draft-ietf-mobileip-ipv6-12.txt   draft-ietf-mobileip-ipv6-13.txt 
IETF Mobile IP Working Group David B. Johnson IETF Mobile IP Working Group David B. Johnson
INTERNET-DRAFT Carnegie Mellon University INTERNET-DRAFT Rice University
Charles Perkins Charles Perkins
Nokia Nokia
27 April 2000 17 November 2000
Mobility Support in IPv6 Mobility Support in IPv6
<draft-ietf-mobileip-ipv6-12.txt> <draft-ietf-mobileip-ipv6-13.txt>
Status of This Memo Status of This Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026. all provisions of Section 10 of RFC 2026.
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 Task Force (IETF), its areas, and its working groups. Note
that other groups may also distribute working documents as that other groups may also distribute working documents as
Internet-Drafts. Internet-Drafts.
skipping to change at page 1, line 91 skipping to change at page 1, line 91
5.7. ICMP Home Agent Address Discovery Reply Message . . . . . 39 5.7. ICMP Home Agent Address Discovery Reply Message . . . . . 39
6. Modifications to IPv6 Neighbor Discovery 41 6. Modifications to IPv6 Neighbor Discovery 41
6.1. Modified Router Advertisement Message Format . . . . . . 41 6.1. Modified Router Advertisement Message Format . . . . . . 41
6.2. Modified Prefix Information Option Format . . . . . . . . 42 6.2. Modified Prefix Information Option Format . . . . . . . . 42
6.3. New Advertisement Interval Option Format . . . . . . . . 44 6.3. New Advertisement Interval Option Format . . . . . . . . 44
6.4. New Home Agent Information Option Format . . . . . . . . 45 6.4. New Home Agent Information Option Format . . . . . . . . 45
6.5. Changes to Sending Router Advertisements . . . . . . . . 47 6.5. Changes to Sending Router Advertisements . . . . . . . . 47
6.6. Changes to Sending Router Solicitations . . . . . . . . . 48 6.6. Changes to Sending Router Solicitations . . . . . . . . . 48
7. Requirements for IPv6 Nodes 50 7. Requirements for Types of IPv6 Nodes 50
7.1. Requirements for All IPv6 Hosts and Routers . . . . . . . 50 7.1. Requirements for All IPv6 Hosts and Routers . . . . . . . 50
7.2. Requirements for All IPv6 Routers . . . . . . . . . . . . 50 7.2. Requirements for All IPv6 Routers . . . . . . . . . . . . 50
7.3. Requirements for IPv6 Home Agents . . . . . . . . . . . . 50 7.3. Requirements for IPv6 Home Agents . . . . . . . . . . . . 50
7.4. Requirements for IPv6 Mobile Nodes . . . . . . . . . . . 51 7.4. Requirements for IPv6 Mobile Nodes . . . . . . . . . . . 51
8. Correspondent Node Operation 53 8. Correspondent Node Operation 53
8.1. Receiving Packets from a Mobile Node . . . . . . . . . . 53 8.1. Receiving Packets from a Mobile Node . . . . . . . . . . 53
8.2. Receiving Binding Updates . . . . . . . . . . . . . . . . 53 8.2. Receiving Binding Updates . . . . . . . . . . . . . . . . 53
8.3. Requests to Cache a Binding . . . . . . . . . . . . . . . 54 8.3. Requests to Cache a Binding . . . . . . . . . . . . . . . 54
8.4. Requests to Delete a Binding . . . . . . . . . . . . . . 55 8.4. Requests to Delete a Binding . . . . . . . . . . . . . . 55
8.5. Sending Binding Acknowledgements . . . . . . . . . . . . 55 8.5. Sending Binding Acknowledgements . . . . . . . . . . . . 55
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8.8. Receiving ICMP Error Messages . . . . . . . . . . . . . . 57 8.8. Receiving ICMP Error Messages . . . . . . . . . . . . . . 57
8.9. Sending Packets to a Mobile Node . . . . . . . . . . . . 58 8.9. Sending Packets to a Mobile Node . . . . . . . . . . . . 58
9. Home Agent Operation 60 9. Home Agent Operation 60
9.1. Receiving Router Advertisement Messages . . . . . . . . . 60 9.1. Receiving Router Advertisement Messages . . . . . . . . . 60
9.2. Dynamic Home Agent Address Discovery . . . . . . . . . . 61 9.2. Dynamic Home Agent Address Discovery . . . . . . . . . . 61
9.3. Primary Care-of Address Registration . . . . . . . . . . 63 9.3. Primary Care-of Address Registration . . . . . . . . . . 63
9.4. Primary Care-of Address De-registration . . . . . . . . . 65 9.4. Primary Care-of Address De-registration . . . . . . . . . 65
9.5. Intercepting Packets for a Mobile Node . . . . . . . . . 66 9.5. Intercepting Packets for a Mobile Node . . . . . . . . . 66
9.6. Tunneling Intercepted Packets to a Mobile Node . . . . . 68 9.6. Tunneling Intercepted Packets to a Mobile Node . . . . . 68
9.7. Renumbering the Home Subnet . . . . . . . . . . . . . . . 69 9.7. Handling Reverse Tunneled Packets from a Mobile Node . . 69
9.8. Renumbering the Home Subnet . . . . . . . . . . . . . . . 70
9.8.1. Building Aggregate List of Home Network Prefixes 70
9.8.2. Sending Changed Prefix Information to the Mobile
Node . . . . . . . . . . . . . . . . . . . 71
9.8.3. Tunneling Router Advertisements to the Mobile Node 73
9.8.4. Lifetimes for Changed Prefixes . . . . . . . . . 74
10. Mobile Node Operation 73 10. Mobile Node Operation 75
10.1. Sending Packets While Away from Home . . . . . . . . . . 73 10.1. Sending Packets While Away from Home . . . . . . . . . . 75
10.2. Interaction with Outbound IPsec Processing . . . . . . . 74 10.2. Interaction with Outbound IPsec Processing . . . . . . . 76
10.3. Receiving Packets While Away from Home . . . . . . . . . 76 10.3. Receiving Packets While Away from Home . . . . . . . . . 78
10.4. Movement Detection . . . . . . . . . . . . . . . . . . . 77 10.4. Movement Detection . . . . . . . . . . . . . . . . . . . 80
10.5. Forming New Care-of Addresses . . . . . . . . . . . . . . 80 10.5. Forming New Care-of Addresses . . . . . . . . . . . . . . 82
10.6. Sending Binding Updates to the Home Agent . . . . . . . . 82 10.6. Sending Binding Updates to the Home Agent . . . . . . . . 84
10.7. Dynamic Home Agent Address Discovery . . . . . . . . . . 83 10.7. Dynamic Home Agent Address Discovery . . . . . . . . . . 86
10.8. Sending Binding Updates to Correspondent Nodes . . . . . 84 10.8. Sending Binding Updates to Correspondent Nodes . . . . . 87
10.9. Establishing Forwarding from a Previous Care-of Address . 87 10.9. Establishing Forwarding from a Previous Care-of Address . 89
10.10. Retransmitting Binding Updates . . . . . . . . . . . . . 88 10.10. Retransmitting Binding Updates . . . . . . . . . . . . . 90
10.11. Rate Limiting for Sending Binding Updates . . . . . . . . 88 10.11. Rate Limiting for Sending Binding Updates . . . . . . . . 91
10.12. Receiving Binding Acknowledgements . . . . . . . . . . . 89 10.12. Receiving Binding Acknowledgements . . . . . . . . . . . 91
10.13. Receiving Binding Requests . . . . . . . . . . . . . . . 90 10.13. Receiving Binding Requests . . . . . . . . . . . . . . . 92
10.14. Receiving ICMP Error Messages . . . . . . . . . . . . . . 90 10.14. Receiving ICMP Error Messages . . . . . . . . . . . . . . 93
10.15. Receiving Local Router Advertisement Messages . . . . . . 91 10.15. Receiving Local Router Advertisement Messages . . . . . . 94
10.16. Receiving Tunneled Router Advertisements . . . . . . . . 92 10.16. Sending Tunneled Router Solicitations . . . . . . . . . . 95
10.17. Using Multiple Care-of Addresses . . . . . . . . . . . . 93 10.17. Receiving Tunneled Router Advertisements . . . . . . . . 96
10.18. Routing Multicast Packets . . . . . . . . . . . . . . . . 94 10.18. Using Multiple Care-of Addresses . . . . . . . . . . . . 97
10.19. Returning Home . . . . . . . . . . . . . . . . . . . . . 95 10.19. Routing Multicast Packets . . . . . . . . . . . . . . . . 97
10.20. Returning Home . . . . . . . . . . . . . . . . . . . . . 98
11. Protocol Constants 97 11. Protocol Constants 100
12. IANA Considerations 98 12. IANA Considerations 101
13. Security Considerations 99 13. Security Considerations 102
13.1. Binding Updates, Acknowledgements, and Requests . . . . . 99 13.1. Binding Updates, Acknowledgements, and Requests . . . . . 102
13.2. Home Address Option . . . . . . . . . . . . . . . . . . . 99 13.2. Security for the Home Address Option . . . . . . . . . . 102
13.3. General Mobile Computing Issues . . . . . . . . . . . . . 100 13.3. General Mobile Computing Issues . . . . . . . . . . . . . 103
Changes from Previous Version of the Draft 102 Changes from Previous Version of the Draft 104
Acknowledgements 105 Acknowledgements 105
References 106 References 106
Chair's Address 108 A. Remote Home Address Configuration 108
Authors' Addresses 109 Chair's Address 109
Authors' Addresses 110
1. Introduction 1. Introduction
This document specifies the operation of mobile computers using This document specifies the operation of mobile computers using
Internet Protocol Version 6 (IPv6) [6]. Without specific support Internet Protocol Version 6 (IPv6) [6]. Without specific support
for mobility in IPv6, packets destined to a mobile node (host or for mobility in IPv6, packets destined to a mobile node (host or
router) would not be able to reach it while the mobile node is away router) would not be able to reach it while the mobile node is away
from its home link (the link on which its home IPv6 subnet prefix is from its home link (the link on which its home IPv6 subnet prefix is
in use), since routing is based on the subnet prefix in a packet's in use), since routing is based on the subnet prefix in a packet's
destination IP address. In order to continue communication in spite destination IP address. In order to continue communication in spite
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home link is thus transparent to transport and higher-layer protocols home link is thus transparent to transport and higher-layer protocols
and applications. and applications.
The Mobile IPv6 protocol is just as suitable for mobility across The Mobile IPv6 protocol is just as suitable for mobility across
homogeneous media as for mobility across heterogeneous media. For homogeneous media as for mobility across heterogeneous media. For
example, Mobile IPv6 facilitates node movement from one Ethernet example, Mobile IPv6 facilitates node movement from one Ethernet
segment to another as well as it facilitates node movement from an segment to another as well as it facilitates node movement from an
Ethernet segment to a wireless LAN cell, with the mobile node's IP Ethernet segment to a wireless LAN cell, with the mobile node's IP
address remaining unchanged in spite of such movement. address remaining unchanged in spite of such movement.
One can think of the Mobile IPv6 protocol as solving the "macro" One can think of the Mobile IPv6 protocol as solving the
mobility management problem. More "micro" mobility management network-layer mobility management problem. Some mobility management
applications -- for example, handoff among wireless transceivers, applications -- for example, handoff among wireless transceivers,
each of which covers only a very small geographic area -- are each of which covers only a very small geographic area -- have been
possibly more suited to other solutions. For example, in many solved using link-layer techniques. For example, in many current
current wireless LAN products, link-layer mobility mechanisms allow a wireless LAN products, link-layer mobility mechanisms allow a
"handoff" of a mobile node from one cell to another, reestablishing "handoff" of a mobile node from one cell to another, reestablishing
link-layer connectivity to the node in each new location. As long link-layer connectivity to the node in each new location. Within
as such handoff occurs only within cells of the mobile node's home the natural limitations imposed by link-management solutions, and as
link, such link-layer mobility mechanisms are likely to offer faster long as such handoff occurs only within cells of the mobile node's
home link, such link-layer mobility mechanisms MAY offer faster
convergence and lower overhead than Mobile IPv6. Extensions to the convergence and lower overhead than Mobile IPv6. Extensions to the
Mobile IPv6 protocol are also possible to support a more local, Mobile IPv6 protocol have been proposed to support a more local,
hierarchical form of mobility management, but such extensions are hierarchical form of mobility management, but such extensions are
beyond the scope of this document. beyond the scope of this document.
The protocol specified in this document solves the problem of The protocol specified in this document solves the problem of
transparently routing packets to and from mobile nodes while away transparently routing packets to and from mobile nodes while away
from home. However, it does not attempt to solve all general from home. However, it does not attempt to solve all general
problems related to the use of mobile computers or wireless networks. problems related to the use of mobile computers or wireless networks.
In particular, this protocol does not attempt to solve: In particular, this protocol does not attempt to solve:
- Handling links with partial reachability, such as typical - Handling links with partial reachability, such as typical
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by IPv6. Mobile IPv6 thus shares many features with Mobile IPv4, by IPv6. Mobile IPv6 thus shares many features with Mobile IPv4,
but the protocol is now fully integrated into IP and provides many but the protocol is now fully integrated into IP and provides many
improvements over Mobile IPv4. This section summarizes the major improvements over Mobile IPv4. This section summarizes the major
differences between Mobile IPv4 and Mobile IPv6: differences between Mobile IPv4 and Mobile IPv6:
- Support for what is known in Mobile IPv4 as "Route - Support for what is known in Mobile IPv4 as "Route
Optimization" [21] is now built in as a fundamental part Optimization" [21] is now built in as a fundamental part
of the protocol, rather than being added on as an optional of the protocol, rather than being added on as an optional
set of extensions that may not be supported by all nodes set of extensions that may not be supported by all nodes
as in Mobile IPv4. This integration of Route Optimization as in Mobile IPv4. This integration of Route Optimization
functionality allows direct routing from any correspondent node functionality allows direct routing from any correspondent
to any mobile node, without needing to pass through the mobile node to any mobile node, without needing to pass through
node's home network and be forwarded by its home agent, and thus the mobile node's home network and be forwarded by its home
eliminates the problem of "triangle routing" present in the base agent, and thus eliminates the problem of "triangle routing"
Mobile IPv4 protocol [19]. This integration also allows the present in the base Mobile IPv4 protocol [19]. The Mobile IPv4
Mobile IPv4 "registration" functionality and the Mobile IPv4 "registration" functionality and the Mobile IPv4 Route
Route Optimization functionality to be performed by a single Optimization functionality are performed by a single protocol
protocol rather than two separate (and different) protocols. rather than two separate (and different) protocols.
- Support is also integrated into Mobile IPv6 -- and into IPv6 - Support is also integrated into Mobile IPv6 -- and into IPv6
itself -- for allowing mobile nodes and Mobile IP to coexist itself -- for allowing mobile nodes and Mobile IP to coexist
efficiently with routers that perform "ingress filtering" [7]. A efficiently with routers that perform "ingress filtering" [7]. A
mobile node now uses its care-of address as the Source Address in mobile node now uses its care-of address as the Source Address in
the IP header of packets it sends, allowing the packets to pass the IP header of packets it sends, allowing the packets to pass
normally through ingress filtering routers. The home address normally through ingress filtering routers. The home address
of the mobile node is carried in the packet in a Home Address of the mobile node is carried in the packet in a Home Address
destination option, allowing the use of the care-of address in destination option, allowing the use of the care-of address in
the packet to be transparent above the IP layer. The ability the packet to be transparent above the IP layer. The ability
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sent by a mobile node. With Mobile IPv4, the mobile node sent by a mobile node. With Mobile IPv4, the mobile node
had to tunnel multicast packets to its home agent in order to had to tunnel multicast packets to its home agent in order to
transparently use its home address as the source of the multicast transparently use its home address as the source of the multicast
packets. With Mobile IPv6, the use of the Home Address option packets. With Mobile IPv6, the use of the Home Address option
allows the home address to be used but still be compatible with allows the home address to be used but still be compatible with
multicast routing that is based in part on the packet's Source multicast routing that is based in part on the packet's Source
Address. Address.
- There is no longer any need to deploy special routers as - There is no longer any need to deploy special routers as
"foreign agents" as are used in Mobile IPv4. In Mobile IPv6, "foreign agents" as are used in Mobile IPv4. In Mobile IPv6,
mobile nodes make use of the enhanced features of IPv6, such mobile nodes make use of IPv6 features, such as Neighbor
as Neighbor Discovery [17] and Address Autoconfiguration [27], Discovery [17] and Address Autoconfiguration [27], to operate in
to operate in any location away from home without any special any location away from home without any special support required
support required from its local router. from its local router.
- Unlike Mobile IPv4, Mobile IPv6 utilizes IP Security - Unlike Mobile IPv4, Mobile IPv6 utilizes IP Security
(IPsec) [11, 12, 13] for all security requirements (sender (IPsec) [11, 12, 13] for all security requirements (sender
authentication, data integrity protection, and replay protection) authentication, data integrity protection, and replay protection)
for Binding Updates (which serve the role of both registration for Binding Updates (which serve the role of both registration
and Route Optimization in Mobile IPv4). Mobile IPv4 relies and Route Optimization in Mobile IPv4). Mobile IPv4 relies
on its own security mechanisms for these functions, based on on its own security mechanisms for these functions, based on
statically configured "mobility security associations". statically configured "mobility security associations".
- The movement detection mechanism in Mobile IPv6 provides - The movement detection mechanism in Mobile IPv6 provides
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to the definition of ICMP for IPv6, the use of tunnel soft state to the definition of ICMP for IPv6, the use of tunnel soft state
is no longer required in IPv6 for correctly relaying ICMP error is no longer required in IPv6 for correctly relaying ICMP error
messages from within the tunnel back to the original sender of messages from within the tunnel back to the original sender of
the packet. the packet.
- The dynamic home agent address discovery mechanism in Mobile IPv6 - The dynamic home agent address discovery mechanism in Mobile IPv6
uses IPv6 anycast [10] and returns a single reply to the mobile uses IPv6 anycast [10] and returns a single reply to the mobile
node, rather than the corresponding Mobile IPv4 mechanism that node, rather than the corresponding Mobile IPv4 mechanism that
used IPv4 directed broadcast and returned a separate reply from used IPv4 directed broadcast and returned a separate reply from
each home agent on the mobile node's home link. The Mobile IPv6 each home agent on the mobile node's home link. The Mobile IPv6
mechanism is more efficient and more reliable, since only mechanism is more efficient and more reliable, since only one
one packet need be sent back to the mobile node and since the packet need be sent back to the mobile node. The mobile node is
mobile node is less likely to lose one of the replies because no less likely to lose one of the replies because no "implosion" of
"implosion" of replies is required by the protocol. replies is required by the protocol.
- Mobile IPv6 defines an Advertisement Interval option on - Mobile IPv6 defines an Advertisement Interval option on
Router Advertisements (equivalent to Agent Advertisements in Router Advertisements (equivalent to Agent Advertisements in
Mobile IPv4), allowing a mobile node to decide for itself how Mobile IPv4), allowing a mobile node to decide for itself how
many Router Advertisements (Agent Advertisements) it is willing many Router Advertisements (Agent Advertisements) it is willing
to miss before declaring its current router unreachable. to miss before declaring its current router unreachable.
- The use of IPv6 destination options allows all Mobile IPv6 - The use of IPv6 destination options allows all Mobile IPv6
control traffic to be piggybacked on any existing IPv6 packets, control traffic to be piggybacked on any existing IPv6 packets,
whereas in Mobile IPv4 and its Route Optimization extensions, whereas in Mobile IPv4 and its Route Optimization extensions,
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care-of address in this binding registered with its home agent is care-of address in this binding registered with its home agent is
known as the mobile node's "primary care-of address". The mobile known as the mobile node's "primary care-of address". The mobile
node's home agent thereafter uses proxy Neighbor Discovery to node's home agent thereafter uses proxy Neighbor Discovery to
intercept any IPv6 packets addressed to the mobile node's home intercept any IPv6 packets addressed to the mobile node's home
address (or home addresses) on the home link, and tunnels each address (or home addresses) on the home link, and tunnels each
intercepted packet to the mobile node's primary care-of address. intercepted packet to the mobile node's primary care-of address.
To tunnel each intercepted packet, the home agent encapsulates the To tunnel each intercepted packet, the home agent encapsulates the
packet using IPv6 encapsulation [4], with the outer IPv6 header packet using IPv6 encapsulation [4], with the outer IPv6 header
addressed to the mobile node's primary care-of address. addressed to the mobile node's primary care-of address.
Section 10.17 discusses the reasons why it may be desirable for When a mobile node moves from one care-of address to a new care-of
address on a new link, it is desirable for packets arriving at the
previous care-of address to be tunneled to the mobile node's care-of
address. Since the purpose of a Binding Update is to establish
exactly this kind of tunneling, it is specified to be used (at
least temporarily) for tunnels originating at the mobile node's
previous care-of address, in exactly the same way that it is used
for establishing tunnels from the mobile node's home address to the
mobile node's current care-of address. Section 10.9 describes the
use of the Binding Update for this purpose.
Section 10.18 discusses the reasons why it may be desirable for
a mobile node to use more than one care-of address at the same a mobile node to use more than one care-of address at the same
time. However, a mobile node's primary care-of address is distinct time. However, a mobile node's primary care-of address is distinct
among these in that the home agent maintains only a single care-of among these in that the home agent maintains only a single care-of
address registered for each mobile node, and always tunnels a mobile address registered for each mobile node, and always tunnels a mobile
node's packets intercepted from its home link to this mobile node's node's packets intercepted from its home link to this mobile node's
registered primary care-of address. The home agent thus need not registered primary care-of address. The home agent thus need not
implement any policy to determine which of possibly many care-of implement any policy to determine which of possibly many care-of
addresses to which to tunnel each intercepted packet, leaving the addresses to which to tunnel each intercepted packet. The mobile
mobile node entirely in control of this policy by which of its node alone controls the policy by which it selects the care-of
care-of addresses it registers with its home agent. addresses to register with its home agent.
