NETLMM WG S. Gundavelli Internet-Draft K. Leung Intended status: Standards Track Cisco Expires: March 7, 2008 V. Devarapalli Azaire Networks K. Chowdhury Starent Networks B. Patil Nokia Siemens Networks September 4, 2007 Proxy Mobile IPv6 draft-ietf-netlmm-proxymip6-02.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on March 7, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This specification describes a network-based mobility management protocol. It is called Proxy Mobile IPv6 and is based on Mobile IPv6 Gundavelli, et al. Expires March 7, 2008 [Page 1] Internet-Draft Proxy Mobile IPv6 September 2007 Protocol [RFC-3775]. This protocol enables mobility support to a host within a domain and without requiring its participation in any mobility related signaling. The design principle in the case of network-based mobility management protocol relies on the network being in control of the mobility management. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions & Terminology . . . . . . . . . . . . . . . . . . 5 2.1. Conventions used in this document . . . . . . . . . . . . 5 2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 3. Proxy Mobile IPv6 Protocol Overview . . . . . . . . . . . . . 8 4. Proxy Mobile IPv6 Protocol Security . . . . . . . . . . . . . 11 4.1. Peer Authorization Database Entries . . . . . . . . . . . 12 4.2. Security Policy Database Entries . . . . . . . . . . . . . 13 5. Local Mobility Anchor Operation . . . . . . . . . . . . . . . 13 5.1. Extensions to Binding Cache Entry Data Structure . . . . . 14 5.2. Supported Home Network Prefix Models . . . . . . . . . . . 14 5.3. Signaling Considerations . . . . . . . . . . . . . . . . . 15 5.3.1. Processing Binding Registrations . . . . . . . . . . . 15 5.4. Timestamp Option for Message Ordering . . . . . . . . . . 19 5.5. Routing Considerations . . . . . . . . . . . . . . . . . . 21 5.5.1. Bi-Directional Tunnel Management . . . . . . . . . . . 21 5.5.2. Forwarding Considerations . . . . . . . . . . . . . . 22 5.6. Local Mobility Anchor Address Discovery . . . . . . . . . 23 5.7. Mobile Prefix Discovery Considerations . . . . . . . . . . 23 5.8. Route Optimizations Considerations . . . . . . . . . . . . 24 6. Mobile Access Gateway Operation . . . . . . . . . . . . . . . 24 6.1. Extensions to Binding Update List Entry Data Structure . . 25 6.2. Mobile Node's Policy Profile . . . . . . . . . . . . . . . 26 6.3. Supported Access Link Types . . . . . . . . . . . . . . . 26 6.4. Supported Address Configuration Models . . . . . . . . . . 26 6.5. Access Authentication & Mobile Node Identification . . . . 27 6.6. Acquiring Mobile Node's Identifier . . . . . . . . . . . . 27 6.7. Home Network Emulation . . . . . . . . . . . . . . . . . . 28 6.8. Link-Local and Global Address Uniqueness . . . . . . . . . 28 6.9. Signaling Considerations . . . . . . . . . . . . . . . . . 30 6.10. Routing Considerations . . . . . . . . . . . . . . . . . . 32 6.10.1. Transport Network . . . . . . . . . . . . . . . . . . 32 6.10.2. Tunneling & Encapsulation Modes . . . . . . . . . . . 32 6.10.3. Routing State . . . . . . . . . . . . . . . . . . . . 33 6.10.4. Local Routing . . . . . . . . . . . . . . . . . . . . 34 6.10.5. Tunnel Management . . . . . . . . . . . . . . . . . . 35 6.10.6. Forwarding Rules . . . . . . . . . . . . . . . . . . . 35 6.11. Interaction with DHCP Relay Agent . . . . . . . . . . . . 35 6.12. Home Network Prefix Renumbering . . . . . . . . . . . . . 36 Gundavelli, et al. Expires March 7, 2008 [Page 2] Internet-Draft Proxy Mobile IPv6 September 2007 6.13. Mobile Node Detachment Detection and Resource Cleanup . . 36 6.14. Allowing network access to other IPv6 nodes . . . . . . . 37 7. Mobile Node Operation . . . . . . . . . . . . . . . . . . . . 37 7.1. Moving into a Proxy Mobile IPv6 Domain . . . . . . . . . . 38 7.2. Roaming in the Proxy Mobile IPv6 Domain . . . . . . . . . 39 7.3. IPv6 Host Protocol Parameters . . . . . . . . . . . . . . 39 8. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 40 8.1. Proxy Binding Update . . . . . . . . . . . . . . . . . . . 41 8.2. Proxy Binding Acknowledgment . . . . . . . . . . . . . . . 42 8.3. Home Network Prefix Option . . . . . . . . . . . . . . . . 42 8.4. Link-local Address Option . . . . . . . . . . . . . . . . 43 8.5. Timestamp Option . . . . . . . . . . . . . . . . . . . . . 44 8.6. Status Values . . . . . . . . . . . . . . . . . . . . . . 45 9. Protocol Configuration Variables . . . . . . . . . . . . . . . 46 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 47 11. Security Considerations . . . . . . . . . . . . . . . . . . . 47 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 48 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 49 13.1. Normative References . . . . . . . . . . . . . . . . . . . 49 13.2. Informative References . . . . . . . . . . . . . . . . . . 50 Appendix A. Proxy Mobile IPv6 interactions with AAA Infrastructure . . . . . . . . . . . . . . . . . . . 51 Appendix B. Supporting Shared-Prefix Model using DHCPv6 . . . . . 51 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 52 Intellectual Property and Copyright Statements . . . . . . . . . . 54 Gundavelli, et al. Expires March 7, 2008 [Page 3] Internet-Draft Proxy Mobile IPv6 September 2007 1. Introduction Mobile IPv6 [RFC-3775] is the enabler for IPv6 mobility. It requires Mobile IPv6 client functionality in the IPv6 stack of a mobile node. Signaling between the mobile node and home agent enables the creation and maintenance of a binding between the mobile node's home address and care-of-address. Mobile IPv6 has been designed to be an integral part of the IPv6 stack in a host. However there exist IPv6 stacks today that do not have Mobile IPv6 functionality and there would likely be IPv6 stacks without Mobile IPv6 client functionality in the future as well. It is desirable to support IP mobility for all hosts irrespective of the presence or absence of mobile IPv6 functionality in the IPv6 stack. It is possible to support mobility for IPv6 nodes by extending Mobile IPv6 [RFC-3775] signaling and reusing the home agent via a proxy mobility agent in the network. This approach to supporting mobility does not require the mobile node to be involved in the signaling required for mobility management. The proxy mobility agent in the network performs the signaling and does the mobility management on behalf of the mobile node. Because of the use and extension of Mobile IPv6 signaling and home agent functionality, this protocol is referred to as Proxy Mobile IPv6 (PMIPv6). Network deployments which are designed to support mobility would be agnostic to the capability in the IPv6 stack of the nodes which it serves. IP mobility for nodes which have mobile IP client functionality in the IPv6 stack as well as those hosts which do not, would be supported by enabling Proxy Mobile IPv6 protocol functionality in the network. The advantages of developing a network based mobility protocol based on Mobile IPv6 are: o Reuse of home agent functionality and the messages/format used in mobility signaling. Mobile IPv6 is a mature protocol with several implementations that have been through interoperability testing. o A common home agent would serve as the mobility agent for all types of IPv6 nodes. o Addresses a real deployment need. The problem statement and the need for a network based mobility protocol solution has been documented in [RFC-4830]. Proxy Mobile IPv6 is a solution that addresses these issues and requirements. Gundavelli, et al. Expires March 7, 2008 [Page 4] Internet-Draft Proxy Mobile IPv6 September 2007 2. Conventions & Terminology 2.1. Conventions used in this document The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" used in this document are to be interpreted as described in RFC 2119. 2.2. Terminology All the general mobility related terms used in this document are to be interpreted as defined in the Mobile IPv6 base specification [RFC- 3775]. This document adopts the terms, Local Mobility Anchor (LMA) and Mobile Access Gateway (MAG) from the NETLMM Goals document [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 Proxy Mobile IPv6 protocol as defined in this specification. The Proxy Mobile IPv6 domain includes local mobility anchors and mobile access gateways between which security associations can be setup and authorization for sending Proxy Binding Updates on behalf of the mobile nodes can be ensured. Local Mobility Anchor (LMA) Local Mobility Anchor is the home agent for the mobile node in the Proxy Mobile IPv6 domain. It is the topological anchor point for the mobile node's home network prefix and is the entity that manages the mobile node's reachability state. It is important to understand that the local mobility anchor has the functional capabilities of a home agent as defined in Mobile IPv6 base specification [RFC-3775] and with the additional required capabilities for supporting Proxy Mobile IPv6 protocol as defined in this specification. Mobile Access Gateway (MAG) Gundavelli, et al. Expires March 7, 2008 [Page 5] Internet-Draft Proxy Mobile IPv6 September 2007 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 attachment to the link and for signaling the mobile node's local mobility anchor. Mobile Node (MN) Through out this document, the term mobile node is used to refer to an IP node whose mobility is managed by the network. The mobile node may be operating in IPv6 mode, IPv4 mode or in IPv4/ IPv6 dual mode. The mobile node is not required to participate in any mobility related signaling for achieving mobility for an IP address that is obtained in that local domain. This document further uses explicit text when referring to a mobile node that is involved in mobility related signaling as per Mobile IPv6 specification [RFC-3775]. LMA Address (LMAA) The address that is configured on the interface of the local mobility anchor and is the transport endpoint of the tunnel between the local mobility anchor and the mobile access gateway. This is the address to where the mobile access gateway sends the Proxy Binding Update messages. When supporting IPv4 traversal, i.e. when the network between the local mobility anchor and the mobile access gateway is an IPv4 network, this address will be an IPv4 address and will be referred to as IPv4-LMAA, as specified in [ID-IPV4-PMIP6]. Proxy Care-of Address (Proxy-CoA) Proxy-CoA is the address configured on the interface of the mobile access gateway and is the transport endpoint of the tunnel between the local mobility anchor and the mobile access gateway. The local mobility anchor views this address as the Care-of Address of the mobile node and registers it in the Binding Cache entry for that mobile node. When the transport network between the mobile access gateway and the local mobility anchor is an IPv4 network and if the care-of address that is registered at the local mobility anchor is an IPv4 address, the term, IPv4-Proxy-CoA is used, as specified in [ID-IPV4-PMIP6]. Mobile Node's Home Address (MN-HoA) Gundavelli, et al. Expires March 7, 2008 [Page 6] Internet-Draft Proxy Mobile IPv6 September 2007 MN-HoA is the home address of a mobile node in a Proxy Mobile IPv6 domain. It is an address from its home network prefix obtained by a mobile node in a Proxy Mobile IPv6 domain. The mobile node can continue to use this address as long as it is attached to the network that is in the scope of that Proxy Mobile IPv6 domain. Mobile Node's Home Network Prefix (MN-HNP) This is the on-link IPv6 prefix that is always present in the Router Advertisements that the mobile node receives on 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. Mobile Node's Home Link This is the link on which the mobile node obtained its initial address configuration after it moved into that Proxy Mobile IPv6 domain. This is the link that conceptually follows the mobile node. The network will ensure the mobile node always sees this link with respect to the layer-3 network configuration, on any access link that it attaches to in that proxy mobile IPv6 domain. Mobile Node 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 using which can predictably identify a mobile node. This is typically an identifier such as Mobile Node NAI [RFC-4282]. 