RFC 5213
Proxy Mobile IPv6
Network Working Group S. Gundavelli, Ed. Request for Comments: 5213 K. Leung Category: Standards Track Cisco V. Devarapalli Wichorus K. Chowdhury Starent Networks B. Patil Nokia August 2008 Proxy Mobile IPv6 Status of This Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.Abstract
Network-based mobility management enables IP mobility for a host without requiring its participation in any mobility-related 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 and Terminology ................................. 5 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 ........... 17 5. Local Mobility Anchor Operation ............................. 17 5.1. Extensions to Binding Cache Entry Data Structure ......... 18 5.2. Supported Home Network Prefix Models ..................... 19 5.3. Signaling Considerations ................................. 20 5.3.1. Processing Proxy Binding Updates ..................... 20 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) ........... 24 5.3.5. Binding De-Registration ............................. 24 5.3.6. Constructing the Proxy Binding Acknowledgement Message ............................................. 25 5.4. Multihoming Support ..................................... 27 5.4.1. Binding Cache Entry Lookup Considerations ........... 28 5.5. Timestamp Option for Message Ordering ................... 34 5.6. Routing Considerations ................................... 37 5.6.1. Bi-Directional Tunnel Management ..................... 37 5.6.2. Forwarding Considerations ........................... 38 5.6.3. Explicit Congestion Notification (ECN) Considerations for Proxy Mobile IPv6 Tunnels ......... 39 5.7. Local Mobility Anchor Address Discovery ................. 40 5.8. Mobile Prefix Discovery Considerations ................... 40 5.9. Route Optimization Considerations ....................... 41 6. Mobile Access Gateway Operation ............................. 41 6.1. Extensions to Binding Update List Entry Data Structure ... 42 6.2. Mobile Node's Policy Profile ............................. 43 6.3. Supported Access Link Types ............................. 44 6.4. Supported Address Configuration Modes ................... 44 6.5. Access Authentication and Mobile Node Identification ..... 45 6.6. Acquiring Mobile Node's Identifier ....................... 45 6.7. Home Network Emulation ................................... 46 6.8. Link-local and Global Address Uniqueness ................. 46 6.9. Signaling Considerations ................................. 48 6.9.1. Binding Registrations ............................... 48 6.9.2. Router Solicitation Messages ......................... 56 6.9.3. Default-Router ....................................... 57 6.9.4. Retransmissions and Rate Limiting ................... 58 6.9.5. Path MTU Discovery ................................... 59 6.10. Routing Considerations ................................... 60
6.10.1. Transport Network ................................... 60
6.10.2. Tunneling and Encapsulation Modes ................... 61
6.10.3. Local Routing ....................................... 62
6.10.4. Tunnel Management ................................... 62
6.10.5. Forwarding Rules ..................................... 62
6.11. Supporting DHCP-Based Address Configuration on the
Access Link ............................................. 64
6.12. Home Network Prefix Renumbering ......................... 66
6.13. Mobile Node Detachment Detection and Resource Cleanup ... 66
6.14. Allowing Network Access to Other IPv6 Nodes ............. 67
7. Mobile Node Operation ....................................... 67
7.1. Moving into a Proxy Mobile IPv6 Domain ................... 67
7.2. Roaming in the Proxy Mobile IPv6 Domain ................. 69
8. Message Formats ............................................. 69
8.1. Proxy Binding Update Message ............................. 69
8.2. Proxy Binding Acknowledgement Message ................... 71
8.3. Home Network Prefix Option ............................... 72
8.4. Handoff Indicator Option ................................. 73
8.5. Access Technology Type Option ........................... 74
8.6. Mobile Node Link-layer Identifier Option ................. 76
8.7. Link-local Address Option ............................... 77
8.8. Timestamp Option ......................................... 77
8.9. Status Values ........................................... 78
9. Protocol Configuration Variables ............................. 80
9.1. Local Mobility Anchor - Configuration Variables ......... 80
9.2. Mobile Access Gateway - Configuration Variables ......... 81
9.3. Proxy Mobile IPv6 Domain - Configuration Variables ....... 82
10. IANA Considerations ......................................... 83
11. Security Considerations ..................................... 84
12. Acknowledgements ............................................. 85
13. References ................................................... 86
13.1. Normative References ..................................... 86
13.2. Informative References ................................... 87
Appendix A. Proxy Mobile IPv6 Interactions with AAA
Infrastructure ..................................... 89
Appendix B. Routing State ....................................... 89
1. Introduction
IP mobility for IPv6 hosts is specified in Mobile IPv6 [RFC3775]. 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 [RFC3775] 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 [RFC3775] 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 that are designed to support mobility would be agnostic to the capability in the IPv6 stack of the nodes that it serves. IP mobility for nodes that have mobile IP client functionality in the IPv6 stack as well as those nodes that 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 [RFC4830]. Proxy Mobile IPv6 is a solution that addresses these issues and requirements.
2. Conventions and Terminology
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 [RFC2119].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 [RFC3775]. This document adopts the terms, Local Mobility Anchor (LMA) and Mobile Access Gateway (MAG) from the NETLMM Goals document [RFC4831]. 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 a Proxy Mobile IPv6 domain. It is the topological anchor point for the mobile node's home network prefix(es) 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 [RFC3775] 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 on an access router 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.
