draft-ietf-mobileip-ipv6-03.txt   draft-ietf-mobileip-ipv6-04.txt 
Mobile IP Working Group David B. Johnson 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
30 July 1997 21 November 1997
Mobility Support in IPv6 Mobility Support in IPv6
<draft-ietf-mobileip-ipv6-03.txt> <draft-ietf-mobileip-ipv6-04.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 a submission by the Mobile IP Working Group of the
Internet Engineering Task Force (IETF). Comments should be submitted Internet Engineering Task Force (IETF). Comments should be submitted
to the Working Group mailing list at "mobile-ip@SmallWorks.COM". to the Working Group mailing list at "mobile-ip@SmallWorks.COM".
Distribution of this memo is unlimited. Distribution of this memo is unlimited.
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
skipping to change at page 1, line 57 skipping to change at page 1, line 57
node directly to it at this care-of address. node directly to it at this care-of address.
Contents Contents
Status of This Memo i Status of This Memo i
Abstract i Abstract i
1. Introduction 1 1. Introduction 1
2. Terminology 2 2. Comparison with Mobile IP for IPv4 3
2.1. General Terms . . . . . . . . . . . . . . . . . . . . . . 2
2.2. Mobile IPv6 Terms . . . . . . . . . . . . . . . . . . . . 3
2.3. Specification Language . . . . . . . . . . . . . . . . . 4
3. Overview of Mobile IPv6 Operation 6 3. Terminology 4
3.1. Protocol Summary . . . . . . . . . . . . . . . . . . . . 6 3.1. General Terms . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Comparison with Mobile IP for IPv4 . . . . . . . . . . . 11 3.2. Mobile IPv6 Terms . . . . . . . . . . . . . . . . . . . . 5
3.3. Specification Language . . . . . . . . . . . . . . . . . 6
4. New IPv6 Destination Options 12 4. Overview of Mobile IPv6 7
4.1. Binding Update Option . . . . . . . . . . . . . . . . . . 12 4.1. Basic Operation . . . . . . . . . . . . . . . . . . . . . 7
4.2. Binding Acknowledgement Option . . . . . . . . . . . . . 16 4.2. New IPv6 Destination Options . . . . . . . . . . . . . . 9
4.3. Binding Request Option . . . . . . . . . . . . . . . . . 20 4.3. Conceptual Data Structures . . . . . . . . . . . . . . . 10
4.4. Home Address Option . . . . . . . . . . . . . . . . . . . 21 4.4. Binding Management . . . . . . . . . . . . . . . . . . . 13
5. Requirements for IPv6 Nodes 23 5. New IPv6 Destination Options 15
5.1. Binding Update Option . . . . . . . . . . . . . . . . . . 15
5.2. Binding Acknowledgement Option . . . . . . . . . . . . . 19
5.3. Binding Request Option . . . . . . . . . . . . . . . . . 23
5.4. Home Address Option . . . . . . . . . . . . . . . . . . . 24
6. Correspondent Node Operation 25 6. Requirements for IPv6 Nodes 26
6.1. Receiving Packets from a Mobile Node . . . . . . . . . . 25
6.2. Receiving Binding Updates . . . . . . . . . . . . . . . . 25
6.3. Requests to Cache a Binding . . . . . . . . . . . . . . . 26
6.4. Requests to Delete a Binding . . . . . . . . . . . . . . 27
6.5. Sending Binding Acknowledgements . . . . . . . . . . . . 27
6.6. Cache Replacement Policy . . . . . . . . . . . . . . . . 28
6.7. Receiving ICMP Error Messages . . . . . . . . . . . . . . 28
6.8. Sending Packets to a Mobile Node . . . . . . . . . . . . 29
7. Home Agent Operation 31 7. Correspondent Node Operation 28
7.1. Dynamic Home Agent Address Discovery . . . . . . . . . . 31 7.1. Receiving Packets from a Mobile Node . . . . . . . . . . 28
7.2. Primary Care-of Address Registration . . . . . . . . . . 31 7.2. Receiving Binding Updates . . . . . . . . . . . . . . . . 28
7.3. Primary Care-of Address De-registration . . . . . . . . . 33 7.3. Requests to Cache a Binding . . . . . . . . . . . . . . . 29
7.4. Tunneling Intercepted Packets to a Mobile Node . . . . . 34 7.4. Requests to Delete a Binding . . . . . . . . . . . . . . 30
7.5. Renumbering the Home Subnet . . . . . . . . . . . . . . . 35 7.5. Sending Binding Acknowledgements . . . . . . . . . . . . 30
7.6. Sending Binding Requests . . . . . . . . . . . . . . . . 30
7.7. Cache Replacement Policy . . . . . . . . . . . . . . . . 31
7.8. Receiving ICMP Error Messages . . . . . . . . . . . . . . 32
7.9. Sending Packets to a Mobile Node . . . . . . . . . . . . 33
8. Mobile Node Operation 37 8. Home Agent Operation 35
8.1. Sending Packets While Away from Home . . . . . . . . . . 37 8.1. Dynamic Home Agent Address Discovery . . . . . . . . . . 35
8.2. Movement Detection . . . . . . . . . . . . . . . . . . . 38 8.2. Primary Care-of Address Registration . . . . . . . . . . 35
8.3. Forming New Care-of Addresses . . . . . . . . . . . . . . 40 8.3. Primary Care-of Address De-registration . . . . . . . . . 38
8.4. Sending Binding Updates to the Home Agent . . . . . . . . 41 8.4. Tunneling Intercepted Packets to a Mobile Node . . . . . 38
8.5. Sending Binding Updates to Correspondent Nodes . . . . . 42 8.5. Renumbering the Home Subnet . . . . . . . . . . . . . . . 39
8.6. Sending Binding Updates to the Previous Default Router . 45 9. Mobile Node Operation 41
8.7. Retransmitting Binding Updates . . . . . . . . . . . . . 45 9.1. Sending Packets While Away from Home . . . . . . . . . . 41
8.8. Rate Limiting for Sending Binding Updates . . . . . . . . 46 9.2. Movement Detection . . . . . . . . . . . . . . . . . . . 42
8.9. Receiving Binding Acknowledgements . . . . . . . . . . . 46 9.3. Forming New Care-of Addresses . . . . . . . . . . . . . . 45
8.10. Using Multiple Care-of Addresses . . . . . . . . . . . . 47 9.4. Sending Binding Updates to the Home Agent . . . . . . . . 46
8.11. Returning Home . . . . . . . . . . . . . . . . . . . . . 47 9.5. Sending Binding Updates to Correspondent Nodes . . . . . 47
9.6. Sending Binding Updates to the Previous Default Router . 49
9.7. Retransmitting Binding Updates . . . . . . . . . . . . . 50
9.8. Rate Limiting for Sending Binding Updates . . . . . . . . 50
9.9. Receiving ICMP Errors in Response to Binding Updates . . 50
9.10. Receiving Binding Acknowledgements . . . . . . . . . . . 50
9.11. Receiving Binding Requests . . . . . . . . . . . . . . . 51
9.12. Using Multiple Care-of Addresses . . . . . . . . . . . . 52
9.13. Returning Home . . . . . . . . . . . . . . . . . . . . . 52
9. Routing Multicast Packets 49 10. Routing Multicast Packets 54
10. Constants 50 11. Constants 55
11. Security Considerations 51 12. IANA Considerations 56
11.1. Binding Updates, Acknowledgements, and Requests . . . . . 51
11.2. Home Address Options . . . . . . . . . . . . . . . . . . 51
11.3. General Mobile Computing Issues . . . . . . . . . . . . . 52
Appendix A. Changes from Previous Draft 53 13. Security Considerations 57
13.1. Binding Updates, Acknowledgements, and Requests . . . . . 57
13.2. Home Address Options . . . . . . . . . . . . . . . . . . 57
13.3. General Mobile Computing Issues . . . . . . . . . . . . . 58
Acknowledgements 54 Appendix A. Changes from Previous Draft 60
References 55 Acknowledgements 62
Chair's Address 57 References 63
Authors' Addresses 58 Chair's Address 65
Authors' Addresses 66
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 for Internet Protocol Version 6 (IPv6) [5]. Without specific support
mobility in IPv6, packets destined to a mobile node (host or router) for mobility in IPv6, packets destined to a mobile node (host or
would not be able to reach it while the mobile node is away from its router) would not be able to reach it while the mobile node is away
home IPv6 subnet, since routing is based on the network prefix in a from its home link (the link on which its home IPv6 subnet prefix is
packet's destination IP address. In order continue communication in use), since routing is based on the subnet prefix in a packet's
in spite of its movement, a mobile node could change its IP address destination IP address. In order to continue communication in spite
each time it moves to a new IPv6 subnet, but the mobile node would of its movement, a mobile node could change its IP address each time
then not be able to maintain transport and higher-layer connections it moves to a new link, but the mobile node would then not be able
when it changes location. Mobility support in IPv6 is particularly to maintain transport and higher-layer connections when it changes
important, as mobile computers are likely to account for a majority location. Mobility support in IPv6 is particularly important, as
or at least a substantial fraction of the population of the Internet mobile computers are likely to account for a majority or at least a
during the lifetime of IPv6. substantial fraction of the population of the Internet during the
lifetime of IPv6.
The protocol operation defined here, known as Mobile IPv6, allows a The protocol operation defined here, known as Mobile IPv6, allows a
mobile node to move from one IPv6 subnet to another without changing mobile node to move from one link to another without changing the
the mobile node's IP address. A mobile node is always addressable mobile node's IP address. A mobile node is always addressable by
by its "home address", the IP address assigned to the mobile node its "home address", an IP address assigned to the mobile node within
within its home IPv6 subnet. Packets may be routed to the mobile its home subnet prefix on its home link. Packets may be routed to
node using this address regardless of the mobile node's current point the mobile node using this address regardless of the mobile node's
of attachment to the Internet, and the mobile node may continue to current point of attachment to the Internet, and the mobile node may
communicate with other nodes (stationary or mobile) after moving continue to communicate with other nodes (stationary or mobile) after
to a new subnet. The movement of a mobile node away from its home moving to a new link. The movement of a mobile node away from its
subnet is thus transparent to transport and higher-layer protocols home link is thus transparent to transport and higher-layer protocols
and applications. and applications.
The Mobile IPv6 protocol is just as suitable for mobility across The Mobile IPv6 protocol is just as suitable for mobility across
homogeneous media as for mobility across heterogeneous media. For homogeneous media as for mobility across heterogeneous media. For
example, Mobile IPv6 facilitates node movement from one Ethernet example, Mobile IPv6 facilitates node movement from one Ethernet
segment to another as well as it facilitates node movement from an segment to another as well as it facilitates node movement from an
Ethernet segment to a wireless LAN cell, with the mobile node's IP Ethernet segment to a wireless LAN cell, with the mobile node's IP
address remaining unchanged in spite of such movement. address remaining unchanged in spite of such movement.
One can think of the Mobile IPv6 protocol as solving the "macro" One can think of the Mobile IPv6 protocol as solving the "macro"
mobility management problem. More "micro" mobility management mobility management problem. More "micro" mobility management
applications -- for example, handoff amongst wireless transceivers, applications -- for example, handoff among wireless transceivers,
each of which covers only a very small geographic area -- are each of which covers only a very small geographic area -- are
possibly more suited to other solutions. For example, as long as possibly more suited to other solutions. For example, in many
node movement does not occur between link-level points of attachment current wireless LAN products, link-layer mobility mechanisms allow a
on different IPv6 subnets, link-layer mobility support offered by a "handoff" of a mobile node from one cell to another, reestablishing
number of current wireless LAN products is likely to offer faster link-layer connectivity to the node in each new location. As long
as such handoff occurs only within cells of the mobile node's home
link, such link-layer mobility mechanisms are likely to offer faster
convergence and lower overhead than Mobile IPv6. Extensions to the convergence and lower overhead than Mobile IPv6. Extensions to the
Mobile IPv6 protocol are also possible to support a more local, Mobile IPv6 protocol are also possible to support a more local,
hierarchical form of handoff, but such extensions are beyond the sope hierarchical form of mobility management, but such extensions are
of this document. beyond the scope of this document.
2. Terminology The protocol specified in this document solves the problem of
transparently routing packets to and from mobile nodes while away
from home. However, it does not attempt to solve all general
problems related to the use of mobile computers or wireless networks.
In particular, this protocol does not attempt to solve:
2.1. General Terms - Handling links with partial reachability, such as typical
wireless networks. Some aspects of this problem are addressed
by the movement detection procedure described in Section 9.2,
but no attempt has been made to fully solve this problem in its
general form. Most aspects of this problem can be solved by the
workaround of restricting such networks to only one router per
link, although there are still possible hidden terminal problems
when two nodes on the same link (on opposite sides of the router)
attempt to communicate directly.
- Access control on a link being visited by a mobile node. This
is a general problem any time an untrusted node is allowed
to connect to any link layer. It is independent whether the
connecting node uses Mobile IP, DHCP [2], or just "borrows" an IP
address on the link.
2. Comparison with Mobile IP for IPv4
[This section will include a comparison between the Mobile IPv6
protocol and the Mobile IPv4 protocol [13, 12, 14]. However, this
comparison has not yet been written. It will be filled in with the
next revision to this draft.]
3. Terminology
3.1. General Terms
IP IP
Internet Protocol Version 6 (IPv6). Internet Protocol Version 6 (IPv6).
node node
A device that implements IP. A device that implements IP.
router router
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link link
A communication facility or medium over which nodes can A communication facility or medium over which nodes can
communicate at the link layer, such as an Ethernet (simple or communicate at the link layer, such as an Ethernet (simple or
bridged). A link is the layer immediately below IP. bridged). A link is the layer immediately below IP.
interface interface
A node's attachment to a link. A node's attachment to a link.
network prefix subnet prefix
A bit string that consists of some number of initial bits of an A bit string that consists of some number of initial bits of an
IP address. IP address.
link-layer address link-layer address
A link-layer identifier for an interface, such as IEEE 802 A link-layer identifier for an interface, such as IEEE 802
addresses on Ethernet links. addresses on Ethernet links.
packet packet
An IP header plus payload. An IP header plus payload.
2.2. Mobile IPv6 Terms 3.2. Mobile IPv6 Terms
home address home address
An IP address assigned to a mobile node within its home subnet. An IP address assigned to a mobile node within its home link.
The network prefix in a mobile node's home address is equal to
the network prefix of the home subnet.
home subnet home subnet prefix
The IP subnet indicated by a mobile node's home address. The IP subnet prefix corresponding to a mobile node's home
Standard IP routing mechanisms will deliver packets destined address.
for a mobile node's home address to its home subnet.
home link
The link on which a mobile node's home subnet prefix is
defined. Standard IP routing mechanisms will deliver packets
destined for a mobile node's home address to its home link.
mobile node mobile node
A node that can change its link-level point of attachment from A node that can change its point of attachment from one link to
one IP subnet to another, while still being reachable via its another, while still being reachable via its home address.
home address.
movement movement
A change in a mobile node's point of attachment to the Internet A change in a mobile node's point of attachment to the Internet
such that it is no longer link-level connected to the same IP such that it is no longer connected to the same link as it was
subnet as it was previously. If a mobile node is not currently previously. If a mobile node is not currently attached to its
link-level connected to its home subnet, the mobile node is home link, the mobile node is said to be "away from home".
said to be "away from home".
correspondent node correspondent node
A peer node with which a mobile node is communicating. The A peer node with which a mobile node is communicating. The
correspondent node may be either mobile or stationary. correspondent node may be either mobile or stationary.
foreign subnet foreign subnet prefix
Any IP subnet other than the mobile node's home subnet. Any IP subnet prefix other than the mobile node's home subnet
prefix.
foreign link
Any link other than the mobile node's home link.
home agent home agent
A router on a mobile node's home subnet with which the mobile A router on a mobile node's home link with which the mobile
node has registered its current care-of address. While the node has registered its current care-of address. While the
mobile node is away from home, the home agent intercepts mobile node is away from home, the home agent intercepts
packets on the home subnet destined to the mobile node's home packets on the home link destined to the mobile node's home
address, encapsulates them, and tunnels them to the mobile address, encapsulates them, and tunnels them to the mobile
node's registered care-of address. node's registered care-of address.
care-of address care-of address
An IP address associated with a mobile node while visiting An IP address associated with a mobile node while visiting a
a foreign subnet, which uses the network prefix of that foreign link; the subnet prefix of this IP address is a foreign
foreign subnet. Among the multiple care-of addresses that a subnet prefix. Among the multiple care-of addresses that a
mobile node may have at a time (e.g., with different network mobile node may have at a time (e.g., with different subnet
prefixes), the one registered with the mobile node's home agent prefixes), the one registered with the mobile node's home agent
is called its "primary" care-of address. is called its "primary" care-of address.
binding binding
The association of the home address of a mobile node with a The association of the home address of a mobile node with a
care-of address for that mobile node, along with the remaining care-of address for that mobile node, along with the remaining
lifetime of that association. lifetime of that association.
2.3. Specification Language 3.3. Specification Language
In this document, several words are used to signify the requirements
of the specification. These words are often capitalized.
MUST
This word, or the adjective "REQUIRED", means that the
definition is an absolute requirement of the specification.
MUST NOT
This phrase means that the definition is an absolute
prohibition of the specification.
SHOULD
This word, or the adjective "RECOMMENDED", means that there may
exist valid reasons in particular circumstances to ignore a
particular item, but the full implications must be understood
and carefully weighed before choosing a different course.
SHOULD NOT
This phrase means that there may exist valid reasons in
particular circumstances when the particular behavior is
acceptable or even useful, but the full implications should be
understood and the case carefully weighed before implementing
any behavior described with this label.
MAY
This word, or the adjective "OPTIONAL", means that an item
is truly optional. For example, one vendor may choose to
include the item because a particular marketplace requires
it or because the vendor feels that it enhances the product,
while another vendor may omit the same item. An implementation
which does not include a particular option MUST be prepared to
interoperate with another implementation which does include the
option.
silently discard
The implementation discards the packet without further The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
processing, and without indicating an error to the sender. The "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
implementation SHOULD provide the capability of logging the document are to be interpreted as described in RFC 2119 [3].
error, including the contents of the discarded packet, and
SHOULD record the event in a statistics counter.
3. Overview of Mobile IPv6 Operation 4. Overview of Mobile IPv6
3.1. Protocol Summary 4.1. Basic Operation
A mobile node is always addressable by its home address, whether it A mobile node is always addressable by its home address, whether it
is currently attached to its home subnet or is away from home. While is currently attached to its home link or is away from home. While
a mobile node is at home, packets addressed to the mobile node's a mobile node is at home, packets addressed to its home address are
home address are routed to it using conventional Internet routing routed to it using conventional Internet routing mechanisms in the
mechanisms in the same way as if the node were never mobile. Since same way as if the node were never mobile. Since the subnet prefix
the network prefix of a mobile node's home address is equal to the of a mobile node's home address is the subnet prefix (or one of the
network prefix of its home subnet, packets addressed to it will be subnet prefixes) on the mobile node's home link (it is the mobile
routed to its home subnet. node's home subnet prefix), packets addressed to it will be routed to
its home link.
