One document matched: draft-wakikawa-mobileip-multiplecoa-02.txt
Differences from draft-wakikawa-mobileip-multiplecoa-01.txt
MIP6 Working Group Ryuji Wakikawa
INTERNET DRAFT Keisuke Uehara
20 Sep 2003 Thierry Ernst
Keio University/WIDE project
Kenichi Nagami
INTEC Netcore
Multiple Care-of Addresses Registration
draft-wakikawa-mobileip-multiplecoa-02.txt
Status of This Memo
This document is a submission to the MIP6 Working Group of the
Internet Engineering Task Force (IETF). Comments should be submitted
to the mip6@ietf.org (mobile-ip@sunroof.eng.sun.com) mailing list.
Distribution of this memo is unlimited.
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at
any time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at:
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at:
http://www.ietf.org/shadow.html.
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 (i.e. interfaces) 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
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receiver to distinguish between the bindings corresponding to the
same home address. Those extensions are targeted to Network Mobility
(NEMO) as well as to Mobile IPv6.
Contents
Status of This Memo 1
Abstract 1
1. Introduction 4
2. Terminology 6
3. Protocol Overview 8
4. Mobile IPv6 Extensions 10
4.1. Binding Cache Structure and Management . . . . . . . . . 10
4.2. Binding Update Structure and Management . . . . . . . . . 11
4.3. Messages Format Changes . . . . . . . . . . . . . . . . . 11
4.3.1. Binding Unique Identifier sub-option . . . . . . 11
4.3.2. Binding Update . . . . . . . . . . . . . . . . . 12
4.3.3. Binding Acknowledgment . . . . . . . . . . . . . 13
5. Mobile Node Operation 13
5.1. Management of care-of addresses . . . . . . . . . . . . . 13
5.2. Sending Binding Update . . . . . . . . . . . . . . . . . 14
5.3. De-registration . . . . . . . . . . . . . . . . . . . . . 15
5.3.1. De-registration to home agent . . . . . . . . . . 15
5.3.2. De-registration to correspondent nodes . . . . . 16
5.4. Using Alternate Care-of Address . . . . . . . . . . . . . 16
5.5. Receiving Binding Acknowledgment . . . . . . . . . . . . 17
5.6. Receiving Binding Refresh Request . . . . . . . . . . . . 17
5.7. Receiving Binding Error . . . . . . . . . . . . . . . . . 18
6. Home Agent and Correspondent Node Operation 18
6.1. Searching Binding Cache with Binding Unique Identification
Number . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.2. Receiving Binding Update . . . . . . . . . . . . . . . . 19
6.3. Sending Binding Acknowledgment . . . . . . . . . . . . . 20
6.4. Sending Binding Refresh Request . . . . . . . . . . . . . 20
6.5. Sending Binding Error . . . . . . . . . . . . . . . . . . 21
7. Network Mobility Applicability 21
Appendices 22
A. Example Configurations 22
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Example Configurations 22
Acknowledgments 25
References 25
Authors' Addresses 27
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1. Introduction
Permanent Internet connectivity is required by some applications
while a mobile node moves across several access networks (i.e.
ISPs, hotspots, etc). For example, it is desirable to maintain
the Internet connectivity while an automobile running on a freeway
receives voice or video streaming data from different access
networks.
Unfortunately, there is no network interfaces assuring global scale
connectivity. Therefore, a mobile node should use various type of
network interfaces to obtain wide area network connectivity [7]. In
addition, users should select the most appropriate network interface
depending on a visiting network environment, since wireless networks
is mutable and less reliable than wired networks and each network
interface has different cost, performance, bandwidth, access range,
and reliability. Users should also select the most appropriate
interface per communication. For example, TCP traffic should be
transmitted over the wireless interface, whereas UDP traffic should
be transmitted over wired the interface to avoid disturbing TCP
connections.
Associating multiple care-of addresses to a single home address
would allow durable Internet connectivity [8] [1] [9]. For example,
when a mobile node loses its Internet connectivity at one of its
interface, the second interface can be used as a backup interface
therefrom maintaining Internet connectivity. In addition, the
mobile node can send each communication flow to a distinct network
interface. This provides efficient network bandwidth consumption. A
user can select the most suitable network interface per application.
