NETLMM WG S. Gundavelli
Internet-Draft K. Leung
Intended status: Standards Track Cisco
Expires: October 10, 2007 V. Devarapalli
Azaire Networks
K. Chowdhury
Starent Networks
B. Patil
Nokia Siemens Networks
April 08, 2007
Proxy Mobile IPv6
draft-ietf-netlmm-proxymip6-00.txt
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
Host based IPv6 mobility is specified in Mobile IPv6 base
specification [RFC3775]. In that model, the mobile node is
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responsible for doing the signaling to its home agent to enable
session continuity as it moves between subnets. The design principle
in the case of host-based mobility relies on the mobile node being in
control of the mobility management. Network based mobility allows IP
session continuity for a mobile node without its involvement in
mobility management. This specification describes a protocol
solution for network based mobility management that relies on Mobile
IPv6 signaling and reuse of home agent functionality. A proxy
mobility agent in the network which manages the mobility for a mobile
node is the reason for referring to this protocol as Proxy Mobile
IPv6.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions & Terminology . . . . . . . . . . . . . . . . . . 5
2.1. Conventions used in this document . . . . . . . . . . . . 5
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
3. Proxy Mobile IPv6 Protocol Overview . . . . . . . . . . . . . 8
4. Proxy Mobile IPv6 Protocol Security . . . . . . . . . . . . . 11
4.1. Peer Authorization Database Entries . . . . . . . . . . . 12
4.2. Security Policy Database Entries . . . . . . . . . . . . . 12
5. Local Mobility Anchor Operation . . . . . . . . . . . . . . . 13
5.1. Extensions to Binding Cache Conceptual Data Structure . . 14
5.2. Bi-Directional Tunnel Management . . . . . . . . . . . . . 15
5.3. Routing Considerations . . . . . . . . . . . . . . . . . . 16
5.4. Local Mobility Anchor Address Discovery . . . . . . . . . 17
5.5. Sequence Number and Time-Stamps for Message Ordering . . . 17
5.6. Route Optimizations Considerations . . . . . . . . . . . . 19
5.7. Mobile Prefix Discovery Considerations . . . . . . . . . . 19
5.8. Local Mobility Anchor Operational Summary . . . . . . . . 19
6. Mobile Access Gateway Operation . . . . . . . . . . . . . . . 21
6.1. Address Configuration Models . . . . . . . . . . . . . . . 22
6.2. Conceptual Data Structures . . . . . . . . . . . . . . . . 23
6.3. Access Authentication . . . . . . . . . . . . . . . . . . 23
6.4. Home Network Emulation . . . . . . . . . . . . . . . . . . 24
6.5. Link-Local and Global Address Uniqueness . . . . . . . . . 24
6.6. Tunnel Management . . . . . . . . . . . . . . . . . . . . 25
6.7. Routing Considerations . . . . . . . . . . . . . . . . . . 26
6.8. Interaction with DHCP Relay Agent . . . . . . . . . . . . 27
6.9. Mobile Node Detachment Detection and Resource Cleanup . . 27
6.10. Coexistence with Mobile Nodes using Host-based Mobility . 28
6.11. Mobile Access Gateway Operation Summary . . . . . . . . . 29
7. Mobile Node Operation . . . . . . . . . . . . . . . . . . . . 31
7.1. Booting up in a Proxy Mobile IPv6 Domain . . . . . . . . . 32
7.2. Roaming in the Proxy Mobile IPv6 Network . . . . . . . . . 33
7.3. IPv6 Host Protocol Parameters . . . . . . . . . . . . . . 33
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8. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 34
8.1. Proxy Binding Update . . . . . . . . . . . . . . . . . . . 35
8.2. Proxy Binding Acknowledgment . . . . . . . . . . . . . . . 35
8.3. Home Network Prefix Option . . . . . . . . . . . . . . . . 36
8.4. Time Stamp Option . . . . . . . . . . . . . . . . . . . . 38
8.5. Status Codes . . . . . . . . . . . . . . . . . . . . . . . 38
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
10. Security Considerations . . . . . . . . . . . . . . . . . . . 39
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 40
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 41
12.1. Normative References . . . . . . . . . . . . . . . . . . . 41
12.2. Informative References . . . . . . . . . . . . . . . . . . 42
Appendix A. Proxy Mobile IPv6 interactions with AAA
Infrastructure . . . . . . . . . . . . . . . . . . . 43
Appendix B. Supporting Shared-Prefix Model using DHCPv6 . . . . . 43
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 44
Intellectual Property and Copyright Statements . . . . . . . . . . 46
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1. Introduction
Mobile IPv6 [RFC-3775] is the enabler for IPv6 mobility. It requires
Mobile IPv6 client functionality in the IPv6 stack of a mobile node.
Signaling between the MN and HA enables the creation and maintenance
of a binding between the MNs home address and care-of-address.
Mobile IPv6 has been designed to be an integral part of the IPv6
stack in a host. However there exist IPv6 stacks today that do not
have Mobile IPv6 functionality and there would likely be IPv6 stacks
without MIPv6 functionality in the future as well. It is desirable
to support IP mobility for all hosts irrespective of the presence or
absence of mobile IPv6 functionality in the IPv6 stack.
It is possible to support mobility for IPv6 nodes by extending Mobile
IPv6 [RFC-3775] signaling and reusing the home agent via a proxy
mobility agent in the network. This approach to supporting mobility
does not require the mobile node to be involved in the signaling
required for mobility management. The proxy agent in the network
performs the signaling and does the mobility management on behalf of
the mobile node. Because of the use and extension of Mobile IPv6
signaling and home agent functionality, it is referred to as Proxy
Mobile IPv6 (PMIP6) in the context of this document.
Network deployments which are designed to support mobility would be
agnostic to the capability in the IPv6 stack of the nodes which it
serves. IP mobility for nodes which have mobile IP client
functionality in the IPv6 stack as well as those hosts which do not,
would be supported by enabling PMIP6 protocol functionality in the
network. The advantages of developing a network based mobility
protocol based on Mobile IPv6 are:
o Reuse of home agent functionality and the messages/format used in
mobility signaling. Mobile IPv6 is a mature protocol with several
implementations that have been through interoperability testing.
o A common home agent would serve as the mobility agent for all
types of IPv6 nodes.
o Addresses a real deployment need.
The problem statement and the need for a network based mobility
protocol solution has been documented in
[draft-ietf-netlmm-nohost-ps-05.txt]. PMIP6 is a solution that
addresses these issues and requirements.
The IP Mobility protocols designed in the IETF so far involve the
host in mobility management. There are some deployment scenarios
where a network-based mobility management protocol is considered
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appropriate. The advantages to using a network-based mobility
protocol include avoiding tunneling overhead over the air and support
for hosts that do not implement any mobility management protocol.
The document describes a network-based mobility management protocol
based on Mobile IPv6. it is called Proxy Mobile IPv6 (PMIPv6). One
of the most important design considerations behind PMIPv6 has been to
re-use as much as possible from the existing mobility protocols.
There are many advantages to develop a protocol based on Mobile IPv6.
Mobile IPv6 is a very mature mobility protocol for IPv6. There have
been many implementations and inter-operability events where Mobile
IPv6 has been tested. There also numerous specifications enhancing
Mobile IPv6 that can be re-used. Further, the Proxy MIPv6 solution
described in this document allows the same Home Agent to provide
mobility to hosts that use Mobile IPv6 and hosts that do not use any
mobility management protocol. Proxy Mobile IPv6 provides solution to
a real deployment problem.
The specific details related to enabling IPv4 home address mobility
for the mobile node and the details related to supporting IPv4
transport network are covered in the companion document.
2. Conventions & Terminology
2.1. Conventions used in this document
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" used in
this document are to be interpreted as described in RFC 2119.
2.2. Terminology
All the general mobility related terms used in this document are to
be interpreted as defined in the Mobile IPv6 base specification [RFC-
3775].
This document adopts the terms, Local Mobility Anchor (LMA) and
Mobile Access Gateway (MAG) from the NETLMM Goals document
[draft-ietf-netlmm-nohost-req-05.txt]. It further provides the
following context specific explanation to these terms, specific to
this solution document.
Local Mobility Anchor (LMA)
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Local Mobility Anchor is the home agent for the mobile node in the
Proxy Mobile IPv6 domain. It is the topological anchor point for
the mobile node's home prefix and is the entity that manages the
mobile node's reachability state. It is important to understand
that the LMA has the functional capabilities of a home agent as
defined in Mobile IPv6 base specification [RFC-3775] and with the
additional required capabilities for supporting Proxy Mobile IPv6
as defined in this specification.
Proxy Mobile Agent (PMA)
Proxy mobility agent is a function that manages the mobility
related signaling for a mobile node that is attached to its access
link. It is responsible for tracking the mobile node's attachment
to the link and for signaling the mobile node's local mobility
anchor.
Mobile Access Gateway (MAG)
It is the entity where the Proxy Mobile Agent function resides.
Mobile Node (MN)
Through out this document, the term mobile node is used to refer
to an IP node whose mobility is provided by the network. The
mobile node may be operating in IPv6 mode, IPv4 mode or in IPv4/
IPv6 dual mode. The mobile node is not required to participate in
any mobility related signaling for achieving mobility for an IP
address that is obtained in that local domain. This document
further uses explicit text when referring to a mobile node that is
involved in mobility related signaling as per Mobile IPv6
specification [RFC-3775]. The mobile node's capability or its
involvement in any mobility related signaling for obtaining
mobility for an address that is obtained outside the current proxy
mobile IPv6 domain, is not relevant in the context of this
document and this definition of the Mobile Node shall survive.
