NETLMM WG S. Gundavelli (Editor)
Internet-Draft K. Leung
Intended status: Standards Track Cisco
Expires: October 26, 2008 V. Devarapalli
Azaire Networks
K. Chowdhury
Starent Networks
B. Patil
Nokia Siemens Networks
April 24, 2008
Proxy Mobile IPv6
draft-ietf-netlmm-proxymip6-12.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
Network-based mobility management enables IP mobility for a host
without requiring its participation in any mobility related
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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 . . . . . . . . . . . . . 9
4. Proxy Mobile IPv6 Protocol Security . . . . . . . . . . . . . 15
4.1. Peer Authorization Database (PAD) Example Entries . . . . 16
4.2. Security Policy Database (SPD) Example Entries . . . . . . 16
5. Local Mobility Anchor Operation . . . . . . . . . . . . . . . 17
5.1. Extensions to Binding Cache Entry Data Structure . . . . . 17
5.2. Supported Home Network Prefix Models . . . . . . . . . . . 19
5.3. Signaling Considerations . . . . . . . . . . . . . . . . . 19
5.3.1. Processing Binding Registrations . . . . . . . . . . . 19
5.3.2. Initial Binding Registration (New Mobility Session) . 22
5.3.3. Binding Lifetime Extension (No handoff) . . . . . . . 23
5.3.4. Binding Lifetime Extension (After handoff) . . . . . . 23
5.3.5. Binding De-Registration . . . . . . . . . . . . . . . 24
5.3.6. Constructing the Proxy Binding Acknowledgement
Message . . . . . . . . . . . . . . . . . . . . . . . 24
5.4. Multihoming Support . . . . . . . . . . . . . . . . . . . 27
5.4.1. Binding Cache entry lookup considerations . . . . . . 27
5.5. Timestamp Option for Message Ordering . . . . . . . . . . 33
5.6. Routing Considerations . . . . . . . . . . . . . . . . . . 36
5.6.1. Bi-Directional Tunnel Management . . . . . . . . . . . 36
5.6.2. Forwarding Considerations . . . . . . . . . . . . . . 36
5.7. Local Mobility Anchor Address Discovery . . . . . . . . . 37
5.8. Mobile Prefix Discovery Considerations . . . . . . . . . . 38
5.9. Route Optimizations Considerations . . . . . . . . . . . . 38
6. Mobile Access Gateway Operation . . . . . . . . . . . . . . . 38
6.1. Extensions to Binding Update List Entry Data Structure . . 39
6.2. Mobile Node's Policy Profile . . . . . . . . . . . . . . . 40
6.3. Supported Access Link Types . . . . . . . . . . . . . . . 41
6.4. Supported Address Configuration Modes . . . . . . . . . . 41
6.5. Access Authentication & Mobile Node Identification . . . . 42
6.6. Acquiring Mobile Node's Identifier . . . . . . . . . . . . 42
6.7. Home Network Emulation . . . . . . . . . . . . . . . . . . 43
6.8. Link-Local and Global Address Uniqueness . . . . . . . . . 43
6.9. Signaling Considerations . . . . . . . . . . . . . . . . . 44
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6.9.1. Binding Registrations . . . . . . . . . . . . . . . . 44
6.9.2. Router Solicitation Messages . . . . . . . . . . . . . 52
6.9.3. Default-Router . . . . . . . . . . . . . . . . . . . . 53
6.9.4. Retransmissions and Rate Limiting . . . . . . . . . . 53
6.10. Routing Considerations . . . . . . . . . . . . . . . . . . 54
6.10.1. Transport Network . . . . . . . . . . . . . . . . . . 54
6.10.2. Tunneling & Encapsulation Modes . . . . . . . . . . . 55
6.10.3. Local Routing . . . . . . . . . . . . . . . . . . . . 56
6.10.4. Tunnel Management . . . . . . . . . . . . . . . . . . 56
6.10.5. Forwarding Rules . . . . . . . . . . . . . . . . . . . 56
6.11. Supporting DHCPv6 based Address Configuration on the
Access Link . . . . . . . . . . . . . . . . . . . . . . . 58
6.12. Home Network Prefix Renumbering . . . . . . . . . . . . . 59
6.13. Mobile Node Detachment Detection and Resource Cleanup . . 59
6.14. Allowing network access to other IPv6 nodes . . . . . . . 60
7. Mobile Node Operation . . . . . . . . . . . . . . . . . . . . 60
7.1. Moving into a Proxy Mobile IPv6 Domain . . . . . . . . . . 61
7.2. Roaming in the Proxy Mobile IPv6 Domain . . . . . . . . . 62
8. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 62
8.1. Proxy Binding Update Message . . . . . . . . . . . . . . . 62
8.2. Proxy Binding Acknowledgement Message . . . . . . . . . . 64
8.3. Home Network Prefix Option . . . . . . . . . . . . . . . . 65
8.4. Handoff Indicator Option . . . . . . . . . . . . . . . . . 66
8.5. Access Technology Type Option . . . . . . . . . . . . . . 67
8.6. Mobile Node Link-layer Identifier Option . . . . . . . . . 69
8.7. Link-local Address Option . . . . . . . . . . . . . . . . 70
8.8. Timestamp Option . . . . . . . . . . . . . . . . . . . . . 71
8.9. Status Values . . . . . . . . . . . . . . . . . . . . . . 71
9. Protocol Configuration Variables . . . . . . . . . . . . . . . 73
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 74
11. Security Considerations . . . . . . . . . . . . . . . . . . . 75
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 76
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 77
13.1. Normative References . . . . . . . . . . . . . . . . . . . 77
13.2. Informative References . . . . . . . . . . . . . . . . . . 78
Appendix A. Proxy Mobile IPv6 interactions with AAA
Infrastructure . . . . . . . . . . . . . . . . . . . 79
Appendix B. Routing State . . . . . . . . . . . . . . . . . . . . 79
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 80
Intellectual Property and Copyright Statements . . . . . . . . . . 82
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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 between a network node and a 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 nodes 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
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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 set up 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
to and from the access link and for signaling the mobile node's
local mobility anchor.
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Mobile Node (MN)
Throughout this document, the term mobile node is used to refer to
an IP host or router whose mobility is managed by the network.
The mobile node may be an IPv4-only node, IPv6-only node or a
dual-stack node and 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.
LMA Address (LMAA)
The global 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 global 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 Network Prefix (MN-HNP)
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 interfaces will
be assigned a unique home network prefix and under a different
mobility session.
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Mobile Node's Home Address (MN-HoA)
MN-HoA is an address from a mobile node's home network prefix
in a Proxy Mobile IPv6 domain. The mobile node will be able to
use this address as long as it is attached to the access
network that is in the scope of that Proxy Mobile IPv6 domain.
Unlike in Mobile IPv6 where the home agent is aware of the home
address of the mobile node, in Proxy Mobile IPv6, the mobility
entities are only aware of the mobile node's home network
prefix and are not always aware of the exact address(es) that
the mobile node configured on its interface from that prefix.
However, in some configurations and based on the enabled
address configuration modes on the access link, the mobility
entities in the network can be certain about the exact address
configured by the mobile node.
Mobile Node's Home Link
This is the point-to-point 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 same 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 Network Access Identifier (NAI) [RFC-4282]
or other identifier such as a Media Access Control (MAC) address.
Mobile Node Link-layer Identifier (MN-LL-Identifier)
An identifier that identifies the attached interface of a mobile
node. For those interfaces that have a link-layer identifier,
this identifier can be based on that. The link-layer identifier
in some cases is generated by the mobile node and conveyed to the
mobile access gateway. This identifier of the attached interface
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must be stable as seen by any of the mobile access gateways in a
given Proxy Mobile IPv6 domain. In some other cases, there might
not be any link-layer identifier associated with the mobile node's
interface.
Policy Profile
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.
Per-MN-Prefix & Shared-Prefix Models
The term, Per-MN-Prefix model, is used to refer to an addressing
model where there is an unique network prefix assigned for each
node. The term, Shared-Prefix model, is used to refer to an
addressing model where the prefix is shared by more than one node.
This specification supports the Per-MN-Prefix model and does not
support the Shared-Prefix model.
ALL_ZERO & NON_ZERO
Protocol message fields initialized with value 0 in each byte of
the field. Ex: An 8-byte link-layer identifier field with the
value set to 0 in each of the 8 bytes, or an IPv6 address with the
value 0 in all of the 16 bytes. Conversely, the term NON_ZERO is
used to refer to any value other than an ALL_ZERO value.