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 MN-HNP and the Proxy-CoA. Proxy Binding Acknowledgement (PBA) A response message sent by a local mobility anchor in response to a Proxy Binding Update message that it received from a mobile access gateway. Gundavelli, et al. Expires March 7, 2008 [Page 7] Internet-Draft Proxy Mobile IPv6 September 2007 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 mobility management support to a mobile node, without requiring the participation of the mobile node in any mobility related signaling. The mobility entities in the network will track the mobile node's movements and will initiate the mobility signaling and setup the required routing state. The core functional entities in the NETLMM infrastructure are the Local Mobility Anchor and the Mobile Access Gateway. The local mobility is responsible for maintaining the mobile node's reachability state and is the topological anchor point for the mobile node's home network prefix. While the mobile access gateway is the entity that performs the mobility management on behalf of a mobile node and it resides on the access link where the mobile node is anchored. The mobile access gateway is responsible for detecting the mobile node's movements on its access link and for sending binding registrations to the mobile node's local mobility anchor. +----+ +----+ |LMA1| |LMA2| +----+ +----+ LMAA1 -> | | <-- LMAA2 | | \\ //\\ \\ // \\ \\ // \\ +---\\------------- //------\\----+ ( \\ IPv4/IPv6 // \\ ) ( \\ Network // \\ ) +------\\--------//------------\\-+ \\ // \\ \\ // \\ \\ // \\ Proxy-CoA1--> | | <-- Proxy-CoA2 +----+ +----+ |MAG1|-----[MN2] |MAG2| +----+ | +----+ | | | MN-HoA1 --> | MN-HoA2 | <-- MN-HoA3 [MN1] [MN3] Gundavelli, et al. Expires March 7, 2008 [Page 8] Internet-Draft Proxy Mobile IPv6 September 2007 Figure 1: Proxy Mobile IPv6 Domain Once a mobile node enters a Proxy Mobile IPv6 domain and attaches to an access network, the mobile access gateway on that access network after identifying the mobile node and acquiring its identifier, will determine if the mobile node is authorized for 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 an address from its home network prefix and move anywhere in that proxy mobile IPv6 domain. 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 changing its point of attachment in that network. The mobile node may be operating in an IPv4-only mode, IPv6-only mode or in dual IPv4/IPv6 mode. Based on what is enabled in the network for that mobile node, the mobile node will be able to obtain an IPv4, IPv6 or dual IPv4/IPv6 addresses and move any where in that Proxy Mobile IPv6 domain. However, the specific details related to the IPv4 addressing or IPv4 transport support is specified in the companion document [ID-IPV4-PMIP6]. Gundavelli, et al. Expires March 7, 2008 [Page 9] Internet-Draft Proxy Mobile IPv6 September 2007 +-----+ +-----+ +-----+ | MN | | MAG | | LMA | +-----+ +-----+ +-----+ | | | MN Attached | | | | | | MN Attached Event | | (Acquire MN-Id and Profile) | | | | | |----- PBU ----------->| | | | | | Accept PBU | | (Allocate MN-HNP, Setup BCE and Tunnel) | | | | |<--------- PBA -------| | | | | Accept PBA | | (Setup Tunnel and Routing) | | | | | |==== Bi-Dir Tunnel ===| | | | |--- Rtr Sol --------->| | | | | |<------- Rtr Adv -----| | | | | IP Address | | Configuration | | | | | Figure 2: Mobile Node Attachment - Signaling Call Flow 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 Acknowledgment message including the mobile node's home network prefix. It also creates the binding cache entry and establishes a bi-directional tunnel to the mobile access gateway. The mobile access gateway on receiving the Proxy Binding Acknowledgment message sets up a bi-directional tunnel to the local mobility anchor and sets up the data path for the mobile node's Gundavelli, et al. Expires March 7, 2008 [Page 10] Internet-Draft Proxy Mobile IPv6 September 2007 traffic. At this point the mobile access gateway will have all the required information for emulating the mobile node's home link. It sends Router Advertisement messages to the mobile node on the access link advertising the mobile node's home network prefix as the hosted on-link-prefix. The mobile node on receiving these Router Advertisement messages on the access link will attempt to configure its interface either using stateful or stateless address configuration modes, based on the modes that are permitted on that access link. At the end of a successful address configuration procedure, the mobile node will end up with an address from its home network prefix. Once the address configuration is complete, the mobile node has a valid address from its home network prefix, at the current point of attachment. The serving mobile access gateway and the local mobility anchor also have proper routing states for handling the traffic sent to and from the mobile node using an address from its home network prefix. The local mobility anchor, being the topological anchor point for the mobile node's home network prefix, receives any packets that are sent by any corresponding node to the mobile node. Local mobility anchor forwards these received packets to the mobile access gateway through the bi-directional tunnel. The mobile access gateway on other end of the tunnel, after receiving the packet, removes the outer header and forwards the packet on the access link to the mobile node. The mobile access gateway typically acts as a default router on the access link and any packet that the mobile node sends to any corresponding node is received by the mobile access gateway and it forwards the packet to 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. After obtaining the address configuration, if the mobile node changes 4. Proxy Mobile IPv6 Protocol Security The mobile access gateway and the local mobility anchor MUST support and SHOULD use IPsec to protect the integrity and authenticity of the signaling messages. The signaling messages, Proxy Binding Update and Proxy Binding Acknowledgement, exchanged between the mobile access gateway and the local mobility anchor SHOULD be protected using IPsec [RFC-4301] and using the established security association between Gundavelli, et al. Expires March 7, 2008 [Page 11] Internet-Draft Proxy Mobile IPv6 September 2007 them. The security association of the specific mobile node for which the signaling message is initiated is not required for protecting these messages. IPsec ESP [RFC-4303] in transport mode with mandatory integrity protection SHOULD be used for protecting the signaling messages. Confidentiality protection of these messages is not required. IKEv2 [RFC-4306] SHOULD be used to setup security associations between the mobile access gateway and the local mobility anchor to protect the Proxy Binding Update and Proxy Binding Acknowledgment messages. The mobile access gateway and the local mobility anchor can use any of the authentication mechanisms, as specified in IKEv2, for mutual authentication. Mobile IPv6 specification [RFC-3775] requires the home agent to prevent a mobile node from creating security associations or creating binding cache entries for another mobile node's home address. In the protocol described in this document, the mobile node is not involved in creating security associations for protecting the signaling messages or sending binding updates. Therefore, this is not a concern. However, the local mobility anchor MUST allow only authorized mobile access gateways to create binding cache entries on behalf of the mobile nodes. The actual mechanism by which the local mobility anchor verifies if a specific mobile access gateway is authorized to send Proxy Binding Updates on behalf of a mobile node is outside the scope of this document. One possible way this could be achieved is by sending a query to the policy store, such as AAA. 4.1. Peer Authorization Database Entries This section describes PAD entries on the mobile access gateway and the local mobility anchor. The PAD entries are only example configurations. Note that the PAD is a logical concept and a particular mobile access gateway or a local mobility anchor implementation can implement the PAD in any implementation specific manner. The PAD state may also be distributed across various databases in a specific implementation. mobile access gateway PAD: - IF remote_identity = lma_identity_1 Then authenticate (shared secret/certificate/EAP) and authorize CHILD_SA for remote address lma_addres_1 local mobility anchor PAD: - IF remote_identity = mag_identity_1 Then authenticate (shared secret/certificate/EAP) Gundavelli, et al. Expires March 7, 2008 [Page 12] Internet-Draft Proxy Mobile IPv6 September 2007 and authorize CHILD_SAs for remote address mag_address_1 The list of authentication mechanisms in the above examples is not exhaustive. There could be other credentials used for authentication stored in the PAD. 4.2. Security Policy Database Entries This section describes the security policy entries on the mobile access gateway and the local mobility anchor required to protect the Proxy Mobile IPv6 signaling messages. The SPD entries are only example configurations. A particular mobile access gateway or a local mobility anchor implementation could configure different SPD entries as long as they provide the required security. In the examples shown below, the identity of the mobile access gateway is assumed to be mag_1, the address of the mobile access gateway is assumed to be mag_address_1, and the address of the local mobility anchor is assumed to be lma_address_1. mobile access gateway SPD-S: - IF local_address = mag_address_1 & remote_address = lma_address_1 & proto = MH & local_mh_type = BU & remote_mh_type = BAck Then use SA ESP transport mode Initiate using IDi = mag_1 to address lma_1 local mobility anchor SPD-S: - IF local_address = lma_address_1 & remote_address = mag_address_1 & proto = MH & local_mh_type = BAck & remote_mh_type = BU Then use SA ESP transport mode 5. Local Mobility Anchor Operation For supporting the Proxy Mobile IPv6 protocol specified in this document, the home agent function, specified in [RFC-3775] requires certain functional modifications and enhancements. The home agent with these modifications and enhanced capabilities for supporting Proxy Mobile IPv6 protocol is referred to as the local mobility anchor. The section describes the operational