NETLMM Working Group R. Wakikawa (Editor)
Internet-Draft Keio University
Intended status: Standards Track S. Gundavelli
Expires: November 23, 2008 Cisco
May 22, 2008
IPv4 Support for Proxy Mobile IPv6
draft-ietf-netlmm-pmip6-ipv4-support-03.txt
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Copyright (C) The IETF Trust (2008).
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Abstract
This document specifies extensions to Proxy Mobile IPv6 protocol for
supporting IPv4 protocol. The scope of this IPv4 support includes
the support for the mobile node's IPv4 home address mobility and for
allowing the mobility entities in the Proxy Mobile IPv6 domain to
exchange signaling messages over an IPv4 transport.
Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Stated Assumptions . . . . . . . . . . . . . . . . . . . . 5
2. Conventions & Terminology . . . . . . . . . . . . . . . . . . 7
2.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 7
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
3. IPv4 Home Address Mobility Support . . . . . . . . . . . . . . 8
3.1. IPv4 Home Address Assignment . . . . . . . . . . . . . . . 8
3.2. Mobile Access Gateway Considerations . . . . . . . . . . . 11
3.2.1. Extensions to Binding Update List Entry . . . . . . . 11
3.2.2. Signaling Considerations . . . . . . . . . . . . . . . 11
3.3. Local Mobility Anchor Considerations . . . . . . . . . . . 15
3.3.1. Extensions to Binding Cache Entry . . . . . . . . . . 15
3.3.2. Signaling Considerations . . . . . . . . . . . . . . . 16
3.3.3. Routing Considerations . . . . . . . . . . . . . . . . 18
3.4. Mobility Options . . . . . . . . . . . . . . . . . . . . . 19
3.4.1. IPv4 Default Router Address Option . . . . . . . . . . 19
4. IPv4 Transport Support . . . . . . . . . . . . . . . . . . . . 20
4.1. NAT Support . . . . . . . . . . . . . . . . . . . . . . . 21
4.2. Mobile Access Gateway Considerations . . . . . . . . . . . 22
4.2.1. Extensions to Binding Update List Entry . . . . . . . 22
4.2.2. Signaling Considerations . . . . . . . . . . . . . . . 22
4.3. Local Mobility Anchor Considerations . . . . . . . . . . . 25
4.3.1. Extensions to Binding Cache Entry . . . . . . . . . . 25
4.3.2. Signaling Considerations . . . . . . . . . . . . . . . 25
4.4. Tunnel Management . . . . . . . . . . . . . . . . . . . . 28
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
6. Security Considerations . . . . . . . . . . . . . . . . . . . 30
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 31
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 31
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9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.1. Normative References . . . . . . . . . . . . . . . . . . . 31
9.2. Informative References . . . . . . . . . . . . . . . . . . 32
Appendix A. DHCP usages for IPv4 home address assignment . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 34
Intellectual Property and Copyright Statements . . . . . . . . . . 35
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1. Overview
The transition from IPv4 to IPv6 is a long process and during this
period of transition, both the protocols will be enabled over the
same network infrastructure. Thus, it is reasonable to assume that a
mobile node in a Proxy Mobile IPv6 domain may operate in an IPv4-only
IPv6-only or in dual-stack mode and additionally the network between
the mobile access gateway and a local mobility anchor may be an IPv4
or an IPv6 network. It is also reasonable to expect the same
mobility infrastructure in a Proxy Mobile IPv6 domain to provide
mobility to the mobile nodes operating in IPv4, IPv6 or in dual mode
and when the network between the local mobility anchor and the mobile
access gateway is an IPv4 or an IPv6 network. The motivation and
scope of IPv4 support in Mobile IPv6 is summarized in [RFC-4977] and
all those requirements apply to Proxy Mobile IPv6 protocol as well.
The Proxy Mobile IPv6 protocol[ID-PMIP6] specifies a mechanism for
providing IPv6 home address mobility support to a mobile node in a
Proxy Mobile IPv6 domain and when there is an IPv6 transport network
separating the entities involved in the mobility management. The
extensions defined in this document are for extending IPv4 support to
the Proxy Mobile IPv6 protocol [ID-PMIP6].
The scope of IPv4 support in Proxy Mobile IPv6 includes the support
for the following two features:
o IPv4 Home Address Mobility Support: A mobile node that has an IPv4
stack enabled will be able to obtain an IPv4 address and be able
to use that address from any of the access networks in that Proxy
Mobile IPv6 domain. The mobile node is not required to be
allocated or assigned an IPv6 address for enabling IPv4 home
address support.
o IPv4 Transport Network Support: The mobility entities in the Proxy
Mobile IPv6 domain will be able to exchange Proxy Mobile IPv6
signaling messages over an IPv4 transport and further the local
mobility anchor or the mobile access gateway may be using IPv4
private addresses and with NAT [RFC-3022] translation devices
separating them.
The DSMIPv6 specification [ID-DSMIP6], defines IPv4 home address
mobility and IPv4 transport support to the Mobile IPv6 protocol [RFC-
3775]. The solution specified in this document leverages some of the
options related to IPv4 support and some processing logic for
extending IPv4 support to Proxy Mobile IPv6 protocol. These two
features, the IPv4 Home Address Mobility support and IPv4 transport
support features, are independent of each other and deployments can
choose to enable any one or both of these features.
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Figure 1 illustrates a Proxy Mobile IPv6 domain supporting IPv4 home
address mobility and IPv4 transport support features. The mobile
nodes MN1, MN2 and MN3 can be operating in IPv4-only, IPv6-only or
dual-stack mode, and the transport network between the local mobility
anchor and the mobile access gateway may be an IPv6 network or an
IPv4 network. Further, when the transport network is IPv4, either
the local mobility anchor or the mobile access gateway, or both can
be behind a NAT [RFC-3022] translation device and configured with an
IPv4 private address.
+----+ +----+
|LMA1| |LMA2|
+----+ +----+
IPv4-LMAA1 -> | | <-- LMAA2
| |
\\ //\\
[NAT] // \\
\\ // \\
+---\\------------- //------\\----+
( \\ IPv4/IPv6 // \\ )
( \\ Network // \\ )
+------\\--------//------------\\-+
\\ // \\
\\ // \\
\\ // \\
IPv4-Proxy-CoA1--> | | <-- Proxy-CoA2
+----+ +----+
|MAG1|-----{MN2} |MAG2|
+----+ | +----+
(IPv6 MN-HoA1) | | | <-- (IPv6 MN-HoA2)
(IPv4-MN-HoA1) --> | (IPv4-MN-HoA2) | <-- (IPv4-MN-HoA3)
{MN1} {MN3}
Figure 1: IPv4 support for Proxy Mobile IPv6
1.1. Stated Assumptions
o This specification requires that the local mobility anchor and the
mobile access gateway are both IPv6 capable and IPv6 enabled.
