Monami6 Working Group R. Wakikawa (Editor)
Internet-Draft Keio University
Intended status: Standards Track T. Ernst
Expires: May 22, 2008 INRIA
K. Nagami
INTEC NetCore
V. Devarapalli
Azaire Networks
November 19, 2007
Multiple Care-of Addresses Registration
draft-ietf-monami6-multiplecoa-04.txt
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Copyright (C) The IETF Trust (2007).
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Abstract
According to the current Mobile IPv6 specification, a mobile node may
have several care-of addresses, but only one, termed the primary
care-of address, can be registered with its home agent and the
correspondent nodes. However, for matters of cost, bandwidth, delay,
etc, it is useful for the mobile node to get Internet access through
multiple access media simultaneously, in which case multiple active
IPv6 care-of addresses would be assigned to the mobile node. We thus
propose Mobile IPv6 extensions designed to register multiple care-of
addresses bound to a single Home Address instead of the sole primary
care-of address. For doing so, a new identification number must be
carried in each binding for the receiver to distinguish between the
bindings corresponding to the same Home Address. Those extensions
are targeted to NEMO (Network Mobility) Basic Support as well as to
Mobile IPv6.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7
4. Mobile IPv6 Extensions . . . . . . . . . . . . . . . . . . . . 10
4.1. Binding Cache Structure and Binding Update List . . . . . 10
4.2. Message Format Changes . . . . . . . . . . . . . . . . . . 10
4.2.1. Binding Unique Identifier sub-option . . . . . . . . . 10
4.3. New Status Values for Binding Acknowledgment . . . . . . . 12
5. Mobile Node Operation . . . . . . . . . . . . . . . . . . . . 13
5.1. Management of Care-of Addresses and Binding Unique
Identifier . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2. Return Routability: Sending CoTI and Receiving CoT . . . . 13
5.3. Binding Registration . . . . . . . . . . . . . . . . . . . 14
5.4. Binding Bulk Registration . . . . . . . . . . . . . . . . 15
5.5. Binding De-Registration and Returning Home . . . . . . . . 16
5.6. Receiving Binding Acknowledgment . . . . . . . . . . . . . 17
5.7. Receiving Binding Refresh Request . . . . . . . . . . . . 18
5.8. Sending Packets to Home Agent . . . . . . . . . . . . . . 19
5.9. Bootstrapping . . . . . . . . . . . . . . . . . . . . . . 19
6. Home Agent and Correspondent Node Operation . . . . . . . . . 21
6.1. Searching Binding Cache with Binding Unique Identifier . . 21
6.2. Receiving CoTI and Sending CoT . . . . . . . . . . . . . . 21
6.3. Processing Binding Update . . . . . . . . . . . . . . . . 22
6.4. Sending Binding Refresh Request . . . . . . . . . . . . . 24
6.5. Receiving Packets from Mobile Node . . . . . . . . . . . . 25
7. Network Mobility Applicability . . . . . . . . . . . . . . . . 26
8. IPsec and IKEv2 interaction . . . . . . . . . . . . . . . . . 27
8.1. Use of Care-of Address in the IKEv2 exchange . . . . . . . 27
8.2. Transport Mode IPsec protected messages . . . . . . . . . 28
8.3. Tunnel Mode IPsec protected messages . . . . . . . . . . . 28
8.3.1. Tunneled HoTi and HoT messages . . . . . . . . . . . . 28
8.3.2. Tunneled Payload Traffic . . . . . . . . . . . . . . . 29
9. Security Considerations . . . . . . . . . . . . . . . . . . . 30
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 32
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12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
12.1. Normative References . . . . . . . . . . . . . . . . . . . 32
12.2. Informative References . . . . . . . . . . . . . . . . . . 33
Appendix A. Example Configurations . . . . . . . . . . . . . . . 34
Appendix B. Changes From Previous Versions . . . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 39
Intellectual Property and Copyright Statements . . . . . . . . . . 41
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1. Introduction
A mobile node should use various type of network interfaces to obtain
durable and wide area network connectivity. The assumed scenarios
and motivations for multiple points of attachment, and benefits for
doing it are discussed at large in [ID-MOTIVATION].
IPv6 [RFC-2460] conceptually allows a node to have several addresses
on a given interface. Consequently, Mobile IPv6 [RFC-3775] has
mechanisms to manage multiple ``Home Addresses'' based on home
agent's managed prefixes such as mobile prefix solicitation and
mobile prefix advertisement. But assigning a single Home Address to
a node is more advantageous than assigning multiple Home Addresses
because applications do not need to be aware of the multiplicity of
Home Addresses. If multiple home addresses are available,
applications must reset the connection information when the mobile
node changes its active network interface (i.e. change the Home
Address).
According to the Mobile IPv6 specification, a mobile node is not
allowed to register multiple care-of addresses bound to a single Home
Address. Since NEMO Basic Support [RFC-3963] is based on Mobile
IPv6, the same issues apply to a mobile node acting as a mobile
router. Multihoming issues pertaining to mobile nodes operating
Mobile IPv6 and mobile routers operating NEMO Basic Support are
respectively discussed [ID-MIP6ANALYSIS] and [RFC-4980] in Monami6
and NEMO Working Group.
In this document, we thus propose a new identification number called
Binding Unique Identification (BID) number for each binding cache
entry to accommodate multiple bindings registration. The mobile node
notifies the BID to both its Home Agent and correspondent nodes by
means of a Binding Update. Correspondent nodes and the home agent
record the BID into their binding cache. The Home Address thus
identifies a mobile node itself whereas the BID identifies each
binding registered by a mobile node. By using the BID, multiple
bindings can then be distinguished.
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC-2119].
Terms used in this draft are defined in [RFC-3775], [RFC-3753] and
[RFC-4885]. In addition or in replacement of these, the following
terms are defined or redefined:
Binding Unique Identification number (BID)
The BID is an identification number used to distinguish multiple
bindings registered by the mobile node. Assignment of distinct
BID allows a mobile node to register multiple binding cache
entries for a given Home Address. The BID is conceptually
assigned to a binding in a way it cannot be duplicated with
another BID. The zero value and a negative value MUST NOT be
used. After being generated by the mobile node, the BID is stored
in the Binding Update List and is sent by the mobile node by means
of a sub-option of a Binding Update. A mobile node MAY change the
value of a BID at any time according to its administrative policy,
for instance to protect its privacy. An implementation must
carefully assign the BID so as to keep using the same BID for the
same binding even when the status of the binding is changed. More
details can be found in Section 5.1.
Binding Unique Identifier sub-option
The Binding Unique Identifier sub-option is used to carry the BID.
Bulk Registration
A mobile node can register multiple bindings at once by sending a
single binding update. The mobile node does not necessarily put
all the available care-of addresses in the binding update, but
several care-of addresses. A mobile node can also replace all the
bindings available at the home agent with the new bindings by
using the bulk registration. The bulk registration is supported
only for home registration and deregistration as explained in
Section 5.5. A mobile node MUST NOT perform bulk registration
with correspondent nodes.
