One document matched: draft-ietf-netlmm-pmip6-ipv4-support-04.txt
Differences from draft-ietf-netlmm-pmip6-ipv4-support-03.txt
NETLMM Working Group R. Wakikawa
Internet-Draft Toyota ITC
Intended status: Standards Track S. Gundavelli
Expires: January 15, 2009 Cisco
July 14, 2008
IPv4 Support for Proxy Mobile IPv6
draft-ietf-netlmm-pmip6-ipv4-support-04.txt
Status of this Memo
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This Internet-Draft will expire on January 15, 2009.
Copyright Notice
Copyright (C) The IETF Trust (2008).
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Abstract
This document specifies extensions to Proxy Mobile IPv6 protocol for
adding IPv4 protocol support. The scope of IPv4 protocol support is
two-fold: 1) For extending IPv4 home address mobility support to the
mobile node. 2) For allowing the mobility entities in the Proxy
Mobile IPv6 domain to exchange signaling messages over an IPv4
transport network.
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Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Stated Assumptions . . . . . . . . . . . . . . . . . . . . 6
2. Conventions & Terminology . . . . . . . . . . . . . . . . . . 8
2.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 8
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 8
3. IPv4 Home Address Mobility Support . . . . . . . . . . . . . . 10
3.1. Local Mobility Anchor Considerations . . . . . . . . . . . 11
3.1.1. Extensions to Binding Cache Entry . . . . . . . . . . 11
3.1.2. Signaling Considerations . . . . . . . . . . . . . . . 11
3.1.3. Routing Considerations for the Local Mobility
Anchor . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2. Mobile Access Gateway Considerations . . . . . . . . . . . 16
3.2.1. Extensions to Binding Update List Entry . . . . . . . 16
3.2.2. Extensions to Mobile Node's Policy Profile . . . . . . 16
3.2.3. Signaling Considerations . . . . . . . . . . . . . . . 17
3.2.4. Routing Considerations for the Mobile Access
Gateway . . . . . . . . . . . . . . . . . . . . . . . 19
3.3. Mobility Options and Status Codes . . . . . . . . . . . . 19
3.3.1. IPv4 Default-Router Address Option . . . . . . . . . . 19
3.3.2. Status Codes . . . . . . . . . . . . . . . . . . . . . 20
3.4. Supporting DHCP Based Address Configuration . . . . . . . 21
3.4.1. DHCP Server co-located with the Mobile Access
Gateway . . . . . . . . . . . . . . . . . . . . . . . 22
3.4.2. DHCP Relay Agent co-located with the Mobile Access
Gateway . . . . . . . . . . . . . . . . . . . . . . . 25
4. IPv4 Transport Support . . . . . . . . . . . . . . . . . . . . 28
4.1. Local Mobility Anchor Considerations . . . . . . . . . . . 29
4.1.1. Extensions to Binding Cache Entry . . . . . . . . . . 29
4.1.2. Extensions to Mobile Node's Policy Profile . . . . . . 30
4.1.3. Signaling Considerations . . . . . . . . . . . . . . . 30
4.1.4. Routing Considerations . . . . . . . . . . . . . . . . 32
4.2. Mobile Access Gateway Considerations . . . . . . . . . . . 34
4.2.1. Extensions to Binding Update List Entry . . . . . . . 34
4.2.2. Signaling Considerations . . . . . . . . . . . . . . . 34
5. Protocol Configuration Variables . . . . . . . . . . . . . . . 38
5.1. Local Mobility Anchor - Configuration Variables . . . . . 38
5.2. Mobile Access Gateway - Configuration Variables . . . . . 38
5.3. Proxy Mobile IPv6 Domain - Configuration Variables . . . . 39
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
7. Security Considerations . . . . . . . . . . . . . . . . . . . 41
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8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 42
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 42
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 42
10.1. Normative References . . . . . . . . . . . . . . . . . . . 42
10.2. Informative References . . . . . . . . . . . . . . . . . . 43
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 44
Intellectual Property and Copyright Statements . . . . . . . . . . 45
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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 the 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 [RFC-5213] specifies a mechanism for
providing IPv6 home address mobility support to a mobile node in a
Proxy Mobile IPv6 domain. The protocol requires IPv6 transport
network between the mobility entities. The extensions defined in
this document extends IPv4 support to the Proxy Mobile IPv6 protocol
[RFC-5213].
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 mobile
access gateway may be using an IPv4 private address and with NAT
[RFC-3022] translation devices on the path to the local mobility
anchor.
These two features, the IPv4 Home Address Mobility support and the
IPv4 transport support features, are independent of each other and
deployments may choose to enable any one or both of these features as
required.
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+----+ +----+
|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
Following are the configuration requirements from the mobility
entities in the Proxy Mobile IPv6 domain for supporting the
extensions defined in this document.
o The local mobility anchor and the mobile access gateway are both
IPv4 and IPv6 enabled. Irrespective of the type of transport
network (IPv4 or IPv6) separating these two entities, the mobility
signaling is always based on Proxy Mobile IPv6 [RFC-5213].
o The mobile node can be operating in IPv4-only, IPv6-only or in
dual mode. Based on what is enabled for a mobile node, it should
be able to obtain IPv4-only, IPv6-only or both IPv4 and IPv6
address(es) for its interface and further achieve mobility support
for those addresses.
o For enabling IPv4 home address mobility support to a mobile node,
it is not required that the IPv6 home address mobility support
needs to enabled. However, the respective protocol(s) support
must be enabled on the access link between the mobile node and the
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mobile access gateway.
o The mobile node can obtain one or more IPv4 addresses for its
attached interface. Based on the type of link, it may be able to
acquire its IPv4 address configuration using DHCP [RFC-2131], IPCP
[RFC-1332], IKEv2 [RFC-4306], static configuration or through
other standard IPv4 address configuration mechanisms.
o The mobile node's IPv4 home subnet is typically a shared address
space. Its is not for the exclusive use of any one mobile node.
There can be more than one mobile node sharing different addresses
from the same IPv4 subnet.
o The mobile access gateway is the IPv4 default-router for the
mobile node on its access link. It will be in the forwarding path
for the mobile node's data traffic.
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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 the Mobile IPv6 specification [RFC-3775]
and Proxy Mobile IPv6 specification [RFC-5213]. In addition this
document introduces the following terms.
IPv4 Proxy Care-of Address (IPv4-Proxy-CoA)
The IPv4 address that is configured on the egress-interface of the
mobile access gateway. When using IPv4 transport, this address
will be the registered care-of address in the mobile node's
Binding Cache entry and will also be the transport-endpoint of the
tunnel between the local mobility anchor and a mobile access
gateway. However, if 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 egress-interface of the
local mobility anchor. When using IPv4 transport, the mobile
access gateway sends the Proxy Binding Update messages to this
address and will be the transport-endpoint of the tunnel between
the local mobility anchor and the mobile access gateway.
Mobile Node's IPv4 Home Address (IPv4-MN-HoA)
This is the IPv4 home address assigned to the mobile node's
attached interface. This IPv4 home address is topologically
anchored at the local mobility anchor. The mobile node configures
this address on its attached interface. There can be more than
one IPv4 home addresses assigned to the mobile node's attached
interface. Further, if the mobile node connects to the Proxy
Mobile IPv6 domain through multiple interfaces and for
simultaneous access, each of the attached interfaces will be
assigned a unique set of IPv4 home addresses and all the IPv4
addresses that are assigned to a given interface of a mobile node
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will be managed under one mobility session.