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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
set up 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 to and from the access link and for
initiating binding registrations to the mobile node's local mobility
anchor. The architecture of a Proxy Mobile IPv6 domain is shown in
Figure 1.
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+----+ +----+
|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
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changing its point of attachment in that network.
The mobile node may be an IPv4-only node, IPv6-only node or a dual
IPv4/IPv6 node. 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. The mobile node will be able to configure an address(es)
on those interfaces from the respective home network prefixes.
However, if the mobile node performs an inter-interface handoff by
moving its address configuration from one interface to the other and
if the local mobility anchor receives a handoff hint from the serving
mobile access gateway about the same, the local mobility anchor will
assign the same home network prefix that it assigned to the
previously attached interface.
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+-----+ +-----+ +-----+
| MN | | MAG | | LMA |
+-----+ +-----+ +-----+
| | |
MN Attached | |
| | |
| MN Attached Event from MN/Network |
| (Acquire MN-Id and Profile) |
| | |
|--- Rtr Sol --------->| |
| | |
| |--- PBU ------------->|
| | |
| | Accept PBU
| | (Allocate MN-HNP, Setup BCE and Tunnel)
| | |
| |<------------- PBA ---|
| | |
| Accept PBA |
| (Setup Tunnel and Routing) |
| | |
| |==== Bi-Dir Tunnel ===|
| | |
|<--------- 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 sets up its endpoint of the bi-directional tunnel to the
mobile access gateway.
The mobile access gateway on receiving the Proxy Binding
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Acknowledgement message sets up its endpoint of the bi-directional
tunnel to the local mobility anchor and also 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
to the mobile node by any node in the network. 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. However, in some cases the traffic sent from a correspondent
node that is locally connected to the mobile access gateway may not
be received by the local mobility anchor and may be routed locally by
the mobile access gateway.
The mobile access gateway acts as the 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. However in some cases the traffic sent to a
correspondent node that is locally connected to the mobile access
gateway may be locally routed by the mobile access gateway.
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+-----+ +-----+ +-----+ +-----+
| 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 received
| | | from MN or from network
| | | (Acquire MN-Id and Profile)
| | | |
|--- Rtr Sol ------------------------------------->|
....
Registration steps as in fig 2.
....
| | |==Bi-Dir Tunnel=|
| | | |
|<------------------------------------ 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). This call flow reflects only
a specific message ordering, it is possible the registration message
from the n-MAG may arrive before the de-registration message from the
p-MAG arrives.
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
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anchor and will remove the binding and routing state for that mobile
node. The local mobility anchor upon receiving this request will
identify the corresponding mobility session for which the binding
update request was received and once it accepts the request will wait
for certain amount of time for allowing the mobile access gateway on
the new link to update the binding. However, if it does not receive
any binding update request within that given amount of time, it will
delete the binding cache entry.
The mobile access gateway on the new access link upon detecting the
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]. That is, IPsec is a mandatory to implement
security mechanism. However, additional documents may specify
alternative mechanisms. As in Mobile IPv6 [RFC-3775], the use of
IPsec for protecting mobile node's data traffic is optional.
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 set up 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 [RFC-
4306], 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
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in creating security associations for protecting the signaling
messages or sending binding updates. Therefore, the local mobility
anchor MUST restrict the creation and manipulation of proxy bindings
to specifically authorized mobile access gateways and prefixes. The
local mobility anchor MUST be locally configurable to authorize such
specific combinations. Additional mechanisms such as a policy store
or AAA may be employed, but these are outside the scope of this
specification.
Unlike in Mobile IPv6 [RFC-3775], these signaling messages do not
carry either the Home Address destination option or the Type 2
Routing header and hence the policy entries and security association
selectors stay the same.
4.1. Peer Authorization Database (PAD) Example 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_address_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 (SPD) Example 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
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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.
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 the Proxy Mobile IPv6 protocol is
referred to as a 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 of [RFC-3775].
For supporting this specification, the Binding Cache Entry data
structure needs to be extended with the following additional fields.
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o A flag indicating whether or not this Binding Cache entry is
created due to a proxy registration. This flag is set to value 1
for Binding Cache entries that are proxy registrations and is set
to value 0 for all other entries.
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.
o The link-layer identifier of the mobile node's connected interface
on the access link. This identifier can be acquired from the
Mobile Node Link-layer Identifier option, present in the received
Proxy Binding Update request. If the option was not present in
the request, the value MUST be set to ALL_ZERO.
o The Link-local address of the mobile access gateway on the point-
to-point link shared with the mobile node. This is generated by
the local mobility anchor after accepting the initial Proxy
Binding Update request.
o The IPv6 home network prefix that is assigned to the mobile node's
connected interface. 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 tunnel interface identifier (If-Id) of the bi-directional
tunnel between the local mobility anchor and the mobile access
gateway where the mobile node is currently anchored. This is
internal to the local mobility anchor. The tunnel interface
identifier is acquired during the tunnel creation.
o The access technology type, using which the mobile node is
currently attached. This is obtained from the Access Technology
Type option, present in the Proxy Binding Update request.
o The 64-bit timestamp value of the most recently accepted Proxy
Binding Update request sent for this mobile node. This is the
time-of-day on the local mobility anchor, when the message was
received. If the Timestamp option is not present in the Proxy
Binding Update request (i.e., when the sequence number based
scheme is in use), the value MUST be set to ALL_ZERO.
Typically, the mobile node's home network prefix is the key for
locating a Binding Cache entry in all cases except when there has
been an handoff of the mobile node's session to a new mobile access
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gateway and that mobile access gateway is unaware of the home network
prefix that was assigned to the handed of session. In such handoff
cases, the Binding Cache entry can be located under the
considerations specified in Section 5.4.1.
5.2. Supported Home Network Prefix Models
This specification supports the Per-MN-Prefix model and does not
support the 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 (other than the Subnet-
Router anycast address [RFC-4291] which is used by the mobile access
gateway hosting the prefix on that link). 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.
5.3.1. Processing Binding Registrations
1. The received Proxy Binding Update message (a Binding Update
message with the 'P' flag set to value of 1, format specified in
Section 8.1) MUST be authenticated as described in Section 4.
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 message.
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2. The local mobility anchor MUST observe the rules described in
Section 9.2 of [RFC-3775] when processing Mobility Header in the
received Proxy Binding Update request.
3. The local mobility anchor MUST ignore the check, specified in
Section 10.3.1 of [RFC-3775], related to the presence of Home
Address destination option in the Proxy Binding Update request.
4. 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
send a Proxy Binding Acknowledgement message with Status field
set to MISSING_MN_IDENTIFIER_OPTION (Missing mobile node
identifier option) and the identifier in the Mobile Node
Identifier Option carried in the message MUST be set to a zero
length identifier.
5. The local mobility anchor MUST apply the required policy checks,
as explained in Section 4, to verify the sender is a trusted
mobile access gateway, authorized to send Proxy Binding Update
requests on behalf of this mobile node.
6. If the local mobility anchor determines that the requesting node
is not authorized to send Proxy Binding Update requests for the
identified mobile node, 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
binding registrations).
7. If the local mobility anchor cannot identify the mobile node
based on the identifier present in the Mobile Node Identifier
option [RFC-4283] of Proxy Binding Update request, it MUST
reject the request and send a Proxy Binding Acknowledgement
message with Status field set to NOT_LMA_FOR_THIS_MOBILE_NODE
(Not local mobility anchor for this mobile node).
8. 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).
9. The local mobility anchor MUST apply the considerations
specified in Section 5.5, for processing the Sequence Number
field and the Timestamp option (if present), in the Proxy
Binding Update request.
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10. If the Home Network Prefix option (containing either ALL_ZERO or
some prefix value) 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 home network
prefix option).
11. If the Handoff Indicator 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_HANDOFF_INDICATOR_OPTION
(Missing handoff indicator option).
12. If the Access Technology Type 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_ACCESS_TECH_TYPE_OPTION
(Missing access technology type option).
13. Considerations specified in Section 5.4.1 MUST be applied for
performing the Binding Cache entry existence test. If those
checks specified in Section 5.4.1, result in associating the
received Proxy Binding Update request to a new mobility session
creation request, considerations from Section 5.3.2 (Initial
Binding Registration - New Mobility Session), MUST be applied.
If those checks result in associating the request to an existing
mobility session, the following checks determine the next set of
processing rules that needs to be applied.
