NETLMM WG S. Gundavelli (Editor)
Internet-Draft K. Leung
Intended status: Standards Track Cisco
Expires: June 27, 2008 V. Devarapalli
Azaire Networks
K. Chowdhury
Starent Networks
B. Patil
Nokia Siemens Networks
December 25, 2007
Proxy Mobile IPv6
draft-ietf-netlmm-proxymip6-08.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on June 27, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
Network-based mobility management enables IP mobility for a host
without requiring its participation in any mobility related
Gundavelli, et al. Expires June 27, 2008 [Page 1]
Internet-Draft Proxy Mobile IPv6 December 2007
signaling. The Network is responsible for managing IP mobility on
behalf of the host. The mobility entities in the network are
responsible for tracking the movements of the host and initiating the
required mobility signaling on its behalf. This specification
describes a network-based mobility management protocol and is
referred to as Proxy Mobile IPv6.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions & Terminology . . . . . . . . . . . . . . . . . . 4
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 . . . . . . . . . . . . . 14
4.1. Peer Authorization Database Entries . . . . . . . . . . . 15
4.2. Security Policy Database Entries . . . . . . . . . . . . . 15
5. Local Mobility Anchor Operation . . . . . . . . . . . . . . . 16
5.1. Extensions to Binding Cache Entry Data Structure . . . . . 16
5.2. Supported Home Network Prefix Models . . . . . . . . . . . 18
5.3. Signaling Considerations . . . . . . . . . . . . . . . . . 18
5.4. Multihoming Support . . . . . . . . . . . . . . . . . . . 24
5.5. Timestamp Option for Message Ordering . . . . . . . . . . 28
5.6. Routing Considerations . . . . . . . . . . . . . . . . . . 30
5.6.1. Bi-Directional Tunnel Management . . . . . . . . . . . 30
5.6.2. Forwarding Considerations . . . . . . . . . . . . . . 31
5.7. Local Mobility Anchor Address Discovery . . . . . . . . . 32
5.8. Mobile Prefix Discovery Considerations . . . . . . . . . . 32
5.9. Route Optimizations Considerations . . . . . . . . . . . . 33
6. Mobile Access Gateway Operation . . . . . . . . . . . . . . . 33
6.1. Extensions to Binding Update List Entry Data Structure . . 34
6.2. Mobile Node's Policy Profile . . . . . . . . . . . . . . . 35
6.3. Supported Access Link Types . . . . . . . . . . . . . . . 35
6.4. Supported Address Configuration Models . . . . . . . . . . 36
6.5. Access Authentication & Mobile Node Identification . . . . 36
6.6. Acquiring Mobile Node's Identifier . . . . . . . . . . . . 36
6.7. Home Network Emulation . . . . . . . . . . . . . . . . . . 37
6.8. Link-Local and Global Address Uniqueness . . . . . . . . . 38
6.9. Signaling Considerations . . . . . . . . . . . . . . . . . 39
6.9.1. Binding Registrations . . . . . . . . . . . . . . . . 39
6.9.2. Router Solicitation Messages . . . . . . . . . . . . . 45
6.9.3. Retransmissions and Rate Limiting . . . . . . . . . . 45
6.10. Routing Considerations . . . . . . . . . . . . . . . . . . 46
6.10.1. Transport Network . . . . . . . . . . . . . . . . . . 46
6.10.2. Tunneling & Encapsulation Modes . . . . . . . . . . . 46
6.10.3. Routing State . . . . . . . . . . . . . . . . . . . . 47
6.10.4. Local Routing . . . . . . . . . . . . . . . . . . . . 48
Gundavelli, et al. Expires June 27, 2008 [Page 2]
Internet-Draft Proxy Mobile IPv6 December 2007
6.10.5. Tunnel Management . . . . . . . . . . . . . . . . . . 49
6.10.6. Forwarding Rules . . . . . . . . . . . . . . . . . . . 49
6.11. Supporting DHCPv6 based Address Configuration on the
Access Link . . . . . . . . . . . . . . . . . . . . . . . 50
6.12. Home Network Prefix Renumbering . . . . . . . . . . . . . 51
6.13. Mobile Node Detachment Detection and Resource Cleanup . . 51
6.14. Allowing network access to other IPv6 nodes . . . . . . . 52
7. Mobile Node Operation . . . . . . . . . . . . . . . . . . . . 53
7.1. Moving into a Proxy Mobile IPv6 Domain . . . . . . . . . . 53
7.2. Roaming in the Proxy Mobile IPv6 Domain . . . . . . . . . 54
7.3. IPv6 Host Protocol Parameters . . . . . . . . . . . . . . 54
8. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 55
8.1. Proxy Binding Update Message . . . . . . . . . . . . . . . 56
8.2. Proxy Binding Acknowledgement Message . . . . . . . . . . 57
8.3. Home Network Prefix Option . . . . . . . . . . . . . . . . 58
8.4. Access Technology Type Option . . . . . . . . . . . . . . 60
8.5. Mobile Node Interface Identifier Option . . . . . . . . . 61
8.6. Link-local Address Option . . . . . . . . . . . . . . . . 62
8.7. Timestamp Option . . . . . . . . . . . . . . . . . . . . . 63
8.8. Status Values . . . . . . . . . . . . . . . . . . . . . . 64
9. Protocol Configuration Variables . . . . . . . . . . . . . . . 66
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 67
11. Security Considerations . . . . . . . . . . . . . . . . . . . 68
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 69
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 69
13.1. Normative References . . . . . . . . . . . . . . . . . . . 69
13.2. Informative References . . . . . . . . . . . . . . . . . . 70
Appendix A. Proxy Mobile IPv6 interactions with AAA
Infrastructure . . . . . . . . . . . . . . . . . . . 71
Appendix B. Supporting Shared-Prefix Model using DHCPv6 . . . . . 71
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 72
Intellectual Property and Copyright Statements . . . . . . . . . . 74
Gundavelli, et al. Expires June 27, 2008 [Page 3]
Internet-Draft Proxy Mobile IPv6 December 2007
1. Introduction
IP mobility for IPv6 hosts is specified in Mobile IPv6 [RFC-3775].
Mobile IPv6 requires client functionality in the IPv6 stack of a
mobile node. Exchange of signaling messages between the mobile node
and home agent enables the creation and maintenance of a binding
between the mobile node's home address and its care-of-address.
Mobility as specified in [RFC-3775] requires the IP host to send IP
mobility management signaling messages to the Home Agent, which is
located in the network.
Network-based mobility is another approach to solving the IP mobility
challenge. It is possible to support mobility for IPv6 nodes without
host involvement by extending Mobile IPv6 [RFC-3775] signaling
messages and reusing the home agent. This approach to supporting
mobility does not require the mobile node to be involved in the
exchange of signaling messages between itself and the Home Agent. A
proxy mobility agent in the network performs the signaling with the
home agent and does the mobility management on behalf of the mobile
node attached to the network. Because of the use and extension of
Mobile IPv6 signaling and home agent functionality, this protocol is
referred to as Proxy Mobile IPv6 (PMIPv6).
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 Proxy Mobile IPv6 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 undergone interoperability testing.
o A common home agent would serve as the mobility agent for all
types of IPv6 nodes.
The problem statement and the need for a network based mobility
protocol solution has been documented in [RFC-4830]. Proxy Mobile
IPv6 is a solution that addresses these issues and requirements.
2. Conventions & Terminology
Gundavelli, et al. Expires June 27, 2008 [Page 4]
Internet-Draft Proxy Mobile IPv6 December 2007
2.1. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC-2119].
2.2. Terminology
All the 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 [RFC-
4831]. This document also provides the following context specific
explanation to the following terms used in this document.
Proxy Mobile IPv6 Domain (PMIPv6-Domain)
Proxy Mobile IPv6 domain refers to the network where the mobility
management of a mobile node is handled using the Proxy Mobile IPv6
protocol as defined in this specification. The Proxy Mobile IPv6
domain includes local mobility anchors and mobile access gateways
between which security associations can be setup and authorization
for sending Proxy Binding Updates on behalf of the mobile nodes
can be ensured.
Local Mobility Anchor (LMA)
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 network prefix and is the entity that
manages the mobile node's binding state. The local mobility
anchor has the functional capabilities of a home agent as defined
in Mobile IPv6 base specification [RFC-3775] with the additional
capabilities required for supporting Proxy Mobile IPv6 protocol as
defined in this specification.
Mobile Access Gateway (MAG)
Mobile Access Gateway 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 movements
on the access link and for signaling the mobile node's local
mobility anchor.
Gundavelli, et al. Expires June 27, 2008 [Page 5]
Internet-Draft Proxy Mobile IPv6 December 2007
Mobile Node (MN)
Throughout this document, the term mobile node is used to refer to
an IP host whose mobility is managed 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 IP
mobility related signaling for achieving mobility for an IP
address that is obtained in that Proxy Mobile IPv6 domain. This
document further uses explicit text when referring to a mobile
node that is involved in mobility related signaling as per the
Mobile IPv6 specification [RFC-3775].
LMA Address (LMAA)
The address that is configured on the interface of the local
mobility anchor and is the transport endpoint of the bi-
directional tunnel established 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, as specified in [ID-IPV4-PMIP6].
Proxy Care-of Address (Proxy-CoA)
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, as specified in [ID-IPV4-PMIP6].
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 from its home network prefix obtained by
a mobile node in a Proxy Mobile IPv6 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.
Mobile Node's Home Network Prefix (MN-HNP)
Gundavelli, et al. Expires June 27, 2008 [Page 6]
Internet-Draft Proxy Mobile IPv6 December 2007
This is the on-link IPv6 prefix that is always present in the
Router Advertisements that the mobile node receives when it is
attached to any of the access links in that Proxy Mobile IPv6
domain. This home network prefix is topologically anchored at the
mobile node's local mobility anchor. The mobile node configures
its interface with an address from this prefix. If the mobile
node connects to the Proxy Mobile IPv6 domain through multiple
interfaces, simultaneously, each of the connected interface will
be assigned a unique home network prefix and under a different
mobility session.
Mobile Node's Home Link
This is the link on which the mobile node obtained its Layer-3
address configuration for the attached interface 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.
Multihomed Mobile Node
A mobile node that connects to the Proxy Mobile IPv6 domain
through more than one interface and uses these interfaces
simultaneously is referred to as a multihomed mobile node.
Mobile Node Identifier (MN-Identifier)
The identity of a mobile node in the Proxy Mobile IPv6 domain.
This is the stable identifier of a mobile node that the mobility
entities in a Proxy Mobile IPv6 domain can always acquire and use
it for predictably identifying a mobile node. This is typically
an identifier such as NAI or other identifier such as a MAC
address.
Mobile Node Interface Identifier (MN-Interface-Identifier)
The interface identifier that identifies a given interface of a
mobile node. For those interfaces that have a layer-2 identifier,
the interface identifier can be based on that layer-2 identifier.
The interface identifier in some cases is generated by the mobile
node and conveyed to the access router or the mobile access
gateway. In some cases, there might not be any interface
identifier associated with the mobile node's interface.
Policy Profile
Gundavelli, et al. Expires June 27, 2008 [Page 7]
Internet-Draft Proxy Mobile IPv6 December 2007
Policy Profile is an abstract term for referring to a set of
configuration parameters that are configured for a given mobile
node. The mobility entities in the Proxy Mobile IPv6 domain
require access to these parameters for providing the mobility
management to a given mobile node. The specific details on how
the network entities obtain this policy profile is outside the
scope of this document.
Proxy Binding Update (PBU)
A binding registration request message sent by a mobile access
gateway to a mobile node's local mobility anchor for establishing
a binding between the mobile node's MN-HNP and the Proxy-CoA.
Proxy Binding Acknowledgement (PBA)
A binding registration reply message sent by a local mobility
anchor in response to a Proxy Binding Update request 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 and is based on Mobile IPv6
[RFC-3775].
Proxy Mobile IPv6 protocol is intended for providing network-based IP
mobility management support to a mobile node, without requiring the
participation of the mobile node in any IP mobility related
signaling. The mobility entities in the network will track the
mobile node's movements and will initiate the mobility signaling and
setup the required routing state.
The core functional entities in the NETLMM infrastructure are the
Local Mobility Anchor (LMA) and the Mobile Access Gateway (MAG). The
local mobility anchor is responsible for maintaining the mobile
node's reachability state and is the topological anchor point for the
mobile node's home network prefix. The mobile access gateway is the
entity that performs the mobility management on behalf of a mobile
node and it resides on the access link where the mobile node is
anchored. The mobile access gateway is responsible for detecting the
mobile node's movements on its access link and for sending binding
registrations to the mobile node's local mobility anchor. The
architecture of a Proxy Mobile IPv6 domain is shown in Figure 1.
Gundavelli, et al. Expires June 27, 2008 [Page 8]
Internet-Draft Proxy Mobile IPv6 December 2007
+----+ +----+
|LMA1| |LMA2|
+----+ +----+
LMAA1 -> | | <-- LMAA2
| |
\\ //\\
\\ // \\
\\ // \\
+---\\------------- //------\\----+
( \\ IPv4/IPv6 // \\ )
( \\ Network // \\ )
+------\\--------//------------\\-+
\\ // \\
\\ // \\
\\ // \\
Proxy-CoA1--> | | <-- Proxy-CoA2
+----+ +----+
|MAG1|-----{MN2} |MAG2|
+----+ | +----+
| | |
MN-HoA1 --> | MN-HoA2 | <-- MN-HoA3
{MN1} {MN3}
Figure 1: Proxy Mobile IPv6 Domain
Once a mobile node enters a Proxy Mobile IPv6 domain and attaches to
an access link, the mobile access gateway on that access link, after
identifying the mobile node and acquiring its identity, will
determine if the mobile node is authorized for the network-based
mobility management service.
If the network determines that the network-based mobility management
service needs to be offered to that mobile node, the network will
ensure that the mobile node using any of the address configuration
mechanisms permitted by the network will be able to obtain the
address configuration on the connected interface and move anywhere in
that Proxy Mobile IPv6 domain. The obtained address configuration
includes the address(es) from its home network prefix, the default-
router address on the link and other related configuration
parameters. From the perspective of the mobile node, the entire
Proxy Mobile IPv6 domain appears as a single link, the network
ensures that the mobile node believes it is always on the same link
where it obtained its initial address configuration, even after
Gundavelli, et al. Expires June 27, 2008 [Page 9]
Internet-Draft Proxy Mobile IPv6 December 2007
changing its point of attachment in that network.