Encapsulation Modes
This document uses the following terms when referring to the
different encapsulation modes.
IPv4-over-IPv6
IPv4 packet carried as a payload of an IPv6 packet
IPv4-over-IPv4
IPv4 packet carried as a payload of an IPv4 packet
IPv4-over-IPv4-UDP
IPv4 packet carried as a payload in an UDP header of an IPv4
packet
IPv4-over-IPv4-UDP-TLV
IPv4 packet carried as a payload in an IPv4 packet with UDP and
TLV headers
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3. IPv4 Home Address Mobility Support
The IPv4 home address mobility support essentially enables a mobile
node in a Proxy Mobile IPv6 domain to obtain IPv4 home address
configuration for its attached interface and be able to retain that
address configuration even after changing its point of attachment in
that Proxy Mobile IPv6 domain. This section describes the protocol
operation and the required extensions to Proxy Mobile IPv6 protocol
for supporting IPv4 home address mobility support.
When an IPv4-enabled or a dual-stack enabled mobile node attaches to
the Proxy Mobile IPv6 domain, the mobile access gateway on the access
network where the mobile node is attached will identify the mobile
node and will initiate the Proxy Mobile IPv6 signaling with the
mobile node's local mobility anchor. The mobile access gateway will
follow the signaling considerations specified in Section 3.2 for
requesting IPv4 home address support. Upon the completion of the
signaling the local mobility anchor and the mobile access gateway
will have the required states for allowing the mobile node to use its
IPv4 home address(es) from the current point of attachment.
The mobile node on the access link using any of the standard IPv4
address configuration mechanisms supported on that access link, such
as IPCP [RFC-1332], IKEv2 [RFC-4306] or using DHCP [RFC-2131], will
be able to obtain one or more IPv4 home addresses (IPv4-MN-HoA) for
the attached interface. Although the address configuration protocol
mechanisms for delivering the address configuration to the mobile
node is independent of the Proxy Mobile IPv6 protocol operation,
however there needs to be some interactions between these two
protocol flows. Section 3.4 identifies these interactions for
supporting DHCP based address configuration.
The support for IPv4 home address mobility is not dependent on the
IPv6 home address support. The mobile node is not required to have
an IPv6 home address for obtaining IPv4 home address mobility. A
mobile node will be able to obtain just IPv4 address configuration or
both IPv4 and IPv6 address configuration on its attached interface.
The mobile node's 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, if the mobile node after obtaining the address
configuration on its interface performs an handoff, either by
changing its point of attachment over the same interface or to a
different interface, the network will ensure the mobile node will be
able to use the same IPv4 address configuration after the handoff.
Additionally, If the mobile node connects to the Proxy Mobile IPv6
domain, through multiple interfaces and simultaneously through
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different access networks, each of the connected interfaces will
obtain one or more IPv4 home addresses from different subnets. In
such scenario, there will be multiple Binding Cache entries for the
mobile node on the local mobility anchor. All the address (IPv4/
IPv6) assigned to a given interface will be managed as part of one
mobility session, as specified in Section 5.4 of [RFC-5213].
3.1. Local Mobility Anchor Considerations
3.1.1. Extensions to Binding Cache Entry
For supporting this feature, the conceptual Binding Cache entry data
structure maintained by the local mobility anchor needs to be
extended with the following additional parameters.
o List of IPv4 home addresses assigned to the mobile node's
interface registered by the mobile access gateway. Each of these
IPv4 home address entries also include the corresponding prefix
length.
o The IPv4 default-router address assigned to the mobile node.
3.1.2. Signaling Considerations
3.1.2.1. Processing Proxy Binding Updates
The processing rules specified in Section 5.3 of [RFC-5213] are
applied for processing the received Proxy Binding Update message.
However, if the received Proxy Binding Update message has one or more
IPv4 Home Address options, the following additional considerations
MUST be applied.
o If there is an IPv4 Home Address option present in the received
Proxy Binding Update message, 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 Section 5.3.1 of [RFC-
5213]. At least one instance of any of these two options MUST be
present. However, if not a single instance of any of these
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 For performing the Binding Cache entry existence test, the
following considerations MUST be applied:
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* If there is at least one Home Network Prefix option with a
NON_ZERO prefix value, or, if there is no IPv4 Home Address
option with a NON_ZERO IPv4 address, considerations from
Section 5.4 of [RFC-5213] MUST be applied.
* If there is at least one IPv4 Home Address option present in
the request with a NON_ZERO IPv4 address value, considerations
from Section 3.2.2.7 MUST be applied.
o If there is no existing Binding Cache entry that can be associated
with the request, the local mobility anchor MUST consider this
request as an initial binding registration request and
considerations from Section 3.2.2.2 MUST be applied.
o If there exists a Binding Cache entry that can be associated with
the request, the local mobility anchor MUST apply considerations
from Section 5.3.1 of [RFC-5213], (point 13), to determine if the
request is re-registration request or a de-registration request
and the respective considerations from below MUST be applied.
3.1.2.2. Initial Binding Registration (New Mobility Session)
o If there is at least one IPv4 Home Address option present in the
Proxy Binding Update message with the IPv4 address value set to
ALL_ZERO, the local mobility anchor MUST allocate one or more IPv4
home addresses to the mobile node and associate them to the new
mobility session created for that mobile node. The decision on
how many IPv4 home addresses to be allocated can be based on a
domain-wide policy or a policy specific to that mobile node.
o If there are one or more IPv4 Home Address options present in the
received Proxy Binding Update message (with the IPv4 address field
in the option set to a NON_ZERO value), the local mobility anchor
before accepting the request, MUST ensure the address is owned by
the local mobility anchor and further the mobile node is
authorized to use that address. If the mobile node is not
authorized for a specific address, the local mobility anchor MUST
reject the request and send a Proxy Binding Acknowledgement
message with Status field set to
NOT_AUTHORIZED_FOR_IPV4_HOME_ADDRESS (mobile node not authorized
for the requesting IPv4 Home Address). It MUST also set the
status field value in the corresponding IPv4 Address
Acknowledgement option [ID-DSMIP6] to 129 (Administratively
prohibited).
o If the local mobility anchor is unable to allocate an IPv4 address
due to lack of resources, it MUST reject the request and send a
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Proxy Binding Acknowledgement message with Status field set to 130
(Insufficient resources). It MUST also set the status field value
in the corresponding IPv4 Address Acknowledgement option [ID-
DSMIP6], to 128 (Failure, reason unspecified).
o Upon accepting the request, the local mobility anchor MUST create
a Binding Cache entry for this mobility session. However, if the
request also contains one or more Home Network Prefix options,
there should still be only one Binding Cache entry that should be
created for this mobility session. The created Binding Cache
entry MUST be used for managing both IPv4 and IPv6 home address
bindings. The fields in the Binding Cache entry MUST be updated
with the accepted values for that binding.
o The local mobility anchor MUST establish a bi-directional tunnel
to the mobile access gateway and with the encapsulation mode as
negotiated. When using IPv6 transport, the encapsulation mode is
IPv4 over IPv6.
o The local mobility anchor MUST create IPv4 host route(s) for
tunneling the packets received for any of the mobile node's home
address(es) associated with this mobility session.
o The local mobility anchor MUST send the Proxy Binding
Acknowledgement message with the Status field set to 0 (Proxy
Binding Update Accepted). The message MUST be constructed as
specified in Section 3.1.2.6.
3.1.2.3. Binding Lifetime Extension (No handoff)
All the consideration from Section 5.3.2 of [RFC-5213] MUST be
applied.