Mobile Node's Home Address (MN-HoA)
MN-HoA is the home address of a mobile node in a Proxy Mobile IPv6
domain. It is an address obtained by the mobile node in that
domain. The mobile node can continue to use this address as long
as it is attached to the network that is in the scope of that
Proxy Mobile IPv6 domain. When supporting IPv4 address mobility
for a mobile node, the term, IPv4 MN-HoA is used to refer to the
IPv4 address of the mobile node.
Proxy Care-of Address (Proxy-CoA)
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Proxy-CoA is the address configured on the interface of the mobile
access gateway and is the transport endpoint of the tunnel between
the local mobility anchor and the mobile access gateway. The
local mobility anchor views this address as the Care-of Address of
the mobile node and registers it in the Binding Cache entry for
that mobile node. When the transport network between the mobile
access gateway and the local mobility anchor is an IPv4 network
and if the care-of address that is registered at the local
mobility anchor is an IPv4 address, the term, IPv4 Proxy-CoA is
used.
LMA Address (LMAA)
The address that is configured on the interface of the local
mobility anchor and is the transport endpoint of the tunnel
between the local mobility anchor and the mobile access gateway.
This is the address to where the mobile access gateway sends the
Proxy Binding Update messages. When supporting IPv4 traversal,
i.e. when the network between the local mobility anchor and the
mobile access gateway is an IPv4 network, this address will be an
IPv4 address and will be referred to as IPv4 LMAA.
Proxy Mobile IPv6 Domain (PMIPv6-Domain)
It is a localized mobility management domain. It is a portion of
the access network where the mobility management of a mobile node
is handled using Proxy Mobile IPv6 protocol as defined in this
specification.
Mobile Node's Home Link
This is the link on which the mobile node obtained its initial
address configuration after it moved into that Proxy Mobile IPv6
domain. This is the link that conceptually follows the mobile
node. The network will ensure the mobile node always sees this
link with respect to the layer-3 network configuration, on any
access link that it attaches to in that proxy mobile IPv6 domain.
Mobile Node's Home Network Prefix (MN-HNP)
This is the on-link prefix that the mobile always sees in the
Proxy Mobile IPv6 domain. The home network prefix is
topologically anchored at the mobile's local mobility anchor. The
mobile node configures its interface with an address from this
prefix. When supporting IPv4 home address mobility, the term,
IPv4 Home Network refers to the mobile node's IPv4 home prefix and
the term, Home Network always refers to the IPv6 home network
prefix.
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Mobile Node Identifier (MN-Identifier)
The identity of the mobile node that is presented to the network
as part of the access authentication. This is typically an
identifier such as Mobile Node NAI [RFC-4283] any other type of
identifier which may be specific to the access technology.
Proxy Binding Update (PBU)
A signaling message sent by the mobile access gateway to a mobile
node's local mobility anchor for establishing a binding between
the mobile node's MN-HoA and the Proxy-CoA.
Proxy Binding Acknowledgement (PBA)
A response message sent by a local mobility anchor in response to
a Proxy Binding Update message that it received from a mobile
access gateway.
3. Proxy Mobile IPv6 Protocol Overview
This specification describes a network-based mobility management
protocol. It is called Proxy Mobile IPv6 (PMIPv6) and is based on
Mobile IPv6 [RFC-3775]. This protocol is for providing network-based
mobility management support to a mobile node, within a restricted and
topologically localized portion of the network and with out requiring
the participation of the mobile node in any mobility related
signaling.
Every mobile node that roams in a Proxy Mobile IPv6 domain, would
typically be identified by an identifier, such as MN-Identifier, and
using that identifier the mobile node's policy profile can be
obtained from the policy store. The policy profile typically
contains the provisioned network-based mobility service
characterstics and other related parameters such as the mobile node's
home network prefix, permitted address configuration modes, roaming
policy and other parameters that are essential for providing network
based mobility service.
Once a mobile node enters its Proxy Mobile IPv6 domain and performs
access authentication, the network will ensure the mobile node is
always on its home network and further ensures the mobile node can
always obtain its home address on the access link and using any of
the address configuration procedures. In other words, there is home
network prefix that is assigned for a mobile node and conceptually
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that address always follows the mobile node, where ever it roams
within that proxy mobile IPv6 domain. From the perspective of the
mobile node, the entire Proxy Mobile IPv6 domain appears as its home
link or a single link.
+----+ +----+
|LMA1| |LMA2|
+----+ +----+
LMAA1---- | | ---- LMAA2
| |
\\ // \\
+--\\------------- //---\\----+
( \\ IPv4/IPv6 // \\ )
( \\ Network // \\ )
+-----\\--------//---------\\-+
\\ // \\
\\ // \\ <--- Tunnel2
\\ // \\
|-- Proxy-CoA1 |-- Proxy-CoA2
+----+ +----+
[MN1].__.|MAG1|.__.[MN2] |MAG2|
+----+ +----+
| |
| |
------------------- [MN5]
| |
[MN3] [MN4]
Figure 1: Proxy Mobile IPv6 Domain
The Proxy Mobile IPv6 scheme introduces a new function, the mobile
access gateway. It is a function that is on the access link where
the mobile is anchored and does the mobility related signaling on
behalf of the mobile node. From the perspective of the local
mobility anchor, the mobile access gateway is a special element in
the network that is authorized to send Mobile IPv6 signaling messages
on behalf of a mobile node.
When the mobile node attaches to an access link connected to the
mobile access gateway, the mobile node presents its identity, MN-
Identifier, as part of the access access authentication procedure.
After a successful access authentication, the mobile access gateway
obtains the mobile node's profile from the policy store, such as from
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a AAA infrastructure. The mobile access gatway would have all the
information for it to emulate the mobile node's home network on the
access link. The mobile access gateway also starts sending periodic
Router Advertisements to the mobile node advertising its home network
prefix.
The mobile node on receiving these Router Advertisement messages on
the access link will attempt to configure its interface either using
statefull or stateless address configuration modes, based on modes
that are permitted on that access link. At the end of a successful
address configuration procedure, the mobile node would have obtained
an address from its home network prefix. If the mobile node is IPv4
capable and if network offers IPv4 network mobility for the mobile
node, the mobile node would have obtained an IPv4 address as well.
The mobile node can be operating in IPv4-only mode, IPv6-only or in
dual-mode and based on the services enabled for that mobile, the
mobility is enabled only for those address types. Also, the network
between the local mobility anchor and the mobile access gateway can
be either IPv4, IPv6, IPv4 with NAT translation devices in the access
network.
For updating the local mobility anchor about the current location of
the mobile node, the mobile access gateway sends a Proxy Binding
Update message to the mobile node's local mobility anchor. The
message will have the mobile node's NAI identifier option and Home
Network Prefix Option and/or IPv4 Home Address option. The source
address of that message will be the address of the mobile access
gateway on its egress interface. Upon accepting the Proxy Binding
Update request, the local mobility anchor sends a Proxy Binding
Acknowledgment message to the mobile access gateway. It also sets up
a route to the mobile node's home network prefix over the tunnel and
sends Proxy Binding Acknowledgment message to the mobile access
gateway.
The mobile access gateway on receiving this Proxy Binding
Acknowledgment message sets up a tunnel to the local mobility anchor
and adds a default route over the tunnel to the local mobility
anchor. All traffic from the mobile node gets routed to the mobile
node's local mobility anchor over the tunnel.
At this point, the mobile node has a valid home address from its home
network prefix, at the current point of attachment. The serving
mobile access gateway and the local mobility anchor also have proper
routing states for handling the traffic sent to and from the mobile
node.
The local mobility anchor, being the topological anchor point for the
mobile node's home network prefix, it receives any packet sent by any
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corresponding node to the mobile node. Local mobility anchor
forwards the received packet to the mobile access gateway through the
tunnel. The mobile access gateway on other end of the tunnel, after
receiving the packet removes the tunnel header and forwards the
packet on the access link to the mobile node.
The mobile access gateway typically acts as a default router on the
access link and any packet that the mobile node sends to any
corresponding node is received by the mobile access gateway and it
forwards the packet to the local mobility anchor through the tunnel.
The local mobility anchor on the other end of the tunnel, after
receiving the packet removes the tunnel header and routes the packet
to the destination.
4. Proxy Mobile IPv6 Protocol Security
The signaling messages, Proxy Binding Update and Proxy Binding
Acknowledgement, exchanged between the mobile access gateway and the
local mobility anchor are protected using IPsec and using the
established security association between them. The security
association of the specific mobile node for which the signaling
message is initiated is not required for protecting these messages.
ESP in transport mode with mandatory integrity protection is used for
protecting the signaling messages. Confidentiality protection is not
required.
IKEv2 is used to setup security associations between the mobile
access gateway and the local mobility anchor to protect the Proxy
Binding Update and Proxy Binding Acknowledgment messages. The mobile
access gateway and the local mobility anchor can use any of the
authentication mechanisms, as specified in IKEv2, for mutual
authentication.