Irrespective of the type of transport network (IPv4 or IPv6)
separating these two entities (i.e., if the entities are reachable
using an IPv4 or IPv6 transport address), the mobility signaling
is always based on Proxy Mobile IPv6.
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o For supporting IPv4/IPv6 home address mobility, the transport
network between the local mobility anchor and the mobile access
gateway can be an IPv6 network or an IPv4 network. However, for
supporting IPv4 transport network feature, as implied, IPv4
transport network is required.
o The mobile node can be operating in IPv4-only, IPv6-only or in
dual mode. If enabled, the mobile node should be able to obtain
IPv4-only, IPv6-only or both IPv4 and IPv6 address(es) on its
interface. However, the respective protocol(s) support must be
enabled on the access link between the mobile node and the mobile
access gateway.
o There can be support for multiple IPv4 home network prefixes for
the mobile node's attached interface. The mobile node should be
able to obtain one or more IPv4 addresses from one or all of its
IPv4 home network prefixes. Based on the type of link, it may be
able to acquire its IPv4 address configuration using DHCP, IPCP,
IKEv2 or through other standard address configuration mechanisms.
o The mobile node's IPv4 home network prefix is a shared prefix
(unlike its IPv6 home network prefix, which is a shared prefix).
There can be more than one mobile node sharing address(es) from
the same IPv4 home network prefix.
o The mobile access gateway is always the IPv4 default-router for
the mobile node on its access link. It will always be able to
receive traffic sent to the mobile node's IPv4 default-router
address.
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2. Conventions & Terminology
2.1. Conventions
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 [RFC-2119].
2.2. Terminology
All the mobility related terms used in this document are to be
interpreted as defined in Mobile IPv6 specification [RFC-3775] and
Proxy Mobile IPv6 specification [ID-PMIP6]. In addition the document
introduces the following terms.
IPv4 Proxy Care-of Address (IPv4-Proxy-CoA)
The IPv4 address that is configured on the interface of the mobile
access gateway and is the transport endpoint of the tunnel between
a local mobility anchor and a mobile access gateway. This address
will be used as the source address for the signaling messages sent
by the mobile access gateway to the local mobility anchor and will
be the registered Care-of address in the mobile node's Binding
Cache entry. However, when the configured address is a private
IPv4 address and with a NAT device in the path to the local
mobility anchor, the care-of address as seen by the local mobility
anchor will be the address allocated by the NAT device for that
flow.
IPv4 Local Mobility Anchor Address (IPv4-LMAA)
The IPv4 address that is configured on the interface of a local
mobility anchor and is the transport endpoint of the tunnel
between the local mobility anchor and the mobile access gateway.
This is the address to where the mobile access gateway sends the
Proxy Binding Update messages when using IPv4 transport. If the
local mobility anchor is configured to be behind a NAT device,
this address will not be directly configured on the local mobility
anchor, but a corresponding mapped private address will be
configured on the local mobility anchor.
Mobile Node's IPv4 Home Network Prefix (IPv4-MN-HNP)
This is the IPv4 prefix from which the mobile node obtains its
home address(es). This IPv4 home network prefix is topologically
anchored at the mobile node's local mobility anchor. The mobile
node configures its interface with address(es) from this prefix.
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3. IPv4 Home Address Mobility Support
An IPv4 enabled mobile node when it attaches to the Proxy Mobile IPv6
domain, the network will ensure the mobile node will be able to
obtain an IPv4 address (IPv4-MN-HoA) from its home network prefix for
the interface attached to the access network in that Proxy Mobile
IPv6 domain. Using the extensions defined in this specification, the
mobile access gateway on the access network will exchange the
signaling messages with the mobile node's local mobility anchor and
will setup the required routing state for that home address.
If the mobile node connects to the Proxy Mobile IPv6 domain, through
multiple interfaces and simultaneously through different access
networks, each of the connected interfaces will obtain an address
from a unique IPv4 home network prefix. In such configuration, there
will be multiple Binding Cache entries on the local mobility anchor
for that mobile node and with one entry for each connected interface,
as specified in Section 5.4 [ID-PMIP6].
The support for IPv4 addressing is orthogonal to the IPv6 addressing
support. Unlike as specified in [ID-DSMIP6], the mobile node is not
required to have an IPv6 home address for obtaining IPv4 home address
mobility. A mobile node attached to an access link in a Proxy Mobile
IPv6 domain will be able to obtain just an IPv4 address configuration
or both IPv4 and IPv6 address configurations on the connected
interface. The mobile nodes' policy profile will determine if the
mobile node is entitled for both the protocols or a single protocol
and based on what is enabled, only those protocols will be enabled on
the access link. Further, when the mobile node after obtaining the
IPv4 or IPv4/IPv6 address configuration on the access link, performs
an inter-technology handoff, the network will ensure the mobile node
will be able to use the same IPv4/IPv6 address configuration on the
new interface. [RYUJI The IPv4 home address MUST be the global IPv4
address. A private IPv4 address assignment as an IPv4 home address
is prohibited. There is no gurantee to assign the IPv4 private home
address which is different from the private address configured at a
mobile access gateway.]
3.1. IPv4 Home Address Assignment
A mobile node on attaching to an access link connected to a mobile
access gateway, and if the network allows the mobile node for IPv4
home address mobility service, the mobile node using any of the IPv4
address configuration procedures, such as DHCP [RFC-2131], IPCP or
IKEv2 that are supported on that access link, will be able to obtain
required information for its IPv4 home address configuration. The
required information includes the IPv4 home address, the IPv4 home
network prefix, IPv4 home network prefix length and the IPv4 default
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router address.
When a mobile node is configured with a static IPv4 home address, the
IPv4 home address information SHOULD be stored in the mobile node's
policy profile. The mobile access gateway where the mobile node
attached obtains the static IPv4 home address from the policy
profile. The mobile access gateway MUST use either the obtained IPv4
home address or the obtained IPv4 home subnet address to initialize
the IPv4 Home Address and Pref fields in the IPv4 Home Address option
[ID-DSMIP6]. This option is carried by a proxy binding update
described in [ID-PMIP6].
On the other hand, if DHCP is used for the IPv4 home address
allocation as specified in [RFC-2131], a DHCP server and/or a DHCP
relay agent on the link will ensure the mobile node is assigned an
IPv4 address from its home network subnet. All the IPv4 home
addresses assigned to mobile nodes must be reachable via local
mobility anchor so that local mobility anchor intercepts packets
meant for an IPv4 home address and tunnels them to the mobile node
via corresponding mobile access gateway. There are several
configurations where the DHCP entities are located in a Proxy Mobile
IPv6 domain. This document recommends following two configurations.