3.1.2.4. Binding Lifetime Extension (After handoff)
o The local mobility anchor MUST remove the previously created host
route(s), towards the mobile access gateway where the mobile node
was anchored prior to the handoff.
o The local mobility anchor MUST create a host route(s) for
tunneling the packets received for any of the mobile node's home
address(es) associated with this mobility session.
o The required forwarding state identified in Section 5.3.6 of [RFC-
5213] is for IPv6 payload traffic. Those considerations apply for
IPv4 payload traffic as well. However, if IPv4 transport is in
use, considerations from Section 4.0 MUST be applied.
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3.1.2.5. Binding De-Registration
All the consideration from Section 5.3.5 of [RFC-5213] MUST be
applied. Additionally, for removing the routing state as part of the
Binding Cache entry deletion, any IPv4 host route(s) added for this
mobility session MUST be removed.
3.1.2.6. Constructing the Proxy Binding Acknowledgement Message
The local mobility anchor when sending the Proxy Binding
Acknowledgement message to the mobile access gateway MUST construct
the message as specified in Section 5.3.6 of [RFC-5213].
Additionally, the following considerations MUST be applied.
o Section 5.3.6 of [RFC-5213] requires the local mobility anchor to
include at least one instance of Home Network Prefix option in the
Proxy Binding Acknowledgement message that it sends to the mobile
access gateway. However, if the received Proxy Binding Update
message has only the IPv4 Home Address option and did not contain
the Home Network Prefix option(s), then the local mobility anchor
MUST NOT include the Home Network Prefix option in the reply.
o The IPv4 Address Acknowledgement option(s) 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 Proxy Binding Update is rejected, then there
MUST be an IPv4 Address Acknowledgement option for each of the
IPv4 Home Address options present in the request and with the
address value and the prefix length in the option set to the
values present in the corresponding request option. The
status field value in the option must be set to the specific
error code.
2. For all other cases, there MUST be an IPv4 Address
Acknowledgement option for each of the assigned IPv4 home
addresses assigned for that mobility session and with the
value in the option set to the allocated address value. The
prefix length in the option MUST be set to the prefix length
of the allocated address. The status field value in the
option must be set to 0 (Success).
o The IPv4 Default-Router Address option MUST be present, if the
Status field value in the Proxy Binding Acknowledgement message is
set to 0 (Proxy Binding Update Accepted). Otherwise, the option
MUST NOT be present. If the option is present, the default-router
address in the option MUST be set to the mobile node's default-
router address.
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3.1.2.7. Binding Cache Entry Lookup Considerations
The Binding Cache entry lookup considerations specified in Section
5.4.1.1 of [RFC-5213] is for using the Home Network Prefix as the key
parameter for identifying the Binding Cache entry. When using an
IPv4 address with a NON_ZERO value, the exact same considerations
specified in Section 5.4.1.1 of [RFC-5213] MUST be applied, with the
exception of using an IPv4 home address in place of an IPv6 home
network prefix.
3.1.3. Routing Considerations for the Local Mobility Anchor
Intercepting Packets Sent to the Mobile Node's IPv4 home address:
o When the local mobility anchor is serving a mobile node, it MUST
be able to receive packets that are sent to any of the mobile
node's IPv4 addresses. 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 address or for its
home subnet. This essentially enables IPv4 routers in that
network to detect the local mobility anchor as the last-hop router
for that subnet.
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.
o The format of the tunneled packet when payload protection is not
enabled:
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 2: Tunneled Packets from LMA to MAG
Forwarding Packets Sent by the Mobile Node:
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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
address field set to the mobile node's IPv4 home address.
3.2. Mobile Access Gateway Considerations
3.2.1. Extensions to Binding Update List Entry
For supporting the IPv4 home address mobility feature, the conceptual
Binding Update List entry data structure needs to be extended with
the following additional fields.
o List of IPv4 home addresses assigned to the mobile node's attached
interface. These IPv4 home addresses may have been statically
configured in the mobile node's policy profile, or, may have been
dynamically allocated by the local mobility anchor through the
received Proxy Binding Acknowledgement message. Each of these
IPv4 home address entries 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 message.
3.2.2. Extensions to Mobile Node's Policy Profile
For supporting this feature the mobile node's policy profile,
specified in Section 6.2 of [RFC-5213] MUST be extended with the
following additional fields.
Extensions to the mandatory section of the policy profile:
o This field indicates the scope of IP address mobility support that
needs to be extended for the mobile node. If the mobile access
gateway should enable support for IPv4, IPv6 or IPv4/IPv6 home
address mobility support.
Extensions to the optional section of the policy profile:
o The IPv4 home addresses assigned to the mobile node's attached
interface. These addresses have to be maintained on a per-
interface basis. The specific details on how the network
maintains the association between the addresses and the interfaces
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is outside the scope of this document. These address entries also
include the corresponding prefix length.
3.2.3. Signaling Considerations
3.2.3.1. Mobile Node Attachment and Initial Binding Registration
After detecting a new mobile node on its access link, the mobile
access gateway on the access link MUST determine if IPv4 home address
mobility support needs to be enabled for that mobile node. The
mobile node's policy profile specifies if IPv4-only, IPv6-only or
IPv4/IPv6 home address mobility service needs to be enabled for that
mobile node. Based on those policy considerations, if it is
determined that IPv4 home address mobility support is required to be
enabled for the mobile node, the considerations from section 6.9.1.1
of [RFC-5213] MUST be applied with the following exceptions.
o The IPv4 Home Address option(s) MUST be present in the Proxy
Binding Update request.
* If the mobile access gateway learns the mobile node's IPv4 home
address(es) either from its policy profile, or from other means
the mobile access gateway MAY choose to request the local
mobility anchor to allocate the requested addresses by
including an IPv4 Home Address option for each of those
addresses. The IPv4 address and the prefix length fields in
the option MUST be set to that specific address and its prefix
length. The (P) flag in the option MUST be set to 0.
* The mobile access gateway MAY also choose to request the local
mobility anchor for dynamic home address allocation. It can
include exactly one instance of the IPv4 home address option
with the IPv4 address value, prefix length fields and (P) flag
in the option set to a ALL_ZERO value. This essentially serves
as a request to the local mobility anchor for the IPv4 home
address allocation.
o The Proxy Binding Update message MUST be constructed as specified
in Section 6.9.1.5. However, the Home Network Prefix option(s)
MUST be present in the Proxy Binding Update only if IPv6 home
address mobility support also needs to be enabled for the mobile
node. Otherwise, the Home Network Prefix option(s) MUST NOT be
present.
o When using IPv4 transport for carrying the signaling messages, the
related considerations from section 4.0 MUST be applied.
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3.2.3.2. Receiving Proxy Binding Acknowledgement
All the considerations from section 6.9.1.2 of [RFC-5213] MUST be
applied with the following exceptions.
o If the received Proxy Binding Acknowledgement message has the
Status field value set to
NOT_AUTHORIZED_FOR_IPV4_HOME_ADDRESS_SUPPORT (The mobile node is
not authorized for IPv4 home address support), the mobile access
gateway SHOULD NOT send a Proxy Binding Update message including
the IPv4 Home Address option(s) till an administrative action is
taken.
o If the received Proxy Binding Acknowledgement message has the
Status field value set to NOT_AUTHORIZED_FOR_REQ_IPV4_HOME_ADDRESS
(The mobile node is not authorized for the requesting IPv4 home
address), the mobile access gateway SHOULD NOT request for the
same address again, but MAY request the local mobility anchor to
do the assignment of address by including exactly one instance if
IPv4 Home Address option with the address value set to ALL_ZERO.
o If there is no IPv4 Address Acknowledgement option present in the
received Proxy Binding Acknowledgement message, the mobile access
gateway MUST NOT enable IPv4 support for the mobile node and the
rest of the considerations from this section can be skipped.