The mobile node may be operating in an IPv4-only mode, IPv6-only mode
or in dual IPv4/IPv6 mode. Based on what is enabled in the network
for that mobile node, the mobile node will be able to obtain an IPv4,
IPv6 or dual IPv4/IPv6 addresses and move anywhere in that Proxy
Mobile IPv6 domain. However, the specific details related to the
IPv4 addressing or IPv4 transport support are specified in the
companion document [ID-IPV4-PMIP6].
If the mobile node connects to the Proxy Mobile IPv6 domain, through
multiple interfaces and over multiple access networks, the network
will allocate a unique home network prefix for each of the connected
interfaces and the mobile node will be able to configure an
address(es) on those interfaces from the respective home network
prefixes. If the mobile node performs a handover from one interface
to another in the same Proxy Mobile IPv6 domain, then the local
mobility anchor will assign the same prefix to the new interface, if
it receives the handover hints from the mobile access gateway in the
signaling messages.
Gundavelli, et al. Expires June 27, 2008 [Page 10]
Internet-Draft Proxy Mobile IPv6 December 2007
+-----+ +-----+ +-----+
| MN | | MAG | | LMA |
+-----+ +-----+ +-----+
| | |
MN Attached | |
| | |
| MN Attached Event |
| (Acquire MN-Id and Profile) |
| | |
| |----- PBU ----------->|
| | |
| | Accept PBU
| | (Allocate MN-HNP, Setup BCE and Tunnel)
| | |
| |<--------- PBA -------|
| | |
| Accept PBA |
| (Setup Tunnel and Routing) |
| | |
| |==== Bi-Dir Tunnel ===|
| | |
|--- Rtr Sol --------->| |
| | |
|<------- Rtr Adv -----| |
| | |
IP Address | |
Configuration | |
| | |
Figure 2: Mobile Node Attachment - Signaling Call Flow
Figure 2 shows the signaling call flow when the mobile node enters
the Proxy Mobile IPv6 domain.
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. Upon
accepting this Proxy Binding Update message, the local mobility
anchor sends a Proxy Binding Acknowledgement message including the
mobile node's home network prefix. It also creates the Binding Cache
entry and establishes a bi-directional tunnel to the mobile access
gateway.
Gundavelli, et al. Expires June 27, 2008 [Page 11]
Internet-Draft Proxy Mobile IPv6 December 2007
The mobile access gateway on receiving the Proxy Binding
Acknowledgement message sets up a bi-directional tunnel to the local
mobility anchor and sets up the data path for the mobile node's
traffic. At this point the mobile access gateway will have all the
required information for emulating the mobile node's home link. It
sends Router Advertisement messages to the mobile node on the access
link advertising the mobile node's home network prefix as the hosted
on-link-prefix.
The mobile node on receiving these Router Advertisement messages on
the access link will attempt to configure its interface either using
stateful or stateless address configuration modes, based on the modes
that are permitted on that access link. At the end of a successful
address configuration procedure, the mobile node will end up with an
address from its home network prefix.
Once the address configuration is complete, the mobile node has a
valid 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 using an address from its home network
prefix.
The local mobility anchor, being the topological anchor point for the
mobile node's home network prefix, receives any packets that are sent
by any correspondent node to the mobile node. The local mobility
anchor forwards these received packets to the mobile access gateway
through the bi-directional tunnel. The mobile access gateway on
other end of the tunnel, after receiving the packet, removes the
outer 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. Any packet that the mobile node sends to any
correspondent node will be received by the mobile access gateway and
will be sent to its local mobility anchor through the bi-directional
tunnel. The local mobility anchor on the other end of the tunnel,
after receiving the packet, removes the outer header and routes the
packet to the destination.
Gundavelli, et al. Expires June 27, 2008 [Page 12]
Internet-Draft Proxy Mobile IPv6 December 2007
+-----+ +-----+ +-----+ +-----+
| MN | |p-MAG| | LMA | |n-MAG|
+-----+ +-----+ +-----+ +-----+
| | | |
| |==Bi-Dir Tunnel=| |
MN Detached | | |
| MN Detached Event | |
| | | |
| |-- DeReg PBU -->| |
| | | |
| | Accept PBU |
| | (Start MinDelayBeforeBCEDelete Timer)
| | | |
| |<-------- PBA --| |
| | | |
MN Attached | | |
| | | MN Attached Event
| | | (Acquire MN-Id and Profile)
....
Registration steps as in fig 2.
....
| | |==Bi-Dir Tunnel=|
|--- Rtr Sol ------------------------------------->|
| | | |
|<------------------------------------ Rtr Adv ----|
| | | |
MN retains HoA/HNP
| | | |
Figure 3: Mobile Node Handoff - Signaling Call Flow
Figure 3 shows the signaling call flow for the mobile node's handoff
from previously attached mobile access gateway (p-MAG) to the newly
attached mobile access gateway (n-MAG).
After obtaining the initial address configuration in the Proxy Mobile
IPv6 domain, if the mobile node changes its point of attachment, the
mobile access gateway on the previous link will detect the mobile
node's detachment from the link and will signal the local mobility
anchor and will remove the binding and routing state for that mobile
node. However, the local mobility anchor upon accepting the request
will wait for certain amount of time before it deletes the binding,
for allowing a smooth handoff.
The mobile access gateway on the new access link upon detecting the
Gundavelli, et al. Expires June 27, 2008 [Page 13]
Internet-Draft Proxy Mobile IPv6 December 2007
mobile node on its access link will signal the local mobility anchor
for updating the binding state. Once that signaling is complete, the
mobile node will continue to receive the Router Advertisements
containing its home network prefix, making it believe it is still on
the same link and it will use the same address configuration on the
new access link.
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 MUST be protected using end-to-end security
association(s) offering integrity and data origin authentication.
The mobile access gateway and the local mobility anchor MUST
implement IPsec for protecting the Proxy Mobile IPv6 signaling
messages [RFC-4301]. IPsec is the default security mechanism for
securing the signaling messages. However in certain deployments of
this protocol, other security mechanisms MAY be applied and the
signaling messages must be protected using the semantics provided by
that respective mechanism. The specification of the other security
mechanisms are beyond the scope of this document
IPsec ESP [RFC-4303] in transport mode with mandatory integrity
protection SHOULD be used for protecting the signaling messages.
Confidentiality protection of these messages is not required.
IKEv2 [RFC-4306] SHOULD be used to setup security associations
between the mobile access gateway and the local mobility anchor to
protect the Proxy Binding Update and Proxy Binding Acknowledgement
messages. The mobile access gateway and the local mobility anchor
can use any of the authentication mechanisms, as specified in IKEv2,
for mutual authentication.
The Mobile IPv6 specification [RFC-3775] 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, 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 by sending a query to the
Gundavelli, et al. Expires June 27, 2008 [Page 14]
Internet-Draft Proxy Mobile IPv6 December 2007
policy store, such as AAA.
4.1. Peer Authorization Database Entries
This section describes PAD entries [RFC-4301] 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 any 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
Figure 4: PAD Entries
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
This section describes the security policy entries [RFC-4301] 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.
Gundavelli, et al. Expires June 27, 2008 [Page 15]
Internet-Draft Proxy Mobile IPv6 December 2007
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 = BA
Then use SA ESP transport mode
Initiate using IDi = mag_1 to address lma_address_1
local mobility anchor SPD-S:
- IF local_address = lma_address_1 &
remote_address = mag_address_1 &
proto = MH & local_mh_type = BA & remote_mh_type = BU
Then use SA ESP transport mode
Figure 5: SPD Entries
5. Local Mobility Anchor Operation
The local mobility anchor MUST support the home agent function as
defined in [RFC-3775] and additionally the extensions defined in this
specification. A home agent with these modifications and enhanced
capabilities for supporting Proxy Mobile IPv6 protocol is referred to
as the local mobility anchor.
This section describes the operational details of the local mobility
anchor.
5.1. Extensions to Binding Cache Entry Data Structure
Every local mobility anchor MUST maintain a Binding Cache entry for
each currently registered mobile node. Binding Cache entry is a
conceptual data structure, described in Section 9.1 [RFC-3775].
For supporting this specification, the Binding Cache Entry data
structure needs to be extended with the following additional 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 created due to the
registrations directly sent by the mobile node.
o The identifier of the registered mobile node, MN-Identifier. This
identifier is obtained from the Mobile Node Identifier Option
[RFC-4283] present in the received Proxy Binding Update request.
Gundavelli, et al. Expires June 27, 2008 [Page 16]
Internet-Draft Proxy Mobile IPv6 December 2007
o The interface identifier of the mobile node's connected interface
on the access link. This identifier can be acquired from the
Mobile Node Interface Identifier option, present in the received
Proxy Binding Update request. If the option was not present in
the request, this value MUST be set to ALL_ZERO.
o The Link-local address of the mobile node on the interface
attached to the access link. This is obtained from the Link-local
Address option, present in the Proxy Binding Update request.
o The IPv6 home network prefix of the registered mobile node. The
home network prefix of the mobile node may have been statically
configured in the mobile node's policy profile, or, it may have
been dynamically allocated by the local mobility anchor. The IPv6
home network prefix also includes the corresponding prefix length.
o The interface identifier of the bi-directional tunnel established
between the local mobility anchor and the mobile access gateway
where the mobile node is currently anchored. The tunnel interface
identifier is acquired during the tunnel creation.
o The access technology through which the mobile node is currently
connected. This is obtained from the Access Technology Type
option, present in the Proxy Binding Update message.
o The 64-bit timestamp value of the most recently accepted Proxy
Binding Update request sent for this mobile node. This is
obtained from the Timestamp option, present in the request.
Typically, the MN-Identifier is the key for locating a Binding Cache
entry. However, when supporting multihoming there MAY be more than
one Binding Cache entry with the same MN-Identifier and in such cases
the entry can be located using any of the following key combinations:
o MN-Identifier, MN-HNP
o MN-Identifier, Proxy-CoA
o MN-Identifier, MN-Interface-Identifier
o MN-Identifier, Access Technology Type (When MN-Interface-
Identifier is not present)
Gundavelli, et al. Expires June 27, 2008 [Page 17]
Internet-Draft Proxy Mobile IPv6 December 2007
5.2. Supported Home Network Prefix Models
This specification supports Per-MN-Prefix model and does not support
Shared-Prefix model. As per the Per-MN-Prefix model, there will be a
unique home network prefix assigned to each mobile node and no other
node shares an address from that prefix. The assigned prefix is
unique to a mobile node and also unique to a given interface of the
mobile node. If the mobile node attaches to the Proxy Mobile IPv6
domain through multiple interfaces and simultaneously, each of those
connected interfaces will be assigned a different prefix.
The mobile node's home network prefix is always hosted on the access
link where the mobile node is anchored. Conceptually, the entire
home network prefix follows the mobile node as it moves within the
Proxy Mobile IPv6 domain. The local mobility anchor is not required
to perform any proxy ND operations [RFC-4861] for defending the
mobile node's home address on the home link. However, from the
routing perspective, the home network prefix is topologically
anchored on the local mobility anchor.
5.3. Signaling Considerations
This section provides the rules for processing the signaling
messages. The processing rules specified in this section and other
related sections are chained and are in a specific order. When
applying these considerations for processing the signaling messages,
the specified order MUST be maintained.
Processing Binding Registrations
Upon receiving a Proxy Binding Update request (a Binding Update
Request with the 'P' flag set) from a mobile access gateway on behalf
of a mobile node, the local mobility anchor MUST process the request
as defined in Section 10.3 [RFC-3775]; additionally the following
considerations must be applied.
1. The local mobility anchor MUST observe the rules described in
Section 9.2 [RFC-3775] when processing Mobility Headers in the
received Proxy Binding Update request.
2. The local mobility anchor MUST identify the mobile node from the
identifier present in the Mobile Node Identifier option [RFC-
4283] of the Proxy Binding Update request. If the Mobile Node
Identifier option is not present in the Proxy Binding Update
request, the local mobility anchor MUST reject the request and
Gundavelli, et al. Expires June 27, 2008 [Page 18]
Internet-Draft Proxy Mobile IPv6 December 2007
send a Proxy Binding Acknowledgement message with Status field
set to MISSING_MN_IDENTIFIER_OPTION (Missing mobile node
identifier) and the identifier in the Mobile Node Identifier
Option MUST be set to a zero length identifier.
3. If the local mobility anchor cannot authorize the mobile node
based on the Mobile Node Identifier option [RFC-4283] present in
the request, it MUST reject the Proxy Binding Update request and
send a Proxy Binding Acknowledgement message with Status field
set to 133 (Not home agent for this mobile node).
4. If the local mobility anchor determines that the mobile node is
not authorized for the network-based mobility management
service, it MUST reject the request and send a Proxy Binding
Acknowledgement message with Status field set to
PROXY_REG_NOT_ENABLED (Proxy Registration not enabled).
5. The local mobility anchor MUST ignore the check, specified in
Section 10.3.1 [RFC-3775], related to the presence of Home
Address destination option in the Proxy Binding Update request.
6. The local mobility anchor MUST authenticate the Proxy Binding
Update request as described in Section 4.0. When IPsec is used
for message authentication, the SPI in the IPsec header [RFC-
4306] of the received packet is needed for locating the security
association, for authenticating the Proxy Binding Update
request.
7. The local mobility anchor MUST apply the required policy checks,
as explained in Section 4.0, to verify the sender is a trusted
mobile access gateway, authorized to send Proxy Binding Update
requests on behalf of this mobile node.
8. If the local mobility anchor determines that the requesting node
is not authorized to send Proxy Binding Update requests, it MUST
reject the request and send a Proxy Binding Acknowledgement
message with Status field set to
MAG_NOT_AUTHORIZED_FOR_PROXY_REG (Not authorized to send proxy
registrations).
9. If the Home Network Prefix option is not present in the Proxy
Binding Update request, the local mobility anchor MUST reject
the request and send a Proxy Binding Acknowledgement message
with Status field set to MISSING_HOME_NETWORK_PREFIX_OPTION
(Missing mobile node's home network prefix option).
10. If the Access Technology Type option is not present in the Proxy
Binding Update request, the local mobility anchor MUST reject
Gundavelli, et al. Expires June 27, 2008 [Page 19]
Internet-Draft Proxy Mobile IPv6 December 2007
the request and send a Proxy Binding Acknowledgement message
with Status field set to MISSING_ACCESS_TECH_TYPE_OPTION
(Missing mobile node's access technology type).
11. The local mobility anchor MUST apply the considerations
specified in Section 5.5, for processing the Sequence Number
field and the Timestamp option, in the Proxy Binding Update
request.