The other configurations are explained in Appendix A.
1. DHCP server is co-located with each mobile access gateway
2. DHCP server is co-located with a local mobility anchor and a DHCP
relay is co-located with each mobile access gateway
Figure 2 shows the operational sequence of the home address
assignment when a DHCP server is co-located with each mobile access
gateway. In this scenario, a DHCP server which is also a mobile
access gateway interacts with a DHCP client on a mobile node. All
mobile access gateways SHOULD support minimal functionality of a DHCP
server in order to send DHCP offer and acknowledgment messages to the
mobile node in reply to the DHCP discovery and request messages.
While the mobile access gateway is seen as a DHCP server from a
mobile node, it actually obtains the IPv4 home address for each
mobile node from the local mobility anchor during proxy binding
procedure (set 0.0.0.0 in the the IPv4 Home Address field of the IPv4
home address option as described in [ID-DSMIP6]). After MAG
receiving the assigned IPv4 address from LMA, it assigns the address
to the requesting mobile node. Note that the mobile access gateway
MUST return its own IP address in the 'server identifier' option when
sending DHCP messages to the mobile node. Thus, whenever the mobile
node changes the attached mobile access gateway, this server
identifier must be updated. The detail can be found in
Section 3.2.2. The second scenario does not have this server
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identifier change when a mobile node changes its mobile access
gateway. Any information carried in DHCP options such as addresses
of domain name server, time server, lpr server, etc. MUST be
configured in all the DHCP server located at mobile access gateways
if necessary.
MN MAG(DHCP-S) LMA
|------>| | 1. DHCP discovery
| |------->| 2. Proxy Binding Update *
| |<-------| 3. Proxy Binding Acknowledgement (IPv4HoA)
| |========| 4. Tunnel/Route Setup*
|<------| | 5. DHCP offer (IPv4 HoA)
|------>| | 6. DHCP request (IPv4 HoA)
|<------| | 7. DHCP acknowledgement
| | |
* DHCP discovery (no.1) and PBU (no.2) are operated in parallel.
* Tunnel/Route setup(no.4) and DHCP offer/request/ack(no.5-7)
are processed in parallel.
Figure 2: An example when LMA assigns an IPv4 home address
In the second scenario, a DHCP relay is co-located at each mobile
access gateway and a DHCP server is co-located at a local mobility
anchor. A mobile access gateway sends a proxy binding update and
retrieves an IPv4 home address for the mobile node from the local
mobility anchor as described in the first scenario. When the mobile
access gateway relays DHCP messages to the DHCP server, it includes
the assigned IPv4 home address information in the DHCP messages as a
hint. The DHCP server SHOULD assign the address stored in the hint
to the mobile node. Figure 3 are the sequence of IPv4 home address
assignment using DHCP Relay. The DHCP discovery message is sent by a
mobile node at any time, but the DHCP relay SHOULD NOT relay the DHCP
discovery message before it learns the IPv4 home address hint during
the proxy binding registration. As shown in Figure 3, the DHCP
messages MAY be sent across an administrative boundaries. The
operators MUST ensure to secure these messages. More remarks can be
found in Section 6. The DHCP server identifier remains the same all
the time, because the server is uniquely located at the local
mobility anchor.
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MN MAG(DHCP-R) LMA(DHCP-S)
| |------->| 1. Proxy Binding Update *
| |<-------| 2. Proxy Binding Acknowledgement (IPv4HoA)
| |========| 3. Tunnel/Route Setup*
|------>|------->| 4. DHCP discovery (IPv4HoA) via DHCP-R
|<------|<-------| 5. DHCP offer (IPv4 HoA) via DHCP-R
|------>|------->| 6. DHCP request (IPv4 HoA) via DHCP-R
|<------|<-------| 7. DHCP acknowledgement via DHCP-R
| | |
* Tunnel/Route setup(no.3) and DHCP offer/request/ack(no.4-7)
are processed in parallel.
Figure 3: The use of DHCP relay
3.2. Mobile Access Gateway Considerations
3.2.1. Extensions to Binding Update List Entry
For supporting this feature, the conceptual Binding Update List entry
data structure needs to be extended with the following additional
fields.
o The IPv4 home address of the attached mobile node. This is
acquired from the mobile node's local mobility anchor through the
received Proxy Binding Acknowledgment message. The IPv4 home
address parameter also includes the corresponding subnet mask.
o The IPv4 default-router address of the mobile node. This is
acquired from the mobile node's local mobility anchor through the
received Proxy Binding Acknowledgment messages.
3.2.2. Signaling Considerations
All the considerations from Section 6.9 of [ID-PMIP6] apply here.
However, the following additional considerations MUST be applied.
Mobile Node Attachment and Initial Binding Registration:
o After detecting a new mobile node on its access link, the mobile
access gateway must identify the mobile node and acquire its MN-
Identifier. If it determines that the IPv4 home address mobility
service needs to be offered to the mobile node [RYUJI by checking
the policy profile], it MUST send a Proxy Binding Update message
for the IPv4 home address to the local mobility anchor. The
message MUST include the IPv4 Home Address option, defined in
section 3.1.1 of [ID-DSMIP6]. The mobile access gateway MAY also
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include the IPv6 Home Network Prefix option in the same message
for requesting IPv6 home address support in addition to IPv4 home
address support for the mobile node. [RYUJI The mobile access
gateway contain either an IPv4 Home Address Option or a Home
Network Prefix option, or both, depending on the mobile node's
type.]
o If the mobile access gateway learns the mobile node's IPv4 home
network prefix or the IPv4 home address either from its policy
store or from the DHCP messages exchanged between the mobile node
and the DHCP server, the mobile access gateway can specify the
same in the IPv4 Home Address option for requesting the local
mobility anchor to allocate that address or to allocate an address
from the specified home network prefix. If the specified value is
0.0.0.0, then the local mobility anchor will consider this as a
request for dynamic address allocation.
o The mobile access gateway on the access link where mobile node is
attached, will register this address with the local mobility
anchor using the IPv4 Home Address option, defined in Section
3.1.1 of [ID-DSMIP6]. The IPv4 Home Address option is sent with a
proxy binding update message. The format of the proxy binding
update is slightly different from the one of [ID-DSMIP6]. In [ID-
DSMIP6], the source address of IPv6 header must be a home address
of the mobile terminal. However, since Proxy Mobile IPv6 supports
also IPv4-only nodes, IPv6 home address is not always available on
the terminal. In addition to this, the originator of this proxy
binding update is not the mobile terminal, but the mobile access
gateway. The mobile access gateway cannot send the proxy binding
update with the mobile node's home address because of security
reasons (IPsec and ingress filtering). Therefore, in this
specification, the mobile access gateway's care-of address (Proxy-
CoA) is used in the IPv6 source address field.
o The proxy binding update MUST be protected by IPsec ESP.