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
forwarding for that specific IPv4 home address.
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 for
that mobile node. The entry MUST be updated with the assigned
IPv4 home address(es).
o The bi-directional established with the local mobility anchor with
IPv4 or IPv6 transport and using any of the supported
encapsulation mode, as per [RFC-5213] or as per this specification
when using IPv4 transport, MUST be enabled to carry IPv4 traffic.
o The mobile access gateway MUST set up the route for forwarding the
IPv4 packets received from the mobile node through the bi-
directional tunnel set up for that mobile node.
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3.2.3.3. Binding Re-Registration and De-Registrations
When sending a Proxy Binding Update either for extending the lifetime
of a mobility session or for de-registering the mobility session, the
respective considerations from [RFC-5213] MUST be applied. However,
the following additional considerations MUST be applied.
o There MUST be an IPv4 Home Address option for each of the assigned
IPv4 home address(es) for that mobility session. The IPv4 address
and the prefix length fields in the option MUST be set to that
specific address and its prefix length. The (P) flag in the
option MUST be set to 0.
o The Home Network Prefix option(s) MUST NOT be present if the same
option(s) was not present in the initial Proxy Binding Update
message. Otherwise considerations from [RFC-5213] with respect to
this option MUST be applied.
3.2.4. Routing Considerations for the Mobile Access Gateway
o On receiving a packet from the bi-directional tunnel established
with the mobile node's local mobility anchor, the mobile access
gateway MUST remove the outer header before forwarding the packet
to the mobile node.
o Considerations from Section 6.10.3 of [RFC-5213] MUST be applied
with respect the local routing and on the use of
EnableMAGLocalRouting flag.
o On receiving a packet from a mobile node connected to its access
link, the packet MUST be forwarded to the local mobility anchor
through the bi-directional tunnel established with the local
mobility anchor. The encapsulation considerations specified in
section 3.1.3 MUST be applied.
3.3. Mobility Options and Status Codes
For supporting IPv4 home address mobility feature, this specification
defines the following new options and Status Codes.
3.3.1. 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.
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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 3: IPv4 Default-Router Address Option
3.3.2. Status Codes
This document defines the following new Status values for use in the
Proxy Binding Acknowledgement message. These values are to be
allocated from the same numbering space, as defined in Section 6.1.8
of [RFC-3775].
NOT_AUTHORIZED_FOR_IPV4_HOME_ADDRESS: IANA
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Mobile node not authorized for the requesting IPv4 home address
3.4. Supporting DHCP Based Address Configuration
This section explains how DHCP based address configuration support
can be enabled for a mobile node in a Proxy Mobile IPv6 domain. It
explains the protocol operation, supported DHCP server deployment
configurations and the protocol interactions between DHCP agents and
mobility entities in each of the supported configurations.
This specification supports the following two DHCP deployment
configurations.
o DHCP relay agent co-located with the mobile access gateway.
o DHCP server co-located in the mobile access gateway.
The following are the configuration requirements:
o The DHCP server or the DHCP relay agent configured on the mobile
access gateway is required to have an IPv4 address for exchanging
the DHCP messages with the mobile node. This address can either
the IPv4 Proxy Care-of Address or the mobile node's default-router
address provided by the local mobility anchor. Optionally, all
the DHCP servers co-located with the mobile access gateways in the
Proxy Mobile IPv6 domain can be configured with a fixed IPv4
address. This can be a virtual address used only for the DHCP
protocol communication on any of the access links. This address
will be the server identifier in the DHCP messages.
o The DHCP server identifies the a DHCP client either from the
client identifier or the client hardware address (chaddr). A
mobile node in a Proxy Mobile IPv6 domain may present any of these
identifiers to the DHCP server as long as the identifier remains
the same through out the mobile node's attachment in that Proxy
Mobile IPv6 domain. If the client hardware address is used as the
identifier and if the mobile node performs an handoff between two
interfaces, this hardware identifier will change and the DHCP
server will not be able to identify the mobile node. Thus, it is
recommended that the DHCP client in the mobile node is configured
to use a stable client identifier that does not change during the
active life of that DHCP session.
o All the DHCP servers co-located with the mobile access gateways in
a Proxy Mobile IPv6 domain SHOULD be configured with the same set
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of DHCP option values (Ex: DNS Server, SIP Server ..etc.).
3.4.1. DHCP Server co-located with the Mobile Access Gateway
Figure 4 shows the operational sequence of the home address
assignment when a DHCP server is co-located with the mobile access
gateways.
MN MAG(DHCP-S) LMA
|------>| | 1. DHCPDISCOVERY
| |------->| 2. Proxy Binding Update *
| |<-------| 3. Proxy Binding Acknowledgement (IPv4HoA)
| |========| 4. Tunnel/Route Setup*
|<------| | 5. DHCPOFFER (IPv4 HoA)
|------>| | 6. DHCPREQUEST (IPv4 HoA)
|<------| | 7. DHCPACK
| | |
* DHCP discovery (no.1) and PBU (no.2) are operated in parallel.
* Tunnel/Route setup(no.4) and DHCPOFFER/REQUEST/ACK(no.5-7)
are processed in parallel.
Figure 4: Overview of DHCP Server located at Mobile Access Gateway
Initial IPv4 Home Address Assignment:
o If the mobile node attached to the access link sends a
DHCPDISCOVERY message, the DHCP server co-located with the mobile
access gateway will trigger the mobile access gateway to complete
the Proxy Mobile IPv6 signaling. This is the required interaction
between these two protocols. If the mobile access gateway is
unable to complete the Proxy Mobile IPv6 signaling or if the local
mobility anchor does not assign an IPv4 address for the mobile
node, the mobile access gateway MUST tear down the point-to-point
link shared with the mobile node.
o After a successful completion of the Proxy Mobile IPv6 signaling
and acquiring the mobile node's IPv4 home address assigned by the
local mobility anchor, the DHCP server on the mobile access
gateway will send a DHCP offer message to the mobile node. The
offered address will the mobile node's IPv4 home address, assigned
by the local mobility anchor. The 'siaddr' field of the DHCPOFFER
message will be set to the mobile node's default-router address or
to the globally fixed address used for all DHCP servers. The
DHCPOFFER message will be unicasted to the mobile node.
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o If the mobile node sends the DHCPREQUEST message, the DHCP server
will send DHCPACK message, as per [RFC-2131].
IPv4 Home Address Renewal with the DHCP server (No Handoff):
o When the DHCP client goes into the DHCP-RENEWING-STATE [RFC-2131],
it simply unicasts DHCPREQUEST message including the assigned IPv4
home address in the 'requested IPv4 address' option. The
DHCPREQUEST is sent to the address specified in 'server
identifier' field of the previously received DHCPOFFER and DHCPACK
messages.
o The DHCP server will send a DHCPACK to the mobile node.