While a mobile node is attached to some foreign subnet away from While a mobile node is attached to some foreign link away from
home, it is also addressable by one or more care-of addresses, in home, it is also addressable by one or more care-of addresses, in
addition to its home address. A care-of address is an IP address addition to its home address. A care-of address is an IP address
associated with a mobile node while visiting a particular foreign associated with a mobile node while visiting a particular foreign
subnet. The network prefix of a mobile node's care-of address is link. The subnet prefix of a mobile node's care-of address is the
equal to the network prefix of the foreign subnet being visited subnet prefix (or one of the subnet prefixes) on the foreign link
by the mobile node; if the mobile node is link-level connected being visited by the mobile node; if the mobile node is connected
to this foreign subnet while using that care-of address, packets to this foreign link while using that care-of address, packets
addressed to this care-of address will be routed to the mobile node addressed to this care-of address will be routed to the mobile node
in its location away from home. The association between a mobile in its location away from home. The association between a mobile
node's home address and care-of address is known as a "binding" node's home address and care-of address is known as a "binding"
for the mobile node. A mobile node typically acquires its care-of for the mobile node. A mobile node typically acquires its care-of
address through stateless [16] or stateful (e.g., DHCPv6 [3]) address through stateless [18] or stateful (e.g., DHCPv6 [2])
address autoconfiguration, according to the methods of IPv6 Neighbor address autoconfiguration, according to the methods of IPv6 Neighbor
Discovery [9], although other methods of acquiring a care-of address Discovery [11]. Other methods of acquiring a care-of address
are also possible. are also possible, but such methods are beyond the scope of this
document.
While away from home, the mobile node registers one of its bindings While away from home, the mobile node registers one of its bindings
with a router in its home subnet, requesting this router to function with a router on its home link, requesting this router to function
as the "home agent" for the mobile node. This binding registration as the "home agent" for the mobile node. This binding registration
is done by the mobile node sending a packet with a "Binding Update" is done by the mobile node sending a packet with a "Binding Update"
destination option to the home agent, which replies by returning a destination option to the home agent, which replies by returning a
packet containing a "Binding Acknowledgement" destination option to packet containing a "Binding Acknowledgement" destination option to
the mobile node. The care-of address in this binding registered the mobile node. The care-of address in this binding registered
with its home agent is known as the mobile node's "primary care-of with its home agent is known as the mobile node's "primary care-of
address". The mobile node's home agent thereafter uses proxy address". The mobile node's home agent thereafter uses proxy
Neighbor Discovery to intercept any IPv6 packets addressed to the Neighbor Discovery to intercept any IPv6 packets addressed to the
mobile node's home address on the home subnet, and tunnels each mobile node's home address (or home addresses) on the home link,
intercepted packet to the mobile node's primary care-of address. and tunnels each intercepted packet to the mobile node's primary
To tunnel each intercepted packet, the home agent encapsulates the care-of address. To tunnel each intercepted packet, the home agent
packet using IPv6 encapsulation [4], addressed to the mobile node's encapsulates the packet using IPv6 encapsulation [4], addressed to
primary care-of address. the mobile node's primary care-of address.
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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communicating with a mobile node is referred to in this document as a communicating with a mobile node is referred to in this document as a
"correspondent node" of the mobile node. "correspondent node" of the 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 [14] or UDP [13]. TCP [16] or UDP [15].
- 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 Destination Options header is case, the Next Header field in the last extension header in the
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
Address" destination option in the packet, giving the mobile node's Address" destination option in the packet, giving the mobile node's
home address. Many routers implement security policies such as home address. Many routers implement security policies such as
"ingress filtering" [6] that do not allow forwarding of packets "ingress filtering" [6] that do not allow forwarding of packets
that appear to have a Source Address that is not topologically that appear to have a Source Address that is not topologically
correct. By using the care-of address as the IPv6 header Source correct. By using the care-of address as the IPv6 header Source
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from non-mobile nodes. By also including the Home Address option, from non-mobile nodes. By also including the Home Address option,
the sending mobile node can communicate its home address to the the sending mobile node can communicate its home address to the
correspondent node receiving this packet, allowing the use of the correspondent node receiving this packet, allowing the use of the
care-of address to be transparent above the Mobile IPv6 support care-of address to be transparent above the Mobile IPv6 support
level (e.g., at the transport layer). The inclusion of a Home level (e.g., at the transport layer). The inclusion of a Home
Address option in a packet affects only the correspondent node's Address option in a packet affects only the correspondent node's
receipt of this single packet; no state is created or modified in the receipt of this single packet; no state is created or modified in the
correspondent node as a result of receiving a Home Address option in correspondent node as a result of receiving a Home Address option in
a packet. a packet.
In summary, the following four new IPv6 destination options are 4.2. New IPv6 Destination Options
defined for Mobile IPv6:
As discussed in general in Section 4.1, the following four new 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 an IPv6 Authentication Binding Update option MUST also include either an AH [7] or
header [1], providing sender authentication, data integrity ESP [8] 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 4.1. 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 an IPv6 Authentication Acknowledgement option MUST also include either an AH [7] or
header [1], providing sender authentication, data integrity ESP [8] 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 4.2. option is described in detail in Section 5.2.
Binding Request Binding Request
A Binding Request option is used to request a mobile node A Binding Request option is used to request a mobile node
to send a Binding Update to the requesting node, containing to send a Binding Update to the requesting node, containing
the mobile node's current binding. This option is typically the mobile node's current binding. This option is typically
used by a correspondent node to refresh a cached binding for used by a correspondent node to refresh a cached binding for
a mobile node, when the cached binding is in active use but a mobile node, when the cached binding is in active use but
the binding's lifetime is close to expiration. No special the binding's lifetime is close to expiration. No special
authentication is required for the Binding Request option. The authentication is required for the Binding Request option. The
Binding Request option is described in detail in Section 4.3. Binding Request option is described in detail in Section 5.3.
Home Address Home Address
A Home Address option is used in a packet sent by a mobile A Home Address option is used in a packet sent by a mobile
node to inform the recipient of that packet of the mobile node to inform the recipient of that packet of the mobile
node's home address. For packets sent by a mobile node while node's home address. For packets sent by a mobile node while
away from home, the mobile node generally uses one of its away from home, the mobile node generally uses one of its
care-of addresses as the Source Address in the packet's IPv6 care-of addresses as the Source Address in the packet's IPv6
header. By including a Home Address option in the packet, the header. By including a Home Address option in the packet, the
correspondent node receiving the packet is able to substitute correspondent node receiving the packet is able to substitute
the mobile node's home address for this care-of address when the mobile node's home address for this care-of address when
processing the packet, thus making the use of the care-of processing the packet, thus making the use of the care-of
address transparent to the correspondent node. The Home address transparent to the correspondent node. If the IP
Address option is described in detail in Section 4.4. header of a packet carrying a Home Address option is covered
by authentication, then the Home Address option MUST also
be covered by this authentication, but no other special
authentication is required for the Home Address option. The
Home Address option is described in detail in Section 5.4.
Extensions to the format of these options may be included after the Extensions to the format of these options MAY be included after the
fixed portion of the option data specified in this document. The fixed portion of the option data specified in this document. The
presence of such extensions will be indicated by the Option Length presence of such extensions will be indicated by the Option Length
field within the option. When the Option Length is greater than the field within the option. When the Option Length is greater than the
length required for the option specified here, the remaining octets length required for the option specified here, the remaining octets
are interpreted as extensions. Currently, no extensions have been are interpreted as extensions. Currently, no extensions have been
defined. defined.
4.3. Conceptual Data Structures
This document describes the Mobile IPv6 protocol in terms of the This document describes the Mobile IPv6 protocol in terms of the
following two conceptual data structures used in the maintenance of following two conceptual data structures used in the maintenance of
cached bindings: cached bindings:
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
nodes. An entry in a node's binding cache for which the node other nodes. The Binding Cache MAY be implemented in any
is serving as a home agent is marked as a "home registration" manner consistent with the external behavior described
in this document, for example by being combined with the
node's Destination Cache as maintained through Neighbor
Discovery [11]. When sending a packet, the Binding Cache
MUST be searched before the Neighbor Discovery conceptual
Destination Cache [11]. Each Binding Cache entry conceptually
contains the following fields:
- The home address of the mobile node for which this is the
Binding Cache entry. This field is used as the key for
searching the Binding Cache for the destination address of
a packet being routed. If the destination address of the
packet matches the home address in the Binding Cache entry,
this entry SHOULD be used in routing that packet.
- The care-of address for the mobile node indicated by
the home address field in this Binding Cache entry. If
the destination address of a packet being routed by a
node matches the home address in this entry, the packet
SHOULD be routed to this care-of address, as described in
Section 7.9, for packets originated by this node, or in
Section 8.4, if this node is the mobile node's home agent
and the packet was intercepted by it on the home link.
- A lifetime value, indicating the remaining lifetime
for this Binding Cache entry. The lifetime value is
initialized from the Lifetime field in the Binding Update
that created or last modified this Binding Cache entry.
Once the lifetime on this entry expires, the entry MUST be
deleted from the Binding Cache.
- A flag indicating whether or not this Binding Cache entry
is a "home registration" entry.
- The value of ID Length field received in the Binding Update
that created or last modified this Binding Cache entry.
- The maximum value of the Sequence Number field received in
previous Binding Updates for this mobile node home address.
All comparisons between Sequence Number values MUST be
performed modulo 2**16.
- Recent usage information for this Binding Cache entry,
as needed for the cache replacement policy in use in the
Binding Cache and to assist in determining whether a
Binding Request should be sent when the lifetime on this
entry nears expiration.
- The time at which a Binding Request was last sent for this
entry, as needed to implement the rate limiting restriction
for sending Binding Requests.
An entry in a node's Binding Cache for which the node is
serving as a home agent is marked as a "home registration"
entry and SHOULD NOT be deleted by the home agent until the entry and SHOULD NOT be deleted by the home agent until the
expiration of its binding lifetime. Other Binding Cache expiration of its binding lifetime. Other Binding Cache
entries MAY be replaced at any time by any reasonable local entries MAY be replaced at any time by any reasonable local
cache replacement policy but SHOULD NOT be unnecessarily cache replacement policy but SHOULD NOT be unnecessarily
deleted. Any node's Binding Cache may contain at most one deleted. Any node's Binding Cache may contain at most one
entry for each mobile node, keyed by the mobile node's home entry for each mobile node home address. The contents of a
address. The contents of a node's Binding Cache MUST NOT be node's Binding Cache MUST NOT be changed in response to a Home
changed in response to a Home Address option in a received Address option in a received packet.
packet. The Binding Cache MAY be implemented in any manner
consistent with the external behavior described in this
document, for example by being combined with the node's
Destination Cache as maintained through Neighbor Discovery [9].
Binding Update List Binding Update List
A list, maintained by each mobile node, recording information A list, maintained by each mobile node, recording information
for each Binding Update sent by this mobile node, for which the for each Binding Update sent by this mobile node, for which
Lifetime of the binding sent in that Binding Update has not the Lifetime sent in that Binding Update has not yet expired.
yet expired. The Binding Update List includes all bindings The Binding Update List includes all bindings sent by the
sent by the mobile node: those to correspondent nodes, to the mobile node: those to correspondent nodes, to the mobile
mobile node's home agent, and to a previous default router node's home agent, and to a previous default router of the
of the mobile node. Each Binding Update List entry records mobile node. The Binding Update List MAY be implemented in any
the IP address of the node to which the Update was sent, the manner consistent with the external behavior described in this
home address for which one Binding Update was sent, and the document. Each Binding Update List entry conceptually contains
remaining lifetime of that binding. The Binding Update List the following fields:
MAY be implemented in any manner consistent with the external
behavior described in this document. - The IP address of the node to which a Binding Update was
sent. This node might still have a Binding Cache entry
derived from this binding update, if the Binding Update was
successfully received by that node (e.g., not lost by the
network) and if that node has not deleted the entry before
its expiration (e.g., to reclaim space in its Binding Cache
for other entries).
- The home address for which that Binding Update was sent.
This will be the mobile node's home address for most
Binding Updates (Sections 9.4 and 9.5), but will be
the mobile node's previous care-of address for Binding
Updates sent to the mobile node's previous default router
(Section 9.6).
- The care-of address sent in that Binding Update. This
value is necessary for determining if the mobile node has
sent a Binding Update giving its new care-of address to
this destination after changing its care-of address.
- The remaining lifetime of that binding. This lifetime is
initialized from the Lifetime value sent in the Binding
Update and is decremented until it reaches zero, at which
time this entry MUST be deleted from the binding update
list.
- The maximum value of the Sequence Number field sent
in previous Binding Updates to this destination. All
comparisons between Sequence Number values MUST be
performed modulo 2**16.
- The state of any retransmissions needed for this Binding
Update, if the Acknowledge (A) bit was set in this Binding
Update. This state includes the time remaining until the
next retransmission attempt for the Binding Update, and
the current state of the exponential back-off process for
retransmissions.
- The time at which a Binding Update was last sent to this
destination, as needed to implement the rate limiting
restriction for sending Binding Updates.
- A flag that, when set, indicates that future Binding
Updates should not be sent to this destination. The
mobile node sets this flag in the Binding Update List
entry when it receives an ICMP Parameter Problem, Code 2,
error message in response to a Binding Update sent to that
destination, as described in Section 9.9.
4.4. Binding Management
When a mobile node configures a new care-of address and decides to When a mobile node configures a new care-of address and decides to
use this new address as its primary care-of address, the mobile use this new address as its primary care-of address, the mobile
node registers this new binding with its home agent by sending node registers this new binding with its home agent by sending
the home agent a Binding Update. The mobile node indicates the home agent a Binding Update. The mobile node indicates
that an acknowledgement is needed for this Binding Update and that an acknowledgement is needed for this Binding Update and
continues to periodically retransmit it until acknowledged. The continues to periodically retransmit it until acknowledged. The
home agent acknowledges the Binding Update by returning a Binding home agent acknowledges the Binding Update by returning a Binding
Acknowledgement to the mobile node. Acknowledgement to the mobile node.
When a mobile node receives a packet tunneled to it from its When a mobile node receives a packet tunneled to it from its
home agent, the mobile node assumes that the original sending home agent, the mobile node assumes that the original sending
correspondent node has no binding cache entry for the mobile node, correspondent node has no Binding Cache entry for the mobile node,
since the correspondent node would otherwise have sent the packet since the correspondent node would otherwise have sent the packet
directly to the mobile node using a Routing header. The mobile node directly to the mobile node using a Routing header. The mobile node
thus returns a Binding Update to the correspondent node, allowing thus returns a Binding Update to the correspondent node, allowing
it to cache the mobile node's binding for routing future packets. it to cache the mobile node's binding for routing future packets.
Although the mobile node may request an acknowledgement for this Although the mobile node may request an acknowledgement for this
Binding Update, it need not, since subsequent packets from the Binding Update, it need not, since subsequent packets from the
correspondent node will continue to be intercepted and tunneled by correspondent node will continue to be intercepted and tunneled by
the mobile node's home agent, effectively causing any needed Binding the mobile node's home agent, effectively causing any needed Binding
Update retransmission. Update retransmission.
A correspondent node with a binding cache entry for a mobile node A correspondent node with a Binding Cache entry for a mobile node
may refresh this binding, for example if the binding's lifetime may refresh this binding, for example if the binding's lifetime
is near expiration, by sending a Binding Request to the mobile is near expiration, by sending a Binding Request to the mobile
node. Normally, a correspondent node will only refresh a binding node. Normally, a correspondent node will only refresh a Binding
cache entry in this way if it is actively communicating with the Cache entry in this way if it is actively communicating with the
mobile node and has indications, such as an open TCP connection to mobile node and has indications, such as an open TCP connection to
the mobile node, that it will continue this communication in the the mobile node, that it will continue this communication in the
future. When a mobile node receives a Binding Request, it replies by future. When a mobile node receives a Binding Request, it replies by
returning a Binding Update to the node sending the Binding Request. returning a Binding Update to the node sending the Binding Request.
A mobile node may use more than one care-of address at the same time, A mobile node may use more than one care-of address at the same
although only one care-of address may be registered for it at its time, although only one care-of address may be registered for it at
home agent as its primary care-of address. The mobile node's home its home agent as its primary care-of address. The mobile node's
agent will tunnel all intercepted packets for the mobile node to its home agent will tunnel all intercepted packets for the mobile node
(single) registered primary care-of address, but the mobile node to its (single) registered primary care-of address, but the mobile
will accept packets that it receives at any of its current care-of node will accept packets that it receives at any of its current
addresses. Use of more than one care-of address by a mobile node may care-of addresses. Use of more than one care-of address by a mobile
be useful, for example, to improve smooth handoff when the mobile node may be useful, for example, to improve smooth handoff when the
node moves from one wireless IP subnet to another. If each wireless mobile node moves from one wireless link to another. If each of
subnet is connected to the Internet through a separate base station, these wireless links is connected to the Internet through a separate
such that the wireless transmission range from the two base stations base station, such that the wireless transmission range from the
overlap, the mobile node may be able to remain link-level connected two base stations overlap, the mobile node may be able to remain
within both subnets while in the area of overlap. In this case, the connected to both links while in the area of overlap. In this case,
mobile node could acquire a new care-of address in the new subnet the mobile node could acquire a new care-of address on the new link
before moving out of transmission range and link-level disconnecting before moving out of transmission range and disconnecting from the
from the old subnet. The mobile node may thus still accept packets old link. The mobile node may thus still accept packets at its
at its old care-of address while it works to update its home agent old care-of address while it works to update its home agent and
and correspondent nodes, notifying them of its new care-of address in correspondent nodes, notifying them of its new care-of address on the
the new subnet. new link.
Since correspondent nodes cache bindings, it is expected that Since correspondent nodes cache bindings, it is expected that
correspondent nodes usually will route packets directly to the mobile correspondent nodes usually will route packets directly to the mobile
node's care-of address, so that the home agent is rarely involved node's care-of address, so that the home agent is rarely involved
with packet transmission to the mobile node. This is essential for with packet transmission to the mobile node. This is essential for
scalability and reliability, and for minimizing overall network load. scalability and reliability, and for minimizing overall network load.
By caching the care-of address of a mobile node, optimal routing of By caching the care-of address of a mobile node, optimal routing of
packets can be achieved from the correspondent node to the mobile packets can be achieved from the correspondent node to the mobile
node. Routing packets directly to the mobile node's care-of address node. Routing packets directly to the mobile node's care-of address
also eliminates congestion at the mobile node's home agent and home also eliminates congestion at the mobile node's home agent and home
subnet. In addition, the impact of of any possible failure of the link. In addition, the impact of of any possible failure of the home
home agent, the home subnet, or intervening networks leading to or agent, the home link, or intervening networks leading to or from the
from the home subnet is reduced, since these nodes and links are not home link is reduced, since these nodes and links are not involved in
involved in the delivery of most packets to the mobile node. the delivery of most packets to the mobile node.
3.2. Comparison with Mobile IP for IPv4
[This section will include a comparison between the Mobile IPv6
protocol and the Mobile IPv4 protocol [11, 10, 12]. However, this
comparison has not yet been written. It will be filled in with the
next revsion to this draft.]
4. New IPv6 Destination Options 5. New IPv6 Destination Options
4.1. Binding Update Option 5.1. Binding Update Option
The Binding Update destination option is used by a mobile node to The Binding Update destination option is used by a mobile node to
notify a correspondent node or the mobile node's home agent of a new notify other nodes of a new care-of address.
care-of address.
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|L| Reserved | |A|H|C| Reserved| ID Length | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime | Sequence Number | | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
| | | |
+ Care-of Address + + Care-of Address +
| (only present if C bit set) | | (only present if C bit set) |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Home Link-Local Address +
| (only present if L bit set) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Type Option Type
192 ??? 195 ???