Correspondent nodes can also re-select a binding of the mobile node
to recover communication when one of mobile node's bindings becomes
invalid. To enable a binding selection policy, a mobile node can
use the particular binding for specified communication type. If a
mobile node does not have enough bandwidth for communications, it
can utilize both bindings to gain network bandwidth. Furthermore,
a mobile node may bicast packets of a particular flow through all
available network interfaces.
IPv6 [2] conceptually allows a node to have several addresses on a
given interface. Consequently, Mobile IPv6 [6] has mechanisms to
manage multiple ``home addresses'' based on home agent's managed
prefixes such as mobile prefix solicitation and mobile prefix
advertisement. However, assigning a single home address to a given
network interface is more advantageous than assigning multiple
home addresses because applications do not need to be aware of the
multiplicity of home addresses. Of course, applications should be
aware of the active home address to be used for communicating. At
the TCP layer, TCP holds the home address as a source address of the
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communication for connection managements. Thus, applications must
reboot to reset the connection information when the the mobile node
changes its active network interface (i.e. change the home address).
However, according to section 11.5.3 of the Mobile IPv6
specification [6], a mobile node is not allowed to register multiple
care-of addresses bound to a single home address. If a mobile node
sends Binding Updates for each care-of address, correspondent nodes
would always overwrite the careof address recorded in the binding
cache with the one contained in the latest received binding update.
It is thus impossible for a mobile node to register multiple care-of
addresses in the correspondent node's binding cache.
In this document, we thus propose a new identification number called
Binding Unique Identification number (BID) for each binding cache
entry to accommodate multiple bindings registration. We also propose
extension of binding cache management to store the BID and a new
sub-option for binding update to carry the BID. The BID is assigned
to either the interfaces or care-of addresses bound to a single
home address of a mobile node. The mobile node notifies the BID
to both its home agent and correspondent nodes by means of a BU.
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.
A user of a mobile node may be able to bind some policies to a BID.
The policy is used to divide flows to multiple network interfaces
by flow type, port number, or destination address, etc. How to
distribute or configure policies is not within the scope of this
draft.
The extensions specified in this draft can also be applied to Network
Mobility (NEMO) basic support [3]. Our extensions can indeed be
applied to either a mobile host (Mobile IPv6) or a mobile router
(MR, see [5]). Network Mobility Support must allow multihoming so
as to provide robustness, better performance, etc described in [4].
Multihoming include in particular the ability to switch from one
egress interface to another.
Thierry: what you wrote in section above is almost exactly the same
content as section 7 so section 7 is useless
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2. Terminology
Most terms used in this draft are defined in [6].
Binding Unique Identification number (BID)
The identification number is used to distinguish multiple
bindings registered by mobile node. Assignment of distinct BID
allows a mobile node to register multiple binding cache entries
for a given home address. BID is generated not to duplicate
each other. The zero value and negative value MUST NOT be used
as a value. After generating BID, BID is stored in the Binding
Update List and is sent by a mobile node as a sub-option of a
Binding Update.
BID is conceptually used to distinguish multiple bindings for
single home address. Therefore, a mobile node can assign
BID to either care-of address or interface depending on
implementations 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
Primary care-of address
In [6], the primary care-of address is defined as ``the care-of
address registered with the mobile node's home agent is called
its ``primary'' care-of address''. In this present draft, the
definition is refined as follows: The care-of address which is
primary associated with a home address.
A mobile node MUST have a primary care-of address all the time.
Once the primary care-of address becomes invalid, the mobile
node MUST reselect a primary careof-address from the multiple
care-of addresses that a mobile node may have at any given
time.
Primary Interface
The interface on which the primary care-of address is assigned.
Once the primary interface becomes invalid due to movements,
the mobile node MUST re-select primary interface from set of
interfaces installed in mobile node.
Binding Unique Identifier sub-option
The Binding Unique Identifier sub-option is used to notify the
BID.
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Multiple Care-of Addresses Flag (M flag)
This flag indicates that a Binding Unique Identifier sub-option
is included in the Binding Update mobility option field.
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3. Protocol Overview
We propose a new identification number to distinguish multiple
bindings pertaining to the same home address. The following
paragraphs described the procedures for the mobile node to register
multiple bindings.
Once a mobile node gets several IPv6 global addresses on distinct
interfaces, it MUST select a primary care-of address from the active
addresses as specified in Section 11.5.3 [6]. After the selection,
the interface which has the primary care-of address becomes the
primary interface for the mobile node.