IPv4 Home Address Renewal with the different DHCP server (After
Handoff):
1. The use of Virtual DHCP server address
MN oMAG(DHCP-S) nMAG(DHCP-S)
| : |
RENEW------------->| 1. DHCPREQUEST (IPv4 HoA)
BOUND<-------------| 2. DHCPACK or DHCPNACK
| : |
2. The use of FORCERENEW [RFC3-203]
MN oMAG(DHCP-S) nMAG(DHCP-S)
| : |
RENEW------------->| 1. DHCPREQUEST*a (IPv4 HoA)
|<---------------| 2. FORCERENEW
|--------------->| 3. DHCPREQUEST*b (IPv4 HoA)
BOUND<-------------| 4. DHCPACK or DHCPNACK
| : |
*a DHCPREQUEST sent to oMAG
*b DHCPREQUEST sent to nMAG
3. The use of Individual DHCP server address
MN oMAG(DHCP-S) nMAG(DHCP-S)
| : |
RENEW------------->| 1. DHCPREQUEST (IPv4 HoA)
| : | (discarding & timeout)
REBINDING--------->| 2. DHCPDISCOVERY
|<---------------| 3. DHCPOFFER (IPv4 HoA)
|--------------->| 4. DHCPREQUEST(IPv4 HoA)
BOUND<-------------| 5. DHCPACK (IPv4 HoA)
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| : |
Figure 5: Renewing Address to different DHCP server
o When the DHCP client goes into the DHCP-RENEWING-STATE [RFC-2131],
it directly unicasts DHCPREQUEST message to the DHCP server. If
the mobile node moves and attaches to a new mobile access gateway,
it needs to update the DHCP server address to the new one (i.e.
the address of the currently attached mobile access gateway).
Thus, one of following operations is required.
o If the IPv4 virtual DHCP address is used, the DHCPREQUEST for
renewing address is received by the mobile access gateway to which
the mobile node is currently attached. The mobile access gateway
SHOULD reply DHCPACK or DHCPNACK depending on the correctness of
the requesting IPv4 home address in the DHCPREQUEST as shown in
Figure 5-1).
o If the IPv4 virtual DHCP address is not used, the mobile node
reconfigures the DHCP server address whenever it changes the
attached mobile access gateway.
* If a mobile access gateway receives any DHCP messages unicasted
to a different mobile access gateway from the mobile node, it
SHOULD unicast FORCERENEW message [RFC-3203] to the mobile node
as shown in Figure 5-2). In the FORCERENEW, the 'server
identifier' field MUST be overwritten by the IPv4 address of
the current mobile access gateway so that the client can update
the DHCP server address.
* If the IPv4 virtual DHCP address is not used and the FORCERENEW
[RFC-3203] is not supported at the mobile access gateway, the
mobile access gateway SHOULD discard any DHCPREQUEST message
sent not to the mobile access gateway itself, so that the
mobile node should go into the DHCP-REBINDING-STATE and
broadcast DHCPDISCOVERY without server identifier as shown in
Figure 5-3).
Additional Operation:
o At an point the mobile access gateway fails to extend the binding
lifetime with the local mobility anchor, it MUST send an
unsolicited DHCPNACK to the mobile node. It MUST also tear down
the point-to-point link shared with the mobile node.
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3.4.2. DHCP Relay Agent co-located with the Mobile Access Gateway
A DHCP relay is co-located with each mobile access gateway. A DHCP
server is located somewhere in the Proxy Mobile IPv6 domain or is co-
located with the local mobility anchor. Figure 6 are the sequence of
IPv4 home address assignment using DHCP Relay.
MN MAG(DHCP-R) LMA DHCP-S
| |------->| | 1. Proxy Binding Update *
| |<-------| | 2. Proxy Binding Acknowledgement (IPv4HoA)
| |========| | 3. Tunnel/Route Setup*
|------>|-------------->| 4. DHCPDISCOVERY (IPv4HoA) via DHCP-R
|<------|<--------------| 5. DHCPOFFER (IPv4 HoA) via DHCP-R
|------>|-------------->| 6. DHCPREQUEST (IPv4 HoA) via DHCP-R
|<------|<--------------| 7. DHCPACK via DHCP-R
| | |
* Tunnel/Route setup(no.3) and DHCPOFFER/REQUEST/ACK (no.4-7)
are processed in parallel.
Figure 6: Overview of the DHCP relay located at mobile access gateway
Initial IPv4 Home Address Assignment:
o When the mobile access gateway receives a DHCPDISCOVERY message
from a mobile node, it MUST check whether it has already obtained
the IPv4 home address for the mobile node from the local mobility
anchor.
o If the IPv4 home address is not yet assigned by the local mobility
anchor, the mobile access gateway MUST send a Proxy Binding Update
for that.
o If the IPv4 home address is not assigned to the mobile node by the
local mobility anchor due to administrative policy or resource
limitation, it MUST discard the DHCPDISCOVERY messages from the
mobile node.
o Otherwise, it MUST add the DHCP relay agent information option
[RFC-3046] to the DHCPDISCOVERY message. The assigned IPv4 home
address (32-bit full address) is included in the Agent Remote ID
Sub-option of the DHCP relay agent information option. This sub-
option is used as a hint of address assignment of the DHCP server.
o When the mobile access gateway receives the DHCPOFFER from the
DHCP server, it MUST verify whether the DHCP server offers the
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correct IPv4 home address which is indicated in the Agent Remote
ID Sub-option of the DHCPDISOCVERY. If the DHCP server offers the
different address from the expected address, the mobile access
gateway MUST drop the DHCPOFFER.
o After the successful relaying the DHCPOFFER, the mobile access
gateway acts as a regular DHCP relay agent as [RFC-2131].
o As shown in Figure 6, the DHCP messages MAY be sent across an
administrative boundaries. The operators MUST ensure to secure
these messages. All the DHCP messages relayed by the mobile
access gateway can be tunneled over the local mobility anchor if
needed. Alternatively, if the networks in the Proxy Mobile IPv6
domain are secured enough, the mobile access gateway just relays
the DHCP messages to the server without the tunnel. For doing
this, all the mobile access gateway MUST have the route toward the
DHCP server. More remarks can be found in Section 7.
IPv4 Home Address Renewal to the same DHCP server: (No Hanover)
o When the DHCP client goes into the DHCP-RENEWING-STATE [RFC-2131],
it directly unicasts DHCPREQUEST message to the DHCP server. The
DHCP relay agent cannot receive the DHCPREQUEST for renewing
addresses. Thus, one of following operations is required.
* The DHCP relay agent SHOULD intercept all the DHCP packets
regardless of the destination address. Since the link between
a mobile node and a mobile access gateway is the point-to-point
link, it is possible to check the DHCP packets at the interface
by enabling the promiscuous mode.
* The cost of packets monitoring is not negligible. Therefore,
The DHCP relay agent MAY use the DHCP Server Identifier
Override Sub-option [RFC-5107] to intercept DHCPREQUESTs for
the address renewal. The DHCP client uses the DHCP server
address which is overridden by the DHCP relay agent address as
a destination address of DHCPREQUEST. The DHCP Server
Identifier Override Sub-option is recommended only when the
Virtual DHCP address is configured on all the mobile access
gateways. Otherwise, the DHCP relay agent address is changed
when the mobile node changes the attached mobile access
gateway. As a result, the DHCP relay agent MUST monitor DHCP
packets by force as described above.
o Once the DHCP relay agent intercepts the DHCPREQUEST from the
mobile node, it MUST verify the requesting IPv4 home address
stored in the DHCPREQUEST message. The verification is operated
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by checking it with the binding update list for the mobile node.
If the requesting IPv4 home address is not registered to the local
mobility anchor, the mobile access gateway MUST NOT relay the
DHCPREQUEST and MUST discard it.
o If the address verification is successfully completed, the DHCP
relay agent SHOULD forward the DHCPREQUEST to the DHCP server.
