above, this option SHOULD NOT be
included in the Router Advertisement messages sent by this home included in the Router Advertisement messages sent by this home
agent. agent.
7.5. Changes to Sending Router Advertisements 7.5. Changes to Sending Router Advertisements
The Neighbor Discovery protocol specification [18] limits routers to The Neighbor Discovery protocol specification [20] limits routers to
a minimum interval of 3 seconds between sending unsolicited multicast a minimum interval of 3 seconds between sending unsolicited multicast
Router Advertisement messages from any given network interface Router Advertisement messages from any given network interface
(limited by MinRtrAdvInterval and MaxRtrAdvInterval), stating that: (limited by MinRtrAdvInterval and MaxRtrAdvInterval), stating that:
"Routers generate Router Advertisements frequently enough that "Routers generate Router Advertisements frequently enough that
hosts will learn of their presence within a few minutes, but not hosts will learn of their presence within a few minutes, but not
frequently enough to rely on an absence of advertisements to frequently enough to rely on an absence of advertisements to
detect router failure; a separate Neighbor Unreachability detect router failure; a separate Neighbor Unreachability
Detection algorithm provides failure detection." Detection algorithm provides failure detection."
skipping to change at page 70, line 17 skipping to change at page 70, line 17
time between unsolicited multicast router advertisements is 50ms. time between unsolicited multicast router advertisements is 50ms.
Use of these modified limits MUST be configurable (see also the Use of these modified limits MUST be configurable (see also the
configuration variable MinDelayBetweenRas in Section 13 which may configuration variable MinDelayBetweenRas in Section 13 which may
also have to be modified accordingly). Systems where these values also have to be modified accordingly). Systems where these values
are available MUST NOT default to them, and SHOULD default to values are available MUST NOT default to them, and SHOULD default to values
specified in RFC 4861. Knowledge of the type of network interface specified in RFC 4861. Knowledge of the type of network interface
and operating environment SHOULD be taken into account in configuring and operating environment SHOULD be taken into account in configuring
these limits for each network interface. This is important with some these limits for each network interface. This is important with some
wireless links, where increasing the frequency of multicast beacons wireless links, where increasing the frequency of multicast beacons
can cause considerable overhead. Routers SHOULD adhere to the can cause considerable overhead. Routers SHOULD adhere to the
intervals specified in RFC 4861 [18], if this overhead is likely to intervals specified in RFC 4861 [20], if this overhead is likely to
cause service degradation. cause service degradation.
Additionally, the possible low values of MaxRtrAdvInterval may cause Additionally, the possible low values of MaxRtrAdvInterval may cause
some problems with movement detection in some mobile nodes. To some problems with movement detection in some mobile nodes. To
ensure that this is not a problem, Routers SHOULD add 20ms to any ensure that this is not a problem, Routers SHOULD add 20ms to any
Advertisement Intervals sent in RAs, which are below 200 ms, in order Advertisement Intervals sent in RAs, which are below 200 ms, in order
to account for scheduling granularities on both the MN and the to account for scheduling granularities on both the MN and the
Router. Router.
Note that multicast Router Advertisements are not always required in Note that multicast Router Advertisements are not always required in
certain wireless networks that have limited bandwidth. Mobility certain wireless networks that have limited bandwidth. Mobility
detection or link changes in such networks may be done at lower detection or link changes in such networks may be done at lower
layers. Router advertisements in such networks SHOULD be sent only layers. Router advertisements in such networks SHOULD be sent only
when solicited. In such networks it SHOULD be possible to disable when solicited. In such networks it SHOULD be possible to disable
unsolicited multicast Router Advertisements on specific interfaces. unsolicited multicast Router Advertisements on specific interfaces.
The MinRtrAdvInterval and MaxRtrAdvInterval in such a case can be set The MinRtrAdvInterval and MaxRtrAdvInterval in such a case can be set
to some high values. to some high values.
Home agents MUST include the Source Link-Layer Address option in all Home agents MUST include the Source Link-Layer Address option in all
Router Advertisements they send. This simplifies the process of Router Advertisements they send. This simplifies the process of
returning home, as discussed in Section 11.5.4. returning home, as discussed in Section 11.5.5.
Note that according to RFC 4861 [18], AdvDefaultLifetime is by Note that according to RFC 4861 [20], AdvDefaultLifetime is by
default based on the value of MaxRtrAdvInterval. AdvDefaultLifetime default based on the value of MaxRtrAdvInterval. AdvDefaultLifetime
is used in the Router Lifetime field of Router Advertisements. Given is used in the Router Lifetime field of Router Advertisements. Given
that this field is expressed in seconds, a small MaxRtrAdvInterval that this field is expressed in seconds, a small MaxRtrAdvInterval
value can result in a zero value for this field. To prevent this, value can result in a zero value for this field. To prevent this,
routers SHOULD keep AdvDefaultLifetime in at least one second, even routers SHOULD keep AdvDefaultLifetime in at least one second, even
if the use of MaxRtrAdvInterval would result in a smaller value. if the use of MaxRtrAdvInterval would result in a smaller value.
8. Requirements for Types of IPv6 Nodes 8. Requirements for Types of IPv6 Nodes
Mobile IPv6 places some special requirements on the functions Mobile IPv6 places some special requirements on the functions
skipping to change at page 73, line 27 skipping to change at page 73, line 27
o The node SHOULD allow route optimization to be administratively o The node SHOULD allow route optimization to be administratively
enabled or disabled. The default SHOULD be enabled. enabled or disabled. The default SHOULD be enabled.
8.3. All IPv6 Routers 8.3. All IPv6 Routers
All IPv6 routers, even those not serving as a home agent for Mobile All IPv6 routers, even those not serving as a home agent for Mobile
IPv6, have an effect on how well mobile nodes can communicate: IPv6, have an effect on how well mobile nodes can communicate:
o Every IPv6 router SHOULD be able to send an Advertisement Interval o Every IPv6 router SHOULD be able to send an Advertisement Interval
option (Section 7.3) in each of its Router Advertisements [18], to option (Section 7.3) in each of its Router Advertisements [20], to
aid movement detection by mobile nodes (as in Section 11.5.1). aid movement detection by mobile nodes (as in Section 11.5.1).
The use of this option in Router Advertisements SHOULD be The use of this option in Router Advertisements SHOULD be
configurable. configurable.
o Every IPv6 router SHOULD be able to support sending unsolicited o Every IPv6 router SHOULD be able to support sending unsolicited
multicast Router Advertisements at the faster rate described in multicast Router Advertisements at the faster rate described in
Section 7.5. If the router supports a faster rate, the used rate Section 7.5. If the router supports a faster rate, the used rate
MUST be configurable. MUST be configurable.
o Each router SHOULD include at least one prefix with the Router o Each router SHOULD include at least one prefix with the Router
skipping to change at page 74, line 10 skipping to change at page 74, line 10
In order for a mobile node to operate correctly while away from home, In order for a mobile node to operate correctly while away from home,
at least one IPv6 router on the mobile node's home link must function at least one IPv6 router on the mobile node's home link must function
as a home agent for the mobile node. The following additional as a home agent for the mobile node. The following additional
requirements apply to all IPv6 routers that serve as a home agent: requirements apply to all IPv6 routers that serve as a home agent:
o Every home agent MUST be able to maintain an entry in its Binding o Every home agent MUST be able to maintain an entry in its Binding
Cache for each mobile node for which it is serving as the home Cache for each mobile node for which it is serving as the home
agent (Section 10.1 and Section 10.3.1). agent (Section 10.1 and Section 10.3.1).
o Every home agent MUST be able to intercept packets (using proxy o Every home agent MUST be able to intercept packets (using proxy
Neighbor Discovery [18]) addressed to a mobile node for which it Neighbor Discovery [20]) addressed to a mobile node for which it
is currently serving as the home agent, on that mobile node's home is currently serving as the home agent, on that mobile node's home
link, while the mobile node is away from home (Section 10.4.1). link, while the mobile node is away from home (Section 10.4.1).
o Every home agent MUST be able to encapsulate [9] such intercepted o Every home agent MUST be able to encapsulate [9] such intercepted
packets in order to tunnel them to the primary care-of address for packets in order to tunnel them to the primary care-of address for
the mobile node indicated in its binding in the home agent's the mobile node indicated in its binding in the home agent's
Binding Cache (Section 10.4.2). Binding Cache (Section 10.4.2).
o Every home agent MUST support decapsulating [9] reverse tunneled o Every home agent MUST support decapsulating [9] reverse tunneled
packets sent to it from a mobile node's home address. Every home packets sent to it from a mobile node's home address. Every home
skipping to change at page 76, line 24 skipping to change at page 76, line 24
o The node MUST allow route optimization to be administratively o The node MUST allow route optimization to be administratively
enabled or disabled. The default SHOULD be enabled. enabled or disabled. The default SHOULD be enabled.
o The node MAY support the multicast address listener part of a o The node MAY support the multicast address listener part of a
multicast group membership protocol as described in multicast group membership protocol as described in
Section 11.3.4. If this support is provided, the mobile node MUST Section 11.3.4. If this support is provided, the mobile node MUST
be able to receive tunneled multicast packets from the home agent. be able to receive tunneled multicast packets from the home agent.
o The node MAY support stateful address autoconfiguration mechanisms o The node MAY support stateful address autoconfiguration mechanisms
such as DHCPv6 [27] on the interface represented by the tunnel to such as DHCPv6 [32] on the interface represented by the tunnel to
the home agent. the home agent.
9. Correspondent Node Operation 9. Correspondent Node Operation
9.1. Conceptual Data Structures 9.1. Conceptual Data Structures
IPv6 nodes with route optimization support maintain a Binding Cache IPv6 nodes with route optimization support maintain a Binding Cache
of bindings for other nodes. A separate Binding Cache SHOULD be of bindings for other nodes. A separate Binding Cache SHOULD be
maintained by each IPv6 node for each of its unicast routable maintained by each IPv6 node for each of its unicast routable
addresses. The Binding Cache MAY be implemented in any manner addresses. The Binding Cache MAY be implemented in any manner
consistent with the external behavior described in this document, for consistent with the external behavior described in this document, for
example by being combined with the node's Destination Cache as example by being combined with the node's Destination Cache as
maintained by Neighbor Discovery [18]. When sending a packet, the maintained by Neighbor Discovery [20]. When sending a packet, the
Binding Cache is searched before the Neighbor Discovery conceptual Binding Cache is searched before the Neighbor Discovery conceptual
Destination Cache [18]. Destination Cache [20].
Each Binding Cache entry conceptually contains the following fields: Each Binding Cache entry conceptually contains the following fields:
o The home address of the mobile node for which this is the Binding o The home address of the mobile node for which this is the Binding
Cache entry. This field is used as the key for searching the Cache entry. This field is used as the key for searching the
Binding Cache for the destination address of a packet being sent. Binding Cache for the destination address of a packet being sent.
o The care-of address for the mobile node indicated by the home o The care-of address for the mobile node indicated by the home
address field in this Binding Cache entry. address field in this Binding Cache entry.
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node MUST silently discard the message. node MUST silently discard the message.
o The MH Type field MUST have a known value (Section 6.1.1). o The MH Type field MUST have a known value (Section 6.1.1).
Otherwise, the node MUST discard the message and issue a Binding Otherwise, the node MUST discard the message and issue a Binding
Error message as described in Section 9.3.3, with Status field set Error message as described in Section 9.3.3, with Status field set
to 2 (unrecognized MH Type value). to 2 (unrecognized MH Type value).
o The Payload Proto field MUST be IPPROTO_NONE (59 decimal). o The Payload Proto field MUST be IPPROTO_NONE (59 decimal).
Otherwise, the node MUST discard the message and SHOULD send ICMP Otherwise, the node MUST discard the message and SHOULD send ICMP
Parameter Problem, Code 0, directly to the Source Address of the Parameter Problem, Code 0, directly to the Source Address of the
packet as specified in RFC 4443 [17]. Thus no Binding Cache packet as specified in RFC 4443 [19]. Thus no Binding Cache
information is used in sending the ICMP message. The Pointer information is used in sending the ICMP message. The Pointer
field in the ICMP message SHOULD point at the Payload Proto field. field in the ICMP message SHOULD point at the Payload Proto field.
o The Header Len field in the Mobility Header MUST NOT be less than o The Header Len field in the Mobility Header MUST NOT be less than
the length specified for this particular type of message in the length specified for this particular type of message in
Section 6.1. Otherwise, the node MUST discard the message and Section 6.1. Otherwise, the node MUST discard the message and
SHOULD send ICMP Parameter Problem, Code 0, directly to the Source SHOULD send ICMP Parameter Problem, Code 0, directly to the Source
Address of the packet as specified in RFC 4443 [17]. (The Binding Address of the packet as specified in RFC 4443 [19]. (The Binding
Cache information is again not used.) The Pointer field in the Cache information is again not used.) The Pointer field in the
ICMP message SHOULD point at the Header Len field. ICMP message SHOULD point at the Header Len field.
Subsequent checks depend on the particular Mobility Header. Subsequent checks depend on the particular Mobility Header.
9.3. Packet Processing 9.3. Packet Processing
This section describes how the correspondent node sends packets to This section describes how the correspondent node sends packets to
the mobile node, and receives packets from it. the mobile node, and receives packets from it.
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9.3.2. Sending Packets to a Mobile Node 9.3.2. Sending Packets to a Mobile Node
Before sending any packet, the sending node SHOULD examine its Before sending any packet, the sending node SHOULD examine its
Binding Cache for an entry for the destination address to which the Binding Cache for an entry for the destination address to which the
packet is being sent. If the sending node has a Binding Cache entry packet is being sent. If the sending node has a Binding Cache entry
for this address, the sending node SHOULD use a type 2 routing header for this address, the sending node SHOULD use a type 2 routing header
to route the packet to this mobile node (the destination node) by way to route the packet to this mobile node (the destination node) by way
of its care-of address. However, the sending node MUST NOT do this of its care-of address. However, the sending node MUST NOT do this
in the following cases: in the following cases:
o When sending an IPv6 Neighbor Discovery [18] packet. o When sending an IPv6 Neighbor Discovery [20] packet.
o Where otherwise noted in Section 6.1. o Where otherwise noted in Section 6.1.