It is possible that while a mobile node is away from home, some nodes It is possible that while a mobile node is away from home, some nodes
on its home link may be reconfigured, such that the router that was on its home link may be reconfigured, such that the router that was
operating as the mobile node's home agent is replaced by a different operating as the mobile node's home agent is replaced by a different
router serving this role. In this case, the mobile node may not router serving this role. In this case, the mobile node may not
know the IP address of its own home agent. Mobile IPv6 provides a know the IP address of its own home agent. Mobile IPv6 provides a
mechanism, known as "dynamic home agent address discovery", that mechanism, known as "dynamic home agent address discovery", that
allows a mobile node to dynamically discover the IP address of a home allows a mobile node to dynamically discover the IP address of a home
agent on its home link with which it may register its care-of address agent on its home link with which it may register its care-of address
while away from home. The mobile node sends an ICMP "Home Agent while away from home. The mobile node sends an ICMP "Home Agent
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tunneled by the mobile node's home agent as described above. Any tunneled by the mobile node's home agent as described above. Any
node communicating with a mobile node is referred to in this document node communicating with a mobile node is referred to in this document
as a "correspondent node" of the mobile node, and may itself be as a "correspondent node" of the mobile node, and may itself be
either a stationary node or a mobile node. either a stationary node or a mobile node.
Since a Binding Update, Binding Acknowledgement, and Binding Request Since a Binding Update, Binding Acknowledgement, and Binding Request
are each represented in a packet as an IPv6 destination option [6], are each represented in a packet as an IPv6 destination option [6],
they may be included in any IPv6 packet. Any of these options can be they may be included in any IPv6 packet. Any of these options can be
sent in either of two ways: sent in either of two ways:
- A Binding Update, Binding Acknowledgement, or Binding Request can - the messages can be included within any IPv6 packet carrying any
be included within any IPv6 packet carrying any payload such as payload such as TCP [25] or UDP [24].
TCP [25] or UDP [24].
- A Binding Update, Binding Acknowledgement, or Binding Request can - the messages can be sent as a separate IPv6 packet containing
be sent as a separate IPv6 packet containing no payload. In this no payload. In this case, the Next Header field in the last
case, the Next Header field in the last extension header in the extension header in the packet is set to the value 59, to
packet is set to the value 59, to indicate "No Next Header" [6]. indicate "No Next Header" [6].
Mobile IPv6 also defines one additional IPv6 destination option. Mobile IPv6 also defines one additional IPv6 destination option.
When a mobile node sends a packet while away from home, it will When a mobile node sends a packet while away from home, it will
generally set the Source Address in the packet's IPv6 header to one generally set the Source Address in the packet's IPv6 header to one
of its current care-of addresses, and will also include a "Home of its current care-of addresses, and will also include a "Home
Address" destination option in the packet, giving the mobile node's Address" destination option in the packet, giving the mobile node's
home address. Many routers implement security policies such as home address. Many routers implement security policies such as
"ingress filtering" [7] that do not allow forwarding of packets that "ingress filtering" [7] that do not allow forwarding of packets
appear to have a Source Address that is not topologically correct. that have a Source Address which appears topologically incorrect.
By using the care-of address as the IPv6 header Source Address, By using the care-of address as the IPv6 header Source Address,
the packet will be able to pass normally through such routers, the packet will be able to pass normally through such routers,
yet ingress filtering rules will still be able to locate the true yet ingress filtering rules will still be able to locate the true
topological source of the packet in the same way as packets from topological source of the packet in the same way as packets from
non-mobile nodes. By also including the Home Address option in each non-mobile nodes. By also including the Home Address option in each
packet, the sending mobile node can communicate its home address to packet, the sending mobile node can communicate its home address to
the correspondent node receiving this packet, allowing the use of the correspondent node receiving this packet, allowing the use of
the care-of address to be transparent above the Mobile IPv6 support the care-of address to be transparent above the Mobile IPv6 support
level (e.g., at the transport layer). The inclusion of a Home level (e.g., at the transport layer). The inclusion of a Home
Address option in a packet affects only the correspondent node's Address option in a packet affects only the correspondent node's
receipt of this single packet; no state is created or modified in the receipt of this single packet; no state is created or modified in the
correspondent node as a result of receiving a Home Address option in correspondent node as a result of receiving a Home Address option in
a packet. a packet.
4.2. New IPv6 Destination Options 4.2. New IPv6 Destination Options
As discussed in general in Section 4.1, the following four new IPv6 As mentioned in Section 4.1, the following four new IPv6 destination
destination options are defined for Mobile IPv6: options are defined for Mobile IPv6:
Binding Update Binding Update
A Binding Update option is used by a mobile node to notify A Binding Update option is used by a mobile node to notify
a correspondent node or the mobile node's home agent of its a correspondent node or the mobile node's home agent of its
current binding. The Binding Update sent to the mobile node's current binding. The Binding Update sent to the mobile node's
home agent to register its primary care-of address is marked home agent to register its primary care-of address is marked
as a "home registration". Any packet that includes a Binding as a "home registration". Any packet that includes a Binding
Update option MUST be protected by IPsec [13], as defined in Update option MUST be protected by IPsec [13], as defined in
Section 4.4, to guard against malicious Binding Updates. The Section 4.4, to guard against malicious Binding Updates. The
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node's home address. For packets sent by a mobile node while node's home address. For packets sent by a mobile node while
away from home, the mobile node generally uses one of its away from home, the mobile node generally uses one of its
care-of addresses as the Source Address in the packet's IPv6 care-of addresses as the Source Address in the packet's IPv6
header. By including a Home Address option in the packet, the header. By including a Home Address option in the packet, the
correspondent node receiving the packet is able to substitute correspondent node receiving the packet is able to substitute
the mobile node's home address for this care-of address when the mobile node's home address for this care-of address when
processing the packet, thus making the use of the care-of processing the packet, thus making the use of the care-of
address transparent to the correspondent node. If the IP address transparent to the correspondent node. If the IP
header of a packet carrying a Home Address option is covered header of a packet carrying a Home Address option is covered
by authentication, then the Home Address option MUST also be by authentication, then the Home Address option MUST also be
covered by this authentication, but no other authentication is covered by this authentication, but no other authentication
required for the Home Address option. The Home Address option is required for the Home Address option. See sections 10.2
is described in detail in Section 5.4. and 5.4 for additional details about requirements for the
calculation and verification of the authentication data. The
Home Address option is described in detail in Section 5.4.
Mobile IPv6 also defines a number of "sub-options" for use within Mobile IPv6 also defines a number of "sub-options" for use within
these destination options; if included, any sub-options MUST these destination options; if included, any sub-options MUST
appear after the fixed portion of the option data specified in this appear after the fixed portion of the option data specified in this
document. The presence of such sub-options will be indicated by the document. The presence of such sub-options will be indicated by the
Option Length field within the option. When the Option Length is Option Length field within the option. When the Option Length is
greater than the length required for the option specified here, the greater than the length required for the option specified here, the
remaining octets are interpreted as sub-options. The encoding and remaining octets are interpreted as sub-options. The encoding and
format of defined sub-options are described in Section 5.5. format of defined sub-options are described in Section 5.5.
skipping to change at page 13, line 38 skipping to change at page 13, line 47
4.4. IPsec Requirements for New Destination Options 4.4. IPsec Requirements for New Destination Options
Any packet that includes a Binding Update or Binding Acknowledgement Any packet that includes a Binding Update or Binding Acknowledgement
option MUST be protected by IPsec [13] to guard against malicious option MUST be protected by IPsec [13] to guard against malicious
Binding Updates or Acknowledgements. Specifically, any packet that Binding Updates or Acknowledgements. Specifically, any packet that
includes a Binding Update or Binding Acknowledgement option MUST includes a Binding Update or Binding Acknowledgement option MUST
utilize IPsec sender authentication, data integrity protection, and utilize IPsec sender authentication, data integrity protection, and
replay protection. replay protection.
Currently, Mobile IPv6 requires that this protection covering a Mobile IPv6 requires that this protection covering a Binding Update
Binding Update or Binding Acknowledgement MUST be provided by use or Binding Acknowledgement MUST be provided by use of AH [11]. If
of AH [11]. If another Security Association applied to the packet another Security Association applied to the packet for other reasons
for other reasons requires use of ESP [12], for example to encrypt requires use of ESP [12], for example to encrypt the transport layer
the transport layer data carried in the packet, this use of ESP data carried in the packet, this use of ESP is not sufficient to
is not sufficient to satisfy the authentication requirements of satisfy the authentication requirements of Mobile IPv6; instead,
Mobile IPv6; instead, the packet MUST use both AH and ESP. Use of the packet MUST use both AH and ESP. Use of ESP for protecting the
ESP for protecting the Binding Update or Binding Acknowledgement is Binding Update or Binding Acknowledgement is not currently defined in
not currently defined in this document, since ESP does not protect this document, since ESP does not protect the portion of the packet
the portion of the packet above the ESP header itself [12]. above the ESP header itself [12].
4.5. New IPv6 ICMP Messages 4.5. New IPv6 ICMP Messages
Mobile IPv6 also introduces two new ICMP message types, for use in Mobile IPv6 also introduces two new ICMP message types, for use in
the dynamic home agent address discovery mechanism. As discussed in the dynamic home agent address discovery mechanism. As discussed in
general in Section 4.1, the following two new ICMP message types are general in Section 4.1, the following two new ICMP message types are
used: used:
Home Agent Address Discovery Request Home Agent Address Discovery Request
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described in detail in Section 5.7. described in detail in Section 5.7.
4.6. Conceptual Data Structures 4.6. Conceptual Data Structures
This document describes the Mobile IPv6 protocol in terms of the This document describes the Mobile IPv6 protocol in terms of the
following three conceptual data structures: following three conceptual data structures:
Binding Cache Binding Cache
A cache, maintained by each IPv6 node, of bindings for other A cache, maintained by each IPv6 node, of bindings for other
nodes. The Binding Cache MAY be implemented in any manner nodes. A separate Binding Cache SHOULD be maintained by each
consistent with the external behavior described in this IPv6 node for each of its IPv6 addresses. The Binding Cache
document, for example by being combined with the node's MAY be implemented in any manner consistent with the external
Destination Cache as maintained by Neighbor Discovery [17]. behavior described in this document, for example by being
When sending a packet, the Binding Cache is searched before the combined with the node's Destination Cache as maintained by
Neighbor Discovery conceptual Destination Cache [17] (i.e., any Neighbor Discovery [17]. When sending a packet, the Binding
Binding Cache entry for this destination SHOULD take precedence Cache is searched before the Neighbor Discovery conceptual
over any Destination Cache entry for the same destination). Destination Cache [17] (i.e., any Binding Cache entry for this
Each Binding Cache entry conceptually contains the following destination SHOULD take precedence over any Destination Cache
fields: entry for the same destination). Each Binding Cache entry
conceptually contains the following fields:
- The home address of the mobile node for which this is the - The home address of the mobile node for which this is the
Binding Cache entry. This field is used as the key for Binding Cache entry. This field is used as the key for
searching the Binding Cache for the destination address of searching the Binding Cache for the destination address of
a packet being sent. If the destination address of the a packet being sent. If the destination address of the
packet matches the home address in the Binding Cache entry, packet matches the home address in the Binding Cache entry,
this entry SHOULD be used in routing that packet. this entry SHOULD be used in routing that packet.
- The care-of address for the mobile node indicated by - The care-of address for the mobile node indicated by
the home address field in this Binding Cache entry. If the home address field in this Binding Cache entry. If
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- The time at which a Binding Request was last sent for this - The time at which a Binding Request was last sent for this
entry, as needed to implement the rate limiting restriction entry, as needed to implement the rate limiting restriction
for sending Binding Requests. for sending Binding Requests.
An entry in a node's Binding Cache for which the node is An entry in a node's Binding Cache for which the node is
serving as a home agent is marked as a "home registration" serving as a home agent is marked as a "home registration"
entry and SHOULD NOT be deleted by the home agent until the entry and SHOULD NOT be deleted by the home agent until the
expiration of its binding lifetime. Other Binding Cache expiration of its binding lifetime. Other Binding Cache
entries MAY be replaced at any time by any reasonable local entries MAY be replaced at any time by any reasonable local
cache replacement policy but SHOULD NOT be unnecessarily cache replacement policy but SHOULD NOT be unnecessarily
deleted. Any node's Binding Cache may contain at most one deleted. The Binding Cache for any one of a node's IPv6
entry for each mobile node home address. The contents of a addresses may contain at most one entry for each mobile node
node's Binding Cache MUST NOT be changed in response to a Home home address. The contents of a node's Binding Cache MUST NOT
Address option in a received packet. be changed in response to a Home Address option in a received
packet. The contents of all of a node's Binding Cache entries,
for each of its IPv6 addresses, must be cleared when the node
reboots.
Binding Update List Binding Update List
A list, maintained by each mobile node, recording information A list, maintained by each mobile node, recording information
for each Binding Update sent by this mobile node, for which the for each Binding Update sent by this mobile node, for which the
Lifetime sent in that Binding Update has not yet expired. The Lifetime sent in that Binding Update has not yet expired. The
Binding Update List includes all bindings sent by the mobile Binding Update List includes all bindings sent by the mobile
node: those to correspondent nodes, those to the mobile node's node: those to correspondent nodes, those to the mobile node's
home agent, and those to a home agent on the link on which the home agent, and those to a home agent on the link on which the
mobile node's previous care-of address is located. However, mobile node's previous care-of address is located. However,
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- The IP address of the node to which a Binding Update was - The IP address of the node to which a Binding Update was
sent. This node might still have a Binding Cache entry sent. This node might still have a Binding Cache entry
created or updated from this Binding Update, if the Binding created or updated from this Binding Update, if the Binding
Update was successfully received by that node (e.g., not Update was successfully received by that node (e.g., not
lost by the network) and if that node has not deleted the lost by the network) and if that node has not deleted the
entry before its expiration (e.g., to reclaim space in its entry before its expiration (e.g., to reclaim space in its
Binding Cache for other entries). Binding Cache for other entries).
- The home address for which that Binding Update was sent. - The home address for which that Binding Update was sent.
This will be one of the mobile node's home addresses for This will be one of the following:
most Binding Updates (Sections 10.6 and 10.8), but will
be the mobile node's previous care-of address for Binding * the mobile node's home addresses for typical Binding
Updates sent to to establish forwarding from by a home Updates (Sections 10.6 and 10.8), or
agent from this previous care-of address (Section 10.9).
* the mobile node's previous care-of address for Binding
Updates sent to establish forwarding from the mobile
node's previous care-of address by a home agent from
this previous care-of address (Section 10.9).
- The care-of address sent in that Binding Update. This - The care-of address sent in that Binding Update. This
value is necessary for the mobile node to determine if it value is necessary for the mobile node to determine if it
has sent a Binding Update giving its new care-of address to has sent a Binding Update giving its new care-of address to
this destination after changing its care-of address. this destination after changing its care-of address.
- The initial value of the Lifetime field sent in that - The initial value of the Lifetime field sent in that
Binding Update. Binding Update.
- The remaining lifetime of that binding. This lifetime is - The remaining lifetime of that binding. This lifetime is
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- The link-local IP address of a router on the link, that - The link-local IP address of a router on the link, that
this node currently believes is operating as a home agent this node currently believes is operating as a home agent
for that link. A new entry is created or an existing for that link. A new entry is created or an existing
entry is updated in the Home Agents List in response to entry is updated in the Home Agents List in response to
receipt of a valid Router Advertisement in which the Home receipt of a valid Router Advertisement in which the Home
Agent (H) bit is set. The link-local address of the home Agent (H) bit is set. The link-local address of the home
agent is learned through the Source Address of the Router agent is learned through the Source Address of the Router
Advertisements received from it [17]. Advertisements received from it [17].
- One or more global IP addresses for this home agent, - One or more global IP addresses for this home agent,
learned through Prefix Information options with the learned through Prefix Information options with
Router Address (R) bit is set, received in Router the Router Address (R) bit set, received in Router
Advertisements from this link-local address. Global Advertisements from this link-local address. Global
addresses for the router in a Home Agents List entry MUST addresses for the router in a Home Agents List entry MUST
be deleted once the prefix associated with that address is be deleted once the prefix associated with that address is
no longer valid [17]. no longer valid [17].
- The remaining lifetime of this Home Agents List entry. If - The remaining lifetime of this Home Agents List entry. If
a Home Agent Information Option is present in a Router a Home Agent Information Option is present in a Router
Advertisement received from a home agent, the lifetime of Advertisement received from a home agent, the lifetime of
the Home Agents List entry representing that home agent the Home Agents List entry representing that home agent
is initialized from the Home Agent Lifetime field in the is initialized from the Home Agent Lifetime field in the
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The Duplicate Address Detection (D) bit is set by the sending The Duplicate Address Detection (D) bit is set by the sending
mobile node to request the receiving node (the mobile node's mobile node to request the receiving node (the mobile node's
home agent) to perform Duplicate Address Detection [27] on home agent) to perform Duplicate Address Detection [27] on
the mobile node's home link for the home address in this the mobile node's home link for the home address in this
binding. This bit is only valid when the Home Registration (H) binding. This bit is only valid when the Home Registration (H)
and Acknowledge (A) bits are also set, and MUST NOT be set and Acknowledge (A) bits are also set, and MUST NOT be set
otherwise. If the Duplicate Address Detection performed by otherwise. If the Duplicate Address Detection performed by
the home agent fails, the Status field in the returned Binding the home agent fails, the Status field in the returned Binding
Acknowledgement will be set to 138 (Duplicate Address Detection Acknowledgement will be set to 138 (Duplicate Address Detection
failed). The mobile node SHOULD set the Duplicate Address failed).
Detection (D) bit based on any requirements for Duplicate
Address Detection that would apply to the mobile node if it
were at home [17, 27].
Reservd Reservd
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.
Prefix Length Prefix Length
The Prefix Length field is valid only for a "home registration" The Prefix Length field is valid only for a "home registration"
Binding Update; this field MUST be zero if the Home Binding Update; this field MUST be zero if the Home
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home agent not only for the individual home address given in home agent not only for the individual home address given in
this binding, but also for all other home addresses for this this binding, but also for all other home addresses for this
mobile node formed from this interface identifier. That is, mobile node formed from this interface identifier. That is,
for each on-link prefix on the home link, the home agent uses for each on-link prefix on the home link, the home agent uses
the interface identifier to form other valid addresses for the interface identifier to form other valid addresses for
the mobile node on the home link, and acts as a home agent the mobile node on the home link, and acts as a home agent
also for those addresses. In addition, the home agent forms also for those addresses. In addition, the home agent forms
the link-local address and site-local address corresponding the link-local address and site-local address corresponding
to this interface identifier, and defends each for purposes to this interface identifier, and defends each for purposes
of Duplicate Address Detection. The home agent also performs of Duplicate Address Detection. The home agent also performs
Duplicate Address Detection on each such address as part of Duplicate Address Detection on at least one such address as
the home registration processing (before returning the Binding part of the home registration processing (before returning
Acknowledgement), if the Duplicate Address Detection (D) bit the Binding Acknowledgement), if the Duplicate Address
is set in the Binding Update. Details of this operation are Detection (D) bit is set in the Binding Update; it is not
described in Section 9.3. necessary to perform Duplicate Address Detection individually
on each of these addresses, since address uniqueness here is
determined solely by the interface identifier [27]. Details of
this operation are described in Section 9.3.
Sequence Number Sequence Number
Used by the receiving node to sequence Binding Updates and by Used by the receiving node to sequence Binding Updates and by
the sending node to match a returned Binding Acknowledgement the sending node to match a returned Binding Acknowledgement
with this Binding Update. Each Binding Update sent by a mobile with this Binding Update. Each Binding Update sent by a mobile
node MUST use a Sequence Number greater than the Sequence node MUST use a Sequence Number greater than the Sequence
Number value sent in the previous Binding Update (if any) to Number value sent in the previous Binding Update (if any) to
the same destination address (modulo 2**16, as defined in the same destination address (modulo 2**16, as defined in
Section overview:data). There is no requirement, however, that Section 4.6). There is no requirement, however, that the
the Sequence Number value strictly increase by 1 with each new Sequence Number value strictly increase by 1 with each new
Binding Update sent or received. Binding Update sent or received.
Lifetime Lifetime
32-bit unsigned integer. The number of seconds remaining 32-bit unsigned integer. The number of seconds remaining
before the binding MUST be considered expired. A value of all before the binding MUST be considered expired. A value of all
one bits (0xffffffff) indicates infinity. A value of zero one bits (0xffffffff) indicates infinity. A value is zero
indicates that the Binding Cache entry for the mobile node MUST indicates that the Binding Cache entry for the mobile node MUST
be deleted. be deleted.
Sub-Options Sub-Options
Additional information, associated with this Binding Update Additional information, associated with this Binding Update
option, that need not be present in all Binding Updates sent. option, that need not be present in all Binding Updates sent.
This use of sub-options also allows for future extensions to This use of sub-options also allows for future extensions to
the format of the Binding Update option to be defined. The the format of the Binding Update option to be defined. The
encoding and format of defined sub-options are described in encoding and format of defined sub-options are described in
skipping to change at page 24, line 7 skipping to change at page 23, line 54
Update option: Update option:
- Unique Identifier Sub-Option - Unique Identifier Sub-Option
- Alternate Care-of Address Sub-Option - Alternate Care-of Address Sub-Option
The alignment requirement [6] for the Binding Update option is 4n+2. The alignment requirement [6] for the Binding Update option is 4n+2.
Any packet that includes a Binding Update option MUST also include Any packet that includes a Binding Update option MUST also include
a Home Address option. The home address of the mobile node in the a Home Address option. The home address of the mobile node in the
binding given in the Binding Update option is indicated by the Home binding given in the Binding Update option is that which was received
Address field in the Home Address option in the packet. as the value of the Home Address field in the Home Address option in
the packet.