* If the Handoff Indicator field in the Handoff Indicator
option present in the request is set to a value of 5 (Handoff
state not changed), considerations from Section 5.3.3
(Binding Lifetime Extension- No handoff) MUST be applied.
* If the received Proxy Binding Update request has the lifetime
value of zero, considerations from Section 5.3.5 (Binding De-
Registration) MUST be applied.
* For all other cases, considerations from Section 5.3.4
(Binding Lifetime Extension - After handoff) MUST be applied.
14. When sending the Proxy Binding Acknowledgement message with any
Status field value, the message MUST be constructed as specified
in Section 5.3.6.
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5.3.2. Initial Binding Registration (New Mobility Session)
1. If the Home Network Prefix option present in the Proxy Binding
Update request has the value set to ALL_ZERO, the local mobility
anchor MUST allocate a prefix and assign it to a new mobility
session created for the mobile node. The local mobility anchor
MUST ensure the allocated prefix is not in use by any other node
or mobility session.
2. If the local mobility anchor is unable to allocate any 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 value, 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).
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
registration.
5. If there is no existing bi-directional tunnel to the mobile
access gateway that sent the request, the local mobility anchor
MUST establish a bi-directional tunnel to that mobile access
gateway. Considerations from Section 5.6.1 MUST be applied for
managing the dynamically created bi-directional tunnel.
6. The local mobility anchor MUST create a prefix route over the
tunnel to the mobile access gateway for forwarding any traffic
received for the mobile node's home network prefix. The created
tunnel and routing state MUST result in the forwarding behavior
on the local mobility anchor as specified in Section 5.6.2.
7. The local mobility anchor MUST send the Proxy Binding
Acknowledgement message with the Status field set to 0 (Proxy
Binding Update Accepted). The message MUST be constructed as
specified in Section 5.3.6.
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5.3.3. Binding Lifetime Extension (No handoff)
1. Upon accepting the Proxy Binding Update request for extending the
binding lifetime, received from the same mobile access gateway
(if the Proxy-CoA address in the Binding Cache entry is the same
as the Proxy-CoA address in the request) that last updated the
binding, the local mobility anchor MUST update the Binding Cache
entry with the accepted registration values.
2. The local mobility anchor MUST send the Proxy Binding
Acknowledgement message with the Status field set to 0 (Proxy
Binding Update Accepted). The message MUST be constructed as
specified in Section 5.3.6.
5.3.4. Binding Lifetime Extension (After handoff)
1. Upon accepting the Proxy Binding Update request for extending the
binding lifetime, received from a new mobile access gateway (if
the Proxy-CoA address in the Binding Cache entry does not match
the Proxy-CoA address in the request) where the mobile node's
session is handed off, the local mobility anchor MUST update the
Binding Cache entry with the accepted registration values.
2. The local mobility anchor MUST remove the previously created
route for the mobile node's home network prefix. Additionally,
if there are no other mobile node sessions sharing the
dynamically created bi-directional tunnel to the previous mobile
access gateway, the tunnel MUST be deleted applying
considerations from section 5.6.1 (if the tunnel is a dynamically
created tunnel and not a fixed pre-established tunnel).
3. If there is no existing bi-directional tunnel to the mobile
access gateway that sent the request, the local mobility anchor
MUST establish a bi-directional tunnel to that mobile access
gateway. Considerations from Section 5.6.1 MUST be applied for
managing the dynamically created bi-directional tunnel.
4. The local mobility anchor MUST create a prefix route over the
tunnel to the mobile access gateway for forwarding any traffic
received for the mobile node's home network prefix. The created
tunnel and routing state MUST result in the forwarding behavior
on the local mobility anchor as specified in Section 5.6.2.
5. The local mobility anchor MUST send the Proxy Binding
Acknowledgement message with the Status field set to 0 (Proxy
Binding Update Accepted). The message MUST be constructed as
specified in Section 5.3.6.
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5.3.5. Binding De-Registration
1. If the received Proxy Binding Update request with the lifetime
value of zero, has a Source Address in the IPv6 header (or the
address in the Alternate Care-of Address option, if the option is
present) different from what is present in the Proxy-CoA address
field in the Binding Cache entry, the local mobility anchor MUST
ignore the request.
2. Upon accepting the Proxy Binding Update request with the lifetime
value of zero, the local mobility anchor MUST wait for
MinDelayBeforeBCEDelete amount of time, before it deletes the
Binding Cache entry. However, it MUST send the Proxy Binding
Acknowledgement message with the Status field set to 0 (Proxy
Binding Update Accepted). The message MUST be constructed as
specified in Section 5.3.6.
* During this wait period, the local mobility anchor SHOULD drop
the mobile node's data traffic.
* During this wait period, if the local mobility anchor receives
a valid Proxy Binding Update request for the same mobility
session 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 and additionally the wait period should be
ended.
* By the end of this wait period, if the local mobility anchor
did not receive any valid Proxy Binding Update request for
this mobility session, then it MUST delete the Binding Cache
entry and remove the routing state created for that mobility
session.
5.3.6. 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.
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IPv6 header (src=LMAA, dst=Proxy-CoA)
Mobility header
- BA /* P flag must be set to value of 1 */
Mobility Options
- Mobile Node Identifier Option (mandatory)
- Home Network Prefix option (mandatory)
- Handoff Indicator option (mandatory)
- Access Technology Type option (mandatory)
- Timestamp Option (optional)
- Mobile Node Link-layer Identifier option (optional)
- Link-local Address option (optional)
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. When there is no Alternate Care-of Address option
present in the request, the destination address is the same as the
Proxy-CoA address, otherwise, the address may not be the same as
the Proxy-CoA.
o The Mobile Node Identifier option [RFC-4283] MUST be present. The
identifier field in the option MUST be copied from the Mobile Node
Identifier option in the received Proxy Binding Update request.
If the option was not present in the request, the identifier in
the option MUST be set to a zero length identifier.
o The Home Network Prefix option MUST be present.
* If the Status field is set to a value greater than or equal to
128, i.e., if the binding request is rejected, then the prefix
value in the Home Network Prefix option MUST be set to the
prefix value in the Home Network Prefix option of the received
Proxy Binding Update request. But, if the option was not
present in the request, the value in the option MUST be set to
ALL_ZERO.
* For all other cases, the prefix value in the option MUST be set
to the allocated prefix value for that mobility session.
o The Handoff Indicator option MUST be present. The handoff
indicator field in the option MUST be copied from the Handoff
Indicator option in the received Proxy Binding Update request. If
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the option was not present in the request, the value in the option
MUST be set to zero.
o The Access Technology Type option MUST be present. The access
technology type field 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, the value
in the option MUST be set to zero.
o The Timestamp option MUST be present, if the same option was
present in the received Proxy Binding Update request.
Considerations from Section 5.5 must be applied for constructing
the Timestamp option.
o The Mobile Node Link-layer Identifier option MUST be present, if
the same option was present in the received Proxy Binding Update
request. The link-layer identifier value MUST be copied from the
Mobile Node Link-layer Identifier option present in the received
Proxy Binding Update request.
o The Link-local Address option MUST be present, if the same option
was present in the received Proxy Binding Update request.
* If the received Proxy Binding Update request has the Link-local
Address option with any value other than ALL_ZERO, the same
value MUST be copied to the Link-local Address field of the
Binding Cache entry and it must also be copied to the Link-
local Address option in the reply.
* If there is no existing Binding Cache entry (i.e., if this is a
request for a new mobility session), then the local mobility
anchor MUST generate the link-local address that the mobile
access gateway can use on the point-to-point link shared with
the mobile node and the same must be copied to the Link-local
Address field of the Binding Cache entry and it must also be
copied to the Link-local Address option in the reply.
* For all other cases, the link-local address in the option MUST
be copied from the Link-local Address field of the Binding
Cache entry.
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 Unlike in Mobile IPv6 [RFC-3775], the Type 2 Routing header MUST
NOT be present in the IPv6 header of the packet.
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5.4. Multihoming Support
This specification allows mobile nodes to connect to a Proxy Mobile
IPv6 domain through multiple interfaces for simultaneous access.
Following are the key aspects of this multihoming support.
o When a mobile node connects to a Proxy Mobile IPv6 domain through
multiple interfaces for simultaneous access, the local mobility
anchor MUST allocate a unique home network prefix for each of the
connected interfaces.
o 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.
o The local mobility anchor MUST allow for an handoff between two
different interfaces of the mobile node. In such a scenario, the
home network prefix that is associated with a specific link-layer
identifier of the mobile node will be updated with the new link-
layer 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 Proxy Binding Update
message and under the considerations specified in this section.