When calculating authentication data in a packet that contains a type When calculating authentication data in a packet that contains a type
2 routing header, the correspondent node MUST calculate the AH 2 routing header, the correspondent node MUST calculate the AH
authentication data as if the following were true: The routing header authentication data as if the following were true: The routing header
contains the care-of address, the destination IPv6 address field of contains the care-of address, the destination IPv6 address field of
the IPv6 header contains the home address, and the Segments Left the IPv6 header contains the home address, and the Segments Left
field is zero. The IPsec Security Policy Database lookup MUST based field is zero. The IPsec Security Policy Database lookup MUST based
on the mobile node's home address. on the mobile node's home address.
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The Home Address field in the Binding Error message MUST be copied The Home Address field in the Binding Error message MUST be copied
from the Home Address field in the Home Address destination option of from the Home Address field in the Home Address destination option of
the offending packet, or set to the unspecified address if no such the offending packet, or set to the unspecified address if no such
option appeared in the packet. option appeared in the packet.
Note that the IPv6 Source Address and Home Address field values Note that the IPv6 Source Address and Home Address field values
discussed above are the values from the wire, i.e., before any discussed above are the values from the wire, i.e., before any
modifications possibly performed as specified in Section 9.3.1. modifications possibly performed as specified in Section 9.3.1.
Binding Error messages SHOULD be subject to rate limiting in the same Binding Error messages SHOULD be subject to rate limiting in the same
manner as is done for ICMPv6 messages [17]. manner as is done for ICMPv6 messages [19].
9.3.4. Receiving ICMP Error Messages 9.3.4. Receiving ICMP Error Messages
When the correspondent node has a Binding Cache entry for a mobile When the correspondent node has a Binding Cache entry for a mobile
node, all traffic destined to the mobile node goes directly to the node, all traffic destined to the mobile node goes directly to the
current care-of address of the mobile node using a routing header. current care-of address of the mobile node using a routing header.
Any ICMP error message caused by packets on their way to the care-of Any ICMP error message caused by packets on their way to the care-of
address will be returned in the normal manner to the correspondent address will be returned in the normal manner to the correspondent
node. node.
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index, sequence number being out of window (Section 9.5.1), or index, sequence number being out of window (Section 9.5.1), or
insufficiency of resources (Section 9.5.2), a Binding insufficiency of resources (Section 9.5.2), a Binding
Acknowledgement MUST be sent. If the node accepts the Binding Acknowledgement MUST be sent. If the node accepts the Binding
Update, the Binding Acknowledgement SHOULD NOT be sent. Update, the Binding Acknowledgement SHOULD NOT be sent.
If the node accepts the Binding Update and creates or updates an If the node accepts the Binding Update and creates or updates an
entry for this binding, the Status field in the Binding entry for this binding, the Status field in the Binding
Acknowledgement MUST be set to a value less than 128. Otherwise, the Acknowledgement MUST be set to a value less than 128. Otherwise, the
Status field MUST be set to a value greater than or equal to 128. Status field MUST be set to a value greater than or equal to 128.
Values for the Status field are described in Section 6.1.8 and in the Values for the Status field are described in Section 6.1.8 and in the
IANA registry of assigned numbers [12]. IANA registry of assigned numbers [13].
If the Status field in the Binding Acknowledgement contains the value If the Status field in the Binding Acknowledgement contains the value
136 (expired home nonce index), 137 (expired care-of nonce index), or 136 (expired home nonce index), 137 (expired care-of nonce index), or
138 (expired nonces) then the message MUST NOT include the Binding 138 (expired nonces) then the message MUST NOT include the Binding
Authorization Data mobility option. Otherwise, the Binding Authorization Data mobility option. Otherwise, the Binding
Authorization Data mobility option MUST be included, and MUST meet Authorization Data mobility option MUST be included, and MUST meet
the specific authentication requirements for Binding Acknowledgements the specific authentication requirements for Binding Acknowledgements
as defined in Section 5.2. as defined in Section 5.2.
If the Source Address field of the IPv6 header that carried the If the Source Address field of the IPv6 header that carried the
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Section 9.1. Section 9.1.
The Home Agents List is maintained by each home agent, recording The Home Agents List is maintained by each home agent, recording
information about each router on the same link that is acting as a information about each router on the same link that is acting as a
home agent. This list is used by the dynamic home agent address home agent. This list is used by the dynamic home agent address
discovery mechanism. A router is known to be acting as a home agent, discovery mechanism. A router is known to be acting as a home agent,
if it sends a Router Advertisement in which the Home Agent (H) bit is if it sends a Router Advertisement in which the Home Agent (H) bit is
set. When the lifetime for a list entry (defined below) expires, set. When the lifetime for a list entry (defined below) expires,
that entry is removed from the Home Agents List. The Home Agents that entry is removed from the Home Agents List. The Home Agents
List is similar to the Default Router List conceptual data structure List is similar to the Default Router List conceptual data structure
maintained by each host for Neighbor Discovery [18]. The Home Agents maintained by each host for Neighbor Discovery [20]. The Home Agents
List MAY be implemented in any manner consistent with the external List MAY be implemented in any manner consistent with the external
behavior described in this document. behavior described in this document.
Each home agent maintains a separate Home Agents List for each link Each home agent maintains a separate Home Agents List for each link
on which it is serving as a home agent. A new entry is created or an on which it is serving as a home agent. A new entry is created or an
existing entry is updated in response to receipt of a valid Router existing entry is updated in response to receipt of a valid Router
Advertisement in which the Home Agent (H) bit is set. Each Home Advertisement in which the Home Agent (H) bit is set. Each Home
Agents List entry conceptually contains the following fields: Agents List entry conceptually contains the following fields:
o The link-local IP address of a home agent on the link. This o The link-local IP address of a home agent on the link. This
address is learned through the Source Address of the Router address is learned through the Source Address of the Router
Advertisements [18] received from the router. Advertisements [20] received from the router.
o One or more global IP addresses for this home agent. Global o One or more global IP addresses for this home agent. Global
addresses are learned through Prefix Information options with the addresses are learned through Prefix Information options with the
Router Address (R) bit set and received in Router Advertisements Router Address (R) bit set and received in Router Advertisements
from this link-local address. Global addresses for the router in from this link-local address. Global addresses for the router in
a Home Agents List entry MUST be deleted once the prefix a Home Agents List entry MUST be deleted once the prefix
associated with that address is no longer valid [18]. associated with that address is no longer valid [20].
o The remaining lifetime of this Home Agents List entry. If a Home o The remaining lifetime of this Home Agents List entry. If a Home
Agent Information Option is present in a Router Advertisement Agent Information Option is present in a Router Advertisement
received from a home agent, the lifetime of the Home Agents List received from a home agent, the lifetime of the Home Agents List
entry representing that home agent is initialized from the Home entry representing that home agent is initialized from the Home
Agent Lifetime field in the option (if present); otherwise, the Agent Lifetime field in the option (if present); otherwise, the
lifetime is initialized from the Router Lifetime field in the lifetime is initialized from the Router Lifetime field in the
received Router Advertisement. If Home Agents List entry lifetime received Router Advertisement. If Home Agents List entry lifetime
reaches zero, the entry MUST be deleted from the Home Agents List. reaches zero, the entry MUST be deleted from the Home Agents List.
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the home address of the mobile node. the home address of the mobile node.
The home agent MUST mark this Binding Cache entry as a home The home agent MUST mark this Binding Cache entry as a home
registration to indicate that the node is serving as a home agent for registration to indicate that the node is serving as a home agent for
this binding. Binding Cache entries marked as a home registration this binding. Binding Cache entries marked as a home registration
MUST be excluded from the normal cache replacement policy used for MUST be excluded from the normal cache replacement policy used for
the Binding Cache (Section 9.6) and MUST NOT be removed from the the Binding Cache (Section 9.6) and MUST NOT be removed from the
Binding Cache until the expiration of the Lifetime period. Binding Cache until the expiration of the Lifetime period.
Unless this home agent already has a binding for the given home Unless this home agent already has a binding for the given home
address, the home agent MUST perform Duplicate Address Detection [19] address, the home agent MUST perform Duplicate Address Detection [21]
on the mobile node's home link before returning the Binding on the mobile node's home link before returning the Binding
Acknowledgement. This ensures that no other node on the home link Acknowledgement. This ensures that no other node on the home link
was using the mobile node's home address when the Binding Update was using the mobile node's home address when the Binding Update
arrived. If this Duplicate Address Detection fails for the given arrived. If this Duplicate Address Detection fails for the given
home address or an associated link local address, then the home agent home address or an associated link local address, then the home agent
MUST reject the complete Binding Update and MUST return a Binding MUST reject the complete Binding Update and MUST return a Binding
Acknowledgement to the mobile node, in which the Status field is set Acknowledgement to the mobile node, in which the Status field is set
to 134 (Duplicate Address Detection failed). When the home agent to 134 (Duplicate Address Detection failed). When the home agent
sends a successful Binding Acknowledgement to the mobile node, the sends a successful Binding Acknowledgement to the mobile node, the
home agent assures to the mobile node that its address(es) will be home agent assures to the mobile node that its address(es) will be
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The lifetime of the Binding Cache entry depends on a number of The lifetime of the Binding Cache entry depends on a number of
factors: factors:
o The lifetime for the Binding Cache entry MUST NOT be greater than o The lifetime for the Binding Cache entry MUST NOT be greater than
the Lifetime value specified in the Binding Update. the Lifetime value specified in the Binding Update.
o The lifetime for the Binding Cache entry MUST NOT be greater than o The lifetime for the Binding Cache entry MUST NOT be greater than
the remaining valid lifetime for the subnet prefix in the mobile the remaining valid lifetime for the subnet prefix in the mobile
node's home address specified with the Binding Update. The node's home address specified with the Binding Update. The
remaining valid lifetime for this prefix is determined by the home remaining valid lifetime for this prefix is determined by the home
agent based on its own Prefix List entry [18]. agent based on its own Prefix List entry [20].
The remaining preferred lifetime SHOULD NOT have any impact on the The remaining preferred lifetime SHOULD NOT have any impact on the
lifetime for the binding cache entry. lifetime for the binding cache entry.
The home agent MUST remove a binding when the valid lifetime of The home agent MUST remove a binding when the valid lifetime of
the prefix associated with it expires. the prefix associated with it expires.
o The home agent MAY further decrease the specified lifetime for the o The home agent MAY further decrease the specified lifetime for the
binding, for example based on a local policy. The resulting binding, for example based on a local policy. The resulting
lifetime is stored by the home agent in the Binding Cache entry, lifetime is stored by the home agent in the Binding Cache entry,
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10.4. Packet Processing 10.4. Packet Processing
10.4.1. Intercepting Packets for a Mobile Node 10.4.1. Intercepting Packets for a Mobile Node
While a node is serving as the home agent for mobile node it MUST While a node is serving as the home agent for mobile node it MUST
attempt to intercept packets on the mobile node's home link that are attempt to intercept packets on the mobile node's home link that are
addressed to the mobile node. addressed to the mobile node.
In order to do this, when a node begins serving as the home agent it In order to do this, when a node begins serving as the home agent it
MUST multicast onto the home link a Neighbor Advertisement message MUST multicast onto the home link a Neighbor Advertisement message
[18] on behalf of the mobile node. For the home address specified in [20] on behalf of the mobile node. For the home address specified in
the Binding Update, the home agent sends a Neighbor Advertisement the Binding Update, the home agent sends a Neighbor Advertisement
message [18] to the all-nodes multicast address on the home link to message [20] to the all-nodes multicast address on the home link to
advertise the home agent's own link-layer address for this IP address advertise the home agent's own link-layer address for this IP address
on behalf of the mobile node. If the Link-Layer Address on behalf of the mobile node. If the Link-Layer Address
Compatibility (L) flag has been specified in the Binding Update, the Compatibility (L) flag has been specified in the Binding Update, the
home agent MUST do the same for the link-local address of the mobile home agent MUST do the same for the link-local address of the mobile
node. node.
All fields in each Neighbor Advertisement message SHOULD be set in All fields in each Neighbor Advertisement message SHOULD be set in
the same way they would be set by the mobile node if it was sending the same way they would be set by the mobile node if it was sending
this Neighbor Advertisement [18] while at home, with the following this Neighbor Advertisement [20] while at home, with the following
exceptions: exceptions:
o The Target Address in the Neighbor Advertisement MUST be set to o The Target Address in the Neighbor Advertisement MUST be set to
the specific IP address for the mobile node. the specific IP address for the mobile node.
o The Advertisement MUST include a Target Link-layer Address option o The Advertisement MUST include a Target Link-layer Address option
specifying the home agent's link-layer address. specifying the home agent's link-layer address.
o The Router (R) bit in the Advertisement MUST be set to zero. o The Router (R) bit in the Advertisement MUST be set to zero.
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advertisement. advertisement.
Any node on the home link that receives one of the Neighbor Any node on the home link that receives one of the Neighbor
Advertisement messages (described above) will update its Neighbor Advertisement messages (described above) will update its Neighbor
Cache to associate the mobile node's address with the home agent's Cache to associate the mobile node's address with the home agent's
link layer address, causing it to transmit any future packets link layer address, causing it to transmit any future packets
normally destined to the mobile node to the mobile node's home agent. normally destined to the mobile node to the mobile node's home agent.
Since multicasting on the local link (such as Ethernet) is typically Since multicasting on the local link (such as Ethernet) is typically
not guaranteed to be reliable, the home agent MAY retransmit this not guaranteed to be reliable, the home agent MAY retransmit this
Neighbor Advertisement message up to MAX_NEIGHBOR_ADVERTISEMENT (see Neighbor Advertisement message up to MAX_NEIGHBOR_ADVERTISEMENT (see
[18]) times to increase its reliability. It is still possible that [20]) times to increase its reliability. It is still possible that
some nodes on the home link will not receive any of the Neighbor some nodes on the home link will not receive any of the Neighbor
Advertisements, but these nodes will eventually be able to detect the Advertisements, but these nodes will eventually be able to detect the
link-layer address change for the mobile node's address through use link-layer address change for the mobile node's address through use
of Neighbor Unreachability Detection [18]. of Neighbor Unreachability Detection [20].
