draft-ietf-mobileip-ipv6-07.txt   draft-ietf-mobileip-ipv6-08.txt 
IETF Mobile IP Working Group David B. Johnson IETF Mobile IP Working Group David B. Johnson
INTERNET-DRAFT Carnegie Mellon University INTERNET-DRAFT Carnegie Mellon University
Charles Perkins Charles Perkins
Sun Microsystems Sun Microsystems
18 November 1998 25 June 1999
Mobility Support in IPv6 Mobility Support in IPv6
<draft-ietf-mobileip-ipv6-07.txt> <draft-ietf-mobileip-ipv6-08.txt>
Status of This Memo Status of This Memo
This document is a submission by the Mobile IP Working Group of the This document is an Internet-Draft and is in full conformance with
Internet Engineering Task Force (IETF). Comments should be submitted all provisions of Section 10 of RFC 2026.
to the Working Group mailing list at "mobile-ip@SmallWorks.COM".
Distribution of this memo is unlimited.
This document is an Internet-Draft. Internet-Drafts are working Internet-Drafts are working documents of the Internet Engineering
documents of the Internet Engineering Task Force (IETF), its areas, Task Force (IETF), its areas, and its working groups. Note
and its working groups. Note that other groups may also distribute that other groups may also distribute working documents as
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and may be updated, replaced, or obsoleted by other documents at and may be updated, replaced, or obsoleted by other documents at
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Abstract Abstract
This document specifies the operation of mobile computers using IPv6. This document specifies the operation of mobile computers using IPv6.
Each mobile node is always identified by its home address, regardless Each mobile node is always identified by its home address, regardless
of its current point of attachment to the Internet. While situated of its current point of attachment to the Internet. While situated
away from its home, a mobile node is also associated with a care-of away from its home, a mobile node is also associated with a care-of
address, which provides information about the mobile node's current address, which provides information about the mobile node's current
location. IPv6 packets addressed to a mobile node's home address are location. IPv6 packets addressed to a mobile node's home address are
transparently routed to its care-of address. The protocol enables transparently routed to its care-of address. The protocol enables
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3. Terminology 6 3. Terminology 6
3.1. General Terms . . . . . . . . . . . . . . . . . . . . . . 6 3.1. General Terms . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Mobile IPv6 Terms . . . . . . . . . . . . . . . . . . . . 7 3.2. Mobile IPv6 Terms . . . . . . . . . . . . . . . . . . . . 7
3.3. Specification Language . . . . . . . . . . . . . . . . . 8 3.3. Specification Language . . . . . . . . . . . . . . . . . 8
4. Overview of Mobile IPv6 9 4. Overview of Mobile IPv6 9
4.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 9 4.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 9
4.2. New IPv6 Destination Options . . . . . . . . . . . . . . 11 4.2. New IPv6 Destination Options . . . . . . . . . . . . . . 11
4.3. Conceptual Data Structures . . . . . . . . . . . . . . . 13 4.3. Conceptual Data Structures . . . . . . . . . . . . . . . 13
4.4. Binding Management . . . . . . . . . . . . . . . . . . . 16 4.4. Binding Management . . . . . . . . . . . . . . . . . . . 17
5. New IPv6 Destination Options 19 5. New IPv6 Destination Options 19
5.1. Binding Update Option Format . . . . . . . . . . . . . . 19 5.1. Binding Update Option Format . . . . . . . . . . . . . . 19
5.2. Binding Acknowledgement Option Format . . . . . . . . . . 23 5.2. Binding Acknowledgement Option Format . . . . . . . . . . 23
5.3. Binding Request Option Format . . . . . . . . . . . . . . 27 5.3. Binding Request Option Format . . . . . . . . . . . . . . 27
5.4. Home Address Option Format . . . . . . . . . . . . . . . 29 5.4. Home Address Option Format . . . . . . . . . . . . . . . 29
5.5. Mobile IPv6 Destination Option Sub-Options . . . . . . . 31 5.5. Mobile IPv6 Destination Option Sub-Options . . . . . . . 31
6. Modifications to IPv6 Neighbor Discovery 33 6. Modifications to IPv6 Neighbor Discovery 33
6.1. Modified Router Advertisement Message Format . . . . . . 33 6.1. Modified Router Advertisement Message Format . . . . . . 33
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9. Home Agent Operation 52 9. Home Agent Operation 52
9.1. Receiving Router Advertisement Messages . . . . . . . . . 52 9.1. Receiving Router Advertisement Messages . . . . . . . . . 52
9.2. Dynamic Home Agent Address Discovery . . . . . . . . . . 53 9.2. Dynamic Home Agent Address Discovery . . . . . . . . . . 53
9.3. Primary Care-of Address Registration . . . . . . . . . . 55 9.3. Primary Care-of Address Registration . . . . . . . . . . 55
9.4. Primary Care-of Address De-registration . . . . . . . . . 57 9.4. Primary Care-of Address De-registration . . . . . . . . . 57
9.5. Intercepting Packets for a Mobile Node . . . . . . . . . 58 9.5. Intercepting Packets for a Mobile Node . . . . . . . . . 58
9.6. Tunneling Intercepted Packets to a Mobile Node . . . . . 60 9.6. Tunneling Intercepted Packets to a Mobile Node . . . . . 60
9.7. Renumbering the Home Subnet . . . . . . . . . . . . . . . 61 9.7. Renumbering the Home Subnet . . . . . . . . . . . . . . . 61
10. Mobile Node Operation 64 10. Mobile Node Operation 65
10.1. Sending Packets While Away from Home . . . . . . . . . . 64 10.1. Sending Packets While Away from Home . . . . . . . . . . 65
10.2. Receiving Packets While Away from Home . . . . . . . . . 66 10.2. Receiving Packets While Away from Home . . . . . . . . . 67
10.3. Movement Detection . . . . . . . . . . . . . . . . . . . 67 10.3. Movement Detection . . . . . . . . . . . . . . . . . . . 68
10.4. Forming New Care-of Addresses . . . . . . . . . . . . . . 70 10.4. Forming New Care-of Addresses . . . . . . . . . . . . . . 71
10.5. Sending Binding Updates to the Home Agent . . . . . . . . 71 10.5. Sending Binding Updates to the Home Agent . . . . . . . . 72
10.6. Dynamic Home Agent Address Discovery . . . . . . . . . . 72 10.6. Dynamic Home Agent Address Discovery . . . . . . . . . . 73
10.7. Sending Binding Updates to Correspondent Nodes . . . . . 73 10.7. Sending Binding Updates to Correspondent Nodes . . . . . 74
10.8. Sending Binding Updates to the Previous Default Router . 75 10.8. Sending Binding Updates to the Previous Default Router . 76
10.9. Retransmitting Binding Updates . . . . . . . . . . . . . 76 10.9. Retransmitting Binding Updates . . . . . . . . . . . . . 77
10.10. Rate Limiting for Sending Binding Updates . . . . . . . . 76 10.10. Rate Limiting for Sending Binding Updates . . . . . . . . 77
10.11. Receiving Binding Acknowledgements . . . . . . . . . . . 76 10.11. Receiving Binding Acknowledgements . . . . . . . . . . . 77
10.12. Receiving Binding Requests . . . . . . . . . . . . . . . 77 10.12. Receiving Binding Requests . . . . . . . . . . . . . . . 78
10.13. Receiving ICMP Error Messages . . . . . . . . . . . . . . 78 10.13. Receiving ICMP Error Messages . . . . . . . . . . . . . . 79
10.14. Receiving Tunneled Router Advertisements . . . . . . . . 78 10.14. Receiving Tunneled Router Advertisements . . . . . . . . 79
10.15. Using Multiple Care-of Addresses . . . . . . . . . . . . 79 10.15. Using Multiple Care-of Addresses . . . . . . . . . . . . 80
10.16. Routing Multicast Packets . . . . . . . . . . . . . . . . 80 10.16. Routing Multicast Packets . . . . . . . . . . . . . . . . 81
10.17. Returning Home . . . . . . . . . . . . . . . . . . . . . 80 10.17. Returning Home . . . . . . . . . . . . . . . . . . . . . 82
11. Constants 82 11. Constants 83
12. IANA Considerations 83 12. IANA Considerations 84
13. Security Considerations 84 13. Security Considerations 85
13.1. Binding Updates, Acknowledgements, and Requests . . . . . 84 13.1. Binding Updates, Acknowledgements, and Requests . . . . . 85
13.2. Home Address Option . . . . . . . . . . . . . . . . . . . 84 13.2. Home Address Option . . . . . . . . . . . . . . . . . . . 85
13.3. General Mobile Computing Issues . . . . . . . . . . . . . 85 13.3. General Mobile Computing Issues . . . . . . . . . . . . . 86
Changes from Previous Draft 87 Changes from Previous Version of the Draft 88
Acknowledgements 89 Acknowledgements 90
References 90 References 91
Chair's Address 92 Chair's Address 93
Authors' Addresses 93 Authors' Addresses 94
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) [5]. Without specific support Internet Protocol Version 6 (IPv6) [5]. 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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- Access control on a link being visited by a mobile node. This - Access control on a link being visited by a mobile node. This
is a general problem any time an untrusted node is allowed is a general problem any time an untrusted node is allowed
to connect to any link layer. It is independent whether the to connect to any link layer. It is independent whether the
connecting node uses Mobile IP, DHCP [2], or just "borrows" an IP connecting node uses Mobile IP, DHCP [2], or just "borrows" an IP
address on the link. address on the link.
2. Comparison with Mobile IP for IPv4 2. Comparison with Mobile IP for IPv4
The design of Mobile IP support in IPv6 (Mobile IPv6) represents a The design of Mobile IP support in IPv6 (Mobile IPv6) represents a
natural combination of the experiences gained from the development natural combination of the experiences gained from the development
of Mobile IP support in IPv4 (Mobile IPv4) [15, 14, 16], together of Mobile IP support in IPv4 (Mobile IPv4) [16, 15, 17], together
with the opportunities provided by the design and deployment of a new with the opportunities provided by the design and deployment of a new
version of IP itself (IPv6) and the new protocol features offered version of IP itself (IPv6) and the new protocol features offered
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" [17] is now built in as a fundamental part Optimization" [18] is now built in as a fundamental part
of the protocol, rather than being added on as a optional of the protocol, rather than being added on as a 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 node
to any mobile node, without needing to pass through the mobile to any mobile node, without needing to pass through the mobile
node's home network and be forwarded by its home agent, and thus node's home network and be forwarded by its home agent, and thus
eliminates the problem of "triangle routing" present in the base eliminates the problem of "triangle routing" present in the base
Mobile IPv4 protocol [15]. This integration also allows the Mobile IPv4 protocol [16]. This integration also allows the
Mobile IPv4 "registration" functionality and the Mobile IPv4 Mobile IPv4 "registration" functionality and the Mobile IPv4
Route Optimization functionality to be performed by a single Route Optimization functionality to be performed by a single
protocol rather than two separate (and different) protocols. protocol 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" [6]. A efficiently with routers that perform "ingress filtering" [6]. 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
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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 the enhanced features of IPv6, such
as Neighbor Discovery [13] and Address Autoconfiguration [22], as Neighbor Discovery [14] and Address Autoconfiguration [23],
to operate in any location away from home without any special to operate in any location away from home without any special
support required from its local router. support required from its local router.
- Unlike Mobile IPv4, Mobile IPv6 utilizes IPsec [8, 9, 10] for - Unlike Mobile IPv4, Mobile IPv6 utilizes IPsec [9, 10, 11] for
all security requirements (sender authentication, data integrity all security requirements (sender authentication, data integrity
protection, and replay protection) for Binding Updates (which protection, and replay protection) for Binding Updates (which
serve the role of both registration and Route Optimization in serve the role of both registration and Route Optimization in
Mobile IPv4). Mobile IPv4 relies on its own security mechanisms Mobile IPv4). Mobile IPv4 relies on its own security mechanisms
for these functions, based on statically configured "mobility for these functions, based on statically configured "mobility
security associations". security associations".
- The movement detection mechanism in Mobile IPv6 provides - The movement detection mechanism in Mobile IPv6 provides
bidirectional confirmation of a mobile node's ability to bidirectional confirmation of a mobile node's ability to
communicate with its default router in its current location communicate with its default router in its current location
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IP encapsulation, whereas Mobile IPv4 must use encapsulation IP encapsulation, whereas Mobile IPv4 must use encapsulation
for all packets. The use of a Routing header requires less for all packets. The use of a Routing header requires less
additional header bytes to be added to the packet, reducing the additional header bytes to be added to the packet, reducing the
overhead of Mobile IP packet delivery. To avoid modifying the overhead of Mobile IP packet delivery. To avoid modifying the
packet in flight, however, packets intercepted and tunneled packet in flight, however, packets intercepted and tunneled
by a mobile node's home agent in Mobile IPv6 must still use by a mobile node's home agent in Mobile IPv6 must still use
encapsulation for tunneling. encapsulation for tunneling.