5.4.1. Binding Cache entry lookup considerations
There can be multiple Binding Cache entries for a given mobile node.
When doing a lookup for a mobile node's Binding Cache entry for
processing a received Proxy Binding Update request message, the local
mobility anchor MUST apply the following multihoming considerations
(in the below specified order). These rules are chained with the
processing rules specified in Section 5.3.
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5.4.1.1. Home Network Prefix Option (NON_ZERO Value) present in the
request
+=====================================================================+
| Registration/De-Registration Message |
+=====================================================================+
| HNP (NON_ZERO Value) |
+=====================================================================+
| ATT |
+=====================================================================+
| MN-LL-Identifier Opt Present | MN-LL-Identifier Opt Not Present |
+=====================================================================+
| HI |
+==================================+==================================+
| BCE Lookup Key: (Home Network Prefix) |
+=====================================================================+
Figure 7: BCE lookup using home network prefix
1. The local mobility anchor MUST verify if there is an existing
Binding Cache entry with the home network prefix value matching
the prefix value in the Home Network Prefix option of the
received Proxy Binding Update request. [BCE(HNP) equals
PBU(HNP)]
2. If there does not exist a Binding Cache entry (matching the MN-
HNP), the request MUST be considered as a request for creating a
new mobility session.
3. If there exists a Binding Cache entry (matching MN-HNP), and if
the mobile node identifier in the entry does not match the mobile
node identifier in the Mobile Node Identifier option of the
received Proxy Binding Update request, the local mobility anchor
MUST reject the request with the Status field value set to
NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX (mobile node is not
authorized for the requesting home network prefix). [BCE(MN-
Identifier) not equals PBU(MN-Identifier)]
4. If there exists a Binding Cache entry (matching MN-Identifier and
MN-HNP) and if any one or more of these below stated conditions
match, the request MUST be considered as a request for updating
that Binding Cache entry. [BCE(MN-Identifier) equals PBU(MN-
Identifier)]
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* If there is a Mobile Node Link-layer Identifier option present
in the request, and if the link-layer identifier value in that
option matches the link-layer identifier value in the Binding
Cache entry and the access technology type field in the Access
Technology Type option present in the request matches the
access technology type in the Binding Cache entry. [BCE(ATT,
MN-LL-Identifier) equals PBU(ATT, MN-LL-Identifier)]
* If the Handoff Indicator field in the Handoff Indicator option
present in the request is set to a value of 2 (Handoff between
two different interfaces of the mobile node). [PBU(HI) equals
2]
* If there is no Mobile Node Link-layer Identifier option
present in the request, the link-layer identifier value in the
Binding Cache entry is set to ALL_ZERO, the access technology
type field in the Access Technology Type option present in the
request matches the access technology type in the Binding
Cache entry and if the Handoff Indicator field in the Handoff
Indicator option present in the request is set to a value of 3
(Handoff between mobile access gateways for the same
interface).
* If the Proxy-CoA address in the Binding Cache entry matches
the source address of the request (or the address in the
alternate Care-of Address option, if the option is present)
and if the access technology type field in the Access
Technology Type option present in the request matches the
access technology type in the Binding Cache entry.
[BCE(Proxy-CoA, ATT) equals PBU(Proxy-CoA, ATT)].
5. For all other cases, the message MUST be considered as a request
for creating a new mobility session.
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5.4.1.2. Mobile Node Link-layer Identifier Option present in the
request
+=====================================================================+
| Registration/De-Registration Message |
+=====================================================================+
| HNP (ALL_ZERO Value) |
+=====================================================================+
| ATT |
+=====================================================================+
| MN-LL-Identifier Option Present (NON_ZERO Value) |
+=====================================================================+
| HI |
+==================================+==================================+
| BCE Lookup Keys: (MN-Identifier + ATT + MN-LL-Identifier) |
+=====================================================================+
Figure 8: BCE Lookup using Link-layer Identifier
1. The local mobility anchor MUST verify if there is an existing
Binding Cache entry, with the mobile node identifier matching the
identifier in the received Mobile Node Identifier option, access
technology type matching the value in the received Access
Technology Type option and the link-layer identifier value
matching the identifier in the received Mobile Node Link-layer
Identifier option. [BCE(MN-Identifier, ATT, MN-LL-Identifier)
equals PBU(MN-Identifier, ATT, MN-LL-Identifier)]
2. If there exists a Binding Cache entry (matching MN-Identifier,
ATT and MN-LL-Identifier), the request MUST be considered as a
request for updating that Binding Cache entry.
3. If there does not exist a Binding Cache entry (matching MN-
Identifier, ATT and MN-LL-Identifier) and the Handoff Indicator
field in the Handoff Indicator option present in the request is
set to a value of 2 (Handoff between two different interfaces of
the mobile node). The local mobility anchor MUST apply the
following additional considerations. [PBU(HI) equals 2]
* The local mobility anchor MUST verify if there exists one and
only one Binding Cache entry with the mobile node identifier
matching the identifier in the Mobile Node Identifier option
present in the request and for any link-layer identifier
value. If there exists only one such entry (matching the MN-
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Identifier), the request MUST be considered as a request for
updating that Binding Cache entry. [BCE(MN-Identifier) equals
PBU(MN-Identifier)]
4. If there does not exist a Binding Cache entry (matching MN-
Identifier, ATT and MN-LL-Identifier) and if the Handoff
Indicator field in the Handoff Indicator option present in the
request is set to a value of 4 (Handoff state unknown), the local
mobility anchor MUST apply the following additional
considerations.
* The local mobility anchor MUST verify if there exists one and
only one Binding Cache entry with the mobile node identifier
matching the identifier in the Mobile Node Identifier option
present in the request and for any link-layer identifier
value. If there exists only one such entry (matching the MN-
Identifier), the local mobility anchor SHOULD wait till the
existing Binding Cache entry is de-registered by the
previously serving mobile access gateway, before the request
can be considered as a request for updating that Binding Cache
entry. However, if there is no de-registration message that
is received within MaxDelayBeforeNewBCEAssign amount of time,
the local mobility anchor upon accepting the request MUST
consider the request as a request for creating a new mobility
session. The local mobility anchor MAY also choose to create
a new mobility session and without waiting for a de-
registration message and this should be configurable on the
local mobility anchor.
5. For all other cases, the message MUST be considered as a request
for creating a new mobility session.
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5.4.1.3. Mobile Node Link-layer Identifier Option not present in the
request
+=====================================================================+
| Registration/De-Registration Message |
+=====================================================================+
| HNP (ALL_ZERO Value) |
+=====================================================================+
| ATT |
+=====================================================================+
| MN-LL-Identifier Option Not Present |
+=====================================================================+
| HI |
+==================================+==================================+
| BCE Lookup Key: (MN-Identifier) |
+=====================================================================+
Figure 9: BCE Lookup using Mobile Node Identifier
1. The local mobility anchor MUST verify if there exists one and
only one Binding Cache entry with the mobile node identifier
matching the identifier in the Mobile Node Identifier option
present in the request.
2. If there exists only one such entry (matching the MN-Identifier)
and the Handoff Indicator field in the Handoff Indicator option
present in the request is set to a value of 2 (Handoff between
two different interfaces of the mobile node), the request MUST be
considered as a request for updating that Binding Cache entry.
[PBU(HI) equals 2]
3. If there exists only one such entry (matching the MN-Identifier)
and the Handoff Indicator field in the Handoff Indicator option
present in the request is set to a value of 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 the request can be considered as a
request for updating that Binding Cache entry. However, if there
is no de-registration message that is received within
MaxDelayBeforeNewBCEAssign amount of time, the local mobility
anchor upon accepting the request MUST consider the request as a
request for creating a new mobility session. The local mobility
anchor MAY also choose to create a new mobility session and
without waiting for a de-registration message and this should be
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configurable on the local mobility anchor.
4. For all other cases, the message MUST be considered as a request
for creating a new mobility session.
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 specified in
[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.
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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.
Using the Timestamps based approach:
1. A local mobility anchor implementation MUST support the 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 the 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 8.8).
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.
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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 (within TimestampValidityWindow amount of time difference)
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.
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 the Sequence Number based approach:
1. If the Timestamp option is not present in the received Proxy
Binding Update request, the local mobility anchor MUST fall back
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 the Sequence Number based scheme,
as specified in [RFC-3775].