details of the local mobility anchor. Gundavelli, et al. Expires March 7, 2008 [Page 13] Internet-Draft Proxy Mobile IPv6 September 2007 5.1. Extensions to Binding Cache Entry Data Structure Every local mobility anchor MUST maintain a Binding Cache Entry for each currently registered mobile node. Binding Cache Entry is a conceptual data structure, described in Section 9.1 [RFC-3775]. For supporting this specification, the Binding Cache Entry data structure needs to be extended with the following additional fields. o A flag indicating whether or not this Binding Cache entry is created due to a proxy registration. This flag is enabled for Binding Cache entries that are proxy registrations and is turned off for all other entries that are created due to the registrations directly sent by the mobile node. o The identifier of the registered mobile node, MN-Identifier. This identifier is obtained from the NAI Option [RFC-4283] present in the received Proxy Binding Update request. o The Link-local address of the mobile node on the interface attached to the access link. This is obtained from the Link-local Address option, present in the Proxy Binding Update request. o The IPv6 home network prefix of the registered mobile node. The home network prefix of the mobile node may have been statically configured in the mobile node's policy profile, or, it may have been dynamically allocated by the local mobility anchor. The IPv6 home network prefix also includes the corresponding prefix length. o The interface identifier of the bi-directional tunnel established between the local mobility anchor and the mobile access gateway where the mobile node is currently anchored. The tunnel interface identifier is acquired during the tunnel creation. o The 64-bit timestamp value of the most recently accepted Proxy Binding Update request sent for this mobile node. This is obtained from the Timestamp option, present in the request. 5.2. Supported Home Network Prefix Models This specification supports Per-MN-Prefix model and does not support Shared-Prefix model. As per the Per-MN-Prefix model, there will be an unique home network prefix assigned to each mobile node and no other node shares an address from that prefix. The mobile node's home network prefix is always hosted on the access link where the mobile node is anchored. Conceptually, the entire Gundavelli, et al. Expires March 7, 2008 [Page 14] Internet-Draft Proxy Mobile IPv6 September 2007 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-2461] 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 and is the gateway to that home network prefix. 5.3. Signaling Considerations 5.3.1. Processing Binding Registrations Upon receiving a Proxy Binding Update request from a mobile access gateway on behalf of a mobile node, the local mobility anchor MUST process the request as defined in Section 10.3 [RFC-3775], with one exception that this request is a proxy binding registration request and hence the following additional considerations must be applied. o The local mobility anchor MUST observe the rules described in Section 9.2 [RFC-3775] when processing Mobility Headers in the received Proxy Binding Update request. o The local mobility anchor MUST identify the mobile node from the identifier present in the NAI option of the Proxy Binding Update request. If the NAI 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). o If the local mobility anchor cannot identify the mobile node, from the NAI option present in the request, it MUST reject the Proxy Binding Update request and send a Proxy Binding Acknowledgement message with Status field set to 133 (Not home agent for this mobile node). o If the local mobility anchor determines that the mobile node is not authorized for 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). o The local mobility anchor MUST ignore the check, specified in Section 10.3.1 [RFC-3775], related to the presence of Home Address destination option in the Proxy Binding Update request. Gundavelli, et al. Expires March 7, 2008 [Page 15] Internet-Draft Proxy Mobile IPv6 September 2007 o The local mobility anchor MUST authenticate the Proxy Binding Update request as described in Section 4.0. It MUST use the SPI in the IPSec header [RFC-4306] of the received packet for locating the security association needed for processing the Proxy Binding Update request. o The local mobility anchor MUST apply the required policy checks, as explained in Section 4.0, to verify the sender is a trusted mobile access gateway, authorized to send proxy binding registration requests on behalf of this mobile node. o If the local mobility anchor determines that the requesting node is not authorized to send proxy binding registration requests, it MUST reject the Proxy Binding Update request and send a Proxy Binding Acknowledgement message with Status field set to MAG_NOT_AUTHORIZED_FOR_PROXY_REG (Not authorized to send proxy registrations). o If the Home Network Prefix option is not present in the Proxy Binding Update request, the local mobility anchor MUST reject the Proxy Binding Update request and send a Proxy Binding Acknowledgement message with Status field set to 129 (Administratively Prohibited). o The local mobility anchor MUST apply the considerations specified in Section 5.4, for processing the Sequence Number field and the Timestamp option, in the Proxy Binding Update request. o The local mobility anchor MUST use the identifier in the NAI option present in the Proxy Binding Update request for performing the Binding Cache entry existence test. If the entry does not exist, the local mobility MUST consider this request as an initial binding registration request. Initial Binding Registration: o If the Home Network Prefix option present in the Proxy Binding Update request has the value 0::/0, the local mobility anchor MUST allocate a prefix for the mobile node and send a Proxy Binding Acknowledgement message with the Home Network Prefix option containing the allocated prefix value. The specific details on how the local mobility anchor allocates the home network prefix is outside the scope of this document. The local mobility anchor MUST ensure the allocated prefix is not in use by any other mobile node. Gundavelli, et al. Expires March 7, 2008 [Page 16] Internet-Draft Proxy Mobile IPv6 September 2007 o If the local mobility anchor is unable to allocate a home network prefix for the mobile node, it MUST reject the request and send a Proxy Binding Acknowledgement message with Status field set to 130 (Insufficient resources). o If the Home Network Prefix option present in the request has a specific prefix hint, the local mobility anchor before accepting that request, MUST ensure the prefix is owned by the local mobility anchor and further the mobile node is authorized to use that prefix. If the mobile node is not authorized to use that prefix, the local mobility anchor MUST reject the request and send a Proxy Binding Acknowledgement message with Status field set to NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX (Mobile node not authorized to use that prefix). o 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 value for that binding. If there is a Link-local Address option present in the request, the address must be copied to the link-local address field in the Binding Cache entry. o Upon accepting the Proxy Binding Update request, the local mobility anchor MUST establish a tunnel to the mobile access gateway, as described in [RFC-2473]. Considerations from Section 5.5 must be applied. Binding Re-Registration: o If the requesting prefix in the Home Network Prefix option is a non 0::/0 value and is different from what is present in the currently active binding cache entry for that mobile node, the local mobility anchor MUST reject the request and send a Proxy Binding Acknowledgement message with Status field set to 129 (Administratively Prohibited). o Upon accepting a Proxy Binding Update request for extending the lifetime of a currently active binding for a mobile node, the local mobility anchor MUST update the existing Binding Cache entry for this mobile node. Unless there exists an established tunnel to the mobile access gateway with the same transport and encapsulation mode, the local mobility anchor MUST create a tunnel to the mobile access gateway, as described in [RFC-2473] and also delete the existing tunnel established with the previous mobile access gateway. It MUST also send a Proxy Binding Acknowledgment message to the mobile access gateway with the Status field set to 0 (Proxy Binding Update Accepted). Gundavelli, et al. Expires March 7, 2008 [Page 17] Internet-Draft Proxy Mobile IPv6 September 2007 Binding De-Registration: o If the received Proxy Binding Update request with the lifetime value of 0, has a Source Address in the IPv6 header, different from what is present in the Proxy-CoA address field in its Binding Cache entry, the local mobility anchor MAY either choose to ignore the request or send a valid Proxy Binding Acknowledgement message with the Status field set to 0 (Proxy Binding Update Accepted). o Upon accepting the Proxy Binding Update request for a mobile node, with the lifetime value of zero, the local mobility anchor MUST wait for MinDelayBeforeBCEDelete [Section 9] amount of time, before it deletes the mobile node's Binding Cache entry. Within this wait period, if the local mobility anchor receives a Proxy Binding Update request message for the same mobile node and from a different mobile access gateway, 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 new values. However, the local mobile anchor MUST send the Proxy Binding Acknowledgment message, immediately upon accepting the request. o Upon accepting the request, the local mobility anchor MUST delete the mobile node's Binding Cache entry and remove the Routing state for the mobile node's home network prefix. Constructing Proxy Binding Acknowledgement Message o The local mobility anchor when sending the Proxy Binding Acknowledgment message to the mobile access gateway MUST construct the message as specified below. IPv6 header (src=LMAA, dst=Proxy-CoA) Mobility header -BA /*P flag is set*/ Mobility Options - Home Network Prefix Option - Link-local Address Option (optional) - Timestamp Option (optional) - NAI Option Proxy Binding Acknowledgment message contents Gundavelli, et al. Expires March 7, 2008 [Page 18] Internet-Draft Proxy Mobile IPv6 September 2007 o The Source Address field in the IPv6 header of the message SHOULD 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 SHOULD be set to the source address of the received Proxy Binding Update request. o If the Status field is set to a value greater less than 128, i.e. if the binding request was rejected, then the prefix value in the Home Network Prefix option MUST be set to the prefix value from the received Home Network Prefix option. For all other cases, the prefix value MUST be set to the allocated prefix value for that mobile node. o The Link-local Address option MUST be present in the Proxy Binding Acknowledgement message, if the same option was present in the corresponding Proxy Binding Update request message. If there is an existing Binding Cache entry for that mobile node with the link-local address value of ALL_ZERO (value not set), or if there was no existing Binding Cache entry, then the link-local address MUST be copied from the received Link-local Address option in the received Proxy Binding Update request. For all other cases, it MUST be copied from the Binding Cache entry. o Considerations from Section 5.4 must be applied for constructing the Timestamp option. o The identifier in the NAI option MUST be copied from the received Proxy Binding Update request. If the Status field value is set to MISSING_MN_IDENTIFIER_OPTION, the NAI option MUST NOT be present in the reply message. o The message SHOULD be protected by using IPsec ESP, using the security association existing between the local mobility anchor and the mobile access gateway, created either dynamically or statically. 