- While a mobile node is away from home, its home agent intercepts - While a mobile node is away from home, its home agent intercepts
any packets for the mobile node that arrive at the home network, any packets for the mobile node that arrive at the home network,
using IPv6 Neighbor Discovery [13] rather than ARP [18] as is using IPv6 Neighbor Discovery [14] rather than ARP [19] as is
used in Mobile IPv4. The use of Neighbor Discovery improves used in Mobile IPv4. The use of Neighbor Discovery improves
the robustness of the protocol (e.g., due to the Neighbor the robustness of the protocol (e.g., due to the Neighbor
Advertisement "override" bit) and simplifies implementation Advertisement "override" bit) and simplifies implementation
of Mobile IP due to the ability to not be concerned with any of Mobile IP due to the ability to not be concerned with any
particular link layer as is required in ARP. particular link layer as is required in ARP.
- The use of IPv6 encapsulation (and the Routing header) removes - The use of IPv6 encapsulation (and the Routing header) removes
the need in Mobile IPv6 to manage "tunnel soft state", which was the need in Mobile IPv6 to manage "tunnel soft state", which was
required in Mobile IPv4 due to limitations in ICMP for IPv4. Due required in Mobile IPv4 due to limitations in ICMP for IPv4. Due
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 and returns a single reply to the mobile node, uses IPv6 anycast [8] and returns a single reply to the mobile
rather than the corresponding Mobile IPv4 mechanism that used node, rather than the corresponding Mobile IPv4 mechanism that
IPv4 directed broadcast and returned a separate reply from each used IPv4 directed broadcast and returned a separate reply from
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 packet need be sent back to the mobile node and since the one packet need be sent back to the mobile node and since the
mobile node is less likely to lose one of the replies because no mobile node is less likely to lose one of the replies because no
"implosion" of replies is required by the protocol. "implosion" of 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.
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with a mobile node while visiting a particular foreign link. The with a mobile node while visiting a particular foreign link. The
subnet prefix of a mobile node's care-of address is the subnet prefix subnet prefix of a mobile node's care-of address is the subnet prefix
(or one of the subnet prefixes) on the foreign link being visited by (or one of the subnet prefixes) on the foreign link being visited by
the mobile node; if the mobile node is connected to this foreign link the mobile node; if the mobile node is connected to this foreign link
while using that care-of address, packets addressed to this care-of while using that care-of address, packets addressed to this care-of
address will be routed to the mobile node in its location away from address will be routed to the mobile node in its location away from
home. home.
The association between a mobile node's home address and care-of The association between a mobile node's home address and care-of
address is known as a "binding" for the mobile node. A mobile node address is known as a "binding" for the mobile node. A mobile node
typically acquires its care-of address through stateless [22] or typically acquires its care-of address through stateless [23] or
stateful (e.g., DHCPv6 [2]) address autoconfiguration, according stateful (e.g., DHCPv6 [2]) Address Autoconfiguration, according
to the methods of IPv6 Neighbor Discovery [13]. Other methods to the methods of IPv6 Neighbor Discovery [14]. Other methods
of acquiring a care-of address are also possible, such as static of acquiring a care-of address are also possible, such as static
pre-assignment by the owner or manager of a particular foreign link, pre-assignment by the owner or manager of a particular foreign link,
but details of such other methods are beyond the scope of this but details of such other methods are beyond the scope of this
document. document.
While away from home, a mobile node registers one of its care-of While away from home, a mobile node registers one of its care-of
addresses with a router on its home link, requesting this router addresses with a router on its home link, requesting this router
to function as the "home agent" for the mobile node. This binding to function as the "home agent" for the mobile node. This binding
registration is done by the mobile node sending to the home agent registration is done by the mobile node sending to the home agent
a packet containing a "Binding Update" destination option; the a packet containing a "Binding Update" destination option; the
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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 a Binding Update to the while away from home. The mobile node sends a Binding Update to the
"Home-Agents anycast address" for its own home subnet prefix and thus "Mobile IPv6 Home-Agents" anycast address for its own home subnet
reaches one of the (possibly many) routers on its home link currently prefix [8] and thus reaches one of the (possibly many) routers on
operating as a home agent. This home agent rejects the mobile its home link currently operating as a home agent. This home agent
node's Binding Update, but returns in the Binding Acknowledgement rejects the mobile node's Binding Update, but returns in the Binding
in response a list of all home agents on the home link. This list Acknowledgement in response a list of all home agents on the home
of home agents is maintained by each home agent on the home link link. This list of home agents is maintained by each home agent on
through use of the Home Agent (H) bit in each home agent's periodic the home link through use of the Home Agent (H) bit in each home
unsolicited multicast Router Advertisements. agent's periodic unsolicited multicast Router Advertisements.
The Binding Update and Binding Acknowledgement destination options, The Binding Update and Binding Acknowledgement destination options,
together with a "Binding Request" destination option, are also used together with a "Binding Request" destination option, are also used
to allow IPv6 nodes communicating with a mobile node, to dynamically to allow IPv6 nodes communicating with a mobile node, to dynamically
learn and cache the mobile node's binding. When sending a packet learn and cache the mobile node's binding. When sending a packet
to any IPv6 destination, a node checks its cached bindings for an to any IPv6 destination, a node checks its cached bindings for an
entry for the packet's destination address. If a cached binding for entry for the packet's destination address. If a cached binding for
this destination address is found, the node uses an IPv6 Routing this destination address is found, the node uses an IPv6 Routing
header [5] (instead of IPv6 encapsulation) to route the packet to header [5] (instead of IPv6 encapsulation) to route the packet to
the mobile node by way of the care-of address indicated in this the mobile node by way of the care-of address indicated in this
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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 [5], are each represented in a packet as an IPv6 destination option [5],
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 - A Binding Update, Binding Acknowledgement, or Binding Request can
be included within any IPv6 packet carrying any payload such as be included within any IPv6 packet carrying any payload such as
TCP [20] or UDP [19]. TCP [21] or UDP [20].
- A Binding Update, Binding Acknowledgement, or Binding Request can - A Binding Update, Binding Acknowledgement, or Binding Request can
be sent as a separate IPv6 packet containing no payload. In this be sent as a separate IPv6 packet containing no payload. In this
case, the Next Header field in the last extension header in the case, the Next Header field in the last extension header in the
packet is set to the value 59, to indicate "No Next Header" [5]. packet is set to the value 59, to indicate "No Next Header" [5].
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
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As discussed in general in Section 4.1, the following four new IPv6 As discussed in general in Section 4.1, the following four new IPv6
destination options are defined for Mobile IPv6: destination 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 a correspondent node or the mobile node's home agent of
its current binding. The Binding Update sent to the mobile its current binding. The Binding Update sent to the mobile
node's home agent to register its primary care-of address is node's home agent to register its primary care-of address is
marked as a "home registration". Any packet that includes a marked as a "home registration". Any packet that includes a
Binding Update option MUST also include either an AH [8] or Binding Update option MUST also include either an AH [9] or
ESP [9] header providing sender authentication, data integrity ESP [10] header providing sender authentication, data integrity
protection, and replay protection. The Binding Update option protection, and replay protection. The Binding Update option
is described in detail in Section 5.1. is described in detail in Section 5.1.
Binding Acknowledgement Binding Acknowledgement
A Binding Acknowledgement option is used to acknowledge receipt A Binding Acknowledgement option is used to acknowledge receipt
of a Binding Update, if an acknowledgement was requested of a Binding Update, if an acknowledgement was requested
in the Binding Update. Any packet that includes a Binding in the Binding Update. Any packet that includes a Binding
Acknowledgement option MUST also include either an AH [8] or Acknowledgement option MUST also include either an AH [9] or
ESP [9] header providing sender authentication, data integrity ESP [10] header providing sender authentication, data integrity
protection, and replay protection. The Binding Acknowledgement protection, and replay protection. The Binding Acknowledgement
option is described in detail in Section 5.2. option is described in detail in Section 5.2.
Binding Request Binding Request
A Binding Request option is used to request a mobile node to A Binding Request option is used to request a mobile node to
send to the requesting node a Binding Update containing the send to the requesting node a Binding Update containing the
mobile node's current binding. This option is typically used mobile node's current binding. This option is typically used
by a correspondent node to refresh a cached binding for a by a correspondent node to refresh a cached binding for a
mobile node, when the cached binding is in active use but the mobile node, when the cached binding is in active use but the
skipping to change at page 13, line 16 skipping to change at page 13, line 16
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. The Binding Cache MAY be implemented in any manner
consistent with the external behavior described in this consistent with the external behavior described in this
document, for example by being combined with the node's document, for example by being combined with the node's
Destination Cache as maintained by Neighbor Discovery [13]. Destination Cache as maintained by Neighbor Discovery [14].
When sending a packet, the Binding Cache is searched before the When sending a packet, the Binding Cache is searched before the
Neighbor Discovery conceptual Destination Cache [13] (i.e., any Neighbor Discovery conceptual Destination Cache [14] (i.e., any
Binding Cache entry for this destination SHOULD take precedence Binding Cache entry for this destination SHOULD take precedence
over any Destination Cache entry for the same destination). over any Destination Cache entry for the same destination).
Each Binding Cache entry conceptually contains the following Each Binding Cache entry conceptually contains the following
fields: 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,
skipping to change at page 13, line 50 skipping to change at page 13, line 50
- A lifetime value, indicating the remaining lifetime - A lifetime value, indicating the remaining lifetime
for this Binding Cache entry. The lifetime value is for this Binding Cache entry. The lifetime value is
initialized from the Lifetime field in the Binding Update initialized from the Lifetime field in the Binding Update
that created or last modified this Binding Cache entry. that created or last modified this Binding Cache entry.
Once the lifetime on this entry expires, the entry MUST be Once the lifetime on this entry expires, the entry MUST be
deleted from the Binding Cache. deleted from the Binding Cache.
- A flag indicating whether or not this Binding Cache entry - A flag indicating whether or not this Binding Cache entry
is a "home registration" entry. is a "home registration" entry.
- A flag indicating whether or not this Binding Cache entry
represents a mobile node that should be advertised as a
router in proxy Neighbor Advertisements sent by this node
on its behalf. This flag is only valid if the Binding
Cache entry indicates that this is a "home registration"
entry.
- The value of the Prefix Length field received in the - The value of the Prefix Length field received in the
Binding Update that created or last modified this Binding Binding Update that created or last modified this Binding
Cache entry. This field is only valid if the "home Cache entry. This field is only valid if the "home
registration" flag is set on this Binding Cache entry. registration" flag is set on this Binding Cache entry.
- The maximum value of the Sequence Number field received - The maximum value of the Sequence Number field received
in previous Binding Updates for this mobile node home in previous Binding Updates for this mobile node home
address. The Sequence Number field is 16 bits long, and address. The Sequence Number field is 16 bits long, and
all comparisons between Sequence Number values MUST be all comparisons between Sequence Number values MUST be
performed modulo 2**16. performed modulo 2**16.
skipping to change at page 16, line 5 skipping to change at page 16, line 17
A list, maintained by each home agent, recording information A list, maintained by each home agent, recording information
about each other home agent on a link on which this node about each other home agent on a link on which this node
is serving as a home agent; each home agent maintains a is serving as a home agent; each home agent maintains a
separate Home Agents List for each such link on which it is separate Home Agents List for each such link on which it is
serving. This list is used in the dynamic home agent address serving. This list is used in the dynamic home agent address
discovery mechanism. The information for the list is learned discovery mechanism. The information for the list is learned
through receipt of the periodic unsolicited multicast Router through receipt of the periodic unsolicited multicast Router
Advertisements from each other home agent on the link, in which Advertisements from each other home agent on the link, in which
the Home Agent (H) bit is set, in a manner similar to the the Home Agent (H) bit is set, in a manner similar to the
Default Router List conceptual data structure maintained by Default Router List conceptual data structure maintained by
each host for Neighbor Discovery [13]. The Home Agents List each host for Neighbor Discovery [14]. The Home Agents List
MAY be implemented in any manner consistent with the external MAY be implemented in any manner consistent with the external
behavior described in this document. Each Home Agents List behavior described in this document. Each Home Agents List
entry conceptually contains the following fields: entry conceptually contains the following fields:
- The link-local IP address of another router on the home - The link-local IP address of another router on the home
link that this node currently believes is operating as link that this node currently believes is operating as
a home agent for this link. A new entry is created or a home agent for this link. A new entry is created or
an existing entry is updated in the Home Agents List in an existing entry is updated in the Home Agents List in
response to receipt of a valid Router Advertisement in response to receipt of a valid Router Advertisement in
which the Home Agent (H) bit is set. The link-local which the Home Agent (H) bit is set. The link-local
address of the home agent is learned through the Source address of the home agent is learned through the Source
Address of the Router Advertisements received from it [13]. Address of the Router Advertisements received from it [14].
- 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 the
Router Address (R) bit is set, received in Router Router Address (R) bit is 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 [13]. no longer valid [14].