Additional Operations:
o If the mobile access gateway sends Proxy Binding Update for the
IPv4 home address and receives the unsuccessful Proxy Binding
Acknowledgement (by indicating the error codes), it MUST send
unsolicited DHCPNACK for the invalid IPv4 home address to the
mobile node. XXXX
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4. IPv4 Transport Support
The Proxy Mobile IPv6 specification [RFC-5213] requires 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 only
IPv4 addresses.
IPv4-Proxy-CoA IPv4-LMAA
| + - - - - - - + |
+--+ +---+ / \ +---+ +--+
|MN|----------|MAG|===== IPv4 Network =====|LMA|----------|CN|
+--+ +---+ \ / +---+ +--+
+ - - - - - - +
Figure 7: IPv4 Transport Network
When the local mobility anchor and the mobile access gateway are
configured and reachable using only IPv4 addresses, the mobile access
gateway serving a mobile node can potentially send the signaling
messages over IPv4 transport and register its IPv4 address as the
care-of address in the mobile node's Binding Cache entry. An IPv4
tunnel (with any of the supported encapsulation modes) can be used
for tunneling the mobile node's data traffic. The following are the
key aspects of this feature.
o The local mobility anchor and the mobile access gateway are both
configured and reachable using only an IPv4 address.
Additionally, both these entities are also IPv6 enabled and have
configured IPv6 addresses on its interfaces, as specified in [RFC-
5213], but are reachable only over an IPv4 transport.
o The mobile access gateway can be potentially in a private IPv4
network behind a NAT [RFC-3022] device, with a private IPv4
address configured on its egress interface. However, the local
mobility anchor must not be behind a NAT and must be using a
globally routable IPv4 address.
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 using the mobility header and the related semantics
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as specified in base Proxy Mobile IPv6 specification [RFC-5213],
but carried as a payload in an IPv4 packet (IPv4-UDP encapsulation
mode).
o 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 that mobile node.
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) will be used for carrying the mobile
node's IPv4 and IPv6 traffic. The supported encapsulation modes
for carrying mobile node's IPv4 or IPv6 packets when using IPv4
transport are as shown below.
* IPv4
* IPv4-UDP (Payload packet carried in an IPv4 packet with UDP
header)
* IPv4-UDP-TLV (Payload packet carried in an IPv4 packet with UDP
and TLV header. Refer to [ID-DSMIP6]).
* IPv4-UDP-ESP (Payload packet carried in an IPv4 packet with UDP
and ESP headers. Refer to [RFC-3948].
4.1. Local Mobility Anchor Considerations
4.1.1. Extensions to Binding Cache Entry
For supporting this feature, the conceptual Binding Cache entry data
structure maintained by the local mobility anchor [RFC-5213] MUST be
extended with the following additional parameters.
o The IPv4 address of the mobile access gateway. This is the
address configured on the egress interface of the mobile access
gateway that sent the Proxy Binding Update message. This address
can be obtained from the IPv4 Care-of Address option, present in
the received Proxy Binding Update message. If the option was not
present in the request, this field MUST be set to the source
address of the IPv4 header of the received Proxy Binding Update
message. However, if the received Proxy Binding Update message is
not sent as an IPv4 packet, this field MUST be set to ALL_ZERO
value.
o The IPv4 NAT translated address of the mobile access gateway. If
the mobile access gateway is not behind a NAT [RFC-3022], this
address will be the same as the address configured on the egress
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interface of the mobile access gateway. This address can be
obtained from the IPv4 header of the received Proxy Binding Update
message. However, if the received Proxy Binding Update message is
not sent as an IPv4 packet, this field MUST be set to ALL_ZERO
value.
4.1.2. Extensions to Mobile Node's Policy Profile
For supporting this feature the mobile node's policy profile,
specified in Section 6.2 of [RFC-5213] MUST be extended with the
following additional fields. This are mandatory fields of the policy
profile required for supporting this feature.
o A flag indicating if IPv4 transport should be used. The value of
this flag can be different at different mobile access gateway.
The specific details on how this flag is maintained on a per
mobile access gateway basis is outside the scope of this document.
o The IPv4 address of the local mobility anchor (IPv4-LMAA).
4.1.3. Signaling Considerations
This section provides the rules for processing the Proxy Mobile IPv6
signaling messages received over IPv4 transport. The local mobility
anchor MUST apply these signaling rules on the IPv4 UDP encapsulated
Proxy Binding Update messages received on DSMIP UDP port [ID-DSMIP6].
4.1.3.1. Processing Proxy Binding Updates
o If the received Proxy Binding Update message (encapsulated in IPv4
UDP packet) is protected using IPsec ESP header, then the message
MUST be authenticated as described in Section 4 of [RFC-5213].
However, if the IPv4 packet is not protected using IPsec ESP
header, then the message MUST be authenticated after removing the
outer IPv4 UDP header.
o All the considerations from Section 5.3.1 of [RFC-5213] MUST be
applied on the encapsulated Proxy Binding Update message, after
removing the outer IPv4 UDP header.
o If there is an IPv4 Care-of Address present in the request, the
NAT presence detection procedure specified in Section 4.1.3.3 MUST
be used for detecting the NAT in the path.
o Upon accepting the request, the local mobility anchor MUST set up
an IPv4 bi-directional tunnel to the mobile access gateway. The
tunnel endpoint addresses are IPv4-LMAA and the IPv4-Proxy-CoA.
The encapsulation mode MUST be determined from the below
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considerations.
* If the NAT is detected on the path, then the encapsulation mode
for the tunnel MUST be set to IPv4-UDP. Otherwise the
encapsulation mode MUST be set to IPv4. However, if the (F)
flag in the received Proxy Binding Update message is set to
value of 1 and even if NAT is not detected, then the
encapsulation mode MUST be set to IPv4-UDP.
* If the (T) flag in the Proxy Binding Update message is set to
value of 1, then the encapsulation mode MUST be set to IPv4-
UDP-TLV.
o The local mobility anchor MUST send the Proxy Binding
Acknowledgement message with the Status field value set to 0
(Proxy Binding Update Accepted). The message MUST be constructed
as specified in Section 4.1.3.2.
4.1.3.2. Constructing the Proxy Binding Acknowledgement Message
The local mobility anchor when sending the Proxy Binding
Acknowledgement message to the mobile access gateway MUST construct
the message as specified in Section 5.3.6 of [RFC-5213]. However, if
the received Proxy Binding Update message was encapsulated in an UDP
header of an IPv4 packet, the following additional considerations
MUST be applied.
o The NAT Detection option [ID-DSMIP6] MUST be present only if there
is a IPv4 Care-of Address option present in the received Proxy
Binding Update and if the NAT detection procedure resulted in
detecting a NAT on path. In all other cases, the option MUST NOT
be present.
o The Proxy Binding Acknowledgement message MUST be encapsulated in
an UDP header of an IPv4 packet.
o The source address in the IPv4 header of the message MUST be set
to the destination IPv4 address of the received request.
o If the mobile access gateway and the local mobility anchor are
using globally routable IPv4 addresses and if there is a security
associated that is based of IPv4 addresses, then the encapsulated
IPv4 packet (containing the IPv6 PBA) MUST be protected using
IPsec ESP [RFC-4301] mode and additionally there is no need to
apply IPsec ESP header on the IPv6 packet. In all other cases,
the Proxy Binding Acknowledgement message MUST be protected using
IPsec prior to the IPv4 UDP encapsulation.