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3. The Sequence Number based approach can be used only when there is
some mechanism (such as context transfer procedure between mobile
access gateways) that allows the serving mobile access gateway to
obtain the last sequence number that was sent in a binding
registration message for updating a given mobile node's binding.
5.6. Routing Considerations
5.6.1. Bi-Directional Tunnel Management
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. A tunnel hides the topology and enables a mobile node to use
an address from its home network prefix from any access link in that
Proxy Mobile IPv6 domain. A tunnel may be created dynamically when
needed and removed when not needed. However, implementations MAY
choose to use static pre-established tunnels instead of dynamically
creating and tearing them down on a need basis. The following
considerations MUST be applied when using dynamic tunnels.
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, the end
points of the tunnel are the IPv4-LMAA and IPv4-Proxy-CoA, as
specified in [ID-IPV4-PMIP6].
o Implementations can 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 can be set to the
accepted binding lifetime and can 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.
o The tunnel MUST be deleted when either the tunnel lifetime expires
or when there are no mobile nodes sharing the 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
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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 set up for that mobile node. The format of the
tunneled packet is shown below. Considerations from [RFC-2473]
MUST be applied for IPv6 encapsulation. However, when using IPv4
transport, the format of the packet is as described in [ID-IPV4-
PMIP6].
IPv6 header (src= LMAA, dst= Proxy-CoA /* Tunnel Header */
IPv6 header (src= CN, dst= MN-HOA ) /* Packet Header */
Upper layer protocols /* Packet Content*/
Figure 10: Tunneled Packets from LMA to MAG
Forwarding Packets Sent by the Mobile Node:
o All the reverse tunneled packets that the local mobility anchor
received 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. Considerations from
[RFC-2473] MUST be applied for IPv6 decapsulation.
5.7. Local Mobility Anchor Address Discovery
Dynamic Home Agent Address Discovery (DHAAD), as explained in Section
10.5 of [RFC-3775], allows a mobile node to discover all the home
agents on its home link by sending an ICMP Home Agent Address
Discovery Request message to the Mobile IPv6 Home-Agents anycast
address, derived from its home network prefix.
The 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
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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
This specification does not support mobile prefix discovery. The
mobile prefix discovery mechanism as specified in [RFC-3775] is not
applicable to Proxy Mobile IPv6.
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 [RFC-3775] 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 to and from the 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
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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.
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 of
[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 link-layer identifier of the mobile node's connected
interface. This 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
Link-layer identifier conveyed by the mobile node; however, the
specific details on how that is conveyed is out of scope for this
specification. If this identifier is not available, the value
MUST be set to ALL_ZERO.
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
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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 point-to-point link
between the mobile node and the mobile access gateway. This is
internal to the mobile access gateway and is used to associate the
Proxy Mobile IPv6 tunnel to the access link where the mobile node
is attached.
o The tunnel 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)
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o The mobile node's IPv6 home network Prefix lifetime
o Supported address configuration procedures (Stateful, Stateless or
both) for the mobile node 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.
6.4. Supported Address Configuration Modes
A mobile node in the Proxy Mobile IPv6 domain can configure one or
more global IPv6 addresses on its interface using Stateless, Stateful
or manual 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 access
link, the mobile node can generate one or more IPv6 addresses by
standard IPv6 mechanisms such as Stateless Autoconfiguration [RFC-
4862] or Privacy extensions [RFC-4941].
When stateful address autoconfiguration is supported on the link, the
mobile node can obtain the address configuration from the DHCPv6
server located in the Proxy Mobile IPv6 domain, by standard DHCPv6
mechanisms, as specified in [RFC-3315]. The obtained address will be
from its respective home network prefix. Section 6.11 specifies the
details on how this configuration can be achieved.
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. This specification does not change the behavior of address
configuration mechanisms in any way.
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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 the 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 and unique across the Proxy Mobile IPv6 domain. The
mobility entities in the Proxy Mobile IPv6 domain MUST be able to use
this identifier in the signaling messages and unambiguously identify
a given mobile node. Following are some of the considerations
related to this MN-Identifier.
o The MN-Identifier is typically obtained as part of the access
authentication or from a notified network attachment event. In
cases where the user identifier authenticated during access
authentication uniquely identifies a mobile node, the MN-
Identifier MAY be the same as the user identifier. However, the
user identifier MUST NOT be used if it identifies a user account
that can be used from more than one mobile node operating in the
same Proxy Mobile IPv6 domain.
o In some cases, the obtained identifier as part of the access
authentication can be a temporary identifier and further that
temporary identifier may be different at each re-authentication.
However, the mobile access gateway MUST be able to use this
temporary identifier and obtain the mobile node's stable
identifier from the policy store. For instance, in AAA-based
systems the RADIUS attribute, Chargeable-User-Identifier [RFC-
4372] may be used, as long as it uniquely identifies a mobile
node, and not a user account that can be used with multiple mobile
nodes.
o In some cases and for privacy reasons, 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.
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o The mobile access gateway MUST be able to identify the mobile node
by its MN-Identifier and it MUST be able to associate this
identity to the point-to-point link shared with the mobile node.
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
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 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 its existing
addresses, which may potentially lead to address collisions after the
mobile node's handoff to a new link.
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The issue of address collision is not relevant to the mobile node's
global address(es). Since there is a unique home network prefix
assigned for each mobile node, no other node shares an address (other
than Subnet-Router anycast address which is configured by the mobile
access gateway) from that prefix and so the uniqueness for the mobile
node's global address is assured on the access link.
The issue of address collision is however relevant to the mobile
node's link-local addresses since the mobile access gateway and the
mobile node will have link-local addresses configured from the same
link-local prefix (FE80::/64). This leaves a room for link-local
address collision between the two neighbors (i.e., the mobile node
and the mobile access gateway) on that access link. For solving this
problem, this specification requires that the link-local address that
the mobile access gateway configures on the point-to-point link
shared with a given mobile node be generated by the local mobility
anchor and be stored in the mobile node's Binding Cache entry. This
address will not change for the duration of that mobile node's
session and can be provided to the serving mobile access gateway at
every mobile node's handoff, as part of the Proxy Mobile IPv6
signaling messages. The specific method by which the local mobility
anchor generates the link-local addresses is out of scope for this
specification.
Optionally, implementations MAY choose to configure a fixed link-
local address across all the access links in a Proxy Mobile IPv6
domain and without a need for carrying this address from the local
mobility anchor to the mobile access gateway in the Proxy Mobile IPv6
signaling messages.
6.9. Signaling Considerations
6.9.1. Binding Registrations
6.9.1.1. 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.
2. The Proxy Binding Update message MUST include the Mobile Node
Identifier option [RFC-4283], carrying the MN-Identifier for
identifying the mobile node.
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3. The Home Network Prefix option MUST be present in the Proxy
Binding Update message. 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,
otherwise it MUST specify a value of ALL_ZERO. If the specified
value is ALL_ZERO, then the local mobility anchor will do the
prefix assignment.
4. The Handoff Indicator option MUST be present in the Proxy
Binding Update message. The Handoff Indicator field in the
Handoff Indicator option MUST be set to a value indicating the
handoff hint.
* The Handoff Indicator field MUST be set to value 1
(Attachment over a new interface), if the mobile access
gateway determines (under the Handoff Indicator
considerations specified in this section) that the mobile
node's current attachment to the network over this interface
is not as a result of a handoff of an existing mobility
session (over the same interface or through a different
interface), but as a result of an attachment over a new
interface. This essentially serves as a request to the local
mobility anchor to create a new 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.
* The Handoff Indicator field MUST be set to value 2 (Handoff
between two different interfaces of the mobile node), if the
mobile access gateway definitively knows the mobile node's
current attachment is due to a handoff of an existing
mobility session, between two different interfaces of the
mobile node.
* The Handoff Indicator field 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 an existing
mobility session between two mobile access gateways and for
the same interface of the mobile node.
* The Handoff Indicator field MUST be set to value 4 (Handoff
state unknown), if the mobile access gateway cannot determine
if the mobile node's current attachment is due to a handoff
of an existing mobility session.
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5. The mobile access gateway MUST apply the below considerations
when choosing the value for the Handoff Indicator field.
* The mobile access gateway can choose to use the value 2
(Handoff between two different interfaces of the mobile
node), only when it knows that the mobile node has on purpose
switched from one interface to another, and the previous
interface is going to be disabled. It may know this due to a
number of factors. For instance, most cellular networks have
controlled handovers where the network knows that the host is
moving from one attachment to another. In this situation the
link layer mechanism can inform the mobility functions that
this is indeed a movement, not a new attachment.