While a node is serving as a home agent for some mobile node, the While a node is serving as a home agent for some mobile node, the
home agent uses IPv6 Neighbor Discovery [18] to intercept unicast home agent uses IPv6 Neighbor Discovery [20] to intercept unicast
packets on the home link addressed to the mobile node. In order to packets on the home link addressed to the mobile node. In order to
intercept packets in this way, the home agent MUST act as a proxy for intercept packets in this way, the home agent MUST act as a proxy for
this mobile node and reply to any received Neighbor Solicitations for this mobile node and reply to any received Neighbor Solicitations for
it. When a home agent receives a Neighbor Solicitation, it MUST it. When a home agent receives a Neighbor Solicitation, it MUST
check if the Target Address specified in the message matches the check if the Target Address specified in the message matches the
address of any mobile node for which it has a Binding Cache entry address of any mobile node for which it has a Binding Cache entry
marked as a home registration. marked as a home registration.
If such an entry exists in the home agent's Binding Cache, the home If such an entry exists in the home agent's Binding Cache, the home
agent MUST reply to the Neighbor Solicitation with a Neighbor agent MUST reply to the Neighbor Solicitation with a Neighbor
Advertisement giving the home agent's own link-layer address as the Advertisement giving the home agent's own link-layer address as the
link-layer address for the specified Target Address. In addition, link-layer address for the specified Target Address. In addition,
the Router (R) bit in the Advertisement MUST be set to zero. Acting the Router (R) bit in the Advertisement MUST be set to zero. Acting
as a proxy in this way allows other nodes on the mobile node's home as a proxy in this way allows other nodes on the mobile node's home
link to resolve the mobile node's address and for the home agent to link to resolve the mobile node's address and for the home agent to
defend these addresses on the home link for Duplicate Address defend these addresses on the home link for Duplicate Address
Detection [18]. Detection [20].
10.4.2. Processing Intercepted Packets 10.4.2. Processing Intercepted Packets
For any packet sent to a mobile node from the mobile node's home For any packet sent to a mobile node from the mobile node's home
agent (in which the home agent is the original sender of the packet), agent (in which the home agent is the original sender of the packet),
the home agent is operating as a correspondent node of the mobile the home agent is operating as a correspondent node of the mobile
node for this packet and the procedures described in Section 9.3.2 node for this packet and the procedures described in Section 9.3.2
apply. The home agent then uses a routing header to route the packet apply. The home agent then uses a routing header to route the packet
to the mobile node by way of the primary care-of address in the home to the mobile node by way of the primary care-of address in the home
agent's Binding Cache. agent's Binding Cache.
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header to the home agent's own IP address and sets the Destination header to the home agent's own IP address and sets the Destination
Address in the tunnel IP header to the mobile node's primary care-of Address in the tunnel IP header to the mobile node's primary care-of
address. When received by the mobile node, normal processing of the address. When received by the mobile node, normal processing of the
tunnel header [9] will result in decapsulation and processing of the tunnel header [9] will result in decapsulation and processing of the
original packet by the mobile node. original packet by the mobile node.
However, packets addressed to the mobile node's link-local address However, packets addressed to the mobile node's link-local address
MUST NOT be tunneled to the mobile node. Instead, these packets MUST MUST NOT be tunneled to the mobile node. Instead, these packets MUST
be discarded and the home agent SHOULD return an ICMP Destination be discarded and the home agent SHOULD return an ICMP Destination
Unreachable, Code 3, message to the packet's Source Address (unless Unreachable, Code 3, message to the packet's Source Address (unless
this Source Address is a multicast address). Packets addressed to this Source Address is a multicast address).
the mobile node's site-local address SHOULD NOT be tunneled to the
mobile node by default.
Interception and tunneling of the following multicast addressed Interception and tunneling of the following multicast addressed
packets on the home network are only done if the home agent supports packets on the home network are only done if the home agent supports
multicast group membership control messages from the mobile node as multicast group membership control messages from the mobile node as
described in the next section. Tunneling of multicast packets to a described in the next section. Tunneling of multicast packets to a
mobile node follows similar limitations to those defined above for mobile node follows similar limitations to those defined above for
unicast packets addressed to the mobile node's link-local address. unicast packets addressed to the mobile node's link-local address.
Multicast packets addressed to a multicast address with link-local Multicast packets addressed to a multicast address with link-local
scope [16], to which the mobile node is subscribed, MUST NOT be scope [18], to which the mobile node is subscribed, MUST NOT be
tunneled to the mobile node. These packets SHOULD be silently tunneled to the mobile node. These packets SHOULD be silently
discarded (after delivering to other local multicast recipients). discarded (after delivering to other local multicast recipients).
Multicast packets addressed to a multicast address with a scope Multicast packets addressed to a multicast address with a scope
larger than link-local, but smaller than global (e.g., site-local and larger than link-local, but smaller than global (e.g., site-local and
organization-local [16]), to which the mobile node is subscribed, organization-local [18]), to which the mobile node is subscribed,
SHOULD NOT be tunneled to the mobile node. Multicast packets SHOULD NOT be tunneled to the mobile node. Multicast packets
addressed with a global scope, to which the mobile node has addressed with a global scope, to which the mobile node has
successfully subscribed, MUST be tunneled to the mobile node. successfully subscribed, MUST be tunneled to the mobile node.
Before tunneling a packet to the mobile node, the home agent MUST Before tunneling a packet to the mobile node, the home agent MUST
perform any IPsec processing as indicated by the security policy data perform any IPsec processing as indicated by the security policy data
base. base.
10.4.3. Multicast Membership Control 10.4.3. Multicast Membership Control
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forwarding, described in the previous section. If this support is forwarding, described in the previous section. If this support is
not provided, multicast group membership control messages are not provided, multicast group membership control messages are
silently ignored. silently ignored.
In order to forward multicast data packets from the home network to In order to forward multicast data packets from the home network to
all the proper mobile nodes, the home agent SHOULD be capable of all the proper mobile nodes, the home agent SHOULD be capable of
receiving tunneled multicast group membership control information receiving tunneled multicast group membership control information
from the mobile node in order to determine which groups the mobile from the mobile node in order to determine which groups the mobile
node has subscribed to. These multicast group membership messages node has subscribed to. These multicast group membership messages
are Listener Report messages specified in MLD [11] or in other are Listener Report messages specified in MLD [11] or in other
protocols such as [34]. protocols such as [40].
The messages are issued by the mobile node, but sent through the The messages are issued by the mobile node, but sent through the
reverse tunnel to the home agent. These messages are issued whenever reverse tunnel to the home agent. These messages are issued whenever
the mobile node decides to enable reception of packets for a the mobile node decides to enable reception of packets for a
multicast group or in response to an MLD Query from the home agent. multicast group or in response to an MLD Query from the home agent.
The mobile node will also issue multicast group control messages to The mobile node will also issue multicast group control messages to
disable reception of multicast packets when it is no longer disable reception of multicast packets when it is no longer
interested in receiving multicasts for a particular group. interested in receiving multicasts for a particular group.
To obtain the mobile node's current multicast group membership the To obtain the mobile node's current multicast group membership the
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section and the multicast forwarding in Section 10.4.2 are to be section and the multicast forwarding in Section 10.4.2 are to be
achieved. At the time of this writing it was thought that a full achieved. At the time of this writing it was thought that a full
IPv6 multicast router function would be necessary on the home agent, IPv6 multicast router function would be necessary on the home agent,
but it may be possible to achieve the same effects through a "proxy but it may be possible to achieve the same effects through a "proxy
MLD" application coupled with kernel multicast forwarding. This may MLD" application coupled with kernel multicast forwarding. This may
be the subject of future specifications. be the subject of future specifications.
10.4.4. Stateful Address Autoconfiguration 10.4.4. Stateful Address Autoconfiguration
This section describes how home agents support the use of stateful This section describes how home agents support the use of stateful
address autoconfiguration mechanisms such as DHCPv6 [27] from the address autoconfiguration mechanisms such as DHCPv6 [32] from the
mobile nodes. If this support is not provided, then the M and O bits mobile nodes. If this support is not provided, then the M and O bits
must remain cleared on the Mobile Prefix Advertisement Messages. Any must remain cleared on the Mobile Prefix Advertisement Messages. Any
mobile node which sends DHCPv6 messages to the home agent without mobile node which sends DHCPv6 messages to the home agent without
this support will not receive a response. this support will not receive a response.
If DHCPv6 is used, packets are sent with link-local source addresses If DHCPv6 is used, packets are sent with link-local source addresses
either to a link-scope multicast address or a link-local address. either to a link-scope multicast address or a link-local address.
Mobile nodes desiring to locate a DHCPv6 service may reverse tunnel Mobile nodes desiring to locate a DHCPv6 service may reverse tunnel
standard DHCPv6 packets to the home agent. Since these link-scope standard DHCPv6 packets to the home agent. Since these link-scope
packets cannot be forwarded onto the home network, it is necessary packets cannot be forwarded onto the home network, it is necessary
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and authentication algorithm MUST be available. It is not necessary and authentication algorithm MUST be available. It is not necessary
to distinguish between different kinds of packets during the return to distinguish between different kinds of packets during the return
routability procedure. routability procedure.
Security associations are needed to provide this protection. When Security associations are needed to provide this protection. When
the care-of address for the mobile node changes as a result of an the care-of address for the mobile node changes as a result of an
accepted Binding Update, special treatment is needed for the next accepted Binding Update, special treatment is needed for the next
packets sent using these security associations. The home agent MUST packets sent using these security associations. The home agent MUST
set the new care-of address as the destination address of these set the new care-of address as the destination address of these
packets, as if the outer header destination address in the security packets, as if the outer header destination address in the security
association had changed [14]. association had changed [15].
The above protection SHOULD be used with all mobile nodes. The use The above protection SHOULD be used with all mobile nodes. The use
is controlled by configuration of the IPsec security policy database is controlled by configuration of the IPsec security policy database
both at the mobile node and at the home agent. both at the mobile node and at the home agent.
As described earlier, the Binding Update and Binding Acknowledgement As described earlier, the Binding Update and Binding Acknowledgement
messages require protection between the home agent and the mobile messages require protection between the home agent and the mobile
node. The Mobility Header protocol carries both these messages as node. The Mobility Header protocol carries both these messages as
well as the return routability messages. From the point of view of well as the return routability messages. From the point of view of
the security policy database these messages are indistinguishable. the security policy database these messages are indistinguishable.
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10.5.1. Receiving Router Advertisement Messages 10.5.1. Receiving Router Advertisement Messages
For each link on which a router provides service as a home agent, the For each link on which a router provides service as a home agent, the
router maintains a Home Agents List recording information about all router maintains a Home Agents List recording information about all
other home agents on that link. This list is used in the dynamic other home agents on that link. This list is used in the dynamic
home agent address discovery mechanism, described in Section 10.5. home agent address discovery mechanism, described in Section 10.5.
The information for the list is learned through receipt of the The information for the list is learned through receipt of the
periodic unsolicited multicast Router Advertisements, in a manner periodic unsolicited multicast Router Advertisements, in a manner
similar to the Default Router List conceptual data structure similar to the Default Router List conceptual data structure
maintained by each host for Neighbor Discovery [18]. In the maintained by each host for Neighbor Discovery [20]. In the
construction of the Home Agents List, the Router Advertisements are construction of the Home Agents List, the Router Advertisements are
from each (other) home agent on the link and the Home Agent (H) bit from each (other) home agent on the link and the Home Agent (H) bit
is set in them. is set in them.
On receipt of a valid Router Advertisement, as defined in the On receipt of a valid Router Advertisement, as defined in the
processing algorithm specified for Neighbor Discovery [18], the home processing algorithm specified for Neighbor Discovery [20], the home
agent performs the following steps in addition to any steps already agent performs the following steps in addition to any steps already
required of it by Neighbor Discovery: required of it by Neighbor Discovery:
o If the Home Agent (H) bit in the Router Advertisement is not set, o If the Home Agent (H) bit in the Router Advertisement is not set,
delete the sending node's entry in the current Home Agents List delete the sending node's entry in the current Home Agents List
(if one exists). Skip all the following steps. (if one exists). Skip all the following steps.
o Otherwise, extract the Source Address from the IP header of the o Otherwise, extract the Source Address from the IP header of the
Router Advertisement. This is the link-local IP address on this Router Advertisement. This is the link-local IP address on this
link of the home agent sending this Advertisement [18]. link of the home agent sending this Advertisement [20].
o Determine the preference for this home agent. If the Router o Determine the preference for this home agent. If the Router
Advertisement contains a Home Agent Information Option, then the Advertisement contains a Home Agent Information Option, then the
preference is taken from the Home Agent Preference field in the preference is taken from the Home Agent Preference field in the
option; otherwise, the default preference of 0 MUST be used. option; otherwise, the default preference of 0 MUST be used.
o Determine the lifetime for this home agent. If the Router o Determine the lifetime for this home agent. If the Router
Advertisement contains a Home Agent Information Option, then the Advertisement contains a Home Agent Information Option, then the
lifetime is taken from the Home Agent Lifetime field in the lifetime is taken from the Home Agent Lifetime field in the
option; otherwise, the lifetime specified by the Router Lifetime option; otherwise, the lifetime specified by the Router Lifetime
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o If more than one global IP address is associated with a home o If more than one global IP address is associated with a home
agent, these addresses SHOULD be listed in a randomized order. agent, these addresses SHOULD be listed in a randomized order.
o The home agent SHOULD reduce the number of home agent IP addresses o The home agent SHOULD reduce the number of home agent IP addresses
so that the packet fits within the minimum IPv6 MTU [8]. The home so that the packet fits within the minimum IPv6 MTU [8]. The home
agent addresses selected for inclusion in the packet SHOULD be agent addresses selected for inclusion in the packet SHOULD be
those from the complete list with the highest preference. This those from the complete list with the highest preference. This
limitation avoids the danger of the Reply message packet being limitation avoids the danger of the Reply message packet being
fragmented (or rejected by an intermediate router with an ICMP fragmented (or rejected by an intermediate router with an ICMP
Packet Too Big message [17]). Packet Too Big message [19]).
10.6. Sending Prefix Information to the Mobile Node 10.6. Sending Prefix Information to the Mobile Node
10.6.1. List of Home Network Prefixes 10.6.1. List of Home Network Prefixes
Mobile IPv6 arranges to propagate relevant prefix information to the Mobile IPv6 arranges to propagate relevant prefix information to the
mobile node when it is away from home, so that it may be used in mobile node when it is away from home, so that it may be used in
mobile node home address configuration and in network renumbering. mobile node home address configuration and in network renumbering.