After selecting the primary care-of address, the mobile node MUST
register it with its home agent (home registration). If the mobile
node wants to register multiple bindings to its home agent, it MUST
generate a BID for the primary care-of address and record it into
the binding update list entry. The mobile node then registers its
primary care-of address by sending a Binding Update containing a
Binding Unique Identifier sub-option. The M flag MUST be set in
the Flag field of the Binding Update and the BID MUST be put in the
Binding Unique Identifier sub-option. After receiving the Binding
Update, the home agent verifies the request and records the binding
in its binding cache. If the newly defined sub-option is present in
the Binding Update, the home agent MUST copy the BID from the BU to
the corresponding field in the binding entry.
After this home registration, the mobile node can register the rest
of care-of addresses to its Home Agent. Even if there is already
an entry for the mobile node, the home agent MUST registers a new
binding entry with the BID stored in the Binding Unique Identifier
sub-option. The registration process is the same as for the
registration of the primary care-of address. The mobile node MUST
register multiple care-of addresses respectively.
There is no optimization such as registering multiple care-of
addresses by using a single Binding Update, because the current
Mobile IPv6 specification does not allow to send multiple bindings by
single Binding Update.
If the mobile node would register its binding to a correspondent
node, it MUST starts return routability operations before sending a
Binding Update. The mobile node MUST sends CoTI for each care-of
addresses and MUST receive CoT for each care-of addresses. The
mobile node also generates BID for each care-of addresses to register
them as individual bindings . The registration step is same as
the home registration except for calculating authenticator with
Binding Unique Identifier sub-option as well as the other sub-options
specified in [6].
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BID is also used as a search key of binding cache database as well as
a home address. When the home agent checks binding cache database
for the mobile node, it searches a correspondent binding entry with
the home address and BID of the desired binding. The desired binding
can be selected with policy and filter information. The capability
of searching the desired binding enables load-sharing and QoS with
flow separation. But this selection and flow separation are out of
scope in this draft. If there is no desired binding, it search the
binding cache database with the home address as well as Mobile IPv6.
The first matched binding entry may be found, but which binding entry
is returned for the normal search depends on implementations.
If a node has multiple bindings and its packets meant for the
mobile node are not delivered correctly, the node can change the
binding entry for the mobile node so as to recover the connection
immediately. The node can detect a binding invalidation by packets
loss or ICMP error messages such as ICMP_UNREACHABLE. This provides
redundancy for Mobile IPv6.
When one of care-of addresses is changed, the mobile node sends a
Binding Update with the new care-of address and the correspondent
BID. The receiver of the Binding Update updates the particular
binding entry that its BID is same as the BID in the received Binding
Unique Identifier sub-option. The mobile node can manage each
binding independently owing to BID.
Once the mobile node decides to register only one binding, it just
sends a Binding Update without M flag and a Binding Unique Identifier
sub-option (i.e. normal Binding Update). The receiver of the
Binding Update registers only single binding for the mobile node.
If the receiver has multiple bindings, one bindings is registered
without BID and the rest of bindings are deleted.
When the mobile node returns home, there are two situations. It is
because the home agent defends the mobile node's home address by
using proxy neighbor advertisement. It is impossible to utilize
all the interfaces when one interface is attached to home and the
others are attached to foreign link. If proxy Neighbor Advertisement
for the home address is stopped, packets are always routed to the
interface attached to the home link. If proxy is not stopped,
packets are never routed to the interface attached to the home link.
The first situation is when the primary interface is attached to the
home link. In this case, the mobile node MUST de-register all the
bindings by sending a Binding Update which lifetime set to zero. The
mobile node MAY NOT put any Binding Unique Identifier sub-options
in this packet. Then, the receiver deletes all the bindings from
its binding cache database. On the other hand, if the mobile node
wants to delete binding entries respectively, it sends multiple
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deregistration Binding Updates for all BID (that is all registered
care-of addresses). In those Binding Updates, the mobile node MUST
store a Binding Unique Identifier sub-option. Only when the care-of
address is the primary one and the destination is the home agent,
the mobile node also set 'P' flag in the Binding Unique Identifier
sub-option to indicates stop proxying for the mobile node to the home
agent. P flag is valid only when the destination of a Binding Update
is a home agent.
The second situation is when non primary interface is attached to
the home link. The primary care-of address takes precedence over
the rest of addresses. The mobile node stops using 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
deregistration Binding Update with the Binding Unique Identifier
sub-option. The mobile node stores the BID of the binding and MUST
NOT set P flag in the sub-option regardless of home agent or not.