5.4. 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 context transfer mechanism, the serving mobile access gateway will be unable to determine the sequence number that Gundavelli, et al. Expires March 7, 2008 [Page 19] Internet-Draft Proxy Mobile IPv6 September 2007 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 RECOMMENDS the use of Timestamp option [Section 8.4]. 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. Alternatively, the specification also allows the use of Sequence Number based scheme, as per [RFC-3775]. The sequence number MUST be maintained on a per mobile node basis and MUST be synchronized between the serving mobile access gateways. However, the specific details on how a mobile node's sequence number is synchronized between different mobile access gateways is outside the scope of this document. Using Timestamps based approach: o An implementation MUST support Timestamp option. If the Timestamp option is present in the received Proxy Binding Update request message, then the local mobility anchor MUST include a valid Timestamp option in the Proxy Binding Acknowledgment message that it sends to the mobile access gateway. o All the mobility entities in a Proxy Mobile IPv6 domain, exchanging binding registration messages using Timestamp option must have adequately synchronized time-of-day clocks. These nodes SHOULD synchronize their clocks to a common time source, such as using Network Time Protocol [RFC-1305] or in any other ways suitable for that specific deployment. o Upon receipt of a Proxy Binding Update message with the Timestamp option, the local mobility anchor MUST check the timestamp field for validity. In order for it to be considered valid, the timestamp value contained in the Timestamp option MUST be close enough to the local mobility anchor's time-of-day clock and the timestamp MUST be greater than all previously accepted timestamps in the Proxy Binding Update messages sent for that mobile node. Gundavelli, et al. Expires March 7, 2008 [Page 20] Internet-Draft Proxy Mobile IPv6 September 2007 o 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. o If the timestamp value in the received Proxy Binding Update is valid, the local mobility anchor MUST return the same timestamp value in the Timestamp option included in the Proxy Binding Acknowledgment message that it sends to the mobile access gateway. o If the timestamp value in the received Proxy Binding Update is not valid, the local mobility anchor MUST reject the Proxy Binding Update and send a Proxy Binding Acknowledgement message with Status field set to TIMESTAMP_MISMATCH (Timestamp mismatch). The message MUST also include the Timestamp option with the value set to the current time-of-day on the local mobility anchor. Using Sequence Number based approach: o If the Timestamp option is not present in the received Proxy Binding Update request, the local mobility anchor MUST fallback to the Sequence Number based scheme. It MUST process the sequence number field as specified in [RFC-3775]. Also, it MUST NOT include the Timestamp option in the Proxy Binding Acknowledgment messages that it sends to the mobile access gateway. 5.5. Routing Considerations 5.5.1. Bi-Directional Tunnel Management o A bi-directional tunnel is established between the local mobility anchor and the mobile access gateway with IP-in-IP encapsulation, as described in [RFC-2473]. The tunnel end points are the Proxy- CoA and LMAA. When using IPv4 transport with a specific encapsulation mode, the end points of the tunnel are the IPv4-LMAA and IPv4-Proxy-CoA, as specified in [ID-IPV4-PMIP6]. o The bi-directional tunnel is used for routing the mobile node's data traffic between the mobile access gateway and the local mobility anchor. The tunnel hides the topology and enables a mobile node to use an address from its home network prefix from any access link attached to the mobile access gateway. o The bi-directional tunnel is established after accepting the Proxy Binding Update request message. The created tunnel may be shared Gundavelli, et al. Expires March 7, 2008 [Page 21] Internet-Draft Proxy Mobile IPv6 September 2007 with other mobile nodes attached to the same mobile access gateway and with the local mobility anchor having a binding cache entry for those mobile nodes. Implementations MAY choose to use static tunnels as supposed to dynamically creating and tearing them down on a need basis. o The tunnel between the local mobility anchor and the mobile access gateway is typically a shared tunnel and can be used for routing traffic streams for different mobile nodes attached to the same mobile access gateway. o Implementations typically 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 will be set to the accepted binding life-time and will be updated after each periodic registrations for extending the lifetime. If the tunnel is shared for multiple mobile nodes, the tunnel lifetime will be set to the highest binding lifetime that is granted to any one of those mobile nodes sharing that tunnel. 5.5.2. Forwarding Considerations Intercepting Packets Sent to the Mobile Node's Home Network o When the local mobility anchor is serving a mobile node, it MUST be able to receive packets that are sent to the mobile node's home network. In order for it to receive those packets, it MUST advertise a connected route in to the Routing Infrastructure for the mobile node's home network prefix or for an aggregated prefix with a larger scope. This essentially enables IPv6 routers in that network to detect the local mobility anchor as the last-hop router for that prefix. Forwarding Packets Sent by the Mobile Node to the Corresponding Node o On receiving a packet from a corresponding node with the destination address matching a mobile node's home network prefix, the local mobility anchor MUST forward the packet through the bi- directional tunnel setup for that mobile node. The format of the tunneled packet is shown below. IPv6 header (src= LMAA, dst= Proxy-CoA /* Tunnel Header */ IPv6 header (src= CN, dst= MN-HNP ) /* Packet Header */ Upper layer protocols /* Packet Content*/ Gundavelli, et al. Expires March 7, 2008 [Page 22] Internet-Draft Proxy Mobile IPv6 September 2007 Figure 6: Tunneled Packets from LMA to MAG Forwarding Packets Sent by the Corresponding Node to the Mobile Node o All the reverse tunneled packets that the local mobility anchor receives from the mobile access gateway, after removing the tunnel header MUST be routed to the destination specified in the inner packet header. These routed packets will have the source address field set to the mobile node's home address. 5.6. Local Mobility Anchor Address Discovery Dynamic Home Agent Address Discovery, as explained in Section 10.5 [RFC-3775], allows a mobile node to discover all the home agents on its home link by sending an ICMP Home Agent Address Discovery Request message to the Mobile IPv6 Home-Agents anycast address, derived from its home network prefix. The DHAAD message in the current form cannot be used in Proxy Mobile IPv6 for discovering the address of the mobile node's local mobility anchor. In Proxy Mobile IPv6, the local mobility anchor will not be able to receive any messages sent to the Mobile IPv6 Home-Agents anycast address corresponding to the mobile node's home network prefix, as the prefix is not hosted on any of its interfaces. Further, the mobile access gateway will not predictably be able to locate the serving local mobility anchor that has the mobile node's binding cache entry. Hence, this specification does not support Dynamic Home Agent Address Discovery protocol. In Proxy Mobile IPv6, the address of the local mobility anchor configured to serve a mobile node can be discovered by the mobility entities in other ways. This may be a configured entry in the mobile node's policy profile, or it may be obtained through mechanisms outside the scope of this document. 5.7. Mobile Prefix Discovery Considerations The ICMP Mobile Prefix Advertisement message, described in Section 6.8 and Section 11.4.3 of [RFC-3775], allows a home agent to send a Mobile Prefix Advertisement to the mobile node. In Proxy Mobile IPv6, the mobile node's home network prefix is hosted on the access link connected to the mobile access gateway. but it is topologically anchored on the local mobility anchor. Since, there is no physical home-link for the mobile node's home network prefix on the local mobility anchor and as the mobile node is always on the link where the prefix is hosted, any prefix change messages can just Gundavelli, et al. Expires March 7, 2008 [Page 23] Internet-Draft Proxy Mobile IPv6 September 2007 be advertised by the mobile access gateway on the access link and thus there is no applicability of this message for Proxy Mobile IPv6. Hence, this specification does not support Mobile Prefix Discovery. 5.8. Route Optimizations Considerations The Route Optimization in Mobile IPv6, as defined in [RFC-3775], enables a mobile node to communicate with a corresponding node directly using its care-of address and further the Return Routability procedure enables the corresponding node to have reasonable trust that the mobile node is reachable at both its home address and care-of address. In Proxy Mobile IPv6, the mobile node is not involved in any mobility related signaling. The mobile node uses only its home address for all its communication and the Care-of address (Proxy-CoA) is not visible to the mobile node. Hence, the Return Routability procedure as defined in Mobile IPv6 cannot be used in Proxy Mobile IPv6. 6. Mobile Access Gateway Operation The Proxy Mobile IPv6 protocol described in this document, introduces a new functional entity, the Mobile Access Gateway (MAG). The mobile access gateway is the entity that is responsible for detecting the mobile node's movements on its access link and sending the binding registration requests to the local mobility anchor. In essence, the mobile access gateway performs mobility management on behalf of a mobile node. The mobile access gateway is a function that typically runs on an access router. However, implementations MAY choose to split this function and run it across multiple systems. The specifics on how that is achieved is 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. Gundavelli, et al. Expires March 7, 2008 [Page 24] Internet-Draft Proxy Mobile IPv6 September 2007 6.1. Extensions to Binding Update List Entry Data Structure Every mobile access gateway MUST maintain a Binding Update List. Each entry in the Binding Update List represents a mobile node's mobility binding with its local mobility anchor. The Binding Update List is a conceptual data structure, described in Section 11.1 [RFC- 3775]. For supporting this specification, the conceptual Binding Update List entry data structure needs be extended with the following additional fields. o The Identifier of the attached mobile node, MN-Identifier. This identifier is acquired during the mobile node's attachment to the access link or through mechanisms outside the scope of this document. o The Link-layer address of the mobile node. This address can be acquired from the received Router Solicitation messages from the mobile node or during the mobile node's attachment to the access network. 