Receiving Binding Acknowledgement Message:
o If the received Proxy Binding Acknowledgement message has neither
an IPv4 Address Acknowledgement option or a Home Network Prefix
option present, the mobile access gateway MUST ignore the Proxy
Binding Acknowledgement and MUST NOT enable routing for the mobile
node's IPv4 Home Address or IPv6 home address traffic. However,
if there is an IPv4 Home Address Acknowledgment option present in
the reply, the option MUST be processed as per the rules specified
in Dual Stack Mobile IPv6 specification [ID-DSMIP6].
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o If the received Proxy Binding Acknowledgement message has the
Status field value in the IPv4 Address Acknowledgement Option set
to a value that indicates that the request was rejected by the
local mobility anchor, the mobile access gateway MUST NOT enable
IPv4 support for the mobile node. However, if there is an IPv6
Home Network Prefix option in the Proxy Binding Acknowledgement
message and the Status field in the message is set to a value 0
(Proxy Binding Update accepted), the mobile access gateway MUST
enable IPv6 support for the mobile node.
o If the received Proxy Binding Acknowledgement message has the
Status field value set to 0 (Proxy Binding Update accepted), the
mobile access gateway MUST update a Binding Update List entry and
must setup a tunnel to the local mobility anchor and must also add
a default route over the tunnel for all the mobile node's IPv4
traffic. The encapsulation mode for the bi-directional tunnel set
to IPv4-In-IPv6 mode. The considerations from Section 6.10 [ID-
PMIP6] apply.
Extending Binding Lifetime:
o For extending the binding lifetime of a currently registered
mobile node , the mobile access gateway MUST send a Proxy Binding
Update message to the local mobility anchor with a non zero
lifetime value. The message MUST contain the IPv4 Home Address
option with the value set to the currently registered IPv4 home
address value. Additionally, if there is a registered IPv6 home
network prefix for the mobile node for the connected interface on
that access link, both the options, Home Network Prefix option and
the IPv4 Home Address option MUST be present and with the values
set to the respective registered values.
Mobile Node Detachment and Binding De-Registration:
o As specified in Section 6.9.1 [ID-PMIP6], at any point in time,
when the mobile access gateway detects that the mobile node has
moved away from its access link, it SHOULD send a Proxy Binding
Update message to the local mobility anchor with the lifetime
value set to zero. The message MUST contain the IPv4 Home Address
option with the value set to the currently registered IPv4 home
address value. Additionally, if there is a registered IPv6 home
network prefix for the mobile node for the connected interface on
that access link, both the options, Home Network Prefix option and
the IPv4 Home Address option MUST be present and with the values
set to the respective registered values.
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Constructing the Proxy Binding Update Message:
The mobile access gateway when sending the Proxy Binding Update
request to the local mobility anchor for requesting IPv4 home address
mobility support MUST construct the message with the following
considerations.
o The message MUST be constructed as specified in Section 6.9 of
[ID-PMIP6]. However, when sending the messages over IPv4
transport, additional considerations from Section 4.0 MUST be
applied.
o The IPv4 Home Address option [ID-DSMIP6] MUST be present. The
address value MAY be set 0.0.0.0 or to a specific value.
DHCP Messages from the mobile node:
The operations of DHCP are almost same for both scenarios listed in
Section 3.1. There is one special operation for address renewing
operation when a mobile access gateway is the DHCP server.
o When a mobile node attached to an access link and attempts to
obtain an IPv4 address configuration, using DHCP or other
procedures, it will get an IPv4 address as an IPv4 home address
from its home subnet as discussed in Section 3.1. The mobile
access gateway on the access link where mobile node is attached,
will register the IPv4 home address with the local mobility anchor
using the IPv4 Home Address option, defined in Section 3.1.1 of
[ID-DSMIP6]. The IPv4 Home Address option is sent with a proxy
binding update.
o When a mobile node attempts to obtain an IPv4 home address by
using DHCP, the mobile access gateway SHOULD complete the proxy
binding registration before starting any DHCP operation. This is
necessary for the mobile access gateway to obtain all the
information required for DHCP operation from the local mobility
anchor.
o The mobile access gateway SHOULD send a proxy binding update with
0.0.0.0 in the the IPv4 Home Address field of the IPv4 home
address option [ID-DSMIP6] and retrieve the assigned IPv4 home
address from the local mobility anchor. The IPv4 home address
assigned by the local mobility anchor is offered to the mobile
node by DHCP.
o When a mobile node changes its attached mobile access gateway, the
new mobile access gateway MUST sends a proxy binding update with
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the IPv4 home address option. If the new mobile access gateway
know the assigned IPv4 home address, for example by context
transfer mechanism or policy profile, it SHOULD include the
address in the IPv4 Home Address field. Otherwise, it uses
0.0.0.0 and obtains the assigned IPv4 home address of the mobile
node from the local mobility anchor, again.
o Except for the mobile node's bootstrap, DHCP runs independently to
the proxy binding registration, for instance, for renewing the
assigned IPv4 home address. It is not necessary to run DHCP
whenever a mobile node changes its attached mobile access gateway.
A DHCP client renew the address according to the address lifetime,
etc. However, whenever a mobile node renews the IPv4 home address
by DHCP (DHCP RENEWING STATE [RFC-2131]), the mobile access
gateway SHOULD send a proxy binding update to the local mobility
anchor regardless of the mobile node's assigned address changes.
o When a mobile node gets IPv4 home address from Local Mobility
Anchor through DHCP interaction with mobile access gateway that
supports DHCP server functionality, the DHCP client in the mobile
node recognizes mobile access gateway's IP address as DHCP
server's IP address. Thus, the DHCP client unicasts DHCP renew to
the mobile access gateway, when the DHCP client goes into the DHCP
RENEWING state [RFC-2131]. However, when the mobile node
handovers to a new mobile access gateway, the mobile node does not
know the link change and the DHCP client would unicast DHCP
request to the previous mobile access gateway whose IP address was
acquired from DHCP offer. The DHCP client in the mobile node
needs to reconfigure its local configuration parameters. The
mobile access gateway SHOULD discard any DHCP request message that
does not belong to the mobile access gateway itself, so that the
mobile node should go into the DHCP REBINDING state and broadcast
DHCP discovery message without server identifier.
3.3. Local Mobility Anchor Considerations
3.3.1. Extensions to Binding Cache Entry
For supporting this feature, the conceptual Binding Cache entry data
structure needs to be extended with the following additional
parameter, as specified in [ID-DSMIP6] specification and is presented
here for convenience.
o The IPv4 home address of the registered mobile node. The IPv4
home address value may have been statically configured in the
mobile node's policy profile, it MAY have been assigned by a DHCP
server, or it MAY have been dynamically allocated by the local
mobility anchor.