* Some link layers have link-layer identifiers that can be used
to distinguish (a) the movement of a particular interface to
a new attachment from (b) the attachment of a new interface
from the same host. Option value 3 (Handoff between mobile
access gateways for the same interface)is appropriate in case
a and value of 1 (Attachment over a new interface) in case b.
* The mobile access gateway MUST NOT set the option value to 2
(Handoff between two different interfaces of the mobile node)
or 3 (Handoff between mobile access gateways for the same
interface) if it can not be determined that the mobile node
can move the address between the interfaces involved in the
handover or that it is the same interface that has moved.
Otherwise Proxy Mobile IPv6-unaware hosts that have multiple
physical interfaces to the same domain may suffer unexpected
failures.
* Where no support from the link layer exists, the host and the
network would need to inform each other about the intended
movement. The Proxy Mobile IPv6 protocol does not specify
this and simply requires that knowledge about movements can
be derived either from the link-layer or from somewhere else.
The method by which this is accomplished is outside the scope
of this specification.
6. Either the Timestamp option or a valid sequence number
maintained on a per mobile node basis (if the Sequence Number
based scheme is in use) MUST be present. When Timestamp option
is added to the message, the mobile access gateway SHOULD also
set the Sequence Number field to a value of a monotonically
increasing counter (not to be confused with the per mobile node
sequence number specified in [RFC-3775]). The local mobility
anchor will ignore this field when there is a Timestamp option
present in the request, but will return the same value in the
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Proxy Binding Acknowledgement message. This will be useful for
matching the reply to the request message.
7. The Mobile Node Link-layer Identifier option carrying the link-
layer identifier of the currently attached interface MUST be
present in the Proxy Binding Update message, if the mobile
access gateway is aware of the same. If the link-layer
identifier of the currently attached interface is not known or
if the identifier value is ALL_ZERO, this option MUST NOT be
present.
8. The Access Technology Type option MUST be present in the Proxy
Binding Update message. The access technology type field in the
option SHOULD be set to the type of access technology using
which the mobile node is currently attached to the mobile access
gateway.
9. The Link-local Address option MAY be present in the Proxy
Binding Update message. Considerations from Section 6.8 MUST be
applied when using the link-local address option.
* When querying the local mobility anchor for the link-local
address that it should use on the point-to-point link shared
with the mobile node, this option MUST be set to ALL_ZERO.
This essentially serves as a request to the local mobility
anchor to return the link-local address of the mobile access
gateway stored in the binding cache entry associated with
this mobility session.
* When uploading the link-local address to the local mobility
anchor, the value in the option MUST be set to the link-local
address that is configured on the point-to-point link shared
with the mobile node. This is allowed only during an initial
mobile node's attachment.
10. The Proxy Binding Update message MUST be constructed as
specified in Section 6.9.1.5.
11. If there is no existing Binding Update List entry for that
mobile node, the mobile access gateway MUST create a Binding
Update List entry for the mobile node upon sending the Proxy
Binding Update request.
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6.9.1.2. Receiving Binding Registration Reply
On receiving a Proxy Binding Acknowledgement message (format
specified in Section 8.2) from the local mobility anchor, the mobile
access gateway MUST process the message as specified below.
1. The received Proxy Binding Acknowledgement message (a Binding
Acknowledgement message with the 'P' flag set to value of 1)
MUST be authenticated as described in Section 4. 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 message.
2. The mobile access gateway MUST observe the rules described in
Section 9.2 of [RFC-3775] when processing Mobility Headers in
the received Proxy Binding Acknowledgement message.
3. The mobile access gateway MUST apply the considerations
specified in Section 5.5 for processing the Sequence Number
field and the Timestamp option (if present), in the message.
4. The mobile access gateway MUST ignore any checks, specified in
[RFC-3775] related to the presence of a Type 2 Routing header in
the Proxy Binding Acknowledgement message.
5. The mobile access gateway MAY use the mobile node identifier
present in the Mobile Node Identifier option for matching the
response to the request messages that it sent recently.
However, if there is more than one request message in its
request queue for the same mobile node, the sequence number
field can be used for identifying the exact message from those
messages. There are other ways to achieve this and
implementations are free to adopt the best approach that suits
their implementation. Additionally, if the received Proxy
Binding Acknowledgement message does not match any of the Proxy
Binding Update messages that it sent recently, the message MUST
be ignored.
6. If the received Proxy Binding Acknowledgement message has any
one or more of the following options, Handoff Indicator option,
Access Technology Type option, Mobile Node Link-layer Identifier
option, Mobile Node Identifier option, carrying option values
that are different from the option values present in the
corresponding request (Proxy Binding Update) message, the
message MUST be ignored as the local mobility anchor is expected
to echo back all these listed options and with the same option
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values in the reply message. Further, the mobile access gateway
MUST NOT retransmit the Proxy Binding Update message till an
administrative action is taken.
7. 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 deny the mobility service to that
mobile node.
8. If the received Proxy Binding Acknowledgement message has the
Status field value set to TIMESTAMP_LOWER_THAN_PREV_ACCEPTED
(Timestamp value lower than previously accepted value), the
mobile access gateway SHOULD try to register again to reassert
the mobile node's presence on its access link. The mobile
access gateway is not specifically required to synchronize its
clock upon receiving this error code.
9. If the received Proxy Binding Acknowledgement message has the
Status field value set to TIMESTAMP_MISMATCH (Invalid timestamp
value), 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.
10. If the received Proxy Binding Acknowledgement message has the
Status field value set to NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX
(mobile node is not authorized for the requesting home network
prefix), the mobile access gateway SHOULD NOT request for the
same prefix again, but can request the local mobility anchor to
dynamically assign a prefix, by specifying a ALL_ZERO value in
the Home Network Prefix option carried in the subsequent Proxy
Binding Update message.
11. 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 MUST deny the
mobility service to the mobile node by not forwarding any
packets using the source address from that home network prefix
and originating from that point-to-point link.
12. If the received Proxy Binding Acknowledgement message has the
Status field value set to 0 (Proxy Binding Update accepted), the
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mobile access gateway MUST update 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.
13. If the received Proxy Binding Acknowledgement message has the
address in the Link-local Address option set to a NON_ZERO
value, the mobile access gateway MUST configure that link-local
address on that point-to-point link and MUST NOT configure any
other link-local address on that point-to-point link. This will
avoid any link-local address collisions on that access link.
6.9.1.3. Extending Binding Lifetime
1. For extending the lifetime of a currently registered mobile node
(i.e., after a successful initial binding registration from the
same mobile access gateway), the mobile access gateway can send a
Proxy Binding Update message to the local mobility anchor with a
new lifetime value. This re-registration message MUST be
constructed with the same set of options as the initial binding
registration message, under the considerations specified in
Section 6.9.1.1. However the following exceptions apply.
2. The prefix value in the Home Network Prefix option MUST be set to
the currently assigned home network prefix.
3. The Handoff Indicator field in the Handoff Indicator option MUST
be set to a value of 5 (Handoff state not changed - Re-
Registration).
6.9.1.4. Mobile Node Detachment and Binding De-Registration
1. If at any point the mobile access gateway detects that the mobile
node has moved away from its access link, or if it decides to
terminate the mobile node's mobility session, it SHOULD send a
Proxy Binding Update message to the local mobility anchor with
the lifetime value set to zero. This de-registration message
MUST be constructed with the same set of options as the initial
binding registration message, under the considerations specified
in Section 6.9.1.1. However, the following exceptions apply.
2. The prefix value in the Home Network Prefix option MUST be set to
the currently assigned home network prefix.
3. The Handoff Indicator field in the Handoff Indicator option MUST
be set to a value of 4 (Handoff state unknown).
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Either upon receipt of a Proxy Binding Acknowledgement message from
the local mobility anchor or after INITIAL_BINDACK_TIMEOUT [RFC-3775]
timeout waiting for the reply, the mobile access gateway MUST do the
following:
1. It MUST remove the Binding Update List entry for the mobile node
from its Binding Update List.
2. It MUST remove the created routing state for tunneling the mobile
node's traffic.
3. If there is a dynamically created tunnel to the mobile node's
local mobility anchor and if there are not other mobile nodes for
which the tunnel is being used, then the tunnel MUST be deleted.
4. It MUST tear down the point-to-point link shared with the mobile
node. This action will force the mobile node to remove any IPv6
address configuration on the interface connected to this point-
to-point link.
6.9.1.5. 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.