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o The format of the Proxy Binding Acknowledgement message
encapsulated in an IPv4 UDP packet and protected using IPv6
security association.
IPv4 header (src=IPv4-LMAA, dst=pbu_src_address)
UDP header (sport=DSMIP_PORT, dport= pbu_sport)
/* IPv6 PBU Packet protected with ESP header */
Figure 8: Proxy Binding Acknowledgment Message encapsulated in
IPv4 header
o The format of the Proxy Binding Acknowledgement message
encapsulated in an IPv4 UDP packet and protected using IPv4
security association.
IPv4 header (src=IPv4-LMAA, dst=pbu_src_address)
ESP Header
UDP header (sport=DSMIP_PORT, dport= pbu_sport)
/* IPv6 PBU Packet protected with no ESP header */
Figure 9: Proxy Binding Acknowledgment encapsulated in IPv4 ESP
header
4.1.3.3. NAT Presence Detection
When the transport network between the local mobility anchor and the
mobile access gateway is an IPv4 network, the mobile access gateway
will send the Proxy Binding Update messages 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 DSMIPv6 specification
[ID-DSMIP6].
4.1.4. Routing Considerations
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4.1.4.1. Forwarding Considerations
Forwarding Packets to the Mobile Node:
o On receiving an IPv4 or an IPv6 packet from a correspondent node
with the destination address matching any of the mobile node's
IPv4 or IPv6 home addresses, the local mobility anchor MUST
forward the packet through the bi-directional tunnel set up for
that mobile node.
o The format of the tunneled packet is shown below.
IPv4 Header (src= IPv4-LMAA, dst= IPv4-Proxy-CoA)] /* Tunnel Header */
[UDP Header (src port=DSMIPv6, dst port=Z] /* If UDP encap nego */
[TLV Header] /* If TLV negotiated */
/* IPv6 or IPv4 Payload Packet */
IPv6 header (src= CN, dst= MN-HOA)
OR
IPv4 header (src= CN, dst= IPv4 MN-HoA)
Figure 10: Tunneled IPv4 Packet from LMA to MAG
o Forwarding Packets Sent by the Mobile Node:
* All the reverse tunneled packets (IPv4 and IPv6) that the local
mobility anchor receives from the mobile access gateway, after
removing the tunnel header (i.e., the outer IPv4 header along
with the UDP and TLV header, if negotiated) MUST be routed to
the destination specified in the inner packet header. These
routed packets will have the source address field set to the
mobile node's home address.
4.1.4.2. ECN Considerations
The ECN considerations specified in Section 5.6.3 of [RFC-5213] apply
for the IPv4 transport tunnels as well. The mobility agents at the
tunnel entry and exit points MUST handle ECN information as specified
in that document.
4.1.4.3. Bi-Directional Tunnel Management
The Tunnel Management considerations specified in section 5.6.1 of
[RFC-5213] apply for the IPv4 transport tunnels as well, with just
one difference that the encapsulation mode is different.
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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 maintained by the mobile access gateway [RFC-5213]
MUST be extended with the following additional parameters.
o The IPv4 address of the local mobility anchor. This address can
be obtained from the mobile node's policy profile.
o The IPv4 address of the mobile access gateway. This is the
address configured on the egress interface of the mobile access
gateway and is registered with the mobile node's local mobility
anchor as the IPv4 Proxy-CoA. However, if the mobile access
gateway is in a private IPv4 network and behind a NAT, the address
that is registered with the mobile node's local mobility anchor is
the NAT translated public IPv4 address.
4.2.2. Signaling Considerations
The mobile access gateway when sending a Proxy Binding Update message
to the local mobility anchor MUST construct the message as specified
in Section 6.9.1.5. However, if the mobile access gateway is in an
IPv4-only access network, the following additional considerations
MUST be applied.
o The Proxy Binding Update message MUST be encapsulated in an UDP
header of an IPv4 packet.
o The IPv4 Care-of Address option [ID-DSMIP6] MUST be present. The
IPv4 address in the option MUST be set to the mobile access
gateway's IPv4-Proxy-CoA.
o The packet MUST be constructed as specified in Section 4.2.3.
o When sending a Proxy Binding message for extending the lifetime of
a currently existing mobility session or for de-registering the
mobility session, the Proxy Binding Update message MUST be
constructed as the initial request.
Receiving Proxy Binding Acknowledgement
o If the received Proxy Binding Acknowledgement message
(encapsulated in IPv4 UDP packet) is protected using IPsec ESP
header, then the message MUST be authenticated as described in
Section 4 of [RFC-5213]. However, if the IPv4 packet is not
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protected using IPsec ESP header, then the message MUST be
authenticated after removing the outer IPv4 UDP header.
o All the considerations from Section 6.9.1.2 of [RFC-5213] MUST be
applied on the encapsulated Proxy Binding Acknowledgement message,
after removing the outer IPv4 UDP header.
o If the Status field indicates Success, the mobile access gateway
MUST setup a bi-directional tunnel to the local mobility anchor.
o Upon accepting the request, the local mobility anchor MUST set up
an IPv4 bi-directional tunnel to the mobile access gateway. The
tunnel endpoint addresses are IPv4-LMAA and the IPv4-Proxy-CoA.
The encapsulation mode MUST be determined from the below
considerations.
* If there is a NAT Detection option [ID-DSMIP6] in the received
Proxy Binding Acknowledgement message, then the encapsulation
mode for the tunnel MUST be set to IPv4-UDP. Otherwise the
encapsulation mode MUST be set to IPv4.
* If the (T) flag in the Proxy Binding Acknowledgement message is
set to value of 1, then the encapsulation mode MUST be set to
IPv4-UDP-TLV.
4.2.2.1. Constructing the Proxy Binding Update Message
o The source address in the IPv4 header MUST be set to IPv4-Proxy-
CoA of the mobile access gateway and the destination address MUST
be set to the local mobility anchor's IPv4-LMAA.
o The IPv4 Care-of Address option [ID-DSMIP6] MUST be present. The
address MUST be set to the mobile access gateway's IPv4-Proxy-CoA.
o If the configuration variable ForceIPv4UDPEncapsulationSupport is
set to value of 1, then the (F) flag in the Proxy Binding Update
message MUST be enabled.
o If the mobile access gateway and the local mobility anchor are
using globally routable IPv4 addresses and if there is a security
associated that is based of IPv4 addresses, then the encapsulated
IPv4 packet (containing the IPv6 PBU) MUST be protected using
IPsec ESP [RFC-4301] mode and additionally there is no need to
apply ESP header on the IPv6 packet. In all other cases, the
Proxy Binding Update message MUST be protected on the IPv6 packet
of the Proxy Binding Update message, prior to the IPv4
encapsulation.
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o The format of the Proxy Binding Update message encapsulated in an
IPv4 UDP packet with IPsec protection on the encapsulated packet:
IPv4 header (src=IPv4-Proxy-CoA, dst=IPv4-LMAA)
UDP header (sport=ANY, dport= DSMIP_PORT)
/* IPv6 PBU Packet protected with ESP header */
Figure 11: Proxy Binding Update Message encapsulated in IPv4 UDP
header
o The format of the Proxy Binding Update message encapsulated in an
IPv4 UDP packet and with IPsec protection on the encapsulated
packet:
IPv4 header (src=IPv4-Proxy-CoA, dst=IPv4-LMAA)
ESP Header
UDP header (sport=ANY, dport= DSMIP_PORT)
/* IPv6 PBU Packet protected with no ESP header */
Figure 12: Proxy Binding Update Message Encapsulated with IPsec
protection
4.2.2.2. Forwarding Considerations
Forwarding Packets Sent by the Mobile Node:
o On receiving an IPv4 or an IPv6 packet from the mobile node to any
destination, the mobile access gateway MUST tunnel the packet to
the local mobility anchor. The format of the tunneled packet is
shown below. However, considerations from Section 6.10.3 of [RFC-
5213] MUST be applied with respect the local routing and on the
use of EnableMAGLocalRouting flag.