In this mechanism, mobile nodes away from home receive Mobile Prefix In this mechanism, mobile nodes away from home receive Mobile Prefix
Advertisements messages. These messages include Prefix Information Advertisements messages. These messages include Prefix Information
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of the home agent. of the home agent.
If there are multiple home agents, differences in the advertisements If there are multiple home agents, differences in the advertisements
sent by different home agents can lead to an inability to use a sent by different home agents can lead to an inability to use a
particular home address when changing to another home agent. In particular home address when changing to another home agent. In
order to ensure that the mobile nodes get the same information from order to ensure that the mobile nodes get the same information from
different home agents, it is preferred that all of the home agents on different home agents, it is preferred that all of the home agents on
the same link be configured in the same manner. the same link be configured in the same manner.
To support this, the home agent monitors prefixes advertised by To support this, the home agent monitors prefixes advertised by
itself and other home agents on the home link. In RFC 4861 [18] it itself and other home agents on the home link. In RFC 4861 [20] it
is acceptable for two routers to advertise different sets of prefixes is acceptable for two routers to advertise different sets of prefixes
on the same link. For home agents, the differences should be on the same link. For home agents, the differences should be
detected for a given home address because the mobile node detected for a given home address because the mobile node
communicates only with one home agent at a time and the mobile node communicates only with one home agent at a time and the mobile node
needs to know the full set of prefixes assigned to the home link. needs to know the full set of prefixes assigned to the home link.
All other comparisons of Router Advertisements are as specified in All other comparisons of Router Advertisements are as specified in
Section 6.2.7 of RFC 4861. Section 6.2.7 of RFC 4861.
10.6.2. Scheduling Prefix Deliveries 10.6.2. Scheduling Prefix Deliveries
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normally, directly between their source and destination without normally, directly between their source and destination without
relying on Mobile IPv6. If application running on the mobile node relying on Mobile IPv6. If application running on the mobile node
has no particular knowledge that the communication being sent fits has no particular knowledge that the communication being sent fits
within this general type of communication, however, the mobile within this general type of communication, however, the mobile
node should not use its care-of address as the source of the node should not use its care-of address as the source of the
packet in this way. packet in this way.
The choice of the most efficient communications method is The choice of the most efficient communications method is
application specific, and outside the scope of this specification. application specific, and outside the scope of this specification.
The APIs necessary for controlling the choice are also out of The APIs necessary for controlling the choice are also out of
scope. scope. One example of such an API is described in the IPv6 Socket
API for Source Address Selection specification [24].
o o While not at its home link, the mobile node MUST NOT use the Home
Address destination option when communicating with link-local
peers.
Similarly, the mobile node MUST NOT use the Home Address Similarly, the mobile node MUST NOT use the Home Address
destination option for IPv6 Neighbor Discovery [18] packets. destination option for IPv6 Neighbor Discovery [20] packets.
Detailed operation of these cases is described later in this section Detailed operation of these cases is described later in this section
and also discussed in [29]. and also discussed in [34].
For packets sent by a mobile node while it is at home, no special For packets sent by a mobile node while it is at home, no special
Mobile IPv6 processing is required. Likewise, if the mobile node Mobile IPv6 processing is required. Likewise, if the mobile node
uses any address other than one of its home addresses as the source uses any address other than one of its home addresses as the source
of a packet sent while away from home, no special Mobile IPv6 of a packet sent while away from home, no special Mobile IPv6
processing is required. In either case, the packet is simply processing is required. In either case, the packet is simply
addressed and transmitted in the same way as any normal IPv6 packet. addressed and transmitted in the same way as any normal IPv6 packet.
For packets sent by the mobile node sent while away from home using For packets sent by the mobile node sent while away from home using
the mobile node's home address as the source, special Mobile IPv6 the mobile node's home address as the source, special Mobile IPv6
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* Change the Source Address field in the packet's IPv6 header to * Change the Source Address field in the packet's IPv6 header to
one of the mobile node's care-of addresses. This will one of the mobile node's care-of addresses. This will
typically be the mobile node's current primary care-of address, typically be the mobile node's current primary care-of address,
but MUST be an address assigned to the interface on the link but MUST be an address assigned to the interface on the link
being used. being used.
By using the care-of address as the Source Address in the IPv6 By using the care-of address as the Source Address in the IPv6
header, with the mobile node's home address instead in the Home header, with the mobile node's home address instead in the Home
Address option, the packet will be able to safely pass through any Address option, the packet will be able to safely pass through any
router implementing ingress filtering [25]. router implementing ingress filtering [30].
Reverse Tunneling Reverse Tunneling
This is the mechanism which tunnels the packets via the home This is the mechanism which tunnels the packets via the home
agent. It is not as efficient as the above mechanism, but is agent. It is not as efficient as the above mechanism, but is
needed if there is no binding yet with the correspondent node. needed if there is no binding yet with the correspondent node.
This mechanism is used for packets that have the mobile node's This mechanism is used for packets that have the mobile node's
home address as the Source Address in the IPv6 header, or with home address as the Source Address in the IPv6 header, or with
multicast control protocol packets as described in Section 11.3.4. multicast control protocol packets as described in Section 11.3.4.
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In order to receive packets sent to some multicast group, a mobile In order to receive packets sent to some multicast group, a mobile
node must join that multicast group. One method, in which a mobile node must join that multicast group. One method, in which a mobile
node MAY join the group, is via a (local) multicast router on the node MAY join the group, is via a (local) multicast router on the
foreign link being visited. In this case, the mobile node MUST use foreign link being visited. In this case, the mobile node MUST use
its care-of address and MUST NOT use the Home Address destination its care-of address and MUST NOT use the Home Address destination
option when sending MLD packets [11]. option when sending MLD packets [11].
Alternatively, a mobile node MAY join multicast groups via a bi- Alternatively, a mobile node MAY join multicast groups via a bi-
directional tunnel to its home agent. The mobile node tunnels its directional tunnel to its home agent. The mobile node tunnels its
multicast group membership control packets (such as those defined in multicast group membership control packets (such as those defined in
[11] or in [34]) to its home agent, and the home agent forwards [11] or in [40]) to its home agent, and the home agent forwards
multicast packets down the tunnel to the mobile node. A mobile node multicast packets down the tunnel to the mobile node. A mobile node
MUST NOT tunnel multicast group membership control packets until (1) MUST NOT tunnel multicast group membership control packets until (1)
the mobile node has a binding in place at the home agent, and (2) the the mobile node has a binding in place at the home agent, and (2) the
latter sends at least one multicast group membership control packet latter sends at least one multicast group membership control packet
via the tunnel. Once this condition is true, the mobile node SHOULD via the tunnel. Once this condition is true, the mobile node SHOULD
assume it does not change as long as the binding does not expire. assume it does not change as long as the binding does not expire.
A mobile node that wishes to send packets to a multicast group also A mobile node that wishes to send packets to a multicast group also
has two options: has two options:
1. Send directly on the foreign link being visited. 1. Send directly on the foreign link being visited.
The application is aware of the care-of address and uses it as a The application uses the care-of address as a source address for
source address for multicast traffic, just like it would use a multicast traffic, just like it would use a stationary address.
stationary address. The mobile node MUST NOT use Home Address This requires that the application either knows the care-of
destination option in such traffic. address, or uses an API such as the IPv6 Socket API for Source
Address Selection specification [24]. to request the stack to use
the care-of address as a source address in sent packets. The
mobile node MUST NOT use Home Address destination option in such
traffic.
2. Send via a tunnel to its home agent. 2. Send via a tunnel to its home agent.
Because multicast routing in general depends upon the Source Because multicast routing in general depends upon the Source
Address used in the IPv6 header of the multicast packet, a mobile Address used in the IPv6 header of the multicast packet, a mobile
node that tunnels a multicast packet to its home agent MUST use node that tunnels a multicast packet to its home agent MUST use
its home address as the IPv6 Source Address of the inner its home address as the IPv6 Source Address of the inner
multicast packet. multicast packet.
Note that direct sending from the foreign link is only applicable Note that direct sending from the foreign link is only applicable
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11.4.3. Receiving Mobile Prefix Advertisements 11.4.3. Receiving Mobile Prefix Advertisements
Section 10.6 describes the operation of a home agent to support boot Section 10.6 describes the operation of a home agent to support boot
time configuration and renumbering a mobile node's home subnet while time configuration and renumbering a mobile node's home subnet while
the mobile node is away from home. The home agent sends Mobile the mobile node is away from home. The home agent sends Mobile
Prefix Advertisements to the mobile node while away from home, giving Prefix Advertisements to the mobile node while away from home, giving
"important" Prefix Information options that describe changes in the "important" Prefix Information options that describe changes in the
prefixes in use on the mobile node's home link. prefixes in use on the mobile node's home link.
The Mobile Prefix Solicitation is similar to the Router Solicitation The Mobile Prefix Solicitation is similar to the Router Solicitation
used in Neighbor Discovery [18], except it is routed from the mobile used in Neighbor Discovery [20], except it is routed from the mobile
node on the visited network to the home agent on the home network by node on the visited network to the home agent on the home network by
usual unicast routing rules. usual unicast routing rules.
When a mobile node receives a Mobile Prefix Advertisement, it MUST When a mobile node receives a Mobile Prefix Advertisement, it MUST
validate it according to the following test: validate it according to the following test:
o The Source Address of the IP packet carrying the Mobile Prefix o The Source Address of the IP packet carrying the Mobile Prefix
Advertisement is the same as the home agent address to which the Advertisement is the same as the home agent address to which the
mobile node last sent an accepted home registration Binding Update mobile node last sent an accepted home registration Binding Update
to register its primary care-of address. Otherwise, if no such to register its primary care-of address. Otherwise, if no such
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Otherwise, the advertisement is unsolicited, and MUST be Otherwise, the advertisement is unsolicited, and MUST be
discarded. In this case the mobile node SHOULD send a Mobile discarded. In this case the mobile node SHOULD send a Mobile
Prefix Solicitation. Prefix Solicitation.
Any received Mobile Prefix Advertisement not meeting these tests MUST Any received Mobile Prefix Advertisement not meeting these tests MUST
be silently discarded. be silently discarded.
For an accepted Mobile Prefix Advertisement, the mobile node MUST For an accepted Mobile Prefix Advertisement, the mobile node MUST
process Managed Address Configuration (M), Other Stateful process Managed Address Configuration (M), Other Stateful
Configuration (O), and the Prefix Information Options as if they Configuration (O), and the Prefix Information Options as if they
arrived in a Router Advertisement [18] on the mobile node's home arrived in a Router Advertisement [20] on the mobile node's home
link. (This specification does not, however, describe how to acquire link. (This specification does not, however, describe how to acquire
home addresses through stateful protocols.) Such processing may home addresses through stateful protocols.) Such processing may
result in the mobile node configuring a new home address, although result in the mobile node configuring a new home address, although
due to separation between preferred lifetime and valid lifetime, such due to separation between preferred lifetime and valid lifetime, such
changes should not affect most communications by the mobile node, in changes should not affect most communications by the mobile node, in
the same way as for nodes that are at home. the same way as for nodes that are at home.
This specification assumes that any security associations and This specification assumes that any security associations and
security policy entries that may be needed for new prefixes have been security policy entries that may be needed for new prefixes have been
pre-configured in the mobile node. Note that while dynamic key pre-configured in the mobile node. Note that while dynamic key
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reachable, in which case the mobile node must discover a new default reachable, in which case the mobile node must discover a new default
router (usually on a new link). However, this detection only occurs router (usually on a new link). However, this detection only occurs
when the mobile node has packets to send, and in the absence of when the mobile node has packets to send, and in the absence of
frequent Router Advertisements or indications from the link-layer, frequent Router Advertisements or indications from the link-layer,
the mobile node might become unaware of an L3 handover that occurred. the mobile node might become unaware of an L3 handover that occurred.
Therefore, the mobile node should supplement this method with other Therefore, the mobile node should supplement this method with other
information whenever it is available to the mobile node (e.g., from information whenever it is available to the mobile node (e.g., from
lower protocol layers). lower protocol layers).
When the mobile node detects an L3 handover, it performs Duplicate When the mobile node detects an L3 handover, it performs Duplicate
Address Detection [19] on its link-local address, selects a new Address Detection [21] on its link-local address, selects a new
default router as a consequence of Router Discovery, and then default router as a consequence of Router Discovery, and then
performs Prefix Discovery with that new router to form new care-of performs Prefix Discovery with that new router to form new care-of
address(es) as described in Section 11.5.2. It then registers its address(es) as described in Section 11.5.3. It then registers its
new primary care-of address with its home agent as described in new primary care-of address with its home agent as described in
Section 11.7.1. After updating its home registration, the mobile Section 11.7.1. After updating its home registration, the mobile
node then updates associated mobility bindings in correspondent nodes node then updates associated mobility bindings in correspondent nodes
that it is performing route optimization with as specified in that it is performing route optimization with as specified in
Section 11.7.2. Section 11.7.2.
Due to the temporary packet flow disruption and signaling overhead Due to the temporary packet flow disruption and signaling overhead
involved in updating mobility bindings, the mobile node should avoid involved in updating mobility bindings, the mobile node should avoid
performing an L3 handover until it is strictly necessary. performing an L3 handover until it is strictly necessary.
Specifically, when the mobile node receives a Router Advertisement Specifically, when the mobile node receives a Router Advertisement
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receive Router Advertisements with the same link-local source receive Router Advertisements with the same link-local source
address. This might be common if routers use the same link-local address. This might be common if routers use the same link-local
address on multiple interfaces. This issue can be avoided when address on multiple interfaces. This issue can be avoided when
routers use the Router Address (R) bit, since that provides a routers use the Router Address (R) bit, since that provides a
global address of the router. global address of the router.