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. For the excluding the Option Type and Option Length fields. For the
current definition of the Binding Update option, the minimum current definition of the Binding Update option, the minimum
value for this field is 6, for the case in which neither the value for this field is 8; this length is increased by 8 if the
Care-of Address Present (C) bit nor the Home Link-Local Address Care-of Address Present (C) bit is set.
Present (L) bit are set, and the maximum value is 38, for the
case in which both of these bits are set.
Acknowledge (A) Acknowledge (A)
The Acknowledge (A) bit is set by the sending node to request a The Acknowledge (A) bit is set by the sending node to request a
Binding Acknowledgement (Section 4.2) be returned upon receipt Binding Acknowledgement (Section 5.2) be returned upon receipt
of the Binding Update option. of the Binding Update option.
Home Registration (H) Home Registration (H)
The Home Registration (H) bit is set by the sending node to The Home Registration (H) bit is set by the sending mobile node
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 Address in the IP header of the packet carrying The Destination Address in the IP header of the packet carrying
this option MUST be that of a router sharing the same network this option MUST be that of a router sharing the same subnet
prefix as the home address of the mobile node in the binding prefix as the home address of the mobile node in the binding
(given by the Home Address field in the Home Address option in (given by the Home Address field in the Home Address option in
the packet). 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 indicates the presence of
the Care-of Address field in the Binding Update. The care-of the Care-of Address field in the Binding Update. The care-of
address for this binding is either the address in the Care-of address for this binding is either the address in the Care-of
Address field in the Binding Update, if this bit is set, or the Address field in the Binding Update, if this bit is set, or the
Source Address in the packet's IPv6 header, if this bit is not Source Address in the packet's IPv6 header, if this bit is not
set. set.
Home Link-Local Address Present (L)
The Home Link-Local Address Present (L) bit indicates the
presence of the Home Link-Local Address field in the Binding
Update. This bit is set by the sending node to request
the receiving node to act as a proxy (for participating in
the Neighbor Discovery Protocol) for the node while it is
away from home. This bit MUST NOT be set unless the Home
Registration (H) bit is also set in the Binding Update.
Reserved Reserved
Sent as 0; ignored on reception. Sent as 0; ignored on reception.
Lifetime ID Length
16-bit unsigned integer. The number of seconds remaining The ID Length field is valid only for a "home registration"
before the binding must be considered expired. A value of all Binding Update. This field MUST be zero if the Home
ones (0xffff) indicates infinity. A value of zero indicates Registration (H) bit is not set in the Binding Update. The
that the Binding Cache entry for the mobile node should be ID Length field is set by the sending mobile node to the
deleted. (nonzero) length of its interface identifier in its home
address (given in the Home Address option in the packet) to
request its home agent to use this interface identifier to form
all other appropriate home addresses for the mobile node. The
home agent becomes the home agent not only for the individual
home address given in this binding, but also for all other
home addresses for this mobile node formed from this interface
identifier. That is, for each on-link prefix on the home link,
the home agent uses this interface identifier to form other
valid addresses for the mobile node on the home link, and acts
as a home agent also for those addresses. In addition, the
home agent forms the link-local address and site-local address
corresponding to this interface identifier, and defends each
for purposes of Duplicate Address Detection. Details of this
operation are described in Section 8.2.
Sequence Number Sequence Number
Used by the receiving node to sequence Binding Updates and by Used by the receiving node to sequence Binding Updates and by
the sending node to match a returned Binding Acknowledgement the sending node to match a returned Binding Acknowledgement
with this Binding Update. Each Binding Update sent by a mobile with this Binding Update. Each Binding Update sent by a mobile
node MUST use a Sequence Number greater than the Sequence node MUST use a Sequence Number greater than the Sequence
Number value sent in the previous Binding Update (if any) to Number value sent in the previous Binding Update (if any) to
the same destination address (modulo 2**16). There is no the same destination address (modulo 2**16). There is no
requirement, however, that the Sequence Number value strictly requirement, however, that the Sequence Number value strictly
increase by 1 with each new Binding Update sent. increase by 1 with each new Binding Update sent or received.
Lifetime
32-bit unsigned integer. The number of seconds remaining
before the binding must be considered expired. A value of all
one bits (0xffffffff) indicates infinity. A value of zero
indicates that the Binding Cache entry for the mobile node
should be deleted.
Care-of Address Care-of Address
This field in the Binding Update is optional and is only This field in the Binding Update is optional and is only
present when the Care-of Address Present (L) bit is set. If present when the Care-of Address Present (C) bit is set. If
present, it gives the care-of address of the mobile node for present, it gives the care-of address of the mobile node for
this binding. For most Binding Updates sent, it is expected this binding. For most Binding Updates sent, it is expected
that this field will not be present, and instead that the that this field will not be present, and instead that the
care-of address for the binding will be given by the Source care-of address for the binding will be given by the Source
Address field in the packet's IPv6 header. Address field in the packet's IPv6 header.
Home Link-Local Address
This field in the Binding Update is optional and is only
present when the Home Link-Local Address Present (L) bit is
set. If present, it gives the link-local address of the mobile
node used by the mobile node when it was last attached to its
home subnet.
Any packet including a Binding Update option MUST also include a Home Any packet including a Binding Update option MUST also include a Home
Address option. The home address of the mobile node in the binding Address option. The home address of the mobile node in the binding
given in the Binding Update option is indicated by the Home Address given in the Binding Update option is indicated by the Home Address
field in the Home Address option in the packet. field in the Home Address option in the packet.
Any packet that includes a Binding Update option MUST include an IPv6 Any packet that includes a Binding Update option MUST also include
Authentication header [1] in order to protect against forged Binding either an AH [7] or ESP [8] header providing sender authentication,
Updates. The authentication MUST provide sender authentication, data data integrity protection, and replay protection.
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 should be deleted. Likewise, if the Lifetime for the mobile node should 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 should option indicates that any existing binding for the mobile node should
be deleted. In each of these cases, no Binding Cache entry for the be deleted. In each of these cases, no Binding Cache entry for the
mobile node should be created in response to receiving the Binding mobile node should be created in response to receiving the Binding
Update. Update.
The last Sequence Number value sent to a destination is stored by the
mobile node in the Binding Update List entry for that destination;
the last Sequence Number value received from a mobile node is stored
by a correspondent node in the Binding Cache entry for that mobile
node. Thus, the mobile node's and the correspondent node's knowledge
of the last sequence number expire at the same time. If the sending
mobile node has no Binding Update List entry, the Sequence Number
may start at any value; if the receiving correspondent node has no
Binding Cache entry, it should accept a Binding Update with any
Sequence Number value.
The three highest-order bits of the Option Type are encoded to The three highest-order bits of the Option Type are encoded to
indicate specific processing of the option [5]. For the Binding indicate specific processing of the option [5]. For the Binding
Update option, these three bits are set to 110, indicating that the Update option, these three bits are set to 110, indicating that any
IPv6 node processing this option that does not recognize the Option
Type must discard the packet and, only if the packet's Destination
Address was not a multicast address, return an ICMP Parameter
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, and that any IPv6 node processing this option that does destination.
not recognize the Option Type must discard the packet and, only if
the packet's Destination Address was not a multicast address, return
an ICMP Parameter Problem, Code 2, message to the packet's Source
Address.
Extensions to the Binding Update option format may be included after Extensions to the Binding Update option format may be included after
the fixed portion of the Binding Update option specified above. The the fixed portion of the Binding Update option specified above.
presence of such extensions will be indicated by the Option Length The presence of such extensions will be indicated by the Option
field. When the Option Length is greater than the length defined Length field. When the Option Length is greater than the length
above, depending on the state of the Care-of Address Present (C) defined above, the remaining octets are interpreted as extensions.
and Home Link-Local Address Present (L) bits, the remaining octets Currently, no extensions have been defined.
are interpreted as extensions. Currently, no extensions have been
defined.
4.2. Binding Acknowledgement Option 5.2. Binding Acknowledgement Option
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 4.1). 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 node of the packet, this node MUST node being the destination node of the packet, this node MUST
return a Binding Acknowledgement to the source of the packet, if the return a Binding Acknowledgement to the source of the packet, if the
Acknowledge (A) bit is set in the Binding Update. Acknowledge (A) bit is set in the Binding Update.
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 | Lifetime | | Option Length | Status | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Refresh | Sequence Number | | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Refresh |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Type Option Type
193 ??? 2 ???
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. For the excluding the Option Type and Option Length fields. For the
current definition of the Binding Acknowledgement option, this current definition of the Binding Acknowledgement option, this
field MUST be set to 9. field MUST be set to 12.
Status Status
8-bit unsigned integer indicating the disposition of the 8-bit unsigned integer indicating the disposition of the
Binding Update. Values of the Status field less than 128 Binding Update. Values of the Status field less than 128
indicate that the Binding Update was accepted by the receiving indicate that the Binding Update was accepted by the receiving
node. The following such Status values are currently defined: node. The following such Status values are currently defined:
0 Binding Update accepted 0 Binding Update accepted
skipping to change at page 17, line 10 skipping to change at page 20, line 10
node. The following such Status values are currently defined: node. The following such Status values are currently defined:
128 Reason unspecified 128 Reason unspecified
129 Poorly formed Binding Update 129 Poorly formed Binding Update
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
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" [15]. the most recent "Assigned Numbers" [17].
Sequence Number
The Sequence Number in the Binding Acknowledgement is copied
from the Sequence Number field in the Binding Update option,
for use by the mobile node in matching this Acknowledgement
with an outstanding Binding Update.
Lifetime Lifetime
The granted lifetime for which this node will attempt to retain The granted lifetime for which this node will attempt to retain
the entry for this mobile node in its binding cache. If the the entry for this mobile node in its Binding Cache. If the
node sending the Binding Acknowledgement is serving as the node sending the Binding Acknowledgement is serving as the
mobile node's home agent, the Lifetime period also indicates mobile node's home agent, the Lifetime period also indicates
the period for which this node will continue this service; if the period for which this node will continue this service; if
the mobile node requires home agent service from this node the mobile node requires home agent service from this node
beyond this period, the mobile node MUST send a new Binding beyond this period, the mobile node MUST send a new Binding
Update to it before the expiration of this period, in order to Update to it before the expiration of this period, in order to
extend the lifetime. extend the lifetime.
Refresh Refresh
The recommended period at which the mobile node SHOULD send The recommended period at which the mobile node SHOULD send
a new Binding Update to this node in order to "refresh" the a new Binding Update to this node in order to "refresh" the
mobile node's binding in this node's binding cache. This mobile node's binding in this node's Binding Cache. This
refreshing of the binding is useful in case the node fails and refreshing of the binding is useful in case the node fails and
loses its cache state. The Refresh period is determined by loses its cache state. The Refresh period is determined by
the node sending the Binding Acknowledgement (the node caching the node sending the Binding Acknowledgement (the node caching
the binding). If this node is serving as the mobile node's the binding). If this node is serving as the mobile node's
home agent, the Refresh value may be set, for example, based on home agent, the Refresh value may be set, for example, based on
whether the node stores the mobile node's binding in volatile whether the node stores the mobile node's binding in volatile
storage or in nonvolatile storage. If the node sending the storage or in nonvolatile storage. If the node sending the
Binding Acknowledgement is not serving as the mobile node's Binding Acknowledgement is not serving as the mobile node's
home agent, the Refresh period SHOULD be set equal to the home agent, the Refresh period SHOULD be set equal to the
Lifetime period in the Binding Acknowledgement; even if this Lifetime period in the Binding Acknowledgement; even if this
node loses this cache entry due to a failure of the node, node loses this cache entry due to a failure of the node,
packets from it can still reach the mobile node through the packets from it can still reach the mobile node through the
mobile node's home agent, causing a new Binding Update to this mobile node's home agent, causing a new Binding Update to this
node to allow it to recreate this cache entry. node to allow it to recreate this cache entry.
Sequence Number
The Sequence Number in the Binding Acknowledgement is copied
from the Sequence Number field in the Binding Update option,
for use by the mobile node in matching this Acknowledgement
with an outstanding Binding Update.
Any packet that includes a Binding Acknowledgement option MUST Any packet that includes a Binding Acknowledgement option MUST
include an IPv6 Authentication header [1] in order to protect also include either an AH [7] or ESP [8] header providing sender
against forged Binding Acknowledgements. The authentication MUST authentication, data integrity protection, and replay protection.
provide sender 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 this node will have an entry for the mobile node in its Binding Cache
Cache, and MUST use this entry (which includes the care-of address and MUST use this entry (which includes the care-of address received
received in the Binding Update) in sending the packet containing the in the Binding Update) in sending the packet containing the Binding
Binding Acknowledgement to the mobile node. The details of sending Acknowledgement to the mobile node. The details of sending this
this packet to the mobile node are the same as for sending any packet packet to the mobile node are the same as for sending any packet to a
to a mobile node using a binding, and are described in Section 6.8. mobile node using a binding, and are described in Section 7.9. The
The packet is sent using a Routing header, routing the packet to the packet is sent using a Routing header, routing the packet to the
mobile node by way of its care-of address recorded in the Binding mobile node by way of its care-of address recorded in the Binding
Cache entry. Cache entry.
If the node returning the Binding Acknowledgement instead If the node returning the Binding Acknowledgement instead
rejected the Binding Update (the value of the Status field in the rejected the Binding Update (the value of the Status field in the
Acknowledgement is greater than or equal to 128), this node MUST Acknowledgement is greater than or equal to 128), this node MUST
similarly use a Routing header in sending the packet containing the similarly use a Routing header in sending the packet containing the
Binding Acknowledgement, as described in Section 6.8, but MUST NOT Binding Acknowledgement, as described in Section 7.9, but MUST NOT
use its Binding Cache in forming the IP header or Routing header use its Binding Cache in forming the IP header or Routing header
in this packet. Rather, the care-of address used by this node in in this packet. Rather, the care-of address used by this node in
sending the packet containing the Binding Acknowledgement MUST be sending the packet containing the Binding Acknowledgement MUST be
copied from the care-of address received in the rejected Binding copied from the care-of address received in the rejected Binding
Update; this node MUST NOT modify its Binding Cache in response Update; this node MUST NOT modify its Binding Cache in response
to receiving this rejected Binding Update and MUST ignore its to receiving this rejected Binding Update and MUST ignore its
Binding Cache in sending the packet in which it returns this Binding Binding Cache in sending the packet in which it returns this Binding
Acknowledgement. The packet is sent using a Routing header, routing Acknowledgement. The packet is sent using a Routing header, routing
the packet to the home address of the rejected Binding Update by way the packet to the home address of the rejected Binding Update by
of the care-of address indicated in the packet containing the Binding way of the care-of address indicated in the packet containing the
Update. Binding Update. When sending a Binding Acknowledgement to reject a
Binding Update, the Binding Acknowledgement MUST be sent in an IPv6
packet containing no payload (with the Next Header field in the last
extension header in the packet set to indicate "No Next Header" [5]).
The three highest-order bits of the Option Type are encoded to The three highest-order bits of the Option Type are encoded to
indicate specific processing of the option [5]. For the Binding indicate specific processing of the option [5]. For the Binding
Acknowledgement option, these three bits are set to 110, indicating Acknowledgement option, these three bits are set to 000, indicating
that the data within the option cannot change en-route to the that any IPv6 node processing this option that does not recognize the
packet's final destination, and that any IPv6 node processing this Option Type must skip over this option and continue processing the
option that does not recognize the Option Type must discard the header, and that the data within the option cannot change en-route to
packet and, only if the packet's Destination Address was not a the packet's final destination.
multicast address, return an ICMP Parameter Problem, Code 2, message
to the packet's Source Address.
Extensions to the Binding Acknowledgement option format may be Extensions to the Binding Acknowledgement option format may be
included after the fixed portion of the Binding Acknowledgement included after the fixed portion of the Binding Acknowledgement
option specified above. The presence of such extensions will be option specified above. The presence of such extensions will be
indicated by the Option Length field. When the Option Length is indicated by the Option Length field. When the Option Length is
greater than 8 octets, the remaining octets are interpreted as greater than the length defined above, the remaining octets are
extensions. Currently, no extensions have been defined. interpreted as extensions. Currently, no extensions have been
defined.
4.3. Binding Request Option 5.3. Binding Request Option
The Binding Request destination option is used to request a mobile The Binding Request destination option is used to request a mobile
node's binding from the mobile node. When a mobile node receives node's binding from the mobile node. When a mobile node receives
a packet containing a Binding Request option, it SHOULD return a a packet containing a Binding Request option, it SHOULD return a
Binding Update (Section 4.1) to the source of the Binding Request. Binding Update (Section 5.1) to the source of the Binding Request.
The Binding Request option is encoded in type-length-value (TLV) The Binding Request option is encoded in type-length-value (TLV)
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 | | Option Type | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Type Option Type
194 ??? 3 ???
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. For the excluding the Option Type and Option Length fields. For the
current definition of the Binding Request option, this field current definition of the Binding Request option, this field
MUST be set to 0. MUST be set to 0.
The three highest-order bits of the Option Type are encoded to The three highest-order bits of the Option Type are encoded to
indicate specific processing of the option [5]. For the Binding indicate specific processing of the option [5]. For the Binding
Request option, these three bits are set to 110, indicating that the Request option, these three bits are set to 000, indicating that any
data within the option cannot change en-route to the packet's final IPv6 node processing this option that does not recognize the Option
destination, and that any IPv6 node processing this option that does Type must skip over this option and continue processing the header,
not recognize the Option Type must discard the packet and, only if and that the data within the option cannot change en-route to the
the packet's Destination Address was not a multicast address, return packet's final destination.
an ICMP Parameter Problem, Code 2, message to the packet's Source
Address.
Extensions to the Binding Request option format may be included after Extensions to the Binding Request option format may be included after
the fixed portion of the Binding Request option specified above. the fixed portion of the Binding Request option specified above.
The presence of such extensions will be indicated by the Option The presence of such extensions will be indicated by the Option
Length field. When the Option Length is greater than 0 octets, Length field. When the Option Length is greater than 0 octets,
the remaining octets are interpreted as extensions. Currently, no the remaining octets are interpreted as extensions. Currently, no
extensions have been defined. extensions have been defined.
4.4. Home Address Option 5.4. Home Address Option
The Home Address destination option is used in a packet sent by a The Home Address destination option is used in a packet sent by a
mobile node to inform the recipient of that packet of the mobile mobile node to inform the recipient of that packet of the mobile
node's home address. For packets sent by a mobile node while node's home address. For packets sent by a mobile node while
away from home, the mobile node generally uses one of its care-of away from home, the mobile node generally uses one of its care-of
addresses as the Source Address in the packet's IPv6 header. By addresses as the Source Address in the packet's IPv6 header. By
including a Home Address option in the packet, the correspondent including a Home Address option in the packet, the correspondent
node receiving the packet is able to substitute the mobile node's node receiving the packet is able to substitute the mobile node's
home address for this care-of address when processing the packet, home address for this care-of address when processing the packet,
thus making the use of the care-of address transparent to the thus making the use of the care-of address transparent to the
skipping to change at page 21, line 37 skipping to change at page 24, line 37
+ + + +
| | | |
+ Home Address + + Home Address +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Type Option Type
195 ??? 196 ???
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. For the excluding the Option Type and Option Length fields. For the
current definition of the Home Address option, this field MUST current definition of the Home Address option, this field MUST
be set to 8. be set to 16.
Home Address Home Address
The home address of the mobile node sending the packet. The home address of the mobile node sending the packet.
