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Keywords: Prefix Delegation, Proxy Mobile IPv6, PMIPv6, Mobile Router
Internet Engineering Task Force (IETF) X. Zhou
Request for Comments: 7148 ZTE Corporation
Category: Standards Track J. Korhonen
ISSN: 2070-1721 Broadcom
C. Williams
Consultant
S. Gundavelli
Cisco
CJ. Bernardos
UC3M
March 2014
Prefix Delegation Support for Proxy Mobile IPv6
Abstract
This specification defines extensions to the Proxy Mobile IPv6
protocol for allowing a mobile router in a Proxy Mobile IPv6 domain
to obtain IP prefixes for its attached mobile networks using DHCPv6
prefix delegation. Network-based mobility management support is
provided for those delegated IP prefixes just as it is provided for
the mobile node's home address. Even if the mobile router performs a
handoff and changes its network point of attachment, mobility support
is ensured for all the delegated IP prefixes and for all the IP nodes
in the mobile network that use IP address configuration from those
delegated IP prefixes.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7148.
Zhou, et al. Standards Track [Page 1]
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Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Zhou, et al. Standards Track [Page 2]
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Table of Contents
1. Introduction ....................................................4
2. Terminology .....................................................6
3. Solution Overview ...............................................7
3.1. Stated Assumptions .........................................7
3.2. Deployment Models ..........................................8
3.2.1. Delegating Router Co-located with Mobile
Access Gateway ......................................8
3.2.2. Delegating Router Co-located with Local
Mobility Anchor .....................................9
3.2.3. Static Configuration of Delegated Mobile
Network Prefixes ...................................12
4. Message Formats ................................................12
4.1. Delegated Mobile Network Prefix Option ....................12
4.2. Status Codes ..............................................14
5. Operational Details ............................................14
5.1. MAG Considerations ........................................14
5.1.1. Extension to Binding Update List Entry Data
Structure ..........................................14
5.1.2. Signaling Considerations ...........................14
5.1.3. DHCP -- MAG Interactions ...........................16
5.1.3.1. Delegating Router Co-located with
Mobile Access Gateway .....................17
5.1.3.2. Delegating Router Co-Located with
Local Mobility Anchor .....................18
5.1.4. Packet Forwarding ..................................19
5.2. LMA Considerations ........................................20
5.2.1. Extensions to Binding Cache Entry Data Structure ...20
5.2.2. Signaling Considerations ...........................20
5.2.3. Packet Forwarding ..................................22
5.3. Security Policy Database (SPD) Example Entries ............22
6. Security Considerations ........................................23
7. IANA Considerations ............................................24
8. Acknowledgements ...............................................24
9. References .....................................................25
9.1. Normative References ......................................25
9.2. Informative References ....................................26
Zhou, et al. Standards Track [Page 3]
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1. Introduction
Proxy Mobile IPv6 [RFC5213] enables network-based mobility management
support for an IP host without requiring its participation in any IP
mobility signaling. In Proxy Mobile IPv6 (PMIPv6), the mobile access
gateway (MAG) performs the mobility management function on behalf of
the mobile node (MN). The local mobility anchor (LMA) is the home
agent for the MN and the topological anchor point. The mobility
elements (LMA and MAGs) in the network allow an IP host to obtain an
IPv4 address and/or a set of IPv6 addresses and be able to obtain IP
mobility support for those IP address(es) within the Proxy Mobile
IPv6 domain. In this context, the mobility management support is
enabled for an individual IP host, which is the mobile node. The
IPv4 home address or the IPv6 home network prefixes are logically
bound to the link shared between the mobile access gateway and the
mobile node, and only the mobile node can use those IP address(es) by
configuring them on the interface attached to that link. Currently,
there is no mobility support for the mobile networks attached to a
mobile router (MR) in a Proxy Mobile IPv6 domain.
This specification defines extensions to the Proxy Mobile IPv6
protocol for allowing mobility support to the mobile networks
attached to a mobile router. These extension include definition of a
new mobility option that can be exchanged in the signaling messages
between the mobile access gateway and the local mobility anchor. The
mobile router can request the mobility entities in the Proxy Mobile
IPv6 domain for delegated IP prefix(es) using DHCP prefix delegation
extensions [RFC3633], static configuration of the prefixes, or
mechanisms specific to the access technology. The mobility entities
in the PMIPv6 network provide network-based mobility management
support for those delegated prefixes just as it is supported for a
home address. The delegated prefixes are hosted in the mobile
network attached to the mobile router. IP mobility is ensured for
all the IP nodes in the mobile network, even as the mobile router
performs a handoff by changing its point of network attachment within
the Proxy Mobile IPv6 domain. The local mobility anchor in the Proxy
Mobile IPv6 domain will not track the individual IP nodes in the
mobile network; it only tracks a single mobile router session that is
hosting the mobile network and associates the delegated IP prefixes
with that session. Although the protocol solution defined in this
specification also allows signaling IPv4 subnets between the mobile
access gateway and the local mobility anchor, the delegation of IPv4
subnets to the mobile router is out of the scope of this
specification.
Zhou, et al. Standards Track [Page 4]
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_----_
+-------+ _( )_
| |---( Internet )
| LMA | (_ _)
| | '----'
+-------+
|
=== === ===
== Proxy ==
== Mobile IPv6 ==
== Domain ==
=== === ===
___________|___________
| |
+-------+ +-------+
| MAG | | MAG |
+-------+ +-------+
.