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3. Protocol Overview
A new identification number (BID) is introduced to distinguish
multiple bindings pertaining to the same Home Address. Once a mobile
node gets several IPv6 global addresses on interfaces, it can
register these addresses with its home agent. If the mobile node
wants to register multiple bindings, it MUST generate a BID for each
care-of address and record the BID into the binding update list. A
mobile node can manage each binding independently owing to BID. The
mobile node then registers its care-of addresses by sending a Binding
Update with a Binding Unique Identifier sub-option. The BID MUST be
included in the Binding Unique Identifier sub-option. After
receiving such Binding Update and Binding Unique Identifier sub-
option, the home agent MUST copy the BID from the Binding Unique
Identifier sub-option to the corresponding field in the binding cache
entry. Even if there is already an entry for the mobile node's home
address, the home agent MUST register a new binding entry for the BID
stored in the Binding Unique Identifier sub-option. The mobile node
registers multiple care-of addresses either independently in
individual Binding Updates or multiple at once in a single Binding
Update.
If the mobile host wishes to register its binding with a
correspondent node, it must operate return routability operations.
The mobile host MUST manage a Care-of Keygen Token per care-of
address. If it is necessary (ex. Care-of Keygen token is expired),
the mobile host exchanges CoTI and CoT for the relative care-of
addresses. When the mobile host registers several care-of addresses
to a correspondent node, it uses the same BID as the one generated
for the home registration's bindings. The binding registration step
is the same as for the home registration except for calculating
authenticator by using Binding Unique Identifier sub-option as well
as the other sub-options specified in [RFC-3775]. For simplicity,
the bulk registration is not supported for correspondent nodes in
this document.
If the mobile node decides to act as a regular mobile node compliant
with [RFC-3775] , it just sends a Binding Update without any Binding
Unique Identifier sub-options (i.e. normal Binding Update). The
receiver of the Binding Update deletes all the bindings registering
with a BID and registers only a single binding for the mobile node.
Note that the mobile node can continue to use BID even if only a
single binding is active at some time.
The BID is used as a search key for a corresponding entry in the
binding cache in addition to the Home Address. When a home agent and
a correspondent node check the binding cache database for the mobile
node, they search a corresponding binding entry with the Home Address
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and BID of the desired binding. If necessary, a mobile node can use
policy and filter information to look up the best binding per
sessions, flow, packets, but this is out of scope in this document
and is currently discussed in Monami6 WG. If there is no desired
binding, it searches the binding cache database with the Home Address
as specified in Mobile IPv6. The first matched binding entry may be
found, although this is implementation dependent.
A mobile node carefully operates the returning home. The Home Agent
needs to defend a mobile node's home address by the proxy NDP for
packet interception, while the mobile node defends its home address
by regular NDP to send and receive packets at the interface attached
to the home link. Two nodes, Home Agent and Mobile Node, compete ND
state. This will causes address duplication problem at the end. If
the proxy neighbor advertisement for the Home Address is stopped,
packets are always routed to the interface attached to the home link.
On the other hand, packets are never routed to the interface attached
to the home link when the proxy is active.
When a mobile node wants to return home with interface attached to
the home link, it MUST de-register all the bindings by sending a
Binding Update with lifetime set to zero as described in [RFC-3775]
and [RFC-3963]. The mobile node does not put any Binding Unique
Identifier sub-option in this Binding Update. The receiver deletes
all the bindings from its binding cache database. On the other hand,
a mobile node does not want to return home and keeps the interfaces
attached to the foreign links active, when one of its interfaces is
attached to its home link. The mobile node disables the interface
attached to the home link and keeps using the rest of interfaces
attached to foreign links. In this case, the mobile node sends a de-
registration Binding Update including the BID for the interface
attached to the home link. The receiver of the de-registration
Binding Update deletes only the relative binding entry from the
binding cache database. The home agent does not stop proxying
neighbor advertisement as long as there are still bindings for the
other interfaces. It is important to understand that this scenario
is not the most efficient because all the traffic from and to the
mobile node is going through the bi-directional tunnel, whereas the
mobile node is now accessible at one hop from its home agent.
In the above two cases, a mobile node cannot use interfaces attached
to both home and foreign links simultaneously. If the proxy NDP is
disabled, the main problem can be solved. In the Multiple Care-of
Address Registration, the elimination of Proxy NDP enables that
Mobile Node and Home Agent maintain multiple bindings for the
interfaces attached to the home link and the foreign links. The
mobile node sends the binding update with H flag set for the
interface attached to the home link. The detail operation can be
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found in Section 5.5.
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4. Mobile IPv6 Extensions
This section summarizes the changes to Mobile IPv6 necessary to
manage multiple bindings bound to a same Home Address.
4.1. Binding Cache Structure and Binding Update List
The BID is required in the binding cache and binding update list
structure.
4.2. Message Format Changes
4.2.1. Binding Unique Identifier sub-option
The Binding Unique Identifier sub-option is included in the Binding
Update, Binding Acknowledgment, Binding Refresh Request, and Care-of
Test Init and Care-of Test message.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Binding Unique ID (BID) | Status |C|O|H|Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
+ +
+ care-of address (CoA) +
+ +
+---------------------------------------------------------------+
Figure 1: BID Sub-Option
Type
Type value for Binding Unique Identifier is TBD
Length
Length value MUST be 4 when C flag is unset. Otherwise, the
Length value MUST be set to 20.
Binding Unique ID (BID)
The BID which is assigned to the binding carried in the Binding
Update with this sub-option. BID is 16-bit unsigned integer. A
value of zero is reserved.
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Status
When the Binding Unique Identifier sub-option is included in a
Binding Acknowledgment, this field overwrites the status field
correspondent to each binding in the Binding Acknowledgment. If
this field is zero, the receiver MUST use the registration status
stored in the Binding Acknowledgment message. This Status field
can be used to carry error information for a Care-of Test message.
The status is 8-bit unsigned integer. The possible status codes
are the same as the status codes of Binding Acknowledgment.
Care-of address (C) flag
When this flag is set, a mobile node can store a Care-of Address
corresponding to the BID in the Binding Unique Identifier sub-
option. This flag must be used whenever a mobile node sends
multiple bindings in a single Binding Update, i.e. bulk
registration or MUST be used as a substitute for an alternate
care-of address option. This flag is valid only for binding
update for the home agent.
Overwrite (O) flag
When this flag is set, a mobile node requests a home agent to
replace all the bindings to binding entries stored in a Binding
Update. This flag is valid only for binding update for the home
agent.
Home Binding (H) flag
This flag indicates that the mobile node is attached to the home
link. This flag is valid only for binding update for the home
agent.