The inclusion of a Home Address option in a packet affects only The inclusion of a Home Address option in a packet affects only
the correspondent node's receipt of this single packet; no state the correspondent node's receipt of this single packet; no state
is created or modified in the correspondent node as a result of is created or modified in the correspondent node as a result of
receiving a Home Address option in a packet. In particular, the receiving a Home Address option in a packet. In particular, the
receipt of a packet containing a Home Address option MUST NOT alter receipt of a packet containing a Home Address option MUST NOT alter
the contents of the receiver's Binding Cache due to the presence of the contents of the receiver's Binding Cache due to the presence of
the Home Address option, and the mapping between the home address the Home Address option, and the mapping between the home address
and care-of address indicated by the Home Address option MUST NOT be and care-of address indicated by the Home Address option MUST NOT be
used as a basis for routing subsequent packets sent by this receiving used as a basis for routing subsequent packets sent by this receiving
node. node.
No special authentication of the Home Address option is required, No special authentication of the Home Address option is required,
except that if the IPv6 header of a packet is covered by except that if the IPv6 header of a packet is covered by
authentication, then that authentication MUST also cover the Home authentication, then that authentication MUST also cover the Home
Address option. If the packet carries no IP authentication, then the Address option; this coverage is achieved automatically by the
definition of the Option Type code for the Home Address option,
since it indicates that the option is included in the authentication
computation. If the packet carries no IP authentication, then the
contents of the Home Address option, as well as the Source Address contents of the Home Address option, as well as the Source Address
field or any other field in the IPv6 header, may have been forged or field or any other field in the IPv6 header, may have been forged or
altered during transit. Upon receipt of a packet containing a Home altered during transit. Upon receipt of a packet containing a Home
Address option, the receiving node replaces the Source Address in Address option, the receiving node replaces the Source Address in
the IPv6 header with the Home Address in the Home Address option. the IPv6 header with the Home Address in the Home Address option.
By requiring that any authentication of the IPv6 header also cover By requiring that any authentication of the IPv6 header also cover
the Home Address option, the security of the Source Address field in the Home Address option, the security of the Source Address field in
the IPv6 header is not compromised by the presence of a Home Address the IPv6 header is not compromised by the presence of a Home Address
option. Security issues related to the Home Address option are option. Security issues related to the Home Address option are
discussed further in Section 11. discussed further in Section 13.
The three highest-order bits of the Option Type are encoded to The three highest-order bits of the Option Type are encoded to
indicate specific processing of the option [5]. For the Home Address indicate specific processing of the option [5]. For the Home Address
option, these three bits are set to 110, indicating that the data option, these three bits are set to 110, indicating that any IPv6
node processing this option that does not recognize the Option Type
must discard the packet and, only if the packet's Destination Address
was not a multicast address, return an ICMP Parameter 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 within the option cannot change en-route to the packet's final
destination, and that any IPv6 node processing this option that does destination.
not recognize the Option Type must discard the packet and, only if
the packet's Destination Address was not a multicast address, return
an ICMP Parameter Problem, Code 2, message to the packet's Source
Address.
Extensions to the Home Address option format may be included after Extensions to the Home Address option format may be included after
the fixed portion of the Home Address option specified above. the fixed portion of the Home Address option specified above.
The presence of such extensions will be indicated by the Option The presence of such extensions will be indicated by the Option
Length field. When the Option Length is greater than 8 octets, Length field. When the Option Length is greater than 8 octets,
the remaining octets are interpreted as extensions. Currently, no the remaining octets are interpreted as extensions. Currently, no
extensions have been defined. extensions have been defined.
5. Requirements for IPv6 Nodes 6. Requirements for IPv6 Nodes
Mobile IPv6 places some special requirements on the functions Mobile IPv6 places some special requirements on the functions
provided by different IPv6 nodes. This section summarizes those provided by different IPv6 nodes. This section summarizes those
requirements, identifying the functionality each requirement is requirements, identifying the functionality each requirement is
intended to support. Further details on this functionality is intended to support. Further details on this functionality is
provided in the following sections. provided in the following sections.
Since any IPv6 node may at any time be a correspondent node of a Since any IPv6 node may at any time be a correspondent node of a
mobile node, the following requirements pertain to all IPv6 nodes: mobile node, the following requirements pertain to all IPv6 nodes:
skipping to change at page 23, line 27 skipping to change at page 26, line 27
received in a packet. received in a packet.
- Every IPv6 node SHOULD be able to process a Binding Update option - Every IPv6 node SHOULD be able to process a Binding Update option
received in a packet, and to return a Binding Acknowledgement received in a packet, and to return a Binding Acknowledgement
option if requested. option if requested.
- Every IPv6 node SHOULD be able to maintain a Binding Cache of the - Every IPv6 node SHOULD be able to maintain a Binding Cache of the
bindings received in accepted Binding Updates. bindings received in accepted Binding Updates.
In order for a mobile node to operate correctly while away from In order for a mobile node to operate correctly while away from
home, at least one IPv6 router in the mobile node's home subnet must home, at least one IPv6 router in the mobile node's home link must
function as a home agent for the mobile node. The following special function as a home agent for the mobile node. The following special
requirements pertain to all IPv6 routers capable of serving as a home requirements pertain to all IPv6 routers capable of serving as a home
agent: agent:
- Every home agent MUST be able to maintain an entry in its Binding - Every home agent MUST be able to maintain an entry in its Binding
Cache for each mobile node for which it is serving as the home Cache for each mobile node for which it is serving as the home
agent. Each such Binding Cache entry records the mobile node's agent. Each such Binding Cache entry records the mobile node's
binding with its primary care-of address and is marked as a "home binding with its primary care-of address and is marked as a "home
registration". registration".
skipping to change at page 24, line 14 skipping to change at page 27, line 12
as a home agent, and MUST be able to participate in dynamic home as a home agent, and MUST be able to participate in dynamic home
agent address discovery. agent address discovery.
Finally, the following requirements pertain all IPv6 nodes capable of Finally, the following requirements pertain all IPv6 nodes capable of
functioning as mobile nodes: 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 Updates, as - Every IPv6 mobile node MUST support sending Binding Updates, as
specified in Sections 8.4, 8.5, and 8.6; and MUST be able to specified in Sections 9.4, 9.5, and 9.6; and MUST be able to
receive and process Binding Acknowledgements, as specified in receive and process Binding Acknowledgements, as specified in
Section 8.9. Section 9.10.
- Every IPv6 mobile node MUST maintain a Binding Update List in - Every IPv6 mobile node MUST maintain a Binding Update List in
which it records the IP address of each other node to which it which it records the IP address of each other node to which it
has sent a Binding Update, for which the Lifetime sent in that has sent a Binding Update, for which the Lifetime sent in that
binding has not yet expired. binding has not yet expired.
6. Correspondent Node Operation - Every IPv6 mobile node MUST support receiving a Binding Request
by responding with a Binding Update.
- Every IPv6 mobile node MUST support sending packets containing a
Home Address option; this option MUST be included in all packets
sent while away from home, if the packet would otherwise have
been sent with the mobile node's home address as the IP Source
Address.
7. Correspondent Node Operation
A correspondent node is any node communicating with a mobile node. A correspondent node is any node communicating with a mobile node.
The correspondent node, itself, may be fixed or mobile, and may The correspondent node, itself, may be fixed or mobile, and may
possibly also be functioning as a home agent for Mobile IPv6. The possibly also be functioning as a home agent for Mobile IPv6. The
procedures in this section thus apply to all IPv6 nodes. procedures in this section thus apply to all IPv6 nodes.
6.1. Receiving Packets from a Mobile Node 7.1. Receiving Packets from a Mobile Node
Packets sent by a mobile node while away from home generally include Packets sent by a mobile node while away from home generally include
a Home Address option. When a node receives a packet containing a Home Address option. When any node receives a packet containing
a Home Address option, it MUST process the option in a manner a Home Address option, it MUST process the option in a manner
consistent with copying the Home Address field from the Home Address consistent with copying the Home Address field from the Home Address
option into the IPv6 header, replacing the original value of the option into the IPv6 header, replacing the original value of the
Source Address field there. Further processing of the packet (e.g., Source Address field there. Further processing of the packet (e.g.,
at the transport layer) thus need not know that the original Source at the transport layer) thus need not know that the original Source
Address was a care-of address, or that the Home Address option was Address was a care-of address, or that the Home Address option was
used in the packet. Since the sending mobile node uses its home used in the packet. Since the sending mobile node uses its home
address at the transport layer when sending such a packet, the use of address at the transport layer when sending such a packet, the use of
the care-of address and Home Address option is thus transparent to the care-of address and Home Address option is thus transparent to
both the mobile node and the correspondent node above the level of both the mobile node and the correspondent node above the level of
the Home Address option generation and processing. the Home Address option generation and processing.
6.2. Receiving Binding Updates 7.2. 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 an IP Authentication header and the - The packet contains a valid AH [7] or ESP [8] header that
authentication is valid [1]. The Authentication header MUST provides sender authentication, integrity protection, and replay
provide sender authentication, integrity protection, and replay
protection. protection.
- 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 4.1. than or equal to the length specified in Section 5.1.
- The Sequence Number field in the Binding Update option is greater - The Sequence Number field in the Binding Update option is greater
than the Sequence Number received in the previous Binding Update than the Sequence Number received in the previous Binding Update
for this home address, if any. The Sequence Number comparison is for this home address, if any. The Sequence Number comparison is
performed modulo 2**16. performed modulo 2**16.
- 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.
Any Binding Update not satisfying all of these tests MUST be silently Any Binding Update not satisfying all of these tests MUST be
ignored, although the remainder of the packet (i.e., other options, silently ignored, and the packet carrying the Binding Update MUST be
extension headers, or payload) SHOULD be processed normally according discarded.
to any procedure defined for that part of the packet.
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 a local subnet and this address Home-Agents anycast address for a local subnet and this address
is assigned to one of this node's network interfaces, then the is assigned to one of this node's network interfaces, then the
mobile node sending this Binding Update is attempting dynamic mobile node sending this Binding Update is attempting dynamic
home agent address discovery. Processing for this type of home agent address discovery. Processing for this type of
received Binding Update is described in Section 7.1. (If the received Binding Update is described in Section 8.1. (If the
Destination Address is not assigned to one of this node's network Destination Address is not assigned to one of this node's network
interfaces, then the packet would have been forwarded as a normal interfaces, then the packet would have been forwarded as a normal
packet and the Binding Update, as a destination option, would not packet and the Binding Update, as a destination option, would not
be processed in any way by this node.) 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, then this is a request to cache a binding for for the binding (as given in the Home Address option in the
the mobile node. Processing for this type of received Binding packet), then this is a request to cache a binding for the mobile
Update is described in Section 6.3. node. Processing for this type of received Binding Update is
described in Section 7.3.
- If the Lifetime specified in the Binding Update is zero or the - If the Lifetime specified in the Binding Update is zero or the
specified Care-of Address matches the home address for the specified Care-of Address matches the home address for the
binding, then this is a request to delete the mobile node's binding, then this is a request to delete the mobile node's
cached binding. Processing for this type of received Binding cached binding. Processing for this type of received Binding
Update is described in Section 6.4. Update is described in Section 7.4.
6.3. Requests to Cache a Binding 7.3. Requests to Cache a Binding
If a node receives a valid Binding Update requesting it to cache a If a node receives a valid Binding Update requesting it to cache a
binding for a mobile node, as specified in Section 6.2, then the node binding for a mobile node, as specified in Section 7.2, then the node
MUST examine the Home Registration (H) bit in the Binding Update MUST examine the Home Registration (H) bit in the Binding Update
to determine how to further process the Binding Update. If the to determine how to further process the Binding Update. If the
Home Registration (H) bit is set, the Binding Update is processed Home Registration (H) bit is set, the Binding Update is processed
according to the procedure specified in Section 7.2. according to the procedure specified in Section 8.2.
If the Home Registration (H) bit is not set, then the receiving node If the Home Registration (H) bit is not set, then the receiving
SHOULD create a new entry in its Binding Cache for this mobile node node SHOULD create a new entry in its Binding Cache for this mobile
(or update its existing Binding Cache entry for this mobile node, if node (or update its existing Binding Cache entry for this mobile
such an entry already exists). The home address of the mobile node node, if such an entry already exists). The home address of the
is taken from the Home Address field in the packet's Home Address mobile node is taken from the Home Address field in the packet's Home
option. The new Binding Cache entry records the association between Address option. The new Binding Cache entry records the association
this address and the care-of address for the binding, as specified between this home address and the care-of address for the binding, as
in either the Care-of Address field of the Binding Update or in the specified in either the Care-of Address field of the Binding Update
Source Address field in the packet's IPv6 header. Any Binding Cache or in the Source Address field in the packet's IPv6 header. Any
entry created or updated in response to processing this Binding Binding Cache entry created or updated in response to processing this
Update MUST be deleted after the expiration of the Lifetime period Binding Update MUST be deleted after the expiration of the Lifetime
specified in the Binding Update. period specified in the Binding Update.
6.4. Requests to Delete a Binding 7.4. Requests to Delete a Binding
If a node receives a valid Binding Update requesting it to delete a If a node receives a valid Binding Update requesting it to delete a
cached binding for a mobile node, as specified in Section 6.2, then cached binding for a mobile node, as specified in Section 7.2, then
the node MUST examine the Home Registration (H) bit in the Binding the node MUST examine the Home Registration (H) bit in the Binding
Update to determine how to further process the Binding Update. If Update to determine how to further process the Binding Update. If
the Home Registration (H) bit is set, the Binding Update is processed the Home Registration (H) bit is set, the Binding Update is processed
according to the procedure specified in Section 7.3. according to the procedure specified in Section 8.3.
If the Home Registration (H) bit is not set, then the receiving node If the Home Registration (H) bit is not set, then the receiving node
MUST delete any existing entry in its Binding Cache for this mobile MUST delete any existing entry in its Binding Cache for this mobile
node. The home address of the mobile node is taken from the Home node. The home address of the mobile node is taken from the Home
Address field in the packet's Home Address option. Address field in the packet's Home Address option.
6.5. Sending Binding Acknowledgements 7.5. Sending Binding Acknowledgements
When any node receives a packet containing a Binding Update option When any node receives a packet containing a Binding Update option
in which the Acknowledge (A) bit is set, it SHOULD return a Binding in which the Acknowledge (A) bit is set, it 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 4.2 and Specific values for the Status field are described in Section 5.2 and
in the most recent "Assigned Numbers" [15]. in the most recent "Assigned Numbers" [17].
As described in Section 4.2, the packet in which the Binding As described in Section 5.2, the packet in which the Binding
Acknowledgement is returned MUST include an IPv6 Authentication Acknowledgement is returned MUST include either an AH [7] or ESP [8]
header [1] in order to protect against forged Binding header providing sender authentication, data integrity protection,
Acknowledgements, 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 not accepted), as using a care-of address (even if the binding was rejected), as
described in Section 6.8. The packet is routed first to the care-of described in Section 7.9. 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.
6.6. Cache Replacement Policy 7.6. Sending Binding Requests
Entries in a node's Binding Cache MUST be deleted when their lifetime
expires. If such an entry is still in active use in sending packets
to a mobile node, the next packet sent to the mobile node will be
routed normally, to the mobile node's home link, where it will be
intercepted and forwarded to the mobile node. The mobile node will
then return a Binding Update to the sender, allowing it to create
a new Binding Cache entry for sending future packets to the mobile
node. Communication with the mobile node continues uninterrupted,
but the forwarding of this packet through the mobile node's home
agent creates additional overhead and latency in delivering packets
to the mobile node.
If the sender knows that the Binding Cache entry is still in active
use, it MAY send a Binding Request to the mobile node in an attempt
to avoid this overhead and latency due to deleting and recreating
the Binding Cache entry. Since a Binding Request is a destination
option, it may, for example, be included in any packet already being
sent to the mobile node, such as a packet that is part of ongoing TCP
communication with the mobile node. When the mobile node receives a
packet from some sender containing a Binding Request, it returns a
Binding Update to that sender, giving its current binding and a new
lifetime.
7.7. Cache Replacement Policy
Any entry in a node's Binding Cache MUST be deleted after the Any entry in a node's Binding Cache MUST be deleted after the
expiration of the Lifetime specified in the Binding Update from which expiration of the Lifetime specified in the Binding Update from which
the entry was created or was last updated. Conceptually, a node the entry was created or was last updated. Conceptually, a node
maintains a separate timer for each entry in its Binding Cache. When maintains a separate timer for each entry in its Binding Cache. When
creating or updating a Binding Cache entry in response to a received creating or updating a Binding Cache entry in response to a received
and accepted Binding Update, the node sets the timer for this entry and accepted Binding Update, the node sets the timer for this entry
to the specified Lifetime period. When a Binding Cache entry's timer to the specified Lifetime period. When a Binding Cache entry's timer
expires, the node deletes the entry. expires, the node deletes the entry.
Each node's Binding Cache will, by necessity, have a finite size. Each node's Binding Cache will, by necessity, have a finite size.
A node MAY use any reasonable local policy for managing the space A node MAY use any reasonable local policy for managing the space
within its Binding Cache, except that any entry marked as a "home within its Binding Cache, except that any entry marked as a "home
registration" (Section 7.2) MUST NOT be deleted from the cache until registration" (Section 8.2) MUST NOT be deleted from the cache until
the expiration of its lifetime period. When attempting to add a the expiration of its lifetime period. When attempting to add a
new "home registration" entry in response to a Binding Update with new "home registration" entry in response to a Binding Update with
the Home Registration (H) bit set, if insufficient space exists (or the Home Registration (H) bit set, if insufficient space exists (or
can be reclaimed) in the node's Binding Cache, the node MUST reject can be reclaimed) in the node's Binding Cache, the node MUST reject
the Binding Update and SHOULD return a Binding Acknowledgement to the Binding Update and SHOULD return a Binding Acknowledgement to
the sending mobile node, in which the Status field is set to 131 the sending mobile node, in which the Status field is set to 131
(insufficient resources). When otherwise attempting to add a new (insufficient resources). When otherwise attempting to add a new
entry to its Binding Cache, a node MAY, if needed, choose to drop any entry to its Binding Cache, a node MAY, if needed, choose to drop any
entry already in its Binding Cache, other than a "home registration" entry already in its Binding Cache, other than a "home registration"
entry, in order to make space for the new entry. For example, a entry, in order to make space for the new entry. For example, a
"least-recently used" (LRU) strategy for cache entry replacement "least-recently used" (LRU) strategy for cache entry replacement
among entries not marked as a "home registration" is likely to work among entries not marked as a "home registration" is likely to work
well. well.
Any binding dropped from a node's Binding Cache due to lack of cache Any binding dropped from a node's Binding Cache due to lack of cache
space will be rediscovered and a new cache entry created, if the space will be rediscovered and a new cache entry created, if the
binding is still in active use by the node for sending packets. If binding is still in active use by the node for sending packets. If
the node sends a packet to a destination for which it has dropped the the node sends a packet to a destination for which it has dropped the
entry from its Binding Cache, the packet will be routed normally, entry from its Binding Cache, the packet will be routed normally,
leading to the mobile node's home subnet. There, the packet will leading to the mobile node's home link. There, the packet will be
be intercepted by the mobile node's home agent and tunneled to the intercepted by the mobile node's home agent and tunneled to the
mobile node's current primary care-of address. As when a Binding mobile node's current primary care-of address. As when a Binding
Cache entry is initially created, this indirect routing to the mobile Cache entry is initially created, this indirect routing to the mobile
node through its home agent will result in the mobile node sending node through its home agent will result in the mobile node sending
a Binding Update to this sending node when it receives the tunneled a Binding Update to this sending node when it receives the tunneled
packet, allowing it to add an entry again for this destination to its packet, allowing it to add an entry again for this destination to its
Binding Cache. Binding Cache.