The care-of address for the binding given in the Binding Update The care-of address for the binding given in the Binding Update
option is normally specified by the Source Address field in the IPv6 option is normally that which was received as the value in the Source
header of the packet carrying the Binding Update option. However, a Address field in the IPv6 header of the packet carrying the Binding
care-of address different from the Source Address MAY be specified Update option. However, a care-of address different from the Source
by including an Alternate Care-of Address sub-option in the Binding Address MAY be specified by including an Alternate Care-of Address
Update option. sub-option in the Binding Update option.
Any packet that includes a Binding Update option MUST be protected by Any packet that includes a Binding Update option MUST be protected by
IPsec [13] to guard against malicious Binding Updates. The specific IPsec [13] to guard against malicious Binding Updates. The specific
requirements for this protection are defined in Section 4.4. requirements for this protection are defined in Section 4.4.
If the care-of address for the binding (specified either in an If the care-of address for the binding (specified either in an
Alternate Care-of Address sub-option in the Binding Update option, if Alternate Care-of Address sub-option in the Binding Update option, if
present, or in the Source Address field in the packet's IPv6 header) present, or in the Source Address field in the packet's IPv6 header)
is equal to the home address of the mobile node, the Binding Update is equal to the home address of the mobile node, the Binding Update
option indicates that any existing binding for the mobile node MUST option indicates that any existing binding for the mobile node MUST
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indicates that the Binding Update was rejected. indicates that the Binding Update was rejected.
Sub-Options Sub-Options
Additional information, associated with this Binding Additional information, associated with this Binding
Acknowledgement option, that need not be present in all Binding Acknowledgement option, that need not be present in all Binding
Acknowledgements sent. This use of sub-options also allows for Acknowledgements sent. This use of sub-options also allows for
future extensions to the format of the Binding Acknowledgement future extensions to the format of the Binding Acknowledgement
option to be defined. The encoding and format of defined option to be defined. The encoding and format of defined
sub-options are described in Section 5.5. Currently, no valid sub-options are described in Section 5.5. Currently, no valid
sub-options are defined for in a Binding Acknowledgement sub-options are defined for a Binding Acknowledgement option.
option.
The alignment requirement [6] for the Binding Acknowledgement option The alignment requirement [6] for the Binding Acknowledgement option
is 4n+3. is 4n+3.
Any packet that includes a Binding Acknowledgement option MUST Any packet that includes a Binding Acknowledgement option MUST
be protected by IPsec [13] to guard against malicious Binding be protected by IPsec [13] to guard against malicious Binding
Acknowledgements. The specific requirements for this protection are Acknowledgements. The specific requirements for this protection are
defined in Section 4.4. defined in Section 4.4.
If the node returning the Binding Acknowledgement accepted the If the node returning the Binding Acknowledgement accepted the
Binding Update for which the Acknowledgement is being returned (the Binding Update for which the Acknowledgement is being returned (the
value of the Status field in the Acknowledgement is less than 128), value of the Status field in the Acknowledgement is less than 128),
this node will have an entry for the mobile node in its Binding Cache this node will have an entry for the mobile node in its Binding Cache
and MUST use this entry (which includes the care-of address received and MUST use this entry (which includes the care-of address received
in the Binding Update) in sending the packet containing the Binding in the Binding Update) in sending the packet containing the Binding
Acknowledgement to the mobile node. The details of sending this Acknowledgement to the mobile node. The details of sending this
packet to the mobile node are the same as for sending any packet to a packet to the mobile node are the same as for sending any packet to
mobile node using a binding, and are described in Section 8.9. The a mobile node using a binding, as are described in Section 8.9. The
packet is sent using a Routing header, routing the packet to the packet is sent using a Routing header, routing the packet to the
mobile node by way of its care-of address recorded in the Binding mobile node by way of its care-of address recorded in the Binding
Cache entry. Cache entry.
If the node returning the Binding Acknowledgement instead If the node returning the Binding Acknowledgement instead
rejected the Binding Update (the value of the Status field in the rejected the Binding Update (the value of the Status field in the
Acknowledgement is greater than or equal to 128), this node MUST Acknowledgement is greater than or equal to 128), this node MUST
similarly use a Routing header in sending the packet containing the similarly use a Routing header in sending the packet containing the
Binding Acknowledgement, as described in Section 8.9, but MUST NOT Binding Acknowledgement, as described in Section 8.9, but MUST NOT
use its Binding Cache in forming the IP header or Routing header use its Binding Cache in forming the IP header or Routing header
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The alignment requirement [6] for the Home Address option is 8n+6. The alignment requirement [6] for the Home Address option is 8n+6.
The inclusion of a Home Address option in a packet affects the The inclusion of a Home Address option in a packet affects the
receiving node's processing of only this single packet; no state is receiving node's processing of only this single packet; no state is
created or modified in the receiving node as a result of receiving a created or modified in the receiving node as a result of receiving a
Home Address option in a packet. In particular, the presence of a Home Address option in a packet. In particular, the presence of a
Home Address option in a received packet MUST NOT alter the contents Home Address option in a received packet MUST NOT alter the contents
of the receiver's Binding Cache and MUST NOT cause any changes in the of the receiver's Binding Cache and MUST NOT cause any changes in the
routing of subsequent packets sent by this receiving node. routing of subsequent packets sent by this receiving node.
No authentication of the Home Address option is required, except that The Home Address option MUST be placed as follows:
if the IPv6 header of a packet is covered by authentication, then
that authentication MUST also cover the Home Address option; this
coverage is achieved automatically by the definition of the Option
Type code for the Home Address option, since it indicates that the
data within the option cannot change en-route to the packet's final
destination, and thus the option is included in the authentication
computation. If the packet carries no IP authentication, then the
contents of the Home Address option, as well as the Source Address
field or any other field in the IPv6 header, may have been forged or
altered during transit.
Upon receipt of a packet containing a Home Address option, the - After the Routing Header, if that header is present
receiving node replaces the Source Address in the IPv6 header with
the Home Address in the Home Address option. By requiring that any - Before the Fragment Header, if that header is present
authentication of the IPv6 header also cover the Home Address option,
the security of the Source Address field in the IPv6 header is not - Before the AH Header or ESP Header, if either one of those
compromised by the presence of a Home Address option. Security headers is present
issues related to the Home Address option are discussed further in
Section 13. No authentication of the Home Address option is required, except
that if the IPv6 header of a packet is covered by authentication,
then that authentication MUST also cover the Home Address option;
this coverage is achieved automatically by the definition of the
Option Type code for the Home Address option, since it indicates
that the data within the option cannot change en-route to the
packet's final destination, and thus the option is included in the
authentication computation. By requiring that any authentication of
the IPv6 header also cover the Home Address option, the security of
the Source Address field in the IPv6 header is not compromised by
the presence of a Home Address option. Security issues related to
the Home Address option are discussed further in Section 13. When
attempting to verify authentication data in a packet that contains
a Home Address option, the receiving node MUST make the calculation
as if the care-of address were present in the Home Address option,
and the home address were present in the source IPv6 address field
of the IPv6 header. This conforms with the calculation specified in
section 10.2.
A packet MUST NOT contain more than one Home Address option, except A packet MUST NOT contain more than one Home Address option, except
that an encapsulated packet [4] MAY contain a separate Home Address that an encapsulated packet [4] MAY contain a separate Home Address
option associated with each encapsulating IP header. option associated with each encapsulating IP header.
The three highest-order bits of the Option Type are encoded to The three highest-order bits of the Option Type are encoded to
indicate specific processing of the option [6]. For the Home Address indicate specific processing of the option [6]. For the Home Address
option, these three bits are set to 110, indicating that any IPv6 option, these three bits are set to 110, indicating that any IPv6
node processing this option that does not recognize the Option Type node processing this option that does not recognize the Option Type
must discard the packet and, only if the packet's Destination Address must discard the packet and, only if the packet's Destination Address
was not a multicast address, return an ICMP Parameter Problem, was not a multicast address, return an ICMP Parameter Problem,
Code 2, message to the packet's Source Address; and that the data Code 2, message to the packet's Source Address; and that the data
within the option cannot change en-route to the packet's final within the option cannot change en-route to the packet's final
destination. destination.
5.5. Mobile IPv6 Destination Option Sub-Options 5.5. Mobile IPv6 Destination Option Sub-Options
In order to allow optional fields that may not be needed in most uses In order to allow optional fields that may not be needed in every
of any given Mobile IPv6 destination option, and to allow future use of any given Mobile IPv6 destination option, and to allow future
extensions to the format of these destination options to be defined, extensions to the format of these destination options to be defined,
any of the Mobile IPv6 destination options defined in this document any of the Mobile IPv6 destination options defined in this document
MAY include one or more sub-options. MAY include one or more sub-options.
Such sub-options are included in the data portion of the destination Such sub-options are included in the data portion of the destination
option itself, after the fixed portion of the option data specified option itself, after the fixed portion of the option data specified
for that particular destination option (Sections 5.1 through 5.4). for that particular destination option (Sections 5.1 through 5.4).
The presence of such sub-options will be indicated by the Option The presence of such sub-options will be indicated by the Option
Length field. When the Option Length is greater than the standard Length field. When the Option Length is greater than the standard
length defined for that destination option, the remaining octets are length defined for that destination option, the remaining octets are
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as follows: 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sub-Option Type| Sub-Option Len| Sub-Option Data... |Sub-Option Type| Sub-Option Len| Sub-Option Data...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sub-Option Type Sub-Option Type
8-bit identifier of the type of sub-option. In processing a 8-bit identifier of the type of sub-option. When processing
Mobile IPv6 destination option containing a sub-option for a Mobile IPv6 destination option containing a sub-option for
which the Sub-Option Type value is not recognized by the which the Sub-Option Type value is not recognized by the
receiver, the receiver SHOULD quietly ignore and skip over the receiver, the receiver SHOULD quietly ignore and skip over the
sub-option, correctly handling any remaining sub-options in the sub-option, correctly handling any remaining sub-options in the
option. option.
Sub-Option Length Sub-Option Length
8-bit unsigned integer. Length of the Sub-Option Data field 8-bit unsigned integer. Length of the Sub-Option Data field
of this sub-option, in octets. The Sub-Option Len does not of this sub-option, in octets. The Sub-Option Len does not
include the length of the Sub-Option Type and Sub-Option Len include the length of the Sub-Option Type and Sub-Option Len
skipping to change at page 36, line 23 skipping to change at page 36, line 21
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Unique Identifier sub-option is valid only in Binding The Unique Identifier sub-option is valid only in Binding
Request and Binding Update destination options. The Unique Request and Binding Update destination options. The Unique
Identifier field contains a 16-bit value that serves to Identifier field contains a 16-bit value that serves to
uniquely identify a Binding Request among those sent by this uniquely identify a Binding Request among those sent by this
Source Address, and to allow the Binding Update to identify Source Address, and to allow the Binding Update to identify
the specific Binding Request to which it responds. This the specific Binding Request to which it responds. This
matching of Binding Updates to Binding Requests is required matching of Binding Updates to Binding Requests is required
in the procedure for renumbering the home subnet while a in the procedure for renumbering the home subnet while a
mobile node is away from home (Section 9.7). mobile node is away from home (Section 9.8).
Alternate Care-of Address Sub-Option (alignment requirement: 8n+6) Alternate Care-of Address Sub-Option (alignment requirement: 8n+6)
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4 | 16 | | 4 | 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
| | | |
+ Alternate Care-of Addresses + + Alternate Care-of Address +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Alternate Care-of Address sub-option is valid only in The Alternate Care-of Address sub-option is valid only in
Binding Update destination options. The Alternate Care-of Binding Update destination options. The Alternate Care-of
Address field contains an address to use as the care-of Address field contains an address to use as the care-of
address for the binding, rather than using the Source address for the binding, rather than using the Source
Address of the packet as the care-of address. Address of the packet as the care-of address.
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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.
Home Agent Preference Home Agent Preference
16-bit signed, twos-complement integer. The preference for 16-bit signed, twos-complement integer. The preference for
the home agent sending this Router Advertisement, for use in the home agent sending this Router Advertisement, for use in
ordering the addresses returned to a mobile node in the Home ordering the addresses returned to a mobile node in the Home
Agent Addresses field of a Home Agent Address Discovery Reply Agent Addresses field of a Home Agent Address Discovery Reply
message. higher values mean more preferable. If this option message. Higher values mean more preferable. If this option
is not included in a Router Advertisement in which the Home is not included in a Router Advertisement in which the Home
Agent (H) bit is set, the preference value for this home agent Agent (H) bit is set, the preference value for this home agent
SHOULD be considered to be 0. Values greater than 0 indicate a SHOULD be considered to be 0. Values greater than 0 indicate a
home agent more preferable than this default value, and values home agent more preferable than this default value, and values
less than 0 indicate a less preferable home agent. less than 0 indicate a less preferable home agent.
In addition to the manual configuration of the Home Agent The manual configuration of the Home Agent Preference value
Preference value as described in Section 7.3, the Home Agent is described in Section 7.3. In addition, the sending home
Preference sent by a home agent could be set dynamically by the agent MAY dynamically set the Home Agent Preference value, for
sending home agent, for example based on the number of mobile example basing it on the number of mobile nodes it is currently
nodes it is currently serving or on its remaining resources for serving or on its remaining resources for serving additional
serving additional mobile nodes, but such dynamic settings are mobile nodes; such dynamic settings are beyond the scope of
beyond the scope of this document. Any such dynamic setting this document. Any such dynamic setting of the Home Agent
of the Home Agent Preference, however, MUST be careful to set Preference, however, MUST set the preference appropriately,
the preference appropriately, relative to the default Home relative to the default Home Agent Preference value of 0 that
Agent Preference value of 0 that may be in use by some home may be in use by some home agents on this link (i.e., a home
agents on this link (i.e., a home agent not including a Home agent not including a Home Agent Information option in its
Agent Information option in its Router Advertisements will be Router Advertisements will be considered to have a Home Agent
considered to have a Home Agent Preference value of 0). Preference value of 0).
Home Agent Lifetime Home Agent Lifetime
16-bit unsigned integer. The lifetime associated with the home 16-bit unsigned integer. The lifetime associated with the home
agent in units of seconds. The maximum value corresponds to agent in units of seconds. The maximum value corresponds to
18.2 hours. A value of 0 MUST NOT be used. The Home Agent 18.2 hours. A value of 0 MUST NOT be used. The Home Agent
Lifetime applies only to this router's usefulness as a home Lifetime applies only to this router's usefulness as a home
agent; it does not apply to information contained in other agent; it does not apply to information contained in other
message fields or options. If this option is not included in message fields or options. If this option is not included in
a Router Advertisement in which the Home Agent (H) bit is set, a Router Advertisement in which the Home Agent (H) bit is set,
the lifetime for this home agent SHOULD be considered to be the the lifetime for this home agent MUST be considered to be the
same as the Router Lifetime specified in the main body of the same as the Router Lifetime specified in the main body of the
Router Advertisement message. Router Advertisement message.
Home agents MAY include this option in their Router Advertisements. Home agents MAY include this option in their Router Advertisements.
This option MUST NOT be included in a Router Advertisement in which This option MUST NOT be included in a Router Advertisement in which
the Home Agent (H) bit (Section 6.1) is not set. the Home Agent (H) bit (see Section 6.1) is not set.
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 If both the Home Agent Preference and Home Agent Lifetime are set
to their default values specified above, this option SHOULD NOT be to 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.
6.5. Changes to Sending Router Advertisements 6.5. Changes to Sending Router Advertisements
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that they can acquire a new care-of address and send Binding Updates that they can acquire a new care-of address and send Binding Updates
to register this care-of address with their home agent and to notify to register this care-of address with their home agent and to notify
correspondent nodes as needed. correspondent nodes as needed.
Thus, to provide good support for mobile nodes, Mobile IPv6 relaxes Thus, to provide good support for mobile nodes, Mobile IPv6 relaxes
this limit such that routers MAY send unsolicited multicast Router this limit such that routers MAY send unsolicited multicast Router
Advertisements more frequently. In particular, on network interfaces Advertisements more frequently. In particular, on network interfaces
where the router is expecting to provide service to visiting mobile where the router is expecting to provide service to visiting mobile
nodes (e.g., wireless network interfaces), or on which it is serving nodes (e.g., wireless network interfaces), or on which it is serving
as a home agent to one or more mobile nodes (who may return home and as a home agent to one or more mobile nodes (who may return home and
need to hear its Advertisements), the home agent SHOULD be configured need to hear its Advertisements), the router SHOULD be configured
with a smaller MinRtrAdvInterval value and MaxRtrAdvInterval value, with a smaller MinRtrAdvInterval value and MaxRtrAdvInterval value,
to allow sending of unsolicited multicast Router Advertisements more to allow sending of unsolicited multicast Router Advertisements more
often. Recommended values for these limits are: often. Recommended values for these limits are:
- MinRtrAdvInterval 0.5 seconds - MinRtrAdvInterval 0.5 seconds
- MaxRtrAdvInterval 1.5 seconds - MaxRtrAdvInterval 1.5 seconds
Use of these modified limits MUST be configurable, and specific Use of these modified limits MUST be configurable, and specific
knowledge of the type of network interface in use SHOULD be taken knowledge of the type of network interface in use SHOULD be taken
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- While still searching for a new default router and care-of - While still searching for a new default router and care-of
address, a mobile node MUST NOT increase the rate at which it address, a mobile node MUST NOT increase the rate at which it
sends Router Solicitations unless it has received a positive sends Router Solicitations unless it has received a positive
indication (such as from lower network layers) that it has moved indication (such as from lower network layers) that it has moved
to a new link. After successfully acquiring a new care-of to a new link. After successfully acquiring a new care-of
address, the mobile node SHOULD also increase the rate at which address, the mobile node SHOULD also increase the rate at which
it will send Router Solicitations when it next begins searching it will send Router Solicitations when it next begins searching
for a new default router and care-of address. for a new default router and care-of address.
- A mobile node that is currently configured with a care-of - A mobile node that is currently configured with a care-of address
address SHOULD NOT send Router Solicitations, until its movement SHOULD NOT send Router Solicitations to the default router
detection algorithm (Section 10.4) determines that it has moved on it current link, until its movement detection algorithm
and that its current care-of address might no longer be valid. (Section 10.4) determines that it has moved and that its current
care-of address might no longer be valid.
7. Requirements for IPv6 Nodes 7. Requirements for Types of IPv6 Nodes
Mobile IPv6 places some special requirements on the functions Mobile IPv6 places some special requirements on the functions
provided by different types of IPv6 nodes. This section summarizes provided by different types of IPv6 nodes. This section summarizes
those requirements, identifying the functionality each requirement those requirements, identifying the functionality each requirement
is intended to support. Further details on this functionality is is intended to support. Further details on this functionality is
provided in the following sections. provided in the following sections.
7.1. Requirements for All IPv6 Hosts and Routers 7.1. Requirements for All IPv6 Hosts and Routers
Since any IPv6 node may at any time be a correspondent node of a Since any IPv6 node may at any time be a correspondent node of a
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A correspondent node is any node communicating with a mobile node. A correspondent node is any node communicating with a mobile node.
The correspondent node, itself, may be stationary or mobile, and may The correspondent node, itself, may be stationary or mobile, and may
possibly also be functioning as a home agent for Mobile IPv6. The possibly also be functioning as a home agent for Mobile IPv6. The
procedures in this section thus apply to all IPv6 nodes. procedures in this section thus apply to all IPv6 nodes.
8.1. Receiving Packets from a Mobile Node 8.1. Receiving Packets from a Mobile Node
Packets sent by a mobile node while away from home generally include Packets sent by a mobile node while away from home generally include
a Home Address option. When any node receives a packet containing a Home Address option. When any node receives a packet containing
a Home Address option, it MUST process the option in a manner a Home Address option, it MUST process the option in a manner
consistent with copying the Home Address field from the Home Address consistent with exchanging the Home Address field from the Home
option into the IPv6 header, replacing the original value of the Address option into the IPv6 header, replacing the original value of
Source Address field there. However, any actual modifications to the Source Address field there. However, any actual modifications
the Source Address field in the packet's IPv6 header MUST not be to the Source Address field in the packet's IPv6 header MUST not
performed until after all processing of other options contained in be performed until after all processing of other options contained
this same Destination Options extension header is completed. in the same Destination Options extension header is completed.
Currently, no other such options are defined.
Further processing of such a packet after option processing (e.g., Further processing of such a packet after all IPv6 options processing
at the transport layer) thus need not know that the original Source (e.g., at the transport layer) thus does not need to know that the
Address was a care-of address, or that the Home Address option was original Source Address was a care-of address, or that the Home
used in the packet. Since the sending mobile node uses its home Address option was used in the packet. Since the sending mobile
address at the transport layer when sending such a packet, the use of node uses its home address at the transport layer when sending such
the care-of address and Home Address option is transparent to both a packet, the use of the care-of address and Home Address option is
the mobile node and the correspondent node above the level of the transparent to both the mobile node and the correspondent node above
Home Address option generation and processing. the level of the Home Address option generation and processing.
8.2. Receiving Binding Updates 8.2. Receiving Binding Updates
Upon receiving a Binding Update option in some packet, the receiving Upon receiving a Binding Update option in some packet, the receiving
node MUST validate the Binding Update according to the following node MUST validate the Binding Update according to the following
tests: tests:
- The packet meets the specific IPsec requirements for Binding - The packet meets the specific IPsec requirements for Binding
Updates, defined in Section 4.4. Updates, defined in Section 4.4.
- The packet MUST contain a valid Home Address option. The home - The packet MUST contain a Home Address option.
address for the binding is specified by the Home Address field of
the Home Address option.
- The Option Length field in the Binding Update option is greater - The Option Length field in the Binding Update option is greater
than or equal to the length specified in Section 5.1. than or equal to the length specified in Section 5.1.
- The Sequence Number field in the Binding Update option is greater - The Sequence Number field in the Binding Update option is greater
than the Sequence Number received in the previous Binding Update than the Sequence Number received in the previous Binding Update
for this home address, if any. As noted in Section 4.6, this for this home address, if any. As noted in Section 4.6, this
Sequence Number comparison MUST be performed modulo 2**16. Sequence Number comparison MUST be performed modulo 2**16.