In addition, the mobile node should consider the following events as In addition, the mobile node should consider the following events as
indications that an L3 handover may have occurred. Upon receiving indications that an L3 handover may have occurred. Upon receiving
such indications, the mobile node needs to perform Router Discovery such indications, the mobile node needs to perform Router Discovery
to discover routers and prefixes on the new link, as described in to discover routers and prefixes on the new link, as described in
Section 6.3.7 of RFC 4861 [18]. Section 6.3.7 of RFC 4861 [20].
o If Router Advertisements that the mobile node receives include an o If Router Advertisements that the mobile node receives include an
Advertisement Interval option, the mobile node may use its Advertisement Interval option, the mobile node may use its
Advertisement Interval field as an indication of the frequency Advertisement Interval field as an indication of the frequency
with which it should expect to continue to receive future with which it should expect to continue to receive future
Advertisements from that router. This field specifies the minimum Advertisements from that router. This field specifies the minimum
rate (the maximum amount of time between successive rate (the maximum amount of time between successive
Advertisements) that the mobile node should expect. If this Advertisements) that the mobile node should expect. If this
amount of time elapses without the mobile node receiving any amount of time elapses without the mobile node receiving any
Advertisement from this router, the mobile node can be sure that Advertisement from this router, the mobile node can be sure that
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default router is still bi-directionally reachable. This can be default router is still bi-directionally reachable. This can be
accomplished by sending a unicast Neighbor Solicitation and accomplished by sending a unicast Neighbor Solicitation and
waiting for a Neighbor Advertisement with the solicited flag set. waiting for a Neighbor Advertisement with the solicited flag set.
Note that this is similar to Neighbor Unreachability detection but Note that this is similar to Neighbor Unreachability detection but
it does not have the same state machine, such as the STALE state. it does not have the same state machine, such as the STALE state.
If the default router does not respond to the Neighbor If the default router does not respond to the Neighbor
Solicitation it makes sense to proceed to multicasting a Router Solicitation it makes sense to proceed to multicasting a Router
Solicitation. Solicitation.
11.5.2. Forming New Care-of Addresses 11.5.2. Home Link Detection
When an MN detects that it has arrived on a new link using the
movement detection algorithm in use (Section Section 11.5.1,) it
performs the following steps to determine if it is on the home link.
o The MN performs the procedure described in Section 11.5.2x and
configures an address. It also keeps track of all the on-link
prefix(es) received in the RA along with their prefix lengths.
o If the home prefix has not been statically configured the MN uses
some form of bootstrapping procedure (e.g. RFC5026 [25]) to
determine the home prefix.
o Given the availability of the home prefix, the MN checks whether
or not the home prefix matches one of the prefixes received in the
RA. If it does, the MN concludes that it has returned home.
11.5.3. Forming New Care-of Addresses
After detecting that it has moved a mobile node SHOULD generate a new After detecting that it has moved a mobile node SHOULD generate a new
primary care-of address using normal IPv6 mechanisms. This SHOULD primary care-of address using normal IPv6 mechanisms. This SHOULD
also be done when the current primary care-of address becomes also be done when the current primary care-of address becomes
deprecated. A mobile node MAY form a new primary care-of address at deprecated. A mobile node MAY form a new primary care-of address at
any time, but a mobile node MUST NOT send a Binding Update about a any time, but a mobile node MUST NOT send a Binding Update about a
new care-of address to its home agent more than MAX_UPDATE_RATE times new care-of address to its home agent more than MAX_UPDATE_RATE times
within a second. within a second.
In addition, a mobile node MAY form new non-primary care-of addresses In addition, a mobile node MAY form new non-primary care-of addresses
even when it has not switched to a new default router. A mobile node even when it has not switched to a new default router. A mobile node
can have only one primary care-of address at a time (which is can have only one primary care-of address at a time (which is
registered with its home agent), but it MAY have an additional registered with its home agent), but it MAY have an additional
care-of address for any or all of the prefixes on its current link. care-of address for any or all of the prefixes on its current link.
Furthermore, since a wireless network interface may actually allow a Furthermore, since a wireless network interface may actually allow a
mobile node to be reachable on more than one link at a time (i.e., mobile node to be reachable on more than one link at a time (i.e.,
within wireless transmitter range of routers on more than one within wireless transmitter range of routers on more than one
separate link), a mobile node MAY have care-of addresses on more than separate link), a mobile node MAY have care-of addresses on more than
one link at a time. The use of more than one care-of address at a one link at a time. The use of more than one care-of address at a
time is described in Section 11.5.3. time is described in Section 11.5.4.
As described in Section 4, in order to form a new care-of address, a As described in Section 4, in order to form a new care-of address, a
mobile node MAY use either stateless [19] or stateful (e.g., DHCPv6 mobile node MAY use either stateless [21] or stateful (e.g., DHCPv6
[27]) Address Autoconfiguration. If a mobile node needs to use a [32]) Address Autoconfiguration. If a mobile node needs to use a
source address (other than the unspecified address) in packets sent source address (other than the unspecified address) in packets sent
as a part of address autoconfiguration, it MUST use an IPv6 link- as a part of address autoconfiguration, it MUST use an IPv6 link-
local address rather than its own IPv6 home address. local address rather than its own IPv6 home address.
RFC 4862 [19] specifies that in normal processing for Duplicate RFC 4862 [21] specifies that in normal processing for Duplicate
Address Detection, the node SHOULD delay sending the initial Neighbor Address Detection, the node SHOULD delay sending the initial Neighbor
Solicitation message by a random delay between 0 and Solicitation message by a random delay between 0 and
MAX_RTR_SOLICITATION_DELAY. Since delaying DAD can result in MAX_RTR_SOLICITATION_DELAY. Since delaying DAD can result in
significant delays in configuring a new care-of address when the significant delays in configuring a new care-of address when the
Mobile Node moves to a new link, the Mobile Node preferably SHOULD Mobile Node moves to a new link, the Mobile Node preferably SHOULD
NOT delay DAD when configuring a new care-of address. The Mobile NOT delay DAD when configuring a new care-of address. The Mobile
Node SHOULD delay according to the mechanisms specified in RFC 4862 Node SHOULD delay according to the mechanisms specified in RFC 4862
unless the implementation has a behavior that desynchronizes the unless the implementation has a behavior that desynchronizes the
steps that happen before the DAD in the case that multiple nodes steps that happen before the DAD in the case that multiple nodes
experience handover at the same time. Such desynchronizing behaviors experience handover at the same time. Such desynchronizing behaviors
might be due to random delays in the L2 protocols or device drivers, might be due to random delays in the L2 protocols or device drivers,
or due to the movement detection mechanism that is used. or due to the movement detection mechanism that is used.
11.5.3. Using Multiple Care-of Addresses 11.5.4. Using Multiple Care-of Addresses
As described in Section 11.5.2, a mobile node MAY use more than one As described in Section 11.5.3, a mobile node MAY use more than one
care-of address at a time. Particularly in the case of many wireless care-of address at a time. Particularly in the case of many wireless
networks, a mobile node effectively might be reachable through networks, a mobile node effectively might be reachable through
multiple links at the same time (e.g., with overlapping wireless multiple links at the same time (e.g., with overlapping wireless
cells), on which different on-link subnet prefixes may exist. The cells), on which different on-link subnet prefixes may exist. The
mobile node MUST ensure that its primary care-of address always has a mobile node MUST ensure that its primary care-of address always has a
prefix that is advertised by its current default router. After prefix that is advertised by its current default router. After
selecting a new primary care-of address, the mobile node MUST send a selecting a new primary care-of address, the mobile node MUST send a
Binding Update containing that care-of address to its home agent. Binding Update containing that care-of address to its home agent.
The Binding Update MUST have the Home Registration (H) and The Binding Update MUST have the Home Registration (H) and
Acknowledge (A) bits set its home agent, as described on Acknowledge (A) bits set its home agent, as described on
Section 11.7.1. Section 11.7.1.
To assist with smooth handovers, a mobile node SHOULD retain its To assist with smooth handovers, a mobile node SHOULD retain its
previous primary care-of address as a (non-primary) care-of address, previous primary care-of address as a (non-primary) care-of address,
and SHOULD still accept packets at this address, even after and SHOULD still accept packets at this address, even after
registering its new primary care-of address with its home agent. registering its new primary care-of address with its home agent.
This is reasonable, since the mobile node could only receive packets This is reasonable, since the mobile node could only receive packets
at its previous primary care-of address if it were indeed still at its previous primary care-of address if it were indeed still
connected to that link. If the previous primary care-of address was connected to that link. If the previous primary care-of address was
allocated using stateful Address Autoconfiguration [27], the mobile allocated using stateful Address Autoconfiguration [32], the mobile
node may not wish to release the address immediately upon switching node may not wish to release the address immediately upon switching
to a new primary care-of address. to a new primary care-of address.
Whenever a mobile node determines that it is no longer reachable Whenever a mobile node determines that it is no longer reachable
through a given link, it SHOULD invalidate all care-of addresses through a given link, it SHOULD invalidate all care-of addresses
associated with address prefixes that it discovered from routers on associated with address prefixes that it discovered from routers on
the unreachable link which are not in the current set of address the unreachable link which are not in the current set of address
prefixes advertised by the (possibly new) current default router. prefixes advertised by the (possibly new) current default router.
11.5.4. Returning Home 11.5.5. Returning Home
A mobile node detects that it has returned to its home link through A mobile node detects that it has returned to its home link through
the movement detection algorithm in use (Section 11.5.1), when the the movement detection algorithm in use (Section 11.5.2). The mobile
mobile node detects that its home subnet prefix is again on-link. node SHOULD then send a Binding Update to its home agent, to instruct
The mobile node SHOULD then send a Binding Update to its home agent, its home agent to no longer intercept or tunnel packets for it. In
to instruct its home agent to no longer intercept or tunnel packets this home registration, the mobile node MUST set the Acknowledge (A)
for it. In this home registration, the mobile node MUST set the and Home Registration (H) bits, set the Lifetime field to zero, and
Acknowledge (A) and Home Registration (H) bits, set the Lifetime set the care-of address for the binding to the mobile node's own home
field to zero, and set the care-of address for the binding to the address. The mobile node MUST use its home address as the source
mobile node's own home address. The mobile node MUST use its home address in the Binding Update.
address as the source address in the Binding Update.
When sending this Binding Update to its home agent, the mobile node When sending this Binding Update to its home agent, the mobile node
must be careful in how it uses Neighbor Solicitation [18] (if needed) must be careful in how it uses Neighbor Solicitation [20] (if needed)
to learn the home agent's link-layer address, since the home agent to learn the home agent's link-layer address, since the home agent
will be currently configured to intercept packets to the mobile will be currently configured to intercept packets to the mobile
node's home address using Duplicate Address Detection (DAD). In node's home address using Duplicate Address Detection (DAD). In
particular, the mobile node is unable to use its home address as the particular, the mobile node is unable to use its home address as the
Source Address in the Neighbor Solicitation until the home agent Source Address in the Neighbor Solicitation until the home agent
stops defending the home address. stops defending the home address.
Neighbor Solicitation by the mobile node for the home agent's address Neighbor Solicitation by the mobile node for the home agent's address
will normally not be necessary, since the mobile node has already will normally not be necessary, since the mobile node has already
learned the home agent's link-layer address from a Source Link-Layer learned the home agent's link-layer address from a Source Link-Layer
Address option in a Router Advertisement. However, if there are Address option in a Router Advertisement. However, if there are
multiple home agents it may still be necessary to send a multiple home agents it may still be necessary to send a
solicitation. In this special case of the mobile node returning solicitation. In this special case of the mobile node returning
home, the mobile node MUST multicast the packet, and in addition set home, the mobile node MUST multicast the packet, and in addition set
the Source Address of this Neighbor Solicitation to the unspecified the Source Address of this Neighbor Solicitation to the unspecified
address (0:0:0:0:0:0:0:0). The target of the Neighbor Solicitation address (0:0:0:0:0:0:0:0). The target of the Neighbor Solicitation
MUST be set to the mobile node's home address. The destination IP MUST be set to the mobile node's home address. The destination IP
address MUST be set to the Solicited-Node multicast address [16]. address MUST be set to the Solicited-Node multicast address [18].
The home agent will send a multicast Neighbor Advertisement back to The home agent will send a multicast Neighbor Advertisement back to
the mobile node with the Solicited flag (S) set to zero. In any the mobile node with the Solicited flag (S) set to zero. In any
case, the mobile node SHOULD record the information from the Source case, the mobile node SHOULD record the information from the Source
Link-Layer Address option or from the advertisement, and set the Link-Layer Address option or from the advertisement, and set the
state of the Neighbor Cache entry for the home agent to REACHABLE. state of the Neighbor Cache entry for the home agent to REACHABLE.
The mobile node then sends its Binding Update to the home agent's The mobile node then sends its Binding Update to the home agent's
link-layer address, instructing its home agent to no longer serve as link-layer address, instructing its home agent to no longer serve as
a home agent for it. By processing this Binding Update, the home a home agent for it. By processing this Binding Update, the home
agent will cease defending the mobile node's home address for agent will cease defending the mobile node's home address for
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the Binding Acknowledgement from the home agent may require the Binding Acknowledgement from the home agent may require
performing Neighbor Discovery, and the mobile node may not be able to performing Neighbor Discovery, and the mobile node may not be able to
distinguish Neighbor Solicitations coming from the home agent from distinguish Neighbor Solicitations coming from the home agent from
other Neighbor Solicitations. Note that a race condition exists other Neighbor Solicitations. Note that a race condition exists
where both the mobile node and the home agent respond to the same where both the mobile node and the home agent respond to the same
solicitations sent by other nodes; this will be only temporary, solicitations sent by other nodes; this will be only temporary,
however, until the Binding Update is accepted. however, until the Binding Update is accepted.
After receiving the Binding Acknowledgement for its Binding Update to After receiving the Binding Acknowledgement for its Binding Update to
its home agent, the mobile node MUST multicast onto the home link (to its home agent, the mobile node MUST multicast onto the home link (to
the all-nodes multicast address) a Neighbor Advertisement [18], to the all-nodes multicast address) a Neighbor Advertisement [20], to
advertise the mobile node's own link-layer address for its own home advertise the mobile node's own link-layer address for its own home
address. The Target Address in this Neighbor Advertisement MUST be address. The Target Address in this Neighbor Advertisement MUST be
set to the mobile node's home address, and the Advertisement MUST set to the mobile node's home address, and the Advertisement MUST
include a Target Link-layer Address option specifying the mobile include a Target Link-layer Address option specifying the mobile
node's link-layer address. The mobile node MUST multicast such a node's link-layer address. The mobile node MUST multicast such a
Neighbor Advertisement for each of its home addresses, as defined by Neighbor Advertisement for each of its home addresses, as defined by
the current on-link prefixes, including its link-local address and the current on-link prefixes, including its link-local address. The
site-local address. The Solicited Flag (S) in these Advertisements Solicited Flag (S) in these Advertisements MUST NOT be set, since
MUST NOT be set, since they were not solicited by any Neighbor they were not solicited by any Neighbor Solicitation. The Override
Solicitation. The Override Flag (O) in these Advertisements MUST be Flag (O) in these Advertisements MUST be set, indicating that the
set, indicating that the Advertisements SHOULD override any existing Advertisements SHOULD override any existing Neighbor Cache entries at
Neighbor Cache entries at any node receiving them. any node receiving them.