12. The local mobility anchor MUST use the identifier from the
Mobile Node Identifier Option [RFC-4283] present in the Proxy
Binding Update request and MUST apply multihoming considerations
specified in Section 5.4 for performing the Binding Cache entry
existence test or for identifying the mobility session. If the
entry does not exist, the local mobility anchor MUST consider
this request as an initial binding registration request. If the
entry exists, the local mobility anchor MUST consider this
request as a binding re-registration request. However, from the
perspective of the mobile access gateway that sent the request,
this binding re-registration request may be an initial Binding
Update request after the mobile node's attachment to that mobile
access gateway.
Initial Binding Registration:
1. If the Home Network Prefix option present in the Proxy Binding
Update request has the value 0::/0, the local mobility anchor
SHOULD allocate a prefix for the mobile node and send a Proxy
Binding Acknowledgement message including the Home Network Prefix
option containing the allocated prefix value. The local mobility
anchor MUST ensure the allocated prefix is not in use by any
other node.
2. If the local mobility anchor is unable to allocate a home network
prefix for the mobile node, it MUST reject the request and send a
Proxy Binding Acknowledgement message with Status field set to
130 (Insufficient resources).
3. If the Home Network Prefix option present in the request has a
specific prefix hint, the local mobility anchor before accepting
that request, MUST ensure the prefix is owned by the local
mobility anchor and further the mobile node is authorized to use
that prefix. If the mobile node is not authorized to use that
prefix, the local mobility anchor MUST reject the request and
send a Proxy Binding Acknowledgement message with Status field
set to NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX (Mobile node not
authorized to use that prefix).
Gundavelli, et al. Expires June 27, 2008 [Page 20]
Internet-Draft Proxy Mobile IPv6 December 2007
4. Upon accepting the request, the local mobility anchor MUST create
a Binding Cache entry for the mobile node. It must set the
fields in the Binding Cache entry to the accepted values for that
binding. If there is a Link-local Address option present in the
request, the address must be copied to the link-local address
field in the Binding Cache entry.
5. Upon accepting the Proxy Binding Update request, the local
mobility anchor MUST establish a bi-directional tunnel to the
mobile access gateway, as described in [RFC-2473].
Considerations from Section 5.6 must be applied.
Binding Re-Registration:
1. If the requesting prefix in the Home Network Prefix option is a
non 0::/0 value and is different from what is present in the
currently active Binding Cache entry for that mobile node, the
local mobility anchor MUST reject the request and send a Proxy
Binding Acknowledgement message with Status field set to 129
(Administratively Prohibited).
2. If there is a Link-local Address option present in the request
with a value other than ALL_ZERO (not set), and upon accepting
the binding re-registration request, the local mobility anchor
MUST update the link-local address field in the Binding Cache
entry to the address value received in the request.
3. Upon accepting a Proxy Binding Update request for extending the
lifetime of a currently active binding for a mobile node, the
local mobility anchor MUST update the existing Binding Cache
entry for this mobile node. Unless there exists an established
bi-directional tunnel to the mobile access gateway with the same
transport and encapsulation mode, the local mobility anchor MUST
create a tunnel to the mobile access gateway, as described in
[RFC-2473] and also delete the existing tunnel route to the
previous mobile access gateway. It MUST also send a Proxy
Binding Acknowledgement message to the mobile access gateway with
the Status field set to 0 (Proxy Binding Update Accepted).
Binding De-Registration:
1. If the received Proxy Binding Update request with the lifetime
value of zero and the prefix in the Home Network Prefix option is
a non 0::/0 value and is different from what is present in the
currently active Binding Cache entry for that mobile node, the
local mobility anchor MUST reject the request and send a Proxy
Gundavelli, et al. Expires June 27, 2008 [Page 21]
Internet-Draft Proxy Mobile IPv6 December 2007
Binding Acknowledgement message with Status field set to 129
(Administratively Prohibited).
2. If the received Proxy Binding Update request with the lifetime
value of zero, has a Source Address in the IPv6 header different
from what is present in the Proxy-CoA address field in the
Binding Cache entry existing for that mobile node, the local
mobility anchor SHOULD ignore the request.
3. Upon accepting the Proxy Binding Update request for a mobile
node, with the lifetime value of zero, the local mobility anchor
MUST wait for MinDelayBeforeBCEDelete amount of time, before it
deletes the mobile node's Binding Cache entry. Within this wait
period, if the local mobility anchor receives a Proxy Binding
Update request message for the same mobile node with the lifetime
value of greater than zero, and if that request is accepted, then
the Binding Cache entry MUST NOT be deleted, but must be updated
with the newly accepted registration values. The local mobility
anchor MUST send the Proxy Binding Acknowledgement message,
immediately upon accepting the request. However, within this
wait period, if the local mobility anchor does not receive any
valid binding registration request for that mobile node, then at
the end of this wait period, it MUST delete the mobile node's
Binding Cache entry and remove the routing state created for that
mobile node. In addition, during this MinDelayBeforeBCEDelete
wait period, the local mobility anchor MUST continue to route the
mobile node's data traffic.
Constructing the Proxy Binding Acknowledgement Message:
o The local mobility anchor when sending the Proxy Binding
Acknowledgement message to the mobile access gateway MUST
construct the message as specified below.
IPv6 header (src=LMAA, dst=Proxy-CoA)
Mobility header
-BA /*P flag is set*/
Mobility Options
- Home Network Prefix Option
- Link-local Address Option (optional)
- Timestamp Option (optional)
- Mobile Node Identifier Option (Mandatory)
- Access Technology Type option (Mandatory)
- Mobile Node Interface Identifier option
(Optional)
Gundavelli, et al. Expires June 27, 2008 [Page 22]
Internet-Draft Proxy Mobile IPv6 December 2007
Figure 6: Proxy Binding Acknowledgement message format
o The Source Address field in the IPv6 header of the message MUST be
set to the destination address of the received Proxy Binding
Update request.
o The Destination Address field in the IPv6 header of the message
MUST be set to the source address of the received Proxy Binding
Update request.
o The Home Network Prefix option MUST be present in the Proxy
Binding Acknowledgement message. If the option was not present in
the request and if the Status field value is set to
MISSING_HOME_NETWORK_PREFIX_OPTION, the value MUST be set to
ALL_ZERO.
o The Access Technology Type option MUST be present. The access
technology type value in the option MUST be copied from the Access
Technology Type option in the received Proxy Binding Update
request. If the option was not present in the request and if the
Status field value is set to MISSING_ACCESS_TECH_TYPE_OPTION, the
value MUST be set to 0.
o The Mobile Node Interface Identifier option MAY be present, if the
same option was present in the corresponding Proxy Binding Update
request message.
o If the Status field is set to a value greater than or equal to
128, i.e., if the binding request was rejected, then the prefix
value in the Home Network Prefix option MUST be set to the prefix
value from the received Home Network Prefix option. For all other
cases, the prefix value MUST be set to the allocated prefix value
for that mobile node.
o The Link-local Address option MUST be present in the Proxy Binding
Acknowledgement message if and only if the same option was present
in the corresponding Proxy Binding Update request message.
o If the Status field is set to a value greater than or equal to
128, i.e., if the binding request was rejected, then the link-
local address value in the Link-local Address option MUST be set
to the value from the received Link-local Address option.
o If there is an existing Binding Cache entry for the mobile node
with the link-local address value of ALL_ZERO (value not set), or
if there was no existing Binding Cache entry, then the link-local
address MUST be copied from the Link-local Address option in the
received Proxy Binding Update request. For all other cases, it
Gundavelli, et al. Expires June 27, 2008 [Page 23]
Internet-Draft Proxy Mobile IPv6 December 2007
MUST be copied from the mobile node's Binding Cache entry.
o Considerations from Section 5.5 must be applied for constructing
the Timestamp option.
o The identifier in the Mobile Node Identifier option [RFC-4283]
MUST be copied from the received Proxy Binding Update request. If
the Status field value is set to MISSING_MN_IDENTIFIER_OPTION, the
identifier in the Mobile Node Identifier Option MUST be set to a
zero length identifier.
o If IPsec is used for protecting the signaling messages, the
message MUST be protected, using the security association existing
between the local mobility anchor and the mobile access gateway.
o The Type 2 Routing header MUST NOT be present in the IPv6 header
of the packet.
5.4. Multihoming Support
When a mobile node connects to a Proxy Mobile IPv6 domain through
multiple interfaces simultaneously, the local mobility anchor MUST
allocate a unique home network prefix for each of the connected
interfaces.
The local mobility anchor MUST manage each of the allocated home
network prefixes as part of a separate mobility session, each under a
separate Binding Cache entry and with its own lifetime.
The local mobility anchor MUST allow for a handover between two
different interfaces of the mobile node. In such a case, the home
network prefix that is associated with a specific interface
identifier of a mobile node will be updated with the new interface
identifier. The decision on when to create a new mobility session
and when to update an existing mobility session MUST be based on the
Handover hint present in the signaling messages and under the
considerations specified in this section.
The local mobility anchor MUST apply the following multihoming
considerations when processing a received Proxy Binding Update
request message.
Processing De-Registration Message:
1. If the received Proxy Binding Update message has lifetime value
of zero, the local mobility anchor MUST verify if there is an
Gundavelli, et al. Expires June 27, 2008 [Page 24]
Internet-Draft Proxy Mobile IPv6 December 2007
existing Binding Cache entry for the mobile node, identified by
the MN-Identifier and with the Proxy-CoA address matching the
source address in the IPv6 header of the received packet. If
there exists a Binding Cache entry, the local mobility anchor
MUST consider the message as a request for de-registering that
specific mobility session. If there does not exist a Binding
Cache entry, the message MUST be ignored.
Home Network Prefix Option (Non-Zero Prefix) present in the request:
1. The local mobility anchor MUST verify if there is an existing
Binding Cache entry for the mobile node, identified by the MN-
Identifier and with the home network prefix value matching the
prefix value in the Home Network Prefix Option of the request.
If there is a Mobile Node Interface Identifier Option present in
the request, it MUST be ignored for this search. If there exists
a Binding Cache entry matching the specified criteria, the local
mobility anchor MUST consider the message as a request for
updating that specific mobility session. The local mobility
anchor upon accepting the request MUST update the existing
Binding Cache entry and assign the home network prefix present in
the Binding Cache entry. If there does not exist a Binding Cache
entry matching this specified criteria, the below considerations
MUST be applied.
Mobile Node Interface Identifier Option not present in the request:
1. The local mobility anchor MUST verify if there is an existing
Binding Cache entry for the mobile node, identified by the MN-
Identifier and with the interface identifier value set to
ALL_ZERO.
2. If there does not exist a Binding Cache entry, the local mobility
anchor upon accepting the request MUST assign a new home network
prefix and create a new Binding Cache entry.
3. If there exists a Binding Cache entry and if the Handoff
Indicator field in the Access Technology Type option present in
the received Proxy Binding Update message is set to value 1
(Attachment over a new interface), the local mobility anchor upon
accepting the request MUST assign a new home network prefix and
create a new Binding Cache entry.
4. If there exists a Binding Cache entry and if the Handoff
Indicator field in the Access Technology Type option present in
the received Proxy Binding Update message is set to either value
Gundavelli, et al. Expires June 27, 2008 [Page 25]
Internet-Draft Proxy Mobile IPv6 December 2007
2 (Handoff between interfaces) or 3 (Handoff between mobile
access gateways for the same mobile node's interface), the local
mobility anchor upon accepting the request MUST update the
existing Binding Cache entry and assign the home network prefix
present in the Binding Cache entry.
5. If there exists a Binding Cache entry and if the Handoff
Indicator field in the Access Technology Type option present in
the received Proxy Binding Update message is set to value 4
(Handoff state unknown), the local mobility anchor SHOULD wait
till the existing Binding Cache entry is de-registered by the
previously serving mobile access gateway, before it assigns the
same home network prefix or updates the existing Binding Cache
entry. However, if there is no de-registration message that is
received within MinDelayBeforeNewBCEAssign amount of time, the
local mobility anchor upon accepting the request MUST assign a
new home network prefix and create a new Binding Cache entry.
The local mobility anchor MAY also choose to assign a new home
network prefix and without waiting for a de-registration message.
It can use the access technology type value present in the
request and as inputs for this decision.
6. Either upon creating a new Binding Cache entry or from matching
an existing Binding Cache entry, after applying the above
considerations, the access technology field in the Binding Cache
entry MUST be copied from the Access Technology type option
present in the received Proxy Binding Update message. The
interface identifier field in the Binding Cache entry MUST be set
to ALL_ZERO.
Mobile Node Interface Identifier Option present in the request:
1. The local mobility anchor MUST verify if there is an existing
Binding Cache entry for the mobile node, identified by the MN-
Identifier and with the interface identifier value matching the
identifier value present in the received Mobile Node Interface
Identifier Option.
2. If there exists a Binding Cache entry, the local mobility anchor
upon accepting the request MUST update the existing Binding Cache
entry and assign the home network prefix present in the Binding
Cache entry.
3. If there does not exist a Binding Cache entry and if the Handoff
Indicator field in the Access Technology Type option present in
the received Proxy Binding Update message is set to value 1
(Attachment over a new interface), the local mobility anchor upon
Gundavelli, et al. Expires June 27, 2008 [Page 26]
Internet-Draft Proxy Mobile IPv6 December 2007
accepting the request MUST assign a new home network prefix and
create a new Binding Cache entry.
4. If there does not exist a Binding Cache entry and if the Handoff
Indicator field in the Access Technology Type option present in
the received Proxy Binding Update message is set to value 2
(Handoff between interfaces), the local mobility anchor MUST
verify if there exists one and only one Binding Cache entry for
the mobile node, identified by the MN-Identifier and with any
interface identifier value. If there exists such an entry, the
local mobility anchor upon accepting the request MUST update the
existing Binding Cache entry and assign the home network prefix
present in the Binding Cache entry.
5. If there does not exist a Binding Cache entry and if the Handoff
Indicator field in the Access Technology Type option present in
the received Proxy Binding Update message is set to value 2
(Handoff between interfaces), the local mobility anchor MUST
verify if there exists a Binding Cache entry for the mobile node,
identified by the MN-Identifier and with the home network prefix
value matching the prefix value in the received Home Network
Prefix option. If there exists a Binding Cache entry, the local
mobility anchor upon accepting the request MUST assign the same
prefix, else it MUST assign a new home network prefix and create
a new Binding Cache entry.
6. If there exists a Binding Cache entry and if the Handoff
Indicator field in the Access Technology Type option present in
the received Proxy Binding Update message is set to value 4
(Handoff state unknown), the local mobility anchor SHOULD wait
till the existing Binding Cache entry is de-registered by the
previously serving mobile access gateway. However, if there is
no de-registration message that is received within a given time,
the local mobility anchor upon accepting the request MUST assign
a new home network prefix and create a new Binding Cache entry.