- 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 this home agent the Home Agents List entry representing this home agent
is initialized from the Home Agent Lifetime field in the is initialized from the Home Agent Lifetime field in the
option; otherwise, the lifetime is initialized from the option; otherwise, the lifetime is initialized from the
Router Lifetime field in the received Router Advertisement. Router Lifetime field in the received Router Advertisement.
The Home Agents List entry lifetime is decremented until it The Home Agents List entry lifetime is decremented until it
reaches zero, at which time this entry MUST be deleted from reaches zero, at which time this entry MUST be deleted from
skipping to change at page 19, line 24 skipping to change at page 19, line 24
packet sent by a mobile node (Section 10.1). packet sent by a mobile node (Section 10.1).
The Binding Update option is encoded in type-length-value (TLV) The Binding Update option is encoded in type-length-value (TLV)
format as follows: format 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | | Option Type | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|H|C| Reserved| Prefix Length | Sequence Number | |A|H|C|R|Reservd| Prefix Length | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime | | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
| | | |
+ Care-of Address + + Care-of Address +
| (only present if C bit set) | | (only present if C bit set) |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Options... | Sub-Options...
+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-
Option Type Option Type
195 ??? 198 = 0xC6
Option Length Option Length
8-bit unsigned integer. Length of the option, in octets, 8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Option Length fields. This field excluding the Option Type and Option Length fields. This field
MUST be set to 8 (or to 24 if the Care-of Address Present (C) MUST be set to 8 (or to 24 if the Care-of Address Present (C)
bit is set), plus the total length of all sub-options present, bit is set), plus the total length of all sub-options present,
including their Sub-Option Type and Sub-Option Len fields. including their Sub-Option Type and Sub-Option Len fields.
Acknowledge (A) Acknowledge (A)
skipping to change at page 20, line 22 skipping to change at page 20, line 22
The Home Registration (H) bit is set by the sending mobile node The Home Registration (H) bit is set by the sending mobile node
to request the receiving node to act as this node's home agent. to request the receiving node to act as this node's home agent.
The destination of the packet carrying this option MUST be that The destination of the packet carrying this option MUST be that
of a router sharing the same subnet prefix as the home address of a router sharing the same subnet prefix as the home address
of the mobile node in the binding (given by the Home Address of the mobile node in the binding (given by the Home Address
field in the Home Address option in the packet). field in the Home Address option in the packet).
Care-of Address Present (C) Care-of Address Present (C)
The Care-of Address Present (C) bit indicates the presence of The Care-of Address Present (C) bit, when set, indicates the
the Care-of Address field in the Binding Update. The care-of presence of the Care-of Address field in the Binding Update.
address for this binding is either the address in the Care-of The care-of address for this binding is either the address in
Address field in the Binding Update, if this bit is set, or the the Care-of Address field in the Binding Update, if this bit is
Source Address in the packet's IPv6 header, if this bit is not set, or the Source Address in the packet's IPv6 header, if this
set. bit is not set.
Reserved Router (R)
Sent as 0; ignored on reception. The Router (R) bit, when set, indicates that the sending
mobile node is a router. This bit is only valid when the
Home Registration (H) bit is also set, and MUST NOT be set
otherwise. This bit is saved in the home agent's "home
registration" Binding Cache entry for the mobile node, and
is copied into the corresponding bit in all proxy Neighbor
Advertisement messages sent on behalf of this mobile node by
the home agent using this Binding Cache entry.
Reservd
Reserved. Sent as 0; ignored on reception.
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
Registration (H) bit is not set in the Binding Update. The Registration (H) bit is not set in the Binding Update. The
Prefix Length field is set by the sending mobile node to the Prefix Length field is set by the sending mobile node to the
(nonzero) length of its subnet prefix in its home address (nonzero) length of its subnet prefix in its home address
(given in the Home Address option in the packet) to request (given in the Home Address option in the packet) to request
its home agent to use the interface identifier in the mobile its home agent to use the interface identifier in the mobile
skipping to change at page 21, line 52 skipping to change at page 22, line 13
Update option: Update option:
- Unique Identifier Sub-Option - Unique Identifier Sub-Option
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 indicated by the Home
Address field in the Home Address option in the packet. Address field in the Home Address option in the packet.
Any packet that includes a Binding Update option MUST also include Any packet that includes a Binding Update option MUST also include
either an AH [8] or ESP [9] header providing sender authentication, either an AH [9] or ESP [10] header providing sender authentication,
data integrity protection, and replay protection. data integrity protection, and replay protection.
If the care-of address in the binding (either the Care-of Address If the care-of address in the binding (either the Care-of Address
field in the Binding Update option or the Source Address field in field in the Binding Update option or the Source Address field in
the packet's IPv6 header) is equal to the home address of the mobile the packet's IPv6 header) is equal to the home address of the mobile
node, the Binding Update option indicates that any existing binding node, the Binding Update option indicates that any existing binding
for the mobile node MUST be deleted. Likewise, if the Lifetime for the mobile node MUST be deleted. Likewise, if the Lifetime
field in the Binding Update option is equal to 0, the Binding Update field in the Binding Update option is equal to 0, 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
be deleted. In each of these cases, a Binding Cache entry for the be deleted. In each of these cases, a Binding Cache entry for the
skipping to change at page 23, line 10 skipping to change at page 23, line 10
Address was not a multicast address, return an ICMP Parameter Address was not a multicast address, return an ICMP Parameter
Problem, Code 2, message to the packet's Source Address; and that the Problem, 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 data within the option cannot change en-route to the packet's final
destination. destination.
5.2. Binding Acknowledgement Option Format 5.2. Binding Acknowledgement Option Format
The Binding Acknowledgement destination option is used to acknowledge The Binding Acknowledgement destination option is used to acknowledge
receipt of a Binding Update option (Section 5.1). When a node receipt of a Binding Update option (Section 5.1). When a node
receives a packet containing a Binding Update option, with this receives a packet containing a Binding Update option, with this
node being the destination of the packet (only the destination node being the destination of the packet (only the destination node
node processes the option since it is a destination option), processes the option since it is a destination option), this node
this node MUST return a Binding Acknowledgement to the source MUST return a Binding Acknowledgement to the source of the packet,
of the packet, if the Acknowledge (A) bit is set in the Binding if the Acknowledge (A) bit is set in the Binding Update. As a
Update. As a destination option, this node MAY included the Binding destination option, this node MAY include the Binding Acknowledgement
Acknowledgement in any existing packet being sent to the mobile node in any existing packet being sent to the mobile node or MAY send it
or MAY send it in a packet by itself. A packet containing a Binding in a packet by itself. A packet containing a Binding Acknowledgement
Acknowledgement is sent in the same way as any packet to a mobile is sent in the same way as any packet to a mobile node, using a
node, using a Routing header to route the packet to the mobile node Routing header to route the packet to the mobile node by way of the
by way of the care-of address in the binding (Section 8.9). care-of address in the binding (Section 8.9).
The Binding Acknowledgement option is encoded in type-length-value The Binding Acknowledgement option is encoded in type-length-value
(TLV) format as follows: (TLV) format 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
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| Option Type | | Option Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Length | Status | Sequence Number | | Option Length | Status | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime | | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Refresh | | Refresh |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Options... | Sub-Options...
+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-
Option Type Option Type
2 ??? 7
Option Length Option Length
8-bit unsigned integer. Length of the option, in octets, 8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Option Length fields. This field excluding the Option Type and Option Length fields. This field
MUST be set to 11 plus the total length of all sub-options MUST be set to 11 plus the total length of all sub-options
present, including their Sub-Option Type and Sub-Option Len present, including their Sub-Option Type and Sub-Option Len
fields. fields.
Status Status
skipping to change at page 24, line 25 skipping to change at page 24, line 25
130 Administratively prohibited 130 Administratively prohibited
131 Insufficient resources 131 Insufficient resources
132 Home registration not supported 132 Home registration not supported
133 Not home subnet 133 Not home subnet
134 Sequence Number field value too small 134 Sequence Number field value too small
135 Dynamic home agent address discovery response 135 Dynamic home agent address discovery response
136 Incorrect interface identifier length 136 Incorrect interface identifier length
137 Not home agent for this mobile node 137 Not home agent for this mobile node
Up-to-date values of the Status field are to be specified in Up-to-date values of the Status field are to be specified in
the most recent "Assigned Numbers" [21]. the most recent "Assigned Numbers" [22].
Sequence Number Sequence Number
The Sequence Number in the Binding Acknowledgement is copied The Sequence Number in the Binding Acknowledgement is copied
from the Sequence Number field in the Binding Update being from the Sequence Number field in the Binding Update being
acknowledged, for use by the mobile node in matching this acknowledged, for use by the mobile node in matching this
Acknowledgement with an outstanding Binding Update. Acknowledgement with an outstanding Binding Update.
Lifetime Lifetime
skipping to change at page 25, line 34 skipping to change at page 25, line 34
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. The following sub-options are described in Section 5.5. The following
sub-options are valid in a Binding Acknowledgement option: sub-options are valid in a Binding Acknowledgement option:
- Home Agents List Sub-Option - Home Agents List Sub-Option
Any packet that includes a Binding Acknowledgement option MUST Any packet that includes a Binding Acknowledgement option MUST
also include either an AH [8] or ESP [9] header providing sender also include either an AH [9] or ESP [10] header providing sender
authentication, data integrity protection, and replay protection. authentication, data integrity protection, and replay protection.
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 a
skipping to change at page 27, line 27 skipping to change at page 27, line 27
format as follows: format as follows:
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
| Option Type | Option Length | Sub-Options... | Option Type | Option Length | Sub-Options...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Option Type Option Type
3 ??? 8
Option Length Option Length
8-bit unsigned integer. Length of the option, in octets, 8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Option Length fields. This field excluding the Option Type and Option Length fields. This field
MUST be set to 0 plus the total length of all sub-options MUST be set to 0 plus the total length of all sub-options
present, including their Sub-Option Type and Sub-Option Len present, including their Sub-Option Type and Sub-Option Len
fields. fields.
Sub-Options Sub-Options
skipping to change at page 29, line 39 skipping to change at page 29, line 39
+ Home Address + + Home Address +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Options... | Sub-Options...
+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-
Option Type Option Type
196 ??? 201 = 0xC9
Option Length Option Length
8-bit unsigned integer. Length of the option, in octets, 8-bit unsigned integer. Length of the option, in octets,
excluding the Option Type and Option Length fields. This field excluding the Option Type and Option Length fields. This field
MUST be set to 16 plus the total length of all sub-options MUST be set to 16 plus the total length of all sub-options
present, including their Sub-Option Type and Sub-Option Len present, including their Sub-Option Type and Sub-Option Len
fields. fields.
Home Address Home Address
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- Sub-Option Type: 1 - Sub-Option Type: 1
- Sub-Option Len: 2 - Sub-Option Len: 2
Home Agents List Sub-Option Home Agents List Sub-Option
This sub-option is valid only in a Binding Acknowledgement This sub-option is valid only in a Binding Acknowledgement
destination option. The Sub-Option Data contains a list of destination option. The Sub-Option Data contains a list of
home agents on the home link for the mobile node to which home agents on the home link for the mobile node to which
this Binding Acknowledgement is sent. This sub-option MUST this Binding Acknowledgement is sent. This sub-option MUST
NOT be present unless the Binding Acknowledgement is sent in NOT be present unless the Binding Acknowledgement is sent
response to an anycast Binding Update sent by a mobile node in response to a "Mobile IPv6 Home-Agents" anycast Binding
attempting dynamic home agent address discovery. In this case, Update sent by a mobile node attempting dynamic home agent
the Status field in the Binding Acknowledgement MUST be set address discovery [8]. In this case, the Status field in the
to 135 (dynamic home agent address discovery response). The Binding Acknowledgement MUST be set to 135 (dynamic home agent
specific construction of the Sub-Option Data field for this address discovery response). The specific construction of
sub-option is defined in Section 9.2. The Sub-Option Type the Sub-Option Data field for this sub-option is defined in
and Sub-Option Len fields for this sub-option MUST be set as Section 9.2. The Sub-Option Type and Sub-Option Len fields for
follows: this sub-option MUST be set as follows:
- Sub-Option Type: 2 - Sub-Option Type: 2
- Sub-Option Len: 16 * N, where N is the number of home - Sub-Option Len: 16 * N, where N is the number of home
agent addresses included in the Sub-Option Data. agent addresses included in the Sub-Option Data.
6. Modifications to IPv6 Neighbor Discovery 6. Modifications to IPv6 Neighbor Discovery
6.1. Modified Router Advertisement Message Format 6.1. Modified Router Advertisement Message Format
Mobile IPv6 modifies the format of the Router Advertisement Mobile IPv6 modifies the format of the Router Advertisement
message [13] by the addition of a single flag bit for use in the message [14] by the addition of a single flag bit for use in the
dynamic home agent address discovery mechanism (Sections 9.2 dynamic home agent address discovery mechanism (Sections 9.2
and 10.6). The format of the Router Advertisement message is and 10.6). The format of the Router Advertisement message is
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum | | Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O|H| Reserved| Router Lifetime | | Cur Hop Limit |M|O|H| Reserved| Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time | | Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer | | Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ... | Options ...