Mobile IPv6 specification requires the home agent to prevent a mobile
node from creating security associations or creating binding cache
entries for another mobile node's home address. In the protocol
described in this document, the mobile node is not involved in
creating security associations for protecting the signaling messages
or sending binding updates. Therefore, this is not a concern.
However, the local mobility anchor MUST allow only authorized mobile
access gateways to create binding cache entries on behalf of the
mobile nodes. The actual mechanism by which the local mobility
anchor verifies if a specific mobile access gateway is authorized to
send Proxy Binding Updates on behalf of a mobile node is outside the
scope of this document. One possible way this could be achieved is
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sending a query to the policy store such as by using AAA
infrastrucure.
4.1. Peer Authorization Database Entries
The following describes PAD entries on the mobile access gateway and
the local mobility anchor. The PAD entries are only example
configurations. Note that the PAD is a logical concept and a
particular mobile access gateway or a local mobility anchor
implementation can implement the PAD in an implementation specific
manner. The PAD state may also be distributed across various
databases in a specific implementation.
mobile access gateway PAD:
- IF remote_identity = lma_identity_1
Then authenticate (shared secret/certificate/EAP)
and authorize CHILD_SA for remote address lma_addres_1
local mobility anchor PAD:
- IF remote_identity = mag_identity_1
Then authenticate (shared secret/certificate/EAP)
and authorize CHILD_SAs for remote address mag_address_1
The list of authentication mechanisms in the above examples is not
exhaustive. There could be other credentials used for authentication
stored in the PAD.
4.2. Security Policy Database Entries
The following describes the security policy entries on the mobile
access gateway and the local mobility anchor required to protect the
Proxy Mobile IPv6 signaling messages. The SPD entries are only
example configurations. A particular mobile access gateway or a
local mobility anchor implementation could configure different SPD
entries as long as they provide the required security.
In the examples shown below, the identity of the mobile access
gateway is assumed to be mag_1, the address of the mobile access
gateway is assumed to be mag_address_1, and the address of the local
mobility anchor is assumed to be lma_address_1.
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mobile access gateway SPD-S:
- IF local_address = mag_address_1 &
remote_address = lma_address_1 &
proto = MH & local_mh_type = BU & remote_mh_type = BAck
Then use SA ESP transport mode
Initiate using IDi = mag_1 to address lma_1
local mobility anchor SPD-S:
- IF local_address = lma_address_1 &
remote_address = mag_address_1 &
proto = MH & local_mh_type = BAck & remote_mh_type = BU
Then use SA ESP transport mode
5. Local Mobility Anchor Operation
For supporting the Proxy Mobile IPv6 scheme defined in this document,
the Mobile IPv6 home agent entity, defined in Mobile IPv6
specification [RFC-3775], needs some protocol enhancements. The
local mobility anchor is the functional entity with these
capabilities for supporting Proxy Mobile IPv6. This section
describes the operational details of the local mobility anchor.
The base Mobile IPv6 specification [RFC-3775], defines home agent and
the mobile node as the two functional entities. The Proxy Mobile
IPv6 scheme introduces a new entity, the mobile access gateway. This
is the entity that will participate in the mobility related
signaling. From the perspective of the local mobility anchor, the
mobile access gateway is a special element in the network that has
the privileges to send mobility related signaling messages on behalf
of the mobile node. Typically, the local mobility anchor is
provisioned with the list of mobile access gateways authorized to
send proxy registrations.
When the local mobility anchor receives a Proxy Binding Update
message from a mobile access gateway, the message is protected using
the IPSec Security Association established between the local mobility
anchor and the mobile access gateway. The local mobility anchor can
distinguish between a Proxy Binding Update message received from a
mobile access gateway from a Binding Update message received directly
from a mobile node. This distinction is important for using the
right security association for validating the Binding Update and this
is achieved by relaxing the MUST requirement for having the Home
Address Option presence in Destination Options header and by
introducing a new flag in the Binding Update message. The local
mobility anchor as a traditional IPSec peer can use the SPI in the
IPSec header [RFC-4306] of the received packet for locating the
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correct security association and for processing the Proxy Binding
Update message in the context of the Proxy Mobile IPv6 scheme.
For protocol simplicity, the current specification supports the Per-
MN-Prefix addressing model. In this addressing model, each mobile
node is allocated an exclusively unique home network prefix and the
prefix is not hosted on the home link. The local mobility anchor in
this addressing model is just a topological anchor point and the
prefix is physically hosted on the access link where the mobile node
is attached. The local mobility anchor is not required to perform
any proxy ND operations [RFC-2461] for defending the mobile node's
home address, MN-HoA, on the home link. However, the local mobility
anchor is required to manage the binding cache entry of the mobile
node for managing the mobility session and also the routing state for
creating a proper route path for traffic to/from the mobile node.
5.1. Extensions to Binding Cache Conceptual Data Structure
The local mobility anchor maintains a Binding Cache entry for each
currently registered mobile node. Binding Cache is a conceptual data
structure, described in Section 9.1 of [RFC3775]. For supporting
this specification, the conceptual Binding Cache entry needs to be
extended with the following new fields.
o A flag indicating whether or not this Binding Cache entry is
created due to a proxy registration. This flag is enabled for
Binding Cache entries that are proxy registrations and is turned
off for all other entries that are direct registrations from the
mobile node.
o A flag indicating if IPv6 HoA mobility is accepted. If this flag
is set, the relevant IPv6 HoA fields in this data structure have
to be set to the configured values. If this flag.
o The identifier of the mobile node, MN-Identifier. This MN-
Identifier is obtained from the NAI Option present in the Proxy
Binding Update request [RFC-4285].
o A flag indicating whether or not the Binding Cache entry has a
home address that is on virtual interface. This flag is enabled,
if the home prefix of the mobile is configured on a virtual
interface. When the configured home prefix of a mobile is on a
virtual interface, the home agent is not required to function as a
Neighbor Discovery proxy for the mobile node.
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o The IPv6 home network prefix of the mobile node.
o The IPv6 home network prefix length of the mobile node.
o The interface id of the tunnel between the local mobility anchor
and the mobile access gateway used for sending and receiving the
mobile node's traffic.
o Tentative binding cache entry with all the above fields. This
entry is populated upon tentatively accepting a proxy binding
update request for a mobile node whose direct registration still
exists, i.e. the mobile has not deregistered and it received a
proxy binding update request.
5.2. Bi-Directional Tunnel Management
The bi-directional tunnel between the local mobility anchor and the
mobile access gateway is used for routing the traffic to and from the
mobile node. The tunnel hides the topology and enables a mobile node
to use an IP address that is topologically anchored at the local
mobility anchor, from any attached access link in that proxy mobile
IPv6 domain. The base Mobile IPv6 specification [RFC-3775], does use
the tunneling scheme for routing traffic to and from the mobile that
is using its home address. However, there are subtle differences in
the way Proxy Mobile IPv6 uses the tunneling scheme.
As in Mobile IPv4 [RFC-3344], the tunnel between the local mobility
anchor and the mobile access gateway is typically a shared tunnel and
can be used for routing traffic streams for different mobile nodes
attached to the same mobile access gateway. This specification
extends that 1:1 relation between a tunnel and a binding cache entry
to 1:m relation, reflecting the shared nature of the tunnel.
The tunnel is creating after accepting a Proxy Binding Update request
for a mobile node from a mobile access gateway. The created tunnel
may be shared with other mobile nodes attached to the same mobile
access gateway and with the local mobility anchor having a binding
cache entry for those mobile nodes. Some implementations may prefer
to use static tunnels as supposed to creating and tearing them down
on a need basis.
The one end point of the tunnel is the address configured on the
interface of the local mobility anchor, LMAA. The other end point of
the tunnel is the address configured on the interface of the mobile
access gateway, Proxy-CoA. The tunnel encapsulation mode can be
either IPv6/IPv6, IPv6/IPv4, IPv6/IPv4-UDP, IPv4/IPv6, IPv4/IPv4-UDP,
based on the transport mode and the presence of NAT translation
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devices on the path.
Implementations typically use a software timer for managing the
tunnel lifetime and a counter for keeping a count of all the mobiles
that are sharing the tunnel. The timer value will be set to the
accepted binding life-time and will be updated after each periodic
registrations for extending the lifetime. If the tunnel is shared
for multiple mobile node's traffic, the tunnel lifetime will be set
to the highest binding life time across all the binding life time
that is granted for all the mobiles sharing that tunnel.
5.3. Routing Considerations
This section describes how the data traffic to/from the mobile node
is handled at the local mobility anchor. The following entries
explains the routing state that is created for the mobile node home
network prefix.
IPv6 traffic for the Mobile Node's home address:
================================================
MN-HoA::/64 via tunnel0, next-hop Proxy-CoA
tunnel0:
========
Source: LMAA
Destination: Proxy-CoA
Tunnel Transport: IPv6
Tunnel Payload: IPv6
The local mobility anchor functions as a topological anchor point for
the mobile node's home network prefix. When the local mobility
anchor receives a data packet from a corresponding node, destined for
the mobile node's home network prefix, the created routing state will
enable the packets to be forwarded to the mobile node through the bi-
directional tunnel established between itself and the serving mobile
access gateway.