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 Acknowledgment messages. The IPv6 home network prefix also includes the corresponding prefix length. o The Link-local address of the mobile node on the interface attached to the access link. o The IPv6 address of the local mobility anchor serving the attached mobile node. This address is acquired from the mobile node's policy profile. o The interface identifier of the access link where the mobile node is currently attached. The interface identifier is acquired during the mobile node's attachment to the access link. o The interface identifier of the bi-directional tunnel between the mobile node's local mobility anchor and the mobile access gateway. The tunnel interface identifier is acquired during the tunnel creation. Gundavelli, et al. Expires March 7, 2008 [Page 25] Internet-Draft Proxy Mobile IPv6 September 2007 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. 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) o Supported address configuration procedures on the link (Stateful, Stateless or both) The following are the optional fields of the policy profile: o The mobile node's IPv6 home network prefix (MN-HNP) 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. 6.4. Supported Address Configuration Models A mobile node in the Proxy Mobile IPv6 domain can configure one or more IPv6 addresses on its interface using Stateless or Stateful address autoconfiguration procedures. The Router Advertisement messages sent on the access link, specify the address configuration methods permitted on that access link for that mobile node. However, the advertised flags with respect 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. Gundavelli, et al. Expires March 7, 2008 [Page 26] Internet-Draft Proxy Mobile IPv6 September 2007 When stateless address autoconfiguration is supported on the link, the mobile node can generate one or more IPv6 addresses by combining the network prefix advertised on the access link with an interface identifier, using the techniques described in Stateless Autoconfiguration specification [RFC-2462] or as per Privacy extension specification [RFC-3041]. When stateful address autoconfiguration is supported on the link, the mobile node can obtain the address configuration from the DHCPv6 server using DHCPv6 client protocol, as specified in DHCPv6 specification [RFC-3315]. Additionally, other address configuration mechanisms specific to the access link between the mobile node and the mobile access gateway may also be used for pushing the address configuration to the mobile node. 6.5. Access Authentication & Mobile Node Identification When a mobile node attaches to an access link connected to the mobile access gateway, the deployed access security protocols on that link SHOULD ensure that the network-based mobility management service is offered only after authenticating and authorizing the mobile node for that service. The exact specifics on how this is achieved or the interactions between the mobile access gateway and the access security service is outside the scope of this document. This specification goes with the stated assumption of having an established trust between the mobile node and mobile access gateway, before the protocol operation begins. 6.6. Acquiring Mobile Node's Identifier All the network entities in a Proxy Mobile IPv6 domain MUST be able to identify a mobile node, using its MN-Identifier. This identifier MUST be stable across the Proxy Mobile IPv6 domain and the entities must be able to use this identifier in the signaling messages. Typically, this identifier is obtained as part of the access authentication or through other means as specified below. o The identifier of the mobile node that the mobile access gateway obtains as part of the access authentication or from the notified network attachment event, can be a temporary identifier and this identifier may also change at each re-authentication. However, the mobile access gateway MUST be able to authenticate the mobile node based on this identifier and MUST be able to obtain the MN- Identifier from the policy store, such as from the RADIUS attribute, Chargeable-User-Identifier. Gundavelli, et al. Expires March 7, 2008 [Page 27] Internet-Draft Proxy Mobile IPv6 September 2007 o The MN-Identifier that the policy store delivers to the mobile access gateway MAY NOT be the true identifier of the mobile node. However, the mobility access gateway MUST be able to use this identifier in the signaling messages exchanged with the local mobility anchor. o The mobile access gateway MUST be able identify the mobile node by its MN-Identifier and it MUST be able to associate this identity to the sender of any IPv4 or IPv6 packets on the access link. 6.7. Home Network Emulation One of the key functions of a mobile access gateway is to emulate the mobile node's home network on the access link. It must ensure, the mobile node believes it is still connected to its home link or on the link where it obtained its initial address configuration after it moved into that Proxy Mobile IPv6 domain. For emulating the mobile node's home link on the access link, the mobile access gateway must be able to send Router Advertisements advertising the mobile node's home network prefix and other address configuration parameters consistent with its home link properties. Typically, 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. 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, it will continue to detect its home network and thus making it believe it is still on the same link. Every time the mobile node attaches to a new link, the event related to the interface state change, will trigger the mobile node to perform DAD operation on the link-local and global addresses. However, if the mobile node is DNAv6 enabled, as specified in [ID- DNAV6], it may not detect the link change due to DNAv6 optimizations and may not trigger the duplicate address detection (DAD) procedure for establishing the link-local address uniqueness on that new link. Further, if the mobile node uses an interface identifier that is not based on EUI-64 identifier, such as specified in IPv6 Stateless Autoconfiguration specification [RFC-2462], there is a possibility, with the odds of 1 to billion, of a link-local address collision between the two neighbors on that access link. Gundavelli, et al. Expires March 7, 2008 [Page 28] Internet-Draft Proxy Mobile IPv6 September 2007 One of the workarounds for this issue is to set the DNAv6 configuration parameter, DNASameLinkDADFlag to TRUE and that will force the mobile node to redo DAD operation every time the interface comes up, even when DNAv6 does detect a link change . However, this issues will not impact point-to-point links based on PPP session. Each time the mobile node moves and attaches to a new mobile access gateway, either the PPP session [RFC-1661] is reestablished or the PPP session may be moved as part of context transfer procedures between the old and the new mobile access gateway. When the mobile node tries to establish a PPP session with the mobile access gateway, the PPP goes through the Network layer Protocol phase and the IPv6 Control Protocol, IPCP6 [RFC-2472] gets triggered. Both the PPP peers negotiate a unique identifier using Interface- Identifier option in IPV6CP and the negotiated identifier is used for generating a unique link-local address on that link. Now, if the mobile node moves to a new mobile access gateway, the PPP session gets torn down with the old mobile access gateway and a new PPP session gets established with the new mobile access gateway, and the mobile node obtains a new link-local address. So, even if the mobile node is DNAv6 capable, the mobile node always configures a new link- local address when ever it moves to a new link. If the PPP session state is moved to the new mobile access gateway, as part of context transfer procedures that are in place, there will not be any change to the interface identifiers of the two nodes on that point-to-point change. The whole link is moved to the new mobile access gateway and there will not be any need for establishing link-local address uniqueness on that link. Alternatively, this specification allows the mobile access gateway to upload the mobile node's link-local address to the local mobility anchor using the Link-local Address option, exchanged in the binding registration messages. The mobile access gateway can learn the mobile node's link-local address, by snooping the DAD messages sent by the mobile node for establishing the link-local address uniqueness on the access link. Subsequently, at each handoff, the mobile access gateway can obtain this address from the local mobility anchor and can change its own link-local address, if it detects an address collision. This issue is not relevant to the mobile node's global address. Since, there is a unique home network prefix for each mobile node, the uniqueness for the mobile node's global address is assured on the access link. Gundavelli, et al. Expires March 7, 2008 [Page 29] Internet-Draft Proxy Mobile IPv6 September 2007 6.9. Signaling Considerations Initial Attachment and binding registration o After detecting a new mobile node on its access link, the mobile access gateway MUST send a Proxy Binding Update message to the mobile node's local mobility anchor. o The Proxy Binding Update message that the mobile access gateway sends to the mobile node's local mobility anchor MUST have the NAI option, identifying the mobile node, the Home Network Prefix option and optionally the Timestamp option or a valid sequence number. o If the mobile access gateway learns the mobile node's home network prefix either from its policy store or from other means, the mobile access gateway MAY choose to specify the same in the Home Network Prefix option for requesting the local mobility anchor to allocate that prefix. If the specified value is 0::/0, then the local mobility anchor will consider this as a request for prefix allocation. o If the mobile access gateway receives a Proxy Binding Acknowledgment with the Status field value set to 0 (Proxy Binding Update accepted), the mobile access gateway MUST create Binding Update List entry for the mobile node and must setup a tunnel to the mobile node's local mobility anchor, as explained in section 6.10. The mobile access gateway MUST also add a policy route for tunneling all the packets that it receives from the mobile node to its local mobility anchor. o If the mobile access gateway receives a Proxy Binding Acknowledgment with the Status field value greater than 128 (binding request is rejected), the mobile access gateways