.
- - - - - - - -
| +------+ |
| | MR | |
| +------+ |
| | |
| ------- |
| | | |
| LFN LFN |
- - - - - - - -
Figure 1: Mobile Router in Proxy Mobile IPv6 Domain
Within the context of this document, the definition of a mobile
router extends the definition of a mobile node from [RFC5213] by
adding routing capability between the mobile network and the point of
attachment of the mobile router. Local fixed nodes (LFNs) are IP
nodes in the mobile network; LFNs all move with the mobile router as
a single cluster. As the mobile router moves, the LFNs are not aware
of the mobility of the MR to a new point of attachment. Figure 1
illustrates a mobile router in a Proxy Mobile IPv6 domain.
The rest of this document identifies the protocol extensions and the
operational details of the local mobility anchor and mobile access
gateway for realizing prefix delegation support for Proxy Mobile
IPv6.
Zhou, et al. Standards Track [Page 5]
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
All the mobility-related terms used in this document are to be
interpreted as defined in Proxy Mobile IPv6 specifications [RFC5213]
and [RFC5844]. All the DHCP-related terms are to be interpreted as
defined in DHCPv6 Prefix Delegation for Network Mobility (NEMO)
[RFC6276], DHCPv6 Prefix Delegation (DHCPv6PD) [RFC3633], and Subnet
Allocation Option for DHCPv4 [RFC6656]. This document also provides
a context-specific explanation of the following terms used here and
originally defined in the Mobile Network terminology document
[RFC4885].
Mobile Router (MR)
The term "mobile router" is used to refer to an IP router whose
mobility is managed by the network while being attached to a Proxy
Mobile IPv6 domain. The mobile router is a mobile node as defined
in [RFC5213] but with additional capabilities for supporting an
attached mobile network. The MR's interface used for attachment
to the mobile access gateway is referred to as the "egress
interface". Any MR's interface used for attachment to the mobile
network is referred to as the "ingress interface". The mobility
entities in the Proxy Mobile IPv6 domain provide mobility for the
IPv4/IPv6 address(es) assigned to the mobile node's egress link
and also mobility support to the network prefixes hosted in the
network attached to the mobile router.
Mobile Network
A mobile network is an IP network attached to a mobile router.
There can be many IP nodes in this IP network. The mobile router
is a gateway for these IP nodes for reaching other IP networks or
the Internet. The mobile router and the attached IP networks move
as a single cluster.
Delegated Mobile Network Prefix (DMNP)
The Delegated Mobile Network Prefix is an IPv4/IPv6 prefix
delegated to a mobile router and is hosted in the mobile network.
The IP nodes in the mobile network will be able to obtain IP
address configuration from the DMNP and will have IP mobility
support for that address configuration. The DMNP is topologically
anchored on the local mobility anchor, and the mobility elements
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in the Proxy Mobile IPv6 domain provide IP mobility support for
the prefix by forwarding the mobile network traffic to the mobile
router.
Local Fixed Node (LFN)
A local fixed node is an IP node in the mobile network. As the
mobile router performs a handoff and changes its network point of
attachment, the local fixed node moves along with the mobile
router.
3. Solution Overview
This section lists the stated assumptions and provides an overview of
the operation of this specification. This document references three
different deployment scenarios and explains the protocol operation.
3.1. Stated Assumptions
o The mobile router is a mobile node as defined in [RFC5213] but
with additional capabilities for routing IP packets between its
egress interface (interface used for attachment to the mobile
access gateway) and any of its ingress interfaces (interfaces used
for attachment to the mobile network).
o This specification assumes that a mobile router is an IPv4 and/or
IPv6 router without any capability for mobility management.
o The mobile router can obtain the delegated IP prefix(es) for its
attached mobile networks using DHCPv6 prefix delegation, static
configuration, or mechanisms specific to access technology. This
document assumes DHCPv6 prefix delegation [RFC3633] in conjunction
with the Prefix Exclude Option [RFC6603] as the default mechanism
for prefix assignment to the mobile node. It defines an
interworking between the mobility entities and the DHCPv6
functional elements in a non-normative way. The mechanism that
delegates IPv4 subnets to a mobile router is out of the scope of
this specification.
o The mobile router obtains the IP address configuration for its
egress roaming interface as specified in [RFC5213] and [RFC5844].
The mobile router, along with its mobile networks, will be able to
perform handoff, change its point of attachment in the network,
and retain IP mobility support.
o When using DHCPv6 prefix delegation, this document assumes that
the mobile router uses its egress interface when making DHCPv6
requests.
Zhou, et al. Standards Track [Page 7]
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3.2. Deployment Models
This section explains the protocol operation used to support prefix
delegation in Proxy Mobile IPv6 for the following three deployment
models: i) delegating router co-located with mobile access gateway,
ii) delegating router co-located with local mobility anchor, and iii)
static configuration of delegated prefixes. High-level message call
flows between the mobile router, mobile access gateway, and the local
mobility anchor are presented while explaining the protocol
operation.
3.2.1. Delegating Router Co-located with Mobile Access Gateway
In this deployment scenario, the delegating router (DR) function, as
specified in [RFC3633], is co-located with the mobile access gateway,
and a requesting router (RR) function is enabled on the mobile
router.