Therefore, the receiver of the deregistration Binding Update deletes
only the binding entry from the binding cache database. The home
agent does not stop proxying neighbor advertisement.
4. Mobile IPv6 Extensions
Mobile IPv6 should be able to manage multiple bindings bound to a
same home address. The changes are described in this section.
4.1. Binding Cache Structure and Management
This document requires to have additional items for the binding cache
structure, which are
- BID
The BID of the binding cache entry. The BID is notified by BU
sub-option by mobile node. If mobile node does not use BID, then
the value of BID MUST be always zero.
If a node gets a BU with a Binding Unique Identifier defined
at 4.3.1, it searches Binding Cache entries with the set of the home
address and the BID. If both does match with the registered binding,
the node MUST update the care-of address and the BID into the matched
binding. Otherwise, the node MUST register a new binding for the
care-of address and the BID, even if there are already the other
binding for the mobile node's home address.
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4.2. Binding Update Structure and Management
This document requires to have additional items for binding update
structure, which are
- BID
The BID MUST be generated whenever mobile node decides to
register multiple bindings for its home address.
- Primary flag
If the care-of address is primary one, this flag MUST be set.
If a mobile node has multiple care-of addresses at a time, it SHOULD
assign a BID to each care-of address. BID should be recorded in
a binding update list. A mobile node MAY update the value of BID
periodically not to be discovered by a third person.
The information of the primary care of address is kept at the Primary
Flag field and is known only by a mobile node. A mobile node does
not need to send the preference information (primary or not) to
correspondent nodes and a home agent except for the case of mobile
node's returning home. When a mobile node returns home, it MUST
tell whether primary or not because the operation of proxy neighbor
advertisement is different between primary and non primary care-of
address.
4.3. Messages Format Changes
4.3.1. Binding Unique Identifier sub-option
The Binding Unique Identifier sub-option is included in Binding
Update, Binding Acknowledgment, Binding Refresh Request, Binding
Error if needed.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD | Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Binding Unique ID (BID) | P| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
Type
Type value for Binding Unique Identifier will be assigned
later.
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Length
The value MUST be always 2.
Binding Unique ID (BID)
The BID which is assigned to the binding sent by the
Binding Update with this sub-option. BID is 16-bit
unsigned integer. A value of zero is reserved.
Flag
Stop Proxy Neighbor Advertisement (P) Flag
When this flag is set, the home agent MUST stop
proxy neighbor advertisement for a mobile node.
This flag is checked only when a Binding Update
is for de-registration and the destination of a
Binding Update is mobile node's home agent (i.e.
home de-registration). Otherwise, this flag MUST be
ignored.
Reserved
15 bit Reserved field. Reserved field must be set with all
0.
4.3.2. Binding Update
If a mobile node wants to register several care-of addresses which
would be bound to a home address, mobile node MUST set 'M' flag and
include a Binding Unique Identifier sub-option.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|H|L|K|R|M| Reserved | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Mobile Router Flag (R)
This flag is proposed by the NEMO working group [3].
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Multiple Care-of Addresses Flag (M)
This flag is used for multiple care-of addresses
registration.
Reserved
Reserved field is reduced to 11 bits.
4.3.3. Binding Acknowledgment
The message format of Binding Acknowledgment is not changed, but
operations listed below are added in this draft.
A receiver who gets a Binding Update with 'M' flag MUST reply a
Binding Acknowledgment if it has 'A' flag or it is home registration.
The receiver MUST also reply a Binding Acknowledgment with
correspondent error number if it finds an error during processing the
Binding Update and its sub-option described in section 4.3.2.
If a Binding Update has 'M' flag and a Binding Unique Identifier
sub-option is present, a receiver node MUST reply a Binding
Acknowledgment containing the same Binding Unique Identifier
sub-option. The mobile node can process the Binding Acknowledgment
for the particular care-of address identified by BID set in the
Binding Unique Identifier sub-option.
This document defines a new number for 'M' flag handling.
140 Conflicting a normal binding without BID and a binding with BID
in binding cache. The number is TBD.
5. Mobile Node Operation
5.1. Management of care-of addresses
There are two cases when a mobile node has several care-of addresses.
- A mobile node uses several physical network interfaces to acquire
a care-of address.
- A mobile node uses single physical network interface, but it
acquires several addresses from the attached network. Since IPv6
allows to have several addresses on single network interface,
it is possible to get several global address with a network
interface at the attached network.