MUST NOT advertise the mobile node's home network prefix on the access link and there by denying mobility service to the mobile node. Extending the binding lifetime o For extending the lifetime of a currently existing binding at the local mobility, the mobile access gateway MUST send a Proxy Binding Update message, before the expiry of the currently accepted binding. De-Registration of the binding o At any point, the mobile access gateway detects that the mobile node has moved away from its access link, it MUST send a Proxy Gundavelli, et al. Expires March 7, 2008 [Page 30] Internet-Draft Proxy Mobile IPv6 September 2007 Binding Update message to the mobile node's local mobility anchor with the lifetime value set to zero. o The mobile access gateway MUST also remove the default route over the tunnel for that mobile node and delete the Binding Update List for that mobile node, either upon receiving an Proxy Binding Acknowledgment message from the local mobility anchor or after a certain timeout waiting for the acknowledgment message. Constructing 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 are set*/ Mobility Options - Home Network Prefix option - Link-local Address option (Optional) - Timestamp Option (optional) - NAI Option Proxy Binding Update message contents o The Source Address field in the IPv6 header of the message SHOULD be set to the address of the mobile access gateway. o The Destination Address field in the IPv6 header of the message SHOULD be set to the local mobility anchor address. o The Home Network Prefix option MUST be present. The prefix value may be set 0::/0 or to a specific value. o The Link-local Address option MAY be present. The value may be set to ALL_ZERO or the mobile node's link-local address. o Considerations from Section 5.4 must be applied for constructing the Timestamp option. o The NAI option MUST be present, the identifier field in the option MUST be set to mobile node's identifier, MN-Identifier. Gundavelli, et al. Expires March 7, 2008 [Page 31] Internet-Draft Proxy Mobile IPv6 September 2007 o The message SHOULD be protected by using IPsec ESP, using the security association existing between the local mobility anchor and the mobile access gateway, created either dynamically or statically. 6.10. Routing Considerations This section describes how the mobile access gateway handles the traffic to/from the mobile node that is attached to one of its access interface. Proxy-CoA LMAA | | +--+ +---+ +---+ +--+ |MN|----------|MAG|======================|LMA|----------|CN| +--+ +---+ +---+ +--+ IPv6 Tunnel 6.10.1. Transport Network The transport network between the local mobility anchor and the mobile access can be either an IPv6 or IPv4 network. However, this specification only deals with the IPv6 transport and the companion document [ID-IPV4-PMIP6] specifies the required extensions for negotiating IPv4 transport and the corresponding encapsulation mode, for supporting this protocol operation. 6.10.2. Tunneling & Encapsulation Modes The IPv6 address that a mobile node uses from its home network prefix is topologically anchored at the local mobility anchor. For a mobile node to use this address from an access network attached to a mobile access gateway, proper tunneling techniques have to be in place. Tunneling hides the network topology and allows the mobile node's IPv6 datagrams to be encapsulated as a payload of another IPv6 packet and 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, tunnels are implemented as a virtual point-to-point interface. The source and the destination address of the two end points of this virtual interface along with the encapsulation mode are specified for this virtual interface. Any Gundavelli, et al. Expires March 7, 2008 [Page 32] Internet-Draft Proxy Mobile IPv6 September 2007 packet that is routed over this interface, get encapsulated with the outer header and the addresses as specified for that point to point tunnel interface. For creating a point to point tunnel to any local mobility anchor, the mobile access gateway may implement a tunnel interface with the source address field set to its Proxy-CoA address and the destination address field set to the LMA address. The following are the supported packet encapsulation modes that can be used by the mobile access gateway and the local mobility anchor for routing mobile node's IPv6 datagrams. o IPv6-In-IPv6 - IPv6 datagram encapsulated in an IPv6 packet. This mechanism is defined in the Generic Packet Tunneling for IPv6 specification [RFC-2473]. o IPv6-In-IPv4 - IPv6 datagram encapsulation in an IPv4 packet. The details related to this encapsulation mode and the specifics on how this mode is negotiated is specified in the companion document, IPv4 support for Proxy Mobile IPv6 [ID-IPV4-PMIP6]. o IPv6-In-IPv4-UDP - IPv6 datagram encapsulation in an IPv4 UDP packet. The details related to this mode are covered in the companion document, IPv4 support for Proxy Mobile IPv6 [ID-IPV4- PMIP6]. 6.10.3. Routing State The following section explain the routing state for a mobile node on the mobile access gateway. This routing state reflects only one specific way of implementation and one MAY choose to implement it in other ways. The policy based route defined below acts as a traffic selection rule for routing a mobile node's traffic through a specific tunnel created between the mobile access gateway and that mobile node's local mobility anchor and with the specific encapsulation mode, as negotiated. The below example identifies the routing state for two visiting mobile nodes, MN1 and MN2 with their respective local mobility anchors LMA1 and LMA2. For all traffic from the mobile node, identified by the mobile node's MAC address, ingress interface or source prefix (MN-HNP) to _ANY_DESTINATION_ route via interface tunnel0, next-hop LMAA. Gundavelli, et al. Expires March 7, 2008 [Page 33] Internet-Draft Proxy Mobile IPv6 September 2007 +==================================================================+ | Packet Source | Destination Address | Destination Interface | +==================================================================+ | MAC_Address_MN1, | _ANY_DESTINATION_ | Tunnel0 | | (IPv6 Prefix or |----------------------------------------------| | Input Interface) | Locally Connected | Tunnel0 | +------------------------------------------------------------------+ | MAC_Address_MN2, | _ANY_DESTINATION_ | Tunnel1 | + (IPv6 Prefix or -----------------------------------------------| | Input Interface | Locally Connected | direct | +------------------------------------------------------------------+ Example - Policy based Route Table +==================================================================+ | Interface | Source Address | Destination Address | Encapsulation | +==================================================================+ | Tunnel0 | Proxy-CoA | LMAA1 | IPv6-in-IPv6 | +------------------------------------------------------------------+ | Tunnel1 |IPv4-Proxy-CoA | IPv4-LMA2 | IPv6-in-IPv4 | +------------------------------------------------------------------+ Example - Tunnel Interface Table 6.10.4. Local Routing If there is data traffic between a visiting mobile node and a corresponding 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. However, this has 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 configured 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 is beyond of the scope of this document. Gundavelli, et al. Expires March 7, 2008 [Page 34] Internet-Draft Proxy Mobile IPv6 September 2007 6.10.5. Tunnel Management All the considerations mentioned in Section 5.5.1, for the tunnel management on the local mobility anchor apply for the mobile access gateway as well. 6.10.6. Forwarding Rules Upon receipt of an encapsulated packet sent to its configured Proxy- CoA address i.e. on receiving a packet from a tunnel, the mobile access gateway MUST use the destination address of the inner packet for forwarding it to the interface where the prefix for that address is hosted. The mobile access gateway MUST remove the outer header before forwarding the packet. If the mobile access gateway cannot find the connected interface for that destination address, it MUST silently drop the packet. For reporting an error in such scenario, in the form of ICMP control message, the considerations from Generic Packet Tunneling specification [RFC-2473] apply. 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. 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's local mobility anchor. On receiving a packet from the mobile node to any destination i.e. not directly connected to the mobile access gateway, the packet MUST be forwarded to the local mobility anchor through the bi-directional tunnel established between itself and the mobile's local mobility anchor. However, the packets that are sent with the link-local source address MUST not be forwarded. 6.11. Interaction with DHCP Relay Agent If Stateful Address Configuration using DHCP is supported on the link where the mobile node is attached, the DHCP relay agent [RFC-3315] needs to be configured on that access link. Gundavelli, et al. Expires March 7, 2008 [Page 35] Internet-Draft Proxy Mobile IPv6 September 2007 When the mobile node sends a DHCPv6 Request message, the DHCP relay agent function on the access link will set the link-address field in the DHCPv6 message to the mobile node's home network prefix, so as to provide a prefix hint to the DHCP Server for the address pool selection. 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 is 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 scenario, the mobile access gateway SHOULD terminate the binding of the mobile node by sending a Proxy Binding Update message to the mobile node's local mobility anchor with lifetime value set to 0. It MUST also remove any local state such as the Binding Update List created for that mobile node. The specific detection mechanism of the loss of a visiting mobile node on the connected link is specific to the access link between the mobile node and the mobile access gateway and is outside the scope of this document. Typically, there are various link-layer specific events specific to each access technology that the mobile access gateway can depend on for detecting the node loss. In general, the mobile access gateway can depend on one or more of the following methods for the detection presence of the mobile node on the connected link: o Link-layer event specific to the access technology o PPP Session termination event on point-to-point link types Gundavelli, et al. Expires March 7, 2008 [Page 36] Internet-Draft Proxy Mobile IPv6 September 2007 o IPv6 Neighbor Unreachability Detection event from IPv6 stack o Notification event from the local mobility anchor o Absence of data traffic from the mobile node on the link for a certain duration of time 6.14. 