Figure 2 shows the high-level message call flow for this case. The
mobile router attaches to the mobile access gateway, which triggers
the Proxy Mobile IPv6 signaling between the mobile access gateway and
the local mobility anchor, setting up the bidirectional tunnel
between them (regular Proxy Mobile IPv6 registration). After that,
the DHCPv6 requesting router function running on the mobile router
sends a Solicit message requesting a prefix. This message is
received by the DHCPv6 delegating router function running on the
mobile access gateway. The mobile access gateway then sends a Proxy
Binding Update message including a Delegated Mobile Network Prefix
(DMNP) option carrying the ALL_ZERO value [RFC5213]. This serves as
a request for the local mobility anchor to allocate a set of
delegated prefixes, conveyed back in one or more DMNP options in a
Proxy Binding Acknowledgement message. The DHCPv6-PD procedure is
then completed as described in [RFC3633], ending with the delegating
router sending a Reply message conveying the delegated prefixes. If
the requesting router includes a Rapid Commit option in its Solicit
message, it is preferable that the MAG respond directly with a Reply
message rather than with an Advertise message, as described in
[RFC3315], Section 17.2.3.
Zhou, et al. Standards Track [Page 8]
RFC 7148 Prefix Delegation Support for PMIPv6 March 2014
+-----+ +-----+ +-----+
| MR | | MAG | | LMA |
|(RR) | | (DR)| | |
+-----+ +-----+ +-----+
1) |-- MN Attach -----| |
| |--Proxy Binding Update----->|
| | |
| |<-------Proxy Binding Ack.--|
| | |
| |o==========================o|
2) | | PMIPv6 tunnel |
| |o==========================o|
3) |--Solicit for---->| |
| delegated prefix | |
4) | |--Proxy Binding Update----->|
| | |
5) | |<--Proxy Binding Ack.(DMNP)-|
| | |
- -<---+ |
6) |<------Advertise--| | |
| | | |
7) |--Request-------->| Optional |
| | | |
- -<---+ |
8) |<---Reply (DMNP)--| |
| | |
Figure 2: Delegating Router Co-located with Mobile Access Gateway
From an operational point of view, this is the simplest deployment
option, as it keeps a single protocol interface between the mobile
access gateway and the local mobility anchor.
3.2.2. Delegating Router Co-located with Local Mobility Anchor
In this deployment scenario, the delegating router (DR) function, as
specified in [RFC3633], is co-located with the local mobility anchor;
the requesting router (RR) function is enabled on the mobile router;
and a DHCPv6 relay agent (DRA) function is co-located on the mobile
access gateway.
Figure 3 shows the high-level message call flow for this case. The
mobile router attaches to the mobile access gateway, which triggers
the Proxy Mobile IPv6 signaling between the mobile access gateway and
the local mobility anchor, setting up the bidirectional tunnel
between them (regular Proxy Mobile IPv6 registration). After that,
the DHCPv6 requesting router function running on the mobile router
requests a prefix by sending a Solicit message. This message is
Zhou, et al. Standards Track [Page 9]
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received by the DHCPv6 relay agent function running on the mobile
access gateway, which then completes the DHCPv6 signaling, according
to [RFC3315]. The relay agent function SHOULD include the relay
agent remote-id option [RFC4649] into Relay-forward messages with
appropriate identity information to enable correlation of mobile
router identities used over DHCPv6 and PMIPv6.
Once the mobile access gateway gets the set of delegated prefixes
from the delegating router function running on the local mobility
anchor, the MAG conveys the delegated prefixes in a Proxy Binding
Update. This ensures that the local mobility anchor properly routes
the traffic addressed to the delegated prefixes via the PMIPv6 tunnel
established with the mobile access gateway and that mobility is
provided to these prefixes while the mobile router roams within the
PMIPv6 domain. Note that the relay agent function in the mobile
access gateway has to queue the Reply message for the duration of the
PMIPv6 signaling (steps 10 and 11) before forwarding the Reply
message to the requesting router. While this does not change
anything from the DHCPv6-PD protocol's point of view, implementations
will need to account for interactions between the timing of PMIPv6
signaling and the DHCPv6 timeout/retry logic.
Zhou, et al. Standards Track [Page 10]
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+-----+ +-----+ +-----+
| MR | | MAG | | LMA |
|(RR) | |(DRA)| |(DR) |
+-----+ +-----+ +-----+
1) |-- MN Attach -----| |
| |--------- PBU ----------->|
| | |
| |<-------- PBA ------------|
| | |
| |o========================o|
2) | | PMIPv6 tunnel |
| |o========================o|
3) |-- Solicit for -->| |
| delegated prefix | |
4) | |--- Solicit ------------->|
- - - <---+
5) | |<-- Advertise ------------| |
| | | |
6) |<- Advertise -----| | |
| | | Optional
7) |-- Request ------>| | |
| | | |
8) | |--- Request ------------->| |
- - - <---+
9) | |<-- Reply (DMNP) ---------|
| | |
10) | |----------PBU (DMNP)----->|
| | |
11) | |<---------PBA (DMNP)------|
| | |
12) |<-- Reply (DMNP) -| |
| | |
Figure 3: Delegating Router Co-located with Local Mobility Anchor
The DR function can also be located in other entities of the home
network aside from the LMA. This deployment model requires some
interworking between the DR and the LMA and is out of the scope of
this specification. Note that this additional interworking would
have no impact on the protocol between the LMA and MAG defined in
this document.