Any Binding Update not satisfying all of these tests MUST be Any Binding Update not satisfying all of these tests MUST be
silently ignored, and the packet carrying the Binding Update MUST be silently ignored, and the packet carrying the Binding Update MUST be
discarded. discarded.
In this section, the care-of address refers to the IPv6 address,
which was originally located in the IPv6 header when the packet was
transmitted by the mobile node.
If the Binding Update is valid according to the tests above, then the If the Binding Update is valid according to the tests above, then the
Binding Update is processed further as follows: Binding Update is processed further as follows:
- If the Lifetime specified in the Binding Update is nonzero and - If the Lifetime specified in the Binding Update is nonzero and
the specified Care-of Address is not equal to the home address the specified Care-of Address is not equal to the home address
for the binding (as given in the Home Address option in the for the binding, then this is a request to cache a binding for
packet), then this is a request to cache a binding for the the mobile node. If the Home Registration (H) bit is set in the
mobile node. If the Home Registration (H) bit is set in the
Binding Update, the Binding Update is processed according to the Binding Update, the Binding Update is processed according to the
procedure specified in Section 9.3; otherwise, it is processed procedure specified in Section 9.3; otherwise, it is processed
according to the procedure specified in Section 8.3. according to the procedure specified in Section 8.3.
- If the Lifetime specified in the Binding Update is zero or the - If the Lifetime specified in the Binding Update is zero or the
specified Care-of Address matches the home address for the specified Care-of Address matches the home address for the
binding, then this is a request to delete the mobile node's binding, then this is a request to delete the mobile node's
cached binding. If the Home Registration (H) bit is set in the cached binding. If the Home Registration (H) bit is set in the
Binding Update, the Binding Update is processed according to the Binding Update, the Binding Update is processed according to the
procedure specified in Section 9.4; otherwise, it is processed procedure specified in Section 9.4; otherwise, it is processed
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When a node receives a Binding Update, it MUST validate it and When a node receives a Binding Update, it MUST validate it and
determine the type of Binding Update according to the steps described determine the type of Binding Update according to the steps described
in Section 8.2. This section describes the processing of a valid in Section 8.2. This section describes the processing of a valid
Binding Update that requests a node to cache a mobile node's binding, Binding Update that requests a node to cache a mobile node's binding,
for which the Home Registration (H) bit is not set in the Binding for which the Home Registration (H) bit is not set in the Binding
Update. Update.
In this case, the receiving node SHOULD create a new entry in its In this case, the receiving node SHOULD create a new entry in its
Binding Cache for this mobile node (or update its existing Binding Binding Cache for this mobile node (or update its existing Binding
Cache entry for this mobile node, if such an entry already exists). Cache entry for this mobile node, if such an entry already exists).
The home address of the mobile node is taken from the Home Address The new Binding Cache entry records the association between this
field in the packet's Home Address option. The new Binding Cache home address and the care-of address for the binding. The lifetime
entry records the association between this home address and the for the Binding Cache entry is initialized from the Lifetime field
care-of address for the binding, as specified in either the Care-of specified in the Binding Update, although this lifetime MAY be
Address field of the Binding Update or in the Source Address field reduced by the node caching the binding; the lifetime for the Binding
in the packet's IPv6 header. The lifetime for the Binding Cache Cache entry MUST NOT be greater than the Lifetime value specified in
entry is initialized from the Lifetime field specified in the Binding the Binding Update. Any Binding Cache entry MUST be deleted after
Update, although this lifetime MAY be reduced by the node caching the the expiration of this lifetime in the Binding Cache entry.
binding; the lifetime for the Binding Cache entry MUST NOT be greater
than the Lifetime value specified in the Binding Update. Any Binding
Cache entry MUST be deleted after the expiration of this lifetime on
the Binding Cache entry.
8.4. Requests to Delete a Binding 8.4. Requests to Delete a Binding
When a node receives a Binding Update, it MUST validate it and When a node receives a Binding Update, it MUST validate it and
determine the type of Binding Update according to the steps described determine the type of Binding Update according to the steps described
in Section 8.2. This section describes the processing of a valid in Section 8.2. This section describes the processing of a valid
Binding Update that requests a node to delete a mobile node's binding Binding Update that requests a node to delete a mobile node's binding
from its Binding Cache, for which the Home Registration (H) bit is from its Binding Cache, for which the Home Registration (H) bit is
not set in the Binding Update. not set in the Binding Update. In this case, the receiving node MUST
delete any existing entry in its Binding Cache for this mobile node.
In this case, the receiving node MUST delete any existing entry in
its Binding Cache for this mobile node. The home address of the
mobile node is taken from the Home Address field in the packet's Home
Address option.
8.5. Sending Binding Acknowledgements 8.5. Sending Binding Acknowledgements
When any node receives a packet containing a Binding Update option When any node receives a packet containing a Binding Update option
in which the Acknowledge (A) bit is set, it SHOULD return a Binding in which the Acknowledge (A) bit is set, it MUST return a Binding
Acknowledgement option acknowledging receipt of the Binding Update. Acknowledgement option acknowledging receipt of the Binding Update.
If the node accepts the Binding Update and creates or updates an If the node accepts the Binding Update and creates or updates
entry in its Binding Cache for this binding, the Status field in an entry in its Binding Cache for this binding, and the `A' bit
the Binding Acknowledgement MUST be set to a value less than 128; was set in the Binding Update, the Status field in the Binding
if the node rejects the Binding Update and does not create or Acknowledgement MUST be set to a value less than 128; if, on the
update an entry for this binding, the Status field in the Binding other hand the Binding Update is accepted and the `A' bit is not set,
Acknowledgement MUST be set to a value greater than or equal to 128. the node SHOULD NOT send a Binding Acknowledgement. If the node
Specific values for the Status field are described in Section 5.2 and rejects the Binding Update and does not create or update an entry for
in the most recent "Assigned Numbers" [26]. this binding, a Binding Acknowledgement MUST be sent even if the `A'
bit was not sent, and the Status field in the Binding Acknowledgement
MUST be set to a value greater than or equal to 128. Specific values
for the Status field are described in Section 5.2 and in the most
recent "Assigned Numbers" [26].
The packet in which the Binding Acknowledgement is returned MUST meet The packet in which the Binding Acknowledgement is returned MUST meet
the specific IPsec requirements for Binding Acknowledgements, defined the specific IPsec requirements for Binding Acknowledgements, defined
in Section 4.4; and the packet MUST be sent using a Routing header in Section 4.4; and the packet MUST be sent using a Routing header
in the same way as any other packet sent to a mobile node using a in the same way as any other packet sent to a mobile node using a
care-of address (even if the binding was rejected), as described care-of address (even if the binding was rejected), as described in
in Section 8.9. The packet is routed first to the care-of address Section 8.9.
contained in the Binding Update being acknowledged, and then to the
mobile node's home address. This use of the Routing header ensures
that the Binding Acknowledgement will be routed to the current
location of the node sending the Binding Update, whether the Binding
Update was accepted or rejected.
8.6. Sending Binding Requests 8.6. Sending Binding Requests
Entries in a node's Binding Cache MUST be deleted when their lifetime Entries in a node's Binding Cache MUST be deleted when their lifetime
expires. If such an entry is still in active use in sending packets expires. If such an entry is still in active use in sending packets
to a mobile node, the next packet sent to the mobile node will be to a mobile node, the next packet sent to the mobile node will be
routed normally to the mobile node's home link, where it will be routed normally to the mobile node's home link, where it will be
intercepted and tunneled to the mobile node. The mobile node will intercepted and tunneled to the mobile node. The mobile node will
then return a Binding Update to the sender, allowing it to create then return a Binding Update to the sender, allowing it to create
a new Binding Cache entry for sending future packets to the mobile a new Binding Cache entry for sending future packets to the mobile
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maintains a separate timer for each entry in its Binding Cache. When maintains a separate timer for each entry in its Binding Cache. When
creating or updating a Binding Cache entry in response to a received creating or updating a Binding Cache entry in response to a received
and accepted Binding Update, the node sets the timer for this entry and accepted Binding Update, the node sets the timer for this entry
to the specified Lifetime period. When a Binding Cache entry's timer to the specified Lifetime period. When a Binding Cache entry's timer
expires, the node deletes the entry. expires, the node deletes the entry.
Each node's Binding Cache will, by necessity, have a finite size. Each node's Binding Cache will, by necessity, have a finite size.
A node MAY use any reasonable local policy for managing the space A node MAY use any reasonable local policy for managing the space
within its Binding Cache, except that any entry marked as a "home within its Binding Cache, except that any entry marked as a "home
registration" (Section 9.3) MUST NOT be deleted from the cache until registration" (Section 9.3) MUST NOT be deleted from the cache until
the expiration of its lifetime period. When attempting to add a the expiration of its lifetime period. When attempting to add a new
new "home registration" entry in response to a Binding Update with "home registration" entry in response to a Binding Update with the
the Home Registration (H) bit set, if insufficient space exists (or Home Registration (H) bit set, if insufficient space exists (and
can be reclaimed) in the node's Binding Cache, the node MUST reject sufficient space cannot be reclaimed) in the node's Binding Cache,
the Binding Update and SHOULD return a Binding Acknowledgement to the node MUST reject the Binding Update and SHOULD return a Binding
the sending mobile node, in which the Status field is set to 131 Acknowledgement to the sending mobile node, in which the Status field
(insufficient resources). When otherwise attempting to add a new is set to 131 (insufficient resources). When otherwise attempting to
entry to its Binding Cache, a node MAY, if needed, choose to drop any add a new entry to its Binding Cache, a node MAY, if needed, choose
entry already in its Binding Cache, other than a "home registration" to drop any entry already in its Binding Cache, other than a "home
entry, in order to make space for the new entry. For example, a registration" entry, in order to make space for the new entry. For
"least-recently used" (LRU) strategy for cache entry replacement example, a "least-recently used" (LRU) strategy for cache entry
among entries not marked as a "home registration" is likely to work replacement among entries not marked as a "home registration" is
well. likely to work well.
Any binding dropped from a node's Binding Cache due to lack of cache Any binding dropped from a node's Binding Cache due to lack of cache
space will be rediscovered and a new cache entry created, if the space will be rediscovered and a new cache entry created, if the
binding is still in active use by the node for sending packets. If binding is still in active use by the node for sending packets. If
the node sends a packet to a destination for which it has dropped the the node sends a packet to a destination for which it has dropped the
entry from its Binding Cache, the packet will be routed normally, entry from its Binding Cache, the packet will be routed normally,
leading to the mobile node's home link. There, the packet will be leading to the mobile node's home link. There, the packet will be
intercepted by the mobile node's home agent and tunneled to the intercepted by the mobile node's home agent and tunneled to the
mobile node's current primary care-of address. As when a Binding mobile node's current primary care-of address. As when a Binding
Cache entry is initially created, this indirect routing to the mobile Cache entry is initially created, this indirect routing to the mobile
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header to deliver the packet to the mobile node through the care-of header to deliver the packet to the mobile node through the care-of
address in the binding recorded in the Binding Cache entry. Any ICMP address in the binding recorded in the Binding Cache entry. Any ICMP
error message caused by the packet on its way to the mobile node will error message caused by the packet on its way to the mobile node will
be returned normally to the correspondent node. be returned normally to the correspondent node.
On the other hand, if the correspondent node has no Binding Cache On the other hand, if the correspondent node has no Binding Cache
entry for the mobile node, the packet will be routed to the mobile entry for the mobile node, the packet will be routed to the mobile
node's home link. There, it will be intercepted by the mobile node's node's home link. There, it will be intercepted by the mobile node's
home agent, encapsulated, and tunneled to the mobile node's primary home agent, encapsulated, and tunneled to the mobile node's primary
care-of address. Any ICMP error message caused by the packet on care-of address. Any ICMP error message caused by the packet on
its way to the mobile node while in the tunnel, will be returned to its way to the mobile node while in the tunnel, will be transmitted
the mobile node's home agent (the source of the tunnel). By the to the mobile node's home agent (the source of the tunnel). By the
definition of IPv6 encapsulation [4], this encapsulating node MUST definition of IPv6 encapsulation [4], this encapsulating node MUST
relay certain ICMP error messages back to the original sender of the relay certain ICMP error messages back to the original sender of the
packet, which in this case is the correspondent node. packet, which in this case is the correspondent node.
Likewise, if a packet for a mobile node arrives at the mobile node's Likewise, if a packet for a mobile node arrives at the mobile node's
previous link and is intercepted there by a home agent for the mobile previous link and is intercepted there by a home agent for the mobile
node's previous care-of address as described in Section 10.9 (e.g., node's previous care-of address as described in Section 10.9 (e.g.,
the mobile node moved after the packet was sent), that home agent the mobile node moved after the packet was sent), that home agent
will encapsulate and tunnel the packet to the mobile node's new will encapsulate and tunnel the packet to the mobile node's new
care-of address. As above, any ICMP error message caused by the care-of address. As above, any ICMP error message caused by the
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the Advertisement was not sent by a home agent. the Advertisement was not sent by a home agent.
- Otherwise, extract the Source Address from the IP header of the - 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 [17]. link of the home agent sending this Advertisement [17].
- Determine from the Router Advertisement the preference for this - Determine from the Router Advertisement the preference for this
home agent. If the Router Advertisement contains a Home Agent home agent. If the Router Advertisement contains a Home Agent
Information Option, then the preference is taken from the Home Information Option, then the preference is taken from the Home
Agent Preference field in the option; otherwise, the default Agent Preference field in the option; otherwise, the default
preference of 0 SHOULD be used. preference of 0 MUST be used.
- Determine from the Router Advertisement the lifetime for - Determine from the Router Advertisement the lifetime for
this home agent. If the Router Advertisement contains a Home this home agent. If the Router Advertisement contains a Home
Agent Information Option, then the lifetime is taken from Agent Information Option, then the lifetime is taken from
the Home Agent Lifetime field in the option; otherwise, the the Home Agent Lifetime field in the option; otherwise, the
lifetime specified by the Router Lifetime field in the Router lifetime specified by the Router Lifetime field in the Router
Advertisement SHOULD be used. Advertisement SHOULD be used.
- If the link-local address of the home agent sending this - If the link-local address of the home agent sending this
Advertisement is already present in this home agent's Home Advertisement is already present in this home agent's Home
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any other reason (e.g., insufficient resources to serve another any other reason (e.g., insufficient resources to serve another
mobile node as a home agent), then the home agent SHOULD return a mobile node as a home agent), then the home agent SHOULD return a
Binding Acknowledgement to the mobile node, in which the Status Binding Acknowledgement to the mobile node, in which the Status
field is set to an appropriate value to indicate the reason for field is set to an appropriate value to indicate the reason for
the rejection. the rejection.
- Finally, if the Duplicate Address Detection (D) bit is set in - Finally, if the Duplicate Address Detection (D) bit is set in
the Binding Update, this home agent MUST perform Duplicate the Binding Update, this home agent MUST perform Duplicate
Address Detection [27] on the mobile node's home link for the Address Detection [27] on the mobile node's home link for the
home address in this binding (before returning the Binding home address in this binding (before returning the Binding
Acknowledgement). Normal processing for Duplicate Address Acknowledgement); if the Prefix Length field is nonzero in the
Detection specifies that, in certain cases, the node SHOULD Binding Update, the home agent MAY choose to perform Duplicate
delay sending the initial Neighbor Solication message of Address Detection for only one of the addresses formed from the
Duplicate Address Detection by a random delay between 0 and interface identifier for this binding, and if so, the address
used for Duplicate Address Detection SHOULD be the mobile
node's link-local address. Normal processing for Duplicate
Address Detection specifies that, in certain cases, the node
SHOULD delay sending the initial Neighbor Solication message
of Duplicate Address Detection by a random delay between 0 and
MAX_RTR_SOLICITATION_DELAY [17, 27]; however, in this case, the MAX_RTR_SOLICITATION_DELAY [17, 27]; however, in this case, the
home agent SHOULD NOT perform such a delay. If this Duplicate home agent SHOULD NOT perform such a delay. If this Duplicate
Address Detection fails, then the home agent MUST reject the Address Detection fails, then the home agent MUST reject the
Binding Update and SHOULD return a Binding Acknowledgement to the Binding Update and SHOULD return a Binding Acknowledgement to the
mobile node, in which the Status field is set to 138 (Duplicate mobile node, in which the Status field is set to 138 (Duplicate
Address Detection failed). Address Detection failed).
If the home agent does not reject the Binding Update as described If the home agent does not reject the Binding Update as described
above, then it becomes the home agent for the mobile node. The new above, then it becomes the home agent for the mobile node. The new
home agent (the receiving node) MUST then create a new entry in its home agent (the receiving node) MUST then create a new entry in its
Binding Cache for this mobile node (or update its existing Binding Binding Cache for this mobile node (or update its existing Binding
Cache entry for this mobile node, if such an entry already exists) Cache entry for this mobile node, if such an entry already exists)
The home address of the mobile node is taken from the Home Address The home address of the mobile node is taken to be the value which,
field in the packet's Home Address option. The care-of address for when the packet was originally received, was located in the Home
this Binding Cache entry is taken from the Alternate Care-of Address Address field in the packet's Home Address option. The care-of
sub-option in the Binding Update option, if present, or from the address for this Binding Cache entry is taken to be the value which,
Source Address field in the packet's IPv6 header, otherwise. when the packet was originally received, was located either in the
Alternate Care-of Address sub-option in the Binding Update option,
if present, or from the Source Address field in the packet's IPv6
header, otherwise.
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 registration" to indicate that the node is serving as a home
agent for this binding. Binding Cache entries marked as a "home agent for this binding. Binding Cache entries marked as a "home
registration" MUST be excluded from the normal cache replacement registration" MUST be excluded from the normal cache replacement
policy used for the Binding Cache (Section 8.7) and MUST NOT be policy used for the Binding Cache (Section 8.7) and MUST NOT be
removed from the Binding Cache until the expiration of the Lifetime removed from the Binding Cache until the expiration of the Lifetime
period. period.
In addition, the home agent MUST copy the Router (R) bit from the In addition, the home agent MUST copy the Router (R) bit from the
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binding lifetime to less than or equal to the prefix valid lifetime. binding lifetime to less than or equal to the prefix valid lifetime.
The home agent MAY further decrease the specified lifetime for the The home agent MAY further decrease the specified lifetime for the
binding, for example based on a local policy implemented by the home binding, for example based on a local policy implemented by the home
agent. The resulting lifetime is stored by the home agent in the agent. The resulting lifetime is stored by the home agent in the
Binding Cache entry, and this Binding Cache entry MUST be deleted by Binding Cache entry, and this Binding Cache entry MUST be deleted by
the home agent after the expiration of this lifetime. the home agent after the expiration of this lifetime.
The Prefix Length in the Binding Update MUST also be saved in the The Prefix Length in the Binding Update MUST also be saved in the
Binding Cache entry. Binding Cache entry.
If the Acknowledge (A) bit is set in the Binding Update (it SHOULD The home agent MUST return a Binding Acknowledgement to the mobile
be), then the home agent MUST return a Binding Acknowledgement to the node, constructed as follows:
mobile node, constructed as follows:
- The Status field MUST be set to a value indicating success (the - The Status field MUST be set to a value indicating success (the
value MUST be less than 128). The only currently defined success value MUST be less than 128). The only currently defined success
Status value is 0, indicating simply that the Binding Update was Status value is 0, indicating simply that the Binding Update was
accepted. accepted.
- The Sequence Number field MUST be copied from the Sequence Number - The Sequence Number field MUST be copied from the Sequence Number
given in the Binding Update. given in the Binding Update.
- The Lifetime field MUST be set to the remaining lifetime for - The Lifetime field MUST be set to the remaining lifetime for
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currently considered by the home agent to be on-link (including currently considered by the home agent to be on-link (including
both the link-local and site-local prefix). both the link-local and site-local prefix).
- For each specific IP address for the mobile node determined - For each specific IP address for the mobile node determined
in the first step above, the home agent multicasts onto the in the first step above, the home agent multicasts onto the
home link (to the all-nodes multicast address) a Neighbor home link (to the all-nodes multicast address) a Neighbor
Advertisement message [17] on behalf of the mobile node, to Advertisement message [17] on behalf of the mobile node, to
advertise the home agent's own link-layer address for this IP advertise the home agent's own link-layer address for this IP
address. address.
All fields in each such Neighbor Advertisement message SHOULD All fields in each such Neighbor Advertisement message SHOULD be
be set in the same way they would be set by the mobile node set in the same way they would be set by the mobile node itself
itself if sending this Neighbor Advertisement while at home [17], if sending this Neighbor Advertisement while at home [17], with
with the following exceptions. The Target Address in the the following exceptions:
Neighbor Advertisement message MUST be set to this IP address
for the mobile node, and the Advertisement MUST include a Target * The Target Address in the Neighbor Advertisement message MUST
Link-layer Address option specifying the home agent's link-layer be set to the specific IP address for the mobile node.
address. In addition, the Router (R) bit in the Advertisement
MUST be copied from the corresponding bit in the home agent's * The Advertisement MUST include a Target Link-layer Address
Binding Cache entry for the mobile node. The Solicited Flag (S) option specifying the home agent's link-layer address.
in the Advertisement MUST NOT be set, since it was not solicited
by any Neighbor Solicitation message. The Override Flag (O) in * The Router (R) bit in the Advertisement MUST be copied from
the Advertisement MUST be set, indicating that the Advertisement the corresponding bit in the home agent's Binding Cache entry
SHOULD override any existing Neighbor Cache entry at any node for the mobile node.
receiving it.
* The Solicited Flag (S) in the Advertisement MUST NOT be set,
since it was not solicited by any Neighbor Solicitation
message.
* The Override Flag (O) in the Advertisement MUST be set,
indicating that the Advertisement SHOULD override any
existing Neighbor Cache entry at any node receiving it.