The local mobility anchor MAY also choose to assign a new home
network prefix and without waiting for a de-registration message.
7. Either upon creating a new Binding Cache entry or from matching
an existing Binding Cache entry, after applying the above
considerations, the interface identifier field in the Binding
Cache entry MUST be set to the value present in the received
Mobile Node Interface Identifier Option and the access technology
type MUST be copied from the Access Technology type option
present in the received Proxy Binding Update message.
Gundavelli, et al. Expires June 27, 2008 [Page 27]
Internet-Draft Proxy Mobile IPv6 December 2007
5.5. Timestamp Option for Message Ordering
Mobile IPv6 [RFC-3775] uses the Sequence Number field in binding
registration messages as a way for the home agent to process the
binding updates in the order they were sent by a mobile node. The
home agent and the mobile node are required to manage this counter
over the lifetime of a binding. However, in Proxy Mobile IPv6, as
the mobile node moves from one mobile access gateway to another and
in the absence of mechanisms such as context transfer between the
mobile access gateways, the serving mobile access gateway will be
unable to determine the sequence number that it needs to use in the
signaling messages. Hence, the sequence number scheme, as specified
in [RFC-3775], will be insufficient for Proxy Mobile IPv6.
If the local mobility anchor cannot determine the sending order of
the received binding registration messages, it may potentially
process an older message sent by a mobile access gateway where the
mobile node was previously anchored, resulting in an incorrect
Binding Cache entry.
For solving this problem, this specification adopts two alternative
solutions. One is based on timestamps and the other based on
sequence numbers, as defined in [RFC-3775].
The basic principle behind the use of timestamps in binding
registration messages is that the node generating the message inserts
the current time-of-day, and the node receiving the message checks
that this timestamp is greater than all previously accepted
timestamps. The timestamp based solution may be used, when the
serving mobile access gateways in a Proxy Mobile IPv6 domain do not
have the ability to obtain the last sequence number that was sent in
a binding registration message for updating a given mobile node's
binding.
As an alternative to the Timestamp based approach, the specification
also allows the use of Sequence Number based scheme, as per [RFC-
3775]. However, for this scheme to work, the serving mobile access
gateways in a Proxy Mobile IPv6 domain MUST have the ability to
obtain the last sequence number that was sent in a binding
registration message for updating a given mobile node's binding. The
sequence number MUST be maintained on a per mobile node basis and
MUST be synchronized between the serving mobile access gateways.
This may be achieved by using context transfer schemes or by
maintaining the sequence number in a policy store. However, the
specific details on how the mobile node's sequence number is
synchronized between different mobile access gateways is outside the
scope of this document.
Gundavelli, et al. Expires June 27, 2008 [Page 28]
Internet-Draft Proxy Mobile IPv6 December 2007
Using Timestamps based approach:
1. A local mobility anchor implementation MUST support Timestamp
option. If the Timestamp option is present in the received Proxy
Binding Update request message, then the local mobility anchor
MUST include a valid Timestamp option in the Proxy Binding
Acknowledgement message that it sends to the mobile access
gateway.
2. All the mobility entities in a Proxy Mobile IPv6 domain that are
exchanging binding registration messages using the Timestamp
option must have adequately synchronized time-of-day clocks.
This is the essential requirement for this solution to work. If
this requirement is not met, the solution will not predictably
work in all cases.
3. The mobility entities in a Proxy Mobile IPv6 domain SHOULD
synchronize their clocks to a common time source. For
synchronizing the clocks, the nodes may use Network Time Protocol
[RFC-4330]. Deployments may also adopt other approaches suitable
for that specific deployment. Alternatively, if there is mobile
node generated timestamp that is increasing at every attachment
to the access link and if that timestamp is available to the
mobile access gateway (Ex: The timestamp option in the SEND
messages that the mobile node sends), the mobile access gateway
can use this timestamp or sequence number in the Proxy Binding
Update messages and does not have to depend on any external clock
source. However, the specific details on how this is achieved is
outside the scope of this document.
4. When generating the timestamp value for building the Timestamp
option, the mobility entities MUST ensure that the generated
timestamp is the elapsed time past the same reference epoch, as
specified in the format for the Timestamp option [Section 8.7].
5. If the Timestamp option is present in the received Proxy Binding
Update message, the local mobility anchor MUST ignore the
sequence number field in the message. However, it MUST copy the
sequence number from the received Proxy Binding Update message to
the Proxy Binding Acknowledgement message.
6. Upon receipt of a Proxy Binding Update message with the Timestamp
option, the local mobility anchor MUST check the timestamp field
for validity. In order for it to be considered valid, the
timestamp value contained in the Timestamp option MUST be close
enough to the local mobility anchor's time-of-day clock and the
timestamp MUST be greater than all previously accepted timestamps
in the Proxy Binding Update messages sent for that mobile node.
Gundavelli, et al. Expires June 27, 2008 [Page 29]
Internet-Draft Proxy Mobile IPv6 December 2007
7. If the timestamp value in the received Proxy Binding Update is
valid (validity as specified in the above considerations), the
local mobility anchor MUST return the same timestamp value in the
Timestamp option included in the Proxy Binding Acknowledgement
message that it sends to the mobile access gateway.
8. If the timestamp value in the received Proxy Binding Update is
lower than the previously accepted timestamp in the Proxy Binding
Update messages sent for that mobility binding, the local
mobility anchor MUST reject the Proxy Binding Update request and
send a Proxy Binding Acknowledgement message with Status field
set to TIMESTAMP_LOWER_THAN_PREV_ACCEPTED (Timestamp lower than
previously accepted timestamp). The message MUST also include
the Timestamp option with the value set to the current time-of-
day on the local mobility anchor.
9. If the timestamp value in the received Proxy Binding Update is
not valid (validity as specified in the above considerations),
the local mobility anchor MUST reject the Proxy Binding Update
and send a Proxy Binding Acknowledgement message with Status
field set to TIMESTAMP_MISMATCH (Timestamp mismatch). The
message MUST also include the Timestamp option with the value set
to the current time-of-day on the local mobility anchor.
Using Sequence Number based approach:
1. If the Timestamp option is not present in the received Proxy
Binding Update request, the local mobility anchor MUST fallback
to the Sequence Number based scheme. It MUST process the
sequence number field as specified in [RFC-3775]. Also, it MUST
NOT include the Timestamp option in the Proxy Binding
Acknowledgement messages that it sends to the mobile access
gateway.
2. An implementation MUST support Sequence Number based scheme, as
per [RFC-3775].
5.6. Routing Considerations
5.6.1. Bi-Directional Tunnel Management
o A bi-directional tunnel MUST be established between the local
mobility anchor and the mobile access gateway with IP-in-IP
encapsulation, as described in [RFC-2473]. The tunnel end points
are the Proxy-CoA and LMAA. When using IPv4 transport with a
specific encapsulation mode, the end points of the tunnel are the
Gundavelli, et al. Expires June 27, 2008 [Page 30]
Internet-Draft Proxy Mobile IPv6 December 2007
IPv4-LMAA and IPv4-Proxy-CoA, as specified in [ID-IPV4-PMIP6].
o The bi-directional tunnel MUST be used for routing the mobile
node's data traffic between the mobile access gateway and the
local mobility anchor. The tunnel hides the topology and enables
a mobile node to use an address from its home network prefix from
any access link attached to the mobile access gateway.
o The bi-directional tunnel is established after accepting the Proxy
Binding Update request message. 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. Implementations MAY choose to use static
tunnels instead of dynamically creating and tearing them down on a
need basis.
o Implementations MAY use a software timer for managing the tunnel
lifetime and a counter for keeping a count of all the mobile nodes
that are sharing the tunnel. The timer value MUST be set to the
accepted binding lifetime and will be updated after each periodic
re-registration for extending the lifetime. If the tunnel is
shared for multiple mobile nodes, the tunnel lifetime MUST be set
to the highest binding lifetime that is granted to any one of
those mobile nodes sharing that tunnel.
5.6.2. Forwarding Considerations
Intercepting Packets Sent to the Mobile Node's Home Network:
o When the local mobility anchor is serving a mobile node, it MUST
be able to receive packets that are sent to the mobile node's home
network. In order for it to receive those packets, it MUST
advertise a connected route in to the Routing Infrastructure for
the mobile node's home network prefix or for an aggregated prefix
with a larger scope. This essentially enables IPv6 routers in
that network to detect the local mobility anchor as the last-hop
router for that prefix.
Forwarding Packets to the Mobile Node:
o On receiving a packet from a correspondent node with the
destination address matching a mobile node's home network prefix,
the local mobility anchor MUST forward the packet through the bi-
directional tunnel setup for that mobile node. The format of the
tunneled packet is shown below. However, when using IPv4
transport, the format of the packet is as described in [ID-IPV4-
PMIP6].
Gundavelli, et al. Expires June 27, 2008 [Page 31]
Internet-Draft Proxy Mobile IPv6 December 2007
IPv6 header (src= LMAA, dst= Proxy-CoA /* Tunnel Header */
IPv6 header (src= CN, dst= MN-HOA ) /* Packet Header */
Upper layer protocols /* Packet Content*/
Figure 7: Tunneled Packets from LMA to MAG
Forwarding Packets Sent by the Mobile Node:
o All the reverse tunneled packets that the local mobility anchor
receives from the mobile access gateway, after removing the tunnel
header MUST be routed to the destination specified in the inner
packet header. These routed packets will have the source address
field set to the mobile node's home address.
5.7. Local Mobility Anchor Address Discovery
Dynamic Home Agent Address Discovery, as explained in Section 10.5
[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 DHAAD message in the current form cannot be used in Proxy Mobile
IPv6 for discovering the address of the mobile node's local mobility
anchor. In Proxy Mobile IPv6, the local mobility anchor will not be
able to receive any messages sent to the Mobile IPv6 Home-Agents
anycast address corresponding to the mobile node's home network
prefix, as the prefix is not hosted on any of its interfaces.
Further, the mobile access gateway will not predictably be able to
locate the serving local mobility anchor that has the mobile node's
binding cache entry. Hence, this specification does not support
Dynamic Home Agent Address Discovery protocol.
In Proxy Mobile IPv6, the address of the local mobility anchor
configured to serve a mobile node can be discovered by the mobility
entities in other 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.
5.8. 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.
Gundavelli, et al. Expires June 27, 2008 [Page 32]
Internet-Draft Proxy Mobile IPv6 December 2007
In Proxy Mobile IPv6, the mobile node's home network prefix is hosted
on the access link connected to the mobile access gateway, but it is
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 node 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 message for Proxy Mobile IPv6.
Hence, this specification does not support Mobile Prefix Discovery.
5.9. Route Optimizations Considerations
The Route Optimization in Mobile IPv6, as defined in [RFC-3775],
enables a mobile node to communicate with a correspondent node
directly using its care-of address and further the Return Routability
procedure enables the correspondent node to have reasonable trust
that the mobile node is reachable at both its home address and
care-of address.
In Proxy Mobile IPv6, the mobile node is not involved in any IP
mobility related signaling. The mobile node uses only its home
address for all its communication and the Care-of address (Proxy-CoA)
is not visible to the mobile node. Hence, the Return Routability
procedure as defined in Mobile IPv6 cannot be used in Proxy Mobile
IPv6.
6. Mobile Access Gateway Operation
The Proxy Mobile IPv6 protocol described in this document introduces
a new functional entity, the Mobile Access Gateway (MAG). The mobile
access gateway is the entity that is responsible for detecting the
mobile node's movements on its access link and sending the binding
registration requests to the local mobility anchor. In essence, the
mobile access gateway performs mobility management on behalf of a
mobile node.
The mobile access gateway is a function that typically runs on an
access router. However, implementations MAY choose to split this
function and run it across multiple systems. The specifics on how
that is achieved or the signaling interactions between those
functional entities are beyond the scope of this document.
The mobile access gateway has the following key functional roles:
o It is responsible for detecting the mobile node's movements on the
access link and for initiating the mobility signaling with the
mobile node's local mobility anchor.
Gundavelli, et al. Expires June 27, 2008 [Page 33]
Internet-Draft Proxy Mobile IPv6 December 2007
o Emulation of the mobile node's home link on the access link by
sending Router Advertisements with the mobile node's home network
prefix information.
o Responsible for setting up the data path for enabling the mobile
node to configure an address from its home network prefix and use
it from its access link.
6.1. Extensions to Binding Update List Entry Data Structure
Every mobile access gateway MUST maintain a Binding Update List.
Each entry in the Binding Update List represents a mobile node's
mobility binding with its local mobility anchor. The Binding Update
List is a conceptual data structure, described in Section 11.1 [RFC-
3775].
For supporting this specification, the conceptual Binding Update List
entry data structure needs be extended with the following additional
fields.
o The Identifier of the attached mobile node, MN-Identifier. This
identifier is acquired during the mobile node's attachment to the
access link through mechanisms outside the scope of this document.
o The interface identifier of the mobile node's connected interface.
This address can be acquired from the received Router Solicitation
messages from the mobile node or during the mobile node's
attachment to the access network. This is typically a Layer-2
identifier conveyed by the mobile node; however, the specific
details on how that is conveyed is out of scope for this
specification.
o The IPv6 home network prefix of the attached mobile node. The
home network prefix of the mobile node is acquired from the mobile
node's local mobility anchor through the received Proxy Binding
Acknowledgement messages. The IPv6 home network prefix also
includes the corresponding prefix length.
o The Link-local address of the mobile node on the interface
attached to the access link.
o The IPv6 address of the local mobility anchor serving the attached
mobile node. This address is acquired from the mobile node's
policy profile or from other means.
o The Interface identifier (If-Id) of the access link where the
mobile node is currently attached. This is internal to the mobile
Gundavelli, et al. Expires June 27, 2008 [Page 34]
Internet-Draft Proxy Mobile IPv6 December 2007
access gateway and is used to associate the Proxy Mobile IPv6
tunnel to the right access link where the mobile node is attached.
o The interface identifier (If-Id) of the bi-directional tunnel
between the mobile node's local mobility anchor and the mobile
access gateway. This is internal to the mobile access gateway.
The tunnel interface identifier is acquired during the tunnel
creation.
6.2. Mobile Node's Policy Profile
A mobile node's policy profile contains the essential operational
parameters that are required by the network entities for managing the
mobile node's mobility service. These policy profiles are stored in
a local or a remote policy store. The mobile access gateway and the
local mobility anchor MUST be able to obtain a mobile node's policy
profile. The policy profile MAY also be handed over to a serving
mobile access gateway as part of a context transfer procedure during
a handoff or the serving mobile access gateway MAY be able to
dynamically generate this profile. The exact details on how this
achieved is outside the scope of this document. However, this
specification requires that a mobile access gateway serving a mobile
node MUST have access to its policy profile.