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3.3.2. Signaling Considerations
All the considerations explained in Section 5.3 [ID-PMIP6] apply
here. For supporting IPv4 home address mobility feature, the
following additional considerations MUST be applied.
Processing Binding Registrations:
o If there is an IPv4 Home Address option present in the request,
but if there is no Home Network Prefix option present in the
request, the local mobility anchor MUST NOT reject the request as
specified in [ID-PMIP6]. At least one of these two options MUST
be present. However, if both the options are not present, the
local mobility anchor MUST reject the request and send a Proxy
Binding Acknowledgement message with Status field set to
MISSING_HOME_NETWORK_PREFIX_OPTION (Missing mobile node's home
network prefix option).
o The local mobility anchor MUST use the identifier from the Mobile
Node Identifier Option [RFC-4283] present in the Proxy Binding
Update request and MUST apply multihoming considerations specified
in Section 5.4 [ID-PMIP6] and from this section for performing the
Binding Cache entry existence test.
o If there is no existing Binding Cache entry that matches the
request, the local mobility anchor MUST consider this request as
an initial binding registration request. If the entry exists, the
local mobility anchor MUST consider this request as a binding re-
registration request.
o The proxy care-of address MUST be retrieved from the source
address field of the proxy binding update message.
o If the IPv4 Home Address option present in the Proxy Binding
Update request has the value of 0.0.0.0, the local mobility anchor
MUST allocate an IPv4 home address for the mobile node and send a
Proxy Binding Acknowledgement message and including the IPv4
Address Acknowledgement option, defined in Section 3.2.1 of [ID-
DSMIP6], containing the allocated address value. The specific
details on how the local mobility anchor allocates the home
address is outside the scope of this document. The local mobility
anchor MUST ensure the allocated prefix is not in use by any other
mobile node.
o If the local mobility anchor is unable to allocate an IPv4 home
address for the mobile node, it MUST reject the request and send a
Proxy Binding Acknowledgement message with Status field set to 130
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(Insufficient resources).
o Upon accepting the request, the local mobility anchor MUST create
a Binding Cache entry for the mobile node. It must set the fields
in the Binding Cache entry to the accepted values for that
binding. It MUST also establish a bi-directional tunnel to the
mobile access gateway, as described in [RFC-2473]. Considerations
from Section 5.6 [ID-PMIP6] MUST be applied. The local mobility
anchor MUST add an IPv4 host route for that allocated IPv4 home
address over the tunnel to the mobile access gateway.
Multihoming Considerations:
o The multihoming considerations specified in Section 5.4 [ID-PMIP6]
allows the local mobility anchor to perform the Binding Cache
entry existence test for identifying the mobility session, by
using the mobile node identifier, interface identifier and the
Home Network Prefix values. When using an IPv4 home address
value, instead of the IPv6 home network prefix for matching the
Binding Cache entry, all those considerations equally apply for
the IPv4 home address as well.
o If there is an Home Network Prefix option present in the Proxy
Binding Update request and with a NON_ZERO value, the local
mobility anchor MUST use this parameter in combination with the
mobile node identifier and interface identifier for matching the
Binding Cache entry, just as specified in Section 5.4 [ID-PMIP6].
For all other cases, the local mobility anchor MUST use the IPv4
home address parameter in combination with the mobile node
identifier and interface identifier for matching the Binding Cache
entry, as specified in Section 5.4 [ID-PMIP6].
Constructing the Proxy Binding Acknowledgement Message:
o The local mobility anchor when sending the Proxy Binding
Acknowledgement message to the mobile access gateway MUST
construct the message as specified in Proxy Mobile IPv6 base
specification [ID-PMIP6]. However, the following considerations
MUST be applied.
o The IPv4 Address Acknowledgement option MUST be present in the
Proxy Binding Acknowledgement message.
1. If the Status field is set to a value greater than or equal to
128, i.e., if the binding request is rejected, then the IPv4
home address value in the IPv4 Address Acknowledgement option
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MUST be set to ALL_ZERO value.
2. For all other cases, the IPv4 home address value in the IPv4
Address Acknowledgement option MUST be set to the allocated
IPv4 home address value for that mobility session.
3.3.3. Routing Considerations
Forwarding Considerations for the mobile node's IPv4 home address
traffic.
Intercepting Packets Sent to the Mobile Node's IPv4 home network:
o When the local mobility anchor is serving a mobile node, it MUST
be able to receive packets that are sent to the mobile node's IPv4
network. In order for it to receive those packets, it MUST
advertise a connected route in to the Routing Infrastructure for
the mobile node's IPv4 home network prefix or for an aggregated
prefix with a larger scope. This essentially enables IPv4 routers
in that network to detect the local mobility anchor as the last-
hop router for that IPv4 prefix.
Forwarding Packets to the Mobile Node:
o On receiving a packet from a correspondent node with the
destination address matching a mobile node's IPv4 home address,
the local mobility anchor MUST forward the packet through the bi-
directional tunnel setup for that mobile node. The format of the
tunneled packet is shown below.
IPv6 header (src= LMAA, dst= Proxy-CoA /* Tunnel Header */
IPv4 header (src= CN, dst= IPv4-MN-HOA ) /* Packet Header */
Upper layer protocols /* Packet Content*/
Figure 4: Tunneled Packets from LMA to MAG
Forwarding Packets Sent by the Mobile Node:
o All the reverse tunneled packets that the local mobility anchor
receives from the mobile access gateway, after removing the tunnel
header MUST be routed to the destination specified in the inner
IPv4 packet header. These routed packets will have the source
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address field set to the mobile node's IPv4 home address.
3.4. Mobility Options
For supporting IPv4 home address mobility feature, this specification
defines the following new option.
3.4.1. IPv4 Default Router Address Option
A new option, IPv4 Default Router Address Option is defined for using
it in the Proxy Binding Acknowledgment message sent by the local
mobility anchor to the mobile access gateway. This option can be
used for sending the mobile node's IPv4 default router address.
The IPv4 Default Router Address option has an alignment requirement
of 4n. Its format is as follows:
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 | Length | Reserved (R) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Default Router Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
<IANA>
Length
8-bit unsigned integer indicating the length of the option in
octets, excluding the type and length fields. This field MUST
be set to 6.
Reserved (R)
This 8-bit field is unused for now. The value MUST be
initialized to 0 by the sender and MUST be ignored by the
receiver.
IPv4 Default Router Address
A four-byte field containing the mobile node's default router
address.