Any node on the home link receiving one of the Neighbor Advertisement Any node on the home link receiving one of the Neighbor Advertisement
messages described above will thus update its Neighbor Cache to messages described above will thus update its Neighbor Cache to
associate the mobile node's address with the home agent's link associate the mobile node's address with the home agent's link
layer address, causing it to transmit any future packets for the layer address, causing it to transmit any future packets for the
mobile node normally destined to this address instead to the mobile mobile node normally destined to this address instead to the mobile
node's home agent. Since multicasts on the local link (such as node's home agent. Since multicasts on the local link (such as
Ethernet) are typically not guaranteed to be reliable, the home Ethernet) are typically not guaranteed to be reliable, the home
agent MAY retransmit this Neighbor Advertisement message up to agent MAY retransmit this Neighbor Advertisement message up to
MAX_ADVERT_REXMIT times to increase its reliability. It is still MAX_ADVERT_REXMIT times to increase its reliability. It is still
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the Binding Update that created this Cache entry) is nonzero. the Binding Update that created this Cache entry) is nonzero.
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 message with a Neighbor agent MUST reply to the Neighbor Solicitation message with a Neighbor
Advertisement message, giving the home agent's own link-layer address Advertisement message, giving the home agent's own link-layer address
as the link-layer address for the specified Target Address. In as the link-layer address for the specified Target Address. In
addition, the Router (R) bit in the Advertisement MUST be copied from addition, the Router (R) bit in the Advertisement MUST be copied from
the corresponding bit in the home agent's Binding Cache entry for the the corresponding bit in the home agent's Binding Cache entry for the
mobile node. Acting as a proxy in this way allows other nodes on mobile node. Acting as a proxy in this way allows other nodes on
the mobile node's home link to resolve the mobile node's IPv6 home the mobile node's home link to resolve the mobile node's IPv6 home
address, and allows the home agent to to defend these addresses on address, and allows the home agent to defend these addresses on the
the home link for Duplicate Address Detection [17]. home link for Duplicate Address Detection [17].
9.6. Tunneling Intercepted Packets to a Mobile Node 9.6. Tunneling Intercepted Packets to a Mobile Node
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 (for which the home agent is the original sender of the agent (for which the home agent is the original sender of the
packet), the home agent is operating as a correspondent node of packet), the home agent is operating as a correspondent node of
the mobile node for this packet and the procedures described in the mobile node for this packet and the procedures described in
Section 8.9 apply. The home agent (as a correspondent node) uses a Section 8.9 apply. The home agent (as a correspondent node) uses a
Routing header to route the packet to the mobile node by way of the Routing header to route the packet to the mobile node by way of the
care-of address in the home agent's Binding Cache (the mobile node's care-of address in the home agent's Binding Cache (the mobile node's
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to the mobile node; such packets SHOULD be silently discarded to the mobile node; such packets SHOULD be silently discarded
(after delivering to other local multicast recipients). Multicast (after delivering to other local multicast recipients). Multicast
packets addressed to a multicast address with scope larger packets addressed to a multicast address with scope larger
than link-local but smaller than global (e.g., site-local and than link-local but smaller than global (e.g., site-local and
organization-local) [9], to which the mobile node is subscribed, organization-local) [9], to which the mobile node is subscribed,
SHOULD be tunneled to the mobile node by default, but this behavior SHOULD be tunneled to the mobile node by default, but this behavior
MUST be configurable to disable it; this default behavior might MUST be configurable to disable it; this default behavior might
change at some point in the future as the definition of these scopes change at some point in the future as the definition of these scopes
become better defined in IPv6. become better defined in IPv6.
9.7. Renumbering the Home Subnet 9.7. Handling Reverse Tunneled Packets from a Mobile Node
A home agent MUST support decapsulating reverse tunneled packets
sent to it from a mobile node. Such reverse tunneled packets MAY be
discarded unless accompanied by a valid AH. This support for reverse
tunneling allows mobile nodes to defeat certain kinds of traffic
analysis. Requiring AH on reverse tunneled packets allows the home
agent to protect the home network against unwarranted intrusions by
malicious nodes masquerading as a mobile node with a home address on
the network served by the home agent.
9.8. Renumbering the Home Subnet
IPv6 provides mechanisms through Neighbor Discovery [17] and Address IPv6 provides mechanisms through Neighbor Discovery [17] and Address
Autoconfiguration [27] to aid in renumbering a subnet, such as when a Autoconfiguration [27] to aid in renumbering a subnet, such as when a
site switches to a new network service provider. In renumbering, new site switches to a new network service provider. In renumbering, new
prefixes and addresses can be introduced for the subnet and old ones prefixes and addresses can be introduced for the subnet and old ones
can be deprecated and removed. These mechanisms are defined to work can be deprecated and removed. These mechanisms are defined to work
while all nodes using the old prefixes are at home, connected to the while all nodes using the old prefixes are at home, connected to the
link using these prefixes. Mobile IPv6 extends these mechanisms for link using these prefixes. Mobile IPv6 extends these mechanisms for
the case in which one or more mobile nodes using the old prefixes are the case in which one or more mobile nodes using the old prefixes are
away from home while the renumbering takes place. away from home while the renumbering takes place.
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tunnel certain Router Advertisements giving "important" Prefix tunnel certain Router Advertisements giving "important" Prefix
Information options to mobile nodes while away from home. To avoid Information options to mobile nodes while away from home. To avoid
the need to tunnel all Router Advertisements from the home link to the need to tunnel all Router Advertisements from the home link to
a mobile node away from home, those Router Advertisements that are a mobile node away from home, those Router Advertisements that are
tunneled to the mobile node are retransmitted until acknowledged. To tunneled to the mobile node are retransmitted until acknowledged. To
avoid possible security attacks from forged Router Advertisements avoid possible security attacks from forged Router Advertisements
tunneled to the mobile node, all such tunneled Router Advertisements tunneled to the mobile node, all such tunneled Router Advertisements
must be authenticated to the mobile node by its home agent using must be authenticated to the mobile node by its home agent using
IPsec [13, 11, 12]. IPsec [13, 11, 12].
Specifically, a home agent serving some mobile node SHOULD construct 9.8.1. Building Aggregate List of Home Network Prefixes
and tunnel to the mobile node a new Router Advertisement when any of
the following conditions occur:
- The preferred or valid lifetime for an existing prefix on the A mobile node on a remote network SHOULD autoconfigure the same
home link is reduced. set of home addresses it would autoconfigure if it were attached
to the home network. To support this, the home agent monitors
prefixes advertised by other routers on the home subnet and passes
the aggregate list of home subnet prefixes on to the mobile node in
Router Advertisements.
The home agent SHOULD construct the aggregate list of home subnet
prefixes as follows:
- Copy prefix information defined in the home agent's AdvPrefixList
on the home subnet's interfaces to the aggregate list. Also
apply any changes made to the AdvPrefixList on the home agent to
the aggregate list.
- Check valid prefixes received in Router Advertisements
from the home network for consistency with the home agent's
AdvPrefixList, as specified in section 6.2.7 of RFC 2461
(Neighbor Discovery [17]). Do not update the aggregate list with
any information from received prefixes that fail this check.
- Add valid prefixes received in Router Advertisements from the
home network that are not yet in the aggregate list to the
aggregate list along with the value of their L and A flags.
Clear the R flag and zero the interface-id portion of the prefix
field to prevent mobile nodes from treating another router's
interface address as belonging to the home agent. Treat the
lifetimes of these prefixes as "deprecating".
- Do not perform consistency checks on valid prefixes received in
Router Advertisements on the home network that do not exist in
the home agent's AdvPrefixList. Instead, if the prefixes already
exist in the aggregate list, update the prefix lifetime fields in
the aggregate list according to the rules specified for hosts in
section 6.3.4 of RFC 2461 (Neighbor Discovery [17]) and section
5.5.3 of RFC 2462 (Stateless Address Autoconfiguration [27]).
- If the L or A flag is set on valid prefixes received in a Router
Advertisement, and that prefix already exists in the aggregate
list, set the corresponding flag in the aggregate list. Ignore
the received L or A flag if it is clear.
- Ignore the R flag and interface id portion of any prefix received
in a Router Advertisement.
- Delete prefixes from the aggregate list when their valid
lifetimes expire.
The home agent uses the information in the aggregate list to
construct Router Advertisements, possibly including Binding
Acknowledgement or Binding Request destination options, for delivery
to a mobile node for which it is maintaining a current binding.
9.8.2. Sending Changed Prefix Information to the Mobile Node
A home agent serving some mobile node MUST schedule the delivery of
new prefix information to the mobile node when any of the following
conditions occur:
- A valid or preferred lifetime of a prefix in the aggregate list
of prefixes changes.
- The state of the flags for a prefix in the aggregate list
changes.
- A new prefix is introduced on the home link. - A new prefix is introduced on the home link.
- The state of the home agent's AdvManagedFlag flag [17] changes - The mobile node requests the information with a Router
from FALSE to TRUE or from TRUE to FALSE. Solicitation (see section 10.16).
The home agent determines these conditions based on its own The home agent determines these conditions based on its own
configuration as a router and based on the Router Advertisements configuration as a router and based on the Router Advertisements that
that it receives on the home link. The home agent constructs a new it receives on the home link.
Router Advertisement message containing no options other than the
Prefix Information options describing the prefixes for which one of
the conditions above has occurred since the last Router Advertisement
tunneled to and acknowledged by the mobile node. When multiple
conditions occur at or near the same time, the home agent SHOULD
attempt to combine them into a single Router Advertisement message to
the mobile node.
In tunneling each such Router Advertisement to the mobile node, the The home agent uses the following algorithm to determine when to send
home agent MUST construct the packet as follows: prefix information to the mobile node.
- If a mobile node sends a solicitation, answer with everything.
- If a prefix changes state in a way that causes a mobile node's
address to go deprecated, send an advertisement right away.
- For any existing previx, if the mobile node's binding expires
before the advertised Preferred Lifetime, do not schedule the
advertisement. The mobile node will get the revised information
in its next Binding Acknowledgement.
- If a prefix is added, or if it changes in any way that does not
cause the mobile node's address to go deprecated, ensure that a
transmission is scheduled at time RAND_ADV_DELAY in the future.
- If a prefix advertisement is scheduled, and a Binding Update
arrives, perform that advertisement and include the information
in a Router Advertisement that has the Binding Acknowledgement as
a Destination Option. Remove the future scheduled advertisement.
The home agent uses the following algorithm to compute
RAND_ADV_DELAY, the offset from the current time for the
scheduled transmission.
If there is a transmission already scheduled, then
if the current RAND_ADV_DELAY would cause another
transmission BEFORE the Preferred Lifetime of the
mobile node's home address derived from the prefix whose
advertisement information has changed, then
add the new information to be transmitted to the
existing scheduled transmission -- return.
otherwise,
continue with the following computation, and add the
data from the existing scheduled transmission to the
newly scheduled transmission, deleting the previously
scheduled transmission event.
If the mobile node's binding expires after the Preferred Lifetime,
then compute
MAX_SCHEDULE_DELAY ==
min (MAX_PFX_ADV_DELAY, Preferred Lifetime)
for the newly advertised Preferred Lifetime.
Then compute RAND_ADV_DELAY =
MinRtrAdvInt + rand()*(MAX_SCHEDULE_DELAY - MinRtrAdvInt)
9.8.3. Tunneling Router Advertisements to the Mobile Node
When tunneling a Router Advertisement to the mobile node, the home
agent MUST construct the packet as follows:
- The Source Address in the packet's IPv6 header MUST be set to the - The Source Address in the packet's IPv6 header MUST be set to the
home agent's IP address to which the mobile node addressed its home agent's IP address to which the mobile node addressed its
current home registration. current home registration.
- The packet MUST be protected by IPsec [13, 11, 12] to guard - The packet MUST be protected by IPsec [13, 11, 12] to guard
against malicious Router Advertisements. The IPsec protection against malicious Router Advertisements. The IPsec protection
MUST provide sender authentication, data integrity protection, MUST provide sender authentication, data integrity protection,
and replay protection, covering the Router Advertisement. and replay protection, covering the Router Advertisement.
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to be tunneled to the mobile node, the home agent SHOULD combine any to be tunneled to the mobile node, the home agent SHOULD combine any
Prefix Information options in the unacknowledged Router Advertisement Prefix Information options in the unacknowledged Router Advertisement
into the new Router Advertisement and then begin retransmitting the into the new Router Advertisement and then begin retransmitting the
new Router Advertisement rather than the old one. When tunneling new Router Advertisement rather than the old one. When tunneling
a new Router Advertisement, even if it contains Prefix Information a new Router Advertisement, even if it contains Prefix Information
options sent previously in an unacknowledged tunneled Router options sent previously in an unacknowledged tunneled Router
Advertisement, the home agent MUST generate a new unique identifer Advertisement, the home agent MUST generate a new unique identifer
for use in the Unique Identifier Sub-Option in the Binding Request for use in the Unique Identifier Sub-Option in the Binding Request
tunneled with the new Router Advertisement. tunneled with the new Router Advertisement.
Whenever a mobile node has a valid binding on a network other than
its home network, the home agent MUST tunnel a router advertisement
with all prefixes in the aggregate list to the mobile node at least
once per HomeRtrAdvInterval seconds, and upon receipt of a valid
Router Solicitation from the mobile node.
9.8.4. Lifetimes for Changed Prefixes
In addition, as described in Section 9.3, the lifetime returned by a In addition, as described in Section 9.3, the lifetime returned by a
mobile node's home agent in its Binding Acknowledgement in response mobile node's home agent in its Binding Acknowledgement in response
to registration of a new primary care-of address by the mobile node to registration of a new primary care-of address by the mobile node
MUST be no greater than the remaining valid lifetime for the subnet MUST be no greater than the remaining valid lifetime for the subnet
prefix in the mobile node's home address. Furthermore, as described prefix in the mobile node's home address. Furthermore, as described
in Section 10.8, Binding Updates sent by the mobile node to other in Section 10.8, Binding Updates sent by the mobile node to other
nodes MUST use a lifetime no greater than the remaining lifetime of nodes MUST use a lifetime no greater than the remaining lifetime of
its home registration of its primary care-of address. These limits its home registration of its primary care-of address. These limits
on a binding lifetimes ensure that no node uses a mobile node's home on the binding lifetime serve to prohibit use of a mobile node's home
address beyond the time that it becomes invalid. The mobile node address after it becomes invalid. The mobile node SHOULD further
SHOULD further limit the lifetimes that it sends on any Binding limit the lifetimes that it sends on any Binding Updates to be within
Updates to be within the remaining preferred lifetime for the prefix the remaining preferred lifetime for the prefix in its home address.
in its home address.
10. Mobile Node Operation 10. Mobile Node Operation
10.1. Sending Packets While Away from Home 10.1. Sending Packets While Away from Home
While a mobile node is away from home, it continues to use its home While a mobile node is away from home, it continues to use its home
address as well as also using one or more care-of addresses. When address as well as also using one or more care-of addresses. When
sending a packet while away from home, a mobile node MAY choose among sending a packet while away from home, a mobile node MAY choose among
these in selecting the address that it will use as the source of the these in selecting the address that it will use as the source of the
packet, as follows: packet, as follows:
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network interface on which the mobile node will transmit the network interface on which the mobile node will transmit the
packet. packet.
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 [7]. router implementing ingress filtering [7].
10.2. Interaction with Outbound IPsec Processing 10.2. Interaction with Outbound IPsec Processing
As a guidance to implementors, this section sketches the interaction This section sketches the interaction between outbound Mobile IP
between outbound Mobile IP processing and outbound IP Security processing and outbound IP Security (IPsec) processing for
(IPsec) processing for packets sent by a mobile node while away packets sent by a mobile node while away from home. Any specific
from home. Any specific implementation MAY use algorithms and data implementation MAY use algorithms and data structures other than
structures other than those suggested here, but its processing MUST those suggested here, but its processing MUST be consistent with the
be consistent with the effect of the operation described here and effect of the operation described here and with the relevant IPsec
with the relevant IPsec specifications. In the steps described specifications. In the steps described below, it is assumed that
below, it is assumed that IPsec is being used in transport mode [13] IPsec is being used in transport mode [13] and that the mobile node
and that the mobile node is using its home address as the source is using its home address as the source for the packet (from the
for the packet (from the point of view of higher protocol layers or point of view of higher protocol layers or applications, as described
applications, as described in Section 10.1): in Section 10.1):
- The packet is created by higher layer protocols and applications - The packet is created by higher layer protocols and applications
(e.g., by TCP) as if the mobile node were at home and Mobile IP (e.g., by TCP) as if the mobile node were at home and Mobile IP
were not being used. Mobile IP is transparent to such higher were not being used. Mobile IP is transparent to such higher
layers. layers.
- As part of outbound packet processing in IP, the packet is - As part of outbound packet processing in IP, the packet is
compared against the IPsec Security Policy Database (SPD) to compared against the IPsec Security Policy Database (SPD) to
determine what processing is required for the packet [13]. determine what processing is required for the packet [13].
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SA bundle) is created for the packet, according to the procedures SA bundle) is created for the packet, according to the procedures
defined for IPsec. defined for IPsec.
- Since the mobile node is away from home, the mobile node inserts - Since the mobile node is away from home, the mobile node inserts
a Home Address option into the packet, replacing the Source a Home Address option into the packet, replacing the Source
Address in the packet's IP header with a care-of address suitable Address in the packet's IP header with a care-of address suitable
for the link on which the packet is being sent, as described in for the link on which the packet is being sent, as described in
Section 10.1. The Destination Options header in which the Home Section 10.1. The Destination Options header in which the Home
Address option is inserted MUST appear in the packet before the Address option is inserted MUST appear in the packet before the
AH [11] (or ESP [12]) header, so that the Home Address option is AH [11] (or ESP [12]) header, so that the Home Address option is
processed by the destination node before the AH or ESP header is processed by the destination node (and, possibly, intermediate
processed. routing nodes) before the AH or ESP header is processed.
- If a Binding Update is being included in the packet, it is - If a Binding Update is being included in the packet, it is
also added to a Destination Options header in the packet. The also added to a Destination Options header in the packet. The
Destination Options header in which the Binding Update option is Destination Options header in which the Binding Update option is
inserted MAY appear either before or after the AH or ESP header. inserted MUST appear after the AH or ESP header.
If it is inserted before the AH or ESP header, it SHOULD be
placed in the same Destination Options header in which the Home
Address option was inserted.
- Finally, once the packet is fully assembled, the necessary IPsec - Finally, once the packet is fully assembled, the necessary IPsec
authentication (and encryption, if required) processing is authentication (and encryption, if required) processing is
performed on the packet, initializing the Authentication Data in performed on the packet, initializing the Authentication Data in
the AH or ESP header. the AH or ESP header. The authentication data MUST be calculated
as if the following were true:
* the IPv6 source address in the IPv6 header contains the
mobile node's home address,
* the Home Address field of the Home Address destination option
(section 5.4) contains the new care-of address.
This allows, but does not require, the receiver of the packet
containing the Binding Update to exchange the two fields of the
incoming packet, simplifying processing for all subsequent packet
headers. The mechanics of implementation do not absolutely
require such an exchange to occur; other implementation
strategies may be more appropriate, as long as the result of the
authentication calculation remain the same.
In addition, when using any automated key management protocol [13] In addition, when using any automated key management protocol [13]
(such as IKE [8]) to create any new SA (or SA bundle) while away from (such as IKE [8]) to create any new SA (or SA bundle) while away from
home (whether due to the inclusion of a Binding Update or Binding home (whether due to the inclusion of a Binding Update or Binding
Acknowledgement in an outgoing packet, or otherwise), a mobile node Acknowledgement in an outgoing packet, or otherwise), a mobile node
MUST take special care in its processing of the key management MUST take special care in its processing of the key management
protocol. Otherwise, other nodes with which the mobile node protocol. Otherwise, other nodes with which the mobile node
must communicate as part of the automated key management protocol must communicate as part of the automated key management protocol
processing may be unable to correctly deliver packets to the mobile processing may be unable to correctly deliver packets to the mobile
node if they and/or the mobile node's home agent do not then have a node if they and/or the mobile node's home agent do not then have a
current Binding Cache entry for the mobile node. For the default current Binding Cache entry for the mobile node. For the default
case of using IKE as the automated key management protocol [8, 13], case of using IKE as the automated key management protocol [8, 13],
such problems can be avoided by the following requirements on the use such problems can be avoided by the following requirements on the use
of IKE by a mobile node while away from home: of IKE by a mobile node while away from home:
- The mobile node MUST use its care-of address as the Source - The mobile node MUST use its care-of address as the Source
Address of all packets it sends as part of the key management Address of all packets it sends as part of the key management
protocol (without use of Mobile IP for these packets, as protocol (without use of Mobile IP for these packets, as
suggested in Section 10.1). suggested in Section 10.1).
- In addition, the mobile node MUST include an ISAKMP - In addition, for all security associations bound to the mobile
node's home address, the mobile node MUST include an ISAKMP
Identification Payload [14] in the IKE exchange, giving the Identification Payload [14] in the IKE exchange, giving the
mobile node's home address as the initiator of the Security mobile node's home address as the initiator of the Security
Association [22]. Association [22].
10.3. Receiving Packets While Away from Home 10.3. Receiving Packets While Away from Home
While away from home, a mobile node will receive packets addressed to While away from home, a mobile node will receive packets addressed to
its home address, by one of three methods: its home address, by one of three methods:
- Packets sent by a correspondent node that does not have a - Packets sent by a correspondent node that does not have a
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its current default router it is willing to tolerate losing before its current default router it is willing to tolerate losing before
deciding to switch to a different router from which it may currently deciding to switch to a different router from which it may currently
be correctly receiving Advertisements. be correctly receiving Advertisements.
On some types of network interfaces, the mobile node MAY also On some types of network interfaces, the mobile node MAY also
supplement this monitoring of Router Advertisements, by setting its supplement this monitoring of Router Advertisements, by setting its
network interface into "promiscuous" receive mode, so that it is able network interface into "promiscuous" receive mode, so that it is able
to receive all packets on the link, including those not link-level to receive all packets on the link, including those not link-level
addressed to it (i.e., disabling link-level address filtering). The addressed to it (i.e., disabling link-level address filtering). The
mobile node will then be able to detect any packets sent by the mobile node will then be able to detect any packets sent by the
router, in order to to detect reachability from the router. This router, in order to detect reachability from the router. This use of
use of promiscuous mode may be useful on very low bandwidth (e.g., promiscuous mode may be useful on very low bandwidth (e.g., wireless)
wireless) links, but its use MUST be configurable on the mobile node. links, but its use MUST be configurable on the mobile node.