If the tunnel between the local mobility anchor and the mobile access
gateway is an IPv6 tunnel, i.e. if the registered care-of address is
the IPv6 Proxy-CoA, any IPv6 packets received from any corresponding
node for the mobile node's home network prefix, MN-HNP, will be
encapsulated in an IPv6 packet, IPv6/IPv6 mode, and will be carried
as an IPv6 packet. And any IPv4 packets for the mobile node's IPv4-
MN-HoA, will be encapsulated in an IPv6 packet, IPv4/IPv6 mode, and
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will be carried as an IPv6 packet.
All the reverse tunneled packets that the local mobility anchor
receives from the tunnel, after removing the packet encapsulation
will get 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.
5.4. Local Mobility Anchor Address Discovery
Dynamic Home Agent Address Discovery, as explained in Section 10.5 of
[RFC-3775], allows a mobile node to discover all the home agents on
its home link by sending an ICMP Home Agent Address Discovery Request
message to the Mobile IPv6 Home-Agents anycast address, derived from
its home network prefix.
The Proxy Mobile IPv6 model assumes that the mobile access gateway
will be able to obtain the address of the local mobility anchor in
one or more ways. This MAY be a configured entry in the mobile
node's policy profile, or it MAY be obtained through mechanisms
outside the scope of this document. It is important to note that
there is little value in using DHAAD for discovering the local
mobility anchor address dynamically. As a mobile moves from one
mobile access gateway to the another, the serving mobile access
gateway will not predictably be able to locate the serving local
mobility anchor for that mobile that has its binding cache entry for
the mobile node. However, if there is only one local mobility anchor
configured to serve a mobile node, the mobile access gateway can use
Dynamic Home Agent Address Discovery scheme for discovering the
address of the local mobility anchor.
With the currently supported Per-MN-Prefix addressing model, every
mobile node is assigned a unique home network prefix, the local
mobility anchor is a topological anchor point for that prefix and
with the prefix being hosted on the access link attached to the
mobile access gateway. For the discovery scheme to work, the local
mobility anchor MUST be able to receive the ICMP discovery packets
sent to the anycast address derived from the mobile node's home
network prefix.
5.5. Sequence Number and Time-Stamps for Message Ordering
Mobile IPv6 [RFC-3775] uses the Sequence Number field in registration
messages as a way to ensure the correct packet ordering. The local
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mobility anchor and the mobile node are required to manage this
counter over the lifetime of a binding.
In Proxy Mobile IPv6, the Proxy Binding Update messages that the
local mobility anchor receives on behalf of a specific mobile node
may not be from the same mobile access gateway as the previously
received message. It creates certain ambiguity and the local
mobility anchor will not be predictably order the messages. This
could lead to the local mobility anchor processing an older message
from a mobile access gateway where the mobile node was previously
attached, while ignoring the latest binding update message.
In the Proxy Mobile IPv6, the ordering of packets has to be
established accross packets received from multiple senders. The
sequence number scheme as specified in [RFC-3775] will not be
sufficient. A global scale, such as a time stamp, can be used to
ensure the correct ordering of the packets. This document proposes
the use of a Time Stamp Option, specified in Section 8.4, in all
Proxy Binding Update messages sent by mobile access gateways. By
leveraging the NTP [RFC-1305] service, all the entities in Proxy
Mobile IPv6 domain will be able to synchronize their respective
clocks. Having a time stamp option in Proxy Binding Update messages
will enable the local mobility anchor to predictably identify the
latest message from a list of messages delivered in an out-of-order
fashion.
The Proxy Mobile IP model, defined in this document requires the
Binding Update messages sent by the mobile access gateway to have the
time stamp option. The local mobility anchor processing a proxy
registration MUST ignore the sequence number field and SHOULD use the
value from the Time Stamp option to establish ordering of the
received Binding Update messages. If the local mobility anchor
receives a Binding Update message with an invalid Time Stamp Option,
the Binding Update MUST be rejected and a Binding Acknowledgement
MUST be returned in which the Status field is set to 148 (invalid
time stamp option).
In the absence of Time Stamp option in the Proxy Binding Update, the
entities can fall back to Sequence Number scheme for message
ordering, as defined in RFC-3775. However, the specifics on how
different mobile access gateways synchronize the sequence number is
outside the scope of this document.
When using the Time Stamp Option, the local mobility anchor or the
mobile access gateway MUST set the the timestamp field to a 64-bit
value formatted as specified by the Network Time Protocol [RFC-1305].
The low-order 32 bits of the NTP format represent fractional seconds,
and those bits which are not available from a time source SHOULD be
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generated from a good source of randomness.
5.6. Route Optimizations Considerations
Mobile IPv6 route optimization, as defined in [RFC-3775], enables a
mobile node to communicate with a corresponding node directly using
its care-of address and further the Return Routability procedure
enables the corresponding node to have reasonable trust that the
mobile node owns both the home address and care-of address.
In the Proxy Mobile IPv6 model, the mobile is not involved in any
mobility related signaling and also it does not operate in the dual-
address mode. Hence, the return routability procedure as defined in
RFC-3775 is not applicable for the proxy model. This document does
not address the Route Optimization problem and leaves this work item
for future enhancements.
5.7. Mobile Prefix Discovery Considerations
The ICMP Mobile Prefix Advertisement message, described in Section
6.8 and Section 11.4.3 of [RFC-3775], allows a home agent to send a
Mobile Prefix Advertisement to the mobile node.
In Proxy Mobile IPv6 deployments, the mobile node's home network
prefix is hosted on the access link shared between the mobile access
gateway and the mobile node, but topologically anchored on the local
mobility anchor. Since, there is no physical home-link for the
mobile node's home network prefix on the local mobility anchor and as
the mobile is always on the link where the prefix is hosted, any
prefix change messages can just be advertised by the mobile access
gateway on the access link and thus there is no applicability of this
messaging for Proxy Mobile IPv6. This specification does not support
Mobile Prefix Discovery.
5.8. Local Mobility Anchor Operational Summary
o For supporting this scheme, the local mobility anchor MUST satisfy
all the requirements listed in Section 8.4 of Mobile IPv6
specification [RFC-3775] with the following considerations.
o For supporting the per-MN-Prefix addressing model as defined in
this specification, the local mobility anchor service MUST NOT be
tied to a specific interface. It SHOULD be able to accept Proxy
Binding Update requests sent to any of the addresses configured on
any of its interfaces.
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o The requirement for a home agent to maintain a list of home agents
for a mobile node's home link is not applicable for the local
mobility anchor, when supporting Per-MN-Prefix addressing model as
there is no link specific relation between the two.
o After receiving a Proxy Binding Update request from a mobile
access gateway on behalf of mobile node, the local mobility anchor
MUST process the request as defined in Section 10, of the base
Mobile IPv6 specification [RFC-3775], with one exception that this
request is a proxy request, the sender is not the mobile node and
so the message has to be processed with the considerations
explained in this section.
o The local mobility anchor MUST apply the required policy checks,
as explained in Section 4.0 of this document to verify the sender
is a a trusted mobile access gateway, authorized to send proxy
binding updates requests on behalf of that mobile nodes, using its
own identity. The local mobility anchor must check the local/
remote policy store to ensure the requesting node is authorized to
send proxy binding update requests.
o Upon accepting a proxy binding update request from a mobile access
gateway, the local mobility anchor must check if there exists a
binding cache entry for that mobile node, identified using the MN-
Identifier, that was created due to a direct registration from the
mobile node. If there exists a binding cache entry with the proxy
registration flag turned off, the local mobility anchor MUST NOT
modify that binding state, instead it must create a tentative
binding cache entry and update the tentative binding cache entry
fields of that binding cache entry.
o Upon receiving a Binding Update request from a mobile node with
lifetime value set to 0, from a tunnel between itself and a
trusted mobile access gateway, the local mobility anchor upon
accepting that de-registration message, MUST forward the Binding
Acknowledgement message in the tunnel from where it received the
Binding Update request. It must also replace the binding cache
entry with the tentative binding cache entry and enable routing
for the mobile node's home prefix through the proxy mobile IPv6
tunnel.
o The local mobility anchor MUST use the MN-Identifier present in
the NAI option of the Proxy Binding Update request for identifying
the mobile node.
o The local mobility anchor MUST ensure the prefix presented in the
Home Network Prefix option of the received Proxy Binding Update
request is owned by itself and further the mobile node identified
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by MN-Identifier is authorized to use this prefix.
o The local mobility anchor MUST ignore the sequence number field in
the Proxy Binding Updates requests, if the Time-Stamp Option is
present in the message. It must also skip all the checks related
to sequence number as suggested in the Mobile IPv6 specification
[RFC-3775]. However, the received sequence number MUST be copied
and returned in the Proxy Binding Acknowledgement sent to the
mobile access gateway.
o Upon accepting this request, the local mobility anchor must create
a Binding Cache entry with the home address from the Home Network
Prefix Option in the Binding Update and must set up a tunnel to
the proxy mobile agent serving the mobile node. This bi-
directional tunnel between the local mobility anchor and the
mobile access gateway is used for routing the mobile traffic.
o The local mobility anchors SHOULD drop all HoTI messages received
for a home address that has corresponding Binding Cache entry with
the proxy registration flag set.
o The local mobility anchor must handle the mobile node's data
traffic as explained in the Routing Considerations section of this
document.
6. Mobile Access Gateway Operation
The Proxy Mobile IPv6 scheme specified in this document, introduces a
new functional entity, the Mobile Access Gateway (MAG). It is the
entity that detects the mobile node's movements and initiates the
signaling with the mobile node's local mobility anchor for updating
the route to the mobile node's home address. In essence, the mobile
access gateway performs mobility management on behalf of the mobile
node.