+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-+-
This format represents the following changes over that originally This format represents the following changes over that originally
specified for Neighbor Discovery [13]: specified for Neighbor Discovery [14]:
Home Agent (H) Home Agent (H)
The Home Agent (H) bit is set in a Router Advertisement to The Home Agent (H) bit is set in a Router Advertisement to
indicate that the router sending this Router Advertisement is indicate that the router sending this Router Advertisement is
also functioning as a Mobile IP home agent. also functioning as a Mobile IP home agent.
Reserved Reserved
Reduced from a 6-bit field to a 5-bit field to account for the Reduced from a 6-bit field to a 5-bit field to account for the
skipping to change at page 34, line 20 skipping to change at page 34, line 20
- To allow a home agent (a router) to learn the address of all - To allow a home agent (a router) to learn the address of all
other home agents on the link for which it is providing home other home agents on the link for which it is providing home
agent service, for use in building its Home Agents List as agent service, for use in building its Home Agents List as
part of the dynamic home agent address discovery mechanism part of the dynamic home agent address discovery mechanism
(Sections 9.2 and 10.6). (Sections 9.2 and 10.6).
- To allow a mobile node to send a Binding Update to its previous - To allow a mobile node to send a Binding Update to its previous
default router, after moving to a new subnet and acquiring a new default router, after moving to a new subnet and acquiring a new
care-of address (Section 10.8). care-of address (Section 10.8).
However, Neighbor Discovery [13] only advertises a router's However, Neighbor Discovery [14] only advertises a router's
link-local address, by requiring this address to be used as the IP link-local address, by requiring this address to be used as the IP
Source Address of each Router Advertisement. Source Address of each Router Advertisement.
Mobile IPv6 extends Neighbor Discovery to allow a router to easily Mobile IPv6 extends Neighbor Discovery to allow a router to easily
and efficiently advertise its global address, by the addition of a and efficiently advertise its global address, by the addition of a
single flag bit in the format of a Prefix Information option for single flag bit in the format of a Prefix Information option for
use in Router Advertisement messages. The format of the Prefix use in Router Advertisement messages. The format of the Prefix
Information option is as follows: Information option is as follows:
0 1 2 3 0 1 2 3
skipping to change at page 34, line 51 skipping to change at page 34, line 51
| | | |
+ + + +
| | | |
+ Prefix + + Prefix +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This format represents the following changes over that originally This format represents the following changes over that originally
specified for Neighbor Discovery [13]: specified for Neighbor Discovery [14]:
Router Address (R) Router Address (R)
1-bit router address flag. When set, indicates that the 1-bit router address flag. When set, indicates that the
Prefix field, in addition to advertising the indicated prefix, Prefix field, in addition to advertising the indicated prefix,
contains a complete IP address assigned to the sending router. contains a complete IP address assigned to the sending router.
This router IP address has the same scope and conforms to the This router IP address has the same scope and conforms to the
same lifetime values as the advertised prefix. This use of same lifetime values as the advertised prefix. This use of
the Prefix field is compatible with its use in advertising the Prefix field is compatible with its use in advertising
the prefix itself, since prefix advertisement uses only the the prefix itself, since prefix advertisement uses only the
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Reserved1 Reserved1
Reduced from a 6-bit field to a 5-bit field to account for the Reduced from a 6-bit field to a 5-bit field to account for the
addition of the Router Address (R) bit. addition of the Router Address (R) bit.
In a solicited Router Advertisement, a router MUST include at least In a solicited Router Advertisement, a router MUST include at least
one Prefix Information option with the Router Address (R) bit set. one Prefix Information option with the Router Address (R) bit set.
Neighbor Discovery specifies that, if including all options in a Neighbor Discovery specifies that, if including all options in a
Router Advertisement causes the size of the Advertisement to exceed Router Advertisement causes the size of the Advertisement to exceed
the link MTU, multiple Advertisements can be sent, each containing the link MTU, multiple Advertisements can be sent, each containing
a subset of the options [13]. In this case, at least one of these a subset of the options [14]. In this case, at least one of these
multiple Advertisements being sent instead of a single larger multiple Advertisements being sent instead of a single larger
solicited Advertisement, MUST include a Prefix Information option solicited Advertisement, MUST include a Prefix Information option
with the Router Address (R) bit set. with the Router Address (R) bit set.
All routers SHOULD include at least on Prefix Information option with All routers SHOULD include at least on Prefix Information option with
the Router Address (R) bit set, in each unsolicited multicast Router the Router Address (R) bit set, in each unsolicited multicast Router
Advertisement that they send. If multiple Advertisements are being Advertisement that they send. If multiple Advertisements are being
sent instead of a single larger unsolicited multicast Advertisement, sent instead of a single larger unsolicited multicast Advertisement,
at least one of these multiple Advertisements SHOULD include a Prefix at least one of these multiple Advertisements SHOULD include a Prefix
Information option with the Router Address (R) bit set. Information option with the Router Address (R) bit set.
skipping to change at page 36, line 22 skipping to change at page 36, line 22
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved | | Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertisement Interval | | Advertisement Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Type
6 ??? 7
Length Length
8-bit unsigned integer. The length of the option (including 8-bit unsigned integer. The length of the option (including
the type and length fields) in units of 8 octets. The value of the type and length fields) in units of 8 octets. The value of
this field MUST be 1. this field MUST be 1.
Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
sender and MUST be ignored by the receiver. sender and MUST be ignored by the receiver.
Advertisement Interval Advertisement Interval
32-bit unsigned integer. The maximum time, in milliseconds, 32-bit unsigned integer. The maximum time, in milliseconds,
between successive unsolicited router Router Advertisement between successive unsolicited router Router Advertisement
messages sent by this router on this network interface. Using messages sent by this router on this network interface. Using
the conceptual router configuration variables defined by the conceptual router configuration variables defined by
Neighbor Discovery [13], this field MUST be equal to the value Neighbor Discovery [14], this field MUST be equal to the value
MaxRtrAdvInterval, expressed in milliseconds. MaxRtrAdvInterval, expressed in milliseconds.
Routers MAY include this option in their Router Advertisements. A Routers MAY include this option in their Router Advertisements. A
mobile node receiving a Router Advertisement containing this option mobile node receiving a Router Advertisement containing this option
SHOULD utilize the specified Advertisement Interval for that router SHOULD utilize the specified Advertisement Interval for that router
in its movement detection algorithm, as described in Section 10.3. in its movement detection algorithm, as described in Section 10.3.
This option MUST be silently ignored for other Neighbor Discovery This option MUST be silently ignored for other Neighbor Discovery
messages. messages.
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0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved | | Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Home Agent Preference | Home Agent Lifetime | | Home Agent Preference | Home Agent Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Type
7 ??? 8
Length Length
8-bit unsigned integer. The length of the option (including 8-bit unsigned integer. The length of the option (including
the type and length fields) in units of 8 octets. The value of the type and length fields) in units of 8 octets. The value of
this field MUST be 1. this field MUST be 1.
Reserved Reserved
This field is unused. It MUST be initialized to zero by the This field is unused. It MUST be initialized to zero by the
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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 the home agent sending this Router Advertisement, for use
in ordering the addresses contained in the Home Agents List in ordering the addresses contained in the Home Agents List
Sub-Option returned in a Binding Acknowledgement; higher values Sub-Option returned in a Binding Acknowledgement; higher values
mean more preferable. If this option is not included in a mean more preferable. If this option is not included in a
Router Advertisement in which the Home Agent (H) bit is set, Router Advertisement in which the Home Agent (H) bit is set,
the preference value for this home agent SHOULD be considered the preference value for this home agent SHOULD be considered
to be 0. Values greater than 0 indicate a home agent more to be 0. Values greater than 0 indicate a home agent more
preferable than this default value, and values less than 0 preferable than this default value, and values less than 0
indicate a less preferable home agent. indicate a less preferable home agent. In addition to the
manual configuration of the Home Agent Preference value as
described in Section 7.3, the Home Agent Preference sent by
a home agent could, for example, be set dynamically by the
sending home agent based on the number of mobile nodes it is
currently serving or on its remaining resources for serving
additional mobile nodes, but such dynamic settings are beyond
the scope of this document.
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,
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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
The Neighbor Discovery protocol specification [13] limits routers to The Neighbor Discovery protocol specification [14] limits routers to
a minimum interval of 3 seconds between sending unsolicited multicast a minimum interval of 3 seconds between sending unsolicited multicast
Router Advertisement messages from any given network interface Router Advertisement messages from any given network interface
(limited by MinRtrAdvInterval and MaxRtrAdvInterval), stating that: (limited by MinRtrAdvInterval and MaxRtrAdvInterval), stating that:
"Routers generate Router Advertisements frequently enough "Routers generate Router Advertisements frequently enough
that hosts will learn of their presence within a few that hosts will learn of their presence within a few
minutes, but not frequently enough to rely on an absence minutes, but not frequently enough to rely on an absence
of advertisements to detect router failure; a separate of advertisements to detect router failure; a separate
Neighbor Unreachability Detection algorithm provides failure Neighbor Unreachability Detection algorithm provides failure
detection." detection."
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- Every home agent MUST be able to encapsulate such intercepted - Every home agent MUST be able to encapsulate such intercepted
packets in order to tunnel them to the primary care-of address packets in order to tunnel them to the primary care-of address
for the mobile node indicated in its binding in the home agent's for the mobile node indicated in its binding in the home agent's
Binding Cache. Binding Cache.
- Every home agent MUST be able to return a Binding Acknowledgement - Every home agent MUST be able to return a Binding Acknowledgement
option in response to a Binding Update option received with the option in response to a Binding Update option received with the
Acknowledge (A) bit set. Acknowledge (A) bit set.
- Every home agent MUST be able to accept packets addressed to the - Every home agent MUST be able to accept packets addressed
Home-Agents anycast address for the subnet on which it is serving to the "Mobile IPv6 Home-Agents" anycast address for the
as a home agent, and MUST be able to participate in dynamic home subnet on which it is serving as a home agent [8], and MUST be
agent address discovery (Section 9.2). able to participate in dynamic home agent address discovery
(Section 9.2).
- Every home agent SHOULD support a configuration mechanism to
allow a system administrator to manually set the value to be sent
by this home agent in the Home Agent Preference field of the Home
Agent Information Option in Router Advertisements that it sends.
7.4. Requirements for IPv6 Mobile Nodes 7.4. Requirements for IPv6 Mobile Nodes
Finally, the following requirements apply to all IPv6 nodes capable Finally, the following requirements apply to all IPv6 nodes capable
of functioning as mobile nodes: of functioning as mobile nodes:
- Every IPv6 mobile node MUST be able to perform IPv6 - Every IPv6 mobile node MUST be able to perform IPv6
decapsulation [4]. decapsulation [4].
- Every IPv6 mobile node MUST support sending Binding Update - Every IPv6 mobile node MUST support sending Binding Update
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the care-of address and Home Address option is transparent to both the care-of address and Home Address option is transparent to both
the mobile node and the correspondent node above the level of the the mobile node and the correspondent node above the level of the
Home Address option generation and processing. 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 contains a valid AH [8] or ESP [9] header that - The packet contains a valid AH [9] or ESP [10] header that
provides sender authentication, integrity protection, and replay provides sender authentication, integrity protection, and replay
protection. protection.
- The packet MUST contain a valid Home Address option. The home - The packet MUST contain a valid Home Address option. The home
address for the binding is specified by the Home Address field of address for the binding is specified by the Home Address field of
the Home Address option. 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.
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performed modulo 2**16. 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.
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 Destination Address in the packet's IPv6 header is the - If the Destination Address in the packet's IPv6 header is the
Home-Agents anycast address for an on-local prefix and this "Mobile IPv6 Home-Agents" anycast address [8] for an on-link
address is assigned to one of this node's network interfaces, prefix and this address is assigned to one of this node's network
then the mobile node sending this Binding Update is attempting interfaces, then the mobile node sending this Binding Update is
dynamic home agent address discovery. Processing for this type attempting dynamic home agent address discovery. Processing for
of received Binding Update is described in Section 9.2. (If the this type of received Binding Update is described in Section 9.2.
Destination Address is not assigned to one of this node's network (If the Destination Address is not assigned to one of this node's
interfaces, then the packet would have been forwarded as a normal network interfaces, then the packet would have been forwarded as
packet and the Binding Update, as a destination option, would not a normal packet and the Binding Update, as a destination option,
be processed in any way by this node.) would not be processed in any way by this node.)
- 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 (as given in the Home Address option in the
packet), then this is a request to cache a binding for the packet), then this is a request to cache a binding for 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.