Although the difference between above two cases is a number of
physical network interfaces, it does not matter in this draft.
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Identification number is used to distinguish multiple bindings so
that mobile node assigns an identification number for each care-of
addresses. The decision how to assign an identification number is up
to implementations.
A mobile node assigns BID to each care-of address when it wants to
simultaneously register with its home address. The value should be
generated from 1 to 65535. Zero and negative value can not be take
as BID. If a mobile node has only one care-of address, assignment of
BID is not needed until it has multiple care-of addresses to register
as a binding.
When a mobile node moves to a new foreign link by one of its
interfaces, the mobile node just updates the binding for the new
care-of address. The mobile node sends a Binding Update with a
Binding Unique Identifier sub-option storing BID of the binding.
When a mobile node moves to a home link by its primary interface, it
MUST start de-registration processing to its home agent as well as
Mobile IPv6. The home agent deletes all bindings for the mobile node
and stops intercepting packets meant for the mobile node. Although
the mobile node MUST deletes the binding from correspondent nodes
as well, the node still can keep a binding of non-primary interface
active at correspondent nodes. In such case, the mobile node still
receives packets at a non primary interface attached to a foreign
link by using route optimization. The mobile node also receives
packets at the primary interface attached to the home link when
correspondent nodes does not use route optimization.
On the other hand, when a mobile node returns to the home link by a
non-primary interface, it MUST delete only the particular binding
from its home agent and correspondent nodes. The home agent does not
delete all bindings and does not stop proxy neighbor advertisement
for the mobile node. Therefore, the mobile node no longer receives
packets at the non primary interface attached to the home link.
All packets are routed to other interfaces attached to a foreign
link. If the mobile node eager to receive packets at the non primary
interface at the home link, it MUST re-select the interface as
primary.
5.2. Sending Binding Update
When a mobile node sends a Binding Update to its home agent (i.e.
home registration) and the BU is aimed to de-register the binding,
the mobile node MUST check whether the care-of address contained in
the BU is primary or not. If the care-of address is primary one, it
MUST set P flag in the Binding Unique Identifier sub-option. More
description about P flag can be found in Section 5.3.
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When a mobile node sends a BU, 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 general Mobile
IPv6 [6].
On the other hand, if a mobile node needs to register multiple
care-of addresses, the mobile node MUST use BID for all care-of
addresses all the time. The mobile node sets M flag in a Binding
Update and puts a Binding Unique Identifier sub-option into the
Option field of the Binding Update. BID is copied from a binding
update list to the Binding Unique Identifier sub-option. If the
mobile node registers bindings to a correspondent node, it MUST
sends multiple CoTI for multiple care-of addresses. After getting
CoTs, it sends Binding Updates with M flag and a Binding Unique
Identifier sub-option for all care-of addresses one by one. In any
case, the mobile node MUST set A flag in Binding Updates and MUST
wait a Binding Acknowledgment to confirm successfully registration as
described in section 5.5.
5.3. De-registration
When a mobile node decides to delete all bindings for its home
address, it sends a normal de-registration Binding Update (i.e.
exclusion of a Binding Unique Identifier sub-option). See
Section 6.2 for details.
If a mobile node wants to delete particular binding from its home
agent and correspondent nodes, it follows below operations.
5.3.1. De-registration to home agent
When a mobile node is attached to its home link by one of its
network interfaces, it MUST de-register an appropriate binding. If a
binding of a primary care-of address becomes invalid in terms of the
mobile node's returning home, it MUST set P flag in a Binding Unique
Identifier sub-option. Otherwise, P flag MUST NOT be set. If P flag
is set, a home agent stop proxy neighbor advertisement for the mobile
node.
When the primary interface is attached to a home link, all
packets are routed to the primary interface because proxy neighbor
advertisement is disabled at the home agent.
If a non primary interface is attached to the home link, the home
agent keeps intercepting packets meant for the mobile node by proxy
neighbor advertisement. Therefore, any packets can not be routed
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to the non-primary interfaces. In NEMO case, a mobile router MUST
NOT use P flag for the configuration of a virtual home link in terms
of extended home address, because its home agent does not use proxy
neighbor advertisement to intercept packets destined to the mobile
router.
5.3.2. De-registration to correspondent nodes
When a mobile node needs to de-register one of care-of addresses, it
sends a Binding Update with a Binding Unique Identifier sub-option.