6.7. Receiving ICMP Error Messages 7.8. Receiving ICMP Error Messages
When a correspondent node sends a packet to a mobile node, if the When a correspondent node sends a packet to a mobile node, if the
correspondent node has a Binding Cache entry for the destination correspondent node has a Binding Cache entry for the destination
address of the packet, then the correspondent node uses a Routing address of the packet, then the correspondent node uses a Routing
header to deliver the packet to the mobile node through the care-of header to deliver the packet to the mobile node through the care-of
address in the binding recorded in the Binding Cache entry. Any ICMP address in the binding recorded in the Binding Cache entry. Any ICMP
error message caused by the packet on its way to the mobile node will error message caused by the packet on its way to the mobile node will
be returned normally to the correspondent node. be returned normally to the correspondent node.
On the other hand, if the correspondent node has no Binding Cache On the other hand, if the correspondent node has no Binding Cache
entry for the mobile node, the packet will be routed to the mobile entry for the mobile node, the packet will be routed to the mobile
node's home subnet, where it will be intercepted by the mobile node's node's home link, where it will be intercepted by the mobile node's
home agent, encapsulated, and tunneled to the mobile node's primary home agent, encapsulated, and tunneled to the mobile node's primary
care-of address. Any ICMP error message caused by the packet on care-of address. Any ICMP error message caused by the packet on
its way to the mobile node while in the tunnel, will be returned to its way to the mobile node while in the tunnel, will be returned to
the mobile node's home agent (the source of the tunnel). By the the mobile node's home agent (the source of the tunnel). By the
definition of IPv6 encapsulation [4], this encapsulating node MUST definition of IPv6 encapsulation [4], this encapsulating node MUST
relay certain ICMP error messages back to the original sender of the relay certain ICMP error messages back to the original sender of the
packet, which in this case is the correspondent node. packet, which in this case is the correspondent node.
Likewise, if a packet for a mobile node arrives at the mobile node's Likewise, if a packet for a mobile node arrives at the mobile node's
previous default router (e.g., the mobile node moved after the packet previous default router (e.g., the mobile node moved after the packet
was sent), the router will encapsulate and tunnel the packet to the was sent), the router will encapsulate and tunnel the packet to the
mobile node's new care-of address (if it has a Binding Cache entry mobile node's new care-of address (if it has a Binding Cache entry
for the mobile node). As above, any ICMP error message caused by the for the mobile node). As above, any ICMP error message caused by the
packet while in this tunnel will be returned to the previous default packet while in this tunnel will be returned to the previous default
router (the source of the tunnel), which MUST relay certain ICMP router (the source of the tunnel), which MUST relay certain ICMP
error messages back to the correspondent node [4]. error messages back to the correspondent node [4].
Thus, in all cases, any meaningful ICMP error messages caused by Thus, in all cases, any meaningful ICMP error messages caused
packets from a correspondent node to a mobile node will be returned by packets from a correspondent node to a mobile node will be
to the correspondent node. If the correspondent node receives returned to the correspondent node. If the correspondent node
persistent ICMP Host Unreachable or Network Unreachable error receives persistent ICMP Destination Unreachable messages after
messages after sending packets to a mobile node based on an entry in sending packets to a mobile node based on an entry in its Binding
its Binding Cache, the correspondent node SHOULD delete this Binding Cache, the correspondent node SHOULD delete this Binding Cache
Cache entry. If the correspondent node subsequently transmits entry. If the correspondent node subsequently transmits another
another packet to the mobile node, the packet will be routed to the packet to the mobile node, the packet will be routed to the mobile
mobile node's home subnet, intercepted by the mobile node's home node's home link, intercepted by the mobile node's home agent, and
agent, and tunneled to the mobile node's primary care-of address tunneled to the mobile node's primary care-of address using IPv6
using IPv6 encapsulation. The mobile node will then return a Binding encapsulation. The mobile node will then return a Binding Update to
Update to the correspondent node, allowing it to recreate a (correct) the correspondent node, allowing it to recreate a (correct) Binding
Binding Cache entry for the mobile node. Cache entry for the mobile node.
6.8. Sending Packets to a Mobile Node 7.9. Sending Packets to a Mobile Node
Before sending any packet, the sending node SHOULD examine its Before sending any packet, the sending node SHOULD examine its
Binding Cache for an entry for the destination address to which the Binding Cache for an entry for the destination address to which the
packet is being sent. If the sending node has a Binding Cache entry packet is being sent. If the sending node has a Binding Cache entry
for this address, the sending node SHOULD use a Routing header to for this address, the sending node SHOULD use a Routing header to
route the packet to this mobile node (the destination node) by way route the packet to this mobile node (the destination node) by way
of the care-of address in the binding recorded in that Binding Cache of the care-of address in the binding recorded in that Binding Cache
entry. For example, assuming use of a Type 0 Routing header [5], if entry. For example, assuming use of a Type 0 Routing header [5], if
no other use of a Routing header is involved in the routing of this no other use of a Routing header is involved in the routing of this
packet, the mobile node sets the fields in the packet's IPv6 header packet, the mobile node sets the fields in the packet's IPv6 header
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If, instead, the sending node has no Binding Cache entry for the If, instead, the sending node has no Binding Cache entry for the
destination address to which the packet is being sent, the sending destination address to which the packet is being sent, the sending
node simply sends the packet normally, with no Routing header. If node simply sends the packet normally, with no Routing header. If
the destination node is not a mobile node (or is a mobile node that the destination node is not a mobile node (or is a mobile node that
is currently at home), the packet will be delivered directly to this is currently at home), the packet will be delivered directly to this
node and processed normally by it. If, however, the destination node node and processed normally by it. If, however, the destination node
is a mobile node that is currently away from home, the packet will is a mobile node that is currently away from home, the packet will
be intercepted by the mobile node's home agent and tunneled (using be intercepted by the mobile node's home agent and tunneled (using
IPv6 encapsulation [4]) to the mobile node's current primary care-of IPv6 encapsulation [4]) to the mobile node's current primary care-of
address, as described in Section 7.4. The mobile node will then send address, as described in Section 8.4. The mobile node will then send
a Binding Update to the sending node, as described in Section 8.5, a Binding Update to the sending node, as described in Section 9.5,
allowing the sending node to create a Binding Cache entry for its use allowing the sending node to create a Binding Cache entry for its use
in sending subsequent packets to this mobile node. in sending subsequent packets to this mobile node.
7. Home Agent Operation 8. Home Agent Operation
7.1. Dynamic Home Agent Address Discovery 8.1. Dynamic Home Agent Address Discovery
If a received Binding Update indicates that the mobile node sending If a received Binding Update indicates that the mobile node sending
it is attempting dynamic home agent address discovery, as described it is attempting dynamic home agent address discovery, as described
in Section 6.2, then the receiving node MUST process the Binding in Section 7.2, then the receiving node MUST process the Binding
Update as specified in this section. Update as specified in this section.
A mobile node attempts dynamic home agent address discovery by A mobile node attempts dynamic home agent address discovery by
sending its "home registration" Binding Update to the Home-Agents sending its "home registration" Binding Update to the Home-Agents
anycast address for its home IP subnet (the packet MUST also include anycast address for its home IP subnet prefix (the packet MUST also
a Home Address option, as described in Section 8.4). A home agent include a Home Address option, as described in Section 9.4). A home
receiving such a Binding Update that is serving this subnet (the agent receiving such a Binding Update that is serving this subnet
home agent is configured with this anycast address on one of its (the home agent is configured with this anycast address on one of its
network interfaces) MUST reject the Binding Update and SHOULD return network interfaces) MUST reject the Binding Update and SHOULD return
a Binding Acknowledgement indicating this rejection and giving its a Binding Acknowledgement indicating this rejection, with the Source
unicast address. The Status field in the Binding Acknowledgement Address of the packet carrying the Binding Acknowledgement set to
MUST be set to 135 (dynamic home agent address discovery response). one of the unicast addresses of the home agent. The Status field in
The mobile node, upon receiving this Binding Acknowledgement, MAY the Binding Acknowledgement MUST be set to 135 (dynamic home agent
then resend its Binding Update to the unicast home agent address address discovery response). The mobile node, upon receiving this
given in the Acknowledgement. Binding Acknowledgement, MAY then resend its Binding Update to the
unicast home agent address given in the Acknowledgement.
7.2. Primary Care-of Address Registration 8.2. Primary Care-of Address Registration
General processing of a received Binding Update that requests a General processing of a received Binding Update that requests a
binding to be cached, is described in Section 6.3. However, if the binding to be cached, is described in Section 7.3. However, if the
Home Registration (H) bit is set in the Binding Update, then the Home Registration (H) bit is set in the Binding Update, then the
receiving node MUST process the Binding Update as specified in this receiving node MUST process the Binding Update as specified in this
section, rather than following the general procedure specified in section, rather than following the general procedure specified in
Section 6.3. Section 7.3.
To begin processing the Binding Update, the home agent MUST perform To begin processing the Binding Update, the home agent MUST perform
the following sequence of tests: the following sequence of tests:
- If the node is not a router that implements home agent - If the node is not a router that implements home agent
functionality, then the node MUST reject the Binding Update and functionality, then the node MUST reject the Binding Update and
SHOULD return a Binding Acknowledgement to the mobile node, in SHOULD return a Binding Acknowledgement to the mobile node, in
which the Status field is set to 132 (home registration not which the Status field is set to 132 (home registration not
supported). supported).
- Else, if the home address for the binding (the Home Address field - Else, if the home address for the binding (the Home Address field
in the packet's Home Address option) is not an on-link IPv6 in the packet's Home Address option) is not an on-link IPv6
address with respect to the home agent's current Prefix List, address with respect to the home agent's current Prefix List,
then the home agent MUST reject the Binding Update and SHOULD then the home agent MUST reject the Binding Update and SHOULD
return a Binding Acknowledgement to the mobile node, in which the return a Binding Acknowledgement to the mobile node, in which the
Status field is set to 133 (not home subnet). Status field is set to 133 (not home subnet).
- Else, if the ID Length field is nonzero in the Binding Update
and this length differs from the length of the home agent's own
interface identifier on the interface for which it is being
asked to serve as home agent for this mobile node (the interface
defined by the subnet prefix in the mobile node's home address in
the binding), then the home agent MUST reject the Binding Update
and SHOULD return a Binding Acknowledgement to the mobile node,
in which the Status field is set to 136 (incorrect interface
identifier length).
- Else, if the home agent chooses to reject the Binding Update for - Else, if the home agent chooses to reject the Binding Update for
any other reason (e.g., insufficient resources to serve another any other reason (e.g., insufficient resources to serve another
mobile node as a home agent), then the home agent SHOULD return a mobile node as a home agent), then the home agent SHOULD return a
Binding Acknowledgement to the mobile node, in which the Status Binding Acknowledgement to the mobile node, in which the Status
field is set to an appropriate value to indicate the reason for field is set to an appropriate value to indicate the reason for
the rejection. the rejection.
If the home agent does not reject the Binding Update as described If the home agent does not reject the Binding Update as described
above, then it becomes the home agent for the mobile node. The new above, then it becomes the home agent for the mobile node. The new
home agent (the receiving node) MUST then create a new entry or home agent (the receiving node) MUST then create a new entry or
update the existing entry in its Binding Cache for this mobile node's update the existing entry in its Binding Cache for this mobile node's
home address, as described in Section 6.3. In addition, the home home address (given in the Home Address option in the packet), as
agent MUST mark this Binding Cache entry as a "home registration" described in Section 7.3. In addition, the home agent MUST mark
to indicate that the node is serving as a home agent for this this Binding Cache entry as a "home registration" to indicate that
binding. Binding Cache entries marked as a "home registration" MUST the node is serving as a home agent for this binding. Binding
be excluded from the normal cache replacement policy used for the Cache entries marked as a "home registration" MUST be excluded from
Binding Cache (Section 6.6) and MUST NOT be removed from the Binding the normal cache replacement policy used for the Binding Cache
Cache until the expiration of the Lifetime period. (Section 7.7) and MUST NOT be removed from the Binding Cache until
the expiration of the Lifetime period.
If the home agent was not already serving as a home agent for this If the home agent was not already serving as a home agent for this
mobile node (the home agent did not already have a Binding Cache mobile node (the home agent did not already have a Binding Cache
entry for this home address marked as a "home registration"), then entry for this home address marked as a "home registration"), then
the home agent MUST multicast onto the home subnet (to the all-nodes the home agent MUST multicast onto the home link a "gratuitous"
multicast address) a Neighbor Advertisement message [9] on behalf Neighbor Advertisement message [11] on behalf of the mobile node, in
of the mobile node, to advertise the home agent's own link-layer order to begin intercepting packets addressed to it while it is away
address for the mobile node's home IP address. The Target Address in from home. Specifically, the home agent follows the following steps:
the Neighbor Advertisement message MUST be set to the mobile node's
home address, and the Advertisement MUST include a Target Link-layer
Address option specifying the home agent's link-layer address. The
Solicited Flag (S) in the Advertisement MUST NOT be set, since it was
not solicited by any Neighbor Solicitation message. The Override
Flag (O) in the Advertisement MUST be set, indicating that the
Advertisement SHOULD override any existing Neighbor Cache entry at
any node receiving it.
Any node on the home subnet receiving this Neighbor Advertisement - The home agent examines the value of the ID Length field in
message will thus update its Neighbor Cache to associate the mobile the Binding Update. If this value is zero, the following step
node's home address with the home agent's link layer address, causing is carried out only for the individual home address specified
it to transmit any future packets for the mobile node instead to (in the Home Address option in the packet) for this binding.
the mobile node's home agent. Since multicasts on the local link If, instead, this field is nonzero, then the following step is
(such as Ethernet) are typically not guaranteed to be reliable, the carried out for each address for the mobile node formed from
home agent MAY retransmit this Neighbor Advertisement message up to the mobile node's interface identifier (from the specified home
address) together with each one of the subnet prefixes currently
considered by the home agent to be on-link (including both the
link-local and site-local prefix).
- For each specific IP address for the mobile node determined in
the first step above, the home agent multicast onto the home link
(to the all-nodes multicast address) a Neighbor Advertisement
message [11] on behalf of the mobile node, to advertise the
home agent's own link-layer address for this IP address. The
Target Address in the Neighbor Advertisement message MUST be set
to this IP address for the mobile node, and the Advertisement
MUST include a Target Link-layer Address option specifying the
home agent's link-layer address. The Solicited Flag (S) in the
Advertisement MUST NOT be set, since it was not solicited by any
Neighbor Solicitation message. The Override Flag (O) in the
Advertisement MUST be set, indicating that the Advertisement
SHOULD override any existing Neighbor Cache entry at any node
receiving it.
Any node on the home link receiving one of the Neighbor Advertisement
messages described above will thus update its Neighbor Cache to
associate the mobile node's address with the home agent's link
layer address, causing it to transmit any future packets for the
mobile node normally destined to this address instead to the mobile
node's home agent. Since multicasts on the local link (such as
Ethernet) are typically not guaranteed to be reliable, the home
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 subnet 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 [9]. home address, through use of Neighbor Unreachability Detection [11].
In addition, while this node is serving as a home agent for this In addition, while this node is serving as a home agent for this
mobile node (it still has a "home registration" entry for this mobile mobile node (it still has a "home registration" entry for this mobile
node in its Binding Cache), it MUST act as a proxy for this mobile node in its Binding Cache), it MUST act as a proxy for this mobile
node to reply to any received Neighbor Solicitation messages for node to reply to any received Neighbor Solicitation messages for
it. When a home agent receives a Neighbor Solicitation message, it it. When a home agent receives a Neighbor Solicitation message, it
MUST check if the Target Address specified in the message matches MUST check if the Target Address specified in the message matches
the home address of any mobile node for which it has a Binding Cache the home address of any mobile node for which it has a Binding
entry marked as a "home registration". If such an entry exists Cache entry marked as a "home registration". This check MUST
in its Binding Cache, the home agent MUST reply to the Neighbor include all possible home addresses for the mobile node, based on
Solicitation message with a Neighbor Advertisement message, giving the subnet prefixes currently considered to be on-link by the home
the home agent's own link-layer address as the link-layer address for agent (including the corresponding link-local address and site-local
the specified Target Address. Likewise, if the mobile node included address), if the ID Length field was nonzero in the Binding Update
its home link-local address and set the Home Link-Local Address that created this "home registration" binding at the home agent. If
Present (L) bit in its Binding Update with which it established such an entry exists in the home agent's Binding Cache, the home
this "home registration" with its home agent, its home agent MUST agent MUST reply to the Neighbor Solicitation message with a Neighbor
also similarly act as a proxy for the mobile node's home link-local Advertisement message, giving the home agent's own link-layer address
address while it has this "home registration" entry in its Binding as the link-layer address for the specified Target Address. Acting
Cache. Acting as a proxy in this way allows other nodes on the as a proxy in this way allows other nodes on the mobile node's home
mobile node's home subnet to resolve the mobile node's IPv6 home link to resolve the mobile node's IPv6 home address, and allows
address and IPv6 link-local address, and allows the home agent to the home agent to to defend these addresses on the home link for
to defend these addresses on the home subnet for Duplicate Address Duplicate Address Detection [11].
Detection [9].
7.3. Primary Care-of Address De-registration Any packet addressed to the mobile node's home address (including
addresses formed from other on-link prefixes, if the ID Length field
was nonzero in the Binding Update) will thus be received by the
mobile node's home agent while the mobile node is registered away
from home. For any such packet received by the home agent for the
mobile node, the home agent SHOULD tunnel the packet to the mobile
node at its primary care-of address, as described in Section 8.4.
However, packets addressed to the mobile node's link-local address or
site-local address MUST NOT be tunneled to the mobile node. Instead,
such packets MUST be discarded, and for each, the home agent SHOULD
return an ICMP Destination Unreachable, Code 3, message to the
packet's Source Address (unless this Source Address is a multicast
address).
8.3. Primary Care-of Address De-registration
General processing of a received Binding Update that requests a General processing of a received Binding Update that requests a
binding to be deleted, is described in Section 6.4. However, if the binding to be deleted, is described in Section 7.4. However, if the
Home Registration (H) bit is set in the Binding Update, then the Home Registration (H) bit is set in the Binding Update, then the
receiving node MUST process the Binding Update as specified in this receiving node MUST process the Binding Update as specified in this
section, rather than following the general procedure specified in section, rather than following the general procedure specified in
Section 6.4. Section 7.4.
To begin processing the Binding Update, the home agent MUST perform To begin processing the Binding Update, the home agent MUST perform
the following sequence of tests: the following sequence of tests:
- If the node is not a router that implements home agent - If the node is not a router that implements home agent
functionality, then the node MUST reject the Binding Update and functionality, then the node MUST reject the Binding Update and
SHOULD return a Binding Acknowledgement to the mobile node, in SHOULD return a Binding Acknowledgement to the mobile node, in
which the Status field is set to 132 (home registration not which the Status field is set to 132 (home registration not
supported). supported).
skipping to change at page 34, line 9 skipping to change at page 38, line 48
field in the packet's Home Address option) is not an on-link field in the packet's Home Address option) is not an on-link
IPv6 address with respect to the home agent's current Prefix IPv6 address with respect to the home agent's current Prefix
List, then it MUST reject the Binding Update and SHOULD return a List, then it MUST reject the Binding Update and SHOULD return a
Binding Acknowledgement to the mobile node, in which the Status Binding Acknowledgement to the mobile node, in which the Status
field is set to 133 (not home subnet). field is set to 133 (not home subnet).