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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 SHOULD 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 an
entry in its Binding Cache for this binding, the Status field in entry in its Binding Cache for this binding, the Status field in
the Binding Acknowledgement MUST be set to a value less than 128; the Binding Acknowledgement MUST be set to a value less than 128;
if the node rejects the Binding Update and does not create or if the node rejects the Binding Update and does not create or
update an entry for this binding, the Status field in the Binding update an entry for this binding, the Status field in the Binding
Acknowledgement MUST be set to a value greater than or equal to 128. 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 Specific values for the Status field are described in Section 5.2 and
in the most recent "Assigned Numbers" [21]. in the most recent "Assigned Numbers" [22].
As described in Section 5.2, the packet in which the Binding As described in Section 5.2, the packet in which the Binding
Acknowledgement is returned MUST include either an AH [8] or ESP [9] Acknowledgement is returned MUST include either an AH [9] or ESP [10]
header providing sender authentication, data integrity protection, header providing sender authentication, data integrity protection,
and replay protection; and the packet MUST be sent using a Routing and replay protection; and the packet MUST be sent using a Routing
header in the same way as any other packet sent to a mobile node header 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 using a care-of address (even if the binding was rejected), as
described in Section 8.9. The packet is routed first to the care-of described in Section 8.9. The packet is routed first to the care-of
address contained in the Binding Update being acknowledged, and address contained in the Binding Update being acknowledged, and
then to the mobile node's home address. This use of the Routing then to the mobile node's home address. This use of the Routing
header ensures that the Binding Acknowledgement will be routed to the header ensures that the Binding Acknowledgement will be routed to the
current location of the node sending the Binding Update, whether the current location of the node sending the Binding Update, whether the
Binding Update was accepted or rejected. Binding Update was accepted or rejected.
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9.1. Receiving Router Advertisement Messages 9.1. Receiving Router Advertisement Messages
For each link on which a router provides service as a home agent, the For each link on which a router provides service as a home agent, the
router maintains a Home Agents List recording information about all router maintains a Home Agents List recording information about all
other home agents on that link. This list is used in the dynamic other home agents on that link. This list is used in the dynamic
home agent address discovery mechanism, described in Section 9.2. home agent address discovery mechanism, described in Section 9.2.
The information for the list is learned through receipt of the The information for the list is learned through receipt of the
periodic unsolicited multicast Router Advertisements from each other periodic unsolicited multicast Router Advertisements from each other
home agent on the link, in which the Home Agent (H) bit is set, in a home agent on the link, in which the Home Agent (H) bit is set, in a
manner similar to the Default Router List conceptual data structure manner similar to the Default Router List conceptual data structure
maintained by each host for Neighbor Discovery [13]. maintained by each host for Neighbor Discovery [14].
On receipt of a valid Router Advertisement, as defined in the On receipt of a valid Router Advertisement, as defined in the
processing algorithm specified for Neighbor Discovery [13], the home processing algorithm specified for Neighbor Discovery [14], the home
agent performs the following steps, in addition to any steps already agent performs the following steps, in addition to any steps already
required of it by Neighbor Discovery: required of it by Neighbor Discovery:
- If the Home Agent (H) bit in the Router Advertisement is not set, - If the Home Agent (H) bit in the Router Advertisement is not set,
skip all of the following steps. There are no special processing skip all of the following steps. There are no special processing
steps required by Mobile IP for this Router Advertisement, since steps required by Mobile IP for this Router Advertisement, since
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 [13]. link of the home agent sending this Advertisement [14].
- 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 SHOULD 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
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9.2. Dynamic Home Agent Address Discovery 9.2. Dynamic Home Agent Address Discovery
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 indicates that the mobile node sending it is Binding Update that indicates that the mobile node sending it is
attempting dynamic home agent address discovery. attempting dynamic home agent address discovery.
As described in Section 10.6, a mobile node attempts dynamic home As described in Section 10.6, a mobile node attempts dynamic home
agent address discovery by sending its "home registration" Binding agent address discovery by sending its "home registration" Binding
Update to the Home-Agents anycast address for its home IP subnet Update to the "Mobile IPv6 Home-Agents" anycast address [8] for its
prefix (the packet MUST also include a Home Address option). A home home IP subnet prefix (the packet MUST also include a Home Address
agent receiving such a Binding Update that is serving this subnet option). A home agent receiving such a Binding Update that is
(the home agent is configured with this anycast address on one of its serving this subnet (the home agent is configured with this anycast
network interfaces) MUST reject the Binding Update and SHOULD return address on one of its network interfaces) MUST reject the Binding
a Binding Acknowledgement indicating this rejection, with the Source Update and SHOULD return a Binding Acknowledgement indicating this
Address of the packet carrying the Binding Acknowledgement set to one rejection, with the Source Address of the packet carrying the Binding
of the global unicast addresses of the home agent. The Status field Acknowledgement set to one of the global unicast addresses of the
in the Binding Acknowledgement MUST be set to 135 (dynamic home agent home agent. The Status field in the Binding Acknowledgement MUST be
address discovery response). set to 135 (dynamic home agent address discovery response).
In this Binding Acknowledgement rejecting the dynamic home agent In this Binding Acknowledgement rejecting the dynamic home agent
address discovery Binding Update, this home agent SHOULD include a address discovery Binding Update, this home agent SHOULD include a
Home Agents List Sub-Option as follows: Home Agents List Sub-Option as follows:
- The Home Agents List Sub-Option in this Binding Acknowledgement - The Home Agents List Sub-Option in this Binding Acknowledgement
SHOULD contain one global IP address for each home agent SHOULD contain one global IP address for each home agent
currently listed in this home agent's own Home Agents List currently listed in this home agent's own Home Agents List
(Section 4.3). However, if this home agent's own global IP (Section 4.3). However, if this home agent's own global IP
address would be placed in the list (as described below) as the address would be placed in the list (as described below) as the
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IPv6 header (otherwise). 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
Binding Update into the corresponding bit in this Binding Cache entry
for this mobile node.
The lifetime for the Binding Cache entry MUST NOT be greater than The lifetime for the Binding Cache entry MUST NOT be greater than
the remaining valid lifetime for the subnet prefix in the mobile the remaining valid lifetime for the subnet prefix in the mobile
node's home address specified with the Binding Update. The remaining node's home address specified with the Binding Update. The remaining
valid lifetime for this prefix is determined by the home agent based valid lifetime for this prefix is determined by the home agent based
on its own Prefix List entry for this prefix [13]. Furthermore, on its own Prefix List entry for this prefix [14]. Furthermore,
if the Prefix Length field in the Binding Update is nonzero, then if the Prefix Length field in the Binding Update is nonzero, then
the lifetime for the Binding Cache entry MUST NOT be greater than the lifetime for the Binding Cache entry MUST NOT be greater than
the minimum remaining valid lifetime for all subnet prefixes on the minimum remaining valid lifetime for all subnet prefixes on
the mobile node's home link. If the value of the Lifetime field the mobile node's home link. If the value of the Lifetime field
specified by the mobile node in its Binding Update is greater than specified by the mobile node in its Binding Update is greater than
this prefix lifetime, the home agent MUST decrease the binding this prefix lifetime, the home agent MUST decrease the binding
lifetime to less than or equal to the prefix valid lifetime. The lifetime to less than or equal to the prefix valid lifetime. The
home agent MAY further decrease the specified lifetime for 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
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node has an entry in its Binding Cache for this mobile node that is node has an entry in its Binding Cache for this mobile node that is
marked as a "home registration"), this node MUST attempt to intercept marked as a "home registration"), this node MUST attempt to intercept
packets on the mobile node's home link addressed to the mobile node, packets on the mobile node's home link addressed to the mobile node,
and MUST tunnel each intercepted packet to the mobile node using and MUST tunnel each intercepted packet to the mobile node using
using IPv6 encapsulation [4]. using IPv6 encapsulation [4].
In order to intercept such packets on the home link, when a node In order to intercept such packets on the home link, when a node
becomes the home agent for some mobile node (it did not already becomes the home agent for some mobile node (it did not already
have a Binding Cache entry for this mobile node marked as a "home have a Binding Cache entry for this mobile node marked as a "home
registration"), then the home agent MUST multicast onto the home link registration"), then the home agent MUST multicast onto the home link
a "gratuitous" Neighbor Advertisement message [13] on behalf of the a "gratuitous" Neighbor Advertisement message [14] on behalf of the
mobile node. Specifically, the home agent performs the following mobile node. Specifically, the home agent performs the following
steps: steps:
- The home agent examines the value of the Prefix Length field - The home agent examines the value of the Prefix Length field
in the new "home registration" Binding Cache entry. If this in the new "home registration" Binding Cache entry. If this
value is zero, the following step is carried out only for the value is zero, the following step is carried out only for the
individual home address specified for this binding. If, instead, individual home address specified for this binding. If, instead,
this field is nonzero, then the following step is carried out this field is nonzero, then the following step is carried out
for each address for the mobile node formed from the interface for each address for the mobile node formed from the interface
identifier in the mobile node's home address in this binding identifier in the mobile node's home address in this binding
(the remaining low-order bits in the address after the indicated (the remaining low-order bits in the address after the indicated
subnet prefix), together with each one of the subnet prefixes subnet prefix), together with each one of the subnet prefixes
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 [13] on behalf of the mobile node, to Advertisement message [14] 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. The Target Address in the Neighbor Advertisement address. The Target Address in the Neighbor Advertisement
message MUST be set to this IP address for the mobile node, and message MUST be set to this IP address for the mobile node, and
the Advertisement MUST include a Target Link-layer Address option the Advertisement MUST include a Target Link-layer Address option
specifying the home agent's link-layer address. The Solicited specifying the home agent's link-layer address. In addition,
Flag (S) in the Advertisement MUST NOT be set, since it was not the Router (R) bit in the Advertisement MUST be copied from the
solicited by any Neighbor Solicitation message. The Override corresponding bit in the home agent's Binding Cache entry for
Flag (O) in the Advertisement MUST be set, indicating that the the mobile node. The Solicited Flag (S) in the Advertisement
Advertisement SHOULD override any existing Neighbor Cache entry MUST NOT be set, since it was not solicited by any Neighbor
at any node receiving it. 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
possible that some nodes on the home link will not receive any of possible that some nodes on the home link will not receive any of
these Neighbor Advertisements, but these nodes will eventually be these Neighbor Advertisements, but these nodes will eventually be
able to detect the link-layer address change for the mobile node's able to detect the link-layer address change for the mobile node's
home address, through use of Neighbor Unreachability Detection [13]. home address, through use of Neighbor Unreachability Detection [14].
While a node is serving as a home agent for some mobile node (it While a node is serving as a home agent for some mobile node (it
still has a "home registration" entry for this mobile node in its still has a "home registration" entry for this mobile node in its
Binding Cache), the home agent uses IPv6 Neighbor Discovery [13] Binding Cache), the home agent uses IPv6 Neighbor Discovery [14]
to intercept unicast packets on the home link addressed the mobile to intercept unicast packets on the home link addressed the mobile
node's home address. In order to intercept packets in this way, node's home address. In order to intercept packets in this way,
the home agent MUST act as a proxy for this mobile node to reply to the home agent MUST act as a proxy for this mobile node to reply to
any received Neighbor Solicitation messages for it. When a home any received Neighbor Solicitation messages for it. When a home
agent receives a Neighbor Solicitation message, it MUST check if the agent receives a Neighbor Solicitation message, it MUST check if the
Target Address specified in the message matches the home address Target Address specified in the message matches the home address
of any mobile node for which it has a Binding Cache entry marked of any mobile node for which it has a Binding Cache entry marked
as a "home registration". This check MUST include all possible as a "home registration". This check MUST include all possible
home addresses for the mobile node, based on the subnet prefixes home addresses for the mobile node, based on the subnet prefixes
currently considered to be on-link by the home agent (including the currently considered to be on-link by the home agent (including the
corresponding link-local address and site-local address), if the corresponding link-local address and site-local address), if the
Prefix Length in the Binding Cache entry for this mobile node (from Prefix Length in the Binding Cache entry for this mobile node (from
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. Acting as the link-layer address for the specified Target Address. In
as a proxy in this way allows other nodes on the mobile node's home addition, the Router (R) bit in the Advertisement MUST be copied from
link to resolve the mobile node's IPv6 home address, and allows the corresponding bit in the home agent's Binding Cache entry for the
the home agent to to defend these addresses on the home link for mobile node. Acting as a proxy in this way allows other nodes on
Duplicate Address Detection [13]. 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
the home link for Duplicate Address Detection [14].
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
primary care-of address, in this case). primary care-of address, in this case).
While the mobile node is away from home and this node is acting While the mobile node is away from home and this node is acting
as the mobile node's home agent, the home agent intercepts any as the mobile node's home agent, the home agent intercepts any
packets on the home link addressed to the mobile node's home address packets on the home link addressed to the mobile node's home address
(including addresses formed from other on-link prefixes, if the (including addresses formed from other on-link prefixes, if the
Prefix Length field was nonzero in the Binding Update), as described Prefix Length field was nonzero in the Binding Update), as described
in Section 9.5. The home agent cannot use a Routing header to in Section 9.5. The home agent cannot use a Routing header to
forward these intercepted packets to the mobile node, since it cannot forward these intercepted packets to the mobile node, since it cannot
modify the packet in flight without invalidating any existing IPv6 modify the packet in flight without invalidating any existing IPv6
AH [8] or ESP [9] header present in the packet. AH [9] or ESP [10] header present in the packet.