The Binding Update MUST have Lifetime field set to zero. The Binding
Unique Identifier sub-option MUST have BID of the target binding.
Then, the mobile node can de-register one binding from multiple
registering bindings. If a receiver receives a Binding Update
without BID, a receiver can not determine which binding should be
deleted for this de-registration. In such case, the receiver deletes
all of bindings for the mobile node.
5.4. Using Alternate Care-of Address
A mobile node can use an alternate care-of address in following
situations.
- One of care-of address becomes invalid due to the link of an
interface is no longer available and MUST be deleted by sending
Binding Update. In such case, a mobile node can not sends a
Binding Update from the care-of address because of interface's
link is lost. A mobile node needs to de-register remote binding
of the care-of address from one of active care-of addresses.
- A mobile node has multiple interfaces, but it wants to sends
Binding Updates for all care-of addresses from a specific
interface which has wider bandwidth depending on interface's
characteristics. A mobile node does not want to send a lot of
control messages through an interface which bandwidth is narrow.
In these cases, a mobile node sends a Binding Update with both
Alternate Care-of Address sub-option and Binding Unique Identifier
sub-option. Processing of Alternate Care-of Address sub-option is
described in Mobile IPv6 specification. If there is an Alternate
Care-of Address sub-option, the BID in a Binding Unique Identifier
sub-option is assigned for the care-of address in the Alternate
Care-of Address sub-option.
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5.5. Receiving Binding Acknowledgment
The verification of a Binding Acknowledgment is same as Mobile
IPv6 (section 11.7.3 of [6]). The operation of sending a Binding
Acknowledgment is described in 6.3.
If a mobile node sends a Binding Update with a Binding Unique
Identifier sub-option, a Binding Acknowledgment MUST have a
Binding Unique Identifier sub-option in Mobility options field. If
there is no such sub-option, the originator node of this Binding
Acknowledgment might not recognize the Binding Unique Identifier
sub-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, the mobile node
checks Status field of the Binding Acknowledgment. If the status
code indicates successful registration (1), the originator registers
a binding information and BID for the mobile node successfully.
If the status code is not zero regardless of Binding Unique
Identifier sub-option availability in BA, the mobile node proceeds an
appropriate operations according to the status code.
If the status code is 140, the mobile node has already registered a
binding without BID before sending a Binding Update with a Binding
Unique Identifier sub-option. In such case, a mobile node SHOULD
stop sending Binding Updates without BID.
5.6. Receiving Binding Refresh Request
The verification of a Binding Refresh Request is same as Mobile IPv6
(section 11.7.4 of [6]). The operation of sending a Binding Refresh
Request is described in the 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 binding indicated by BID. The mobile node SHOULD update only the
respective binding. The mobile node MUST put a Binding Unique
Identifier sub-option into a Binding Update.
If no Binding Unique Identifier sub-option presents in a Binding
Refresh Request, a mobile node sends a Binding Update according to
its binding update list for the requesting node. On the other hand,
if the mobile node does not have any binding update lists for the
requesting node, the mobile node needs to register either single
binding or multiple bindings depending on its binding management
policy.
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5.7. Receiving Binding Error
When a mobile node receives a Binding Error with a Binding Unique
Identifier sub-option, the message is for a binding indicated by BID
in the Binding Unique Identifier sub-option. Further operations
except for the text below are same as [6]. The operation of sending
BE is described in the section 6.5.
When a mobile node receives a Binding Error with Status field set
to 2 (unrecognized MH Type value) , it MAY stop trying to register
multiple care-of addresses and registers only primary care-of address
as well as Mobile IPv6.
6. Home Agent and Correspondent Node Operation
6.1. Searching Binding Cache with Binding Unique Identification
Number
If a correspondent node has multiple bindings for a mobile node
in its binding cache database, it can use any of the bindings for
communications to the mobile node. How to select the most suitable
binding from the binding cache database is out of scope in this
document. Once a correspondent node decides one binding and gets
BID for the desired binding mostly by using policy and filter
information, it searches the desired binding with BID.
Whenever a correspondent node searches a binding cache for a home
address, it SHOULD uses both the home address and BID as a key of
search if it knows BID of the desired binding. Below is an example
of multiple bindings for a home address in binding cache database.