Zhou, et al. Standards Track [Page 11]
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3.2.3. Static Configuration of Delegated Mobile Network Prefixes
In this deployment scenario, the DMNPs of the mobile router are
statically configured in the mobile node's policy profile [RFC5213].
The DMNPs are statically configured in the mobile network attached to
the mobile router. The mobile router is the default-router for the
mobile networks.
Figure 4 shows a high-level message call flow for this example. The
mobile access gateway obtains statically configured mobile network
prefixes from the policy profile and registers them with the local
mobility anchor using the extensions specified in this document, that
is, the use of the Delegated Mobile Network Prefix (DMNP) option in
the Proxy Mobile IPv6 signaling. There is no explicit trigger from
the mobile router for registering or de-registering those prefixes.
As long as there is a mobility session for the mobile router's home
address, the local mobility anchor enables mobility support for the
mobile network prefixes.
+-----+ +-----+ +-----+
| MR | | MAG | | LMA |
| | | | | |
+-----+ +-----+ +-----+
1) |-- MN Attach -----| |
2) | - (Policy Profile) |
| | |
3) | |--------- PBU (DMNP) ---->|
| | |
4) | |<-------- PBA (DMNP) -----|
| | |
| |o========================o|
5) | | PMIPv6 tunnel |
| |o========================o|
| | |
Figure 4: Static Configuration of Delegated Mobile Network Prefixes
4. Message Formats
This section defines extensions to Proxy Mobile IPv6 [RFC5213]
protocol messages.
4.1. Delegated Mobile Network Prefix Option
A new mobility header option, the Delegated Mobile Network Prefix
option, is defined for use with Proxy Binding Update and Proxy
Binding Acknowledgement messages exchanged between a local mobility
anchor and a mobile access gateway. This option is used for
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exchanging the mobile router's IPv4/IPv6 DMNP. There can be multiple
instances of the Delegated Mobile Network Prefix option present in a
message.
The Delegated Mobile Network Prefix option has an alignment
requirement of 8n+2. 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 |V| Reserved | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
. .
+ IPv4 or IPv6 Delegated Mobile Network Prefix +
| (DMNP) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
55
Length
8-bit unsigned integer indicating the length of the option in
octets, excluding the Type and Length fields.
IPv4 Prefix (V)
If the IPv4 Prefix (V) flag is set to a value of (1), then it
indicates that the prefix that is included in the DMNP field is an
IPv4 prefix. If the IPv4 Prefix (V) flag is set to a value of
(0), then it indicates that the prefix that is included in the
DMNP field is an IPv6 prefix.
Reserved
This field is unused for now. The value MUST be initialized to 0
by the sender and MUST be ignored by the receiver.
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Prefix Length
8-bit unsigned integer indicating the number of leftmost bits
covering the network part of the address contained in the Prefix
field.
Delegated Mobile Network Prefix
Contains a mobile router's 4-byte IPv4 or a 16-byte IPv6 Delegated
Mobile Network Prefix.
4.2. Status Codes
This document defines the following new status code values for use in
the Proxy Binding Acknowledgement message. These values have been
allocated from the same number space as defined in Section 6.1.8 of
[RFC6275].
NOT_AUTHORIZED_FOR_DELEGATED_MNP: 177
Not authorized for DMNP
REQUESTED_DMNP_IN_USE: 178
Requested DMNP is in use
5. Operational Details
5.1. MAG Considerations
5.1.1. Extension to Binding Update List Entry Data Structure
In order to support this specification, the conceptual Binding Update
List Entry (BULE) data structure [RFC5213] needs to be extended to
include a Delegated Mobile Network Prefix (DMNP) list. Each entry in
the list is used for storing an IPv4/IPv6 mobile network prefix
delegated to the mobile router.
5.1.2. Signaling Considerations
During the mobile router's initial attachment procedure, the mobile
access gateway obtains the mobile router's policy profile, as per the
procedures defined in [RFC5213]. The mobile node's policy profile
defined in [RFC5213] is extended to include a parameter that
indicates Delegated Prefix support. If the policy profile indicates
that the mobile router is authorized for Delegated Prefix support,
then the considerations described next apply.
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The mobile access gateway MUST include one or more Delegated Mobile
Network Prefix (DMNP) options in the Proxy Binding Update message in
order to request the local mobility anchor to allocate DMNP(s) for
the mobile router.
If the mobile access gateway requests the local mobility anchor to
perform the prefix assignment, then:
o There MUST be exactly one instance of the Delegated Mobile Network
Prefix option with an ALL_ZERO value and with the (V) flag set to
a value of (0). This serves as a request to the local mobility
anchor to allocate a set of IPv6 DMNPs.
o There MUST be exactly one instance of the Delegated Mobile Network
Prefix option with an ALL_ZERO value and with the (V) flag set to
a value of (1). This serves as a request to the local mobility
anchor to allocate a set of IPv4 DMNP.
o If the received Proxy Binding Acknowledgement message has the
status field value set to NOT_AUTHORIZED_FOR_DELEGATED_MNP (not
authorized for DMNP), the mobile access gateway MUST NOT enable
mobility support for any of the prefixes in the mobile network,
and prefix delegation support has to be disabled.
o If the received Proxy Binding Acknowledgement message has the
status field value set to REQUESTED_DMNP_IN_USE (Requested DMNP is
in use), the mobile access gateway MUST NOT enable mobility
support for the requested prefixes. The mobile access gateway MAY
choose to send Proxy Binding Update message requesting the local
mobility anchor to perform the prefix assignment.