From the perspective of the local mobility anchor, the mobile access
gateway is a special element in the network that sends Mobile IPv6
signaling messages on behalf of a mobile node, but using its own
identity. It is the entity that binds the mobile node's home address
to an address on its own access interface.
The mobile access gateway has the following functional roles.
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o It is responsible for detecting the mobile node's attachment or
detachment on the connected access link and for initiating the
mobility signaling to the mobile node's local mobility anchor.
o Emulation of the mobile node's home link on the access link.
o It is responsible for setting up the data path for enabling the
mobile node to use its home address for communication from the
access link.
This Proxy Mobile IPv6 scheme is independent of the underlying access
technology or the link model. The interface between the mobile node
and the mobile access gateway can be either:
o Point-to-Point Link
o Shared Link
This specification does not support split links.
6.1. Address Configuration Models
Currently, this specification only supports Per-MN-Prefix model In
the Per-MN-Prefix model, there is a unique home network prefix
assigned for each mobile node and that prefix is hosted on the access
link. Conceptually, the prefix just follows the mobile node as it
moves within the proxy mobile IPv6 domain. In this addressing model,
based on the administrative policy, the mobile node can use either
Stateless Address Autoconfiguration or Statefull Address
Configuration using DHCP for obtaining the IPv6 address configuration
for its interface on the access link. Further, the mobile node can
also generate interface identifiers with privacy considerations, as
specified in Privacy Extensions specification [RFC-3041] and as per
CGA specification [RFC-3042]. For IPv4 home address configuration,
the mobile node can obtain the address configuration using DHCP or
optionally by using IPCP. In addition to this, Other address
configuration mechanisms specific to the access link between the
mobile node and the mobile access gateway may also be used by the
mobile node.
The configured administrative policy for the mobile dictates the type
of addressing model that is supported for a mobile on the access
link. The mobile access gateway on the access router will control
this by setting the relevant flags in the Router Advertisement that
it sends on the access link.
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6.2. Conceptual Data Structures
Every mobile access gateway maintains a Binding Update List for each
currently attached mobile node. The Binding Update List is a
conceptual data structure, described in Section 11.1 of Mobile IPv6
base specification [RFC-3775]. For supporting this specification,
the conceptual Binding Update List data structure must be extended
with the following new additional fields.
o The Identifier of the mobile node, MN-Identifier. The format of
the MN-Identifier is specific to the access technology. This MN
identifier is obtained as part of the Access Authentication
procedure and is used for downloading the mobile node's profile
from the policy store.
o The physical address or the MAC address of the mobile node's
connected interface.
o The IPv6 home network prefix of the mobile node.
o The IPv6 home network prefix length of the mobile node.
o The link-local address of the mobile node on the link. This
address MAY be learnt from the source address of the Router
Solicitation message received from the mobile node.
o The tunnel identifier of the tunnel between the mobile access
gateway and the local mobility anchor used for reverse tunneling
the mobile node's traffic. On a given implementation, if a tunnel
appears like a virtual interface, that applies the proper
encapsulation on every packet that is routed through that
interface, then the interface identifier is stored in the binding
update list. entry.
6.3. Access Authentication
When a mobile node attaches to the access link connected to the
mobile access gateway, the deployed access security protocols will
ensure that only authorized mobile nodes will be able to access the
link and further the mobile access gateway will be able to identify
the mobile node by its MN-Identifier and optionally will be able to
detect the mobile node's attachment or detachment to the link. The
exact specifics on how this is achieved is outside the scope of this
document. This document goes with the stated assumption of having an
established trust between the mobile node and mobile access gateway
on the access link before the protocol operation begins. The mobile
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access gateway will be able to use the mobile node's MN-Identity and
will be obtain its policy profile from the network policy store or
from the local policy store.
6.4. Home Network Emulation
One of the key functions of the mobile access gateway is to emulate
the mobile node's home network on the access link. It has to ensure,
the mobile node believes it is connected to its home link or the link
where it obtained its address configuration after it moved into that
proxy mobile IPv6 domain. After the access authentication is
complete, the mobile access gateway will have access to the mobile
node's profile, obtained from querying a local/network policy store
or provided to it as part of some context transfer procedure. After
this point, the mobile access gateway will have enough information to
emulate the mobile node's home link. It must send the Router
Advertisement messages advertising the mobile node's home network
prefix and other parameters.
If the access link connecting the mobile access gateway and the
mobile node is a point-to-point link, the Router Advertisements
advertising a specific home network prefix is received only by the
respective mobile node and hence there is clearly a unique link for
each mobile node that is attached to that mobile access gateway.
If the access link connecting the mobile access gateway and the
mobile node is a shared-link, the mobile access gateway MUST ensure
that each of the mobile node that is attached to that link receives
Router Advertisements with its respective home network prefix as the
on-link prefix. For this to happen, the mobile access gateway MUST
unicast the Router Advertisement to the mobile node. The destination
field of the link-layer header in the Router Advertisement MUST be
the mobile's node's interface physical/MAC address and however, the
destination field in the IPv6 header set to the all-nodes-multicast
address.
6.5. Link-Local and Global Address Uniqueness
A mobile node in a proxy mobile IPv6 domain, as it moves from one
access link to the other, will continue to detect its home network
and hence the issue of link-local address uniqueness arises. The
link-local that the mobile node attempts to use on the new link must
be unique.
On a point-to-point link, such as in a PPP session, when the mobile
node tries to establish a PPP session [RFC-1661] with the mobile
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access gateway, the PPP goes through the Network layer Protocol phase
and the IPv6 Control Protocol, IPCP6 [RFC-2472] gets triggered. Both
the PPP peers negotiate a unique identifier using Interface-
Identifier option in IPV6CP and the negotiated identifier is used for
generating a unique link-local address on that link. Now, if the
mobile node moves to a new access router, the PPP session gets torn
down and new PPP session with the new mobile access gateway will be
established and the mobile obtains a new link-local address. Now,
even if the mobile is DNAv6 capable, as specified in the DNAv6
specification [draft-ietf-dna-protocol-03], the mobile node always
configures a new link-local address when ever it moves to a new link.
However, if the link between the mobile node and the mobile access
gateway is a shared link and if a DNAv6 capable mobile node moves
from one access link to the other, the mobile node may not detect a
link change due to the optimizations from DNAv6 and hence there is a
possibility of the link-local address collision on the connected
access link, One of the work around for this issue to the set
following flag on the mobile node, DNASameLinkDADFlag to TRUE and
that will force the mobile node to redo DAD operation even when DNAv6
detects no link change.
The global address or the MN-HoA uniqueness is assured as the
uniqueness is established by the local mobility anchor before
accepting a proxy binding update for a mobile node. This is further
assured with the currently supported per-mn-prefix model, as there
are two mobile nodes that share the same home network prefix.
Further, if the address configuration is based on statefull address
configuration using DHCP, the DHCP server will ensure the uniqueness.
6.6. Tunnel Management
In the traditional Mobile IPv6 model, there is a separate tunnel from
the local mobility anchor to every mobile node that has a binding
cache entry. The one end-point of these tunnels is the respective
mobile node's care-of address and that is unique to that mobile node.
In the case of Proxy Mobile IPv6, the care-of address or the tunnel
end-point is the address of the mobile access gateway and there could
be multiple mobile nodes attached to the same mobile access gateway
and hence the tunnel is a shared tunnel serving multiple mobile
nodes. This is identical to the Mobile IPv4 model [RFC-3344], where
a tunnel between the foreign agent and the home agent is shared by
many visiting mobile nodes and hence the tunnel management needs to
be on a global basis and not be dependent on a specific mobile node's
binding.
The life of the Proxy Mobile IPv6 tunnel should not be based on a
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single binding cache entry. The tunnel may get created as part of
creating a mobility state for a mobile node and later the same tunnel
may be associated with other mobile nodes. So, the tearing down
logic of the tunnel must be based on the number of visitors over that
tunnel. Implementations are free to pre-establish tunnels between
every local mobility anchor and every mobile access gateway in a
proxy mobile IPv6 domain and with out having to create and destroy
the tunnels on a need basis.
6.7. Routing Considerations
This section describes how the data traffic to/from the mobile node
is handled at the mobile access gateway. The following entries
explains the routing state for the mobile node on the mobile access
gateway.
Mobile Node's IPv6 traffic:
===========================
For all traffic from the source address MN-HoA to destination 0::/0
route via tunnel0, next-hop LMAA.
MN-HoA::/64 is reachable via the directly connected interface.
tunnel0:
========
Source: Proxy-CoA
Destination: LMAA
Tunnel Payload: IPv6
Tunnel Transport: IPv6
When the mobile access gateway receives any packets from the mobile
node to any destination, the packet will be forwarded to the local
mobility anchor through the bi-directional tunnel established between
itself and the mobile's local mobility anchor. However, the packets
that are sent with link-local source address are not forwarded.
If the tunnel between the mobile access gateway and local mobility
anchor is an IPv6 tunnel i.e. if the registered care-of address is an
IPv6 Proxy-CoA, any IPv6 packet from the mobile node with the source
MN-HoA, will be encapsulated in an IPv6 packet, IPv6/IPv6 mode and
will be carried as an IPv6 packet. And any IPv4 packet from the
mobile node with the source IPv4 Mobile-HoA, will be encapsulated in
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an IPv6 packet, IPv4/IPv6 mode, and will be carried as an IPv6
packet.