The following are the mandatory fields of the policy profile:
o The mobile node's identifier (MN-Identifier)
o The IPv6 address of the local mobility anchor (LMAA)
The following are the optional fields of the policy profile:
o The mobile node's IPv6 home network prefix (MN-HNP)
o Supported address configuration procedures (Stateful, Stateless or
both) on the access links in the Proxy Mobile IPv6 domain
6.3. Supported Access Link Types
This specification supports only point-to-point access link types and
thus it assumes that the mobile node and the mobile access gateway
are the only two nodes on the access link. The link is assumed to
have multicast capability. This protocol may also be used on other
link types, as long as the link is configured in such a way that it
guarantees a point-to-point delivery between the mobile node and the
mobile access gateway for all the protocol traffic.
Gundavelli, et al. Expires June 27, 2008 [Page 35]
Internet-Draft Proxy Mobile IPv6 December 2007
6.4. Supported Address Configuration Models
A mobile node in the Proxy Mobile IPv6 domain can configure one or
more IPv6 addresses on its interface using Stateless or Stateful
address autoconfiguration procedures. The Router Advertisement
messages sent on the access link specify the address configuration
methods permitted on that access link for that mobile node. However,
the advertised flags with respect to the address configuration will
be consistent for a mobile node, on any of the access links in that
Proxy Mobile IPv6 domain. Typically, these configuration settings
will be based on the domain wide policy or based on a policy specific
to each mobile node.
When stateless address autoconfiguration is supported on the link,
the mobile node can generate one or more IPv6 addresses by combining
the network prefix advertised on the access link with an interface
identifier, using the techniques described in Stateless
Autoconfiguration specification [RFC-4862] or as per Privacy
extension specification [RFC-4941].
When stateful address autoconfiguration is supported on the link, the
mobile node can obtain the address configuration from the DHCPv6
server using DHCPv6 client protocol, as specified in DHCPv6
specification [RFC-3315].
Additionally, other address configuration mechanisms specific to the
access link between the mobile node and the mobile access gateway may
also be used for pushing the address configuration to the mobile
node.
6.5. Access Authentication & Mobile Node Identification
When a mobile node attaches to an access link connected to the mobile
access gateway, the deployed access security protocols on that link
SHOULD ensure that the network-based mobility management service is
offered only after authenticating and authorizing the mobile node for
that service. The exact specifics on how this is achieved or the
interactions between the mobile access gateway and the access
security service is outside the scope of this document. This
specification goes with the stated assumption of having an
established trust between the mobile node and mobile access gateway,
before the protocol operation begins.
6.6. Acquiring Mobile Node's Identifier
All the network entities in a Proxy Mobile IPv6 domain MUST be able
to identify a mobile node, using its MN-Identifier. This identifier
MUST be stable across the Proxy Mobile IPv6 domain and the entities
Gundavelli, et al. Expires June 27, 2008 [Page 36]
Internet-Draft Proxy Mobile IPv6 December 2007
must be able to use this identifier in the signaling messages.
Typically, this identifier is obtained as part of the access
authentication or through other means as specified below.
o The identifier of the mobile node that the mobile access gateway
obtains typically as part of the access authentication or from the
notified network attachment event, can be a temporary identifier
and this identifier may also change at each re-authentication.
However, the mobile access gateway MUST be able to use this
identifier and obtain the mobile node's MN-Identifier from the
policy store, such as from the RADIUS attribute, Chargeable-User-
Identifier [RFC-4372].
o The MN-Identifier that the policy store delivers to the mobile
access gateway may not be the true identifier of the mobile node.
However, the mobility access gateway MUST be able to use this
identifier in the signaling messages exchanged with the local
mobility anchor.
o The mobile access gateway MUST be able identify the mobile node by
its MN-Identifier and it MUST be able to associate this identity
to the sender of any IPv4 or IPv6 packets on the access link.
6.7. Home Network Emulation
One of the key functions of a mobile access gateway is to emulate the
mobile node's home network on the access link. It must ensure, the
mobile node believes it is still connected to its home link or on the
link where it obtained its initial address configuration after it
moved into that Proxy Mobile IPv6 domain.
For emulating the mobile node's home link on the access link, the
mobile access gateway must be able to send Router Advertisements
advertising the mobile node's home network prefix and other address
configuration parameters consistent with its home link properties.
Typically, these configuration settings will be based on the domain
wide policy or based on a policy specific to each mobile node.
Typically, the mobile access gateway learns the mobile node's home
network prefix information from the received Proxy Binding
Acknowledgement message or it may be obtained from the mobile node's
policy profile. However, the mobile access gateway SHOULD send the
Router Advertisements advertising the mobile node's home network
prefix only after successfully completing the binding registration
with the mobile node's local mobility anchor.
When advertising the home network prefix in the Router Advertisement
messages, the mobile access gateway MAY set the prefix lifetime value
Gundavelli, et al. Expires June 27, 2008 [Page 37]
Internet-Draft Proxy Mobile IPv6 December 2007
for the advertised prefix to any chosen value at its own discretion.
An implementation MAY choose to tie the prefix lifetime to the mobile
node's binding lifetime. The prefix lifetime can also be an optional
configuration parameter in the mobile node's policy profile.
6.8. Link-Local and Global Address Uniqueness
A mobile node in the Proxy Mobile IPv6 domain, as it moves from one
mobile access gateway to the other, will continue to detect its home
network and thus making it believe it is still on the same link.
Every time the mobile node attaches to a new link, the event related
to the interface state change will trigger the mobile node to perform
DAD operation on the link-local and global addresses. However, if
the mobile node is DNAv6 enabled, as specified in [ID-DNAV6], it may
not detect the link change due to DNAv6 optimizations and may not
trigger the duplicate address detection (DAD) procedure for
establishing the link-local address uniqueness on that new link.
Further, if the mobile node uses an interface identifier that is not
based on EUI-64 identifier, such as specified in IPv6 Stateless
Autoconfiguration specification [RFC-4862], there is a very low
possibility of a link-local address collision between the two
neighbors on that access link.
For solving this problem, this specification allows the mobile access
gateway to upload the mobile node's link-local address to the local
mobility anchor using the Link-local Address option, exchanged in the
binding registration messages. The mobile access gateway can learn
the mobile node's link-local address, by snooping the DAD messages
sent by the mobile node for establishing the link-local address
uniqueness on the access link. Subsequently, at each handoff, the
mobile access gateway can obtain this address from the local mobility
anchor to ensure link-local address uniqueness and change its own
link-local address, if it detects a collision.
Alternatively, one of the workarounds for this issue is to set the
DNAv6 configuration parameter, DNASameLinkDADFlag to TRUE and that
will force the mobile node to redo DAD operation on the global and
link-local addresses every time the interface detects a handover,
even when DNAv6 does not detect a link change.
However, this issue will not impact point-to-point links based on a
PPP session. Each time the mobile node moves and attaches to a new
mobile access gateway, either the PPP session [RFC-1661] is
reestablished or the PPP session may be moved as part of context
transfer procedures between the old and the new mobile access
gateway.
When the mobile node tries to establish a PPP session with the mobile
Gundavelli, et al. Expires June 27, 2008 [Page 38]
Internet-Draft Proxy Mobile IPv6 December 2007
access gateway, the PPP goes through the Network layer Protocol phase
and the IPv6 Control Protocol, IPV6CP [RFC-5072] 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 mobile access gateway, the PPP session
gets torn down with the old mobile access gateway and a new PPP
session gets established with the new mobile access gateway, and the
mobile node obtains a new link-local address. So, even if the mobile
node is DNAv6 capable, the mobile node always configures a new link-
local address whenever it moves to a new link.
If the PPP session state is moved to the new mobile access gateway as
part of context transfer procedures that are in place, there will not
be any change to the interface identifiers of the two nodes on that
point-to-point change. The whole link is moved to the new mobile
access gateway and there will not be any need for establishing link-
local address uniqueness on that link.
The issue of address collision is not relevant to the mobile node's
global address. Since there is a unique home network prefix assigned
for each mobile node, the uniqueness for the mobile node's global
address is assured on the access link.
6.9. Signaling Considerations
6.9.1. Binding Registrations
Mobile Node Attachment and Initial Binding Registration:
1. After detecting a new mobile node on its access link, the mobile
access gateway must identify the mobile node and acquire its MN-
Identifier. If it determines that the network-based mobility
management service needs to be offered to the mobile node, it
MUST send a Proxy Binding Update message to the local mobility
anchor. If there is no existing Binding Update List entry for
that mobile node, the mobile access gateway MUST create a
Binding Update List entry upon sending the Proxy Binding Update
request.
2. The Proxy Binding Update message MUST include the Mobile Node
Identifier option [RFC-4283], identifying the mobile node, the
Home Network Prefix option, either the Timestamp option or a
valid sequence number and optionally the Link-local Address
option. When Timestamp option is added to the message, the
mobile access gateway MAY set the Sequence Number field to a
value of a monotonically increasing counter and the local
mobility anchor will ignore this field, but will return the same
Gundavelli, et al. Expires June 27, 2008 [Page 39]
Internet-Draft Proxy Mobile IPv6 December 2007
value in the Proxy Binding Acknowledgement message. This will
be useful for matching the reply to the request message.
3. The Home Address option MUST NOT be present in the Destination
Option extension header of the Proxy Binding Update message.
4. The Access Technology Type option MUST be present in the Proxy
Binding Update message. The access technology Type field in the
option MUST be set to the access technology using which the
mobile node is currently attached to the mobile access gateway.
The Handoff Indicator field in the Access Technology Type option
MUST be set to the appropriate value. The specific details on
how the mobile access gateway is able to determine if the mobile
node's current attachment is due to a handoff of an existing
mobility session or if it is as a result of an attachment over a
different interface is outside the scope of this document.
5. The Handoff Indicator field in the Access Technology Type option
MUST be set to value 1 (Attachment over a new interface), if the
mobile access gateway predictably knows that the mobile node's
attachment to the network using the current interface is due to
neither a handover between two interfaces of the mobile node nor
a handover of the mobility session for the same interface of the
mobile node between two mobile access gateways. This
essentially serves as a request to the local mobility anchor to
allocate a new home network prefix for this mobility session and
not update any existing Binding Cache entry created for the same
mobile node connected to the Proxy Mobile IPv6 domain through a
different interface.
6. The Handoff Indicator field in the Access Technology Type option
MUST be set to value 2 (Handoff between interfaces), if the
mobile access gateway definitively knows the mobile node's
current attachment is due to a handoff of the mobility session
between two interfaces of the mobile node.
7. The Handoff Indicator field in the Access Technology Type option
MUST be set to value 3 (Handoff between mobile access gateways
for the same interface), if the mobile access gateway
definitively knows the mobile node's current attachment is due
to a handoff of the mobility session between different mobile
access gateways and for the same interface of the mobile node.
8. The Handoff Indicator field in the Access Technology Type option
MUST be set to value 4 (Handoff State Unknown), if the mobile
access gateway cannot predictably know if the mobile node's
session is due to a handoff.
Gundavelli, et al. Expires June 27, 2008 [Page 40]
Internet-Draft Proxy Mobile IPv6 December 2007
9. The Mobile Node Interface Identifier option carrying the
identifier of the currently attached interface MUST be present
in the Proxy Binding Update message, if the mobile access
gateway knows the interface identifier of the mobile node's
currently attached interface. The "P" Flag in the option MUST
be set to 0, indicating that the carried identifier is the
currently attached interface identifier. If the interface
identifier is not known, this identifier MUST NOT be present.
10. If the mobile access gateway learns the mobile node's home
network prefix either from its policy store or from other means,
the mobile access gateway MAY choose to specify the same in the
Home Network Prefix option for requesting the local mobility
anchor to allocate that prefix. If the specified value is
0::/0, then the local mobility anchor will consider this as a
request for prefix allocation.
Receiving Binding Registration Reply:
1. The mobile access gateway MUST observe the rules described in
Section 9.2 [RFC-3775] when processing Mobility Headers in the
received Proxy Binding Acknowledgement message (a Binding
Acknowledgement message with the 'P' flag set).
2. The message MUST be authenticated as described in Section 4.0.
When IPsec is used for message authentication, the SPI in the
IPsec header [RFC-4306] of the received packet is needed for
locating the security association, for authenticating the Proxy
Binding Acknowledgement reply.
3. The mobile access gateway MUST apply the considerations
specified in Section 5.5 for processing the Sequence Number
field and the Timestamp option, in the message.
4. The mobile access gateway MUST ignore any checks, specified in
[RFC-3775] related to the presence of Type 2 Routing header in
the Proxy Binding Acknowledgement message.
5. If the Timestamp option is present in the received Proxy Binding
Acknowledgement message and with the Status field value set to
any value other than TIMESTAMP_MISMATCH (Invalid Timestamp), the
mobile access gateway MAY use the timestamp value for matching
the response to the request message that it sent recently. For
all other cases, it MAY use the sequence number in combination
with the identifier present in the Mobile Node Identifier option
for matching the response to the request.
Gundavelli, et al. Expires June 27, 2008 [Page 41]
Internet-Draft Proxy Mobile IPv6 December 2007
6. If the received Proxy Binding Acknowledgement message has the
Status field value set to PROXY_REG_NOT_ENABLED (Proxy
registration not enabled for the mobile node), the mobile access
gateway SHOULD NOT send binding registration requests again for
that mobile node. It must also deny the mobility service to
that mobile node.
7. If the received Proxy Binding Acknowledgement message has the
Status field value set to TIMESTAMP_LOWER_THAN_PREV_ACCEPTED
(Timestamp lower than previously accepted timestamp), the mobile
access gateway SHOULD try to register again to reassert the
mobile node's presence to the mobility anchor. The mobile
access gateway is not specifically required to synchronize its
clock upon receiving this error code.
8. If the received Proxy Binding Acknowledgement message has the
Status field value set to TIMESTAMP_MISMATCH (Invalid
Timestamp), the mobile access gateway SHOULD try to register
again only after it has synchronized its clock to a common time
source that is used by all the mobility entities in that domain
for their clock synchronization. The mobile access gateway
SHOULD NOT synchronize its clock to the local mobility anchor's
system clock, based on the timestamp present in the received
message.
9. If the received Proxy Binding Acknowledgement message has the
Status field value set to NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX
(Not authorized for that prefix), the mobile access gateway
SHOULD try to request for that prefix in the binding
registration request, only after it learned the validity of that
prefix.