Reserved
5 bits Reserved field. Reserved field must be set with all 0.
Care-of Address
When C flag is set, a Care-of Address matched to the BID is
stored. This field is valid only if a Binding Unique Identifier
sub-option is stored in Binding Update message. Otherwise, this
field can be omitted. The receiver SHOULD ignore this field if
the sub-option is presented in other than Binding Update.
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4.3. New Status Values for Binding Acknowledgment
New status values for the status field in a Binding Acknowledgment
are defined for handling the multiple Care-of Addresses registration:
MCOA INCOMPLIANT (TBD)
Registration failed because Binding Unique Identifier sub-option
is not compliant.
MCOA BID CONFLICT (TBD)
It indicates that a regular binding (i.e. without the BID set) is
already registered for the home address, and is conflicting with a
received Binding Update which BID is set.
MCOA PROHIBITED(TBD)
It implies the multiple care-of address registration is
administratively prohibited.
MCOA BULK REGISTRATION NOT SUPPORTED (TBD)
The bulk binding registration is not supported.
MCOA FLAG CONFLICTS (TBD)
The flags of the sub-options presented in a Binding Unique
Identifier sub-options conflicts.
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5. Mobile Node Operation
5.1. Management of Care-of Addresses and Binding Unique Identifier
There are two cases when a mobile node has several Care-of Addresses:
1. A mobile node uses several physical network interfaces and
acquires a care-of address on each of its interfaces.
2. A mobile node uses a single physical network interface, but
multiple prefixes are announced on the link the interface is
attached to. Several global addresses are configured on this
interface for each of the announced prefixes.
The difference between the above two cases is only a number of
physical network interfaces and therefore does not matter in this
document. The Identification number is used to identify a binding.
To implement this, a mobile node MAY assign an identification number
for each care-of addresses. How to assign an identification number
is up to implementers.
A mobile node assigns a BID to each care-of address when it wants to
register them simultaneously with its Home Address . The value
should be generated from a value comprised between 1 to 65535. Zero
and negative values MUST NOT be taken as a BID. If a mobile node has
only one care-of address, the assignment of a BID is not needed until
it has multiple care-of addresses to register with.
5.2. Return Routability: Sending CoTI and Receiving CoT
When a mobile node wants to register bindings to a Correspondent
Node, it MUST have the valid care-of Keygen token per care-of
address, while the HoTI and HoT can be exchanged only once for a Home
Address.
If the Mobile Node manages bindings with BID, it MUST include a
Binding Unique Identifier sub-option in a Care-of Test Init message.
It MUST NOT set the any flags in the sub-option. The receiver (i.e.
correspondent node) will calculate a care-of Keygen token as
specified in [RFC-3775] and reply a Care-of Test message and the
Binding Unique Identifier sub-option as described in Section 6.2.
When the mobile node receives the Care-of Test message, the Care-of
Test message is verified as same as in [RFC-3775]. If a Binding
Unique Identifier sub-option is not presented in CoT in reply to the
CoTI containing the Binding Unique Identifier sub-option, the
correspondent node does not support the Multiple Care-of Address
registration. Thus, the mobile node MUST NOT use a Binding Unique
Identifier sub-option in the future Binding Update. The Mobile Node
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MAY skip resending regular CoTI message and keep the received care-of
Keygen token for the regular Binding Update, because the
correspondent node just ignores and skip the Binding Unique
Identifier sub-option and calculates the care-of Keygen token as
[RFC-3775] specified.
5.3. Binding Registration
When a mobile node sends a Binding Update, it MUST decide whether it
registers multiple care-of addresses or not. However, this decision
is out-of scope in this document. If a mobile node decides not to
register multiple care-of addresses, it completely follows the
RFC3775 specification.
For the multiple Care-of Addresses registration, the mobile node MUST
include a Binding Unique Identifier sub-option(s) in the Mobility
Option field of a Binding Update as shown in Figure 2. The BID is
copied from a corresponding Binding Update List entry to the BID
field of the Binding Unique Identifier sub-option. When ESP is used
for binding update, the care-of address MUST be stored in the Care-of
Address field by setting C flag as a substitute for the alternate
care-of address option. The alternate care-of address option MUST be
omitted. Additionally for binding registration to a correspondent
node, the mobile node MUST have both active home and care-of Keygen
tokens for Kbm (see Section 5.2.5 of [RFC-3775]). The care-of Keygen
tokens MUST be maintained for each care-of address that the mobile
node wants to register to the correspondent node, as described in
Section 5.2. After computing an Authenticator value for the Binding
Authorization sub-option, it sends a Binding Update which contains a
Binding Unique Identifier sub-option. The Binding Update is
protected by a Binding Authorization Data sub-option placed after the
Binding Unique Identifier sub-option.
IPv6 header (src=CoA, dst=HA)
IPv6 Home Address Option
ESP Header (for home registration)
Mobility header
-BU
Mobility Options
- Binding Unique Identifier sub-option
- Binding Authorization sub-option
(for Route Optimization)
Figure 2: Binding Update for Binding Registration
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5.4. Binding Bulk Registration
The bulk registration is an optimization for registering multiple
care-of addresses only to a home agent by using a single Binding
Update. If a mobile node, for instance, does not want to send a lot
of control messages through an interface which bandwidth is scarce,
it can use this bulk registration and send a Binding Update
containing multiple or all the valid care-of addresses.
A mobile node sets the C flag in a Binding Unique Identifier sub-
option and stores the particular care-of address in the Binding
Unique Identifier sub-option. The mobile node stores multiple sets
of a Binding Unique Identifier sub-option in a Binding Update as
shown in Figure 3. When multiple Binding Unique Identifier sub-
options are presented in a Binding Update, the flag field of all the
sub-options MUST have the same value. For example, if C flag is set,
the same flag MUST be set to all the sub-options. Otherwise, the
mobile node will receive errors [MCOA FLAG CONFLICTS] by a Binding
Acknowledgment. In the bulk registration, all the other binding
information such as Lifetime, Sequence Number, binding Flags are
shared among the bulked Care-of Addresses. The alternate care-of
address option MUST be omitted when ESP is used to protect a binding
update. In the bulk registration, the Sequence Number field of a
Binding Update SHOULD be carefully configured. If each binding uses
different sequence number, a mobile node MUST use the largest
sequence number from the binding update list used for the bulk
registration. If it cannot select a sequence number for all the
bindings due to sequence number out of window, it MUST NOT use the
bulk registration for the binding which sequence number is out of
window and uses a separate Binding Update for the binding.
IPv6 header (src=CoA, dst=HA)
IPv6 Home Address Option
ESP Header
Mobility header
-BU
Mobility Options
- Binding Unique Identifier sub-options
(C flag is set, O flag is optional,
BID and CoA are stored)
Figure 3: Binding Update for Binding Bulk Registration
If the mobile node wants to replace existing registered bindings on
the home agent with the bindings in the sent Binding Update, it can
set O flag. Section 6.3 describes this registration procedure in
detail.