IPv6 header (src=Proxy-CoA, dst=LMAA)
Mobility header
- BU /* P & A flags MUST be set to value 1 */
Mobility Options
- Mobile Node Identifier option (mandatory)
- Home Network Prefix option (mandatory)
- Handoff Indicator option (mandatory)
- Access Technology Type option (mandatory)
- Timestamp option (optional)
- Mobile Node Link-layer Identifier option (optional)
- Link-local Address option (optional)
Figure 11: Proxy Binding Update message format
o The Source Address field in the IPv6 header of the message MUST be
set to the global address configured on the egress interface of
the mobile access gateway. When there is no Alternate Care-of
Address option present in the request, this address will be
considered as the Proxy-CoA address for this binding registration
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request. However, when there is Alternate Care-of Address option
present in the request, this address will be not be considered as
the Proxy-CoA address, but the address in the alternate Care-of
Address option will be considered as the Proxy-CoA address.
o The Destination Address field in the IPv6 header of the message
MUST be set to the local mobility anchor address.
o The Mobile Node Identifier option [RFC-4283] MUST be present.
o The Home Network Prefix option MUST be present.
o The Handoff Indicator option MUST be present.
o The Access Technology Type option MUST be present.
o The Timestamp option MAY be present.
o The Mobile Node Link-layer Identifier option MAY be present.
o The Link-local Address option MAY be present.
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 Unlike in Mobile IPv6 [RFC-3775], the Home Address option [RFC-
3775] MUST NOT be present in the IPv6 Destination Options
extension header of the Proxy Binding Update message.
6.9.2. Router Solicitation Messages
A mobile node may send a Router Solicitation message on the access
link shared with the mobile access gateway. The Router Solicitation
message that the mobile node sends is as specified in [RFC-4861].
The mobile access gateway on receiving the Router Solicitation
message or before sending a Router Advertisement message MUST apply
the following considerations.
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.
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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 reason, 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.
3. The mobile access gateway SHOULD add the MTU option, as specified
in [RFC-4861], to the Router Advertisement messages that it sends
on the access link. This will ensure the mobile node on the link
uses the advertised MTU value. The MTU value MUST reflect the
tunnel MTU for the bi-directional tunnel between the mobile
access gateway and the local mobility anchor.
6.9.3. Default-Router
In Proxy Mobile IPv6, the mobile access gateway is the IPv6 default-
router for the mobile node on the access link, as it is the entity
that sends the Router Advertisements on the access link. However, as
the mobile node moves from one access link to another, the serving
mobile access gateway on those respective links will send the Router
Advertisements. If these Router Advertisements are sent using a
different link-local address or a different link-layer address, the
mobile node will always detect a new default-router after every
handoff. For solving this problem, this specification requires all
the mobile access gateways in the Proxy Mobile IPv6 domain to use the
same link-local and link-layer address on any of the access links
where ever the mobile node attaches. The link-layer address can be a
fixed address across that all the mobile access gateways can use on
any of the point-to-point links. However, the link-local address can
be an address provided by the local mobility anchor, or a fixed
address.
6.9.4. Retransmissions and Rate Limiting
The mobile access gateway is responsible for retransmissions and rate
limiting the binding registration requests that it sends to the local
mobility anchor. The Retransmission and the Rate Limiting rules are
as specified in [RFC-3775]. However, the following considerations
MUST be applied.
1. When the mobile access gateway sends a Proxy Binding Update
request, it should use the constant, INITIAL_BINDACK_TIMEOUT
[RFC-3775], for configuring the retransmission timer, as
specified in Section 11.8 [RFC-3775]. However, the mobile access
gateway is not required to use a longer retransmission interval
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of InitialBindackTimeoutFirstReg as specified in [RFC-3775] for
the initial binding registration request.
2. If the mobile access gateway fails to receive a valid matching
response for a registration or re-registration message 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 of [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
MAY continue to send these messages at this slower rate
indefinitely.
4. If the Timestamp based scheme is in use, the retransmitted Proxy
Binding Update messages MUST use the latest timestamp. If the
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
interfaces.
Proxy-CoA LMAA
| |
+--+ +---+ +---+ +--+
|MN|----------|MAG|======================|LMA|----------|CN|
+--+ +---+ +---+ +--+
IPv6 Tunnel
Figure 12: Proxy Mobile IPv6 Tunnel
6.10.1. Transport Network
As per this specification, the transport network between the local
mobility anchor and the mobile access gateway is an IPv6 network.
The companion document [ID-IPV4-PMIP6] specifies the required
extensions for negotiating IPv4 transport and the corresponding
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encapsulation mode.
6.10.2. Tunneling & Encapsulation Modes
Each 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
same tunneling mechanism between the local mobility anchor and the
mobile access gateway.
On most operating systems, a tunnel is 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 is the supported packet encapsulation mode 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].
The companion document [ID-IPV4-PMIP6] specifies other encapsulation
modes for supporting IPv4 transport.
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].
o IPv6-In-IPv4-UDP-TLV - IPv6 datagram encapsulation in an IPv4 UDP
packet with a TLV header. This mode is specified in [ID-IPV4-
PMIP6].
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6.10.3. 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.
6.10.4. 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.
6.10.5. 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. Considerations from [RFC-
2473] MUST be applied for IPv6 decapsulation. 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 [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
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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,
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.
o The format of the tunneled packet is shown below. Considerations
from [RFC-2473] MUST be applied for IPv6 encapsulation.
Additionally, 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 13: Tunneled Packets from MAG to LMA
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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 point-to-point link between the mobile node and
the mobile access gateway and how a mobile node attached to that link
can obtain an address from its home network prefix and using DHCPv6.
o For supporting Stateful Address Configuration using DHCPv6, the
DHCPv6 relay agent [RFC-3315] service MUST be configured on each
of the mobile access gateways in the Proxy Mobile IPv6 domain.
Further, as specified in Section 20 of [RFC-3315], the DHCPv6
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 A DHCPv6 server in the Proxy Mobile IPv6 domain can be configured
with a set of prefixes (P1, P2, ..., Pn). Each one of these
prefixes in this prefix list is a home network prefix that the
local mobility anchor(s) can assign to any mobile node. However,
the DHCPv6 server will not know the relation between a given
prefix and a mobile node to which the corresponding prefix is
allocated. It just views these prefixes as hosted prefixes on
different links in that domain and assigns individual addresses
from the respective prefixes based on the prefix value present in
the link-address option of the received DHCPv6 request.
o When a mobile node sends a DHCPv6 request message, the DHCPv6
relay agent function on the mobile access gateway will set the
link-address field in the DHCPv6 message to an address in the
mobile node's home network prefix. The address is generated as
per [RFC-4862] by combining the mobile node's home network prefix
(assigned by the local mobility anchor for this mobility session)
and its own interface identifier on the access link shared with
the mobile node, so as to provide a prefix hint to the DHCPv6
Server for the prefix selection. The DHCPv6 server on receiving
the request from the mobile node, will allocate an address from
the prefix pointed to by the link-address field of the request.
o Once the mobile node obtains an address and moves to a different
link and sends a DHCPv6 request (at any time) for extending the
DHCP lease, the DHCPv6 relay agent on the new link will set the
prefix hint in the DHCPv6 message to the mobile node's home
network prefix (assigned by the local mobility anchor for this
mobility session). The DHCPv6 server will identify the client
from the Client-DUID option present in the request and will
allocate the same address as before.
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o The DHCPv6 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 DHCPv6
request messages from a given mobile node anchored on any of the
access links in that domain, will always be handled by the same
DHCPv6 server or by a server from the same group of coordinated
DHCPv6 servers serving that domain.
o The DHCPv6 server should be configured to offer low address lease
times. A lease time that is too large prevents the DHCPv6 server
from reclaiming the address even after the local mobility anchor
deletes the mobile node's binding cache entry. It is recommended
that the configured lease time be lower than the accepted binding
lifetime for any mobility binding.
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
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 a 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 entry 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
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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 a scenario the normal IPv6 considerations
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 without impacting its host-based mobility
protocol operation.
7. Mobile Node Operation
This non-normative section explains the mobile node's operation in a
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Proxy Mobile IPv6 domain.
7.1. Moving into a Proxy Mobile IPv6 Domain
When 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 set up 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 a 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 completes 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 a 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
an IPv6 address using any of the standard IPv6 address configuration
mechanisms permitted for that mode.
If the mobile node is IPv4 enabled and if the network permits, it
will be able to obtain the IPv4 address configuration as 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.