10. If the received Proxy Binding Acknowledgement message has the
Status field value set to any value greater than or equal to 128
(i.e., if the binding is rejected), the mobile access gateway
MUST NOT advertise the mobile node's home network prefix in the
Router Advertisements sent on that access link and there by
denying mobility service to the mobile node.
11. If the received Proxy Binding Acknowledgement message has the
Status field value set to 0 (Proxy Binding Update accepted), the
mobile access gateway MUST setup the routing state, as explained
in section 6.10, and MUST also update the Binding Update List
entry for reflecting the accepted binding registration status.
12. If the received Proxy Binding Acknowledgement message has the
address in the Link-local Address option set to a value that
matches its own link-local address on that access interface
Gundavelli, et al. Expires June 27, 2008 [Page 42]
Internet-Draft Proxy Mobile IPv6 December 2007
where the mobile node is anchored, the mobile access gateway
MUST change its link-local address on that interface.
Extending Binding Lifetime:
1. For extending the lifetime of a currently registered mobile node
(i.e., if there exists a Binding Update List entry for that
mobile node), the mobile access gateway MUST send a Proxy Binding
Update message to the local mobility anchor. The prefix value in
the Home Network Prefix option present in the request SHOULD be
set to the currently registered home network prefix and the value
in the Link-local Address option MAY be set to ALL_ZERO or to the
link-local address of the mobile node.
Mobile Node Detachment and Binding De-Registration:
1. At any point, if the mobile access gateway detects that the
mobile node has moved away from its access link, it SHOULD send a
Proxy Binding Update message to the local mobility anchor with
the lifetime value set to zero.
2. Either upon receipt of a Proxy Binding Acknowledgement message
from the local mobility anchor or after a MinPBUReplyTime timeout
waiting for the reply, the mobile access gateway MUST remove the
Binding Cache entry for that mobile node from its Binding Update
List and withdraw the mobile node's home network prefix as the
hosted on-link prefix on that access link.
Constructing the Proxy Binding Update Message:
o The mobile access gateway when sending the Proxy Binding Update
request to the local mobility anchor MUST construct the message as
specified below.
Gundavelli, et al. Expires June 27, 2008 [Page 43]
Internet-Draft Proxy Mobile IPv6 December 2007
IPv6 header (src=Proxy-CoA, dst=LMAA)
Mobility header
-BU /*P & A flags are set*/
Mobility Options
- Home Network Prefix option
- Link-local Address option (Optional)
- Timestamp Option (optional)
- Mobile Node Identifier option
- Access Technology Type option (Mandatory)
- Mobile Node Interface Identifier option
(Optional)
Figure 8: Proxy Binding Update message format
o The Source Address field in the IPv6 header of the message MUST be
set to the address of the mobile access gateway.
o The Destination Address field in the IPv6 header of the message
MUST be set to the local mobility anchor address.
o The Home Network Prefix option MUST be present. The prefix value
MAY be set 0::/0 or to a specific prefix value.
o The Link-local Address option MAY be present. The value MAY be
set to ALL_ZERO or the mobile node's link-local address.
o The Access Technology Type option MUST be present. The value MUST
be set to the type of the access technology using which the mobile
node is currently attached to the mobile access gateway.
o The Mobile Node Interface Identifier option MAY be present.
o Considerations from Section 5.5 must be applied for constructing
the Timestamp option.
o The Mobile Node Identifier option [RFC-4283] MUST be present, the
identifier field in the option MUST be set to mobile node's
identifier, MN-Identifier.
o If IPsec is used for protecting the signaling messages, the
message MUST be protected, using the security association existing
between the local mobility anchor and the mobile access gateway.
Gundavelli, et al. Expires June 27, 2008 [Page 44]
Internet-Draft Proxy Mobile IPv6 December 2007
6.9.2. Router Solicitation Messages
The mobile node may send a Router Solicitation message on the access
link whenever the link-layer detects a media change. The Source
Address in the IPv6 header of the Router Solicitation message may
either be the link-local address of the mobile node or an unspecified
address (::).
1. The mobile access gateway on receiving the Router Solicitation
message SHOULD send a Router Advertisement containing the mobile
node's home network prefix as the on-link prefix. However,
before sending the Router Advertisement message containing the
mobile node's home network prefix, it SHOULD complete the binding
registration process with the mobile node's local mobility
anchor.
2. If the local mobility anchor rejects the binding registration
request, or, if the mobile access gateway failed to complete the
binding registration process for whatever reasons, the mobile
access gateway MUST NOT advertise the mobile node's home network
prefix in the Router Advertisement messages that it sends on the
access link. However, it MAY choose to advertise a local visited
network prefix to enable the mobile node for regular IPv6 access.
6.9.3. Retransmissions and Rate Limiting
The mobile access gateway is responsible for retransmissions and rate
limiting the binding registration requests that it sends for updating
a mobile node's binding. Implementations MUST follow the below
guidelines.
1. When the mobile access gateway sends a Proxy Binding Update
request, it should use the constant, INITIAL_BINDINGACK_TIMEOUT
[RFC-3775], for configuring the retransmission timer.
2. If the mobile access gateway fails to receive a valid matching
response within the retransmission interval, it SHOULD retransmit
the message until a response is received. However, the mobile
access gateway MUST ensure the mobile node is still attached to
the connected link before retransmitting the message.
3. As specified in Section 11.8 [RFC-3775], the mobile access
gateway MUST use an exponential back-off process in which the
timeout period is doubled upon each retransmission, until either
the node receives a response or the timeout period reaches the
value MAX_BINDACK_TIMEOUT [RFC-3775]. The mobile access gateway
Gundavelli, et al. Expires June 27, 2008 [Page 45]
Internet-Draft Proxy Mobile IPv6 December 2007
MAY continue to send these messages at this slower rate
indefinitely.
4. If Timestamp based scheme is in use, the retransmitted Proxy
Binding Update messages MUST use the latest timestamp. If
Sequence number scheme is in use, the retransmitted Proxy Binding
Update messages MUST use a Sequence Number value greater than
that used for the previous transmission of this Proxy Binding
Update message, just as specified in [RFC-3775].
6.10. Routing Considerations
This section describes how the mobile access gateway handles the
traffic to/from the mobile node that is attached to one of its access
interface.
Proxy-CoA LMAA
| |
+--+ +---+ +---+ +--+
|MN|----------|MAG|======================|LMA|----------|CN|
+--+ +---+ +---+ +--+
IPv6 Tunnel
Figure 9: Proxy Mobile IPv6 Tunnel
6.10.1. Transport Network
The transport network between the local mobility anchor and the
mobile access gateway can be either an IPv6 or IPv4 network.
However, this specification only deals with the IPv6 transport and
the companion document [ID-IPV4-PMIP6] specifies the required
extensions for negotiating IPv4 transport and the corresponding
encapsulation mode for supporting this protocol operation.
6.10.2. Tunneling & Encapsulation Modes
The IPv6 address that a mobile node uses from its home network prefix
is topologically anchored at the local mobility anchor. For a mobile
node to use this address from an access network attached to a mobile
access gateway, proper tunneling techniques have to be in place.
Tunneling hides the network topology and allows the mobile node's
IPv6 datagram to be encapsulated as a payload of another IPv6 packet
and to be routed between the local mobility anchor and the mobile
access gateway. The Mobile IPv6 base specification [RFC-3775]
defines the use of IPv6-over-IPv6 tunneling, between the home agent
and the mobile node and this specification extends the use of the
Gundavelli, et al. Expires June 27, 2008 [Page 46]
Internet-Draft Proxy Mobile IPv6 December 2007
same tunneling mechanism between the local mobility anchor and the
mobile access gateway.
On most operating systems, tunnels are implemented as a virtual
point-to-point interface. The source and the destination address of
the two end points of this virtual interface along with the
encapsulation mode are specified for this virtual interface. Any
packet that is routed over this interface gets encapsulated with the
outer header and the addresses as specified for that point to point
tunnel interface. For creating a point to point tunnel to any local
mobility anchor, the mobile access gateway may implement a tunnel
interface with the source address field set to its Proxy-CoA address
and the destination address field set to the LMA address.
The following are the supported packet encapsulation modes that can
be used by the mobile access gateway and the local mobility anchor
for routing mobile node's IPv6 datagrams.
o IPv6-In-IPv6 - IPv6 datagram encapsulated in an IPv6 packet [RFC-
2473].
o IPv6-In-IPv4 - IPv6 datagram encapsulation in an IPv4 packet. The
details on how this mode is negotiated is specified in [ID-IPV4-
PMIP6].
o IPv6-In-IPv4-UDP - IPv6 datagram encapsulation in an IPv4 UDP
packet. This mode is specified in [ID-IPV4-PMIP6].
6.10.3. Routing State
The following section explains the routing state for a mobile node on
the mobile access gateway. This routing state reflects only one
specific way of implementation and one MAY choose to implement it in
other ways. The policy based route defined below acts as a traffic
selection rule for routing a mobile node's traffic through a specific
tunnel created between the mobile access gateway and that mobile
node's local mobility anchor and with the specific encapsulation
mode, as negotiated.
The below example identifies the routing state for two visiting
mobile nodes, MN1 and MN2 with their respective local mobility
anchors LMA1 and LMA2.
For all traffic from the mobile node, identified by the mobile node's
MAC address, ingress interface or source prefix (MN-HNP) to
_ANY_DESTINATION_ route via interface tunnel0, next-hop LMAA.
Gundavelli, et al. Expires June 27, 2008 [Page 47]
Internet-Draft Proxy Mobile IPv6 December 2007
+==================================================================+
| Packet Source | Destination Address | Destination Interface |
+==================================================================+
| MAC_Address_MN1, | _ANY_DESTINATION_ | Tunnel0 |
| (IPv6 Prefix or |----------------------------------------------|
| Input Interface) | Locally Connected | Tunnel0 |
+------------------------------------------------------------------+
| MAC_Address_MN2, | _ANY_DESTINATION_ | Tunnel1 |
+ (IPv6 Prefix or -----------------------------------------------|
| Input Interface | Locally Connected | direct |
+------------------------------------------------------------------+
Figure 10: Example - Policy based Route Table
+==================================================================+
| Interface | Source Address | Destination Address | Encapsulation |
+==================================================================+
| Tunnel0 | Proxy-CoA | LMAA1 | IPv6-in-IPv6 |
+------------------------------------------------------------------+
| Tunnel1 |IPv4-Proxy-CoA | IPv4-LMA2 | IPv6-in-IPv4 |
+------------------------------------------------------------------+
Figure 11: Example - Tunnel Interface Table
6.10.4. Local Routing
If there is data traffic between a visiting mobile node and a
correspondent node that is locally attached to an access link
connected to the mobile access gateway, the mobile access gateway MAY
optimize on the delivery efforts by locally routing the packets and
by not reverse tunneling them to the mobile node's local mobility
anchor. The configuration variable, EnableMAGLocalRouting MAY be
used for controlling this aspect. However, in some systems, this may
have an implication on the mobile node's accounting and policy
enforcement as the local mobility anchor is not in the path for that
traffic and it will not be able to apply any traffic policies or do
any accounting for those flows.
This decision of path optimization SHOULD be based on the policy
configured on the mobile access gateway, but enforced by the mobile
node's local mobility anchor. The specific details on how this is
achieved are beyond of the scope of this document.
Gundavelli, et al. Expires June 27, 2008 [Page 48]
Internet-Draft Proxy Mobile IPv6 December 2007
6.10.5. Tunnel Management
All the considerations mentioned in Section 5.6.1 for the tunnel
management on the local mobility anchor apply for the mobile access
gateway as well.
6.10.6. Forwarding Rules
Forwarding Packets sent to the Mobile Node's Home Network:
o On receiving a packet from the bi-directional tunnel established
with the mobile node's local mobility anchor, the mobile access
gateway MUST use the destination address of the inner packet for
forwarding it on the interface where the destination network
prefix is hosted. The mobile access gateway MUST remove the outer
header before forwarding the packet. If the mobile access gateway
cannot find the connected interface for that destination address,
it MUST silently drop the packet. For reporting an error in such
a scenario, in the form of ICMP control message, the
considerations from Generic Packet Tunneling specification [RFC-
2473] must be applied.
o On receiving a packet from a correspondent node that is locally
connected and which is destined to a mobile node that is on
another locally connected access link, the mobile access gateway
MUST check the configuration variable, EnableMAGLocalRouting, to
ensure the mobile access gateway is allowed to route the packet
directly to the mobile node. If the mobile access gateway is not
allowed to route the packet directly, it MUST route the packet
through the bi-directional tunnel established between itself and
the mobile node's local mobility anchor. Otherwise, it can route
the packet directly to the mobile node.
Forwarding Packets Sent by the Mobile Node:
o On receiving a packet from a mobile node connected to its access
link, the mobile access gateway MUST ensure that there is an
established binding for that mobile node with its local mobility
anchor before forwarding the packet directly to the destination or
before tunneling the packet to the mobile node's local mobility
anchor.
o On receiving a packet from a mobile node connected to its access
link to a destination that is locally connected, the mobile access
gateway MUST check the configuration variable,
EnableMAGLocalRouting, to ensure the mobile access gateway is
allowed to route the packet directly to the destination. If the
mobile access gateway is not allowed to route the packet directly,
Gundavelli, et al. Expires June 27, 2008 [Page 49]
Internet-Draft Proxy Mobile IPv6 December 2007
it MUST route the packet through the bi-directional tunnel
established between itself and the mobile node's local mobility
anchor. Otherwise, it can route the packet directly to the
destination.
o On receiving a packet from the mobile node connected to its access
link, to a destination that is not directly connected, the packet
MUST be forwarded to the local mobility anchor through the bi-
directional tunnel established between itself and the mobile
node's local mobility anchor. However, the packets that are sent
with the link-local source address MUST NOT be forwarded. The
format of the tunneled packet is shown below. However, when using
IPv4 transport, the format of the tunneled packet is as described
in [ID-IPV4-PMIP6].