IPv4 Header (src= IPv4-Proxy-CoA, dst= IPv4-LMAA)] /* Tunnel Header */
[UDP Header (src port=DSMIPv6, dst port=Z] /* If UDP encap nego */
[TLV Header] /* If TLV negotiated */
/* IPv6 or IPv4 Payload Packet */
IPv6 header (src= CN, dst= MN-HOA)
OR
IPv4 header (src= CN, dst= IPv4 MN-HoA)
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Figure 13: Tunneled IPv4 Packet from LMA to MAG
o Forwarding Packets received from the bi-directional tunnel:
o On receiving a packet from the bi-directional tunnel established
with the mobile node's local mobility anchor, the mobile access
gateway MUST remove the outer header before forwarding the packet
to the mobile node.
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5. Protocol Configuration Variables
5.1. Local Mobility Anchor - Configuration Variables
The local mobility anchor MUST allow the following variables to be
configured by the system management. The configured values for these
protocol variables MUST survive server reboots and service restarts.
AcceptIPv4UDPEncapsulationRequest
This flag indicates whether or not the local mobility anchor
should accept IPv4 UDP encapsulation support if there is NAT
detected in the path.
The default value for this flag is set to value of 1, indicating
that the local mobility anchor MUST enable IPv4 UDP encapsulation
support on detecting NAT in the path.
When the value for this flag is set to value of 0, the local
mobility anchor MUST NOT enable IPv4 UDP encapsulation support.
5.2. Mobile Access Gateway - Configuration Variables
The mobile access gateway MUST allow the following variables to be
configured by the system management. The configured values for these
protocol variables MUST survive server reboots and service restarts.
RequestIPv4UDPEncapsulationSupport
This flag indicates whether or not the mobile access gateway
should request the mobile node's local mobility anchor for IPv4
UDP encapsulation support if NAT is detected in the path.
The default value for this flag is set to value of 0, indicating
that the mobile access gateway MUST NOT request the mobile node's
local mobility anchor for IPv4 UDP encapsulation support.
When the value for this flag is set to value of 1, the mobile
access gateway MUST request the mobile node's local mobility
anchor for IPv4 UDP encapsulation support if there is NAT detected
in the path.
ForceIPv4UDPEncapsulationSupport
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This flag indicates whether or not the mobile access gateway
should request the mobile node's local mobility anchor for forcing
IPv4 UDP encapsulation support even when NAT is not detected in
path.
The default value for this flag is set to value of 0, indicating
that the mobile access gateway MUST NOT request the mobile node's
local mobility anchor for forcing IPv4 UDP encapsulation support
even when NAT is not detected in path.
When the value for this flag is set to value of 1, the mobile
access gateway MUST force the mobile node's local mobility anchor
for IPv4 UDP encapsulation support.
This flag is applicable only when the flag
RequestIPv4UDPEncapsulationSupport is set to a value of 1.
5.3. Proxy Mobile IPv6 Domain - Configuration Variables
All the mobile entities (local mobility anchors and mobile access
gateways) in a Proxy Mobile IPv6 domain MUST allow the following
variables to be configured by the system management. The configured
values for these protocol variables MUST survive server reboots and
service restarts. These variables MUST be globally fixed for a given
Proxy Mobile IPv6 domain resulting in the same values being enforced
on all the mobility entities in that domain.
FixedDHCPServerId
This variable indicates the DHCP server id that all the DHCP
servers co-located with the mobile access gateways SHOULD
configure in that Proxy Mobile IPv6 domain. If this variable is
initialized to ALL_ZERO value, it implies the use of fixed address
is not enabled for that Proxy Mobile IPv6 domain.
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6. IANA Considerations
This document defines a new Mobility Header option, IPv4 Default
Router Address option. This option is described in Section 3.3.1.
The Type value for this option needs to be assigned from the same
numbering space as allocated for the other mobility options, as
defined in [RFC-3775].
This document also defines new Binding Acknowledgement status values,
as described in Section 3.3.2. The status values MUST be assigned
from the same number space used for Binding Acknowledgement status
values, as defined in [RFC3775]. The allocated values for each of
these status values must be greater than 128.
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7. Security Considerations
All the security considerations from the base Proxy Mobile IPv6
protocol [RFC-5213] apply when using the extensions defined in this
document. Additionally, the following security considerations need
to be applied.
This document defines news mobility options for supporting the IPv4
Home Address assignment and IPv4 Transport Support features. It also
uses some of the mobility options from DSMIPv6 specification [ID-
DSMIP6]. These options are to be carried in Proxy Binding Update and
Proxy Binding Acknowledgement messages. The required security
mechanisms specified in the base Proxy Mobile IPv6 protocol for
protecting these signaling messages are sufficient when carrying
these mobility options.
This specification describes the use of IPv4 transport for exchanging
the signaling messages between the local mobility anchor and the
mobile access gateway. These messages are protected using IPsec
using the security associations established using the IPv4 transport
addresses and offer the same security as when the messages are
protected when using IPv6 transport.
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8. 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
9. Acknowledgments
The IPv4 support for Proxy Mobile IPv6 was initially covered in the
internet-draft [draft-sgundave-mip6-proxymip6-02.txt]. We would like
to thank all the authors of the document and acknowledge that initial
work.
Thanks to Jonne Soinnen, Julien Laganier, Zu Qiang, Premec Domagoj,
Sammy Touati and Niklas Nuemann for their helpful review of this
document.
10. References
10.1. 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.
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[RFC-2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, December 1998.
[RFC-3775] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in
IPv6", RFC 3775, June 2004.
[ID-DSMIP6] Soliman, H. et al, "Mobile IPv6 support for dual stack
Hosts and Routers (DSMIPv6)",
draft-ietf-mip6-mext-nemo-v4traversal-05.txt,July 2008.
[RFC-5213] Gundavelli, S., et.al, "Proxy Mobile IPv6", RFC 5213,
November 2007.
10.2. Informative References
[RFC-2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC-3011] G. Waters, "The IPv4 Subnet Selection Option for DHCP",
RFC 3011, November 2000.
[RFC-3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022, January 2001.
[RFC-3203] Y. T'Joens and C. Hublet and P. De Schrijver, "DHCP
reconfigure extension", RFC 3203, December 2001.
[RFC-4977] Tsirtsis, G., Soliman, H., "Problem Statement: Dual Stack
Mobility", RFC 4977, August 2007.
[RFC-5107] R. Johnson and J. Jumarasamy and K. Kinnear and M. Stapp,
"DHCP Server Identifier Override Suboption", RFC 5107, February 2008.
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Authors' Addresses
Ryuji Wakikawa
Toyota ITC / Keio University
6-6-20 Akasaka, Minato-ku
Tokyo 107-0052
Japan
Phone: +81-3-5561-8276
Fax: +81-3-5561-8292
Email: ryuji@jp.toyota-itc.com
Sri Gundavelli
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sgundave@cisco.com
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