If the above means do not provide indication that the mobile node is If the above means do not provide indication that the mobile node is
still reachable from its current default router (i.e., the mobile still reachable from its current default router (i.e., the mobile
node receives no packets from the router for a period of time), then node receives no packets from the router for a period of time), then
the mobile node SHOULD attempt to actively probe the router with the mobile node SHOULD attempt to actively probe the router with
Neighbor Solicitation messages, even if it is not otherwise actively Neighbor Solicitation messages, even if it is not otherwise actively
sending packets to the router. If it receives a solicited Neighbor sending packets to the router. If it receives a solicited Neighbor
Advertisement message in response from the router, then the mobile Advertisement message in response from the router, then the mobile
node can deduce that it is still reachable. It is expected that the node can deduce that it is still reachable. It is expected that the
mobile node will in most cases be able to determine its reachability mobile node will in most cases be able to determine its reachability
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node MAY form a new (non-primary) care-of address using that subnet node MAY form a new (non-primary) care-of address using that subnet
prefix, even when it has not switched to a new default router. A prefix, 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 mobile node can have only one primary care-of address at a time
(which is registered with its home agent), but it MAY have an (which is registered with its home agent), but it MAY have an
additional care-of address for any or all of the prefixes on its additional care-of address for any or all of the prefixes on its
current link. Furthermore, since a wireless network interface may current link. Furthermore, since a wireless network interface may
actually allow a mobile node to be reachable on more than one link at actually allow a mobile node to be reachable on more than one link at
a time (i.e., within wireless transmitter range of routers on more a time (i.e., within wireless transmitter range of routers on more
than one separate link), a mobile node MAY have care-of addresses than one 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 on more than one link at a time. The use of more than one care-of
address at a time is described in Section 10.17. address at a time is described in Section 10.18.
As described in Section 4, in order to form a new care-of address, As described in Section 4, in order to form a new care-of address,
a mobile node MAY use either stateless [27] or stateful (e.g., a mobile node MAY use either stateless [27] or stateful (e.g.,
DHCPv6 [2]) Address Autoconfiguration. If a mobile node needs to DHCPv6 [2]) Address Autoconfiguration. If a mobile node needs to
send packets as part of the method of address autoconfiguration, send packets as part of the method of address autoconfiguration,
it MUST use an IPv6 link-local address rather than its own IPv6 it MUST use an IPv6 link-local address rather than its own IPv6
home address as the Source Address in the IPv6 header of each such home address as the Source Address in the IPv6 header of each such
autoconfiguration packet. autoconfiguration packet.
In some cases, a mobile node may already know a (constant) IPv6 In some cases, a mobile node may already know a (constant) IPv6
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new care-of address using this subnet prefix, the mobile node MAY use new care-of address using this subnet prefix, the mobile node MAY use
its own pre-assigned address as its care-of address on this link. its own pre-assigned address as its care-of address on this link.
After forming a new care-of address, a mobile node MAY perform After forming a new care-of address, a mobile node MAY perform
Duplicate Address Detection [27] on that new address to confirm its Duplicate Address Detection [27] on that new address to confirm its
uniqueness. However, doing so represents a tradeoff between safety uniqueness. However, doing so represents a tradeoff between safety
(ensuring that the new address is not used if it is a duplicate (ensuring that the new address is not used if it is a duplicate
address) and overhead (performing Duplicate Address Detection address) and overhead (performing Duplicate Address Detection
requires the sending of one or more additional packets over what requires the sending of one or more additional packets over what
may be, for example, a slow wireless link through which the mobile may be, for example, a slow wireless link through which the mobile
node is connected). Performing Duplicate Address Detection also node is connected). Performing Duplicate Address Detection also in
in general would cause a delay before the mobile node could use general would cause a delay before the mobile node could use the
the new care-of address, possibly causing the mobile node to be new care-of address, possibly causing the mobile node to be unable
unable to continue communication with correspondent nodes for some to continue communication with correspondent nodes for some period
period of time. For these reasons, a mobile node a mobile node, of time. For these reasons, a mobile node, after forming a new
after forming a new care-of address, MAY begin using the new care-of care-of address, MAY begin using the new care-of address without
address without performing Duplicate Address Detection. Furthermore, performing Duplicate Address Detection. Furthermore, the mobile node
the mobile node MAY continue using the address without performing MAY continue using the address without performing Duplicate Address
Duplicate Address Detection, although it SHOULD in most cases (e.g., Detection, although it SHOULD in most cases (e.g., unless network
unless network bandwidth or battery consumption for communication is bandwidth or battery consumption for communication is of primary
of primary concern) begin Duplicate Address Detection asynchronously concern) begin Duplicate Address Detection asynchronously when it
when it begins use of the address, allowing the Duplicate Address begins use of the address, allowing the Duplicate Address Detection
Detection procedure to complete in parallel with normal communication procedure to complete in parallel with normal communication using the
using the address. address.
In addition, normal processing for Duplicate Address Detection In addition, normal processing for Duplicate Address Detection
specifies that, in certain cases, the node SHOULD delay sending the specifies that, in certain cases, the node SHOULD delay sending the
initial Neighbor Solication message of Duplicate Address Detection initial Neighbor Solication message of Duplicate Address Detection
by a random delay between 0 and MAX_RTR_SOLICITATION_DELAY [17, 27]; by a random delay between 0 and MAX_RTR_SOLICITATION_DELAY [17, 27];
however, in this case, the mobile node SHOULD NOT perform such a however, in this case, the mobile node SHOULD NOT perform such a
delay in its use of Duplicate Address Detection, unless the mobile delay in its use of Duplicate Address Detection, unless the mobile
node is intializing after rebooting. node is intializing after rebooting.
10.6. Sending Binding Updates to the Home Agent 10.6. Sending Binding Updates to the Home Agent
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If the mobile node has additional home addresses using a different If the mobile node has additional home addresses using a different
interface identifier, then the mobile node SHOULD send an additional interface identifier, then the mobile node SHOULD send an additional
packet containing a Binding Update to its home agent to register the packet containing a Binding Update to its home agent to register the
care-of address for each such other home address (or set of home care-of address for each such other home address (or set of home
addresses sharing an interface identifier). These additional Binding addresses sharing an interface identifier). These additional Binding
Updates MUST each be sent as a separate packet, since each MUST be Updates MUST each be sent as a separate packet, since each MUST be
protected by IPsec [13, 11, 12] to authenticate the Binding Update as protected by IPsec [13, 11, 12] to authenticate the Binding Update as
coming from the home address being bound, as defined in Section 4.4. coming from the home address being bound, as defined in Section 4.4.
While the mobile node is away from home, it relies on the home agent
to participate in Duplicate Address Detection (DAD) to defend its
home address against stateless autoconfiguration performed by another
node. Therefore, the mobile node SHOULD set the Duplicate Address
Detection (D) bit based on any requirements for DAD Detection that
would apply to the mobile node if it were at home [17, 27].
The home agent will only perform DAD for the mobile node's home
address when the mobile node has supplied a valid binding between
its home address and a care-of address. If some time elapses during
which the mobile node has no binding at the home agent, it might be
possible for another node to autoconfigure the mobile node's home
address. Therefore, the mobile node MUST treat creation of a new
binding with the home agent using an existing home address the same
as creation of a new home address. In the unlikely event that the
mobile node's home address is autoconfigured as the IPv6 address
of another network node on the home network, the home agent will
reply to the mobile node's subsequent Binding Update with a Binding
Acknowledgement showing Status 138, Duplicate Address Detection
failed. See section 10.10 for information about retransmitting
Binding Updates.
10.7. Dynamic Home Agent Address Discovery 10.7. Dynamic Home Agent Address Discovery
It is possible that when the mobile node needs to send a Binding It is possible that when the mobile node needs to send a Binding
Update to its home agent to register its new primary care-of address, Update to its home agent to register its new primary care-of address,
as described in Section 10.6, the mobile node may not know the as described in Section 10.6, the mobile node may not know the
address of any router on its home link that can serve as a home agent address of any router on its home link that can serve as a home agent
for it. For example, some nodes on its home link may have been for it. For example, some nodes on its home link may have been
reconfigured while the mobile node has been away from home, such that reconfigured while the mobile node has been away from home, such that
the router that was operating as the mobile node's home agent has the router that was operating as the mobile node's home agent has
been replaced by a different router serving this role. been replaced by a different router serving this role.
In this case, the mobile node MAY use the dynamic home agent address In this case, the mobile node MAY use the dynamic home agent address
discovery mechanism to find the address of a suitable home agent on discovery mechanism to find the address of a suitable home agent on
its home link. To do so, the mobile node sends an ICMP Home Agent its home link. To do so, the mobile node sends an ICMP Home Agent
Address Discovery Request message to the "Mobile IPv6 Home-Agents" Address Discovery Request message to the "Mobile IPv6 Home-Agents"
anycast address [10] for its home subnet prefix. This packet MUST anycast address [10] for its home subnet prefix. This packet MUST
NOT a Home Address option and must be sent using the mobile node's NOT contain a Home Address option and must be sent using the mobile
care-of address as the Source Address in the packet's IP header node's care-of address as the Source Address in the packet's IP
(the packet is sent from the care-of address, not using Mobile IP). header (the packet is sent from the care-of address, not using
As described in Section 9.2, the home agent on its home link that Mobile IP). As described in Section 9.2, the home agent on its home
receives this Request message will return an ICMP Home Agent Address link that receives this Request message will return an ICMP Home
Discovery Reply message, giving this home agent's own global unicast Agent Address Discovery Reply message, giving this home agent's own
IP address along with a list of the global unicast IP address of each global unicast IP address along with a list of the global unicast IP
other home agent operating on the home link. address of each other home agent operating on the home link.
The mobile node, upon receiving this Home Agent Address Discovery The mobile node, upon receiving this Home Agent Address Discovery
Reply message, MAY then send its home registration Binding Update to Reply message, MAY then send its home registration Binding Update to
the home agent address given as the IP Source Address of the packet the home agent address given as the IP Source Address of the packet
carrying the Reply message or to any of the unicast IP addresses carrying the Reply message or to any of the unicast IP addresses
listed in the Home Agent Addresses field in the Reply. For example, listed in the Home Agent Addresses field in the Reply. For example,
if necessary, the mobile node MAY attempt its home registration if necessary, the mobile node MAY attempt its home registration
with each of these home agents, in turn, by sending each a Binding with each of these home agents, in turn, by sending each a Binding
Update and waiting for the matching Binding Acknowledgement, until Update and waiting for the matching Binding Acknowledgement, until
its registration is accepted by one of these home agents. In trying its registration is accepted by one of these home agents. In trying
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Update). Update).
- The initial lifetime of the binding, initialized from the - The initial lifetime of the binding, initialized from the
Lifetime field sent in the Binding Update. Lifetime field sent in the Binding Update.
- The remaining lifetime of the binding, also initialized from - The remaining lifetime of the binding, also initialized from
the Lifetime field sent in the Binding Update. This remaining the Lifetime field sent in the Binding Update. This remaining
lifetime value counts down and may also be reduced when the lifetime value counts down and may also be reduced when the
matching Binding Acknowledgement is received, based on the matching Binding Acknowledgement is received, based on the
Lifetime value specified in that Binding Acknowledgement, as Lifetime value specified in that Binding Acknowledgement, as
described in Section 10.12. When the this remaining lifetime described in Section 10.12. When the remaining lifetime reaches
reaches zero, the Binding Update List entry MUST be deleted. zero, the Binding Update List entry MUST be deleted.
The mobile node MUST retain in its Binding Update List information The mobile node MUST retain in its Binding Update List information
about all Binding Updates sent, for which the lifetime of the binding about all Binding Updates sent, for which the lifetime of the binding
has not yet expired. However, when sending a Binding Update, if an has not yet expired. However, when sending a Binding Update, if an
entry already exists in the mobile node's Binding Update List for entry already exists in the mobile node's Binding Update List for
an earlier Binding Update sent to that same destination node, the an earlier Binding Update sent to that same destination node, the
existing Binding Update List entry is updated to reflect the new existing Binding Update List entry is updated to reflect the new
Binding Update rather than creating a new Binding Update List entry. Binding Update rather than creating a new Binding Update List entry.
In general, when a mobile node sends a Binding Update to its home In general, when a mobile node sends a Binding Update to its home
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the following tests: the following tests:
- The packet was tunneled using IPv6 encapsulation. - The packet was tunneled using IPv6 encapsulation.
- The Destination Address in the tunnel (outer) IPv6 header is - The Destination Address in the tunnel (outer) IPv6 header is
equal to any of the mobile node's care-of addresses. equal to any of the mobile node's care-of addresses.
- The Destination Address in the original (inner) IPv6 header - The Destination Address in the original (inner) IPv6 header
is equal to one of the mobile node's home addresses; or this is equal to one of the mobile node's home addresses; or this
Destination Address is equal to one of the mobile node's previous Destination Address is equal to one of the mobile node's previous
care-of addresses, if the mobile node has an entry in its Binding care-of addresses for which the mobile node has an entry in its
Update List representing an unexpired Binding Update sent to a Binding Update List, representing an unexpired Binding Update
home agent on the link on which its previous care-of address is sent to a home agent on the link on which its previous care-of
located (Section 10.9). address is located (Section 10.9).
- The Source Address in the tunnel (outer) IPv6 header differs from - The Source Address in the tunnel (outer) IPv6 header differs from
the Source Address in the original (inner) IPv6 header. the Source Address in the original (inner) IPv6 header.
The destination address to which the Binding Update should be sent The destination address to which the Binding Update should be sent
in response to receiving a packet meeting all of the above tests is in response to receiving a packet meeting all of the above tests is
the Source Address in the original (inner) IPv6 header of the packet. the Source Address in the original (inner) IPv6 header of the packet.
The home address for which this Binding Update is sent should be the The home address for which this Binding Update is sent should be the
Destination Address of the original (inner) packet. Destination Address of the original (inner) packet.
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The packet carrying the Binding Update MUST be addressed to The packet carrying the Binding Update MUST be addressed to
this home agent's global unicast address. Normally, this global this home agent's global unicast address. Normally, this global
unicast address is learned by the mobile node based on the Router unicast address is learned by the mobile node based on the Router
Advertisements received by the mobile node (Section 6.2) while Advertisements received by the mobile node (Section 6.2) while
attached to the link on which this previous care-of address and this attached to the link on which this previous care-of address and this
home agent are located; the mobile node obtains this home agent home agent are located; the mobile node obtains this home agent
address from its Home Agents List (Section 4.6). Alternatively, address from its Home Agents List (Section 4.6). Alternatively,
the mobile node MAY use dynamic home agent address discovery the mobile node MAY use dynamic home agent address discovery
(Section 10.7) to discover the global unicast address of a home agent (Section 10.7) to discover the global unicast address of a home agent
on this previous link, but it SHOULD use an address from its Home on this previous link, but it SHOULD use an address from its Home
Agents List if available for the prefix it used in this previous Agents List if available for the prefix it used to form this previous
care-of address. care-of address.
As with any packet containing a Binding Update 5.1, the Binding As with any packet containing a Binding Update (see section 5.1),
Update packet to this home agent MUST meet the IPsec requirements for the Binding Update packet to this home agent MUST meet the IPsec
Binding Updates, defined in Section 4.4. requirements for Binding Updates, defined in Section 4.4.
10.10. Retransmitting Binding Updates 10.10. Retransmitting Binding Updates
If, after sending a Binding Update in which the Acknowledge (A) When the mobile node sends a Binding Update, it has to determine
bit is set, a mobile node fails to receive a valid, matching a value for the initial retransmission timer. If the mobile node
Binding Acknowledgement within INITIAL_BINDACK_TIMEOUT seconds, the is changing or updating an existing binding at the home agent, it
mobile node SHOULD retransmit the Binding Update, until a Binding should use the specified value of INITIAL_BINDACK_TIMEOUT for this
Acknowledgement is received. Such a retransmitted Binding Update initial retransmission timer. If on the other hand the mobile node
MUST use a Sequence Number value greater than that used for the does not have an existing binding at the home agent, it SHOULD use a
previous transmission of this Binding Update. The retransmissions by value for the initial retransmission timer that is at least 1.5 times
the mobile node MUST use an exponential back-off process, in which longer than (RetransTimer * DupAddrDetectTransmits). This value is
the timeout period is doubled upon each retransmission until either likely to be substantially longer than the otherwise specified value
the node receives a Binding Acknowledgement or the timeout period of INITIAL_BINDACK_TIMEOUT that would be used by the mobile node.
reaches the value MAX_BINDACK_TIMEOUT. This longer retransmission interval will allow the the home agent
to complete the DAD procedure which is mandated in this case, as
detailed in section 10.6.
If, after sending a Binding Update in which the care-of address has
changed and the Acknowledge (A) bit is set, a mobile node fails
to receive a valid, matching Binding Acknowledgement within the
selected initial retransmission interval, the mobile node SHOULD
retransmit the Binding Update, until a Binding Acknowledgement is
received. Such a retransmitted Binding Update MUST use a Sequence
Number value greater than that used for the previous transmission of
this Binding Update. The retransmissions by the mobile node MUST
use an exponential back-off process, in which the timeout period
is doubled upon each retransmission until either the node receives
a Binding Acknowledgement or the timeout period reaches the value
MAX_BINDACK_TIMEOUT.
10.11. Rate Limiting for Sending Binding Updates 10.11. Rate Limiting for Sending Binding Updates
A mobile node MUST NOT send Binding Updates about the same binding to A mobile node MUST NOT send Binding Updates about the same binding to
any individual node more often than once per MAX_UPDATE_RATE seconds. any individual node more often than once per MAX_UPDATE_RATE seconds.
After sending MAX_FAST_UPDATES consecutive Binding Updates to a After sending MAX_FAST_UPDATES consecutive Binding Updates to a
particular node with the same care-of address, the mobile node SHOULD particular node with the same care-of address, the mobile node SHOULD
reduce its rate of sending Binding Updates to that node, to the rate reduce its rate of sending Binding Updates to that node, to the rate
of SLOW_UPDATE_RATE per second. The mobile node MAY continue to send of SLOW_UPDATE_RATE per second. The mobile node MAY continue to send
Binding Updates at this slower rate indefinitely, in hopes that the Binding Updates at this slower rate indefinitely, in hopes that the
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address. address.
10.12. Receiving Binding Acknowledgements 10.12. Receiving Binding Acknowledgements
Upon receiving a packet carrying a Binding Acknowledgement, a mobile Upon receiving a packet carrying a Binding Acknowledgement, a mobile
node MUST validate the packet according to the following tests: node MUST validate the packet according to the following tests:
- The packet meets the specific IPsec requirements for Binding - The packet meets the specific IPsec requirements for Binding
Acknowledgements, defined in Section 4.4. Acknowledgements, defined in Section 4.4.
- The Option Length field in the option is greater than or equal to - The Option Length field in the Binding Acknowledgement option is
11 octets. greater than or equal to the length specified in Section 5.2.
- The Sequence Number field matches the Sequence Number sent by the - 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.
Any Binding Acknowledgement not satisfying all of these tests MUST be Any Binding Acknowledgement not satisfying all of these tests MUST be
silently ignored, although the remainder of the packet (i.e., other silently ignored, although the remainder of the packet (i.e., other
options, extension headers, or payload) SHOULD be processed normally options, extension headers, or payload) SHOULD be processed normally
according to any procedure defined for that part of the packet. according to any procedure defined for that part of the packet.
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In addition, if the value specified in the Lifetime field in the In addition, if the value specified in the Lifetime field in the
Binding Acknowledgement is less than the Lifetime value sent Binding Acknowledgement is less than the Lifetime value sent
in the Binding Update being acknowledged, then the mobile node in the Binding Update being acknowledged, then the mobile node
MUST subtract the difference between these two Lifetime values MUST subtract the difference between these two Lifetime values
from the remaining lifetime for the binding as maintained in the from the remaining lifetime for the binding as maintained in the
corresponding Binding Update List entry (with a minimum value corresponding Binding Update List entry (with a minimum value
for the Binding Update List entry lifetime of 0). That is, if for the Binding Update List entry lifetime of 0). That is, if
the Lifetime value sent in the Binding Update was L_update, the the Lifetime value sent in the Binding Update was L_update, the
Lifetime value received in the Binding Acknowledgement was L_ack, Lifetime value received in the Binding Acknowledgement was L_ack,
and the current remaining lifetime of the Binding Update List and the current remaining lifetime of the Binding Update List
entry is L_remain, then the new value for the remaing lifetime of entry is L_remain, then the new value for the remaining lifetime
the Binding Update List entry should be of the Binding Update List entry should be
max((L_remain - (L_update - L_ack)), 0) max((L_remain - (L_update - L_ack)), 0)
where max(X, Y) is the maximum of X and Y. The effect of this where max(X, Y) is the maximum of X and Y. The effect of this
step is to correctly manage the mobile node's view of the step is to correctly manage the mobile node's view of the
binding's remaining lifetime (as maintained in the corresponding binding's remaining lifetime (as maintained in the corresponding
Binding Update List entry) so that it correctly counts down from Binding 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 the timer countdown beginning at the time that the Binding Update
was sent. was sent.
- If the Status field indicates that the Binding Update was - If the Status field indicates that the Binding Update was
rejected (the Status field is greater than or equal to 128), then rejected (the Status field is greater than or equal to 128), then
the mobile node MUST delete the corresponding Binding Update List the mobile node MUST delete the corresponding Binding Update List
entry (and MUST also stop retransmitting the Binding Update). entry, and it MUST also stop retransmitting the Binding Update.
Optionally, the mobile node MAY then take steps to correct the Optionally, the mobile node MAY then take steps to correct the
cause of the error and retransmit the Binding Update (with a new cause of the error and retransmit the Binding Update (with a new
Sequence Number value), subject to the rate limiting restriction Sequence Number value), subject to the rate limiting restriction
specified in Section 10.11. specified in Section 10.11.