If the mobile access gateway provides the local mobility anchor with
the prefix(es) to be allocated, then:
o There MUST be exactly one instance of the Delegated Mobile Network
Prefix option with NON_ZERO prefix value [RFC5213] for each of the
mobile network prefixes that the mobile access gateway is
requesting the local mobility anchor to allocate. The prefix
value in the option is the prefix that is either statically
configured for that mobile router in the mobile node's policy
profile or obtained via interactions with the DHCP PD functions.
This serves as a request to the local mobility anchor to allocate
the requested IPv4/IPv6 prefix.
If the received Proxy Binding Acknowledgement message has the status
field value set to 0 (Proxy Binding Update accepted), the mobile
access gateway has to apply the following considerations.
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o The Delegated Mobile Network Prefix (DMNP) list in the mobile
router's Binding Update List entry has to be updated with the
allocated prefix(es). However, if the received message was in
response to a de-registration request with a lifetime value of
(0), then the DMNP list has to be removed along with the Binding
Update List entry.
o The mobile access gateway has to set up a policy-based route for
forwarding the IP packets received from the mobile network (with
the source IP address from any of the IPv4/IPv6 DMNPs) through the
bidirectional tunnel set up for that mobile router. However, if
the received message was in response to a de-registration request
with a lifetime value of (0), then the created forwarding state
has to be removed.
This specification assumes that all the mobile access gateways of a
PMIPv6 domain support the same prefix delegation mechanism. Any
differences will result in DMNPs getting de-registered and the mobile
network losing the prefix(es). This would result in the attached
local fixed nodes losing the assigned IP addresses. The mobile
router MAY explicitly deprecate these prefixes. Alternatively, the
lifetime of the addresses may expire.
5.1.3. DHCP -- MAG Interactions
This section describes the interactions between the DHCP and PMIPv6
logical entities running on the mobile access gateway. This section
is applicable only for deployments that use DHCPv6-based prefix
delegation (i.e., it does not apply if static configuration is used).
As described next, these interactions vary slightly depending on the
considered deployment model at the mobile access gateway (described
in Section 3.2).
The mobile router, acting as a requesting router as described in
[RFC3633], sends a Solicit message including one or more IA_PD
option(s) to the delegating router / DHCPv6 relay agent co-located on
the mobile access gateway. This message provides the needed trigger
for the mobile access gateway to request the local mobility anchor to
enable DMNP support for that mobility session. We next describe the
subsequent interactions depending on the deployment model.
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5.1.3.1. Delegating Router Co-located with Mobile Access Gateway
The mobile access gateway applies the considerations in Section 5.1.2
for requesting the local mobility anchor to enable delegated prefix
support. For example, if the mobile router is soliciting an IPv4
prefix, the mobile access gateway includes in the Proxy Binding
Update signaling a Delegated Mobile Network Prefix option with an
ALL_ZERO value and with the (V) flag set to a value of (1).
The mobile access gateway, upon successfully completing the Proxy
Binding Update signaling with the local mobility anchor (following
the considerations described in Section 5.1.2), adds the DMNPs to the
Binding Update List. Then, the mobile access gateway provides the
obtained prefixes to the DHCPv6 delegating router for prefix
assignment. The way in which these prefixes are passed to the DHCPv6
delegating router function is beyond the scope of this document.
o In case the Proxy Binding Update signaling with the local mobility
anchor is not completed successfully, for example, because the
local mobility anchor is not authorized for DMNP or the requested
prefix is in use, the DHCPv6 delegating router will send a Reply
message to the requesting router with no IA_PREFIX suboptions and
with a Status Code option as described in [RFC3633], Section 11.2.
The standard DHCPv6 considerations will be applied with respect to
the interactions between the delegating router and the requesting
router. The requesting router is provided with the delegated
prefix(es), which can then be then advertised in the mobile network
and therefore used by the local fixed nodes to autoconfigure IP
addresses, allowing them to gain access to the Internet.
Any time the requesting router releases the delegated prefixes, the
delegating router removes the assigned prefixes. To do so, the
mobile access gateway will send an Updated Proxy Binding Update
following the considerations described in Section 5.1.2 for
de-registering those prefixes. The way in which the DHCPv6
delegating router triggers the mobile access gateway in order to
de-register the prefixes is beyond the scope of this document.
In case the mobile router performs a handover and attaches to a
different mobile access gateway, the following cases are possible:
o The new mobile access gateway does not support the delegation of
mobile network prefixes described in this specification. In this
case, forwarding of the previously DMNPs is no longer performed.