IPv6 header (src= Proxy-CoA, dst= LMAA /* Tunnel Header */
IPv6 header (src= MN-HoA, dst= CN ) /* Packet Header */
Upper layer protocols /* Packet Content*/
Figure 12: Tunneled Packets from MAG to LMA
6.11. Supporting DHCPv6 based Address Configuration on the Access Link
This section explains how Stateful Address Configuration using DHCPv6
can be enabled on the access link attached to a mobile access gateway
and how a mobile node attached to that link can obtain an address
from its home network prefix using DHCPv6.
o For supporting Stateful Address Configuration using DHCPv6, the
DHCPv6 relay agent [RFC-3315] service MUST be enabled on each of
the access links in the Proxy Mobile IPv6 domain. Further, as
specified in Section 20 [RFC-3315], the relay agent should be
configured to use a list of destination addresses, which MAY
include unicast addresses, the All_DHCP_Servers multicast address,
or other addresses selected by the network administrator.
o The DHCPv6 server in the Proxy Mobile IPv6 domain can be
configured with a list of prefix pools (P1, P2, ..., Pn). Each
one of these prefix pools corresponds to a home network prefix
that a local mobility anchor allocates to a mobile node in that
domain. However, the DHCPv6 server will not know the relation
between a given address pool and a mobile node to which the
corresponding prefix is allocated. It just views these pools as
prefixes hosted on different links in that domain.
Gundavelli, et al. Expires June 27, 2008 [Page 50]
Internet-Draft Proxy Mobile IPv6 December 2007
o When a mobile node sends a DHCPv6 request message, the DHCP relay
agent function on the access link will set the link-address field
in the DHCP message to an address in the mobile node's home
network prefix, so as to provide a prefix hint to the DHCP Server
for the address pool selection. The DHCP server on receiving the
request from the mobile node, will allocate an address from the
prefix pool present in the link-address field of the request.
o Once the mobile node obtains an address and moves to a different
link and sends a DHCP request, the DHCP relay agent on the new
link will set the prefix hint in the DHCP messages to the mobile
node's home network prefix. The DHCP server will identify the
client from the Client-DUID option and present in the request and
will allocate the same address as before.
o The DHCP based address configuration is not recommended for
deployments where the local mobility anchor and the mobile access
gateways are located in different administrative domains. For
this configuration to work, all the mobile access gateways in the
Proxy Mobile IPv6 domain should be able to ensure that the DHCP
requests from a given mobile node anchored on any of the access
links in that domain, will always be handled by the same DHCP
server.
o The DHCP server should be configured to offer low address lease
times. A lease time that is too large prevents the DHCP server
from reclaiming the address even after the local mobility anchor
deletes the mobile node's binding cache entry.
6.12. Home Network Prefix Renumbering
If the mobile node's home network prefix gets renumbered or becomes
invalid during the middle of a mobility session, the mobile access
gateway MUST withdraw the prefix by sending a Router Advertisement on
the access link with zero prefix lifetime for the mobile node's home
network prefix. Also, the local mobility anchor and the mobile
access gateway MUST delete the routing state for that prefix.
However, the specific details on how the local mobility anchor
notifies the mobile access gateway about the mobile node's home
network prefix renumbering are outside the scope of this document.
6.13. 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
Gundavelli, et al. Expires June 27, 2008 [Page 51]
Internet-Draft Proxy Mobile IPv6 December 2007
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 SHOULD 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 the
Binding Update List 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
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
6.14. Allowing network access to other IPv6 nodes
In some Proxy Mobile IPv6 deployments, network operators may want to
provision the mobile access gateway to offer network-based mobility
management service only to some visiting mobile nodes and enable just
regular IP access to some other nodes. This requires the network to
have control on when to enable network-based mobility management
service to a mobile node and when to enable regular IPv6 access.
This specification does not disallow such configuration.
Upon detecting a mobile node on its access link and after policy
considerations, the mobile access gateway MUST determine if network-
based mobility management service should be offered to that mobile
node. If the mobile node is entitled for network-based mobility
management service, then the mobile access gateway must ensure the
mobile node believes it is on its home link, as explained in various
sections of this specification.
If the mobile node is not entitled for the network-based mobility
management service, as determined from the policy considerations, the
mobile access gateway MAY choose to offer regular IPv6 access to the
mobile node and in such scenario the normal IPv6 considerations
Gundavelli, et al. Expires June 27, 2008 [Page 52]
Internet-Draft Proxy Mobile IPv6 December 2007
apply. If IPv6 access is enabled, the mobile node SHOULD be able to
obtain an IPv6 address using normal IPv6 address configuration
procedures. The obtained address must be from a local visitor
network prefix. This essentially ensures that the mobile access
gateway functions as a normal access router to a mobile node attached
to its access link and with out impacting its host-based mobility
protocol operation.
7. Mobile Node Operation
This non-normative section explains the mobile node's operation in a
Proxy Mobile IPv6 domain.
7.1. Moving into a Proxy Mobile IPv6 Domain
Once a mobile node enters a Proxy Mobile IPv6 domain and attaches to
an access network, the mobile access gateway on the access link
detects the attachment of the mobile node and completes the binding
registration with the mobile node's local mobility anchor. If the
binding update operation is successfully performed, the mobile access
gateway will create the required state and setup the data path for
the mobile node's data traffic.
If the mobile node is IPv6 enabled, on attaching to the access link,
it will typically send Router Solicitation message [RFC-4861]. The
mobile access gateway on the access 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.
If the mobile access gateway on the access link, receives a Router
Solicitation message from the mobile node, before it completed the
signaling with the mobile node's local mobility anchor, the mobile
access gateway may not know the mobile node's home network prefix and
may not be able to emulate the mobile node's home link on the access
link. In such scenario, the mobile node may notice a slight delay
before it receives a Router Advertisement message.
If the received Router Advertisement has the Managed Address
Configuration flag set, the mobile node, as it would normally do,
will send a DHCPv6 Request [RFC-3315]. The DHCP relay service
enabled on that access link will ensure the mobile node will obtain
its IPv6 address as a lease from its home network prefix.
If the received 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 be able to obtain
Gundavelli, et al. Expires June 27, 2008 [Page 53]
Internet-Draft Proxy Mobile IPv6 December 2007
an IPv6 address using an interface identifier generated as per the
Autoconf specification [RFC-4862] or as per the Privacy Extensions
specification [RFC-4941].
If the mobile node is IPv4 enabled and if the network permits, it
will be able to obtain the IPv4 address configuration for the
connected interface by using DHCP [RFC-2131]. The details related to
IPv4 support is specified in the companion document [ID-IPV4-PMIP6].
Once the address configuration is complete, the mobile node can
continue to use this address configuration as long as it is attached
to the network that is in the scope of that Proxy Mobile IPv6 domain.
7.2. Roaming in the Proxy Mobile IPv6 Domain
After obtaining the address configuration in the Proxy Mobile IPv6
domain, as the mobile node moves and changes its point of attachment
from one mobile access gateway to the other, it can still continue to
use the same address configuration. As long as the attached access
network is in the scope of that Proxy Mobile IPv6 domain, the mobile
node will always detect the same link, where it obtained its initial
address configuration. If the mobile node performs DHCP operation,
it will always obtain the same address as before.
However, the mobile node will always detect a new default-router on
each connected link, but still advertising the mobile node's home
network prefix as the on-link prefix and with the other configuration
parameters consistent with its home link properties.
7.3. IPv6 Host Protocol Parameters
This specification does not require any changes to the mobile node's
IP stack. It assumes the mobile node to be a normal IPv4/IPv6 node,
with its protocol operation consistent with the respective
specifications.
However, for achieving protocol efficiency and for faster hand-offs,
implementations may choose to adjust the following IPv6 operating
parameters on the mobile node be adjusted to the below recommended
values.
Lower Default-Router List Cache Time-out:
As per the base IPv6 specification [RFC-4861], each IPv6 host is
required to 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
Gundavelli, et al. Expires June 27, 2008 [Page 54]
Internet-Draft Proxy Mobile IPv6 December 2007
routers on that link. The Router Lifetime field in the received
Router Advertisement defines the life of this entry.
In case of Proxy Mobile IPv6, when a mobile node moves from one link
to another, the source address of the received Router Advertisement
messages advertising the mobile node's home network prefix will be
from a different 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
and not the previously known 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 [RFC-4861]. This action
will help in minimizing packet losses during a hand off switch.
On detecting a reachability problem, the mobile node will certainly
detect the default-router loss by performing the 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.
In access network where SEND [RFC-3971] is not deployed, the mobile
access gateway may withdraw the previous default-router entry, by
sending a Router Advertisement using the link-local address that of
the previous mobile access gateway and with the Router Lifetime field
set to value 0, then this will force the flush of the Previous
Default-Router entry from the mobile node's cache. This certainly
requires 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 fixed link-local address for all the mobility
entities in a Proxy Mobile IPv6 domain and where SEND [RFC-3971] is
not deployed. In such scenario, the mobile node is not required to
update the default-router entry. However, 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.
Gundavelli, et al. Expires June 27, 2008 [Page 55]
Internet-Draft Proxy Mobile IPv6 December 2007
8.1. Proxy Binding Update Message
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A Binding Update message that is sent by a mobile access gateway to a
local mobility anchor is referred to as the "Proxy Binding Update"
message. A new flag (P) is included in the Binding Update message.
The rest of the Binding Update message format remains the same as
defined in [RFC-3775] and with the additional (R) and (M) flags as
specified in [RFC-3963] and [RFC-4140] respectively.
Proxy Registration Flag (P)
A new flag (P) is included in the Binding Update message to
indicate to the local mobility anchor that the Binding Update
message is a proxy registration. The flag MUST be set to the
value of 1 for proxy registrations and MUST be set to 0 for direct
registrations sent by a mobile node.
Mobility Options
Variable-length field of such length that the complete Mobility
Header is an integer multiple of 8 octets long. This field
contains zero or more TLV-encoded mobility options. The encoding
and format of defined options are described in Section 6.2 [RFC-
3775]. The local mobility anchor MUST ignore and skip any options
which it does not understand.
Gundavelli, et al. Expires June 27, 2008 [Page 56]
Internet-Draft Proxy Mobile IPv6 December 2007
As per this specification, the following mobility options are
valid in a Proxy Binding Update message:
Home Network Prefix option
Link-local Address option
Mobile Node Identifier Option
Access Technology Type option
Mobile Node Interface Identifier option
Timestamp option
For descriptions of other fields present in this message, refer to
section 6.1.7 [RFC-3775].
8.2. Proxy Binding Acknowledgement Message
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A Binding Acknowledgement message that is sent by a local mobility
anchor to a mobile access gateway is referred to as the "Proxy
Binding Acknowledgement" message. A new flag (P) is included in the
Binding Acknowledgement message. The rest of the Binding
Acknowledgement message format remains the same as defined in [RFC-
3775] and with the additional (R) and (M) flags as specified in [RFC-
3963] and [RFC-4140] respectively.
Proxy Registration Flag (P)
Gundavelli, et al. Expires June 27, 2008 [Page 57]
Internet-Draft Proxy Mobile IPv6 December 2007
A new flag (P) is included in the Binding Acknowledgement message
to indicate that the local mobility anchor that processed the
corresponding Proxy Binding Update message supports proxy
registrations. The flag is set only if the corresponding Proxy
Binding Update had the Proxy Registration Flag (P) set to value of
1.
Mobility Options
Variable-length field of such length that the complete Mobility
Header is an integer multiple of 8 octets long. This field
contains zero or more TLV-encoded mobility options. The encoding
and format of defined options are described in Section 6.2 [RFC-
3775]. The mobile access gateway MUST ignore and skip any options
which it does not understand.
As per this specification, the following mobility options are
valid in a Proxy Binding Acknowledgement message:
Home Network Prefix option
Link-local Address option
Mobile Node Identifier option
Access Technology Type option
Mobile Node Interface Identifier option
Timestamp option
Status
8-bit unsigned integer indicating the disposition of the Proxy
Binding Update. Values of the Status field less than 128 indicate
that the Proxy Binding Update was accepted by the local mobility
anchor. Values greater than or equal to 128 indicate that the
binding registration was rejected by the local mobility anchor.
Section 8.8 defines the Status values that can used in Proxy
Binding Acknowledgement message.
For descriptions of other fields present in this message, refer to
the section 6.1.8 [RFC-3775].
8.3. Home Network Prefix Option
A new option, Home Network Prefix Option is defined for using it in
the Proxy Binding Update and Proxy Binding Acknowledgement messages
Gundavelli, et al. Expires June 27, 2008 [Page 58]
Internet-Draft Proxy Mobile IPv6 December 2007
exchanged between a local mobility anchor and a mobile access
gateway. This option is used for exchanging the mobile node's home
network prefix information.
The Home Network Prefix Option has an alignment requirement of 8n+4.
Its format is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Home Network Prefix +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
<IANA>
Length
8-bit unsigned integer indicating the length of the option
in octets, excluding the type and length fields. This field
MUST be set to 18.
Reserved (R)
This 8-bit field is unused for now. The value MUST be
initialized to 0 by the sender and MUST be ignored by the
receiver.
Prefix Length
8-bit unsigned integer indicating the prefix length of the
IPv6 prefix contained in the option.
Home Network Prefix
A sixteen-byte field containing the mobile node's IPv6 Home
Network Prefix.
Gundavelli, et al. Expires June 27, 2008 [Page 59]
Internet-Draft Proxy Mobile IPv6 December 2007
8.4. Access Technology Type Option
A new option, Access Technology Type Option is defined for using it
in the Proxy Binding Update and Proxy Binding Acknowledgement
messages exchanged between a local mobility anchor and a mobile
access gateway. This option is used for exchanging the type of the
access technology using which the mobile node is currently attached
to the mobile access gateway.
The Access Technology Type Option has no alignment requirement. 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 | Acc Tech | HI | Reserved|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
<IANA>
Length
8-bit unsigned integer indicating the length of the option
in octets, excluding the type and length fields. This field
MUST be set to 2.
Access Technology Type (Acc Tech)
A 8-bit field that specifies the access technology through
which the mobile node is connected to the access link on the
mobile access gateway.
The values 0-255 will be allocated and managed by IANA. The
following values are currently reserved for the below specified
access technology types.
0x00: Reserved
0x01: Virtual
0x02: PPP
0x02: 802.3 (Ethernet)
0x03: 802.11a
0x04: 802.11b
0x05: 802.11g
0x06: 802.16e
Gundavelli, et al. Expires June 27, 2008 [Page 60]
Internet-Draft Proxy Mobile IPv6 December 2007
0x07: CDMA2000 1xEV-DO Release 0
0x08: CDMA2000 1xEV-DO Revision A
0x09: CDMA2000 1xEV-DO Revision B
0x0a: 3GPP LTE
Handoff Indicator (HI)
A 3-bit field that specifies the type of handoff. The values
(0-3) will be allocated and managed by IANA. The following
values are currently reserved.
0: Reserved
1: Attachment over a new interface
2: Handoff between interfaces
3: Handoff between mobile access gateways for the same interface
4: Handoff state unknown
Reserved (R)
This 5-bit field is unused for now. The value MUST be
initialized to 0 by the sender and MUST be ignored by the
receiver.