Figure 5: IPv4 Default Router Address Option
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4. IPv4 Transport Support
The Proxy Mobile IPv6 specification [ID-PMIP6] requires the network
between the local mobility anchor and the mobile access gateway to be
an IPv6 network and the signaling messages exchanged between the
local mobility anchor and the mobile access gateway to be over an
IPv6 transport. The extensions defined in this section allow the
exchange of signaling messages over an IPv4 transport when the local
mobility anchor and the mobile access gateway are separated by an
IPv4 network and are reachable using an IPv4 address.
IPv4-Proxy-CoA IPv4-LMAA
| + - - - - - - + |
+--+ +---+ / \ +---+ +--+
|MN|----------|MAG|===== IPv4 Network =====|LMA|----------|CN|
+--+ +---+ \ / +---+ +--+
+ - - - - - - +
Figure 6: IPv4 Transport Network
When the network between the local mobility anchor and the mobile
access gateway is an IPv4 network, i.e., when both these mobility
entities are configured and reachable using an IPv4 address, the
mobile access gateway serving a mobile node can potentially register
its IPv4 address with the local mobility anchor, as the care-of
address in the mobile node's Binding Cache entry and can negotiate
and IPv4 transport tunnel for tunneling the mobile node's data
traffic.
The Dual Stack Mobile IPv6 specification [ID-DSMIP6] defines protocol
extensions to Mobile IPv6 protocol for allowing a mobile node to roam
into an IPv4 network and registers an IPv4 care-of address with the
home agent. The same mechanism is leveraged for extending IPv4
transport support to Proxy Mobile IPv6 protocol. The mobility
options for requesting IPv4 transport support, the processing logic
and the on-path NAT detection logic is just as described in [ID-
DSMIP6]. The following are the key properties of this feature.
o The local mobility anchor and the mobile access gateway are both
configured and reachable using an IPv4 address.
o The configured address on the mobile access gateway can be an IPv4
private address and when it is behind a NAT translation device and
the mechanism specified in Dual Stack Mobile IPv6 specification
[ID-DSMIP6] is again leveraged for NAT detection and traversal.
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o The Proxy Mobile IPv6 signaling messages exchanged between the
local mobility anchor and the mobile access gateway for
negotiating the IPv4 transport will be encapsulated and carried as
IPv4 packets. However, these signaling messages are fundamentally
IPv6 messages with the mobility header and the semantics as
specified in base Proxy Mobile IPv6 specification [ID-PMIP6], but
carried as payload in IPv4 packets. Additionally, the mobility
options defined in Dual Stack Mobile IPv6 specification [ID-
DSMIP6] are used for negotiating IPv4 transport support and with a
specific encapsulation mode.
o The IPv4 tunnel established between the local mobility anchor and
the mobile access gateway (with any of the supported encapsulation
modes over IPv4 transport) is used for carrying the mobile node's
IPv4 and IPv6 traffic. The mobile node can be an IPv6, IPv4 or a
dual IPv4/IPv6 node and the IPv4 transport support specified in
this section is agnostic to the type of address mobility enabled
for the mobile node.
4.1. NAT Support
When the transport network between the local mobility anchor and the
mobile access gateway is an IPv4 network, the mobile access gateway
MUST send Proxy Binding Update message encapsulated in the IPv4-UDP
packet. On receiving this Proxy Binding Update packet encapsulated
in an IPv4-UDP packet, the local mobility anchor if it detects a NAT
on the path, will send the Proxy Binding Acknowledgment message with
the NAT Detection Option. The presence of this option in the Proxy
Binding Acknowledgment is an indication to the mobile access gateway
about the presence of NAT in the path. On detecting the NAT in the
path, both the local mobility anchor and the mobile access gateway
MUST set the encapsulation mode of the tunnel to IPv4-UDP-based
encapsulation. The specific details around the NAT detection and the
related logic is described in in DSMIPv6 specification [ID-DSMIP6].
There are discussions on how to incorporate the NAT detection
mechanism of IKE with DSMIPv6 in the MEXT Working Groups. This
documentation will follow the conclusion of their discussions.
[RYUJI Private addresses MUST NOT be configured at both mobile access
gateways and a local mobility anchor in the same Proxy Mobile IPv6
domain. At least one of Proxy Mobile IPv6's tunnel end points MUST
have a global address. Otherwise, the packets might not be exchanged
in the tunnel due to NAT.]
[RYUJI When a mobile access gateway is configured with an IPv4
private address, it MUST NOT operate the local routing (described in
Section 6.10.3 of [ID-PMIP6]) for packets destined to an IPv4 address
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assigned to a correspondent node. The address translation MUST
happen before the packets are arrived at the correspondent node. To
ensure this, the packets MUST be sent to the local mobility anchor
and routed back to the correspondent node.]
4.2. Mobile Access Gateway Considerations
4.2.1. Extensions to Binding Update List Entry
For supporting this feature, the conceptual Binding Update List entry
data structure needs to be extended with the following additional
parameters, as specified in [ID-DSMIP6] specification and is reviewed
here for convenience.
o The IPv4 address registered with the local mobility anchor as the
mobile node's care-of address.
4.2.2. Signaling Considerations
All the considerations as explained in Section 6.11 of the base Proxy
Mobile IPv6 specification apply here.
Network Configurations for IPv4 Transport Signaling Support:
o If IPv4 transport support is enabled in order to place a mobile
access gateway at IPv4 only network, the mobile access gateway
MUST have an IPv4 address at the visiting network. In addition to
that, the mobile access gateway MUST obtain an IPv6 address
configured for the Proxy Mobile IPv6 operation. Even if the
mobile access gateway does not have connectivity to the IPv6
network, it MUST configure with an IPv6 address for sending the
proxy binding registration to the local mobility anchor.
Processing Binding Registrations:
o As explained in the DSMIPv6 specification, the mobile access
gateway can encapsulate a Proxy Binding Update message and carry
it in IPv4 and UDP packet. The processing logic for handling the
NAT detection at the mobile node is applicable to the mobile
access gateway as described in Section 4.1.
o An example of proxy binding update sent by mobile access gateway
is shown in Figure 7. The source address of the inner IPv6 header
MUST set to the IPv6 address assigned to the mobile access gateway
and the destination address MUST be the local mobility anchor's
IPv6 address (LMAA). This is slightly different from [ID-DSMIP6]
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. The reason is already mentioned in Section 3.2.2.
o The source address of the outer packet MUST be the IPv4-Proxy-CoA
and the destination MUST be the local mobility anchor's IPv4
address (IPv4-LMAA).
o The IPv4-Proxy-CoA MUST be set in the IPv4 Care-of Address option
defined in section 3.1.2 of [ID-DSMIP6].
o For the NAT handling, the UDP-based encapsulation MUST be always
used for the proxy binding update. The UDP port number is defined
in [ID-DSMIP6].
o If the mobile access gateway requested to use the TLV header for
the UDP encapsulation, it MUST insert a TLV header after the UDP
header and MUST set T flag in the proxy binding update message.