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o The new mobile access gateway supports the delegation of mobile
network prefixes described in this specification. There are two
possible cases upon the reception of the Solicit message by the
delegating router. If the MAG already knows the DMNPs, it conveys
them in a DMNP option included in the Proxy Binding Update sent to
the local mobility anchor, which then authorizes them based on: a)
the content of the associated Binding Cache entry (if one exists),
b) the user profile (if the allocation is static), or c) checking
that the DMNPs are not already allocated. On the other hand, if
the mobile access gateway is not aware of the DMNPs, it will
include 0.0.0.0 / :: in a DMNP option included in the Proxy
Binding Update sent to the LMA, which will provide the right
prefixes back in the Proxy Binding Acknowledgement based on a) the
content of the associated Binding Cache entry (if one exits), b)
the profile (if static allocation is used), or c) dynamic
assignment.
5.1.3.2. Delegating Router Co-Located with Local Mobility Anchor
A DHCPv6 relay agent function running on the mobile access gateway
will forward the DHCP messages to the local mobility anchor that has
the co-located delegating router function. The requesting router and
the delegating router complete the DHCP messages related to prefix
delegation.
During the DHCPv6 exchange, the standard DHCPv6 considerations apply
with respect to the interactions between the delegating router,
DHCPv6 relay agent, and requesting router.
The mobile access gateway learns from the co-located DHCPv6 relay
agent the prefixes allocated by the delegating router. The way in
which the mobile access gateway obtains this information from the
DHCPv6 relay agent function is beyond the scope of this document.
The mobile access gateway will apply the considerations in
Section 5.1.2 for requesting the local mobility anchor to enable
delegated prefix support. The mobile access gateway will include
exactly one instance of the Delegated Mobile Network Prefix option
with NON_ZERO prefix value for each of the mobile network prefixes
that the mobile access gateway is requesting the local mobility
anchor to allocate. The prefix value(s) in the option will be the
prefix(es) obtained via DHCP prefix delegation.
The mobile access gateway, upon successfully completing the Proxy
Binding Update signaling with the local mobility anchor, will provide
the obtained prefixes to the DHCPv6 relay agent for prefix
assignment. The delegating router is provided with the delegated
prefix(es) completing the standard DHCPv6 signaling. These prefixes
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can then be advertised in the mobile network and therefore used by
the local fixed nodes to autoconfigure IP addresses, allowing them to
gain access to the Internet.
o In case the Proxy Binding Update signaling with the local mobility
anchor is not completed successfully, for example, because the
local mobility anchor is not authorized for DMNP, the requested
prefix is in use, or the delegated prefix(es) do not match the
ones allocated by DHCP prefix delegation, the DHCPv6 relay agent
MAY send a Reply message to the requesting router with no
IA_PREFIX suboptions and with a Status Code option as described in
[RFC3633], Section 11.2.
In case the mobile router performs a handover and attaches to a
different mobile access gateway, the following cases are possible:
o The new mobile access gateway does not support the delegation of
mobile network prefixes described in this specification. In this
case, forwarding of the previously delegated mobile network
prefixes is no longer performed.
o The new mobile access gateway supports the delegation of mobile
network prefixes described in this specification. There are two
possible cases upon the reception of the Solicit message by the
DHCPv6 relay agent. If the MAG already knows the DMNPs, it
conveys them in a DMNP option included in the Proxy Binding Update
sent to the local mobility anchor, which then authorizes them
based on: a) the content of the associated Binding Cache entry (if
one exists), b) the user profile (if the allocation is static), or
c) checking that the DMNPs are not already allocated. On the
other hand, if the mobile access gateway is not aware of the
DMNPs, it will include 0.0.0.0 / :: in a DMNP option included in
the Proxy Binding Update sent to the LMA, which will provide the
right prefixes back in the Proxy Binding Acknowledgement based on
a) the content of the associated Binding Cache entry (if one
exits), b) the profile (if static allocation is used), or c)
dynamic assignment.
5.1.4. Packet Forwarding
On receiving an IP packet from a mobile router, the mobile access
gateway MUST ensure, before tunneling the packet to the local
mobility anchor, that there is an established binding for the mobile
router and that the source IP address of the packet is a prefix
delegated to that mobile router. If the source address of the
received IP packet is not part of the DMNP, then the mobile access
gateway MUST NOT tunnel the packet to the local mobility anchor.
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On receiving an IP packet from the bidirectional tunnel established
with the local mobility anchor, the mobile access gateway MUST first
decapsulate the packet (remove the outer header) and then use the
destination address of the (inner) packet to forward it on the
interface through which the mobile router is reachable.
The above forwarding considerations are not applicable to the IP
traffic sent/received to/from the mobile router's home address (IPv4
HoA / Home Network Prefix (HNP)). For the mobile router's home
address traffic, forwarding considerations from [RFC5213] and
[RFC5844] continue to apply.
5.2. LMA Considerations
5.2.1. Extensions to Binding Cache Entry Data Structure
In order to support this specification, the conceptual Binding Cache
entry (BCE) data structure [RFC5213] needs to be extended to include
the Delegated Mobile Network Prefix (DMNP) list. Each entry in the
list represents a DMNP.
5.2.2. Signaling Considerations
If the Proxy Binding Update message does not include any Delegated
Mobile Network Prefix option(s) (Section 4.1), then the local
mobility anchor MUST NOT enable Delegated Prefix support for the
mobility session, and the Proxy Binding Acknowledgement message that
is sent in response MUST NOT contain any Delegated Mobile Network
Prefix option(s).