For forwarding each intercepted packet to the mobile node, the For forwarding each intercepted packet to the mobile node, the
home agent MUST tunnel the packet to the mobile node using IPv6 home agent MUST tunnel the packet to the mobile node using IPv6
encapsulation [4]; the tunnel entry point node is the home agent, encapsulation [4]; the tunnel entry point node is the home agent,
and the tunnel exit point node is the primary care-of address as and the tunnel exit point node is the primary care-of address as
registered with the home agent (which is an address of the mobile registered with the home agent (which is an address of the mobile
node itself). When a home agent encapsulates an intercepted packet node itself). When a home agent encapsulates an intercepted packet
for forwarding to the mobile node, the home agent sets the Source for forwarding to the mobile node, the home agent sets the Source
Address in the prepended tunnel IP header to the home agent's own IP Address in the prepended tunnel IP header to the home agent's own IP
address, and sets the Destination Address in the tunnel IP header address, and sets the Destination Address in the tunnel IP header
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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) [7], to which the mobile node is subscribed, organization-local) [7], 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. Renumbering the Home Subnet
IPv6 provides mechanisms through Neighbor Discovery [13] and Address IPv6 provides mechanisms through Neighbor Discovery [14] and Address
Autoconfiguration [22] to aid in renumbering a subnet, such as when a Autoconfiguration [23] 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.
The IPv6 renumbering mechanisms are based on nodes on the link The IPv6 renumbering mechanisms are based on nodes on the link
receiving Prefix Information options in Router Advertisement messages receiving Prefix Information options in Router Advertisement messages
giving the valid lifetime and preferred lifetime for different giving the valid lifetime and preferred lifetime for different
prefixes on the link [13]. Mobile IPv6 arranges to tunnel certain prefixes on the link [14]. Mobile IPv6 arranges to tunnel certain
Router Advertisements giving "important" Prefix Information options Router Advertisements giving "important" Prefix Information options
to mobile nodes while away from home. To avoid the need to tunnel to mobile nodes while away from home. To avoid the need to tunnel
all Router Advertisements from the home link to a mobile node away all Router Advertisements from the home link to a mobile node away
from home, those Router Advertisements that are tunneled to the from home, those Router Advertisements that are tunneled to the
mobile node are retransmitted until acknowledged. To avoid possible mobile node are retransmitted until acknowledged. To avoid possible
security attacks from forged Router Advertisements tunneled to security attacks from forged Router Advertisements tunneled to
the mobile node, all such tunneled Router Advertisements must be the mobile node, all such tunneled Router Advertisements must be
authenticated to the mobile node by its home agent using AH [8] or authenticated to the mobile node by its home agent using AH [9] or
ESP [9]. ESP [10].
Specifically, a home agent serving some mobile node SHOULD construct Specifically, a home agent serving some mobile node SHOULD construct
and tunnel to the mobile node a new Router Advertisement when any of and tunnel to the mobile node a new Router Advertisement when any of
the following conditions occur: the following conditions occur:
- The preferred or valid lifetime for an existing prefix on the - The preferred or valid lifetime for an existing prefix on the
home link is reduced. home link is reduced.
- 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 [13] changes - The state of the home agent's AdvManagedFlag flag [14] changes
from FALSE to TRUE or from TRUE to FALSE. from FALSE to TRUE or from TRUE to FALSE.
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 it receives on the home link. The home agent constructs a new that it receives on the home link. The home agent constructs a new
Router Advertisement message containing no options other than the Router Advertisement message containing no options other than the
Prefix Information options describing the prefixes for which one of Prefix Information options describing the prefixes for which one of
the conditions above has occurred since the last Router Advertisement the conditions above has occurred since the last Router Advertisement
tunneled to and acknowledged by the mobile node. When multiple tunneled to and acknowledged by the mobile node. When multiple
conditions occur at or near the same time, the home agent SHOULD conditions occur at or near the same time, the home agent SHOULD
attempt to combine them into a single Router Advertisement message to attempt to combine them into a single Router Advertisement message to
the mobile node. the mobile node.
In tunneling each such Router Advertisement to the mobile node, the In tunneling each such Router Advertisement to the mobile node, the
home agent MUST construct the packet as follows: 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 include either an AH [8] or ESP [9] header - The packet MUST include either an AH [9] or ESP [10] header
providing sender authentication, data integrity protection, and providing sender authentication, data integrity protection, and
replay protection. replay protection.
- The packet MUST include a Binding Request destination option. - The packet MUST include a Binding Request destination option.
- The Binding Request destination option MUST include a Unique - The Binding Request destination option MUST include a Unique
Identifier Sub-Option (Section 5.5), with the unique identifier Identifier Sub-Option (Section 5.5), with the unique identifier
in the sub-option data set to a value different than that in in the sub-option data set to a value different than that in
any other Binding Request sent recently by this node. The word any other Binding Request sent recently by this node. The word
"recently" here means within the maximum likely lifetime of a "recently" here means within the maximum likely lifetime of a
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the packet are then reversed in the node receiving the packet, the packet are then reversed in the node receiving the packet,
restoring the mobile node's home address to be the packet's restoring the mobile node's home address to be the packet's
Source Address before processing by higher protocol layers and Source Address before processing by higher protocol layers and
applications. applications.
- For short-term communication, particularly for communication that - For short-term communication, particularly for communication that
may easily be retried if it fails, the mobile node MAY choose may easily be retried if it fails, the mobile node MAY choose
to directly use one of its care-of addresses as the source of to directly use one of its care-of addresses as the source of
the packet, thus not requiring the use of a Home Address option the packet, thus not requiring the use of a Home Address option
in the packet. An example of this type of communication might in the packet. An example of this type of communication might
be DNS queries sent by the mobile node [11, 12]. Using the be DNS queries sent by the mobile node [12, 13]. Using the
mobile node's care-of address as the source for such queries will mobile node's care-of address as the source for such queries will
generally have a lower overhead than using the mobile node's generally have a lower overhead than using the mobile node's
home address, since no extra options need be used in either the home address, since no extra options need be used in either the
query or its reply, and all packets can be routed normally, query or its reply, and all packets can be routed normally,
directly between their source and destination without relying directly between their source and destination without relying
on Mobile IP. If the mobile node has no particular knowledge on Mobile IP. If the mobile node has no particular knowledge
that the communication being sent fits within this general type that the communication being sent fits within this general type
of communication, however, the mobile node SHOULD NOT use its of communication, however, the mobile node SHOULD NOT use its
care-of address as the source of the packet in this way. care-of address as the source of the packet in this way.
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- Change the Source Address field in the packet's IPv6 header to - Change the Source Address field in the packet's IPv6 header to
one of the mobile node's care-of addresses. This will typically one of the mobile node's care-of addresses. This will typically
be the mobile node's current primary care-of address, but MUST be the mobile node's current primary care-of address, but MUST
be a care-of address with a subnet prefix that is on-link on the be a care-of address with a subnet prefix that is on-link on the
network interface on which the mobile node will transmit the network interface on which the mobile node will transmit the
packet. packet.
This addition of the Home Address option to a packet MUST be This addition of the Home Address option to a packet MUST be
performed before outgoing IPsec processing, such as the addition of performed before outgoing IPsec processing, such as the addition of
an AH [8] or ESP [9] header to the packet, is performed. Likewise, an AH [9] or ESP [10] header to the packet, is performed. Likewise,
IPsec processing for a received packet containing a Home Address IPsec processing for a received packet containing a Home Address
option MUST be performed before the packet is possibly modified as option MUST be performed before the packet is possibly modified as
part of processing the Home Address option. By using the care-of part of processing the Home Address option. By using the care-of
address as the Source Address in the IPv6 header, with the mobile address as the Source Address in the IPv6 header, with the mobile
node's home address instead in the Home Address option, the packet node's home address instead in the Home Address option, the packet
will be able to safely pass through any router implementing ingress will be able to safely pass through any router implementing ingress
filtering [6]. filtering [6].
10.2. Receiving Packets While Away from Home 10.2. Receiving Packets While Away from Home
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SHOULD NOT include a Routing header. SHOULD NOT include a Routing header.
10.3. Movement Detection 10.3. Movement Detection
A mobile node MAY use any combination of mechanisms available to it A mobile node MAY use any combination of mechanisms available to it
to detect when it has moved from one link to another. The primary to detect when it has moved from one link to another. The primary
movement detection mechanism for Mobile IPv6 defined here uses the movement detection mechanism for Mobile IPv6 defined here uses the
facilities of IPv6 Neighbor Discovery, including Router Discovery and facilities of IPv6 Neighbor Discovery, including Router Discovery and
Neighbor Unreachability Detection. The description here is based on Neighbor Unreachability Detection. The description here is based on
the conceptual model of the organization and data structures defined the conceptual model of the organization and data structures defined
by Neighbor Discovery [13]. by Neighbor Discovery [14].
Mobile nodes SHOULD use Router Discovery to discover new routers and Mobile nodes SHOULD use Router Discovery to discover new routers and
on-link subnet prefixes; a mobile node MAY send Router Solicitation on-link subnet prefixes; a mobile node MAY send Router Solicitation
messages, or MAY wait for unsolicited (periodic) multicast Router messages, or MAY wait for unsolicited (periodic) multicast Router
Advertisement messages, as specified for Router Discovery [13]. Advertisement messages, as specified for Router Discovery [14].
Based on received Router Advertisement messages, a mobile node (in Based on received Router Advertisement messages, a mobile node (in
the same way as any other node) maintains an entry in its Default the same way as any other node) maintains an entry in its Default
Router List for each router, and an entry in its Prefix List for each Router List for each router, and an entry in its Prefix List for each
subnet prefix, that it currently considers to be on-link. Each entry subnet prefix, that it currently considers to be on-link. Each entry
in these lists has an associated invalidation timer value (extracted in these lists has an associated invalidation timer value (extracted
from the Router Advertisement) used to expire the entry when it from the Router Advertisement) used to expire the entry when it
becomes invalid. becomes invalid.
While away from home, a mobile node SHOULD select one router from While away from home, a mobile node SHOULD select one router from
its Default Router List to use as its default router, and one subnet its Default Router List to use as its default router, and one subnet
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switch to a new default router and to a new primary care-of address. switch to a new default router and to a new primary care-of address.
Since some links (notably wireless) do not necessarily work equally Since some links (notably wireless) do not necessarily work equally
well in both directions, it is likewise important for the mobile well in both directions, it is likewise important for the mobile
node to detect when it becomes unreachable to packets sent from its node to detect when it becomes unreachable to packets sent from its
default router, so that the mobile node can take steps to ensure that default router, so that the mobile node can take steps to ensure that
any correspondent nodes attempting to communicate with it can still any correspondent nodes attempting to communicate with it can still
reach it through some other route. reach it through some other route.
To detect when its default router becomes unreachable, a mobile To detect when its default router becomes unreachable, a mobile
node SHOULD use Neighbor Unreachability Detection. As specified in node SHOULD use Neighbor Unreachability Detection. As specified in
Neighbor Discovery [13], while the mobile node is actively sending Neighbor Discovery [14], while the mobile node is actively sending
packets to (or through) its default router, the mobile node can packets to (or through) its default router, the mobile node can
detect that the router (as its neighbor) is still reachable either detect that the router (as its neighbor) is still reachable either
through indications from upper layer protocols on the mobile node through indications from upper layer protocols on the mobile node
that a connection is making "forward progress" (e.g., receipt of TCP that a connection is making "forward progress" (e.g., receipt of TCP
acknowledgements for new data transmitted), or through receipt of a acknowledgements for new data transmitted), or through receipt of a
Neighbor Advertisement message from its default router in response Neighbor Advertisement message from its default router in response
to an explicit Neighbor Solicitation messages to it. Note that to an explicit Neighbor Solicitation messages to it. Note that
although this mechanism detects that the mobile node's default router although this mechanism detects that the mobile node's default router
has become unreachable to the mobile node only while the mobile node has become unreachable to the mobile node only while the mobile node
is actively sending packets to it, this is the only time that this is actively sending packets to it, this is the only time that this
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primary care-of address using that router rather than its current primary care-of address using that router rather than its current
default router (and current primary care-of address). Even though default router (and current primary care-of address). Even though
the mobile node's current default router may still be reachable in the mobile node's current default router may still be reachable in
terms of Neighbor Unreachability Detection, the mobile node MAY use terms of Neighbor Unreachability Detection, the mobile node MAY use
such lower-layer information to determine that switching to a new such lower-layer information to determine that switching to a new
default router would provide a better connection. default router would provide a better connection.