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5.5. Binding De-Registration and Returning Home
When a mobile node decides to delete all the bindings for its home
address at a visiting network, it simply sends a regular de-
registration Binding Update which lifetime is set to zero. A Binding
Unique Identifier sub-option is not required.
If a mobile node wants to delete a particular binding(s) from its
home agent and correspondent nodes (e.g. from foreign link), the
mobile node simply sets zero lifetime for the sending binding update.
The Binding Update MUST contain a relative Binding Unique Identifier
Sub-option(s). The receiver will remove only the care-of address(es)
that matches to the specified BID. For the bulk de-registration, the
care-of addresses field of each sub-option SHOULD be omitted, because
the receiver will remove all the care-of addresses which matches the
specified BID.
When a mobile node returns home, it SHOULD de-register all bindings
with the home agent by sending a regular de-registration binding
update to flush all the registered bindings. However, there are
several scenarios for returning home described in Appendix A
(Figure 7, Figure 8, Figure 9). We have discussed this feature in
Monami6 working group now. This part might be updated in the next
revision.
As shown in Figure 7 in Appendix A, a mobile node de-registers all
the binding from the home agent, while it MAY still keep the bindings
of the other interface active attached to foreign links only at the
Correspondent Nodes. By doing this, the mobile node still receives
packets from the Correspondent Node at the interface attached to a
foreign link thanks to route optimization. If the correspondent
nodes does not use route optimization, the mobile node receives such
packets at the interface attached to the home link.
In Figure 8, a mobile node does not want to return home even if one
of interfaces is attached to the home link. The mobile node MUST
disable the interface attached to the home link. Otherwise, address
duplication will be observed because the home agent still defend the
Home Address by the proxy neighbor advertisement and the mobile node
also enables the same Home Address on the home link. After disabling
the interface attached to the home link, the mobile node MUST delete
the binding for the disabled interface by sending a de-registration
binding update. The de-registration binding update is sent from one
of active interfaces attached to foreign links. As a result, the
mobile node no longer receives packets at the interface attached to
the home link. All packets are routed to other interfaces attached
to a foreign link.
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Alternatively, the Mobile Node may choose to activate both the
interfaces attached to the home link and the foreign link, and
communicates with all of the interfaces. The Mobile Node notifies
the Home Agent using the H flag which means the Mobile Node is
attached to the home link. The Mobile Node may notify the care-of
address of the interface(s) attached to the foreign link(s) in the
same message using bulk registration. The Home Agent then no longer
uses Proxy Neighbor Advertisement to intercept packets and the Mobile
Node can utilize both of interfaces attached to the home link and the
foreign link simultaneously. The Home Agent can intercept packets by
IP routing, but not by proxy Neighbor Discovery. The detailed
operation of no NDP operation can be found in [ID-NONDP].
When the Mobile Node returns home, it de-registers a binding for the
interface. While the bindings for the interfaces attached to the
foreign link are still active. Intercepting packets, the Home Agent
can decide whether it tunnels to the foreign interface or routes to
the home interface of the Mobile Node. To do so, the Home Agent must
know that the Mobile Node is back to the home link. However, if the
binding is deleted, there is no way for the Home Agent to know that
the Mobile Node is at the home, too. The Home Agent SHOULD
invalidate the binding for the interface attached to the home link
and MAY NOT delete it. It can alternatively mark that the Mobile
Node is at the home link, too. As an example, the Home Agent inserts
the Home Address of the Mobile Node in the Care-of Address field of
the Mobile Node. The binding is named "Home Binding" in this
documentation. The Home Agent MAY manage this home binding as same
as the other binding entry in terms of lifetime validation, etc. The
Mobile Node MAY send multiple binding de- registration to keep this
home binding active. Alternatively, the Home Agent can use infinity
lifetime for the lifetime of the home binding. When the Mobile Node
leaves the Home Link, it can update the home binding to the normal
binding. Before that, the Home Agent believes the Mobile Node is at
the home and may route packets for the Mobile Node to the Home Link.
5.6. Receiving Binding Acknowledgment
The verification of a Binding Acknowledgment is the same as Mobile
IPv6 (section 11.7.3 of [RFC-3775]). The operation for sending a
Binding Acknowledgment is described in Section 6.3.
If a mobile node includes a Binding Unique Identifier sub-option in a
Binding Update with A flag set, a Binding Acknowledgment MUST carry a
Binding Unique Identifier sub-option in the Mobility Options field.
If no such sub-option is appeared in the Binding Acknowledgment
replied to the Binding Update for the multiple care-of address
registration, this indicates that the originator node of this Binding
Acknowledgment might not recognize the Binding Unique Identifier sub-
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option. The mobile node SHOULD stop registering multiple care-of
addresses by using a Binding Unique Identifier sub-option.
If a Binding Unique Identifier sub-option is present in the received
Binding Acknowledgment, the mobile node checks the registration
status for the Care-of address(es). The status value MUST be
retrieved as follows. If the status value in the Binding Unique
Identifier sub-option is zero, the mobile node uses the value in the
Status field of the Binding Acknowledgment. Otherwise, it uses the
value in the Status field of the Binding Unique Identifier sub-
option.
If the status code is greater than or equal to 128, the mobile node
starts relevant operations according to the error code. Otherwise,
the originator (home agent or correspondent node) successfully
registered the binding information and BID for the mobile node.
o If the Status value is [MCOA PROHIBITED], the mobile node MUST
give up registering multiple bindings to the peer sending the
Binding Acknowledgment. It MUST return to the regular Mobile IPv6
[RFC-3775] for the peer node.
o If the Status value is [MCOA BULK REGISTRATION NOT SUPPORT], the
mobile node SHOULD stop using bulk registration to the peer
sending the Binding Acknowledgment.
o If [MCOA FLAG CONFLICTS] is specified, it indicates that the
different flag values are used in Binding Unique Identifier sub-
options in a Binding Update. If the C flag is set, all sub-
options MUST have C flag. It is same for O flag. How to handle
other error status codes is specified in [RFC-3775].
o If [MCOA BID CONFLICT] is specified, the binding entry specified
by the Binding Unique Identifier sub-option is already registered
as a regular binding. In such case, the mobile node SHOULD stop
sending Binding Updates with BID, or SHOULD use O flag for the
peer to reset all the registered bindings.
5.7. Receiving Binding Refresh Request
The verification of a Binding Refresh Request is the same as in
Mobile IPv6 (section 11.7.4 of [RFC-3775]). The operation of sending
a Binding Refresh Request is described in section Section 6.4.
If a mobile node receives a Binding Refresh Request with a Binding
Unique Identifier sub-option, this Binding Refresh Request requests a
new binding indicated by the BID. The mobile node SHOULD update only
the respective binding. The mobile node MUST put a Binding Unique
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Identifier sub-option into the Binding Update sent to refresh the
entry.