If the Proxy Binding Update message includes one or more Delegated
Mobile Network Prefix options, but the local mobility anchor is not
configured with Delegated Prefix support, then the local mobility
anchor will ignore the option(s) and process the rest of the option
as specified in [RFC5213]. This would have no effect on the
operation of the rest of the protocol. The Proxy Binding
Acknowledgement message that is sent in response will not include any
Delegated Mobile Network Prefix option(s).
If the Proxy Binding Update message has the Delegated Mobile Network
Prefix option(s) and if the local mobility anchor is configured for
Delegated Prefix support, then the local mobility anchor MUST enable
the Delegated Mobile Network Prefix option for that mobility session.
The Proxy Binding Acknowledgement message that is sent in response
MUST include the Delegated Mobile Network Prefix option(s). The
following considerations apply.
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o If there is at least one instance of the Delegated Mobile Network
Prefix option with an ALL_ZERO [RFC5213] prefix value, then this
serves as a request for the local mobility anchor to perform the
assignment of one or more DMNPs.
* A Delegated Mobile Network option with an ALL_ZERO value and
with the (V) flag set to a value of (0) is a request for the
local mobility anchor to allocate one or more IPv6 prefixes.
* A Delegated Mobile Network option with an ALL_ZERO value and
with the (V) flag set to a value of (1) is a request for the
local mobility anchor to allocate one or more IPv4 prefixes.
* Inclusion of multiple instances of Delegated Mobile Network
options with ALL_ZERO values, one with the (V) flag set to a
value of (1) and another instance with the (V) flag set to a
value of (0), is a request to allocate both IPv4 and IPv6
prefixes.
o If there are no instances of the Delegated Mobile Network Prefix
option present in the request with an ALL_ZERO value but a
specific prefix value exists, then this serves as a request for
the local mobility anchor to perform the allocation of the
requested prefix(es).
* If any one of the requested prefixes are assigned to some other
mobility node, or not from an authorized pool that the local
mobility can allocate for that mobility session, then the Proxy
Binding Update MUST be rejected by sending a Proxy Binding
Acknowledgement message with the Status field set to
REQUESTED_DMNP_IN_USE (Requested DMNP is in use).
Upon accepting the Proxy Binding Update, the local mobility anchor
MUST send a Proxy Binding Acknowledgement message with the Status
field set to 0 (Proxy Binding Update accepted).
o The message MUST include one instance of the Delegated Mobile
Network Prefix option for each of the allocated IPv4/IPv6 DMNPs.
o The Delegated Mobile Network Prefix (DMNP) list in the mobile
router's Binding Cache entry has to be updated with the allocated
prefix(es). However, if the request is a de-registration request
with a lifetime value of (0), the DMNP list has to be removed
along with the Binding Cache entry.
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o A route (or a platform-specific equivalent function that sets up
the forwarding) for each of the allocated prefixes over the tunnel
has to be added. However, if the request is a de-registration
request, with a lifetime value of (0), all the IPv4/IPv6 delegated
prefix routes created for that session have to be removed.
5.2.3. Packet Forwarding
The local mobility anchor MUST advertise a connected route into the
routing infrastructure for the IP prefixes delegated to all of the
mobile routers that it is serving. This step essentially enables the
local mobility anchor to be a routing anchor for those IP prefixes
and be able to intercept IP packets sent to those mobile networks.
On receiving a packet from a correspondent node with the destination
address matching any of the mobile router's DMNPs, the local mobility
anchor MUST forward the packet through the bidirectional tunnel set
up with the mobile access gateway where the mobile router is
attached.
On receiving an IP packet from the bidirectional tunnel established
with the mobile access gateway, the local mobility anchor MUST first
decapsulate the packet (remove the outer header) and then use the
destination address of the (inner) packet for forwarding decisions.
The local mobility anchor MUST ensure that there is an established
binding for the mobile router and that the source IP address of the
packet is a prefix delegated to a mobile router reachable over that
bidirectional tunnel.
The above forwarding considerations are not applicable to the IP
traffic sent/received to/from the mobile router's home address (IPv4
HoA/HNP). For the mobile router's home address traffic, forwarding
considerations from [RFC5213] and [RFC5844] continue to apply.
5.3. Security Policy Database (SPD) Example Entries
The use of DHCPv6, as described in this document, requires message
integrity protection and source authentication. The IPsec security
mechanism used by Proxy Mobile IPv6 [RFC5213] for securing the
signaling messages between the mobile access gateway and the local
mobility anchor can be used for securing the DHCP signaling between
the mobile access gateway and the local mobility anchor.
The Security Policy Database (SPD) and Security Association Database
(SAD) entries necessary to protect the DHCP signaling is specified
below. The format of these entries is based on [RFC4877]
conventions. The SPD and SAD entries are only example
configurations. A particular implementation of mobile access gateway
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and local mobility anchor implementation can configure different SPD
and SAD entries as long as they provide the required security for
protecting DHCP signaling messages.