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 IPv6/IPv4 access to some other nodes attached to that mobile access gateway. This requires the network to have the 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 obtaining the mobile node's profile after a successful access authentication and after a policy consideration, the mobile access gateway MUST determine if the network based mobility service should be offered to that mobile node. If the mobile node is entitled for such service, then the 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 enforced by the policy, the mobile access gateway MAY choose to offer regular IPv6 access to the mobile node and hence the normal IPv6 considerations apply. If IPv6 access is enabled, the mobile node SHOULD be able to obtain any IPv6 address using normal IPv6 address configuration mechanisms. The obtained address must be from a local visitor network prefix. This essentially ensures, the mobile access gateway functions as any other access router and does not impact the protocol operation of a mobile node attempting to use host-based mobility management service when it attaches to an access link connected to a mobile access gateway in a Proxy Mobile IPv6 domain. 7. Mobile Node Operation This non-normative section explains the mobile node's operation in a Proxy Mobile IPv6 domain. Gundavelli, et al. Expires March 7, 2008 [Page 37] Internet-Draft Proxy Mobile IPv6 September 2007 7.1. Moving into a Proxy Mobile IPv6 Domain Once a mobile node enters a Proxy Mobile IPv6 domain and attaches to an access network, the mobile access gateway on the access link detects the attachment of the mobile node and completes the binding registration with the mobile node's local mobility anchor. If the binding update operation is successfully performed, the mobile access gateway will create the required state and setup the data path for the mobile node's data traffic. If the mobile node is IPv6 enabled, on attaching to the access link, it will typically send Router Solicitation message [RFC-2461]. The mobile access gateway on the access link will respond to the Router Solicitation message with a Router Advertisement. The Router Advertisement will have the mobile node's home network prefix, default-router address and other address configuration parameters. If the mobile access gateway on the access link, receives a Router Solicitation message from the mobile node, before it completed the signaling with the mobile node's local mobility anchor, the mobile access gateway may not know the mobile node's home network prefix and may not be able to emulate the mobile node's home link on the access link. In such scenario, the mobile node may notice a slight delay before it receives a Router Advertisement message. If the received Router Advertisement has the Managed Address Configuration flag set, the mobile node, as it would normally do, will send a DHCPv6 Request [RFC-3315]. The DHCP relay service enabled on that access link will ensure the mobile node will obtain its IPv6 address as a lease from its home network prefix. If the received Router Advertisement does not have the Managed Address Configuration flag set and if the mobile node is allowed to use an autoconfigured address, the mobile node will be able to obtain an IPv6 address using an interface identifier generated as per the Autoconf specification [RFC-2462] or as per the Privacy Extensions specification [RFC-3041]. If the mobile node is IPv4 enabled and if the network permits, it will be able to obtain the IPv4 address configuration for the connected interface by using DHCP [RFC-2131]. The details related to IPv4 support is specified in the companion document [ID-IPV4-PMIP6]. Once the address configuration is complete, the mobile node can continue to use this address configuration as long as it is attached to the network that is in the scope of that Proxy Mobile IPv6 domain. Gundavelli, et al. Expires March 7, 2008 [Page 38] Internet-Draft Proxy Mobile IPv6 September 2007 7.2. Roaming in the Proxy Mobile IPv6 Domain After obtaining the address configuration in the Proxy Mobile IPv6 domain, as the mobile node moves and changes its point of attachment from one mobile access gateway to the other, it can still continue to use the same address configuration. As long as the attached access network is in the scope of that Proxy Mobile IPv6 domain, the mobile node will always detect the same link, where it obtained its initial address configuration. If the mobile node performs DHCP operation, it will always obtain the same address as before. However, the mobile node will always detect a new default-router on each connected link, but still advertising the mobile node's home network prefix as the on-link prefix and with the other configuration parameters consistent with its home link properties. 7.3. IPv6 Host Protocol Parameters This specification does not require any changes to the mobile node's IP stack. It assumes the mobile node to be a normal IPv4/IPv6 node, with its protocol operation consistent with the respective specifications. However, this specification recommends that the following IPv6 operating parameters on the mobile node be adjusted to the below recommended values for protocol efficiency and for achieving faster hand-offs. Lower Default-Router List Cache Time-out: As per the base IPv6 specification [RFC-2461], each IPv6 host is required to maintain certain host data structures including a Default-Router list. This is the list of on-link routers that have sent Router Advertisement messages and are eligible to be default routers on that link. The Router Lifetime field in the received Router Advertisement defines the life of this entry. In case of Proxy Mobile IPv6, when a mobile node moves from one link to another, the source address of the received Router Advertisement messages advertising the mobile node's home network prefix will be from a different link-local address and thus making the mobile node believe that there is a new default-router on the link. It is important that the mobile node uses the newly learnt default-router as supposed to the previously known default-router. The mobile node must update its default-router list with the new default router entry and must age out the previously learnt default router entry from its cache, just as specified in Section 6.3.5 [RFC-2461]. This action is Gundavelli, et al. Expires March 7, 2008 [Page 39] Internet-Draft Proxy Mobile IPv6 September 2007 critical for minimizing packet losses during a hand off switch. On detecting a reachability problem, the mobile node will certainly detect the default-router loss by performing the Neighbor Unreachability Detection procedure, but it is important that the mobile node times out the previous default router entry at the earliest. If a given IPv6 host implementation has the provision to adjust these flush timers, still conforming to the base IPv6 ND specification, it is desirable to keep the flush-timers to suit the above consideration. In access network where SEND [RFC-3971] is not deployed, the mobile access gateway may withdraw the previous default-router entry, by sending a Router Advertisement using the link-local address that of the previous mobile access gateway and with the Router Lifetime field set to value 0, then this will force the flush of the Previous Default-Router entry from the mobile node's cache. This certainly requires context-transfer mechanisms in place for notifying the link- local address of the default-router on the previous link to the mobile access gateway on the new link. There are other solutions possible for this problem, including the assignment of a unique link-local address for all the mobile access gateways in a Proxy Mobile IPv6 domain and where SEND [RFC-3971] is not deployed. In such scenario, the mobile node is not required to update the default-router entry. However, this is an implementation choice and has no bearing on the protocol interoperability. Implementations are free to adopt the best approach that suits their target deployments. 8. Message Formats This section defines extensions to the Mobile IPv6 [RFC-3775] protocol messages. Gundavelli, et al. Expires March 7, 2008 [Page 40] Internet-Draft Proxy Mobile IPv6 September 2007 8.1. Proxy Binding Update 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A|H|L|K|M|R|P| Reserved | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 11: Proxy Binding Update Message 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]. 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. For descriptions of other fields present in this message, refer to section 6.1.7 [RFC-3775]. Gundavelli, et al. Expires March 7, 2008 [Page 41] Internet-Draft Proxy Mobile IPv6 September 2007 8.2. Proxy Binding Acknowledgment 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Status |K|R|P|Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence # | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 12: Proxy Binding Acknowledgment Message 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 Acknowledgment message. The rest of the Binding Acknowledgment message format remains the same as defined in [RFC- 3775]. 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 only if the corresponding Proxy Binding Update had the Proxy Registration Flag (P) set to value of 1. For descriptions of other fields present in this message, refer to the section 6.1.8 [RFC-3775]. 8.3. Home Network Prefix Option A new option, Home Network Prefix Option is defined for using it in the Proxy Binding Update and Proxy Binding Acknowledgment 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: Gundavelli, et al. Expires March 7, 2008 [Page 42] Internet-Draft Proxy Mobile IPv6 September 2007 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | Prefix Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Home Network Prefix + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 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 This field is unused for now. The value MUST be initialized to 0 by the sender and MUST be ignored by the receiver. Prefix Length 8-bit unsigned integer indicating the prefix length of the IPv6 prefix contained in the option. Home Network Prefix A sixteen-byte field containing the mobile node's IPv6 Home Network Prefix. Figure 13: Home Network Prefix Option 8.4. Link-local Address Option A new option, Link-local Address Option is defined for using it in the Proxy Binding Update and Proxy Binding Acknowledgment messages exchanged between a local mobility anchor and a mobile access gateway. This option is used for exchanging the mobile node's link- local address. Gundavelli, et al. Expires March 7, 2008 [Page 43] Internet-Draft Proxy Mobile IPv6 September 2007 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 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. Figure 14: Link-local Address Option 8.5. Timestamp Option A new option, Timestamp Option is defined for use in the Proxy Binding Update and Proxy Binding Acknowledgement messages. The Timestamp option has an alignment requirement of 8n+2. Its format is as follows: Gundavelli, et al. Expires March 7, 2008 [Page 44] Internet-Draft Proxy Mobile IPv6 September 2007 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Option Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Timestamp + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type 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 1/64K fractions of a second. Figure 15: Timestamp Option 8.6. Status Values This document defines the following new Status values for use in Proxy Binding Acknowledgment message. These values are to be allocated from the same number space, as defined in Section 6.1.8 [RFC-3775]. Status values less than 128 indicate that the Proxy Binding Update was processed successfully 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: Gundavelli, et al. Expires March 7, 2008 [Page 45] Internet-Draft Proxy Mobile IPv6 September 2007 Proxy Registration not enabled for the mobile node. MAG_NOT_AUTHORIZED_FOR_PROXY_REG: The mobile access gateway is not authorized to send proxy binding. updates. NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX The mobile node is not authorized for the requesting home network prefix. TIMESTAMP_MISMATCH: Invalid Timestamp value in the received Proxy Binding Update message. MISSING_MN_IDENTIFIER_OPTION: Missing mobile node identifier in the Proxy Binding Update message. 