If the home agent does not reject the Binding Update as described If the home agent does not reject the Binding Update as described
above, then it MUST delete any existing entry in its Binding Cache above, then it MUST delete any existing entry in its Binding Cache
for this mobile node. for this mobile node.
In addition, in this case, the home agent MUST multicast a Neighbor 8.4. Tunneling Intercepted Packets to a Mobile Node
Advertisement message (to the all-nodes multicast address), giving
the mobile node's home address as the Target Address, and specifying
the mobile node's link-layer address in a Target Link-layer
Address option in the Neighbor Advertisement message. The home
agent MAY retransmit this Neighbor Advertisement message up to
MAX_ADVERT_REXMIT times to increase its reliability; any nodes on the
home subnet that miss all of these Neighbor Advertisements can also
eventually detect the link-layer address change for the mobile node's
home address, through use of Neighbor Unreachability Detection [9].
7.4. 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 6.8 apply. The home agent (as a correspondent node) uses a Section 7.9 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).
In addition, while the mobile node is away from home and this node In addition, while the mobile node is away from home and this node is
is acting as the mobile node's home agent, the home agent intercepts acting as the mobile node's home agent, the home agent intercepts any
any packets on the home subnet addressed to the mobile node's packets on the home link addressed to the mobile node's home address,
home address, as described in Section 7.2. The home agent cannot as described in Section 8.2. The home agent cannot use a Routing
use a Routing header to forward these intercepted packets to the header to forward these intercepted packets to the mobile node,
mobile node, since it cannot modify the packet in flight without since it cannot modify the packet in flight without invalidating any
invalidating any existing IPv6 Authentication header present in the existing IPv6 Authentication header present in the packet [7].
packet [1].
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 mobile node itself (using its and the tunnel exit point node is the mobile node itself (using its
primary care-of address as registered with the home agent). When a primary care-of address as registered with the home agent). When a
home agent encapsulates an intercepted packet for forwarding to the home agent encapsulates an intercepted packet for forwarding to the
mobile node, the home agent sets the Source Address in the prepended mobile node, the home agent sets the Source Address in the prepended
tunnel IP header to the home agent's own IP address, and sets the tunnel IP header to the home agent's own IP address, and sets the
Destination Address in the tunnel IP header to the mobile node's Destination Address in the tunnel IP header to the mobile node's
primary care-of address. When received by the mobile node (using its primary care-of address. When received by the mobile node (using its
primary care-of address), normal processing of the tunnel header [4] primary care-of address), normal processing of the tunnel header [4]
will result in decapsulation and processing of the original packet by will result in decapsulation and processing of the original packet by
the mobile node. the mobile node.
7.5. Renumbering the Home Subnet 8.5. Renumbering the Home Subnet
Neighbor Discovery [9] specifies a mechanism by which all nodes on a Neighbor Discovery [11] specifies a mechanism by which all nodes on a
subnet can gracefully autoconfigure new addresses, say by each node subnet can gracefully autoconfigure new addresses, say by each node
combining a new routing prefix with its existing link-layer address. combining a new routing prefix with its existing link-layer address.
As currently specified, this mechanism works when the nodes are on As currently specified, this mechanism works when the nodes are on
the same link as the router issuing the necessary multicast packets the same link as the router issuing the necessary multicast packets
to advertise the new routing prefix(es) appropriate for the link. to advertise the new routing prefix(es) appropriate for the link.
However, for mobile nodes away from home, special care must be taken However, for mobile nodes away from home, special care must be taken
to allow the mobile nodes to renumber gracefully. The most direct to allow the mobile nodes to renumber gracefully. The most direct
method of ensuring this is for the home agent to encapsulate and method of ensuring this is for the home agent to encapsulate and
tunnel the multicast packets to the primary care-of address of each tunnel the multicast packets to the primary care-of address of each
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- The mobile node's home agent serves as a proxy for the mobile - The mobile node's home agent serves as a proxy for the mobile
node's home address and link-local address, including defending node's home address and link-local address, including defending
these addresses for Duplicate Address Detection, while the mobile these addresses for Duplicate Address Detection, while the mobile
node is registered with the home agent away from home. node is registered with the home agent away from home.
- When a home subnet prefix changes, the home agent tunnels Router - When a home subnet prefix changes, the home agent tunnels Router
Advertisement packets to each mobile node registered with it that Advertisement packets to each mobile node registered with it that
is currently away from home and using a home address with the is currently away from home and using a home address with the
affected routing prefix. Such tunneled Router Advertisements affected routing prefix. Such tunneled Router Advertisements
MUST be authenticated [1]. MUST be authenticated [7].
- When a mobile node receives a tunneled Router Advertisement - When a mobile node receives a tunneled Router Advertisement
containing a new routing prefix, it MUST perform the standard containing a new routing prefix, it MUST perform the standard
autoconfiguration operation to create its new address. autoconfiguration operation to create its new address.
- When a mobile node returns to its home subnet, it must again - When a mobile node returns to its home link, it must again
perform Duplicate Address Detection at the earliest possible perform Duplicate Address Detection at the earliest possible
moment after it has deleted its "home registration" binding with moment after it has deleted its "home registration" binding with
its home agent. its home agent.
- A mobile node MAY send a Router Solicitation to its home agent at - A mobile node MAY send a Router Solicitation to its home agent at
any time, within the constraints imposed by rate control defined any time, within the constraints imposed by rate control defined
by Neighbor Discovery [9]. by Neighbor Discovery [11].
8. Mobile Node Operation 9. Mobile Node Operation
8.1. Sending Packets While Away from Home 9.1. Sending Packets While Away from Home
While a mobile node is away from home, it continues to use its home While a mobile node is away from home, it continues to use its home
address as well as also using one or more care-of addresses. When address as well as also using one or more care-of addresses. When
sending a packet while away from home, a mobile node MAY choose among sending a packet while away from home, a mobile node MAY choose among
these in selecting the address that it will use as the source of the these in selecting the address that it will use as the source of the
packet, as follows: packet, as follows:
- For most packets, the mobile node will generally use its home - For most packets, the mobile node will generally use its home
address as the source of the packet. Doing so makes its mobility address as the source of the packet. Doing so makes its mobility
and the fact that it is currently away from home transparent to and the fact that it is currently away from home transparent to
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while the mobile node was at home, the mobile node MUST use while the mobile node was at home, the mobile node MUST use
its home address. Likewise, for packets sent that are part of its home address. Likewise, for packets sent that are part of
transport-level connections that the mobile node may still be transport-level connections that the mobile node may still be
using after moving to a new location, the mobile node SHOULD use using after moving to a new location, the mobile node SHOULD use
its home address. its home address.
- For short-term communication, particularly for communication - For short-term communication, particularly for communication
that may easily be retried if it fails, the mobile node MAY that may easily be retried if it fails, the mobile node MAY
choose to use one of its care-of addresses as the source of the choose to use one of its care-of addresses as the source of the
packet. An example of this type of communication might be DNS packet. An example of this type of communication might be DNS
queries sent by the mobile node [7, 8]. Using the mobile node's queries sent by the mobile node [9, 10]. Using the mobile node's
care-of address as the source for such queries will generally care-of address as the source for such queries will generally
have a lower overhead than using the mobile node's home address, have a lower overhead than using the mobile node's home address,
since no extra options need be used in either the query or its since no extra options need be used in either the query or its
reply, and all packets can be routed normally, directly between reply, and all packets can be routed normally, directly between
their source and destination without relying on Mobile IP. If the their source and destination without relying on Mobile IP. If the
mobile node has no particular knowledge that the communication mobile node has no particular knowledge that the communication
being sent fits within this type of communication, however, the being sent fits within this type of communication, however, the
mobile node SHOULD use its home address. mobile node SHOULD use its home address.
If the mobile node uses one of its care-of addresses as the source If the mobile node uses one of its care-of addresses as the source
of some packet while away from home, no special Mobile IP processing of some packet while away from home, no special Mobile IP processing
is required for sending this packet. The packet is simply addressed is required for sending this packet. The packet is simply addressed
and transmitted in the same way as any normal IPv6 packet, setting and transmitted in the same way as any normal IPv6 packet, setting
the Source Address field in the packet's IPv6 header to this care-of the Source Address field in the packet's IPv6 header to this care-of
address. address.
On the other hand, if the mobile node uses its home address as the On the other hand, if the mobile node uses its home address as the
source of a packet while away from home, the mobile node SHOULD source of a packet while away from home, special Mobile IP processing
construct the packet as follows: of this packet is required. Since Mobile IP is transparent to higher
protocol layers (e.g., to TCP), the packet is initially constructed
using the mobile node's home address as the packet's Source Address,
in the same way as if the mobile node were at home. However, while
away from home, Mobile IP processes each outgoing packet as follows:
- The Source Address field in the packet's IPv6 header is set to - If the Source Address field in the packet's IPv6 header is not
one of the mobile node's care-of addresses. the mobile node's home address, skip all following steps and send
the packet normally.
- A Home Address option is included in the packet, with the Home - Otherwise, insert a Home Address option into the packet, with the
Address field set to the mobile node's home address. Home Address field copied from the original value of the Source
Address field in the packet.
Without this use of the care-of address in the IPv6 header, with the - Change the Source Address field in the packet's IPv6 header to
mobile node's home address instead in the Home Address option, the one of the mobile node's care-of addresses This will typically
packet will likely be discarded by any router implementing ingress 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
network interface on which the mobile node will transmit the
packet.
This addition of the Home Address option to a packet MUST be
performed before outgoing IPsec processing, such as the addition of
an AH [7] or ESP [8] header to the packet, is performed. Likewise,
IPsec processing for a received packet containing a Home Address
option MUST be performed before the packet is possibly modified as
part of processing the Home Address option. By using the care-of
address as the Source Address in the IPv6 header, with the mobile
node's home address instead in the Home Address option, the packet
will be able to safely pass through any router implementing ingress
filtering [6]. filtering [6].
8.2. Movement Detection 9.2. Movement Detection
A mobile node MAY use any combination of mechanisms available to A mobile node MAY use any combination of mechanisms available to it
it to detect when its link-level point of attachment has moved to detect when it has moved from one link to another. The primary
from one IP subnet to another. The primary movement detection movement detection mechanism for Mobile IPv6 defined here uses the
mechanism for Mobile IPv6 defined here uses the facilities of facilities of IPv6 Neighbor Discovery, including Router Discovery and
IPv6 Neighbor Discovery, including Router Discovery and Neighbor Neighbor Unreachability Detection. The description here is based on
Unreachability Detection. The description here is based on the the conceptual model of the organization and data structures defined
conceptual model of the organization and data structures defined by by Neighbor Discovery [11].
Neighbor Discovery [9].
Mobile nodes SHOULD use Router Discovery to discover new routers and Mobile nodes SHOULD use Router Discovery to discover new routers and
on-link network 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) Router Advertisement messages, or MAY wait for unsolicited (periodic) Router Advertisement
messages, as specified for Router Discovery [9]. Based on received messages, as specified for Router Discovery [11]. Based on received
Router Advertisement messages, a mobile node (in the same way as any Router Advertisement messages, a mobile node (in the same way as any
other node) maintains an entry in its Default Router List for each other node) maintains an entry in its Default Router List for each
router, and an entry in its Prefix List for each network prefix, that router, and an entry in its Prefix List for each subnet prefix, that
it currently considers to be on-link. Each entry in these lists has it currently considers to be on-link. Each entry in these lists has
an associated invalidation timer value (extracted from the Router an associated invalidation timer value (extracted from the Router
Advertisement) used to expire the entry when it becomes invalid. Advertisement) used to expire the entry when it becomes invalid.
While away from home, a mobile node SHOULD select one router from its While away from home, a mobile node SHOULD select one router from
Default Router List to use as its default router, and one network its Default Router List to use as its default router, and one subnet
prefix advertised by that router from its Prefix List to use as prefix advertised by that router from its Prefix List to use as
the network prefix in its primary care-of address. A mobile node the subnet prefix in its primary care-of address. A mobile node
MAY also have associated additional care-of addresses, using other MAY also have associated additional care-of addresses, using other
network prefixes from its Prefix List. The method by which a mobile subnet prefixes from its Prefix List. The method by which a mobile
node selects and forms a care-of address from the available network node selects and forms a care-of address from the available subnet
prefixes is described in Section 8.3. The mobile node registers prefixes is described in Section 9.3. The mobile node registers
its primary care-of address with its home agent, as described in its primary care-of address with its home agent, as described in
Section 8.4. Section 9.4.
While a mobile node is away from home and using some router as its While a mobile node is away from home and using some router as its
default router, it is important for the mobile node to be able to default router, it is important for the mobile node to be able to
quickly detect when that router becomes unreachable, so that it can quickly detect when that router becomes unreachable, so that it can
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 the it can any correspondent nodes attempting to communicate with it can still
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 [9], while the mobile node is actively sending Neighbor Discovery [11], 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 is still reachable either through indications detect that the router (as its neighbor) is still reachable either
from upper layer protocols on the mobile node that a connection is through indications from upper layer protocols on the mobile node
making "forward progress" (e.g., receipt of TCP acknowledgements for that a connection is making "forward progress" (e.g., receipt of TCP
new data transmitted), or through receipt of a Neighbor Advertisement acknowledgements for new data transmitted), or through receipt of a
message form its default router in response to an explicit Neighbor Neighbor Advertisement message form its default router in response
Solicitation messages to it. Note that although this mechanism only to an explicit Neighbor Solicitation messages to it. Note that
detects that the mobile node's default router has become unreachable although this mechanism only detects that the mobile node's default
to the mobile node while the mobile node is actively sending packets router has become unreachable to the mobile node while the mobile
to it, this is the only time that this direction of reachability node is actively sending packets to it, this is the only time that
confirmation is needed. Confirmation that the mobile node is still this direction of reachability confirmation is needed. Confirmation
reachable from the router is handled separately, as described below. that the mobile node is still reachable from the router is handled
separately, as described below.
For a mobile node to detect when it has become unreachable to its For a mobile node to detect when it has become unreachable to its
default router, however, the mobile node cannot efficiently rely on default router, however, the mobile node cannot efficiently rely on
Neighbor Unreachability Detection alone, since the network overhead Neighbor Unreachability Detection alone, since the network overhead
would be prohibitively high in many cases for a mobile node to would be prohibitively high in many cases for a mobile node to
continually probe its default router with Neighbor Solicitation continually probe its default router with Neighbor Solicitation
messages even when it is not otherwise actively sending packets to messages even when it is not otherwise actively sending packets to
it. Instead, a mobile node SHOULD consider receipt of any IPv6 it. Instead, a mobile node SHOULD consider receipt of any IPv6
packets from its current default router as an indication that it is packets from its current default router as an indication that it is
still reachable from the router. Both packets from the router's IP still reachable from the router. Both packets from the router's IP
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mobile node will in most cases be able to determine its reachability mobile node will in most cases be able to determine its reachability
from the router by listening for packets from the router as described from the router by listening for packets from the router as described
above, and thus, such extra Neighbor Solicitation probes should above, and thus, such extra Neighbor Solicitation probes should
rarely be necessary. rarely be necessary.
With some types of networks, it is possible that additional With some types of networks, it is possible that additional
indications about link-layer mobility can be obtained from indications about link-layer mobility can be obtained from
lower-layer protocol or device driver software within the mobile lower-layer protocol or device driver software within the mobile
node. However, a mobile node MUST NOT assume that all link-layer node. However, a mobile node MUST NOT assume that all link-layer
mobility indications from lower layers indicate a movement of the mobility indications from lower layers indicate a movement of the
mobile node's link-layer connection to a new IP subnet, such that the mobile node to a new link, such that the mobile node would need to
mobile node would need to switch to a new default router and primary switch to a new default router and primary care-of address. For
care-of address. Upon lower-layer indication of link-layer mobility, example, movement of a mobile node from one cell to another in many
wireless LANs can be made transparent to the IP level through use of
a link-layer "roaming" protocol, as long as the different wireless
LAN cells all operate as part of the same IP link with the same
subnet prefix. Upon lower-layer indication of link-layer mobility,
the mobile node SHOULD send Router Solicitation messages to determine the mobile node SHOULD send Router Solicitation messages to determine
if new routers (and new on-link network prefixes) are present on its if new routers (and new on-link subnet prefixes) are present on its
new link. new link.
Such lower-layer information might also be useful to a mobile node in Such lower-layer information might also be useful to a mobile node in
deciding to switch its primary care-of address to one of the other deciding to switch its primary care-of address to one of the other
care-of addresses it has formed from the on-link network prefixes care-of addresses it has formed from the on-link subnet prefixes
currently available through different default routers from which the currently available through different routers from which the mobile
mobile node is reachable. For example, a mobile node MAY use signal node is reachable. For example, a mobile node MAY use signal
strength or signal quality information (with suitable hysteresis) strength or signal quality information (with suitable hysteresis) for
for its link with the available default routers to decide when to its link with the available routers to decide when to switch to a new
switch to a new primary care-of address using that default router primary care-of address using that router rather than its current
rather than its current default router (and current primary care-of default router (and current primary care-of address). Even though
address). Even though the mobile node's current default router may the mobile node's current default router may still be reachable in
still be reachable in terms of Neighbor Unreachability Detection, the terms of Neighbor Unreachability Detection, the mobile node MAY use
mobile node MAY use such lower-layer information to determine that such lower-layer information to determine that switching to a new
switching to a new default router would provide a better connection. default router would provide a better connection.
8.3. Forming New Care-of Addresses 9.3. Forming New Care-of Addresses
After detecting that its link-layer point of attachment has moved After detecting that it has moved from one link to another (i.e., its
from one IPv6 subnet to another (i.e., its current default router current default router has become unreachable and it has discovered a
has become unreachable and it has discovered a new default router), new default router), a mobile node SHOULD form a new primary care-of
a mobile node SHOULD form a new primary care-of address using one of address using one of the on-link subnet prefixes advertised by the
the on-link network prefixes advertised by the new router. A mobile new router. A mobile node MAY form a new primary care-of address
node MAY form a new primary care-of address at any time, except at any time, except that it MUST NOT do so too frequently (not more
that it MUST NOT do so too frequently (not more often than once per often than once per MAX_UPDATE_RATE seconds).
MAX_UPDATE_RATE seconds).
In addition, after discovering a new on-link network prefix, a In addition, after discovering a new on-link subnet prefix, a mobile
mobile node MAY form a new (non-primary) care-of address using that node MAY form a new (non-primary) care-of address using that subnet
network prefix, even when it has not switched to a new default prefix, even when it has not switched to a new default router. A
router. A mobile node can have only one primary care-of address at mobile node can have only one primary care-of address at a time
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 network prefixes on additional care-of address for any or all of the subnet prefixes on
its current link. Furthermore, since a wireless network interface its current link. Furthermore, since a wireless network interface
may actually allow a mobile node to be reachable on more than one may actually allow a mobile node to be reachable on more than one
link at a time (i.e., within wireless transmitter range of routers link at a time (i.e., within wireless transmitter range of routers
on more than one separate link), a mobile node MAY have care-of on more 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 addresses on more than one link at a time. The use of more than one
care-of address at a time is described in Section 8.10. care-of address at a time is described in Section 9.12.