All the packets that the mobile access gateway receives from the
tunnel, after removing the tunnel encapsulation, will forward it to
the mobile node on the connected interface.
6.8. Interaction with DHCP Relay Agent
If Statefull Address Configuration using DHCP is supported on the
link on which the mobile node is attached, the DHCP relay agent [RFC-
3315] needs to be configured on the access router. When the mobile
node sends a DHCPv6 Request message, the relay agent function on the
access router must set the link-address field in the DHCPv6 message
to the mobile node's home network prefix, so as to provide a prefix
hint to the DHCP Server. On a point-to-point link, this is just a
normal DHCP relay agent configuration. However, on the shared links
supporting multiple mobile nodes with different home prefixes, there
is some interaction required between the relay agent and the mobile
access gateway, for setting the link-address field to the requesting
mobile node's home network prefix.
6.9. Mobile Node Detachment Detection and Resource Cleanup
Before sending a Proxy Binding Update message to the local mobility
anchor for extending the lifetime of a currently existing binding of
a mobile node, the mobile access gateway MUST make sure the mobile
node is still attached to the connected link by using some reliable
method. If the mobile access gateway cannot predictably detect the
presence of the mobile node on the connected link, it MUST NOT
attempt to extend the registration lifetime of the mobile node.
Further, in such scenario, the mobile access gateway MUST terminate
the binding of the mobile node by sending a Proxy Binding Update
message to the mobile node's local mobility anchor with lifetime
value set to 0. It MUST also remove any local state such as binding
update list entry that was created for that mobile node.
The specific detection mechanism of the loss of a visiting mobile
node on the connected link is specific to the access link between the
mobile node and the mobile access gateway and is outside the scope of
this document. Typically, there are various link-layer specific
events specific to each access technology that the mobile access
gateway can depend on for detecting the node loss. In general, the
mobile access gateway can depend on one or more of the following
methods for the detection presence of the mobile node on the
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connected link:
o Link-layer event specific to the access technology
o PPP Session termination event on point-to-point link types
o IPv6 Neighbor Unreachability Detection event from IPv6 stack
o Notification event from the local mobility anchor
o Absence of data traffic from the mobile node on the link for a
certain duration of time
6.10. Coexistence with Mobile Nodes using Host-based Mobility
In some operating environments, network operators may want to
provision the access link attached to the mobile access gateway to
offer network-based mobility service only to some nodes and enable
normal IP access support for some other nodes on that link. This
specification supports access links with such mixture of nodes. The
network has the control on when to enable the mobile node with the
network mobility service.
Upon obtaining the mobile node's profile after a successful access
authentication and after a policy consideration, the mobile access
gateway MUST determine if the network based mobility service should
be offered to that mobile node. If the mobile node is entitled for
such service, then the network should ensure the mobile node believes
it is on its home link, as explained in various sections of this
document.
If the mobile node is not entitled for the network based mobility
service, as determined from the policy, the mobile access gateway
MUST ensure the mobile node can obtain an IPv6 address using normal
IPv6 address configuration mechanisms. The obtained address should
be from a local visitor network prefix. In other words the mobile
node should be able to operate as a traditional mobile node roaming
in a visitor network and with the ability to obtain an address from
the local visitor network prefix hosted on that link. This
essentially ensures, the proxy mobile IPv6 protocol will not impact
the behavior of a mobile node that is using host-based mobility, as
per [RFC-3775].
If the stateless address configuration mode is supported on that
link, the prefix information option in the router advertisements
should contain local visitor network prefix. If statefull address
configuration mode is enforced on the link and if DHCP is in used,
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the mobile node should be able to obtain the IPv6 care-of address
from the local visitor network prefix.
If the link between the mobile access gateway and the mobile node is
a shared link, the Router Advertisement has to unicasted to the
mobile node with the destination address in the layer-2 header set to
the mobile's MAC address and the destination address in the IPv6
header set to the all-nodes multicast address.
6.11. Mobile Access Gateway Operation Summary
o After detecting a new mobile node on its access link and after the
successful access authentication and authorization of the mobile
node, the mobile access gateway MUST be able to able to access the
mobile node's profile. This may be downloaded from the local/
network policy store using MN-Identity or may be obtained as part
of a context transfer procedure. The mobile node's profile at the
minimum MUST have the mobile node's local mobility anchor address
and the MN-Identity. Optionally, it may have the mobile node's
home network prefix and other configuration parameters.
o The mobile access gateway MAY use one or more ways to detect the
attachment of a mobile node on to the link. The techniques can be
specific to the access technology or can be other generic events
as mentioned in the above sections.
o If the network determines that the mobile node will not be offered
the network-based mobility service, the mobile access gateway MUST
ensure that the Router Advertisements it sends will not contain
the mobile node's home prefix, but will be the hosted on-link
prefix. Also, if the mobile node attempts to obtain an IPv6
address, the mobile access gateway or the DHCP relay agent on the
link MUST ensure that the prefix hint that gets added to the DHCP
message will be of the local hosted prefix.
o `The mobile access gateway on receiving a Router Solicitation
message from a mobile node MUST send a Router Advertisement
message containing the mobile node's home network prefix.
o The mobile access gateway MUST send the periodic Router
Advertisement messages, as per the ND specification [RFC-2461],
advertising the mobile node's home network prefix on the access
link.
o If the link between the mobile node and the mobile access gateway
is a shared-link, then the Router Advertisement MUST be unicasted
to the mobile node by setting the destination address in the link-
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layer header to the mobile node's MAC address and with the
destination address in the IPv6 header set to the all-nodes
multicast address.
o If the mobile node uses DHCP for address configuration, the mobile
access gateway or specifically the DHCP relay agent on the link
MUST ensure the DHCPv4/v6 packets are properly tagged with the
sending mobile node's MN-HoA, as the prefix hint.
o The Proxy Binding Update message that the mobile access gateway
sends to the local mobility anchor, MUST have the configured IPv6
address of the egress interface. The Proxy Binding Update message
MUST have the NAI option identifying the mobile node, home network
prefix option and optionally the time stamp option. If the home
network prefix option is set to value 0, the local mobility anchor
will assign the home network prefix and will return them in the
Proxy Binding Acknowledgment. This message MUST be protected by
using IPSec security association created between the mobile access
gateway and local mobility anchor.
o After receiving a Proxy Binding Acknowledgment with the status
code indicating the acceptance of the Binding Update, the mobile
access gateway MUST setup a tunnel to the mobile node's local
mobility anchor, as explained in the above sections, if there is
exists no tunnel. The mobile access gateway MUST also add a
default route over the tunnel for all the traffic from the mobile
node.
o If the local mobility anchor denies the Proxy Binding Update
request, the mobile access gateways MUST NOT advertise the mobile
node's home prefix on the access link and there by denying
mobility service to the mobile node.
o Before attempting to extend binding lifetime of a mobile node, the
mobile access gateway MUST make sure the mobile node is still
attached to the connected link by using some reliable method. If
the mobile access gateway cannot predictably detect the presence
of the mobile node on the connected link, it MUST NOT attempt to
extend the registration lifetime of the mobile node. Also, it
MUST terminate the binding of the mobile node by sending a Proxy
Binding Update message to the mobile node's local mobility anchor
with lifetime value set to 0.
o At any point, if the mobile access gateway detects that the mobile
node has roamed away from its access link, it MUST send a Proxy
Binding Update to the local mobility anchor with the lifetime
value set to 0 and it must also remove the default route over the
tunnel for that mobile and also remove the Binding Update list
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entry and any other local state created for that mobile node.
7. Mobile Node Operation
The Network-based mobility scheme defined in this document, allows a
mobile node to obtain IP mobility within the proxy mobile IPv6
domain, with out requiring the mobile node to involve in any mobility
management.
When a mobile node enters a proxy mobile IPv6 domain and attached to
an access link, the network identifies the mobile node as part of the
access authentication and establishes an identity for the mobile
node. This identity has a binding to a cryptographic state and
potentially associating the mobile node's link-layer address of the
attached interface. The specifics on how this is achieved is beyond
the scope of this document and is very much specific to the access
technology and depends on the applied security protocols in place.
For all practical purposes, this document assumes that the mobile
node's access to the network is secure.
Once the mobile node enters a Proxy Mobile IPv6 domain and attaches
to an access network, the network identifies the mobile as part of
the access authentication procedure and ensures the mobile using any
of the address configuration mechanisms permitted by the network for
that mobile, will be able to obtain an address and move anywhere in
that managed domain. From the perspective of the mobile, the entire
Proxy Mobile IPv6 domain appears as a single link, the network
ensures the mobile believes it is always on the same link.
The mobile node can be operating in an IPv4-only mode, IPv6-only mode
or in dual IPv4/IPv6 mode. Typically, the configured policy in the
network determines the type of home address(es) i.e. MN-HoA, IPv4
MN-HoA or both, that the network mobility is supported for. If the
configured policy for a mobile node is for IPv6-only home address
mobility, the mobile node will be able to obtain its MN-HoA, any
where in that proxy mobile IPv6 domain and if policy allows only
IPv4-only home address mobility, the mobile node will be able to
obtain its IPv4 MN-HoA, any where in that domain. Similarly, if the
policy permits both the IPv4 and IPv6 home address mobility, the
mobile node will be able to obtain its MN-HoA and IPv4 MN-HoA and
move anywhere in the network. However, if the mobile node is
configured for IPv6-only mobility and if the mobile node attempts to
obtain an IPv4 address configuration via DHCP mechanism, the obtained
address configuration will not have any mobility properties, i.e. the
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obtained address will be from a local prefix and not from a prefix
that is topologically anchored at the local mobility anchor and hence
the mobile will loose that address as it moves to a different link.