9. Protocol Configuration Variables The mobile access gateway MUST allow the following variables to be configured by the system management. 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 corresponding node that is locally connected to one of the interfaces of the mobile access gateway. The corresponding node can be another visiting mobile node as well, or a local fixed node. The default value for this flag is set to "FALSE", indicating that the mobile access gateway MUST reverse tunnel all the traffic to the mobile node's local mobility anchor. Gundavelli, et al. Expires March 7, 2008 [Page 46] Internet-Draft Proxy Mobile IPv6 September 2007 When the value of this flag is set to "TRUE", the mobile access gateway MUST route the traffic locally. This aspect of local routing MAY be defined as policy on a per mobile basis and when present will take precedence over this flag. The local mobility anchor MUST allow the following variables to be configured by the system management. MinDelayBeforeBCEDelete This variable specifies the amount of time in milli-seconds 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 mobile node, identified by its MN-Identifier, with lifetime value greater than 0, then it must update the binding cache entry with the accepted binding values. At the end of this wait-time, if the local mobility anchor did not receive any valid Proxy Binding Update message, it MUST delete the binding cache entry for that mobile node. The default value for this variable is 1000 milli-seconds. 10. IANA Considerations This document defines a three new Mobility Header Options, the Home Network Prefix option, Link-local Address option and the Timestamp option. These options are described in Sections 8.3, 8.4 and 8.5 respectively. The Type value for these options needs to be assigned from the same numbering space as allocated for the other mobility options, as defined in [RFC-3775]. This document also defines new Binding Acknowledgement status values as described in Section 8.6. 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 Gundavelli, et al. Expires March 7, 2008 [Page 47] Internet-Draft Proxy Mobile IPv6 September 2007 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 do a denial-of-service attacks. To prevent this attack, this specification requires the local mobility anchor to allow only authorized mobile access gateways to send binding registration messages on behalf of a mobile node. To eliminate the threats on the interface between the mobile access gateway and the mobile node, this specification requires an established trust between the mobile access gateway and the mobile node and to authenticate and authorize the mobile node before it is allowed to access the network. To eliminate the threats related to a compromised mobile access gateway, this specification recommends that the local mobility anchor before accepting a Proxy Binding Update message for a given mobile node, to reasonably ensure, using some out of band mechanisms, that the given mobile node is attached to that mobile access gateway that sent the request. The issues related to a compromised mobile access gateway in the scenario where the local mobility anchor and the mobile access gateway in different domains, is outside the scope of this document. This scenario is beyond the applicability of this document. 12. Acknowledgements The authors would like to specially thank Julien Laganier, Christian Vogt, Pete McCann, Brian Haley, Ahmad Muhanna, JinHyeock Choi for their thorough review of this document. The authors would also like to thank Alex Petrescu, Alice Qinxia, Alper Yegin, Ashutosh Dutta, Behcet Sarikaya, Fred Templing, Genadi Velev, George Tsirtsis, Gerardo Giaretta, Henrik Levkowetz, Hesham Soliman, James Kempf, Jari Arkko, Jean-Michel Combes, John Zhao, Gundavelli, et al. Expires March 7, 2008 [Page 48] Internet-Draft Proxy Mobile IPv6 September 2007 Jong-Hyouk Lee, Jonne Soininen, Jouni Korhonen, Kilian Weniger, Marco Liebsch, Mohamed Khalil, Nishida Katsutoshi, Phil Roberts, Ryuji Wakikawa, Sangjin Jeong, Suresh Krishnan, Vidya Narayanan, Youn-Hee Han and many others for their passionate discussions in the working group mailing list on the topic of localized mobility management solutions. These discussions stimulated much of the thinking and shaped the draft to the current form. We acknowledge that ! The authors would also like to thank Ole Troan, Akiko Hattori, Parviz Yegani, Mark Grayson, Michael Hammer, Vojislav Vucetic, Jay Iyer and Tim Stammers for their input on this document. 13. References 13.1. Normative References [RFC-2030] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI", RFC 2030, October 1996. [RFC-2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [RFC-2461] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. [RFC-2462] Thompson, S., Narten, T., "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998. [RFC-2473] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 Specification", RFC 2473, December 1998. [RFC-3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M.Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [RFC-3775] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in IPv6", RFC 3775, June 2004. [RFC-3776] Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to Protect Mobile IPv6 Signaling Between Mobile Nodes and Home Agents", RFC 3776, June 2004. [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The Network Access Identifier", RFC 4282, November 2005. [RFC-4283] Patel, A., Leung, K., Khalil, M., Akhtar, H., and K. Chowdhury, "Mobile Node Identifier Option for Mobile IPv6", RFC 4283, Gundavelli, et al. Expires March 7, 2008 [Page 49] Internet-Draft Proxy Mobile IPv6 September 2007 November 2005. [RFC-4301] Kent, S. and Atkinson, R., "Security Architecture for the Internet Protocol", RFC 4301, December 2005. [RFC-4303] Kent, S. "IP Encapsulating Security Protocol (ESP)", RFC 4303, December 2005. [RFC-4306] Kaufman, C, et al, "Internet Key Exchange (IKEv2) Protocol", RFC 4306, December 2005. [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-4877] Devarapalli, V. and Dupont, F., "Mobile IPv6 Operation with IKEv2 and the revised IPsec Architecture", RFC 4877, April 2007. 13.2. Informative References [RFC-1332] McGregor, G., "The PPP Internet Protocol Control Protocol (IPCP)", RFC 1332, May 1992. [RFC-1661] Simpson, W., Ed., "The Point-To-Point Protocol (PPP)", STD 51, RFC 1661, July 1994. [RFC-2472] Haskin, D. and Allen, E., "IP version 6 over PPP", RFC 2472, December 1998. [RFC-2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [RFC-3041] Narten, T. and Draves, R., "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 3041, January 2001. [RFC-3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, August 2002. [RFC-3756] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor Discovery (ND) Trust Models and Threats", RFC 3756, May 2004. Gundavelli, et al. Expires March 7, 2008 [Page 50] Internet-Draft Proxy Mobile IPv6 September 2007 [ID-IPV4-PMIP6] Wakikawa, R. and Gundavelli, S., "IPv4 Support for Proxy Mobile IPv6", draft-ietf-netlmm-pmip6-ipv4-support-00.txt, May 2007. [ID-DNAV6] Kempf, J., et al "Detecting Network Attachment in IPv6 Networks (DNAv6)", draft-ietf-dna-protocol-03.txt, October 2006. [ID-MN-AR-INTERFACE] Laganier, J. and Narayanan, S., "Network-based Localized Mobility Management Interface between Mobile Node and Mobility Access Gateway", draft-ietf-netlmm-mn-ar-if-02.txt, May 2007. [ID-DSMIP6] Soliman, H. et al, "Mobile IPv6 support for dual stack Hosts and Routers (DSMIPv6)", draft-ietf-mip6-nemo-v4traversal-03.txt, October 2006. Appendix A. Proxy Mobile IPv6 interactions with AAA Infrastructure Every mobile node that roams in a proxy Mobile IPv6 domain, would typically be identified by an identifier, MN-Identifier, and that identifier will have an associated policy profile that identifies the mobile node's home network prefix, permitted address configuration modes, roaming policy and other parameters that are essential for providing network-based mobility service. This information is typically configured in AAA. It is possible the home network prefix is dynamically allocated for the mobile node when it boots up for the first time in the network, or it could be a statically configured value on per mobile node basis. However, for all practical purposes, the network entities in the proxy Mobile IPv6 domain, while serving a mobile node will have access to this profile and these entities can query this information using RADIUS/DIAMETER protocols. Appendix B. Supporting Shared-Prefix Model using DHCPv6 This specification supports Per-MN-Prefix model. However, it is possible to support Shared-Prefix model under the following guidelines. The mobile node is allowed to use stateful address configuration using DHCPv6 for obtaining its address configuration. The mobile node is not allowed to use any of the stateless autoconfiguration techniques. The permitted address configuration models for the mobile node on the access link can be enforced by the mobile access Gundavelli, et al. Expires March 7, 2008 [Page 51] Internet-Draft Proxy Mobile IPv6 September 2007 gateway, by setting the relevant flags in the Router Advertisements, as per [RFC-2461]. The Home Network Prefix option that is sent by the mobile access gateway in the Proxy Binding Update message, must contain the 128-bit host address that the mobile node obtained via DHCPv6. Routing state at the mobile access gateway: For all IPv6 traffic from the source MN-HoA::/128 to _ANY_DESTINATION_, route via tunnel0, next-hop LMAA, where tunnel0 is the MAG to LMA tunnel. Routing state at the local mobility anchor: For all IPv6 traffic to destination MN-HoA::/128, route via tunnel0, next-hop Proxy-CoA, where tunnel0 is the LMA to MAG tunnel. Authors' Addresses Sri Gundavelli Cisco 170 West Tasman Drive San Jose, CA 95134 USA Email: sgundave@cisco.com Kent Leung Cisco 170 West Tasman Drive San Jose, CA 95134 USA Email: kleung@cisco.com Vijay Devarapalli Azaire Networks 4800 Great America Pkwy Santa Clara, CA 95054 USA Email: vijay.devarapalli@azairenet.com Gundavelli, et al. Expires March 7, 2008 [Page 52] Internet-Draft Proxy Mobile IPv6 September 2007 Kuntal Chowdhury Starent Networks 30 International Place Tewksbury, MA Email: kchowdhury@starentnetworks.com Basavaraj Patil Nokia Siemens Networks 6000 Connection Drive Irving, TX 75039 USA Email: basavaraj.patil@nsn.com Gundavelli, et al. Expires March 7, 2008 [Page 53] Internet-Draft Proxy Mobile IPv6 September 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Gundavelli, et al. Expires March 7, 2008 [Page 54]