As described in Section 3.1, 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 [16] or stateful (e.g., a mobile node MAY use either stateless [18] or stateful (e.g.,
DHCPv6 [3]) 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 visiting address that has been assigned to it for its use only while
a specific foreign subnet. 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 subnet, for its use while visiting that administrator of some foreign link, for its use while visiting that
subnet. If so, rather than using address autoconfiguration to form link. If so, rather than using address autoconfiguration to form a
a new care-of address using this network prefix, the mobile node new care-of address using this subnet prefix, the mobile node MAY use
MAY use its own pre-assigned address as its care-of address on this its own pre-assigned address as its care-of address on this link.
subnet.
8.4. Sending Binding Updates to the Home Agent 9.4. 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 8.2 and 8.3, a mobile node MUST register this care-of in Sections 9.2 and 9.3, a mobile node MUST register this care-of
address with its home agent in order to make this its primary care-of address with its home agent in order to make this its primary care-of
address. 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
follows: follows:
- The Home Registration (H) bit MUST be set in the Binding Update. - The Home Registration (H) bit MUST be set in the Binding Update.
- The Acknowledge (A) bit MUST be set in the Binding Update. - The Acknowledge (A) bit MUST be set in the Binding Update.
- The packet MUST contain a Home Address option, giving the mobile - The packet MUST contain a Home Address option, giving the mobile
node's home address for the binding. node's home address for the binding.
- The care-of address for the binding MUST be used as the Source - The care-of address for the binding MUST be used as the Source
Address in the packet's IPv6 header, or the Care-of Address Address in the packet's IPv6 header, or the Care-of Address
Present (C) bit MUST be set in the Binding Update and the care-of Present (C) bit MUST be set in the Binding Update and the care-of
address for binding MUST be specified in the Care-of Address address for binding MUST be specified in the Care-of Address
field in the Binding Update. field in the Binding Update.
- The ID Length field SHOULD be set to the length of the mobile
node's interface identifier in its home address, to request
the mobile node's home agent to serve as a home agent for all
home addresses for the mobile node based on all on-link subnet
prefixes on the home link. Otherwise, this field MUST be set to
zero.
The Acknowledge (A) bit in the Binding Update requests the home The Acknowledge (A) bit in the Binding Update requests the home
agent to return a Binding Acknowledgement in response to this agent to return a Binding Acknowledgement in response to this
Binding Update. As described in Section 4.2, the mobile node SHOULD Binding Update. As described in Section 5.2, the mobile node SHOULD
retransmit this Binding Update to its home agent until it receives retransmit this Binding Update to its home agent until it receives
a matching Binding Acknowledgement. Once reaching a retransmission a matching Binding Acknowledgement. Once reaching a retransmission
timeout period of MAX_BINDACK_TIMEOUT, the mobile node SHOULD timeout period of MAX_BINDACK_TIMEOUT, the mobile node SHOULD
continue to periodically retransmit the Binding Update at this rate continue to periodically retransmit the Binding Update at this rate
until acknowledged (or until it begins attempting to register a until acknowledged (or until it begins attempting to register a
different primary care-of address). different primary care-of address).
The ID Length field in the Binding Update allows the mobile node to
request its home agent to serve all home addresses for the mobile
node defined by the mobile node's interface identifier, based on all
on-link subnet prefixes on the home link. If the mobile node has
additional home addresses using a different interface identifier,
then the mobile node SHOULD send an additional Binding Update to its
home agent to register the care-of address for each such other home
address (or set of home addresses sharing an interface identifier).
It is possible that when the mobile node needs to send such a Binding It is possible that when the mobile node needs to send such a Binding
Update to its home agent, that the mobile node does not know the Update to its home agent, that the mobile node does not know the
address of any router in its home subnet that can serve as a home address of any router on its home link that can serve as a home agent
agent for it. In this case, the mobile node SHOULD use the dynamic for it. In this case, the mobile node SHOULD use the dynamic home
home agent address resolution procedure to find the address of a agent address discovery procedure to find the address of a suitable
suitable home agent in its home subnet. To do so, the mobile node home agent on its home link. To do so, the mobile node sends the
sends the packet, as described above, with the Destination Address in packet, as described above, with the Destination Address in the
the packet's IPv6 header set the Home-Agents anycast address for its packet's IPv6 header set to the Home-Agents anycast address for its
home subnet. The home agent in its home subnet that receives this home subnet prefix. The home agent on its home link that receives
Binding Update will reject the Update, returning to the mobile node this Binding Update will reject the Update, returning to the mobile
the home agent's unicast IP address. The mobile node SHOULD then node the home agent's unicast IP address. The mobile node SHOULD
retransmit its Binding Update to this home agent using the provided then retransmit its Binding Update to this home agent using the
unicast address. provided unicast address.
If the mobile node has a current registration with some home agent If the mobile node has a current registration with some home agent
in its home subnet (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 in its home reattempt this registration with another home agent on its home link.
subnet. If the mobile node knows of no other suitable home agent, If the mobile node knows of no other suitable home agent, then it MAY
then it MAY attempt the dynamic home agent address resolution attempt the dynamic home agent address discovery procedure described
procedure described above. above.
8.5. Sending Binding Updates to Correspondent Nodes 9.5. 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 any time to allow it to cache its current care-of address (subject
to the rate limiting defined in Section 8.8). In any Binding Update to the rate limiting defined in Section 9.8). In any Binding Update
sent by a mobile node, the care-of address (either the Source Address sent by a mobile node, the care-of address (either the Source Address
in the packet's IPv6 header or the Care-of Address field in the in the packet's IPv6 header or the Care-of Address field in the
Binding Update) MUST be set to one of the care-of addresses currently Binding Update) MUST be set to one of the care-of addresses currently
in use by the mobile node or to the mobile node's home address. 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. If, instead, the care-of sending future packets to the mobile node. If, instead, the care-of
skipping to change at page 43, line 38 skipping to change at page 48, line 17
The mobile node MUST retain in its Binding Update List information The mobile node MUST retain in its Binding Update List information
about all Binding Updates sent, for which the lifetime of the about all Binding Updates sent, for which the lifetime of the
binding has not yet expired. When sending a Binding Update, if an binding has not yet expired. When sending a Binding Update, if an
entry already exists in the mobile node's Binding Update List for entry already exists in the mobile node's Binding Update List for
an earlier Binding Update sent to that same destination node, the an earlier Binding Update sent to that same destination node, the
existing Binding Update List entry is updated to reflect the new existing Binding Update List entry is updated to reflect the new
Binding Update rather than creating a new Binding Update List entry. Binding Update rather than creating a new Binding Update List entry.
In general, when a mobile node sends a Binding Update to its home In general, when a mobile node sends a Binding Update to its home
agent to register a new primary care-of address (as described in agent to register a new primary care-of address (as described in
Section 8.4), the mobile node will also send a Binding Update to each Section 9.4), the mobile node will also send a Binding Update to each
correspondent node for which an entry exists in the mobile node's correspondent node for which an entry exists in the mobile node's
Binding Update List. Thus, correspondent nodes are generally kept Binding Update List. Thus, correspondent nodes are generally kept
updated about the mobile node's binding and can send packets directly updated about the mobile node's binding and can send packets directly
to the mobile node using the mobile node's current care-of address. to the mobile node using the mobile node's current care-of address.
The mobile node, however, need not send these Binding Updates The mobile node, however, need not send these Binding Updates
immediately after configuring a new care-of address. For example, immediately after configuring a new care-of address. For example,
since the Binding Update is a destination option and can be included since the Binding Update is a destination option and can be included
in any packet sent by a mobile node, the mobile node MAY delay in any packet sent by a mobile node, the mobile node MAY delay
sending a new Binding Update to any correspondent node for a sending a new Binding Update to any correspondent node for a
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by setting the Acknowledge (A) bit in the Binding Update. In this by setting the Acknowledge (A) bit in the Binding Update. In this
case, however, the mobile node SHOULD NOT continue to retransmit the case, however, the mobile node SHOULD NOT continue to retransmit the
Binding Update once the retransmission timeout period has reached Binding Update once the retransmission timeout period has reached
MAX_BINDACK_TIMEOUT. MAX_BINDACK_TIMEOUT.
A mobile node MAY choose to keep its location private from certain A mobile node MAY choose to keep its location private from certain
correspondent nodes, and thus need not send new Binding Updates to correspondent nodes, and thus need not send new Binding Updates to
those correspondents. A mobile node MAY also send a Binding Update those correspondents. A mobile node MAY also send a Binding Update
to such a correspondent node to instruct it to delete any existing to such a correspondent node to instruct it to delete any existing
binding for the mobile node from its Binding Cache, as described in binding for the mobile node from its Binding Cache, as described in
Section 4.1. No other IPv6 nodes are authorized to send Binding Section 5.1. No other IPv6 nodes are authorized to send Binding
Updates on behalf of a mobile node. Updates on behalf of a mobile node.
8.6. Sending Binding Updates to the Previous Default Router 9.6. Sending Binding Updates to the Previous Default Router
After switching to a new default router (and thus also changing its After switching to a new default router (and thus also changing its
primary care-of address), a mobile node SHOULD send a Binding Update primary care-of address), a mobile node MAY send a Binding Update
to its previous default router, giving its new care-of address. If to its previous default router, giving its new care-of address.
the mobile node sends such a Binding Update, the home address for If the mobile node sends such a Binding Update, the home address
the binding, specified in the Home Address option included in the for the binding, specified in the Home Address option included in
packet carrying this Binding Update, MUST be set the mobile node's the packet carrying this Binding Update, MUST be set the mobile
old primary care-of address (that it used while using this default node's old primary care-of address (that it used while using this
router), and the care-of address for the binding (either the Source default router), and the care-of address for the binding (either the
Address in the packet's IPv6 header or the Care-of Address field in Source Address in the packet's IPv6 header or the Care-of Address
the Binding Update) MUST be set to the mobile node's new primary field in the Binding Update) MUST be set to the mobile node's new
care-of address. In addition, the Home Registration (H) bit MUST primary care-of address. In addition, the Home Registration (H)
also be set in this Binding Update, to request the mobile node's bit MUST also be set in this Binding Update, to request the mobile
previous default router to temporarily act as a home agent for the node's previous default router to temporarily act as a home agent
mobile node's old primary care-of address. Note that the previous for the mobile node's old primary care-of address. The previous
router does not necessarily know the mobile node's (permanent) home default router will thus tunnel packets for the mobile node to its
address as part of this registration. new care-of address. All of the procedures defined for home agent
operation must be followed by this previous default router for this
If any subsequent packets arrive at this previous router for registration. Note that the previous router does not necessarily
forwarding to the mobile node's old primary care-of address, know the mobile node's (permanent) home address as part of this
the router SHOULD encapsulate each such packet (using IPv6 registration.
encapsulation [4]) and tunnel it to the mobile node at its new
primary care-of address. Moreover, for the lifetime of the "home
registration" Binding Cache entry for the mobile node at this
router, this router MUST act as a proxy for the mobile node's
previous care-of address, for purposes of participation in Neighbor
Discovery [9], in the same way as any home agent does for a mobile
node's home address (Section 7.2). This allows the router to
intercept packets addressed to the mobile node's previous care-of
address, and to encapsulate and tunnel them to the mobile node's new
care-of address, as described in Section 7.4.
8.7. Retransmitting Binding Updates 9.7. Retransmitting Binding Updates
If, after sending a Binding Update in which the Acknowledge (A) bit If, after sending a Binding Update in which the Acknowledge (A) bit
is set, a mobile node fails to receive a Binding Acknowledgement is set, a mobile node fails to receive a Binding Acknowledgement
within INITIAL_BINDACK_TIMEOUT seconds, the mobile node SHOULD within INITIAL_BINDACK_TIMEOUT seconds, the mobile node SHOULD
retransmit the Binding Update until a Binding Acknowledgement retransmit the Binding Update until a Binding Acknowledgement
is received. Such a retransmitted Binding Update MUST use he is received. Such a retransmitted Binding Update MUST use he
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.
8.8. Rate Limiting for Sending Binding Updates 9.8. 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 more often than once per
MAX_UPDATE_RATE seconds to any node. After sending MAX_FAST_UPDATES MAX_UPDATE_RATE seconds to any node. After sending MAX_FAST_UPDATES
consecutive Binding Updates to a particular node with the same consecutive Binding Updates to a particular node with the same
care-of address, the mobile node SHOULD reduce its rate of sending care-of address, the mobile node SHOULD reduce its rate of sending
Binding Updates to that node, to the rate of SLOW_UPDATE_RATE per Binding Updates to that node, to the rate of SLOW_UPDATE_RATE per
second. The mobile node MAY continue to send Binding Updates at the second. The mobile node MAY continue to send Binding Updates at the
slower rate indefinitely, in hopes that the node will eventually slower rate indefinitely, in hopes that the node will eventually
be able to process a Binding Update and begin to route its packets be able to process a Binding Update and begin to route its packets
directly to the mobile node at its new care-of address. directly to the mobile node at its new care-of address.
8.9. Receiving Binding Acknowledgements 9.9. Receiving ICMP Errors in Response to Binding Updates
The Option Type value for a Binding Update option specifies that
any node receiving this option that does not recognize the Option
Type SHOULD return an ICMP Parameter Problem, Code 2, message to the
sender of the Binding Update. If a node sending a Binding Update
receives such an ICMP error message in response, it should record in
its Binding Update List that future Binding Updates should not be
sent to this destination.
9.10. 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 an IP Authentication header and the - The packet contains either an AH [7] or ESP [8] header providing
authentication is valid [1]. The Authentication header MUST sender authentication, data integrity protection, and replay
provide both sender authentication, integrity protection, and protection.
replay 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
9 octets. 12 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.
Any Binding Acknowledgement not satisfying all of these tests MUST be Any Binding Acknowledgement not satisfying all of these tests MUST be
silently ignored, although the remainder of the packet (i.e., other silently ignored, although the remainder of the packet (i.e., other
options, extension headers, or payload) SHOULD be processed normally options, extension headers, or payload) SHOULD be processed normally
according to any procedure defined for that part of the packet. according to any procedure defined for that part of the packet.
When a mobile node receives a packet carrying a valid Binding When a mobile node receives a packet carrying a valid Binding
Acknowledgement, the mobile node MUST examine the Status field as Acknowledgement, the mobile node MUST examine the Status field as
follows: follows:
- If the Status field indicates that the Binding Update was - If the Status field indicates that the Binding Update was
accepted (the Status field is less than 128), then the mobile accepted (the Status field is less than 128), then the mobile
node MUST update the corresponding entry in its Binding Update node MUST update the corresponding entry in its Binding Update
List to indicate that the Binding Update has been acknowledged. List to indicate that the Binding Update has been acknowledged.
The mobile node MUST thus stop retransmitting the Binding Update. The mobile node MUST thus stop retransmitting the Binding Update.
- If the Status field indicates that the Binding Update was not - If the Status field indicates that the Binding Update was
accepted (the Status field is greater than or equal to 128), then rejected (the Status field is greater than or equal to 128), then
the mobile node MUST delete the corresponding Binding Update List the mobile node MUST delete the corresponding Binding Update List
entry (and MUST also stop retransmitting the Binding Update). entry (and MUST also stop retransmitting the Binding Update).
Optionally, the mobile node MAY then take steps to correct the Optionally, the mobile node MAY then take steps to correct the
cause of the error and retransmit the Binding Update (with a new cause of the error and retransmit the Binding Update (with a new
Sequence Number value), subject to the rate limiting restriction Sequence Number value), subject to the rate limiting restriction
specified in Section 8.8. specified in Section 9.8.
8.10. Using Multiple Care-of Addresses 9.11. Receiving Binding Requests
As described in Section 8.3, a mobile node MAY have more than one When a mobile node receives a packet containing a Binding Request,
it SHOULD return to the sender a packet containing a Binding Update.
The Lifetime field in this Binding Update SHOULD be set to a new
lifetime, extending any current lifetime remaining from a previous
Binding Update sent to this node (as indicated in any existing
Binding Update List entry for this node). When sending this Binding
Update, the mobile node MUST update its Binding Update List in the
same way as for any other Binding Update sent by the mobile node.
Note, however, that the mobile node MAY choose to keep its current
binding private from the sender of the Binding Request. In this
case, the mobile node instead SHOULD returns a Binding Update to the
sender, in which the Lifetime field is set to zero.
9.12. Using Multiple Care-of Addresses
As described in Section 9.3, a mobile node MAY use more than one
care-of address at a time. Particularly in the case of many wireless care-of address at a time. Particularly in the case of many wireless
networks, a mobile node effectively might be reachable through networks, a mobile node effectively might be reachable through
multiple link-level points of attachment at the same time (e.g., multiple links at the same time (e.g., with overlapping wireless
with overlapping wireless cells), on which different on-link network cells), on which different on-link subnet prefixes may exist. A
prefixes may exist. A mobile node SHOULD select a primary care-of mobile node SHOULD select a primary care-of address from among those
address from among those care-of addresses it has formed using any care-of addresses it has formed using any of these subnet prefixes,
of these network prefixes, based on the movement detection mechanism based on the movement detection mechanism in use, as described in
in use, as described in Section 8.2. When the mobile node selects Section 9.2. When the mobile node selects a new primary care-of
a new primary care-of address, it MUST register it with its home address, it MUST register it with its home agent through a Binding
agent through a Binding Update with the Home Registration (H) and Update with the Home Registration (H) and Acknowledge (A) bits set,
Acknowledge (A) bits set, as described in Section 8.4. as described in Section 9.4.
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 connected to that link. If the previous primary care-of address
was allocated using stateful address autoconfiguration [3], the was allocated using stateful address autoconfiguration [2], the
mobile node may not wish to release the address immediately upon mobile node may not wish to release the address immediately upon
switching to a new primary care-of address. The stateful address switching to a new primary care-of address. The stateful address
autoconfiguration server will allow mobile nodes to acquire new autoconfiguration server will allow mobile nodes to acquire new
addresses while still using previously allocated addresses. addresses while still using previously allocated addresses.
8.11. Returning Home 9.13. Returning Home
A mobile node detects that it has returned to its home subnet through A mobile node detects that it has returned to its home link through
the movement detection algorithm in use (Section 8.2), when the the movement detection algorithm in use (Section 9.2), when the
mobile node detects that the network prefix of its home subnet is mobile node detects that its home subnet prefix is again on-link.
again on-link. The mobile node SHOULD then send a Binding Update to The mobile node SHOULD then send a Binding Update to its home agent,
its home agent, to instruct its home agent to no longer intercept to instruct its home agent to no longer intercept or tunnel packets
or tunnel packets for it. In this Binding Update, the mobile node for it. In this Binding Update, the mobile node MUST set the care-of
MUST set the care-of address for the binding (Source Address field in address for the binding (the Source Address field in the packet's
the packet's IPv6 header) to the mobile node's own home address. As IPv6 header) to the mobile node's own home address. As with other
with other Binding Updates sent to register with its home agent, the Binding Updates sent to register with its home agent, the mobile
mobile node MUST set the Acknowledge (A) and Home Registration (H) node MUST set the Acknowledge (A) and Home Registration (H) bits,
bits, and SHOULD retransmit the Binding Update until a matching and SHOULD retransmit the Binding Update until a matching Binding
Binding Acknowledgement is received. Acknowledgement is received.