The specifics on how this is achieved is the operational logic of the
mobile access gateway on the access link.
7.1. Booting up in a Proxy Mobile IPv6 Domain
When a mobile node moves into a proxy mobile IPv6 domain and attaches
to an access link, the mobile node will present its identity, MN-
Identity, to the network as part of the access authentication
procedure. Once the authentication procedure is complete and the
mobile node is authorized to access the network, the network or
specifically the mobile access gateway on the access link will have
the mobile node's profile and so it would know the mobile node's home
network prefix and the permitted address configuration modes. The
mobile node's home network prefix may also be dynamically assigned by
the mobile node's local mobility anchor and the same may be learnt by
the mobile access gateway.
If the mobile node is IPv6 enabled, on attaching to the link and
after access authentication, the mobile node typically would send a
Router Solicitation message. The mobile access gateway on the
attached link will respond to the Router Solicitation message with a
Router Advertisement. The Router Advertisement will have the mobile
node's home network prefix, default-router address and other address
configuration parameters. The address configuration parameters such
as Managed Address Configuration, Statefull Configuration flag values
will typically be consistent through out that domain for that mobile
node.
If the Router Advertisement has the Managed Address Configuration
flag set, the mobile node, as it would normally do, will send a
DHCPv6 Request and the mobile access gateway on that access link will
ensure, the mobile node node gets the MN-HoA as a lease from the DHCP
server.
If the Router Advertisement does not have the Managed Address
Configuration flag set and if the mobile node is allowed to use an
autoconfigured address, the mobile node will generate an interface
identifier, as per the Autoconf specification [RFC-2462] or using
privacy extensions as specified in Privacy Extensions specification
[RFC-3041].
If the mobile node is IPv4 enabled or IPv4-only enabled, the mobile
node after the access authentication, will be able to obtain the IPv4
address configuration for the connected interface by using DHCPv4.
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Once the address configuration is complete, the mobile node will have
the MN-HoA, IPv4 MN-HoA or both, that it can continue to use as long
as it is with in the scope of that proxy mobile IPv6 domain.
7.2. Roaming in the Proxy Mobile IPv6 Network
After booting in the Proxy Mobile IPv6 domain and obtaining the
address configuration, the mobile node as it roams in the network
between access links, will always detect its home network prefix on
the link, as long as the attached access network is in the scope of
that proxy mobile IPv6 domain. The mobile node can continue to use
its IPv4/IPv6 MN-HoA for sending and receiving packets. If the
mobile node uses DHCP for address configuration, it will always be
able to obtain its MN-HoA using DHCP. However, the mobile node will
always detect a new default-router on each connected link, but still
advertising the mobile node's home prefix as the on-link prefix and
with the other configuration parameters consistent with the link
properties as before.
7.3. IPv6 Host Protocol Parameters
This specification assumes the mobile node to be a normal IPv6 node,
with its protocol operation consistent with the base IPv6
specification [RFC-2460]. All aspects of Neighbor Discovery
Protocol, including Router Discovery, Neighbor Discovery, Address
Configuration procedures will just remain consistent with the base
IPv6 Neighbor Discovery Specification [RFC-2461]. However, this
specification recommends that the following IPv6 operating parameters
on the mobile node be adjusted to the below recommended values for
protocol efficiency and for achieving faster hand-offs.
Lower Default-Router List Cache Time-out:
As per the base IPv6 specification [RFC-2460], each IPv6 host will
maintain certain host data structures including a Default-Router
list. This is the list of on-link routers that have sent Router
Advertisement messages and are eligible to be default routers on that
link. The Router Lifetime field in the received Router Advertisement
defines the life of this entry.
In the Proxy Mobile IPv6 scenario, when the mobile node moves from
one link to another, the received Router Advertisement messages
advertising the mobile's home network prefix will be from a different
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link-local address and thus making the mobile node believe that there
is a new default-router on the link. It is important that the mobile
node uses the newly learnt default-router as supposed to the
previously learnt default-router. The mobile node must update its
default-router list with the new default router entry and must age
out the previously learnt default router entry from its cache, just
as specified in Section 6.3.5 of the base IPv6 ND specification [RFC-
2461]. This action is critical for minimizing packet losses during a
hand off switch
On detecting a reachability problem, the mobile node will certainly
detect the neighbor or the default-router unreachability by
performing a Neighbor Unreachability Detection procedure, but it is
important that the mobile node times out the previous default router
entry at the earliest. If a given IPv6 host implementation has the
provision to adjust these flush timers, still conforming to the base
IPv6 ND specification, it is desirable to keep the flush-timers to
suit the above consideration.
However, if the mobile access gateway has the ability to with draw
the previous default-router entry, by multicasting a Router
Advertisement using the link-local address that of the previous
mobility proxy agent and with the Router Lifetime field set to value
0, then it is possible to force the flush out of the Previous
Default-Router entry from the mobile node's cache. This certainly
requires some context-transfer mechanisms in place for notifying the
link-local address of the default-router on the previous link to the
mobile access gateway on the new link.
There are other solutions possible for this problem, including the
assignment of a unique link-local address for all the access routers
in the Proxy Mobile IPv6 Network. In either case, this is an
implementation choice and has no bearing on the protocol
interoperability. Implementations are free to adopt the best
approach that suits their target deployments.
8. Message Formats
This section defines extensions to the Mobile IPv6 [RFC-3775]
protocol messages.
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8.1. Proxy Binding Update
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|H|L|K|M|R|P| Reserved | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Proxy Binding Update Message
A Binding Update message that is sent by mobile access gateway is
referred to as the Proxy Binding Update message.
Proxy Registration Flag (P)
The Proxy Registration Flag is set to indicate to the local mobility
anchor that the Binding Update is from a mobile access gateway acting
as a proxy mobility agent. The flag MUST be set to the value of 1
for proxy registrations and MUST be set to 0 for direct registration
send my a mobile node using host-base mobility.
For descriptions of other fields present in this message, refer to
the section 6.1.7 of Mobile IPv6 specification [RFC3775].
8.2. Proxy Binding Acknowledgment
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status |K|R|P|Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Proxy Binding Acknowledgment Message
Proxy Registration Flag (P)
A new flag (P) is included in the Binding Acknowledgement message to
indicate that the local mobility anchor Agent that processed the
corresponding Binding Update supports Proxy Registrations. The flag
is set only if the corresponding Proxy Binding Update had the Proxy
Registration Flag (P) set to 1. The rest of the Binding
Acknowledgement format remains the same, as defined in [RFC-3775].
For descriptions of other fields present in this message, refer to
the Mobile IPv6 base specificatoin [RFC-3775].
A Binding Acknowledgment message that is sent by the mobile access
gateway is also referred to as "Proxy Binding Acknowledgement".
8.3. Home Network Prefix Option
A new option, Home Network Prefix Option is defined for using it in
the Proxy Binding Update and Acknowledgment messages exchanged
between the local mobility anchor to the mobile access gateway. This
option can be used for exchanging the mobile node's home prefix and
home address information.
The home network prefix Option has an alignment requirement of 8n+4.
Its format is as follows:
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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 | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Home Network Prefix +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
<IANA>
Length
8-bit unsigned integer indicating the length in octets of
the option, excluding the type and length fields. This field
MUST be set to 18.
Reserved
This field is unused for now. The value MUST be initialized
to 0 by the sender and MUST be ignored by the receiver.
Prefix Length
8-bit unsigned integer indicating the prefix length of the
IPv6 prefix contained in the option. If the prefix length
is set to the value 128, indicates the presence of the
mobile node's 128-bit home address.
Home Network Prefix
A sixteen-byte field containing the Home Network Prefix
Figure 8: Home Network Prefix Option
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8.4. Time Stamp Option
A new option, Time Stamp Option is defined for use in Proxy Binding
Update and Acknowledgement messages. This option MUST be present in
all Proxy Binding Update and Acknowledgement messages.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Timestamp +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
<IANA>
Length
8-bit unsigned integer indicating the length in octets of
the option, excluding the type and length fields. This field
MUST be set to 18.
Timestamp
64-bit time stamp
Figure 9: Time Stamp Option
8.5. Status Codes
This document defines the following new Binding Acknowledgement
status values:
145: Proxy Registration not supported by the local mobility anchor
146: Proxy Registrations from this mobile access gateway not allowed
147: No home address for this NAI is configured and the Home Network
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Prefix Option not present in the Binding Update.
148: Invalid Time Stamp Option in the Binding Update
Status values less than 128 indicate that the Binding Update was
processed successfully by the receiving nodes. Values greater than
128 indicate that the Binding Update was rejected by the local
mobility anchor.
The value allocation for this usage needs to be approved by the IANA
and must be updated in the IANA registry.
9. IANA Considerations
This document defines a new Mobility Header Option, the Mobile Home
Network Prefix Option. This option is described in Section 8.3. The
Type value for this option needs to be assigned from the same
numbering space as allocated for the other mobility options defined
in [RFC-3775].