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]
A correspondent node basically learns BID when it receives an 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 Binding Update. If a correspondent node does
not know BID, the correspondent node searches a binding with only a
home address as well as base Mobile IPv6. In such case, the first
matched binding MAY be found. But which binding entry is returned
for the normal search depends on implementations. If a correspondent
node does not desire to use multiple bindings for a mobile node, the
correspondent node can ignore knowing BID.
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6.2. Receiving Binding Update
If a Binding Update does not contain a Binding Unique Identifier
sub-option and it does not have 'M' flag set, the processing of the
Binding Update is same as [6]. But if the receiver already has
multiple bindings for the home address, it MUST overwrite existing
bindings for the mobile node with the received binding. After
processing the Binding Update which does not contain a Binding Unique
Identifier sub-option, 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 for the mobile node.
On the other hand, if a Binding Update contains a Binding Unique
Identifier sub-option or 'M' flag set, a receiver node MUST operate
additional validations as follows.
- A receiver node MUST validate the Binding Update according to the
section 9.5.1 of [6].
- If the Binding Update has 'M' flag at Flag field, a Binding
Unique Identifier sub-option MUST be present in Mobility options
field of the Binding Update.
- If there is no Binding Unique Identifier sub-option with M flag
set, the receiver node MUST silently drop the Binding Update.
- If the Binding Unique Identifier sub-option is present, the
receiver node MUST process the Binding Update.
- If the Lifetime field is not zero, the receiver node registers a
binding with BID as a mobile node's binding.
* If the receiver does not have any binding for the mobile
node, it registers a binding with BID.
* If the receiver has a normal binding without BID for the
mobile node, it de-registers the normal binding and registers
a new binding with BID according to the Binding Update. In
this case, the receiver MUST send Binding Acknowledgment with
status code set to 140.
* If the receiver node has already registered the binding which
BID is matched with requesting BID , then it MUST update
the binding up-to-date with the Binding Update. Meanwhile,
if the receiver does not have a binding entry which BID is
matched with the requesting BID, it registers a new binding
with the BID.
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- If Lifetime field is zero, the receiver node deletes the
registering 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 ignores the Binding Update.
Note if the mobile node sends multiple Binding Updates with a
different BID but for same care-of address (i.e. same home address,
same care-of address, and different BID) , the receiver SHOULD
register both bindings into its binding cache.
6.3. Sending Binding Acknowledgment
If a Binding Update does not contain a Binding Unique Identifier
sub-option, a node, either a correspondent node or a home agent, MUST
reply Binding Acknowledgment according to the section 9.5.4 of [6].
Otherwise, the node MUST follow the additional procedure below.
Whenever a Binding Unique Identifier present, the node MUST reply a
Binding Acknowledgment regardless of 'A' flag in Binding Update.
If the node successfully registers a binding with BID stored
in a Binding Unique Identifier sub-option, it returns a Binding
Acknowledgment with Status field set to '0' (Successful registration)
and a Binding Unique Identifier sub-option copied from the received
Binding Update. If the node deletes the existing binding which
does not have BID and registers a new binding with BID, it MUST
return a Binding Acknowledgment with Status field set to '140'. On
the other hand, if the node encounters an error during processing
a Binding Update, it must returns a Binding Acknowledgment with
appropriate error number described in [6]. The node SHOULD put a
Binding Unique Identifier sub-option if BID is available for the
Binding Acknowledgment.
6.4. Sending Binding Refresh Request
When a correspondent node notices that a registered binding will
be expired soon, it SHOULD send a Binding Refresh Request. If the
registered binding has BID, the correspondent node SHOULD contain
a Binding Unique Identifier sub-option in the Binding Refresh
Request. Then, the correspondent node can receive a Binding Update
with a Binding Unique Identifier sub-option and can update only the
particular binding. If the registered binding does not have BID,
then the correspondent node sends a Binding Refresh Request without
the sub-option.
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6.5. Sending Binding Error
When a correspondent node sends a Binding Error with Status field
set to 1 (Unrecognized MH Type value), it MAY put a Binding Unique
Identifier sub-option into Mobility Options field if BID is available
in a received binding message.
When a correspondent node receives data packets with a home address
destination option, it verifies an IPv6 source address field. If the
source address is not registered in the correspondent node's binding
cache, the correspondent node MUST return Binding Error to the
sender with the status set to zero (Unknown binding for Home Address
destination option). The correspondent node can not put a Binding
Unique Identifier sub-option, because there is no binding cache entry
for the source address.
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 [4]).