8.5. Mobile Node Interface Identifier Option
A new option, Mobile Node Interface Identifier Option is defined for
using it in the Proxy Binding Update and Proxy Binding
Acknowledgement messages exchanged between a local mobility anchor
and a mobile access gateway. This option is used for exchanging the
mobile node's interface identifier.
The format of the Interface Identifier option when the interface
identifier is 8 bytes is shown below. When the size is different,
the option MUST be aligned appropriately, as per mobility option
alignment requirements specified in [RFC-3775].
Gundavelli, et al. Expires June 27, 2008 [Page 61]
Internet-Draft Proxy Mobile IPv6 December 2007
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Interface Identifier +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
<IANA>
Length
8-bit unsigned integer indicating the length of the option
in octets, excluding the type and length fields. This field
MUST be set to 10.
Reserved
This field is unused for now. The value MUST be initialized to
0 by the sender and MUST be ignored by the receiver.
Interface Identifier
A variable length field containing the mobile node's interface
identifier.
8.6. Link-local Address Option
A new option, Link-local Address Option is defined for using it in
the Proxy Binding Update and Proxy Binding Acknowledgement messages
exchanged between a local mobility anchor and a mobile access
gateway. This option is used for exchanging the mobile node's link-
local address.
The Link-local Address option has an alignment requirement of 8n+6.
Its format is as follows:
Gundavelli, et al. Expires June 27, 2008 [Page 62]
Internet-Draft Proxy Mobile IPv6 December 2007
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Link-local Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
<IANA>
Length
8-bit unsigned integer indicating the length of the option
in octets, excluding the type and length fields. This field
MUST be set to 16.
Link-local Address
A sixteen-byte field containing the mobile node's link-local
address.
8.7. Timestamp Option
A new option, Timestamp Option is defined for use in the Proxy
Binding Update and Proxy Binding Acknowledgement messages.
The Timestamp option has an alignment requirement of 8n+2. Its
format is as follows:
Gundavelli, et al. Expires June 27, 2008 [Page 63]
Internet-Draft Proxy Mobile IPv6 December 2007
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Timestamp +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
<IANA>
Length
8-bit unsigned integer indicating the length in octets of
the option, excluding the type and length fields. The value
for this field MUST be set to 8.
Timestamp
A 64-bit unsigned integer field containing a timestamp. The value
indicates the number of seconds since January 1, 1970, 00:00 UTC,
by using a fixed point format. In this format, the integer number
of seconds is contained in the first 48 bits of the field, and the
remaining 16 bits indicate the number of 1/65536 fractions of a
second.
8.8. Status Values
This document defines the following new Status values for use in
Proxy Binding Acknowledgement message. These values are to be
allocated from the same number space, as defined in Section 6.1.8
[RFC-3775].
Status values less than 128 indicate that the Proxy Binding Update
request was accepted by the local mobility anchor. Status values
greater than 128 indicate that the Proxy Binding Update was rejected
by the local mobility anchor.
PROXY_REG_NOT_ENABLED:
Proxy Registration not enabled for the mobile node.
MAG_NOT_AUTHORIZED_FOR_PROXY_REG:
Gundavelli, et al. Expires June 27, 2008 [Page 64]
Internet-Draft Proxy Mobile IPv6 December 2007
The mobile access gateway is not authorized to send proxy binding.
updates.
NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX
The mobile node is not authorized for the requesting home network
prefix.
TIMESTAMP_MISMATCH:
Invalid timestamp value in the received Proxy Binding Update
message (the clocks are out of sync).
TIMESTAMP_LOWER_THAN_PREV_ACCEPTED:
The timestamp value in the received Proxy Binding Update message
is lower than the previously accepted value.
MISSING_HOME_NETWORK_PREFIX_OPTION
Missing mobile node home network prefix option.
MISSING_MN_IDENTIFIER_OPTION:
Missing mobile node identifier in the Proxy Binding Update
message.
MISSING_ACCESS_TECH_TYPE_OPTION
Missing mobile node's access technology type in the Proxy Binding
Update message.
Additionally, the following Status values defined in [RFC-3775] can
also be used in Proxy Binding Acknowledgement message.
0 Proxy Binding Update accepted
128 Reason unspecified
129 Administratively prohibited
Gundavelli, et al. Expires June 27, 2008 [Page 65]
Internet-Draft Proxy Mobile IPv6 December 2007
130 Insufficient resources
133 Not local mobility anchor for this mobile node
9. Protocol Configuration Variables
The local mobility anchor MUST allow the following variables to be
configured by the system management.
MinDelayBeforeBCEDelete
This variable specifies the amount of time in milliseconds the
local mobility anchor MUST wait before it deletes a Binding Cache
entry of a mobile node, upon receiving a Proxy Binding Update
message from a mobile access gateway with a lifetime value of 0.
During this wait time, if the local mobility anchor receives a
Proxy Binding Update for the same mobility binding, with lifetime
value greater than 0, then it must update the binding cache entry
with the accepted binding values. By the end of this wait-time,
if the local mobility anchor did not receive any valid Proxy
Binding Update message for that mobility binding, it MUST delete
the Binding Cache entry. This delay essentially ensures a mobile
node's Binding Cache entry is not deleted too quickly and allows
some time for the new mobile access gateway to complete the
signaling for the mobile node.
The default value for this variable is 10000 milliseconds.
MinDelayBeforeNewBCEAssign
This variable specifies the amount of time in milliseconds the
local mobility anchor MUST wait for the de-registration message
for an existing mobility session before it decides to create a new
mobility session.
The default value for this variable is 500 milliseconds.
The mobile access gateway MUST allow the following variables to be
configured by the system management.
EnableMAGLocalrouting
Gundavelli, et al. Expires June 27, 2008 [Page 66]
Internet-Draft Proxy Mobile IPv6 December 2007
This flag indicates whether or not the mobile access gateway is
allowed to enable local routing of the traffic exchanged between a
visiting mobile node and a correspondent node that is locally
connected to one of the interfaces of the mobile access gateway.
The correspondent node can be another visiting mobile node as
well, or a local fixed node.
The default value for this flag is set to "FALSE", indicating that
the mobile access gateway MUST reverse tunnel all the traffic to
the mobile node's local mobility anchor.
When the value of this flag is set to "TRUE", the mobile access
gateway MUST route the traffic locally.
This aspect of local routing MAY be defined as policy on a per
mobile basis and when present will take precedence over this flag.
MinPBUReplyTime
This variable specifies the amount of time in milliseconds the
mobile access gateway SHOULD wait for the reply message for the
Proxy Binding Update request that it sent to the local mobility
anchor.
The default value for this variable is 2000 milliseconds.
10. IANA Considerations
This document defines five new Mobility Header Options, the Home
Network Prefix option, Access Technology Type option, Interface
Identifier option, Link-local Address option and Timestamp option.
These options are described in Sections 8.3, 8.4, 8.5, 8.6 and 8.7
respectively. The Type value for these options needs to be assigned
from the same numbering space as allocated for the other mobility
options, as defined in [RFC-3775].
The Mobility Header Option, Access Technology Type option defined in
Section 8.4 of this document introduces a new Access Technology type
numbering space, where the values from 0 to 5 have been reserved by
this document. Approval of new Access Technology type numbers are to
be made through IANA Expert Review.
This document also defines new Binding Acknowledgement status values
as described in Section 8.8. The status values MUST be assigned from
the same number space used for Binding Acknowledgement status values,
as defined in [RFC-3775]. The allocated values for each of these
status values MUST be greater than 128.
Gundavelli, et al. Expires June 27, 2008 [Page 67]
Internet-Draft Proxy Mobile IPv6 December 2007
11. Security Considerations
The potential security threats against any network-based mobility
management protocol are described in [RFC-4832]. This section
explains how Proxy Mobile IPv6 protocol defends itself against those
threats.
Proxy Mobile IPv6 protocol requires the signaling messages, Proxy
Binding Update and Proxy Binding Acknowledgement, exchanged between
the mobile access gateway and the local mobility anchor to be
protected using IPsec, using the established security association
between them. This essentially eliminates the threats related to the
impersonation of the mobile access gateway or the local mobility
anchor.
This specification allows a mobile access gateway to send binding
registration messages on behalf of a mobile node. If proper
authorization checks are not in place, a malicious node may be able
to hijack a mobile node's session or may carry out a denial-of-
service attack. To prevent this attack, this specification requires
the local mobility anchor to allow only authorized mobile access
gateways that are part of that Proxy Mobile IPv6 domain to send
binding registration messages on behalf of a mobile node.
To eliminate the threats on the interface between the mobile access
gateway and the mobile node, this specification requires an
established trust between the mobile access gateway and the mobile
node and to authenticate and authorize the mobile node before it is
allowed to access the network. Further, the established
authentication mechanisms enabled on that access link will ensure
that there is a secure binding between the mobile node's identity and
its link-layer address. The mobile access gateway will definitively
identify the mobile node from the packets that it receives on that
access link.
To address the threat related to a compromised mobile access gateway,
the local mobility anchor, before accepting a Proxy Binding Update
message for a given mobile node, may ensure that the mobile node is
definitively attached to the mobile access gateway that sent the
proxy binding registration request. This may be accomplished by
contacting a trusted entity which is able to track the mobile node's
current point of attachment. However, the specific details of the
actual mechanisms for achieving this is outside the scope of this
document.
Gundavelli, et al. Expires June 27, 2008 [Page 68]
Internet-Draft Proxy Mobile IPv6 December 2007
12. Acknowledgements
The authors would like to specially thank Julien Laganier, Christian
Vogt, Pete McCann, Brian Haley, Ahmad Muhanna, JinHyeock Choi for
their thorough review of this document.
The authors would also like to thank Alex Petrescu, Alice Qinxia,
Alper Yegin, Ashutosh Dutta, Behcet Sarikaya, Fred Templin, Genadi
Velev, George Tsirtsis, Gerardo Giaretta, Henrik Levkowetz, Hesham
Soliman, James Kempf, Jari Arkko, Jean-Michel Combes, John Zhao,
Jong-Hyouk Lee, Jonne Soininen, Jouni Korhonen, Kalin Getov, Kilian
Weniger, Marco Liebsch, Mohamed Khalil, Nishida Katsutoshi, Phil
Roberts, Ryuji Wakikawa, Sangjin Jeong, Suresh Krishnan, Ved Kafle,
Vidya Narayanan, Youn-Hee Han 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, Parviz
Yegani, Mark Grayson, Michael Hammer, Vojislav Vucetic, Jay Iyer and
Tim Stammers for their input on this document.
13. References
13.1. Normative References
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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-3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
January 2005.
[RFC-4283] Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
Chowdhury, "Mobile Node Identifier Option for Mobile IPv6", RFC 4283,
November 2005.
Gundavelli, et al. Expires June 27, 2008 [Page 69]
Internet-Draft Proxy Mobile IPv6 December 2007
[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-4861] Narten, T., Nordmark, E. and W. Simpson, Soliman, H.,
"Neighbor Discovery for IP Version 6 (IPv6)", RFC 4861, September
2007.
13.2. Informative References
[RFC-1661] Simpson, W., Ed., "The Point-To-Point Protocol (PPP)", STD
51, RFC 1661, July 1994.
[RFC-2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC-3971] Arkko, J., Ed., Kempf, J., Sommerfeld, B., Zill, B., and
P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March
2005.
[RFC-4140] Soliman, H., Castelluccia, C., El Malki, K., and L.
Bellier, "Hierarchical Mobile IPv6 Mobility Management (HMIPv6)", RFC
4140, August 2005.
[RFC-4306] Kaufman, C, et al, "Internet Key Exchange (IKEv2)
Protocol", RFC 4306, December 2005.
[RFC-4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
for IPv4, IPv6 and OSI", RFC 2030, October 1996.
[RFC-4372] Adrangi, F., Lior, A., Korhonen, J., and J. Loughney,
"Chargeable User Identity", RFC 4372, January 2006.
[RFC-4830] Kempf, J., Leung, K., Roberts, P., Nishida, K., Giaretta,
G., Liebsch, M., "Problem Statement for Network-based Localized
Mobility Management", September 2006.
[RFC-4831] Kempf, J., Leung, K., Roberts, P., Nishida, K., Giaretta,
G., Liebsch, M., "Goals for Network-based Localized Mobility
Management", October 2006.
[RFC-4832] Vogt, C., Kempf, J., "Security Threats to Network-Based
Localized Mobility Management", September 2006.
[RFC-4862] Thompson, S., Narten, T., Jinmei, T., "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
Gundavelli, et al. Expires June 27, 2008 [Page 70]
Internet-Draft Proxy Mobile IPv6 December 2007
[RFC-4941] Narten, T., Draves, R., Krishnan, S., "Privacy Extensions
for Stateless Address Autoconfiguration in IPv6", RFC 4941, September
2007.
[RFC-5072] Varada, S., Haskin, D. and Allen, E., "IP version 6 over
PPP", RFC 5072, September 2007.
[ID-IPV4-PMIP6] Wakikawa, R. and Gundavelli, S., "IPv4 Support for
Proxy Mobile IPv6", draft-ietf-netlmm-pmip6-ipv4-support-02.txt,
November 2007.
[ID-DNAV6] Kempf, J., et al "Detecting Network Attachment in IPv6
Networks (DNAv6)", draft-ietf-dna-protocol-06.txt, October 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
This specification supports Per-MN-Prefix model. However, it is
possible to support Shared-Prefix model under the following
guidelines.
The mobile node is allowed to use stateful address configuration
using DHCPv6 for obtaining its address configuration. The mobile
node 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 [RFC-4861].
Gundavelli, et al. Expires June 27, 2008 [Page 71]
Internet-Draft Proxy Mobile IPv6 December 2007
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
_ANY_DESTINATION_, 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
Vijay Devarapalli
Azaire Networks
4800 Great America Pkwy
Santa Clara, CA 95054
USA
Email: vijay.devarapalli@azairenet.com
Gundavelli, et al. Expires June 27, 2008 [Page 72]
Internet-Draft Proxy Mobile IPv6 December 2007
Kuntal Chowdhury
Starent Networks
30 International Place
Tewksbury, MA
Email: kchowdhury@starentnetworks.com
Basavaraj Patil
Nokia Siemens Networks
6000 Connection Drive
Irving, TX 75039
USA
Email: basavaraj.patil@nsn.com
Gundavelli, et al. Expires June 27, 2008 [Page 73]
Internet-Draft Proxy Mobile IPv6 December 2007
Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Gundavelli, et al. Expires June 27, 2008 [Page 74]