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 which 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 [IPV4-PMIP6].
Proxy Care-of Address (Proxy-CoA)
Proxy-CoA is the global address configured on the egress 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 [IPV4-PMIP6].
Mobile Node's Home Network Prefix (MN-HNP)
The MN-HNP is a prefix assigned to the link between the mobile
node and the mobile access gateway. More than one prefix can be
assigned to the link between the mobile node and the mobile access
gateway, in which case, all of the assigned prefixes are managed
as a set associated with a mobility session. The mobile node
configures its interface with one or more addresses from its home
network prefix(es). If the mobile node connects to the Proxy
Mobile IPv6 domain through multiple interfaces, simultaneously,
each of the attached interfaces will be assigned a unique set of
home network prefixes, and all the prefixes assigned to a given
interface of a mobile node will be managed under one mobility
session. For example, home network prefixes P1 and P2 assigned to
interface I1 will be managed under one mobility session and
prefixes P3, P4, and P5 assigned to interface I2 of the mobile
node will be managed under a different mobility session.
Additionally, in some configurations the assigned prefix can be of
128-bit prefix length.
Mobile Node's Home Address (MN-HoA)
MN-HoA is an address from a mobile node's home network prefix.
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. If the mobile node uses more than one address
from its home network prefix(es), any one of these addresses is
referred to as mobile node's home address. 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(es) and are not always
aware of the exact address(es) that the mobile node configured on
its interface from its home network prefix(es). 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(es) configured by the mobile
node.
Mobile Node's Home Link
This is the link on which the mobile node obtained its layer-3
address configuration for the attached interface after it moved
into that Proxy Mobile IPv6 domain. This is the link that
conceptually follows the mobile node. The network will ensure the
mobile node always sees this link with respect to the layer-3
network configuration, on any access link that it attaches to in
that Proxy Mobile IPv6 domain.
Multihomed Mobile Node
A mobile node that connects to the 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
for predictably identifying a mobile node. This is typically an
identifier such as a Network Access Identifier (NAI) [RFC4282] 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
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. An identifier value of ALL_ZERO is not considered a
valid identifier and cannot be used as an interface identifier.
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 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 home network prefix(es) assigned to a given
interface of a mobile node and its current care-of address (Proxy-
CoA).
Proxy Binding Acknowledgement (PBA)
A reply message sent by a local mobility anchor in response to a
Proxy Binding Update message that it received from a mobile access
gateway.
Per-MN-Prefix and Shared-Prefix Models
The term Per-MN-Prefix model is used to refer to an addressing
model where there is a unique network prefix or prefixes assigned
for each node. The term Shared-Prefix model is used to refer to
an addressing model where the prefix(es) are shared by more than
one node. This specification supports the Per-MN-Prefix model and
does not support the Shared-Prefix model.
Mobility Session
In the context of Proxy Mobile IPv6 specification, the term
mobility session refers to the creation or existence of state
associated with the mobile node's mobility binding on the local
mobility anchor and on the serving mobile access gateway.
DHCP
Throughout this document, the acronym DHCP refers to DHCP for
IPv6, as defined in [RFC3315].
ALL_ZERO and NON_ZERO
Protocol message fields initialized with value 0 in each byte of
the field. For example, 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.
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
[RFC3775].
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(es). 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. There can be multiple local mobility anchors in a Proxy
Mobile IPv6 domain each serving a different group of mobile nodes.
The architecture of a Proxy Mobile IPv6 domain is shown in Figure 1.
+----+ +----+ |LMA1| |LMA2| +----+ +----+ LMAA1 -> | | <-- LMAA2 | | \\ //\\ \\ // \\ \\ // \\ +---\\------------- //------\\----+ ( \\ IPv4/IPv6 // \\ ) ( \\ Network // \\ ) +------\\--------//------------\\-+ \\ // \\ \\ // \\ \\ // \\ Proxy-CoA1--> | | <-- Proxy-CoA2 +----+ +----+ |MAG1|-----{MN2} |MAG2| +----+ | +----+ | | | MN-HNP1 --> | MN-HNP2 | <-- MN-HNP3, MN-HNP4 {MN1} {MN3} Figure 1: Proxy Mobile IPv6 Domain When 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 mobile node is authorized for network-based mobility service, 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(es), the default-router address on the link, and other related configuration parameters. From the perspective of each mobile node, the entire Proxy Mobile IPv6 domain appears as a single link, the network ensures that the mobile node does not detect any change with respect to its layer-3 attachment even after changing its point of attachment in the network.
The mobile node may be an IPv4-only node, IPv6-only node, or a dual- stack (IPv4/v6) node. Based on the policy profile information that indicates the type of address or prefixes to be assigned for the mobile node in the network, the mobile node will be able to obtain an IPv4, IPv6, or dual IPv4/IPv6 address and move anywhere in that Proxy Mobile IPv6 domain. However, this specification only supports IPv6 address/prefix mobility with the transport network being IPv6. The support for IPv4 addressing or an IPv4 transport network is specified in the companion document [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 set of home network prefixes for each of the connected interfaces. The mobile node will be able to configure address(es) on those interfaces from the respective home network prefix(es). However, if the mobile node performs a 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(es) that it previously assigned prior to the handoff. The mobile node will also be able to perform a handoff by changing its point of attachment from one mobile access gateway to a different mobile access gateway using the same interface and will be able to retain the address configuration on the attached interface.