If no Binding Unique Identifier sub-option is present in a Binding
Refresh Request, the mobile node sends a Binding Update according to
its Binding Update List. On the other hand, if the mobile node does
not have any Binding Update List entry for the requesting node, the
mobile node needs to register either a single binding or multiple
bindings depending on its binding management policy.
5.8. Sending Packets to Home Agent
When a multihomed mobile node sends packets to its home agent, there
are conceptually two ways to construct packets.
1. Using Home Address Option. (required additional 24 bytes)
2. Using IPv6-IPv6 tunnel. (required additional 40 bytes)
Beside the additional size of packets, no difference is observed
between these two. The routing path is always the same and no
redundant path such as dog-leg route occurs. However, in this
document, the mobile node is capable of using multiple care-of
addresses for outgoing packets. This is problem in home agent side
because they must verify the Care-of address for all the packets
received from the mobile node (i.e. ingress filtering). When it uses
the Home Address option, the home agent MAY check the care-of address
in the packet with the registering binding entries. This causes
additional overhead to the home agent. Therefore, the mobile node
SHOULD use the bi-directional tunnel even if it registers a
binding(s) to the home agent.
5.9. Bootstrapping
When a mobile node bootstraps and registers multiple bindings at the
first time, it SHOULD set O flag in the Binding Unique Identifier
sub-option. If old bindings still exists at the Home Agent, the
mobile node has no way to know which bindings are remained as a
garbage. This scenario happens when a mobile node reboots without
correct deregistration. If O flag is used, all the bindings are
replaced to the new binding(s). Thus, the garbage bindings are
surely replaced by new bindings registered with the first Binding
Update. If the mobile node receives the Binding Acknowledgment with
the status code set to 135 [Sequence number out of window], it MUST
retry sending a Binding Update with the last accepted sequence number
which is notified by the Binding Acknowledgment.
For Correspondent nodes, the mobile node cannot use the O flag
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because of no bulk registration support. Thus, if necessary, it MUST
sends a regular binding first to overwrite the remaining bindings at
the correspondent node. Then, it can re-register the set of bindings
by using Multiple Care-of Address Registration.
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6. Home Agent and Correspondent Node Operation
6.1. Searching Binding Cache with Binding Unique Identifier
If either a correspondent node or a home agent has multiple bindings
for a mobile node in their binding cache database, it can use any of
the bindings to communicate with the mobile node. How to select the
most suitable binding from the binding cache database is out of scope
in this document.
Whenever a correspondent node searches a binding cache for a home
address, it SHOULD uses both the Home Address and the BID as the
search key if it knows the corresponding BID. In the example below,
if a correspondent node searches the binding with the Home Address
and BID2, it gets binding2 for this mobile node.
binding1 [a:b:c:d::EUI, care-of address1, BID1]
binding2 [a:b:c:d::EUI, care-of address2, BID2]
binding3 [a:b:c:d::EUI, care-of address3, BID3]
Figure 4: Searching the Binding Cache
A correspondent node basically learns the BID when it receives a
Binding Unique Identifier sub-option. At the time, the correspondent
node MUST look up its binding cache database with the Home Address
and the BID retrieved from the Binding Update. If the correspondent
node does not know the BID, it searches for a binding with only a
Home Address as performed in Mobile IPv6. In such case, the first
matched binding is found. But which binding entry is returned for
the normal search depends on implementations. If the correspondent
node does not desire to use multiple bindings for a mobile node, it
can simply ignore the BID.
6.2. Receiving CoTI and Sending CoT
When a correspondent node receives a CoTI message which contains a
Binding Unique Identifier sub-option, it MUST process it with
following steps.
First of all, the CoTI message is verified according to [RFC-3775].
The Binding Unique Identifier sub-option MUST be, then, processed as
follows:
o If a correspondent node does not understand a Binding Unique
Identifier sub-option, it just ignores and skip this option. The
calculation of a care-of Keygen token will thus be done without a
BID value. The correspondent node returns a CoT message without a
Binding Unique Identifier sub-option. The mobile node can thus
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know whether the correspondent can process the Binding Unique
Identifier sub-option or not, by checking if such option is
present in the CoT message.
o If either or both C and O flag is set in the sub-option, the
Correspondent Node SHOULD NOT calculate a care-of Keygen token and
MUST include a Binding Unique Identifier sub-option which status
value set to [MCOA INCOMPLIANT] in the returned Care-of Test
message.
o Otherwise, the correspondent node MUST include a Binding Unique
Identifier sub-option which status value MUST be set to zero in
the returning a CoT message.
o All the Binding Unique Identifier sub-options SHOULD be copied
from the received one except for the Status Field for CoT. The
Care-of address field of each Binding Unique Identifier sub-
option, however, can be omitted, because the mobile node can match
a corresponding binding update list by using BID.
6.3. Processing Binding Update
If a Binding Update does not contain a Binding Unique Identifier sub-
option, its processing is same as in [RFC-3775]. But if the receiver
already has multiple bindings for the home address, it MUST replace
all the existing bindings by the received binding. As a result, the
receiver node MUST have only a binding for the mobile node. If the
Binding Update is for de-registration, the receiver MUST delete all
existing bindings from its Binding Cache.
If a Binding Update contains a Binding Unique Identifier sub-
option(s), it is validated according to section 9.5.1 of [RFC-3775]
and the following step.
o If the home registration flag is set in the Binding Update, the
home agent MUST carefully operate DAD for the received Home
Address. If the home agent has already had a binding(s) for the
Mobile Node, it MUST avoid running DAD check when it receives the
Binding Update.
The receiver node MUST process the Binding Unique Identifier sub-
option(s) in the following steps. When a correspondent node sends a
Binding Acknowledgment, the status value is always stored in the
Status field of the Binding Acknowledgment and keep the Status field
of Binding Unique Identifier sub-option to zero. For the Home Agent,
the status value can be stored in the Status field of either a
Binding Acknowledgment or a Binding Unique Identifier sub-option. If
the status value is specific to one of bindings in the bulk
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registration, the status value MUST be stored in the Status field in
the corresponding Binding Unique Identifier sub-option.
o The length value is examined. The length value MUST be either 4
or 20 depending on C flag. If the length is incorrect, the
receiver MUST rejects the Binding Update and returns the status
value set to [MCOA INCOMPLIANT].
o When C flag is specified, the care-of address MUST be given in the
Binding Unique Identifier sub-option. Otherwise, the receiver
MUST reject the Binding Unique Identifier sub-option and returns
the status value set to [MCOA INCOMPLIANT].
o When multiple binding Unique Identifier sub-options are presented,
the receiver MUST support the bulk registration. Only a home
agent can accept the bulk registration. Otherwise, it MUST reject
the Binding Update and returns the status value set to [MCOA BULK
REGISTRATION NOT SUPPORT] in the Binding Acknowledgment.