The format of the TLV header is defined in section 4.1 of [ID-
DSMIP6].
o The proxy binding update MUST be protected by IPsec ESP. The
security association for IPv4 addresses of the mobile access
gateway and local mobility anchor are pre-established.
Constructing the Proxy Binding Update Message:
o For requesting IPv4 transport support, the mobile access gateway
when sending the Proxy Binding Update request to the local
mobility anchor from an IPv4 networks MUST construct the message
as specified below.
IPv4 header (src=IPv4-Proxy-CoA, dst=IPv4-LMAA)
UDP header
IPv6 header (src=Proxy-CoA, dst=LMAA)
Mobility header
-BU (P flag is set. F/T flags are optional)
Mobility Options
- The IPv4 Care-of Address option(Mandatory)
-
- All the options as required by [ID-PMIP6]
- or as required by any extension documents
-
Figure 7: Proxy Binding Update Message Format for IPv4 Transport
Support
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o
o The IPv4 Care-of Address option [ID-DSMIP6] MUST be present. The
address value MUST be set to mobile access gateway's IPv4 address.
o All the other fields and the options MUST be constructed, as
specified in [ID-PMIP6].
Receiving Binding Registration Reply:
o After receiving a Proxy Binding Acknowledgment message
encapsulated in an IPv4 packet, the mobile access gateway MUST
verify the Proxy Binding Acknowledgment according to the Section
4.3 of Dual Stack Mobile IPv6 specification [ID-DSMIP6].
o If the Status field indicates Success, the mobile access gateway
MUST setup a tunnel to the local mobility anchor and add a default
route over the tunnel for all the mobile node's traffic.
o If the NAT is available and the NAT detection option is presented
in the Proxy Binding Acknowledgment, the mobile access gateway
MUST use the UDP tunnel to traverse the NAT for mobile node's
traffic and MUST send a proxy binding update every refresh time
specified in the NAT detection option. The detailed operation can
be found in Dual Stack Mobile IPv6 specification [ID-DSMIP6].
o If the Status field in the proxy binding acknowledgment indicates
the rejection of the binding registration, the mobile access
gateway MUST NOT enable IPv4 transport for the mobile node's
traffic.
Forwarding Packets to Local Mobility Anchor
o On receiving any packets from the mobile node's IPv6 home address
and/or IPv4 home address, the mobile access gateway tunnels the
packets to local mobility anchor as shown in Figure 8. If the
mobile access gateway and the local mobility anchor agreed to use
the TLV header for the UDP tunnel during the binding registration,
the TLV header MUST be presented after the UDP header as shown in
Figure 9.
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IPv4 header (src=IPv4-Proxy-CoA, dst=IPv4-LMAA)
[UDP header] /*Only if NAT is detected*/
union { /*following either v6 or v4 header */
IPv4 header (src=MN's IPv4-HoA, dst=IPv4 CN)
IPv6 header (src=MN's IPv6-HoA, dst=IPv6 CN)
}
Upper layer protocols /*TCP,UDP,SCTP*/
Figure 8: Tunneled Packets from MAG to LMA
IPv4 header (src=IPv4-Proxy-CoA, dst=IPv4-LMAA)
UDP header
TLV header
union {
IPv4 header (src=MN's IPv4-HoA, dst=IPv4 CN)
IPv6 header (src=MN's IPv6-HoA, dst=IPv6 CN)
IPsec
GRE
}
Upper layer protocols /*TCP,UDP,SCTP*/
Figure 9: Tunneled Packets from MAG to LMA using the TLV header
4.3. Local Mobility Anchor Considerations
4.3.1. Extensions to Binding Cache Entry
For supporting this feature, the conceptual Binding Cache entry data
structure needs to be extended with the following additional
parameter as specified in [ID-DSMIP6] specification and are reviewed
here for convenience.
o The IPv4 Care-of address of the attached mobile node. In this
specification, it can be translated to IPv4 Care-of address of the
mobile access gateway to which a mobile node is attached.
4.3.2. Signaling Considerations
When a mobile node is attached to a mobile access gateway that is
reachable only through an IPv4 transport network, the local mobility
anchor must establish an IPv4 tunnel for routing the mobile node's
IPv4 and IPv6 home address traffic. The DSMIPv6 specification
provides the semantics on how the IPv4 tunnel needs to be negotiated
and the detection logic of the NAT devices. This specification
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leverages the NAT Detection Option, defined in the Dual Stack Mobile
IPv6 specification for the use in Binding Acknowledgment message and
extends it to Proxy Binding Acknowledgment messages. The operational
steps are defined below.
Processing Binding Registrations:
o After accepting the registration from the mobile access gateway
locating at the IPv4 only network, the local mobility anchor MUST
setup a tunnel to the mobile access gateway. The tunnel is
established between the v4-LMAA and the IPv4-Proxy-CoA of the
mobile access gateway.
o If the NAT is available, the local mobility anchor MUST use UDP
encapsulation for the tunnel.
o If the T flag is set in the proxy binding update message and the
TLV header is presented, the specified tunnel type must be used.
o The local mobility anchor also setup a host routes for the IPv4
home address and the IPv6 home address of the mobile node over the
tunnel to the mobile access gateway. Any traffic that the local
mobility anchor receives from a correspondent node will be
tunneled to the mobile access gateway over the bi-directional
tunnel and then routed accordingly after removing the tunnel
headers. The encapsulation modes for the bi-directional tunnel
are as specified in Section 5.3 of Proxy Mobile IPv6 specification
[ID-PMIP6] and as in this specification.
o Upon receiving a Proxy Binding Update message encapsulated in an
IPv4 packet, the local mobility anchor MUST send the Proxy Binding
Acknowledgment to the mobile access gateway's IPv4-Proxy-CoA by
using IPv4 encapsulation.
o If the NAT is detected, the NAT detection option MUST be used in
the Proxy Binding Acknowledgment. How to detect NAT is described
in Section 4.1 of [ID-DSMIP6] and Section 4.1.
Constructing the Proxy Binding Acknowledgement Message:
o The proxy binding acknowledgment MUST be protected by IPsec ESP.
The security association for IPv4 addresses of the mobile access
gateway and local mobility anchor are pre-established.
o For the IPv4 transport support, no special mobility options are
required. Only when NAT is detected, the NAT detection option
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MUST be present. The local mobility anchor MUST construct the
proxy binding Acknowledgement as specified in [ID-PMIP6].
o An example of proxy binding acknowledgment sent by local mobility
anchor is shown below. The same illustration for Mobile IPv6 can
be found in Section 4.1 of [ID-DSMIP6].