10.13. Receiving Binding Requests 10.13. Receiving Binding Requests
When a mobile node receives a packet containing a Binding Request, When a mobile node receives a packet containing a Binding Request,
it SHOULD return to the sender a packet containing a Binding Update. it SHOULD return to the sender a packet containing a Binding Update.
The Lifetime field in this Binding Update SHOULD be set to a new The Lifetime field in this Binding Update SHOULD be set to a new
lifetime, extending any current lifetime remaining from a previous lifetime, extending any current lifetime remaining from a previous
Binding Update sent to this node (as indicated in any existing Binding Update sent to this node (as indicated in any existing
Binding Update List entry for this node), except that this lifetime Binding Update List entry for this node), except that this lifetime
MUST NOT exceed the remaining lifetime for the mobile node's primary MUST NOT exceed the remaining lifetime for the mobile node's primary
care-of address registration at its home agent. When sending this care-of address registration at its home agent. When sending this
Binding Update, the mobile node MUST update its Binding Update List Binding Update, the mobile node MUST update its Binding Update List
in the same way as for any other Binding Update sent by the mobile in the same way as for any other Binding Update sent by the mobile
node. node.
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Binding Update sent to this node (as indicated in any existing Binding Update sent to this node (as indicated in any existing
Binding Update List entry for this node), except that this lifetime Binding Update List entry for this node), except that this lifetime
MUST NOT exceed the remaining lifetime for the mobile node's primary MUST NOT exceed the remaining lifetime for the mobile node's primary
care-of address registration at its home agent. When sending this care-of address registration at its home agent. When sending this
Binding Update, the mobile node MUST update its Binding Update List Binding Update, the mobile node MUST update its Binding Update List
in the same way as for any other Binding Update sent by the mobile in the same way as for any other Binding Update sent by the mobile
node. node.
Note, however, that the mobile node MAY choose to keep its current Note, however, that the mobile node MAY choose to keep its current
binding private from the sender of the Binding Request. In this binding private from the sender of the Binding Request. In this
case, the mobile node instead SHOULD returns a Binding Update to the case, the mobile node instead SHOULD return a Binding Update to the
sender, in which the Lifetime field is set to zero and the care-of sender, in which the Lifetime field is set to zero and the care-of
address is set to the mobile node's home address. address is set to the mobile node's home address.
If the Binding Request for which the Binding Update is being returned If the Binding Request for which the Binding Update is being returned
contains a Unique Identifer Sub-Option, the Binding Update MUST also contains a Unique Identifer Sub-Option, the Binding Update MUST also
include a Unique Identifier Sub-Option. The unique identifier in the include a Unique Identifier Sub-Option. The unique identifier in the
SUb-Option Data field of the Unique Identifier Sub-Option MUST be Sub-Option Data field of the Unique Identifier Sub-Option MUST be
copied from the unique identifier carried in the Binding Request. copied from the unique identifier carried in the Binding Request.
10.14. Receiving ICMP Error Messages 10.14. Receiving ICMP Error Messages
The Option Type value for a Binding Update option specifies that The Option Type value for a Binding Update option specifies that
any node receiving this option that does not recognize the Option any node receiving this option that does not recognize the Option
Type SHOULD return an ICMP Parameter Problem, Code 2, message to Type SHOULD return an ICMP Parameter Problem, Code 2, message to
the sender of the packet containing the Binding Update option. If the sender of the packet containing the Binding Update option. If
a node sending a Binding Update receives such an ICMP error message a node sending a Binding Update receives such an ICMP error message
in response, it SHOULD record in its Binding Update List that future in response, it SHOULD record in its Binding Update List that future
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home agent. home agent.
- Otherwise, extract the Source Address from the IP header of the - 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 [17]. link of the home agent sending this Advertisement [17].
- Determine from the Router Advertisement the preference for this - Determine from the Router Advertisement the preference for this
home agent. If the Router Advertisement contains a Home Agent home agent. If the Router Advertisement contains a Home Agent
Information Option, then the preference is taken from the Home Information Option, then the preference is taken from the Home
Agent Preference field in the option; otherwise, the default Agent Preference field in the option; otherwise, the default
preference of 0 SHOULD be used. preference of 0 MUST be used.
- Determine from the Router Advertisement the lifetime for - Determine from the Router Advertisement the lifetime for
this home agent. If the Router Advertisement contains a Home this home agent. If the Router Advertisement contains a Home
Agent Information Option, then the lifetime is taken from Agent Information Option, then the lifetime is taken from
the Home Agent Lifetime field in the option; otherwise, the the Home Agent Lifetime field in the option; otherwise, the
lifetime specified by the Router Lifetime field in the Router lifetime specified by the Router Lifetime field in the Router
Advertisement SHOULD be used. Advertisement SHOULD be used.
- If the link-local address of the home agent sending this - If the link-local address of the home agent sending this
Advertisement is already present in this mobile node's Home Advertisement is already present in this mobile node's Home
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agent based on each Prefix Information option received in agent based on each Prefix Information option received in
this Advertisement in which the Router Address (R) bit is set this Advertisement in which the Router Address (R) bit is set
(Section 6.2). For each such global address determined from this (Section 6.2). For each such global address determined from this
Advertisement, add this global address to the list of global Advertisement, add this global address to the list of global
addresses for this home agent in this Home Agents List entry. addresses for this home agent in this Home Agents List entry.
A mobile node SHOULD maintain an entry in its Home Agents List for A mobile node SHOULD maintain an entry in its Home Agents List for
each such valid home agent address until that entry's lifetime each such valid home agent address until that entry's lifetime
expires, after which time the entry MUST be deleted. expires, after which time the entry MUST be deleted.
10.16. Receiving Tunneled Router Advertisements 10.16. Sending Tunneled Router Solicitations
Section 9.7 describes the operation of a home agent to support When a mobile node has a home address that is about to become
invalid, it tunnels a Router Solicitation to its home agent in
an attempt to acquire fresh routing prefix information. The new
information enables the mobile node to participate in renumbering
operations affecting the home network, as described in section 9.8.
The mobile node SHOULD tunnel a Router Solicitation to the home agent
when its home address will become invalid within MaxRtrAdvInterval
seconds, where this value is acquired in a previous Router
Advertisement from the home agent. If no such value is known, the
value MAX_PFX_ADV_DELAY seconds is used instead.
The mobile node tunnels (using IPv6 encapsulation [4]) the
solicitation, including the following IPv6 header fields:
Outer src = care-of address
Outer dst = Home Agent's global address
Inner src = home address
Inner dst = Home Agent's global address
If the mobile node does not have a valid home address available for
use as the Inner src address, it MAY use the unspecified IPv6 address
(0:0:0:0:0:0:0:0).
This solicitation follows the same retransmission rules as already
specified for Router Solicitations [17], except that the initial
retransmission interval is specified to be INITIAL_SOLICIT_TIMER.
10.17. Receiving Tunneled Router Advertisements
Section 9.8 describes the operation of a home agent to support
renumbering a mobile node's home subnet while the mobile node is renumbering a mobile node's home subnet while the mobile node is
away from home. The home agent tunnels certain Router Advertisement away from home. The home agent tunnels certain Router Advertisement
messages to the mobile node while away from home, giving "important" messages to the mobile node while away from home, giving "important"
Prefix Information options that describe changes in the prefixes in Prefix Information options that describe changes in the prefixes in
use on the mobile node's home link. use on the mobile node's home link.
When a mobile node receives a tunneled Router Advertisement, it MUST When a mobile node receives a tunneled Router Advertisement, it MUST
validate it according to the following tests: validate it according to the following tests:
- The Source Address of the IP packet carrying the Router - The Source Address of the IP packet carrying the Router
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In addition, if processing of this Router Advertisement resulted in In addition, if processing of this Router Advertisement resulted in
the mobile node configuring a new home address, and if the method the mobile node configuring a new home address, and if the method
used for this new home address configuration would require the mobile used for this new home address configuration would require the mobile
node to perform Duplicate Address Detection [27] for the new address node to perform Duplicate Address Detection [27] for the new address
if the mobile node were located at home, then the mobile node MUST if the mobile node were located at home, then the mobile node MUST
set the Duplicate Address Detection (D) bit in this Binding Update to set the Duplicate Address Detection (D) bit in this Binding Update to
its home agent, to request the home agent to perform this Duplicate its home agent, to request the home agent to perform this Duplicate
Address Detection on behalf of the mobile node. Address Detection on behalf of the mobile node.
10.17. Using Multiple Care-of Addresses 10.18. Using Multiple Care-of Addresses
As described in Section 10.5, a mobile node MAY use more than one As described in Section 10.5, 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. A cells), on which different on-link subnet prefixes may exist. A
mobile node SHOULD select a primary care-of address from among those mobile node SHOULD select a primary care-of address from among those
care-of addresses it has formed using any of these subnet prefixes, care-of addresses it has formed using any of these subnet prefixes,
based on the movement detection mechanism in use, as described in based on the movement detection mechanism in use, as described in
Section 10.4. When the mobile node selects a new primary care-of Section 10.4. When the mobile node selects a new primary care-of
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its previous primary care-of address as a (non-primary) care-of its previous primary care-of address as a (non-primary) care-of
address, and SHOULD still accept packets at this address, even after address, 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 [2], the mobile allocated using stateful Address Autoconfiguration [2], 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.
10.18. Routing Multicast Packets 10.19. Routing Multicast Packets
A mobile node that is connected to its home link functions in the A mobile node that is connected to its home link functions in the
same way as any other (stationary) node. Thus, when it is at home, same way as any other (stationary) node. Thus, when it is at home,
a mobile node functions identically to other multicast senders and a mobile node functions identically to other multicast senders and
receivers. This section therefore describes the behavior of a mobile receivers. This section therefore describes the behavior of a mobile
node that is not on its home link. node that is not on its home link.
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 by which a mobile node must join that multicast group. One method by 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. The mobile node SHOULD use its care-of foreign link being visited. The mobile node SHOULD use one of its
address sharing a subnet prefix with the multicast router, as care-of addresses that shares a subnet prefix with the multicast
the source IPv6 address of its multicast group membership control router, as the source IPv6 address of its multicast group membership
messages. control messages. The mobile node MUST insert a Home Address
destination option in such outgoing multicast packets, so that any
multicast applications that depend on the address of the sending node
will correctly use the mobile node's home address for that value.
Alternatively, a mobile node MAY join multicast groups via a Alternatively, a mobile node MAY join multicast groups via a
bi-directional tunnel to its home agent. The mobile node tunnels its bi-directional tunnel to its home agent. The mobile node tunnels its
multicast group membership control packets to its home agent, and the multicast group membership control packets to its home agent, and the
home agent forwards multicast packets down the tunnel to the mobile home agent forwards multicast packets down the tunnel to the mobile
node. node.
A mobile node that wishes to send packets to a multicast group A mobile node that wishes to send packets to a multicast group
also has two options: (1) send directly on the foreign link being also has two options: (1) send directly on the foreign link being
visited; or (2) send via a tunnel to its home agent. Because visited; or (2) send via a tunnel to its home agent. Because
multicast routing in general depends upon the Source Address used in multicast routing in general depends upon the Source Address used in
the IPv6 header of the multicast packet, a mobile node that tunnels a the IPv6 header of the multicast packet, a mobile node that tunnels a
multicast packet to its home agent MUST use its home address as the multicast packet to its home agent MUST use its home address as the
IPv6 Source Address of the inner multicast packet. IPv6 Source Address of the inner multicast packet.
10.19. Returning Home 10.20. 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 10.4), when the the movement detection algorithm in use (Section 10.4), when the
mobile node detects that its home subnet prefix is again on-link. mobile node detects that its home subnet prefix is again on-link.
The mobile node SHOULD then send a Binding Update to its home agent, The mobile node SHOULD then send a Binding Update to its home agent,
to instruct its home agent to no longer intercept or tunnel packets to instruct its home agent to no longer intercept or tunnel packets
for it. In this Binding Update, the mobile node MUST set the care-of for it. In this Binding Update, the mobile node MUST set the care-of
address for the binding (the Source Address field in the packet's address for the binding (the Source Address field in the packet's
IPv6 header) to the mobile node's own home address. As with other IPv6 header) to the mobile node's own home address. As with other
Binding Updates sent to register with its home agent, the mobile Binding Updates sent to register with its home agent, the mobile
node MUST set the Acknowledge (A) and Home Registration (H) bits, node MUST set the Acknowledge (A) and Home Registration (H) bits,
and SHOULD retransmit the Binding Update until a matching Binding and SHOULD retransmit the Binding Update until a matching Binding
Acknowledgement is received. Acknowledgement is received.
When sending this Binding Update to its home agent, the mobile When sending this Binding Update to its home agent, the mobile
node must be careful in how it uses Neighbor Soliciation [17] (if node must be careful in how it uses Neighbor Solicitation [17] (if
needed) to learn the home agent's link-layer address, since the home needed) to learn the home agent's link-layer address, since the home
agent will be currently configured to defend the mobile node's home agent will be currently configured to defend the mobile node's home
address for Duplicate Address Detection. In particular, a Neighbor address for Duplicate Address Detection. In particular, a Neighbor
Solicitation from the mobile node using its home address as the Solicitation from the mobile node using its home address as the
Source Address would be detected by the home agent as a duplicate Source Address would be detected by the home agent as a duplicate
address. In many cases, Neighbor Solicitation by the mobile node address. In many cases, Neighbor Solicitation by the mobile node
for the home agent's address will not be necessary, since the mobile for the home agent's address will not be necessary, since the mobile
node may have already learned the home agent's link-layer address, node may have already learned the home agent's link-layer address,
for example from a Source Link-Layer Address option in the Router for example from a Source Link-Layer Address option in the Router
Advertisement from which it learned that its home address was on-link Advertisement from which it learned that its home address was on-link
and that the mobile node had thus returned home. If the mobile node and that the mobile node had thus returned home. If the mobile node
does Neighbor Solicitation to learn the home agent's link-layer does Neighbor Solicitation to learn the home agent's link-layer
address, in this special case of the mobile node returning home, the address, in this special case of the mobile node returning home, the
mobile node MUST set the Source Address of this Neighbor Solicitation mobile node MUST unicast the packet, and in addition set the Source
to the unspecified address. Address of this Neighbor Solicitation to the unspecified address
(0:0:0:0:0:0:0:0). Since the solicitation is unicast, the home agent
will be able to distinguish from a similar packet that would only be
used for DAD.
The mobile node then sends its Binding Update using the home agent's The mobile node then sends its Binding Update using the home agent's
link-layer address, instructing its home agent to no longer serve link-layer address, instructing its home agent to no longer serve
as a home agent for it. By processing this Binding Update, the as a home agent for it. By processing this Binding Update, the
home agent will cease defending the mobile node's home address for home agent will cease defending the mobile node's home address for
Duplicate Address Detection and will no longer respond to Neighbor Duplicate Address Detection and will no longer respond to Neighbor
Solicitations for the mobile node's home address. The mobile node is Solicitations for the mobile node's home address. The mobile node is
then the only node on the link using the mobile node's home address. then the only node on the link using the mobile node's home address.
In addition, when returning home and configuring its home address In addition, when returning home prior to the expiration of a current
on its network interface on its home link, the mobile node MUST NOT binding for its home address, and configuring its home address on its
perform Duplicate Address Detection on its own home address, in order network interface on its home link, the mobile node MUST NOT perform
to avoid confusion or conflict with its home agent's use of the same Duplicate Address Detection on its own home address, in order to
address. avoid confusion or conflict with its home agent's use of the same
address. If the mobile node returns home after the bindings for all
of its care-of addresses have expired, then it SHOULD perform DAD.
After receiving the Binding Acknowledgement for its Binding Update After receiving the Binding Acknowledgement for its Binding Update
to its home agent, the mobile node MUST multicast onto the home to its home agent, the mobile node MUST multicast onto the home
link (to the all-nodes multicast address) a Neighbor Advertisement link (to the all-nodes multicast address) a Neighbor Advertisement
message [17], to advertise the mobile node's own link-layer address message [17], to advertise the mobile node's own link-layer address
for its own home address. The Target Address in this Neighbor for its own home address. The Target Address in this Neighbor
Advertisement message MUST be set to the mobile node's home address, Advertisement message MUST be set to the mobile node's home address,
and the Advertisement MUST include a Target Link-layer Address option and the Advertisement MUST include a Target Link-layer Address option
specifying the mobile node's link-layer address. The mobile node specifying the mobile node's link-layer address. The mobile node
MUST multicast such a Neighbor Advertisement message for each of its MUST multicast such a Neighbor Advertisement message for each of its
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Neighbor Advertisement messages up to MAX_ADVERT_REXMIT times to Neighbor Advertisement messages up to MAX_ADVERT_REXMIT times to
increase their reliability. It is still possible that some nodes on increase their reliability. It is still possible that some nodes on
the home link will not receive any of these Neighbor Advertisements, the home link will not receive any of these Neighbor Advertisements,
but these nodes will eventually be able to recover through use of but these nodes will eventually be able to recover through use of
Neighbor Unreachability Detection [17]. Neighbor Unreachability Detection [17].
11. Protocol Constants 11. Protocol Constants
INITIAL_BINDACK_TIMEOUT 1 second INITIAL_BINDACK_TIMEOUT 1 second
INITIAL_SOLICIT_TIMER 2 seconds
MAX_BINDACK_TIMEOUT 256 seconds MAX_BINDACK_TIMEOUT 256 seconds
MAX_UPDATE_RATE once per second MAX_UPDATE_RATE once per second
SLOW_UPDATE_RATE once per 10 seconds SLOW_UPDATE_RATE once per 10 seconds
MAX_FAST_UPDATES 5 transmissions MAX_FAST_UPDATES 5 transmissions
MAX_ADVERT_REXMIT 3 transmissions MAX_ADVERT_REXMIT 3 transmissions
MAX_PFX_ADV_DELAY 1,000 seconds
HomeRtrAdvInterval 1,000 seconds
12. IANA Considerations 12. IANA Considerations
This document defines four new types of IPv6 destination options, This document defines four new types of IPv6 destination options,
each of which must be assigned an Option Type value: each of which must be assigned an Option Type value:
- The Binding Update option, described in Section 5.1; - The Binding Update option, described in Section 5.1;
- The Binding Acknowledgement option, described in Section 5.2; - The Binding Acknowledgement option, described in Section 5.2;
- The Binding Request option, described in Section 5.3; and - The Binding Request option, described in Section 5.3; and
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The existing IPsec replay protection mechanisms allow a "replay The existing IPsec replay protection mechanisms allow a "replay
protection window" to support receiving packets out of order. protection window" to support receiving packets out of order.
Although appropriate for many forms of communication, Binding Updates Although appropriate for many forms of communication, Binding Updates
MUST be applied only in the order sent. The Binding Update option MUST be applied only in the order sent. The Binding Update option
thus includes a Sequence Number field to provide this necessary thus includes a Sequence Number field to provide this necessary
sequencing. The use of this Sequence Number together with IPsec sequencing. The use of this Sequence Number together with IPsec
replay protection is similar in many ways, for example, to the the replay protection is similar in many ways, for example, to the the
sequence number in TCP. IPsec provides strong replay protection but sequence number in TCP. IPsec provides strong replay protection but
no ordering, and the sequence number provides ordering but need not no ordering, and the sequence number provides ordering but need not
worry about replay protection such as through the sequence number protect against replays such as may occur when the sequence number
wrapping around. wraps around.
13.2. Home Address Option 13.2. Security for the Home Address Option
No special authentication of the Home Address option is required, No special authentication of the Home Address option is required,
except that if the IPv6 header of a packet is covered by except that if the IPv6 header of a packet is covered by
authentication, then that authentication MUST also cover the Home authentication, then that authentication MUST also cover the Home
Address option; this coverage is achieved automatically by the Address option; this coverage is achieved automatically by the
definition of the Option Type code for the Home Address option definition of the Option Type code for the Home Address option
(Section 5.4), since it indicates that the option is included in the (Section 5.4), since it indicates that the option is included in the
authentication computation. Thus, even when authentication is used authentication computation. Thus, even when authentication is used
in the IPv6 header, the security of the Source Address field in the in the IPv6 header, the security of the Source Address field in the
IPv6 header is not compromised by the presence of a Home Address IPv6 header is not compromised by the presence of a Home Address
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of the packet, including the Home Address option, can be forged or of the packet, including the Home Address option, can be forged or
modified in transit. In this case, the contents of the Home Address modified in transit. In this case, the contents of the Home Address
option is no more suspect than any other part of the packet. option is no more suspect than any other part of the packet.
The use of the Home Address option allows packets sent by a The use of the Home Address option allows packets sent by a
mobile node to pass normally through routers implementing ingress mobile node to pass normally through routers implementing ingress
filtering [7]. Since the care-of address used in the Source Address filtering [7]. Since the care-of address used in the Source Address
field of the packet's IPv6 header is topologically correct for the field of the packet's IPv6 header is topologically correct for the
sending location of the mobile node, ingress filtering can trace the sending location of the mobile node, ingress filtering can trace the
location of the mobile node in the same way as can be done with any location of the mobile node in the same way as can be done with any
sender when ingress filtering is in use. sender when ingress filtering is in use. A node receiving a packet
that includes a Home Address option MAY implement the processing of
However, if a node receiving a packet that includes a Home Address this option by physically exchanging the Home Address option field
option implements the processing of this option by physically with the source IPv6 address in the IPv6 header.
copying the Home Address field from the option into the IPv6 header,
replacing the Source Address field there, then the ability to
trace the true location of the sender is removed once this step
in the processing is performed. This diminishing of the power of
ingress filtering only occurs once the packet has been received at
its ultimate destination, and does not affect the capability of
ingress filtering while the packet is in transit. Furthermore, this
diminishing can be entirely eliminated by appropriate implementation
techniques in the receiving node. For example, the original contents
of the Source Address field (the sending care-of address) could be
saved elsewhere in memory with the packet, until all processing of
the packet is completed.