o When multiple binding Unique Identifier sub-options are presented,
the flags field of all the Binding Unique Identifier sub-option
stored in the same Binding Update MUST be equal. Otherwise, the
receiver MUST reject the Binding Update and returns the status
value set to [MCOA FLAG CONFLICTS] in the Binding Acknowledgment.
o If the Lifetime field of the Binding Update is zero, the receiver
node deletes the binding entry which BID is same as BID sent by
the Binding Unique Identifier sub-option. If the receiver node
does not have appropriate binding which BID is matched with the
Binding Update, it MUST reject this de-registration Binding Update
for the binding cache. If the receiver is a Home Agent, it SHOULD
also return the status value set to [not Home Agent for this
mobile node, 133].
o If O flag is set in the deregistering Binding Update, the receiver
can ignore this flag for deregistration. If the H flag is set,
the home agent stores a Home Address in the Care-of Address field
of the binding cache entry. The home agent no longer performs
proxy NDP for this mobile node until this entry is deleted.
o If the Lifetime field is not zero, the receiver node registers a
binding with the specified BID as a mobile node's binding. The
Care-of address is picked from the Binding Update packet as
follows:
* If C flag is set in the Binding Unique Identifier sub-option,
the care-of address must be taken from the care-of address
field in each Binding Unique Identifier sub-option.
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* If C flag is not set in the Binding Unique Identifier sub-
option, the care-of address must be taken from the Source
Address field of the IPv6 header.
* If C flag is not set and an alternate care-of address is
present, the care-of address is taken from the Alternate
Care-of address sub-option.
o Once the care-of address(es) has been retrieved from the Binding
Update, it starts registering binding(s).
* Only if O flag is set in the sub-option, the home agent first
removes all the existing bindings and registers the received
bindings.
* If the receiver has a regular binding which does not have BID
for the mobile node, it de-registers the regular binding and
registers a new binding including BID according to the Binding
Update. In this case, the receiver MUST return [MCOA BID
CONFLICT].
* If the receiver node has already registered the binding which
BID is matched with requesting BID, then it MUST update the
binding with the Binding Update and returns [0 Binding Update
accepted].
* If the receiver does not have a binding entry which BID is
matched with the requesting BID, it registers a new binding for
the BID and returns [0 Binding Update accepted].
If all the above operations are successfully finished, the Binding
Acknowledgment containing the Binding Unique Identifier sub-options
MUST be replied to the mobile node if A flag is set in the Binding
Acknowledgment. Whenever a Binding Acknowledgment is returned, all
the Binding Unique Identifier sub-options stored in the Binding
Update MUST be copied to the Binding Acknowledgment. The Care-of
address field of each Binding Unique Identifier sub-option, however,
can be omitted, because the mobile node can match a corresponding
binding update list by using BID.
6.4. Sending Binding Refresh Request
When a node sends a Binding Refresh Request for a particular binding
registering with BID, the node SHOULD contain a Binding Unique
Identifier sub-option in the Binding Refresh Request.
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6.5. Receiving Packets from Mobile Node
When a node receives packets with a Home Address destination option
from a mobile node, it MUST check that the care-of address appeared
in the Source Address field MUST be equal to one of the care-of
addresses in the binding cache entry. If no binding is found, the
packets MUST be silently discarded and MUST send a Binding Error
message according to RFC3775. This verification MUST NOT be done for
a Binding Update.
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7. Network Mobility Applicability
Support of multihomed mobile routers is advocated in the NEMO working
group (see R12 "The solution MUST function for multihomed MR and
multihomed mobile networks" in [RFC-4886]. Issues regarding mobile
routers with multiple interfaces and other multihoming configurations
are documented in [RFC-4980].
Since the binding management mechanisms are the same for a mobile
host operating Mobile IPv6 and for a mobile router operating NEMO
Basic Support (RFC 3963), our extensions can also be used to deal
with multiple care-of addresses registration sent from a multihomed
mobile router. Figure 5 shows the example format of a Binding Update
used by a mobile router.
IPv6 header (src=CoA, dst=HA)
IPv6 Home Address Option
ESP Header
Mobility header
-BU
Mobility Options
- Binding Unique Identifier sub-option
- Mobile Network Prefix sub-option
Figure 5: NEMO Binding Update
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8. IPsec and IKEv2 interaction
Mobile IPv6 [RFC-3775] and the NEMO protocol [RFC-3963] require the
use of IPsec to protect signaling messages like Binding Updates,
Binding Acknowledgments and return routability messages. IPsec may
also be used protect all reverse tunneled data traffic. The Mobile
IPv6-IKEv2 specification [RFC-4877] specifies how IKEv2 can be used
to setup the required IPsec security associations. The following
assumptions were made in [RFC-3775], [RFC-3963] and the MIP6-IKEv2
specification with respect to the use of IKEv2 and IPsec.
o There is only one primary care-of address per mobile node.
o The primary care-of address is stored in the IPsec database for
tunnel encapsulation and decapsulation.
o When the home agent receives a packet from the mobile node, the
source address is verified against the care-of address in the
corresponding binding cache entry. If the packet is a reverse
tunneled packet from the mobile node, the care-of address check is
done against the source address on the outer IPv6 header. The
reverse tunnel packet could either be a tunneled HoTi message or
tunneled data traffic to the correspondent node.
o The mobile node runs IKEv2 (or IKEv1) with the home agent using
the care-of address. The IKE SA is based on the care-of address
of the mobile node.
The above assumptions may not be valid when multiple care-of
addresses are used by the mobile node. In the following sections,
the main issues with the use of multiple care-of address with IPsec
are addressed.
8.1. Use of Care-of Address in the IKEv2 exchange
For each home address the mobile node sets up security associations
with the home agent, the mobile node must pick one care-of address
and use that as the source address for all IKEv2 messages exchanged
to create and maintain the IPsec security associations associated
with the home address. The resultant IKEv2 security association is
created based on this care-of address.
If the mobile node needs to change the care-of address, it just sends
a Binding Update with the care-of address it wants to use, with the
corresponding Binding Unique Identifier sub-option, and with the 'K'
bit set. This will force the home agent to update the IKEv2 security
association to use the new care-of address. If the 'K' bit is not
supported on the mobile node or the home agent, the mobile node MUST
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re-establish the IKEv2 security association with the new care-of
address. This will also result in new IPsec security associations
being setup for the home address.
8.2. Transport Mode IPsec protected messages
For Mobile IPv6 signaling message protected using IPsec in transport
mode, the use of a particular care-of address among multiple care-of
addresses does not matter for IPsec processing.