In addition, the mobile node MUST multicast onto the home subnet 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 [9], to advertise the mobile node's own link-layer address message [11], 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 and the Advertisement MUST include a Target Link-layer Address option
option specifying the mobile node's link-layer address. Similarly, specifying the mobile node's link-layer address. The mobile node
the mobile node MUST multicast a Neighbor Advertisement message to MUST multicast such a Neighbor Advertisement message for each of its
advertise its link-layer address for its IPv6 link-local address. home addresses, as defined by the current on-link prefixes, including
The Solicited Flag (S) in these Advertisements MUST NOT be set, since its link-local address and site-local address. The Solicited
they were not solicited by any Neighbor Solicitation message. The Flag (S) in these Advertisements MUST NOT be set, since they were
Override Flag (O) in these Advertisements MUST be set, indicating not solicited by any Neighbor Solicitation message. The Override
that the Advertisements SHOULD override any existing Neighbor Cache Flag (O) in these Advertisements MUST be set, indicating that the
entries at any node receiving them. Advertisements SHOULD override any existing Neighbor Cache entries at
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 not guaranteed to be reliable, the mobile node MAY retransmit these
these Neighbor Advertisement messages up to MAX_ADVERT_REXMIT times Neighbor Advertisement messages up to MAX_ADVERT_REXMIT times to
to increase their reliability. It is still possible that some increase their reliability. It is still possible that some nodes on
nodes on the home subnet will not receive any of these Neighbor the home link will not receive any of these Neighbor Advertisements,
Advertisements, but these nodes will eventually be able to recover but these nodes will eventually be able to recover through use of
through use of Neighbor Unreachability Detection [9]. Neighbor Unreachability Detection [11].
9. Routing Multicast Packets 10. Routing Multicast Packets
A mobile node that is connected to its home subnet 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 subnet. node that is not on its home link.
In order receive packets sent to some multicast group, a mobile node In order receive packets sent to some multicast group, a mobile
must join the that multicast group. One method by which a mobile node must join the that multicast group. One method by which a
node MAY join the group is via a (local) multicast router on the mobile node MAY join the group is via a (local) multicast router
foreign subnet being visited. This option assumes that there is a on the foreign link being visited. The mobile node SHOULD use its
multicast router present on the foreign subnet. The mobile node care-of address sharing a subnet prefix with the multicast router,
SHOULD use its care-of address sharing a network prefix with the as the source IPv6 address of its multicast group membership control
multicast router, as the source IPv6 address of its multicast group messages.
membership control messages.
Alternatively, a mobile node MAY join multicast groups via a Alternatively, a mobile node MAY join multicast groups via a
bi-directional tunnel to its home agent, assuming that its home agent bi-directional tunnel to its home agent. The mobile node tunnels the
is a multicast router. The mobile node tunnels the appropriate appropriate multicast group membership control packets to its home
multicast group membership control packets to its home agent, and the agent, and the home agent forwards multicast packets down the tunnel
home agent forwards multicast packets down the tunnel to the mobile to the mobile node.
node.
A mobile node that wishes to send packets to a multicast group A mobile node that wishes to send packets to a multicast group
also has two options: (1) send directly on the foreign subnet also has two options: (1) send directly on the foreign link being
being visited; or (2) send via a tunnel to its home agent. Because visited; or (2) send via a tunnel to its home agent. Because
multicast routing in general depends upon the Source Address used multicast routing in general depends upon the Source Address used in
in the IPv6 header of the multicast packet, a mobile node that the IPv6 header of the multicast packet, a mobile node that tunnels a
sends multicast packets directly on the foreign subnet MUST use its multicast packet to its home agent MUST use its home address as the
care-of address as the IPv6 Source Address of each multicast packet. IPv6 Source Address of the inner multicast packet.
Similarly, a mobile node that tunnels a multicast packet to its home
agent MUST use its home address as the IPv6 Source Address of the
inner multicast packet. This second option assumes that the home
agent is a multicast router.
10. 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
MAX_FAST_UPDATES 5 MAX_FAST_UPDATES 5
MAX_ADVERT_REXMIT 3 MAX_ADVERT_REXMIT 3
11. Security Considerations 12. IANA Considerations
11.1. Binding Updates, Acknowledgements, and Requests This document defines four new types of IPv6 destination option, each
of which must be assigned an Option Type value:
- The Binding Update option, described in Section 5.1
- The Binding Acknowledgement option, described in Section 5.2
- The binding Request option, described in Section 5.3
- The Home Address option, described in Section 5.4
In addition, this document defines a new type of anycast address, the
Home-Agents anycast address, used in the dynamic home agent address
discovery procedure described in Sections 8.1 and 9.4. This anycast
address must be assigned.
13. Security Considerations
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
redirection", for instance as performed by the Binding Update option, redirection", for instance as performed by the Binding Update option,
is widely understood to be a security problem in the current Internet is widely understood to be a security problem in the current Internet
if not authenticated [2]. if not authenticated [1].
The Binding Acknowledgement option also requires authentication, The Binding Acknowledgement option also requires authentication,
since, for example, an attacker could otherwise trick a mobile node since, for example, an attacker could otherwise trick a mobile node
into believing a different outcome from a registration attempt with into believing a different outcome from a registration attempt with
its home agent. its home agent.
No authentication is required for the Binding Request option, since No authentication is required for the Binding Request option, since
the use of this option does not modify or create any state in either the use of this option does not modify or create any state in either
the sender or the receiver. This Option Does open some issues with the sender or the receiver. The Binding Request option does open
binding privacy, but those issues can be dealt with either through some issues with binding privacy, but those issues can be dealt with
existing IPsec encryption mechanisms or through use of firewalls. either through existing IPsec encryption mechanisms or through use of
firewalls.
The existing IPsec replay protection mechanisms allow a "replay The existing IPsec replay protection mechanisms allow a "replay
protection window" to support receiving packets out of order. protection window" to support receiving packets out of order.
Although appropriate for many forms of communication, Binding Updates Although appropriate for many forms of communication, Binding Updates
MUST be applied only in the order sent. The Binding Update option MUST be applied only in the order sent. The Binding Update option
thus includes a Sequence Number field to provide this necessary thus includes a Sequence Number field to provide this necessary
sequencing. The use of this Sequence Number together with IPsec sequencing. The use of this Sequence Number together with IPsec
replay protection is similar in many ways, for example, to the the replay protection is similar in many ways, for example, to the the
sequence number in TCP. IPsec provides strong replay protection but sequence number in TCP. IPsec provides strong replay protection but
no ordering, and the sequence number provides ordering but need not no ordering, and the sequence number provides ordering but need not
worry about replay protection such as through the sequence number worry about replay protection such as through the sequence number
wrapping around. wrapping around.
11.2. Home Address Options 13.2. Home Address Options
No special authentication of the Home Address option is required, No special authentication of the Home Address option is required,
except that if the IPv6 header of a packet is covered by except that if the IPv6 header of a packet is covered by
authentication, then that authentication MUST also cover the Home authentication, then that authentication MUST also cover the Home
Address option. Thus, even when authentication is used in the IPv6 Address option; this coverage is achieved automatically by the
header, the security of the Source Address field in the IPv6 header definition of the Option Type code for the Home Address option
is not compromised by the presence of a Home Address option. Without (Section 5.4), since it indicates that the option is included in the
authentication of the packet, then any field in the IPv6 header, authentication computation. Thus, even when authentication is used
including the Source Address field, and any other parts of the in the IPv6 header, the security of the Source Address field in the
packet, including the Home Address option, can be forged or modified IPv6 header is not compromised by the presence of a Home Address
in transit. In this case, the contents of the Home Address option is option. Without authentication of the packet, then any field in the
no more suspect than any other part of the packet. IPv6 header, including the Source Address field, and any other parts
of the packet, including the Home Address option, can be forged or
modified in transit. In this case, the contents of the Home Address
option is no more suspect than any other part of the packet.
The use of the Home Address option allows packets sent by a The use of the Home Address option allows packets sent by a
mobile node to pass normally through routers implementing ingress mobile node to pass normally through routers implementing ingress
filtering [6]. Since the care-of address used in Source Address filtering [6]. Since the care-of address used in Source Address
field of the packet's IPv6 header is topologically correct for the field of the packet's IPv6 header is topologically correct for the
sending location of the mobile node, ingress filtering can trace the sending location of the mobile node, ingress filtering can trace the
location of the mobile node in the same way as can be done with any location of the mobile node in the same way as can be done with any
sender when ingress filtering is in use. sender when ingress filtering is in use.
However, if a node receiving a packet that includes a Home Address However, if a node receiving a packet that includes a Home Address
skipping to change at page 52, line 30 skipping to change at page 58, line 32
in the processing is performed. This diminishing of the power of in the processing is performed. This diminishing of the power of
ingress filtering only occurs once the packet has been received at ingress filtering only occurs once the packet has been received at
its ultimate destination, and does not affect the capability of its ultimate destination, and does not affect the capability of
ingress filtering while the packet is in transit. Furthermore, this ingress filtering while the packet is in transit. Furthermore, this
diminishing can be entirely eliminated by appropriate implementation diminishing can be entirely eliminated by appropriate implementation
techniques in the receiving node. For example, the original contents techniques in the receiving node. For example, the original contents
of the Source Address field (the sending care-of address) could be of the Source Address field (the sending care-of address) could be
saved elsewhere in memory with the packet, until all processing of saved elsewhere in memory with the packet, until all processing of
the packet is completed. the packet is completed.
11.3. General Mobile Computing Issues 13.3. General Mobile Computing Issues
The mobile computing environment is potentially very different from The mobile computing environment is potentially very different from
the ordinary computing environment. In many cases, mobile computers the ordinary computing environment. In many cases, mobile computers
will be connected to the network via wireless links. Such links will be connected to the network via wireless links. Such links
are particularly vulnerable to passive eavesdropping, active replay are particularly vulnerable to passive eavesdropping, active replay
attacks, and other active attacks. Furthermore, mobile computers attacks, and other active attacks. Furthermore, mobile computers
are more susceptible to loss or theft than stationary computers. are more susceptible to loss or theft than stationary computers.
Any secrets such as authentication or encryption keys stored on the Any secrets such as authentication or encryption keys stored on the
mobile computer are thus subject to compromise in ways generally not mobile computer are thus subject to compromise in ways generally not
common in the non-mobile environment. common in the non-mobile environment.
Users who have sensitive data that they do not wish others to see Users who have sensitive data that they do not wish others to have
should use mechanisms outside the scope of this document (such as access to should use additional mechanisms (such as encryption) to
encryption) to provide appropriate protection. Users concerned about provide privacy protection, but such mechanisms are beyond the scope
traffic analysis should consider appropriate use of link encryption. of this document. Users concerned about traffic analysis should
If stronger location privacy is desired, the mobile node can create a consider appropriate use of link encryption. If stronger location
tunnel to its home agent. Then, packets destined for correspondent privacy is desired, the mobile node can create a tunnel to its home
nodes will appear to emanate from the home subnet, and it may be agent. Then, packets destined for correspondent nodes will appear
more difficult to pinpoint the location of the mobile node. Such to emanate from the home subnet, and it may be more difficult to
mechanisms are all beyond the scope of this document. pinpoint the location of the mobile node. Such mechanisms are all
beyond the scope of this document.
Appendix A. Changes from Previous Draft Appendix A. Changes from Previous 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-ipv6-02.txt: draft-ietf-mobileip-ipv6-03.txt:
- Added a comparison to Mobile IP for IPv4 and added this section - Added a statement of some non-goals of the protocol in Section 1.
listing changes from the previous version of this draft.
- Introduced the Home Address destination option, to allow packets - Added definition for "home link" and "home subnet prefix",
sent by a mobile node while away from home to pass normally replacing the old term "home subnet". The new terms "foreign
through routers implementing ingress filtering. link" and "foreign subnet prefix" likewise replace the old term
"foreign subnet". This change is more in line with current IPv6
terminology.
- Added the requirement that all IPv6 nodes MUST be able to - Moved the "Comparison with Mobile IP for IPv4" section (now
correctly process a Home Address destination option in a received Section 2) to earlier in the document to allow those familiar
packet. with Mobile IPv4 to quickly see the major differences.
- Changed the interpretation of the Binding Update option such - Added specific language in Section overview listing the fields
that the home address in the binding is the address in the Home conceptually present in each Binding Cache entry and in each
Address option, not the Source Address in the IPv6 header. Binding Update List entry.
- Made the Care-of Address field in the Binding Update optional, - Changed the Option Type values for the Binding Acknowledgement
controlled by whether or not the new Care-of Address Present (C) and Binding Request options such that they now indicate that the
bit is set in the option. With the new use of the Home Address option should be ignored if not recognized, rather than returning
option, the care-of address for a binding will usually be an ICMP error message as they were previously defined.
specified by the Source Address field in the packet's IPv6
header, but by retaining this field (and making it optional),
it is possible to send a binding update using a Source Address
different from the care-of address for the binding.
- Changed the 32-bit Identification field in the Binding Update and - Increased the Lifetime field in a Binding Update from 16 bits
Binding Acknowledgement to a 16-bit Sequence Number field, and to 32 bits, to allow consistency with other lifetime values
clarified the use of this field. Replay protection for Binding used in IPv6 (e.g., the lifetime of a subnet prefix in Neighbor
Updates and Binding Acknowledgements is provided by the IPsec Discovery [11]). Similarly increased the Lifetime and Refresh
authentication in the packet, but this replay protection does fields in the Binding Acknowledgement from 16 bits to 32 bits.
not provide sequencing due to the use of the replay protection
window. This field satisfies that the additional sequencing
requirement.
- Added a description of the dynamic home agent address discovery - Replaced the Home Link-Local Address Present (L) bit and the
procedure and the use of the new Home-Agents anycast address. Home Link-Local Address field in the Binding Update with a new
mechanism implemented by the ID Length field in the Binding
Update. By specifying the length of the interface identifier in
its home address in this field, the mobile node can request its
home agent to essentially fully participate in Neighbor Discovery
on the home link as a proxy for the mobile node, while the mobile
node is away from home.
- Clarified that packets addressed to a mobile node's link-local
address or site-local address are not forwarded to the mobile
node while away from home. When intercepted by the mobile node's
home agent, such packets now cause the home agent to return an
ICMP Destination Unreachable, Code 3, message to the packet's
Source Address (unless this Source Address is a multicast
address). As the use of link-local addresses or site-local
addresses evolves over time in IPv6, this disposition of such
packets may need to change, however.
- Added a discussion of sending Binding Requests in Section 7.6,
and added a discussion of receiving Binding Requests in
Section 9.11.
- Change the requirement for sending a Binding Update to a mobile
node's previous default router in Section 9.6 from "SHOULD" to
"MAY".
- Added Section 12 on "IANA Considerations".
- Replaced the description of specification language keywords,
"MUST", "MAY", "SHOULD", etc., in Section 3.3 with the new
standard reference to RFC 2119.
- Updated the References to point to the most recent version of
each cited RFC or Internet-Draft.
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 Thomas Narten and Erik Nordmark for particularly like to thank Thomas Narten, Erik Nordmark, and Jim
their detailed reviews of earlier versions of this draft. Their Solomon for their detailed reviews of earlier versions of this
suggestions have helped to improve both the design and presentation draft. Their suggestions have helped to improve both the design and
of the protocol. presentation of the protocol.
References References
[1] Randall Atkinson. IP Authentication header. RFC 1826, August [1] S. M. Bellovin. Security problems in the TCP/IP protocol suite.
1995.
[2] 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.
[3] 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). Internet-Draft,
draft-ietf-dhc-dhcpv6-10.txt, May 1997. 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
requirement levels. RFC 2119, March 1997.
[4] Alex Conta and Stephen Deering. Generic packet [4] Alex Conta and Stephen Deering. Generic packet
tunneling in IPv6 specification. Internet-Draft, tunneling in IPv6 specification. Internet-Draft,
draft-ietf-ipngwg-ipv6-tunnel-07.txt, December 1996. draft-ietf-ipngwg-ipv6-tunnel-07.txt, December 1996.
Work in progress. Work in progress.
[5] Stephen E. Deering and Robert M. Hinden. Internet Protocol [5] Stephen E. Deering and Robert M. Hinden. Internet
version 6 (IPv6) specification. RFC 1883, December 1995. Protocol version 6 (IPv6) specification. Internet-Draft,
draft-ietf-ipngwg-ipv6-spec-v2-00.txt, July 1997. Work in
progress.
[6] Paul Ferguson, editor. Network ingress filtering: Defeating [6] Paul Ferguson and Daniel Senie. Network ingress
IP source address spoofing denial of service attacks. filtering: Defeating denial of service attacks which
Internet-Draft, draft-ferguson-ingress-filtering-02.txt, July employ IP source address spoofing. Internet-Draft,
draft-ferguson-ingress-filtering-03.txt, October 1997. Work in
progress.
[7] Stephen Kent and Randall Atkinson. IP Authentication header.
Internet-Draft, draft-ietf-ipsec-auth-header-02.txt, October
1997. Work in progress. 1997. Work in progress.
[7] P. Mockapetris. Domain Names---concepts and facilities. [8] Stephen Kent and Randall Atkinson. IP Encapsulating Security
Payload (ESP). Internet-Draft, draft-ietf-ipsec-esp-v2-01.txt,
October 1997. Work in progress.
[9] P. Mockapetris. Domain Names---concepts and facilities.
RFC 1034, November 1987. RFC 1034, November 1987.
[8] P. Mockapetris. Domain Names---implementation and [10] P. Mockapetris. Domain Names---implementation and
specification. RFC 1035, November 1987. specification. RFC 1035, November 1987.
[9] Thomas Narten, Erik Nordmark, and William Allen Simpson. [11] Thomas Narten, Erik Nordmark, and William Allen Simpson.
Neighbor Discovery for IP version 6 (IPv6). RFC 1970, August Neighbor Discovery for IP version 6 (IPv6). Internet-Draft,
1996. draft-ietf-ipngwg-discovery-v2-00.txt, July 1997. Work in
progress.
[10] Charles Perkins. IP encapsulation within IP. RFC 2003, October [12] Charles Perkins. IP encapsulation within IP. RFC 2003, October
1996. 1996.
[11] Charles Perkins, editor. IP mobility support. RFC 2002, [13] Charles Perkins, editor. IP mobility support. RFC 2002,
October 1996. October 1996.
[12] Charles Perkins. Minimal encapsulation within IP. RFC 2004, [14] Charles Perkins. Minimal encapsulation within IP. RFC 2004,
October 1996. October 1996.
[13] J. B. Postel. User Datagram Protocol. RFC 768, August 1980. [15] J. B. Postel. User Datagram Protocol. RFC 768, August 1980.
[14] J. B. Postel, editor. Transmission Control Protocol. RFC 793, [16] J. B. Postel, editor. Transmission Control Protocol. RFC 793,
September 1981. September 1981.
[15] Joyce K. Reynolds and Jon Postel. Assigned numbers. RFC 1700, [17] Joyce K. Reynolds and Jon Postel. Assigned numbers. RFC 1700,
October 1994. October 1994.
[16] Susan Thomson and Thomas Narten. IPv6 stateless address [18] Susan Thomson and Thomas Narten. IPv6 stateless address
autoconfiguration. RFC 1971, August 1996. autoconfiguration. Internet-Draft,
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 Jim Solomon
Motorola, Inc. Motorola, Inc.
1301 E. Algonquin Rd. 1301 E. Algonquin Rd.
Schaumburg, IL 60196 Schaumburg, IL 60196
USA USA
 End of changes. 

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