Since multicasting on the local link (such as Ethernet) is typically Since multicasting on the local link (such as Ethernet) is typically
not guaranteed to be reliable, the mobile node MAY retransmit these not guaranteed to be reliable, the mobile node MAY retransmit these
Neighbor Advertisements [18] up to MAX_NEIGHBOR_ADVERTISEMENT times Neighbor Advertisements [20] up to MAX_NEIGHBOR_ADVERTISEMENT times
to increase their reliability. It is still possible that some nodes to increase their reliability. It is still possible that some nodes
on the home link will not receive any of these Neighbor on the home link will not receive any of these Neighbor
Advertisements, but these nodes will eventually be able to recover Advertisements, but these nodes will eventually be able to recover
through use of Neighbor Unreachability Detection [18]. through use of Neighbor Unreachability Detection [20].
Note that the tunnel via the home agent typically stops operating at Note that the tunnel via the home agent typically stops operating at
the same time that the home registration is deleted. the same time that the home registration is deleted.
11.6. Return Routability Procedure 11.6. Return Routability Procedure
This section defines the rules that the mobile node must follow when This section defines the rules that the mobile node must follow when
performing the return routability procedure. Section 11.7.2 performing the return routability procedure. Section 11.7.2
describes the rules when the return routability procedure needs to be describes the rules when the return routability procedure needs to be
initiated. initiated.
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outgoing tunnel packets to the current primary care-of address. The outgoing tunnel packets to the current primary care-of address. The
mobile node starts to use a new primary care-of address immediately mobile node starts to use a new primary care-of address immediately
after sending a Binding Update to the home agent to register this new after sending a Binding Update to the home agent to register this new
address. address.
11.7. Processing Bindings 11.7. Processing Bindings
11.7.1. Sending Binding Updates to the Home Agent 11.7.1. Sending Binding Updates to the Home Agent
After deciding to change its primary care-of address as described in After deciding to change its primary care-of address as described in
Section 11.5.1 and Section 11.5.2, a mobile node MUST register this Section 11.5.1 and Section 11.5.3, a mobile node MUST register this
care-of address with its home agent in order to make this its primary care-of address with its home agent in order to make this its primary
care-of address. care-of address.
Also, if the mobile node wants the services of the home agent beyond Also, if the mobile node wants the services of the home agent beyond
the current registration period, the mobile node should send a new the current registration period, the mobile node should send a new
Binding Update to it well before the expiration of this period, even Binding Update to it well before the expiration of this period, even
if it is not changing its primary care-of address. However, if the if it is not changing its primary care-of address. However, if the
home agent returned a Binding Acknowledgement for the current home agent returned a Binding Acknowledgement for the current
registration with Status field set to 1 (accepted but prefix registration with Status field set to 1 (accepted but prefix
discovery necessary), the mobile node should not try to register discovery necessary), the mobile node should not try to register
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protocol will not be able to protect care-of addresses in the IPv6 protocol will not be able to protect care-of addresses in the IPv6
header. (Mobile IPv6 implementations that know they are using header. (Mobile IPv6 implementations that know they are using
IPsec AH to protect a particular message might avoid this option. IPsec AH to protect a particular message might avoid this option.
For brevity the usage of AH is not discussed in this document.) For brevity the usage of AH is not discussed in this document.)
o If the mobile node's link-local address has the same interface o If the mobile node's link-local address has the same interface
identifier as the home address for which it is supplying a new identifier as the home address for which it is supplying a new
care-of address, then the mobile node SHOULD set the Link-Local care-of address, then the mobile node SHOULD set the Link-Local
Address Compatibility (L) bit. Address Compatibility (L) bit.
o If the home address was generated using RFC 4941 [20], then the o If the home address was generated using RFC 4941 [23], then the
link local address is unlikely to have a compatible interface link local address is unlikely to have a compatible interface
identifier. In this case, the mobile node MUST clear the Link- identifier. In this case, the mobile node MUST clear the Link-
Local Address Compatibility (L) bit. Local Address Compatibility (L) bit.
o If the IPsec security associations between the mobile node and the o If the IPsec security associations between the mobile node and the
home agent have been established dynamically, and the mobile node home agent have been established dynamically, and the mobile node
has the capability to update its endpoint in the used key has the capability to update its endpoint in the used key
management protocol to the new care-of address every time it management protocol to the new care-of address every time it
moves, the mobile node SHOULD set the Key Management Mobility moves, the mobile node SHOULD set the Key Management Mobility
Capability (K) bit in the Binding Update. Otherwise, the mobile Capability (K) bit in the Binding Update. Otherwise, the mobile
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if the Binding Update was sent to the home agent, underlying IPsec if the Binding Update was sent to the home agent, underlying IPsec
protection is used. If the Binding Update was sent to the protection is used. If the Binding Update was sent to the
correspondent node, the Binding Authorization Data mobility option correspondent node, the Binding Authorization Data mobility option
MUST be present and have a valid value. MUST be present and have a valid value.
o The Binding Authorization Data mobility option, if present, MUST o The Binding Authorization Data mobility option, if present, MUST
be the last option and MUST NOT have trailing padding. be the last option and MUST NOT have trailing padding.
o The Sequence Number field matches the Sequence Number sent by the o The Sequence Number field matches the Sequence Number sent by the
mobile node to this destination address in an outstanding Binding mobile node to this destination address in an outstanding Binding
Update. Update, and the Status field is not 135.
Any Binding Acknowledgement not satisfying all of these tests MUST be Any Binding Acknowledgement not satisfying all of these tests MUST be
silently ignored. silently ignored.
When a mobile node receives a packet carrying a valid Binding When a mobile node receives a packet carrying a valid Binding
Acknowledgement, the mobile node MUST examine the Status field as Acknowledgement, the mobile node MUST examine the Status field as
follows: follows:
o If the Status field indicates that the Binding Update was accepted o If the Status field indicates that the Binding Update was accepted
(the Status field is less than 128), then the mobile node MUST (the Status field is less than 128), then the mobile node MUST
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Update List entry) so that it correctly counts down from the Update List entry) so that it correctly counts down from the
Lifetime value given in the Binding Acknowledgement, but with the Lifetime value given in the Binding Acknowledgement, but with the
timer countdown beginning at the time that the Binding Update was timer countdown beginning at the time that the Binding Update was
sent. sent.
Mobile nodes SHOULD send a new Binding Update well before the Mobile nodes SHOULD send a new Binding Update well before the
expiration of this period in order to extend the lifetime. This expiration of this period in order to extend the lifetime. This
helps to avoid disruptions in communications which might otherwise helps to avoid disruptions in communications which might otherwise
be caused by network delays or clock drift. be caused by network delays or clock drift.
o Additionally, if the Status field value is 1 (accepted but prefix o If the Binding Acknowledgement correctly passes authentication and
discovery necessary), the mobile node SHOULD send a Mobile Prefix the Status field value is 135 (Sequence Number out of window),
then the mobile node MUST update its binding sequence number
appropriately to match the sequence number given in the Binding
Acknowledgement. Otherwise, if the Status field value is 135 but
the Binding Acknowledgement does not pass authentication, the
message MUST be silently ignored.
o If the Status field value is 1 (accepted but prefix discovery
necessary), the mobile node SHOULD send a Mobile Prefix
Solicitation message to update its information about the available Solicitation message to update its information about the available
prefixes. prefixes.
o If the Status field indicates that the Binding Update was rejected o If the Status field indicates that the Binding Update was rejected
(the Status field is greater than or equal to 128), then the (the Status field is greater than or equal to 128), then the
mobile node can take steps to correct the cause of the error and mobile node can take steps to correct the cause of the error and
retransmit the Binding Update (with a new Sequence Number value), retransmit the Binding Update (with a new Sequence Number value),
subject to the rate limiting restriction specified in subject to the rate limiting restriction specified in
Section 11.8. If this is not done or it fails, then the mobile Section 11.8. If this is not done or it fails, then the mobile
node SHOULD record in its Binding Update List that future Binding node SHOULD record in its Binding Update List that future Binding
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MinDelayBetweenRAs Default: 3 seconds, MinDelayBetweenRAs Default: 3 seconds,
Min: 0.03 seconds Min: 0.03 seconds
MinMobPfxAdvInterval Default: 600 seconds MinMobPfxAdvInterval Default: 600 seconds
InitialBindackTimeoutFirstReg Default: 1.5 seconds InitialBindackTimeoutFirstReg Default: 1.5 seconds
Home agents MUST allow the first three variables to be configured by Home agents MUST allow the first three variables to be configured by
system management, and mobile nodes MUST allow the last variable to system management, and mobile nodes MUST allow the last variable to
be configured by system management. be configured by system management.
The default value for InitialBindackTimeoutFirstReg has been The default value for InitialBindackTimeoutFirstReg has been
calculated as 1.5 times the default value of RetransTimer [18] times calculated as 1.5 times the default value of RetransTimer [20] times
the default value of DupAddrDetectTransmits [19]. the default value of DupAddrDetectTransmits [21].
The value MinDelayBetweenRAs overrides the value of the protocol The value MinDelayBetweenRAs overrides the value of the protocol
constant MIN_DELAY_BETWEEN_RAS, as specified in RFC 4861 [18]. This constant MIN_DELAY_BETWEEN_RAS, as specified in RFC 4861 [20]. This
variable SHOULD be set to MinRtrAdvInterval, if MinRtrAdvInterval is variable SHOULD be set to MinRtrAdvInterval, if MinRtrAdvInterval is
less than 3 seconds. less than 3 seconds.
14. IANA Considerations 14. IANA Considerations
This document defines a new IPv6 protocol, the Mobility Header, This document defines a new IPv6 protocol, the Mobility Header,
described in Section 6.1. This protocol has been assigned protocol described in Section 6.1. This protocol has been assigned protocol
number 135. number 135.
This document also creates a new name space "Mobility Header Type", This document also creates a new name space "Mobility Header Type",
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4 Care-of Test 4 Care-of Test
5 Binding Update 5 Binding Update
6 Binding Acknowledgement 6 Binding Acknowledgement
7 Binding Error 7 Binding Error
Future values of the MH Type can be allocated using Standards Action Future values of the MH Type can be allocated using Standards Action
or IESG Approval [21]. or IESG Approval [26].
Furthermore, each mobility message may contain mobility options as Furthermore, each mobility message may contain mobility options as
described in Section 6.2. This document defines a new name space described in Section 6.2. This document defines a new name space
"Mobility Option" to identify these options. The current mobility "Mobility Option" to identify these options. The current mobility
options are defined starting from Section 6.2.2 and are the options are defined starting from Section 6.2.2 and are the
following: following:
0 Pad1 0 Pad1
1 PadN 1 PadN
2 Binding Refresh Advice 2 Binding Refresh Advice
3 Alternate Care-of Address 3 Alternate Care-of Address
4 Nonce Indices 4 Nonce Indices
5 Authorization Data 5 Authorization Data
Future values of the Option Type can be allocated using Standards Future values of the Option Type can be allocated using Standards
Action or IESG Approval [21]. Action or IESG Approval [26].
Finally, this document creates a third new name space "Status Code" Finally, this document creates a third new name space "Status Code"
for the Status field in the Binding Acknowledgement message. The for the Status field in the Binding Acknowledgement message. The
current values are described in Section 6.1.8, and are the following: current values are described in Section 6.1.8, and are the following:
0 Binding Update accepted 0 Binding Update accepted
1 Accepted but prefix discovery necessary 1 Accepted but prefix discovery necessary
128 Reason unspecified 128 Reason unspecified
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136 Expired home nonce index 136 Expired home nonce index
137 Expired care-of nonce index 137 Expired care-of nonce index
138 Expired nonces 138 Expired nonces
139 Registration type change disallowed 139 Registration type change disallowed
Future values of the Status field can be allocated using Standards Future values of the Status field can be allocated using Standards
Action or IESG Approval [21]. Action or IESG Approval [26].
All fields labeled "Reserved" are only to be assigned through All fields labeled "Reserved" are only to be assigned through
Standards Action or IESG Approval. Standards Action or IESG Approval.
This document also defines a new IPv6 destination option, the Home This document also defines a new IPv6 destination option, the Home
Address option, described in Section 6.3. This option has been Address option, described in Section 6.3. This option has been
assigned the Option Type value 0xC9. assigned the Option Type value 0xC9.
This document also defines a new IPv6 type 2 routing header, This document also defines a new IPv6 type 2 routing header,
described in Section 6.4. The value 2 has been allocated by IANA. described in Section 6.4. The value 2 has been allocated by IANA.
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o The Home Agent Address Discovery Request message, described in o The Home Agent Address Discovery Request message, described in
Section 6.5; Section 6.5;
o The Home Agent Address Discovery Reply message, described in o The Home Agent Address Discovery Reply message, described in
Section 6.6; Section 6.6;
o The Mobile Prefix Solicitation, described in Section 6.7; and o The Mobile Prefix Solicitation, described in Section 6.7; and
o The Mobile Prefix Advertisement, described in Section 6.8. o The Mobile Prefix Advertisement, described in Section 6.8.
This document also defines two new Neighbor Discovery [18] options, This document also defines two new Neighbor Discovery [20] options,
which have been assigned Option Type values within the option which have been assigned Option Type values within the option
numbering space for Neighbor Discovery messages: numbering space for Neighbor Discovery messages:
o The Advertisement Interval option, described in Section 7.3; and o The Advertisement Interval option, described in Section 7.3; and
o The Home Agent Information option, described in Section 7.4. o The Home Agent Information option, described in Section 7.4.