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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
link is in the scope of that Proxy Mobile IPv6 domain, the mobile
node will always detect the same default-router advertising the
mobile node's home network prefix on each connected link. If the
mobile node performs DHCP operation, it will always obtain the same
address as before.
8. Message Formats
This section defines extensions to the Mobile IPv6 [RFC-3775]
protocol messages.
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.
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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 of
[RFC-3775]. The local mobility anchor 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 Update message. There can be only one
instance of each of these options present in the message and in
any order.
Mobile Node Identifier option
Home Network Prefix option
Handoff Indicator option
Access Technology Type option
Timestamp option
Mobile Node Link-layer Identifier option
Link-local Address option
For descriptions of other fields present in this message, refer to
section 6.1.7 of [RFC-3775].
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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) flag as specified in [RFC-3963].
Proxy Registration Flag (P)
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 to value of 1 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 of
[RFC-3775]. The mobile access gateway MUST ignore and skip any
options which it does not understand.
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As per this specification, the following mobility options are
valid in a Proxy Binding Acknowledgement message. There can be
only one instance of each of these options present in the message
and in any order.
Mobile Node Identifier option
Home Network Prefix option
Handoff Indicator option
Access Technology Type option
Timestamp option
Mobile Node Link-layer Identifier option
Link-local Address 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 8.9 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 of [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
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:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Home Network Prefix +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
<IANA>
Length
8-bit unsigned integer indicating the length 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.
8.4. Handoff Indicator Option
A new option, Handoff Indicator 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
handoff related hints.
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The Handoff Indicator 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 | Reserved (R) | HI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
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.
Handoff Indicator (HI)
A 8-bit field that specifies the type of handoff. The values
(0 - 255) will be allocated and managed by IANA. The following
values are currently defined.
0: Reserved
1: Attachment over a new interface
2: Handoff between two different interfaces of the mobile node
3: Handoff between mobile access gateways for the same interface
4: Handoff state unknown
5: Handoff state not changed (Re-registration)
8.5. 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
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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 | Reserved (R) | ATT |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
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.
Access Technology Type (ATT)
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.
0: Reserved
1: Virtual
2: PPP
3: 802.3 (Ethernet)
4: 802.11a/b/g
5: 802.16e
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8.6. Mobile Node Link-layer Identifier Option
A new option, Mobile Node Link-layer 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 link-layer identifier.
The format of the Link-layer Identifier option is shown below. Based
on the size of the identifier, the option MUST be aligned
appropriately, as per mobility option alignment requirements
specified in [RFC-3775].
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Link-layer Identifier +
. ... .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
<IANA>
Length
8-bit unsigned integer indicating the length of the option
in octets, excluding the type and length fields.
Reserved
This field is unused for now. The value MUST be initialized to
0 by the sender and MUST be ignored by the receiver.
Link-layer Identifier
A variable length field containing the mobile node's link-layer
identifier.
The content and format of this field (including byte and bit
ordering) is as specified in Section 4.6 of [RFC-4861] for
carrying Link-Layer Address. On certain access links, where
the link-layer address is not used or cannot be determined,
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this option cannot be used.
8.7. 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 link-local address
of the mobile access gateway.
The Link-local Address option has an alignment requirement of 8n+6.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ 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.
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8.8. 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:
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.
8.9. 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 of
[RFC-3775].
Status values less than 128 indicate that the Proxy Binding Update
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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: IANA
Proxy registration not enabled for the mobile node
NOT_LMA_FOR_THIS_MOBILE_NODE: IANA
Not local mobility anchor for this mobile node
MAG_NOT_AUTHORIZED_FOR_PROXY_REG: IANA
The mobile access gateway is not authorized to send proxy binding
registrations
NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX: IANA
The mobile node is not authorized for the requesting home network
prefix
TIMESTAMP_MISMATCH: IANA
Invalid timestamp value (the clocks are out of sync)
TIMESTAMP_LOWER_THAN_PREV_ACCEPTED: IANA
The timestamp value is lower than the previously accepted value
MISSING_HOME_NETWORK_PREFIX_OPTION: IANA
Missing home network prefix option
MISSING_MN_IDENTIFIER_OPTION: IANA
Missing mobile node identifier option
MISSING_HANDOFF_INDICATOR_OPTION: IANA
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Missing handoff indicator option
MISSING_ACCESS_TECH_TYPE_OPTION: IANA
Missing access technology type option
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
130 Insufficient resources
9. Protocol Configuration Variables
The local mobility anchor MUST allow the following variables to be
configured by the system management. The configured values for these
protocol variables MUST survive server reboots and service restarts.
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.
MaxDelayBeforeNewBCEAssign
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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.
TimestampValidityWindow
This variable specifies the maximum amount of time difference in
milliseconds between the timestamp in the received Proxy Binding
Update message and the current time-of-day on the local mobility
anchor, that is allowed by the local mobility anchor for the
received message to be considered valid.
The default value for this variable is 300 milliseconds. This
variable must be adjusted to suit the deployments.
The mobile access gateway MUST allow the following variables to be
configured by the system management. The configured values for these
protocol variables MUST survive server reboots and service restarts.
EnableMAGLocalRouting
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 value of 0, 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 value of 1, 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.
10. IANA Considerations
This document defines six new Mobility Header options, the Home
Network Prefix option, Handoff Indicator option, Access Technology
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Type option, Mobile Node Link-layer Identifier option, Link-local
Address option and Timestamp option. These options are described in
Section 8. 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 Handoff Indicator option defined in Section 8.4 of this document
introduces a new Handoff Indicator (HI) numbering space, where the
values from 0 to 5 have been reserved by this document. Approval of
new Handoff Indicator type values are to be made through IANA Expert
Review.
The Access Technology Type option defined in Section 8.5 of this
document introduces a new Access Technology type (ATT) numbering
space, where the values from 0 to 5 have been reserved by this
document. Approval of new Access Technology type values are to be
made through IANA Expert Review.
This document also defines new Binding Acknowledgement status values
as described in Section 8.9. 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.
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.
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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.
12. Acknowledgements
The authors would like to specially thank Julien Laganier, Christian
Vogt, Dave Thaler, Pete McCann, Brian Haley, Ahmad Muhanna, JinHyeock
Choi, Jari Arkko and Elwyn Davies 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, Jean-Michel Combes, Jun Awano, 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, Uri
Blumenthal, 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 and 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.
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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-4140] Soliman, H., Castelluccia, C., El Malki, K., and L.
Bellier, "Hierarchical Mobile IPv6 Mobility Management (HMIPv6)", RFC
4140, August 2005.
[RFC-4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
Network Access Identifier", RFC 4282, December 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.
[RFC-4291] Hinden, R., Deering, S., "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[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.
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13.2. Informative References
[RFC-1661] Simpson, W., Ed., "The Point-To-Point Protocol (PPP)", STD
51, RFC 1661, July 1994.
[RFC-2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)", RFC 2865, June
2000.
[RFC-3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
[RFC-3971] Arkko, J., Ed., Kempf, J., Sommerfeld, B., Zill, B., and
P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March
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 4330, 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.
[RFC-4941] Narten, T., Draves, R., Krishnan, S., "Privacy Extensions
for Stateless Address Autoconfiguration in IPv6", RFC 4941, 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] Narayanan, S., et al "Detecting Network Attachment in IPv6
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Networks (DNAv6)", draft-ietf-dna-protocol-07.txt, February 2008.
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 [RFC-2865] or DIAMETER [RFC-3588]
protocols.
Appendix B. 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.
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+==================================================================+
| 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 22: Example - Policy based Route Table
+==================================================================+
| Interface | Source Address | Destination Address | Encapsulation |
+==================================================================+
| Tunnel0 | Proxy-CoA | LMAA1 | IPv6-in-IPv6 |
+------------------------------------------------------------------+
| Tunnel1 | Proxy-CoA | LMAA2 | IPv6-in-IPv6 |
+------------------------------------------------------------------+
Figure 23: Example - Tunnel Interface Table
Authors' Addresses
Sri Gundavelli
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sgundave@cisco.com
Kent Leung
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: kleung@cisco.com
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Vijay Devarapalli
Azaire Networks
4800 Great America Pkwy
Santa Clara, CA 95054
USA
Email: vijay.devarapalli@azairenet.com
Kuntal Chowdhury
Starent Networks
30 International Place
Tewksbury, MA
Email: kchowdhury@starentnetworks.com
Basavaraj Patil
Nokia Siemens Networks
6000 Connection Drive
Irving, TX 75039
USA
Email: basavaraj.patil@nsn.com
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