IPv4 header (src=IPv4-LMAA, dst=IPv4-Proxy-CoA)
UDP header
[TLV-header] /* optional, if T flag is set */
IPv6 header (src=LMAA, dst=Proxy-CoA)
Mobility header
-BA /* P flag/T flag(option) */
Mobility Options
- Home Network Prefix Option
- IPv4 Address Acknowledgement option
- Timestamp option (optional)
- Mobile Node Identifier Option
- Access Technology Type option (Mandatory)
- Mobile Node Interface Identifier option
(Optional)
- NAT Detection Option (Optional)
Figure 10: Proxy Binding Acknowledgment in IPv4 network
Forwarding Packets to Mobile Access Gateway
o When sending any packets meant to a mobile node's IPv4 home
address or IPv6 home address, the local mobility anchor tunnels
the packet to mobile access gateway as shown in Figure 11.
IPv4 header (src=IPv4-LMAA, dst=IPv4-Proxy-CoA)
[UDP header] /*Only if NAT is detected*/
union { /*following either v6 or v4 header */
IPv4 header (src=IPv4-CN, dst=IPv4-HoA)
IPv6 header (src=IPv6-CN, dst=IPv6-HoA)
}
Upper layer protocols /*TCP,UDP,SCTP*/
Figure 11: Tunneled Packets from LMA to MAG
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o If the mobile access gateway and the local mobility anchor agreed
to use the TLV header for the UDP tunnel during the binding
registration, the TLV header MUST be presented after the UDP
header as shown in Figure 12.
IPv4 header (src=IPv4-Proxy-CoA, dst=IPv4-LMAA)
UDP header
TLV header
union {
IPv4 header (src=IPv4-CN, dst=IPv4-HoA)
IPv6 header (src=IPv6-CN, dst=IPv6-HoA)
IPsec
GRE
}
Upper layer protocols /*TCP,UDP,SCTP*/
Figure 12: Tunneled Packets from LMA to MAG using the TLV header
4.4. Tunnel Management
As specified in the Proxy Mobile IPv6 specification, the bi-
directional tunnel between the local mobility anchor and the mobile
access gateway, is a shared tunnel and all the considerations from
Section 6.6 of Proxy Mobile IPv6 [ID-PMIP6] apply for IPv4 transport
as well.
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5. IANA Considerations
This document does not require IANA Action.
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6. Security Considerations
The security mechanisms specified for Proxy Mobile IPv6 protocol are
used when using the extensions defined in this document.
When supporting IPv4 address assignment from a DHCP server, all the
IPv4 home addresses managed in the DHCP server must be reachable via
local mobility anchor so that local mobility anchor intercepts
packets meant for an IPv4 home address and tunnels them to the mobile
node via corresponding mobile access gateway. Moreover, all the DHCP
messages between a DHCP relay and the DHCP server SHOULD be securely
exchanged.
After receiving a Proxy Binding Update message with an IPv4 Home
Address Option, the local mobility anchor MUST be able to verify that
the mobile node is authorized to use that address before setting up
forwarding for that host route.
When supporting dynamic IPv4 address assignment by DHCP and also from
local mobility anchor, it should be ensured both the entities are
configured with different address pools, so as to avoid both entities
do not allocate the same address to different mobile nodes.
This specification describes the use of IPv4 transport network
between the local mobility anchor and the mobile access gateway. All
the signaling messages exchanged between the mobile access gateway
and the local mobility anchor over the IPv4 transport MUST be
protected using IPsec, just as the messages must be protected when
using IPv6 transport and as specified in the Section 4.0, of the
Proxy Mobile IPv6 specification [ID-PMIP6].
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7. Contributors
This document reflects discussions and contributions from several
people (in alphabetical order):
Kuntal Chowdhury
kchowdhury@starentnetworks.com
Vijay Devarapalli
vijay.devarapalli@azairenet.com
Sangjin Jeong
sjjeong@etri.re.kr
Basavaraj Patil
basavaraj.patil@nsn.com
Myungki Shin
myungki.shin@gmail.com
8. Acknowledgments
The IPv4 support for Proxy Mobile IPv6 was initially covered in the
internet-draft [draft-sgundave-mip6-proxymip6-02.txt]. This document
leverages lot of text from that document. We would like to thank all
the authors of the document and acknowledge that initial work.
9. References
9.1. Normative References
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC-2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC-2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, December 1998.
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[RFC-3775] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in
IPv6", RFC 3775, June 2004.
[RFC-4283] Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
Chowdhury, "Mobile Node Identifier Option for Mobile IPv6", RFC 4283,
November 2005.
[ID-DSMIP6] Soliman, H. et al, "Mobile IPv6 support for dual stack
Hosts and Routers (DSMIPv6)", draft-ietf-mip6-nemo-v4traversal-05.txt
,July 2007.
[ID-PMIP6] Gundavelli, S., et.al, "Proxy Mobile IPv6",
draft-ietf-netlmm-proxymip6-16.txt, November 2007.
9.2. Informative References
[RFC-2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC-3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022, January 2001.
[RFC-4977] Tsirtsis, G., Soliman, H., "Problem Statement: Dual Stack
Mobility", RFC 4977, August 2007.
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Appendix A. DHCP usages for IPv4 home address assignment
There are several other configurations of DHCP entities [RFC-2131] in
a Proxy Mobile IPv6 domain other than the two configurations listed
in Section 3.1. Although this specification recommends the two
configurations described in Section 3.1, operators should select the
best configuration according to their deployments scenario. The
mobile node behavior for all scenarios does not change. We do not
have major interoperability concerns between multiple scenarios. A
mobile access gateway and local mobility anchor make sure that which
scenario is used in the same Proxy Mobile IPv6 domain based on
deployment requirements. The optional DHCP configurations for IPv4
home address assignment are described below.
o DHCP relay is co-located with each mobile access gateway and DHCP
server is solely located in the Proxy Mobile IPv6 domain.
o DHCP relay is co-located with both each mobile access gateway and
a local mobility anchor. DHCP server is solely located behind the
local mobility anchor in the Proxy Mobile IPv6 domain.
The operations are same as described in Section 3.1. Before relaying
any DHCP messages, a mobile access gateway　SHOULD complete the
proxy binding registration so that it learns the assigned address to
provide the IPv4 home address hint to the DHCP server. However, when
DHCP relays are located at both a mobile access gateway and a local
mobility anchor, the DHCP relay at the local mobility anchor can
simply insert the address hint retrieved from its local address
management pool in the DHCP messages. Thus, the IPv4 home address
option [ID-DSMIP6] can be omitted from the Proxy Binding Update and
Acknowledgement messages.
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Authors' Addresses
Ryuji Wakikawa
Keio University
Department of Environmental Information, Keio University.
5322 Endo
Fujisawa, Kanagawa 252-8520
Japan
Email: ryuji@sfc.wide.ad.jp
Sri Gundavelli
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sgundave@cisco.com
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