For Mobile Prefix Discovery messages, [RFC-3775] requires the home
agent to verify that the mobile node is using the care-of address
that is in the binding cache entry that corresponds to the mobile
node's home address. If a different address is used as the source
address, the message is silently dropped by the home agent. This
document requires the home agent implementation to process the
message as long as the source address is is one of the care-of
addresses in the binding cache entry for the mobile node.
8.3. Tunnel Mode IPsec protected messages
The use of IPsec in tunnel mode with multiple care-of address
introduces a few issues that require changes to how the mobile node
and the home agent send and receive tunneled traffic. The route
optimization mechanism described in [RFC-3775] mandates the use of
IPsec protection in tunnel mode for the HoTi and HoT messages. The
mobile node and the home agent may also choose to protect all reverse
tunneled payload traffic with IPsec in tunnel mode. The following
sections address multiple care-of address support for these two types
of messages.
8.3.1. Tunneled HoTi and HoT messages
The mobile node MAY use the same care-of address for all HoTi
messages sent reverse tunneled through the home agent. The mobile
node may use the same care-of address irrespective of which
correspondent node the HoTi message is being sent. RFC 3775 requires
the home agent to verify that the mobile node is using the care-of
address that is in the binding cache entry, when it receives a
reverse tunneled HoTi message. If a different address is used as the
source address, the message is silently dropped by the home agent.
This document requires the home agent implementation to decapsulate
and forward the HoTi message as long as the source address is one of
the care-of addresses in the binding cache entry for the mobile node.
When the home agent tunnels a HoT message to the mobile node, the
care-of address used in the outer IPv6 header is not relevant to the
HoT message. So regular IPsec tunnel encapsulation with the care-of
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address known to the IPsec implementation on the home agent is
sufficient.
8.3.2. Tunneled Payload Traffic
When the mobile sends and receives multiple traffic flows protected
by IPsec to different care-of addresses, the use of the correct
care-of address for each flow becomes important. Support for this
requires the following two considerations on the home agent.
o When the home agent receives a reverse tunneled payload message
protected by IPsec in tunnel mode, it must check that the care-of
address is one of the care-of addresses in the binding cache
entry. According to RFC 4306, the IPsec implementation on the
home agent does not check the source address on the outer IPv6
header. Therefore the care-of address used in the reverse
tunneled traffic can be different from the care-of address used as
the source address in the IKEv2 exchange. However, the Mobile
IPv6 stack on the home agent MUST verify that the source address
is one of the care-of addresses registered by the mobile node
before decapsulating and forwarding the payload traffic towards
the correspondent node.
o For tunneled IPsec traffic from the home agent to the mobile node,
The IPsec implementation on the home agent may not be aware of
which care-of address to use when performing IPsec tunnel
encapsulation. The Mobile IP stack on the home agent must specify
the tunnel end point for the IPsec tunnel. This may require tight
integration between the IPsec and Mobile IP implementations on the
home agent.
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9. Security Considerations
As shown in Section 8, the Multiple Care-of Addresses Registration
requires IPsec protected all the signaling between a mobile node and
its home agent.
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10. IANA Considerations
The following Extension Types MUST be assigned by IANA:
o Binding Unique Identifier sub-option type
o New Status of Binding Acknowledgment
* MCOA INCOMPLIANT (TBD)
* MCOA BID CONFLICT (TBD)
* MCOA PROHIBITED(TBD)
* MCOA BULK REGISTRATION NOT SUPPORTED (TBD)
* MCOA FLAG CONFLICTS (TBD)
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11. Acknowledgments
The authors would like to thank Masafumi Aramoto (Sharp Corporation),
Keigo Aso (Panasonic), Julien Charbon, Tero Kauppinen (Ericsson),
Benjamin Koh (Panasonic), Susumu Koshiba, Martti Kuparinen
(Ericsson), Romain Kuntz (Keio-U), Heikki Mahkonen (Ericsson), Hiroki
Matutani (Tokyo-U), Koshiro Mitsuya (Keio-U), Nicolas Montavont, Koji
Okada (Keio-U), Keisuke Uehara (Keio-U), Masafumi Watari (KDDI R&D)
in alphabetical order, the Jun Murai Lab. at KEIO University.
12. References
12.1. Normative References
[RFC-2460] Deering, S. and R. Hinden, "Internet Protocol Version 6
(IPv6)", IETF RFC 2460, December 1998.
[RFC-3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[RFC-3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
January 2005.
[ID-MIP6ANALYSIS] Montavont, N., Wakikawa, R., Ernst, T., Ng, C., and
K. Kuladinithi, "Analysis of Multihoming in Mobile IPv6",
draft-ietf-monami6-mipv6-analysis-02 (work in progress), February
2007.
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC-3753] Manner, J. and M. Kojo, "Mobility Related Terminology",
RFC 3753, June 2004.
[RFC-4885] Ernst, T. and H. Lach, "Network Mobility Support
Terminology", RFC 4885, July 2007.
[RFC-4886] Ernst, T., "Network Mobility Support Goals and
Requirements", RFC 4886, July 2007.
[RFC-4877] Devarapalli, V. and F. Dupont, "Mobile IPv6 Operation with
IKEv2 and the revised IPsec Architecture", RFC 4877, April 2007.
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12.2. Informative References
[ID-MOTIVATION] Ernst, T., Montavont, N., Wakikawa, R., Ng, C., and
K. Kuladinithi, "Motivations and Scenarios for Using Multiple
Interfaces and Global Addresses",
draft-ietf-monami6-multihoming-motivation-scenario-02 (work in
progress), July 2007
[RFC-4980] Ng, C., Paik, Ernst, and C. Bagnulo, "Analysis of
Multihoming in Network Mobility Support", RFC 4980, October 2007.
[ID-NONDP] Wakikawa, R, Aramoto, M., Thubert, P., "Elimination of
Proxy NDP from Home Agent Operations",
draft-wakikawa-mip6-no-ndp-02.txt (work in progress), November 2007.
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Appendix A. Example Configurations
In this section, we describe typical scenarios when a mobile node has
multiple network interfaces and acquires multiple Care-of Addresses
bound to a Home Address. The Home Address of the mobile node (MN in
figures) is a:b:c:d::EUI. MN has 3 different interfaces and possibly
acquires care-of addresses 1-3 (CoA1, CoA2, CoA3). The MN assigns
BID1, BID2 and BID3 to each care-of address.
+----+
| CN |
+--+-+
|
+---+------+ +----+
+------+ Internet |----------+ HA |
| +----+---+-+ +--+-+
CoA2| | | | Home Link
+--+--+ | | ------+------
| MN +========+ |
+--+--+ CoA1 |
CoA3| |
+---------------+
Binding Cache Database:
home agent's binding (Proxy neighbor advertisement is active)
binding [a:b:c:d::EUI care-of address1 BID1]
binding [a:b:c:d::EUI care-of address2 BID2]
binding [a:b:c:d::EUI care-of address3 BID3]
correspondent node's binding
binding [a:b:c:d::EUI care-of address1 BID1]
binding [a:b:c:d::EUI care-of address2 BID2]
binding [a:b:c:d::EUI care-of address3 BID3]
Figure 6: Multiple Interfaces Attached to a Foreign Link
Figure 6 depicts the scenario where all interfaces of the mobile node
are attached to foreign links. After binding registrations, the home
agent (HA) and the Correspondent Node (CN) have the binding entries
listed in their binding cache database. The mobile node can utilize
all the interfaces.