15. Security Considerations 15. Security Considerations
15.1. Threats 15.1. Threats
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Service attack. For example, the correspondent node might be a Service attack. For example, the correspondent node might be a
site that will send a high-bandwidth stream of video to anyone who site that will send a high-bandwidth stream of video to anyone who
asks for it. Note that the use of flow-control protocols such as asks for it. Note that the use of flow-control protocols such as
TCP does not necessarily defend against this type of attack, TCP does not necessarily defend against this type of attack,
because the attacker can fake the acknowledgements. Even keeping because the attacker can fake the acknowledgements. Even keeping
TCP initial sequence numbers secret does not help, because the TCP initial sequence numbers secret does not help, because the
attacker can receive the first few segments (including the ISN) at attacker can receive the first few segments (including the ISN) at
its own address, and only then redirect the stream to the victim's its own address, and only then redirect the stream to the victim's
address. These types of attacks may also be directed to networks address. These types of attacks may also be directed to networks
instead of nodes. Further variations of this threat are described instead of nodes. Further variations of this threat are described
elsewhere [26] [31]. elsewhere [31] [36].
An attacker might also attempt to disrupt a mobile node's An attacker might also attempt to disrupt a mobile node's
communications by replaying a Binding Update that the node had communications by replaying a Binding Update that the node had
sent earlier. If the old Binding Update was accepted, packets sent earlier. If the old Binding Update was accepted, packets
destined for the mobile node would be sent to its old location as destined for the mobile node would be sent to its old location as
opposed to its current location. opposed to its current location.
In conclusion, there are Denial-of-Service, Man-in-the-Middle, In conclusion, there are Denial-of-Service, Man-in-the-Middle,
Confidentiality, and Impersonation threats against the parties Confidentiality, and Impersonation threats against the parties
involved in sending legitimate Binding Updates, and Denial-of- involved in sending legitimate Binding Updates, and Denial-of-
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Address destination option, a new routing header type (type 2), Address destination option, a new routing header type (type 2),
and uses tunneling headers in the payload packets. The protocol and uses tunneling headers in the payload packets. The protocol
must protect against potential new threats involving the use of must protect against potential new threats involving the use of
these mechanisms. these mechanisms.
Third parties become exposed to a reflection threat via the Home Third parties become exposed to a reflection threat via the Home
Address destination option, unless appropriate security Address destination option, unless appropriate security
precautions are followed. The Home Address destination option precautions are followed. The Home Address destination option
could be used to direct response traffic toward a node whose IP could be used to direct response traffic toward a node whose IP
address appears in the option. In this case, ingress filtering address appears in the option. In this case, ingress filtering
would not catch the forged "return address" [33] [36]. would not catch the forged "return address" [39] [42].
A similar threat exists with the tunnels between the mobile node A similar threat exists with the tunnels between the mobile node
and the home agent. An attacker might forge tunnel packets and the home agent. An attacker might forge tunnel packets
between the mobile node and the home agent, making it appear that between the mobile node and the home agent, making it appear that
the traffic is coming from the mobile node when it is not. Note the traffic is coming from the mobile node when it is not. Note
that an attacker who is able to forge tunnel packets would that an attacker who is able to forge tunnel packets would
typically also be able to forge packets that appear to come typically also be able to forge packets that appear to come
directly from the mobile node. This is not a new threat as such. directly from the mobile node. This is not a new threat as such.
However, it may make it easier for attackers to escape detection However, it may make it easier for attackers to escape detection
by avoiding ingress filtering and packet tracing mechanisms. by avoiding ingress filtering and packet tracing mechanisms.
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The above mechanisms do not show that the care-of address given in The above mechanisms do not show that the care-of address given in
the Binding Update is correct. This opens the possibility for the Binding Update is correct. This opens the possibility for
Denial-of-Service attacks against third parties. However, since the Denial-of-Service attacks against third parties. However, since the
mobile node and home agent have a security association, the home mobile node and home agent have a security association, the home
agent can always identify an ill-behaving mobile node. This allows agent can always identify an ill-behaving mobile node. This allows
the home agent operator to discontinue the mobile node's service, and the home agent operator to discontinue the mobile node's service, and
possibly take further actions based on the business relationship with possibly take further actions based on the business relationship with
the mobile node's owner. the mobile node's owner.
Note that the use of a single pair of manually keyed security Note that the use of a single pair of manually keyed security
associations conflicts with the generation of a new home address [20] associations conflicts with the generation of a new home address [23]
for the mobile node, or with the adoption of a new home subnet for the mobile node, or with the adoption of a new home subnet
prefix. This is because IPsec security associations are bound to the prefix. This is because IPsec security associations are bound to the
used addresses. While certificate-based automatic keying alleviates used addresses. While certificate-based automatic keying alleviates
this problem to an extent, it is still necessary to ensure that a this problem to an extent, it is still necessary to ensure that a
given mobile node cannot send Binding Updates for the address of given mobile node cannot send Binding Updates for the address of
another mobile node. In general, this leads to the inclusion of home another mobile node. In general, this leads to the inclusion of home
addresses in certificates in the Subject AltName field. This again addresses in certificates in the Subject AltName field. This again
limits the introduction of new addresses without either manual or limits the introduction of new addresses without either manual or
automatic procedures to establish new certificates. Therefore, this automatic procedures to establish new certificates. Therefore, this
specification restricts the generation of new home addresses (for any specification restricts the generation of new home addresses (for any
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vulnerability exists if either the sequence number space is cycled vulnerability exists if either the sequence number space is cycled
through, or if the home agent reboots and forgets its sequence through, or if the home agent reboots and forgets its sequence
numbers (and uses volatile memory to store the sequence numbers). numbers (and uses volatile memory to store the sequence numbers).
Assuming the mobile node moves continuously every 10 minutes, it Assuming the mobile node moves continuously every 10 minutes, it
takes roughly 455 days before the sequence number space has been takes roughly 455 days before the sequence number space has been
cycled through. Typical movement patterns rarely reach this high cycled through. Typical movement patterns rarely reach this high
frequency today. frequency today.
o A mobile node and its home agent belong to the same domain. If o A mobile node and its home agent belong to the same domain. If
this were not the case, manual keying would not be possible [35], this were not the case, manual keying would not be possible [41],
but in Mobile IPv6 only these two parties need to know the but in Mobile IPv6 only these two parties need to know the
manually configured keys. Similarly, we note that Mobile IPv6 manually configured keys. Similarly, we note that Mobile IPv6
employs standard block ciphers in IPsec, and is not vulnerable to employs standard block ciphers in IPsec, and is not vulnerable to
problems associated with stream ciphers and manual keying. problems associated with stream ciphers and manual keying.
o It is expected that the owner of the mobile node and the o It is expected that the owner of the mobile node and the
administrator of the home agent agree on the used keys and other administrator of the home agent agree on the used keys and other
parameters with some off-line mechanism. parameters with some off-line mechanism.
The use of IKEv1 with Mobile IPv6 is documented in more detail in The use of IKEv1 with Mobile IPv6 is documented in more detail in
[14]. The following should be observed from the use of IKEv1: [15]. The following should be observed from the use of IKEv1:
o It is necessary to prevent a mobile node from claiming another o It is necessary to prevent a mobile node from claiming another
mobile node's home address. The home agent must verify that the mobile node's home address. The home agent must verify that the
mobile node trying to negotiate the SA for a particular home mobile node trying to negotiate the SA for a particular home
address is authorized for that home address. This implies that address is authorized for that home address. This implies that
even with the use of IKE, a policy entry needs to be configured even with the use of IKE, a policy entry needs to be configured
for each home address served by the home agent. for each home address served by the home agent.
It may be possible to include home addresses in the Subject It may be possible to include home addresses in the Subject
AltName field of certificate to avoid this. However, AltName field of certificate to avoid this. However,
skipping to change at page 152, line 43 skipping to change at page 153, line 43
approach would require user-specific tasks in the certificate approach would require user-specific tasks in the certificate
authority. authority.
o If preshared secret authentication is used, IKEv1 main mode cannot o If preshared secret authentication is used, IKEv1 main mode cannot
be used. Aggressive mode or group preshared secrets need to be be used. Aggressive mode or group preshared secrets need to be
used with corresponding security implications instead. used with corresponding security implications instead.
Note that, like many other issues, this is a general IKEv1 issue Note that, like many other issues, this is a general IKEv1 issue
related to the ability to use different IP addresses, and not related to the ability to use different IP addresses, and not
specifically related to Mobile IPv6. For further information, see specifically related to Mobile IPv6. For further information, see
Section 4.4 in [14]. Section 4.4 in [15].
o Due to the problems outlined in Section 11.3.2, IKE phase 1 o Due to the problems outlined in Section 11.3.2, IKE phase 1
between the mobile node and its home agent is established using between the mobile node and its home agent is established using
the mobile node's current care-of address. This implies that when the mobile node's current care-of address. This implies that when
the mobile node moves to a new location, it may have to re- the mobile node moves to a new location, it may have to re-
establish phase 1. A Key Management Mobility Capability (K) flag establish phase 1. A Key Management Mobility Capability (K) flag
is provided for implementations that can update the IKE phase 1 is provided for implementations that can update the IKE phase 1
endpoints without re-establishing phase 1, but the support for endpoints without re-establishing phase 1, but the support for
this behavior is optional. this behavior is optional.
o When certificates are used, IKE fragmentation can occur as o When certificates are used, IKE fragmentation can occur as
discussed in Section 7 in [14]. discussed in Section 7 in [15].
o Nevertheless, even if per-mobile node configuration is required o Nevertheless, even if per-mobile node configuration is required
with IKE, an important benefit of IKE is that it automates the with IKE, an important benefit of IKE is that it automates the
negotiation of cryptographic parameters, including the SPIs, negotiation of cryptographic parameters, including the SPIs,
cryptographic algorithms, and so on. Thus, less configuration cryptographic algorithms, and so on. Thus, less configuration
information is needed. information is needed.
o The frequency of movements in some link layers or deployment o The frequency of movements in some link layers or deployment
scenarios may be high enough to make replay and reordering attacks scenarios may be high enough to make replay and reordering attacks
possible, if only manual keying is used. IKE SHOULD be used in possible, if only manual keying is used. IKE SHOULD be used in
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o Similarly, in some deployment scenarios the number of mobile nodes o Similarly, in some deployment scenarios the number of mobile nodes
may be very large. In these cases, it can be necessary to use may be very large. In these cases, it can be necessary to use
automatic mechanisms to reduce the management effort in the automatic mechanisms to reduce the management effort in the
administration of cryptographic parameters, even if some per- administration of cryptographic parameters, even if some per-
mobile node configuration is always needed. IKE SHOULD also be mobile node configuration is always needed. IKE SHOULD also be
used in such cases. used in such cases.
o Other automatic key management mechanisms exist beyond IKEv1, but o Other automatic key management mechanisms exist beyond IKEv1, but
this document does not address the issues related to them. We this document does not address the issues related to them. We
note, however, that most of the above discussion applies to IKEv2 note, however, that most of the above discussion applies to IKEv2
[37] as well, at least as it is currently specified. [43] as well, at least as it is currently specified.
15.4. Binding Updates to Correspondent Nodes 15.4. Binding Updates to Correspondent Nodes
The motivation for designing the return routability procedure was to The motivation for designing the return routability procedure was to
have sufficient support for Mobile IPv6, without creating significant have sufficient support for Mobile IPv6, without creating significant
new security problems. The goal for this procedure was not to new security problems. The goal for this procedure was not to
protect against attacks that were already possible before the protect against attacks that were already possible before the
introduction of Mobile IPv6. introduction of Mobile IPv6.
The next sections will describe the security properties of the used The next sections will describe the security properties of the used
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available. available.
The resulting level of security is in theory the same even without The resulting level of security is in theory the same even without
this additional protection: the return routability tokens are this additional protection: the return routability tokens are
still exposed only to one path within the whole Internet. still exposed only to one path within the whole Internet.
However, the mobile nodes are often found on an insecure link, However, the mobile nodes are often found on an insecure link,
such as a public access Wireless LAN. Thus, in many cases, this such as a public access Wireless LAN. Thus, in many cases, this
addition makes a practical difference. addition makes a practical difference.
For further information about the design rationale of the return For further information about the design rationale of the return
routability procedure, see [26] [31] [30] [36]. The mechanisms used routability procedure, see [31] [36] [35] [42]. The mechanisms used
have been adopted from these documents. have been adopted from these documents.
15.4.2. Achieved Security Properties 15.4.2. Achieved Security Properties
The return routability procedure protects Binding Updates against all The return routability procedure protects Binding Updates against all
attackers who are unable to monitor the path between the home agent attackers who are unable to monitor the path between the home agent
and the correspondent node. The procedure does not defend against and the correspondent node. The procedure does not defend against
attackers who can monitor this path. Note that such attackers are in attackers who can monitor this path. Note that such attackers are in
any case able to mount an active attack against the mobile node when any case able to mount an active attack against the mobile node when
it is at its home location. The possibility of such attacks is not it is at its home location. The possibility of such attacks is not
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particular if these links are publicly accessible wireless LANs. particular if these links are publicly accessible wireless LANs.
Attacks against the routers or switches on the path are typically Attacks against the routers or switches on the path are typically
harder to accomplish. The security on layer 2 of the links plays harder to accomplish. The security on layer 2 of the links plays
then a major role in the resulting overall network security. then a major role in the resulting overall network security.
Similarly, security of IPv6 Neighbor and Router Discovery on these Similarly, security of IPv6 Neighbor and Router Discovery on these
links has a large impact. If these were secured using some new links has a large impact. If these were secured using some new
technology in the future, this could change the situation technology in the future, this could change the situation
regarding the easiest point of attack. regarding the easiest point of attack.
For a more in-depth discussion of these issues, see [36]. For a more in-depth discussion of these issues, see [42].
15.4.4. Replay Attacks 15.4.4. Replay Attacks
The return routability procedure also protects the participants The return routability procedure also protects the participants
against replayed Binding Updates. The attacker is unable replay the against replayed Binding Updates. The attacker is unable replay the
same message due to the sequence number which is a part of the same message due to the sequence number which is a part of the
Binding Update. It is also unable to modify the Binding Update since Binding Update. It is also unable to modify the Binding Update since
the MAC verification would fail after such a modification. the MAC verification would fail after such a modification.