10.4. Forming New Care-of Addresses 10.4. Forming New Care-of Addresses
After detecting that it has moved from one link to another (i.e., its After detecting that it has moved from one link to another (i.e., its
current default router has become unreachable and it has discovered a current default router has become unreachable and it has discovered
new default router), a mobile node SHOULD form a new primary care-of a new default router), a mobile node SHOULD form a new primary
address using one of the on-link subnet prefixes advertised by the care-of address using one of the on-link subnet prefixes advertised
new router. A mobile node MAY form a new primary care-of address by the new router. A mobile node MAY form a new primary care-of
at any time, except that it MUST NOT do so too frequently (not more address at any time, except that it MUST NOT do so too frequently.
often than once per MAX_UPDATE_RATE seconds). Specifically, a mobile node MUST NOT send a Binding Update about a
new care-of address to its home agent (which is required to register
the new address as its primary care-of address) more often than once
per MAX_UPDATE_RATE seconds.
In addition, after discovering a new on-link subnet prefix, a mobile In addition, after discovering a new on-link subnet prefix, a mobile
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 10.15. address at a time is described in Section 10.15.
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 [22] or stateful (e.g., a mobile node MAY use either stateless [23] 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
address that has been assigned to it for its use only while address that has been assigned to it for its use only while
visiting a specific foreign link. For example, a mobile node may be visiting a specific foreign link. For example, a mobile node may be
statically configured with an IPv6 address assigned by the system statically configured with an IPv6 address assigned by the system
administrator of some foreign link, for its use while visiting that administrator of some foreign link, for its use while visiting that
link. If so, rather than using address autoconfiguration to form a link. If so, rather than using Address Autoconfiguration to form a
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.
10.5. Sending Binding Updates to the Home Agent 10.5. Sending Binding Updates to the Home Agent
After deciding to change its primary care-of address as described After deciding to change its primary care-of address as described
in Sections 10.3 and 10.4, a mobile node MUST register this care-of in Sections 10.3 and 10.4, a mobile node MUST register this care-of
address with its home agent in order to make this its primary care-of address with its home agent in order to make this its primary care-of
address. To do so, the mobile node sends a packet to its home agent address. To do so, the mobile node sends a packet to its home agent
containing a Binding Update option, with the packet constructed as containing a Binding Update option, with the packet constructed as
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mobile node. As the set of on-link subnet prefixes on the home link mobile node. As the set of on-link subnet prefixes on the home link
changes over time, the home agent changes the set of home addresses changes over time, the home agent changes the set of home addresses
for this mobile node for which it is serving as the home agent. for this mobile node for which it is serving as the home agent.
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 packet containing a Binding Update to its home agent to register
the care-of address for each such other home address (or set of the care-of address for each such other home address (or set of
home addresses sharing an interface identifier). These additional home addresses sharing an interface identifier). These additional
Binding Updates MUST each be sent as a separate packet, since each Binding Updates MUST each be sent as a separate packet, since each
MUST contain an AH [8] or ESP [9] header to authenticate the Binding MUST contain an AH [9] or ESP [10] header to authenticate the Binding
Update as coming from the home address being bound. Update as coming from the home address being bound.
10.6. Dynamic Home Agent Address Discovery 10.6. 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 10.5, the mobile node may not know the as described in Section 10.5, 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 SHOULD use the dynamic home agent In this case, the mobile node SHOULD use the dynamic home agent
address discovery procedure to find the address of a suitable home address discovery procedure to find the address of a suitable home
agent on its home link. To do so, the mobile node sends the packet, agent on its home link. To do so, the mobile node sends the packet,
as described above, with the Destination Address in the packet's IPv6 as described above, with the Destination Address in the packet's
header set to the Home-Agents anycast address for its home subnet IPv6 header set to the "Mobile IPv6 Home-Agents" anycast address [8]
prefix. As described in Section 9.2, the home agent on its home link for its home subnet prefix. As described in Section 9.2, the
that receives this Binding Update will reject the Update, returning home agent on its home link that receives this Binding Update will
to the mobile node the home agent's own global unicast IP address reject the Update, returning to the mobile node the home agent's own
along with a list of the global unicast IP addresses of each other global unicast IP address along with a list of the global unicast IP
home agent operating on the home link. The mobile node SHOULD then addresses of each other home agent operating on the home link. The
retransmit its Binding Update to one of these homes agent using the mobile node SHOULD then retransmit its Binding Update to one of these
provided global unicast address; the mobile node MAY re-attempt homes agent using the provided global unicast address; the mobile
this home registration with each of these home agents in turn, by node MAY re-attempt this home registration with each of these home
sending each a Binding Update and waiting for the matching Binding agents in turn, by sending each a Binding Update and waiting for the
Acknowledgement, until its registration is accepted by one of these matching Binding Acknowledgement, until its registration is accepted
home agents. by one of these home agents.
If the mobile node has a current registration with some home agent If the mobile node has a current registration with some home agent
on its home link (the Lifetime for that registration has not yet on its home link (the Lifetime for that registration has not yet
expired), then the mobile node MUST attempt any new registration expired), then the mobile node MUST attempt any new registration
first with that home agent. If that registration attempt fails first with that home agent. If that registration attempt fails
(e.g., times out or is rejected), the mobile node SHOULD then (e.g., times out or is rejected), the mobile node SHOULD then
reattempt this registration with another home agent on its home link. reattempt this registration with another home agent on its home link.
If the mobile node knows of no other suitable home agent, then it MAY If the mobile node knows of no other suitable home agent, then it MAY
attempt the dynamic home agent address discovery procedure described attempt the dynamic home agent address discovery procedure described
above. above.
10.7. Sending Binding Updates to Correspondent Nodes 10.7. Sending Binding Updates to Correspondent Nodes
A mobile node MAY send a Binding Update to any correspondent node at A mobile node MAY send a Binding Update to any correspondent node at
any time to allow it to cache its current care-of address (subject to any time to allow the correspondent node to cache the mobile node's
the rate limiting defined in Section 10.10). In any Binding Update current care-of address (subject to the rate limiting defined in
sent by a mobile node, the care-of address (either the Source Address Section 10.10). In any Binding Update sent by a mobile node, the
in the packet's IPv6 header or the Care-of Address field in the care-of address (either the Source Address in the packet's IPv6
Binding Update) MUST be set to one of the care-of addresses currently header or the Care-of Address field in the Binding Update) MUST be
in use by the mobile node or to the mobile node's home address. set to one of the care-of addresses currently in use by the mobile
node or to the mobile node's home address.
If set to one of the mobile node's current care-of addresses (the If set to one of the mobile node's current care-of addresses (the
care-of address given MAY differ from the mobile node's primary care-of address given MAY differ from the mobile node's primary
care-of address), the Binding Update requests the correspondent node care-of address), the Binding Update requests the correspondent node
to create or update an entry for the mobile node in the correspondent to create or update an entry for the mobile node in the correspondent
node's Binding Cache to record this care-of address for use in node's Binding Cache to record this care-of address for use in
sending future packets to the mobile node. In this case, the sending future packets to the mobile node. In this case, the
Lifetime value sent in the Binding Update MUST be no greater than Lifetime value sent in the Binding Update MUST be no greater than
the remaining lifetime of the mobile node's home registration of its the remaining lifetime of the mobile node's home registration of its
primary care-of address at its home agent. primary care-of address at its home agent.
skipping to change at page 76, line 21 skipping to change at page 77, line 26
is received. Such a retransmitted Binding Update MUST use the is received. Such a retransmitted Binding Update MUST use the
same Sequence Number value as the original transmission. The same Sequence Number value as the original transmission. The
retransmissions by the mobile node MUST use an exponential retransmissions by the mobile node MUST use an exponential
back-off process, in which the timeout period is doubled back-off process, in which the timeout period is doubled
upon each retransmission until either the node receives a upon each retransmission until either the node receives a
Binding Acknowledgement or the timeout period reaches the value Binding Acknowledgement or the timeout period reaches the value
MAX_BINDACK_TIMEOUT. MAX_BINDACK_TIMEOUT.
10.10. Rate Limiting for Sending Binding Updates 10.10. Rate Limiting for Sending Binding Updates
A mobile node MUST NOT send Binding Updates more often than once per A mobile node MUST NOT send Binding Updates about the same binding
MAX_UPDATE_RATE seconds to any node. After sending MAX_FAST_UPDATES to any node more often than once per MAX_UPDATE_RATE seconds. After
consecutive Binding Updates to a particular node with the same sending MAX_FAST_UPDATES consecutive Binding Updates to a particular
care-of address, the mobile node SHOULD reduce its rate of sending node with the same care-of address, the mobile node SHOULD reduce
Binding Updates to that node, to the rate of SLOW_UPDATE_RATE per its rate of sending Binding Updates to that node, to the rate of
second. The mobile node MAY continue to send Binding Updates at this SLOW_UPDATE_RATE per second. The mobile node MAY continue to send
slower rate indefinitely, in hopes that the node will eventually Binding Updates at this slower rate indefinitely, in hopes that the
be able to process a Binding Update and begin to route its packets node will eventually be able to process a Binding Update and begin
directly to the mobile node at its new care-of address. to route its packets directly to the mobile node at its new care-of
address.
10.11. Receiving Binding Acknowledgements 10.11. 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 contains a valid AH [8] or ESP [9] header providing - The packet contains a valid AH [9] or ESP [10] header providing
sender authentication, data integrity protection, and replay sender authentication, data integrity protection, and replay
protection. protection.
- The Option Length field in the option is greater than or equal to - The Option Length field in the option is greater than or equal to
11 octets. 11 octets.
- 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.
skipping to change at page 79, line 7 skipping to change at page 80, line 15
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
Advertisement is the same as the home agent address to which the Advertisement is the same as the home agent address to which the
mobile node last sent an accepted "home registration" Binding mobile node last sent an accepted "home registration" Binding
Update to register its primary care-of address. Update to register its primary care-of address.
- The packet contains either an AH [8] or ESP [9] header providing - The packet contains either an AH [9] or ESP [10] header providing
sender authentication, data integrity protection, and replay sender authentication, data integrity protection, and replay
protection. protection.
- The packet contains a Binding Request destination option. - The packet contains a Binding Request destination option.
- The Binding Request option contains a Unique Identifier - The Binding Request option contains a Unique Identifier
Sub-Option. Sub-Option.
Any received tunneled Router Advertisement not meeting all of these Any received tunneled Router Advertisement not meeting all of these
tests MUST be silently discarded. tests MUST be silently discarded.
If a received tunneled Router Advertisement is not discarded If a received tunneled Router Advertisement is not discarded
according to the tests listed above, the mobile node MUST process the according to the tests listed above, the mobile node MUST process the
Router Advertisement as if it were connected to its home link [13]. Router Advertisement as if it were connected to its home link [14].
Such processing MAY result in the mobile node configuring a new home Such processing MAY result in the mobile node configuring a new home
address, although due to separation between preferred lifetime and address, although due to separation between preferred lifetime and
valid lifetime, such changes should not affect most communication by valid lifetime, such changes should not affect most communication by
the mobile node, in the same way as for nodes that are at home. the mobile node, in the same way as for nodes that are at home.
In addition, in processing the packet containing this Router In addition, in processing the packet containing this Router
Advertisement, the mobile node SHOULD return to the home agent a Advertisement, the mobile node SHOULD return to the home agent a
Binding Update in response to the Binding Request carried in the Binding Update in response to the Binding Request carried in the
packet. The correct formation of this Binding Update by the mobile packet. The correct formation of this Binding Update by the mobile
node and processing of it by the home agent will be viewed by the node and processing of it by the home agent will be viewed by the
skipping to change at page 80, line 9 skipping to change at page 81, line 17
Binding Update with the Home Registration (H) and Acknowledge (A) Binding Update with the Home Registration (H) and Acknowledge (A)
bits set, as described in Section 10.5. bits set, as described in Section 10.5.
To assist with smooth handoffs, a mobile node SHOULD retain To assist with smooth handoffs, a mobile node SHOULD retain
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.
10.16. Routing Multicast Packets 10.16. 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.
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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.
In addition, the mobile node MUST multicast onto the home link In addition, the mobile node MUST multicast onto the home link
(to the all-nodes multicast address) a Neighbor Advertisement (to the all-nodes multicast address) a Neighbor Advertisement
message [13], to advertise the mobile node's own link-layer address message [14], 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
home addresses, as defined by the current on-link prefixes, including home addresses, as defined by the current on-link prefixes, including
its link-local address and site-local address. The Solicited its link-local address and site-local address. The Solicited
Flag (S) in these Advertisements MUST NOT be set, since they were Flag (S) in these Advertisements MUST NOT be set, since they were
not solicited by any Neighbor Solicitation message. The Override not solicited by any Neighbor Solicitation message. The Override
Flag (O) in these Advertisements MUST be set, indicating that the Flag (O) in these Advertisements MUST be set, indicating that the
Advertisements SHOULD override any existing Neighbor Cache entries at Advertisements SHOULD override any existing Neighbor Cache entries at
any node receiving them. any node receiving them.