+-----+ +-----+ +-----+ | MN | | MAG | | LMA | +-----+ +-----+ +-----+ | | | MN Attached | | | | | | MN Attached Event from MN/Network | | (Acquire MN-Id and Profile) | | | | |--- Rtr Sol --------->| | | | | | |--- PBU ------------->| | | | | | Accept PBU | | (Allocate MN-HNP(s), Setup BCE and Tunnel) | | | | |<------------- PBA ---| | | | | Accept PBA | | (Set Up 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. The Router Solicitation message from the mobile node may arrive at any time after the mobile node's attachment and has no strict ordering relation with the other messages in the call flow. 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(es). 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 Acknowledgement message sets up its endpoint of the bi-directional tunnel to the local mobility anchor and also sets up the forwarding for the mobile node's traffic. At this point, the mobile access gateway has 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(es) as the hosted on-link prefix(es). The mobile node, on receiving these Router Advertisement messages on the access link, attempts to configure its interface using either stateful or stateless address configuration modes, based on the modes that are permitted on that access link as indicated in Router Advertisement messages. At the end of a successful address configuration procedure, the mobile node has one or more addresses from its home network prefix(es). After address configuration, the mobile node has one or more valid addresses from its home network prefix(es) 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 any one or more of the addresses from its home network prefix(es). The local mobility anchor, being the topological anchor point for the mobile node's home network prefix(es), receives any packets that are sent to the mobile node by any node in or outside the Proxy Mobile IPv6 domain. 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 (refer to Section 6.10.3). The mobile access gateway acts as the default router on the point-to- point link shared with the mobile node. 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 (refer to Section 6.10.3).
+-----+ +-----+ +-----+ +-----+ | 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(s) | | | | Figure 3: Mobile Node Handoff - Signaling Call Flow Figure 3 shows the signaling call flow for the mobile node's handoff from the previously attached mobile access gateway (p-MAG) to the newly attached mobile access gateway (n-MAG). This call flow only reflects 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. It will signal the local mobility 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 request was
received, and accepts the request after which it waits for a certain amount of time to allow the mobile access gateway on the new link to update the binding. However, if it does not receive any Proxy Binding Update message within the 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 to update the binding state. After completion of the signaling, the serving mobile access gateway will send the Router Advertisements containing the mobile node's home network prefix(es), and this will ensure the mobile node will not detect any change with respect to the layer-3 attachment of its interface.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 [RFC4301]. IPsec is a mandatory-to-implement security mechanism. However, additional documents may specify alternative mechanisms and the mobility entities can enable a specific mechanism for securing Proxy Mobile IPv6 signaling messages, based on either a static configuration or after a dynamic negotiation using any standard security negotiation protocols. As in Mobile IPv6 [RFC3775], the use of IPsec for protecting a mobile node's data traffic is optional. IPsec Encapsulating Security Payload (ESP) [RFC4303] in transport mode with mandatory integrity protection SHOULD be used for protecting the signaling messages. Confidentiality protection of these messages is not required. IPsec ESP [RFC4303] in tunnel mode MAY be used to protect the mobile node's tunneled data traffic, if protection of data traffic is required. Internet Key Exchange Protocol version 2 (IKEv2) [RFC4306] 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 [RFC4306], for mutual authentication.
The Mobile IPv6 specification [RFC3775] requires the home agent to prevent a mobile node from creating security associations or creating binding cache entries for another mobile node's home address. In the protocol described in this document, the mobile node is not involved in creating security associations for protecting the signaling messages or sending binding updates. Therefore, the local mobility anchor MUST 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 Authentication, Authorization, and Accounting (AAA) may be employed, but these are outside the scope of this specification. Unlike in Mobile IPv6 [RFC3775], 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 and require no special IPsec related considerations.4.1. Peer Authorization Database (PAD) Example Entries
This section describes PAD entries [RFC4301] 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. In the example shown below, the identity of the local mobility anchor is assumed to be lma_identity_1 and the identity of the mobile access gateway is assumed to be mag_identity_1. mobile access gateway PAD: - IF remote_identity = lma_identity_1 Then authenticate (shared secret/certificate/EAP) and authorize CHILD_SAs 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 [RFC4301] on the mobile access gateway and the local mobility anchor required to protect the Proxy Mobile IPv6 signaling messages. The SPD entries are only example configurations. A particular mobile access gateway or a local mobility anchor implementation could configure different SPD entries as long as they provide the required security. In the example shown below, the identity of the mobile access gateway is assumed to be mag_identity_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. The acronym MH represents the protocol number for the Mobility Header [RFC3775], while the terms local_mh_type and remote_mh_type stand for local mobility header type and remote mobility header type, respectively. 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_identity_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
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