This document defines a new Mobility Header Option, the Time Stamp
Option. This option is described in Section 8.4. The type value for
this option needs to be assigned from the same numbering space as
allocated for the other mobility options defined in [RFC-3775].
This document also defines new Binding Acknowledgement status values
as described in Section 8.5. The status values MUST be assigned from
the same space used for Binding Acknowledgement status values in
[RFC-3775].
10. Security Considerations
The security threats against any general network-based mobility
management protocol are covered in the document, Security Threats to
Network-Based Localized Mobility Management
[draft-ietf-netlmm-threats-04.txt]. This section analyses those
vulnerabilities in the context of Proxy Mobile IPv6 protocol and
covers all aspects around those identified vulnerabilities.
A compromised mobile access gateway can send Proxy Binding Update
requests for mobile nodes that are not attached to its access link.
This threat is similar to an attack on a typical routing protocol or
equivalent to the compromise of a on-path router and hence this
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threat exists in the network today and this specification does not
make this vulnerability any worse than what it is. However, to
eliminate this attack, the local mobility anchor can ensure that the
mobile node is attached to the access link of the requesting mobile
access gateway. This can be achieved using out of band mechanisms,
such as from the mobile node's access authentication to the network
and the specifics of how that is achieved is beyond the scope of this
document.
This document does not cover the security requirements for
authorizing the mobile node for the use of the access link. It is
assumed that there are proper Layer-2 based authentication
procedures, such as EAP, in place and will ensure the mobile node is
properly identified and authorized before permitting it to access the
network. It is further assumed that the same security mechanism will
ensure the mobile session is not hijacked by malicious nodes on the
access link.
This specification requires that all the signaling messages exchanged
between the mobile access gateway and the local mobility anchor MUST
be authenticated by IPsec [RFC-4301]. The use of IPsec to protect
Mobile IPv6 signaling messages is described in detail in the HA-MN
IPsec specification [RFC-3776] and the extension of that security
model to Proxy Mobile IPv6 is covered in Section 4.0 of this
document.
As described in the base Mobile IPv6 specification [RFC-3775],
Section 5.1 both the mobile client (in this case, its the mobile
access gateway) and the local mobility anchor MUST support and SHOULD
use the Encapsulating Security Payload (ESP) header in transport mode
and MUST use a non-NULL payload authentication algorithm to provide
data origin authentication, data integrity and optional anti-replay
protection.
The proxy solution allows one device creating a routing state for
some other device at the local mobility anchor. It is important that
the local mobility anchor has proper authorization services in place
to ensure a given mobile access gateway is permitted to be a proxy
for a specific mobile node. If proper security checks are not in
place, a malicious node may be able to hijack a session or may do a
denial-of-service attacks.
11. Acknowledgements
The authors would like to specially thank Julien Laganier, Christian
Vogt, Pete McCann, Brian Haley and Ahmad Muhanna for their thorough
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review of this document.
The authors would also like to thank the Gerardo Giaretta, Kilian
Weniger, Alex Petrescu, Mohamed Khalil, Fred Templing, Nishida
Katsutoshi, James Kempf, Vidya Narayanan, Henrik Levkowetz, Phil
Roberts, Jari Arkko, Ashutosh Dutta, Hesham Soliman, Behcet Sarikaya,
George Tsirtsis and many others for their passionate discussions in
the working group mailing list on the topic of localized mobility
management solutions. These discussions stimulated much of the
thinking and shaped the draft to the current form. We acknowledge
that !
The authors would also like to thank Ole Troan, Akiko Hattori, Perviz
Yegani, Mark Grayson, Michael Hammer, Vojislav Vucetic, Jay Iyer and
Tim Stammers for their input on this document.
12. References
12.1. Normative References
[RFC-1305] Mills, D., "Network Time Protocol (Version 3)
Specification, Implementation", RFC 1305, March 1992.
[RFC-2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC-2461] Narten, T., Nordmark, E. and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998.
[RFC-2462] Thompson, S., Narten, T., "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
[RFC-2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, December 1998.
[RFC-3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and
M.Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 3315, July 2003.
[RFC-3775] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in
IPv6", RFC 3775, June 2004.
[RFC-3776] Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to
Protect Mobile IPv6 Signaling Between Mobile Nodes and Home Agents",
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RFC 3776, June 2004.
[RFC-4283] Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
Chowdhury, "Mobile Node Identifier Option for Mobile IPv6", RFC 4283,
November 2005.
[RFC-4301] Kent, S. and Atkinson, R., "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC-4303] Kent, S. "IP Encapsulating Security Protocol (ESP)", RFC
4303, December 2005.
[RFC-4306] Kaufman, C, et al, "Internet Key Exchange (IKEv2)
Protocol", RFC 4306, December 2005.
[draft-ietf-netlmm-nohost-req-05.txt] Kempf, J., Leung, K., Roberts,
P., Nishida, K., Giaretta, G., Liebsch, M., "Goals for Network-based
Localized Mobility Management", October 2006.
[draft-ietf-netlmm-nohost-ps-05.txt] Kempf, J., Leung, K., Roberts,
P., Nishida, K., Giaretta, G., Liebsch, M., "Problem Statement for
Network-based Localized Mobility Management", September 2006.
[draft-ietf-netlmm-threats-04.txt] Vogt, C., Kempf, J., "Security
Threats to Network-Based Localized Mobility Management", September
2006.
[draft-ietf-mip6-nemo-v4traversal-03.txt] Soliman, H. et al, "Mobile
IPv6 support for dual stack Hosts and Routers (DSMIPv6)", October
2006.
12.2. Informative References
[RFC-1332] McGregor, G., "The PPP Internet Protocol Control Protocol
(IPCP)", RFC 1332, May 1992.
[RFC-1661] Simpson, W., Ed., "The Point-To-Point Protocol (PPP)", STD
51, RFC 1661, July 1994.
[RFC-2472] Haskin, D. and Allen, E., "IP version 6 over PPP", RFC
2472, December 1998.
[RFC-2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[RFC-3041] Narten, T. and Draves, R., "Privacy Extensions for
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Stateless Address Autoconfiguration in IPv6", RFC 3041, January 2001.
[RFC-3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002.
[RFC-3756] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor
Discovery (ND) Trust Models and Threats", RFC 3756, May 2004.
[draft-iab-multilink-subnet-issues-03.txt] Thaler, D., "Multilink
Subnet Issues", January 2006.
[draft-ietf-dna-protocol-03] Kempf, J., et al "Detecting Network
Attachment in IPv6 Networks (DNAv6)", draft-ietf-dna-protocol-03,
October 2006.
[draft-ietf-mip6-ikev2-ipsec-08] Devarapalli, V. and Dupont, F.,
"Mobile IPv6 Operation with IKEv2 and the revised IPsec
Architecture", December 2006.
Appendix A. Proxy Mobile IPv6 interactions with AAA Infrastructure
Every mobile node that roams in a proxy Mobile IPv6 domain, would
typically be identified by an identifier, MN-Identifier, and that
identifier will have an associated policy profile that identifies the
mobile node's home network prefix, permitted address configuration
modes, roaming policy and other parameters that are essential for
providing network-based mobility service. This information is
typically configured in AAA. It is possible the home network prefix
is dynamically allocated for the mobile node when it boots up for the
first time in the network, or it could be a statically configured
value on per mobile node basis. However, for all practical purposes,
the network entities in the proxy Mobile IPv6 domain, while serving a
mobile node will have access to this profile and these entities can
query this information using RADIUS/DIAMETER protocols.
Appendix B. Supporting Shared-Prefix Model using DHCPv6
For supporting shared-prefix model, i.e, if multiple mobile nodes are
configured with a common IPv6 network prefix, as in Mobile IPv6
specification, it is possible to support that configuration under the
following guidelines:
The mobile node is allowed to use statefull address configuration
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using DHCPv6 for obtaining its address configuration. The mobile
nodes is not allowed to use any of the stateless autoconfiguration
techniques. The permitted address configuration models for the
mobile node on the access link can be enforced by the mobile access
gateway by setting the relevant flags in the Router Advertisements,
as per ND Specification, [RFC-2461]
The Home Network Prefix Option that is sent by the mobile access
gateway in the Proxy Binding Update message, must contain the 128-bit
host address that the mobile node obtained via DHCPv6.
Routing state at the mobile access gateway:
For all IPv6 traffic from the source MN-HoA::/128 to destination
0::/0, route via tunnel0, next-hop LMAA, where tunnel0 is the MAG to
LMA tunnel.
Routing state at the local mobility anchor:
For all IPv6 traffic to destination MN-HoA::/128, route via tunnel0,
next-hop Proxy-CoA, where tunnel0 is the LMA to MAG tunnel.
Authors' Addresses
Sri Gundavelli
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sgundave@cisco.com
Kent Leung
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: kleung@cisco.com
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Vijay Devarapalli
Azaire Networks
4800 Great America Pkwy
Santa Clara, CA 95054
USA
Email: vijay.devarapalli@azairenet.com
Kuntal Chowdhury
Starent Networks
30 International Place
Tewksbury, MA
Email: kchowdhury@starentnetworks.com
Basavaraj Patil
Nokia Siemens Networks
6000 Connection Drive
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Internet-Draft Proxy Mobile IPv6 April 2007
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