For the examples described in this document, a mobile access gateway
with address "mag_address_1" and a local mobility anchor with address
"lma_address_1" are assumed.
mobile access gateway SPD-S:
- IF local_address = mag_address_1 &
remote_address = lma_address_1 & proto = UDP &
local_port = any & remote_port = DHCP
Then use SA1 (OUT) and SA2 (IN)
mobile access gateway SAD:
- SA1(OUT, spi_a, lma_address_1, ESP, TRANSPORT):
local_address = mag_address_1 &
remote_address = lma_address_1 &
proto = UDP & remote_port = DHCP
- SA2(IN, spi_b, mag_address_1, ESP, TRANSPORT):
local_address = lma_address_1 &
remote_address = mag_address_1 &
proto = UDP & local_port = DHCP
local mobility anchor SPD-S:
- IF local_address = lma_address_1 &
remote_address = mag_address_1 & proto = UDP &
local_port = DHCP & remote_port = any
Then use SA2 (OUT) and SA1 (IN)
local mobility anchor SAD:
- SA2(OUT, spi_b, mag_address_1, ESP, TRANSPORT):
local_address = lma_address_1 &
remote_address = mag_address_1 &
proto = UDP & local_port = DHCP
- SA1(IN, spi_a, lma_address_1, ESP, TRANSPORT):
local_address = mag_address_1 &
remote_address = lma_address_1 &
proto = UDP & remote_port = DHCP
6. Security Considerations
The Delegated Mobile Network Prefix option defined in this
specification is for use in Proxy Binding Update and Proxy Binding
Acknowledgement messages. This option is carried like any other
mobility header option as specified in [RFC5213]. Therefore, it
inherits from [RFC5213] its security guidelines and does not require
any additional security considerations.
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The use of DHCPv6 in this specification is as defined in the DHCPv6
base specification [RFC3315] and DHCPv6 prefix delegation
specification [RFC3633]. The security considerations specified in
those specifications apply to this document.
If IPsec is used, the IPsec security association that is used for
protecting the Proxy Binding Update and Proxy Binding Acknowledgement
also needs to be used for protecting the DHCPv6 signaling between the
mobile access gateway and the local mobility anchor. Considerations
specified in Section 5.3 identify the extensions to security policy
entries [RFC4301]
7. IANA Considerations
o This specification defines a new mobility header option, the
Delegated Mobile Network Prefix option. This mobility option is
described in Section 4.1. The type value 55 for this message has
been allocated from the "Mobility Options" registry at http://
www.iana.org/assignments/mobility-parameters.
o This document also defines two new status code values for use in
the Proxy Binding Acknowledgement message, as described in
Section 4.2. These status codes are
NOT_AUTHORIZED_FOR_DELEGATED_MNP (not authorized for DMNP) with a
status code value of 177 and REQUESTED_DMNP_IN_USE (Requested DMNP
is in use) with a status code value of 178. These values have
been assigned from the same number space as allocated for other
status codes [RFC6275].
8. Acknowledgements
The authors would like to acknowledge Ryuji Wakikawa, Alexandru
Petrescu, Behcet Sarikaya, Seil Jeon, Basavaraj Patil, Brian
Haberman, and Michal Hoeft for all the discussions and reviews of
this document.
The work of Carlos J. Bernardos has also been partially supported by
the European Community's Seventh Framework Programme (FP7-ICT-2009-5)
under grant agreement n. 258053 (MEDIEVAL project) and by the
Ministry of Science and Innovation of Spain under the QUARTET project
(TIN2009-13992-C02-01).
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9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC4649] Volz, B., "Dynamic Host Configuration Protocol for IPv6
(DHCPv6) Relay Agent Remote-ID Option", RFC 4649, August
2006.
[RFC4877] Devarapalli, V. and F. Dupont, "Mobile IPv6 Operation with
IKEv2 and the Revised IPsec Architecture", RFC 4877, April
2007.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
Mobile IPv6", RFC 5844, May 2010.
[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.
[RFC6276] Droms, R., Thubert, P., Dupont, F., Haddad, W., and C.
Bernardos, "DHCPv6 Prefix Delegation for Network Mobility
(NEMO)", RFC 6276, July 2011.
[RFC6603] Korhonen, J., Savolainen, T., Krishnan, S., and O. Troan,
"Prefix Exclude Option for DHCPv6-based Prefix
Delegation", RFC 6603, May 2012.
Zhou, et al. Standards Track [Page 25]
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9.2. Informative References
[RFC4885] Ernst, T. and H-Y. Lach, "Network Mobility Support
Terminology", RFC 4885, July 2007.
[RFC6656] Johnson, R., Kinnear, K., and M. Stapp, "Description of
Cisco Systems' Subnet Allocation Option for DHCPv4", RFC
6656, July 2012.
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Authors' Addresses
Xingyue Zhou
ZTE Corporation
No.50 Software Avenue, Yuhuatai District
Nanjing
China
Phone: +86-25-8801-4634
EMail: zhou.xingyue@zte.com.cn
Jouni Korhonen
Broadcom
Porkkalankatu 24
Helsinki FIN-00180
Finland
EMail: jouni.nospam@gmail.com
Carl Williams
Consultant
San Jose, CA
USA
EMail: carlw@mcsr-labs.org
Sri Gundavelli
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
EMail: sgundave@cisco.com
Carlos J. Bernardos
Universidad Carlos III de Madrid
Av. Universidad, 30
Leganes, Madrid 28911
Spain
Phone: +34 91624 6236
EMail: cjbc@it.uc3m.es
URI: http://www.it.uc3m.es/cjbc/
Zhou, et al. Standards Track [Page 27]