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+----+
| CN |
+--+-+
|
+---+------+ +----+
+------+ Internet |----------+ HA |
| +--------+-+ +--+-+
CoA2| | | Home Link
+--+--+ | --+---+------
| MN +========+ | |
+--+--+ | | |
CoA3| +---|-----------+
+---------------+
Binding Cache Database:
home agent's binding (Proxy neighbor advertisement is inactive)
none
correspondent node's binding
binding [a:b:c:d::EUI care-of address2 BID2]
binding [a:b:c:d::EUI care-of address3 BID3]
Figure 7: One of Interface Attached to Home Link and Returning Home
Figure 7 depicts the scenario where MN returns home with one of its
interfaces. After the successful de-registration of the binding to
HA, HA and CN have the binding entries listed in their binding cache
database of Figure 7. MN can communicate with the HA through only
the interface attached to the home link. On the other hand, the
mobile node can communicate with CN from the other interfaces
attached to foreign links (i.e. route optimization). Even when MN is
attached to the home link, it can still send Binding Updates for
other active care-of addresses (CoA2 and CoA3). If CN has bindings,
packets are routed to each Care-of Addresses directly. Any packet
arrived at HA are routed to the primary interface.
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+----+
| CN |
+--+-+
|
+---+------+ +----+
+------+ Internet |----------+ HA |
| +----+-----+ +--+-+
CoA2| | | Home Link
+--+--+ | --+---+------
| MN +========+ |
+--+--+ CoA1 |
| |
+---------------------------+
(Disable interface)
Binding Cache Database:
home agent's binding (Proxy neighbor advertisement is active)
binding [a:b:c:d::EUI care-of address1 BID1]
binding [a:b:c:d::EUI care-of address2 BID2]
correspondent node's binding
binding [a:b:c:d::EUI care-of address1 BID1]
binding [a:b:c:d::EUI care-of address2 BID2]
Figure 8: One of Interface Attached to Home Link and Not Returning
Home
Figure 8 depicts the scenario where MN disables the interface
attached to the home link and communicates with the interfaces
attached to foreign links. The HA and the CN have the binding
entries listed in their binding cache database. MN disable the
interface attached to the home link, because the HA still defends the
home address of the MN by proxy neighbor advertisements. All packets
routed to the home link are intercepted by the HA and tunneled to the
other interfaces attached to the foreign link according to the
binding entries.
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+----+
| CN |
+--+-+
|
+---+------+ +----+
+------+ Internet |----------+ HA |
| +----------+ +--+-+
CoA2| | Home Link
+--+--+ --+----+---+------
| MN +===================+ |
+--+--+ |
| |
+---------------------------+
Binding Cache Database:
home agent's binding (Proxy neighbor advertisement is inactive)
none
correspondent node's binding
binding [a:b:c:d::EUI care-of address2 BID2]
Figure 9: Several Interfaces Attached to Home Link and Returning Home
Figure 9 depicts the scenario where multiple interfaces of MN are
attached to the home link. The HA and CN have the binding entries
listed in Figure 9 in their binding cache database. The MN can not
use the interface attached to a foreign link unless a CN has a
binding for the interface. All packets which arrive at the HA are
routed to one of the MN's interfaces attached to the home link.
Figure 10 depicts the scenario where interfaces of MN are attached to
the foreign links. One of foreign link is managed by the home agent.
The HA and CN have the binding entries listed in Figure 10 in their
binding cache database. The home agent advertises a prefix which is
other than home prefix. The mobile node will generate a care-of
address from the prefix and registers it to the home agent. Even if
the mobile node attaches to a foreign link, the link is managed by
its home agent. It will tunnel the packets to the home agent, but
the home agent is one-hop neighbor. The cost of tunnel is
negligible. If the mobile node wants to utilize not only an
interface attached to home but also interfaces attached to foreign
link, it can use this foreign link of the home agent to return a one
hop foreign link on behalf of a home link. This is different from
the general returning home, but this enable the capability of using
interfaces attached to both home and foreign link without any
modifications to Mobile IPv6 and NEMO basic support.
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+----+
| CN |
+--+-+
|
+---+------+ +----+
+------+ Internet |----------+ HA |
| +----+-----+ ++-+-+
CoA2| | | | Home Link
+--+--+ | ----|-+------
| MN +========+ |
+--+--+ CoA1 ---+-+------
CoA3 | | Foreign Link
+---------------------------+
Binding Cache Database:
home agent's binding (Proxy neighbor advertisement is active)
binding [a:b:c:d::EUI care-of address1 BID1]
binding [a:b:c:d::EUI care-of address2 BID2]
binding [a:b:c:d::EUI care-of address3 BID3]
correspondent node's binding
binding [a:b:c:d::EUI care-of address1 BID1]
binding [a:b:c:d::EUI care-of address2 BID2]
binding [a:b:c:d::EUI care-of address3 BID3]
Figure 10: Emulating to Utilize Interfaces Attached to both Home and
Foreign Links
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Appendix B. Changes From Previous Versions
Changes from draft-ietf-monami6-multiplecoa-03.txt
o Change the handling of Status field. All the status value is
defined for BA
o Alternate CoA option is omitted, but using C flag is recommended.
o Adding examples of BU
o Many editorial updates
Authors' Addresses
Ryuji Wakikawa (Editor)
Faculty of Environment and Information Studies, Keio University
5322 Endo
Fujisawa, Kanagawa 252-8520
Japan
Phone: +81-466-49-1100
Fax: +81-466-49-1395
Email: ryuji@sfc.wide.ad.jp
URI: http://www.wakikawa.org/
Thierry Ernst
INRIA
INRIA Rocquencourt
Domaine de Voluceau B.P. 105
Le Chesnay, 78153
France
Phone: +33-1-39-63-59-30
Fax: +33-1-39-63-54-91
Email: thierry.ernst@inria.fr
URI: http://www.nautilus6.org/~thierry
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Kenichi Nagami
INTEC NetCore Inc.
1-3-3, Shin-suna
Koto-ku, Tokyo 135-0075
Japan
Phone: +81-3-5565-5069
Fax: +81-3-5565-5094
Email: nagami@inetcore.com
Vijay Devarapalli
Azaire Networks
3121 Jay Street
Santa Clara, CA 95054
USA
Email: vijay.devarapalli@azairenet.com
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Wakikawa (Editor), et al. Expires May 22, 2008 [Page 41]