Since multicasts on the local link (such as Ethernet) are typically Since multicasts on the local link (such as Ethernet) are typically
not guaranteed to be reliable, the mobile node MAY retransmit these not guaranteed to be reliable, the mobile node MAY retransmit these
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 [13]. Neighbor Unreachability Detection [14].
11. Constants 11. Constants
INITIAL_BINDACK_TIMEOUT 1 second INITIAL_BINDACK_TIMEOUT 1 second
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
skipping to change at page 83, line 18 skipping to change at page 84, line 18
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 - The Binding Request option, described in Section 5.3
- The Home Address option, described in Section 5.4 - The Home Address option, described in Section 5.4
In addition, this document defines two new Neighbor Discovery [13] In addition, this document defines two new Neighbor Discovery [14]
options, which must be assigned Option Type values within the option options, which must be assigned Option Type values within the option
numbering space for Neighbor Discovery messages: numbering space for Neighbor Discovery messages:
- The Advertisement Interval option, described in Section 6.3. - The Advertisement Interval option, described in Section 6.3.
- The Home Agent Information option, described in Section 6.4. - The Home Agent Information option, described in Section 6.4.
Finally, this document defines a new type of anycast address, which Finally, this document defines a new type of anycast address, which
must be assigned a reserved value for use with any subnet prefix to must be assigned a reserved value for use with any subnet prefix to
define this anycast address on each subnet: define this anycast address on each subnet:
- The Home-Agents anycast address, used in the dynamic home agent - The "Mobile IPv6 Home-Agents" anycast address [8], used in the
address discovery procedure described in Sections 9.2 and 10.6. dynamic home agent address discovery procedure described in
Sections 9.2 and 10.6.
13. Security Considerations 13. Security Considerations
13.1. Binding Updates, Acknowledgements, and Requests 13.1. Binding Updates, Acknowledgements, and Requests
The Binding Update option described in this document will result The Binding Update option described in this document will result
in packets addressed to a mobile node being delivered instead to in packets addressed to a mobile node being delivered instead to
its care-of address. This ability to change the routing of these its care-of address. This ability to change the routing of these
packets could be a significant vulnerability if any packet containing packets could be a significant vulnerability if any packet containing
a Binding Update option was not authenticated. Such use of "remote a Binding Update option was not authenticated. Such use of "remote
skipping to change at page 87, line 5 skipping to change at page 88, line 5
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.
Changes from Previous 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-ipv6-06.txt: draft-ietf-mobileip-ipv6-07.txt:
- Changed the way in which optional information is included in - Changed the listed Option Type codes for the destination options
Mobile IPv6 destination options. In pervious versions of this and Type codes Router Advertisement options to their official
draft, optional data was in an unspecified format (except for values, now that IPv6 has finally officially assigned these.
the Home Agents List in a Binding Acknowledgement, which was
a simple list of IP addresses). Instead, such optional data
is now specified as sub-options within the option data field,
encoded in type-length-value (TLV) format. Added Section 5.5
to define the general format of sub-options and to specify the
sub-option data format for each defined sub-option, and updated
relevant references to such optional information throughout
the draft. This new TLV encoding of optional information
allows much more flexibility in future versions of the protocol
specification, and solves the problem that the previous encoding
of the Home Agents List in a Binding Acknowledgement prevented
other optional information from also being included in a Binding
Acknowledgement.
- Specified in Section 9.2 that a home agent returning a Binding - Added a Router (R) bit in the Binding Update option format, for
Acknowledgement containing a Home Agents List Sub-Option SHOULD use in "home registration" Binding Updates. This flag bit tells
limit the size of the list so as to avoid the possibility of the the home agent that the mobile node is a router, so that the
packet carrying the Binding Acknowledgement being fragmented. home agent can set the corresponding bit correctly in all proxy
Neighbor Advertisements that it sends on behalf of this mobile
node. Also added a bit to save this flag in the definition of
the Binding Cache entry format, and defined how it is used in
sending proxy Neighbor Advertisements.
- Specified in Section 4.3 that each Home Agents List entry - Added a bit of text in a few places to clarify the meaning of
represents a single home agent by its link-local address MAX_UPDATE_RATE.
(the Source Address used in its Router Advertisements),
and contains one or more global IP addresses for this home
agent, learned through Prefix Information options received
in Router Advertisements from this link-local address, in
which the Router Address (R) bit is set. Also specified in
Section ha-advert how to add global addresses to this list of
global addresses associated with a home agent in the Home Agents
List.
- Specified in Section 9.2 that in forming the Home Agents - Added to Section 7.3 a requirement that every home agent SHOULD
List Sub-Option to return to a mobile node in a Binding support a configuration mechanism to allow a system administrator
Acknowledgement, only home agent global IP addresses sharing a to manually set the value to be sent by this home agent in the
prefix with the mobile node's home address are returned in the Home Agent Preference field of the Home Agent Information Option
Binding Acknowledgement. in Router Advertisements that it sends.
- Specified in Section 8 that in processing a Home Address option - Added a suggestion in Section 6.4 that the Home Agent Preference
in a received packet, any actual modifications to the Source field in a Home Agent Information option being sent by a home
Address field in the packet's IPv6 header MUST not be performed agent could be set dynamically by the sending home agent based
until after all processing of other options contained in this on factors such as the number of mobile nodes it is currently
same Destination Options extension header is completed. This serving or the remaining resources it has for serving additional
restriction prevents confusion in the meaning of these other mobile nodes. However, the details of such dynamic settings
destination options. are beyond the scope of this document since they do not involve
protocol standardization issues.
- General clarification and correction of minor typographical - Normalized all references to the "Mobile IPv6 Home-Agents"
errors throughout. anycast address to use the full name of this specific anycast
address and to point to the new definition of reserved IPv6
subnet anycast addresses, RFC 2526.
- Updated all references to their most recent versions, including
changing old Internet-Draft references into new RFC references
where available. Changed remaining specific Internet-Draft
references to be generic "Work in progress" references.
- Updated the "Status of This Memo" section to the new official
version of this text.
- Corrected a few minor typographical errors in places.
Acknowledgements Acknowledgements
We would like to thank the members of the Mobile IP and IPng Working We would like to thank the members of the Mobile IP and IPng Working
Groups for their comments and suggestions on this work. We would Groups for their comments and suggestions on this work. We would
particularly like to thank (in alphabetical order) Josh Broch particularly like to thank (in alphabetical order) Josh Broch
(Carnegie Mellon University), Thomas Narten (IBM), Erik Nordmark (Sun (Carnegie Mellon University), Thomas Narten (IBM), Erik Nordmark (Sun
Microsystems), Simon Nybroe (Telebit Communications), Patrice Romand Microsystems), Simon Nybroe (Telebit Communications), Patrice Romand
(Bull S.A.), Tom Soderlund (Nokia Research), and Jim Solomon (RedBack (Bull S.A.), Tom Soderlund (Nokia Research), and Jim Solomon (RedBack
Networks) for their detailed reviews of earlier versions of this Networks) for their detailed reviews of earlier versions of this
draft. Their suggestions have helped to improve both the design and draft. Their suggestions have helped to improve both the design and
presentation of the protocol. presentation of the protocol.
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). Internet-Draft, Protocol for IPv6 (DHCPv6), February 1999. Work in progress.
draft-ietf-dhc-dhcpv6-10.txt, May 1997. 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 [4] Alex Conta and Stephen Deering. Generic packet tunneling in
tunneling in IPv6 specification. Internet-Draft, IPv6 specification. RFC 2473, December 1998.
draft-ietf-ipngwg-ipv6-tunnel-07.txt, December 1996.
Work in progress.
[5] Stephen E. Deering and Robert M. Hinden. Internet [5] Stephen E. Deering and Robert M. Hinden. Internet Protocol
Protocol version 6 (IPv6) specification. Internet-Draft, version 6 (IPv6) specification. RFC 2460, December 1998.
draft-ietf-ipngwg-ipv6-spec-v2-00.txt, July 1997. Work in
progress.
[6] Paul Ferguson and Daniel Senie. Network ingress filtering: [6] 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.
[7] Robert M. Hinden and Stephen E. Deering. IP Version 6 [7] Robert M. Hinden and Stephen E. Deering. IP Version 6
addressing architecture. Internet-Draft, addressing architecture. RFC 2373, July 1998.
draft-ietf-ipngwg-addr-arch-v2-06.txt, January 1998. Work in
progress.
[8] Stephen Kent and Randall Atkinson. IP Authentication header. [8] David B. Johnson and Stephen E. Deering. Reserved ipv6 subnet
Internet-Draft, draft-ietf-ipsec-auth-header-02.txt, October anycast addresses. RFC 2526, March 1999.
1997. Work in progress.
[9] Stephen Kent and Randall Atkinson. IP Encapsulating Security [9] Stephen Kent and Randall Atkinson. IP Authentication header.
Payload (ESP). Internet-Draft, draft-ietf-ipsec-esp-v2-01.txt, RFC 2402, November 1998.
October 1997. Work in progress.
[10] Stephen Kent and Randall Atkinson. Security architecture for [10] Stephen Kent and Randall Atkinson. IP Encapsulating Security
the Internet Protocol. Internet-Draft, Payload (ESP). RFC 2406, November 1998.
draft-ietf-ipsec-arch-sec-02.txt, November 1997. Work in
progress.
[11] P. Mockapetris. Domain Names -- concepts and facilities. [11] Stephen Kent and Randall Atkinson. Security architecture for
the Internet Protocol. RFC 2401, November 1998.
[12] P. Mockapetris. Domain Names -- concepts and facilities.
RFC 1034, November 1987. RFC 1034, November 1987.
[12] P. Mockapetris. Domain Names -- implementation and [13] P. Mockapetris. Domain Names -- implementation and
specification. RFC 1035, November 1987. specification. RFC 1035, November 1987.
[13] Thomas Narten, Erik Nordmark, and William Allen Simpson. [14] Thomas Narten, Erik Nordmark, and William Allen Simpson.
Neighbor Discovery for IP version 6 (IPv6). Internet-Draft, Neighbor Discovery for IP version 6 (IPv6). RFC 2461, December
draft-ietf-ipngwg-discovery-v2-00.txt, July 1997. Work in 1998.
progress.
[14] Charles Perkins. IP encapsulation within IP. RFC 2003, October [15] Charles Perkins. IP encapsulation within IP. RFC 2003, October
1996. 1996.
[15] Charles Perkins, editor. IP mobility support. RFC 2002, [16] Charles Perkins, editor. IP mobility support. RFC 2002,
October 1996. October 1996.
[16] Charles Perkins. Minimal encapsulation within IP. RFC 2004, [17] Charles Perkins. Minimal encapsulation within IP. RFC 2004,
October 1996. October 1996.
[17] Charles Perkins and David B. Johnson. Route optimization in [18] Charles Perkins and David B. Johnson. Route optimization in
Mobile IP. Internet-Draft, draft-ietf-mobileip-optim-07.txt, Mobile IP, February 1999. Work in progress.
November 1997. Work in progress.
[18] David C. Plummer. An Ethernet address resolution protocol: [19] 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.
[19] J. B. Postel. User Datagram Protocol. RFC 768, August 1980. [20] J. B. Postel. User Datagram Protocol. RFC 768, August 1980.
[20] J. B. Postel, editor. Transmission Control Protocol. RFC 793, [21] J. B. Postel, editor. Transmission Control Protocol. RFC 793,
September 1981. September 1981.
[21] Joyce K. Reynolds and Jon Postel. Assigned numbers. RFC 1700, [22] Joyce K. Reynolds and Jon Postel. Assigned numbers. RFC 1700,
October 1994. October 1994.
[22] Susan Thomson and Thomas Narten. IPv6 stateless address [23] Susan Thomson and Thomas Narten. IPv6 stateless address
autoconfiguration. Internet-Draft, autoconfiguration. RFC 2462, December 1998.
draft-ietf-ipngwg-addrconf-v2-00.txt, July 1997.
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:
Jim Solomon
RedBack Networks
1389 Moffett Park Drive
Sunnyvale, CA 94089-1134
USA
Phone: +1 408 548-3583
Fax: +1 408 548-3599
E-mail: solomon@rback.com
Erik Nordmark Erik Nordmark
Sun Microsystems, Inc. Sun Microsystems, Inc.
2550 Garcia Avenue 2550 Garcia Avenue
Mt. View, CA 94041 Mt. View, CA 94041
USA USA
Phone: +1 415 786-5166 Phone: +1 415 786-5166
Fax: +1 415 786-5896 Fax: +1 415 786-5896
E-mail: nordmark@sun.com E-mail: nordmark@sun.com
Basavaraj Patil
Nortel Networks, Inc.
2201 Lakeside Blvd.
Richardson, TX 75082-4399
USA
Phone: +1 972 684-1489
E-mail: bpatil@nortelnetworks.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 Carnegie Mellon University
Computer Science Department Computer Science Department
5000 Forbes Avenue 5000 Forbes Avenue
Pittsburgh, PA 15213-3891 Pittsburgh, PA 15213-3891
USA USA
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