13.3. General Mobile Computing Issues 13.3. General Mobile Computing Issues
The mobile computing environment is potentially very different from The mobile computing environment is potentially very different from
the ordinary computing environment. In many cases, mobile computers the ordinary computing environment. In many cases, mobile computers
will be connected to the network via wireless links. Such links will be connected to the network via wireless links. Such links
are particularly vulnerable to passive eavesdropping, active replay are particularly vulnerable to passive eavesdropping, active replay
attacks, and other active attacks. Furthermore, mobile computers attacks, and other active attacks. Furthermore, mobile computers
are more susceptible to loss or theft than stationary computers. are more susceptible to loss or theft than stationary computers.
Any secrets such as authentication or encryption keys stored on the Any secrets such as authentication or encryption keys stored on the
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access to SHOULD use additional mechanisms (such as encryption) to access to SHOULD use additional mechanisms (such as encryption) to
provide privacy protection, but such mechanisms are beyond the scope provide privacy protection, but such mechanisms are beyond the scope
of this document. Users concerned about traffic analysis SHOULD of this document. Users concerned about traffic analysis SHOULD
consider appropriate use of link encryption. If stronger location consider appropriate use of link encryption. If stronger location
privacy is desired, the mobile node can create a tunnel to its home privacy is desired, the mobile node can create a tunnel to its home
agent. Then, packets destined for correspondent nodes will appear agent. Then, packets destined for correspondent nodes will appear
to emanate from the home subnet, and it may be more difficult to to emanate from the home subnet, and it may be more difficult to
pinpoint the location of the mobile node. Such mechanisms are all pinpoint the location of the mobile node. Such mechanisms are all
beyond the scope of this document. beyond the scope of this document.
Whether or not the mobile node is away from home is likely to
influence the choice of security policy from the SPD. For instance,
if a mobile node is connected to its home network and it communicates
with a correspondent node on its home network, no security may be
needed. If, on the other hand, the mobile node is attached to
foreign network and has sent a Binding Update to its home agent, then
the mobile node may need to make use of security features in order to
communicate with that same correspondent node.
Changes from Previous Version of the Draft Changes from Previous Version of the Draft
This appendix briefly lists some of the major changes in this This appendix briefly lists some of the major changes in this
draft relative to the previous version of this same draft, draft relative to the previous version of this same draft,
draft-ietf-mobileip-ipv6-11.txt: draft-ietf-mobileip-ipv6-12.txt:
- Moved the definition of IPsec requirements for Binding Updates
and Binding Acknowledgements to Section 4.4), giving this
important information its own specific section with a section
title (IPsec Requirements for Mobile IPv6 Destination Options)
that will be identifiable in the table of contents for this
document. This makes these requirements harder to miss than
where they were defined in Sections 5.1 and 5.2, mixed in with
the definition of the format of these destination options.
- In Section 4.6, added a precise definition of Sequence Number
value comparison modulo 2**16. Also added a reference to this
definition in each other place where Sequence Number comparison
is discussed.
- Added a statement in Section 9.5 to clarify the sending of a - Specified that the Home Address destination option MUST be
Neighbor Advertisement message by the home agent on behalf of the inserted between Routing Header and Fragment Header
mobile node in order to intercept packets addressed to the mobile
node. Except for the specific fields defined there, all fields
in each such Neighbor Advertisement SHOULD be set in the same
way they would be set by the mobile node itself if sending this
Neighbor Advertisement while at home [17].
- In Section 10.6, specified that the Lifetime in the Binding - Specified that the Binding Update MUST be located after the IPsec
Update sent by a mobile node to its home agent SHOULD be less header(s).
than or equal to the remaining lifetime of the home address and
the care-of address specified for the binding.
- In Section 10.8, modified the specification that was there - Specified that the AH is to be calculated as if the home address
about the correct setting of the Lifetime in the Binding were in the IPv6 header, and the care-of address were in the Home
Update sent by a mobile node to a correspondent node. The Address destination option.
original specification stated that the Lifetime value MUST be no
greater than the remaining lifetime of the mobile node's home
registration of its primary care-of address at its home agent.
However, there should be no necessary relationship between the
remaining lifetime of a home registration and the lifetime of
a binding at a correspondent node. Instead, as with the home
registration Binding Update, the Lifetime in the Binding Update
sent by a mobile node to a correspondent node SHOULD be less than
or equal to the remaining lifetime of the home address and the
care-of address specified for the binding.
- In Section 5.4, added a statement that a packet MUST NOT contain - Changed SHOULD to MUST for treating unspecified home agent
more than one Home Address option, except that an encapsulated preferences as 0.
packet [4] MAY contain a separate Home Address option associated
with each encapsulating IP header.
- In Section 4.6, added a new field in the Binding Update List - Introduced the notion of scheduling Router Advertisements to
entry format to record the initial value of the Lifetime field be sent to the mobile node whenever a prefix advertisement or
sent in that Binding Update. internal reconfiguration causes a mobile node's home address to
be in danger of becoming deprecated.
- In Section 10.12, defined a new step in processing a received - Specified that the mobile node MUST set the `D' bit whenever it
Binding Acknowledgement: if the value specified in the Lifetime sends a Binding Update that is new, instead of simply updating an
field in the Binding Acknowledgement is less than the Lifetime existing binding to a new care-of address or binding lifetime.
value sent in the Binding Update being acknowledged, then the
mobile node MUST subtract the difference between these two
Lifetime values from the remaining lifetime for the binding
as maintained in the corresponding Binding Update List entry.
The effect of this step is to correctly manage the mobile
node's view of the binding's remaining lifetime (as maintained
in the corresponding Binding Update List entry) so that it
correctly counts down from the Lifetime value given in the
Binding Acknowledgement, but with the timer countdown beginning
at the time that the Binding Update was sent. This change also
affected Section 10.8 in sending Binding Updates, to record both
the original lifetime and the remaining lifetime in the Binding
Update List.
- In Sections 5.1 and 9.3, clarified that the Duplicate Address - Added new section on mobile node tunneling Router Solicitations
Detection performed by the home agent if the Duplicate Address
Detection (D) bit is set in the Binding Update, is performed
before returning the Binding Acknowledgement for that Binding
Update.
- In Section 5.1, clarified that the mobile node SHOULD set the - Added appendix about remote autoconfiguration for home addresses.
Duplicate Address Detection (D) bit in its home registration
Binding Updates based on any requirements for Duplicate Address
Detection that would apply to the mobile node if it were at
home [17, 27].
- In Section 9.3, specified that a home agent, when performing - Added specification about picking a longer initial retransmission
Duplicate Address Detection for a mobile node when the interval for initial Binding Updates sent to the home agent,
Duplicate Address Detection (D) bit is set in a received because the home agent will take longer since it has to perform
Binding Update, SHOULD NOT delay sending the initial Neighbor DAD.
Solicitation message of Duplicate Address Detection by the random
delay specified for normal processing of Duplicate Address
Detection [17, 27].
- In Section 10.5, defined special considerations for a mobile - Added the following protocol constants:
node's use of Duplicate Address Detection upon forming a new
care-of address. In particular, the mobile node MAY begin
using the new care-of address without performing Duplicate
Address Detection, and MAY optionally bypass Duplicate Address
Detection or begin Duplicate Address Detection asynchronously
when it begins use of the address, allowing the Duplicate
Address Detection procedure to complete in parallel with
normal communication using the address. In addition, the
mobile node SHOULD NOT delay sending the initial Neighbor
Solicitation message of Duplicate Address Detection by the random
delay specified for normal processing of Duplicate Address
Detection [17, 27], unless the mobile node is initializing after
rebooting.
- In Section 4.6, added a clarification to the definition of the INITIAL_SOLICIT_TIMER: 2 seconds
Binding Update List, that for multiple Binding Updates sent to
the same destination address, the Binding Update List contains
only the most recent Binding Update (i.e., with the greatest
Sequence Number value) sent to that destination. This was
already noted in previous versions of the draft in the sending of
Binding Updates, as defined in Section update-corresp, but was
not previously stated explicitly in the definition of the Binding
Update List conceptual data structure.
- In Section 9.3, added a specification that the lifetime for the MAX_PFX_ADV_DELAY: 1,000 seconds
Binding Cache entry (and thus the Lifetime value returned in the
Binding Acknowledgement) MUST NOT be greater than the Lifetime
value specified in the Binding Update. Also added a similar
specification (and clarification) in Section 8.3 for the Binding
Cache entry in a correspondent node.
- In Section 10.6, added a clarification that, when sending a HomeRtrAdvInterval: 1,000 seconds
Binding Update to its home agent, the mobile node MUST also
create or update the corresponding Binding Update List entry, as
specified in Section 10.8.
Acknowledgements Acknowledgements
We would like to thank the members of the Mobile IP and IPng We would like to thank the members of the Mobile IP and IPng Working
Working Groups for their comments and suggestions on this work. Groups for their comments and suggestions on this work. We would
We would particularly like to thank (in alphabetical order) particularly like to thank (in alphabetical order) Fred Baker
Fred Baker (Cisco), Josh Broch (Carnegie Mellon University), (Cisco), Josh Broch (Carnegie Mellon University), Robert Chalmers
Rich Draves (Microsoft Research), Francis Dupont (INRIA), Thomas (University of California at Santa Barbara), Rich Draves (Microsoft
Eklund (SwithCore), Jun-Ichiro Hagino (IIJ Research Laboratory), Research), Francis Dupont (ENST Bretagne), Thomas Eklund (SwithCore),
Aime Lerouzic (Bull S.A.), Thomas Narten (IBM), Erik Nordmark Jun-Ichiro Itojun Hagino (IIJ Research Laboratory), Aime Lerouzic
(Sun Microsystems), Simon Nybroe (Ericsson Telebit), David Oran (Bull S.A.), Thomas Narten (IBM), Erik Nordmark (Sun Microsystems),
(Cisco), Basavaraj Patil (Nokia), Ken Powell (Compaq), Phil Roberts Simon Nybroe (Ericsson Telebit), David Oran (Cisco), Basavaraj Patil
(Motorola), Patrice Romand (Bull S.A.), Tom Soderlund (Nokia (Nokia), Ken Powell (Compaq), Phil Roberts (Motorola), Patrice
Research), Hesham Soliman (Ericsson), Jim Solomon (RedBack Networks), Romand (Bull S.A.), Tom Soderlund (Nokia Research), Hesham Soliman
Benny Van Houdt (University of Antwerp), Jon-Olov Vatn (KTH), and (Ericsson), Jim Solomon (RedBack Networks), Tapio Suihko (Technical
Xinhua Zhao (Stanford University) for their detailed reviews of Research Center of Finland), Benny Van Houdt (University of Antwerp),
earlier versions of this document. Their suggestions have helped to Jon-Olov Vatn (KTH), and Xinhua Zhao (Stanford University) for
improve both the design and presentation of the protocol. their detailed reviews of earlier versions of this document. Their
suggestions have helped to improve both the design and presentation
of the protocol.
We would also like to thank the participants in the Mobile IPv6 We would also like to thank the participants in the Mobile IPv6
testing event held at Nancy, France, September 15-17, 1999, for testing event held at Nancy, France, September 15-17, 1999, for
their valuable feedback as a result of interoperability testing their valuable feedback as a result of interoperability testing
of four Mobile IPv6 implementations coming from four different of four Mobile IPv6 implementations coming from four different
organizations: Bull (AIX), Ericsson Telebit (FreeBSD), NEC organizations: Bull (AIX), Ericsson Telebit (FreeBSD), NEC
(FreeBSD), and INRIA (FreeBSD). Finally, we would like to thank the (FreeBSD), and INRIA (FreeBSD). Further, we would like to thank the
feedback from the implementors who participated in the Mobile IPv6 feedback from the implementors who participated in the Mobile IPv6
interoperability testing at Connectathon 2000 in San Jose, interoperability testing at Connectathon 2000 in San Jose,
California, March 6-9, 2000. California, March 6-9, 2000. Finally, we would like to thank the
participants at the ETSI interoperability testing at ETSI, in Sophia
Antipolis, France, during October 2-6, 2000, including teams from
Compaq, Ericsson, INRIA, Nokia, and Technical University of Helsinki.
References References
[1] S. M. Bellovin. Security problems in the TCP/IP protocol suite. [1] S. M. Bellovin. Security Problems in the TCP/IP Protocol Suite.
ACM Computer Communications Review, 19(2), March 1989. ACM Computer Communications Review, 19(2), March 1989.
[2] Jim Bound and Charles Perkins. Dynamic Host Configuration [2] Jim Bound and Charles Perkins. Dynamic Host Configuration
Protocol for IPv6 (DHCPv6), February 1999. Work in progress. Protocol for IPv6 (DHCPv6), February 1999. Work in progress.
[3] Scott Bradner. Key words for use in RFCs to indicate [3] Scott Bradner. Key words for use in RFCs to Indicate
requirement levels. RFC 2119, March 1997. Requirement Levels. RFC 2119, March 1997.
[4] Alex Conta and Stephen Deering. Generic packet tunneling in [4] Alex Conta and Stephen Deering. Generic Packet Tunneling in
IPv6 specification. RFC 2473, December 1998. IPv6 Specification. RFC 2473, December 1998.
[5] Alex Conta and Stephen Deering. Internet Control Message [5] Alex Conta and Stephen Deering. Internet Control Message
Protocol (ICMPv6) for the Internet Protocol version 6 (IPv6) Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6)
specification. RFC 2463, December 1998. Specification. RFC 2463, December 1998.
[6] Stephen E. Deering and Robert M. Hinden. Internet Protocol [6] Stephen E. Deering and Robert M. Hinden. Internet Protocol
version 6 (IPv6) specification. RFC 2460, December 1998. Version 6 (IPv6) Specification. RFC 2460, December 1998.
[7] Paul Ferguson and Daniel Senie. Network ingress filtering: [7] Paul Ferguson and Daniel Senie. Network Ingress Filtering:
Defeating denial of service attacks which employ IP source Defeating Denial of Service Attacks which employ IP Source
address spoofing. RFC 2267, January 1998. Address Spoofing. RFC 2267, January 1998.
[8] Dan Harkins and Dave Carrel. The Internet Key Exchange (IKE). [8] Dan Harkins and Dave Carrel. The Internet Key Exchange (IKE).
RFC 2409, November 1998. RFC 2409, November 1998.
[9] Robert M. Hinden and Stephen E. Deering. IP Version 6 [9] Robert M. Hinden and Stephen E. Deering. IP Version 6
addressing architecture. RFC 2373, July 1998. Addressing Architecture. RFC 2373, July 1998.
[10] David B. Johnson and Stephen E. Deering. Reserved IPv6 subnet [10] David B. Johnson and Stephen E. Deering. Reserved IPv6 Subnet
anycast addresses. RFC 2526, March 1999. Anycast Addresses. RFC 2526, March 1999.
[11] Stephen Kent and Randall Atkinson. IP Authentication header. [11] Stephen Kent and Randall Atkinson. IP Authentication Header.
RFC 2402, November 1998. RFC 2402, November 1998.
[12] Stephen Kent and Randall Atkinson. IP Encapsulating Security [12] Stephen Kent and Randall Atkinson. IP Encapsulating Security
Payload (ESP). RFC 2406, November 1998. Payload (ESP). RFC 2406, November 1998.
[13] Stephen Kent and Randall Atkinson. Security architecture for [13] Stephen Kent and Randall Atkinson. Security Architecture for
the Internet Protocol. RFC 2401, November 1998. the Internet Protocol. RFC 2401, November 1998.
[14] Douglas Maughan, Mark Schneider, Mark Schertler, and Jeff [14] Douglas Maughan, Mark Schneider, Mark Schertler, and Jeff
Turner. Internet Security Association and Key Management Turner. Internet Security Association and Key Management
Protocol (ISAKMP). RFC 2408, November 1998. Protocol (ISAKMP). RFC 2408, November 1998.
[15] P. Mockapetris. Domain Names -- concepts and facilities. [15] P. Mockapetris. Domain Names -- Concepts and Facilities.
RFC 1034, November 1987. RFC 1034, November 1987.
[16] P. Mockapetris. Domain Names -- implementation and [16] P. Mockapetris. Domain Names -- Implementation and
specification. RFC 1035, November 1987. Specification. RFC 1035, November 1987.
[17] Thomas Narten, Erik Nordmark, and William Allen Simpson. [17] Thomas Narten, Erik Nordmark, and William Allen Simpson.
Neighbor Discovery for IP version 6 (IPv6). RFC 2461, December Neighbor Discovery for IP Version 6 (IPv6). RFC 2461, December
1998. 1998.
[18] Charles Perkins. IP encapsulation within IP. RFC 2003, October [18] Charles Perkins. IP Encapsulation within IP. RFC 2003, October
1996. 1996.
[19] Charles Perkins, editor. IP mobility support. RFC 2002, [19] Charles Perkins, editor. IP Mobility Support. RFC 2002,
October 1996. October 1996.
[20] Charles Perkins. Minimal encapsulation within IP. RFC 2004, [20] Charles Perkins. Minimal Encapsulation within IP. RFC 2004,
October 1996. October 1996.
[21] Charles Perkins and David B. Johnson. Route optimization in [21] Charles Perkins and David B. Johnson. Route Optimization in
Mobile IP, February 1999. Work in progress. Mobile IP, February 1999. Work in progress.
[22] Derrell Piper. The Internet IP security domain of [22] Derrell Piper. The Internet IP Security Domain of
interpretation for ISAKMP. RFC 2407, November 1998. Interpretation for ISAKMP. RFC 2407, November 1998.
[23] David C. Plummer. An Ethernet address resolution protocol: [23] David C. Plummer. An Ethernet Address Resolution Protocol:
Or converting network protocol addresses to 48.bit Ethernet Or Converting Network Protocol Addresses to 48.bit Ethernet
addresses for transmission on Ethernet hardware. RFC 826, Addresses for Transmission on Ethernet Hardware. RFC 826,
November 1982. November 1982.
[24] J. B. Postel. User Datagram Protocol. RFC 768, August 1980. [24] J. B. Postel. User Datagram Protocol. RFC 768, August 1980.
[25] J. B. Postel, editor. Transmission Control Protocol. RFC 793, [25] J. B. Postel, editor. Transmission Control Protocol. RFC 793,
September 1981. September 1981.
[26] Joyce K. Reynolds and Jon Postel. Assigned numbers. RFC 1700, [26] Joyce K. Reynolds and Jon Postel. Assigned Numbers. RFC 1700,
October 1994. See also http://www.iana.org/numbers.html. October 1994. See also http://www.iana.org/numbers.html.
[27] Susan Thomson and Thomas Narten. IPv6 stateless address [27] Susan Thomson and Thomas Narten. IPv6 Stateless Address
autoconfiguration. RFC 2462, December 1998. Autoconfiguration. RFC 2462, December 1998.
A. Remote Home Address Configuration
The method for initializing a mobile node's home addresses on
power-up or after an extended period of being disconnected from
the network is beyond the scope of this specification. Whatever
procedure is used should result in the mobile node having the same
stateless or stateful (e.g., DHCPv6) home address autoconfiguration
information it would have if it were attached to the home network.
Due to the possibility that the home network could be renumbered
while the mobile node is disconnected, a robust mobile node would not
rely solely on storing these addresses locally.
A mobile node MAY generate a temporary home address using the
following information:
- the subnet prefix from the home network's mobile agent anycast
address, and
- the globally unique interface identifier that would have been
used to generate the link local address if the mobile node were
attached directly to the home network.
Such a temporary address could be used to establish a binding with
a home agent in the absence of any other known home addresses. It
could be created with short valid lifetime and a preferred lifetime
of zero to ensure a quick transition to other addresses generated
when stateless or stateful (DHCPv6) address autoconfiguration runs.
Such a mobile node could initialize by using the following procedure:
1. Generate a care-of address using stateless or stateful
autoconfiguration.
2. Query DNS for the home network's mobile agent anycast address.
3. Send a Home Agent Address Discovery Request message to the home
network.
4. Receive Home Agent Address Discovery Reply message.
5. Select the most preferred home agent address and use it to
generate a temporary home address for the mobile node using the
rules defined above.
6. Send a binding update option with a Router Solicitation to the
home agent. This registers the mobile node's temporary home
address and requests a router advertisement to initiate stateless
address autoconfiguration at the same time.
7. Receive binding acknowledgement and binding request options with
a router advertisement from the home agent.
8. Parse the Router Advertisement and configure all prefixes and
addresses according to the method stated there. If the M or O
flags are set in the router advertisement, follow the stateful
(DHCPv6) configuration procedures. These procedures could make
the temporary home address permanent by increasing its valid and
preferred lifetimes.
9. Send binding update option(s) to update the binding for the
temporary home address and to establish bindings for any new home
addresses.
Chair's Address Chair's Address
The Working Group can be contacted via its current chairs: The Working Group can be contacted via its current chairs:
Phil Roberts Phil Roberts
Motorola Motorola
1501 West Shure Drive 1501 West Shure Drive
Arlington Heights, IL 60004 Arlington Heights, IL 60004
skipping to change at page 109, line 10 skipping to change at page 110, line 10
Phone: +1 972 894-6709 Phone: +1 972 894-6709
Fax: +1 972 894-5349 Fax: +1 972 894-5349
E-mail: raj.patil@nokia.com E-mail: raj.patil@nokia.com
Authors' Addresses Authors' Addresses
Questions about this document can also be directed to the authors: Questions about this document can also be directed to the authors:
David B. Johnson David B. Johnson
Carnegie Mellon University Rice University
Computer Science Department Department of Computer Science, MS 132
5000 Forbes Avenue 6100 Main Street
Pittsburgh, PA 15213-3891 Houston, TX 77005-1892
USA USA
Phone: +1 412 268-7399 Phone: +1 713 348-3063
Fax: +1 412 268-5576 Fax: +1 713 348-5930
E-mail: dbj@cs.cmu.edu E-mail: dbj@cs.rice.edu
Charles Perkins Charles Perkins
Nokia Nokia
313 Fairchild Drive 313 Fairchild Drive
Mountain View, CA 94043 Mountain View, CA 94043
USA USA
Phone: +1 650 625-2986 Phone: +1 650 625-2986
Fax: +1 650 691-2170 Fax: +1 650 625-2502
E-mail: charliep@iprg.nokia.com E-mail: charliep@iprg.nokia.com
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