Care must be taken when removing bindings at the correspondent node, Care must be taken when removing bindings at the correspondent node,
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Binding Update arrives. This is achieved through the construct of Binding Update arrives. This is achieved through the construct of
keygen tokens from the nonces and node keys that are not specific to keygen tokens from the nonces and node keys that are not specific to
individual mobile nodes. The keygen tokens can be reconstructed by individual mobile nodes. The keygen tokens can be reconstructed by
the correspondent node, based on the home and care-of address the correspondent node, based on the home and care-of address
information that arrives with the Binding Update. This means that information that arrives with the Binding Update. This means that
the correspondent nodes are safe against memory exhaustion attacks the correspondent nodes are safe against memory exhaustion attacks
except where on-path attackers are concerned. Due to the use of except where on-path attackers are concerned. Due to the use of
symmetric cryptography, the correspondent nodes are relatively safe symmetric cryptography, the correspondent nodes are relatively safe
against CPU resource exhaustion attacks as well. against CPU resource exhaustion attacks as well.
Nevertheless, as [26] describes, there are situations in which it is Nevertheless, as [31] describes, there are situations in which it is
impossible for the mobile and correspondent nodes to determine if impossible for the mobile and correspondent nodes to determine if
they actually need a binding or whether they just have been fooled they actually need a binding or whether they just have been fooled
into believing so by an attacker. Therefore, it is necessary to into believing so by an attacker. Therefore, it is necessary to
consider situations where such attacks are being made. consider situations where such attacks are being made.
Even if route optimization is a very important optimization, it is Even if route optimization is a very important optimization, it is
still only an optimization. A mobile node can communicate with a still only an optimization. A mobile node can communicate with a
correspondent node even if the correspondent refuses to accept any correspondent node even if the correspondent refuses to accept any
Binding Updates. However, performance will suffer because packets Binding Updates. However, performance will suffer because packets
from the correspondent node to the mobile node will be routed via the from the correspondent node to the mobile node will be routed via the
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learn the addresses of home agents in the home network. learn the addresses of home agents in the home network.
The ability to learn addresses of nodes may be useful to attackers The ability to learn addresses of nodes may be useful to attackers
because brute-force scanning of the address space is not practical because brute-force scanning of the address space is not practical
with IPv6. Thus, they could benefit from any means which make with IPv6. Thus, they could benefit from any means which make
mapping the networks easier. For example, if a security threat mapping the networks easier. For example, if a security threat
targeted at routers or even home agents is discovered, having a targeted at routers or even home agents is discovered, having a
simple ICMP mechanism to easily find out possible targets may prove simple ICMP mechanism to easily find out possible targets may prove
to be an additional (though minor) security risk. to be an additional (though minor) security risk.
This document does not define any authentication mechanism for
dynamic home agent address discovery messages. Therefore the home
agent cannot verify the home address of the mobile node that
requested the list of home agents.
Apart from discovering the address(es) of home agents, attackers will Apart from discovering the address(es) of home agents, attackers will
not be able to learn much from this information, and mobile nodes not be able to learn much from this information, and mobile nodes
cannot be tricked into using wrong home agents, as all other cannot be tricked into using wrong home agents, as all other
communication with the home agents is secure. communication with the home agents is secure.
In cases where additional security is needed, one may consider
instead the use of MIPv6 bootstrapping [25], (based on DNS SRV
Resource Records [12]) in conjunction with security mechanisms
suggested in these specifications. In that solution, security is
provided by the DNSSEC [16] framework. The needed pre-configured
data on the mobile node for this mechanism is the domain name of the
mobile service provider, which is marginally better than the home
subnet prefix. For the security, a trust anchor which dominates the
domain is needed.
15.6. Mobile Prefix Discovery 15.6. Mobile Prefix Discovery
The mobile prefix discovery function may leak interesting information The mobile prefix discovery function may leak interesting information
about network topology and prefix lifetimes to eavesdroppers; for about network topology and prefix lifetimes to eavesdroppers; for
this reason, requests for this information has to be authenticated. this reason, requests for this information has to be authenticated.
Responses and unsolicited prefix information needs to be Responses and unsolicited prefix information needs to be
authenticated to prevent the mobile nodes from being tricked into authenticated to prevent the mobile nodes from being tricked into
believing false information about the prefixes and possibly believing false information about the prefixes and possibly
preventing communications with the existing addresses. Optionally, preventing communications with the existing addresses. Optionally,
encryption may be applied to prevent leakage of the prefix encryption may be applied to prevent leakage of the prefix
skipping to change at page 160, line 49 skipping to change at page 162, line 16
used to send site local traffic from another location. used to send site local traffic from another location.
Administrators should be aware of this when allowing such home Administrators should be aware of this when allowing such home
addresses. In particular, the outer IP address check described above addresses. In particular, the outer IP address check described above
is not sufficient against all attackers. The use of encrypted is not sufficient against all attackers. The use of encrypted
tunnels is particularly useful for these kinds of home addresses. tunnels is particularly useful for these kinds of home addresses.
15.8. Home Address Option 15.8. Home Address Option
When the mobile node sends packets directly to the correspondent When the mobile node sends packets directly to the correspondent
node, the Source Address field of the packet's IPv6 header is the node, the Source Address field of the packet's IPv6 header is the
care-of address. Therefore, ingress filtering [25] works in the care-of address. Therefore, ingress filtering [30] works in the
usual manner even for mobile nodes, as the Source Address is usual manner even for mobile nodes, as the Source Address is
topologically correct. The Home Address option is used to inform the topologically correct. The Home Address option is used to inform the
correspondent node of the mobile node's home address. correspondent node of the mobile node's home address.
However, the care-of address in the Source Address field does not However, the care-of address in the Source Address field does not
survive in replies sent by the correspondent node unless it has a survive in replies sent by the correspondent node unless it has a
binding for this mobile node. Also, not all attacker tracing binding for this mobile node. Also, not all attacker tracing
mechanisms work when packets are being reflected through mechanisms work when packets are being reflected through
correspondent nodes using the Home Address option. For these correspondent nodes using the Home Address option. For these
reasons, this specification restricts the use of the Home Address reasons, this specification restricts the use of the Home Address
skipping to change at page 163, line 10 skipping to change at page 164, line 10
should be able to distinguish between a type 2 routing header and should be able to distinguish between a type 2 routing header and
other routing headers, as required in Section 8.3. This is necessary other routing headers, as required in Section 8.3. This is necessary
in order to allow Mobile IPv6 traffic while still having the option in order to allow Mobile IPv6 traffic while still having the option
of filtering out other uses of routing headers. of filtering out other uses of routing headers.
16. Contributors 16. Contributors
Tuomas Aura, Mike Roe, Greg O'Shea, Pekka Nikander, Erik Nordmark, Tuomas Aura, Mike Roe, Greg O'Shea, Pekka Nikander, Erik Nordmark,
and Michael Thomas worked on the return routability protocols and Michael Thomas worked on the return routability protocols
eventually led to the procedures used in this protocol. The eventually led to the procedures used in this protocol. The
procedures described in [31] were adopted in the protocol. procedures described in [36] were adopted in the protocol.
Significant contributions were made by members of the Mobile IPv6 Significant contributions were made by members of the Mobile IPv6
Security Design Team, including (in alphabetical order) Gabriel Security Design Team, including (in alphabetical order) Gabriel
Montenegro, Erik Nordmark and Pekka Nikander. Montenegro, Erik Nordmark and Pekka Nikander.
17. Acknowledgements 17. Acknowledgements
We would like to thank the members of the Mobile IP and IPng Working We would like to thank the members of the Mobile IP and IPng Working
Groups for their comments and suggestions on this work. We would Groups for their comments and suggestions on this work. We would
particularly like to thank (in alphabetical order) Fred Baker, Josh particularly like to thank (in alphabetical order) Fred Baker, Josh
skipping to change at page 165, line 43 skipping to change at page 166, line 43
[9] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 [9] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6
Specification", RFC 2473, December 1998. Specification", RFC 2473, December 1998.
[10] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast [10] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast
Addresses", RFC 2526, March 1999. Addresses", RFC 2526, March 1999.
[11] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener [11] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener
Discovery (MLD) for IPv6", RFC 2710, October 1999. Discovery (MLD) for IPv6", RFC 2710, October 1999.
[12] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by an On- [12] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[13] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by an On-
line Database", RFC 3232, January 2002. line Database", RFC 3232, January 2002.
[13] National Institute of Standards and Technology, "Secure Hash [14] National Institute of Standards and Technology, "Secure Hash
Standard", FIPS PUB 180-1, April 1995, Standard", FIPS PUB 180-1, April 1995,
<http://www.itl.nist.gov/fipspubs/fip180-1.htm>. <http://www.itl.nist.gov/fipspubs/fip180-1.htm>.
[14] Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to [15] Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to
Protect Mobile IPv6 Signaling Between Mobile Nodes and Home Protect Mobile IPv6 Signaling Between Mobile Nodes and Home
Agents", RFC 3776, June 2004. Agents", RFC 3776, June 2004.
[15] Eastlake, D., Schiller, J., and S. Crocker, "Randomness [16] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
"DNS Security Introduction and Requirements", RFC 4033,
March 2005.
[17] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005. Requirements for Security", BCP 106, RFC 4086, June 2005.
[16] Hinden, R. and S. Deering, "IP Version 6 Addressing [18] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006. Architecture", RFC 4291, February 2006.
[17] Conta, A., Deering, S., and M. Gupta, "Internet Control Message [19] Conta, A., Deering, S., and M. Gupta, "Internet Control Message
Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6)
Specification", RFC 4443, March 2006. Specification", RFC 4443, March 2006.
[18] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, [20] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007. September 2007.
[19] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address [21] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address
Autoconfiguration", RFC 4862, September 2007. Autoconfiguration", RFC 4862, September 2007.
[20] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions [22] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.
[23] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions
for Stateless Address Autoconfiguration in IPv6", RFC 4941, for Stateless Address Autoconfiguration in IPv6", RFC 4941,
September 2007. September 2007.
[21] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [24] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6 Socket
API for Source Address Selection", RFC 5014, September 2007.
[25] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6
Bootstrapping in Split Scenario", RFC 5026, October 2007.
[26] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
18.2. Informative References 18.2. Informative References
[22] Perkins, C., "IP Encapsulation within IP", RFC 2003, [27] Perkins, C., "IP Encapsulation within IP", RFC 2003,
October 1996. October 1996.
[23] Perkins, C., "Minimal Encapsulation within IP", RFC 2004, [28] Perkins, C., "Minimal Encapsulation within IP", RFC 2004,
October 1996. October 1996.
[24] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing [29] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing
for Message Authentication", RFC 2104, February 1997. for Message Authentication", RFC 2104, February 1997.
[25] Ferguson, P. and D. Senie, "Network Ingress Filtering: [30] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000. Address Spoofing", BCP 38, RFC 2827, May 2000.
[26] Aura, T. and J. Arkko, "MIPv6 BU Attacks and Defenses", [31] Aura, T. and J. Arkko, "MIPv6 BU Attacks and Defenses",
draft-aura-mipv6-bu-attacks-01 (work in progress), March 2002. draft-aura-mipv6-bu-attacks-01 (work in progress), March 2002.
[27] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. [32] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
Carney, "Dynamic Host Configuration Protocol for IPv6 Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003. (DHCPv6)", RFC 3315, July 2003.
[28] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, [33] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002. August 2002.
[29] Draves, R., "Default Address Selection for Internet Protocol [34] Draves, R., "Default Address Selection for Internet Protocol
version 6 (IPv6)", RFC 3484, February 2003. version 6 (IPv6)", RFC 3484, February 2003.
[30] Nordmark, E., "Securing MIPv6 BUs using return routability [35] Nordmark, E., "Securing MIPv6 BUs using return routability
(BU3WAY)", draft-nordmark-mobileip-bu3way-00 (work in (BU3WAY)", draft-nordmark-mobileip-bu3way-00 (work in
progress), November 2001. progress), November 2001.
[31] Roe, M., "Authentication of Mobile IPv6 Binding Updates and [36] Roe, M., "Authentication of Mobile IPv6 Binding Updates and
Acknowledgments", draft-roe-mobileip-updateauth-02 (work in Acknowledgments", draft-roe-mobileip-updateauth-02 (work in
progress), March 2002. progress), March 2002.
[32] Savola, P., "Use of /127 Prefix Length Between Routers [37] Chowdhury, K. and A. Yegin, "MIP6-bootstrapping for the
Integrated Scenario",
draft-ietf-mip6-bootstrapping-integrated-dhc-06 (work in
progress), April 2008.
[38] Savola, P., "Use of /127 Prefix Length Between Routers
Considered Harmful", RFC 3627, September 2003. Considered Harmful", RFC 3627, September 2003.
[33] Savola, P., "Security of IPv6 Routing Header and Home Address [39] Savola, P., "Security of IPv6 Routing Header and Home Address
Options", draft-savola-ipv6-rh-ha-security-02 (work in Options", draft-savola-ipv6-rh-ha-security-02 (work in
progress), March 2002. progress), March 2002.
[34] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 [40] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2
(MLDv2) for IPv6", RFC 3810, June 2004. (MLDv2) for IPv6", RFC 3810, June 2004.
[35] Bellovin, S. and R. Housley, "Guidelines for Cryptographic Key [41] Bellovin, S. and R. Housley, "Guidelines for Cryptographic Key
Management", BCP 107, RFC 4107, June 2005. Management", BCP 107, RFC 4107, June 2005.
[36] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E. [42] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E.
Nordmark, "Mobile IP Version 6 Route Optimization Security Nordmark, "Mobile IP Version 6 Route Optimization Security
Design Background", RFC 4225, December 2005. Design Background", RFC 4225, December 2005.
[37] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", [43] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005. RFC 4306, December 2005.
Appendix A. Future Extensions Appendix A. Future Extensions
A.1. Piggybacking A.1. Piggybacking
This document does not specify how to piggyback payload packets on This document does not specify how to piggyback payload packets on
the binding related messages. However, it is envisioned that this the binding related messages. However, it is envisioned that this
can be specified in a separate document when issues such as the can be specified in a separate document when issues such as the
interaction between piggybacking and IPsec are fully resolved (see interaction between piggybacking and IPsec are fully resolved (see
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