Since the binding management mechanisms are the same for a mobile
host operating Mobile IPv6 and for a mobile router operating NEMO
Basic Support [3], our extensions can also be used to deal with
multiple care-of addresses registration sent from a multihomed mobile
router.
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A. Example Configurations
In this section, we describes typical scenarios when a mobile
node has multiple network interfaces and acquires multiple care-of
addresses bound to a home address.
A home address of a mobile node (MN in figures) is a:b:c:d::EUI
address. The mobile node has 3 different interfaces and possibly
acquires care-of addresses 1-3 (CoA1, CoA2, CoA3). The mobile node
assigns BID1, BID2 and BID3 to each care-of addresses.
Figure 1 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) has listed binding entries
of Figure 1 in their binding cache database. The mobile node can
utilize all the interfaces.
+----+
| 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 1: Multiple Interfaces are attached to Foreign Link
Figure 2 depicts the scenario where the primary interface of the
mobile node is attached to the home link.
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After bindings registration, the home agent and the correspondent
node has listed binding entries of Figure 2 in their binding cache
database. The mobile node can communicate with the home agent
through only the primary interface attached to the home link. On the
other hand, the mobile node can communicate with the correspondent
node by using route optimization. Even when the mobile node is
attached to the home link, it can still send Binding Updates for
other active care-of addresses (CoA2 and CoA3). If the correspondent
node has bindings, packets are routed to each care-of addresses
directly. Any packets arrived at the home agent are routed to the
primary interface.
+----+
| 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 2: Primary Interface is attached to Home Link
Figure 3 depicts the scenario where a non primary interface of a
mobile node is attached to the home link.
The home agent and the correspondent node has listed binding entries
of Figure 3 in their binding cache database. The mobile node can
not utilize the non primary interface attached to the home link,
because the home agent still defends the home address of the mobile
node by proxy neighbor advertisements. All packets routed to the
home link are intercepted by the home agent 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 +========+ |
+--+--+ CoA1 |
| |
+---------------------------+
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 3: One of Non Primary Interfaces is attached to Home Link
Figure 4 depicts the scenario where primary and a non primary
interface of a mobile node are attached to the home link. The
home agent and the correspondent node has listed binding entries
of Figure 4 in their binding cache database. The mobile node can
not use the non primary interface attached to a foreign link unless
a correspondent node has a binding for the non primary interface.
All packets which arrive at the home agent are routed to one of
interfaces attached to the mobile node. The home agent decides an
interface anyway, for example, by using policy and filters.
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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 4: Primary and Non Primary Interfaces are
attached to Home Link
Acknowledgments
The authors would like to thank Julien Charbon, Susumu Koshiba,
Hiroki Matutani, Koshiro Mitsuya, Nicolas Montavont, Koji Okada,
Masafumi Watari (in alphabetical order), the nacm group at KEIO
University, and WIDE project for their contributions.
References
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[3] V. Devarapalli, R. Wakikawa, A. Petrescu, and P. Thubert. Nemo
Basic Support Protocol (work in progress). Internet Draft
(draft-ietf-nemo-basic-support-00), Internet Engineering Task
Force, June 2003.
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[4] T. Ernst. Nemo Mobility Support Goals and Requirements (work in
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[5] T. Ernst and H. Lach. Nemo Mobility Support Terminology (work
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[7] M. Stemm and R. H. Katz. Vertical handoffs in wireless overlay
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Authors' Addresses
Ryuji Wakikawa Thierry Ernst
Keio University and WIDE Keio University and WIDE
5322 Endo Fujisawa Kanagawa 5322 Endo Fujisawa Kanagawa
252 JAPAN 252 JAPAN
Phone: +81-466-49-1394 Phone: +81-466-49-1394
EMail: ryuji@sfc.wide.ad.jp EMail: ernst@sfc.wide.ad.jp
Fax: +81-466-49-1395 Fax: +81-466-49-1395
Keisuke Uehara Kenichi Nagami
Keio University and WIDE INTEC NetCore
5322 Endo Fujisawa Kanagawa 1-3-3 Shinsuna Koto-ku Tokyo
252 JAPAN 135-0075 JAPAN
Phone: +81-466-49-1394 Phone: +81-3-5665-5069
EMail: kei@wide.ad.jp EMail: nagami@inetcore.com
Fax: +81-466-49-1395 FAX : +81-3-5665-5094
R. Wakikawa et.al. Expires 20 Mar 2003 [Page 27]
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